Energies

13 pages, 5434 KiB

Open AccessArticle

Development of a Diesel Engine Thermal Overload Monitoring System with Applications and Test Results

by Sangram Kishore Nanda^1,2, Boru Jia^2,*

, Andrew Smallbone² and Anthony Paul Roskilly²

¹ Wärtsilä Services Switzerland Ltd., CH-8401 Winterthur, Switzerland

² Sir Joseph Swan Centre for Energy Research, Newcastle University, Newcastle upon Tyne NE1 7RU, UK

Energies 2017, 10(7), 830; https://doi.org/10.3390/en10070830 - 22 Jun 2017

Cited by 3 | Viewed by 5533

Abstract

In this research, the development of a diesel engine thermal overload monitoring system is presented with applications and test results. The designed diesel engine thermal overload monitoring system consists of two set of sensors, i.e., a lambda sensor to measure the oxygen concentration [...] Read more.

In this research, the development of a diesel engine thermal overload monitoring system is presented with applications and test results. The designed diesel engine thermal overload monitoring system consists of two set of sensors, i.e., a lambda sensor to measure the oxygen concentration and a fast response thermocouple to measure the temperature of the gas leaving the cylinder. A medium speed Ruston diesel engine is instrumented to measure the required engine process parameters, measurements are taken at constant load and variable fuel delivery i.e., normal and excessive injection. It is indicated that with excessive injection, the test engine is of high risk to be operated at thermal overload condition. Further tests were carried out on a Sulzer 7RTA84T engine to explore the influence of engine operating at thermal overload condition on exhaust gas temperature and oxygen concentration in the blow down gas. It is established that a lower oxygen concentration in the blow down gas corresponds to a higher exhaust gas temperature. The piston crown wear rate will then be much higher due to the high rate of heat transfer from a voluminous flame. Full article

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

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15 pages, 2119 KiB

Open AccessArticle

A Computational Tool for Comparative Energy Cost Analysis of Multiple-Crop Production Systems

by Efthymios Rodias¹, Remigio Berruto^1,*

, Dionysis Bochtis²

, Patrizia Busato¹ and Alessandro Sopegno¹

¹ Department of Agriculture, Forestry and Food Science (DISAFA), University of Turin, Largo Braccini 2, 10095 Grugliasco, Italy

² Institute for Research and Technology—Thessaly IRETETH/Centre for Research & Technology Hellas CERTH, Dimitriados Str. 95, GR 38333 Volos, Greece

Energies 2017, 10(7), 831; https://doi.org/10.3390/en10070831 - 22 Jun 2017

Cited by 14 | Viewed by 6002

Abstract

Various crops can be considered as potential bioenergy and biofuel production feedstocks. The selection of the crops to be cultivated for that purpose is based on several factors. For an objective comparison between different crops, a common framework is required to assess their [...] Read more.

Various crops can be considered as potential bioenergy and biofuel production feedstocks. The selection of the crops to be cultivated for that purpose is based on several factors. For an objective comparison between different crops, a common framework is required to assess their economic or energetic performance. In this paper, a computational tool for the energy cost evaluation of multiple-crop production systems is presented. All the in-field and transport operations are considered, providing a detailed analysis of the energy requirements of the components that contribute to the overall energy consumption. A demonstration scenario is also described. The scenario is based on three selected energy crops, namely Miscanthus, Arundo donax and Switchgrass. The tool can be used as a decision support system for the evaluation of different agronomical practices (such as fertilization and agrochemicals application), machinery systems, and management practices that can be applied in each one of the individual crops within the production system. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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19 pages, 5610 KiB

Open AccessFeature PaperArticle

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

by Simona Silvia Merola^*, Adrian Irimescu, Silvana Di Iorio and Bianca Maria Vaglieco

Istituto Motori-Consiglio Nazionale delle Ricerche, 80125 Naples, Italy

Energies 2017, 10(7), 832; https://doi.org/10.3390/en10070832 - 22 Jun 2017

Cited by 14 | Viewed by 6213

Abstract

Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms [...] Read more.

Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms involved in the formation of carbonaceous structures during combustion and their evolution in the exhaust line. In-cylinder pressure was recorded in combination with cycle-resolved flame imaging, gaseous emissions and particle size distribution. This complete characterization was performed at three injection phasing settings, with butanol and commercial gasoline. Optical accessibility from below the combustion chamber allowed visualization of diffusive flames induced by fuel deposits; these localized phenomena were correlated to observed changes in engine performance and pollutant species. With gasoline fueling, minor modifications were observed with respect to combustion parameters, when varying the start of injection. The alcohol, on the other hand, featured marked sensitivity to the fuel delivery strategy. Even though the start of injection was varied in a relatively narrow crank angle range during the intake stroke, significant differences were recorded, especially in the values of particle emissions. This was correlated to the fuel jet-wall interactions; the analysis of diffusive flames, their location and size confirmed the importance of liquid film formation in direct injection engines, especially at medium and high load. Full article

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

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13 pages, 1702 KiB

Open AccessArticle

Break-Even Points of Battery Energy Storage Systems for Peak Shaving Applications

by Claudia Rahmann^1,*

, Benjamin Mac-Clure¹, Vijay Vittal² and Felipe Valencia¹

¹ Department of Electrical Engineering, University of Chile, 8370451 Santiago, Chile

² School of Electrical, Computer and Energy Engineering, Arizona State University, P.O. Box 875706, Tempe, AZ 85287, USA

Energies 2017, 10(7), 833; https://doi.org/10.3390/en10070833 - 22 Jun 2017

Cited by 45 | Viewed by 9450

Abstract

In the last few years, several investigations have been carried out in the field of optimal sizing of energy storage systems (ESSs) at both the transmission and distribution levels. Nevertheless, most of these works make important assumptions about key factors affecting ESS profitability [...] Read more.

In the last few years, several investigations have been carried out in the field of optimal sizing of energy storage systems (ESSs) at both the transmission and distribution levels. Nevertheless, most of these works make important assumptions about key factors affecting ESS profitability such as efficiency and life cycles and especially about the specific costs of the ESS, without considering the uncertainty involved. In this context, this work aims to answer the question: what should be the costs of different ESS technologies in order to make a profit when considering peak shaving applications? The paper presents a comprehensive sensitivity analysis of the interaction between the profitability of an ESS project and some key parameters influencing the project performance. The proposed approach determines the break-even points for different ESSs considering a wide range of life cycles, efficiencies, energy prices, and power prices. To do this, an optimization algorithm for the sizing of ESSs is proposed from a distribution company perspective. From the results, it is possible to conclude that, depending on the values of round trip efficiency, life cycles, and power price, there are four battery energy storage systems (BESS) technologies that are already profitable when only peak shaving applications are considered: lead acid, NaS, ZnBr, and vanadium redox. Full article

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

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24 pages, 8670 KiB

Open AccessArticle

Hybrid Photovoltaic Systems with Accumulation—Support for Electric Vehicle Charging

by Petr Mastny^1,*, Jan Moravek¹, Martin Vojtek² and Jiri Drapela¹

¹ Department of Electrical Power Engineering, Brno University of Technology, Technicka 12, Brno 61600, Czech Republic

² Department of Electric Power Engineering, Technical University of Košice, Mäsiarska 74, Košice 04001, Slovakia

Energies 2017, 10(7), 834; https://doi.org/10.3390/en10070834 - 22 Jun 2017

Cited by 9 | Viewed by 6315

Abstract

The paper presents the concept of a hybrid power system with additional energy storage to support electric vehicles (EVs) charging stations. The aim is to verify the possibilities of mutual cooperation of individual elements of the system from the point of view of [...] Read more.

The paper presents the concept of a hybrid power system with additional energy storage to support electric vehicles (EVs) charging stations. The aim is to verify the possibilities of mutual cooperation of individual elements of the system from the point of view of energy balances and to show possibilities of utilization of accumulation for these purposes using mathematical modeling. The description of the technical solution of the concept is described by a mathematical model in the Matlab Simulink programming environment. Individual elements of the assembled model are described in detail, together with the algorithm of the control logic of charging the supporting storage system. The resulting model was validated via an actual small-scale hybrid system (HS). Within the outputs of the mathematical model, two simulation scenarios are presented, with the aid of which the benefits of the concept presented were verified. Full article

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

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19 pages, 1536 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Economic Optimization of Component Sizing for Residential Battery Storage Systems

by Holger C. Hesse^1,*

, Rodrigo Martins²

, Petr Musilek^2,3

, Maik Naumann¹

, Cong Nam Truong¹

and Andreas Jossen¹

¹ Department of Electrical and Computer Engineering, Technical University of Munich (TUM), 80333 Munich, Germany

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

³ Electrical Engineering and Computer Science, VSB-Technical University Ostrava, 70800 Ostrava, Czech Republic

Energies 2017, 10(7), 835; https://doi.org/10.3390/en10070835 - 22 Jun 2017

Cited by 181 | Viewed by 15383

Abstract

Battery energy storage systems (BESS) coupled with rooftop-mounted residential photovoltaic (PV) generation, designated as PV-BESS, draw increasing attention and market penetration as more and more such systems become available. The manifold BESS deployed to date rely on a variety of different battery technologies, [...] Read more.

Battery energy storage systems (BESS) coupled with rooftop-mounted residential photovoltaic (PV) generation, designated as PV-BESS, draw increasing attention and market penetration as more and more such systems become available. The manifold BESS deployed to date rely on a variety of different battery technologies, show a great variation of battery size, and power electronics dimensioning. However, given today’s high investment costs of BESS, a well-matched design and adequate sizing of the storage systems are prerequisites to allow profitability for the end-user. The economic viability of a PV-BESS depends also on the battery operation, storage technology, and aging of the system. In this paper, a general method for comprehensive PV-BESS techno-economic analysis and optimization is presented and applied to the state-of-art PV-BESS to determine its optimal parameters. Using a linear optimization method, a cost-optimal sizing of the battery and power electronics is derived based on solar energy availability and local demand. At the same time, the power flow optimization reveals the best storage operation patterns considering a trade-off between energy purchase, feed-in remuneration, and battery aging. Using up to date technology-specific aging information and the investment cost of battery and inverter systems, three mature battery chemistries are compared; a lead-acid (PbA) system and two lithium-ion systems, one with lithium-iron-phosphate (LFP) and another with lithium-nickel-manganese-cobalt (NMC) cathode. The results show that different storage technology and component sizing provide the best economic performances, depending on the scenario of load demand and PV generation. Full article

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

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13 pages, 1793 KiB

Open AccessArticle

Power Quality and Energy Efficiency in the Pre-Evaluation of an Outdoor Lighting Renewal with Light-Emitting Diode Technology: Experimental Study and Amortization Analysis

by Manuel Jesús Hermoso-Orzáez¹

, Alfonso Gago-Calderón^2,*

and José Ignacio Rojas-Sola¹

¹ Department of Engineering Graphics, Design and Projects, Universidad de Jaén, Campus de las Lagunillas, s/n, 23071 Jaén, Spain

² Department of Engineering Graphics, Design and Projects, Escuela de Ingenierías, Universidad de Málaga, 3089-D. C/Doctor Ortiz Ramos, s/n, Campus de Teatinos, 29071 Málaga, Spain

Energies 2017, 10(7), 836; https://doi.org/10.3390/en10070836 - 22 Jun 2017

Cited by 26 | Viewed by 4101

Abstract

In this work, a practical methodology is proposed to analyze, before undertaking a large investment, an outdoor lighting installation renewal with light-emitting diode (LED) luminaires. The main problems found in many of the luminaires tested are associated with inrush peak currents in cold [...] Read more.

In this work, a practical methodology is proposed to analyze, before undertaking a large investment, an outdoor lighting installation renewal with light-emitting diode (LED) luminaires. The main problems found in many of the luminaires tested are associated with inrush peak currents in cold start (which may cause ignition problems with random shutdowns), the harmonic distortions caused by their AC/DC associated electronic nature driver, and their working and efficiency dependency on the ambient temperature. All these issues have been tested in the context of a large metal halide (MH) to LED luminaires lighting point renewal where six commercial LED projectors have been analyzed with the above considerations. This research has isolated a single-phase circuit powered with constant stabilized 230 V_AC voltage source in a real public lighting installation. All of them have been sequentially installed and their main electrical and power-quality parameters measured and recorded. The results indicate that each luminaire option will influence the expected long-term reliability (>50.000 h or more as expressed by the U.S. Department of Energy) of the lighting installation (in the case poor power quality is generated on the grid). The economic analysis made to estimate the profitability of the investment may be severely affected by the difference between the declared and the real consumption values in which they perform in our specific installation. Full article

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

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33 pages, 1916 KiB

Open AccessArticle

Data Analysis and Neuro-Fuzzy Technique for EOR Screening: Application in Angolan Oilfields

by Geraldo A. R. Ramos^1,2,3 and Lateef Akanji^1,*

¹ School of Engineering, College of Physical Sciences, University of Aberdeen, Aberdeen AB24 3FX, UK

² Polytechnic Institute of Technology and Sciences (ISPTEC), Department of Engineering and Technology (DET), Av. Luanda Sul, Rua Lateral Via S10, Talatona, Luanda PO Box 1316, Angola

³ Sonangol EP; Academia Sonangol, Av. Luanda Sul, Rua Lateral Via S10, Talatona, Luanda PO Box 1316, Angola

Energies 2017, 10(7), 837; https://doi.org/10.3390/en10070837 - 22 Jun 2017

Cited by 13 | Viewed by 5872

Abstract

In this work, a neuro-fuzzy (NF) simulation study was conducted in order to screen candidate reservoirs for enhanced oil recovery (EOR) projects in Angolan oilfields. First, a knowledge pattern is extracted by combining both the searching potential of fuzzy-logic (FL) and the learning [...] Read more.

In this work, a neuro-fuzzy (NF) simulation study was conducted in order to screen candidate reservoirs for enhanced oil recovery (EOR) projects in Angolan oilfields. First, a knowledge pattern is extracted by combining both the searching potential of fuzzy-logic (FL) and the learning capability of neural network (NN) to make a priori decisions. The extracted knowledge pattern is validated against rock and fluid data trained from successful EOR projects around the world. Then, data from Block K offshore Angolan oilfields are then mined and analysed using box-plot technique for the investigation of the degree of suitability for EOR projects. The trained and validated model is then tested on the Angolan field data (Block K) where EOR application is yet to be fully established. The results from the NF simulation technique applied in this investigation show that polymer, hydrocarbon gas, and combustion are the suitable EOR techniques. Full article

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11 pages, 3917 KiB

Open AccessArticle

Preliminary Study on Integration of Fiber Optic Bragg Grating Sensors in Li-Ion Batteries and In Situ Strain and Temperature Monitoring of Battery Cells

by Aleksandra Fortier^1,*, Max Tsao¹, Nick D. Williard², Yinjiao Xing³ and Michael G. Pecht³

¹ University of Dayton Research Institute and the Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH 45433, USA

² 1430 Enclave Pkwy, Schlumberger, Houston, TX 77077, USA

³ Mechanical Engineering Department, Center for Advanced Life Cycle Engineering, University of Maryland, College Park, MD 20742, USA

Energies 2017, 10(7), 838; https://doi.org/10.3390/en10070838 - 23 Jun 2017

Cited by 81 | Viewed by 8928

Abstract

Current commercial battery management systems (BMSs) do not provide adequate information in real time to mitigate issues of battery cells such as thermal runway. This paper explores and evaluates the integration of fiber optic Bragg grating (FBG) sensors inside lithium-ion battery (LiB) coin [...] Read more.

Current commercial battery management systems (BMSs) do not provide adequate information in real time to mitigate issues of battery cells such as thermal runway. This paper explores and evaluates the integration of fiber optic Bragg grating (FBG) sensors inside lithium-ion battery (LiB) coin cells. Strain and internal and external temperatures were recorded using FBG sensors, and the battery cells were evaluated at a cycling C/20 rate. The preliminary results present scanning electron microscope (SEM) images of electrode degradation upon sensor integration and the systematic process of sensor integration to eliminate degradation in electrodes during cell charge/discharge cycles. Recommendation for successful FBG sensor integration is given, and the strain and temperature data is presented. The FBG sensor was placed on the inside of the coin cell between the electrodes and the separator layers towards the most electrochemically active area. On the outside, the temperature of the coin cell casing as well as the ambient temperature was recorded. Results show stable strain behavior within the cell and about 10 °C difference between the inside of the coin cell and the ambient environment over time during charging/discharging cycles. This study is intended to contribute to the safe integration of FBG sensors inside hermetically sealed batteries and to detection of real-time temperature and strain gradient inside a cell, ultimately improving reliability of current BMSs. Full article

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17 pages, 967 KiB

Open AccessArticle

Technical Assessment of Different Operating Conditions of an On-Board Autothermal Reformer for Fuel Cell Vehicles

by Laura Tribioli^*

, Raffaello Cozzolino

and Daniele Chiappini

Department of Engineering, Niccolò Cusano University, via Don Carlo Gnocchi 3, 00166 Rome, Italy

Energies 2017, 10(7), 839; https://doi.org/10.3390/en10070839 - 23 Jun 2017

Cited by 9 | Viewed by 4549

Abstract

This paper evaluates the performance of a fuel cell/battery vehicle with an on-board autothermal reformer, fed by different liquid and gaseous hydrocarbon fuels. A sensitivity analysis is performed to investigate the system behavior under the variation of the steam to carbon and oxygen [...] Read more.

This paper evaluates the performance of a fuel cell/battery vehicle with an on-board autothermal reformer, fed by different liquid and gaseous hydrocarbon fuels. A sensitivity analysis is performed to investigate the system behavior under the variation of the steam to carbon and oxygen to carbon ratios. This is done in order to identify the most suitable operating conditions for a direct on-board production of hydrogen to be used in a high temperature polymer electrolyte membrane fuel cell. The same system should be able to process different fuels, to allow the end-user to freely decide which one to use to refuel the vehicle. Hence, the obtained operating conditions result in a trade-off between system flexibility as the feeding fuel changes, CO poisoning effect on the fuel cell and overall efficiency. The system is thus coupled to a high temperature fuel cell, modeled by means of a self-made tool, able to reproduce the polarization curve as the input syngas composition varies, and the overall system is afterwards tested on a plug-in fuel cell/battery vehicle simulator, in order to provide a thorough feasibility analysis, focusing on the entire system efficiency. Results show that a proper energy management strategy can mitigate the effect of the fuel variation on the reformer efficiency, allowing for good overall powertrain performance. Full article

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

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17 pages, 796 KiB

Open AccessFeature PaperArticle

Simulation versus Optimisation: Theoretical Positions in Energy System Modelling

by Henrik Lund^1,*

, Finn Arler¹, Poul Alberg Østergaard¹

, Frede Hvelplund¹, David Connolly², Brian Vad Mathiesen² and Peter Karnøe²

¹ Department of Planning, Aalborg University, Rendsburggade 14, 9000 Aalborg, Denmark

² Department of Planning, Aalborg University, A.C. Meyers Vænge 15, 2450 Copenhagen, Denmark

Energies 2017, 10(7), 840; https://doi.org/10.3390/en10070840 - 23 Jun 2017

Cited by 208 | Viewed by 14053

Abstract

In recent years, several tools and models have been developed and used for the design and analysis of future national energy systems. Many of these models focus on the integration of various renewable energy resources and the transformation of existing fossil-based energy systems [...] Read more.

In recent years, several tools and models have been developed and used for the design and analysis of future national energy systems. Many of these models focus on the integration of various renewable energy resources and the transformation of existing fossil-based energy systems into future sustainable energy systems. The models are diverse and often end up with different results and recommendations. This paper analyses this diversity of models and their implicit or explicit theoretical backgrounds. In particular, two archetypes are defined and compared. On the one hand, the prescriptive investment optimisation or optimal solutions approach. On the other hand the analytical simulation or alternatives assessment approach. Awareness of the dissimilar theoretical assumption behind the models clarifies differences between the models, explains dissimilarities in results, and provides a theoretical and methodological foundation for understanding and interpreting results from the two archetypes. Full article

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

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18 pages, 1621 KiB

Open AccessFeature PaperArticle

Highly Efficient 3rd Generation Multi-Junction Solar Cells Using Silicon Heterojunction and Perovskite Tandem: Prospective Life Cycle Environmental Impacts

by René Itten^* and Matthias Stucki

Institute of Natural Resource Sciences, Zurich University of Applied Sciences, 8820 Wädenswil, Switzerland

Energies 2017, 10(7), 841; https://doi.org/10.3390/en10070841 - 23 Jun 2017

Cited by 27 | Viewed by 8174

Abstract

In this study, the environmental impacts of monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) and single junction organometallic perovskite solar cells (PSC) are compared with the impacts of crystalline silicon based solar cells using a prospective life cycle assessment with a time [...] Read more.

In this study, the environmental impacts of monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) and single junction organometallic perovskite solar cells (PSC) are compared with the impacts of crystalline silicon based solar cells using a prospective life cycle assessment with a time horizon of 2025. This approach provides a result range depending on key parameters like efficiency, wafer thickness, kerf loss, lifetime, and degradation, which are appropriate for the comparison of these different solar cell types with different maturity levels. The life cycle environmental impacts of SHJ-PSC and PSC solar cells are similar or lower compared to conventional crystalline silicon solar cells, given comparable lifetimes, with the exception of mineral and fossil resource depletion. A PSC single-junction cell with 20% efficiency has to exceed a lifetime of 24 years with less than 3% degradation per year in order to be competitive with the crystalline silicon single-junction cells. If the installed PV capacity has to be maximised with only limited surface area available, the SHJ-PSC tandem is preferable to the PSC single-junction because their environmental impacts are similar, but the surface area requirement of SHJ-PSC tandems is only 70% or lower compared to PSC single-junction cells. The SHJ-PSC and PSC cells have to be embedded in proper encapsulation to maximise the stability of the PSC layer as well as handled and disposed of correctly to minimise the potential toxicity impacts of the heavy metals used in the PSC layer. Full article

(This article belongs to the Special Issue Environmental Impact Assessment of Energy Technologies)

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20 pages, 10443 KiB

Open AccessArticle

Applicability of an Artificial Neural Network for Predicting Water-Alternating-CO₂ Performance

by Si Le Van

and Bo Hyun Chon^*

Department of Energy Resources Engineering, Inha University, Incheon 402-751, Korea

Energies 2017, 10(7), 842; https://doi.org/10.3390/en10070842 - 24 Jun 2017

Cited by 16 | Viewed by 5217

Abstract

The injection of CO₂ as part of the water-alternating-gas (WAG) process has been widely employed in many mature oil fields for effectively enhancing oil production and sequestrating carbon permanently inside the reservoirs. In addition to simulations, the use of intelligent tools is [...] Read more.

The injection of CO₂ as part of the water-alternating-gas (WAG) process has been widely employed in many mature oil fields for effectively enhancing oil production and sequestrating carbon permanently inside the reservoirs. In addition to simulations, the use of intelligent tools is of particular interest for evaluating the uncertainties in the WAG process and predicting technical or economic performance. This study proposed the comprehensive evaluations of a water-alternating-CO₂ process utilizing the artificial neural network (ANN) models that were initially generated from a qualified numerical data set. Totally two uncertain reservoir parameters and three installed surface operating factors were designed as input variables in each of the three-layer ANN models to predicting a series of WAG production performances after 5, 15, 25, and 35 injection cycles. In terms of the technical view point, the relationships among parameters and important outputs, including oil recovery, CO₂ production, and net CO₂ storage were accurately reflected by integrating the generated network models. More importantly, since the networks could simulate a series of injection processes, the sequent variations of those technical issues were well presented, indicating the distinct application of ANN in this study compared to previous works. The economic terms were also briefly introduced for a given fiscal condition which included sufficient concerns for a general CO₂ flooding project, in a range of possible oil prices. Using the ANN models, the net present value (NPV) optimization results for several specific cases apparently expressed the profitability of the present enhanced oil recovery (EOR) project according to the unstable oil prices, and most importantly provided the most relevant injection schedules corresponding with each different scenario. Obviously, the methodology of applying traditional ANN as shown in this study can be adaptively adjusted for any other EOR project, and in particular, since the models have demonstrated their flexible capacity for economic analyses, the method can be promisingly developed to engage with other economic tools on comprehensively assessing the project. Full article

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13 pages, 2173 KiB

Open AccessArticle

An Improved Droop Control Method for Multi-Terminal VSC-HVDC Converter Stations

by Hao Wang^1,2, Yue Wang¹, Guozhao Duan¹, Weihao Hu^2,*, Wenti Wang¹ and Zhe Chen²

¹ Power Electronics & Renewable Energy Research Center, Xi’an Jiaotong University, No. 28, Xianning West Road, Xi’an 710049, China

² Department of Energy Technology, Aalborg University, Pontoppidanstraede 101, Aalborg DK-9220, Denmark

Energies 2017, 10(7), 843; https://doi.org/10.3390/en10070843 - 23 Jun 2017

Cited by 16 | Viewed by 4991

Abstract

Multi-terminal high voltage direct current transmission based on voltage source converter (VSC-HVDC) grids can connect non-synchronous alternating current (AC) grids to a hybrid alternating current and direct current (AC/DC) power system, which is one of the key technologies in the construction of smart [...] Read more.

Multi-terminal high voltage direct current transmission based on voltage source converter (VSC-HVDC) grids can connect non-synchronous alternating current (AC) grids to a hybrid alternating current and direct current (AC/DC) power system, which is one of the key technologies in the construction of smart grids. However, it is still a problem to control the converter to achieve the function of each AC system sharing the reserve capacity of the entire network. This paper proposes an improved control strategy based on the slope control of the DC voltage and AC frequency (V–f slope control), in which the virtual inertia is introduced. This method can ensure that each AC sub-system shares the primary frequency control function. Additionally, with the new control method, it is easy to apply the secondary frequency control method of traditional AC systems to AC/DC hybrid systems to achieve the steady control of the DC voltage and AC frequency of the whole system. Most importantly, the new control method is better than the traditional control method in terms of dynamic performance. In this paper, a new control method is proposed, and the simulation model has been established in Matlab/Simulink to verify the effectiveness of the proposed control method. Full article

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

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19 pages, 13895 KiB

Open AccessArticle

Prediction of Polymer Flooding Performance with an Artificial Neural Network: A Two-Polymer-Slug Case

by Jestril Ebaga-Ololo

and Bo Hyun Chon^*

Department of Energy Resources Engineering, Inha University, Incheon 402-751, Korea

Energies 2017, 10(7), 844; https://doi.org/10.3390/en10070844 - 1 Jul 2017

Cited by 28 | Viewed by 5172

Abstract

Many previous contributions to methods of forecasting the performance of polymer flooding using artificial neural networks (ANNs) have been made by numerous researchers previously. In most of those forecasting cases, only a single polymer slug was employed to meet the objective of the [...] Read more.

Many previous contributions to methods of forecasting the performance of polymer flooding using artificial neural networks (ANNs) have been made by numerous researchers previously. In most of those forecasting cases, only a single polymer slug was employed to meet the objective of the study. The intent of this manuscript is to propose an efficient recovery factor prediction tool at different injection stages of two polymer slugs during polymer flooding using an ANN. In this regard, a back-propagation algorithm was coupled with six input parameters to predict three output parameters via a hidden layer composed of 10 neurons. Evaluation of the ANN model performance was made with multiple linear regression. With an acceptable correlation coefficient, the proposed ANN tool was able to predict the recovery factor with errors of <1%. In addition, to understand the influence of each parameter on the output parameters, a sensitivity analysis was applied to the input parameters. The results showed less impact from the second polymer concentration, owing to changes in permeability after the injection of the first polymer slug. Full article

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20 pages, 10424 KiB

Open AccessArticle

Performance Evaluation of a Modular Design of Wind Tower with Wetted Surfaces

by Sajad M.R. Khani¹, Mehdi N. Bahadori², Alireza Dehghani-Sanij^3,*

and Ahmad Nourbakhsh⁴

¹ Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, QC H3G 1M8, Canada

² School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran

³ Department of Mechanical Engineering, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada

⁴ Hydraulic Machinery Research Institute, Department of Mechanical Engineering, University of Tehran, Tehran, Iran

Energies 2017, 10(7), 845; https://doi.org/10.3390/en10070845 - 25 Jun 2017

Cited by 19 | Viewed by 7204

Abstract

Wind towers or wind catchers, as passive cooling systems, can provide natural ventilation in buildings located in hot, arid regions. These natural cooling systems can provide thermal comfort for the building inhabitants throughout the warm months. In this paper, a modular design of [...] Read more.

Wind towers or wind catchers, as passive cooling systems, can provide natural ventilation in buildings located in hot, arid regions. These natural cooling systems can provide thermal comfort for the building inhabitants throughout the warm months. In this paper, a modular design of a wind tower is introduced. The design, called a modular wind tower with wetted surfaces, was investigated experimentally and analytically. To determine the performance of the wind tower, air temperature, relative humidity (RH) and air velocity were measured at different points. Measurements were carried out when the wind speed was zero. The experimental results were compared with the analytical ones. The results illustrated that the modular wind tower can decrease the air temperature significantly and increase the relative humidity of airflow into the building. The average differences for air temperature and air relative humidity between ambient air and air exiting from the wind tower were approximately 10 °C and 40%, respectively. The main advantage of the proposed wind tower is that it is a modular design that can reduce the cost of wind tower construction. Full article

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11 pages, 4000 KiB

Open AccessArticle

Cross-Regulation Assessment of DIDO Buck-Boost Converter for Renewable Energy Application

by Deepak Elamalayil Soman^*

and Mats Leijon

Division of Electricity, Department of Engineering Sciences, Angstrom Laboratory, Box: 534, Uppsala University, SE-75121 Uppsala, Sweden

Energies 2017, 10(7), 846; https://doi.org/10.3390/en10070846 - 25 Jun 2017

Cited by 6 | Viewed by 5269

Abstract

When medium- or high-voltage power conversion is preferred for renewable energy sources, multilevel power converters have received much of the interest in this area as methods for enhancing the conversion efficiency and cost effectiveness. In such cases, multilevel, multi-input multi-output (MIMO) configurations of [...] Read more.

When medium- or high-voltage power conversion is preferred for renewable energy sources, multilevel power converters have received much of the interest in this area as methods for enhancing the conversion efficiency and cost effectiveness. In such cases, multilevel, multi-input multi-output (MIMO) configurations of DC-DC converters come to the scenario for integrating several sources together, especially considering the stringent regulatory needs and the requirement of multistage power conversion systems. Considering the above facts, a three-level dual input dual output (DIDO) buck-boost converter, as the simplest form of MIMO converter, is proposed in this paper for DC-link voltage regulation. The capability of this converter for cross regulating the DC-link voltage is analyzed in detail to support a three-level neutral point clamped inverter-based grid connection in the future. The cross-regulation capability is examined under a new type of pulse delay control (PDC) strategy and later compared with a three-level boost converter (TLBC). Compared to conventional boost converters, the high-voltage three-level buck boost converter (TLBBC) with PDC exhibits a wide controllability range and cross regulation capability. These enhanced features are extremely important for better regulating variable output renewable energy sources such as solar, wind, wave, marine current, etc. The simulation and experimental results are provided to validate the claim. Full article

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

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15 pages, 1250 KiB

Open AccessArticle

Potential of Livestock Generated Biomass: Untapped Energy Source in India

by Gagandeep Kaur^1,*, Yadwinder Singh Brar¹ and D.P. Kothari²

¹ I. K. Gujral Punjab Technical University, 144603 Punjab, India

² Ex-Vice Chancellor, VIT, Vellore, 632014 Tamil Nadu, India

Energies 2017, 10(7), 847; https://doi.org/10.3390/en10070847 - 25 Jun 2017

Cited by 53 | Viewed by 11800

Abstract

Modern economies run on the backbone of electricity as one of major factors behind industrial development. India is endowed with plenty of natural resources and the majority of electricity within the country is generated from thermal and hydro-electric plants. A few nuclear plants [...] Read more.

Modern economies run on the backbone of electricity as one of major factors behind industrial development. India is endowed with plenty of natural resources and the majority of electricity within the country is generated from thermal and hydro-electric plants. A few nuclear plants assist in meeting the national requirements for electricity but still many rural areas remain uncovered. As India is primarily a rural agrarian economy, providing electricity to the remote, undeveloped regions of the country remains a top priority of the government. A vital, untapped source is livestock generated biomass which to some extent has been utilized to generate electricity in small scale biogas based plants under the government's thrust on rural development. This study is a preliminary attempt to correlate developments in this arena in the Asian region, as well as the developed world, to explore the possibilities of harnessing this resource in a better manner. The current potential of 2600 million tons of livestock dung generated per year, capable of yielding 263,702 million m³ of biogas is exploited. Our estimates suggest that if this resource is utilized judiciously, it possesses the potential of generating 477 TWh (Terawatt hour) of electrical energy per annum. Full article

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

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31 pages, 10759 KiB

Open AccessArticle

Optimization of a Solar-Driven Trigeneration System with Nanofluid-Based Parabolic Trough Collectors

by Evangelos Bellos^*

and Christos Tzivanidis

Solar Energy Laboratory, Thermal Department, School of Mechanical Engineering, National Technical University of Athens, Zografou, Heroon Polytechniou 9, Athens 15780, Greece

Energies 2017, 10(7), 848; https://doi.org/10.3390/en10070848 - 25 Jun 2017

Cited by 67 | Viewed by 5769

Abstract

The objective of this work was to optimize and to evaluate a solar-driven trigeneration system which operates with nanofluid-based parabolic trough collectors. The trigeneration system includes an organic Rankine cycle (ORC) and an absorption heat pump operating with LiBr-H₂O which is [...] Read more.

The objective of this work was to optimize and to evaluate a solar-driven trigeneration system which operates with nanofluid-based parabolic trough collectors. The trigeneration system includes an organic Rankine cycle (ORC) and an absorption heat pump operating with LiBr-H₂O which is powered by the rejected heat of the ORC. Toluene, n-octane, Octamethyltrisiloxane (MDM) and cyclohexane are the examined working fluids in the ORC. The use of CuO and Al₂O₃ nanoparticles in the Syltherm 800 (base fluid) is investigated in the solar field loop. The analysis is performed with Engineering Equation Solver (EES) under steady state conditions in order to give the emphasis in the exergetic optimization of the system. Except for the different working fluid investigation, the system is optimized by examining three basic operating parameters in all the cases. The pressure in the turbine inlet, the temperature in the ORC condenser and the nanofluid concentration are the optimization variables. According to the final results, the combination of toluene in the ORC with the CuO nanofluid is the optimum choice. The global maximum exergetic efficiency is 24.66% with pressure ratio is equal to 0.7605, heat rejection temperature 113.7 °C and CuO concentration 4.35%. Full article

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22 pages, 8568 KiB

Open AccessArticle

Parametric Analysis of Design Parameter Effects on the Performance of a Solar Desiccant Evaporative Cooling System in Brisbane, Australia

by Yunlong Ma¹

, Suvash C. Saha^1,*

, Wendy Miller¹

and Lisa Guan²

¹ School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia

² Faculty of Design, Architecture & Building, University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW 2007, Australia

Energies 2017, 10(7), 849; https://doi.org/10.3390/en10070849 - 25 Jun 2017

Cited by 17 | Viewed by 5934

Abstract

Solar desiccant cooling is widely considered as an attractive replacement for conventional vapor compression air conditioning systems because of its environmental friendliness and energy efficiency advantages. The system performance of solar desiccant cooling strongly depends on the input parameters associated with the system [...] Read more.

Solar desiccant cooling is widely considered as an attractive replacement for conventional vapor compression air conditioning systems because of its environmental friendliness and energy efficiency advantages. The system performance of solar desiccant cooling strongly depends on the input parameters associated with the system components, such as the solar collector, storage tank and backup heater, etc. In order to understand the implications of different design parameters on the system performance, this study has conducted a parametric analysis on the solar collector area, storage tank volume, and backup heater capacity of a solid solar desiccant cooling system for an office building in Brisbane, Australia climate. In addition, a parametric analysis on the outdoor air humidity ratio control set-point which triggers the operation of the desiccant wheel has also been investigated. The simulation results have shown that either increasing the storage tank volume or increasing solar collector area would result in both increased solar fraction (SF) and system coefficient of performance (COP), while at the same time reduce the backup heater energy consumption. However, the storage tank volume is more sensitive to the system performance than the collector area. From the economic aspect, a storage capacity of 30 m³/576 m² has the lowest life cycle cost (LCC) of $405,954 for the solar subsystem. In addition, 100 kW backup heater capacity is preferable for the satisfaction of the design regeneration heating coil hot water inlet temperature set-point with relatively low backup heater energy consumption. Moreover, an outdoor air humidity ratio control set-point of 0.008 kgWater/kgDryAir is more reasonable, as it could both guarantee the indoor design conditions and achieve low backup heater energy consumption. Full article

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

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12 pages, 3214 KiB

Open AccessArticle

Characterization and Production of Fuel Briquettes Made from Biomass and Plastic Wastes

by Maria Angeles Garrido

, Juan A. Conesa^*

and Maria Dolores Garcia

Department of Chemical Engineering, University of Alicante, P.O. Box 99, E-03080 Alicante, Spain

Energies 2017, 10(7), 850; https://doi.org/10.3390/en10070850 - 26 Jun 2017

Cited by 47 | Viewed by 8150

Abstract

In this study, the physical properties of briquettes produced from two different biomass feedstocks (sawdust and date palm trunk) and different plastic wastes, without using any external binding agent, were investigated. The biomass feedstocks were blended with different ratios of two waste from [...] Read more.

In this study, the physical properties of briquettes produced from two different biomass feedstocks (sawdust and date palm trunk) and different plastic wastes, without using any external binding agent, were investigated. The biomass feedstocks were blended with different ratios of two waste from electrical and electronic equipment (WEEE) plastics (halogen-free wire and printed circuit boards (PCBs)) and automotive shredder residues (ASR). The briquettes production is studied at different waste proportions (10–30%), pressures (22–67 MPa) and temperatures (room–130 °C). Physical properties as density and durability rating were measured, usually increasing with temperature. Palm trunk gave better results than sawdust in most cases, due to its moisture content and the extremely fine particles that are easily obtained. Full article

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

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15 pages, 2730 KiB

Open AccessConference Report

Hybrid, Multi-Megawatt HVDC Transformer Topology Comparison for Future Offshore Wind Farms

by Michael Smailes^1,*

, Chong Ng¹, Paul Mckeever¹, Jonathan Shek², Gerasimos Theotokatos³

and Mohammad Abusara⁴

¹ Research and Disruptive Innovation, Offshore Renewable Energy Catapult (ORE Catapult), Blyth NE24 1LZ, UK

² Institute for Energy Systems, Edinburgh University, Edinburgh EH8 9YL, UK

³ Naval Architecture, Ocean & Marine, Strathclyde University, Glasgow G1 1XW, UK

⁴ Renewable Energy, Exeter University, Exeter EX4 4SB, UK

Energies 2017, 10(7), 851; https://doi.org/10.3390/en10070851 - 27 Jun 2017

Cited by 8 | Viewed by 5278

Abstract

With the wind industry moving further offshore, High Voltage Direct Current (HVDC) transmission is becoming increasingly popular. HVDC transformer substations are not optimized for the offshore industry though, increasing costs and reducing redundancy. A suggested medium frequency, modular hybrid HVDC transformer located within [...] Read more.

With the wind industry moving further offshore, High Voltage Direct Current (HVDC) transmission is becoming increasingly popular. HVDC transformer substations are not optimized for the offshore industry though, increasing costs and reducing redundancy. A suggested medium frequency, modular hybrid HVDC transformer located within each wind turbine nacelle could mitigate these problems, but the overall design must be considered carefully to minimize losses. This paper’s contribution is a detailed analysis of the hybrid transformer, using practical design considerations including component library minimization. The configurations investigated include combinations of single phase H-Bridge and Modular Multilevel Converter topologies operating under minimum switching frequency control strategies. These were modelled in the MATLAB/Simulink environment. The impact of the minimum switching control strategy and converter topology on power transfer stability and overall efficiency is then investigated. It was found that the H-Bridge converter generated the lowest overall losses, but there was a trade off with power flow sensitivity due in part to the additional harmonics generated. Full article

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

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17 pages, 16605 KiB

Open AccessArticle

A Data-Driven, Cooperative Approach for Wind Farm Control: A Wind Tunnel Experimentation

by Jinkyoo Park^1,*, Soon-Duck Kwon² and Kincho Law³

¹ Department of Industrial and Systems Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea

² Department of Civil Engineering, Chonbuk National University, Jeonju 5896, Korea

³ Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA

Energies 2017, 10(7), 852; https://doi.org/10.3390/en10070852 - 27 Jun 2017

Cited by 16 | Viewed by 4250

Abstract

This paper discusses a data-driven, cooperative control strategy to maximize wind farm power production. Conventionally, every wind turbine in a wind farm is operated to maximize its own power production without taking into account the interactions between the wind turbines in a wind [...] Read more.

This paper discusses a data-driven, cooperative control strategy to maximize wind farm power production. Conventionally, every wind turbine in a wind farm is operated to maximize its own power production without taking into account the interactions between the wind turbines in a wind farm. Because of wake interference, such greedy control strategy can significantly lower the power production of the downstream wind turbines and, thus, reduce the overall wind farm power production. As an alternative to the greedy control strategy, we study a cooperative wind farm control strategy that determines and executes the optimum coordinated control actions for maximizing the total wind farm power production. To determine the optimum coordinated control actions of the wind turbines, we employ a data-driven optimization method that seeks to find the optimum control actions using only the power measurement data collected from the wind turbines in a wind farm. In particular, we employ the Bayesian Ascent (BA) algorithm, a probabilistic optimization method constructed based on Gaussian Process regression and the trust region concept. Wind tunnel experiments using 6 scaled wind turbine models are conducted to assess (1) the effectiveness of the cooperative control strategy in improving the power production; and (2) the efficiency of the BA algorithm in determining the optimum control actions of the wind turbines using only the input control actions and the output power measurement data. Full article

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

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18 pages, 1279 KiB

Open AccessArticle

Screening of Available Tools for Dynamic Mooring Analysis of Wave Energy Converters

by Jonas Bjerg Thomsen^*

, Francesco Ferri

and Jens Peter Kofoed

Department of Civil Engineering, Aalborg University, Thomas Manns Vej 23, Aalborg Ø 9220, Denmark

Energies 2017, 10(7), 853; https://doi.org/10.3390/en10070853 - 27 Jun 2017

Cited by 18 | Viewed by 6338

Abstract

The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which mooring [...] Read more.

The focus on alternative energy sources has increased significantly throughout the last few decades, leading to a considerable development in the wave energy sector. In spite of this, the sector cannot yet be considered commercialized, and many challenges still exist, in which mooring of floating wave energy converters is included. Different methods for assessment and design of mooring systems have been described by now, covering simple quasi-static analysis and more advanced and sophisticated dynamic analysis. Design standards for mooring systems already exist, and new ones are being developed specifically forwave energy converter moorings, which results in other requirements to the chosen tools, since these often have been aimed at other offshore sectors. The present analysis assesses a number of relevant commercial software packages for full dynamic mooring analysis in order to highlight the advantages and drawbacks. The focus of the assessment is to ensure that the software packages are capable of fulfilling the requirements of modeling, as defined in design standards and thereby ensuring that the analysis can be used to get a certified mooring system. Based on the initial assessment, the two software packages DeepC and OrcaFlex are found to best suit the requirements. They are therefore used in a case study in order to evaluate motion and mooring load response, and the results are compared in order to provide guidelines for which software package to choose. In the present study, the OrcaFlex code was found to satisfy all requirements. Full article

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24 pages, 6579 KiB

Open AccessFeature PaperArticle

Influence of High Pressure and Temperature on the Mechanical Behavior and Permeability of a Fractured Coal

by Hossein Akbarzadeh Kasani^*

and Richard J. Chalaturnyk

Department of Civil and Environmental Engineering, University of Alberta, 9211-116 Street NW, Edmonton, AB T6G 1H9, Canada

Energies 2017, 10(7), 854; https://doi.org/10.3390/en10070854 - 27 Jun 2017

Cited by 12 | Viewed by 5526

Abstract

Understanding mechanical behavior and permeability of coal at ambient and high temperature is key in optimizing high-temperature in-situ processes such as underground coal gasification. The main objectives of this study were to characterize thermal deformation, stress-strain behavior, and gas permeability of coal samples [...] Read more.

Understanding mechanical behavior and permeability of coal at ambient and high temperature is key in optimizing high-temperature in-situ processes such as underground coal gasification. The main objectives of this study were to characterize thermal deformation, stress-strain behavior, and gas permeability of coal samples acquired from the Genesee coal mine in Central Alberta, Canada under various temperatures and confining stresses. These measurements were conducted in a high-pressure high-temperature triaxial apparatus. Initial thermal expansion of the coal was followed by contraction in both axial and lateral directions at about 140 °C. This temperature corresponds to occurrence of pyrolysis in the coal. All specimens showed brittle behavior during shear while forming complex shear planes. The specimens exhibited compressional volumetric strain responses at all temperatures. Deformation localization initiated at various stage during shearing. Specimens sheared at 200 °C showed higher peak stresses and larger axial strains compared to those tested at room temperature (24 °C). Fluctuations of permeability were observed with confining stress and temperature. Permeability dropped at 80 °C due to thermal expansion of coal and closure of initial fractures; however, it increased at 140 and 200 °C due to a combined response of thermal expansion and pyrolysis. Small axial strain during shear was observed to reduce permeability. Full article

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

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13 pages, 1982 KiB

Open AccessArticle

Experimental Investigation on CO₂ Methanation Process for Solar Energy Storage Compared to CO₂-Based Methanol Synthesis

by Beatrice Castellani^1,*

, Alberto Maria Gambelli¹, Elena Morini¹

, Benedetto Nastasi²

, Andrea Presciutti¹

, Mirko Filipponi¹

, Andrea Nicolini¹

and Federico Rossi¹

¹ Engineering Department, University of Perugia, CIRIAF, Via G. Duranti 67, 06125 Perugia, Italy

² Department of Architectural Engineering & Technology, Environmental & Computational Design Section, TU Delft University of Technology, Julianalaan 134, 2628 BL Delft, The Netherlands

Energies 2017, 10(7), 855; https://doi.org/10.3390/en10070855 - 27 Jun 2017

Cited by 63 | Viewed by 9642

Abstract

The utilization of the captured CO₂ as a carbon source for the production of energy storage media offers a technological solution for overcoming crucial issues in current energy systems. Solar energy production generally does not match with energy demand because of its [...] Read more.

The utilization of the captured CO₂ as a carbon source for the production of energy storage media offers a technological solution for overcoming crucial issues in current energy systems. Solar energy production generally does not match with energy demand because of its intermittent and non-programmable nature, entailing the adoption of storage technologies. Hydrogen constitutes a chemical storage for renewable electricity if it is produced by water electrolysis and is also the key reactant for CO₂ methanation (Sabatier reaction). The utilization of CO₂ as a feedstock for producing methane contributes to alleviate global climate changes and sequestration related problems. The produced methane is a carbon neutral gas that fits into existing infrastructure and allows issues related to the aforementioned intermittency and non-programmability of solar energy to be overcome. In this paper, an experimental apparatus, composed of an electrolyzer and a tubular fixed bed reactor, is built and used to produce methane via Sabatier reaction. The objective of the experimental campaign is the evaluation of the process performance and a comparison with other CO₂ valorization paths such as methanol production. The investigated pressure range was 2–20 bar, obtaining a methane volume fraction in outlet gaseous mixture of 64.75% at 8 bar and 97.24% at 20 bar, with conversion efficiencies of, respectively, 84.64% and 99.06%. The methanol and methane processes were compared on the basis of an energy parameter defined as the spent energy/stored energy. It is higher for the methanol process (0.45), with respect to the methane production process (0.41–0.43), which has a higher energy storage capability. Full article

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

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17 pages, 3543 KiB

Open AccessReview

Review of Reactive Power Dispatch Strategies for Loss Minimization in a DFIG-based Wind Farm

by Baohua Zhang¹, Weihao Hu^1,*, Peng Hou¹, Jin Tan², Mohsen Soltani¹ and Zhe Chen¹

¹ Department of Energy Technology, Aalborg University, Aalborg 9220, Denmark

² National Renewable Energy Laboratory, Golden, CO 80401, USA

Energies 2017, 10(7), 856; https://doi.org/10.3390/en10070856 - 27 Jun 2017

Cited by 16 | Viewed by 6281

Abstract

This paper reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive [...] Read more.

This paper reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive power control strategies are investigated. All of the combined strategies are formulated based on the comprehensive loss models of WFs, including the loss models of DFIGs, converters, filters, transformers, and cables of the collection system. Optimization problems are solved by a Modified Particle Swarm Optimization (MPSO) algorithm. The effectiveness of these strategies is evaluated by simulations on a carefully designed WF under a series of cases with different wind speeds and reactive power requirements of the WF. The wind speed at each WT inside the WF is calculated using the Jensen wake model. The results show that the best reactive power dispatch strategy for loss minimization comes when the WF level strategy and WT level control are coordinated and the losses from each device in the WF are considered in the objective. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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16 pages, 4826 KiB

Open AccessArticle

Next Generation Real-Time Smart Meters for ICT Based Assessment of Grid Data Inconsistencies

by Mihai Sanduleac^1,6,*, Gianluca Lipari²

, Antonello Monti², Artemis Voulkidis³, Gianluca Zanetto⁴, Antonello Corsi⁵, Lucian Toma⁶, Giampaolo Fiorentino⁵ and Dumitru Federenciuc⁷

¹ Romanian Energy Center, 011838 Bucharest, Romania

² Rheinisch-Westfälische Technische Hochschule Aachen—RWTH, 52062 Aachen, Germany

³ Synelixis, GR-34100 Chalkida, Greece

⁴ R&D Department, Teamware, 20128 Milan, Italy

⁵ Engineering Ingegneria Informatica S.p.A, Engineering, 00148 Rome, Italy

⁶ Department of Electrical Power Systems, University Politehnica of Bucharest, 060042 Bucharest, Romania

⁷ Department of Strategy, Electrica, 010621 Bucharest, Romania

Energies 2017, 10(7), 857; https://doi.org/10.3390/en10070857 - 27 Jun 2017

Cited by 30 | Viewed by 6779

Abstract

The latest technological developments are challenging for finding new solutions to mitigate the massive integration of renewable-based electricity generation in the electrical networks and to support new and dynamic energy and ancillary services markets. Smart meters have become ubiquitous equipment in the low [...] Read more.

The latest technological developments are challenging for finding new solutions to mitigate the massive integration of renewable-based electricity generation in the electrical networks and to support new and dynamic energy and ancillary services markets. Smart meters have become ubiquitous equipment in the low voltage grid, enabled by the decision made in many countries to support massive deployments. The smart meter is the only equipment mandatory to be mounted when supplying a grid connected user, as it primarily has the function to measure delivered and/or produced energy on its common coupling point with the network, as technical and legal support for billing. Active distribution networks need new functionalities, to cope with the bidirectional energy flow behaviour of the grid, and many smart grid requirements need to be implemented in the near future. However there is no real coupling between smart metering systems and smart grids, as there is not yet a synergy using the opportunity of the high deployment level in smart metering. The paper presents a new approach for managing the smart metering and smart grid orchestration by presenting a new general design based on an unbundled smart meter (USM) concept, labelled as next generation open real-time smart meters (NORM), for integrating the smart meter, phasor measurement unit (PMU) and cyber-security through an enhanced smart metering gateway (SMG). NORM is intended to be deployed everywhere at the prosumer’s interface to the grid, as it is usually now done with the standard meter. Furthermore, rich data acquired from NORM is used to demonstrate the potential of assessing grid data inconsistencies at a higher level, as function to be deployed in distribution security monitoring centers, to address the higher level cyber-security threats, such as false data injections and to allow secure grid operations and complex market activities at the same time. The measures are considering only non-sensitive data from a privacy perspective, and is therefore able to be applied everywhere in the grid, down to the end-customer level, where a citizen’s personal data protection is an important aspect. Full article

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

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20 pages, 1989 KiB

Open AccessArticle

Bandwidth and Accuracy-Aware State Estimation for Smart Grids Using Software Defined Networks

by Alessio Meloni^*

, Paolo Attilio Pegoraro

, Luigi Atzori

and Sara Sulis

DIEE - Department of Electrical and Electronic Engineering, University of Cagliari, Piazza D’Armi, 09123 Cagliari, Italy

Energies 2017, 10(7), 858; https://doi.org/10.3390/en10070858 - 27 Jun 2017

Cited by 7 | Viewed by 5230

Abstract

Smart grid (SG) will be one of the major application domains that will present severe pressures on future communication networks due to the expected huge number of devices that will be connected to it and that will impose stringent quality transmission requirements. To [...] Read more.

Smart grid (SG) will be one of the major application domains that will present severe pressures on future communication networks due to the expected huge number of devices that will be connected to it and that will impose stringent quality transmission requirements. To address this challenge, there is a need for a joint management of both monitoring and communication systems, so as to achieve a flexible and adaptive management of the SG services. This is the issue addressed in this paper, which provides the following major contributions. We define a new strategy to optimize the accuracy of the state estimation (SE) of the electric grid based on available network bandwidth resources and the sensing intelligent electronic devices (IEDs) installed in the field. In particular, we focus on phasor measurement units (PMUs) as measurement devices. We propose the use of the software defined networks (SDN) technologies to manage the available network bandwidth, which is then assigned by the controller to the forwarding devices to allow for the flowing of the data streams generated by the PMUs, by considering an optimization routine to maximize the accuracy of the resulting SE. Additionally, the use of SDN allows for adding and removing PMUs from the monitoring architecture without any manual intervention. We also provide the details of our implementation of the SDN solution, which is used to make simulations with an IEEE 14-bus test network in order to show performance in terms of bandwidth management and estimation accuracy. Full article

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

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12 pages, 4923 KiB

Open AccessArticle

Integration of the Production Logging Tool and Production Data for Post-Fracturing Evaluation by the Ensemble Smoother

by Seungpil Jung

E&P Business Division, SK Innovation, Seoul 03188, Korea

Energies 2017, 10(7), 859; https://doi.org/10.3390/en10070859 - 27 Jun 2017

Cited by 4 | Viewed by 4497

Abstract

A post-fracturing evaluation is essential to optimize a fracturing design for a multi-stage fractured well located in unconventional reservoirs. To accomplish this task, a production logging tool (PLT) can be utilized to provide the oil production rate of each fracturing stage. In this [...] Read more.

