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20 pages, 3225 KB

Open AccessArticle

Development of an Optimal Power Control Scheme for Wave-Offshore Hybrid Generation Systems

by Seungmin Jung and Gilsoo Jang

Energies 2015, 8(9), 9009-9028; https://doi.org/10.3390/en8099009 - 25 Aug 2015

Cited by 6 | Viewed by 5010

Abstract

Integration technology of various distribution systems for improving renewable energy utilization has been receiving attention in the power system industry. The wave-offshore hybrid generation system (HGS), which has a capacity of over 10 MW, was recently developed by adopting several voltage source converters [...] Read more.

Integration technology of various distribution systems for improving renewable energy utilization has been receiving attention in the power system industry. The wave-offshore hybrid generation system (HGS), which has a capacity of over 10 MW, was recently developed by adopting several voltage source converters (VSC), while a control method for adopted power conversion systems has not yet been configured in spite of the unique system characteristics of the designated structure. This paper deals with a reactive power assignment method for the developed hybrid system to improve the power transfer efficiency of the entire system. Through the development and application processes for an optimization algorithm utilizing the real-time active power profiles of each generator, a feasibility confirmation of power transmission loss reduction was implemented. To find the practical effect of the proposed control scheme, the real system information regarding the demonstration process was applied from case studies. Also, an evaluation for the loss of the improvement rate was calculated. Full article

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

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20 pages, 895 KB

Open AccessArticle

Real-Time Recognition Non-Intrusive Electrical Appliance Monitoring Algorithm for a Residential Building Energy Management System

by Kofi Afrifa Agyeman, Sekyung Han and Soohee Han

Energies 2015, 8(9), 9029-9048; https://doi.org/10.3390/en8099029 - 26 Aug 2015

Cited by 38 | Viewed by 7808

Abstract

The concern of energy price hikes and the impact of climate change because of energy generation and usage forms the basis for residential building energy conservation. Existing energy meters do not provide much information about the energy usage of the individual appliance apart [...] Read more.

The concern of energy price hikes and the impact of climate change because of energy generation and usage forms the basis for residential building energy conservation. Existing energy meters do not provide much information about the energy usage of the individual appliance apart from its power rating. The detection of the appliance energy usage will not only help in energy conservation, but also facilitate the demand response (DR) market participation as well as being one way of building energy conservation. However, energy usage by individual appliance is quite difficult to estimate. This paper proposes a novel approach: an unsupervised disaggregation method, which is a variant of the hidden Markov model (HMM), to detect an appliance and its operation state based on practicable measurable parameters from the household energy meter. Performing experiments in a practical environment validates our proposed method. Our results show that our model can provide appliance detection and power usage information in a non-intrusive manner, which is ideal for enabling power conservation efforts and participation in the demand response market. Full article

(This article belongs to the Collection Smart Grid)

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23 pages, 2059 KB

Open AccessArticle

Incorporating Cyber Layer Failures in Composite Power System Reliability Evaluations

by Yuqi Han, Yunfeng Wen, Chuangxin Guo and Han Huang

Energies 2015, 8(9), 9064-9086; https://doi.org/10.3390/en8099064 - 26 Aug 2015

Cited by 42 | Viewed by 6970

Abstract

This paper proposes a novel approach to analyze the impacts of cyber layer failures (i.e., protection failures and monitoring failures) on the reliability evaluation of composite power systems. The reliability and availability of the cyber layer and its protection and monitoring [...] Read more.

This paper proposes a novel approach to analyze the impacts of cyber layer failures (i.e., protection failures and monitoring failures) on the reliability evaluation of composite power systems. The reliability and availability of the cyber layer and its protection and monitoring functions with various topologies are derived based on a reliability block diagram method. The availability of the physical layer components are modified via a multi-state Markov chain model, in which the component protection and monitoring strategies, as well as the cyber layer topology, are simultaneously considered. Reliability indices of composite power systems are calculated through non-sequential Monte-Carlo simulation. Case studies demonstrate that operational reliability downgrades in cyber layer function failure situations. Moreover, protection function failures have more significant impact on the downgraded reliability than monitoring function failures do, and the reliability indices are especially sensitive to the change of the cyber layer function availability in the range from 0.95 to 1. Full article

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

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20 pages, 645 KB

Open AccessArticle

A Power System Optimal Dispatch Strategy Considering the Flow of Carbon Emissions and Large Consumers

by Jun Yang, Xin Feng, Yufei Tang, Jun Yan, Haibo He and Chao Luo

Energies 2015, 8(9), 9087-9106; https://doi.org/10.3390/en8099087 - 26 Aug 2015

Cited by 12 | Viewed by 6289

Abstract

The carbon emissions trading market and direct power purchases by large consumers are two promising directions of power system development. To trace the carbon emission flow in the power grid, the theory of carbon emission flow is improved by allocating power loss to [...] Read more.

The carbon emissions trading market and direct power purchases by large consumers are two promising directions of power system development. To trace the carbon emission flow in the power grid, the theory of carbon emission flow is improved by allocating power loss to the load side. Based on the improved carbon emission flow theory, an optimal dispatch model is proposed to optimize the cost of both large consumers and the power grid, which will benefit from the carbon emissions trading market. Moreover, to better simulate reality, the direct purchase of power by large consumers is also considered in this paper. The OPF (optimal power flow) method is applied to solve the problem. To evaluate our proposed optimal dispatch strategy, an IEEE 30-bus system is used to test the performance. The effects of the price of carbon emissions and the price of electricity from normal generators and low-carbon generators with regards to the optimal dispatch are analyzed. The simulation results indicate that the proposed strategy can significantly reduce both the operation cost of the power grid and the power utilization cost of large consumers. Full article

(This article belongs to the Collection Smart Grid)

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10 pages, 385 KB

Open AccessArticle

Efficient Synthesis of an Aluminum Amidoborane Ammoniate

by Junzhi Yang, Paul R. Beaumont, Terry D. Humphries, Craig M. Jensen and Xingguo Li

Energies 2015, 8(9), 9107-9116; https://doi.org/10.3390/en8099107 - 26 Aug 2015

Cited by 19 | Viewed by 6115

Abstract

A novel species of metal amidoborane ammoniate, [Al(NH₂BH₃)₆³⁻][Al(NH₃)₆³⁺] has been successfully synthesized in up to 95% via the one-step reaction of AlH₃·OEt₂ with liquid NH₃BH₃ [...] Read more.

A novel species of metal amidoborane ammoniate, [Al(NH₂BH₃)₆³⁻][Al(NH₃)₆³⁺] has been successfully synthesized in up to 95% via the one-step reaction of AlH₃·OEt₂ with liquid NH₃BH₃·nNH₃ (n = 1~6) at 0 °C. This solution based reaction method provides an alternative pathway to the traditional mechano-chemical ball milling methods, avoiding possible decomposition. MAS ²⁷Al NMR spectroscopy confirms the formulation of the compound as an Al(NH₂BH₃)₆³⁻ complex anion and an Al(NH₃)₆³⁺ cation. Initial dehydrogenation studies of this aluminum based M-N-B-H compound demonstrate that hydrogen is released at temperatures as low as 65 °C, totaling ~8.6 equivalents of H₂ (10.3 wt %) upon heating to 105 °C. This method of synthesis offers a promising route towards the large scale production of metal amidoborane ammoniate moieties. Full article

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

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20 pages, 600 KB

Open AccessArticle

Detuning Minimization of Induction Motor Drive System for Alternative Energy Vehicles

by Habibur Rehman

Energies 2015, 8(9), 9117-9136; https://doi.org/10.3390/en8099117 - 26 Aug 2015

Cited by 5 | Viewed by 7038

Abstract

This paper evaluates different types of AC machines and various control techniques for their suitability for the drive system of Alternative Energy Vehicles (AEV). An Indirect Field Oriented (IFO) drive system for the AEV application is chosen and its major problem of detuning [...] Read more.

This paper evaluates different types of AC machines and various control techniques for their suitability for the drive system of Alternative Energy Vehicles (AEV). An Indirect Field Oriented (IFO) drive system for the AEV application is chosen and its major problem of detuning is addressed by designing an offline and an online rotor resistance adaptation technique. The offline scheme sets the slip gain at various operating conditions based on the fact that if the rotor resistance is set correctly and field orientation is achieved, then there should be a linear relationship between the torque current and the output torque. The online technique is designed using Model Reference Adaptive System (MRAS) for the rotor resistance adaptation. For an ideal field oriented machine, the rotor flux along the q-axis should be zero. This condition acts as a reference model for the proposed MRAS scheme. The current model flux observer in the synchronous frame of reference is selected as an adjustable model and its rotor resistance is tuned so that the flux along the q-axis becomes zero. The effectiveness of the offline tuning scheme is evident through performance validation of the drive system, which is implemented in a real Ford vehicle. The experimental results obtained while driving the test vehicle are included in the paper while the proposed online scheme is validated on a 3.75 kW prototype induction motor. Full article

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

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18 pages, 526 KB

Open AccessArticle

Planning for a Low Carbon Future? Comparing Heat Pumps and Cogeneration as the Energy System Options for a New Residential Area

by Jukka Heinonen, Jani Laine, Karoliina Pluuman, Eeva-Sofia Säynäjoki, Risto Soukka and Seppo Junnila

Energies 2015, 8(9), 9137-9154; https://doi.org/10.3390/en8099137 - 27 Aug 2015

Cited by 12 | Viewed by 6114

Abstract

The purpose of this paper is to compare, from an urban planning perspective, the choice between combined heat and power (CHP) and a ground-source heat pump (HP) as the energy systems of a new residential area in the light of the uncertainty related [...] Read more.

The purpose of this paper is to compare, from an urban planning perspective, the choice between combined heat and power (CHP) and a ground-source heat pump (HP) as the energy systems of a new residential area in the light of the uncertainty related to the assessments. There has been a strong push globally for CHP due to its climate mitigation potential compared to separate production, and consequently it is often prioritized in planning without questioning. However, the uncertainties in assessing the emissions from CHP and alternative options in a certain planning situation make it very difficult to give robust decision guidelines. In addition, even the order of magnitude of the climate impact of a certain plan is actually difficult to assess robustly. With a case study of the new residential development of Härmälänranta in Tampere, Finland, we show how strongly the uncertainties related to (1) utilizing average or marginal electricity as the reference; (2) assigning emissions intensities for the production; and (3) allocating the emissions from CHP to heat and electricity affect the results and lead to varying decision guidelines. We also depict how a rather rarely utilized method in assigning the emissions from CHP is the most robust for planning support. Full article

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18 pages, 2108 KB

Open AccessArticle

Changes in Sunlight and Outdoor Thermal Environment Conditions Based on the Layout Plan of Flat Type Apartment Houses

by Sukjin Jung and Seonghwan Yoon

Energies 2015, 8(9), 9155-9172; https://doi.org/10.3390/en8099155 - 27 Aug 2015

Cited by 13 | Viewed by 5905

Abstract

Economic growths lead to population increases in large cities. This has brought about the growing necessity for apartment housing which has resulted in higher density populations living in high-rise apartment complexes. Therefore, the urban microclimate is aggravated due to the increasing ratio of [...] Read more.

Economic growths lead to population increases in large cities. This has brought about the growing necessity for apartment housing which has resulted in higher density populations living in high-rise apartment complexes. Therefore, the urban microclimate is aggravated due to the increasing ratio of artificial coverage and substandard daylight availability. To achieve a comfortable living environment and improve urban microclimates, a process considering the daylight availability and the outdoor thermal environment is required when designing apartment housing complexes. This study selected a total of 27 valid cases using an orthogonal array, L₂₇(3¹³) design of experiments (DOE). As a result of significance probability obtained in DOE analysis, the design factors that have an effect on the outdoor thermal environment and daylight availability were found to be building coverage ratio, distance between buildings, and azimuth. The rankings of the effect of design factors were shown to be in the order of azimuth > building coverage ratio > distance between buildings > floor area ratio > width/depth ratio. The surface temperature of the whole building decreased by 0.3 °C and Mean Radiant Temperature (MRT) decreased by 1.1 °C as a result of applying the greenery coverage ratio to apartment complexes. Heat Island Potential (HIP) also showed a decrease of 5.4 °C (at noon). Full article

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

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18 pages, 3169 KB

Open AccessArticle

Combined X-ray and Raman Studies on the Effect of Cobalt Additives on the Decomposition of Magnesium Borohydride

by Olena Zavorotynska, Stefano Deledda, Jenny G. Vitillo, Ivan Saldan, Matylda N. Guzik, Marcello Baricco, John C. Walmsley, Jiri Muller and Bjørn C. Hauback

Energies 2015, 8(9), 9173-9190; https://doi.org/10.3390/en8099173 - 27 Aug 2015

Cited by 33 | Viewed by 8359

Abstract

Magnesium borohydride (Mg(BH₄)₂) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal [...] Read more.

Magnesium borohydride (Mg(BH₄)₂) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal compounds as additives. In this work the decomposition of Mg(BH₄)₂ ball-milled with CoCl₂ and CoF₂ additives, was studied by means of a combination of several in-situ techniques. Synchrotron X-ray diffraction and Raman spectroscopy were used to follow the phase transitions and decomposition of Mg(BH₄)₂. By comparison with pure milled Mg(BH₄)₂, the temperature for the γ → ε phase transition in the samples with CoF₂ or CoCl₂ additives was reduced by 10–45 °C. In-situ Raman measurements showed the formation of a decomposition phase with vibrations at 2513, 2411 and 766 cm⁻¹ in the sample with CoF₂. Simultaneous X-ray absorption measurements at the Co K-edge revealed that the additives chemically transformed to other species. CoF₂ slowly reacted upon heating till ~290 °C, whereas CoCl₂ transformed drastically at ~180 °C. Full article

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

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20 pages, 894 KB

Open AccessArticle

Blade Fault Diagnosis in Small Wind Power Systems Using MPPT with Optimized Control Parameters

by Jui-Ho Chen and Weir Hung

Energies 2015, 8(9), 9191-9210; https://doi.org/10.3390/en8099191 - 27 Aug 2015

Cited by 6 | Viewed by 6941

Abstract

A systematic experiment verification of Chaos Embedded Sliding Mode Extremum Seeking Control for maximum power point tracking and a method for detecting possible faults in small wind turbine systems in advance are proposed in this paper. The chaotic logistic map is used to [...] Read more.

A systematic experiment verification of Chaos Embedded Sliding Mode Extremum Seeking Control for maximum power point tracking and a method for detecting possible faults in small wind turbine systems in advance are proposed in this paper. The chaotic logistic map is used to replace the random function in the particle swarm optimization algorithm for faster searching the optimal control parameter . From the experimental results, it is verified that the Chaos Embedded Sliding Mode Extremum Seeking Control scheme has a better dynamic response than traditional Extremum Seeking Control scheme and Hill-Climbing Search scheme for maximum power point tracking. In the proposed scheme for fault detection, a chaotic synchronization method is used to transform the maximum power point tracking signal into a chaos synchronization error distribution diagram. It is then taken as the characteristic for fault diagnosis purposes. Finally, an extension theory pattern recognition technique is applied to diagnose the fault. Notably, the use of the chaotic dynamic errors as the fault diagnosis characteristic reduces the number of extracted features required, and therefore greatly reduces both the computation time and the hardware implementation cost. From the experimental results, it is shown that the fault diagnosis rate of the proposed method exceeds 98% not only in non-real-time but also in real-time of faults detection of the blades. Full article

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

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16 pages, 436 KB

Open AccessArticle

An Approach to Identify the Suitable Plant Location for Miscanthus-Based Ethanol Industry: A Case Study in Ontario, Canada

by Poritosh Roy, Animesh Dutta and Bill Deen

Energies 2015, 8(9), 9266-9281; https://doi.org/10.3390/en8099266 - 28 Aug 2015

Cited by 10 | Viewed by 6183

Abstract

The life cycle (LC) of ethanol extracted from Miscanthus has been evaluated to identify the potential location for the Miscanthus-based ethanol industry in Ontario, Canada to mitigate greenhouse gas (GHG) emissions and minimize the production cost of ethanol. Four scenarios are established [...] Read more.

