Energies

Editorial

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9 pages, 183 KiB

Open AccessEditorial

Simulation of Polygeneration Systems

by Francesco Calise^*

and Massimo Dentice D’Accadia

Department of Industrial Engineering, University of Naples Federico II, 80125 Napoli, Italy

Energies 2016, 9(11), 925; https://doi.org/10.3390/en9110925 - 8 Nov 2016

Cited by 13 | Viewed by 5610

Abstract

This Special Issue aims at collecting the recent studies dealing with polygeneration systems, with a special focus on the possible integration of different technologies into a single system, able to convert one or multiple energy sources into energy services (electricity, heat and cooling) [...] Read more.

This Special Issue aims at collecting the recent studies dealing with polygeneration systems, with a special focus on the possible integration of different technologies into a single system, able to convert one or multiple energy sources into energy services (electricity, heat and cooling) and other useful products (e.g., desalinized water, hydrogen, glycerin, ammonia, etc.). Renewable sources (solar, wind, hydro, biomass and geothermal), as well as fossil fuels, feeding advanced energy systems such as fuel cells and cogeneration systems, are considered. Special attention is paid to control strategies and to the management of the systems in general. Studies including thermoeconomic analyses and system optimizations are presented. Full article

(This article belongs to the Special Issue Simulation of Polygeneration Systems)

Research

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18 pages, 6251 KiB

Open AccessArticle

Cooperative Energy Management of Hybrid DC Renewable Grid Using Decentralized Control Strategies

by Mehrdad Beykverdi^1,*

, Abolfazl Jalilvand²

and Mehdi Ehsan³

¹ Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Tehran 15785, Iran

² Department of Electrical Engineering, University of Zanjan, Zanjan 45195, Iran

³ Department of Electrical Engineering, Sharif University of Technology, Tehran 11155, Iran

Energies 2016, 9(11), 859; https://doi.org/10.3390/en9110859 - 25 Oct 2016

Cited by 9 | Viewed by 5127

Abstract

This paper attempted to control a hybrid DC microgrid in islanded operation mode using decentralized power management strategies. Proposed adaptive I/V characteristic for hybrid photovoltaic (PV) and battery energy storage system (BESS) and wind turbine generator (WTG) adapts the distributed energy resources (DER) [...] Read more.

This paper attempted to control a hybrid DC microgrid in islanded operation mode using decentralized power management strategies. Proposed adaptive I/V characteristic for hybrid photovoltaic (PV) and battery energy storage system (BESS) and wind turbine generator (WTG) adapts the distributed energy resources (DER) behavior independently in accordance with the load demand. Hence, the PV module can spend its maximum power on load demand and spend the extra power for charging the BESS, which will regulate DC bus voltage and maintain the power balance within the microgrid. When load demand is beyond the maximum generation power of PV unit, WTG will supply the energy shortage. The proposed control system was applied on the DC microgrid in order to achieve control objectives through a decentralized procedure, without telecommunication links. In order to validate the proposed strategies, the control system was implemented on a DC microgrid within MATLAB/SIMULINK, where the simulation results were analyzed and validated. Full article

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15 pages, 4008 KiB

Open AccessArticle

Simplified Minimum Copper Loss Remedial Control of a Five-Phase Fault-Tolerant Permanent-Magnet Vernier Machine under Short-Circuit Fault

by Chenyu Gu, Wenxiang Zhao^* and Bufeng Zhang

School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China

Energies 2016, 9(11), 860; https://doi.org/10.3390/en9110860 - 25 Oct 2016

Cited by 5 | Viewed by 5799

Abstract

A fault-tolerant permanent-magnet vernier (FT-PMV) machine incorporates the merits of high fault-tolerant capability and high torque density. In this paper, a new remedial control is proposed for a five-phase FT-PMV machine with short-circuit fault of stator windings. Based on the principle of copper [...] Read more.

A fault-tolerant permanent-magnet vernier (FT-PMV) machine incorporates the merits of high fault-tolerant capability and high torque density. In this paper, a new remedial control is proposed for a five-phase FT-PMV machine with short-circuit fault of stator windings. Based on the principle of copper loss minimization, the aims of the proposed control strategy are to keep magnetic motive force (MMF) unchanged and minimize torque ripple. The proposed remedial control strategy contains two parts. Firstly, the remedial currents of the healthy phases are used to compensate for the ripple of MMF caused by the short-circuit current. Secondly, an open-circuit fault-tolerant control strategy is used to compensate for the lack of normal torque in the fault phase. Finally, the vector sum of two parts is adopted to derive the remedial currents. The final expression of the proposed remedial current is simpler than that than these previous methods. In addition, the proposed remedial currents are sinusoidal, which can reduce the reactive component in instantaneous power produced by pulsating torque and iron loss of a sine back-EMF machine. A FT-PMV prototype is built. The simulations and the experiments verify the effectiveness of the proposed strategy. Full article

(This article belongs to the Special Issue Techniques of Control for Energy Optimization in Actuators, Motors and Power Generation Systems)

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14 pages, 2249 KiB

Open AccessArticle

Influence of Icing on the Modal Behavior of Wind Turbine Blades

by Sudhakar Gantasala^*

, Jean-Claude Luneno and Jan-Olov Aidanpää

Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå 97187, Sweden

Energies 2016, 9(11), 862; https://doi.org/10.3390/en9110862 - 26 Oct 2016

Cited by 27 | Viewed by 7046

Abstract

Wind turbines installed in cold climate sites accumulate ice on their structures. Icing of the rotor blades reduces turbine power output and increases loads, vibrations, noise, and safety risks due to the potential ice throw. Ice accumulation increases the mass distribution of the [...] Read more.

Wind turbines installed in cold climate sites accumulate ice on their structures. Icing of the rotor blades reduces turbine power output and increases loads, vibrations, noise, and safety risks due to the potential ice throw. Ice accumulation increases the mass distribution of the blade, while changes in the aerofoil shapes affect its aerodynamic behavior. Thus, the structural and aerodynamic changes due to icing affect the modal behavior of wind turbine blades. In this study, aeroelastic equations of the wind turbine blade vibrations are derived to analyze modal behavior of the Tjaereborg 2 MW wind turbine blade with ice. Structural vibrations of the blade are coupled with a Beddoes-Leishman unsteady attached flow aerodynamics model and the resulting aeroelastic equations are analyzed using the finite element method (FEM). A linearly increasing ice mass distribution is considered from the blade root to half-length and thereafter constant ice mass distribution to the blade tip, as defined by Germanischer Lloyd (GL) for the certification of wind turbines. Both structural and aerodynamic properties of the iced blades are evaluated and used to determine their influence on aeroelastic natural frequencies and damping factors. Blade natural frequencies reduce with ice mass and the amount of reduction in frequencies depends on how the ice mass is distributed along the blade length; but the reduction in damping factors depends on the ice shape. The variations in the natural frequencies of the iced blades with wind velocities are negligible; however, the damping factors change with wind velocity and become negative at some wind velocities. This study shows that the aerodynamic changes in the iced blade can cause violent vibrations within the operating wind velocity range of this turbine. Full article

(This article belongs to the Special Issue Modeling and Simulation for Wind Turbine Loads Analysis)

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13 pages, 787 KiB

Open AccessArticle

Quantification of the Lifecycle Greenhouse Gas Emissions from Nuclear Power Generation Systems

by Akhil Kadiyala¹, Raghava Kommalapati^1,2,*

and Ziaul Huque^1,3

¹ Center for Energy & Environmental Sustainability, Prairie View A & M University, Prairie View, TX 77446, USA

² Department of Civil & Environmental Engineering, Prairie View A & M University, Prairie View, TX 77446, USA

³ Department of Mechanical Engineering, Prairie View A & M University, Prairie View, TX 77446, USA

Energies 2016, 9(11), 863; https://doi.org/10.3390/en9110863 - 25 Oct 2016

Cited by 17 | Viewed by 8104

Abstract

This paper statistically quantifies the lifecycle greenhouse gas (GHG) emissions from six distinct reactor-based (boiling water reactor (BWR), pressurized water reactor (PWR), light water reactor (LWR), heavy-water-moderated reactor (HWR), gas-cooled reactor (GCR), fast breeder reactor (FBR)) nuclear power generation systems by following a [...] Read more.

This paper statistically quantifies the lifecycle greenhouse gas (GHG) emissions from six distinct reactor-based (boiling water reactor (BWR), pressurized water reactor (PWR), light water reactor (LWR), heavy-water-moderated reactor (HWR), gas-cooled reactor (GCR), fast breeder reactor (FBR)) nuclear power generation systems by following a two-step approach that included (a) performing a review of the lifecycle assessment (LCA) studies on the reactor-based nuclear power generation systems; and (b) statistically evaluating the lifecycle GHG emissions (expressed in grams of carbon dioxide equivalent per kilowatt hour, gCO₂e/kWh) for each of the reactor-based nuclear power generation systems to assess the role of different types of nuclear reactors in the reduction of the lifecycle GHG emissions. Additionally, this study quantified the impacts of fuel enrichment methods (centrifuge, gaseous diffusion) on GHG emissions. The mean lifecycle GHG emissions resulting from the use of BWR (sample size, N = 15), PWR (N = 21), LWR (N = 7), HWR (N = 3), GCR (N = 1), and FBR (N = 2) in nuclear power generation systems are 14.52 gCO₂e/kWh, 11.87 gCO₂e/kWh, 20.5 gCO₂e/kWh, 28.2 gCO₂e/kWh, 8.35 gCO₂e/kWh, and 6.26 gCO₂e/kWh, respectively. The FBR nuclear power generation systems produced the minimum lifecycle GHGs. The centrifuge enrichment method produced lower GHG emissions than the gaseous diffusion enrichment method. Full article

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15 pages, 1567 KiB

Open AccessArticle

Control Optimization of Solar Thermally Driven Chillers

by Antoine Dalibard^*

, Daniel Gürlich

, Dietrich Schneider and Ursula Eicker

Research Center of Sustainable Energy Technology, Stuttgart University of Applied Sciences, Schellingstr. 24, 70174 Stuttgart, Germany

Energies 2016, 9(11), 864; https://doi.org/10.3390/en9110864 - 25 Oct 2016

Cited by 10 | Viewed by 5472

Abstract

Many installed solar thermally driven cooling systems suffer from high auxiliary electric energy consumption which makes them not more efficient than conventional compression cooling systems. A main reason for this is the use of non-efficient controls with constant set points that do not [...] Read more.

Many installed solar thermally driven cooling systems suffer from high auxiliary electric energy consumption which makes them not more efficient than conventional compression cooling systems. A main reason for this is the use of non-efficient controls with constant set points that do not allow a chiller power modulation at partial-load and therefore lead to unnecessary high power consumption of the parasitics. The aims of this paper are to present a method to control efficiently solar thermally driven chillers, to demonstrate experimentally its applicability and to quantify the benefits. It has been shown that the cooling capacity of a diffusion absorption chiller can be modulated very effectively by adjusting both the temperature and the flow rate of the cooling water. With the developed approach and the use of optimization algorithms, both the temperature and the flow rate can be controlled simultaneously in a way that the cooling load is matched and the electricity consumption is minimized. Depending on the weather and operating conditions, electricity savings between 20% and 60% can be achieved compared to other tested control approaches. The highest savings are obtained when the chiller is operated at partial load. The presented method is not restricted to solar cooling systems and can also be applied to other conventional heating ventilation and air conditioning (HVAC) systems. Full article

(This article belongs to the Special Issue Solar Cooling and Heating)

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18 pages, 1359 KiB

Open AccessArticle

Modeling of a Pouch Lithium Ion Battery Using a Distributed Parameter Equivalent Circuit for Internal Non-Uniformity Analysis

by Dafen Chen^1,2, Jiuchun Jiang^1,2,*, Xue Li^1,2, Zhanguo Wang^1,2 and Weige Zhang^1,2

¹ National Active Distribution Network Technology Research Center, Beijing Jiaotong University, No. 3 Shang Yuan Cun, Haidian District, Beijing 100044, China

² Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Jiaotong University, No. 3 Shang Yuan Cun, Haidian District, Beijing 100044, China

Energies 2016, 9(11), 865; https://doi.org/10.3390/en9110865 - 25 Oct 2016

Cited by 21 | Viewed by 7866

Abstract

A battery model that has the capability of analyzing the internal non-uniformity of local state variables, including the state of charge (SOC), temperature and current density, is proposed in this paper. The model is built using a set of distributed parameter equivalent circuits. [...] Read more.

A battery model that has the capability of analyzing the internal non-uniformity of local state variables, including the state of charge (SOC), temperature and current density, is proposed in this paper. The model is built using a set of distributed parameter equivalent circuits. In order to validate the accuracy of the model, a customized battery with embedded T-type thermocouple sensors inside the battery is tested. The simulated temperature conforms well with the measured temperature at each test point, and the maximum difference is less than 1 °C. Then, the model is applied to analyze the evolution processes of local state variables’ distribution inside the battery during the discharge process. The simulation results demonstrate drastic distribution changes of the local state variables inside the battery during the discharge process. The internal non-uniformity is originally caused by the resistance of positive and negative foils, while also influenced by the change rate of open circuit voltage and the total resistance of the battery. Hence, the factors that affect the distribution of the local state variables are addressed. Full article

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

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23 pages, 5044 KiB

Open AccessArticle

Energy Efficiency Strategies for Ecological Greenhouses: Experiences from Murcia (Spain)

by Hilario Becerril^1,* and Ignacio De los Rios²

¹ Area de Ciencias Sociales. Colegio de Postgraduados, Campus Tabasco, México. Periferico Carlos A. Molina S/N, Cardenas 86500, Tabasco, Mexico

² Agroforestry Engineering Department, School of Agricultural, Food and Biosystems Engineering, Universidad Politécnica de Madrid. Av. Puerta de Hierro No. 2 CP, Madrid 28040, Spain

Energies 2016, 9(11), 866; https://doi.org/10.3390/en9110866 - 25 Oct 2016

Cited by 16 | Viewed by 7780

Abstract

There has been a continuous growth in ecological agriculture (EA) in recent years. It is recognized as a production system with rational energy use and low demand for fossil fuels. There are many studies relating to this subject, in contrast to the few [...] Read more.

There has been a continuous growth in ecological agriculture (EA) in recent years. It is recognized as a production system with rational energy use and low demand for fossil fuels. There are many studies relating to this subject, in contrast to the few studies regarding the use of energy and its impact on the environment in ecological greenhouses. This article analyzes the strategies adopted by a Transformational Agricultural Society (Sociedad Agraria de Transformación) in order to improve energy efficiency in ecological greenhouses, with regards to the use of fossil fuels. The methodology is based on the Working With People (WWP) Model, which involves social learning processes over 30 years in one of the largest regions of ecological crops in Spain. The results show that the measures taken to manage the greenhouses have achieved a decrease of over 80% in terms of fossil fuel consumption. The experience demonstrates that EA, as opposed to conventional agriculture (CA), is a system with great potential when it comes to reducing energy consumption and environmental improvements through various strategies. Full article

(This article belongs to the Special Issue Contemporary Environmental Paradigms and the Renewable Energy in Rural Economies)

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14 pages, 4272 KiB

Open AccessArticle

A Novel Modulation Function-Based Control of Modular Multilevel Converters for High Voltage Direct Current Transmission Systems

by Majid Mehrasa^1,†, Edris Pouresmaeil^2,3,†

, Sasan Zabihi^4,†, Juan C. Trujillo Caballero^5,† and João P. S. Catalão^2,3,6,*,†

¹ Young Researchers and Elite Club, Sari Branch, Islamic Azad University, Sari 47136, Iran

² INESC-ID, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, Lisbon 1049-001, Portugal

³ C-MAST, University of Beira Interior, R. Fonte do Lameiro, Covilhã 6201-001, Portugal

⁴ ABB Australia Pty Limited, Berrimah, Northern Territory 0828, Australia

⁵ Departamento de Ingeniería Eléctrica, Instituto Tecnológico de Orizaba (ITO), Orizaba, Veracruz 94320, Mexico

⁶ INESC TEC and Faculty of Engineering of the University of Porto, R. Dr. Roberto Frias, Porto 4200-465, Portugal

^† The authors contributed equally to this work.

Energies 2016, 9(11), 867; https://doi.org/10.3390/en9110867 - 25 Oct 2016

Cited by 21 | Viewed by 4783

Abstract

In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs) in high voltage direct current (HVDC) transmission systems. The proposed modulation function-based control technique is developed based on [...] Read more.

In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs) in high voltage direct current (HVDC) transmission systems. The proposed modulation function-based control technique is developed based on thorough and precise analyses of all MMC voltages and currents in the a-b-c reference frame in which the alternating current (AC)-side voltage is the first target to be obtained. Using the AC-side voltage, the combination of the MMC upper and lower arm voltages is achieved as the main structure of the proposed modulation function. The main contribution of this paper is to obtain two very simple new modulation functions to control MMC performance in different operating conditions. The features of the modulation function-based control technique are as follows: (1) this control technique is very simple and can be easily achieved in a-b-c reference frame without the need of using Park transformation; and (2) in addition, the inherent properties of the MMC model are considered in the proposed control technique. Considering these properties leads to constructing a control technique that is robust against MMC parameters changes and also is a very good tracking method for the components of MMC input currents. These features lead to improving the operation of MMC significantly, which can act as a rectifier in the HVDC structure. The simulation studies are conducted through MATLAB/SIMULINK software, and the results obtained verify the effectiveness of the proposed modulation function-based control technique. Full article

(This article belongs to the Special Issue Advances in Power System Operations and Planning)

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16 pages, 1298 KiB

Open AccessArticle

Risk-Limiting Scheduling of Optimal Non-Renewable Power Generation for Systems with Uncertain Power Generation and Load Demand

by Shin-Yeu Lin^* and Ai-Chih Lin

Department of Electrical Engineering, Chang Gung University, 259 Wen-Hwa 1st Road Kwei-Shan, Tao-Yuan 33302, Taiwan

Energies 2016, 9(11), 868; https://doi.org/10.3390/en9110868 - 26 Oct 2016

Cited by 3 | Viewed by 3325

Abstract

This study tackles a risk-limiting scheduling problem of non-renewable power generation for large power systems, and addresses potential violations of the security constraints owing to the volatility of renewable power generation and the uncertainty of load demand. To cope with the computational challenge [...] Read more.

This study tackles a risk-limiting scheduling problem of non-renewable power generation for large power systems, and addresses potential violations of the security constraints owing to the volatility of renewable power generation and the uncertainty of load demand. To cope with the computational challenge that arises from the probabilistic constraints in the considered problem, a computationally efficient solution algorithm that involves a bisection method, an off-line constructed artificial neural network (ANN) and an on-line point estimation method is proposed and tested on the IEEE 118-bus system. The results of tests and comparisons reveal that the proposed solution algorithm is applicable to large power systems in real time, and the solution obtained herein is much better than the conventional optimal power flow (OPF) solution in obtaining a much higher probability of satisfying the security constraints. Full article

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14 pages, 2886 KiB

Open AccessArticle

Effects of Biochar Amendment on Chloropicrin Adsorption and Degradation in Soil

by Pengfei Liu¹, Qiuxia Wang^2,*, Dongdong Yan², Wensheng Fang², Liangang Mao², Dong Wang³, Yuan Li², Canbin Ouyang², Meixia Guo² and Aocheng Cao^2,*

¹ Southwest Research and Design Institute of Chemical Industry Co., Ltd., Chengdu 610225, China

² Plant Protection Institute of Chinese Academy of Agricultural Sciences, State Key Laboratory for Biology of Plant Disease and Insect Pest, Beijing 100193, China

³ U.S. Department of Agriculture—Agricultural Research Service (USDA-ARS), Water Management Research Unit, Parlier 93648, CA, USA

Energies 2016, 9(11), 869; https://doi.org/10.3390/en9110869 - 26 Oct 2016

Cited by 9 | Viewed by 5389

Abstract

The characteristics of biochar vary with pyrolysis temperature. Chloropicrin (CP) is an effective fumigant for controlling soil-borne pests. This study investigated the characteristics of biochars prepared at 300, 500, and 700 °C by michelia alba (Magnolia denudata) wood and evaluated their [...] Read more.

The characteristics of biochar vary with pyrolysis temperature. Chloropicrin (CP) is an effective fumigant for controlling soil-borne pests. This study investigated the characteristics of biochars prepared at 300, 500, and 700 °C by michelia alba (Magnolia denudata) wood and evaluated their capacity to adsorb CP. The study also determined the potential influence of biochar, which was added to sterilized and unsterilized soils at rates of 0%, 1%, 5%, and 100%, on CP degradation. The specific surface area, pore volume, and micropores increased considerably with an increase in the pyrolytic temperature. The adsorption rate of biochar for CP increased with increasing pyrolytic temperature. The maximum adsorption amounts of CP were similar for the three biochars. Next, the study examined the degradation ability of the biochar for CP. The degradation rate constant (k) of CP increased when biochar was added to the soil, and k increased with increased amendment rate and pyrolysis temperature. The results indicate that biochar can accelerate CP degradation in soil. The findings will be instructive in using biochar as a new fertilizer in fumigating soil with CP. Full article

(This article belongs to the Special Issue Biomass Chars: Elaboration, Characterization and Applications)

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15 pages, 1236 KiB

Open AccessArticle

Operational Modal Analysis of a Spar-Type Floating Platform Using Frequency Domain Decomposition Method

by Carlo Ruzzo¹, Giuseppe Failla², Maurizio Collu³, Vincenzo Nava⁴

, Vincenzo Fiamma¹ and Felice Arena^1,*

¹ Natural Ocean Engineering Laboratory (NOEL), Mediterranea University of Reggio Calabria, Reggio Calabria 89122, Italy

² DICEAM Department, Mediterranea University of Reggio Calabria, Reggio Calabria 89122, Italy

³ Energy and Power Department, Cranfield University, Cranfield MK43 0AL, UK

⁴ Tecnalia Research & Innovation, Energy and Environment Division, Bilbao 48160, Spain

Energies 2016, 9(11), 870; https://doi.org/10.3390/en9110870 - 26 Oct 2016

Cited by 22 | Viewed by 6430

Abstract

System identification of offshore floating platforms is usually performed by testing small-scale models in wave tanks, where controlled conditions, such as still water for free decay tests, regular and irregular wave loading can be represented. However, this approach may result in constraints on [...] Read more.

System identification of offshore floating platforms is usually performed by testing small-scale models in wave tanks, where controlled conditions, such as still water for free decay tests, regular and irregular wave loading can be represented. However, this approach may result in constraints on model dimensions, testing time, and costs of the experimental activity. For such reasons, intermediate-scale field modelling of offshore floating structures may become an interesting as well as cost-effective alternative in a near future. Clearly, since the open sea is not a controlled environment, traditional system identification may become challenging and less precise. In this paper, a new approach based on Frequency Domain Decomposition (FDD) method for Operational Modal Analysis is proposed and validated against numerical simulations in ANSYS AQWA v.16.0 on a simple spar-type structure. The results obtained match well with numerical predictions, showing that this new approach, opportunely coupled with more traditional wave tanks techniques, proves to be very promising to perform field-site identification of the model structures. Full article

(This article belongs to the Special Issue Modeling and Simulation for Wind Turbine Loads Analysis)

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12 pages, 2127 KiB

Open AccessArticle

Novel Interleaved Converter with Extra-High Voltage Gain to Process Low-Voltage Renewable-Energy Generation

by Chih-Lung Shen^*, Po-Chieh Chiu and Yan-Chi Lee

Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 82445, Taiwan

Energies 2016, 9(11), 871; https://doi.org/10.3390/en9110871 - 25 Oct 2016

Cited by 11 | Viewed by 5240

Abstract

This paper presents a novel interleaved converter (NIC) with extra-high voltage gain to process the power of low-voltage renewable-energy generators such as photovoltaic (PV) panel, wind turbine, and fuel cells. The NIC can boost a low input voltage to a much higher voltage [...] Read more.

This paper presents a novel interleaved converter (NIC) with extra-high voltage gain to process the power of low-voltage renewable-energy generators such as photovoltaic (PV) panel, wind turbine, and fuel cells. The NIC can boost a low input voltage to a much higher voltage level to inject renewable energy to DC bus for grid applications. Since the NIC has two circuit branches in parallel at frond end to share input current, it is suitable for high power applications. In addition, the NIC is controlled in an interleaving pattern, which has the advantages that the NIC has lower input current ripple, and the frequency of the ripple is twice the switching frequency. Two coupled inductors and two switched capacitors are incorporated to achieve a much higher voltage gain than conventional high step-up converters. The proposed NIC has intrinsic features such as leakage energy totally recycling and low voltage stress on power semiconductor. Thorough theoretical analysis and key parameter design are presented in this paper. A prototype is built for practical measurements to validate the proposed NIC. Full article

(This article belongs to the Special Issue Next-Generation Low-Carbon Power and Energy Systems)

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26 pages, 477 KiB

Open AccessArticle

Fuzzy Logic Based Multi-Criteria Wind Turbine Selection Strategy—A Case Study of Qassim, Saudi Arabia

by Shafiqur Rehman¹ and Salman A. Khan^2,*

¹ Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

² Computer Science Department, University of Pretoria, Pretoria 0002, South Africa

Energies 2016, 9(11), 872; https://doi.org/10.3390/en9110872 - 26 Oct 2016

Cited by 43 | Viewed by 6281

Abstract

The emergence of wind energy as a potential alternative to traditional sources of fuel has prompted notable research in recent years. One primary factor contributing to efficient utilization of wind energy from a wind farm is the type of turbines used. However, selection [...] Read more.

The emergence of wind energy as a potential alternative to traditional sources of fuel has prompted notable research in recent years. One primary factor contributing to efficient utilization of wind energy from a wind farm is the type of turbines used. However, selection of a specific wind turbine type is a difficult task due to several criteria involved in the selection process. Important criteria include turbine’s power rating, height of tower, energy output, rotor diameter, cut-in wind speed, and rated wind speed. The complexity of this selection process is further amplified by the presence of conflicts between the decision criteria. Therefore, a decision is desired that provides the best balance between all selection criteria. Considering the complexities involved in the decision-making process, this paper proposes a two-level decision turbine selection strategy based on fuzzy logic and multi-criteria decision-making (MCDM) approach. More specifically, the fuzzy arithmetic mean operator is used in the decision process. The proposed approach is applied to wind data collected from the site of Qassim, Saudi Arabia. Results indicate that the proposed approach was effective in finding the optimal turbine from a set of 20 turbines of various capacities. Full article

(This article belongs to the Collection Wind Turbines)

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16 pages, 1706 KiB

Open AccessArticle

Application of Hybrid Quantum Tabu Search with Support Vector Regression (SVR) for Load Forecasting

by Cheng-Wen Lee¹ and Bing-Yi Lin^2,*

¹ Department of International Business, Chung Yuan Christian University/200 Chung Pei Rd., Chungli District, Taoyuan City 32023, Taiwan

² Ph.D. Program in Business, College of Business, Chung Yuan Christian University/200 Chung Pei Rd., Chungli District, Taoyuan City 32023, Taiwan

Energies 2016, 9(11), 873; https://doi.org/10.3390/en9110873 - 26 Oct 2016

Cited by 27 | Viewed by 5557

Abstract

Hybridizing chaotic evolutionary algorithms with support vector regression (SVR) to improve forecasting accuracy is a hot topic in electricity load forecasting. Trapping at local optima and premature convergence are critical shortcomings of the tabu search (TS) algorithm. This paper investigates potential improvements of [...] Read more.