A post-fracturing evaluation is essential to optimize a fracturing design for a multi-stage fractured well located in unconventional reservoirs. To accomplish this task, a production logging tool (PLT) can be utilized to provide the oil production rate of each fracturing stage. In this research, a practical method is proposed to integrate PLT and surface production data into a reservoir model. It applies the ensemble smoother for history-matching to integrate various kinds of dynamic data. To investigate the validity of the proposed method, three cases are designed according to the frequency of PLT surveys. Each fracture half-length calibrated by PLT data is similar to the true value, and the dynamic behavior also has the same trend as true production behavior. Integration with PLT data can reduce error ratios for fracture half-length down to 48%. In addition, it presents the applicability of reserve prediction and uncertainty assessment. It has been proven that the more frequently PLTs are surveyed, the more accurate the results. By sensitivity analysis of PLT frequency—a cost-effective strategy—a combination of only one PLT survey and continuous surface production data is employed to demonstrate this proposed concept. Full article

(This article belongs to the Special Issue Oil and Gas Engineering)

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15 pages, 1564 KiB

Open AccessEditor’s ChoiceArticle

Site-Dependent Environmental Impacts of Industrial Hydrogen Production by Alkaline Water Electrolysis

by Jan Christian Koj^*

, Christina Wulf

, Andrea Schreiber and Petra Zapp

Forschungszentrum Jülich, Institute of Energy and Climate Research–Systems Analysis and Technology Evaluation (IEK-STE), D-52425 Jülich, Germany

Energies 2017, 10(7), 860; https://doi.org/10.3390/en10070860 - 28 Jun 2017

Cited by 120 | Viewed by 18153

Abstract

Industrial hydrogen production via alkaline water electrolysis (AEL) is a mature hydrogen production method. One argument in favor of AEL when supplied with renewable energy is its environmental superiority against conventional fossil-based hydrogen production. However, today electricity from the national grid is widely [...] Read more.

Industrial hydrogen production via alkaline water electrolysis (AEL) is a mature hydrogen production method. One argument in favor of AEL when supplied with renewable energy is its environmental superiority against conventional fossil-based hydrogen production. However, today electricity from the national grid is widely utilized for industrial applications of AEL. Also, the ban on asbestos membranes led to a change in performance patterns, making a detailed assessment necessary. This study presents a comparative Life Cycle Assessment (LCA) using the GaBi software (version 6.115, thinkstep, Leinfelden-Echterdingen, Germany), revealing inventory data and environmental impacts for industrial hydrogen production by latest AELs (6 MW, Zirfon membranes) in three different countries (Austria, Germany and Spain) with corresponding grid mixes. The results confirm the dependence of most environmental effects from the operation phase and specifically the site-dependent electricity mix. Construction of system components and the replacement of cell stacks make a minor contribution. At present, considering the three countries, AEL can be operated in the most environmentally friendly fashion in Austria. Concerning the construction of AEL plants the materials nickel and polytetrafluoroethylene in particular, used for cell manufacturing, revealed significant contributions to the environmental burden. Full article

(This article belongs to the Special Issue Environmental Impact Assessment of Energy Technologies)

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15 pages, 1244 KiB

Open AccessArticle

Do We Need Gas as a Bridging Fuel? A Case Study of the Electricity System of Switzerland

by Paula Díaz^*, Oscar Van Vliet and Anthony Patt

Climate Policy Group, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 22, 8092 Zurich, Switzerland

Energies 2017, 10(7), 861; https://doi.org/10.3390/en10070861 - 28 Jun 2017

Cited by 20 | Viewed by 6011

Abstract

Many future electricity scenarios, including those from the International Energy Agency, use natural gas to bridge the transition to renewables, in particular as a means of balancing intermittent generation from new renewables. Given that such strategies may be inconsistent with strategies to limit [...] Read more.

Many future electricity scenarios, including those from the International Energy Agency, use natural gas to bridge the transition to renewables, in particular as a means of balancing intermittent generation from new renewables. Given that such strategies may be inconsistent with strategies to limit climate change to below 2 °C, we address the question of whether such use of gas is necessary or cost effective. We conduct a techno-economic case study of Switzerland, using a cost optimization model. We explore a range of electricity costs, comparing scenarios in which gas is used as a source of base-load power, a source of balancing capacity, and not used at all. Costs at the high end of the range show that a complete decarbonization increases system-wide costs by 3% compared to a gas bridging scenario, and 13–46% compared to a carbon-intensive scenario, depending on the relative shares of solar and wind. Costs at the low end of the range show that system-wide costs are equal or lower for both completely decarbonized and gas bridging scenarios. In conclusion, gas delivers little to no cost savings as a bridging fuel in a system that switches to wind and solar. Full article

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

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23 pages, 2283 KiB

Open AccessArticle

Complementary Power Control for Doubly Fed Induction Generator-Based Tidal Stream Turbine Generation Plants

by Khaoula Ghefiri^1,2,*

, Soufiene Bouallègue¹, Izaskun Garrido², Aitor J. Garrido² and Joseph Haggège¹

¹ Laboratory of Research in Automatic Control—LA.R.A, National Engineering School of Tunis (ENIT), University of Tunis El Manar (UTM), BP 37, Le Belvédère, 1002 Tunis, Tunisia

² Automatic Control Group—ACG, Department of Automatic Control and Systems Engineering, Engineering School of Bilbao, University of the Basque Country (UPV/EHU), 48012 Bilbao, Spain

Energies 2017, 10(7), 862; https://doi.org/10.3390/en10070862 - 28 Jun 2017

Cited by 23 | Viewed by 5576

Abstract

The latest forecasts on the upcoming effects of climate change are leading to a change in the worldwide power production model, with governments promoting clean and renewable energies, as is the case of tidal energy. Nevertheless, it is still necessary to improve the [...] Read more.

The latest forecasts on the upcoming effects of climate change are leading to a change in the worldwide power production model, with governments promoting clean and renewable energies, as is the case of tidal energy. Nevertheless, it is still necessary to improve the efficiency and lower the costs of the involved processes in order to achieve a Levelized Cost of Energy (LCoE) that allows these devices to be commercially competitive. In this context, this paper presents a novel complementary control strategy aimed to maximize the output power of a Tidal Stream Turbine (TST) composed of a hydrodynamic turbine, a Doubly-Fed Induction Generator (DFIG) and a back-to-back power converter. In particular, a global control scheme that supervises the switching between the two operation modes is developed and implemented. When the tidal speed is low enough, the plant operates in variable speed mode, where the system is regulated so that the turbo-generator module works in maximum power extraction mode for each given tidal velocity. For this purpose, the proposed back-to-back converter makes use of the field-oriented control in both the rotor side and grid side converters, so that a maximum power point tracking-based rotational speed control is applied in the Rotor Side Converter (RSC) to obtain the maximum power output. Analogously, when the system operates in power limitation mode, a pitch angle control is used to limit the power captured in the case of high tidal speeds. Both control schemes are then coordinated within a novel complementary control strategy. The results show an excellent performance of the system, affording maximum power extraction regardless of the tidal stream input. Full article

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

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18 pages, 9519 KiB

Open AccessConcept Paper

Offset Voltage Control Scheme for Modular Multilevel Converter Operated in Nearest Level Control

by Jae-Hyuk Kim, Do-Hyun Kim and Byung-Moon Han^*

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

Energies 2017, 10(7), 863; https://doi.org/10.3390/en10070863 - 28 Jun 2017

Cited by 3 | Viewed by 3961

Abstract

This paper proposes an offset voltage control scheme for the modular multilevel converter (MMC) operated in nearest level control (NLC) to improve the total harmonic distortion (THD) of AC phase voltages. The offset (neutral-to-zero-point) voltage is adjusted so that the magnitude of each [...] Read more.

This paper proposes an offset voltage control scheme for the modular multilevel converter (MMC) operated in nearest level control (NLC) to improve the total harmonic distortion (THD) of AC phase voltages. The offset (neutral-to-zero-point) voltage is adjusted so that the magnitude of each AC pole voltage maintains constant value with N + 1 level in the range of whole modulation index (MI). The validity of the proposed scheme was confirmed by computer simulations for the MMC with 22.9 kV/25 MVA and experimental works for the scaled MMC with 380 V/10 kVA. It was confirmed that the proposed control scheme can generate linearly variable AC phase voltages with improved THD in the over-modulation region as well as the normal-modulation region. Full article

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

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16 pages, 5223 KiB

Open AccessFeature PaperArticle

Numerical Modeling of Oxygen Carrier Performances (NiO/NiAl₂O₄) for Chemical-Looping Combustion

by Lucia Blas¹, Patrick Dutournié², Mejdi Jeguirim^2,*

, Ludovic Josien², David Chiche³, Stephane Bertholin³ and Arnold Lambert³

¹ LGRE, Laboratoire Gestion des Risques, Environnement 3 bis, rue Alfred Werner, 68093 Mulhouse, France

² IS2M, Institut de Sciences des Matériaux de Mulhouse, UMR 7361 CNRS, Université de Strasbourg, Université de Haute Alsace, 3 bis, rue Alfred Werner, 68098 Mulhouse CEDEX, France

³ IFP Energies Nouvelles, Rond-Point de l’échangeur de Solaize, BP 3, 69360 Solaize, France

Energies 2017, 10(7), 864; https://doi.org/10.3390/en10070864 - 28 Jun 2017

Cited by 9 | Viewed by 3491

Abstract

This work was devoted to study experimentally and numerically the oxygen carrier (NiO/NiAl₂O₄) performances for Chemical-Looping Combustion applications. Various kinetic models including Shrinking Core, Nucleation Growth and Modified Volumetric models were investigated in a one-dimensional approach to simulate the [...] Read more.

This work was devoted to study experimentally and numerically the oxygen carrier (NiO/NiAl₂O₄) performances for Chemical-Looping Combustion applications. Various kinetic models including Shrinking Core, Nucleation Growth and Modified Volumetric models were investigated in a one-dimensional approach to simulate the reactive mass transfer in a fixed bed reactor. The preliminary numerical results indicated that these models are unable to fit well the fuel breakthrough curves. Therefore, the oxygen carrier was characterized after several operations using Scanning Electronic Microscopy (SEM) coupled with equipped with an energy dispersive X-ray spectrometer (EDX). These analyses showed a layer rich in nickel on particle surface. Below this layer, to a depth of about 10 µm, the material was low in nickel, being the consequence of nickel migration. From these observations, two reactive sites were proposed relative to the layer rich in nickel (particle surface) and the bulk material, respectively. Then, a numerical model, taking into account of both reactive sites, was able to fit well fuel breakthrough curves for all the studied operating conditions. The extracted kinetic parameters showed that the fuel oxidation was fully controlled by the reaction and the effect of temperature was not significant in the tested operating conditions range. Full article

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19 pages, 2777 KiB

Open AccessArticle

A Chaotic Improved Artificial Bee Colony for Parameter Estimation of Photovoltaic Cells

by Diego Oliva^1,2,3,*, Ahmed A. Ewees^3,4, Mohamed Abd El Aziz^3,5,6, Aboul Ella Hassanien^3,7 and Marco Peréz-Cisneros¹

¹ Departamento de Ciencias Computacionales, Universidad de Guadalajara, CUCEI. Av. Revolución 1500, Guadalajara, 44430 Jalisco, Mexico

² Institute of Cybernetics, Tomsk Polytechnic University, 634050 Tomsk, Russia

³ Scientific Research Group in Egypt (SRGE), Cairo 12613, Egypt

⁴ Department of Computer, Damietta University, Damietta 34517, Egypt

⁵ School of Computer Science and Technology, Wuhan University of Technology, Wuhan 430070, China

⁶ Department of Mathematics, Faculty of Science, Zagazig University, Zagazig 44519, Egypt

⁷ Faculty of Computers Information, Cairo University, Cairo 12637, Egypt

Energies 2017, 10(7), 865; https://doi.org/10.3390/en10070865 - 28 Jun 2017

Cited by 107 | Viewed by 5462

Abstract

The search for new energy resources is a crucial task nowadays. Research on the use of solar energy is growing every year. The aim is the design of devices that can produce a considerable amount of energy using the Sun’s radiation. The modeling [...] Read more.

The search for new energy resources is a crucial task nowadays. Research on the use of solar energy is growing every year. The aim is the design of devices that can produce a considerable amount of energy using the Sun’s radiation. The modeling of solar cells (SCs) is based on the estimation of the intrinsic parameters of electrical circuits that simulate their behavior based on the current vs. voltage characteristics. The problem of SC design is defined by highly nonlinear and multimodal objective functions. Most of the algorithms proposed to find the best solutions become trapped into local solutions. This paper introduces the Chaotic Improved Artificial Bee Colony (CIABC) algorithm for the estimation of SC parameters. It combines the use of chaotic maps instead random variables with the search capabilities of the Artificial Bee Colony approach. CIABC has also been modified to avoid the generation of new random solutions, preserving the information of previous iterations. In comparison with similar optimization methods, CIABC is able to find the global solution of complex and multimodal objective functions. Experimental results and comparisons prove that the proposed technique can design SCs, even with the presence of noise. Full article

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26 pages, 479 KiB

Open AccessArticle

Data–Driven Fault Diagnosis of a Wind Farm Benchmark Model

by Silvio Simani^1,*

, Paolo Castaldi²

and Saverio Farsoni¹

¹ Dipartimento di Ingegneria, Università degli Studi di Ferrara, Via Saragat 1E, 44122 Ferrara (FE), Italy

² Dipartimento di Ingegneria dell’Energia Elettrica e dell’Informazione “Guglielmo Marconi”—DEI, Alma Mater Studiorum Università di Bologna, Viale Risorgimento 2, 40136 Bologna (BO), Italy

Energies 2017, 10(7), 866; https://doi.org/10.3390/en10070866 - 28 Jun 2017

Cited by 14 | Viewed by 5520

Abstract

The fault diagnosis of wind farms has been proven to be a challenging task, and motivates the research activities carried out through this work. Therefore, this paper deals with the fault diagnosis of a wind park benchmark model, and it considers viable solutions [...] Read more.

The fault diagnosis of wind farms has been proven to be a challenging task, and motivates the research activities carried out through this work. Therefore, this paper deals with the fault diagnosis of a wind park benchmark model, and it considers viable solutions to the problem of earlier fault detection and isolation. The design of the fault indicator involves data-driven approaches, as they can represent effective tools for coping with poor analytical knowledge of the system dynamics, noise, uncertainty, and disturbances. In particular, the proposed data-driven solutions rely on fuzzy models and neural networks that are used to describe the strongly nonlinear relationships between measurement and faults. The chosen architectures rely on nonlinear autoregressive with exogenous input models, as they can represent the dynamic evolution of the system over time. The developed fault diagnosis schemes are tested by means of a high-fidelity benchmark model that simulates the normal and the faulty behaviour of a wind farm installation. The achieved performances are also compared with those of a model-based approach relying on nonlinear differential geometry tools. Finally, a Monte-Carlo analysis validates the robustness and reliability of the proposed solutions against typical parameter uncertainties and disturbances. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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21 pages, 3379 KiB

Open AccessArticle

On a Long Term Strategy for the Success of Nuclear Power

by Bruno Merk^1,2,3,*, Dzianis Litskevich¹, Karl R. Whittle¹, Mark Bankhead², Richard J. Taylor⁴ and Dan Mathers²

¹ School of Engineering, University of Liverpool, Liverpool L69 3GH, UK

² National Nuclear Laboratory, Chadwick House, Warrington WA3 6AE, UK

³ Helmholtz-Zentrum Dresden—Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany

⁴ School of Mechanical Aerospace & Civil Engineering, The University of Manchester, Manchester M1 3BB, UK

Energies 2017, 10(7), 867; https://doi.org/10.3390/en10070867 - 28 Jun 2017

Cited by 24 | Viewed by 6129

Abstract

The current generation of nuclear reactors are evolutionary in design, mostly based on the technology originally designed to power submarines, and dominated by light water reactors. The aims of the Generation IV consortium are driven by sustainability, safety and reliability, economics, and proliferation [...] Read more.

The current generation of nuclear reactors are evolutionary in design, mostly based on the technology originally designed to power submarines, and dominated by light water reactors. The aims of the Generation IV consortium are driven by sustainability, safety and reliability, economics, and proliferation resistance. The aims are extended here to encompass the ultimate and universal vision for strategic development of energy production, the “perpetuum mobile”—at least as close as possible. We propose to rethink nuclear reactor design with the mission to develop an innovative system which uses no fresh resources and produces no fresh waste during operation as well as generates power safe and reliably in economic way. The results of the innovative simulations presented here demonstrate that, from a theoretical perspective, it is feasible to fulfil the mission through the direct reuse of spent nuclear fuel from currently operating reactors as the fuel for a proposed new reactor. The produced waste is less burdensome than current spent nuclear fuel which is used as feed to the system. However, safety, reliability and operational economics will need to be demonstrated to create the basis for the long term success of nuclear reactors as a major carbon free, sustainable, and applied highly reliable energy source. Full article

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

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27 pages, 2723 KiB

Open AccessFeature PaperArticle

A Stochastic Programming Approach for the Planning and Operation of a Power to Gas Energy Hub with Multiple Energy Recovery Pathways

by Ushnik Mukherjee¹

, Azadeh Maroufmashat¹, Apurva Narayan²

, Ali Elkamel¹ and Michael Fowler^1,*

¹ Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

² Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

Energies 2017, 10(7), 868; https://doi.org/10.3390/en10070868 - 28 Jun 2017

Cited by 32 | Viewed by 5237

Abstract

There is a need for energy storage to improve the efficiency and effectiveness of energy distribution with the increasing penetration of renewable energy sources. Among the various energy storage technologies being developed, ‘power-to-gas’ is one such concept which has gained interest due to [...] Read more.

There is a need for energy storage to improve the efficiency and effectiveness of energy distribution with the increasing penetration of renewable energy sources. Among the various energy storage technologies being developed, ‘power-to-gas’ is one such concept which has gained interest due to its ability to provide long term energy storage and recover the energy stored through different energy recovery pathways. Incorporation of such systems within the energy infrastructure requires analysis of the key factors influencing the operation of electrolyzers and hydrogen storage. This study focusses on assessing the benefits power-to-gas energy storage while accounting for uncertainty in the following three key parameters that could influence the operation of the energy system: (1) hourly electricity price; (2) the number of fuel cell vehicles serviced; and (3) the amount of hydrogen refueled. An hourly time index is adopted to analyze how the energy hub should operate under uncertainty. The results show that there is a potential economic benefit for the power-to-gas system if it is modeled using the two-stage stochastic programming approach in comparison to a deterministic optimization study. The power-to-gas system also offers environmental benefits both from the perspective of the producer and end user of hydrogen. Full article

(This article belongs to the Special Issue Energy Production Systems)

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27 pages, 3855 KiB

Open AccessArticle

Investigating a Small Oil-Flooded Twin-Screw Expander for Waste-Heat Utilisation in Organic Rankine Cycle Systems

by Alexander Nikolov^* and Andreas Brümmer

Chair of Fluidics, Faculty of Mechanical Engineering, TU Dortmund University, 44227 Dortmund, Germany

Energies 2017, 10(7), 869; https://doi.org/10.3390/en10070869 - 28 Jun 2017

Cited by 27 | Viewed by 6555

Abstract

Screw-type expanders offer excellent prospects for energy conversion in lower and medium power ranges, for instance as expansion engines in Rankine cycles with regard to either waste or geothermal heat recovery. With the aim of identifying the potential in organic Rankine cycle (ORC) [...] Read more.

Screw-type expanders offer excellent prospects for energy conversion in lower and medium power ranges, for instance as expansion engines in Rankine cycles with regard to either waste or geothermal heat recovery. With the aim of identifying the potential in organic Rankine cycle (ORC) power systems, an oil-flooded twin-screw expander without timing gears was designed and experimentally investigated in an ORC with R245fa as working fluid. Here, the scope for the experimental determination of the expander characteristic map was limited by the test rig specifications. Based on the experimental results, a multi-chamber model of the test twin-screw expander was calibrated and theoretical approaches according to mechanical and hydraulic loss calculation were applied. Consequently, the expander’s complete characteristic map could be calculated. Furthermore, relevant mechanisms influencing the operational behaviour of oil-flooded twin-screw expanders were identified and analysed in-depth. Full article

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23 pages, 9029 KiB

Open AccessArticle

Increased Wind Energy Yield and Grid Utilisation with Continuous Feed-In Management

by Clemens Jauch^*, Arne Gloe, Sebastian Hippel and Henning Thiesen

Wind Energy Technology Institute, Flensburg University of Applied Sciences, Kanzleistraße 91-93, Flensburg 24943, Germany

Energies 2017, 10(7), 870; https://doi.org/10.3390/en10070870 - 28 Jun 2017

Cited by 6 | Viewed by 4843

Abstract

This paper presents a study to assess how wind turbines could increase their energy yield when their grid connection point is not strong enough for the rated power. It is state of the art that in such situations grid operators impose feed-in management [...] Read more.

This paper presents a study to assess how wind turbines could increase their energy yield when their grid connection point is not strong enough for the rated power. It is state of the art that in such situations grid operators impose feed-in management on the affected wind turbines, i.e., the maximum power is limited. For this study a 5 MW wind turbine is introduced in a small grid that has only limited power transfer capabilities to the upstream power system. Simulations of one particular day are conducted with the electric load, the temperature, and the wind speed as measured on that day. This simulation is conducted twice: once with the 5 MW wind turbine controlled with conventional feed-in management, and a second time when its power is controlled flexibly, i.e., with continuous feed-in management. The results of these two simulations are compared in terms of grid performance, and in terms of mechanical stress on the 5 MW wind turbine. Finally, the conclusion can be drawn that continuous feed-in management is clearly superior to conventional feed-in management. It exhibits much better performance in the grid in terms of energy yield and also in terms of constancy of voltage and temperature of grid equipment. Although it causes somewhat more frequent stress for the wind turbine, the maximum stress level is not increased. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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17 pages, 11240 KiB

Open AccessArticle

A High-Power DC-DC Converter Topology for Battery Charging Applications

by Il-Oun Lee^*

and Jun-Young Lee

Department of Electric Engineering, Myongji Unversity, Yongin-Si 449-728, Korea

Energies 2017, 10(7), 871; https://doi.org/10.3390/en10070871 - 28 Jun 2017

Cited by 14 | Viewed by 6903

Abstract

A DC-DC converter that can be applied for battery chargers with the power-capacity of over 7-kW for electric vehicles (EVs) is presented in this paper. Due to a new architecture, the proposed converter achieves a reduction of conduction losses at the primary side [...] Read more.

A DC-DC converter that can be applied for battery chargers with the power-capacity of over 7-kW for electric vehicles (EVs) is presented in this paper. Due to a new architecture, the proposed converter achieves a reduction of conduction losses at the primary side by as much as 50% and has many benefits such as much smaller circulating current, less duty-cycle loss, and lower secondary-voltage stress. In addition, its power handing capacity can be upsized easily with the use of two full-bridge inverters and two transformers. Besides, all the switches in the converter achieve zero-voltage switching (ZVS) during whole battery charging process, and the size of output filter can be significantly reduced. The circuit configuration, operation, and relevant analysis are presented, followed by the experiment on a prototype realized with a 7-kW charger. The experimental results validate the theoretical analysis and show the effectiveness of the proposed converter as battery charger. Full article

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

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22 pages, 10519 KiB

Open AccessArticle

Numerical Analysis of Flatback Trailing Edge Airfoil to Reduce Noise in Power Generation Cycle

by Hyungki Shin¹, Hogeon Kim², Taehyung Kim³, Soo-Hyun Kim¹

, Soogab Lee⁴, Young-Jin Baik¹ and Gilbong Lee^1,*

¹ Energy Efficiency and Materials Research Division, Korea Institute of Energy Research, Daejeon 305-343, Korea

² Siemens Industry Software Ltd., Seoul 08502, Korea

³ Hyundai Heavy Industries Co. Ltd., Seoul 03058, Korea

⁴ Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea

Energies 2017, 10(7), 872; https://doi.org/10.3390/en10070872 - 29 Jun 2017

Cited by 2 | Viewed by 4945

Abstract

Turbo machinery is an essential part in the power generation cycle. However, it is the main source of noise that annoys workers and users, and contributes to environmental problems. Thus, it is important to reduce this noise when operating the power generation cycle. [...] Read more.

Turbo machinery is an essential part in the power generation cycle. However, it is the main source of noise that annoys workers and users, and contributes to environmental problems. Thus, it is important to reduce this noise when operating the power generation cycle. This noise is created by a flow instability on the trailing edge of the rotor blade—an airfoil that becomes a section of the rotor blade of the rotating machine—manufactured as a blunt trailing edge (T.E.), with a round or flatback shape, rather than the ideal sharp T.E. shape, for the purposes of production and durability. This increases the tonal noise and flow-induced vibrations at a low frequency, owing to vortex shedding behind T.E. when compared with a sharp T.E. In order to overcome this problem, the present study investigates the oblique T.E. shape using numerical simulations. In order to do so, flow was simulated using large eddy simulation (LES) and the noise was analyzed by acoustic analogy coupled with the LES result. Once the simulation results were verified using the flatback airfoil measurements of the Sandia National Laboratories, numerical prediction was performed to analyze the flow and the noise characteristics for the airfoils, which were modified to have oblique trailing edge angles of 60°, 45°, and 30°. From the simulation results of the oblique T.E. airfoil, it could be seen that the vortex shedding frequency moves in accordance with the oblique angle and that the vortex shedding noise characteristics change according to the angle, when compared to the flatback T.E. airfoil. Therefore, it is considered that modifying the flatback T.E. airfoil with an appropriate oblique angle can reduce noise and change the tonal frequency to a bandwidth that is suitable for mechanical systems. Full article

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

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22 pages, 6064 KiB

Open AccessArticle

Small-Signal Stability Analysis of Interaction Modes in VSC MTDC Systems with Voltage Margin Control

by Goran Grdenić^* and Marko Delimar

Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, 10000 Zagreb, Croatia

Energies 2017, 10(7), 873; https://doi.org/10.3390/en10070873 - 29 Jun 2017

Cited by 3 | Viewed by 4187

Abstract

Multi-terminal Direct Current Transmission (MTDC) is an emerging and promising technology for the transmission of electricity and the main initiator of the development of MTDC grids is offshore wind generation. However, prior to their construction, a thorough investigation of different aspects of their [...] Read more.

Multi-terminal Direct Current Transmission (MTDC) is an emerging and promising technology for the transmission of electricity and the main initiator of the development of MTDC grids is offshore wind generation. However, prior to their construction, a thorough investigation of different aspects of their implementation and operation is required. In this research, an MTDC grid with voltage margin control consisting of voltage source converters (VSCs) and a high frequency cable model was implemented in Matlab/SIMULINK (R2015b, The MathWorks, Inc., Natick, MA, USA). Small-signal stability analysis was carried out to investigate the sensitivity of the grid’s interaction modes to the operating point, the structure of the grid, and the selection of the voltage controlling converter. Based on the findings of these analyses, a strategy for droop control method is proposed and demonstrated. Full article

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

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15 pages, 3583 KiB

Open AccessArticle

by Haoran Zhao, Sen Guo^* and Huiru Zhao

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

Energies 2017, 10(7), 874; https://doi.org/10.3390/en10070874 - 29 Jun 2017

Cited by 55 | Viewed by 4352

Abstract

Accurate and reliable forecasting on energy-related carbon dioxide (CO₂) emissions is of great significance for climate policy decision making and energy planning. Due to the complicated nonlinear relationships of CO₂ emissions with its driving forces, the accurate forecasting for CO [...] Read more.

Accurate and reliable forecasting on energy-related carbon dioxide (CO₂) emissions is of great significance for climate policy decision making and energy planning. Due to the complicated nonlinear relationships of CO₂ emissions with its driving forces, the accurate forecasting for CO₂ emissions is a tedious work, which is an important issue worth studying. In this study, a novel CO₂ emissions prediction method is proposed which employs the latest nature-enlightened optimization method, named the Whale optimization algorithm (WOA), to search the optimized values of two parameters of LSSVM (least squares support vector machine), namely the WOA-LSSVM model. Meanwhile, the driving forces of CO₂ emissions including GDP (gross domestic product), energy consumption and population are chosen to be the import variables of the proposed WOA-LSSVM method. Taking China’s CO₂ emissions as an instance, the effectiveness of WOA-LSSVM-based CO₂ emissions forecasting is verified. The comparative analysis results indicate that the WOA-LSSVM model is significantly superior to other selected models, namely FOA (fruit fly optimization algorithm)-LSSVM, LSSVM, and OLS (ordinary least square) models in terms of CO₂ emissions forecasting. The proposed WOA-LSSVM model has the potential to effectively improve the accuracy of CO₂ emissions forecasting. Meanwhile, as a new nature-enlightened heuristic optimization algorithm, the WOA has the prospect for wide application. Full article

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15 pages, 2866 KiB

Open AccessArticle

Efficiency of Recycling Double-Pass V-Corrugated Solar Air Collectors

by Chii-Dong Ho^*, Ching-Fang Hsiao, Hsuan Chang, Yi-En Tien and Zih-Syuan Hong

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

Energies 2017, 10(7), 875; https://doi.org/10.3390/en10070875 - 29 Jun 2017

Cited by 13 | Viewed by 3976

Abstract

The influence of recycling on double-pass solar air collectors with welding of the V-corrugated absorber has been studied experimentally and theoretically. Welding the V-corrugated absorber and the recycle-effect concept to the solar air collector was proposed to strengthen the convective heat-transfer coefficient due [...] Read more.

The influence of recycling on double-pass solar air collectors with welding of the V-corrugated absorber has been studied experimentally and theoretically. Welding the V-corrugated absorber and the recycle-effect concept to the solar air collector was proposed to strengthen the convective heat-transfer coefficient due to turbulence promotion. Both the recycle effect and the V-corrugated absorber can effectively enhance the heat transfer efficiency compared to various designs such as single-pass, flat-plate double-pass, and double-pass wire mesh packed devices. Recycling operations and welding the V-corrugated absorber could enhance the collector efficiency by increasing the recycle ratio, incident solar radiations, and air mass flow rates. The most efficient and economical operating conditions were found at R ≈ 0.5, with relatively small hydraulic dissipated energy compensation. It was found that the turbulence intensity increase from welding the V-corrugated absorber into the solar air collector channel could compensate for the power consumption increase, when considering economic feasibility. Full article

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

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17 pages, 2355 KiB

Open AccessArticle

SVR-Based Model to Forecast PV Power Generation under Different Weather Conditions

by Utpal Kumar Das¹, Kok Soon Tey^1,*, Mehdi Seyedmahmoudian², Mohd Yamani Idna Idris¹, Saad Mekhilef³

, Ben Horan²

and Alex Stojcevski⁴

¹ Department of Computer System and Technology, Faculty of Computer Science and Information Technology, University of Malaya, Kuala Lumpur 50603, Malaysia

² School of Engineering, Deakin University, Melbourne 3216, Australia

³ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

⁴ School of Software and Electrical Engineering, Swinburne University of Technology, Melbourne, Victoria 3122, Australia

Energies 2017, 10(7), 876; https://doi.org/10.3390/en10070876 - 29 Jun 2017

Cited by 123 | Viewed by 8020

Abstract

Inaccurate forecasting of photovoltaic (PV) power generation is a great concern in the planning and operation of stable and reliable electric grid systems as well as in promoting large-scale PV deployment. The paper proposes a generalized PV power forecasting model based on support [...] Read more.

Inaccurate forecasting of photovoltaic (PV) power generation is a great concern in the planning and operation of stable and reliable electric grid systems as well as in promoting large-scale PV deployment. The paper proposes a generalized PV power forecasting model based on support vector regression, historical PV power output, and corresponding meteorological data. Weather conditions are broadly classified into two categories, namely, normal condition (clear sky) and abnormal condition (rainy or cloudy day). A generalized day-ahead forecasting model is developed to forecast PV power generation at any weather condition in a particular region. The proposed model is applied and experimentally validated by three different types of PV stations in the same location at different weather conditions. Furthermore, a conventional artificial neural network (ANN)-based forecasting model is utilized, using the same experimental data-sets of the proposed model. The analytical results showed that the proposed model achieved better forecasting accuracy with less computational complexity when compared with other models, including the conventional ANN model. The proposed model is also effective and practical in forecasting existing grid-connected PV power generation. Full article

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21 pages, 3086 KiB

Open AccessArticle

Life Cycle Cost and Sensitivity Analysis of Reutealis trisperma as Non-Edible Feedstock for Future Biodiesel Production

by Teuku Meurah Indra Riayatsyah¹, Hwai Chyuan Ong^1,*

, Wen Tong Chong¹

, Lisa Aditya¹, Heri Hermansyah² and Teuku Meurah Indra Mahlia^3,4

¹ Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia

² Department of Chemical Engineering, Universitas Indonesia, Depok 16424, Indonesia

³ Department of Mechanical Engineering, Universiti Tenaga Nasional, 43000 Kajang, Selangor, Malaysia

⁴ Faculty of Integrated Technologies, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE1410, Brunei Darussalam

Energies 2017, 10(7), 877; https://doi.org/10.3390/en10070877 - 29 Jun 2017

Cited by 31 | Viewed by 5313

Abstract

The use of non-edible, second-generation feedstocks for the production of biodiesel has been an active area of research, due to its potential in replacing fossil diesel as well as its environmentally friendly qualities. Despite this, more needs to be done to remove the [...] Read more.

The use of non-edible, second-generation feedstocks for the production of biodiesel has been an active area of research, due to its potential in replacing fossil diesel as well as its environmentally friendly qualities. Despite this, more needs to be done to remove the technical barriers associated with biodiesel production and usage, to increase its quality as well as to widen the choice of available feedstocks; so as to avoid over-dependence on limited sources. This paper assesses the feasibility of using a local plant, Reutealis trisperma, whose seeds contain a high percentage of oil of up to 51%, as one of the possible feedstocks. The techno-economic and sensitivity analysis of biodiesel production from Reutealis trisperma oil as well as implementation aspects and environmental effects of the biodiesel plant are discussed. Analysis indicates that the 50 kt Reutealis trisperma biodiesel production plant has a life cycle cost of approximately $710 million, yielding a payback period of 4.34 years. The unit cost of the biodiesel is calculated to be $0.69/L with the feedstock cost accounting for the bulk of the cost. The most important finding from this study is that the biodiesel from Reutealis trisperma oil can compete with fossil diesel, provided that appropriate policies of tax exemptions and subsidies can be put in place. To conclude, further studies on biodiesel production and its limitations are necessary before the use of biodiesel from Reutealis trisperma oil may be used as a fuel source to replace fossil diesel. Full article

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

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19 pages, 7768 KiB

Open AccessArticle

Influence Analysis and Prediction of ESDD and NSDD Based on Random Forests

by Ang Ren^1,2

, Qingquan Li^1,2,* and Huaishuo Xiao^1,2

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

² Shandong Provincial Key Laboratory of Ultra High Voltage Transmission Technology and Equipments, #17923 Jingshi Road, Jinan 250061, China

Energies 2017, 10(7), 878; https://doi.org/10.3390/en10070878 - 30 Jun 2017

Cited by 16 | Viewed by 5056

Abstract

Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) measurements are a basic requirement of power systems. In order to predict the site pollution severity (SPS) of insulators, a new method based on random forests (RFs) is proposed. Using mutual information (MI) [...] Read more.

Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) measurements are a basic requirement of power systems. In order to predict the site pollution severity (SPS) of insulators, a new method based on random forests (RFs) is proposed. Using mutual information (MI) theory and RFs, the weights of factors related to the SPS of insulators are analyzed. The samples of contaminated insulators are extracted from the transmission lines of high voltage alternating current (HVAC) and high voltage direct current transmission (HVDC). The regression models of RFs and support vector machines (SVM) are constructed and compared, which helps to support the lack of information in predicting NSDD in previous works. The results are as follows: according to the mean decrease accuracy (MDA), mean decrease Gini, (MDG), and MI, the types of the insulators (including surface area, surface orientation, and total length) as well as the hydrophobicity are the main factors affecting both ESDD and NSDD. Compared with NSDD, the electrical parameters have a significant effect on ESDD. For the influence factors of ESDD, the weights of the insulator type, hydrophobicity, and meteorological factors are 52.94%, 6.35%, and 21.88%, respectively. For the influence factors of NSDD, the weights of the insulator type, hydrophobicity, and meteorological factors are 55.37%, 11.04%, and 14.26%, respectively. The influence voltage level (vl), voltage type (vt), polarity/phases (pp) exerted on ESDD are 1.5 times, 3 times, and 4.5 times of NSDD, respectively. The influence that distance from the coastline (d), wind velocity (wv), and rainfall (rf) exert on NSDD are 1.5 times, 2 times, and 2.5 times that of ESDD, respectively. Compared with the natural contamination test and the SVM regression model, the RFs regression model can effectively predict the contamination degree of insulators, and the relative error of the predicted ESDD and NSDD is 8.31% and 9.62%, respectively. Full article

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

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14 pages, 2946 KiB

Open AccessArticle

Demand Response Resource Allocation Method Using Mean-Variance Portfolio Theory for Load Aggregators in the Korean Demand Response Market

by Jaeyong Chae and Sung-Kwan Joo^*

School of Electrical Engineering, Korea University, Seoul 02841, Korea

Energies 2017, 10(7), 879; https://doi.org/10.3390/en10070879 - 29 Jun 2017

Cited by 7 | Viewed by 3668

Abstract

Since the demand response (DR) market was introduced in Korea, load aggregators have also been allowed to participate in the electricity market. However, a risk-management-based method for the efficient operation of demand response resources (DRRs) has not been studied from the load aggregators’ [...] Read more.

Since the demand response (DR) market was introduced in Korea, load aggregators have also been allowed to participate in the electricity market. However, a risk-management-based method for the efficient operation of demand response resources (DRRs) has not been studied from the load aggregators’ perspective. In this paper, a systematic DRR allocation method is proposed for load aggregators to operate DRRs using mean-variance portfolio theory. The proposed method is designed to determine the lowest-risk DRR portfolio for a given level of expected return using mean-variance portfolio theory from the perspective of load aggregators. The numerical results show that the proposed method can be used to reduce the risk compared to that obtained by the baseline method, in which all individual DRRs are allocated in a DRR group by maximum curtailment capability. Full article

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

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17 pages, 5619 KiB

Open AccessArticle

Investigation of the Energy Performance of a Novel Modular Solar Building Envelope

by Gang Ren¹, Xudong Zhao^1,2,*, Changhong Zhan^1,*, Hong Jin¹ and Aishen Zhou³

¹ School of Architecture, Heilongjiang Cold Climate Architectural Science Key Laboratory, Harbin Institute of Technology, 66 Xidazhi Street, Harbin 150001, China

² School of Engineering and Computer Science, University of Hull, Hull HU178XH, UK

³ Heilongjiang Environmental Monitoring Center Station, Harbin 150056, China

Energies 2017, 10(7), 880; https://doi.org/10.3390/en10070880 - 30 Jun 2017

Cited by 8 | Viewed by 5112

Abstract

The major challenges for the integration of solar collecting devices into a building envelope are related to the poor aesthetic view of the appearance of buildings in addition to the low efficiency in collection, transportation, and utilization of the solar thermal and electrical [...] Read more.

The major challenges for the integration of solar collecting devices into a building envelope are related to the poor aesthetic view of the appearance of buildings in addition to the low efficiency in collection, transportation, and utilization of the solar thermal and electrical energy. To tackle these challenges, a novel design for the integration of solar collecting elements into the building envelope was proposed and discussed. This involves the dedicated modular and multiple-layer combination of the building shielding, insulation, and solar collecting elements. On the basis of the proposed modular structure, the energy performance of the solar envelope was investigated by using the Energy-Plus software. It was found that the solar thermal efficiency of the modular envelope is in the range of 41.78–59.47%, while its electrical efficiency is around 3.51% higher than the envelopes having photovoltaic (PV) alone. The modular solar envelope can increase thermal efficiency by around 8.49% and the electrical efficiency by around 0.31%, compared to the traditional solar photovoltaic/thermal (PV/T) envelopes. Thus, we have created a new envelope solution with enhanced solar efficiency and an improved aesthetic view of the entire building. Full article

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

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15 pages, 5863 KiB

Open AccessArticle

A Single-Phase Bidirectional AC/DC Converter for V2G Applications

by Tao Peng¹, Peng Yang¹

, Hanbing Dan^1,*, Hui Wang¹, Hua Han¹, Jian Yang¹, Hao Wang¹, Hui Dong¹ and Patrick Wheeler²

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

² Department of Electrical and Electronic Engineering, The University of Nottingham, Nottingham NG7 2RD, UK

Energies 2017, 10(7), 881; https://doi.org/10.3390/en10070881 - 30 Jun 2017

Cited by 22 | Viewed by 11721

Abstract

This paper presents a single-phase bidirectional current-source AC/DC converter for vehicle to grid (V2G) applications. The presented converter consists of a line frequency commutated unfolding bridge and an interleaved buck-boost stage. The low semiconductor losses of the line frequency commutated unfolding bridge contribute [...] Read more.

This paper presents a single-phase bidirectional current-source AC/DC converter for vehicle to grid (V2G) applications. The presented converter consists of a line frequency commutated unfolding bridge and an interleaved buck-boost stage. The low semiconductor losses of the line frequency commutated unfolding bridge contribute to the comparatively good efficiency of this converter. The buck and boost operating modes of the interleaved buck-boost stage provide operation over a wide battery voltage range. The interleaved structure of the interleaved buck-boost stage results in lower battery current ripple. In addition, sinusoidal input current, bidirectional power flow and reactive power compensation capability are also guaranteed. This paper presents the topology and operating principles of the presented converter. The feasibility of the converter is validated using MATLAB simulations, as well as experimental results. Full article

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19 pages, 2015 KiB

Open AccessArticle

Impact Analysis of Demand Response Intensity and Energy Storage Size on Operation of Networked Microgrids

by Akhtar Hussain

, Van-Hai Bui and Hak-Man Kim^*

Department of Electrical Engineering, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406840, Korea

Energies 2017, 10(7), 882; https://doi.org/10.3390/en10070882 - 30 Jun 2017

Cited by 21 | Viewed by 5154

Abstract

Integration of demand response (DR) programs and battery energy storage system (BESS) in microgrids are beneficial for both microgrid owners and consumers. The intensity of DR programs and BESS size can alter the operation of microgrids. Meanwhile, the optimal size for BESS units [...] Read more.

Integration of demand response (DR) programs and battery energy storage system (BESS) in microgrids are beneficial for both microgrid owners and consumers. The intensity of DR programs and BESS size can alter the operation of microgrids. Meanwhile, the optimal size for BESS units is linked with the uncertainties associated with renewable energy sources and load variations. Similarly, the participation of enrolled customers in DR programs is also uncertain and, among various other factors, uncertainty in market prices is a major cause. Therefore, in this paper, the impact of DR program intensity and BESS size on the operation of networked microgrids is analyzed while considering the prevailing uncertainties. The uncertainties associated with forecast load values, output of renewable generators, and market price are realized via the robust optimization method. Robust optimization has the capability to provide immunity against the worst-case scenario, provided the uncertainties lie within the specified bounds. The worst-case scenario of the prevailing uncertainties is considered for evaluating the feasibility of the proposed method. The two representative categories of DR programs, i.e., price-based and incentive-based DR programs are considered. The impact of change in DR intensity and BESS size on operation cost of the microgrid network, external power trading, internal power transfer, load profile of the network, and state-of-charge (SOC) of battery energy storage system (BESS) units is analyzed. Simulation results are analyzed to determine the integration of favorable DR program and/or BESS units for different microgrid networks with diverse objectives. Full article

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

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18 pages, 1323 KiB

Open AccessArticle

An Ad-Hoc Initial Solution Heuristic for Metaheuristic Optimization of Energy Market Participation Portfolios

by Ricardo Faia¹

, Tiago Pinto^1,2,*

, Zita Vale¹

and Juan Manuel Corchado²

¹ Research Group on Intelligent Engineering and Computing for Advanced Innovation and Development (GECAD), Institute of Engineering, Polytechnic of Porto (ISEP/IPP), Rua Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal

² Bioinformatics, Intelligent Systems and Educational Technology (BISITE) Research Centre, University of Salamanca, Calle Espejo, s/n, 37007 Salamanca, Spain

Energies 2017, 10(7), 883; https://doi.org/10.3390/en10070883 - 30 Jun 2017

Cited by 8 | Viewed by 3625

Abstract

The deregulation of the electricity sector has culminated in the introduction of competitive markets. In addition, the emergence of new forms of electric energy production, namely the production of renewable energy, has brought additional changes in electricity market operation. Renewable energy has significant [...] Read more.

The deregulation of the electricity sector has culminated in the introduction of competitive markets. In addition, the emergence of new forms of electric energy production, namely the production of renewable energy, has brought additional changes in electricity market operation. Renewable energy has significant advantages, but at the cost of an intermittent character. The generation variability adds new challenges for negotiating players, as they have to deal with a new level of uncertainty. In order to assist players in their decisions, decision support tools enabling assisting players in their negotiations are crucial. Artificial intelligence techniques play an important role in this decision support, as they can provide valuable results in rather small execution times, namely regarding the problem of optimizing the electricity markets participation portfolio. This paper proposes a heuristic method that provides an initial solution that allows metaheuristic techniques to improve their results through a good initialization of the optimization process. Results show that by using the proposed heuristic, multiple metaheuristic optimization methods are able to improve their solutions in a faster execution time, thus providing a valuable contribution for players support in energy markets negotiations. Full article

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24 pages, 2094 KiB

Open AccessArticle

The Comparison Study of Short-Term Prediction Methods to Enhance the Model Predictive Controller Applied to Microgrid Energy Management

by César Hernández-Hernández^1,*, Francisco Rodríguez¹

, José Carlos Moreno¹

, Paulo Renato Da Costa Mendes²

, Julio Elias Normey-Rico² and José Luis Guzmán¹

¹ Department of Informatics, Agrifood Campus of International Excellence ceiA3, CIESOL Research Center on Solar Energy, University of Almería, 04120 Almería, Spain

² Department of Automation and Systems (DAS), Federal University of Santa Catarina, Federal University of Santa Catarina, Florianópolis-SC CEP 88040-970, Brazil

Energies 2017, 10(7), 884; https://doi.org/10.3390/en10070884 - 30 Jun 2017

Cited by 16 | Viewed by 6001

Abstract

Electricity load forecasting, optimal power system operation and energy management play key roles that can bring significant operational advantages to microgrids. This paper studies how methods based on time series and neural networks can be used to predict energy demand and production, allowing [...] Read more.

Electricity load forecasting, optimal power system operation and energy management play key roles that can bring significant operational advantages to microgrids. This paper studies how methods based on time series and neural networks can be used to predict energy demand and production, allowing them to be combined with model predictive control. Comparisons of different prediction methods and different optimum energy distribution scenarios are provided, permitting us to determine when short-term energy prediction models should be used. The proposed prediction models in addition to the model predictive control strategy appear as a promising solution to energy management in microgrids. The controller has the task of performing the management of electricity purchase and sale to the power grid, maximizing the use of renewable energy sources and managing the use of the energy storage system. Simulations were performed with different weather conditions of solar irradiation. The obtained results are encouraging for future practical implementation. Full article

(This article belongs to the Collection Smart Grid)

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16 pages, 4726 KiB

Open AccessArticle

Modeling of Monthly Residential and Commercial Electricity Consumption Using Nonlinear Seasonal Models—The Case of Hong Kong

by Wai-Ming To¹

, Peter Ka Chun Lee^2,*

and Tsz-Ming Lai¹

¹ School of Business, Macao Polytechnic Institute, Macao, China

² Department of Logistics and Maritime Studies, The Hong Kong Polytechnic University, Hong Kong, China

Energies 2017, 10(7), 885; https://doi.org/10.3390/en10070885 - 30 Jun 2017

Cited by 31 | Viewed by 5281

Abstract

Accurate modeling and forecasting monthly electricity consumption are the keys to optimizing energy management and planning. This paper examines the seasonal characteristics of electricity consumption in Hong Kong—a subtropical city with 7 million people. Using the data from January 1970 to December 2014, [...] Read more.

Accurate modeling and forecasting monthly electricity consumption are the keys to optimizing energy management and planning. This paper examines the seasonal characteristics of electricity consumption in Hong Kong—a subtropical city with 7 million people. Using the data from January 1970 to December 2014, two novel nonlinear seasonal models for electricity consumption in the residential and commercial sectors were obtained. The models show that the city’s monthly residential and commercial electricity consumption patterns have different seasonal variations. Specifically, monthly residential electricity consumption (mainly for appliances and cooling in summer) has a quadratic relationship with monthly mean air temperature, while monthly commercial electricity consumption has a linear relationship with monthly mean air temperature. The nonlinear seasonal models were used to predict residential and commercial electricity consumption for the period January 2015–December 2016. The correlations between the predicted and actual values were 0.976 for residential electricity consumption and 0.962 for commercial electricity consumption, respectively. The root mean square percentage errors for the predicted monthly residential and commercial electricity consumption were 7.0% and 6.5%, respectively. The new nonlinear seasonal models can be applied to other subtropical urban areas, and recommendations on the reduction of commercial electricity consumption are given. Full article

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7 pages, 2004 KiB

Open AccessArticle

Direct Coal Liquefaction with Fe₃O₄ Nanocatalysts Prepared by a Simple Solid-State Method

by Yizhao Li^1,2

, Yali Cao^1,* and Dianzeng Jia^1,*

¹ Key Laboratory of Energy Materials Chemistry, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, China

² College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, Xinjiang, China

Energies 2017, 10(7), 886; https://doi.org/10.3390/en10070886 - 1 Jul 2017

Cited by 9 | Viewed by 4223

Abstract

Fe₃O₄ nanoparticles were prepared by a simple solid-state method under ambient conditions. The obtained nanoparticles, with small size and large surface area, were used as a catalyst for direct coal liquefaction (DCL). The results display that high conversion and oil [...] Read more.

Fe₃O₄ nanoparticles were prepared by a simple solid-state method under ambient conditions. The obtained nanoparticles, with small size and large surface area, were used as a catalyst for direct coal liquefaction (DCL). The results display that high conversion and oil yield were achieved with the nanocatalysts in direct liquefaction of two kinds of coals, i.e., Heishan coal and Dahuangshan coal. The effects of the temperature, initial H₂ pressure, and holding time on conversion and product distribution have been investigated in the catalytic hydrogenation of Dahuangshan coal. The optimal reaction condition for DCL in which conversion and oil yield are 96.6 and 60.4 wt % was determined with Fe₃O₄ nanocatalysts. This facile solid-state route is beneficial for scale-up synthesis of iron-based catalysts with good performance for DCL. Full article

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

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19 pages, 7435 KiB

Open AccessArticle

A Vertical Flux-Switching Permanent Magnet Based Oscillating Wave Power Generator with Energy Storage

by Yu Zou and Ka Wai Eric Cheng^*

Power Electronics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong

Energies 2017, 10(7), 887; https://doi.org/10.3390/en10070887 - 30 Jun 2017

Cited by 5 | Viewed by 4802

Abstract

In this paper, an effective low-speed oscillating wave power generator and its energy storage system have been proposed. A vertical flux-switching permanent magnet (PM) machine is designed as the generator while supercapacitors and batteries are used to store the energy. First, the overall [...] Read more.

In this paper, an effective low-speed oscillating wave power generator and its energy storage system have been proposed. A vertical flux-switching permanent magnet (PM) machine is designed as the generator while supercapacitors and batteries are used to store the energy. First, the overall power generation system is established and principles of the machine are introduced. Second, three modes are proposed for the energy storage system and sliding mode control (SMC) is employed to regulate the voltage of the direct current (DC) bus, observe the mechanical input, and feedback the status of the storage system. Finally, experiments with load and sinusoidal mechanical inputs are carried out to validate the effectiveness and stability of power generation for wave energy. The results show that the proposed power generation system can be employed in low-speed environment around 1 m/s to absorb random wave power, achieving over 60% power efficiency. The power generation approach can be used to capture wave energy in the future. Full article

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

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16 pages, 5467 KiB

Open AccessArticle

Sensorless Control for the EVT-Based New Dual Power Flow Wind Energy Conversion System

by Ying Zhu^1,*

, Ming Cheng²

and Haixiang Zang¹

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

² School of Electrical Engineering, Southeast University, Nanjing 210096, China

Energies 2017, 10(7), 888; https://doi.org/10.3390/en10070888 - 30 Jun 2017

Cited by 4 | Viewed by 4637 | Correction

Abstract

The dual power flow wind energy conversion system (DPF-WECS) is a novel system which is based on the electrical variable transmission (EVT) machine. The proposed sensorless control for the DPF-WECS is based on the model reference adaptive system (MRAS) observer by combining the [...] Read more.

The dual power flow wind energy conversion system (DPF-WECS) is a novel system which is based on the electrical variable transmission (EVT) machine. The proposed sensorless control for the DPF-WECS is based on the model reference adaptive system (MRAS) observer by combining the sliding mode (SM) theory. The SM-MRAS observer is on account of the calculations without the requirement of the proportional-integral (PI) loop which exists in the classical MRAS observer. Firstly, the sensorless algorithm is applied in the maximum power point tracking (MPPT) control considering the torque loss for the outer rotor of the EVT. Secondly, the sensorless control is adopted for the inner rotor control of the EVT machine. The proposed sensorless control method based on the SM-MRAS for the DPF-WECS is verified by the simulation and experimental results. Full article

(This article belongs to the Special Issue Electric Machines and Drives for Renewable Energy Harvesting 2017)

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9 pages, 1989 KiB

Open AccessFeature PaperCommunication

Synthesis, Structure, and Sodium Mobility of Sodium Vanadium Nitridophosphate: A Zero-Strain and Safe High Voltage Cathode Material for Sodium-Ion Batteries

by Huang Zhang^1,2

, Daniel Buchholz^1,2,* and Stefano Passerini^1,2,*

¹ Helmholtz Institute Ulm, Helmholtzstraße 11, 89081 Ulm, Germany

² Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany

Energies 2017, 10(7), 889; https://doi.org/10.3390/en10070889 - 30 Jun 2017

Cited by 22 | Viewed by 5544

Abstract

Herein, the nitridophosphate Na₃V(PO₃)₃N is synthesized by solid state method. X-ray diffraction (XRD) and Rietveld refinement confirm the cubic symmetry with P2₁3 space group. The material exhibits very good thermal stability and high operating [...] Read more.

Herein, the nitridophosphate Na₃V(PO₃)₃N is synthesized by solid state method. X-ray diffraction (XRD) and Rietveld refinement confirm the cubic symmetry with P2₁3 space group. The material exhibits very good thermal stability and high operating voltage of 4.0 V vs. Na/Na⁺ due to V³⁺/V⁴⁺ redox couple. In situ X-ray diffraction studies confirm the two-phase (de-)sodiation process to occur with very low volume changes. The refinement of the sodium occupancies reveal the low accessibility of sodium cations in the Na2 and Na3 sites as the main origin for the lower experimental capacity (0.38 eq. Na⁺, 28 mAh g⁻¹) versus the theoretical one (1.0 eq. Na⁺, 74 mAh g⁻¹). These observations provide valuable information for the further optimization of this materials class in order to access their theoretical electrochemical performance as a potentially interesting zero-strain and safe high-voltage cathode material for sodium-ion batteries. Full article

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

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20 pages, 2053 KiB

Open AccessArticle

Minimization of Construction Costs for an All Battery-Swapping Electric-Bus Transportation System: Comparison with an All Plug-In System

by Shyang-Chyuan Fang¹, Bwo-Ren Ke^2,* and Chen-Yuan Chung²

¹ Department of Tourism and Leisure, National Penghu University of Science and Technology, Makung 880, Taiwan

² Department of Electrical Engineering, National Penghu University of Science and Technology, Makunk 880, Taiwan

Energies 2017, 10(7), 890; https://doi.org/10.3390/en10070890 - 30 Jun 2017

Cited by 18 | Viewed by 5293

Abstract

The greenhouse gases and air pollution generated by extensive energy use have exacerbated climate change. Electric-bus (e-bus) transportation systems help reduce pollution and carbon emissions. This study analyzed the minimization of construction costs for an all battery-swapping public e-bus transportation system. A simulation [...] Read more.