The life cycle (LC) of ethanol extracted from Miscanthus has been evaluated to identify the potential location for the Miscanthus-based ethanol industry in Ontario, Canada to mitigate greenhouse gas (GHG) emissions and minimize the production cost of ethanol. Four scenarios are established considering the land classes, land use, and cropping patterns in Ontario, Canada. The net energy consumption, emissions, and cost of ethanol are observed to be dependent on the processing plant location and scenarios. The net energy consumption, emissions, and cost vary from 12.9 MJ/L to 13.4 MJ/L, 0.79 $/L to 0.84 $/L, and 0.45 kg-CO₂e/L to 1.32 kg-CO₂e/L, respectively, which are reliant on the scenarios. Eastern Ontario has emerged as the best option. This study reveals that Miscanthus is a potential feedstock for the ethanol industries in Ontario, even if it is cultivated on marginal land. This study also highlights the contribution of energy crops (Miscanthus) to avoid the potential technical and economic constraints of lignocellulosic biomass for the renewable energy industry. Miscanthus may help avoid competition with food crops for prime land (higher quality land that is suitable for food crops), avoid the food versus fuel debate, help meet the ethanol demand, and achieve the GHG emissions abatement target of Canada. Full article

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

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14 pages, 499 KB

Open AccessArticle

A Two-Stage Algorithm to Estimate the Fundamental Frequency of Asynchronously Sampled Signals in Power Systems

by Joon-Hyuck Moon, Sang-Hee Kang, Dong-Hun Ryu, Jae-Lim Chang and Soon-Ryul Nam

Energies 2015, 8(9), 9282-9295; https://doi.org/10.3390/en8099282 - 28 Aug 2015

Cited by 3 | Viewed by 5394

Abstract

A two-stage algorithm is proposed for the estimation of the fundamental frequency of asynchronously sampled signals in power systems. In the first stage, time-domain interpolation reconstructs the power system signal at a new sampling time and the reconstructed signal passes through a tuned [...] Read more.

A two-stage algorithm is proposed for the estimation of the fundamental frequency of asynchronously sampled signals in power systems. In the first stage, time-domain interpolation reconstructs the power system signal at a new sampling time and the reconstructed signal passes through a tuned sine filter to eliminate harmonics. In the second stage, the fundamental frequency is estimated using a modified curve fitting, which is robust to noise. The evaluation results confirm the efficiency and validity of the two-stage algorithm for accurate estimation of the fundamental frequency even for asynchronously sampled signals contaminated with noise, harmonics, and an inter-harmonic component. Full article

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

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24 pages, 8297 KB

Open AccessArticle

Formulation and Analysis of an Approximate Expression for Voltage Sensitivity in Radial DC Distribution Systems

by Ho-Yong Jeong, Jong-Chan Choi, Dong-Jun Won, Seon-Ju Ahn and Seung-il Moon

Energies 2015, 8(9), 9296-9319; https://doi.org/10.3390/en8099296 - 28 Aug 2015

Cited by 11 | Viewed by 6217

Abstract

Voltage is an important variable that reflects system conditions in DC distribution systems and affects many characteristics of a system. In a DC distribution system, there is a close relationship between the real power and the voltage magnitude, and this is one of [...] Read more.

Voltage is an important variable that reflects system conditions in DC distribution systems and affects many characteristics of a system. In a DC distribution system, there is a close relationship between the real power and the voltage magnitude, and this is one of major differences from the characteristics of AC distribution systems. One such relationship is expressed as the voltage sensitivity, and an understanding of voltage sensitivity is very useful to describe DC distribution systems. In this paper, a formulation for a novel approximate expression for the voltage sensitivity in a radial DC distribution system is presented. The approximate expression is derived from the power flow equation with some additional assumptions. The results of approximate expression is compared with an exact calculation, and relations between the voltage sensitivity and electrical quantities are analyzed analytically using both the exact form and the approximate voltage sensitivity equation. Full article

(This article belongs to the Collection Smart Grid)

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24 pages, 3921 KB

Open AccessArticle

Development of the Hybrid Operation Method of a Multi-Geothermal Heat Pump System and Absorption Chiller-Heater

by Young-Ju Jung, Hyo-Jun Kim, Kyung-Ju Shin, Jae-Hun Jo, Yong-Shik Kim and Young-Hum Cho

Energies 2015, 8(9), 9320-9343; https://doi.org/10.3390/en8099320 - 31 Aug 2015

Cited by 3 | Viewed by 6196

Abstract

Considerable efforts have been made to reduce the energy consumption of buildings due to the energy crisis, and, the Korean government has supported the use of renewable energy through various grants. Among the possible renewable energy sources, geothermal energy can be used regardless [...] Read more.

Considerable efforts have been made to reduce the energy consumption of buildings due to the energy crisis, and, the Korean government has supported the use of renewable energy through various grants. Among the possible renewable energy sources, geothermal energy can be used regardless of the outside weather. Therefore, energy consumption can be reduced considerably in summer and winter. Despite the increasing use of renewable energy, the use of renewables has not been operating appropriately. Therefore, this study examined some of the problems of the operation of renewable energy and some possible improvements. The aim of the study is to evaluate a building containing an actual installed multi-geothermal heat pump (Multi-GHP) system, in terms of the energy efficiency. In addition, this study evaluated the present control system and the method of complex operation regarding existing heat sources systems and GHP systems through a simulation. The results can be regarded as the result of a hybrid operation method for the improvement of an existing operation. Therefore, the Multi-GHP system energy use of a hybrid operation condition of the Multi-GHP systems and the absorption (ABS) chiller-heater system was reduced compared to the operation condition of the Multi-GHP system, and the total energy consumption of the heat source equipment was reduced. The proposed operation plan was evaluated after applying the system to a building. These results showed that the efficient operation of a Multi-GHP hybrid operation method is possible. As a result, the GHP energy use of Multi-GHP systems and the ABS chiller-heater system was reduced by 30% compared to existing operation and the total energy consumption of heat source equipment was reduced by 78%. Full article

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

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21 pages, 1228 KB

Open AccessArticle

Experimental Evaluation of Simple Thermal Storage Control Strategies in Low-Energy Solar Houses to Reduce Electricity Consumption during Grid On-Peak Periods

by Kyoung-Ho Lee, Moon-Chang Joo and Nam-Choon Baek

Energies 2015, 8(9), 9344-9364; https://doi.org/10.3390/en8099344 - 31 Aug 2015

Cited by 14 | Viewed by 7317

Abstract

There is growing interest in zero-energy and low-energy buildings, which have a net energy consumption (on an annual basis) of almost zero. Because they can generate both electricity and thermal energy through the use of solar photovoltaic (PV) and solar thermal collectors, and [...] Read more.

There is growing interest in zero-energy and low-energy buildings, which have a net energy consumption (on an annual basis) of almost zero. Because they can generate both electricity and thermal energy through the use of solar photovoltaic (PV) and solar thermal collectors, and with the help of reduced building thermal demand, low-energy buildings can not only make a significant contribution to energy conservation on an annual basis, but also reduce energy consumption and peak demand. This study focused on electricity consumption during the on-peak period in a low-energy residential solar building and considers the use of a building’s thermal mass and thermal storage to reduce electricity consumption in summer and winter by modulation of temperature setpoints for heat pump and indoor thermostats in summer and additional use of a solar heating loop in winter. Experiments were performed at a low-energy solar demonstration house that has solar collectors, hot water storage, a ground-coupled heat pump, and a thermal storage tank. It was assumed that the on-peak periods were from 2 pm to 5 pm on hot summer days and from 5 pm to 8 pm on cold winter days. To evaluate the potential for utilizing the building’s thermal storage capacity in space cooling and heating, the use of simple control strategies on three test days in summer and two test days in the early spring were compared in terms of net electricity consumption and peak demand, which also considered the electricity generation from solar PV modules on the roof of the house. Full article

(This article belongs to the Special Issue PCM Applications in Building Energy)

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18 pages, 474 KB

Open AccessArticle

Power Quality Prediction, Early Warning, and Control for Points of Common Coupling with Wind Farms

by Jingjing Bai, Wei Gu, Xiaodong Yuan, Qun Li, Feng Xue and Xuchong Wang

Energies 2015, 8(9), 9365-9382; https://doi.org/10.3390/en8099365 - 31 Aug 2015

Cited by 22 | Viewed by 5248

Abstract

Wind farms can affect the power quality (PQ) of the power supply grid, with subsequent impacts on the safe and stable operation of other electrical equipment. A novel PQ prediction, early warning, and control approach for the common coupling points between wind farms [...] Read more.

Wind farms can affect the power quality (PQ) of the power supply grid, with subsequent impacts on the safe and stable operation of other electrical equipment. A novel PQ prediction, early warning, and control approach for the common coupling points between wind farms and the network is proposed in this paper. We then quantify PQ problems and provide rational support measures. To obtain predicted PQ data, we first establish a trend analysis model. The model incorporates a distance-based cluster analysis, probability distribution analysis based on polynomial fitting, pattern matching based on similarity, and Monte Carlo random sampling. A data mining algorithm then uses the PQ early warning flow to analyze limit-exceeding and abnormal data, quantify their severity, and output early warning prompts. Finally, PQ decision support is applied to inform both the power suppliers and users of anomalous changes in PQ, and advise on corresponding countermeasures to reduce relevant losses. Case studies show that the proposed approach is effective and feasible, and it has now been applied to an actual PQ monitoring platform. Full article

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9 pages, 264 KB

Open AccessArticle

Structural Properties of Liquid Water and Ice Ih from Ab-Initio Molecular Dynamics with a Non-Local Correlation Functional

by Niall J. English

Energies 2015, 8(9), 9383-9391; https://doi.org/10.3390/en8099383 - 31 Aug 2015

Cited by 25 | Viewed by 6466

Abstract

Equilibrium Born-Oppenheimer molecular dynamics simulations have been performed in the canonical ensemble to investigate the structural properties of liquid water and ice Ih (hexagonal ice) at 298 and 273 K, respectively, using a state-of-the-art non-local correlation functional, whilst size effects have been [...] Read more.

Equilibrium Born-Oppenheimer molecular dynamics simulations have been performed in the canonical ensemble to investigate the structural properties of liquid water and ice Ih (hexagonal ice) at 298 and 273 K, respectively, using a state-of-the-art non-local correlation functional, whilst size effects have been examined explicitly in the case of liquid water. This has led to improved agreement with experiments for pair distribution functions, in addition to molecular dipole moments, vis-à-vis previous flavours of ab-initio molecular dynamics simulation of water, highlighting the importance of appropriate dispersion. Intramolecular geometry has also been examined, in addition to hydrogen-bonding interactions; it was found that an improved description of dispersion via non-local correlation helps to reduce over-structuring associated with the Perdew-Becke-Ernzerhof (PBE) and other commonly-used functionals. Full article

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15 pages, 262 KB

Open AccessArticle

The Relationship between Energy Consumption and Economic Growth: Evidence from China’s Industrial Sectors

by Yi Hu, Dongmei Guo, Mingxi Wang, Xi Zhang and Shouyang Wang

Energies 2015, 8(9), 9392-9406; https://doi.org/10.3390/en8099392 - 31 Aug 2015

Cited by 47 | Viewed by 7125

Abstract

In this article, the relationship between energy consumption and economic growth is examined from the viewpoint of China’s industrial sectors. Panel data from 37 industrial sectors in China covering the period from 1998 to 2010 was used in this study. Not only first [...] Read more.

In this article, the relationship between energy consumption and economic growth is examined from the viewpoint of China’s industrial sectors. Panel data from 37 industrial sectors in China covering the period from 1998 to 2010 was used in this study. Not only first generation panel unit root tests and panel cointegration tests, but also second generation tests that account for dependence between cross-sectional units were employed. The empirical results reveal that both energy consumption and economic growth are integrated as order one, and they are cointegrated. Panel fully modified ordinary least squares estimators show that a 1% increase in energy consumption increases the real value added of industrial sectors by 0.871%, and a 1% increase in real value added of industrial sectors increases energy consumption by 1.103%. The panel vector error correction models for causality tests are estimated by a system generalized moment method. We find a unidirectional causal relation running from economic growth to energy consumption in the shortrun. In the long run, however, there is evidence of a unidirectional causality running from energy consumption to economic growth. Full article

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27 pages, 295 KB

Open AccessArticle

Can the BestGrid Process Improve Stakeholder Involvement in Electricity Transmission Projects?

by Nadejda Komendantova, Marco Vocciante and Antonella Battaglini

Energies 2015, 8(9), 9407-9433; https://doi.org/10.3390/en8099407 - 31 Aug 2015

Cited by 31 | Viewed by 8512

Abstract

The European Union has set ambitious targets for deployment of renewable energy sources to reach goals of climate change mitigation and energy security policies. However, the current state of electricity transmission infrastructure is a major bottleneck for further scaling up of renewable energy [...] Read more.

The European Union has set ambitious targets for deployment of renewable energy sources to reach goals of climate change mitigation and energy security policies. However, the current state of electricity transmission infrastructure is a major bottleneck for further scaling up of renewable energy in the EU. Several thousands of kilometers of new lines have to be constructed and upgraded to accommodate growing volumes of intermittent renewable electricity. In many countries, construction of electricity transmission projects has been delayed for several years due to concerns of local stakeholders. The innovative BESTGRID approach, reported here, brings together transmission system operators (TSOs) and non-governmental organizations (NGOs) to discuss and understand the nature of stakeholder concerns. This paper has three objectives: (1) to understand stakeholder concerns about the deployment of electricity transmission grids in four pilot projects according to five guiding principles: need, transparency, engagement, environment, and impacts on human health as well as benefits; (2) to understand how these principles can be addressed to provide a basis for better decision-making outcomes; and (3) to evaluate the BESTGRID process based on feedback received from stakeholders and the level of participation achieved according to the ladder of Arnstein. This paper goes beyond a discussion of “measures to mitigate opposition” to understand how dialogue between TSOs and the public—represented mainly by NGOs and policy-makers—might lead to a better decision-making process and more sustainable electricity transmission infrastructure deployment. Full article

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

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18 pages, 457 KB

Open AccessArticle

Numerical Simulation Research on the Process of Reburning South American Coal and Cornstalk

by Xiang Gou, Zifang Wang, Yurou Liu, Meng Si, Surjit Singh, Enyu Wang, Liansheng Liu and Jinxiang Wu

Energies 2015, 8(9), 9434-9451; https://doi.org/10.3390/en8099434 - 1 Sep 2015

Viewed by 4933

Abstract

Photo-chemical smog and acid rain formed from many pollutants including NO_x are serious problems that have attracted much attention due to their negative influences on the atmosphere, plants, animals and even building materials. Effective measures of controlling NO_x emissions are necessary. [...] Read more.