Hybridizing chaotic evolutionary algorithms with support vector regression (SVR) to improve forecasting accuracy is a hot topic in electricity load forecasting. Trapping at local optima and premature convergence are critical shortcomings of the tabu search (TS) algorithm. This paper investigates potential improvements of the TS algorithm by applying quantum computing mechanics to enhance the search information sharing mechanism (tabu memory) to improve the forecasting accuracy. This article presents an SVR-based load forecasting model that integrates quantum behaviors and the TS algorithm with the support vector regression model (namely SVRQTS) to obtain a more satisfactory forecasting accuracy. Numerical examples demonstrate that the proposed model outperforms the alternatives. Full article

(This article belongs to the Special Issue Kernel Methods and Hybrid Evolutionary Algorithms in Energy Forecasting)

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19 pages, 11933 KiB

Open AccessArticle

Investigation the Influence of Different Salts on the Degradation of Organic Dyes Using Non-Thermal Plasma

by Ahmed El-Tayeb^1,2,*, Ahmed H. El-Shazly² and Marwa F. Elkady^2,3

¹ Electric Engineering Department, Faculty of Energy Engineering, Aswan University, Aswan 81528, Egypt

² Chemical and Petrochemicals Engineering Department, Egypt-Japan University of Science and Technology, New Borg El-Arab City, Alexandria 21934, Egypt

³ Fabrication Technology Department, Advanced Technology and New Materials Research Institute (ATNMRI), City of Scientific Research and Technology Applications (SRTA City), Alexandria 21934, Egypt

Energies 2016, 9(11), 874; https://doi.org/10.3390/en9110874 - 26 Oct 2016

Cited by 22 | Viewed by 5341

Abstract

In dye decolorization tests a non-thermal plasma (NTP) corona discharge generated by a high voltage pin-to-ground plate displayed 82% color removal within 11 min. Total color removal was accomplished after 28 min. Different salts such as KCl, NaCl, CaCl₂ and AlCl₃ [...] Read more.

In dye decolorization tests a non-thermal plasma (NTP) corona discharge generated by a high voltage pin-to-ground plate displayed 82% color removal within 11 min. Total color removal was accomplished after 28 min. Different salts such as KCl, NaCl, CaCl₂ and AlCl₃ were utilized to check the influence of conductivity changes on the dye decolorization process. Higher dye solution conductivity improved the color removal efficiency. The discharge energy and degradation efficiency were computed for diverse concentrations for NaCl, KCl, CaCl₂ and AlCl₃, whereby it was noticed that the salts generally have a small impact on the level of dye decolorization using corona discharge. In addition, the essential reactive species involved in the oxidation of organic dye compounds such as ozone (O₃) generated in treated water and hydrogen peroxide (H₂O₂) were investigated and the energetic species that produced the non-thermal plasma at the optimum operation time were determined. Energy yields for decolorization and Electrical Energy per Order (EE/O) were calculated for different concentrations of NaCl, KCl, CaCl₂ and AlCl₃. This work may help in designing plasma systems appropriate for treatment of industrial wastewaters polluted by dyes. Full article

(This article belongs to the Special Issue Selected Papers from 16 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2016))

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25 pages, 4679 KiB

Open AccessArticle

Condensation Risk Due to Variations in Airtightness and Thermal Insulation of an Office Building in Warm and Wet Climate

by Wanghee Cho^1,*, Shizuo Iwamoto² and Shinsuke Kato¹

¹ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

² Department of Architecture, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Energies 2016, 9(11), 875; https://doi.org/10.3390/en9110875 - 27 Oct 2016

Cited by 20 | Viewed by 6265

Abstract

Condensation in a building encourages microbial growth, which can have an adverse effect on the health of occupants. Furthermore, it induces the deterioration of the building. To prevent problems caused by condensation, from the design step of a building, predictions of the spatial, [...] Read more.

Condensation in a building encourages microbial growth, which can have an adverse effect on the health of occupants. Furthermore, it induces the deterioration of the building. To prevent problems caused by condensation, from the design step of a building, predictions of the spatial, temporal and causation for condensation occurrences are necessary. By using TRNSYS simulation coupled with TRNFLOW, condensation assessment of an entire office building in Tokyo, Japan, was conducted throughout the year, including when the air-conditioning system was not operated, by considering the absorption-desorption properties of the building materials and papers in the office and the airflow within the entire building. It was found that most of the condensation occurred during winter and was observed mainly in the non-air-conditioned core parts, especially the topmost floor. Additional analyses, which identified the effect of variations in the thermal insulation of the external walls, roof and windows and the airtightness of the windows on condensation, showed that the lower airtightness of windows resulted in decreased condensation risks, and condensation within the building was suppressed completely when the thermal insulation material thickness of the external walls was greater than 75 mm, that of the roof was greater than 105 mm and the windows had triple float glass. Full article

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

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23 pages, 7179 KiB

Open AccessArticle

Lumped Parameters Model of a Crescent Pump

by Massimo Rundo^*

and Alessandro Corvaglia

Dipartimento Energia, Politecnico di Torino, 10129 Turin, Italy

Energies 2016, 9(11), 876; https://doi.org/10.3390/en9110876 - 26 Oct 2016

Cited by 31 | Viewed by 7842

Abstract

This paper presents the lumped parameters model of an internal gear crescent pump with relief valve, able to estimate the steady-state flow-pressure characteristic and the pressure ripple. The approach is based on the identification of three variable control volumes regardless of the number [...] Read more.

This paper presents the lumped parameters model of an internal gear crescent pump with relief valve, able to estimate the steady-state flow-pressure characteristic and the pressure ripple. The approach is based on the identification of three variable control volumes regardless of the number of gear teeth. The model has been implemented in the commercial environment LMS Amesim with the development of customized components. Specific attention has been paid to the leakage passageways, some of them affected by the deformation of the cover plate under the action of the delivery pressure. The paper reports the finite element method analysis of the cover for the evaluation of the deflection and the validation through a contactless displacement transducer. Another aspect described in this study is represented by the computational fluid dynamics analysis of the relief valve, whose results have been used for tuning the lumped parameters model. Finally, the validation of the entire model of the pump is presented in terms of steady-state flow rate and of pressure oscillations. Full article

(This article belongs to the Special Issue Energy Efficiency and Controllability of Fluid Power Systems)

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15 pages, 1224 KiB

Open AccessArticle

Energy Saving in Water Distribution Network through Pump as Turbine Generators: Economic and Environmental Analysis

by Mauro De Marchis

, Barbara Milici, Roberto Volpe and Antonio Messineo^*

Faculty of Engineering and Architecture, University of Enna Kore, Cittadella Universitaria, Enna 94100, Italy

Energies 2016, 9(11), 877; https://doi.org/10.3390/en9110877 - 26 Oct 2016

Cited by 61 | Viewed by 6364

Abstract

Complex systems of water distribution networks (WDS) are used to supply water to users. WDSs are systems where a lot of distributed energy is available. Historically, this energy is artificially dissipated by pressure reduction valves (PRVs), thanks to which water utilities manage the [...] Read more.

Complex systems of water distribution networks (WDS) are used to supply water to users. WDSs are systems where a lot of distributed energy is available. Historically, this energy is artificially dissipated by pressure reduction valves (PRVs), thanks to which water utilities manage the pressure level in selected nodes of the network. The present study explores the use of economic hydraulic machines, pumps as turbines (PATs) to produce energy in a small network located in a town close to Palermo (Italy). The main idea is to avoid dissipation in favor of renewable energy production. The proposed study is applied to a WDN typical of the Mediterranean countries, where the users, to collect water during the period of water scarcity conditions, install private tanks. The presence of private tanks deeply modifies the network from its designed condition. In the proposed analysis, the economic benefit of PATs application in water distribution networks has been investigated, accounting for the presence of users’ private tanks. The analysis, carried out by mean of a mathematical model able to dynamically simulate the water distribution network with PATs, shows the advantage of their installation in terms of renewable energy recovery, even though the energy production of PATs is strictly conditioned by their installation position. Full article

(This article belongs to the Special Issue Energy Saving Design for Manufacturing Process, Product, and System)

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22 pages, 7632 KiB

Open AccessArticle

An Interoperable Approach for Energy Systems Simulation: Electricity Market Participation Ontologies

by Gabriel Santos

, Tiago Pinto^*

, Isabel Praça and Zita Vale

GECAD, Research Group on Intelligent Engineering and Computing for Advanced Innovation and Development, Institute of Engineering, Polytechnic of Porto (ISEP/IPP), Rua Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal

Energies 2016, 9(11), 878; https://doi.org/10.3390/en9110878 - 27 Oct 2016

Cited by 16 | Viewed by 4528

Abstract

Electricity markets are complex environments with very particular characteristics. Some of the main ones for this complexity are the need for an adequate integration of renewable energy sources and the electricity markets’ restructuring process. The growth of simulation tool usage is driven by [...] Read more.

Electricity markets are complex environments with very particular characteristics. Some of the main ones for this complexity are the need for an adequate integration of renewable energy sources and the electricity markets’ restructuring process. The growth of simulation tool usage is driven by the need to understand those mechanisms and how the involved players’ interactions affect the markets’ outcomes. Several modelling tools directed to the study of restructured wholesale electricity markets have emerged. Although, they share a common limitation: the lack of interoperability between the various systems to allow the exchange of information and knowledge, to test different market models and to allow players from different systems to interact in common market environments. This paper proposes the use of ontologies for semantic interoperability between multi-agent platforms in the scope of electricity markets simulation. The achieved results allow the identification of the added value gained by using the proposed ontologies. They facilitate the integration of independent multi-agent simulators, by providing a way for communications to be understood by heterogeneous agents from different systems. Full article

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14 pages, 3971 KiB

Open AccessArticle

Master–Slave Based Hierarchical Control for a Small Power DC-Distributed Microgrid System with a Storage Device

by Seung-Woon Lee and Bo-Hyung Cho^*

Department of Electrical Engineering, Seoul National University 301-617, DaeHak-dong, GwanAk-gu, Seoul 151-742, Korea

Energies 2016, 9(11), 880; https://doi.org/10.3390/en9110880 - 27 Oct 2016

Cited by 24 | Viewed by 9031

Abstract

In this paper, we analyze one of the main drawbacks of droop control-based DC microgrid systems, and propose a novel control method to overcome this problem. Typically, DC microgrid systems use droop control techniques to enable communication independency and expandability. However, as these [...] Read more.

In this paper, we analyze one of the main drawbacks of droop control-based DC microgrid systems, and propose a novel control method to overcome this problem. Typically, DC microgrid systems use droop control techniques to enable communication independency and expandability. However, as these advantages are based on bus quality and regulation abandonment, droop-based schemes have limitations in terms of high bus impedance and bus regulation. This paper proposes a novel master–slave based hierarchical control technique for a DC distribution system, in which a DC bus signaling method is used to overcome the communication dependency and the expandability limitations of conventional master–slave control methods. The concept and design considerations of the proposed control method are presented, and a 1 kW simulation under a Powersim (PSIM) environment and hardware prototype—built to verify the system—is described. Full article

(This article belongs to the Special Issue Microgrids 2016)

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11 pages, 2230 KiB

Open AccessArticle

A Study on Electric Vehicle Heat Pump Systems in Cold Climates

by Ziqi Zhang, Wanyong Li, Junye Shi and Jiangping Chen^*

Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240, China

Energies 2016, 9(11), 881; https://doi.org/10.3390/en9110881 - 27 Oct 2016

Cited by 26 | Viewed by 9661

Abstract

Electric vehicle heat pumps are drawing more and more attention due to their energy-saving and high efficiency designs. Some problems remain, however, in the usage of the heat pumps in electric vehicles, such as a drainage problem regarding the external heat exchangers while [...] Read more.

Electric vehicle heat pumps are drawing more and more attention due to their energy-saving and high efficiency designs. Some problems remain, however, in the usage of the heat pumps in electric vehicles, such as a drainage problem regarding the external heat exchangers while in heat pump mode, and the decrease in heating performance when operated in a cold climate. In this article, an R134a economized vapor injection (EVI) heat pump system was built and tested. The drainage problem common amongst external heat exchangers was solved by an optimized 5 mm diameter tube-and-fin heat exchanger, which can meet both the needs of a condenser and evaporator based on simulation and test results. The EVI system was also tested under several ambient temperatures. It was found that the EVI was a benefit to the system heating capacity. Under a −20 °C ambient temperature, an average improvement of 57.7% in heating capacity was achieved with EVI and the maximum capacity was 2097 W, with a coefficient of performance (COP) of 1.25. The influences of injection pressure and economizer capacity are also discussed in this article. Full article

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21 pages, 5915 KiB

Open AccessArticle

A Short-Term Outage Model of Wind Turbines with Doubly Fed Induction Generators Based on Supervisory Control and Data Acquisition Data

by Peng Sun, Jian Li^*, Junsheng Chen and Xiao Lei

The State Key Laboratory of Power Transmission Equipment and System Security and New Technology, College of Electrical Engineering, Chongqing University, Chongqing 400044, China

Energies 2016, 9(11), 882; https://doi.org/10.3390/en9110882 - 28 Oct 2016

Cited by 3 | Viewed by 6403

Abstract

This paper presents a short-term wind turbine (WT) outage model based on the data collected from a wind farm supervisory control and data acquisition (SCADA) system. Neural networks (NNs) are used to establish prediction models of the WT condition parameters that are dependent [...] Read more.

This paper presents a short-term wind turbine (WT) outage model based on the data collected from a wind farm supervisory control and data acquisition (SCADA) system. Neural networks (NNs) are used to establish prediction models of the WT condition parameters that are dependent on environmental conditions such as ambient temperature and wind speed. The prediction error distributions are discussed and used to calculate probabilities of the operation of protection relays (POPRs) that were caused by the threshold exceedance of the environmentally sensitive parameters. The POPRs for other condition parameters are based on the setting time of the operation of protection relays. The union probability method is used to integrate the probabilities of operation of each protection relay to predict the WT short term outage probability. The proposed method has been used for real 1.5 MW WTs with doubly fed induction generators (DFIGs). The results show that the proposed method is more effective in WT outage probability prediction than traditional methods. Full article

(This article belongs to the Collection Wind Turbines)

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19 pages, 4900 KiB

Open AccessArticle

Nonlinear Coupled Dynamics of a Rod Fastening Rotor under Rub-Impact and Initial Permanent Deflection

by Liang Hu^*, Yibing Liu^*, Wei Teng and Chao Zhou

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

Energies 2016, 9(11), 883; https://doi.org/10.3390/en9110883 - 28 Oct 2016

Cited by 30 | Viewed by 6044

Abstract

A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D’Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance [...] Read more.

A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D’Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance mass, etc. The contact effects between disks was modeled as a flexural spring with cubical nonlinear stiffness. The coupled nonlinear dynamic phenomena of the rub-impact rod fastening rotor bearing system with initial permanent deflection were investigated by the fourth-order Runge-Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincaré map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that the coupled dynamic responses of the rod fastening rotor bearing system under rub-impact and initial permanent deflection exhibit a rich nonlinear dynamic diversity, synchronous periodic-1 motion, multiple periodic motion, quasi-periodic motion and chaotic motion can be observed under certain conditions. Larger radial stiffness of the stator will simplify the system motion and make the oil whirl weaker or even disappear at a certain rotating speed. With the increase of initial permanent deflection length, the instability speed of the system gradually rises, and the chaotic motion region gets smaller and smaller. The corresponding results can provide guidance for the fault diagnosis of a rub-impact rod fastening rotor with initial permanent deflection and contribute to the further understanding of the nonlinear dynamic characteristics of the rod fastening rotor bearing system. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2017)

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23 pages, 6850 KiB

Open AccessArticle

Effects of Power Tracking Algorithms on Lifetime of Power Electronic Devices Used in Solar Systems

by Canras Batunlu¹, Mohamad Alrweq² and Alhussein Albarbar^2,3,*

¹ Department of Electrical and Electronics Engineering, Middle East Technical University, Northern Cyprus Campus, 99738 Kalkanli, Guzelyurt, Mersin 10, Turkey

² Advanced Industrial Diagnostics Research Centre, School of Engineering, Manchester Metropolitan University, Manchester M1 5GD, UK

³ Faculty of Marine Studies, King Abdulaziz University, Jeddah 21589, Saudi Arabia

Energies 2016, 9(11), 884; https://doi.org/10.3390/en9110884 - 29 Oct 2016

Cited by 13 | Viewed by 6256

Abstract

In photovoltaic solar energy systems, power management algorithms (PMAs), usually called maximum power point tracking (MPPT) algorithms, are widely used for extracting maximum available power at every point in time. However, tracking the maximum power has negative effects on the availability of solar [...] Read more.

In photovoltaic solar energy systems, power management algorithms (PMAs), usually called maximum power point tracking (MPPT) algorithms, are widely used for extracting maximum available power at every point in time. However, tracking the maximum power has negative effects on the availability of solar energy systems. This is due, mainly, to the created disturbances and thermal stresses on the associated power electronic converters (PECs). This work investigates the effects of PMA on the lifetime consumption, thermal stresses and failures on DC-DC converters used in solar systems. Firstly theoretical analysis and modelling of photovoltaic solar systems including converter’s electro thermal characteristics were developed. Subsequently, experiments on photovoltaic solar systems were carried out using two different PMAs, namely, perturb and observe (P&O) and incremental conductance (IC). Real-time data was collected, under different operating conditions, including thermal behavior using thermal imaging camera and dSPACE. Converters’ thermal cycling was found to be approximately 3 °C higher with the IC algorithm. The steady state temperature was 52.7 °C, for the IC while it was 42.6 °C for P&O. Although IC algorithm offers more accurate power management tool, it causes more severe thermal stresses which, in this study, has led to approximately 1.4 times greater life consumption compared to P&O. Full article

(This article belongs to the Special Issue Solar Photovoltaics Trilemma: Efficiency, Stability and Cost Reduction 2017)

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17 pages, 1774 KiB

Open AccessArticle

Exergy and Thermoeconomic Analyses of Central Receiver Concentrated Solar Plants Using Air as Heat Transfer Fluid

by Claudia Toro^1,*, Matteo V. Rocco² and Emanuela Colombo²

¹ CNR Institute of Environmental Geology and Geoengineering, c/o Department of Mechanical and Aerospace Engineering, “Sapienza” University of Rome, Rome 00184, Italy

² Politecnico di Milano, Milan 20156, Italy

Energies 2016, 9(11), 885; https://doi.org/10.3390/en9110885 - 28 Oct 2016

Cited by 15 | Viewed by 5617

Abstract

The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the [...] Read more.

The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To supply thermal needs when the solar source is unavailable, an auxiliary burner is requested. This configuration is adopted in the Julich CSP (J-CSP) plant, operating in Germany and characterized by a nominal power of 1.5 MW, the heat transfer fluid (HTF) is air which is heated in the solar tower and used to produce steam for the bottoming Rankine cycle. In this paper, the J-CSP plant with thermal energy storage has been compared with a hybrid CSP plant (H-CSP) using air as the working fluid. Thermodynamic and economic performances of all the simulated plants have been evaluated by applying both exergy analysis and thermoeconomic analysis (TA) to determine the yearly average operation at nominal conditions. The exergy destructions and structure as well as the exergoeconomic costs of products have been derived for all the components of the plants. Based on the obtained results, the thermoeconomic design evaluation and optimization of the plants has been performed, allowing for improvement of the thermodynamic and economic efficiency of the systems as well as decreasing the exergy and exergoeconomic cost of their products. Full article

(This article belongs to the Special Issue Exergy Analysis of Energy Systems)

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17 pages, 2507 KiB

Open AccessArticle

Two-Stage Multi-Objective Collaborative Scheduling for Wind Farm and Battery Switch Station

by Zhe Jiang^1,2,*

, Xueshan Han^3,4, Zhimin Li¹, Wenbo Li², Mengxia Wang^3,4 and Mingqiang Wang^3,4

¹ Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150001, China

² Electric Power Research Institute, State Grid Shandong Electric Power Company, Jinan 250003, China

³ Key Laboratory of Power System Intelligent Dispatch and Control, Shandong University, Jinan 250061, China

⁴ Collaborative Innovation Center for Global Energy Interconnection (Shandong), Jinan 250061, China

Energies 2016, 9(11), 886; https://doi.org/10.3390/en9110886 - 29 Oct 2016

Cited by 3 | Viewed by 4585

Abstract

In order to deal with the uncertainties of wind power, wind farm and electric vehicle (EV) battery switch station (BSS) were proposed to work together as an integrated system. In this paper, the collaborative scheduling problems of such a system were studied. Considering [...] Read more.

In order to deal with the uncertainties of wind power, wind farm and electric vehicle (EV) battery switch station (BSS) were proposed to work together as an integrated system. In this paper, the collaborative scheduling problems of such a system were studied. Considering the features of the integrated system, three indices, which include battery swapping demand curtailment of BSS, wind curtailment of wind farm, and generation schedule tracking of the integrated system are proposed. In addition, a two-stage multi-objective collaborative scheduling model was designed. In the first stage, a day-ahead model was built based on the theory of dependent chance programming. With the aim of maximizing the realization probabilities of these three operating indices, random fluctuations of wind power and battery switch demand were taken into account simultaneously. In order to explore the capability of BSS as reserve, the readjustment process of the BSS within each hour was considered in this stage. In addition, the stored energy rather than the charging/discharging power of BSS during each period was optimized, which will provide basis for hour-ahead further correction of BSS. In the second stage, an hour-ahead model was established. In order to cope with the randomness of wind power and battery swapping demand, the proposed hour-ahead model utilized ultra-short term prediction of the wind power and the battery switch demand to schedule the charging/discharging power of BSS in a rolling manner. Finally, the effectiveness of the proposed models was validated by case studies. The simulation results indicated that the proposed model could realize complement between wind farm and BSS, reduce the dependence on power grid, and facilitate the accommodation of wind power. Full article

(This article belongs to the Special Issue Applied Energy System Modeling 2016)

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16 pages, 7281 KiB

Open AccessArticle

Application of a LiFePO₄ Battery Energy Storage System to Primary Frequency Control: Simulations and Experimental Results

by Fabio Massimo Gatta¹, Alberto Geri¹, Regina Lamedica¹, Stefano Lauria¹, Marco Maccioni^1,*, Francesco Palone², Massimo Rebolini² and Alessandro Ruvio¹

¹ Department of Astronautics, Electric and Energy Engineering, Sapienza University of Rome, Rome 00184, Italy

² Terna S.p.A., Rome 00156, Italy

Energies 2016, 9(11), 887; https://doi.org/10.3390/en9110887 - 29 Oct 2016

Cited by 30 | Viewed by 7456

Abstract

This paper presents an experimental application of LiFePO₄ battery energy storage systems (BESSs) to primary frequency control, currently being performed by Terna, the Italian transmission system operator (TSO). BESS performance in the primary frequency control role was evaluated by means of a [...] Read more.

This paper presents an experimental application of LiFePO₄ battery energy storage systems (BESSs) to primary frequency control, currently being performed by Terna, the Italian transmission system operator (TSO). BESS performance in the primary frequency control role was evaluated by means of a simplified electrical-thermal circuit model, taking into account also the BESS auxiliary consumptions, coupled with a cycle-life model, in order to assess the expected life of the BESS. Numerical simulations have been carried out considering the system response to real frequency measurements taken in Italy, spanning a whole year; a parametric study taking into account different values of governor droop and of BESS charge/discharge rates (C-rates) was also performed. Simulations, fully validated by experimental results obtained thus far, evidenced a severe trade-off between expected lifetime and overall efficiency, which significantly restricts the choice of operating parameters for frequency control. Full article

(This article belongs to the Special Issue Control of Energy Storage)

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25 pages, 22524 KiB

Open AccessArticle

Design and Analysis of Generic Energy Management Strategy for Controlling Second-Life Battery Systems in Stationary Applications

by Mohamed Abdel-Monem^1,2,*, Omar Hegazy¹, Noshin Omar¹, Khiem Trad², Sven De Breucker², Peter Van Den Bossche¹ and Joeri Van Mierlo¹

¹ Mobility, Logistics and Automotive Technology Research Center, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium

² Vito, Unit of Energy Technology, Boeretang 200, Mol 2400, Belgium

Energies 2016, 9(11), 889; https://doi.org/10.3390/en9110889 - 29 Oct 2016

Cited by 19 | Viewed by 6932

Abstract

Recently, second-life battery systems have received a growing interest as one of the most promising alternatives for decreasing the overall cost of the battery storage systems in stationary applications. The high-cost of batteries represents a prominent barrier for their use in traction and [...] Read more.

Recently, second-life battery systems have received a growing interest as one of the most promising alternatives for decreasing the overall cost of the battery storage systems in stationary applications. The high-cost of batteries represents a prominent barrier for their use in traction and stationary applications. To make second-life batteries economically viable for stationary applications, an effective power-electronics converter should be selected as well. This converter should be supported by an energy management strategy (EMS), which is needed for controlling the power flow among the second-life battery modules based on their available capacity and performance. This article presents the design, analysis and implementation of a generic energy management strategy (GEMS). The proposed GEMS aims to control and distribute the load demand between battery storage systems under different load conditions and disturbances. This manuscript provides the experimental verification of the proposed management strategy. The results have demonstrated that the GEMS can robustly handle any level of performance inequality among the used-battery modules with the aim to integrate different levels (i.e., size, capacity, and chemistry type) of the second-life battery modules at the same time and in the same application. Full article

(This article belongs to the Special Issue Advances in Electric Vehicles and Plug-in Hybrid Vehicles 2017)

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21 pages, 2311 KiB

Open AccessArticle

Dimensionless Maps for the Validity of Analytical Ground Heat Transfer Models for GSHP Applications

by Paolo Conti^1,2

¹ BETTER—Building Energy Technique and Technology Research Group, University of Pisa, Largo Lucio Lazzarino, Pisa 56122, Italy

² DESTEC—Department of Energy, Systems, Territory and Constructions Engineering, University of Pisa, Largo Lucio Lazzarino, Pisa 56122, Italy

Energies 2016, 9(11), 890; https://doi.org/10.3390/en9110890 - 29 Oct 2016

Cited by 20 | Viewed by 5087

Abstract

This article provides plain and handy expressions to decide the most suitable analytical model for the thermal analysis of the ground source in vertical ground-coupled heat pump applications. We perform a comprehensive dimensionless analysis of the reciprocal deviation among the classical infinite, finite, [...] Read more.

