Energies

24 pages, 3688 KiB

Open AccessArticle

A New Platform for Automatic Bottom-Up Electric Load Aggregation

by Alfredo Bartolozzi¹, Salvatore Favuzza²

, Mariano Giuseppe Ippolito², Diego La Cascia², Eleonora Riva Sanseverino² and Gaetano Zizzo^2,*

¹ Direzione Territoriale Lazio Abruzzo Molise (DTR LAM)-e-distribuzione SPA, ENEL Group, via della Bufalotta 255, 00139 Rome, Italy

² Department of Energy, Information Engineering and Mathematical Models (DEIM)-University of Palermo, viale delle Scienze-Edificio 9, 90128 Palermo, Italy

Energies 2017, 10(11), 1682; https://doi.org/10.3390/en10111682 - 25 Oct 2017

Cited by 7 | Viewed by 4181

Abstract

In this paper, a new virtual framework for load aggregation in the context of the liberalized energy market is proposed. Since aggregation is managed automatically through a dedicated platform, the purchase of energy can be carried out without intermediation as it happens in [...] Read more.

In this paper, a new virtual framework for load aggregation in the context of the liberalized energy market is proposed. Since aggregation is managed automatically through a dedicated platform, the purchase of energy can be carried out without intermediation as it happens in peer-to-peer energy transaction models. Differently from what was done before, in this new framework, individual customers can join a load aggregation program through the proposed aggregation platform. Through the platform, their features are evaluated and they are clustered according to their reliability and to the width of range of regulation allowed. The simulations show the deployment of an effective clustering and the possibility to meet the target power demand at a given hour according to each customer’s availability. Full article

(This article belongs to the Section F: Electrical Engineering)

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9 pages, 2351 KiB

Open AccessFeature PaperArticle

Performance of an Active Micro Direct Methanol Fuel Cell Using Reduced Catalyst Loading MEAs

by D.S. Falcão^1,*

, R.A. Silva², C.M. Rangel²

and A.M.F.R. Pinto^1,*

¹ CEFT, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal

² LNEG, Laboratório Nacional de Energia e Geologia, Fuel Cells and Hydrogen, Paço do Lumiar, 22, 1649-038 Lisboa, Portugal

Energies 2017, 10(11), 1683; https://doi.org/10.3390/en10111683 - 25 Oct 2017

Cited by 16 | Viewed by 6384

Abstract

The micro direct methanol fuel cell (MicroDMFC) is an emergent technology due to its special interest for portable applications. This work presents the results of a set of experiments conducted at room temperature using an active metallic MicroDMFC with an active area of [...] Read more.

The micro direct methanol fuel cell (MicroDMFC) is an emergent technology due to its special interest for portable applications. This work presents the results of a set of experiments conducted at room temperature using an active metallic MicroDMFC with an active area of 2.25 cm². The MicroDMFC uses available commercial materials with low platinum content in order to reduce the overall fuel cell cost. The main goal of this work is to provide useful information to easily design an active MicroDMFC with a good performance recurring to cheaper commercial Membrane Electrode Assemblies MEAs. A performance/cost analysis for each MEA tested is provided. The maximum power output obtained was 18.1 mW/cm² for a hot-pressed MEA with materials purchased from Quintech with very low catalyst loading (3 mg/cm² Pt–Ru at anode side and 0.5 mg/cm² PtB at the cathode side) costing around 15 euros. Similar power values are reported in literature for the same type of micro fuel cells working at higher operating temperatures and substantially higher cathode catalyst loadings. Experimental studies using metallic active micro direct methanol fuel cells operating at room temperature are very scarce. The results presented in this work are, therefore, very useful for the scientific community. Full article

(This article belongs to the Special Issue Direct Alcohol Fuel Cells 2018)

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16 pages, 4315 KiB

Open AccessArticle

Torque Coordination Control during Braking Mode Switch for a Plug-in Hybrid Electric Vehicle

by Yang Yang^1,2,*, Chao Wang², Quanrang Zhang² and Xiaolong He²

¹ State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China

² School of Automotive Engineering, Chongqing University, Chongqing 400044, China

Energies 2017, 10(11), 1684; https://doi.org/10.3390/en10111684 - 25 Oct 2017

Cited by 14 | Viewed by 8534

Abstract

Hybrid vehicles usually have several braking systems, and braking mode switches are significant events during braking. It is difficult to coordinate torque fluctuations caused by mode switches because the dynamic characteristics of braking systems are different. In this study, a new type of [...] Read more.

Hybrid vehicles usually have several braking systems, and braking mode switches are significant events during braking. It is difficult to coordinate torque fluctuations caused by mode switches because the dynamic characteristics of braking systems are different. In this study, a new type of plug-in hybrid vehicle is taken as the research object, and braking mode switches are divided into two types. The control strategy of type one is achieved by controlling the change rates of clutch hold-down and motor braking forces. The control strategy of type two is achieved by simultaneously changing the target braking torque during different mode switch stages and controlling the motor to participate in active coordination control. Finally, the torque coordination control strategy is modeled in MATLAB/Simulink, and the results show that the proposed control strategy has a good effect in reducing the braking torque fluctuation and vehicle shocks during braking mode switches. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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23 pages, 6793 KiB

Open AccessArticle

Using IEC 61850 GOOSE Service for Adaptive ANSI 67/67N Protection in Ring Main Systems with Distributed Energy Resources

by Ángel Silos¹

, Aleix Señís¹, Ramon Martín De Pozuelo^2,*

and Agustín Zaballos²

¹ Schneider Electric, Energy, 08019 Barcelona, Spain

² La Salle—Ramon Llull University, GRITS—Research Group in Internet Technologies and Storage, 08022 Barcelona, Spain

Energies 2017, 10(11), 1685; https://doi.org/10.3390/en10111685 - 25 Oct 2017

Cited by 20 | Viewed by 9561

Abstract

Smart Grids are electricity networks that use digital technology to co-ordinate the needs and capabilities of all generators, grid operators, end users and electricity market stakeholders in such a way that it can optimize asset utilization and operation while maintaining system reliability, resilience [...] Read more.

Smart Grids are electricity networks that use digital technology to co-ordinate the needs and capabilities of all generators, grid operators, end users and electricity market stakeholders in such a way that it can optimize asset utilization and operation while maintaining system reliability, resilience and stability. However, Smart Grids are increasingly proposing a much more distributed architecture with the integration of multiple Distributed Energy Resources (DERs) that demand different control and protection schemes. In that sense, the implementation of standards such as IEC 61850 and the integration with Ethernet-based communication networks provide novel tools to manage DER efficiently. This paper analyses the potential usage and benefits of ANSI 67/67N protection in combination with Generic Object Oriented Substation Event (GOOSE) communication service, from the standard 61850 of the International Electro-technical Commission (IEC), for providing adaptive network protection, specifying the configuration and implementation and exposing the obtained results. Full article

(This article belongs to the Special Issue Control and Communication in Distributed Generation Systems)

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17 pages, 4804 KiB

Open AccessFeature PaperArticle

A Market-Based Analysis on the Main Characteristics of Gearboxes Used in Onshore Wind Turbines

by Cristina Vázquez-Hernández¹, Javier Serrano-González^2,* and Gabriel Centeno³

¹ European Commission, Joint Research Centre, Directorate C-Energy, Transport and Climate, Westerduinweg 3, NL-1755 LE Petten, The Netherlands

² Department of Electrical Engineering, School of Engineering, University of Seville, 41092 Seville, Spain

³ Department of Mechanical and Manufacturing Engineering, School of Engineering, University of Seville, 41092 Seville, Spain

Energies 2017, 10(11), 1686; https://doi.org/10.3390/en10111686 - 25 Oct 2017

Cited by 17 | Viewed by 5841

Abstract

Even though wind energy is one of the most mature renewable technologies, it is in continuous development not only because of the trend towards larger wind turbines but also because of the development of new technological solutions. The gearbox is one of the [...] Read more.

Even though wind energy is one of the most mature renewable technologies, it is in continuous development not only because of the trend towards larger wind turbines but also because of the development of new technological solutions. The gearbox is one of the components of the drive train in which the industry is concentrating more effort on research and development. Larger rotor blades lead to more demanding requirements for this component as a consequence of a higher mechanical torque and multiplication ratio (due to lower rotational speed of blades while the rotational speed on the generator side remains at similar values). In addition, operating conditions become increasingly demanding in terms of reliability, performance, and compactness. This paper analyses the different gearbox arrangements that are implemented by manufacturers of onshore wind turbines, as well as their market penetration (including different aspects that affect the design of the gearbox, such as drive train configuration and turbine size). The analysis carried out shows a clear convergence towards gearboxes with three stages. However, there is a noticeable diversity in the types of gears used, depending to a large extent on the preferences of each manufacturer but also on the nominal power of the wind turbine and drive train configuration. Full article

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24 pages, 1310 KiB

Open AccessArticle

A Novel Multi-Phase Stochastic Model for Lithium-Ion Batteries’ Degradation with Regeneration Phenomena

by Jianxun Zhang^1,2, Xiao He², Xiaosheng Si¹, Changhua Hu^1,* and Donghua Zhou^2,3,*

¹ Department of Automation, Xi’an Research Institute of High-Tech, Xi’an 710025, China

² Department of Automation, Tsinghua University, Beijing 100084, China

³ College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266510, China

Energies 2017, 10(11), 1687; https://doi.org/10.3390/en10111687 - 25 Oct 2017

Cited by 22 | Viewed by 4455

Abstract

A lithium-Ion battery is a typical degradation product, and its performance will deteriorate over time. In its degradation process, regeneration phenomena have been frequently encountered, which affect both the degradation state and rate. In this paper, we focus on how to build the [...] Read more.

A lithium-Ion battery is a typical degradation product, and its performance will deteriorate over time. In its degradation process, regeneration phenomena have been frequently encountered, which affect both the degradation state and rate. In this paper, we focus on how to build the degradation model and estimate the lifetime. Toward this end, we first propose a multi-phase stochastic degradation model with random jumps based on the Wiener process, where the multi-phase model and random jumps at the changing point are used to describe the variation of degradation rate and state caused by regeneration phenomena accordingly. Owing to the complex structure and random variables, the traditional Maximum Likelihood Estimation (MLE) is not suitable for the proposed model. In this case, we treat these random variables as latent parameters, and then develop an approach for model identification based on expectation conditional maximum (ECM) algorithm. Moreover, depending on the proposed model, how to estimate the lifetime with fixed changing point is presented via the time-space transformation technique, and the approximate analytical solution is derived. Finally, a numerical simulation and a practical case are provided for illustration. Full article

(This article belongs to the Special Issue 2017 Prognostics and System Health Management Conference)

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Graphical abstract

18 pages, 4757 KiB

Open AccessArticle

Comparison of Modelled and Measured Tilted Solar Irradiance for Photovoltaic Applications

by Riyad Mubarak^1,*, Martin Hofmann^1,2

, Stefan Riechelmann³ and Gunther Seckmeyer¹

¹ Institute for Meteorology and Climatology, Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419 Hannover, Germany

² Valentin Software GmbH, Stralauer Platz 34, 10243 Berlin, Germany

³ Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany

Energies 2017, 10(11), 1688; https://doi.org/10.3390/en10111688 - 25 Oct 2017

Cited by 40 | Viewed by 7027

Abstract

This work assesses the performance of five transposition models that estimate the global and diffuse solar irradiance on tilted planes based on the global horizontal irradiance. The modelled tilted irradiance values are compared to measured one-minute values from pyranometers and silicon sensors tilted [...] Read more.

This work assesses the performance of five transposition models that estimate the global and diffuse solar irradiance on tilted planes based on the global horizontal irradiance. The modelled tilted irradiance values are compared to measured one-minute values from pyranometers and silicon sensors tilted at different angles at Hannover (Germany) and NREL (Golden, CO, USA). It can be recognized that the deviations of the model of Liu and Jordan, Klucher and Perez from the measurements increases as the tilt angle increases and as the sensors are oriented away from the south direction, where they receive lower direct radiation than south-oriented surfaces. Accordingly, the vertical E, W and N planes show the highest deviation. Best results are found by the models from Hay and Davies and Reindl, when horizontal pyranometer measurements and a constant albedo value of 0.2 are used. The relative root mean squared difference (rRMSD) of the anisotropic models does not exceed 11% for south orientation and low inclination angles (β = 10–60°), but reaches up to 28.9% at vertical planes. For sunny locations such as Golden, the Perez model provides the best estimates of global tilted irradiance for south-facing surfaces. The relative mean absolute difference (rMAD) of the Perez model at NREL ranges from 4.2% for 40° tilt to 8.7% for 90° tilt angle, when horizontal pyranometer measurements and a measured albedo value are used; the use of measured albedo values instead of a constant value of 0.2 leads to a reduction of the deviation to 3.9% and 6.0%, respectively. The use of higher albedo values leads to a significant increase of rMAD. We also investigated the uncertainty resulting from using horizontal pyranometer measurements, in combination with constant albedo values, to estimate the incident irradiance on tilted photovoltaic (PV) modules. We found that these uncertainties are small or negligible. Full article

(This article belongs to the Section L: Energy Sources)

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22 pages, 5439 KiB

Open AccessFeature PaperArticle

Biodiesel from Mandarin Seed Oil: A Surprising Source of Alternative Fuel

by A. K. Azad

School of Engineering and Technology, Central Queensland University, Melbourne VIC 3000, Australia

Energies 2017, 10(11), 1689; https://doi.org/10.3390/en10111689 - 26 Oct 2017

Cited by 44 | Viewed by 8216

Abstract

Mandarin (Citrus reticulata) is one of the most popular fruits in tropical and sub-tropical countries around the world. It contains about 22–34 seeds per fruit. This study investigated the potential of non-edible mandarin seed oil as an alternative fuel in Australia. The seeds [...] Read more.

Mandarin (Citrus reticulata) is one of the most popular fruits in tropical and sub-tropical countries around the world. It contains about 22–34 seeds per fruit. This study investigated the potential of non-edible mandarin seed oil as an alternative fuel in Australia. The seeds were prepared after drying in the oven for 20 h to attain an optimum moisture content of around 13.22%. The crude oil was extracted from the crushed seed using 98% n-hexane solution. The biodiesel conversion reaction (transesterification) was designed according to the acid value (mg KOH/g) of the crude oil. The study also critically examined the effect of various reaction parameters (such as effect of methanol: oil molar ratio, % of catalyst concentration, etc.) on the biodiesel conversion yield. After successful conversion of the bio-oil into biodiesel, the physio-chemical fuel properties of the virgin biodiesel were measured according to relevant ASTM standards and compared with ultra-low sulphur diesel (ULSD) and standard biodiesel ASTM D6751. The fatty acid methyl esters (FAMEs) were analysed by gas chromatography (GC) using the EN 14103 standard. The behaviour of the biodiesel (variation of density and kinematic viscosity) at various temperatures (10–40 °C) was obtained and compared with that of diesel fuel. Finally, mass and energy balances were conducted for both the oil extraction and biodiesel conversion processes to analyse the total process losses of the system. The study found 49.23 wt % oil yield from mandarin seed and 96.82% conversion efficiency for converting oil to biodiesel using the designated transesterification reaction. The GC test identified eleven FAMEs. The biodiesel mainly contains palmitic acid (C16:0) 26.80 vol %, stearic acid (C18:0) 4.93 vol %, oleic acid (C18:1) 21.43 vol % (including cis. and trans.), linoleic acid (C18:2) 4.07 vol %, and less than one percent each of other fatty acids. It is an important source of energy because it has a higher heating value of 41.446 MJ/kg which is close to ULSD (45.665 MJ/kg). In mass and energy balances, 49.23% mass was recovered as crude bio-oil and 84.48% energy was recovered as biodiesel from the total biomass. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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17 pages, 7518 KiB

Open AccessFeature PaperArticle

Control Applied to a Reciprocating Internal Combustion Engine Test Bench under Transient Operation: Impact on Engine Performance and Pollutant Emissions

by Ismael Payo

, Luis Sánchez

, Enrique Caño

and Octavio Armas^*

Escuela de Ingeniería Industrial, Campus de Excelencia Internacional en Energía y Medioambiente, Universidad de Castilla La Mancha, Edificio Sabatini, Av. Carlos III, s/n, 45071 Toledo, Spain

Energies 2017, 10(11), 1690; https://doi.org/10.3390/en10111690 - 25 Oct 2017

Cited by 7 | Viewed by 6168

Abstract

This work presents a methodology to adjust the electronic control system of a reciprocating internal combustion engine test bench and the effect of the control parameters on emissions produced by the engine under two extreme situations: unadjusted and adjusted, both under transient operation. [...] Read more.

This work presents a methodology to adjust the electronic control system of a reciprocating internal combustion engine test bench and the effect of the control parameters on emissions produced by the engine under two extreme situations: unadjusted and adjusted, both under transient operation. The aim is to provide a tuning guide to those in charge of this equipment not needed to be experts in control engineering. The proposed methodology covers from experimental plant modelling to control parameters determination and experimental validation. The methodology proposed includes the following steps: (i) Understanding of test bench and mathematical modeling; (ii) Model parameters identification; (iii) Control law proposal and tuning from simulation and (iv) Experimental validation. The work has been completed by presenting a comparative experimental study about the effect of the test bench control parameters on engine performance profiles (engine speed, engine torque and relative fuel air ratio) and on regulated gaseous emissions (nitrogen oxides and hydrocarbons concentrations) and the profile of number of particles emitted. The whole process, including experimental validation, has been carried out in a test bench composed of a turbocharged, with common rail injection system, light duty diesel engine coupled to a Schenck E-90 eddy current dynamometric brake and its related Schenk X-act control electronics. The work demonstrates the great effect of the test bench control tuning under transient operation on performance and emissions produced by the engine independently of the engine accelerator position demanded before and after the test bench tuning. Full article

(This article belongs to the Special Issue Automotive Engines Emissions and Control)

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28 pages, 10556 KiB

Open AccessArticle

Thermodynamic Optimization of a Geothermal- Based Organic Rankine Cycle System Using an Artificial Bee Colony Algorithm

by Osman Özkaraca^1,*, Pınar Keçebaş², Cihan Demircan³ and Ali Keçebaş^4,*

¹ Department of Information Systems Engineering, Technology Faculty, Muğla Sıtkı Koçman University, 48000 Muğla, Turkey

² Department of Energy, Graduate School of Natural and Applied Sciences, Muğla Sıtkı Koçman University, 48000 Muğla, Turkey

³ Department of Energy Systems Engineering, Graduate School of Natural and Applied Sciences, Süleyman Demirel University, 32260 Isparta, Turkey

⁴ Department of Energy Systems Engineering, Technology Faculty, Muğla Sıtkı Koçman University, 48000 Muğla, Turkey

Energies 2017, 10(11), 1691; https://doi.org/10.3390/en10111691 - 25 Oct 2017

Cited by 26 | Viewed by 5950

Abstract

Geothermal energy is a renewable form of energy, however due to misuse, processing and management issues, it is necessary to use the resource more efficiently. To increase energy efficiency, energy systems engineers carry out careful energy control studies and offer alternative solutions. With [...] Read more.

Geothermal energy is a renewable form of energy, however due to misuse, processing and management issues, it is necessary to use the resource more efficiently. To increase energy efficiency, energy systems engineers carry out careful energy control studies and offer alternative solutions. With this aim, this study was conducted to improve the performance of a real operating air-cooled organic Rankine cycle binary geothermal power plant (GPP) and its components in the aspects of thermodynamic modeling, exergy analysis and optimization processes. In-depth information is obtained about the exergy (maximum work a system can make), exergy losses and destruction at the power plant and its components. Thus the performance of the power plant may be predicted with reasonable accuracy and better understanding is gained for the physical process to be used in improving the performance of the power plant. The results of the exergy analysis show that total exergy production rate and exergy efficiency of the GPP are 21 MW and 14.52%, respectively, after removing parasitic loads. The highest amount of exergy destruction occurs, respectively, in condenser 2, vaporizer HH2, condenser 1, pumps 1 and 2 as components requiring priority performance improvement. To maximize the system exergy efficiency, the artificial bee colony (ABC) is applied to the model that simulates the actual GPP. Under all the optimization conditions, the maximum exergy efficiency for the GPP and its components is obtained. Two of these conditions such as Case 4 related to the turbine and Case 12 related to the condenser have the best performance. As a result, the ABC optimization method provides better quality information than exergy analysis. Based on the guidance of this study, the performance of power plants based on geothermal energy and other energy resources may be improved. Full article

(This article belongs to the Special Issue Integration of Renewable Technologies in Water, Electricity, Heating and Cooling Networks)

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21 pages, 17716 KiB

Open AccessArticle

Ideal Point Design and Operation of CO₂-Based Transcritical Rankine Cycle (CTRC) System Based on High Utilization of Engine’s Waste Heats

by Lingfeng Shi, Gequn Shu, Hua Tian^*, Guangdai Huang, Liwen Chang, Tianyu Chen and Xiaoya Li

State Key Laboratory of Engines, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China

Energies 2017, 10(11), 1692; https://doi.org/10.3390/en10111692 - 25 Oct 2017

Cited by 21 | Viewed by 4055

Abstract

This research conducted a study specially to systematically analyze combined recovery of exhaust gas and engine coolant and related influence mechanism, including a detailed theoretical study and an assistant experimental study. In this research, CO₂-based transcritical Rankine cycle (CTRC) was used [...] Read more.

This research conducted a study specially to systematically analyze combined recovery of exhaust gas and engine coolant and related influence mechanism, including a detailed theoretical study and an assistant experimental study. In this research, CO₂-based transcritical Rankine cycle (CTRC) was used for fully combining the wastes heats. The main objective of theoretical research was to search an ‘ideal point’ of the recovery system and related influence mechanism, which was defined as operating condition of complete recovery of two waste heats. The theoretical methodology of this study could also provide a design reference for effective combined recovery of two or multiple waste heats in other fields. Based on a kW-class preheated CTRC prototype that was designed by the ‘ideal point’ method, an experimental study was conducted to verify combined utilization degree of two engine waste heats by the CTRC system. The operating results showed that the prototype can gain 44.4–49.8 kW and 22.7–26.7 kW heat absorption from exhaust gas and engine coolant, respectively. To direct practical operation, an experimental optimization work on the operating process was conducted for complete recovery of engine coolant exactly, which avoided deficient or excessive recovery. Full article

(This article belongs to the Section F: Electrical Engineering)

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18 pages, 2294 KiB

Open AccessArticle

The Amalgamation of SVR and ANFIS Models with Synchronized Phasor Measurements for On-Line Voltage Stability Assessment

by Mohammed Amroune¹, Ismail Musirin^2,*, Tarek Bouktir¹ and Muhammad Murtadha Othman²

¹ Department of Electrical Engineering, University of Ferhat Abbas Setif 1, Setif 19000, Algeria

² Faculty of Electrical Engineering, Universiti Teknologi MARA, Shah Alam 40450, Malaysia

Energies 2017, 10(11), 1693; https://doi.org/10.3390/en10111693 - 25 Oct 2017

Cited by 23 | Viewed by 3753

Abstract

This paper presents the application of support vector regression (SVR) and adaptive neuro-fuzzy inference system (ANFIS) models that are amalgamated with synchronized phasor measurements for on-line voltage stability assessment. As the performance of SVR model extremely depends on the good selection of its [...] Read more.

This paper presents the application of support vector regression (SVR) and adaptive neuro-fuzzy inference system (ANFIS) models that are amalgamated with synchronized phasor measurements for on-line voltage stability assessment. As the performance of SVR model extremely depends on the good selection of its parameters, the recently developed ant lion optimizer (ALO) is adapted to seek for the SVR’s optimal parameters. In particular, the input vector of ALO-SVR and ANFIS soft computing models is provided in the form of voltage magnitudes provided by the phasor measurement units (PMUs). In order to investigate the effectiveness of ALO-SVR and ANFIS models towards performing the on-line voltage stability assessment, in-depth analyses on the results have been carried out on the IEEE 30-bus and IEEE 118-bus test systems considering different topologies and operating conditions. Two statistical performance criteria of root mean square error (RMSE) and correlation coefficient (R) were considered as metrics to further assess both of the modeling performances in contrast with the power flow equations. The results have demonstrated that the ALO-SVR model is able to predict the voltage stability margin with greater accuracy compared to the ANFIS model. Full article

(This article belongs to the Section F: Electrical Engineering)

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32 pages, 2200 KiB

Open AccessReview

A Review of Online Partial Discharge Measurement of Large Generators

by Yuanlin Luo^1,*

, Zhaohui Li² and Hong Wang³

¹ School of Hydropower and Information Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

² State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, China

³ Three Gorges Hydropower Plant, China Yangtze Power Corporation, Yichang 443002, China

Energies 2017, 10(11), 1694; https://doi.org/10.3390/en10111694 - 25 Oct 2017

Cited by 84 | Viewed by 11883

Abstract

Online partial discharge (PD) measurements have long been used as an effective means to assess the condition of the stator windings of large generators. An increase in the use of PD online measurement systems during the last decade is evident. Improvements in the [...] Read more.

Online partial discharge (PD) measurements have long been used as an effective means to assess the condition of the stator windings of large generators. An increase in the use of PD online measurement systems during the last decade is evident. Improvements in the detection capabilities are partly the reason for the increased popularity. Another reason has been the development of digital signal processing techniques. In addition, rapid progress is being made in automated single PD source classification. However, there are still some factors hindering wider application of the system, such as the complex PD mechanism and PD pulse propagation in stator windings, the presence of detrimental noise and disturbances on-site, and multiple PD sources occurring simultaneously. To avoid repetition of past work and to provide an overview for fresh researchers in this area, this paper presents a comprehensive survey of the state-of-the-art knowledge on PD mechanism, PD pulse propagation in stator windings, PD signal detection methods and signal processing techniques. Areas for further research are also presented. Full article

(This article belongs to the Section F: Electrical Engineering)

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12 pages, 3556 KiB

Open AccessArticle

Combustion Characteristics of Single Particles from Bituminous Coal and Pine Sawdust in O₂/N₂, O₂/CO₂, and O₂/H₂O Atmospheres

by Kai Lei^1,2, Buqing Ye^1,2, Jin Cao^1,2, Rui Zhang^1,2,* and Dong Liu^1,2,*

¹ Ministry of Industry and Information Technology Key Laboratory of Thermal Control of Electronic Equipment, School of Energy and Power Engineering, Nanjing University of Science & Technology, Nanjing 210094, China

² Advanced Combustion Laboratory, School of Energy and Power Engineering, Nanjing University of Science & Technology, Nanjing 210094, China

Energies 2017, 10(11), 1695; https://doi.org/10.3390/en10111695 - 25 Oct 2017

Cited by 49 | Viewed by 5263

Abstract

Burning fuels in an O₂/H₂O atmosphere is regarded as the next generation of oxy-fuel combustion for CO₂ capture and storage (CCS). By combining oxy-fuel combustion and biomass utilization technology, CO₂ emissions could be further reduced. Therefore, this [...] Read more.

Burning fuels in an O₂/H₂O atmosphere is regarded as the next generation of oxy-fuel combustion for CO₂ capture and storage (CCS). By combining oxy-fuel combustion and biomass utilization technology, CO₂ emissions could be further reduced. Therefore, this work focuses on investigating the combustion characteristics of single particles from bituminous coal (BC) and pine sawdust (PS) in O₂/N₂, O₂/CO₂ and O₂/H₂O atmospheres at different O₂ mole fractions (21%, 30%, and 40%). The experiments were carried out in a drop tube furnace (DTF), and a high-speed camera was used to record the combustion processes of fuel particles. The combustion temperatures were measured by a two-color method. The results reveal that the particles from BC and PS all ignite homogeneously. Replacing N₂ by CO₂ results in a longer ignition delay time and lower combustion temperatures. After substituting H₂O for N₂, the ignition delay time is shortened, which is mainly caused by the steam gasification reaction (C + H₂O → CO + H₂) and steam shift reaction (CO + H₂O → CO₂ + H₂). In addition, the combustion temperatures are first decreased at low O₂ mole fractions, and then increased at high O₂ mole fractions because the oxidation effect of H₂O performs a more important role than its volumetric heat capacity and thermal radiation capacity. At the same condition, particles from PS ignite earlier because of their higher reactivity, but the combustion temperatures are lower than those of BC, which is owing to their lower calorific values. Full article

(This article belongs to the Section L: Energy Sources)

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23 pages, 7882 KiB

Open AccessArticle

The Effects of Plant Growth Regulators on Cell Growth, Protein, Carotenoid, PUFAs and Lipid Production of Chlorella pyrenoidosa ZF Strain

by Huanmin Du¹, Faruq Ahmed², Bin Lin¹, Zhe Li¹, Yuhan Huang¹, Guang Sun¹, Huan Ding¹, Chang Wang¹, Chunxiao Meng^1,* and Zhengquan Gao^1,*

¹ School of Life Sciences, Shandong University of Technology, Zibo 255049, China

² Centre for Marine Bioproducts Development, Department of Medical Biotechnology, Flinders University, Bedford Park, SA 5042, Australia

Energies 2017, 10(11), 1696; https://doi.org/10.3390/en10111696 - 25 Oct 2017

Cited by 40 | Viewed by 6749

Abstract

In the present study, eight kinds plant growth regulators—salicylic acid (SA), 1-naphthaleneacetic acid (NAA), gibberellic acid (GA₃), 6-benzylaminopurine (6-BA), 2, 4-epi-brassinolide (EBR), abscisic acid (ABA), ethephon (ETH), and spermidine (SPD)—were used to investigate the impact on microalgal biomass, lipid, total soluble [...] Read more.

In the present study, eight kinds plant growth regulators—salicylic acid (SA), 1-naphthaleneacetic acid (NAA), gibberellic acid (GA₃), 6-benzylaminopurine (6-BA), 2, 4-epi-brassinolide (EBR), abscisic acid (ABA), ethephon (ETH), and spermidine (SPD)—were used to investigate the impact on microalgal biomass, lipid, total soluble protein, carotenoids, and polyunsaturated fatty acids (PUFAS) production of Chlorella pyrenoidosa ZF strain. The results showed the quickest biomass enhancement was induced by 50 mg·L⁻¹ NAA, with a 6.3-fold increase over the control; the highest protein content was increased by 0.005 mg·L⁻¹ ETH, which produced 3.5-fold over the control; total carotenoids content was induced most effectively by 1 mg·L⁻¹ NAA with 3.6-fold higher production than the control; the most efficient elicitor for lipid production was 5 mg·L⁻¹ GA₃ at 1.9-fold of the control; 0.2 mg·L⁻¹ ETH induced the abundant production of 1.82 ± 0.23% linoleic acid; 0.65 ± 0.01% linolenic acid was induced by 1 mg·L⁻¹ NAA; 2.53 ± 0.15% arachidonic acid and 0.44 ± 0.05% docosahexaenoic acid were induced by 5 mg·L⁻¹ GA₃. Transcriptional expression levels of seven lipid-related genes, including ACP, BC, FAD, FATA, KAS, MCTK, and SAD, were studied by real-time RT-q-PCR. 5 mg·L⁻¹ GA₃ was the most effective regulator for transcriptional expressions of these seven genes, producing 23-fold ACP, 31-fold BC, 25-fold FAD, 6-fold KAS, 12-fold MCTK compared with the controls, respectively. Full article

(This article belongs to the Special Issue Algae Fuel 2017)

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25 pages, 3001 KiB

Open AccessArticle

A Comparison Study of a Generic Coupling Methodology for Modeling Wake Effects of Wave Energy Converter Arrays

by Tim Verbrugghe^1,*

, Vicky Stratigaki¹

, Peter Troch¹

, Raphael Rabussier² and Andreas Kortenhaus¹

¹ Department of Civil Engineering, Ghent University, Technologiepark 904, B-9052 Zwijnaarde, Belgium

² Department of General Engineering, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Écully, France

Energies 2017, 10(11), 1697; https://doi.org/10.3390/en10111697 - 25 Oct 2017

Cited by 23 | Viewed by 5318

Abstract

Wave Energy Converters (WECs) need to be deployed in large numbers in an array layout in order to have a significant power production. Each WEC has an impact on the incoming wave field, by diffracting, reflecting and radiating waves. Simulating the wave transformations [...] Read more.

Wave Energy Converters (WECs) need to be deployed in large numbers in an array layout in order to have a significant power production. Each WEC has an impact on the incoming wave field, by diffracting, reflecting and radiating waves. Simulating the wave transformations within and around a WEC array is complex; it is difficult, or in some cases impossible, to simulate both these near-field and far-field wake effects using a single numerical model, in a time- and cost-efficient way in terms of computational time and effort. Within this research, a generic coupling methodology is developed to model both near-field and far-field wake effects caused by floating (e.g., WECs, platforms) or fixed offshore structures. The methodology is based on the coupling of a wave-structure interaction solver (Nemoh) and a wave propagation model. In this paper, this methodology is applied to two wave propagation models (OceanWave3D and MILDwave), which are compared to each other in a wide spectrum of tests. Additionally, the Nemoh-OceanWave3D model is validated by comparing it to experimental wave basin data. The methodology proves to be a reliable instrument to model wake effects of WEC arrays; results demonstrate a high degree of agreement between the numerical simulations with relative errors lower than

5 %

and to a lesser extent for the experimental data, where errors range from

4 %

to

17 %

. Full article

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25 pages, 14758 KiB

Open AccessArticle

Non-Newtonian Flow Characteristics of Heavy Oil in the Bohai Bay Oilfield: Experimental and Simulation Studies

by Xiankang Xin¹

, Yiqiang Li¹, Gaoming Yu^2,*, Weiying Wang², Zhongzhi Zhang³

, Maolin Zhang², Wenli Ke², Debin Kong¹, Keliu Wu⁴

and Zhangxin Chen⁴

¹ College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China

² College of Petroleum Engineering, Yangtze University, Wuhan 430100, China

³ College of Chemical Engineering, China University of Petroleum, Beijing 102249, China

⁴ Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada

Energies 2017, 10(11), 1698; https://doi.org/10.3390/en10111698 - 25 Oct 2017

Cited by 21 | Viewed by 4511

Abstract

In this paper, physical experiments and numerical simulations were applied to systematically investigate the non-Newtonian flow characteristics of heavy oil in porous media. Rheological experiments were carried out to determine the rheology of heavy oil. Threshold pressure gradient (TPG) measurement experiments performed by [...] Read more.

In this paper, physical experiments and numerical simulations were applied to systematically investigate the non-Newtonian flow characteristics of heavy oil in porous media. Rheological experiments were carried out to determine the rheology of heavy oil. Threshold pressure gradient (TPG) measurement experiments performed by a new micro-flow method and flow experiments were conducted to study the effect of viscosity, permeability and mobility on the flow characteristics of heavy oil. An in-house developed novel simulator considering the non-Newtonian flow was designed based on the experimental investigations. The results from the physical experiments indicated that heavy oil was a Bingham fluid with non-Newtonian flow characteristics, and its viscosity-temperature relationship conformed to the Arrhenius equation. Its viscosity decreased with an increase in temperature and a decrease in asphaltene content. The TPG measurement experiments was impacted by the flow rate, and its critical flow rate was 0.003 mL/min. The TPG decreased as the viscosity decreased or the permeability increased and had a power-law relationship with mobility. In addition, the critical viscosity had a range of 42–54 mPa∙s, above which the TPG existed for a given permeability. The validation of the designed simulator was positive and acceptable when compared to the simulation results run in ECLIPSE V2013.1 and Computer Modelling Group (CMG) V2012 software as well as when compared to the results obtained during physical experiments. The difference between 0.0005 and 0.0750 MPa/m in the TPG showed a decrease of 11.55% in the oil recovery based on the simulation results, which demonstrated the largely adverse impact the TPG had on heavy oil production. Full article

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21 pages, 1160 KiB

Open AccessArticle

Critical Speed Control for a Fixed Blade Variable Speed Wind Turbine

by Morgan Rossander^*

, Anders Goude

and Sandra Eriksson

Division of Electricity, Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala, Sweden

Energies 2017, 10(11), 1699; https://doi.org/10.3390/en10111699 - 25 Oct 2017

Cited by 4 | Viewed by 5992

Abstract

A critical speed controller for avoiding a certain rotational speed is presented. The controller is useful for variable speed wind turbines with a natural frequency in the operating range. The controller has been simulated, implemented and tested on an open site 12 kW [...] Read more.

A critical speed controller for avoiding a certain rotational speed is presented. The controller is useful for variable speed wind turbines with a natural frequency in the operating range. The controller has been simulated, implemented and tested on an open site 12 kW vertical axis wind turbine prototype. The controller is based on an adaptation of the optimum torque control. Two lookup tables and a simple state machine provide the control logic of the controller. The controller requires low computational resources, and no wind speed measurement is needed. The results suggest that the controller is a feasible method for critical speed control. The skipping behavior can be adjusted using only two parameters. While tested on a vertical axis wind turbine, it may be used on any variable speed turbine with the control of generator power. Full article

(This article belongs to the Special Issue Wind Generators Modelling and Control)

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16 pages, 6483 KiB

Open AccessFeature PaperArticle

Optimal Design of Permanent Magnet Arrangement in Synchronous Motors

by Xiaoyu Liu, Qifang Lin and Weinong Fu^*

Department of Electrical Engineering, the Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, China

Energies 2017, 10(11), 1700; https://doi.org/10.3390/en10111700 - 25 Oct 2017

Cited by 33 | Viewed by 7537

Abstract

A general pattern, which can include different types of permanent magnet (PM) arrangement in PM synchronous motors (PMSMs) is presented. By varying the geometric parameters of the general pattern, the template can automatically produce different types of PM arrangement in the rotor. By [...] Read more.

A general pattern, which can include different types of permanent magnet (PM) arrangement in PM synchronous motors (PMSMs) is presented. By varying the geometric parameters of the general pattern, the template can automatically produce different types of PM arrangement in the rotor. By choosing the best arrangement of PMs using optimization method, one can obtain a better performance and lower manufacturing cost. Six of the most widely used conventional types of rotor structures can be obtained through the parameter variation of the general pattern. These types include five embedded PM types and a traditional surface-mounted PM type. The proposed approach combines optimization method embedded with finite element method (FEM) for solving the multi-objective optimization for the PM structures. To save computing load, this paper employs a strategy of sub-group optimization, which is on account of the impact levels of the design parameters on the objective functions, and a parallel computation, which is a valid method to shorten the computing time. As an application example, a PMSM is optimally designed. Its simulation results and prototype experiments are provided to showcase the effectiveness of the proposed method. Full article

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24 pages, 9913 KiB

Open AccessArticle

The Fuzzy Logic Method to Efficiently Optimize Electricity Consumption in Individual Housing

by Sébastien Bissey, Sébastien Jacques^*

and Jean-Charles Le Bunetel

Research Group on Materials, Microelectronics, Acoustics, and Nanotechnology, University of Tours, 37000 Tours, France

Energies 2017, 10(11), 1701; https://doi.org/10.3390/en10111701 - 25 Oct 2017

Cited by 32 | Viewed by 7347

Abstract

Electricity demand shifting and reduction still raise a huge interest for end-users at the household level, especially because of the ongoing design of a dynamic pricing approach. In particular, end-users must act as the starting point for decreasing their consumption during peak hours [...] Read more.

Electricity demand shifting and reduction still raise a huge interest for end-users at the household level, especially because of the ongoing design of a dynamic pricing approach. In particular, end-users must act as the starting point for decreasing their consumption during peak hours to prevent the need to extend the grid and thus save considerable costs. This article points out the relevance of a fuzzy logic algorithm to efficiently predict short term load consumption (STLC). This approach is the cornerstone of a new home energy management (HEM) algorithm which is able to optimize the cost of electricity consumption, while smoothing the peak demand. The fuzzy logic modeling involves a strong reliance on a complete database of real consumption data from many instrumented show houses. The proposed HEM algorithm enables any end-user to manage his electricity consumption with a high degree of flexibility and transparency, and “reshape” the load profile. For example, this can be mainly achieved using smart control of a storage system coupled with remote management of the electric appliances. The simulation results demonstrate that an accurate prediction of STLC gives the possibility of achieving optimal planning and operation of the HEM system. Full article

(This article belongs to the Special Issue Decentralised Energy Supply Systems)

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16 pages, 1981 KiB

Open AccessArticle

An Analysis of Photo-Voltaic Hosting Capacity in Finnish Low Voltage Distribution Networks

by Ammar Arshad^*

, Martin Lindner and Matti Lehtonen

Department of Electrical Engineering and Automation, Aalto University, Maarintie 8, 02150 Espoo, Finland

Energies 2017, 10(11), 1702; https://doi.org/10.3390/en10111702 - 26 Oct 2017

Cited by 55 | Viewed by 4543 | Correction

Abstract

The ascending trend of photo-voltaic (PV) utilization on a domestic scale in Finland, calls for a technical aspects review of low voltage (LV) networks. This work investigates the technical factors that limit the PV hosting capacity, in realistic case networks, designed relative to [...] Read more.

The ascending trend of photo-voltaic (PV) utilization on a domestic scale in Finland, calls for a technical aspects review of low voltage (LV) networks. This work investigates the technical factors that limit the PV hosting capacity, in realistic case networks, designed relative to different geographical areas of Finland. A Monte Carlo method based analysis was performed, in order to quantify the hosting capacity of the formulated networks, with balanced and unbalanced feeds, in PV systems and their limiting constraints were evaluated. Finally, the effectiveness of on-load tap changer (OLTC) in increasing the PV penetration, when employed in the LV system, was investigated. Full article

(This article belongs to the Section F: Electrical Engineering)

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50 pages, 8539 KiB

Open AccessReview

Metaheuristic Techniques in Enhancing the Efficiency and Performance of Thermo-Electric Cooling Devices

by Pandian Vasant^1,2,*, Utku Kose³

and Junzo Watada⁴

¹ Modeling Evolutionary Algorithms Simulation and Artificial Intelligence, Faculty of Electrical & Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

² Department of Fundamental and Applied Sciences, Universiti Teknologi Petronas, Seri Iskandar, Perak 32610, Malaysia

³ Department of Computer Engineering, Suleyman Demirel University, Isparta 32260, Turkey

⁴ Department of Computer & Information System, Universiti Teknologi Petronas, Seri Iskandar, Perak 32610, Malaysia

Energies 2017, 10(11), 1703; https://doi.org/10.3390/en10111703 - 25 Oct 2017

Cited by 35 | Viewed by 6366

Abstract

The objective of this paper is to focus on the technical issues of single-stage thermo-electric coolers (TECs) and two-stage TECs and then apply new methods in optimizing the dimensions of TECs. In detail, some metaheuristics—simulated annealing (SA) and differential evolution (DE)—are applied to [...] Read more.

The objective of this paper is to focus on the technical issues of single-stage thermo-electric coolers (TECs) and two-stage TECs and then apply new methods in optimizing the dimensions of TECs. In detail, some metaheuristics—simulated annealing (SA) and differential evolution (DE)—are applied to search the optimal design parameters of both types of TEC, which yielded cooling rates and coefficients of performance (COPs) individually and simultaneously. The optimization findings obtained by using SA and DE are validated by applying them in some defined test cases taking into consideration non-linear inequality and non-linear equality constraint conditions. The performance of SA and DE are verified after comparing the findings with the ones obtained applying the genetic algorithm (GA) and hybridization technique (HSAGA and HSADE). Mathematical modelling and parameter setting of TEC is combined with SA and DE to find better optimal findings. The work revealed that SA and DE can be applied successfully to solve single-objective and multi-objective TEC optimization problems. In terms of stability, reliability, robustness and computational efficiency, they provide better performance than GA. Multi-objective optimizations considering both objective functions are useful for the designer to find the suitable design parameters of TECs which balance the important roles of cooling rate and COP. Full article

(This article belongs to the Section L: Energy Sources)

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14 pages, 2955 KiB

Open AccessFeature PaperArticle

Pressure-Drop Coefficients for Cushioning System of Hydraulic Cylinder With Grooved Piston: A Computational Fluid Dynamic Simulation

by Robert Castilla^1,*

, Ignasi Alemany¹, Antonio Algar¹

, Pedro Javier Gamez-Montero¹

, Pedro Roquet² and Esteban Codina¹

¹ Department of Fluid Mechanics, LABSON, Technical University of Catalonia, Colom 7, 08222 Terrassa, Spain

² ROQCAR Antonio Figueras, 68, Tona, 08551 Barcelona, Spain

Energies 2017, 10(11), 1704; https://doi.org/10.3390/en10111704 - 25 Oct 2017

Cited by 7 | Viewed by 5016

Abstract

Cushioning is an important aspect in hydraulic cylinder performance. The piston has to be decelerated before it strikes the end cap in order to avoid stresses in the cylinder components and reduce vibration that can be transmitted to the machine. One of the [...] Read more.

Cushioning is an important aspect in hydraulic cylinder performance. The piston has to be decelerated before it strikes the end cap in order to avoid stresses in the cylinder components and reduce vibration that can be transmitted to the machine. One of the least-studied methods is internal cushioning by grooves in the piston. In this method, the flow is throttled with adequately designed grooves when the piston reaches the outlet port position. The purpose of the present work is to present a method to estimate the pressure-drop coefficients for a certain design of piston grooves in order to provide a model to develop a dynamic system simulation of the cushion system. The method is based on a computational fluid dynamic simulation of flow through piston grooves to the outlet port for each piston’s static position. The results are compared with experimental measurements, and a correction, based on Reynolds number, is proposed. Good agreement, below 16%, was obtained for all the positions but particularly for the last grooves, for which the numerical result’s deviation to the experimental measurements was less than 10%. In general, the numerical simulation tended to underestimate the pressure drop for the first grooves and overestimate the calculation for the last grooves. Full article

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10 pages, 1783 KiB

Open AccessArticle

A Two-Dimensional Multiphysics Coupling Model of a Middle and Low Temperature Solar Receiver/Reactor for Methanol Decomposition

by Yanjuan Wang¹, Qibin Liu^2,*, Jing Lei¹, Jiwei Li¹ and Can Chen³

¹ School of Energy, Power and Mechanical Engineering, North China Electric Power University, Changping District, Beijing 102206, China

² Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China

³ State Grid Information & Telecommunication Branch, Beijing 100761, China

Energies 2017, 10(11), 1705; https://doi.org/10.3390/en10111705 - 25 Oct 2017

Cited by 2 | Viewed by 3267

Abstract

Abstract: In this paper, the endothermic methanol decomposition reaction is used to obtain syngas by transforming middle and low temperature solar energy into chemical energy. A two-dimensional multiphysics coupling model of a middle and low temperature of 150~300 °C solar receiver/reactor was [...] Read more.

Abstract: In this paper, the endothermic methanol decomposition reaction is used to obtain syngas by transforming middle and low temperature solar energy into chemical energy. A two-dimensional multiphysics coupling model of a middle and low temperature of 150~300 °C solar receiver/reactor was developed, which couples momentum equation in porous catalyst bed, the governing mass conservation with chemical reaction, and energy conservation incorporating conduction/convection/radiation heat transfer. The complex thermochemical conversion process of the middle and low temperature solar receiver/reactor (MLTSRR) system was analyzed. The numerical finite element method (FEM) model was validated by comparing it with the experimental data and a good agreement was obtained, revealing that the numerical FEM model is reliable. The characteristics of chemical reaction, coupled heat transfer, the components of reaction products, and the temperature fields in the receiver/reactor were also revealed and discussed. The effects of the annulus vacuum space and the glass tube on the performance of the solar receiver/reactor were further studied. It was revealed that when the direct normal irradiation increases from 200 W/m² to 800 W/m², the theoretical efficiency of solar energy transformed into chemical energy can reach 0.14–0.75. When the methanol feeding rate is 13 kg/h, the solar flux increases from 500 W/m² to 1000 W/m², methanol conversion can fall by 6.8–8.9% with air in the annulus, and methanol conversion can decrease by 21.8–28.9% when the glass is removed from the receiver/reactor. Full article

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12 pages, 5252 KiB

Open AccessArticle

Field Measurement and Evaluation of the Passive and Active Solar Heating Systems for Residential Building Based on the Qinghai-Tibetan Plateau Case

by Zhijian Liu^1,*, Di Wu¹, Miao Jiang¹, Hancheng Yu² and Wensheng Ma³

¹ Department of Power Engineering, North China Electric Power University, Baoding 071003, China

² Department of Building Energy Conservation, Qinghai College of Architectural Technology, Xining 810002, China

³ Institute of Building Environment and Energy, China Academy of Building Research, Beijing 100000, China

Energies 2017, 10(11), 1706; https://doi.org/10.3390/en10111706 - 26 Oct 2017

Cited by 20 | Viewed by 4340

Abstract

Passive and active solar heating systems have drawn much attention and are widely used in residence buildings in the Qinghai-Tibetan plateau due to its high radiation intensity. In fact, there is still lack of quantitative evaluation of the passive and active heating effect, [...] Read more.

Passive and active solar heating systems have drawn much attention and are widely used in residence buildings in the Qinghai-Tibetan plateau due to its high radiation intensity. In fact, there is still lack of quantitative evaluation of the passive and active heating effect, especially for residential building in the Qinghai-Tibetan plateau areas. In this study, three kinds of heating strategies, including reference condition, passive solar heating condition and active solar heating condition, were tested in one demonstration residential building. The hourly air temperatures of each room under different conditions were obtained and analyzed. The results show the indoor air temperature in the living room and bedrooms (core zones) was much higher than that of other rooms under both passive and active solar heating conditions. In addition, the heating effect with different strategies for core zones of the building was evaluated by the ratio of indoor and outdoor degree hour, which indicates that solar heating could effectively reduce the traditional energy consumption and improve the indoor thermal environment. The passive solar heating could undertake 49.8% degree hours for heating under an evaluation criterion of 14 °C and the active solar heating could undertake 75% degree hours for heating under evaluation criterion of 18 °C, which indicated that solar heating could effectively reduce the traditional energy consumption and improve the indoor thermal environment in this area. These findings could provide reference for the design and application of solar heating in similar climate areas. Full article

(This article belongs to the Special Issue Solar Energy Application in Buildings)

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13 pages, 257 KiB

Open AccessArticle

The Battle between Battery and Fuel Cell Powered Electric Vehicles: A BWM Approach

by Geerten Van de Kaa^*, Daniel Scholten, Jafar Rezaei

and Christine Milchram

Faculty of Technology, Policy, and Management, Delft University of Technology, Jaffalaan 5, 2628 BX Delft, The Netherlands

Energies 2017, 10(11), 1707; https://doi.org/10.3390/en10111707 - 26 Oct 2017

Cited by 73 | Viewed by 8663

Abstract

The transition to a more sustainable personal transportation sector requires the widespread adoption of electric vehicles. However, a dominant design has not yet emerged and a standards battle is being fought between battery and hydrogen fuel cell powered electric vehicles. The aim of [...] Read more.

The transition to a more sustainable personal transportation sector requires the widespread adoption of electric vehicles. However, a dominant design has not yet emerged and a standards battle is being fought between battery and hydrogen fuel cell powered electric vehicles. The aim of this paper is to analyze which factors are most likely to influence the outcome of this battle, thereby reducing the uncertainty in the industry regarding investment decisions in either of these technologies. We examine the relevant factors for standard dominance and apply a multi-criteria decision-making method, best worst method, to determine the relative importance of these factors. The results indicate that the key factors include technological superiority, compatibility, and brand reputation and credibility. Our findings show that battery powered electric vehicles have a greater chance of winning the standards battle. This study contributes to theory by providing further empirical evidence that the outcome of standards battles can be explained and predicted by applying factors for standard success. We conclude that technology dominance in the automotive industry is mostly driven by technological characteristics and characteristics of the format supporter. Full article

(This article belongs to the Section D: Energy Storage and Application)

16 pages, 3403 KiB

Open AccessArticle

Approach to Hybrid Energy Storage Systems Dimensioning for Urban Electric Buses Regarding Efficiency and Battery Aging

by Jorge Nájera^1,*

, Pablo Moreno-Torres², Marcos Lafoz³

, Rosa M. De Castro¹ and Jaime R. Arribas¹

¹ Department of Electrical Engineering, E.T.S.I. Industriales, Universidad Politécnica de Madrid, 28006 Madrid, Spain

² Wynnertech S.L., 28906 Madrid, Spain

³ CIEMAT, Government of Spain, 28040 Madrid, Spain

Energies 2017, 10(11), 1708; https://doi.org/10.3390/en10111708 - 26 Oct 2017

Cited by 19 | Viewed by 4776

Abstract

This paper focuses on Hybrid Energy Storage Systems (HESS), consisting of a combination of batteries and Electric Double Layer Capacitors (EDLC), for electric urban busses. The aim of the paper is to develop a methodology to determine the hybridization percentage that allows the [...] Read more.

This paper focuses on Hybrid Energy Storage Systems (HESS), consisting of a combination of batteries and Electric Double Layer Capacitors (EDLC), for electric urban busses. The aim of the paper is to develop a methodology to determine the hybridization percentage that allows the electric bus to work with the highest efficiency while reducing battery aging, depending on the chosen topology, control strategy, and driving cycle. Three power electronic topologies are qualitatively analyzed based on different criteria, with the topology selected as the favorite being analyzed in detail. The whole system under study is comprised of the following elements: a battery pack (LiFePO4 batteries), an EDLC pack, up to two DC-DC converters (depending on the topology), and an equivalent load, which behaves as an electric bus drive (including motion resistances and inertia). Mathematical models for the battery, EDLCs, DC-DC converter, and the vehicle itself are developed for this analysis. The methodology presented in this work, as the main scientific contribution, considers performance variation (energy efficiency and battery aging) and hybridization percentage (ratio between batteries and EDLCs, defined in terms of mass), using a power load profile based on standard driving cycles. The results state that there is a hybridization percentage that increases energy efficiency and reduces battery aging, maximizing the economic benefits of the vehicle, for every combination of topology, type of storage device, control strategy, and driving cycle. Full article

(This article belongs to the Section D: Energy Storage and Application)

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26 pages, 5267 KiB

Open AccessReview

Modular Multilevel Converters: Control and Applications

by Fernando Martinez-Rodrigo^1,*

, Dionisio Ramirez²

, Alexis B. Rey-Boue³, Santiago De Pablo⁴ and Luis Carlos Herrero-de Lucas¹

¹ Department of Electronics Technology, University of Valladolid, 47014 Valladolid, Spain

² Department of Automation, Electrical and Electronic Engineering and Industrial Computing, Technical University of Madrid (UPM), 28006 Madrid, Spain

³ Department of Electronics, Computers Technology and Projects, Universidad Politecnica de Cartagena, 30202 Cartagena, Murcia, Spain

⁴ Department of Electronics Technology, University of Valladolid, 47011 Valladolid, Spain

Energies 2017, 10(11), 1709; https://doi.org/10.3390/en10111709 - 26 Oct 2017

Cited by 104 | Viewed by 13446

Abstract

This review article is mainly oriented to the control and applications of modular multilevel converters (MMC). The main topologies of the switching modules are presented, for normal operation and for the elimination of DC faults. Methods to keep the capacitor voltage balanced are [...] Read more.

This review article is mainly oriented to the control and applications of modular multilevel converters (MMC). The main topologies of the switching modules are presented, for normal operation and for the elimination of DC faults. Methods to keep the capacitor voltage balanced are included. The voltage and current modulators, that are the most internal loops of control, are detailed. Voltage control and current control schemes are included which regulate DC link voltage and reactive power. The cases of unbalanced and distorted networks are analyzed, and schemes are proposed so that MMC contribute to improve the quality of the grid in these situations. The main applications in high voltage direct current (HVDC) transmission along with other medium voltage (MV) and low voltage (LV) applications are included. Finally, the application to offshore wind farms is specifically analyzed. Full article

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13 pages, 3478 KiB

Open AccessArticle

Human Thermal Comfort and Heat Removal Efficiency for Ventilation Variants in Passenger Cars

by Saboora Khatoon and Man-Hoe Kim^*

Department of Mechanical Engineering, Kyungpook National University, Daegu 41566, Korea

Energies 2017, 10(11), 1710; https://doi.org/10.3390/en10111710 - 26 Oct 2017

Cited by 32 | Viewed by 4903

Abstract

The realization of a comfortable thermal environment with low energy consumption and improved ventilation in a car has become the aim of manufacturers in recent decades. Novel ventilation concepts with more flexible cabin usage and layouts are appealing owing to their potential for [...] Read more.

The realization of a comfortable thermal environment with low energy consumption and improved ventilation in a car has become the aim of manufacturers in recent decades. Novel ventilation concepts with more flexible cabin usage and layouts are appealing owing to their potential for improving passenger comfort and driving power. In this study, three variant ventilation concepts are investigated and their performance is compared with respect to energy efficiency and human comfort of the driver and passenger in front and a child in the rear compartment. FLUENT 16.0, a commercial three-dimensional (3D) software, are used for the simulation. A surface-to-surface radiation model is applied under transient conditions for a car parked in summer conditions with its engine in the running condition. The results for the standard Fanger’s model and modified Fanger’s model are analyzed, discussed, and compared for the driver, passenger, and child. The modified Fanger’s model determines the thermal sensation on the basis of mean arterial pressure. Full article

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16 pages, 528 KiB

Open AccessArticle

Rethinking Participation in Smart Energy System Planning

by Imke Lammers^*

and Maarten J. Arentsen

Department of Governance and Technology for Sustainability (CSTM), University of Twente; Enschede 7500 AE, The Netherlands

Energies 2017, 10(11), 1711; https://doi.org/10.3390/en10111711 - 26 Oct 2017

Cited by 3 | Viewed by 3949

Abstract

While the technical layout of smart energy systems is well advanced, the implementation of these systems is slowed down by the current decision-making practice regarding such energy infrastructures. We call for a reorganisation of the decision-making process on local energy planning and address [...] Read more.

