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22 pages, 6620 KiB

Open AccessArticle

A Smart Forecasting Approach to District Energy Management

by Baris Yuce^1,2,*,†, Monjur Mourshed^1,*

and Yacine Rezgui¹

¹ BRE Trust Centre for Sustainable Engineering, School of Engineering, Cardiff University, Cardiff CF24 3AA, UK

² College of Engineering, Mathematics, and Physical Sciences, School of Engineering, Streatham Campus University of Exeter, Exeter EX4 4QJ, UK

^† The research reported in this study was conducted while Baris Yuce was affiliated with Cardiff University.

Energies 2017, 10(8), 1073; https://doi.org/10.3390/en10081073 - 25 Jul 2017

Cited by 25 | Viewed by 6011

Abstract

This study presents a model for district-level electricity demand forecasting using a set of Artificial Neural Networks (ANNs) (parallel ANNs) based on current energy loads and social parameters such as occupancy. A comprehensive sensitivity analysis is conducted to select the inputs of the [...] Read more.

This study presents a model for district-level electricity demand forecasting using a set of Artificial Neural Networks (ANNs) (parallel ANNs) based on current energy loads and social parameters such as occupancy. A comprehensive sensitivity analysis is conducted to select the inputs of the ANN by considering external weather conditions, occupancy type, main income providers’ employment status and related variables for the fuel poverty index. Moreover, a detailed parameter tuning is conducted using various configurations for each individual ANN. The study also demonstrates the strength of the parallel ANN models in different seasons of the years. In the proposed district level energy forecasting model, the training and testing stages of parallel ANNs utilise dataset of a group of six buildings. The aim of each individual ANN is to predict electricity consumption and the aggregated demand in sub-hourly time-steps. The inputs of each ANN are determined using Principal Component Analysis (PCA) and Multiple Regression Analysis (MRA) methods. The accuracy and consistency of ANN predictions are evaluated using Pearson coefficient and average percentage error, and against four seasons: winter, spring, summer, and autumn. The lowest prediction error for the aggregated demand is about 4.51% for winter season and the largest prediction error is found as 8.82% for spring season. The results demonstrate that peak demand can be predicted successfully, and utilised to forecast and provide demand-side flexibility to the aggregators for effective management of district energy systems. Full article

(This article belongs to the Special Issue Zero-Carbon Buildings)

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13 pages, 5009 KiB

Open AccessFeature PaperArticle

Parametric Investigation Using Computational Fluid Dynamics of the HVAC Air Distribution in a Railway Vehicle for Representative Weather and Operating Conditions

by Christian Suárez¹, Alfredo Iranzo^2,*

, José Antonio Salva¹, Elvira Tapia², Gonzalo Barea³ and José Guerra²

¹ AICIA, Andalusian Association for Research & Industrial Cooperation, Camino de los Descubrimientos s/n, Edf. Escuela Superior de Ingenieros de Sevilla, 41092 Seville, Spain

² Thermal Engineering Group, Energy Engineering Department, School of Engineering, University of Seville, Camino de los Descubrimientos s/n, 41092 Seville, Spain

³ Hispacold, C/Pino Alepo 1, Polígono Industrial El Pino, 41016 Seville, Spain

Energies 2017, 10(8), 1074; https://doi.org/10.3390/en10081074 - 25 Jul 2017

Cited by 22 | Viewed by 5427

Abstract

A computational fluid dynamics (CFD) analysis of air distribution in a representative railway vehicle equipped with a heating, ventilation, air conditioning (HVAC) system is presented in this paper. Air distribution in the passenger’s compartment is a very important factor to regulate temperature and [...] Read more.

A computational fluid dynamics (CFD) analysis of air distribution in a representative railway vehicle equipped with a heating, ventilation, air conditioning (HVAC) system is presented in this paper. Air distribution in the passenger’s compartment is a very important factor to regulate temperature and air velocity in order to achieve thermal comfort. A complete CFD model, including the car’s geometry in detail, the passengers, the luminaires, and other the important features related to the HVAC system (air supply inlets, exhaust outlets, convectors, etc.) are developed to investigate eight different typical scenarios for Northern Europe climate conditions. The results, analyzed and discussed in terms of temperature and velocity fields in different sections of the tram, and also in terms of volumetric parameters representative of the whole tram volume, show an adequate behavior from the passengers’ comfort point of view, especially for summer climate conditions. Full article

(This article belongs to the Special Issue Engineering Fluid Dynamics)

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19 pages, 4826 KiB

Open AccessArticle

Estimating Lithium-Ion Battery State of Charge and Parameters Using a Continuous-Discrete Extended Kalman Filter

by Yasser Diab^1,2,*, François Auger¹

, Emmanuel Schaeffer¹ and Moutassem Wahbeh²

¹ Institut de Recherche en Energie Electrique de Nantes Atlantique (IREENA), Université de Nantes, Centre de Recherche et de Transfert de Technologie (CRTT), B.P. 406, 37 Bd de l’Université, Saint Nazaire CEDEX 44602, France

² Department of Electrical Power Engineering, Damascus University, Damascus B.P. 86, Syria

Energies 2017, 10(8), 1075; https://doi.org/10.3390/en10081075 - 25 Jul 2017

Cited by 36 | Viewed by 6995

Abstract

A real-time determination of battery parameters is challenging because batteries are non-linear, time-varying systems. The transient behaviour of lithium-ion batteries is modelled by a Thevenin-equivalent circuit with two time constants characterising activation and concentration polarization. An experimental approach is proposed for directly determining [...] Read more.

A real-time determination of battery parameters is challenging because batteries are non-linear, time-varying systems. The transient behaviour of lithium-ion batteries is modelled by a Thevenin-equivalent circuit with two time constants characterising activation and concentration polarization. An experimental approach is proposed for directly determining battery parameters as a function of physical quantities. The model’s parameters are a function of the state of charge and of the discharge rate. These can be expressed by regression equations in the model to derive a continuous-discrete extended Kalman estimator of the state of charge and of other parameters. This technique is based on numerical integration of the ordinary differential equations to predict the state of the stochastic dynamic system and the corresponding error covariance matrix. Then a standard correction step of the extended Kalman filter (EKF) is applied to increase the accuracy of estimated parameters. Simulations resulting from this proposed estimator model were compared with experimental results under a variety of operating scenarios—analysis of the results demonstrate the accuracy of the estimator for correctly identifying battery parameters. Full article

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23 pages, 9458 KiB

Open AccessArticle

Real-Time Analysis of a Modified State Observer for Sensorless Induction Motor Drive Used in Electric Vehicle Applications

by Mohan Krishna S.¹

, Febin Daya J.L.²

, Sanjeevikumar Padmanaban^3,*

and Lucian Mihet-Popa⁴

¹ Department of Electrical and Electronics Engineering, MITS (Madanapalle Institute of Technology and Science), Madanapalle 517325, AP, India

² School of Electrical Engineering, VIT University—Chennai Campus, Chennai 600 048, India

³ Department of Electrical and Electronics Engineering Science, University of Johannesburg, Auckland Park, Johannesburg 2006, South Africa

⁴ Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Kråkeroy, Norway

Energies 2017, 10(8), 1077; https://doi.org/10.3390/en10081077 - 25 Jul 2017

Cited by 17 | Viewed by 5769

Abstract

The purpose of this work is to present an adaptive sliding mode Luenberger state observer with improved disturbance rejection capability and better tracking performance under dynamic conditions. The sliding hyperplane is altered by incorporating the estimated disturbance torque with the stator currents. In [...] Read more.

The purpose of this work is to present an adaptive sliding mode Luenberger state observer with improved disturbance rejection capability and better tracking performance under dynamic conditions. The sliding hyperplane is altered by incorporating the estimated disturbance torque with the stator currents. In addition, the effects of parameter detuning on the speed convergence are observed and compared with the conventional disturbance rejection mechanism. The entire drive system is first built in the Simulink environment. Then, the Simulink model is integrated with real-time (RT)-Lab blocksets and implemented in a relatively new real-time environment using OP4500 real-time simulator. Real-time simulation and testing platforms have succeeded offline simulation and testing tools due to their reduced development time. The real-time results validate the improvement in the proposed state observer and also correspond to the performance of the actual physical model. Full article

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

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11 pages, 3924 KiB

Open AccessArticle

Heat Transfer Fluid Temperature Control in a Thermoelectric Solar Power Plant

by Lourdes A. Barcia¹, Rogelio Peon²

, Juan Díaz^3,*

, A.M. Pernía³

and Juan Ángel Martínez³

¹ Normagrup Technology S.A., 33420 Llanera, Asturias, Spain

² Grupo TSK PCyT de Gijón, 33203 Gijón, Spain

³ Department of Electrical Engineering, University of Oviedo, 33203 Gijón, Asturias, Spain

Energies 2017, 10(8), 1078; https://doi.org/10.3390/en10081078 - 25 Jul 2017

Cited by 6 | Viewed by 5172

Abstract

Thermoelectric solar plants transform solar energy into electricity. Unlike photovoltaic plants, the sun’s energy heats a fluid (heat transfer fluid (HTF)) and this, in turn, exchanges its energy, generating steam. Finally, the steam generates electricity in a Rankine cycle. One of the main [...] Read more.

Thermoelectric solar plants transform solar energy into electricity. Unlike photovoltaic plants, the sun’s energy heats a fluid (heat transfer fluid (HTF)) and this, in turn, exchanges its energy, generating steam. Finally, the steam generates electricity in a Rankine cycle. One of the main advantages of this double conversion (sun energy to heat in the HTF-Rankine cycle) is the fact that it facilitates energy storage without using batteries. It is possible to store the heat energy in melted salts in such a way that this energy will be recovered when necessary, i.e., during the night. These molten salts are stored in containers in a liquid state at high temperature. The HTF comes into the solar field at a given temperature and increases its energy thanks to the solar collectors. In order to optimize the sun to HTF energy transference, it is necessary to keep an adequate temperature control of the fluid at the output of the solar fields. This paper describes three different algorithms to control the HTF output temperature. Full article

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

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12 pages, 4569 KiB

Open AccessArticle

Analysis and Experiment of Hot-Spot Temperature Rise of 110 kV Three-Phase Three-Limb Transformer

by Ruohan Gong^*, Jiangjun Ruan, Jingzhou Chen, Yu Quan, Jian Wang and Cihan Duan

School of Electrical Engineering, Wuhan University, No. 8, South Road of Eastern Lake, Wuhan 430072, China

Energies 2017, 10(8), 1079; https://doi.org/10.3390/en10081079 - 25 Jul 2017

Cited by 32 | Viewed by 5870

Abstract

This paper presents a fluid-thermal coupled analysis method to compute the temperature distribution in a 31.5 MVA/110 kV oil natural air natural (ONAN) three-phase three-limb transformer. The power losses of windings and core are measured by load-loss test and no-load test respectively. The [...] Read more.

This paper presents a fluid-thermal coupled analysis method to compute the temperature distribution in a 31.5 MVA/110 kV oil natural air natural (ONAN) three-phase three-limb transformer. The power losses of windings and core are measured by load-loss test and no-load test respectively. The convective heat transfer process, radiation and oil flow inside the transformer are investigated by finite volume method (FVM). In order to validate the feasibility and accuracy of the presented method, the temperature measuring system based on fiber Brag grating (FBG) sensor is constructed for the temperature rise test of the 31.5 MVA/110 kV ONAN transformer. The simulation results deduced from the proposed method agree well with experimental data. This model can be applied to optimizing design and load scheduling. Full article

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18 pages, 2193 KiB

Open AccessArticle

An Improved Droop Control Strategy Based on Changeable Reference in Low-Voltage Microgrids

by Chunxia Dou^1,2,*, Zhanqiang Zhang^1,*

, Dong Yue² and Hanxiao Gao³

¹ Institute of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China

² Institute of Advanced Technology, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

³ Institute of Marxism, Yanshan University, Qinhuangdao 066004, China

Energies 2017, 10(8), 1080; https://doi.org/10.3390/en10081080 - 26 Jul 2017

Cited by 11 | Viewed by 4569

Abstract

This paper proposes an improved droop control strategy based on changeable reference in low-voltage microgrids. To restore running frequency of distributed generation to a rated value without affecting its reactive power output, changeable frequency reference, mainly compensating for frequency deviation, are proposed corresponding [...] Read more.

This paper proposes an improved droop control strategy based on changeable reference in low-voltage microgrids. To restore running frequency of distributed generation to a rated value without affecting its reactive power output, changeable frequency reference, mainly compensating for frequency deviation, are proposed corresponding to various load demands. In terms of active power sharing inaccuracy associated with mismatched line impedance, changeable voltage amplitude reference is proposed to obtain a droop line suitable for the actual voltage of distributed generations. By further improvement of the active droop coefficient, power sharing is accurate with a difference in actual voltages of distributed generations. Virtual negative inductance is used to neutralize the redundant line inductance for strictly improving sharing accuracy. A robust control method based on Lyapunov function is used to handle the robustness problem in case of load variation. The control scheme is entirely decentralized, so communication links among distributed generations are redundant. Finally, simulation studies demonstrate the effectiveness of a control strategy. Full article

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

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22 pages, 6465 KiB

Open AccessArticle

Automatic Faulted Feeder Section Location and Isolation Method for Power Distribution Systems Considering the Change of Topology

by Kongming Sun, Qing Chen^*

and Pu Zhao

Key Laboratory of Power System Intelligent Dispatch and Control, Shandong University, Ministry of Education, Jinan 250061, China

Energies 2017, 10(8), 1081; https://doi.org/10.3390/en10081081 - 25 Jul 2017

Cited by 12 | Viewed by 5875

Abstract

The increasing use of modern measuring devices, such as Feeder Terminal Units (FTUs), on power networks can provide multiple types of information for fault location on distribution systems. Using these devices, in this paper, a novel automatic matrix-based algorithm for the identification and [...] Read more.

The increasing use of modern measuring devices, such as Feeder Terminal Units (FTUs), on power networks can provide multiple types of information for fault location on distribution systems. Using these devices, in this paper, a novel automatic matrix-based algorithm for the identification and isolation of faulted feeder sections on distribution systems is proposed. The algorithm works in two stages: the first stage automatically identifies the radial feeders that make up the whole system and represents the feeders’ topology in matrix form; and the second stage automatically identifies the faulted section of the identified feeder and opens the relevant switches to isolate it. The algorithm can be applied to single and multiple faults, as it operates using measuring device information and detecting the status of switch devices. It does not require any electrical parameters and it is not affected by the fault type or fault resistance. The algorithm was thoroughly tested using a large distribution system and was found to efficiently identify and isolate the faulted feeder section in each case. Full article

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

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16 pages, 4771 KiB

Open AccessArticle

Nonlinear Observer-Based Robust Passive Control of Doubly-Fed Induction Generators for Power System Stability Enhancement via Energy Reshaping

by Jun Dong¹, Shengnan Li², Shuijun Wu², Tingyi He², Bo Yang³, Hongchun Shu^3,* and Jilai Yu¹

¹ School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China

² Electric Power Research Institute of Yunnan Power Grid Co., Ltd., Kunming 650217, China

³ Faculty of Electric Power Engineering, Kunming University of Science and Technology, Kunming 650500, China

Energies 2017, 10(8), 1082; https://doi.org/10.3390/en10081082 - 25 Jul 2017

Cited by 16 | Viewed by 4910

Abstract

The large-scale penetration of wind power might lead to degradation of the power system stability due to its inherent feature of randomness. Hence, proper control designs which can effectively handle various uncertainties become very crucial. This paper designs a novel robust passive control [...] Read more.

The large-scale penetration of wind power might lead to degradation of the power system stability due to its inherent feature of randomness. Hence, proper control designs which can effectively handle various uncertainties become very crucial. This paper designs a novel robust passive control (RPC) scheme of a doubly-fed induction generator (DFIG) for power system stability enhancement. The combinatorial effect of generator nonlinearities and parameter uncertainties, unmodelled dynamics, wind speed randomness, is aggregated into a perturbation, which is rapidly estimated by a nonlinear extended state observer (ESO) in real-time. Then, the perturbation estimate is fully compensated by a robust passive controller to realize a globally consistent control performance, in which the energy of the closed-loop system is carefully reshaped through output feedback passification, such that a considerable system damping can be injected to improve the transient responses of DFIG in various operation conditions of power systems. Six case studies are carried out while simulation results verify that RPC can rapidly stabilize the disturbed DFIG system much faster with less overshoot, as well as supress power oscillations more effectively compared to that of linear proportional-integral-derivative (PID) control and nonlinear feedback linearization control (FLC). Full article

(This article belongs to the Special Issue Sustainable Energy Technologies)

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25 pages, 2560 KiB

Open AccessFeature PaperArticle

A Polar Fuzzy Control Scheme for Hybrid Power System Using Vehicle-To-Grid Technique

by Mohammed Elsayed Lotfy^1,2

, Tomonobu Senjyu^2,*

, Mohammed Abdel-Fattah Farahat¹, Amal Farouq Abdel-Gawad¹ and Hidehito Matayoshi²

¹ Department of Electrical Power and Machines, Zagazig University, Zagazig 44519, Egypt

² Department of Electrical and Electronics Engineering, University of the Ryukyus, Okinawa 903-0213, Japan

Energies 2017, 10(8), 1083; https://doi.org/10.3390/en10081083 - 25 Jul 2017

Cited by 15 | Viewed by 5753

Abstract

A novel polar fuzzy (PF) control approach for a hybrid power system is proposed in this research. The proposed control scheme remedies the issues of system frequency and the continuity of demand supply caused by renewable sources’ uncertainties. The hybrid power system consists [...] Read more.

A novel polar fuzzy (PF) control approach for a hybrid power system is proposed in this research. The proposed control scheme remedies the issues of system frequency and the continuity of demand supply caused by renewable sources’ uncertainties. The hybrid power system consists of a wind turbine generator (WTG), solar photovoltaics (PV), a solar thermal power generator (STPG), a diesel engine generator (DEG), an aqua-electrolyzer (AE), an ultra-capacitor (UC), a fuel-cell (FC), and a flywheel (FW). Furthermore, due to the high cost of the battery energy storage system (BESS), a new idea of vehicle-to-grid (V2G) control is applied to use the battery of the electric vehicle (EV) as equivalent to large-scale energy storage units instead of small batteries to improve the frequency stability of the system. In addition, EV customers’ convenience is taken into account. A minimal-order observer is used to estimate the supply error. Then, the area control error (ACE) signal is calculated in terms of the estimated supply error and the frequency deviation. ACE is considered in the frequency domain. Two PF approaches are utilized in the intended system. The mission of each controller is to mitigate one frequency component of ACE. The responsibility for ACE compensation is shared among all parts of the system according to their speed of response. The performance of the proposed control scheme is compared to the conventional fuzzy logic control (FLC). The effectiveness and robustness of the proposed control technique are verified by numerical simulations under various scenarios. Full article

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

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21 pages, 9025 KiB

Open AccessArticle

An Approach of Quantifying Gear Fatigue Life for Wind Turbine Gearboxes Using Supervisory Control and Data Acquisition Data

by Yingning Qiu^1,*, Lang Chen¹, Yanhui Feng¹ and Yili Xu²

¹ School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

² Zhejiang Windey Ltd. by Share Ltd, 22F, Building A, the West Lake International Plaza S&T, No. 391, Wen’er Road, Hangzhou 310012, China

Energies 2017, 10(8), 1084; https://doi.org/10.3390/en10081084 - 25 Jul 2017

Cited by 24 | Viewed by 4572

Abstract

Quantifying wind turbine (WT) gearbox fatigue life is a critical problem for preventive maintenance when unsolved. This paper proposes a practical approach that uses ten minutes’ average wind speed of Supervisory Control and Data Acquisition (SCADA) data to quantify a WT gearbox’s gear [...] Read more.

Quantifying wind turbine (WT) gearbox fatigue life is a critical problem for preventive maintenance when unsolved. This paper proposes a practical approach that uses ten minutes’ average wind speed of Supervisory Control and Data Acquisition (SCADA) data to quantify a WT gearbox’s gear fatigue life. Wind turbulence impacts on gearbox fatigue are studied thoroughly. Short-term fatigue assessment for the gearbox is then performed using linear fatigue theory by considering WT responses under external and internal excitation. The results shows that for a three stage gearbox, the sun gear in the first stage and pinions in the 2nd and 3rd stage are the most vulnerable parts. High mean wind speed, especially above the rated range, leads to a high risk of gearbox fatigue damage. Increase of wind turbulence may not increase fatigue damage as long as a WT has an instant response to external excitation. An approach of using SCADA data recorded every ten minutes to quantify gearbox long-term damages is presented. The calculation results show that the approach effectively presents gears’ performance degradation by quantifying their fatigue damage. This is critical to improve WT reliability and meaningful for WT gearbox fatigue assessment theory. The result provides useful tools for future wind farm prognostic maintenance. Full article

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12 pages, 6316 KiB

Open AccessArticle

Correlation Characteristics Comparison of SF₆ Decomposition versus Gas Pressure under Negative DC Partial Discharge Initiated by Two Typical Defects

by Dong Yang¹, Ju Tang¹, Xu Yang¹, Ke Li¹, Fuping Zeng^1,*, Qiang Yao², Yulong Miao² and Lincong Chen³

¹ School of Electrical Engineering, Wuhan University, Wuhan 430072, China

² Electric Power Research Institute, Chongqing Power Company, Chongqing 401123, China

³ Electric Power Research Institute, Hainan Power Grid Co., Ltd. Haikou 570100, China

Energies 2017, 10(8), 1085; https://doi.org/10.3390/en10081085 - 25 Jul 2017

Cited by 3 | Viewed by 4055

Abstract

Aimed to clarify the correlation characteristics between the internal partial discharge (PD) in negative direct current (DC) gas insulated system (GIS) and gas pressure initiated by two typical defects (i.e., free-metal particles and metal protrusion), this study on PD decomposition of sulfur hexafluoride [...] Read more.

Aimed to clarify the correlation characteristics between the internal partial discharge (PD) in negative direct current (DC) gas insulated system (GIS) and gas pressure initiated by two typical defects (i.e., free-metal particles and metal protrusion), this study on PD decomposition of sulfur hexafluoride (SF₆) was investigated under different pressures on the basis of constructing a SF₆ decomposition experimental platform with DC PD. Free-metal particles and metal protrusion in a GIS were simulated using a spherical-bowl electrode and a needle-plate electrode, respectively. Trends and differences in the performance of SF₆ decomposition components SOF₂, SO₂F₂, CO_2, and SO₂ at different pressures were compared and analyzed by experiments under different defects. Based on gas microscopic ionization theory, the relationship between the decomposition component and gas pressure was deduced and verified. The concentrations of different decomposition components were found to vary with the change in gas pressure under different defects, whereas the characteristic ratios of decomposition components versus gas pressure showed a similar trend. Full article

(This article belongs to the Special Issue Selected Papers from 2016 IEEE International Conference on High Voltage Engineering (ICHVE 2016))

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24 pages, 7156 KiB

Open AccessEditor’s ChoiceArticle

Investigation on the Development of a Sliding Mode Controller for Constant Power Loads in Microgrids

by Eklas Hossain¹

, Ron Perez², Sanjeevikumar Padmanaban^3,*

and Pierluigi Siano⁴

¹ Department of Electrical Engineering & Renewable Energy, Oregon Tech, Klamath Falls, OR 97601, USA

² Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA

³ Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland Park 2006, South Africa

⁴ Department of Industrial Engineering, University of Salerno, 84084 Salerno, Italy

Energies 2017, 10(8), 1086; https://doi.org/10.3390/en10081086 - 26 Jul 2017

Cited by 39 | Viewed by 6731

Abstract

To implement renewable energy resources, microgrid systems have been adopted and developed into the technology of choice to assure mass electrification in the next decade. Microgrid systems have a number of advantages over conventional utility grid systems, however, they face severe instability issues [...] Read more.

To implement renewable energy resources, microgrid systems have been adopted and developed into the technology of choice to assure mass electrification in the next decade. Microgrid systems have a number of advantages over conventional utility grid systems, however, they face severe instability issues due to the continually increasing constant power loads. To improve the stability of the entire system, the load side compensation technique is chosen because of its robustness and cost effectiveness. In this particular occasion, a sliding mode controller is developed for a microgrid system in the presence of constant power loads to assure a certain control objective of keeping the output voltage constant at 480 V. After that, a robustness analysis of the sliding mode controller against parametric uncertainties was performed and the sliding mode controller’s robustness against parametric uncertainties, frequency variations, and additive white Gaussian noise (AWGN) are presented. Later, the performance of the proportional integral derivative (PID) and sliding mode controller are compared in the case of nonlinearity, parameter uncertainties, and noise rejection to justify the selection of the sliding mode controller over the PID controller. All the necessary calculations are reckoned mathematically and results are verified in a virtual platform such as MATLAB/Simulink with a positive outcome. Full article

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

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17 pages, 3634 KiB

Open AccessArticle

A Comparative Study of the Effect of Turbocompounding and ORC Waste Heat Recovery Systems on the Performance of a Turbocharged Heavy-Duty Diesel Engine

by Amin Mahmoudzadeh Andwari^1,2,*

, Apostolos Pesiridis², Vahid Esfahanian¹, Ali Salavati-Zadeh¹

, Apostolos Karvountzis-Kontakiotis^2,3

and Vishal Muralidharan²

¹ Vehicle, Fuel and Environment Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran 14174, Iran

² Centre for Advanced Powertrain and Fuels Research (CAPF), Department of Mechanical, Aerospace and Civil Engineering, Brunel University London, London UB8 3PH, UK

³ Department of Mechanical Engineering & Aeronautics, City University of London, Northampton Square, London EC1V 0HB, UK

Energies 2017, 10(8), 1087; https://doi.org/10.3390/en10081087 - 26 Jul 2017

Cited by 34 | Viewed by 7932

Abstract

In this study the influence of utilization of two Waste Heat Recovery (WHR) strategies, namely organic Rankine cycle (ORC) and turbocompounding, have been investigated based on the performance of a heavy-duty diesel engine using 1-D simulation engine code (GT-Power) in terms of Brake [...] Read more.

In this study the influence of utilization of two Waste Heat Recovery (WHR) strategies, namely organic Rankine cycle (ORC) and turbocompounding, have been investigated based on the performance of a heavy-duty diesel engine using 1-D simulation engine code (GT-Power) in terms of Brake Specific Fuel Consumptions (BSFC) at various engine speeds and Brake Mean Effective Pressures (BMEP). The model of a 6-cylinder turbocharged engine (Holset HDX55V) was calibrated using an experimental BSFC map to predict engine exhaust thermodynamic conditions such as exhaust mass flow rate and exhaust temperature under various operating conditions. These engine exhaust conditions were then utilized to feed the inlet conditions for both the ORC and turbocompounding models, evaluating the available exhaust energy to be recovered by each technology. Firstly the ORC system model was simulated to obtain the power that can be generated from the system. Having this additional power converted to useful work, the BSFC was observed to reduce around 2–5% depending upon engine’s speed and BMEP. The initial model of the engine was then modified by considering a second turbine representing turbocompounding heat recovery system. The BSFC was increased due to the back-pressure from the second turbine, but the energy generated from the turbine was sufficient to reduce the BSFC further. However, by application of turbocompounding no improvement in BSFC was achieved at low engine’s speeds. It is concluded that ORC heat recovery system produces a satisfactory results at low engine speeds with both low and high loads whereas at medium and high engine speeds turbocompounding heat recovery system causes higher BSFC reduction. Full article

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

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14 pages, 1929 KiB

Open AccessArticle

Power System Event Ranking Using a New Linear Parameter-Varying Modeling with a Wide Area Measurement System-Based Approach

by Mohammad Bagher Abolhasani Jabali^1,2 and Mohammad Hosein Kazemi^1,*

¹ Electrical Engineering Department, Shahed University, Tehran 3319118651, Iran

² Iran Grid Management Company (IGMC), Teheran 1996836111, Iran

Energies 2017, 10(8), 1088; https://doi.org/10.3390/en10081088 - 26 Jul 2017

Cited by 2 | Viewed by 3286

Abstract

Detecting critical power system events for Dynamic Security Assessment (DSA) is required for reliability improvement. The approach proposed in this paper investigates the effects of events on dynamic behavior during nonlinear system response while common approaches use steady-state conditions after events. This paper [...] Read more.

Detecting critical power system events for Dynamic Security Assessment (DSA) is required for reliability improvement. The approach proposed in this paper investigates the effects of events on dynamic behavior during nonlinear system response while common approaches use steady-state conditions after events. This paper presents some new and enhanced indices for event ranking based on time-domain simulation and polytopic linear parameter-varying (LPV) modeling of a power system. In the proposed approach, a polytopic LPV representation is generated via linearization about some points of the nonlinear dynamic behavior of power system using wide-area measurement system (WAMS) concepts and then event ranking is done based on the frequency response of the system models on the vertices. Therefore, the nonlinear behaviors of the system in the time of fault occurrence are considered for events ranking. The proposed algorithm is applied to a power system using nonlinear simulation. The comparison of the results especially in different fault conditions shows the advantages of the proposed approach and indices. Full article

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

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12 pages, 2918 KiB

Open AccessArticle

An Improved Time-Frequency Analysis Method for Hydrocarbon Detection Based on EWT and SET

by Hui Chen¹

, Jiaxing Kang¹, Yuanchun Chen¹, Dan Xu¹ and Ying Hu^1,2,*

¹ Geomathematics Key Laboratory of Sichuan Province, Chengdu University of Technology, Chengdu 610059, China

² Postdoctoral Station of Geophysics, Chengdu University of Technology, Chengdu 610059, China

Energies 2017, 10(8), 1090; https://doi.org/10.3390/en10081090 - 26 Jul 2017

Cited by 28 | Viewed by 5464

Abstract

Oil and gas reservoirs can cause increased attenuation of seismic waves, which can be revealed by time-frequency analysis for direct detection of hydrocarbons. In this paper, a new method applying the empirical wavelet transform (EWT) in association with the synchroextracting transform (SET), named [...] Read more.

Oil and gas reservoirs can cause increased attenuation of seismic waves, which can be revealed by time-frequency analysis for direct detection of hydrocarbons. In this paper, a new method applying the empirical wavelet transform (EWT) in association with the synchroextracting transform (SET), named EWT-SET, is proposed as an improved time-frequency analysis method for hydrocarbon detection. The SET is a novel time-frequency analysis method which can be considered as a post-processing procedure of short-time Fourier transform and can improve the energy concentration of the time-frequency representation by retaining only the time-frequency information most related to the signal time-varying features. Given the potential limitations of SET for broadband nonstationary seismic signals, using the EWT-SET method which applies SET to the signal after EWT decomposition, not only effectively extracts time-varying features of seismic signals but also improves the performance of SET in concentrating instantaneous energy. The preliminary model tests demonstrate that EWT-SET can effectively depict the location and extent of attenuation anomalies related to hydrocarbons with changing thicknesses of the gas-bearing layer. Application to field data further confirms the capacity for hydrocarbon detection of the presented method. Thus, the EWT-SET method shows significant application prospects and promotion value for hydrocarbon detection. Full article

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21 pages, 7505 KiB

Open AccessArticle

Maintenance Tools applied to Electric Generators to Improve Energy Efficiency and Power Quality of Thermoelectric Power Plants

by Milton Fonseca Junior^1,*

, Ubiratan Holanda Bezerra², Jandecy Cabral Leite¹ and Jorge Laureano Moya Rodríguez¹

¹ Galileo Institute of Technology and Education of the Amazon, Institute Manaus, 69020-030 Amazonas, Brazil

² Department of Electrical Engineering—CEAMAZON, Federal University of Para, 66075-110 Belem, Para, Brazil

Energies 2017, 10(8), 1091; https://doi.org/10.3390/en10081091 - 26 Jul 2017

Cited by 11 | Viewed by 7608

Abstract

This paper presents a specific method to improve the reliability of the equipment and the quality of power supplied to the electrical systems with the frequency and voltage control of a thermoelectric plant, to guarantee a more stable system. The method has the [...] Read more.

This paper presents a specific method to improve the reliability of the equipment and the quality of power supplied to the electrical systems with the frequency and voltage control of a thermoelectric plant, to guarantee a more stable system. The method has the novelty of combining Total Productive Maintenance (TPM) using only four pillars, with Electrical Predictive Maintenance based in failure analysis and diagnostic. It prevents voltage drops caused by excessive reactive consumption, thus guaranteeing the company a perfect functioning of its equipment and providing a longer life of them. The Maintenance Management Program (MMP) seeks to prevent failures from causing the equipment to be shut down from the electrical system, which means large financial losses, either by reducing billing or by paying fines to the regulatory agency, in addition to prejudice the reliability of the system. Using management tools, but applying only four TPM pillars, it was possible to achieve innovation in power plants with internal combustion engines. This study aims to provide maintenance with a more reliable process, through the implantation of measurement, control and diagnostic devices, thus allowing the management to reduce breakdown of plant equipment. Some results have been achieved after the implementation, such as reduction of annual maintenance cost, reduction of corrective maintenance, increase of MTBF (Mean Time between Failures) and reduction of MTTR (Mean Time to Repair) in all areas. Probabilistic models able to describe real processes in a more realistic way, and facilitate the optimization at maximum reliability or minimum costs are presented. Such results are reflected in more reliable and continual power generation. Full article

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16 pages, 3245 KiB

Open AccessArticle

Nonlinear Synergetic Governor Controllers for Steam Turbine Generators to Enhance Power System Stability

by Xingbao Ju¹, Ping Zhao^2,*, Haishun Sun¹, Wei Yao¹

and Jinyu Wen¹

¹ State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China

² College of Electrical Engineering & New Energy, China Three Gorges University, 8 College Road, Yichang 443002, China

Energies 2017, 10(8), 1092; https://doi.org/10.3390/en10081092 - 26 Jul 2017

Cited by 11 | Viewed by 5094

Abstract

This paper proposes a decentralized nonlinear synergetic governor controller (NSGC) for turbine generators to enhance power system stability by using synergetic control theory and the feedback linearization technique. The precise feedback linearization model of a turbine-generator with a steam valve control is obtained, [...] Read more.

This paper proposes a decentralized nonlinear synergetic governor controller (NSGC) for turbine generators to enhance power system stability by using synergetic control theory and the feedback linearization technique. The precise feedback linearization model of a turbine-generator with a steam valve control is obtained, at first, by using a feedback linearization technique. Then based on this model, a manifold is defined as a linear combination of the deviation of the rotor angle, speed deviation, and speed derivative. The control law of the proposed NSGC is deduced and the stability condition of the whole closed-loop system is subsequently analyzed. According to the requirement of the primary frequency regulation, an additional proportional integral (PI) controller is designed to dynamically track the steady-state value of the rotor angle. Case studies are undertaken based on a single-machine infinite-bus system and the New England system, respectively. Simulation results show that the proposed NSGC can suppress the power oscillations and improve transient stability more effectively in comparison with the conventional proportional-integral-derivative (PID) governor controller. Moreover, the proposed NSGC is robust to the variations of the system operating conditions. Full article

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

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16 pages, 7883 KiB

Open AccessArticle

Hygrothermal Dynamic and Mould Growth Risk Predictions for Concrete Tiles by Using Least Squares Support Vector Machines

by Roberto Zanetti Freire^1,*

, Gerson Henrique dos Santos² and Leandro dos Santos Coelho^1,3

¹ Industrial and Systems Engineering Graduate Program—PPGEPS, Polytechnic School—EP, Pontifical Catholic University of Parana—PUCPR, Rua Imaculada Conceição, 1155, Curitiba 80215-901, Brazil

² Department of Mechanical Engineering, Federal Technological University of Parana—UTFPR, Av. Monteiro Lobato, Km 04, Ponta Grossa 84016-210, Brazil

³ Department of Electrical Engineering, Electrical Engineering Graduate Program—PPGEE, Federal University of Parana—UFPR, Av. Cel. Francisco H. dos Santos, 210, Curitiba 81531-970, Brazil

Energies 2017, 10(8), 1093; https://doi.org/10.3390/en10081093 - 26 Jul 2017

Cited by 21 | Viewed by 3426

Abstract

The hygrothermal analysis of roofs is relevant due to the large areas exposed to a wide range of weather conditions, these directly affecting the energy performance and thermal comfort of buildings. However, after a long life service, the solar absorptivity coatings of roofs [...] Read more.

The hygrothermal analysis of roofs is relevant due to the large areas exposed to a wide range of weather conditions, these directly affecting the energy performance and thermal comfort of buildings. However, after a long life service, the solar absorptivity coatings of roofs can be altered by mould accumulation. Based on two well established mathematical models, one that adopts driving potentials to calculate temperature, moist air pressure and water vapor pressure gradients, and the other to estimate the mould growth risk on surfaces, this research introduces an approach to predict mould growth considering a reduced computational effort and simulation time. By adopting multiple MISO (Multiple-Input, Single-Output) Nonlinear AutoRegressive with eXogenous inputs (NARX) models, a machine learning technique known as Least Squares Support Vector Machines (LS-SVM), a maximum margin model based on structural risk minimization, was used to predict vapor flux, sensible heat flux, latent heat flux, and mould growth risk on roof surfaces. The proposed model was validated in terms of the Multiple Correlation Coefficient (R2R2R2), Mean Square Error (MSE) and Mean Absolute Error (MAE) performance indices considering as input the weather file from Curitiba city—Brazil, showing consistent precision when compared to the results of a validated numerical model. Full article

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15 pages, 5656 KiB

Open AccessArticle

Numerical Investigations of the Combined Effects of Flow Rate and Methanol Concentration on DMFC Performance

by Xuqu Hu¹, Xingyi Wang¹, Juanzhong Chen¹, Qinwen Yang^1,*

, Dapeng Jin¹ and Xiang Qiu²

¹ State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China

² College of Science, Shanghai Institute of Technology, Shanghai 201418, China

Energies 2017, 10(8), 1094; https://doi.org/10.3390/en10081094 - 26 Jul 2017

Cited by 11 | Viewed by 5157

Abstract

A modified 3D numerical model on the energy conversion process in the anode side of a Direct Methanol Fuel Cell (DMFC) system was constructed and validated to published experimental results. Systematic simulations were performed to investigate the underlying mechanisms of the energy conversion [...] Read more.

A modified 3D numerical model on the energy conversion process in the anode side of a Direct Methanol Fuel Cell (DMFC) system was constructed and validated to published experimental results. Systematic simulations were performed to investigate the underlying mechanisms of the energy conversion process, and the combined effects of inlet flow rate and input methanol concentration were summarized systematically. The increase of flow rate was found to be an effective strategy to accelerate the internal flow fields, while the diffusion layer was proposed to be a critical component in the design of high-performance DMFC. The frontier for optimal conditions of DMFC’s output was also determined, which can be helpful to improve the energy conversion performance of DMFC in practical applications. Full article

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

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12 pages, 2445 KiB

Open AccessArticle

Optimizing the District Heating Primary Network from the Perspective of Economic-Specific Pressure Loss

by Haichao Wang^1,2, Lin Duanmu¹, Xiangli Li^1,* and Risto Lahdelma²

¹ Institute of Building Environment and Facility Engineering, School of Civil Engineering, Dalian University of Technology, Dalian 116024, China

² Department of Energy Technology, Aalto University School of Engineering, P.O. Box 14100, FI-00076 Aalto, Finland

Energies 2017, 10(8), 1095; https://doi.org/10.3390/en10081095 - 26 Jul 2017

Cited by 21 | Viewed by 5178

Abstract

A district heating (DH) system is one of the most important components of infrastructures in cold areas. Proper DH network design should balance the initial investment and the heat distribution cost of the DH network. Currently, this design is often based on a [...] Read more.

