Energies

26 pages, 1960 KiB

Open AccessArticle

Simulation of Forestland Dynamics in a Typical Deforestation and Afforestation Area under Climate Scenarios

by Qun'ou Jiang^1,2,3,4,*, Yuwei Cheng¹, Qiutong Jin¹

, Xiangzheng Deng^3,4 and Yuanjing Qi^1,2,*

¹ School of Soil and Water Conservation, Beijing Forestry University, Beijing 100038, China

² Key Laboratory of Soil and Water Conservation & Desertification Combat, Beijing Forest University, Beijing 100038, China

³ Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

⁴ Center for Chinese Agricultural Policy, Chinese Academy of Sciences, Beijing 100101, China

Energies 2015, 8(10), 10558-10583; https://doi.org/10.3390/en81010558 - 24 Sep 2015

Cited by 15 | Viewed by 5475

Abstract

Forestland dynamics can affect the ecological security of a country and even the global environment, and therefore it is of great practical significance to understand the characteristics of temporal and spatial variations of forestland. Taking Jiangxi Province as the study area, this study [...] Read more.

Forestland dynamics can affect the ecological security of a country and even the global environment, and therefore it is of great practical significance to understand the characteristics of temporal and spatial variations of forestland. Taking Jiangxi Province as the study area, this study first explored the driving mechanism of the natural environment and social economy on deforestation and afforestation using a simultaneous equation model. The results indicate that population size, topographic and geomorphologic factors, climate, and location play leading roles in influencing forestland density fluctuations. Specifically, the population size, economic development level, gross value of forestry production, climate conditions, and government policies are key influencing factors of afforestation. Deforestation is mainly influenced by agricultural population, non-agricultural economy, forestry production, forestry density, location, transportation, and climate. In addition, this study simulated the spatial distribution of land use and analyzed the spatial characteristics and variation trends of forestland area and quality under the Representative Concentration Pathways (RCPs) climate scenarios from 2010 to 2030 using the Conversion of Land Use and its Effects (CLUE) model. The results indicate that forestland declines under the Asia-Pacific integrated model (AIM) climate scenario. The environment tends to be heavily damaged under this kind of scenarios, and measures should be taken in order to protect the environment. Although the model for energy supply strategy alternatives and their general environmental impact (MESSAGE) scenario is to some extent better than the AIM scenario, destruction of the environment will still occur, and it is necessary to restrain deforestation and convert shrub land into forestland or garden land. These results can provide significant information for environmental protection, forest resource exploitation, and utilization in the areas experiencing deforestation and afforestation. Full article

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

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21 pages, 867 KiB

Open AccessArticle

Failures during Load-Frequency Control Maneuvers in an Upgraded Hydropower Plant: Causes, Identification of Causes and Solution Proposals

by Juan I. Pérez-Díaz^* and José I. Sarasúa

Department of Hydraulic, Energy and Environmental Engineering, Escuela de Ingenieros de Caminos, Canales y Puertos, Technical University of Madrid (UPM), c/Profesor Aranguren s/n, Madrid 28040, Spain

Energies 2015, 8(10), 10584-10604; https://doi.org/10.3390/en81010584 - 24 Sep 2015

Cited by 12 | Viewed by 6302

Abstract

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and [...] Read more.

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and to propose solutions that allow the power plant to continue providing secondary LFC in a safe and reliable manner. For this purpose, a simulation model has been developed and calibrated from data gathered during several on-site tests. Two different solutions are proposed in order to cope with the observed problem: using a state-dependent load change rate limiter or modifying the hydro turbine governor gains; the turbine governor remains the same as before the runner replacement. The proposed solutions are tested against a set of realistic secondary LFC signals by means of simulations and compared to each other as a function of the probability that the surge tank water level descends below a minimum safe level and the quality of the secondary LFC response. The results presented in the paper demonstrate the validity of the methodology proposed to determine the state-dependent ramp limit, as well as its effectiveness to prevent the surge tank drawdown and to provide clear insight into the trade-off between response quality and power plant safety. Full article

(This article belongs to the Special Issue Hydropower)

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Graphical abstract

31 pages, 1471 KiB

Open AccessReview

Chemical-Looping Combustion and Gasification of Coals and Oxygen Carrier Development: A Brief Review

by Ping Wang^1,*, Nicholas Means², Dushyant Shekhawat³, David Berry³ and Mehrdad Massoudi¹

¹ Department of Energy, National Energy Technology Laboratory, 626 Cochrans Mill Road, Pittsburgh, PA 15236, USA

² AECOM, 626 Cochrans Mill Road, PO Box 10940, Pittsburgh, PA 15236, USA

³ Department of Energy, National Energy Technology Laboratory, 3610 Collins Ferry Road, Morgantown, WV 26507, USA

Energies 2015, 8(10), 10605-10635; https://doi.org/10.3390/en81010605 - 24 Sep 2015

Cited by 115 | Viewed by 14606

Abstract

Chemical-looping technology is one of the promising CO₂ capture technologies. It generates a CO₂ enriched flue gas, which will greatly benefit CO₂ capture, utilization or sequestration. Both chemical-looping combustion (CLC) and chemical-looping gasification (CLG) have the potential to be used [...] Read more.

Chemical-looping technology is one of the promising CO₂ capture technologies. It generates a CO₂ enriched flue gas, which will greatly benefit CO₂ capture, utilization or sequestration. Both chemical-looping combustion (CLC) and chemical-looping gasification (CLG) have the potential to be used to generate power, chemicals, and liquid fuels. Chemical-looping is an oxygen transporting process using oxygen carriers. Recently, attention has focused on solid fuels such as coal. Coal chemical-looping reactions are more complicated than gaseous fuels due to coal properties (like mineral matter) and the complex reaction pathways involving solid fuels. The mineral matter/ash and sulfur in coal may affect the activity of oxygen carriers. Oxygen carriers are the key issue in chemical-looping processes. Thermogravimetric analysis (TGA) has been widely used for the development of oxygen carriers (e.g., oxide reactivity). Two proposed processes for the CLC of solid fuels are in-situ Gasification Chemical-Looping Combustion (iG-CLC) and Chemical-Looping with Oxygen Uncoupling (CLOU). The objectives of this review are to discuss various chemical-looping processes with coal, summarize TGA applications in oxygen carrier development, and outline the major challenges associated with coal chemical-looping in iG-CLC and CLOU. Full article

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

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28 pages, 566 KiB

Open AccessReview

Flywheel Energy Storage for Automotive Applications

by Magnus Hedlund^*, Johan Lundin, Juan De Santiago, Johan Abrahamsson and Hans Bernhoff

Division for Electricity, Uppsala University, Lägerhyddsvägen 1, Uppsala 752 37, Sweden

Energies 2015, 8(10), 10636-10663; https://doi.org/10.3390/en81010636 - 25 Sep 2015

Cited by 114 | Viewed by 32028

Abstract

A review of flywheel energy storage technology was made, with a special focus on the progress in automotive applications. We found that there are at least 26 university research groups and 27 companies contributing to flywheel technology development. Flywheels are seen to excel [...] Read more.

A review of flywheel energy storage technology was made, with a special focus on the progress in automotive applications. We found that there are at least 26 university research groups and 27 companies contributing to flywheel technology development. Flywheels are seen to excel in high-power applications, placing them closer in functionality to supercapacitors than to batteries. Examples of flywheels optimized for vehicular applications were found with a specific power of 5.5 kW/kg and a specific energy of 3.5 Wh/kg. Another flywheel system had 3.15 kW/kg and 6.4 Wh/kg, which can be compared to a state-of-the-art supercapacitor vehicular system with 1.7 kW/kg and 2.3 Wh/kg, respectively. Flywheel energy storage is reaching maturity, with 500 flywheel power buffer systems being deployed for London buses (resulting in fuel savings of over 20%), 400 flywheels in operation for grid frequency regulation and many hundreds more installed for uninterruptible power supply (UPS) applications. The industry estimates the mass-production cost of a specific consumer-car flywheel system to be 2000 USD. For regular cars, this system has been shown to save 35% fuel in the U.S. Federal Test Procedure (FTP) drive cycle. Full article

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

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20 pages, 949 KiB

Open AccessArticle

Design Considerations for Wireless Charging Systems with an Analysis of Batteries

by Zhenshi Wang^1,2 and Xuezhe Wei^2,*

¹ Clean Energy Automotive Engineering Center, Tongji University, Shanghai 201804, China

² College of Automotive Studies, Tongji University, Shanghai 201804, China

Energies 2015, 8(10), 10664-10683; https://doi.org/10.3390/en81010664 - 25 Sep 2015

Cited by 10 | Viewed by 7447

Abstract

Three criteria, including charging time, effective charging capacity and charging energy efficiency, are introduced to evaluate the CC (constant current) and CC/CV (constant current/constant voltage) charging strategies. Because the CC strategy presents a better performance and most resonant topologies have the CC characteristic, [...] Read more.

Three criteria, including charging time, effective charging capacity and charging energy efficiency, are introduced to evaluate the CC (constant current) and CC/CV (constant current/constant voltage) charging strategies. Because the CC strategy presents a better performance and most resonant topologies have the CC characteristic, the CC strategy is more suitable for the design of wireless charging systems than the CC/CV strategy. Then, the state space model of the receiver is built to study the system dynamic characteristics, and the design of nonuse output filter capacitors is proposed, which can improve the system power density and avoid the drop in efficiency caused by capacitor degradation. At last, an electrochemical impedance spectrum (EIS) based analysis method is introduced to validate that the design without output filter capacitors has no effects on the battery characteristics when the charging frequency is higher than 460 Hz. A prototype is fabricated to verify our research results. Full article

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

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34 pages, 1338 KiB

Open AccessArticle

A New Approach for Modeling Darrieus-Type Vertical Axis Wind Turbine Rotors Using Electrical Equivalent Circuit Analogy: Basis of Theoretical Formulations and Model Development

by Pierre Tchakoua^1,2,*, René Wamkeue², Mohand Ouhrouche¹, Tommy Andy Tameghe^1,2 and Gabriel Ekemb^1,2

¹ Department des Sciences Appliquées, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada

² Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, QC J9X 5E4, Canada

Energies 2015, 8(10), 10684-10717; https://doi.org/10.3390/en81010684 - 25 Sep 2015

Cited by 24 | Viewed by 16617

Abstract

Models are crucial in the engineering design process because they can be used for both the optimization of design parameters and the prediction of performance. Thus, models can significantly reduce design, development and optimization costs. This paper proposes a novel equivalent electrical model [...] Read more.

Models are crucial in the engineering design process because they can be used for both the optimization of design parameters and the prediction of performance. Thus, models can significantly reduce design, development and optimization costs. This paper proposes a novel equivalent electrical model for Darrieus-type vertical axis wind turbines (DTVAWTs). The proposed model was built from the mechanical description given by the Paraschivoiu double-multiple streamtube model and is based on the analogy between mechanical and electrical circuits. This work addresses the physical concepts and theoretical formulations underpinning the development of the model. After highlighting the working principle of the DTVAWT, the step-by-step development of the model is presented. For assessment purposes, simulations of aerodynamic characteristics and those of corresponding electrical components are performed and compared. Full article

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

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18 pages, 412 KiB

Open AccessArticle

Optimal Scheduling of a Battery Energy Storage System with Electric Vehicles’ Auxiliary for a Distribution Network with Renewable Energy Integration

by Yuqing Yang^1,2, Weige Zhang^1,2,*, Jiuchun Jiang^1,2, Mei Huang^1,2 and Liyong Niu^1,2

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

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

Energies 2015, 8(10), 10718-10735; https://doi.org/10.3390/en81010718 - 25 Sep 2015

Cited by 21 | Viewed by 6762

Abstract

With global conventional energy depletion, as well as environmental pollution, utilizing renewable energy for power supply is the only way for human beings to survive. Currently, distributed generation incorporated into a distribution network has become the new trend, with the advantages of controllability, [...] Read more.

With global conventional energy depletion, as well as environmental pollution, utilizing renewable energy for power supply is the only way for human beings to survive. Currently, distributed generation incorporated into a distribution network has become the new trend, with the advantages of controllability, flexibility and tremendous potential. However, the fluctuation of distributed energy resources (DERs) is still the main concern for accurate deployment. Thus, a battery energy storage system (BESS) has to be involved to mitigate the bad effects of DERs’ integration. In this paper, optimal scheduling strategies for BESS operation have been proposed, to assist with consuming the renewable energy, reduce the active power loss, alleviate the voltage fluctuation and minimize the electricity cost. Besides, the electric vehicles (EVs) considered as the auxiliary technique are also introduced to attenuate the DERs’ influence. Moreover, both day-ahead and real-time operation scheduling strategies were presented under the consideration with the constraints of BESS and the EVs’ operation, and the optimization was tackled by a fuzzy mathematical method and an improved particle swarm optimization (IPSO) algorithm. Furthermore, the test system for the proposed strategies is a real distribution network with renewable energy integration. After simulation, the proposed scheduling strategies have been verified to be extremely effective for the enhancement of the distribution network characteristics. Full article

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

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39 pages, 5002 KiB

Open AccessArticle

Rotor Design for Diffuser Augmented Wind Turbines

by Søren Hjort^* and Helgi Larsen

Volu Ventis ApS, Ferskvandscentret, 8600 Silkeborg, Denmark

Energies 2015, 8(10), 10736-10774; https://doi.org/10.3390/en81010736 - 28 Sep 2015

Cited by 18 | Viewed by 8515

Abstract

Diffuser augmented wind turbines (DAWTs) can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several [...] Read more.

Diffuser augmented wind turbines (DAWTs) can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several factors can induce wake stall scenarios causing significant energy loss. The causality between these stall mechanisms and earlier DAWT failures is discussed. First, a swirled actuator disk CFD code is validated through comparison with results from a far wake swirl corrected blade-element momentum (BEM) model, and horizontal-axis wind turbine (HAWT) reference results. Then, power efficiency versus thrust is computed with the swirled actuator disk (AD) code for low and high values of tip-speed ratios (TSR), for different centerbodies, and for different spanwise rotor thrust loading distributions. Three different configurations are studied: The bare propeller HAWT, the classical DAWT, and the high-performance multi-element DAWT. In total nearly 400 high-resolution AD runs are generated. These results are presented and discussed. It is concluded that dedicated DAWT rotors can successfully convert the available energy to shaft energy, provided the identified design requirements for swirl and axial loading distributions are satisfied. Full article

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

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21 pages, 945 KiB

Open AccessArticle

ANN-Based Prediction and Optimization of Cooling System in Hotel Rooms

by Jin Woo Moon^1,*, Kyungjae Kim² and Hyunsuk Min²

¹ School of Architecture and Building Science, Chung-Ang University, Seoul 06974, Korea

² DMC R&D Center, Samsung Electronic, Suwon-si 443-742, Gyeonggi-do, Korea

Energies 2015, 8(10), 10775-10795; https://doi.org/10.3390/en81010775 - 28 Sep 2015

Cited by 27 | Viewed by 5805

Abstract

This study aimed at developing an artificial-neural-network (ANN)-based model that can calculate the required time for restoring the current indoor temperature during the setback period in accommodation buildings to the normal set-point temperature in the cooling season. By applying the calculated time in [...] Read more.

This study aimed at developing an artificial-neural-network (ANN)-based model that can calculate the required time for restoring the current indoor temperature during the setback period in accommodation buildings to the normal set-point temperature in the cooling season. By applying the calculated time in the control logic, the operation of the cooling system can be predetermined to condition the indoor temperature comfortably in a more energy-efficient manner. Three major steps employing the numerical computer simulation method were conducted for developing an ANN model and testing its prediction performance. In the development process, the initial ANN model was determined to have input neurons that had a significant statistical relationship with the output neuron. In addition, the structure of the ANN model and learning methods were optimized through the parametrical analysis of the prediction performance. Finally, through the performance tests in terms of prediction accuracy, the optimized ANN model presented a lower mean biased error (MBE) rate between the simulation and prediction results under generally accepted levels. Thus, the developed ANN model was proven to have the potential to be applied to thermal control logic. Full article

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

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22 pages, 3685 KiB

Open AccessArticle

Assessment of Gas Production Potential from Hydrate Reservoir in Qilian Mountain Permafrost Using Five-Spot Horizontal Well System

by Yun-Pei Liang^1,2, Xiao-Sen Li³ and Bo Li^1,2,*

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

² College of Resources and Environmental Science, Chongqing University, Chongqing 400044, China

³ Key Laboratory of Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China

Energies 2015, 8(10), 10796-10817; https://doi.org/10.3390/en81010796 - 28 Sep 2015

Cited by 29 | Viewed by 7642

Abstract

The main purpose of this study is to investigate the production behaviors of gas hydrate at site DK-2 in the Qilian Mountain permafrost using the novel five-spot well (5S) system by means of numerical simulation. The whole system is composed of several identical [...] Read more.