This article provides plain and handy expressions to decide the most suitable analytical model for the thermal analysis of the ground source in vertical ground-coupled heat pump applications. We perform a comprehensive dimensionless analysis of the reciprocal deviation among the classical infinite, finite, linear and cylindrical heat source models in purely conductive media. Besides, we complete the framework of possible boreholes model with the “hollow” finite cylindrical heat source solution, still lacking in the literature. Analytical expressions are effective tools for both design and performance assessment: they are able to provide practical and general indications on the thermal behavior of the ground with an advantageous tradeoff between calculation efforts and solution accuracy. This notwithstanding, their applicability to any specific case is always subjected to the coherence of the model assumptions, also in terms of length and time scales, with the specific case of interest. We propose several dimensionless criteria to evaluate when one model is practically equivalent to another one and handy maps that can be used for both design and performance analysis. Finally, we found that the finite line source represents the most suitable model for borehole heat exchangers (BHEs), as it is applicable to a wide range of space and time scales, practically providing the same results of more complex models. Full article

(This article belongs to the Special Issue Low Enthalpy Geothermal Energy)

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21 pages, 1627 KiB

Open AccessArticle

Economic Growth, Electricity Consumption, Labor Force and Capital Input: A More Comprehensive Analysis on North China Using Panel Data

by Huiru Zhao¹, Haoran Zhao¹, Xiaoyu Han¹, Zhonghua He² and Sen Guo^1,*

¹ School of Economics and Management, North China Electric Power University, Beijing 102206, China

² North China Grid Company Limited, Beijing Xuanwu District No. 482 Canton Avenue, Beijing 100053, China

Energies 2016, 9(11), 891; https://doi.org/10.3390/en9110891 - 29 Oct 2016

Cited by 26 | Viewed by 6334

Abstract

Over the past three decades, China’s economy has witnessed remarkable growth, with an average annual growth rate over 9%. However, China also faces great challenges to balance this spectacular economic growth and continuously increasing energy use like many other economies in the world. [...] Read more.

Over the past three decades, China’s economy has witnessed remarkable growth, with an average annual growth rate over 9%. However, China also faces great challenges to balance this spectacular economic growth and continuously increasing energy use like many other economies in the world. With the aim of designing effective energy and environmental policies, policymakers are required to master the relationship between energy consumption and economic growth. Therefore, in the case of North China, a multivariate model employing panel data analysis method based on the Cobb-Douglas production function which introduces electricity consumption as a main factor was established in this paper. The equilibrium relationship and causal relationship between real GDP, electricity consumption, total investment in fixed assets, and the employment were explored using data during the period of 1995–2014 for six provinces in North China, including Beijing City, Tianjin City, Hebei Province, Shanxi Province, Shandong Province and Inner Mongolia. The results of panel co-integration tests clearly state that all variables are co-integrated in the long term. Finally, Granger causality tests were used to examine the causal relationship between economic growth, electricity consumption, labor force and capital. From the Granger causality test results, we can draw the conclusions that: (1) There exist bi-directional causal relationships between electricity consumption and real GDP in six provinces except Hebei; and (2) there is a bi-directional relationship between capital input and economic growth and between labor force input and economic growth except Beijing and Hebei. Therefore, the ways to solve the contradiction of economic growth and energy consumption in North China are to reduce fossil energy consumption, develop renewable and sustainable energy sources, improve energy efficiency, and increase the proportion of the third industry, especially the sectors which hold the characteristics of low energy consumption and high value-added. Full article

(This article belongs to the Special Issue Applied Energy System Modeling 2016)

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19 pages, 9744 KiB

Open AccessArticle

Analytical Modeling of Static Eccentricities in Axial Flux Permanent-Magnet Machines with Concentrated Windings

by Yunkai Huang¹

, Baocheng Guo^1,*

, Ahmed Hemeida² and Peter Sergeant²

¹ Engineering Research Center for Motion Control of Ministry of Education, Southeast University, Nanjing 210096, China

² Department of Electrical Energy, Systems and Automation, Ghent University, Ghent B-9000, Belgium

Energies 2016, 9(11), 892; https://doi.org/10.3390/en9110892 - 29 Oct 2016

Cited by 28 | Viewed by 10016

Abstract

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the [...] Read more.

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell’s equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predictions agree well with the FE results. Finally, the results of analytical model are verified via experimental results. Full article

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

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17 pages, 4758 KiB

Open AccessArticle

Communication Channel Reconstruction for Transmission Line Differential Protection: System Arrangement and Routing Protocol

by Xu Chen^1,2,*, Xianggen Yin^1,2, Bin Yu^1,2 and Zhe Zhang^1,2

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

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

Energies 2016, 9(11), 893; https://doi.org/10.3390/en9110893 - 29 Oct 2016

Cited by 3 | Viewed by 6478

Abstract

Natural disasters may be of significant impact on overhead transmission lines and cause communication outage related to pilot protection. This paper aims at reconstructing communication channels and maintaining functions of pilot-wire differential protections after the main channel fails. With the development of smart [...] Read more.

Natural disasters may be of significant impact on overhead transmission lines and cause communication outage related to pilot protection. This paper aims at reconstructing communication channels and maintaining functions of pilot-wire differential protections after the main channel fails. With the development of smart grids as well as new communication technologies, wireless sensor networks (WSNs) have been potential means for realizing reconstructed communication channels (RCCs) without further installation. For a reliable design, system arrangement and the communication structure were presented. Theoretical planning of sensor nodes was formulated, which enjoys advantages such as high reliability, cost optimization, and capacity of satisfying the connectivity of the communication network. To meet the need of time delay, a novel routing protocol for WSNs was proposed with three stages including route establishment, route discovery and route maintenance, which ensured the directional propagation of data packets. Practical experiments and simulation results indicate that the proposed RCC scheme can satisfy time delay of protection relaying in emergency communication channel, as well as guarantee the connectivity of networks when some WSN nodes are damaged. Full article

(This article belongs to the Special Issue Advances in Power System Operations and Planning)

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20 pages, 2646 KiB

Open AccessArticle

A Long-Term Wind Speed Ensemble Forecasting System with Weather Adapted Correction

by Yiqi Chu¹

, Chengcai Li^1,*

, Yefang Wang^1,2, Jing Li¹

and Jian Li¹

¹ Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China

² Baicheng Ordnance Test Center of China, Baicheng 137001, China

Energies 2016, 9(11), 894; https://doi.org/10.3390/en9110894 - 31 Oct 2016

Cited by 9 | Viewed by 5246

Abstract

Wind forecasting is critical in the wind power industry, yet forecasting errors often exist. In order to effectively correct the forecasting error, this study develops a weather adapted bias correction scheme on the basis of an average bias-correction method, which considers the deviation [...] Read more.

Wind forecasting is critical in the wind power industry, yet forecasting errors often exist. In order to effectively correct the forecasting error, this study develops a weather adapted bias correction scheme on the basis of an average bias-correction method, which considers the deviation of estimated biases associated with the difference in weather type within each unit of the statistical sample. This method is tested by an ensemble forecasting system based on the Weather Research and Forecasting (WRF) model. This system provides high resolution wind speed deterministic forecasts using 40 members generated by initial perturbations and multi-physical schemes. The forecasting system outputs 28–52 h predictions with a temporal resolution of 15 min, and is evaluated against collocated anemometer towers observations at six wind fields located on the east coast of China. Results show that the information contained in weather types produces an improvement in the forecast bias correction. Full article

(This article belongs to the Special Issue Energy Time Series Forecasting)

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18 pages, 2800 KiB

Open AccessArticle

Assessment of the Agronomic Feasibility of Bioenergy Crop Cultivation on Marginal and Polluted Land: A GIS-Based Suitability Study from the Sulcis Area, Italy

by Giuseppe Pulighe^1,*

, Guido Bonati¹, Stefano Fabiani¹

, Tommaso Barsali², Flavio Lupia¹

, Silvia Vanino¹, Pasquale Nino¹, Pasquale Arca³ and Pier Paolo Roggero^3,4

¹ Council for Agricultural Research and Economics—Centro di Ricerca di Politiche e Bioeconomia, Via Po 14, Rome 00198, Italy

² Biochemtex SpA, Strada Ribrocca 11, Tortona 15057, Italy

³ Department of Agricultural Sciences, University of Sassari, Viale Italia 39, Sassari 07100, Italy

⁴ Desertification Research Centre, University of Sassari, Viale Italia 39, Sassari 07100, Italy

Energies 2016, 9(11), 895; https://doi.org/10.3390/en9110895 - 31 Oct 2016

Cited by 35 | Viewed by 8203

Abstract

In the context of environmental sustainability there has been an increasing interest in bioenergy production from renewable resources, and is expected that European biofuel production from energy crops will increase as a consequence of the achievement of policy targets. The aim of this [...] Read more.

In the context of environmental sustainability there has been an increasing interest in bioenergy production from renewable resources, and is expected that European biofuel production from energy crops will increase as a consequence of the achievement of policy targets. The aim of this paper is to assess the agronomic feasibility of biomass crop cultivation to provide profitable renewable feedstocks in a marginal and heavy-metal polluted area located in the Sulcis district, Sardinia (Italy). Results from literature review and unpublished data from field trials carried out in Sardinia were analysed to establish the main agronomic traits of crops (e.g., yield potential and input requirements). A Geographical Information System (GIS)-based procedure with remotely sensed data is also used to evaluate the land suitability and the actual land use/cover, considering a future scenario of expansion of energy crops on these marginal areas avoiding potential conflicts with food production. The results of the review suggests that giant reed, native perennial grasses and milk thistle are the most suitable energy crops for this area. The land suitability analysis shows that about 5700 ha and 1000 ha could be available for feedstock cultivation in the study area and in the most polluted area, respectively. The results obtained from land suitability process and agronomic evaluation will serve as a base to support technical and economical feasibility studies, as well as for the evaluation of environmental sustainability of the cultivation in the study area. Full article

(This article belongs to the Special Issue Agriculture and Energy)

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18 pages, 2248 KiB

Open AccessArticle

A Rest Time-Based Prognostic Framework for State of Health Estimation of Lithium-Ion Batteries with Regeneration Phenomena

by Taichun Qin^1,2, Shengkui Zeng^1,3

, Jianbin Guo^1,3,* and Zakwan Skaf²

¹ School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China

² IVHM Centre, Cranfield University, Cranfield MK43 0AL, UK

³ Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing 100191, China

Energies 2016, 9(11), 896; https://doi.org/10.3390/en9110896 - 1 Nov 2016

Cited by 49 | Viewed by 6519

Abstract

State of health (SOH) prognostics is significant for safe and reliable usage of lithium-ion batteries. To accurately predict regeneration phenomena and improve long-term prediction performance of battery SOH, this paper proposes a rest time-based prognostic framework (RTPF) in which the beginning time interval [...] Read more.

State of health (SOH) prognostics is significant for safe and reliable usage of lithium-ion batteries. To accurately predict regeneration phenomena and improve long-term prediction performance of battery SOH, this paper proposes a rest time-based prognostic framework (RTPF) in which the beginning time interval of two adjacent cycles is adopted to reflect the rest time. In this framework, SOH values of regeneration cycles, the number of cycles in regeneration regions and global degradation trends are extracted from raw SOH time series and predicted respectively, and then the three sets of prediction results are integrated to calculate the final overall SOH prediction values. Regeneration phenomena can be found by support vector machine and hyperplane shift (SVM-HS) model by detecting long beginning time intervals. Gaussian process (GP) model is utilized to predict the global degradation trend, and nonlinear models are utilized to predict the regeneration amplitude and the cycle number of each regeneration region. The proposed framework is validated through experimental data from the degradation tests of lithium-ion batteries. The results demonstrate that both the global degradation trend and the regeneration phenomena of the testing batteries can be well predicted. Moreover, compared with the published methods, more accurate SOH prediction results can be obtained under this framework. Full article

(This article belongs to the Special Issue Energy Storage Systems for Plug-in Electric Vehicles and Vehicle to Power Grid Integration)

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20 pages, 1443 KiB

Open AccessArticle

Carbon Auction Revenue and Market Power: An Experimental Analysis

by Noah Dormady

John Glenn College of Public Affairs, The Ohio State University, 1810 College Rd, Columbus, OH 43210, USA

Energies 2016, 9(11), 897; https://doi.org/10.3390/en9110897 - 1 Nov 2016

Cited by 6 | Viewed by 5170

Abstract

State and regional governments in the U.S. and abroad are looking to market-based approaches to mitigating greenhouse gas emissions from the electric sector, and in the U.S. as a compliance approach to meeting the aggressive targets of the Environmental Protection Agency (EPA)’s Clean [...] Read more.

State and regional governments in the U.S. and abroad are looking to market-based approaches to mitigating greenhouse gas emissions from the electric sector, and in the U.S. as a compliance approach to meeting the aggressive targets of the Environmental Protection Agency (EPA)’s Clean Power Plan. Auction-based approaches, like those used in the Northeast U.S. and California, are both recommended strategies under the Plan and attractive to state governments because they can generate significant revenue from the sale of emissions permits. However, given the nature of imperfect competition in existing electricity markets, particularly at the state and regional level, the issue of market power is a concern at the forefront. This paper provides the results from a controlled laboratory experiment of an auction-based emissions market in the electricity sector. The results show that government revenue from auctioning emissions permits is substantially lower when market concentration is only moderately increased. The results hold significant implications for states and other subnational governments that have high revenue expectations from the auctioning of emissions permits. Full article

(This article belongs to the Special Issue Contemporary Sustainable Energy Paradigms and the Multifunctional Economy)

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19 pages, 3691 KiB

Open AccessArticle

Using Trajectory Clusters to Define the Most Relevant Features for Transient Stability Prediction Based on Machine Learning Method

by Luyu Ji^*

, Junyong Wu, Yanzhen Zhou and Liangliang Hao

School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China

Energies 2016, 9(11), 898; https://doi.org/10.3390/en9110898 - 1 Nov 2016

Cited by 35 | Viewed by 5101

Abstract

To achieve rapid real-time transient stability prediction, a power system transient stability prediction method based on the extraction of the post-fault trajectory cluster features of generators is proposed. This approach is conducted using data-mining techniques and support vector machine (SVM) models. First, the [...] Read more.

To achieve rapid real-time transient stability prediction, a power system transient stability prediction method based on the extraction of the post-fault trajectory cluster features of generators is proposed. This approach is conducted using data-mining techniques and support vector machine (SVM) models. First, the post-fault rotor angles and generator terminal voltage magnitudes are considered as the input vectors. Second, we construct a high-confidence dataset by extracting the 27 trajectory cluster features obtained from the chosen databases. Then, by applying a filter–wrapper algorithm for feature selection, we obtain the final feature set composed of the eight most relevant features for transient stability prediction, called the global trajectory clusters feature subset (GTCFS), which are validated by receiver operating characteristic (ROC) analysis. Comprehensive simulations are conducted on a New England 39-bus system under various operating conditions, load levels and topologies, and the transient stability predicting capability of the SVM model based on the GTCFS is extensively tested. The experimental results show that the selected GTCFS features improve the prediction accuracy with high computational efficiency. The proposed method has distinct advantages for transient stability prediction when faced with incomplete Wide Area Measurement System (WAMS) information, unknown operating conditions and unknown topologies and significantly improves the robustness of the transient stability prediction system. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2017)

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19 pages, 9539 KiB

Open AccessArticle

A Current Control Approach for an Abnormal Grid Supplied Ultra Sparse Z-Source Matrix Converter with a Particle Swarm Optimization Proportional-Integral Induction Motor Drive Controller

by Seyed Sina Sebtahmadi¹, Hanieh Borhan Azad², Didarul Islam¹, Mehdi Seyedmahmoudian³, Ben Horan³

and Saad Mekhilef^1,*

¹ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

² School of Electrical Engineering and Telecommunications, University of New South Wales, 330 Anzac Parade, Kensington, NSW 2033, Australia

³ School of Engineering, Deakin University, Mont Iris Ave, Burwood, VIC 3146, Australia

Energies 2016, 9(11), 899; https://doi.org/10.3390/en9110899 - 2 Nov 2016

Cited by 12 | Viewed by 4789

Abstract

A rotational d-q current control scheme based on a Particle Swarm Optimization- Proportional-Integral (PSO-PI) controller, is used to drive an induction motor (IM) through an Ultra Sparse Z-source Matrix Converter (USZSMC). To minimize the overall size of the system, the lowest [...] Read more.

A rotational d-q current control scheme based on a Particle Swarm Optimization- Proportional-Integral (PSO-PI) controller, is used to drive an induction motor (IM) through an Ultra Sparse Z-source Matrix Converter (USZSMC). To minimize the overall size of the system, the lowest feasible values of Z-source elements are calculated by considering the both timing and aspects of the circuit. A meta-heuristic method is integrated to the control system in order to find optimal coefficient values in a single multimodal problem. Henceforth, the effect of all coefficients in minimizing the total harmonic distortion (THD) and balancing the stator current are considered simultaneously. Through changing the reference point of magnitude or frequency, the modulation index can be automatically adjusted and respond to changes without heavy computational cost. The focus of this research is on a reliable and lightweight system with low computational resources. The proposed scheme is validated through both simulation and experimental results. Full article

(This article belongs to the Special Issue Power Electronics Optimal Design and Control)

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16 pages, 3710 KiB

Open AccessArticle

A Generalized SOC-OCV Model for Lithium-Ion Batteries and the SOC Estimation for LNMCO Battery

by Caiping Zhang^1,2, Jiuchun Jiang^1,2,*, Linjing Zhang^1,2, Sijia Liu^1,2, Leyi Wang³ and Poh Chiang Loh^1,2

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

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

³ Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, USA

Energies 2016, 9(11), 900; https://doi.org/10.3390/en9110900 - 1 Nov 2016

Cited by 156 | Viewed by 26045

Abstract

A state-of-charge (SOC) versus open-circuit-voltage (OCV) model developed for batteries should preferably be simple, especially for real-time SOC estimation. It should also be capable of representing different types of lithium-ion batteries (LIBs), regardless of temperature change and battery degradation. It must therefore be [...] Read more.

A state-of-charge (SOC) versus open-circuit-voltage (OCV) model developed for batteries should preferably be simple, especially for real-time SOC estimation. It should also be capable of representing different types of lithium-ion batteries (LIBs), regardless of temperature change and battery degradation. It must therefore be generic, robust and adaptive, in addition to being accurate. These challenges have now been addressed by proposing a generalized SOC-OCV model for representing a few most widely used LIBs. The model is developed from analyzing electrochemical processes of the LIBs, before arriving at the sum of a logarithmic, a linear and an exponential function with six parameters. Values for these parameters are determined by a nonlinear estimation algorithm, which progressively shows that only four parameters need to be updated in real time. The remaining two parameters can be kept constant, regardless of temperature change and aging. Fitting errors demonstrated with different types of LIBs have been found to be within 0.5%. The proposed model is thus accurate, and can be flexibly applied to different LIBs, as verified by hardware-in-the-loop simulation designed for real-time SOC estimation. Full article

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

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16 pages, 5106 KiB

Open AccessArticle

Auto-Mapping and Configuration Method of IEC 61850 Information Model Based on OPC UA

by In-Jae Shin¹, Byung-Kwen Song^2,* and Doo-Seop Eom¹

¹ Department of Electrical Engineering, Korea University, Seoul 02841, Korea

² Department of Electrical Engineering, Seokyeong University, Seoul 02173, Korea

Energies 2016, 9(11), 901; https://doi.org/10.3390/en9110901 - 1 Nov 2016

Cited by 17 | Viewed by 9306

Abstract

The open-platform communication (OPC) unified architecture (UA) (IEC62541) is introduced as a key technology for realizing a variety of smart grid (SG) use cases enabling relevant automation and control tasks. The OPC UA can expand interoperability between power systems. The top-level SG management [...] Read more.

The open-platform communication (OPC) unified architecture (UA) (IEC62541) is introduced as a key technology for realizing a variety of smart grid (SG) use cases enabling relevant automation and control tasks. The OPC UA can expand interoperability between power systems. The top-level SG management platform needs independent middleware to transparently manage the power information technology (IT) systems, including the IEC 61850. To expand interoperability between the power system for a large number of stakeholders and various standards, this paper focuses on the IEC 61850 for the digital substation. In this paper, we propose the interconnection method to integrate communication with OPC UA and convert OPC UA AddressSpace using system configuration description language (SCL) of IEC 61850. We implemented the mapping process for the verification of the interconnection method. The interconnection method in this paper can expand interoperability between power systems for OPC UA integration for various data structures in the smart grid. Full article

(This article belongs to the Special Issue Advances in Power System Operations and Planning)

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11 pages, 256 KiB

Open AccessArticle

The Impact and Determinants of Environmental Taxation on Economic Growth Communities in Romania

by Jean Andrei^1,*, Mihai Mieila², Gheorghe H. Popescu³, Elvira Nica⁴ and Manole Cristina⁴

¹ Petroleum-Gas University of Ploiesti, 39 Bucuresti Blvd., Prahova 100680, Romania

² Valahia University of Targoviste, Aleea Sinaia Street, No. 13, Targoviste, Dambovita 130004, Romania

³ Dimitrie Cantemir Christian University, 176 Splaiul Unirii, Bucharest 030134, Romania

⁴ Bucharest University of Economic Study, 6 Roman Place, Bucharest 010374, Romania

Energies 2016, 9(11), 902; https://doi.org/10.3390/en9110902 - 1 Nov 2016

Cited by 120 | Viewed by 8782

Abstract

Environmental taxation represents a key influence on sustainable development in post-transition countries. Romania has experienced important transformations of environmental policy, including taxation, due to sustained reliance on traditional energy sources to satisfy its energy needs. The aim of this paper is to show [...] Read more.

Environmental taxation represents a key influence on sustainable development in post-transition countries. Romania has experienced important transformations of environmental policy, including taxation, due to sustained reliance on traditional energy sources to satisfy its energy needs. The aim of this paper is to show a possible causal relationship between the Romanian GDP and several explanatory variables related to taxation of environmental damage and energy generation and consumption in the country. In order to do this, the authors make use of several statistical tests to verify the existence of a meaningful relationship between economic variables expressed in time series. The study has also attempted to identify the influence of environmental taxation on ensuring green economic development, starting from the premise that for emergent economies these taxes provide both a GDP increase and prevent environmental degradation by decreasing the pollution and environmentally harmful supplies and practices. Full article

(This article belongs to the Special Issue Contemporary Environmental Paradigms and the Renewable Energy in Rural Economies)

23 pages, 8701 KiB

Open AccessArticle

Using CPE Function to Size Capacitor Storage for Electric Vehicles and Quantifying Battery Degradation during Different Driving Cycles

by Cong Zhang¹

, Haitao Min¹, Yuanbin Yu^1,*, Dai Wang², Justin Luke³, Daniel Opila⁴ and Samveg Saxena²

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

² Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94710, USA

³ Engineering Science, University of California, Berkeley, CA 94720, USA

⁴ Electrical and Computer Engineering Department, United States Naval Academy, Annapolis, MD 21402, USA

Energies 2016, 9(11), 903; https://doi.org/10.3390/en9110903 - 2 Nov 2016

Cited by 19 | Viewed by 8378

Abstract

Range anxiety and battery cycle life are two major factors which restrict the development of electric vehicles. Battery degradation can be reduced by adding supercapacitors to create a Hybrid Energy Storage System. This paper proposes a systematic approach to configure the hybrid energy [...] Read more.

Range anxiety and battery cycle life are two major factors which restrict the development of electric vehicles. Battery degradation can be reduced by adding supercapacitors to create a Hybrid Energy Storage System. This paper proposes a systematic approach to configure the hybrid energy storage system and quantifies the battery degradation for electric vehicles when using supercapacitors. A continuous power-energy function is proposed to establish supercapacitor size based on national household travel survey statistics. By analyzing continuous driving action in standard driving cycles and special driving phases (start up and acceleration), the supercapacitor size is calculated to provide a compromise between the capacitor size and battery degradation. Estimating the battery degradation after 10 years, the battery capacity loss value decreases 17.55% and 21.6%, respectively, under the urban dynamometer driving schedule and the US06. Furthermore, the battery lifespan of the continuous power-energy configured system is prolonged 28.62% and 31.39%, respectively, compared with the battery alone system. Full article

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15 pages, 9751 KiB

Open AccessArticle

A Novel Flux Focusing Magnetically Geared Machine with Reduced Eddy Current Loss

by Jin Liu^1,2, Wenxiang Zhao^1,2,*, Jinghua Ji^1,2, Guohai Liu^1,2 and Tao Tao^1,2

¹ School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China

² Jiangsu Key Laboratory of Drive and Intelligent Control for Electric Vehicle, Zhenjiang 212013, China

Energies 2016, 9(11), 904; https://doi.org/10.3390/en9110904 - 2 Nov 2016

Cited by 4 | Viewed by 5565

Abstract

This paper proposes a novel flux focusing magnetically geared (MG) machine for wind power generation, considering the permanent magnets (PMs) eddy current loss and the balance between the pull-out torque of MG machine and the back-electromotive force (EMF)of the PM brushless machine. The [...] Read more.

This paper proposes a novel flux focusing magnetically geared (MG) machine for wind power generation, considering the permanent magnets (PMs) eddy current loss and the balance between the pull-out torque of MG machine and the back-electromotive force (EMF)of the PM brushless machine. The PM eddy current loss in the two rotors of the conventional surface-mounted MG machine is calculated and analyzed by using finite-element method. By adopting serial-spoke structure in the inner rotor, a novel rotor structure for a MG machine is proposed to reduce the PM eddy current loss. Moreover, in order to balance the pull-out torque and the back-EMF, several serial-spoke structures and the main design parameters are investigated. Then, a quantitative comparison between the proposed topology and the conventional surface-mounted MG machine is performed. The analysis results indicate that the PM eddy current loss of the proposed MG machine can be significantly reduced and its pull-out torque and back-EMF can be balanced well. Full article

(This article belongs to the Special Issue Electric Machines and Drives for Renewable Energy Harvesting)

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17 pages, 6681 KiB

Open AccessArticle

Basic Characteristics and Design of a Novel Hybrid Magnetic Bearing for Wind Turbines

by Yanjun Yu^*, Weiyu Zhang, Yuxin Sun and Peifeng Xu

School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China

Energies 2016, 9(11), 905; https://doi.org/10.3390/en9110905 - 2 Nov 2016

Cited by 10 | Viewed by 6350

Abstract

This paper proposes a five-degree-of-freedom (5-DOF) hybrid magnetic bearing (HMB) for direct-drive wind turbines, which can realize suspension in the 4-DOF radial and 1-DOF axial directions. Only two sets of radial control windings are employed in the proposed HMB because only one set [...] Read more.