While the technical layout of smart energy systems is well advanced, the implementation of these systems is slowed down by the current decision-making practice regarding such energy infrastructures. We call for a reorganisation of the decision-making process on local energy planning and address the question ‘how can decision-making on the design and implementation of Smart Energy Systems be accelerated?’ Inspired by engineering design thinking and based on two workshop sessions, we identify five design phases and an implementation phase, and distinguish between a design component and a participation component. This allows for the effective participation of external stakeholders at four specific moments in the decision-making process. This way, efficiency and effectiveness in smart energy system planning can be increased, without compromising on participation. When applied to the Dutch context of energy planning, the developed decision-making model is useful for project participants as well as policy-makers in a wide variety of settings. Full article

(This article belongs to the Special Issue Selected Papers from International Workshop of Energy-Open)

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6 pages, 2569 KiB

Open AccessArticle

Design and Production of Animated Image Photovoltaic Modules

by Yu-Chih Ou¹, Hsin-Yu Wu², Chia-Hsun Hsu³, Yeu-Long Jiang² and Shui-Yang Lien^1,3,*

¹ Department of Electrical Engineering, Da-Yeh University, Chunghua 51591, Taiwan

² Graduate Institute of Optoelectronic Engineering and Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan

³ Department of Materials Science and Engineering, Da-Yeh University, Chunghua 51591, Taiwan

Energies 2017, 10(11), 1712; https://doi.org/10.3390/en10111712 - 26 Oct 2017

Cited by 1 | Viewed by 4732

Abstract

This paper develops fifth-generation-sized silicon thin-film tandem photovoltaic (PV) modules with animated images. Front PV cell stripes are created using a laser scribing technique, and specially edited and shifted images are printed onto the back glass. After encapsulating the front PV module with [...] Read more.

This paper develops fifth-generation-sized silicon thin-film tandem photovoltaic (PV) modules with animated images. Front PV cell stripes are created using a laser scribing technique, and specially edited and shifted images are printed onto the back glass. After encapsulating the front PV module with the back glass, the animated image effect can then be clearly seen from various positions. The PV module that can display three images has a stabilized power output of 87 W. The remarkable features of this module such as its animated image display, semitransparency, and acceptable power loss give it great potential for use in building-integrated photovoltaics. This paper could help improve the aesthetic appearance of PV modules, which may increase users’ or architects’ willingness to install PV modules on buildings. Full article

(This article belongs to the Special Issue Solar Energy Application in Buildings)

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22 pages, 5121 KiB

Open AccessArticle

Applications of Hybrid EMD with PSO and GA for an SVR-Based Load Forecasting Model

by Guo-Feng Fan¹, Li-Ling Peng¹, Xiangjun Zhao² and Wei-Chiang Hong^2,*

¹ College of Mathematics & Information Science, Ping Ding Shan University, Pingdingshan 467000, China

² School of Education Intelligent Technology, Jiangsu Normal University, 101 Shanghai Rd., Tongshan District, Xuzhou 221116, China

Energies 2017, 10(11), 1713; https://doi.org/10.3390/en10111713 - 26 Oct 2017

Cited by 57 | Viewed by 5265

Abstract

Providing accurate load forecasting plays an important role for effective management operations of a power utility. When considering the superiority of support vector regression (SVR) in terms of non-linear optimization, this paper proposes a novel SVR-based load forecasting model, namely EMD-PSO-GA-SVR, by hybridizing [...] Read more.

Providing accurate load forecasting plays an important role for effective management operations of a power utility. When considering the superiority of support vector regression (SVR) in terms of non-linear optimization, this paper proposes a novel SVR-based load forecasting model, namely EMD-PSO-GA-SVR, by hybridizing the empirical mode decomposition (EMD) with two evolutionary algorithms, i.e., particle swarm optimization (PSO) and the genetic algorithm (GA). The EMD approach is applied to decompose the load data pattern into sequent elements, with higher and lower frequencies. The PSO, with global optimizing ability, is employed to determine the three parameters of a SVR model with higher frequencies. On the contrary, for lower frequencies, the GA, which is based on evolutionary rules of selection and crossover, is used to select suitable values of the three parameters. Finally, the load data collected from the New York Independent System Operator (NYISO) in the United States of America (USA) and the New South Wales (NSW) in the Australian electricity market are used to construct the proposed model and to compare the performances among different competitive forecasting models. The experimental results demonstrate the superiority of the proposed model that it can provide more accurate forecasting results and the interpretability than others. Full article

(This article belongs to the Special Issue Hybrid Advanced Optimization Methods with Evolutionary Computation Techniques in Energy Forecasting)

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16 pages, 2238 KiB

Open AccessFeature PaperArticle

Risk-Based Bi-Level Model for Simultaneous Profit Maximization of a Smart Distribution Company and Electric Vehicle Parking Lot Owner

by S. Muhammad Bagher Sadati¹, Jamal Moshtagh^1,*, Miadreza Shafie-khah²

and João P. S. Catalão^2,3,4,*

¹ Department of Electrical and Computer Engineering, University of Kurdistan, Sanandaj 66177-15177, Kurdistan, Iran

² C-MAST, University of Beira Interior, R. Fonte do Lameiro, 6201-001 Covilha, Portugal

³ INESC-TEC, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

⁴ INESC-ID, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

Energies 2017, 10(11), 1714; https://doi.org/10.3390/en10111714 - 26 Oct 2017

Cited by 11 | Viewed by 4099

Abstract

In this paper, the effect of renewable energy resources (RERs), demand response (DR) programs and electric vehicles (EVs) is evaluated on the optimal operation of a smart distribution company (SDISCO) in the form of a new bi-level model. According to the existence of [...] Read more.

In this paper, the effect of renewable energy resources (RERs), demand response (DR) programs and electric vehicles (EVs) is evaluated on the optimal operation of a smart distribution company (SDISCO) in the form of a new bi-level model. According to the existence of private electric vehicle parking lots (PLs) in the network, the aim of both levels is to maximize the profits of SDISCO and the PL owners. Furthermore, due to the uncertainty of RERs and EVs, the conditional value-at-risk (CVaR) method is applied in order to limit the risk of expected profit. The model is transformed into a linear single-level model by the Karush–Kuhn–Tucker (KKT) conditions and tested on the IEEE 33-bus distribution system over a 24-h period. The results show that by using a proper charging/discharging schedule, as well as a time of use program, SDISCO gains more profit. Furthermore, by increasing the risk aversion parameter, this profit is reduced. Full article

(This article belongs to the Special Issue Risk-Based Methods Applied to Power and Energy Systems)

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27 pages, 4473 KiB

Open AccessReview

A Review of Optimal Planning Active Distribution System: Models, Methods, and Future Researches

by Rui Li^1,2,*, Wei Wang^1,2, Zhe Chen³, Jiuchun Jiang^1,2 and Weige Zhang^1,2

¹ National Active Distribution Network Technology Research Center (NANTEC), Beijing JiaoTong University, Beijing 100044, China

² Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing 100081, China

³ Department of Energy Technology, Aalborg University, DK9220 Aalborg, Denmark

Energies 2017, 10(11), 1715; https://doi.org/10.3390/en10111715 - 26 Oct 2017

Cited by 76 | Viewed by 9049

Abstract

Due to the widespread deployment of distributed energy resources (DERs) and the liberalization of electricity market, traditional distribution networks are undergoing a transition to active distribution systems (ADSs), and the traditional deterministic planning methods have become unsuitable under the high penetration of DERs. [...] Read more.

Due to the widespread deployment of distributed energy resources (DERs) and the liberalization of electricity market, traditional distribution networks are undergoing a transition to active distribution systems (ADSs), and the traditional deterministic planning methods have become unsuitable under the high penetration of DERs. Aiming to develop appropriate models and methodologies for the planning of ADSs, the key features of ADS planning problem are analyzed from the different perspectives, such as the allocation of DGs and ESS, coupling of operation and planning, and high-level uncertainties. Based on these analyses, this comprehensive literature review summarizes the latest research and development associated with ADS planning. The planning models and methods proposed in these research works are analyzed and categorized from different perspectives including objectives, decision variables, constraint conditions, and solving algorithms. The key theoretical issues and challenges of ADS planning are extracted and discussed. Meanwhile, emphasis is also given to the suitable suggestions to deal with these abovementioned issues based on the available literature and comparisons between them. Finally, several important research prospects are recommended for further research in ADS planning field, such as planning with multiple micro-grids (MGs), collaborative planning between ADSs and information communication system (ICS), and planning from different perspectives of multi-stakeholders. Full article

(This article belongs to the Special Issue Innovative Methods for Smart Grids Planning and Management)

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19 pages, 5446 KiB

Open AccessArticle

Core Loss Analysis of Interior Permanent Magnet Synchronous Machines under SVPWM Excitation with Considering Saturation

by Yanli Feng and Chengning Zhang^*

National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology, No. 5 South Zhongguancun Street, Haidian District, Beijing 100081, China

Energies 2017, 10(11), 1716; https://doi.org/10.3390/en10111716 - 26 Oct 2017

Cited by 11 | Viewed by 4513

Abstract

Core loss is one of the significant factors affecting the high power density of permanent magnet machines; thus, it is necessary to consider core loss in machine design. This paper presents a novel method for calculating the core loss of permanent magnet synchronous [...] Read more.

Core loss is one of the significant factors affecting the high power density of permanent magnet machines; thus, it is necessary to consider core loss in machine design. This paper presents a novel method for calculating the core loss of permanent magnet synchronous machines under space vector pulse width modulation (SVPWM) excitation, taking magnetic saturation and cross coupling into account. In order to accurately obtain the direct and quadrature (d-q) axis, current in the given load condition, the permanent magnet motor model under SVPWM excitation has been modified, so as to consider the influence of magnetic saturation and cross coupling effects on the d-q axis flux-linkage. Based on the magnetic field distribution caused by permanent magnet and armature reactions, the stator core loss can be calculated with the core loss analytical model, corresponding to the rotational magnetic field. In this study, the method has been applied to analyze core loss in an interior permanent magnet synchronous machine, and has been validated by the experimental results. The influence of pole/slot number combinations on core loss in the same on-load condition is also investigated. This study provides a potential method to guide motor design optimization. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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18 pages, 4760 KiB

Open AccessArticle

A Computed River Flow-Based Turbine Controller on a Programmable Logic Controller for Run-Off River Hydroelectric Systems

by Razali Jidin^1,* and Abdul Bahari Othman²

¹ College of Engineering, Universiti Tenaga Nasional (UNITEN), Jalan Ikram-Uniten, Kajang 43000, Selangor, Malaysia

² Generation Research Department, Tenaga Nasional Berhad Research (TNBR), Kajang 43000, Selangor, Malaysia

Energies 2017, 10(11), 1717; https://doi.org/10.3390/en10111717 - 27 Oct 2017

Cited by 2 | Viewed by 7373

Abstract

The main feature of a run-off river hydroelectric system is a small size intake pond that overspills when river flow is more than turbines’ intake. As river flow fluctuates, a large proportion of the potential energy is wasted due to the spillages which [...] Read more.

The main feature of a run-off river hydroelectric system is a small size intake pond that overspills when river flow is more than turbines’ intake. As river flow fluctuates, a large proportion of the potential energy is wasted due to the spillages which can occur when turbines are operated manually. Manual operation is often adopted due to unreliability of water level-based controllers at many remote and unmanned run-off river hydropower plants. In order to overcome these issues, this paper proposes a novel method by developing a controller that derives turbine output set points from computed mass flow rate of rivers that feed the hydroelectric system. The computed flow is derived by summation of pond volume difference with numerical integration of both turbine discharge flows and spillages. This approach of estimating river flow allows the use of existing sensors rather than requiring the installation of new ones. All computations, including the numerical integration, have been realized as ladder logics on a programmable logic controller. The implemented controller manages the dynamic changes in the flow rate of the river better than the old point-level based controller, with the aid of a newly installed water level sensor. The computed mass flow rate of the river also allows the controller to straightforwardly determine the number of turbines to be in service with considerations of turbine efficiencies and auxiliary power conservation. Full article

(This article belongs to the Special Issue Hydropower 2017)

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18 pages, 2191 KiB

Open AccessArticle

Improved Load Frequency Control Using a Fast Acting Active Disturbance Rejection Controller

by Md Mijanur Rahman^1,*, A. Hasib Chowdhury² and Md Alamgir Hossain³

¹ Department of Electrical and Electronic Engineering, Dhaka University of Engineering and Technology, Gazipur1700, Bangladesh

² Department of Electrical and Electronic Engineering, Bangladesh University of Engineering and Technology, Dhaka1205, Bangladesh

³ School of Engineering and Information Technology, University of New South Wales-Canberra, Northcott Dr, Campbell ACT 2612, Australia

Energies 2017, 10(11), 1718; https://doi.org/10.3390/en10111718 - 27 Oct 2017

Cited by 14 | Viewed by 5295

Abstract

System frequency may change from defined values while transmitting power from one area to another in an interconnected power system due to various reasons such as load changes and faults. This frequency change causes a frequency error in the system. However, the system [...] Read more.

System frequency may change from defined values while transmitting power from one area to another in an interconnected power system due to various reasons such as load changes and faults. This frequency change causes a frequency error in the system. However, the system frequency should always be maintained close to the nominal value even in the presence of model uncertainties and physical constraints. This paper proposes an Active Disturbance Rejection Controller (ADRC)-based load frequency control (LFC) of an interconnected power system. The controller incorporates effects of generator inertia and generator electrical proximity to the point of disturbances. The proposed controller reduces the magnitude error of the area control error (ACE) of an interconnected power system compared to the standard controller. The simulation results verify the effectiveness of proposed ADRC in the application of LFC of an interconnected power system. Full article

(This article belongs to the Section F: Electrical Engineering)

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13 pages, 2777 KiB

Open AccessArticle

Impact of the Complementarity between Variable Generation Resources and Load on the Flexibility of the Korean Power System

by Chang-Gi Min and Mun-Kyeom Kim^*

Department of Energy System Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Korea

Energies 2017, 10(11), 1719; https://doi.org/10.3390/en10111719 - 27 Oct 2017

Cited by 19 | Viewed by 3359

Abstract

This study examines the effect of the complementarity between the variable generation resources (VGRs) and the load on the flexibility of the power system. The complementarity may change the ramping capability requirement, and thereby, the flexibility. This effect is quantified using a flexibility [...] Read more.

This study examines the effect of the complementarity between the variable generation resources (VGRs) and the load on the flexibility of the power system. The complementarity may change the ramping capability requirement, and thereby, the flexibility. This effect is quantified using a flexibility index called the ramping capability shortage expectation (RSE). The flexibility is evaluated for different VGR mix scenarios under the same VGR penetration level, and an optimal VGR mix (i.e., one that maximizes flexibility) is obtained. The effect of the complementarity of the wind and PV outputs on the flexibility is investigated for the peak-load day of 2016 for the Korean power system. The result shows that the RSE value for the optimal VGR mix scenario is 6.95% larger than that for the original mix scenario. Full article

(This article belongs to the Special Issue Risk-Based Methods Applied to Power and Energy Systems)

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17 pages, 3624 KiB

Open AccessArticle

A Fuzzy-Based PI Controller for Power Management of a Grid-Connected PV-SOFC Hybrid System

by Shivashankar Sukumar^1,*

, Marayati Marsadek¹, Agileswari Ramasamy², Hazlie Mokhlis³

and Saad Mekhilef⁴

¹ Institute of Power Engineering (IPE), Universit Tenaga Nasional, Selangor 43000, Malaysia

² Department of Electronics and Communication Engineering, Universiti Tenaga Nasional, Selangor 43000, Malaysia

³ Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

⁴ Power Electronics and Renewable Energy Research Laboratory (PEARL), University of Malaya, Kuala Lumpur 50603, Malaysia

Energies 2017, 10(11), 1720; https://doi.org/10.3390/en10111720 - 27 Oct 2017

Cited by 18 | Viewed by 6280

Abstract

Solar power generation is intermittent in nature. It is nearly impossible for a photovoltaic (PV) system to supply power continuously and consistently to a varying load. Operating a controllable source like a fuel cell in parallel with PV can be a solution to [...] Read more.

Solar power generation is intermittent in nature. It is nearly impossible for a photovoltaic (PV) system to supply power continuously and consistently to a varying load. Operating a controllable source like a fuel cell in parallel with PV can be a solution to supply power to variable loads. In order to coordinate the power supply from fuel cells and PVs, a power management system needs to be designed for the microgrid system. This paper presents a power management system for a grid-connected PV and solid oxide fuel cell (SOFC), considering variation in the load and solar radiation. The objective of the proposed system is to minimize the power drawn from the grid and operate the SOFC within a specific power range. Since the PV is operated at the maximum power point, the power management involves the control of SOFC active power where a proportional and integral (PI) controller is used. The control parameters of the PI controller K_p (proportional constant) and T_i (integral time constant) are determined by the genetic algorithm (GA) and simplex method. In addition, a fuzzy logic controller is also developed to generate appropriate control parameters for the PI controller. The performance of the controllers is evaluated by minimizing the integral of time multiplied by absolute error (ITAE) criterion. Simulation results showed that the fuzzy-based PI controller outperforms the PI controller tuned by the GA and simplex method in managing the power from the hybrid source effectively under variations of load and solar radiation. Full article

(This article belongs to the Section F: Electrical Engineering)

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18 pages, 17063 KiB

Open AccessArticle

Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

by Yanzhao Yang^1,2, Zhiping Guo^1,*, Yanfeng Zhang^1,2, Ho Jinyama² and Qingan Li^3,*

¹ College of Mechanical Engineering, Inner Mongolia University of Technology, Hohhot 010051, China

² Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan

³ Division of Mechanical Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan

Energies 2017, 10(11), 1721; https://doi.org/10.3390/en10111721 - 27 Oct 2017

Cited by 34 | Viewed by 8521

Abstract

Wind velocity distribution and the vortex around the wind turbine present a significant challenge in the development of straight-bladed vertical axis wind turbines (VAWTs). This paper is intended to investigate influence of tip vortex on wind turbine wake by Computational Fluid Dynamics (CFD) [...] Read more.

Wind velocity distribution and the vortex around the wind turbine present a significant challenge in the development of straight-bladed vertical axis wind turbines (VAWTs). This paper is intended to investigate influence of tip vortex on wind turbine wake by Computational Fluid Dynamics (CFD) simulations. In this study, the number of blades is two and the airfoil is a NACA0021 with chord length of c = 0.265 m. To capture the tip vortex characteristics, the velocity fields are investigated by the Q-criterion iso-surface (Q = 100) with shear-stress transport (SST) k-ω turbulence model at different tip speed ratios (TSRs). Then, mean velocity, velocity deficit and torque coefficient acting on the blade in the different spanwise positions are compared. The wind velocities obtained by CFD simulations are also compared with the experimental data from wind tunnel experiments. As a result, we can state that the wind velocity curves calculated by CFD simulations are consistent with Laser Doppler Velocity (LDV) measurements. The distribution of the vortex structure along the spanwise direction is more complex at a lower TSR and the tip vortex has a longer dissipation distance at a high TSR. In addition, the mean wind velocity shows a large value near the blade tip and a small value near the blade due to the vortex effect. Full article

(This article belongs to the Collection Wind Turbines)

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17 pages, 5410 KiB

Open AccessArticle

Optimal and Learning-Based Demand Response Mechanism for Electric Water Heater System

by Bo Lin^1,*

, Shuhui Li¹ and Yang Xiao²

¹ Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, AL 35487, USA

² Department of Computer Science, The University of Alabama, Tuscaloosa, AL 35487, USA

Energies 2017, 10(11), 1722; https://doi.org/10.3390/en10111722 - 27 Oct 2017

Cited by 25 | Viewed by 4832

Abstract

This paper investigates how to develop a learning-based demand response approach for electric water heater in a smart home that can minimize the energy cost of the water heater while meeting the comfort requirements of energy consumers. First, a learning-based, data-driven model of [...] Read more.

This paper investigates how to develop a learning-based demand response approach for electric water heater in a smart home that can minimize the energy cost of the water heater while meeting the comfort requirements of energy consumers. First, a learning-based, data-driven model of an electric water heater is developed by using a nonlinear autoregressive network with external input (NARX) using neural network. The model is updated daily so that it can more accurately capture the actual thermal dynamic characteristics of the water heater especially in real-life conditions. Then, an optimization problem, based on the NARX water heater model, is formulated to optimize energy management of the water heater in a day-ahead, dynamic electricity price framework. A genetic algorithm is proposed in order to solve the optimization problem more efficiently. MATLAB (R2016a) is used to evaluate the proposed learning-based demand response approach through a computational experiment strategy. The proposed approach is compared with conventional method for operation of an electric water heater. Cost saving and benefits of the proposed water heater energy management strategy are explored. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 5068 KiB

Open AccessArticle

Determination of the Optimum Heat Transfer Coefficient and Temperature Rise Analysis for a Lithium-Ion Battery under the Conditions of Harbin City Bus Driving Cycles

by Xiaogang Wu^1,2,*, Siyu Lv¹ and Jizhong Chen³

¹ College of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China

² State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China

³ State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems, China Electric Power Research Institute, Beijing 100192, China

Energies 2017, 10(11), 1723; https://doi.org/10.3390/en10111723 - 27 Oct 2017

Cited by 27 | Viewed by 7108

Abstract

This study investigated the heat problems that occur during the operation of power batteries, especially thermal runaway, which usually take place in high temperature environments. The study was conducted on a ternary polymer lithium-ion battery. In addition, a lumped parameter thermal model was [...] Read more.

This study investigated the heat problems that occur during the operation of power batteries, especially thermal runaway, which usually take place in high temperature environments. The study was conducted on a ternary polymer lithium-ion battery. In addition, a lumped parameter thermal model was established to analyze the thermal behavior of the electric bus battery system under the operation conditions of the driving cycles of the Harbin city electric buses. Moreover, the quantitative relationship between the optimum heat transfer coefficient of the battery and the ambient temperature was investigated. The relationship between the temperature rise (T_r), the number of cycles (c), and the heat transfer coefficient (h) under three Harbin bus cycles have been investigated at 30 °C, because it can provide a basis for the design of the battery thermal management system. The results indicated that the heat transfer coefficient that meets the requirements of the battery thermal management system is the cubic power function of the ambient temperature. Therefore, if the ambient temperature is 30 °C, the heat transfer coefficient should be at least 12 W/m²K in the regular bus lines, 22 W/m²K in the bus rapid transit lines, and 32 W/m²K in the suburban lines. Full article

(This article belongs to the Special Issue The International Symposium on Electric Vehicles (ISEV2017))

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31 pages, 4158 KiB

Open AccessArticle

CO₂ Storage Capacity for Multi-Well Pads Scheme in Depleted Shale Gas Reservoirs

by Zhan Meng¹, Shenglai Yang^1,*, Lu Wang¹, Jie Zou²

, Yun Jiang³, Chenggang Liang⁴, Junru Wang¹ and Ziyao Zhong¹

¹ Key Laboratory of Petroleum Engineering of the Ministry of Education, China University of Petroleum, Beijing 102249, China

² Department of Petroleum Engineering, Curtin University, Kensington, WA 6151, Australia

³ Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China

⁴ Xinjiang Oilfield Branch, PetroChina, Changji Hui Autonomous Prefecture 831511, China

Energies 2017, 10(11), 1724; https://doi.org/10.3390/en10111724 - 27 Oct 2017

Cited by 2 | Viewed by 4996

Abstract

As a promising technology to improve shale gas (SG) recovery and CO₂ storage capacity, the multi-well pads (MWPs) scheme has gained more and more attention. The semi-analytical pressure-buildup method has been used to estimate CO₂ storage capacity. It focuses on single [...] Read more.

As a promising technology to improve shale gas (SG) recovery and CO₂ storage capacity, the multi-well pads (MWPs) scheme has gained more and more attention. The semi-analytical pressure-buildup method has been used to estimate CO₂ storage capacity. It focuses on single multi-fractured horizontal wells (SMFHWs) and does not consider multi-well pressure interference (MWPI) induced by the MWPs scheme. This severely limits the application of this method as incidences of multi-well pressure interference have been widely reported. This paper proposed a new methodology to optimize the injection strategy of the MWPs scheme and maximize CO₂ storage capacity. The new method implements numerical discretization, the superposition theory, Gauss elimination, and the Stehfest numerical algorithm to obtain pressure-buildup solutions for the MWPs scheme. The solution by the new method was validated with numerical simulation and pressure-buildup curves were generated to identify MWPI. Using the new method, we observed that the fracture number and fracture half-length have a positive influence on CO₂ storage capacity. Both can be approximately related to the CO₂ storage capacity by a linear correlation. For a given injection pressure, there is an optimal fracture number; the bigger the limited injection pressure, the smaller the optimal fracture number. Stress sensitivity has positive influences on CO₂ storage capacity, thus extending the injection period would improve CO₂ storage capacity. This work gains some insights into the CO₂ storage capacity of the MWPs scheme in depleted SG reservoirs, and provides considerable guidance on injection strategies to maximize CO₂ storage capacity in depleted SG reservoirs. Full article

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11 pages, 2019 KiB

Open AccessArticle

Testing Open-Air Storage of Stumps to Provide Clean Biomass for Energy Production

by Luigi Pari

, Antonio Scarfone^*, Vincenzo Alfano

, Simone Bergonzoli

, Francesco Gallucci and Enrico Santangelo

Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria (CREA)—Centro di Ricerca Ingegneria e Trasformazioni Agroalimentari (CREA IT), 00015 Rome, Italy

Energies 2017, 10(11), 1725; https://doi.org/10.3390/en10111725 - 27 Oct 2017

Cited by 2 | Viewed by 3155

Abstract

When orchards reach the end of the productive cycle, the stumps removal becomes a mandatory operation to allow new soil preparation and to establish new cultivations. The exploitation of the removed stump biomass seems a valuable option, especially in the growing energy market [...] Read more.

When orchards reach the end of the productive cycle, the stumps removal becomes a mandatory operation to allow new soil preparation and to establish new cultivations. The exploitation of the removed stump biomass seems a valuable option, especially in the growing energy market of the biofuels; however, the scarce quality of the material obtained after the extraction compromises its marketability, making this product a costly waste to be disposed. In this regard, the identification of affordable strategies for the extraction and the cleaning of the material will be crucial in order to provide to plantation owners the chance to sell the biomass and offset the extraction costs. Mechanical extraction and cleaning technologies have been already tested on forest stumps, but these systems work on the singular piece and would be inefficient in the conditions of an intensive orchard, where stumps are small and numerous. The objective of this study was to test the possibility to exploit a natural stumps cleaning system through open-air storage. The tested stumps were obtained from two different vineyards, extracted with an innovative stump puller specifically designed for continuous stump removal in intensively-planted orchards. The effects of weathering were evaluated to determine the fuel quality immediately after the extraction and after a storage period of six months with respect to moisture content, ash content, and heating value. Results indicated interesting storage performance, showing also different dynamics depending on the stumps utilized. Full article

(This article belongs to the Section L: Energy Sources)

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25 pages, 9443 KiB

Open AccessArticle

Implementation, Comparison and Application of an Average Simulation Model of a Wind Turbine Driven Doubly Fed Induction Generator

by Lidula N. Widanagama Arachchige^1,*, Athula D. Rajapakse² and Dharshana Muthumuni³

¹ Department of Electrical Engineering, University of Moratuwa, Moratuwa 10400, Sri Lanka

² Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada

³ Manitoba HVDC Research Centre, Winnipeg, MB R3P 1A3, Canada

Energies 2017, 10(11), 1726; https://doi.org/10.3390/en10111726 - 27 Oct 2017

Cited by 11 | Viewed by 4481

Abstract

Wind turbine driven doubly-fed induction generators (DFIGs) are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven [...] Read more.

Wind turbine driven doubly-fed induction generators (DFIGs) are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven DFIGs using the conventional vector controls in a detailed model of a DFIG that represents power electronics (PE) converters with device level models and proposes an average model eliminating the PE converters. The PSCAD/EMTDC™ (4.6) electromagnetic transient simulation software is used to develop the detailed and the proposing average model of a DFIG. The comparison of the two models reveals that the designed average DFIG model is adequate for simulating and analyzing most of the transient conditions. Full article

(This article belongs to the Section F: Electrical Engineering)

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36 pages, 9182 KiB

Open AccessArticle

Devising Hourly Forecasting Solutions Regarding Electricity Consumption in the Case of Commercial Center Type Consumers

by Alexandru Pîrjan^1,*

, Simona-Vasilica Oprea²

, George Căruțașu¹

, Dana-Mihaela Petroșanu^1,3

, Adela Bâra² and Cristina Coculescu¹

¹ Department of Informatics, Statistics and Mathematics, Romanian-American University, Expoziției 1B, Bucharest 012101, Romania

² Department of Economic Informatics and Cybernetics, The Bucharest Academy of Economic Studies, Romana Square 6, Bucharest 010374, Romania

³ Department of Mathematics-Informatics, University Politehnica of Bucharest, Splaiul Independenței 313, Bucharest 060042, Romania

Energies 2017, 10(11), 1727; https://doi.org/10.3390/en10111727 - 27 Oct 2017

Cited by 26 | Viewed by 6581

Abstract

This paper focuses on an important issue regarding the forecasting of the hourly energy consumption in the case of large electricity non-household consumers that account for a significant percentage of the whole electricity consumption, the accurate forecasting being a key-factor in achieving energy [...] Read more.

This paper focuses on an important issue regarding the forecasting of the hourly energy consumption in the case of large electricity non-household consumers that account for a significant percentage of the whole electricity consumption, the accurate forecasting being a key-factor in achieving energy efficiency. In order to devise the forecasting solutions, we have developed a series of dynamic neural networks for solving nonlinear time series problems, based on the non-linear autoregressive (NAR) and non-linear autoregressive with exogenous inputs (NARX) models. In both cases, we have used large datasets comprising the hourly energy consumption recorded by the smart metering device from a commercial center type of consumer (a large hypermarket), while in the NARX case we have used supplementary temperature and time stamps datasets. Of particular interest was to research and obtain an optimal mix between the training algorithm (Levenberg-Marquardt, Bayesian Regularization, Scaled Conjugate Gradient), the hidden number of neurons and the delay parameter. Using performance metrics and forecasting scenarios, we have obtained results that highlight an increased accuracy of the developed forecasting solutions. The developed hourly consumption forecasting solutions can bring significant benefits to both the consumers and electricity suppliers. Full article

(This article belongs to the Section F: Electrical Engineering)

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18 pages, 2498 KiB

Open AccessArticle

Controllability and Leader-Based Feedback for Tracking the Synchronization of a Linear-Switched Reluctance Machine Network

by Bo Zhang^1,2

, Jianping Yuan^2,*, Jianfei Pan^1,*

, Xiaoyu Wu¹, Jianjun Luo² and Li Qiu¹

¹ College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China

² Laboratory of Advanced Unmanned Systems Technology, Research Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518060, China

Energies 2017, 10(11), 1728; https://doi.org/10.3390/en10111728 - 27 Oct 2017

Cited by 2 | Viewed by 3298

Abstract

This paper investigates the controllability of a closed-loop tracking synchronization network based on multiple linear-switched reluctance machines (LSRMs). The LSRM network is constructed from a global closed-loop manner, and the closed loop only replies to the input and output information from the leader [...] Read more.

This paper investigates the controllability of a closed-loop tracking synchronization network based on multiple linear-switched reluctance machines (LSRMs). The LSRM network is constructed from a global closed-loop manner, and the closed loop only replies to the input and output information from the leader node. Then, each local LSRM node is modeled as a general second-order system, and the model parameters are derived by the online system identification method based on the least square method. Next, to guarantee the LSRM network’s controllability condition, a theorem is deduced that clarifies the relationship among the LSRM network’s controllability, the graph controllability of the network and the controllability of the node dynamics. A state feedback control strategy with the state observer located on the leader is then proposed to improve the tracking performance of the LSRM network. Last, both the simulation and experiment results prove the effectiveness of the network controller design scheme and the results also verify that the leader-based global feedback strategy not only improves the tracking performance but also enhances the synchronization accuracy of the LSRM network experimentally. Full article

(This article belongs to the Special Issue Networked and Distributed Control Systems)

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39 pages, 4091 KiB

Open AccessReview

Modelling of Spouted and Spout-Fluid Beds: Key for Their Successful Scale Up

by Cristina Moliner^1,*

, Filippo Marchelli²

, Barbara Bosio¹ and Elisabetta Arato¹

¹ Dipartimento di Ingegneria Civile, Chimica e Ambientale (DICCA), Università degli Studi di Genova, Via Opera Pia 15, 16145 Genova, Italy

² Faculty of Sciences and Technology, Libera Università di Bolzano, Piazza Università 5, 39100 Bolzano, Italy

Energies 2017, 10(11), 1729; https://doi.org/10.3390/en10111729 - 28 Oct 2017

Cited by 56 | Viewed by 9094

Abstract

The development of robust mathematical models could provide the necessary tools for a more rapid, efficient, and reliable spouted bed technology development. Computer simulations can be very useful to aid this design and scale-up process: firstly, they can contribute to obtain a fundamental [...] Read more.

The development of robust mathematical models could provide the necessary tools for a more rapid, efficient, and reliable spouted bed technology development. Computer simulations can be very useful to aid this design and scale-up process: firstly, they can contribute to obtain a fundamental insight into their complex dynamic behavior by understanding the elementary physical principles such as drag, friction, dissipation etc.; secondly, the simulations can be used as a design tool where the ultimate goal is to have a numerical model with predictive capabilities for gas-particle flows at engineering scale. Clearly, one single simulation method will not be able to achieve this goal, but a hierarchy of methods modelling phenomena on different length and time scales can achieve this. The most fruitful approach will be when they are simultaneously followed, so that they can mutually benefit from each other. In this sense, this paper presents a review of the current state of the art of modelling on spouted and spout-fluid beds through an analysis of recent literature following a multiscale approach (molecular and particle, lab, plant and industrial scale). The main features of the different scales together with their current limits are discussed and specific topics are highlighted as paths that still need to be explored. In summary, the paper aims to define the theoretical setline and the basis of improvement that would lead to a robust multiscale model with solid links between micro and macroscopic phenomena. If done with the correct balance between accuracy and computational costs it will gear SB towards their reliable and successful implementation. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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25 pages, 2455 KiB

Open AccessFeature PaperReview

Review: Characterization and Modeling of the Mechanical Properties of Lithium-Ion Batteries

by Golriz Kermani¹ and Elham Sahraei^1,2,*

¹ Electric Vehicle Safety Lab (EVSL), George Mason University, Fairfax, VA 22030, USA

² Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Energies 2017, 10(11), 1730; https://doi.org/10.3390/en10111730 - 30 Oct 2017

Cited by 88 | Viewed by 13470

Abstract

Li-ion batteries have become a dominant power source in consumer electronics and vehicular applications. The mobile use of batteries subjects them to various mechanical loads. The mechanisms that follow a mechanical deformation and lead to damage and failure in Li-ion batteries have only [...] Read more.

Li-ion batteries have become a dominant power source in consumer electronics and vehicular applications. The mobile use of batteries subjects them to various mechanical loads. The mechanisms that follow a mechanical deformation and lead to damage and failure in Li-ion batteries have only been studied in recent years. This paper is a comprehensive review of advancements in experimental and computational techniques for characterization of Li-ion batteries under mechanical abuse loading scenarios. A number of recent studies have used experimental methods to characterize deformation and failure of batteries and their components under various tensile and compressive loading conditions. Several authors have used the test data to propose material laws and develop finite element (FE) models. Then the models have been validated against tests at different levels from comparison of shapes to predicting failure and onset of short circuit. In the current review main aspects of each study have been discussed and their approach in mechanical testing, material characterization, FE modeling, and validation is analyzed. The main focus of this review is on mechanical properties at the level of a single battery. Full article

(This article belongs to the Section D: Energy Storage and Application)

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21 pages, 7356 KiB

Open AccessArticle

Simulating Extreme Directional Wave Conditions

by Samuel Draycott^*

, Thomas Davey and David M. Ingram

School of Engineering, Institute for Energy Systems, The University of Edinburgh, Edinburgh EH9 3DW, UK

Energies 2017, 10(11), 1731; https://doi.org/10.3390/en10111731 - 28 Oct 2017

Cited by 10 | Viewed by 4533

Abstract

Wave tank tests often involve simulating extreme wave conditions as they enable the maximum expected loads to be inferred: a vital parameter for structural design. The definition, and simulation of, extreme conditions are often fairly simplistic, which can result in conditions and associated [...] Read more.

Wave tank tests often involve simulating extreme wave conditions as they enable the maximum expected loads to be inferred: a vital parameter for structural design. The definition, and simulation of, extreme conditions are often fairly simplistic, which can result in conditions and associated loads that are not representative of those that would be observed at the deployment location. Here we present a method of defining, simulating at scale, and validating realistic site-specific extreme wave conditions for survival testing of wave energy converters. Bivariate inverse-first order reliability method (I-FORM) environmental contours define extreme pairs of significant wave height and energy period (

H_{m 0}

–

T_{E}

), while observed extreme conditions are used to define realistic frequency and directional distributions. These sea states are scaled, simulated and validated at the FloWave Ocean Energy Research Facility to demonstrate that the site-specific extreme wave conditions can be re-created with accuracy. The presented approach enables greater realism to be incorporated into tank testing with survival sea states. The techniques outlined and explored here can provide further and more realistic insight into the response of offshore structures and devices, and can help make important design decisions prior to full-scale deployment. Full article

(This article belongs to the Special Issue Marine Energy)

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21 pages, 3485 KiB

Open AccessArticle

Investigation on the Energy Saving Potential of Using a Novel Dew Point Cooling System in Data Centres

by Yin Bi^1,2, Yugang Wang^1,3, Xiaoli Ma^1,* and Xudong Zhao^1,*

¹ School of Engineering and Computer Science, University of Hull, Kingston upon Hull HU6 7RX, UK

² School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou, 510006, China

³ School of Mechanical and Energy Engineering, Jimei University, Xiamen, 361021, China

Energies 2017, 10(11), 1732; https://doi.org/10.3390/en10111732 - 28 Oct 2017

Cited by 12 | Viewed by 4301

Abstract

Abstract: Information technology (IT) has brought significant changes in people’s lives. As an important part of the IT industry, data centres (DCs) have been rapidly growing in both the number and size over the past 40 years. Around 30% to 40% of [...] Read more.

Abstract: Information technology (IT) has brought significant changes in people’s lives. As an important part of the IT industry, data centres (DCs) have been rapidly growing in both the number and size over the past 40 years. Around 30% to 40% of electricity consumption in DCs is used for space cooling, thus leading to very inefficient DC operation. To identify ways to reduce the energy consumption for space cooling and increase the energy efficiency of DCs’ operation, a dedicated investigation into the energy usage in DCs has been undertaken and a novel high performance dew point cooling system was introduced into a DC operational scheme. Based on the cooling load in DCs, a case study was carried out to evaluate the energy consumptions and energy usage effectiveness when using the novel dew point cooling system in different scales of DCs in various climates. It was found that by using the novel dew point cooling system, for 10 typical climates a DC can have a much lower power usage effectiveness (PUE) of 1.10 to 1.22 compared to that of 1.7 to 3.7 by using existing traditional cooling systems, leading to significantly increased energy efficiency of the DC operation. In addition, the energy performance by managing the cooling air supply at the different levels in DCs, i.e., room, row and rack level, was simulated by using a dynamic computer model. It was found that cooling air supply at rack level can provide a higher energy efficiency in DCs. Based on the above work, the energy saving potential in DCs was conducted by comparing DCs using an the novel dew point cooling system and the optimum management scheme for the cooling air supply to that using traditional air cooling systems and the same supply air management. Annual electricity consumptions for the two cases were given. It was found that by using the novel dew point cooling system and optimum management system for the cooling air supply, an 87.7~91.6% electricity consumption saving for space cooling in DCs could be achieved in 10 typical cities at 10 selected climatic conditions. Full article

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17 pages, 2545 KiB

Open AccessArticle

Multi-Objective Optimization Approach for Placement of Multiple DGs for Voltage Sensitive Loads

by Navdeep Kaur^* and Sanjay Kumar Jain

Eelctrical and Instrumentation Engineering Department, Thapar University, Patiala 147004, India

Energies 2017, 10(11), 1733; https://doi.org/10.3390/en10111733 - 29 Oct 2017

Cited by 13 | Viewed by 3843

Abstract

This paper presents the optimal placement of multiple Dispersed Generators using multi-objective optimization. The optimization is carried out with objectives namely active power loss, reactive power loss, voltage deviation and overall economy. The multi-objective optimization and accounting conflicting objectives are realized through Particle [...] Read more.

This paper presents the optimal placement of multiple Dispersed Generators using multi-objective optimization. The optimization is carried out with objectives namely active power loss, reactive power loss, voltage deviation and overall economy. The multi-objective optimization and accounting conflicting objectives are realized through Particle Swarm Optimization with fuzzy decision approach to find the optimal sizes and sites of Dispersed Generators for voltage dependent residential, commercial and industrial loads. The clusters of buses are formulated from base case load flow to limit the search space for finding the placement of the Dispersed Generators. The effectiveness of the proposed approach is tested on a 69-bus radial distribution. It is found that the optimal placement of the Dispersed Generators improves the overall performance of the system and the optimal allocation is affected by the type of load. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 3447 KiB

Open AccessArticle

Supercritical Water Gasification of Biomass in a Ceramic Reactor: Long-Time Batch Experiments

by Daniele Castello^1,2

, Birgit Rolli³, Andrea Kruse^3,4

and Luca Fiori^1,*

¹ Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, 38123 Trento, Italy

² Department of Energy Technology, Aalborg University, Pontoppidanstræde 111, 9220 Aalborg Øst, Denmark

³ Institute of Catalysis Research and Technology (IKFT), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

⁴ Institute of Agricultural Engineering, Conversion Technology and LCA of Renewable Resources, University of Hohenheim, Gerbenstrasse 9, 70593 Stuttgart, Germany

Energies 2017, 10(11), 1734; https://doi.org/10.3390/en10111734 - 30 Oct 2017

Cited by 40 | Viewed by 7702

Abstract

Supercritical water gasification (SCWG) is an emerging technology for the valorization of (wet) biomass into a valuable fuel gas composed of hydrogen and/or methane. The harsh temperature and pressure conditions involved in SCWG (T > 375 °C, p > 22 MPa) are [...] Read more.

Supercritical water gasification (SCWG) is an emerging technology for the valorization of (wet) biomass into a valuable fuel gas composed of hydrogen and/or methane. The harsh temperature and pressure conditions involved in SCWG (T > 375 °C, p > 22 MPa) are definitely a challenge for the manufacturing of the reactors. Metal surfaces are indeed subject to corrosion under hydrothermal conditions, and expensive special alloys are needed to overcome such drawbacks. A ceramic reactor could be a potential solution to this issue. Finding a suitable material is, however, complex because the catalytic effect of the material can influence the gas yield and composition. In this work, a research reactor featuring an internal alumina inlay was utilized to conduct long-time (16 h) batch tests with real biomasses and model compounds. The same experiments were also conducted in batch reactors made of stainless steel and Inconel 625. The results show that the three devices have similar performance patterns in terms of gas production, although in the ceramic reactor higher yields of C₂₊ hydrocarbons were obtained. The SEM observation of the reacted alumina surface revealed a good resistance of such material to supercritical conditions, even though some intergranular corrosion was observed. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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13 pages, 6568 KiB

Open AccessArticle

A New Approach of Minimizing Commutation Torque Ripple for BLDCM

by Bo Tan^1,*, Zhiguang Hua¹, Lu Zhang² and Chun Fang¹

¹ Shaanxi Key Laboratory of Small & Special Electrical Machine and Drive Technology, Northwestern Polytechnical University, Xi’an 710072, China

² Xi’an Flight Automatic Control Research Institute, Xi’an 710065, China

Energies 2017, 10(11), 1735; https://doi.org/10.3390/en10111735 - 30 Oct 2017

Cited by 13 | Viewed by 4926

Abstract

The properties of brushless DC motor (BLDCM) are similar to the fractional, slot-concentrated winding of permanent-magnet synchronous machines, and they fit well for electric vehicle application. However, BLDCM still suffers from the high commutation torque ripple in the case of the traditional square-wave [...] Read more.

The properties of brushless DC motor (BLDCM) are similar to the fractional, slot-concentrated winding of permanent-magnet synchronous machines, and they fit well for electric vehicle application. However, BLDCM still suffers from the high commutation torque ripple in the case of the traditional square-wave current control (SWC) method, where the current vector rotates asynchronously with back-EMF. A current optimizing control (COC) method for BLDCM is proposed in the paper to minimize the commutation torque ripple. The trajectories of the three phase currents are planned by the given torque and the optimized result of the copper loss and motor torque equations. The properties of COC are analyzed and compared with that of SWC in the stationary reference frame. The results show that the way of making the current vector rotate synchronously with back-EMF (back-Electromotive Force) can minimize the modulus and velocity of the current vector in the commutation region, and reduce the torque ripple. Experimental tests obtained from an 82 W BLDCM are done to confirm the theoretical findings. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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21 pages, 10562 KiB

Open AccessArticle

A Transient Stability Numerical Integration Algorithm for Variable Step Sizes Based on Virtual Input

by Yifan Gao

, Jianquan Wang^*, Tannan Xiao and Daozhuo Jiang

College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

Energies 2017, 10(11), 1736; https://doi.org/10.3390/en10111736 - 30 Oct 2017

Cited by 3 | Viewed by 3244

Abstract

In order to reduce the online calculations for power system simulations of transient stability, and dramatically improve numerical integration efficiency, a transient stability numerical integration algorithm for variable step sizes based on virtual input is proposed. The method for fully constructing the nonhomogeneous [...] Read more.

In order to reduce the online calculations for power system simulations of transient stability, and dramatically improve numerical integration efficiency, a transient stability numerical integration algorithm for variable step sizes based on virtual input is proposed. The method for fully constructing the nonhomogeneous virtual input for a certain integration scheme is given, and the calculation method for the local truncation error of the power angle for the corresponding integration scheme is derived. A step size control strategy based on the predictor corrector variable step size method is proposed, which performs an adaptive control of the step size in the numerical integration process. The proposed algorithm was applied to both the IEEE39 system and a regional power system (5075 nodes, 496 generators) in China, and demonstrated a high level of accuracy and efficiency in practical simulations compared to the conventional numerical integration algorithm. Full article

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18 pages, 3064 KiB

Open AccessArticle

A Human-Machine-Cooperative-Driving Controller Based on AFS and DYC for Vehicle Dynamic Stability

by Jian Wu¹

, Shuo Cheng^2,*

, Binhao Liu² and Congzhi Liu²

¹ School of Mechanical and Automotive Engineering, Liaocheng University, Liaocheng 252000, China

² State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China

Energies 2017, 10(11), 1737; https://doi.org/10.3390/en10111737 - 30 Oct 2017

Cited by 100 | Viewed by 6857

Abstract

It is a difficult and important project to coordinate active front steering (AFS) and direct yaw moment control (DYC), which has great potential to improve vehicle dynamic stability. Moreover, the balance between driver’s operation and advanced technologies’ intervention is a critical problem. This [...] Read more.

It is a difficult and important project to coordinate active front steering (AFS) and direct yaw moment control (DYC), which has great potential to improve vehicle dynamic stability. Moreover, the balance between driver’s operation and advanced technologies’ intervention is a critical problem. This paper proposes a human-machine-cooperative-driving controller (HMCDC) with a hierarchical structure for vehicle dynamic stability and it consists of a supervisor, an upper coordination layer, and two lower layers (AFS and DYC). The range of AFS additional angle is constrained, with consideration of the influence of AFS on drivers’ feeling. First, in the supervisor, a nonlinear vehicle model was utilized to predict vehicle states, and the reference yaw rate, and side slip angle values were calculated. Then, the upper coordination layer decides the control object and control mode. At last, DYC and AFS calculate brake pressures and the range of active steering angle, respectively. The proposed HMCDC is evaluated by co-simulation of CarSim and MATLAB. Results show that the proposed controller could improve vehicle dynamic stability effectively for the premise of ensuring the driver’s intention. Full article

(This article belongs to the Special Issue The International Symposium on Electric Vehicles (ISEV2017))

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23 pages, 10474 KiB

Open AccessArticle

New Approach for Optimal Location and Parameters Setting of UPFC for Enhancing Power Systems Stability under Contingency Analysis

by Muhammad Zahid^1,*, Jinfu Chen¹, Yinhong Li¹, Xianzhong Duan¹, Qi Lei¹, Wang Bo², Ghulam Mohy-ud-din^3,4

and Asad Waqar⁵

¹ School of Electrical and Electronics Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

² State Grid Hubei Electric Power Company Technology, Project No. 52153816000Y, Wuhan 430074, China

³ School of Electrical, Computer and Telecommunication Engineering, University of Wollongong, Wollongong, NSW 2522, Australia

⁴ Department of Electrical Engineering, COMSATS Institute of Information Technology, Wah Cantt 47040, Pakistan

⁵ Department of Electrical Engineering, Bahria University, Islamabad 44000, Pakistan

Energies 2017, 10(11), 1738; https://doi.org/10.3390/en10111738 - 30 Oct 2017

Cited by 17 | Viewed by 5367

Abstract

Operation of power system within specified limits of voltage and frequency are the major concerns in power system stability studies. As power system is always prone to disturbances, which consequently affect the voltage instability and optimal power flow, and therefore risks the power [...] Read more.

Operation of power system within specified limits of voltage and frequency are the major concerns in power system stability studies. As power system is always prone to disturbances, which consequently affect the voltage instability and optimal power flow, and therefore risks the power systems stability and security. In this paper, a novel technique based on the “Artificial Algae Algorithm” (AAA) is introduced, to identify the optimal location and the parameters setting of Unified Power Flow Controller (UPFC) under N-1 contingency criterion. In the first part, we have carried out a contingency operation and ranking process for the most parlous lines outage contingencies while taking the transmission lines overloading (NOLL) and voltage violation of buses (NVVB) as a performance parameter (PP = NOLL + NVVB). As UPFC possesses too much prohibitive cost and larger size, its optimal location and size must be identified before the actual deployment. In the second part, we have applied a novel AAA technique to identify the optimal location and parameters setting of UPFC under the discovered contingencies. The simulations have been executed on IEEE 14 bus and 30 bus networks. The results reveals that the location of UPFC is significantly optimized using AAA technique, which has improved the stability and security of the power system by curtailing the overloaded transmission lines and limiting the voltage violations of buses. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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15 pages, 4115 KiB

Open AccessArticle

Stability Analysis of Aircraft Power Systems Based on a Unified Large Signal Model

by Yanbo Che¹, Jianmei Xu¹, Kun Shi², Huanan Liu³

, Weihua Chen⁴ and Dongmin Yu^3,*

¹ Key Laboratory of Smart Grid of Ministry of Education, Tianjin University, Tianjin 300072, China

² Department of Power Consumption, China Electric Power Research Institute, Beijing 100192, China

³ Department of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China

⁴ China Energy Equipment CO., LTD. 2, Beijing 100044, China

Energies 2017, 10(11), 1739; https://doi.org/10.3390/en10111739 - 30 Oct 2017

Cited by 13 | Viewed by 3867

Abstract

Complex power electronic conversion devices, most of which have high transmission performance, are important power conversion units in modern aircraft power systems. However, these devices can also affect the stability of the aircraft power system more and more prominent due to their dynamic [...] Read more.

Complex power electronic conversion devices, most of which have high transmission performance, are important power conversion units in modern aircraft power systems. However, these devices can also affect the stability of the aircraft power system more and more prominent due to their dynamic and nonlinear characteristics. To analyze the stability of aircraft power systems in a simple, accurate and comprehensive way, this paper develops a unified large signal model of aircraft power systems. In this paper, first the Lyapunov linearization method and the mixed potential theory are employed to analyze small signal and large signal stability, respectively, and then a unified stability criterion is proposed to estimate small and large signal stability problems. Simulation results show that the unified large signal model of aircraft power systems presented in this paper can be used to analyze the stability problem of aircraft power systems in an accurate and comprehensive way. Furthermore, with simplicity, universality and structural uniformity, the unified large signal model lays a good foundation for the optimal design of aircraft power systems. Full article

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16 pages, 1680 KiB

Open AccessArticle

Approximate Analysis of Multi-State Weighted k-Out-of-n Systems Applied to Transmission Lines

by Xiaogang Song¹

, Zhengjun Zhai¹, Yangming Guo¹, Peican Zhu^1,* and Jie Han^2,*

¹ School of Computer Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China

² Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada

Energies 2017, 10(11), 1740; https://doi.org/10.3390/en10111740 - 30 Oct 2017

Cited by 4 | Viewed by 3724

Abstract

Multi-state weighted k-out-of-n systems are widely applied in various scenarios, such as multiple line (power/oil transmission line) transmission systems where the capability of fault tolerance is desirable. However, the complex operating environment and the dynamic features of load demands influence the [...] Read more.

Multi-state weighted k-out-of-n systems are widely applied in various scenarios, such as multiple line (power/oil transmission line) transmission systems where the capability of fault tolerance is desirable. However, the complex operating environment and the dynamic features of load demands influence the evaluation of system reliability. In this paper, a stochastic multiple-valued (SMV) approach is proposed to efficiently predict the reliability of two models of systems with non-repairable components and dynamically repairable components. The weights/performances and reliabilities of multi-state components (MSCs) are represented by stochastic sequences consisting of a fixed number of multi-state values with the positions being randomly permutated. Using stochastic sequences with L multiple values, linear computational complexities with parameters n and L are required by the SMV approach to compute the reliability of different multi-state k-out-of-n systems at a reasonable accuracy, compared to the complexities of universal generating functions (UGF) and fuzzy universal generating functions (FUGF) that increase exponentially with the value of n. The analysis of two benchmarks shows that the proposed SMV approach is more efficient than the analysis using UGF or FUGF. Full article

(This article belongs to the Special Issue 2017 Prognostics and System Health Management Conference)

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18 pages, 9978 KiB

Open AccessArticle

The Effects of Additives on the Dehydrogenation of Amorphous Manganese Borohydride and Its Crystalline Form after Solvent Filtration/Extraction

by Robert A. Varin^1,*, Deepak K. Mattar¹, Marek Polanski², Amirreza Shirani Bidabadi¹ and Leszek Stobinski³

¹ Department of Mechanical and Mechatronics Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada

² Faculty of New Technologies and Chemistry, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland

³ Faculty of Materials Science and Engineering, Graphene Laboratory, Warsaw University of Technology, Warynskiego 1, 00-645 Warsaw, Poland

Energies 2017, 10(11), 1741; https://doi.org/10.3390/en10111741 - 30 Oct 2017

Cited by 4 | Viewed by 3496

Abstract

A non-stoichiometric, amorphous a-Mn(BH₄)_(2x) hydride, accompanied by a NaCl-type salt, was mechanochemically synthesized from the additive-free mixture of (2NaBH₄ + MnCl₂), as well as from the mixtures containing the additives of ultrafine filamentary carbonyl nickel (Ni), graphene, [...] Read more.

A non-stoichiometric, amorphous a-Mn(BH₄)_(2x) hydride, accompanied by a NaCl-type salt, was mechanochemically synthesized from the additive-free mixture of (2NaBH₄ + MnCl₂), as well as from the mixtures containing the additives of ultrafine filamentary carbonyl nickel (Ni), graphene, and LiNH₂. It is shown that both graphene and LiNH₂ suppressed the release of B₂H₆ during thermal gas desorption, with the LiNH₂ additive being the most effective suppressor of B₂H₆. During solvent filtration and extraction of additive-free, as well as additive-bearing, (Ni and graphene) samples from diethyl ether (Et₂O), the amorphous a-Mn(BH₄)_(2x) hydride transformed into a crystalline c-Mn(BH₄)₂ hydride, exhibiting a microstructure containing nanosized crystallites (grains). In contrast, the LiNH₂ additive most likely suppressed the formation of a crystalline c-Mn(BH₄)₂ hydride during solvent filtration/extraction. In a differential scanning calorimeter (DSC), the thermal decomposition peaks of both amorphous a-Mn(BH₄)_(2x) and crystalline c-Mn(BH₄)₂ were endothermic for the additive-free samples, as well as the samples with added graphene and Ni. The samples with LiNH₂ exhibited an exothermic DSC decomposition peak. Full article

(This article belongs to the Section D: Energy Storage and Application)

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15 pages, 5355 KiB

Open AccessArticle

Evaluation of Comfort Level and Harvested Energy in the Vehicle Using Controlled Damping

by Vytautas Bucinskas¹

, Peter Mitrouchev², Ernestas Sutinys¹, Nikolaj Sesok¹, Igor Iljin¹ and Inga Morkvenaite-Vilkonciene^1,*

¹ Department of Mechatronics and Robotics, Vilnius Gediminas Technical University, J. Basanavičiaus g. 28, 03224 Vilnius, Lithuania

² G-SCOP, Grenoble INP, University Grenoble Alpes, F-38000 Grenoble, France

Energies 2017, 10(11), 1742; https://doi.org/10.3390/en10111742 - 30 Oct 2017

Cited by 13 | Viewed by 4317

Abstract

Shock absorbers allow the damping of suspension vibrations, by dissipating kinetic energy. This energy theoretically can be harvested; however, practical solutions are not easily obtainable. This paper is dedicated to analyzing and evaluating the vibration energy in a vehicle’s suspension that is generated [...] Read more.