The main purpose of this study is to investigate the production behaviors of gas hydrate at site DK-2 in the Qilian Mountain permafrost using the novel five-spot well (5S) system by means of numerical simulation. The whole system is composed of several identical units, and each single unit consists of one injection well and four production wells. All the wells are placed horizontally in the hydrate deposit. The combination method of depressurization and thermal stimulation is employed for hydrate dissociation in the system. Simulation results show that favorable gas production and hydrate dissociation rates, gas-to-water ratio, and energy ratio can be acquired using this kind of multi-well system under suitable heat injection and depressurization driving forces, and the water production rate is manageable in the entire production process under current technology. In addition, another two kinds of two-spot well (2S) systems have also been employed for comparison. It is found that the 5S system will be more commercially profitable than the 2S configurations for gas production under the same operation conditions. Sensitivity analysis indicates that the gas production performance is dependent on the heat injection rate and the well spacing of the 5S system. Full article

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24 pages, 747 KiB

Open AccessArticle

Active Participation of Air Conditioners in Power System Frequency Control Considering Users’ Thermal Comfort

by Rongxiang Zhang, Xiaodong Chu^*, Wen Zhang and Yutian Liu

Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education, Shandong University, 17923 Jingshi Road, Jinan 250061, China

Energies 2015, 8(10), 10818-10841; https://doi.org/10.3390/en81010818 - 28 Sep 2015

Cited by 12 | Viewed by 6874

Abstract

Air conditioners have great potential to participate in power system frequency control. This paper proposes a control strategy to facilitate the active participation of air conditioners. For each air conditioner, a decentralized control law is designed to adjust its temperature set point in [...] Read more.

Air conditioners have great potential to participate in power system frequency control. This paper proposes a control strategy to facilitate the active participation of air conditioners. For each air conditioner, a decentralized control law is designed to adjust its temperature set point in response to the system frequency deviation. The decentralized control law accounts for the user’s thermal comfort that is evaluated by a fuzzy algorithm. The aggregation of air conditioners’ response is conducted by using the Monte Carlo simulation method. A structure preserving model is applied to the multi-bus power system, in which air conditioners are aggregated at certain load buses. An inner-outer iteration scheme is adopted to solve power system dynamics. An experiment is conducted on a test air conditioner to examine the performance of the proposed decentralized control law. Simulation results on a test power system verify the effectiveness of the proposed strategy for air conditioners participating in frequency control. Full article

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

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19 pages, 3139 KiB

Open AccessArticle

A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation

by Cuidong Xu and Ka Wai Eric Cheng^*

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

Energies 2015, 8(10), 10842-10860; https://doi.org/10.3390/en81010842 - 29 Sep 2015

Cited by 4 | Viewed by 8769

Abstract

A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage [...] Read more.

A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell). In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell). The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation. Full article

(This article belongs to the Collection Wind Turbines)

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22 pages, 2278 KiB

Open AccessArticle

Effect of Various Excitation Conditions on Vibrational Energy in a Multi-Degree-of-Freedom Torsional System with Piecewise-Type Nonlinearities

by Jong-Yun Yoon¹ and Byeongil Kim^2,*

¹ Division of Mechanical and Automotive Engineering, Kongju National University, Cheonan-si, Chungcheongnam-do 314-701, Korea

² School of Mechanical Engineering, Yeungnam University, Gyeongsan-si, Gyeongsangbuk-do 712-749, Korea

Energies 2015, 8(10), 10861-10882; https://doi.org/10.3390/en81010861 - 29 Sep 2015

Cited by 1 | Viewed by 5265

Abstract

Dynamic behaviors in practical driveline systems for wind turbines or vehicles are inherently affected by multiple nonlinearities such as piecewise-type torsional springs. However, various excitation conditions with different levels of magnitudes also show strong relationships to the dynamic behaviors when system responses are [...] Read more.

Dynamic behaviors in practical driveline systems for wind turbines or vehicles are inherently affected by multiple nonlinearities such as piecewise-type torsional springs. However, various excitation conditions with different levels of magnitudes also show strong relationships to the dynamic behaviors when system responses are examined in both frequency and time domains. This study investigated the nonlinear responses of torsional systems under various excitations by using the harmonic balance method and numerical analysis. In order to understand the effect of piecewise-type nonlinearities on vibrational energy with different excitations, the nonlinear responses were investigated with various comparisons. First, two different jumping phenomena with frequency up- and down-sweeping conditions were determined under severe excitation levels. Second, practical system analysis using the phase plane and Poincaré map was conducted in various ways. When the system responses were composed of quasi-periodic components, Poincaré map analysis clearly revealed the nonlinear dynamic characteristics and thus it is suggested to investigate complicated nonlinear dynamic responses in practical driveline systems. Full article

(This article belongs to the Collection Wind Turbines)

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21 pages, 2176 KiB

Open AccessArticle

Electro-Plating and Characterisation of CdTe Thin Films Using CdCl₂ as the Cadmium Source

by Nor A. Abdul-Manaf^1,2,*, Hussein I. Salim¹, Mohammad L. Madugu¹, Olajide I. Olusola¹ and Imyhamy M. Dharmadasa¹

¹ Electronic Materials and Sensors Group, Materials and Engineering Research Institute, Faculty of Arts, Computing, Engineering and Sciences, Sheffield Hallam University, Sheffield S1 1WB, UK

² Department of Physics, Centre for Defence Foundation Studies, National Defence University of Malaysia, Kem Sungai Besi, Kuala Lumpur 57000, Malaysia

Energies 2015, 8(10), 10883-10903; https://doi.org/10.3390/en81010883 - 29 Sep 2015

Cited by 37 | Viewed by 7701

Abstract

Cadmium telluride (CdTe) thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride (CdCl₂)·H₂O and tellurium dioxide (TeO₂) using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films [...] Read more.

Cadmium telluride (CdTe) thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride (CdCl₂)·H₂O and tellurium dioxide (TeO₂) using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films have been characterised using X-ray diffraction (XRD), Raman spectroscopy, optical profilometry, DC current-voltage (I-V) measurements, photoelectrochemical (PEC) cell measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectrophotometry. It is observed that the best cathodic potential is 698 mV with respect to standard calomel electrode (SCE) in a three electrode system. Structural analysis using XRD shows polycrystalline crystal structure in the as-deposited CdTe thin films and the peaks intensity increase after CdCl₂ treatment. PEC cell measurements show the possibility of growing p-, i- and n-type CdTe layers by varying the growth potential during electrodeposition. The electrical resistivity of the as-deposited layers are in the order of 10⁴Ω·cm. SEM and AFM show that the CdCl₂ treated samples are more roughness and have larger grain size when compared to CdTe grown by CdSO₄ precursor. Results obtained from the optical absorption reveal that the bandgap of as-deposited CdTe (1.48–1.52) eV reduce to (1.45–1.49) eV after CdCl₂ treatment. Full characterisation of this material is providing new information on crucial CdCl₂ treatment of CdTe thin films due to its built-in CdCl₂ treatment during the material growth. The work is progressing to fabricate solar cells with this material and compare with CdTe thin films grown by conventional sulphate precursors. Full article

(This article belongs to the Special Issue Key Developments in Thin Film Solar Cells)

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38 pages, 1020 KiB

Open AccessReview

Sustainable Power Supply Solutions for Off-Grid Base Stations

by Asma Mohamad Aris^1,* and Bahman Shabani²

¹ School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Room 12, Level 3, Building 57, Carlton VIC 3053, Australia

² School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, PO Box 71, Bundoora VIC 3083, Australia

Energies 2015, 8(10), 10904-10941; https://doi.org/10.3390/en81010904 - 29 Sep 2015

Cited by 110 | Viewed by 13454

Abstract

The telecommunication sector plays a significant role in shaping the global economy and the way people share information and knowledge. At present, the telecommunication sector is liable for its energy consumption and the amount of emissions it emits in the environment. In the [...] Read more.

The telecommunication sector plays a significant role in shaping the global economy and the way people share information and knowledge. At present, the telecommunication sector is liable for its energy consumption and the amount of emissions it emits in the environment. In the context of off-grid telecommunication applications, off-grid base stations (BSs) are commonly used due to their ability to provide radio coverage over a wide geographic area. However, in the past, the off-grid BSs usually relied on emission-intensive power supply solutions such as diesel generators. In this review paper, various types of solutions (including, in particular, the sustainable solutions) for powering BSs are discussed. The key aspects in designing an ideal power supply solution are reviewed, and these mainly include the pre-feasibility study and the thermal management of BSs, which comprise heating and cooling of the BS shelter/cabinets and BS electronic equipment and power supply components. The sizing and optimization approaches used to design the BSs’ power supply systems as well as the operational and control strategies adopted to manage the power supply systems are also reviewed in this paper. Full article

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16 pages, 1321 KiB

Open AccessArticle

Wind Tunnel Studies of a Pedestrian-Level Wind Environment in a Street Canyon between a High-Rise Building with a Podium and Low-Level Attached Houses

by Chien-Yuan Kuo^1,2, Chun-Ta Tzeng¹, Ming-Chin Ho² and Chi-Ming Lai^3,*

¹ Department of Architecture, National Cheng Kung University, No. 1, University Road, Tainan 701, Taiwan

² Architecture and Building Research Institute, Ministry of the Interior, No. 200, Sec. 3, Beisin Rd., Sindian District, New Taipei 23143, Taiwan

³ Department of Civil Engineering, National Cheng Kung University, No. 1, University Road, Tainan 701, Taiwan

Energies 2015, 8(10), 10942-10957; https://doi.org/10.3390/en81010942 - 29 Sep 2015

Cited by 41 | Viewed by 7631

Abstract

The pedestrian-level wind environment quality in street canyons formed by high-rise buildings and other low-level buildings could be affected by multiple factors, such as the height and geometry of the surrounding buildings, street width, wind direction, and wind speed. This study conducted wind [...] Read more.

The pedestrian-level wind environment quality in street canyons formed by high-rise buildings and other low-level buildings could be affected by multiple factors, such as the height and geometry of the surrounding buildings, street width, wind direction, and wind speed. This study conducted wind tunnel experiments to determine the characteristics of the pedestrian-level wind environment in street canyons under different conditions, including different street widths, podium heights, and approaching wind directions. The experimental results revealed that the effects of the street canyon width on the pedestrian-level wind in a street canyon can be categorized into three different flow regimes. A higher podium creates stronger wind speeds of the flow within the street canyon, and different approaching wind directions change the high-wind-speed zone within the street canyon accordingly. Full article

(This article belongs to the Special Issue Energy Efficient Building Design)

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13 pages, 1569 KiB

Open AccessArticle

Enhancing Thermoelectric Properties of Si₈₀Ge₂₀ Alloys Utilizing the Decomposition of NaBH₄ in the Spark Plasma Sintering Process

by Ali Lahwal^1,*, Xiaoyu Zeng¹, Sriparna Bhattacharya^1,2, Menghan Zhou¹, Dale Hitchcock¹, Mehmet Karakaya^1,2, Jian He¹, Apparao M. Rao^1,2 and Terry M. Tritt^1,3,*

¹ Department of Physics & Astronomy, Clemson University, Clemson, SC 29634, USA

² Clemson Nanomaterials Center, and Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29625, USA

³ Department of Materials Science & Engineering, Clemson University, Clemson, SC 29634, USA

Energies 2015, 8(10), 10958-10970; https://doi.org/10.3390/en81010958 - 29 Sep 2015

Cited by 10 | Viewed by 6381

Abstract

The thermoelectric properties of spark plasma sintered, ball-milled, p-type Si₈₀Ge₂₀-(NaBH₄)_x (x = 0.7,1.7 and 2.7), and Si₈₀Ge₂₀B_1.7-y-(NaBH₄)_y (y = 0.2 and 0.7) samples have been investigated [...] Read more.

The thermoelectric properties of spark plasma sintered, ball-milled, p-type Si₈₀Ge₂₀-(NaBH₄)_x (x = 0.7,1.7 and 2.7), and Si₈₀Ge₂₀B_1.7-y-(NaBH₄)_y (y = 0.2 and 0.7) samples have been investigated from 30 K to 1100 K. These samples were prepared by spark plasma sintering of an admixture of Si, Ge, B and NaBH₄ powders. In particular, the degasing process during the spark plasma sintering process, the combined results of X-ray powder diffraction, Raman spectroscopy, Hall coefficient, electrical resistivity, and Seebeck coefficient measurements indicated that NaBH₄ decomposed into Na, B, Na₂B₂₉, and H₂ during the spark plasma sintering process; Na and B were doped into the SiGe lattice, resulting in favorable changes in the carrier concentration and the power factor. In addition, the ball milling process and the formation of Na₂B₂₉ nanoparticles resulted in stronger grain boundary scattering of heat-carrying phonons, leading to a reduced lattice thermal conductivity. As a result, a significant improvement in the figure of merit ZT (60%) was attained in p-type Si₈₀Ge₂₀-(NaBH₄)_1.7 and Si₈₀Ge₂₀-B_1.5(NaBH₄)_0.7 at 1100 K as compared to the p-type B-doped Si₈₀Ge₂₀ material used in the NASA’s radioactive thermoelectric generators. This single-step “doping-nanostructuring” procedure can possibly be applied to other thermoelectric materials. Full article

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

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22 pages, 397 KiB

Open AccessArticle

Fault Current Characteristics of the DFIG under Asymmetrical Fault Conditions

by Fan Xiao^*, Zhe Zhang and Xianggen Yin

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

Energies 2015, 8(10), 10971-10992; https://doi.org/10.3390/en81010971 - 30 Sep 2015

Cited by 33 | Viewed by 6591

Abstract

During non-severe fault conditions, crowbar protection is not activated and the rotor windings of a doubly-fed induction generator (DFIG) are excited by the AC/DC/AC converter. Meanwhile, under asymmetrical fault conditions, the electrical variables oscillate at twice the grid frequency in synchronous dq frame. [...] Read more.

During non-severe fault conditions, crowbar protection is not activated and the rotor windings of a doubly-fed induction generator (DFIG) are excited by the AC/DC/AC converter. Meanwhile, under asymmetrical fault conditions, the electrical variables oscillate at twice the grid frequency in synchronous dq frame. In the engineering practice, notch filters are usually used to extract the positive and negative sequence components. In these cases, the dynamic response of a rotor-side converter (RSC) and the notch filters have a large influence on the fault current characteristics of the DFIG. In this paper, the influence of the notch filters on the proportional integral (PI) parameters is discussed and the simplified calculation models of the rotor current are established. Then, the dynamic performance of the stator flux linkage under asymmetrical fault conditions is also analyzed. Based on this, the fault characteristics of the stator current under asymmetrical fault conditions are studied and the corresponding analytical expressions of the stator fault current are obtained. Finally, digital simulation results validate the analytical results. The research results are helpful to meet the requirements of a practical short-circuit calculation and the construction of a relaying protection system for the power grid with penetration of DFIGs. Full article

(This article belongs to the Collection Wind Turbines)

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2 pages, 286 KiB

Open AccessCorrection

Serrano, J., et al. A Novel Ground Fault Identification Method for 2 × 5 kV Railway Power Supply Systems. Energies 2015, 8, 7020-7039

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(10), 10993-10994; https://doi.org/10.3390/en81010993 - 30 Sep 2015

Cited by 1 | Viewed by 3807

Abstract

The authors wish to make the following corrections to this paper [1]: [...] Full article

0 pages, 143 KiB

Open AccessRetraction

RETRACTED: Jin et al. A Robust WLS Power System State Estimation Method Integrating a Wide-Area Measurement System and SCADA Technology. Energies 2015, 8, 2769–2787

by Energies Editorial Office

MDPI AG, Klybeckstrasse 64, Basel CH-4057, Switzerland

Energies 2015, 8(10), 10995; https://doi.org/10.3390/en81010995 - 1 Oct 2015

Viewed by 4591

Abstract

The corresponding author has requested the withdrawal of [...] Full article

34 pages, 497 KiB

Open AccessReview

A Review of Approaches for Sensing, Understanding, and Improving Occupancy-Related Energy-Use Behaviors in Commercial Buildings

by Hamed Nabizadeh Rafsanjani, Changbum R. Ahn^* and Mahmoud Alahmad

The Durham School of Architectural Engineering and Construction, University of Nebraska-Lincoln, 113 NH, Lincoln, NE 68588-0500, USA

Energies 2015, 8(10), 10996-11029; https://doi.org/10.3390/en81010996 - 1 Oct 2015

Cited by 67 | Viewed by 10050

Abstract

Buildings currently account for 30–40 percent of total global energy consumption. In particular, commercial buildings are responsible for about 12 percent of global energy use and 21 percent of the United States’ energy use, and the energy demand of this sector continues to [...] Read more.