A district heating (DH) system is one of the most important components of infrastructures in cold areas. Proper DH network design should balance the initial investment and the heat distribution cost of the DH network. Currently, this design is often based on a recommended value for specific pressure loss (R = ∆P/L) in the main lines. This will result in a feasible network design, but probably not be optimal in most cases. The paper develops a novel optimization model to facilitate the design by considering the initial investment in the pipes and the heat distribution costs. The model will generate all possible network scenarios consisting of different series of diameters for each pipe in the flow direction of the network. Then, the annuity on the initial investment, the heat distribution cost, and the total annual cost will be calculated for each network scenario, taking into account the uncertainties of the material prices and the yearly operating time levels. The model is applied to a sample DH network and the results indicate that the model works quite well, clearly identifying the optimal network design and demonstrating that the heat distribution cost is more important than the initial investment in DH network design. Full article

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28 pages, 1115 KiB

Open AccessArticle

Real-Time Distributed Economic Model Predictive Control for Complete Vehicle Energy Management

by Constantijn Romijn^1,*,†

, Tijs Donkers^1,†

, John Kessels^2,† and Siep Weiland^1,†

¹ Department of Electrical Engineering, Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands

² DAF Trucks NV, Vehicle Control Group, 5643 TW Eindhoven, The Netherlands

^† All authors contributed equally to this work.

Energies 2017, 10(8), 1096; https://doi.org/10.3390/en10081096 - 27 Jul 2017

Cited by 10 | Viewed by 5471

Abstract

In this paper, a real-time distributed economic model predictive control approach for complete vehicle energy management (CVEM) is presented using a receding control horizon in combination with a dual decomposition. The dual decomposition allows the CVEM optimization problem to be solved by solving [...] Read more.

In this paper, a real-time distributed economic model predictive control approach for complete vehicle energy management (CVEM) is presented using a receding control horizon in combination with a dual decomposition. The dual decomposition allows the CVEM optimization problem to be solved by solving several smaller optimization problems. The receding horizon control problem is formulated with variable sample intervals, allowing for large prediction horizons with only a limited number of decision variables and constraints in the optimization problem. Furthermore, a novel on/off control concept for the control of the refrigerated semi-trailer, the air supply system and the climate control system is introduced. Simulation results on a low-fidelity vehicle model show that close to optimal fuel reduction performance can be achieved. The fuel reduction for the on/off controlled subsystems strongly depends on the number of switches allowed. By allowing up to 15-times more switches, a fuel reduction of 1.3% can be achieved. The approach is also validated on a high-fidelity vehicle model, for which the road slope is predicted by an e-horizon sensor, leading to a prediction of the propulsion power and engine speed. The prediction algorithm is demonstrated with measured ADASIS information on a public road around Eindhoven, which shows that accurate prediction of the propulsion power and engine speed is feasible when the vehicle follows the most probable path. A fuel reduction of up to 0.63% is achieved for the high-fidelity vehicle model. Full article

(This article belongs to the Special Issue Energy Management Control)

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31 pages, 4636 KiB

Open AccessArticle

Optimizing the Structure of Distribution Smart Grids with Renewable Generation against Abnormal Conditions: A Complex Networks Approach with Evolutionary Algorithms

by Lucas Cuadra^1,*

, Miguel Del Pino¹, José Carlos Nieto-Borge² and Sancho Salcedo-Sanz¹

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

² Department of Physics and Mathematics, University of Alcalá, Alcalá de Henares, 28805 Madrid, Spain

Energies 2017, 10(8), 1097; https://doi.org/10.3390/en10081097 - 26 Jul 2017

Cited by 29 | Viewed by 6095

Abstract

In this work, we describe an approach that allows for optimizing the structure of a smart grid (SG) with renewable energy (RE) generation against abnormal conditions (imbalances between generation and consumption, overloads or failures arising from the inherent SG complexity) by combining the [...] Read more.

In this work, we describe an approach that allows for optimizing the structure of a smart grid (SG) with renewable energy (RE) generation against abnormal conditions (imbalances between generation and consumption, overloads or failures arising from the inherent SG complexity) by combining the complex network (CN) and evolutionary algorithm (EA) concepts. We propose a novel objective function (to be minimized) that combines cost elements, related to the number of electric cables, and several metrics that quantify properties that are beneficial for SGs (energy exchange at the local scale and high robustness and resilience). The optimized SG structure is obtained by applying an EA in which the chromosome that encodes each potential network (or individual) is the upper triangular matrix of its adjacency matrix. This allows for fully tailoring the crossover and mutation operators. We also propose a domain-specific initial population that includes both small-world and random networks, helping the EA converge quickly. The experimental work points out that the proposed method works well and generates the optimum, synthetic, small-world structure that leads to beneficial properties such as improving both the local energy exchange and the robustness. The optimum structure fulfills a balance between moderate cost and robustness against abnormal conditions. Our approach should be considered as an analysis, planning and decision-making tool to gain insight into smart grid structures so that the low level detailed design is carried out by using electrical engineering techniques. Full article

(This article belongs to the Special Issue Modelling Distribution Systems with Renewable Generation under Abnormal Conditions)

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24 pages, 4261 KiB

Open AccessArticle

A Predictive Power Control Strategy for DFIGs Based on a Wind Energy Converter System

by Xiaoliang Yang^1,2

, Guorong Liu^1,3, Anping Li¹ and Le Van Dai^4,5,*

¹ College of Electrical and Information Engineering, Hunan University, Changsha 410082, China

² College of Electrical and Information Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China

³ College of Electrical and Information Engineering, Hunan Institute of Engineering, Xiangtan 411100, China

⁴ Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

⁵ Faculty of Electrical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City 700000, Vietnam

Energies 2017, 10(8), 1098; https://doi.org/10.3390/en10081098 - 26 Jul 2017

Cited by 30 | Viewed by 6638

Abstract

A feasible control strategy is proposed to control a doubly fed induction generator based on the wind energy converter system (DFIG-WECS). The main aim is to enhance the steady state and dynamic performance under the condition of the parameter perturbations and external disturbances [...] Read more.

A feasible control strategy is proposed to control a doubly fed induction generator based on the wind energy converter system (DFIG-WECS). The main aim is to enhance the steady state and dynamic performance under the condition of the parameter perturbations and external disturbances and to satisfy the stator power response of the system. Within the proposed control method, the control scheme for the rotor side converter (RSC) is developed on the model predictive control. Firstly, the self-adaptive reference trajectory is established from the deduced discrete state-space equation of the generator. Then, the rotor voltage is calculated by minimizing the global performance index under the current prediction steps at the sampling instant. Through the control scheme for the grid side converter (GSC) and wind turbine, we have re-applied the conventional control. The effectiveness of the proposed control strategy is verified via time domain simulation of a 150 kW-575 V DFIG-WECS using Matlab/Simulink. The simulation result shows that the control of the DFIG with the proposed control method can enhance the steady and dynamic response capability better than the conventional ones when the system faces errors due to the parameter perturbations, external disturbances and the rotor speed. Full article

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

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24 pages, 6548 KiB

Open AccessArticle

A Large Scale Grid Data Analysis Platform for DSOs

by Serdar Kadam^1,*, Benoît Bletterie¹ and Wolfgang Gawlik²

¹ Center for Energy - Electric Energy Systems, AIT Austrian Institute of Technology, Vienna 1210, Austria

² Institute of Energy Systems and Electrical Drives, TU Wien, Vienna 1040, Austria

Energies 2017, 10(8), 1099; https://doi.org/10.3390/en10081099 - 27 Jul 2017

Cited by 7 | Viewed by 3874

Abstract

The number of fluctuating distributed energy resources (DER) in electricity grids is continuously rising. Due to the lack of operational information on low-voltage (LV) networks, conservative assumptions are necessary to assess the connection of generators to the grid. This paper introduces the hosting [...] Read more.

The number of fluctuating distributed energy resources (DER) in electricity grids is continuously rising. Due to the lack of operational information on low-voltage (LV) networks, conservative assumptions are necessary to assess the connection of generators to the grid. This paper introduces the hosting capability (HC) as a measure to assess the amount of DER that can be integrated in LV-feeders. The HC of a feeder is the minimum amount of DER that can be hosted in a feeder without reinforcement needs for a given DER-scenario and for a given admissible voltage rise. The hosting capability assessment was performed on the entire LV-grid data of two Austrian Distribution System Operators (DSOs) with more than 36,000 LV-feeders. In total, 40 HC-scenarios were calculated with varying admissible voltage rise levels, DER-scenarios and reactive power control strategies. It turned out that only few feeder parameters such as the resistance at the end node and the lowest ampacity value of feeders show a high correlation with the calculated HC. Further, the impact of the DER-scenario on the share of voltage and loading constrained feeders is rather limited. The gathered results are suitable to validate equivalent LV-feeders models to perform integrated power flow studies on the transmission and distribution grids. Besides the results obtained for the network data of the two DSOs, a performant, modular and parallelizable tool has been developed to automatically analyze large LV network sets. Full article

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19 pages, 10204 KiB

Open AccessArticle

Potential Arbitrage Revenue of Energy Storage Systems in PJM

by Mauricio B. C. Salles^1,*

, Junling Huang², Michael J. Aziz³ and William W. Hogan²

¹ Laboratory of Advanced Electric Grids - LGrid, Polytechnic School, University of São Paulo, São Paulo 05508-010, Brazil

² John F. Kennedy School of Government, Harvard University, Cambridge, MA 02138, USA

³ John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA

Energies 2017, 10(8), 1100; https://doi.org/10.3390/en10081100 - 27 Jul 2017

Cited by 48 | Viewed by 9029

Abstract

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), [...] Read more.

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), the largest U.S. regional transmission organization, using hourly locational marginal prices over the seven-year period 2008–2014. Assuming a price-taking ESS with perfect foresight in the real-time market, we optimized the charge-discharge profile to determine the maximum potential revenue for a 1 MW system as a function of energy/power ratio, or rated discharge duration, from 1 to 14 h, including a limited analysis of sensitivity to round-trip efficiency. We determined minimum potential revenue with a similar analysis of the day-ahead market. We presented the distribution over the set of nodes and years of price, price volatility, and maximum potential arbitrage revenue. From these results, we determined the breakeven overnight installed cost of an ESS below which arbitrage would be profitable, its dependence on rated discharge duration, its distribution over grid nodes, and its variation over the years. We showed that dispatch into real-time markets based on day-ahead market settlement prices is a simple, feasible method that raises the lower bound on the achievable arbitrage revenue. Full article

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

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11 pages, 3921 KiB

Open AccessArticle

Study on Electrode Potential of Zinc Nickel Single-Flow Battery during Charge

by Shouguang Yao^1,*, Peng Liao¹, Min Xiao¹, Jie Cheng² and Wenwen Cai²

¹ School of Energy and Power Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China

² Zhangjiagang Smartgrid Fanghua Electrical Energy Storage Research Institute Co., Ltd., Zhangjiagang 215600, China

Energies 2017, 10(8), 1101; https://doi.org/10.3390/en10081101 - 27 Jul 2017

Cited by 19 | Viewed by 7355

Abstract

In this study of zinc nickel single-flow batteries (ZNB), the ion concentration of the convection area and the electrode surface of the battery runner were investigated first. Then, the relationships between the electrode over-potential (or equilibrium potential) and the charge time were studied. [...] Read more.

In this study of zinc nickel single-flow batteries (ZNB), the ion concentration of the convection area and the electrode surface of the battery runner were investigated first. Then, the relationships between the electrode over-potential (or equilibrium potential) and the charge time were studied. This was based on the electrochemical reaction rate equation and the equilibrium potential equation, from which a mathematical model of the stack voltage (as affected by the internal parameters of the battery) was obtained. By comparison with experimental data, it was determined that the relative error of the simulated stack voltage of a 300 Ah battery was restricted to <0.62% while charging under the condition of 100 A constant-current charging. This shows that the mathematical model can accurately describe the dynamic characteristics of the battery stack voltage, and is very accurate for predicting the stack voltage of the battery during charging under 100 A constant-current charging conditions. Full article

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

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22 pages, 2809 KiB

Open AccessArticle

A New Methodology for Assessing the Energy Consumption of Building Stocks

by Ilaria Ballarini^*

and Vincenzo Corrado

Department of Energy, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

Energies 2017, 10(8), 1102; https://doi.org/10.3390/en10081102 - 27 Jul 2017

Cited by 27 | Viewed by 5497

Abstract

The refurbishment of the existing building stocks represents a great potential for energy savings. To make the refurbishment effective, proper modeling of the current energy performance is needed. In most European countries, few and low quality data on the energy performance and on [...] Read more.

The refurbishment of the existing building stocks represents a great potential for energy savings. To make the refurbishment effective, proper modeling of the current energy performance is needed. In most European countries, few and low quality data on the energy performance and on the refurbishment of building stocks are revealed, which increases the risk of not getting representative results. The article presents a new methodology for an effective bottom-up energy modeling, aimed at evaluating the current energy performance of housing stocks. The model is set up according to the IEE-EPISCOPE Project (Energy Performance Indicator Tracking Schemes for the Continuous Optimisation of Refurbishment Processes in European Housing Stocks, 2013–2016), which developed a framework of reliable data and clearly stated model assumptions, as to overcome the lack of data while guaranteeing transparency. The model, applied to an Italian region, is based on statistical data and uses the building typology approach. The energy performance is calculated by means of a quasi-steady state method. A correlation between the estimated and the real energy consumption is obtained. The model allows disaggregating the residential building stock in subsets to identify the main potential for energy savings in specific contexts. Improvements of the current data availability are strongly advisable to keep the model updated. Full article

(This article belongs to the Special Issue 17th CIRIAF National Congress – Sustainable Development, Environment and Human Health Protection)

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16 pages, 3046 KiB

Open AccessArticle

A PMU-Based Method for Smart Transmission Grid Voltage Security Visualization and Monitoring

by Heng-Yi Su^* and Tzu-Yi Liu

Department of Electrical Engineering, Feng Chia University (FCU), No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan

Energies 2017, 10(8), 1103; https://doi.org/10.3390/en10081103 - 27 Jul 2017

Cited by 13 | Viewed by 8081

Abstract

With the rapid growth of usage of phasor measurement units (PMUs) for modern power grids, the application of synchronized phasors (synchrophasors) to real-time voltage security monitoring has become an active research area. This paper presents a novel approach for fast determination of loading [...] Read more.

With the rapid growth of usage of phasor measurement units (PMUs) for modern power grids, the application of synchronized phasors (synchrophasors) to real-time voltage security monitoring has become an active research area. This paper presents a novel approach for fast determination of loading margin using PMU data from a wide-area monitoring system (WAMS) to construct the voltage stability boundary (VSB) of a transmission grid. Specifically, a new approach for online loading margin estimation that considers system load trends is proposed based on the Thevenin equivalent (TE) technique and the Mobius transformation (MT) technique. A VSB is then computed by means of real-time PMU measurements and is presented in a complex load power space. VSB can be utilized as a visualization tool that is able to provide real-time visualization of the current voltage stability situation. The proposed method is fast and adequate for online voltage security assessment. Furthermore, it enables us to significantly increase a system operator’s situational awareness for operational decision making. Simulation studies were carried out using different sized power grid models under various operating conditions. The simulation results are shown to validate the capability of the proposed method. Full article

(This article belongs to the Collection Smart Grid)

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24 pages, 2224 KiB

Open AccessArticle

Assessment of Credible Capacity for Intermittent Distributed Energy Resources in Active Distribution Network

by Chen Sun¹, Dong Liu^1,*

, Yun Wang¹ and Yi You²

¹ Key Laboratory of Control of Power Transmission and Conversion, Ministry of Education, Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

² Electric Power Research Institute of Guangdong Power Grid Corporation, Guangzhou 510080, China

Energies 2017, 10(8), 1104; https://doi.org/10.3390/en10081104 - 27 Jul 2017

Cited by 2 | Viewed by 4373

Abstract

The irregularity and randomness of distributed energy sources’ (DERs) output power characteristic usually brings difficulties for grid analysis. In order to reliably and deterministically evaluate intermittent distributed generation’s active power output, a credible capacity index for active distribution network (ADN) is proposed. According [...] Read more.

The irregularity and randomness of distributed energy sources’ (DERs) output power characteristic usually brings difficulties for grid analysis. In order to reliably and deterministically evaluate intermittent distributed generation’s active power output, a credible capacity index for active distribution network (ADN) is proposed. According to the definition, it is a certain interval that the stochastic active power output of DERs may fall in with larger probability in all kinds of possible dynamic and time varying operation scenarios. Based on the description and analysis on the time varying scenarios, multiple scenarios considered dynamic power flow method for and are proposed. The method to calculate and evaluate credible capacity based on dynamic power flow (DPF) result is illustrated. A study case of an active distribution network with DERs integrated and containing 32 nodes is selected; multiple operation scenarios with various fractal dimension are established and used. Results of calculated credible capacity based on several groups of scenarios have been analyzed, giving the variance analysis of groups of credible capacity values. A deterministic value with the maximum occurrence probability representing credible capacity is given. Based on the same network case, an application of credible capacity to grid extension planning is given, which contributes to expenditure and cost reduction. The effectiveness and significance of the proposed credible capacity and solution method have been demonstrated and verified. Full article

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

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14 pages, 2773 KiB

Open AccessArticle

Effects of Combined Sorbitan Monolaurate Anti-Agglomerants on Viscosity of Water-in-Oil Emulsion and Natural Gas Hydrate Slurry

by Yining Lv¹, Yintang Guan², Shudi Guo², Qinglan Ma^2,*

, Jing Gong^1,*, Guangjin Chen², Changyu Sun², Kai Guo², Lanying Yang², Bohui Shi¹, Wei Qin³ and Yubo Qiao³

¹ National Engineering Laboratory for Pipeline Safety, MOE Key Laboratory of Petroleum Engineering, Beijing Key Laboratory of Urban Oil and Gas Distribution Technology, China University of Petroleum Beijing, 18 Fuxue Road, Changping District, Beijing 102249, China

² State Key Laboratory of Heavy Oil Processing, China University of Petroleum Beijing, Fuxue Road, Changping District, Beijing 102249, China

³ PetroChina Oil & Gas Pipeline Control Center, Beijing 100007, China

Energies 2017, 10(8), 1105; https://doi.org/10.3390/en10081105 - 27 Jul 2017

Cited by 14 | Viewed by 4500

Abstract

Hydrate plugging is the major challenge in the flow assurance of deep-sea pipelines. For water-in-oil emulsions, this risk could be significantly reduced with the addition of anti-agglomerants (AAs). Hydrates often form from water-in-oil emulsions and the measurement of emulsion and slurry viscosity constitutes [...] Read more.

Hydrate plugging is the major challenge in the flow assurance of deep-sea pipelines. For water-in-oil emulsions, this risk could be significantly reduced with the addition of anti-agglomerants (AAs). Hydrates often form from water-in-oil emulsions and the measurement of emulsion and slurry viscosity constitutes the basis for the application of hydrate slurry flow technology. In this work, using a novel high-pressure viscometer, emulsion and slurry viscosity with different AAs for water content ranging from 5% to 30% was obtained. The viscosity-temperature curves of emulsions were determined and correlated. The variation of system viscosity during hydrate formation from water-in-oil emulsions was examined, the sensitivity of stable slurry viscosity to water cut and the effects of temperature on annealed slurry viscosity were investigated. The results indicated that the variation of viscosity during hydrate formation relies on the conversion ratio. It also implied that the sensitivity of slurry viscosity to change in its water cut or temperature was reduced with AA addition. Full article

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20 pages, 1277 KiB

Open AccessArticle

Design, Implementation and Demonstration of Embedded Agents for Energy Management in Non-Residential Buildings

by Ana Constantin^1,*

, Artur Löwen^2,†, Ferdinanda Ponci²

, Dirk Müller¹ and Antonello Monti²

¹ Institute for Energy Efficient Buildings and Indoor Climate, RWTH Aachen University, Aachen 52074,Germany

² Institute for Automation of Complex Power Systems, RWTH Aachen University, Aachen 52074, Germany

^† Current address: Gridhound UG, Aachen 52068, Germany.

Energies 2017, 10(8), 1106; https://doi.org/10.3390/en10081106 - 29 Jul 2017

Cited by 4 | Viewed by 4228

Abstract

With the building sector being responsible for 30% of the total final energy consumption, great interest lies in implementing adequate policies and deploying efficient technologies that would decrease this number. However, building comfort and energy management systems (BCEM) are challenging to manage on [...] Read more.

With the building sector being responsible for 30% of the total final energy consumption, great interest lies in implementing adequate policies and deploying efficient technologies that would decrease this number. However, building comfort and energy management systems (BCEM) are challenging to manage on account of their increasing complexity with regard to the integration of renewable energy sources or the connection of electrical, thermal and gas grids. Multi-agent~systems (MAS) deal well with such complex issues. This paper presents an MAS for non-residential buildings from the design, implementation and demonstration, both simulation based and in a field test. Starting from an ontology and an attached data model for BCEM application, we elaborated use cases for developing and testing the MAS framework. The building and technical equipment are modeled using the modeling language Modelica under Dymola. The agents are programmed in JADE and communicate with Dymola via TCP/IP and with the real devices via BACnet. Operatively, the~agents can take on different control strategies: normal operation with no optimization, optimization of energy costs, where energy is delivered through the room through the devices that have the lowest operating costs, and relaxation of the comfort constraint, where the costs of the productivity loss under sub-optimal comfort conditions is taken into account during optimization. Comfort is expressed as a function of indoor air temperature. Simulation, including a comparison with a benchmark system, and field test results are presented to demonstrate the features of the proposed BCEM. Full article

(This article belongs to the Special Issue ICT for Energy)

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12 pages, 13686 KiB

Open AccessArticle

The Effect of Hydrogen Addition on the Combustion Characteristics of RP-3 Kerosene/Air Premixed Flames

by Wen Zeng^*, Jing Liu, Yu Liu, Baodong Chen and Aiguo Liu

Liaoning Key Lab of Advanced Test Technology for Aerospace Propulsion System, Shenyang Aerospace University, Shenyang 110136, China

Energies 2017, 10(8), 1107; https://doi.org/10.3390/en10081107 - 30 Jul 2017

Cited by 26 | Viewed by 5150

Abstract

Experimental studies have been performed to investigate the effects of hydrogen addition on the combustion characteristics of Chinese No.3 jet fuel (RP-3 kerosene/air premixed flames. Experiments were carried out in a constant volume chamber and the influences of the initial temperatures of 390 [...] Read more.

Experimental studies have been performed to investigate the effects of hydrogen addition on the combustion characteristics of Chinese No.3 jet fuel (RP-3 kerosene/air premixed flames. Experiments were carried out in a constant volume chamber and the influences of the initial temperatures of 390 and 420 K, initial pressures of 0.1 and 0.3 MPa, equivalence ratios of 0.6–1.6 and hydrogen additions of 0.0–0.5 on the laminar burning velocities, and Markstein numbers of Hydrogen (H₂)/RP-3/air mixtures were investigated. The results show that the flame front surfaces of RP-3/air mixtures remain smooth throughout the entire flame propagation process at a temperature of 390 K, pressure of 0.3 MPa, equivalence ratio of 1.3 and without hydrogen addition, but when the hydrogen addition increases from 0.0 to 0.5 under the same conditions, flaws and protuberances occur at the flame surfaces. It was also found that with the increase of the equivalence ratio from 0.9 to 1.5, the laminar burning velocities of the mixtures increase at first and then decrease, and the highest laminar burning velocity was measured at an equivalence ratio of 1.2. Meanwhile, with the increase of hydrogen addition, laminar burning velocities of H₂/RP-3/air mixtures increase. However, the Markstein numbers of H₂/RP-3/air mixtures decrease with the increase of hydrogen addition, which means that the flames of H₂/RP-3/air mixtures become unstable with the increase of hydrogen addition. Full article

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

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18 pages, 2170 KiB

Open AccessArticle

Optimization of Active Current for Large-Scale Wind Turbines Integrated into Weak Grids for Power System Transient Stability Improvement

by Dongliang Zhang and Xiaoming Yuan^*

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

Energies 2017, 10(8), 1108; https://doi.org/10.3390/en10081108 - 31 Jul 2017

Cited by 3 | Viewed by 4205

Abstract

Power system transient stability is a challenge when integrating large-scale wind turbines into weak grids. This paper addresses the issue of transient stability in such situations by optimizing a wind turbine’s active current behavior. A wind turbine’s active current reference controller and its [...] Read more.

Power system transient stability is a challenge when integrating large-scale wind turbines into weak grids. This paper addresses the issue of transient stability in such situations by optimizing a wind turbine’s active current behavior. A wind turbine’s active current reference controller and its setting optimization method are proposed based on analyses of two associated problems: the mechanism for improving transient stability of a single (synchronous) machine infinite bus (SMIB) system, as well as the various physical factor dependencies dictating how active and reactive wind turbine currents affect the swing dynamics of synchronous machines. Analysis of the first problem guided the design of the controller’s main structure. Analysis of the second problem guided selection of the control object within a wind turbine’s active and reactive currents, as well as helped recognition of the influential physical factors that must be considered in the parameter setting process. The efficiency of the controller and the validity of the analyses were verified by case studies using Kundur’s two-area system. Full article

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

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14 pages, 12673 KiB

Open AccessArticle

Evaporation and Ignition Characteristics of Water Emulsified Diesel under Conventional and Low Temperature Combustion Conditions

by Zhaowen Wang¹

, Shang Wu¹, Yuhan Huang²

, Yulin Chen³, Shuguo Shi¹, Xiaobei Cheng^1,* and Ronghua Huang^1,*

¹ State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

² School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia

³ Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720, USA

Energies 2017, 10(8), 1109; https://doi.org/10.3390/en10081109 - 31 Jul 2017

Cited by 13 | Viewed by 5375

Abstract

The combination of emulsified diesel and low temperature combustion (LTC) technology has great potential in reducing engine emissions. A visualization study on the spray and combustion characteristics of water emulsified diesel was conducted experimentally in a constant volume chamber under conventional and LTC [...] Read more.

The combination of emulsified diesel and low temperature combustion (LTC) technology has great potential in reducing engine emissions. A visualization study on the spray and combustion characteristics of water emulsified diesel was conducted experimentally in a constant volume chamber under conventional and LTC conditions. The effects of ambient temperature on the evaporation, ignition and combustion characteristics of water emulsified diesel were studied under cold, evaporating and combustion conditions. Experimental results showed that the ambient temperature had little effect on the spray structures, in terms of the liquid core length, the spray shape and the spray area. However, higher ambient temperature slightly reduced the Sauter Mean Diameter (SMD) of the spray droplets. The auto-ignition delay time increased significantly with the decrease of the ambient temperature. The ignition process always occurred at the entrainment region near the front periphery of the liquid core. This entrainment region was evolved from the early injected fuel droplets which were heated and mixed by the continuous entrainment until the local temperature and equivalence ratio reached the ignition condition. The maximum value of integrated natural flame luminosity (INFL) reduced by 60% when the ambient temperature dropped from 1000 to 800 K, indicating a significant decrease of the soot emissions could be achieved by LTC combustion mode than the conventional diesel engines. Full article

(This article belongs to the Special Issue Internal Combustion Engines 2017)

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14 pages, 4602 KiB

Open AccessArticle

Characterization of Particle and Gaseous Emissions from Marine Diesel Engines with Different Fuels and Impact of After-Treatment Technology

by Jinxi Zhou, Song Zhou and Yuanqing Zhu^*

College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China

Energies 2017, 10(8), 1110; https://doi.org/10.3390/en10081110 - 31 Jul 2017

Cited by 36 | Viewed by 6059

Abstract

The International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC) and some countries have gradually strengthened the laws regulating ship exhaust emissions. The aim of this paper is to estimate the impact of an after-treatment technology exhaust gas cleaning (EGC) system on marine [...] Read more.

The International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC) and some countries have gradually strengthened the laws regulating ship exhaust emissions. The aim of this paper is to estimate the impact of an after-treatment technology exhaust gas cleaning (EGC) system on marine diesel engine emissions and the cost advantage compared to using low-sulfur fuel oil. The emission characteristics of SO₂ and particulate matter (PM) produced from high sulfur oil and low sulfur oil in a low-speed two-stroke marine diesel engine were also presented. The removal efficiency of SO₂ has been tested and the PM removal efficiency was also predicted in this study. When using high sulfur oil, the emission factor of SO₂ and PM were from 8.73 g/kWh to 11.6 g/kWh and 2.0 g/kWh to 2.7 g/kWh, respectively. These values are significantly higher than the emission values from using low sulfur oil. The fuel sulfur content (FSC) was the key factor affecting the emission factors of SO₂ and PM. The fuel change could reduce the mass emission factor of PM, which is above 90% for the total particle emission with the two fuels. When using the EGC system, the desulfurization efficiencies were above 99%. The pH values at a 25, 39, 53, and 67% load were also stabilized to be around 7.5, 7.6, 7.7, and 8, respectively. The EGC system can also capture part of the primary PM and secondary PM formed from SO₂. The EGC system was more effective for PM of the size larger than 1 μm. Thus, according to this study, the usage of low sulfur oil and EGC will also substantially decrease the emission of currently unregulated hazardous chemical species in the exhaust gas of ships in addition to satisfying future emissions regulations of ship. Furthermore, the EGC system also had a significant cost advantage compared to using low-sulfur fuel oil. Full article

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19 pages, 3931 KiB

Open AccessArticle

Optimal Dynamic Analysis of Electrical/Electronic Components in Wind Turbines

by Fausto Pedro García Márquez^1,*

, Alberto Pliego Marugán¹, Jesús María Pinar Pérez², Stuart Hillmansen³ and Mayorkinos Papaelias⁴

¹ Ingenium Research Group, Universidad Castilla-La Mancha, 13071 Ciudad Real, Spain

² CUNEF-Ingenium, University College of Financial Studies, 28040 Madrid, Spain

³ School of Electronic, Electrical & Computer Engineering, University of Birmingham, Birmingham B15 2TT, UK

⁴ School of Metallurgy and Materials, University of Birmingham, Birmingham B15 2TT, UK

Energies 2017, 10(8), 1111; https://doi.org/10.3390/en10081111 - 31 Jul 2017

Cited by 66 | Viewed by 6615

Abstract

Electrical and electronic components are very important subcomponents in modern industrial wind turbines. Complex multimegawatt wind turbines are continuously being installed both onshore and offshore, continuously increasing the demand for sophisticated electronic and electrical components. In this work, most critical electrical and electronic [...] Read more.

Electrical and electronic components are very important subcomponents in modern industrial wind turbines. Complex multimegawatt wind turbines are continuously being installed both onshore and offshore, continuously increasing the demand for sophisticated electronic and electrical components. In this work, most critical electrical and electronic components in industrial wind turbines have been identified and the applicability of appropriate condition monitoring processes simulated. A fault tree dynamic analysis has been carried out by binary decision diagrams to obtain the system failure probability over time and using different time increments to evaluate the system. This analysis allows critical electrical and electronic components of the converters to be identified in different conditions. The results can be used to develop a scheduled maintenance that improves the decision making and reduces the maintenance costs. Full article

(This article belongs to the Collection Wind Turbines)

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20 pages, 9070 KiB

Open AccessArticle

Study of a High-Pressure External Gear Pump with a Computational Fluid Dynamic Modeling Approach

by Emma Frosina^1,*

, Adolfo Senatore¹

and Manuel Rigosi²

¹ Department of Industrial Engineering, University of Naples Federico II, Via Claudio, 21-80125 Naples, Italy

² Casappa S.p.A., Via Balestrieri 1, Lemignano di Collecchio, 43044 Parma, Italy

Energies 2017, 10(8), 1113; https://doi.org/10.3390/en10081113 - 31 Jul 2017

Cited by 81 | Viewed by 11335

Abstract

A study on the internal fluid dynamic of a high-pressure external gear pump is described in this paper. The pump has been analyzed with both numerical and experimental techniques. Starting from a geometry of the pump, a three-dimensional computational fluid dynamics (CFD) model [...] Read more.

A study on the internal fluid dynamic of a high-pressure external gear pump is described in this paper. The pump has been analyzed with both numerical and experimental techniques. Starting from a geometry of the pump, a three-dimensional computational fluid dynamics (CFD) model has been built up using the commercial code PumpLinx^®. All leakages have been taken into account in order to estimate the volumetric efficiency of the pump. Then the pump has been tested on a test bench of Casappa S.p.A. Model results like the volumetric efficiency, absorbed torque, and outlet pressure ripple have been compared with the experimental data. The model has demonstrated the ability to predict with good accuracy the performance of the real pump. The CFD model has been also used to evaluate the effect on the pump performance of clearances in the meshing area. With the validated model the pressure inside the chambers of both driving and driven gears have been studied underlining cavitation in meshing fluid volume of the pump. For this reason, the model has been implemented in order to predict the cavitation phenomena. The analysis has allowed the detection of cavitating areas, especially at high rotation speeds and delivery pressure. Isosurfaces of the fluid volume have been colored as a function of the total gas fraction to underline where the cavitation occurs. Full article

(This article belongs to the Special Issue Engineering Fluid Dynamics)

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16 pages, 1598 KiB

Open AccessArticle

The Optimal Generation Cost-Based Tariff Rates for Onshore Wind Energy in Malaysia

by Aliashim Albani^1,2

, Mohd Zamri Ibrahim^1,2,5,*

, Che Mohd Imran Che Taib^1,3 and Abd Aziz Azlina^1,4

¹ Eastern Corridor Renewable Energy (ECRE) Research Group, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu 21030, Malaysia

² School of Ocean Engineering, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu 21030, Malaysia

³ School of Informatics and Applied Mathematics, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu 21030, Malaysia

⁴ School of Social and Economic Development, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu 21030, Malaysia

⁵ TATI University College, Teluk Kalong, Kemaman, Terengganu 24100, Malaysia

Energies 2017, 10(8), 1114; https://doi.org/10.3390/en10081114 - 31 Jul 2017

Cited by 22 | Viewed by 4837

Abstract

The government of Malaysia has recently decided to explore the feasibility of wind energy to generate electricity in the country. Their ambition is to achieve a measureable target in the percentage contribution of electricity generated by renewable energy technology in the national electricity [...] Read more.

The government of Malaysia has recently decided to explore the feasibility of wind energy to generate electricity in the country. Their ambition is to achieve a measureable target in the percentage contribution of electricity generated by renewable energy technology in the national electricity generation mix. As part of this initiative, a study of wind energy policy has been conducted by identifying the optimal feed-in tariff (FiT) rates to support the development of wind energy in the country. The aim of this paper is to calculate the optimal level of tariff that is suitable with local wind conditions. A closed-form equation for optimal feed-in tariff rate of wind energy with consideration of the availability of capital allowance has been developed. The focus is on small- and utility-scale wind turbine installations. As a result, by considering the availability of capital allowance, the optimal FiT rates for small-scale wind turbines in Malaysia are between 0.9245–1.1313 RM/kWh, while utility-scale rates are between 0.7396 and 0.9050 RM/kWh. The level of FiT is changed with the changing value of economic parameters. Kudat, in northern Borneo, has been identified as a prime site for wind energy development in the country; however, more work needs to be conducted, including the development of a regional wind map and measurement of wind data at more new potential sites. Full article

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

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15 pages, 2719 KiB

Open AccessArticle

A Current Frequency Component-Based Fault-Location Method for Voltage-Source Converter-Based High-Voltage Direct Current (VSC-HVDC) Cables Using the S Transform

by Pu Zhao

, Qing Chen^*

, Kongming Sun and Chuanxin Xi

Key Laboratory of Power System Intelligent Dispatch and Control, Shandong University, Ministry of Education, Jinan 17923, China

Energies 2017, 10(8), 1115; https://doi.org/10.3390/en10081115 - 31 Jul 2017

Cited by 11 | Viewed by 3561

Abstract

This paper proposes a fault-location method for voltage-source converter (VSC)-based high-voltage direct current (VSC-HVDC) systems. This method relies on the current frequency components generated by faults in the cable, and requires the arrival time of the frequency components at two terminals. The S [...] Read more.

This paper proposes a fault-location method for voltage-source converter (VSC)-based high-voltage direct current (VSC-HVDC) systems. This method relies on the current frequency components generated by faults in the cable, and requires the arrival time of the frequency components at two terminals. The S transform is a time–frequency analysis tool that is superior to the wavelet transform in some respects. Therefore, the S transform was employed to determine the arrival time in this paper. To obtain a reliable criterion, a novel phase-mode transform method for bipolar cables was developed, and the propagation characteristics of the current frequency components through out the cable were analyzed. A two-terminal VSC-HVDC system was modeled in power system computer aided design/electromagnetic transients including DC (PSCAD/EMTDC). Various faults under different conditions were simulated on the basis of this model, and the simulation results verified a high accuracy, robustness against fault-resistance, and noise immunity of the proposed method. Full article

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

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17 pages, 4429 KiB

Open AccessArticle

A DC Microgrid Coordinated Control Strategy Based on Integrator Current-Sharing

by Liyuan Gao^1,*, Yao Liu²

, Huisong Ren¹ and Josep M. Guerrero³

¹ Department of Electrical Engineering, Shandong University, Jinan 250061, China

² Zhuhai Power Supply Bureau of Guangdong Power Grid Corporation, Zhuhai 519000, China

³ Department of Energy Technology, Aalborg University, DK-9220 Aalborg East, Denmark

Energies 2017, 10(8), 1116; https://doi.org/10.3390/en10081116 - 1 Aug 2017

Cited by 40 | Viewed by 7726

Abstract

The DC microgrid has become a new trend for microgrid study with the advantages of high reliability, simple control and low losses. With regard to the drawbacks of the traditional droop control strategies, an improved DC droop control strategy based on integrator current-sharing [...] Read more.

The DC microgrid has become a new trend for microgrid study with the advantages of high reliability, simple control and low losses. With regard to the drawbacks of the traditional droop control strategies, an improved DC droop control strategy based on integrator current-sharing is introduced. In the strategy, the principle of eliminating deviation through an integrator is used, constructing the current-sharing term in order to make the power-sharing between different distributed generation (DG) units uniform and reasonable, which can reduce the circulating current between DG units. Furthermore, at the system coordinated control level, a hierarchical/droop control strategy based on the DC bus voltage is proposed. In the strategy, the operation modes of the AC main network and micro-sources are determined through detecting the DC voltage variation, which can ensure the power balance of the DC microgrid under different operating conditions. Meanwhile, communication is not needed between different DG units, while each DG unit needs to sample the DC bus voltage, which retains the plug-and-play feature of the DC microgrid. The proposed control strategy is validated by simulation on a DC microgrid with permanent magnet synchronous generator-based wind turbines, solar arrays and energy storage batteries, which can be applied to small commercial or residential buildings. Full article

(This article belongs to the Collection Wind Turbines)

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24 pages, 8430 KiB

Open AccessFeature PaperArticle

Energy Refurbishment of an Office Building with Hybrid Photovoltaic System and Demand-Side Management

by Giovani Almeida Dávi^1,*

, José López de Asiain², Juan Solano¹, Estefanía Caamaño-Martín¹ and César Bedoya²

¹ Instituto de Energía Solar, Universidad Politécnica de Madrid, Av. Complutense 30, 28040 Madrid, Spain

² ETS Arquitectura, Universidad Politécnica de Madrid, Av. Juan de Herrera 4, 28040 Madrid, Spain

Energies 2017, 10(8), 1117; https://doi.org/10.3390/en10081117 - 1 Aug 2017

Cited by 10 | Viewed by 4750

Abstract

On-site photovoltaic (PV) and battery systems intend to improve buildings energy performance, however battery costs and monetary incentives are a major drawback for the introduction of these technologies into the electricity grids. This paper proposes an energy refurbishment of an office building based [...] Read more.

