Energies

26 pages, 2494 KiB

Open AccessArticle

FHT: A Novel Approach for Filtering High-Availability Seamless Redundancy (HSR) Traffic

by Nguyen Xuan Tien

and Jong Myung Rhee^*

Department of Information and Communications Engineering, MPEES ARC, Myongji University, Yongin-si, Gyeonggi-do 449-728, Korea

Energies 2015, 8(7), 6249-6274; https://doi.org/10.3390/en8076249 - 25 Jun 2015

Cited by 11 | Viewed by 6574

Abstract

High-availability seamless redundancy (HSR) is a protocol for Ethernet networks that provides duplicated frames with zero recovery time in the event of any network component’s failure. It is suited for applications that demand high availability and a very short time-outs such as substation [...] Read more.

High-availability seamless redundancy (HSR) is a protocol for Ethernet networks that provides duplicated frames with zero recovery time in the event of any network component’s failure. It is suited for applications that demand high availability and a very short time-outs such as substation automation systems (SAS). However, HSR generates excessive unnecessary unicast frames and spreads them throughout connected-ring networks, whether or not the destination node exists in network’s rings. This unnecessary redundant traffic causes high bandwidth consumption, resulting in degradation of network performance. In this paper, we introduce a novel approach for filtering and reducing HSR unicast traffic in connected-ring networks, called “filtering HSR traffic” (FHT). The purpose of FHT is to filter HSR unicast traffic and remove circulated traffic for all rings in connected-ring networks. Therefore, FHT significantly reduces network unicast traffic in connected-ring networks. The traffic performance of FHT has been analyzed, evaluated, and compared to that of standard HSR protocol and the port locking (PL) approach. Various simulations were conducted to validate the traffic performance analysis. Analytical and simulation results showed that, for our sample network, FHT reduced network unicast traffic by about 82% compared with standard HSR and by about 56% compared with the PL approach, thus freeing up network bandwidth and improving network traffic performance. Full article

(This article belongs to the Collection Smart Grid)

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11 pages, 1775 KiB

Open AccessArticle

Investigation of the Anisotropic Thermoelectric Properties of Oriented Polycrystalline SnSe

by Yulong Li^1,2,3, Xun Shi^1,2,*, Dudi Ren^1,2, Jikun Chen^1,2 and Lidong Chen^1,2

¹ State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

² CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

³ University of Chinese Academy of Sciences, Beijing 100049, China

Energies 2015, 8(7), 6275-6285; https://doi.org/10.3390/en8076275 - 25 Jun 2015

Cited by 118 | Viewed by 9610

Abstract

Polycrystalline SnSe was synthesized by a melting-annealing-sintering process. X-ray diffraction reveals the sample possesses pure phase and strong orientation along [h00] direction. The degree of the orientations was estimated and the anisotropic thermoelectric properties are characterized. The polycrystalline sample shows a [...] Read more.

Polycrystalline SnSe was synthesized by a melting-annealing-sintering process. X-ray diffraction reveals the sample possesses pure phase and strong orientation along [h00] direction. The degree of the orientations was estimated and the anisotropic thermoelectric properties are characterized. The polycrystalline sample shows a low electrical conductivity and a positive and large Seebeck coefficient. The low thermal conductivity is also observed in polycrystalline sample, but slightly higher than that of single crystal. The minimum value of thermal conductivity was measured as 0.3 W/m·K at 790 K. With the increase of the orientation factor, both electrical and thermal conductivities decrease, but the thermopowers are unchanged. As a consequence, the zT values remain unchanged in the polycrystalline samples despite the large variation in the degree of orientation. Full article

(This article belongs to the Special Issue Thermoelectric Energy Harvesting)

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16 pages, 815 KiB

Open AccessArticle

Effects of Yaw Error on Wind Turbine Running Characteristics Based on the Equivalent Wind Speed Model

by Shuting Wan^1,*, Lifeng Cheng^1,* and Xiaoling Sheng^1,2

¹ School of Energy Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, China

² Department of Electrical Engineering, North China Electric Power University, Baoding 071003, China

Energies 2015, 8(7), 6286-6301; https://doi.org/10.3390/en8076286 - 25 Jun 2015

Cited by 69 | Viewed by 12240

Abstract

Natural wind is stochastic, being characterized by its speed and direction which change randomly and frequently. Because of the certain lag in control systems and the yaw body itself, wind turbines cannot be accurately aligned toward the wind direction when the wind speed [...] Read more.

Natural wind is stochastic, being characterized by its speed and direction which change randomly and frequently. Because of the certain lag in control systems and the yaw body itself, wind turbines cannot be accurately aligned toward the wind direction when the wind speed and wind direction change frequently. Thus, wind turbines often suffer from a series of engineering issues during operation, including frequent yaw, vibration overruns and downtime. This paper aims to study the effects of yaw error on wind turbine running characteristics at different wind speeds and control stages by establishing a wind turbine model, yaw error model and the equivalent wind speed model that includes the wind shear and tower shadow effects. Formulas for the relevant effect coefficients T_c, S_c and P_c were derived. The simulation results indicate that the effects of the aerodynamic torque, rotor speed and power output due to yaw error at different running stages are different and that the effect rules for each coefficient are not identical when the yaw error varies. These results may provide theoretical support for optimizing the yaw control strategies for each stage to increase the running stability of wind turbines and the utilization rate of wind energy. Full article

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26 pages, 2001 KiB

Open AccessArticle

Power Management Optimization of an Experimental Fuel Cell/Battery/Supercapacitor Hybrid System

by Farouk Odeim^*, Jürgen Roes and Angelika Heinzel

Chair of Energy Technology, University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany

Energies 2015, 8(7), 6302-6327; https://doi.org/10.3390/en8076302 - 25 Jun 2015

Cited by 103 | Viewed by 10614

Abstract

In this paper, an experimental fuel cell/battery/supercapacitor hybrid system is investigated in terms of modeling and power management design and optimization. The power management strategy is designed based on the role that should be played by each component of the hybrid power source. [...] Read more.

In this paper, an experimental fuel cell/battery/supercapacitor hybrid system is investigated in terms of modeling and power management design and optimization. The power management strategy is designed based on the role that should be played by each component of the hybrid power source. The supercapacitor is responsible for the peak power demands. The battery assists the supercapacitor in fulfilling the transient power demand by controlling its state-of-energy, whereas the fuel cell system, with its slow dynamics, controls the state-of-charge of the battery. The parameters of the power management strategy are optimized by a genetic algorithm and Pareto front analysis in a framework of multi-objective optimization, taking into account the hydrogen consumption, the battery loading and the acceleration performance. The optimization results are validated on a test bench composed of a fuel cell system (1.2 kW, 26 V), lithium polymer battery (30 Ah, 37 V), and a supercapacitor (167 F, 48 V). Full article

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

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22 pages, 892 KiB

Open AccessArticle

Improving Transient Stability in a Grid-Connected Squirrel-Cage Induction Generator Wind Turbine System Using a Fuzzy Logic Controller

by Minh Quan Duong^1,2,*, Francesco Grimaccia¹

, Sonia Leva¹

, Marco Mussetta¹

and Kim Hung Le²

¹ Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, 20156 Milano, Italy

² Department of Electrical Engineering, University of Science and Technology—The University of Da Nang, Block A, 54 Nguyen Luong Bang Street, LienChieu District, DaNang City 59000, Vietnam

Energies 2015, 8(7), 6328-6349; https://doi.org/10.3390/en8076328 - 25 Jun 2015

Cited by 51 | Viewed by 8415

Abstract

A common problem in wind power plants involves fixed-speed wind turbines. In fact, being equipped with a squirrel-cage induction generator (SCIG), they tend to drain a relevant amount of reactive power from the grid, potentially causing voltage drops and possible voltage instability. To [...] Read more.

A common problem in wind power plants involves fixed-speed wind turbines. In fact, being equipped with a squirrel-cage induction generator (SCIG), they tend to drain a relevant amount of reactive power from the grid, potentially causing voltage drops and possible voltage instability. To improve SCIG power quality and transient stability, this paper investigates a new control strategy for pitch angle control based on proportional-integral (PI) controller and a fuzzy logic controller (FLC), considering both normal and fault ride-through (FRT) schemes. In the literature, often, the mechanical torque output is assumed constant for a specific wind speed. This might not be accurate, because the mechanical torque-speed typical of a wind turbine depends also on the power coefficient or pitch angle. In this paper, an analytic model of transient stability is proposed using the equivalent circuit of the SCIG and using the concepts of stable and unstable electrical-mechanical equilibrium. The method has been evaluated by comparing the results obtained by the analytic method with the dynamic simulation. The results show that the proposed hybrid controller is effective at smoothing the output power and complying with FRT requirements for SCIG in the power system. Full article

(This article belongs to the Collection Wind Turbines)

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15 pages, 541 KiB

Open AccessArticle

Bio-Refining of Carbohydrate-Rich Food Waste for Biofuels

by Hoang-Tuong Nguyen Hao¹, Obulisamy Parthiba Karthikeyan^1,2 and Kirsten Heimann^1,2,3,4,*

¹ College of Marine and Environmental Sciences, James Cook University, Townsville 4811, Queensland, Australia

² Comparative Genomics Centre, James Cook University, Townsville 4811, Queensland, Australia

³ Centre for Bio-discovery and Molecular Development of Therapeutics, James Cook University, Townsville 4811, Queensland, Australia

⁴ Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville 4811, Queensland, Australia

Energies 2015, 8(7), 6350-6364; https://doi.org/10.3390/en8076350 - 25 Jun 2015

Cited by 35 | Viewed by 11803

Abstract

The global dependence on finite fossil fuel-derived energy is of serious concern given the predicted population increase. Over the past decades, bio-refining of woody biomass has received much attention, but data on food waste refining are sorely lacking, despite annual and global deposition [...] Read more.

The global dependence on finite fossil fuel-derived energy is of serious concern given the predicted population increase. Over the past decades, bio-refining of woody biomass has received much attention, but data on food waste refining are sorely lacking, despite annual and global deposition of 1.3 billion tons in landfills. In addition to negative environmental impacts, this represents a squandering of valuable energy, water and nutrient resources. The potential of carbohydrate-rich food waste (CRFW) for biofuel (by Rhodotorulla glutinis fermentation) and biogas production (by calculating theoretical methane yield) was therefore investigated using a novel integrated bio-refinery approach. In this approach, hydrolyzed CRFW from three different conditions was used for Rhodotorulla glutinis cultivation to produce biolipids, whilst residual solids after hydrolysis were characterized for methane recovery potential via anaerobic digestion. Initially, CRFW was hydrolysed using thermal- (Th), chemical- (Ch) and Th-Ch combined hydrolysis (TCh), with the CRFW-leachate serving as a control (Pcon). Excessive foaming led to the loss of TCh cultures, while day-7 biomass yields were similar (3.4–3.6 g dry weight (DW) L⁻¹) for the remaining treatments. Total fatty acid methyl ester (FAME) content of R. glutinis cultivated on CRFW hydrolysates were relatively low (~6.5%) but quality parameters (i.e., cetane number, density, viscosity and higher heating values) of biomass extracted biodiesel complied with ASTM standards. Despite low theoretical RS-derived methane potential, further research under optimised and scaled conditions will reveal the potential of this approach for the bio-refining of CRFW for energy recovery and value-added co-product production. Full article

(This article belongs to the Special Issue Bioenergy and Biorefining)

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17 pages, 1253 KiB

Open AccessArticle

An Experimental Investigation on the Combustion and Heat Release Characteristics of an Opposed-Piston Folded-Cranktrain Diesel Engine

by Fukang Ma^1,2

, Changlu Zhao¹, Fujun Zhang¹, Zhenfeng Zhao^1,*, Zhenyu Zhang¹, Zhaoyi Xie¹ and Hao Wang¹

¹ School of Mechanical and Vehicle Engineering, Beijing Institute of Technology, Zhongguancun South Street No.5, Beijing 100081, China

² School of Mechanical and Power Engineering, North University of China, University Road No.3, Taiyuan 030051, China

Energies 2015, 8(7), 6365-6381; https://doi.org/10.3390/en8076365 - 25 Jun 2015

Cited by 40 | Viewed by 8121

Abstract

In opposed-piston folded-cranktrain diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. The combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine under different operating conditions were investigated. [...] Read more.

In opposed-piston folded-cranktrain diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. The combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine under different operating conditions were investigated. Four phases: ignition delay, premixed combustion, diffusion combustion and after combustion are used to describe the heat release process of the engine. Load changing has a small effect on premixed combustion duration while it influences diffusion combustion duration significantly. The heat release process has more significant isochoric and isobaric combustion which differs from the conventional diesel engine situation, except at high exhaust pressure and temperature, due to its two-stroke and uniflow scavenging characteristics. Meanwhile, a relatively high-quality exhaust heat energy is produced in opposed-piston folded-cranktrain diesel engines. Full article

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

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Graphical abstract

17 pages, 1847 KiB

Open AccessArticle

Behavior of Beech Sawdust during Densification into a Solid Biofuel

by Peter Križan^*

, Miloš Matú, Ľubomír Šooš and Juraj Beniak

Institute of Manufacturing Systems, Environmental Technology and Quality Management, Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava, Nám. Slobody 17, 81231 Bratislava, Slovakia

Energies 2015, 8(7), 6382-6398; https://doi.org/10.3390/en8076382 - 25 Jun 2015

Cited by 54 | Viewed by 7883

Abstract

In solid biofuel manufacture technological and material variables influence the densification process and thus also the final briquette quality. The impact of these technological variables, especially compression pressure and compression temperature, and also of the material parameters (particle size and moisture content) can [...] Read more.

In solid biofuel manufacture technological and material variables influence the densification process and thus also the final briquette quality. The impact of these technological variables, especially compression pressure and compression temperature, and also of the material parameters (particle size and moisture content) can generally be observed during biomass densification in the quality indicators, where the abovementioned variables have a significant influence, especially on the mechanical indicators of quality (briquette density, mechanical durability, etc.). This paper presents the results of experimental research dealing with determining the relationship between the technological and the material variables during densification of beech sawdust. The main goal of the paper is to determine the mutual interaction between compression pressure, compression temperature and material particle size. Research findings were obtained using single-axis densification. The influence of the particle size interacting with compression pressure and compression temperature on the final briquette density was determined. The research findings obtained should prove valuable in briquette production and also in the engineering of densification machines. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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28 pages, 5014 KiB

Open AccessArticle

A Four-Phase High Voltage Conversion Ratio Bidirectional DC-DC Converter for Battery Applications

by Li-Kun Xue, Ping Wang, Yi-Feng Wang^*

, Tai-Zhou Bei and Hai-Yun Yan

School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China

Energies 2015, 8(7), 6399-6426; https://doi.org/10.3390/en8076399 - 25 Jun 2015

Cited by 9 | Viewed by 9619

Abstract

This study presents a four-phase interleaved high voltage conversion ratio bidirectional DC-DC converter circuit based on coupled inductors and switched capacitors, which can eliminate the defects of conventional high voltage conversion ratio bidirectional DC-DC converters in terms of high-voltage/current stress, less efficiency and [...] Read more.