This paper proposes a five-degree-of-freedom (5-DOF) hybrid magnetic bearing (HMB) for direct-drive wind turbines, which can realize suspension in the 4-DOF radial and 1-DOF axial directions. Only two sets of radial control windings are employed in the proposed HMB because only one set of radial control windings can achieve the 2-DOF suspension in the radial direction. Unlike the traditional active thrust magnetic bearings, this paper uses a cylindrical rotor core without a large thrust disc in the novel HMB. The numbers of the controller, power amplifier and system volume can be reduced in the magnetic suspension system. This paper also presents the structure and basic characteristics of the proposed magnetic bearing. A precision equivalent magnetic circuit analysis of the permanent magnet ring and control magnetic field is conducted in this study, in consideration of the non-uniform distribution of magnetic density. Accordingly, the mathematical models, including the suspension force expression, are derived based on the accurate equivalent magnetic circuit. The basic principle of the structure parameter design is presented, based on the given key parameters. The accuracy of the analytical method is further validated by 3D finite element analysis. Full article

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13 pages, 5644 KiB

Open AccessArticle

Cost-Effectiveness Comparison of Coupler Designs of Wireless Power Transfer for Electric Vehicle Dynamic Charging

by Weitong Chen¹, Chunhua Liu^1,*

, Christopher H.T. Lee²

and Zhiqiang Shan¹

¹ School of Energy and Environment, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong, China

² Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Energies 2016, 9(11), 906; https://doi.org/10.3390/en9110906 - 2 Nov 2016

Cited by 81 | Viewed by 9185

Abstract

This paper presents a cost-effectiveness comparison of coupler designs for wireless power transfer (WPT), meant for electric vehicle (EV) dynamic charging. The design comparison of three common types of couplers is first based on the raw material cost, output power, transfer efficiency, tolerance [...] Read more.

This paper presents a cost-effectiveness comparison of coupler designs for wireless power transfer (WPT), meant for electric vehicle (EV) dynamic charging. The design comparison of three common types of couplers is first based on the raw material cost, output power, transfer efficiency, tolerance of horizontal offset, and flux density. Then, the optimal cost-effectiveness combination is selected for EV dynamic charging. The corresponding performances of the proposed charging system are compared and analyzed by both simulation and experimentation. The results verify the validity of the proposed dynamic charging system for EVs. Full article

(This article belongs to the Special Issue Wireless Power Transfer 2016)

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20 pages, 6096 KiB

Open AccessArticle

Numerical Investigation of Wind Conditions for Roof-Mounted Wind Turbines: Effects of Wind Direction and Horizontal Aspect Ratio of a High-Rise Cuboid Building

by Takaaki Kono^1,*, Tetsuya Kogaki² and Takahiro Kiwata¹

¹ Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan

² National Instiute of Advanced Industrial Science and Technology, Koriyama 963-0298, Japan

Energies 2016, 9(11), 907; https://doi.org/10.3390/en9110907 - 3 Nov 2016

Cited by 35 | Viewed by 6583

Abstract

From the viewpoint of installing small wind turbines (SWTs) on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length) of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs). [...] Read more.

From the viewpoint of installing small wind turbines (SWTs) on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length) of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs). The LES results confirmed that as HAR decreases (i.e., as the building width decreases), the variation in wind velocity over the roof tends to decrease. This tendency is more prominent as the angle between the wind direction and the normal vector of the building’s leeward face with longer roof edge increases. Moreover, at windward corners of the roof, wind conditions are generally favorable at relatively low heights. In contrast, at the midpoint of the roof's windward edge, wind conditions are generally not favorable at relatively low heights. At leeward representative locations of the roof, the bottoms of the height range of favorable wind conditions are typically higher than those at the windward representative locations, but the favorable wind conditions are much better at the leeward representative locations. When there is no prevailing wind direction, the center of the roof is more favorable for installing SWTs than the corners or the edge midpoints of the roof. Full article

(This article belongs to the Collection Wind Turbines)

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15 pages, 2814 KiB

Open AccessEditor’s ChoiceArticle

Promise and Challenges of High-Voltage SiC Bipolar Power Devices

by Tsunenobu Kimoto^*, Kyosuke Yamada, Hiroki Niwa and Jun Suda

Department of Electronic Science and Engineering, Kyoto University, Kyoto 615 8510, Japan

Energies 2016, 9(11), 908; https://doi.org/10.3390/en9110908 - 3 Nov 2016

Cited by 40 | Viewed by 8798

Abstract

Although various silicon carbide (SiC) power devices with very high blocking voltages over 10 kV have been demonstrated, basic issues associated with the device operation are still not well understood. In this paper, the promise and limitations of high-voltage SiC bipolar devices are [...] Read more.

Although various silicon carbide (SiC) power devices with very high blocking voltages over 10 kV have been demonstrated, basic issues associated with the device operation are still not well understood. In this paper, the promise and limitations of high-voltage SiC bipolar devices are presented, taking account of the injection-level dependence of carrier lifetimes. It is shown that the major limitation of SiC bipolar devices originates from band-to-band recombination, which becomes significant at a high-injection level. A trial of unipolar/bipolar hybrid operation to reduce power loss is introduced, and an 11 kV SiC hybrid (merged pin-Schottky) diodes is experimentally demonstrated. The fabricated diodes with an epitaxial anode exhibit much better forward characteristics than diodes with an implanted anode. The temperature dependence of forward characteristics is discussed. Full article

(This article belongs to the Special Issue Semiconductor Power Devices)

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17 pages, 4005 KiB

Open AccessArticle

Multi-Objective Distribution Network Expansion Incorporating Electric Vehicle Charging Stations

by Yue Xiang^1,*

, Wei Yang¹, Junyong Liu¹ and Furong Li²

¹ School of Electrical Engineering and Information, Sichuan University, Chengdu 610065, China

² Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK

Energies 2016, 9(11), 909; https://doi.org/10.3390/en9110909 - 3 Nov 2016

Cited by 30 | Viewed by 6304

Abstract

The paper develops a multi-objective planning framework for distribution network expansion with electric vehicle charging stations. Charging loads are modeled in the first place, and then integrated into the optimal distribution network expansion planning. The formulation is extended from the single objective of [...] Read more.

The paper develops a multi-objective planning framework for distribution network expansion with electric vehicle charging stations. Charging loads are modeled in the first place, and then integrated into the optimal distribution network expansion planning. The formulation is extended from the single objective of the economic cost minimization into three objectives with the additional maximization of the charging station utilization, and maximization of the reliability level. Compared with the existing models, it captures the interactive impacts between charging infrastructures planning and distribution network planning from the aspects of economy, utilization, and reliability. A multi-stage search strategy is designed to solve the multi-objective problem. The models and the strategy are demonstrated by the test case. The results show that the proposed planning framework can make a trade-off among the three objectives, and offer a perspective to effectively integrate the network constraints from both the transportation network and distribution network. Full article

(This article belongs to the Collection Smart Grid)

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11 pages, 1307 KiB

Open AccessArticle

Thermal Cracking of Jatropha Oil with Hydrogen to Produce Bio-Fuel Oil

by Yi-Yu Wang¹, Chia-Chi Chang¹, Ching-Yuan Chang^1,2,*, Yi-Hung Chen³, Je-Lueng Shie⁴, Min-Hao Yuan⁵, Yen-Hau Chen¹, Li-Xuan Huang¹, Cesar Augusto Andrade-Tacca¹, Do Van Manh⁶, Min-Yi Tsai¹ and Michael Huang¹

¹ Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 10617, Taiwan

² Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan

³ Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 10608, Taiwan

⁴ Department of Environmental Engineering, National Ilan University, I-Lan 26047, Taiwan

⁵ Department of Occupational Safety and Health, China Medical University, Taichung 40402, Taiwan

⁶ Danang Environmental Technology Center, Institute of Environmental Technology, Vietnam Academy of Science and Technology, Da Nang City 550000, Vietnam

Energies 2016, 9(11), 910; https://doi.org/10.3390/en9110910 - 3 Nov 2016

Cited by 3 | Viewed by 4981

Abstract

This study used thermal cracking with hydrogen (HTC) to produce bio-fuel oil (BFO) from jatropha oil (JO) and to improve its quality. We conducted HTC with different hydrogen pressures (P_H2; 0–2.07 MPa or 0–300 psig), retention times (t_r [...] Read more.

This study used thermal cracking with hydrogen (HTC) to produce bio-fuel oil (BFO) from jatropha oil (JO) and to improve its quality. We conducted HTC with different hydrogen pressures (P_H2; 0–2.07 MPa or 0–300 psig), retention times (t_r; 40–780 min), and set temperatures (T_C; 623–683 K). By applying HTC, the oil molecules can be hydrogenated and broken down into smaller molecules. The acid value (AV), iodine value, kinematic viscosity (KV), density, and heating value (HV) of the BFO produced were measured and compared with the prevailing standards for oil to assess its suitability as a substitute for fossil fuels or biofuels. The results indicate that an increase in P_H2 tends to increase the AV and KV while decreasing the HV of the BFO. The BFO yield (Y_BFO) increases with P_H2 and t_r. The above properties decrease with increasing T_C. Upon HTC at 0.69 MPa (100 psig) H₂ pressure, 60 min time, and 683 K temperature, the Y_BFO was found to be 86 wt%. The resulting BFO possesses simulated distillation characteristics superior to those of boat oil and heavy oil while being similar to those of diesel oil. The BFO contains 15.48% light naphtha, 35.73% heavy naphtha, 21.79% light gas oil, and 27% heavy gas oil and vacuum residue. These constituents can be further refined to produce gasoline, diesel, lubricants, and other fuel products. Full article

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15 pages, 14080 KiB

Open AccessArticle

Solar Resource for Urban Communities in the Baja California Peninsula, Mexico

by Alberto-Jesús Perea-Moreno^1,*

and Quetzalcoatl Hernandez-Escobedo²

¹ Department of Applied Physics, University of Cordoba, CEIA3, Campus de Rabanales, 14071 Córdoba, Spain

² Faculty of Engineering Campus Coatzacoalcos, University of Veracruz, Harrapa, Veracruz 0052229, Mexico

Energies 2016, 9(11), 911; https://doi.org/10.3390/en9110911 - 3 Nov 2016

Cited by 7 | Viewed by 7716

Abstract

Several studies have determined that Mexico has great renewable energy potential, and one of its most abundant resources is solar energy, a source that could be exploited to provide development opportunities to its population, however it is necessary to calculate the amount of [...] Read more.

Several studies have determined that Mexico has great renewable energy potential, and one of its most abundant resources is solar energy, a source that could be exploited to provide development opportunities to its population, however it is necessary to calculate the amount of this source available. The aim of this study was to assess solar irradiance at urban communities in the Baja California Peninsula. For this purpose data recorded every 10 min during 6 years (2010–2015) by the Automatic Meteorological Stations (AMSs) and Synoptic Automatic Meteorological Stations (SAMSs) of the National Meteorological System of Mexico (NMS) were analyzed. Satellite data from the Surface and Meteorology Energy System (SMSE) were also used, and a linear regression was performed to compare the measured and satellite data. The highest R-square value found was 0.97 and the lowest was 0.82. Daily patterns show that Cabo San Lucas had the highest average solar irradiation/day, with 1000 W/m². Considering the urban areas, total solar irradiation reaching the Peninsula is about 447 × 10⁶ kWh, which represents around 447 times the total Baja California Peninsula yearly energy consumption. Geographic Information System (GIS) helped to identify the zones and months with higher solar resources. May is the month registering the highest irradiation, more than 8.1 kWh/m²/day, while the average solar resource for the whole Peninsula is 5.7 kWh/m²/day. Full article

(This article belongs to the Special Issue Urban Generation of Renewable Energy and Sustainable Cities)

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12 pages, 9628 KiB

Open AccessArticle

Experimental Optimization of Passive Cooling of a Heat Source Array Flush-Mounted on a Vertical Plate

by Antoine Baudoin^1,*, Didier Saury²

, Bo Zhu² and Cecilia Boström¹

¹ Division for Electricity, Uppsala University, Box 534, 751 21 Uppsala, Sweden

² Institut PPRIME, CNRS, ENSMA, Université de Poitiers, BP 40109, F-86961 Futuroscope Chasseneuil CEDEX, France

Energies 2016, 9(11), 912; https://doi.org/10.3390/en9110912 - 4 Nov 2016

Cited by 9 | Viewed by 5195

Abstract

Heat sources, such as power electronics for offshore power, could be cooled passively—mainly by conduction and natural convection. The obvious advantage of this strategy is its high reliability. However, it must be implemented in an efficient manner (i.e., the area needs to be [...] Read more.

Heat sources, such as power electronics for offshore power, could be cooled passively—mainly by conduction and natural convection. The obvious advantage of this strategy is its high reliability. However, it must be implemented in an efficient manner (i.e., the area needs to be kept low to limit the construction costs). In this study, the placement of multiple heat sources mounted on a vertical plate was studied experimentally for optimization purposes. We chose a regular distribution, as this is likely to be the preferred choice in the construction process. We found that optimal spacing can be determined for a targeted source density by tuning the vertical and horizontal spacing between the heat sources. The optimal aspect ratio was estimated to be around two. Full article

(This article belongs to the Special Issue Renewable Energy Technologies for Small Scale Applications)

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12 pages, 1574 KiB

Open AccessArticle

A Principal Component Analysis in Switchgrass Chemical Composition

by Mario Aboytes-Ojeda¹, Krystel K. Castillo-Villar^1,*

, Tun-hsiang E. Yu², Christopher N. Boyer², Burton C. English², James A. Larson², Lindsey M. Kline³ and Nicole Labbé³

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

² Department of Agricultural and Resource Economics, University of Tennessee, Knoxville, TN 37996, USA

³ Center for Renewable Carbon, University of Tennessee, Knoxville, TN 37996, USA

Energies 2016, 9(11), 913; https://doi.org/10.3390/en9110913 - 4 Nov 2016

Cited by 10 | Viewed by 7303

Abstract

In recent years, bioenergy has become a promising renewable energy source that can potentially reduce the greenhouse emissions and generate economic growth in rural areas. Gaining understanding and controlling biomass chemical composition contributes to an efficient biofuel generation. This paper presents a principal [...] Read more.

In recent years, bioenergy has become a promising renewable energy source that can potentially reduce the greenhouse emissions and generate economic growth in rural areas. Gaining understanding and controlling biomass chemical composition contributes to an efficient biofuel generation. This paper presents a principal component analysis (PCA) that shows the influence and relevance of selected controllable factors over the chemical composition of switchgrass and, therefore, in the generation of biofuels. The study introduces the following factors: (1) storage days; (2) particle size; (3) wrap type; and (4) weight of the bale. Results show that all the aforementioned factors have an influence in the chemical composition. The number of days that bales have been stored was the most significant factor regarding changes in chemical components due to its effect over principal components 1 and 2 (PC1 and PC2, approximately 80% of the total variance). The storage days are followed by the particle size, the weight of the bale and the type of wrap utilized to enclose the bale. An increment in the number of days (from 75–150 days to 225 days) in storage decreases the percentage of carbohydrates by −1.03% while content of ash increases by 6.56%. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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14 pages, 2532 KiB

Open AccessArticle

Definition and Experimental Validation of a Simplified Model for a Microgrid Thermal Network and its Integration into Energy Management Systems

by Andrea Bonfiglio^1,*

, Massimo Brignone¹, Federico Delfino¹, Alessandro Nilberto² and Renato Procopio¹

¹ Department of Naval, Electrical, and ICT Engineering, University of Genova, I-16145 Genoa, Italy

² Mechanical, Energy, Management and Transportation Engineering Department, University of Genova, I-16145 Genoa, Italy

Energies 2016, 9(11), 914; https://doi.org/10.3390/en9110914 - 4 Nov 2016

Cited by 3 | Viewed by 4144

Abstract

The present paper aims at defining a simplified but effective model of a thermal network that links the thermal power generation with the resulting temperature time profile in a heated or refrigerated environment. For this purpose, an equivalent electric circuit is proposed together [...] Read more.

The present paper aims at defining a simplified but effective model of a thermal network that links the thermal power generation with the resulting temperature time profile in a heated or refrigerated environment. For this purpose, an equivalent electric circuit is proposed together with an experimental procedure to evaluate its input parameters. The paper also highlights the simplicity of implementation of the proposed model into a microgrid Energy Management System. This allows the optimal operation of the thermal network to be achieved on the basis of available data (desired temperature profile) instead of a less realistic basis (such as the desired thermal power profile). The validation of the proposed model is performed on the Savona Campus Smart Polygeneration Microgrid (SPM) with the following steps: (i) identification of the parameters involved in the equivalent circuit (performed by minimizing the difference between the temperature profile, as calculated with the proposed model, and the measured one in a set of training days); (ii) test of the model accuracy on a set of testing days (comparing the measured temperature profiles with the calculated ones); (iii) implementation of the model into an Energy Management System in order to optimize the thermal generation starting from a desired temperature hourly profile. Full article

(This article belongs to the Special Issue Thermally Driven Systems)

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15 pages, 7984 KiB

Open AccessArticle

A Procedure to Perform Multi-Objective Optimization for Sustainable Design of Buildings

by Cristina Brunelli¹, Francesco Castellani^1,*, Alberto Garinei², Lorenzo Biondi² and Marcello Marconi²

¹ Department of Engineering, University of Perugia, via G. Duranti 93, 06125 Perugia, Italy

² Department of Sustainability Engineering, Guglielmo Marconi University, Via Plinio 44, 00193 Roma, Italy

Energies 2016, 9(11), 915; https://doi.org/10.3390/en9110915 - 4 Nov 2016

Cited by 21 | Viewed by 5268

Abstract

When dealing with sustainable design concepts in new construction or in retrofitting existing buildings, it is useful to define both economic and environmental performance indicators, in order to select the optimal technical solutions. In most of the cases, the definition of the optimal [...] Read more.

When dealing with sustainable design concepts in new construction or in retrofitting existing buildings, it is useful to define both economic and environmental performance indicators, in order to select the optimal technical solutions. In most of the cases, the definition of the optimal strategy is not trivial because it is necessary to solve a multi-objective problem with a high number of the variables subjected to nonlinear constraints. In this study, a powerful multi-objective optimization genetic algorithm, NSGAII (Non-dominated Sorting Genetic Algorithm-II), is used to derive the Pareto optimal solutions, which can illustrate the whole trade-off relationship between objectives. A method is then proposed, to introduce uncertainty evaluation in the optimization procedure. A new university building is taken as a case study to demonstrate how each step of the optimization process should be performed. The results achieved turn out to be reliable and show the suitableness of this procedure to define both economic and environmental performance indicators. Similar analysis on a set of buildings representatives of a specific region might be used to assist local/national administrations in the definition of appropriate legal limits that will permit a strategic optimized extension of renewable energy production. Finally, the proposed approach could be applied to similar optimization models for the optimal planning of sustainable buildings, in order to define the best solutions among non-optimal ones. Full article

(This article belongs to the Special Issue 16th CIRIAF National Congress – Sustainable Development, Environment and Human Health Protection)

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16 pages, 6679 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Degradation on Aluminum Reflectors for Solar Collectors due to Outdoor Exposure and Accelerated Aging

by Johannes Wette^1,*, Florian Sutter¹, Aránzazu Fernández-García², Stefan Ziegler³ and Reinhard Dasbach⁴

¹ DLR German Aerospace Center, Institute of Solar Research, Plataforma Solar de Almería, Ctra. Senés Km. 4, Apartado 39, E04200 Tabernas, Almería, Spain

² Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Plataforma Solar de Almería, Ctra. Senés Km. 4, P.O. Box 44, E04200 Tabernas, Almería, Spain

³ Alanod GmbH & Co. KG, Egerstr. 12, 58256 Ennepetal, Germany

⁴ Almeco GmbH, Claude Breda Straße 3, 06406 Bernburg, Germany

Energies 2016, 9(11), 916; https://doi.org/10.3390/en9110916 - 5 Nov 2016

Cited by 14 | Viewed by 6302

Abstract

Reflectors for concentrated solar thermal technologies need to withstand 20 or even 30 years of outdoor exposure without significant loss of solar specular reflectance. In order to test the durability of innovative reflectors within a shorter period of time, an accelerated aging methodology [...] Read more.

Reflectors for concentrated solar thermal technologies need to withstand 20 or even 30 years of outdoor exposure without significant loss of solar specular reflectance. In order to test the durability of innovative reflectors within a shorter period of time, an accelerated aging methodology is required. The problem with accelerated testing is that poor correlation between laboratory and field test results has been achieved in the past. This is mainly because unrealistic degradation mechanisms are accelerated in the weathering chambers. In order to define a realistic testing procedure, a high number of accelerated aging tests have been performed on differently coated aluminum reflectors. The degradation mechanisms of the accelerated tests have been classified and systematically compared to samples that have been exposed at nine different exposure sites outdoors. Besides the standardized aging tests, innovative aging procedures have been developed in such way that the agreement to the degradation pattern observed outdoors is increased. Although degradation depends on materials and location, five generic degradation mechanisms were detected. Standardized tests only reproduced one or two of the five mechanisms detected outdoors. Additionally, several degradation effects that were not observed outdoors appeared. The innovative accelerated aging tests of artificially soiled samples were able to reproduce three of the five mechanisms observed outdoors, presenting a much more realistic overall degradation pattern. Full article

(This article belongs to the Special Issue Urban Generation of Renewable Energy and Sustainable Cities)

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15 pages, 980 KiB

Open AccessArticle

Comparing Apples to Apples: Why the Net Energy Analysis Community Needs to Adopt the Life-Cycle Analysis Framework

by David J. Murphy^1,*, Michael Carbajales-Dale² and Devin Moeller³

¹ Environmental Studies Department, St. Lawrence University, Canton, NY 13617, USA

² Environmental Engineering & Earth Sciences, Clemson University, Clemson, SC 29634, USA

³ Department of Civil and Environmental Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA

Energies 2016, 9(11), 917; https://doi.org/10.3390/en9110917 - 5 Nov 2016

Cited by 41 | Viewed by 7937

Abstract

How do we know which energy technologies or resources are worth pursuing and which aren’t? One way to answer that question is to compare the energy return of a certain technology—i.e., how much energy is remaining after accounting for the amount of energy [...] Read more.

How do we know which energy technologies or resources are worth pursuing and which aren’t? One way to answer that question is to compare the energy return of a certain technology—i.e., how much energy is remaining after accounting for the amount of energy expended in the production and delivery process. Such energy return ratios (the most famous of which is energy return on investment (EROI)) fall within the field of net energy analysis (NEA), and provide an easy way to determine which technology is “better”; i.e., higher Energy Return Ratios (ERRs) are, certeris paribus, better than lower ERRs. Although useful as a broad measure of energy profitability, comparisons can also be misleading, particularly if the units being compared are different. For example, the energy content of electricity produced from a photovoltaic cell is different than the energy content of coal at the mine-mouth, yet these are often compared directly within the literature. These types of inconsistencies are common within the NEA literature. In this paper, we offer life cycle assessment (LCA) and the LCA methodology as a possible solution to the persistent methodological issues within the NEA community, and urge all NEA practitioners to adopt this methodology in the future. Full article

(This article belongs to the Special Issue Life-Cycle Assessment of Energy Systems in Current and Evolving Grids)

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10 pages, 2640 KiB

Open AccessArticle

Minimization of Cogging Force in Fractional-Slot Permanent Magnet Linear Motors with Double-Layer Concentrated Windings

by Qian Wang

, Bo Zhao^*, Jibin Zou and Yong Li

Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150001, China

Energies 2016, 9(11), 918; https://doi.org/10.3390/en9110918 - 5 Nov 2016

Cited by 8 | Viewed by 7151

Abstract

Permanent magnet linear motors (PMLMs) with double-layer concentrated windings generally show significant cogging forces due to the introduction of auxiliary teeth for eliminating the end-effect induced phase unbalance, even when the fractional-slot technology is applied. This paper presents a novel approach to reduce [...] Read more.

Permanent magnet linear motors (PMLMs) with double-layer concentrated windings generally show significant cogging forces due to the introduction of auxiliary teeth for eliminating the end-effect induced phase unbalance, even when the fractional-slot technology is applied. This paper presents a novel approach to reduce the cogging force by adjusting the armature core dimensions in fractional-slot PMLMs with double-layer concentrated windings, together with magnet skewing. It is shown that the proposed technique is capable of reducing the cogging force of the motor in an effective way, with the peak value minimized to less than 0.4% of the rated thrust force in the case study. Such a technique can also be applicable to other linear motors with appropriate changes. Full article

(This article belongs to the Special Issue Electric Machines and Drives for Renewable Energy Harvesting)

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26 pages, 7881 KiB

Open AccessArticle

A Supervisory Control Algorithm of Hybrid Electric Vehicle Based on Adaptive Equivalent Consumption Minimization Strategy with Fuzzy PI

by Fengqi Zhang^1,2, Haiou Liu^2,*, Yuhui Hu² and Junqiang Xi²

¹ School of Mechanical and Precision Instrument Engineering, Xi’an University of Technology, Xi’an 710000, China

² School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

Energies 2016, 9(11), 919; https://doi.org/10.3390/en9110919 - 8 Nov 2016

Cited by 38 | Viewed by 6882

Abstract

This paper presents a new energy management system based on equivalent consumption minimization strategy (ECMS) for hybrid electric vehicles. The aim is to enhance fuel economy and impose state of charge (SoC) charge-sustainability. First, the relationship between the equivalent factor (EF) [...] Read more.

This paper presents a new energy management system based on equivalent consumption minimization strategy (ECMS) for hybrid electric vehicles. The aim is to enhance fuel economy and impose state of charge (SoC) charge-sustainability. First, the relationship between the equivalent factor (EF) of ECMS and the co-state of pontryagin’s minimum principle (PMP) is derived. Second, a new method of implementing the adaptation law using fuzzy proportional plus integral (PI) controller is developed to adjust EF for ECMS in real-time. This adaptation law is more robust than one with constant EF due to the variation of EF as well as driving cycle. Finally, simulations for two driving cycles using ECMS are conducted as opposed to the commonly used rule-based (RB) control strategy, indicating that the proposed adaptation law can provide a promising blend in terms of fuel economy and charge-sustainability. The results confirm that ECMS with Fuzzy PI adaptation law is more robust than ECMS with constant EF as well as PI adaptation law and it achieves significant improvements compared with RB in terms of fuel economy, which is enhanced by 4.44% and 14.7% for china city bus cycle and economic commission of Europe (ECE) cycle, respectively. Full article

(This article belongs to the Special Issue Energy Storage Systems for Plug-in Electric Vehicles and Vehicle to Power Grid Integration)

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12 pages, 3497 KiB

Open AccessArticle

Combustion and Emission Characteristics According to the Fuel Injection Ratio of an Ultra-Lean LPG Direct Injection Engine

by Cheolwoong Park^*, Taeyoung Kim, Gyubaek Cho and Janghee Lee

Department of Engine Research, Environmental and Energy Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 34103, Korea

Energies 2016, 9(11), 920; https://doi.org/10.3390/en9110920 - 7 Nov 2016

Cited by 10 | Viewed by 5178

Abstract

The effect of the fuel injection ratio on the combustion and emission characteristics of stratified lean mixture combustion was investigated for a spray-guided liquefied petroleum gas (LPG) direct injection engine. Inter-injection spark-ignition combustion—a specially designed combustion strategy for LPG fuel derived from a [...] Read more.