On-site photovoltaic (PV) and battery systems intend to improve buildings energy performance, however battery costs and monetary incentives are a major drawback for the introduction of these technologies into the electricity grids. This paper proposes an energy refurbishment of an office building based on multi-objective simulations. An innovative demand-side management approach is analyzed through the PV and battery control with the purpose of reducing grid power peaks and grid imported energy, as well as improving the project economy. Optimization results of load matching and grid interaction parameters, complemented with an economic analysis, are investigated in different scenarios. By means of battery use, the equivalent use of the grid connection is reduced by 12%, enhancing the grid interaction potential, and 10% of load matching rates can be increased. Project improvements indicate the grid connection capacity can be reduced by 13% and significant savings of up to 48% are achieved on yearly bills. The economy demonstrates the grid parity is only achieved for battery costs below 100 €/kWh and the payback period is large: 28 years. In the case with only PV system, the grid parity achieves better outcomes and the payback time is reduced by a half, making this a more attractive option. Full article

(This article belongs to the Special Issue Energy Conservation in Infrastructures 2016)

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17 pages, 4979 KiB

Open AccessArticle

Investigation on a Power Coupling Steering System for Dual-Motor Drive Tracked Vehicles Based on Speed Control

by Li Zhai^1,2,*

, Hong Huang^1,2 and Steven Kavuma^1,2

¹ National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology, Beijing 100081, China

² Co-Innovation Center of Electric Vehicles in Beijing, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(8), 1118; https://doi.org/10.3390/en10081118 - 1 Aug 2017

Cited by 14 | Viewed by 6280

Abstract

Double-motor drive tracked vehicles (2MDTV) are widely used in the tracked vehicle industry due to the development of electric vehicle drive systems. The aim of this paper is to solve the problem of insufficient propulsion motor torque in low-speed, small-radius steering and insufficient [...] Read more.

Double-motor drive tracked vehicles (2MDTV) are widely used in the tracked vehicle industry due to the development of electric vehicle drive systems. The aim of this paper is to solve the problem of insufficient propulsion motor torque in low-speed, small-radius steering and insufficient power in high-speed large-radius steering. In order to do this a new type of steering system with a coupling device is designed and a closed-loop control strategy based on speed is adopted to improve the lateral stability of the vehicle. The work done entails modeling and simulating the 2MDTV and the proposed control strategy in RecurDyn and Matlab/Simulink. The simulation results show that the 2MDTV with the coupling device outputs more torque and power in both steering cases compared to the 2MDTV without the coupling device, and the steering stability of the vehicle is improved by using the strategy based on speed. Full article

(This article belongs to the Special Issue Methods to Improve Energy Use in Road Vehicles)

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17 pages, 2826 KiB

Open AccessArticle

Using SF₆ Decomposed Component Analysis for the Diagnosis of Partial Discharge Severity Initiated by Free Metal Particle Defect

by Ju Tang¹, Xu Yang¹, Dong Yang¹, Qiang Yao², Yulong Miao², Chaohai Zhang³ and Fuping Zeng^1,*

¹ School of Electrical Engineering, Wuhan University, Wuhan 430072, China

² Chongqing Electric Power Research Institute, Chongqing Power Company, Chongqing 401123, China

³ State Grid Electric Power Research Institute, Wuhan NARI Co., Ltd., Wuhan 430072, China

Energies 2017, 10(8), 1119; https://doi.org/10.3390/en10081119 - 1 Aug 2017

Cited by 21 | Viewed by 4372

Abstract

The decomposition characteristics of a SF₆ gas-insulated medium were used to diagnose the partial discharge (PD) severity in DC gas-insulated equipment (DC-GIE). First, the PD characteristics of the whole process were studied from the initial PD to the breakdown initiated by a [...] Read more.

The decomposition characteristics of a SF₆ gas-insulated medium were used to diagnose the partial discharge (PD) severity in DC gas-insulated equipment (DC-GIE). First, the PD characteristics of the whole process were studied from the initial PD to the breakdown initiated by a free metal particle defect. The average discharge magnitude in a second was used to characterize the PD severity and the PD was divided into three levels: mild PD, medium PD, and dangerous PD. Second, two kinds of voltage in each of the above PD levels were selected for the decomposition experiments of SF₆. Results show that the negative DC-PD in these six experiments decomposes the SF₆ gas and generates five stable decomposed components, namely, CF₄, CO₂, SO₂F₂, SOF₂, and SO₂. The concentrations and concentration ratios of the SF₆ decomposed components can be associated with the PD severity. A minimum-redundancy-maximum-relevance (mRMR)-based feature selection algorithm was used to sort the concentrations and concentration ratios of the SF₆ decomposed components. Back propagation neural network (BPNN) and support vector machine (SVM) algorithms were used to diagnose the PD severity. The use of C(CO₂)/CT₁, C(CF₄)/C(SO₂), C(CO₂)/C(SOF₂), and C(CF₄)/C(CO₂) shows good performance in diagnosing PD severity. This finding serves as a foundation in using the SF₆ decomposed component analysis (DCA) method to diagnose the insulation faults in DC-GIE and assess its insulation status. Full article

(This article belongs to the Special Issue Selected Papers from 2016 IEEE International Conference on High Voltage Engineering (ICHVE 2016))

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24 pages, 4634 KiB

Open AccessArticle

Proposal of Physical-Statistical Model of Thermal Aging Respecting Threshold Value

by Jakub Souček¹, Pavel Trnka^2,*

and Jaroslav Hornak²

¹ ALFMEIER CZ s.r.o., 301 00 Pilsen, Czech Republic

² Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia, 306 14 Pilsen, Czech Republic

Energies 2017, 10(8), 1120; https://doi.org/10.3390/en10081120 - 2 Aug 2017

Cited by 8 | Viewed by 4809

Abstract

The aging of electrical insulation material or a system is a main issue for designers of high-voltage (HV) machines. Precise determination of the life cycle of electrical insulation is one way of improving the efficiency of electrical machines involved in the production and [...] Read more.

The aging of electrical insulation material or a system is a main issue for designers of high-voltage (HV) machines. Precise determination of the life cycle of electrical insulation is one way of improving the efficiency of electrical machines involved in the production and transmission of electrical energy. Much effort has been devoted to preparing statistical or physical methods of Electrical Insulating System (EIS) life time estimation in the real operation of electrical machinery. The main aim of this paper is to introduce a new physical-statistical model of thermal aging respecting the threshold value. This model is based on thermal aging model and the main difference between this model and previously published models is taking into account the threshold value of degradation factor. The complete design of this model is presented in this paper, including functions defining the threshold value of the effect of the degradation factor depending on the temperature. Proposed model was verified by accelerated thermal aging test at selected temperatures (160, 170, 180 °C) and time intervals (0, 120, 240 h) on a commonly used transformer board. The breakdown voltage was set as an indicating parameter of the level of thermal aging and was measured according to standard IEC 60243-1. Collected data from these measurements were used for threshold value determination (431.23 K) and verification of proposed physical-statistical model of thermal aging respecting the threshold value. Full article

(This article belongs to the Special Issue Selected Papers from 2016 IEEE International Conference on High Voltage Engineering (ICHVE 2016))

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15 pages, 3253 KiB

Open AccessArticle

Analysis of Low Temperature Preheating Effect Based on Battery Temperature-Rise Model

by Xiaogang Wu^1,2,*, Zhe Chen¹ and Zhiyang Wang¹

¹ College of Electrical and Electronics Engineering, Harbin University of Science and Technology, Harbin 150000, China

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

Energies 2017, 10(8), 1121; https://doi.org/10.3390/en10081121 - 1 Aug 2017

Cited by 46 | Viewed by 7057

Abstract

It is difficult to predict the heating time and power consumption associated with the self-heating process of lithium-ion batteries at low temperatures. A temperature-rise model considering the dynamic changes in battery temperature and state of charge is thus proposed. When this model is [...] Read more.

It is difficult to predict the heating time and power consumption associated with the self-heating process of lithium-ion batteries at low temperatures. A temperature-rise model considering the dynamic changes in battery temperature and state of charge is thus proposed. When this model is combined with the ampere-hour integral method, the quantitative relationship among the discharge rate, heating time, and power consumption, during the constant-current discharge process in an internally self-heating battery, is realized. Results show that the temperature-rise model can accurately reflect actual changes in battery temperature. The results indicate that the discharge rate and the heating time present an exponential decreasing trend that is similar to the discharge rate and the power consumption. When a 2 C discharge rate is selected, the battery temperature can rise from −10 °C to 5 °C in 280 s. In this scenario, power consumption of the heating process does not exceed 15% of the rated capacity. As the discharge rate gradually reduced, the heating time and power consumption of the heating process increase slowly. When the discharge rate is 1 C, the heating time is more than 1080 s and the power consumption approaches 30% of the rated capacity. The effect of discharge rate on the heating time and power consumption during the heating process is significantly enhanced when it is less than 1 C. Full article

(This article belongs to the Special Issue Advanced Energy Storage Technologies and Their Applications (AESA))

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15 pages, 3896 KiB

Open AccessArticle

Electret Length Optimization of Output Power for Double-End Fixed Beam Out-of-Plane Electret-Based Vibration Energy Harvesters

by Chunhui Gao, Shiqiao Gao, Haipeng Liu^*, Lei Jin and Junhu Lu

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(8), 1122; https://doi.org/10.3390/en10081122 - 1 Aug 2017

Cited by 15 | Viewed by 3879

Abstract

Thanks to miniaturization, it is now possible to imagine self-powered systems that can harvest energy from the environment to produce electrical energy. Out-of-plane electret-based vibration energy harvesters (E-EVHs) are an effective and inexpensive energy harvester type that has attracted much attention. Increasing the [...] Read more.

Thanks to miniaturization, it is now possible to imagine self-powered systems that can harvest energy from the environment to produce electrical energy. Out-of-plane electret-based vibration energy harvesters (E-EVHs) are an effective and inexpensive energy harvester type that has attracted much attention. Increasing the capacitance of variable capacitors is an effective way to improve the output power of E-EVHs. In this paper, firstly an accurate capacitance theoretical model of a double-ended fixed beam out-of-plane E-EVHs which has 97% reliability compared with FEM (COMSOL Multiphysics) results is presented. A comparison of capacitance between the double-ended fixed beam structure and a cantilever structure of the same size indicates that the double-ended fixed beam structure has greater capacitance and capacitance variation. We apply this theoretical capacitance model to the mechanical-electrical coupling model of double-ended fixed beam out-of-plane E-EVHs and study harvesters’ output performances for different electret lengths by numerical and experimental method, respectively. There exists an optimal electret length to harvest maximum power in our simulation results. Enhanced electrostatic forces with increasing the electret length emphasizes the soft spring effect, which widens the half power bandwidth and lowers the resonance frequency. Increasing the length of the electret can reduce the resistance of the optimum load. The experimental results show trend consistent with the numerical predictions. The maximum output power can reach 404 µW (134.66 µW/cm²/g) at the electret length of 40 mm when the external acceleration and the frequency were 5 m/s² and 74 Hz, respectively. The maximum bandwidth reaches 2.5 Hz at the electret length of 60 mm. Therefore, the electret length should be placed between 40 mm and 60 mm, while ensuring a higher output power and also get a larger bandwidth in practical applications. Full article

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

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17 pages, 2465 KiB

Open AccessArticle

Techno-Economic Assessment of Heat Transfer Fluid Buffering for Thermal Energy Storage in the Solar Field of Parabolic Trough Solar Thermal Power Plants

by Jorge M. Llamas^1,*

, David Bullejos¹

and Manuel Ruiz de Adana²

¹ Department of Electrical Engineering, Escuela Politécnica Superior de Córdoba (EPSC), Universidad de Córdoba, Ctra. Madrid-Cádiz Km. 396, 14071 Cordoba, Spain

² Department of Thermal Engines, Escuela Politécnica Superior de Córdoba (EPSC), Universidad de Córdoba, Ctra. Madrid-Cádiz Km. 396, 14071 Cordoba, Spain

Energies 2017, 10(8), 1123; https://doi.org/10.3390/en10081123 - 1 Aug 2017

Cited by 11 | Viewed by 6191

Abstract

Currently, operating parabolic trough (PT) solar thermal power plants, either solar-only or with thermal storage block, use the solar field as a heat transfer fluid (HTF) thermal storage system to provide extra thermal capacity when it is needed. This is done by circulating [...] Read more.

Currently, operating parabolic trough (PT) solar thermal power plants, either solar-only or with thermal storage block, use the solar field as a heat transfer fluid (HTF) thermal storage system to provide extra thermal capacity when it is needed. This is done by circulating heat transfer fluid into the solar field piping in order to create a heat fluid buffer. In the same way, by oversizing the solar field, it can work as an alternative thermal energy storage (TES) system to the traditionally applied methods. This paper presents a solar field TES model for a standard solar field from a 50-MW_e solar power plant. An oversized solar model is analyzed to increase the capacity storage system (HTF buffering). A mathematical model has been developed and different simulations have been carried out over a cycle of one year with six different solar multiples considered to represent the different oversized solar field configurations. Annual electricity generation and levelized cost of energy (LCOE) are calculated to find the solar multiple (SM) which makes the highest solar field thermal storage capacity possible within the minimum LCOE. Full article

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

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7 pages, 2444 KiB

Open AccessCommunication

The Performance of a Direct Borohydride/Peroxide Fuel Cell Using Graphite Felts as Electrodes

by Heng-Yi Lee¹, Yi-Hsuan Hsu¹, Po-Hong Tsai¹, Jiunn-Yih Lee² and Yong-Song Chen^1,*

¹ Advanced Institute of Manufacturing with High-tech Innovations and Department of Mechanical Engineering, National Chung Cheng University, 168, University Rd., Minhsiung Township, Chiayi 62102, Taiwan

² National Chung-Shan Institute of Science & Technology, Materials & Electro-Optics Research Division, P.O. Box No. 90008-8-2, Longtan, Taoyuan 32599, Taiwan

Energies 2017, 10(8), 1124; https://doi.org/10.3390/en10081124 - 1 Aug 2017

Cited by 1 | Viewed by 4303

Abstract

A direct borohydride/peroxide fuel cell (DBPFC) generates electrical power by recirculating liquid anolyte and catholyte between the stack and reservoirs, which is similar to the operation of flow batteries. To enhance the accessibility of the catalyst layer to the liquid anolyte/catholyte, graphite felts [...] Read more.

A direct borohydride/peroxide fuel cell (DBPFC) generates electrical power by recirculating liquid anolyte and catholyte between the stack and reservoirs, which is similar to the operation of flow batteries. To enhance the accessibility of the catalyst layer to the liquid anolyte/catholyte, graphite felts are employed as the porous diffusion layer of a single-cell DBPFC instead of carbon paper/cloth. The effects of the type of anode alkaline solution and operating conditions, including flow rate and temperature of the anolyte/catholyte, on DBPFC performance are investigated and discussed. The durability of the DBPFC is also evaluated by galvanostatic discharge at 0.1 A∙cm⁻² for over 50 h. The results of this preliminary study show that a DBPFC with porous graphite electrodes can provide a maximum power density of 0.24 W∙cm⁻² at 0.8 V. The performance of the DBPFC drops slightly after 50 h of operation; however, the discharge capacity shows no significant decrease. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells 2017)

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18 pages, 2367 KiB

Open AccessArticle

The Coupled Effect of Fines Mobilization and Salt Precipitation on CO₂ Injectivity

by Yen Adams Sokama-Neuyam^*, Sindre Langås Forsetløkken, Jhon-eirik Lien and Jann Rune Ursin

Department of Petroleum Engineering, University of Stavanger, 4036 Stavanger, Norway

Energies 2017, 10(8), 1125; https://doi.org/10.3390/en10081125 - 1 Aug 2017

Cited by 13 | Viewed by 5695

Abstract

In terms of storage capacity and containment efficiency, deep saline aquifers are among the best candidates for CO₂ storage. However, salt precipitation in the wellbore vicinity and fines mobilization ensued from in situ mineral dissolution could impair CO₂ injectivity and reduce [...] Read more.

In terms of storage capacity and containment efficiency, deep saline aquifers are among the best candidates for CO₂ storage. However, salt precipitation in the wellbore vicinity and fines mobilization ensued from in situ mineral dissolution could impair CO₂ injectivity and reduce the quality and capacity of deep saline reservoirs for CO₂ storage. The mechanisms of salt precipitation and its impact on CO₂ injectivity have been studied, but the effects of fines mobilization have not been properly investigated. We conducted core-flood experiments and theoretical studies to investigate the impact of fines mobilization on CO₂ injectivity, the relative contribution of fines mobilization and salt precipitation toinjectivity impairment, and the coupled effect of salt precipitation and fines mobilization. We found that, mineral dissolution and transport effects could induce up to about 26% injectivity impairment. The findings also suggest that about 0.3 wt % particle concentration in the pore fluid could induce over twofold injectivity impairment compared to about 10 wt % of total dissolved salt in the formation water. Salt precipitation was also found to compound injectivity impairment induced by fines mobilization. The present study provides important insight, and could serve as a foundation to inspire further experimental and theoretical investigation into the effects of mineral dissolution and fines mobilization in the context of CO₂ injectivity. Full article

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16 pages, 2471 KiB

Open AccessArticle

An Energy Efficient Lighting Design Strategy to Enhance Visual Comfort in Offices with Windows

by Mehdi Amirkhani^1,*

, Veronica Garcia-Hansen¹

, Gillian Isoardi²

and Alicia Allan¹

¹ School of Design, Creative Industries Faculty, Queensland University of Technology (QUT), Brisbane 4001, Australia

² School of Chemistry, Physics and Mathematical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), Brisbane 4001, Australia

Energies 2017, 10(8), 1126; https://doi.org/10.3390/en10081126 - 1 Aug 2017

Cited by 13 | Viewed by 8383

Abstract

A high luminance contrast between windows and surrounding surfaces can increase the risk of discomfort glare, which can diminish office workers’ satisfaction and productivity. Accordingly, it can lead to occupant interventions, such as drawing window blinds or increasing electric light levels, which are [...] Read more.

A high luminance contrast between windows and surrounding surfaces can increase the risk of discomfort glare, which can diminish office workers’ satisfaction and productivity. Accordingly, it can lead to occupant interventions, such as drawing window blinds or increasing electric light levels, which are intended to enhance indoor visual comfort but counterproductively act to increase energy consumption. Increasing the luminance of the areas surrounding the windows using a supplementary lighting system, such as wall-washing with light emitting diode (LED) linear luminaires, could reduce discomfort glare arising from windowed walls. This paper reports on the results of a study in a typical office room in Brisbane, Australia. The outcomes of this study indicate that creating a luminance contrast of between 11:1 and 12:1 on the window wall in an office room with a 45% window-to-exterior-wall ratio using a supplementary LED system leads to improved subjective assessments of window appearance. The results suggest that such an enhancement could significantly reduce discomfort glare from windows, as well as diminishing the likelihood of the users intending to turn on the ceiling lights or to move the blinds. Full article

(This article belongs to the Special Issue Smart Lighting Environments: Sensing and Control)

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19 pages, 611 KiB

Open AccessArticle

A Demand-Side Perspective on Developing a Future Electricity Generation Mix: Identifying Heterogeneity in Social Preferences

by Sung-Yoon Huh¹ and Chul-Yong Lee^2,*

¹ Haas School of Business, University of California Berkeley, 2220 Piedmont Avenue, Berkeley, CA 94720, USA

² Korea Energy Economics Institute (KEEI), 405-11 Jongga-ro, Jung-gu, Ulsan 44543, Korea

Energies 2017, 10(8), 1127; https://doi.org/10.3390/en10081127 - 1 Aug 2017

Cited by 5 | Viewed by 3048

Abstract

Public support is an important factor in failure or success of the government decisions with respect to the electricity generation mix, which highlights the necessity of developing an electricity mix that reflects social preferences and acceptance. This study explores heterogeneity in social preferences [...] Read more.

Public support is an important factor in failure or success of the government decisions with respect to the electricity generation mix, which highlights the necessity of developing an electricity mix that reflects social preferences and acceptance. This study explores heterogeneity in social preferences for power sources and develops an electricity mix from a demand-side perspective. The study utilizes the choice-based conjoint survey and latent class model, and bases its empirical analysis on South Korea’s electric power sector. Results demonstrate that preferences for power sources in Korean society consist of two classes: one that is sensitive to the environment and one that is sensitive to risk. An electricity mix for Korea that reflects social preferences is 16.5–19.8% coal-fired, 13.3–24.9% liquefied natural gas (LNG), 9.0–11.2% oil, 22.3–32.9% nuclear, and 18.5–38.9% renewables, depending on the scenario. The study confirms that renewables are the power source with the least potential to cause social conflict, compared to nuclear and coal-fired sources. Moreover, increasing the proportion of renewables (currently only 3.9%) while decreasing the proportion of coal-fired power sources (currently 39.9%) to less than half its current level will result in an electricity mix that is accordance with social preferences in the long run. Full article

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

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20 pages, 10688 KiB

Open AccessArticle

A New Combined Boost Converter with Improved Voltage Gain as a Battery-Powered Front-End Interface for Automotive Audio Amplifiers

by Ching-Ming Lai¹

, Yu-Huei Cheng^2,*

, Jiashen Teh³

and Yuan-Chih Lin⁴

¹ Department of Vehicle Engineering, National Taipei University of Technology, 1, Sec. 3, Chung-Hsiao E. Road, Taipei 106, Taiwan

² Department of Information and Communication Engineering, Chaoyang University of Technology, Taichung 41349, Taiwan

³ School of Electrical and Electronic Engineering, Universiti Sains Malaysia, USM Engineering Campus, Nibong Tebal, Seberang Perai Selatan 14300, Penang, Malaysia

⁴ Department of Electrical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan

Energies 2017, 10(8), 1128; https://doi.org/10.3390/en10081128 - 1 Aug 2017

Cited by 8 | Viewed by 7995

Abstract

High boost DC/DC voltage conversion is always indispensable in a power electronic interface of certain battery-powered electrical equipment. However, a conventional boost converter works for a wide duty cycle for such high voltage gain, which increases power consumption and has low reliability problems. [...] Read more.

High boost DC/DC voltage conversion is always indispensable in a power electronic interface of certain battery-powered electrical equipment. However, a conventional boost converter works for a wide duty cycle for such high voltage gain, which increases power consumption and has low reliability problems. In order to solve this issue, a new battery-powered combined boost converter with an interleaved structure consisting of two phases used in automotive audio amplifier is presented. The first phase uses a conventional boost converter; the second phase employs the inverted type. With this architecture, a higher boost voltage gain is able to be achieved. A derivation of the operating principles of the converter, analyses of its topology, as well as a closed-loop control designs are performed in this study. Furthermore, simulations and experiments are also performed using input voltage of 12 V for a 120 W circuit. A reasonable duty cycle is selected to reach output voltage of 60 V, which corresponds to static voltage gain of five. The converter achieves a maximum measured conversion efficiency of 98.7% and the full load efficiency of 89.1%. Full article

(This article belongs to the Special Issue Energy Management, Control, and System Architectures for Electric Vehicle Applications)

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18 pages, 9057 KiB

Open AccessArticle

Investigation of the Dynamic Melting Process in a Thermal Energy Storage Unit Using a Helical Coil Heat Exchanger

by Xun Yang^1,2, Teng Xiong^1,2

, Jing Liang Dong^1,2

, Wen Xin Li^1,2 and Yong Wang^1,2,*

¹ National Centre for International Research of Low-Carbon and Green Buildings, Ministry of Science & Technology, Chongqing University, Chongqing 400045, China

² Joint International Research Laboratory of Green Buildings and Built Environments, Ministry of Education, Chongqing University, Chongqing 400045, China

Energies 2017, 10(8), 1129; https://doi.org/10.3390/en10081129 - 1 Aug 2017

Cited by 34 | Viewed by 7058

Abstract

In this study, the dynamic melting process of the phase change material (PCM) in a vertical cylindrical tube-in-tank thermal energy storage (TES) unit was investigated through numerical simulations and experimental measurements. To ensure good heat exchange performance, a concentric helical coil was inserted [...] Read more.

In this study, the dynamic melting process of the phase change material (PCM) in a vertical cylindrical tube-in-tank thermal energy storage (TES) unit was investigated through numerical simulations and experimental measurements. To ensure good heat exchange performance, a concentric helical coil was inserted into the TES unit to pipe the heat transfer fluid (HTF). A numerical model using the computational fluid dynamics (CFD) approach was developed based on the enthalpy-porosity method to simulate the unsteady melting process including temperature and liquid fraction variations. Temperature measurements using evenly spaced thermocouples were conducted, and the temperature variation at three locations inside the TES unit was recorded. The effects of the HTF inlet parameters were investigated by parametric studies with different temperatures and flow rate values. Reasonably good agreement was achieved between the numerical prediction and the temperature measurement, which confirmed the numerical simulation accuracy. The numerical results showed the significance of buoyancy effect for the dynamic melting process. The system TES performance was very sensitive to the HTF inlet temperature. By contrast, no apparent influences can be found when changing the HTF flow rates. This study provides a comprehensive solution to investigate the heat exchange process of the TES system using PCM. Full article

(This article belongs to the Special Issue Solar Technologies for Buildings)

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25 pages, 3589 KiB

Open AccessArticle

Advanced Measurement and Simulation Procedure for the Identification of Heat and Mass Transfer Parameters in Dynamic Adsorption Experiments

by Andreas Velte

, Gerrit Füldner^*, Eric Laurenz

and Lena Schnabel

Department Heating and Cooling Technologies, Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg, Germany

Energies 2017, 10(8), 1130; https://doi.org/10.3390/en10081130 - 2 Aug 2017

Cited by 18 | Viewed by 4837

Abstract

Thermally-driven heat pumps can help to mitigate CO₂ emissions by enhancing the efficiency of heating systems or by driving cooling systems with waste or solar heat. In order to make the thermally-driven systems more attractive for the end consumer, these systems need [...] Read more.

Thermally-driven heat pumps can help to mitigate CO₂ emissions by enhancing the efficiency of heating systems or by driving cooling systems with waste or solar heat. In order to make the thermally-driven systems more attractive for the end consumer, these systems need a higher power density. A higher power density can be achieved by intensifying the heat and mass transfer processes within the adsorption heat exchanger. For the optimization of this key component, a numerical model of the non-isothermal adsorption dynamics can be applied. The calibration of such a model can be difficult, since heat and mass transfer processes are strongly coupled. We present a measurement and simulation procedure that makes it possible to calibrate the heat transfer part of the numerical model separately from the mass transfer part. Furthermore, it is possible to identify the parts of the model that need to be improved. For this purpose, a modification of the well-known large temperature jump method is developed. The newly-introduced measurements are conducted under an inert N₂ atmosphere, and the surface temperature of the sample is measured with an infrared sensor. We show that the procedure is applicable for two completely different types of samples: a loose grains configuration and a fibrous structure that is directly crystallized. Full article

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

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29 pages, 890 KiB

Open AccessArticle

Demand Side Management in Nearly Zero Energy Buildings Using Heuristic Optimizations

by Nadeem Javaid^1,*

, Sardar Mehboob Hussain¹, Ibrar Ullah^2,3

, Muhammad Asim Noor¹, Wadood Abdul⁴

, Ahmad Almogren⁴

and Atif Alamri⁴

¹ Department of Computer Science, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan

² University of Engineering and Technology Peshawar, Bannu 28100, Pakistan

³ Capital University of Science and Technology, Islamabad 44000, Pakistan

⁴ Research Chair of Pervasive and Mobile Computing, College of Computer and Information Sciences, King Saud University, Riyadh 11633, Saudi Arabia

Energies 2017, 10(8), 1131; https://doi.org/10.3390/en10081131 - 2 Aug 2017

Cited by 58 | Viewed by 6637

Abstract

Today’s buildings are responsible for about 40% of total energy consumption and 30–40% of carbon emissions, which are key concerns for the sustainable development of any society. The excessive usage of grid energy raises sustainability issues in the face of global changes, such [...] Read more.

Today’s buildings are responsible for about 40% of total energy consumption and 30–40% of carbon emissions, which are key concerns for the sustainable development of any society. The excessive usage of grid energy raises sustainability issues in the face of global changes, such as climate change, population, economic growths, etc. Traditionally, the power systems that deliver this commodity are fuel operated and lead towards high carbon emissions and global warming. To overcome these issues, the recent concept of the nearly zero energy building (nZEB) has attracted numerous researchers and industry for the construction and management of the new generation buildings. In this regard, this paper proposes various demand side management (DSM) programs using the genetic algorithm (GA), teaching learning-based optimization (TLBO), the enhanced differential evolution (EDE) algorithm and the proposed enhanced differential teaching learning algorithm (EDTLA) to manage energy and comfort, while taking the human preferences into consideration. Power consumption patterns of shiftable home appliances are modified in response to the real-time price signal in order to get monetary benefits. To further improve the cost and user discomfort objectives along with reduced carbon emission, renewable energy sources (RESs) are also integrated into the microgrid (MG). The proposed model is implemented in a smart residential complex of multiple homes under a real-time pricing environment. We figure out two feasible regions: one for electricity cost and the other for user discomfort. The proposed model aims to deal with the stochastic nature of RESs while introducing the battery storage system (BSS). The main objectives of this paper include: (1) integration of RESs; (2) minimization of the electricity bill (cost) and discomfort; and (3) minimizing the peak to average ratio (PAR) and carbon emission. Additionally, we also analyze the tradeoff between two conflicting objectives, like electricity cost and user discomfort. Simulation results validate both the implemented and proposed techniques. Full article

(This article belongs to the Special Issue Battery Energy Storage Applications in Smart Grid)

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17 pages, 9310 KiB

Open AccessArticle

Design of a Control System for a Maglev Planar Motor Based on Two-Dimension Linear Interpolation

by Feng Xing

, Baoquan Kou^*, Lu Zhang, Xiangrui Yin and Yiheng Zhou

School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China

Energies 2017, 10(8), 1132; https://doi.org/10.3390/en10081132 - 2 Aug 2017

Cited by 9 | Viewed by 6051

Abstract

In order to realize the high speed and high-precision control of a maglev planar motor, a high-precision electromagnetic model is needed in the first place, which can also contribute to meeting the real-time running requirements. Traditionally, the electromagnetic model is based on analytical [...] Read more.

In order to realize the high speed and high-precision control of a maglev planar motor, a high-precision electromagnetic model is needed in the first place, which can also contribute to meeting the real-time running requirements. Traditionally, the electromagnetic model is based on analytical calculations. However, this neglects the model simplification and the manufacturing errors, which may bring certain errors to the model. Aiming to handle this inaccuracy, this paper proposes a novel design method for a maglev planar motor control system based on two-dimensional linear interpolation. First, the magnetic field is divided into several regions according to the symmetry of the Halbach magnetic array, and the uniform grid method is adopted to partition one of these regions. Second, targeting this region, it is possible to sample the electromagnetic forces and torques on each node of the grid and obtain the complete electromagnetic model in this region through the two-dimensional linear interpolation method. Third, the whole electromagnetic model of the maglev planar motor can be derived according to the symmetry of the magnetic field. Finally, the decoupling method and controller are designed according to this electromagnetic model, and thereafter, the control model can be established. The designed control system is demonstrated through simulations and experiments to feature better accuracy and meet the requirements of real-time control. Full article

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

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16 pages, 7870 KiB

Open AccessArticle

Model Predictive Direct Power Control for Nonredundant Fault Tolerant Grid-Connected Bidirectional Voltage Source Converter

by Nan Jin^1,2, Leilei Guo^1,* and Gang Yao³

¹ Department of Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China

² Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996, USA

³ Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2017, 10(8), 1133; https://doi.org/10.3390/en10081133 - 2 Aug 2017

Cited by 16 | Viewed by 4892

Abstract

This paper proposes a model predictive direct power control scheme for nonredundant fault tolerant grid-connected bidirectional voltage source converter (BVSC) with balanced dc-link split capacitor voltage and high reliability. Based on the operation analysis of fault-tolerant BVSC with phase leg faults, a power [...] Read more.

This paper proposes a model predictive direct power control scheme for nonredundant fault tolerant grid-connected bidirectional voltage source converter (BVSC) with balanced dc-link split capacitor voltage and high reliability. Based on the operation analysis of fault-tolerant BVSC with phase leg faults, a power predictive model of three-phase four-switch fault-tolerant topology in αβ coordinates is established, and the space voltage vectors with unbalanced dc-link split capacitor voltage are analyzed. According to the power predictive model and cost function, the optimal space voltage vector is selected to achieve a flexible, smooth transition between inverter and rectifier mode with direct power control. Pulse width modulation and phase locked loop are not required in the proposed method. The constraint of dc-link voltage constraint is designed for the cost function to achieve a central point of dc-link voltage offset suppression, which can reduce the risk of electrolytic capacitor failure for over-voltage operation. With the proposed control method, the converter can work continuously in both inverter mode and rectifier mode, even if phase leg faults occur. The simulation and experimental results show good steady-state and dynamic performance of the proposed control scheme to enhance the reliability of bidirectional power conversion. Full article

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

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18 pages, 5032 KiB

Open AccessArticle

Improving the Traffic Model to Be Used in the Optimisation of Mass Transit System Electrical Infrastructure

by Álvaro J. López-López^*, Ramón R. Pecharromán, Antonio Fernández-Cardador and Asunción P. Cucala

Institute for Research in Technology, ICAI School of Engineering, Comillas Pontifical University, 28015 Madrid, Spain

Energies 2017, 10(8), 1134; https://doi.org/10.3390/en10081134 - 2 Aug 2017

Cited by 8 | Viewed by 4273

Abstract

Among the different approaches for minimising the energy consumption of mass transit systems (MTSs), a common concern for MTS operators is the improvement of the electrical infrastructure. The traffic on the lines under analysis is one of the most important inputs to the [...] Read more.

Among the different approaches for minimising the energy consumption of mass transit systems (MTSs), a common concern for MTS operators is the improvement of the electrical infrastructure. The traffic on the lines under analysis is one of the most important inputs to the studies devoted to improving MTS infrastructure, since it represents where and how frequently it is possible to save energy. However, on the one hand, MTS electrical studies usually simplify the traffic model, which may lead to a misrepresentation of the energy interactions between trains. On the other hand, if the stochastic traffic is rigorously modelled, the size of the simulation problem could grow excessively, which in turn could make the time to obtain results unmanageable. To cope with this issue, this paper presents a method to obtain a reduced-size set of representative scenarios. Firstly, a traffic model including the most representative stochastic traffic variables is developed. Secondly, a function highly correlated with energy savings is proposed to make it possible to properly characterise the traffic scenarios. Finally, this function is used to select the most representative scenarios. The representative scenario set obtained by the application of this method is shown to be sufficiently accurate with a limited number of scenarios. The traffic approach in this paper improves the accuracy with respect to the usual traffic approach used in the literature. Full article

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

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18 pages, 3250 KiB

Open AccessArticle

Transformer Paper Expected Life Estimation Using ANFIS Based on Oil Characteristics and Dissolved Gases (Case Study: Indonesian Transformers)

by Rahman A. Prasojo^1,*, Karunika Diwyacitta¹, Suwarno¹

and Harry Gumilang²

¹ School of Electrical Engineering and Informatics, Institut Teknologi Bandung, Bandung 40132, Indonesia

² PT. PLN (Persero) TJBT, Bandung 40243, Indonesia

Energies 2017, 10(8), 1135; https://doi.org/10.3390/en10081135 - 2 Aug 2017

Cited by 48 | Viewed by 6119

Abstract

This article presents an algorithm for modelling an Adaptive Neuro Fuzzy Inference System (ANFIS) for power transformer paper conditions in order to estimate the transformer’s expected life. The dielectric characteristics, dissolved gasses, and furfural of 108 running transformers were collected, which were divided [...] Read more.

This article presents an algorithm for modelling an Adaptive Neuro Fuzzy Inference System (ANFIS) for power transformer paper conditions in order to estimate the transformer’s expected life. The dielectric characteristics, dissolved gasses, and furfural of 108 running transformers were collected, which were divided into 76 training datasets and another 32 testing datasets. The degree of polymerization (DP) of the transformer paper was predicted using the ANFIS model based on using the dielectric characteristics and dissolved gases as input. These inputs were analyzed, and the best combination was selected, whereas CO + CO₂, acidity, interfacial tension, and color were correlated with the paper’s deterioration condition and were chosen as the input variables. The best combination of input variables and membership function was selected to build the optimal ANFIS model, which was then compared and evaluated. The proposed ANFIS model has 89.07% training accuracy and 85.75% testing accuracy and was applied to a transformer paper insulation assessment and an estimation of the expected life of four Indonesian transformers for which furfural data is unavailable. This proposed algorithm can be used as a furfural alternative for the general assessment of transformer paper conditions and the estimation of expected life and provides a helpful assistance for experts in transformer condition assessment. Full article

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17 pages, 9140 KiB

Open AccessArticle

Computational Fluid Dynamics Simulation Study of a Novel Membrane Contactor for Simultaneous Carbon Dioxide Absorption and Stripping

by Hsuan Chang^*

, Hau-Yu Gan, Yih-Hang Chen and Chii-Dong Ho

Energy and Opto-Electronic Materials Research Center, Department of Chemical and Materials Engineering, Tamkang University, Tamsui, New Taipei 251, Taiwan

Energies 2017, 10(8), 1136; https://doi.org/10.3390/en10081136 - 2 Aug 2017

Cited by 5 | Viewed by 4406

Abstract

Physical absorption is a potential technology for economic carbon capture due to its low energy consumption, however, the absorption efficiency of current systems must be improved. In this study, novel hybrid absorption/stripping membrane contactors (HASMCs) for physical solvent carbon capture are proposed. The [...] Read more.

Physical absorption is a potential technology for economic carbon capture due to its low energy consumption, however, the absorption efficiency of current systems must be improved. In this study, novel hybrid absorption/stripping membrane contactors (HASMCs) for physical solvent carbon capture are proposed. The simultaneous absorption and stripping within one module provides instant regeneration of the solvent and results in the enhancement of absorption. HASMCs with parallel-flow and cross-flow configurations and using empty or spacer-filled channels are investigated by rigorous computational fluid dynamics simulation. The internal profiles of transmembrane mass fluxes reveal that cross-flow HASMCs are much more effective than the parallel-flow ones and the modules using spacer-filled channels give better performance than the ones using empty channels. The mass transfer coefficients of HASMCs are much higher than predicted by correlations in the literature. Full article

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29 pages, 7694 KiB

Open AccessFeature PaperArticle

Development of the IBSAL-SimMOpt Method for the Optimization of Quality in a Corn Stover Supply Chain

by Hernan Chavez¹

, Krystel K. Castillo-Villar^1,*

and Erin Webb²

¹ Mechanical Engineering Department, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA

² Environmental Sciences Division, Oak Ridge National Laboratory, One Bethel Rd., Oak Ridge, TN 37831, USA

Energies 2017, 10(8), 1137; https://doi.org/10.3390/en10081137 - 3 Aug 2017

Cited by 5 | Viewed by 7153

Abstract

Variability on the physical characteristics of feedstock has a relevant effect on the reactor’s reliability and operating cost. Most of the models developed to optimize biomass supply chains have failed to quantify the effect of biomass quality and preprocessing operations required to meet [...] Read more.