This study presents a four-phase interleaved high voltage conversion ratio bidirectional DC-DC converter circuit based on coupled inductors and switched capacitors, which can eliminate the defects of conventional high voltage conversion ratio bidirectional DC-DC converters in terms of high-voltage/current stress, less efficiency and low-power limitation. Parallel channels are used to reduce current stress at the low-voltage side and series connected switched capacitors are used to enlarge voltage conversion ratio, reduce voltage stress and achieve auto current sharing. This paper proposes the operation principle, feature analysis and optimization design considerations. On this basis the objectives of high voltage conversion ratio, low voltage/current stress, high power density, high efficiency and high-power applications can be achieved. Some experimental results based on a 500 W prototype converter (24 V to 48 V at low-voltage side, 400 V at high-voltage side) are given to verify the theoretical analysis and the effectiveness of the proposed converter. Full article

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

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24 pages, 713 KiB

Open AccessArticle

Single-Source Multi-Battery Solar Charger: Analysis and Stability Issues

by Alon Kuperman^1,*

, Moshe Sitbon¹, Shlomo Gadelovits¹, Moshe Averbukh¹ and Teuvo Suntio²

¹ Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel

² Department of Electrical Engineering, Tampere University of Technology, Tampere FI-33101, Finland

Energies 2015, 8(7), 6427-6450; https://doi.org/10.3390/en8076427 - 25 Jun 2015

Cited by 11 | Viewed by 6029

Abstract

In this paper, dynamic analysis of a multi-battery dual mode charger, powered by a single solar array and suitable for lead-acid and lithium-ion cell-based batteries is presented. Each battery is interfaced to the solar array by means of a current-controlled buck power stage, [...] Read more.

In this paper, dynamic analysis of a multi-battery dual mode charger, powered by a single solar array and suitable for lead-acid and lithium-ion cell-based batteries is presented. Each battery is interfaced to the solar array by means of a current-controlled buck power stage, operating either in constant power or constant voltage mode. Operation in former/latter charging mode implies regulating input/output voltage of the converter, which is a non-trivial situation since while feeding different batteries, all the converters share the same input terminals, connected to the solar array. It is revealed that when at least one of the batteries operates in constant power charging mode, open-loop instability occurs whenever converter input voltage is lower than maximum power point voltage of the solar array. Consequently, input voltage regulating controller must be designed to stabilize closed-loop dynamics for the worst case of instability, which is also derived. Moreover, it is shown that the dynamics of the converters operating under output voltage control are perceived as disturbances by input voltage control loop and must be properly rejected. Simple loop shaping design is proposed based on a PI controller, allowing stabilizing the system in case of worst case instability and rejecting output voltage control induced disturbances at the expense of non-constant, operating-point dependent closed-loop damping. Full article

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17 pages, 356 KiB

Open AccessReview

Extrapolation of Transport Properties and Figure of Merit of a Thermoelectric Material

by H. Julian Goldsmid^1,* and Jeff Sharp²

¹ School of Physics, University of New South Wales, Sydney 2052, Australia

² Marlow Industries, Inc. (Subsidiary of II-VI Incorporated) 10451 Vista Park Rd., Dallas, TX 75238, USA

Energies 2015, 8(7), 6451-6467; https://doi.org/10.3390/en8076451 - 26 Jun 2015

Cited by 16 | Viewed by 6533

Abstract

The accurate determination of the thermoelectric properties of a material becomes increasingly difficult as the temperature rises. However, it is the properties at elevated temperatures that are important if thermoelectric generator efficiency is to be improved. It is shown that the dimensionless figure [...] Read more.

The accurate determination of the thermoelectric properties of a material becomes increasingly difficult as the temperature rises. However, it is the properties at elevated temperatures that are important if thermoelectric generator efficiency is to be improved. It is shown that the dimensionless figure of merit, ZT, might be expected to rise with temperature for a given material provided that minority carrier conduction can be avoided. It is, of course, also necessary that the material should remain stable over the whole operating range. We show that the prediction of high temperature properties in the extrinsic region is possible if the temperature dependence of carrier mobility and lattice thermal conductivity are known. Also, we show how the undesirable effects arising from mixed or intrinsic conduction can be calculated from the energy gap and the relative mobilities of the electrons and the positive holes. The processes involved are discussed in general terms and are illustrated for different systems. These comprise the bismuth telluride alloys, silicon-germanium alloys, magnesium-silicon-tin and higher manganese silicide. Full article

(This article belongs to the Special Issue Thermoelectric Energy Harvesting)

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29 pages, 5201 KiB

Open AccessArticle

Unraveling the Mysteries of Turbulence Transport in a Wind Farm

by Pankaj K. Jha¹, Earl P. N. Duque², Jessica L. Bashioum¹ and Sven Schmitz^1,*

¹ Department of Aerospace Engineering, the Pennsylvania State University, University Park, PA 16802, USA

² Applied Research Group, Intelligent Light, Rutherford, NJ 07070, USA

Energies 2015, 8(7), 6468-6496; https://doi.org/10.3390/en8076468 - 26 Jun 2015

Cited by 17 | Viewed by 8346

Abstract

A true physical understanding of the mysteries involved in the recovery process of the wake momentum deficit, downstream of utility-scale wind turbines in the atmosphere, has not been obtained to date. Field data are not acquired at sufficient spatial and temporal resolutions to [...] Read more.

A true physical understanding of the mysteries involved in the recovery process of the wake momentum deficit, downstream of utility-scale wind turbines in the atmosphere, has not been obtained to date. Field data are not acquired at sufficient spatial and temporal resolutions to dissect some of the mysteries of wake turbulence. It is here that the actuator line method has evolved to become the technology standard in the wind energy community. This work presents the actuator line method embedded into an Open source Field Operation and Manipulation (OpenFOAM) large-eddy simulation solver and applies it to two small wind farms, the first one consisting of an array of two National Renewable Energy Laboratory 5 Megawatt (NREL 5-MW) turbines separated by seven rotor diameters in neutral and unstable atmospheric boundary-layer flow and the second one consisting of five NREL 5-MW wind turbines in unstable atmospheric conditions arranged in two staggered arrays of two and three turbines, respectively. Detailed statistics involving power spectral density (PSD) of turbine power along with standard deviations reveal the effects of atmospheric turbulence and its space and time scales. High-resolution surface data extracts provide new insight into the complex recovery process of the wake momentum deficit governed by turbulence transport phenomena. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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Graphical abstract

12 pages, 1200 KiB

Open AccessArticle

Penetration of Photovoltaics in Greece

by Eugenia Giannini^1,*, Antonia Moropoulou¹, Zacharias Maroulis¹

and Glykeria Siouti²

¹ Department of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece

² Department of Law, National and Kapodistrian University of Athens, 10672 Athens, Greece

Energies 2015, 8(7), 6497-6508; https://doi.org/10.3390/en8076497 - 26 Jun 2015

Cited by 14 | Viewed by 5603

Abstract

Recently, an interesting experiment was completed in Greece concerning photovoltaic penetration into the electricity production sector. Based on the relevant laws and in accordance to the related European directives, an explosive penetration process was completed in less than three years, resulting in a [...] Read more.

Recently, an interesting experiment was completed in Greece concerning photovoltaic penetration into the electricity production sector. Based on the relevant laws and in accordance to the related European directives, an explosive penetration process was completed in less than three years, resulting in a 7% share of photovoltaics in electricity production instead of the previous negligible share. The legislation was based on licensing simplification and generous feed-in-tariffs. This approach transformed photovoltaic technology from a prohibitively expensive to a competitive one. This work aims to summarize the relevant legislation and illustrate its effect on the resulting penetration. A sigmoid-shape penetration was observed which was explained by a pulse-type driving force. The return on investment indicator was proposed as an appropriate driving force, which incorporates feed-in-tariffs and turnkey-cost. Furthermore, the resulting surcharge on the electricity price due to photovoltaic penetration was also analyzed. Full article

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

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19 pages, 501 KiB

Open AccessArticle

Model-based Sensor Fault Diagnosis of a Lithium-ion Battery in Electric Vehicles

by Zhentong Liu and Hongwen He^*

Collaborative Innovation Center of Electric Vehicles in Beijing, National Engineering Laboratory for Electric Vehicles, Beijing Institute of Technology, Beijing 100081, China

Energies 2015, 8(7), 6509-6527; https://doi.org/10.3390/en8076509 - 26 Jun 2015

Cited by 95 | Viewed by 10633

Abstract

The battery critical functions such as State-of-Charge (SoC) and State-of-Health (SoH) estimations, over-current, and over-/under-voltage protections mainly depend on current and voltage sensor measurements. Therefore, it is imperative to develop a reliable sensor fault diagnosis scheme to guarantee the battery performance, safety and [...] Read more.

The battery critical functions such as State-of-Charge (SoC) and State-of-Health (SoH) estimations, over-current, and over-/under-voltage protections mainly depend on current and voltage sensor measurements. Therefore, it is imperative to develop a reliable sensor fault diagnosis scheme to guarantee the battery performance, safety and life. This paper presents a systematic model-based fault diagnosis scheme for a battery cell to detect current or voltage sensor faults. The battery model is developed based on the equivalent circuit technique. For the diagnostic scheme implementation, the extended Kalman filter (EKF) is used to estimate the terminal voltage of battery cell, and the residual carrying fault information is then generated by comparing the measured and estimated voltage. Further, the residual is evaluated by a statistical inference method that determines the presence of a fault. To highlight the importance of battery sensor fault diagnosis, the effects of sensors faults on battery SoC estimation and possible influences are analyzed. Finally, the effectiveness of the proposed diagnostic scheme is experimentally validated, and the results show that the current or voltage sensor fault can be accurately detected. Full article

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

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15 pages, 1061 KiB

Open AccessArticle

Nonlinear Passive Control of a Wave Energy Converter Subject to Constraints in Irregular Waves

by Liguo Wang^*

and Jan Isberg

Department of Engineering Sciences, Swedish Centre for Renewable Electric Energy Conversion, Division of Electricity, the Ångström Laboratory, Uppsala University, P.O. Box 534, 75121 Uppsala, Sweden

Energies 2015, 8(7), 6528-6542; https://doi.org/10.3390/en8076528 - 29 Jun 2015

Cited by 42 | Viewed by 6905

Abstract

This paper investigates a passive control method of a point absorbing wave energy converter by considering the displacement and velocity constraints under irregular waves in the time domain. A linear generator is used as a power take-off unit, and the equivalent damping force [...] Read more.

This paper investigates a passive control method of a point absorbing wave energy converter by considering the displacement and velocity constraints under irregular waves in the time domain. A linear generator is used as a power take-off unit, and the equivalent damping force is optimized to improve the power production of the wave energy converter. The results from nonlinear and linear passive control methods are compared, and indicate that the nonlinear passive control method leads to the excitation force in phase with the velocity of the converter that can significantly improve the energy production of the converter. Full article

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23 pages, 1471 KiB

Open AccessArticle

A New Data-Stream-Mining-Based Battery Equalization Method

by Cheng Lin, Hao Mu, Li Zhao^* and Wanke Cao

National Engineering Laboratory for Electric Vehicles, Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Institute of Technology, Beijing 100081, China

Energies 2015, 8(7), 6543-6565; https://doi.org/10.3390/en8076543 - 30 Jun 2015

Cited by 9 | Viewed by 5638

Abstract

Balancing battery cells is a key task for battery management systems (BMS). Imbalances of cells decrease the capacity and lifetime of the battery pack. Many balancing topologies and strategies have been proposed to balance the electric charges among cells and most of the [...] Read more.

Balancing battery cells is a key task for battery management systems (BMS). Imbalances of cells decrease the capacity and lifetime of the battery pack. Many balancing topologies and strategies have been proposed to balance the electric charges among cells and most of the intelligent control strategies select cells (to shuttle charges) by comparing their terminal voltages. However, the nature of battery equalization is to balance the energy stored in individual cells. The measured terminal voltage is just an external characteristic and cannot accurately reflect the state of charge (SOC) of the cell, especially in a noisy environment. Additionally, when the consistencies of cells are very poor, balancing the cells with terminal voltages will lead to serious errors. In this paper, we introduced a novel battery balancing method, in which the charge-balancing criterion was not the cell voltage, but the shuttling capacities among cells. Data stream mining (DSM) technique was used to calculate the shuttling capacities. A single switched capacitor (SSC) based cell balancing topology was used to test the performance of the proposed method. With the obtained summary information, the cells, the sequence, and the quantity of the equalized charge can be decided automatically by the proposed algorithm. The simulation and experiment results have shown that the proposed method was effective and convenient. Full article

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19 pages, 1304 KiB

Open AccessArticle

Design and Experimental Analysis of an Exhaust Air Energy Recovery Wind Turbine Generator

by Ahmad Fazlizan¹, Wen Tong Chong^1,*

, Sook Yee Yip², Wooi Ping Hew² and Sin Chew Poh¹

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

² UM Power Energy Dedicated Advanced Centre, University of Malaya, Level 4, Wisma R&D, Jalan Pantai Baharu, 59990 Kuala Lumpur, Malaysia

Energies 2015, 8(7), 6566-6584; https://doi.org/10.3390/en8076566 - 30 Jun 2015

Cited by 23 | Viewed by 11372

Abstract

A vertical axis wind turbine (VAWT) was positioned at the discharge outlet of a cooling tower electricity generator. To avoid a negative impact on the performance of the cooling tower and to optimize the turbine performance, the determination of the VAWT position in [...] Read more.

