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Energies, Volume 10, Issue 11 (November 2017)

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Cover Story In this article, PROSA—a new multi-criteria decision-making method—is proposed. While PROSA has [...] Read more.
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Editorial

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Open AccessFeature PaperEditorial Diesel and Spark Ignition Engines Emissions and After-Treatment Control: Research and Advancements
Energies 2017, 10(11), 1882; doi:10.3390/en10111882
Received: 26 October 2017 / Revised: 3 November 2017 / Accepted: 3 November 2017 / Published: 16 November 2017
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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)

Research

Jump to: Editorial, Review, Other

Open AccessArticle A New Platform for Automatic Bottom-Up Electric Load Aggregation
Energies 2017, 10(11), 1682; doi:10.3390/en10111682
Received: 23 August 2017 / Revised: 5 October 2017 / Accepted: 18 October 2017 / Published: 25 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessFeature PaperArticle Performance of an Active Micro Direct Methanol Fuel Cell Using Reduced Catalyst Loading MEAs
Energies 2017, 10(11), 1683; doi:10.3390/en10111683
Received: 11 September 2017 / Revised: 20 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle Torque Coordination Control during Braking Mode Switch for a Plug-in Hybrid Electric Vehicle
Energies 2017, 10(11), 1684; doi:10.3390/en10111684
Received: 15 September 2017 / Revised: 13 October 2017 / Accepted: 16 October 2017 / Published: 25 October 2017
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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
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Open AccessArticle Using IEC 61850 GOOSE Service for Adaptive ANSI 67/67N Protection in Ring Main Systems with Distributed Energy Resources
Energies 2017, 10(11), 1685; doi:10.3390/en10111685
Received: 28 August 2017 / Revised: 17 October 2017 / Accepted: 19 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle A Market-Based Analysis on the Main Characteristics of Gearboxes Used in Onshore Wind Turbines
Energies 2017, 10(11), 1686; doi:10.3390/en10111686
Received: 1 October 2017 / Revised: 19 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle A Novel Multi-Phase Stochastic Model for Lithium-Ion Batteries’ Degradation with Regeneration Phenomena
Energies 2017, 10(11), 1687; doi:10.3390/en10111687
Received: 1 October 2017 / Revised: 16 October 2017 / Accepted: 16 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle Comparison of Modelled and Measured Tilted Solar Irradiance for Photovoltaic Applications
Energies 2017, 10(11), 1688; doi:10.3390/en10111688
Received: 9 August 2017 / Revised: 10 October 2017 / Accepted: 16 October 2017 / Published: 25 October 2017
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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
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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 Energy Sources)
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Open AccessFeature PaperArticle Biodiesel from Mandarin Seed Oil: A Surprising Source of Alternative Fuel
Energies 2017, 10(11), 1689; doi:10.3390/en10111689
Received: 1 October 2017 / Accepted: 20 October 2017 / Published: 26 October 2017
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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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Open AccessFeature PaperArticle Control Applied to a Reciprocating Internal Combustion Engine Test Bench under Transient Operation: Impact on Engine Performance and Pollutant Emissions
Energies 2017, 10(11), 1690; doi:10.3390/en10111690
Received: 8 September 2017 / Revised: 15 October 2017 / Accepted: 17 October 2017 / Published: 25 October 2017
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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.
