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Energies, Volume 4, Issue 12 (December 2011) – 12 articles , Pages 2132-2310

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247 KiB  
Article
Alternative Scenarios for the Development of a Low-Carbon City: A Case Study of Beijing, China
by Lixiao Zhang, Yueyi Feng and Bin Chen
Energies 2011, 4(12), 2295-2310; https://doi.org/10.3390/en4122295 - 20 Dec 2011
Cited by 71 | Viewed by 9726
Abstract
The establishment of low-carbon cities has been suggested all over the World, since cities are key drivers of energy usage and the associated carbon emissions. This paper presents a scenario analysis of future energy consumption and carbon emissions for the city of Beijing. [...] Read more.
The establishment of low-carbon cities has been suggested all over the World, since cities are key drivers of energy usage and the associated carbon emissions. This paper presents a scenario analysis of future energy consumption and carbon emissions for the city of Beijing. The Long-range Energy Alternatives Planning (LEAP) model is used to simulate a range of pathways and to analyze how these would change energy consumption and carbon emissions from 2007 to 2030. Three scenarios have been designed to describe future energy strategies in relation to the development of Beijing city, namely a reference scenario (RS), control scenario (CS), and integrated scenario (IS). The results show that under the IS the total energy demand in Beijing is expected to reach 88.61 million tonnes coal equivalent (Mtce) by 2030 (59.32 Mtce in 2007), 55.82% and 32.72% lower than the values under the RS and the CS, respectively. The total carbon emissions in 2030 under the IS, although higher than the 2007 level, will be 62.22% and 40.27% lower than under the RS and the CS, respectively, with emissions peaking in 2026 and declining afterwards. In terms of the potential for reduction of energy consumption and carbon emissions, the industrial sector will continue to act as the largest contributor under the IS and CS compared with the RS, while the building and transport sectors are identified as promising fields for achieving effective control of energy consumption and carbon emissions over the next two decades. The calculation results show that an integrated package of measures is the most effective in terms of energy savings and carbon emissions mitigation, although it also faces the largest challenge to achieve the related targets. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
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430 KiB  
Article
Effects of Viscous Dissipation on the Slip MHD Flow and Heat Transfer past a Permeable Surface with Convective Boundary Conditions
by Mohammad H. Yazdi, Shahrir Abdullah, Ishak Hashim and Kamaruzzaman Sopian
Energies 2011, 4(12), 2273-2294; https://doi.org/10.3390/en4122273 - 20 Dec 2011
Cited by 41 | Viewed by 6539
Abstract
This paper presents an analysis of the energy exchange resulting from a 2D steady magnetohydrodynamics (MHD) flow past a permeable surface with partial slip in the presence of the viscous dissipation effect under convective heating boundary conditions. A magnetic field can effectively control [...] Read more.
This paper presents an analysis of the energy exchange resulting from a 2D steady magnetohydrodynamics (MHD) flow past a permeable surface with partial slip in the presence of the viscous dissipation effect under convective heating boundary conditions. A magnetic field can effectively control the motion of an electrically conducting fluid in micro scale systems, which can be applied for fluid transportation. Local similarity solutions for the transformed governing equations are obtained, and the reduced ordinary differential equations solved numerically via an explicit Runge-Kutta (4, 5) formula, the Dormand-Prince pair and shooting method, which is valid for fixed positions along the surface. The effects of various physical parameters, such as the magnetic parameter, the slip coefficient, the suction/injection parameter, the Biot number, the Prandtl number and the Eckert number, on the flow and heat transfer characteristics are presented graphically and discussed. The results indicate that the heat transfer rate increases with the increase in Biot number, slip coefficient, suction and magnetic parameter, whereas it decreases with the increase in Eckert number and injection. Full article
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485 KiB  
Article
Study on the Decomposition of Factors Affecting Energy-Related Carbon Emissions in Guangdong Province, China
by Wenxiu Wang, Yaoqiu Kuang and Ningsheng Huang
Energies 2011, 4(12), 2249-2272; https://doi.org/10.3390/en4122249 - 19 Dec 2011
Cited by 54 | Viewed by 8053
Abstract
Guangdong is China’s largest province in terms of energy consumption. The energy-related carbon emissions in Guangdong province are calculated, and two extended and improved decomposition models for energy-related carbon emissions are established with the Logarithmic Mean Divisia Index method based on the basic [...] Read more.