A vertical axis wind turbine (VAWT) was positioned at the discharge outlet of a cooling tower electricity generator. To avoid a negative impact on the performance of the cooling tower and to optimize the turbine performance, the determination of the VAWT position in the discharge wind stream was conducted by experiment. The preferable VAWT position is where the higher wind velocity matches the positive torque area of the turbine rotation. With the proper matching among the VAWT configurations (blade number, airfoil type, operating tip-speed-ratio, etc.) and exhaust air profile, the turbine system was not only able to recover the wasted kinetic energy, it also reduced the fan motor power consumption by 4.5% and increased the cooling tower intake air flow-rate by 11%. The VAWT had a free running rotational speed of 479 rpm, power coefficient of 10.6%, and tip-speed-ratio of 1.88. The double multiple stream tube theory was used to explain the VAWT behavior in the non-uniform wind stream. For the actual size of a cooling tower with a 2.4 m outlet diameter and powered by a 7.5 kW fan motor, it was estimated that a system with two VAWTs (side-by-side) can generate 1 kW of power which is equivalent to 13% of energy recovery. Full article

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

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23 pages, 5006 KiB

Open AccessArticle

Wind Speed Forecasting Based on FEEMD and LSSVM Optimized by the Bat Algorithm

by Wei Sun^†, Mohan Liu^* and Yi Liang^†

¹ Department of Business Administration, North China Electric Power University, Baoding 071000, China

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6585-6607; https://doi.org/10.3390/en8076585 - 30 Jun 2015

Cited by 46 | Viewed by 6651

Abstract

Affected by various environmental factors, wind speed presents high fluctuation, nonlinear and non-stationary characteristics. To evaluate wind energy properly and efficiently, this paper proposes a modified fast ensemble empirical model decomposition (FEEMD)-bat algorithm (BA)-least support vector machines (LSSVM) (FEEMD-BA-LSSVM) model combined with input [...] Read more.

Affected by various environmental factors, wind speed presents high fluctuation, nonlinear and non-stationary characteristics. To evaluate wind energy properly and efficiently, this paper proposes a modified fast ensemble empirical model decomposition (FEEMD)-bat algorithm (BA)-least support vector machines (LSSVM) (FEEMD-BA-LSSVM) model combined with input selected by deep quantitative analysis. The original wind speed series are first decomposed into a limited number of intrinsic mode functions (IMFs) with one residual series. Then a LSSVM is built to forecast these sub-series. In order to select input from environment variables, Cointegration and Granger causality tests are proposed to check the influence of temperature with different leading lengths. Partial correlation is applied to analyze the inner relationships between the historical speeds thus to select the LSSVM input. The parameters in LSSVM are fine-tuned by BA to ensure the generalization of LSSVM. The forecasting results suggest the hybrid approach outperforms the compared models. Full article

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19 pages, 1364 KiB

Open AccessArticle

Development of an Axial Flux MEMS BLDC Micromotor with Increased Efficiency and Power Density

by Xiaofeng Ding¹, Guanliang Liu^1,†, Min Du^1,†, Hong Guo¹, Hao Qian^1,* and Christopher Gerada²

¹ School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China

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

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6608-6626; https://doi.org/10.3390/en8076608 - 30 Jun 2015

Cited by 12 | Viewed by 8307 | Correction

Abstract

This paper presents a rigorous design and optimization of an axial flux microelectromechanical systems (MEMS) brushless dc (BLDC) micromotor with dual rotor improving both efficiency and power density with an external diameter of only around 10 mm. The stator is made of two [...] Read more.

This paper presents a rigorous design and optimization of an axial flux microelectromechanical systems (MEMS) brushless dc (BLDC) micromotor with dual rotor improving both efficiency and power density with an external diameter of only around 10 mm. The stator is made of two layers of windings by MEMS technology. The rotor is developed by film permanent magnets assembled over the rotor yoke. The characteristics of the MEMS micromotor are analyzed and modeled through a 3-D magnetic equivalent circuit (MEC) taking the leakage flux and fringing effect into account. Such a model yields a relatively accurate prediction of the flux in the air gap, back electromotive force (EMF) and electromagnetic torque, whilst being computationally efficient. Based on 3-D MEC model the multi-objective firefly algorithm (MOFA) is developed for the optimal design of this special machine. Both 3-D finite element (FE) simulation and experiments are employed to validate the MEC model and MOFA optimization design. Full article

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14 pages, 1316 KiB

Open AccessCase Report

The Role of Technical Innovation and Sustainability on Energy Consumption: A Case Study on the Taiwanese Automobile Industry

by Chao-Wu Chou¹, Wen-Chih Liao¹, Simon Wu² and Hui-Ming Wee^3,*

¹ Department of Business Administration, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

² Vigor Management Technology Academy, Vigor Management Technology Group, C7, Far Eastern Part, Yu Yao Economic Development Section, Ningbo 315211, Zhejiang, China

³ Department of Industrial and Systems Engineering, Chung Yuan Christian University, 200 Chung Pei Rd., Chungli 32023, Taiwan

Energies 2015, 8(7), 6627-6640; https://doi.org/10.3390/en8076627 - 30 Jun 2015

Cited by 7 | Viewed by 6089

Abstract

The impact of global warming and climate change is one of the most critical challenges of the 21st century. The greenhouse effect caused by technological development and industrial pollution has accelerated the speed of global warming. The continuous improvement in automobile energy consumption [...] Read more.

The impact of global warming and climate change is one of the most critical challenges of the 21st century. The greenhouse effect caused by technological development and industrial pollution has accelerated the speed of global warming. The continuous improvement in automobile energy consumption is one of the most effective ways to reduce global warming. A comparative analysis is proposed to examine the various automobiles that utilize technological innovation to improve their energy consumption. Their contribution to CO₂ emissions is then investigated. This study focuses on technical innovation and output power of a conventional engine. The results indicate that innovative engines (such as the Ford turbo petrol/diesel engine, the EcoBoost/TDCi) have improved energy consumption and reduce CO₂ emissions. In addition, the Toyota hybrid vehicles have also improved energy consumption and reduced greenhouse gases emissions. Full article

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17 pages, 1243 KiB

Open AccessArticle

Proof of Concept of an Irradiance Estimation System for Reconfigurable Photovoltaic Arrays

by Vincenzo Li Vigni, Damiano La Manna, Eleonora Riva Sanseverino^*, Vincenzo Di Dio, Pietro Romano

, Pietro Di Buono, Maurizio Pinto, Rosario Miceli and Costantino Giaconia

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

Energies 2015, 8(7), 6641-6657; https://doi.org/10.3390/en8076641 - 30 Jun 2015

Cited by 31 | Viewed by 6643

Abstract

In order to reduce the mismatch effect caused by non-uniform shadows in PV arrays, reconfigurable interconnections approaches have been recently proposed in the literature. These systems usually require the knowledge of the solar radiation affecting every solar module. The aim of this work [...] Read more.

In order to reduce the mismatch effect caused by non-uniform shadows in PV arrays, reconfigurable interconnections approaches have been recently proposed in the literature. These systems usually require the knowledge of the solar radiation affecting every solar module. The aim of this work is to evaluate the effectiveness of three irradiance estimation approaches in order to define which can be well suited for reconfigurable PV arrays. It is presented a real-time solar irradiance estimation device (IrradEst), implementing the three different estimation methods. The proposed system is based on mathematical models of PV modules enabling to estimate irradiation values by sensing a combination of temperature, voltage and current of a PV module. Experimental results showed generally good agreement between the estimated irradiances and the measurements performed by a standard pyranometer taken as reference. Finally one of the three methods was selected as possible solution for a reconfigurable PV system. Full article

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14 pages, 1733 KiB

Open AccessArticle

Savings in Cooling Energy with a Thermal Management System for LED Lighting in Office Buildings

by Byung-Lip Ahn^1,2, Ji-Woo Park¹, Seunghwan Yoo¹, Jonghun Kim¹, Seung-Bok Leigh² and Cheol-Yong Jang^1,*

¹ Energy Saving Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Korea

² Department of Architectural Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea

Energies 2015, 8(7), 6658-6671; https://doi.org/10.3390/en8076658 - 30 Jun 2015

Cited by 22 | Viewed by 7359

Abstract

Light-emitting diode (LED) lighting should be considered for lighting efficiency enhancement, however, waste heat from light-emitting diode (LED) lighting increases the internal cooling load during the summer season. In order to solve this problem we propose a thermal management system for light-emitting diode [...] Read more.

Light-emitting diode (LED) lighting should be considered for lighting efficiency enhancement, however, waste heat from light-emitting diode (LED) lighting increases the internal cooling load during the summer season. In order to solve this problem we propose a thermal management system for light-emitting diode (LED) lighting with a heat exchanger module integrated with the building’s heating, ventilation, and air conditioning (HVAC) system to move the lighting’s waste heat outdoors. An experiment was carried out to investigate the thermal effects in a test chamber and the heat exchange rate between the heat sink and the duct air. The heat generated by the light-emitting diode (LED) lighting was calculated as 78.1% of light-emitting diode (LED) input power and the heat exchange rate of the lighting heat exchange module was estimated to be between 86.5% and 98.1% according to the light-emitting diode (LED) input power and the flow rate of air passing the heat sink. As a result, the average light-emitting diode (LED) lighting heat contribution rate for internal heat gain was determined as 0.05; this value was used to calculate the heating and cooling energy demand of the office building through an energy simulation program. In the simulation results, the cooling energy demand was reduced by 19.2% compared with the case of conventionally installed light-emitting diode (LED) lighting. Full article

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33 pages, 5041 KiB

Open AccessArticle

Three-Phase High-Power and Zero-Current-Switching OBC for Plug-In Electric Vehicles

by Cheng-Shan Wang¹, Wei Li^1,†, Zhun Meng^1,†, Yi-Feng Wang^1,*

and Jie-Gui Zhou²

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

² The Third Railway Survey and Design Institute Group Corporation, Tianjin 300251, China

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6672-6704; https://doi.org/10.3390/en8076672 - 30 Jun 2015

Cited by 5 | Viewed by 8633

Abstract

In this paper, an interleaved high-power zero-current-switching (ZCS) onboard charger (OBC) based on the three-phase single-switch buck rectifier is proposed for application to plug-in electric vehicles (EVs). The multi-resonant structure is used to achieve high efficiency and high power density, which are necessary [...] Read more.

In this paper, an interleaved high-power zero-current-switching (ZCS) onboard charger (OBC) based on the three-phase single-switch buck rectifier is proposed for application to plug-in electric vehicles (EVs). The multi-resonant structure is used to achieve high efficiency and high power density, which are necessary to reduce the volume and weight of the OBC. This study focuses on the border conditions of ZCS converting with a battery load, which means the variation ranges of the output voltage and current are very large. Furthermore, a novel hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation (PWM) together is presented to ensure a driving frequency higher than 10 kHz, and this will reduce the unexpected inner resonant power flow and decrease the total harmonic distortion (THD) of the input current under a light load at the end of the charging process. Finally, a prototype is established, and experiments are carried out. According to the experimental results, the conversion efficiency is higher than 93.5%, the THD about 4.3% and power factor (PF) 0.98 under the maximum power output condition. Besides, a three-stage charging process is also carried out the experimental platform. Full article

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

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10 pages, 1758 KiB

Open AccessArticle

Simulation of Syngas Production from Lignin Using Guaiacol as a Model Compound

by Nancy Eloísa Rodríguez-Olalde¹, Erick Alejandro Mendoza-Chávez¹, Agustín Jaime Castro-Montoya^1,*, Jaime Saucedo-Luna¹, Rafael Maya-Yescas¹, José Guadalupe Rutiaga-Quiñones² and José María Ponce Ortega¹

¹ Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo. Edificio "V1", Ciudad Universitaria, 58060, Morelia, Michoacán, Mexico

² Facultad de Ingeniería en Tecnología de la Madera, Universidad Michoacana de San Nicolás de Hidalgo. Edificio "D", Ciudad Universitaria, 58060, Morelia, Michoacán, Mexico

Energies 2015, 8(7), 6705-6714; https://doi.org/10.3390/en8076705 - 30 Jun 2015

Cited by 18 | Viewed by 6026

Abstract

Lignin is an abundant component in biomass that can be used a feedstock for producing several value-added products, including biofuels. However, lignin is a complex molecule (involving in its structure three types of phenylpropane units: coumaryl, coniferyl and sinapyl), which is difficult to [...] Read more.

Lignin is an abundant component in biomass that can be used a feedstock for producing several value-added products, including biofuels. However, lignin is a complex molecule (involving in its structure three types of phenylpropane units: coumaryl, coniferyl and sinapyl), which is difficult to implement in any process simulation task. The lignin from softwood is formed mainly by coniferyl units; therefore, in this work the use of the guaiacol molecule to model softwood lignin in the simulation of the syngas process (H₂ + CO) is proposed. A Gibbs reactor in ASPEN PLUS^® was feed with ratios of water and guaiacol from 0.5 to 20. The pressure was varied from 0.05 to 1.01 MPa and the temperature in the range of 200–3200 °C. H₂, CO, CO₂, CH₄, O₂ and C as graphite were considered in the output stream. The pressure, temperature and ratio water/guaiacol conditions for syngas production for different H₂/CO ratio are discussed. The obtained results allow to determine the operating conditions to improve the syngas production and show that C as graphite and water decomposition can be avoided. Full article

(This article belongs to the Special Issue Recent Advances in Coal Combustion and Gasification)

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23 pages, 2752 KiB

Open AccessArticle

Battery Design for Successful Electrification in Public Transport

by Susanne Rothgang^1,2,*, Matthias Rogge^1,2, Jan Becker^1,2 and Dirk Uwe Sauer^1,2,3

¹ Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, Jägerstr. 17/19, 52066 Aachen, Germany

² Aachen Research Alliance, JARA-Energy, 52425 Jülich, Germany

³ Institute for Power Generation and Storage Systems (PGS), E.ON Energy Research Center, RWTH Aachen University, Mathieustr. 10, 52074 Aachen, Germany

Energies 2015, 8(7), 6715-6737; https://doi.org/10.3390/en8076715 - 30 Jun 2015

Cited by 44 | Viewed by 10891

Abstract

Public transport is an especially promising sector for full electric vehicles due to the high amount of cycles and predictable workload. This leads to a high amount of different vehicle concepts ranging from large batteries, designed for a full day of operation without [...] Read more.

