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Energies, Volume 4, Issue 9 (September 2011), Pages 1258-1477

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Research

Jump to: Review, Other

Open AccessArticle An S-Transform and Support Vector Machine (SVM)-Based Online Method for Diagnosing Broken Strands in Transmission Lines
Energies 2011, 4(9), 1278-1300; doi:10.3390/en4091278
Received: 13 July 2011 / Revised: 8 August 2011 / Accepted: 23 August 2011 / Published: 29 August 2011
Cited by 7 | PDF Full-text (1294 KB) | HTML Full-text | XML Full-text
Abstract
During their long-term outdoor field service, overhead transmission lines will be exposed to strikes by lightning, corrosion by chemical contaminants, ice-shedding, wind vibration of conductors, line galloping, external destructive forces and so on, which will generally cause a series of latent faults such
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During their long-term outdoor field service, overhead transmission lines will be exposed to strikes by lightning, corrosion by chemical contaminants, ice-shedding, wind vibration of conductors, line galloping, external destructive forces and so on, which will generally cause a series of latent faults such as aluminum strand fracture. This may lead to broken transmission lines which will have a very strong impact on the safe operation of power grids that if the latent faults cannot be recognized and fixed as soon as possible. The detection of broken strands in transmission lines using inspection robots equipped with suitable detectors is a method with good prospects. In this paper, a method for detecting broken strands in transmission lines using an eddy current transducer (ECT) carried by a robot is developed, and an approach for identifying broken strands in transmission lines based on an S-transform is proposed. The proposed approach utilizes the S-transform to extract the module and phase information at each frequency point from detection signals. Through module phase and comparison, the characteristic frequency points are ascertained, and the fault information of the detection signal is constructed. The degree of confidence of broken strand identification is defined by the Shannon fuzzy entropy (SFE-BSICD). The proposed approach combines module information while utilizing phase information, SFE-BSICD, and the energy, so the reliability is greatly improved. These characteristic qualities of broken strands in transmission lines are used as the input of a multi-classification SVM, allowing the number of broken strands to be determined. Through experimental field verification, it can be shown that the proposed approach displays high accuracy and the SFE-BSICD is defined reasonably. Full article
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Open AccessArticle Classification of Fundamental Ferroresonance, Single Phase-to-Ground and Wire Breakage Over-Voltages in Isolated Neutral Networks
Energies 2011, 4(9), 1301-1320; doi:10.3390/en4091301
Received: 23 June 2011 / Revised: 12 August 2011 / Accepted: 23 August 2011 / Published: 29 August 2011
Cited by 3 | PDF Full-text (441 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a simple and effective method for classification of fundamental ferroresonance, single phase-to-ground and wire breakage over-voltages. In isolated neutral networks, power frequency over-voltages due to ferroresonance, single phase-to-ground and wire breakage may exist for a long time, and have very
[...] Read more.
This paper proposes a simple and effective method for classification of fundamental ferroresonance, single phase-to-ground and wire breakage over-voltages. In isolated neutral networks, power frequency over-voltages due to ferroresonance, single phase-to-ground and wire breakage may exist for a long time, and have very highly similar voltage features. If the improper suppression operation is applied due to incorrect identification, the accident is likely to worsen further. In this paper, the voltage and current features of these faults are analyzed, and a new effective classification criterion for fundamental ferroresonance and single phase-to-ground based on zero sequence current is proposed. A comprehensive identification method based on voltage, current and zero sequence current features is proposed, which is feasible and promising for real applications. Full article
Open AccessArticle Traveling Wave Reactor and Condition of Existence of Nuclear Burning Soliton-Like Wave in Neutron-Multiplying Media
Energies 2011, 4(9), 1337-1361; doi:10.3390/en4091337
Received: 16 June 2011 / Revised: 1 August 2011 / Accepted: 2 August 2011 / Published: 9 September 2011
Cited by 9 | PDF Full-text (1605 KB) | HTML Full-text | XML Full-text
Abstract
Physical fundamentals of traveling wave reactor are considered. We show that the condition of existence of nuclear burning soliton-like wave in a neutron-multiplying medium is determined in general by two conditions. The first condition (necessary) is determined by relationship between the equilibrium concentration
[...] Read more.