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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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Open AccessArticle Thermodynamic Optimization of a Geothermal- Based Organic Rankine Cycle System Using an Artificial Bee Colony Algorithm
Energies 2017, 10(11), 1691; doi:10.3390/en10111691
Received: 5 September 2017 / Revised: 16 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
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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
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Open AccessArticle Ideal Point Design and Operation of CO2-Based Transcritical Rankine Cycle (CTRC) System Based on High Utilization of Engine’s Waste Heats
Energies 2017, 10(11), 1692; doi:10.3390/en10111692
Received: 28 September 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessArticle The Amalgamation of SVR and ANFIS Models with Synchronized Phasor Measurements for On-Line Voltage Stability Assessment
Energies 2017, 10(11), 1693; doi:10.3390/en10111693
Received: 3 September 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 25 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessArticle Combustion Characteristics of Single Particles from Bituminous Coal and Pine Sawdust in O2/N2, O2/CO2, and O2/H2O Atmospheres
Energies 2017, 10(11), 1695; doi:10.3390/en10111695
Received: 25 September 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 25 October 2017
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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
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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 Energy Sources)
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Open AccessArticle The Effects of Plant Growth Regulators on Cell Growth, Protein, Carotenoid, PUFAs and Lipid Production of Chlorella pyrenoidosa ZF Strain
Energies 2017, 10(11), 1696; doi:10.3390/en10111696
Received: 11 September 2017 / Revised: 12 October 2017 / Accepted: 16 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle A Comparison Study of a Generic Coupling Methodology for Modeling Wake Effects of Wave Energy Converter Arrays
Energies 2017, 10(11), 1697; doi:10.3390/en10111697
Received: 31 August 2017 / Revised: 6 October 2017 / Accepted: 18 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle Non-Newtonian Flow Characteristics of Heavy Oil in the Bohai Bay Oilfield: Experimental and Simulation Studies
Energies 2017, 10(11), 1698; doi:10.3390/en10111698
Received: 11 September 2017 / Revised: 20 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle Critical Speed Control for a Fixed Blade Variable Speed Wind Turbine
Energies 2017, 10(11), 1699; doi:10.3390/en10111699
Received: 12 September 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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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
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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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Open AccessFeature PaperArticle Optimal Design of Permanent Magnet Arrangement in Synchronous Motors
Energies 2017, 10(11), 1700; doi:10.3390/en10111700
Received: 1 October 2017 / Revised: 19 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle The Fuzzy Logic Method to Efficiently Optimize Electricity Consumption in Individual Housing
Energies 2017, 10(11), 1701; doi:10.3390/en10111701
Received: 28 September 2017 / Revised: 12 October 2017 / Accepted: 24 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle An Analysis of Photo-Voltaic Hosting Capacity in Finnish Low Voltage Distribution Networks
Energies 2017, 10(11), 1702; doi:10.3390/en10111702
Received: 19 September 2017 / Revised: 20 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessFeature PaperArticle Pressure-Drop Coefficients for Cushioning System of Hydraulic Cylinder With Grooved Piston: A Computational Fluid Dynamic Simulation
Energies 2017, 10(11), 1704; doi:10.3390/en10111704
Received: 1 October 2017 / Revised: 18 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle A Two-Dimensional Multiphysics Coupling Model of a Middle and Low Temperature Solar Receiver/Reactor for Methanol Decomposition
Energies 2017, 10(11), 1705; doi:10.3390/en10111705
Received: 16 September 2017 / Revised: 13 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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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
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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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Open AccessArticle Field Measurement and Evaluation of the Passive and Active Solar Heating Systems for Residential Building Based on the Qinghai-Tibetan Plateau Case
Energies 2017, 10(11), 1706; doi:10.3390/en10111706
Received: 28 September 2017 / Revised: 16 October 2017 / Accepted: 20 October 2017 / Published: 26 October 2017
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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,
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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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Open AccessArticle The Battle between Battery and Fuel Cell Powered Electric Vehicles: A BWM Approach
Energies 2017, 10(11), 1707; doi:10.3390/en10111707
Received: 29 September 2017 / Revised: 13 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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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
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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 Energy Storage and Application)
Open AccessArticle Approach to Hybrid Energy Storage Systems Dimensioning for Urban Electric Buses Regarding Efficiency and Battery Aging
Energies 2017, 10(11), 1708; doi:10.3390/en10111708
Received: 28 September 2017 / Revised: 20 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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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
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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 Energy Storage and Application)
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Open AccessArticle Human Thermal Comfort and Heat Removal Efficiency for Ventilation Variants in Passenger Cars
Energies 2017, 10(11), 1710; doi:10.3390/en10111710
Received: 31 August 2017 / Revised: 19 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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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
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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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Open AccessArticle Rethinking Participation in Smart Energy System Planning
Energies 2017, 10(11), 1711; doi:10.3390/en10111711
Received: 3 October 2017 / Revised: 23 October 2017 / Accepted: 24 October 2017 / Published: 26 October 2017
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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
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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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Open AccessArticle Design and Production of Animated Image Photovoltaic Modules
Energies 2017, 10(11), 1712; doi:10.3390/en10111712
Received: 30 September 2017 / Revised: 23 October 2017 / Accepted: 24 October 2017 / Published: 26 October 2017
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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