Photo-chemical smog and acid rain formed from many pollutants including NO_x are serious problems that have attracted much attention due to their negative influences on the atmosphere, plants, animals and even building materials. Effective measures of controlling NO_x emissions are necessary. In this study, a computational fluid dynamics (CFD) software, Ansys Fluent 14.5, has been applied to research the processes of South American coal (SAm) reburning and cornstalk reburning. The influences of reburn zone excess air coefficient, reburning fuel fraction (R_ff) and the secondary air temperature on the furnace combustion and NO_x reduction have been determined. Results show that, in the simulated data range, the lower reburn zone excess air coefficient, the greater the rate of denitration for both SAm reburning and cornstalk reburning. The highest rates of denitration for SAm reburning and cornstalk reburning were 56.15% and 66.89%, respectively, in comparison to the conventional combustion. The denitration rate increases with the increase of reburning fuel fraction. However, when the reburning fuel fraction increases beyond a certain level, fuels within the furnace will undergo incomplete combustion. Under the premise of the fuel burnout, a relatively good case occurs at the reburning fuel fraction of 20% for the two kinds of reburning, and the NO_x removal rate is 60.57% for cornstalk reburning, which is 7.61% higher than that of the SAm reburning. Temperature also has certain influences on the denitration effect and it shows that, in the lower temperature range, the higher the temperature of the secondary air, the higher the denitration rate. However, as temperature reaches a certain value, the denitration effect is no longer enhanced but reduced. For the two kinds of reburning, the case with the secondary air at 500 K is a relatively good one, and the NO_x removal rate reaches 66.36% for cornstalk reburning, while it is 55% for SAm reburning. Overall, cornstalk reburning provides a higher NO_x reduction rate in comparison to SAm reburning. Full article

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12 pages, 935 KB

Open AccessArticle

Further Improvements of an End-Effector for Robotic Assembly of Polymer Electrolyte Membrane Fuel Cells

by Vladimir Gurau and Terri Armstrong-Koch

Energies 2015, 8(9), 9452-9463; https://doi.org/10.3390/en8099452 - 1 Sep 2015

Cited by 12 | Viewed by 6950

Abstract

This paper presents a technology for robotic assembly of Polymer Electrolyte Membrane Fuel Cells (PEMFCs). We describe the most recent configuration of the end-effector used for robotic assembly of PEMFCs, the robot workcell, the fuel cell components and the method of automated assembling [...] Read more.

This paper presents a technology for robotic assembly of Polymer Electrolyte Membrane Fuel Cells (PEMFCs). We describe the most recent configuration of the end-effector used for robotic assembly of PEMFCs, the robot workcell, the fuel cell components and the method of automated assembling fuel cell stacks. In this second generation of end-effector and workcell designs, the productivity of the automated assembly process and the capability of the robot to assemble larger scale fuel cell stacks have been improved. The advantage of the technology presented here consists in its low cost, its simplicity, in its capability of rapidly assembling fuel cell stacks containing a large number of cells due to a passive compliance system of the end-effector and in its capability of accurately aligning the fuel cell components in the stack. Full article

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

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22 pages, 5473 KB

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Levelized Cost of Energy Analysis of a Wind Power Generation System at Búrfell in Iceland

by Birgir Freyr Ragnarsson, Gudmundur V. Oddsson, Runar Unnthorsson and Birgir Hrafnkelsson

Energies 2015, 8(9), 9464-9485; https://doi.org/10.3390/en8099464 - 1 Sep 2015

Cited by 31 | Viewed by 10588

Abstract

Wind energy harnessing is a new energy production alternative in Iceland. Current installed wind power in Iceland sums to 1.8 MW, which in contrast is 0.1% of the country’s total electricity production. This article is dedicated to the exploration of the potential cost [...] Read more.

Wind energy harnessing is a new energy production alternative in Iceland. Current installed wind power in Iceland sums to 1.8 MW, which in contrast is 0.1% of the country’s total electricity production. This article is dedicated to the exploration of the potential cost of wind energy production at Búrfell in the south of Iceland. A levelized cost of energy (LCOE) approach was applied to the estimation of the potential cost. Weibull simulation is used to simulate wind data for calculations. A confirmation of the power law is done by comparing real data to calculated values. A modified Weibull simulation is verified by comparing results with actual on-site test wind turbines. A wind farm of 99MWis suggested for the site. Key results were the capacity factor (CF) at Búrfell being 38.15% on average and that the LCOE for wind energy was estimated as 0.087–0.088 USD/kWh (assuming 10% weighted average cost of capital (WACC)), which classifies Búrfell among the lowest LCOE sites for wind energy in Europe. Full article

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9 pages, 490 KB

Open AccessArticle

Glucose-Treated Manganese Hexacyanoferrate for Sodium-Ion Secondary Battery

by Yutaka Moritomo, Kensuke Goto and Takayuki Shibata

Energies 2015, 8(9), 9486-9494; https://doi.org/10.3390/en8099486 - 1 Sep 2015

Cited by 16 | Viewed by 6666

Abstract

Manganese hexacyanoferrate (Mn-PBA) is a promising cathode material forsodium-ion secondary battery (SIB) with high average voltage (=3.4 V) against Na. Here,we find that the thermal decomposition of glucose modifies the surface state of Mn-PBA,without affecting the bulk crystal structure. The glucose treatment significantly [...] Read more.

Manganese hexacyanoferrate (Mn-PBA) is a promising cathode material forsodium-ion secondary battery (SIB) with high average voltage (=3.4 V) against Na. Here,we find that the thermal decomposition of glucose modifies the surface state of Mn-PBA,without affecting the bulk crystal structure. The glucose treatment significantly improves therate properties of Mn-PBA in SIB. The critical discharge rate increases from 1 C (as-grown)to 15 C (glucose-treated). Our observation suggests that thermal treatment is quite effectivefor insulating coordination polymers. Full article

(This article belongs to the Special Issue Electrochemical Energy Storage - 2015)

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14 pages, 357 KB

Open AccessArticle

Analysis of a New Liquefaction Combined with Desublimation System for CO₂ Separation Based on N₂/CO₂ Phase Equilibrium

by Wenchao Yang, Shuhong Li, Xianliang Li, Yuanyuan Liang and Xiaosong Zhang

Energies 2015, 8(9), 9495-9508; https://doi.org/10.3390/en8099495 - 1 Sep 2015

Cited by 28 | Viewed by 7027

Abstract

Cryogenic CO₂ capture is considered as a promising CO₂ capture method due to its energy saving and environmental friendliness. The phase equilibrium analysis of CO₂-mixtures at low temperature is crucial for the design and operation of a cryogenic system [...] Read more.

Cryogenic CO₂ capture is considered as a promising CO₂ capture method due to its energy saving and environmental friendliness. The phase equilibrium analysis of CO₂-mixtures at low temperature is crucial for the design and operation of a cryogenic system because it plays an important role in analysis of recovery and purity of the captured CO₂. After removal of water and toxic gas, the main components in typical boiler gases are N₂/CO₂. Therefore, this paper evaluates the reliabilities of different cubic equations of state (EOS) and mixing rules for N₂/CO₂. The results show that Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) fit the experimental data well, PR combined with the van der Waals (vdW) mixing rule is more accurate than the other models. With temperature decrease, the accuracy of the model improves and the deviation of the N₂ vapor fraction is 0.43% at 220 K. Based on the selected calculation model, the thermodynamic properties of N₂/CO₂ at low temperature are analyzed. According to the results, a new liquefaction combined with a desublimation system is proposed. The total recovery and purity of CO₂ production of the new system are satisfactory enough for engineering applications. Additionally, the total energy required by the new system to capture the CO₂ is about 3.108 MJ·kg⁻¹ CO₂, which appears to be at least 9% lower than desublimation separation when the initial concentration of CO₂ is 40%. Full article

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32 pages, 3442 KB

Open AccessArticle

Taxi Fleet Renewal in Cities with Improved Hybrid Powertrains: Life Cycle and Sensitivity Analysis in Lisbon Case Study

by António P. Castel-Branco, João P. Ribau and Carla M. Silva

Energies 2015, 8(9), 9509-9540; https://doi.org/10.3390/en8099509 - 2 Sep 2015

Cited by 10 | Viewed by 8476

Abstract

Stringent emissions regulations in cities and the high amount of daily miles driven by taxi vehicles enforce the need to renew these fleets with more efficient and cleaner technologies. Hybrid vehicles are potential candidates due to their enhanced powertrain, and slower battery depletion [...] Read more.

Stringent emissions regulations in cities and the high amount of daily miles driven by taxi vehicles enforce the need to renew these fleets with more efficient and cleaner technologies. Hybrid vehicles are potential candidates due to their enhanced powertrain, and slower battery depletion and fewer lifetime issues, relative to full electric vehicles. This paper proposes a methodology to analyze the best theoretical hybrid powertrain candidate with maximum in-use efficiency, minimum life cycle greenhouse gas emissions, and minimum additional cost, for a Lisbon taxi fleet case study. A multi-objective genetic algorithm integrated with a vehicle simulator is used to achieve several trade-off optimal solutions for different driving patterns. Potential improvements in taxi carbon footprint are discussed as a function of its lifetime, urban/extra-urban driving and maintenance/fuel life cycle uncertainty. Hybrid powertrains reveal to be advantageous comparatively to the conventional vehicle, especially in urban conditions. Specifically optimized solutions could reduce in-use energy consumption by 43%–47% in urban driving, and 27%–34% in extra-urban driving conditions, and reduce life cycle emissions by 47%–49% and 34%–36% respectively, relative to the conventional taxi. A financial gain of 50 $/km/fleet in extra-urban and 226 $/km/fleet in urban routes could be achieved by replacing the taxi fleet with the optimal solutions. Full article

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

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19 pages, 332 KB

Open AccessArticle

Bio-Wastes as an Alternative Household Cooking Energy Source in Ethiopia

by Gudina Terefe Tucho and Sanderine Nonhebel

Energies 2015, 8(9), 9565-9583; https://doi.org/10.3390/en8099565 - 2 Sep 2015

Cited by 46 | Viewed by 13531

Abstract

Up to the present day, wood has been used to supply the needs for cooking in rural Africa. Due to the ongoing deforestation, households need to change to other energy sources. To cover this need, a large amount of people are using residues [...] Read more.

Up to the present day, wood has been used to supply the needs for cooking in rural Africa. Due to the ongoing deforestation, households need to change to other energy sources. To cover this need, a large amount of people are using residues from agriculture (straw, manure) instead. However, both straw and manure also have a function in agriculture for soil improvement. Using all the straw and manure will seriously affect the food production. In this paper we first determine the amount of energy that households need for cooking (about 7 GJ per year). Then we estimate the amount of residues that can be obtained from the agricultural system and the amount of energy for cooking that can be derived from this amount when different conversion techniques are used. The amount of residues needed is strongly affected by the technology used. The traditional three stone fires require at least two times as much resource than the more advanced technologies. Up to 4 ha of land or 15 cows are needed to provide enough straw and manure to cook on the traditional three stone fires. When more efficient techniques are used (briquetting, biogas) this can be reduced to 2 ha and six cows. Due to large variation in resource availability between households, about 80% of the households own less than 2 ha and 70% holds less than four cows. This means that even when modern, energy efficient techniques are used the largest share of the population is not able to generate enough energy for cooking from their own land and/or cattle. Most rural households in Sub-Saharan Africa may share similar resource holding characteristics for which the results from the current findings on Ethiopia can be relevant. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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10 pages, 1299 KB

Open AccessArticle

Electrochemical Properties for Co-Doped Pyrite with High Conductivity

by Yongchao Liu and Shengping Wang

Energies 2015, 8(9), 9584-9593; https://doi.org/10.3390/en8099584 - 2 Sep 2015

Cited by 12 | Viewed by 5836

Abstract

In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS₂). The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Co in the crystal lattice of [...] Read more.

In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS₂). The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Co in the crystal lattice of FeS₂ could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS₂ batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g⁻¹) with a doping ratio of 7% was significantly higher than that of the original FeS₂ (574.6 mAh·g⁻¹) because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS₂. Full article

(This article belongs to the Special Issue Electrochemical Energy Storage - 2015)

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26 pages, 3839 KB

Open AccessArticle

The “Weather Intelligence for Renewable Energies” Benchmarking Exercise on Short-Term Forecasting of Wind and Solar Power Generation

by Simone Sperati, Stefano Alessandrini, Pierre Pinson and George Kariniotakis

Energies 2015, 8(9), 9594-9619; https://doi.org/10.3390/en8099594 - 3 Sep 2015

Cited by 50 | Viewed by 8535

Abstract

A benchmarking exercise was organized within the framework of the European Action Weather Intelligence for Renewable Energies (“WIRE”) with the purpose of evaluating the performance of state of the art models for short-term renewable energy forecasting. The exercise consisted in forecasting the power [...] Read more.

A benchmarking exercise was organized within the framework of the European Action Weather Intelligence for Renewable Energies (“WIRE”) with the purpose of evaluating the performance of state of the art models for short-term renewable energy forecasting. The exercise consisted in forecasting the power output of two wind farms and two photovoltaic power plants, in order to compare the merits of forecasts based on different modeling approaches and input data. It was thus possible to obtain a better knowledge of the state of the art in both wind and solar power forecasting, with an overview and comparison of the principal and the novel approaches that are used today in the field, and to assess the evolution of forecast performance with respect to previous benchmarking exercises. The outcome of this exercise consisted then in proposing new challenges in the renewable power forecasting field and identifying the main areas for improving accuracy in the future. Full article

(This article belongs to the Special Issue Forecasting Methods and Measurements of Forecasting Errors for Renewable Energy Sources)

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20 pages, 585 KB

Open AccessArticle

Carbon as Investment Risk—The Influence of Fossil Fuel Divestment on Decision Making at Germany’s Main Power Providers

by Dagmar Kiyar and Bettina B. F. Wittneben

Energies 2015, 8(9), 9620-9639; https://doi.org/10.3390/en8099620 - 3 Sep 2015

Cited by 16 | Viewed by 12393

Abstract

German electricity giants have recently taken high-level decisions to remove selected fossil fuel operations from their company portfolio. This new corporate strategy could be seen as a direct response to the growing global influence of the fossil fuel divestment campaign. In this paper [...] Read more.

German electricity giants have recently taken high-level decisions to remove selected fossil fuel operations from their company portfolio. This new corporate strategy could be seen as a direct response to the growing global influence of the fossil fuel divestment campaign. In this paper we ask whether the divestment movement currently exerts significant influence on decision-making at the top four German energy giants—E.On, RWE, Vattenfall and EnBW. We find that this is not yet the case. After describing the trajectory of the global fossil fuel divestment campaign, we outline four alternative influences on corporate strategy that, currently, are having a greater impact than the divestment movement on Germany’s power sector. In time, however, clear political decisions and strong civil support may increase the significance of climate change concerns in the strategic management of the German electricity giants. Full article

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

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15 pages, 581 KB

Open AccessArticle

Chemical Composition of Apricot Pit Shells and Effect of Hot-Water Extraction

by Derek B. Corbett, Neil Kohan, Grazielle Machado, Chengyan Jing, Aditi Nagardeolekar and Biljana M. Bujanovic

Energies 2015, 8(9), 9640-9654; https://doi.org/10.3390/en8099640 - 3 Sep 2015

Cited by 51 | Viewed by 9964

Abstract

Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS) were studied in this work [...] Read more.

Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS) were studied in this work to assess their potential for use in a biorefinery. Hot water extraction (HWE; 160 °C, 2 h), proposed to remove easily accessible hemicelluloses, was performed to evaluate the susceptibility of APS to this mild pretreatment process. The chemical composition of APS before and after HWE (EAPS) was analyzed by standard methods and ¹H-NMR. A low yield of the remaining HW-extracted APS (~59%) indicated that APS are highly susceptible to this pretreatment method. ¹H-NMR analysis of EAPS revealed that ~77% of xylan present in raw APS was removed along with ~24% of lignin. The energy of combustion of APS was measured before and after HWE showing a slight increase due to HWE (1.61% increase). Near infrared radiation spectroscopy (NIRS), proposed as a quick non-invasive method of biomass analysis, was performed. NIRS corroborated results of traditional analysis and ¹H-NMR. Determination of antioxidizing activity (AOA) of APS extracts was also undertaken. AOA of organic APS extracts were shown to be more than 20 times higher than that of a synthetic antioxidizing agent. Full article

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

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15 pages, 3026 KB

Open AccessArticle

A Novel Choice Procedure of Magnetic Component Values for Phase Shifted Full Bridge Converters with a Variable Dead-Time Control Method

by Lei Zhao, Haoyu Li, Yanxue Yu and Yantian Wang

Energies 2015, 8(9), 9655-9669; https://doi.org/10.3390/en8099655 - 4 Sep 2015

Cited by 9 | Viewed by 7922

Abstract

Magnetic components are important parts of the phase shifted full bridge (PSFB) converter. During the dead-time of switches located in the same leg, the converter can achieve zero-voltage-switching (ZVS) by using the energies stored in magnetic components to discharge or charge the output [...] Read more.

Magnetic components are important parts of the phase shifted full bridge (PSFB) converter. During the dead-time of switches located in the same leg, the converter can achieve zero-voltage-switching (ZVS) by using the energies stored in magnetic components to discharge or charge the output capacitances of switches. Dead-time is usually calculated under a given set of pre-defined load condition which results in that the available energies are insufficient and ZVS capability is lost at light loads. In this paper, the PSFB converter is controlled by variable dead-time method and thus full advantage can be taken of the energies stored in magnetic components. Considering that dead-time has a great effect on ZVS, the relationship between available energies and magnetic component values is formulated by analyzing the equivalent circuits during dead-time intervals. Magnetic component values are chosen based on such relationship. The proposed choice procedure can make the available energies greater than the required energies for ZVS operation over a wide range of load conditions. Moreover, the burst mode control is adopted in order to reduce the standby power loss. Experimental results coincide with the theoretical analysis. The proposed method is a simple and practical solution to extend the ZVS range. Full article

(This article belongs to the Special Issue Smart Metering)

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18 pages, 2460 KB

Open AccessArticle

Phase-Shifted Carrier Pulse Width Modulation Based on Particle Swarm Optimization for Cascaded H-bridge Multilevel Inverters with Unequal DC Voltages

by Xin-Jian Cai, Zhen-Xing Wu, Quan-Feng Li and Shu-Xiu Wang

Energies 2015, 8(9), 9670-9687; https://doi.org/10.3390/en8099670 - 8 Sep 2015

Cited by 22 | Viewed by 6852

Abstract

High-voltage cascaded H-bridge multilevel (CHBML) inverters usually include many isolated dc voltage sources. Some dc source faults result in a drop in the dc voltage, thereby leading to unequal cell dc voltages. On the other hand, the differences in cell dc source parameters [...] Read more.

High-voltage cascaded H-bridge multilevel (CHBML) inverters usually include many isolated dc voltage sources. Some dc source faults result in a drop in the dc voltage, thereby leading to unequal cell dc voltages. On the other hand, the differences in cell dc source parameters result in unequal dc voltages too. At present, riding through the faults of dc sources and operating under the condition of unequal dc voltages are required to improve the reliability of CHBML inverters. Unfortunately, the conventional phase-shifted carrier pulse width modulation (PSCPWM), which is widely used for CHBML inverters, cannot eliminate low-frequency sideband harmonics when cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM based on the particle swarm optimization algorithm. This modulation technique eliminates low-frequency sideband harmonics by calculating and regulating the carrier phases according to different cell dc voltages. The proposed PSCPWM enhances the reliability of the CHBML inverter and extends the range of its application. Simulation and experimental results obtained from the prototype of the CHBML inverter verify the theoretical analysis and the achievements made in this paper. Full article

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31 pages, 8157 KB

Open AccessArticle

Investigation of Electromagnetic, Thermal and Mechanical Characteristics of a Five-Phase Dual-Rotor Permanent-Magnet Synchronous Motor

by Jing Zhao, Wei Liu, Bin Li, Xiangdong Liu, Congzhe Gao and Zhongxin Gu

Energies 2015, 8(9), 9688-9718; https://doi.org/10.3390/en8099688 - 9 Sep 2015

Cited by 20 | Viewed by 12635

Abstract

This paper investigates of a kind of five-phase dual-rotor permanent-magnet synchronous motor (DRPMSM), which contains dual rotors and a single stator. This kind of motor has the potential advantages of high power density, high reliability and high efficiency, which make it more appropriate [...] Read more.

This paper investigates of a kind of five-phase dual-rotor permanent-magnet synchronous motor (DRPMSM), which contains dual rotors and a single stator. This kind of motor has the potential advantages of high power density, high reliability and high efficiency, which make it more appropriate for using in electric vehicles (EVs). In order to evaluate the most suitable power level for this kind of structure, the electromagnetic, the thermal and the mechanical characteristics are investigated in this paper. The length to diameter ratio of motors is researched to obtain the highest power density and then the optimum ratio is obtained. Based on the optimum ratio, the thermal characteristics are researched under natural condition and forced-air cooling condition with different wind speeds. In addition, the mechanical characteristics are analyzed under no-load and different loads conditions, respectively. All of the results are analyzed by two-dimension (2-D) and three-dimension (3-D) finite element method (FEM) simulation, which provide a good reference to select suitable power level for this kind of motor structure. Finally, a DRPMSM prototype is manufactured and tested. The experimental results effectively verify the FEM results. Full article

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

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12 pages, 1184 KB

Open AccessArticle

Determining the Frequency for Load-Independent Output Current in Three-Coil Wireless Power Transfer System

by Longzhao Sun, Houjun Tang and Yingyi Zhang

Energies 2015, 8(9), 9719-9730; https://doi.org/10.3390/en8099719 - 9 Sep 2015

Cited by 14 | Viewed by 7491

Abstract

Conditions for load-independent output voltage or current in two-coil wireless power transfer (WPT) systems have been studied. However, analysis of load-independent output current in three-coil WPT system is still lacking in previous studies. This paper investigates the output current characteristics of a three-coil [...] Read more.

Conditions for load-independent output voltage or current in two-coil wireless power transfer (WPT) systems have been studied. However, analysis of load-independent output current in three-coil WPT system is still lacking in previous studies. This paper investigates the output current characteristics of a three-coil WPT system against load variations, and determines the operating frequency to achieve a constant output current. First, a three-coil WPT system is modeled by circuit theory, and the analytical expression of the root-mean-square of the output current is derived. By substituting the coupling coefficients, the quality factor, and the resonant frequency of each coil, we propose a method of calculating the frequency for load-independent output current in a three-coil WPT system, which indicates that there are two frequencies that can achieve load-independent output current. Experiments are conducted to validate these analytical results. Full article

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

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20 pages, 548 KB

Open AccessArticle

The Economic Viability of Renewable Portfolio Standard Support for Offshore Wind Farm Projects in Korea

by Chang-Gi Min, Jong Keun Park, Don Hur and Mun-Kyeom Kim

Energies 2015, 8(9), 9731-9750; https://doi.org/10.3390/en8099731 - 9 Sep 2015

Cited by 11 | Viewed by 5418

Abstract

Offshore wind farm (WF) projects have been promoted by support schemes as part of the expansion of renewable energy resources in Korea. This paper examines in detail how the Renewable Portfolio Standard (RPS), which was adopted post the Feed-in-Tariff scheme in 2012, has [...] Read more.

Offshore wind farm (WF) projects have been promoted by support schemes as part of the expansion of renewable energy resources in Korea. This paper examines in detail how the Renewable Portfolio Standard (RPS), which was adopted post the Feed-in-Tariff scheme in 2012, has had a profound impact on the economic benefits of offshore WFs in Korea. A framework for analyzing the economic viability of RPS is presented and applied to the sixth basic plan for long-term electricity supply and demand in Korea. The electricity market price is forecast using a reformulated probabilistic production cost (PPC) model, and the renewable energy certificate (REC) price is calculated using its determination rule. The results show that the existing RPS will be ineffective in increasing the penetration of offshore WFs in Korea; however, they also indicate that the economic viability of offshore WFs could be improved by adjusting the existing RPS. Full article

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26 pages, 6995 KB

Open AccessArticle

Parametric Optimization of Regenerative Organic Rankine Cycle System for Diesel Engine Based on Particle Swarm Optimization

by Hongjin Wang, Hongguang Zhang, Fubin Yang, Songsong Song, Ying Chang, Chen Bei and Kai Yang

Energies 2015, 8(9), 9751-9776; https://doi.org/10.3390/en8099751 - 9 Sep 2015

Cited by 17 | Viewed by 8525

Abstract

To efficiently recover the waste heat from a diesel engine exhaust, a regenerative organic Rankine cycle (RORC) system was employed, and butane, R124, R416A, and R134a were used as the working fluids. The resulting diesel engine-RORC combined system was defined and the relevant [...] Read more.

To efficiently recover the waste heat from a diesel engine exhaust, a regenerative organic Rankine cycle (RORC) system was employed, and butane, R124, R416A, and R134a were used as the working fluids. The resulting diesel engine-RORC combined system was defined and the relevant evaluation indexes were proposed. First, the variation tendency of the exhaust energy rate under various diesel engine operating conditions was analyzed using experimental data. The thermodynamic model of the RORC system was established based on the first and second laws of thermodynamics, and the net power output and exergy destruction rate of the RORC system were selected as the objective functions. A particle swarm optimization (PSO) algorithm was used to optimize the operating parameters of the RORC system, including evaporating pressure, intermediate pressure, and degree of superheat. The operating performances of the RORC system and diesel engine-RORC combined system were studied for the four selected working fluids under various operating conditions of the diesel engine. The results show that the operating performances of the RORC system and the combined system using butane are optimal on the basis of optimizing the operating parameters; when the engine speed is 2200 r/min and engine torque is 1215 N·m, the net power output of the RORC system using butane is 36.57 kW, and the power output increasing ratio (POIR) of the combined system using butane is 11.56%. Full article

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17 pages, 313 KB

Open AccessArticle

An Application of Spectral Kurtosis to Separate Hybrid Power Quality Events

by Juan José González De la Rosa, José María Sierra-Fernández, José Carlos Palomares-Salas, Agustín Agüera-Pérez and Álvaro Jiménez Montero

Energies 2015, 8(9), 9777-9793; https://doi.org/10.3390/en8099777 - 9 Sep 2015

Cited by 13 | Viewed by 5107

Abstract

For the development of the future smart grid, the detection of power quality events is a key issue for the power system monitoring. Voltage sags, swells, harmonics (variations) and interruptions, which produce large losses for commercial and industrial consumers, are the main events [...] Read more.

For the development of the future smart grid, the detection of power quality events is a key issue for the power system monitoring. Voltage sags, swells, harmonics (variations) and interruptions, which produce large losses for commercial and industrial consumers, are the main events to be considered due to the sensitivity of equipment to these electrical anomalies. The steady-state events are even more frequently accompanied by transients, the discrimination and localization being far more exigent and requiring advanced signal separating tools to be incorporated in the measurement equipment. This paper shows the event detection performance of the spectral kurtosis as a signal separating tool in the frequency domain. The disturbances under test are hybrid signals resulting from the coupling between amplitude defects and non-desired higher frequencies. Being a fourth-order spectrum, the kurtosis is confirmed as a noise-resistant tool that enhances impulsiveness, therefore characterizing the electrical anomalies. In the beginning of the analysis, the voltage sag is established as a reference; then, the disturbances (oscillatory transients and harmonics) are coupled at the starting and ending instants of the sag, resulting in complex hybrid events. The results show that the spectral kurtosis enhances the detection Energies 2015, 8 9778 of both types of events (steady state and transients), which are outlined in a bump shape in the fourth-order frequency pattern and centered in the main carrier frequency. Indeed, while the oscillatory transients are associated with softer and lower-amplitude peaks, the harmonics correspond to crisper and higher ones. As these mixed electrical faults are very common in the actual power grid, the article postulates the higher-order spectra to be implemented in prospective online measurement instruments. Full article

(This article belongs to the Special Issue Smart Metering)

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23 pages, 1198 KB

Open AccessArticle

Influence of Combustion Parameters on Fouling Composition after Wood Pellet Burning in a Lab-Scale Low-Power Boiler

by Lara Febrero, Enrique Granada, Araceli Regueiro and José Luis Míguez

Energies 2015, 8(9), 9794-9816; https://doi.org/10.3390/en8099794 - 9 Sep 2015

Cited by 38 | Viewed by 7326

Abstract

The present study aims to evaluate the effect of different operating conditions on fouling composition after woody biomass combustion in an experimental low-power fixed-bed boiler. The boiler was built specifically for research purposes and allows easy removal of areas susceptible to fouling and [...] Read more.

The present study aims to evaluate the effect of different operating conditions on fouling composition after woody biomass combustion in an experimental low-power fixed-bed boiler. The boiler was built specifically for research purposes and allows easy removal of areas susceptible to fouling and the control, modification and registry of combustion parameters. The influences of the total airflow supplied and the deposition probe temperature were studied in fouling; differentiating between the layers of fouling adhered to the tube and those deposited over the tube. Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were performed in order to determine a relationship between the fouling composition and the combustion parameters used. Upon increasing the total airflow supplied and the deposition probe temperature, the amount of organic matter, namely unburned carbon, decreased, indicating a better combustion efficiency. Chemical analysis results of fouling deposits showed that inorganic elements presented different behaviors depending on the collection area and the combustion parameters. Non-volatile elements such as Si and Ca were mostly found in the coarse fraction of the bottom ash and minor amounts were deposited over the tube. Small amounts of Cl in biomass generated serious deposition problems, especially during combustions with low airflow rates. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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26 pages, 869 KB

Open AccessArticle

Decision Support for Energy Contracts Negotiation with Game Theory and Adaptive Learning

by Tiago Pinto, Zita Vale, Isabel Praça, E. J. Solteiro Pires and Fernando Lopes

Energies 2015, 8(9), 9817-9842; https://doi.org/10.3390/en8099817 - 9 Sep 2015

Cited by 35 | Viewed by 6180

Abstract

This paper presents a decision support methodology for electricity market players’ bilateral contract negotiations. The proposed model is based on the application of game theory, using artificial intelligence to enhance decision support method’s adaptive features. This model is integrated in AiD-EM (Adaptive Decision [...] Read more.

This paper presents a decision support methodology for electricity market players’ bilateral contract negotiations. The proposed model is based on the application of game theory, using artificial intelligence to enhance decision support method’s adaptive features. This model is integrated in AiD-EM (Adaptive Decision Support for Electricity Markets Negotiations), a multi-agent system that provides electricity market players with strategic behavior capabilities to improve their outcomes from energy contracts’ negotiations. Although a diversity of tools that enable the study and simulation of electricity markets has emerged during the past few years, these are mostly directed to the analysis of market models and power systems’ technical constraints, making them suitable tools to support decisions of market operators and regulators. However, the equally important support of market negotiating players’ decisions is being highly neglected. The proposed model contributes to overcome the existing gap concerning effective and realistic decision support for electricity market negotiating entities. The proposed method is validated by realistic electricity market simulations using real data from the Iberian market operator—MIBEL. Results show that the proposed adaptive decision support features enable electricity market players to improve their outcomes from bilateral contracts’ negotiations. Full article

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17 pages, 1403 KB

Open AccessArticle

Integrated Three-Voltage-Booster DC-DC Converter to Achieve High Voltage Gain with Leakage-Energy Recycling for PV or Fuel-Cell Power Systems

by Chih-Lung Shen, Hong-Yu Chen and Po-Chieh Chiu

Energies 2015, 8(9), 9843-9859; https://doi.org/10.3390/en8099843 - 9 Sep 2015

Cited by 8 | Viewed by 8026

Abstract

In this paper, an integrated three-voltage-booster DC-DC (direct current to direct current) converter is proposed to achieve high voltage gain for renewable-energy generation systems. The proposed converter integrates three voltage-boosters into one power stage, which is composed of an active switch, a coupled-inductor, [...] Read more.