Shock absorbers allow the damping of suspension vibrations, by dissipating kinetic energy. This energy theoretically can be harvested; however, practical solutions are not easily obtainable. This paper is dedicated to analyzing and evaluating the vibration energy in a vehicle’s suspension that is generated by road excitations. Also, it estimates the possible amount of harvested energy required to diminish accelerations of the vehicle body, the driver, or the passenger center of mass. The control of damper is realized by optimizing the best damping coefficient for different road roughness. Analytical results, obtained from the proposed dynamic model of the car, were compared with experimental data, showing a good coherence between them. These results allow us to evaluate the amount of energy circulating within shock absorbers and give information about the amount of the possible harvested energy. There is a very good relationship between energy needed for control and gained energy. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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14 pages, 8302 KiB

Open AccessArticle

Stress Inversion of Coal with a Gas Drilling Borehole and the Law of Crack Propagation

by Tianjun Zhang^1,2,3, Lei Zhang^2,3,*

, Shugang Li^2,3, Jialei Liu⁴, Hongyu Pan^2,3 and Shuang Song^2,3

¹ College of Science, Xi’an University of Science and Technology, Xi’an 710054, China

² School of Safety Engineering, Xi’an University of Science and Technology, Xi’an 710054, China

³ Key Laboratory of Western Mine Exploitation and Hazard Prevention of the Ministry of Education, Xi’an 710054, China

⁴ China Gezhouba Group No.5 Engineering Co., Ltd., Yichang 443002, China

Energies 2017, 10(11), 1743; https://doi.org/10.3390/en10111743 - 30 Oct 2017

Cited by 13 | Viewed by 3385

Abstract

For studying the law of crack propagation around a gas drilling borehole, an experimental study about coal with a cavity under uniaxial compression was carried out, with the digital speckle correlation method capturing the images of coal failure. A sequence of coal failure [...] Read more.

For studying the law of crack propagation around a gas drilling borehole, an experimental study about coal with a cavity under uniaxial compression was carried out, with the digital speckle correlation method capturing the images of coal failure. A sequence of coal failure images and the full-field strain of failure were obtained. The strain softening characteristic was shown by the curve. A method of curve dividing—named fitting-damaging—was proposed, combining the least square fitting residual norm and damage fraction. By this method, the five stages and four key points of a stress-strain curve were defined. Then, the full-field stress was inverted by means of the theory of elasticity and the adjacent element weight sharing model. The results show that σ_ci was 30.28–41.71 percent of σ_f and σ_cd was 83.08–87.34 percent of σ_f, calculated by the fitting-damaging method, agreeing with former research. The results of stress inversion showed that under a low stress level (0.15 σ_f < σ < 0.5 σ_f), microdamage evolving into plastic failure later was formed around the cavity. Under a high stress level (0.5 σ_f < σ < 0.85 σ_f), the region of stress concentration suddenly crazed and formed a brittle crack. When σ ≥ 0.85 σ_f, the crack was developing, crack lines were connecting with each other, and the coal finally failed. The outcome of the stress inversion was completely concomitant with the images of crack propagation. Additionally, the stress around the cavity was able to be calculated accurately. Full article

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17 pages, 9411 KiB

Open AccessArticle

Advanced Wind Speed Prediction Model Based on a Combination of Weibull Distribution and an Artificial Neural Network

by Athraa Ali Kadhem^1,*, Noor Izzri Abdul Wahab¹

, Ishak Aris¹, Jasronita Jasni¹ and Ahmed N. Abdalla²

¹ Department of Electrical and Electronic Engineering, University Putra Malaysia, Selangor 43400, Malaysia

² Faculty of Electronics Information Engineering, Huaiyin Institute of Technology, Huai’an 223003, China

Energies 2017, 10(11), 1744; https://doi.org/10.3390/en10111744 - 30 Oct 2017

Cited by 55 | Viewed by 5875

Abstract

One of the most crucial prerequisites for effective wind power planning and operation in power systems is precise wind speed forecasting. Highly random fluctuations of wind influenced by the conditions of the atmosphere, weather and terrain result in difficulties of forecasting regardless of [...] Read more.

One of the most crucial prerequisites for effective wind power planning and operation in power systems is precise wind speed forecasting. Highly random fluctuations of wind influenced by the conditions of the atmosphere, weather and terrain result in difficulties of forecasting regardless of whether it is short-term or long-term. The current study has developed a method to model wind speed data predictions with dependence on seasonal wind variations over a particular time frame, usually a year, in the form of a Weibull distribution model with an artificial neural network (ANN). As a result, the essential dependencies between the wind speed and seasonal weather variation are exploited. The proposed model utilizes the ANN to predict the wind speed data, which has similar chronological and seasonal characteristics to the actual wind data. This model was applied to wind speed databases from selected sites in Malaysia, namely Mersing, Kudat, and Kuala Terengganu, to validate the proposed model. The results indicate that the proposed hybrid artificial neural network (HANN) model is capable of depicting the fluctuating wind speed during different seasons of the year at different locations. Full article

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14 pages, 3058 KiB

Open AccessArticle

Assessment of Methods for Forecasting Shale Gas Supply in China Based on Economic Considerations

by Xiaoqian Guo^1,2

, Qiang Yan^1,2 and Anjian Wang^2,*

¹ MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, China Academy of Geological Science, Beijing 100037, China

² Research Center for Strategy of Global Mineral Resources, Institute of Mineral Resources, China Academy of Geological Science, Beijing 100037, China

Energies 2017, 10(11), 1745; https://doi.org/10.3390/en10111745 - 30 Oct 2017

Cited by 3 | Viewed by 3796

Abstract

Shale gas, with its lower carbon content and pollution potential, is the most promising natural gas resource in China. When modeling the shale gas supply in a specific gas field, it is of paramount importance to determine the gas supply under economic considerations. [...] Read more.

Shale gas, with its lower carbon content and pollution potential, is the most promising natural gas resource in China. When modeling the shale gas supply in a specific gas field, it is of paramount importance to determine the gas supply under economic considerations. Two common calculation methods are used in China for this purpose: Method 1 (M1) is the breakeven analysis, where the gas supply is based on the relationship between costs and revenues, while Method 2 (M2) is the Geologic Resource Supply-Demand Model, where the supply relies on demand and price scenarios. No comparisons has been made between these two methods. In this study, the Fuling shale gas field in the Sichuan Basin was chosen as a study case to forecast the shale gas supply using these two different methods. A sensitivity analysis was performed to discuss the influencing factors of each method and error measures were used to compare the different shale gas supply values calculated by each method. The results shows that M1 is more sensitive to initial production, while M2 is more sensitive to gas price. In addition, M2 is more feasible for its simplicity and accuracy at high price scenarios and M1 is considered to be reliable for low price scenarios with profit. This study can provide a quick and comprehensive assessment method for the shale gas supply in China. Full article

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26 pages, 5909 KiB

Open AccessArticle

Comprehensive Parametric Study of a Solar Absorption Refrigeration System to Lower Its Cut In/Off Temperature

by Osman Wageiallah Mohammed and Guo Yanling^*

College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin 150000, China

Energies 2017, 10(11), 1746; https://doi.org/10.3390/en10111746 - 31 Oct 2017

Cited by 9 | Viewed by 8041

Abstract

Solar-driven ammonia-water absorption refrigeration system (AARS) has been considered as an alternative for the conventional refrigeration and air-conditioning systems. However, its high initial cost seems to be the main problem that postpones its wide spread use. In the present study, a single-stage NH [...] Read more.

Solar-driven ammonia-water absorption refrigeration system (AARS) has been considered as an alternative for the conventional refrigeration and air-conditioning systems. However, its high initial cost seems to be the main problem that postpones its wide spread use. In the present study, a single-stage NH₃/H₂O ARS is analyzed in depth on the basis of energetic and exergetic coefficients of performance (COP and ECOP, respectively) to decrease its cut in/off temperature. This study was carried out to lower the required heat source temperature, so that a less-expensive solar collector could be used. Effects of all parameters that could influence the system’s performance and cut in/off temperature were investigated in detail. Presence of water in the refrigerant and evaporator temperature glide was considered. Results revealed that appropriate selection of system’s working condition can effectively reduce the driving temperature. Besides, the cut in/off temperature can be significantly decreased by inserting an effective solution heat exchanger (SHX). Required driving temperature can be lowered by up to 10 °C using SHX with 0.80 effectiveness. The results also showed that effects of water content in the refrigerant could not be neglected in studying NH₃/H₂O ARS because it affects both COP and ECOP. Additionally, a large temperature glide in the evaporator can substantially decrease the ECOP. Full article

(This article belongs to the Special Issue Solar-Assisted Heat Pump Systems for Heating and Cooling)

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16 pages, 1000 KiB

Open AccessArticle

Decomposed Driving Factors of Carbon Emissions and Scenario Analyses of Low-Carbon Transformation in 2020 and 2030 for Zhejiang Province

by Chuyu Xia^1,2, Yan Li^1,2,*, Yanmei Ye^1,2, Zhou Shi³

and Jingming Liu⁴

¹ Institute of Land Science and Property, School of Public Affairs, Zhejiang University, Hangzhou 310058, China

² Laboratory of Rural-Urban Construction Land Economical and Intensive Use, Ministry of Land and Resources, Beijing 100812, China

³ Institute of Agricultural Remote Sensing and Information Technology Application, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China

⁴ School of Public Policy and Administration Department of Public Administration, Xi’an JiaoTong University, Xi’an 710049, China

Energies 2017, 10(11), 1747; https://doi.org/10.3390/en10111747 - 31 Oct 2017

Cited by 39 | Viewed by 4277

Abstract

Climate change has gained widespread attention, and the rapid growth of the economy in China has generated a considerable amount of carbon emissions. Zhejiang Province was selected as a study area. First, the energy-related carbon emissions from 2000 to 2014 were accounted for, [...] Read more.

Climate change has gained widespread attention, and the rapid growth of the economy in China has generated a considerable amount of carbon emissions. Zhejiang Province was selected as a study area. First, the energy-related carbon emissions from 2000 to 2014 were accounted for, and then the Logarithmic Mean Divisia Index (LMDI) decomposition model was applied to analyse the driving factors underlying the carbon emissions. Finally, three scenarios (inertia, comparative decoupling and absolute decoupling) for 2020 and 2030 were simulated based on the low-carbon city and Human Impact Population Affluence Technology (IPAT) models. The results showed (1) carbon emissions increased by 1.66 times from 2000 to 2014, and trends of carbon emissions were used to divide the study period into three phases (rapid, medium growth and slow decrease phases, with annual growth rates of 12.60%, 4.77% and −1.24%, respectively); (2) the energy intensity effect from 2000–2011 inhibited carbon emissions but was exceeded by the economic output effect, which increased emissions, whereas the energy intensity effect from 2011–2014 outweighed the economic output effect; (3) the scenario analyses revealed that both the comparative and absolute decoupling scenarios would remain consistent with the carbon emissions boundaries in 2020 and 2030, but the comparative decoupling scenario was more reasonable for sustainable development. In addition, appropriate design of emission trading scheme could help to achieve the comparative decoupling by financial incentives. Full article

(This article belongs to the Special Issue Lessons from the Evaluation of Existing Emission Trading Schemes)

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42 pages, 21709 KiB

Open AccessReview

A Review of Lithium-Air Battery Modeling Studies

by Kisoo Yoo¹

, Soumik Banerjee², Jonghoon Kim³

and Prashanta Dutta^2,*

¹ School of Mechanical Engineering, Yeungnam University, Gyeongsan 38541, Korea

² School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920, USA

³ Department of Electrical Engineering, Chungnam National University, Daejeon 34134, Korea

Energies 2017, 10(11), 1748; https://doi.org/10.3390/en10111748 - 1 Nov 2017

Cited by 21 | Viewed by 12984

Abstract

Li-air batteries have attracted interest as energy storage devices due to their high energy and power density. Li-air batteries are expected to revolutionize the automobile industry (for use in electric and hybrid vehicles) and electrochemical energy storage systems by surpassing the energy capacities [...] Read more.

Li-air batteries have attracted interest as energy storage devices due to their high energy and power density. Li-air batteries are expected to revolutionize the automobile industry (for use in electric and hybrid vehicles) and electrochemical energy storage systems by surpassing the energy capacities of conventional Li-ion batteries. However, the practical implementation of Li-air batteries is still hindered by many challenges, such as low cyclic performance and high charging voltage, resulting from oxygen transport limitations, electrolyte degradation, and the formation of irreversible reduction products. Therefore, various methodologies have been attempted to mitigate the issues causing performance degradation of Li-air batteries. Among myriad studies, theoretical and numerical modeling are powerful tools for describing and investigating the chemical reactions, reactive ion transportation, and electrical performance of batteries. Herein, we review the various multi-physics/scale models used to provide mechanistic insights into processes in Li-air batteries and relate these to overall battery performance. First, continuum-based models describing ion transport, pore blocking phenomena, and reduction product precipitation are presented. Next, atomistic modeling-based studies that provide an understanding of the reaction mechanisms in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), as well as ion–ion interactions in the electrolyte, are described. Full article

(This article belongs to the Section D: Energy Storage and Application)

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19 pages, 2808 KiB

Open AccessArticle

Influence of Trust on Biomass Supply Decision-Making in China

by Lingling Wang¹ and Tsunemi Watanabe^1,2,*

¹ School of Economics and Management, Kochi University of Technology, 2-22 Eikokuji-cho, Kochi City, Kochi 780-8515, Japan

² Graduate School of Engineering, Kochi University of Technology, Miyanokuchi 185, Tosayamada-cho, Kami City, Kochi 782-0003, Japan

Energies 2017, 10(11), 1749; https://doi.org/10.3390/en10111749 - 31 Oct 2017

Cited by 4 | Viewed by 3787

Abstract

Given the abundant straw resources in Northeast China and the huge external costs associated with fossil fuels, straw-based biomass power plants have emerged as a popular alternative to coal-fired power plants. The sustainability of these green alternatives depends on straw supply from farmers, [...] Read more.

Given the abundant straw resources in Northeast China and the huge external costs associated with fossil fuels, straw-based biomass power plants have emerged as a popular alternative to coal-fired power plants. The sustainability of these green alternatives depends on straw supply from farmers, yet little is known about their perceptions regarding such supply because of a lack of cooperation in the supply chain. To better understand farmers’ opinions on supplying straw, this study examined their trust in middlemen, perceptions regarding risk in straw supply, the possibility of reducing transaction costs, and their willingness to supply straw. Data were collected from 275 farmers in the national bioenergy industry area in Wangkui County, Northeast China. We investigated the theoretical and empirical connections between trust and risk perception, trust and the possibility of reducing transaction costs, and trust and willingness to supply straw. The results indicated that education, income, and trust factors explained farmers’ risk perceptions, the possibility that they will reduce transaction costs, and their willingness to supply straw. On the basis of the analysis, a model of the influence of trust on straw supply was established. The overall findings indicated that biomass power plants and middlemen must build trusting relationships with farmers to ensure sustainable biomass supply. Full article

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12 pages, 1049 KiB

Open AccessArticle

Alternative Diesel from Waste Plastics

by Stella Bezergianni^1,*

, Athanasios Dimitriadis¹, Gian-Claudio Faussone²

and Dimitrios Karonis³

¹ Chemical Process & Energy Resources Institute, Centre for Research & Technology Hellas, 57001 Thermi-Thessaloniki, Greece

² INSER SpA, 10121 Turin, Italy

³ School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece

Energies 2017, 10(11), 1750; https://doi.org/10.3390/en10111750 - 31 Oct 2017

Cited by 75 | Viewed by 10203

Abstract

The long term ambition of energy security and solidarity, coupled with the environmental concerns of problematic waste accumulation, is addressed via the proposed waste-to-fuel technology. Plastic waste is converted into automotive diesel fuel via a two-step thermochemical process based on pyrolysis and hydrotreatment. [...] Read more.

The long term ambition of energy security and solidarity, coupled with the environmental concerns of problematic waste accumulation, is addressed via the proposed waste-to-fuel technology. Plastic waste is converted into automotive diesel fuel via a two-step thermochemical process based on pyrolysis and hydrotreatment. Plastic waste was pyrolyzed in a South East Asia plant rendering pyrolysis oil, which mostly consisted of middle-distillate (naphtha and diesel) hydrocarbons. The diesel fraction (170–370 °C) was fractionated, and its further upgrade was assessed in a hydroprocessing pilot plant at the Centre for Research and Technology Hellas (CERTH) in Greece. The final fuel was evaluated with respect to the diesel fuel quality specifications EN 590, which characterized it as a promising alternative diesel pool component with excellent ignition quality characteristics and low back end volatility. Full article

(This article belongs to the Section L: Energy Sources)

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16 pages, 4420 KiB

Open AccessArticle

A Novel Methodology for Estimating State-Of-Charge of Li-Ion Batteries Using Advanced Parameters Estimation

by Ibrahim M. Safwat^*, Weilin Li^*

and Xiaohua Wu

Electrical Engineering Department, Northwestern Polytechnical University, Xi’an 710065, China

Energies 2017, 10(11), 1751; https://doi.org/10.3390/en10111751 - 1 Nov 2017

Cited by 11 | Viewed by 3657

Abstract

State-of-charge (SOC) estimations of Li-ion batteries have been the focus of many research studies in previous years. Many articles discussed the dynamic model’s parameters estimation of the Li-ion battery, where the fixed forgetting factor recursive least square estimation methodology is employed. However, the [...] Read more.

State-of-charge (SOC) estimations of Li-ion batteries have been the focus of many research studies in previous years. Many articles discussed the dynamic model’s parameters estimation of the Li-ion battery, where the fixed forgetting factor recursive least square estimation methodology is employed. However, the change rate of each parameter to reach the true value is not taken into consideration, which may tend to poor estimation. This article discusses this issue, and proposes two solutions to solve it. The first solution is the usage of a variable forgetting factor instead of a fixed one, while the second solution is defining a vector of forgetting factors, which means one factor for each parameter. After parameters estimation, a new idea is proposed to estimate state-of-charge (SOC) of the Li-ion battery based on Newton’s method. Also, the error percentage and computational cost are discussed and compared with that of nonlinear Kalman filters. This methodology is applied on a 36 V 30 A Li-ion pack to validate this idea. Full article

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30 pages, 5618 KiB

Open AccessReview

A Review on the Recent Development of Capacitive Wireless Power Transfer Technology

by Fei Lu

, Hua Zhang and Chris Mi^*

Department of Electrical and Computer Engineering, San Diego State University, San Diego, CA 92182, USA

Energies 2017, 10(11), 1752; https://doi.org/10.3390/en10111752 - 1 Nov 2017

Cited by 248 | Viewed by 17285

Abstract

Capacitive power transfer (CPT) technology is an effective and important alternative to the conventional inductive power transfer (IPT). It utilizes high-frequency electric fields to transfer electric power, which has three distinguishing advantages: negligible eddy-current loss, relatively low cost and weight, and excellent misalignment [...] Read more.

Capacitive power transfer (CPT) technology is an effective and important alternative to the conventional inductive power transfer (IPT). It utilizes high-frequency electric fields to transfer electric power, which has three distinguishing advantages: negligible eddy-current loss, relatively low cost and weight, and excellent misalignment performance. In recent years, the power level and efficiency of CPT systems has been significantly improved and has reached the power level suitable for electric vehicle charging applications. This paper reviews the latest developments in CPT technology, focusing on two key technologies: the compensation circuit topology and the capacitive coupler structure. The comparison with the IPT system and some critical issues in practical applications are also discussed. Based on these analyses, the future research direction can be developed and the applications of the CPT technology can be promoted. Full article

(This article belongs to the Special Issue Wireless Power Transfer and Energy Harvesting Technologies)

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18 pages, 2799 KiB

Open AccessArticle

Analysis of the Optimum Solar Collector Installation Angle from the Viewpoint of Energy Use Patterns

by Yong-Joon Jun¹, Young-Hak Song², Dae-Young Kim³ and Kyung-Soon Park^1,*

¹ Architectural Engineering Major, Division of Urban, Architecture and Civil Engineering, Dong-Eui University, Busan 47340, Korea

² Department of Architectural Engineering, ERI, Gyeongsang National University, Jinju 52828, Korea

³ Department of Architectural Engineering, Pusan National University, Busan 46241, Korea

Energies 2017, 10(11), 1753; https://doi.org/10.3390/en10111753 - 2 Nov 2017

Cited by 2 | Viewed by 3661

Abstract

While solar energy is the most efficient energy source for heating, many problems can occur when the capacity selection of the system is wrong: a definite possibility in a place where the seasonal climate change is large, such as Korea. For example, if [...] Read more.

While solar energy is the most efficient energy source for heating, many problems can occur when the capacity selection of the system is wrong: a definite possibility in a place where the seasonal climate change is large, such as Korea. For example, if a system is designed for use in the winter, the system will be overloaded if it does not discard the energy it collects during the summer months. Conversely, if the capacity of the system is in accordance with the summer season demand, it will be necessary to input supplementary energy in the winter season. Solar energy also depends on the altitude and azimuth of the sun, and the amount of energy collected on the slope depends on the latitude of the area in which it is installed. Therefore, this study is divided into investigating the collection energy, heat radiation energy and auxiliary energy input according to the installation angle of the solar collector and the capacity of the heat storage tank according to latitude of the installation area. To this end, we formulate appropriate energy equations. Simulation coding was performed to track the temperature changes in each part. Additionally, we considered the amount of solar energy that can be effectively used, not simply the amount of solar energy collected, by substituting the actual hot water usage schedule. Full article

(This article belongs to the Section D: Energy Storage and Application)

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17 pages, 2055 KiB

Open AccessArticle

Quantification of Forecast Error Costs of Photovoltaic Prosumers in Italy

by Giovanni Brusco

, Alessandro Burgio

, Daniele Menniti, Anna Pinnarelli

, Nicola Sorrentino

and Pasquale Vizza^*

Department of Mechanical, Energy and Management Engineering—DIMEG, University of Calabria, Arcavacata di Rende, 87036 Rende (CS), Italy

Energies 2017, 10(11), 1754; https://doi.org/10.3390/en10111754 - 1 Nov 2017

Cited by 11 | Viewed by 3347

Abstract

In recent years, the diffusion of electric plants based on renewable non-dispatchable sources has caused large imbalances between the power generation schedule and the actual generation in real time operations, resulting in increased costs for dispatching electric power systems. Although this type of [...] Read more.

In recent years, the diffusion of electric plants based on renewable non-dispatchable sources has caused large imbalances between the power generation schedule and the actual generation in real time operations, resulting in increased costs for dispatching electric power systems. Although this type of source cannot be programmed, their production can be predicted using soft computing techniques that consider weather forecasts, reducing the imbalance costs paid to the transmission system operator (TSO). The problem is mainly that the forecasting procedures used by the TSO, distribution system operator (DSO) or large producers and they are too expensive, as they use complex algorithms and detailed meteorological data that have to be bought, this can represent an excessive charge for small-scale producers, such as prosumers. In this paper, a cheap photovoltaic (PV) production forecasting method, in terms of reduced computational effort, free-available meteorological data and implementation is discussed, and the economic results regarding the imbalance costs due to the utilization of this method are analyzed. The economic analysis is carried out considering several factors, such as the month, the day type, and the accuracy of the forecasting method. The user can utilize the implemented method to know and reduce the imbalance costs, by adopting particular load management strategies. Full article

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20 pages, 9438 KiB

Open AccessArticle

Using the PROSA Method in Offshore Wind Farm Location Problems

by Paweł Ziemba¹

, Jarosław Wątróbski^2,*, Magdalena Zioło³ and Artur Karczmarczyk⁴

¹ Faculty of Technology, The Jacob of Paradies University, Teatralna 25, 66-400 Gorzów Wielkopolski, Poland

² Faculty of Economics and Management, University of Szczecin, Mickiewicza 64, 71-101 Szczecin, Poland

³ Faculty of Management and Economics of Services, University of Szczecin, Cukrowa 8, 71-004 Szczecin, Poland

⁴ Faculty of Computer Science, West Pomeranian University of Technology in Szczecin, Żołnierska 49, 71-210 Szczecin, Poland

Energies 2017, 10(11), 1755; https://doi.org/10.3390/en10111755 - 1 Nov 2017

Cited by 84 | Viewed by 6354

Abstract

Wind is the most used renewable energy source (RES) in the European Union and Poland. Due to the legal changes in the scope of RES in Poland, there are plans to develop offshore wind farms at the expense of onshore ones. On the [...] Read more.

Wind is the most used renewable energy source (RES) in the European Union and Poland. Due to the legal changes in the scope of RES in Poland, there are plans to develop offshore wind farms at the expense of onshore ones. On the other hand, the success of an offshore wind farm is primarily determined by its location. Therefore, the aim of this study is to select offshore wind farm locations in Poland, based on sustainability assessment, which is an inherent aspect of RES decision-making issues. To accomplish the objectives of this research, PROSA (PROMETHEE for Sustainability Assessment) method, a new multi-criteria method is proposed. Like PROMETHEE (Preference Ranking Organization METHod for Enrichment Evaluation), PROSA is transparent for decision makers and is easy to use; moreover, it provides the analytical tools available in PROMETHEE, i.e., the sensitivity and GAIA (Geometrical Analysis for Interactive Assistance) analyses. However, PROSA is characterized by a lower degree of criteria compensation than PROMETHEE. Thus, it adheres in a higher degree to the strong sustainability paradigm. The study also compared the solutions of the decision problem obtained with the use of PROSA and PROMETHEE methods. The compared methods demonstrated a high concurrence of the recommended decision-making variant of location selection, from methodological and practical points of view. At the same time, the conducted research allowed to confirm that the PROSA method recommends more sustainable decision-making variants, and that the ranking it builds is less sensitive to changes in criteria weights. Therefore, it is more stable than the PROMETHEE-based ranking. Full article

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22 pages, 5416 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Game Theory Approach to Multi-Agent Decentralized Energy Management of Autonomous Polygeneration Microgrids

by Christos-Spyridon Karavas^*

, Konstantinos Arvanitis

and George Papadakis

Department of Natural Resources Management and Agricultural Engineering, School of Agricultural Production, Infrastructure and Environment, Agricultural University of Athens, 75 Iera Odos Street, Botanikos, 11855 Athens, Greece

Energies 2017, 10(11), 1756; https://doi.org/10.3390/en10111756 - 1 Nov 2017

Cited by 98 | Viewed by 10540

Abstract

Energy management systems are essential and indispensable for the secure and optimal operation of autonomous polygeneration microgrids which include distributed energy technologies and multiple electrical loads. In this paper, a multi-agent decentralized energy management system was designed. In particular, the devices of the [...] Read more.

Energy management systems are essential and indispensable for the secure and optimal operation of autonomous polygeneration microgrids which include distributed energy technologies and multiple electrical loads. In this paper, a multi-agent decentralized energy management system was designed. In particular, the devices of the microgrid under study were controlled as interactive agents. The energy management problem was formulated here through the application of game theory, in order to model the set of strategies between two players/agents, as a non-cooperative power control game or a cooperative one, according to the level of the energy produced by the renewable energy sources and the energy stored in the battery bank, for the purpose of accomplishing optimal energy management and control of the microgrid operation. The Nash equilibrium was used to compromise the possible diverging goals of the agents by maximizing their preferences. The proposed energy management system was then compared with a multi-agent decentralized energy management system where all the agents were assumed to be cooperative and employed agent coordination through Fuzzy Cognitive Maps. The results obtained from this comparison, demonstrate that the application of game theory based control, in autonomous polygeneration microgrids, can ensure operational and financial benefits over known energy management approaches incorporating distributed intelligence. Full article

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12 pages, 3146 KiB

Open AccessArticle

Hardware Implementation and a New Adaptation in the Winding Scheme of Standard Three Phase Induction Machine to Utilize for Multifunctional Operation: A New Multifunctional Induction Machine

by Mahajan Sagar Bhaskar¹

, Sanjeevikumar Padmanaban^1,*

, Sonali A. Sabnis², Lucian Mihet-Popa³

, Frede Blaabjerg⁴

and Vigna K. Ramachandaramurthy⁵

¹ Department of Electrical and Electronics Engineering, University of Johannesburg, PO Box 524, Auckland Park, Johannesburg 2006, South Africa

² Department of Electrical and Electronics Engineering, Marathwada Institute of Technology, Aurangabad 431001, India

³ Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Kråkeroy-Fredrikstad, Norway

⁴ Centre for Reliable Power Electronics (CORPE), Department of Energy Technology, Aalborg University, Aalborg 9000, Denmark

⁵ Institute of Power Engineering, Department of Electrical Power Engineering, Universiti Tenaga Nasional, 43000 Kajang, Selangor, Malaysia

Energies 2017, 10(11), 1757; https://doi.org/10.3390/en10111757 - 1 Nov 2017

Cited by 2 | Viewed by 6143

Abstract

In this article a new distinct winding scheme is articulated to utilize three phase induction machines for multifunctional operation. Because of their rugged construction and reduced maintenance induction machines are very popular and well-accepted for agricultural as well as industrial purposes. The proposed [...] Read more.

In this article a new distinct winding scheme is articulated to utilize three phase induction machines for multifunctional operation. Because of their rugged construction and reduced maintenance induction machines are very popular and well-accepted for agricultural as well as industrial purposes. The proposed winding scheme is used in a three phase induction machine to utilize the machine for multifunctional operation. It can be used as a three-phase induction motor, welding transformer and phase converter. The proposed machine design also works as a single phase induction motor at the same time it works as a three-phase to single phase converter. This new design does not need any kind of special arrangement and can be constructed with small modifications to any standard three-phase induction motor. This modified induction machine is thoroughly tested to determine its efficiency and other parameters and also hardware implementation results are provided in the article, which validate the design and construction. Full article

(This article belongs to the Special Issue Energy Storage Systems and Power Conversion Electronics for E-Transportation and Smart Grid)

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21 pages, 461 KiB

Open AccessArticle

Contribution to Energy Management of the Main Standards for Environmental Management Systems: The Case of ISO 14001 and EMAS

by Iker Laskurain^*, Ander Ibarloza

, Ainara Larrea and Erlantz Allur

Department of Management, University of the Basque Country UPV/EHU, 20018 San Sebastian, Spain

Energies 2017, 10(11), 1758; https://doi.org/10.3390/en10111758 - 1 Nov 2017

Cited by 41 | Viewed by 6656

Abstract

The adoption of Energy Management Systems (EnMSs) based on international standards has gained momentum since the ISO 50001 standard was launched in 2011. Before that, the potential to improve the energy management with Environmental Management Systems (EMSs) based on ISO 14001 and EMAS [...] Read more.

The adoption of Energy Management Systems (EnMSs) based on international standards has gained momentum since the ISO 50001 standard was launched in 2011. Before that, the potential to improve the energy management with Environmental Management Systems (EMSs) based on ISO 14001 and EMAS was identified in the literature. However, no in-depth analysis reported in the literature has explored this claim. The need for research is now even more evident with the development of new versions of the standards for environmental management―ISO 14001:2015 and EMAS III. Since many companies that already have a certified EMSs might be uncertain whether to adopt an ISO 50001 based EnMSs, the present work aims to shed light on the contribution of ISO 14001:2015 and EMAS III to energy management. Furthermore, the work summarizes the results of an empirical exploratory study carried out in eight Spanish organizations, four with an EMS implemented and certified based on ISO 14001:2015 and four more with an EMS registered to EMAS III. The findings show that both ISO14001 and EMAS certified organizations carry out energy management practices, even though they have no formal EnMSs implemented. Implications for managers and policy makers are discussed, together with avenues for further research. Full article

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17 pages, 6944 KiB

Open AccessArticle

Partial Discharge of Needle-Plane Defect in Oil-Paper Insulation under AC and DC Combined Voltages: Developing Processes and Characteristics

by Jiantao Sun¹, Xining Li², Lingyu Zhu^2,*

, Shengchang Ji² and Yanjie Cui²

¹ China Electric Power Research Institute, Beijing 100192, China

² State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China

Energies 2017, 10(11), 1759; https://doi.org/10.3390/en10111759 - 1 Nov 2017

Cited by 3 | Viewed by 4444

Abstract

Partial discharge (PD) behaviors of oil-paper insulation is distinctive in AC and DC combined electric fields in converter transformers from PD behaviors in pure AC or DC electric fields. The present study focuses on the PD developing processes and characteristics of oil-paper insulation [...] Read more.

Partial discharge (PD) behaviors of oil-paper insulation is distinctive in AC and DC combined electric fields in converter transformers from PD behaviors in pure AC or DC electric fields. The present study focuses on the PD developing processes and characteristics of oil-paper insulation systems with needle-plane defects under different AC/DC proportions. The degradation of oil-paper insulation can be accelerated by PD pulses incurred by needle-plane defects. AC-DC combined voltages are applied to the needle-plane defect model simultaneously in the established experimental platform, and the proportions of AC/DC voltages are decided according to the cases in actual converter transformers. The developing processes from the initiation of partial discharge until final breakdown were observed for each AC/DC proportion. PD parameters and patterns were acquired by a detector using the pulse current method. The test results indicate that the inception and breakdown voltages increase with the increase of the DC component in AC-DC combined voltages. However, pulse repetition rate and amplitude of PD shows a descending trend when AC/DC proportion decreases. Meanwhile, the PD recurrence rate in the phase between 180° and 360° becomes higher than that in the phase between 0° and 180° at the initial stage as the DC proportion increases; high-amplitude discharges mainly occur in the phase range between 180° and 360° when the pressboard is close to breakdown. The current study is useful in further research on fault diagnosis in converter transformers. Full article

(This article belongs to the Section F: Electrical Engineering)

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39 pages, 2480 KiB

Open AccessArticle

Battery Storage Technologies for Electrical Applications: Impact in Stand-Alone Photovoltaic Systems

by Daniel Akinyele^1,2,*, Juri Belikov³

and Yoash Levron¹

¹ Andrew and Erna Viterbi Faculty of Electrical Engineering, Technion—Israel Institute of Technology, Haifa 3200003, Israel

² Department of Electrical and Computer Engineering, Elizade University, P. M. B 002, Ilara-Mokin, Ondo State, Nigeria

³ Department of Computer Systems, Tallinn University of Technology, Akadeemia tee 15a, 12618 Tallinn, Estonia

Energies 2017, 10(11), 1760; https://doi.org/10.3390/en10111760 - 2 Nov 2017

Cited by 112 | Viewed by 14174

Abstract

Batteries are promising storage technologies for stationary applications because of their maturity, and the ease with which they are designed and installed compared to other technologies. However, they pose threats to the environment and human health. Several studies have discussed the various battery [...] Read more.

Batteries are promising storage technologies for stationary applications because of their maturity, and the ease with which they are designed and installed compared to other technologies. However, they pose threats to the environment and human health. Several studies have discussed the various battery technologies and applications, but evaluating the environmental impact of batteries in electrical systems remains a gap that requires concerted research efforts. This study first presents an overview of batteries and compares their technical properties such as the cycle life, power and energy densities, efficiencies and the costs. It proposes an optimal battery technology sizing and selection strategy, and then assesses the environmental impact of batteries in a typical renewable energy application by using a stand-alone photovoltaic (PV) system as a case study. The greenhouse gas (GHG) impact of the batteries is evaluated based on the life cycle emission rate parameter. Results reveal that the battery has a significant impact in the energy system, with a GHG impact of about 36–68% in a 1.5 kW PV system for different locations. The paper discusses new batteries, strategies to minimize battery impact and provides insights into the selection of batteries with improved cycling capacity, higher lifespan and lower cost that can achieve lower environmental impacts for future applications. Full article

(This article belongs to the Section D: Energy Storage and Application)

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12 pages, 5149 KiB

Open AccessArticle

An Impact-Based Frequency Up-Converting Hybrid Vibration Energy Harvester for Low Frequency Application

by Zhenlong Xu^1,*

, Wen Wang¹

, Jin Xie², Zhonggui Xu², Maoying Zhou¹ and Hong Yang³

¹ School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

² State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China

³ School of Medicine, Zhejiang University, Hangzhou 310058, China

Energies 2017, 10(11), 1761; https://doi.org/10.3390/en10111761 - 2 Nov 2017

Cited by 17 | Viewed by 4629

Abstract

In this paper, a novel impact-based frequency up-converting hybrid energy harvester (FUCHEH) was proposed. It consisted of a piezoelectric cantilever beam and a driving beam with a magnetic tip mass. A solenoid coil was attached at the end of the piezoelectric beam. This [...] Read more.

In this paper, a novel impact-based frequency up-converting hybrid energy harvester (FUCHEH) was proposed. It consisted of a piezoelectric cantilever beam and a driving beam with a magnetic tip mass. A solenoid coil was attached at the end of the piezoelectric beam. This innovative configuration amplified the relative motion velocity between magnet and coil, resulting in an enhancement of the induced electromotive force in the coil. An electromechanical coupling model was developed and a numerical simulation was performed to study the principle of impact-based frequency up-converting. A prototype was fabricated and experimentally tested. The time-domain and frequency-domain analyses were performed. Fast Fourier transform (FFT) analysis verified that fundamental frequencies and coupled vibration frequency contributes most of the output voltage. The measured maximum output power was 769.13 µW at a frequency of 13 Hz and an acceleration amplitude of 1 m/s², which was 3249.4%- and 100.6%-times larger than that of the frequency up-converting piezoelectric energy harvesters (FUCPEH) and frequency up-converting electromagnetic energy harvester (FUCEMEH), respectively. The root mean square (RMS) voltage of the piezoelectric energy harvester subsystem (0.919 V) was more than 16 times of that of the stand-alone PEH (0.055 V). This paper provided a new scheme to improve generating performance of the vibration energy harvester with high resonant frequency working in the low-frequency vibration environment. Full article

(This article belongs to the Special Issue Wireless Power Transfer and Energy Harvesting Technologies)

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12 pages, 3378 KiB

Open AccessArticle

Disturbance Elimination for Partial Discharge Detection in the Spacer of Gas-Insulated Switchgears

by Guoming Wang¹

, Gyung-Suk Kil^1,*

, Hong-Keun Ji² and Jong-Hyuk Lee³

¹ Department of Electrical and Electronics Engineering, Korea Maritime and Ocean University, Busan 49112, Korea

² Forensic Safety Section, National Forensic Service Busan Institute, Yangsan 50612, Korea

³ HVDC Production Team, LSIS Co., Ltd., Busan 46739, Korea

Energies 2017, 10(11), 1762; https://doi.org/10.3390/en10111762 - 2 Nov 2017

Cited by 12 | Viewed by 3936

Abstract

With the increasing demand for precise condition monitoring and diagnosis of gas-insulated switchgears (GISs), it has become a challenge to improve the detection sensitivity of partial discharge (PD) induced in the GIS spacer. This paper deals with the elimination of the capacitive component [...] Read more.

With the increasing demand for precise condition monitoring and diagnosis of gas-insulated switchgears (GISs), it has become a challenge to improve the detection sensitivity of partial discharge (PD) induced in the GIS spacer. This paper deals with the elimination of the capacitive component from the phase-resolved partial discharge (PRPD) signal generated in GIS spacers based on discrete wavelet transform (WT). Three types of typical insulation defects were simulated using PD cells. The single PD pulses were detected and were further used to determine the optimal mother wavelet. As a result, the bior6.8 was selected to decompose the PD signal into 8 levels and the signal energy at each level was calculated. The decomposed components related with capacitive disturbance were discarded, whereas those associated with PD were de-noised by a threshold and a thresholding function. Finally, the PRPD signals were reconstructed using the de-noised components. Full article

(This article belongs to the Section F: Electrical Engineering)

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23 pages, 718 KiB

Open AccessArticle

Optimization of Bioethanol In Silico Production Process in a Fed-Batch Bioreactor Using Non-Linear Model Predictive Control and Evolutionary Computation Techniques

by Hanniel Ferreira Sarmento de Freitas^1,2,*, José Eduardo Olivo² and Cid Marcos Gonçalves Andrade²

¹ Chemical Engineering Department, State University of Maringá, Colombo Av. 5790, 87020-900 Maringá, Brazil

² Federal Institute of Education, Science and Technology—Currais Novos Campus, Manoel Lopes Filho St., 773, 59380-000 Currais Novos, Brazil

Energies 2017, 10(11), 1763; https://doi.org/10.3390/en10111763 - 2 Nov 2017

Cited by 23 | Viewed by 4776

Abstract

Due to growing worldwide energy demand, the search for diversification of the energy matrix stands out as an important research topic. Bioethanol represents a notable alternative of renewable and environmental-friendly energy sources extracted from biomass, the bioenergy. Thus, the assurance of optimal growth [...] Read more.

Due to growing worldwide energy demand, the search for diversification of the energy matrix stands out as an important research topic. Bioethanol represents a notable alternative of renewable and environmental-friendly energy sources extracted from biomass, the bioenergy. Thus, the assurance of optimal growth conditions in the fermenter through operational variables manipulation is cardinal for the maximization of the ethanol production process yield. The current work focuses in the determination of optimal control scheme for the fermenter feed rate and batch end-time, evaluating different parametrization profiles, and comparing evolutionary computation techniques, the genetic algorithm (GA) and differential evolution (DE), using a dynamic real-time optimization (DRTO) approach for the in silico ethanol production optimization. The DRTO was able to optimize the reactor feed rate considering disturbances in the process input. Open-loop tests results obtained for the algorithms were superior to several works presented in the literature. The results indicate that the interaction between the intervals of DRTO cycles and parametrization profile is more significant for the GA, both in terms of ethanol productivity and batch time. In general lines, the present work presents a methodology for control and optimization studies applicable to other bioenergy generation systems. Full article

(This article belongs to the Section L: Energy Sources)

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26 pages, 13031 KiB

Open AccessArticle

Voltage Optimisation Technology for an Australian Abattoir—A Techno-Economic Evaluation

by GM Shafiullah^1,*

, Bond Watson², Christopher Lund¹, Md Moktadir Rahman¹, Gloria Rupf¹ and Jonathan Whale¹

¹ School of Engineering and IT, Murdoch University, Perth 6150, Australia

² Snowy Mountains Engineering Company (SMEC), Fortitude Valley, Brisbane 4006, Australia

Energies 2017, 10(11), 1764; https://doi.org/10.3390/en10111764 - 2 Nov 2017

Cited by 2 | Viewed by 5120

Abstract

Optimising voltage levels to a controlled stable level at a facility can not only reduce the cost of energy but also enhance equipment performance, prolong equipment life, reduce maintenance costs and reduce greenhouse gas emissions. Voltage optimisation (VO) technology has been widely used [...] Read more.

Optimising voltage levels to a controlled stable level at a facility can not only reduce the cost of energy but also enhance equipment performance, prolong equipment life, reduce maintenance costs and reduce greenhouse gas emissions. Voltage optimisation (VO) technology has been widely used in a number of different industries locally and internationally, but not to a large extent within the red meat processing sector in Australia. To determine whether VO technology can be implemented, and whether it is technically and economically viable for red meat processing sites, this study investigated, through case study analyses, the potential effectiveness of VO technology in Australian abattoirs. Through an extensive literature survey, the study initially explored the need and considerations of deploying VO technologies at a typical red meat processing plant. To determine the advantages of using VO technology the study then performed site analyses to investigate power quality (PQ) issues, such as voltage regulation, harmonics and power factor, at two typical medium-sized abattoirs, one in Western Australia and another in Queensland. Finally, an economic assessment of the use of VO in the red meat processing industry was undertaken to identify the potential electricity savings and payback periods. From the case study analyses, it is evident that power quality issues, such as under voltage, overvoltage, and harmonic distortion, can be reduced and significant energy savings can be achieved with the optimum selection of VO technology and voltage level. The outcomes of this study will enable engineering and operations staff to be better informed about the economic and technical benefits of (and possible issues with) using VO technologies in an abattoir. Full article

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29 pages, 5803 KiB

Open AccessFeature PaperArticle

A Decision Support Tool for Building Integrated Renewable Energy Microgrids Connected to a Smart Grid

by Damilola A. Asaleye

, Michael Breen and Michael D. Murphy^*

Department of Process, Energy and Transport Engineering, Cork Institute of Technology, Co. Cork T12 P928, Ireland

Energies 2017, 10(11), 1765; https://doi.org/10.3390/en10111765 - 2 Nov 2017

Cited by 20 | Viewed by 4803

Abstract

The objective of this study was to create a tool that will enable renewable energy microgrid (REμG) facility users to make informed decisions on the utilization of electrical power output from a building integrated REμG connected to a smart grid. A decision support [...] Read more.

The objective of this study was to create a tool that will enable renewable energy microgrid (REμG) facility users to make informed decisions on the utilization of electrical power output from a building integrated REμG connected to a smart grid. A decision support tool for renewable energy microgrids (DSTREM) capable of predicting photovoltaic array and wind turbine power outputs was developed. The tool simulated users’ daily electricity consumption costs, avoided CO₂ emissions and incurred monetary income relative to the usage of the building integrated REμG connected to the national electricity smart grid. DSTREM forecasted climate variables, which were used to predict REμG power output over a period of seven days. Control logic was used to prioritize supply of electricity to consumers from the renewable energy sources and the national smart grid. Across the evaluated REμG electricity supply options and during working days, electricity exported by the REμG to the national smart grid ranged from 0% to 61% of total daily generation. The results demonstrated that both monetary saving and CO₂ offsets can be substantially improved through the application of DSTREM to a REμG connected to a building. Full article

(This article belongs to the Section L: Energy Sources)

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17 pages, 3115 KiB

Open AccessArticle

A Novel Active Online State of Charge Based Balancing Approach for Lithium-Ion Battery Packs during Fast Charging Process in Electric Vehicles

by Xiudong Cui¹, Weixiang Shen^1,*

, Yunlei Zhang²

and Cungang Hu^2,*

¹ Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia

² School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China

Energies 2017, 10(11), 1766; https://doi.org/10.3390/en10111766 - 2 Nov 2017

Cited by 24 | Viewed by 5577

Abstract

Abstract: Non-uniformity of Lithium-ion cells in a battery pack is inevitable and has become the bottleneck to the pack capacity, especially in the fast charging process. Therefore, a balancing approach is essentially required. This paper proposes an active online cell balancing approach [...] Read more.

Abstract: Non-uniformity of Lithium-ion cells in a battery pack is inevitable and has become the bottleneck to the pack capacity, especially in the fast charging process. Therefore, a balancing approach is essentially required. This paper proposes an active online cell balancing approach in a fast charging process using the state of charge (SOC) as balancing criterion. The goal of this approach is to complete pack balancing within the limited charging time. An adaptive extended Kalman filter (AEKF) is applied to estimate the pack cell SOC during the charging process to obtain accurate results under modeling errors and measurement noises. To implement the proposed AEKF, only one additional current sensor is required to obtain the current of each cell required for the SOC estimation. An experimental platform is established to verify the effectiveness of the proposed approach. The results show that the proposed balancing approach with the SOC as a balancing criterion can overcome the challenges of non-uniformity and flat voltage plateau and charge more capacity into a LiFePO₄battery pack than those with the terminal voltage as a balancing criterion in the fast charging process. Full article

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11 pages, 2375 KiB

Open AccessArticle

Heat Modeling and Material Development of Mg-Based Nanomaterials Combined with Solid Oxide Fuel Cell for Stationary Energy Storage

by Huaiyu Shao^1,2

¹ Institute of Applied Physics and Materials Engineering (IAPME), University of Macau, Macau SAR, China

² International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan

Energies 2017, 10(11), 1767; https://doi.org/10.3390/en10111767 - 2 Nov 2017

Cited by 23 | Viewed by 4821

Abstract

Mg-based materials have been investigated as hydrogen storage materials, especially for possible onboard storage in fuel cell vehicles for decades. Recently, with the development of large-scale fuel cell technologies, the development of Mg-based materials as stationary storage to supply hydrogen to fuel-cell components [...] Read more.

Mg-based materials have been investigated as hydrogen storage materials, especially for possible onboard storage in fuel cell vehicles for decades. Recently, with the development of large-scale fuel cell technologies, the development of Mg-based materials as stationary storage to supply hydrogen to fuel-cell components and provide electricity and heat is becoming increasingly promising. In this work, numerical analysis of heat balance management for stationary solid oxide fuel cell (SOFC) systems combined with MgH₂ materials based on a carbon-neutral design concept was performed. Waste heat from the SOFC is supplied to hydrogen desorption as endothermic heat for the MgH₂ materials. The net efficiency of this model achieves 82% lower heating value (LHV), and the efficiency of electrical power output becomes 68.6% in minimizing heat output per total energy output when all available heat of waste gas and system is supplied to warm up the storage. For the development of Mg-based hydrogen storage materials, various nano-processing techniques have been widely applied to synthesize Mg-based materials with small particle and crystallite sizes, resulting in good hydrogen storage kinetics, but poor thermal conductivity. Here, three kinds of Mg-based materials were investigated and compared: 325 mesh Mg powers, 300 nm Mg nanoparticles synthesized by hydrogen plasma metal reaction, and Mg₅₀Co₅₀ metastable alloy with body-centered cubic structure. Based on the overall performances of hydrogen capacity, absorption kinetics and thermal conductivity of the materials, the Mg nanoparticle sample by plasma synthesis is the most promising material for this potential application. The findings in this paper may shed light on a new energy conversion and utilization technology on MgH₂-SOFC combined concept. Full article

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20 pages, 2841 KiB

Open AccessReview

A Comprehensive Study of Energy Conservation in Electric-Hydraulic Injection-Molding Equipment

by Hongjuan Zhang^1,*, Lu Ren¹, Yan Gao¹ and Baoquan Jin²

¹ College of Electrical and Power Engineering, Taiyuan University of Technology, Taiyuan 030024, China

² Key Laboratory of Advanced Transducers and Intelligent Control Systems, Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China

Energies 2017, 10(11), 1768; https://doi.org/10.3390/en10111768 - 2 Nov 2017

Cited by 18 | Viewed by 12268

Abstract

An injection-molding machine (IMM) is equipment that produces all kinds of plastic products. At present, the global production of IMMs amounts to more than 30 million units each year, and its total production accounts for 50% of all plastic molding equipment. Now, the [...] Read more.

An injection-molding machine (IMM) is equipment that produces all kinds of plastic products. At present, the global production of IMMs amounts to more than 30 million units each year, and its total production accounts for 50% of all plastic molding equipment. Now, the main energy consumption equipment of plastic processing plants consists in IMMs. Therefore, energy conservation research on IMMs has become urgent. This paper initially introduces the current development of IMMs. The working principle and the distribution of energy consumption of IMMs are then analyzed in detail. In addition, the methods and characteristics of the energy conservation technology in hydraulic control circuits and electrical control circuits are developed. Meanwhile, the recovery and the reuse of braking energy of IMMs are proposed. Moreover, some control strategies are discussed in order to improve energy efficiency. Finally, challenges and prospects for hydraulic IMMs are carried out. This paper thus provides a comprehensive review on energy-saving technology of electric-hydraulic injection-molding equipment for researchers. Full article

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18 pages, 5828 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study of Hydrogen Addition Effects on a Swirl-Stabilized Methane-Air Flame

by Mao Li^*, Yiheng Tong, Jens Klingmann and Marcus Thern

Department of Energy Sciences, Lund University, Ole Römers väg 1, SE-22100 Lund, Sweden

Energies 2017, 10(11), 1769; https://doi.org/10.3390/en10111769 - 3 Nov 2017

Cited by 10 | Viewed by 5205

Abstract

The effects of H₂ addition on a premixed methane-air flame was studied experimentally with a swirl-stabilized gas turbine model combustor. Experiments with 0%, 25%, and 50% H₂ molar fraction in the fuel mixture were conducted under atmospheric pressure. The primary objectives [...] Read more.

The effects of H₂ addition on a premixed methane-air flame was studied experimentally with a swirl-stabilized gas turbine model combustor. Experiments with 0%, 25%, and 50% H₂ molar fraction in the fuel mixture were conducted under atmospheric pressure. The primary objectives are to study the impacts of H₂ addition on flame lean blowout (LBO) limits, flame shapes and anchored locations, flow field characteristics, precessing vortex core (PVC) instability, as well as the CO emission performance. The flame LBO limits were identified by gradually reducing the equivalence ratio until the condition where the flame physically disappeared. The time-averaged CH chemiluminescence was used to reveal the characteristics of flame stabilization, e.g., flame structure and stabilized locations. In addition, the inverse Abel transform was applied to the time-averaged CH results so that the distribution of CH signal on the symmetric plane of the flame was obtained. The particle image velocimetry (PIV) was used to detect the characteristics of the flow field with a frequency of 2 kHz. The snapshot method of POD (proper orthogonal decomposition) and fast Fourier transform (FFT) were adopted to capture the most prominent coherent structures in the turbulent flow field. CO emission was monitored with an exhaust probe that was installed close to the combustor exit. The experimental results indicated that the H₂ addition extended the flame LBO limits and the operation range of low CO emission. The influence of H₂ addition on the flame shape, location, and flow field was observed. With the assistance of POD and FFT, the combustion suppression impacts on PVC was found. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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21 pages, 2986 KiB

Open AccessArticle

Probabilistic Optimal Power Dispatch in Multi-Carrier Networked Microgrids under Uncertainties

by Vahid Amir¹

, Shahram Jadid^2,*

and Mehdi Ehsan³

¹ Department of Electrical Engineering, Faculty of Electrical Engineering, Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran

² Department of Electrical Engineering, Faculty of Electrical Engineering, Iran University of Science and Technology, Tehran 1684613114, Iran

³ Department of Electrical Engineering, Faculty of Electrical Engineering, Sharif University of Technology, Tehran PO Box 1136511155, Iran

Energies 2017, 10(11), 1770; https://doi.org/10.3390/en10111770 - 3 Nov 2017

Cited by 19 | Viewed by 4304

Abstract

A microgrid (MG) is a small-scale version of the power system which makes possible the integration of renewable resources as well as achieving maximum demand side management (DSM) utilization. The future power system will be faced with severe uncertainties owing to penetration of [...] Read more.

A microgrid (MG) is a small-scale version of the power system which makes possible the integration of renewable resources as well as achieving maximum demand side management (DSM) utilization. The future power system will be faced with severe uncertainties owing to penetration of renewable resources. Consequently, the uncertainty assessment of system performance is essential. The conventional energy scheduling in an MG may not be suitable for active distribution networks. Hence, this study focuses on the probabilistic analysis of optimal power dispatch considering economic aspects in a multi-carrier networked microgrid. The aim is to study the impact of uncertain behavior of loads, renewable resources, and electricity market on the optimal management of a multi-carrier networked microgrid. Furthermore, a novel time-based demand side management is proposed in order to reshape the load curve, as well as preventing the excessive use of energy in peak hours. The optimization model is formulated as a mixed integer nonlinear program (MINLP) and is solved using MATLAB and GAMS software. Results show that the energy sharing capability between MCMGs and MCMGs and the main grids as well as utilization of demand side management can decrease operating costs for smart distribution grids. Full article

(This article belongs to the Section F: Electrical Engineering)

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22 pages, 2413 KiB

Open AccessArticle

A New Concept of Active Demand Side Management for Energy Efficient Prosumer Microgrids with Smart Building Technologies

by Andrzej Ożadowicz

AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering, al. Mickiewicza 30, 30-059 Krakow, Poland

Energies 2017, 10(11), 1771; https://doi.org/10.3390/en10111771 - 3 Nov 2017

Cited by 40 | Viewed by 7206

Abstract

Energy efficient prosumer microgrids (PMGs) with active and flexible demand side management (DSM) mechanisms are considered to be crucial elements of future smart grids. Due to an increasing share of renewable energy and the growing power demand, appropriate tools to manage not only [...] Read more.

Energy efficient prosumer microgrids (PMGs) with active and flexible demand side management (DSM) mechanisms are considered to be crucial elements of future smart grids. Due to an increasing share of renewable energy and the growing power demand, appropriate tools to manage not only the loads but also small generation units, heating and cooling systems, storage units and electric vehicles should be provided for them. Therefore, this paper proposes an innovative approach to both physical and logical organization of an active DSM system for future building-integrated prosumer microgrids (BIPMGs), based on standard building automation and control systems (BACS) as well as Internet of Things (IoT) paradigm. New event-triggered control functions with developed universal, logical interfaces for open BACS and IoT network nodes are presented and their implementation in smart metering as well as fully integrated energy management mechanisms is analyzed. Finally, potential energy efficiency improvements with proposed BACS functions are discussed, based on BACS efficiency requirements defined in the EN 15232 standard. Full article

(This article belongs to the Special Issue From Smart Metering to Demand Side Management)

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10 pages, 2997 KiB

Open AccessArticle

Switching Device Dead Time Optimization of Resonant Double-Sided LCC Wireless Charging System for Electric Vehicles

by Xi Zhang^1,*

, Ziyang Lai¹, Rui Xiong^2,*

, Zhe Li¹, Zhimin Zhang¹ and Liang Song¹

¹ School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

² National Engineering Laboratory for Electric Vehicles, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(11), 1772; https://doi.org/10.3390/en10111772 - 3 Nov 2017

Cited by 14 | Viewed by 5316

Abstract

Aiming at the reduction of the influence of the dead time setting on power level and efficiency of the inverter of double-sided LCC resonant wireless power transfer (WPT) system, a dead time soft switching optimization method for metal–oxide–semiconductor field-effect transistor (MOSFET) is proposed. [...] Read more.