Public transport is an especially promising sector for full electric vehicles due to the high amount of cycles and predictable workload. This leads to a high amount of different vehicle concepts ranging from large batteries, designed for a full day of operation without charging, to fast-charging systems with charging power up to a few hundred kilowatts. Hence, many different issues have to be addressed in the whole design and production process regarding high-voltage (HV) batteries for buses. In this work, the design process for electric public buses is analyzed in detail, based on two systems developed by the research projects Smart Wheels/econnect and SEB eÖPNV. The complete development process starting, with the demand analysis and the operating scenario, including the charging routine, is discussed. This paper also features details on cell selection and cost estimations as well as technical details on the system layout, such as the management system and passive components as well as thermal management. Full article

(This article belongs to the Special Issue Electrical Power and Energy Systems for Transportation Applications)

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27 pages, 9474 KiB

Open AccessArticle

Models of Talik, Permafrost and Gas Hydrate Histories—Beaufort Mackenzie Basin, Canada

by Jacek Majorowicz^1,*, Kirk Osadetz^2,† and Jan Safanda^3,†

¹ Northern Geothermal Consult, 105 Carlson Close, Edmonton, AB T6R 2J8, Canada

² Containment and Monitoring Institute (CaMI), CMC Research Institutes Inc., 3535 Research Road NW, Calgary, AB T2L 2K8, Canada

³ Institute of Geophysics, Czech Academy of Science, Prague 14131, Czech Republic

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6738-6764; https://doi.org/10.3390/en8076738 - 30 Jun 2015

Cited by 14 | Viewed by 6643

Abstract

Models of talik, permafrost and gas hydrate (GH) histories below shallow lakes are investigated and compared to models of Beaufort Mackenzie Basin (BMB) GH occurrences to describe lacustrine inundation effects, which are compared against factors controlling the variations among Mackenzie Delta (MD) permafrost, [...] Read more.

Models of talik, permafrost and gas hydrate (GH) histories below shallow lakes are investigated and compared to models of Beaufort Mackenzie Basin (BMB) GH occurrences to describe lacustrine inundation effects, which are compared against factors controlling the variations among Mackenzie Delta (MD) permafrost, GH and talik occurrence. Models using a 2–4 °C boundary temperature range indicate that geological setting, specifically underlying lithology and porosity, are the primary controls in talik formation below lakes. Below a lake of any size, where the underlying lithology is sandy it is practically impossible to produce a pervasive talik or to completely degrade significant GH accumulations in response to the boundary condition thermal effects alone. Models predict that talik formation is, in such cases, restricted to the upper few tens of meters below the lake. Permafrost degradation appears common where porosities are <40% and water bottom temperatures reach 2–4 °C, in both marine and lacustrine settings. Where porosities are higher a thin GH stability zone can persist, even where deep taliks have formed. Full article

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30 pages, 861 KiB

Open AccessReview

A Review of Hydrothermal Liquefaction Bio-Crude Properties and Prospects for Upgrading to Transportation Fuels

by Jerome A. Ramirez¹, Richard J. Brown^1,2,† and Thomas J. Rainey^1,2,*,†

¹ School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, 2 George St, Brisbane, Queensland 4000, Australia

² Biofuel Engine Research Facility, Queensland University of Technology, 2 George St, Brisbane, Queensland 4000, Australia

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6765-6794; https://doi.org/10.3390/en8076765 - 1 Jul 2015

Cited by 226 | Viewed by 31118

Abstract

Hydrothermal liquefaction (HTL) presents a viable route for converting a vast range of materials into liquid fuel, without the need for pre-drying. Currently, HTL studies produce bio-crude with properties that fall short of diesel or biodiesel standards. Upgrading bio-crude improves the physical and [...] Read more.

Hydrothermal liquefaction (HTL) presents a viable route for converting a vast range of materials into liquid fuel, without the need for pre-drying. Currently, HTL studies produce bio-crude with properties that fall short of diesel or biodiesel standards. Upgrading bio-crude improves the physical and chemical properties to produce a fuel corresponding to diesel or biodiesel. Properties such as viscosity, density, heating value, oxygen, nitrogen and sulphur content, and chemical composition can be modified towards meeting fuel standards using strategies such as solvent extraction, distillation, hydrodeoxygenation and catalytic cracking. This article presents a review of the upgrading technologies available, and how they might be used to make HTL bio-crude into a transportation fuel that meets current fuel property standards. Full article

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11 pages, 547 KiB

Open AccessArticle

Effect of Recycle Solvent Hydrotreatment on Oil Yield of Direct Coal Liquefaction

by Shansong Gao¹, Dexiang Zhang^1,* and Kejian Li²

¹ School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China

² National Engineering Laboratory for Direct Coal Liquefaction, Shanghai 201108, China

Energies 2015, 8(7), 6795-6805; https://doi.org/10.3390/en8076795 - 1 Jul 2015

Cited by 16 | Viewed by 5381

Abstract

Effects of the recycle solvent hydrotreatment on oil yield of direct coal liquefaction were carried out in the 0.18 t/day direct coal liquefaction bench support unit of National Engineering Laboratory for Direct Coal Liquefaction (China). Results showed that the hydrogen-donating ability of the [...] Read more.

Effects of the recycle solvent hydrotreatment on oil yield of direct coal liquefaction were carried out in the 0.18 t/day direct coal liquefaction bench support unit of National Engineering Laboratory for Direct Coal Liquefaction (China). Results showed that the hydrogen-donating ability of the hydrogenated recycle solvent improved and the hydrogen consumption of solvent hydrotreatment was increased by decreasing liquid hourly space velocity (LHSV) from 1.5 to 1.0 h⁻¹ and increasing reaction pressure from 13.7 to 19.0 MPa. The hydrogen-donating ability of the hydrogenated recycle solvent was enhanced, thus promoting the oil yield and coal conversion of the liquefaction reaction. The coal conversion and distillates yield of coal liquefaction were increased from 88.74% to 88.82% and from 47.41% to 49.10%, respectively, with the increase in the solvent hydrotreatment pressure from 13.7 to 19.0 MPa. The coal conversion and distillates of coal liquefaction were increased from 88.82% to 89.27% and from 49.10% to 54.49%, respectively, when the LHSV decreased from 1.5 to 1.0 h⁻¹ under the solvent hydrotreatment pressure of 19.0 MPa. Full article

(This article belongs to the Special Issue Recent Advances in Coal Combustion and Gasification)

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14 pages, 3190 KiB

Open AccessArticle

An Electric Bus with a Battery Exchange System

by Jeongyong Kim^1,†, Inho Song^2,† and Woongchul Choi^3,*,†

¹ Graduate School of Automotive Engineering, Kookmin University, 77 Jeongneung-Ro, Seongbuk-Gu, Seoul 136-702, Korea

² Department of Automotive and Transportation Design, Kookmin University, 77 Jeongneung-Ro, Seongbuk-Gu, Seoul 136-702, Korea

³ Department of Automotive Engineering, Kookmin University, 77 Jeongneung-Ro, Seongbuk-Gu, Seoul 136-702, Korea

^† These authors contributed equally to this work.

Energies 2015, 8(7), 6806-6819; https://doi.org/10.3390/en8076806 - 7 Jul 2015

Cited by 34 | Viewed by 10636

Abstract

As part of the ongoing effort to be independent of petroleum resources and to be free from pollutant emission issues, various electric vehicles have been developed and tested through their integration with real world systems. In the current paper, yet another application specific [...] Read more.

As part of the ongoing effort to be independent of petroleum resources and to be free from pollutant emission issues, various electric vehicles have been developed and tested through their integration with real world systems. In the current paper, yet another application specific EV for public transportation, an electric bus, is introduced and explained with results from the pilot test program which was carried out under real traffic conditions. The main feature of the current system is a battery exchanging mechanism mounted on the roof of the bus. The current configuration certainly requires an externally fabricated battery exchanging robot system that would complement the electric bus for a fully automated battery exchanging process. The major advantage of the current system is the quick re-charging of the electric energy through the physical battery exchange and the possible utilization of the battery exchange station as a mini scale energy storage system for grid system peak power shaving. With the total system solution approach for the public transportation system, it is fully expected to create outstanding business opportunities in number of areas such as battery suppliers, battery exchanging station management, battery leasing and many more. Full article

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

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21 pages, 3613 KiB

Open AccessArticle

Wheel Slip Control for Improving Traction-Ability and Energy Efficiency of a Personal Electric Vehicle

by Kanghyun Nam¹, Yoichi Hori² and Choonyoung Lee^3,*

¹ School of Mechanical Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan 712-749, Korea

² Department of Advanced Energy, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Chiba 277-8561, Japan

³ School of Mechanical Engineering, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 702-701, Korea

Energies 2015, 8(7), 6820-6840; https://doi.org/10.3390/en8076820 - 7 Jul 2015

Cited by 76 | Viewed by 15852

Abstract

In this paper, a robust wheel slip control system based on a sliding mode controller is proposed for improving traction-ability and reducing energy consumption during sudden acceleration for a personal electric vehicle. Sliding mode control techniques have been employed widely in the development [...] Read more.

In this paper, a robust wheel slip control system based on a sliding mode controller is proposed for improving traction-ability and reducing energy consumption during sudden acceleration for a personal electric vehicle. Sliding mode control techniques have been employed widely in the development of a robust wheel slip controller of conventional internal combustion engine vehicles due to their application effectiveness in nonlinear systems and robustness against model uncertainties and disturbances. A practical slip control system which takes advantage of the features of electric motors is proposed and an algorithm for vehicle velocity estimation is also introduced. The vehicle velocity estimator was designed based on rotational wheel dynamics, measurable motor torque, and wheel velocity as well as rule-based logic. The simulations and experiments were carried out using both CarSim software and an experimental electric vehicle equipped with in-wheel-motors. Through field tests, traction performance and effectiveness in terms of energy saving were all verified. Comparative experiments with variations of control variables proved the effectiveness and practicality of the proposed control design. Full article

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

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18 pages, 1750 KiB

Open AccessArticle

A High Performance PSO-Based Global MPP Tracker for a PV Power Generation System

by Kuei-Hsiang Chao

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

Energies 2015, 8(7), 6841-6858; https://doi.org/10.3390/en8076841 - 7 Jul 2015

Cited by 13 | Viewed by 7255

Abstract

This paper aims to present an improved version of a typical particle swarm optimization (PSO) algorithm, such that the global maximum power point (MPP) on a P-V characteristic curve with multiple peaks can be located in an efficient and precise manner for a [...] Read more.

This paper aims to present an improved version of a typical particle swarm optimization (PSO) algorithm, such that the global maximum power point (MPP) on a P-V characteristic curve with multiple peaks can be located in an efficient and precise manner for a photovoltaic module array. A series of instrumental measurements are conducted on variously configured arrays built with SANYO HIP2717 PV modules, either unshaded, partially shaded, or malfunctioning, as the building blocks. There appear two, triple and quadruple peaks on the corresponding P-V characteristic curves. Subsequently, the tracking performance comparisons, made by some practical experiments, indicate the superiority of this improved MPP tracking algorithm over the typical one. Full article

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22 pages, 2280 KiB

Open AccessArticle

Modeling on the Effect of Coal Loads on Kinetic Energy of Balls for Ball Mills

by Yan Bai and Fang He^*

School of Control and Computer Engineering, North China Electric Power University, Beijing 102206, China

Energies 2015, 8(7), 6859-6880; https://doi.org/10.3390/en8076859 - 9 Jul 2015

Cited by 6 | Viewed by 6577

Abstract

This paper presents a solution for the detection and control of coal loads that is more accurate and convenient than those currently used. To date, no research has addressed the use of a grinding medium as the controlled parameter. To improve the accuracy [...] Read more.

This paper presents a solution for the detection and control of coal loads that is more accurate and convenient than those currently used. To date, no research has addressed the use of a grinding medium as the controlled parameter. To improve the accuracy of the coal load detection based on the kinetic energy of balls in a tubular ball mill, a Discrete Element Method (DEM) model for ball kinematics based on coal loads is proposed. The operating process for a ball mill and the ball motion, as influenced by the coal quality and the coal load, was analyzed carefully. The relationship between the operating efficiency of a coal pulverizing system, coal loads, and the balls’ kinetic energy was obtained. Origin and Matlab were utilized to draw the variation of parameters with increasing coal loads in the projectile and cascading motion states. The parameters include the balls’ real-time kinetic energy, the friction energy consumption, and the mill’s total work. Meanwhile, a method of balanced adjacent degree and a physical experiment were proposed to verify the considerable effect of the balls’ kinetic energy on coal loads. The model and experiment results indicate that a coal load control method based on the balls’ kinetic energy is therefore feasible for the optimized operation of a coal pulverizing system. Full article

(This article belongs to the Special Issue Recent Advances in Coal Combustion and Gasification)

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17 pages, 1245 KiB

Open AccessArticle

Coal and Coalbed Methane Co-Extraction Technology Based on the Ground Movement in the Yangquan Coalfield, China

by Guozhong Hu^1,2,3, Jialin Xu^1,2,*, Fuxi Zhang³, Changchun Zhao³, Wei Qin² and Yiran Zhu¹

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

² State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China

³ Post-Doctoral Research Station, Yangquan Coal Industry (Group) CO., LTD, Yangquan 045000, Shanxi, China

Energies 2015, 8(7), 6881-6897; https://doi.org/10.3390/en8076881 - 9 Jul 2015

Cited by 27 | Viewed by 6795

Abstract

The Yangquan coalfield is one of the typical highly gassy mining areas in China. However, its coal seams are of lower permeability, which are not conductive to coalbed methane (CBM) drainage. In this study, based on the theory of the ground movement, we [...] Read more.

The Yangquan coalfield is one of the typical highly gassy mining areas in China. However, its coal seams are of lower permeability, which are not conductive to coalbed methane (CBM) drainage. In this study, based on the theory of the ground movement, we analyzed the principle of coal and CBM coextraction in the Yangquan coalfield, and established the technology system of coal and CBM coextraction which was further implemented in the coal and CBM coextraction in the Yangquan coalfield. The coal and CBM coextraction technologies based on the “pressure-relief and permeability-increase” effect caused by the mining overburden movement can optimally ensure the safe and efficient mining and improve the gas drainage rate. A series of developed coal and CBM coextraction technologies for the Yangquan coalfield were mainly characterized by the high-level gas drainage roadway. This reached a maximum gas drainage amount of 270,000 m³/day for single drainage roadway and a pressure-relief gas drainage rate of >90%. Those technologies significantly improved the gas drainage effect safely and efficiently achieving the coal and CBM coextraction. Full article

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12 pages, 4435 KiB

Open AccessArticle

The improved Hydrogen Storage Performances of the Multi-Component Composite: 2Mg(NH₂)₂–3LiH–LiBH₄

by Han Wang^1,2, Hujun Cao¹, Guotao Wu^1,*, Teng He¹ and Ping Chen¹

¹ Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China

² Graduate School of the Chinese Academy of Sciences, Beijing 100049, China

Energies 2015, 8(7), 6898-6909; https://doi.org/10.3390/en8076898 - 10 Jul 2015

Cited by 22 | Viewed by 5806

Abstract

2Mg(NH₂)₂–3LiH–LiBH₄ composite exhibits an improved kinetic and thermodynamic properties in hydrogen storage in comparison with 2Mg(NH₂)₂–3LiH. The peak temperature of hydrogen desorption drops about 10 K and the peak width shrinks about 50 K [...] Read more.