In this paper, an integrated three-voltage-booster DC-DC (direct current to direct current) converter is proposed to achieve high voltage gain for renewable-energy generation systems. The proposed converter integrates three voltage-boosters into one power stage, which is composed of an active switch, a coupled-inductor, five diodes, and five capacitors. As compared with conventional high step-up converters, it has a lower component count. In addition, the features of leakage-energy recycling and switching loss reduction can be accomplished for conversion efficiency improvement. While the active switch is turned off, the converter can inherently clamp the voltage across power switch and suppress voltage spikes. Moreover, the reverse-recovery currents of all diodes can be alleviated by leakage inductance. A 200 W prototype operating at 100 kHz switching frequency with 36 V input and 400 V output is implemented to verify the theoretical analysis and to demonstrate the feasibility of the proposed high step-up DC-DC converter. Full article

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18 pages, 957 KB

Open AccessArticle

Numerical Analysis on the Stability of Hydraulic Fracture Propagation

by Zhaobin Zhang, Xiao Li, Jianming He, Yanfang Wu and Bo Zhang

Energies 2015, 8(9), 9860-9877; https://doi.org/10.3390/en8099860 - 11 Sep 2015

Cited by 23 | Viewed by 6426

Abstract

The formation of dense spacing fracture network is crucial to the hydraulic fracturing treatment of unconventional reservoir. However, one difficulty for fracturing treatment is the lack of clear understanding on the nature of fracture complexity created during the treatment. In this paper, fracture [...] Read more.

The formation of dense spacing fracture network is crucial to the hydraulic fracturing treatment of unconventional reservoir. However, one difficulty for fracturing treatment is the lack of clear understanding on the nature of fracture complexity created during the treatment. In this paper, fracture propagation is numerically investigated to find the conditions needed for the stable propagation of complex fracture network. Firstly, starting from a parallel fracture system, the stability of fracture propagation is analyzed and a dimensionless number M is obtained. Then, by developing a hydraulic fracturing simulation model based on displacement discontinuity method, the propagation of parallel fractures is simulated and a clear relation between M and the stability of parallel fractures is obtained. Finally, the investigation on parallel fractures is extended to complex fracture networks. The propagation of complex fracture networks is simulated and the results show that the effects of M on complex fracture networks is the same to that of parallel fractures. The clear relation between M and fracture propagation stability is important for the optimization of hydraulic fracturing operation. Full article

(This article belongs to the Special Issue Hydropower)

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14 pages, 2090 KB

Open AccessArticle

Fuel Economy Improvement of a Heavy-Duty Powertrain by Using Hardware-in-Loop Simulation and Calibration

by Bolan Liu, Xiaowei Ai, Pan Liu, Chuang Zhang, Xingqi Hu and Tianpu Dong

Energies 2015, 8(9), 9878-9891; https://doi.org/10.3390/en8099878 - 11 Sep 2015

Cited by 5 | Viewed by 4931

Abstract

Fuel economy efficiency is one of the most important parameters for vehicle powertrains, which is of particular interest for heavy-duty powertrain calibration. Conventionally, this work relies heavily on road tests, which cost more and may lead to long duration product development cycles. The [...] Read more.

Fuel economy efficiency is one of the most important parameters for vehicle powertrains, which is of particular interest for heavy-duty powertrain calibration. Conventionally, this work relies heavily on road tests, which cost more and may lead to long duration product development cycles. The paper proposes a novel hardware-in-loop modeling and calibration method to work it out. A dSPACE hardware-based test bench was successfully established and validated, which is valuable for a more efficient and easier shift schedule in calibration. Meanwhile, a real-time dynamic powertrain model, including a diesel engine, torque converter, gear box and driver model was built. Typical driving cycles that both velocity and slope information were constructed for different road conditions. A basic economic shift schedule was initially calculated and then optimal calibrated by the test bench. The results show that there is an optimal relationship between an economic shift schedule and speed regulation. By matching the best economic shift schedule regulation to different road conditions; the fuel economy of vehicles can be improved. In a smooth driving cycle; when the powertrain applies a larger speed regulation such as 12% and the corresponding shift schedule; the fuel consumption is smaller and is reduced by 13%. In a complex driving cycle, when the powertrain applies a smaller speed regulation such as 5% along with the corresponding shift schedule; the fuel consumption is smaller and is reduced by 5%. The method thus can provide guidance for economic calibration experiments of off-road heavy-duty vehicles. Full article

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23 pages, 477 KB

Open AccessArticle

Economic and Environmental Performances of Small-Scale Rural PV Solar Projects under the Clean Development Mechanism: The Case of Cambodia

by Ellen De Schepper, Sebastien Lizin, Bart Durlinger, Hossein Azadi and Steven Van Passel

Energies 2015, 8(9), 9892-9914; https://doi.org/10.3390/en8099892 - 11 Sep 2015

Cited by 11 | Viewed by 5428

Abstract

The two core objectives of the Clean Development Mechanism (CDM) are cost-effective emission reduction and sustainable development. Despite the potential to contribute to both objectives, solar projects play a negligible role under the CDM. In this research, the greenhouse gas mitigation cost is [...] Read more.

The two core objectives of the Clean Development Mechanism (CDM) are cost-effective emission reduction and sustainable development. Despite the potential to contribute to both objectives, solar projects play a negligible role under the CDM. In this research, the greenhouse gas mitigation cost is used to evaluate the economic and environmental performances of small-scale rural photovoltaic solar projects. In particular, we compare the use of absolute and relative mitigation costs to evaluate the attractiveness of these projects under the CDM. We encourage the use of relative mitigation costs, implying consideration of baseline costs that render the projects profitable. Results of the mitigation cost analysis are dependent on the baseline chosen. To overcome this drawback, we complement the analysis with a multi-objective optimization approach, which allows quantifying the trade-off between economic and environmental performances of the optimal technologies without requiring a baseline. Full article

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15 pages, 1981 KB

Open AccessArticle

A Traction Three-Phase to Single-Phase Cascade Converter Substation in an Advanced Traction Power Supply System

by Xiaoqiong He, Aiping Guo, Xu Peng, Yingying Zhou, Zhanghai Shi and Zeliang Shu

Energies 2015, 8(9), 9915-9929; https://doi.org/10.3390/en8099915 - 11 Sep 2015

Cited by 40 | Viewed by 10846

Abstract

The advanced traction power supply system (ATPSS) is a new directional development for traction power supply systems, which can totally remove the neutral sections and effectively promote power quality. However, the existing converters suffer from small substation capacity. In this paper, a new [...] Read more.

The advanced traction power supply system (ATPSS) is a new directional development for traction power supply systems, which can totally remove the neutral sections and effectively promote power quality. However, the existing converters suffer from small substation capacity. In this paper, a new configuration based on a three-level neutral point clamped (3L-NPC) three-phase to single-phase cascade converter in a substation is proposed for ATPSS, which can be used to match the capacity of the converter for high voltage and large power applications. The control strategy of the proposed converter is analyzed in depth, and the phase disposition sinusoidal pulse width modulation (PD-SPWM) with phase shift carrier SPWM (PSC-SPWM) is employed in the inverters. Then, the inductance equalizing circuit is applied for the voltage balance on the DC-link. Besides, a LC filter circuit is designed to eliminate the double line-frequency ripple of DC voltage. Afterwards, a simulation model and an experimental prototype are developed, respectively. The simulation results show that the proposed converter in this paper can not only meet the requirements of voltage and capacity for the traction network, but also improve power quality. Finally, the experimental results verify the correctness and feasibility of the proposed control strategy. Full article

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16 pages, 2079 KB

Open AccessArticle

Swirling Combustor Energy Converter: H₂/Air Simulations of Separated Chambers

by Angelo Minotti and Paolo Teofilatto

Energies 2015, 8(9), 9930-9945; https://doi.org/10.3390/en8099930 - 14 Sep 2015

Cited by 7 | Viewed by 4330

Abstract

This work reports results related to the “EU-FP7-HRC-Power” project aiming at developing micro-meso hybrid sources of power. One of the goals of the project is to achieve surface temperatures up to more than 1000 K, with a ∆T ≤ 100 K, in [...] Read more.

This work reports results related to the “EU-FP7-HRC-Power” project aiming at developing micro-meso hybrid sources of power. One of the goals of the project is to achieve surface temperatures up to more than 1000 K, with a ∆T ≤ 100 K, in order to be compatible with a thermal/electrical conversion by thermo-photovoltaic cells. The authors investigate how to reach that goal adopting swirling chambers integrated in a thermally-conductive and emitting element. The converter consists of a small parallelepiped brick inside two separated swirling meso-combustion chambers, which heat up the parallelepiped, emitting material by the combustion of H₂ and air at ambient pressure. The overall dimension is of the order of cm. Nine combustion simulations have been carried out assuming detailed chemistry, several length/diameter ratios (Z/D = 3, 5 and 11) and equivalence ratios (0.4, 0.7 and 1); all are at 400 W of injected chemical power. Among the most important results are the converter surfaces temperatures, the heat loads, provided to the environment, and the chemical efficiency. The high chemical efficiency, h > 99.9%, is due to the relatively long average gas residence time coupled with the fairly good mixing due to the swirl motion and the impinging air/fuel jets that provide heat and radicals to the flame. Full article

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23 pages, 1169 KB

Open AccessArticle

Map-Based Power-Split Strategy Design with Predictive Performance Optimization for Parallel Hybrid Electric Vehicles

by Jixiang Fan, Jiangyan Zhang and Tielong Shen

Energies 2015, 8(9), 9946-9968; https://doi.org/10.3390/en8099946 - 14 Sep 2015

Cited by 14 | Viewed by 10892

Abstract

In this paper, a map-based optimal energy management strategy is proposed to improve the consumption economy of a plug-in parallel hybrid electric vehicle. In the design of the maps, which provide both the torque split between engine and motor and the gear shift, [...] Read more.

In this paper, a map-based optimal energy management strategy is proposed to improve the consumption economy of a plug-in parallel hybrid electric vehicle. In the design of the maps, which provide both the torque split between engine and motor and the gear shift, not only the current vehicle speed and power demand, but also the optimality based on the predicted trajectory of vehicle dynamics are considered. To seek the optimality, the equivalent consumption, which trades off the fuel and electricity usages, is chosen as the cost function. Moreover, in order to decrease the model errors in the process of optimization conducted in the discrete time domain, the variational integrator is employed to calculate the evolution of the vehicle dynamics. To evaluate the proposed energy management strategy, the simulation results performed on a professional GT-Suit simulator are demonstrated and the comparison to a real-time optimization method is also given to show the advantage of the proposed off-line optimization approach. Full article

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23 pages, 2064 KB

Open AccessArticle

Study and Implementation of a Two-Phase Interleaved Bidirectional DC/DC Converter for Vehicle and DC-Microgrid Systems

by Ching-Ming Lai, Yuan-Chih Lin and Dasheng Lee

Energies 2015, 8(9), 9969-9991; https://doi.org/10.3390/en8099969 - 14 Sep 2015

Cited by 73 | Viewed by 14377

Abstract

The objective of this paper is to implement a two-phase, interleaved, bidirectional DC/DC converter topology with an improved voltage conversion ratio for electric vehicle (EV) and DC-microgrid systems. In this study, a two-phase interleaved charge-pump topology is introduced to achieve a high voltage [...] Read more.

The objective of this paper is to implement a two-phase, interleaved, bidirectional DC/DC converter topology with an improved voltage conversion ratio for electric vehicle (EV) and DC-microgrid systems. In this study, a two-phase interleaved charge-pump topology is introduced to achieve a high voltage conversion ratio with very simple control circuits. In discharge mode, the circuit topology acts as a voltage-multiplier boost converter to achieve a high step-up conversion ratio (48 V to 240 V). In charge mode, the circuit topology acts as a voltage-divider buck converter to achieve a high voltage step-down conversion ratio (240 V to 48 V). The circuit configuration, operating principle, steady-state analysis and the closed-loop control of the proposed converter are presented. Experiments conducted on a laboratory prototype with 500 W power-rating are presented to verify the effectiveness. The maximum efficiency levels in discharge and charge modes are about 97.7% and 98.4% respectively. Full article

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

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25 pages, 763 KB

Open AccessArticle

Online Energy Management of City Cars with Multi-Objective Linear Parameter-Varying L₂-Gain Control

by Boe-Shong Hong and Mei-Hung Wu

Energies 2015, 8(9), 9992-10016; https://doi.org/10.3390/en8099992 - 15 Sep 2015

Cited by 3 | Viewed by 5222

Abstract

This work aims at online regulating transient current out of the batteries of small-sized electric cars that transport people and goods around cities. In a city with heavy traffic, transient current dominates the energy economy and propulsion capability, which are in opposition to [...] Read more.

This work aims at online regulating transient current out of the batteries of small-sized electric cars that transport people and goods around cities. In a city with heavy traffic, transient current dominates the energy economy and propulsion capability, which are in opposition to each other. In order to manage the trade-off between energy consumption per distance and propulsion capability in transience, the authors improve on previous work on multi-objective linear parameter-varying (LPV) L₂-gain control. The observer embedded into this multi-objective controller no longer assumes Kalman-filtering structure, and structural conservatism is thus removed. A full-spectrum set of experiments is performed. The results reveal that the feedback design significantly improves energy-motion management. Full article

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26 pages, 7654 KB

Open AccessArticle

Thermal Behaviour Investigation of a Large and High Power Lithium Iron Phosphate Cylindrical Cell

by Odile Capron, Ahmadou Samba, Noshin Omar, Peter Van Den Bossche and Joeri Van Mierlo

Energies 2015, 8(9), 10017-10042; https://doi.org/10.3390/en80910017 - 15 Sep 2015

Cited by 25 | Viewed by 9270

Abstract

This paper investigates the thermal behaviour of a large lithium iron phosphate (LFP) battery cell based on its electrochemical-thermal modelling for the predictions of its temperature evolution and distribution during both charge and discharge processes. The electrochemical-thermal modelling of the cell is performed [...] Read more.

This paper investigates the thermal behaviour of a large lithium iron phosphate (LFP) battery cell based on its electrochemical-thermal modelling for the predictions of its temperature evolution and distribution during both charge and discharge processes. The electrochemical-thermal modelling of the cell is performed for two cell geometry approaches: homogeneous (the internal region is considered as a single region) and discrete (the internal region is split into smaller regions for each layer inside the cell). The experimental measurements and the predictions of the cell surface temperature achieved with the simulations for both approaches are in good agreement with 1.5 °C maximum root mean square error. From the results, the maximum cell surface temperature and temperature gradient between the internal and the surface regions are around 31.3 °C and 1.6 °C. The temperature gradient in the radial direction is observed to be greater about 1.1 °C compared to the longitudinal direction, which is caused by the lower thermal conductivity of the cell in the radial compared to the longitudinal direction. During its discharge, the reversible, the ohmic and the reaction heat generations inside the cell reach up to 2 W, 7 W and 17 W respectively. From the comparison of the two modelling approaches, this paper establishes that the homogeneous modelling of the cell internal region is suitable for the study of a single cylindrical cell and is appropriate for the two-dimensional thermal behaviour investigation of a battery module made of multiple cells. Full article

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15 pages, 1568 KB

Open AccessArticle

Reducing Carbon Emissions from Shopping Trips: Evidence from China

by Jing Li, Pingyu Zhang, Kevin Lo, Meng Guo and Mark Wang

Energies 2015, 8(9), 10043-10057; https://doi.org/10.3390/en80910043 - 15 Sep 2015

Cited by 14 | Viewed by 6502

Abstract

With rising income and the emergence of modern shopping centers in urban China, shopping trips by private car becomes more and more common, leading to higher carbon emissions in the transport sector. Encouraging car owners to shift transport mode from private car to [...] Read more.