Aiming at the reduction of the influence of the dead time setting on power level and efficiency of the inverter of double-sided LCC resonant wireless power transfer (WPT) system, a dead time soft switching optimization method for metal–oxide–semiconductor field-effect transistor (MOSFET) is proposed. At first, the mathematic description of double-sided LCC resonant wireless charging system is established, and the operating mode is analyzed as well, deducing the quantitative characteristic that the secondary side compensation capacitor C₂ can be adjusted to ensure that the circuit is inductive. A dead time optimization design method is proposed, contributing to achieving zero-voltage switching (ZVS) of the inverter, which is closely related to the performance of the WPT system. In the end, a prototype is built. The experimental results verify that dead time calculated by this optimized method can ensure the soft switching of the inverter MOSFET and promote the power and efficiency of the WPT. Full article

(This article belongs to the Special Issue The International Symposium on Electric Vehicles (ISEV2017))

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20 pages, 3964 KiB

Open AccessArticle

Hydrodynamic Modelling of Municipal Solid Waste Residues in a Pilot Scale Fluidized Bed Reactor

by João Cardoso¹, Valter Silva^1,2,*

, Daniela Eusébio¹ and Paulo Brito¹

¹ C3i—Interdisciplinary Center for Research and Innovation, Polytechnic Institute of Portalegre, 7300-110 Portalegre, Portugal

² INEGI-FEUP, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal

Energies 2017, 10(11), 1773; https://doi.org/10.3390/en10111773 - 3 Nov 2017

Cited by 12 | Viewed by 7179

Abstract

The present study investigates the hydrodynamics and heat transfer behavior of municipal solid waste (MSW) gasification in a pilot scale bubbling fluidized bed reactor. A multiphase 2-D numerical model following an Eulerian-Eulerian approach within the FLUENT framework was implemented. User defined functions (UDFs) [...] Read more.

The present study investigates the hydrodynamics and heat transfer behavior of municipal solid waste (MSW) gasification in a pilot scale bubbling fluidized bed reactor. A multiphase 2-D numerical model following an Eulerian-Eulerian approach within the FLUENT framework was implemented. User defined functions (UDFs) were coupled to improve hydrodynamics and heat transfer phenomena, and to minimize deviations between the experimental and numerical results. A grid independence study was accomplished through comparison of the bed volume fraction profiles and by reasoning the grid accuracy and computational cost. The standard deviation concept was used to determine the mixing quality indexes. Simulated results showed that UDFs improvements increased the accuracy of the mathematical model. Smaller size ratio of the MSW-dolomite mixture revealed a more uniform mixing, and larger ratios enhanced segregation. Also, increased superficial gas velocity promoted the solid particles mixing. Heat transfer within the fluidized bed showed strong dependence on the MSW solid particles sizes, with smaller particles revealing a more effective process. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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23 pages, 4050 KiB

Open AccessArticle

Energy-Saving Benefits of Adiabatic Humidification in the Air Conditioning Systems of Semiconductor Cleanrooms

by Min-Suk Jo, Jang-Hoon Shin, Won-Jun Kim and Jae-Weon Jeong^*

Department of Architectural Engineering, College of Engineering, Hanyang University, 222 Wangsimni-Ro, Seongdong-Gu, Seoul 04763, Korea

Energies 2017, 10(11), 1774; https://doi.org/10.3390/en10111774 - 3 Nov 2017

Cited by 28 | Viewed by 12812

Abstract

This paper aimed to evaluate the applicability of adiabatic humidification in the heating, ventilation, and air conditioning (HVAC) systems of semiconductor cleanrooms. Accurate temperature and humidity control are essential in semiconductor cleanrooms and high energy consumption steam humidification is commonly used. Therefore, we [...] Read more.

This paper aimed to evaluate the applicability of adiabatic humidification in the heating, ventilation, and air conditioning (HVAC) systems of semiconductor cleanrooms. Accurate temperature and humidity control are essential in semiconductor cleanrooms and high energy consumption steam humidification is commonly used. Therefore, we propose an adiabatic humidification system employing a pressurized water atomizer to reduce the energy consumption. The annual energy consumption of three different HVAC systems were analyzed to evaluate the applicability of adiabatic humidification. The studied cases were as follows: (1) CASE 1: a make-up air unit (MAU) with a steam humidifier, a dry cooling coil (DCC), and a fan filter unit (FFU); (2) CASE 2: a MAU with the pressurized water atomizer, a DCC, and a FFU; and (3) CASE 3: a MAU, a DCC, and a FFU, and the pressurized water atomizer installed in the return duct. The energy saving potential of adiabatic humidification over steam humidification has been proved, with savings of 8% and 23% in CASE 2 and CASE 3 compared to CASE 1, respectively. Furthermore, the pressurized water atomizer installed in the return duct exhibits greater energy saving effect than when installed in the MAU. Full article

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23 pages, 16039 KiB

Open AccessArticle

An Economical Route Planning Method for Plug-In Hybrid Electric Vehicle in Real World

by Yuanjian Zhang¹, Liang Chu¹, Zicheng Fu¹, Nan Xu^1,*

, Chong Guo¹, Yukuan Li¹, Zhouhuan Chen², Hanwen Sun², Qin Bai² and Yang Ou²

¹ State Key Laboratory of Automotive Dynamic Simulation and Control, Jilin University, Changchun 130022, China

² China Automotive Engineering Research Institute Co., Ltd, Chongqing 401122, China

Energies 2017, 10(11), 1775; https://doi.org/10.3390/en10111775 - 3 Nov 2017

Cited by 5 | Viewed by 6008

Abstract

Relieving the adverse effects of automobiles on the environment and natural resources has drawn the attention of numerous researchers. This paper seeks a new path to reach a target by focusing on the synergy of the vehicle and the environment. A real-time economical [...] Read more.

Relieving the adverse effects of automobiles on the environment and natural resources has drawn the attention of numerous researchers. This paper seeks a new path to reach a target by focusing on the synergy of the vehicle and the environment. A real-time economical route planning method for a plug-in hybrid electric vehicle (PHEV) is proposed. Three main contributions have been made. Firstly, a real comparison test is performed to provide rudimentary understanding of the difference in energy usage and route planning between PHEVs and conventional vehicles. Secondly, an approach to obtain PHEV customized data is developed for road weight calculation, which is the essential step in route planning. This method incorporates traffic data from conventional vehicles with the PHEV simulation model, obtaining the required data. Thirdly, the travel expense estimation model (TEEM) is designed. The TEEM could be applied to calculate the road weight of each road segment considering the impact on energy consumption with respect to environmental factors, providing the grounds for route planning. The proposed method to plan an economical route is evaluated, and the results justify its validation and ability to improve fuel economy. Full article

(This article belongs to the Special Issue Energy Management in Vehicle–Grid–Traffic Nexus)

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15 pages, 813 KiB

Open AccessArticle

Applicability of Compressive Sensing for Wireless Energy Harvesting Nodes

by Thu L. N. Nguyen¹

, Yoan Shin^1,*, Jin Young Kim² and Dong In Kim³

¹ School of Electronic Engineering, Soongsil University, Seoul 06978, Korea

² Department of Wireless Communications Engineering, Kwangwoon University, Seoul 01897, Korea

³ College of Information and Communication Engineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Korea

Energies 2017, 10(11), 1776; https://doi.org/10.3390/en10111776 - 3 Nov 2017

Viewed by 3224

Abstract

This paper proposes an approach toward solving an issue pertaining to measuring compressible data in large-scale energy-harvesting wireless sensor networks with channel fading. We consider a scenario in which N sensors observe hidden phenomenon values, transmit their observations using amplify-and-forward protocol over fading [...] Read more.

This paper proposes an approach toward solving an issue pertaining to measuring compressible data in large-scale energy-harvesting wireless sensor networks with channel fading. We consider a scenario in which N sensors observe hidden phenomenon values, transmit their observations using amplify-and-forward protocol over fading channels to a fusion center (FC), and the FC needs to choose a number of sensors to collect data and recover them according to the desired approximation error using the compressive sensing. In order to reduce the communication cost, sparse random matrices are exploited in the pre-processing procedure. We first investigate the sparse representation for sensors with regard to recovery accuracy. Then, we present the construction of sparse random projection matrices based on the fact that the energy consumption can vary across the energy harvesting sensor nodes. The key ingredient is the sparsity level of the random projection, which can greatly reduce the communication costs. The corresponding number of measurements is chosen according to the desired approximation error. Analysis and simulation results validate the potential of the proposed approach. Full article

(This article belongs to the Special Issue Wireless Power Transfer and Energy Harvesting Technologies)

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15 pages, 5665 KiB

Open AccessArticle

Enhancement of Condensation Heat Transfer Rate of the Air-Steam Mixture on a Passive Condenser System Using Annular Fins

by Yeong-Jun Jang¹, Dong-Jae Choi¹, Sin Kim², Myung-Taek Hyun³ and Yeon-Gun Lee^1,*

¹ Department of Nuclear and Energy Engineering, Jeju National University, 66 Jejudaehakno, Jeju-si, Jeju 63243, Korea

² School of Energy Systems Engineering, Chung-Ang University, Seoul 156-756, Korea

³ Department of Mechanical Engineering, Jeju National University, 66 Jejudaehakno, Jeju-si, Jeju 63243, Korea

Energies 2017, 10(11), 1777; https://doi.org/10.3390/en10111777 - 4 Nov 2017

Cited by 13 | Viewed by 6944

Abstract

This paper presents an experimental investigation on the enhancement of the heat transfer rate of steam condensation on the external surfaces of a vertical tube with annular fins. A cylindrical condenser tube, which is 40 mm in outer diameter and 1000 mm in [...] Read more.

This paper presents an experimental investigation on the enhancement of the heat transfer rate of steam condensation on the external surfaces of a vertical tube with annular fins. A cylindrical condenser tube, which is 40 mm in outer diameter and 1000 mm in length, with annular disks of uniform cross-sectional area is fabricated in the manner of ensuring perfect contact between the base surface and fins. A total of 13 annular fins of 80 mm diameter were installed along the tube height in order to increase the effective heat transfer area by 85%. Through a series of condensation tests for the air-steam mixture under natural convection conditions, the heat transfer data was measured in the pressure range of between 2 and 5 bar, and the air mass fraction from 0.3 to 0.7. The rates of heat transfer of the finned tube are compared to those that are measured on a bare tube to demonstrate the enhanced performance by extended surfaces. In addition, based on the experimental results and the characteristics of steam condensation, the applicability of finned tubes to a large condenser system with a bundle layout is evaluated. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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18 pages, 2843 KiB

Open AccessFeature PaperArticle

Energy and Reserve under Distributed Energy Resources Management—Day-Ahead, Hour-Ahead and Real-Time

by Tiago Soares¹

, Marco Silva²

, Tiago Sousa^2,3,*

, Hugo Morais²

and Zita Vale²

¹ INESC Technology and Science (INESC TEC), 4200-465 Porto, Portugal

² Department of Electrical Engineering, Research Group on Intelligent Engineering and Computing for Advanced Innovation and Development (GECAD), Institute of Engineering-Polytechnic of Porto (ISEP/IPP), 4249-015 Porto, Portugal

³ Department of Electrical Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark

Energies 2017, 10(11), 1778; https://doi.org/10.3390/en10111778 - 4 Nov 2017

Cited by 14 | Viewed by 4074

Abstract

The increasing penetration of distributed energy resources based on renewable energy sources in distribution systems leads to a more complex management of power systems. Consequently, ancillary services become even more important to maintain the system security and reliability. This paper proposes and evaluates [...] Read more.

The increasing penetration of distributed energy resources based on renewable energy sources in distribution systems leads to a more complex management of power systems. Consequently, ancillary services become even more important to maintain the system security and reliability. This paper proposes and evaluates a generic model for day-ahead, intraday (hour-ahead) and real-time scheduling, considering the joint optimization of energy and reserve in the scope of the virtual power player concept. The model aims to minimize the operation costs in the point of view of one aggregator agent taking into account the balance of the distribution system. For each scheduling stage, previous scheduling results and updated forecasts are considered. An illustrative test case of a distribution network with 33 buses, considering a large penetration of distribution energy resources allows demonstrating the benefits of the proposed model. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 1826 KiB

Open AccessReview

Analysis of Determinants of the Impact and the Grid Capability to Evaluate and Improve Grid Resilience from Extreme Weather Event

by Fauzan Hanif Jufri¹, Jun-Sung Kim²

and Jaesung Jung^1,*

¹ Department of Energy Systems Research, Ajou University, Suwon 16499, Korea

² Korea Electric Power Research Institute, Daejeon 34056, Korea

Energies 2017, 10(11), 1779; https://doi.org/10.3390/en10111779 - 5 Nov 2017

Cited by 36 | Viewed by 4897

Abstract

Concerns about the power outages caused by extreme weather events have led the study of grid resilience. Among the grid resilience studies, this paper presents an overview to evaluate and improve grid resilience through the analysis of determinants of the impact and the [...] Read more.

Concerns about the power outages caused by extreme weather events have led the study of grid resilience. Among the grid resilience studies, this paper presents an overview to evaluate and improve grid resilience through the analysis of determinants of the impact and the grid capability. The impact is determined by the extreme weather events, grid exposure, and grid vulnerability. Whereas, the determinants of the grid capability are physical durability, operational versatility, and rehabilitation capacity. Conceptual knowledge for quantifying the impact and the grid capability is also presented. Then, some improvement strategies to reduce the impact and to improve the grid capability based on their determinants are discussed. The study of the impact and the grid capability provides a preliminary guideline to plan appropriate grid resilience improvement strategies. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 5137 KiB

Open AccessArticle

Sliding Mode and Neural Network Control of Sensorless PMSM Controlled System for Power Consumption and Performance Improvement

by Ming-Shyan Wang^* and Tse-Ming Tsai

Department of Electrical Engineering, Southern Taiwan University of Science and Technology, 1, Nan-Tai St., Yung Kang District, Tainan City 710, Taiwan

Energies 2017, 10(11), 1780; https://doi.org/10.3390/en10111780 - 5 Nov 2017

Cited by 48 | Viewed by 6081

Abstract

This paper deals with the design of sliding mode control and neural network compensation for a sensorless permanent magnet synchronous motor (PMSM) controlled system that is able to improve both power consumption and speed response performance. The position sensor of PMSM is unreliable [...] Read more.

This paper deals with the design of sliding mode control and neural network compensation for a sensorless permanent magnet synchronous motor (PMSM) controlled system that is able to improve both power consumption and speed response performance. The position sensor of PMSM is unreliable in harsh environments. Therefore, the sensorless control technique is widely proposed in industry. A sliding mode observer can estimate the rotor angle and has the robustness to load disturbance and parameter variations. However, the sliding mode observer is not conducive to standstill and low speed conditions because the amplitude of the back EMF is almost zero. As a result, this paper combines an iterative sliding mode observer (ISMO) and neural networks (NNs) as an angle compensator to improve the above problems. A dsPIC30F6010A-based PMSM sensorless drive system is implemented to validate the proposed algorithm. The simulation and experimental results prove its effectiveness. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)

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14 pages, 5729 KiB

Open AccessArticle

The Thermoelectric Analysis of Different Heat Flux Conduction Materials for Power Generation Board

by Siyang Li

, Kwok Ho Lam and Ka Wai Eric Cheng^*

Power Electronics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University, 11, Hong Chong Road, Kowloon, Hong Kong

Energies 2017, 10(11), 1781; https://doi.org/10.3390/en10111781 - 5 Nov 2017

Cited by 9 | Viewed by 5716

Abstract

The development of the thermoelectric (TE) power generation is rapid, and the applications have extensively been studied. The principle is based on the Seebeck effect, in which the temperature difference between hot and cold sides of the TE material converts to electrical energy. [...] Read more.

The development of the thermoelectric (TE) power generation is rapid, and the applications have extensively been studied. The principle is based on the Seebeck effect, in which the temperature difference between hot and cold sides of the TE material converts to electrical energy. In this paper, a design is proposed to convert the thermal energy between indoor and outdoor of a board to electrical energy by the thermoelectric generator (TEG). Furthermore, the electrical energy generated is charged to supercapacitors as a battery or a power supply to the loads (e.g., lights) of the house. Besides the experimental work, a thermal model and an electrical model of the TEG have been proposed. To study the power generation performance in terms of materials, the simulation of the conversion efficiency of the TE board using materials with different thermal conductance have also been conducted. It was found that, using graphene as the thermally conductive material, the conversion efficiency was enhanced by 1.6% and 1.7%, when the temperature difference was 15 °C and 40 °C, respectively. Full article

(This article belongs to the Section F: Electrical Engineering)

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16 pages, 1168 KiB

Open AccessArticle

Smart Grid Applications for a Practical Implementation of IP over Narrowband Power Line Communications

by Noelia Uribe-Pérez¹, Itziar Angulo²

, David De la Vega^2,*

, Txetxu Arzuaga³, Igor Fernández² and Amaia Arrinda²

¹ Centre for the Development of Renewable Energy Sources—Research Centre for Energy, Environment and Technology (CEDER—CIEMAT), 42290 Lubia, Spain

² Department of Communications Engineering, ESI Bilbao, University of the Basque Country (UPV/EHU), 48013 Bilbao, Spain

³ ZIV Automation, 48170 Zamudio, Spain

Energies 2017, 10(11), 1782; https://doi.org/10.3390/en10111782 - 6 Nov 2017

Cited by 30 | Viewed by 6399

Abstract

Currently, Advanced Metering Infrastructure (AMI) systems have equipped the low voltage section with a communication system that is being used mainly for metering purposes, but it can be further employed for additional applications related to the Smart Grid (SG) concept. This paper explores [...] Read more.

Currently, Advanced Metering Infrastructure (AMI) systems have equipped the low voltage section with a communication system that is being used mainly for metering purposes, but it can be further employed for additional applications related to the Smart Grid (SG) concept. This paper explores the potential applications beyond metering of the available channel in a Power Line Communication-based AMI system. To that end, IP has been implemented over Narrow Band-Power Line Communication (NB-PLC) in a real microgrid, which includes an AMI system. A thorough review of potential applications for the SG that might be implemented for this representative case is included in order to provide a realistic analysis of the potentiality of NB-PLC beyond smart metering. The results demonstrate that existing AMI systems based on NB-PLC have the capacity to implement additional applications such as remote commands or status signals, which entails an added value for deployed AMI systems. Full article

(This article belongs to the Collection Smart Grid)

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26 pages, 10835 KiB

Open AccessArticle

Time Effect of Water Injection on the Mechanical Properties of Coal and Its Application in Rockburst Prevention in Mining

by Xiaofei Liu^1,2,*, Guang Xu³

, Chong Zhang^1,2, Biao Kong², Jifa Qian¹, Dong Zhu² and Mingyao Wei⁴

¹ Key Laboratory of Gas and Fire Control for Coal Mines (China University of Mining and Technology), Ministry of Education, Xuzhou 221116, China

² School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China

³ Department of Mining Engineering and Metallurgical Engineering, Western Australian School of Mines, Curtin University, Kalgoorlie, WA 6430, Australia

⁴ Institute of Rock and Soil Mechanic, Chinese Academy of Sciences, Wuhan 430071, China

Energies 2017, 10(11), 1783; https://doi.org/10.3390/en10111783 - 6 Nov 2017

Cited by 42 | Viewed by 4587

Abstract

Coal seam water injection is widely used to prevent rockbursts in coal mines, and the duration of water injection is an important parameter related to the effectiveness of rockburst prevention, making it of practical importance to optimize the effective water injection duration. This [...] Read more.

Coal seam water injection is widely used to prevent rockbursts in coal mines, and the duration of water injection is an important parameter related to the effectiveness of rockburst prevention, making it of practical importance to optimize the effective water injection duration. This paper presents the test results of the mechanical properties and pore structure of samples with different soaking time, obtained from a working face where rockburst occurred. Soaking time changes the mechanical properties of samples, and this time effect differs with the coal size (from centimeter to nanometer size). Results of numerical simulation and on-site tests in the Changgouyu coal mine demonstrated that water injection can effectively soften coal bodies and release or transfer stresses, and the time effect of water injection on rock prevention and control is apparent. Full article

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27 pages, 763 KiB

Open AccessArticle

Wind Power Ramp Events Prediction with Hybrid Machine Learning Regression Techniques and Reanalysis Data

by Laura Cornejo-Bueno¹, Lucas Cuadra^1,*

, Silvia Jiménez-Fernández¹

, Javier Acevedo-Rodríguez¹

, Luis Prieto² and Sancho Salcedo-Sanz¹

¹ Department of Signal Processing and Communications, Universidad de Alcalá, Alcalá de Henares, 28805 Madrid, Spain

² Iberdrola, 28033 Madrid, Spain

Energies 2017, 10(11), 1784; https://doi.org/10.3390/en10111784 - 6 Nov 2017

Cited by 28 | Viewed by 5757

Abstract

Wind Power Ramp Events (WPREs) are large fluctuations of wind power in a short time interval, which lead to strong, undesirable variations in the electric power produced by a wind farm. Its accurate prediction is important in the effort of efficiently integrating wind [...] Read more.

Wind Power Ramp Events (WPREs) are large fluctuations of wind power in a short time interval, which lead to strong, undesirable variations in the electric power produced by a wind farm. Its accurate prediction is important in the effort of efficiently integrating wind energy in the electric system, without affecting considerably its stability, robustness and resilience. In this paper, we tackle the problem of predicting WPREs by applying Machine Learning (ML) regression techniques. Our approach consists of using variables from atmospheric reanalysis data as predictive inputs for the learning machine, which opens the possibility of hybridizing numerical-physical weather models with ML techniques for WPREs prediction in real systems. Specifically, we have explored the feasibility of a number of state-of-the-art ML regression techniques, such as support vector regression, artificial neural networks (multi-layer perceptrons and extreme learning machines) and Gaussian processes to solve the problem. Furthermore, the ERA-Interim reanalysis from the European Center for Medium-Range Weather Forecasts is the one used in this paper because of its accuracy and high resolution (in both spatial and temporal domains). Aiming at validating the feasibility of our predicting approach, we have carried out an extensive experimental work using real data from three wind farms in Spain, discussing the performance of the different ML regression tested in this wind power ramp event prediction problem. Full article

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22 pages, 9824 KiB

Open AccessArticle

An Innovative Approach for Gob-Side Entry Retaining in Thick Coal Seam Longwall Mining

by Manchao He^1,†, Yubing Gao^1,2,*,†, Jun Yang^1,2 and Weili Gong^1,2

¹ State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Beijing 100083, China

² School of Mechanics and Civil Engineering, China University of Mining & Technology, Beijing 100083, China

^† These authors contributed equally to this work.

Energies 2017, 10(11), 1785; https://doi.org/10.3390/en10111785 - 6 Nov 2017

Cited by 134 | Viewed by 7423

Abstract

Gob-side entry retaining (GER) is a popular non-pillar mining technique regarding how to reserve a gateroad for the use of next panel mining. When used in thick coal seams, the conventional entry retaining method requires a huge amount of filling materials and may [...] Read more.

Gob-side entry retaining (GER) is a popular non-pillar mining technique regarding how to reserve a gateroad for the use of next panel mining. When used in thick coal seams, the conventional entry retaining method requires a huge amount of filling materials and may cause entry (gateroad) accidents. Thus, an innovative non-pillar longwall mining approach is introduced. First, structural and mechanical models were built to explore the mechanism of the new approach. The modeling results indicate that effective bulking of the gob roof and reasonable support of the entry roof were key governing factors in improving entry stabilities and reducing roof deformations. Accordingly, a directional roof fracturing technique was proposed to contribute to gob roof caving, and a constant resistance and large deformation anchor (CRLDA) cable was used to stabilize the entry roof. Subsequently, the evolutionary laws of the roof structure and stresses were explored using numerical simulation. It was found that the structure of the surrounding rocks around the retained entry changed significantly after roof fracturing. The stress-bearing center was transferred to the gob area, and the entry roof was in a low stress environment after adopting the approach. Finally, the approach was tested on a thick coal seam longwall mining panel. Field monitoring indicates that the retained entry was in a stable state and the index of the retained entry met the requirement of the next mining panel. This work provides an effective and economical approach to non-pillar longwall mining in thick coal seams. Full article

(This article belongs to the Special Issue Mathematical and Computational Modeling in Geothermal Engineering)

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15 pages, 1210 KiB

Open AccessArticle

Universal Generating Function Based Probabilistic Production Simulation Approach Considering Wind Speed Correlation

by Yan Li¹, Ming Zhou^1,*, Dawei Wang¹, Yuehui Huang² and Zifen Han³

¹ State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China

² China Electric Power Research Institute (CEPRI), Beijing 100192, China

³ State Grid Gansu Electric Power Company, Lanzhou 730070, China

Energies 2017, 10(11), 1786; https://doi.org/10.3390/en10111786 - 6 Nov 2017

Cited by 11 | Viewed by 3535

Abstract

Due to the volatile and correlated nature of wind speed, a high share of wind power penetration poses challenges to power system production simulation. Existing power system probabilistic production simulation approaches are in short of considering the time-varying characteristics of wind power and [...] Read more.

Due to the volatile and correlated nature of wind speed, a high share of wind power penetration poses challenges to power system production simulation. Existing power system probabilistic production simulation approaches are in short of considering the time-varying characteristics of wind power and load, as well as the correlation between wind speeds at the same time, which brings about some problems in planning and analysis for the power system with high wind power penetration. Based on universal generating function (UGF), this paper proposes a novel probabilistic production simulation approach considering wind speed correlation. UGF is utilized to develop the chronological models of wind power that characterizes wind speed correlation simultaneously, as well as the chronological models of conventional generation sources and load. The supply and demand are matched chronologically to not only obtain generation schedules, but also reliability indices both at each simulation interval and the whole period. The proposed approach has been tested on the improved IEEE-RTS 79 test system and is compared with the Monte Carlo approach and the sequence operation theory approach. The results verified the proposed approach with the merits of computation simplicity and accuracy. Full article

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21 pages, 4818 KiB

Open AccessFeature PaperReview

A Critical Review of Spinel Structured Iron Cobalt Oxides Based Materials for Electrochemical Energy Storage and Conversion

by Hongyan Gao¹, Shuai Liu², Yafei Li², Eric Conte¹ and Yan Cao^1,2,*

¹ Department of Chemistry, Western Kentucky University, Bowling Green, KY 42101, USA

² College of Chemistry & Chemical Engineering, Anhui University, Hefei 230601, China

Energies 2017, 10(11), 1787; https://doi.org/10.3390/en10111787 - 6 Nov 2017

Cited by 61 | Viewed by 8252

Abstract

Iron cobalt oxides, such as typical FeCo₂O₄ and CoFe₂O₄, are two spinel structured transitional metal oxide materials with excellent electrochemical performance. As the electrodes, they have been widely applied in the current energy storage and conversion [...] Read more.

Iron cobalt oxides, such as typical FeCo₂O₄ and CoFe₂O₄, are two spinel structured transitional metal oxide materials with excellent electrochemical performance. As the electrodes, they have been widely applied in the current energy storage and conversion processes such as supercapacitors, Lithium-ion batteries and fuel cells. Based on synthesis approaches and controlled conditions, these two materials exhibited broad morphologies and nanostructures and thus distinct electrochemical performance. Some of them have shown promising applications as electrodes in energy storage and conversion. The incorporation with other materials to form composites further improved their performance. This review briefly summarized the recent applications of FeCo₂O₄ and CoFe₂O₄in energy storage and conversion, current understandings on mechanisms and especially the relevance of morphologies and structures and composites to electrochemical performance. Some recommendations were finally put forward addressing current issues and future prospects on electrodes of FeCo₂O₄ and CoFe₂O₄based materials in energy storage and conversion, implying there was still space to further optimize their performance. Full article

(This article belongs to the Section D: Energy Storage and Application)

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19 pages, 8213 KiB

Open AccessArticle

Sliding Mode Control of DFIG Wind Turbines with a Fast Exponential Reaching Law

by Linyun Xiong, Penghan Li, Hao Li and Jie Wang^*

School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2017, 10(11), 1788; https://doi.org/10.3390/en10111788 - 7 Nov 2017

Cited by 38 | Viewed by 5451

Abstract

This paper proposes a novel sliding mode control (SMC) technique for doubly fed induction generators (DFIGs) based on the fast exponential reaching law (FERL). The proposed FERL-based SMC is capable of reducing to a large extent the chattering phenomena existing in the sliding [...] Read more.

This paper proposes a novel sliding mode control (SMC) technique for doubly fed induction generators (DFIGs) based on the fast exponential reaching law (FERL). The proposed FERL-based SMC is capable of reducing to a large extent the chattering phenomena existing in the sliding stage. Meanwhile, the reaching stage is accelerated with the introduction of an adaptive gain. The proposed method is employed in a DFIG-based wind energy conversion system (WECS) for direct power control (DPC). The FERL-based DPC approach is tested with simulations conducted in Matlab/Simulink under the scenarios of unbalanced grid voltage, grid fault conditions and highly unstable wind speed accompanied by an experimental study. The simulations and experimental results reveal the better performance of the proposed control method in active/reactive power tracking and dc-link voltage maintenance. Full article

(This article belongs to the Section F: Electrical Engineering)

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14 pages, 4509 KiB

Open AccessArticle

Evaluation of Electrical Tree Degradation in Cross-Linked Polyethylene Cable Using Weibull Process of Propagation Time

by Donguk Jang¹ and Seonghee Park^2,*

¹ Metropolitan Transportation Research Center, Korea Railroad Research Institute, Uiwang 16105, Korea

² ICT Fusion Green Energy Center, Wonkwang University, Iksan 54538, Korea

Energies 2017, 10(11), 1789; https://doi.org/10.3390/en10111789 - 7 Nov 2017

Cited by 6 | Viewed by 4136

Abstract

The main purpose of this paper is to evaluate electrical tree degradation for cross-linked polyethylene (XLPE) cable insulation for three difference models. In order to show the distribution characteristics using phase resolved partial discharge (PD), we acquire data by using a PD detecting [...] Read more.

The main purpose of this paper is to evaluate electrical tree degradation for cross-linked polyethylene (XLPE) cable insulation for three difference models. In order to show the distribution characteristics using phase resolved partial discharge (PD), we acquire data by using a PD detecting system. These acquired data presented four 2D distributions such as phase angle-average discharge distribution, pulse magnitude-pulse number distribution, phase angle-pulse number distribution, and phase angle-maximum discharge derived from the distribution of PD. From the analysis of these distributions, each of the tree models are proved to hold its unique characteristics and the results were then applied as basic specific qualities. In order to evaluate the progresses of an electrical tree, we proposed methods using parameters by means of Weibull distribution to the time of tree propagation. We measured the time of tree propagation for 16 specimens of each artificial tree models from initiation stage, middle stage, and final stage respectively, using these breakdown data, we estimated the shape parameter, scale parameter, and mean time to failure. It is possible to analyze the difference in lifetime between the initial stage, the middle stage, and the final stage, and could be used to predict the lifetime of an XLPE cable from these results. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 1076 KiB

Open AccessReview

Environmentally-Benign Dimethyl Carbonate-Mediated Production of Chemicals and Biofuels from Renewable Bio-Oil

by Keon Hee Kim and Eun Yeol Lee^*

Department of Chemical Engineering, Kyung Hee University, Gyeonggi-do 17104, Korea

Energies 2017, 10(11), 1790; https://doi.org/10.3390/en10111790 - 7 Nov 2017

Cited by 36 | Viewed by 8110

Abstract

Due to the increasing emission of carbon dioxide (CO₂), the development of fuels and chemicals based on renewable resources has attracted much attention. Bio-oil, as a carbon rich material, has been considered as a feedstock for biodiesel production. In conventional methanol-mediated [...] Read more.

Due to the increasing emission of carbon dioxide (CO₂), the development of fuels and chemicals based on renewable resources has attracted much attention. Bio-oil, as a carbon rich material, has been considered as a feedstock for biodiesel production. In conventional methanol-mediated transesterification of bio-oil for biodiesel production, significant amounts of glycerol are being generated as a byproduct. In order to overcome these issues, dimethyl carbonate (DMC) has been recently used as an alternative acyl acceptor to avoid the generation of glycerol. DMC is an environmentally-benign chemical reagent and reactive solvent due to safety, health, and environmental benefits. Moreover, DMC can be produced from CO₂. Co-production of biodiesel and chemicals such as glycerol carbonate is possible as the concept of zero-waste utilization of bio-oil. Value-added chemicals can be synthesized using DMC as a reagent. This paper provides a review on the physical and chemical properties of DMC as a solvent, as well as the production methods for DMC. DMC-mediated production of various chemicals and fuels in both chemical and enzymatic processes are discussed together with their pros and cons. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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14 pages, 6422 KiB

Open AccessArticle

Deterministic Algorithm for Selective Shunt Active Power Compensators According to IEEE Std. 1459

by Nicolás Muñoz-Galeano¹

, Salvador Orts-Grau^2,*

, Salvador Seguí-Chilet², Francisco J. Gimeno-Sales² and Jesús M. López-Lezama¹

¹ Departamento de Ingeniería Eléctrica, Facultad de Ingeniería, Universidad de Antioquia, calle 67 No 53-108, 050010 Medellín, Colombia

² Instituto Interuniversitario de Investigación de Reconocimiento Molecular y Desarrollo Tecnológico, Universitat Politècnica de València, Camino de Vera 14, 46022 Valencia, Spain

Energies 2017, 10(11), 1791; https://doi.org/10.3390/en10111791 - 7 Nov 2017

Cited by 1 | Viewed by 2865

Abstract

This paper proposes a deterministic algorithm to scale the reference currents of a shunt active power compensator (SAPC) based on IEEE Std. 1459 power decomposition when SAPC maximum output compensating current is going to be exceeded. The selective SAPC is proposed to improve [...] Read more.

This paper proposes a deterministic algorithm to scale the reference currents of a shunt active power compensator (SAPC) based on IEEE Std. 1459 power decomposition when SAPC maximum output compensating current is going to be exceeded. The selective SAPC is proposed to improve power quality and energy efficiency in power networks by means of the cancelation or reduction of the non-efficient powers (Q₁⁺, S_U₁, S_eN). The non-efficient powers can be reduced in six possible sequences according to the priority of compensation. When SAPC maximum output current capacity is exceeded, the proposed algorithm limits the SAPC output compensating currents and the non-efficient currents can only be partially reduced in the power network. The reduction of the non-efficient powers depends on the selected compensation sequence. Experimental results for several compensation sequences demonstrate the appropriate operation of the selective SAPC using the proposed scaling algorithm. Full article

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18 pages, 17687 KiB

Open AccessArticle

A 3D-Space Vector Modulation Algorithm for Three Phase Four Wire Neutral Point Clamped Inverter Systems as Power Quality Compensator

by Palanisamy Ramasamy^*

and Vijayakumar Krishnasamy

Department of EEE, SRM University, Chennai 60203, India

Energies 2017, 10(11), 1792; https://doi.org/10.3390/en10111792 - 7 Nov 2017

Cited by 20 | Viewed by 9893

Abstract

A Unified Power Quality Conditioner (UPQC) is designed using a Neutral Point Clamped (NPC) multilevel inverter to improve the power quality. When designed for high/medium voltage and power applications, the voltage stress across the switches and harmonic content in the output voltage are [...] Read more.

A Unified Power Quality Conditioner (UPQC) is designed using a Neutral Point Clamped (NPC) multilevel inverter to improve the power quality. When designed for high/medium voltage and power applications, the voltage stress across the switches and harmonic content in the output voltage are increased. A 3-phase 4-wire NPC inverter system is developed as Power Quality Conditioner using an effectual three dimensional Space Vector Modulation (3D-SVM) technique. The proposed system behaves like a UPQC with shunt and series active filter under balanced and unbalanced loading conditions. In addition to the improvement of the power quality issues, it also balances the neutral point voltage and voltage balancing across the capacitors under unbalanced condition. The hardware and simulation results of proposed system are compared with 2D-SVM and 3D-SVM. The proposed system is stimulated using MATLAB and the hardware is designed using FPGA. From the results it is evident that effectual 3D-SVM technique gives better performance compared to other control methods. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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19 pages, 3247 KiB

Open AccessArticle

Harmonic Adaptability Remote Testing Method for Offshore Wind Turbines

by Zimin Jiang¹, Changgang Li^1,*, Xiaohao Liu¹, Yutian Liu¹ and Ruiming Wang²

¹ Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education, Shandong University, Jinan 250061, China

² China Electric Power Research Institute, Beijing 100192, China

Energies 2017, 10(11), 1793; https://doi.org/10.3390/en10111793 - 7 Nov 2017

Cited by 3 | Viewed by 3181

Abstract

Harmonic adaptability (HA) capability is required for large-scale onshore and offshore wind turbines (WTs) connected to the grid. To ensure that the distortion of the harmonic voltage at the grid access point generated by grid simulator is in accordance with the required value, [...] Read more.

Harmonic adaptability (HA) capability is required for large-scale onshore and offshore wind turbines (WTs) connected to the grid. To ensure that the distortion of the harmonic voltage at the grid access point generated by grid simulator is in accordance with the required value, this paper proposes an on-site HA remote testing method for offshore WTs to eliminate submarine cable effects. The deviation compensation method detects the integer harmonic voltage distortion based on instantaneous reactive power theory, and the deviation from the required value is compensated by series active power filter. In order to further reduce the capacity of the designed device, integer harmonics close to the resonant frequency are suppressed by the selective harmonic damping (SHD) method initially. Owing to the attenuation of extreme amplification, the deviation determining the equipment capacity is decreased correspondingly. As a small synthesized impedance working for the selected frequency can suppress the amplification significantly, a low power ratings design for the SHD method can be achieved, and undesired resonance can be avoided. Simulation results indicate that the proposed method can make the harmonic distortion within the error tolerance. Full article

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6 pages, 1090 KiB

Open AccessLetter

An Affine Arithmetic-Based Power Flow Algorithm Considering the Regional Control of Unscheduled Power Fluctuation

by Lizi Luo¹, Wei Gu^1,*, Yonghui Wang² and Chunxi Chen²

¹ School of Electrical Engineering, Southeast University, Nanjing 210096, China

² Ninghai Power Supply Company, Zhejiang Electric Power Company of State Grid, Ningbo 315600, China

Energies 2017, 10(11), 1794; https://doi.org/10.3390/en10111794 - 7 Nov 2017

Cited by 13 | Viewed by 3345

Abstract

With consideration of the intermittency of renewable generation and uncertain load, a regional control strategy is presented to smooth the unscheduled power fluctuation in this letter. Then, an affine arithmetic-based modeling method is proposed to describe the unscheduled power tracking characteristic of dispatchable [...] Read more.

With consideration of the intermittency of renewable generation and uncertain load, a regional control strategy is presented to smooth the unscheduled power fluctuation in this letter. Then, an affine arithmetic-based modeling method is proposed to describe the unscheduled power tracking characteristic of dispatchable generation resources (DGRs), based on which interval power flow solutions with narrower ranges can be obtained. Finally, the proposed algorithm is applied to a modified IEEE 33-bus distribution system to demonstrate its effectiveness. Full article

(This article belongs to the Section F: Electrical Engineering)

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16 pages, 2698 KiB

Open AccessArticle

A Real-Time Digital Solver for Smart Substation Based on Orders

by Bingda Zhang^*, Yanjie Wu, Zhao Jin and Yang Wang

The Key Laboratory of Smart Grid of Ministry of Education, Tianjin University, Tianjin 300072, China

Energies 2017, 10(11), 1795; https://doi.org/10.3390/en10111795 - 7 Nov 2017

Cited by 15 | Viewed by 3255

Abstract

In order to expand the simulation scale of smart substation, a simulation model of the inlet-outlet line unit, as described by the 0/10⁸ S conductance for multivalued coefficients pre-storage is presented in this paper. As a part of orders decomposition, the address [...] Read more.

In order to expand the simulation scale of smart substation, a simulation model of the inlet-outlet line unit, as described by the 0/10⁸ S conductance for multivalued coefficients pre-storage is presented in this paper. As a part of orders decomposition, the address conversion circuit for multivalued coefficients can reduce the computational burden of processing elements. For the convenience of the generalization of the real-time digital solver based on FPGA (FRTDS, FPGA: Field–Programmable Gate Array), the address conversion circuit for multivalued coefficients is matched with the guide word, the formation module of sampled value (SV) packet, and the resolution module of generic object oriented substation event (GOOSE) packet are associated with the application identification (APPID) in the Ethernet frame. The address conversion circuit for multivalued coefficients, the formation module of SV packet, and the resolution module of GOOSE packet are reconstructed via the orders. A hardware-in-the-loop real-time simulation platform for smart substation is built based on the novel FRTDS. A case is given to demonstrate the simulation calculating capability and the hardware-in-the-loop ability of the novel FRTDS. Full article

(This article belongs to the Section F: Electrical Engineering)

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19 pages, 8257 KiB

Open AccessArticle

Freeway Driving Cycle Construction Based on Real-Time Traffic Information and Global Optimal Energy Management for Plug-In Hybrid Electric Vehicles

by Hongwen He^1,2,*, Jinquan Guo^1,2,*, Nana Zhou^1,2, Chao Sun^1,2 and Jiankun Peng^1,2

¹ National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology, Beijing 100081, China

² Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(11), 1796; https://doi.org/10.3390/en10111796 - 8 Nov 2017

Cited by 21 | Viewed by 5355

Abstract

This paper presents a freeway driving cycle (FDC) construction method based on traffic information. A float car collected different type of roads in California and we built a velocity fragment database. We selected a real freeway driving cycle (RFDC) and established the corresponding [...] Read more.

This paper presents a freeway driving cycle (FDC) construction method based on traffic information. A float car collected different type of roads in California and we built a velocity fragment database. We selected a real freeway driving cycle (RFDC) and established the corresponding time traffic information tensor model by using the data in California Department of Transportation performance measure system (PeMS). The correlation of road velocity in the time dimension and spatial dimension are analyzed. According to the average velocity of road sections at different times, the kinematic fragments are stochastically selected in the velocity fragment database to construct a real-time FDC of each section. The comparison between construction freeway driving cycle (CFDC) and real freeway driving cycle (RFDC) show that the CFDC well reflects the RFDC characteristic parameters. Compared to its application in plug-in electric hybrid vehicle (PHEV) optimal energy management based on a dynamic programming (DP) algorithm, CFDC and RFDC fuel consumption are similar within approximately 5.09% error, and non-rush hour fuel economy is better than rush hour 3.51 (L/100 km) at non-rush hour, 4.29 (L/km) at rush hour)). Moreover, the fuel consumption ratio can be up to 13.17% in the same CFDC at non-rush hour. Full article

(This article belongs to the Special Issue The International Symposium on Electric Vehicles (ISEV2017))

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18 pages, 4366 KiB

Open AccessArticle

An Extended System Frequency Response Model Considering Wind Power Participation in Frequency Regulation

by Yi Tang¹, Jianfeng Dai^1,*, Jia Ning¹, Jie Dang², Yan Li³ and Xinshou Tian³

¹ Jiangsu Provincial Key Laboratory of Smart Grid Technology & Equipment, Southeast University, Nanjing 210096, China

² Technology Center of Central China Grid, Wuhan 430077, China

³ State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems, China Electric Power Research Institute, Beijing 100192, China

Energies 2017, 10(11), 1797; https://doi.org/10.3390/en10111797 - 8 Nov 2017

Cited by 12 | Viewed by 4803

Abstract

With increasing penetration of wind power into the power system, wind power participation in frequency regulation is regarded as a beneficial strategy to improve the dynamic frequency response characteristics of power systems. The traditional power system frequency response (SFR) model, which only includes [...] Read more.

With increasing penetration of wind power into the power system, wind power participation in frequency regulation is regarded as a beneficial strategy to improve the dynamic frequency response characteristics of power systems. The traditional power system frequency response (SFR) model, which only includes synchronous generators, is no longer suitable for power systems with high penetrated wind power. An extended SFR model, based on the reduced-order model of wind turbine generator (WTG) and the traditional SFR model, is presented in this paper. In the extended SFR model, the reduced-order model of WTG with combined frequency control is deduced by employing small signal analysis theory. Afterwards, the stability analysis of a closed-loop control system for the extended SFR model is carried out. Time-domain simulations using a test system are performed to validate the effectiveness of the extended SFR model; this model can provide a simpler, clearer and faster way to analyze the dynamic frequency response characteristic for a high-wind integrated power systems. The impact of additional frequency control parameters and wind speed disturbances on the system dynamic frequency response characteristics are investigated. Full article

(This article belongs to the Special Issue Wind Generators Modelling and Control)

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23 pages, 3689 KiB

Open AccessArticle

Minimization of the Electromagnetic Torque Ripple Caused by the Coils Inter-Turn Short Circuit Fault in Dual-Redundancy Permanent Magnet Synchronous Motors

by Yiguang Chen^* and Bo Zhang

Key Laboratory of Smart Grid of Ministry of Education, Tianjin University, Tianjin 300072, China

Energies 2017, 10(11), 1798; https://doi.org/10.3390/en10111798 - 8 Nov 2017

Cited by 18 | Viewed by 5133

Abstract

With the development of electric vehicles and More-Electric/All-Electric aircraft, high reliability is required in motor servo systems. The redundancy technique is one of the most effective methods to improve the reliability of motor servo systems. In this paper, the structure of dual-redundancy permanent [...] Read more.

With the development of electric vehicles and More-Electric/All-Electric aircraft, high reliability is required in motor servo systems. The redundancy technique is one of the most effective methods to improve the reliability of motor servo systems. In this paper, the structure of dual-redundancy permanent magnet synchronous motor (DRPMSM) with weak thermal coupling and no electromagnetic coupling is analyzed and the mathematical model of this motor is established. However, there is little research on how to suppress the torque ripple caused by short-circuited coils in the DRPMSM. The main contribution of this paper is to present the advantages of DRPMSM and to find a way to suppress the torque ripple caused by the short circuit fault in DRPMSM. In order to improve operation quality and enhance the reliability of DRPMSM after a short circuit occurs, the torque ripple caused by the coils inter-turn short circuit fault in DRPMSM is analyzed in detail. Then, a control method for suppressing the electromagnetic torque ripple of a short-circuited coil is proposed for the first time by using an improved adaptive proportional resonant (PR) controller and a proportional integral (PI) controller in parallel. PR control is a method of controlling alternating components without steady-state error, and it can be used to suppress torque ripple. DRPMSM adopts speed and current double closed-loop control strategies. An improved adaptive PR controller and a PI controller are employed in parallel for the speed loop, while traditional PI control is adopted in current loop. From the simulation and experimental results, the torque ripple is reduced from 45.4 to 5.6% when the torque ripple suppression strategy proposed in this paper is adopted, in the case that the speed is 600 r/min. The torque ripple suppression strategy based on the PR controller can quickly and effectively suppress the torque ripple caused by the short-circuited coils, which makes the motor speed more stable. Full article

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26 pages, 12026 KiB

Open AccessArticle

Interlink Converter with Linear Quadratic Regulator Based Current Control for Hybrid AC/DC Microgrid

by Dwi Riana Aryani, Jung-Su Kim and Hwachang Song^*

Department of Electrical and Information Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea

Energies 2017, 10(11), 1799; https://doi.org/10.3390/en10111799 - 8 Nov 2017

Cited by 19 | Viewed by 5930

Abstract

A hybrid alternate current/direct current (AC/DC) microgrid consists of an AC subgrid and a DC subgrid, and the subgrids are connected through the interlink bidirectional AC/DC converter. In the stand-alone operation mode, it is desirable that the interlink bidirectional AC/DC converter manages proportional [...] Read more.

A hybrid alternate current/direct current (AC/DC) microgrid consists of an AC subgrid and a DC subgrid, and the subgrids are connected through the interlink bidirectional AC/DC converter. In the stand-alone operation mode, it is desirable that the interlink bidirectional AC/DC converter manages proportional power sharing between the subgrids by transferring power from the under-loaded subgrid to the over-loaded one. In terms of system security, the interlink bidirectional AC/DC converter takes an important role, so proper control strategies need to be established. In addition, it is assumed that a battery energy storage system is installed in one subgrid, and the coordinated control of interlink bidirectional AC/DC converter and battery energy storage system converter is required so that the power sharing scheme between subgrids becomes more efficient. For the purpose of designing a tracking controller for the power sharing by interlink bidirectional AC/DC converter in a hybrid AC/DC microgrid, a droop control method generates a power reference for interlink bidirectional AC/DC converter based on the deviation of the system frequency and voltages first and then interlink bidirectional AC/DC converter needs to transfer the power reference to the over-loaded subgrid. For efficiency of this power transferring, a linear quadratic regulator with exponential weighting for the current regulation of interlink bidirectional AC/DC converter is designed in such a way that the resulting microgrid can operate robustly against various uncertainties and the power sharing is carried out quickly. Simulation results show that the proposed interlink bidirectional AC/DC converter control strategy provides robust and efficient power sharing scheme between the subgrids without deteriorating the secure system operation. Full article

(This article belongs to the Section F: Electrical Engineering)

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20 pages, 5796 KiB

Open AccessArticle

A New Reactive-Power Sharing Scheme for Two Inverter-Based Distributed Generations with Unequal Line Impedances in Islanded Microgrids

by Jae-Hyuk Kim, Yoon-Seok Lee, Hyun-Jun Kim and Byung-Moon Han^*

Department of Electrical Engineering, Myong-ji University, 116 Myongji-ro, Yongin-si, Gyeonggi-do 449-728, Korea

Energies 2017, 10(11), 1800; https://doi.org/10.3390/en10111800 - 8 Nov 2017

Cited by 11 | Viewed by 4209

Abstract

This paper proposes a new reactive-power sharing scheme to reduce the circulating current when two inverter-based distributed generations (DGs) operate in parallel through unequal line impedances in an islanded microgrid. If the terminal voltages of the two DGs are not equal due to [...] Read more.

This paper proposes a new reactive-power sharing scheme to reduce the circulating current when two inverter-based distributed generations (DGs) operate in parallel through unequal line impedances in an islanded microgrid. If the terminal voltages of the two DGs are not equal due to the unequal line impedances, a circulating current due to reactive-power unbalance occurs, which increases system loss. The proposed droop control compensates the terminal voltage difference to reduce the circulating current by considering a feed-forward path of the line voltage drop. The feasibility of the proposed droop control was first verified through computer simulations, and then experiments with a hardware set-up in the lab. The experimental results were compared with the simulation results to confirm the feasibility of the proposed droop control. Full article

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24 pages, 3303 KiB

Open AccessArticle

Communication Characteristics of Faulted Overhead High Voltage Power Lines at Low Radio Frequencies

by Nermin Suljanović¹, Aljo Mujčić¹ and Matej Zajc^2,*

¹ Faculty of Electrical Engineering, University of Tuzla, Franjevačka 2, 75000 Tuzla, Bosnia and Herzegovina

² Faculty of Electrical Engineering, University of Ljubljana, Trzaška 25, SI-1000 Ljubljana, Slovenia

Energies 2017, 10(11), 1801; https://doi.org/10.3390/en10111801 - 8 Nov 2017

Cited by 2 | Viewed by 4128

Abstract

This paper derives a model of high-voltage overhead power line under fault conditions at low radio frequencies. The derived model is essential for design of communication systems to reliably transfer information over high voltage power lines. In addition, the model can also benefit [...] Read more.

This paper derives a model of high-voltage overhead power line under fault conditions at low radio frequencies. The derived model is essential for design of communication systems to reliably transfer information over high voltage power lines. In addition, the model can also benefit advanced systems for power-line fault detection and classification exploiting the phenomenon of changed conditions on faulted power line, resulting in change of low radio frequency signal propagation. The methodology used in the paper is based on the multiconductor system analysis and propagation of electromagnetic waves over the power lines. The model for the high voltage power line under normal operation is validated using actual measurements obtained on 400 kV power line. The proposed model of faulted power lines extends the validated power-line model under normal operation. Simulation results are provided for typical power line faults and typical fault locations. Results clearly indicate sensitivity of power-line frequency response on different fault types. Full article

(This article belongs to the Section F: Electrical Engineering)

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19 pages, 9078 KiB

Open AccessArticle

Using an Integrated Script Control Unit (ISCU) to Assist the Power Electronics Education

by Zhigang Gao^*

and Qi Lu

School of Automation, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(11), 1802; https://doi.org/10.3390/en10111802 - 8 Nov 2017

Viewed by 4464

Abstract

An integrated script control unit (ISCU) is invented to work as the digital controller in power electronics educations. The ISCU mainly consists of two parts, a control board and computer software. The computer software enables college students to write specific scripts, which can [...] Read more.

An integrated script control unit (ISCU) is invented to work as the digital controller in power electronics educations. The ISCU mainly consists of two parts, a control board and computer software. The computer software enables college students to write specific scripts, which can be compiled and saved on the control board, to design the control flow and algorithms. The processor on the board will realize the algorithms that are designed by the user. All of the variables can be monitored by the computer software, which is helpful to find the bugs in the algorithms. ISCU can help the under-graduate students to design converters even if they are unfamiliar with the programming languages and developing environment. Users can write and validate algorithms for converters quickly without writing any tedious codes (such as initialization, dealing with the interrupts) for specific processors with ISCU. The college students who lack the necessary skills to program the processor, can benefit when they are studying the power electronic techniques. Importantly, the ISCU is considered to be free for everyone. The details and the principles of ISCU are introduced, and a bi-directional DC-DC converter is built based on ISCU to validate the proposed characteristics. Full article

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9 pages, 4368 KiB

Open AccessArticle

Silicon-Carbon Composite Electrode Materials Prepared by Pyrolysis of a Mixture of Manila Hemp, Silicon Powder, and Flake Artificial Graphite for Lithium Batteries

by Qin Si, Daisuke Mori, Yasuo Takeda, Osamu Yamamoto^* and Nobuyuki Imanishi

Graduate School of Engineering, Mie University, Tsu 514-8507, Japan

Energies 2017, 10(11), 1803; https://doi.org/10.3390/en10111803 - 8 Nov 2017

Cited by 7 | Viewed by 5353

Abstract

A high performance lithium anode is a key component for high energy density lithium batteries. Silicon based lithium anode materials are attractive for the lithium anode due to their high theoretical capacity. However, a severe problem is the huge volume change that occurs [...] Read more.

A high performance lithium anode is a key component for high energy density lithium batteries. Silicon based lithium anode materials are attractive for the lithium anode due to their high theoretical capacity. However, a severe problem is the huge volume change that occurs during cycling, resulting in a poor capacity retention. We have developed a silicon based anode that disperses silicon particles on a carbon paper made from Manila hemp. The composite silicon electrode materials showed a high initial coulombic efficiency of 83%. The initial capacity of 566 mAh g⁻¹ based on the total weight of the electrode was retained at 491 mAh g⁻¹ after 70 cycles at the charge and discharge rate of 100 mA g⁻¹ and at room temperature. Full article

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15 pages, 2537 KiB

Open AccessArticle

Multi-Time Scale Coordinated Scheduling Strategy with Distributed Power Flow Controllers for Minimizing Wind Power Spillage

by Yi Tang^1,*, Yuqian Liu¹, Jia Ning¹ and Jingbo Zhao²

¹ Jiangsu Provincial Key Laboratory of Smart Grid Technology & Equipment, Southeast University, Nanjing 210096, Jiangsu, China

² Jiangsu Electric Power Company Research Institute, Nanjing 211103, Jiangsu, China

Energies 2017, 10(11), 1804; https://doi.org/10.3390/en10111804 - 9 Nov 2017

Cited by 14 | Viewed by 3396

Abstract

The inherent variability and randomness of large-scale wind power integration have brought great challenges to power flow control and dispatch. The distributed power flow controller (DPFC) has the higher flexibility and capacity in power flow control in the system with wind generation. This [...] Read more.

The inherent variability and randomness of large-scale wind power integration have brought great challenges to power flow control and dispatch. The distributed power flow controller (DPFC) has the higher flexibility and capacity in power flow control in the system with wind generation. This paper proposes a multi-time scale coordinated scheduling model with DPFC to minimize wind power spillage. Configuration of DPFCs is initially determined by stochastic method. Afterward, two sequential procedures containing day-head and real-time scales are applied for determining maximum schedulable wind sources, optimal outputs of generating units and operation setting of DPFCs. The generating plan is obtained initially in day-ahead scheduling stage and modified in real-time scheduling model, while considering the uncertainty of wind power and fast operation of DPFC. Numerical simulation results in IEEE-RTS79 system illustrate that wind power is maximum scheduled with the optimal deployment and operation of DPFC, which confirms the applicability and effectiveness of the proposed method. Full article

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17 pages, 2042 KiB

Open AccessArticle

Energy Balance Control of a Cascaded Multilevel Inverter for Standalone Solar Photovoltaic Applications

by Lei Wang, Qinghua Wu and Wenhu Tang^*

School of Electric Power Engineering, South China University of Technology, Guangzhou 510641, China

Energies 2017, 10(11), 1805; https://doi.org/10.3390/en10111805 - 9 Nov 2017

Cited by 10 | Viewed by 4731

Abstract

This paper presents a clock phase-shifting (CPS) energy balance control (EBC) method for cascaded half-bridge multilevel inverters in standalone solar photovoltaic (PV) systems. It is based on the conservation of energy in each cascaded unit. By shifting the phase of the clock pulse [...] Read more.

This paper presents a clock phase-shifting (CPS) energy balance control (EBC) method for cascaded half-bridge multilevel inverters in standalone solar photovoltaic (PV) systems. It is based on the conservation of energy in each cascaded unit. By shifting the phase of the clock pulse of each cascaded unit, a staircase-like output voltage is obtained. The CPS EBC not only regulates the staircase-like output voltage of the cascaded multilevel inverters accurately under static conditions, but also suppresses the fluctuations of DC sources and improves its dynamic responses to load steps. Thus, the problems existing in solar PV systems using the cascaded multilevel inverters are avoided. Results obtained from simulations and experiments are presented to verify the feasibility and advantages of the proposed control method. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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27 pages, 686 KiB

Open AccessArticle

Cost Assessment Methodology and Economic Viability of Tidal Energy Projects

by Eva Segura¹, Rafael Morales^1,*

and José A. Somolinos²

¹ Escuela de Ingenieros Industriales de Albacete, Universidad de Castilla-La Mancha, 02071 Albacete, Spain

² Escuela Técnica Superior de Ingenieros Navales, Universidad Politécnica de Madrid, 28040 Madrid, Spain

Energies 2017, 10(11), 1806; https://doi.org/10.3390/en10111806 - 9 Nov 2017

Cited by 54 | Viewed by 10317

Abstract

The exploitation of technologies with which to harness the energy from ocean currents will have considerable possibilities in the future thanks to their enormous potential for electricity production and their high predictability. In this respect, the development of methodologies for the economic viability [...] Read more.