Buildings currently account for 30–40 percent of total global energy consumption. In particular, commercial buildings are responsible for about 12 percent of global energy use and 21 percent of the United States’ energy use, and the energy demand of this sector continues to grow faster than other sectors. This increasing rate therefore raises a critical concern about improving the energy performance of commercial buildings. Recently, researchers have investigated ways in which understanding and improving occupants’ energy-consuming behaviors could function as a cost-effective approach to decreasing commercial buildings’ energy demands. The objective of this paper is to present a detailed, up-to-date review of various algorithms, models, and techniques employed in the pursuit of understanding and improving occupants’ energy-use behaviors in commercial buildings. Previous related studies are introduced and three main approaches are identified: (1) monitoring occupant-specific energy consumption; (2) Simulating occupant energy consumption behavior; and (3) improving occupant energy consumption behavior. The first approach employs intrusive and non-intrusive load-monitoring techniques to estimate the energy use of individual occupants. The second approach models diverse characteristics related to occupants’ energy-consuming behaviors in order to assess and predict such characteristics’ impacts on the energy performance of commercial buildings; this approach mostly utilizes agent-based modeling techniques to simulate actions and interactions between occupants and their built environment. The third approach employs occupancy-focused interventions to change occupants’ energy-use characteristics. Based on the detailed review of each approach, critical issues and current gaps in knowledge in the existing literature are discussed, and directions for future research opportunities in this field are provided. Full article

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

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17 pages, 945 KiB

Open AccessArticle

Sensorless Speed Control with Initial Rotor Position Estimation for Surface Mounted Permanent Magnet Synchronous Motor Drive in Electric Vehicles

by Xuan Wu^*, Hui Wang, Shoudao Huang, Keyuan Huang and Li Wang

Green Car Collaborative Innovation Center of Hunan Province, Hunan University, Changsha 410082, China

Energies 2015, 8(10), 11030-11046; https://doi.org/10.3390/en81011030 - 1 Oct 2015

Cited by 19 | Viewed by 7468

Abstract

The accurate information of the initial rotor position is very critical for successful starting of the Surface-mounted Permanent Magnet Synchronous Motor (SPMSM). In order to solve the problems of low accuracy and unreliability in the conventional estimation strategy, in this paper, an improved [...] Read more.

The accurate information of the initial rotor position is very critical for successful starting of the Surface-mounted Permanent Magnet Synchronous Motor (SPMSM). In order to solve the problems of low accuracy and unreliability in the conventional estimation strategy, in this paper, an improved initial rotor position estimation strategy without any position sensor for SPMSM at standstill is proposed based on rectangular pulse voltage injection. In the work, when the second series of pulse voltages were applied. By the ways of strengthening the effect of weakening or strengthening magnetic fields and increasing the difference between each current of the vector. The improved strategy enhanced reliability and raised the initial position estimation accuracy from 7.5° to 1.875°. The improved strategy does not need any additional hardware. Experimental results demonstrate the validity and usefulness of the improved strategy. Full article

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29 pages, 748 KiB

Open AccessArticle

Energy and Environmental Evaluation of Non-Transparent Constructions of Building Envelope for Wooden Houses

by Silvia Vilčeková^1,*

, Monika Čuláková², Eva Krídlová Burdová¹

and Jana Katunská²

¹ Institute of Environmental Engineering, Technical University of Kosice, Vysokoškolská 4, Košice 042 00, Slovakia

² Institute of Architectural Engineering, Technical University of Kosice, Vysokoškolská 4, Košice 042 00, Slovakia

Energies 2015, 8(10), 11047-11075; https://doi.org/10.3390/en81011047 - 2 Oct 2015

Cited by 18 | Viewed by 6188

Abstract

The contribution of embodied energy (EE) and greenhouse gas emissions to building materials and structures has been recognized as significant, especially for nearly-zero energy-efficient buildings. The aim of this paper is to evaluate the composition of non-transparent structures of building envelopes from energy [...] Read more.

The contribution of embodied energy (EE) and greenhouse gas emissions to building materials and structures has been recognized as significant, especially for nearly-zero energy-efficient buildings. The aim of this paper is to evaluate the composition of non-transparent structures of building envelopes from energy and environmental perspectives using the life-cycle assessment method. The study assesses environmental indicators such as EE from non-renewable resources and CO_2eq and SO_2eq emissions from proposed assemblies of building structures for nearly-zero energy wooden houses. Material compositions are also calculated in terms of selected thermal-physical aspects (U-value, phase shift of thermal oscillation, relaxation time) to ensure the reduction of energy consumption during building operation. All results are compared using a multi-dimensional evaluation approach through mathematical methods. The multi-criteria decision analysis demonstrates that material optimization of building structures is possible to ensure a marked reduction of the energy consumption and carbon footprint of buildings. Full article

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19 pages, 3034 KiB

Open AccessArticle

An Integrated Environmental Indicator for Urban Transportation Systems: Description and Application

by Maria La Gennusa^*, Patrizia Ferrante^†, Barbara Lo Casto^† and Gianfranco Rizzo^†

¹ Dipartimento di Energia, ingegneria dell'Informazione e modelli Matematici (DEIM), Polytechnic School, University of Palermo, Viale delle Scienze, Ed. 9, 90128 Palermo, Italy

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11076-11094; https://doi.org/10.3390/en81011076 - 6 Oct 2015

Cited by 4 | Viewed by 4392

Abstract

A simplified version of the ecological footprint method is proposed for assessing the environmental performances of urban transportation systems. The method, starting from the knowledge of the composition of the running vehicular fleet, is here applied to a southern Italian province. It represents [...] Read more.

A simplified version of the ecological footprint method is proposed for assessing the environmental performances of urban transportation systems. The method, starting from the knowledge of the composition of the running vehicular fleet, is here applied to a southern Italian province. It represents a synthetic indicator of the environmental pressure exerted by the system also matching the pollutant emissions with the carrying capacity of the site. Particularly, the forested area needed to absorb the CO₂ emissions of the system is compared with the total forested area of the province. The results of the case-study indicates the yearly maximum distance that each vehicle of the fleet can cover in order for their emissions to be absorbed by the surrounding forested area. Specifically, if all cars of the fleet would travel for 10,000 km/year, 97% of the forested area would be involved. Thanks to its features, this indicator can be usefully adopted for ranking different transportation options. Therefore, it could allow local administrations to environmentally hierarchize alternative plans concerning urban transportation choices. Full article

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25 pages, 1619 KiB

Open AccessArticle

Scheduling of Multiple Chillers in Trigeneration Plants

by Chris Underwood^1,*, Bobo Ng¹ and Francis Yik²

¹ Department of Mechanical and Construction Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK

² Atal Engineering Ltd, North Point, Hong Kong SAR, China

Energies 2015, 8(10), 11095-11119; https://doi.org/10.3390/en81011095 - 7 Oct 2015

Cited by 8 | Viewed by 6536

Abstract

The scheduling of both absorption cycle and vapour compression cycle chillers in trigeneration plants is investigated in this work. Many trigeneration plants use absorption cycle chillers only but there are potential performance advantages to be gained by using a combination of absorption and [...] Read more.

The scheduling of both absorption cycle and vapour compression cycle chillers in trigeneration plants is investigated in this work. Many trigeneration plants use absorption cycle chillers only but there are potential performance advantages to be gained by using a combination of absorption and compression chillers especially in situations where the building electrical demand to be met by the combined heat and power (CHP) plant is variable. Simulation models of both types of chillers are developed together with a simple model of a variable-capacity CHP engine developed by curve-fitting to supplier’s data. The models are linked to form an optimisation problem in which the contribution of both chiller types is determined at a maximum value of operating cost (or carbon emission) saving. Results show that an optimum operating condition arises at moderately high air conditioning demands and moderately low power demand when the air conditioning demand is shared between both chillers, all recovered heat is utilised, and the contribution arising from the compression chiller results in an increase in CHP power generation and, hence, engine efficiency. Full article

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

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19 pages, 1598 KiB

Open AccessArticle

The Effect of Electric Load Profiles on the Performance of Off-Grid Residential Hybrid Renewable Energy Systems

by Stephen Treado

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

Energies 2015, 8(10), 11120-11138; https://doi.org/10.3390/en81011120 - 7 Oct 2015

Cited by 13 | Viewed by 6715

Abstract

This paper investigates the energy performance of off-grid residential hybrid renewable electric power systems, particularly the effect of electric load profiles on the ability to harvest available solar energy and avoid the consumption of auxiliary energy in the form of propane. The concepts [...] Read more.

This paper investigates the energy performance of off-grid residential hybrid renewable electric power systems, particularly the effect of electric load profiles on the ability to harvest available solar energy and avoid the consumption of auxiliary energy in the form of propane. The concepts are illustrated by an analysis of the energy performance of electric and propane-fired refrigerators. Off-grid electric power systems frequently incorporate a renewable source, such as wind or solar photovoltaic (PV), with a back-up power provided by a propane fueled motor/generator. Among other design decisions, residential consumers face the choice of employing an electric refrigerator with a conventional vapor compression refrigeration system, or a fuel-fired refrigerator operating as an absorption refrigeration system. One interesting question is whether it is more advantageous from an energy perspective to use electricity to run the refrigerator, which might be provided by some combination of the PV and propane motor/generator, thereby taking advantage of the relatively higher electric refrigerator Coefficient of Performance (COP) and free solar energy but having to accept a low electrical conversion efficiency of the motor/generator, or use thermal energy from the combustion of propane to produce the refrigeration effect via an absorption system, albeit with a much lower COP. The analysis is complicated by the fact that most off-grid renewable electrical power systems utilize a battery bank to provide electrical power when it is not available from the wind turbine or PV system, so the state of charge of the battery bank will have a noticeable impact on what energy source is available at any moment in time. Daily electric load profiles combined with variable solar energy input determine the state of charge of the battery bank, with the degree of synchronization between the two being a critical factor in determining performance. The annual energy usage and fuel input depend strongly on the ability to make use of the renewable sources in real time to avoid battery bank conversion losses and dumping of excess electrical power, as well as to have sufficient battery storage capacity to minimize the need for operation of the motor/generator to meet electric loads which occur during periods when the renewable energy is not available. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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14 pages, 3053 KiB

Open AccessArticle

Indoor Thermal Environment of Temporary Mobile Energy Shelter Houses (MeSHs) in South Korea

by Jeong-Gook Kim¹, Junghun Lee¹, Byung-Lip Ahn², Hwayeon Shin³, Seunghwan Yoo², Cheol-Yong Jang², Doosam Song¹ and Jonghun Kim^2,*

¹ Department of Architectural Engineering, Sungkyunkwan University, Suwon KS002, Republic of Korea

² Energy Saving Laboratory, Korea Institute of Energy Research, Daejeon KS015, Republic of Korea

³ Qualification Development & Certification Laboratory, Korea Productivity Center, Seoul KS013, Republic of Korea

Energies 2015, 8(10), 11139-11152; https://doi.org/10.3390/en81011139 - 7 Oct 2015

Cited by 15 | Viewed by 6399

Abstract

Temporary housing must be developed to support the long-term residence needs of disaster victims. The present study assesses a temporary housing unit, the so-called Mobile Energy Shelter House (MeSH), incorporating the “Korean Dwelling Insulation Standard” in order to reduce energy usage for cooling [...] Read more.

Temporary housing must be developed to support the long-term residence needs of disaster victims. The present study assesses a temporary housing unit, the so-called Mobile Energy Shelter House (MeSH), incorporating the “Korean Dwelling Insulation Standard” in order to reduce energy usage for cooling and heating. To assess energy performance, the characteristics of the indoor thermal environment were measured during the winter and summer seasons. In summer, at maximum insolation, the outdoor temperature was 37.6 °C and the indoor temperature of the MeSH ranged from 18 to 24 °C when the cooling system was not used. Conversely, during winter, the average outdoor temperature was −11.3 °C and the indoor temperature ranged from 16.09 to 20.63 °C when a temperature-controlled floor-heating was installed. Furthermore, the Predicted Mean Vote (PMV) was adopted to determine whether the ISO 7730 comfort criterion (i.e., PMV range from −0.5 to +0.5) was achieved. Based on the calculations presented here, PMV in summer ranged from −1.21 to +1.07 and that in winter ranged from −0.08 to −0.85, suggesting that the thermal environment is not always comfortable for occupants in either summer or winter. Nevertheless, the ISO comfort criterion can be achieved through varying air velocity in summer and changing clothing characteristics in winter. A comparison between yearly energy demand of existing characteristic temporary housing (Shelter House) and the MeSH modules used in this study was performed. The simulation results show a 60% difference in energy demand between MeSH and existing temporary housing shelter houses. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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14 pages, 2107 KiB

Open AccessArticle

Determination of Enhanced Oil Recovery Candidate Fields in the Volga-Ural Oil and Gas Region Territory

by Mikhail Turbakov

and Аleksandr Shcherbakov^*

Department of Oil and Gas Technologies, Perm National Research Polytechnic University, 29, Komsomolskii av., Perm 614990, Russia

Energies 2015, 8(10), 11153-11166; https://doi.org/10.3390/en81011153 - 9 Oct 2015

Cited by 6 | Viewed by 6261

Abstract

Most of the current Russian oil production comes from mature fields. The application of enhanced oil recovery methods on oil fields increases recovery efficiency. This article presents an analysis of the increased field development efficiency methods of the Volga-Ural oil and gas region, [...] Read more.

Most of the current Russian oil production comes from mature fields. The application of enhanced oil recovery methods on oil fields increases recovery efficiency. This article presents an analysis of the increased field development efficiency methods of the Volga-Ural oil and gas region, which allows the full and efficient development of last-stage fields with unconventional reserves and production stabilization. The selection of the optimum method for a given field is a complex procedure consisting of many stages, from collecting data about the field, through more advanced data interpretation, to working out a detailed proposal for the most efficient extraction method. In this article the instantaneous and average annual growth above wells average was taken as a performance criterion for enhanced oil recovery methods. Based on the performed analysis, it follows that candidate wells for enhanced oil recovery method use must meet the I group parameters (high values of the remaining recoverable reserves and improved reservoir properties, low water cut, obtained oil rate increase). In order to assess the possible increase in production rate after enhanced oil recovery methods hydrodynamic modeling of radial drilling, acid treatment and water-alternated-gas injection for two oil fields of the Volga-Ural oil and gas region were performed. Full article

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20 pages, 913 KiB

Open AccessArticle

An Online Learning Control Strategy for Hybrid Electric Vehicle Based on Fuzzy Q-Learning

by Yue Hu^1,2,3, Weimin Li^1,3,*, Hui Xu³ and Guoqing Xu¹

¹ Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China

² Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen 518055, China

³ Jining Institutes of Advanced Technology, Chinese Academy of Sciences, Jining 272000, China

Energies 2015, 8(10), 11167-11186; https://doi.org/10.3390/en81011167 - 9 Oct 2015

Cited by 31 | Viewed by 8149

Abstract

In order to realize the online learning of a hybrid electric vehicle (HEV) control strategy, a fuzzy Q-learning (FQL) method is proposed in this paper. FQL control strategies consists of two parts: The optimal action-value function Q*(x,u) estimator [...] Read more.

In order to realize the online learning of a hybrid electric vehicle (HEV) control strategy, a fuzzy Q-learning (FQL) method is proposed in this paper. FQL control strategies consists of two parts: The optimal action-value function Q*(x,u) estimator network (QEN) and the fuzzy parameters tuning (FPT). A back propagation (BP) neural network is applied to estimate Q*(x,u) as QEN. For the fuzzy controller, we choose a Sugeno-type fuzzy inference system (FIS) and the parameters of the FIS are tuned online based on Q*(x,u). The action exploration modifier (AEM) is introduced to guarantee all actions are tried. The main advantage of a FQL control strategy is that it does not rely on prior information related to future driving conditions and can self-tune the parameters of the fuzzy controller online. The FQL control strategy has been applied to a HEV and simulation tests have been done. Simulation results indicate that the parameters of the fuzzy controller are tuned online and that a FQL control strategy achieves good performance in fuel economy. Full article

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

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16 pages, 333 KiB

Open AccessReview

Controllable Load Management Approaches in Smart Grids

by Jingshuang Shen, Chuanwen Jiang^* and Bosong Li

Department of Electrical Engineering, Shanghai Jiaotong University, Shanghai 200240, China

Energies 2015, 8(10), 11187-11202; https://doi.org/10.3390/en81011187 - 9 Oct 2015

Cited by 84 | Viewed by 9743

Abstract

With rapid smart grid technology development, the customer can actively participate in demand-side management (DSM) with the mutual information communication between the distributor operation company and the smart devices in real-time. Controllable load management not only has the advantage of peak shaving, load [...] Read more.

With rapid smart grid technology development, the customer can actively participate in demand-side management (DSM) with the mutual information communication between the distributor operation company and the smart devices in real-time. Controllable load management not only has the advantage of peak shaving, load balance, frequency regulation, and voltage stability, but is also effective at providing fast balancing services to the renewable energy grid in the distributed power system. The load management faces an enormous challenge as the customer has a large number of both small residential loads and dispersed renewable sources. In this paper, various controllable load management approaches are discussed. The traditional controllable load approaches such as the end users’ controllable appliances, storage battery, Vehicle-to-Grid (V2G), and heat storage are reviewed. The “broad controllable loads” management, such as the microgrid, Virtual Power Plant (VPP), and the load aggregator are also presented. Furthermore, the load characteristics, control strategies, and control effectiveness are analyzed. Full article

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

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31 pages, 3211 KiB

Open AccessArticle

Design Parameters Analysis of Point Absorber WEC via an evolutionary-algorithm-based Dimensioning Tool

by Marcos Blanco^1,*, Pablo Moreno-Torres¹, Marcos Lafoz¹

and Dionisio Ramírez²

¹ Division of Electrical Engineering, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Avda. Complutense, 40, Madrid 28040, Spain

² Department of Automatica, Electrical, Electronic and Computer Engineering, Universidad Politécnica de Madrid, Madrid 28006, Spain

Energies 2015, 8(10), 11203-11233; https://doi.org/10.3390/en81011203 - 12 Oct 2015

Cited by 27 | Viewed by 7545

Abstract

Wave energy conversion has an essential difference from other renewable energies since the dependence between the devices design and the energy resource is stronger. Dimensioning is therefore considered a key stage when a design project of Wave Energy Converters (WEC) is undertaken. Location, [...] Read more.