With rising income and the emergence of modern shopping centers in urban China, shopping trips by private car becomes more and more common, leading to higher carbon emissions in the transport sector. Encouraging car owners to shift transport mode from private car to public transport could achieve significant emissions reductions. This study estimate carbon emissions savings by shifting from private cars to public transport for shopping trips in urban China, using Shenyang, one of the largest cities in China, as a case study. Our results show that the average carbon emissions per shopper is 426.9 g, and the carbon emissions on weekends is 13% higher than weekdays. Moreover, shoppers travelling by private car emitted five times more carbon emission than those by public transport. We also found that car ownership gradually increased as accessibility to public transport decreased, and that more car owners chose to travel by private cars than public transport in areas with limited access. This study, thus, highlights the potential for high-quality public transport to reduce the transport sector’s carbon emissions in urban China. Full article

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24 pages, 627 KB

Open AccessArticle

Study on Thermal Degradation Characteristics and Regression Rate Measurement of Paraffin-Based Fuel

by Songqi Hu, Guanjie Wu, Yijin Hua, Noor Fatima Rashid and Hongyun Hu

Energies 2015, 8(9), 10058-10081; https://doi.org/10.3390/en80910058 - 15 Sep 2015

Cited by 8 | Viewed by 6757

Abstract

Paraffin fuel has been found to have a regression rate that is higher than conventional HTPB (hydroxyl-terminated polybutadiene) fuel and, thus, presents itself as an ideal energy source for a hybrid rocket engine. The energy characteristics of paraffin-based fuel and HTPB fuel have [...] Read more.

Paraffin fuel has been found to have a regression rate that is higher than conventional HTPB (hydroxyl-terminated polybutadiene) fuel and, thus, presents itself as an ideal energy source for a hybrid rocket engine. The energy characteristics of paraffin-based fuel and HTPB fuel have been calculated by the method of minimum free energy. The thermal degradation characteristics were measured for paraffin, pretreated paraffin, HTPB and paraffin-based fuel in different working conditions by the using differential scanning calorimetry (DSC) and a thermogravimetric analyzer (TGA). The regression rates of paraffin-based fuel and HTPB fuel were tested by a rectangular solid-gas hybrid engine. The research findings showed that: the specific impulse of paraffin-based fuel is almost the same as that of HTPB fuel; the decomposition temperature of pretreated paraffin is higher than that of the unprocessed paraffin, but lower than that of HTPB; with the increase of paraffin, the initial reaction exothermic peak of paraffin-based fuel is reached in advance, and the initial reaction heat release also increases; the regression rate of paraffin-based fuel is higher than the common HTPB fuel under the same conditions; with the increase of oxidizer mass flow rate, the regression rate of solid fuel increases accordingly for the same fuel formulation. Full article

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24 pages, 2376 KB

Open AccessArticle

Integrated Electrical and Thermal Grid Facility - Testing of Future Microgrid Technologies

by Sundar Raj Thangavelu, Inam Ullah Nutkani, Chia Meng Hwee, Aung Myat and Ashwin Khambadkone

Energies 2015, 8(9), 10082-10105; https://doi.org/10.3390/en80910082 - 16 Sep 2015

Cited by 13 | Viewed by 8869

Abstract

This paper describes the Experimental Power Grid Centre (EPGC) microgrid test facility, which was developed to enable research, development and testing for a wide range of distributed generation and microgrid technologies. The EPGC microgrid facility comprises a integrated electrical and thermal grid with [...] Read more.

This paper describes the Experimental Power Grid Centre (EPGC) microgrid test facility, which was developed to enable research, development and testing for a wide range of distributed generation and microgrid technologies. The EPGC microgrid facility comprises a integrated electrical and thermal grid with a flexible and configurable architecture, and includes various distributed energy resources and emulators, such as generators, renewable, energy storage technologies and programmable load banks. The integrated thermal grid provides an opportunity to harness waste heat produced by the generators for combined heat, power and cooling applications, and support research in optimization of combined electrical-thermal systems. Several case studies are presented to demonstrate the testing of different control and operation strategies for storage systems in grid-connected and islanded microgrids. One of the case studies also demonstrates an integrated thermal grid to convert waste heat to useful energy, which thus far resulted in a higher combined energy efficiency. Experiment results confirm that the facility enables testing and evaluation of grid technologies and practical problems that may not be apparent in a computer simulated environment. Full article

(This article belongs to the Special Issue Microgrids)

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21 pages, 5300 KB

Open AccessArticle

A Study of Fuel Economy Improvement in a Plug-in Hybrid Electric Vehicle using Engine on/off and Battery Charging Power Control Based on Driver Characteristics

by Seulgi Lee, Jingyu Choi, Kiyun Jeong and Hyunsoo Kim

Energies 2015, 8(9), 10106-10126; https://doi.org/10.3390/en80910106 - 16 Sep 2015

Cited by 12 | Viewed by 8192

Abstract

In this study, driving data for various types of drivers are collected using a VIDE (virtual integrated driving environment), and a driver model is developed. To represent the driver tendencies quantitatively, the DDA (degree of driver aggression) is proposed based on fuzzy logic. [...] Read more.

In this study, driving data for various types of drivers are collected using a VIDE (virtual integrated driving environment), and a driver model is developed. To represent the driver tendencies quantitatively, the DDA (degree of driver aggression) is proposed based on fuzzy logic. DDA has a 0-1 value; the closer the DDA is to one, the more aggressive the driver. Using the DDA, an engine on/off and battery charging power control algorithm are developed to improve the fuel economy of a power-split-type plug-in hybrid electric vehicle. The engine on/off control reduces the frequent engine on/off caused by aggressive driving, whereas the battery charging power control maintains the battery state of charge (SOC) by operating the engine according to the DDA. It is found that the proposed control algorithm improves fuel economy by 17.3% compared to the existing control for an aggressive driver. Full article

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

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14 pages, 1818 KB

Open AccessArticle

Design Optimization and Analysis of a Dual-Permanent-Magnet-Excited Machine Using Response Surface Methodology

by Linni Jian, Yujun Shi, Jin Wei, Yanchong Zheng and Zhengxing Deng

Energies 2015, 8(9), 10127-10140; https://doi.org/10.3390/en80910127 - 16 Sep 2015

Cited by 15 | Viewed by 6537

Abstract

The dual-permanent-magnet-excited (DPME) machine employs permanent magnets (PMs) both on the stator and the rotor. It relies on the bi-directional field modulation effect (BFME) to achieve stable electromechanical energy conversion. Therefore, this new type of machine is capable of offering much higher torque [...] Read more.

The dual-permanent-magnet-excited (DPME) machine employs permanent magnets (PMs) both on the stator and the rotor. It relies on the bi-directional field modulation effect (BFME) to achieve stable electromechanical energy conversion. Therefore, this new type of machine is capable of offering much higher torque capability than its traditional counterparts. This paper is devoted to investigating the optimum design method for improving the BFME of DPME machines, so as to further improve their produced electromagnetic torques. Response surface methodology is engaged to investigate the impacts of shape factors of the stator and rotor slots on the torque capability of the DPME machine, and the fitted models are built up by using both the finite element method (FEM) and the least-squares method. After that, the optimum shape factors are obtained from the fitted models. The results estimated by using both two-dimensional (2D)-FEM and three-dimensional (3D)-FEM demonstrate that the pull-out torque of the optimum case is 24.5% larger than that of the initial case, while the usage of PM material of the optimum case is 8.9% less than that of the initial case. Full article

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12 pages, 435 KB

Open AccessArticle

Experimental Research on Water Boiling Heat Transfer on Horizontal Copper Rod Surface at Sub-Atmospheric Pressure

by Li-Hua Yu, Shu-Xue Xu, Guo-Yuan Ma and Jun Wang

Energies 2015, 8(9), 10141-10152; https://doi.org/10.3390/en80910141 - 16 Sep 2015

Cited by 9 | Viewed by 6045

Abstract

In recent years, water (R718) as a kind of natural refrigerant—which is environmentally-friendly, safe and cheap—has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, [...] Read more.

In recent years, water (R718) as a kind of natural refrigerant—which is environmentally-friendly, safe and cheap—has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important issue. There are many research papers on the evaporation of water, but there is a lack of data on the characteristics at sub-atmospheric pressures, especially lower than 3 kPa (the saturation temperature is 24 °C). In this paper, the experimental research on water boiling heat transfer on a horizontal copper rod surface at 1.8–3.3 kPa is presented. Regression equations of the boiling heat transfer coefficient are obtained based on the experimental data, which are convenient for practical application. Full article

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20 pages, 2351 KB

Open AccessArticle

Effective Local-Global Upscaling of Fractured Reservoirs under Discrete Fractured Discretization

by Junchao Li, Zhengdong Lei, Guan Qin and Bin Gong

Energies 2015, 8(9), 10178-10197; https://doi.org/10.3390/en80910178 - 17 Sep 2015

Cited by 21 | Viewed by 7604

Abstract

The subsurface flow in fractured reservoirs is strongly affected by the distribution of fracture networks. Discrete fracture models, which represent all fractures individually by unstructured grid systems, are thus developed and act as a more accurate way for fractured reservoir simulation. However, it [...] Read more.

The subsurface flow in fractured reservoirs is strongly affected by the distribution of fracture networks. Discrete fracture models, which represent all fractures individually by unstructured grid systems, are thus developed and act as a more accurate way for fractured reservoir simulation. However, it is usually not realistic to directly apply discrete fracture models to simulate field scale models for efficiency reasons. There is a need for upscaling techniques to coarsen the high resolution fracture descriptions to sizes that can be accommodated by reservoir simulators. In this paper, we extended the adaptive local-global upscaling technique to construct a transmissibility-based dual-porosity dual-permeability model from discrete fracture characterizations. An underlying unstructured fine-scale grid is firstly generated as a base grid. A global coarse-scale simulation is performed to provide boundary conditions for local regions and local upscaling procedures are carried out in every local region for transmissibility calculations. Iterations are performed until the consistency between the global and local properties is achieved. The procedure is applied to provide dual-porosity dual-permeability (DPDK) parameters including coarse-scale matrix-matrix, fracture-fracture and matrix-fracture flux transmissibilities. The methodology is applied to several cases. The simulation results demonstrate the accuracy, efficiency and robustness of the proposed method. Full article

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21 pages, 4076 KB

Open AccessArticle

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

by Zhicheng Shi, Hongguang Zhang, Hao Liu, Haitao Lu, Jiazheng Li and Xiang Gao

Energies 2015, 8(9), 10198-10218; https://doi.org/10.3390/en80910198 - 17 Sep 2015

Cited by 12 | Viewed by 6277

Abstract

Experimental and numerical studies are conducted on the thermal, chemical and dilution effects of buffer gas composition on autoignition of dimethyl ether (DME). The buffer gases considered are nitrogen (N₂), a mixture of N₂ and argon (Ar) at a mole [...] Read more.

Experimental and numerical studies are conducted on the thermal, chemical and dilution effects of buffer gas composition on autoignition of dimethyl ether (DME). The buffer gases considered are nitrogen (N₂), a mixture of N₂ and argon (Ar) at a mole ratio of 50%/50% and a mixture of Ar and carbon dioxide (CO₂) at a mole ratio of 61.2%/38.8%. Experiments are performed using a rapid compression machine (RCM) at compressed pressure of 10 bar, equivalence ratio (φ) of 1, and compressed temperature from 670 K to 795 K. The N₂ dilution ratio considered ranges from 36.31% to 55.04%. The experimental results show that buffer gas composition has little impact on the first-stage ignition delay. However, significant differences in the total ignition delay as a function of buffer gas composition are observed in the negative temperature coefficient (NTC) region. Compared to N₂, N₂/Ar (50%/50%) mixture decreases the total ignition delay by 31%. The chemical effects of buffer gas composition on the first-stage and total ignition delays are negligible. With increasing N₂ dilution ratio, the first-stage ignition delay slightly increases, while a significant increase in the total ignition delay is observed. Moreover, the NTC behavior of total ignition delay is noted to become more pronounced at high N₂ dilution ratio. The heat release during the first-stage ignition decreases as N₂ dilution ratio increases. Results of numerical simulations with the Zhao DME mechanism over a wider range of temperature show good agreement with that of experiments. Further numerical simulations are conducted using pure N₂, Ar and CO₂ as buffer gases. Results indicate that the thermal effects are the dominant factor in low temperature and NTC regions. The chemical effects become pronounced in the NTC region, and the chemical effect of CO₂ exceeds the thermal effect at the compressed temperature higher than 880 K. Full article

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20 pages, 1371 KB

Open AccessArticle

A New Application of the Multi-Resonant Zero-Current Switching Buck Converter: Analysis and Simulation in a PMSG Based WECS

by Tiara Freitas, Paulo Menegáz and Domingos Simonetti

Energies 2015, 8(9), 10219-10238; https://doi.org/10.3390/en80910219 - 17 Sep 2015

Cited by 5 | Viewed by 6896

Abstract

A new application of the three-phase buck-resonant converter is presented in this paper. It is shown that the analyzed converter is suitable to operate as the rectifier stage in low power wind energy conversion systems (WECS) based on permanent magnet synchronous generators (PMSG) [...] Read more.

A new application of the three-phase buck-resonant converter is presented in this paper. It is shown that the analyzed converter is suitable to operate as the rectifier stage in low power wind energy conversion systems (WECS) based on permanent magnet synchronous generators (PMSG) with variable wind speed. As main features, it presents a single controlled switch, simple implementation and control, and operates with a high power factor and low harmonic distortion over all wind speed ranges. The converter topology, its design equations and its operation are presented, as well as the simulation results of the PMSG based conversion system. From the analysis carried out in the paper it is concluded that the converter is indicated to be employed in distributed generation and hybrid systems where wind generation is associated with other sources. Full article

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

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21 pages, 1572 KB

Open AccessArticle

Data-Driven Baseline Estimation of Residential Buildings for Demand Response

by Saehong Park, Seunghyoung Ryu, Yohwan Choi, Jihyo Kim and Hongseok Kim

Energies 2015, 8(9), 10239-10259; https://doi.org/10.3390/en80910239 - 17 Sep 2015

Cited by 53 | Viewed by 8255

Abstract

The advent of advanced metering infrastructure (AMI) generates a large volume of data related with energy service. This paper exploits data mining approach for customer baseline load (CBL) estimation in demand response (DR) management. CBL plays a significant role in measurement and verification [...] Read more.

The advent of advanced metering infrastructure (AMI) generates a large volume of data related with energy service. This paper exploits data mining approach for customer baseline load (CBL) estimation in demand response (DR) management. CBL plays a significant role in measurement and verification process, which quantifies the amount of demand reduction and authenticates the performance. The proposed data-driven baseline modeling is based on the unsupervised learning technique. Specifically we leverage both the self organizing map (SOM) and K-means clustering for accurate estimation. This two-level approach efficiently reduces the large data set into representative weight vectors in SOM, and then these weight vectors are clustered by K-means clustering to find the load pattern that would be similar to the potential load pattern of the DR event day. To verify the proposed method, we conduct nationwide scale experiments where three major cities’ residential consumption is monitored by smart meters. Our evaluation compares the proposed solution with the various types of day matching techniques, showing that our approach outperforms the existing methods by up to a 68.5% lower error rate. Full article

(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)

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16 pages, 1093 KB

Open AccessArticle

A Mathematical Model and Its Application for Hydro Power Units under Different Operating Conditions

by Weijia Yang, Jiandong Yang, Wencheng Guo, Wei Zeng, Chao Wang, Linn Saarinen and Per Norrlund

Energies 2015, 8(9), 10260-10275; https://doi.org/10.3390/en80910260 - 17 Sep 2015

Cited by 94 | Viewed by 15521 | Correction

Abstract

This paper presents a mathematical model of hydro power units, especially the governor system model for different operating conditions, based on the basic version of the software TOPSYS. The mathematical model consists of eight turbine equations, one generator equation, and one governor equation, [...] Read more.