The exploitation of technologies with which to harness the energy from ocean currents will have considerable possibilities in the future thanks to their enormous potential for electricity production and their high predictability. In this respect, the development of methodologies for the economic viability of these technologies is fundamental to the attainment of a consistent quantification of their costs and the discovery of their economic viability, while simultaneously attracting investment in these technologies. This paper presents a methodology with which to determine the economic viability of tidal energy projects, which includes a technical study of the life-cycle costs into which the development of a tidal farm can be decomposed: concept and definition, design and development, manufacturing, installation, operation and maintenance and dismantling. These cost structures are additionally subdivided by considering their sub-costs and bearing in mind the main components of the tidal farm: the nacelle, the supporting tidal energy converter structure and the export power system. Furthermore, a technical study is developed in order to obtain an estimation of the annual energy produced (and, consequently, the incomes generated if the electric tariff is known) by considering its principal attributes: the characteristics of the current, the ability of the device to capture energy and its ability to convert and export the energy. The methodology has been applied (together with a sensibility analysis) to the particular case of a farm composed of first generation tidal energy converters in one of the Channel Island Races, the Alderney Race, in the U.K., and the results have been attained by means of the computation of engineering indexes, such as the net present value, the internal rate of return, the discounted payback period and the levelized cost of energy, which indicate that the proposed project is economically viable for all the case studies. Full article

(This article belongs to the Special Issue Marine Energy)

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11 pages, 3193 KiB

Open AccessArticle

Dynamic Thermal Features of Insulated Blocks: Actual Behavior and Myths

by Marta Cianfrini¹, Roberto De Lieto Vollaro¹

and Emanuele Habib^2,*

¹ Dipartimento di Ingegneria Meccanica e Industriale, Università degli Studi Roma Tre, Via della Vasca Navale 79, 00146 Rome, Italy

² Dipartimento di Ingegneria Astronautica, Elettrica ed Energetica, Sapienza Università di Roma, Via Eudossiana 18, 00184 Rome, Italy

Energies 2017, 10(11), 1807; https://doi.org/10.3390/en10111807 - 9 Nov 2017

Cited by 6 | Viewed by 3336

Abstract

The latest updates in the European directive on energy performance of buildings have introduced the fundamental “nearly zero-energy building (NZEB)” concept. Thus, a special focus needs to be addressed to the thermal performance of building envelopes, especially concerning the role played by thermal [...] Read more.

The latest updates in the European directive on energy performance of buildings have introduced the fundamental “nearly zero-energy building (NZEB)” concept. Thus, a special focus needs to be addressed to the thermal performance of building envelopes, especially concerning the role played by thermal inertia in the energy requirements for cooling applications. In fact, a high thermal inertia of the outer walls results in a mitigation of the daily heat wave, which reduces the cooling peak load and the related energy demand. The common assumption that high mass means high thermal inertia typically leads to the use of high-mass blocks. Numerical and experimental studies on thermal inertia of hollow envelope components have not confirmed this general assumption, even though no systematic analysis is readily available in the open literature. Yet, the usually employed methods for the calculation of unsteady heat transfer through walls are based on the hypothesis that such walls are composed of homogeneous layers. In this framework, a study of the dynamic thermal performance of insulated blocks is brought forth in the present paper. A finite-volume method is used to solve the two-dimensional equation of conduction heat transfer, using a triangular-pulse temperature excitation to analyze the heat flux response. The effects of both the type of clay and the insulating filler are investigated and discussed at length. The results obtained show that the wall front mass is not the basic independent variable, since clay and insulating filler thermal diffusivities are more important controlling parameters. Full article

(This article belongs to the Special Issue 17th CIRIAF National Congress – Sustainable Development, Environment and Human Health Protection)

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34 pages, 6850 KiB

Open AccessArticle

Envelope Design Optimization by Thermal Modelling of a Building in a Warm Climate

by Cristina Baglivo¹, Paolo Maria Congedo¹

, Matteo Di Cataldo², Luigi Damiano Coluccia¹ and Delia D’Agostino^3,*

¹ Department of Engineering for Innovation, University of Salento, 73100 Lecce, Italy

² Design Innovation Building (DIB) Studio Limited, Kemp House 152 City Road, London EC1V 2NX, UK

³ European Commission, Joint Research Centre (JRC), Directorate C—Energy, Transport and Climate, Energy Efficiency and Renewables, Via E. Fermi 2749, Ispra, I-21027 Varese, Italy

Energies 2017, 10(11), 1808; https://doi.org/10.3390/en10111808 - 9 Nov 2017

Cited by 38 | Viewed by 5355

Abstract

Finding the most appropriate configuration of building components at the design stage can reduce energy consumption in new buildings. This study aims to optimize the design of the envelope of a new residential building located in a warm climate (southern Italy). The thermal [...] Read more.

Finding the most appropriate configuration of building components at the design stage can reduce energy consumption in new buildings. This study aims to optimize the design of the envelope of a new residential building located in a warm climate (southern Italy). The thermal behaviour of the building has been analysed to evaluate the indoor operative air temperature for several configurations. The building prototype has been modelled using the dynamic simulation software TRNSYS 17 (A transient system simulation program, University of Wisconsin, Solar Energy Laboratory, USA, 2010) using a sequential search technique. Starting from the simplest building configuration, the main evaluated components are: walls, slab-on-ground floor, roof, shading, windows and internal heat loads. For each of these components, different design options have been modelled and compared in terms of indoor thermal comfort. Comfort parameters have also been taken into account to evaluate users’ satisfaction with the optimized configurations. The study of the operative air temperature demonstrates that the absence of insulating layers in the ground floor ensures a lower internal temperature in summer. The paper shows how each component impacts the thermal behaviour of the whole building. It highlights the usefulness of the envelope design optimization that is characterized by high values of heat storage capacity, enabling internal temperature fluctuations to be kept under control, especially during summer. Full article

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16 pages, 3125 KiB

Open AccessArticle

Identification of Combined Power Quality Disturbances Using Singular Value Decomposition (SVD) and Total Least Squares-Estimation of Signal Parameters via Rotational Invariance Techniques (TLS-ESPRIT)

by Huaishuo Xiao^1,2, Jianchun Wei^1,2 and Qingquan Li^1,2,*

¹ Department of Electrical Engineering, Shandong University, Jinan 250061, China

² Shandong Provincial Key Laboratory of UHV Transmission Technology and Equipment, 17923 Jingshi Road, Jinan 250061, China

Energies 2017, 10(11), 1809; https://doi.org/10.3390/en10111809 - 9 Nov 2017

Cited by 4 | Viewed by 4080

Abstract

In order to identify various kinds of combined power quality disturbances, the singular value decomposition (SVD) and the improved total least squares-estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT) are combined as the basis of disturbance identification in this paper. SVD is [...] Read more.

In order to identify various kinds of combined power quality disturbances, the singular value decomposition (SVD) and the improved total least squares-estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT) are combined as the basis of disturbance identification in this paper. SVD is applied to identify the catastrophe points of disturbance intervals, based on which the disturbance intervals are segmented. Then the improved TLS-ESPRIT optimized by singular value norm method is used to analyze each data segment, and extract the amplitude, frequency, attenuation coefficient and initial phase of various kinds of disturbances. Multi-group combined disturbance test signals are constructed by MATLAB and the proposed method is also tested by the measured data of IEEE Power and Energy Society (PES) Database. The test results show that the new method proposed has a relatively higher accuracy than conventional TLS-ESPRIT, which could be used in the identification of measured data. Full article

(This article belongs to the Section F: Electrical Engineering)

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14 pages, 2792 KiB

Open AccessArticle

Diagnosis Method for Li-Ion Battery Fault Based on an Adaptive Unscented Kalman Filter

by Changwen Zheng

, Yunlong Ge, Ziqiang Chen^*

, Deyang Huang, Jian Liu and Shiyao Zhou

State Key Laboratory of Ocean Engineering, Collaborative Innovation Center for Advanced Ship and Deep-sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2017, 10(11), 1810; https://doi.org/10.3390/en10111810 - 9 Nov 2017

Cited by 23 | Viewed by 4059

Abstract

The reliability of battery fault diagnosis depends on an accurate estimation of the state of charge and battery characterizing parameters. This paper presents a fault diagnosis method based on an adaptive unscented Kalman filter to diagnose the parameter bias faults for a Li-ion [...] Read more.

The reliability of battery fault diagnosis depends on an accurate estimation of the state of charge and battery characterizing parameters. This paper presents a fault diagnosis method based on an adaptive unscented Kalman filter to diagnose the parameter bias faults for a Li-ion battery in real time. The first-order equivalent circuit model and relationship between the open circuit voltage and state of charge are established to describe the characteristics of the Li-ion battery. The parameters in the equivalent circuit model are treated as system state variables to set up a joint state and parameter space equation. The algorithm for fault diagnosis is designed according to the estimated parameters. Two types of fault of the Li-ion battery, including internal ohmic resistance fault and diffusion resistance faults, are studied as a case to validate the effectiveness of the algorithm. The experimental results show that the proposed approach in this paper has effective tracking ability, better estimation accuracy, and reliable diagnosis for Li-ion batteries. Full article

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16 pages, 3612 KiB

Open AccessArticle

Parameter Identification of Electrochemical Model for Vehicular Lithium-Ion Battery Based on Particle Swarm Optimization

by Xiao Yang¹, Long Chen^1,2, Xing Xu^1,2,*, Wei Wang¹, Qiling Xu¹, Yuzhen Lin¹ and Zhiguang Zhou³

¹ School of Automotive and Traffic Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China

² Automotive Engineering Research Institute, Jiangsu University, Zhenjiang 212013, Jiangsu, China

³ New Energy Development Department Powertrain Technology Center, Chery Automobile Co., Ltd., Wuhu 241009, Anhui, China

Energies 2017, 10(11), 1811; https://doi.org/10.3390/en10111811 - 9 Nov 2017

Cited by 37 | Viewed by 5028

Abstract

The dynamic characteristics of power batteries directly affect the performance of electric vehicles, and the mathematical model is the basis for the design of a battery management system (BMS).Based on the electrode-averaged model of a lithium-ion battery, in view of the solid phase [...] Read more.

The dynamic characteristics of power batteries directly affect the performance of electric vehicles, and the mathematical model is the basis for the design of a battery management system (BMS).Based on the electrode-averaged model of a lithium-ion battery, in view of the solid phase lithium-ion diffusion equation, the electrochemical model is simplified through the finite difference method. By analyzing the characteristics of the model and the type of parameters, the solid state diffusion kinetics are separated, and then the cascade parameter identifications are implemented with Particle Swarm Optimization. Eventually, the validity of the electrochemical model and the accuracy of model parameters are verified through 0.2–2 C multi-rates battery discharge tests of cell and road simulation tests of a micro pure electric vehicle under New European Driving Cycle (NEDC) conditions. The results show that the estimated parameters can guarantee the output accuracy. In the test of cell, the voltage deviation of discharge is generally less than 0.1 V except the end; in road simulation test, the output is close to the actual value at low speed with the error around ±0.03 V, and at high speed around ±0.08 V. Full article

(This article belongs to the Section L: Energy Sources)

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23 pages, 5100 KiB

Open AccessArticle

Performance Analysis of an Updraft Tower System for Dry Cooling in Large-Scale Power Plants

by Haotian Liu

, Justin Weibel and Eckhard Groll^*

Ray W. Herrick Laboratories, School of Mechanical Engineering , Purdue University, West Lafayette, IN 47906, USA

Energies 2017, 10(11), 1812; https://doi.org/10.3390/en10111812 - 9 Nov 2017

Cited by 7 | Viewed by 5305

Abstract

An updraft tower cooling system is assessed for elimination of water use associated with power plant heat rejection. Heat rejected from the power plant condenser is used to warm the air at the base of an updraft tower; buoyancy-driven air flows through a [...] Read more.

An updraft tower cooling system is assessed for elimination of water use associated with power plant heat rejection. Heat rejected from the power plant condenser is used to warm the air at the base of an updraft tower; buoyancy-driven air flows through a recuperative turbine inside the tower. The secondary loop, which couples the power plant condenser to a heat exchanger at the tower base, can be configured either as a constant-pressure pump cycle or a vapor compression cycle. The novel use of a compressor can elevate the air temperature in the tower base to increases the turbine power recovery and decrease the power plant condensing temperature. The system feasibility is evaluated by comparing the net power needed to operate the system versus alternative dry cooling schemes. A thermodynamic model coupling all system components is developed for parametric studies and system performance evaluation. The model predicts that constant-pressure pump cycle consumes less power than using a compressor; the extra compression power required for temperature lift is much larger than the gain in turbine power output. The updraft tower system with a pumped secondary loop can allow dry cooling with less power plant efficiency penalty compared to air-cooled condensers. Full article

(This article belongs to the Section F: Electrical Engineering)

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9 pages, 5134 KiB

Open AccessArticle

Band Gap Tuning of Cu₂ZnGeS_xSe_4-x Absorbers for Thin-Film Solar Cells

by Thomas Schnabel^*

, Mahmoud Seboui and Erik Ahlswede

Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg, Meitnerstraße 1, 70563 Stuttgart, Germany

Energies 2017, 10(11), 1813; https://doi.org/10.3390/en10111813 - 9 Nov 2017

Cited by 33 | Viewed by 4720

Abstract

In this work, kesterite-type Cu₂ZnGeS_xSe_4-x absorbers were prepared by a two-step process for use in thin-film solar cells. Their high band gap makes them an interesting candidate as top cells in multijunction solar cells. However, an exact tuning [...] Read more.

In this work, kesterite-type Cu₂ZnGeS_xSe_4-x absorbers were prepared by a two-step process for use in thin-film solar cells. Their high band gap makes them an interesting candidate as top cells in multijunction solar cells. However, an exact tuning of the band gap is essential. Therefore, for the first time, the [S]/([S] + [Se]) ratio was controlled via addition of a variable amount of GeS during the annealing step, which allowed precise control of the band gap between 1.5 and 1.7 eV. The changes in morphology and crystallinity of the absorber are discussed in detail. An additional focus was directed toward the parameters of the resulting solar cells. Although the efficiency declined as the [S]/([S] + [Se]) ratio increases, the open-circuit voltage was considerably increased. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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8 pages, 4573 KiB

Open AccessArticle

Yield, Composition, and Property of Biochar Obtained from the Two-Step Pyrolysis of Rice Husk Impregnated with Boric Acid

by Xu Cheng and Biao Wang^*

College of Materials Science and Engineering, State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China

Energies 2017, 10(11), 1814; https://doi.org/10.3390/en10111814 - 9 Nov 2017

Cited by 14 | Viewed by 4350

Abstract

Adding catalysts such as boric acid into biomass is a flexible method to achieve high biochar yield with low carbon emission levels. This work is directed towards investigating the effects of boric acid content on biochar yield, composition, and property through a two-step [...] Read more.

Adding catalysts such as boric acid into biomass is a flexible method to achieve high biochar yield with low carbon emission levels. This work is directed towards investigating the effects of boric acid content on biochar yield, composition, and property through a two-step pyrolysis of rice husk. The results showed that biochar yields, compositions, and properties were associated with the amounts of boric acid impregnated. Yield, C content, and calorific value of biochar were improved by adding 2.0 wt % of boric acid into rice husk, and those values were 46.4 wt %, 59.3 wt %, and 22.6 MJ/kg, respectively. However, the fixed-carbon content of biochar was around 55.4 wt % and was barely affected by the changes in the amounts of boric acid absorbed. Therefore, the optimized boric acid content of rice husk was 2.0 wt % when biochar was applied to the fields of carbon storage and solid fuel. Meanwhile, the specific surface area of biochar continuously decreased with increasing boric acid content of rice husk, indicating that the boric acid had a negative influence on the pore structure of biochar. Thus, the addition of boric acid is not recommended when preparing a biochar to be used as an absorbent. Full article

(This article belongs to the Section L: Energy Sources)

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21 pages, 2746 KiB

Open AccessArticle

Robust Sliding Mode Control of Air Handling Unit for Energy Efficiency Enhancement

by Awais Shah, Deqing Huang

, Yixing Chen, Xin Kang and Na Qin^*

School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China

Energies 2017, 10(11), 1815; https://doi.org/10.3390/en10111815 - 9 Nov 2017

Cited by 21 | Viewed by 13251

Abstract

In order to achieve feasible and copacetic low energy consuming building, a robust and efficient air conditioning system is necessary. Since heating ventilation and air conditioning systems are nonlinear and temperature and humidity are coupled, application of conventional control is inappropriate. A multi-input [...] Read more.

In order to achieve feasible and copacetic low energy consuming building, a robust and efficient air conditioning system is necessary. Since heating ventilation and air conditioning systems are nonlinear and temperature and humidity are coupled, application of conventional control is inappropriate. A multi-input multi-output nonlinear model is presented. The temperature and humidity of thermal zone are ascendance by the manipulation of the water and air flow rates. A sliding mode controller (SMC) is designed to ensure robust performance of air handling unit in the presence of uncertainties. A simple proportional-integral-derivative (PID) controller is used as a comparison template to highlight the efficiency of the proposed controller. To accomplish tracking targets, a variety of desired temperature and relative humidity commands (including ramp and combination with sequence of steps) are investigated. According to simulation results, SMC transcends the PID controller in terms of settling time, steady state and rise time, which makes SMC more energy efficient. Full article

(This article belongs to the Section F: Electrical Engineering)

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16 pages, 5070 KiB

Open AccessFeature PaperArticle

Design and Performance of Test Cells as an Energy Evaluation Model of Facades in a Mediterranean Building Area

by Ángel Luis León-Rodríguez

, Rafael Suárez^*

, Pedro Bustamante

, Miguel Ángel Campano

and David Moreno-Rangel

Instituto Universitario de Arquitectura y Ciencias de la Construcción, Escuela Técnica Superior de Arquitectura, Universidad de Sevilla, Av. de Reina Mercedes 2, Seville 41012, Spain

Energies 2017, 10(11), 1816; https://doi.org/10.3390/en10111816 - 9 Nov 2017

Cited by 31 | Viewed by 4857

Abstract

The current European energy policies have an influence on the need to rehabilitate the housing stock in order to meet the objectives of the European Union. Most of this housing stock was built without any type of energy regulation in adverse technical and [...] Read more.

The current European energy policies have an influence on the need to rehabilitate the housing stock in order to meet the objectives of the European Union. Most of this housing stock was built without any type of energy regulation in adverse technical and economic conditions and thus is now energetically obsolete. The major rehabilitation effort required must be approached through actions based on previous quantitative energy knowledge of the existing buildings in order to guarantee the efficiency of energy-retrofitted solutions. This assessment can be carried out through monitoring dwellings conditioned by use patterns; through simulation programs, which do not usually offer faithful representations of energy conditions; or by using test cells, which allow us to evaluate a controlled indoor environment without the influence of users. The objective of this paper is to present the design and performance of test cells as an experimental method for vertical facade analysis in order to tackle the problem of retrofitting residential buildings in a Mediterranean climate, taking into account energy and environment. With this equipment, efficiency and energy savings, as well as illumination and interior air quality, can be simultaneously and comprehensively evaluated. Full article

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36 pages, 1778 KiB

Open AccessReview

Upgrading the Glycerol from Biodiesel Production as a Source of Energy Carriers and Chemicals—A Technological Review for Three Chemical Pathways

by Abel Rodrigues^1,2, João Carlos Bordado³ and Rui Galhano dos Santos^3,*

¹ INIAV, Ministry of Agriculture, 2780-159 Oeiras, Portugal

² MARETEC—Research Center, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

³ CERENA—Centre for Natural Resources and the Environment, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Energies 2017, 10(11), 1817; https://doi.org/10.3390/en10111817 - 9 Nov 2017

Cited by 135 | Viewed by 18304

Abstract

Glycerol is a by-product of biodiesel obtained from biomass, accounting for 10% of the biodiesel production. In the context of a green economy, aiming for a reduction of the emission of atmospheric greenhouse gases emissions, the demand of biodiesel is expected to increase [...] Read more.

Glycerol is a by-product of biodiesel obtained from biomass, accounting for 10% of the biodiesel production. In the context of a green economy, aiming for a reduction of the emission of atmospheric greenhouse gases emissions, the demand of biodiesel is expected to increase vastly, in parallel with a side glut supply of glycerol. Given the high cost of biodiesel compared with its fossil congener, upgrading of glycerol into added-value products can represent a secondary income source and turn the production of such alternative fuels economically sustainable in the long term. The glycerol obtained as by-product of biodiesel from biomass is in a crude form and must be purified. Some industrial solutions and applications were therein geared. The survey presented in this work, based on a reviewing of the existing literature, examines three routes for the valuing glycerol into energy carriers and chemicals, namely, carbonation, acylation, and steam reforming to hydrogen. The latter is embodied of great interest and importance, insofar that hydrogen by itself is considered as straighforward clean fuel for transportation uses, due to its high calorific power and to recent advances in fuel cells. We also have focused on the chain value from biomass to energies carriers through these pathways. Full article

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21 pages, 4534 KiB

Open AccessArticle

An Improved Optimization Function for Maximizing User Comfort with Minimum Energy Consumption in Smart Homes

by Israr Ullah

and DoHyeun Kim^*

Computer Engineering Department, Jeju National University, Jeju 63243, Korea

Energies 2017, 10(11), 1818; https://doi.org/10.3390/en10111818 - 9 Nov 2017

Cited by 51 | Viewed by 6291

Abstract

In the smart home environment, efficient energy management is a challenging task. Solutions are needed to achieve a high occupant comfort level with minimum energy consumption. User comfort is measured in terms of three fundamental parameters: (a) thermal comfort, (b) visual comfort and [...] Read more.

In the smart home environment, efficient energy management is a challenging task. Solutions are needed to achieve a high occupant comfort level with minimum energy consumption. User comfort is measured in terms of three fundamental parameters: (a) thermal comfort, (b) visual comfort and (c) air quality. Temperature, illumination and CO

_{2}

sensors are used to collect indoor contextual information. In this paper, we have proposed an improved optimization function to achieve maximum user comfort in the building environment with minimum energy consumption. A comprehensive formulation is done for energy optimization with detailed analysis. The Kalman filter algorithm is used to remove noise in sensor readings by predicting actual parameter values. For optimization, we have used genetic algorithm (GA) and particle swarm optimization (PSO) algorithms and performed comparative analysis with a baseline scheme on real data collected for a one-month duration in our lab’s indoor environment. Experimental results show that the proposed optimization function has achieved a

27.32 %

and a

31.42 %

reduction in energy consumption with PSO and GA, respectively. The user comfort index was also improved by

10 %

i.e., from

0.86

to

0.96

. GA-based optimization results were better than PSO, as it has achieved almost the same user comfort with

4.19 %

reduced energy consumption. Results show that the proposed optimization function gives better results than the baseline scheme in terms of user comfort and the amount of consumed energy. The proposed system can help with collecting the data about user preferences and energy consumption for long-term analysis and better decision making in the future for efficient resource utilization and overall profit maximization. Full article

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12 pages, 2588 KiB

Open AccessArticle

Design of a PM Vernier Machine with Consideration for Modulation Flux and Comparison with Conventional PM motors

by Byungtaek Kim

Department of Electrical Engineering, Kunsan National University, Gunsan 54150, Korea

Energies 2017, 10(11), 1819; https://doi.org/10.3390/en10111819 - 9 Nov 2017

Cited by 13 | Viewed by 4531

Abstract

This study deals with the core design of a PM vernier machine considering modulation flux effects, and the comparative investigation on volume and performance characteristics of the vernier over conventional PM machines are addressed. To these ends, for a PM vernier machine in [...] Read more.

This study deals with the core design of a PM vernier machine considering modulation flux effects, and the comparative investigation on volume and performance characteristics of the vernier over conventional PM machines are addressed. To these ends, for a PM vernier machine in operation at the base-speed, the flux density equations for teeth and yokes considering the flux modulation effects are derived, where the air gap harmonic permeance function is used. Using the derived equations, a PM vernier motor with specified yoke flux densities is designed. To identify the predicted flux yoke densities, the flux distribution and iron losses in core parts are analyzed through time-step finite element (FE) simulations. Through Fourier series expansion of the air gap flux waves obtained by FE analysis at several specified times, the harmonic components constituting the flux waves are investigated and their speeds are also evaluated in numerical ways. Finally, to estimate the competitiveness of vernier machines versus conventional machines, the designed PM vernier motor is compared against two different conventional PM motors designed through the same design procedures in various aspects such as volume, torque capacity, efficiency, and power factor, in which, in particular, the core losses are included in efficiency calculation. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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15 pages, 15283 KiB

Open AccessArticle

Moderate Collapse in a Shale Cap of a Nearly Depleted Reservoir

by Kai Zhao^1,2,*, Jiyong Han¹, Liangbin Dou¹ and Yongcun Feng^3,*

¹ College of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China

² Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil & Gas Reservoirs, Xi’an Shiyou University, Xi’an 710065, China

³ Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, Austin, TX 78712, USA

Energies 2017, 10(11), 1820; https://doi.org/10.3390/en10111820 - 9 Nov 2017

Cited by 3 | Viewed by 5314

Abstract

Reservoir depletion will cause the safe equivalent circulation density (ECD) operating window of drilling fluids to narrow, or even disappear. Previous studies have proposed a set of two specific casings at the top and bottom of the depleted reservoir, respectively, or [...] Read more.

Reservoir depletion will cause the safe equivalent circulation density (ECD) operating window of drilling fluids to narrow, or even disappear. Previous studies have proposed a set of two specific casings at the top and bottom of the depleted reservoir, respectively, or conducted wellbore strengthening to increase fracture pressure, but these will cause a waste of time and costs, or differential pressure sticking. Aiming at resolving this problem, a novel concept and evaluation method of moderate collapse in the shale cap was developed and case calculations were performed. The results show that the degree of collapse is different for wells drilled in different types of fault regimes, and it can be controlled by optimizing the well trajectory. The collapse pressure within the shale cap was decreased due to reservoir depletion, and when a certain degree of collapse was acceptable, the collapse pressure can be even lower and a safe operating window will appear which can be beneficial to optimizing the casing program and drilling design. The research results provide a theoretical basis and new design idea for successfully and economically drilling into new untapped reservoirs in deeper horizons through depleted zones in the future. Full article

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16 pages, 1259 KiB

Open AccessArticle

Economical Efficiency of Combined Cooling Heating and Power Systems Based on an Enthalpy Method

by Yan Xu¹, Wenyu Li² and Jiahai Yuan^2,*

¹ School of Management Science and Engineering, Shanxi University of Finance and Economics, Shanxi 030006, China

² School of Economics and Management, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(11), 1821; https://doi.org/10.3390/en10111821 - 9 Nov 2017

Cited by 3 | Viewed by 3144

Abstract

As the living standards of Chinese people have been improving, the energy demand for cooling and heating, mainly in the form of electricity, has also expanded. Since an integrated cooling, heating and power supply system (CCHP) will serve this demand better, the government [...] Read more.

As the living standards of Chinese people have been improving, the energy demand for cooling and heating, mainly in the form of electricity, has also expanded. Since an integrated cooling, heating and power supply system (CCHP) will serve this demand better, the government is now attaching more importance to the application of CCHP energy systems. Based on the characteristics of the combined cooling heating and power supply system, and the method of levelized cost of energy, two calculation methods for the evaluation of the economical efficiency of the system are employed when the energy production in the system is dealt with from the perspective of exergy. According to the first method, fuel costs account for about 75% of the total cost. In the second method, the profits from heating and cooling are converted to fuel costs, resulting in a significant reduction of fuel costs, accounting for 60% of the total cost. Then the heating and cooling parameters of gas turbine exhaust, heat recovery boiler, lithium-bromide heat-cooler and commercial tariff of provincial capitals were set as benchmark based on geographic differences among provinces, and the economical efficiency of combined cooling heating and power systems in each province were evaluated. The results shows that the combined cooling heating and power system is economical in the developed areas of central and eastern China, especially in Hubei and Zhejiang provinces, while in other regions it is not. The sensitivity analysis was also made on related influencing factors of fuel cost, demand intensity in heating and cooling energy, and bank loans ratio. The analysis shows that the levelized cost of energy of combined cooling heating and power systems is very sensitive to exergy consumption and fuel costs. When the consumption of heating and cooling energy increases, the unit cost decreases by 0.1 yuan/kWh, and when the on-grid power ratio decreases by 20%, the cost may increase by 0.1 yuan/kWh. Finally, some suggestions were offered from the perspective of the power grid, gas sector reform, heating and cooling systems and other aspects to promote the use of combined cooling heating and power systems in the future. Full article

(This article belongs to the Section F: Electrical Engineering)

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20 pages, 5742 KiB

Open AccessArticle

Methodology for Analysing Energy Demand in Biogas Production Plants—A Comparative Study of Two Biogas Plants

by Emma Lindkvist^1,2

, Maria T. Johansson^1,2,*

and Jakob Rosenqvist³

¹ Department of Management and Engineering, Division of Energy Systems, Linköping University, SE-581 83 Linköping, Sweden

² Biogas Research Center, Linköping University, SE-581 83 Linköping, Sweden

³ Tranås Energi, SE-573 24 Tranås, Sweden

Energies 2017, 10(11), 1822; https://doi.org/10.3390/en10111822 - 10 Nov 2017

Cited by 16 | Viewed by 11255

Abstract

Biogas production through anaerobic digestion may play an important role in a circular economy because of the opportunity to produce a renewable fuel from organic waste. However, the production of biogas may require energy in the form of heat and electricity. Therefore, resource-effective [...] Read more.

Biogas production through anaerobic digestion may play an important role in a circular economy because of the opportunity to produce a renewable fuel from organic waste. However, the production of biogas may require energy in the form of heat and electricity. Therefore, resource-effective biogas production must consider both biological and energy performance. For the individual biogas plant to improve its energy performance, a robust methodology to analyse and evaluate the energy demand on a detailed level is needed. Moreover, to compare the energy performance of different biogas plants, a methodology with a consistent terminology, system boundary and procedure is vital. The aim of this study was to develop a methodology for analysing the energy demand in biogas plants on a detailed level. In the methodology, the energy carriers are allocated to: (1) sub-processes (e.g., pretreatment, anaerobic digestion, gas cleaning), (2) unit processes (e.g., heating, mixing, pumping, lighting) and (3) a combination of these. For a thorough energy analysis, a combination of allocations is recommended. The methodology was validated by applying it to two different biogas plants. The results show that the methodology is applicable to biogas plants with different configurations of their production system. Full article

(This article belongs to the Section L: Energy Sources)

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32 pages, 5799 KiB

Open AccessArticle

A Design of a Hybrid Non-Linear Control Algorithm

by Farinaz Behrooz^1,2,*

, Norman Mariun^1,2, Mohammad Hamiruce Marhaban¹, Mohd Amran Mohd Radzi¹

and Abdul Rahman Ramli³

¹ Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

² Centre for Advanced Power and Energy Research, Faculty of Engineering, University Putra Malaysia, Serdang 43400, Selangor, Malaysia

³ Department of Computer and Communication Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

Energies 2017, 10(11), 1823; https://doi.org/10.3390/en10111823 - 10 Nov 2017

Cited by 3 | Viewed by 4087

Abstract

One of the high energy consuming devices in the buildings is the air-conditioning system. Designing a proper controller to consider the thermal comfort and simultaneously control the energy usage of the device will impact on the system energy efficiency and its performance. The [...] Read more.

One of the high energy consuming devices in the buildings is the air-conditioning system. Designing a proper controller to consider the thermal comfort and simultaneously control the energy usage of the device will impact on the system energy efficiency and its performance. The aim of this study was to design a Multiple-Input and Multiple-Output (MIMO), non-linear, and intelligent controller on direct expansion air-conditioning system The control algorithm uses the Fuzzy Cognitive Map method as a main controller and the Generalized Predictive Control method is used for assigning the initial weights of the main controller. The results of the proposed controller shows that the controller was successfully designed and works in set point tracking and under disturbance rejection tests. The obtained results of the Generalized Predictive Control-Fuzzy Cognitive Map controller are compared with the previous MIMO Linear Quadratic Gaussian control design on the same direct expansion air-conditioning system under the same conditions. The comparative results indicate energy savings would be achieved with the proposed controller with long-term usage. Energy efficiency and thermal comfort conditions are achieved by the proposed controller. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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11 pages, 1227 KiB

Open AccessArticle

Estimation of Transformers Health Index Based on the Markov Chain

by Muhammad Sharil Yahaya^1,2, Norhafiz Azis^1,3,*, Mohd Zainal Abidin Ab Kadir¹

, Jasronita Jasni¹, Mohd Hendra Hairi⁴ and Mohd Aizam Talib⁵

¹ Centre for Electromagnetic and Lightning Protection Research, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

² Faculty of Engineering Technology, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia

³ Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

⁴ Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia

⁵ TNB Research Sdn. Bhd., No. 1, Lorong Ayer Itam, Kawasan Institut Penyelidikan, 43000 Kajang, Selangor, Malaysia

Energies 2017, 10(11), 1824; https://doi.org/10.3390/en10111824 - 10 Nov 2017

Cited by 38 | Viewed by 4807

Abstract

This paper presents a study on the application of the Markov Model (MM) to determine the transformer population states based on Health Index (HI). In total, 3195 oil samples from 373 transformers ranging in age from 1 to 25 years were analyzed. First, [...] Read more.

This paper presents a study on the application of the Markov Model (MM) to determine the transformer population states based on Health Index (HI). In total, 3195 oil samples from 373 transformers ranging in age from 1 to 25 years were analyzed. First, the HI of transformers was computed based on yearly individual oil condition monitoring data that consisted of oil quality, dissolved gases, and furanic compounds. Next, the average HI for each age was computed and the transition probabilities were obtained based on a nonlinear optimization technique. Finally, the future deterioration performance curve of the transformers was determined based on the MM chain algorithm. It was found that the MM can be used to predict the future transformers condition states. The chi-squared goodness-of-fit analysis revealed that the predicted HI for the transformer population obtained based on MM agrees with the average computed HI along the years, and the average error is 3.59%. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 3956 KiB

Open AccessArticle

Assessment of the Use of Venetian Blinds as Solar Thermal Collectors in Double Skin Facades in Mediterranean Climates

by Abel Velasco¹, Sergi Jiménez García¹, Alfredo Guardo^1,2,*

, Alfred Fontanals¹ and Mònica Egusquiza^1,2

¹ Centre de Diagnòstic Industrial i Fluidodinàmica, Universitat Politècnica de Catalunya BarcelonaTECH (UPC CDIF), Av. Diagonal 647, 08028 Barcelona, Spain

² Càtedra JG per a l’Estudi de la Sostenibilitat d’Edificis, Universitat Politècnica de Catalunya BarcelonaTECH, Av. Diagonal 647, 08028 Barcelona, Spain

Energies 2017, 10(11), 1825; https://doi.org/10.3390/en10111825 - 10 Nov 2017

Cited by 12 | Viewed by 4433

Abstract

The global trend on energy integration and building efficiency is making both researchers and building developers look for technical solutions to use facade surfaces for energy harvesting. In this work, the assessment of the thermal performance of a double-skin facade (DSF) with a [...] Read more.

The global trend on energy integration and building efficiency is making both researchers and building developers look for technical solutions to use facade surfaces for energy harvesting. In this work, the assessment of the thermal performance of a double-skin facade (DSF) with a venetian blind-type of structure used as a solar thermal collector by means of computational fluid dynamics (CFD) is presented. A Venetian blind collector would allow for heat rejection/energy harvesting and exterior views simultaneously and can be easily integrated into the DSF aesthetical design. For the purposes of this study, the modeled facades (south, west, and east-oriented) were set to be located in Barcelona (Spain), where large solar gains are a constant condition throughout the year, and such large semi-transparent envelopes lead to interior over-heating in buildings, even during the winter. For the studied facades, both the reductions in radiative heat gains entering the building and the heat recovery in the Venetian blind collector were evaluated for a yearlong operation. Full article

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17 pages, 18129 KiB

Open AccessArticle

A Cellular Approach to Net-Zero Energy Cities

by Miguel Amado^1,*

, Francesca Poggi²

, António Ribeiro Amado³ and Sílvia Breu⁴

¹ CERIS Civil Engineering Research and Innovation for Sustainability, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal

² CICS.NOVA—Interdisciplinary Center of Social Sciences, Faculdade de Ciências Sociais e Humanas, Universidade NOVA de Lisboa, Av. de Berna, 26-C, 1069-061 Lisbon, Portugal

³ CIAUD Centro de Investigação em Arquitectura, Urbanismo e Design, Faculdade de Arquitectura, Universidade de Lisboa, R. Sá Nogueira, 1349-063 Lisbon, Portugal

⁴ Municipal Development Office, 2784-214 Oeiras Municipality, Portugal

Energies 2017, 10(11), 1826; https://doi.org/10.3390/en10111826 - 10 Nov 2017

Cited by 22 | Viewed by 6081

Abstract

Recent growth in the use of photovoltaic technology and a rapid reduction in its cost confirms the potential of solar power on a large scale. In this context, planning for the deployment of smart grids is among the most important challenges to support [...] Read more.

Recent growth in the use of photovoltaic technology and a rapid reduction in its cost confirms the potential of solar power on a large scale. In this context, planning for the deployment of smart grids is among the most important challenges to support the increased penetration of solar energy in urban areas and to ensure the resilience of the electricity system. As part this effort, the present paper describes a cellular approach to a Net-Zero energy concept, based on the balance between the potential solar energy supply and the existing consumption patterns at the urban unit scale. To do that, the Geographical Urban Units Delimitation model (GUUD) has been developed and tested on a case study. By applying the GUUD model, which combines Geographic Information Systems (GIS), parametric modelling, and solar dynamic analysis, the whole area of the city was divided into urban cells, categorized as solar producers and energy consumers. The discussion around three theoretical scenarios permits us to explore how smart grids can be approached and promoted from an urban planning perspective. The paper provides insights into how urban planning can be a driver to optimize and manage energy balance across the city if the deployment of smart grids is correctly integrated in its operative process. Full article

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22 pages, 7888 KiB

Open AccessArticle

Characteristic Analysis and Fault-Tolerant Control of Circulating Current for Modular Multilevel Converters under Sub-Module Faults

by Wen Wu¹, Xuezhi Wu^1,2,*, Jingyuan Yin³, Long Jing¹, Shuai Wang¹ and Jinke Li¹

¹ National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China

² Collaborative Innovation Center of Electric Vehicles, Beijing 100044, China

³ The Institute of Electrical Engineering Chinese Academy of Sciences, Beijing 100190, China

Energies 2017, 10(11), 1827; https://doi.org/10.3390/en10111827 - 10 Nov 2017

Cited by 16 | Viewed by 4060

Abstract

A modular multilevel converter (MMC) is considered to be a promising topology for medium- or high-power applications. However, a significantly increased amount of sub-modules (SMs) in each arm also increase the risk of failures. Focusing on the fault-tolerant operation issue for the MMC [...] Read more.

A modular multilevel converter (MMC) is considered to be a promising topology for medium- or high-power applications. However, a significantly increased amount of sub-modules (SMs) in each arm also increase the risk of failures. Focusing on the fault-tolerant operation issue for the MMC under SM faults, the operation characteristics of MMC with different numbers of faulty SMs in the arms are analyzed and summarized in this paper. Based on the characteristics, a novel circulating current-suppressing (CCS) fault-tolerant control strategy comprised of a basic control unit (BCU) and virtual resistance compensation control unit (VRCCU) in two parts is proposed, which has three main features: (i) it can suppress the multi-different frequency components of the circulating current under different SM fault types simultaneously; (ii) it can help fast limiting of the transient fault current caused at the faulty SM bypassed moment; and (iii) it does not need extra communication systems to acquire the information of the number of faulty SMs. Moreover, by analyzing the stability performance of the proposed controller using the Root-Locus criterion, the election principle of the value of virtual resistance is revealed. Finally, the efficiency of the control strategy is confirmed with the simulation and experiment studies under different fault conditions. Full article

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18 pages, 5725 KiB

Open AccessArticle

Numerical Investigation on the Flow and Heat Transfer Characteristics of Supercritical Liquefied Natural Gas in an Airfoil Fin Printed Circuit Heat Exchanger

by Zhongchao Zhao^*, Kai Zhao, Dandan Jia, Pengpeng Jiang and Rendong Shen

School of Energy and Power, Jiangsu University of Science and Technology, Zhenjiang 210000, China

Energies 2017, 10(11), 1828; https://doi.org/10.3390/en10111828 - 10 Nov 2017

Cited by 45 | Viewed by 7705

Abstract

As a new kind of highly compact and efficient micro-channel heat exchanger, the printed circuit heat exchanger (PCHE) is a promising candidate satisfying the heat exchange requirements of liquefied natural gas (LNG) vaporization at low and high pressure. The effects of airfoil fin [...] Read more.

As a new kind of highly compact and efficient micro-channel heat exchanger, the printed circuit heat exchanger (PCHE) is a promising candidate satisfying the heat exchange requirements of liquefied natural gas (LNG) vaporization at low and high pressure. The effects of airfoil fin arrangement on heat transfer and flow resistance were numerically investigated using supercritical liquefied natural gas (LNG) as working fluid. The thermal properties of supercritical LNG were tested by utilizing the REFPROF software database. Numerical simulations were performed using FLUENT. The inlet temperature of supercritical LNG was 121 K, and its pressure was 10.5 MPa. The reference mass flow rate of LNG was set as 1.22 g/s for the vertical pitch L_v = 1.67 mm and the staggered pitch L_s = 0 mm, with the Reynolds number of about 3750. The SST k-ω model was selected and verified by comparing with the experimental data using supercritical liquid nitrogen as cold fluid. The airfoil fin PCHE had better thermal-hydraulic performance than that of the straight channel PCHE. Moreover, the airfoil fins with staggered arrangement displayed better thermal performance than that of the fins with parallel arrangement. The thermal-hydraulic performance of airfoil fin PCHE was improved with increasing L_s and L_v. Moreover, L_v affected the Nusselt number and pressure drop of airfoil fin PCHE more obviously. In conclusion, a sparser staggered arrangement of fins showed a better thermal-hydraulic performance in airfoil fin PCHE. Full article

(This article belongs to the Special Issue Liquefied Natural Gas)

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14 pages, 5141 KiB

Open AccessArticle

Research on the Temperature Field of High-Voltage High Power Line Start Permanent Magnet Synchronous Machines with Different Rotor Cage Structure

by Zhaobin Cao¹

, Weili Li¹, Jinyang Li², Xiaochen Zhang^1,*, Dong Li¹ and Meiwei Zhang¹

¹ School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China

² School of Electrical Engineering & Automation, Harbin Institute of Technology, Harbin 150001, China

Energies 2017, 10(11), 1829; https://doi.org/10.3390/en10111829 - 10 Nov 2017

Cited by 15 | Viewed by 4563

Abstract

For line start permanent magnet synchronous machines (LSPMSMs), the eddy current loss in the rotor, which has of significant effects on rotor working temperature, may cause thermal demagnetization to permanent magnet. Therefore, this paper addresses an investigation on the temperature distribution in LSPMSM [...] Read more.

For line start permanent magnet synchronous machines (LSPMSMs), the eddy current loss in the rotor, which has of significant effects on rotor working temperature, may cause thermal demagnetization to permanent magnet. Therefore, this paper addresses an investigation on the temperature distribution in LSPMSM based on a 6 kV, 315 kW prototype with solid starting cage bar. Firstly, the loss distributions, obtained from a 2-D transient electromagnetic field calculation, are determined as the distributed heat source in thermal analyses. Then, the fluid-thermal coupled analyses are performed, by which the temperature distributions in the machine are determined. Meanwhile, the calculated motor performance is verified via comparison with the measured results. The calculation results show that the temperatures in the rotor core and permanent magnets are relatively high. To find the solution for reducing the rotor working temperature, a rotor air slot structure was proposed in this analysis. The theoretical calculation indicates that the rotor working temperature reduction is obvious with the rotor air slot in the machine. Therefore, the operating situation of solid rotor LSPMSM could be improved effectively with the proposed rotor thermal solution, which also benefits the machine reliability and safety. Full article

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24 pages, 4121 KiB

Open AccessArticle

An Accurate CT Saturation Classification Using a Deep Learning Approach Based on Unsupervised Feature Extraction and Supervised Fine-Tuning Strategy

by Muhammad Ali

, Dae-Hee Son, Sang-Hee Kang

and Soon-Ryul Nam^*

Department of Electrical Engineering, Myongji University, Yongin 449-728, Korea

Energies 2017, 10(11), 1830; https://doi.org/10.3390/en10111830 - 10 Nov 2017

Cited by 49 | Viewed by 8906

Abstract

Current transformer (CT) saturation is one of the significant problems for protection engineers. If CT saturation is not tackled properly, it can cause a disastrous effect on the stability of the power system, and may even create a complete blackout. To cope with [...] Read more.

Current transformer (CT) saturation is one of the significant problems for protection engineers. If CT saturation is not tackled properly, it can cause a disastrous effect on the stability of the power system, and may even create a complete blackout. To cope with CT saturation properly, an accurate detection or classification should be preceded. Recently, deep learning (DL) methods have brought a subversive revolution in the field of artificial intelligence (AI). This paper presents a new DL classification method based on unsupervised feature extraction and supervised fine-tuning strategy to classify the saturated and unsaturated regions in case of CT saturation. In other words, if protection system is subjected to a CT saturation, proposed method will correctly classify the different levels of saturation with a high accuracy. Traditional AI methods are mostly based on supervised learning and rely heavily on human crafted features. This paper contributes to an unsupervised feature extraction, using autoencoders and deep neural networks (DNNs) to extract features automatically without prior knowledge of optimal features. To validate the effectiveness of proposed method, a variety of simulation tests are conducted, and classification results are analyzed using standard classification metrics. Simulation results confirm that proposed method classifies the different levels of CT saturation with a remarkable accuracy and has unique feature extraction capabilities. Lastly, we provided a potential future research direction to conclude this paper. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 3399 KiB

Open AccessArticle

Speed Synchronization Control of Integrated Motor–Transmission Powertrain over CAN through Active Period-Scheduling Approach

by Wanke Cao^1,*

, Helin Liu¹, Cheng Lin¹, Yuhua Chang^2,*, Zhiyin Liu² and Antoni Szumanowski²

¹ National Engineering Laboratory for Electric Vehicles and Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Institute of Technology (BIT), Beijing 100081, China

² Department of Multisource Propulsion system, Faculty of Automotive and Construction Machinery Engineering, Warsaw University of Technology (WUT), 02-524 Warsaw, Poland

Energies 2017, 10(11), 1831; https://doi.org/10.3390/en10111831 - 10 Nov 2017

Cited by 13 | Viewed by 4916

Abstract

This paper deals with the speed synchronization control of integrated motor–transmission (IMT) powertrain systems in pure electric vehicles (EVs) over a controller area network (CAN) subject to both network-induced delays and network congestion. A CAN has advantages over point-to-point communication; however, it imposes [...] Read more.

This paper deals with the speed synchronization control of integrated motor–transmission (IMT) powertrain systems in pure electric vehicles (EVs) over a controller area network (CAN) subject to both network-induced delays and network congestion. A CAN has advantages over point-to-point communication; however, it imposes network-induced delays and network congestion into the control system, which can deteriorate the shifting quality and make system integration difficult. This paper presents a co-design scheme combining active period scheduling and discrete-time slip mode control (SMC) to deal with both network-induced delays and network congestion of the CAN, which improves the speed synchronization control for high shifting quality and prevents network congestion for the system’s integration. The results of simulations and hardware-in-loop experiments show the effectiveness of the proposed scheme, which can ensure satisfactory speed synchronization performance while significantly reducing the network’s utilization. Full article

(This article belongs to the Special Issue The International Symposium on Electric Vehicles (ISEV2017))

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18 pages, 2622 KiB

Open AccessArticle

Applications of the Chaotic Quantum Genetic Algorithm with Support Vector Regression in Load Forecasting

by Cheng-Wen Lee¹ and Bing-Yi Lin^2,*

¹ Department of International Business, Chung Yuan Christian University, 200 Chung Pei Rd., Chungli District, Taoyuan City 32023, Taiwan

² Ph.D. Program in Business, College of Business, Chung Yuan Christian University, 200 Chung Pei Rd., Chungli District, Taoyuan City 32023, Taiwan

Energies 2017, 10(11), 1832; https://doi.org/10.3390/en10111832 - 10 Nov 2017

Cited by 19 | Viewed by 5428

Abstract

Accurate electricity forecasting is still the critical issue in many energy management fields. The applications of hybrid novel algorithms with support vector regression (SVR) models to overcome the premature convergence problem and improve forecasting accuracy levels also deserve to be widely explored. This [...] Read more.

Accurate electricity forecasting is still the critical issue in many energy management fields. The applications of hybrid novel algorithms with support vector regression (SVR) models to overcome the premature convergence problem and improve forecasting accuracy levels also deserve to be widely explored. This paper applies chaotic function and quantum computing concepts to address the embedded drawbacks including crossover and mutation operations of genetic algorithms. Then, this paper proposes a novel electricity load forecasting model by hybridizing chaotic function and quantum computing with GA in an SVR model (named SVRCQGA) to achieve more satisfactory forecasting accuracy levels. Experimental examples demonstrate that the proposed SVRCQGA model is superior to other competitive models. Full article

(This article belongs to the Special Issue Hybrid Advanced Optimization Methods with Evolutionary Computation Techniques in Energy Forecasting)

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15 pages, 7859 KiB

Open AccessArticle

Research on Stress Sensitivity of Fractured Carbonate Reservoirs Based on CT Technology

by Yongfei Yang^1,*

, Zhihui Liu¹, Zhixue Sun¹, Senyou An¹, Wenjie Zhang¹, Pengfei Liu¹, Jun Yao^1,* and Jingsheng Ma²

¹ Research Centre of Multiphase Flow in Porous Media, China University of Petroleum (East China), Qingdao 266580, China

² Institute of Petroleum Engineering, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK

Energies 2017, 10(11), 1833; https://doi.org/10.3390/en10111833 - 10 Nov 2017

Cited by 51 | Viewed by 5286

Abstract

Fracture aperture change under stress has long been considered as one of primary causes of stress sensitivity of fractured gas reservoirs. However, little is known about the evolution of the morphology of fracture apertures on flow property in loading and unloading cycles. This [...] Read more.

Fracture aperture change under stress has long been considered as one of primary causes of stress sensitivity of fractured gas reservoirs. However, little is known about the evolution of the morphology of fracture apertures on flow property in loading and unloading cycles. This paper reports a stress sensitivity experiment on carbonate core plugs in which Computed Tomography (CT) technology is applied to visualize and quantitatively evaluate morphological changes to the fracture aperture with respect to confining pressure. Fracture models were obtained at selected confining pressures on which pore-scale flow simulations were performed to estimate the equivalent absolute permeability. The results showed that with the increase of confining pressure from 0 to 0.6 MPa, the fracture aperture and equivalent permeability decreased at a greater gradient than their counterparts after 0.6 MPa. This meant that the rock sample is more stress-sensitive at low effective stress than at high effective stress. On the loading path, an exponential fitting was found to fit well between the effective confining pressure and the calculated permeability. On the unloading path, the relationship is found partially reversible, which can evidently be attributed to plastic deformation of the fracture as observed in CT images. Full article

(This article belongs to the Special Issue Flow and Transport Properties of Unconventional Reservoirs)

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23 pages, 6816 KiB

Open AccessArticle

Power Quality Improvement in a Cascaded Multilevel Inverter Interfaced Grid Connected System Using a Modified Inductive–Capacitive–Inductive Filter with Reduced Power Loss and Improved Harmonic Attenuation

by Meenakshi Jayaraman and Sreedevi VT^*

School of Electrical Engineering, Vellore Institute of Technology University (VIT University), Chennai 600127, India

Energies 2017, 10(11), 1834; https://doi.org/10.3390/en10111834 - 10 Nov 2017

Cited by 18 | Viewed by 6498

Abstract

Recently, multilevel inverters are more researched due to the advantages they offer over conventional voltage source inverters in grid connected applications. Passive filters are connected at the output of these inverters to produce sinusoidal waveforms with reduced harmonics and to satisfy grid interconnection [...] Read more.

Recently, multilevel inverters are more researched due to the advantages they offer over conventional voltage source inverters in grid connected applications. Passive filters are connected at the output of these inverters to produce sinusoidal waveforms with reduced harmonics and to satisfy grid interconnection standard requirements. This work proposes a new passive filter topology for a pulse width modulated five-level cascaded inverter interfaced grid connected system. The proposed passive filter inserts an additional resistance-capacitance branch in parallel to the filter capacitor of the traditional inductive–capacitive–inductive filter in addition to a resistance in series with it to reduce damping power loss. It can attenuate the switching frequency harmonic current components much better than the traditional filter while maintaining the same overall inductance, reduced capacitance and resistance values. The basic parameter design procedure and an approach to discover the parameters of the proposed filter is introduced. Further, a novel methodology using Particle Swarm Optimization (PSO) is recommended to guarantee minimum damping loss while ensuring reduced peak during resonance. In addition, PSO algorithm is newly employed in this work to maximize harmonic attenuation in and around the switching frequency on the premise of allowable values of filter inductance and capacitance. A comparative discussion considering traditional passive filters and the proposed filter is presented and evaluated through experiments conducted on a 110 V, 1 kW five-level grid connected inverter. The modulation algorithm for the multilevel inverter is implemented using a SPARTAN 6-XC6SLX25 Field Programmable Gate Array (FPGA) processor. The analysis shows that the proposed filter not only provides decreased damping power loss but also is capable of providing considerable harmonic ripple reduction in the high frequency band, improved output waveforms and lesser Total Harmonic Distortion (THD) with improved power quality for the multilevel inverter based grid connected system. Full article

(This article belongs to the Special Issue Power Electronics and Power Quality)

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13 pages, 1652 KiB

Open AccessArticle

On the Feasibility of Independently Controllable Transmissions

by Milan Perkušić^*, Damir Jelaska

, Srdjan Podrug

and Vjekoslav Tvrdić

Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, 21000 Split, Croatia

Energies 2017, 10(11), 1835; https://doi.org/10.3390/en10111835 - 10 Nov 2017

Cited by 1 | Viewed by 2930

Abstract

The present research is carried out to determine whether the independently controllable transmission (ICTs) are able to transmit the energy/power from the arbitrary variable speed input shaft to the variable or constant speed of the output shaft, independent of each other and without [...] Read more.

The present research is carried out to determine whether the independently controllable transmission (ICTs) are able to transmit the energy/power from the arbitrary variable speed input shaft to the variable or constant speed of the output shaft, independent of each other and without a control system. For this purpose, the novel ICT proposed in this study has the required features and is simpler than those proposed so far. However, this ICT and any other proposed ICT, while being feasible from a kinematic point of view, results in the conclusion that the transmissions are practically inapplicable, as will be demonstrated from the detailed power flow analysis carried out and presented in this paper. This is because either one shaft, the so called “free shaft”, has variable uncontrollable speed, or a couple of the shafts have powers close to zero. Full article

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17 pages, 1549 KiB

Open AccessArticle

Electrolyzers Enhancing Flexibility in Electric Grids

by Manish Mohanpurkar^1,*

, Yusheng Luo¹, Danny Terlip², Fernando Dias¹

, Kevin Harrison², Joshua Eichman², Rob Hovsapian¹ and Jennifer Kurtz²

¹ Idaho National Laboratory, 2525 Fremont Ave, Idaho Falls, ID 83402, USA

² National Renewable Energy Laboratory, 15013 Denver W Pkwy, Golden, CO 80401, USA

Energies 2017, 10(11), 1836; https://doi.org/10.3390/en10111836 - 10 Nov 2017

Cited by 47 | Viewed by 6751

Abstract

This paper presents a real-time simulation with a hardware-in-the-loop (HIL)-based approach for verifying the performance of electrolyzer systems in providing grid support. Hydrogen refueling stations may use electrolyzer systems to generate hydrogen and are proposed to have the potential of becoming smarter loads [...] Read more.

This paper presents a real-time simulation with a hardware-in-the-loop (HIL)-based approach for verifying the performance of electrolyzer systems in providing grid support. Hydrogen refueling stations may use electrolyzer systems to generate hydrogen and are proposed to have the potential of becoming smarter loads that can proactively provide grid services. On the basis of experimental findings, electrolyzer systems with balance of plant are observed to have a high level of controllability and hence can add flexibility to the grid from the demand side. A generic front end controller (FEC) is proposed, which enables an optimal operation of the load on the basis of market and grid conditions. This controller has been simulated and tested in a real-time environment with electrolyzer hardware for a performance assessment. It can optimize the operation of electrolyzer systems on the basis of the information collected by a communication module. Real-time simulation tests are performed to verify the performance of the FEC-driven electrolyzers to provide grid support that enables flexibility, greater economic revenue, and grid support for hydrogen producers under dynamic conditions. The FEC proposed in this paper is tested with electrolyzers, however, it is proposed as a generic control topology that is applicable to any load. Full article

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12 pages, 1508 KiB

Open AccessArticle

Kiwi Clear‐Cut: First Evaluation of Recovered Biomass for Energy Production

by Marco Manzone^*

, Fabrizio Gioelli

and Paolo Balsari

Department of Agricultural, Forest and Food Sciences, University of Torino, Largo Paolo Braccini, 2, 10095 Grugliasco, Italy

Energies 2017, 10(11), 1837; https://doi.org/10.3390/en10111837 - 10 Nov 2017

Cited by 12 | Viewed by 3426

Abstract

Among the various types of agricultural waste, significant amounts of energy can be obtained from woodchips derived from comminuted pruning residues. This study aimed to assess the feasibility of using kiwi orchard clear-cut biomass for energy production. The field trial was conducted in [...] Read more.