Guangdong is China’s largest province in terms of energy consumption. The energy-related carbon emissions in Guangdong province are calculated, and two extended and improved decomposition models for energy-related carbon emissions are established with the Logarithmic Mean Divisia Index method based on the basic principle of Kaya identity. Main results are as follows: (1) the energy-related carbon emissions from the three strata of industry, except the primary industry, and household energy consumption in Guangdong province show increasing trend from 1995 to 2009; (2) the main driving and inhibiting factors which influence energy-related carbon emissions are economic output and energy intensity, respectively, while the contributions of energy mix, industrial structures, population size and living standards are not significant during the period of interest. It is concluded that optimizing the energy mix by exploiting new energy sources and cutting down energy intensity by developing low-carbon technologies are the two most effective approaches to reduce carbon emissions for Guangdong province in the future. The results and proposals in this paper provided reference for relevant administrative departments in the Government of Guangdong province to develop policies for energy conservation and emission reduction as well as to promote development of low-carbon economy. Full article
(This article belongs to the Special Issue Energy Policy on Climate Change)
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1329 KiB  
Article
Reliability Assessment of Solder Joints in Power Electronic Modules by Crack Damage Model for Wind Turbine Applications
by Erik E. Kostandyan and John D. Sørensen
Energies 2011, 4(12), 2236-2248; https://doi.org/10.3390/en4122236 - 15 Dec 2011
Cited by 22 | Viewed by 6639
Abstract
Wind turbine reliability is an important issue for wind energy cost minimization, especially by reduction of operation and maintenance costs for critical components and by increasing wind turbine availability. To develop an optimal operation and maintenance plan for critical components, it is necessary [...] Read more.
Wind turbine reliability is an important issue for wind energy cost minimization, especially by reduction of operation and maintenance costs for critical components and by increasing wind turbine availability. To develop an optimal operation and maintenance plan for critical components, it is necessary to understand the physics of their failure and be able to develop reliability prediction models. Such a model is proposed in this paper for an IGBT power electronic module. IGBTs are critical components in wind turbine converter systems. These are multilayered devices where layers are soldered to each other and they operate at a thermal-power cycling environment. Temperature loadings affect the reliability of soldered joints by developing cracks and fatigue processes that eventually result in failure. Based on Miner’s rule a linear damage model that incorporates a crack development and propagation processes is discussed. A statistical analysis is performed for appropriate model parameter selection. Based on the proposed model, a layout for component life prediction with crack movement is described in details. Full article
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1045 KiB  
Article
Analysis of a Single-Phase Z-Source Inverter for Battery Discharging in Vehicle to Grid Applications
by Yifan Yu, Qianfan Zhang, Bin Liang, Xiaofei Liu and Shumei Cui
Energies 2011, 4(12), 2224-2235; https://doi.org/10.3390/en4122224 - 15 Dec 2011
Cited by 21 | Viewed by 8035
Abstract
Vehicle to Grid technology allows the batteries of electric vehicles to operate as energy storage elements for renewable energy power systems. The Z-Source inverter is a new and attractive topology for the power electronics interface. In this paper, the equivalent DC-link voltage ripple [...] Read more.
Vehicle to Grid technology allows the batteries of electric vehicles to operate as energy storage elements for renewable energy power systems. The Z-Source inverter is a new and attractive topology for the power electronics interface. In this paper, the equivalent DC-link voltage ripple of a single-phase Z-Source inverter for Vehicle to Grid applications is analyzed in this paper before deriving a general design approach for the Z-Source network. These theoretical findings, and design rule for a Z-Source network have been confirmed by computer simulations and a laboratory-implemented prototype. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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236 KiB  
Article
Biodiesel Production from Acidified Oils via Supercritical Methanol
by Jincheng Ding, Benqiao He and Jianxin Li
Energies 2011, 4(12), 2212-2223; https://doi.org/10.3390/en4122212 - 14 Dec 2011
Cited by 22 | Viewed by 6742
Abstract
In biodiesel production, the vegetable oil used as raw material for transesterification should be free of water and free fatty acids (FFAs), which may consume catalyst and reduce catalyst efficiency. In this work biodiesel was prepared from acidified oils (AO) through a supercritical [...] Read more.