The effect of the fuel injection ratio on the combustion and emission characteristics of stratified lean mixture combustion was investigated for a spray-guided liquefied petroleum gas (LPG) direct injection engine. Inter-injection spark-ignition combustion—a specially designed combustion strategy for LPG fuel derived from a two-staged injection—was employed to maximize the improvement in thermal efficiency when combustion stability is secured. When changing the fuel injection ratio, the optimum spark advance and fuel injection timings were experimentally determined to maximize the thermal efficiency based on sweeping timings. The optimum fuel injection ratio with the highest thermal efficiency (42.76%) and stable operation was 60%/40%, with the optimization of the spark advance and fuel injection timing, because of the locally rich mixture region in the recirculation zone. NO_x emissions were at their highest level with a fuel injection ratio of 60%/40% because of the high combustion temperature, and the levels of total hydrocarbon and CO emissions with 50%/50% and 60%/40% fuel injection ratios were similar, whereas emissions at 70%/30% were significantly higher because of fuel wetting and the formation of over-lean mixture. Full article

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17 pages, 847 KiB

Open AccessArticle

Measurement Research on the Decoupling Effect of Industries’ Carbon Emissions—Based on the Equipment Manufacturing Industry in China

by Lu Wan^*, Zi-Long Wang and Jhony Choon Yeong Ng

Department of Economics and Management, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

Energies 2016, 9(11), 921; https://doi.org/10.3390/en9110921 - 8 Nov 2016

Cited by 34 | Viewed by 5173

Abstract

Economic development usually leads to increased energy consumption, which in turn will result in an increase in carbon emissions. To break the relationship between economic development and carbon emissions, scholars have turned their attention to the phenomenon of decoupling. In this paper, we [...] Read more.

Economic development usually leads to increased energy consumption, which in turn will result in an increase in carbon emissions. To break the relationship between economic development and carbon emissions, scholars have turned their attention to the phenomenon of decoupling. In this paper, we studied the decoupling relationship between carbon emissions and economic growth of the equipment manufacturing industry in China from 2000 to 2014. We adapted the LMDI decomposition method, and we used the Tapio decoupling evaluation model to analyze our data. We found that the decoupling relationship between carbon emissions and economic growth of China’s equipment manufacturing industry is weak, which indicates the industry is experiencing faster economic growth than carbon emission growth. We found the economic output is the factor that has the strongest influence on the industry’s carbon emission, and energy consumption intensity has the strongest relationship with the decoupling of economic growth and carbon emission. The indicators of the industry’s decoupling-effort are all less than 1.0, which indicates that the industry is in the state of weak decoupling, and we also observed an annual decreasing trend in the industry’s indicators. Toward the end of this paper, we used the Grey forecasting model to predict the decoupling relationship between carbon emission and economic growth for 2015–2024, and we discussed the implications of our research. Full article

(This article belongs to the Special Issue Energy-Efficient and Sustainable Networking)

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15 pages, 1977 KiB

Open AccessArticle

Biomass Residues to Renewable Energy: A Life Cycle Perspective Applied at a Local Scale

by Esmeralda Neri¹, Daniele Cespi^1,2,*, Leonardo Setti^1,3, Erica Gombi⁴, Elena Bernardi^1,3

, Ivano Vassura^1,3

and Fabrizio Passarini^1,3,*

¹ Department of Industrial Chemistry “Toso Montanari”, ALMA Mater Studiorum—University of Bologna, Viale del Risorgimento 4, 40136 Bologna, Italy

² Environmental management and consulting (EMC) Innovation Lab S.r.l., Viale Italia 29, 47921 Rimini, Italy

³ Centro Interdipartimentale di Ricerca Industriale “Energia e Ambiente”, Via Angherà 22, 47900 Rimini, Italy

⁴ Consorzio Azienda Multiservizi Intercomunale (Con.Ami), 40026 Imola, Italy

Energies 2016, 9(11), 922; https://doi.org/10.3390/en9110922 - 8 Nov 2016

Cited by 35 | Viewed by 6898

Abstract

Italy, like every country member of the European Union (EU), will have to achieve the objectives required by the Energy Roadmap 2050. The purpose of the study was to evaluate the environmental impacts of residue recovery arising from the management of public and [...] Read more.

Italy, like every country member of the European Union (EU), will have to achieve the objectives required by the Energy Roadmap 2050. The purpose of the study was to evaluate the environmental impacts of residue recovery arising from the management of public and private green feedstocks, activity of the cooperative “Green City” in the Bologna district, and usage in a centralized heating system to produce thermal energy for public buildings. Results, obtained using the ReCipe impact assessment method, are compared with scores achieved by a traditional methane boiler. The study shows some advantages of the biomass-based system in terms of greenhouse gases (GHGs) emissions and consumption of non-renewable fuels, which affect climate change (−41%) and fossil resources depletion (−40%), compared to the use of natural gas (NG). Moreover, scores from network analysis denote the great contribution of feedstock transportation (98% of the cumulative impact). The main reason is attributable to all requirements to cover distances, in particular due to stages involved in the fuel supply chains. Therefore, it is clear that greater environmental benefits could be achieved by reducing supply transport distances or using more sustainable engines. Full article

(This article belongs to the Special Issue Renewable Energy Technologies for Small Scale Applications)

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15 pages, 576 KiB

Open AccessArticle

Analysis and Speed Ripple Mitigation of a Space Vector Pulse Width Modulation-Based Permanent Magnet Synchronous Motor with a Particle Swarm Optimization Algorithm

by Xing Liu, Jinhua Du and Deliang Liang^*

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

Energies 2016, 9(11), 923; https://doi.org/10.3390/en9110923 - 8 Nov 2016

Cited by 16 | Viewed by 5740

Abstract

A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs) controlled by space vector pulse width modulation (SVPWM). A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P [...] Read more.

A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs) controlled by space vector pulse width modulation (SVPWM). A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P (P refers to pole pairs of the PMSM) time harmonic of rotor mechanical speed is the main harmonic component in the SVPWM control PMSM system. To reduce PMSM speed ripple, harmonics are superposed on a SVPWM reference signal. A particle swarm optimization (PSO) algorithm is proposed to determine the optimal phase and multiplier coefficient of the superposed harmonics. The results of a Fourier decomposition and an optimized simulation model verified the accuracy of the analysis as well as the effectiveness of the speed ripple reduction methods, respectively. Full article

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15 pages, 5680 KiB

Open AccessArticle

SoC-Based Output Voltage Control for BESS with a Lithium-Ion Battery in a Stand-Alone DC Microgrid

by Seung-Yeong Yu, Hyun-Jun Kim, Jae-Hyuk Kim and Byung-Moon Han^*

Department of Electrical Engineering, Myong-ji University, 116 Myongji-ro, Yongin-si, Gyeonggi-do 449-728, Korea

Energies 2016, 9(11), 924; https://doi.org/10.3390/en9110924 - 8 Nov 2016

Cited by 15 | Viewed by 8344

Abstract

This paper proposes a new DC output voltage control for a battery energy storage system (BESS) with a lithium-ion battery based on the state of charge (SoC). The proposed control scheme was verified through computer simulations for a typical stand-alone DC microgrid, which [...] Read more.

This paper proposes a new DC output voltage control for a battery energy storage system (BESS) with a lithium-ion battery based on the state of charge (SoC). The proposed control scheme was verified through computer simulations for a typical stand-alone DC microgrid, which consists of a BESS, photovoltaic (PV) panel, engine generator (EG), and DC load. A scaled hardware prototype for a stand-alone DC microgrid was set up in the lab, in which the proposed control scheme was loaded in a DSP controller. The experimental results were compared with the simulation results for performance verification. The proposed control scheme provides relatively lower variation of the DC grid voltage than the conventional droop control. Full article

(This article belongs to the Special Issue Microgrids 2016)

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16 pages, 1968 KiB

Open AccessArticle

Modeling and Experimental Validation of a Low-Cost Radiation Sensor Based on the Photovoltaic Effect for Building Applications

by Ángel Gómez-Moreno^1,*, Pedro José Casanova-Peláez², José Manuel Palomar-Carnicero¹ and Fernando Cruz-Peragón¹

¹ Department of Mechanical and Mining Engineering, Escuela Politécnica Superior de Jaén, University of Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain

² Department of Electronic Engineering, Escuela Politécnica Superior de Jaén, University of Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain

Energies 2016, 9(11), 926; https://doi.org/10.3390/en9110926 - 8 Nov 2016

Cited by 1 | Viewed by 4359

Abstract

The energy consumed to cool buildings is very elevated and solar gains represent a high percentage of these cooling loads. To minimize the thermal load it is necessary to control external shading systems. This control requires continuous measurement of solar radiation in different [...] Read more.

The energy consumed to cool buildings is very elevated and solar gains represent a high percentage of these cooling loads. To minimize the thermal load it is necessary to control external shading systems. This control requires continuous measurement of solar radiation in different locations of the building. However, for such applications the use of conventional irradiance sensors increases the cost and reduces the profitability of the installation. This paper is focused on the development, modeling, and experimental validation of low cost irradiation sensors based on photovoltaic effect in order to reduce the costs of dynamic external shading devices and to improve the profitability of the system. With this proposal, firstly, small commercial photovoltaic cells have been adapted for use as an irradiation measurement device. Subsequently, quasi-stationary and continuous experimental measurements of these silicon cells, facing south and installed horizontally, have been carried out in Jaén (Spain) in 2009 and 2010. Finally, a nonlinear multiparameter function has been developed to evaluate the irradiance using the electric current generated by the cell, cell temperature, ambient temperature, and absolute humidity. A favorable agreement between the model predictions and experimental data has been observed with a coefficient of determination around 0.996 for all cells. Full article

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21 pages, 1549 KiB

Open AccessArticle

Power Quality Disturbances Feature Selection and Recognition Using Optimal Multi-Resolution Fast S-Transform and CART Algorithm

by Nantian Huang^*, Hua Peng, Guowei Cai and Jikai Chen

School of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China

Energies 2016, 9(11), 927; https://doi.org/10.3390/en9110927 - 9 Nov 2016

Cited by 32 | Viewed by 5286

Abstract

In order to improve the recognition accuracy and efficiency of power quality disturbances (PQD) in microgrids, a novel PQD feature selection and recognition method based on optimal multi-resolution fast S-transform (OMFST) and classification and regression tree (CART) algorithm is proposed. Firstly, OMFST is [...] Read more.

In order to improve the recognition accuracy and efficiency of power quality disturbances (PQD) in microgrids, a novel PQD feature selection and recognition method based on optimal multi-resolution fast S-transform (OMFST) and classification and regression tree (CART) algorithm is proposed. Firstly, OMFST is carried out according to the frequency domain characteristic of disturbance signal, and 67 features are extracted by time-frequency analysis to construct the original feature set. Subsequently, the optimal feature subset is determined by Gini importance and sorted according to an embedded feature selection method based on the Gini index. Finally, one standard error rule subtree evaluation methods were applied for cost complexity pruning. After pruning, the optimal decision tree (ODT) is obtained for PQD classification. The experiments show that the new method can effectively improve the classification efficiency and accuracy with feature selection step. Simultaneously, the ODT can be constructed automatically according to the ability of feature classification. In different noise environments, the classification accuracy of the new method is higher than the method based on probabilistic neural network, extreme learning machine, and support vector machine. Full article

(This article belongs to the Special Issue Microgrids 2016)

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16 pages, 3282 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Cooling System Designs for an Exhaust Heat Recovery System Using an Organic Rankine Cycle on a Heavy Duty Truck

by Nicolas Stanzel¹, Thomas Streule¹, Markus Preißinger^2,*

and Dieter Brüggemann²

¹ Daimler AG, Group Research & Advanced Engineering Powertrain, 70546 Stuttgart, Germany

² Chair of Engineering Thermodynamics and Transport Processes (LTTT), Center of Energy Technology (ZET), University of Bayreuth, 95440 Bayreuth, Germany

Energies 2016, 9(11), 928; https://doi.org/10.3390/en9110928 - 9 Nov 2016

Cited by 20 | Viewed by 7807

Abstract

A complex simulation model of a heavy duty truck, including an Organic Rankine Cycle (ORC) based waste heat recovery system and a vehicle cooling system, was applied to determine the system fuel economy potential in a typical drive cycle. Measures to increase the [...] Read more.

A complex simulation model of a heavy duty truck, including an Organic Rankine Cycle (ORC) based waste heat recovery system and a vehicle cooling system, was applied to determine the system fuel economy potential in a typical drive cycle. Measures to increase the system performance were investigated and a comparison between two different cooling system designs was derived. The base design, which was realized on a Mercedes-Benz Actros vehicle revealed a fuel efficiency benefit of 2.6%, while a more complicated design would generate 3.1%. Furthermore, fully transient simulation results were performed and are compared to steady state simulation results. It is shown that steady state simulation can produce comparable results if averaged road data are used as boundary conditions. Full article

(This article belongs to the Special Issue Waste Heat Recovery)

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14 pages, 2527 KiB

Open AccessArticle

New Requirements of the Voltage/VAR Function for Smart Inverter in Distributed Generation Control

by Yun-Su Kim^*

, Gyeong-Hun Kim, Jae-Duck Lee and Changhee Cho

Korea Electrotechnology Research Institute, Changwon 51543, Korea

Energies 2016, 9(11), 929; https://doi.org/10.3390/en9110929 - 9 Nov 2016

Cited by 9 | Viewed by 5474

Abstract

International Electronical Committee (IEC) 61850-90-7 is a part of the IEC 61850 series which specifies the advanced functions and object models for power converter based Distributed Energy Resources (DERs). One of its functions, the Voltage/VAR (V/V) control function, is used to enhance the [...] Read more.

International Electronical Committee (IEC) 61850-90-7 is a part of the IEC 61850 series which specifies the advanced functions and object models for power converter based Distributed Energy Resources (DERs). One of its functions, the Voltage/VAR (V/V) control function, is used to enhance the stability and the reliability of the voltage in the distribution system. The conventional V/V function acts mainly for flattening the voltage profile as for a basic grid support function. Currently, other objectives such as the minimization of line loss and the operational costs reduction are coming into the spotlight. In order to attain these objectives, the V/V function and hence the DER units shall actively respond to the change of distribution system conditions. In this paper, the modification of V/V function and new requirements are proposed. To derive new requirements of V/V function, loss minimization is applied to a particle swarm optimization (PSO) algorithm where the condition of voltage constraint is considered not to deteriorate the voltage stability of the distribution system. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2017)

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14 pages, 9899 KiB

Open AccessArticle

Horizontal Air-Ground Heat Exchanger Performance and Humidity Simulation by Computational Fluid Dynamic Analysis

by Paolo Maria Congedo¹

, Caterina Lorusso¹, Maria Grazia De Giorgi¹

, Riccardo Marti¹ and Delia D’Agostino^2,*

¹ Department of Engineering for Innovation, University of Salento, 73100 Lecce, Italy

² Energy efficiency and Renewables Unit, Energy, Transport and Climate Institute, Joint Research Centre (JRC)-European Commission, 21027 Ispra, Italy

Energies 2016, 9(11), 930; https://doi.org/10.3390/en9110930 - 10 Nov 2016

Cited by 31 | Viewed by 8268

Abstract

Improving energy efficiency in buildings and promoting renewables are key objectives of European energy policies. Several technological measures are being developed to enhance the energy performance of buildings. Among these, geothermal systems present a huge potential to reduce energy consumption for mechanical ventilation [...] Read more.

Improving energy efficiency in buildings and promoting renewables are key objectives of European energy policies. Several technological measures are being developed to enhance the energy performance of buildings. Among these, geothermal systems present a huge potential to reduce energy consumption for mechanical ventilation and cooling, but their behavior depending on varying parameters, boundary and climatic conditions is not fully established. In this paper a horizontal air-ground heat exchanger (HAGHE) system is studied by the development of a computational fluid dynamics (CFD) model. Summer and winter conditions representative of the Mediterranean climate are analyzed to evaluate operation and thermal performance differences. A particular focus is given to humidity variations as this parameter has a major impact on indoor air quality and comfort. Results show the benefits that HAGHE systems can provide in reducing energy consumption in all seasons, in summer when free-cooling can be implemented avoiding post air treatment using heat pumps. Full article

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

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11 pages, 2761 KiB

Open AccessArticle

Forecasting Electricity Market Risk Using Empirical Mode Decomposition (EMD)—Based Multiscale Methodology

by Kaijian He^1,*, Hongqian Wang², Jiangze Du³ and Yingchao Zou^4,5

¹ School of Business, Hunan University of Science and Technology, Xiangtan 411201, China

² Payment and Settlement Department, Software Center, Bank of China, Beijing 100094, China

³ School of Finance, Jiangxi University of Finance and Economics, Nanchang 330013, China

⁴ College of Information Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China

⁵ School of Economics and Management, Beijing University of Chemical Technology, Beijing 100029, China

Energies 2016, 9(11), 931; https://doi.org/10.3390/en9110931 - 9 Nov 2016

Cited by 18 | Viewed by 4888

Abstract

The electricity market has experienced an increasing level of deregulation and reform over the years. There is an increasing level of electricity price fluctuation, uncertainty, and risk exposure in the marketplace. Traditional risk measurement models based on the homogeneous and efficient market assumption [...] Read more.

The electricity market has experienced an increasing level of deregulation and reform over the years. There is an increasing level of electricity price fluctuation, uncertainty, and risk exposure in the marketplace. Traditional risk measurement models based on the homogeneous and efficient market assumption no longer suffice, facing the increasing level of accuracy and reliability requirements. In this paper, we propose a new Empirical Mode Decomposition (EMD)-based Value at Risk (VaR) model to estimate the downside risk measure in the electricity market. The proposed model investigates and models the inherent multiscale market risk structure. The EMD model is introduced to decompose the electricity time series into several Intrinsic Mode Functions (IMF) with distinct multiscale characteristics. The Exponential Weighted Moving Average (EWMA) model is used to model the individual risk factors across different scales. Experimental results using different models in the Australian electricity markets show that EMD-EWMA models based on Student’s t distribution achieves the best performance, and outperforms the benchmark EWMA model significantly in terms of model reliability and predictive accuracy. Full article

(This article belongs to the Special Issue Energy Time Series Forecasting)

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19 pages, 10519 KiB

Open AccessArticle

The Coupling Fields Characteristics of Cable Joints and Application in the Evaluation of Crimping Process Defects

by Fan Yang¹, Kai Liu^1,*, Peng Cheng², Shaohua Wang³, Xiaoyu Wang³, Bing Gao¹, Yalin Fang¹, Rong Xia⁴ and Irfan Ullah¹

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing 400044, China

² Chengdu Electrical Power Department, SiChuan Electrical Power Company, Chengdu 610041, China

³ State Grid Zhejiang Electric Power Company, Hangzhou 310008, China

⁴ The Wuhan Branch of China Electric Power Research Institute, Wuhan 430071, China

Energies 2016, 9(11), 932; https://doi.org/10.3390/en9110932 - 9 Nov 2016

Cited by 22 | Viewed by 9220

Abstract

The internal defects of cable joints always accelerate the deterioration of insulation, until finally accidents can arise due to the explosion of the joints. The formation process of this damage often involves changes in the electromagnetic, temperature and stress distribution of the cable [...] Read more.

The internal defects of cable joints always accelerate the deterioration of insulation, until finally accidents can arise due to the explosion of the joints. The formation process of this damage often involves changes in the electromagnetic, temperature and stress distribution of the cable joint, therefore, it is necessary to analyze the electromagnetic-thermal-mechanical distribution of cable joints. Aiming at solving this problem, the paper sets up a 3-D electromagnetic-thermal-mechanical coupling model of cable joints under crimping process defects. Based on the model, the electromagnetic losses distribution, temperature distribution and stress distribution of a cable joint and body are calculated. Then, the coupling fields characteristics in different contact coefficient k, ambient temperature T_amb and load current I were analyzed, and according to the thermal-mechanical characteristics of a cable joint under internal defects, the temperature difference ΔT_f and stress difference Δσ_f of cable surface are applied to evaluate the internal cable joint defects. Finally, a simplified model of the cable joint is set up to verify the accuracy of the coupling field model proposed in this paper, which indicates that the model can be used to analyze the coupling fields characteristics of cable joints and the method can be applied to evaluate crimping process defects of cable joints. Full article

(This article belongs to the Special Issue Advanced Thermal Simulation of Energy Systems)

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13 pages, 1271 KiB

Open AccessArticle

Analysis of Power Quality Signals Using an Adaptive Time-Frequency Distribution

by Nabeel A. Khan¹

, Faisal Baig², Syed Junaid Nawaz^3,*

, Naveed Ur Rehman³ and Shree K. Sharma⁴

¹ Department of Electrical Engineering, Foundation University, Islamabad 44000, Pakistan

² Department of Electrical Engineering, Federal Urdu University of Arts Science and Technology, Islamabad 44000, Pakistan

³ Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan

⁴ SnT - securityandtrust.lu, University of Luxembourg, Kirchberg, Luxembourg 1359, Luxembourg

Energies 2016, 9(11), 933; https://doi.org/10.3390/en9110933 - 9 Nov 2016

Cited by 5 | Viewed by 6074

Abstract

Spikes frequently occur in power quality (PQ) disturbance signals due to various causes such as switching of the inductive loads and the energization of the capacitor bank. Such signals are difficult to analyze using existing time-frequency (TF) methods as these signals have two [...] Read more.

Spikes frequently occur in power quality (PQ) disturbance signals due to various causes such as switching of the inductive loads and the energization of the capacitor bank. Such signals are difficult to analyze using existing time-frequency (TF) methods as these signals have two orthogonal directions in a TF plane. To address this issue, this paper proposes an adaptive TF distribution (TFD) for the analysis of PQ signals. In the proposed adaptive method, the smoothing kernel’s direction is locally adapted based on the direction of energy in the joint TF domain, and hence an improved TF resolution can be obtained. Furthermore, the performance of the proposed adaptive technique in analyzing electrical PQ is thoroughly studied for both synthetic and real world electrical power signals with the help of extensive simulations. The simulation results (specially for empirical data) indicate that the adaptive TFD method achieves high energy concentration in the TF domain for signals composed of tones and spikes. Moreover, the local adaptation of the smoothing kernel in the adaptive TFD enables the extraction of TF signature of spikes from TF images, which further helps in measuring the energy of spikes in a given signal. This new measure can be used to both detect the spikes as well as to quantify the extent of distortion caused by the spikes in a given signal. Full article

(This article belongs to the Special Issue Power Electronics in Power Quality)

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15 pages, 7585 KiB

Open AccessArticle

Analysis and Design of an Active Stabilizer for a Boost Power Converter System

by Yigeng Huangfu¹, Shengzhao Pang^1,*, Babak Nahid-Mobarakeh², Akshay Rathore³, Fei Gao⁴

and Dongdong Zhao¹

¹ School of Automation, Northwestern Polytechnical University, Xi’an 710072, China

² Research Group in Electrical and Electronics, Université de Lorraine, 54518 Vandoeuvre-les-Nancy, France

³ Department of Electrical and Computer Engineering, Concordia University, Montreal, QC H3G 1M8, Canada

⁴ Research Institute of Transport, Energy and Society (IRTES), University of Technology of Belfort-Montbeliard, 90010 Belfort CEDEX, France

Energies 2016, 9(11), 934; https://doi.org/10.3390/en9110934 - 10 Nov 2016

Cited by 17 | Viewed by 4974

Abstract

In electrical power converter systems, the presence of an LC input filter can efficiently reduce the Electromagnetic Interference (EMI) effect, and at the same time protect the converter and the load from being impacted by sharp input impulse voltages. However, for transportation applications, [...] Read more.

In electrical power converter systems, the presence of an LC input filter can efficiently reduce the Electromagnetic Interference (EMI) effect, and at the same time protect the converter and the load from being impacted by sharp input impulse voltages. However, for transportation applications, the weight and size limitations of input LC filters for power converters have to be taken into consideration. The reduction of LC filter size may impair the system stability margin and dynamic response. In serve cases, the system may even become unstable. Thus, in order to ensure the system stability while minimizing the input LC filter size, the implementation of a stabilizer for the system control is needed. In this paper, a novel digital stabilizer design method is proposed for a boost power converter with a small input LC filter. The proposed method is based on input filter inductance current measurements and DSP (Digital Signal Processor) -based digital stabilizer design. Simulation and experimentation confirm the validity of the proposed approach. Full article

(This article belongs to the Special Issue Advanced Power Electronics and Control for Wireless Power Transfer Systems)

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18 pages, 1663 KiB

Open AccessArticle

Application of a Method for Intelligent Multi-Criteria Analysis of the Environmental Impact of Tailing Ponds in Northern Kosovo and Metohija

by Gordana Milentijević¹, Blagoje Nedeljković¹, Milena Lekić^2,*, Zoran Nikić³, Ivica Ristović²

and Jelena Djokić¹

¹ Faculty of Techinal Sciences, University of Pristina, 38220 Kosovska Mitrovica, Serbia

² Faculty of Mining and Geology, University of Belgrade, 11000 Belgrade, Serbia

³ Faculty of Forestry, University of Belgrade, 11030 Belgrade, Serbia

Energies 2016, 9(11), 935; https://doi.org/10.3390/en9110935 - 10 Nov 2016

Cited by 14 | Viewed by 5769

Abstract

The technological process of exploitation of mineral resources and processing of mined ores to cater to the market results, among other things, in a large amount of tailings deposed on tailing ponds. Because of the chemical composition of the material, the increasing amount [...] Read more.

The technological process of exploitation of mineral resources and processing of mined ores to cater to the market results, among other things, in a large amount of tailings deposed on tailing ponds. Because of the chemical composition of the material, the increasing amount of waste, and the mismanagement of recovery and reclamation of ponds, these ponds have become a significant element of negative impact on the surrounding ecosystem. Economics was behind the discharging of this material, resulting in tailing ponds created in inappropriate areas. There is an ongoing process of depositing tailings on old tailing ponds, although no special attention has been paid to the subsequent effect on the environment. Application of intelligent multi-criteria analysis AHP and PROMETHEE has been performed in this paper for the purpose of ranking the degree of negative impact on the environment of tailing ponds. Analysis is performed for five tailing ponds of MMCC (Mining Metallurgy Chemical Combine) “Trepča”, whereby two of the ponds are active and three inactive. The ponds are in relatively close proximity to the municipalities of Zvečan and Kosovska Mitrovica, to the north of Kosovo and Metohija, Republic of Serbia. In order to achieve the most objective results, the AHP and PROMETHEE methods were applied. By using these methods for calculations, the following ranking for the flotation tailing waste deposits was obtained, regarding their environmental impact: Žitkovac, Tvrđanski Do, Bostanište, Gornje Polje and Žarkov Potok. This result can contribute to the decision-making process of a prioritizing strategy for rehabilitation and remediation of these five flotation tailings. The analysis illustrates that application of intelligent multi-criteria analysis is a useful environmental management tool to be included in the decision-making process. Full article

(This article belongs to the Special Issue Selected Papers from the 5th International Symposium on Mining and Environmental Protection)

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20 pages, 3349 KiB

Open AccessArticle

Analysis of Power Network for Line Reactance Variation to Improve Total Transmission Capacity

by Ikram Ullah^1,*, Wolfgang Gawlik²

and Peter Palensky³

¹ Energy Department, Complex Energy Systems, Austrian Institute of Technology GmbH, Department Electrical Sustainable Energy, Faculty Electrical Engineering, 1220 Wien, Austria

² Faculty of Electrical Engineering and IT, Technical University Vienna, 1040 Wien, Austria

³ Department Electrical Sustainable Energy Faculty, Electrical Engineering, Mathematics and Computer Science, TU Delft, 2628 CD Delft, The Netherlands

Energies 2016, 9(11), 936; https://doi.org/10.3390/en9110936 - 10 Nov 2016

Cited by 20 | Viewed by 5859

Abstract

The increasing growth in power demand and the penetration of renewable distributed generations in competitive electricity market demands large and flexible capacity from the transmission grid to reduce transmission bottlenecks. The bottlenecks cause transmission congestion, reliability problems, restrict competition, and limit the maximum [...] Read more.