2Mg(NH₂)₂–3LiH–LiBH₄ composite exhibits an improved kinetic and thermodynamic properties in hydrogen storage in comparison with 2Mg(NH₂)₂–3LiH. The peak temperature of hydrogen desorption drops about 10 K and the peak width shrinks about 50 K compared with the neat 2Mg(NH₂)₂–3LiH. Its isothermal dehydrogenation and re-hydrogenation rates are respectively 2 times and 18 times as fast as those of 2Mg(NH₂)₂–3LiH. A slope desorption region with higher equilibrium pressure is observed. By means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses, the existence of Li₂BNH₆ is identified and its roles in kinetic and thermodynamic enhancement are discussed. Full article

(This article belongs to the Special Issue Hydrides: Fundamentals and Applications)

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16 pages, 560 KiB

Open AccessArticle

Exergy Analysis of a Two-Pass Reverse Osmosis (RO) Desalination Unit with and without an Energy Recovery Turbine (ERT) and Pressure Exchanger (PX)

by Nuri M. Eshoul¹, Brian Agnew^1,*, Mohammed A. Al-Weshahi² and Mohanad S. Atab¹

¹ School of Mechanical and Systems Engineering, Newcastle University, Newcastle Upon Tyne NE1 8ST, UK

² Shinas College of Technology, Al-Aqur, P.O. Box 77, Shinas 324, Oman

Energies 2015, 8(7), 6910-6925; https://doi.org/10.3390/en8076910 - 10 Jul 2015

Cited by 37 | Viewed by 9689

Abstract

This paper presents an exergy analysis of an actual two-pass (RO) desalination system with the seawater solution treated as a real mixture and not an ideal mixture. The actual 127 ton/h two pass RO desalination plant was modeled using IPSEpro software and validated [...] Read more.

This paper presents an exergy analysis of an actual two-pass (RO) desalination system with the seawater solution treated as a real mixture and not an ideal mixture. The actual 127 ton/h two pass RO desalination plant was modeled using IPSEpro software and validated against operating data. The results show that using the (ERT) and (PX) reduced the total power consumption of the SWRO desalination by about 30% and 50% respectively, whereas, the specific power consumption for the SWRO per m³ water decreased from 7.2 kW/m³ to 5.0 kW/m³ with (ERT) and 3.6 kW/m³ with (PX). In addition, the exergy efficiency of the RO desalination improved by 49% with ERT and 77% with PX and exergy destruction was reduced by 40% for (ERT) and 53% for (PX). The results also showed that, when the (ERT) and (PX) were not in use, accounted for 42% of the total exergy destruction. Whereas, when (ERT) and (PX) are in use, the rejected seawater account maximum is 0.64%. Moreover, the (PX) involved the smallest area and highest minimum separation work. Full article

(This article belongs to the Special Issue Tri-Generation Cycles, Combined Heat, Power and Cooling (CHPC))

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19 pages, 2784 KiB

Open AccessArticle

An Environmentally-Friendly Tourist Village in Egypt Based on a Hybrid Renewable Energy System––Part One: What Is the Optimum City?

by Fahd Diab^1,2, Hai Lan^1,*, Lijun Zhang¹ and Salwa Ali²

¹ College of Automation, Harbin Engineering University, Harbin 150001, China

² Electrical Engineering Department, Faculty of Engineering, Assiut University, Assiut 71516, Egypt

Energies 2015, 8(7), 6926-6944; https://doi.org/10.3390/en8076926 - 10 Jul 2015

Cited by 34 | Viewed by 7691

Abstract

The main objective of this work is to select the optimum city from five touristic Egyptian cities (Luxor, Giza, Alexandria, Qena and Aswan) to establish an environmentally-friendly tourist village. The selection of the city, according to the economic cost (cost of energy (COE), [...] Read more.

The main objective of this work is to select the optimum city from five touristic Egyptian cities (Luxor, Giza, Alexandria, Qena and Aswan) to establish an environmentally-friendly tourist village. The selection of the city, according to the economic cost (cost of energy (COE), net present cost (NPC)) and the amount of greenhouse gases (GHG) emitted, is carried out with respect to four cases, based on the effects of ambient temperature and applying GHG emission penalties. According to the simulation results, using the well-known Homer software, Alexandria is the economic city for hybrid photovoltaics (PV)/wind/diesel/battery and wind/diesel/battery systems, while Aswan is the most economic city for a hybrid PV/diesel/battery system. However, for a diesel/battery system there is no significant economic difference between the cities in the study. On the other hand, according to the amount of GHG emitted from a hybrid PV/wind/diesel/battery system, Qena is the optimum city if the effects of ambient temperature are considered. However, if the GHG emission penalties are applied, Aswan will be the optimum city. Furthermore, Alexandria is the optimum city if the effects of ambient temperature are considered and the GHG emission penalties are applied. Additionally, the effects of ambient temperature and applying GHG emission penalties are studied on hybrid PV/diesel/battery, wind/diesel/battery and diesel/battery systems in this study. Full article

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17 pages, 4609 KiB

Open AccessArticle

An Environmentally-Friendly Tourist Village in Egypt Based on a Hybrid Renewable Energy System––Part Two: A Net Zero Energy Tourist Village

by Fahd Diab^1,2, Hai Lan^1,*, Lijun Zhang¹ and Salwa Ali²

¹ College of Automation, Harbin Engineering University, Harbin 150001, China

² Electrical Engineering Department, Faculty of Engineering, Assiut University, Assiut 71516, Egypt

Energies 2015, 8(7), 6945-6961; https://doi.org/10.3390/en8076945 - 10 Jul 2015

Cited by 22 | Viewed by 7369

Abstract

The main objective of this study is to discuss the economical and the environmental analysis of a net zero energy (NZE) tourist village in Alexandria, Egypt, by maximizing the renewable energy fraction and minimizing the greenhouse gases (GHG) emissions. The hybrid photovoltaics (PV)/wind/diesel/battery [...] Read more.

The main objective of this study is to discuss the economical and the environmental analysis of a net zero energy (NZE) tourist village in Alexandria, Egypt, by maximizing the renewable energy fraction and minimizing the greenhouse gases (GHG) emissions. The hybrid photovoltaics (PV)/wind/diesel/battery system is found to be the optimum hybrid renewable energy system (HRES) for the proposed tourist village under the study. The optimum HRES consists of 1600 kW of PV panels (58.09% solar energy penetration), 1000 kW of wind turbines (41.34% wind energy penetration), 1000 kW of power converters, 200 kW diesel generator (only 0.57% diesel generator penetration) in addition to 2000 batteries with the capacity of 589 Ah each. The levelized cost of energy (COE) from the optimum HRES is $0.17/kWh and the total net present cost (NPC) of this system is $15,383,360. Additionally, the maximum renewable energy fraction is 99.1% and the amount of GHG emitted from the optimum HRES is only 31,289 kg/year, which is negligible in comparison with the other system configurations, therefore the optimum HRES can be considered as a green system. In addition to this, the achieved percentage of the capacity shortage and the unmet load in the optimal HRES is only 0% for both. Full article

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15 pages, 968 KiB

Open AccessArticle

Multi-Objective Reservoir Optimization Balancing Energy Generation and Firm Power

by Fang-Fang Li^1,*

and Jun Qiu^2,*

¹ College of Water Resources & Civil Engineering, China Agricultural University, Beijing 100083, China

² Institute for Aero-Engine, School of Aerospace Engineering, Tsinghua University, Beijing 100084, China

Energies 2015, 8(7), 6962-6976; https://doi.org/10.3390/en8076962 - 10 Jul 2015

Cited by 27 | Viewed by 6288

Abstract

To maximize annual power generation and to improve firm power are important but competing goals for hydropower stations. The firm power output is decisive for the installed capacity in design, and represents the reliability of the power generation when the power plant is [...] Read more.

To maximize annual power generation and to improve firm power are important but competing goals for hydropower stations. The firm power output is decisive for the installed capacity in design, and represents the reliability of the power generation when the power plant is put into operation. To improve the firm power, the whole generation process needs to be as stable as possible, while the maximization of power generation requires a rapid rise of the water level at the beginning of the storage period. Taking the minimal power output as the firm power, both the total amount and the reliability of the hydropower generation are considered simultaneously in this study. A multi-objective model to improve the comprehensive benefits of hydropower stations are established, which is optimized by Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The Three Gorges Cascade Hydropower System (TGCHS) is taken as the study case, and the Pareto Fronts in different search spaces are obtained. The results not only prove the effectiveness of the proposed method, but also provide operational references for the TGCHS, indicating that there is room of improvement for both the annual power generation and the firm power. Full article

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18 pages, 2609 KiB

Open AccessArticle

Analysis on the Initial Cracking Parameters of Cross-Measure Hydraulic Fracture in Underground Coal Mines

by Yiyu Lu^1,2, Liang Cheng^1,*

, Zhaolong Ge^1,2,*, Binwei Xia^1,2, Qian Li^1,2 and Jiufu Chen³

¹ State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

² National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China

³ Songzao Coal-Electricity Limited Liability Company, Chongqing 401445, China

Energies 2015, 8(7), 6977-6994; https://doi.org/10.3390/en8076977 - 10 Jul 2015

Cited by 32 | Viewed by 5803

Abstract

Initial cracking pressure and locations are important parameters in conducting cross-measure hydraulic fracturing to enhance coal seam permeability in underground coalmines, which are significantly influenced by in-situ stress and occurrence of coal seam. In this study, stress state around cross-measure fracturing boreholes was [...] Read more.

Initial cracking pressure and locations are important parameters in conducting cross-measure hydraulic fracturing to enhance coal seam permeability in underground coalmines, which are significantly influenced by in-situ stress and occurrence of coal seam. In this study, stress state around cross-measure fracturing boreholes was analyzed using in-situ stress coordinate transformation, then a mathematical model was developed to evaluate initial cracking parameters of borehole assuming the maximum tensile stress criterion. Subsequently, the influences of in-situ stress and occurrence of coal seams on initial cracking pressure and locations in underground coalmines were analyzed using the proposed model. Finally, the proposed model was verified with field test data. The results suggest that the initial cracking pressure increases with the depth cover and coal seam dip angle. However, it decreases with the increase in azimuth of major principle stress. The results also indicate that the initial cracking locations concentrated in the second and fourth quadrant in polar coordinate, and shifted direction to the strike of coal seam as coal seam dip angle and azimuth of maximum principle stress increase. Field investigation revealed consistent rule with the developed model that the initial cracking pressure increases with the coal seam dip angle. Therefore, the proposed mathematical model provides theoretical insight to analyze the initial cracking parameters during cross-measure hydraulic fracturing for underground coalmines. Full article

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25 pages, 2722 KiB

Open AccessArticle

Transformation toward a Secure and Precaution-Oriented Energy System with the Guiding Concept of Resilience—Implementation of Low-Exergy Solutions in Northwestern Germany

by Urte Brand^* and Arnim Von Gleich

Department of Technology Design and Development, University of Bremen, Enrique-Schmidt-Str. 7, 28359 Bremen, Germany

Energies 2015, 8(7), 6995-7019; https://doi.org/10.3390/en8076995 - 10 Jul 2015

Cited by 13 | Viewed by 9312

Abstract

Climate changes, incidents like nuclear disasters, and associated political objectives call for significant changes to the current energy system. Despite these far-reaching transformation processes, within the intended changes security of supply and precautions against the possible consequences of climate change must be ensured. [...] Read more.

Climate changes, incidents like nuclear disasters, and associated political objectives call for significant changes to the current energy system. Despite these far-reaching transformation processes, within the intended changes security of supply and precautions against the possible consequences of climate change must be ensured. Consequently, the question arises how to direct energy systems. In this context the processes of guiding orientations with the help of the guiding concept of “resilient systems” and feasible and addressee-oriented guiding design principles can be an option to provide guidance in transformation processes. However, it is questionable whether and how such processes are effective in the long term and if they are able to give direction by doing so. Within the framework of empirical studies of a regional guiding orientation process for the energy system of Northwestern Germany, the long-term effectiveness of the process and its spread resilient guiding design principles of “low-exergy solutions” and “climate-adapted and energy-efficient refrigeration” has been confirmed. Such effectiveness requires the implementation of a four-phase guiding orientation process which takes content-related and process-related effectiveness factors into account. Therefore, the study shows how regional energy systems can be designed toward the major challenges of ensuring security and precaution. Full article

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

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20 pages, 4522 KiB

Open AccessArticle

A Novel Ground Fault Identification Method for 2 × 5 kV Railway Power Supply Systems

by Jesus Serrano, Carlos A. Platero^*

, Maximo López-Toledo and Ricardo Granizo

Department of Electrical Engineering, Escuela Técnica Superior Ingenieros Industriales, Technical University of Madrid, C/José Gutierrez Abascal, 2, Madrid 28006, Spain

Energies 2015, 8(7), 7020-7039; https://doi.org/10.3390/en8077020 - 13 Jul 2015

Cited by 16 | Viewed by 9028 | Correction

Abstract

The location of ground faults in railway electric lines in 2 × 5 kV railway power supply systems is a difficult task. In both 1 × 25 kV and transmission power systems it is common practice to use distance protection relays to clear [...] Read more.

The location of ground faults in railway electric lines in 2 × 5 kV railway power supply systems is a difficult task. In both 1 × 25 kV and transmission power systems it is common practice to use distance protection relays to clear ground faults and localize their positions. However, in the particular case of this 2 × 25 kV system, due to the widespread use of autotransformers, the relation between the distance and the impedance seen by the distance protection relays is not linear and therefore the location is not accurate enough. This paper presents a simple and economical method to identify the subsection between autotransformers and the conductor (catenary or feeder) where the ground fault is happening. This method is based on the comparison of the angle between the current and the voltage of the positive terminal in each autotransformer. Consequently, after the identification of the subsection and the conductor with the ground defect, only the subsection where the ground fault is present will be quickly removed from service, with the minimum effect on rail traffic. This method has been validated through computer simulations and laboratory tests with positive results. Full article

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18 pages, 4685 KiB

Open AccessArticle

Ejin Oasis Land Use and Vegetation Change between 2000 and 2011: The Role of the Ecological Water Diversion Project

by Xiaoli Hu^1,2, Ling Lu^1,*, Xin Li^1,3, Jianhua Wang¹ and Xuegang Lu⁴

¹ Key Laboratory of Remote Sensing of Gansu Province, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, No. 320 Donggang West Road, Lanzhou 730000, Gansu, China

² University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China

³ CAS Center for Excellence in Tibetan Plateau Earth Sciences, No. 16 Lincui Road, Chaoyang District, Beijing 100101, China

⁴ Heihe River Bureau, No. 458 Qingyang Road, Lanzhou 730030, Gansu, China

Energies 2015, 8(7), 7040-7057; https://doi.org/10.3390/en8077040 - 13 Jul 2015

Cited by 35 | Viewed by 6858

Abstract

Ejin Oasis, located in the lower reaches of the Heihe River Basin (HRB), has experienced severe ecosystem decline between the 1960s and 1990s. In response, the Chinese Government implemented the Ecological Water Diversion Project (EWDP) in 2000. To evaluate the effects of the [...] Read more.