The greenhouse gases and air pollution generated by extensive energy use have exacerbated climate change. Electric-bus (e-bus) transportation systems help reduce pollution and carbon emissions. This study analyzed the minimization of construction costs for an all battery-swapping public e-bus transportation system. A simulation was conducted according to existing timetables and routes. Daytime charging was incorporated during the hours of operation; the two parameters of the daytime charging scheme were the residual battery capacity and battery-charging energy during various intervals of daytime peak electricity hours. The parameters were optimized using three algorithms: particle swarm optimization (PSO), a genetic algorithm (GA), and a PSO–GA. This study observed the effects of optimization on cost changes (e.g., number of e-buses, on-board battery capacity, number of extra batteries, charging facilities, and energy consumption) and compared the plug-in and battery-swapping e-bus systems. The results revealed that daytime charging can reduce the construction costs of both systems. In contrast to the other two algorithms, the PSO–GA yielded the most favorable optimization results for the charging scheme. Finally, according to the cases investigated and the parameters of this study, the construction cost of the plug-in e-bus system was shown to be lower than that of the battery-swapping e-bus system. Full article

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17 pages, 7272 KiB

Open AccessArticle

Loss Characteristics of 6.5 kV RC-IGBT Applied to a Traction Converter

by Xianjin Huang^*

, Chao Ling, Dengwei Chang, Xiaojie You and Trillion Q. Zheng

School of Electrical Engineering, Beijing Jiaotong University, No. 3 Shangyuancun, Beijing 100044, China

Energies 2017, 10(7), 891; https://doi.org/10.3390/en10070891 - 1 Jul 2017

Cited by 4 | Viewed by 7387

Abstract

6.5 kV level IGBT (Insulated Gate Bipolar Transistor) modules are widely applied in megawatt locomotive (MCUs) traction converters, to achieve an upper 3.5 kV DC link, which is beneficial for decreasing power losses and increasing the power density. Reverse Conducting IGBT (RC-IGBT) constructs [...] Read more.

6.5 kV level IGBT (Insulated Gate Bipolar Transistor) modules are widely applied in megawatt locomotive (MCUs) traction converters, to achieve an upper 3.5 kV DC link, which is beneficial for decreasing power losses and increasing the power density. Reverse Conducting IGBT (RC-IGBT) constructs the conventional IGBT function and freewheel diode function in a single chip, which has a greater flow ability in the same package volume. In the same cooling conditions, RC-IGBT allows for a higher operating temperature. In this paper, a mathematic model is developed, referring to the datasheets and measurement data, to study the 6.5 kV/1000 A RC-IGBT switching features. The relationship among the gate desaturated pulse, conducting losses, and recovery losses is discussed. Simulations and tests were carried out to consider the influence of total losses on the different amplitudes and durations of the desaturated pulse. The RC-IGBT traction converter system with gate pulse desaturated control is built, and the simulation and measurements show that the total losses of RC-IGBT with desaturated control decreased comparing to the RC-IGBT without desaturated control or conventional IGBT. Finally, a proportional small power platform is developed, and the test results prove the correction of the theory analysis. Full article

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

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28 pages, 4097 KiB

Open AccessArticle

An Improved Ångström-Type Model for Estimating Solar Radiation over the Tibetan Plateau

by Jiandong Liu^1,2, Tao Pan^3,4,*, Deliang Chen², Xiuji Zhou¹, Qiang Yu⁵, Gerald N. Flerchinger⁶, De Li Liu⁷, Xintong Zou^3,8, Hans W. Linderholm², Jun Du⁹, Dingrong Wu¹ and Yanbo Shen¹⁰

¹ State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China

² Regional Climate Group, Department of Earth Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden

³ Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

⁴ Center for System Integration and Sustainability, Michigan State University, East Lansing, MI 48823, USA

⁵ Plant Functional and Climate Change Cluster, University of Technology, Sydney 2007, Australia

⁶ USDA-ARS, Northwest Watershed Research Center, Boise, ID 83712, USA

⁷ NSW Department of Primary Industries, Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650, Australia

⁸ University of Chinese Academy of Sciences, Beijing 100049, China

⁹ Climate Center, Tibet Autonomous Meteorological Administration, Lhasa 850000, China

¹⁰ Centre for Solar and Wind Energy Research, China Meteorological Administration, Beijing 100081, China

Energies 2017, 10(7), 892; https://doi.org/10.3390/en10070892 - 1 Jul 2017

Cited by 17 | Viewed by 4914

Abstract

For estimating the annual mean of daily solar irradiation in plateau mountainous regions, observed data from 15 radiation stations were used to validate different empirical estimation methods over the Tibetan Plateau. Calibration indicates that sunshine-based site-dependent models perform better than temperature-based ones. Then, [...] Read more.

For estimating the annual mean of daily solar irradiation in plateau mountainous regions, observed data from 15 radiation stations were used to validate different empirical estimation methods over the Tibetan Plateau. Calibration indicates that sunshine-based site-dependent models perform better than temperature-based ones. Then, the highly rated sunshine-based Ångström model and temperature-based Bristow model were selected for regional application. The geographical models perform much better than the average models, but still not ideally. To achieve better performance, the Ångström-type model was improved using altitude and water vapor pressure as the leading factors. The improved model can accurately predict the coefficients at all the stations, and performs the best among all models with an average Nash-Sutcliffe Efficiency value of 0.856. Spatial distribution of the annual mean of daily solar irradiation was then estimated with the improved model. It is indicated that there is an increasing trend of radiation from east to west, with a great center of the annual mean of daily solar irradiation on southwest Tibetan Plateau ranging from 20 to 24 MJ·m⁻². The improved model should be further validated against observations before its applications in other plateau mountainous regions. Full article

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19 pages, 612 KiB

Open AccessArticle

Combined Heat and Power Dispatch Considering Heat Storage of Both Buildings and Pipelines in District Heating System for Wind Power Integration

by Ping Li

, Haixia Wang, Quan Lv and Weidong Li^*

Department of Electrical Engineering, Dalian University of Technology, Dalian 116024, China

Energies 2017, 10(7), 893; https://doi.org/10.3390/en10070893 - 30 Jun 2017

Cited by 77 | Viewed by 5588

Abstract

The strong coupling between electric power and heat supply highly restricts the electric power generation range of combined heat and power (CHP) units during heating seasons. This makes the system operational flexibility very low, which leads to heavy wind power curtailment, especially in [...] Read more.

The strong coupling between electric power and heat supply highly restricts the electric power generation range of combined heat and power (CHP) units during heating seasons. This makes the system operational flexibility very low, which leads to heavy wind power curtailment, especially in the region with a high percentage of CHP units and abundant wind power energy such as northeastern China. The heat storage capacity of pipelines and buildings of the district heating system (DHS), which already exist in the urban infrastructures, can be exploited to realize the power and heat decoupling without any additional investment. We formulate a combined heat and power dispatch model considering both the pipelines’ dynamic thermal performance (PDTP) and the buildings’ thermal inertia (BTI), abbreviated as the CPB-CHPD model, emphasizing the coordinating operation between the electric power and district heating systems to break the strong coupling without impacting end users’ heat supply quality. Simulation results demonstrate that the proposed CPB-CHPD model has much better synergic benefits than the model considering only PDTP or BTI on wind power integration and total operation cost savings. Full article

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

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20 pages, 4487 KiB

Open AccessReview

An Overview of Resonant Circuits for Wireless Power Transfer

by Chaoqiang Jiang^1,*, K. T. Chau¹

, Chunhua Liu²

and Christopher H. T. Lee³

¹ Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China

² School of Energy and Environment, City University of Hong Kong, Hong Kong, China

³ Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Energies 2017, 10(7), 894; https://doi.org/10.3390/en10070894 - 30 Jun 2017

Cited by 166 | Viewed by 20005

Abstract

With ever-increasing concerns for the safety and convenience of the power supply, there is a fast growing interest in wireless power transfer (WPT) for industrial devices, consumer electronics, and electric vehicles (EVs). As the resonant circuit is one of the cores of both [...] Read more.

With ever-increasing concerns for the safety and convenience of the power supply, there is a fast growing interest in wireless power transfer (WPT) for industrial devices, consumer electronics, and electric vehicles (EVs). As the resonant circuit is one of the cores of both the near-field and far-field WPT systems, it is a pressing need for researchers to develop a high-efficiency high-frequency resonant circuit, especially for the mid-range near-field WPT system. In this paper, an overview of resonant circuits for the near-field WPT system is presented, with emphasis on the non-resonant converters with a resonant tank and resonant inverters with a resonant tank as well as compensation networks and selective resonant circuits. Moreover, some key issues including the zero-voltage switching, zero-voltage derivative switching and total harmonic distortion are addressed. With the increasing usage of wireless charging for EVs, bidirectional resonant inverters for WPT based vehicle-to-grid systems are elaborated. Full article

(This article belongs to the Special Issue Advanced Electric Devices and Technologies for Electric-Drive Robotics)

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17 pages, 5638 KiB

Open AccessArticle

A Hybrid Reliability Evaluation Method for Meshed VSC-HVDC Grids

by Haipeng Xie¹, Zhaohong Bie^1,*, Yanling Lin¹ and Chao Zheng²

¹ The State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China

² The Department of Research and Application of New Technology, China Electric Power Research Institution, Beijing 100192, China

Energies 2017, 10(7), 895; https://doi.org/10.3390/en10070895 - 1 Jul 2017

Cited by 7 | Viewed by 4470

Abstract

High-voltage direct current (HVDC) grids are emerging, and their reliability has been an increasing concern for the utilities. HVDC grids are different from typical two-terminal HVDC transmission systems due to the loops in their topology, which makes it difficult to evaluate the reliability [...] Read more.

High-voltage direct current (HVDC) grids are emerging, and their reliability has been an increasing concern for the utilities. HVDC grids are different from typical two-terminal HVDC transmission systems due to the loops in their topology, which makes it difficult to evaluate the reliability by conventional analytical methods. This paper proposes an innovative hybrid method to evaluate the reliability of meshed HVDC grids. First, steady-state models and reliability models are established for the components in HVDC grids, especially for converters and power flow controllers. In the models, virtual buses are introduced to represent the external AC connections to the HVDC grid. Then a hybrid reliability evaluation method is proposed based on an analytical approach and Monte Carlo simulation. One innovation of the paper is the application of an analytical analysis method to accelerate state evaluation in Monte Carlo simulation by skipping unnecessary optimization. The proposed models and methods are verified on two HVDC grids. Test results show that HVDC grids under most failure states (approximately 70%) tend to shed no load except on buses connected to faulted converters, and the application of the analytical method could promote evaluation efficiency significantly. Full article

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

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23 pages, 6206 KiB

Open AccessArticle

A Single-Degree-of-Freedom Energy Optimization Strategy for Power-Split Hybrid Electric Vehicles

by Chaoying Xia^*, Zhiming DU

and Cong Zhang

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

Energies 2017, 10(7), 896; https://doi.org/10.3390/en10070896 - 1 Jul 2017

Cited by 7 | Viewed by 6410

Abstract

This paper presents a single-degree-of-freedom energy optimization strategy to solve the energy management problem existing in power-split hybrid electric vehicles (HEVs). The proposed strategy is based on a quadratic performance index, which is innovatively designed to simultaneously restrict the fluctuation of battery state [...] Read more.

This paper presents a single-degree-of-freedom energy optimization strategy to solve the energy management problem existing in power-split hybrid electric vehicles (HEVs). The proposed strategy is based on a quadratic performance index, which is innovatively designed to simultaneously restrict the fluctuation of battery state of charge (SOC) and reduce fuel consumption. An extended quadratic optimal control problem is formulated by approximating the fuel consumption rate as a quadratic polynomial of engine power. The approximated optimal control law is obtained by utilizing the solution properties of the Riccati equation and adjoint equation. It is easy to implement in real-time and the engineering significance is explained in details. In order to validate the effectiveness of the proposed strategy, the forward-facing vehicle simulation model is established based on the ADVISOR software (Version 2002, National Renewable Energy Laboratory, Golden, CO, USA). The simulation results show that there is only a little fuel consumption difference between the proposed strategy and the Pontryagin’s minimum principle (PMP)-based global optimal strategy, and the proposed strategy also exhibits good adaptability under different initial battery SOC, cargo mass and road slope conditions. Full article

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

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20 pages, 272 KiB

Open AccessArticle

Influencing Mechanism Analysis of Holiday Activity–Travel Patterns on Transportation Energy Consumption and Emissions in China

by Bobin Wang^*, Chunfu Shao^* and Xun Ji

MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044, China

Energies 2017, 10(7), 897; https://doi.org/10.3390/en10070897 - 1 Jul 2017

Cited by 11 | Viewed by 3616

Abstract

Energy shortage and atmospheric pollution problems are getting more serious in China, and transportation is the main source of energy consumption, pollutants, and carbon emissions. This study combined the activity-based analysis method with emission models, and investigated the influence mechanism of people’s activity [...] Read more.

Energy shortage and atmospheric pollution problems are getting more serious in China, and transportation is the main source of energy consumption, pollutants, and carbon emissions. This study combined the activity-based analysis method with emission models, and investigated the influence mechanism of people’s activity travel scheduling on transportation energy consumption and emissions on holidays. Based on the holiday travel behavior survey data, the multinomial logistic regression model was first applied to explore the decision mechanisms of individual travel-mode choices in holidays. Next, the emission model was integrated with an activity-based travel demand model to calculate and compare transportation energy consumption and emissions under different policy scenarios. The results showed that socio-demographic characteristics had significant effects on holiday activity–travel patterns, and combined mode chains had a larger number of activity points than single mode chains. With an increase in the trip time of cars, and decrease of travel distance and the number of activity points, transportation energy consumption and emissions could be reduced greatly with an adjustment of holiday activity–travel patterns. The reduced portion is mainly attracted by slow traffic and public transport. However, the effects of a single policy strategy are very limited, thus portfolio policies need to be considered by policy makers. Full article

15 pages, 4691 KiB

Open AccessArticle

Diagnosis and Early Warning of Wind Turbine Faults Based on Cluster Analysis Theory and Modified ANFIS

by Quan Zhou¹, Taotao Xiong^1,*, Mubin Wang², Chenmeng Xiang¹ and Qingpeng Xu³

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

² State Grid Lishui Electric Power Supply Company, Lishui 323000, China

³ State Grid Chengdu Power Supply Company, Chengdu 610041, China

Energies 2017, 10(7), 898; https://doi.org/10.3390/en10070898 - 1 Jul 2017

Cited by 19 | Viewed by 4608

Abstract

The construction of large-scale wind farms results in a dramatic increase of wind turbine (WT) faults. The failure mode is also becoming increasingly complex. This study proposes a new model for early warning and diagnosis of WT faults to solve the problem of [...] Read more.

The construction of large-scale wind farms results in a dramatic increase of wind turbine (WT) faults. The failure mode is also becoming increasingly complex. This study proposes a new model for early warning and diagnosis of WT faults to solve the problem of Supervisory Control And Data Acquisition (SCADA) systems, given that the traditional threshold method cannot provide timely warning. First, the characteristic quantity of fault early warning and diagnosis analyzed by clustering analysis can obtain in advance abnormal data in the normal threshold range by considering the effects of wind speed. Based on domain knowledge, Adaptive Neuro-fuzzy Inference System (ANFIS) is then modified to establish the fault early warning and diagnosis model. This approach improves the accuracy of the model under the condition of absent and sparse training data. Case analysis shows that the effect of the early warning and diagnosis model in this study is better than that of the traditional threshold method. Full article

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12 pages, 3651 KiB

Open AccessArticle

Hydropyrolysis of n-Hexane and Toluene to Acetylene in Rotating-Arc Plasma

by Jie Ma, Ming Zhang, Jianhua Wu, Qiwei Yang^*

, Guangdong Wen, Baogen Su^* and Qilong Ren

Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China

Energies 2017, 10(7), 899; https://doi.org/10.3390/en10070899 - 1 Jul 2017

Cited by 25 | Viewed by 5131

Abstract

Thermal plasma pyrolysis is a powerful technology for converting waste or low-value materials to valuable gaseous hydrocarbons. This paper presents for the first time the hydropyrolysis of n-hexane and toluene in a rotating-arc plasma reactor. Effects of the mole ratio of H/C [...] Read more.

Thermal plasma pyrolysis is a powerful technology for converting waste or low-value materials to valuable gaseous hydrocarbons. This paper presents for the first time the hydropyrolysis of n-hexane and toluene in a rotating-arc plasma reactor. Effects of the mole ratio of H/C in the feed, power input and magnetic induction were investigated to evaluate the reaction performance. A lower H/C ratio could lead to a lower yield of C₂H₂ and lower specific energy consumption, and there existed an optimum range of power input for both n-hexane and toluene pyrolysis within the investigated range. The yield of C₂H₂ in n-hexane and toluene pyrolysis could reach 85% and 68%, respectively, with respective specific energy consumption (SEC) of 13.8 kWh/kg·C₂H₂ and 19.9 kWh/kg·C₂H₂. Compared with the results reported in literature, the rotating-arc plasma process showed higher C₂H₂ yield and lower energy consumption, which is attributed to the better initial mixing of the reactant with the hot plasma gas and the more uniform temperature distribution. Full article

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

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16 pages, 5428 KiB

Open AccessArticle

An Investigation of Fuel Mixing and Reaction in a CH₄/Syngas/Air Premixed Impinging Flame with Varied H₂/CO Proportion

by Chih-Pin Chiu, Szu-I Yeh, Yu-Ching Tsai and Jing-Tang Yang^*

Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan

Energies 2017, 10(7), 900; https://doi.org/10.3390/en10070900 - 1 Jul 2017

Cited by 6 | Viewed by 5093

Abstract

For industrial applications, we propose a concept of clean and efficient combustion through burning syngas on an impinging burner. We performed experimental measurements of particle image velocimetry, OH radical (OH*) chemiluminescence, flame temperature, and CO emission to examine the fuel mixing and reaction [...] Read more.

For industrial applications, we propose a concept of clean and efficient combustion through burning syngas on an impinging burner. We performed experimental measurements of particle image velocimetry, OH radical (OH*) chemiluminescence, flame temperature, and CO emission to examine the fuel mixing and reaction of premixed impinging flames of CH₄/syngas/air with H₂/CO in varied proportions. The velocity distribution of the combustion flow field showed that a deceleration area in the main flow formed through the mutual impingement of two jet flows, which enhanced the mixing of fuel and air because of an increased momentum transfer. The deceleration area expanded with an increased CO proportion, which indicated that the mixing of fuel and air also increased with the increased CO proportion. Our examination of the OH* chemiluminescence demonstrated that its intensity increased with increased CO proportion, which showed that the reaction between fuel and air accordingly increased. CO provided in the syngas hence participated readily in the reaction of the CH₄/syngas/air premixed impinging flames when the syngas contained CO in a large proportion. Although the volume flow rate of the provided CO quadrupled, the CO emission increased by only 12% to 15%. The results of this work are useful to improve the feasibility of fuel-injection systems using syngas as an alternative fuel. Full article

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

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14 pages, 3282 KiB

Open AccessArticle

Study on the Gas-Insulated Line Equivalent Model and Simplified Model

by Botong Li^*

, Tianfeng Gu, Bin Li and Yunke Zhang

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

Energies 2017, 10(7), 901; https://doi.org/10.3390/en10070901 - 1 Jul 2017

Cited by 3 | Viewed by 3758

Abstract

The gas-insulated line (GIL) is one technical solution to allow the transmission of electricity underground at a high voltage level, yet its equivalent model is quite complicated. Based on an examination of the geometrical structure of the GIL and the way the metallic [...] Read more.

The gas-insulated line (GIL) is one technical solution to allow the transmission of electricity underground at a high voltage level, yet its equivalent model is quite complicated. Based on an examination of the geometrical structure of the GIL and the way the metallic enclosure is grounded, this paper analyzed the electromagnetic and electrostatic coupling among the inner conductors and the metallic enclosures of the three phases. Then, the paper proposes a modeling method for the widely-used short-distance GIL based on the PI-model (the model consisting of two lumped admittance at each terminal and a lumped impedance in between). The GIL parameters were later simplified with the coupling effect of the metallic enclosure considered, and a simplified PI-model was produced. Finally, the proposed PI-model and its simplified version were built on the Power Systems Computer Aided Design (PSCAD) platform, and their effectiveness verified by simulation results. Full article

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13 pages, 1964 KiB

Open AccessArticle

Numerical and Experimental Studies on the Heat Transfer Performance of Copper Foam Filled with Paraffin

by Huanpei Zheng and Changhong Wang^*

School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China

Energies 2017, 10(7), 902; https://doi.org/10.3390/en10070902 - 2 Jul 2017

Cited by 15 | Viewed by 3876

Abstract

Abstract: The pore-scale numerical works on the effective thermal conductivity and melting process of copper foam filled with paraffin, and a phase-change material (PCM) with low thermal conductivity, were conducted by utilizing the two-dimensional (2D) hexahedron Calmidi-Mahajan (C-M) model and the three-dimensional [...] Read more.

Abstract: The pore-scale numerical works on the effective thermal conductivity and melting process of copper foam filled with paraffin, and a phase-change material (PCM) with low thermal conductivity, were conducted by utilizing the two-dimensional (2D) hexahedron Calmidi-Mahajan (C-M) model and the three-dimensional (3D) dodecahedron Boomsma-Poulikakos (B-P) model. The unidirectional heat transfer experiment was established to investigate the effective thermal conductivity of the composite. The simulation results of the effective thermal conductivity of the composite in 2D C-M model were 6.93, 5.41, 4.22 and 2.75 W/(m·K), for porosity of 93%, 95%, 96% and 98% respectively, while the effective thermal conductivity of the composite in 3D B-P model were 7.07, 5.24, 3.07 and 1.22 W/(m·K). The simulated results were in agreement with the experimental data obtained for the composite. It was found that the copper foam can effectively enhance the thermal conductivity of the paraffin, i.e., the smaller the porosity of copper foam, the higher the effective thermal conductivity of the composite. In addition, the Fluent Solidification/Melting model was applied to numerically investigate the melting process of the paraffin in the pore. Lastly, the solid–liquid interface development, completely melted time and temperature field distribution of paraffin in the pore of copper foam were also discussed. Full article

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

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21 pages, 4783 KiB

Open AccessArticle

Diffusion Strategy-Based Distributed Operation of Microgrids Using Multiagent System

by Van-Hai Bui¹, Akhtar Hussain¹

and Hak-Man Kim^1,2,*

¹ Department of Electrical Engineering, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406840, Korea

² Research Institute for Northeast Asian Super Grid, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406840, Korea

Energies 2017, 10(7), 903; https://doi.org/10.3390/en10070903 - 2 Jul 2017

Cited by 26 | Viewed by 5502

Abstract

In distributed operation, each unit is operated by its local controller instead of using a centralized controller, which allows the action to be based on local information rather than global information. Most of the distributed solutions have implemented the consensus method, however, convergence [...] Read more.

In distributed operation, each unit is operated by its local controller instead of using a centralized controller, which allows the action to be based on local information rather than global information. Most of the distributed solutions have implemented the consensus method, however, convergence time of the consensus method is quite long, while diffusion strategy includes a stochastic gradient term and can reach convergence much faster compared with consensus method. Therefore, in this paper, a diffusion strategy-based distributed operation of microgrids (MGs) is proposed using multiagent system for both normal and emergency operation modes. In normal operation, the MG system is operated by a central controller instead of the distributed controller to minimize the operation cost. If any event (fault) occurs in the system, MG system can be divided into two parts to isolate the faulty region. In this case, the MG system is changed to emergency operation mode. The normal part is rescheduled by the central controller while the isolated part schedules its resources in a distributed manner. The isolated part carries out distributed communication using diffusion between neighboring agents for optimal operation of this part. The proposed method enables peer-to-peer communication among the agents without the necessity of a centralized controller, and simultaneously performs resource optimization. Simulation results show that the system can be operated in an economic way in both normal operation and emergency operation modes. Full article

(This article belongs to the Special Issue Distributed Energy Resources Management)

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15 pages, 1469 KiB

Open AccessArticle

Output Impedance Control Method of Inverter-Based Distributed Generators for Autonomous Microgrid

by Youn-Ok Choi

and Jaehong Kim^*

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

Energies 2017, 10(7), 904; https://doi.org/10.3390/en10070904 - 2 Jul 2017

Cited by 6 | Viewed by 4218

Abstract

The droop method is the most favorable alternative in microgrid implementations for autonomous control of grid-forming inverter-based distributed generators (DGs) connected in parallel. However, the dynamic characteristic of the conventional droop method is poor because the inertias of inverter-based DG units are extremely [...] Read more.

The droop method is the most favorable alternative in microgrid implementations for autonomous control of grid-forming inverter-based distributed generators (DGs) connected in parallel. However, the dynamic characteristic of the conventional droop method is poor because the inertias of inverter-based DG units are extremely low and the transmission line is normally very short. An output impedance control method to enhance the dynamic performance and minimize the circulating current between grid-forming DGs is devised in this study. It is shown that it also enhances the power and harmonic sharing accuracy. The proposed method utilizes the virtual output impedance as a control signal for reactive power flow management. The effectiveness of the proposed scheme is validated using the high-speed field programmable gate array (FPGA)-based real-time hardware-in-the-loop test results. Full article

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

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16 pages, 1599 KiB

Open AccessArticle

Multi-Party Energy Management for Networks of PV-Assisted Charging Stations: A Game Theoretical Approach

by Nian Liu^1,*

, Minyang Cheng¹ and Li Ma^1,2

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

² Power Distribution Department, China Electric Power Research Institute, Beijing 100192, China

Energies 2017, 10(7), 905; https://doi.org/10.3390/en10070905 - 2 Jul 2017

Cited by 5 | Viewed by 3398

Abstract

Motivated by the development of electric vehicles (EVs), this paper addresses the energy management problem for the PV-assisted charging station (PVCS) network. An hour-ahead optimization model for the operation of PVCS is proposed, considering the profit of the PVCS, the local consumption of [...] Read more.

Motivated by the development of electric vehicles (EVs), this paper addresses the energy management problem for the PV-assisted charging station (PVCS) network. An hour-ahead optimization model for the operation of PVCS is proposed, considering the profit of the PVCS, the local consumption of the photovoltaic (PV) energy and the impacts on the grid. Moreover, a two-level feasible charging region (FCR) model is built to guarantee the service quality for EVs and learning-based decision-making is designed to assist the optimization of the PVCS in various scenarios. The multi-party energy management problem, including several kinds of energy flows of the PVCS network, is formulated as a non-cooperative game. Then, the strategies of the PVCSs are modeled as the demand response (DR) activities to achieve their own optimization goals and a two-level distributed heuristic algorithm is introduced to solve the problem. The simulation results show that the economic profit of the network is increased by 6.34% compared with the common time of use (TOU) prices approach. Besides, the percentage of the PV energy in total charging load (PPTCL) and load rate are promoted by 28.93% and 0.3125, respectively, which demonstrates the validity and practicability of the proposed method. Full article

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17 pages, 6503 KiB

Open AccessArticle

Thermo-Fluidic Comparison between Sandwich Panels with Tetrahedral Lattice Cores Fabricated by Casting and Metal Sheet Folding

by Xiaoqing Zhang¹, Xin Jin², Gongnan Xie³ and Hongbin Yan^3,*

¹ Air-Breathing Hypersonic Technology Research Centre, China Aerodynamics Research and Development Centre, Mianyang 621000, China

² School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China

³ School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

Energies 2017, 10(7), 906; https://doi.org/10.3390/en10070906 - 2 Jul 2017

Cited by 35 | Viewed by 7114

Abstract

This numerical study compares single-phase forced convective heat transfer between two sandwich panels with tetrahedral metallic lattice cores separately fabricated by investment casting and the more cost-effective metal sheet folding method. The numerical model is validated against available experimental data. For a given [...] Read more.

This numerical study compares single-phase forced convective heat transfer between two sandwich panels with tetrahedral metallic lattice cores separately fabricated by investment casting and the more cost-effective metal sheet folding method. The numerical model is validated against available experimental data. For a given Reynolds number and core porosity, the results reveal that the brazed sandwich outperforms the casted sandwich, exhibiting a 13% to 16% higher Nusselt number. Bigger vertexes and more evident blockage of mainstream by the ligaments are found to intensify the horseshoe vortex and the counter-rotating vortex pair upstream and downstream of each vertex. Relative to the casted sandwich panel, therefore, endwall heat transfer is enhanced by 22% to 27%, while similar heat transfer is achieved on the ligaments. It is also found that, for a given Reynolds number, the brazed sandwich induces a 1.6 to 1.7 times higher pressure drop relative to the casted sandwich due to more severe flow separation caused by the sharp edges of the rectangular ligaments. Finally, for a given pumping power, both sandwiches provide a similar heat transfer performance. Given that the brazed sandwich is more cost-effective and easier to fabricate than the casted one, the former may be superior from an engineering application point of view. Full article

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

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25 pages, 8094 KiB

Open AccessArticle

Finite Control Set–Model Predictive Control with Modulation to Mitigate Harmonic Component in Output Current for a Grid-Connected Inverter under Distorted Grid Conditions

by Tien Hai Nguyen and Kyeong-Hwa Kim^*

Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea

Energies 2017, 10(7), 907; https://doi.org/10.3390/en10070907 - 2 Jul 2017

Cited by 27 | Viewed by 5196

Abstract

This paper presents an improved current control strategy for a three-phase grid-connected inverter under distorted grid conditions. In terms of performance, it is important for a grid-connected inverter to maintain the harmonic contents of inverter output currents below the specified limit even when [...] Read more.

This paper presents an improved current control strategy for a three-phase grid-connected inverter under distorted grid conditions. In terms of performance, it is important for a grid-connected inverter to maintain the harmonic contents of inverter output currents below the specified limit even when the grid is subject to harmonic distortion. To address this problem, this paper proposes a modulated finite control set–model predictive control (FCS-MPC) scheme, which effectively mitigates the harmonic components in output current of a grid-connected inverter. In the proposed scheme, the system behavior in the future is predicted from the system model in the discrete-time domain. Then, the cost function is selected based on the control objective of system. This cost function is minimized during the optimization process to determine the control signals that minimize the cost function. In addition, since the proposed scheme requires pure sinusoidal reference currents in the stationary frame to work successfully, the moving average filter (MAF) is employed to enhance the performance of the traditional phase lock loop (PLL). Due to the control performance of the FCS-MPC scheme as well as the harmonic disturbance rejection capability of the MAF-PLL, the proposed scheme is able to suppress the harmonic distortion even in the presence of distorted grid condition, while retaining fast transient response. Comparative simulation results of different controllers verify the effectiveness of the proposed control scheme in compensating the harmonic disturbance. To validate the practical feasibility of the proposed scheme, the whole control algorithm is implemented on a 32-bit floating-point digital signal processor (DSP) TMS320F28335 to control a 2 kW three-phase grid-connected inverter. As a result, the proposed scheme is a promising approach toward improving the current quality of a grid-connected inverter under distorted grid conditions. Full article

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

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19 pages, 1423 KiB

Open AccessArticle

A New Miniature Wind Turbine for Wind Tunnel Experiments. Part I: Design and Performance

by Majid Bastankhah and Fernando Porté-Agel^*

Wind Engineering and Renewable Energy Laboratory (WIRE), École Polytechnique Fédérale de Lausanne (EPFL), EPFL-ENAC-IIE-WIRE, Lausanne 1015, Switzerland

Energies 2017, 10(7), 908; https://doi.org/10.3390/en10070908 - 3 Jul 2017

Cited by 86 | Viewed by 14454

Abstract

Miniature wind turbines, employed in wind tunnel experiments to study the interaction of turbines with turbulent boundary layers, usually suffer from poor performance with respect to their large-scale counterparts in the field. Moreover, although wakes of wind turbines have been extensively examined in [...] Read more.

Miniature wind turbines, employed in wind tunnel experiments to study the interaction of turbines with turbulent boundary layers, usually suffer from poor performance with respect to their large-scale counterparts in the field. Moreover, although wakes of wind turbines have been extensively examined in wind tunnel studies, the proper characterization of the performance of wind turbines has received relatively less attention. In this regard, the present study concerns the design and the performance analysis of a new three-bladed horizontal-axis miniature wind turbine with a rotor diameter of 15 cm. Due to its small size, this turbine, called WiRE-01, is particularly suitable for studies of wind farm flows and the interaction of the turbine with an incoming boundary-layer flow. Especial emphasis was placed on the accurate measurement of the mechanical power extracted by the miniature turbine from the incoming wind. In order to do so, a new setup was developed to directly measure the torque of the rotor shaft. Moreover, to provide a better understanding on the connection between the mechanical and electrical aspects of miniature wind turbines, the performance of three different direct-current (DC) generators was studied. It is found that electrical outputs of the tested generators can be used to provide a rather acceptable estimation of the mechanical input power. Force and power measurements showed that the thrust and power coefficients of the miniature turbine can reach

0.8

and

0.4

, respectively, which are close to the ones of large-scale turbines in the field. In Part II of this study, the wake structure and dynamic flow characteristics are studied for the new miniature turbine immersed in a turbulent boundary-layer flow. Full article

(This article belongs to the Collection Wind Turbines)

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17 pages, 1079 KiB

Open AccessArticle

Optimal Power Allocation for a Relaying-Based Cognitive Radio Network in a Smart Grid

by Kai Ma^1,*

, Xuemei Liu¹, Jie Yang^1,2, Zhixin Liu¹ and Yazhou Yuan¹

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

² Key Laboratory of System Control and Information Processing, Ministry of Education, Department of Automation, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2017, 10(7), 909; https://doi.org/10.3390/en10070909 - 3 Jul 2017

Cited by 8 | Viewed by 4919

Abstract

This paper obtains optimal power allocation to the data aggregator units (DAUs) and relays for cognitive wireless networks in a smart grid (SG). Firstly, the mutual interference between the primary user and the DAU are considered, and the expressions of the DAU transmission [...] Read more.

This paper obtains optimal power allocation to the data aggregator units (DAUs) and relays for cognitive wireless networks in a smart grid (SG). Firstly, the mutual interference between the primary user and the DAU are considered, and the expressions of the DAU transmission signal are derived based on the sensing information. Secondly, we use the particle swarm optimization (PSO) algorithm to search for the optimal power allocation to minimize the costs to the utility company. Finally, the impact of the sensing information on the network performance is studied. Then two special cases (namely, that only one relay is selected, and that the channel is not occupied by the primary user) are discussed. Simulation results demonstrate that the optimal power allocation and the sensing information of the relays can reduce the costs to the utility company for cognitive wireless networks in a smart grid. Full article

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

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13 pages, 1919 KiB

Open AccessArticle

Production of Torrefied Solid Bio-Fuel from Pulp Industry Waste

by Michael Huang¹, Chia-Chi Chang¹, Min-Hao Yuan², Ching-Yuan Chang^1,3,*, Chao-Hsiung Wu⁴, Je-Lueng Shie⁵, Yen-Hau Chen¹, Yi-Hung Chen⁶, Chungfang Ho⁷, Wei-Ren Chang¹, Tzu-Yi Yang¹ and Far-Ching Lin⁸

¹ Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan

² Department of Occupational Safety and Health, China Medical University, Taichung 404, Taiwan

³ Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan

⁴ Department of Environmental Engineering, Da-Yeh University, Changhua 515, Taiwan

⁵ Department of Environmental Engineering, National I-Lan University, I-Lan 260, Taiwan

⁶ Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 106, Taiwan

⁷ Department of International Business, Chung Yuan Christian University, Chung-Li 320, Taiwan

⁸ Department of Forestry and Resource Conservation, National Taiwan University, Taipei 106, Taiwan

Energies 2017, 10(7), 910; https://doi.org/10.3390/en10070910 - 3 Jul 2017

Cited by 17 | Viewed by 4709

Abstract

The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application [...] Read more.

The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application or to soil conditioners. However, due to energy demand, the WPS can be utilized in a beneficial way to mitigate an energy shortage. This study elucidated the performance of applying torrefaction, a bio-waste to energy method, to transform the WPS into solid bio-fuel. Two batches of the tested WPS (i.e., WPS1 and WPS2) were generated from a virgin pulp factory in eastern Taiwan. The WPS1 and WPS2 samples contained a large amount of organics and had high heating values (HHV) on a dry-basis (H_HD) of 18.30 and 15.72 MJ/kg, respectively, exhibiting a potential for their use as a solid bio-fuel. However, the wet WPS as received bears high water and volatile matter content and required de-watering, drying, and upgrading. After a 20 min torrefaction time (t_T), the H_HD of torrefied WPS1 (WPST1) can be enhanced to 27.49 MJ/kg at a torrefaction temperature (T_T) of 573 K, while that of torrefied WPS2 (WPST2) increased to 19.74 MJ/kg at a T_T of 593 K. The corresponding values of the energy densification ratio of torrefied solid bio-fuels of WPST1 and WPST2 can respectively rise to 1.50 and 1.25 times that of the raw bio-waste. The H_HD of WPST1 of 27.49 MJ/kg is within the range of 24–35 MJ/kg for bituminous coal. In addition, the wet-basis HHV of WPST1 with an equilibrium moisture content of 5.91 wt % is 25.87 MJ/kg, which satisfies the Quality D coal specification of the Taiwan Power Co. requiring a value of above 20.92 MJ/kg. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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23 pages, 6858 KiB

Open AccessArticle

Optimization of Guide Vane Closing Schemes of Pumped Storage Hydro Unit Using an Enhanced Multi-Objective Gravitational Search Algorithm

by Jianzhong Zhou^1,2,*, Yanhe Xu^1,2,*

, Yang Zheng^1,2 and Yuncheng Zhang^1,2

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

² Hubei Key Laboratory of Digital Valley Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China

Energies 2017, 10(7), 911; https://doi.org/10.3390/en10070911 - 3 Jul 2017

Cited by 38 | Viewed by 4481

Abstract

The optimization of guide vane closing schemes (OGVCS) of pumped storage hydro units (PSHUs) is a cooperative control and optimal operation research field in renewable energy power generation technology. This paper presents an OGVCS model of PSHUs considering the rise rate of the [...] Read more.

The optimization of guide vane closing schemes (OGVCS) of pumped storage hydro units (PSHUs) is a cooperative control and optimal operation research field in renewable energy power generation technology. This paper presents an OGVCS model of PSHUs considering the rise rate of the unit rotational speed, the specific node pressure of each hydraulic unit, as well as various complicated hydraulic and mechanical constraints. The OGVCS model is formulated as a multi-objective optimization problem to optimize conflicting objectives, i.e., unit rotational speed and water hammer pressure criteria. In order to realize an efficient solution of the OGVCS model, an enhanced multi-objective bacterial-foraging chemotaxis gravitational search algorithm (EMOBCGSA) is proposed to solve this problem, which adopts population reconstruction, adaptive selection chemotaxis operator of local searching strategy and elite archive set to efficiently solve the multi-objective problem. In particular a novel constraints-handling strategy with elimination and local search based on violation ranking is used to balance the various hydraulic and mechanical constraints. Finally, simulation cases of complex extreme operating conditions (i.e., load rejection and pump outage) of a ‘single tube-double units’ type PSHU system are conducted to verify the feasibility and effectiveness of the proposed EMOBCGSA in solving OGVCS problems. The simulation results indicate that the proposed EMOBCGSA can provide a lower rise rate of the unit rotational speed and smaller water hammer pressure than other methods established recently while considering various complex constraints in OGVCS problems. Full article

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

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21 pages, 11765 KiB

Open AccessArticle

Research on Inverter Integrated Reactive Power Control Strategy in the Grid-Connected PV Systems

by Hua Li¹, Che Wen¹, Kuei-Hsiang Chao^2,* and Ling-Ling Li¹

¹ Province-Ministry Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability, School of Electrical Engineering, Hebei University of Technology, Tianjin 300130, China

² Department of Electrical Engineering, National Chin-Yi University of Technology, Taichung 41170, Taiwan

Energies 2017, 10(7), 912; https://doi.org/10.3390/en10070912 - 3 Jul 2017

Cited by 31 | Viewed by 5985

Abstract

In order to solve the problems caused by the susceptibility to changing weather conditions and the complex load conditions of photovoltaic (PV) systems, and the fact a single target inverter control strategy cannot effectively mitigate large voltage fluctuations at point of common coupling [...] Read more.

In order to solve the problems caused by the susceptibility to changing weather conditions and the complex load conditions of photovoltaic (PV) systems, and the fact a single target inverter control strategy cannot effectively mitigate large voltage fluctuations at point of common coupling (PCC), an integrated reactive power control strategy for PV inverters is proposed. According to the weather and load conditions, this strategy is divided into four control modes: normal operation control mode, reverse power control mode, cloudy control mode and night control mode. The four control modes switch between each other under the specific switching rules to ensure an appropriate quantity of reactive power injection or consumption in the PV inverter. The effects of the four control modes in isolated operation were significant. The deviation rate of PCC voltage from its standard value was mitigated at about 2% under the integrated control strategy. Therefore, the proposed control strategy has a high application value in improving power quality and maximizing utilization of PV inverters. Full article

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

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13 pages, 3672 KiB

Open AccessArticle

Gelation Behavior Study of a Resorcinol–Hexamethyleneteramine Crosslinked Polymer Gel for Water Shut-Off Treatment in Low Temperature and High Salinity Reservoirs

by Yongpeng Sun¹, Yanchao Fang¹, Ang Chen¹, Qing You^2,*, Caili Dai^1,*, Rui Cheng¹ and Yifei Liu¹

¹ School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

² School of Energy Resources, China University of Geosciences, Beijing 100083, China

Energies 2017, 10(7), 913; https://doi.org/10.3390/en10070913 - 3 Jul 2017

Cited by 34 | Viewed by 5648

Abstract

Mature oilfields usually encounter the problem of high watercut. It is practical to use chemical methods for water-shutoff in production wells, however conventional water-shutoff agents have problems of long gelation time, low gel strength, and poor stability under low temperature and high salinity [...] Read more.

Mature oilfields usually encounter the problem of high watercut. It is practical to use chemical methods for water-shutoff in production wells, however conventional water-shutoff agents have problems of long gelation time, low gel strength, and poor stability under low temperature and high salinity conditions. In this work a novel polymer gel for low temperature and high salinity reservoirs was developed. This water-shutoff agent had controllable gelation time, adjustable gel strength and good stability performance. The crosslinking process of this polymer gel was studied by rheological experiments. The process could be divided into an induction period, a fast crosslinking period, and a stable period. Its gelation behaviors were investigated in detail. According to the Gel Strength Code (GSC) and vacuum breakthrough method, the gel strength was displayed in contour maps. The composition of the polymer gel was optimized to 0.25~0.3% YG100 + 0.6~0.9% resorcinol + 0.2~0.4% hexamethylenetetramine (HMTA) + 0.08~0.27% conditioner (oxalic acid). With the concentration increase of the polymer gel and temperature, the decrease of pH, the induction period became shorter and the crosslinking was more efficient, resulting in better stability performance. Various factors of the gelation behavior which have an impact on the crosslinking reaction process were examined. The relationships between each impact factor and the initial crosslinking time were described with mathematical equations. Full article

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

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33 pages, 48212 KiB

Open AccessArticle

Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

by Zhaohui Chong^1,2, Xuehua Li^1,*

, Xiangyu Chen¹, Ji Zhang³ and Jingzheng Lu¹

¹ Key Laboratory of Deep Coal Resource, Ministry of Education of China, School of Mines, China University of Mining and Technology, Xuzhou 221116, China

² Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong 2522, Australia

³ Beijing Computational Science Research Center, Beijing 100193, China

Energies 2017, 10(7), 914; https://doi.org/10.3390/en10070914 - 3 Jul 2017

Cited by 27 | Viewed by 5521

Abstract

Hydraulic fracturing is an important method to enhance permeability in oil and gas exploitation projects and weaken hard roofs of coal seams to reduce dynamic disasters, for example, rock burst. It is necessary to fully understand the mechanism of the initiation, propagation, and [...] Read more.

Hydraulic fracturing is an important method to enhance permeability in oil and gas exploitation projects and weaken hard roofs of coal seams to reduce dynamic disasters, for example, rock burst. It is necessary to fully understand the mechanism of the initiation, propagation, and coalescence of hydraulic fracture network (HFN) caused by fluid flow in rock formations. In this study, a coupled hydro-mechanical model was built based on synthetic rock mass (SRM) method to investigate the effects of natural fracture (NF) density on HFN propagation. Firstly, the geometrical structures of NF obtained from borehole images at the field scale were applied to the model. Secondly, the micro-parameters of the proposed model were validated against the interaction between NF and hydraulic fracture (HF) in physical experiments. Finally, a series of numerical simulations were performed to study the mechanism of HFN propagation. In addition, confining pressure ratio (CPR) and injection rate were also taken into consideration. The results suggested that the increase of NF density drives the growth of stimulated reservoir volume (SRV), concentration area of injection pressure (CAIP), and the number of cracks caused by NF. The number of tensile cracks caused by rock matrix decrease gradually with the increase of NF density, and the number of shear cracks caused by rock matrix are almost immune to the change of NF density. The propagation orientation of HFN and the breakdown pressure in rock formations are mainly controlled by CPR. Different injection rates would result in a relatively big difference in the gradient of injection pressure, but this difference would be gradually narrowed with the increase of NF density. Natural fracture density is the key factor that influences the percentages of different crack types in HFN, regardless of the value of CPR and injection rate. The proposed model may help predict HFN propagation and optimize fracturing treatment designs in fractured rock formations. Full article

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15 pages, 4075 KiB

Open AccessArticle

Explosion Behaviour of 30% Hydrogen/70% Methane-Blended Fuels in a Weak Turbulent Environment

by Fu-Sheng Li, Guo-Xiu Li and Zuo-Yu Sun^*

School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China

Energies 2017, 10(7), 915; https://doi.org/10.3390/en10070915 - 3 Jul 2017

Cited by 13 | Viewed by 4049

Abstract

In the present investigation the explosion characteristics of 30% H₂/70% CH₄-blended fuels have been experimentally studied in different turbulent environments. Some important indicators about the explosion characteristics, including maximum explosion pressure (p_max), explosion duration (t [...] Read more.

In the present investigation the explosion characteristics of 30% H₂/70% CH₄-blended fuels have been experimentally studied in different turbulent environments. Some important indicators about the explosion characteristics, including maximum explosion pressure (p_max), explosion duration (t_c), maximum rate of pressure rise ((dp/dt)_max), deflagration index (K_G), and fast burn period (t_b) have been studied. Furthermore, the influences of turbulent intensity associated with the equivalence ratio on explosion characteristics have been compressively analysed. The results indicated that, with the increase of turbulent intensity (u’_rms), the value of p_max will be correspondingly raised while the equivalent ratio (φ) corresponding to the peak value of p_max gradually changes from stoichiometric to 1.2. Based upon the value of p_max in laminar condition, the growth extent of p_max monotonically rises to u’_rms, but under a same u’_rms the growth extent of p_max first declines and then rises with the increase of φ in the rage of 0.6 to 1.2. Under a laminar environment, the peak value of (dp/dt)_max is attained at φ = 1.0; although such a conclusion is maintained in the studied range of turbulent intensity, the difference on the value of (dp/dt)_max between φ = 1.0 and φ = 1.2 is obviously reduced with the increase of u’_rms. Meanwhile, from the variation of K_G, it could be found that turbulence can raise the hazardous potential of disaster. With the increase of u’_rms, both the values of t_c and t_b reduce, the quota of t_b in the explosion performs a similar regulation, but the detailed variation extent is also controlled by u’_rms. Full article

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

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14 pages, 3660 KiB

Open AccessArticle

Economic Power Schedule and Transactive Energy through an Intelligent Centralized Energy Management System for a DC Residential Distribution System

by Jingpeng Yue^1,*, Zhijian Hu¹

, Chendan Li², Juan C. Vasquez²

and Josep M. Guerrero²

¹ School of Electrical Engineering, Wuhan University, Wuhan 430047, China

² Department of Energy Technology, Aalborg University, Aalborg 9220, Denmark

Energies 2017, 10(7), 916; https://doi.org/10.3390/en10070916 - 3 Jul 2017

Cited by 29 | Viewed by 5105

Abstract

Direct current (DC) residential distribution systems (RDS) consisting of DC living homes will be a significant integral part of future green transmission. Meanwhile, the increasing number of distributed resources and intelligent devices will change the power flow between the main grid and the [...] Read more.

Direct current (DC) residential distribution systems (RDS) consisting of DC living homes will be a significant integral part of future green transmission. Meanwhile, the increasing number of distributed resources and intelligent devices will change the power flow between the main grid and the demand side. The utilization of distributed generation (DG) requires an economic operation, stability, and an environmentally friendly approach in the whole DC system. This paper not only presents an optimization schedule and transactive energy (TE) approach through a centralized energy management system (CEMS), but also a control approach to implement and ensure DG output voltages to various DC buses in a DC RDS. Based on data collection, prediction and a certain objectives, the expert system in a CEMS can work out the optimization schedule, after this, the voltage droop control for steady voltage is aligned with the command of the unit power schedule. In this work, a DC RDS is used as a case study to demonstrate the process, the RDS is associated with unit economic models, and a cost minimization objective is proposed that is to be achieved based on the real-time electrical price. The results show that the proposed framework and methods will help the targeted DC residential system to reduce the total cost and reach stability and efficiency. Full article

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25 pages, 2456 KiB

Open AccessArticle

Coordinated Operation and Control of Combined Electricity and Natural Gas Systems with Thermal Storage

by Yu Liu¹

, Shan Gao^1,*, Xin Zhao¹, Chao Zhang¹ and Ningyu Zhang²

¹ School of Electrical Engineering, Southeast University, Nanjing 210018, China

² State Grid Jiangsu Electric Power Company Research Institute, Nanjing 211103, China

Energies 2017, 10(7), 917; https://doi.org/10.3390/en10070917 - 3 Jul 2017

Cited by 14 | Viewed by 4220

Abstract

As one of the most effective approaches in dealing with the energy crisis, combined electricity and natural gas systems have become more and more popular worldwide. To take full advantages of such hybrid energy networks, a proper operation and control method is required. [...] Read more.

As one of the most effective approaches in dealing with the energy crisis, combined electricity and natural gas systems have become more and more popular worldwide. To take full advantages of such hybrid energy networks, a proper operation and control method is required. In this paper, a novel approach coordinating combined heating and power generation is proposed. First, state excursion rate, a criterion describing the deviation of system operation, is defined for system state evaluation. Then, thermal energy storage is allocated to provide more and better operation modes for combined generation. By investigating the state excursion rate of hybrid energy systems, the optimal operation mode is chosen through an analytical strategy. Case studies on hybrid energy networks show that all state variables, including voltages in electric systems and pressures in gas networks, are adjusted to follow proper operation constraints by the implementations of the proposed strategy. In addition to providing sufficient auxiliary services for hybrid systems, it is also possible to maintain the economic and energy-efficient benefits of energy supply. This study provides an effective method to utilize the regulation capability of combined heating and power generations, which is a technical basis of energy internet. Full article

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

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22 pages, 4524 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Energy-Based Design of Powertrain for a Re-Engineered Post-Transmission Hybrid Electric Vehicle

by Laura Tribioli

Department of Engineering, Niccolò Cusano University, via Don Carlo Gnocchi 3, 00166 Rome, Italy

Energies 2017, 10(7), 918; https://doi.org/10.3390/en10070918 - 3 Jul 2017

Cited by 23 | Viewed by 6858

Abstract

This paper presents a systematic approach for the design of post-transmission hybrid electric vehicle powertrains, as an instrument aiding the designer in making the right decision. In particular, a post-transmission series/parallel hybrid electric powertrain is considered, and all of the possible energy paths [...] Read more.

This paper presents a systematic approach for the design of post-transmission hybrid electric vehicle powertrains, as an instrument aiding the designer in making the right decision. In particular, a post-transmission series/parallel hybrid electric powertrain is considered, and all of the possible energy paths are taken into account, in order to automatically select the configuration that gives the lowest fuel consumption, thus better fitting to the considered mission. The optimization problem is solved with the Dijkstra algorithm, which is more computationally efficient than other optimization algorithms in the case of massive design spaces. In this way, it is possible to design a vehicle in terms of architecture and component sizes, without making any a priori choices, which are usually based on common sense, likely compromising the overall system efficiency. In order to demonstrate the effectiveness of the methodology, different driving cycles have been simulated, and some results are presented. The methodology is particularly applied to re-engineered vehicles, aimed at maximizing the benefits of the vehicle hybridization process. Results show how the introduction, in the optimization algorithm, of the engine load factor and sharing factor, for the engine torque split between the generator and the wheels, is crucial. For example, a 10% reduction of the original engine size, suggested by a low load factor, is able to allow for a 24% reduction in the fuel consumption. On the other hand, the sharing factor is of particular importance in suggesting if the vehicle architecture should be series, parallel or rather combined. Full article

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

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16 pages, 15729 KiB

Open AccessArticle

Big-Data-Based Thermal Runaway Prognosis of Battery Systems for Electric Vehicles

by Jichao Hong^1,2, Zhenpo Wang^1,2,* and Peng Liu^1,2,*

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

² Beijing Co-Innovation Center for Electric Vehicles Lecturer, Beijing 100081, China

Energies 2017, 10(7), 919; https://doi.org/10.3390/en10070919 - 4 Jul 2017

Cited by 93 | Viewed by 10841

Abstract

A thermal runaway prognosis scheme for battery systems in electric vehicles is proposed based on the big data platform and entropy method. It realizes the diagnosis and prognosis of thermal runaway simultaneously, which is caused by the temperature fault through monitoring battery temperature [...] Read more.

A thermal runaway prognosis scheme for battery systems in electric vehicles is proposed based on the big data platform and entropy method. It realizes the diagnosis and prognosis of thermal runaway simultaneously, which is caused by the temperature fault through monitoring battery temperature during vehicular operations. A vast quantity of real-time voltage monitoring data is derived from the National Service and Management Center for Electric Vehicles (NSMC-EV) in Beijing. Furthermore, a thermal security management strategy for thermal runaway is presented under the Z-score approach. The abnormity coefficient is introduced to present real-time precautions of temperature abnormity. The results illustrated that the proposed method can accurately forecast both the time and location of the temperature fault within battery packs. The presented method is flexible in all disorder systems and possesses widespread application potential in not only electric vehicles, but also other areas with complex abnormal fluctuating environments. Full article

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

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14 pages, 3296 KiB

Open AccessArticle

Advantages of Using Supercapacitors and Silicon Carbide on Hybrid Vehicle Series Architecture

by Massimiliano Passalacqua¹, Damiano Lanzarotto¹, Matteo Repetto² and Mario Marchesoni^1,*

¹ Electrical, Electronic, and Telecommunications Engineering and Naval Architecture Department (DITEN), University of Genova, via all’Opera Pia 11a, 16145 Genova, Italy

² Department of Mechanical, Energy, Management and Transportation Engineering (DIME), University of Genova, via all’Opera Pia 15, 16145 Genova, Italy

Energies 2017, 10(7), 920; https://doi.org/10.3390/en10070920 - 4 Jul 2017

Cited by 21 | Viewed by 5628

Abstract

In recent years enormous growth has taken place in the hybrid vehicle sector; parallel architecture is the most widespread configuration regarding medium size cars. At the same time, storage systems and power electronics have experienced some important innovations. The development of supercapacitors has [...] Read more.