Among the various types of agricultural waste, significant amounts of energy can be obtained from woodchips derived from comminuted pruning residues. This study aimed to assess the feasibility of using kiwi orchard clear-cut biomass for energy production. The field trial was conducted in a commercial kiwi (Actinidia chinensis) orchard located in Northwest Italy. We evaluated the biomass yield, woodchip quality, energy consumption, and economic sustainability of this practice. Processed data determined the available biomass to be 20.6 tonnes dry matter ha⁻¹. Woodchip analysis showed a biomass moisture content of 53% and a relatively low heating value of about 7.5 MJ·kg⁻¹. Furthermore, the average ash content was 2.4%. Production cost was 99.6 €·t⁻¹ dry matter, which was slightly less than the market price of 100 €·t⁻¹ dry matter for woodchips. In summary, kiwi clear-cut recovered biomass may be a valid alternative biomass source. Full article

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24 pages, 3581 KiB

Open AccessFeature PaperArticle

Re-Creating Waves in Large Currents for Tidal Energy Applications

by Samuel Draycott^*

, Duncan Sutherland, Jeffrey Steynor

, Brian Sellar and Vengatesan Venugopal

School of Engineering, Institute for Energy Systems, The University of Edinburgh, Edinburgh EH9 3DW, UK

Energies 2017, 10(11), 1838; https://doi.org/10.3390/en10111838 - 10 Nov 2017

Cited by 12 | Viewed by 4362

Abstract

Unsteady wave loading on tidal turbines impacts significantly the design, and expected life-time, of turbine blades and other key components. Model-scale testing of tidal turbines in the wave-current environment can provide vital understanding by emulating real-world load cases; however, to reduce uncertainty, it [...] Read more.

Unsteady wave loading on tidal turbines impacts significantly the design, and expected life-time, of turbine blades and other key components. Model-scale testing of tidal turbines in the wave-current environment can provide vital understanding by emulating real-world load cases; however, to reduce uncertainty, it is important to isolate laboratory-specific artefacts from real-world behaviour. In this paper, a variety of realistic combined current-wave scenarios is re-created at the FloWave basin, where the main objective is to understand the characteristics of testing in a combined wave-current environment and assess whether wave effects on the flow field can be predicted. Here, we show that a combination of linear wave-current theory and frequency-domain reflection analysis can be used to effectively predict wave-induced particle velocities and identify velocity components that are experimental artefacts. Load-specific mechanisms present in real-world conditions can therefore be isolated, and equivalent full-scale load cases can be estimated with greater confidence. At higher flow speeds, a divergence from the theory presented is observed due to turbulence-induced non-stationarity. The methodology and results presented increase learning about the wave-current testing environment and provide analysis tools able to improve test outputs and conclusions from scale model testing. Full article

(This article belongs to the Special Issue Marine Energy)

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19 pages, 8161 KiB

Open AccessArticle

Wind Turbine Loads Induced by Terrain and Wakes: An Experimental Study through Vibration Analysis and Computational Fluid Dynamics

by Francesco Castellani^1,*, Marco Buzzoni², Davide Astolfi¹, Gianluca D’Elia², Giorgio Dalpiaz² and Ludovico Terzi³

¹ Department of Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy

² Department of Engineering, University of Ferrara, Via G. Saragat 1, 44122 Ferrara, Italy

³ Renvico s.r.l., Via San Gregorio 34, 20124 Milano, Italy

Energies 2017, 10(11), 1839; https://doi.org/10.3390/en10111839 - 10 Nov 2017

Cited by 11 | Viewed by 4992

Abstract

A wind turbine is a very well-known archetype of energy conversion system working at non-stationary regimes. Despite this, a deep mechanical comprehension of wind turbines operating in complicated conditions is still challenging, especially as regards the analysis of experimental data. In particular, wind [...] Read more.

A wind turbine is a very well-known archetype of energy conversion system working at non-stationary regimes. Despite this, a deep mechanical comprehension of wind turbines operating in complicated conditions is still challenging, especially as regards the analysis of experimental data. In particular, wind turbines in complex terrain represent a very valuable testing ground because of the possible combination of wake effects among nearby turbines and flow accelerations caused by the terrain morphology. For these reasons, in this work, a cluster of four full-scale wind turbines from a very complex site is studied. The object of investigation is vibrations, at the level of the structure (tower) and drive-train. Data collected by the on-board condition monitoring system are analyzed and interpreted in light of the knowledge of wind conditions and operating parameters collected by the Supervisory Control And Data Acquisition (SCADA). A free flow Computational Fluid Dynamics (CFD) simulation is also performed, and it allows one to better interpret the vibration analysis. The main outcome is the interpretation of how wakes and flow turbulences appear in the vibration signals, both at the structural level and at the drive-train level. Therefore, this wind to gear approach builds a connection between flow phenomena and mechanical phenomena in the form of vibrations, representing a precious tool for assessing loads in different working conditions. Full article

(This article belongs to the Special Issue Wind Turbine Loads and Wind Plant Performance)

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23 pages, 5212 KiB

Open AccessArticle

An Adaptive Model Predictive Load Frequency Control Method for Multi-Area Interconnected Power Systems with Photovoltaic Generations

by Guo-Qiang Zeng^1,*, Xiao-Qing Xie¹ and Min-Rong Chen²

¹ National-Local Joint Engineering Laboratory of Digitalize Electrical Design Technology, Wenzhou University, Wenzhou 325035, China

² School of Computer, South China Normal University, Guangzhou 510631, China

Energies 2017, 10(11), 1840; https://doi.org/10.3390/en10111840 - 11 Nov 2017

Cited by 60 | Viewed by 7431

Abstract

As the penetration level of renewable distributed generations such as wind turbine generator and photovoltaic stations increases, the load frequency control issue of a multi-area interconnected power system becomes more challenging. This paper presents an adaptive model predictive load frequency control method for [...] Read more.

As the penetration level of renewable distributed generations such as wind turbine generator and photovoltaic stations increases, the load frequency control issue of a multi-area interconnected power system becomes more challenging. This paper presents an adaptive model predictive load frequency control method for a multi-area interconnected power system with photovoltaic generation by considering some nonlinear features such as a dead band for governor and generation rate constraint for steam turbine. The dynamic characteristic of this system is formulated as a discrete-time state space model firstly. Then, the predictive dynamic model is obtained by introducing an expanded state vector, and rolling optimization of control signal is implemented based on a cost function by minimizing the weighted sum of square predicted errors and square future control values. The simulation results on a typical two-area power system consisting of photovoltaic and thermal generator have demonstrated the superiority of the proposed model predictive control method to these state-of-the-art control techniques such as firefly algorithm, genetic algorithm, and population extremal optimization-based proportional-integral control methods in cases of normal conditions, load disturbance and parameters uncertainty. Full article

(This article belongs to the Section F: Electrical Engineering)

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28 pages, 2334 KiB

Open AccessArticle

Aggregation Methods for Modelling Hydropower and Its Implications for a Highly Decarbonised Energy System in Europe

by Philipp Härtel^1,*

and Magnus Korpås²

¹ Energy Economy and Grid Operation, Fraunhofer Institute for Wind Energy and Energy System Technology (IWES), Königstor 59, 34119 Kassel, Germany

² Department of Electric Power Engineering, Norwegian University of Science and Technology (NTNU), O. S. Bragstads Plass 2E, 7034 Trondheim, Norway

Energies 2017, 10(11), 1841; https://doi.org/10.3390/en10111841 - 11 Nov 2017

Cited by 37 | Viewed by 5984

Abstract

Given the pursuit of long-term decarbonisation targets, future power systems face the task of integrating the renewable power and providing flexible backup production capacity. Due to its general ability to be dispatched, hydropower offers unique features and a backup production option not to [...] Read more.

Given the pursuit of long-term decarbonisation targets, future power systems face the task of integrating the renewable power and providing flexible backup production capacity. Due to its general ability to be dispatched, hydropower offers unique features and a backup production option not to be neglected, especially when taking the flexibility potential of multireservoir systems into account. Adequate hydropower representations are a necessity when analysing future power markets and aggregation methods are crucial for overcoming computational challenges. However, a major issue is that the aggregation must not be a too flexible representation. In a first step, a novel equivalent hydro system model implementation including a possibility to integrate pumping capacity and appropriate handling of multiple water paths (hydraulic coupling) by making use of an ex-ante optimisation is proposed. In a second step, a clustered equivalent hydro system model implementation employing k-means clustering is presented. A comparison of both aggregation approaches against the detailed reference system shows that both aggregated model variants yield significant reductions in computation time while keeping an adequate level of accuracy for a highly decarbonised power system scenario in Europe. The aggregation methods can easily be applied in different model types and may also be helpful in the stochastic case. Full article

(This article belongs to the Special Issue Hydropower 2017)

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17 pages, 5933 KiB

Open AccessEditor’s ChoiceArticle

Study on Quantitative Correlations between the Ageing Condition of Transformer Cellulose Insulation and the Large Time Constant Obtained from the Extended Debye Model

by Yiyi Zhang^1,2,†

, Jiefeng Liu^1,3,*,†

, Hanbo Zheng^1,4,*,†

, Hua Wei¹ and Ruijin Liao⁵

¹ Guangxi Key Laboratory of Power System Optimization and Energy Technology, Guangxi University, Nanning 530004, China

² National Demonstration Center for Experimental Electrical Engineering Education, Guangxi University, Nanning 530004, China

³ Shijiazhuang Power Supply Branch of State Grid Electric Power Company, Shijiazhuang 050000, China

⁴ State Grid Henan Electric Power Research Institute, Zhengzhou 450052, China

⁵ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China

^† These authors contributed equally to this work.

Energies 2017, 10(11), 1842; https://doi.org/10.3390/en10111842 - 11 Nov 2017

Cited by 29 | Viewed by 5648

Abstract

Polarization-depolarization current (PDC) measurements are now being used as a diagnosis tool to predict the ageing condition of transformer oil-paper insulation. Unfortunately, it is somewhat difficult to obtain the ageing condition of transformer cellulose insulation using the PDC technique due to the variation [...] Read more.

Polarization-depolarization current (PDC) measurements are now being used as a diagnosis tool to predict the ageing condition of transformer oil-paper insulation. Unfortunately, it is somewhat difficult to obtain the ageing condition of transformer cellulose insulation using the PDC technique due to the variation in transformer insulation geometry. In this literature, to quantify the ageing condition of transformer cellulose insulation using the PDC technique, we firstly designed a series of experiments under controlled laboratory conditions, and then obtained the branch parameters of an extended Debye model using the technique of curve fitting the PDC data. Finally, the ageing effect and water effect on the parameters of large time constant branches were systematically investigated. In the present paper, it is observed that there is a good exponential correlation between large time constants and degree of polymerization (DP). Therefore, the authors believe that the large time constants may be regard as a sensitive ageing indicator and the nice correlations might be utilized for the quantitative assessment of ageing condition in transformer cellulose insulation in the future due to the geometry independence of large time constants. In addition, it is found that the water in cellulose pressboards has a predominant effect on large time constants. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 5290 KiB

Open AccessArticle

A Simplified Top-Oil Temperature Model for Transformers Based on the Pathway of Energy Transfer Concept and the Thermal-Electrical Analogy

by Muhammad Hakirin Roslan^1,2, Norhafiz Azis^2,3,*, Mohd Zainal Abidin Ab Kadir²

, Jasronita Jasni², Zulkifli Ibrahim^2,4 and Azalan Ahmad⁵

¹ Faculty of Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sg Besi 57000, Malaysia

² Centre for Electromagnetic and Lightning Protection Research, Universiti Putra Malaysia, Serdang 43400, Malaysia

³ Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

⁴ Faculty of Engineering Technology, Universiti Teknikal Malaysia Melaka, Durian Tunggal 76100, Malaysia

⁵ Malaysia Transformer Manufacturing Sdn. Bhd, Ampang 54200, Selangor, Malaysia

Energies 2017, 10(11), 1843; https://doi.org/10.3390/en10111843 - 11 Nov 2017

Cited by 20 | Viewed by 6242

Abstract

This paper presents an alternative approach to determine the simplified top-oil temperature (TOT) based on the pathway of energy transfer and thermal-electrical analogy concepts. The main contribution of this study is the redefinition of the nonlinear thermal resistance based on these concepts. An [...] Read more.

This paper presents an alternative approach to determine the simplified top-oil temperature (TOT) based on the pathway of energy transfer and thermal-electrical analogy concepts. The main contribution of this study is the redefinition of the nonlinear thermal resistance based on these concepts. An alternative approximation of convection coefficient, h, based on heat transfer theory was proposed which eliminated the requirement of viscosity. In addition, the lumped capacitance method was applied to the thermal-electrical analogy to derive the TOT thermal equivalent equation in differential form. The TOT thermal model was evaluated based on the measured TOT of seven transformers with either oil natural air natural (ONAN) or oil natural air forced (ONAF) cooling modes obtained from temperature rise tests. In addition, the performance of the TOT thermal model was tested on step-loading of a transformer with an ONAF cooling mode obtained from previous studies. A comparison between the TOT thermal model and the existing TOT Thermal-Electrical, Exponential (IEC 60076-7), and Clause 7 (IEEE C57.91-1995) models was also carried out. It was found that the measured TOT of seven transformers are well represented by the TOT thermal model where the highest maximum and root mean square (RMS) errors are 6.66 °C and 2.76 °C, respectively. Based on the maximum and RMS errors, the TOT thermal model performs better than Exponential and Clause 7 models and it is comparable with the Thermal-Electrical 1 (TE1) and Thermal-Electrical 2 (TE2) models. The same pattern is found for the TOT thermal model under step-loading where the maximum and RMS errors are 5.77 °C and 2.02 °C. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 5114 KiB

Open AccessReview

Novel Carbon Materials in the Cathode Formulation for High Rate Rechargeable Hybrid Aqueous Batteries

by Xiao Zhu, Tuan K. A. Hoang and Pu Chen^*

Department of Chemical Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

Energies 2017, 10(11), 1844; https://doi.org/10.3390/en10111844 - 11 Nov 2017

Cited by 10 | Viewed by 4932

Abstract

Novel carbon materials, carbon nanotubes (CNTs) and porous graphene (PG), were exploited and used as conductive additives to improve the rate performance of LiMn₂O₄ cathode for the rechargeable aqueous Zn/LiMn₂O₄ battery, namely the rechargeable hybrid aqueous battery [...] Read more.

Novel carbon materials, carbon nanotubes (CNTs) and porous graphene (PG), were exploited and used as conductive additives to improve the rate performance of LiMn₂O₄ cathode for the rechargeable aqueous Zn/LiMn₂O₄ battery, namely the rechargeable hybrid aqueous battery (ReHAB). Thanks to the long-range conductivity and stable conductive network provided by CNTs, the rate and cycling performances of LiMn₂O₄ cathode in ReHAB are highly improved—up to about 100 mAh·g⁻¹ capacity is observed at 10 C (1 C = 120 mAh·g⁻¹). Except for CNTs, porous graphene (PG) with a high surface area, an abundant porous structure, and an excellent electrical conductivity facilitates the transportation of Li ions and electrons, which can also obviously enhance the rate capability of the ReHAB. This is important because the ReHAB could be charged/discharged in a few minutes, and this leads to potential application of the ReHAB in automobile industry. Full article

(This article belongs to the Section D: Energy Storage and Application)

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17 pages, 5518 KiB

Open AccessArticle

Research on Single-Phase PWM Converter with Reverse Conducting IGBT Based on Loss Threshold Desaturation Control

by Xianjin Huang^*

, Dengwei Chang, Chao Ling and Trillion Q. Zheng

School of Electrical Engineering, Beijing Jiaotong University, No. 3 Shangyuancun, Beijing 100044, China

Energies 2017, 10(11), 1845; https://doi.org/10.3390/en10111845 - 12 Nov 2017

Cited by 6 | Viewed by 8602

Abstract

In the application of vehicle power supply and distributed power generation, there are strict requirements for the pulse width modulation (PWM) converter regarding power density and reliability. When compared with the conventional insulated gate bipolar transistor (IGBT) module, the Reverse Conducting-Insulated Gate Bipolar [...] Read more.

In the application of vehicle power supply and distributed power generation, there are strict requirements for the pulse width modulation (PWM) converter regarding power density and reliability. When compared with the conventional insulated gate bipolar transistor (IGBT) module, the Reverse Conducting-Insulated Gate Bipolar Transistor (RC-IGBT) with the same package has a lower thermal resistance and higher current tolerance. By applying the gate desaturation control, the reverse recovery loss of the RC-IGBT diode may be reduced. In this paper, a loss threshold desaturation control method is studied to improve the output characteristics of the single-phase PWM converter with a low switching frequency. The gate desaturation control characteristics of the RC-IGBT’s diode are studied. A proper current limit is set to avoid the ineffective infliction of the desaturation pulse, while the bridge arm current crosses zero. The expectation of optimized loss decrease is obtained, and the better performance for the RC-IGBTs of the single-phase PWM converter is achieved through the optimized desaturation pulse distribution. Finally, the improved predictive current control algorithm that is applied to the PWM converter with RC-IGBTs is simulated, and is operated and tested on the scaled reduced power platform. The results prove that the gate desaturation control with the improved predictive current algorithm may effectively improve the RC-IGBT’s characteristics, and realize the stable output of the PWM converter. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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19 pages, 1076 KiB

Open AccessArticle

Battery Energy Management in a Microgrid Using Batch Reinforcement Learning

by Brida V. Mbuwir^1,2,*, Frederik Ruelens^1,2, Fred Spiessens^2,3 and Geert Deconinck^1,2

¹ ESAT/Electa, KU Leuven, Kasteelpark Arenberg 10 bus 2445, BE-3001 Leuven, Belgium

² Energy Department, EnergyVille, Thor Park, Poort Genk 8130, 3600 Genk, Belgium

³ Energy Department, Vlaamse Instelling voor Technologisch Onderzoek (VITO), Boeretang 200, B-2400 Mol, Belgium

Energies 2017, 10(11), 1846; https://doi.org/10.3390/en10111846 - 12 Nov 2017

Cited by 162 | Viewed by 9351

Abstract

Motivated by recent developments in batch Reinforcement Learning (RL), this paper contributes to the application of batch RL in energy management in microgrids. We tackle the challenge of finding a closed-loop control policy to optimally schedule the operation of a storage device, in [...] Read more.

Motivated by recent developments in batch Reinforcement Learning (RL), this paper contributes to the application of batch RL in energy management in microgrids. We tackle the challenge of finding a closed-loop control policy to optimally schedule the operation of a storage device, in order to maximize self-consumption of local photovoltaic production in a microgrid. In this work, the fitted Q-iteration algorithm, a standard batch RL technique, is used by an RL agent to construct a control policy. The proposed method is data-driven and uses a state-action value function to find an optimal scheduling plan for a battery. The battery’s charge and discharge efficiencies, and the nonlinearity in the microgrid due to the inverter’s efficiency are taken into account. The proposed approach has been tested by simulation in a residential setting using data from Belgian residential consumers. The developed framework is benchmarked with a model-based technique, and the simulation results show a performance gap of 19%. The simulation results provide insight for developing optimal policies in more realistically-scaled and interconnected microgrids and for including uncertainties in generation and consumption for which white-box models become inaccurate and/or infeasible. Full article

(This article belongs to the Special Issue Selected Papers from International Workshop of Energy-Open)

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26 pages, 2636 KiB

Open AccessArticle

Design and Control of a Buck–Boost Charger-Discharger for DC-Bus Regulation in Microgrids

by Carlos Andrés Ramos-Paja^1,*,†

, Juan David Bastidas-Rodríguez²

, Daniel González³

, Santiago Acevedo³ and Julián Peláez-Restrepo³

¹ Facultad de Minas, Universidad Nacional de Colombia, Medellín 050040, Colombia

² Escuela de Ingenierías Eléctrica, Electrónica y de Telecomunicaciones, Universidad Industrial de Santander, Bucaramanga 680002, Colombia

³ Departamento de Electrónica y Telecomunicaciones, Instituto Tecnologico Metropolitano, Medellín 050034, Colombia

^† Current address: Carrera 80 No 65-223, Block M8—Office 206-113, Medellín 050040, Colombia

Energies 2017, 10(11), 1847; https://doi.org/10.3390/en10111847 - 12 Nov 2017

Cited by 19 | Viewed by 6730

Abstract

In DC and hybrid microgrids (MG), the DC-bus regulation using Energy Storage Devices (ESD) is important for the stable operation of both the generators and loads. There are multiple commercial voltage levels for both ESD and DC-bus; therefore, the ESD voltage may be [...] Read more.

In DC and hybrid microgrids (MG), the DC-bus regulation using Energy Storage Devices (ESD) is important for the stable operation of both the generators and loads. There are multiple commercial voltage levels for both ESD and DC-bus; therefore, the ESD voltage may be higher, equal or lower than the DC-bus voltage depending on the application. Moreover, most of the ESD converter controllers are linear-based, hence they ensure stability in a limited operation range. This paper proposes a system to regulate the DC-bus voltage of an MG accounting for any voltage relation between the ESD and the DC-bus voltage. The proposed system is formed by an ESD connected to a DC-bus through a bidirectional Buck–Boost converter, which is regulated by a Sliding-Mode Controller (SMC) to ensure the system stability in the entire operation range. The SMC drives the Buck–Boost charger–discharger to regulate the DC-bus voltage, at the desired reference value, by charging or discharging the ESD. This paper also provides detailed procedures to design the parameters of both the SMC and the charger–dischager. Finally, simulation and experimental results validate the proposed solution and illustrate its performance. Full article

(This article belongs to the Section D: Energy Storage and Application)

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14 pages, 4922 KiB

Open AccessArticle

Impact-Based Electromagnetic Energy Harvester with High Output Voltage under Low-Level Excitations

by Qian Luo¹, Xuefeng He^1,2,*, Senlin Jiang^1,2 and Xingchang Wang¹

¹ Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China

² College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China

Energies 2017, 10(11), 1848; https://doi.org/10.3390/en10111848 - 14 Nov 2017

Cited by 15 | Viewed by 4522

Abstract

To expand the applications of vibrational energy harvesters (VEHs) as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs) are [...] Read more.

To expand the applications of vibrational energy harvesters (VEHs) as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs) are usually low, which complicates the power management circuit by an indispensable voltage boosting element. To this end, an impact-based non-resonant EMVEH mainly composed of an outer frame and an inner frame on rollers is proposed. Numerical simulations based on a mathematical model of the harvester are conducted to analyze the effects of structural parameters on the output performance. Under base excitation of 0.1 and 0.3 (where

g

is the gravitational acceleration, 1

g = 9.8 m \cdot s^{- 2}

), the experimental maximum root mean square voltages of a harvester prototype across a resistor of 11 kΩ are as high as 7.6 and 16.5 V at 6.0 and 8.5 Hz, respectively, with the maximum output powers of 5.3 and 24.8 mW, or the power densities of 54.6 and 256 μW cm⁻³. By using a management circuit without a voltage boosting element, a wireless sensor node driven by the prototype can measure and transmit the temperature and humidity every 20 s under base excitation of 0.1

g

at 5.4 Hz. Full article

(This article belongs to the Section L: Energy Sources)

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18 pages, 3317 KiB

Open AccessArticle

Analysis of Analytical Models Developed under the Uniaxial Strain Condition for Predicting Coal Permeability during Primary Depletion

by Chuanming Li¹, Zhiqiang Wang², Lei Shi² and Ruimin Feng^3,*

¹ Anhui Province Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mine, Anhui University of Science and Technology, Huainan 232001, China

² College of Resources & Safety Engineering, China University of Mining and Technology, Beijing 100083, China

³ Department of Mining and Mineral Resources Engineering, Southern Illinois University, Carbondale, IL 62901, USA

Energies 2017, 10(11), 1849; https://doi.org/10.3390/en10111849 - 12 Nov 2017

Cited by 14 | Viewed by 3854

Abstract

The stress-dependent permeability of coal during coalbed methane production has been extensively studied both experimentally and theoretically. However, how permeability changes as a function of stress variation is somewhat unclear to date, and currently used analytical models fail to accurately predict permeability evolution [...] Read more.

The stress-dependent permeability of coal during coalbed methane production has been extensively studied both experimentally and theoretically. However, how permeability changes as a function of stress variation is somewhat unclear to date, and currently used analytical models fail to accurately predict permeability evolution with gas depletion. Considering that the role played by changes in in situ stress in permeability evolution is critical, a comprehensive theoretical study was first conducted, through which it was found that coal permeability is determined by mean effective stress. Moreover, the influence of matrix shrinkage on cleat deformation and then coal permeability was overestimated by currently used models, leading to inaccuracy of the predicted permeability. By taking both mean effective stress and the influence of matrix shrinkage on cleat deformation into account, a new permeability model was developed under the uniaxial strain condition in order to precisely estimate permeability evolution during gas depletion. An in-depth investigation and comparison among four commonly-used permeability models, the Palmer and Mansoori (P&M) model, Improved P&M model, Shi and Durucan (S&D) model, and Cui and Bustin (C&B) model, was then conducted. It was experimentally verified that a good match can be achieved between the lab data and the results predicted by the proposed model. Permeability variation of coalbed reservoirs associated with gas depletion is a consequence of two opposing effects: mechanical compaction and matrix shrinkage. In comparison, it was found that the coefficients of these two effects incorporated in those four models have a significant impact on permeability variation; and the accuracy of the values of initial cleat porosity and cleat compressibility, the bridges connecting permeability, and those two effects in analytical models, is extremely critical to permeability estimations. This study can shed light on improving the accuracy of analytical coal permeability models and the prediction of gas production. Full article

(This article belongs to the Section L: Energy Sources)

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15 pages, 6707 KiB

Open AccessArticle

Effect of Charcoal and Kraft-Lignin Addition on Coke Compression Strength and Reactivity

by Hannu Suopajärvi^*, Essi Dahl, Antti Kemppainen, Stanislav Gornostayev, Aki Koskela and Timo Fabritius

Process Metallurgy Research Unit, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland

Energies 2017, 10(11), 1850; https://doi.org/10.3390/en10111850 - 13 Nov 2017

Cited by 39 | Viewed by 6644

Abstract

The aim of this research was to investigate the effects of charcoal and Kraft-lignin additions on the structure, cold compression strength, and reactivity of bio-cokes produced at the laboratory scale. Bio-cokes were prepared by adding charcoal and Kraft-lignin (2.5, 5.0, 7.5, and 10.0 [...] Read more.

The aim of this research was to investigate the effects of charcoal and Kraft-lignin additions on the structure, cold compression strength, and reactivity of bio-cokes produced at the laboratory scale. Bio-cokes were prepared by adding charcoal and Kraft-lignin (2.5, 5.0, 7.5, and 10.0 wt %) to medium-volatile coal and coking the mixture with controlled heating rate (3.5 °C/min) up to 1200 °C. In addition, four particle sizes of charcoal were added with a 5 wt % addition rate to investigate the effect of particle size on the compression strength and reactivity. Thermogravimetric analysis was used to evaluate the pyrolysis behavior of coal and biomasses. Optical microscopy was used to investigate the interaction of coal and biomass components. It was found that by controlling the amount of charcoal and Kraft-lignin in the coal blend, the compression strength of the bio-cokes remains at an acceptable level compared to the reference coke without biomass addition. The cold compression strength of the charcoal bio-cokes was higher compared to Kraft-lignin bio-cokes. The reactivity of the bio-cokes with charcoal addition was markedly higher compared to reference coke and Kraft-lignin bio-cokes, mainly due to the differences in the physical properties of the parental biomass. By increasing the bulk density of the coal/biomass charge, the cold compression strength of the bio-cokes can be improved substantially. Full article

(This article belongs to the Special Issue Thermo Fluid Conversion of Biomass)

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17 pages, 3955 KiB

Open AccessArticle

Combining Life Cycle Environmental and Economic Assessments in Building Energy Renovation Projects

by Roberta Moschetti^* and Helge Brattebø

Industrial Ecology Programme, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway

Energies 2017, 10(11), 1851; https://doi.org/10.3390/en10111851 - 13 Nov 2017

Cited by 32 | Viewed by 4767

Abstract

Buildings currently play a fundamental role for the achievement of the sustainable development goals as they are responsible for several environmental, social, and economic impacts. Energy renovation projects of existing buildings can support the reduction of environmental impacts by leading, at the same [...] Read more.

Buildings currently play a fundamental role for the achievement of the sustainable development goals as they are responsible for several environmental, social, and economic impacts. Energy renovation projects of existing buildings can support the reduction of environmental impacts by leading, at the same time, to economic and social advantages. In this paper, the life cycle assessment and life cycle costing methodologies were used in a combined performance assessment applied to a case study, i.e., the energy renovation project of a single-family house in Norway. Several scenarios based on alternative energy efficiency measures were analyzed, and life cycle environmental and economic indicators were computed, i.e., global warming potential (GWP), cumulative energy demand (CED), and net present cost (NPC). The results demonstrated the close to negative linear regression between the environmental and economic indicators computed. However, the values of CED and GWP for the best scenarios in environmental terms were respectively 50% and 32% lower than the values of the worst scenarios, while their NPC was around 6% higher than the lowest values. The findings can be helpful in the decision-making context towards a meaningful combination of environmental and economic assessments in building energy renovation projects for selecting the most sustainable scenario. Full article

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17 pages, 855 KiB

Open AccessArticle

Online Area Load Modeling in Power Systems Using Enhanced Reinforcement Learning

by Xiaoya Shang¹, Zhigang Li^1,*

, Tianyao Ji¹, P. Z. Wu² and Qinghua Wu¹

¹ School of Electric Power Engineering, South China University of Technology, Guangzhou 510641, China

² Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences, Shenzhen 518055, China

Energies 2017, 10(11), 1852; https://doi.org/10.3390/en10111852 - 13 Nov 2017

Cited by 11 | Viewed by 4220

Abstract

The accuracy of load modeling directly influences power system operation and control. Previous modeling studies have mainly concentrated on the loads connected to a single boundary bus, without thoroughly considering the static load characteristics of the voltage. To remedy this oversight, this paper [...] Read more.

The accuracy of load modeling directly influences power system operation and control. Previous modeling studies have mainly concentrated on the loads connected to a single boundary bus, without thoroughly considering the static load characteristics of the voltage. To remedy this oversight, this paper proposes an accurate modeling approach for area loads with multiple boundary buses and ZIP loads (a combination of constant-impedance, constant-current and constant-power loads) based on Ward equivalence. Furthermore, to satisfy the requirements for real-time monitoring, the model parameters are identified in an online manner using an enhanced reinforcement learning (ERL) algorithm. Parallel tables of value functions are implemented in the ERL algorithm to improve its tracking performance. Three simulation cases are addressed, the first involving a single ZIP load and the second and third involving area loads in the IEEE 57-bus system and in a real 1209-bus power system in China, respectively. The results demonstrate that the ERL algorithm outperforms an existing reinforcement learning algorithm and the improved least-squares method in terms of convergence and the ability to track both step-changing and time-varying loads. Additionally, the results obtained on test cases confirm that the proposed area load model is more accurate than a previously introduced model. Full article

(This article belongs to the Section F: Electrical Engineering)

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14 pages, 3338 KiB

Open AccessArticle

Indicative Fault Diagnosis of Wind Turbine Generator Bearings Using Tower Sound and Vibration

by Ehsan Mollasalehi

, David Wood^*

and Qiao Sun

Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada

Energies 2017, 10(11), 1853; https://doi.org/10.3390/en10111853 - 13 Nov 2017

Cited by 39 | Viewed by 6491

Abstract

The idea of indicative fault diagnosis based on measuring the wind turbine tower sound and vibration is presented. It had been reported by a wind farm operator that a major fault on the generator bearing causes shock and noise to be heard from [...] Read more.

The idea of indicative fault diagnosis based on measuring the wind turbine tower sound and vibration is presented. It had been reported by a wind farm operator that a major fault on the generator bearing causes shock and noise to be heard from the bottom of the wind turbine tower. The work in this paper was conceived to test whether tower top faults could be identified by taking simple measurements at the tower base. Two accelerometers were attached inside the wind turbine tower, and vibration data was collected while the wind turbine was in operation. Tower vibration signals were analyzed using Empirical Mode Decomposition and the outcomes were correlated with the vibration signals acquired directly from the generator bearings. It is shown that the generator bearing fault signatures were present in the vibrations from the tower. The results suggest that useful condition monitoring of nacelle components can be done even when there is no condition monitoring system installed on the generator bearings, as is often the case for older wind turbines. In the second part of the paper, acoustic measurements from a healthy and a faulty wind turbine are shown. The preliminary analysis suggests that the generator bearing fault increases the overall sound pressure level at the bottom of the tower, and is not buried in the background noise. Full article

(This article belongs to the Special Issue Wind Turbine Loads and Wind Plant Performance)

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10 pages, 2626 KiB

Open AccessArticle

Life-Cycle Assessment of an Innovative Ground-Source Heat Pump System with Upstream Thermal Storage

by Emanuele Bonamente^1,2,*

and Andrea Aquino²

¹ Department of Engineering, University of Perugia, 06125 Perugia, Italy

² Interuniversity Research Center on Pollution and Environment, University of Perugia, 06125 Perugia, Italy

Energies 2017, 10(11), 1854; https://doi.org/10.3390/en10111854 - 13 Nov 2017

Cited by 32 | Viewed by 5855

Abstract

An innovative space-conditioning system is proposed and a life-cycle assessment (LCA) is presented. The layout is obtained starting from a ground-source heat pump system (GSHP) and includes upstream thermal storage (TS). A prototype of the system, implemented following this new approach, is currently [...] Read more.

An innovative space-conditioning system is proposed and a life-cycle assessment (LCA) is presented. The layout is obtained starting from a ground-source heat pump system (GSHP) and includes upstream thermal storage (TS). A prototype of the system, implemented following this new approach, is currently in use for space heating and cooling of an industrial building. As a result of the TS designed to decouple the geothermal side from the heat-pump side, the system is able to provide the required thermal energy to the building with a reduced-size geothermal installation (i.e., shorter/fewer boreholes (BHs)). The performance was monitored for over 2 years, both in cooling and heating modes. A LCA study of this system is performed on the basis of specific data for implementation and operation phases. The results are given in terms of the comprehensive ReCiPe midpoint and endpoint indicator suite and are compared with literature studies of other conventional technologies for space conditioning. Full article

(This article belongs to the Special Issue 17th CIRIAF National Congress – Sustainable Development, Environment and Human Health Protection)

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18 pages, 1937 KiB

Open AccessArticle

Coal Supply Chains: A Whole-Process-Based Measurement of Carbon Emissions in a Mining City of China

by Guangfang Luo^1,2, Jianjun Zhang^1,3,*, Yongheng Rao¹, Xiaolei Zhu¹ and Yiqiang Guo^3,4

¹ School of Land Science and Technology, China University of Geosciences, Beijing 100083, China

² China Three Gorges Corporation Chongqing Branch, Chongqing 401147, China

³ Key Laboratory of Land Consolidation and Rehabilitation, Ministry of Land and Resources, Beijing 100083, China

⁴ Land Consolidation and Rehabilitation Center, Ministry of Land and Resources, Beijing 100035, China

Energies 2017, 10(11), 1855; https://doi.org/10.3390/en10111855 - 13 Nov 2017

Cited by 17 | Viewed by 7447

Abstract

The purpose of the study is to understand the carbon emissions in the coal supply chains of a mining city. The paper employed a conceptual methodology for the estimation of carbon emissions in the four processes of coal mining, selection and washing, transportation [...] Read more.

The purpose of the study is to understand the carbon emissions in the coal supply chains of a mining city. The paper employed a conceptual methodology for the estimation of carbon emissions in the four processes of coal mining, selection and washing, transportation and consumption. The results show that the total carbon emission of the coal supply chain in Wu’an is up to 3.51 × 10¹⁰ kg and is mainly sourced from the coal mining and consumption, respectively accounting for 13.10% and 84.62%, which indicates that deep coal processing plays a more critical determinant in coal production and consumption. Among the pillar industries, the carbon emissions from the steel industry accounts for 85.41% of the total in the coal consumption process, which indicates that the structure of carbon emissions is dependent on the local industrial structure. Additionally, the carbon directly from CO₂ accounts for 89.46%. Our study is not only to be able to supply references for the formulation strategy of a low carbon city, but also to provide a new approach to urban development patterns with a new view for coal resource management. Full article

(This article belongs to the Special Issue Selected Papers from the 8th Annual Conference of Energy Economics and Management)

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16 pages, 3984 KiB

Open AccessArticle

Development Patterns of Fractured Water-Conducting Zones in Longwall Mining of Thick Coal Seams—A Case Study on Safe Mining Under the Zhuozhang River

by Feng Du^1,2,3 and Rui Gao^4,*

¹ School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China

² The State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China

³ The State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China

⁴ Key Laboratory of Deep Coal Resource Mining, School of Mines, China University of Mining and Technology, Xuzhou 221116, China

Energies 2017, 10(11), 1856; https://doi.org/10.3390/en10111856 - 13 Nov 2017

Cited by 28 | Viewed by 4141

Abstract

The key to the safe mining of thick coal seams under rivers is understanding the development patterns of fractured water-conducting zones (FWCZ) when various mining methods are used. To solve this problem, we employed numerical simulation to investigate FWCZ when slice mining and [...] Read more.

The key to the safe mining of thick coal seams under rivers is understanding the development patterns of fractured water-conducting zones (FWCZ) when various mining methods are used. To solve this problem, we employed numerical simulation to investigate FWCZ when slice mining and longwall caving mining are performed. When slice mining was carried out, the maximum height of the FWCZ in the higher slice was 88 m. When the lower slice was mined, the maximum height became 95 m, and the ratio of the fracture height to the coal seam thickness was 15.8. For longwall caving mining, the height of the FWCZ reached 126 m, which was 31 m more than that of slice mining, and the ratio of the fracture height to the coal seam thickness was 21. Through field measurements, the height of the FWCZ during longwall caving mining of thick coal seams was verified. The measured height was 108.87–112.57 m, and the measured ratio was 19.08–19.28. Under the same stratigraphic conditions, changes in the bulking factor and structural stability of key strata were the dominant factors that determined how mining methods affected the height of the FWCZ. These development patterns can provide significant theoretical insights for effectively preventing water hazards on mine roofs. Full article

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15 pages, 13436 KiB

Open AccessArticle

Study on the Effects of Thermal Aging on Insulating Paper for High Voltage Transformer Composite with Natural Ester from Palm Oil Using Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDS)

by Abi Munajad^*

, Cahyo Subroto

and Suwarno

School of Electrical Engineering and Informatics, Institut Teknologi Bandung, 40132 Bandung, Indonesia

Energies 2017, 10(11), 1857; https://doi.org/10.3390/en10111857 - 13 Nov 2017

Cited by 50 | Viewed by 6370

Abstract

Mineral oil is widely used as liquid insulation in high voltage equipment. Due to environmental considerations, recently natural esters have been considered as naturally friendly liquid insulation candidates for high voltage transformers. In this experiment, transformer insulation paper was subjected to get accelerated [...] Read more.

Mineral oil is widely used as liquid insulation in high voltage equipment. Due to environmental considerations, recently natural esters have been considered as naturally friendly liquid insulation candidates for high voltage transformers. In this experiment, transformer insulation paper was subjected to get accelerated aging test with copper strip in natural ester in a hermeneutical heat-resistant glass bottle at temperatures of 120 °C and 150 °C for 336 h, 672 h and 1008 h. The experimental results of Fourier transform infrared spectroscopy (FTIR) showed that the intensity of the absorbance peak of the O–H functional group decreased with aging, while the intensity of the C–H and C=O functional group absorbance peaks have increased with aging and the intensity of the C–O functional group absorbance peak has a tendency to increase with aging. The energy dispersive X-ray spectroscopy (EDS) experimental results showed that the weight percent of the element C increased with aging and the weight percent of the element O has decreased with aging. The experimental results show a good correlation between the degree of polymerization (DP) and the weight percent of O element. This indicates that EDS may be used as a new method for estimating the DP of transformer insulation paper. Full article

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24 pages, 10557 KiB

Open AccessArticle

The Future of Sustainable Energy Production in Pakistan: A System Dynamics-Based Approach for Estimating Hubbert Peaks

by Syed Aziz Ur Rehman¹, Yanpeng Cai^1,2,*, Nayyar Hussain Mirjat³, Gordhan Das Walasai⁴

, Izaz Ali Shah⁵ and Sharafat Ali⁵

¹ State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China

² Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, SK S4S 0A2, Canada

³ Department of Electrical Engineering, Energy Environmental Engineering Research Group, Mehran University of Engineering and Technology, Jamshoro 76062, Pakistan

⁴ Department of Mechanical Engineering, Quaid-e-Awam University of Engineering, Science and Technology, Nawabshah 67450, Pakistan

⁵ State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China

Energies 2017, 10(11), 1858; https://doi.org/10.3390/en10111858 - 13 Nov 2017

Cited by 34 | Viewed by 7655

Abstract

This paper presents an effort pertaining to the simulation of the future production in Pakistan of different primary energy resources, i.e., coal, natural gas and crude oil, thereby constructing Hubbert peaks. In this context, the past 45 years’ production data of primary energy [...] Read more.

This paper presents an effort pertaining to the simulation of the future production in Pakistan of different primary energy resources, i.e., coal, natural gas and crude oil, thereby constructing Hubbert peaks. In this context, the past 45 years’ production data of primary energy resources of Pakistan have been analyzed and simulated using a generic STELLA (Systems Thinking, Experimental Learning Laboratory with Animation) model. The results show that the Hubbert peak of Pakistan’s crude oil production has been somehow already achieved in 2013, with the highest production of 4.52 million toe, which is 1.51 times the production in 2000. Similarly, the natural gas peak production is expected in 2024 with a production of 32.70 million toe which shall be 1.96-fold the extraction of the resource in the year 2000. On the other hand, the coal production in the country has been historically very low and with a constant production rate that is gradually picking up, the peak production year for the coal is anticipated to be in the year 2080 with an estimated production of 134.06 million. Based on the results of this study, which provide a greater understanding of future energy patterns, it is recommended that an energy security policy be devised for the country to ensure sustained supplies in the future. Full article

(This article belongs to the Section L: Energy Sources)

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22 pages, 3787 KiB

Open AccessFeature PaperArticle

100% Renewable Energy Supply for Brazil—The Role of Sector Coupling and Regional Development

by Hans Christian Gils^1,*

, Sonja Simon¹

and Rafael Soria^2,3

¹ DLR—German Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

² Energy Planning Program, Graduate School of Engineering, Universidade Federal do Rio de Janeiro, Centro de Tecnologia, Bloco C, Sala 211, Cidade Universitária, Ilha do Fundão, 21941-972 Rio de Janeiro, RJ, Brazil

³ Departamento de Ingeniería Mecánica, Escuela Politécnica Nacional, Ladrón de Guevara E11-253, 17-01-2759 Quito, Ecuador

Energies 2017, 10(11), 1859; https://doi.org/10.3390/en10111859 - 13 Nov 2017

Cited by 72 | Viewed by 9832

Abstract

With its abundance of renewable energy potentials, not only for hydropower and bioenergy, but also for wind and solar, Brazil provides good prospects for a carbon neutral energy system. The role of an enhanced coupling of the power, heat and transport sectors in [...] Read more.

With its abundance of renewable energy potentials, not only for hydropower and bioenergy, but also for wind and solar, Brazil provides good prospects for a carbon neutral energy system. The role of an enhanced coupling of the power, heat and transport sectors in such systems is not yet fully understood. This paper analyses the least-cost composition and operation of a fully renewable power supply system as part of a carbon neutral energy supply in Brazil. It relies on the application of the high-resolution energy system model REMix. Our analysis reveals that the expansion of wind and solar power is more cost-efficient than the construction of additional hydroelectric plants. This is favoured because the existing hydroelectric plants offer large capacity of dispatchable power to compensate for fluctuations, and thus no additional storage is necessary. Furthermore, the REMix analysis indicates that varying shares of solar and wind power technologies as well as the spatial distribution of power generation have only a small influence on supply costs. This implies that the transformation strategy in Brazil can be primarily based on other criteria such as regional development, public acceptance, environmental impact or industrial policy without major impacts on system costs. Full article

(This article belongs to the Section D: Energy Storage and Application)

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17 pages, 4174 KiB

Open AccessReview

Studies on Cup Anemometer Performances Carried out at IDR/UPM Institute. Past and Present Research

by Elena Roibas-Millan¹

, Javier Cubas^1,2

and Santiago Pindado^1,2,*

¹ Instituto Universitario de Microgravedad “Ignacio Da Riva” (IDR/UPM), ETSI Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Pza. del Cardenal Cisneros 3, 28040 Madrid, Spain

² Departamento de Sistemas Aeroespaciales, Transporte Aéreo y Aeropuertos (SATAA), ETSI Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Pza. del Cardenal Cisneros 3, 28040 Madrid, Spain

Energies 2017, 10(11), 1860; https://doi.org/10.3390/en10111860 - 14 Nov 2017

Cited by 15 | Viewed by 11226

Abstract

In the present work, the research derived from a wide experience on cup anemometer calibration works at IDR/UPM Institute (Instituto Universitario de Microgravedad “Ignacio Da Riva”) is summarized. This research started in 2008, analyzing large series of calibrations, and is [...] Read more.

In the present work, the research derived from a wide experience on cup anemometer calibration works at IDR/UPM Institute (Instituto Universitario de Microgravedad “Ignacio Da Riva”) is summarized. This research started in 2008, analyzing large series of calibrations, and is focused on two main aspects: (1) developing a procedure to predict the degradation level of these wind sensors when working on the field and (2) modeling cup anemometer performances. The wear and tear level of this sensor is evaluated studying the output signal and its main frequencies through Fourier analysis. The modeling of the cup anemometer performances is carried out analyzing first the cup aerodynamics. As a result of this process, carried out through several testing and analytical studies since 2010, a new analytical method has been developed. This methodology might represent an alternative to the classic approach used in the present standards of practice such as IEC 64000-12. Full article

(This article belongs to the Section F: Electrical Engineering)

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14 pages, 3379 KiB

Open AccessArticle

Case Library Construction Technology of Energy Loss in Distribution Networks Considering Regional Differentiation Theory

by Ze Yuan¹, Weizhou Wang², Jing Peng², Fuchao Liu² and Jianhua Yang^1,*

¹ College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China

² State Grid Gansu Electric Power Company, Lanzhou 730046, China

Energies 2017, 10(11), 1861; https://doi.org/10.3390/en10111861 - 14 Nov 2017

Cited by 1 | Viewed by 3306

Abstract

The grid structures, load levels, and running states of distribution networks in different supply regions are known as the influencing factors of energy loss. In this paper, the case library of energy loss is constructed to differentiate the crucial factors of energy loss [...] Read more.

The grid structures, load levels, and running states of distribution networks in different supply regions are known as the influencing factors of energy loss. In this paper, the case library of energy loss is constructed to differentiate the crucial factors of energy loss in the different supply regions. First of all, the characteristic state values are selected as the representation of the cases based on the analysis of energy loss under various voltage classes and in different types of regions. Then, the methods of Grey Relational Analysis and the K-Nearest Neighbor are utilized to implement the critical technologies of case library construction, including case representation, processing, analysis, and retrieval. Moreover, the analysis software of the case library is designed based on the case library construction technology. Some case studies show that there are many differences and similarities concerning the factors that influence the energy loss in different types of regions. In addition, the most relevant sample case can be retrieved from the case library. Compared with the traditional techniques, constructing a case library provides a new way to find out the characteristics of energy loss in different supply regions and constitutes differentiated loss-reducing programs. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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18 pages, 2569 KiB

Open AccessArticle

Ice Cover Prediction of a Power Grid Transmission Line Based on Two-Stage Data Processing and Adaptive Support Vector Machine Optimized by Genetic Tabu Search

by Xiaomin Xu^*, Dongxiao Niu, Lihui Zhang, Yongli Wang and Keke Wang

School of Economics and Management, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(11), 1862; https://doi.org/10.3390/en10111862 - 14 Nov 2017

Cited by 27 | Viewed by 4681

Abstract

With the increase in energy demand, extreme climates have gained increasing attention. Ice disasters on transmission lines can cause gap discharge and icing flashover electrical failures, which can lead to mechanical failure of the tower, conductor, and insulators, causing significant harm to people’s [...] Read more.

With the increase in energy demand, extreme climates have gained increasing attention. Ice disasters on transmission lines can cause gap discharge and icing flashover electrical failures, which can lead to mechanical failure of the tower, conductor, and insulators, causing significant harm to people’s daily life and work. To address this challenge, an intelligent combinational model is proposed based on improved empirical mode decomposition and support vector machine for short-term forecasting of ice cover thickness. Firstly, in light of the characteristics of ice cover thickness data, fast independent component analysis (FICA) is implemented to smooth the abnormal situation on the curve trend of the original data for prediction. Secondly, ensemble empirical mode decomposition (EEMD) decomposes data after denoising it into different components from high frequency to low frequency, and support vector machine (SVM) is introduced to predict the sequence of different components. Then, some modifications are performed on the standard SVM algorithm to accelerate the convergence speed. Combined with the advantages of genetic algorithm and tabu search, the combination algorithm is introduced to optimize the parameters of support vector machine. To improve the prediction accuracy, the kernel function of the support vector machine is adaptively adopted according to the complexity of different sequences. Finally, prediction results for each component series are added to obtain the overall ice cover thickness. A 220 kV DC transmission line in the Hunan Region is taken as the case study to verify the practicability and effectiveness of the proposed method. Meanwhile, we select SVM optimized by genetic algorithm (GA-SVM) and traditional SVM algorithm for comparison, and use the error function of mean absolute percentage error (MAPE), root mean square error (RMSE) and mean absolute error (MAE) to compare prediction accuracy. Finally, we find that these improvements facilitate the forecasting efficiency and improve the performance of the model. As a result, the proposed model obtains more ideal solutions and has higher accuracy and stronger generalization than other algorithms. Full article

(This article belongs to the Special Issue Hybrid Advanced Optimization Methods with Evolutionary Computation Techniques in Energy Forecasting)

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14 pages, 1724 KiB

Open AccessArticle

Short-Term Frequency Response of a DFIG-Based Wind Turbine Generator for Rapid Frequency Stabilization

by Dejian Yang¹

, Moses Kang¹, Eduard Muljadi²

, Wenzhong Gao³, Junhee Hong⁴, Jaeseok Choi⁵

and Yong Cheol Kang^4,*

¹ Department of Electrical Engineering and Wind Energy Grid-Adaptive Technology (WeGAT) Research Centre, Chonbuk National University, Chonju 54896, Korea

² National Renewable Energy Laboratory, Golden, CO 80401, USA

³ Department of Electrical and Computer Engineering, University of Denver, Denver, CO 80208, USA

⁴ Department of Energy IT, Gachon University, Seoul 13120, Korea

⁵ Department of Electrical Engineering, Gyeongsang National University, Jinju 52828, Korea

Energies 2017, 10(11), 1863; https://doi.org/10.3390/en10111863 - 14 Nov 2017

Cited by 7 | Viewed by 4443

Abstract

This paper proposes a short-term frequency-response scheme of a doubly-fed induction generator (DFIG)-based wind turbine generator (WTG) for improving rotor speed recovery and frequency nadir. In the energy-releasing period, to improve the frequency nadir and rotor speed convergence by releasing a large amount [...] Read more.

This paper proposes a short-term frequency-response scheme of a doubly-fed induction generator (DFIG)-based wind turbine generator (WTG) for improving rotor speed recovery and frequency nadir. In the energy-releasing period, to improve the frequency nadir and rotor speed convergence by releasing a large amount of kinetic energy stored in the rotating masses in a DFIG-based WTG, the power reference is increased up to the torque limit referred to the power and reduces along with it for a predefined period which is determined based on the occurrence time of the frequency nadir in a power grid. Then, the reference decreases so that the rotor speed is forced to be converged to the preset value in the stable operating region of the rotor speed. In the energy-absorbing period, to quickly recover the rotor speed, the reference smoothly decreases with the rotor speed and time during a predefined period until it intersects with the maximum power point tracking curve. The simulation results demonstrate that the proposed scheme successfully achieves rapid frequency stabilization with the improved frequency nadir under various wind conditions based on the IEEE 14-bus system. Full article

(This article belongs to the Section F: Electrical Engineering)

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30 pages, 3358 KiB

Open AccessReview

Progress on Protection Strategies to Mitigate the Impact of Renewable Distributed Generation on Distribution Systems

by Mohamad Norshahrani^1,2

, Hazlie Mokhlis^1,*

, Ab. Halim Abu Bakar³, Jasrul Jamani Jamian⁴

and Shivashankar Sukumar⁵

¹ Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Public Works Department, Menara Kerja Raya, Jalan Sultan Salahuddin, 50580 Kuala Lumpur, Malaysia

³ University of Malaya Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4, Wisma R&D UM, University of Malaya, 59990 Kuala Lumpur, Malaysia

⁴ Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia

⁵ Institute of Power Engineering (IPE), Universiti Tenaga Nasional, Jalan Ikram-Uniten, 43000 Kajang, Selangor, Malaysia

Energies 2017, 10(11), 1864; https://doi.org/10.3390/en10111864 - 14 Nov 2017

Cited by 77 | Viewed by 7486

Abstract

The benefits of distributed generation (DG) based on renewable energy sources leads to its high integration in the distribution network (DN). Despite its well-known benefits, mainly in improving the distribution system reliability and security, there are challenges encountered from a protection system perspective. [...] Read more.

The benefits of distributed generation (DG) based on renewable energy sources leads to its high integration in the distribution network (DN). Despite its well-known benefits, mainly in improving the distribution system reliability and security, there are challenges encountered from a protection system perspective. Traditionally, the design and operation of the protection system are based on a unidirectional power flow in the distribution network. However, the integration of distributed generation causes multidirectional power flows in the system. Therefore, the existing protection systems require some improvement or modification to address this new feature. Various protection strategies for distribution system have been proposed so that the benefits of distributed generation can be fully utilized. This paper reviews the current progress in protection strategies to mitigate the impact of distributed generation in the distribution network. In general, the reviewed strategies in this paper are divided into: (1) conventional protection systems and (2) modifications of the protection systems. A comparative study is presented in terms of the respective benefits, shortcomings and implementation cost. Future directions for research in this area are also presented. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 2034 KiB

Open AccessArticle

A Novel Short-Term Maintenance Strategy for Power Transmission and Transformation Equipment Based on Risk-Cost-Analysis

by Hang Yang^1,*, Zhe Zhang¹, Xianggen Yin¹, Jiexiang Han¹, Yong Wang² and Guoyan Chen²

¹ State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China

² Guangzhou Power Supply Company, Ltd., Guangzhou 510000, China

Energies 2017, 10(11), 1865; https://doi.org/10.3390/en10111865 - 14 Nov 2017

Cited by 8 | Viewed by 3371

Abstract

Current studies on preventive condition-based maintenance of power transmission and transformation equipment mainly focus on mid-term or long-term maintenance, and cannot meet the requirements of short-term especially temporary maintenance. In order to solve the defects of the present preventive maintenance strategies, according to [...] Read more.

Current studies on preventive condition-based maintenance of power transmission and transformation equipment mainly focus on mid-term or long-term maintenance, and cannot meet the requirements of short-term especially temporary maintenance. In order to solve the defects of the present preventive maintenance strategies, according to the engineering application and based on risk-cost analysis, a short-term maintenance strategy is proposed in this manuscript. For the equipment working in bad health condition, its active maintenance costs and operation risk costs are evaluated, respectively. Then the latest maintenance time is calculated in accordance with the principle that its operation risk costs are no higher than active maintenance costs. Utilizing the latest maintenance time, the best maintenance time is calculated by setting the maximum relative earnings of postponing maintenance as the target, which provides the operation staffs with comprehensive maintenance-decision support. In the end, different cases on the IEEE 24-bus system are simulated. The effectiveness and advantages of the proposed strategy are demonstrated by the simulation results. Full article

(This article belongs to the Section F: Electrical Engineering)

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20 pages, 4164 KiB

Open AccessArticle

Joint Evaluation of the Wave and Offshore Wind Energy Resources in the Developing Countries

by Eugen Rusu

and Florin Onea^*

Department of Mechanical Engineering, Faculty of Engineering, “Dunărea de Jos” University of Galati, 47 Domneasca Street, 800008 Galati, Romania

Energies 2017, 10(11), 1866; https://doi.org/10.3390/en10111866 - 15 Nov 2017

Cited by 35 | Viewed by 5829

Abstract

The objective of the present work is to assess the global wind and wave resources in the vicinity of some developing countries by evaluating 16-year of data (2001–2016), coming from the European Centre for Medium range Weather Forecast (ECMWF). Until now, not much [...] Read more.

The objective of the present work is to assess the global wind and wave resources in the vicinity of some developing countries by evaluating 16-year of data (2001–2016), coming from the European Centre for Medium range Weather Forecast (ECMWF). Until now, not much work has been done to evaluate and use the renewable energy sources from these marine environments. This is because most of the attention was focused on more promising areas, such as the European coasts, which are more advanced in terms of technical and economical aspects. A general perspective of the current energy market from the selected target areas is first presented, indicating at the same time the progresses that have been reported in the field of the renewable energy. Besides the spatial and seasonal variations of the marine resources considered, the results also indicate the energy potential of these coastal environments as well as the performances of some offshore wind turbines, which may operate in these regions. Full article

(This article belongs to the Section L: Energy Sources)

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11 pages, 5547 KiB

Open AccessArticle

Experimental Studies of Phase Change and Microencapsulated Phase Change Materials in a Cold Storage/Transportation System with Solar Driven Cooling Cycle

by Lin Zheng

, Wei Zhang^*, Fei Liang, Shuang Lin and Xiangyu Jin

Key Laboratory Deep Underground Science and Engineering (Ministry of Education), School of Architecture and Environment, Sichuan University, Chengdu 610065, China

Energies 2017, 10(11), 1867; https://doi.org/10.3390/en10111867 - 14 Nov 2017

Cited by 8 | Viewed by 5103

Abstract

The paper presents the different properties of phase change material (PCM) and Microencapsulated phase change material (MEPCM) employed to cold storage/transportation system with a solar-driven cooling cycle. Differential Scanning Calorimeter (DSC) tests have been performed to analyze the materials enthalpy, melting temperature range, [...] Read more.