Wave energy conversion has an essential difference from other renewable energies since the dependence between the devices design and the energy resource is stronger. Dimensioning is therefore considered a key stage when a design project of Wave Energy Converters (WEC) is undertaken. Location, WEC concept, Power Take-Off (PTO) type, control strategy and hydrodynamic resonance considerations are some of the critical aspects to take into account to achieve a good performance. The paper proposes an automatic dimensioning methodology to be accomplished at the initial design project stages and the following elements are described to carry out the study: an optimization design algorithm, its objective functions and restrictions, a PTO model, as well as a procedure to evaluate the WEC energy production. After that, a parametric analysis is included considering different combinations of the key parameters previously introduced. A variety of study cases are analysed from the point of view of energy production for different design-parameters and all of them are compared with a reference case. Finally, a discussion is presented based on the results obtained, and some recommendations to face the WEC design stage are given. Full article

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

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20 pages, 3095 KiB

Open AccessArticle

Practical Experience of Operational Diagnostics and Defectoscopy on Photovoltaic Installations in the Czech Republic

by Petr Mastny^*, Jan Moravek and Jiri Drapela

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

Energies 2015, 8(10), 11234-11253; https://doi.org/10.3390/en81011234 - 12 Oct 2015

Cited by 9 | Viewed by 5983

Abstract

Fundamental changes concerning the development of photovoltaic (PV) installations in the Czech Republic (CR) have occurred after 2010. The limits (and subsequent termination) of support for the newly installed PV power plants (cancellation of purchase prices for produced electricity) were the most important. [...] Read more.

Fundamental changes concerning the development of photovoltaic (PV) installations in the Czech Republic (CR) have occurred after 2010. The limits (and subsequent termination) of support for the newly installed PV power plants (cancellation of purchase prices for produced electricity) were the most important. This change of approach was advised by the relevant state authorities before the end of the year 2010 and resulted in a massive increase in PV installations during 2010. The goal of investors was to get more favorable conditions for the purchase of the electricity produced. A considerable amount of PV installations had been registered by the end of 2010, which do not reach the projected operating performance—this is caused by errors during installation and in many cases by inappropriately used (poor quality) components. This paper is focused on the operation of PV power plants in the conditions of the CR. A final analysis of the operational measurements performed and potential approaches and methods applicable to operational diagnosis of defects on PV panels are presented. A brief mention is also made of the economic situation of PV systems operating in the current legislative conditions in the CR. Full article

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

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22 pages, 3521 KiB

Open AccessArticle

Energy Management of a Hybrid-Power Gas Engine-Driven Heat Pump

by Qingkun Meng, Liang Cai^*, Wenxiu Ji, Jie Yan, Tao Zhang and Xiaosong Zhang

Air Conditioning and Refrigeration Laboratory, School of Energy and Environment, Southeast University, 2 Sipailou Street, Xuanwu District, Nanjing 210096, China

Energies 2015, 8(10), 11254-11275; https://doi.org/10.3390/en81011254 - 12 Oct 2015

Cited by 5 | Viewed by 5031

Abstract

The hybrid-power gas engine-driven heat pump (HPGHP) combines hybrid power technology with a gas engine heat pump. The engine in the power system is capable of operating constantly with high thermal efficiency and low emissions during different operating modes. In this paper, the [...] Read more.

The hybrid-power gas engine-driven heat pump (HPGHP) combines hybrid power technology with a gas engine heat pump. The engine in the power system is capable of operating constantly with high thermal efficiency and low emissions during different operating modes. In this paper, the mathematical models of various components is established, including the engine thermal efficiency map and the motor efficiency map. The comprehensive charging/discharging efficiency model and energy management optimization strategy model which is proposed to maximize the efficiency of instantaneous HPGHP system are established. Then, different charging/discharging torque limits are obtained. Finally, a novel gas engine economical zone control strategy which combined with the SOC of battery in real time is put forward. The main operating parameters of HPGHP system under energy management are simulated by Matlab/Simulink and validated by experimental data, such as engine and motor operating torque, fuel consumption rate and comprehensive efficiency, etc. The results show that during 3600 s’ run-time, the SOC value of battery packs varies between 0.58 and 0.705, the fuel consumption rate reaches minimum values of approximately 291.3 g/(kW h) when the compressor speed is nearly 1550 rpm in mode D, the engine thermal efficiency and comprehensive efficiency reach maximum values of approximately 0.2727 and 0.2648 when the compressor speed is 1575 rpm and 1475 rpm, respectively, in mode D. In general, the motor efficiency can be maintained above 0.85 in either mode. Full article

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19 pages, 823 KiB

Open AccessArticle

Four-Wire Delta Service Sinusoidal Operation and Compensation Simulator

by Vicente León-Martínez^1,†

, Joaquín Montañana-Romeu^1,*,†

, Peter Radda^2,† and Antonio Cazorla-Navarro^1,†

¹ Electrical Engineering Department, Universitat Politécnica de Valencia, Camino de Vera 14, Valencia 46022, Spain

² Fluke Vertriebsgesellschaft (Fluke Design Center Vienna for Power and Power Quality), Liebermannstraße F01, Brunn am Gebirge A-2345, Austria

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11276-11294; https://doi.org/10.3390/en81011276 - 13 Oct 2015

Cited by 1 | Viewed by 3874

Abstract

An off-line simulator based on Excel used to evaluate the operation of four-wire delta (4WD) services as well as the effects of reactive and imbalance compensators in sinusoidal steady-state conditions is described in this paper. Voltages, currents and powers in the primary and [...] Read more.

An off-line simulator based on Excel used to evaluate the operation of four-wire delta (4WD) services as well as the effects of reactive and imbalance compensators in sinusoidal steady-state conditions is described in this paper. Voltages, currents and powers in the primary and secondary windings of the transformer as well as in the high voltage (HV) and low voltage (LV) lines and in the loads are calculated through that simulator. The apparent powers in the mains, transformer and loads are determined applying Buchholz’s and unified power measurement (UPM) formulations in both scalar and vector notations. The effects of the neutral current are especially examined, in order to minimize them, and the optimal wye load distribution is determined by the simulator. The simulator provides the necessary elements of passive reactive and unbalanced compensators that optimize the 4WD transformer operation too. Those compensators are determined for each load, and they can be separately selected and included in the simulation process or not. An application example is finally used to step by step explain how the simulator runs. Full article

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20 pages, 891 KiB

Open AccessArticle

Peak Operation of Cascaded Hydropower Plants Serving Multiple Provinces

by Jianjian Shen^1,*, Chuntian Cheng^1,*, Jun Zhang² and Jianyu Lu³

¹ Institute of Hydropower and Hydroinformatics, Dalian University of Technology, Dalian 116024, Liaoning, China

² State Grid Zhejiang Electric Power Company, Hangzhou 310000, Zhejiang, China

³ East China Electric Power Control Center, Shanghai 200122, China

Energies 2015, 8(10), 11295-11314; https://doi.org/10.3390/en81011295 - 13 Oct 2015

Cited by 21 | Viewed by 5772

Abstract

The bulk hydropower transmission via trans-provincial and trans-regional power networks in China provides great operational flexibility to dispatch power resources between multiple power grids. This is very beneficial to alleviate the tremendous peak load pressure of most provincial power grids. This study places [...] Read more.

The bulk hydropower transmission via trans-provincial and trans-regional power networks in China provides great operational flexibility to dispatch power resources between multiple power grids. This is very beneficial to alleviate the tremendous peak load pressure of most provincial power grids. This study places the focus on peak operations of cascaded hydropower plants serving multiple provinces under a regional connected AC/DC network. The objective is to respond to peak loads of multiple provincial power grids simultaneously. A two-stage search method is developed for this problem. In the first stage, a load reconstruction strategy is proposed to combine multiple load curves of power grids into a total load curve. The purpose is to deal with different load features in load magnitudes, peaks and valleys. A mutative-scale optimization method is then used to determine the generation schedules of hydropower plants. In the second stage, an exterior point search method is established to allocate the generation among multiple receiving power grids. This method produces an initial solution using the load shedding algorithm, and further improves it by iteratively coordinating the generation among different power grids. The proposed method was implemented to the operations of cascaded hydropower plants on Xin-Fu River and another on Hongshui River. The optimization results in two cases satisfied the peak demands of receiving provincial power grids. Moreover, the maximum load difference between peak and valley decreased 12.67% and 11.32% in Shanghai Power Grid (SHPG) and Zhejiang Power Grid (ZJPG), exceeding by 4.85% and 6.72% those of the current operational method, respectively. The advantage of the proposed method in alleviating peak-shaving pressure is demonstrated. Full article

(This article belongs to the Special Issue Hydropower)

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27 pages, 39009 KiB

Open AccessArticle

A Tabu Search Algorithm for the Power System Islanding Problem

by Fei Tang¹

, Huizhi Zhou¹, Qinghua Wu^2,*, Hu Qin², Jun Jia¹ and Ke Guo¹

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

² School of Management, Huazhong University of Science and Technology, No.1037, Luoyu Road, Wuhan 430074, China

Energies 2015, 8(10), 11315-11341; https://doi.org/10.3390/en81011315 - 13 Oct 2015

Cited by 14 | Viewed by 8469

Abstract

The power system islanding problem aims to divide the power system into several different islands after serious disturbances occur. The objective of this problem is to minimize the total generation-load imbalance of all islands while placing the coherent generators in the same island [...] Read more.

The power system islanding problem aims to divide the power system into several different islands after serious disturbances occur. The objective of this problem is to minimize the total generation-load imbalance of all islands while placing the coherent generators in the same island and maintaining the connectivity of each island. Two main challenges of solving this problem are the large scale of the power system and the requirement of a short computation time. In this study, we propose a tailored tabu search algorithm to solve this problem, which employs a novel initial solution generation procedure and a neighborhood operation based on the movement of the boundary nodes. The numerical experiments on 15 test instances show that this algorithm can deal with the power systems with up to 3120 nodes within 0.7 s. Then, the comparisons with some existing islanding methods based on the IEEE 39-bus system and the IEEE 118-bus system prove the validity and accuracy of our method. Finally, time-domain simulations based on three power systems demonstrate the importance of our tabu search algorithm in minimizing the impacts of the disastrous disturbances. The computational results imply that our tabu search algorithm is very effective and efficient and satisfies the requirements of islanding power systems of various sizes. Full article

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21 pages, 1080 KiB

Open AccessArticle

Investigation of High-Efficiency Wireless Power Transfer Criteria of Resonantly-Coupled Loops and Dipoles through Analysis of the Figure of Merit

by Charles Moorey^*, William Holderbaum

and Ben Potter

School of Systems Engineering, University of Reading, Whiteknights, Reading RG6 6AY, UK

Energies 2015, 8(10), 11342-11362; https://doi.org/10.3390/en81011342 - 13 Oct 2015

Cited by 13 | Viewed by 5992

Abstract

The efficiency of a Wireless Power Transfer (WPT) system is greatly dependent on both the geometry and operating frequency of the transmitting and receiving structures. By using Coupled Mode Theory (CMT), the figure of merit is calculated for resonantly-coupled loop and dipole systems. [...] Read more.

The efficiency of a Wireless Power Transfer (WPT) system is greatly dependent on both the geometry and operating frequency of the transmitting and receiving structures. By using Coupled Mode Theory (CMT), the figure of merit is calculated for resonantly-coupled loop and dipole systems. An in-depth analysis of the figure of merit is performed with respect to the key geometric parameters of the loops and dipoles, along with the resonant frequency, in order to identify the key relationships leading to high-efficiency WPT. For systems consisting of two identical single-turn loops, it is shown that the choice of both the loop radius and resonant frequency are essential in achieving high-efficiency WPT. For the dipole geometries studied, it is shown that the choice of length is largely irrelevant and that as a result of their capacitive nature, low-MHz frequency dipoles are able to produce significantly higher figures of merit than those of the loops considered. The results of the figure of merit analysis are used to propose and subsequently compare two mid-range loop and dipole WPT systems of equal size and operating frequency, where it is shown that the dipole system is able to achieve higher efficiencies than the loop system of the distance range examined. Full article

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

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17 pages, 443 KiB

Open AccessArticle

Designing a Profit-Maximizing Critical Peak Pricing Scheme Considering the Payback Phenomenon

by Sung Chan Park¹, Young Gyu Jin^2,* and Yong Tae Yoon¹

¹ Department of Electrical Engineering and Computer Science, Seoul National University, Daehak-dong, Gwanak-gu, Seoul 151-742, Korea

² Center for Advanced Power & Environmental Technology (APET), the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Energies 2015, 8(10), 11363-11379; https://doi.org/10.3390/en81011363 - 13 Oct 2015

Cited by 13 | Viewed by 4709

Abstract

Critical peak pricing (CPP) is a demand response program that can be used to maximize profits for a load serving entity in a deregulated market environment. Like other such programs, however, CPP is not free from the payback phenomenon: a rise in consumption [...] Read more.

Critical peak pricing (CPP) is a demand response program that can be used to maximize profits for a load serving entity in a deregulated market environment. Like other such programs, however, CPP is not free from the payback phenomenon: a rise in consumption after a critical event. This payback has a negative effect on profits and thus must be appropriately considered when designing a CPP scheme. However, few studies have examined CPP scheme design considering payback. This study thus characterizes payback using three parameters (duration, amount, and pattern) and examines payback effects on the optimal schedule of critical events and on the optimal peak rate for two specific payback patterns. This analysis is verified through numerical simulations. The results demonstrate the need to properly consider payback parameters when designing a profit-maximizing CPP scheme. Full article

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

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24 pages, 2732 KiB

Open AccessArticle

Analysis and Optimization Design of a Solar Water Heating System Based on Life Cycle Cost Using a Genetic Algorithm

by Myeong Jin Ko

Urban Development Institute, Incheon National University, Incheon 406-772, Korea

Energies 2015, 8(10), 11380-11403; https://doi.org/10.3390/en81011380 - 13 Oct 2015

Cited by 32 | Viewed by 7227

Abstract

This paper presents an optimization method to design a solar water heating (SWH) system based on life cycle cost (LCC). A genetic algorithm is employed to optimize its configuration and sizing as the optimization technique. To ensure that the optimal solution obtained from [...] Read more.

This paper presents an optimization method to design a solar water heating (SWH) system based on life cycle cost (LCC). A genetic algorithm is employed to optimize its configuration and sizing as the optimization technique. To ensure that the optimal solution obtained from the proposed method is a practical design, three constraint conditions, including the energy balance, solar fraction, and available space to install solar collectors, have been set. In addition, the real devices available in the marketplace are considered in the optimization process that searches for optimal configuration and sizing, which is represented by the type and number of each component. By using the proposed method, a SWH system in an office building, South Korea has been designed and optimized. It is observed that a low solar fraction does not always present a decrease in the LCC. A trade-off between the equipment cost and the energy cost results in an optimal design of the SWH system that yields the minimum LCC. Full article

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26 pages, 908 KiB

Open AccessArticle

Re-Industrialisation and Low-Carbon Economy—Can They Go Together? Results from Stakeholder-Based Scenarios for Energy-Intensive Industries in the German State of North Rhine Westphalia

by Stefan Lechtenböhmer^1,*, Clemens Schneider^1,†, María Yetano Roche^1,†

and Samuel Höller^2,†

¹ Wuppertal Institute for Climate, Energy and Environment, Döppersberg 19, 42103 Wuppertal, Germany

² Umweltbundesamt, Deutsche Emissionshandelsstelle (DEHSt), Bismarckplatz 1, 14193 Berlin, Germany

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11404-11429; https://doi.org/10.3390/en81011404 - 13 Oct 2015

Cited by 25 | Viewed by 8729

Abstract

The German federal state of North Rhine-Westphalia (NRW) is home to one of the most important industrial regions in Europe, and is the first German state to have adopted its own Climate Protection Law (CPL). This paper describes the long-term (up to 2050) [...] Read more.