Physical fundamentals of traveling wave reactor are considered. We show that the condition of existence of nuclear burning soliton-like wave in a neutron-multiplying medium is determined in general by two conditions. The first condition (necessary) is determined by relationship between the equilibrium concentration and critical concentration of active (fissionable) isotope that is a consequence of the Bohr–Sommerfeld quantization condition. The second condition (sufficient) is set by the so-called Wigner quantum statistics, or more accurately, by a statistics of the Gaussian simplectic ensembles with respect to the parameter that describes the squared width of burning wave front of nuclear fuel active component. Full article
(This article belongs to the Special Issue Advances in Nuclear Energy)
Open AccessArticle Reliability Evaluation Method for Oil–Paper Insulation in Power Transformers
Energies 2011, 4(9), 1362-1375; doi:10.3390/en4091362
Received: 30 May 2011 / Revised: 11 July 2011 / Accepted: 5 September 2011 / Published: 9 September 2011
Cited by 7 | PDF Full-text (486 KB) | HTML Full-text | XML Full-text
Abstract
The overall life of oil-immersed power transformers depends on the long-term life of the oil–paper insulation system throughout continuous operation. Studying the reliability assessment methods for oil–paper insulation can help determine the reliability level of power transformers accurately, and ensure their safe and
[...] Read more.
The overall life of oil-immersed power transformers depends on the long-term life of the oil–paper insulation system throughout continuous operation. Studying the reliability assessment methods for oil–paper insulation can help determine the reliability level of power transformers accurately, and ensure their safe and stable operation. In the present paper, the life of oil–paper insulation is proven to obey the Weibull distribution under eight different temperatures set by the Weibull reliability probability paper; the failure mechanisms of the different temperatures are highly consistent. The Weibull distribution reliability curve cluster of oil–paper insulation is plotted under different temperatures by which an oil–paper insulation reliability assessment method is proposed. Lastly, the statistical validation experiment of the proposed method is conducted, which proves its theoretical validity. Thus, the present study puts forward a simple and effective method for the oil–paper insulation reliability assessment of power transformers under different temperatures at different life stages. Full article
Open AccessArticle Temporal and Spatial Analysis of Integrated Energy and Environment Efficiency in China Based on a Green GDP Index
Energies 2011, 4(9), 1376-1390; doi:10.3390/en4091376
Received: 30 May 2011 / Revised: 18 July 2011 / Accepted: 5 September 2011 / Published: 9 September 2011
Cited by 14 | PDF Full-text (394 KB) | HTML Full-text | XML Full-text
Abstract
China is experiencing a high speed economic development which may exert great pressure on the environment and energy systems. To measure the environmental and energy performance during the economic development process, this paper selected 30 provinces, cities or autonomous regions as the decision making
[...] Read more.
China is experiencing a high speed economic development which may exert great pressure on the environment and energy systems. To measure the environmental and energy performance during the economic development process, this paper selected 30 provinces, cities or autonomous regions as the decision making unit (DMU), and proposed a Green GDP index (GGI) in view of energy intensity and pollution intensity using the generalized Data Envelopment Analysis (DEA) method, and the developing trends of integrated energy and environment efficiency of DMUs from 2006 to 2010 are also demonstrated by the Malmquist index. Results show that the integrated energy and environment efficiency varies for each DMU. GGI were both 1 in Beijing and Shanghai. GGI values for the developed cities in Eastern China, such as Guangdong, Fujian, Zhejiang, Tianjin, Jiangsu, and Hainan, ranked high, while those in the Northeast and Middle China remained relatively low. Moreover, there is a positive relationship between the GGI and per capita GDP with a correlation coefficient of 0.75. Increases in GGI are also observed in the results, representing great achievements are acquired in energy conservation and emission reduction. However, the GGIs do not converge to the green frontier across the provinces. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
Open AccessArticle Improved Methods for Production Manufacturing Processes in Environmentally Benign Manufacturing
Energies 2011, 4(9), 1391-1409; doi:10.3390/en4091391
Received: 13 June 2011 / Revised: 2 September 2011 / Accepted: 2 September 2011 / Published: 14 September 2011
Cited by 7 | PDF Full-text (1599 KB) | HTML Full-text | XML Full-text
Abstract
How to design a production process with low carbon emissions and low environmental impact as well as high manufacturing performance is a key factor in the success of low-carbon production. It is important to address concerns about climate change for the large carbon
[...] Read more.