Ejin Oasis, located in the lower reaches of the Heihe River Basin (HRB), has experienced severe ecosystem decline between the 1960s and 1990s. In response, the Chinese Government implemented the Ecological Water Diversion Project (EWDP) in 2000. To evaluate the effects of the EWDP, this study monitored changes in land use and vegetation in the Ejin Oasis since 2000 and examined driving factors behind such changes. Results demonstrated that the Ejin Oasis ecosystem generally improved between 2000 and 2011. Water body area significantly increased. Lake area of once dried-up Sogo Nuur increased to 45 km². Accordingly, vegetation cover restoration has also significantly increased. For example, the Seasonally Integrated Normalized Difference Vegetation Index (SINDVI) has shown that 31.18% of the entire study area experienced an increase in vegetation area. On the other hand, even though the EWDP has been successful in driving vegetation recovery and lake restoration, farmland reclamation has counteracted such restoration initiatives. Farmland area almost doubled between 2000 and 2011. Thus, farmland expansion management is necessary for the full restoration of the Ejin Oasis ecosystems as well as HRB sustainable development. The results of this study can provide a reference for the management of the HRB. Full article

(This article belongs to the Special Issue Large Scale LUCC, Ecosystem Service, Water Balance and Energy Use)

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12 pages, 872 KiB

Open AccessArticle

A Mathematical Model of Hourly Solar Radiation in Varying Weather Conditions for a Dynamic Simulation of the Solar Organic Rankine Cycle

by Taehong Sung¹

, Sang Youl Yoon^2,* and Kyung Chun Kim^1,*

¹ School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea

² Rolls-Royce and Pusan National University Technology Centre, Pusan National University, Busan 609-735, Korea

Energies 2015, 8(7), 7058-7069; https://doi.org/10.3390/en8077058 - 13 Jul 2015

Cited by 32 | Viewed by 7885

Abstract

A mathematical model of hourly solar radiation with weather variability is proposed based on the simple sky model. The model uses a superposition of trigonometric functions with short and long periods. We investigate the effects of the model variables on the clearness ( [...] Read more.

A mathematical model of hourly solar radiation with weather variability is proposed based on the simple sky model. The model uses a superposition of trigonometric functions with short and long periods. We investigate the effects of the model variables on the clearness (k_D) and the probability of persistence (POP_D) indices and also evaluate the proposed model for all of the k_D-POP_D weather classes. A simple solar organic Rankine cycle (SORC) system with thermal storage is simulated using the actual weather conditions, and then, the results are compared with the simulation results using the proposed model and the simple sky model. The simulation results show that the proposed model provides more accurate system operation characteristics than the simple sky model. Full article

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14 pages, 2212 KiB

Open AccessArticle

Development and Characterization of Non-Conventional Micro-Porous Layers for PEM Fuel Cells

by Riccardo Balzarotti^*, Saverio Latorrata^†

, Paola Gallo Stampino^†, Cinzia Cristiani^† and Giovanni Dotelli^†

¹ Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Piazza Leonardo da Vinci 32, 20133 Milano, Italy

^† These authors contributed equally to this work.

Energies 2015, 8(7), 7070-7083; https://doi.org/10.3390/en8077070 - 13 Jul 2015

Cited by 19 | Viewed by 6665

Abstract

Gas diffusion medium (GDM) is a crucial component in proton exchange membrane fuel cells (PEMFCs). Being composed of a gas diffusion layer (GDL) with a micro-porous layer (MPL) coated onto it, it ensures a proper water management due to the highly hydrophobic materials [...] Read more.

Gas diffusion medium (GDM) is a crucial component in proton exchange membrane fuel cells (PEMFCs). Being composed of a gas diffusion layer (GDL) with a micro-porous layer (MPL) coated onto it, it ensures a proper water management due to the highly hydrophobic materials employed in cell assembly. In current commercial applications, the desired water repellent behaviour is usually obtained by using polytetrafluoroethylene (PTFE). In this work, Fluorolink^® P56 (Solvay Specialty Polymers, Milan, Italy), a commercially available, anionic, segmented high molecular weight polyfluorourethane with perfluoropolyether groups was extensively evaluated as an alternative to PTFE for micro-porous layer hydrophobization. A change in polymer used is desirable in order to simplify the production process, both in terms of ink formulation and thermal treatment, as well as to get a higher hydrophobicity and, consequently, more efficient water management. Innovative prepared samples were compared to a PTFE-based GDM, in order to assess differences both from morphological and from an electrochemical point of view. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells 2015)

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16 pages, 1430 KiB

Open AccessArticle

Characterization of Anion Exchange Membrane Containing Epoxy Ring and C–Cl Bond Quaternized by Various Amine Groups for Application in Fuel Cells

by Sung Kuk Jeong, Ju Sung Lee

, Sahng Hyuck Woo, Jin Ah Seo and Byoung Ryul Min^*

Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea

Energies 2015, 8(7), 7084-7099; https://doi.org/10.3390/en8077084 - 14 Jul 2015

Cited by 29 | Viewed by 8737

Abstract

Anion exchange membranes were synthesized from different compositions of glycidyl methacrylate (GMA) and vinylbenzyl chloride (VBC), with constant content of divinyl benzene (DVB) by radical polymerization using benzoyl peroxide (BPO) on non-woven polyethylene terephthalate (PET) substrate. Polymerized membranes were then quaternized by soaking [...] Read more.

Anion exchange membranes were synthesized from different compositions of glycidyl methacrylate (GMA) and vinylbenzyl chloride (VBC), with constant content of divinyl benzene (DVB) by radical polymerization using benzoyl peroxide (BPO) on non-woven polyethylene terephthalate (PET) substrate. Polymerized membranes were then quaternized by soaking in trimethylamine (TMA), triethylamine (TEA), tripropylamine (TPA), and 1,4-diazabicyclo [2.2.2] octane (DABCO). Characteristics of membranes were confirmed by Fourier transform infrared spectroscopy, water uptake, ion exchange capacity, ion conductivity, thermal, and alkaline stability. The results revealed that membranes quaternized by TPA and DABCO showed high affinity when GMA content was 15 wt% and 75 wt%, respectively. IEC and ion conductivity of membranes quaternized by TPA were 1.34 meq·g⁻¹ and 0.022 S·cm⁻¹ (at 60 °C), respectively. IEC and ion conductivity of membranes were quaternized by DABCO were 1.34 meq·g⁻¹ and 0.021 S·cm⁻¹ (at 60 °C), respectively. The results indicate that the membrane containing GMA 15 wt% quaternized by TPA showed the highest thermal stability among membranes and exhibited high ion conductivity compared to existing researches using GMA, VBC, and DVB monomers. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells 2015)

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22 pages, 480 KiB

Open AccessArticle

Improved Adaptive Droop Control Design for Optimal Power Sharing in VSC-MTDC Integrating Wind Farms

by Xiaohong Ran, Shihong Miao^* and Yingjie Wu

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

Energies 2015, 8(7), 7100-7121; https://doi.org/10.3390/en8077100 - 14 Jul 2015

Cited by 9 | Viewed by 8692

Abstract

With the advance of insulated gate bipolar transistor (IGBT) converters, Multi-Terminal DC (MTDC) based on the voltage-source converter (VSC) has developed rapidly in renewable and electric power systems. To reduce the copper loss of large capacity and long distance DC transmission line, an [...] Read more.

With the advance of insulated gate bipolar transistor (IGBT) converters, Multi-Terminal DC (MTDC) based on the voltage-source converter (VSC) has developed rapidly in renewable and electric power systems. To reduce the copper loss of large capacity and long distance DC transmission line, an improved droop control design based on optimal power sharing in VSC-MTDC integrating offshore wind farm is proposed. The proposed approach provided a calculation method for power-voltage droop coefficients under two different scenarios either considering local load or not. The available headroom of each converter station was considered as a converter outage, to participate in the power adjustment according to their ability. A four-terminal MTDC model system including two large scale wind farms was set up in PSCAD/EMTDC. Then, the proposed control strategy was verified through simulation under the various conditions, including wind speed variation, rectifier outage and inverter outage, and a three-phase short-circuit of the converter. Full article

(This article belongs to the Special Issue Electrical Power and Energy Systems for Transportation Applications)

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18 pages, 4318 KiB

Open AccessReview

A Supply-Chain Analysis Framework for Assessing Densified Biomass Solid Fuel Utilization Policies in China

by Wenyan Wang^†, Wei Ouyang^* and Fanghua Hao^†

¹ School of Environment, State Key Laboratory of Water Environment Simulation, Beijing Normal University, No. 9 Xinjiekouwai Street, Haidian District, Beijing 100875, China

^† These authors contributed equally to this work.

Energies 2015, 8(7), 7122-7139; https://doi.org/10.3390/en8077122 - 14 Jul 2015

Cited by 18 | Viewed by 10196

Abstract

Densified Biomass Solid Fuel (DBSF) is a typical solid form of biomass, using agricultural and forestry residues as raw materials. DBSF utilization is considered to be an alternative to fossil energy, like coal in China, associated with a reduction of environmental pollution. China [...] Read more.

Densified Biomass Solid Fuel (DBSF) is a typical solid form of biomass, using agricultural and forestry residues as raw materials. DBSF utilization is considered to be an alternative to fossil energy, like coal in China, associated with a reduction of environmental pollution. China has abundant biomass resources and is suitable to develop DBSF. Until now, a number of policies aimed at fostering DBSF industry have been proliferated by policy makers in China. However, considering the seasonality and instability of biomass resources, these inefficiencies could trigger future scarcities of biomass feedstocks, baffling the resilience of biomass supply chains. Therefore, this review paper focuses on DBSF policies and strategies in China, based on the supply chain framework. We analyzed the current developing situation of DBSF industry in China and developed a framework for policy instruments based on the supply chain steps, which can be used to identify and assess the deficiencies of current DBSF industry policies, and we proposed some suggestions. These findings may inform policy development and identify synergies at different steps in the supply chain to enhance the development of DBSF industry. Full article

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

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21 pages, 898 KiB

Open AccessArticle

Online Fault Identification Based on an Adaptive Observer for Modular Multilevel Converters Applied to Wind Power Generation Systems

by Hui Liu^*, Ke Ma, Poh Chiang Loh and Frede Blaabjerg

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

Energies 2015, 8(7), 7140-7160; https://doi.org/10.3390/en8077140 - 15 Jul 2015

Cited by 27 | Viewed by 7084

Abstract

Due to the possibility of putting a large number of modules consisting of switches and capacitors connected in series, the modular multilevel converter (MMC) can easily be scaled to high power and high voltage power conversion, which is an attractive feature for filter-less [...] Read more.

Due to the possibility of putting a large number of modules consisting of switches and capacitors connected in series, the modular multilevel converter (MMC) can easily be scaled to high power and high voltage power conversion, which is an attractive feature for filter-less and transformer-less design and helpful to achieve high efficiency. However, a significantly increased amount of sub-modules in a MMC may increase the requirements for sensors and also increase the risk of failures. As a result, fault detection and diagnosis of MMC sub-modules are of great importance for continuous operation and post-fault maintenance. Therefore, in this paper, an effective fault diagnosis technique for real-time diagnosis of the switching device faults covering both the open-circuit faults and the short-circuit faults in MMC sub-modules is proposed, in which the faulty phase and the fault type is detected by analyzing the difference among the three output load currents, while the localization of the faulty switches is achieved by comparing the estimation results by the adaptive observer. In contrast to other methods that use additional sensors or devices, the presented technique uses the measured phase currents only, which are already available for MMC control. In additional, its operation, effectiveness and robustness are confirmed by simulation results under different operating conditions and load conditions. Full article

(This article belongs to the Collection Wind Turbines)

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24 pages, 1134 KiB

Open AccessArticle

Effects of Low-Carbon Technologies and End-Use Electrification on Energy-Related Greenhouse Gases Mitigation in China by 2050

by Zheng Guo, Pei Liu^*, Linwei Ma and Zheng Li

State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

Energies 2015, 8(7), 7161-7184; https://doi.org/10.3390/en8077161 - 15 Jul 2015

Cited by 17 | Viewed by 5764

Abstract

Greenhouse gas emissions in China have been increasing in line with its energy consumption and economic growth. Major means for energy-related greenhouse gases mitigation in the foreseeable future are transition to less carbon intensive energy supplies and structural changes in energy consumption. In [...] Read more.

Greenhouse gas emissions in China have been increasing in line with its energy consumption and economic growth. Major means for energy-related greenhouse gases mitigation in the foreseeable future are transition to less carbon intensive energy supplies and structural changes in energy consumption. In this paper, a bottom-up model is built to examine typical projected scenarios for energy supply and demand, with which trends of energy-related carbon dioxide emissions by 2050 can be analyzed. Results show that low-carbon technologies remain essential contributors to reducing emissions and altering emissions trends up to 2050. By pushing the limit of current practicality, emissions reduction can reach 20 to 28 percent and the advent of carbon peaking could shift from 2040 to 2030. In addition, the effect of electrification at end-use sectors is studied. Results show that electrifying transport could reduce emissions and bring the advent of carbon peaking forward, but the effect is less significant compared with low-carbon technologies. Moreover, it implies the importance of decarbonizing power supply before electrifying end-use sectors. Full article

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17 pages, 4493 KiB

Open AccessArticle

Development of Optical Fiber-Based Daylighting System and Its Comparison

by Irfan Ullah¹ and Allen Jong-Woei Whang^1,2,3,*

¹ Graduate Institute of Color and Illumination Technology, National Taiwan University of Science and Technology, #43, Section 4, Keelung Road, Taipei 106, Taiwan

² Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, #43, Section 4, Keelung Road, Taipei 106, Taiwan

³ Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, #43, Section 4, Keelung Road, Taipei 106, Taiwan

Energies 2015, 8(7), 7185-7201; https://doi.org/10.3390/en8077185 - 15 Jul 2015

Cited by 50 | Viewed by 12563

Abstract

Fiber-optic daylighting systems have been shown to be a promising and effective way to transmit sunlight in the interior space whilst reducing electric lighting energy consumption. To increase efficiency in terms of providing uniform illumination in the interior, the current need is to [...] Read more.