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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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Open AccessArticle Applications of Hybrid EMD with PSO and GA for an SVR-Based Load Forecasting Model
Energies 2017, 10(11), 1713; doi:10.3390/en10111713
Received: 30 September 2017 / Revised: 19 October 2017 / Accepted: 21 October 2017 / Published: 26 October 2017
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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
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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
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Open AccessFeature PaperArticle Risk-Based Bi-Level Model for Simultaneous Profit Maximization of a Smart Distribution Company and Electric Vehicle Parking Lot Owner
Energies 2017, 10(11), 1714; doi:10.3390/en10111714
Received: 24 September 2017 / Revised: 17 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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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
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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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Open AccessArticle Core Loss Analysis of Interior Permanent Magnet Synchronous Machines under SVPWM Excitation with Considering Saturation
Energies 2017, 10(11), 1716; doi:10.3390/en10111716
Received: 22 September 2017 / Revised: 10 October 2017 / Accepted: 16 October 2017 / Published: 26 October 2017
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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
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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
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Open AccessArticle A Computed River Flow-Based Turbine Controller on a Programmable Logic Controller for Run-Off River Hydroelectric Systems
Energies 2017, 10(11), 1717; doi:10.3390/en10111717
Received: 31 July 2017 / Revised: 15 September 2017 / Accepted: 18 September 2017 / Published: 27 October 2017
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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
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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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Open AccessArticle Improved Load Frequency Control Using a Fast Acting Active Disturbance Rejection Controller
Energies 2017, 10(11), 1718; doi:10.3390/en10111718
Received: 6 September 2017 / Revised: 12 October 2017 / Accepted: 23 October 2017 / Published: 27 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessArticle Impact of the Complementarity between Variable Generation Resources and Load on the Flexibility of the Korean Power System
Energies 2017, 10(11), 1719; doi:10.3390/en10111719
Received: 18 September 2017 / Revised: 20 October 2017 / Accepted: 26 October 2017 / Published: 27 October 2017
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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
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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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Open AccessArticle A Fuzzy-Based PI Controller for Power Management of a Grid-Connected PV-SOFC Hybrid System
Energies 2017, 10(11), 1720; doi:10.3390/en10111720
Received: 11 September 2017 / Revised: 13 October 2017 / Accepted: 16 October 2017 / Published: 27 October 2017
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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
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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 Kp (proportional constant) and Ti (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 Electrical Power and Energy System)
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Open AccessArticle Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades
Energies 2017, 10(11), 1721; doi:10.3390/en10111721
Received: 5 September 2017 / Revised: 23 October 2017 / Accepted: 23 October 2017 / Published: 27 October 2017
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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)
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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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Open AccessArticle Optimal and Learning-Based Demand Response Mechanism for Electric Water Heater System
Energies 2017, 10(11), 1722; doi:10.3390/en10111722
Received: 16 September 2017 / Revised: 6 October 2017 / Accepted: 24 October 2017 / Published: 27 October 2017
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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
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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 Electrical Power and Energy System)
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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
Energies 2017, 10(11), 1723; doi:10.3390/en10111723
Received: 25 September 2017 / Revised: 23 October 2017 / Accepted: 24 October 2017 / Published: 27 October 2017
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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
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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 (Tr), 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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Open AccessArticle CO2 Storage Capacity for Multi-Well Pads Scheme in Depleted Shale Gas Reservoirs
Energies 2017, 10(11), 1724; doi:10.3390/en10111724
Received: 12 October 2017 / Revised: 19 October 2017 / Accepted: 23 October 2017 / Published: 27 October 2017
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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
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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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Open AccessArticle Testing Open-Air Storage of Stumps to Provide Clean Biomass for Energy Production
Energies 2017, 10(11), 1725; doi:10.3390/en10111725
Received: 15 September 2017 / Revised: 23 October 2017 / Accepted: 25 October 2017 / Published: 27 October 2017
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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
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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 Energy Sources)
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Open AccessArticle Implementation, Comparison and Application of an Average Simulation Model of a Wind Turbine Driven Doubly Fed Induction Generator
Energies 2017, 10(11), 1726; doi:10.3390/en10111726
Received: 4 October 2017 / Revised: 22 October 2017 / Accepted: 25 October 2017 / Published: 27 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessArticle Devising Hourly Forecasting Solutions Regarding Electricity Consumption in the Case of Commercial Center Type Consumers
Energies 2017, 10(11), 1727; doi:10.3390/en10111727
Received: 24 September 2017 / Revised: 14 October 2017 / Accepted: 25 October 2017 / Published: 27 October 2017
PDF Full-text (9182 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
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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 Electrical Power and Energy System)
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Open AccessArticle Controllability and Leader-Based Feedback for Tracking the Synchronization of a Linear-Switched Reluctance Machine Network