The German federal state of North Rhine-Westphalia (NRW) is home to one of the most important industrial regions in Europe, and is the first German state to have adopted its own Climate Protection Law (CPL). This paper describes the long-term (up to 2050) mitigation scenarios for NRW’s main energy-intensive industrial sub-sectors which served to support the implementation of the CPL. It also describes the process of scenario development, as these scenarios were developed through stakeholder participation. The scenarios considered three different pathways (best-available technologies, break-through technologies, and CO₂ capture and storage). All pathways had optimistic assumptions on the rate of industrial growth and availability of low-carbon electricity. We find that a policy of “re-industrialisation” for NRW based on the current industrial structures (assumed here to represent an average growth of NRWs industrial gross value added (GVA) of 1.6% per year until 2030 and 0.6% per year from 2030 to 2050), would pose a significant challenge for the achievement of overall energy demand and German greenhouse gas (GHG) emission targets, in particular as remaining efficiency potentials in NRW are limited. In the best-available technology (BAT) scenario CO₂ emission reductions of only 16% are achieved, whereas the low carbon (LC) and the carbon capture and storage (CCS) scenario achieve 50% and 79% reduction respectively. Our results indicate the importance of successful development and implementation of a decarbonised electricity supply and breakthrough technologies in industry—such as electrification, hydrogen-based processes for steel, alternative cements or CCS—if significant growth is to be achieved in combination with climate mitigation. They, however, also show that technological solutions alone, together with unmitigated growth in consumption of material goods, could be insufficient to meet GHG reduction targets in industry. Full article

(This article belongs to the Special Issue Applied Energy System Modeling 2015)

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22 pages, 945 KiB

Open AccessArticle

Hybrid Intelligent Control Method to Improve the Frequency Support Capability of Wind Energy Conversion Systems

by Shin Young Heo, Mun Kyeom Kim^* and Jin Woo Choi

Department of Energy System Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 604-714, Korea

Energies 2015, 8(10), 11430-11451; https://doi.org/10.3390/en81011430 - 13 Oct 2015

Cited by 13 | Viewed by 6293

Abstract

This paper presents a hybrid intelligent control method that enables frequency support control for permanent magnet synchronous generators (PMSGs) wind turbines. The proposed method for a wind energy conversion system (WECS) is designed to have PMSG modeling and full-scale back-to-back insulated-gate bipolar transistor [...] Read more.

This paper presents a hybrid intelligent control method that enables frequency support control for permanent magnet synchronous generators (PMSGs) wind turbines. The proposed method for a wind energy conversion system (WECS) is designed to have PMSG modeling and full-scale back-to-back insulated-gate bipolar transistor (IGBT) converters comprising the machine and grid side. The controller of the machine side converter (MSC) and the grid side converter (GSC) are designed to achieve maximum power point tracking (MPPT) based on an improved hill climb searching (IHCS) control algorithm and de-loaded (DL) operation to obtain a power margin. Along with this comprehensive control of maximum power tracking mode based on the IHCS, a method for kinetic energy (KE) discharge control of the supporting primary frequency control scheme with DL operation is developed to regulate the short-term frequency response and maintain reliable operation of the power system. The effectiveness of the hybrid intelligent control method is verified by a numerical simulation in PSCAD/EMTDC. Simulation results show that the proposed approach can improve the frequency regulation capability in the power system. Full article

(This article belongs to the Collection Wind Turbines)

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18 pages, 2340 KiB

Open AccessArticle

Impact of the Converter Control Strategies on the Drive Train of Wind Turbine during Voltage Dips

by Fenglin Miao, Hongsheng Shi^* and Xiaoqing Zhang

National Active Distribution Network Technology Research Center, School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China

Energies 2015, 8(10), 11452-11469; https://doi.org/10.3390/en81011452 - 13 Oct 2015

Cited by 4 | Viewed by 6785

Abstract

The impact of converter control strategies on the drive train of wind turbines during voltage dips is investigated in this paper using a full electromechanical model. Aerodynamics and tower vibration are taken into consideration by means of a simulation program, named FAST. Detailed [...] Read more.

The impact of converter control strategies on the drive train of wind turbines during voltage dips is investigated in this paper using a full electromechanical model. Aerodynamics and tower vibration are taken into consideration by means of a simulation program, named FAST. Detailed gearbox and electrical subsystems are represented in MATLAB. The dynamic response of electromagnetic torque and its impact on the mechanical variables are the concern in this paper and the response of electrical variables is less discussed. From the mechanical aspects, the effect of rising power recovery speed and unsymmetrical voltage dips are analyzed on the basis of the dynamic response of the high-speed shaft (HSS). A comparison of the impact on the drive train is made for two converter control strategies during small voltage dips. Through the analysis of torque, speed and tower vibration, the results indicate that both power recovery speed and the sudden torque sag have a significant impact on drive trains, and the effects depend on the different control strategies. Moreover, resonance might be excited on the drive train by an unbalanced voltage. Full article

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

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23 pages, 5284 KiB

Open AccessReview

Recent Advances in Ocean Nuclear Power Plants

by Kang-Heon Lee¹, Min-Gil Kim², Jeong Ik Lee² and Phill-Seung Lee^1,*

¹ Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

² Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Energies 2015, 8(10), 11470-11492; https://doi.org/10.3390/en81011470 - 14 Oct 2015

Cited by 89 | Viewed by 16781

Abstract

In this paper, recent advances in Ocean Nuclear Power Plants (ONPPs) are reviewed, including their general arrangement, design parameters, and safety features. The development of ONPP concepts have continued due to initiatives taking place in France, Russia, South Korea, and the United States. [...] Read more.

In this paper, recent advances in Ocean Nuclear Power Plants (ONPPs) are reviewed, including their general arrangement, design parameters, and safety features. The development of ONPP concepts have continued due to initiatives taking place in France, Russia, South Korea, and the United States. Russia’s first floating nuclear power stations utilizing the PWR technology (KLT-40S) and the spar-type offshore floating nuclear power plant designed by a research group in United States are considered herein. The APR1400 and SMART mounted Gravity Based Structure (GBS)-type ONPPs proposed by a research group in South Korea are also considered. In addition, a submerged-type ONPP designed by DCNS of France is taken into account. Last, issues and challenges related to ONPPs are discussed and summarized. Full article

(This article belongs to the Special Issue Sustainable Future of Nuclear Power)

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22 pages, 694 KiB

Open AccessArticle

Optimal Power Flow in Islanded Microgrids Using a Simple Distributed Algorithm

by Eleonora Riva Sanseverino^1,*,†, Maria Luisa Di Silvestre^1,†, Romina Badalamenti^1,†, Ninh Quang Nguyen^1,†, Josep Maria Guerrero^2,†

and Lexuan Meng^2,†

¹ Department of Energy, Information Engineering and Mathematical Models (DEIM), University of Palermo, Viale delle Scienze, Edificio 9, Palermo 90128, Italy

² Department of Energy Technology, Aalborg University, Pontoppi-danstræde, Aalborg 9220, Denmark

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11493-11514; https://doi.org/10.3390/en81011493 - 15 Oct 2015

Cited by 21 | Viewed by 7089

Abstract

In this paper, the problem of distributed power losses minimization in islanded distribution systems is dealt with. The problem is formulated in a very simple manner and a solution is reached after a few iterations. The considered distribution system, a microgrid, will not [...] Read more.

In this paper, the problem of distributed power losses minimization in islanded distribution systems is dealt with. The problem is formulated in a very simple manner and a solution is reached after a few iterations. The considered distribution system, a microgrid, will not need large bandwidth communication channels, since only closeby nodes will exchange information. The correction of generated active powers is possible by means of the active power losses partition concept that attributes a portion of the overall power losses in each branch to each generator. The experimental part shows the first results of the proposed method on an islanded microgrid. Simulation results of the distributed algorithm are compared to a centralized Optimal Power Flow approach and very small errors can be observed. Full article

(This article belongs to the Special Issue Microgrids)

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16 pages, 887 KiB

Open AccessArticle

Optimal Tilt Angle of Photovoltaic Arrays and Economic Allocation of Energy Storage System on Large Oil Tanker Ship

by Hai Lan¹, Jinfeng Dai¹, Shuli Wen^1,*, Ying-Yi Hong², David C. Yu³ and Yifei Bai¹

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

² Department of Electrical Engineering, Chung Yuan Christian University, Chung Li 32023, Taiwan

³ Department of Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA

Energies 2015, 8(10), 11515-11530; https://doi.org/10.3390/en81011515 - 15 Oct 2015

Cited by 34 | Viewed by 7105

Abstract

This study optimizes the tilt angle of photovoltaic (PV) panels on a large oil tanker ship system and considers the impact of partial shading to improve the performance of the PV system. This work presents a novel method that considers the difference between [...] Read more.

This study optimizes the tilt angle of photovoltaic (PV) panels on a large oil tanker ship system and considers the impact of partial shading to improve the performance of the PV system. This work presents a novel method that considers the difference between the expected and real outputs of PV modules to optimize the size of energy storage system (ESS). The method also takes into account the cost of wasted power, the capital cost of the system, fuel cost and the CO₂ emissions. Unlike on land, power generation using a PV on a ship depends on the date, latitude and longitude of the navigation. Accordingly, this work considers a route from Dalian in China to Aden in Yemen, accounting for the seasonal and geographical variations of solar irradiation. This proposed method adopts five conditions associated with the navigation route to model the total shipload. Various cases are discussed in detail to demonstrate the effectiveness of the proposed algorithm. Full article

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

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15 pages, 990 KiB

Open AccessArticle

Molecular Simulation Studies of Flue Gas Purification by Bio-MOF

by Zhi Li^1,2, Gangqiang Xu², Bei Liu^1,2,*, Xin Lv¹, Guangjin Chen², Changyu Sun², Peng Xiao² and Yifei Sun²

¹ State Key Laboratory of Offshore Oil Exploitation, Beijing 100027, China

² State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China

Energies 2015, 8(10), 11531-11545; https://doi.org/10.3390/en81011531 - 15 Oct 2015

Cited by 9 | Viewed by 6499

Abstract

As a new branch of MOFs which are composed of biocompatible metal ions and organic ligands, bio-metal-organic frameworks (bio-MOFs) have attracted much attention recently. Bio-MOFs feature multiple Lewis basic sites which have strong interaction with CO₂ molecules, thus they have great potential [...] Read more.

As a new branch of MOFs which are composed of biocompatible metal ions and organic ligands, bio-metal-organic frameworks (bio-MOFs) have attracted much attention recently. Bio-MOFs feature multiple Lewis basic sites which have strong interaction with CO₂ molecules, thus they have great potential in the separation and purification of gas mixtures containing CO₂. In this work, molecular simulation studies were carried out to investigate the adsorption and diffusion behaviors of CO₂/N₂ gas mixtures in bio-MOF-11. Results show that bio-MOF-11 displays excellent adsorption selectivity towards CO₂ in CO₂/N₂ gas mixtures which was dominated by electrostatic interaction between material and CO₂. In addition, we found both CO₂ and N₂ molecules were preferably adsorbed around the pyrimidine ring and exocyclic amino and transferred to the secondary favorable adsorption sites (methyl groups) with increasing pressure. Bio-MOF-11 membranes show superior permeation selectivity, but low permeability for CO₂/N₂ gas systems. The reason is that the small pores restrict the movement of gas molecules, leading to the observed low permeability. The information obtained in this work can be applied to other theoretical and experimental studies of bio-MOFs adsorbents and membranes in the future. Full article

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29 pages, 1947 KiB

Open AccessArticle

Effects of Shear Dependent Viscosity and Variable Thermal Conductivity on the Flow and Heat Transfer in a Slurry

by Ling Miao¹ and Mehrdad Massoudi^2,*

¹ Department of Mechanical Engineering and Material Science, University of Pittsburgh, 3700 O’Hara Street, Pittsburgh, PA 15213, USA

² Department of Energy, National Energy Technology Laboratory (NETL), 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236, USA

Energies 2015, 8(10), 11546-11574; https://doi.org/10.3390/en81011546 - 15 Oct 2015

Cited by 14 | Viewed by 5963

Abstract

In this paper we study the effects of variable viscosity and thermal conductivity on the heat transfer in the pressure-driven fully developed flow of a slurry (suspension) between two horizontal flat plates. The fluid is assumed to be described by a constitutive relation [...] Read more.

In this paper we study the effects of variable viscosity and thermal conductivity on the heat transfer in the pressure-driven fully developed flow of a slurry (suspension) between two horizontal flat plates. The fluid is assumed to be described by a constitutive relation for a generalized second grade fluid where the shear viscosity is a function of the shear rate, temperature and concentration. The heat flux vector for the slurry is assumed to follow a generalized form of the Fourier’s equation where the thermal conductivity k depends on the temperature as well as the shear rate. We numerically solve the governing equations of motion in the non-dimensional form and perform a parametric study to see the effects of various dimensionless numbers on the velocity, volume fraction and temperature profiles. The different cases of shear thinning and thickening, and the effect of the exponent in the Reynolds viscosity model, for the temperature variation in viscosity, are also considered. The results indicate that the variable thermal conductivity can play an important role in controlling the temperature variation in the flow. Full article

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

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17 pages, 380 KiB

Open AccessArticle

Estimation of Downtime and of Missed Energy Associated with a Wave Energy Converter by the Equivalent Power Storm Model

by Felice Arena^1,2,*

, Valentina Laface^1,†, Giovanni Malara^1,2,† and Alessandra Romolo^1,2,†

¹ Natural Ocean Engineering Laboratory (NOEL), “Mediterranea” University of Reggio Calabria, Loc. Feo di Vito, Reggio Calabria 89122, Italy

² Wavenergy.it srl. Via F. Baracca Trav. De Salvo 8/A, Reggio Calabria 89123, Italy

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11575-11591; https://doi.org/10.3390/en81011575 - 15 Oct 2015

Cited by 11 | Viewed by 4685

Abstract

The design of any wave energy converter involves the determination of relevant statistical data on the wave energy resource oriented to the evaluation of the structural reliability and energy performance of the device. Currently, limited discussions concern the estimation of parameters connected to [...] Read more.

The design of any wave energy converter involves the determination of relevant statistical data on the wave energy resource oriented to the evaluation of the structural reliability and energy performance of the device. Currently, limited discussions concern the estimation of parameters connected to the energy performance of a device. Thus, this paper proposes a methodology for determining average downtime and average missed energy, which is the energy that is not harvested because of device deactivations during severe sea storms. These quantities are fundamental for evaluating the expected inactivity of a device during a year or during its lifetime and are relevant for assessing the effectiveness of a device working at a certain site. For this purpose, the equivalent power storm method is used for their derivation, starting from concepts pertaining to long-term statistical analysis. The paper shows that the proposed solutions provide reliable estimations via comparison with results obtained by processing long wave data. Full article

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

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26 pages, 5101 KiB

Open AccessArticle

A Novel Design Method for Optimizing an Indirect Forced Circulation Solar Water Heating System Based on Life Cycle Cost Using a Genetic Algorithm

by Myeong Jin Ko

Urban Development Institute, Incheon National University, Incheon 406-772, Korea

Energies 2015, 8(10), 11592-11617; https://doi.org/10.3390/en81011592 - 16 Oct 2015

Cited by 16 | Viewed by 7641

Abstract

To maximize the energy performance and economic benefits of solar water heating (SWH) systems, the installation and operation-related design variables as well as those related to capacity must be optimized. This paper presents a novel design method for simultaneously optimizing the various design [...] Read more.

To maximize the energy performance and economic benefits of solar water heating (SWH) systems, the installation and operation-related design variables as well as those related to capacity must be optimized. This paper presents a novel design method for simultaneously optimizing the various design variables of an indirect forced-circulation SWH system that is based on the life cycle cost and uses a genetic algorithm. The effectiveness of the proposed method is assessed by evaluating the long-term performance corresponding to four cases, which are optimized using different annual solar fractions and sets of the design variables. When the installation and operation-related design variables were taken into consideration, it resulted in an efficient and economic design and an extra cost reduction of 3.2%–6.1% over when only the capacity-related design variables were considered. In addition, the results of parametric studies show that the slope and mass flow rate of the collector have a significant impact on the energy and economic performances of SWH systems. In contrast, the mass flow rate in the secondary circuit and the differences in the temperatures of the upper and lower dead bands of the differential controller have a smaller impact. Full article

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

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23 pages, 1674 KiB

Open AccessArticle

Optimal Energy Management, Location and Size for Stationary Energy Storage System in a Metro Line Based on Genetic Algorithm

by Huan Xia^*, Huaixin Chen, Zhongping Yang, Fei Lin and Bin Wang

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

Energies 2015, 8(10), 11618-11640; https://doi.org/10.3390/en81011618 - 16 Oct 2015

Cited by 81 | Viewed by 8228

Abstract

The installation of stationary super-capacitor energy storage system (ESS) in metro systems can recycle the vehicle braking energy and improve the pantograph voltage profile. This paper aims to optimize the energy management, location, and size of stationary super-capacitor ESSes simultaneously and obtain the [...] Read more.