In recent years enormous growth has taken place in the hybrid vehicle sector; parallel architecture is the most widespread configuration regarding medium size cars. At the same time, storage systems and power electronics have experienced some important innovations. The development of supercapacitors has permitted management of high power with elevated efficiency. Moreover, the availability on the market of silicon carbide components has allowed a significant reduction of power electronic losses. These improvements may challenge the hybrid architecture used in medium size cars nowadays. On one hand, series architecture would relevantly benefit from an electric powertrain efficiency increase, on the other hand, these innovations would generate low benefits in parallel architectures. The aim of this paper is to evaluate electric component average efficiency over different road missions, in order to estimate fuel economy over various working conditions and finally to establish which hybrid configuration is most efficient in vehicle applications. Full article

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17 pages, 6243 KiB

Open AccessArticle

Design and Implementation of a STATCOM Based on a Multilevel FHB Converter with Delta-Connected Configuration for Unbalanced Load Compensation

by Wei-Neng Chang^1,* and Ching-Huan Liao²

¹ Department of Electrical Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan Dist., 333 Tao-Yuan City, Taiwan

² National Chung-Shan Institute of Science and Technology, 486, 6th Neighborhood, Sec. Jia’an, Zhongzheng Road, Longtan Dist., 325 Tao-Yuan City, Taiwan

Energies 2017, 10(7), 921; https://doi.org/10.3390/en10070921 - 4 Jul 2017

Cited by 16 | Viewed by 6108

Abstract

A delta-connected STATCOM with cascade multilevel full H-bridge (FHB) converter has been applied for phase balancing and power factor correction of unbalanced load in a three-phase, three-wire power distribution system. In this paper, a feedforward compensation formula is presented for the STATCOM by [...] Read more.

A delta-connected STATCOM with cascade multilevel full H-bridge (FHB) converter has been applied for phase balancing and power factor correction of unbalanced load in a three-phase, three-wire power distribution system. In this paper, a feedforward compensation formula is presented for the STATCOM by using the symmetrical components method to compensate unbalanced load. Computer simulation is performed for preliminary verification. Accordingly, a hardware prototype employing a TMS320F2812 DSP-based system is built for final verification test. Experimental results show that the proposed STATCOM is very effective for real-time unbalanced load compensation. Full article

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

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20 pages, 3920 KiB

Open AccessArticle

A New Hybrid Wind Power Forecaster Using the Beveridge-Nelson Decomposition Method and a Relevance Vector Machine Optimized by the Ant Lion Optimizer

by Sen Guo^1,2,*, Haoran Zhao^1,2,* and Huiru Zhao^1,2

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

² Beijing Key Laboratory of New Energy and Low-Carbon Development, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(7), 922; https://doi.org/10.3390/en10070922 - 4 Jul 2017

Cited by 12 | Viewed by 4625

Abstract

As one of the most promising kinds of the renewable energy power, wind power has developed rapidly in recent years. However, wind power has the characteristics of intermittency and volatility, so its penetration into electric power systems brings challenges for their safe and [...] Read more.

As one of the most promising kinds of the renewable energy power, wind power has developed rapidly in recent years. However, wind power has the characteristics of intermittency and volatility, so its penetration into electric power systems brings challenges for their safe and stable operation, therefore making accurate wind power forecasting increasingly important, which is also a challenging task. In this paper, a new hybrid wind power forecasting method, named the BND-ALO-RVM forecaster, is proposed. It combines the Beveridge-Nelson decomposition method (BND), relevance vector machine (RVM) and ant lion optimizer (ALO). Considering the nonlinear and non-stationary characteristics of wind power data, the wind power time series were firstly decomposed into deterministic, cyclical and stochastic components using BND. Then, these three decomposed components were respectively forecasted using RVM. Meanwhile, to improve the forecasting performance, the kernel width parameter of RVM was optimally determined by ALO, a new Nature-inspired meta-heuristic algorithm. Finally, the wind power forecasting result was obtained by multiplying the forecasting results of those three components. The proposed BND-ALO-RVM wind power forecaster was tested with real-world hourly wind power data from the Xinjiang Uygur autonomous region in China. To verify the effectiveness and feasibility of the proposed forecaster, it was compared with single RVM without time series decomposition and parameter optimization, RVM with time series decomposition based on BND (BND-RVM), RVM with parameter optimization (ALO-RVM), and Generalized Regression Neural Network with data decomposition based on Wavelet Transform (WT-GRNN) using three forecasting performance criteria, namely MAE (Mean Absolute Error), MAPE (Mean Absolute Percentage Error) and RMSE (Root Mean Square Error). The results indicate the proposed BND-ALO-RVM wind power forecaster has the best forecasting performance of all the tested options, which confirms its validity. Full article

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

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19 pages, 2697 KiB

Open AccessArticle

A New Miniature Wind Turbine for Wind Tunnel Experiments. Part II: Wake Structure and Flow Dynamics

by Majid Bastankhah and Fernando Porté-Agel^*

Wind Engineering and Renewable Energy Laboratory (WIRE), École Polytechnique Fédérale de Lausanne (EPFL), EPFL-ENAC-IIE-WIRE, 1015 Lausanne, Switzerland

Energies 2017, 10(7), 923; https://doi.org/10.3390/en10070923 - 4 Jul 2017

Cited by 59 | Viewed by 8192

Abstract

An optimized three-bladed horizontal-axis miniature wind turbine, called WiRE-01, with the rotor diameter of 15 cm is designed and fully characterized in Part I of this study. In the current part of the study, we investigate the interaction of the turbine with a [...] Read more.

An optimized three-bladed horizontal-axis miniature wind turbine, called WiRE-01, with the rotor diameter of 15 cm is designed and fully characterized in Part I of this study. In the current part of the study, we investigate the interaction of the turbine with a turbulent boundary layer. The comparison of the spectral density of the thrust force and the one of the incoming velocity revealed new insights on the use of turbine characteristics to estimate incoming flow conditions. High-resolution stereoscopic particle image-velocimetry (S-PIV) measurements were also performed in the wake of the turbine operating at optimal conditions. Detailed information on the velocity and turbulence structure of the turbine wake is presented and discussed, which can serve as a complete dataset for the validation of numerical models. The PIV data are also used to better understand the underlying mechanisms leading to unsteady loads on a downstream turbine at different streamwise and spanwise positions. To achieve this goal, a new method is developed to quantify and compare the effect of both turbulence and mean shear on the moment of the incoming momentum flux for a hypothetical turbine placed downstream. The results show that moment fluctuations caused by turbulence are bigger under full-wake conditions, whereas those caused by mean shear are clearly dominant under partial-wake conditions. Especial emphasis is also placed on how the mean wake flow distribution is affected by wake meandering. Conditional averaging based on the instantaneous position of the wake center revealed that when the wake meanders laterally to one side, a high-speed region exists on the opposite side. The results show that, due to this high-speed region, large lateral meandering motions do not lead to the expansion of the mean wake cross-section in the lateral direction. Full article

(This article belongs to the Collection Wind Turbines)

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27 pages, 4569 KiB

Open AccessArticle

Day-Ahead Market Modeling for Strategic Wind Power Producers under Robust Market Clearing

by Huiru Zhao, Yuwei Wang, Mingrui Zhao, Qingkun Tan and Sen Guo^*

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

Energies 2017, 10(7), 924; https://doi.org/10.3390/en10070924 - 4 Jul 2017

Cited by 12 | Viewed by 3897

Abstract

In this paper, considering real time wind power uncertainties, the strategic behaviors of wind power producers adopting two different bidding modes in day-ahead electricity market is modeled and experimentally compared. These two different bidding modes only provide a wind power output plan and [...] Read more.

In this paper, considering real time wind power uncertainties, the strategic behaviors of wind power producers adopting two different bidding modes in day-ahead electricity market is modeled and experimentally compared. These two different bidding modes only provide a wind power output plan and a bidding curve consisting of bidding price and power output, respectively. On the one hand, to significantly improve wind power accommodation, a robust market clearing model is employed for day-ahead market clearing implemented by an independent system operator. On the other hand, since the Least Squares Continuous Actor-Critic algorithm is demonstrated as an effective method in dealing with Markov decision-making problems with continuous state and action sets, we propose the Least Squares Continuous Actor-Critic-based approaches to model and simulate the dynamic bidding interaction processes of many wind power producers adopting two different bidding modes in the day-head electricity market under robust market clearing conditions, respectively. Simulations are implemented on the IEEE 30-bus test system with five strategic wind power producers, which verify the rationality of our proposed approaches. Moreover, the quantitative analysis and comparisons conducted in our simulations put forward some suggestions about leading wind power producers to reasonably bid in market and bidding mode selections. Full article

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18 pages, 2332 KiB

Open AccessArticle

Integration of Degradation Processes in a Strategic Offshore Wind Farm O&M Simulation Model

by Thomas Michael Welte^*, Iver Bakken Sperstad

, Espen Høegh Sørum

and Magne Lorentzen Kolstad

SINTEF Energy Research, Department of Energy Systems, Trondheim 7465, Norway

Energies 2017, 10(7), 925; https://doi.org/10.3390/en10070925 - 4 Jul 2017

Cited by 15 | Viewed by 6769

Abstract

Decision support models for offshore wind farm operation and maintenance (O&M) are required to represent the failure behavior of wind turbine components. Detailed degradation modelling is already incorporated in models for specific components and applications. However, component degradation is only one of many [...] Read more.

Decision support models for offshore wind farm operation and maintenance (O&M) are required to represent the failure behavior of wind turbine components. Detailed degradation modelling is already incorporated in models for specific components and applications. However, component degradation is only one of many effects that must be captured in high-level strategic decision support models that simulate entire wind farms. Thus, for practical applications, a trade-off is needed between detailed degradation modelling and the level of simplicity of input data representation. To this end, this paper discusses two alternative approaches for taking into account component degradation processes in strategic offshore wind farm O&M simulation models: (1) full integration of the degradation process in the O&M simulation model; and (2) loose integration where the degradation process is translated into simplified input to the O&M model. As a proof-of-concept, a Markov process for blade degradation has been considered. Simulations using the NOWIcob O&M model show that the difference between full and loose integration is small in terms of aggregated output parameters such as average wind turbine availability and O&M costs. Although loose integration models some effects less accurately than full integration, the former is more flexible and convenient, and the accuracy is for most purposes sufficient for such O&M models. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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20 pages, 13988 KiB

Open AccessFeature PaperArticle

Grid Synchronization of a Seven-Phase Wind Electric Generator Using d-q PLL

by Kalaivani Chandramohan¹, Sanjeevikumar Padmanaban^2,*

, Rajambal Kalyanasundaram¹, Mahajan Sagar Bhaskar²

and Lucian Mihet-Popa³

¹ Department of Electrical and Electronics Engineering, Pondicherry Engineering College, Kalapet, Puducherry 605014, India

² Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland Park 2006, South Africa

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

Energies 2017, 10(7), 926; https://doi.org/10.3390/en10070926 - 4 Jul 2017

Cited by 21 | Viewed by 8030

Abstract

The evolving multiphase induction generators (MPIGs) with more than three phases are receiving prominence in high power generation systems. This paper aims at the development of a comprehensive model of the wind turbine driven seven-phase induction generator (7PIG) along with the necessary power [...] Read more.

The evolving multiphase induction generators (MPIGs) with more than three phases are receiving prominence in high power generation systems. This paper aims at the development of a comprehensive model of the wind turbine driven seven-phase induction generator (7PIG) along with the necessary power electronic converters and the controller for grid interface. The dynamic model of the system is developed in MATLAB/Simulink (R2015b, The MathWorks, Inc., Natick, MA, USA). A synchronous reference frame phase-locked loop (SRFPLL) system is incorporated for grid synchronization. The modeling aspects are detailed and the system response is observed for various wind velocities. The effectiveness of the seven phase induction generator is demonstrated with the fault tolerant capability and high output power with reduced phase current when compared to the conventional 3-phase wind generation scheme. The response of the PLL is analysed and the results are presented. Full article

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

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12 pages, 1253 KiB

Open AccessArticle

Design of Ecological CO₂ Enrichment System for Greenhouse Production using TBAB + CO₂ Semi-Clathrate Hydrate

by Satoshi Takeya^1,*, Sanehiro Muromachi¹, Tatsuo Maekawa¹, Yoshitaka Yamamoto¹, Hiroko Mimachi², Takahiro Kinoshita², Tetsuro Murayama², Hiroki Umeda^3,†, Dong-Hyuk Ahn³, Yasunaga Iwasaki³, Hidenori Hashimoto^1,4, Tsutomu Yamaguchi^1,4, Katsunori Okaya⁵ and Seiji Matsuo^5,*

¹ National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan

² Mitsui Engineering & Shipbuilding, Co., Ltd., 16-1, Tamahara 3, Tamano, Okayama 706-0014, Japan

³ National Agriculture and Food Research Organization, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan

⁴ Graduate School of Environment, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan

⁵ Graduate School of Engineering, The University of Tokyo, 73-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

^† Present address: College of Bioresource Sciences, Nihon University, Tokyo 113-8656, Japan

Energies 2017, 10(7), 927; https://doi.org/10.3390/en10070927 - 4 Jul 2017

Cited by 27 | Viewed by 6564

Abstract

This paper proposes an innovative CO₂ enrichment system for crop production under a controlled greenhouse environment by means of tetra-n-butylammonium bromide (TBAB) + CO₂ semi-clathrate hydrate (SC). In this system, CO₂ is captured directly from exhaust gas from [...] Read more.

This paper proposes an innovative CO₂ enrichment system for crop production under a controlled greenhouse environment by means of tetra-n-butylammonium bromide (TBAB) + CO₂ semi-clathrate hydrate (SC). In this system, CO₂ is captured directly from exhaust gas from a combustion heater at night, which can be used for stimulating photosynthesis of crops in greenhouses during daytime. Although the gas capacity of TBAB + CO₂ SC is less than that of CO₂ gas hydrate, it is shown that TBAB + CO₂ SC can store CO₂ for CO₂ enrichment in crop production even under moderate pressure conditions (<1.0 MPa) at 283 K. Full article

(This article belongs to the Special Issue Methane Hydrate Research and Development)

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22 pages, 3333 KiB

Open AccessArticle

Power Balancing Control for Grid Energy Storage System in Photovoltaic Applications—Real Time Digital Simulation Implementation

by Sridhar Vavilapalli¹, Sanjeevikumar Padmanaban^2,*

, Umashankar Subramaniam¹

and Lucian Mihet-Popa³

¹ Department of Energy and Power Electronics, School of Electrical Engineering, VIT University, Vellore 632014, India

² Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland, Johannesburg 2006, South Africa

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

Energies 2017, 10(7), 928; https://doi.org/10.3390/en10070928 - 5 Jul 2017

Cited by 44 | Viewed by 8272

Abstract

A grid energy storage system for photo voltaic (PV) applications contains three different power sources i.e., PV array, battery storage system and the grid. It is advisable to isolate these three different sources to ensure the equipment safety. The configuration proposed in this [...] Read more.

A grid energy storage system for photo voltaic (PV) applications contains three different power sources i.e., PV array, battery storage system and the grid. It is advisable to isolate these three different sources to ensure the equipment safety. The configuration proposed in this paper provides complete isolation between the three sources. A Power Balancing Control (PBC) method for this configuration is proposed to operate the system in three different modes of operation. Control of a dual active bridge (DAB)-based battery charger which provides a galvanic isolation between batteries and other sources is explained briefly. Various modes of operation of a grid energy storage system are also presented in this paper. Hardware-In-the-Loop (HIL) simulation is carried out to check the performance of the system and the PBC algorithm. A power circuit (comprised of the inverter, dual active bridge based battery charger, grid, PV cell, batteries, contactors, and switches) is simulated and the controller hardware and user interface panel are connected as HIL with the simulated power circuit through Real Time Digital Simulator (RTDS). HIL simulation results are presented to explain the control operation, steady-state performance in different modes of operation and the dynamic response of the system. Full article

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

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11 pages, 12963 KiB

Open AccessArticle

Stochastic Navigation in Smart Cities

by Rubén Martín García^1,*

, Francisco Prieto-Castrillo^1,2,3,*, Gabriel Villarrubia González¹

, Javier Prieto Tejedor^1,4

and Juan Manuel Corchado¹

¹ BISITE Research Group, University of Salamanca, Edificio I+D+i, 37008 Salamanca, Spain

² Media Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA

³ Harvard T.H. Chan School of Public Health, Harvard University, Boston, MA 02115, USA

⁴ StageMotion, R&D Department, C/Orfebres 10, 34005 Palencia, Spain

Energies 2017, 10(7), 929; https://doi.org/10.3390/en10070929 - 5 Jul 2017

Cited by 3 | Viewed by 4074

Abstract

In this work we show how a simple model based on chemical signaling can reduce the exploration times in urban environments. The problem is relevant for smart city navigation where electric vehicles try to find recharging stations with unknown locations. To this end [...] Read more.

In this work we show how a simple model based on chemical signaling can reduce the exploration times in urban environments. The problem is relevant for smart city navigation where electric vehicles try to find recharging stations with unknown locations. To this end we have adapted the classical ant foraging swarm algorithm to urban morphologies. A perturbed Markov chain model is shown to qualitatively reproduce the observed behaviour. This consists of perturbing the lattice random walk with a set of perturbing sources. As the number of sources increases the exploration times decrease consistently with the swarm algorithm. This model provides a better understanding of underlying process dynamics. An experimental campaign with real prototypes provided experimental validation of our models. This enables us to extrapolate conclusions to optimize electric vehicle routing in real city topologies. Full article

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

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15 pages, 959 KiB

Open AccessArticle

Capacitive Emulation for LCL-Filtered Grid-Connected Converters

by Jose Miguel Espi

, Rafael Garcia-Gil^*

and Jaime Castello

Department of Electrical Engineering, University of Valencia, Avd. Universitat S/N, 46100 Burjassot-Valencia, Spain

Energies 2017, 10(7), 930; https://doi.org/10.3390/en10070930 - 5 Jul 2017

Cited by 6 | Viewed by 3746

Abstract

This paper proposes an effective capacitive emulation (CE) technique to reduce the grid current distortion when the converter currents are controlled (converter current feedback (CCF)) in grid-connected converters with an LCL filter. Although the CCF scheme is preferable to the grid current feedback [...] Read more.

This paper proposes an effective capacitive emulation (CE) technique to reduce the grid current distortion when the converter currents are controlled (converter current feedback (CCF)) in grid-connected converters with an LCL filter. Although the CCF scheme is preferable to the grid current feedback (GCF) scheme in terms of stability and inherent current limitation of the power semiconductors, the former presents a problem of additional grid-current harmonic distortion due to the LCL capacitor, which generates a distorted current by line voltage differentiation. To solve this problem, the distorting capacitive current is reproduced on the converter output, so that both cancel out each other on the grid. That is, the converter emulates a negative capacitance while delivering the active and reactive power at the fundamental frequency. This is achieved by adding an estimation of the distorting capacitive current to the converter current reference. Moreover, an effective CE technique requires a current control capable of tracking all harmonics added to the current reference and compensating for any control delay. To compensate this delay, the paper proposes a buffer-based method to advance and filter the current reference. The effectiveness of the CE method has been tested on a 10-kVA transformerless inverter with CCF and a simple proportional-integral (PI) control with grid-voltage feedforward cancellation. Experimental results prove that the proposed solution reduces the line current THD (total harmonic distortion) compared with the GCF strategy with proportional-resonant (PR) control. Full article

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23 pages, 6533 KiB

Open AccessArticle

Optimizing the Weather Research and Forecasting (WRF) Model for Mapping the Near-Surface Wind Resources over the Southernmost Caribbean Islands of Trinidad and Tobago

by Xsitaaz T. Chadee^1,*

, Naresh R. Seegobin²

and Ricardo M. Clarke¹

¹ Environmental Physics Laboratory, Department of Physics, Faculty of Science and Technology, The University of the West Indies, St. Augustine, Trinidad and Tobago

² Department of Computing and Information Technology, Faculty of Science and Technology, The University of the West Indies, St. Augustine, Trinidad and Tobago

Energies 2017, 10(7), 931; https://doi.org/10.3390/en10070931 - 5 Jul 2017

Cited by 27 | Viewed by 5613

Abstract

Numerical wind mapping is currently the wind power industry’s standard for preliminary assessments for sites of good wind resources. Of the various available numerical models, numerical weather prediction (NWP) models are best suited for modeling mesoscale wind flows across small islands. In this [...] Read more.

Numerical wind mapping is currently the wind power industry’s standard for preliminary assessments for sites of good wind resources. Of the various available numerical models, numerical weather prediction (NWP) models are best suited for modeling mesoscale wind flows across small islands. In this study, the Weather Research and Forecast (WRF) NWP model was optimized for simulating the wind resources of the Caribbean islands of Trinidad and Tobago in terms of spin-up period for developing mesoscale features, the input initial and boundary conditions, and the planetary boundary layer (PBL) parameterizations. Hourly model simulations of wind speed and wind direction for a one-month period were compared with corresponding 10 m level wind observations. The National Center for Environmental Prediction (NCEP)-Department of Energy (DOE) reanalysis of 1.875° horizontal resolution was found to be better suited to provide initial and boundary conditions (ICBCs) over the 1° resolution NCEP final analysis (FNL); 86% of modeled wind speeds were within ±2 m/s of measured values at two locations when the coarse resolution NCEP reanalysis was used as compared with 55–64% of modeled wind speeds derived from FNL. Among seven PBL schemes tested, the Yonsei University PBL scheme with topographic drag enabled minimizes the spatial error in wind speed (mean bias error +0.16 m/s, root-mean-square error 1.53 m/s and mean absolute error 1.21 m/s) and is capable of modeling the bimodal wind speed histogram. These sensitivity tests provide a suitable configuration for the WRF model for mapping the wind resources over Trinidad and Tobago, which is a factor in developing a wind energy sector in these islands. Full article

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13 pages, 851 KiB

Open AccessArticle

Harmonic Distortion Minimization in Power Grids with Wind and Electric Vehicles

by Ritam Misra¹, Sumit Paudyal^2,*, Oğuzhan Ceylan³ and Paras Mandal⁴

¹ Midcontinent Independent System Operator, Eagan, MN 55122, USA

² Department of Electrical and Computer Engineering, Michigan Technological University, Houghton, MI 49931, USA

³ Department of Electrical and Electronics Engineering, Istanbul Kemerburgaz University, Istanbul 34000, Turkey

⁴ Department of Electrical and Computer Engineering, University of Texas at El Paso, El Paso, TX 79901, USA

Energies 2017, 10(7), 932; https://doi.org/10.3390/en10070932 - 5 Jul 2017

Cited by 13 | Viewed by 5189

Abstract

Power-electronic interfacing based devices such as wind generators (WGs) and electrical vehicles (EVs) cause harmonic distortions on the power grid. Higher penetration and uncoordinated operation of WGs and EVs can lead to voltage and current harmonic distortions, which may exceed IEEE limits. It [...] Read more.

Power-electronic interfacing based devices such as wind generators (WGs) and electrical vehicles (EVs) cause harmonic distortions on the power grid. Higher penetration and uncoordinated operation of WGs and EVs can lead to voltage and current harmonic distortions, which may exceed IEEE limits. It is interesting to note that WGs and EVs have some common harmonic profiles. Therefore, when EVs are connected to the grid, the harmonic pollution EVs impart onto the grid can be reduced to some extent by the amount of wind power injecting into the grid and vice versa. In this context, this work studies the impact of EVs on harmonic distortions and careful utilization of wind power to minimize the distortions in distribution feeders. For this, a harmonic unbalanced distribution feeder model is developed in OpenDSS and interfaced with Genetic Algorithm (GA) based optimization algorithm in MATLAB to solve optimal harmonic power flow (OHPF) problems. The developed OHPF model is first used to study impact of EV penetration on current/voltage total harmonic distortions (THDs) in distribution grids. Next, dispatch of WGs are found at different locations on the distribution grid to demonstrate reduction in the current/voltage THDs when EVs are charging. Full article

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

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15 pages, 414 KiB

Open AccessArticle

Optimal Scheduling for Electric Vehicle Charging under Variable Maximum Charging Power

by Jinil Han¹, Jongyoon Park² and Kyungsik Lee^2,*

¹ Department of Industrial and Information Systems Engineering, Soongsil University, Seoul 06978, Korea

² Department of Industrial Engineering, Seoul National University, Seoul 08826, Korea

Energies 2017, 10(7), 933; https://doi.org/10.3390/en10070933 - 5 Jul 2017

Cited by 39 | Viewed by 6188

Abstract

The large-scale integration of electric vehicles (EVs) into power systems is expected to lead to challenges in the operation of the charging infrastructure. In this paper, we deal with the problem of an aggregator coordinating charging schedules of EVs with the objective of [...] Read more.

The large-scale integration of electric vehicles (EVs) into power systems is expected to lead to challenges in the operation of the charging infrastructure. In this paper, we deal with the problem of an aggregator coordinating charging schedules of EVs with the objective of minimizing the total charging cost. In particular, unlike most previous studies, which assumed constant maximum charging power, we assume that the maximum charging power can vary according to the current state of charge (SOC). Under this assumption, we propose two charging schemes, namely non-preemptive and preemptive charging. The difference between these two is whether interruptions during the charging process are allowed or not. We formulate the EV charging-scheduling problem for each scheme and propose a formulation that can prevent frequent interruptions. Our numerical simulations compare different charging schemes and demonstrate that preemptive charging with limited interruptions is an attractive alternative in terms of both cost and practicality. We also show that the proposed formulations can be applied in practice to solve large-scale charging-scheduling problems. Full article

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

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22 pages, 32227 KiB

Open AccessArticle

A High-Efficiency Isolated LCLC Multi-Resonant Three-Port Bidirectional DC-DC Converter

by Cheng-Shan Wang, Wei Li, Yi-Feng Wang^*

, Fu-Qiang Han^† and Bo Chen^†

¹ School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China

^† These authors contributed equally to this work.

Energies 2017, 10(7), 934; https://doi.org/10.3390/en10070934 - 5 Jul 2017

Cited by 11 | Viewed by 4767

Abstract

In this paper, an isolated multi-resonant three-port bidirectional direct current-direct current (DC-DC) converter is proposed, which is composed of three full bridges, two inductor-capacitor-inductor-capacitor (LCLC) multi-resonant tanks and a three-winding transformer. The phase shift control method is employed to manage the power transmission [...] Read more.

In this paper, an isolated multi-resonant three-port bidirectional direct current-direct current (DC-DC) converter is proposed, which is composed of three full bridges, two inductor-capacitor-inductor-capacitor (LCLC) multi-resonant tanks and a three-winding transformer. The phase shift control method is employed to manage the power transmission among three ports. Relying on the appropriate parameter selection, both of the fundamental and the third order power can be delivered through the multi-element LCLC resonant tanks, and consequently, it contributes to restrained circulating energy and the desirable promoted efficiency. Besides, by adjusting the driving frequency under different load conditions, zero-voltage-switching (ZVS) characteristics of all the switches of three ports are guaranteed. Therefore, lower switching loss and higher efficiency are achieved in full load range. In order to verify the feasibility of the proposed topology, a 1.5 kW prototype is established, of which the maximum efficiencies under forward and reverse operating conditions are 96.7% and 96.9% respectively. In addition, both of the bidirectional efficiencies maintain higher than 95.5% when the power level is above 0.5 kW. Full article

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18 pages, 3456 KiB

Open AccessFeature PaperArticle

Internal Balance during Low-Voltage-Ride-Through of the Modular Multilevel Converter STATCOM

by Georgios Tsolaridis¹, Epameinondas Kontos^2,*

, Sanjay K. Chaudhary¹

, Pavol Bauer² and Remus Teodorescu¹

¹ Department of Energy Technology, Aalborg University, 9220 Aalborg East, Denmark

² Department of Electrical Sustainable Energy, Delft University of Technology, 2628 CD Delft, The Netherlands

Energies 2017, 10(7), 935; https://doi.org/10.3390/en10070935 - 5 Jul 2017

Cited by 15 | Viewed by 4574

Abstract

Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The [...] Read more.

Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The study focuses on the challenging internal control of the converter to allow the independent control of the energy levels of each arm, with the goal to maintain internal balancing of the MMC during contingencies. Extensive experimental results highlight the need for a sophisticated internal control. Moreover, the experimental analysis verifies that, by using the proposed control structure, the MMC can effectively ride through a fault on the AC side without tripping, while injecting the necessary positive and negative sequence reactive current levels according to the most recent grid codes. Full article

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20 pages, 3264 KiB

Open AccessArticle

A Piecewise Bound Constrained Optimization for Harmonic Responsibilities Assessment under Utility Harmonic Impedance Changes

by Tianlei Zang^1,2,3

, Zhengyou He^1,*, Yan Wang¹, Ling Fu¹, Zhiyu Peng² and Qingquan Qian¹

¹ School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China

² Guizhou Key Laboratory of Electric Power Big Data, Guizhou Institute of Technology, Guiyang 550003, China

³ State Key Laboratory of Security Control and Simulation of Power Systems and Large Scale Generation Equipment, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China

Energies 2017, 10(7), 936; https://doi.org/10.3390/en10070936 - 6 Jul 2017

Cited by 7 | Viewed by 3579

Abstract

Considering the effect of the utility harmonic impedance variations on harmonic responsibility, a method based on piecewise bound constrained optimization is proposed in this paper to evaluate the load harmonic responsibilities. The wavelet packet transform is employed to determine the change times of [...] Read more.

Considering the effect of the utility harmonic impedance variations on harmonic responsibility, a method based on piecewise bound constrained optimization is proposed in this paper to evaluate the load harmonic responsibilities. The wavelet packet transform is employed to determine the change times of the utility harmonic impedances. The harmonic monitoring data is divided into several segments where the utility harmonic impedances are considered as constants. Then, the problem of harmonic responsibility assessment under utility harmonic impedance changes are settled by the piecewise bound constrained optimization model. Furthermore, the interior point, the sequential quadratic programming and the active set algorithm are respectively adopted to calculate all the instantaneous harmonic responsibilities of harmonic loads. Finally, the weighted summation is used to calculate the total harmonic responsibility. To demonstrate the validity, simulation tests are carried out on an experimental circuit and the IEEE 13-bus distribution system. Full article

(This article belongs to the Special Issue Distribution Power Systems and Power Quality)

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19 pages, 6469 KiB

Open AccessArticle

A Novel Modular-Stator Outer-Rotor Flux-Switching Permanent-Magnet Motor

by Jing Zhao^1,2, Yun Zheng^1,2, Congcong Zhu^1,2, Xiangdong Liu^1,2,* and Bin Li^1,2

¹ School of Automation, Beijing Institute of Technology, Beijing 100081, China

² Key Laboratory for Intelligent Control & Decision of Complex Systems, Beijing Institute of Technology, Beijing 100081, China

Energies 2017, 10(7), 937; https://doi.org/10.3390/en10070937 - 6 Jul 2017

Cited by 14 | Viewed by 10004

Abstract

A novel modular-stator outer-rotor flux-switching permanent-magnet (MSOR-FSPM) motor is proposed and studied in this paper. Structure, operation and design principles of the MSOR-FSPM motor are introduced and analyzed. Considering that the combination of different pole number and slot number has a great influence [...] Read more.

A novel modular-stator outer-rotor flux-switching permanent-magnet (MSOR-FSPM) motor is proposed and studied in this paper. Structure, operation and design principles of the MSOR-FSPM motor are introduced and analyzed. Considering that the combination of different pole number and slot number has a great influence on the motor performance, the optimum rotor pole number for the 12-stator-slot MSOR-FSPM motor is researched to obtain good performance and make full use of the space in the MSOR-FSPM motor. The influences of rotor pole number on cogging torque, torque ripple and electromagnetic torque are analyzed and a 12-slot/10-pole MSOR-FSPM motor was chosen for further study. Then, several main parameters of the 12-slot/10-pole MSOR-FSPM motor were optimized to reduce the torque ripple. Finally, the utilization of permanent magnet (PM) in the MSOR-FSPM motor and a conventional outer-rotor flux-switching permanent-magnet (COR-FSPM) motor are compared and analyzed from the point of view of magnetic flux path, and verified by the finite element method (FEM). The FEM results show that the PM volume of MSOR-FSPM motor is only 54.04% of that in a COR-FSPM motor, but its average electromagnetic torque can reach more than 75% of the torque of COR-FSPM motor. Full article

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

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13 pages, 3337 KiB

Open AccessArticle

Influence of Copper Particles on Breakdown Voltage and Frequency-Dependent Dielectric Property of Vegetable Insulating Oil

by Jing Zhang¹, Feipeng Wang^1,*, Jian Li^1,*, Hehuan Ran¹ and Dali Huang²

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

² Guangzhou Power Supply Co. Ltd., Guangzhou 510000, China

Energies 2017, 10(7), 938; https://doi.org/10.3390/en10070938 - 6 Jul 2017

Cited by 30 | Viewed by 5616

Abstract

The insulating performance of oil is vulnerable to particles especially the conductive particles. This paper investigated the influence of copper particles of micrometer size on the breakdown strength and frequency-dependent properties of vegetable oil. The AC breakdown voltage of contaminated vegetable oil with [...] Read more.

The insulating performance of oil is vulnerable to particles especially the conductive particles. This paper investigated the influence of copper particles of micrometer size on the breakdown strength and frequency-dependent properties of vegetable oil. The AC breakdown voltage of contaminated vegetable oil with copper particles of different numbers (ranging from 10³ to 10⁶) was measured. The frequency-dependent dielectric properties including volume resistivity, relative permittivity and dissipation factor of the contaminated vegetable oil with copper particles of various volumetric concentrations (0.011%, 0.056% and 0.112%) were measured. Identical experiments were conducted with mineral oil for comparison. Results show that the AC breakdown voltage of vegetable oil decreases with the increase of copper particle concentration. The mineral oil exhibits a similar trend, but the influence of copper particles on the AC breakdown voltage of vegetable oil is less significant than that on mineral oil because of its greater viscosity. The relative permittivity and dissipation factor increase with increasing copper volumetric concentration while the volume resistivity decreases. The influence of copper particles on them is significant at low frequencies and this influence becomes inconspicuous as the frequency increases. Similar results were observed for mineral oil. Full article

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

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19 pages, 3181 KiB

Open AccessArticle

A Flexible Maximum Power Point Tracking Control Strategy Considering Both Conversion Efficiency and Power Fluctuation for Large-inertia Wind Turbines

by Hongmin Meng^*

, Tingting Yang, Ji-zhen Liu and Zhongwei Lin

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

Energies 2017, 10(7), 939; https://doi.org/10.3390/en10070939 - 6 Jul 2017

Cited by 10 | Viewed by 5560

Abstract

In wind turbine control, maximum power point tracking (MPPT) control is the main control mode for partial-load regimes. Efficiency potentiation of energy conversion and power smoothing are both two important control objectives in partial-load regime. However, on the one hand, low power fluctuation [...] Read more.

In wind turbine control, maximum power point tracking (MPPT) control is the main control mode for partial-load regimes. Efficiency potentiation of energy conversion and power smoothing are both two important control objectives in partial-load regime. However, on the one hand, low power fluctuation signifies inefficiency of energy conversion. On the other hand, enhancing efficiency may increase output power fluctuation as well. Thus the two objectives are contradictory and difficult to balance. This paper proposes a flexible MPPT control framework to improve the performance of both conversion efficiency and power smoothing, by adaptively compensating the torque reference value. The compensation was determined by a proposed model predictive control (MPC) method with dynamic weights in the cost function, which improved control performance. The computational burden of the MPC solver was reduced by transforming the cost function representation. Theoretical analysis proved the good stability and robustness. Simulation results showed that the proposed method not only kept efficiency at a high level, but also reduced power fluctuations as much as possible. Therefore, the proposed method could improve wind farm profits and power grid reliability. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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15 pages, 741 KiB

Open AccessArticle

Crop Factors Influencing Ethanol Production from Sorghum Juice and Bagasse

by Lorenzo Capecchi, Lorenzo Nissen

, Monica Modesto, Giuseppe Di Girolamo, Luciano Cavani

and Lorenzo Barbanti^*

Department of Agricultural Sciences, University of Bologna, Viale Fanìn 44, 40127 Bologna, Italy

Energies 2017, 10(7), 940; https://doi.org/10.3390/en10070940 - 7 Jul 2017

Cited by 6 | Viewed by 3644

Abstract

This study investigated the effects of two soil moisture levels (SM) (30% and 70% soil available water) and three harvests (90 days, 118 days, and 151 days after seeding) on sweet (S506) and fiber (B133) sorghum genotypes under rain-sheltered conditions. Juice and bagasse-derived [...] Read more.

This study investigated the effects of two soil moisture levels (SM) (30% and 70% soil available water) and three harvests (90 days, 118 days, and 151 days after seeding) on sweet (S506) and fiber (B133) sorghum genotypes under rain-sheltered conditions. Juice and bagasse-derived ethanol and their sum (EtOH_BJ, EtOH_B, and EtOH_J+B, respectively) were assessed. Water use efficiency (WUE) was determined for sorghum dry weight (DW) and EtOH_J+B. S506 had similar DW, but higher sugar content than B133, resulting in higher EtOH_J (+32%) and EtOH_J+B (+9%). High SM-enhanced DW, juice and sugars content, determining a strong EtOH_J+B increase (+99% vs. low SM). Late harvest enhanced DW and EtOH_J+B (+107% vs. early harvest), despite decreasing extractives and increasing structural fiber components. Water use efficiency of EtOH_J+B improved with high vs. low SM, although differences faded in late harvest. Upscale of EtOH_J+B and WUE data indicated a range of 21,000–82,000 ha of sorghum cultivation and 60–117 Mm³ of irrigation water, as amounts of resources needed to supply an 85,000 m³·yr⁻¹ bio-ethanol plant. This large variation in land and water needs depended on specific combinations between crop factors SM and harvests. Full article

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

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22 pages, 15714 KiB

Open AccessArticle

Efficiency Improved Load Sensing System—Reduction of System Inherent Pressure Losses

by Jan Siebert^*, Marco Wydra and Marcus Geimer

Institute of Mobile Machines (Mobima), Karlsruhe Institute of Technology (KIT), Rintheimer Querallee 2, 76131 Karlsruhe, Germany

Energies 2017, 10(7), 941; https://doi.org/10.3390/en10070941 - 7 Jul 2017

Cited by 25 | Viewed by 7847

Abstract

Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different [...] Read more.

Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different pressure levels. This paper introduces a novel hydraulic LS system architecture with reduced SIPL. In the new circuit, each actuator section is automatically connected either to the tank or to a hydraulic accumulator in dependence of its individual and the systems load situation via an additional valve. When connected to the accumulator, the additional pressure potential in the return line increases the load on the actuator and thus reduces the pressure difference to be throttled at the pressure compensator. The new circuit was developed and analyzed in simulation. For this, the hydraulic simulation model of a hydraulic excavator was used. To validate the sub-models of both machine and new circuit, two separate test rigs were developed and used. Both valid sub-models then were combined to the model of the optimized system. The final simulation results showed, that under the applied conditions, the novel hydraulic circuit was able to decrease SIPL of the examined system by approximately 44% and thus increasing the machines’ total energy efficiency. With the successful completion of the project, the gathered knowledge will be used to further develop the proposed circuit and its components. Full article

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

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12 pages, 5110 KiB

Open AccessArticle

Experimental Investigation on Propagation Characteristics of PD Radiated UHF Signal in Actual 252 kV GIS

by Tianhui Li^1,*, Mingzhe Rong^2,*, Xiaohua Wang² and Jin Pan¹

¹ State Grid Hebei Electric Power Research Institute, Shijiazhuang 050021, China

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

Energies 2017, 10(7), 942; https://doi.org/10.3390/en10070942 - 7 Jul 2017

Cited by 11 | Viewed by 4334

Abstract

For partial discharge (PD) diagnostics in gas insulated switchgears (GISs) based on the ultra-high-frequency (UHF) method, it is essential to study the attenuation characteristics of UHF signals so as to improve the application of the UHF technique. Currently, the performance of UHF has [...] Read more.

For partial discharge (PD) diagnostics in gas insulated switchgears (GISs) based on the ultra-high-frequency (UHF) method, it is essential to study the attenuation characteristics of UHF signals so as to improve the application of the UHF technique. Currently, the performance of UHF has not been adequately considered in most experimental research, while the constructive conclusions about the installation and position of UHF sensors are relatively rare. In this research, by using a previously-designed broadband sensor, the output signal is detected and analyzed experimentally in a 252 kV GIS with L-shaped structure and disconnecting switch. Since the relative position of the sensor and the defect is usually fixed by prior research, three circumferential angle positions of the defect in cross section are performed. The results are studied by time, statistics and frequency analyses. This identifies that the discontinuity conductor of DS will lead to a rise of both the peak to peak value (Vpp) and the transmission rate of the UHF signal. Then, the frequency analysis indicates that the reason for the distinction of signal amplitude and transmission rate is that the mode components of the PD signal are distinctively affected by the special structure of GIS. Finally, the optimal circumferential angle position of the UHF Sensor is given based on the comparison of transmission rates. Full article

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

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31 pages, 924 KiB

Open AccessArticle

Analysis of On-Board Photovoltaics for a Battery Electric Bus and Their Impact on Battery Lifespan

by Kevin R. Mallon^*, Francis Assadian and Bo Fu

Department of Mechanical and Aerospace Engineering, University of California, Davis, CA 95616, USA

Energies 2017, 10(7), 943; https://doi.org/10.3390/en10070943 - 7 Jul 2017

Cited by 77 | Viewed by 9290

Abstract

Heavy-duty electric powertrains provide a potential solution to the high emissions and low fuel economy of trucks, buses, and other heavy-duty vehicles. However, the cost, weight, and lifespan of electric vehicle batteries limit the implementation of such vehicles. This paper proposes supplementing the [...] Read more.

Heavy-duty electric powertrains provide a potential solution to the high emissions and low fuel economy of trucks, buses, and other heavy-duty vehicles. However, the cost, weight, and lifespan of electric vehicle batteries limit the implementation of such vehicles. This paper proposes supplementing the battery with on-board photovoltaic modules. In this paper, a bus model is created to analyze the impact of on-board photovoltaics on electric bus range and battery lifespan. Photovoltaic systems that cover the bus roof and bus sides are considered. The bus model is simulated on a suburban bus drive cycle on a bus route in Davis, CA, USA for a representative sample of yearly weather conditions. Roof-mounted panels increased vehicle driving range by 4.7% on average annually, while roof and side modules together increased driving range by 8.9%. However, variations in weather conditions meant that this additional range was not reliably available. For constant vehicle range, rooftop photovoltaic modules extended battery cycle life by up to 10% while modules on both the roof and sides extended battery cycle life by up to 19%. Although side-mounted photovoltaics increased cycle life and range, they were less weight- and cost-effective compared to the roof-mounted panels. Full article

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

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13 pages, 1963 KiB

Open AccessArticle

Concept of an Accelerator-Driven Advanced Nuclear Energy System

by Xuesong Yan, Lei Yang^*, Xunchao Zhang and Wenlong Zhan

Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China

Energies 2017, 10(7), 944; https://doi.org/10.3390/en10070944 - 7 Jul 2017

Cited by 32 | Viewed by 7709

Abstract

The utilization of clean energy is a matter of primary importance for sustainable development as well as a vital approach for solving worldwide energy-related issues. If the low utilization rate of nuclear fuel, nuclear proliferation, and insufficient nuclear safety can be solved, nuclear [...] Read more.

The utilization of clean energy is a matter of primary importance for sustainable development as well as a vital approach for solving worldwide energy-related issues. If the low utilization rate of nuclear fuel, nuclear proliferation, and insufficient nuclear safety can be solved, nuclear fission energy could be used as a sustainable and low-carbon clean energy form for thousands of years, providing steady and base-load electrical resources. To address these challenges, we propose an accelerator-driven advanced nuclear energy system (ADANES), consisting of a burner system and a fuel recycle system. In ADANES, the ideal utilization rate of nuclear fuel will be >95%, and the final disposal of nuclear waste will be minimized. The design of a high-temperature ceramic reactor makes the burner system safer. Part of fission products (FPs) are removed during the simple reprocessing in the fuel recycle system, significantly reducing the risks of nuclear proliferation of nuclear technology and materials. The ADANES concept integrates nuclear waste transmutation, nuclear fuel breeding, and safety power production, with an ideal closed loop operation of nuclear fission energy, constituting a major innovation of great potential interest for future energy applications. Full article

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

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16 pages, 8166 KiB

Open AccessArticle

Performance Characteristics of a 4 × 6 Oil-Free Twin-Screw Compressor

by Sun-Seok Byeon¹, Jae-Young Lee² and Youn-Jea Kim^3,*

¹ Graduate School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea

² YUJIN Machinery Ltd, Ansan 15433, Korea

³ School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea

Energies 2017, 10(7), 945; https://doi.org/10.3390/en10070945 - 7 Jul 2017

Cited by 14 | Viewed by 7171

Abstract

The screw compressor in the early stage of development is generally known as the oil-injection type. However, escalating environmental problems and advances in electronic components have spurred continuous R & D to minimize the oil content in compressed air. The oil-free twin-screw compressor [...] Read more.

The screw compressor in the early stage of development is generally known as the oil-injection type. However, escalating environmental problems and advances in electronic components have spurred continuous R & D to minimize the oil content in compressed air. The oil-free twin-screw compressor is continuously compressed by inner volumetric change between rotors and casing. For this reason, in order to predict the overall performance of the screw compressor at the early stage of the design process, industry still relies on the empirical method. However, it is difficult using the existing empirical method to gain more information of the inner fluid flow of the twin-screw compressor. Flow simulation techniques using CFD are required. This study presents applications of a recently proposed overset grid method to the solution of the flow around a moving boundary. In order to analyze the performance of a 4 × 6 oil-free screw compressor, the 3-D, unsteady and compressible flow fields were numerically calculated with a shear stress transport (SST) turbulence model, and implemented by the commercial software, Star-CCM+. The pressure distributions were calculated and graphically depicted. Results also showed that the volumetric and adiabatic efficiencies of the screw compressor measured by the experiments were 78% and 71%, respectively. Full article

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14 pages, 3892 KiB

Open AccessArticle

Fault Diagnosis of On-Load Tap-Changer Based on Variational Mode Decomposition and Relevance Vector Machine

by Jinxin Liu¹

, Guan Wang¹, Tong Zhao^1,*

and Li Zhang²

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

² Shandong Provincial Key Lab of UHV Transmission Technology and Equipment, Jinan 250061, China

Energies 2017, 10(7), 946; https://doi.org/10.3390/en10070946 - 8 Jul 2017

Cited by 37 | Viewed by 4814

Abstract

In order to improve the intelligent diagnosis level of an on-load tap-changer’s (OLTC) mechanical condition, a feature extraction method based on variational mode decomposition (VMD) and weight divergence was proposed. The harmony search (HS) algorithm was used to optimize the parameter selection of [...] Read more.

In order to improve the intelligent diagnosis level of an on-load tap-changer’s (OLTC) mechanical condition, a feature extraction method based on variational mode decomposition (VMD) and weight divergence was proposed. The harmony search (HS) algorithm was used to optimize the parameter selection of the relevance vector machine (RVM). Firstly, the OLTC vibration signal was decomposed into a series of finite-bandwidth intrinsic mode function (IMF) by VMD under different working conditions. The weight divergence was extracted to characterize the complexity of the vibration signal. Then, weight divergence was used as training and test samples of the harmony search optimization-relevance vector machine (HS-RVM). The experimental results suggested that the proposed integrated model has high fault diagnosis accuracy. This model can accurately extract the characteristics of the mechanical condition, and provide a reference for the practical OLTC intelligent fault diagnosis. Full article

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

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18 pages, 6366 KiB

Open AccessArticle

Vehicle Stability Enhancement through Hierarchical Control for a Four-Wheel-Independently-Actuated Electric Vehicle

by Zhenpo Wang¹, Yachao Wang¹, Lei Zhang^1,*

and Mingchun Liu²

¹ Collaborative Innovation Center for Electric Vehicles in Beijing & National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology, Beijing 100081, China; wangzhenpo@bit.edu.cn (Z.W.); wangyachaoa@126.com (Y.W.)

² School of Mechatronics Engineering, Nanchang University, Nanchang 330031, China; liumingchun@ncu.edu.cn

Energies 2017, 10(7), 947; https://doi.org/10.3390/en10070947 - 8 Jul 2017

Cited by 75 | Viewed by 7972

Abstract

In this paper, an optimal control strategy for a four-wheel-independently-actuated electric vehicle (FWIA EV) is proposed to improve vehicle dynamics stability and handling performance. The proposed scheme has a hierarchical structure composed of an upper and a lower controller. The desired longitudinal and [...] Read more.

In this paper, an optimal control strategy for a four-wheel-independently-actuated electric vehicle (FWIA EV) is proposed to improve vehicle dynamics stability and handling performance. The proposed scheme has a hierarchical structure composed of an upper and a lower controller. The desired longitudinal and lateral forces and yaw moment are determined based on the sliding-mode control (SMC) scheme in the upper controller, which takes the longitudinal and lateral velocity and the yaw rate as control variables. In the lower controller, an optimization algorithm is adopted to allocate the driving/braking torques to each in-wheel motor. A cost function with adjustable weight coefficients is specially designed by taking the motor power capability and the tire workload into consideration. The simulation and hardware-in-loop experimental results show that the proposed control strategy exhibits superior performance in comparison to commonly-used rule-based control strategies, and has the capability of online implementation. Full article

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21 pages, 4744 KiB

Open AccessArticle

A Novel Sectionalizing Method for Power System Parallel Restoration Based on Minimum Spanning Tree

by Changcheng Li

, Jinghan He, Pei Zhang and Yin Xu^*

School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China; 12117367@bjtu.edu.cn (C.L.); jhhe@bjtu.edu.cn (J.H.); peizhang@bjtu.edu.cn (P.Z.)

Energies 2017, 10(7), 948; https://doi.org/10.3390/en10070948 - 8 Jul 2017

Cited by 20 | Viewed by 4829

Abstract

Parallel restoration is a way to accelerate the black-start procedure of power systems following a blackout. An efficient sectionalizing scheme can reduce the restoration time of a system, taking into account the black-start ability, generation-load balance of subsystems, restoration time of branches, start-up [...] Read more.

Parallel restoration is a way to accelerate the black-start procedure of power systems following a blackout. An efficient sectionalizing scheme can reduce the restoration time of a system, taking into account the black-start ability, generation-load balance of subsystems, restoration time of branches, start-up time of generating units, and effects of dispatchable loads and faulted devices. Solving the sectionalizing problem is challenging since it needs to handle a large number of Boolean variables corresponding to the branches and nonlinear constraints associated with system topology. This paper investigates power system sectionalizing problem for parallel restoration to minimize the system restoration time (SRT). A novel sectionalizing method considering the restoration of generating units and network branches is proposed. Firstly, the minimum spanning tree (MST) algorithm is used to determine the skeleton network of a power system. Secondly, the number of subsystems is determined according to the number of black-start units. Based on the skeleton network, candidate boundary lines among subsystems are identified. Then, constraints are evaluated to identify feasible sectionalizing schemes. Except commonly used constraints on power balancing and black-start units, this paper also considers using dispatchable loads to meet the minimum output requirements of generating units. Finally, the sectionalizing scheme with the minimum SRT is selected as the final solution. The effectiveness of the proposed method is validated by the IEEE 39-bus and 118-bus test systems. The simulation results indicate that the proposed method can balance the restoration time of subsystems and minimize the SRT. Full article

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

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15 pages, 1241 KiB

Open AccessArticle

Tracking Control with Zero Phase-Difference for Linear Switched Reluctance Machines Network

by Bo Zhang^1,2

, J.F. Pan¹

, Jianping Yuan^2,*, Wufeng Rao^1,2, Li Qiu¹, Jianjun Luo² and Honghua Dai²

¹ College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China;zhangbo@szu.edu.cn (B.Z.); pjf@szu.edu.cn (J.F.P.); michaelmile@qq.com (W.R.); qiuli@szu.edu.cn (L.Q.)

² Laboratory of Advanced Unmanned Systems Technology, Northwestern Polytechnical University,Shenzhen 518060, China; jjluo@nwpu.edu.cn (J.L.); hhdai@nwpu.edu.cn (H.D.)

Energies 2017, 10(7), 949; https://doi.org/10.3390/en10070949 - 8 Jul 2017

Cited by 4 | Viewed by 3983

Abstract

This paper discusses the control of the linear switched reluctance machines (LSRMs) network for the zero phase-difference tracking to a sinusoidal reference. The dynamics of each LSRM is derived by online system identification and modeled as a second-order linear system. Accordingly, based on [...] Read more.

This paper discusses the control of the linear switched reluctance machines (LSRMs) network for the zero phase-difference tracking to a sinusoidal reference. The dynamics of each LSRM is derived by online system identification and modeled as a second-order linear system. Accordingly, based on the coupled harmonic oscillators synchronization manner, a distributed control strategy is proposed to synchronize each LSRM state to a virtual LSRM node representing the external sinusoidal reference for tracking it with zero phase-difference. Subsequently, a simulation scenario and an experimental platform with the identical parameter setup are designed to investigate the tracking performance of the LSRMs network constructed by the proposed distributed control strategy. Finally, the simulation and experimental results verify the effectiveness of the proposed LSRMs network controller, and also prove that the coupled harmonic oscillators synchronization method can improve the synchronization tracking performance and precision. Full article

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

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21 pages, 9208 KiB

Open AccessArticle

Synchronous Power Control of Grid-Connected Power Converters under Asymmetrical Grid Fault

by Weiyi Zhang^1,*

, Joan Rocabert¹, J. Ignacio Candela¹

and Pedro Rodriguez^1,2

¹ Electrical Engineering Department, Technical University of Catalonia, Barcelona 08222, Spain; rocabert@ee.upc.edu (J.R.); candela@ee.upc.edu (J.I.C.); prodriguez@uloyola.es (P.R.)

² Department of Engineering, Loyola University of Andalucia, Seville 41014, Spain

Energies 2017, 10(7), 950; https://doi.org/10.3390/en10070950 - 8 Jul 2017

Cited by 29 | Viewed by 6793

Abstract

Control of grid-connected power converters is continuously developing to meet the grid codes, according to which the generation units should keep connected to the grid and further provide ancillary services, such as voltage and frequency support, negative sequence current injection, inertia emulation, etc. [...] Read more.