The increasing growth in power demand and the penetration of renewable distributed generations in competitive electricity market demands large and flexible capacity from the transmission grid to reduce transmission bottlenecks. The bottlenecks cause transmission congestion, reliability problems, restrict competition, and limit the maximum dispatch of low cost generations in the network. The electricity system requires efficient utilization of the current transmission capability to improve the Available Transfer Capability (ATC). To improve the ATC, power flow among the lines can be managed by using Flexible AC Transmission System (FACTS) devices as power flow controllers, which alter the parameters of power lines. It is important to place FACTS devices on suitable lines to vary the reactance for improving Total Transmission Capacity (TTC) of the network and provide flexibility in the power flow. In this paper a transmission network is analyzed based on line parameters variation to improve TTC of the interconnected system. Lines are selected for placing FACTS devices based on real power flow Performance Index (PI) sensitivity factors. TTC is computed using the Repeated Power Flow (RPF) method using the constraints of lines thermal limits, bus voltage limits and generator limits. The reactance of suitable lines, selected on the basis of PI sensitivity factors are changed to divert the power flow to other lines with enough transfer capacity available. The improvement of TTC using line reactance variation is demonstrated with three IEEE test systems with multi-area networks. The results show the variation of the selected lines’ reactance in improving TTC for all the test networks with defined contingency cases. Full article

(This article belongs to the Special Issue Electric Power Systems Research 2017)

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13 pages, 3399 KiB

Open AccessArticle

Coil Design for High Misalignment Tolerant Inductive Power Transfer System for EV Charging

by Kafeel Ahmed Kalwar¹, Saad Mekhilef^1,*

, Mehdi Seyedmahmoudian² and Ben Horan²

¹ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

² School of Engineering, Deakin University, Waurn Ponds, VIC 3216, Australia

Energies 2016, 9(11), 937; https://doi.org/10.3390/en9110937 - 10 Nov 2016

Cited by 68 | Viewed by 12046

Abstract

The inductive power transfer (IPT) system for electric vehicle (EV) charging has acquired more research interest in its different facets. However, the misalignment tolerance between the charging coil (installed in the ground) and pick-up coil (mounted on the car chassis), has been a [...] Read more.

The inductive power transfer (IPT) system for electric vehicle (EV) charging has acquired more research interest in its different facets. However, the misalignment tolerance between the charging coil (installed in the ground) and pick-up coil (mounted on the car chassis), has been a challenge and fundamental interest in the future market of EVs. This paper proposes a new coil design QDQ (Quad D Quadrature) that maintains the high coupling coefficient and efficient power transfer during reasonable misalignment. The QDQ design makes the use of four adjacent circular coils and one square coil, for both charging and pick-up side, to capture the maximum flux at any position. The coil design has been modeled in JMAG software for calculation of inductive parameters using the finite element method (FEM), and its hardware has been tested experimentally at various misaligned positions. The QDQ coils are shown to be capable of achieving good coupling coefficient and high efficiency of the system until the misalignment displacement reaches 50% of the employed coil size. Full article

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

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22 pages, 5786 KiB

Open AccessArticle

Flow Induced Vibration and Energy Extraction of an Equilateral Triangle Prism at Different System Damping Ratios

by Jun Zhang, Fang Liu

, Jijian Lian^*, Xiang Yan

and Quanchao Ren

State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China

Energies 2016, 9(11), 938; https://doi.org/10.3390/en9110938 - 10 Nov 2016

Cited by 30 | Viewed by 5363

Abstract

The flow induced vibration and energy extraction of an equilateral triangle prism elastically mounted in a water channel are investigated experimentally at different system damping ratios ζ_total with the constant oscillating mass M_osc and system stiffness K. A power take-off [...] Read more.

The flow induced vibration and energy extraction of an equilateral triangle prism elastically mounted in a water channel are investigated experimentally at different system damping ratios ζ_total with the constant oscillating mass M_osc and system stiffness K. A power take-off system with a variable damping function is developed. The translation-rotation equation of the vibration system deduced in the study indicates that the total oscillating mass includes the material mass, and the equivalent mass due to the rotation of the gears and rotor. Besides, increasing load resistance can result in a decrease in ζ_total when K and M_osc remain unchanged. The prism experiences, in turn, soft galloping, hard galloping 1 and hard galloping 2 with increasing ζ_total. As ζ_total increases up to 0.335, only the vortex-induced vibration is observed because the extremely high ζ_total prevents the prism from galloping. The response amplitude decreases with the increasing ζ_total. In addition, higher ζ_total promotes the galloping to start at a higher reduced velocity. The galloping characteristics of the prism, including large amplitude responses in an extremely large range of flow velocities, excellent vibration stationarity, and steady vibration frequencies, are beneficial for improving energy conversion. The prism can extract hydraulic energy for the flow velocity U > 0.610 m/s. The harnessed power P_out and the energy conversion efficiency η_out increase with increasing ζ_total in the galloping zone. The maximum P_out and η_out reach 53.56 W and 40.44%, respectively. The optimal system damping ratio for extracting energy is the maximum system damping ratio that the prism can overcome to experience stable galloping. Full article

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

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14 pages, 4347 KiB

Open AccessArticle

Perturb and Observe Control for an Embedded Point Pivoted Absorber

by Gianluca Brando^1,*, Domenico Pietro Coiro², Marino Coppola¹, Adolfo Dannier¹

, Andrea Del Pizzo¹ and Ivan Spina¹

¹ Department of Electrical Engineering and Information Technology, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy

² Department of Industrial Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy

Energies 2016, 9(11), 939; https://doi.org/10.3390/en9110939 - 10 Nov 2016

Cited by 1 | Viewed by 4360

Abstract

Marine energy sources represent an attractive and inexhaustible reservoir able to contribute to the fulfillment of the world energy demand in accordance with climate/energy regulatory frameworks. Wave energy converter (WEC) integration into the main grid requires both the maximization of the harvested energy [...] Read more.

Marine energy sources represent an attractive and inexhaustible reservoir able to contribute to the fulfillment of the world energy demand in accordance with climate/energy regulatory frameworks. Wave energy converter (WEC) integration into the main grid requires both the maximization of the harvested energy and the proper management of the generation variability. The present paper focuses on both these mentioned issues. More specifically, it presents an embedded point pivoted absorber (PPA) and its related control strategy aimed at maximizing the harvested energy. Experimental and numerical investigations have been carried out in a wave/towing tank facility in order to derive the design characteristics of the full-scale model and demonstrate the validity and effectiveness of the proposed control strategy. Full article

(This article belongs to the Special Issue Numerical Modelling of Wave and Tidal Energy)

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16 pages, 4661 KiB

Open AccessArticle

Effect of Air Staging Ratios on the Burning Rate and Emissions in an Underfeed Fixed-Bed Biomass Combustor

by Araceli Regueiro^*

, David Patiño, Jacobo Porteiro, Enrique Granada

and José Luis Míguez

Industrial Engineering School, University of Vigo, Campus Lagoas-Marcosende, s/n, 36310 Vigo, Spain

Energies 2016, 9(11), 940; https://doi.org/10.3390/en9110940 - 11 Nov 2016

Cited by 29 | Viewed by 5264

Abstract

This experimental work studies a small-scale biomass combustor (5–12 kW) with an underfed fixed bed using low air staging ratios (15%–30%). This document focuses on the influence of the operative parameters on the combustion process, so gaseous emissions and the distribution and concentration [...] Read more.

This experimental work studies a small-scale biomass combustor (5–12 kW) with an underfed fixed bed using low air staging ratios (15%–30%). This document focuses on the influence of the operative parameters on the combustion process, so gaseous emissions and the distribution and concentration of particulate matter have also been recorded. The facility shows good stability and test repeatability. For the studied airflow ranges, the results show that increasing the total airflow rate does not increase the overall air excess ratio because the burning rate is proportionally enhanced (with some slight differences that depend on the air staging ratio). Consequently, the heterogeneous reactions at the bed remain in the so-called oxygen-limited region, and thus the entire bed operates under sub-stoichiometric conditions with regards of the char content of the biomass. In addition, tests using only primary air (no staging) may increase the fuel consumption, but in a highly incomplete way, approaching a gasification regime. Some measured burning rates are almost 40% higher than previous results obtained in batch combustors due to the fixed position of the ignition front. The recorded concentration of particulate matter varies between 15 and 75 mg/Nm³, with a main characteristic diameter between 50 and 100 nm. Full article

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22 pages, 2462 KiB

Open AccessArticle

Analysis and Modeling for China’s Electricity Demand Forecasting Using a Hybrid Method Based on Multiple Regression and Extreme Learning Machine: A View from Carbon Emission

by Yi Liang^1,*, Dongxiao Niu¹, Ye Cao² and Wei-Chiang Hong³

¹ School of Economics and Management, North China Electric Power University, Beijing 102206, China

² College of Management and Economy, Beijing Institute of Technology, Beijing 100081, China

³ Department of Information Management, Oriental Institute of Technology, New Taipei 220, Taiwan

Energies 2016, 9(11), 941; https://doi.org/10.3390/en9110941 - 11 Nov 2016

Cited by 22 | Viewed by 5903

Abstract

The power industry is the main battlefield of CO₂ emission reduction, which plays an important role in the implementation and development of the low carbon economy. The forecasting of electricity demand can provide a scientific basis for the country to formulate a [...] Read more.

The power industry is the main battlefield of CO₂ emission reduction, which plays an important role in the implementation and development of the low carbon economy. The forecasting of electricity demand can provide a scientific basis for the country to formulate a power industry development strategy and further promote the sustained, healthy and rapid development of the national economy. Under the goal of low-carbon economy, medium and long term electricity demand forecasting will have very important practical significance. In this paper, a new hybrid electricity demand model framework is characterized as follows: firstly, integration of grey relation degree (GRD) with induced ordered weighted harmonic averaging operator (IOWHA) to propose a new weight determination method of hybrid forecasting model on basis of forecasting accuracy as induced variables is presented; secondly, utilization of the proposed weight determination method to construct the optimal hybrid forecasting model based on extreme learning machine (ELM) forecasting model and multiple regression (MR) model; thirdly, three scenarios in line with the level of realization of various carbon emission targets and dynamic simulation of effect of low-carbon economy on future electricity demand are discussed. The resulting findings show that, the proposed model outperformed and concentrated some monomial forecasting models, especially in boosting the overall instability dramatically. In addition, the development of a low-carbon economy will increase the demand for electricity, and have an impact on the adjustment of the electricity demand structure. Full article

(This article belongs to the Special Issue Kernel Methods and Hybrid Evolutionary Algorithms in Energy Forecasting)

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14 pages, 4786 KiB

Open AccessArticle

Simple Design Approach for Low Torque Ripple and High Output Torque Synchronous Reluctance Motors

by Mohamed Nabil Fathy Ibrahim^1,2,*

, Peter Sergeant^1,3

and Essam Rashad⁴

¹ Department of Electrical Energy, Systems and Automation, Ghent University, 9000 Ghent, Belgium

² Electrical Engineering Department, Kafrelshiekh University, 33511 Kafr El Sheikh, Egypt

³ Flanders Make, the Strategic Research Center for the Manufacturing Industry, B-8500 Kortrijk, Belgium

⁴ Electrical Power and Machines Department, Tanta University, 31527 Tanta, Egypt

Energies 2016, 9(11), 942; https://doi.org/10.3390/en9110942 - 11 Nov 2016

Cited by 39 | Viewed by 7349

Abstract

The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is [...] Read more.

The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is a good tool for the optimization. However, the computation time is an obstacle as there are many geometrical parameters to be optimized. The flux-barrier widths and angles are the two most crucial parameters for the SynRM output torque and torque ripple. This paper proposes an easy-to-use set of parametrized equations to select appropriate values for these two rotor parameters. With these equations, the reader can design a SynRM of distributed windings with a low torque ripple and with a better average torque. The methodology is valid for a wide range of SynRMs. To check the validity of the proposed equations, the sensitivity analysis for the variation of these two parameters on the SynRM torque and torque ripple is carried out. In addition, the analysis in this paper gives insight into the behavior of the machine as a function of these two parameters. Furthermore, the torque and torque ripple of SynRMs having a rotor with three, four and five flux-barriers are compared with three literature approaches. The comparison shows that the proposed equations are effective in choosing the flux-barrier angles and widths for low torque ripple and better average torque. Experimental results have been obtained to confirm the FEM results and to validate the methodology for choosing the rotor parameters. Full article

(This article belongs to the Special Issue Electric Machines and Drives for Renewable Energy Harvesting)

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19 pages, 9565 KiB

Open AccessArticle

Conventional P-ω/Q-V Droop Control in Highly Resistive Line of Low-Voltage Converter-Based AC Microgrid

by Xiaochao Hou¹, Yao Sun¹, Wenbin Yuan¹, Hua Han^1,*, Chaolu Zhong¹ and Josep M. Guerrero²

¹ School of Information Science and Engineering, Central South University, Changsha 410083, China

² Department of Energy Technology, Aalborg University, DK-9220 Aalborg East, Denmark

Energies 2016, 9(11), 943; https://doi.org/10.3390/en9110943 - 11 Nov 2016

Cited by 53 | Viewed by 9001

Abstract

In low-voltage converter-based alternating current (AC) microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB) is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, [...] Read more.

In low-voltage converter-based alternating current (AC) microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB) is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, the conventional P-ω/Q-V droop control is adopted in the low-voltage AC microgrid. As a result, the active power sharing among the distributed generators (DGs) is easily obtained without communication. More importantly, this study clears up the previous misunderstanding that conventional P-ω/Q-V droop control is only applicable to microgrids with highly inductive lines, and lays a foundation for the application of conventional droop control under different line impedances. Moreover, in order to guarantee the accurate reactive power sharing, a guide for designing Q-V droop gains is given, and virtual resistance is adopted to shape the desired output impedance. Finally, the effects of power sharing and transient response are verified through simulations and experiments in converter-based AC Microgrid. Full article

(This article belongs to the Special Issue Microgrids 2016)

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31 pages, 22502 KiB

Open AccessArticle

The Recent Change in the Italian Policies for Photovoltaics: Effects on the Energy Demand Coverage of Grid-Connected PV Systems Installed in Urban Contexts

by Aldo Orioli^*, Vincenzo Franzitta

, Alessandra Di Gangi

and Ferdinando Foresta

Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici (D.E.I.M.), Università degli Studi di Palermo, Viale delle Scienze Edificio 9, 90128 Palermo, Italy

Energies 2016, 9(11), 944; https://doi.org/10.3390/en9110944 - 12 Nov 2016

Cited by 47 | Viewed by 7609

Abstract

In July 2013, the Italian photovoltaic (PV) support policies changed the feed-in tariff (FIT) mechanism and turned to a tax credits program, which is currently in force. The aim of this paper is to investigate how such a radical change has influenced the [...] Read more.

In July 2013, the Italian photovoltaic (PV) support policies changed the feed-in tariff (FIT) mechanism and turned to a tax credits program, which is currently in force. The aim of this paper is to investigate how such a radical change has influenced the electricity demand coverage of the PV systems installed in urban contexts. A methodology, which connects the economic assessment to a detailed architectural and energy suitability analysis, was applied to some case studies to analyse the relationships between the physical parameters related to multi-storey buildings (roof shapes, number of floors and area of flats) and the most relevant economic and financial features affecting the viability of rooftop PV systems. The study, which considers only the electricity produced by the PV systems that are economically profitable, highlighted that the tax credits scheme is even more effective in covering the electrical consumption of densely urbanised Italian city districts. The results, which are significantly influenced by the latitude of the analysed districts, underline the opportunity for governments to adopt PV promoting policies that are more sensitive to the amount of solar energy available in the different regions of their national territory. Full article

(This article belongs to the Special Issue Grid-Connected Photovoltaic Systems)

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17 pages, 1440 KiB

Open AccessArticle

Long Term Expected Revenue of Wind Farms Considering the Bidding Admission Uncertainty

by Mazaher Haji Bashi^1,*, Gholamreza Yousefi^1,*, Claus Leth Bak² and Jayakrishnan Radhakrishna Pillai²

¹ Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

² Energy Technology Department, Aalborg University of Denmark, 9100 Aalborg, Denmark

Energies 2016, 9(11), 945; https://doi.org/10.3390/en9110945 - 19 Nov 2016

Cited by 4 | Viewed by 5762

Abstract

As a long term bidding behavior, bid shading is exhibited by wind farms participating in real Uniform Price (UP) markets. This signifies that the wind farm owners bid far below their true long run marginal cost. In this paper, a method is proposed [...] Read more.

As a long term bidding behavior, bid shading is exhibited by wind farms participating in real Uniform Price (UP) markets. This signifies that the wind farm owners bid far below their true long run marginal cost. In this paper, a method is proposed to consider the uncertainty of bidding admission in the long term expected revenue of wind farms. We show that this consideration could perfectly explain the observed bid shading behavior of wind farm owners. We use a novel market price model with a stochastic model of a wind farm to derive indices describing the uncertainty of bidding admission. The optimal behavior of the wind farm is then obtained by establishing a multi objective optimization problem and subsequently solved using genetic algorithm. The method is applied to the analysis of long term bidding behavior of a wind farm participating in a Pay-as-Bid (PAB) auction such as Iran Electricity Market (IEM). The results demonstrate that wind farm owners change their bid shading behavior in a PAB Auction. However, the expected revenue of the wind farm will also decrease in a PAB auction. As a result, it is not recommended to make an obligation for the wind farms to participate in a PAB auction as a normal market player. Full article

(This article belongs to the Special Issue Energy Policy and Climate Change 2016)

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14 pages, 4986 KiB

Open AccessArticle

Raman Spectral Characteristics of Oil-Paper Insulation and Its Application to Ageing Stage Assessment of Oil-Immersed Transformers

by Jingxin Zou, Weigen Chen^*, Fu Wan, Zhou Fan and Lingling Du

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

Energies 2016, 9(11), 946; https://doi.org/10.3390/en9110946 - 12 Nov 2016

Cited by 38 | Viewed by 6251

Abstract

The aging of oil-paper insulation in power transformers may cause serious power failures. Thus, effective monitoring of the condition of the transformer insulation is the key to prevent major accidents. The purpose of this study was to explore the feasibility of confocal laser [...] Read more.

The aging of oil-paper insulation in power transformers may cause serious power failures. Thus, effective monitoring of the condition of the transformer insulation is the key to prevent major accidents. The purpose of this study was to explore the feasibility of confocal laser Raman spectroscopy (CLRS) for assessing the aging condition of oil-paper insulation. Oil-paper insulation samples were subjected to thermal accelerated ageing at 120 °C for up to 160 days according to the procedure described in the IEEE Guide. Meanwhile, the dimension of the Raman spectrum of the insulation oil was reduced by principal component analysis (PCA). The 160 oil-paper insulation samples were divided into five aging stages as training samples by clustering analysis and with the use of the degree of polymerization of the insulating papers. In addition, the features of the Raman spectrum were used as the inputs of a multi-classification support vector machine. Finally, 105 oil-paper insulation testing samples aged at a temperature of 130 °C were used to further test the diagnostic capability and universality of the established algorithm. Results demonstrated that CLRS in conjunction with the PCA-SVM technique provides a new way for aging stage assessment of oil-paper insulation equipment in the field. Full article

(This article belongs to the Special Issue Power Transformer Diagnostics, Monitoring and Design Features)

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22 pages, 3663 KiB

Open AccessArticle

Exergy Accounting: A Quantitative Comparison of Methods and Implications for Energy-Economy Analysis

by Jack Miller^*

, Timothy J. Foxon and Steve Sorrell

Centre on Innovation and Energy Demand and Sussex Energy Group, Science Policy Research Unit (SPRU), University of Sussex, Brighton BN1 9SL, UK

Energies 2016, 9(11), 947; https://doi.org/10.3390/en9110947 - 14 Nov 2016

Cited by 14 | Viewed by 8746

Abstract

Assessments of the feasibility of decoupling energy consumption from economic growth could benefit from an improved understanding of the size, nature and value of different energy flows. This understanding may be enhanced by focusing upon so-called “useful exergy”—a measure of both the quantity [...] Read more.

Assessments of the feasibility of decoupling energy consumption from economic growth could benefit from an improved understanding of the size, nature and value of different energy flows. This understanding may be enhanced by focusing upon so-called “useful exergy”—a measure of both the quantity and “quality” of energy (defined here as its thermodynamic ability to perform physical work) at the “useful” stage of the energy conversion chain. Useful exergy flows within national economies are increasingly being quantified and their role in economic activity explored. However, this so-called “exergy economics” field currently lacks a consistent methodology. This paper contributes to the development of a more consistent approach. By constructing a “useful exergy account” for the United Kingdom covering the period 1960–2012, we explore how different methodological choices influence estimates of useful exergy for different categories of end-use as well as estimates of total national useful exergy consumption. Specifically, we evaluate the sensitivity of estimates to: (a) the method of estimating the exergy efficiency of different end-uses; (b) the boundaries between end-use categories; and (c) the method of estimating the primary exergy associated with renewable electricity. We also improve upon the current method of accounting for industrial uses of heat. This leads to suggestions for best practice when constructing useful exergy accounts, and the identification of areas where further methodological development is required. Full article

(This article belongs to the Special Issue Low Carbon Economy)

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11 pages, 4485 KiB

Open AccessArticle

Spray Formation of a Liquid Carbon Dioxide-Water Mixture at Elevated Pressures

by Hakduck Kim, Changyeon Kim, Heechang Lim

and Juhun Song^*

School of Mechanical Engineering, Pusan National University, Busan 46241, Korea

Energies 2016, 9(11), 948; https://doi.org/10.3390/en9110948 - 14 Nov 2016

Cited by 2 | Viewed by 4515

Abstract

Liquid carbon dioxide-assisted (LCO₂-assisted) atomization can be used in coal-water slurry gasification plants to prevent the agglomeration of coal particles. It is essential to understand the atomization behavior of the water-LCO₂ mixture leaving the injector nozzle under various conditions, including [...] Read more.

Liquid carbon dioxide-assisted (LCO₂-assisted) atomization can be used in coal-water slurry gasification plants to prevent the agglomeration of coal particles. It is essential to understand the atomization behavior of the water-LCO₂ mixture leaving the injector nozzle under various conditions, including the CO₂ blending ratio, injection pressure, and chamber pressure. In this study, the flash-atomization behavior of a water-LCO₂ mixture was evaluated with regard to the spray angle and penetration length during a throttling process. The injector nozzle was mounted downstream of a high-pressure spray-visualization system. Based on the results, the optimal condition for the effective transport of coal particles was proposed. Full article

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17 pages, 4557 KiB

Open AccessArticle

Experimental Investigation on Wall Film Distribution of Dimethyl Ether/Diesel Blended Fuels Formed during Spray Wall Impingement

by Hanzhengnan Yu¹, Xingyu Liang^1,*, Gequn Shu¹, Xu Wang²

, Yuesen Wang¹ and Hongsheng Zhang¹

¹ State Key Laboratory of Engines, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China

² School of Aerospace Mechanical and Manufacturing Engineering, The Royal Melbourne Institute of Technology University, 124 La Trobe Street, Melbourne, VIC 3000, Australia

Energies 2016, 9(11), 949; https://doi.org/10.3390/en9110949 - 16 Nov 2016

Cited by 19 | Viewed by 5739

Abstract

Dimethyl ether (DME)/diesel blended fuels are used to improve the emissions caused by spray wall impingement during the early injection period. However, experimental results have showed that the spray wall impingement still cannot be avoided due to the engine structure and low density [...] Read more.

Dimethyl ether (DME)/diesel blended fuels are used to improve the emissions caused by spray wall impingement during the early injection period. However, experimental results have showed that the spray wall impingement still cannot be avoided due to the engine structure and low density of the in-cylinder charge at the early injection timing. Furthermore, the wall film formed in the spray wall impingement process directly affects fuel/air mixture formation, combustion, exhaust emissions and oil quality subsequently. In this paper, the wall film distribution of DME/diesel blended fuels formed during the spray wall impingement process has been experimentally investigated. The variations of wall film distribution, wall film area and average thickness with different injection pressures, impingement distances, impingement angles and blending ratios have been discussed under both dry wall and wet wall conditions. Results showed that the wall film distribution styles were mainly determined by the spray impingement momentum. The variation of the wall film area and average thickness were affected by three factors including the impingement momentum, wall film mass and fuel properties. Correlation analysis was introduced in order to evaluate the effect of each impact factor on the variation of wall film area and average thickness. Full article

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

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14 pages, 2049 KiB

Open AccessArticle

A Novel Algorithm for Efficient Downlink Packet Scheduling for Multiple-Component-Carrier Cellular Systems

by Yao-Liang Chung

Department of Communications, Navigation and Control Engineering, National Taiwan Ocean University, Keelung City 20224, Taiwan

Energies 2016, 9(11), 950; https://doi.org/10.3390/en9110950 - 15 Nov 2016

Cited by 5 | Viewed by 4023

Abstract

The simultaneous aggregation of multiple component carriers (CCs) for use by a base station constitutes one of the more promising strategies for providing substantially enhanced bandwidths for packet transmissions in 4th and 5th generation cellular systems. To the best of our knowledge, however, [...] Read more.