How to design a production process with low carbon emissions and low environmental impact as well as high manufacturing performance is a key factor in the success of low-carbon production. It is important to address concerns about climate change for the large carbon emission source manufacturing industries because of their high energy consumption and environmental impact during the manufacturing stage of the production life cycle. In this paper, methodology for determining a production process is developed. This methodology integrates process determination from three different levels: new production processing, selected production processing and batch production processing. This approach is taken within a manufacturing enterprise based on prior research. The methodology is aimed at providing decision support for implementing Environmentally Benign Manufacturing (EBM) and low-carbon production to improve the environmental performance of the manufacturing industry. At the first level, a decision-making model for new production processes based on the Genetic Simulated Annealing Algorithm (GSAA) is presented. The decision-making model considers not only the traditional factors, such as time, quality and cost, but also energy and resource consumption and environmental impact, which are different from the traditional methods. At the second level, a methodology is developed based on an IPO (Input-Process-Output) model that integrates assessments of resource consumption and environmental impact in terms of a materials balance principle for batch production processes. At the third level, based on the above two levels, a method for determining production processes that focus on low-carbon production is developed based on case-based reasoning, expert systems and feature technology for designing the process flow of a new component. Through the above three levels, a method for determining the production process to identify, quantify, assess, and optimize the production process with the goal of reducing and ultimately minimizing the environmental impact while maximizing the resource efficiency is effectively presented. The feasibility of the method is verified by a case study of a whole production process design at the above three levels. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
Open AccessArticle Mixed Over-Voltage Decomposition Using Atomic Decompositions Based on a Damped Sinusoids Atom Dictionary
Energies 2011, 4(9), 1410-1427; doi:10.3390/en4091410
Received: 29 June 2011 / Revised: 11 September 2011 / Accepted: 15 September 2011 / Published: 20 September 2011
Cited by 4 | PDF Full-text (788 KB) | HTML Full-text | XML Full-text
Abstract
The main purpose of this paper is to establish a signal decomposition system aiming at mixed over-voltages in power systems. In an electric power system, over-voltage presents a great threat for the system safety. Analysis and identification of over-voltages is helpful to improve
[...] Read more.
The main purpose of this paper is to establish a signal decomposition system aiming at mixed over-voltages in power systems. In an electric power system, over-voltage presents a great threat for the system safety. Analysis and identification of over-voltages is helpful to improve the stability and safety of power systems. Through statistical analysis of a collection of field over-voltage records, it was found that a kind of complicated signals created by mixing of multiple different over-voltages is difficult to identify correctly with current classification algorithms. In order to improve the classification and identification accuracy of over-voltages, a mixed over-voltage decomposition system based on the atomic decomposition and a damped sinusoid atom dictionary has been established. This decomposition system is optimized by using particle swarm optimization and the fast Fourier transform. Aiming at possible fault decomposition results during decomposition of the over-voltage signal, a double-atom decomposition algorithm is proposed in this paper. By taking three typical mixed over-voltages as examples, the validity of the algorithm is demonstrated. Full article
Open AccessArticle Emergy-Based Adjustment of the Agricultural Structure in a Low-Carbon Economy in Manas County of China
Energies 2011, 4(9), 1428-1442; doi:10.3390/en4091428
Received: 11 July 2011 / Revised: 16 September 2011 / Accepted: 16 September 2011 / Published: 21 September 2011
Cited by 7 | PDF Full-text (337 KB) | HTML Full-text | XML Full-text
Abstract
The emergy concept, integrated with a multi-objective linear programming method, was used to model the agricultural structure of Xinjiang Uygur Autonomous Region under the consideration of the need to develop a low-carbon economy. The emergy indices before and after the structural optimization were
[...] Read more.