The installation of stationary super-capacitor energy storage system (ESS) in metro systems can recycle the vehicle braking energy and improve the pantograph voltage profile. This paper aims to optimize the energy management, location, and size of stationary super-capacitor ESSes simultaneously and obtain the best economic efficiency and voltage profile of metro systems. Firstly, the simulation platform of an urban rail power supply system, which includes trains and super-capacitor energy storage systems, is established. Then, two evaluation functions from the perspectives of economic efficiency and voltage drop compensation are put forward. Ultimately, a novel optimization method that combines genetic algorithms and a simulation platform of urban rail power supply system is proposed, which can obtain the best energy management strategy, location, and size for ESSes simultaneously. With actual parameters of a Chinese metro line applied in the simulation comparison, certain optimal scheme of ESSes’ energy management strategy, location, and size obtained by a novel optimization method can achieve much better performance of metro systems from the perspectives of two evaluation functions. The simulation result shows that with the increase of weight coefficient, the optimal energy management strategy, locations and size of ESSes appear certain regularities, and the best compromise between economic efficiency and voltage drop compensation can be obtained by a novel optimization method, which can provide a valuable reference to subway company. Full article

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

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26 pages, 1055 KiB

Open AccessArticle

Mapping and Measuring European Local Governments’ Priorities for a Sustainable and Low-Carbon Energy Future

by Stelios Grafakos^1,*, Elena Marie Enseñado¹, Alexandros Flamos²

and Jan Rotmans³

¹ Institute for Housing and Urban Development Studies (IHS), Erasmus University Rotterdam (EUR), Burgemeester Oudlaan 50, Rotterdam 3062PA, The Netherlands

² Department of Industrial Management and Technology, University of Piraeus, Karaoli and Dimitriou 80,18534 Piraeus, Greece

³ Dutch Research Institute for Transitions (DRIFT), Erasmus University Rotterdam (EUR), Burgemeester Oudlaan 50, Rotterdam 3062PA, The Netherlands

Energies 2015, 8(10), 11641-11666; https://doi.org/10.3390/en81011641 - 16 Oct 2015

Cited by 7 | Viewed by 5951

Abstract

The main objective of this article is to assess the priorities of local governments (LGs) in Europe regarding climate change mitigation technologies evaluation in the electricity sector and to provide important insights for energy policy design. The study applies a hybrid weighting methodology [...] Read more.

The main objective of this article is to assess the priorities of local governments (LGs) in Europe regarding climate change mitigation technologies evaluation in the electricity sector and to provide important insights for energy policy design. The study applies a hybrid weighting methodology to elicit LGs’ preferences in a constructive and iterative way regarding the evaluation criteria of low-carbon energy technologies. Furthermore, the study employs three data collection and preference elicitation methods, namely: survey, workshop, and webinar. The study was conducted across thirty one (31) European LGs that were categorized according to three variables: population size, geographical region and gross domestic product (GDP) per capita. The analysis shows that “CO₂ emissions” is the most important criterion among European LGs, followed by “mortality and morbidity” and “ecosystem damages”. The results illustrate the potential synergies of climate and energy policies for addressing both CO₂ emissions and air pollution. It was also found, based on a correlation analysis, that LGs with higher GDP per capita tend to provide higher weights to criteria related to security of energy supply and technological innovation. The current study provides insights on the actual LGs’ priorities that are important to consider during low-carbon energy technologies evaluation and energy policy design. Interestingly, the results of the European LGs’ preferences clearly show that the EU climate policy objectives have reached different levels of governance—and at this particular case, the local level. Furthermore, the developed methodology could be applied at different geographical regions to map other regions’ LG priorities, but also at a group decision making context to elicit relevant stakeholders’ preferences regarding low-carbon energy technologies and policy objectives. Full article

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18 pages, 4796 KiB

Open AccessArticle

An Energy Management Service for the Smart Office

by Cristina Rottondi^1,*, Markus Duchon², Dagmar Koss², Andrei Palamarciuc¹, Alessandro Pití¹, Giacomo Verticale¹

and Bernhard Schätz²

¹ Department of Electronics, Information and Bioengineering, Polytechnic University of Milan, P.zza L. da Vinci, 32, Milan 20133, Italy

² Fortiss GmbH, Guerickestrasse 25, 80805 Munich, Germany

Energies 2015, 8(10), 11667-11684; https://doi.org/10.3390/en81011667 - 16 Oct 2015

Cited by 19 | Viewed by 9438

Abstract

The evolution of the electricity grid towards the smart grid paradigm is fostering the integration of distributed renewable energy sources in smart buildings: a combination of local power generation, battery storage and controllable loads can greatly increase the energetic self-sufficiency of a smart [...] Read more.

The evolution of the electricity grid towards the smart grid paradigm is fostering the integration of distributed renewable energy sources in smart buildings: a combination of local power generation, battery storage and controllable loads can greatly increase the energetic self-sufficiency of a smart building, enabling it to maximize the self-consumption of photovoltaic electricity and to participate in the energy market, thus taking advantage of time-variable tariffs to achieve economic savings. This paper proposes an energy management infrastructure specifically tailored for a smart office building, which relies on measured data and on forecasting algorithms to predict the future patterns of both local energy generation and power loads. The performance is compared to the optimal energy usage scheduling, which would be obtained assuming the exact knowledge of the future energy production and consumption trends, showing gaps below 10% with respect to the optimum. Full article

(This article belongs to the Collection Smart Grid)

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17 pages, 2826 KiB

Open AccessArticle

A Non-Unity Torque Sharing Function for Torque Ripple Minimization of Switched Reluctance Generators in Wind Power Systems

by Hye-Ung Shin¹, Kiwoo Park² and Kyo-Beum Lee^1,*

¹ Department of Electrical and Computer Engineering, Ajou University, 206, World cup-ro, Yeongtong-gu, Suwon 443-749, Korea

² LSIS limited company, LS Tower, 127, LS-ro, Dongan-gu, Anyang-si, Gyeonggi-Do 431-848, Korea

Energies 2015, 8(10), 11685-11701; https://doi.org/10.3390/en81011685 - 16 Oct 2015

Cited by 19 | Viewed by 7347

Abstract

This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry. [...] Read more.

This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry. One of the major drawbacks of the SRG is its high torque ripple that results in high noise operation of the generator. In this paper, a non-unity Torque Sharing Function (TSF) is proposed to minimize the torque ripple over a wide speed range of operation. Simulations as well as experimental results are presented to verify the effectiveness of the proposed torque ripple minimization technique. Full article

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

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16 pages, 738 KiB

Open AccessArticle

Linear Modeling and Regulation Quality Analysis for Hydro-Turbine Governing System with an Open Tailrace Channel

by Jiandong Yang¹, Mingjiang Wang^1,2, Chao Wang¹ and Wencheng Guo^1,3,*

¹ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China

² HYDROCHINA Northwest Engineering Corporation, Xi’an 710065, China

³ Maha Fluid Power Research Center, Agricultural and Biological Engineering Department, Purdue University, West Lafayette, IN 47907, USA

Energies 2015, 8(10), 11702-11717; https://doi.org/10.3390/en81011702 - 19 Oct 2015

Cited by 23 | Viewed by 7324

Abstract

On the basis of the state–space method (SSM), a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model [...] Read more.

On the basis of the state–space method (SSM), a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model has been verified by several examples of numerical simulation, which are based on a finite difference technique. Then, the complete mathematical model for the hydro-turbine governing system of hydropower station with an open tailrace channel, which is used for simulating the transient process of the hydro-turbine governing system under load disturbance, is established by combining the models of hydro-turbine, generator, governor and open tailrace channel. Finally, according to the complete model, the regulation quality for hydro-turbine governing system with an open tailrace channel under load disturbance is studied, and the effects of open tailrace channel and tailrace surge tank on regulation quality are analyzed. The results indicate that: The open tailrace channel has a strong influence on the regulation quality by observing the water level fluctuations in tailrace surge tank. The surge shows a piecewise periodical change along with the variation in the length of an open channel. The open tailrace channel can be used to improve the regulation quality of hydro-turbine governing system. Full article

(This article belongs to the Special Issue Hydropower)

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19 pages, 637 KiB

Open AccessArticle

Maximum Energy Output of a DFIG Wind Turbine Using an Improved MPPT-Curve Method

by Dinh-Chung Phan^1,2 and Shigeru Yamamoto^3,*

¹ Faculty of Electrical Engineering, Danang University of Science and Technology, 54-Nguyen Luong Bang, Danang 550000, Vietnam

² Division of Electrical Engineering and Computer Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan

³ Faculty of Electrical and Computer Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan

Energies 2015, 8(10), 11718-11736; https://doi.org/10.3390/en81011718 - 19 Oct 2015

Cited by 29 | Viewed by 7899

Abstract

A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed [...] Read more.

A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed under assumptions that represent physical conditions. Several control parameters may be adjusted to ensure the quality of control performance. In particular, a DFIG state-space model and a control technique based on the Lyapunov function are adopted to derive the control method. The effectiveness of the proposed method is verified via numerical simulations of a 1.5-MW DFIG wind turbine using MATLAB/Simulink. The simulation results show that when the proposed method is used, the wind turbine is capable of properly tracking the optimal operation point; furthermore, the generator’s available energy output is higher when the proposed method is used than it is when the conventional method is used instead. Full article

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

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18 pages, 666 KiB

Open AccessEditorial

Geothermal Energy: Delivering on the Global Potential

by Paul L. Younger

School of Engineering, University of Glasgow, Glasgow G23 5EB, Scotland, UK

Energies 2015, 8(10), 11737-11754; https://doi.org/10.3390/en81011737 - 19 Oct 2015

Cited by 42 | Viewed by 10723

Abstract

Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of [...] Read more.

Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of solar and wind. This is mainly attributable to (i) uncertainties over resource availability in poorly-explored reservoirs and (ii) the concentration of full-lifetime costs into early-stage capital expenditure (capex). Recent advances in reservoir characterization techniques are beginning to narrow the bounds of exploration uncertainty, both by improving estimates of reservoir geometry and properties, and by providing pre-drilling estimates of temperature at depth. Advances in drilling technologies and management have potential to significantly lower initial capex, while operating expenditure is being further reduced by more effective reservoir management—supported by robust models—and increasingly efficient energy conversion systems (flash, binary and combined-heat-and-power). Advances in characterization and modelling are also improving management of shallow low-enthalpy resources that can only be exploited using heat-pump technology. Taken together with increased public appreciation of the benefits of geothermal, the technology is finally ready to take its place as a mainstream renewable technology, exploited far beyond its traditional confines in the world’s volcanic regions. Full article

(This article belongs to the Special Issue Geothermal Energy: Delivering on the Global Potential)

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15 pages, 3445 KiB

Open AccessArticle

Miniaturized Air-Driven Planar Magnetic Generators

by Jingjing Zhao^1,2, Gengchen Shi¹ and Lin Du^1,*

¹ National Lab of Mechatronics Engineering and Control, Beijing Institute of Technology, Beijing 100081, China

² Department of Precision Instrument, Tsinghua University, Beijing 100084, China

Energies 2015, 8(10), 11755-11769; https://doi.org/10.3390/en81011755 - 19 Oct 2015

Cited by 11 | Viewed by 10377

Abstract

This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole [...] Read more.

This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole permanent-magnet (PM) rotors on both sides of the coil. To further decrease the starting torque and save more space, Generator 2 adopts the multilayer planar coil as the rotor and the multi-pole PMs as the stator, eliminating the casing without compromising the magnetic structure or output performance. The prototypes were tested gathering energy from wind which can work at a low wind speed of 1~2 m/s. Prototype of Generator 1 is with a volume of 2.61 cm³ and its normalized voltage reaches 485 mV/krpm. Prototype of Generator 2 has a volume of 0.92 cm³ and a normalized voltage as high as 538 mV/krpm. Additionally, output voltage can be estimated at better than 96% accuracy by the theoretical model developed in this paper. The two micro generators are capable of producing substantial electricity with little volume to serve as compact power conversion devices. Full article

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30 pages, 1970 KiB

Open AccessArticle

Co-Movement Analysis of Italian and Greek Electricity Market Wholesale Prices by Using a Wavelet Approach

by George P. Papaioannou^1,4,*, Christos Dikaiakos^1,†, George Evangelidis^1,†, Panagiotis G. Papaioannou^2,† and Dionysios S. Georgiadis^3,†

¹ Research, Technology & Development Department, Independent Power Transmission Operator (IPTO) S.A., 89 Dyrrachiou & Kifisou Street, Athens 10443, Greece

² Applied Mathematics and Physical Sciences, National Technical University of Athens, Zografou 15780, Greece

³ Department of Management, Technology and Economics, ETH Zurich, Chair of Entrepreneurial Risks, Zurich 8092, Switzerland

⁴ Center for Research and Applications in Nonlinear Systems (CRANS), Department of Mathematics, University of Patras, Patras 26500, Greece

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11770-11799; https://doi.org/10.3390/en81011770 - 20 Oct 2015

Cited by 11 | Viewed by 6075

Abstract

We study the co-evolution of the dynamics or co-movement of two electricity markets, the Italian and Greek, by studying the dynamics of their wholesale day-ahead prices, simultaneously in the time-frequency domain. Co-movement is alternatively referred as market integration in financial economics and markets [...] Read more.

We study the co-evolution of the dynamics or co-movement of two electricity markets, the Italian and Greek, by studying the dynamics of their wholesale day-ahead prices, simultaneously in the time-frequency domain. Co-movement is alternatively referred as market integration in financial economics and markets are internationally integrated if the reward for risk is identical regardless the market one trades in. The innovation of this work is the application of wavelet analysis and more specifically the wavelet coherence to estimate the dynamic interaction between these two prices. Our method is compared to other generic econometric tools used in Economics and Finance namely the dynamic correlation and coherence analysis, to study the co-movement of variables of the type related to these two fields. Our study reveals valuable information that we believe will be extremely useful to the authorities as well as other agents participating in these markets to better prepare the national markets towards the European target model, a framework in which the two markets will be coupled. Full article

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21 pages, 1065 KiB

Open AccessArticle

Numerical Validation of a Vortex Model against ExperimentalData on a Straight-Bladed Vertical Axis Wind Turbine

by Eduard Dyachuk^* and Anders Goude

Division of Electricity, Department of Engineering Sciences, Uppsala University, Box 534, Uppsala 751 21, Sweden

Energies 2015, 8(10), 11800-11820; https://doi.org/10.3390/en81011800 - 20 Oct 2015

Cited by 15 | Viewed by 7485

Abstract

Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an [...] Read more.

Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an open site. The results on the normal force on one blade are analyzed. The model is assessed against the measured data in the wide range of tip speed ratios: from 1.8 to 4.6. The predicted results within one revolution have a similar shape and magnitude as the measured data, though the model does not reproduce every detail of the experimental data. The present model can be used when dimensioning the turbine for maximum loads. Full article

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

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25 pages, 1368 KiB

Open AccessReview

Recent Advances in Osmotic Energy Generation via Pressure-Retarded Osmosis (PRO): A Review

by Jihye Kim¹, Kwanho Jeong¹, Myoung Jun Park², Ho Kyong Shon²

and Joon Ha Kim^1,*

¹ School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Korea

² School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Post Box 129, Broadway, Sydney, NSW 2007, Australia

Energies 2015, 8(10), 11821-11845; https://doi.org/10.3390/en81011821 - 20 Oct 2015

Cited by 74 | Viewed by 13490

Abstract

Global energy consumption has been highly dependent on fossil fuels which cause severe climate change and, therefore, the exploration of new technologies to produce effective renewable energy plays an important role in the world. Pressure-retarded osmosis (PRO) is one of the promising candidates [...] Read more.

Global energy consumption has been highly dependent on fossil fuels which cause severe climate change and, therefore, the exploration of new technologies to produce effective renewable energy plays an important role in the world. Pressure-retarded osmosis (PRO) is one of the promising candidates to reduce the reliance on fossil fuels by harnessing energy from the salinity gradient between seawater and fresh water. In PRO, water is transported though a semi-permeable membrane from a low-concentrated feed solution to a high-concentrated draw solution. The increased volumetric water flow then runs a hydro-turbine to generate power. PRO technology has rapidly improved in recent years; however, the commercial-scale PRO plant is yet to be developed. In this context, recent developments on the PRO process are reviewed in terms of mathematical models, membrane modules, process designs, numerical works, and fouling and cleaning. In addition, the research requirements to accelerate PRO commercialization are discussed. It is expected that this article can help comprehensively understand the PRO process and thereby provide essential information to activate further research and development. Full article

(This article belongs to the Special Issue Osmotic Power)

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25 pages, 4612 KiB

Open AccessArticle

A New Building-Integrated Wind Turbine System Utilizing the Building

by Jeongsu Park^1,†, Hyung-Jo Jung^1,*,†, Seung-Woo Lee^2,† and Jiyoung Park^3,†

¹ Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea

² TESolution Co. Ltd., Sungdu-Ri 724-12, Gongdo-Eup, Anseong-Si, Gyunggi-Do 456-825, Korea

³ Division of Architecture, Inha University, Incheon 402-751, Korea

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11846-11870; https://doi.org/10.3390/en81011846 - 21 Oct 2015

Cited by 67 | Viewed by 14064

Abstract

This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to [...] Read more.

This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to effectively collect the incoming wind and increase its speed and a rotor with an appropriate shape for specific conditions. To this end, several important design issues for the guide vane as well as the rotor were thoroughly investigated and accordingly addressed in this paper. A series of computational fluid dynamics (CFD) analyses was performed to determine the optimal configuration of the proposed system. Finally, it is demonstrated from performance evaluation tests that the prototype with the specially designed guide vane and rotor for the proposed BIWT system accelerates the wind speed to a sufficient level and consequently increases the power coefficient significantly. Thus, it was confirmed that the proposed system is a promising environment-friendly energy production system for urban areas. Full article

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

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12 pages, 333 KiB

Open AccessArticle

Optimal Subinterval Selection Approach for Power System Transient Stability Simulation

by Soobae Kim¹ and Thomas J. Overbye^2,*

¹ Korea Electric Power Research Institute (KEPRI), Korea Electric Power Corporation (KEPCO), 105 Munji-Ro, Yuseong-Gu, Daejeon 305-760, Korea

² Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 306 N. Wright St., Urbana, IL 61801, USA

Energies 2015, 8(10), 11871-11882; https://doi.org/10.3390/en81011871 - 21 Oct 2015

Cited by 11 | Viewed by 6558

Abstract

Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called [...] Read more.

Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB) system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval time step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system. Full article

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

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33 pages, 306 KiB

Open AccessReview

State of the Art Authentication, Access Control, and Secure Integration in Smart Grid

by Neetesh Saxena^1,2,* and Bong Jun Choi^1,2,*

¹ Department of Computer Science, State University of New York (SUNY) Korea, 119 Songdo, Moonhwa-ro, Yeonsu-Gu, Incheon 406840, Korea

² Department of Computer Science, Stony Brook University, New York, NY 11794, USA

Energies 2015, 8(10), 11883-11915; https://doi.org/10.3390/en81011883 - 21 Oct 2015

Cited by 66 | Viewed by 13201

Abstract

The smart grid (SG) is a promising platform for providing more reliable, efficient, and cost effective electricity to the consumers in a secure manner. Numerous initiatives across the globe are taken by both industry and academia in order to compile various security issues [...] Read more.

The smart grid (SG) is a promising platform for providing more reliable, efficient, and cost effective electricity to the consumers in a secure manner. Numerous initiatives across the globe are taken by both industry and academia in order to compile various security issues in the smart grid network. Unfortunately, there is no impactful survey paper available in the literature on authentications in the smart grid network. Therefore, this paper addresses the required objectives of an authentication protocol in the smart grid network along with the focus on mutual authentication, access control, and secure integration among different SG components. We review the existing authentication protocols, and analyze mutual authentication, privacy, trust, integrity, and confidentiality of communicating information in the smart grid network. We review authentications between the communicated entities in the smart grid, such as smart appliance, smart meter, energy provider, control center (CC), and home/building/neighborhood area network gateways (GW). We also review the existing authentication schemes for the vehicle-to-grid (V2G) communication network along with various available secure integration and access control schemes. We also discuss the importance of the mutual authentication among SG entities while providing confidentiality and privacy preservation, seamless integration, and required access control with lower overhead, cost, and delay. This paper will help to provide a better understanding of current authentication, authorization, and secure integration issues in the smart grid network and directions to create interest among researchers to further explore these promising areas. Full article

(This article belongs to the Collection Smart Grid)

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23 pages, 646 KiB

Open AccessArticle

A Solution Based on Bluetooth Low Energy for Smart Home Energy Management

by Mario Collotta^*

and Giovanni Pau

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

Energies 2015, 8(10), 11916-11938; https://doi.org/10.3390/en81011916 - 21 Oct 2015

Cited by 83 | Viewed by 12354

Abstract

The research and the implementation of home automation are getting more popular because the Internet of Things holds promise for making homes smarter through wireless technologies. The installation of systems based on wireless networks can play a key role also in the extension [...] Read more.

The research and the implementation of home automation are getting more popular because the Internet of Things holds promise for making homes smarter through wireless technologies. The installation of systems based on wireless networks can play a key role also in the extension of the smart grid towards smart homes, that can be deemed as one of the most important components of smart grids. This paper proposes a fuzzy-based solution for smart energy management in a home automation wireless network. The approach, by using Bluetooth Low Energy (BLE), introduces a Fuzzy Logic Controller (FLC) in order to improve a Home Energy Management (HEM) scheme, addressing the power load of standby appliances and their loads in different hours of the day. Since the consumer is involved in the choice of switching on/off of home appliances, the approach introduced in this work proposes a fuzzy-based solution in order to manage the consumer feedbacks. Simulation results show that the proposed solution is efficient in terms of reducing peak load demand, electricity consumption charges with an increase comfort level of consumers. The performance of the proposed BLE-based wireless network scenario are validated in terms of packet delivery ratio, delay, and jitter and are compared to IEEE 802.15.4 technology. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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16 pages, 547 KiB

Open AccessArticle

Techno-Economic Performance Evaluation for Olive Mills Powered by Grid-Connected Photovoltaic Systems

by Ovidio Rabaza^1,*

, José Contreras-Montes^1,†, María Jesús García-Ruiz^1,2,†

, Fernando Delgado-Ramos^2,3,†

and Daniel Gómez-Lorente^1,†

¹ Department of Civil Engineering, University of Granada, 18071 Granada, Spain

² Institute of Water Research, University of Granada, 18012 Granada, Spain

³ Department of Structural Mechanics and Hydraulic Engineering, University of Granada, 18071 Granada, Spain

^† These authors contributed equally to this work.

Energies 2015, 8(10), 11939-11954; https://doi.org/10.3390/en81011939 - 21 Oct 2015

Cited by 10 | Viewed by 5440

Abstract

In recent years, due to the rise in petroleum prices and greenhouse gas emissions, renewable energy has been recommended as a power source for different types of facilities. For the period 2010 to 2020 the European Commission has established three key objectives related [...] Read more.

In recent years, due to the rise in petroleum prices and greenhouse gas emissions, renewable energy has been recommended as a power source for different types of facilities. For the period 2010 to 2020 the European Commission has established three key objectives related to climatic change and energy sustainability, such as reductions of CO₂ emissions, increases in the use of renewable energy, and improvements in energy efficiency. A key industry is olive oil production in olive mills, where there is a great opportunity to reduce electricity consumption, increase additional profits related to the reduction of technologies that are harmful to the environment, and to cut back maintenance costs. For this reason, a feasibility study of grid-connected photovoltaics (PV) systems has been carried out for different types of olive mills in Andalusia (southern Spain). This region is highly energy dependent, but has an abundance of “green” resources to be exploited. The results of this study contemplate a reduction in spending on electrical power of between 2% and 37%, and an increase in the use of renewable energy of between 2% and 26%. These results are according to the self-consumption or net metering policy and the production capacity of olive oil. Full article

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

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18 pages, 2852 KiB

Open AccessArticle

An Experimental Study on the Effects ofWinglets on the Wake and Performance of a ModelWind Turbine

by Nicolas Tobin¹, Ali M. Hamed¹ and Leonardo P. Chamorro^1,2,*

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

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

Energies 2015, 8(10), 11955-11972; https://doi.org/10.3390/en81011955 - 21 Oct 2015

Cited by 55 | Viewed by 9104

Abstract

Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the [...] Read more.

Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the power and thrust coefficients of 8.2% and 15.0% for the wingletted case. A simple theoretical treatment of a two-turbine system suggests a possible positive tradeoff between increasing power and thrust coefficients at a wind farm scale. The higher thrust coefficient created a region of enhanced mean shear and turbulence in the outer portion of the wake. The winglets did not significantly change the tip-vortex strength, but higher levels of turbulence in the far wake decreased the tip-vortex strength. Because of the increased mean shear in the wingletted turbine’s wake, the Reynolds stresses were higher, potentially leading to a higher energy flux downstream. Full article

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

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31 pages, 2335 KiB

Open AccessArticle

An Efficient Model for NPD Performance Evaluation Using DEMATEL and Fuzzy ANP—Applied to the TFT-LCD Touch Panel Industry in Taiwan

by Wen-Chin Chen^1,*, Hui-Pin Chang², Kuan-Ming Lin³ and Neng-Hao Kan¹

¹ Department of Industrial Management, Chung-Hua University, No. 707, Sec. 2, WuFu Rd., Hsinchu 30012, Taiwan

² College of Management, Chung-Hua University, No. 707, Sec. 2, WuFu Rd., Hsinchu 30012, Taiwan

³ Department of Foreign Languages & Literatures, Chung-Hua University, No. 707, Sec. 2, WuFu Rd., Hsinchu 30012, Taiwan

Energies 2015, 8(10), 11973-12003; https://doi.org/10.3390/en81011973 - 22 Oct 2015

Cited by 9 | Viewed by 5908

Abstract

As the competitive market nowadays shortens the life cycle of products, new products should be designed to meet the customer’s demand under a dynamic marketing environment so as to efficiently enhance the product strength of new products with maximization of profit. Hence, the [...] Read more.

As the competitive market nowadays shortens the life cycle of products, new products should be designed to meet the customer’s demand under a dynamic marketing environment so as to efficiently enhance the product strength of new products with maximization of profit. Hence, the key solution for enterprises to succeed will be the precise evaluation of new product development (NPD) performance, particularly for those who manage to survive in the intensely competitive market in Taiwan. This study is to identify the thin film transistor-liquid crystal display (TFT-LCD) touch panel industry and then establish an integrated model of NPD performance evaluation for enterprises. Firstly, literature review and interviews with experts are conducted to select the four aspects and 15 criteria as the main factors affecting NDP performance evaluation. Secondly, Decision Making Trial and Evaluation Laboratory (DEMATEL) is employed to identify the interrelationships among those factors. Finally, a Fuzzy theory is applied to resolve the linguistic hedges and an Analytic Network Process (ANP) is adopted to obtain the weights of all factors. A case study is performed to validate the proposed model in a Taiwanese TFT-LCD company. It not only provides the decision maker with a guidance system but also increases the competitive advantages for the TFT-LCD industry to design new products in the future. Full article

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16 pages, 645 KiB

Open AccessArticle

Analysing Performance Characteristics of Biomass Haulage in Ireland for Bioenergy Markets with GPS, GIS and Fuel Diagnostic Tools

by Amanda Sosa¹, Kevin McDonnell¹

and Ger Devlin^2,*

¹ School of Biosystems Engineering, University College Dublin, Dublin 4, Ireland

² UCD Forestry, University College Dublin, Dublin 4, Ireland

Energies 2015, 8(10), 12004-12019; https://doi.org/10.3390/en81012004 - 22 Oct 2015

Cited by 11 | Viewed by 6115

Abstract

In Ireland, truck transport by road dominates and will remain the main transportation mode of biomass. Cost efficiency and flexibility of forest transport can be typically improved by optimising routes. It is important to know every process and attributes within the workflow of [...] Read more.

In Ireland, truck transport by road dominates and will remain the main transportation mode of biomass. Cost efficiency and flexibility of forest transport can be typically improved by optimising routes. It is important to know every process and attributes within the workflow of roundwood transport. This study aimed to analyse characteristics of timber trucking in Ireland, and to estimate the least-cost route for the distribution of biomass with the use of geographic information systems (GIS). Firstly, a tracking system that recorded the truck’s movements and fuel consumption was installed. A total of 152 trips were recorded, routes were chosen by the truck driver. The recorded information was used to analyse the distances and times travelled loaded and unloaded per road class, breaks, loading and unloading times as well as fuel consumption. Secondly, the routes taken by the truck where compared with routes created using Network Analyst (NA), an extension of ArcGIS. Four scenarios based on route selection criteria were selected: shortest distance (S1), shorted time (S2), and prioritising high-class roads with shortest distance (S3) and time (S4). Results from the analysis of the tracking system data showed that driving both loaded and unloaded occupied on average 69% of the driver’s working shift; with an average time driving loaded of 49%. The travel distance per trip varied from 112 km and 197 km, with the truck driver using mostly national and regional roads. An average 2% of the total distance and 11% of the total time was spent driving on forest roads. In general, the truck’s speed recorded on the different road classes was on average 30% lower than the legal maximum speed. The average fuel consumption was 0.64 L/km. In terms of the route comparison, the driving directions from the truck routes coincided with 77% of the directions of the routes based on shortest driving time (S2 and S4). All the routes chosen by the driver had 22% longer distance than the routes in S1 (shortest distance). The routes selected based on shortest distance (S1 and S3) had the longest travelling time, approximately 19% more than the ones taken by the truck and 30% more than S2 and S4. The average running cost for the truck was 0.83 €/km. Choosing the shortest distance routes (S1 and S3) not only implies reducing travelling costs but also a reduction of CO₂ emissions by 12% in comparison to routes in S2 and S4. However, when selecting the routes, travel time can be a much more crucial parameter to analyse rather than distance in terms of transportation costs. Choosing the routes generated in scenario S2 over S1 implied an increase in distance by 12% but a decrease in time of 30%. Less driving time translates into better driving conditions across higher classes or roads; less wear and tear of trucks; and lesser fuel used. It also complies with local authorities preferences of having timber trucks move on higher road types in order to minimise the expenses associated with road maintenance. Full article

(This article belongs to the Special Issue Economics of Bioenergy 2015)

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9 pages, 681 KiB

Open AccessArticle

Expression of Heat Shock Proteins in Human Fibroblast Cells under Magnetic Resonant Coupling Wireless Power Transfer

by Kohei Mizuno^*, Naoki Shinohara and Junji Miyakoshi

Laboratory of Applied Radio Engineering for Humanosphere, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

Energies 2015, 8(10), 12020-12028; https://doi.org/10.3390/en81012020 - 22 Oct 2015

Cited by 1 | Viewed by 5997

Abstract

Since 2007, resonant coupling wireless power transfer (WPT) technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based [...] Read more.

Since 2007, resonant coupling wireless power transfer (WPT) technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based on the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. However, there has not been much experimental evaluation of the potential health risks of this WPT technology. In this study, to evaluate whether magnetic resonant coupling WPT induces cellular stress, we focused on heat shock proteins (Hsps) and determined the expression level of Hsps 27, 70 and 90 in WI38VA13 subcloned 2RA human fibroblast cells using a western blotting method. The expression level of Hsps under conditions of magnetic resonant coupling WPT for 24 h was not significantly different compared with control cells, although the expression level of Hsps for cells exposed to heat stress conditions was significantly increased. These results suggested that exposure to magnetic resonant coupling WPT did not cause detectable cell stress. Full article

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

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32 pages, 2269 KiB

Open AccessArticle

A Comparison of Techniques for Reducing Unicast Traffic in HSR Networks

by Nguyen Xuan Tien

, Saad Allawi Nsaif and Jong Myung Rhee^*

Department of Information and Communications Engineering, Myongji University, Yongin, Gyeonggi 449-728, Korea

Energies 2015, 8(10), 12029-12060; https://doi.org/10.3390/en81012029 - 23 Oct 2015

Cited by 8 | Viewed by 6337

Abstract

This paper investigates several existing techniques for reducing high-availability seamless redundancy (HSR) unicast traffic in HSR networks for substation automation systems (SAS). HSR is a redundancy protocol for Ethernet networks that provides duplicate frames for separate physical paths with zero recovery time. This [...] Read more.

This paper investigates several existing techniques for reducing high-availability seamless redundancy (HSR) unicast traffic in HSR networks for substation automation systems (SAS). HSR is a redundancy protocol for Ethernet networks that provides duplicate frames for separate physical paths with zero recovery time. This feature of HSR makes it very suited for real-time and mission-critical applications such as SAS systems. HSR is one of the redundancy protocols selected for SAS systems. However, the standard HSR protocol generates too much unnecessary redundant unicast traffic in connected-ring networks. This drawback degrades network performance and may cause congestion and delay. Several techniques have been proposed to reduce the redundant unicast traffic, resulting in the improvement of network performance in HSR networks. These HSR traffic reduction techniques are broadly classified into two categories based on their traffic reduction manner, including traffic filtering-based techniques and predefined path-based techniques. In this paper, we provide an overview and comparison of these HSR traffic reduction techniques found in the literature. The concepts, operational principles, network performance, advantages, and disadvantages of these techniques are investigated, summarized. We also provide a comparison of the traffic performance of these HSR traffic reduction techniques. Full article

(This article belongs to the Collection Smart Grid)

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19 pages, 2771 KiB

Open AccessArticle

Numerical Analysis on the Optimization of Hydraulic Fracture Networks

by Zhaobin Zhang¹, Xiao Li^1,*, Weina Yuan², Jianming He¹

, Guanfang Li¹ and Yusong Wu¹

¹ Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

² School of Geology Engineering and Geomatics, Chang’an University, Xi’an 710064, China

Energies 2015, 8(10), 12061-12079; https://doi.org/10.3390/en81012061 - 23 Oct 2015

Cited by 41 | Viewed by 6931

Abstract

The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of [...] Read more.

The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of natural fractures. In this work, a real natural fracture network is reconstructed from shale samples. Moreover, a virtual fracture system is proposed to simulate the large number of small fractures that are difficult to identify. A numerical model based on the displacement discontinuity method is developed to simulate the fluid-rock coupling system. A dimensionless stress difference that is normalized by rock strength is proposed to quantify the anisotropy of crustal stress. The hydraulic fracturing processes under different stress conditions are simulated. The most complex fracture configurations are obtained when the maximum principle stress direction is perpendicular to the principle natural fracture direction. In contrast, the worst results are obtained when these two directions are parallel to each other. Moreover, the side effects of the unfavorable geological conditions caused by crustal stress anisotropy can be partly suppressed by increasing the viscous effect of the fluid. Full article

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20 pages, 292 KiB

Open AccessArticle

Forecasting China’s Annual Biofuel Production Using an Improved Grey Model

by Nana Geng^1,*, Yong Zhang¹, Yixiang Sun², Yunjian Jiang¹ and Dandan Chen¹

¹ School of Transportation, Southeast University, Nanjing 210096, Jiangsu, China

² School of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, Jiangsu, China

Energies 2015, 8(10), 12080-12099; https://doi.org/10.3390/en81012080 - 23 Oct 2015

Cited by 21 | Viewed by 5756

Abstract

Biofuel production in China suffers from many uncertainties due to concerns about the government’s support policy and supply of biofuel raw material. Predicting biofuel production is critical to the development of this energy industry. Depending on the biofuel’s characteristics, we improve the prediction [...] Read more.