Fiber-optic daylighting systems have been shown to be a promising and effective way to transmit sunlight in the interior space whilst reducing electric lighting energy consumption. To increase efficiency in terms of providing uniform illumination in the interior, the current need is to illuminate optical fiber-bundle with uniform light flux. To this end, we propose a method for achieving collimated light, which illuminates the fiber-bundle uniformly. Light is collected through a parabolic concentrator and focused toward a collimating lens, which distributes the light over each optical fiber. An optics diffusing structure is utilized at the end side of the fiber bundle to spread light in the interior. The results clearly reveal that the efficiency in terms of uniform illumination, which also reduces the heat problem for optical fibers, is improved. Furthermore, a comparison study is conducted between current and previous approaches. As a result, the proposed daylighting system turns out convenient in terms of energy saving and reduction in greenhouse gas emissions. Full article

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22 pages, 3361 KiB

Open AccessArticle

Investigation of Fault Permeability in Sands with Different Mineral Compositions (Evaluation of Gas Hydrate Reservoir)

by Sho Kimura, Hiroaki Kaneko, Takuma Ito^† and Hideki Minagawa^*

¹ Reservoir Modeling Team, Methane Hydrate Research Centre, National Institute of Advanced Industrial Science and Technology (AIST), 2-17-2-1 Tsukisamu-Higashi, Toyohira-ku, Sapporo 062-8517, Japan

^† Current Address: Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawa-dai, Kizugawa, Kyoto 619-0292, Japan;

Energies 2015, 8(7), 7202-7223; https://doi.org/10.3390/en8077202 - 16 Jul 2015

Cited by 17 | Viewed by 6469

Abstract

We used a ring-shear apparatus to examine the perpendicular permeability of sands with different mineral compositions to evaluate fault behavior around gas hydrate reservoirs. The effect of effective normal stress on the permeability of two sand types was investigated under constant effective normal [...] Read more.

We used a ring-shear apparatus to examine the perpendicular permeability of sands with different mineral compositions to evaluate fault behavior around gas hydrate reservoirs. The effect of effective normal stress on the permeability of two sand types was investigated under constant effective normal stresses of 0.5–8.0 MPa. Although Toyoura sand and silica sand No. 7 mainly comprise quartz, silica sand No. 7 contains small amounts of feldspar. For Toyoura sand, the permeability after ring-shearing dramatically decreased with increasing effective normal stress up to 3.0 MPa, then gradually decreased for stresses over 3.0 MPa, whereas the permeability after ring-shearing of silica sand No. 7 rapidly decreased with increasing effective normal stress up to 2.0 MPa. Although the relationships between the permeability after ring-shearing and effective normal stress for both sands could be expressed by exponential equations up to 3.0 MPa, a more gradual change in slope was shown for Toyoura sand. The permeabilities of both sands were almost equal for effective normal stresses over 3.0 MPa. The mineralogical properties of the small amount of feldspar in the sample indicate that both mineralogy and original grain size distribution affect the fault permeability and shear zone formation. Full article

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19 pages, 867 KiB

Open AccessArticle

Coordinated Control Strategies of VSC-HVDC-Based Wind Power Systems for Low Voltage Ride Through

by Xinyin Zhang^1,2,*, Zaijun Wu¹, Minqiang Hu¹, Xianyun Li² and Ganyun Lv²

¹ School of Electrical Engineering, Southeast University, No.2 Sipailou, Nanjing 210096, China

² Nanjing Institute of Technology, No.1 Hongjindadao, Nanjing 211167, China

Energies 2015, 8(7), 7224-7242; https://doi.org/10.3390/en8077224 - 16 Jul 2015

Cited by 24 | Viewed by 8946

Abstract

The Voltage Source Converter-HVDC (VSC-HVDC) system applied to wind power generation can solve large scale wind farm grid-connection and long distance transmission problems. However, the low voltage ride through (LVRT) of the VSC-HVDC connected wind farm is a key technology issue that must [...] Read more.

The Voltage Source Converter-HVDC (VSC-HVDC) system applied to wind power generation can solve large scale wind farm grid-connection and long distance transmission problems. However, the low voltage ride through (LVRT) of the VSC-HVDC connected wind farm is a key technology issue that must be solved, and it is currently lacking an economic and effective solution. In this paper, a LVRT coordinated control strategy is proposed for the VSC-HVDC-based wind power system. In this strategy, the operation and control of VSC-HVDC and wind farm during the grid fault period is improved. The VSC-HVDC system not only provides reactive power support to the grid, but also effectively maintains the power balance and DC voltage stability by reducing wind-farm power output, without increasing the equipment investment. Correspondingly, to eliminate the influence on permanent magnet synchronous generator (PMSG)-based wind turbine (WT) systems, a hierarchical control strategy is designed. The speed and validity of the proposed LVRT coordinated control strategy and hierarchical control strategy were verified by MATLAB/Simulink simulations. Full article

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18 pages, 783 KiB

Open AccessArticle

Reinforcement Learning–Based Energy Management Strategy for a Hybrid Electric Tracked Vehicle

by Teng Liu, Yuan Zou^*, Dexing Liu and Fengchun Sun

Collaborative Innovation Center of Electric Vehicles in Beijing, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

Energies 2015, 8(7), 7243-7260; https://doi.org/10.3390/en8077243 - 16 Jul 2015

Cited by 94 | Viewed by 9785

Abstract

This paper presents a reinforcement learning (RL)–based energy management strategy for a hybrid electric tracked vehicle. A control-oriented model of the powertrain and vehicle dynamics is first established. According to the sample information of the experimental driving schedule, statistical characteristics at various velocities [...] Read more.

This paper presents a reinforcement learning (RL)–based energy management strategy for a hybrid electric tracked vehicle. A control-oriented model of the powertrain and vehicle dynamics is first established. According to the sample information of the experimental driving schedule, statistical characteristics at various velocities are determined by extracting the transition probability matrix of the power request. Two RL-based algorithms, namely Q-learning and Dyna algorithms, are applied to generate optimal control solutions. The two algorithms are simulated on the same driving schedule, and the simulation results are compared to clarify the merits and demerits of these algorithms. Although the Q-learning algorithm is faster (3 h) than the Dyna algorithm (7 h), its fuel consumption is 1.7% higher than that of the Dyna algorithm. Furthermore, the Dyna algorithm registers approximately the same fuel consumption as the dynamic programming–based global optimal solution. The computational cost of the Dyna algorithm is substantially lower than that of the stochastic dynamic programming. Full article

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

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18 pages, 524 KiB

Open AccessArticle

Energy Performance Database of Building Heritage in the Region of Umbria, Central Italy

by Cinzia Buratti¹

, Francesco Asdrubali^2,*, Domenico Palladino¹ and Antonella Rotili²

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

² CIRIAF (Inter-University Research Center on Pollution and Environment "Mauro Felli"), University of Perugia, Via G. Duranti 63, Perugia 06125, Italy

Energies 2015, 8(7), 7261-7278; https://doi.org/10.3390/en8077261 - 17 Jul 2015

Cited by 17 | Viewed by 5851

Abstract

Household energy consumption has been increasing in the last decades; the residential sector is responsible for about 40% of the total final energy use in Europe. Energy efficiency measures can both reduce energy needs of buildings and energy-related CO₂ emissions. For this [...] Read more.

Household energy consumption has been increasing in the last decades; the residential sector is responsible for about 40% of the total final energy use in Europe. Energy efficiency measures can both reduce energy needs of buildings and energy-related CO₂ emissions. For this reason, in recent years, the European Union has been making efforts to enhance energy saving in buildings by introducing various policies and strategies; in this context, a common methodology was developed to assess and to certify energy performance of buildings. The positive effects obtained by energy efficiency measures need to be verified, but measuring and monitoring building energy performance is time consuming and financially demanding. Alternatively, energy efficiency can also be evaluated by specific indicators based on energy consumption. In this work, a methodology to investigate the level of energy efficiency reached in the Umbria Region (Central Italy) is described, based on data collected by energy certificates. In fact, energy certificates, which are the outcomes of simulation models, represent a useful and available tool to collect data related to the energy use of dwellings. A database of building energy performance was developed, in which about 6500 energy certificates of residential buildings supplied by Umbria region were inserted. On the basis of this data collection, average energy and CO₂ indicators related to the building heritage in Umbria were estimated and compared to national and international indicators derived from official sources. Results showed that the adopted methodology in this work can be an alternative method for the evaluation of energy indicators; in fact, the ones calculated considering simulation data were similar to the ones reported in national and international sources. This allowed to validate the adopted methodology and the efficiency of European policies. Full article

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33 pages, 1046 KiB

Open AccessReview

Smart Home Communication Technologies and Applications: Wireless Protocol Assessment for Home Area Network Resources

by Tiago D. P. Mendes^1,†, Radu Godina^1,†

, Eduardo M. G. Rodrigues^1,†, João C. O. Matias^1,*,† and João P. S. Catalão^1,2,*,†

^† These authors contributed equally to this work.

¹ Department of Electromechanical Engineering, University of Beira Interior, 6201-001 Covilha, Portugal

² Instituto de Engenharia de Sistemas e Computadores, Investigação e Desenvolvimento em Lisboa (INESC-ID), Instituto Superior Técnico (IST), University of Lisbon, 1049-001 Lisbon, Portugal

^† These authors contributed equally to this work.

Energies 2015, 8(7), 7279-7311; https://doi.org/10.3390/en8077279 - 20 Jul 2015

Cited by 123 | Viewed by 22299

Abstract

The paper discusses Home Area Networks (HAN) communication technologies for smart home and domestic application integration. The work is initiated by identifying the application areas that can benefit from this integration. A broad and inclusive home communication interface is analysed utilizing as a [...] Read more.

The paper discusses Home Area Networks (HAN) communication technologies for smart home and domestic application integration. The work is initiated by identifying the application areas that can benefit from this integration. A broad and inclusive home communication interface is analysed utilizing as a key piece a Gateway based on machine-to-machine (M2M) communications that interacts with the surrounding environment. Then, the main wireless networks are thoroughly assessed, and later, their suitability to the requirements of HAN considering the application area is analysed. Finally, a qualitative analysis is portrayed. Full article

(This article belongs to the Special Issue Smart Metering)

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14 pages, 860 KiB

Open AccessArticle

Effects of Pilot Injection Timing and EGR on Combustion, Performance and Exhaust Emissions in a Common Rail Diesel Engine Fueled with a Canola Oil Biodiesel-Diesel Blend

by Jun Cong Ge¹, Min Soo Kim¹, Sam Ki Yoon² and Nag Jung Choi^1,*

¹ Division of Mechanical Design Engineering, Chonbuk National University, 567 Baekje-daero, Jeonjusi, Jeollabuk-do 561-756, Korea

² Technical Education Center, GM Korea Company, 72 Saengmuol-ro, Gunsansi, Jeollabuk-do 573-882, Korea

Energies 2015, 8(7), 7312-7325; https://doi.org/10.3390/en8077312 - 20 Jul 2015

Cited by 40 | Viewed by 11004

Abstract

Biodiesel as a clean energy source could reduce environmental pollution compared to fossil fuel, so it is becoming increasingly important. In this study, we investigated the effects of different pilot injection timings from before top dead center (BTDC) and exhaust gas recirculation (EGR) [...] Read more.

Biodiesel as a clean energy source could reduce environmental pollution compared to fossil fuel, so it is becoming increasingly important. In this study, we investigated the effects of different pilot injection timings from before top dead center (BTDC) and exhaust gas recirculation (EGR) on combustion, engine performance, and exhaust emission characteristics in a common rail diesel engine fueled with canola oil biodiesel-diesel (BD) blend. The pilot injection timing and EGR rate were changed at an engine speed of 2000 rpm fueled with BD20 (20 vol % canola oil and 80 vol % diesel fuel blend). As the injection timing advanced, the combustion pressure, brake specific fuel consumption (BSFC), and peak combustion pressure (P_max) changed slightly. Carbon monoxide (CO) and particulate matter (PM) emissions clearly decreased at BTDC 20° compared with BTDC 5°, but nitrogen oxide (NO_x) emissions increased slightly. With an increasing EGR rate, the combustion pressure and indicated mean effective pressure (IMEP) decreased slightly at BTDC 20° compared to other injection timings. However, the P_max showed a remarkable decrease. The BSFC and PM emissions increased slightly, but the NO_x emission decreased considerably. Full article

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18 pages, 509 KiB

Open AccessArticle

Autonomous Household Energy Management Based on a Double Cooperative Game Approach in the Smart Grid

by Bingtuan Gao^1,2,*, Xiaofeng Liu¹, Wenhu Zhang¹ and Yi Tang^1,2

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

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

Energies 2015, 8(7), 7326-7343; https://doi.org/10.3390/en8077326 - 20 Jul 2015

Cited by 33 | Viewed by 6415

Abstract

Taking advantage of two-way communication infrastructure and bidirectional energy trading between utility companies and customers in the future smart grid (SG), autonomous energy management programs become crucial to the demand-side management (DSM). Most of the existing autonomous energy management schemes are for the [...] Read more.

Taking advantage of two-way communication infrastructure and bidirectional energy trading between utility companies and customers in the future smart grid (SG), autonomous energy management programs become crucial to the demand-side management (DSM). Most of the existing autonomous energy management schemes are for the scenario with a single utility company or the scenario with one-way energy trading. In this paper, an autonomous household energy management system with multiple utility companies and multiple residential customers is studied by considering the bidirectional energy trading. To minimize the overall costs of both the utility companies and the residential customers, the energy management system is formulated as a double cooperative game. That is, the interaction among the residential users is formulated as a cooperative game, where the players are the customers and the strategies are the daily schedules of their household appliances; and the interaction among the utility companies is also formulated as a cooperative game, where the players are the suppliers and the strategies are the proportions of the daily total energy they provide for the customers. Without loss of generality, the bidirectional energy trading in the double cooperative game is formulated by allowing plug-in electric vehicles (PEVs) to discharge and sell energy back. Two distributed algorithms will be provided to realize the global optimal performance in terms of minimizing the energy costs, which can be guaranteed at the Nash equilibriums of the formulated cooperative games. Finally, simulation results illustrated that the proposed double cooperative game can benefit both the utility companies and residential users significantly. Full article

(This article belongs to the Collection Smart Grid)

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23 pages, 801 KiB

Open AccessReview

Enhancing Wave Energy Competitiveness through Co-Located Wind and Wave Energy Farms. A Review on the Shadow Effect

by Sharay Astariz^1,* and Gregorio Iglesias²

¹ Department of Hydraulic Engineering, EPS, University of Santiago de Compostela, Campus Universitario s/n, Lugo 27002, Spain

² School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK

Energies 2015, 8(7), 7344-7366; https://doi.org/10.3390/en8077344 - 21 Jul 2015

Cited by 89 | Viewed by 10971

Abstract

Wave energy is one of the most promising alternatives to fossil fuels due to the enormous available resource; however, its development may be slowed as it is often regarded as uneconomical. The largest cost reductions are expected to be obtained through economies of [...] Read more.