In biodiesel production, the vegetable oil used as raw material for transesterification should be free of water and free fatty acids (FFAs), which may consume catalyst and reduce catalyst efficiency. In this work biodiesel was prepared from acidified oils (AO) through a supercritical methanol route, in which the esterification of FFAs and transesterification of glyceride with methanol occurred simultaneously. The effects of the mass ratio of methanol to AO, the operation temperature as well as the water content on the FFAs conversion and glycerol yield were investigated. The results indicated that the FFAs conversion for esterification under the condition of 1:1 methanol/oil ratio, 310 °C and 15 min reaction time reached 98.7%, and the glycerol yield for transesterification under 0.25:1 methanol/oil ratio, 290 °C and 20 min reaction time reached 63.5% respectively. Full article
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695 KiB  
Article
Numerical Analysis of the Magnetic Field of High-Current Busducts and GIL Systems
by Petar Sarajcev
Energies 2011, 4(12), 2196-2211; https://doi.org/10.3390/en4122196 - 13 Dec 2011
Cited by 11 | Viewed by 6187
Abstract
This paper presents a numerical computation method for determining the magnetic field of high-current busducts of circular cross-section geometry, based on the subdivision of the busduct phase conductors and screens into the conductor filaments and the subsequent application of the mesh-current method, with [...] Read more.
This paper presents a numerical computation method for determining the magnetic field of high-current busducts of circular cross-section geometry, based on the subdivision of the busduct phase conductors and screens into the conductor filaments and the subsequent application of the mesh-current method, with the aid of the geometric mean distance method. The mathematical model takes into account the skin effect and the proximity effects, as well as the complete electromagnetic coupling between phase conductors and metal enclosures (i.e., screens) of the single-phase isolated busduct system (of circular cross-section geometry). This model could be readily applied to the computation of the magnetic field of the Gas Insulated Transmission Lines (GIL) as well. Full article
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473 KiB  
Article
Comparison of Extremum-Seeking Control Techniques for Maximum Power Point Tracking in Photovoltaic Systems
by Her-Terng Yau and Chen-Han Wu
Energies 2011, 4(12), 2180-2195; https://doi.org/10.3390/en4122180 - 08 Dec 2011
Cited by 46 | Viewed by 7978
Abstract
Due to Japan’s recent nuclear crisis and petroleum price hikes, the search for renewable energy sources has become an issue of immediate concern. A promising candidate attracting much global attention is solar energy, as it is green and also inexhaustible. A maximum power [...] Read more.
Due to Japan’s recent nuclear crisis and petroleum price hikes, the search for renewable energy sources has become an issue of immediate concern. A promising candidate attracting much global attention is solar energy, as it is green and also inexhaustible. A maximum power point tracking (MPPT) controller is employed in such a way that the output power provided by a photovoltaic (PV) system is boosted to its maximum level. However, in the context of abrupt changes in irradiance, conventional MPPT controller approaches suffer from insufficient robustness against ambient variation, inferior transient response and a loss of output power as a consequence of the long duration required of tracking procedures. Accordingly, in this work the maximum power point tracking is carried out successfully using a sliding mode extremum-seeking control (SMESC) method, and the tracking performances of three controllers are compared by simulations, that is, an extremum-seeking controller, a sinusoidal extremum-seeking controller and a sliding mode extremum-seeking controller. Being able to track the maximum power point promptly in the case of an abrupt change in irradiance, the SMESC approach is proven by simulations to be superior in terms of system dynamic and steady state responses, and an excellent robustness along with system stability is demonstrated as well. Full article
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864 KiB  
Article
A Novel Cogging Torque Simulation Method for Permanent-Magnet Synchronous Machines
by Chun-Yu Hsiao, Sheng-Nian Yeh and Jonq-Chin Hwang
Energies 2011, 4(12), 2166-2179; https://doi.org/10.3390/en4122166 - 06 Dec 2011
Cited by 29 | Viewed by 10426
Abstract
Cogging torque exists between rotor mounted permanent magnets and stator teeth due to magnetic attraction and this is an undesired phenomenon which produces output ripple, vibration and noise in machines. The purpose of this paper is to study the existence and effects of [...] Read more.
Cogging torque exists between rotor mounted permanent magnets and stator teeth due to magnetic attraction and this is an undesired phenomenon which produces output ripple, vibration and noise in machines. The purpose of this paper is to study the existence and effects of cogging torque, and to present a novel, rapid, half magnet pole pair technique for forecasting and evaluating cogging torque. The technique uses the finite element method as well as Matlab research and development oriented software tools to reduce numerous computing jobs and simulation time. An example of a rotor-skewed structure used to reduce cogging torque of permanent magnet synchronous machines is evaluated and compared with a conventional analysis method for the same motor to verify the effectiveness of the proposed approach. The novel method is proved valuable and suitable for large-capacity machine design. Full article
(This article belongs to the Special Issue Wind Turbines)
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341 KiB  
Article
Optimal Design of Cogeneration Systems in Industrial Plants Combined with District Heating/Cooling and Underground Thermal Energy Storage
by Andrea Reverberi, Adriana Del Borghi and Vincenzo Dovì
Energies 2011, 4(12), 2151-2165; https://doi.org/10.3390/en4122151 - 06 Dec 2011
Cited by 19 | Viewed by 7230
Abstract
Combined heat and power (CHP) systems in both power stations and large plants are becoming one of the most important tools for reducing energy requirements and consequently the overall carbon footprint of fundamental industrial activities. While power stations employ topping cycles where the [...] Read more.