Biofuel production in China suffers from many uncertainties due to concerns about the government’s support policy and supply of biofuel raw material. Predicting biofuel production is critical to the development of this energy industry. Depending on the biofuel’s characteristics, we improve the prediction precision of the conventional prediction method by creating a dynamic fuzzy grey–Markov prediction model. Our model divides random time series decomposition into a change trend sequence and a fluctuation sequence. It comprises two improvements. We overcome the problem of considering the status of future time from a static angle in the traditional grey model by using the grey equal dimension new information and equal dimension increasing models to create a dynamic grey prediction model. To resolve the influence of random fluctuation data and weak anti-interference ability in the Markov chain model, we improve the traditional grey–Markov model with classification of states using the fuzzy set theory. Finally, we use real data to test the dynamic fuzzy prediction model. The results prove that the model can effectively improve the accuracy of forecast data and can be applied to predict biofuel production. However, there are still some defects in our model. The modeling approach used here predicts biofuel production levels based upon past production levels dictated by economics, governmental policies, and technological developments but none of which can be forecast accurately based upon past events. Full article

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16 pages, 1073 KiB

Open AccessArticle

Integrating Auto-Associative Neural Networks with Hotelling T² Control Charts for Wind Turbine Fault Detection

by Hsu-Hao Yang^*, Mei-Ling Huang

and Shih-Wei Yang

Department of Industrial Engineering and Management, National Chin-Yi University of Technology, Taichung City 41170, Taiwan

Energies 2015, 8(10), 12100-12115; https://doi.org/10.3390/en81012100 - 23 Oct 2015

Cited by 33 | Viewed by 6747

Abstract

This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means [...] Read more.

This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means clustering method to process outlier data and verifies the clustering results by comparing quartiles of boxplots, and applies the auto-associative neural networks to implement the residual approach that transforms the data to be approximately normally distributed. Hotelling T² multivariate quality control charts are constructed for monitoring the turbine’s performance and relative contribution of each attribute is calculated for the data points out of upper limits to determine the set of potential attributes. A case using the historical data and the alarm log is given and illustrates that our methodology has the advantage of detecting a set of susceptible attributes at the same time compared with only one independent attribute is monitored. Full article

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

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31 pages, 921 KiB

Open AccessArticle

Dual Search Maximum Power Point (DSMPP) Algorithm Based on Mathematical Analysis under Shaded Conditions

by Shahrooz Hajighorbani^1,2,*, Mohd Amran Mohd Radzi^1,2

, Mohd Zainal Abidin Ab Kadir¹

and Suhaidi Shafie¹

¹ Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

² Centre for Advanced Power and Energy Research, Faculty of Engineering, University Putra Malaysia, 43400 UPM Serdang, Malaysia

Energies 2015, 8(10), 12116-12146; https://doi.org/10.3390/en81012116 - 27 Oct 2015

Cited by 10 | Viewed by 6504

Abstract

Photovoltaic (PV) systems represent a clean, renewable source of energy that has non-linear current-voltage (I-V) and power-voltage (P-V) characteristics. To increase the efficiency, a PV system must operate at the maximum power point (MPP) to [...] Read more.

Photovoltaic (PV) systems represent a clean, renewable source of energy that has non-linear current-voltage (I-V) and power-voltage (P-V) characteristics. To increase the efficiency, a PV system must operate at the maximum power point (MPP) to produce the maximum available power. Under uniform conditions, there is only a single MPP in the P-V curve of a PV system; however, determining the MPP is more complicated under partially shaded conditions (PSCs) because multiple peak power points exist. In recent years, various studies have been performed to obtain the highest peak power point under PSCs, which is referred to as the global maximum power point (GMPP). In this paper, a novel method based on mathematical analysis that reduces the search zone and simultaneously identifies the possible MPPs in the specified zone is proposed; this proposed method is called the dual search maximum power point (DSMPP) algorithm. To evaluate the effectiveness of the proposed method, simulation and hardware implementations are carried out. The results show that the search time of GMPP is significantly reduced and the GMPP is detected in the minimum amount of time with high accuracy and minimum oscillation in the power produced. Full article

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

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40 pages, 490 KiB

Open AccessReview

Effect of Loads and Other Key Factors on Oil-Transformer Ageing: Sustainability Benefits and Challenges

by Radu Godina¹

, Eduardo M. G. Rodrigues¹, João C. O. Matias¹ and João P. S. Catalão^1,2,3,*

¹ University of Beira Interior, R. Fonte do Lameiro, Covilha 6201-001, Portugal

² Faculty of Engineering of the University of Porto, R. Dr. Roberto Frias, Porto 4200-465, Portugal

³ INESC-ID, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, Lisbon 1049-001, Portugal

Energies 2015, 8(10), 12147-12186; https://doi.org/10.3390/en81012147 - 27 Oct 2015

Cited by 100 | Viewed by 13091

Abstract

Transformers are one of the more expensive pieces of equipment found in a distribution network. The transformer’s role has not changed over the last decades. With simple construction and at the same time mechanically robust, they offer long term service that on average [...] Read more.

Transformers are one of the more expensive pieces of equipment found in a distribution network. The transformer’s role has not changed over the last decades. With simple construction and at the same time mechanically robust, they offer long term service that on average can reach half a century. Today, with the ongoing trend to supply a growing number of non-linear loads along with the notion of distributed generation (DG), a new challenge has arisen in terms of transformer sustainability, with one of the possible consequences being accelerated ageing. In this paper we carefully review the existing studies in the literature of the effect of loads and other key factors on oil-transformer ageing. The state-of-the-art is reviewed, each factor is analysed in detail, and in the end a smart transformer protection method is sought in order to monitor and protect it from upcoming challenges. Full article

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24 pages, 6837 KiB

Open AccessReview

Recent Progress on the Resilience of Complex Networks

by Jianxi Gao¹, Xueming Liu^2,3, Daqing Li^4,5,* and Shlomo Havlin⁶

¹ Center for Complex Network Research and Department of Physics, Northeastern University, Boston, MA 02115, USA

² Key Laboratory of Image Information Processing and Intelligent Control, School of Automation, Huazhong University of Science and Technology, Wuhan 430074, China

³ Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215, USA

⁴ School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China

⁵ Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing 100191, China

⁶ Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel

Energies 2015, 8(10), 12187-12210; https://doi.org/10.3390/en81012187 - 27 Oct 2015

Cited by 110 | Viewed by 12727

Abstract

Many complex systems in the real world can be modeled as complex networks, which has captured in recent years enormous attention from researchers of diverse fields ranging from natural sciences to engineering. The extinction of species in ecosystems and the blackouts of power [...] Read more.

Many complex systems in the real world can be modeled as complex networks, which has captured in recent years enormous attention from researchers of diverse fields ranging from natural sciences to engineering. The extinction of species in ecosystems and the blackouts of power girds in engineering exhibit the vulnerability of complex networks, investigated by empirical data and analyzed by theoretical models. For studying the resilience of complex networks, three main factors should be focused on: the network structure, the network dynamics and the failure mechanism. In this review, we will introduce recent progress on the resilience of complex networks based on these three aspects. For the network structure, increasing evidence shows that biological and ecological networks are coupled with each other and that diverse critical infrastructures interact with each other, triggering a new research hotspot of “networks of networks” (NON), where a network is formed by interdependent or interconnected networks. The resilience of complex networks is deeply influenced by its interdependence with other networks, which can be analyzed and predicted by percolation theory. This review paper shows that the analytic framework for Energies 2015, 8 12188 NON yields novel percolation laws for n interdependent networks and also shows that the percolation theory of a single network studied extensively in physics and mathematics in the last 60 years is a specific limited case of the more general case of n interacting networks. Due to spatial constraints inherent in critical infrastructures, including the power gird, we also review the progress on the study of spatially-embedded interdependent networks, exhibiting extreme vulnerabilities compared to their non-embedded counterparts, especially in the case of localized attack. For the network dynamics, we illustrate the percolation framework and methods using an example of a real transportation system, where the analysis based on network dynamics is significantly different from the structural static analysis. For the failure mechanism, we here review recent progress on the spontaneous recovery after network collapse. These findings can help us to understand, realize and hopefully mitigate the increasing risk in the resilience of complex networks. Full article

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

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17 pages, 324 KiB

Open AccessArticle

Economically Efficient Power Storage Operation by Dealing with the Non-Normality of Power Prediction

by Shiro Yano^1,*

and Tadahiro Taniguchi²

¹ Division of Advanced Information Technology & Computer Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan

² Department of Human & Computer Intelligence, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan

Energies 2015, 8(10), 12211-12227; https://doi.org/10.3390/en81012211 - 27 Oct 2015

Cited by 6 | Viewed by 4418

Abstract

Various predictive models about the residential energy demand and residential renewable energy production have been proposed. Recent studies have confirmed that they are not normally distributed over time. The increase in renewable energy installation has brought the issue of energy storage charge and [...] Read more.

Various predictive models about the residential energy demand and residential renewable energy production have been proposed. Recent studies have confirmed that they are not normally distributed over time. The increase in renewable energy installation has brought the issue of energy storage charge and discharge control. Thus, storage control methods that properly address non-normality are required. In this paper, we formulated the economically optimal storage control problem using Markov decision process (MDP) and the conditional value at risk (CVaR) measure to deal with the non-normality of predictive distribution about the household’s net load. The CVaR measure was employed to treat with the chance constraint on the battery capacitor, in other words, overcharge risk and over-discharge risk. We conducted a simulation to compare the annual economic saving performances between two MDPs: one is the MDP with a Gaussian predictive distribution and the other is the MDP with a normalized frequency distribution (non-normal). We used the real time series of 35 residential energy consumption and PV generation data in Japan. The importance of addressing the non-normality of random variables was shown by our simulation. Full article

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14 pages, 1026 KiB

Open AccessArticle

Echo State Network with Bayesian Regularization for Forecasting Short-Term Power Production of Small Hydropower Plants

by Gang Li^*, Bao-Jian Li, Xu-Guang Yu and Chun-Tian Cheng

Institute of Hydropower System and Hydroinformatics, Dalian University of Technology, Dalian 116024, China

Energies 2015, 8(10), 12228-12241; https://doi.org/10.3390/en81012228 - 27 Oct 2015

Cited by 24 | Viewed by 8540

Abstract

As a novel recurrent neural network (RNN), an echo state network (ESN) that utilizes a reservoir with many randomly connected internal units and only trains the readout, avoids increased complexity of training procedures faced by traditional RNN. The ESN can cope with complex [...] Read more.

As a novel recurrent neural network (RNN), an echo state network (ESN) that utilizes a reservoir with many randomly connected internal units and only trains the readout, avoids increased complexity of training procedures faced by traditional RNN. The ESN can cope with complex nonlinear systems because of its dynamical properties and has been applied in hydrological forecasting and load forecasting. Due to the linear regression algorithm usually adopted by generic ESN to train the output weights, an ill-conditioned solution might occur, degrading the generalization ability of the ESN. In this study, the ESN with Bayesian regularization (BESN) is proposed for short-term power production forecasting of small hydropower (SHP) plants. According to the Bayesian theory, the weights distribution in space is considered and the optimal output weights are obtained by maximizing the posterior probabilistic distribution. The evidence procedure is employed to gain optimal hyperparameters for the BESN model. The recorded data obtained from the SHP plants in two different counties, located in Yunnan Province, China, are utilized to validate the proposed model. For comparison, the feed-forward neural networks with Levenberg-Marquardt algorithm (LM-FNN) and the generic ESN are also employed. The results indicate that BESN outperforms both LM-FNN and ESN. Full article

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24 pages, 2241 KiB

Open AccessArticle

Electricity Customer Clustering Following Experts’ Principle for Demand Response Applications

by Jimyung Kang^1,2 and Jee-Hyong Lee^1,*

¹ Department of Electrical and Computer Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Korea

² Korea Electrotechnology Research Institute, 111 Hanggaul-ro, Sangnok-gu, Ansan 15588, Korea

Energies 2015, 8(10), 12242-12265; https://doi.org/10.3390/en81012242 - 27 Oct 2015

Cited by 19 | Viewed by 5998

Abstract

The clustering of electricity customers might have an effective meaning if, and only if, it is verified by domain experts. Most of the previous studies on customer clustering, however, do not consider real applications, but only the structure of clusters. Therefore, there is [...] Read more.

The clustering of electricity customers might have an effective meaning if, and only if, it is verified by domain experts. Most of the previous studies on customer clustering, however, do not consider real applications, but only the structure of clusters. Therefore, there is no guarantee that the clustering results are applicable to real domains. In other words, the results might not coincide with those of domain experts. In this paper, we focus on formulating clusters that are applicable to real applications based on domain expert knowledge. More specifically, we try to define a distance between customers that generates clusters that are applicable to demand response applications. First, the k-sliding distance, which is a new distance between two electricity customers, is proposed for customer clustering. The effect of k-sliding distance is verified by expert knowledge. Second, a genetic programming framework is proposed to automatically determine a more improved distance measure. The distance measure generated by our framework can be considered as a reflection of the clustering principles of domain experts. The results of the genetic programming demonstrate the possibility of deriving clustering principles. Full article

(This article belongs to the Collection Smart Grid)

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17 pages, 744 KiB

Open AccessArticle

A First-Order Study of Reduced Energy Consumption via Increased Thermal Capacitance with Thermal Storage Management in a Micro-Building

by Mary B. Wilson, Rogelio Luck and Pedro J. Mago^*

Department of Mechanical Engineering, Mississippi State University, Mississippi State, MS 39762, USA

Energies 2015, 8(10), 12266-12282; https://doi.org/10.3390/en81012266 - 27 Oct 2015

Cited by 13 | Viewed by 6274

Abstract

This study uses a first-order approximation of a micro-building to investigate the major factors determining how increased thermal capacitance (ITC) with thermal storage management (TSM) can reduce energy consumption in locations with relatively mild weather conditions such as the southeastern part of the [...] Read more.

This study uses a first-order approximation of a micro-building to investigate the major factors determining how increased thermal capacitance (ITC) with thermal storage management (TSM) can reduce energy consumption in locations with relatively mild weather conditions such as the southeastern part of the United States of America. In this study, ITC is achieved through water circulation between a large storage tank and pipes embedded within the building envelope. Although ITC results in a larger dominant time constant for the thermal response of a building, an adaptive allocation and control of the added capacitance through TSM significantly improves the benefits of the extra capacitance. This paper compares two first-order models for a micro-building: a reference case model with a single lumped thermal capacitance associated with the building, and another model, with the building’s capacitance plus the capacitance of the water system. Results showed that the ITC/TSM system reduced the cost of conditioning the building by reducing the operating time of both the cooling and the heating systems. May through September, the air conditioning operating time was reduced by an average of 70%, and October through April, the operation of the heating system was reduced by an average of 25%. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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21 pages, 323 KiB

Open AccessArticle

Model Property Based Material Balance and Energy Conservation Analysis for Process Industry Energy Transfer Systems

by Fumin Ma^1,*, Gregory M. P. O’Hare^2,4, Tengfei Zhang³

and Michael J. O’Grady²

¹ College of Information Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China

² School of Computer Science, University College Dublin, Dublin 4, Ireland

³ College of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

⁴ Earth Institute, Science Centre East, University College Dublin, Dublin 4, Ireland

Energies 2015, 8(10), 12283-12303; https://doi.org/10.3390/en81012283 - 27 Oct 2015

Cited by 3 | Viewed by 6768

Abstract

Conventional historical data based material and energy balance analyses are static and isolated computations. Such methods cannot embody the cross-coupling effect of energy flow, material flow and information flow in the process industry; furthermore, they cannot easily realize the effective evaluation and comparison [...] Read more.

Conventional historical data based material and energy balance analyses are static and isolated computations. Such methods cannot embody the cross-coupling effect of energy flow, material flow and information flow in the process industry; furthermore, they cannot easily realize the effective evaluation and comparison of different energy transfer processes by alternating the model module. In this paper, a novel method for material balance and energy conservation analysis of process industry energy transfer system is developed based on model property. Firstly, a reconfigurable energy transfer process model, which is independent of energy types and energy-consuming equipment, is presented from the viewpoint of the cross-coupling effect of energy flow, material flow and information flow. Thereafter the material balance determination is proposed based on both a dynamic incidence matrix and dynamic balance quantity. Moreover, the model-weighted conservation determination theorem is proved, and the energy efficiency analysis method is also discussed. Results confirmed the efficacy of the proposed methods, confirming its potential for use by process industry in energy efficiency analyses. Full article

(This article belongs to the Special Issue Applied Energy System Modeling 2015)

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