Control of grid-connected power converters is continuously developing to meet the grid codes, according to which the generation units should keep connected to the grid and further provide ancillary services, such as voltage and frequency support, negative sequence current injection, inertia emulation, etc. A virtual admittance controller is proposed in this paper for the objective of voltage support under asymmetrical grid faults. By using independent and selective admittances for positive and negative sequence current injection, the unbalanced voltage can be significantly compensated during asymmetrical faults. The controller is based on the generic control framework of the synchronous power controller (SPC), which is able to control a power converter with emulated and improved synchronous generator characteristics. Simulation and experimental results based on two paralleled 100 kW grid-connected power converters demonstrate the controller to be effective in supporting unbalanced voltage sags. Full article

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

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10 pages, 2870 KiB

Open AccessArticle

A Study on the Matching Relationship of Polymer Molecular Weight and Reservoir Permeability in ASP Flooding for Duanxi Reservoirs in Daqing Oil Field

by Bin Huang^1,2, Wei Zhang¹, Rui Xu¹, Zhenzhong Shi¹, Cheng Fu^1,3,*, Ying Wang⁴ and Kaoping Song¹

¹ College of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China

² Beijing Deweijiaye Technology Corporation Ltd., Beijing 100027, China

³ Post-Doctoral Scientific Research Station, Daqing Oilfield Company, Daqing 163413, China

⁴ Harold Vance Department of Petroleum Engineering, Texas A&M University, College Station, TX 77843, USA

Energies 2017, 10(7), 951; https://doi.org/10.3390/en10070951 - 9 Jul 2017

Cited by 22 | Viewed by 4841

Abstract

In order to determine the matching relationship of polymer molecular weight and reservoir permeability in ASP (alkaline/surfactant/polymer) flooding, a number of core flooding experiments with different polymer molecular weights are performed. Two types of curves for the relationship between the pressure difference and [...] Read more.

In order to determine the matching relationship of polymer molecular weight and reservoir permeability in ASP (alkaline/surfactant/polymer) flooding, a number of core flooding experiments with different polymer molecular weights are performed. Two types of curves for the relationship between the pressure difference and the injection pore volume multiples are obtained. One describes the characteristics of the core plugging; the other describes the characteristics of the injection well. The relationship between the polymer molecular cyclotron radius and the pore throat radius used to describe the relationship between the polymer molecular weight and the core permeability. The results indicate that when the ratio of the pore throat radius (r_h) to the polymer molecular cyclotron radius (r_p) is greater than 7, the injection of ASP system with a variety of molecular weights will not be blocked; on contrary, when the ratio is less than 7, the core will be blocked. The range of water permeability of the core is determined by the value of the polymer molecular weight. The ratio between the pore throat radius (r_h) to the polymer molecular cyclotron radius (r_p) for the ASP system is greater than that of polymer system (r_h/r_p = 5). A scanning electron microscope (SEM) is used to compare the morphology of polymer molecules in polymer solution and ASP solution, and shows that the dimension of polymer molecular coils in ASP solution is smaller than that in polymer solution, which is caused by the double effect of alkali and surfactant. Full article

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15 pages, 3482 KiB

Open AccessArticle

Optimal Planning of Charging for Plug-In Electric Vehicles Focusing on Users’ Benefits

by Su Su¹, Hao Li^1,* and David Wenzhong Gao²

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

² Department of Electrical and Computer Engineering, University of Denver, Denver, CO 80210, USA

Energies 2017, 10(7), 952; https://doi.org/10.3390/en10070952 - 9 Jul 2017

Cited by 28 | Viewed by 5411

Abstract

Many electric vehicles’ (EVs) charging strategies were proposed to optimize the operations of the power grid, while few focus on users’ benefits from the viewpoint of EV users. However, low participation is always a problem of those strategies since EV users also need [...] Read more.

Many electric vehicles’ (EVs) charging strategies were proposed to optimize the operations of the power grid, while few focus on users’ benefits from the viewpoint of EV users. However, low participation is always a problem of those strategies since EV users also need a charging strategy to serve their needs and interests. This paper proposes a method focusing on EV users’ benefits that reduce the cost of battery capacity degradation, electricity cost, and waiting time for different situations. A cost model of battery capacity degradation under different state of charge (SOC) ranges is developed based on experimental data to estimate the cost of battery degradation. The simulation results show that the appropriate planning of the SOC range reduces 80% of the cost of battery degradation, and the queuing theory also reduces over 60% of the waiting time in the busy situations. Those works can also become a premise of charging management to increase the participation. The proposed strategy focusing on EV users’ benefits would not give negative impacts on the power grid, and the grid load is also optimized by an artificial fish swarm algorithm (AFSA) in the solution space of the charging time restricted by EV users’ benefits. Full article

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

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18 pages, 2570 KiB

Open AccessArticle

Switched Control Strategies of Aggregated Commercial HVAC Systems for Demand Response in Smart Grids

by Kai Ma¹

, Chenliang Yuan¹, Jie Yang^1,*, Zhixin Liu¹ and Xinping Guan²

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

² Key Laboratory of System Control and Information Processing, Ministry of Education, Shanghai Jiao Tong University, Shanghai, 200240, China

Energies 2017, 10(7), 953; https://doi.org/10.3390/en10070953 - 9 Jul 2017

Cited by 20 | Viewed by 4649

Abstract

This work proposes three switched control strategies for aggregated heating, ventilation, and air conditioning (HVAC) systems in commercial buildings to track the automatic generation control (AGC) signal in smart grid. The existing control strategies include the direct load control strategy and the setpoint [...] Read more.

This work proposes three switched control strategies for aggregated heating, ventilation, and air conditioning (HVAC) systems in commercial buildings to track the automatic generation control (AGC) signal in smart grid. The existing control strategies include the direct load control strategy and the setpoint regulation strategy. The direct load control strategy cannot track the AGC signal when the state of charge (SOC) of the aggregated thermostatically controlled loads (TCLs) exceeds their regulation capacity, while the setpoint regulation strategy provides flexible regulation capacity, but causes larger tracking errors. To improve the tracking performance, we took the advantages of the two control modes and developed three switched control strategies. The control strategies switch between the direct load control mode and the setpoint regulation mode according to different switching indices. Specifically, we design a discrete-time controller and optimize the controller parameter for the setpoint regulation strategy using the Fibonacci optimization algorithm, enabling us to propose two switched control strategies across multiple time steps. Furthermore, we extend the switched control strategies by introducing a two-stage regulation in a single time step. Simulation results demonstrate that the proposed switched control strategies can reduce the tracking errors for frequency regulation. Full article

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

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29 pages, 4779 KiB

Open AccessArticle

An Innovative Hybrid Model Based on Data Pre-Processing and Modified Optimization Algorithm and Its Application in Wind Speed Forecasting

by Ping Jiang¹, Zeng Wang^1,*, Kequan Zhang² and Wendong Yang¹

¹ School of Statistics, Dongbei University of Finance and Economics, Dalian 116025, China

² Key Laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China

Energies 2017, 10(7), 954; https://doi.org/10.3390/en10070954 - 9 Jul 2017

Cited by 3 | Viewed by 5191

Abstract

Wind speed forecasting has an unsuperseded function in the high-efficiency operation of wind farms, and is significant in wind-related engineering studies. Back-propagation (BP) algorithms have been comprehensively employed to forecast time series that are nonlinear, irregular, and unstable. However, the single model usually [...] Read more.

Wind speed forecasting has an unsuperseded function in the high-efficiency operation of wind farms, and is significant in wind-related engineering studies. Back-propagation (BP) algorithms have been comprehensively employed to forecast time series that are nonlinear, irregular, and unstable. However, the single model usually overlooks the importance of data pre-processing and parameter optimization of the model, which results in weak forecasting performance. In this paper, a more precise and robust model that combines data pre-processing, BP neural network, and a modified artificial intelligence optimization algorithm was proposed, which succeeded in avoiding the limitations of the individual algorithm. The novel model not only improves the forecasting accuracy but also retains the advantages of the firefly algorithm (FA) and overcomes the disadvantage of the FA while optimizing in the later stage. To verify the forecasting performance of the presented hybrid model, 10-min wind speed data from Penglai city, Shandong province, China, were analyzed in this study. The simulations revealed that the proposed hybrid model significantly outperforms other single metaheuristics. Full article

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

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18 pages, 1840 KiB

Open AccessArticle

Well-Being Analysis of Power Systems Considering Increasing Deployment of Gas Turbines

by Bomiao Liang¹, Weijia Liu¹, Fushuan Wen^2,3,* and Md. Abdus Salam⁴

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

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

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

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

Energies 2017, 10(7), 955; https://doi.org/10.3390/en10070955 - 9 Jul 2017

Cited by 3 | Viewed by 3975

Abstract

With the significant decrease in natural gas prices in many parts of the world, the employment of gas turbine (GT) units has increased steadily in recent years. The ever-increasing deployment of GT units is strengthening the interconnections between electric power and natural gas [...] Read more.

With the significant decrease in natural gas prices in many parts of the world, the employment of gas turbine (GT) units has increased steadily in recent years. The ever-increasing deployment of GT units is strengthening the interconnections between electric power and natural gas systems, which could provide a higher level of operational flexibility and reliability. As a result, the planning and operation issues in the interconnected electric power and natural gas systems have aroused concern. In these circumstances, the impacts of increasing deployment of GT units in power system operation are studied and evaluated through well-being analysis (WBA). The fast responsive characteristics of GT units are analyzed first, and the definition and adaption of WBA in a power system with increasing deployment of GT units are addressed. Then the equivalent reserve capacity of GT units is estimated, taking demand fluctuations, commitment plans, and operational risks of GT units into account. The WBA of a power system with increasing deployment of GT units is conducted considering the uncertainties of system operation states and renewable energy sources. Finally, the proposed methods are validated through an integrated version of the IEEE 118-bus power system and a 10-bus natural gas system, and the impacts of GT units on power system security under various penetration levels are examined. Simulation results demonstrate that the role of a GT unit as a low-cost electricity producer may conflict with its role as a reserve provider, but through maintaining a proper proportion of idle GT capacities for reserve, the well-being performance of the power system concerned can be significantly improved. Full article

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

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22 pages, 4422 KiB

Open AccessArticle

Linking the Power and Transport Sectors—Part 1: The Principle of Sector Coupling

by Martin Robinius^1,*

, Alexander Otto¹, Philipp Heuser¹, Lara Welder¹, Konstantinos Syranidis¹, David S. Ryberg¹

, Thomas Grube¹

, Peter Markewitz¹, Ralf Peters¹ and Detlef Stolten^1,2

¹ Institute of Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Street, 52428 Jülich, Germany

² Chair of Fuel Cells, RWTH Aachen University, c/o Institute of Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Street, 52428 Jülich, Germany

Energies 2017, 10(7), 956; https://doi.org/10.3390/en10070956 - 21 Jul 2017

Cited by 175 | Viewed by 18618

Abstract

The usage of renewable energy sources (RESs) to achieve greenhouse gas (GHG) emission reduction goals requires a holistic transformation across all sectors. Due to the fluctuating nature of RESs, it is necessary to install more wind and photovoltaics (PVs) generation in terms of [...] Read more.

The usage of renewable energy sources (RESs) to achieve greenhouse gas (GHG) emission reduction goals requires a holistic transformation across all sectors. Due to the fluctuating nature of RESs, it is necessary to install more wind and photovoltaics (PVs) generation in terms of nominal power than would otherwise be required in order to ensure that the power demand can always be met. In a near fully RES-based energy system, there will be times when there is an inadequate conventional load to meet the overcapacity of RESs, which will lead to demand regularly being exceeded and thereby a surplus. One approach to making productive use of this surplus, which would lead to a holistic transformation of all sectors, is “sector coupling” (SC). This paper describes the general principles behind this concept and develops a working definition intended to be of utility to the international scientific community. Furthermore, a literature review provides an overview of relevant scientific papers on the topic. Due to the challenge of distinguishing between papers with or without SC, the approach adopted here takes the German context as a case study that can be applied to future reviews with an international focus. Finally, to evaluate the potential of SC, an analysis of the linking of the power and transport sectors on a worldwide, EU and German level has been conducted and is outlined here. Full article

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

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23 pages, 6828 KiB

Open AccessArticle

Linking the Power and Transport Sectors—Part 2: Modelling a Sector Coupling Scenario for Germany

by Martin Robinius^1,*

, Alexander Otto¹, Konstantinos Syranidis¹, David S. Ryberg¹

, Philipp Heuser¹, Lara Welder¹, Thomas Grube¹

, Peter Markewitz¹, Vanessa Tietze¹ and Detlef Stolten^1,2

¹ Institute of Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany

² Chair of fuel cells, RWTH Aachen University, c/o Institute of Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany

Energies 2017, 10(7), 957; https://doi.org/10.3390/en10070957 - 20 Jul 2017

Cited by 119 | Viewed by 10882

Abstract

“Linking the power and transport sectors—Part 1” describes the general principle of “sector coupling” (SC), develops a working definition intended of the concept to be of utility to the international scientific community, contains a literature review that provides an overview of relevant scientific [...] Read more.

“Linking the power and transport sectors—Part 1” describes the general principle of “sector coupling” (SC), develops a working definition intended of the concept to be of utility to the international scientific community, contains a literature review that provides an overview of relevant scientific papers on this topic and conducts a rudimentary analysis of the linking of the power and transport sectors on a worldwide, EU and German level. The aim of this follow-on paper is to outline an approach to the modelling of SC. Therefore, a study of Germany as a case study was conducted. This study assumes a high share of renewable energy sources (RES) contributing to the grid and significant proportion of fuel cell vehicles (FCVs) in the year 2050, along with a dedicated hydrogen pipeline grid to meet hydrogen demand. To construct a model of this nature, the model environment “METIS” (models for energy transformation and integration systems) we developed will be described in more detail in this paper. Within this framework, a detailed model of the power and transport sector in Germany will be presented in this paper and the rationale behind its assumptions described. Furthermore, an intensive result analysis for the power surplus, utilization of electrolysis, hydrogen pipeline and economic considerations has been conducted to show the potential outcomes of modelling SC. It is hoped that this will serve as a basis for researchers to apply this framework in future to models and analysis with an international focus. Full article

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

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12 pages, 3761 KiB

Open AccessArticle

Audible Noise Performance of Conductor Bundles Based on Cage Test Results and Comparison with Long Term Data

by Baoquan Wan¹, Wangling He^2,*, Chunming Pei³, Xiaorui Wu¹, Yuchao Chen⁴, Yemao Zhang¹ and Lei Lan²

¹ State Key Laboratory of Power Grid Environmental Protection, China Electric Power Research Institute, Wuhan 430074, China

² School of Electrical Engineering, Wuhan University, Wuhan 430072, China

³ Wuhan NARI Group Corporation, Wuhan 430074, China

⁴ State Grid Corporation of China, Beijing 100031, China

Energies 2017, 10(7), 958; https://doi.org/10.3390/en10070958 - 10 Jul 2017

Cited by 18 | Viewed by 4657

Abstract

A reasonable acoustic power formula is vital to precisely evaluate the audible noise (AN) level of ultra-high-voltage (UHV) AC power lines. This study derived a formula by taking several AN measurements under heavy rain conditions, using multiple conductor bundles in a UHV corona [...] Read more.

A reasonable acoustic power formula is vital to precisely evaluate the audible noise (AN) level of ultra-high-voltage (UHV) AC power lines. This study derived a formula by taking several AN measurements under heavy rain conditions, using multiple conductor bundles in a UHV corona cage, and then subjecting these measured values to least squares fitting. The validity of the proposed formula was subsequently verified with statistical data obtained from two long-term stations at Henan and Hubei Province, which are located under the Jindongnan-Nanyang-Jingmen UHV AC transmission lines operating at 1000 kV. The deviation between the prediction and the long-term (L50) value was 0.76 dB for the Henan station and 0.17 dB for the Hubei station. It shows that the acoustic power formula derived in this paper is more accurate than the widely used Bonneville Power Administration formula, in which the corresponding deviations are much larger (3.07 and 2.53 dB). Full article

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

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19 pages, 2145 KiB

Open AccessArticle

Impact of Distributed Generation on the Voltage Sag Performance of Transmission Systems

by Pierluigi Caramia¹

, Enrica Di Mambro², Pietro Varilone³

and Paola Verde^3,*

¹ Department of Engineering, Università di Napoli Parthenope, 80143 Napoli, Italy

² TERNA Rete Italiana S.p.A, 80078 Pozzuoli (NA), Italy

³ Department of Electrical and Information Engineering, Università di Cassino e del Lazio Meridionale, 03043 Cassino (FR), Italy

Energies 2017, 10(7), 959; https://doi.org/10.3390/en10070959 - 11 Jul 2017

Cited by 20 | Viewed by 4987

Abstract

In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG) with transmission systems, we considered the abnormal operating conditions caused by short circuits [...] Read more.

In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG) with transmission systems, we considered the abnormal operating conditions caused by short circuits in the transmission systems and the resulting voltage sags that occur in the network. A systematic method is presented for analysing the voltage sag behaviour of any transmission system in which large DG units are connected to the transmission system by means of High Voltage/Medium Voltage (HV/MV) stations. The method proposed for obtaining the voltage sags is the fault position method (FPM), from which we derived a graphical visualization of the during-fault voltage (DFV) matrix as a valuable tool to obtain an immediate measure of the propagation of voltage sags in the network. The results obtained were based on a portion of a real transmission system. The system that we considered is an actual portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO). Full article

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

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13 pages, 1463 KiB

Open AccessArticle

Electric Power Grids Distribution Generation System for Optimal Location and Sizing—A Case Study Investigation by Various Optimization Algorithms

by Ahmed Ali, Sanjeevikumar Padmanaban^*

, Bhekisipho Twala and Tshilidzi Marwala

Faculty of Engineering and Built Environment, Department of Electrical and Electronics Engineering Science, University of Johannesburg, Auckland Park 2006, South Africa

Energies 2017, 10(7), 960; https://doi.org/10.3390/en10070960 - 10 Jul 2017

Cited by 33 | Viewed by 4967

Abstract

In this paper, the approach focused on the variables involved in assessing the quality of a distributed generation system are reviewed in detail, for its investigation and research contribution. The aim to minimize the electric power losses (unused power consumption) and optimize the [...] Read more.

In this paper, the approach focused on the variables involved in assessing the quality of a distributed generation system are reviewed in detail, for its investigation and research contribution. The aim to minimize the electric power losses (unused power consumption) and optimize the voltage profile for the power system under investigation. To provide this assessment, several experiments have been made to the IEEE 34-bus test case and various actual test cases with the respect of multiple Distribution Generation DG units. The possibility and effectiveness of the proposed algorithm for optimal placement and sizing of DG in distribution systems have been verified. Finally, four algorithms were trailed: simulated annealing (SA), hybrid genetic algorithm (HGA), genetic algorithm (GA), and variable neighbourhood search. The HGA algorithm was found to produce the best solution at a cost of a longer processing time. Full article

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

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11 pages, 7222 KiB

Open AccessLetter

On the Response of Nascent Soot Nanostructure and Oxidative Reactivity to Photoflash Exposure

by Wei Wang^1,2, Dong Liu^1,2,*, Yaoyao Ying^1,2, Guannan Liu^1,2 and Ye Wu^1,2,*

¹ Key Laboratory of Thermal Control of Electronic Equipment, Ministry of Industry and Information Technology, Nanjing University of Science and Technology, Nanjing 210094, China

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

Energies 2017, 10(7), 961; https://doi.org/10.3390/en10070961 - 10 Jul 2017

Cited by 14 | Viewed by 3762

Abstract

Soot particles are a kind of major pollutant from fuel combustion. To enrich the understanding of soot, this work focuses on investigating detailed influences of instantaneous external irradiation (conventional photoflash exposure) on nanostructure as well as oxidation reactivity of nascent soot particles. By [...] Read more.

Soot particles are a kind of major pollutant from fuel combustion. To enrich the understanding of soot, this work focuses on investigating detailed influences of instantaneous external irradiation (conventional photoflash exposure) on nanostructure as well as oxidation reactivity of nascent soot particles. By detailed soot characterizations flash can reduce the mass of soot and soot nanostructure can be reconstructed substantially without burning. After flash, the degree of soot crystallization increases while the soot reactive rate decreases and the activation energy increases. In addition, nanostructure and oxidative reactivity of soot in air and Ar after flash are different due to their different thermal conductivities. Full article

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24 pages, 5054 KiB

Open AccessArticle

A Novel Method for Idle-Stop-Start Control of Micro Hybrid Construction Equipment—Part A: Fundamental Concepts and Design

by Truong Quang Dinh^1,*, James Marco¹, Hui Niu¹, David Greenwood¹

, Lee Harper² and David Corrochano²

¹ Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL, UK

² JCB, Rocester, Straffordshire ST14 5JP, UK

Energies 2017, 10(7), 962; https://doi.org/10.3390/en10070962 - 10 Jul 2017

Cited by 7 | Viewed by 6356

Abstract

Although micro hybrid propulsion (MHP) systems are recognized as a feasible solution for off-highway construction machines (OHCMs), there is still a lack of understanding how existing MHP technologies can be transferred effectively from the automotive sector to the construction sector. To fill this [...] Read more.

Although micro hybrid propulsion (MHP) systems are recognized as a feasible solution for off-highway construction machines (OHCMs), there is still a lack of understanding how existing MHP technologies can be transferred effectively from the automotive sector to the construction sector. To fill this gap, this paper is the first of a two-part study which focuses on micro hybrid construction machines paying attention to a novel idle-stop-start control (ISSC) strategy. Part A presents the system concepts and design procedure while Part B studies on a hardware-in-the-loop test platform for a comprehensive analysis on the potential fuel/emission saving of the proposed system in real-time. In this study—Part A—different types of OHCMs are briefly discussed to identify the target machine. The procedure to model the machine powertrain is also concisely introduced. Next, to minimize the fuel consumption and emissions without degrading the machine performance, a prediction-based idle-stop-start control (PISSC) approach is properly designed. The core of the PISSC is to estimate online the future engine working state changes in order to directly shut down the engine or shift it to low power regions during idle periods. Numerical simulations have been carried out to validate the potential of the proposed PISSC method. Full article

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

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13 pages, 5705 KiB

Open AccessArticle

Numerical and Experimental Study on a Solar Water Heating System in Lhasa

by Xun Yang^1,2, Yong Wang^1,2,* and Teng Xiong^1,2

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

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

Energies 2017, 10(7), 963; https://doi.org/10.3390/en10070963 - 10 Jul 2017

Cited by 4 | Viewed by 4423

Abstract

Lhasa is a “solar city” with high altitude, located in a cold zone in China. Due to the lack of mineral energy sources and the fragility of its ecological environment, solar heating technology is the first choice to satisfy the demand of indoor [...] Read more.

Lhasa is a “solar city” with high altitude, located in a cold zone in China. Due to the lack of mineral energy sources and the fragility of its ecological environment, solar heating technology is the first choice to satisfy the demand of indoor thermal comfort for building heating. In this study, an accurate solar heating system in Lhasa was investigated under the simultaneous charging and discharging operation mode. Based on the solar heating system, a numerical calculation method of the tank temperature distribution under the simultaneous charging and discharging operation mode was proposed and validated by experiments. This numerical method offers a correlation between the output water temperatures of the tank and the input water temperatures of the tank, which can be used to optimize the thermal performance of the solar heating system in future studies. To evaluate the system performance under the simultaneous charging and discharging operation mode, the transient coefficient of performance (COP) of the heating system was calculated based on the experimental measurements. The calculated results showed that the system COP reached an average number of 3.0, which was nearly equal to that of gas-boiler heating system and much higher than that of electrical heating systems. A north-facing room and a south-facing room were both selected to test whether the room temperatures met the heating requirements. The test results showed that the north-facing room had an average temperature over 17 °C while the south-facing room was over 20 °C, which illustrated that a good heating effect was achieved. Although a relatively high system COP was shown with a good heating effect for the solar heating system under the simultaneous charging and discharging operation mode, further recommendations were proposed for the mass flow rates of the solar collecting cycles and control stagey of the fan coil unit (FCU). Full article

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

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16 pages, 7980 KiB

Open AccessArticle

Characteristics of Early Flame Development in a Direct-Injection Spark-Ignition CNG Engine Fitted with a Variable Swirl Control Valve

by Abd Rashid Abd Aziz¹, Yohannes Tamirat Anbese¹, Ftwi Yohaness Hagos^2,3,*

, Morgan R. Heikal¹ and Firmansyah¹

¹ Center for Automotive Research, Universiti Teknologi Petronas, Tronoh 31750, Perak, Malaysia

² Automotive Engineering Research Group (AERG), Faculty of Mechanical Engineering, Universiti Malaysia Pahang, Pekan 26600, Pahang, Malaysia

³ Automotive Engineering Center (AEC), Universiti Malaysia Pahang, Pekan 26600, Pahang, Malaysia

Energies 2017, 10(7), 964; https://doi.org/10.3390/en10070964 - 10 Jul 2017

Cited by 10 | Viewed by 4847

Abstract

An experimental study was conducted to investigate the effect of the structure of the induction flow on the characteristics of early flames in a lean-stratified and lean-homogeneous charge combustion of compressed natural gas (CNG) fuel in a direct injection (DI) engine at different [...] Read more.

An experimental study was conducted to investigate the effect of the structure of the induction flow on the characteristics of early flames in a lean-stratified and lean-homogeneous charge combustion of compressed natural gas (CNG) fuel in a direct injection (DI) engine at different engine speeds. The engine speed was varied at 1500 rpm, 1800 rpm and 2100 rpm, and the ignition timing was set at a 38.5° crank angle (CA) after top dead center (TDC) for all conditions. The engine was operated in a partial-load mode and a homogeneous air/fuel charge was achieved by injecting the fuel early (before the intake valve closure), while late injection during the compression stroke was used to produce a stratified charge. Different induction flow structures were obtained by adjusting the swirl control valves (SCV). Using an endoscopic intensified CCD (ICCD) camera, flame images were captured and analyzed. Code was developed to analyze the level of distortion of the flame and its wrinkledness, displacement and position relative to the spark center, as well as the flame growth rate. The results showed a higher flame growth rate with the flame kernel in the homogeneous charge, compared to the stratified combustion case. In the stratified charge combustion scenario, the 10° SCV closure (medium-tumble) resulted in a higher early flame growth rate, whereas a homogeneous charge combustion (characterized by strong swirl) resulted in the highest rate of flame growth. Full article

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

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19 pages, 1763 KiB

Open AccessArticle

Two-Stage Coordinated Operational Strategy for Distributed Energy Resources Considering Wind Power Curtailment Penalty Cost

by Jing Qiu^1,*

, Junhua Zhao², Dongxiao Wang³ and Yu Zheng⁴

¹ Commonwealth Scientific and Industrial Research Organization (CSIRO), Mayfield West, Newcastle, NSW 2304, Australia

² School of Science and Engineering, Chinese University of Hong Kong (Shenzhen), Shenzhen 518172, China

³ Centre for Intelligent Electricity Networks, University of Newcastle, Newcastle, NSW 2308, Australia

⁴ Electric Power Research Institute, CSG, Guangzhou 510080, China

Energies 2017, 10(7), 965; https://doi.org/10.3390/en10070965 - 10 Jul 2017

Cited by 17 | Viewed by 4522

Abstract

The concept of virtual power plant (VPP) has been proposed to facilitate the integration of distributed renewable energy. VPP behaves similar to a single entity that aggregates a collection of distributed energy resources (DERs) such as distributed generators, storage devices, flexible loads, etc., [...] Read more.

The concept of virtual power plant (VPP) has been proposed to facilitate the integration of distributed renewable energy. VPP behaves similar to a single entity that aggregates a collection of distributed energy resources (DERs) such as distributed generators, storage devices, flexible loads, etc., so that the aggregated power outputs can be flexibly dispatched and traded in electricity markets. This paper presents an optimal scheduling model for VPP participating in day-ahead (DA) and real-time (RT) markets. In the DA market, VPP aims to maximize the expected profit and reduce the risk in relation to uncertainties. The risk is measured by a risk factor based on the mean-variance Markowitz theory. In the RT market, VPP aims to minimize the imbalance cost and wind power curtailment by adjusting the scheduling of DERs in its portfolio. In case studies, the benefits (e.g., surplus profit and reduced wind power curtailment) of aggregated VPP operation are assessed. Moreover, we have investigated how these benefits are affected by different risk-aversion levels and uncertainty levels. According to the simulation results, the aggregated VPP scheduling approach can effectively help the integration of wind power, mitigate the impact of uncertainties, and reduce the cost of risk-aversion. Full article

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

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21 pages, 4022 KiB

Open AccessArticle

Quick Screening of Pareto-Optimal Operating Conditions for Expanding Solvent–Steam Assisted Gravity Drainage Using Hybrid Multi-Objective Optimization Approach

by Baehyun Min^1,*

, Krupa Kannan² and Sanjay Srinivasan³

¹ Department of Climate and Energy Systems Engineering, Division of Sustainable Systems Engineering, Ewha Womans University, 52 Ewhayeodae-gil, Daehyeon-dong, Seodaemun-gu, Seoul 03760, Korea

² Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, TX 78712, USA

³ Department of Energy and Mineral Engineering, College of Earth and Mineral Sciences, Pennsylvania State University, University Park, PA 16802, USA

Energies 2017, 10(7), 966; https://doi.org/10.3390/en10070966 - 10 Jul 2017

Cited by 8 | Viewed by 4630

Abstract

Solvent–steam mixture is a key factor in controlling the economic efficiency of the solvent-aided thermal injection process for producing bitumen in a highly viscous oil sands reservoir. This paper depicts a strategy to quickly provide trade-off operating conditions of the Expanding Solvent–Steam Assisted [...] Read more.

Solvent–steam mixture is a key factor in controlling the economic efficiency of the solvent-aided thermal injection process for producing bitumen in a highly viscous oil sands reservoir. This paper depicts a strategy to quickly provide trade-off operating conditions of the Expanding Solvent–Steam Assisted Gravity Drainage (ES-SAGD) process based on Pareto-optimality. Response surface models are employed to evaluate multiple ES-SAGD scenarios at low computational costs. The surrogate models play a role of objective-estimators in the multi-objective optimization that provides qualified ES-SAGD scenarios regarding bitumen recovery, steam–energy efficiency, and solvent-energy efficiency. The developed hybrid approach detects positive or negative correlations among the performance indicators of the ES-SAGD process. The derived Pareto-optimal operating conditions give flexibility in field development planning and thereby help decision makers determine the operating parameters of the ES-SAGD process based on their preferences. Full article

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

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12 pages, 2097 KiB

Open AccessArticle

A Novel Method to Directly Analyze Dissolved Acetic Acid in Transformer Oil without Extraction Using Raman Spectroscopy

by Fu Wan^1,*, Lingling Du^1,2, Weigen Chen^1,*, Pinyi Wang¹, Jianxin Wang¹ and Haiyang Shi¹

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

² Chengdu Power Supply Company of State Grid, Chengdu 610041, China

Energies 2017, 10(7), 967; https://doi.org/10.3390/en10070967 - 10 Jul 2017

Cited by 34 | Viewed by 10534

Abstract

Analyzing the concentration of low molecular acids dissolved in oil is vital in the oil-paper insulation aging diagnostic procedure of power transformers. The existing methods cannot distinguish between different acid types and their strengths. In this study, an improved solution Raman detection platform [...] Read more.

Analyzing the concentration of low molecular acids dissolved in oil is vital in the oil-paper insulation aging diagnostic procedure of power transformers. The existing methods cannot distinguish between different acid types and their strengths. In this study, an improved solution Raman detection platform is fabricated. The direct measurement of dissolved acetic acid, a kind of low molecular acids, is observed in transformer oil without extraction. The Raman shift line of oil-dissolved acetic acid at 891 cm⁻¹ corresponding to H–C–H symmetrical swing and O–H swing modes is taken as its characteristic value. Taking Raman shift line of pure oil at 932 cm⁻¹ as an internal standard, a linear regression curve for quantitative analysis is obtained with a slope of 0.19. The best platform parameter of accumulation number is 300, which is determined by Allan deviation analysis. The current concentration detection limit and accuracy for oil-dissolved acetic acid are obtained at about 0.68 mg/mL and 91.66%, separately. The results show that Raman spectroscopy could be a useful alternative method for evaluation insulation aging state of an operating power transformer in the future. Full article

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

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12 pages, 1086 KiB

Open AccessArticle

The Optimal Configuration Scheme of the Virtual Power Plant Considering Benefits and Risks of Investors

by Jingmin Wang¹, Wenhai Yang¹, Huaxin Cheng^2,*, Lingyu Huang² and Yajing Gao^3,*

¹ School of Economics and Management, North China Electric Power University, Baoding 071003, China

² State Grid Longyan Electric Power Company, Longyan 364000, China

³ School of Electrical and Electronic Engineering, North China Electric Power University, Baoding 071003, China

Energies 2017, 10(7), 968; https://doi.org/10.3390/en10070968 - 11 Jul 2017

Cited by 17 | Viewed by 3865

Abstract

A virtual power plant (VPP) is a special virtual unit that integrates various distributed energy resources (DERs) distributed in the generation and consumption sides. The optimal configuration scheme of the VPP needs to break the geographical restrictions to make full use of DERs, [...] Read more.

A virtual power plant (VPP) is a special virtual unit that integrates various distributed energy resources (DERs) distributed in the generation and consumption sides. The optimal configuration scheme of the VPP needs to break the geographical restrictions to make full use of DERs, considering the uncertainties. First, the components of the DERs and the structure of the VPP are briefly introduced. Next, the cubic exponential smoothing method is adopted to predict the VPP load requirement. Finally, the optimal configuration of the DER capacities inside the VPP is calculated by using portfolio theory and genetic algorithms (GA). The results show that the configuration scheme can optimize the DER capacities considering uncertainties, guaranteeing economic benefits of investors, and fully utilizing the DERs. Therefore, this paper provides a feasible reference for the optimal configuration scheme of the VPP from the perspective of investors. Full article

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

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11 pages, 2996 KiB

Open AccessArticle

Force and Motion Characteristics of Contamination Particles near the High Voltage End of UHVDC Insulator

by Lei Lan, Gongda Zhang

, Yu Wang^* and Xishan Wen

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

Energies 2017, 10(7), 969; https://doi.org/10.3390/en10070969 - 11 Jul 2017

Cited by 3 | Viewed by 3921

Abstract

It is important to reveal the relations of physical factors to deposition of contaminants on insulator. In this paper, the simulation model of high voltage end of insulator was established to study the force and motion characteristics of particles affected by electric force [...] Read more.

It is important to reveal the relations of physical factors to deposition of contaminants on insulator. In this paper, the simulation model of high voltage end of insulator was established to study the force and motion characteristics of particles affected by electric force and airflow drag force near the ultra-high voltage direct current (UHVDC) insulator. By finite element method, the electric field was set specially to be similar to the one near practical insulator, the steady fluid field was simulated. The electric force and air drag force were loaded on the uniformly charged particles. The characteristics of the two forces on particles, the relationship between quantity of electric charge on particles and probability of particles contacting the insulator were analyzed. It was found that, near the sheds, airflow drag force on particles is significantly greater than electric force with less electric charge. As the charge multiplies, electric force increases linearly, airflow drag force grows more slowly. There is a trend that the magnitude of electric force and drag force is going to similar. Meanwhile, the probability of particles contacting the insulator is increased too. However, at a certain level of charge which has different value with different airflow velocity, the contact probability has extremum here. After exceeding the value, as the charge increasing, the contact probability decreases gradually. Full article

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

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15 pages, 3915 KiB

Open AccessArticle

Experimental Investigation of the Effect of Biodiesel Blends on a DI Diesel Engine’s Injection and Combustion

by Dimitrios N Tziourtzioumis and Anastassios M Stamatelos^*

Laboratory of Thermodynamics and Thermal Engines, Department of Mechanical Engineering, University of Thessaly, Volos 38334, Greece

Energies 2017, 10(7), 970; https://doi.org/10.3390/en10070970 - 11 Jul 2017

Cited by 27 | Viewed by 5398

Abstract

Differences in the evolution of combustion in a single cylinder, DI (direct injection) diesel engine fuelled by B20 were observed upon processing of the respective indicator diagrams. Aiming to further investigate the effects of biodiesel on the engine injection and combustion process, the [...] Read more.

Differences in the evolution of combustion in a single cylinder, DI (direct injection) diesel engine fuelled by B20 were observed upon processing of the respective indicator diagrams. Aiming to further investigate the effects of biodiesel on the engine injection and combustion process, the injection characteristics of B0, B20, B40, B60, B80 and B100 were measured at low injection pressure and visualized at low and standard injection pressures. The fuel atomization characteristics were investigated in terms of mean droplet velocity, Sauter mean diameter, droplet velocity and diameter distributions by using a spray visualization system and Laser Doppler Velocimetry. The jet break-up characteristics are mainly influenced by the Weber number, which is lower for biodiesel, mainly due to its higher surface tension. Thus, Sauter mean diameter (SMD) of sprays with biodiesel blended-fuel is higher. Volume mean diameter (VMD) and arithmetic mean diameter (AMD) values also increase with blending ratio. Kinematic viscosity and surface tension become higher as the biodiesel blending ratio increases. The SMD, VMD and AMD of diesel and biodiesel blended fuels decreased with an increase in the axial distance from spray tip. Comparison of estimated fuel burning rates for 60,000 droplets’ samples points to a decrease in mean fuel burning rate for B20 and higher blends. Full article

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

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19 pages, 5426 KiB

Open AccessFeature PaperArticle

Predictive Models for Photovoltaic Electricity Production in Hot Weather Conditions

by Jabar H. Yousif¹

, Hussein A. Kazem²

and John Boland^3,*

¹ Computing & Information Technology, Sohar University, P.O. Box 44, Sohar 311, Oman

² Faculty of Engineering, Sohar University, P.O. Box 44, Sohar 311, Oman

³ Centre for Industrial and Applied Mathematics, University of South Australia, Adelaide 5095, Australia

Energies 2017, 10(7), 971; https://doi.org/10.3390/en10070971 - 11 Jul 2017

Cited by 38 | Viewed by 7530

Abstract

The process of finding a correct forecast equation for photovoltaic electricity production from renewable sources is an important matter, since knowing the factors affecting the increase in the proportion of renewable energy production and reducing the cost of the product has economic and [...] Read more.

The process of finding a correct forecast equation for photovoltaic electricity production from renewable sources is an important matter, since knowing the factors affecting the increase in the proportion of renewable energy production and reducing the cost of the product has economic and scientific benefits. This paper proposes a mathematical model for forecasting energy production in photovoltaic (PV) panels based on a self-organizing feature map (SOFM) model. The proposed model is compared with other models, including the multi-layer perceptron (MLP) and support vector machine (SVM) models. Moreover, a mathematical model based on a polynomial function for fitting the desired output is proposed. Different practical measurement methods are used to validate the findings of the proposed neural and mathematical models such as mean square error (MSE), mean absolute error (MAE), correlation (R), and coefficient of determination (R²). The proposed SOFM model achieved a final MSE of 0.0007 in the training phase and 0.0005 in the cross-validation phase. In contrast, the SVM model resulted in a small MSE value equal to 0.0058, while the MLP model achieved a final MSE of 0.026 with a correlation coefficient of 0.9989, which indicates a strong relationship between input and output variables. The proposed SOFM model closely fits the desired results based on the R² value, which is equal to 0.9555. Finally, the comparison results of MAE for the three models show that the SOFM model achieved a best result of 0.36156, whereas the SVM and MLP models yielded 4.53761 and 3.63927, respectively. A small MAE value indicates that the output of the SOFM model closely fits the actual results and predicts the desired output. Full article

(This article belongs to the Special Issue Solar Forecasting)

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13 pages, 3560 KiB

Open AccessArticle

An Enhanced Empirical Wavelet Transform for Features Extraction from Wind Turbine Condition Monitoring Signals

by Pu Shi¹, Wenxian Yang^2,3,*

, Meiping Sheng⁴ and Minqing Wang⁴

¹ School of Mechanical and Electrical Engineering, Henan University of Technology, Zhengzhou 450001, China

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

³ Hunan Province Cooperative Innovation Centre for Wind Power Equipment and Energy Conversion, Hunan Institute of Engineering, Xiangtan 411104, China

⁴ School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

Energies 2017, 10(7), 972; https://doi.org/10.3390/en10070972 - 11 Jul 2017

Cited by 33 | Viewed by 5659

Abstract

Feature extraction from nonlinear and non-stationary (NNS) wind turbine (WT) condition monitoring (CM) signals is challenging. Previously, much effort has been spent to develop advanced signal processing techniques for dealing with CM signals of this kind. The Empirical Wavelet Transform (EWT) is one [...] Read more.

Feature extraction from nonlinear and non-stationary (NNS) wind turbine (WT) condition monitoring (CM) signals is challenging. Previously, much effort has been spent to develop advanced signal processing techniques for dealing with CM signals of this kind. The Empirical Wavelet Transform (EWT) is one of the achievements attributed to these efforts. The EWT takes advantage of Empirical Mode Decomposition (EMD) in dealing with NNS signals but is superior to the EMD in mode decomposition and robustness against noise. However, the conventional EWT meets difficulty in properly segmenting the frequency spectrum of the signal, especially when lacking pre-knowledge of the signal. The inappropriate segmentation of the signal spectrum will inevitably lower the accuracy of the EWT result and thus raise the difficulty of WT CM. To address this issue, an enhanced EWT is proposed in this paper by developing a feasible and efficient spectrum segmentation method. The effectiveness of the proposed method has been verified by using the bearing and gearbox CM data that are open to the public for the purpose of research. The experiment has shown that, after adopting the proposed method, it becomes much easier and more reliable to segment the frequency spectrum of the signal. Moreover, benefitting from the correct segmentation of the signal spectrum, the fault-related features of the CM signals are presented more explicitly in the time-frequency map of the enhanced EWT, despite the considerable noise contained in the signal and the shortage of pre-knowledge about the machine being investigated. Full article

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

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22 pages, 5365 KiB

Open AccessArticle

Power Take-Off Simulation for Scale Model Testing of Wave Energy Converters

by Scott Beatty^1,*

, Francesco Ferri²

, Bryce Bocking³, Jens Peter Kofoed²

and Bradley Buckham³

¹ Cascadia Coast Research Ltd., 26 Bastion Square, Third Floor Burnes House, Victoria, BC V8W-1H9, Canada

² Wave Energy Research Group, Aalborg University, P.O. Box 159, Aalborg DK - 9100, Denmark

³ Department of Mechanical Engineering, University of Victoria, P.O. Box 3055, Stn. CSC, Victoria, BC V8W-3P6, Canada

Energies 2017, 10(7), 973; https://doi.org/10.3390/en10070973 - 11 Jul 2017

Cited by 21 | Viewed by 5260

Abstract

Small scale testing in controlled environments is a key stage in the development of potential wave energy conversion technology. Furthermore, it is well known that the physical design and operational quality of the power-take off (PTO) used on the small scale model can [...] Read more.

Small scale testing in controlled environments is a key stage in the development of potential wave energy conversion technology. Furthermore, it is well known that the physical design and operational quality of the power-take off (PTO) used on the small scale model can have vast effects on the tank testing results. Passive mechanical elements such as friction brakes and air dampers or oil filled dashpots are fraught with nonlinear behaviors such as static friction, temperature dependency, and backlash, the effects of which propagate into the wave energy converter (WEC) power production data, causing very high uncertainty in the extrapolation of the tank test results to the meaningful full ocean scale. The lack of quality in PTO simulators is an identified barrier to the development of WECs worldwide. A solution to this problem is to use actively controlled actuators for PTO simulation on small scale model wave energy converters. This can be done using force (or torque)-controlled feedback systems with suitable instrumentation, enabling the PTO to exert any desired time and/or state dependent reaction force. In this paper, two working experimental PTO simulators on two different wave energy converters are described. The first implementation is on a 1:25 scale self-reacting point absorber wave energy converter with optimum reactive control. The real-time control system, described in detail, is implemented in LabVIEW. The second implementation is on a 1:20 scale single body point absorber under model-predictive control, implemented with a real-time controller in MATLAB/Simulink. Details on the physical hardware, software, and feedback control methods, as well as results, are described for each PTO. Lastly, both sets of real-time control code are to be web-hosted, free for download, modified and used by other researchers and WEC developers. Full article

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12 pages, 4438 KiB

Open AccessFeature PaperArticle

Thermal Performance of a Vertical U-Shaped Thermosyphon Containing a Phase-Change Material Suspension Fluid

by Ching Jenq Ho^1,*, Heng-I Hsu¹, Tai-Ann Ho¹ and Chi-Ming Lai^2,*

¹ Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan

² Department of Civil Engineering, National Cheng Kung University, Tainan 701, Taiwan

Energies 2017, 10(7), 974; https://doi.org/10.3390/en10070974 - 11 Jul 2017

Cited by 7 | Viewed by 3425

Abstract

This study investigated the thermal performance of a vertical U-shaped thermosyphon containing a phase-change material (PCM) suspension fluid via experimentation. The heating and cooling sections were located at the top and bottom of the loop, respectively. The lengths of the heating and cooling [...] Read more.

This study investigated the thermal performance of a vertical U-shaped thermosyphon containing a phase-change material (PCM) suspension fluid via experimentation. The heating and cooling sections were located at the top and bottom of the loop, respectively. The lengths of the heating and cooling sections each accounted for one fifth of the height of the loop. Pure water and a PCM (octadecane) suspension fluid were used to fill the loop to compare the thermal performance of the thermosyphon under different heating power, cooling temperature, and PCM suspension concentration conditions. The results showed that, when the PCM suspension concentration was higher than a critical value, the addition of the PCM suspension had no positive effect on reducing the highest temperature of the fluid in the loop but instead resulted in an increase in fluid temperature. More detailed experiments are needed to observe the phenomena and decide critical values under different experimental parameters. Full article

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16 pages, 12074 KiB

Open AccessArticle

Multi-Objective Optimization Considering Battery Degradation for a Multi-Mode Power-Split Electric Vehicle

by Xuerui Ma, Yong Zhang, Chengliang Yin^* and Shifei Yuan

National Engineering Laboratory for Automotive Electronic Control Technology, Shanghai Jiao Tong University, 800 Dongchuan Rd, Shanghai 200240, China

Energies 2017, 10(7), 975; https://doi.org/10.3390/en10070975 - 11 Jul 2017

Cited by 9 | Viewed by 4610

Abstract

A multi-mode power-split (MMPS) hybrid electric vehicle (HEV) has two planetary gearsets and clutches/grounds which results in several operation modes with enhanced electric drive capability and better fuel economy. Basically, the battery storage system is involved in different operation modes to satisfy the [...] Read more.

A multi-mode power-split (MMPS) hybrid electric vehicle (HEV) has two planetary gearsets and clutches/grounds which results in several operation modes with enhanced electric drive capability and better fuel economy. Basically, the battery storage system is involved in different operation modes to satisfy the power demand and minimize the fuel consumption, whereas the complicated operation modes with frequent charging/discharging will absolutely influence the battery life because of degradation. In this paper, firstly, we introduce the solid electrolyte interface (SEI) film growth model based on the previous study of the battery degradation principles and was verified according to the test data. We consider both the fuel economy and battery degradation as a multi-objective problem for MMPS HEV by normalization with a weighting factor. An instantaneous optimization is implemented based on the equivalent fuel consumption concept. Then the control strategy is implemented on a simulation framework integrating the MMPS powertrain model and the SEI film growth map model over some typical driving cycles, such as New European Driving Cycle (NEDC) and Urban Dynamometer Driving Schedule (UDDS). Finally, the result demonstrates that these two objectives are conflicting and the trade-off reduces the battery degradation with fuel sacrifice. Additionally, the analysis reveals how the mode selection will reflect the battery degradation. Full article

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

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17 pages, 1320 KiB

Open AccessArticle

Profitability of Residential Battery Energy Storage Combined with Solar Photovoltaics

by Christoph Goebel^1,*, Vicky Cheng² and Hans-Arno Jacobsen¹

¹ Chair of Business Information Systems, Technical University of Munich, Boltzmannstr. 3, 85748 Garching, Germany

² Munich School of Engineering, Technical University of Munich, Lichtenbergstr. 4a, 85748 Garching, Germany

Energies 2017, 10(7), 976; https://doi.org/10.3390/en10070976 - 11 Jul 2017

Cited by 34 | Viewed by 7002

Abstract

Lithium-ion (Li-Ion) batteries are increasingly being considered as bulk energy storage in grid applications. One such application is residential energy storage combined with solar photovoltaic (PV) panels to enable higher self-consumption rates, which has become financially more attractive recently due to decreasing feed-in [...] Read more.

Lithium-ion (Li-Ion) batteries are increasingly being considered as bulk energy storage in grid applications. One such application is residential energy storage combined with solar photovoltaic (PV) panels to enable higher self-consumption rates, which has become financially more attractive recently due to decreasing feed-in subsidies. Although residential energy storage solutions are commercially mature, it remains unclear which system configurations and circumstances, including aggregator-based applications such as the provision of ancillary services, lead to profitable consumer investments. Therefore, we conduct an extensive simulation study that is able to jointly capture these aspects. Our results show that, at current battery module prices, even optimal system configurations still do not lead to profitable investments into Li-Ion batteries if they are merely used as a buffer for solar energy. The first settings in which they will become profitable, as prices are further declining, will be larger households at locations with higher average levels of solar irradiance. If the batteries can be remote-controlled by an aggregator to provide overnight negative reserve, their profitability increases significantly. Full article

(This article belongs to the Special Issue Energy Efficient and Smart Cities)

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22 pages, 11556 KiB

Open AccessArticle

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

by Markel Penalba^1,*

, Nathan P. Sell², Andy J. Hillis² and John V. Ringwood¹

¹ Centre for Ocean Energy Research, Maynooth University, Maynooth, Co. Kildare, Ireland

² Department of Mechanical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK

Energies 2017, 10(7), 977; https://doi.org/10.3390/en10070977 - 12 Jul 2017

Cited by 40 | Viewed by 7767

Abstract

Considering the full dynamics of the different conversion stages from ocean waves to the electricity grid is essential to evaluate the realistic power flow in the drive train and design accurate model-based control formulations. The power take-off system for wave energy converters (WECs) [...] Read more.

Considering the full dynamics of the different conversion stages from ocean waves to the electricity grid is essential to evaluate the realistic power flow in the drive train and design accurate model-based control formulations. The power take-off system for wave energy converters (WECs) is one of the essential parts of wave-to-wire (W2W) models, for which hydraulic transmissions are a robust solution and offer the flexibility to design specific drive-trains for specific energy absorption requirements of different WECs. The potential hydraulic drive train topologies can be classified into two main configuration groups (constant-pressure and variable-pressure configurations), each of which uses specific components and has a particular impact on the preceding and following stages of the drive train. The present paper describes the models for both configurations, including the main nonlinear dynamics, losses and constraints. Results from the mathematical model simulations are compared against experimental results obtained from two independent test rigs, which represent the two main configurations, and high-fidelity software. Special attention is paid to the impact of friction in the hydraulic cylinder and flow and torque losses in the hydraulic motor. Results demonstrate the effectiveness of the models in reproducing experimental results, capturing friction effects and showing similar losses. Full article

(This article belongs to the Special Issue Marine Energy)

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14 pages, 1615 KiB

Open AccessArticle

Rev-Changes in Primary Energy Use and CO₂ Emissions—An Impact Assessment for a Building with Focus on the Swedish Proposal for Nearly Zero Energy Buildings

by Mattias Gustafsson^1,*

, Richard Thygesen¹

, Björn Karlsson¹ and Louise Ödlund²

¹ Division of Building, Energy and Environment Technology, Department of Technology and Environment, University of Gävle, Gävle 802 67, Sweden

² Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping 581 83, Sweden

Energies 2017, 10(7), 978; https://doi.org/10.3390/en10070978 - 12 Jul 2017

Cited by 17 | Viewed by 7845

Abstract

In the European Union’s Energy Performance of Buildings Directive, the energy efficiency goal for buildings is set in terms of primary energy use. In the proposal from the National Board of Housing, Building, and Planning, for nearly zero energy buildings in Sweden, the [...] Read more.

In the European Union’s Energy Performance of Buildings Directive, the energy efficiency goal for buildings is set in terms of primary energy use. In the proposal from the National Board of Housing, Building, and Planning, for nearly zero energy buildings in Sweden, the use of primary energy is expressed as a primary energy number calculated with given primary energy factors. In this article, a multi-dwelling building is simulated and the difference in the primary energy number is investigated when the building uses heat from district heating systems or from heat pumps, alone or combined with solar thermal or solar photovoltaic systems. It is also investigated how the global CO₂ emissions are influenced by the different energy system combinations and with different fuels used. It is concluded that the calculated primary energy number is lower for heat pump systems, but the global CO₂ emissions are lowest when district heating uses mostly biofuels and is combined with solar PV systems. The difference is up to 140 tonnes/year. If the aim with the Swedish building code is to decrease the global CO₂ emissions then the ratio between the primary energy factors for electricity and heat should be larger than three and considerably higher than today. Full article

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21 pages, 3021 KiB

Open AccessArticle

Exergy Replacement Cost of Fossil Fuels: Closing the Carbon Cycle

by Kai Whiting^1,2,*, Luis Gabriel Carmona¹, Angeles Carrasco²

and Tânia Sousa¹

¹ MARETEC, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049-001 Lisboa, Portugal

² Mining and Industrial Engineering School of Almadén, Universidad de Castilla–La Mancha, Plaza Manuel Meca 1, 13400 Almadén, Spain

Energies 2017, 10(7), 979; https://doi.org/10.3390/en10070979 - 12 Jul 2017

Cited by 11 | Viewed by 6339

Abstract

The Exergy Replacement Cost (ERC) is an indicator that is used to ascertain the sustainability of non-renewable resource depletion. Specifically, it measures the amount of exergy society would have to expend if it were forced to re-capture and re-concentrate dispersed minerals [...] Read more.

The Exergy Replacement Cost (ERC) is an indicator that is used to ascertain the sustainability of non-renewable resource depletion. Specifically, it measures the amount of exergy society would have to expend if it were forced to re-capture and re-concentrate dispersed minerals back into a manmade usable deposit. Due to an assumption regarding the non-substitutability of fossil fuels, the original method failed to properly account for them. In fact, it sub-estimated their exergy replacement cost forty-seven-fold, on average, when considering solar radiation to fuel, and by approximately fivefold when going from crop to fuel. This new method, via the cumulative exergy consumption (CExC), calculates the exergy replacement cost of photosynthesis and bio-energy production, as together they form the best available technology when it comes to closing the carbon cycle. This approach ties together the “cradle to grave” to the “grave to cradle”, standardises the ERC calculations and enables comparisons between fuel and non-fuel mineral consumption. It also opens a discussion as to the role of the ERC in sustainability debates and whether resource depletion should be a matter of geological patrimony or material/energy services. Full article

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17 pages, 2403 KiB

Open AccessArticle

Trends in CO₂ Emissions from China-Oriented International Marine Transportation Activities and Policy Implications

by Hualong Yang^*, Xuefei Ma and Yuwei Xing

Collaborative Innovation Center for Transport Studies, Dalian Maritime University, Dalian 116026, China

Energies 2017, 10(7), 980; https://doi.org/10.3390/en10070980 - 12 Jul 2017

Cited by 22 | Viewed by 5074

Abstract

The demand for marine transportation and its associated CO₂ emissions are growing rapidly as a result of increasing international trade and economic growth. An activity-based approach is developed for forecasting CO₂ emissions from the China-oriented international seaborne trade sector. To accurately [...] Read more.