The simultaneous aggregation of multiple component carriers (CCs) for use by a base station constitutes one of the more promising strategies for providing substantially enhanced bandwidths for packet transmissions in 4th and 5th generation cellular systems. To the best of our knowledge, however, few previous studies have undertaken a thorough investigation of various performance aspects of the use of a simple yet effective packet scheduling algorithm in which multiple CCs are aggregated for transmission in such systems. Consequently, the present study presents an efficient packet scheduling algorithm designed on the basis of the proportional fair criterion for use in multiple-CC systems for downlink transmission. The proposed algorithm includes a focus on providing simultaneous transmission support for both real-time (RT) and non-RT traffic. This algorithm can, when applied with sufficiently efficient designs, provide adequate utilization of spectrum resources for the purposes of transmissions, while also improving energy efficiency to some extent. According to simulation results, the performance of the proposed algorithm in terms of system throughput, mean delay, and fairness constitute substantial improvements over those of an algorithm in which the CCs are used independently instead of being aggregated. Full article

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28 pages, 4025 KiB

Open AccessArticle

Optimization of Electrochemically Deposited Highly Doped ZnO Bilayers on Ga-Rich Chalcopyrite Selenide for Cost-Effective Photovoltaic Device Technology

by Dimitra N. Papadimitriou^1,*, Georgios Roupakas¹, Georgios G. Roumeliotis¹, Patrick Vogt² and Tristan Köhler³

¹ National Technical University of Athens, Heroon Polytechniou 9, GR-15780 Athens, Greece

² Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, DE-10623 Berlin, Germany

³ Helmholtz Zentrum Berlin für Materialien und Energie, Institut für Heterogene Materialsysteme, Hahn-Meitner-Platz 1, DE-14109 Berlin, Germany

Energies 2016, 9(11), 951; https://doi.org/10.3390/en9110951 - 15 Nov 2016

Cited by 6 | Viewed by 5814

Abstract

High quality polycrystalline bilayers of aluminium doped ZnO (Al:ZnO) were successively electrodeposited in the form of columnar structures preferentially oriented along the

(10 \bar{1} 1)

crystallographic direction from aqueous solution of zinc nitrate (Zn(NO₃)₂) at negative [...] Read more.

High quality polycrystalline bilayers of aluminium doped ZnO (Al:ZnO) were successively electrodeposited in the form of columnar structures preferentially oriented along the

(10 \bar{1} 1)

crystallographic direction from aqueous solution of zinc nitrate (Zn(NO₃)₂) at negative electrochemical potential of E_C = (−0.8)–(−1.2) V and moderate temperature of 80 °C on gallium rich (30% Ga) chalcopyrite selenide Cu(In,Ga)Se₂ (CIGS) with chemically deposited ZnSe buffer (ZnSe/Cu(In,Ga)Se₂/Mo/glass). The aluminium doped ZnO layer properties have initially been probed by deposition of Al:ZnO/i-ZnO bilayers directly on Mo/glass substrates. The band-gap energy of the Al:ZnO/i-ZnO reference layers was found to vary from 3.2 to 3.7 eV by varying the AlCl₃ solute dopant concentration from 1 to 20 mM. The electrical resistivity of indium-pellet contacted highly doped Al:ZnO sheet of In/Al:ZnO/i-ZnO/Mo/glass reference samples was of the order ρ ~10⁻⁵ Ω·cm; the respective carrier concentration of the order 10²² cm⁻³ is commensurate with that of sputtered Al:ZnO layers. For crystal quality optimization of the bilayers by maintenance of the volatile selenium content of the chalcopyrite, they were subjected to 2-step annealing under successive temperature raise and N₂ flux regulation. The hydrostatic compressive strain due to Al³⁺ incorporation in the ZnO lattice of bilayers processed successively with 5 and 12 mM AlCl₃ dopant was ε_h = −0.046 and the respective stress σ_h = −20 GPa. The surface reflectivity of maximum 5% over the scanned region of 180–900 nm and the (optical) band gap of E_g = 3.67 eV were indicative of the high optical quality of the electrochemically deposited (ECD) Al:ZnO bilayers. Full article

(This article belongs to the Special Issue Nano-Structured Solar Cells)

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15 pages, 5852 KiB

Open AccessArticle

Retrofitted Solar Domestic Hot Water Systems for Swedish Single-Family Houses—Evaluation of a Prototype and Life-Cycle Cost Analysis

by Luis Ricardo Bernardo^1,*, Henrik Davidsson¹ and Erik Andersson²

¹ Department of Architecture and the Built Environment, Division of Energy and Building Design, Lund University, Box 118, 221 00 Lund, Sweden

² Efficax Energy AB, Ideon Science Park, Scheelevägen 15, 223 70 Lund, Sweden

Energies 2016, 9(11), 953; https://doi.org/10.3390/en9110953 - 15 Nov 2016

Cited by 6 | Viewed by 8216

Abstract

According to recent technology road maps, system cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly [...] Read more.

According to recent technology road maps, system cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly reduce both material and installation costs. Previous studies have investigated such retrofitting, using theoretical simulations and laboratory tests, but no actual installations were made and tested in practice. This article describes the installation, measured performance and cost effectiveness of a retrofitting solution that converts existing domestic hot water heaters to a solar domestic hot water system. The measured performance is characterised by the monthly and annual solar fractions. The cost effectiveness is evaluated by a life-cycle cost analysis, comparing the retrofitted system to a conventional solar domestic hot water system and the case without any solar heating system. Measurements showed that approximately 50% of the 5000 kWh/year of domestic hot water consumption was saved by the retrofitted system in south Sweden. Such savings are in agreement with previous estimations and are comparable to the energy savings when using a conventional solar domestic hot water system. The life-cycle cost analysis showed that, according to the assumptions and given climate, the return on investment of the retrofitted system is approximately 17 years, while a conventional system does not reach profitability during its lifetime of 25 years. Full article

(This article belongs to the Special Issue Solar Cooling and Heating)

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14 pages, 2718 KiB

Open AccessArticle

Study on Insulator Flashover Voltage Gradient Correction Considering Soluble Pollution Constituents

by Dongdong Zhang¹, Zhijin Zhang^1,*, Xingliang Jiang¹, Zhongyi Yang¹, Jiayao Zhao¹ and Yongfu Li²

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Shapingba District, Chongqing 400044, China

² State Grid Chongqing Electric Power Co. Electric Power Research Institute, Yubei District, Chongqing 401121, China

Energies 2016, 9(11), 954; https://doi.org/10.3390/en9110954 - 15 Nov 2016

Cited by 7 | Viewed by 5272

Abstract

Natural polluted insulator surfaces are always coated with various kinds of soluble constituents, and those constituents affect flashover performance differentially. Currently, this fact is not considered either in laboratory experiments or field pollution degree measurements, causing the existing insulation selection method to be [...] Read more.

Natural polluted insulator surfaces are always coated with various kinds of soluble constituents, and those constituents affect flashover performance differentially. Currently, this fact is not considered either in laboratory experiments or field pollution degree measurements, causing the existing insulation selection method to be deficient. In this paper, a systematic study on insulator flashover voltage gradient correction involving different types of soluble pollution constituents is presented. Using a typical type glass insulator as the sample, its flashover tests, polluted by typical soluble chemicals (NaCl, NaNO₃, KNO₃, NH₄NO₃, MgSO₄, Ca(NO₃)₂ and CaSO₄), were carried out. Then, the flashover gradient correction was made by combining the flashover performance of each soluble constituent, the equivalent salt deposit density (ESDD) contribution of the seven constituents, and the saturation performance of CaSO₄. The correction agreed with the flashover test results of insulator polluted by three types of soluble mixture. Research results indicate that the flashover gradient correction method proposed in this paper performs well in reducing the calculating error. It is recommended to carry out component measurements and flashover gradient correction to better select outdoor insulation configuration. Full article

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14 pages, 738 KiB

Open AccessArticle

The Demand Side Management Potential to Balance a Highly Renewable European Power System

by Alexander Kies^1,2,*, Bruno U. Schyska^1,2 and Lueder Von Bremen¹

¹ ForWind, Center for Wind Energy Research, Küpkersweg 70, 26129 Oldenburg, Germany

² Institute of Physics, University of Oldenburg, Ammerländer Heerstr. 114, 26129 Oldenburg, Germany

Energies 2016, 9(11), 955; https://doi.org/10.3390/en9110955 - 15 Nov 2016

Cited by 51 | Viewed by 7231

Abstract

Shares of renewables continue to grow in the European power system. A fully renewable European power system will primarily depend on the renewable power sources of wind and photovoltaics (PV), which are not dispatchable but intermittent and therefore pose a challenge to the [...] Read more.

Shares of renewables continue to grow in the European power system. A fully renewable European power system will primarily depend on the renewable power sources of wind and photovoltaics (PV), which are not dispatchable but intermittent and therefore pose a challenge to the balancing of the power system. To overcome this issue, several solutions have been proposed and investigated in the past, including storage, backup power, reinforcement of the transmission grid, and demand side management (DSM). In this paper, we investigate the potential of DSM to balance a simplified, fully renewable European power system. For this purpose, we use ten years of weather and historical load data, a power-flow model and the implementation of demand side management as a storage equivalent, to investigate the impact of DSM on the need for backup energy. We show that DSM has the potential to reduce the need for backup energy in Europe by up to one third and can cover the need for backup up to a renewable share of 67%. Finally, it is demonstrated that the optimal mix of wind and PV is shifted by the utilisation of DSM towards a higher share of PV, from 19% to 36%. Full article

(This article belongs to the Special Issue Control of Energy Storage)

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24 pages, 12756 KiB

Open AccessArticle

Distributed Generation Islanding Effect on Distribution Networks and End User Loads Using the Load Sharing Islanding Method

by Maen Z. Kreishan¹, George P. Fotis²

, Vasiliki Vita¹ and Lambros Ekonomou^1,*

¹ Department of Electrical and Electronic Engineering, City, University of London, London EC1V 0HB, UK

² Department of Electrical and Electronic Engineering Educators, School of Pedagogical and Technological Education, Ν. Ηeraklion, 141 21 Athens, Greece

Energies 2016, 9(11), 956; https://doi.org/10.3390/en9110956 - 16 Nov 2016

Cited by 24 | Viewed by 5202

Abstract

In this paper a realistic medium voltage (MV) network with four different distributed generation technologies (diesel, gas, hydro and wind) along with their excitation and governor control systems is modelled and simulated. Moreover, an exponential model was used to represent the loads in [...] Read more.

In this paper a realistic medium voltage (MV) network with four different distributed generation technologies (diesel, gas, hydro and wind) along with their excitation and governor control systems is modelled and simulated. Moreover, an exponential model was used to represent the loads in the network. The dynamic and steady state behavior of the four distributed generation technologies was investigated during grid-connected operation and two transition modes to the islanding situation, planned and unplanned. This study aims to address the feasibility of planned islanding operation and to investigate the effect of unplanned islanding. The load sharing islanding method has been used for controlling the distributed generation units during grid-connected and islanding operation. The simulation results were validated through various case studies and have shown that properly planned islanding transition could provide support to critical loads at the event of utility outages. However, a reliable protection scheme would be required to mitigate the adverse effect of unplanned islanding as all unplanned sub-cases returned severe negative results. Full article

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16 pages, 1915 KiB

Open AccessArticle

Robust Unit Commitment Including Frequency Stability Constraints

by Felipe Pérez-Illanes¹, Eduardo Álvarez-Miranda^2,*, Claudia Rahmann¹

and Camilo Campos-Valdés³

¹ Department of Electrical Engineering, Universidad de Chile, Santiago 8370000, Chile

² Department of Industrial Engineering, Universidad de Talca, Curicó 3340000, Chile

³ Facultad de Ingeniería, Universidad Autónoma de Chile, Talca 3460000, Chile

Energies 2016, 9(11), 957; https://doi.org/10.3390/en9110957 - 16 Nov 2016

Cited by 23 | Viewed by 5560

Abstract

An increased use of variable generation technologies such as wind power and photovoltaic generation can have important effects on system frequency performance during normal operation as well as contingencies. The main reasons are the operational principles and inherent characteristics of these power plants [...] Read more.

An increased use of variable generation technologies such as wind power and photovoltaic generation can have important effects on system frequency performance during normal operation as well as contingencies. The main reasons are the operational principles and inherent characteristics of these power plants like operation at maximum power point and no inertial response during power system imbalances. This has led to new challenges for Transmission System Operators in terms of ensuring system security during contingencies. In this context, this paper proposes a Robust Unit Commitment including a set of additional frequency stability constraints. To do this, a simplified dynamic model of the initial system frequency response is used in combination with historical frequency nadir data during contingencies. The proposed approach is especially suitable for power systems with cost-based economic dispatch like those in most Latin American countries. The study is done considering the Northern Interconnected System of Chile, a 50-Hz medium size isolated power system. The results obtained were validated by means of dynamic simulations of different system contingencies. Full article

(This article belongs to the Special Issue Advances in Power System Operations and Planning)

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15 pages, 3280 KiB

Open AccessArticle

Parametric Density Recalibration of a Fundamental Market Model to Forecast Electricity Prices

by Antonio Bello¹, Derek Bunn^2,*

, Javier Reneses¹ and Antonio Muñoz¹

¹ Institute for Research in Technology, Technical School of Engineering (ICAI), Universidad Pontificia Comillas, 28015 Madrid, Spain

² London Business School, London NW1 4SA, UK

Energies 2016, 9(11), 959; https://doi.org/10.3390/en9110959 - 17 Nov 2016

Cited by 25 | Viewed by 5041

Abstract

This paper proposes a new approach to hybrid forecasting methodology, characterized as the statistical recalibration of forecasts from fundamental market price formation models. Such hybrid methods based upon fundamentals are particularly appropriate to medium term forecasting and in this paper the application is [...] Read more.

This paper proposes a new approach to hybrid forecasting methodology, characterized as the statistical recalibration of forecasts from fundamental market price formation models. Such hybrid methods based upon fundamentals are particularly appropriate to medium term forecasting and in this paper the application is to month-ahead, hourly prediction of electricity wholesale prices in Spain. The recalibration methodology is innovative in seeking to perform the recalibration into parametrically defined density functions. The density estimation method selects from a wide diversity of general four-parameter distributions to fit hourly spot prices, in which the first four moments are dynamically estimated as latent functions of the outputs from the fundamental model and several other plausible exogenous drivers. The proposed approach demonstrated its effectiveness against benchmark methods across the full range of percentiles of the price distribution and performed particularly well in the tails. Full article

(This article belongs to the Special Issue Forecasting Models of Electricity Prices)

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22 pages, 1611 KiB

Open AccessArticle

Estimation of Energy Consumption and Greenhouse Gas Emissions of Transportation in Beef Cattle Production

by Narayanan Kannan^1,*

, Ali Saleh¹ and Edward Osei²

¹ Texas Institute for Applied Environmental Research, Tarleton State University, Stephenville, TX 76402, USA

² Department of Agriculture and Consumer Sciences, Tarleton State University, Stephenville, TX 76402, USA

Energies 2016, 9(11), 960; https://doi.org/10.3390/en9110960 - 18 Nov 2016

Cited by 14 | Viewed by 9620

Abstract

Accounting for transportation is an important part of the life cycle analysis (LCA) of beef cattle production because it is associated with energy consumption and greenhouse gas emissions. This paper describes the development and application of a model that estimates energy consumption and [...] Read more.

Accounting for transportation is an important part of the life cycle analysis (LCA) of beef cattle production because it is associated with energy consumption and greenhouse gas emissions. This paper describes the development and application of a model that estimates energy consumption and greenhouse gas emissions of transport in beef cattle production. The animal transport model is based on the weight and number of animals in each weight category, type of trailer, vehicle, and fuel used. The energy consumption and greenhouse gas emission estimates of animal feed transportation are based on the weight of a truckload and the number of truckloads of feed transported. Our results indicate that a truckload is travelling approximately 326 km in connection with beef cattle production in the study region. The fuel consumption amounts to 24 L of fossil fuel per 1000 kg of boneless beef. The corresponding greenhouse gas emission is 83 kg. It appears from our results that the majority of energy consumption and greenhouse gas emissions are associated with sending the finished cattle to slaughterhouses and bringing feeder cattle to feedlots. Our results point out appreciable reductions in energy consumption and greenhouse gas emissions by changing from conventional fuel to bio-fuel. Full article

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16 pages, 1257 KiB

Open AccessArticle

An Adaptive Speed Control Approach for DC Shunt Motors

by Ruben Tapia-Olvera¹, Francisco Beltran-Carbajal², Omar Aguilar-Mejia³ and Antonio Valderrabano-Gonzalez^4,*

¹ Departamento de Ingeniería Eléctrica, Universidad Nacional Autónoma de México, Av. Universidad 3000, Cd. Universitaria, Delegación Coyoacán, C.P. 04510 Mexico City, Mexico

² Departamento de Energía, Universidad Autónoma Metropolitana, Unidad Azcapotzalco, Av. San Pablo No. 180, Col. Reynosa Tamaulipas, C.P. 02200 Mexico City, Mexico

³ Departamento de Ingeniería, Universidad Politécnica de Tulancingo, Ingenierías No. 100. Col. Huapalcalco, C.P. 43629 Tulancingo, Mexico

⁴ Facultad de Ingeniería, Universidad Panamericana (Campus Guadalajara), Prolongación Calzada Circunvalación Poniente 49, C.P. 45010 Zapopan, Mexico

Energies 2016, 9(11), 961; https://doi.org/10.3390/en9110961 - 17 Nov 2016

Cited by 10 | Viewed by 7481

Abstract

A B-spline neural networks-based adaptive control technique for angular speed reference trajectory tracking tasks with highly efficient performance for direct current shunt motors is proposed. A methodology for adaptive control and its proper training procedure are introduced. This algorithm sets the control signal [...] Read more.

A B-spline neural networks-based adaptive control technique for angular speed reference trajectory tracking tasks with highly efficient performance for direct current shunt motors is proposed. A methodology for adaptive control and its proper training procedure are introduced. This algorithm sets the control signal without using a detailed mathematical model nor exact values of the parameters of the nonlinear dynamic system. The proposed robust adaptive tracking control scheme only requires measurements of the velocity output signal. Thus, real-time measurements or estimations of acceleration, current and disturbance signals are avoided. Experimental results confirm the efficient and robust performance of the proposed control approach for highly demanding motor operation conditions exposed to variable-speed reference trajectories and completely unknown load torque. Hence, laboratory experimental tests on a direct current shunt motor prove the viability of the proposed adaptive output feedback trajectory tracking control approach. Full article

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16 pages, 4518 KiB

Open AccessArticle

Linearization and Control of Series-Series Compensated Inductive Power Transfer System Based on Extended Describing Function Concept

by Kunwar Aditya

and Sheldon Williamson^*

Department of Electrical, Computer and Software Engineering, University of Ontario Institute of Technology, Oshawa, ON L1H 7K4, Canada

Energies 2016, 9(11), 962; https://doi.org/10.3390/en9110962 - 17 Nov 2016

Cited by 22 | Viewed by 7851

Abstract

The extended describing function (EDF) is a well-known method for modelling resonant converters due to its high accuracy. However, it requires complex mathematical formulation effort. This paper presents a simplified non-linear mathematical model of series-series (SS) compensated inductive power transfer (IPT) system, considering [...] Read more.

The extended describing function (EDF) is a well-known method for modelling resonant converters due to its high accuracy. However, it requires complex mathematical formulation effort. This paper presents a simplified non-linear mathematical model of series-series (SS) compensated inductive power transfer (IPT) system, considering zero-voltage switching in the inverter. This simplified mathematical model permits the user to derive the small-signal model using the EDF method, with less computational effort, while maintaining the accuracy of an actual physical model. The derived model has been verified using a frequency sweep method in PLECS. The small-signal model has been used to design the voltage loop controller for a SS compensated IPT system. The designed controller was implemented on a 3.6 kW experimental setup, to test its robustness. Full article

(This article belongs to the Special Issue Advanced Power Electronics and Control for Wireless Power Transfer Systems)

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22 pages, 1178 KiB

Open AccessEditor’s ChoiceArticle

Expert Opinion Analysis on Renewable Hydrogen Storage Systems Potential in Europe

by Davide Astiaso Garcia^1,*

, Federica Barbanera¹, Fabrizio Cumo², Umberto Di Matteo³

and Benedetto Nastasi⁴

¹ DIAEE—Department of Astronautic, Energetic and Electric Engineering, Sapienza University, Corso Vittorio Emanuele II 244, 00186 Rome, Italy

² CITERA—Interdisciplinary Centre for Housing, Heritage and Environment, Sapienza University, Via Gramsci 53, 00197 Rome, Italy

³ Department of Engineering Sustainability, Marconi University, 00186 Rome, Italy

⁴ Department of Architectural Engineering & Technology, Climate Design Section, TU Delft University of Technology, Julianalaan 134, 2628 BL Delft, The Netherlands

Energies 2016, 9(11), 963; https://doi.org/10.3390/en9110963 - 18 Nov 2016

Cited by 65 | Viewed by 10675

Abstract

Among the several typologies of storage technologies, mainly on different physical principles (mechanical, electrical and chemical), hydrogen produced by power to gas (P2G) from renewable energy sources complies with chemical storage principle and is based on the conversion of electrical energy into chemical [...] Read more.

Among the several typologies of storage technologies, mainly on different physical principles (mechanical, electrical and chemical), hydrogen produced by power to gas (P2G) from renewable energy sources complies with chemical storage principle and is based on the conversion of electrical energy into chemical energy by means of the electrolysis of water which does not produce any toxic or climate-relevant emission. This paper aims to pinpoint the potential uses of renewable hydrogen storage systems in Europe, analysing current and potential locations, regulatory framework, governments’ outlooks, economic issues, and available renewable energy amounts. The expert opinion survey, already used in many research articles on different topics including energy, has been selected as an effective method to produce realistic results. The obtained results highlight strategies and actions to optimize the storage of hydrogen produced by renewables to face varying electricity demand and generation-driven fluctuations reducing the negative effects of the increasing share of renewables in the energy mix of European Countries. Full article

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20 pages, 7551 KiB

Open AccessArticle

Novel Auto-Reclosing Blocking Method for Combined Overhead-Cable Lines in Power Networks

by Ricardo Granizo Arrabé^1,*

, Carlos Antonio Platero Gaona¹

, Fernando Álvarez Gómez²

and Emilio Rebollo López¹

¹ Department of Electrical Engineering, ETS Ingenieros Industriales, Technical University of Madrid, C/José Gutierrez Abascal, 2, 28006 Madrid, Spain

² Department of Electrical Engineering, ETS Ingeniería y Diseño Industrial, Technical University of Madrid, C/Ronda de Valencia, 3, 28012 Madrid, Spain

Energies 2016, 9(11), 964; https://doi.org/10.3390/en9110964 - 17 Nov 2016

Cited by 6 | Viewed by 5283

Abstract

This paper presents a novel auto-reclosing blocking method for combined overhead-cable lines in power distribution networks that are solidly or impedance grounded, with distribution transformers in a delta connection in their high-voltage sides. The main contribution of this new technique is that it [...] Read more.

This paper presents a novel auto-reclosing blocking method for combined overhead-cable lines in power distribution networks that are solidly or impedance grounded, with distribution transformers in a delta connection in their high-voltage sides. The main contribution of this new technique is that it can detect whether a ground fault has been produced at the overhead line side or at the cable line side, thus improving the performance of the auto-reclosing functionality. This localization technique is based on the measurements and analysis of the argument differences between the load currents in the active conductors of the cable and the currents in the shields at the cable end where the transformers in delta connection are installed, including a wavelet analysis. This technique has been verified through computer simulations and experimental laboratory tests. Full article

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

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23 pages, 2195 KiB

Open AccessArticle

The Effect of Biogas Production on Farmland Rental Prices: Empirical Evidences from Northern Italy

by Eugenio Demartini^1,*

, Anna Gaviglio¹

, Marco Gelati¹

and Daniele Cavicchioli²

¹ Department of Health, Animal Science and Food Safety (VESPA), University of Milan, 20133 Milan, Italy

² Department of Economics, Management, and Quantitative Methods (DEMM), University of Milan, 20133 Milan, Italy

Energies 2016, 9(11), 965; https://doi.org/10.3390/en9110965 - 18 Nov 2016

Cited by 27 | Viewed by 5675

Abstract

In the last decade, increased environmental awareness has prompted the adoption of incentives for exploiting renewable energy sources. Among these, biogas production has received a certain attention in developed countries. Nonetheless, the subsidies provided have posed the problem of an activity (the production [...] Read more.

In the last decade, increased environmental awareness has prompted the adoption of incentives for exploiting renewable energy sources. Among these, biogas production has received a certain attention in developed countries. Nonetheless, the subsidies provided have posed the problem of an activity (the production of bioenergy) that engages in direct competition with food and feed production for limited resources, like agricultural land. Even if this competition may be softened by allocating marginal land and/or using dedicated non-agricultural crops, empirical evidence shows that biogas plants have been developed in highly-productive agricultural areas, using increasing amounts of maize silage as feedstock. Thus, studies aimed at measuring the effect of biogas production on agricultural activities are needed in order to avoid this socially undesirable outcome. The paper presents an econometric estimation of the impact of biogas plants on farmland rental values of a Northern Italian rural area. Results show that biogas has a non-linear effect on rental prices, suggesting that incentive schemes specifically accounting for plants’ dimensions and technologies would improve the social sustainability of the bioenergy sector and its coexistence with agricultural activity. Full article

(This article belongs to the Special Issue Economics of Bioenergy 2016)

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22 pages, 8789 KiB

Open AccessArticle

Study on the Static Load Capacity and Synthetic Vector Direct Torque Control of Brushless Doubly Fed Machines

by Chaoying Xia^* and Xiaoxin Hou

School of Electrical Engineering and Automation, Tianjin University, No. 92 Weijin Road, Tianjin 300072, China

Energies 2016, 9(11), 966; https://doi.org/10.3390/en9110966 - 18 Nov 2016

Cited by 16 | Viewed by 4493

Abstract

Compared to the doubly fed machine, the brushless doubly fed machine (BDFM) has high reliability and low maintenance requirements. First, by taking the negative conjugation of the control motor variables in rotor reference frame, a state-space model of BDFM is derived. It is [...] Read more.

Compared to the doubly fed machine, the brushless doubly fed machine (BDFM) has high reliability and low maintenance requirements. First, by taking the negative conjugation of the control motor variables in rotor reference frame, a state-space model of BDFM is derived. It is then transformed into synchronous reference frame, called synchronous reference frame state-space model (SSSM). In this way, all the variables of the SSSM are DC under the static state. Second, on the basis of the analysis of static equations, the possible output torque limits are obtained. Third, the causes of losing control are analyzed by the flux and the torque derivatives. A new control strategy called synthetic vector direct torque control (SVDTC) is proposed to solve the losing control problems of the conventional direct torque control (DTC). Finally, the correctness of the results of this paper is verified by calculation examples and simulation results, the losing control problems can be solved, and the theoretical output capacity limits can be reached using SVDTC. Full article

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29 pages, 22521 KiB

Open AccessArticle

A Detailed Assessment of the Wave Energy Resource at the Atlantic Marine Energy Test Site

by Reduan Atan^1,2,3, Jamie Goggins^1,2,3

and Stephen Nash^1,2,3,*

¹ College of Engineering and Informatics, National University of Ireland, Galway, Ireland

² Centre for Marine and Renewable Energy Ireland (MaREI), Galway, Ireland

³ Ryan Institute for Environmental, Marine and Energy Research, Galway, Ireland

Energies 2016, 9(11), 967; https://doi.org/10.3390/en9110967 - 18 Nov 2016

Cited by 34 | Viewed by 9828

Abstract

Wave characteristic assessments of wave energy test sites provide a greater understanding of prevailing wave conditions and are therefore extremely important to both wave energy test site operators and clients as they can inform wave energy converter design, optimisation, deployment, operation and maintenance. [...] Read more.