Variability on the physical characteristics of feedstock has a relevant effect on the reactor’s reliability and operating cost. Most of the models developed to optimize biomass supply chains have failed to quantify the effect of biomass quality and preprocessing operations required to meet biomass specifications on overall cost and performance. The Integrated Biomass Supply Analysis and Logistics (IBSAL) model estimates the harvesting, collection, transportation, and storage cost while considering the stochastic behavior of the field-to-biorefinery supply chain. This paper proposes an IBSAL-SimMOpt (Simulation-based Multi-Objective Optimization) method for optimizing the biomass quality and costs associated with the efforts needed to meet conversion technology specifications. The method is developed in two phases. For the first phase, a SimMOpt tool that interacts with the extended IBSAL is developed. For the second phase, the baseline IBSAL model is extended so that the cost for meeting and/or penalization for failing in meeting specifications are considered. The IBSAL-SimMOpt method is designed to optimize quality characteristics of biomass, cost related to activities intended to improve the quality of feedstock, and the penalization cost. A case study based on 1916 farms in Ontario, Canada is considered for testing the proposed method. Analysis of the results demonstrates that this method is able to find a high-quality set of non-dominated solutions. Full article

(This article belongs to the Special Issue Biomass for Energy Country Specific Show Case Studies)

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17 pages, 1865 KiB

Open AccessArticle

Evaluation of Voltage Control Approaches for Future Smart Distribution Networks

by Pengfei Wang¹, Jialiang Yi^2,*, Mansoureh Zangiabadi², Pádraig Lyons² and Phil Taylor²

¹ TNEI services, 2nd Floor Bainbridge House, 86 - 90 London Road, Manchester M1 2PW, UK

² School of Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK

Energies 2017, 10(8), 1138; https://doi.org/10.3390/en10081138 - 3 Aug 2017

Cited by 5 | Viewed by 3917

Abstract

This paper evaluates meta-heuristic and deterministic approaches for distribution network voltage control. As part of this evaluation, a novel meta-heuristic algorithm, Cuckoo Search, is applied for distribution network voltage control and compared with a deterministic voltage control algorithm, the oriented discrete coordinate decent [...] Read more.

This paper evaluates meta-heuristic and deterministic approaches for distribution network voltage control. As part of this evaluation, a novel meta-heuristic algorithm, Cuckoo Search, is applied for distribution network voltage control and compared with a deterministic voltage control algorithm, the oriented discrete coordinate decent method (ODCDM). ODCDM has been adopted in a state-of-the-art industrial product and applied in real distribution networks. These two algorithms have been evaluated under a set of test cases, which were generated to represent the voltage control problems in current and future distribution networks. Sampled test results have been presented, and findings have been discussed regarding the adoption of different optimization algorithms for current and future distribution networks. Full article

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

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13 pages, 1364 KiB

Open AccessArticle

Passivity-Based Control of a Doubly Fed Induction Generator System under Unbalanced Grid Voltage Conditions

by Jiawei Huang^1,*

, Honghua Wang¹ and Chong Wang²

¹ College of Energy and Electrical Engineering, Hohai University, Nanjing 211100, China

² Department of Electrical & Computer Engineering, Iowa State University, Ames, IA 50011, USA

Energies 2017, 10(8), 1139; https://doi.org/10.3390/en10081139 - 3 Aug 2017

Cited by 9 | Viewed by 4119

Abstract

According to the theory of passivity-based control (PBC), this paper establishes a port-controlled Hamiltonian system with dissipation (PCHD) model for a doubly fed induction generator (DFIG) system under unbalanced grid voltage conditions and proposes a method of interconnection and damping assignment passivity-based control [...] Read more.

According to the theory of passivity-based control (PBC), this paper establishes a port-controlled Hamiltonian system with dissipation (PCHD) model for a doubly fed induction generator (DFIG) system under unbalanced grid voltage conditions and proposes a method of interconnection and damping assignment passivity-based control (IDA-PBC) of the system under such conditions. By using this method, the rotor-side converter and grid-side converter can be controlled simultaneously in order to improve fault ride-through capability of the DFIG system. Simulation results indicate that this IDA-PBC strategy effectively suppresses fluctuations of output current and power in the DFIG system during unbalanced grid voltage sag/swell, enhances dynamic performance, and improves the robustness of the system. Full article

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

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12 pages, 3818 KiB

Open AccessArticle

Windbreak Effects Within Infinite Wind Farms

by Nicolas Tobin¹ and Leonardo P. Chamorro^1,2,3,*

¹ Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801, USA

² Department of Civil and Environmental Engineering, University of Illinois, Urbana, IL 61801, USA

³ Department of Aerospace Engineering, University of Illinois, Urbana, IL 61801, USA

Energies 2017, 10(8), 1140; https://doi.org/10.3390/en10081140 - 3 Aug 2017

Cited by 9 | Viewed by 6085

Abstract

Building upon a recent study that showed windbreaks to be effective in increasing the power output of a wind turbine, the potential of windbreaks in a large wind farm is explored using simplified formulations. A top-down boundary layer approach is combined with methods [...] Read more.

Building upon a recent study that showed windbreaks to be effective in increasing the power output of a wind turbine, the potential of windbreaks in a large wind farm is explored using simplified formulations. A top-down boundary layer approach is combined with methods of estimating both the roughness effects of windbreaks and the induced inviscid speed-up for nearby turbines to investigate power production impact for several layouts of infinite wind farms. Results suggest that the negative impact of windbreak wakes for an infinite wind farm will outweigh the local inviscid speed-up for realistic inter-turbine spacings, with the break-even point expected at a spacing of ∼25 rotor diameters. However, the possibility that windbreaks may be applicable in finite and other wind farm configurations remains open. Inspection of the windbreak porosity reveals an impact on the magnitude of power perturbation, but not whether the change is positive or negative. Predictions from the boundary-layer approach are validated with power measurements from large-eddy simulations. Full article

(This article belongs to the Collection Wind Turbines)

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28 pages, 12467 KiB

Open AccessFeature PaperArticle

A Simplified Microgrid Model for the Validation of Islanded Control Logics

by Andrea Bonfiglio^*

, Massimo Brignone

, Marco Invernizzi, Alessandro Labella, Daniele Mestriner and Renato Procopio

DITEN Department of Electrical, Electronic, TLC Engineering and Naval Architecture, University of Genoa, 16145 Genoa, Italy

Energies 2017, 10(8), 1141; https://doi.org/10.3390/en10081141 - 3 Aug 2017

Cited by 30 | Viewed by 5126

Abstract

Microgrids (MGs) may represent a solution in the near future to many problems in the energy and electric world scenarios; such as pollution, high reliability, efficiency and so on. In particular, MGs’ capability to work in an islanded configuration represents one of their [...] Read more.

Microgrids (MGs) may represent a solution in the near future to many problems in the energy and electric world scenarios; such as pollution, high reliability, efficiency and so on. In particular, MGs’ capability to work in an islanded configuration represents one of their most interesting features in terms of the improvement of the reliability of the system, the integration of renewable energy sources and the exploitation of the quick response and flexibility of power electronic devices in a stand-alone system. In order to study and validate innovative solutions and control strategies for islanded operation, there is a need to develop models for MG structures that can be reliable and sufficiently simple to be used for the purpose of the design and validation of innovative control systems. This paper proposes a simplified, first harmonic model for a generic structure of MG characterized by its use of only electronic power converter interfaced generation. The main advantages of the proposed method lie in the model’s simplicity and its reduced solving time, thanks to the limited number of necessary parameters to describe the system. Moreover, the developed formulation allows the avoidance of specific (and often licensed) software to simulate the system. The performances of the proposed model have been validated by means of a comparative analysis of the results obtained against a more accurate representation of the system performed in the power system CAD—electromagnetic transient and DC (PSCAD—EMTDC) environment, which allows for the representation of each component with a very high level of detail. Such comparison has been performed using the University of Genoa Savona Campus Smart Polygeneration Microgrid testbed facility, due to the availability of all the necessary numerical values. Full article

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14 pages, 7084 KiB

Open AccessArticle

Design and Construction of 1 MW Class Floating PV Generation Structural System Using FRP Members

by Sun-Hee Kim¹

, Soon-Jong Yoon² and Wonchang Choi^1,*

¹ Department of Architectural Engineering, Gachon University, Seongnam 13120, Korea

² Department of Civil Engineering, Hongik University, Seoul 04066, Korea

Energies 2017, 10(8), 1142; https://doi.org/10.3390/en10081142 - 3 Aug 2017

Cited by 76 | Viewed by 14060

Abstract

The paper investigates overview of construction process of a 1 MW class floating photovoltaic (PV) generation structural system fabricated with fiber reinforced polymer (FRP) members. The floating PV generation system consists of unit structures linked by a hinge type connection of which the [...] Read more.

The paper investigates overview of construction process of a 1 MW class floating photovoltaic (PV) generation structural system fabricated with fiber reinforced polymer (FRP) members. The floating PV generation system consists of unit structures linked by a hinge type connection of which the effect of bending moment between the unit structures, induced by the unstable movement of the water surface, was minimized. Moreover, the unit structures were classified into three types of structures by combining the floating PV generation system and pontoon bridges, which are constructed to install the electrical equipment and a route of movement for workers. The structural safety of the connection system among the unit structures and/or the mooring system is confirmed by referring to the relevant design codes. In addition, structural analysis using the finite element method was performed to ensure the safety of the floating PV generation structure, and commercial viability evaluation was performed based on the construction cost. The FRP member shows superior performance in construction and cost effectiveness in a floating PV generation system. Full article

(This article belongs to the Special Issue PV System Design and Performance)

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15 pages, 3851 KiB

Open AccessArticle

AC Transmission Emulation Control Strategies for the BTB VSC HVDC System in the Metropolitan Area of Seoul

by Sungyoon Song

, Jongin Kim, Junghun Lee

and Gilsoo Jang^*

School of Electrical Engineering, Korea University, Anam-ro, Sungbuk-gu, Seoul 02841, Korea

Energies 2017, 10(8), 1143; https://doi.org/10.3390/en10081143 - 3 Aug 2017

Cited by 9 | Viewed by 6789

Abstract

In the Korean power system, growing power loads have recently created the problems of voltage instability and fault current in the Seoul Capital Area (SCA). Accordingly, the back-to-back (BTB) voltage source converter (VSC) high-voltage direct-current (HVDC) system is emerging to resolve such problems [...] Read more.

In the Korean power system, growing power loads have recently created the problems of voltage instability and fault current in the Seoul Capital Area (SCA). Accordingly, the back-to-back (BTB) voltage source converter (VSC) high-voltage direct-current (HVDC) system is emerging to resolve such problems with grid segmentation. However, non-convergence problems occur in this metropolitan area, due to the large change of power flow in some contingencies. Therefore, this paper proposes two kinds of AC transmission emulation control (ATEC) strategies to improve the metropolitan transient stability, and to resolve the non-convergence problem. The proposed ATEC strategies are able to mitigate possible overloading of adjacent AC transmission, and maintain power balance between metropolitan regions. The first ATEC strategy uses a monitoring system that permits the reverse power flow of AC transmission, and thus effectively improves the grid stability based on the power transfer equation. The second ATEC strategy emulates AC transmission with DC link capacitors in a permissible DC-link voltage range according to angle difference, and securely improves the gird stability, without requiring grid operator schedule decisions. This paper compares two kinds of ATEC schemes: it demonstrates the first ATEC strategy with specific fault scenario with PSS/E (Power Transmission System Planning Software), and evaluates the second ATEC strategy with internal controller performance with PSCAD/EMTDC (Power System Electromagnetic Transients Simulation Software). Full article

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

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22 pages, 3777 KiB

Open AccessArticle

A Governance Perspective on Net Zero Energy Building Niche Development in India: The Case of New Delhi

by Mansi Jain¹, Thomas Hoppe^2,*

and Hans Bressers¹

¹ Department of Technology and Governance for Sustainability (CSTM), Institute for Innovation and Governance Studies (IGS), Faculty of Behavioral, Management and Social Studies (BMS), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

² Policy, Organisation, Law and Gaming (POLG), Department of Multi-Actor Systems (MAS), Faculty of Technology, Policy and Management (TPM), Delft University of Technology, Jaffalaan 5, 2628 BX Delft, The Netherlands

Energies 2017, 10(8), 1144; https://doi.org/10.3390/en10081144 - 3 Aug 2017

Cited by 19 | Viewed by 4599

Abstract

The net zero-energy building (NZEB) concept has recently gained prominence worldwide. Large scale adoption and implementation of NZEBs would potentially contribute greatly to greening of the building sector. However, it is still at a nascent stage of niche formation. This paper aims to [...] Read more.

The net zero-energy building (NZEB) concept has recently gained prominence worldwide. Large scale adoption and implementation of NZEBs would potentially contribute greatly to greening of the building sector. However, it is still at a nascent stage of niche formation. This paper aims to assess the governance context for adoption and uptake of NZEBs through niche formation in India by addressing the research question: What is the state of governance in New Delhi regarding NZEB niche development? A case study research design is used to answer this question. The Governance Assessment Tool (GAT) and Strategic Niche Management (SNM) are used to analyze the New Delhi case. Data collection involved in-depth interviews with fourteen key stakeholders. Data were analyzed using the qualitative data analysis software (ATLAS.ti). The results reveal that the governance context is only marginally supportive towards NZEB niche formation due to qualities of moderate extent, flexibility and intensity. Actor network formation was identified as an important driver which influences other elements of governance, as well as factors stimulating strategic niche management. Full article

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22 pages, 1545 KiB

Open AccessArticle

Smart Integrated Renewable Energy Systems (SIRES): A Novel Approach for Sustainable Development

by Zeel Maheshwari^1,*

and Rama Ramakumar²

¹ Graduate Research Associate, Engineering Energy Laboratory, Oklahoma State University, Stillwater, OK 74075, USA

² Director, Engineering Energy Laboratory, Oklahoma State University, Stillwater, OK 74075, USA

Energies 2017, 10(8), 1145; https://doi.org/10.3390/en10081145 - 4 Aug 2017

Cited by 31 | Viewed by 13960

Abstract

Technical and economic aspects of the viability of SIRES (Smart Integrated Renewable Energy Systems) for sustainable development of remote and rural areas of the world are discussed. The hallmark of the proposed SIRES is the smart utilization of several renewable resources in an [...] Read more.

Technical and economic aspects of the viability of SIRES (Smart Integrated Renewable Energy Systems) for sustainable development of remote and rural areas of the world are discussed. The hallmark of the proposed SIRES is the smart utilization of several renewable resources in an integrated fashion and matching of resources and needs a priori with the ultimate goal of “energization”, not just “electrification”. Historical background leading to this approach is succinctly presented along with a comprehensive schematic diagram. Modeling of various components and their collective use in optimizing SIRES with the aid of genetic algorithm are presented using a typical hypothetical example. SIRES is also compared with various approaches for rural development based on Annualized Cost of System (ACS) and installation costs. Implementation of SIRES will lead to overall sustainable development of rural communities. Full article

(This article belongs to the Special Issue Sustainable Energy Technologies)

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21 pages, 1726 KiB

Open AccessArticle

Virtual Synchronous Generator Based Auxiliary Damping Control Design for the Power System with Renewable Generation

by Bingtuan Gao^1,*, Chaopeng Xia¹, Ning Chen², Khalid Mehmood Cheema¹, Libin Yang³ and Chunlai Li³

¹ School of Electrical Engineering, Southeast University, Nanjing 210096, China

² State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems, China Electric Power Research Institute, Nanjing 210003, China

³ Qinghai Province Key Laboratory of Photovoltaic Grid Connected Power Generation Technology, State Grid Qinghai Electric Power Research Institute, Xining 810008, China

Energies 2017, 10(8), 1146; https://doi.org/10.3390/en10081146 - 4 Aug 2017

Cited by 34 | Viewed by 8158

Abstract

Aiming for large-scale renewable energy sources (RES) integrated to power systems with power electronic devices, the technology of virtual synchronous generator (VSG) has been developed and studied in recent years. It is necessary to analyze the damping characteristics of the power system with [...] Read more.

Aiming for large-scale renewable energy sources (RES) integrated to power systems with power electronic devices, the technology of virtual synchronous generator (VSG) has been developed and studied in recent years. It is necessary to analyze the damping characteristics of the power system with RES generation based on VSG and develop its corresponding damping controller to suppress the possible low frequency oscillation. Firstly, the mathematical model of VSG in a per unit (p.u) system is presented. Based on the single-machine infinite bus system integrated with an RES power plant, the influence of VSG on the damping characteristics of the power system is studied qualitatively by damping torque analysis. Furthermore, the small-signal model of the considered system is established and the damping ratio of the system is studied quantitatively by eigenvalue analysis, which concluded that adjusting the key control parameters has limited impacts on the damping ratio of the system. Consequently, referring to the configuration of traditional power system stabilizer (PSS), an auxiliary damping controller (ADC) for VSG is designed to suppress the low frequency oscillation of the power system. Finally, simulations were performed to verify the validity of theoretical analysis and the effectiveness of designed ADC. Full article

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

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16 pages, 8814 KiB

Open AccessArticle

Capacity Decay Mechanism of the LCO + NMC532/Graphite Cells Combined with Post-Mortem Technique

by Linjing Zhang^1,2, Jiuchun Jiang^1,2,* and Weige Zhang^1,2

¹ National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China

² Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Jiaotong University, Beijing 100044, China

Energies 2017, 10(8), 1147; https://doi.org/10.3390/en10081147 - 4 Aug 2017

Cited by 24 | Viewed by 8143

Abstract

Lithium ion batteries are widely used in portable electronics and transportations due to their high energy and high power with low cost. However, they suffer from capacity degradation during long cycling, thus making it urgent to study their decay mechanisms. Commercial 18650-type LiCoO [...] Read more.

Lithium ion batteries are widely used in portable electronics and transportations due to their high energy and high power with low cost. However, they suffer from capacity degradation during long cycling, thus making it urgent to study their decay mechanisms. Commercial 18650-type LiCoO₂ + LiNi_0.5Mn_0.3Co_0.2O₂/graphite cells are cycled at 1 C rate for 700 cycles, and a continuous post-mortem analysis is performed. Based on these tests, the decay mechanism of the cells is finally proposed. The changes of differential capacity curves of the full cells show that the loss of active materials, loss of lithium ions and cell polarization are the main factors contributing to capacity loss. Non-fully charging of the electrodes is also one of the reasons, but only takes up a minor portion. Impedance results indicate that the charge transfer resistance becomes larger during cycling, especially at low state of charge. Morphology and surface chemistry analysis demonstrates that the electrode particles after cycling exhibit some minor cracks and some additional layers are formed on surfaces of both the cathode and anode electrodes. All of these effects may contribute to the impedance increase, and consequently lead to degradation of the full cells. Thus, a good protection of the surface of the cathode and anode shows great potential to improve the capacity maintenance and prolong the cycle life of the cells. Full article

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17 pages, 4384 KiB

Open AccessArticle

Performance Study of Hybrid Magnetic Coupler Based on Magneto Thermal Coupled Analysis

by Shuang Wang¹, Yongcun Guo^1,*, Gang Cheng^1,2 and Deyong Li¹

¹ Anhui Mining Machinery and Electrical Equipment Collaborative Innovation Center, Anhui University of Science and Technology, Huainan 232001, China

² Hefei Institute of Material Science, Chinese Academy of Sciences, Hefei 230000, China

Energies 2017, 10(8), 1148; https://doi.org/10.3390/en10081148 - 4 Aug 2017

Cited by 15 | Viewed by 4931

Abstract

Specific to a problem of large vibro-impact aris ing from the cutting unit of the hard rock tunnel boring machine (TBM), a hybrid magnetic coupler based on soft start was proposed in this paper. The mathematical model for total eddy current losses of [...] Read more.

Specific to a problem of large vibro-impact aris ing from the cutting unit of the hard rock tunnel boring machine (TBM), a hybrid magnetic coupler based on soft start was proposed in this paper. The mathematical model for total eddy current losses of such a coupler was established by field-circuit method. Then, magnetic-thermal coupling simulation was performed by virtue of three-dimensional finite element software. In addition, an experimental prototype was independently designed; by comparing the model with experimental data, validity of the above mathematical model was verified. The relevant research results indicated that calculated values were consistent with experimental values, and the magneto thermal coupling method could be applied to accurately analyze temperature distribution of the hybrid magnetic coupler. By contrast to the existing magnetic coupling of the same dimension, output efficiency of the hybrid magnetic coupler was improved by 1.2%. Therefore, this research technique can provide references for designing the cutting unit of hard rock TBM with a high start impact. Full article

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

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14 pages, 3055 KiB

Open AccessArticle

A Comparative Study of Three Improved Algorithms Based on Particle Filter Algorithms in SOC Estimation of Lithium Ion Batteries

by Bizhong Xia¹, Zhen Sun¹

, Ruifeng Zhang^1,2,*, Deyu Cui¹, Zizhou Lao¹, Wei Wang², Wei Sun², Yongzhi Lai² and Mingwang Wang²

¹ Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China

² Sunwoda Electronic Co. Ltd., Shenzhen 518108, China

Energies 2017, 10(8), 1149; https://doi.org/10.3390/en10081149 - 4 Aug 2017

Cited by 52 | Viewed by 4781

Abstract

The state of charge (SOC) is an important parameter for batteries, especially those for electric vehicles. Since SOC cannot be obtained directly by measurement, SOC estimation methods are required. In this paper, three model-based methods, including the extended particle filter (EPF), cubature particle [...] Read more.

The state of charge (SOC) is an important parameter for batteries, especially those for electric vehicles. Since SOC cannot be obtained directly by measurement, SOC estimation methods are required. In this paper, three model-based methods, including the extended particle filter (EPF), cubature particle filter (CPF), and unscented particle filter (UPF), are compared in terms of complexity, accuracy, and robustness. The second-order resistor-capacitor (RC) equivalent circuit model is selected as the circuit model of the lithium-ion battery, and the parameters of the model are obtained by off-line identification. Then, the City test is applied to compare the performance of the methods. The experimental results show that the EPF method exhibits low complexity and fast running speed, but poor accuracy and robustness. Compared with the EPF method, the complexity of the CPF and UPF methods is relatively high, but these models offer improved accuracy and robustness. Full article

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20 pages, 9137 KiB

Open AccessArticle

A Novel Observer for Lithium-Ion Battery State of Charge Estimation in Electric Vehicles Based on a Second-Order Equivalent Circuit Model

by Bizhong Xia, Wenhui Zheng, Ruifeng Zhang^*, Zizhou Lao and Zhen Sun

Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China

Energies 2017, 10(8), 1150; https://doi.org/10.3390/en10081150 - 5 Aug 2017

Cited by 45 | Viewed by 7706

Abstract

Accurate state of charge (SOC) estimation can prolong lithium-ion battery life and improve its performance in practice. This paper proposes a new method for SOC estimation. The second-order resistor-capacitor (2RC) equivalent circuit model (ECM) is applied to describe the dynamic behavior of lithium-ion [...] Read more.

Accurate state of charge (SOC) estimation can prolong lithium-ion battery life and improve its performance in practice. This paper proposes a new method for SOC estimation. The second-order resistor-capacitor (2RC) equivalent circuit model (ECM) is applied to describe the dynamic behavior of lithium-ion battery on deriving state space equations. A novel method for SOC estimation is then presented. This method does not require any matrix calculation, so the computation cost can be very low, making it more suitable for hardware implementation. The Federal Urban Driving Schedule (FUDS), The New European Driving Cycle (NEDC), and the West Virginia Suburban Driving Schedule (WVUSUB) experiments are carried to evaluate the performance of the proposed method. Experimental results show that the SOC estimation error can converge to 3% error boundary within 30 seconds when the initial SOC estimation error is 20%, and the proposed method can maintain an estimation error less than 3% with 1% voltage noise and 5% current noise. Further, the proposed method has excellent robustness against parameter disturbance. Also, it has higher estimation accuracy than the extended Kalman filter (EKF), but with decreased hardware requirements and faster convergence rate. Full article

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17 pages, 4494 KiB

Open AccessArticle

Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media

by Zhongliang Hu¹, Jin Zhao¹, Hui Gao¹, Ehsan Nourafkan¹

and Dongsheng Wen^1,2,*

¹ School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK

² School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China

Energies 2017, 10(8), 1151; https://doi.org/10.3390/en10081151 - 5 Aug 2017

Cited by 35 | Viewed by 6534 | Correction

Abstract

Carbon nanoparticles (CNPs) are becoming promising candidates for oil/gas applications due to their biocompatibility and size-dependent optical and electronic properties. Their applications, however, are always associated with the flow of nanoparticles inside a reservoir, i.e., a porous medium, where insufficient studies have been [...] Read more.

Carbon nanoparticles (CNPs) are becoming promising candidates for oil/gas applications due to their biocompatibility and size-dependent optical and electronic properties. Their applications, however, are always associated with the flow of nanoparticles inside a reservoir, i.e., a porous medium, where insufficient studies have been conducted. In this work, we synthesized CNPs with two different size categories in 200 nm carbon balls (CNP-200) and 5 nm carbon dots (CNP-5), via a hydrothermal carbonation process. Comprehensive experiments in packed glass bead columns, as well as mathematical simulations, were conducted to understand the transport and deposition of CNPs under various ionic strength, particle sizes and concentration conditions. Our results show that the retention of CNP-200 is highly sensitive to the salinity and particle concentrations, while both of them are unaffected in the transport of small CNP-5. Supplemented with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the clean bed filtration theory with blocking effect can successfully fit the experimental breakthrough curves of CNP-200. However, the high breakthrough ability for CNP-5 regardless of ionic strength change is in conflict with the energy interactions predicted by traditional DLVO theory. Full article

(This article belongs to the Special Issue Nanotechnology for Oil and Gas Applications)

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13 pages, 3767 KiB

Open AccessArticle

Exploring PANI-TiN Nanoparticle Coatings in a PEFC Environment: Enhancing Corrosion Resistance and Conductivity of Stainless Steel Bipolar Plates

by Surbhi Sharma^*

, Kun Zhang, Gaurav Gupta

and Daniel G. Santamaria

Centre for Fuel Cells and their Fuels, Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK

Energies 2017, 10(8), 1152; https://doi.org/10.3390/en10081152 - 7 Aug 2017

Cited by 18 | Viewed by 5708

Abstract

Electrochemically-deposited polymer-metal composites, although explored for various uses, have only recently attracted attention for metallic bipolar plates used in fuel cells. Utilising a facile electrochemical deposition process, composite polyaniline and titanium nitride nanoparticle (PANI-TiN) coatings of varying thickness (5–50 cyclic voltammetry cycles) and [...] Read more.

Electrochemically-deposited polymer-metal composites, although explored for various uses, have only recently attracted attention for metallic bipolar plates used in fuel cells. Utilising a facile electrochemical deposition process, composite polyaniline and titanium nitride nanoparticle (PANI-TiN) coatings of varying thickness (5–50 cyclic voltammetry cycles) and composition (TiN nanoparticle concentration, 0.1 g L⁻¹ and 0.5 g L⁻¹) were deposited on stainless steel 304L (SS304) substrates. As compared to the pristine PANI coatings, which displayed an interfacial contact resistance (ICR) value of 367.5 mΩ cm² and corrosion resistance (E_corr) of 214 mV_SHE, the composite PANI-TiN_0.5 coatings displayed significantly reduced ICR values of 32.6 mΩ cm² while maintaining similar corrosion resistance. The superior properties of these thin (~10 nm) composite coatings with low TiN loading (0.05–0.1 mg cm⁻²) show potential for further improvement in ICR with the possible use of higher TiN (or slightly lower PANI) concentrations. The study also demonstrated an interesting dynamic between PANI and TiN simultaneous deposition where the concentration of TiN NPs negatively affects the deposition rate for PANI, allowing the deposition of even thinner PANI coatings and possibly enabling control over the composition of the composite coating. The TiN NPs not only impart better conductivity for use as bipolar plates but, at higher loading, also assist PANI in enhancing corrosion resistance. Even for the lowest number of coating cycles (five cycles), the PANI-TiN_0.5 composite films showed a remarkable 48 mV shift towards more positive/higher corrosion potential (E_corr = 5 mV_SHE) with respect to PANI (E_corr = −57 mV_SHE). The coatings demonstrated a reduction in corrosion current density to values of ~0.5 µA cm⁻² achieving beyond the DoE 2020 target of 1 µA cm⁻². Full article

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

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18 pages, 9526 KiB

Open AccessArticle

Numerical Investigation for the Impact of Single Groove on the Stall Margin Improvement and the Unsteadiness of Tip Leakage Flow in a Counter-Rotating Axial Flow Compressor

by Xiaochen Mao^*, Bo Liu and Hang Zhao

School of Power and Energy, Northwestern Polytechnical University, Xi’an 710072, China

Energies 2017, 10(8), 1153; https://doi.org/10.3390/en10081153 - 7 Aug 2017

Cited by 8 | Viewed by 4537

Abstract

A low-speed counter-rotating axial flow compressor (CRAC) with single circumferential grooved casing treatment (CT) was investigated numerically. Both steady and time-accurate numerical calculations were performed to study the effects of the single grooved CTs over the rear rotor on the stability enhancement and [...] Read more.

A low-speed counter-rotating axial flow compressor (CRAC) with single circumferential grooved casing treatment (CT) was investigated numerically. Both steady and time-accurate numerical calculations were performed to study the effects of the single grooved CTs over the rear rotor on the stability enhancement and the unsteadiness of tip leakage flow (TLF) in the CRAC. Parametric studies indicate that the best position of the single groove should be located near about 20% axial tip chord in terms of the stall margin improvement (SMI). The coincidence of the effective CT locations and the high fluctuating region on blade pressure surface in the smooth wall case shows that the unsteadiness of TLF plays an important role in the stall inception process. Frequency analysis for the static pressure signals near the blade tip shows that both the disappearance of the low frequency components and the suppression of unsteady TLF are beneficial to the SMI. Detailed observation of the flow structures illustrates that the action of the grooves on the different parts of TLF is responsible for the difference of SMI in the CTs. It is more effective to improve the flow stability by controlling the critical TLF released from near the mid-chord. Full article

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

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19 pages, 26444 KiB

Open AccessArticle

Analysis of Roadheader for Breaking Rock Containing Holes under Confining Pressures

by Zenghui Liu^1,2, Changlong Du^1,*, Hongxiang Jiang¹ and Kai Liu²

¹ School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou 221116, China

² Department of Civil Engineering, Monash University, Melbourne, VIC 3800, Australia

Energies 2017, 10(8), 1154; https://doi.org/10.3390/en10081154 - 7 Aug 2017

Cited by 20 | Viewed by 5562

Abstract

Deep underground mines have high energy consumption due to the need to overcome the confining pressure. This study investigates the characteristics of the roadheader used for breaking rock containing a different number and size of holes under different confining pressures. A series of [...] Read more.

Deep underground mines have high energy consumption due to the need to overcome the confining pressure. This study investigates the characteristics of the roadheader used for breaking rock containing a different number and size of holes under different confining pressures. A series of simulations were conducted using the LS-DYNA software to study the cutting torque, thrust force, specific energy, and failure mode during the rock-breaking process. Following this, the results were further validated with experimental data. It was found that the decrease in energy rates of rock containing different numbers (1, 5, 9, and 13) of holes are 12.7%, 19.3%, 25.9%, and 38.4%, respectively. Meanwhile, the decrease in energy rates of rock with different hole diameters (35, 45, 55, and 65 mm) are 10.5%, 19.3%, 24.6%, and 28.1%, respectively. Under the confining pressure of 10 MPa, the increase in the torque of the rock without holes is 23.5%, while this increase in the rock with five holes is 7.9%. This indicates that the high torque and energy consumption caused by the confining pressure can be reduced by drilling holes in the rock. Full article

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12 pages, 748 KiB

Open AccessArticle

Nonlinear Adaptive Control of Heat Transfer Fluid Temperature in a Parabolic Trough Solar Power Plant

by Antonio Nevado Reviriego^1,*,†, Félix Hernández-del-Olmo²

and Lourdes Álvarez-Barcia³

¹ Departamento Ingeniería Eléctrica, Eletrónica y de Control, Universidad Nacional de Educación a Distancia (UNED), 28040 Madrid, Spain

² Departamento Inteligencia Artificial, UNED, 28040 Madrid, Spain

³ Departamento Ingeniería Eléctrica, Eletrónica, Computadoras y Sistemas, Universidad de Oviedo, 33203 Gijón, Spain

^† Current address: Escuela Técnica Superior de Ingenieros Industriales, UNED, Juan del Rosal 12, Ciudad Universitaria, 28040 Madrid, Spain.

Energies 2017, 10(8), 1155; https://doi.org/10.3390/en10081155 - 7 Aug 2017

Cited by 15 | Viewed by 3985

Abstract

Control of highly nonlinear processes such as solar collector fields is usually a challenging task. A common approach to this problem involves deploying a set of operation point range-specific controllers, whose actions are to be combined in a switching strategy. Discontinuities in control [...] Read more.

Control of highly nonlinear processes such as solar collector fields is usually a challenging task. A common approach to this problem involves deploying a set of operation point range-specific controllers, whose actions are to be combined in a switching strategy. Discontinuities in control actions upon switching may lead to instabilities and, therefore, achieving bumpless transitions is always a concern. In addition, linear adaptive predictive controllers need to cope with nonlinearities by using high adaptation speeds, often leading to model vulnerability in the presence of aggressive perturbations. Finally, most of the proposed solutions rely on complex plant model developments. In this work, a multivariable nonlinear model-based adaptive predictive controller has been developed and tested against a parabolic trough solar power plant simulation. Since the model employed by this controller accounts for process nonlinearities, adaptation speed can be dramatically reduced, therefore increasing model robustness. The controller is easily initialized and is able to identify and track the process dynamics, including its nonlinearities as it evolves with time, thus requiring neither process up-front modeling nor switching. The presented controller outperforms its linear counterpart both in terms of accuracy and robustness and, due to the generality of its design, it is expected to be applicable to a wide class of linear and nonlinear processes. Full article

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19 pages, 8978 KiB

Open AccessArticle

Numerical Investigation of the Effect of Variable Baffle Spacing on the Thermal Performance of a Shell and Tube Heat Exchanger

by Halil Bayram^1,2 and Gökhan Sevilgen^1,*

¹ Faculty of Engineering, Department of Automotive Engineering, Uludağ University, Görükle, Bursa 16059, Turkey

² Faculty of Technology, Department of Automotive Engineering, Amasya University, Amasya 05100, Turkey

Energies 2017, 10(8), 1156; https://doi.org/10.3390/en10081156 - 7 Aug 2017

Cited by 33 | Viewed by 11091 | Correction

Abstract

In this present study, numerical and theoretical analysis were both used to investigate the effect of the variable baffle spacing on the thermal characteristics of a small shell and tube heat exchanger. The numerical study was performed by using a three dimensional computational [...] Read more.

In this present study, numerical and theoretical analysis were both used to investigate the effect of the variable baffle spacing on the thermal characteristics of a small shell and tube heat exchanger. The numerical study was performed by using a three dimensional computational fluid dynamics (CFD) method and the computations were performed under steady-state conditions. We employed five different cases where the first had equal baffle spacing and the others had variable ones considering different configurations for balancing the pressure drop on the shell side. Theoretical calculations were run using the Bell-Delaware and Kern methods which are the most commonly used methods in the available literature. We show that the thermal performance of a shell and tube heat exchanger can be improved by evaluating together the results of the CFD and Bell-Delaware methods. From the numerical results, we can say that variable spacing with centered baffle spacing scheme can be proposed as an alternative shell side construction layout compared to an equal baffle spacing scheme. The numerical results were in good agreement with the theoretical data in the available literature. Full article

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17 pages, 5729 KiB

Open AccessArticle

Analysis of Cooling Effectiveness and Temperature Uniformity in a Battery Pack for Cylindrical Batteries

by Seham Shahid^* and Martin Agelin-Chaab

Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, ON L1H 7K4, Canada

Energies 2017, 10(8), 1157; https://doi.org/10.3390/en10081157 - 7 Aug 2017

Cited by 84 | Viewed by 8256

Abstract

In this paper, techniques to improve cooling and temperature uniformity in a simple battery pack are examined. Four battery pack configurations are developed. In the first configuration, an inlet plenum is added to a simple battery pack. In the second configuration, jet inlets [...] Read more.

In this paper, techniques to improve cooling and temperature uniformity in a simple battery pack are examined. Four battery pack configurations are developed. In the first configuration, an inlet plenum is added to a simple battery pack. In the second configuration, jet inlets are incorporated along with the inlet plenum, and in the third configuration, multiple vortex generators are added in addition to the inlet plenum. Finally, in the fourth configuration, an inlet plenum, jet inlets, and multiple vortex generators are incorporated into the battery pack. The results conclude that by adding inlet plenum, multiple vortex generators, and jet inlets in the same configuration, significant improvements are observed. The results also show that the maximum temperature of the battery pack is reduced by ~5%, and the temperature difference between the maximum temperature and the minimum temperature exhibited by the battery pack is reduced by 21.5%. Moreover, there is a ~16% improvement in the temperature uniformity of a single cell. Full article

(This article belongs to the Collection Electric and Hybrid Vehicles Collection)

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19 pages, 4789 KiB

Open AccessArticle

A Full Frequency-Dependent Cable Model for the Calculation of Fast Transients

by Abdullah Hoshmeh^1,* and Uwe Schmidt²

¹ Department of Electrical Engineering and Information Technology, Chemnitz University of Technology, 09126 Chemnitz, Germany

² Department of Electrical Engineering and Informatics, University of Applied Sciences Zittau/Goerlitz, 02763 Zittau, Germany

Energies 2017, 10(8), 1158; https://doi.org/10.3390/en10081158 - 7 Aug 2017

Cited by 15 | Viewed by 5490

Abstract

The calculation of frequency-dependent cable parameters is essential for simulations of transient phenomena in electrical power systems. The simulation of transients is more complicated than the calculation of currents and voltages in the nominal frequency range. The model has to represent the frequency [...] Read more.

The calculation of frequency-dependent cable parameters is essential for simulations of transient phenomena in electrical power systems. The simulation of transients is more complicated than the calculation of currents and voltages in the nominal frequency range. The model has to represent the frequency dependency and the wave propagation behavior of cable lines. The introduced model combines an improved subconductor method for the determination of the frequency-dependent parameters and a PI section wave propagation model. The subconductor method considers the skin and proximity effect in all conductors for frequency ranges up to few megahertz. The subconductor method method yields accurate results. The wave propagation part of the cable model is based on a cascaded PI section model. A modal transformation technique has been used for the calculation in the time domain. The frequency-dependent elements of the related modal transformation matrices have been fitted with rational functions. The frequency dependence of cable parameters has been reproduced using a vector fitting algorithm and has been implemented into an resistor-inductor-capacitor network (RLC network) for each PI section. The proposed full model has been validated with measured data. Full article

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17 pages, 2704 KiB

Open AccessArticle

A Residential Energy Hub Model with a Concentrating Solar Power Plant and Electric Vehicles

by Feng Qi¹, Fushuan Wen^2,3,*, Xunyuan Liu¹ and Md. Abdus Salam⁴

¹ School of Electrical Engineering, Zhejiang University, No. 38 Zheda Rd., Hangzhou 310027, China

² Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Vietnam

³ Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

⁴ Department of Electrical and Electronic Engineering, Universiti Teknologi Brunei, Bandar Seri Begawan BE1410, Brunei

Energies 2017, 10(8), 1159; https://doi.org/10.3390/en10081159 - 7 Aug 2017

Cited by 31 | Viewed by 5850

Abstract

Renewable energy generation and electric vehicles (EVs) have attracted much attention in the past decade due to increasingly serious environmental problems as well as less and less fossil energy reserves. Moreover, the forms of energy utilization are changing with the development of information [...] Read more.