This paper presents a mathematical model of hydro power units, especially the governor system model for different operating conditions, based on the basic version of the software TOPSYS. The mathematical model consists of eight turbine equations, one generator equation, and one governor equation, which are solved for ten unknown variables. The generator and governor equations, which are different under various operating conditions, are presented and discussed in detail. All the essential non-linear factors in the governor system (dead-zone, saturation, rate limiting, and backlash) are also considered. Case studies are conducted based on one Swedish hydro power plant (HPP) and three Chinese plants. The simulation and on-site measurements are compared for start-up, no-load operation, normal operation, and load rejection in different control modes (frequency, opening, and power feedback). The main error in each simulation is also discussed in detail. As a result, the model application is proved trustworthy for simulating different physical quantities of the unit (e.g., guide vane opening, active power, rotation speed, and pressures at volute and draft tube). The model has already been applied effectively in consultant analyses and scientific studies. Full article

(This article belongs to the Special Issue Hydropower)

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17 pages, 2705 KB

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Determination of Priority Study Areas for Coupling CO2 Storage and CH₄ Gas Hydrates Recovery in the Portuguese Offshore Area

by Luís Bernardes, Júlio Carneiro, Pedro Madureira, Filipe Brandão and Cristina Roque

Energies 2015, 8(9), 10276-10292; https://doi.org/10.3390/en80910276 - 18 Sep 2015

Cited by 6 | Viewed by 6480

Abstract

Gas hydrates in sub-seabed sediments is an unexploited source of energy with estimated reserves larger than those of conventional oil. One of the methods for recovering methane from gas hydrates involves injection of Carbon Dioxide (CO2), causing the dissociation of methane and storing [...] Read more.

Gas hydrates in sub-seabed sediments is an unexploited source of energy with estimated reserves larger than those of conventional oil. One of the methods for recovering methane from gas hydrates involves injection of Carbon Dioxide (CO2), causing the dissociation of methane and storing CO2. The occurrence of gas hydrates offshore Portugal is well known associated to mud volcanoes in the Gulf of Cadiz. This article presents a determination of the areas with conditions for the formation of biogenic gas hydrates in Portugal’s mainland geological continental margin and assesses their overlap with CO2 hydrates stability zones defined in previous studies. The gas hydrates stability areas are defined using a transfer function recently published by other authors and takes into account the sedimentation rate, the particulate organic carbon content and the thickness of the gas hydrate stability zone. An equilibrium equation for gas hydrates, function of temperature and pressure, was adjusted using non-linear regression and the maximum stability zone thickness was found to be 798 m. The gas hydrates inventory was conducted in a Geographic Information System (GIS) environment and a full compaction scenario was adopted, with localized vertical flow assumed in the accrecionary wedge where mud volcanoes occur. Four areas where temperature and pressure conditions may exist for formation of gas hydrates were defined at an average of 60 km from Portugal’s mainland coastline. Two of those areas coincide with CO2 hydrates stability areas previously defined and should be the subject of further research to evaluate the occurrence of gas hydrate and the possibility of its recovery coupled with CO2 storage in sub-seabed sediments. Full article

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

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22 pages, 375 KB

Open AccessArticle

An Advanced Bayesian Method for Short-Term Probabilistic Forecasting of the Generation of Wind Power

by Antonio Bracale and Pasquale De Falco

Energies 2015, 8(9), 10293-10314; https://doi.org/10.3390/en80910293 - 21 Sep 2015

Cited by 33 | Viewed by 6243

Abstract

Currently, among renewable distributed generation systems, wind generators are receiving a great deal of interest due to the great economic, technological, and environmental incentives they involve. However, the uncertainties due to the intermittent nature of wind energy make it difficult to operate electrical [...] Read more.

Currently, among renewable distributed generation systems, wind generators are receiving a great deal of interest due to the great economic, technological, and environmental incentives they involve. However, the uncertainties due to the intermittent nature of wind energy make it difficult to operate electrical power systems optimally and make decisions that satisfy the needs of all the stakeholders of the electricity energy market. Thus, there is increasing interest determining how to forecast wind power production accurately. Most the methods that have been published in the relevant literature provided deterministic forecasts even though great interest has been focused recently on probabilistic forecast methods. In this paper, an advanced probabilistic method is proposed for short-term forecasting of wind power production. A mixture of two Weibull distributions was used as a probability function to model the uncertainties associated with wind speed. Then, a Bayesian inference approach with a particularly-effective, autoregressive, integrated, moving-average model was used to determine the parameters of the mixture Weibull distribution. Numerical applications also are presented to provide evidence of the forecasting performance of the Bayesian-based approach. Full article

(This article belongs to the Special Issue Forecasting Methods and Measurements of Forecasting Errors for Renewable Energy Sources)

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20 pages, 2356 KB

Open AccessArticle

Inductive-Based Wireless Power Recharging System for an Innovative Endoscopic Capsule

by Giuseppe Tortora, Francesca Mulana, Gastone Ciuti, Paolo Dario and Arianna Menciassi

Energies 2015, 8(9), 10315-10334; https://doi.org/10.3390/en80910315 - 21 Sep 2015

Cited by 20 | Viewed by 8733

Abstract

Wireless capsule endoscopic devices are adopted for painless diagnosis of cancer and other diseases affecting the gastrointestinal tract as an alternative to traditional endoscopy. Although much work has been done to improve capsule performance in terms of active navigation, a major drawback is [...] Read more.

Wireless capsule endoscopic devices are adopted for painless diagnosis of cancer and other diseases affecting the gastrointestinal tract as an alternative to traditional endoscopy. Although much work has been done to improve capsule performance in terms of active navigation, a major drawback is the limited available energy on board the capsule, usually provided by a battery. Another key shortcoming of active capsules is their limitation in terms of active functionalities and related costs. An inductive-based wireless recharging system for the development of an innovative capsule for colonoscopy is proposed in this paper; the aim is to provide fast off-line battery recovery for improving capsule lifecycle and thus reducing the cost of a single endoscopic procedure. The wireless recharging system has been properly designed to fit the dimensions of a capsule for colonoscopy but it can be applied to any biomedical devices to increase the number of times it can be used after proper sterilization. The current system is able to provide about 1 W power and is able to recharge the battery capsule in 20 min which is a reasonable time considering capsule operation time (10–15 min). Full article

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

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19 pages, 5088 KB

Open AccessArticle

Control and Performance Evaluation of Multiphase FSPM Motor in Low-Speed Region for Hybrid Electric Vehicles

by Feng Yu, Ming Cheng, Kwok Tong Chau and Feng Li

Energies 2015, 8(9), 10335-10353; https://doi.org/10.3390/en80910335 - 21 Sep 2015

Cited by 13 | Viewed by 8812

Abstract

The flux-switching permanent-magnet (FSPM) motor has been viewed as a highly reliable machine with both armature windings and magnets on the stator. Owing to the high torque-production capability with low torque ripple, FSPM motors with a higher number of phases are potential candidates [...] Read more.

The flux-switching permanent-magnet (FSPM) motor has been viewed as a highly reliable machine with both armature windings and magnets on the stator. Owing to the high torque-production capability with low torque ripple, FSPM motors with a higher number of phases are potential candidates for traction applications in hybrid electric vehicles (HEVs). However, existing research has mostly focused on the principles and static performance of multiphase FSPM motors, and little attention has been paid to advanced control strategies. In this paper, the fully decoupled current control of a 36/34-pole nine-phase FSPM (NP-FSPM) motor is developed and the performance under different operating conditions is investigated. The aim of the design is to alleviate cross coupling effects and unwanted low-order stator harmonic currents, to guarantee fast transient response and small steady-state error. In addition, its fault-tolerance is further elaborated. These features are very important in automotive applications where low torque pulsation, high fault-tolerant capability and high dynamic performance are of major importance. Firstly, the research status of multiphase FSPM motors is briefly reviewed. Secondly, the mathematical model in the dq reference frames and control strategies are presented. Then, the control and performance of the NP-FSPM motor are evaluated by using MATLAB/Simulink. Finally, experiments on an NP-FSPM motor prototype are carried out to validate the study. Full article

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

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16 pages, 1288 KB

Open AccessArticle

Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications

by Le Quang Minh, Nguyen Van Duc Long, Pham Luu Trung Duong, Youngmi Jung, Alireza Bahadori and Moonyong Lee

Energies 2015, 8(9), 10354-10369; https://doi.org/10.3390/en80910354 - 21 Sep 2015

Cited by 10 | Viewed by 10685

Abstract

Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl₄) and hafnium tetrachloride (HfCl [...] Read more.

Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl₄) and hafnium tetrachloride (HfCl₄) for nuclear power reactor applications through extractive distillation using a NaCl-KCl molten salt mixture. The vapor–liquid equilibrium behavior of ZrCl₄ and HfCl₄ over the molten salt system was correlated with Raoult’s law. The molten salt-based extractive distillation column was designed optimally using a rigorous commercial simulator for the feasible separation of ZrCl₄ and HfCl₄. The molten salt-based extractive distillation approach has many potential advantages for the commercial separation of ZrCl₄ and HfCl₄ compared to the conventional distillation because of its milder temperatures and pressure conditions, smaller number of required separation trays in the column, and lower energy requirement for separation, while still taking the advantage of environmentally benign feature by distillation. A heat-pump-assisted configuration was also explored to improve the energy efficiency of the extractive distillation process. The proposed enhanced configuration reduced the energy requirement drastically. Extractive distillation can be a promising option competing with the existing extraction-based separation process for zirconium purification for nuclear power reactor applications. Full article

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

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19 pages, 2260 KB

Open AccessArticle

Assessment of the Wave Energy in the Black Sea Based on a 15-Year Hindcast with Data Assimilation

by Liliana Rusu

Energies 2015, 8(9), 10370-10388; https://doi.org/10.3390/en80910370 - 21 Sep 2015

Cited by 79 | Viewed by 8701

Abstract

The principal target of the present work is to assess the wave energy potential in the Black Sea, identifying also some relevant energetic features and possible patterns. A wave prediction system based on the Simulating Waves Nearshore model (SWAN) has been implemented and [...] Read more.

The principal target of the present work is to assess the wave energy potential in the Black Sea, identifying also some relevant energetic features and possible patterns. A wave prediction system based on the Simulating Waves Nearshore model (SWAN) has been implemented and intensively tested in the entire sea basin. Moreover, considering an optimal interpolation technique, an assimilation scheme of the satellite data has been developed, leading to a visible improvement of the wave model predictions in terms of significant wave heights and, consequently, also in terms of wave power. Using this wave prediction system with data assimilation, simulations have been performed for a 15-year period (1999–2013). Considering the results of this 15-year wave hindcast, an analysis of the wave energy conditions in the basin of the Black Sea has been carried out. This provided a more comprehensive picture concerning the wave energy patterns in the coastal environment of the Black Sea focused on the average wave conditions that might be expected in this sea. Following the results presented, it can be concluded that the wave energy extraction in the Black Sea can become an issue of interest, especially from the perspective of the hybrid solutions. Full article

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

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20 pages, 557 KB

Open AccessArticle

Real-Time Control of Active and Reactive Power for Doubly Fed Induction Generator (DFIG)-Based Wind Energy Conversion System

by Aman Abdulla Tanvir, Adel Merabet and Rachid Beguenane

Energies 2015, 8(9), 10389-10408; https://doi.org/10.3390/en80910389 - 21 Sep 2015

Cited by 71 | Viewed by 10504

Abstract

This paper presents the modeling, rapid control prototyping, and hardware-in-the-loop testing for real-time simulation and control of a grid-connected doubly fed induction generator (DFIG) in a laboratory-size wind turbine emulator for wind energy conversation systems. The generator is modeled using the direct-quadrature rotating [...] Read more.

This paper presents the modeling, rapid control prototyping, and hardware-in-the-loop testing for real-time simulation and control of a grid-connected doubly fed induction generator (DFIG) in a laboratory-size wind turbine emulator for wind energy conversation systems. The generator is modeled using the direct-quadrature rotating reference frame circuit along with the aligned stator flux, and the field-oriented control approach is applied for independent control of the active and reactive power and the DC-link voltage at the grid side. The control of the active, reactive power and the DC-link voltage are performed using a back-to-back converter at sub- and super-synchronous as well as at variable speeds. The control strategy is experimentally validated on an emulated wind turbine driven by the Opal-RT real-time simulator (OP5600) for simultaneous control of the DC-link voltage, active and reactive power. Full article

(This article belongs to the Special Issue Wind Turbines)

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21 pages, 1412 KB

Open AccessArticle

Increasing Fuel Efficiency of Direct Methanol Fuel Cell Systems with Feedforward Control of the Operating Concentration

by Youngseung Na, Federico Zenith and Ulrike Krewer

Energies 2015, 8(9), 10409-10429; https://doi.org/10.3390/en80910409 - 21 Sep 2015

Cited by 19 | Viewed by 9472

Abstract

Most of the R&D on fuel cells for portable applications concentrates on increasing efficiencies and energy densities to compete with other energy storage devices, especially batteries. To improve the efficiency of direct methanol fuel cell (DMFC) systems, several modifications to system layouts and [...] Read more.

Most of the R&D on fuel cells for portable applications concentrates on increasing efficiencies and energy densities to compete with other energy storage devices, especially batteries. To improve the efficiency of direct methanol fuel cell (DMFC) systems, several modifications to system layouts and operating strategies are considered in this paper, rather than modifications to the fuel cell itself. Two modified DMFC systems are presented, one with an additional inline mixer and a further modification of it with a separate tank to recover condensed water. The set point for methanol concentration control in the solution is determined by fuel efficiency and varies with the current and other process variables. Feedforward concentration control enables variable concentration for dynamic loads. Simulation results were validated experimentally with fuel cell systems. Full article

(This article belongs to the Special Issue Methanol and Alcohol Fuel Cells)

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23 pages, 515 KB

Open AccessArticle

Explanatory Information Analysis for Day-Ahead Price Forecasting in the Iberian Electricity Market

by Claudio Monteiro, L. Alfredo Fernandez-Jimenez and Ignacio J. Ramirez-Rosado

Energies 2015, 8(9), 10464-10486; https://doi.org/10.3390/en80910464 - 22 Sep 2015

Cited by 23 | Viewed by 6990

Abstract

This paper presents the analysis of the importance of a set of explanatory (input) variables for the day-ahead price forecast in the Iberian Electricity Market (MIBEL). The available input variables include extensive hourly time series records of weather forecasts, previous prices, and regional [...] Read more.