Wave characteristic assessments of wave energy test sites provide a greater understanding of prevailing wave conditions and are therefore extremely important to both wave energy test site operators and clients as they can inform wave energy converter design, optimisation, deployment, operation and maintenance. This research presents an assessment of the wave resource at the Atlantic Marine Energy Test Site (AMETS) on the west coast of Ireland based on 12-years of modelled data from January 2004 to December 2015. The primary aim is to provide an assessment of annual and seasonal wave characteristics and resource variability at the two deployment berths which comprise the site. A nested model has been developed using Simulating WAves Nearshore (SWAN) to replicate wave propagations from regional to local scale with a 0.05° resolution model covering the northeast Atlantic and a 0.0027° resolution model covering AMETS. The coarse and fine models have been extensively validated against available measured data within Irish waters. 12-year model outputs from the high resolution model were analysed to determine mean and maximum conditions and operational, high and extreme event conditions for significant wave height, energy period and power. Annual and seasonal analyses are presented. The 12-year annual mean P were 68 kW/m at Berth A (BA) and 57 kW/m at Berth B (BB). The resource shows strong seasonal and annual variations and the winter mean power levels were found to be strongly correlated with the North Atlantic Oscillation (NAO). Full article

(This article belongs to the Special Issue Numerical Modelling of Wave and Tidal Energy)

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13 pages, 2885 KiB

Open AccessArticle

Suitability Assessment of an ICE-Based Micro-CCHP Unit in Different Spanish Climatic Zones: Application of an Experimental Model in Transient Simulation

by Guillermo Rey^1,*

, Carlos Ulloa¹, José Luís Míguez² and Antón Cacabelos¹

¹ Defense University Center, Naval Academy, 36920 Marín, Spain

² Industrial Engineering School, University of Vigo, Campus Lagoas Marcosende, 36310 Vigo, Spain

Energies 2016, 9(11), 969; https://doi.org/10.3390/en9110969 - 20 Nov 2016

Cited by 4 | Viewed by 4927

Abstract

Tri-generation plants will have an important role in the near future in the residential sector where heating and cooling demands come into play throughout the year. Depending on the building’s location, the characteristics of its enclosure and its use, the thermal loads and [...] Read more.

Tri-generation plants will have an important role in the near future in the residential sector where heating and cooling demands come into play throughout the year. Depending on the building’s location, the characteristics of its enclosure and its use, the thermal loads and demands will be different. This article analyses and compares a combined cooling, heating and power (CCHP) system tested in the laboratory and a single household located in Spain. The cooling capacity is obtained using a reversible heat pump where the compressor is driven directly by a gas engine with internal combustion engine (ICE) technology. The tests were carried out in a work bench at three different operating speeds. A variable-speed model is developed in the TRNSYS simulation environment with an operating strategy following the thermal load (FTL). Once the micro-CCHP system was modeled with experimental data and validated, it was dynamically simulated to analyze its performance in different climatic zones defined in the Spanish “Código Técnico de la Edificación” (CTE). This study reveals that the micro-CCHP system is suitable in mild weathers during the summer season. Full article

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14 pages, 2346 KiB

Open AccessArticle

Multi-Objective Optimization of a Solar Chimney Power Plant with Inclined Collector Roof Using Genetic Algorithm

by Ehsan Gholamalizadeh and Man-Hoe Kim^*

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

Energies 2016, 9(11), 971; https://doi.org/10.3390/en9110971 - 21 Nov 2016

Cited by 27 | Viewed by 5424

Abstract

This paper presents an optimization of a solar chimney power plant with an inclined collector roof using genetic algorithms. Five design parameters that affect the system performance are the collector radius, collector inlet height, collector outlet height, chimney height and diameter. A multi-objective [...] Read more.

This paper presents an optimization of a solar chimney power plant with an inclined collector roof using genetic algorithms. Five design parameters that affect the system performance are the collector radius, collector inlet height, collector outlet height, chimney height and diameter. A multi-objective design to simultaneously optimize three conflicting objectives including system efficiency, power output and expenditure is used. Based on this approach, obtaining the best combination of the possible geometrical parameters, performance of two built pilot power plants in Kerman (Iran) and Manzanares (Spain) are optimized thermo-economically. The heights of the zero-slope collectors of the Kerman and Manzanares systems are 2 m and 1.85 m, respectively. The results show that in the Kerman pilot the optimal collector inlet and outlet heights are 1.5 m and 2.95 m, respectively, while those optimal heights in the Manzanares prototype are 1.5 m and 4.6 m, respectively. It is found that selecting the optimal collector roof configuration in addition to the other design parameters has a significant effect in the system optimization process. Full article

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17 pages, 6318 KiB

Open AccessArticle

Failure Criteria of Gas-Infiltrated Sandy Shale Based on the Effective Stress Principle

by Wenpu Li^1,2

, Dongming Zhang^1,2,* and Minghui Li^1,2

¹ State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China

² College of Resource and Environmental Sciences, Chongqing University, Chongqing 400030, China

Energies 2016, 9(11), 972; https://doi.org/10.3390/en9110972 - 22 Nov 2016

Cited by 11 | Viewed by 4737

Abstract

Pore gas has a significant influence on rock strength. This study performed triaxial compression tests of gas-infiltrated sandy shale samples to investigate the strength characteristics under gas pressures of 0 and 2 MPa. The effective stress coefficient was evaluated while considering the gas [...] Read more.

Pore gas has a significant influence on rock strength. This study performed triaxial compression tests of gas-infiltrated sandy shale samples to investigate the strength characteristics under gas pressures of 0 and 2 MPa. The effective stress coefficient was evaluated while considering the gas and solid coupling effect, and was found to decrease with increasing confining pressure. The calculated and different assumed coefficient values (0 and 1) were applied to obtain the effective principal stress. The experimental results would serve as fundamental strength data for fitting analysis in failure criterion work. The Mohr-Coulomb, Hoek-Brown, Drucker-Prager, linear Mogi, and non-linear Mogi criteria were modified based on the effective stress principle of porous rock. In addition, the RMSE, cohesion, and internal friction angle were utilized for a quantitative criterion comparison. The results showed that the Mohr-Coulomb, Drucker-Prager, and linear Mogi failure criteria led to higher errors, whereas the Hoek-Brown criterion gave an apparent distortion as a result of the empirical strength parameters. Moreover, the non-linear Mogi criterion showed a good fit. The predicted strength was overestimated when α = 0 and underestimated when α = 1, with a more accurate strength estimated when the effective stress coefficient was calculated using the effective stress principle. Full article

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18 pages, 5167 KiB

Open AccessArticle

Accelerated Model Predictive Control for Electric Vehicle Integrated Microgrid Energy Management: A Hybrid Robust and Stochastic Approach

by Zhenya Ji^1,2, Xueliang Huang^1,2,*, Changfu Xu³ and Houtao Sun^1,2

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

² Jiangsu Key Laboratory of Smart Grid Technology and Equipment, Nanjing 210096, China

³ Electric Power Research Institute, State Grid Jiangsu Power Supply Company, Nanjing 211103, China

Energies 2016, 9(11), 973; https://doi.org/10.3390/en9110973 - 22 Nov 2016

Cited by 43 | Viewed by 7461

Abstract

A microgrid with an advanced energy management approach is a feasible solution for accommodating the development of distributed generators (DGs) and electric vehicles (EVs). At the primary stage of development, the total number of EVs in a microgrid is fairly small but increases [...] Read more.

A microgrid with an advanced energy management approach is a feasible solution for accommodating the development of distributed generators (DGs) and electric vehicles (EVs). At the primary stage of development, the total number of EVs in a microgrid is fairly small but increases promptly. Thus, it makes most prediction models for EV charging demand difficult to apply at present. To overcome the inadaptability, a novel robust approach is proposed to handle EV charging demand predictions along with demand-side management (DSM) on the condition of satisfying each EV user’s demand. Variables with stochastic forecast models join the objective function in the form of probability-constrained scenarios. This paper proposes a scenario-based model predictive control (MPC) approach combining both robust and stochastic models to minimize the total operational cost for energy management. To overcome the concern about the convergence time increasing from the combination of scenarios, the Benders decomposition (BD) technique is further adopted to improve computational efficiency. Simulation results on a combined heat and power microgrid indicate that the proposed scenario-based MPC approach achieves a better economic performance than a traditional deterministic MPC (DMPC) approach, while ensuring EV charging demands, as well as minimizing the trade-off between optimal solutions and computing times. Full article

(This article belongs to the Special Issue Smart Microgrids: Developing the Intelligent Power Grid of Tomorrow)

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16 pages, 7398 KiB

Open AccessArticle

Improving the Stability and Accuracy of Power Hardware-in-the-Loop Simulation Using Virtual Impedance Method

by Xiaoming Zha¹, Chenxu Yin¹, Jianjun Sun^1,*, Meng Huang¹ and Qionglin Li²

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

² State Grid Henan Electric Power Research Institute, Zhengzhou 450000, China

Energies 2016, 9(11), 974; https://doi.org/10.3390/en9110974 - 22 Nov 2016

Cited by 9 | Viewed by 6539

Abstract

Power hardware-in-the-loop (PHIL) systems are advanced, real-time platforms for combined software and hardware testing. Two paramount issues in PHIL simulations are the closed-loop stability and simulation accuracy. This paper presents a virtual impedance (VI) method for PHIL simulations that improves the simulation’s stability [...] Read more.

Power hardware-in-the-loop (PHIL) systems are advanced, real-time platforms for combined software and hardware testing. Two paramount issues in PHIL simulations are the closed-loop stability and simulation accuracy. This paper presents a virtual impedance (VI) method for PHIL simulations that improves the simulation’s stability and accuracy. Through the establishment of an impedance model for a PHIL simulation circuit, which is composed of a voltage-source converter and a simple network, the stability and accuracy of the PHIL system are analyzed. Then, the proposed VI method is implemented in a digital real-time simulator and used to correct the combined impedance in the impedance model, achieving higher stability and accuracy of the results. The validity of the VI method is verified through the PHIL simulation of two typical PHIL examples. Full article

(This article belongs to the Special Issue Next-Generation Low-Carbon Power and Energy Systems)

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6 pages, 1274 KiB

Open AccessArticle

Aluminum–Titanium Alloy Back Contact Reducing Production Cost of Silicon Thin-Film Solar Cells

by Hsin-Yu Wu¹, Chia-Hsun Hsu², Shui-Yang Lien^2,*

and Yeu-Long Jiang¹

¹ Graduate Institute of Optoelectronic Engineering and Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan

² Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan

Energies 2016, 9(11), 975; https://doi.org/10.3390/en9110975 - 22 Nov 2016

Cited by 3 | Viewed by 5998

Abstract

In this study, metal films are fabricated by using an in-line reactive direct current magnetron sputtering system. The aluminum–titanium (AlTi) back contacts are prepared by changing the pressure from 10 mTorr to 25 mTorr. The optical, electrical and structural properties of the metal [...] Read more.

In this study, metal films are fabricated by using an in-line reactive direct current magnetron sputtering system. The aluminum–titanium (AlTi) back contacts are prepared by changing the pressure from 10 mTorr to 25 mTorr. The optical, electrical and structural properties of the metal back contacts are investigated. The solar cells with the AlTi had lower contact resistance than those with the silver (Ag) back contact, resulting in a higher fill factor. The AlTi contact can achieve a solar cell conversion efficiency as high as that obtained from the Ag contact. These findings encourage the potential adoption of AlTi films as an alternative back contact to silver for silicon thin-film solar cells. Full article

(This article belongs to the Special Issue Solar Photovoltaics Trilemma: Efficiency, Stability and Cost Reduction 2017)

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18 pages, 4598 KiB

Open AccessArticle

A Three-Stage Optimal Approach for Power System Economic Dispatch Considering Microgrids

by Wei-Tzer Huang^1,*, Kai-Chao Yao¹

, Chun-Ching Wu¹, Yung-Ruei Chang², Yih-Der Lee² and Yuan-Hsiang Ho²

¹ Department of Industrial Education and Technology, National Changhua University of Education, Changhua 500, Taiwan

² The Institute of Nuclear Energy Research, Taoyuan City 325, Taiwan

Energies 2016, 9(11), 976; https://doi.org/10.3390/en9110976 - 22 Nov 2016

Cited by 9 | Viewed by 5933

Abstract

The inclusion of microgrids (MGs) in power systems, especially distribution-substation-level MGs, significantly affects power systems because of the large volumes of import and export power flows. Consequently, power dispatch has become complicated, and finding an optimal solution is difficult. In this study, a [...] Read more.

The inclusion of microgrids (MGs) in power systems, especially distribution-substation-level MGs, significantly affects power systems because of the large volumes of import and export power flows. Consequently, power dispatch has become complicated, and finding an optimal solution is difficult. In this study, a three-stage optimal power dispatch model is proposed to solve such dispatch problems. In the proposed model, the entire power system is divided into two parts, namely, the main power grid and MGs. The optimal power dispatch problem is resolved on the basis of multi-area concepts. In stage I, the main power system economic dispatch (ED) problem is solved by sensitive factors. In stage II, the optimal power dispatches of the local MGs are addressed via an improved direct search method. In stage III, the incremental linear models for the entire power system can be established on the basis of the solutions of the previous two stages and can be subjected to linear programming to determine the optimal reschedules from the original dispatch solutions. The proposed method is coded using Matlab and tested by utilizing an IEEE 14-bus test system to verify its feasibility and accuracy. Results demonstrated that the proposed approach can be used for the ED of power systems with MGs as virtual power plants. Full article

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

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16 pages, 6042 KiB

Open AccessArticle

An Improved Adaptive-Torque-Gain MPPT Control for Direct-Driven PMSG Wind Turbines Considering Wind Farm Turbulences

by Xiaolian Zhang^1,*, Can Huang², Sipeng Hao¹, Fan Chen¹ and Jingjing Zhai¹

¹ School of Electric Power Engineering, Nanjing Institute of Technology, Nanjing 211167, China

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

Energies 2016, 9(11), 977; https://doi.org/10.3390/en9110977 - 22 Nov 2016

Cited by 36 | Viewed by 8756

Abstract

Maximum power point tracking (MPPT) plays an important role in increasing the efficiency of a wind energy conversion system (WECS). In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF) control, decreased torque gain (DTG) control, and adaptive torque gain [...] Read more.

Maximum power point tracking (MPPT) plays an important role in increasing the efficiency of a wind energy conversion system (WECS). In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF) control, decreased torque gain (DTG) control, and adaptive torque gain (ATG) control, and their potential challenges are investigated. It is found out that the conventional MPPT method ignores the effect of wind turbine inertia and wind speed fluctuations, which lowers WECS efficiency. Accordingly, an improved adaptive torque gain (IATG) method is proposed, which customizes adaptive torque gains and enhances MPPT performances. Specifically, the IATG control considers wind farm turbulences and works out the relationship between the optimal torque gains and the wind speed characteristics, which has not been reported in the literature. The IATG control is promising, especially under the ongoing trend of building wind farms with large-scale wind turbines and at low and medium wind speed sites. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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15 pages, 710 KiB

Open AccessArticle

Improved Direct Deadbeat Voltage Control with an Actively Damped Inductor-Capacitor Plant Model in an Islanded AC Microgrid

by Jaehong Kim¹

, Jitae Hong² and Hongju Kim^2,*

¹ Department of Electrical Engineering, Chosun University, 309, Pilmun-daero, Dong-gu, Gwangju 61452, Korea

² Precision Control Research Center, Korea Electrotechnology Research Institute (KERI), 12, Bulmosan-ro 10beon-gil, Seongsan-gu, Changwon-si, Gyeongsangnam-do 51543, Korea

Energies 2016, 9(11), 978; https://doi.org/10.3390/en9110978 - 22 Nov 2016

Cited by 25 | Viewed by 6561

Abstract

A direct deadbeat voltage control design method for inverter-based microgrid applications is proposed in this paper. When the inductor-capacitor (LC) filter output voltage is directly controlled using voltage source inverters (VSIs), the plant dynamics exhibit second-order resonant characteristics with a load current disturbance. [...] Read more.

A direct deadbeat voltage control design method for inverter-based microgrid applications is proposed in this paper. When the inductor-capacitor (LC) filter output voltage is directly controlled using voltage source inverters (VSIs), the plant dynamics exhibit second-order resonant characteristics with a load current disturbance. To effectively damp the resonance caused by the output LC filter, an active damping strategy that does not cause additional energy loss is utilized. The proposed direct deadbeat voltage control law is devised from a detailed, actively damped LC plant model. The proposed deadbeat control method enhances voltage control performance owing to its better disturbance rejection capability than the conventional deadbeat or proportional-integral-based control methods. The most important advantage of the proposed deadbeat control method is that it makes the deadbeat control more robust by bringing discrete closed-loop poles closer to the origin. Simulation and experimental results are shown to verify the enhanced voltage control performance and stability of the proposed voltage control method. Full article

(This article belongs to the Collection Smart Grid)

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16 pages, 6144 KiB

Open AccessArticle

Experimental Investigation of Thermal Behaviors in Window Systems by Monitoring of Surface Condensation Using Full-Scale Measurements and Simulation Tools

by Goopyo Hong¹, Daeung Danny Kim²

and Byungseon Sean Kim^1,*

¹ Department of Architectural Engineering, Yonsei University, 50 Yonsei Street, Seodaemun-gu, Seoul 03722, Korea

² Architectural Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

Energies 2016, 9(11), 979; https://doi.org/10.3390/en9110979 - 22 Nov 2016

Cited by 7 | Viewed by 5686

Abstract

The aim of the present study was to investigate the thermal performance of window systems using full-scale measurements and simulation tools. A chamber was installed on the balcony of an apartment to control the temperatures which can create condensation on the interior surfaces [...] Read more.

The aim of the present study was to investigate the thermal performance of window systems using full-scale measurements and simulation tools. A chamber was installed on the balcony of an apartment to control the temperatures which can create condensation on the interior surfaces of window systems. The condensation process on the window was carefully scrutinized when outdoor and indoor temperature and indoor relative humidity ranged from −15 °C to −20 °C, 23 °C to 24 °C, and 50% to 65%, respectively. The results of these investigations were analyzed to determine how the moisture is influenced by changing temperatures. It appears that the glass-edge was highly susceptible to the temperature variations and the lowest temperature on the glass edge was caused by the heat transfer through the spacer, between the two glass panels of the window. The results from the simulation used in this study confirm that the thermal performance of window systems can be improved the use of super insulated or thermally broken spacers. If the values of the indoor humidity and temperature are given, then the outdoor temperature when condensation forms can be obtained by using Temperature Difference Ratio (TDR). This methodology can be employed to predict the possible occurrence of condensation. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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Review

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20 pages, 4244 KiB

Open AccessReview

Perovskite Solar Cells: Progress and Advancements

by Naveen Kumar Elumalai^*, Md Arafat Mahmud, Dian Wang and Ashraf Uddin^*

School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052, Australia

Energies 2016, 9(11), 861; https://doi.org/10.3390/en9110861 - 25 Oct 2016

Cited by 130 | Viewed by 32233

Abstract

Organic–inorganic hybrid perovskite solar cells (PSCs) have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, [...] Read more.

Organic–inorganic hybrid perovskite solar cells (PSCs) have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost. Perovskite solar cells have demonstrated unprecedented progress in efficiency and its architecture evolved over the period of the last 5–6 years, achieving a high power conversion efficiency of about 22% in 2016, serving as a promising candidate with the potential to replace the existing commercial PV technologies. This review discusses the progress of perovskite solar cells focusing on aspects such as superior electronic properties and unique features of halide perovskite materials compared to that of conventional light absorbing semiconductors. The review also presents a brief overview of device architectures, fabrication methods, and interface engineering of perovskite solar cells. The last part of the review elaborates on the major challenges such as hysteresis and stability issues in perovskite solar cells that serve as a bottleneck for successful commercialization of this promising PV technology. Full article

(This article belongs to the Special Issue Selected Papers from 2nd Energy Future Conference)

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17 pages, 3408 KiB

Open AccessReview

A Review of Frequency Response Analysis Methods for Power Transformer Diagnostics

by Saleh Alsuhaibani¹, Yasin Khan¹, Abderrahmane Beroual^2,*

and Nazar Hussain Malik¹

¹ Electrical Engineering Department, College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia

² Ecole Centrale de Lyon, University of Lyon, AMPERE Lab, CNRS UMR 5005, 36 Avenue Guy de Collongue, Ecully 69134, France

Energies 2016, 9(11), 879; https://doi.org/10.3390/en9110879 - 27 Oct 2016

Cited by 77 | Viewed by 10322

Abstract

Power transformers play a critical role in electric power networks. Such transformers can suffer failures due to multiple stresses and aging. Thus, assessment of condition and diagnostic techniques are of great importance for improving power network reliability and service continuity. Several techniques are [...] Read more.

Power transformers play a critical role in electric power networks. Such transformers can suffer failures due to multiple stresses and aging. Thus, assessment of condition and diagnostic techniques are of great importance for improving power network reliability and service continuity. Several techniques are available to diagnose the faults within the power transformer. Frequency response analysis (FRA) method is a powerful technique for diagnosing transformer winding deformation and several other types of problems that are caused during manufacture, transportation, installation and/or service life. This paper provides a comprehensive review on FRA methods and their applications in diagnostics and fault identification for power transformers. The paper discusses theory and applications of FRA methods as well as various issues and challenges faced in the application of this method. Full article

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

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26 pages, 1028 KiB

Open AccessReview

Scrap Tyre Management Pathways and Their Use as a Fuel—A Review

by Amir Rowhani¹ and Thomas J. Rainey^1,2,*

¹ School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, 2 George St, Brisbane, QLD 4000, Australia

² Biofuel Engine Research Facility, Queensland University of Technology, 2 George St, Brisbane, QLD 4000, Australia

Energies 2016, 9(11), 888; https://doi.org/10.3390/en9110888 - 29 Oct 2016

Cited by 153 | Viewed by 14159

Abstract

This article provides a review of different methods for managing waste tyres. Around 1.5 billion scrap tyres make their way into the environmental cycle each year, so there is an extreme demand to manage and mitigate the environmental impact which occurs from landfilling [...] Read more.

This article provides a review of different methods for managing waste tyres. Around 1.5 billion scrap tyres make their way into the environmental cycle each year, so there is an extreme demand to manage and mitigate the environmental impact which occurs from landfilling and burning. Numerous approaches are targeted to recycle and reuse the tyre rubber in various applications. Among them, one of the most important methods for sustainable environmental stewardship is converting tyre rubber components into bio-oil. In this study, scrap tyre management techniques including landfill, retreading, recycling, combustion, and conversion to liquid fuels was reviewed (including gasification, hydrothermal liquefaction, and pyrolysis). The effects of parameters such as reactor types, pyrolysis temperature, and catalyst on the oil, gas and solid products in pyrolysis process were investigated. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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31 pages, 4378 KiB

Open AccessEditor’s ChoiceReview

An Alternative to Conventional Rock Fragmentation Methods Using SCDA: A Review

by Radhika Vidanage De Silva¹, Ranjith Pathegama Gamage^1,*

and Mandadige Samintha Anne Perera^1,2

¹ Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University, Building 60, Melbourne 3800, Victoria, Australia

² Department of Infrastructure Engineering, Faculty of Engineering, the University of Melbourne, Building 176, Block D, Grattan Street, Parkville 3010, Victoria, Australia

Energies 2016, 9(11), 958; https://doi.org/10.3390/en9110958 - 17 Nov 2016

Cited by 81 | Viewed by 10810

Abstract

Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications [...] Read more.

Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material’s behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different applications. Full article

(This article belongs to the Special Issue Unconventional Natural Gas (UNG) Recoveries)

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18 pages, 3075 KiB

Open AccessReview

An Overview of Modeling Approaches Applied to Aggregation-Based Fleet Management and Integration of Plug-in Electric Vehicles †

by Shi You^*, Junjie Hu

and Charalampos Ziras

Department of Electrical Engineering, Technical University of Denmark, Elektrovej 325, DK-2800 Kgs. Lyngby, Denmark

Energies 2016, 9(11), 968; https://doi.org/10.3390/en9110968 - 18 Nov 2016

Cited by 15 | Viewed by 8429

Abstract

The design and implementation of management policies for plug-in electric vehicles (PEVs) need to be supported by a holistic understanding of the functional processes, their complex interactions, and their response to various changes. Models developed to represent different functional processes and systems are [...] Read more.

The design and implementation of management policies for plug-in electric vehicles (PEVs) need to be supported by a holistic understanding of the functional processes, their complex interactions, and their response to various changes. Models developed to represent different functional processes and systems are seen as useful tools to support the related studies for different stakeholders in a tangible way. This paper presents an overview of modeling approaches applied to support aggregation-based management and integration of PEVs from the perspective of fleet operators and grid operators, respectively. We start by explaining a structured modeling approach, i.e., a flexible combination of process models and system models, applied to different management and integration studies. A state-of-the-art overview of modeling approaches applied to represent several key processes, such as charging management, and key systems, such as the PEV fleet, is then presented, along with a detailed description of different approaches. Finally, we discuss several considerations that need to be well understood during the modeling process in order to assist modelers and model users in the appropriate decisions of using existing, or developing their own, solutions for further applications. Full article

(This article belongs to the Special Issue Selected Papers from 2nd Energy Future Conference)

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25 pages, 989 KiB

Open AccessReview

A Review of Factors Influencing the Cost Development of Electricity Generation Technologies

by Sascha Samadi

Wuppertal Institute for Climate, Environment and Energy, Döppersberg 19, 42103 Wuppertal, Germany

Energies 2016, 9(11), 970; https://doi.org/10.3390/en9110970 - 19 Nov 2016

Cited by 13 | Viewed by 6759

Abstract

This article reviews the literature on the past cost dynamics of various renewable, fossil fuel and nuclear electricity generation technologies. It identifies 10 different factors which have played key roles in influencing past cost developments according to the literature. These 10 factors are: [...] Read more.

This article reviews the literature on the past cost dynamics of various renewable, fossil fuel and nuclear electricity generation technologies. It identifies 10 different factors which have played key roles in influencing past cost developments according to the literature. These 10 factors are: deployment-induced learning, research, development and demonstration (RD&D)-induced learning, knowledge spillovers from other technologies, upsizing, economies of manufacturing scale, economies of project scale, changes in material and labour costs, changes in fuel costs, regulatory changes, and limits to the availability of suitable sites. The article summarises the relevant literature findings for each of these 10 factors and provides an overview indicating which factors have impacted on which generation technologies. The article also discusses the insights gained from the review for a better understanding of possible future cost developments of electricity generation technologies. Finally, future research needs, which may support a better understanding of past and future cost developments, are identified. Full article

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