Renewable energy generation and electric vehicles (EVs) have attracted much attention in the past decade due to increasingly serious environmental problems as well as less and less fossil energy reserves. Moreover, the forms of energy utilization are changing with the development of information technology and energy technology. The term “energy hub” has been introduced to represent an entity with the capability of energy production, conversion and storage. A residential quarter energy-hub-optimization model including a concentrating solar power (CSP) unit is proposed in this work, with solar energy and electricity as its inputs to supply thermal and electrical demands, and the operating objective is to minimize the involved operation costs. The optimization model is a mixed integer linear programming (MILP) problem. Demand side management (DSM) is next implemented by modeling shiftable electrical loads such as EVs and washers, as well as flexible thermal loads such as hot water. Finally, the developed optimization model is solved with the commercial CPLEX solver based on the YALMIP/MATLAB toolbox, and sample examples are provided for demonstrating the features of the proposed method. Full article

(This article belongs to the Special Issue Theory and Application of Computational Intelligence in Electric Vehicles and their Integration within Smart Energy Networks)

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16 pages, 14892 KiB

Open AccessArticle

A Back-EMF Estimation Error Compensation Method for Accurate Rotor Position Estimation of Surface Mounted Permanent Magnet Synchronous Motors

by Tae-Uk Jung, Jung-Hoon Jang and Chang-Seok Park^*

Department of Electrical Engineering, Kyungnam University, Changwon 51767, Korea

Energies 2017, 10(8), 1160; https://doi.org/10.3390/en10081160 - 7 Aug 2017

Cited by 16 | Viewed by 6993

Abstract

This paper proposes a back electromotive force estimation error compensation method for accurate rotor position estimation of surface mounted permanent magnet synchronous motors. When estimating the rotor position of surface mounted permanent magnet synchronous motor sensorless drives, a direct current offset error component [...] Read more.

This paper proposes a back electromotive force estimation error compensation method for accurate rotor position estimation of surface mounted permanent magnet synchronous motors. When estimating the rotor position of surface mounted permanent magnet synchronous motor sensorless drives, a direct current offset error component occurs in the voltage sensor. As a result, the rotor position is distorted and the sensorless control in surface mounted permanent magnet synchronous motor is degraded. In addition, the dq-axis voltages in the synchronous reference frame have the direct current offset error component, ripples compared with the motor frequency under the distorted rotor position. In this paper, the effects of the direct current offset errors are analyzed based on the synchronous reference frame phase locked loop. To remove this direct current offset error component, a d-axis voltage is converted into a synchronous reference frame again to compensate. In other words, it is a dual synchronous coordinate conversion compensation method. The compensator utilizes a proportional-integral controller that compensates by estimating the direct current offset error component. The proposed method is useful for the improvement of surface mounted permanent magnet synchronous motor sensorless control and operating performance. The effectiveness of the proposed algorithm is verified through PSIM simulation and experimental results. Full article

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

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17 pages, 4188 KiB

Open AccessArticle

Single-Phase Autonomous Induction Generator with Single-Phase Rotor

by Yotam Frechter, Natan Ben Hail and Raul Rabinovici^*

Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel

Energies 2017, 10(8), 1162; https://doi.org/10.3390/en10081162 - 7 Aug 2017

Viewed by 2962

Abstract

An autonomous induction generator (IG) with an asymmetric configuration, in which both the stator and the rotor are single-phase, is often formed when a triple-phase wound rotor loses connection to a winding component while running. The machine still works and is shown to [...] Read more.

An autonomous induction generator (IG) with an asymmetric configuration, in which both the stator and the rotor are single-phase, is often formed when a triple-phase wound rotor loses connection to a winding component while running. The machine still works and is shown to be capable of generating modulated waveforms. Equations can help as an IG design guideline. The first harmonics of the mutual inductance effect on the IG is explained by its steady-state equivalent circuit. Full article

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15 pages, 4409 KiB

Open AccessArticle

A Methodology for Determining Permissible Operating Region of Power Systems According to Conditions of Static Stability Limit

by Van Duong Ngo¹, Dinh Duong Le^2,*, Kim Hung Le², Van Kien Pham² and Alberto Berizzi³

¹ The University of Danang, 41 Le Duan st., Danang 59000, Vietnam

² Department of Electrical Engineering, The University of Danang—University of Science and Technology, 54 Nguyen Luong Bang st., Danang 59000, Vietnam

³ Department of Energy, Polytechnic University of Milan, via La Masa, 34, 20156 Milan, Italy

Energies 2017, 10(8), 1163; https://doi.org/10.3390/en10081163 - 17 Aug 2017

Cited by 6 | Viewed by 4415

Abstract

For power systems with long-distance ultra-high-voltage (UHV) transmission lines, power transmission limits are often determined by static stability limits. Therefore, the assessment of stability and finding solutions to improve the stability reserve are essential for the operation of the system. This article presents [...] Read more.

For power systems with long-distance ultra-high-voltage (UHV) transmission lines, power transmission limits are often determined by static stability limits. Therefore, the assessment of stability and finding solutions to improve the stability reserve are essential for the operation of the system. This article presents an analytical approach to construct limit characteristics according to static stability conditions on a power plane. Based on the approach proposed, a program is developed and tested on a system with long-distance UHV transmission lines, showing a good performance. Full article

(This article belongs to the Special Issue Distributed and Renewable Power Generation)

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14 pages, 2538 KiB

Open AccessArticle

Impact of Firms’ Observation Network on the Carbon Market

by Song-min Yu¹

and Lei Zhu^2,*

¹ Institute of Science and Development, Chinese Academy of Sciences, Beijing 100190, China

² School of Economics & Management, Beihang University, Beijing 100191, China

Energies 2017, 10(8), 1164; https://doi.org/10.3390/en10081164 - 8 Aug 2017

Cited by 5 | Viewed by 3618

Abstract

Given the important role of the carbon market in fighting against global warming, the impact of information on the efficiency of the scheme is a critical issue for both its designers and the central authority. At least two aspects of information are worthy [...] Read more.

Given the important role of the carbon market in fighting against global warming, the impact of information on the efficiency of the scheme is a critical issue for both its designers and the central authority. At least two aspects of information are worthy of attention. First is the incompleteness of information, with which the firms make decisions to minimize their abatement cost and maximize their profit. Second is the mechanism of information transmission. Based on an agent-based framework we established in our previous work, we explicitly depicted the first aspect and analysed its impact on firms’ decision-making and consequent market results. In this paper, we focus on the second aspect, transmission mechanism of information, which is depicted as an observation network among firms. The basis in reality is that the firms in the carbon market are usually from different industries or areas, and it is relatively easier to observe the conditions of firms from the same industry or area, corresponding to neighbours in the network. Four scenarios are considered, including no network, regular network, random network, and small-world network. We find that the existence of an observation network has a significant influence on the market results. Full article

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

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15 pages, 2352 KiB

Open AccessArticle

An Economical Evaluation of Anaerobic Digestion Plants Fed with Organic Agro-Industrial Waste

by Maurizio Carlini¹

, Enrico Maria Mosconi¹

, Sonia Castellucci^1,*

, Mauro Villarini²

and Andrea Colantoni²

¹ Department of Economic, Engineering, Society and Business Organization (DEIM), Tuscia University, 01100 Viterbo, Italy

² Department of Agriculture and Forestry Science (DAFNE), Tuscia University, 01100 Viterbo, Italy

Energies 2017, 10(8), 1165; https://doi.org/10.3390/en10081165 - 8 Aug 2017

Cited by 82 | Viewed by 7435

Abstract

Anaerobic co-digestion technology is increasingly used to simultaneously treat solid and liquid organic waste to balance nutrient content, to reduce the negative effects of toxic compounds in the process, and to increase biogas yield. The aim of this study was to analyze the [...] Read more.

Anaerobic co-digestion technology is increasingly used to simultaneously treat solid and liquid organic waste to balance nutrient content, to reduce the negative effects of toxic compounds in the process, and to increase biogas yield. The aim of this study was to analyze the economic performance of co-digestion plants fed with agro-industrial wastes as a function of installed power, with a method of discounted cash flow. The study focused on Italian framework conditions concerning payment for electricity produced by anaerobic digestion (AD) plants as well as the production costs. The economic analysis was carried out using three different plant sizes: 100 kW, 500 kW, and 1000 kW, which are representative of biogas plants in Italy. The study showed that the improvement of the break-point is closely linked to the increase in corresponding plant size. Given the assumptions of the simulation, the payback for the 100 kW plant was nine years for both the all-inclusive tariff and the basic feed-in tariff (BFT). Regarding the 500 kW and 1000 kW plants, the payback periods were five and four years, respectively. Full article

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

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20 pages, 2279 KiB

Open AccessArticle

How Can China Achieve Its Nationally Determined Contribution Targets Combining Emissions Trading Scheme and Renewable Energy Policies?

by Jie Wu¹, Ying Fan²

and Yan Xia^3,4,*

¹ School of Statistics and Management, Shanghai University of Finance and Economics, Shanghai 200433, China

² School of Economics and Management, Beihang University, Beijing 100191, China

³ Institutes of Science and Development, Chinese Academy of Sciences, Beijing 100190, China

⁴ School of Public Policy and Management, University of Chinese Academy of Sciences, Beijing 100049, China

Energies 2017, 10(8), 1166; https://doi.org/10.3390/en10081166 - 8 Aug 2017

Cited by 33 | Viewed by 6676

Abstract

The adoption of emissions trading scheme (ETS) and renewable energy sources (RES) policies have been essential to achieving China’s national targets for reducing CO₂ emissions and developing non-fossil energy sources. The combination of ETS and RES policies raises an important issue: What [...] Read more.

The adoption of emissions trading scheme (ETS) and renewable energy sources (RES) policies have been essential to achieving China’s national targets for reducing CO₂ emissions and developing non-fossil energy sources. The combination of ETS and RES policies raises an important issue: What is the effect of combining ETS and RES policies on the existing carbon market and economy? Focusing on the design of the nationwide carbon market, this paper uses a multi-regional computable general equilibrium (CGE) model to analyze the economic impacts of ETS policy when combined with RES policies in China. The results show that China’s annual ETS emissions cap should decrease by 0.3% to maintain stable CO₂ prices and achieve the targets in China’s intended nationally determined contribution (INDC). It is estimated that the CO₂ price on the nationwide carbon market would decrease by 11–64% when the renewable energy subsidy rate increases from 20 to 100%, and the total trading volume would decrease by 3–25%. The results also show that the combination of an ETS and a feed-in tariff (FIT) results in greater GDP cost and welfare loss in all Chinese regions, increasing the total social cost by 0.01–0.06%. Full article

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

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17 pages, 2336 KiB

Open AccessArticle

Optimizing Energy Efficiency in Operating Built Environment Assets through Building Information Modeling: A Case Study

by Ioan Petri^1,*

, Sylvain Kubicki²

, Yacine Rezgui¹, Annie Guerriero² and Haijiang Li¹

¹ BRE Institute in Sustainable Engineering, School of Engineering, Cardiff University, Cardiff CF243AA, UK

² Luxembourg Institute of Science and Technology (LIST), L-4362 Esch-sur-Alzette, Luxembourg, Luxembourg

Energies 2017, 10(8), 1167; https://doi.org/10.3390/en10081167 - 8 Aug 2017

Cited by 84 | Viewed by 15392

Abstract

Reducing carbon emissions and addressing environmental policies in the construction domain has been intensively explored with solutions ranging from energy efficiency techniques with building informatics to user behavior modelling and monitoring. Such strategies have managed to improve current practices in managing buildings, however [...] Read more.

Reducing carbon emissions and addressing environmental policies in the construction domain has been intensively explored with solutions ranging from energy efficiency techniques with building informatics to user behavior modelling and monitoring. Such strategies have managed to improve current practices in managing buildings, however decarbonizing the built environment and reducing the energy performance gap remains a complex undertaking that requires more comprehensive and sustainable solutions. In this context, building information modelling (BIM), can help the sustainability agenda as the digitalization of product and process information provides a unique opportunity to optimize energy-efficiency-related decisions across the entire lifecycle and supply chain. BIM is foreseen as a means to waste and emissions reduction, performance gap minimization, in-use energy enhancements, and total lifecycle assessment. It also targets the whole supply chain related to design, construction, as well as management and use of facilities, at the different qualifications levels (including blue-collar workers). In this paper, we present how building information modelling can be utilized to address energy efficiency in buildings in the operation phase, greatly contributing to achieving carbon emissions targets. In this paper, we provide two main contributions: (i) we present a BIM-oriented methodology for supporting building energy optimization, based on which we identify few training directions with regards to BIM, and (ii) we provide an application use case as identified in the European research project “Sporte2” to demonstrate the advantages of BIM in energy efficiency with respect to several energy metrics. Full article

(This article belongs to the Special Issue Zero-Carbon Buildings)

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20 pages, 3589 KiB

Open AccessArticle

Short-Term Load Forecasting Using EMD-LSTM Neural Networks with a Xgboost Algorithm for Feature Importance Evaluation

by Huiting Zheng^*,†, Jiabin Yuan^† and Long Chen^†

¹ College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

^† These authors contributed equally to this work.

Energies 2017, 10(8), 1168; https://doi.org/10.3390/en10081168 - 8 Aug 2017

Cited by 574 | Viewed by 27070

Abstract

Accurate load forecasting is an important issue for the reliable and efficient operation of a power system. This study presents a hybrid algorithm that combines similar days (SD) selection, empirical mode decomposition (EMD), and long short-term memory (LSTM) neural networks to construct a [...] Read more.

Accurate load forecasting is an important issue for the reliable and efficient operation of a power system. This study presents a hybrid algorithm that combines similar days (SD) selection, empirical mode decomposition (EMD), and long short-term memory (LSTM) neural networks to construct a prediction model (i.e., SD-EMD-LSTM) for short-term load forecasting. The extreme gradient boosting-based weighted k-means algorithm is used to evaluate the similarity between the forecasting and historical days. The EMD method is employed to decompose the SD load to several intrinsic mode functions (IMFs) and residual. Separated LSTM neural networks were also employed to forecast each IMF and residual. Lastly, the forecasting values from each LSTM model were reconstructed. Numerical testing demonstrates that the SD-EMD-LSTM method can accurately forecast the electric load. Full article

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

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16 pages, 7996 KiB

Open AccessArticle

Parametric Design of an Ultrahigh-Head Pump-Turbine Runner Based on Multiobjective Optimization

by Linhai Liu¹, Baoshan Zhu^1,*

, Li Bai², Xiaobing Liu² and Yue Zhao³

¹ Department of Thermal Engineering, State Key Laboratory of Hydro Science and Engineering, Tsinghua University, Beijing 100084, China

² School of Energy and Power Engineering, Xihua University, Chengdu 610039, China

³ Harbin Institute of Large Electrical Machinery, Harbin 150040, China

Energies 2017, 10(8), 1169; https://doi.org/10.3390/en10081169 - 8 Aug 2017

Cited by 39 | Viewed by 7099

Abstract

Pumped hydro energy storage (PHES) is currently the only proven large-scale energy storage technology. Frequent changes between pump and turbine operations pose significant challenges in the design of a pump-turbine runner with high efficiency and stability, especially for ultrahigh-head reversible pump-turbine runners. In [...] Read more.

Pumped hydro energy storage (PHES) is currently the only proven large-scale energy storage technology. Frequent changes between pump and turbine operations pose significant challenges in the design of a pump-turbine runner with high efficiency and stability, especially for ultrahigh-head reversible pump-turbine runners. In the present paper, a multiobjective optimization design system is used to develop an ultrahigh-head runner with good overall performance. An optimum configuration was selected from the optimization results. The effects of key design parameters—namely blade loading and blade lean—were then investigated in order to determine their effects on runner efficiency and cavitation characteristics. The paper highlights the guidelines for application of inverse design method to high-head reversible pump-turbine runners. Middle-loaded blade loading distribution on the hub, back-loaded distribution on the shroud, and large positive blade lean angle on the high pressure side are good for the improvement of runner power performance. The cavitation characteristic is mainly influenced by the blade loading distribution near the low pressure side, and large blade lean angles have a negative impact on runner cavitation characteristics. Full article

(This article belongs to the Special Issue Advanced Energy Storage Technologies and Their Applications (AESA))

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11 pages, 2092 KiB

Open AccessArticle

Insulation Strength and Decomposition Characteristics of a C₆F₁₂O and N₂ Gas Mixture

by Xiaoxing Zhang^*, Shuangshuang Tian, Song Xiao, Zaitao Deng, Yi Li

and Ju Tang

School of Electrical Engineering, Wuhan University, Wuhan 430072, China

Energies 2017, 10(8), 1170; https://doi.org/10.3390/en10081170 - 9 Aug 2017

Cited by 59 | Viewed by 5578

Abstract

This paper explores the decomposition characteristics of a new type of environmentally friendly insulating gas C₆F₁₂O and N₂ mixed gas under AC voltage. The breakdown behavior of 3% C₆F₁₂O and N₂ mixed gas [...] Read more.

This paper explores the decomposition characteristics of a new type of environmentally friendly insulating gas C₆F₁₂O and N₂ mixed gas under AC voltage. The breakdown behavior of 3% C₆F₁₂O and N₂ mixed gas in quasi-uniform field was investigated through a breakdown experiment. The self-recovery of the mixed gas was analyzed by 100 breakdown experiments. The decomposition products of C₆F₁₂O and N₂ under breakdown voltage were determined by gas chromatography–mass spectrometer (GC-MS). Finally, the decomposition process of the products was calculated by density functional theory, and the ionization energy, affinity, and molecular orbital gap of the decomposition products were also calculated. The properties of the decomposition products were analyzed from the aspects of insulation and environmental protection. The experimental results show that the 3% C₆F₁₂O and N₂ mixed gas did not show a downward trend over 100 breakdown tests under a 0.10 MPa breakdown voltage. The decomposition products after breakdown were CF₄, C₂F₆, C₃F₆, C₃F₈, C₄F₁₀, and C₅F₁₂. The ionization energies of several decomposition products are more than 10 eV. The Global Warming Potential (GWP) values of the main products are lower than SF₆. C₂F₆, C₃F₈, and C₄F₁₀ have better insulation properties. Full article

(This article belongs to the Special Issue Selected Papers from 2016 IEEE International Conference on High Voltage Engineering (ICHVE 2016))

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28 pages, 6367 KiB

Open AccessArticle

A Techno-Economic Study of an Entirely Renewable Energy-Based Power Supply for North America for 2030 Conditions

by Arman Aghahosseini^*

, Dmitrii Bogdanov and Christian Breyer

Department of Electrical Engineering, School of Energy Systems, Lappeenranta University of Technology, Skinnarilankatu 34, Lappeenranta 53850, Finland

Energies 2017, 10(8), 1171; https://doi.org/10.3390/en10081171 - 9 Aug 2017

Cited by 84 | Viewed by 14780

Abstract

In this study power generation and demand are matched through a least-cost mix of renewable energy (RE) resources and storage technologies for North America by 2030. The study is performed using an hourly resolved model based on a linear optimization algorithm. The geographical, [...] Read more.

In this study power generation and demand are matched through a least-cost mix of renewable energy (RE) resources and storage technologies for North America by 2030. The study is performed using an hourly resolved model based on a linear optimization algorithm. The geographical, technical and economic potentials of different forms of RE resources enable the option of building a super grid between different North American regions. North America (including the U.S., Canada and Mexico in this paper), is divided into 20 sub-regions based on their population, demand, area and electricity grid structure. Four scenarios have been evaluated: region-wide, country-wide, area-wide and an integrated scenario. The levelised cost of electricity is found to be quite attractive in such a system, with the range from 63 €/MWh_el in a decentralized case and 42 €/MWh_el in a more centralized and integrated scenario. Electrical grid interconnections significantly reduce the storage requirement and overall cost of the energy system. Among all RE resources, wind and solar PV are found to be the least-cost options and hence the main contributors to fossil fuel substitution. The results clearly show that a 100% RE-based system is feasible and a real policy option at a modest cost. However, such a tremendous transition will not be possible in a short time if policy-makers, energy investors and other relevant organizations do not support the proposed system. Full article

(This article belongs to the Special Issue Sustainable Energy Technologies)

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26 pages, 3922 KiB

Open AccessArticle

Identification of Financing Barriers to Energy Efficiency in Small and Medium-Sized Enterprises by Integrating the Fuzzy Delphi and Fuzzy DEMATEL Approaches

by Jun Dong and Huijuan Huo^*

School of Economics and Management, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(8), 1172; https://doi.org/10.3390/en10081172 - 9 Aug 2017

Cited by 31 | Viewed by 5967

Abstract

Energy efficiency is one of the most practical ways for China to simultaneously tackle environmental issues and achieve sustainable development. However, the issue of inadequate capital inflows is a bottleneck in energy efficiency projects, especially for small and medium-sized enterprises (SMEs). This study [...] Read more.

Energy efficiency is one of the most practical ways for China to simultaneously tackle environmental issues and achieve sustainable development. However, the issue of inadequate capital inflows is a bottleneck in energy efficiency projects, especially for small and medium-sized enterprises (SMEs). This study focuses on the complicated financial barriers to effectively promoting such projects for SMEs. A hybrid framework was proposed to recognize the most obvious financing barriers under uncertain circumstances. Potential barriers were collected firstly to build an index system, including the five dimensions of “policy and regulation”, “economic market”, “financial institutions”, “behavior” and “economic non-market”. Then, this paper introduced a novel way to combine a fuzzy Delphi and a fuzzy decision making trial and evaluation laboratory (DEMATEL) method. The fuzzy Delphi method was applied to extract significant factors from potential barriers. To analyze a series of causal relationships, the fuzzy DEMATEL approach was employed. Moreover, triangular fuzzy numbers (TFNs) are used firstly to express vague linguistic ratings in the proposed framework. Based on the experts’ opinions, seventeen significant factors were chosen to assemble a final evaluation system. Eleven key barriers were identified by analyzing cause-effect relations, including “slight fiscal incentives”, “inadequate energy market trading mechanisms”, “a low priority of energy saving issues”, etc. The key barriers affiliated with “market” and “policy and regulation” are much more important than the others. Except for B11 and B53, the others are the original factors. Finally, we listed relevant suggested measures to help SMEs, government departments and financial institutions overcome the key barriers. Full article

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25 pages, 3959 KiB

Open AccessArticle

A “New-Deal” for the Development of Photovoltaic Investments in Greece? A Parametric Techno-Economic Assessment

by Panagiotis Anagnostopoulos^1,2, Niki-Artemis Spyridaki³

and Alexandros Flamos^3,*

¹ School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), 9, Iroon Polytechniou Str., 15780 Athens, Greece

² Public Power Corporation Renewables (PPCR), 3, Kapodistriou Str., Ag. Paraskevi, 15343 Athens, Greece

³ Department of Industrial Management & Technology, University of Piraeus (UNIPI), 80, Karaoli & Dimitriou Str., 18534 Piraeus, Greece

Energies 2017, 10(8), 1173; https://doi.org/10.3390/en10081173 - 9 Aug 2017

Cited by 20 | Viewed by 5301

Abstract

The aim of this paper is to identify the financial impact imposed by cost containment measures and especially by the feed in tariff (FiT) reduction upon the profitability of different photovoltaic (PV) investments and the electricity charge faced by consumers. A fully parametric [...] Read more.

The aim of this paper is to identify the financial impact imposed by cost containment measures and especially by the feed in tariff (FiT) reduction upon the profitability of different photovoltaic (PV) investments and the electricity charge faced by consumers. A fully parametric analysis is carried out by varying the following parameters: total installation costs based on their activation date, interest rate for a bank loan, use of a construction subsidy, tax imposition levels, the solidarity surcharge differentiated by the activation and the purchase agreement date and the issuance of credit invoice. During the simulations the simple payback period, the internal rate of return and the profitability index were calculated for the most common investment cases. These were identified through empirical observations on the deployment of PV stations. The profitability of PV stations connected to the medium voltage network were by far affected the most by the cutback while farmers’ PV stations and PV rooftop systems were comparatively less affected. Parameters such as the size of the station and the PV activation date were crucial for the assessment of the viability of PV stations. From a social perspective, the FiT cutback prevented an additional 40% increase in the electricity charge paid by electricity consumers. Full article

(This article belongs to the Special Issue Sustainable and Renewable Energy Systems)

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10 pages, 2859 KiB

Open AccessArticle

Collaborative Scheduling between OSPPs and Gasholders in Steel Mill under Time-of-Use Power Price

by Juxian Hao, Xiancong Zhao and Hao Bai^*

School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

Energies 2017, 10(8), 1174; https://doi.org/10.3390/en10081174 - 9 Aug 2017

Cited by 7 | Viewed by 3856

Abstract

Byproduct gases generated during steel production process are the main fuels for on-site power plants (OSPPs) in steel enterprises. Recently, with the implementation of time-of-use (TOU) power price in China, increasing attention has been paid to the collaborative scheduling between OSPPs and gasholders. [...] Read more.

Byproduct gases generated during steel production process are the main fuels for on-site power plants (OSPPs) in steel enterprises. Recently, with the implementation of time-of-use (TOU) power price in China, increasing attention has been paid to the collaborative scheduling between OSPPs and gasholders. However, the load shifting potential of OSPPs has seldom been discussed in previous studies. In this paper, a mixed integer linear programming (MILP)-based scheduling model is built to evaluate the load shifting potential and the corresponding economic benefits. A case study is conducted on two steel enterprises with different configurations of OSPPs, and the optimal operation strategy is also discussed. Full article

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

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17 pages, 10665 KiB

Open AccessArticle

A Sliding Surface-Regulated Current-Mode Pulse-Width Modulation Controller for a Digital Signal Processor-Based Single Ended Primary Inductor Converter-Type Power Factor Correction Rectifier

by Hsin-Jang Shieh^* and Ying-Zuo Chen

Department of Electrical Engineering, National Dong Hwa University, Hualien 97401, Taiwan

Energies 2017, 10(8), 1175; https://doi.org/10.3390/en10081175 - 9 Aug 2017

Cited by 7 | Viewed by 5200

Abstract

To efficiently supply wide-range DC voltage from a pulse-width modulation (PWM) rectifier, this paper presents a single-phase, full-wave, diode-bridge, single-ended primary-inductor converter-type (SEPIC-type) power-factor-correction (PFC) rectifier in continuous conduction mode with a sliding surface-regulated current-mode PWM controller. According to the switched-mode operation of [...] Read more.

To efficiently supply wide-range DC voltage from a pulse-width modulation (PWM) rectifier, this paper presents a single-phase, full-wave, diode-bridge, single-ended primary-inductor converter-type (SEPIC-type) power-factor-correction (PFC) rectifier in continuous conduction mode with a sliding surface-regulated current-mode PWM controller. According to the switched-mode operation of the rectifier, a fourth-order switch model of the SEPIC is derived. From the fourth-order model, a simplified state-averaged model which approximately describes the dynamic behaviors of both the output voltage and inductor current is proposed. Then, from the simplified state-averaged model, the sliding surface-regulated current-mode PWM controller for the SEPIC-type PFC rectifier is proposed. The sliding surface-regulated current-mode PWM controller comprises a sliding-mode voltage controller in outer loop for robust control of the output DC-voltage and a sliding-mode current controller in inner loop for phase-synchronized control of the inductor current. For experimental studies, implementation of the proposed control algorithm in a DSP controller and a laboratory prototype of the SEPIC-type rectifier with the DSP-based PWM controller were carried out. Experimental results from the DSP controller-applied SEPIC-type rectifier are illustrated to confirm the validity of the proposed controller for practical applications. Full article

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

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19 pages, 1980 KiB

Open AccessArticle

Risk Assessment of Micro Energy Grid Protection Layers

by Hossam A. Gabbar^1,2,* and Yahya Koraz²

¹ Faculty of Energy Systems and Nuclear Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON L1H7K4, Canada

² Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON L1H7K4, Canada

Energies 2017, 10(8), 1176; https://doi.org/10.3390/en10081176 - 10 Aug 2017

Cited by 6 | Viewed by 6041

Abstract

Micro energy grids (MEGs) are used extensively to meet the combined electricity, heating, and cooling energy demands for all types of customers. This paper develops a hazard matrix for a MEG and utilizes two advanced risk modeling approaches (fault tree and layer of [...] Read more.

Micro energy grids (MEGs) are used extensively to meet the combined electricity, heating, and cooling energy demands for all types of customers. This paper develops a hazard matrix for a MEG and utilizes two advanced risk modeling approaches (fault tree and layer of protection analysis (LOPA)) for MEGs’ risk analysis. A number of independent protection layers (IPLs) have been proposed to achieve a resilient MEG, hence increasing its safety integrity level (SIL). IPLs are applied using co-generators and thermal energy storage (TES) techniques to minimize the hazards of system failure, increase efficiency, and minimize greenhouse gas emissions. The proposed modeling and risk assessment approach aims to design a resilient MEG, which can utilize those potentials efficiently. In addition, an energy risk analysis has been applied on each MEGs’ physical domains such as electrical, thermal, mechanical and chemical. The concurrent objectives achieve an increased resiliency, reduced emissions, and sustained economy. Full article

(This article belongs to the Special Issue Energy Conservation in Infrastructures 2016)

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17 pages, 10085 KiB

Open AccessArticle

Retrofit Planning for the Performance Gap: Results of a Workshop on Addressing Energy, Health and Comfort Needs in a Protected Building

by Eugene Mohareb¹, Arman Hashemi^2,*

, Mehdi Shahrestani¹ and Minna Sunikka-Blank³

¹ School of the Built Environment, University of Reading, Reading RG6 6DF, UK

² School of Environment and Technology, University of Brighton, Brighton BN2 4GJ, UK

³ Department of Architecture, University of Cambridge, Cambridge CB2 1PX, UK

Energies 2017, 10(8), 1177; https://doi.org/10.3390/en10081177 - 10 Aug 2017

Cited by 10 | Viewed by 5021

Abstract

Research on the performance gap suggests that the actual energy consumption in buildings can be twice as much as expected from modelled estimates. Energy models rely on predictive indicators and assumptions that are usually done at the design stage, without acknowledging behavioral patterns [...] Read more.

Research on the performance gap suggests that the actual energy consumption in buildings can be twice as much as expected from modelled estimates. Energy models rely on predictive indicators and assumptions that are usually done at the design stage, without acknowledging behavioral patterns of actual users, amongst other uncertain elements. Moreover, in the context of the performance gap, it is evident that energy efficiency is overemphasized while other key issues such as health and comfort of occupants associated with indoor air quality, noise levels etc., have been less stressed and discussed. This paper discusses physical measurements of indoor temperature in a case study building at the University of Cambridge and reports findings of a workshop with researchers, building professionals and graduate students working on environmental performance in the built environment. The workshop addressed research issues related to energy, comfort and health (couched in terms of thermal performance), used as a means to understand the complexities of and trade-off between different aspects of sustainable buildings. Retrofit measures were suggested while considering how to balance energy and comfort needs, with some these measures being modelled to determine their efficacy. This research concludes with a reflection on how to implement these retrofit measures in a manner that addresses the performance gap. Full article

(This article belongs to the Special Issue Selected Papers from ZEMCH 2016: Building Energy Performance Evaluation/Simulation)

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13 pages, 4135 KiB

Open AccessArticle

Spectral Response of Polycrystalline Silicon Photovoltaic Cells under Real-Use Conditions

by Evaldo C. Gouvêa^*

, Pedro M. Sobrinho and Teófilo M. Souza

Renewable Energy Center, School of Engineering, São Paulo State University (UNESP), Guaratinguetá, Avenida Ariberto Pereira da Cunha 333, Guaratinguetá 12516-410, São Paulo, Brazil

Energies 2017, 10(8), 1178; https://doi.org/10.3390/en10081178 - 10 Aug 2017

Cited by 40 | Viewed by 6446

Abstract

The standard test conditions for photovoltaic modules are not capable of reproducing the environmental variations to which the modules are subjected under real operating conditions. The objective of this experimental work is to be an initial study on how the electric energy generation [...] Read more.

The standard test conditions for photovoltaic modules are not capable of reproducing the environmental variations to which the modules are subjected under real operating conditions. The objective of this experimental work is to be an initial study on how the electric energy generation of photovoltaic cells varies according to the different wavelength ranges of the solar light spectrum under real operating conditions. Two modules were installed outdoors; color filters, which allow the passage of light at specific wavelengths, were installed on one of them. The amount of energy produced by the module with the filter was compared to the reference module, and the relative efficiency of each filter was defined. As a result, it was found that crystalline silicon modules do not respond uniformly to sunlight, being more sensitive to the red band (relative efficiency of 23.83%) and less sensitive to the green band (19.15%). The infrared contributes to a significant portion of energy production (relative efficiency of 13.56%), overcoming its negative effect of reducing energy generation capacity due to high photovoltaic cell temperature. Full article

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22 pages, 3919 KiB

Open AccessArticle

Chemical Looping Combustion of Hematite Ore with Methane and Steam in a Fluidized Bed Reactor

by Samuel Bayham, Ronald Breault^* and Justin Weber

National Energy Technology Laboratory, 3610 Collins Ferry Road, Morgantown, WV 26505, USA

Energies 2017, 10(8), 1179; https://doi.org/10.3390/en10081179 - 10 Aug 2017

Cited by 6 | Viewed by 5527

Abstract

Chemical looping combustion is considered an indirect method of oxidizing a carbonaceous fuel, utilizing a metal oxide oxygen carrier to provide oxygen to the fuel. The advantage is the significantly reduced energy penalty for separating out the CO₂ for reuse or sequestration [...] Read more.

Chemical looping combustion is considered an indirect method of oxidizing a carbonaceous fuel, utilizing a metal oxide oxygen carrier to provide oxygen to the fuel. The advantage is the significantly reduced energy penalty for separating out the CO₂ for reuse or sequestration in a carbon-constrained world. One of the major issues with chemical looping combustion is the cost of the oxygen carrier. Hematite ore is a proposed oxygen carrier due to its high strength and resistance to mechanical attrition, but its reactivity is rather poor compared to tailored oxygen carriers. This problem is further exacerbated by methane cracking, the subsequent deposition of carbon and the inability to transfer oxygen at a sufficient rate from the core of the particle to the surface for fuel conversion to CO₂. Oxygen needs to be readily available at the surface to prevent methane cracking. The purpose of this work was to demonstrate the use of steam to overcome this issue and improve the conversion of the natural gas to CO₂, as well as to provide data for computational fluid dynamics (CFD) validation. The steam will gasify the deposited carbon to promote the methane conversion. This work studies the performance of hematite ore with methane and steam mixtures in a 5 cm fluidized bed up to approximately 140 kPa. Results show an increased conversion of methane in the presence of steam (from 20–45% without steam to 60–95%) up to a certain point, where performance decreases. Adding steam allows the methane conversion to carbon dioxide to be similar to the overall methane conversion; it also helped to prevent carbon accumulation from occurring on the particle. In general, the addition of steam to the feed gas increased the methane conversion. Furthermore, the addition of steam caused the steam methane reforming reaction to form more hydrogen and carbon monoxide at higher steam and methane concentrations, which was not completely converted at higher concentrations and at these residence times. Full article

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

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19 pages, 4339 KiB

Open AccessArticle

Optimal Voltage Control Using an Equivalent Model of a Low-Voltage Network Accommodating Inverter-Interfaced Distributed Generators

by Mu-Gu Jeong¹, Young-Jin Kim², Seung-Il Moon¹ and Pyeong-Ik Hwang^3,*

¹ Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

² Department of Electrical Engineering, Pohang University of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang 37673, Korea

³ Department of Electrical Engineering, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea

Energies 2017, 10(8), 1180; https://doi.org/10.3390/en10081180 - 10 Aug 2017

Cited by 12 | Viewed by 4077

Abstract

The penetration of inverter-based distributed generators (DGs), which can control their reactive power outputs, has increased for low-voltage (LV) systems. The power outputs of DGs affect the voltage and power flow of both LV and medium-voltage (MV) systems that are connected to the [...] Read more.

The penetration of inverter-based distributed generators (DGs), which can control their reactive power outputs, has increased for low-voltage (LV) systems. The power outputs of DGs affect the voltage and power flow of both LV and medium-voltage (MV) systems that are connected to the LV system. Therefore, the effects of DGs should be considered in the volt/var optimization (VVO) problem of LV and MV systems. However, it is inefficient to utilize a detailed LV system model in the VVO problem because the size of the VVO problem is increased owing to the detailed LV system models. Therefore, in order to formulate and solve the VVO problem in an efficient way, in this paper, a new equivalent model for an LV system including inverter-based DGs is proposed. The proposed model is developed based on an analytical approach rather than a heuristic-fitting one, and it therefore enables the VVO problem to be solved using a deterministic algorithm (e.g., interior point method). In addition, a method to utilize the proposed model for the VVO problem is presented. In the case study, the results verify that the computational burden to solve the VVO problem is significantly reduced without loss of accuracy by the proposed model. Full article

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

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17 pages, 1625 KiB

Open AccessArticle

Model, Characterization, and Analysis of Steady-State Security Region in AC/DC Power System with a Large Amount of Renewable Energy

by Zhong Chen¹, Hui Chen^1,*, Minhui Zhuang² and Siqi Bu³

¹ School of Electrical Engineering, Southeast University, Nanjing 210096, China

² Danyang Power Supply Company, Jiangsu Electric Power Company, Danyang 211106, China

³ Department of Electrical Engineering, Hong Kong Polytechnic University, Hong Kong, China

Energies 2017, 10(8), 1181; https://doi.org/10.3390/en10081181 - 10 Aug 2017

Cited by 5 | Viewed by 3564

Abstract

A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of [...] Read more.

A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of HVDC (High Voltage Direct Current) and the fluctuation of renewable energy have significantly affected the operation and control of a conventional AC system, the definition of the steady-state security region of the AC/DC power system is proposed in this paper based on the AC/DC power flow calculation model including LCC/VSC (Line Commutated Converter/Voltage Sourced Converter)-HVDC transmission and various AC/DC constraints, and hence the application of the security region is extended. In order to ensure that the proposed security region can accurately provide global security information of the power system under the fluctuations of renewable energy, this paper presents four methods (i.e., a screening method of effective boundary surfaces, a fitting method of boundary surfaces, a safety judging method, and a calculation method of distances and corrected distance between the steady-state operating point and the effective boundary surfaces) based on the relation analysis between the steady-state security region geometry and constraints. Also, the physical meaning and probability analysis of the corrected distance are presented. Finally, a case study is demonstrated to test the feasibility of the proposed methods. Full article

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

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16 pages, 1976 KiB

Open AccessArticle

Nonlinear Controllers Based on Exact Feedback Linearization for Series-Compensated DFIG-Based Wind Parks to Mitigate Sub-Synchronous Control Interaction

by Penghan Li^*, Jie Wang, Linyun Xiong and Fei Wu

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

Energies 2017, 10(8), 1182; https://doi.org/10.3390/en10081182 - 10 Aug 2017

Cited by 19 | Viewed by 3781

Abstract

The increasing penetration of wind power in the grid has driven the integration of wind farms with power systems that are series-compensated to enhance power transfer capability and dynamic stability. This may lead to sub-synchronous control interaction (SSCI) problems in series-compensated doubly-fed induction [...] Read more.

The increasing penetration of wind power in the grid has driven the integration of wind farms with power systems that are series-compensated to enhance power transfer capability and dynamic stability. This may lead to sub-synchronous control interaction (SSCI) problems in series-compensated doubly-fed induction generator (DFIG)-based wind farms. To mitigate SSCI, nonlinear controllers based on exact feedback linearization (EFL) are proposed in this paper. Before deriving the control laws, the exact feedback linearizability of the studied system is scrutinized. Frequency scanning analysis is employed to test the designed EFL controllers. Moreover, the performance of the EFL controllers is compared to that of classical proportional-integral (PI) controllers. A series-compensated 100 MW DFIG-based wind park is utilized to assess the performance of the designed controllers through the alleviation of sub-synchronous resonance. Analyses of the studied system reveal that the resistance is negative under sub-synchronous frequency conditions, whereas the reactance becomes negative at approximately 44 Hz. The designed EFL controllers effectively alleviate SSCI and result in positive reactance and resistance values within the whole sub-synchronous frequency range. The results from the frequency scanning method are also validated through the time domain simulation and the eigenvalue analysis. Full article

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

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13 pages, 5252 KiB

Open AccessEditor’s ChoiceArticle

Nusselt Number Correlation for Vertical Tubes with Inverted Triangular Fins under Natural Convection

by Byeong Dong Kang, Hyun Jung Kim and Dong-Kwon Kim^*

Department of Mechanical Engineering, Ajou University, Suwon 443-749, Korea

Energies 2017, 10(8), 1183; https://doi.org/10.3390/en10081183 - 10 Aug 2017

Cited by 4 | Viewed by 6584

Abstract

Vertical tubes with inverted triangular fins under natural convection are investigated experimentally. The thermal resistances of tubes with inverted triangular fins are measured for various fin numbers, fin heights, and heat inputs. A Nusselt number correlation that best predicts the measured thermal resistances [...] Read more.