Energies 2017, 10(11), 1728; doi:10.3390/en10111728
Received: 28 September 2017 / Revised: 14 October 2017 / Accepted: 24 October 2017 / Published: 27 October 2017
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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
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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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Open AccessArticle Simulating Extreme Directional Wave Conditions
Energies 2017, 10(11), 1731; doi:10.3390/en10111731
Received: 22 September 2017 / Revised: 17 October 2017 / Accepted: 24 October 2017 / Published: 28 October 2017
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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
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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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Open AccessArticle Investigation on the Energy Saving Potential of Using a Novel Dew Point Cooling System in Data Centres
Energies 2017, 10(11), 1732; doi:10.3390/en10111732
Received: 22 September 2017 / Revised: 11 October 2017 / Accepted: 26 October 2017 / Published: 28 October 2017
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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
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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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Open AccessArticle Multi-Objective Optimization Approach for Placement of Multiple DGs for Voltage Sensitive Loads
Energies 2017, 10(11), 1733; doi:10.3390/en10111733
Received: 19 September 2017 / Revised: 12 October 2017 / Accepted: 23 October 2017 / Published: 29 October 2017
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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
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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 Electrical Power and Energy System)
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Open AccessArticle Supercritical Water Gasification of Biomass in a Ceramic Reactor: Long-Time Batch Experiments
Energies 2017, 10(11), 1734; doi:10.3390/en10111734
Received: 29 September 2017 / Revised: 23 October 2017 / Accepted: 26 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle A New Approach of Minimizing Commutation Torque Ripple for BLDCM
Energies 2017, 10(11), 1735; doi:10.3390/en10111735
Received: 21 August 2017 / Revised: 14 September 2017 / Accepted: 26 October 2017 / Published: 30 October 2017
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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
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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 Energy Fundamentals and Conversion)
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Open AccessArticle A Transient Stability Numerical Integration Algorithm for Variable Step Sizes Based on Virtual Input
Energies 2017, 10(11), 1736; doi:10.3390/en10111736
Received: 26 September 2017 / Revised: 21 October 2017 / Accepted: 26 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle A Human-Machine-Cooperative-Driving Controller Based on AFS and DYC for Vehicle Dynamic Stability
Energies 2017, 10(11), 1737; doi:10.3390/en10111737
Received: 20 September 2017 / Revised: 12 October 2017 / Accepted: 24 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle New Approach for Optimal Location and Parameters Setting of UPFC for Enhancing Power Systems Stability under Contingency Analysis
Energies 2017, 10(11), 1738; doi:10.3390/en10111738
Received: 13 September 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 30 October 2017
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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
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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
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Open AccessArticle Stability Analysis of Aircraft Power Systems Based on a Unified Large Signal Model
Energies 2017, 10(11), 1739; doi:10.3390/en10111739
Received: 5 September 2017 / Revised: 25 September 2017 / Accepted: 26 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle Approximate Analysis of Multi-State Weighted k-Out-of-n Systems Applied to Transmission Lines
Energies 2017, 10(11), 1740; doi:10.3390/en10111740
Received: 11 September 2017 / Revised: 23 October 2017 / Accepted: 24 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle The Effects of Additives on the Dehydrogenation of Amorphous Manganese Borohydride and Its Crystalline Form after Solvent Filtration/Extraction
Energies 2017, 10(11), 1741; doi:10.3390/en10111741
Received: 4 October 2017 / Revised: 24 October 2017 / Accepted: 27 October 2017 / Published: 30 October 2017
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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,
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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 Energy Storage and Application)
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Open AccessArticle Evaluation of Comfort Level and Harvested Energy in the Vehicle Using Controlled Damping
Energies 2017, 10(11), 1742; doi:10.3390/en10111742
Received: 29 September 2017 / Revised: 20 October 2017 / Accepted: 25 October 2017 / Published: 30 October 2017
PDF Full-text (5355 KB) | HTML Full-text | XML Full-text
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
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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 Energy Fundamentals and Conversion)
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Open AccessArticle Stress Inversion of Coal with a Gas Drilling Borehole and the Law of Crack Propagation
Energies 2017, 10(11), 1743; doi:10.3390/en10111743
Received: 24 September 2017 / Revised: 18 October 2017 / Accepted: 27 October 2017 / Published: 30 October 2017
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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
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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 σci was 30.28–41.71 percent of σf and σcd was 83.08–87.34 percent of σf, calculated by the fitting-damaging method, agreeing with former research. The results of stress inversion showed that under a low stress level (0.15 σf < σ < 0.5 σf), microdamage evolving into plastic failure later was formed around the cavity. Under a high stress level (0.5 σf < σ < 0.85 σf), the region of stress concentration suddenly crazed and formed a brittle crack. When σ ≥ 0.85 σf, 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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Open AccessArticle Advanced Wind Speed Prediction Model Based on a Combination of Weibull Distribution and an Artificial Neural Network
Energies 2017, 10(11), 1744; doi:10.3390/en10111744
Received: 20 September 2017 / Revised: 18 October 2017 / Accepted: 20 October 2017 / Published: 30 October 2017
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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
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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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Open AccessArticle Assessment of Methods for Forecasting Shale Gas Supply in China Based on Economic Considerations
Energies 2017, 10(11), 1745; doi:10.3390/en10111745
Received: 25 September 2017 / Revised: 25 October 2017 / Accepted: 26 October 2017 / Published: 30 October 2017
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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.