The demand for marine transportation and its associated CO₂ emissions are growing rapidly as a result of increasing international trade and economic growth. An activity-based approach is developed for forecasting CO₂ emissions from the China-oriented international seaborne trade sector. To accurately estimate the aggregated emissions, CO₂ emissions are calculated individually for five categories of vessels: crude oil tanker, product tanker, chemical tanker, bulk carrier, and container. A business-as-usual (BAU) scenario was developed to describe the current situation without additional mitigation policies, whilst three alternative scenarios were developed to describe scenarios with various accelerated improvements of the key factors. The aggregated CO₂ emissions are predicted to reach 419.97 Mt under the BAU scenario, and 258.47 Mt under the optimal case, AD3. These predictions are 4.5 times and 2.8 times that of the aggregated emissions in 2007. Our analysis suggests that regulations for monitoring, reporting, and verifying the activities of vessels should be proposed, in order to quantify the CO₂ emissions of marine transportation activities in Chinese territorial waters. In the long-term future, mitigation policies should be employed to reduce CO₂ emissions from the marine trade sector and to address the climatic impact of shipping. Full article

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14 pages, 5886 KiB

Open AccessArticle

Standby-Loss Elimination in Server Power Supply

by Jong-Woo Kim¹, Gun-Woo Moon¹ and Il-Oun Lee^2,*

¹ KAIST—Korea Advanced Institute of Science and Technology, Deajon 341-41, Korea

² Department of Electric Engineering, Myongji Unversity, Yongin-Si 449-728, Korea

Energies 2017, 10(7), 981; https://doi.org/10.3390/en10070981 - 12 Jul 2017

Cited by 2 | Viewed by 4033

Abstract

In a server power system, a standby converter is required in order to provide the standby output, monitor the system’s status, and communicate with the server power system. Since these functions are always required, losses from the standby converter are produced even though [...] Read more.

In a server power system, a standby converter is required in order to provide the standby output, monitor the system’s status, and communicate with the server power system. Since these functions are always required, losses from the standby converter are produced even though the system operates in normal mode. For these reasons, the losses deteriorate the total efficiency of the system. In this paper, a new structure is proposed to eliminate the losses from the standby converter of a server power supply. The key feature of the proposed structure is that the main direct current (DC)/DC converter substitutes all of the output power of the standby converter, and the standby converter is turned off in normal mode. With the proposed structure, the losses from the standby converter can be eliminated in normal mode, and this leads to a higher efficiency in overall load conditions. Although the structure has been proposed in the previous work, very important issues such as a steady state analysis, the transient responses, and how to control the standby converter are not discussed. This paper presents these issues further. The feasibility of the proposed structure has been verified with 400 V link voltage, 12 V/62.5 A main output, and a 12 V/2.1 A standby output server power system. Full article

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

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14 pages, 2057 KiB

Open AccessArticle

Adaptive Fuzzy Control for Power-Frequency Characteristic Regulation in High-RES Power Systems

by Evangelos Rikos^1,*, Chris Caerts², Mattia Cabiati³, Mazheruddin Syed⁴

and Graeme Burt⁴

¹ Centre for Renewable Energy Sources and Saving, Pikermi Attiki 19009, Greece

² Flemish Institute for Technological Research, Mol 2400, Belgium

³ Ricerca sul Sistema Energetico-RSE S.p.A., Milano 20134, Italy

⁴ Institute for Energy and Environment, University of Strathclyde, Glasgow G1 1XQ, UK

Energies 2017, 10(7), 982; https://doi.org/10.3390/en10070982 - 12 Jul 2017

Cited by 6 | Viewed by 4572

Abstract

Future power systems control will require large-scale activation of reserves at distribution level. Despite their high potential, distributed energy resources (DER) used for frequency control pose challenges due to unpredictability, grid bottlenecks, etc. To deal with these issues, this study presents a novel [...] Read more.

Future power systems control will require large-scale activation of reserves at distribution level. Despite their high potential, distributed energy resources (DER) used for frequency control pose challenges due to unpredictability, grid bottlenecks, etc. To deal with these issues, this study presents a novel strategy of power frequency characteristic dynamic adjustment based on the imbalance state. This way, the concerned operators become aware of the imbalance location but also a more accurate redistribution of responsibilities in terms of reserves activations is achieved. The proposed control is based on the concept of “cells” which are power systems with operating capabilities and responsibilities similar to control areas (CAs), but fostering the use of resources at all voltage levels, particularly distribution grids. Control autonomy of cells allows increased RES hosting. In this study, the power frequency characteristic of a cell is adjusted in real time by means of a fuzzy controller, which curtails part of the reserves, in order to avoid unnecessary deployment throughout a synchronous area, leading to a more localised activation and reducing losses, congestions and reserves exhaustion. Simulation tests in a four-cell reference power system prove that the controller significantly reduces the use of reserves without compromising the overall stability. Full article

(This article belongs to the Special Issue Methods and Concepts for Designing and Validating Smart Grid Systems)

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13 pages, 742 KiB

Open AccessArticle

System-Level Value of a Gas Engine Power Plant in Electricity and Reserve Production

by Antti Alahäivälä^1,*, Juha Kiviluoma², Jyrki Leino³ and Matti Lehtonen¹

¹ Department of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, FI-00076 AALTO Espoo, Finland

² VTT Technical Research Centre of Finland, 02044 VTT Espoo, Finland

³ Wärtsilä, Energy Solutions, FI-00530 Helsinki, Finland

Energies 2017, 10(7), 983; https://doi.org/10.3390/en10070983 - 12 Jul 2017

Cited by 2 | Viewed by 3910

Abstract

Power systems require a certain amount of flexibility to meet varying demand and to be able to cope with unexpected events, and this requirement is expected to increase with the emergence of variable power generation. In this paper, we focus on gas engine [...] Read more.

Power systems require a certain amount of flexibility to meet varying demand and to be able to cope with unexpected events, and this requirement is expected to increase with the emergence of variable power generation. In this paper, we focus on gas engine power plant technology and the beneficial influence its flexible operation can have on a power system. The study introduces the concept of a combined-cycle gas engine power plant (CCGE), which comprises a combination of several gas-fired combustion engines and a steam turbine. The operation of CCGE is then comprehensively analyzed in electricity and reserve production in the South African power system and compared with combined-cycle gas turbine (CCGT) technology. Even though CCGE is a form of technology that has already been commercialized, it is rarely considered as a source of flexibility in the academic research. That is the notion providing the motivation for this study. Our core contribution is to show that the flexibility of CCGE can be valuable in power systems. The methodology is based on the unit-level model of the studied system and the solving of a day-ahead unit commitment problem for each day of the simulated 11-year period. The simulation studies reveal how a CCGE is able to offer system flexibility to follow hourly load variations and capacity to provide reserve power effectively. Full article

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18 pages, 6847 KiB

Open AccessArticle

A Quantification Index for Power Systems Transient Stability

by Shengen Chen¹, Amamihe Onwuachumba², Mohamad Musavi^1,* and Paul Lerley²

¹ Department of Electrical & Computer Engineering, University of Maine, Orono, ME 04469, USA

² RLC Engineering LLC., Hallowell, ME 04347, USA

Energies 2017, 10(7), 984; https://doi.org/10.3390/en10070984 - 12 Jul 2017

Cited by 4 | Viewed by 5160

Abstract

In order to assess the reliability of power systems, transient stability simulations must be conducted in addition to steady state study. The transient stability component of reliability studies usually involves extensive simulations generating large amounts of data to be analyzed. Conventional stability analysis [...] Read more.

In order to assess the reliability of power systems, transient stability simulations must be conducted in addition to steady state study. The transient stability component of reliability studies usually involves extensive simulations generating large amounts of data to be analyzed. Conventional stability analysis relies on a visual examination of selected simulation data plots to classify the severity of disturbances. This conventional examination, which aims to compare the simulations results to established performance criteria, is not comprehensive, is time consuming and prone to subjective interpretation. This paper presents a quantification method for power system performance evaluation. It applies a range of criteria such as rotor angle separation, loss of source, damping, and voltage sag directly to the simulation data files to achieve a more efficient and objective stability assessment. By using stability modules, the proposed method evaluates the performance of every fault location, numerically, by providing a local stability index, as well as an overall global stability index. The method also provides an evaluation of dispatches and their impacts on system stability. The IEEE 39-bus test system and the Northeast Interconnection Power System were used to show the results of this method. This method will free engineers from tedious, time-consuming and error-susceptible offline visual analysis and yield significantly quantified results. Full article

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

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15 pages, 4000 KiB

Open AccessCommunication

Alternative for Summer Use of Solar Air Heaters in Existing Buildings

by Sergio L. González-González¹

, Ana Tejero-González^1,*

, Francisco J. Rey-Martínez¹

and Manuel Andrés-Chicote²

¹ Department of Energy Engineering and Fluidmechanics, University of Valladolid, 47002 Valladolid, Spain

² CARTIF Technology Centre, Parque Tecnológico de Boecillo, 205, Boecillo, 47151 Valladolid, Spain

Energies 2017, 10(7), 985; https://doi.org/10.3390/en10070985 - 12 Jul 2017

Cited by 3 | Viewed by 5316

Abstract

Among solar thermal technologies for indoor heating, solar air heaters (SAH) are appealing for implementation on existing buildings due to their simplicity, fewer risks related to the working fluid, and possible independence from the building structure. However, existing research work mainly focuses on [...] Read more.

Among solar thermal technologies for indoor heating, solar air heaters (SAH) are appealing for implementation on existing buildings due to their simplicity, fewer risks related to the working fluid, and possible independence from the building structure. However, existing research work mainly focuses on winter use and still fails in providing effective solutions for yearly operation, which would enhance their interest. With the aim of analysing an alternative summer use, this work firstly characterises a double channel-single pass solar air collector through experimentation. From the obtained results, modelling and simulation tasks have been conducted to evaluate the possibilities of using hot air, provided by the SAH, while operating under summer conditions within a closed loop, to feed an air-to-water heat exchanger for domestic hot water (DHW) production. The system is studied through simulation under two different configurations for a case study in Valladolid (Spain), during the period from May to September for different airflows in the closed loop. Results show that daily savings can vary from 27% to 85% among the different operating conditions; a configuration where make-up water is fed to the heat exchanger being preferable, with a dedicated water tank for the solar heated water storage of the minimum possible volume. The more favourable results for the harshest months highlight the interest of extending the use of the solar air heaters to the summer period. Full article

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

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21 pages, 3129 KiB

Open AccessArticle

Multi-Objective Scheduling Optimization Based on a Modified Non-Dominated Sorting Genetic Algorithm-II in Voltage Source Converter−Multi-Terminal High Voltage DC Grid-Connected Offshore Wind Farms with Battery Energy Storage Systems

by Ho-Young Kim, Mun-Kyeom Kim^* and San Kim

Department of Energy System Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Korea

Energies 2017, 10(7), 986; https://doi.org/10.3390/en10070986 - 12 Jul 2017

Cited by 15 | Viewed by 4949

Abstract

Improving the performance of power systems has become a challenging task for system operators in an open access environment. This paper presents an optimization approach for solving the multi-objective scheduling problem using a modified non-dominated sorting genetic algorithm in a hybrid network of [...] Read more.

Improving the performance of power systems has become a challenging task for system operators in an open access environment. This paper presents an optimization approach for solving the multi-objective scheduling problem using a modified non-dominated sorting genetic algorithm in a hybrid network of meshed alternating current (AC)/wind farm grids. This approach considers voltage and power control modes based on multi-terminal voltage source converter high-voltage direct current (MTDC) and battery energy storage systems (BESS). To enhance the hybrid network station performance, we implement an optimal process based on the battery energy storage system operational strategy for multi-objective scheduling over a 24 h demand profile. Furthermore, the proposed approach is formulated as a master problem and a set of sub-problems associated with the hybrid network station to improve the overall computational efficiency using Benders’ decomposition. Based on the results of the simulations conducted on modified institute of electrical and electronics engineers (IEEE-14) bus and IEEE-118 bus test systems, we demonstrate and confirm the applicability, effectiveness and validity of the proposed approach. Full article

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

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10 pages, 3158 KiB

Open AccessArticle

State-of-Charge Estimation with State-of-Health Calibration for Lithium-Ion Batteries

by Tsung-Hsi Wu^*

and Chin-Sien Moo

Department of Electrical Engineering, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 80424, Taiwan

Energies 2017, 10(7), 987; https://doi.org/10.3390/en10070987 - 13 Jul 2017

Cited by 30 | Viewed by 7789

Abstract

This research is focused on state-of-charge (SOC) estimation with state-of-health (SOH) calibration for lithium-ion batteries on the basis of the coulomb counting method. The proposed approach intends to present an easy-to-use solution with high accuracy for estimating battery statuses [...] Read more.

This research is focused on state-of-charge (SOC) estimation with state-of-health (SOH) calibration for lithium-ion batteries on the basis of the coulomb counting method. The proposed approach intends to present an easy-to-use solution with high accuracy for estimating battery statuses without the need for demanding calculations or hard-earned databases. To estimate the SOC of an aged battery more accurately, the degradation of its full capacity has to be taken into account. By scheduling the battery’s charging/discharging current and monitoring the battery’s status, the existing full capacity can be updated regularly by regular calibration or occasionally by partial calibration, in which the charging/discharging rates are normalized with the latest updated full capacity to agree with the battery’s statuses. To exclude the misestimation caused by current measuring error, the SOC is reset to 0% when the battery is exhausted and 100% for a fully charged battery. With an updated SOH, the battery C-rate is re-scaled accordingly. Experimental tests are carried out to demonstrate that the proposed approach can provide an accurate online indication of batteries’ SOCs. With an implanted error of 0.3% in current measuring, the SOC estimation error can always be less than 1.905% after a number of SOH calibrations. Full article

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

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22 pages, 7654 KiB

Open AccessFeature PaperArticle

Numerical Study on the Internal Flow Field of a Reversible Turbine during Continuous Guide Vane Closing

by Xiuli Mao^1,*,†

, Andrea Dal Monte^2,†, Ernesto Benini²

and Yuan Zheng^1,3

¹ College of Water Conservancy and Hydropower Engineering, Hohai University, Xikang Road 1, Nanjing 210098, China

² Department of Industrial Engineering, University of Padua, Via Venezia 1, Padua I-35131, Italy

³ National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Xikang Road 1, Nanjing 210098, China

^† These authors contributed equally to this work.

Energies 2017, 10(7), 988; https://doi.org/10.3390/en10070988 - 13 Jul 2017

Cited by 17 | Viewed by 5708

Abstract

The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. [...] Read more.

The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. In this way, the instability of the flow field is analyzed by continuously changing the guide vane openings from the best efficiency point (BEP). Unsteady flow characteristics are described by post-processing signals for several monitoring points including mass flow, torque, head and pressure in the frequency and time-frequency domains. The formation of vortices of different scales is observed from the origin to further enlargement and stabilization; the effect of the rotating structures on the flow passage is analyzed, and the influence of unsteady flow development on the performance of the turbine is investigated. Finally, the evolution during the period of load rejection is characterized in order to determine the hydrodynamic conditions causing the vibrations in the machine. Full article

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

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34 pages, 6685 KiB

Open AccessArticle

System-Level Operational and Adequacy Impact Assessment of Photovoltaic and Distributed Energy Storage, with Consideration of Inertial Constraints, Dynamic Reserve and Interconnection Flexibility

by Lingxi Zhang¹, Yutian Zhou¹, Damian Flynn², Joseph Mutale¹ and Pierluigi Mancarella^1,3,*

¹ School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, UK

² School of Electrical and Electronic Engineering, University College Dublin, Dublin D04 V1W8, Ireland

³ Melbourne School of Engineering, University of Melbourne, Melbourne, VIC 3010, Australia

Energies 2017, 10(7), 989; https://doi.org/10.3390/en10070989 - 13 Jul 2017

Cited by 19 | Viewed by 7493

Abstract

The growing penetration of solar photovoltaic (PV) systems requires a fundamental understanding of its impact at a system-level. Furthermore, distributed energy storage (DES) technologies, such as batteries, are attracting great interest owing to their ability to provide support to systems with large-scale renewable [...] Read more.

The growing penetration of solar photovoltaic (PV) systems requires a fundamental understanding of its impact at a system-level. Furthermore, distributed energy storage (DES) technologies, such as batteries, are attracting great interest owing to their ability to provide support to systems with large-scale renewable generation, such as PV. In this light, the system-level impacts of PV and DES are assessed from both operational and adequacy perspectives. Different control strategies for DES are proposed, namely: (1) centralised, to support system operation in the presence of increasing requirements on system ramping and frequency control; and (2) decentralised, to maximise the harnessing of solar energy from individual households while storing electricity generated by PV panels to provide system capacity on request. The operational impacts are assessed by deploying a multi-service unit commitment model with consideration of inertial constraints, dynamic reserve allocation, and interconnection flexibility, while the impacts on adequacy of supply are analysed by assessing the capacity credit of PV and DES through different metrics. The models developed are then applied to different future scenarios for the Great Britain power system, whereby an electricity demand increase due to electrification is also considered. The numerical results highlight the importance of interconnectors to provide flexibility. On the other hand, provision of reserves, as opposed to energy arbitrage, from DES that are integrated into system operation is seen as the most effective contribution to improve system performance, which in turn also decreases the role of interconnectors. DES can also contribute to providing system capacity, but to an extent that is limited by their individual and aggregated energy availability under different control strategies. Full article

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

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17 pages, 2368 KiB

Open AccessArticle

On the Convenience of Using Simulation Models to Optimize the Control Strategy of Molten-Salt Heat Storage Systems in Solar Thermal Power Plants

by Miguel J. Prieto^1,*

, Juan Á. Martínez¹, Rogelio Peón², Lourdes Á. Barcia³ and Fernando Nuño¹

¹ Department of Electrical Engineering, Universidad de Oviedo, 33203 Gijón, Asturias, Spain

² Group TSK, 33203 Gijón, Asturias, Spain

³ González Soriano S.A., 33420 Llanera, Asturias, Spain

Energies 2017, 10(7), 990; https://doi.org/10.3390/en10070990 - 13 Jul 2017

Cited by 3 | Viewed by 4485

Abstract

Thermal oil has been used as heat transfer fluid in many solar thermal power plants, which also use molten salts as thermal energy storage system. Since the engineering of these plants is relatively new, control of the thermal energy storage system is currently [...] Read more.

Thermal oil has been used as heat transfer fluid in many solar thermal power plants, which also use molten salts as thermal energy storage system. Since the engineering of these plants is relatively new, control of the thermal energy storage system is currently achieved in manual or semiautomatic ways, controlling its variables with proportional-integral-derivative (PID) regulators. Once the plant is running, it is very difficult to obtain permission to try new control strategies. Hence, most plants keep running on these simple, sometimes inefficient control algorithms. This paper explores the results obtained with different control strategies implemented on a complete model of energy storage systems based on molten salt. The results provided by the model allow the optimum control strategy to be selected. Comparison of the results obtained by simulation of these control strategies and actual results obtained from a real plant, confirm the accuracy of the selection made. Full article

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

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22 pages, 6484 KiB

Open AccessReview

Overview of Compressed Air Energy Storage and Technology Development

by Jidai Wang^1,*, Kunpeng Lu¹, Lan Ma¹, Jihong Wang^2,3, Mark Dooner², Shihong Miao³, Jian Li³ and Dan Wang^3,*

¹ College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao 266590, China

² School of Engineering, University of Warwick, West Midlands, Coventry CV47AL, UK

³ State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Energies 2017, 10(7), 991; https://doi.org/10.3390/en10070991 - 13 Jul 2017

Cited by 267 | Viewed by 29905

Abstract

With the increase of power generation from renewable energy sources and due to their intermittent nature, the power grid is facing the great challenge in maintaining the power network stability and reliability. To address the challenge, one of the options is to detach [...] Read more.

With the increase of power generation from renewable energy sources and due to their intermittent nature, the power grid is facing the great challenge in maintaining the power network stability and reliability. To address the challenge, one of the options is to detach the power generation from consumption via energy storage. The intention of this paper is to give an overview of the current technology developments in compressed air energy storage (CAES) and the future direction of the technology development in this area. Compared with other energy storage technologies, CAES is proven to be a clean and sustainable type of energy storage with the unique features of high capacity and long-duration of the storage. Its scale and cost are similar to pumped hydroelectric storage (PHS), thus CAES has attracted much attention in recent years while further development for PHS is restricted by the availability of suitable geological locations. The paper presents the state-of-the-art of current CAES technology development, analyses the major technological barriers/weaknesses and proposes suggestions for future technology development. This paper should provide a useful reference for CAES technology research and development strategy. Full article

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

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22 pages, 594 KiB

Open AccessFeature PaperArticle

Bluetooth 5 Energy Management through a Fuzzy-PSO Solution for Mobile Devices of Internet of Things

by Giovanni Pau^*

, Mario Collotta

and Vincenzo Maniscalco

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

Energies 2017, 10(7), 992; https://doi.org/10.3390/en10070992 - 13 Jul 2017

Cited by 34 | Viewed by 5553

Abstract

Energy efficiency is a fundamental requirement for a wireless protocol to be suitable for use within the Internet of Things. New technologies are emerging aiming at an energy-efficient communication. Among them, Bluetooth Low Energy is an appealing solution. Recently, the specifications of Bluetooth [...] Read more.

Energy efficiency is a fundamental requirement for a wireless protocol to be suitable for use within the Internet of Things. New technologies are emerging aiming at an energy-efficient communication. Among them, Bluetooth Low Energy is an appealing solution. Recently, the specifications of Bluetooth 5 have been presented with the purpose to offer significant enhancements compared to the earlier versions of the protocol. Bluetooth 5 comes with new communication modes that differ in range, speed, and energy consumption. This paper proposes a fuzzy-based solution to cope with the selection of the communication mode, among those introduced with Bluetooth 5, that allows the best energy efficiency. This communication mode, used by mobile devices, is dynamically regulated by varying the transmission power, returned as the output of a Fuzzy Logic Controller (FLC). A Particle Swarm Optimization (PSO) algorithm is presented to achieve the optimal parameters of the proposed FLC, i.e., optimizing the triangular membership functions, by varying their range, to reach the best results concerning the battery life of mobile devices. The proposed FLC is based on triangular membership functions because they represent a good trade-off between computation cost and efficiency. The paper presents a detailed description of the FLC design, a logical analysis of the PSO algorithm for the derivation of best performance conditions values, and experimental assessments, obtained through testbed scenarios. Full article

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26 pages, 1015 KiB

Open AccessArticle

An Assisted Workflow for the Early Design of Nearly Zero Emission Healthcare Buildings

by Hassan A. Sleiman^1,*, Steffen Hempel², Roberto Traversari³

and Sander Bruinenberg⁴

¹ CEA, LIST, Laboratoire d’Analyse de Données et Intelligence des Systèmes, Digiteo Labs Saclay, 91191 Gif Sur Yvette, France

² Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

³ TNO Innovation Centre Buildings, PO box Postbus 49, 2600 AA Delft, The Netherlands

⁴ DEMO Consultants, P.O. Box 642, 2600 AP Delft, The Netherlands

Energies 2017, 10(7), 993; https://doi.org/10.3390/en10070993 - 13 Jul 2017

Cited by 17 | Viewed by 6457

Abstract

Energy efficiency in buildings is one of the main goals of many governmental policies due to their high impact on the carbon dioxide emissions in Europe. One of these targets is to reduce the energy consumption in healthcare buildings, which are known to [...] Read more.

Energy efficiency in buildings is one of the main goals of many governmental policies due to their high impact on the carbon dioxide emissions in Europe. One of these targets is to reduce the energy consumption in healthcare buildings, which are known to be among the most energy-demanding building types. Although design decisions made at early design phases have a significant impact on the energy performance of the realized buildings, only a small portion of possible early designs is analyzed, which does not ensure an optimal building design. We propose an automated early design support workflow, accompanied by a set of tools, for achieving nearly zero emission healthcare buildings. It is intended to be used by decision makers during the early design phase. It starts with the user-defined brief and the design rules, which are the input for the Early Design Configurator (EDC). The EDC generates multiple design alternatives following an evolutionary algorithm while trying to satisfy user requirements and geometric constraints. The generated alternatives are then validated by means of an Early Design Validator (EDV), and then, early energy and cost assessments are made using two early assessment tools. A user-friendly dashboard is used to guide the user and to illustrate the workflow results, whereas the chosen alternative at the end of the workflow is considered as the starting point for the next design phases. Our proposal has been implemented using Building Information Models (BIM) and validated by means of a case study on a healthcare building and several real demonstrations from different countries in the context of the European project STREAMER. Full article

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

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15 pages, 4282 KiB

Open AccessArticle

Offshore Wind Speed Forecasting: The Correlation between Satellite-Observed Monthly Sea Surface Temperature and Wind Speed over the Seas around the Korean Peninsula

by Jin-Young Kim, Hyun-Goo Kim^*

and Yong-Heack Kang

New & Renewable Energy Data Center, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 34129, Korea

Energies 2017, 10(7), 994; https://doi.org/10.3390/en10070994 - 14 Jul 2017

Cited by 7 | Viewed by 4184

Abstract

Wind power forecasting is a key role for large-scale wind power penetration on conventional electric power systems by understanding stochastic nature of winds. This paper proposes an empirical statistical model for forecasting monthly offshore wind speeds as a function of remotely sensed sea [...] Read more.

Wind power forecasting is a key role for large-scale wind power penetration on conventional electric power systems by understanding stochastic nature of winds. This paper proposes an empirical statistical model for forecasting monthly offshore wind speeds as a function of remotely sensed sea surface temperatures over the seas around the Korean Peninsula. The model uses the optimal lagged multiple linear regression method, and predictors are characterized by mixed periodicities derived from the autocorrelation between spatially variable satellite-observed sea surface temperatures and wind speeds at all grid points over a period of about ten years (2001 to 2008). Offshore wind speeds were found to be correlated with sea surface temperatures within a seasonal range of two- to four-month lags. In particular, offshore wind speeds were closely associated with the sea surface temperature at lag 4 M, followed by lag 3 M and lag 2 M. Correlation is less at lag 1 M as compared lag 2 M, lag 3 M and lag 4 M. The results demonstrate that this approach successfully produces accurate depictions of monthly wind speeds at the gridded network. The hindcast offshore wind speeds and wind power density showed slightly improved skills compared to the seasonally varying climatology with the value of root-mean square errors, +18% and +23%, respectively. The spatial distributions of the monthly gridded wind speed and wind power density remained fairly stable from one month to another, whereas individual regions displayed slight differences in variability. The results of this study are expected to be useful in establishing guidelines for operating and managing nascent offshore farms around the Korean Peninsula. Full article

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

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20 pages, 3457 KiB

Open AccessArticle

Low Voltage Ride-through Scheme of the PMSG Wind Power System Based on Coordinated Instantaneous Active Power Control

by Cheng Zhong^*, Lai Wei and Gangui Yan

Ministry of Education Key Laboratory of Modern Power System Simulation Control and Green Power Technology, Northeast Dianli University, Jilin 132012, China

Energies 2017, 10(7), 995; https://doi.org/10.3390/en10070995 - 14 Jul 2017

Cited by 12 | Viewed by 4331

Abstract

Fast control DC-link voltage is the key to enhance Low-Voltage Ride-Through (LVRT) for the Permanent Magnet Synchronous Generator (PMSG). When grid voltage dips deeply, by the constraint of the capacity of the grid-side converter and reactive power support by the grid-code required, the [...] Read more.

Fast control DC-link voltage is the key to enhance Low-Voltage Ride-Through (LVRT) for the Permanent Magnet Synchronous Generator (PMSG). When grid voltage dips deeply, by the constraint of the capacity of the grid-side converter and reactive power support by the grid-code required, the active power capacity of the grid-side converter will be reduced. Therefore, it cannot stabilize the DC-link voltage relying solely on the grid-side converter. This paper proposes an improved control strategy to combine generator-side and grid-side converter active power. Reactive power support and negative sequence feed-forward compensation are also considered in the paper. The effectiveness of the control strategy is verified by both simulation and the experimental results. Full article

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

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13 pages, 6136 KiB

Open AccessArticle

Impact of Stress-Dependent Matrix and Fracture Properties on Shale Gas Production

by Huiying Tang¹

, Yuan Di¹, Yongbin Zhang² and Hangyu Li^3,*

¹ College of Engineering, Peking University, Beijing 100871, China

² Tarim Oil Company, PetroChina, Korla 841000, Xinjiang, China

³ Department of Energy Resources Engineering, Stanford University, Stanford, CA 94305, USA

Energies 2017, 10(7), 996; https://doi.org/10.3390/en10070996 - 14 Jul 2017

Cited by 5 | Viewed by 4224

Abstract

Unconventional shale gas production is often characterized by a short period of high production followed by a rapid decline in the production rate. Given the high costs of hydraulic fracturing and horizontal drilling, it is critical to identify the mechanisms behind the production [...] Read more.

Unconventional shale gas production is often characterized by a short period of high production followed by a rapid decline in the production rate. Given the high costs of hydraulic fracturing and horizontal drilling, it is critical to identify the mechanisms behind the production loss. The existing shale gas production models often assume constant matrix permeability. However, laboratory observations show that matrix permeability can decrease significantly with increasing effective stress, which highlights the necessity of considering the stress-dependent properties of shale matrix in production analysis. Moreover, the compaction of pore space will also increase the matrix permeability by enhancing the gas-slippage effect. In this paper, a matrix permeability model which couples the effect of pore volume compaction and non-Darcy slip flow is derived. Numerical simulations are conducted to understand the role of matrix permeability evolution during production. Changes of fractures’ permeability and contact area during depletion process are also taken into account. The results indicate that the loss of fracture permeability has a greater impact at the early stage of the depletion process, while matrix permeability evolution is more important for the long-term production. Full article

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11 pages, 1204 KiB

Open AccessArticle

by Esperanza Monedero^1,*

, Juan José Hernández²

and Rocío Collado²

¹ Universidad de Castilla-La Mancha, Instituto de Investigación en Energías Renovables, 02006 Albacete, Spain

² Escuela Técnica Superior de Ingenieros Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain

Energies 2017, 10(7), 997; https://doi.org/10.3390/en10070997 - 14 Jul 2017

Cited by 25 | Viewed by 3947

Abstract

The physical and thermochemical properties of three short rotation forestry crops (poplar, willow and black locust) have been determined and compared in order to evaluate their suitability (energy potential and combustion-related operation problems) to be used in energy devices. The planting density was [...] Read more.

The physical and thermochemical properties of three short rotation forestry crops (poplar, willow and black locust) have been determined and compared in order to evaluate their suitability (energy potential and combustion-related operation problems) to be used in energy devices. The planting density was 6666 in a rotation of four years and the analysis were performed at the end of the first rotation. The three species showed significant differences regarding production, moisture and ash content, heating value and bulk density. The results obtained allow to establish priorities between species according to the expectable combustion behavior, willow being the most appropriate. Results indicate no problems related to SO_x and NO_x emissions. Moreover, the alkali metals determined in the fuel together with the chlorine content suggest no operation problems related with fouling or harmful corrosion. Full article

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

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12 pages, 4680 KiB

Open AccessArticle

Low-Cost Solar Irradiance Sensing for PV Systems

by Miguel Carrasco¹, Antonino Laudani²

, Gabriele Maria Lozito^2,*, Fernando Mancilla-David¹, Francesco Riganti Fulginei²

and Alessandro Salvini²

¹ Department of Electrical Engineering, University of Colorado Denver, Denver, CO 80217, USA

² Department of Engineering, Università degli Studi Roma Tre, 00149 Roma, Italy

Energies 2017, 10(7), 998; https://doi.org/10.3390/en10070998 - 14 Jul 2017

Cited by 35 | Viewed by 6447

Abstract

Determination of solar irradiance is a critical asset to ensure efficient working conditions for a photovoltaic (PV) system. This work analyze the feasibility of assessing solar irradiance on a PV device assuming the knowledge of the device temperature and the voltage/current operating point. [...] Read more.

Determination of solar irradiance is a critical asset to ensure efficient working conditions for a photovoltaic (PV) system. This work analyze the feasibility of assessing solar irradiance on a PV device assuming the knowledge of the device temperature and the voltage/current operating point. This work proposes an approach based on a manipulation of the analytic expressions found in the reduced form of the “single diode” circuit model for a silicon PV device. The approach was validated through different practical experiments, and the results obtained are comparable to the ones of a commercial instrument for irradiance sensing. The ease of construction and the reduced costs involved make a device based on the proposed approach suitable for large-scale integration in a PV plant. 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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19 pages, 1463 KiB

Open AccessArticle

Using a Multiobjective Approach to Compare Multiple Design Alternatives—An Application to Battery Dynamic Model Tuning

by Alberto Pajares^*

, Xavier Blasco

, Juan Manuel Herrero

and Raúl Simarro

Instituto Universitario de Automática e Informática Industrial (ai2), Universitat Politècnica de València, Camí de Vera s/n, 46022 València, Spain

Energies 2017, 10(7), 999; https://doi.org/10.3390/en10070999 - 14 Jul 2017

Cited by 2 | Viewed by 2900

Abstract

A design problem is usually solvable in different ways or by design alternatives. In this work, the term “concept” is used to refer to the design alternatives. Additionally, it is quite common that a design problem has to satisfy conflicting objectives. In these [...] Read more.

A design problem is usually solvable in different ways or by design alternatives. In this work, the term “concept” is used to refer to the design alternatives. Additionally, it is quite common that a design problem has to satisfy conflicting objectives. In these cases, the design problem can be formulated as a multiobjective optimization problem (MOP). One of the aims of this work was to show how to combine multiobjective requirements with concepts’ comparisons, in order to attain a satisfactory design. The second aim of this work was to take advantage of this methodology to obtain a battery model that described the dynamic behavior of the main electrical variables. Two objectives related to the model accuracy during the charge and discharge processes were used. In the final model selection, three different concepts were compared. These concepts differed in the complexity of their model structure. More complex models usually provide a good approximation of the process when identification data are used, but the approximation could be worse when validation data are applied. In this article, it is shown that a model with an intermediate complexity supplies a good approximation for both identification and validation data sets. Full article

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16 pages, 9519 KiB

Open AccessArticle

A Phase-Shifted Control for Wireless Power Transfer System by Using Dual Excitation Units

by Xin Dai^1,*

, Jincheng Jiang¹, Yanling Li¹ and Ting Yang²

¹ School of Automation, Chongqing University, 174 Shazheng Street, Shapingba District, Chongqing 400030, China

² No. 24 Research Institute of CETC, Nanping Huayuan Road No. 14, Nan’an District, Chongqing 400060, China

Energies 2017, 10(7), 1000; https://doi.org/10.3390/en10071000 - 14 Jul 2017

Cited by 13 | Viewed by 5699

Abstract

Wireless power transfer (WPT) technology can provide intelligent robots with a flexible, robust, and safe power supply, especially in very harsh environments including high humidity and high temperature. To meet increasing power requirement for robotic applications, this paper proposes a novel method to [...] Read more.

Wireless power transfer (WPT) technology can provide intelligent robots with a flexible, robust, and safe power supply, especially in very harsh environments including high humidity and high temperature. To meet increasing power requirement for robotic applications, this paper proposes a novel method to increase system power transfer capability without increasing voltage and current stress, realized by using dual excitation units at the primary side. On this basis, this paper proposes a phase-shifted control method for output power regulation which can keep efficiency high. At the same time, the system is proved to have a better output robust characteristic by analysis under the condition of parameter variation. Finally, experimental results show the proposed dual excitation units (DEU)-WPT system can increase output power by at least three times compared to classical WPT system, and the efficiency is improved by 9%. Full article

(This article belongs to the Special Issue Advanced Electric Devices and Technologies for Electric-Drive Robotics)

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18 pages, 56310 KiB

Open AccessArticle

Investigation of Processes of Interaction between Hydraulic and Natural Fractures by PFC Modeling Comparing against Laboratory Experiments and Analytical Models

by Jian Zhou¹

, Luqing Zhang^1,*, Anika Braun¹ and Zhenhua Han^1,2

¹ Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China

² College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China

Energies 2017, 10(7), 1001; https://doi.org/10.3390/en10071001 - 14 Jul 2017

Cited by 41 | Viewed by 5991

Abstract

Hydraulic fracturing technology is usually used to stimulate tight gas reservoirs for increasing gas production. The stimulated volume depends in part on the pre-existing natural fractures in a reservoir. The mechanisms influencing the interaction between hydraulic fractures and natural fractures have to be [...] Read more.

Hydraulic fracturing technology is usually used to stimulate tight gas reservoirs for increasing gas production. The stimulated volume depends in part on the pre-existing natural fractures in a reservoir. The mechanisms influencing the interaction between hydraulic fractures and natural fractures have to be well understood in order to achieve a successful application of hydraulic fracturing. In this paper, hydraulic fracturing simulations were performed based on a two-dimensional Particle Flow Code with an embedded Smooth Joint Model to investigate the interactions between hydraulic fractures and natural fractures and compare these against laboratory experimental results and analytical models. Firstly, the ability of the Smooth Joint Model to mimic the natural rock joints was validated. Secondly, the interactions between generated hydraulic fractures and natural fractures were simulated. Lastly, the influence of angle of approach, in situ differential stress, and the permeability of natural fractures was studied. It is found that the model is capable of simulating the variety of interactions between hydraulic fractures and natural fractures such as Crossed type, Arrested type and Dilated type, and the modeling examples agree well with the experimental results. Under high approach angles and high differential stresses, the hydraulic fractures tend to cross pre-existing natural fractures. Under contrary conditions, a hydraulic fracture is more likely to propagate along the natural fracture and re-initiate at a weak point or the tip of the natural fracture. Moreover, these numerical results are in good agreement compared with Blanton’s criterion. The variety of permeability of natural fractures has a great effect on their interactions, which should not be overlooked in hydraulic fracturing studies. Full article

(This article belongs to the Special Issue Oil and Gas Engineering)

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24 pages, 13395 KiB

Open AccessArticle

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part II: The Electrical System

by Markel Penalba^1,*, José-Antonio Cortajarena²

and John V. Ringwood¹

¹ Centre for Ocean Energy Research, Maynooth University, Maynooth, Ireland

² Engineering School of Eibar, University of the Basque Country, 20600 Eibar, Spain

Energies 2017, 10(7), 1002; https://doi.org/10.3390/en10071002 - 14 Jul 2017

Cited by 29 | Viewed by 6195

Abstract

The incorporation of the full dynamics of the different conversion stages of wave energy converters (WECs), from ocean waves to the electricity grid, is essential for a realistic evaluation of the power flow in the drive train. WECs with different power take-off (PTO) [...] Read more.

The incorporation of the full dynamics of the different conversion stages of wave energy converters (WECs), from ocean waves to the electricity grid, is essential for a realistic evaluation of the power flow in the drive train. WECs with different power take-off (PTO) systems, including diverse transmission mechanisms, have been developed in recent decades. However, all the different PTO systems for electricity-producing WECs, regardless of any intermediate transmission mechanism, include an electric generator, linear or rotational. Therefore, accurately modelling the dynamics of electric generators is crucial for all wave-to-wire (W2W) models. This paper presents the models for three popular rotational electric generators (squirrel cage induction machine, permanent magnet synchronous generator and doubly-fed induction generator) and a back-to-back (B2B) power converter and validates such models against experimental data generated using three real electric machines. The input signals for the validation of the mathematical models are designed so that the whole operation range of the electrical generators is covered, including input signals generated using the W2W model that mimic the behaviour of different hydraulic PTO systems. Results demonstrate the effectiveness of the models in accurately reproducing the characteristics of the three electrical machines, including power losses in the different machines and the B2B converter. Full article

(This article belongs to the Special Issue Marine Energy)

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25 pages, 13480 KiB

Open AccessArticle

Prediction in Photovoltaic Power by Neural Networks

by Antonello Rosato¹, Rosa Altilio¹, Rodolfo Araneo²

and Massimo Panella^1,*

¹ Department of Information Engineering, Electronics and Telecommunications, University of Rome “La Sapienza”, via Eudossiana, 18, Rome 00184, Italy

² Electrical Engineering Division of Department of Astronautical, Electrical and Energy Engineering, University of Rome “La Sapienza”, via Eudossiana, 18, Rome 00184, Italy

Energies 2017, 10(7), 1003; https://doi.org/10.3390/en10071003 - 15 Jul 2017

Cited by 54 | Viewed by 4868

Abstract

The ability to forecast the power produced by renewable energy plants in the short and middle term is a key issue to allow a high-level penetration of the distributed generation into the grid infrastructure. Forecasting energy production is mandatory for dispatching and distribution [...] Read more.

The ability to forecast the power produced by renewable energy plants in the short and middle term is a key issue to allow a high-level penetration of the distributed generation into the grid infrastructure. Forecasting energy production is mandatory for dispatching and distribution issues, at the transmission system operator level, as well as the electrical distributor and power system operator levels. In this paper, we present three techniques based on neural and fuzzy neural networks, namely the radial basis function, the adaptive neuro-fuzzy inference system and the higher-order neuro-fuzzy inference system, which are well suited to predict data sequences stemming from real-world applications. The preliminary results concerning the prediction of the power generated by a large-scale photovoltaic plant in Italy confirm the reliability and accuracy of the proposed approaches. 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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16 pages, 3649 KiB

Open AccessArticle

New Adaptive Reclosing Technique in Unbalanced Distribution System

by Hun-Chul Seo

School of IT Engineering, Yonam Institute of Technology, Jinju 52821, Korea

Energies 2017, 10(7), 1004; https://doi.org/10.3390/en10071004 - 15 Jul 2017

Cited by 8 | Viewed by 4037

Abstract

The conventional reclosing of a distribution system is performed after a fixed dead time. However, it may lead to the increased outage time due to delayed reclosing. To solve this problem, this paper proposes a new adaptive reclosing scheme. The electrostatic induction is [...] Read more.

The conventional reclosing of a distribution system is performed after a fixed dead time. However, it may lead to the increased outage time due to delayed reclosing. To solve this problem, this paper proposes a new adaptive reclosing scheme. The electrostatic induction is analyzed under at during-fault and post-fault conditions. Based on this analysis, the method to judge the fault clearance using the load current is proposed. The reclosing is adaptively performed after fault clearance. The distribution system and reclosing scheme are modelled by the electromagnetic transient program (EMTP). The various simulations according to the unbalanced ratio and various fault conditions are performed and analyzed. The superiority of the proposed scheme is verified by comparing with the conventional reclosing method. Full article

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

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18 pages, 8605 KiB

Open AccessArticle

Numerical Modelling of Mechanical Behavior of Coal Mining Hard Roofs in Different Backfill Ratios: A Case Study

by Meng Li, Nan Zhou^*, Jixiong Zhang and Zhicheng Liu

Key Laboratory of Deep Coal Resources Mining, School of Mines, Ministry of Education of China, China University of Mining & Technology, Xuzhou 221116, China

Energies 2017, 10(7), 1005; https://doi.org/10.3390/en10071005 - 15 Jul 2017

Cited by 16 | Viewed by 4131

Abstract

In coal mining hard roofs are one of the main factors causing the occurrence of rock bursts in working panels. To solve this problem, the solid backfill coal mining (SBCM) technique is proposed and used as an effective measure to prevent the rock [...] Read more.

In coal mining hard roofs are one of the main factors causing the occurrence of rock bursts in working panels. To solve this problem, the solid backfill coal mining (SBCM) technique is proposed and used as an effective measure to prevent the rock bursts induced by hard roofs. However, due to the different backfill ratios of working planes, the control effects on hard roofs are quite unique. By using a numerical simulation, this study simulates the deformation of hard roofs and distributions of stress and strain energies in different roof-control backfill ratios, so as to reveal the control mechanisms of SBCM on hard roofs. The results show that, when the roof-controlled backfill ratio are 0, 40% and 60%, the ratio exerts no influence on the distributions of advanced abutment stress and strain energies. While for roof-control backfill ratios of 82.5%, 91% and 93%, the advanced abutment stress and strain energies decrease significantly, but the increment of the ratio exerts little influence on the decrease. When the roof-control backfill ratio reaches 97%, the advanced abutment stress and strain energies again decrease. In this context, the stress concentration factor is only 1.5 and the peak strain energy is 544 kJ/m³, the stress concentration factor and peak strain energy decrease by 45.7% and 63.9%, respectively, compared with the caving method. As the roof-controlled backfill ratio rises, backfill materials tend to support hard roofs, thus significantly preventing dynamic hazards. Full article

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11 pages, 1705 KiB

Open AccessArticle

Transverse Thermoelectricity in Fibrous Composite Materials

by Bosen Qian and Fei Ren^*

Department of Mechanical Engineering, Temple University, Philadelphia, PA 19122, USA

Energies 2017, 10(7), 1006; https://doi.org/10.3390/en10071006 - 16 Jul 2017

Cited by 7 | Viewed by 4512

Abstract

Transverse thermoelectric elements have the potential to decouple the electric current and the heat flow, which could lead to new designs of thermoelectric devices. While many theoretical and experimental studies of transverse thermoelectricity have focused on layered structures, this work examines composite materials [...] Read more.

Transverse thermoelectric elements have the potential to decouple the electric current and the heat flow, which could lead to new designs of thermoelectric devices. While many theoretical and experimental studies of transverse thermoelectricity have focused on layered structures, this work examines composite materials with aligned fibrous inclusions. A simplified mathematical model was derived based on the Kirchhoff Circuit Laws (KCL), which were used to calculate the equivalent transport properties of the composite structures. These equivalent properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, compared well with finite element analysis (FEA) results. Peltier cooling performance was also examined using FEA, which exhibited good agreement to KCL model predictions. In addition, a survey was conducted on selected combinations of thermoelectric materials and metals to rank their transverse thermoelectricity with respect to the dimensionless figure of merit. Full article

(This article belongs to the Special Issue Thermoelectric Materials for Energy Conversion)

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14 pages, 1442 KiB

Open AccessEditor’s ChoiceArticle

An Open-Access Web-Based Tool to Access Global, Hourly Wind and Solar PV Generation Time-Series Derived from the MERRA Reanalysis Dataset

by Madeleine McPherson^1,*

, Theofilos Sotiropoulos-Michalakakos¹

, LD Danny Harvey² and Bryan Karney¹

¹ Department of Civil Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada

² Department of Geography, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3, Canada

Energies 2017, 10(7), 1007; https://doi.org/10.3390/en10071007 - 16 Jul 2017

Cited by 21 | Viewed by 6944

Abstract

Wind and solar energy resources are an increasingly large fraction of generation in global electricity systems. However, the variability of these resources necessitates new datasets and tools for understanding their economics and integration in electricity systems. To enable such analyses and more, we [...] Read more.

Wind and solar energy resources are an increasingly large fraction of generation in global electricity systems. However, the variability of these resources necessitates new datasets and tools for understanding their economics and integration in electricity systems. To enable such analyses and more, we have developed a free web-based tool (Global Renewable Energy Atlas & Time-series, or GRETA) that produces hourly wind and solar photovoltaic (PV) generation time series for any location on the globe. To do so, this tool applies the Boland–Ridley–Laurent and Perez models to NASA’s (National Aeronautics and Space Administration) Modern-Era Retrospective Analysis for Research and Applications (MERRA) solar irradiance reanalysis dataset, and the Archer and Jacobson model to the MERRA wind reanalysis dataset to produce resource and power data, for a given technology’s power curve. This paper reviews solar and wind resource datasets and models, describes the employed algorithms, and introduces the web-based tool. Full article

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16 pages, 2866 KiB

Open AccessArticle

Efficient Model Predictive Control Strategies for Resource Management in an Islanded Microgrid

by Seaseung Oh^1,*, Suyong Chae¹, Jason Neely²

, Jongbok Baek¹ and Marvin Cook²

¹ Energy Efficiency Research Division, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 34129, Korea

² Sandia National Laboratories, Albuquerque, NM 87185, USA

Energies 2017, 10(7), 1008; https://doi.org/10.3390/en10071008 - 16 Jul 2017

Cited by 25 | Viewed by 4632

Abstract

The energy research community is continuously pursuing improvements in power system resiliency and reliability. Microgrids offer a unique opportunity for enhanced reliability and resiliency by utilizing localized generation and energy storage when grid power is unavailable or too expensive. Energy management is a [...] Read more.

The energy research community is continuously pursuing improvements in power system resiliency and reliability. Microgrids offer a unique opportunity for enhanced reliability and resiliency by utilizing localized generation and energy storage when grid power is unavailable or too expensive. Energy management is a critical aspect of these systems to ensure proper balancing of sources and ensuring power supply to critical loads with minimum cost, especially in an islanded microgrid. This paper presents a hierarchical real-time optimization with mathematical formulations to achieve optimal operation for an islanded microgrid. The optimization is implemented using simple numerically tractable model predictive control strategies and enables appropriate decisions in response to constantly changing conditions. The optimization method is extended for experimentation within the real-time simulation. Simulation results show that the proposed resource management algorithm shows near-optimal performance while effectively dealing with uncertainties in forecasting. Full article

(This article belongs to the Special Issue Advanced Operation and Control of Smart Microgrids)

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11 pages, 6630 KiB

Open AccessArticle

Geothermal Resource Exploration by Stream pH Mapping in Mutsu Hiuchi Dake Volcano, Japan

by Yota Suzuki^1,*, Seiichiro Ioka² and Hirofumi Muraoka²

¹ Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan

² North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813, Japan

Energies 2017, 10(7), 1009; https://doi.org/10.3390/en10071009 - 16 Jul 2017

Cited by 4 | Viewed by 4737

Abstract

Although pH measurements of hot spring water are taken in conventional geothermal resource research, previous studies have seldom created pH distribution maps of stream and spring waters for an entire geothermal field as a technique for geothermal exploration. In this study, a pH [...] Read more.

Although pH measurements of hot spring water are taken in conventional geothermal resource research, previous studies have seldom created pH distribution maps of stream and spring waters for an entire geothermal field as a technique for geothermal exploration. In this study, a pH distribution map was created by measuring stream and spring water pH at 75 sites in the Mutsu Hiuchi Dake geothermal field, Japan. Areas of abnormally high pH were detected in midstream sections of the Ohaka and Koaka rivers; these matched the location of the Mutsu Hiuchi Dake East Slope Fault, which is believed to have formed a geothermal reservoir. The abnormally high pH zone is attributed to the trapping of rising volcanic gases in a mature geothermal reservoir with neutral geothermal water. This causes the gas to dissolve and prevents it from reaching the surface. Thus, the mapping of stream water pH distribution in a geothermal field could provide a new and effective method for estimating the locations of geothermal reservoirs. As the proposed method does not require laboratory analysis, and is more temporally and economically efficient than conventional methods, it might help to promote geothermal development in inaccessible and remote regions. Full article

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5 pages, 669 KiB

Open AccessEditorial

Control of Energy Storage

by Timur Yunusov^1,*

, Maximilian J. Zangs¹

and William Holderbaum²

¹ Technologies for Sustainable Built Environments Centre, School of Built Environment,University of Reading, Reading RG6 6AF, UK

² School of Engineering, Manchester Metropolitan University, Manchester M1 5GD, UK

Energies 2017, 10(7), 1010; https://doi.org/10.3390/en10071010 - 16 Jul 2017

Cited by 2 | Viewed by 4156

Abstract

In the attempt to tackle the issue of climate change, governments across the world have agreed to set global carbon reduction targets. [...] Full article

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

15 pages, 5535 KiB

Open AccessArticle

A Novel Layered Bidirectional Equalizer Based on a Buck-Boost Converter for Series-Connected Battery Strings

by Shubiao Wang^1,3, Longyun Kang^1,3,*, Xiangwei Guo², Zefeng Wang^1,3 and Ming Liu^1,3

¹ New Energy Research Center, School of Electric Power, South China University of Technology, Guangzhou 510640, China

² College of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454000, China

³ Guangdong Key Laboratory of Clean Energy Technology, School of Electric Power, South China University of Technology, Guangzhou 510640, China

Energies 2017, 10(7), 1011; https://doi.org/10.3390/en10071011 - 17 Jul 2017

Cited by 35 | Viewed by 6047

Abstract

To eliminate the influence of the inconsistency on the cycle life and the available capacity of battery packs, and improve the balancing speed, a novel inductor-based layered bidirectional equalizer (IBLBE) is proposed. The equalizer is composed of two layers of balancing circuits connected [...] Read more.

To eliminate the influence of the inconsistency on the cycle life and the available capacity of battery packs, and improve the balancing speed, a novel inductor-based layered bidirectional equalizer (IBLBE) is proposed. The equalizer is composed of two layers of balancing circuits connected in parallel. Each layer contains multiple balancing sub-circuits based on buck-boost converters. These balancing sub-circuits can equalize the corresponding cells simultaneously, and allow the dynamic adjustment of equalization path and equalization threshold. Analysis and simulation results demonstrate the IBLBE has a higher level balancing speed than other equalizers based on switched-capacitor or switched-inductor converters, and reduces the balancing time by 30% compared to existing inductor-based parallel architecture equalizers (PAEs). Experimental results are presented to validate the analysis and effectiveness of the proposed equalizer. Full article

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26 pages, 1353 KiB

Open AccessArticle

Performance Predictions of Dry and Wet Vapors Ejectors Over Entire Operational Range

by Fenglei Li¹, Zhao Chang¹, Qi Tian^1,*, Changzhi Wu² and Xiangyu Wang²

¹ College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China

² Australasian Joint Research Centre for Building Information Modelling, School of Built Environment, Curtin University, Perth, WA 6845, Australia

Energies 2017, 10(7), 1012; https://doi.org/10.3390/en10071012 - 17 Jul 2017

Cited by 9 | Viewed by 3857

Abstract

If a traditional ideal-gas ejector model is used to evaluate the performance of a wet vapor ejector, large deviations from the experimental results will be unavoidable. Moreover, the model usually fails to assess the ejector performance at subcritical mode. In this paper, we [...] Read more.