Vertical tubes with inverted triangular fins under natural convection are investigated experimentally. The thermal resistances of tubes with inverted triangular fins are measured for various fin numbers, fin heights, and heat inputs. A Nusselt number correlation that best predicts the measured thermal resistances is proposed. The proposed correlation is applicable to the following conditions: Rayleigh numbers of 1000–125,000, fin height to fin length ratios of 0.2–0.6, and fin numbers of 9–72. Finally, a contour map of the thermal resistances calculated from the proposed correlation for various fin thicknesses and fin numbers is presented. The contour map shows that there exist optimal values of the fin thickness and fin number at which the thermal resistance of the inverted-triangular-finned tube is minimized. Therefore, the proposed correlation enables a search for the optimal dimensions and has potential to be used in the designing of inverted-triangular-finned tubes of various cooling devices. Full article

(This article belongs to the Special Issue Thermal Energy Storage and Thermal Management (TESM2017))

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16 pages, 899 KiB

Open AccessArticle

Interference-Aware PAPR Reduction Scheme to Increase the Energy Efficiency of Large-Scale MIMO-OFDM Systems

by Byung Moo Lee¹

and Youngok Kim^2,*

¹ School of Intelligent Mechatronics Engineering, Sejong University, Seoul 05006, Korea

² Department of Electronic Engineering, Kwangwoon University, Seoul 01897, Korea

Energies 2017, 10(8), 1184; https://doi.org/10.3390/en10081184 - 10 Aug 2017

Cited by 10 | Viewed by 3551

Abstract

Large-scale (LS) multi-user (MU) multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is considered to be a desirable signal transmission scheme because it can significantly improve the energy efficiency (EE) and spectral efficiency (SE) of the system. However, there are many difficulties [...] Read more.

Large-scale (LS) multi-user (MU) multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is considered to be a desirable signal transmission scheme because it can significantly improve the energy efficiency (EE) and spectral efficiency (SE) of the system. However, there are many difficulties in realizing an LS-MU-MIMO-OFDM system, and one of these is its high peak-to-average power ratio (PAPR), which results in serious nonlinear signal distortion and power inefficiency of the power amplifier (PA). LS-MIMO-OFDM systems require a lot of PAs, which are necessary to be connected to each antenna. To compensate for the PA nonlinearity and increase the efficiency, a digital pre-distorter (DPD) is very popular and has been successfully implemented in current base stations (BSs). However, a DPD is very difficult to use in an LS-MU-MIMO-OFDM system because it is expensive, but should be applied to each antenna. Therefore, a considerate scheme of signal processing is necessary to cope with the PA nonliearity issue of the LS-MU-MIMO-OFDM system. In this paper, we propose an interference-aware iterative clipping and filtering peak-to-average power ratio (PAPR) reduction scheme for LS-MU-MIMO-OFDM systems. In the proposed scheme, the clipping level in the clipping process is adaptively adjusted based on any kind of interference level that exists in the general communication environment. In particular, when matched filtering (MF) precoding is used for the LS-MU-MIMO-OFDM, the inter-user interference (IUI) always exists with a practical number of transmitter (TX) antennas, and this inevitable IUI level can be a decision point for the clipping ratio (CR). Choosing a proper CR to make the clipping noise lower than IUI has a very high benefit for the EE improvement of the system. The results of numerical analysis show that the proposed scheme can induce a very effective peak-to-average power ratio (PAPR) performance with little SE loss. Full article

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25 pages, 5480 KiB

Open AccessArticle

Off-Design Performances of Subcritical and Supercritical Organic Rankine Cycles in Geothermal Power Systems under an Optimal Control Strategy

by Tieyu Gao^* and Changwei Liu

Institute of Turbomachinery, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Energies 2017, 10(8), 1185; https://doi.org/10.3390/en10081185 - 11 Aug 2017

Cited by 13 | Viewed by 5298

Abstract

The conditions of heat source and heat sink in a geothermal ORC system may frequently vary due to variations in geological conditions, ambient temperature and actual operation. In this study, an off-design performance prediction model for geothermal ORC systems is developed according to [...] Read more.

The conditions of heat source and heat sink in a geothermal ORC system may frequently vary due to variations in geological conditions, ambient temperature and actual operation. In this study, an off-design performance prediction model for geothermal ORC systems is developed according to special designs of critical components, and an optimal control strategy which regards the turbine guide vane angle, the refrigerant pump rotational speed and the cooling water mass flow rate as control variables is proposed to maximize the net power output. Off-design performances of both subcritical and supercritical ORCs are analyzed. The results indicate that, under the optimal control strategy, the net power output of both ORCs increase with greater geothermal water mass flow rate, higher geothermal water inlet temperature and lower cooling water inlet temperature, which is mainly due to a greater working fluid mass flow rate, higher turbine inlet pressure and lower condensing pressure, respectively. The net power output of supercritical ORC is always greater than that of subcritical ORC within the range of this study, but the difference tends to decrease when supercritical ORC activates the geothermal water reinjection temperature restriction. Full article

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16 pages, 1585 KiB

Open AccessArticle

An Ensemble Model Based on Machine Learning Methods and Data Preprocessing for Short-Term Electric Load Forecasting

by Yanbing Lin¹, Hongyuan Luo^1,*, Deyun Wang^1,2, Haixiang Guo^1,2 and Kejun Zhu¹

¹ School of Economics and Management, China University of Geosciences, Wuhan 430074, China

² Mineral Resource Strategy and Policy Research Center, China University of Geosciences, Wuhan 430074, China

Energies 2017, 10(8), 1186; https://doi.org/10.3390/en10081186 - 11 Aug 2017

Cited by 54 | Viewed by 6403

Abstract

The experience with deregulated electricity market has shown the increasingly important role of short-term electric load forecasting in the energy producing and scheduling. However, because of nonlinear, stochastic and nonstable characteristics associated with the electric load series, it is extremely difficult to precisely [...] Read more.

The experience with deregulated electricity market has shown the increasingly important role of short-term electric load forecasting in the energy producing and scheduling. However, because of nonlinear, stochastic and nonstable characteristics associated with the electric load series, it is extremely difficult to precisely forecast the electric load. This paper aims to establish a novel ensemble model based on variational mode decomposition (VMD) and extreme learning machine (ELM) optimized by differential evolution (DE) algorithm for multi-step ahead electric load forecasting. The proposed model is novel in the sense that VMD is firstly applied to decompose the original electric load series into a set of components with different frequencies in order to effectively eliminate the stochastic fluctuation characteristic so as to improve the overall prediction accuracy. The proposed ensemble model is tested using two electric load series collected from New South Wales (NSW) and Queensland (QLD) in the Australian electricity market. The experimental results show that: (1) the data preprocessing by VMD can effectively decrease the stochastic fluctuation characteristics that existed in the electric load series, consequently improving the whole forecasting accuracy, and; (2) the proposed forecasting model performs better than all other benchmark models for both one-step and multi-step ahead electric load forecasting. Full article

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

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17 pages, 4302 KiB

Open AccessArticle

An Improved Method for Energy and Resource Assessment of Waves in Finite Water Depths

by Wanan Sheng¹

, Hui Li^2,* and Jimmy Murphy¹

¹ Centre for Marine and Renewable Energy Ireland, Environmental Research Institute, University College Cork, Cork P43 C573, Ireland

² College of Mechanical and Energy Engineering, Jimei University, Xiamen 361021, China

Energies 2017, 10(8), 1188; https://doi.org/10.3390/en10081188 - 11 Aug 2017

Cited by 12 | Viewed by 4050

Abstract

For cost savings and ease of operation, nearshore regions have been considered as ideal regions for deploying wave energy converters (WECs) and wave farms. As the water depths of these regions may be frequently limited to 50 m or less, they can be [...] Read more.

For cost savings and ease of operation, nearshore regions have been considered as ideal regions for deploying wave energy converters (WECs) and wave farms. As the water depths of these regions may be frequently limited to 50 m or less, they can be considered as being transitional/intermediate to shallow when compared to the wave lengths of interest for wave energy conversion. Since the impact of water depths on propagation of waves is significant, it cannot be ignored in wave energy assessment. According to the basic wave theory, in order to work out accurate wave energy amounts in finite water depth, detailed wave spectral distributions should be given. However, for some practical reasons, there are still some cases where only scatter diagrams and/or the statistical wave parameters are available, whilst the detailed wave spectra are discarded. As a result, the assessments of wave energy and resources are frequently determined by ignoring the effect of water depths or using very simplified approximations. This research paper aims to develop more accurate approximation methods by utilising a number of available parameters such that a better estimate on the wave resource assessment can be achieved even if the detailed wave spectra are not available. As one important goal, the research can provide some important indications on how the measured wave data are effectively presented so that they can be very useful for assessing the wave energy resource, especially in the cases including the effects of finite water depths. Full article

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16 pages, 7526 KiB

Open AccessArticle

Theoretical and Experimental Investigation of Switching Ripple in the DC-Link Voltage of Single-Phase H-Bridge PWM Inverters

by Marija Vujacic

, Manel Hammami

, Milan Srndovic

and Gabriele Grandi^*

Department of Electrical, Electronic and Information Engineering, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy

Energies 2017, 10(8), 1189; https://doi.org/10.3390/en10081189 - 11 Aug 2017

Cited by 28 | Viewed by 8107

Abstract

Direct current (DC)-link voltage ripple analysis is essential for determining harmonic noise and for DC-link capacitor design and selection in single-phase pulse-width modulation (PWM) inverters. This paper provides an extensive theoretical analysis of DC-link voltage ripple for full-bridge (H-bridge) inverters, with simulation and [...] Read more.

Direct current (DC)-link voltage ripple analysis is essential for determining harmonic noise and for DC-link capacitor design and selection in single-phase pulse-width modulation (PWM) inverters. This paper provides an extensive theoretical analysis of DC-link voltage ripple for full-bridge (H-bridge) inverters, with simulation and experimental verifications, considering a DC source impedance (non-ideal DC voltage source). The DC voltage ripple amplitude is theoretically estimated as a function of the output current, both amplitude and phase angle, and the modulation index. It consists of a switching frequency component and a double-fundamental frequency component (i.e., 100 Hz), thereby both components are considered in the analysis. In particular, the peak-to-peak distribution, maximum amplitude, and root mean square (RMS) values of the voltage switching ripple over the fundamental period are obtained. Based on the DC voltage requirements, simple and effective guidelines for designing DC-link capacitors are obtained. Full article

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19 pages, 4722 KiB

Open AccessArticle

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

by Wei-Chen Tseng¹, Yu-Shu Kuo^2,* and Jing-Wen Chen¹

¹ Department of Civil Engineering, National Cheng Kung University, Tainan 701, Taiwan

² Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Tainan 701, Taiwan

Energies 2017, 10(8), 1190; https://doi.org/10.3390/en10081190 - 11 Aug 2017

Cited by 28 | Viewed by 5197

Abstract

Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The so-called p-y curves method is suggested in the existing design recommendations to determine the behavior of monopiles unprotected against scour and the reduction of effective [...] Read more.

Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The so-called p-y curves method is suggested in the existing design recommendations to determine the behavior of monopiles unprotected against scour and the reduction of effective soil stress is accounted for by the extreme scour depth. This conservative design approach does not consider the geometry of the scour hole and the effect of pile diameter on the soil resistance. An underestimated foundation stiffness would be obtained, thereby influencing the predicted overall response of the support structure of an offshore wind turbine. In this study, we calculated the load-deformation response and foundation stiffness of a monopile when scour occurred. The influence of pile diameter on the initial modulus of subgrade reaction, and the modification of the ultimate soil resistance of a monopile subject to scour are evaluated. The commercial software BLADED was used to simulate the dynamic response of the reference offshore wind turbine with monopile unprotected against scour at Chang-Bin offshore wind farm in Taiwan Strait. The results showed that when the p-y curve suggested by existing design regulation was used to calculate the load-deformation response, the foundation stiffness was underestimated where the scour depth was greater than the pile diameter, but the foundation stiffness was overestimated when the scour depth was less than the pile diameter. Full article

(This article belongs to the Special Issue Wind Turbine Loads and Wind Plant Performance)

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25 pages, 2300 KiB

Open AccessArticle

Bioenergy Potential and Utilization Costs for the Supply of Forest Woody Biomass for Energetic Use at a Regional Scale in Mexico

by Ulises Flores Hernández^1,*

, Dirk Jaeger¹ and Jorge Islas Samperio²

¹ Chair of Forest Operations, University of Freiburg, Freiburg im Breisgau 79085, Germany

² Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco Morelos 62580, Mexico

Energies 2017, 10(8), 1192; https://doi.org/10.3390/en10081192 - 12 Aug 2017

Cited by 11 | Viewed by 4842

Abstract

While considering constraints in regard to sustainability, this paper reviews the development of a methodology to assess the introduction of bioenergy supply chains in Mexico based on forest woody biomass. Three research modules include analyses of forest biomass utilization residues that originated from: [...] Read more.

While considering constraints in regard to sustainability, this paper reviews the development of a methodology to assess the introduction of bioenergy supply chains in Mexico based on forest woody biomass. Three research modules include analyses of forest biomass utilization residues that originated from: (1) harvesting activities, (2) non-extracted stands and (3) sawmills. A regional case study focusing on tree species of commercial importance (pine, oak and fir) in the 10 provinces with the highest timber production located in the north and central-south part of the country, is analyzed. After applying the methodology, the theoretical potential of available woody biomass for energetic use amounts to 6,357,482 m³. When applying the sustainability constraints, the technically feasible supply of forest woody biomass for energetic use sums up to 5,798,722 m³, which relate to a technical energy potential of 45.96 PJ for 2013. Moreover, a biomass energy flow chart showing energy values for each analyzed source and species is presented. Monte Carlo simulations were carried out for each cost involved in utilizing the resulting available woody biomass for energetic use. In the absence of national studies which include forest operations and bioenergy transformation to calculate the sustainable energy potential, the developed methodology adds innovation for assessing woody biomass availability. Full article

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

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17 pages, 2091 KiB

Open AccessArticle

Economic Dispatch with Demand Response in Smart Grid: Bargaining Model and Solutions

by Kai Ma¹

, Congshan Wang¹, Jie Yang^1,*, Qiuxia Yang¹ and Yazhou Yuan^1,2

¹ School of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China

² Key Laboratory of System Control and Information Processing, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2017, 10(8), 1193; https://doi.org/10.3390/en10081193 - 12 Aug 2017

Cited by 17 | Viewed by 5142

Abstract

This paper proposes an economic dispatch strategy for the electricity system with one generation company, multiple utility companies and multiple consumers, which participate in demand response to keep the electricity real-time balance. In the wholesale markets, multiple utility companies will commonly select a [...] Read more.

This paper proposes an economic dispatch strategy for the electricity system with one generation company, multiple utility companies and multiple consumers, which participate in demand response to keep the electricity real-time balance. In the wholesale markets, multiple utility companies will commonly select a reliable agent to negotiate with the generation company on the wholesale price. It is challengeable to find a wholesale price to run the electricity market fairly and effectively. In this study, we use the multiple utility companies’ profits to denote the utility function of the agent and formulate the interaction between the agent and the generation company as a bargaining problem, where the wholesale price was enforced in the bargaining outcome. Then, the Raiffa–Kalai–Smorodinsky bargaining solution (RBS) was utilized to achieve the fair and optimal outcome. In the retail markets, the unfavorable disturbances exist in the power management and price when the consumers participate in the demand response to keep the electricity real-time balance, which motivates us to further consider the dynamic power management algorithm with the additive disturbances, and then obtain the optimal power consumption and optimal retail price. Based on the consumers’ utility maximization, we establish a price regulation model with price feedback in the electricity retail markets, and then use the iterative algorithm to solve the optimal retail price and the consumer’s optimal power consumption. Hence, the input-to-state stability condition with additive electricity measurement disturbance and price disturbance is given. Numerical results demonstrate the effectiveness of the economic dispatch strategy. Full article

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

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15 pages, 4465 KiB

Open AccessArticle

A New Method for Evaluating Moisture Content and Aging Degree of Transformer Oil-Paper Insulation Based on Frequency Domain Spectroscopy

by Guoqiang Xia¹, Guangning Wu^1,*, Bo Gao¹, Haojie Yin¹ and Feibao Yang²

¹ School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China

² Energy China HEPDI, Changsha 410007, China

Energies 2017, 10(8), 1195; https://doi.org/10.3390/en10081195 - 12 Aug 2017

Cited by 34 | Viewed by 5904

Abstract

The condition of oil-paper insulation is closely related to the life expectancy of a transformer. The accurate results of oil-paper have not been obtained due to the impact of influencing factors. Therefore, in order to improve the evaluation accuracy of oil-paper insulation, in [...] Read more.

The condition of oil-paper insulation is closely related to the life expectancy of a transformer. The accurate results of oil-paper have not been obtained due to the impact of influencing factors. Therefore, in order to improve the evaluation accuracy of oil-paper insulation, in this paper, oil-paper samples which were prepared with different aging and moisture content were analyzed by frequency domain spectroscopy (FDS). Results show that when the moisture content is less than 2%, the range of 10¹~10³ Hz is mainly affected by moisture and aging has little effect. However, with the increase of moisture content, the effect of aging degree on this band became increasingly prominent. S_m, which represents the integral value from 10⁻¹ to 10⁻³ Hz, and S_DP, which represents the integral value from 10¹ to 10³ Hz, were extracted as characteristic parameters of moisture content and aging degree respectively. Compensation factors γ which represents the influence ratio of moisture on S_DP and φ which represents the influence ratio of aging on S_m were introduced to compensate for the influence of moisture content and aging degree on characteristics respectively. Then, a new method was proposed to evaluate the condition of oil-paper based on compensation factors. Through this method, the influence in characteristics can be eliminated by the obtained actual compensation factors, thus distinguishing the internal influence between moisture content and aging degree on FDS. Finally, this method was verified by field test. Full article

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21 pages, 2322 KiB

Open AccessArticle

Icing Forecasting of Transmission Lines with a Modified Back Propagation Neural Network-Support Vector Machine-Extreme Learning Machine with Kernel (BPNN-SVM-KELM) Based on the Variance-Covariance Weight Determination Method

by Dongxiao Niu¹, Yi Liang^1,*, Haichao Wang¹, Meng Wang¹ and Wei-Chiang Hong^2,3

¹ School of Economics and Management, North China Electric Power University, Beijing 102206, China

² School of Education Intelligent Technology, Jiangsu Normal University, Xuzhou 221116, China

³ Department of Information Management, Oriental Institute of Technology, New Taipei 220, Taiwan

Energies 2017, 10(8), 1196; https://doi.org/10.3390/en10081196 - 13 Aug 2017

Cited by 25 | Viewed by 5625

Abstract

Stable and accurate forecasting of icing thickness is of great significance for the safe operation of the power grid. In order to improve the robustness and accuracy of such forecasting, this paper proposes an innovative combination forecasting model using a modified Back Propagation [...] Read more.

Stable and accurate forecasting of icing thickness is of great significance for the safe operation of the power grid. In order to improve the robustness and accuracy of such forecasting, this paper proposes an innovative combination forecasting model using a modified Back Propagation Neural Network-Support Vector Machine-Extreme Learning Machine with Kernel (BPNN-SVM-KELM) based on the variance-covariance (VC) weight determination method. Firstly, the initial weights and thresholds of BPNN are optimized by mind evolutionary computation (MEC) to prevent the BPNN from falling into local optima and speed up its convergence. Secondly, a bat algorithm (BA) is utilized to optimize the key parameters of SVM. Thirdly, the kernel function is introduced into an extreme learning machine (ELM) to improve the regression prediction accuracy of the model. Lastly, after adopting the above three modified models to predict, the variance-covariance weight determination method is applied to combine the forecasting results. Through performance verification of the model by real-world examples, the results show that the forecasting accuracy of the three individual modified models proposed in this paper has been improved, but the stability is poor, whereas the combination forecasting method proposed in this paper is not only accurate, but also stable. As a result, it can provide technical reference for the safety management of power grid. Full article

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

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13 pages, 850 KiB

Open AccessArticle

The Climate-Independent Need for Renewable Energy in the 21st Century

by Kevin J. Warner^1,2,*

and Glenn A. Jones¹

¹ Department of Marine Sciences, Texas A&M University Galveston Campus, Galveston, TX 77554, USA

² Department of Marine Biology, Texas A&M University Galveston Campus, Galveston, TX 77554, USA

Energies 2017, 10(8), 1197; https://doi.org/10.3390/en10081197 - 13 Aug 2017

Cited by 26 | Viewed by 6793

Abstract

In December 2015 the nations of the world agreed, in principle, to limit global warming to no more than 2 °C above pre-industrial levels. In order to achieve this goal, recent publications have shown that (1) more than 50% of known fossil fuel [...] Read more.

In December 2015 the nations of the world agreed, in principle, to limit global warming to no more than 2 °C above pre-industrial levels. In order to achieve this goal, recent publications have shown that (1) more than 50% of known fossil fuel reserves need to remain unused, and (2) the timing of the transition away from fossil fuels needs to achieve 50% renewable energy by 2028, an expansion of renewable sources of 37-fold in the next 12 years. This rate of expansion is unprecedented and unlikely to be achieved. Even utilizing the 50% of fossil fuels untapped in a <2 °C scenario results in significant expansion of renewable energy sources by 2100. Here we examine three fossil fuel reserve estimates and two per capita energy consumption tracks to understand how dominant renewable energy sources need to be during the second half of the 21st century. We find that per capita energy consumption rates are a more significant factor in the demand for renewable energy infrastructure, as wide ranging estimates of fossil fuel reserves still result in peak production by mid-century. At either of the consumption rates, attempting to uphold the 2 °C global warming goal would demand more energy from renewable sources than was produced from all sources in 2014. In total, the world will likely require between 600 and 2000 exajoules of renewable energy by the year 2100, a significant expansion from the 13 produced in 2014. Despite meaningful gains in renewable energy sources, the transition away from fossil fuels is not keeping pace with rising global population, and expansion of global per capita consumption. Even in the absence of global warming concerns, renewable energy infrastructure needs to immediately begin significant expansion. Full article

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21 pages, 1943 KiB

Open AccessArticle

Theoretical Study of the Effects of Spark Timing on the Performance and Emissions of a Light-Duty Spark Ignited Engine Running under Either Gasoline or Ethanol or Butanol Fuel Operating Modes

by Roussos G. Papagiannakis¹, Dimitrios C. Rakopoulos²

and Constantine D. Rakopoulos^2,*

¹ Thermodynamic & Propulsion Systems Section, Aeronautical Sciences Department, Hellenic Air Force Academy, Dekelia Air Force Base, 1010 Dekelia, Attiki, Greece

² Internal Combustion Engines Laboratory, Department of Thermal Engineering, School of Mechanical Engineering, National Technical University of Athens, Zografou Campus, 9 Heroon Polytechniou Street, 15780 Athens, Greece

Energies 2017, 10(8), 1198; https://doi.org/10.3390/en10081198 - 13 Aug 2017

Cited by 22 | Viewed by 5508

Abstract

Much research is ongoing to find suitable alternate fuels in order to reduce the exhaust emission levels without deteriorating the basic performance characteristics of conventional spark-ignited (SI) engines. One of the methods to achieve the above problem is the use of alcohols as [...] Read more.

Much research is ongoing to find suitable alternate fuels in order to reduce the exhaust emission levels without deteriorating the basic performance characteristics of conventional spark-ignited (SI) engines. One of the methods to achieve the above problem is the use of alcohols as full supplement fuels to normal gasoline. At the same time, many related research studies have shown that the use of alcohols has a negative impact on some basic engine performance characteristics, e.g., brake power output, etc. On the other hand, spark timing is one of the critical engine operating parameters that significantly influences the combustion mechanism inside the combustion chamber of a SI engine. Therefore, the primary objective of the present work is to investigate the effect of spark timing on the performance and emissions characteristics of a conventional, four-stroke, SI engine running under three different fuel operating modes, viz. with conventional gasoline or ethanol or butanol. The specific investigation is conducted by using an in-house, comprehensive, two-zone phenomenological model. The predictive ability of the model is tested against pertinent experimental data and it is found that the computed results are in good agreement with the respective experimental ones. For all test cases examined herein, the results concern basic engine performance characteristics, i.e., cylinder pressure, power output, specific fuel consumption etc., as well as NO and CO emissions. The main objectives of the work were to record and evaluate the impact that spark timing has on the performance characteristics and emitted pollutants of a conventional SI engine, operating under either conventional gasoline or ethanol or butanol fuel operating modes. Moreover, it deals with the determination of an optimum combination between the type of fuel used and the spark timing, so that probable undesirable effects on engine performance characteristics would be avoided. By comparing this investigation results, it is revealed that the use of alcohols as a full substitute fuel of gasoline accompanied with an appropriate alteration of the spark timing, could be a promising solution to improving both the efficiency and environmental behavior of a light-duty, spark-ignited (SI) engine, without causing any harmful problems to the engine operational lifetime. The conclusions from the study may prove valuable for the application of this technological solution to existing conventional SI engines. Full article

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

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15 pages, 1913 KiB

Open AccessArticle

Preventive Security-Constrained Optimal Power Flow Considering UPFC Control Modes

by Xi Wu^1,*, Zhengyu Zhou¹, Gang Liu², Wanchun Qi² and Zhenjian Xie²

¹ School of Electrical Engineering, Southeast University, Nanjing 210096, China

² Jiangsu Electric Power Company Economic Research Institute, Nanjing 211102, China

Energies 2017, 10(8), 1199; https://doi.org/10.3390/en10081199 - 13 Aug 2017

Cited by 16 | Viewed by 4416

Abstract

The successful application of the unified power flow controller (UPFC) provides a new control method for the secure and economic operation of power system. In order to make the full use of UPFC and improve the economic efficiency and static security of a [...] Read more.

The successful application of the unified power flow controller (UPFC) provides a new control method for the secure and economic operation of power system. In order to make the full use of UPFC and improve the economic efficiency and static security of a power system, a preventive security-constrained power flow optimization method considering UPFC control modes is proposed in this paper. Firstly, an iterative method considering UPFC control modes is deduced for power flow calculation. Taking into account the influence of different UPFC control modes on the distribution of power flow after N-1 contingency, the optimization model is then constructed by setting a minimal system operation cost and a maximum static security margin as the objective. Based on this model, the particle swarm optimization (PSO) algorithm is utilized to optimize power system operating parameters and UPFC control modes simultaneously. Finally, a standard IEEE 30-bus system is utilized to demonstrate that the proposed method fully exploits the potential of static control of UPFC and significantly increases the economic efficiency and static security of the power system. Full article

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11 pages, 8078 KiB

Open AccessArticle

Combustion and Heat Release Characteristics of Biogas under Hydrogen- and Oxygen-Enriched Condition

by Jun Li¹, Hongyu Huang^2,*, Huhetaoli², Yugo Osaka³, Yu Bai², Noriyuki Kobayashi^1,* and Yong Chen²

¹ Department of Chemical Engineering, Nagoya University, Nagoya, Aichi 464-8603, Japan

² Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China

³ Faculty of Mechanical Engineering, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan

Energies 2017, 10(8), 1200; https://doi.org/10.3390/en10081200 - 13 Aug 2017

Cited by 34 | Viewed by 8365

Abstract

Combustion and heat release characteristics of biogas non-premixed flames under various hydrogen-enriched and oxygen-enriched conditions were investigated through chemical kinetics simulation using detailed chemical mechanisms. The heat release rates, chemical reaction rates, and molar fraction of all species of biogas at various methane [...] Read more.

Combustion and heat release characteristics of biogas non-premixed flames under various hydrogen-enriched and oxygen-enriched conditions were investigated through chemical kinetics simulation using detailed chemical mechanisms. The heat release rates, chemical reaction rates, and molar fraction of all species of biogas at various methane contents (35.3–58.7%, mass fraction), hydrogen addition ratios (10–50%), and oxygen enrichment levels (21–35%) were calculated considering the GRI 3.0 mechanism and P1 radiation model. Results showed that the net reaction rate of biogas increases with increasing hydrogen addition ratio and oxygen levels, leading to a higher net heat release rate of biogas flame. Meanwhile, flame length was shortened with the increase in hydrogen addition ratio and oxygen levels. The formation of free radicals, such as H, O, and OH, are enhanced with increase in hydrogen addition ratio and oxygen levels. Higher reaction rates of exothermic elementary reactions, especially those with OH free radical are increased, are beneficial to the improvement in combustion and heat release characteristics of biogas in practical applications. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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18 pages, 1265 KiB

Open AccessArticle

Efficiency Evaluation and Policy Analysis of Industrial Wastewater Control in China

by Weixin Yang¹

and Lingguang Li^2,*

¹ Business School, University of Shanghai for Science and Technology, Shanghai 200093, China

² School of Mathematical Sciences, Tongji University, Shanghai 200092, China

Energies 2017, 10(8), 1201; https://doi.org/10.3390/en10081201 - 14 Aug 2017

Cited by 49 | Viewed by 5992

Abstract

With increasing emissions of industrial wastewater and poor control measures, environmental pollution has become a serious issue haunting China’s economic development. Meanwhile, the current pollution management policy system in China is mainly under the supervision of the central government and executed by local [...] Read more.

With increasing emissions of industrial wastewater and poor control measures, environmental pollution has become a serious issue haunting China’s economic development. Meanwhile, the current pollution management policy system in China is mainly under the supervision of the central government and executed by local governments. Under the current economic growth model of China, the industrial sector remains the dominant segment of our economy, which makes the Total Factor Efficiency (TFE) evaluation and policy analysis of industrial wastewater control decisive factors concerning China’s future economic growth and sustainable development. Based on existing studies of China and abroad, and with the help of a Data Envelope Analysis (DEA) model, this paper used 39 industrial sectors and their input-output data from 2003 to 2014 of China as Decision Making Units to calculate the TFE of wastewater control in different industrial sectors of China. Moreover, we have designed and adopted our own MATLAB programming for optimization solutions of multi-variable constrained nonlinear functions in order to obtain a more accurate estimation of the TFE of wastewater control. Based on our calculation results, this paper further explained the difference in TFE and policy implications across typical industries in China, and offered policy recommendations accordingly. Full article

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24 pages, 11472 KiB

Open AccessArticle

Development of an Integrated, Personalized Comfort Methodology for Office Buildings

by Panagiota Antoniadou^*

and Agis M. Papadopoulos

Process Equipment Design Laboratory, Department of Mechanical Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece

Energies 2017, 10(8), 1202; https://doi.org/10.3390/en10081202 - 14 Aug 2017

Cited by 9 | Viewed by 3832

Abstract

Despite the significant progress observed over the last decades, the European building stock still consumes significant amounts of energy (39% of the total final energy), whilst it does not always provide the conditions required for occupants’ well-being and thermal comfort sensation. In order [...] Read more.

Despite the significant progress observed over the last decades, the European building stock still consumes significant amounts of energy (39% of the total final energy), whilst it does not always provide the conditions required for occupants’ well-being and thermal comfort sensation. In order to achieve the goal of nearly or even zero energy buildings, a deep refurbishment of the building stock is imperative. As the literature indicates, a firm evaluation of indoor conditions is essential, while having at the epicenter the occupants’ comfort perception, with emphasis on their individual characteristics. In this respect, a methodological framework is developed and a preliminary implementation is performed. The main goal of the methodological approach is the consideration of both the classical comfort parameters along with the occupants’ socioeconomic and personalized characteristics that affect their perception and can differentiate their needs even under the same conditions. Among other important findings this preliminary implementation achieved some very promising results, highlighting that occupants’ individual characteristics such as recycling and exercising can affect the occupants’ comfort perception. Full article

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28 pages, 1771 KiB

Open AccessArticle

DG Placement in Loop Distribution Network with New Voltage Stability Index and Loss Minimization Condition Based Planning Approach under Load Growth

by Syed Ali Abbas Kazmi^*

and Dong Ryeol Shin^*

Department of Electrical and Computer Engineering, College of Information and Communication Engineering (CICE), Sungkyunkwan University (SKKU), Suwon 16419, Korea

Energies 2017, 10(8), 1203; https://doi.org/10.3390/en10081203 - 14 Aug 2017

Cited by 26 | Viewed by 4420

Abstract

This paper presents a new planning approach based on voltage stability index (VSI) together with improved loss minimization (LM) formulations. The method has employed for application of distributed generation (DG) unit placement (location and size) in a loop (configured) test distribution network (LDN). [...] Read more.

This paper presents a new planning approach based on voltage stability index (VSI) together with improved loss minimization (LM) formulations. The method has employed for application of distributed generation (DG) unit placement (location and size) in a loop (configured) test distribution network (LDN). Initially, VSI relationship for equivalent loop model has employed to find out potential locations for DG placement in LDN. Later, loss minimization formulations and loss minimization conditions (LMC) have been derived on the basis of an equivalent electrical model of LDN, for single and two DGs operating at various power factors, respectively. The proposed approach is comprised of two variants and has demonstrated on the 69-bus test distribution network. The first planning variant as a single case has applied for DG allocation (location, size, number) in LDN under normal load. Similarly, the second planning variant has demonstrated with three cases (six scenarios per case), evaluated under normal load and impact of load growth (across five years), respectively. The proposed approach has analyzed in terms of various performance indicators and results obtained have compared and found in close agreement with existed works in literature. Simulation results verify the validity of the proposed planning approach and establish that LDN performs better than radial distribution network from the perspective of load growth. Full article

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

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19 pages, 852 KiB

Open AccessArticle

A Multi-Objective Optimization Approach for Corrective Switching of Transmission Systems in Emergency Scenarios

by Xin Xu¹

, Yongji Cao¹, Hengxu Zhang^1,*

, Shiying Ma², Yunting Song² and Dezhi Chen²

¹ Key Laboratory of Power System Intelligent Dispatch and Control of the Ministry of Education, Shandong University, Jinan 250061, China

² China Electric Power Research Institute, Beijing 100192, China

Energies 2017, 10(8), 1204; https://doi.org/10.3390/en10081204 - 14 Aug 2017

Cited by 16 | Viewed by 3402

Abstract

The large capacity transmission of power over long distance and the rapid development of renewable energy increase the probability of unexpected emergencies such as overload and under-voltage. To tackle these emergencies and defend future disturbances, the corrective switching is implemented as an online [...] Read more.

The large capacity transmission of power over long distance and the rapid development of renewable energy increase the probability of unexpected emergencies such as overload and under-voltage. To tackle these emergencies and defend future disturbances, the corrective switching is implemented as an online control and a multi-objective scheme-making approach is proposed. A multi-objective 0-1 integer optimization model is established to cover a set of contradictory objectives from the aspects of economics, security and reliability. A two-phase optimization approach is proposed to ensure computation efficiency and coordinate the trade-off between these objectives: in the first phase, a feasible set silting method is utilized to quickly search for a set of candidate corrective switching schemes; in the second phase, the technique for order preference by similarity to an ideal solution (TOPSIS) method is applied to the candidate set to coordinate the contradictory objectives and determine the ultimate engineering scheme. Two case studies are conducted to verify the proposed approach in overload and under-voltage scenarios. The results are discussed to show the strengths when the performance indices of economics, security and reliability are considered. Full article

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

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17 pages, 2633 KiB

Open AccessArticle

Physical and Compression Properties of Pellets Manufactured with the Biomass of Five Woody Tropical Species of Costa Rica Torrefied at Different Temperatures and Times

by Johanna Gaitán-Alvarez¹

, Roger Moya^1,*

, Allen Puente-Urbina²

and Ana Rodriguez-Zuñiga¹

¹ Instituto Tecnológico de Costa Rica, Escuela de Ingeniería Forestal, Apartado 159-7050, Cartago, Costa Rica

² Instituto Tecnológico de Costa Rica, Centro de Investigación y de Servicios Químicos y Microbiológicos (CEQIATEC), Escuela de Química, Apartado 159-7050, Cartago, Costa Rica

Energies 2017, 10(8), 1205; https://doi.org/10.3390/en10081205 - 14 Aug 2017

Cited by 26 | Viewed by 5211

Abstract

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture [...] Read more.

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture content, water absorption, and compression force of torrefied biomass pellets of five wood species (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) under three torrefaction temperature conditions (light, middle, and severe) and three torrefaction times (8, 10, and 12 min). The results showed that the bulk density of the pellets was 0.90–1.30 g/cm³. The density variation of the pellets was higher with torrefaction at 250 °C. The moisture content decreased with increasing torrefaction temperature from 3% to 1%. Water absorption was lower in the pellets torrefied at 250 °C. The compression force was lower in the pellets torrefied at 250 °C with approximate loads of 700 N. Based on the above results, it was concluded that pellets made with biomass torrefied at 200 °C have better energy properties and evaluated properties. According to these results, pellets fabricated with the torrefied biomass of tropical species can be used in stove, gas, and hydrogen production because the pellet presents adequate characteristics. Full article

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

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17 pages, 908 KiB

Open AccessArticle

A Comparison between Voltage and Reactive Power Feedback Schemes of DFIGs for Inter-Area Oscillation Damping Control

by Kai Liao^1,* and Yao Wang²

¹ School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China

² College of Electrical and Information Engineering, Southwest Minzu University, Chengdu 610041, China

Energies 2017, 10(8), 1206; https://doi.org/10.3390/en10081206 - 14 Aug 2017

Cited by 2 | Viewed by 4320

Abstract

Reactive power modulation of wind power plants is an effective way to damp inter-area oscillation in wind power penetrated power systems. For doubly fed induction generator (DFIG) based wind farms, there are two different ways to achieve reactive power modulation: one is via [...] Read more.

Reactive power modulation of wind power plants is an effective way to damp inter-area oscillation in wind power penetrated power systems. For doubly fed induction generator (DFIG) based wind farms, there are two different ways to achieve reactive power modulation: one is via reactive power feedback control, and the other method is via voltage feedback control. While both of the control schemes are feasible, their effectiveness may differ, and there has not been a systematic comparison between them. This paper investigates the differences between these two feedback schemes for inter-area oscillation damping control. The principles of utilizing DFIG for damping control is introduced at first. Then, analytical techniques including the frequency domain analysis,

μ

-analysis and time domain analysis are used to systematically study the performance of the two control schemes against inter-area oscillation. The robustness of the control schemes with respect to the variety of system operation points is also studied. The results from this paper can provide an insight into the understatement of DFIG reactive modulation against oscillation and guidance for controller design. Full article

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7 pages, 1143 KiB

Open AccessCommunication

Enhanced Production of Bioethanol by Fermentation of Autohydrolyzed and C₄mimOAc-Treated Sugarcane Bagasse Employing Various Yeast Strains

by Muzna Hashmi^1,2, Aamer Ali Shah¹, Abdul Hameed^1,3 and Arthur J. Ragauskas^2,4,5,*

¹ Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan

² Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996-2200, USA

³ SA-CIRBS, International Islamic University, Islamabad 45320, Pakistan

⁴ Joint Institute for Biological Sciences, Biosciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA

⁵ Center of Renewable Carbon, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN 37996-4542, USA

Energies 2017, 10(8), 1207; https://doi.org/10.3390/en10081207 - 14 Aug 2017

Cited by 9 | Viewed by 3918

Abstract

This study examines the fermentation of autohydrolyzed and 1-n-butyl-3-methylimidazolium acetate (C₄mimOAc) pretreated sugarcane bagasse, using four different yeast strains to determine the efficiency of bioethanol production. Three strains of Saccharomyces cerevisiae (S. cerevisiae) and one of Scheffersomyces stipitis ( [...] Read more.