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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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Open AccessArticle Comprehensive Parametric Study of a Solar Absorption Refrigeration System to Lower Its Cut In/Off Temperature
Energies 2017, 10(11), 1746; doi:10.3390/en10111746
Received: 6 September 2017 / Revised: 15 October 2017 / Accepted: 25 October 2017 / Published: 31 October 2017
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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
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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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Open AccessArticle Decomposed Driving Factors of Carbon Emissions and Scenario Analyses of Low-Carbon Transformation in 2020 and 2030 for Zhejiang Province
Energies 2017, 10(11), 1747; doi:10.3390/en10111747
Received: 9 September 2017 / Revised: 16 October 2017 / Accepted: 26 October 2017 / Published: 31 October 2017
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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,
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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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Open AccessArticle Influence of Trust on Biomass Supply Decision-Making in China
Energies 2017, 10(11), 1749; doi:10.3390/en10111749
Received: 9 August 2017 / Revised: 29 September 2017 / Accepted: 27 October 2017 / Published: 31 October 2017
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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,
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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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Open AccessArticle Alternative Diesel from Waste Plastics
Energies 2017, 10(11), 1750; doi:10.3390/en10111750
Received: 8 September 2017 / Revised: 20 October 2017 / Accepted: 20 October 2017 / Published: 31 October 2017
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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.
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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 Energy Sources)
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Open AccessArticle A Novel Methodology for Estimating State-Of-Charge of Li-Ion Batteries Using Advanced Parameters Estimation
Energies 2017, 10(11), 1751; doi:10.3390/en10111751
Received: 4 October 2017 / Revised: 26 October 2017 / Accepted: 26 October 2017 / Published: 1 November 2017
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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
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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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Open AccessArticle Analysis of the Optimum Solar Collector Installation Angle from the Viewpoint of Energy Use Patterns
Energies 2017, 10(11), 1753; doi:10.3390/en10111753
Received: 8 September 2017 / Revised: 21 October 2017 / Accepted: 21 October 2017 / Published: 2 November 2017
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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
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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 Energy Storage and Application)
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Open AccessArticle Quantification of Forecast Error Costs of Photovoltaic Prosumers in Italy
Energies 2017, 10(11), 1754; doi:10.3390/en10111754
Received: 25 September 2017 / Revised: 13 October 2017 / Accepted: 24 October 2017 / Published: 1 November 2017
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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
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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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Open AccessArticle Using the PROSA Method in Offshore Wind Farm Location Problems
Energies 2017, 10(11), 1755; doi:10.3390/en10111755
Received: 29 September 2017 / Revised: 21 October 2017 / Accepted: 26 October 2017 / Published: 1 November 2017
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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
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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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Open AccessArticle A Game Theory Approach to Multi-Agent Decentralized Energy Management of Autonomous Polygeneration Microgrids
Energies 2017, 10(11), 1756; doi:10.3390/en10111756
Received: 21 September 2017 / Revised: 22 October 2017 / Accepted: 26 October 2017 / Published: 1 November 2017
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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
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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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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
Energies 2017, 10(11), 1757; doi:10.3390/en10111757
Received: 23 July 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 1 November 2017
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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
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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
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Open AccessArticle Contribution to Energy Management of the Main Standards for Environmental Management Systems: The Case of ISO 14001 and EMAS
Energies 2017, 10(11), 1758; doi:10.3390/en10111758
Received: 5 September 2017 / Revised: 19 October 2017 / Accepted: 27 October 2017 / Published: 1 November 2017
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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
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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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Open AccessArticle Partial Discharge of Needle-Plane Defect in Oil-Paper Insulation under AC and DC Combined Voltages: Developing Processes and Characteristics
Energies 2017, 10(11), 1759; doi:10.3390/en10111759
Received: 28 September 2017 / Revised: 26 October 2017 / Accepted: 27 October 2017 / Published: 1 November 2017
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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
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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