If a traditional ideal-gas ejector model is used to evaluate the performance of a wet vapor ejector, large deviations from the experimental results will be unavoidable. Moreover, the model usually fails to assess the ejector performance at subcritical mode. In this paper, we proposed a novel model to evaluate the performance of both dry and wet vapors ejectors over the entire operational range at critical or subcritical modes. The model was obtained by integrating the linear characteristic equations of ejector with critical and breakdown points models, which were developed based on the assumptions of constant-pressure mixing and constant-pressure disturbing. In the models, the equations of the two-phase speed of sound and the property of real gas were introduced and ejector component efficiencies were optimized to improve the accuracy of evaluation. It was validated that the proposed model for the entire operational range can achieve a better performance than those existing for R134a, R141b and R245fa. The critical and breakdown points models were further used to investigate the effect of operational parameters on the performance of an ejector refrigeration system (ERS). The theoretical results indicated that decreasing the saturated generating temperature when the actual condensing temperature decreases, and/or increasing the saturated evaporating temperature can improve the performance of ERS significantly. Moreover, superheating the primary flow before it enters the ejector can further improve the performance of an ERS using R134a as a working fluid. Full article

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14 pages, 2397 KiB

Open AccessArticle

Optimal Power Flow Using Particle Swarm Optimization of Renewable Hybrid Distributed Generation

by Usama Khaled^1,2,*

, Ali M. Eltamaly^3,4 and Abderrahmane Beroual⁵

¹ Electrical Engineering Department, College of Engineering, King Saud University, P.O. Box. 800, Riyadh 11421, Saudi Arabia

² Electrical Engineering Department, Faculty of Energy Engineering, Aswan University, Aswan Governorate 81528, Egypt

³ Electrical Engineering Department, Mansoura University, Mansoura 35516, Egypt

⁴ Sustainable Energy Technology Center, King Saud University, Riyadh 11421, Saudi Arabia

⁵ Ecole Centrale de Lyon, University of Lyon, Ampere CNRS UMR 5005, 36 avenue Guy Collongue, Ecully 69134, France

Energies 2017, 10(7), 1013; https://doi.org/10.3390/en10071013 - 17 Jul 2017

Cited by 70 | Viewed by 7054

Abstract

The problem of voltage collapse in power systems due to increased loads can be solved by adding renewable energy sources like wind and photovoltaic (PV) to some bus-bars. This option can reduce the cost of the generated energy and increase the system efficiency [...] Read more.

The problem of voltage collapse in power systems due to increased loads can be solved by adding renewable energy sources like wind and photovoltaic (PV) to some bus-bars. This option can reduce the cost of the generated energy and increase the system efficiency and reliability. In this paper, a modified smart technique using particle swarm optimization (PSO) has been introduced to select the hourly optimal load flow with renewable distributed generation (DG) integration under different operating conditions in the 30-bus IEEE system. Solar PV and wind power plants have been introduced to selected buses to evaluate theirs benefits as DG. Different solar radiation and wind speeds for the Dammam site in Saudi Arabia have been used as an example to study the feasibility of renewable energy integration and its effect on power system operation. Sensitivity analysis to the load and the other input data has been carried out to predict the sensitivity of the results to any deviation in the input data of the system. The obtained results from the proposed system prove that using of renewable energy sources as a DG reduces the generation and operation cost of the overall power system. Full article

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

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12 pages, 2311 KiB

Open AccessCommunication

Proposal for an Experimental Methodology for Evaluation of Natural Lighting Systems Applied in Buildings

by Anderson Diogo Spacek¹, João Mota Neto¹, Luciano Dagostin Biléssimo¹, Oswaldo Hideo Ando Junior^2,*

, Gustavo Pedro De Freitas Neto¹, Rodrigo Da Silva Giansella¹, Marcus Vinícius Ferreira De Santana³ and Celia De Fraga Malfatti⁴

¹ Department of Mechanic and Automation, SATC, Beneficent Association of Santa Catarina Coal Industry, Street Pascoal Meller, 73, Criciúma-SC CEP 88805-380, Brazil

² Department of Renewable Energies, UNILA, Federal University of Latin American Integration, Av. Sílvio Américo Sasdelli, 1842, Foz do Iguaçu-PR CEP 85866-000, Brazil

³ Hidroelectric Power Plant, BAESA, Energética Barra Grande S/A, Street Madre Benvenuta, 1168, Florianópolis-SC CEP 88035-000, Brazil

⁴ Corrosion Research Department, Federal University of Rio Grande do Sul, Avenue Bento Gonçalves, 9500, Porto Alegre-RS CEP 91501-970, Brazil

Energies 2017, 10(7), 1014; https://doi.org/10.3390/en10071014 - 17 Jul 2017

Cited by 9 | Viewed by 4556

Abstract

This work has the objective of developing a methodology for the evaluation of indoor natural lighting systems, which, with speed and practicality, provides from real conditions of use a reliable result about the quality and performance of the proposed system. The methodology is [...] Read more.

This work has the objective of developing a methodology for the evaluation of indoor natural lighting systems, which, with speed and practicality, provides from real conditions of use a reliable result about the quality and performance of the proposed system. The methodology is based on the construction of two real-size test environments, which will be subjected to a natural light system through reflexive tubes made from recycled material, and to a commercial system already certified and consolidated, creating the possibility of comparison. Furthermore, the data acquired in the test environments will be examined in light of the values of solar radiation obtained from a digital meteorological station, such that it is possible to stipulate the lighting capacity of the systems at different times of the year. Full article

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

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18 pages, 5274 KiB

Open AccessArticle

Finite Element Computation of Transient Parameters of a Salient-Pole Synchronous Machine

by Yang Xiao

, Libing Zhou, Jin Wang^* and Rui Yang

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

Energies 2017, 10(7), 1015; https://doi.org/10.3390/en10071015 - 17 Jul 2017

Cited by 8 | Viewed by 4414

Abstract

This paper presents a novel method for calculating the transient parameters of a saturated salient-pole synchronous machine (SPSM) with damper cage using finite element analysis. All detailed leakage inductances in a modified d-q model are discussed and separately extracted. In addition; the frozen [...] Read more.

This paper presents a novel method for calculating the transient parameters of a saturated salient-pole synchronous machine (SPSM) with damper cage using finite element analysis. All detailed leakage inductances in a modified d-q model are discussed and separately extracted. In addition; the frozen permeability method is used in a 2-D finite element analysis to consider saturation and skin effects for determining the inductances. The terminal reactance parameters are obtained from all elements of the d- and q-axis equivalent circuits in all the chosen time constants during the transient process. The variation of leakage inductances of the SPSM in transient processes is also investigated and discussed. To determine transient time constant parameters; the Prony algorithm is applied in the presented method. A program developed to automatically solve the simulation and computation with the proposed method is described. This method is applied to a prototype and validated by experimental results. Some discussion about the relationship between rotor geometric design and the transient parameters of SPSMs is provided. The variation of leakage magnetic field of SPSMs in transient processes is also investigated. This method can be applied in transient parameter estimation and optimization of SPSMs in the design stage. Full article

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

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26 pages, 2344 KiB

Open AccessArticle

Multi-Objective Optimization of Building Energy Design to Reconcile Collective and Private Perspectives: CO₂-eq vs. Discounted Payback Time

by Mohamed Hamdy^1,2,*

and Gerardo Maria Mauro³

¹ Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, Byggteknisk, 2-236, Gløshaugen, Høgskoleringen 7A, Trondheim 7491, Norway

² Department of Mechanical Power Engineering, Helwan University, Cairo 11790, Egypt

³ Department of Industrial Engineering, Università degli studi di Napoli Federico II, Piazzale Tecchio 80, Naples 80125, Italy

Energies 2017, 10(7), 1016; https://doi.org/10.3390/en10071016 - 18 Jul 2017

Cited by 27 | Viewed by 5259

Abstract

Building energy design is a multi-objective optimization problem where collective and private perspectives conflict each other. For instance, whereas the collectivity pursues the minimization of environmental impact, the private pursues the maximization of financial viability. Solving such trade-off design problems usually involves a [...] Read more.

Building energy design is a multi-objective optimization problem where collective and private perspectives conflict each other. For instance, whereas the collectivity pursues the minimization of environmental impact, the private pursues the maximization of financial viability. Solving such trade-off design problems usually involves a big computational cost for exploring a huge solution domain including a large number of design options. To reduce that computational cost, a bi-objective simulation-based optimization algorithm, developed in a previous study, is applied in the present investigation. The algorithm is implemented for minimizing the CO₂-eq emissions and the discounted payback time (DPB) of a single-family house in cold climate, where 13,456 design solutions including building envelope and heating system options are explored and compared to a predefined reference case. The whole building life is considered by assuming a calculation period of 30 years. The results show that the type of heating system significantly affects energy performance; notably, the ground source heat pump leads to the highest reduction in CO₂-eq emissions, around 1300 kgCO₂-eq/m², with 17 year DPB; the oil fire boiler can provide the lowest DPB, equal to 8.5 years, with 850 kgCO₂-eq/m² reduction. In addition, it is shown that using too high levels of thermal insulation is not an effective solution as it causes unacceptable levels of summertime overheating. Finally a multi-objective decision making approach is proposed in order to enable the stakeholders to choice among the optimal solutions according to the weight given to each objective, and thus to each perspective. Full article

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

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16 pages, 2649 KiB

Open AccessArticle

Distributed Coordination Control Strategy for a Multi-Microgrid Based on a Consensus Algorithm

by Sang-Ji Lee¹, Jin-Young Choi², Hyung-Joo Lee³ and Dong-Jun Won^3,*

¹ Central Area Branch Office, KPX, 32, Yongam 6-gil, Buk-myeon, Dongnam-gu, Cheonan-si, Chungcheongnam-do 31242, Korea

² LG CNS, 28F, FKI Tower, 24, Yeoui-daero, Yeongdeungpo-gu, Seoul 07320, Korea

³ Department of Electrical Engineering, Inha University, 100, Inha-ro, Nam-gu, Incheon 22212, Korea

Energies 2017, 10(7), 1017; https://doi.org/10.3390/en10071017 - 18 Jul 2017

Cited by 22 | Viewed by 3927

Abstract

Microgrids (MGs) in which power generation and consumption occur locally have gained prominence, and MG demonstration tests have been widely carried out. In accordance with the increase in the number of MG installations, studies regarding the cooperative control of multiple MGs are proceeding [...] Read more.

Microgrids (MGs) in which power generation and consumption occur locally have gained prominence, and MG demonstration tests have been widely carried out. In accordance with the increase in the number of MG installations, studies regarding the cooperative control of multiple MGs are proceeding in various forms. In this paper, the distributed control strategy of a multi-microgrid (MMG) is proposed. Distributed control is the method in which agents of the electric power facility autonomously control their facility through communication with the neighboring agents only. In this process, a consensus algorithm is utilized to obtain the global information required to control the overall system. In this distributed control strategy, a single MG is operated at an optimal economic point using the equality incremental cost constraints while maintaining the balance between the generation and demand. The control strategy of a MMG is that the flow of the point of common coupling (PCC) is maintained at a particular value needed by the utility and the internal change in power is distributed to the MGs according to their reserves. The proposed algorithm is verified in the MG level and the MMG level through a simulation model using PSCAD/EMTDC software in the C language. Full article

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13 pages, 2748 KiB

Open AccessArticle

Matching Relationship and Alternating Injection for Polymer Flooding in Heterogeneous Formations: A Laboratory Case Study of Daqing Oilfield

by Songyuan Liu¹, Anqi Shen^2,*

, Feng Qiu³, Shuang Liang² and Fengjiao Wang²

¹ Department of Petroleum Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

² College of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China

³ SINOPEC Research Institute of Safety Engineering, Qingdao 266000, China

Energies 2017, 10(7), 1018; https://doi.org/10.3390/en10071018 - 18 Jul 2017

Cited by 6 | Viewed by 4542

Abstract

A series of experiments were carried out to study the relationship between polymer and reservoir permeability, as well as the alternating injection pattern for heterogeneous formations. The polymer molecular size (MS) was studied using dynamic light scattering. The parameters such as hydraulic radius, [...] Read more.

A series of experiments were carried out to study the relationship between polymer and reservoir permeability, as well as the alternating injection pattern for heterogeneous formations. The polymer molecular size (MS) was studied using dynamic light scattering. The parameters such as hydraulic radius, molecular weight (MW), concentrations and salinity were studied. The injection capacity and the relationship between polymer and formation were obtained using injection experiments with natural cores, which represent different regions in the Daqing oilfield. Moreover, an improved injection pattern, alternating injection in heterogeneous formation was studied based on the injection experiments of parallel and in-layer heterogeneous artificial cores. The alternate cycle and slug size were investigated. It was proven that the alternating injection can improve the efficiency of low permeability layers up to 7.3% and a mean value of 4.27%. It was also found that the mechanism of alternating injection is blocking the high permeability layers and improving the water injection profile. We suggest that other fields with high heterogeneity could try the alternating injection to optimize the polymer flooding. Meanwhile, further pilot tests or numerical simulation of polymer alternating injection in heterogeneous formation (formation type II) should be conducted. Full article

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

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22 pages, 21424 KiB

Open AccessArticle

Comparison of Various Analysis Methods Based on Heat Flowmeters and Infrared Thermography Measurements for the Evaluation of the In Situ Thermal Transmittance of Opaque Exterior Walls

by Doo Sung Choi¹ and Myeong Jin Ko^2,*

¹ Department of Building Equipment & Fire Protection System, Chungwoon University, Incheon 22100, Korea

² Nabi Building Environment & Equipment Design Consultant Co., Ltd, Seoul 06226, Korea

Energies 2017, 10(7), 1019; https://doi.org/10.3390/en10071019 - 18 Jul 2017

Cited by 34 | Viewed by 4231

Abstract

There are several methods to obtain the in situ thermal transmittance value (U-value) of building envelopes from on-site data, including the three approaches of the progressive average method, average method considering the thermal storage effect, and dynamic method for deriving the U-value from [...] Read more.

There are several methods to obtain the in situ thermal transmittance value (U-value) of building envelopes from on-site data, including the three approaches of the progressive average method, average method considering the thermal storage effect, and dynamic method for deriving the U-value from heat flowmeter (HFM) measurements and the four methods with different formulas to analyze infrared thermography (IRT) measurement data. Since each of these methods considers different parameters and the non-steady characteristics of the heat transfer in building walls in their own way, discrepancies may occur among the obtained results. This study evaluates and compares the in situ U-values by using various methods of analyzing HFM and IRT measurement data. Further, by investigating buildings with similar materials and identical stratigraphies, but with different construction years, we analyze the discrepancy between the designed and measured values caused by material deterioration and evaluate the errors according to the analysis method. The percentage deviation between the U-values obtained by the three methods from the HFM data is found to be satisfactory, being within 10%. When compared with the results of the progressive average method, the deviations for the four different IRT-measurement-based methods vary greatly, being in the range of 6–43%. Full article

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

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31 pages, 3582 KiB

Open AccessArticle

Thermodynamic Analysis of Three Compressed Air Energy Storage Systems: Conventional, Adiabatic, and Hydrogen-Fueled

by Hossein Safaei and Michael J. Aziz^*

Harvard John A. Paulson School of Engineering and Applied Sciences, Pierce Hall, 29 Oxford Street, Cambridge, MA 02138, USA

Energies 2017, 10(7), 1020; https://doi.org/10.3390/en10071020 - 18 Jul 2017

Cited by 30 | Viewed by 6717

Abstract

We present analyses of three families of compressed air energy storage (CAES) systems: conventional CAES, in which the heat released during air compression is not stored and natural gas is combusted to provide heat during discharge; adiabatic CAES, in which the compression heat [...] Read more.

We present analyses of three families of compressed air energy storage (CAES) systems: conventional CAES, in which the heat released during air compression is not stored and natural gas is combusted to provide heat during discharge; adiabatic CAES, in which the compression heat is stored; and CAES in which the compression heat is used to assist water electrolysis for hydrogen storage. The latter two methods involve no fossil fuel combustion. We modeled both a low-temperature and a high-temperature electrolysis process for hydrogen production. Adiabatic CAES (A-CAES) with physical storage of heat is the most efficient option with an exergy efficiency of 69.5% for energy storage. The exergy efficiency of the conventional CAES system is estimated to be 54.3%. Both high-temperature and low-temperature electrolysis CAES systems result in similar exergy efficiencies (35.6% and 34.2%), partly due to low efficiency of the electrolyzer cell. CAES with high-temperature electrolysis has the highest energy storage density (7.9 kWh per m³ of air storage volume), followed by A-CAES (5.2 kWh/m³). Conventional CAES and CAES with low-temperature electrolysis have similar energy densities of 3.1 kWh/m³. Full article

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

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13 pages, 2167 KiB

Open AccessArticle

Controlled Operation of the Islanded Portion of the International Council on Large Electric Systems (CIGRE) Low Voltage Distribution Network

by Ghullam Mustafa Bhutto^1,2,*, Claus Leth Bak² and Ehsan Ali³

¹ Department of Electrical Engineering, Quaid-E-Awam University of Engineering, Sciences and Technology (QUEST), Nawabshah 67480, Pakistan

² Department of Energy Technology, Aalborg University, Aalborg 9200, Denmark

³ Department of Electronic Engineering, Quaid-E-Awam University of Engineering, Sciences and Technology (QUEST), Nawabshah 67480, Pakistan

Energies 2017, 10(7), 1021; https://doi.org/10.3390/en10071021 - 18 Jul 2017

Cited by 4 | Viewed by 4197

Abstract

In islanding, a portion of the power network, comprised of the loads and distributed generation (DG) units, is isolated from the rest of the power grid and forms a micro grid (MG). In this condition, it becomes essential for the islanded MG to [...] Read more.

In islanding, a portion of the power network, comprised of the loads and distributed generation (DG) units, is isolated from the rest of the power grid and forms a micro grid (MG). In this condition, it becomes essential for the islanded MG to operate in a stable and controlled manner by providing ancillary services. When the MG is cut off from the main grid, the islanding must be detected by the DG units. In this condition it is essential that one of the controllers should be switched to the voltage-frequency (VF) control mode. In islanding, the network loses it slack reference and this reference is established by a VF controller. The voltage and the frequency of the islanded MG deviate when disconnected from the transmission grid and these deviations are caused by the load-generation imbalance. The voltage and the frequency of the islanded MG can be restored to the permissible limits if the desired/exceeded amount of active and reactive power is injected/absorbed by the locally available sources in islanded MG. This paper proposes a control strategy which can compensate the voltage and the frequency deviations in the islanded portion of the International Council on Large Electric Systems (CIGRE) low voltage distribution network by using advanced power electronics devices such as STATCOMs) for Photovoltaic (PV) Units and Battery Energy Storage Systems (BESS) STATCOMs (for battery units). The selection of the VF controller for the most suitable DG unit of this test network is also presented in this paper, and the effectiveness of the controllers is verified by presenting simulation results using DIgSILENT (DIgSILENT GmbH, Gomaringen, Germany) power factory software version 15.0. Full article

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

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28 pages, 1355 KiB

Open AccessReview

Opportunities and Challenges for Near-Field Wireless Power Transfer: A Review

by Aqeel Mahmood Jawad^1,2,*, Rosdiadee Nordin¹

, Sadik Kamel Gharghan³

, Haider Mahmood Jawad^1,2 and Mahamod Ismail¹

¹ Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor 43600, Malaysia

² Department of Computer Communication Engineering, Al-Rafidain University College, Filastin, Baghdad 10064, Iraq

³ Department of Medical Instrumentation Techniques Engineering, Electrical Engineering Technical College, Middle Technical University (MTU), Al Doura, Baghdad 10022, Iraq

Energies 2017, 10(7), 1022; https://doi.org/10.3390/en10071022 - 18 Jul 2017

Cited by 225 | Viewed by 18299

Abstract

Traditional power supply cords have become less important because they prevent large-scale utilization and mobility. In addition, the use of batteries as a substitute for power cords is not an optimal solution because batteries have a short lifetime, thereby increasing the cost, weight, [...] Read more.

Traditional power supply cords have become less important because they prevent large-scale utilization and mobility. In addition, the use of batteries as a substitute for power cords is not an optimal solution because batteries have a short lifetime, thereby increasing the cost, weight, and ecological footprint of the hardware implementation. Their recharging or replacement is impractical and incurs operational costs. Recent progress has allowed electromagnetic wave energy to be transferred from power sources (i.e., transmitters) to destinations (i.e., receivers) wirelessly, the so-called wireless power transfer (WPT) technique. New developments in WPT technique motivate new avenues of research in different applications. Recently, WPT has been used in mobile phones, electric vehicles, medical implants, wireless sensor network, unmanned aerial vehicles, and so on. This review highlights up-to-date studies that are specific to near-field WPT, which include the classification, comparison, and potential applications of these techniques in the real world. In addition, limitations and challenges of these techniques are highlighted at the end of the article. Full article

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

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16 pages, 2543 KiB

Open AccessArticle

Combustion, Performance, and Emission Evaluation of a Diesel Engine with Biodiesel Like Fuel Blends Derived From a Mixture of Pakistani Waste Canola and Waste Transformer Oils

by Muhammad Qasim^*

, Tariq Mahmood Ansari and Mazhar Hussain

Institute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800, Pakistan

Energies 2017, 10(7), 1023; https://doi.org/10.3390/en10071023 - 18 Jul 2017

Cited by 57 | Viewed by 6493

Abstract

The aim of this work was to study the combustion, performance, and emission characteristics of a 5.5 kW four-stroke single-cylinder water-cooled direct-injection diesel engine operated with blends of biodiesel-like fuel (BLF15, BLF20 & BLF25) obtained from a 50:50 mixture of transesterified waste transformer [...] Read more.

The aim of this work was to study the combustion, performance, and emission characteristics of a 5.5 kW four-stroke single-cylinder water-cooled direct-injection diesel engine operated with blends of biodiesel-like fuel (BLF15, BLF20 & BLF25) obtained from a 50:50 mixture of transesterified waste transformer oil (TWTO) and waste canola oil methyl esters (WCOME) with petroleum diesel. The mixture of the waste oils was named as biodiesel-like fuel (BLF).The engine fuelled with BLF blends was evaluated in terms of combustion, performance, and emission characteristics. FTIR analysis was carried out to know the functional groups in the BLF fuel. The experimental results revealed the shorter ignition delay and marginally higher brake specific fuel consumption (BSFC), brake thermal efficiency (BTE) and exhaust gas temperature (EGT) values for BLF blends as compared to diesel. The hydrocarbon (HC) and carbon monoxide (CO) emissions were decreased by 10.92–31.17% and 3.80–6.32%, respectively, as compared to those of diesel fuel. Smoke opacity was significantly reduced. FTIR analysis has confirmed the presence of saturated alkanes and halide groups in BLF fuel. In comparison to BLF20 and BLF25, the blend BLF15 has shown higher brake thermal efficiency and lower fuel consumption values. The HC, CO, and smoke emissions of BLF15 were found lower than those of petroleum diesel. The fuel blend BLF15 is suggested to be used as an alternative fuel for diesel engines without any engine modification. Full article

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

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23 pages, 3633 KiB

Open AccessArticle

Secure Plug-in Electric Vehicle (PEV) Charging in a Smart Grid Network

by Khaled Shuaib^1,*, Ezedin Barka¹, Juhar Ahmed Abdella¹, Farag Sallabi¹

, Mohammed Abdel-Hafez²

and Ala Al-Fuqaha³

¹ College of Information Technology, The United Arab Emirates University, Sheik Khalifa Bin Zayed Street P.O. Box 15551, Al Ain, UAE

² College of Engineering, The United Arab Emirates University, Sheik Khalifa Bin Zayed Street P.O. Box 15551, Al Ain, UAE

³ Department of Computer Science, Western Michigan University, Kalamazoo, MI 49008, USA

Energies 2017, 10(7), 1024; https://doi.org/10.3390/en10071024 - 19 Jul 2017

Cited by 10 | Viewed by 6376

Abstract

Charging of plug-in electric vehicles (PEVs) exposes smart grid systems and their users to different kinds of security and privacy attacks. Hence, a secure charging protocol is required for PEV charging. Existing PEV charging protocols are usually based on insufficiently represented and simplified [...] Read more.

Charging of plug-in electric vehicles (PEVs) exposes smart grid systems and their users to different kinds of security and privacy attacks. Hence, a secure charging protocol is required for PEV charging. Existing PEV charging protocols are usually based on insufficiently represented and simplified charging models that do not consider the user’s charging modes (charging at a private location, charging as a guest user, roaming within one’s own supplier network or roaming within other suppliers’ networks). However, the requirement for charging protocols depends greatly on the user’s charging mode. Consequently, available solutions do not provide complete protocol specifications. Moreover, existing protocols do not support anonymous user authentication and payment simultaneously. In this paper, we propose a comprehensive end-to-end charging protocol that addresses the security and privacy issues in PEV charging. The proposed protocol uses nested signatures to protect users’ privacy from external suppliers, their own suppliers and third parties. Our approach supports anonymous user authentication, anonymous payment, as well as anonymous message exchange between suppliers within a hierarchical smart grid architecture. We have verified our protocol using the AVISPA software verification tool and the results showed that our protocol is secure and works as desired. Full article

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

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21 pages, 6001 KiB

Open AccessArticle

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

by Yuzhen Lv

, Muhammad Rafiq^*, Chengrong Li and Bingliang Shan

Beijing Key Laboratory of High Voltage & EMC, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(7), 1025; https://doi.org/10.3390/en10071025 - 19 Jul 2017

Cited by 65 | Viewed by 9525

Abstract

Research on the transformer oil-based nanofluids (NFs) has been raised expeditiously over the past decade. Although, there is discrepancy in the stated results and inadequate understanding of the mechanisms of improvement of dielectric nanofluids, these nanofluids have emerged as a potential substitute of [...] Read more.

Research on the transformer oil-based nanofluids (NFs) has been raised expeditiously over the past decade. Although, there is discrepancy in the stated results and inadequate understanding of the mechanisms of improvement of dielectric nanofluids, these nanofluids have emerged as a potential substitute of mineral oils as insulating and heat removal fluids for high voltage equipment. The transformer oil (TO) based magnetic fluids (ferrofluids) may be regarded as the posterity insulation fluids as they propose inspiring unique prospectus to improve dielectric breakdown strength, as well as heat transfer efficiency, as compared to pure transformer oils. In this work, transformer oil-based magnetic nanofluids (MNFs) are prepared by dispersal of Fe₃O₄ nanoparticles (MNPs) into mineral oil as base oil, with various NPs loading from 5 to 80% w/v. The lightning impulse breakdown voltages (BDV) measurement was conducted in accordance with IEC 60897 by using needle to sphere electrodes geometry. The test results showed that dispersion of magnetic NPs may improve the insulation strength of MO. With the increment of NPs concentrations, the positive lightning impulse (LI) breakdown strength of TO is first raised, up to the highest value at 40% loading, and then tends to decrease at higher concentrations. The outcomes of negative LI breakdown showed that BDV of MNFs, with numerous loadings, were inferior to the breakdown strength of pure MO. The 40% concentration of nanoparticles (optimum concentration) was selected, and positive and negative LI breakdown strength was also further studied at different sizes (10 nm, 20 nm, 30 nm and 40 nm) of NPs and different electrode gap distances. Augmentation in the BDV of the ferrofluids (FFs) is primarily because of dielectric and magnetic features of Fe₃O₄ nanoaprticles, which act as electron scavengers and decrease the rate of free electrons produced in the ionization process. Research challenges and technical difficulties associated with ferrofluids for practical applications are mentioned. The advantages and disadvantages linked with magnetic fluids are also presented. Full article

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

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31 pages, 24274 KiB

Open AccessArticle

Design of a H_∞ Robust Controller with μ-Analysis for Steam Turbine Power Generation Applications

by Vincenzo Iannino¹

, Valentina Colla^1,*, Mario Innocenti²

and Annamaria Signorini³

¹ TeCIP Institute PERCRO Laboratory, Scuola Superiore Sant’Anna, via Alamanni 13B, Ghezzano, 56010 Pisa, Italy

² Department of Information Engineering, Università di Pisa, via G. Caruso 16, 56122 Pisa, Italy

³ General Electric Oil & Gas, via F. Matteucci 2, 50127 Firenze, Italy

Energies 2017, 10(7), 1026; https://doi.org/10.3390/en10071026 - 19 Jul 2017

Cited by 7 | Viewed by 6254

Abstract

Concentrated Solar Power plants are complex systems subjected to quite sensitive variations of the steam production profile and external disturbances, thus advanced control techniques that ensure system stability and suitable performance criteria are required. In this work, a multi-objective H_∞ robust controller [...] Read more.

Concentrated Solar Power plants are complex systems subjected to quite sensitive variations of the steam production profile and external disturbances, thus advanced control techniques that ensure system stability and suitable performance criteria are required. In this work, a multi-objective H_∞ robust controller is designed and applied to the power control of a Concentered Solar Power plant composed by two turbines, a gear and a generator. In order to provide robust performance and stability in presence of disturbances, not modeled plant dynamics and plant-parameter variations, the advanced features of the μ-analysis are exploited. A high order controller is obtained from the process of synthesis that makes the implementation of the controller difficult and computational more demanding for a Programmable Logic Controller. Therefore, the controller order is reduced through the Balanced Truncation method and then discretized. The obtained robust control is compared to the current Proportional Integral Derivative-based governing system in order to evaluate its performance, considering unperturbed as well as perturbed scenarios, taking into account variations of steam conditions, sensor measurement delays and power losses. The simulations results show that the proposed controller achieves better robustness and performance compared to the existing Proportional Integral Derivative controller. Full article

(This article belongs to the Special Issue Energy Production Systems)

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18 pages, 956 KiB

Open AccessArticle

Analysis of GHG Emission Reduction in South Korea Using a CO₂ Transportation Network Optimization Model

by Suk Ho Jin¹, Lianxi Bai¹, Jang Yeop Kim¹, Suk Jae Jeong^2,*

and Kyung Sup Kim^1,*

¹ Department of Industrial Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea

² Business School, Kwangwoon University, 20 Kwangwoon-ro, Nowon-gu, Seoul 01897, Korea

Energies 2017, 10(7), 1027; https://doi.org/10.3390/en10071027 - 19 Jul 2017

Cited by 14 | Viewed by 4509

Abstract

Korea’s national carbon capture and storage (CCS) master plan aims to commercialize CCS projects by 2030. Furthermore, the Korean government is forced to reduce emissions from various sectors, including industries and power generation, by 219 million tons by 2030. This study analyzes a [...] Read more.

Korea’s national carbon capture and storage (CCS) master plan aims to commercialize CCS projects by 2030. Furthermore, the Korean government is forced to reduce emissions from various sectors, including industries and power generation, by 219 million tons by 2030. This study analyzes a few scenarios of Korean CCS projects with a CO₂ pipeline transportation network optimization model for minimizing the total facility cost and pipeline cost. Our scenarios are based on the “2030 basic roadmap for reducing greenhouse gases” established by the government. The results for each scenario demonstrate that the effective design and implementation of CO₂ pipeline network enables the lowering of CO₂ units cost. These suggest that CO₂ transportation networks, which connect the capture and sequestration parts, will be more important in the future and can be used to substitute and supplement the emission reduction target in case the execution of other reduction options faces uncertainty. Our mathematical model and scenario designs will be helpful for various countries which plan to introduce CCS technology. Full article

(This article belongs to the Special Issue Energy Production Systems)

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12 pages, 979 KiB

Open AccessArticle

Parameter Design and Energy Control of the Power Train in a Hybrid Electric Boat

by Diju Gao^1,*, Wei Zhang¹, Aidi Shen¹ and Yide Wang^1,2

¹ Key Laboratory Marine Technology and Control Engineering, Ministry of Communications, Shanghai Maritime University, Shanghai 201306, China

² Institut d’Electronique et Telecommunications de Rennes, UMR CNRS 6164, Universite de Nantes, 44300 Nantes, France

Energies 2017, 10(7), 1028; https://doi.org/10.3390/en10071028 - 19 Jul 2017

Cited by 8 | Viewed by 5298

Abstract

With the continuous development worldwide of the inland shipping industry, emissions to the atmosphere have become a serious threat in terms of pollution. Hybrid power technology is an important means for reducing pollution due to emissions from ships. This paper considers a power [...] Read more.

With the continuous development worldwide of the inland shipping industry, emissions to the atmosphere have become a serious threat in terms of pollution. Hybrid power technology is an important means for reducing pollution due to emissions from ships. This paper considers a power train series in a hybrid electric inland waterway boat. From the analysis of the structure and principle of the power train, the parameter design for its key devices is presented, and a novel energy control strategy is proposed. Navigation experience shows that the proposed design method and control strategy are useful and satisfactory. Full article

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

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17 pages, 3204 KiB

Open AccessArticle

Economic Impact of the Use of Inertia in an Urban Bus Company

by Alejandro G. Tuero^1,*,†

, Laura Pozueco¹

, Roberto García¹, Gabriel Díaz², Xabiel G. Pañeda¹

, David Melendi¹

, Abel Rionda³ and David Martínez³

¹ Informatics Department, University of Oviedo, 33204 Gijón, Spain

² Electrical, Electronic, Control and Telematics Engineering, and Engineering applied Chemistry Department, Spanish University for Distance Education (UNED), 28040 Madrid, Spain

³ ADN Context-Aware Mobile Solutions S.L., 33394 Gijón, Spain

^† This author is an Industrial Technologies Ph.D. Candidate, at Spanish University for Distance Education (UNED), 28040 Madrid, Spain.

Energies 2017, 10(7), 1029; https://doi.org/10.3390/en10071029 - 19 Jul 2017

Cited by 3 | Viewed by 3252

Abstract

Public transport companies face great expenses. In order to be profitable companies, they need to reduce costs in all aspects. In addition, many countries have increased taxes to force transport companies to reduce their fuel consumption and, thus, greenhouse effect emissions. Efficient driving [...] Read more.

Public transport companies face great expenses. In order to be profitable companies, they need to reduce costs in all aspects. In addition, many countries have increased taxes to force transport companies to reduce their fuel consumption and, thus, greenhouse effect emissions. Efficient driving is the cheapest way to achieve this goal. In this paper, we analyze the economic impact of one of the most influential efficient driving techniques in an urban bus company. We calculate the difference of consumption between a well-performed deceleration using the inertia of the vehicle and a loss of speed obtained by using the brakes. For this purpose, we compare a real track performed by any driver in a precise vehicle with a simulated ideal track. To obtain the deceleration of the simulation, we develop a linear regression model on over 170,000 samples captured from the same vehicle over a period of one month. The results show that the costs of the vehicle under test in one month may be reduced by more than

2500 €

Full article

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13 pages, 2937 KiB

Open AccessArticle

Influence of Catalytic Formulation and Operative Conditions on Coke Deposition over CeO₂-SiO₂ Based Catalysts for Ethanol Reforming

by Vincenzo Palma, Concetta Ruocco^*

, Eugenio Meloni

and Antonio Ricca

Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 83040 Fisciano (SA), Italy

Energies 2017, 10(7), 1030; https://doi.org/10.3390/en10071030 - 19 Jul 2017

Cited by 31 | Viewed by 4965

Abstract

In this work, a series of CeO₂-SiO₂ (30 wt % of ceria)-based catalysts was prepared by the wetness impregnation method and tested for ESR (ethanol steam reforming) at 450–500 °C, atmospheric pressure and a water/ethanol ratio increasing from 4 to [...] Read more.

In this work, a series of CeO₂-SiO₂ (30 wt % of ceria)-based catalysts was prepared by the wetness impregnation method and tested for ESR (ethanol steam reforming) at 450–500 °C, atmospheric pressure and a water/ethanol ratio increasing from 4 to 6 (the ethanol concentration being fixed to 10 vol %); after every test, coke gasification measurements were performed at the same water partial pressure, and the temperature of the test and the gasified carbon was measured from the areas under the CO and CO₂ profiles. Finally, oxidation measurements under a 5% O₂/N₂ stream made it possible to calculate the total carbon deposited. In an attempt to improve the coke resistance of a Pt-Ni/CeO₂-SiO₂ catalyst, the effect of support basification by alkali addition (K and Cs), as well as Pt substitution by Rh was investigated. The novel catalysts, especially those containing Rh, displayed a lowering in the carbon formation rate; however, a faster reduction of ethanol conversion with time-on-stream and lessened hydrogen selectivities were recorded. In addition, no significant gain in terms of coke gasification rates was observed. The most active catalyst (Pt-Ni/CeO₂-SiO₂) was also tested under different operative conditions, in order to study the effect of temperature and water/ethanol ratio on carbon formation and gasification. The increase in the water content resulted in an enhanced reactor-plugging time due to reduced carbonaceous deposits formation; however, no effect of steam concentration on the carbon gasification rate were recorded. On the other hand, the increase in temperature from 450–500 °C lowered the coke selectivity by almost one order of magnitude improving, at the same time, the contribution of the gasification reactions. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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10 pages, 2147 KiB

Open AccessArticle

High Breakdown Field CaCu₃Ti₄O₁₂ Ceramics: Roles of the Secondary Phase and of Sr Doping

by Zhuang Tang, Kangning Wu, Yuwei Huang and Jianying Li^*

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

Energies 2017, 10(7), 1031; https://doi.org/10.3390/en10071031 - 19 Jul 2017

Cited by 18 | Viewed by 5932

Abstract

In this work, two methods of CaCu₃Ti₄O₁₂-CuAl₂O₄ composite and SrCu₃Ti₄O₁₂-CaCu₃Ti₄O₁₂ composite were prepared to improve the breakdown field in CaCu₃Ti₄ [...] Read more.

In this work, two methods of CaCu₃Ti₄O₁₂-CuAl₂O₄ composite and SrCu₃Ti₄O₁₂-CaCu₃Ti₄O₁₂ composite were prepared to improve the breakdown field in CaCu₃Ti₄O₁₂ ceramics. CaCu₃Ti₄O₁₂-0.5CuAl₂O₄ and 0.4SrCu₃Ti₄O₁₂-0.6CaCu₃Ti₄O₁₂ samples with proper sintering conditions were found to have greatly enhanced breakdown fields of more than 20 kV·cm⁻¹ compared to the ordinary value of 1–2 kV·cm⁻¹ in CaCu₃Ti₄O₁₂ ceramics. In addition, reduced dielectric loss tangent of these samples remained about 0.1 at a low frequency of 0.1 Hz, indicating superior dielectric properties. No abnormal grain growth was found in either composite with a high breakdown field, which was attributed to the pining effect and consumption of Cu-rich phase at grain boundaries. Under analysis of the relaxation process by electric modulus, compared to conventional CaCu₃Ti₄O₁₂ ceramics, interstitial Al_i··· and increasing interfaces were responsible for variation in activation energy in CaCu₃Ti₄O₁₂-0.5CuAl₂O₄ composites, while the integrated action of a strong solid solution effect and weak Sr-stretching effect contributed to the elevated potential barrier height and enhanced breakdown field in 0.4SrCu₃Ti₄O₁₂-0.6CaCu₃Ti₄O₁₂ composites. Full article

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

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17 pages, 9121 KiB

Open AccessArticle

Multidisciplinary Energy Assessment of Tertiary Buildings: Automated Geomatic Inspection, Building Information Modeling Reconstruction and Building Performance Simulation

by Faustino Patiño-Cambeiro^1,*, Guillermo Bastos², Julia Armesto³ and Faustino Patiño-Barbeito²

¹ Industrial Engineering School, University of Vigo, Rúa Maxwell, 36310 Vigo, Spain

² Industrial Engineering School, University of Vigo, Rúa Conde de Torrecedeira 86, 36208 Vigo, Spain

³ Mining Engineering School, University of Vigo, Campus as Lagoas Marcosende, 36310 Vigo, Spain

Energies 2017, 10(7), 1032; https://doi.org/10.3390/en10071032 - 19 Jul 2017

Cited by 19 | Viewed by 5039

Abstract

There is an urgent need for energy efficiency in buildings within the European framework, considering its environmental implications, and Europe’s energy dependence. Furthermore, the need for enhancing and increasing productivity in the building industry turns new technologies and building energy performance simulation environments [...] Read more.

There is an urgent need for energy efficiency in buildings within the European framework, considering its environmental implications, and Europe’s energy dependence. Furthermore, the need for enhancing and increasing productivity in the building industry turns new technologies and building energy performance simulation environments into extremely interesting solutions towards rigorous analysis and decision making in renovation within acceptable risk levels. The present work describes a multidisciplinary approach for the estimation of the energy performance of an educational building. The research involved data acquisition with advanced geomatic tools, the development of an optimized building information model, and energy assessment in Building Performance Simulation (BPS) software. Interoperability issues were observed in the different steps of the process. The inspection and diagnostic phases were conducted in a timely, accurate manner thanks to automated data acquisition and subsequent analysis using Building Information Modeling based tools (BIM-based tools). Energy simulation was performed using Design Builder, and the results obtained were compared with those yielded by the official software tool established by Spanish regulations for energy certification. The discrepancies between the results of both programs have proven that the official software program is conservative in this sense. This may cause the depreciation of the assessed buildings. Full article

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23 pages, 10308 KiB

Open AccessArticle

Grid-Forming-Mode Operation of Boost-Power-Stage Converter in PV-Generator-Interfacing Applications

by Jukka Viinamäki¹, Alon Kuperman²

and Teuvo Suntio^1,*

¹ Laboratory of Electrical Energy Engineering, Tampere University of Technology, 33720 Tampere, Finland

² Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel

Energies 2017, 10(7), 1033; https://doi.org/10.3390/en10071033 - 19 Jul 2017

Cited by 19 | Viewed by 4433

Abstract

The application of constant power control and inclusion of energy storage in grid-connected photovoltaic (PV) energy systems may increase the use of two-stage system structures composed of DC–DC-converter-interfaced PV generator and grid-connected inverter connected in cascade. A typical PV-generator-interfacing DC–DC converter is a [...] Read more.

The application of constant power control and inclusion of energy storage in grid-connected photovoltaic (PV) energy systems may increase the use of two-stage system structures composed of DC–DC-converter-interfaced PV generator and grid-connected inverter connected in cascade. A typical PV-generator-interfacing DC–DC converter is a boost-power-stage converter. The renewable energy system may operate in three different operation modes—grid-forming, grid-feeding, and grid-supporting modes. In the last two operation modes, the outmost feedback loops are taken from the input terminal of the associated power electronic converters, which usually does not pose stability problems in terms of their input sources. In the grid-forming operation mode, the outmost feedback loops have to be connected to the output terminal of the associated power electronic converters, and hence the input terminal will behave as a negative incremental resistor at low frequencies. This property will limit the operation of the PV interfacing converter in either the constant voltage or constant current region of the PV generator for ensuring stable operation. The boost-power-stage converter can be applied as a voltage or current-fed converter limiting the stable operation region accordingly. The investigations of this paper show explicitly that only the voltage-fed mode would provide feasible dynamic and stability properties as a viable interfacing converter. Full article

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16 pages, 6705 KiB

Open AccessArticle

A Fast Multi-Switched Inductor Balancing System Based on a Fuzzy Logic Controller for Lithium-Ion Battery Packs in Electric Vehicles

by Xiudong Cui¹, Weixiang Shen^1,*

, Yunlei Zhang²

and Cungang Hu²

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

² School of Electrical Engineering and Automation, Anhui University, Hefei 230000, China

Energies 2017, 10(7), 1034; https://doi.org/10.3390/en10071034 - 19 Jul 2017

Cited by 28 | Viewed by 5673

Abstract

Based on a low cost multi-switched inductor balancing circuit (MSIBC), a fuzzy logic (FL) controller is proposed to improve the balancing performances of lithium-ion battery packs instead of an existing proportional-integral (PI) controller. In the proposed FL controller, a cell’s open circuit voltages [...] Read more.

Based on a low cost multi-switched inductor balancing circuit (MSIBC), a fuzzy logic (FL) controller is proposed to improve the balancing performances of lithium-ion battery packs instead of an existing proportional-integral (PI) controller. In the proposed FL controller, a cell’s open circuit voltages (OCVs) and their differences in the pack are used as the inputs, and the output of the FL controller is the balancing current. The FL controller for the MSIBC has the advantage of maintaining high balancing currents over the existing PI controller in almost the entire balancing process for different lithium battery types. As a result, the proposed FL controller takes a much shorter time to achieve battery pack balancing, and thus more pack capacity can be recovered. This will help to improve the pack performance in electric vehicles and extend the serving time of the battery pack. Full article

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

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14 pages, 1799 KiB

Open AccessArticle

A Robust Battery Grouping Method Based on a Characteristic Distribution Model

by Yuxiang Yang¹

, Mingyu Gao¹, Zhiwei He¹

and Caisheng Wang^2,*

¹ Department of Electronics and Information, Hangzhou Dianzi University, 2nd Street, Xiasha Higher Education Zone, Hangzhou 310018, China

² Departmant of Electric and Computer Engineering, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202, USA

Energies 2017, 10(7), 1035; https://doi.org/10.3390/en10071035 - 19 Jul 2017

Cited by 9 | Viewed by 3325

Abstract

The inconsistent characteristics of individual power batteries in a battery pack can seriously affect the performance and service life of the whole pack. Battery grouping is an effective approach for dealing with the inconsistency problem by grouping batteries with similar characteristics in the [...] Read more.

The inconsistent characteristics of individual power batteries in a battery pack can seriously affect the performance and service life of the whole pack. Battery grouping is an effective approach for dealing with the inconsistency problem by grouping batteries with similar characteristics in the same battery pack. In actual production, the battery grouping process still relies on the traditional manual method, which results in high labor and time costs. In this paper, a robust and effective battery grouping method based on the characteristic distribution model is developed. Specifically, a novel characteristic distribution model is proposed to determine the grouping priority of different batteries. Then, an improved k-nearest-neighbor algorithm is used to decide which batteries should be group into the same battery pack. Experimental results demonstrate the effectiveness of the proposed method. Full article

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20 pages, 2486 KiB

Open AccessArticle

Flexible Multi-Objective Transmission Expansion Planning with Adjustable Risk Aversion

by Jing Qiu¹

, Junhua Zhao^2,* and Dongxiao Wang³

¹ Energy Flagship, The Commonwealth Scientific and Industrial Research Organization (CSIRO), Mayfield West, NSW 2304, Australia

² School of Science and Engineering, Chinese University of Hong Kong (Shenzhen), Shenzhen 518172, China

³ Center for Intelligent Electricity Networks, The University of Newcastle, Callaghan, NSW 2308, Australia

Energies 2017, 10(7), 1036; https://doi.org/10.3390/en10071036 - 20 Jul 2017

Cited by 5 | Viewed by 3414

Abstract

This paper presents a multi-objective transmission expansion planning (TEP) framework. Rather than using the conventional deterministic reliability criterion, a risk component based on the probabilistic reliability criterion is incorporated into the TEP objectives. This risk component can capture the stochastic nature of power [...] Read more.

This paper presents a multi-objective transmission expansion planning (TEP) framework. Rather than using the conventional deterministic reliability criterion, a risk component based on the probabilistic reliability criterion is incorporated into the TEP objectives. This risk component can capture the stochastic nature of power systems, such as load and wind power output variations, component availability, and incentive-based demand response (IBDR) costs. Specifically, the formulation of risk value after risk aversion is explicitly given, and it aims to provide network planners with the flexibility to conduct risk analysis. Thus, a final expansion plan can be selected according to individual risk preferences. Moreover, the economic value of IBDR is modeled and integrated into the cost objective. In addition, a relatively new multi-objective evolutionary algorithm called the MOEA/D is introduced and employed to find Pareto optimal solutions, and tradeoffs between overall cost and risk are provided. The proposed approach is numerically verified on the Garver’s six-bus, IEEE 24-bus RTS and Polish 2383-bus systems. Case study results demonstrate that the proposed approach can effectively reduce cost and hedge risk in relation to increasing wind power integration. Full article

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

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22 pages, 12654 KiB

Open AccessArticle

Seismic Fragility Analysis of Monopile Offshore Wind Turbines under Different Operational Conditions

by Renjie Mo¹, Haigui Kang^1,*, Miao Li²

and Xuanlie Zhao¹

¹ State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

² Engineering, Faculty of Business, Justice and Behavioural Sciences, Charles Sturt University, Panorama Avenue, Bathurst, NSW 2795, Australia

Energies 2017, 10(7), 1037; https://doi.org/10.3390/en10071037 - 20 Jul 2017

Cited by 85 | Viewed by 9670

Abstract

Offshore wind turbines in seismic active areas suffer from earthquake impacts. In this study, seismic fragility analysis of a monopile offshore wind turbine considering different operational conditions was performed. A finite element model for a 5 MW monopile offshore wind turbine was developed [...] Read more.

Offshore wind turbines in seismic active areas suffer from earthquake impacts. In this study, seismic fragility analysis of a monopile offshore wind turbine considering different operational conditions was performed. A finite element model for a 5 MW monopile offshore wind turbine was developed using the OpenSees platform. The interaction between the monopile and the seabed soil was modeled as a beam-on-nonlinear-winkler-foundation (BNWF). A nonlinear time history truncated incremental dynamic analysis (TIDA) was conducted to obtain seismic responses and engineering demand parameters. Potential damage states (DSs) were defined as excessive displacement at the nacelle, rotation at the tower top, and the allowable and yield stresses at the transition piece. Fragility curves were plotted to assess the probability of exceeding different damage states. It was found that seismic responses of the wind turbine are considerably influenced by environmental wind and wave loads. Subject to earthquake motions, wind turbines in normal operation at the rated wind speed experience higher levels of probability of exceeding damage states than those in other operational conditions, i.e., in idling or operating at higher or lower wind speed conditions. Full article

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18 pages, 4783 KiB

Open AccessArticle

Regenerative Braking Control Strategy of Electric-Hydraulic Hybrid (EHH) Vehicle

by Yang Yang^1,2,*, Chang Luo^1,2 and Pengxi Li^1,2

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

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

Energies 2017, 10(7), 1038; https://doi.org/10.3390/en10071038 - 20 Jul 2017

Cited by 26 | Viewed by 12356

Abstract

A novel electric-hydraulic hybrid drivetrain incorporating a set of hydraulic systems is proposed for application in a pure electric vehicle. Models of the electric and hydraulic components are constructed. Two control strategies, which are based on two separate rules, are developed; the maximum [...] Read more.

A novel electric-hydraulic hybrid drivetrain incorporating a set of hydraulic systems is proposed for application in a pure electric vehicle. Models of the electric and hydraulic components are constructed. Two control strategies, which are based on two separate rules, are developed; the maximum energy recovery rate strategy adheres to the rule of the maximization of the braking energy recovery rate, while the minimum current impact strategy adheres to the rule of the minimization of the charge current to the battery. The simulation models were established to verify the effects of these two control strategies. An ABS (Anti-lock Braking System) fuzzy control strategy is also developed and simulated. The simulation results demonstrate that the developed control strategy can effectively absorb the braking energy, suppress the current impact, and assure braking safety. Full article

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

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14 pages, 1069 KiB

Open AccessArticle

Total-Factor Energy Efficiency (TFEE) Evaluation on Thermal Power Industry with DEA, Malmquist and Multiple Regression Techniques

by Jin-Peng Liu^1,*, Qian-Ru Yang¹ and Lin He²

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

² Economy and Technology Research Institute, State Grid Xin Jiang Electric Power Corporation, Wulumuqi 830011, China

Energies 2017, 10(7), 1039; https://doi.org/10.3390/en10071039 - 21 Jul 2017

Cited by 34 | Viewed by 5008

Abstract

Under the background of a new round of power market reform, realizing the goals of energy saving and emission reduction, reducing the coal consumption and ensuring the sustainable development are the key issues for thermal power industry. With the biggest economy and energy [...] Read more.

Under the background of a new round of power market reform, realizing the goals of energy saving and emission reduction, reducing the coal consumption and ensuring the sustainable development are the key issues for thermal power industry. With the biggest economy and energy consumption scales in the world, China should promote the energy efficiency of thermal power industry to solve these problems. Therefore, from multiple perspectives, the factors influential to the energy efficiency of thermal power industry were identified. Based on the economic, social and environmental factors, a combination model with Data Envelopment Analysis (DEA) and Malmquist index was constructed to evaluate the total-factor energy efficiency (TFEE) in thermal power industry. With the empirical studies from national and provincial levels, the TFEE index can be factorized into the technical efficiency index (TECH), the technical progress index (TPCH), the pure efficiency index (PECH) and the scale efficiency index (SECH). The analysis showed that the TFEE was mainly determined by TECH and PECH. Meanwhile, by panel data regression model, unit coal consumption, talents and government supervision were selected as important indexes to have positive effects on TFEE in thermal power industry. In addition, the negative indexes, such as energy price and installed capacity, were also analyzed to control their undesired effects. Finally, considering the analysis results, measures for improving energy efficiency of thermal power industry were discussed widely, such as strengthening technology research and design (R&D), enforcing pollutant and emission reduction, distributing capital and labor rationally and improving the government supervision. Relative study results and suggestions can provide references for Chinese government and enterprises to enhance the energy efficiency level. Full article

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

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19 pages, 4847 KiB

Open AccessArticle

Health Parameter Estimation with Second-Order Sliding Mode Observer for a Turbofan Engine

by Xiaodong Chang

, Jinquan Huang^* and Feng Lu

Jiangsu Province Key Laboratory of Aerospace Power System, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Energies 2017, 10(7), 1040; https://doi.org/10.3390/en10071040 - 20 Jul 2017

Cited by 16 | Viewed by 3850

Abstract

In this paper the problem of health parameter estimation in an aero-engine is investigated by using an unknown input observer-based methodology, implemented by a second-order sliding mode observer (SOSMO). Unlike the conventional state estimator-based schemes, such as Kalman filters (KF) and sliding mode [...] Read more.

In this paper the problem of health parameter estimation in an aero-engine is investigated by using an unknown input observer-based methodology, implemented by a second-order sliding mode observer (SOSMO). Unlike the conventional state estimator-based schemes, such as Kalman filters (KF) and sliding mode observers (SMO), the proposed scheme uses a “reconstruction signal” to estimate health parameters modeled as artificial inputs, and is not only applicable to long-time health degradation, but reacts much quicker in handling abrupt fault cases. In view of the inevitable uncertainties in engine dynamics and modeling, a weighting matrix is created to minimize such effect on estimation by using the linear matrix inequalities (LMI). A big step toward uncertainty modeling is taken compared with our previous SMO-based work, in that uncertainties are considered in a more practical form. Moreover, to avoid chattering in sliding modes, the super-twisting algorithm (STA) is employed in observer design. Various simulations are carried out, based on the comparisons between the KF-based scheme, the SMO-based scheme in our earlier research, and the proposed method. The results consistently demonstrate the capabilities and advantages of the proposed approach in health parameter estimation. Full article

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19 pages, 5375 KiB

Open AccessArticle

Study on the Bearing Mode and Force Transfer Path of Composite Bucket Foundations

by Shaohua He², Puyang Zhang^1,2,* and Hongyan Ding^1,2

¹ State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China

² School of Civil Engineering, Tianjin University, Tianjin 300072, China

Energies 2017, 10(7), 1041; https://doi.org/10.3390/en10071041 - 20 Jul 2017

Cited by 21 | Viewed by 4618

Abstract

This paper elaborates on a new composite bucket foundation (CBF) structural system for offshore wind turbines. The proposed CBF consists of a special force transition section, a beam system structure upper steel bucket cover and a large-scale steel bucket with honeycomb structure rooms. [...] Read more.