The paper presents the different properties of phase change material (PCM) and Microencapsulated phase change material (MEPCM) employed to cold storage/transportation system with a solar-driven cooling cycle. Differential Scanning Calorimeter (DSC) tests have been performed to analyze the materials enthalpy, melting temperature range, and temperature range of solidification. KD2 Pro is used to test the thermal conductivities of phase change materials slurry and the results were used to compare the materials heat transfer performance. The slurry flow characteristics of MEPCM slurry also have been tested. Furthermore, in order to analyze the improvement effect on stability, the stability of MEPCM slurry with different surfactants have been tested. The researches of the PCM and MEPCM thermal properties revealed a more prospective application for phase change materials in energy storage/transportation systems. The study aims to find the most suitable chilling medium to further optimize the design of the cold storage/transportation systems with solar driven cooling cycles. Full article

(This article belongs to the Special Issue Solar Technologies for Buildings)

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23 pages, 2113 KiB

Open AccessArticle

An Integrated Modeling Approach for Forecasting Long-Term Energy Demand in Pakistan

by Syed Aziz Ur Rehman¹, Yanpeng Cai^1,2,*, Rizwan Fazal³, Gordhan Das Walasai⁴

and Nayyar Hussain Mirjat⁵

¹ State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China

² Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, SK S4S 0A2, Canada

³ Pakistan Institute of Development Economics (PIDE), Quaid-e-Azam University Campus, P.O. Box 1091, Islamabad 44000, Pakistan

⁴ Department of Mechanical Engineering, Quaid-e-Awam University of Engineering, Science and Technology, Nawabshah 67480, Pakistan

⁵ Department of Electrical Engineering, Mehran University of Engineering and Technology, Jamshoro 76062, Pakistan

Energies 2017, 10(11), 1868; https://doi.org/10.3390/en10111868 - 15 Nov 2017

Cited by 94 | Viewed by 8980

Abstract

Energy planning and policy development require an in-depth assessment of energy resources and long-term demand forecast estimates. Pakistan, unfortunately, lacks reliable data on its energy resources as well do not have dependable long-term energy demand forecasts. As a result, the policy makers could [...] Read more.

Energy planning and policy development require an in-depth assessment of energy resources and long-term demand forecast estimates. Pakistan, unfortunately, lacks reliable data on its energy resources as well do not have dependable long-term energy demand forecasts. As a result, the policy makers could not come up with an effective energy policy in the history of the country. Energy demand forecast has attained greatest ever attention in the perspective of growing population and diminishing fossil fuel resources. In this study, Pakistan’s energy demand forecast for electricity, natural gas, oil, coal and LPG across all the sectors of the economy have been undertaken. Three different energy demand forecasting methodologies, i.e., Autoregressive Integrated Moving Average (ARIMA), Holt-Winter and Long-range Energy Alternate Planning (LEAP) model were used. The demand forecast estimates of each of these methods were compared using annual energy demand data. The results of this study suggest that ARIMA is more appropriate for energy demand forecasting for Pakistan compared to Holt-Winter model and LEAP model. It is estimated that industrial sector’s demand shall be highest in the year 2035 followed by transport and domestic sectors. The results further suggest that energy fuel mix will change considerably, such that oil will be the most highly consumed energy form (38.16%) followed by natural gas (36.57%), electricity (16.22%), coal (7.52%) and LPG (1.52%) in 2035. In view of higher demand forecast of fossil fuels consumption, this study recommends that government should take the initiative for harnessing renewable energy resources for meeting future energy demand to not only avert huge import bill but also achieving energy security and sustainability in the long run. Full article

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19 pages, 12992 KiB

Open AccessFeature PaperArticle

Photovoltaic Device Performance Evaluation Using an Open-Hardware System and Standard Calibrated Laboratory Instruments

by Jesús Montes-Romero¹, Michel Piliougine²

, José Vicente Muñoz¹, Eduardo F. Fernández^1,*

and Juan De la Casa¹

¹ IDEA Research Group, Universidad de Jaén, Campus de Las Lagunillas, 23071 Jaén, Spain

² Dpto. de Lenguajes y Ciencias de la Computación, Universidad de Málaga, Bulevar Louis Pasteur 35, 29071 Málaga, Spain

Energies 2017, 10(11), 1869; https://doi.org/10.3390/en10111869 - 15 Nov 2017

Cited by 22 | Viewed by 4625

Abstract

This article describes a complete characterization system for photovoltaic devices designed to acquire the current-voltage curve and to process the obtained data. The proposed system can be replicated for educational or research purposes without having wide knowledge about electronic engineering. Using standard calibrated [...] Read more.

This article describes a complete characterization system for photovoltaic devices designed to acquire the current-voltage curve and to process the obtained data. The proposed system can be replicated for educational or research purposes without having wide knowledge about electronic engineering. Using standard calibrated instrumentation, commonly available in any laboratory, the accuracy of measurements is ensured. A capacitive load is used to bias the device due to its versatility and simplicity. The system includes a common part and an interchangeable part that must be designed depending on the electrical characteristics of each PV device. Control software, developed in LabVIEW, controls the equipment, performs automatic campaigns of measurements, and performs additional calculations in real time. These include different procedures to extrapolate the measurements to standard test conditions and methods to obtain the intrinsic parameters of the single diode model. A deep analysis of the uncertainty of measurement is also provided. Finally, the proposed system is validated by comparing the results obtained from some commercial photovoltaic modules to the measurements given by an independently accredited laboratory. Full article

(This article belongs to the Section F: Electrical Engineering)

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21 pages, 10307 KiB

Open AccessArticle

Heat Transfer Characteristics and Prediction Model of Supercritical Carbon Dioxide (SC-CO₂) in a Vertical Tube

by Can Cai^1,2,3, Xiaochuan Wang^1,2,3,*

, Shaohua Mao⁴, Yong Kang^1,2,3, Yiyuan Lu^1,2,3, Xiangdong Han^1,2,3 and Wenchuan Liu^1,2,3

¹ Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, Wuhan University, Wuhan 430072, China

² Hubei Key Laboratory of Waterjet Theory and New Technology, Wuhan University, Wuhan 430072, China

³ School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

⁴ China Ship Development and Design Center, Wuhan 430072, China

Energies 2017, 10(11), 1870; https://doi.org/10.3390/en10111870 - 15 Nov 2017

Cited by 15 | Viewed by 5245

Abstract

Due to its distinct capability to improve the efficiency of shale gas production, supercritical carbon dioxide (SC-CO₂) fracturing has attracted increased attention in recent years. Heat transfer occurs in the transportation and fracture processes. To better predict and understand the heat [...] Read more.

Due to its distinct capability to improve the efficiency of shale gas production, supercritical carbon dioxide (SC-CO₂) fracturing has attracted increased attention in recent years. Heat transfer occurs in the transportation and fracture processes. To better predict and understand the heat transfer of SC-CO₂ near the critical region, numerical simulations focusing on a vertical flow pipe were performed. Various turbulence models and turbulent Prandtl numbers (Pr_t) were evaluated to capture the heat transfer deterioration (HTD). The simulations show that the turbulent Prandtl number model (TWL model) combined with the Shear Stress Transport (SST) k-ω turbulence model accurately predicts the HTD in the critical region. It was found that Pr_t has a strong effect on the heat transfer prediction. The HTD occurred under larger heat flux density conditions, and an acceleration process was observed. Gravity also affects the HTD through the linkage of buoyancy, and HTD did not occur under zero-gravity conditions. Full article

(This article belongs to the Special Issue Mathematical and Computational Modeling in Geothermal Engineering)

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18 pages, 2119 KiB

Open AccessArticle

Intelligent Energy Management Control for Extended Range Electric Vehicles Based on Dynamic Programming and Neural Network

by Lihe Xi¹, Xin Zhang^1,*, Chuanyang Sun¹, Zexing Wang², Xiaosen Hou¹ and Jibao Zhang¹

¹ Beijing Key Laboratory of Powertrain for New Energy Vehicle, Beijing Jiaotong University, Beijing 100044, China

² Beijing Electric Vehicle Co. LTD., Beijing 102606, China

Energies 2017, 10(11), 1871; https://doi.org/10.3390/en10111871 - 15 Nov 2017

Cited by 32 | Viewed by 7223

Abstract

The extended range electric vehicle (EREV) can store much clean energy from the electric grid when it arrives at the charging station with lower battery energy. Consuming minimum gasoline during the trip is a common goal for most energy management controllers. To achieve [...] Read more.

The extended range electric vehicle (EREV) can store much clean energy from the electric grid when it arrives at the charging station with lower battery energy. Consuming minimum gasoline during the trip is a common goal for most energy management controllers. To achieve these objectives, an intelligent energy management controller for EREV based on dynamic programming and neural networks (IEMC_NN) is proposed. The power demand split ratio between the extender and battery are optimized by DP, and the control objectives are presented as a cost function. The online controller is trained by neural networks. Three trained controllers, constructing the controller library in IEMC_NN, are obtained from training three typical lengths of the driving cycle. To determine an appropriate NN controller for different driving distance purposes, the selection module in IEMC_NN is developed based on the remaining battery energy and the driving distance to the charging station. Three simulation conditions are adopted to validate the performance of IEMC_NN. They are target driving distance information, known and unknown, changing the destination during the trip. Simulation results using these simulation conditions show that the IEMC_NN had better fuel economy than the charging deplete/charging sustain (CD/CS) algorithm. More significantly, with known driving distance information, the battery SOC controlled by IEMC_NN can just reach the lower bound as the EREV arrives at the charging station, which was also feasible when the driver changed the destination during the trip. Full article

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21 pages, 3534 KiB

Open AccessArticle

Anti-Freezing Mechanism Analysis of a Finned Flat Tube in an Air-Cooled Condenser

by Yonghong Guo, Tongrui Cheng, Xiaoze Du^*

and Lijun Yang

Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, North China Electric Power University, Ministry of Education, Beijing 102206, China

Energies 2017, 10(11), 1872; https://doi.org/10.3390/en10111872 - 15 Nov 2017

Cited by 7 | Viewed by 4027

Abstract

In cold winter weather, the air-cooled condensers (ACCs) face serious freezing risks, especially with part load of the power generating unit. Therefore, it is of benefit to investigate the heat transfer process between the turbine exhaust steam and cooling air, by which the [...] Read more.

In cold winter weather, the air-cooled condensers (ACCs) face serious freezing risks, especially with part load of the power generating unit. Therefore, it is of benefit to investigate the heat transfer process between the turbine exhaust steam and cooling air, by which the freezing mechanism of the finned tube bundles can be revealed. In this work, the flow and heat transfer models of the cooling air coupling with the circulating water, are developed and numerically simulated for the anti-freezing analysis on basis of the finned tube bundles of the condenser cell. The local air-side heat transfer coefficient, condensate film development, and non-condensable gas development are obtained and analyzed in detail. The results show that, the most freezing risk happens at the fin base due to the highest air-side cooling capacity, besides the windward velocity, ambient temperature and turbine back pressure all determine the freezing risk with the constant inlet flow rate of the non-condensable gas. Furthermore, increasing fin thickness and decreasing fan rotating speed are the most effective anti-freezing measures. Additionally, increasing turbine back pressure can also be adopted to avoid ACC freezing, however the adjustment of outlet steam-air flow is not recommended. Full article

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12 pages, 5836 KiB

Open AccessArticle

Seasonal Solar Thermal Energy Sand-Bed Storage in a Region with Extended Freezing Periods: Part I Experimental Investigation

by Getu Hailu^1,*

, Philip Hayes¹ and Mark Masteller²

¹ Department of Mechanical Engineering, University of Alaska Anchorage, 3211 Providence Drive, ECB 301K, Anchorage, AK 99508, USA

² Bristol Bay Campus, University of Alaska Fairbanks, P.O. Box 1070, Dillingham, AK 99576, USA

Energies 2017, 10(11), 1873; https://doi.org/10.3390/en10111873 - 15 Nov 2017

Cited by 15 | Viewed by 6153

Abstract

We present the first experimental study of sand-bed thermal energy storage conducted in a region with extended freezing period. The study was carried out on a home situated in Palmer, Alaska, 61.6° N, and 149.1° W. The home is equipped with evacuated tube [...] Read more.

We present the first experimental study of sand-bed thermal energy storage conducted in a region with extended freezing period. The study was carried out on a home situated in Palmer, Alaska, 61.6° N, and 149.1° W. The home is equipped with evacuated tube solar thermal collectors that are connected to a seasonal sand-bed solar thermal energy storage system. Fourteen weeks of data was collected from a period of 28 January 2017 through 7 May 2017. Results suggest that seasonal sand-bed solar thermal storage systems are an excellent option for storing heat for climates in regions with long periods of freezing temperatures. The present study shows a proof of concept of a sand-bed seasonal solar thermal storage that needs additional controls for residential heating application. The system could also be used to provide heat for unoccupied spaces such as garages and greenhouses. Full article

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16 pages, 5484 KiB

Open AccessArticle

Application of Confined Blasting in Water-Filled Deep Holes to Control Strong Rock Pressure in Hard Rock Mines

by Jingxuan Yang^1,*, Changyou Liu¹ and Bin Yu²

¹ Key Laboratory of Deep Coal Resource Mining, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China

² Datong Coal Mine Group Co. Ltd., Datong 037000, China

Energies 2017, 10(11), 1874; https://doi.org/10.3390/en10111874 - 15 Nov 2017

Cited by 37 | Viewed by 6148

Abstract

In extra-thick coal seams, mining operations can lead to large-scale disturbances, complex overburden structures, and frequent and strong strata behavior in the stope, which are serious threats to mine safety. This study analyzed the overburden structure and strata behavior and proposed the technique [...] Read more.

In extra-thick coal seams, mining operations can lead to large-scale disturbances, complex overburden structures, and frequent and strong strata behavior in the stope, which are serious threats to mine safety. This study analyzed the overburden structure and strata behavior and proposed the technique of confined blasting in water-filled deep holes as a measure to prevent strong rock pressure. It found that there are two primary reasons for the high effectiveness of the proposed technique in presplitting hard coal and rock. First, the fracture water enables much more efficient transfer of dynamic load due to its incompressibility. Second, the subsequent expansion of water can further split the rock by compression. A mechanical model was used to reveal how the process of confined blasting in water-filled deep holes presplit roof. Moreover, practical implementation of this technique was found to improve the structure of hard, thick roof and prevent strong rock pressure, demonstrating its effectiveness in roof control. Full article

(This article belongs to the Special Issue Mathematical and Computational Modeling in Geothermal Engineering)

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19 pages, 14892 KiB

Open AccessArticle

Enhanced Regenerative Braking Strategies for Electric Vehicles: Dynamic Performance and Potential Analysis

by Boyi Xiao¹, Huazhong Lu^1,2,*, Hailin Wang¹, Jiageng Ruan³ and Nong Zhang³

¹ College of Engineering, South China Agricultural University, Guangzhou 510640, China

² Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China

³ University of Technology Sydney, 15 Broadway, Ultimo, NSW 2007, Australia

Energies 2017, 10(11), 1875; https://doi.org/10.3390/en10111875 - 15 Nov 2017

Cited by 71 | Viewed by 17689

Abstract

A regenerative braking system and hydraulic braking system are used in conjunction in the majority of electric vehicles worldwide. We propose a new regenerative braking distribution strategy that is based on multi-input fuzzy control logic while considering the influences of the battery’s state [...] Read more.

A regenerative braking system and hydraulic braking system are used in conjunction in the majority of electric vehicles worldwide. We propose a new regenerative braking distribution strategy that is based on multi-input fuzzy control logic while considering the influences of the battery’s state of charge, the brake strength and the motor speed. To verify the braking performance and recovery economy, this strategy was applied to a battery electric vehicle model and compared with two other improved regenerative braking strategies. The performance simulation was performed using standard driving cycles (NEDC, LA92, and JP1015) and a real-world-based urban cycle in China. The tested braking strategies satisfied the general safety requirements of Europe (as specified in ECE-13H), and the emergency braking scenario and economic potential were tested. The simulation results demonstrated the differences in the braking force distribution performance of these three regenerative braking strategies, the feasibility of the braking methods for the proposed driving cycles and the energy economic potential of the three strategies. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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13 pages, 894 KiB

Open AccessArticle

Energy Recovery Efficiency of Poultry Slaughterhouse Sludge Cake by Hydrothermal Carbonization

by Seung-Yong Oh and Young-Man Yoon^*

Biogas Research Center, Hankyong National University, 327 Jungang-ro, Anseong-si, Gyeonggi-do 17579, Korea

Energies 2017, 10(11), 1876; https://doi.org/10.3390/en10111876 - 16 Nov 2017

Cited by 27 | Viewed by 6290

Abstract

Hydrothermal carbonization (HTC) is a promising technology used for bioenergy conversion from bio-wastes such as sewage sludge, livestock manure, and food waste. To determine the optimum HTC reaction temperature in maximizing the gross energy recovery efficiency of poultry slaughterhouse sludge cake, a pilot-scale [...] Read more.

Hydrothermal carbonization (HTC) is a promising technology used for bioenergy conversion from bio-wastes such as sewage sludge, livestock manure, and food waste. To determine the optimum HTC reaction temperature in maximizing the gross energy recovery efficiency of poultry slaughterhouse sludge cake, a pilot-scale HTC reactor was designed and operated under reaction temperatures of 170, 180, 190, 200 and 22 °C. During the HTC reaction, the gross energy recovery efficiency was determined based on the calorific value of the HTC-biochar and ultimate methane potential of the HTC-hydrolysate. The poultry slaughterhouse sludge cake was assessed as a useful source for the bioenergy conversion with a high calorific value of approximately 27.7 MJ/kg. The calorific values of the HTC-biochar increased from 29.6 MJ/kg to 31.3 MJ/kg in accordance with the change in the reaction temperature from 170 °C to 220 °C. The ultimate methane potential of the HTC-hydrolysate was 0.222, 0.242, 0.237, 0.228 and 0.197 Nm³/kg-COD_added for the reaction temperatures of 170, 180, 190, 200 and 220 °C, respectively. The potential energy of feedstock was 4.541 MJ/kg. The total gross energy recovery (GER_total) was 4318 MJ/kg, of which the maximum value in the HTC reaction temperature was attained at 180 °C. Thus, the optimum temperature of the HTC reaction was 180 °C with a maximum GER_total efficiency of 95.1%. Full article

(This article belongs to the Special Issue Biomass Chars: Elaboration, Characterization and Applications Ⅱ)

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13 pages, 1105 KiB

Open AccessArticle

The Use of an Improved LSSVM and Joint Normalization on Temperature Prediction of Gearbox Output Shaft in DFWT

by Yancai Xiao^1,*, Ruolan Dai¹, Guangjian Zhang¹ and Weijia Chen²

¹ School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China

² Department of Electrical Engineering, North China Electric Power University, Baoding 071003, China

Energies 2017, 10(11), 1877; https://doi.org/10.3390/en10111877 - 16 Nov 2017

Cited by 9 | Viewed by 3078

Abstract

In the working process of Double-Fed Wind Turbines (DFWT), it is very important to monitor and predict the temperature of the high-speed output shaft of the gearbox timely and effectively. Support vector machine has more advantages in the temperature prediction of wind turbines. [...] Read more.

In the working process of Double-Fed Wind Turbines (DFWT), it is very important to monitor and predict the temperature of the high-speed output shaft of the gearbox timely and effectively. Support vector machine has more advantages in the temperature prediction of wind turbines. Least squares support vector machine is suitable for online prediction due to reducing the computational complexity of support vector machine. In order to solve the sparsity of least squares support vector machine, an improved least squares support vector machine based on pruning algorithm is proposed in this paper to predict the temperature of the high-speed output shaft of gearbox using the practical data of Double-Fed Wind Turbines. At the same time, in order to improve the prediction accuracy and to solve the problem of few links between different feature parameters in common normalization method, the paper uses the method of joint normalization to preprocess the data. The principal component analysis is used to reduce the dimension of the data. Particle swarm optimization algorithm is used to optimize the parameters of the pruning least squares support vector machine. The proposed model that is established in this paper is a new model to forecast the temperature of the high-speed output shaft. The results show that its prediction accuracy is higher than that of other algorithms. Full article

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13 pages, 3567 KiB

Open AccessArticle

Comparative Research on Solar Phase Change Material Storage Wall Systems under Different Summer Working Conditions

by Lijie Xu¹, Jie Ji^1,*, Chenglong Luo^2,*, Dan Sun², Jihai Xiong² and Mengyin Liao²

¹ Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, China

² Institute of Energy Research, Jiangxi Academy of Sciences, Nanchang 330096, China

Energies 2017, 10(11), 1878; https://doi.org/10.3390/en10111878 - 16 Nov 2017

Cited by 3 | Viewed by 3650

Abstract

To study and analyze the performance characteristics and the effectiveness of the system under practical application scenarios, the present work compares the performance of solar energy phase change material storage wall systems suitable for buildings in hot summer and cold winter regions under [...] Read more.

To study and analyze the performance characteristics and the effectiveness of the system under practical application scenarios, the present work compares the performance of solar energy phase change material storage wall systems suitable for buildings in hot summer and cold winter regions under different summer working conditions. The experimental facility was installed on light-weight insulation wall and ordinary wall; ventilation conditions of shutting/opening doors and windows, respectively, were set. The experimental facility showed different thermal characteristics when it was installed on insulation wall and on solid wall whether it was vented or not; under vented working condition, the temperature of the external surface of the south-facing wall which attached to the solid wall experimental system was lower, demonstrating that under practical building scenarios the present technology could better reveal its capability of avoiding the overheating issue of the solar heating wall in summer. Full article

(This article belongs to the Section D: Energy Storage and Application)

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13 pages, 874 KiB

Open AccessFeature PaperArticle

Assessing the Quality of Natural Gas Consumption Forecasting: An Application to the Italian Residential Sector

by Federico Scarpa

and Vincenzo Bianco^*

Dipartimento di Ingegneria meccanica, energetica, gestionale e dei trasporti (DIME), University of Genoa, via All’Opera Pia 15 A, 16145 Genoa, Italy

Energies 2017, 10(11), 1879; https://doi.org/10.3390/en10111879 - 16 Nov 2017

Cited by 22 | Viewed by 2961

Abstract

(1) Background: The present paper aims at estimating the quality of the forecasts obtained by using one equation models. In particular, the focus is on the effect that the explanatory variables have on the forecasted quantity. The analysis is performed on the [...] Read more.

(1) Background: The present paper aims at estimating the quality of the forecasts obtained by using one equation models. In particular, the focus is on the effect that the explanatory variables have on the forecasted quantity. The analysis is performed on the long term natural gas consumption in the Italian residential sector, but the same methodology can be applied to other contexts; (2) Methods: Different ex ante knowledge scenarios are built by associating different levels of confidence to the same set of explanatory variables. Forecasting results, coming from a standard regression algorithm and confirmed by a Kalman filter, are analyzed by means of covariance matrix propagation to assess the quality of the provided estimates; (3) Results: The outcomes show that one-equation models are very sensitive to the quality of the explanatory variables, therefore their erroneous estimation may have a relevant detrimental effect on the predictive accuracy of the model; (4) Conclusions: The overall ex ante forecasting accuracy of an example of one equation model is assessed. It has emerged that long-term forecasts need particular attention when the covered time horizon spans over decades. The information contained in the present paper is of interest for energy planners, supply network managers and policy makers in order to support their decisions. Full article

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21 pages, 7388 KiB

Open AccessArticle

Minimization of Load Variance in Power Grids—Investigation on Optimal Vehicle-to-Grid Scheduling

by Kang Miao Tan¹, Vigna K. Ramachandaramurthy¹

, Jia Ying Yong¹, Sanjeevikumar Padmanaban^2,*

, Lucian Mihet-Popa³

and Frede Blaabjerg⁴

¹ Power Quality Research Group, Institute of Power Engineering, Department of Electrical Power Engineering, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, Kajang, Selangor 43000, Malaysia

² Department of Electrical and Electronics Engineering, University of Johannesburg, 2006 Auckland Park, South Africa

³ Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Kråkeroy-Fredrikstad, Norway

⁴ Centre for Reliable Power Electronics (CORPE), Department of Energy Technology, Aalborg University, 9000 Aalborg, Denmark

Energies 2017, 10(11), 1880; https://doi.org/10.3390/en10111880 - 16 Nov 2017

Cited by 62 | Viewed by 7906

Abstract

The introduction of electric vehicles into the transportation sector helps reduce global warming and carbon emissions. The interaction between electric vehicles and the power grid has spurred the emergence of a smart grid technology, denoted as vehicle-to grid-technology. Vehicle-to-grid technology manages the energy [...] Read more.

The introduction of electric vehicles into the transportation sector helps reduce global warming and carbon emissions. The interaction between electric vehicles and the power grid has spurred the emergence of a smart grid technology, denoted as vehicle-to grid-technology. Vehicle-to-grid technology manages the energy exchange between a large fleet of electric vehicles and the power grid to accomplish shared advantages for the vehicle owners and the power utility. This paper presents an optimal scheduling of vehicle-to-grid using the genetic algorithm to minimize the power grid load variance. This is achieved by allowing electric vehicles charging (grid-to-vehicle) whenever the actual power grid loading is lower than the target loading, while conducting electric vehicle discharging (vehicle-to-grid) whenever the actual power grid loading is higher than the target loading. The vehicle-to-grid optimization algorithm is implemented and tested in MATLAB software (R2013a, MathWorks, Natick, MA, USA). The performance of the optimization algorithm depends heavily on the setting of the target load, power grid load and capability of the grid-connected electric vehicles. Hence, the performance of the proposed algorithm under various target load and electric vehicles’ state of charge selections were analysed. The effectiveness of the vehicle-to-grid scheduling to implement the appropriate peak load shaving and load levelling services for the grid load variance minimization is verified under various simulation investigations. This research proposal also recommends an appropriate setting for the power utility in terms of the selection of the target load based on the electric vehicle historical data. Full article

(This article belongs to the Special Issue Energy Storage Systems and Power Conversion Electronics for E-Transportation and Smart Grid)

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11 pages, 4098 KiB

Open AccessArticle

Characteristics of Pore Structure and Fractal Dimension of Isometamorphic Anthracite

by Di Gao^1,2,3,*

, Meng Li^2,*, Baoyu Wang¹, Bin Hu² and Jianguo Liu²

¹ State Key Laboratory of Coal and Coalbed Methane Co-mining, Jincheng 048006, China

² School of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China

³ Collaborative Innovation Center of Coalbed Methane (Shale Gas) for Central Plains Economic Region, Jiaozuo 454000, China

Energies 2017, 10(11), 1881; https://doi.org/10.3390/en10111881 - 16 Nov 2017

Cited by 12 | Viewed by 3917

Abstract

The geologic conditions of No. 3 coal seams are similar to Sihe and Zhaozhuang Collieries, however, the gas production is significantly different. To better understand the effect of pores, by means of experimental measurements and quantitative analysis, the pore properties of high-rank isometamorphic [...] Read more.

The geologic conditions of No. 3 coal seams are similar to Sihe and Zhaozhuang Collieries, however, the gas production is significantly different. To better understand the effect of pores, by means of experimental measurements and quantitative analysis, the pore properties of high-rank isometamorphic anthracite were thoroughly studied. Our study showed that the pore structures were predominantly adsorptive, accounting for more than 88% of the specific surface area. The coal pores showed typical three-stage fractal characteristics at boundary points of 1 nm and 9 nm (7 nm of coal samples from Zhaozhuang Colliery), and the fractal dimension with 1–9 nm (or 1–7 nm), as being significantly larger than those measured outside the given ranges. Pores in samples from Sihe Colliery were mainly open spherical or ellipsoidal pores in shape; conversely, those from Zhaozhuang Colliery were mainly Y-shaped, V-shaped, or ‘ink-bottle’ type. Full article

(This article belongs to the Section L: Energy Sources)

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4 pages, 183 KiB

Open AccessEditorial

Diesel and Spark Ignition Engines Emissions and After-Treatment Control: Research and Advancements

by Evangelos G. Giakoumis

Internal Combustion Engines Laboratory, School of Mechanical Engineering, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece

Energies 2017, 10(11), 1882; https://doi.org/10.3390/en10111882 - 16 Nov 2017

Cited by 7 | Viewed by 3765

Abstract

One of the major risks mankind has encountered during recent years is, without a doubt, the anthropogenic contribution to environmental pollution [...]
Full article

(This article belongs to the Special Issue Automotive Engines Emissions and Control)

13 pages, 1216 KiB

Open AccessArticle

Energy Consumption and Economic Development in Hong Kong, China

by Wai-Ming To¹

and Peter K. C. Lee^2,*

¹ School of Business, Macao Polytechnic Institute, Macao, China

² Department of Logistics and Maritime Studies, The Hong Kong Polytechnic University, Hong Kong, China

Energies 2017, 10(11), 1883; https://doi.org/10.3390/en10111883 - 16 Nov 2017

Cited by 25 | Viewed by 8963

Abstract

The economic structure of a city evolves as the city develops, resulting in a change in energy consumption. This paper presents a historical review of Hong Kong’s economic development and energy consumption from 1970 to 2015. Based on the official data from the [...] Read more.

The economic structure of a city evolves as the city develops, resulting in a change in energy consumption. This paper presents a historical review of Hong Kong’s economic development and energy consumption from 1970 to 2015. Based on the official data from the Hong Kong government, it was found that Hong Kong’s gross domestic product increased from HKD 208 billion in 1970 to HKD 2398 billion in 2015 in which the contribution from the manufacturing sector peaked in 1985. Energy consumption increased by 9.3 times from 140.2 PJ in 1970 (mostly oil products) to 1298.2 PJ (including oil products, natural gas, coal, and imported electricity) in 2015. The greenhouse gas (GHG) emissions due to energy consumption were determined based on emission factors for different fuels. Results show that GHG emissions increased from 10.7 million tons (Mt) of CO₂-equivalent in 1970 to 99.1 Mt of CO₂-equivalent in 2015. Full article

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17 pages, 3778 KiB

Open AccessReview

Grid-Tied Photovoltaic and Battery Storage Systems with Malaysian Electricity Tariff—A Review on Maximum Demand Shaving

by Gopinath Subramani¹, Vigna K. Ramachandaramurthy²

, Sanjeevikumar Padmanaban^3,*

, Lucian Mihet-Popa⁴

, Frede Blaabjerg⁵

and Josep M. Guerrero⁶

¹ Department of Electrical Engineering, Nilai University, Nilai 71800, Malaysia

² Institute of Power Engineering, Universiti Tenaga Nasional, Kajang 43000, Malaysia

³ Department of Electrical and Electronics Engineering, University of Johannesburg, Johannesburg 2006, South Africa

⁴ Faculty of Engineering, Østfold University College, 1671 Kråkeroy-Fredrikstad, Norway

⁵ Centre for Reliable Power Electronics, Department of Energy Technology, Aalborg University,9000 Aalborg, Denmark

⁶ Department of Energy Technology, Aalborg University, 9000 Aalborg, Denmark

Energies 2017, 10(11), 1884; https://doi.org/10.3390/en10111884 - 16 Nov 2017

Cited by 40 | Viewed by 8833

Abstract

Under the current energy sector framework of electricity tariff in Malaysia, commercial and industrial customers are required to pay the maximum demand (MD) charge apart from the net consumption charges every month. The maximum demand charge will contribute up to 20% of the [...] Read more.

Under the current energy sector framework of electricity tariff in Malaysia, commercial and industrial customers are required to pay the maximum demand (MD) charge apart from the net consumption charges every month. The maximum demand charge will contribute up to 20% of the electricity bill, and will hence result in commercial and industrial customers focussing on alternative energy supply to minimize the billing cost. This paper aims to review the technical assessment methods of a grid-connected solar photovoltaic (PV)—battery storage system—with respect to maximum demand shaving. An effective battery storage system can provide the extra energy needed during the peak energy consumption periods, as well as when renewable energy (RE) sources go offline. Based on the reviews, maximum demand shaving with good Return-of-Investment (ROI) can be achieved by considering the actual load profile, technical, and economic aspects of the solar PV-battery system and the Malaysian electricity tariff for commercial and industrial customers. Full article

(This article belongs to the Special Issue Innovative Methods for Smart Grids Planning and Management)

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20 pages, 1780 KiB

Open AccessArticle

Novel Strategy for Accurate Locating of Voltage Sag Sources in Smart Distribution Networks with Inverter-Interfaced Distributed Generators

by Rusi Chen^1,2, Tao Lin^1,2,*, Ruyu Bi^1,2 and Xialing Xu³

¹ School of Electrical Engineering, Wuhan University, Wuhan 430072, China

² Hubei Collaborative Innovation Center for High-efficiency Utilization of Solar Energy, Wuhan 430068, China

³ Central China Branch of State Grid Corporation of China, Wuhan 430063, China

Energies 2017, 10(11), 1885; https://doi.org/10.3390/en10111885 - 16 Nov 2017

Cited by 14 | Viewed by 3026

Abstract

With the aid of power quality monitoring systems (PQMSs), accurate locating of voltage sag sources, which has important significance for guiding maintenance personnel in finding and repairing faults as well as improving power supply reliability, has been becoming a new research hotspot. However, [...] Read more.

With the aid of power quality monitoring systems (PQMSs), accurate locating of voltage sag sources, which has important significance for guiding maintenance personnel in finding and repairing faults as well as improving power supply reliability, has been becoming a new research hotspot. However, existing methods have unsatisfactory locating accuracy due to the integration of distributed generators (DGs) and fault resistance. In this paper, a novel strategy for accurately locating voltage sag sources in smart distribution networks is proposed. Based on inverse theory, which is well applied in geophysics, the accurate location issue is treated as a two-step optimization model. It aims at making the distribution of voltage phasors and current phasors obtained by theoretical short-circuit calculation match those actually observed as closely as possible. To guarantee the feasibility of the strategy, the effect of inverter-interfaced DGs (IIDGs) which are the main form of DG is considered in the short-circuit calculations. To guarantee the location accuracy of the strategy, fault resistance is treated as an optimization variable in the two-step optimization model to eliminate estimation error of fault resistance. Via two modified IEEE benchmarks with different scales, the validity and the superiorities in applicability and accuracy of the proposed strategy are verified. Full article

(This article belongs to the Section F: Electrical Engineering)

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10 pages, 2925 KiB

Open AccessFeature PaperArticle

Charging Characteristics of Lithium Ion Battery Using Semi-Solar Modules of Polymer:Fullerene Solar Cells

by Myeonghun Song¹, Sooyong Lee¹, Dohan Kim¹, Chulyeon Lee¹, Jaehoon Jeong¹, Jooyeok Seo¹, Hwajeong Kim^1,2,*, Dong-Ik Song³, Donghyun Kim⁴ and Youngkyoo Kim^1,*

¹ Organic Nanoelectronics Laboratory and KNU Institute for Nanophotonics Applications (KINPA), Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University, University Road 80, Daegu 41566, Korea

² Priority Research Center, Research Institute of Advanced Energy Technology, Kyungpook National University, University Road 80, Daegu 41566, Korea

³ Polymer Rheology Laboratory, Department of Chemical Engineering, School of Applied Chemical Engineering, Kyungpook National University, University Road 80, Daegu 41566, Korea

⁴ Department of Chemical Engineering, Kyungpook National University, University Road 80, Daegu 41566, Korea

Energies 2017, 10(11), 1886; https://doi.org/10.3390/en10111886 - 16 Nov 2017

Cited by 4 | Viewed by 4961

Abstract

The combination of lithium ion battery (LIB) and organic (polymer) solar cells is expected to deliver versatile self-rechargeable portable energy sources, but less attention has been paid to the charging characteristics of LIB-using polymer solar cells. Here we demonstrate that the LIB packs, [...] Read more.

The combination of lithium ion battery (LIB) and organic (polymer) solar cells is expected to deliver versatile self-rechargeable portable energy sources, but less attention has been paid to the charging characteristics of LIB-using polymer solar cells. Here we demonstrate that the LIB packs, which were prepared by using lithium cobalt oxide (LiCoO₂) and graphite as a cathode and an anode, respectively, can be effectively charged by semi-solar modules of polymer:fullerene solar cells, of which bulk heterojunction (BHJ) layers are composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM). Results showed that the performance of semi-solar modules was not much degraded by connecting four single solar cells in series or in parallel, but their output power density was noticeably reduced by extending the number of single cells up to eight. The charging test disclosed that the output current density is of importance to speed up the LIB charging at the same output voltage. Full article

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27 pages, 4229 KiB

Open AccessReview

Characteristics of Clay-Abundant Shale Formations: Use of CO₂ for Production Enhancement

by Chengpeng Zhang¹

, Ranjith Pathegama Gamage^1,*

, Mandadige Samintha Anna Perera²

and Jian Zhao¹

¹ Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia

² Department of Infrastructure Engineering, The University of Melbourne, Building 176, Parkville, VIC 3010, Australia

Energies 2017, 10(11), 1887; https://doi.org/10.3390/en10111887 - 16 Nov 2017

Cited by 47 | Viewed by 5065

Abstract

Clay-abundant shale formations are quite common worldwide shale plays. This particular type of shale play has unique physico-chemical characteristics and therefore responds uniquely to the gas storage and production process. Clay minerals have huge surface areas due to prevailing laminated structures, and the [...] Read more.

Clay-abundant shale formations are quite common worldwide shale plays. This particular type of shale play has unique physico-chemical characteristics and therefore responds uniquely to the gas storage and production process. Clay minerals have huge surface areas due to prevailing laminated structures, and the deficiency in positive charges in the combination of tetrahedral and octahedral sheets in clay minerals produces strong cation exchange capacities (CECs), all of which factors create huge gas storage capacity in clay-abundant shale formations. However, the existence of large amounts of tiny clay particles separates the contacts between quartz particles, weakening the shale formation and enhancing its ductile properties. Furthermore, clay minerals’ strong affinity for water causes clay-abundant shale formations to have large water contents and therefore reduced gas storage capacities. Clay-water interactions also create significant swelling in shale formations. All of these facts reduce the productivity of these formations. The critical influences of clay mineral-water interaction on the productivity of this particular type of shale plays indicates the inappropriateness of using traditional types of water-based fracturing fluids for production enhancement. Non-water-based fracturing fluids are therefore preferred, and CO₂ is preferable due to its many unique favourable characteristics, including its minor swelling effect, its ability to create long and narrow fractures at low breakdown pressures due to its ultralow viscosity, its contribution to the mitigation of the greenhouse gas effect, rapid clean-up and easy residual water removal capability. The aim of this paper is to obtain comprehensive knowledge of utilizing appropriate production enhancement techniques in clay-abundant shale formations based on a thorough literature review. Full article

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13 pages, 4197 KiB

Open AccessArticle

Numeric Investigation of Gas Distribution in the Intake Manifold and Intake Ports of a Multi-Cylinder Diesel Engine Refined for Exhaust Gas Stratification

by Zhaojie Shen^1,2

, Wenzheng Cui¹, Xiaodong Ju¹, Zhongchang Liu³, Shaohua Wu² and Jianguo Yang^1,*

¹ School of Automotive Engineering, Harbin Institute of Technology, Weihai 264209, China

² School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

³ State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130025, China

Energies 2017, 10(11), 1888; https://doi.org/10.3390/en10111888 - 17 Nov 2017

Cited by 1 | Viewed by 3269

Abstract

In-cylinder exhaust gas recirculation (EGR) stratification, generally achieved by supplying EGR asymmetrically into intake ports on a four-valve diesel engine, is sensitive to trapped exhaust gas in the intake manifold and intake ports that is caused by the continuous supply of EGR during [...] Read more.

In-cylinder exhaust gas recirculation (EGR) stratification, generally achieved by supplying EGR asymmetrically into intake ports on a four-valve diesel engine, is sensitive to trapped exhaust gas in the intake manifold and intake ports that is caused by the continuous supply of EGR during the valve-close periods of the intake valves. The subject of this study is to evaluate the distribution of trapped exhaust gas in the diesel intake system using commercial Star-CD software (version 4.22.018). Numeric simulations of the intake flow of fresh air and recycled exhaust in the diesel intake system were initialized following previous experiments that were conducted on a reformed six-cylinder diesel engine by supplying CO₂ instead of EGR to the tangential intake port alone to establish CO₂ stratification in the first cylinder. The distributions of the intake CO₂ in the intake manifold and intake ports under the conditions of 1330 r/min and 50% load with different mass flow rates of CO₂ are discussed. This indicates that CO₂ supplied to one intake port alone would escape to another intake port, which not only weakens the CO₂ stratification by diminishing the mass fraction disparity of the CO₂ between the two intake ports of cylinder 1, but also influences the total mass of CO₂ in the cylinder. There is 4% CO₂ by mass fraction in the intake port without CO₂ supply under the condition that the CO₂ mass flow rate is 5 kg/h during the intake process, and 10% CO₂ under the condition of 50 kg/h. Full article

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13 pages, 5248 KiB

Open AccessArticle

Transmittance and Reflectance Studies of Thermotropic Material for a Novel Building Integrated Concentrating Photovoltaic (BICPV) ‘Smart Window’ System

by Karen Connelly¹, Yupeng Wu^1,*

, Xiaoyu Ma² and Yu Lei^2,3

¹ Department of Architecture and Built Environment, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK

² Department of Biomedical Engineering, University of Connecticut, 260 Glenbrook Road, Unit 3247, Storrs, CT 06269, USA

³ Department of Chemical and Biomolecular Engineering, University of Connecticut, 191 Auditorium Road, Unit 3222, Storrs, CT 06269, USA

Energies 2017, 10(11), 1889; https://doi.org/10.3390/en10111889 - 17 Nov 2017

Cited by 28 | Viewed by 6631

Abstract

A novel Building Integrated Concentrating Photovoltaic (BICPV) Smart Window has been designed and developed as a next generation intelligent window system. In response to climatic conditions, the smart window varies solar light transmission into the building for provision of light and heat with [...] Read more.

A novel Building Integrated Concentrating Photovoltaic (BICPV) Smart Window has been designed and developed as a next generation intelligent window system. In response to climatic conditions, the smart window varies solar light transmission into the building for provision of light and heat with the reflection of light to the photovoltaic (PV) for electricity generation. This unique function is realised using an integrated thermotropic layer in conjunction with embedded PVs. As commercial PVs are readily available, the success of this novel BICPV design depends solely on the performance of the thermotropic material. This study aimed to develop a suitable reflective thermotropic layer for the proposed smart Concentrating Photovoltaic (CPV) system. A Hydroxypropyl cellulose (HPC) polymer was tested for its applicability as a potential reflective thermotropic material for this purpose. HPC concentration was systematically varied from 1 wt. % to 6 wt. % in aqueous solution so as to provide insight into the relationship between transmittance/reflectance properties, the concentration of the thermotropic material and their dependence upon the environmental temperature. The degree of hysteresis of light transmittance upon subjecting HPC to heating and cooling cycles was also investigated. Specifically, for the HPC liquid samples the measured threshold temperature/transition temperature (T_s) was observed to be approximately 40 °C for 6 wt. % HPC, increasing to approximately 44 °C for 1 wt. % HPC. No hysteresis was observed upon heating and cooling HPC samples. Reflectance below the T_s was recorded at ~10%, increasing up to ~70% above the T_s for 6 wt. % HPC. Finally, a HPC-based hydrogel membrane sample was developed and exhibited good thermotropic activity therefore demonstrating its suitability for use within the BICPV smart window. This study corroborates that HPC is a suitable thermotropic material in the application of next generation BICPV smart window systems. Full article

(This article belongs to the Special Issue Solar Technologies for Buildings)

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10 pages, 1193 KiB

Open AccessArticle

Gasification under CO₂–Steam Mixture: Kinetic Model Study Based on Shared Active Sites

by Xia Liu^†, Juntao Wei^†, Wei Huo and Guangsuo Yu^*

¹ Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

^† These authors contributed equally to this work.

Energies 2017, 10(11), 1890; https://doi.org/10.3390/en10111890 - 17 Nov 2017

Cited by 12 | Viewed by 3936

Abstract

In this work, char gasification of two coals (i.e., Shenfu bituminous coal and Zunyi anthracite) and a petroleum coke under a steam and CO₂ mixture (steam/CO₂ partial pressures, 0.025–0.075 MPa; total pressures, 0.100 MPa) and CO₂/steam chemisorption of char [...] Read more.

In this work, char gasification of two coals (i.e., Shenfu bituminous coal and Zunyi anthracite) and a petroleum coke under a steam and CO₂ mixture (steam/CO₂ partial pressures, 0.025–0.075 MPa; total pressures, 0.100 MPa) and CO₂/steam chemisorption of char samples were conducted in a Thermogravimetric Analyzer (TGA). Two conventional kinetic models exhibited difficulties in exactly fitting the experimental data of char–steam–CO₂ gasification. Hence, a modified model based on Langmuir–Hinshelwood model and assuming that char–CO₂ and char–steam reactions partially shared active sites was proposed and had indicated high accuracy for estimating the interactions in char–steam–CO₂ reaction. Moreover, it was found that two new model parameters (respectively characterized as the amount ratio of shared active sites to total active sites in char–CO₂ and char–steam reactions) in the modified model hardly varied with gasification conditions, and the results of chemisorption indicate that these two new model parameters mainly depended on the carbon active sites in char samples. Full article

(This article belongs to the Special Issue Biomass Chars: Elaboration, Characterization and Applications Ⅱ)

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17 pages, 4835 KiB

Open AccessArticle

Transactive-Market-Based Operation of Distributed Electrical Energy Storage with Grid Constraints

by M. Nazif Faqiry¹, Lawryn Edmonds¹, Haifeng Zhang¹, Amin Khodaei² and Hongyu Wu^1,*

¹ Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA

² Department of Electrical and Computer Engineering, University of Denver, Denver, CO 80210, USA

Energies 2017, 10(11), 1891; https://doi.org/10.3390/en10111891 - 17 Nov 2017

Cited by 30 | Viewed by 5459

Abstract

In a transactive energy market, distributed energy resources (DERs) such as dispatchable distributed generators (DGs), electrical energy storages (EESs), distribution-scale load aggregators (LAs), and renewable energy sources (RESs) have to earn their share of supply or demand through a bidding process. In such [...] Read more.

In a transactive energy market, distributed energy resources (DERs) such as dispatchable distributed generators (DGs), electrical energy storages (EESs), distribution-scale load aggregators (LAs), and renewable energy sources (RESs) have to earn their share of supply or demand through a bidding process. In such a market, the distribution system operator (DSO) may optimally schedule these resources, first in a forward market, i.e., day-ahead, and in a real-time market later on, while maintaining a reliable and economic distribution grid. In this paper, an efficient day-ahead scheduling of these resources, in the presence of interaction with wholesale market at the locational marginal price (LMP), is studied. Due to inclusion of EES units with integer constraints, a detailed mixed integer linear programming (MILP) formulation that incorporates simplified DistFlow equations to account for grid constraints is proposed. Convex quadratic line and transformer apparent power flow constraints have been linearized using an outer approximation. The proposed model schedules DERs based on distribution locational marginal price (DLMP), which is obtained as the Lagrange multiplier of the real power balance constraint at each distribution bus while maintaining physical grid constraints such as line limits, transformer limits, and bus voltage magnitudes. Case studies are performed on a modified IEEE 13-bus system with high DER penetration. Simulation results show the validity and efficiency of the proposed model. Full article

(This article belongs to the Special Issue Battery Energy Storage Applications in Smart Grid)

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14 pages, 6946 KiB

Open AccessArticle

Tidal Turbines’ Layout in a Stream with Asymmetry and Misalignment

by Nicolas Guillou^*

and Georges Chapalain

Laboratoire de Génie Côtier et Environnement (LGCE), Cerema, Direction Eau Mer et Fleuves, ER, 155 rue Pierre Bouguer, Technopôle Brest-Iroise, BP 5, 29280 Plouzané, France

Energies 2017, 10(11), 1892; https://doi.org/10.3390/en10111892 - 17 Nov 2017

Cited by 11 | Viewed by 4514

Abstract

A refined assessment of tidal currents variability is a prerequisite for successful turbine deployment in the marine environment. However, the numerical evaluation of the tidal kinetic energy resource relies, most of the time, on integrated parameters, such as the averaged or maximum stream [...] Read more.

A refined assessment of tidal currents variability is a prerequisite for successful turbine deployment in the marine environment. However, the numerical evaluation of the tidal kinetic energy resource relies, most of the time, on integrated parameters, such as the averaged or maximum stream powers. Predictions from a high resolution three-dimensional model are exploited here to characterize the asymmetry and misalignment between the flood and ebb tidal currents in the “Raz de Sein”, a strait off western Brittany (France) with strong potential for array development. A series of parameters is considered to assess resource variability and refine the cartography of local potential tidal stream energy sites. The strait is characterized by strong tidal flow divergence with currents’ asymmetry liable to vary output power by 60% over a tidal cycle. Pronounced misalignments over 20

^{\circ}

are furthermore identified in a great part of energetic locations, and this may account for a deficit of the monthly averaged extractable energy by more than 12%. As sea space is limited for turbines, it is finally suggested to aggregate flood and ebb-dominant stream powers on both parts of the strait to output energy with reduced asymmetry. Full article

(This article belongs to the Section L: Energy Sources)

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16 pages, 3695 KiB

Open AccessArticle

Energy-Efficient Use of Licensed and Unlicensed Bands in D2D-Assisted Cellular Network Systems

by Yao-Liang Chung

Department of Communications, Navigation and Control Engineering, National Taiwan Ocean University, Keelung City 20224, Taiwan

Energies 2017, 10(11), 1893; https://doi.org/10.3390/en10111893 - 17 Nov 2017

Cited by 3 | Viewed by 3056

Abstract

To date, the amount of research conducted regarding the subject of energy-efficient transmission in device-to-device (D2D)-assisted cellular network systems simultaneously utilizing both licensed and unlicensed bands is lacking. This topic is of substantial relevance to emerging 5th-generation (5G) cellular network systems, so the [...] Read more.

To date, the amount of research conducted regarding the subject of energy-efficient transmission in device-to-device (D2D)-assisted cellular network systems simultaneously utilizing both licensed and unlicensed bands is lacking. This topic is of substantial relevance to emerging 5th-generation (5G) cellular network systems, so the present study was conducted in order to address it in a practical manner. Specifically, this study proposes a simple yet effective algorithm aimed at ensuring efficient energy usage when such network systems make transmissions while utilizing both licensed and unlicensed bands. Based on novel system configurations with respect to bandwidth and link mode configurations, the proposed D2D-assisted transmission algorithm was designed with a system-level perspective in mind in order to yield greater efficiency in terms of transmission mode selection and link mode selection. As a result of these features, the proposed algorithm can not only maintain acceptable rates of transmission for all the connected users, but can also enhance system performance by a significant degree in terms of both energy efficiency and connection efficiency. Moreover, the results of simulations conducted to test the algorithm indicate that it is not only feasible, but, given its simple yet effective design, also easy to implement, such that it can serve as a valuable reference for the operators of 5G networks. Full article

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21 pages, 1948 KiB

Open AccessArticle

Energy Management Strategy in Consideration of Battery Health for PHEV via Stochastic Control and Particle Swarm Optimization Algorithm

by Yuying Wang, Xiaohong Jiao^*

, Zitao Sun and Ping Li

Institute of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China

Energies 2017, 10(11), 1894; https://doi.org/10.3390/en10111894 - 17 Nov 2017

Cited by 34 | Viewed by 4597

Abstract

This paper presents an energy management strategy for plug-in hybrid electric vehicles (PHEVs) that not only tries to minimize the energy consumption, but also considers the battery health. First, a battery model that can be applied to energy management optimization is given. In [...] Read more.

This paper presents an energy management strategy for plug-in hybrid electric vehicles (PHEVs) that not only tries to minimize the energy consumption, but also considers the battery health. First, a battery model that can be applied to energy management optimization is given. In this model, battery health damage can be estimated in the different states of charge (SOC) and temperature of the battery pack. Then, because of the inevitability that limiting the battery health degradation will increase energy consumption, a Pareto energy management optimization problem is formed. This multi-objective optimal control problem is solved numerically by using stochastic dynamic programming (SDP) and particle swarm optimization (PSO) for satisfying the vehicle power demand and considering the tradeoff between energy consumption and battery health at the same time. The optimization solution is obtained offline by utilizing real historical traffic data and formed as mappings on the system operating states so as to implement online in the actual driving conditions. Finally, the simulation results carried out on the GT-SUITE-based PHEV test platform are illustrated to demonstrate that the proposed multi-objective optimal control strategy would effectively yield benefits. Full article

(This article belongs to the Section L: Energy Sources)

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18 pages, 2847 KiB

Open AccessArticle

Reliable Biomass Supply Chain Design under Feedstock Seasonality and Probabilistic Facility Disruptions

by Zhixue Liu¹, Shukun Wang^1,* and Yanfeng Ouyang²

¹ School of Management, Huazhong University of Science and Technology, Wuhan 403374, China

² Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

Energies 2017, 10(11), 1895; https://doi.org/10.3390/en10111895 - 18 Nov 2017

Cited by 32 | Viewed by 5280

Abstract

While biomass has been recognized as an important renewable energy source which has a range of positive impacts on the economy, environment, and society, the existence of feedstock seasonality and risk of service disruptions at collection facilities potentially compromises the efficiency and reliability [...] Read more.

While biomass has been recognized as an important renewable energy source which has a range of positive impacts on the economy, environment, and society, the existence of feedstock seasonality and risk of service disruptions at collection facilities potentially compromises the efficiency and reliability of the energy supply system. In this paper, we consider reliable supply chain design for biomass collection against feedstock seasonality and time-varying disruption risks. We optimize facility location, inventory, biomass quantity, and shipment decisions in a multi-period planning horizon setting. A real-world case in Hubei, China is studied to offer managerial insights. Our computational results show that: (1) the disruption risk significantly affects both the optimal facility locations and the supply chain cost; (2) no matter how the failure probability changes, setting backup facilities can significantly decrease the total cost; and (3) the feedstock seasonality does not affect locations of the collection facilities, but it affects the allocations of collection facilities and brings higher inventory cost for the biomass supply chain. Full article

(This article belongs to the Section L: Energy Sources)

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14 pages, 1751 KiB

Open AccessReview

A Review of Power Distribution Test Feeders in the United States and the Need for Synthetic Representative Networks

by Fernando E. Postigo Marcos^1,*

, Carlos Mateo Domingo¹, Tomás Gómez San Román¹

, Bryan Palmintier², Bri-Mathias Hodge², Venkat Krishnan², Fernando De Cuadra García¹ and Barry Mather²

¹ Institute for Research in Technology (IIT), Comillas Pontifical University, Madrid 28015, Spain

² National Renewable Energy Laboratory (NREL), Golden, CO 80401, USA

Energies 2017, 10(11), 1896; https://doi.org/10.3390/en10111896 - 18 Nov 2017

Cited by 83 | Viewed by 11615

Abstract

Under the increasing penetration of distributed energy resources and new smart network technologies, distribution utilities face new challenges and opportunities to ensure reliable operations, manage service quality, and reduce operational and investment costs. Simultaneously, the research community is developing algorithms for advanced controls [...] Read more.

Under the increasing penetration of distributed energy resources and new smart network technologies, distribution utilities face new challenges and opportunities to ensure reliable operations, manage service quality, and reduce operational and investment costs. Simultaneously, the research community is developing algorithms for advanced controls and distribution automation that can help to address some of these challenges. However, there is a shortage of realistic test systems that are publically available for development, testing, and evaluation of such new algorithms. Concerns around revealing critical infrastructure details and customer privacy have severely limited the number of actual networks published and that are available for testing. In recent decades, several distribution test feeders and US-featured representative networks have been published, but the scale, complexity, and control data vary widely. This paper presents a first-of-a-kind structured literature review of published distribution test networks with a special emphasis on classifying their main characteristics and identifying the types of studies for which they have been used. This both aids researchers in choosing suitable test networks for their needs and highlights the opportunities and directions for further test system development. In particular, we highlight the need for building large-scale synthetic networks to overcome the identified drawbacks of current distribution test feeders. Full article

(This article belongs to the Section F: Electrical Engineering)

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21 pages, 5348 KiB

Open AccessEditor’s ChoiceArticle

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

by Eloisa Di Sipio^*

and David Bertermann

Department of Geology, GeoZentrum Nordbayern, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany

Energies 2017, 10(11), 1897; https://doi.org/10.3390/en10111897 - 18 Nov 2017

Cited by 40 | Viewed by 7152

Abstract

The performance of very shallow geothermal systems (VSGs), interesting the first 2 m of depth from ground level, is strongly correlated to the kind of sediment locally available. These systems are attractive due to their low installation costs, less legal constraints, easy maintenance [...] Read more.