Wave energy is one of the most promising alternatives to fossil fuels due to the enormous available resource; however, its development may be slowed as it is often regarded as uneconomical. The largest cost reductions are expected to be obtained through economies of scale and technological progress. In this sense, the incorporation of wave energy systems into offshore wind energy farms is an opportunity to foster the development of wave energy. The synergies between both renewables can be realised through these co-located energy farms and, thus, some challenges of offshore wind energy can be met. Among them, this paper focuses on the longer non-operational periods of offshore wind turbines—relative to their onshore counterparts—typically caused by delays in maintenance due to the harsh marine conditions. Co-located wave energy converters would act as a barrier extracting energy from the waves and resulting in a shielding effect over the wind farm. On this basis, the aim of this paper is to analyse wave energy economics in a holistic way, as well as the synergies between wave and offshore wind energy, focusing on the shadow effect and the associated increase in the accessibility to the wind turbines. Full article

(This article belongs to the Special Issue Tools and Techniques for Economic Delivery of Ocean Energy)

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14 pages, 883 KiB

Open AccessArticle

A Solar Automatic Tracking System that Generates Power for Lighting Greenhouses

by Qi-Xun Zhang¹, Hai-Ye Yu^2,*, Qiu-Yuan Zhang³, Zhong-Yuan Zhang⁴, Cheng-Hui Shao¹ and Di Yang⁵

¹ College of Mechanical Science and Engineering, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

² College of Biological and Agricultural Engineering, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

³ MI Ninth Design & Research Institute, No. 1958 Chuangye Street, Changchun 130000, China

⁴ College of Automotive Engineering, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

⁵ Department of Biostatistics, School of Public Health, University of Michigan, 500 S. State Street, Ann Arbor, MI 48109 USA

Energies 2015, 8(7), 7367-7380; https://doi.org/10.3390/en8077367 - 21 Jul 2015

Cited by 22 | Viewed by 7587

Abstract

In this study we design and test a novel solar tracking generation system. Moreover, we show that this system could be successfully used as an advanced solar power source to generate power in greenhouses. The system was developed after taking into consideration the [...] Read more.

In this study we design and test a novel solar tracking generation system. Moreover, we show that this system could be successfully used as an advanced solar power source to generate power in greenhouses. The system was developed after taking into consideration the geography, climate, and other environmental factors of northeast China. The experimental design of this study included the following steps: (i) the novel solar tracking generation system was measured, and its performance was analyzed; (ii) the system configuration and operation principles were evaluated; (iii) the performance of this power generation system and the solar irradiance were measured according to local time and conditions; (iv) the main factors affecting system performance were analyzed; and (v) the amount of power generated by the solar tracking system was compared with the power generated by fixed solar panels. The experimental results indicated that compared to the power generated by fixed solar panels, the solar tracking system generated about 20% to 25% more power. In addition, the performance of this novel power generating system was found to be closely associated with solar irradiance. Therefore, the solar tracking system provides a new approach to power generation in greenhouses. Full article

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

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26 pages, 1102 KiB

Open AccessArticle

Automated Linear Function Submission-Based Double Auction as Bottom-up Real-Time Pricing in a Regional Prosumers’ Electricity Network

by Tadahiro Taniguchi^1,*, Koki Kawasaki², Yoshiro Fukui¹, Tomohiro Takata³ and Shiro Yano⁴

¹ College of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan

² Graduate School of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan

³ Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan

⁴ Division of Advanced Information Technology & Computer Science, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei, Tokyo 184-8588, Japan

Energies 2015, 8(7), 7381-7406; https://doi.org/10.3390/en8077381 - 22 Jul 2015

Cited by 16 | Viewed by 8267

Abstract

A linear function submission-based double auction (LFS-DA) mechanism for a regional electricity network is proposed in this paper. Each agent in the network is equipped with a battery and a generator. Each agent simultaneously becomes a producer and consumer of electricity, i.e., a [...] Read more.

A linear function submission-based double auction (LFS-DA) mechanism for a regional electricity network is proposed in this paper. Each agent in the network is equipped with a battery and a generator. Each agent simultaneously becomes a producer and consumer of electricity, i.e., a prosumer, and trades electricity in the regional market at a variable price. In the LFS-DA, each agent uses linear demand and supply functions when they submit bids and asks to an auctioneer in the regional market. The LFS-DA can achieve an exact balance between electricity demand and supply for each time slot throughout the learning phase and was shown capable of solving the primal problem of maximizing the social welfare of the network without any central price setter, e.g., a utility or a large electricity company, in contrast with conventional real-time pricing (RTP). This paper presents a clarification of the relationship between the RTP algorithm derived on the basis of a dual decomposition framework and LFS-DA. Specifically, we proved that the changes in the price profile of the LFS-DA mechanism are equal to those achieved by the RTP mechanism derived from the dual decomposition framework, except for a constant factor. Full article

(This article belongs to the Collection Smart Grid)

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21 pages, 1603 KiB

Open AccessArticle

Data Mining Techniques for Detecting Household Characteristics Based on Smart Meter Data

by Krzysztof Gajowniczek^*

and Tomasz Ząbkowski

Department of Informatics, Faculty of Applied Informatics and Mathematics, Warsaw University of Life Sciences, Nowoursynowska 159, 02-787 Warsaw, Poland

Energies 2015, 8(7), 7407-7427; https://doi.org/10.3390/en8077407 - 22 Jul 2015

Cited by 62 | Viewed by 8541

Abstract

The main goal of this research is to discover the structure of home appliances usage patterns, hence providing more intelligence in smart metering systems by taking into account the usage of selected home appliances and the time of their usage. In particular, we [...] Read more.

The main goal of this research is to discover the structure of home appliances usage patterns, hence providing more intelligence in smart metering systems by taking into account the usage of selected home appliances and the time of their usage. In particular, we present and apply a set of unsupervised machine learning techniques to reveal specific usage patterns observed at an individual household. The work delivers the solutions applicable in smart metering systems that might: (1) contribute to higher energy awareness; (2) support accurate usage forecasting; and (3) provide the input for demand response systems in homes with timely energy saving recommendations for users. The results provided in this paper show that determining household characteristics from smart meter data is feasible and allows for quickly grasping general trends in data. Full article

(This article belongs to the Special Issue Smart Metering)

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13 pages, 2790 KiB

Open AccessArticle

Facile and Economical Preparation of SiAlON-Based Composites Using Coal Gangue: From Fundamental to Industrial Application

by Jinfu Li¹, Changsheng Yue², Mei Zhang², Xidong Wang³ and Zuotai Zhang^3,*

¹ Department of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China

² School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

³ Beijing Key Laboratory for Solid Waste Utilization and Management, College of Engineering, Peking University, Beijing 100871, China

Energies 2015, 8(7), 7428-7440; https://doi.org/10.3390/en8077428 - 22 Jul 2015

Cited by 8 | Viewed by 6104

Abstract

The present study aims to synthesize SiAlON-based composites utilizing coal gangue. Different types of SiAlON-based composites were synthesized using coal gangue by carbothermal reduction nitridation method through control of different reaction atmospheres. The experimental results indicate that the oxygen partial pressure was an [...] Read more.

The present study aims to synthesize SiAlON-based composites utilizing coal gangue. Different types of SiAlON-based composites were synthesized using coal gangue by carbothermal reduction nitridation method through control of different reaction atmospheres. The experimental results indicate that the oxygen partial pressure was an essential factor in the manufacture of SiAlON-based composites and under proper control of the atmospheres, SiAlON-based composites with different crystal structures could be synthesized. The optimum conditions of synthesis of different SiAlON-based composites were respectively determined. Based on the laboratory results, a prototype plant was proposed and constructed, and β-SiAlON composite was successfully produced using coal gangue. The synthesized β-SiAlON composite was applied in preparation of iron ladle brick instead of SiC, which showed that the compression strength, refractoriness under load and high temperature bending strength were increased from 44.5 ± 6.7 MPa, 1618 ± 21 °C and 5.4 ± 1.2 MPa to 64.1 ± 2.5 MPa, 1700 ± 28 °C and 7.1 ± 1.6 MPa, respectively. Compared with the traditional synthesis method, the present technique is expected to save energy both in raw materials and technical process. Full article

(This article belongs to the Special Issue Recent Advances in Coal Combustion and Gasification)

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24 pages, 1466 KiB

Open AccessArticle

Characteristic Analysis and Control of a Hybrid Excitation Linear Eddy Current Brake

by Baoquan Kou^*, Yinxi Jin, Lu Zhang and He Zhang

Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150080, China

Energies 2015, 8(7), 7441-7464; https://doi.org/10.3390/en8077441 - 22 Jul 2015

Cited by 20 | Viewed by 9292

Abstract

In this paper, a novel hybrid excitation linear eddy current brake is presented as a braking system for high-speed road and rail vehicles. The presence of the permanent magnets (PMs), whose flux lines in the primary core are oppositely directed with respect to [...] Read more.

In this paper, a novel hybrid excitation linear eddy current brake is presented as a braking system for high-speed road and rail vehicles. The presence of the permanent magnets (PMs), whose flux lines in the primary core are oppositely directed with respect to the flux lines by the excitation windings, has the effect of mitigating the saturation of the iron in the teeth of the primary core. This allows the brake to be fed with more intense currents, improving the braking force. First, using the magnetic equivalent circuit method and the layer theory approach, the analytical model of the hybrid excitation linear eddy current brake was developed, which can account for the saturation effects occurring in the iron parts. The saturation effects make the design and control of eddy current brakes more difficult. Second, the relationship between the braking force characteristics and the design parameters were analyzed to provide useful information to the designers of eddy current brakes. Then, the controller of the hybrid excitation linear eddy current brake was designed to control the amplitude of the braking force. Finally, experimental measurements were conducted to verify the validity of the theoretical analysis. Full article

(This article belongs to the Special Issue Electrical Power and Energy Systems for Transportation Applications)

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13 pages, 3775 KiB

Open AccessArticle

Study on Pyroelectric Harvesters Integrating Solar Radiation with Wind Power

by Chun-Ching Hsiao^1,*

, Jia-Wai Jhang¹ and An-Shen Siao²

¹ Department of Mechanical Design Engineering, National Formosa University, No. 64, Wunhua Rd., Huwei Township, Yunlin County 632, Taiwan

² Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Keelung Rd., Sec. 4, Taipei 10607, Taiwan

Energies 2015, 8(7), 7465-7477; https://doi.org/10.3390/en8077465 - 22 Jul 2015

Cited by 22 | Viewed by 5933

Abstract

Pyroelectric harvesters use temperature fluctuations to generate electrical outputs. Solar radiation and waste heat are rich energy sources that can be harvested. Pyroelectric energy converters offer a novel and direct energy-conversion technology by transforming time-dependent temperatures directly into electricity. Moreover, the great challenge [...] Read more.

Pyroelectric harvesters use temperature fluctuations to generate electrical outputs. Solar radiation and waste heat are rich energy sources that can be harvested. Pyroelectric energy converters offer a novel and direct energy-conversion technology by transforming time-dependent temperatures directly into electricity. Moreover, the great challenge for pyroelectric energy harvesting lies in finding promising temperature variations or an alternating thermal loading in real situations. Hence, in this article, a novel pyroelectric harvester integrating solar radiation with wind power by the pyroelectric effect is proposed. Solar radiation is a thermal source, and wind is a dynamic potential. A disk generator is used for harvesting wind power. A mechanism is considered to convert the rotary energy of the disk generator to drive a shutter for generating temperature variations in pyroelectric cells using a planetary gear system. The optimal period of the pyroelectric cells is 35 s to harvest the stored energy, about 70 μJ, while the rotary velocity of the disk generator is about 31 RPM and the wind speed is about 1 m/s. In this state, the stored energy acquired from the pyroelectric harvester is about 75% more than that from the disk generator. Although the generated energy of the proposed pyroelectric harvester is less than that of the disk generator, the pyroelectric harvester plays a complementary role when the disk generator is inactive in situations of low wind speed. Full article

(This article belongs to the Special Issue Thermoelectric Energy Harvesting)

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24 pages, 2326 KiB

Open AccessArticle

Flow Regime Changes: From Impounding a Temperate Lowland River to Small Hydropower Operations

by Petras Punys^*, Antanas Dumbrauskas, Egidijus Kasiulis, Gitana Vyčienė and Linas Šilinis

Institute of Water Resources Engineering, Aleksandras Stulginskis University, 10 Universiteto str., Akademija, Kaunas District LT-53361, Lithuania

Energies 2015, 8(7), 7478-7501; https://doi.org/10.3390/en8077478 - 22 Jul 2015

Cited by 14 | Viewed by 7425

Abstract

This article discusses the environmental issues facing small hydropower plants (SHPs) operating in temperate lowland rivers of Lithuania. The research subjects are two medium head reservoir type hydro schemes considered within a context of the global fleet of SHPs in the country. This [...] Read more.

This article discusses the environmental issues facing small hydropower plants (SHPs) operating in temperate lowland rivers of Lithuania. The research subjects are two medium head reservoir type hydro schemes considered within a context of the global fleet of SHPs in the country. This research considers general abiotic indicators (flow, level, water retention time in the reservoirs) of the stream that may affect the aquatic systems. The main idea was to test whether the hydrologic regime has been altered by small hydropower dams. The analysis of changes in abiotic indicators is a complex process, including both pre- and post-reservoir construction and post commissioning of the SHPs under operation. Downstream hydrograph (flow and stage) ramping is also an issue for operating SHPs that can result in temporary rapid changes in flow and consequently negatively impact aquatic resources. This ramping has been quantitatively evaluated. To avoid the risk of excessive flow ramping, the types of turbines available were evaluated and the most suitable types for the natural river flow regime were identified. The results of this study are to allow for new hydro schemes or upgrades to use water resources in a more sustainable way. Full article

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

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