Combined heat and power (CHP) systems in both power stations and large plants are becoming one of the most important tools for reducing energy requirements and consequently the overall carbon footprint of fundamental industrial activities. While power stations employ topping cycles where the heat rejected from the cycle is supplied to domestic and industrial consumers, the plants that produce surplus heat can utilise bottoming cycles to generate electrical power. Traditionally the waste heat available at high temperatures was used to generate electrical power, whereas energy at lower temperatures was either released to the environment or used for commercial or domestic heating. However the introduction of new engines, such as the ones using the organic Rankine cycle, capable of employing condensing temperatures very close to the ambient temperature, has made the generation of electrical power at low temperatures also convenient. On the other hand, district heating is becoming more and more significant since it has been extended to include cooling in the warm months and underground storage of thermal energy to cope with variable demand. These developments imply that electric power generation and district heating/cooling may become alternative and not complementary solutions for waste energy of industrial plants. Therefore the overall energy management requires the introduction of an optimisation algorithm to select the best strategy. In this paper we propose an algorithm for the minimisation of a suitable cost function, for any given variable heat demand from commercial and domestic users, with respect to all independent variables, i.e., temperatures and flowrates of warm fluid streams leaving the plants and volume and nature of underground storage. The results of the preliminary process integration analysis based on pinch technology are used in this algorithm to provide bounds on the values of temperatures. Full article
(This article belongs to the Special Issue Energy Policy on Climate Change)
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2007 KiB  
Article
Dielectric Barrier Discharge Characteristics of Multineedle-to-Cylinder Configuration
by Xiaojing Wang, Qing Yang, Chenguo Yao, Xiaoxing Zhang and Caixin Sun
Energies 2011, 4(12), 2133-2150; https://doi.org/10.3390/en4122133 - 02 Dec 2011
Cited by 33 | Viewed by 7919
Abstract
A dielectric barrier discharge (DBD) produces a homogenous discharge with low energy consumption, offering broad developmental prospects, and this discharge process is also the mechanism through which charges are transported. Higher reaction efficiency is achieved when more charges are transported. Focusing on the [...] Read more.
A dielectric barrier discharge (DBD) produces a homogenous discharge with low energy consumption, offering broad developmental prospects, and this discharge process is also the mechanism through which charges are transported. Higher reaction efficiency is achieved when more charges are transported. Focusing on the electrode configuration of the multineedle-to-cylinder (MC) system, i.e., the structure of needles arrayed on the inner coaxial rod, the effect of needle arrangement, including needle length (NL), inter axial needle distance (ID), and inter axial needle rotation angle (INRA), on the transported charge per cycle and discharge power in DBDs is investigated. The finite-element method (FEM) and quasi-static field simulation are adopted to study the active region (AR) where the electric field strength exceeds the breakdown electric field strength between MC electrodes because this region plays a dominant role in DBD. The improvement of its volume ratio in the reactor allows an increase in discharge power. The simulation results are in accordance with the experimental results, which illustrate that quasi-static field simulation is effective and reliable. Simulation results show that mutual effects of nearby needles and between needles and the inner rod exist. As a result, shorter ID (1.5 mm), needles with similar lengths (3.5 mm) are arranged, and an INRA of 0° is proven to be the optimal structure because it produces the highest AR volume ratio. The result is experimentally validated by transported charges per cycle and discharge power obtained through Lissajous figures. Full article
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147 KiB  
Correction
Correction: Hu, X.; Sun, F. and Zou, Y. Estimation of State of Charge of a Lithium-Ion Battery Pack for Electric Vehicles Using an Adaptive Luenberger Observer. Energies 2010, 3, 1586–1603
by Xiaosong Hu, Fengchun Sun and Yuan Zou
Energies 2011, 4(12), 2132; https://doi.org/10.3390/en4122132 - 30 Nov 2011
Cited by 1 | Viewed by 6590
Abstract
The authors would like to make the following corrections to their published paper in Energies [1]. [...] Full article
(This article belongs to the Special Issue Hybrid Vehicles)
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