The performance of very shallow geothermal systems (VSGs), interesting the first 2 m of depth from ground level, is strongly correlated to the kind of sediment locally available. These systems are attractive due to their low installation costs, less legal constraints, easy maintenance and possibility for technical improvements. The Improving Thermal Efficiency of horizontal ground heat exchangers Project (ITER) aims to understand how to enhance the heat transfer of the sediments surrounding the pipes and to depict the VSGs behavior in extreme thermal situations. In this regard, five helices were installed horizontally surrounded by five different backfilling materials under the same climatic conditions and tested under different operation modes. The field test monitoring concerned: (a) monthly measurement of thermal conductivity and moisture content on surface; (b) continuous recording of air and ground temperature (inside and outside each helix); (c) continuous climatological and ground volumetric water content (VWC) data acquisition. The interactions between soils, VSGs, environment and climate are presented here, focusing on the differences and similarities between the behavior of the helix and surrounding material, especially when the heat pump is running in heating mode for a very long time, forcing the ground temperature to drop below 0 °C. Full article

(This article belongs to the Special Issue Low Enthalpy Geothermal Energy)

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19 pages, 6598 KiB

Open AccessArticle

Fault Ride-through Capability Enhancement of Voltage Source Converter-High Voltage Direct Current Systems with Bridge Type Fault Current Limiters

by Md Shafiul Alam

and Mohammad Ali Yousef Abido^*

Department of Electrical Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

Energies 2017, 10(11), 1898; https://doi.org/10.3390/en10111898 - 18 Nov 2017

Cited by 29 | Viewed by 5817

Abstract

This paper proposes the use of bridge type fault current limiters (BFCLs) as a potential solution to reduce the impact of fault disturbance on voltage source converter-based high voltage DC (VSC-HVDC) systems. Since VSC-HVDC systems are vulnerable to faults, it is essential to [...] Read more.

This paper proposes the use of bridge type fault current limiters (BFCLs) as a potential solution to reduce the impact of fault disturbance on voltage source converter-based high voltage DC (VSC-HVDC) systems. Since VSC-HVDC systems are vulnerable to faults, it is essential to enhance the fault ride-through (FRT) capability with auxiliary control devices like BFCLs. BFCL controllers have been developed to limit the fault current during the inception of system disturbances. Real and reactive power controllers for the VSC-HVDC have been developed based on current control mode. DC link voltage control has been achieved by a feedback mechanism such that net power exchange with DC link capacitor is zero. A grid-connected VSC-HVDC system and a wind farm integrated VSC-HVDC system along with the proposed BFCL and associated controllers have been implemented in a real time digital simulator (RTDS). Symmetrical three phase as well as different types of unsymmetrical faults have been applied in the systems in order to show the effectiveness of the proposed BFCL solution. DC link voltage fluctuation, machine speed and active power oscillation have been greatly suppressed with the proposed BFCL. Another significant feature of this work is that the performance of the proposed BFCL in VSC-HVDC systems is compared to that of series dynamic braking resistor (SDBR). Comparative results show that the proposed BFCL is superior over SDBR in limiting fault current as well as improving system fault ride through (FRT) capability. Full article

(This article belongs to the Section F: Electrical Engineering)

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20 pages, 3508 KiB

Open AccessArticle

Visualizing National Electrification Scenarios for Sub-Saharan African Countries

by Paul Bertheau¹, Ayobami Solomon Oyewo^2,*, Catherina Cader^1,3, Christian Breyer²

and Philipp Blechinger¹

¹ Reiner Lemoine Institut gGmbH, Rudower Chaussee 12, 12489 Berlin, Germany

² School of Energy Systems, Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta, Finland

³ Justus Liebig University Gießen, Senckenbergstraße 1, 35390 Gießen, Germany

Energies 2017, 10(11), 1899; https://doi.org/10.3390/en10111899 - 18 Nov 2017

Cited by 54 | Viewed by 8105

Abstract

Some 630 million people representing two-thirds of all Africans have no access to electricity, which is identified as a key barrier towards further development. Three main electrification options are considered within our work: grid extensions, mini-grids and solar home systems (SHS). A methodology [...] Read more.

Some 630 million people representing two-thirds of all Africans have no access to electricity, which is identified as a key barrier towards further development. Three main electrification options are considered within our work: grid extensions, mini-grids and solar home systems (SHS). A methodology is applied to all sub-Saharan African countries to identify in high geospatial resolution which electrification option is appropriate taking into account datasets for night light imagery, population distribution and grid infrastructure. Four different scenarios are considered reflecting grid development and electrification constraints due to low population density. The results clearly indicate a dominating role of SHS for achieving a fast electrification of the not supplied people. The share of supplied people by mini-grids is found to be rather low while grid extension serves a large share of the population. The decisive factors for these distinctions are population density and distance to grid. We applied several scenarios and sensitivities to understand the influence of these key parameters. The highest trade-off happens between SHS and grid extension depending on the selected thresholds. Mini-grid deployments remain in the range of 8 to 21%. Full article

(This article belongs to the Special Issue Sustainable and Renewable Energy Systems)

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22 pages, 15742 KiB

Open AccessEditor’s ChoiceArticle

Modeling of Supersonic Combustion Systems for Sustained Hypersonic Flight

by Stephen M. Neill¹ and Apostolos Pesyridis^2,*

¹ Aerospace Engineering Graduate, College of Engineering and Design, Brunel University London, Uxbridge UB8 3PN, UK

² Metapulsion Engineering Ltd, 2C Eastbury Avenue, Northwood HA6 3LG, UK

Energies 2017, 10(11), 1900; https://doi.org/10.3390/en10111900 - 18 Nov 2017

Cited by 18 | Viewed by 8852

Abstract

Through Computational Fluid Dynamics and validation, an optimal scramjet combustor has been designed based on twin-strut Hydrogen injection to sustain flight at a desired speed of Mach 8. An investigation undertaken into the efficacy of supersonic combustion through various means of injection saw [...] Read more.

Through Computational Fluid Dynamics and validation, an optimal scramjet combustor has been designed based on twin-strut Hydrogen injection to sustain flight at a desired speed of Mach 8. An investigation undertaken into the efficacy of supersonic combustion through various means of injection saw promising results for Hydrogen-based systems, whereby strut-style injectors were selected over transverse injectors based on their pressure recovery performance and combustive efficiency. The final configuration of twin-strut injectors provided robust combustion and a stable region of net thrust (1873 kN) in the nozzle. Using fixed combustor inlet parameters and injection equivalence ratio, the finalized injection method advanced to the early stages of two-dimensional (2-D) and three-dimensional (3-D) scramjet engine integration. The overall investigation provided a feasible supersonic combustion system, such that Mach 8 sustained cruise could be achieved by the aircraft concept in a computational design domain. Full article

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17 pages, 8346 KiB

Open AccessArticle

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

by Xuanlin Peng^1,2,*

, Jianzhong Zhou^1,2,*, Chu Zhang^1,2, Ruhai Li^1,2, Yanhe Xu^1,2 and Diyi Chen³

¹ School of Hydropower and Information Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

² Hubei Key Laboratory of Digital Valley Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China

³ Institute of Water Resources and Hydropower Research, Northwest A&F University, Yangling 712100, China

Energies 2017, 10(11), 1901; https://doi.org/10.3390/en10111901 - 19 Nov 2017

Cited by 6 | Viewed by 6189

Abstract

In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration [...] Read more.

In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM) is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane’s trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM) and particle swarm optimization (PSO) is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD) simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry. Full article

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14 pages, 2561 KiB

Open AccessArticle

LNG–Air Mixture as a Supplementary Energy Injection into a Biogas Distribution Network

by Yang Zhou^1,4

, Shini Peng¹, Xiaomei Huang^1,2,3,*, Chang Wu¹ and Jing Zhang¹

¹ School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400045, China

² Key Laboratory of Three Gorges Reservoir Region’s Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China

³ Joint International Laboratory of Green Building and Built Environments, Ministry of Education, Chongqing University, Chongqing 400045, China

⁴ Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, UK

Energies 2017, 10(11), 1902; https://doi.org/10.3390/en10111902 - 19 Nov 2017

Cited by 3 | Viewed by 4643

Abstract

Biogas production efficiency fluctuates with climate variations and agricultural arrangements, which pose a limiting factor upon its single supply to end users via a regional exclusive network, especially in peak demand. In this paper, an appropriate methodology to address the contradiction between biogas [...] Read more.

Biogas production efficiency fluctuates with climate variations and agricultural arrangements, which pose a limiting factor upon its single supply to end users via a regional exclusive network, especially in peak demand. In this paper, an appropriate methodology to address the contradiction between biogas supply and demand is proposed. Methane conditioned by the addition of air is described, and can be a supplementary energy injected into a biogas distribution network. To accomplish the mixing process and also inject the exhaust mixture into the distribution system, a mixer–ejector was introduced and integrated into the biogas grid. Finally, the fundamental combustion behaviors of mixed gases were estimated through the analysis of flame appearance, contamination emissions, and the flame stability region. The results showed that the methane/air mixture with a mixing ratio ranging from 49/51 to 53/47 could interchange biogas commendably, and good combustion behavior was obtained on a typical biogas-burning appliance. Full article

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15 pages, 1601 KiB

Open AccessArticle

A Naive Bayesian Wind Power Interval Prediction Approach Based on Rough Set Attribute Reduction and Weight Optimization

by Xiyun Yang, Guo Fu^*, Yanfeng Zhang, Ning Kang and Feng Gao

School of Control and Computer Engineering, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(11), 1903; https://doi.org/10.3390/en10111903 - 19 Nov 2017

Cited by 29 | Viewed by 4951

Abstract

Intermittency and uncertainty pose great challenges to the large-scale integration of wind power, so research on the probabilistic interval forecasting of wind power is becoming more and more important for power system planning and operation. In this paper, a Naive Bayesian wind power [...] Read more.

Intermittency and uncertainty pose great challenges to the large-scale integration of wind power, so research on the probabilistic interval forecasting of wind power is becoming more and more important for power system planning and operation. In this paper, a Naive Bayesian wind power prediction interval model, combining rough set (RS) theory and particle swarm optimization (PSO), is proposed to further improve wind power prediction performance. First, in the designed prediction interval model, the input variables are identified based on attribute significance using rough set theory. Next, the Naive Bayesian Classifier (NBC) is established to obtain the prediction power class. Finally, the upper and lower output weights of NBC are optimized segmentally by PSO, and are used to calculate the upper and lower bounds of the optimal prediction intervals. The superiority of the proposed approach is demonstrated by comparison with a Naive Bayesian model with fixed output weight, and a rough set-Naive Bayesian model with fixed output weight. It is shown that the proposed rough set-Naive Bayesian-particle swarm optimization method has higher coverage of the probabilistic prediction intervals and a narrower average bandwidth under different confidence levels. Full article

(This article belongs to the Special Issue Wind Generators Modelling and Control)

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27 pages, 597 KiB

Open AccessReview

Performance and Reliability of Wind Turbines: A Review

by Sebastian Pfaffel^*

, Stefan Faulstich

and Kurt Rohrig

Fraunhofer Institute for Wind Energy and Energy System Technology—IWES, Königstor 59, 34119 Kassel, Germany

Energies 2017, 10(11), 1904; https://doi.org/10.3390/en10111904 - 19 Nov 2017

Cited by 180 | Viewed by 17296

Abstract

Performance (availability and yield) and reliability of wind turbines can make the difference between success and failure of wind farm projects and these factors are vital to decrease the cost of energy. During the last years, several initiatives started to gather data on [...] Read more.

Performance (availability and yield) and reliability of wind turbines can make the difference between success and failure of wind farm projects and these factors are vital to decrease the cost of energy. During the last years, several initiatives started to gather data on the performance and reliability of wind turbines on- and offshore and published findings in different journals and conferences. Even though the scopes of the different initiatives are similar, every initiative follows a different approach and results are therefore difficult to compare. The present paper faces this issue, collects results of different initiatives and harmonizes the results. A short description and assessment of every considered data source is provided. To enable this comparison, the existing reliability characteristics are mapped to a system structure according to the Reference Designation System for Power Plants (RDS-PP^®). The review shows a wide variation in the performance and reliability metrics of the individual initiatives. Especially the comparison on onshore wind turbines reveals significant differences between the results. Only a few publications are available on offshore wind turbines and the results show an increasing performance and reliability of offshore wind turbines since the first offshore wind farms were erected and monitored. Full article

(This article belongs to the Section F: Electrical Engineering)

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17 pages, 3102 KiB

Open AccessFeature PaperArticle

Machine Learning-Based Short-Term Prediction of Air-Conditioning Load through Smart Meter Analytics

by Manoj Manivannan

, Behzad Najafi^* and Fabio Rinaldi

Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, Milano 20156, Italy

Energies 2017, 10(11), 1905; https://doi.org/10.3390/en10111905 - 19 Nov 2017

Cited by 38 | Viewed by 6099

Abstract

The present paper is focused on short-term prediction of air-conditioning (AC) load of residential buildings using the data obtained from a conventional smart meter. The AC load, at each time step, is separated from smart meter’s aggregate consumption through energy disaggregation methodology. The [...] Read more.

The present paper is focused on short-term prediction of air-conditioning (AC) load of residential buildings using the data obtained from a conventional smart meter. The AC load, at each time step, is separated from smart meter’s aggregate consumption through energy disaggregation methodology. The obtained air-conditioning load and the corresponding historical weather data are then employed as input features for the prediction procedure. In the prediction step, different machine learning algorithms, including Artificial Neural Networks, Support Vector Machines, and Random Forests, are used in order to conduct hour-ahead and day-ahead predictions. The predictions obtained using Random Forests have been demonstrated to be the most accurate ones leading to hour-ahead and day-ahead prediction with R² scores of 87.3% and 83.2%, respectively. The main advantage of the present methodology is separating the AC consumption from the consumptions of other residential appliances, which can then be predicted employing short-term weather forecasts. The other devices’ consumptions are largely dependent upon the occupant’s behaviour and are thus more difficult to predict. Therefore, the harsh alterations in the consumption of AC equipment, due to variations in the weather conditions, can be predicted with a higher accuracy; which in turn enhances the overall load prediction accuracy. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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17 pages, 4113 KiB

Open AccessArticle

Neural Adaptive Sliding-Mode Control of a Vehicle Platoon Using Output Feedback

by Maode Yan^*, Jiacheng Song

, Lei Zuo and Panpan Yang

School of Electronic and Control Engineering, Chang’an University, Xi’an 710064, China

Energies 2017, 10(11), 1906; https://doi.org/10.3390/en10111906 - 20 Nov 2017

Cited by 28 | Viewed by 4835

Abstract

This paper investigates the output feedback control problem of a vehicle platoon with a constant time headway (CTH) policy, where each vehicle can communicate with its consecutive vehicles. Firstly, based on the integrated-sliding-mode (ISM) technique, a neural adaptive sliding-mode control algorithm is developed [...] Read more.

This paper investigates the output feedback control problem of a vehicle platoon with a constant time headway (CTH) policy, where each vehicle can communicate with its consecutive vehicles. Firstly, based on the integrated-sliding-mode (ISM) technique, a neural adaptive sliding-mode control algorithm is developed to ensure that the vehicle platoon is moving with the CTH policy and full state measurement. Then, to further decrease the measurement complexity and reduce the communication load, an output feedback control protocol is proposed with only position information, in which a higher order sliding-mode observer is designed to estimate the other required information (velocities and accelerations). In order to avoid collisions among the vehicles, the string stability of the whole vehicle platoon is proven through the stability theorem. Finally, numerical simulation results are provided to verify its effectiveness and advantages over the traditional sliding-mode control method in vehicle platoons. Full article

(This article belongs to the Special Issue Networked and Distributed Control Systems)

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19 pages, 5865 KiB

Open AccessArticle

Investigation of the Effect of Physical and Optical Factors on the Optical Performance of a Parabolic Trough Collector

by Majedul Islam^1,3, Sarah Miller², Prasad Yarlagadda¹

and Azharul Karim^1,*

¹ Science and Engineering Faculty, Queensland University of Technology, Brisbane CBD, QLD 4001, Australia

² Commonwealth Scientific and Industrial Research (CSIRO), 10 Murray Dwyer Circuit, Mayfield West, NSW 2304, Australia

³ Department of Mechanical Engineering, Chittagong University of Engineering & Technology, Chittagong 4349, Bangladesh

Energies 2017, 10(11), 1907; https://doi.org/10.3390/en10111907 - 20 Nov 2017

Cited by 17 | Viewed by 5080

Abstract

The overall thermal performance of a Parabolic Trough Collector (PTC) depends on its optical performance, particularly the uniformity of the irradiance distribution and the resultant optical efficiency of the collector. Local Concentration Ratio (LCR), optical efficiency and average light concentration are three fundamental [...] Read more.

The overall thermal performance of a Parabolic Trough Collector (PTC) depends on its optical performance, particularly the uniformity of the irradiance distribution and the resultant optical efficiency of the collector. Local Concentration Ratio (LCR), optical efficiency and average light concentration are three fundamental parameters of the optical performance of a PTC. These parameters are affected by various optical and physical factors. The effects of these individual factors on the performance parameters were investigated in this study using a verified Monte Carlo ray tracing optical simulation model. The investigation revealed that all three performance parameters are directly related to the optical properties of the collector components. The values decreased gradually with the increase of focal length of the mirror. Uniformity of the LCR profile was observed to decrease with increasing rim angle and geometric concentration. Defocus dislocation of the receiver was found to improve the uniformity of the LCR distribution by decreasing its peak concentrations, C_max. Off-focus dislocation of the receiver, and inward angular deviation of the mirror profile were observed to increase the C_max and decrease the uniformity of the LCR distribition. Out-focus dislocation of the receiver and solar tracking error distort the bi-symmetry of a normal LCR profile. Full article

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13 pages, 1406 KiB

Open AccessArticle

Influence of Different Types of Obstacles on the Propagation of Premixed Methane-Air Flames in a Half-Open Tube

by Quan Wang^1,2,*

, Shanghao Liu^1,*, Chi-min Shu³, Yibin Ding⁴ and Zhimin Li¹

¹ School of Chemical Engineering, Anhui University of Science & Technology, Huainan 232001, China

² Postdoctoral Mobile Research Station for Civil Engineering, Anhui University of Science & Technology, Huainan 232001, China

³ Process Safety and Disaster Prevention Laboratory, National Yunlin University of Science and Technology, Douliu, Yunlin 64002, Taiwan

⁴ Safety Engineering Technology Institute, Anhui Province Academy of Science and Technology, Hefei 230061, China

Energies 2017, 10(11), 1908; https://doi.org/10.3390/en10111908 - 20 Nov 2017

Cited by 10 | Viewed by 4322

Abstract

To understand the propagation characteristics of methane-air deflagration flames and in an obstacle-filled tube, a high-speed color video camera, photoelectric sensors, and pressure transducers were used to test the deflagration flame propagating parameters. The tests were run in a 1500 mm long plexiglass [...] Read more.

To understand the propagation characteristics of methane-air deflagration flames and in an obstacle-filled tube, a high-speed color video camera, photoelectric sensors, and pressure transducers were used to test the deflagration flame propagating parameters. The tests were run in a 1500 mm long plexiglass tube with a 100 × 100 mm square cross-section. The obstacles included four types of repeated baffles and five forms of solid structure obstacles. The results showed that: (1) the flame front was constantly distorted, stretched, and deformed by different types of obstacles and, consequently, the flame propagating parameters increased; (2) plates and triple prisms increased the speed of the flame and overpressure to the highest extent, whereas cuboids and quadrangulars exerted an intermediate effect. However, the effect of cylindrical obstacles was comparatively limited. It was suggested that the obstacle’s surface edge mutation or curvature changes were the main factors stimulating the flame acceleration; (3) the peak pressure of deflagration was relatively low near the ignition end, increased gradually until it reached the maximum at the middle of the tube, and decreased rapidly near the open end; and (4) the fixed obstacles in front of the flame exhibited a blocking effect on flame propagation during the initial stages; the flame speed and overpressure increased when the flame came into contact with the obstacles. This study is of significance because it explains the methane-air propagation mechanism induced by different types of obstacles. The findings have value for preventing or controlling gas explosion disasters. Full article

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21 pages, 30287 KiB

Open AccessArticle

An Optimal Power and Energy Management by Hybrid Energy Storage Systems in Microgrids

by Alessandro Serpi^*

, Mario Porru

and Alfonso Damiano

Department of Electrical and Electronic Engineering, University of Cagliari, I-09123 Cagliari, Italy

Energies 2017, 10(11), 1909; https://doi.org/10.3390/en10111909 - 20 Nov 2017

Cited by 37 | Viewed by 5107

Abstract

A novel optimal power and energy management (OPEM) for centralized hybrid energy storage systems (HESS) in microgrids is presented in this paper. The proposed OPEM aims at providing multiple grid services by suitably exploiting the different power/energy features of electrochemical batteries (B [...] Read more.

A novel optimal power and energy management (OPEM) for centralized hybrid energy storage systems (HESS) in microgrids is presented in this paper. The proposed OPEM aims at providing multiple grid services by suitably exploiting the different power/energy features of electrochemical batteries (B) and supercapacitors (S). The first part of the paper focuses on the design and analysis of the proposed OPEM, by highlighting the advantages of employing hand-designed solutions based on Pontryagin’s minimum principle rather than resorting to pre-defined optimization tools. Particularly, the B power profile is synthesized optimally over a given time horizon in order to provide both peak shaving and reduced grid energy buffering, while S is employed in order to compensate for short-term forecasting errors and to prevent B from handling sudden and high-frequency power fluctuations. Both the B and S power profiles are computed in real-time in order to benefit from more accurate forecasting, as well as to support each other. Then, the effectiveness of the proposed OPEM is tested through numerical simulations, which have been carried out based on real data from the German island of Borkum. Particularly, an extensive and detailed performance analysis is performed by comparing OPEM with a frequency-based management strategy (FBM) in order to highlight the superior performance achievable by the proposed OPEM in terms of both power and energy management and HESS exploitation. Full article

(This article belongs to the Section D: Energy Storage and Application)

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18 pages, 5745 KiB

Open AccessArticle

Ground-Fault Characteristic Analysis of Grid-Connected Photovoltaic Stations with Neutral Grounding Resistance

by Zheng Li^1,*, Jiping Lu¹, Ya Zhu² and Wang Jiang³

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, School of Electrical Engineering of Chongqing University, Shapingba District, Chongqing 400044, China

² Maintenance Branch of Chongqing Electric Power Company of (State Grid), No. 12 Zhongshan Road, Yuzhong District, Chongqing 400015, China

³ Electric Power Research Institute of Chongqing Electric Power Company of (State Grid), Chongqing 401120, China

Energies 2017, 10(11), 1910; https://doi.org/10.3390/en10111910 - 20 Nov 2017

Cited by 7 | Viewed by 5258

Abstract

A centralized grid-connected photovoltaic (PV) station is a widely adopted method of neutral grounding using resistance, which can potentially make pre-existing protection systems invalid and threaten the safety of power grids. Therefore, studying the fault characteristics of grid-connected PV systems and their impact [...] Read more.

A centralized grid-connected photovoltaic (PV) station is a widely adopted method of neutral grounding using resistance, which can potentially make pre-existing protection systems invalid and threaten the safety of power grids. Therefore, studying the fault characteristics of grid-connected PV systems and their impact on power-grid protection is of great importance. Based on an analysis of the grid structure of a grid-connected PV system and of the low-voltage ride-through control characteristics of a photovoltaic power supply, this paper proposes a short-circuit calculation model and a fault-calculation method for this kind of system. With respect to the change of system parameters, particularly the resistance connected to the neutral point, and the possible impact on protective actions, this paper achieves the general rule of short-circuit current characteristics through a simulation, which provides a reference for devising protection configurations. Full article

(This article belongs to the Section F: Electrical Engineering)

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15 pages, 3983 KiB

Open AccessArticle

Economic Analysis of Flat-Plate and U-Tube Solar Collectors Using an Al₂O₃ Nanofluid

by Woobin Kang¹, Yunchan Shin¹ and Honghyun Cho^2,*

¹ Graduate School of Chosun University, Chosun University, 303 Pilmun-daero, Dong-gu, Gwangju 61452, Korea

² Department of Mechanical Engineering, Chosun University, 303 Pilmun-daero, Dong-gu, Gwangju 61452, Korea

Energies 2017, 10(11), 1911; https://doi.org/10.3390/en10111911 - 20 Nov 2017

Cited by 55 | Viewed by 7475

Abstract

In this study, the efficiencies of flat-plate and U-tube solar collectors were investigated experimentally when an Al₂O₃ nanofluid was used as a working fluid and compared to those of solar collectors using water. The energy savings and CO₂ and [...] Read more.

In this study, the efficiencies of flat-plate and U-tube solar collectors were investigated experimentally when an Al₂O₃ nanofluid was used as a working fluid and compared to those of solar collectors using water. The energy savings and CO₂ and SO₂ generated were calculated and compared to those of solar collectors using water. In addition, based on the experimental results, an economic analysis of the use of solar collectors in various countries was performed. As the concentration of the Al₂O₃ nanofluid increased, the performance of the solar collector improved. The highest efficiency for the solar collectors was shown at the concentration of 1.0 vol % with the nanoparticle size of 20 nm. The maximum efficiencies of the flat-plate and U-tube solar collectors using a 1.0 vol %-Al₂O₃ nanofluid with 20-nm nanoparticles was 74.9% and 72.4%, respectively, when the heat loss parameter was zero. The efficiencies of the flat-plate and U-tube solar collectors using Al₂O₃ nanofluid were 14.8% and 10.7% higher, respectively, than those using water. When 50 EA (each) flat-plate solar collectors were operated for one year using an Al₂O₃ nanofluid, the coal use, generated CO₂, and generated SO₂ were 189.99 kg, 556.69 kg, and 2.03 kg less than those of solar collectors using water, respectively. In addition, the largest electricity cost reduction was in Germany. Full article

(This article belongs to the Section D: Energy Storage and Application)

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21 pages, 4107 KiB

Open AccessArticle

Modeling and Control of Fluid Flow Networks with Application to a Nuclear-Solar Hybrid Plant

by Zhe Dong^*

, Yifei Pan, Zuoyi Zhang, Yujie Dong and Xiaojin Huang

Institute of Nuclear and New Energy Technology, Collaborative Innovation Centre of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084, China

Energies 2017, 10(11), 1912; https://doi.org/10.3390/en10111912 - 20 Nov 2017

Cited by 4 | Viewed by 4987

Abstract

Fluid flow networks (FFNs) can be utilized to integrate multiple once-through heat supply system (OTHSS) modules based on either the same or different energy resources such as the renewable, nuclear and fossil for multi-modular and hybrid energy systems. Modeling and control is very [...] Read more.

Fluid flow networks (FFNs) can be utilized to integrate multiple once-through heat supply system (OTHSS) modules based on either the same or different energy resources such as the renewable, nuclear and fossil for multi-modular and hybrid energy systems. Modeling and control is very important for the safe, stable and efficient operation of the FFNs, whose objective is to maintain both the flowrates and pressure-drops of the network branches within specific bounds. In this paper, a differential-algebraic nonlinear dynamic model for general FFNs with multiple pump branches is proposed based on both the branch hydraulics and network graph properties. Then, an adaptive decentralized FFN flowrate-pressure control law, which takes a proportional-integral (PI) form with saturation on the integral terms, is established. This newly-built control not only guarantees satisfactory closed-loop global stability but also has no need for the values of network hydraulic parameters. This adaptive control is then applied to the flowrate-pressure regulation of the secondary FFN of a two-modular nuclear-solar hybrid energy system and numerical simulation results show the feasibility and high performance of this network control strategy. Due to its concise form, this new flowrate-pressure FFN controller can be easily implemented practically. Full article

(This article belongs to the Special Issue The Future of Solar Thermal Energy)

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20 pages, 4441 KiB

Open AccessArticle

Failure Prognosis of High Voltage Circuit Breakers with Temporal Latent Dirichlet Allocation

by Gaoyang Li

, Xiaohua Wang^*, Aijun Yang, Mingzhe Rong^* and Kang Yang

State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Energies 2017, 10(11), 1913; https://doi.org/10.3390/en10111913 - 20 Nov 2017

Cited by 5 | Viewed by 6694

Abstract

The continual accumulation of power grid failure logs provides a valuable but rarely used source for data mining. Sequential analysis, aiming at exploiting the temporal evolution and exploring the future trend in power grid failures, is an increasingly promising alternative for predictive scheduling [...] Read more.

The continual accumulation of power grid failure logs provides a valuable but rarely used source for data mining. Sequential analysis, aiming at exploiting the temporal evolution and exploring the future trend in power grid failures, is an increasingly promising alternative for predictive scheduling and decision-making. In this paper, a temporal Latent Dirichlet Allocation (TLDA) framework is proposed to proactively reduce the cardinality of the event categories and estimate the future failure distributions by automatically uncovering the hidden patterns. The aim was to model the failure sequence as a mixture of several failure patterns, each of which was characterized by an infinite mixture of failures with certain probabilities. This state space dependency was captured by a hierarchical Bayesian framework. The model was temporally extended by establishing the long-term dependency with new co-occurrence patterns. Evaluation of the high voltage circuit breakers (HVCBs) demonstrated that the TLDA model had higher fidelities of 51.13%, 73.86%, and 92.93% in the Top-1, Top-5, and Top-10 failure prediction tasks over the baselines, respectively. In addition to the quantitative results, we showed that the TLDA can be successfully used for extracting the time-varying failure patterns and capture the failure association with a cluster coalition method. Full article

(This article belongs to the Special Issue 2017 Prognostics and System Health Management Conference)

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23 pages, 5004 KiB

Open AccessArticle

An Interval Fuzzy-Stochastic Chance-Constrained Programming Based Energy-Water Nexus Model for Planning Electric Power Systems

by Jing Liu¹, Yongping Li^1,2,3,*, Guohe Huang^1,2,3, Cai Suo⁴ and Shuo Yin⁵

¹ Department of Environmental Engineering, Xiamen University of Technology, Xiamen 361024, China

² School of Environment, Beijing Normal University, Beijing 100875, China

³ Institute for Energy, Environment and Sustainability Research, University of Regina, Regina, SK S4S 0A2, Canada

⁴ Sino-Canada Energy and Environmental Research Center, North China Electric Power University, Beijing 102206, China

⁵ State Grid Henan Economic Research Institute; No. 87 South Songshan Road, Zhengzhou 450052, China

Energies 2017, 10(11), 1914; https://doi.org/10.3390/en10111914 - 20 Nov 2017

Cited by 10 | Viewed by 3957

Abstract

In this study, an interval fuzzy-stochastic chance-constrained programming based energy-water nexus (IFSCP-WEN) model is developed for planning electric power system (EPS). The IFSCP-WEN model can tackle uncertainties expressed as possibility and probability distributions, as well as interval values. Different credibility (i.e., γ) [...] Read more.

In this study, an interval fuzzy-stochastic chance-constrained programming based energy-water nexus (IFSCP-WEN) model is developed for planning electric power system (EPS). The IFSCP-WEN model can tackle uncertainties expressed as possibility and probability distributions, as well as interval values. Different credibility (i.e., γ) levels and probability (i.e., q_i) levels are set to reflect relationships among water supply, electricity generation, system cost, and constraint-violation risk. Results reveal that different γ and q_i levels can lead to a changed system cost, imported electricity, electricity generation, and water supply. Results also disclose that the study EPS would tend to the transition from coal-dominated into clean energy-dominated. Gas-fired would be the main electric utility to supply electricity at the end of the planning horizon, occupying [28.47, 30.34]% (where 28.47% and 30.34% present the lower bound and the upper bound of interval value, respectively) of the total electricity generation. Correspondingly, water allocated to gas-fired would reach the highest, occupying [33.92, 34.72]% of total water supply. Surface water would be the main water source, accounting for more than [40.96, 43.44]% of the total water supply. The ratio of recycled water to total water supply would increase by about [11.37, 14.85]%. Results of the IFSCP-WEN model present its potential for sustainable EPS planning by co-optimizing energy and water resources. Full article

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23 pages, 6425 KiB

Open AccessFeature PaperArticle

The Techno-Economics of Small-Scale Residential Heating in Low Carbon Futures

by Avinash Vijay^* and Adam Hawkes

Department of Chemical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK

Energies 2017, 10(11), 1915; https://doi.org/10.3390/en10111915 - 21 Nov 2017

Cited by 15 | Viewed by 4609

Abstract

Existing studies that consider the techno-economics of residential heating systems typically focus on their performance within present-day energy systems. However, the energy system within which these technologies operate will need to change radically if climate change mitigation is to be achieved. This article [...] Read more.

Existing studies that consider the techno-economics of residential heating systems typically focus on their performance within present-day energy systems. However, the energy system within which these technologies operate will need to change radically if climate change mitigation is to be achieved. This article addresses this problem by modelling small-scale heating techno-economics in the context of significant electricity system decarbonisation. The current electricity market price regime based on short run marginal costs is seen to provide a very weak investment signal for electricity system investors, so an electricity price regime based on long run marginal energy costs is also considered, using a case study of the UK in 2035. The economic case for conventional boilers remains stronger in most dwelling types. The exception to this is for dwellings with high annual heat demand. Sensitivity studies demonstrate the impact of factors such as price of natural gas, carbon intensity of the central grid and thermodynamic performance. Fuel cell micro combined heat and power shows most potential under the long run electricity price regime, and heat pumps under the short run electricity price regime. This difference highlights the importance of future electricity market structure on consumer choice of heating systems in the future. Full article

(This article belongs to the Section I: Energy Fundamentals and Conversion)

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17 pages, 2238 KiB

Open AccessArticle

Aging Cost Optimization for Planning and Management of Energy Storage Systems

by Saman Korjani¹, Mario Mureddu¹

, Angelo Facchini² and Alfonso Damiano^1,*

¹ Dipartimento di Ingegneria Elettrica ed Elettronica, Università di Cagliari, Italy, Via Marengo 1, 09123 Cagliari, Italy

² IMT School for Advanced Studies Lucca, Piazza S. Francesco 19, 55100 Lucca, Italy

Energies 2017, 10(11), 1916; https://doi.org/10.3390/en10111916 - 21 Nov 2017

Cited by 18 | Viewed by 4591

Abstract

In recent years, many studies have proposed the use of energy storage systems (ESSs) for the mitigation of renewable energy source (RES) intermittent power output. However, the correct estimation of the ESS degradation costs is still an open issue, due to the difficult [...] Read more.

In recent years, many studies have proposed the use of energy storage systems (ESSs) for the mitigation of renewable energy source (RES) intermittent power output. However, the correct estimation of the ESS degradation costs is still an open issue, due to the difficult estimation of their aging in the presence of intermittent power inputs. This is particularly true for battery ESSs (BESSs), which have been proven to exhibit complex aging functions. Unfortunately, this collides with considering aging costs when performing ESS planning and management procedures, which are crucial for the exploitation of this technology. In order to overcome this issue, this paper presents the genetic algorithm-based multi-period optimal power flow (GA-MPOPF) procedure, which aims to economically optimize the management of ESSs by taking into account their degradation costs. The proposed methodology has been tested in two different applications: the planning of the correct positioning of a Li-ion BESS in the PG& E 69 bus network in the presence of high RES penetration, and the definition of its management strategy. Simulation results show that GA-MPOPF is able to optimize the ESS usage for time scales of up to one month, even for complex operative costs functions, showing at the same time excellent convergence properties. Full article

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12 pages, 642 KiB

Open AccessArticle

Considering Maintenance Cost in Unit Commitment Problems

by Hyeongon Park¹

, Joonhyung Park², Jong-Young Park³

and Jae-Haeng Heo^4,*

¹ Department of Statistics, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

² School of Information Technology & Electrical Engineering, The University of Queensland, St. Lucia, QLD 4072, Australia

³ Korea Railroad Research Institute, 176 Cheoldobangmulgwan-ro, Uiwang-si, Gyeonggi-do 16105, Korea

⁴ Raon Friends, 267 Simin-daero, Dongan-gu, Anyang-si, Gyeonggi-do 14054, Korea

Energies 2017, 10(11), 1917; https://doi.org/10.3390/en10111917 - 21 Nov 2017

Cited by 4 | Viewed by 3200

Abstract

Electric power systems worldwide are receiving an increasing volume of wind power generation (WPG) because of environmental concerns and cost declines associated with technological innovation. To manage the uncertainty of WPG, a system operator must commit sufficient conventional generators to provide an appropriate [...] Read more.

Electric power systems worldwide are receiving an increasing volume of wind power generation (WPG) because of environmental concerns and cost declines associated with technological innovation. To manage the uncertainty of WPG, a system operator must commit sufficient conventional generators to provide an appropriate reserve. At times, frequent start and stop operations are applied to certain generators, which incurs maintenance costs associated with thermal-mechanical fatigue. In this paper, we suggest a comprehensive approach to unit commitment (UC) that considers maintenance cost: the parameters of equivalent start (ES) and equivalent base load hours (EBHs) are adopted in the UC problem to determine optimal generation scheduling. A new formulation for the maintenance cost that can be readily combined with an existing mixed integer linear programming algorithm is presented. The effectiveness of the proposed UC method is verified through simulations based on an IEEE 118-bus test system. The simulation results show that considering maintenance cost in the UC problem effectively restricts frequent start and stop operation scheduling. Furthermore, the operating cost is reduced, the required reserve level is maintained, and the computational time is comparable with that of the conventional UC method. Full article

(This article belongs to the Section F: Electrical Engineering)

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12 pages, 667 KiB

Open AccessArticle

Modeling of Electricity Demand for Azerbaijan: Time-Varying Coefficient Cointegration Approach

by Jeyhun I. Mikayilov^1,2,3, Fakhri J. Hasanov^1,4,5,*, Carlo A. Bollino^1,6 and Ceyhun Mahmudlu⁷

¹ King Abdullah Petroleum Studies and Research Center, PO Box 88550, Riyadh 11672, Saudi Arabia

² Department of Statistics, Azerbaijan State University of Economics (UNEC), Istiqlaliyyat Str. 6, Baku AZ1141, Azerbaijan

³ Institute for Scientific Research on Economic Reforms, 88a, Hasan Bey Zardabi Avenue, Baku AZ1011, Azerbaijan

⁴ Research Program on Forecasting, Economics Department, The George Washington University, 2115 G Street, NW, Washington, DC 20052, USA

⁵ Institute of Control Systems, Azerbaijan National Academy of Sciences, B. Vahabzade Street 9, Baku AZ1141, Azerbaijan

⁶ Department of Economics, University of Perugia, Via Pascoli 20, 06123 Perugia, Italy

⁷ Department of International Relations, Baku Engineering University, Hasan Aliyev 120, Khirdalan AZ0101, Azerbaijan

Energies 2017, 10(11), 1918; https://doi.org/10.3390/en10111918 - 21 Nov 2017

Cited by 10 | Viewed by 3956

Abstract

Recent literature has shown that electricity demand elasticities may not be constant over time and this has investigated using time-varying estimation methods. As accurate modeling of electricity demand is very important in Azerbaijan, which is a transitional country facing significant change in its [...] Read more.

Recent literature has shown that electricity demand elasticities may not be constant over time and this has investigated using time-varying estimation methods. As accurate modeling of electricity demand is very important in Azerbaijan, which is a transitional country facing significant change in its economic outlook, we analyze whether the response of electricity demand to income and price is varying over time in this economy. We employed the Time-Varying Coefficient cointegration approach, a cutting-edge time-varying estimation method. We find evidence that income elasticity demonstrates sizeable variation for the period of investigation ranging from 0.48% to 0.56%. The study has some useful policy implications related to the income and price aspects of the electricity consumption in Azerbaijan. Full article

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10 pages, 640 KiB

Open AccessArticle

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

by Agnieszka Dudzińska¹, Natalia Howaniec²

and Adam Smoliński^2,*

¹ Central Mining Institute, Department of Mining Aerology, Pl. Gwarków 1, 40-166 Katowice, Poland

² Central Mining Institute, Department of Energy Saving and Air Protection, Pl. Gwarków 1, 40-166 Katowice, Poland

Energies 2017, 10(11), 1919; https://doi.org/10.3390/en10111919 - 21 Nov 2017

Cited by 15 | Viewed by 3272

Abstract

Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed [...] Read more.

Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed on coal, while migrating through the mine workings. Coal crushed during the mining process is characterized by a high sorption capacity, which facilitates the sorption phenomena. This results in the decrease in hydrocarbons content in mine air, and in the subsequent incorrect assessment of the development of the self-heating process. The results of the experimental study on propylene and acetylene sorption on Polish coals acquired from operating coal mines are presented in this paper. Bituminous coal is characterized by a high sorption capacity with respect to unsaturated hydrocarbons, like propylene and acetylene. The sorbed volumes depend on the grade of metamorphism, porosity, and chemical characteristics of coal. Low level of metamorphism, increased porosity, and oxygen content result in higher sorption capacity of coals. The reduction in grain size of coals also results in the increased sorption capacity with respect to hydrocarbons. The most significant increase in the volumes of sorbed propylene and acetylene with the decrease in grain class was observed for coals of low porosity, high grade of metamorphism, and low to medium sorption capacities. The 10-fold decrease in coal grain size resulted in the 3 to 6-fold increase in the volume of sorbed propylene, and 2-fold increase for acetylene. The decrease in grain size results in higher accessibility of pore structure, increased pore volume and area, and higher number of active centers interacting with hydrocarbons of dipole characteristics. For coals with low grade metamorphism, high porosity, and high sorption capacity the volumes of sorbed propylene and acetylene increased only slightly with the decrease in coal grain size. Full article

(This article belongs to the Section L: Energy Sources)

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18 pages, 4919 KiB

Open AccessArticle

Kinetics and Mechanism of NaOH-Impregnated Calcined Oyster Shell-Catalyzed Transesterification of Soybean Oil

by Han Jin¹, Praveen Kolar^1,*, Steven W. Peretti², Jason A. Osborne³ and Jay J. Cheng¹

¹ Department of Biological and Agricultural Engineering, North Carolina State University, Raleigh, NC 27695-2765, USA

² Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-2765, USA

³ Department of Statistics, North Carolina State University, Raleigh, NC 27695-8203, USA

Energies 2017, 10(11), 1920; https://doi.org/10.3390/en10111920 - 21 Nov 2017

Cited by 12 | Viewed by 5323

Abstract

The objective of this research is to develop a kinetic model to describe the transesterification of soybean oil with methanol using NaOH-impregnated calcined oyster shell (Na-COS). Batch experiments were performed via a two-factor randomized complete block design using a molar ratio of methanol [...] Read more.

The objective of this research is to develop a kinetic model to describe the transesterification of soybean oil with methanol using NaOH-impregnated calcined oyster shell (Na-COS). Batch experiments were performed via a two-factor randomized complete block design using a molar ratio of methanol to oil (MR) of 6, 12, and 18 and catalyst loadings (CL) (mass of catalyst/mass of oil in %) of 2%, 4%, 6%, and 8% to obtain fatty acid methyl ester yields. In addition, the catalyst was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion spectrometry (TOF-SIMS) to elucidate the role of the catalyst in the transesterification reaction. XRD and XPS analyses suggested that the formation of sodium peroxide (Na₂O₂) on the surface contributed to catalytic activity. The TOF-SIMS analysis suggested that the transesterification occurred between adsorbed triglyceride and free methanol, similar to the Eley-Rideal mechanism. The transesterification of adsorbed triglyceride to adsorbed diglyceride was found to be the rate-determining step with a rate constant of 0.0059 ± 0.0002 L mol⁻¹ min⁻¹. Full article

(This article belongs to the Section L: Energy Sources)

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14 pages, 2831 KiB

Open AccessArticle

Optimal Design of Thermal Radiative Heating of Horizontal Thin Plates Using the Entropy Generation Minimization Method

by Ehsan Gholamalizadeh¹

, Mohammad Yaghoub Abdollahzadeh Jamalabadi^2,*

and Majid Oveisi³

¹ Department of Mechanical Engineering, Sejong University, Seoul 05006, Korea

² Department of Mechanical, Robotics and Energy Engineering, Dongguk University-Seoul, Seoul 04620, Korea

³ Faculty of Marine Engineering, Chabahar Maritime University, Chabahar 99717-56499, Iran

Energies 2017, 10(11), 1921; https://doi.org/10.3390/en10111921 - 21 Nov 2017

Cited by 3 | Viewed by 3543

Abstract

Thermal radiant heating through distinct heat sources is of interest for the thermal loading of thin objects as it is used in residential applications, furnaces, and insulator designs. In this paper, an optimal design for a thermal radiant system by discrete suspended heat [...] Read more.

Thermal radiant heating through distinct heat sources is of interest for the thermal loading of thin objects as it is used in residential applications, furnaces, and insulator designs. In this paper, an optimal design for a thermal radiant system by discrete suspended heat sources is analyzed in a side open cavity used for heating the top plate, while the bottom plate is kept at a constant temperature, using the entropy generation minimization method. To avoid pressure fluctuations, the semi-implicit method for pressure linked equations method is used, which solves the continuity, Navier-Stokes, fluid energy, and surface energy equations simultaneously. The system is optimized based on the characteristic length of discrete heat sources, height of discrete heat sources from the bottom plate, the distance between discrete heat sources, the number of discrete heat sources, and the aspect ratio of the cavity that finds the optimal location of heating elements. In addition to the geometrical parameters, the effects of the thermal loading parameters on the optimal position are investigated. Full article

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14 pages, 2402 KiB

Open AccessArticle

Analysis of the Potential of Low-Temperature Heat Pump Energy Sources

by Pavel Neuberger^* and Radomír Adamovský

Department of Mechanical Engineering, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague-Suchdol, Czech Republic

Energies 2017, 10(11), 1922; https://doi.org/10.3390/en10111922 - 21 Nov 2017

Cited by 7 | Viewed by 3956

Abstract

The paper deals with an analysis of temperatures of ground masses in the proximities of linear and slinky-type HGHE (horizontal ground heat exchanger). It evaluates and compares the potentials of HGHEs and ambient air. The reason and aim of the verification was to [...] Read more.

The paper deals with an analysis of temperatures of ground masses in the proximities of linear and slinky-type HGHE (horizontal ground heat exchanger). It evaluates and compares the potentials of HGHEs and ambient air. The reason and aim of the verification was to gain knowledge of the temperature course of the monitored low-temperature heat pump energy sources during heating periods and periods of stagnation and to analyse the knowledge in terms of the potential to use those sources for heat pumps. The study was conducted in the years 2012–2015 during three heating periods and three periods of HGHEs stagnation. The results revealed that linear HGHE had the highest temperature potential of the observed low-temperature heat pump energy sources. The average daily temperatures of the ground mass surrounding the linear HGHE were the highest ranging from 7.08 °C to 9.20 °C during the heating periods, and having the lowest temperature variation range of 12.62–15.14 K, the relative frequency of the average daily temperatures of the ground mass being the highest at 22.64% in the temperature range containing the mode of all monitored temperatures in a recorded interval of [4.10, 6.00] °C. Ambient air had lower temperature potential than the monitored HGHEs. Full article

(This article belongs to the Section L: Energy Sources)

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21 pages, 4803 KiB

Open AccessArticle

Energy Management and Control of Plug-In Hybrid Electric Vehicle Charging Stations in a Grid-Connected Hybrid Power System

by Sidra Mumtaz¹

, Saima Ali¹, Saghir Ahmad¹, Laiq Khan^1,*, Syed Zulqadar Hassan²

and Tariq Kamal³

¹ Department of Electrical Engineering, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan

² Department of Power System and Its Automation, Chongqing University, Chongqing 400044, China

³ Department of Electrical and Electronics Engineering, Faculty of Engineering, Sakarya University, Serdivan/Sakarya 54050, Turkey

Energies 2017, 10(11), 1923; https://doi.org/10.3390/en10111923 - 21 Nov 2017

Cited by 33 | Viewed by 7532

Abstract

The charging infrastructure plays a key role in the healthy and rapid development of the electric vehicle industry. This paper presents an energy management and control system of an electric vehicle charging station. The charging station (CS) is integrated to a [...] Read more.

The charging infrastructure plays a key role in the healthy and rapid development of the electric vehicle industry. This paper presents an energy management and control system of an electric vehicle charging station. The charging station (CS) is integrated to a grid-connected hybrid power system having a wind turbine maximum power point tracking (MPPT) controlled subsystem, photovoltaic (PV) MPPT controlled subsystem and a controlled solid oxide fuel cell with electrolyzer subsystem which are characterized as renewable energy sources. In this article, an energy management system is designed for charging and discharging of five different plug-in hybrid electric vehicles (PHEVs) simultaneously to fulfil the grid-to-vehicle (G2V), vehicle-to-grid (V2G), grid-to-battery storage system (G2BSS), battery storage system-to-grid (BSS2G), battery storage system-to-vehicle (BSS2V), vehicle-to-battery storage system (V2BSS) and vehicle-to-vehicle (V2V) charging and discharging requirements of the charging station. A simulation test-bed in Matlab/Simulink is developed to evaluate and control adaptively the AC-DC-AC converter of non-renewable energy source, DC-DC converters of the storage system, DC-AC grid side inverter and the converters of the CS using adaptive proportional-integral-derivate (AdapPID) control paradigm. The effectiveness of the AdapPID control strategy is validated through simulation results by comparing with conventional PID control scheme. Full article

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15 pages, 2173 KiB

Open AccessArticle

Optimization of a Heliostat Field Layout on Annual Basis Using a Hybrid Algorithm Combining Particle Swarm Optimization Algorithm and Genetic Algorithm

by Chao Li

, Rongrong Zhai^* and Yongping Yang

School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(11), 1924; https://doi.org/10.3390/en10111924 - 21 Nov 2017

Cited by 28 | Viewed by 5567

Abstract

Of all the renewable power generation technologies, solar tower power system is expected to be the most promising technology that is capable of large-scale electricity production. However, the optimization of heliostat field layout is a complicated process, in which thousands of heliostats have [...] Read more.

Of all the renewable power generation technologies, solar tower power system is expected to be the most promising technology that is capable of large-scale electricity production. However, the optimization of heliostat field layout is a complicated process, in which thousands of heliostats have to be considered for any heliostat field optimization process. Therefore, in this paper, in order to optimize the heliostat field to obtain the highest energy collected per unit cost (ECUC), a mathematical model of a heliostat field and a hybrid algorithm combining particle swarm optimization algorithm and genetic algorithm (PSO-GA) are coded in Matlab and the heliostat field in Lhasa is investigated as an example. The results show that, after optimization, the annual efficiency of the heliostat field increases by approximately six percentage points, and the ECUC increases from 12.50 MJ/USD to 12.97 MJ/USD, increased about 3.8%. Studies on the key parameters indicate that: for un-optimized filed, ECUC first peaks and then decline with the increase of the number of heliostats in the first row of the field (Nhel₁). By contrast, for optimized field, ECUC increases with Nhel₁. What is more, for both the un-optimized and optimized field, ECUC increases with tower height and decreases with the cost of heliostat mirror collector. Full article

(This article belongs to the Section F: Electrical Engineering)

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23 pages, 4572 KiB

Open AccessArticle

Impact of Reference Years on the Outcome of Multi-Objective Optimization for Building Energy Refurbishment

by Giovanni Pernigotto^1,*

, Alessandro Prada²

, Francesca Cappelletti³

and Andrea Gasparella¹

¹ Faculty of Science and Technology, Free University of Bozen-Bolzano, piazza Università 5, 39100 Bolzano, Italy

² Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, 38123 Trento, Italy

³ Department of Design and Planning in Complex Environments, University Iuav of Venice, Dorsoduro 2206, 30123 Venezia, Italy

Energies 2017, 10(11), 1925; https://doi.org/10.3390/en10111925 - 21 Nov 2017

Cited by 18 | Viewed by 5182

Abstract

There are several methods in the literature for the definition of weather data for building energy simulation and the most popular ones, such as typical meteorological years and European test reference years, are based on Finkelstein–Schafer statistics. However, even starting from the same [...] Read more.

There are several methods in the literature for the definition of weather data for building energy simulation and the most popular ones, such as typical meteorological years and European test reference years, are based on Finkelstein–Schafer statistics. However, even starting from the same multi-year weather data series, the developed reference years can present different levels of representativeness, which can affect the simulation outcome. In this work, we investigated to which extent the uncertainty in the determination of typical weather conditions can affect the results of building energy refurbishment when cost-optimal approach is implemented for the selection of energy efficiency measures by means of the NSGA-II genetic algorithm coupled with TRNSYS simulations. Six different reference years were determined for two north Italy climates, Trento and Monza, respectively in the Alpine and in the continental temperate regions. Four types of energy efficiency measures, related to both building envelope and HVAC system, were applied to six existing building typologies. Results showed how the choice of reference year can alter the shape of the Pareto fronts, the number of solutions included and the selection among the alternatives of the energy efficiency measures, for the entire front and, in particular, for energy and economic optima. Full article

(This article belongs to the Section D: Energy Storage and Application)

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15 pages, 344 KiB

Open AccessFeature PaperArticle

Optimal Curtailment of Non-Synchronous Renewable Generation on the Island of Tenerife Considering Steady State and Transient Stability Constraints

by Pablo Ledesma^*

, Francisco Arredondo

and Edgardo D. Castronuovo

Electrical Engineering Department, Universidad Carlos III de Madrid. Av. Universidad 30, Leganés, 28911 Madrid, Spain

Energies 2017, 10(11), 1926; https://doi.org/10.3390/en10111926 - 21 Nov 2017

Cited by 7 | Viewed by 4543

Abstract

The increasing penetration of non-synchronous, renewable energy in modern power systems displaces synchronous generation and affects transient stability. This is just one of the factors that has led to preventive curtailment of renewable energy sources in an increasing number of electrical grids. Transient [...] Read more.

The increasing penetration of non-synchronous, renewable energy in modern power systems displaces synchronous generation and affects transient stability. This is just one of the factors that has led to preventive curtailment of renewable energy sources in an increasing number of electrical grids. Transient stability constrained optimal power flow (OPF) techniques provide a tool to optimize the dispatch of power systems while ensuring a secure operation. This work proposes a transient stability-constrained OPF model that includes non-synchronous generation with fault ride-through capability and reactive support during voltage dips. The model is applied it to the IEEE 39 Bus benchmark test case and to the power system of the Spanish island of Tenerife, and solved using the open-source library IPOPT that implements a primal-dual interior point algorithm. The solution of the model makes it possible to optimize the dispatch of conventional plants and the curtailment of non-synchronous generation, as well as to explore methods to reduce generation cost. Fault ride-through capability, synchronous inertia and fault clearing times are identified as useful tools to reduce the curtailment of non-synchronous generation, especially during periods of low load and high availability of renewable energy sources. Full article

(This article belongs to the Section F: Electrical Engineering)

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21 pages, 8428 KiB

Open AccessArticle

Model-Based Predictive Current Control Method with Constant Switching Frequency for Single-Phase Voltage Source Inverters

by Roh Chan and Sangshin Kwak^*

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea

Energies 2017, 10(11), 1927; https://doi.org/10.3390/en10111927 - 21 Nov 2017

Cited by 10 | Viewed by 6076

Abstract

Voltage source inverters operated by predictive control methods generally lead to a variable switching frequency, because predictive control methods generate switching operation based on an optimal voltage state selected at every sampling period. Varying switching frequencies make it difficult to design output filters [...] Read more.

Voltage source inverters operated by predictive control methods generally lead to a variable switching frequency, because predictive control methods generate switching operation based on an optimal voltage state selected at every sampling period. Varying switching frequencies make it difficult to design output filters of voltage source inverters. This paper proposes a predictive control algorithm with a constant switching frequency for the load current control of single-phase voltage source inverters. This method selects two future optimal voltage states used in the subsequent sampling period, which are a zero-voltage state and a future optimal voltage state, based on the slope of the reference current at each sampling period. After selecting the two future voltages, the proposed method distributes them to produce a constant switching frequency and symmetric switching pattern. The performance of the proposed method is validated with both simulation and experimental results for single-phase voltage source inverters. Full article

(This article belongs to the Special Issue Emerging Power Electronics Technologies for Power Systems and Machine Drives)

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14 pages, 3393 KiB

Open AccessFeature PaperArticle

All-Polyamide Composite Coated-Fabric as an Alternative Material of Construction for Textile-Bioreactors (TBRs)

by Mostafa Jabbari^*

, Osagie A. Osadolor

, Ramkumar B. Nair and Mohammad J. Taherzadeh

Swedish Centre for Resource Recovery, University of Borås, SE-50190 Borås, Sweden

Energies 2017, 10(11), 1928; https://doi.org/10.3390/en10111928 - 21 Nov 2017

Cited by 5 | Viewed by 5228

Abstract

All-polyamide composite coated-fabric (APCCF) was used as an alternative material for the construction of textile-bioreactors (TBRs), which are prepared as a replacement of the traditional stainless steel bioreactors (SSBRs) or concrete-based bioreactors. The material characteristics, as well as the fermentation process performance of [...] Read more.

All-polyamide composite coated-fabric (APCCF) was used as an alternative material for the construction of textile-bioreactors (TBRs), which are prepared as a replacement of the traditional stainless steel bioreactors (SSBRs) or concrete-based bioreactors. The material characteristics, as well as the fermentation process performance of the APCCF-TBR, was compared with a TBR made using the polyvinyl chloride (PVC)-coated polyester fabric (PVCCF). The TBRs were used for the anaerobic fermentation process using baker’s yeast; and, for aerobic fermentation process using filamentous fungi, primarily by using waste streams from ethanol industries as the substrates. The results from the fermentation experiments were similar with those that were obtained from the cultivations that were carried out in conventional bioreactors. The techno-economic analysis conducted using a 5000 m³ APCCF-TBR for a typical fermentation facility would lead to a reduction of the annual production cost of the plant by $128,000,000 when compared to similar processes in SSBR. The comparative analyses (including mechanical and morphological studies, density measurements, thermal stability, ageing, and techno-economic analyses) revealed that the APCCF is a better candidate for the material of construction of the TBR. As the APCCF is a 100% recyclable single-polymer composite, which was prepared from Nylon 66 textile production-line waste, it could be considered as an environmentally sustainable product. Full article

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Energies, Volume 10, Issue 11 (November 2017) – 248 articles

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