This paper elaborates on a new composite bucket foundation (CBF) structural system for offshore wind turbines. The proposed CBF consists of a special force transition section, a beam system structure upper steel bucket cover and a large-scale steel bucket with honeycomb structure rooms. It can be prefabricated onshore, self-floated on the sea and then towed to the appointed sea area before sinking to the sea soil under negative pressure. This is called the “one-step” installation technology. Arc- and line-type bucket foundations are calculated by both theory and the finite element method to discuss their force transfer paths and bearing modes. Owning to the special structural form, the transition section can effectively convert the huge load and bending moment into controllable tension and compressive stress, as well as adjust the structure balance. The bearing model and percentage of each part of the composite foundation under monotonous and ultimate load conditions are also calculated. Results indicate that the bearing mode of CBF is a typical top cover mode. In addition, the curvature impact of arc-type is studied and the results reveal that the structure type of the transition section is more important than the diameter ratio between the bottom transition section and the bucket. Full article

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

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23 pages, 14617 KiB

Open AccessArticle

Location Study of Solar Thermal Power Plant in the State of Pernambuco Using Geoprocessing Technologies and Multiple-Criteria Analysis

by Verônica Wilma B. Azevêdo¹, Ana Lúcia B. Candeias²

and Chigueru Tiba^1,*

¹ Departamento de Energia Nuclear, Centro de Tecnologias e Geociências, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, 1000, Cidade Universitária, Recife PE 50.740-540, Brazil

² Departamento de Engenharia Cartográfica, Centro de Tecnologias e Geociências, Universidade Federal de Pernambuco, Av. Acadêmico Hélio Ramos, s/n, 2nd Floor, Cidade Universitária, Recife PE 50.740-530, Brazil

Energies 2017, 10(7), 1042; https://doi.org/10.3390/en10071042 - 20 Jul 2017

Cited by 18 | Viewed by 6400

Abstract

Solar Thermal Technology for the generation of electricity in large scale has been a reality in the world since the 1980s, when the first large-sized solar plants in the United States were introduced. Brazil presents great potential for the development of large-scale projects, [...] Read more.

Solar Thermal Technology for the generation of electricity in large scale has been a reality in the world since the 1980s, when the first large-sized solar plants in the United States were introduced. Brazil presents great potential for the development of large-scale projects, although it is noted that the main barriers for the insertion of this technology in Brazilian market are the lack of incentives and goals and associated costs. In a way to contribute to the insertion of solar thermal technology in Brazil, this paper presents a macro-spatial approach, based on the use of Multiple-Criteria Decision Analysis and Geoprocessing, for the location of solar thermal power plants. The applied methodology for Pernambuco, located in the Northeast Region of Brazil, considered the implantation of parabolic trough solar power plant of 80 MW, operating only in solar mode, without heat storage. Based on performed analysis, it was confirmed that Pernambuco presents great potential for the installation of solar power plants, especially in the backlands of Pernambuco. Performed validations in the model demonstrate that the methodology attended the objective once the consistence between the assigned weights to the thematic layers, individually, and the final Map of site suitability were evidenced. Full article

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15 pages, 6921 KiB

Open AccessArticle

A Control Strategy for Mode Transition with Gear Shifting in a Plug-In Hybrid Electric Vehicle

by Kyuhyun Sim

, Sang-Min Oh, Ku-Young Kang and Sung-Ho Hwang^*

Department of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon-si 16419, Korea

Energies 2017, 10(7), 1043; https://doi.org/10.3390/en10071043 - 20 Jul 2017

Cited by 11 | Viewed by 8038

Abstract

The mode transition from electric propulsion mode to hybrid propulsion mode is important with regard to the power management strategy of plug-in hybrid electric vehicles (PHEVs). This is because mode transitions can occur frequently depending on the power management strategies and driving cycles, [...] Read more.

The mode transition from electric propulsion mode to hybrid propulsion mode is important with regard to the power management strategy of plug-in hybrid electric vehicles (PHEVs). This is because mode transitions can occur frequently depending on the power management strategies and driving cycles, and because inadequate mode transitions worsen the fuel efficiency and drivability. A pre-transmission parallel PHEV uses a clutch between the internal combustion engine (ICE) and the electric motor (EM) to connect or disconnect the power source of the ICE for a mode transition. The mode transition requires additional energy consumption for clutch speed synchronization, and is accompanied by a drivetrain shock due to clutch engagement. This paper proposes a control strategy for the mode transition with gear-shifting to resolve the problems of energy consumption and drivetrain shock. Through the development of a PHEV performance simulator, we analyze the mode transition characteristics and propose a control strategy considering the vehicle acceleration and gear state. The control strategy reduces the duration required for the mode transition by moving the start time of the mode transition. This helps to improve energy efficiency while maintaining adequate drivability. Full article

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

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15 pages, 3700 KiB

Open AccessArticle

Configuration Synthesis of Novel Series-Parallel Hybrid Transmission Systems with Eight-Bar Mechanisms

by Ngoc-Tan Hoang and Hong-Sen Yan^*

Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan

Energies 2017, 10(7), 1044; https://doi.org/10.3390/en10071044 - 20 Jul 2017

Cited by 20 | Viewed by 7036

Abstract

This paper presents a design approach for the configuration synthesis of series-parallel hybrid transmissions with eight-bar mechanisms. The final design consists of 54 mechanisms with eight members and twelve joints including a simple planetary gear train (PGT) and a double planet PGT. Then, [...] Read more.

This paper presents a design approach for the configuration synthesis of series-parallel hybrid transmissions with eight-bar mechanisms. The final design consists of 54 mechanisms with eight members and twelve joints including a simple planetary gear train (PGT) and a double planet PGT. Then, by using the techniques of power and clutch arrangements, new series-parallel hybrid transmissions are synthesized. The power arrangement process generates 97 clutchless hybrid systems. The clutch arrangement process generates 100 corresponding series-parallel transmissions. To demonstrate the feasibility of the synthesized configurations, a new hybrid transmission is selected as an example to analyze the working principle with operation modes and power flow paths. Full article

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

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13 pages, 10911 KiB

Open AccessArticle

Simulation of Contamination Deposition on Typical Shed Porcelain Insulators

by Yukun Lv¹, Weiping Zhao^1,*

, Jingang Li²

and Yazhao Zhang¹

¹ School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, China

² Jinneng Clean Energy Ltd. Company, Taiyuan 030002, China

Energies 2017, 10(7), 1045; https://doi.org/10.3390/en10071045 - 20 Jul 2017

Cited by 16 | Viewed by 4202

Abstract

The contamination deposition characteristics of insulators can be used in the development of antifouling work. Using COMSOL software, numerical simulations on the pollution-deposited performance of a porcelain three-umbrella insulator and porcelain bell jar insulator in a wind tunnel were conducted, and the simulated [...] Read more.

The contamination deposition characteristics of insulators can be used in the development of antifouling work. Using COMSOL software, numerical simulations on the pollution-deposited performance of a porcelain three-umbrella insulator and porcelain bell jar insulator in a wind tunnel were conducted, and the simulated results were compared with the tested results. The comparison shows that the deposit amount is consistent with the order of magnitude and presents a similar tendency with Direct Current (DC) voltage variation; then the rationality of the simulation is verified. Based on these results, simulations of the natural contamination deposition on porcelain insulators and the distribution of pollution along the umbrella skirt were performed. The results indicates that, under a same wind speed, contamination of the porcelain three-umbrella insulator and porcelain bell jar insulator under DC voltage was positively correlated with the particle size. With the same particle size, the proportion of the deposit amount under DC voltage (NSDD_DC) to the deposit amount under AC voltage (NSDD_AC) of both insulators decreases with the increase in wind speed. However, the ratio increases as particle size increase. At a small wind speed, the deposit amount along the umbrella skirt of the two insulators displays a U-shaped distribution under DC voltage while there is little difference in the contamination amount of each skirt under Alternating Current (AC) voltage. Full article

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

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16 pages, 6065 KiB

Open AccessArticle

Optimal Power Transmission of Offshore Wind Power Using a VSC-HVdc Interconnection

by Miguel E. Montilla-DJesus^*

, Santiago Arnaltes

, Edgardo D. Castronuovo

and David Santos-Martin

Electrical Engineering Department, Carlos III University of Madrid, Av. de la Universidad 30, 28911 Leganés, Madrid, Spain

Energies 2017, 10(7), 1046; https://doi.org/10.3390/en10071046 - 20 Jul 2017

Cited by 11 | Viewed by 5660

Abstract

High-voltage dc transmission based on voltage-source converter (VSC-HVdc) is quickly increasing its power rating, and it can be the most appropriate link for the connection of offshore wind farms (OWFs) to the grid in many locations. This paper presents a steady-state operation model [...] Read more.

High-voltage dc transmission based on voltage-source converter (VSC-HVdc) is quickly increasing its power rating, and it can be the most appropriate link for the connection of offshore wind farms (OWFs) to the grid in many locations. This paper presents a steady-state operation model to calculate the optimal power transmission of an OWF connected to the grid through a VSC-HVdc link. The wind turbines are based on doubly fed induction generators (DFIGs), and a detailed model of the internal OWF grid is considered in the model. The objective of the optimization problem is to maximize the active power output of the OWF, i.e., the reduction of losses, by considering the optimal reactive power allocation while taking into account the restrictions imposed by the available wind power, the reactive power capability of the DFIG, the DC link model, and the operating conditions. Realistic simulations are performed to evaluate the proposed model and to execute optimal operation analyses. The results show the effectiveness of the proposed method and demonstrate the advantages of using the reactive control performed by DFIG to achieve the optimal operation of the VSC-HVdc. Full article

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

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20 pages, 2642 KiB

Open AccessArticle

Improved Linear Active Disturbance Rejection Control for Microgrid Frequency Regulation

by Xiao Qi^* and Yan Bai

School of Control and Computer Engineering, North China Electric Power University, Beijing 102206, China

Energies 2017, 10(7), 1047; https://doi.org/10.3390/en10071047 - 20 Jul 2017

Cited by 15 | Viewed by 5210

Abstract

The frequency regulation has become one of the major subjects in microgrid power system due to the complexity structure of microgrid. In order to solve this problem, this paper proposes an improved linear active disturbance rejection control algorithm (ILADRC) that can significantly improve [...] Read more.

The frequency regulation has become one of the major subjects in microgrid power system due to the complexity structure of microgrid. In order to solve this problem, this paper proposes an improved linear active disturbance rejection control algorithm (ILADRC) that can significantly improve system performances through changing feedback control law to reduce the disturbance estimation error of extended state observer. Then, the proposed algorithm is employed in microgrid power system frequency regulation problem, which demonstrates its effectiveness. The parameters of controllers are optimized by particle swarm optimization (PSO) algorithm improved by genetic algorithm (GA). Simulations with different disturbances including sudden and stochastic change of load demand and wind turbine generation are carried out in comparison with previous studies. And robustness testing based on Monte-Carlo approach also shows better performance. So frequency stability of microgrid power system can be well guaranteed by proposed control algorithm. Full article

(This article belongs to the Special Issue Advanced Operation and Control of Smart Microgrids)

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19 pages, 12116 KiB

Open AccessArticle

A Study on the Effects of Starches on the Properties of Alkali-Activated Cement and the Potential of Starch as a Self-Degradable Additive

by Huijing Tan, Xiuhua Zheng^*, Limenglu Ma, Haixiao Huang and Bairu Xia

School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China

Energies 2017, 10(7), 1048; https://doi.org/10.3390/en10071048 - 20 Jul 2017

Cited by 14 | Viewed by 4281

Abstract

An urgent problem of geothermal energy source development is how to cut down the production costs. The use of temporary sealing materials can reduce the costs associated with the circulation lost by plugging, and increase the production by self-degradation. Based on the utilization [...] Read more.

An urgent problem of geothermal energy source development is how to cut down the production costs. The use of temporary sealing materials can reduce the costs associated with the circulation lost by plugging, and increase the production by self-degradation. Based on the utilization of starches as self-degradable additives in the medical field, this paper investigated the effects of three kinds of starches, namely corn starch (CS), hydroxypropyl starch (HPS) and carboxymethyl starch (CMS) on the properties of alkali-activated cement (AAC). In addition, the thermal properties of starch, the compressive strength and microstructures of the cement with starch were tested, to evaluate the potentiality of starch as self-degradable additive for geothermal cement. The analysis showed that: (1) all the starches have the effect of increasing the apparent viscosity, prolonging the setting time and reducing the static fluid loss of alkali-activated cement; (2) the addition of starch increased the number of pores in 200 °C-heated cement, facilitated the leaching process, and thus promoted the self-degradation; and (3) among the three starches, CMS has the most potential as a self-degradable additive. Full article

(This article belongs to the Special Issue Selected Papers from Sixth Annual Conference for the Development and Utilization of Deep Geothermal Energy)

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28 pages, 1087 KiB

Open AccessArticle

A Heuristic Algorithm to Compute Multimodal Criterial Function Weights for Demand Management in Residential Areas

by Vaclav Kaczmarczyk^*, Zdenek Bradac^† and Petr Fiedler^†

¹ CEITEC—Central European Institute of Technology, Brno University of Technology, Purkynova 656/123, 612 00 Brno, Czech Republic

^† These authors contributed equally to this work.

Energies 2017, 10(7), 1049; https://doi.org/10.3390/en10071049 - 20 Jul 2017

Cited by 17 | Viewed by 3754

Abstract

We present the conceptual design of a collective control scheme for appliances within a smart home. Based on the relevant energy acquisition procedures, three appliance groups are defined, modeled, and completed with an energy storage as well as a generator using renewable sources. [...] Read more.

We present the conceptual design of a collective control scheme for appliances within a smart home. Based on the relevant energy acquisition procedures, three appliance groups are defined, modeled, and completed with an energy storage as well as a generator using renewable sources. At the following stage, a mixed quadratic optimization problem is presented, with the solution consisting in a time plan to regulate the operation of the individual devices. Importantly, the paper also proposes a heuristic algorithm securing consistent functionality of the computational process even despite the varying input and user conditions given in the receding horizon. Full article

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

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20 pages, 1032 KiB

Open AccessArticle

The Potential of Smart Technologies and Micro-Generation in UK SMEs

by Peter Warren

School of Public Policy, University College London, 30 Tavistock Square, Bloomsbury, London WC1H 9QU, UK

Energies 2017, 10(7), 1050; https://doi.org/10.3390/en10071050 - 20 Jul 2017

Cited by 16 | Viewed by 5422

Abstract

Small-to-medium-sized enterprises (SMEs) make up 99% of businesses and contribute 13% of energy demand globally. However, much of the demand-side energy research and policy attention to date has focused on the domestic, large commercial and industrial sectors. Previous research on SMEs has primarily [...] Read more.

Small-to-medium-sized enterprises (SMEs) make up 99% of businesses and contribute 13% of energy demand globally. However, much of the demand-side energy research and policy attention to date has focused on the domestic, large commercial and industrial sectors. Previous research on SMEs has primarily concentrated on the drivers and barriers to the adoption of energy efficiency measures. However, less attention has been given to other areas of demand-side management in SMEs, such as the role of ‘smart’ technologies and micro-generation. The paper aims to contribute to filling this gap. To analyse the potential of smart technologies in UK SMEs, a quantitative model is developed to assess seven categories of smart technologies in ten non-domestic sectors. Overall, the results suggest that smart technologies within the UK SME market offer significant estimated annual energy savings potential of ~£8.6 billion against an estimated energy spend of ~£49.7 billion (representing ~17% savings potential on energy expenditures). From the smart technology categories examined, fleet management, integrated building management systems and smart meters have the potential to offer the greatest energy savings to SMEs, providing estimated total energy savings of ~£7.5 billion annually. To analyse the potential of micro-generation in UK SMEs, interview-based qualitative research was undertaken with 17 SMEs to explore the drivers and barriers to its adoption. The research found that the initial costs, technical feasibility and planning permission on historical buildings were the main barriers, and that the ‘green’ marketing potential of micro-generation, coupled with ethical reasons and feed-in tariffs, were the main drivers. Full article

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

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12 pages, 1714 KiB

Open AccessArticle

Non-Convex Economic Dispatch of a Virtual Power Plant via a Distributed Randomized Gradient-Free Algorithm

by Jun Xie^1,2,*

and Chi Cao¹

¹ College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

² College of Energy and Electrical Engineering, Hohai University, Nanjing 211100, China

Energies 2017, 10(7), 1051; https://doi.org/10.3390/en10071051 - 21 Jul 2017

Cited by 13 | Viewed by 4013

Abstract

The economic dispatch problem of a virtual power plant (VPP) is becoming non-convex for distributed generators’ characteristics of valve-point loading effects, prohibited operating zones, and multiple fuel options. In this paper, the economic dispatch model of VPP is established and then solved by [...] Read more.

The economic dispatch problem of a virtual power plant (VPP) is becoming non-convex for distributed generators’ characteristics of valve-point loading effects, prohibited operating zones, and multiple fuel options. In this paper, the economic dispatch model of VPP is established and then solved by a distributed randomized gradient-free algorithm. To deal with the non-smooth objective function, its Gauss approximation is used to construct distributed randomized gradient-free oracles in optimization iterations. A projection operator is also introduced to solve the discontinuous variable space problem. An example simulation is implemented on a modified IEEE-34 bus test system, and the results demonstrate the effectiveness and applicability of the proposed algorithm. Full article

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

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25 pages, 3350 KiB

Open AccessArticle

A Chaos-Embedded Gravitational Search Algorithm for the Identification of Electrical Parameters of Photovoltaic Cells

by Arturo Valdivia-González^*, Daniel Zaldívar

, Erik Cuevas, Marco Pérez-Cisneros

, Fernando Fausto^* and Adrián González

Departamento de Electrónica, Universidad de Guadalajara, CUCEI Av. Revolución 1500, 44430 Guadalajara, Mexico

Energies 2017, 10(7), 1052; https://doi.org/10.3390/en10071052 - 21 Jul 2017

Cited by 20 | Viewed by 5231

Abstract

Solar energy is used worldwide to alleviate the daily increasing demands for electric power. Photovoltaic (PV) cells, which are used to convert solar energy into electricity, can be represented as equivalent circuit models, in which a series of electrical parameters must be identified [...] Read more.

Solar energy is used worldwide to alleviate the daily increasing demands for electric power. Photovoltaic (PV) cells, which are used to convert solar energy into electricity, can be represented as equivalent circuit models, in which a series of electrical parameters must be identified in order to determine their operating characteristics under different test conditions. Intelligent approaches, like those based in population-based optimization algorithms like Particle Swarm Optimization (PSO), Genetic Algorithms (GAs), and Simulated Annealing (SA), have been demonstrated to be powerful methods for the accurate identification of such parameters. Recently, chaos theory have been highlighted as a promising alternative to increase the performance of such approaches; as a result, several chaos-based optimization methods have been devised to solve many different and complex engineering problems. In this paper, the Chaotic Gravitational Search Algorithm (CGSA) is proposed to solve the problem of accurate PV cell parameter estimation. To prove the feasibility of the proposed approach, a series of comparative experiments against other similar parameters extraction methods were performed. As shown by our experimental results, our proposed approach outperforms all other methods compared in this work, and proves to be an excellent alternative to tackle the challenging problem of solar cell parameters identification. Full article

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13 pages, 3881 KiB

Open AccessArticle

High-Precision Spectral Decomposition Method Based on VMD/CWT/FWEO for Hydrocarbon Detection in Tight Sandstone Gas Reservoirs

by Hui Chen^1,*, Dan Xu¹, Xinyue Zhou¹, Ying Hu^1,2

and Ke Guo¹

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

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

Energies 2017, 10(7), 1053; https://doi.org/10.3390/en10071053 - 21 Jul 2017

Cited by 4 | Viewed by 4243

Abstract

Seismic time-frequency analysis methods can be used for hydrocarbon detection because of the phenomena of energy and abnormal attenuation of frequency when the seismic waves travel across reservoirs. A high-resolution method based on variational mode decomposition (VMD), continuous-wavelet transform (CWT) and frequency-weighted energy [...] Read more.

Seismic time-frequency analysis methods can be used for hydrocarbon detection because of the phenomena of energy and abnormal attenuation of frequency when the seismic waves travel across reservoirs. A high-resolution method based on variational mode decomposition (VMD), continuous-wavelet transform (CWT) and frequency-weighted energy operator (FWEO) is proposed for hydrocarbon detection in tight sandstone gas reservoirs. VMD can decompose seismic signals into a set of intrinsic mode functions (IMF) in the frequency domain. In order to avoid meaningful frequency loss, the CWT method is used to obtain the time-frequency spectra of the selected IMFs. The energy separation algorithm based on FWEO can improve the resolution of time-frequency spectra and highlight abnormal energy, which is applied to track the instantaneous energy in the time-frequency spectra. The difference between the high-frequency section and low-frequency section acquired by applying the proposed method is utilized to detect hydrocarbons. Applications using the model and field data further demonstrate that the proposed method can effectively detect hydrocarbons in tight sandstone reservoirs, with good anti-noise performance. The newly-proposed method can be used as an analysis tool to detect hydrocarbons. Full article

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12 pages, 10198 KiB

Open AccessArticle

RTV Silicone Rubber Degradation Induced by Temperature Cycling

by Xishan Wen¹, Xiaoqing Yuan¹

, Lei Lan^1,*, Lu Hao¹, Yu Wang¹, Shaodong Li¹, Hailiang Lu^1,*

and Zhenghong Bao²

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

² Electric Power Research Institute, State Grid Qinghai Electric Power Company, Xining 810008, China

Energies 2017, 10(7), 1054; https://doi.org/10.3390/en10071054 - 21 Jul 2017

Cited by 42 | Viewed by 8373

Abstract

Room temperature vulcanized (RTV) silicone rubber is extensively used in power system due to its hydrophobicity and hydrophobicity transfer ability. Temperature has been proven to markedly affect the performance of silicone rubbers. This research investigated the degradation of RTV silicone rubber under temperature [...] Read more.

Room temperature vulcanized (RTV) silicone rubber is extensively used in power system due to its hydrophobicity and hydrophobicity transfer ability. Temperature has been proven to markedly affect the performance of silicone rubbers. This research investigated the degradation of RTV silicone rubber under temperature cycling treatment. Hydrophobicity and its transfer ability, hardness, functional groups, microscopic appearance, and thermal stability were analyzed using the static contact angle method, a Shore A durometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG), respectively. Some significant conclusions were drawn. After the temperature was cycled between −25 °C and 70 °C, the hydrophobicity changed modestly, but its transfer ability changed remarkably, which may result from the competition between the formation of more channels for the transfer of low molecular weight (LMW) silicone fluid and the reduction of LMW silicone fluid in the bulk. A hardness analysis and FTIR analysis demonstrated that further cross-linking reactions occurred during the treatment. SEM images showed the changes in roughness of the RTV silicone rubber surfaces. TG analysis also demonstrated the degradation of RTV silicone rubber by presenting evidence that the content of organic materials decreased during the temperature cycling treatment. Full article

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

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10 pages, 3105 KiB

Open AccessArticle

Effect of Altitude on the Audible Noise Level of AC Power lines

by Wangling He¹, Baoquan Wan², Lei Lan¹, Chunming Pei³, Jiangong Zhang², Yuchao Chen⁴, Xiaoyue Chen^1,* and Xishan Wen¹

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

² State Key Laboratory of Power Grid Environmental Protection (China Electric Power Research Institute), Wuhan 430072, China

³ Wuhan NARI Group Corporation, Wuhan 430074, China

⁴ State Grid Corporation of China, Beijing 100031, China

Energies 2017, 10(7), 1055; https://doi.org/10.3390/en10071055 - 21 Jul 2017

Cited by 14 | Viewed by 4826

Abstract

The audible noise (AN) induced by corona discharge of AC transmission lines is more severe at high altitudes than at low altitudes; this has become a crucial limiting factor for the structural design of power lines and their environmental impact assessment. To determine [...] Read more.

The audible noise (AN) induced by corona discharge of AC transmission lines is more severe at high altitudes than at low altitudes; this has become a crucial limiting factor for the structural design of power lines and their environmental impact assessment. To determine the altitude effect and correction of AN level for AC power lines, a corona cage test system was used to measure the acoustic power level of four bundled conductors at five elevations, namely Wuhan (23 m), Tianshui (1100 m), Xining (2261 m), Gonghe (2943 m), and Yangbajain (4300 m). We obtained the AN characteristics for different altitudes, bundle numbers, and subconductor diameters through a statistical analysis of measured data. The analysis and comparison results indicate that the actual AN correction values are slightly less than the Bonneville Power Administration term of 1 dB/300 m at altitudes below 3200 m. Above 3200 m, the difference increases gradually. A correction term 2.85 dB/1000 m is recommended for more accurate evaluation. Full article

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

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34 pages, 1461 KiB

Open AccessEditor’s ChoiceReview

State of the Art and Trends in the Monitoring, Detection and Diagnosis of Failures in Electric Induction Motors

by Yuri Merizalde¹, Luis Hernández-Callejo^2,*

and Oscar Duque-Perez³

¹ PhD School of University of Valladolid (UVA), Faculty of Chemical Engineering, University of Guayaquil, Clemente Ballen 2709 and Ismael Perez Pazmiño, Guayaquil 593, Ecuador

² Department of Agricultural Engineering and Forestry, University of Valladolid (UVA), Campus Universitario Duques de Soria, 42004 Soria, Spain

³ Department of Electrical Engineering, University of Valladolid (UVA), Escuela de Ingenierías Industriales, Paseo del Cauce 59, 47011 Valladolid, Spain

Energies 2017, 10(7), 1056; https://doi.org/10.3390/en10071056 - 21 Jul 2017

Cited by 87 | Viewed by 8977

Abstract

Despite the complex mathematical models and physical phenomena on which it is based, the simplicity of its construction, its affordability, the versatility of its applications and the relative ease of its control have made the electric induction motor an essential element in a [...] Read more.

Despite the complex mathematical models and physical phenomena on which it is based, the simplicity of its construction, its affordability, the versatility of its applications and the relative ease of its control have made the electric induction motor an essential element in a considerable number of processes at the industrial and domestic levels, in which it converts electrical energy into mechanical energy. The importance of this type of machine for the continuity of operation, mainly in industry, is such that, in addition to being an important part of the study programs of careers related to this branch of electrical engineering, a large number of investigations into monitoring, detecting and quickly diagnosing its incipient faults due to a variety of factors have been conducted. This bibliographic research aims to analyze the conceptual aspects of the first discoveries that served as the basis for the invention of the induction motor, ranging from the development of the Fourier series, the Fourier transform mathematical formula in its different forms and the measurement, treatment and analysis of signals to techniques based on artificial intelligence and soft computing. This research also includes topics of interest such as fault types and their classification according to the engine, software and hardware parts used and modern approaches or maintenance strategies. Full article

(This article belongs to the Special Issue Electric Machines and Drives for Renewable Energy Harvesting 2017)

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16 pages, 4761 KiB

Open AccessArticle

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

by Yanli Huang^1,2, Jixiong Zhang^1,2,*, Wei Yin³ and Qiang Sun^1,2

¹ State Key Laboratory of Coal Resources and Safe Mining, School of Mines, China University of Mining & Technology, Xuzhou 221116, China

² Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China, School of Mines, China University of Mining and Technology, Xuzhou 221116, China

³ Faculty of Transportation Engineering, Huaiyin Institute of Technology, Xuzhou 221116, China

Energies 2017, 10(7), 1057; https://doi.org/10.3390/en10071057 - 21 Jul 2017

Cited by 33 | Viewed by 4666

Abstract

Based on techniques of close upper protective coal-rock layer mining, relieved gas extraction, and underground gangue washing-discharging-backfilling, this paper initiates the concept of mixed fully-mechanized coal mining, which combines a solid backfilling method and a caving method (hereinafter referred to as “backfill and [...] Read more.

Based on techniques of close upper protective coal-rock layer mining, relieved gas extraction, and underground gangue washing-discharging-backfilling, this paper initiates the concept of mixed fully-mechanized coal mining, which combines a solid backfilling method and a caving method (hereinafter referred to as “backfill and caving mixed mining”). After the principle and key techniques are introduced, a physical simulation experiment and a numerical simulation are used to study the characteristics of the overlying strata’s fracture development, the main roof subsidence, the stress field and its influence area in the transition area with the length ratios of the backfilling section and the caving section, and the advancing distance of the mixed longwall face. Thus, the lengths of the caving section and the backfilling section, the parameters of the support system in the transition section, and the design process of the mixed longwall face are presented. In practice, the mixed longwall face Ji₁₅-31010 in Ping-dingshan No. 12 Colliery proves that the designed lengths of 120 m and 100 m for the backfilling section and the caving section, respectively, are appropriate. The monitoring results of the hydraulic support working resistance show that the supports were working well in general; the maximum growth height of the overlying strata fracture is 18 m; the gas drainage efficiency is up to 80% and the average gas concentration is 0.1 g/m³; a large quantity of gangue generated in the Ji₁₄ seam is disposed underground; coal and gas are extracted simultaneously; and significant environmental and economic benefits are realized. Full article

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17 pages, 4664 KiB

Open AccessArticle

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

by Zujin Pan^* and Jianzhong Wu

School of Mechanical Engineering, Tongji University, Shanghai 200092, China

Energies 2017, 10(7), 1058; https://doi.org/10.3390/en10071058 - 21 Jul 2017

Cited by 9 | Viewed by 5465

Abstract

Wind turbine blades have to withstand the rigorous test of 20–25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter [...] Read more.

Wind turbine blades have to withstand the rigorous test of 20–25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter and saves testing energy consumption. The amplitude, phase, and frequency characteristics of the fatigue test system and, moreover, the relationship between the excitation force, damping, and the amplitude variation of the blade, are analyzed by the Lagrangian equation and the finite element simulation method. The full-scale fatigue test of an equivalent full cycle life in the flapwise direction is carried out by multi-excitation. When the frequency and phase of the multi-point exciters are consistent, the maximum vibration effect can be exerted. When the phase difference of the dual exciters is 180°, the vibration effect produced by the dual exciters can be equivalent to each other. The blade amplitude is proportional to excitation forces, while inversely proportional to the damping ratio. The bending moment deviation of the blade is controlled within 9.2%; moreover, the energy consumption is 40% lower than that of the single-point excitation. The use of multi-point excitation allows loading the blade with high precision, stable operation, and low cost, which provides the theoretical and experimental basis for the fatigue test of large wind turbine blades. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

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17 pages, 5486 KiB

Open AccessArticle

Pole-to-Ground Fault Analysis and Fast Protection Scheme for HVDC Based on Overhead Transmission Lines

by Shimin Xue^*, Jie Lian, Jinlong Qi and Boyang Fan

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

Energies 2017, 10(7), 1059; https://doi.org/10.3390/en10071059 - 21 Jul 2017

Cited by 45 | Viewed by 7333

Abstract

Flexible direct current (DC) transmission network technology is an effective method for large capacity clean energy access to power grids, but the DC short-circuit fault detection for it is a difficult problem. In this paper, the pole-to-ground fault transient characteristics in a multi-terminal [...] Read more.

Flexible direct current (DC) transmission network technology is an effective method for large capacity clean energy access to power grids, but the DC short-circuit fault detection for it is a difficult problem. In this paper, the pole-to-ground fault transient characteristics in a multi-terminal DC power grid, based on overhead transmission lines and DC circuit breakers, are analyzed firstly. Then, a fast protection scheme is proposed according to the fault transient characteristics. Only local information is utilized for fault detection and location in the proposed scheme. Moreover, the scheme is verified to have the advantages of fast action speed, high reliability and the ability to resist the transition resistance. A four terminal DC power grid model based on actual engineering parameters is established in PSCAD/EMTDC, and the validity of the protection scheme under different fault conditions is verified by simulation results. Full article

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

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20 pages, 5569 KiB

Open AccessArticle

Comparison of the Performance of Artificial Neural Networks and Fuzzy Logic for Recognizing Different Partial Discharge Sources

by Abdullahi Abubakar Mas’ud^1,*

, Jorge Alfredo Ardila-Rey²

, Ricardo Albarracín³

, Firdaus Muhammad-Sukki⁴

and Nurul Aini Bani⁵

¹ Department of Electrical and Electronics Engineering, Jubail Industrial College, P.O. Box 10099, Jubail 31961, Saudi Arabia

² Department of Electrical Engineering, Universidad Técnica Federico Santa María, Santiago de Chile 8940000, Chile

³ Departamento de Ingeniería Eléctrica, Electrónica, Automática y Física Aplicada, Escuela Técnica Superior de Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Ronda de Valencia 3, 28012 Madrid, Spain

⁴ School of Engineering, Robert Gordon University, Aberdeen AB10 7GJ, UK

⁵ UTM Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur, Malaysia

Energies 2017, 10(7), 1060; https://doi.org/10.3390/en10071060 - 21 Jul 2017

Cited by 34 | Viewed by 5211

Abstract

This paper compared the capabilities of the artificial neural network (ANN) and the fuzzy logic (FL) approaches for recognizing and discriminating partial discharge (PD) fault classes. The training and testing parameters for the ANN and FL comprise statistical fingerprints from different phase-amplitude-number ( [...] Read more.

This paper compared the capabilities of the artificial neural network (ANN) and the fuzzy logic (FL) approaches for recognizing and discriminating partial discharge (PD) fault classes. The training and testing parameters for the ANN and FL comprise statistical fingerprints from different phase-amplitude-number (φ-q-n) measurements. Two PD fault classes considered are internal discharges in voids and surface discharges. In the void class, there are single voids, serial voids and parallel voids in polyethylene terephthalate (PET), while the surface discharge class comprises four different surface discharge arrangements on pressboard in oil at different voltages and angular positioning of the ground electrode on the respective pressboards. Previously, the ANN and FL have been investigated for PD classification, but there is no work reported in the literature that compares their performance, specifically when applied for real time PD detection problem. As expected, both the ANN and FL can recognize PD defect classes, but the results show that the ANN appears to be more robust as compared to the FL, but these conclusions required to be further investigated with complex PD examples. Finally, both the ANN and FL were assessed as practical PD classification. Despite of the limitations of the ANN, it is concluded that the ANN is better suited for practical PD recognition because of its ability to provide accurate recognition values and the severity level of PD defects. Full article

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12 pages, 607 KiB

Open AccessArticle

Biomass Production from Crops Residues: Ranking of Agro-Energy Regions

by Christina Moulogianni and Thomas Bournaris^*

Department of Agricultural Economics, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece

Energies 2017, 10(7), 1061; https://doi.org/10.3390/en10071061 - 22 Jul 2017

Cited by 14 | Viewed by 4294

Abstract

The aim of the paper is to rank the agro-energy regions according to their potentials of biomass production in the Region of Central Macedonia (RCM). For this reason, a model of Multi-Criteria Analysis (MCDA) is developed with the ELimination and Et Choix Traduisant [...] Read more.

The aim of the paper is to rank the agro-energy regions according to their potentials of biomass production in the Region of Central Macedonia (RCM). For this reason, a model of Multi-Criteria Analysis (MCDA) is developed with the ELimination and Et Choix Traduisant la REalite (ELECTRE) ΙΙΙ method, with the construction of outranking relations. The aim is to compare in a comprehensive way each pair of action, in our case the agro-energy regions of the RCM, in order to satisfy the main goal which is to rank the seven regions as regards their biomass production. The final goal is to select the optimal crop plan as a pilot case for biomass production in the region. In the case of ELECTRE III multicriteria model, we used several conflicting criteria such as the farm income, the biomass production from crop residues, the variable costs, and the production of thermal energy and electrical energy. Alongside a technical and economic analysis of the study area is conducted for the existent crop plans of each agro-energy region. The results show that agro-energy regions with cereals and arable crops have better results than regions with fruit trees and other crops. Full article

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

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26 pages, 5271 KiB

Open AccessArticle

An Optimization Framework for Investment Evaluation of Complex Renewable Energy Systems

by David Olave-Rojas¹, Eduardo Álvarez-Miranda^2,*, Alejandro Rodríguez² and Claudio Tenreiro³

¹ DSc Program on Complex Engineering Systems, Universidad de Talca, Curicó 3341717, Chile;

² Department of Industrial Engineering, Universidad de Talca, Curicó 3341717, Chile

³ Department of Industrial Technologies, Universidad de Talca, Curicó 3341717, Chile

Energies 2017, 10(7), 1062; https://doi.org/10.3390/en10071062 - 22 Jul 2017

Cited by 6 | Viewed by 5980

Abstract

Enhancing the role of renewable energies in existing power systems is one of the most crucial challenges that society faces today. However, the high variability of their generation potential and the temporal disparity between the demand and the generation potential represent technological and [...] Read more.

Enhancing the role of renewable energies in existing power systems is one of the most crucial challenges that society faces today. However, the high variability of their generation potential and the temporal disparity between the demand and the generation potential represent technological and operational gaps that burden the massive incorporation of renewable sources into power systems. Energy storage technologies are an alternative to tackle this gap; nonetheless, their incorporation within large-scale power grids calls for decision-making tools that ensure an appropriate design and sizing of power systems that exploit the benefits of incorporating storage facilities along with renewable generation power. In this paper, we present an optimization framework for aiding the evaluation of the strategic design of complex renewable power systems. The developed tool relies on an optimization problem, the generation, transmission, storage energy location and sizing problem, which allows one to compute economically-attractive investment plans given by the location and sizing of generation and storage energy systems, along with the corresponding layout of transmission lines. Results on a real case study (located in the central region of Chile), characterized by carefully-curated data, show the potential of the developed tool for aiding long-term investment planning. Full article

(This article belongs to the Special Issue Energy Production Systems)

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21 pages, 5381 KiB

Open AccessArticle

Adaptive Model Predictive Control-Based Energy Management for Semi-Active Hybrid Energy Storage Systems on Electric Vehicles

by Fang Zhou

, Feng Xiao, Cheng Chang, Yulong Shao and Chuanxue Song^*

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

Energies 2017, 10(7), 1063; https://doi.org/10.3390/en10071063 - 22 Jul 2017

Cited by 53 | Viewed by 6220

Abstract

This paper deals with the energy management strategy (EMS) for an on-board semi-active hybrid energy storage system (HESS) composed of a Li-ion battery (LiB) and ultracapacitor (UC). Considering both the nonlinearity of the semi-active structure and driving condition uncertainty, while ensuring HESS operation [...] Read more.

This paper deals with the energy management strategy (EMS) for an on-board semi-active hybrid energy storage system (HESS) composed of a Li-ion battery (LiB) and ultracapacitor (UC). Considering both the nonlinearity of the semi-active structure and driving condition uncertainty, while ensuring HESS operation within constraints, an adaptive model predictive control (AMPC) method is adopted to design the EMS. Within AMPC, LiB Ah-throughput is minimized online to extend its life. The proposed AMPC determines the optimal control action by solving a quadratic programming (QP) problem at each control interval, in which the QP solver receives control-oriented model matrices and current states for calculation. The control-oriented model is constructed by linearizing HESS online to approximate the original nonlinear model. Besides, a time-varying Kalman filter (TVKF) is introduced as the estimator to improve the state estimation accuracy. At the same time, sampling time, prediction horizon and scaling factors of AMPC are determined through simulation. Compared with standard MPC, TVKF reduces the estimation error by 1~3 orders of magnitude, and AMPC reduces LiB Ah-throughput by 4.3% under Urban Dynamometer Driving Schedule (UDDS) driving cycle condition, indicating superior model adaptivity. Furthermore, LiB Ah-throughput of AMPC under various classical driving cycles differs from that of dynamic programming by an average of 6.5% and reduces by an average of 10.6% compared to rule-based strategy of LiB Ah-throughput, showing excellent adaptation to driving condition uncertainty. Full article

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

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17 pages, 3231 KiB

Open AccessArticle

Utilizing Non-Equilibrium Thermodynamics and Reactive Transport to Model CH₄ Production from the Nankai Trough Gas Hydrate Reservoir

by Khadijeh Qorbani^*

, Bjørn Kvamme and Tatiana Kuznetsova

University of Bergen, Physics and Technology department, Allegaten 55, 5007 Bergen, Norway

Energies 2017, 10(7), 1064; https://doi.org/10.3390/en10071064 - 22 Jul 2017

Cited by 2 | Viewed by 4794

Abstract

The ongoing search for new sources of energy has brought natural gas hydrate (NGH) reservoirs to the forefront of attention in both academia and the industry. The amount of gas reserves trapped within these reservoirs surpasses all of the conventional fossil fuel sources [...] Read more.

The ongoing search for new sources of energy has brought natural gas hydrate (NGH) reservoirs to the forefront of attention in both academia and the industry. The amount of gas reserves trapped within these reservoirs surpasses all of the conventional fossil fuel sources explored so far, which makes it of utmost importance to predict their production potential and safety. One of the challenges facing those attempting to analyse their behaviour is that the large number of involved phases make NGHs unable to ever reach equilibrium in nature. Field-scale experiments are expensive and time consuming. However, computer simulations have now become capable of modelling different gas production scenarios, as well as production optimization analyses. In addition to temperature and pressure, independent thermodynamic parameters for hydrate stabilization include the hydrate composition and concentrations for all co-existing phases. It is therefore necessary to develop and implement realistic kinetic models accounting for all significant routes for dissociation and reformation. The reactive transport simulator makes it easy to deploy nonequilibrium thermodynamics for the study of CH₄ production from hydrate-bearing sediments by considering each hydrate-related transition as a separate pseudo reaction. In this work, we have used the expanded version of the RetrasoCodeBright (RCB) reactive transport simulator to model exploitation of the methane hydrate (MH) reservoir located in the Nankai Trough, Japan. Our results showed that higher permeabilities in the horizontal direction dominated the pressure drop propagation throughout the hydrate layers and affected their hydrate dissociation rates. Additionally, the comparison of the vertical well versus the horizontal well pattern indicated that hydrate dissociation was slightly higher in the vertical well scenario compared to the horizontal. Full article

(This article belongs to the Special Issue Methane Hydrate Research and Development)

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19 pages, 4459 KiB

Open AccessArticle

Effects of Anisotropic Thermal Conductivity and Lorentz Force on the Flow and Heat Transfer of a Ferro-Nanofluid in a Magnetic Field

by Yubai Li¹, Hongbin Yan²

, Mehrdad Massoudi³ and Wei-Tao Wu^4,*

¹ Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, State College, PA 16803, USA

² School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China

³ Department of Energy, U. S. National Energy Technology Laboratory (NETL), Pittsburgh, PA 15236, USA

⁴ Department of Biomedical Engineering and Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA

Energies 2017, 10(7), 1065; https://doi.org/10.3390/en10071065 - 22 Jul 2017

Cited by 19 | Viewed by 7540

Abstract

In this paper, we study the effects of the Lorentz force and the induced anisotropic thermal conductivity due to a magnetic field on the flow and the heat transfer of a ferro-nanofluid. The ferro-nanofluid is modeled as a single-phase fluid, where the viscosity [...] Read more.

In this paper, we study the effects of the Lorentz force and the induced anisotropic thermal conductivity due to a magnetic field on the flow and the heat transfer of a ferro-nanofluid. The ferro-nanofluid is modeled as a single-phase fluid, where the viscosity depends on the concentration of nanoparticles; the thermal conductivity shows anisotropy due to the presence of the nanoparticles and the external magnetic field. The anisotropic thermal conductivity tensor, which depends on the angle of the applied magnetic field, is suggested considering the principle of material frame indifference according to Continuum Mechanics. We study two benchmark problems: the heat conduction between two concentric cylinders as well as the unsteady flow and heat transfer in a rectangular channel with three heated inner cylinders. The governing equations are made dimensionless, and the flow and the heat transfer characteristics of the ferro-nanofluid with different angles of the magnetic field, Hartmann number, Reynolds number and nanoparticles concentration are investigated systematically. The results indicate that the temperature field is strongly influenced by the anisotropic behavior of the nanofluids. In addition, the magnetic field may enhance or deteriorate the heat transfer performance (i.e., the time-spatially averaged Nusselt number) in the rectangular channel depending on the situations. Full article

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

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13 pages, 6438 KiB

Open AccessArticle

Thermal and Performance Analysis of a Gasification Boiler and Its Energy Efficiency Optimization

by Jan Valíček^1,2,3,*, Zuzana Palková¹

, Marta Harničárová^2,3, Milena Kušnerová^2,3 and Ondrej Lukáč¹

¹ Technical Faculty, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949-76 Nitra, Slovakia

² Faculty of Mining and Geology, Vysoká škola báňská—Technical University of Ostrava, 17. Listopadu 15, 708-33 Ostrava, Czech Republic

³ Regional Materials Science and Technology Centre, Vysoká škola báňská—Technical University of Ostrava, 17. Listopadu 15, 708-33 Ostrava, Czech Republic

Energies 2017, 10(7), 1066; https://doi.org/10.3390/en10071066 - 22 Jul 2017

Cited by 6 | Viewed by 5464

Abstract

The purpose of this study was to determine a method for multi-parametric output regulation of a gasification boiler especially designed for heating or for hot water heating in buildings. A new method of regulation is offered, namely more parametric regulation via proportional-integral-derivative (PID) [...] Read more.

The purpose of this study was to determine a method for multi-parametric output regulation of a gasification boiler especially designed for heating or for hot water heating in buildings. A new method of regulation is offered, namely more parametric regulation via proportional-integral-derivative (PID) controllers that are capable of controlling the calculated values of pressure, temperature and fan speed. These values of pressure, temperature and fan speed are calculated in a completely new way, and calculations of setpoints for determination of optimal parameters lead to an increase in boilers efficiency and power output. Results of measurements show that changes at the mouth of the stack draft due atmospheric influences occur in times with high intensity and high frequency, while power parameters, or boiler power output amplitudes and fan speed automatically “copy” those changes proportionally due to instantaneous fan speed changes. The proposed method of regulation of the gasification boiler power output according to the technical solution enables a simple, cheap, express and continuous maintenance of high power output at low concentrations of the exhaust gases of the gasification boilers from the viewpoint of the boiler user, as well as from the perspective of development and production it allows a continuous control monitoring of these parameters. Full article

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

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17 pages, 8653 KiB

Open AccessArticle

Control Strategy for a Grid-Connected Inverter under Unbalanced Network Conditions—A Disturbance Observer-Based Decoupled Current Approach

by Emre Ozsoy¹

, Sanjeevikumar Padmanaban^1,*

, Lucian Mihet-Popa²

, Viliam Fedák³

, Fiaz Ahmad⁴

, Rasool Akhtar⁴

and Asif Sabanovic⁴

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

² Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Krakeroy-Fredrikstad, Norway

³ Department of Electrical Engineering & Mechatronics, Technical University of Kosice, Rampová 1731/7, 040 01 Košice, Džung’a-Džung’a, Slovakia

⁴ Mechatronics Engineering, Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul 34956, Turkey

Energies 2017, 10(7), 1067; https://doi.org/10.3390/en10071067 - 22 Jul 2017

Cited by 33 | Viewed by 8609

Abstract

This paper proposes a new approach on the novel current control strategy for grid-tied voltage-source inverters (VSIs) with circumstances of asymmetrical voltage conditions. A standard grid-connected inverter (GCI) allows the degree of freedom to integrate the renewable energy system to enhance the penetration [...] Read more.

This paper proposes a new approach on the novel current control strategy for grid-tied voltage-source inverters (VSIs) with circumstances of asymmetrical voltage conditions. A standard grid-connected inverter (GCI) allows the degree of freedom to integrate the renewable energy system to enhance the penetration of total utility power. However, restrictive grid codes require that renewable sources connected to the grid must support stability of the grid under grid faults. Conventional synchronously rotating frame dq current controllers are insufficient under grid faults due to the low bandwidth of proportional-integral (PI) controllers. Hence, this work proposes a proportional current controller with a first-order low-pass filter disturbance observer (DOb). The proposed controller establishes independent control on positive, as well as negative, sequence current components under asymmetrical grid voltage conditions. The approach is independent of parametric component values, as it estimates nonlinear feed-forward terms with the low-pass filter DOb. A numerical simulation model of the overall power system was implemented in a MATLAB/Simulink (2014B, MathWorks, Natick, MA, USA). Further, particular results show that double-frequency active power oscillations are suppressed by injecting appropriate negative-sequence currents. Moreover, a set of simulation results provided in the article matches the developed theoretical background for its feasibility. Full article

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

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20 pages, 10671 KiB

Open AccessArticle

Modeling Noise Sources and Propagation in External Gear Pumps

by Sangbeom Woo^1,*, Timothy Opperwall¹, Andrea Vacca¹

and Manuel Rigosi²

¹ Maha Fluid Power Research Center, Purdue University, 1500 Kepner dr., Lafayette, IN 47905, USA

² Casappa SpA, Via Balestrieri 1, Lemignano di Collecchio, 43044 Parma, Italy

Energies 2017, 10(7), 1068; https://doi.org/10.3390/en10071068 - 22 Jul 2017

Cited by 28 | Viewed by 9090

Abstract

As a key component in power transfer, positive displacement machines often represent the major source of noise in hydraulic systems. Thus, investigation into the sources of noise and discovering strategies to reduce noise is a key part of improving the performance of current [...] Read more.

As a key component in power transfer, positive displacement machines often represent the major source of noise in hydraulic systems. Thus, investigation into the sources of noise and discovering strategies to reduce noise is a key part of improving the performance of current hydraulic systems, as well as applying fluid power systems to a wider range of applications. The present work aims at developing modeling techniques on the topic of noise generation caused by external gear pumps for high pressure applications, which can be useful and effective in investigating the interaction between noise sources and radiated noise and establishing the design guide for a quiet pump. In particular, this study classifies the internal noise sources into four types of effective load functions and, in the proposed model, these load functions are applied to the corresponding areas of the pump case in a realistic way. Vibration and sound radiation can then be predicted using a combined finite element and boundary element vibro-acoustic model. The radiated sound power and sound pressure for the different operating conditions are presented as the main outcomes of the acoustic model. The noise prediction was validated through comparison with the experimentally measured sound power levels. Full article

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

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20 pages, 7825 KiB

Open AccessArticle

A Novel Workflow for Geothermal Prospectively Mapping Weights-of-Evidence in Liaoning Province, Northeast China

by Xuejia Sang¹, Linfu Xue^1,*, Jiwen Liu¹ and Liang Zhan^2,3

¹ College of Earth Science, Jilin University, Changchun 130061, China

² Xinjiang Uyghur Autonomous Region Academy of Surveying and Mapping, No. 231 Sandaowan East Road, Urumchi 830002, China

³ College of Information Sciences and Technology, Chengdu University of Technology, Chengdu 610059, China

Energies 2017, 10(7), 1069; https://doi.org/10.3390/en10071069 - 22 Jul 2017

Cited by 14 | Viewed by 4537

Abstract

Geological faults are highly developed in the eastern Liaoning Province in China, where Mesozoic granitic intrusions and Archean and Paleoproterozoic metamorphic rocks are widely distributed. Although the heat flow value in eastern Liaoning Province is generally low, the hot springs are very developed. [...] Read more.

Geological faults are highly developed in the eastern Liaoning Province in China, where Mesozoic granitic intrusions and Archean and Paleoproterozoic metamorphic rocks are widely distributed. Although the heat flow value in eastern Liaoning Province is generally low, the hot springs are very developed. It is obvious that the faults have significant control over the distribution of hot springs, and traditional methods of spatial data analysis such as WofE (weight of evidence) usually do not take into account the direction of the distribution of geothermal resources in the geothermal forecast process, which seriously affects the accuracy of the prediction results. To overcome the deficiency of the traditional evidence weight method, wherein it does not take the direction of evidence factor into account, this study put forward a combination of the Fry and WofE methods, Fry-WofE, based on geological observation, gravity, remote sensing, and DEM (digital elevation model) multivariate data. This study takes eastern Liaoning Province in China as an example, and the geothermal prospect was predicted respectively by the Fry-WofE and WofE methods from the statistical data on the spatial distribution of the exposed space of geothermal anomalies the surface. The result shows that the Fry-WofE method can achieve better prediction results when comparing the accuracy of these two methods. Based on the results of Fry-WofE prediction and water system extraction, 13 favorable geothermal prospect areas are delineated in eastern Liaoning Province. The Fry-WofE method is effective in study areas where the geothermal distribution area is obviously controlled by the fault. We provide not only a new method for solving the similar issue of geothermal exploration, but also a new insight into the distribution of geothermal resources in Liaoning Province. Full article

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

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16 pages, 8070 KiB

Open AccessArticle

Influence of the Steam Addition on Premixed Methane Air Combustion at Atmospheric Pressure

by Mao Li^*

, Yiheng Tong, Marcus Thern

and Jens Klingmann

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

Energies 2017, 10(7), 1070; https://doi.org/10.3390/en10071070 - 23 Jul 2017

Cited by 11 | Viewed by 5188

Abstract

Steam-diluted combustion in gas turbine systems is an effective approach to control pollutant emissions and improve the gas turbine efficiency. The primary purpose of the present research is to analyze the influence of steam dilution on the combustion stability, flame structures, and CO [...] Read more.

Steam-diluted combustion in gas turbine systems is an effective approach to control pollutant emissions and improve the gas turbine efficiency. The primary purpose of the present research is to analyze the influence of steam dilution on the combustion stability, flame structures, and CO emissions of a swirl-stabilized gas turbine model combustor under atmospheric pressure conditions. The premixed methane/air/steam flame was investigated with three preheating temperatures (384 K/434 K/484 K) and the equivalence ratio was varied from stoichiometric conditions to the flammability limits where the flame was physically blown out from the combustor. In order to represent the steam dilution intensity, the steam fraction Ω defined as the steam to air mass flow rate ratio was used in this work. Exhaust gases were sampled with a water-cooled emission probe which was mounted at the combustor exit. A 120 mm length quartz liner was used which enabled the flame visualization and optical measurement. Time-averaged CH chemiluminescence imaging was conducted to characterize the flame location and it was further analyzed with the inverse Abel transform method. Chemical kinetics calculation was conducted to support and analyze the experimental results. It was found that the LBO (lean blowout) limits were increased with steam fraction. CH chemiluminescence imaging showed that with a high steam fraction, the flame length was elongated, but the flame structure was not altered. CO emissions were mapped as a function of the steam fraction, inlet air temperature, and equivalence ratios. Stable combustion with low CO emission can be achieved with an appropriate steam fraction operation range. Full article

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

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16 pages, 1250 KiB

Open AccessArticle

Research on Capacitance Current Compensation Scheme of Current Differential Protection of Complex Four-Circuit Transmission Lines on the Same Tower

by Cui Tang^1,2,*

, Xianggen Yin^1,2 and Zhe Zhang^1,2

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

² Electric Power Security and High Efficiency Laboratory, Huazhong University of Science and Technology, Wuhan 430074, China

Energies 2017, 10(7), 1071; https://doi.org/10.3390/en10071071 - 23 Jul 2017

Cited by 5 | Viewed by 3840

Abstract

Current differential protection is the main protection of transmission lines which include multi-circuit lines on the same tower, and whose sensitivity and reliability of differential protection is mainly affected by the distributed capacitive current. For the four-circuit line on the same tower, due [...] Read more.

Current differential protection is the main protection of transmission lines which include multi-circuit lines on the same tower, and whose sensitivity and reliability of differential protection is mainly affected by the distributed capacitive current. For the four-circuit line on the same tower, due to the influence of coupling between the loop road, the distributed capacitance current increases significantly when compared with ordinary lines, affecting the sensitivity of the current differential protection, especially for different voltage levels throughout the four-circuit lines on the same tower. The relationship of the electrostatic coupling between the circuits is more complex, and increases the difficulty of the compensating the distributed capacitance current. This paper is based on the electrostatic coupling principle of four-circuit lines on the same tower, establishes the distributed parameter model of four-circuit transmission lines on the same tower, and discusses the effect of circuit operation mode on the compensation of capacitance current differential protection when different faults occur on the complex four-circuit transmission lines on the same tower. A new compensation scheme suitable for capacitive current compensation is proposed. Simulation results show that this capacitive current compensation scheme can effectively improve the performance of current differential protection. Full article

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

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