This paper presents the analysis of the importance of a set of explanatory (input) variables for the day-ahead price forecast in the Iberian Electricity Market (MIBEL). The available input variables include extensive hourly time series records of weather forecasts, previous prices, and regional aggregation of power generations and power demands. The paper presents the comparisons of the forecasting results achieved with a model which includes all these available input variables (EMPF model) with respect to those obtained by other forecasting models containing a reduced set of input variables. These comparisons identify the most important variables for forecasting purposes. In addition, a novel Reference Explanatory Model for Price Estimations (REMPE) that achieves hourly price estimations by using actual power generations and power demands of such day is described in the paper, which offers the lowest limit for the forecasting error of the EMPF model. All the models have been implemented using the same technique (artificial neural networks) and have been satisfactorily applied to the real-world case study of the Iberian Electricity Market (MIBEL). The relative importance of each explanatory variable is identified for the day-ahead price forecasts in the MIBEL. The comparisons also allow outlining guidelines of the value of the different types of input information. Full article

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17 pages, 457 KB

Open AccessArticle

Eicosapentaenoic Acid from Porphyridium Cruentum: Increasing Growth and Productivity of Microalgae for Pharmaceutical Products

by Maryam Asgharpour, Brigitte Rodgers and Jamie A. Hestekin

Energies 2015, 8(9), 10487-10503; https://doi.org/10.3390/en80910487 - 22 Sep 2015

Cited by 48 | Viewed by 10195

Abstract

An alternative source of eicosapentaenoic acid (EPA) or omega-3 could be microalgae lipids instead of fish oils. However, EPA and lipid contents extracted from microalgae vary at different growth conditions. Therefore, it is of paramount importance to optimize the growth conditions of microalgae [...] Read more.

An alternative source of eicosapentaenoic acid (EPA) or omega-3 could be microalgae lipids instead of fish oils. However, EPA and lipid contents extracted from microalgae vary at different growth conditions. Therefore, it is of paramount importance to optimize the growth conditions of microalgae to maximize EPA production. In this paper, the effects of temperature (16 °C and 20 °C), light intensity (140 µE m⁻² s⁻¹ and 180 µE m⁻² s⁻¹) and nitrate level (0.075, 0.3, 0.5, and 0.7 g/L) on the cell growth, lipid productivity, and omega-6/omega-3 ratio of Porphyridium cruentum, one of the most promising oil-rich species of microalgae, are investigated. The ratio of the fatty acids with omega-6 and omega-3 groups at various growth conditions were compared, since an appropriate proportion of ω-6 (arachidonic acid (ARA)) to ω-3 (EPA) is vital for healthy nutrition. Lower EPA production and consequently a higher ARA/EPA ratio occurred when 5% CO₂/air was utilized as CO₂ supplementation compared to pure CO₂. The highest EPA (13.08% (w/w) of total fatty acids) and biomass productivity (143 mg L⁻¹ day⁻¹) was achieved at 140 µE m⁻² s⁻¹, 20 °C, and 0.3 g/L nitrate, while lipid content was the lowest (0.5% w/w) at this condition. The optimal condition with minimum ARA/EPA ratio (2.5) was identified at 20 °C, 140 µE m⁻² s⁻¹, and 0.5 g/L nitrate concentration. Full article

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

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18 pages, 525 KB

Open AccessArticle

Optimal Energy Reduction Schedules for Ice Storage Air-Conditioning Systems

by Whei-Min Lin, Chia-Sheng Tu, Ming-Tang Tsai and Chi-Chun Lo

Energies 2015, 8(9), 10504-10521; https://doi.org/10.3390/en80910504 - 22 Sep 2015

Cited by 16 | Viewed by 6346

Abstract

This paper proposes a hybrid algorithm to solve the optimal energy dispatch of an ice storage air-conditioning system. Based on a real air-conditioning system, the data, including the return temperature of chilled water, the supply temperature of chilled water, the return temperature of [...] Read more.

This paper proposes a hybrid algorithm to solve the optimal energy dispatch of an ice storage air-conditioning system. Based on a real air-conditioning system, the data, including the return temperature of chilled water, the supply temperature of chilled water, the return temperature of ice storage water, and the supply temperature of ice storage water, are measured. The least-squares regression (LSR) is used to obtain the input-output (I/O) curve for the cooling load and power consumption of chillers and ice storage tank. The objective is to minimize overall cost in a daily schedule while satisfying all constraints, including cooling loading under the time-of-use (TOU) rate. Based on the Radial Basis Function Network (RBFN) and Ant Colony Optimization, an Ant-Based Radial Basis Function Network (ARBFN) is constructed in the searching process. Simulation results indicate that reasonable solutions provide a practical and flexible framework allowing the economic dispatch of ice storage air-conditioning systems, and offering greater energy efficiency in dispatching chillers. Full article

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15 pages, 446 KB

Open AccessArticle

Classification of Household Appliance Operation Cycles: A Case-Study Approach

by Zeyu Wang and Ravi S. Srinivasan

Energies 2015, 8(9), 10522-10536; https://doi.org/10.3390/en80910522 - 22 Sep 2015

Cited by 17 | Viewed by 6856

Abstract

In recent years, a new generation of power grid system, referred to as the Smart Grid, with an aim of managing electricity demand in a sustainable, reliable, and economical manner has emerged. With greater knowledge of operational characteristics of individual appliances, necessary automation [...] Read more.

In recent years, a new generation of power grid system, referred to as the Smart Grid, with an aim of managing electricity demand in a sustainable, reliable, and economical manner has emerged. With greater knowledge of operational characteristics of individual appliances, necessary automation control strategies can be developed in the Smart Grid to operate appliances in an efficient manner. This paper provides a way of classifying different operational cycles of a household appliance by introducing an unsupervised learning algorithm called k-means clustering. An intrinsic method known as silhouette coefficient was used to measure the classification quality. An identification process is also discussed in this paper to help users identify the operation mode each types of operation cycle stands for. A case study using a typical household refrigerator is presented to validate the proposed method. Results show that the proposed the classification and identification method can partition and identify different operation cycles adequately. Classification of operation cycles for such appliances is beneficial for Smart Grid as it provides a clear and convincing understanding of the operation modes for effective power management. Full article

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

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21 pages, 743 KB

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A Comparison of Household Carbon Emission Patterns of Urban and Rural China over the 17 Year Period (1995–2011)

by Jiansheng Qu, Tek Maraseni, Lina Liu, Zhiqiang Zhang and Talal Yusaf

Energies 2015, 8(9), 10537-10557; https://doi.org/10.3390/en80910537 - 22 Sep 2015

Cited by 43 | Viewed by 7776

Abstract

The household sector consumes a large amount of goods and services and is therefore a major source of global carbon emissions. This study aims to analyze per person household carbon emission (HCEs) patterns of urban and rural China over the period from 1995 [...] Read more.

The household sector consumes a large amount of goods and services and is therefore a major source of global carbon emissions. This study aims to analyze per person household carbon emission (HCEs) patterns of urban and rural China over the period from 1995 to 2011. Annual macroeconomic data for the study were obtained from authentic Chinese government sources. Direct HCE estimates for each fossil fuel were obtained using the IPCC’s reference approach, and indirect HCEs were calculated by input-output analysis. In 1995, per person HCEs from direct sources for urban and rural China were 0.50 tCO₂ and 0.22 tCO₂, respectively; by 2011, these values had increased to 0.60 tCO₂ and 0.61 tCO₂, an increase of 20% and 177.27%, respectively. Similarly, in 1995, per person HCEs from indirect sources for urban and rural China were 0.43 tCO₂ and 0.16 tCO₂, respectively; by 2011, these values had increased to 1.77 tCO₂ and 0.53 tCO₂, respectively, an increase of 306% and 235%. The reasons for these differences and the sets of policies required to rectify increasing emissions are discussed. If current trends and practices continue, with a RMB1000 increase in per capita income from 2011 levels, per person HCEs in urban and rural China will increase by 0.119 tCO₂ and 0.197 tCO₂, respectively. This result indicates that the sector of society which is most vulnerable will contribute most to China’s increasing HCEs. Therefore, while developing energy consumption and emissions reduction policies and programs, principles of fairness and equity need to be followed. Full article

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

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15 pages, 157 KB

Open AccessReview

Optimal Rule-Based Power Management for Online, Real-Time Applications in HEVs with Multiple Sources and Objectives: A Review

by Bedatri Moulik and Dirk Söffker

Energies 2015, 8(9), 9049-9063; https://doi.org/10.3390/en8099049 - 26 Aug 2015

Cited by 18 | Viewed by 5770

Abstract

The field of hybrid vehicles has undergone intensive research and development, primarily due to the increasing concern of depleting resources and increasing pollution. In order to investigate further options to optimize the performance of hybrid vehicles with regards to different criteria, such as [...] Read more.

The field of hybrid vehicles has undergone intensive research and development, primarily due to the increasing concern of depleting resources and increasing pollution. In order to investigate further options to optimize the performance of hybrid vehicles with regards to different criteria, such as fuel economy, battery aging, etc., a detailed state-of-the-art review is presented in this contribution. Different power management and optimization techniques are discussed focusing on rule-based power management and multi-objective optimization techniques. The extent of rule-based power management and optimization in solving battery aging issues is investigated along with an implementation in real-time driving scenarios where no pre-defined drive cycle is followed. The goal of this paper is to illustrate the significance and applications of rule-based power management optimization based on previous contributions. Full article

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

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55 pages, 3063 KB

Open AccessReview

A Critical Review of Robustness in Power Grids Using Complex Networks Concepts

by Lucas Cuadra, Sancho Salcedo-Sanz, Javier Del Ser, Silvia Jiménez-Fernández and Zong Woo Geem

Energies 2015, 8(9), 9211-9265; https://doi.org/10.3390/en8099211 - 28 Aug 2015

Cited by 255 | Viewed by 16646

Abstract

This paper reviews the most relevant works that have investigated robustness in power grids using Complex Networks (CN) concepts. In this broad field there are two different approaches. The first one is based solely on topological concepts, and uses metrics such as mean [...] Read more.

This paper reviews the most relevant works that have investigated robustness in power grids using Complex Networks (CN) concepts. In this broad field there are two different approaches. The first one is based solely on topological concepts, and uses metrics such as mean path length, clustering coefficient, efficiency and betweenness centrality, among many others. The second, hybrid approach consists of introducing (into the CN framework) some concepts from Electrical Engineering (EE) in the effort of enhancing the topological approach, and uses novel, more efficient electrical metrics such as electrical betweenness, net-ability, and others. There is however a controversy about whether these approaches are able to provide insights into all aspects of real power grids. The CN community argues that the topological approach does not aim to focus on the detailed operation, but to discover the unexpected emergence of collective behavior, while part of the EE community asserts that this leads to an excessive simplification. Beyond this open debate it seems to be no predominant structure (scale-free, small-world) in high-voltage transmission power grids, the vast majority of power grids studied so far. Most of them have in common that they are vulnerable to targeted attacks on the most connected nodes and robust to random failure. In this respect there are only a few works that propose strategies to improve robustness such as intentional islanding, restricted link addition, microgrids and Energies 2015, 8 9212 smart grids, for which novel studies suggest that small-world networks seem to be the best topology. Full article

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

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24 pages, 1380 KB

Open AccessReview

Advanced Electrical Machines and Machine-Based Systems for Electric and Hybrid Vehicles

by Ming Cheng, Le Sun, Giuseppe Buja and Lihua Song

Energies 2015, 8(9), 9541-9564; https://doi.org/10.3390/en8099541 - 2 Sep 2015

Cited by 131 | Viewed by 18332

Abstract

The paper presents a number of advanced solutions on electric machines and machine-based systems for the powertrain of electric vehicles (EVs). Two types of systems are considered, namely the drive systems designated to the EV propulsion and the power split devices utilized in [...] Read more.

The paper presents a number of advanced solutions on electric machines and machine-based systems for the powertrain of electric vehicles (EVs). Two types of systems are considered, namely the drive systems designated to the EV propulsion and the power split devices utilized in the popular series-parallel hybrid electric vehicle architecture. After reviewing the main requirements for the electric drive systems, the paper illustrates advanced electric machine topologies, including a stator permanent magnet (stator-PM) motor, a hybrid-excitation motor, a flux memory motor and a redundant motor structure. Then, it illustrates advanced electric drive systems, such as the magnetic-geared in-wheel drive and the integrated starter generator (ISG). Finally, three machine-based implementations of the power split devices are expounded, built up around the dual-rotor PM machine, the dual-stator PM brushless machine and the magnetic-geared dual-rotor machine. As a conclusion, the development trends in the field of electric machines and machine-based systems for EVs are summarized. Full article

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

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25 pages, 1081 KB

Open AccessReview

Theoretical Modelling Methods for Thermal Management of Batteries

by Bahman Shabani and Manu Biju

Energies 2015, 8(9), 10153-10177; https://doi.org/10.3390/en80910153 - 17 Sep 2015

Cited by 121 | Viewed by 14725

Abstract

The main challenge associated with renewable energy generation is the intermittency of the renewable source of power. Because of this, back-up generation sources fuelled by fossil fuels are required. In stationary applications whether it is a back-up diesel generator or connection to the [...] Read more.

The main challenge associated with renewable energy generation is the intermittency of the renewable source of power. Because of this, back-up generation sources fuelled by fossil fuels are required. In stationary applications whether it is a back-up diesel generator or connection to the grid, these systems are yet to be truly emissions-free. One solution to the problem is the utilisation of electrochemical energy storage systems (ESS) to store the excess renewable energy and then reusing this energy when the renewable energy source is insufficient to meet the demand. The performance of an ESS amongst other things is affected by the design, materials used and the operating temperature of the system. The operating temperature is critical since operating an ESS at low ambient temperatures affects its capacity and charge acceptance while operating the ESS at high ambient temperatures affects its lifetime and suggests safety risks. Safety risks are magnified in renewable energy storage applications given the scale of the ESS required to meet the energy demand. This necessity has propelled significant effort to model the thermal behaviour of ESS. Understanding and modelling the thermal behaviour of these systems is a crucial consideration before designing an efficient thermal management system that would operate safely and extend the lifetime of the ESS. This is vital in order to eliminate intermittency and add value to renewable sources of power. This paper concentrates on reviewing theoretical approaches used to simulate the operating temperatures of ESS and the subsequent endeavours of modelling thermal management systems for these systems. The intent of this review is to present some of the different methods of modelling the thermal behaviour of ESS highlighting the advantages and disadvantages of each approach. Full article

(This article belongs to the Special Issue Electrochemical Energy Storage - 2015)

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34 pages, 968 KB

Open AccessReview

A Critical Review of Mineral Matter Related Issues during Gasification of Coal in Fixed, Fluidized, and Entrained Flow Gasifiers

by Vijayaragavan Krishnamoorthy and Sarma V. Pisupati

Energies 2015, 8(9), 10430-10463; https://doi.org/10.3390/en80910430 - 22 Sep 2015

Cited by 98 | Viewed by 16644

Abstract

Gasification of coal is gaining more popularity due to its clean operation, and its ability to generate products for various markets. However, these technologies are not widely commercialized due to reliability and economic issues. Mineral matter in coal plays an important role in [...] Read more.

Gasification of coal is gaining more popularity due to its clean operation, and its ability to generate products for various markets. However, these technologies are not widely commercialized due to reliability and economic issues. Mineral matter in coal plays an important role in affecting the availability/reliability of a gasifier. Agglomeration in the bed, slag mobility and blockage of the syngas exit section are some of the operations related concerns in fixed-bed gasifiers, while ash deposition and sudden defluidization are the major concerns in fluidized bed gasifiers. In the case of entrained flow gasifiers, syngas cooler fouling and blockage, corrosion and erosion of refractory, and slag mobility are some of the major issues affecting the operations and the reliability of the gasifier. This review is aimed at critically examining various mineral matter related issues contributing to the operation and reliability problems in three types of generic gasifiers (fixed bed, fluidized bed and entrained flow gasifiers). Based on the review, some strategies to counter the potential mineral matter related issues are presented. Full article

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

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Energies, Volume 8, Issue 9 (September 2015) – 78 articles , Pages 9009-10557

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