This study examines the fermentation of autohydrolyzed and 1-n-butyl-3-methylimidazolium acetate (C₄mimOAc) pretreated sugarcane bagasse, using four different yeast strains to determine the efficiency of bioethanol production. Three strains of Saccharomyces cerevisiae (S. cerevisiae) and one of Scheffersomyces stipitis (S. stipitis) were employed in this study. It was observed that the sugarcane bagasse autohydrolyzed at 205 °C for 6 min with subsequent enzymatic hydrolysis exhibited the maximum ethanol yield of 70.92 ± 0.09 mg/g-substrate when S. cerevisiae MZ-4 was used. However, a slightly higher ethanol yield of 78.78 ± 0.94 mg/g-substrate was obtained from C₄mimOAc pretreated bagasse employing S. cerevisiae MZ-4. The study showed that the newly isolated MZ-4 strain exhibited better ethanol yield as compared to commercially available yeast strains S. cerevisiae Uvaferm-43, S. cerevisiae Lalvin EC-1118, and S. stipitis. Full article

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

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25 pages, 9030 KiB

Open AccessArticle

Comparative Analysis of Solar-Powered Base Stations for Green Mobile Networks

by Mohammed H. Alsharif

Department of Electrical Engineering, College of Electronics and Information Engineering, Sejong University, Seoul 05006, Korea

Energies 2017, 10(8), 1208; https://doi.org/10.3390/en10081208 - 14 Aug 2017

Cited by 27 | Viewed by 5888

Abstract

The rapid growth of mobile communication technology and the corresponding significant increase in the number of cellular base stations (BSs) have increased operational expenses (OPEX) for mobile operators, due to increased electricity prices and fossil fuel consumption. Thus, identifying alternative solutions to reduce [...] Read more.

The rapid growth of mobile communication technology and the corresponding significant increase in the number of cellular base stations (BSs) have increased operational expenses (OPEX) for mobile operators, due to increased electricity prices and fossil fuel consumption. Thus, identifying alternative solutions to reduce OPEX has become a major priority of mobile operators. Solar energy is considered an economically attractive and eco-friendly option. This paper examines solar energy solutions for different generations of mobile communications by conducting a comparative analysis of solar-powered BSs based on three aspects: architecture, energy production, and optimal system cost. In addition, the economic feasibility of the solar energy solution compared with conventional sources is discussed. The simulation results suggest that solar-powered BSs would be a suitable long-term solution for the mobile cellular network industry. Full article

(This article belongs to the Special Issue Sustainable and Renewable Energy Systems)

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15 pages, 10431 KiB

Open AccessArticle

Reduction of Stress Acting on a Thick, Deep Coal Seam by Protective-Seam Mining

by Rui Gao¹

, Bin Yu^1,2,*, Hongchun Xia³ and Hongfei Duan²

¹ Key Laboratory of Deep Coal Resource Mining, School of Mines, China University of Mining and Technology, Xuzhou 221116, China

² Datong Coal Mine Group Co. Ltd., Datong 037000, China

³ College of Civil and Architectural Engineering, Dalian University, Dalian 116622, China

Energies 2017, 10(8), 1209; https://doi.org/10.3390/en10081209 - 15 Aug 2017

Cited by 28 | Viewed by 4798

Abstract

Aiming to reduce the high mining stress observed in large-space roof structures during mechanized mining of thick coal seams, a control technique based on protective-seam mining is proposed. This technique was used to investigate the 8108 working face of the No. 3–5 thick [...] Read more.

Aiming to reduce the high mining stress observed in large-space roof structures during mechanized mining of thick coal seams, a control technique based on protective-seam mining is proposed. This technique was used to investigate the 8108 working face of the No. 3–5 thick coal seam of the Tashan mine located in the Datong area of Shanxi, China, by means of simulations and field measurements. The numerical simulation revealed that the No. 3–5 coal seam undergoes expansion and deformation, accompanied by stress relief due to the mining of the overlying No. 4 coal seam. The physical simulation demonstrated that mining the protective seam changes the structural characteristics of the overlying strata in advance and reduces the integrity of the roof in the No. 3–5 coal seam. Field measurements showed that the support loads in the 8108 working face are significantly weaker than those in the adjacent 8107 working face, where protective-seam mining was not performed. In the absence of high resistance on the support and distinct periodic weighting characteristics, the rock masses around the 8108 working face and roadway could be easily supported. Full article

(This article belongs to the Special Issue Energy Management Control)

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17 pages, 1519 KiB

Open AccessArticle

Fault Prediction and Diagnosis of Wind Turbine Generators Using SCADA Data

by Yingying Zhao¹

, Dongsheng Li^2,*, Ao Dong¹, Dahai Kang³, Qin Lv⁴ and Li Shang^1,4

¹ Department of Computer Science and Technology, Tongji University, Shanghai 201804, China

² IBM Research–China, Shanghai 201203, China

³ Concord New Energy Group Limited–China, Beijing 100048, China

⁴ Department of Computer Science, University of Colorado Boulder, Boulder, CO 80309, USA

Energies 2017, 10(8), 1210; https://doi.org/10.3390/en10081210 - 15 Aug 2017

Cited by 120 | Viewed by 10323

Abstract

The fast-growing wind power industry faces the challenge of reducing operation and maintenance (O&M) costs for wind power plants. Predictive maintenance is essential to improve wind turbine reliability and prolong operation time, thereby reducing the O&M cost for wind power plants. This study [...] Read more.

The fast-growing wind power industry faces the challenge of reducing operation and maintenance (O&M) costs for wind power plants. Predictive maintenance is essential to improve wind turbine reliability and prolong operation time, thereby reducing the O&M cost for wind power plants. This study presents a solution for predictive maintenance of wind turbine generators. The proposed solution can: (1) predict the remaining useful life (RUL) of wind turbine generators before a fault occurs and (2) diagnose the state of the wind turbine generator when the fault occurs. Moreover, the proposed solution implies low-deployment costs because it relies solely on the information collected from the widely available supervisory control and data acquisition (SCADA) system. Extra sensing hardware is needless. The proposed solution has been deployed and evaluated in two real-world wind power plants located in China. The experimental study demonstrates that the RUL of the generators can be predicted 18 days ahead with about an 80% prediction accuracy. When faults occur, the specific type of generator fault can be diagnosed with an accuracy of 94%. Full article

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

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23 pages, 5923 KiB

Open AccessArticle

Performance Evaluation of a Hydrogen-Based Clean Energy Hub with Electrolyzers as a Self-Regulating Demand Response Management Mechanism

by Weiliang Wang¹, Dan Wang^1,*, Hongjie Jia¹, Guixiong He², Qing’e Hu¹, Pang-Chieh Sui³ and Menghua Fan⁴

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

² China Electric Power Research Institute, Haidian District, Beijing 100192, China

³ School of Automotive Engineering, Wuhan University of Technology, Wuhan 430070, China

⁴ State Grid Energy Research Institute, Changping District, Beijing 102249, China

Energies 2017, 10(8), 1211; https://doi.org/10.3390/en10081211 - 15 Aug 2017

Cited by 10 | Viewed by 4076

Abstract

Energy management of hybrid resources has become a critical issue in integrated energy system analysis. In this study, as a self-regulating demand response (DR) management mechanism, deferrable electrolyzers are used as a main controlled resource in a hydrogen-based clean energy hub (CEH), which [...] Read more.

Energy management of hybrid resources has become a critical issue in integrated energy system analysis. In this study, as a self-regulating demand response (DR) management mechanism, deferrable electrolyzers are used as a main controlled resource in a hydrogen-based clean energy hub (CEH), which includes a traditional generation plant (TGP), a low-carbon generation plant (LGP), and wind energy. Based on the hysteresis control model for aggregated electrolyzers, a comfort-constrained optimal energy state regulation (OESR) control strategy is implemented to model the deregulation feature of aggregated electrolyzers. The electrolyzers’ population can be integrated as a controlled efficient power plant (EPP) to provide the virtual spinning reserve for CEH. As a flexible and self-regulating participant, the electrolyzer-based EPP is integrated into the hybrid resource constrained optimization model; this reduces the total cost of CEH and carbon emissions and improves the integration of wind energy. Combined with TGP, LGP, and wind energy, the simulation results show that the deployment of aggregated electrolyzers on both the supply and demand sides of the CEH contributes to significant amounts of low-carbon hydrogen. The simulation also illustrates that the DR control strategy has a positive effect on active power and reserve re-dispatch. Full article

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

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16 pages, 2978 KiB

Open AccessArticle

Coordinated Control of Multi-Type Energy Storage for Wind Power Fluctuation Suppression

by Xisheng Tang¹, Yushu Sun^1,*

, Guopeng Zhou² and Fufeng Miao³

¹ Institute of Electrical Engineering, Chinese Academy of Sciences, Haidian District, Beijing 100190, China

² North China Electric Power Research Institute Co., Ltd, Beijing 100045, China

³ Henan Electric Power Company Economic Research Institute, Zhengzhou 450052, China

Energies 2017, 10(8), 1212; https://doi.org/10.3390/en10081212 - 15 Aug 2017

Cited by 25 | Viewed by 4521

Abstract

The fluctuations of wind power impact the stable operation of a power system as its penetration grows high. Energy storage may be a potential solution to suppress these fluctuations and has drawn much attention in recent years. As the time scale of wind [...] Read more.

The fluctuations of wind power impact the stable operation of a power system as its penetration grows high. Energy storage may be a potential solution to suppress these fluctuations and has drawn much attention in recent years. As the time scale of wind power fluctuations is in a range of seconds to hours, multi-type energy storage with complementary characteristics, such as the combination of energy-type storage devices (ESD) and power-type storage device (PSD), may be technically and economically feasible to suppress multi-time-scale wind power fluctuations. Therefore, system control is very important when the power allocation among each of the energy storage units is considered. In this paper, a novel coordinated control strategy based on model predictive control (MPC) was proposed for wind power fluctuation suppression, which employs MPC for the total power required for the whole energy storage system and then allocates it between ESD and PSD with the low-pass filter algorithm (LFA) method. Due to the predictive feature of MPC, the power requirement of the energy storage system can be obtained with little time delay, which means less energy is needed. The effectiveness of the proposed control strategy was verified in a time-domain simulation system. The influence of wind speed conditions and LFA time constant on the wind/storage system were further discussed. Full article

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14 pages, 3915 KiB

Open AccessArticle

Photovoltaic Cell Parameter Estimation Using Hybrid Particle Swarm Optimization and Simulated Annealing

by Muhammad Ali Mughal, Qishuang Ma and Chunyan Xiao^*

School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

Energies 2017, 10(8), 1213; https://doi.org/10.3390/en10081213 - 15 Aug 2017

Cited by 81 | Viewed by 6578

Abstract

Accurate parameter estimation of solar cells is vital to assess and predict the performance of photovoltaic energy systems. For the estimation model to accurately track the experimentally measured current-voltage (I-V) data, the parameter estimation problem is converted into an [...] Read more.

Accurate parameter estimation of solar cells is vital to assess and predict the performance of photovoltaic energy systems. For the estimation model to accurately track the experimentally measured current-voltage (I-V) data, the parameter estimation problem is converted into an optimization problem and a metaheuristic optimization algorithm is used to solve it. Metaheuristics present a fairly acceptable solution to the parameter estimation but the problem of premature convergence still endures. The paper puts forward a new optimization approach using hybrid particle swarm optimization and simulated annealing (HPSOSA) to estimate solar cell parameters in single and double diode models using experimentally measured I-V data. The HPSOSA was capable of achieving a global minimum in all test runs and was significant in alleviating the premature convergence problem. The performance of the algorithm was evaluated by comparing it with five different optimization algorithms and performing a statistical analysis. The analysis results clearly indicated that the method was capable of estimating all the model parameters with high precision indicated by low root mean square error RMSE and mean absolute error MAE. The parameter estimation was accurately performed for a commercial (RTC France) solar cell. Full article

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17 pages, 4026 KiB

Open AccessArticle

Effect of Summer Ventilation on the Thermal Performance and Energy Efficiency of Buildings Utilizing Phase Change Materials

by Yi Zhang¹, Hongzhi Cui^1,*, Waiching Tang²

, Guochen Sang³ and Hong Wu¹

¹ Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, College of Civil Engineering, Shenzhen University, Shenzhen 518060, China

² School of Architecture and Built Environment, University of Newcastle, Callaghan, NSW 2308, Australia

³ School of Civil Engineering and Architecture, Xi’an University of Technology, Xi’an 710055, China

Energies 2017, 10(8), 1214; https://doi.org/10.3390/en10081214 - 16 Aug 2017

Cited by 18 | Viewed by 4341

Abstract

To analyze the effect of summer ventilation on the thermal performance and energy efficiency of buildings utilizing phase change materials (PCMs), this paper simulated the indoor temperature variation and energy saving performance of buildings constructed with PCM under different ventilation conditions from June [...] Read more.

To analyze the effect of summer ventilation on the thermal performance and energy efficiency of buildings utilizing phase change materials (PCMs), this paper simulated the indoor temperature variation and energy saving performance of buildings constructed with PCM under different ventilation conditions from June to September. With EnergyPlus and degree-day method, 48 ventilation schemes, including eight ventilation periods (3 h per period) and six ventilation quantities (0.5 ac/h to 3 ac/h), were modeled and simulated in five cities located in different climate regions in China. According to the results, it is believed that the simultaneous use of PCM and ventilation can significantly improve the indoor thermal comfort and offer a good energy saving performance in summer. Considering the economic benefits, different optimal ventilation schemes (including ventilation periods and ventilation quantities) were suggested for different climate regions. Full article

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

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10 pages, 2470 KiB

Open AccessArticle

Studies on the Effect of Nano-Sized MgO in Magnesium-Ion Conducting Gel Polymer Electrolyte for Rechargeable Magnesium Batteries

by Na Wu^1,*, Wei Wang¹, Yu Wei^1,* and Taohai Li^2,*

¹ Key Laboratory of Inorganic Nanomaterials of Hebei Province, College of Chemistry and Material Science, Hebei Advance Thin Films Laboratory, College of Physical Science and Information Engineering, National Demonstration Center for Experimental Chemistry Education, Hebei Normal University, Shijiazhuang 050024, China

² Key Lab of Environment Friendly Chemistry and Application in Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105, China

Energies 2017, 10(8), 1215; https://doi.org/10.3390/en10081215 - 16 Aug 2017

Cited by 21 | Viewed by 4856

Abstract

Magnesium-ion conducting gel polymer electrolytes (GPEs) with different contents of nano-sized MgO have been prepared and investigated by various electrical and electrochemical techniques. The Mg²⁺ ion conduction in GPEs was confirmed from cyclic voltammetry and impedance analysis. It was found that doping [...] Read more.

Magnesium-ion conducting gel polymer electrolytes (GPEs) with different contents of nano-sized MgO have been prepared and investigated by various electrical and electrochemical techniques. The Mg²⁺ ion conduction in GPEs was confirmed from cyclic voltammetry and impedance analysis. It was found that doping appropriate nano-sized MgO in the GPE can induce significant improvements in both the electrochemical and the mechanical properties of GPEs. The composite GPE with 7% MgO shows a high ionic conductivity of 4.6 × 10⁻³ S/cm with electrochemical stability up to 4.7 V versus Mg²⁺/Mg at room temperature. Furthermore, it is free-standing and flexible with high tensile strength (9.7 ± 0.1 MPa) and elongation at break (91.7 ± 0.2%), further ensuring their potential applications as GPEs for rechargeable Mg batteries. Full article

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

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21 pages, 4054 KiB

Open AccessArticle

Valuation of Real Options in Crude Oil Production

by Luis Mª Abadie¹

and José M. Chamorro^2,*

¹ Basque Centre for Climate Change, Sede Building 1, 1st Floor, Scientific Campus, University of the Basque Country, 48940 Leioa, Spain

² Department of Financial Economics II and Institute of Public Economics, University of the Basque Country, Av. Lehendakari Aguirre 83, 48015 Bilbao, Spain

Energies 2017, 10(8), 1218; https://doi.org/10.3390/en10081218 - 17 Aug 2017

Cited by 10 | Viewed by 4972

Abstract

Oil producers are going through a hard period. They have a number of real options at their disposal. This paper addresses the valuation of two of them: the option to delay investment and the option to abandon a producing field. A prerequisite for [...] Read more.

Oil producers are going through a hard period. They have a number of real options at their disposal. This paper addresses the valuation of two of them: the option to delay investment and the option to abandon a producing field. A prerequisite for this is to determine the value of a producing well. For this purpose we draw on a stochastic model of oil price with three risk factors: spot price, long-term price, and spot price volatility. This model is estimated with spot and futures West Texas Intermediate (WTI) oil prices. The numerical estimates of the underlying parameters allow calculate the value of a producing well over a fixed time horizon. We delineate the optimal boundary that separates the investment region from the wait region in the spot price/unit cost space. We similarly draw the boundary governing the optimal exercise of the option to abandon and the one governing the active/inactive production decision when there is no such option. Full article

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31 pages, 10326 KiB

Open AccessArticle

Do the Different Exergy Accounting Methodologies Provide Consistent or Contradictory Results? A Case Study with the Portuguese Agricultural, Forestry and Fisheries Sector

by Ricardo Manso^*, Tânia Sousa and Tiago Domingos

Marine, Environment and Technology Centre—MARETEC, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1, 1049-001 Lisbon, Portugal

Energies 2017, 10(8), 1219; https://doi.org/10.3390/en10081219 - 17 Aug 2017

Cited by 10 | Viewed by 5168

Abstract

Three exergy accounting approaches are used to evaluate exergy efficiency: the Energy Resources Exergy Accounting (EREA), the Natural Resources’ Exergy Accounting (NREA) and the Extended Exergy Accounting (EEA). To test the consistency of the results provided by these methodologies, we apply them to [...] Read more.

Three exergy accounting approaches are used to evaluate exergy efficiency: the Energy Resources Exergy Accounting (EREA), the Natural Resources’ Exergy Accounting (NREA) and the Extended Exergy Accounting (EEA). To test the consistency of the results provided by these methodologies, we apply them to evaluate the Portuguese agricultural, forestry and fisheries (AFF) sector, from 2000 to 2012. EREA shows an increase of 30% in the efficiency of the Portuguese AFF sector, while NREA and EEA methodologies increases of 27% and 43%, respectively. Although the results are consistent for the AFF sector, the same does not happen in the fisheries subsector, whose exergetic efficiency increases 14% with the EREA but decreases 42% with the NREA approach. The ratio of output to useful exergy reveals that a better thermodynamic efficiency is not translated into a higher energy service efficiency because fishing vessels have to travel more to get the same fish. Thus, results provided by the EREA and NREA approaches are complementary and both are needed to provide a realistic picture of exergy efficiency. On the other hand, results obtained by the EEA approach are dominated by capital and environmental impacts, revealing the disproportionality between material and immaterial inputs in this methodology. Full article

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22 pages, 30967 KiB

Open AccessArticle

The UK Solar Farm Fleet: A Challenge for the National Grid? ^†

by Diane Palmer^*

, Elena Koubli, Tom Betts and Ralph Gottschalg

Centre for Renewable Energy Systems Technology (CREST), Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, UK

Energies 2017, 10(8), 1220; https://doi.org/10.3390/en10081220 - 17 Aug 2017

Cited by 8 | Viewed by 7966

Abstract

Currently, in the UK, it is widely believed that supply from renewable energy sources is capable of reaching proportions too great for the transmission system. This research investigates this topic objectively by offering an understanding of year-to-year and area-to-area variability of PV (photovoltaic) [...] Read more.

Currently, in the UK, it is widely believed that supply from renewable energy sources is capable of reaching proportions too great for the transmission system. This research investigates this topic objectively by offering an understanding of year-to-year and area-to-area variability of PV (photovoltaic) performance, measured in terms of specific yield (kWh/kWp). The dataset is created using publicly available data that gives an indication of impact on the grid. The daily and seasonal variance is determined, demonstrating a surprisingly good energy yield in April (second only to August). The geographic divergence of generation from large scale solar systems is studied for various sized regions. Generation is compared to demand. Timing of output is analyzed and probability of achieving peak output ascertained. Output and demand are not well matched, as regards location. Nevertheless, the existing grid infrastructure is shown to have sufficient capacity to handle electricity flow from large scale PV. Full nameplate capacity is never reached by the examples studied. Although little information is available about oversizing of array-to-inverter ratios, this is considered unlikely to be a major contributor to grid instability. It is determined that output from UK solar farms currently presents scant danger to grid stability. Full article

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13 pages, 2244 KiB

Open AccessArticle

Net Load Carrying Capability of Generating Units in Power Systems

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

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

Energies 2017, 10(8), 1221; https://doi.org/10.3390/en10081221 - 17 Aug 2017

Cited by 13 | Viewed by 5376

Abstract

This paper proposes an index called net load carrying capability (NLCC) to evaluate the contribution of a generating unit to the flexibility of a power system. NLCC is defined as the amount by which the load can be increased when a generating unit [...] Read more.

This paper proposes an index called net load carrying capability (NLCC) to evaluate the contribution of a generating unit to the flexibility of a power system. NLCC is defined as the amount by which the load can be increased when a generating unit is added to the system, while still maintaining the flexibility of the system. This index is based on the flexibility index termed ramping capability shortage expectation (RSE), which has been used to quantify the risk associated with system flexibility. This paper argues that NLCC is more effective than effective load carrying capability (ELCC) in quantifying the contribution of the generating unit to flexibility. This is explained using an illustrative example. A case study has been performed with a modified IEEE-RTS-96 to confirm the applicability of the NLCC index. The simulation results demonstrate the effect of operating conditions such as operating point and ramp rate on NLCC, and show which kind of unit is more helpful in terms of flexibility. Full article

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

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16 pages, 3637 KiB

Open AccessArticle

Quantifying Cathode Water Transport via Anode Relative Humidity Measurements in a Polymer Electrolyte Membrane Fuel Cell

by Logan Battrell¹, Aubree Trunkle¹, Erica Eggleton¹, Lifeng Zhang² and Ryan Anderson^1,3,*

¹ Chemical and Biological Engineering Department, Montana State University, Bozeman, MT 59717, USA

² Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada

³ Energy Research Institute, Montana State University, Bozeman, MT 59717, USA

Energies 2017, 10(8), 1222; https://doi.org/10.3390/en10081222 - 17 Aug 2017

Cited by 5 | Viewed by 5788

Abstract

A relative humidity (RH) measurement based on pressure drop analysis is presented as a diagnostic tool to experimentally quantify the amount of excess water on the cathode side of a polymer electrolyte membrane fuel cell (PEMFC). Ex-situ pressure drop calibration curves collected at [...] Read more.

A relative humidity (RH) measurement based on pressure drop analysis is presented as a diagnostic tool to experimentally quantify the amount of excess water on the cathode side of a polymer electrolyte membrane fuel cell (PEMFC). Ex-situ pressure drop calibration curves collected at fixed RH values, used with a set of well-defined equations for the anode pressure drop, allows for an estimate of in-situ relative humidity values. During the in-situ test, a dry anode inlet stream at increasing flow rates is used to create an evaporative gradient to drive water from the cathode to the anode. This combination of techniques thus quantitatively determines the changing net cell water flux. Knowing the cathodic water production rate, the net water flux to the anode can explain the influence of liquid and vapor transport as a function of GDL selection. Experimentally obtained quantified values for the water removal rate for a variety of cathode gas diffusion layer (GDL) setups are presented, which were chosen to experimentally vary a range of water management abilities, from high to low performance. The results show that more water is transported to the anode when a GDL with poor water management capabilities is used, due to the higher levels of initial saturation occurring on the cathode. At sufficiently high concentration gradients, the anode removes more water than is produced by the reaction, allowing for the quantification of excess water saturating the cathode. The protocol is broadly accessible and applicable as a quantitative diagnostic tool of water management in PEMFCs. Full article

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19 pages, 10179 KiB

Open AccessArticle

Sensitivity Analysis of Heavy Fuel Oil Spray and Combustion under Low-Speed Marine Engine-Like Conditions

by Lei Zhou, Aifang Shao, Haiqiao Wei^* and Xi Chen

¹ State Key Laboratory of Engines, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China

^† These authors contributed equally to this work and should be considered co-first authors.

Energies 2017, 10(8), 1223; https://doi.org/10.3390/en10081223 - 17 Aug 2017

Cited by 16 | Viewed by 6822

Abstract

On account of their high power, thermal efficiency, good reliability, safety, and durability, low-speed two-stroke marine diesel engines are used as the main drive devices for large fuel and cargo ships. Most marine engines use heavy fuel oil (HFO) as the primary fuel, [...] Read more.

On account of their high power, thermal efficiency, good reliability, safety, and durability, low-speed two-stroke marine diesel engines are used as the main drive devices for large fuel and cargo ships. Most marine engines use heavy fuel oil (HFO) as the primary fuel, however, the physical and chemical characteristics of HFO are not clear because of its complex thermophysical properties. The present study was conducted to investigate the effects of fuel properties on the spray and combustion characteristics under two-stroke marine engine-like conditions via a sensitivity analysis. The sensitivity analysis of fuel properties for non-reacting and reacting simulations are conducted by comparing two fuels having different physical properties, such as fuel density, dynamic viscosity, critical temperature, and surface tension. The performances of the fuels are comprehensively studied under different ambient pressures, ambient temperatures, fuel temperatures, and swirl flow conditions. From the results of non-reacting simulations of HFO and diesel fuel properties in a constant volume combustion chamber, it can be found that the increase of the ambient pressure promotes fuel evaporation, resulting in a reduction in the steady liquid penetration of both diesel and HFO; however, the difference in the vapor penetrations of HFO and diesel reduces. Increasing the swirl flow significantly influences the atomization of both HFO and diesel, especially the liquid distribution of diesel. It is also found that the ambient temperature and fuel temperature have the negative effects on Sauter mean diameter (SMD) distribution. For low-speed marine engines, the combustion performance of HFO is not sensitive to activation energy in a certain range of activation energy. At higher engine speed, the difference in the effects of different activation energies on the in-cylinder pressure increases. The swirl flow in the cylinder can significantly promote fuel evaporation and reduce soot production. Full article

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

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13 pages, 6504 KiB

Open AccessArticle

Best Practices for Recovering Rural Abandoned Towers through the Installation of Small-Scale Biogas Plants

by Mattia Manni

, Valentina Coccia, Gianluca Cavalaglio

, Andrea Nicolini

and Alessandro Petrozzi^*

Department of Engineering, CIRIAF—Interuniversity Research Center on Pollution and Environment “Mauro Felli”, Via G. Duranti 67, 06125 Perugia, Italy

Energies 2017, 10(8), 1224; https://doi.org/10.3390/en10081224 - 17 Aug 2017

Cited by 8 | Viewed by 4452

Abstract

The massive and continuous development of renewable energy systems is making it possible to achieve the European goals regarding environment and sustainability. On the other hand, it leads to the progression of significant problems such as low renewable energy density (i), social acceptability [...] Read more.

The massive and continuous development of renewable energy systems is making it possible to achieve the European goals regarding environment and sustainability. On the other hand, it leads to the progression of significant problems such as low renewable energy density (i), social acceptability (ii), and non-programmability of renewable energy sources (iii). The rural architecture, which is largely present in the countryside of central Italy, is generally equipped with several annexes such as dovecotes (i), grain stores (ii), and tobacco drying kilns (iii). Nowadays, those towers appear in decay because of the decline of agricultural activities, although they are classed as Environmental and Historical Heritage sites. The present work aims to propose a methodology for improving the energy grid in the countryside, while reusing abandoned buildings by modifying their function and maintaining their aspect as much as possible. The proposed workflow was applied to a rural silo, which has fallen into disuse, in Sant’Apollinare (Marsciano, Perugia) by converting it into a mini-biogas plant. The function of the annex which was chosen as the case study changes from agricultural use to energy production: it becomes an on-site renewable energy-based electric grid that can produce clean energy from agricultural and forestry residues. The project turns out to be sustainable not only in terms of energy and the environment, but also from an economic point of view as a result of the recent regulations and incentives for renewable energy production. Full article

(This article belongs to the Special Issue 17th CIRIAF National Congress – Sustainable Development, Environment and Human Health Protection)

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20 pages, 7870 KiB

Open AccessArticle

Hydrogen Storage Capacity of Tetrahydrofuran and Tetra-N-Butylammonium Bromide Hydrates Under Favorable Thermodynamic Conditions

by Joshua T. Weissman¹ and Stephen M. Masutani^2,*

¹ Hawaiian Electric Company, Honolulu, HI 96814, USA

² Hawaii Natural Energy Institute, University of Hawaii, Honolulu, HI 96822, USA

Energies 2017, 10(8), 1225; https://doi.org/10.3390/en10081225 - 17 Aug 2017

Cited by 11 | Viewed by 5882

Abstract

An experimental study was conducted to evaluate the feasibility of employing binary hydrates as a medium for H₂storage. Two reagents, tetrahydrofuran (THF) and tetra-n-butylammonium bromide (TBAB), which had been reported previously to have potential to form binary hydrates with [...] Read more.

An experimental study was conducted to evaluate the feasibility of employing binary hydrates as a medium for H₂storage. Two reagents, tetrahydrofuran (THF) and tetra-n-butylammonium bromide (TBAB), which had been reported previously to have potential to form binary hydrates with H₂ under favorable conditions (i.e., low pressures and high temperatures), were investigated using differential scanning calorimetry and Raman spectroscopy. A scale-up facility was employed to quantify the hydrogen storage capacity of THF binary hydrate. Gas chromatography (GC) and pressure drop analyses indicated that the weight percentages of H₂ in hydrate were less than 0.1%. The major conclusions of this investigation were: (1) H₂ can be stored in binary hydrates at relatively modest pressures and temperatures which are probably feasible for transportation applications; and (2) the storage capacity of H₂ in binary hydrate formed from aqueous solutions of THF over a concentration range extending from 2.78 to 8.34 mol % and at temperatures above 263 K and pressures below 11 MPa was <0.1 wt %. Full article

(This article belongs to the Special Issue Methane Hydrate Research and Development)

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17 pages, 2410 KiB

Open AccessArticle

A Sensitivity Analysis of a Computer Model-Based Leak Detection System for Oil Pipelines

by Zhe Lu, Yuntong She^*

and Mark Loewen

Department of Civil and Environmental Engineering, University of Alberta, 7-203 Donadeo Innovation Centre for Engineering, 9211 116 Street NW, Edmonton, AB T6G 1H9, Canada

Energies 2017, 10(8), 1226; https://doi.org/10.3390/en10081226 - 17 Aug 2017

Cited by 11 | Viewed by 4844

Abstract

Improving leak detection capability to eliminate undetected releases is an area of focus for the energy pipeline industry, and the pipeline companies are working to improve existing methods for monitoring their pipelines. Computer model-based leak detection methods that detect leaks by analyzing the [...] Read more.

Improving leak detection capability to eliminate undetected releases is an area of focus for the energy pipeline industry, and the pipeline companies are working to improve existing methods for monitoring their pipelines. Computer model-based leak detection methods that detect leaks by analyzing the pipeline hydraulic state have been widely employed in the industry, but their effectiveness in practical applications is often challenged by real-world uncertainties. This study quantitatively assessed the effects of uncertainties on leak detectability of a commonly used real-time transient model-based leak detection system. Uncertainties in fluid properties, field sensors, and the data acquisition system were evaluated. Errors were introduced into the input variables of the leak detection system individually and collectively, and the changes in leak detectability caused by the uncertainties were quantified using simulated leaks. This study provides valuable quantitative results contributing towards a better understanding of how real-world uncertainties affect leak detection. A general ranking of the importance of the uncertainty sources was obtained: from high to low it is time skew, bulk modulus error, viscosity error, and polling time. It was also shown that inertia-dominated pipeline systems were less sensitive to uncertainties compared to friction-dominated systems. Full article

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14 pages, 5269 KiB

Open AccessArticle

An All-Electric-Aircraft Tailored SiC-Based Power Factor Correction Converter with Adaptive DC-Link Regulator

by Gianluca Brando¹, Adolfo Dannier^1,*

, Andrea Del Pizzo¹ and Marino Coppola²

¹ Department of Electrical Engineering and IT, DIETI, University of Naples Federico II, 80125 Naples, Italy

² Power Naples Prototype Laboratory, PNP LAB srl, 80122 Naples, Italy

Energies 2017, 10(8), 1227; https://doi.org/10.3390/en10081227 - 18 Aug 2017

Cited by 7 | Viewed by 4987

Abstract

In recent years the aerospace industry has made a growing effort to develop a quieter and more environmentally friendly aircraft. In particular, several research activities have been focused on innovative solutions aimed at the design/optimization of an on-board electric system fully compatible with [...] Read more.

In recent years the aerospace industry has made a growing effort to develop a quieter and more environmentally friendly aircraft. In particular, several research activities have been focused on innovative solutions aimed at the design/optimization of an on-board electric system fully compatible with this new approach. A first important step in the evolution towards an All Electric Aircraft (AEA) is the replacement of the hydraulic actuators with fully electric ones. The transition process is not easy to carry out, since weight, size and reliability represent highly critical issues for aircraft applications. In this context, the significant improvements in semiconductor technologies can be exploited as a critical means to overcome the constraints mentioned. Indeed, this work proposes a Silicon Carbide (SiC) based Power Factor Correction (PFC) converter, whose design and control have been tailored in order to properly supply a wide range of on-board Electro-Mechanical Actuators (EMA). In particular, while the adopted circuit topology allows for power factor correction and bi-directional power flow, the SiC technology, thanks to the higher efficiency with respect to other semiconductor-based technologies, leads to a significant reduction in the overall system weight/volume. Furthermore, to meet the strict requirements in terms of dynamic and steady state performance imposed by the application, a novel adaptive regulator is conceived. A reduced-scale laboratory prototype of the SiC-based converter (3 kVA) is realized in order to verify the effectiveness of the proposed design and control approach. Full article

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13 pages, 2605 KiB

Open AccessArticle

Optimization of Drilling Layouts Based on Controlled Presplitting Blasting through Strata for Gas Drainage in Coal Roadway Strips

by Zhicheng Xie^1,2, Dongming Zhang^1,2,*, Zhenlong Song^1,2

, Minghui Li^1,2, Chao Liu^1,2 and Dongling Sun³

¹ State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China

² College of Resources and Environmental Sciences, Chongqing University, Chongqing 400030, China

³ Gas Research Institute, Chongqing Research Institute of China Coal Technology and Engineering Group Corp, Chongqing 400037, China

Energies 2017, 10(8), 1228; https://doi.org/10.3390/en10081228 - 18 Aug 2017

Cited by 33 | Viewed by 5461

Abstract

The controlled presplitting blasting technique is widely used in mining engineering to improve the permeability and gas extraction efficiency of coal seams. One of the key factors is the appropriate arrangement of the blasting and drainage holes, which can help improve the gas [...] Read more.

The controlled presplitting blasting technique is widely used in mining engineering to improve the permeability and gas extraction efficiency of coal seams. One of the key factors is the appropriate arrangement of the blasting and drainage holes, which can help improve the gas drainage quantity. To optimize the drilling layout to enhance gas-drainage efficiency, a series of controlled presplitting blasting tests were conducted at the Pingdingshan No. 8 coal mine. Based on the analysis of variations in stress and longitudinal-wave velocity of the coal in different blasting ranges, the results show that the stress on the coal at a distance of 1 m from the blasting hole decreased significantly after blasting; thus, the coal exhibited negligible bearing capacity and the longitudinal-wave velocity decreased by 56%. However, the coal exhibited particular bearing capacity at a distance of 3 m away from the blasting hole, and the longitudinal-wave velocity decreased by 35%. The stress and longitudinal-wave velocity at a distance of 5 m from the blasting hole were unaffected by the blasting. The blasting integrity rate of coal k_v was defined to characterize the effect of blasting on the coal-seam fracture. The effective cracking and effective influence radii of blasting under these working conditions were predicted to be in the ranges 3.3–3.4 m and 7.2–7.3 m, respectively. According to the test results, the borehole layout was optimized in the field testes for gas drainage in coal roadway strips, and the amounts of pure gas extracted after blasting were thus increased by 1.54–2.24 times the amount before blasting. Full article

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

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13 pages, 5926 KiB

Open AccessArticle

Wind Energy Potential of Gaza Using Small Wind Turbines: A Feasibility Study

by Mohamed Elnaggar¹, Ezzaldeen Edwan¹ and Matthias Ritter^2,*

¹ Department of Engineering, Palestine Technical College, College street, 920, Deir El-Balah, Gaza Strip, Palestine

² Department of Agricultural Economics, Humboldt-Universität zu Berlin, Philippstr. 13, 10115 Berlin, Germany

Energies 2017, 10(8), 1229; https://doi.org/10.3390/en10081229 - 18 Aug 2017

Cited by 34 | Viewed by 9634

Abstract

In this paper, we conduct a feasibility study of the wind energy potential in Gaza, which suffers from a severe shortage of energy supplies. Our calculated energy harvested from the wind is based on data for a typical meteorological year, which are fed [...] Read more.

In this paper, we conduct a feasibility study of the wind energy potential in Gaza, which suffers from a severe shortage of energy supplies. Our calculated energy harvested from the wind is based on data for a typical meteorological year, which are fed into a small wind turbine of 5 kW power rating installable on the roof of residential buildings. The expected annual energy output at a height of 10 m amounts to 2695 kWh, but it can be increased by 35–125% at higher altitudes between 20 m and 70 m. The results also depict the great potential of wind energy to complement other renewable resources such as solar energy: the harvested energy of a wind system constitutes to up to 84% of the annual output of an equivalent power rating photovoltaic system and even outperforms the solar energy in the winter months. We also show that one wind turbine and one comparable photovoltaic system together could provide enough energy for 3.7 households. Hence, a combination of wind and solar energy could stabilize the decentralized energy production in Gaza. This is very important in a region where people seek to reach energy self-sufficient buildings due to the severe electricity shortage in the local grid. Full article

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

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14 pages, 4338 KiB

Open AccessArticle

Heat Conduction in Porous Media Characterized by Fractal Geometry

by Zilong Deng², Xiangdong Liu³

, Yongping Huang², Chengbin Zhang^2,* and Yongping Chen^1,2,3,*

¹ Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, Jiangsu, China

² Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, Jiangsu, China

³ School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225127, Jiangsu, China

Energies 2017, 10(8), 1230; https://doi.org/10.3390/en10081230 - 18 Aug 2017

Cited by 33 | Viewed by 6256

Abstract

Fractal geometry (fractional Brownian motion—FBM) is introduced to characterize the pore distribution of porous material. Based on this fractal characterization, a mathematical model of heat conduction is presented to study heat conduction behaviors in porous material with a focus on effective thermal conductivity. [...] Read more.

Fractal geometry (fractional Brownian motion—FBM) is introduced to characterize the pore distribution of porous material. Based on this fractal characterization, a mathematical model of heat conduction is presented to study heat conduction behaviors in porous material with a focus on effective thermal conductivity. The role of pore structure on temperature distribution and heat flux is examined and investigated for fractal porous material. In addition, the effects of fractal dimension, porosity, and the ratio of solid-matrix-to-fluid-phase thermal conductivity (k_s/k_f) on effective thermal conductivity are evaluated. The results indicate that pore structure has an important effect on heat conduction inside porous material. Increasing porosity lowers thermal conductivity. Even when porosity remains constant, effective thermal conductivity is affected by the fractal dimensions of the porous material. For porous material, the heat conduction capability weakens with increased fractal dimension. Additionally, fluid-phase thermal conduction across pores is effective in porous material only when k_s/k_f < 50. Otherwise, effective thermal conductivity for porous material with a given pore structure depends primarily on the thermal conductivity of the solid matrix. Full article

(This article belongs to the Special Issue Geothermal Heating and Cooling)

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21 pages, 4231 KiB

Open AccessArticle

A New MCP Method of Wind Speed Temporal Interpolation and Extrapolation Considering Wind Speed Mixed Uncertainty

by Xiao Liu¹, Xu Lai^1,* and Jin Zou²

¹ School of Water Resource and Hydro Electric Engineering, Wuhan University, Wuhan 430072, Hubei, China

² Electric Power Research Institute, China Southern Power Grid, Guangzhou 510080, Guangdong, China

Energies 2017, 10(8), 1231; https://doi.org/10.3390/en10081231 - 18 Aug 2017

Cited by 7 | Viewed by 5117

Abstract

In this paper, a missing wind speed data temporal interpolation and extrapolation method in the wind energy industry was investigated. Given that traditional methods have previously ignored part of mixed uncertainty of wind speed, a concrete granular computing method is constructed and a [...] Read more.

In this paper, a missing wind speed data temporal interpolation and extrapolation method in the wind energy industry was investigated. Given that traditional methods have previously ignored part of mixed uncertainty of wind speed, a concrete granular computing method is constructed and a new Measure–Correlate–Predict (MCP) method of wind speed data temporal interpolation and extrapolation considering all mixed uncertainties is proposed, based on granular computing theory by adopting the cloud model method, support vector regression method, artificial neural network, genetic algorithm, and fuzzy c-means clustering algorithm as tools. The importance of considering mixed wind speed uncertainty and the suitability of using granular computing method are illustrated, and wind speed mixed uncertainty analysis is implemented, then, recommended values and estimation tools for wind speed measurement uncertainty and combined uncertainty are provided. An interpolation case of two practical meteorological sites in central Southern China was used to implement and validate the method proposed in this paper. The following conclusions are reached: (a) by using the method proposed in this paper, mixed uncertainty of wind speed can be considered, comparing to other MCP methods used for purposes of comparison, a better estimation of the wind speed is provided, and most evaluation metrics employed in this analysis were superior to other methods, that is to say, the accuracy of the wind resource assessment improved, and the risks of wind farm construction were reduced; (b) granular computing method is suitable for the issue of wind speed data interpolation and extrapolation considering wind speed mixed uncertainty; (c) mixed uncertainty of wind speed can be divided into three levels, and recommended values of granularity are minimum interval of records, 0.3–0.8 m/s, and 1–3 m/s, respectively. Full article

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19 pages, 5903 KiB

Open AccessArticle

Numerical and Experimental Investigation of Equivalence Ratio (ER) and Feedstock Particle Size on Birchwood Gasification

by Rukshan Jayathilake

and Souman Rudra^*

Department of Engineering and Sciences, University of Agder, Grimstad 4879, Norway

Energies 2017, 10(8), 1232; https://doi.org/10.3390/en10081232 - 19 Aug 2017

Cited by 44 | Viewed by 8240

Abstract

This paper discusses the characteristics of Birchwood gasification using the simulated results of a Computational Fluid Dynamics (CFD) model. The CFD model is developed and validated with the experimental results obtained with the fixed bed downdraft gasifier available at the University of Agder [...] Read more.

This paper discusses the characteristics of Birchwood gasification using the simulated results of a Computational Fluid Dynamics (CFD) model. The CFD model is developed and validated with the experimental results obtained with the fixed bed downdraft gasifier available at the University of Agder (UIA), Norway. In this work, several parameters are examined and given importance, such as producer gas yield, syngas composition, lower heating value (LHV), and cold gas efficiency (CGE) of the syngas. The behavior of the parameters mentioned above is examined by varying the biomass particle size. The diameters of the two biomass particles are 11.5 mm and 9.18 mm. All the parameters investigate within the Equivalences Ratio (ER) range from 0.2 to 0.5. In the simulations, a variable air inflow rate is used to achieve different ER values. For the different biomass particle sizes, CO, CO₂, CH₄, and H₂ mass fractions of the syngas are analyzed along with syngas yield, LHV, and CGE. At an ER value of 0.35, 9.18 mm diameter particle shows average maximum values of 60% of CGE and 2.79 Nm³/h of syngas yield, in turn showing 3.4% and 0.09 Nm³/h improvement in the respective parameters over the 11.5 mm diameter biomass particle. Full article

(This article belongs to the Special Issue Engineering Fluid Dynamics)

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14 pages, 4027 KiB

Open AccessEditor’s ChoiceArticle

A Metric-Based Validation Process to Assess the Realism of Synthetic Power Grids

by Adam B. Birchfield^1,*

, Eran Schweitzer²

, Mir Hadi Athari³

, Ti Xu¹, Thomas J. Overbye¹, Anna Scaglione² and Zhifang Wang³

¹ Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA

² School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85287, USA

³ Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA

Energies 2017, 10(8), 1233; https://doi.org/10.3390/en10081233 - 19 Aug 2017

Cited by 70 | Viewed by 7841

Abstract

Public power system test cases that are of high quality benefit the power systems research community with expanded resources for testing, demonstrating, and cross-validating new innovations. Building synthetic grid models for this purpose is a relatively new problem, for which a challenge is [...] Read more.

Public power system test cases that are of high quality benefit the power systems research community with expanded resources for testing, demonstrating, and cross-validating new innovations. Building synthetic grid models for this purpose is a relatively new problem, for which a challenge is to show that created cases are sufficiently realistic. This paper puts forth a validation process based on a set of metrics observed from actual power system cases. These metrics follow the structure, proportions, and parameters of key power system elements, which can be used in assessing and validating the quality of synthetic power grids. Though wide diversity exists in the characteristics of power systems, the paper focuses on an initial set of common quantitative metrics to capture the distribution of typical values from real power systems. The process is applied to two new public test cases, which are shown to meet the criteria specified in the metrics of this paper. Full article

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

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12 pages, 4827 KiB

Open AccessArticle

Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal

by Hongwei Zhang^1,2,†, Zhijun Wan^1,*, Dan Ma^3,†, Bo Zhang⁴ and Peng Zhou¹

¹ Key Laboratory of Deep Coal Resource Mining (CUMT), Ministry of Education of China, School of Mines, China University of Mining & Technology, Xuzhou 221116, China

² Department of Energy and Mineral Engineering, EMS Energy Institute, and G3 Center, The Pennsylvania State University, University Park, PA 16802, USA

³ School of Resources & Safety Engineering, Central South University, Changsha 410083, China

⁴ Changping Coal Mine, Jincheng Anthracite Mining Group, Jincheng 048000, China

^† These authors contributed equally to this work.

Energies 2017, 10(8), 1234; https://doi.org/10.3390/en10081234 - 20 Aug 2017

Cited by 11 | Viewed by 6873

Abstract

Injecting water into a coal seam to enhance the cohesive strength of coal and thus minimize and reduce the coal wall spalling risk must be considered in underground coal mining systems. In general, coal with low cohesive strength contains clay minerals which may [...] Read more.

Injecting water into a coal seam to enhance the cohesive strength of coal and thus minimize and reduce the coal wall spalling risk must be considered in underground coal mining systems. In general, coal with low cohesive strength contains clay minerals which may affect the stability of coal by interacting with water. Therefore, the coupled effects of moisture content and inherent clay minerals on the physical properties (i.e., cohesive strength and internal friction angle) of coal samples should be addressed. In this paper, direct shear tests were conducted by remodelling the Yiluo coal with various moisture contents ranging from 6.6% to 20.7%. According to Mohr–Coulomb failure criterion, cohesive strength and internal friction angle of coal were obtained. Afterwards, effects of moisture content and clay minerals (i.e., Kaolinite, Smectite and Illite) on the cohesive strength of coal were analysed using X-ray diffraction (XRD) method. The results show that cohesive strength increases when the moisture content rises from 6.6% to 17.6%, after which it decreases with increasing moisture content. This trend can be well illustrated by the relationship between typical water retention curve (WRC) and suction stress of soil. Therefore, a moisture content of 17.6% would be an optimal value to enhance the stability of the Yiluo coal seam. Full article

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13 pages, 6286 KiB

Open AccessArticle

Extended Kalman Filter-Based State of Charge and State of Power Estimation Algorithm for Unmanned Aerial Vehicle Li-Po Battery Packs

by Sunghun Jung^1,* and Heon Jeong²

¹ Department of Drone System, Chodang University, Muan-gun 58530, Jeollanam-do, Korea

² Department of Fire Administration, Chodang University, Muan-gun 58530, Jeollanam-do, Korea

Energies 2017, 10(8), 1237; https://doi.org/10.3390/en10081237 - 21 Aug 2017

Cited by 30 | Viewed by 5417

Abstract

Customer requirements for unmanned aerial vehicles (UAVs) with long flight times are increasing exponentially in the personal, commercial, and military use areas. Due to their limited payload, large numbers of on-board battery packs cannot be used and this is the main reason behind [...] Read more.

Customer requirements for unmanned aerial vehicles (UAVs) with long flight times are increasing exponentially in the personal, commercial, and military use areas. Due to their limited payload, large numbers of on-board battery packs cannot be used and this is the main reason behind the need for battery management software (BMS) packages with state of charge (SOC) estimation functions to increase the flight time. At the same time, as the UAV application range has extended widely, the size of UAVs has increased and heavy-duty UAVs are slowly appearing. As a result, the system operating power of the UAVs has been increased tremendously and their safe system power operation has become an issue. This is the main reason for the need of BMS having state of power (SOP) estimation functions. In this work a 6 S Li-Po battery pack is simulated with two ladder equivalent circuit models (ECMs) considering an impedance effect whose parameters are found using hybrid pulse power characterization (HPPC) current patterns with parameter determination using the table-based linear interpolation (TBLI) method. Two state estimation methods, including the current integration method and the extended Kalman filter (EKF) method are developed and the estimation accuracies of SOC and SOP are compared. Results show that the most accurate SOC estimation turns out to be 0.1477% (indoor test with HPPC), 0.1324% (outdoor test with 0 kg payload), and 0.2021% (outdoor test with 10 kg payload). Also, the most accurate SOP estimation error turns out to be 1.2% (indoor test with HPPC), 3.6% (outdoor test with 0 kg payload), and 4.2% (outdoor test with 10 kg payload). Full article

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

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42 pages, 25716 KiB

Open AccessArticle

Noise Sources, Effects and Countermeasures in Narrowband Power-Line Communications Networks: A Practical Approach

by Gregorio López^1,*, José Ignacio Moreno¹

, Eutimio Sánchez²

, Cristina Martínez³ and Fernando Martín⁴

¹ Telematics Engineering Department, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Madrid, Spain

² Smart Grids Area, Energy & Environment Division, Fundación Tecnalia Research & Innovation, Parque Tecnológico de Bizkaia, 700, 48160 Derio, Spain

³ Application Engineering Division, ZIV Metering Solutions, Parque Tecnológico de Bizkaia, 210, 48170 Zamudio, Spain

⁴ Smart Grid Operation & Maintenance Division, Unión Fenosa Distribución, Antonio López 193, 28026 Madrid, Spain

Energies 2017, 10(8), 1238; https://doi.org/10.3390/en10081238 - 21 Aug 2017

Cited by 31 | Viewed by 9097

Abstract

The integration of Distributed Generation, Electric Vehicles, and storage without compromising the quality of the power delivery requires the deployment of a communications overlay that allows monitoring and controlling low voltage networks in almost real time. Power Line Communications are gaining momentum for [...] Read more.

The integration of Distributed Generation, Electric Vehicles, and storage without compromising the quality of the power delivery requires the deployment of a communications overlay that allows monitoring and controlling low voltage networks in almost real time. Power Line Communications are gaining momentum for this purpose since they present a great trade-off between economic and technical features. However, the power lines also represent a harsh communications medium which presents different problems such as noise, which is indeed affected by Distributed Generation, Electric Vehicles, and storage. This paper provides a comprehensive overview of the types of noise that affects Narrowband Power Line Communications, including normative noises, noises coming from common electronic devices measured in actual operational power distribution networks, and noises coming from photovoltaic inverters and electric vehicle charging spots measured in a controlled environment. The paper also reviews several techniques to mitigate the effects of noise, paying special attention to passive filtering, as for being one of the most widely used solution to avoid this kind of problems in the field. In addition, the paper presents a set of tests carried out to evaluate the impact of some representative noises on Narrowband Power Line Communications network performance, as well as the effectiveness of different passive filter configurations to mitigate such an impact. In addition, the considered sources of noise can also bring value to further improve PLC communications in the new scenarios of the Smart Grid as an input to theoretical models or simulations. Full article

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

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17 pages, 2669 KiB

Open AccessArticle

A Novel FPGA-Based Real-Time Simulator for Micro-Grids

by Bingda Zhang^*, Shaowen Fu, Zhao Jin and Ruizhao Hu

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

Energies 2017, 10(8), 1239; https://doi.org/10.3390/en10081239 - 21 Aug 2017

Cited by 15 | Viewed by 4619

Abstract

To meet the requirements of micro-grid real-time simulation, a novel real-time simulator for micro-grids based on Field-Programmable Gate Array (FPGA) and orders (FO-RTDS) is designed. We describe the design idea of the real-time solver and the order generator. Multi-valued parameter prestorage and multi-rate [...] Read more.

To meet the requirements of micro-grid real-time simulation, a novel real-time simulator for micro-grids based on Field-Programmable Gate Array (FPGA) and orders (FO-RTDS) is designed. We describe the design idea of the real-time solver and the order generator. Multi-valued parameter prestorage and multi-rate simulation are introduced to reduce the computational pressure. The data scheduling is carried out following the principle of saving the resources and the minimizing the average distance between variables. An example is performed on XC7VX690T-2FFG1761 chip, which proves the novel FO-RTDS method greatly improves the scale of real-time simulation of micro-grids. Full article

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

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15 pages, 8054 KiB

Open AccessArticle

Energy Performance Assessment of a 2nd-Generation Vacuum Double Glazing Depending on Vacuum Layer Position and Building Type in South Korea

by Seung-Chul Kim

, Jong-Ho Yoon^*

and Ru-Da Lee

Department of Architectural Engineering, Hanbat National University, Daejeon Metropolitan City 34158, Korea

Energies 2017, 10(8), 1240; https://doi.org/10.3390/en10081240 - 21 Aug 2017

Cited by 9 | Viewed by 4620

Abstract

(1) Background: The application of high insulation to a building envelope helps reduce the heating load, but increases the cooling load. Evaluating the installation of high insulation glazing to buildings in climate zones with four distinct seasons, as in the case of South [...] Read more.

(1) Background: The application of high insulation to a building envelope helps reduce the heating load, but increases the cooling load. Evaluating the installation of high insulation glazing to buildings in climate zones with four distinct seasons, as in the case of South Korea, is very important; (2) Methods: This study compared the heating energy performance of four types of glazing, inside vacuum double glazing, outside vacuum double glazing, single vacuum glazing, and low-e double glazing, with fixed low-e coating positions on the inside of the room in a mock-up chamber under the same conditions. The annual energy consumption according to the building type was analyzed using a simulation; (3) Results: As the insulation performance of building envelopes has increased, the energy saving rate of inside vacuum double glazing has been increased further in office buildings. In residential buildings, the energy saving rate of inside vacuum double glazing with a low SHGC (solar heat gain coefficient) has become higher than that of outside vacuum double glazing; (4) Conclusions: Since the effects of SHGC on the energy saving rates are greater in high insulation buildings, SHGC should be considered carefully when selecting glazing in climate zones with distinct winter and summer seasons. Full article

(This article belongs to the Special Issue Zero-Carbon Buildings)

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16 pages, 3115 KiB

Open AccessArticle

Simulation Study on the Effect of Fracturing Technology on the Production Efficiency of Natural Gas Hydrate

by Chen Chen^1,2, Lin Yang^1,2,*, Rui Jia^1,2,*, Youhong Sun^1,2, Wei Guo^1,2, Yong Chen^1,2 and Xitong Li^1,2

¹ Engineering College, Jilin University, Changchun 130026, China

² Key Laboratory of Drilling and Exploitation Technology in Complex Conditions, Ministry of Land and Resources, Changchun 130026, China

Energies 2017, 10(8), 1241; https://doi.org/10.3390/en10081241 - 21 Aug 2017

Cited by 94 | Viewed by 5705

Abstract

Natural gas hydrate (NGH) concentrations hold large reserves of relatively pure unconventional natural gases, consisting mainly of methane. Depressurization is emerging as the optimum conversion technology for converting NGH in its reservoir to its constituent water and natural gas. NGH concentrations commonly have [...] Read more.

Natural gas hydrate (NGH) concentrations hold large reserves of relatively pure unconventional natural gases, consisting mainly of methane. Depressurization is emerging as the optimum conversion technology for converting NGH in its reservoir to its constituent water and natural gas. NGH concentrations commonly have a pore fill of over 80%, which means that NGH is a low-permeability reservoir, as NGH has displaced water in terms of porosity. Fracturing technology (fracking) is a technology employed for increasing permeability-dependent production, and has been proven in conventional and tight oil and gas reservoirs. In this work, we carried out numerical simulations to investigate the effects on depressurization efficiency of a variably-fractured NGH reservoir, to make a first order assessment of fracking efficiency. We performed calculations for the variations in original NGH saturation, pressure distribution, CH₄ gas production rate, and cumulative production under different fracturing conditions. Our results show that the rate of the pressure drop within the NGH-saturated host strata increases with increased fracturing. The CH₄ gas production rate and cumulative production are greatly improved with fracturing. Crack quantity and spacing per volume have a significant effect on the improvement of NGH conversion efficiencies. Possibly most important, we identified an optimum fracking value beyond which further fracking is not required. Full article

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

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25 pages, 4535 KiB

Open AccessFeature PaperArticle

Modelling and Control of Parallel-Connected Transformerless Inverters for Large Photovoltaic Farms

by Marian Liberos^*

, Raúl González-Medina

, Gabriel Garcerá

and Emilio Figueres

Grupo de Sistemas Electrónicos Industriales del Departamento de Ingeniería Electrónica, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain

Energies 2017, 10(8), 1242; https://doi.org/10.3390/en10081242 - 21 Aug 2017

Cited by 9 | Viewed by 5103

Abstract

This paper presents a control structure for transformerless photovoltaic inverters connected in parallel to manage photovoltaic fields in the MW range. Large photovoltaic farms are usually divided into several photovoltaic fields, each one of them managed by a centralized high power inverter. The [...] Read more.

This paper presents a control structure for transformerless photovoltaic inverters connected in parallel to manage photovoltaic fields in the MW range. Large photovoltaic farms are usually divided into several photovoltaic fields, each one of them managed by a centralized high power inverter. The current tendency to build up centralized inverters in the MW range is the use of several transformerless inverters connected in parallel, a topology that provokes the appearance of significant zero-sequence circulating currents among inverters. To eliminate this inconvenience, this paper proposes a control structure that avoids the appearance of circulating currents by controlling the zero-sequence component of the inverters. A second contribution of the paper is the development of a model of n parallel-connected inverters. To validate the concept, the proposed control structure has been applied to a photovoltaic field of 2 MW managed by four 500 kW photovoltaic inverters connected in parallel. Full article

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

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29 pages, 10657 KiB

Open AccessArticle

Feasibility Study of a Heating, Cooling and Domestic Hot Water System Combining a Photovoltaic-Thermal System and a Ground Source Heat Pump

by Yong-Dae Jeong¹, Min Gyung Yu² and Yujin Nam^2,*

¹ Building Energy Technology Center & Center for Climatic Environment Real-Scale Testing, 7 Jeongtong-ro, Deoksan-myeon, Jincheon-gun, Chungcheongbuk-do 27872, Korea

² Department of Architectural Engineering, Pusan National University, 2 Busandaehak-ro 63, Geomjeong-gu, Busan 46241, Korea

Energies 2017, 10(8), 1243; https://doi.org/10.3390/en10081243 - 21 Aug 2017

Cited by 29 | Viewed by 7029

Abstract

Renewable energy systems have received a lot of attention as sustainable technology in building sector. However, the efficiency of the renewable energy systems depends on the surrounding conditions, and it could gradually decrease by excessive and long-term operation. As a solution, a hybrid [...] Read more.

Renewable energy systems have received a lot of attention as sustainable technology in building sector. However, the efficiency of the renewable energy systems depends on the surrounding conditions, and it could gradually decrease by excessive and long-term operation. As a solution, a hybrid system can increase the reliability of energy production and decrease investment costs through by reducing the system capacity. The hybrid system operates at the ideal performance, but the design and operation method for hybrid system have not been established. In this paper, the performance of the hybrid system combined with photovoltaic/thermal (PVT) system and ground source heat pump (GSHP) system was analyzed using TRNSYS 17 and feasibility was assessed. The energy consumption and performance efficiency of hybrid system were calculated according to operating modes. Furthermore, seasonal performance factor (SPF) of hybrid system was compared with that of conventional GSHP system. System performance was analyzed in various conditions such as the usage of storage tank heating and set temperature for solar heating. As a result, the average SPF of the developed system increased about 55.3% compared with the GSHP system. Full article

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Review

Jump to: Research, Other

25 pages, 9164 KiB

Open AccessReview

Review of PV Generator as an Input Source for Power Electronic Converters

by Teuvo Suntio^1,*

, Tuomas Messo¹, Aapo Aapro¹, Jyri Kivimäki¹ and Alon Kuperman²

¹ Laboratory of Electrical Energy Engineering, Tampere University of Technology, Tampere 33720, Finland

² Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel

Energies 2017, 10(8), 1076; https://doi.org/10.3390/en10081076 - 25 Jul 2017

Cited by 21 | Viewed by 4566

Abstract

Voltage-type sources have dominated as an input source for power electronics converters for a long type. The existence of duality implies that there are also current-type sources. The growing application of renewable energy sources such as wind and solar energy has evidently shown [...] Read more.

Voltage-type sources have dominated as an input source for power electronics converters for a long type. The existence of duality implies that there are also current-type sources. The growing application of renewable energy sources such as wind and solar energy has evidently shown that the current-type input sources exist in reality such as photovoltaic (PV) generator or the feedback technique used in controlling the power electronics converters in the renewable energy systems changes the power electronic converters to behaving as such. The recent research on renewable energy systems has indicated that the current-type input sources are very challenging input sources affecting the dynamics of the interfacing converters profoundly. This paper provides a comprehensive survey of the effects of the PV generator on the dynamic behavior of the corresponding interfacing power electronic converters. Full article

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22 pages, 1957 KiB

Open AccessFeature PaperReview

Transition of Future Energy System Infrastructure; through Power-to-Gas Pathways

by Azadeh Maroufmashat and Michael Fowler^*

Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

Energies 2017, 10(8), 1089; https://doi.org/10.3390/en10081089 - 26 Jul 2017

Cited by 139 | Viewed by 14300

Abstract

Power-to-gas is a promising option for storing interment renewables, nuclear baseload power, and distributed energy and it is a novel concept for the transition to increased renewable content of current fuels with an ultimate goal of transition to a sustainable low-carbon future energy [...] Read more.

Power-to-gas is a promising option for storing interment renewables, nuclear baseload power, and distributed energy and it is a novel concept for the transition to increased renewable content of current fuels with an ultimate goal of transition to a sustainable low-carbon future energy system that interconnects power, transportation sectors and thermal energy demand all together. The aim of this paper is to introduce different Power-to-gas “pathways”, including Power to Hydrogen, Power to Natural Gas End-users, Power to Renewable Content in Petroleum Fuel, Power to Power, Seasonal Energy Storage to Electricity, Power to Zero Emission Transportation, Power to Seasonal Storage for Transportation, Power to Micro grid, Power to Renewable Natural Gas (RNG) to Pipeline (“Methanation”), and Power to Renewable Natural Gas (RNG) to Seasonal Storage. In order to compare the different pathways, the review of key technologies of Power-to-gas systems are studied and the qualitative efficiency and benefits of each pathway is investigated from the technical points of view. Moreover, different Power-to-gas pathways are discussed as an energy policy option that can be implemented to transition towards a lower carbon economy for Ontario’s energy systems. Full article

(This article belongs to the Special Issue Energy Production Systems)

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20 pages, 1829 KiB

Open AccessEditor’s ChoiceReview

The Concept of Segmented Wind Turbine Blades: A Review

by Mathijs Peeters^1,*

, Gilberto Santo²

, Joris Degroote²

and Wim Van Paepegem¹

¹ Department of Materials, Textiles and Chemical Engineering, Ghent University, Tech Lane Ghent Science Park—Campus A, Technologiepark-Zwijnaarde 903, 9052 Zwijnaarde, Belgium

² Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium

Energies 2017, 10(8), 1112; https://doi.org/10.3390/en10081112 - 31 Jul 2017

Cited by 42 | Viewed by 16515

Abstract

There is a trend to increase the length of wind turbine blades in an effort to reduce the cost of energy (COE). This causes manufacturing and transportation issues, which have given rise to the concept of segmented wind turbine blades. In this concept, [...] Read more.

There is a trend to increase the length of wind turbine blades in an effort to reduce the cost of energy (COE). This causes manufacturing and transportation issues, which have given rise to the concept of segmented wind turbine blades. In this concept, multiple segments can be transported separately. While this idea is not new, it has recently gained renewed interest. In this review paper, the concept of wind turbine blade segmentation and related literature is discussed. The motivation for dividing blades into segments is explained, and the cost of energy is considered to obtain requirements for such blades. An overview of possible implementations is provided, considering the split location and orientation, as well as the type of joint to be used. Many implementations draw from experience with similar joints such as the joint at the blade root, hub and root extenders and joints used in rotor tips and glider wings. Adhesive bonds are expected to provide structural and economic efficiency, but in-field assembly poses a big issue. Prototype segmented blades using T-bolt joints, studs and spar bridge concepts have proven successful, as well as aerodynamically-shaped root and hub extenders. Full article

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32 pages, 4866 KiB

Open AccessReview

Modeling of MMC for Fast and Accurate Simulation of Electromagnetic Transients: A Review

by Salman Saeed Khan^*

and Elisabetta Tedeschi

Department of Electric Power Engineering, Norwegian University of Science and Technology (NTNU), O.S. Bragstads Plass 2E, 7491 Trondheim, Norway

Energies 2017, 10(8), 1161; https://doi.org/10.3390/en10081161 - 7 Aug 2017

Cited by 29 | Viewed by 8173

Abstract

Over the past decade, modular multilevel converters have evolved as the preferred choice for high voltage conversion systems. The design of the converter poses a computational challenge to the classical electromagnetic transient simulation techniques, for which the existing literature proposes numerous simplified and [...] Read more.

Over the past decade, modular multilevel converters have evolved as the preferred choice for high voltage conversion systems. The design of the converter poses a computational challenge to the classical electromagnetic transient simulation techniques, for which the existing literature proposes numerous simplified and computationally-efficient equivalent representations. Despite the extensive collection of proposed models, the literature lacks a systematic comparison of these representations, which could enable their appropriate selection based on the specific simulation objectives. In light of these requirements, this article presents a comprehensive review of MMC models and discusses their applicability for parallel and real-time simulation. Using PSCAD/EMTDC simulations, the models are objectively compared with regards to computational efficiency and accuracy for various transient conditions. In addition, the paper also presents a brief account of MMC operation and the associated control and modulation system. Full article

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27 pages, 2973 KiB

Open AccessReview

The Internet of Lights: An Open Reference Architecture and Implementation for Intelligent Solid State Lighting Systems

by Emi Mathews^1,*

, Salih Serdar Guclu², Qingzhi Liu², Tanir Ozcelebi² and Johan J. Lukkien²

¹ Embedded Systems Innovation by TNO, 5612 AP Eindhoven, The Netherlands

² Department of Mathematics and Computer Science, Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands

Energies 2017, 10(8), 1187; https://doi.org/10.3390/en10081187 - 11 Aug 2017

Cited by 17 | Viewed by 6858

Abstract

The Internet of Things (IoT) is opening up new services and is stimulating changes in industries. The lighting industry is also embracing this change by establishing an Internet of Lights (IoL). This article highlights the main benefits and the challenges to face while [...] Read more.

The Internet of Things (IoT) is opening up new services and is stimulating changes in industries. The lighting industry is also embracing this change by establishing an Internet of Lights (IoL). This article highlights the main benefits and the challenges to face while going towards IoL. To address these challenges and cater to the specific requirements of lighting networks, an IoL reference architecture, Open Architecture for Intelligent Solid State Lighting Systems (OpenAIS), has been proposed. This article provides an overview of the OpenAIS architecture and explains how one can design specific systems based on this architecture. It also zooms into the configurations and design choices made in a pilot system in a real office building showing the validity of the architecture. A comparison of the OpenAIS system with a state-of-the-art commercial solution shows that IoL systems can exceed proprietary systems in several key performance indicators, such as security, interoperability, extensibility and openness. Full article

(This article belongs to the Special Issue Smart Lighting Environments: Sensing and Control)

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19 pages, 1533 KiB

Open AccessFeature PaperReview

General Design Procedures for Airport-Based Solar Photovoltaic Systems

by Anurag Anurag¹, Jiemin Zhang¹, Jephias Gwamuri^2,3

and Joshua M. Pearce^1,2,*

¹ Department of Electrical & Computer Engineering, Michigan Technological University, Houghton, MI 49931, USA

² Department of Materials Science & Engineering, Michigan Technological University, Houghton, MI 49931, USA

³ Department of Applied Physics, National University of Science & Technology, P.O. Box AC 939, Ascot, Bulawayo 939, Zimbabwe

Energies 2017, 10(8), 1194; https://doi.org/10.3390/en10081194 - 12 Aug 2017

Cited by 24 | Viewed by 18394

Abstract

A source of large surface areas for solar photovoltaic (PV) farms that has been largely overlooked in the 13,000 United States of America (U.S.) airports. This paper hopes to enable PV deployments in most airports by providing an approach to overcome the three [...] Read more.

A source of large surface areas for solar photovoltaic (PV) farms that has been largely overlooked in the 13,000 United States of America (U.S.) airports. This paper hopes to enable PV deployments in most airports by providing an approach to overcome the three primary challenges identified by the Federal Aviation Administration (FAA): (1) reflectivity and glare; (2) radar interference; and (3) physical penetration of airspace. First, these challenges and precautions that must be adhered to for safe PV projects deployment at airports are reviewed and summarized. Since one of the core concerns for PV and airport symbiosis is solar panel reflectivity, and because this data is largely estimated, a controlled experiment is conducted to determine worst-case values of front panel surface reflectivity and compare them to theoretical calculations. Then a general approach to implement solar PV systems in an airport is outlined and this approach is applied to a case study airport. The available land was found to be over 570 acres, which would generate more than 39,000% of the actual annual power demand of the existing airport. The results are discussed while considering the scaling potential of airport-based PV systems throughout the U.S. Full article

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

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20 pages, 9222 KiB

Open AccessReview

Recent Advances in the Quest for a New Insulation Gas with a Low Impact on the Environment to Replace Sulfur Hexafluoride (SF₆) Gas in High-Voltage Power Network Applications

by Abderrahmane Beroual^1,*

and Abderrahmane (Manu) Haddad²

¹ Ecole Centrale de Lyon, University of Lyon, Ampere CNRS UMR 5005, 36 Avenue Guy Collongue, 69134 Ecully, France

² Advanced High Voltage Engineering Research Centre, School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK

Energies 2017, 10(8), 1216; https://doi.org/10.3390/en10081216 - 16 Aug 2017

Cited by 215 | Viewed by 11555

Abstract

The growing environmental challenge of electrical energy systems has prompted a substantial increase in renewable energy generation. Such generation systems allow for significant reduction of CO₂ emissions compared with a traditional fossil fuel plant. Furthermore, several improvements in power systems network configuration [...] Read more.

The growing environmental challenge of electrical energy systems has prompted a substantial increase in renewable energy generation. Such generation systems allow for significant reduction of CO₂ emissions compared with a traditional fossil fuel plant. Furthermore, several improvements in power systems network configuration and operation combined with new technologies have enabled reduction of losses and energy demand, thus contributing to reduction of CO₂ emissions. Another environmental threat identified in electrical networks is the leaking of insulating sulfur hexafluoride (SF₆) gas used in electrical gas insulated substations (GIS) and equipment. Because of its Global Warming Potential (GWP) of nearly 24,000 and its long life in the atmosphere (over 3000 years), SF₆ gas was recognized as a greenhouse gas at the 1997 COP3; since then its use and emissions in the atmosphere have been regulated by international treaties. It is expected that as soon as an alternative insulating gas is found, SF₆ use in high-voltage (HV) equipment will be banned. This paper presents an overview of the key research advances made in recent years in the quest to find eco-friendly gases to replace SF₆. The review reports the main properties of candidate gases that are being investigated; in particular, natural gases (dry air, N₂ or CO₂) and polyfluorinated gases especially Trifluoroiodomethane (CF₃I), Perfluorinated Ketones, Octafluorotetra-hydrofuran, Hydrofluoroolefin (HFOs), and Fluoronitriles are presented and their strengths and weaknesses are discussed with an emphasis on their dielectric properties (especially their dielectric strength), GWP, and boiling point with respect to the minimum operating temperature for HV power network applications. Full article

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

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84 pages, 28972 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Study of Key Electric Vehicle (EV) Components, Technologies, Challenges, Impacts, and Future Direction of Development

by Fuad Un-Noor¹

, Sanjeevikumar Padmanaban^2,*

, Lucian Mihet-Popa³

, Mohammad Nurunnabi Mollah¹ and Eklas Hossain^4,*

¹ Department of Electrical and Electronic Engineering, Khulna University of Engineering and Technology, Khulna 9203, Bangladesh

² Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland Park 2006, South Africa

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

⁴ Department of Electrical Engineering & Renewable Energy, Oregon Tech, Klamath Falls, OR 97601, USA

Energies 2017, 10(8), 1217; https://doi.org/10.3390/en10081217 - 17 Aug 2017

Cited by 648 | Viewed by 87845

Abstract

Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is [...] Read more.

Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept. There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major obstacles for EVs to overcome before totally replacing ICE vehicles. This paper is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this sector. Full article

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

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16 pages, 943 KiB

Open AccessReview

A Review of the Nuclear Fuel Cycle Strategies and the Spent Nuclear Fuel Management Technologies

by Laura Rodríguez-Penalonga^*

and B. Yolanda Moratilla Soria

Cátedra Rafael Mariño de Nuevas Tecnologías Energéticas, Universidad Pontificia Comillas, 28015 Madrid, Spain

Energies 2017, 10(8), 1235; https://doi.org/10.3390/en10081235 - 21 Aug 2017

Cited by 87 | Viewed by 13685

Abstract

Nuclear power has been questioned almost since its beginnings and one of the major issues concerning its social acceptability around the world is nuclear waste management. In recent years, these issues have led to a rise in public opposition in some countries and, [...] Read more.

Nuclear power has been questioned almost since its beginnings and one of the major issues concerning its social acceptability around the world is nuclear waste management. In recent years, these issues have led to a rise in public opposition in some countries and, thus, nuclear energy has been facing even more challenges. However, continuous efforts in R&D (research and development) are resulting in new spent nuclear fuel (SNF) management technologies that might be the pathway towards helping the environment and the sustainability of nuclear energy. Thus, reprocessing and recycling of SNF could be one of the key points to improve the social acceptability of nuclear energy. Therefore, the purpose of this paper is to review the state of the nuclear waste management technologies, its evolution through time and the future advanced techniques that are currently under research, in order to obtain a global vision of the nuclear fuel cycle strategies available, their advantages and disadvantages, and their expected evolution in the future. Full article

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Other

Jump to: Research, Review

13 pages, 2107 KiB

Open AccessOpinion

Pyrolysis Characteristics and Kinetics of Food Wastes

by Jun-Ho Jo¹, Seung-Soo Kim², Jae-Wook Shim², Ye-Eun Lee¹

and Yeong-Seok Yoo^1,*

¹ Division of Environmental and Plant Engineering, Korea Institute of Civil Engineering and Building Technology, 283 Goyangdae-ro, Ilsanseo-gu, Goyang-si-Gyeonggi-do 10223, Korea

² Department of Chemical Engineering, Kangwon National University, 346 Joongang-ro, Samcheok, Gangwon-do 25913, Korea

Energies 2017, 10(8), 1191; https://doi.org/10.3390/en10081191 - 11 Aug 2017

Cited by 65 | Viewed by 8092

Abstract

Pyrolysis is an environmental friendly alternative method compared with incineration, and the least time-consuming and smallest infrastructure footprint method compared with bio-chemical and thermo-chemical conversion. Baseline data for the pyrolysis of food waste was obtained in a kinetic study of the thermal decompositions [...] Read more.

Pyrolysis is an environmental friendly alternative method compared with incineration, and the least time-consuming and smallest infrastructure footprint method compared with bio-chemical and thermo-chemical conversion. Baseline data for the pyrolysis of food waste was obtained in a kinetic study of the thermal decompositions by thermogravimetric analysis. To simulate the difference in the types of food waste, the study was done using model compounds, such as cereals, meat, vegetable, and mixed food waste; the pyrolysis commenced at 150 °C for most food waste and the process terminated at 450 °C to 500 °C. Between one and three peaks were observed on a differential thermogravimetry (DTG) graph, depending on the type of waste being pyrolyzed, reflecting the difference in the time required for pyrolysis of different components of food waste to take place. Depending on the composition of each food, one or four peaks were found, and the pyrolysis patterns of carbohydrate, protein, fat, and cellulose were found. Activation energies and frequency factors were calculated from the rates of conversion, using differential equation analyses. The activation energy increased from 10 kJ/mol to 50 kJ/mol as conversions increased from the 10% to 90%, regardless of the food waste type. The activation energy was measured as 50 kJ/mol, with a slight variation among the type of the food waste. Due to the activation energy being low, food waste consists of carbohydrates and other substances rather than cellulose, hemicellulose, and lignin. Full article

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15 pages, 6491 KiB

Open AccessCase Report

Improving Tube Design of a Problematic Heat Exchanger for Enhanced Safety at Minimal Costs

by In-Bok Lee^1,* and Seunghee Park²

¹ Environment Technology and Safety Technology Convergence, Inha University, Incheon 22212, Korea

² School of Civil, Architectural & Environmental Engineering, Sungkyunkwan University, Suwon 16419, Korea

Energies 2017, 10(8), 1236; https://doi.org/10.3390/en10081236 - 21 Aug 2017

Viewed by 6774

Abstract

As part of a preliminary hazard analysis for a new phenol plant, the results of a hazard and operability study (HAZOP) conducted in the initial stages of the project design were re-evaluated due mechanical failure detected during the test operation. Out of the [...] Read more.

As part of a preliminary hazard analysis for a new phenol plant, the results of a hazard and operability study (HAZOP) conducted in the initial stages of the project design were re-evaluated due mechanical failure detected during the test operation. Out of the possible mechanical defects for the crude phenol column (CPC), the fact that the lowest risk grade was given to the column without consideration for any safety devices, was recognized as the cause of failure. After examining the design specifications of the safety valves of CPC, it was confirmed that the tube rupture case of the overhead condenser was also not taken into consideration. With this case included in HAZOP, the size of the safety valve had to be increased from 6Q8 to 8T10. In summary, when taking into consideration the economic impact on modification and re-purchase of the safety valve and the redesign of the piping system might have, it was determined that completely removing any possibility for the tube rupture case by mechanically reinforcing the overhead condenser would be the most economic decision. Therefore, the overhead condenser was mechanically reinforced in areas determined to require strengthening according to the results of the vibration analysis, and by adding these results to the safety device factors of the mechanical defects of CPC, the lowest safety risk grade could have been maintained. Full article

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