The emergy concept, integrated with a multi-objective linear programming method, was used to model the agricultural structure of Xinjiang Uygur Autonomous Region under the consideration of the need to develop a low-carbon economy. The emergy indices before and after the structural optimization were evaluated. In the reconstructed model, the proportions of agriculture, forestry and artificial grassland should be adjusted from 19:2:1 to 5.2:1:2.5; the Emergy Yield Ratio (1.48) was higher than the average local (0.49) and national levels (0.27); and the Emergy Investment Ratio (11.1) was higher than the current structure (4.93) and that obtained from the 2003 data (0.055) in Xinjiang Uygur Autonomous Region, the Water Emergy Cost (0.055) should be reduced compared to that before the adjustment (0.088). The measurement of all the parameters validated the positive impact of the modeled agricultural structure. The self-sufficiency ratio of the system increased from the original level of 0.106 to 0.432, which indicated a better coupling effect among the subsystems within the whole system. The comparative advantage index between the two systems before and after optimization was approximately 2:1. When the mountain ecosystem service value was considered, excessive animal husbandry led to a 1.41 × 1010 RMB·a−1 indirect economic loss, which was 4.15 times the GDP during the same time period. The functional improvement of the modeled structure supports the plan to “construct a central oasis and protect the surrounding mountains and deserts” to develop a sustainable agricultural system. Conserved natural grassland can make a large contribution to the carbon storage; and therefore, it is wise alternative that promote a low-carbon economic development strategy. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
Open AccessArticle Designing an Energy Storage System Fuzzy PID Controller for Microgrid Islanded Operation
Energies 2011, 4(9), 1443-1460; doi:10.3390/en4091443
Received: 1 August 2011 / Revised: 29 August 2011 / Accepted: 15 September 2011 / Published: 22 September 2011
Cited by 16 | PDF Full-text (713 KB) | HTML Full-text | XML Full-text
Abstract
Recently, interest in microgrids, which are composed of distributed generation (DG), distributed storage (DS), and loads, has been growing as a potentially effective clean energy system to mitigate against climate change. The microgrid is operated in the grid-connected mode and the islanded mode
[...] Read more.
Recently, interest in microgrids, which are composed of distributed generation (DG), distributed storage (DS), and loads, has been growing as a potentially effective clean energy system to mitigate against climate change. The microgrid is operated in the grid-connected mode and the islanded mode according to the conditions of the upstream power grid. The role of the energy storage system (ESS) is especially important to maintain constant the frequency and voltage of an islanded microgrid. For this reason, various approaches for ESS control have been put forth. In this paper, a fuzzy PID controller is proposed to improve the frequency control performance of the ESS. This fuzzy PID controller consists of a fuzzy logic controller and a conventional PI controller, connected in series. The fuzzy logic controller has two input signals, and then the output signal of the fuzzy logic controller is the input signal of the conventional PI controller. For comparison of control performance, gains of each PI controller and fuzzy PID controller are tuned by the particle swam optimization (PSO) algorithm. In the simulation study, the control performance of the fuzzy PID was also tested under various operating conditions using the PSCAD/EMTDC simulation platform. Full article
Open AccessArticle An Intelligent Regenerative Braking Strategy for Electric Vehicles
Energies 2011, 4(9), 1461-1477; doi:10.3390/en4091461
Received: 12 May 2011 / Revised: 2 September 2011 / Accepted: 6 September 2011 / Published: 22 September 2011
Cited by 32 | PDF Full-text (2332 KB) | HTML Full-text | XML Full-text
Abstract
Regenerative braking is an effective approach for electric vehicles (EVs) to extend their driving range. A fuzzy-logic-based regenerative braking strategy (RBS) integrated with series regenerative braking is developed in this paper to advance the level of energy-savings. From the viewpoint of securing car
[...] Read more.
Regenerative braking is an effective approach for electric vehicles (EVs) to extend their driving range. A fuzzy-logic-based regenerative braking strategy (RBS) integrated with series regenerative braking is developed in this paper to advance the level of energy-savings. From the viewpoint of securing car stability in braking operations, the braking force distribution between the front and rear wheels so as to accord with the ideal distribution curve are considered to prevent vehicles from experiencing wheel lock and slip phenomena during braking. Then, a fuzzy RBS using the driver’s braking force command, vehicle speed, battery SOC, battery temperature are designed to determine the distribution between friction braking force and regenerative braking force to improve the energy recuperation efficiency. The experimental results on an “LF620” prototype EV validated the feasibility and effectiveness of regenerative braking and showed that the proposed fuzzy RBS was endowed with good control performance. The maximum driving range of LF620 EV was improved by 25.7% compared with non-RBS conditions. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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Review

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Open AccessReview Tools for Small Hydropower Plant Resource Planning and Development: A Review of Technology and Applications
Energies 2011, 4(9), 1258-1277; doi:10.3390/en4091258
Received: 27 June 2011 / Revised: 22 August 2011 / Accepted: 22 August 2011 / Published: 26 August 2011
Cited by 17 | PDF Full-text (736 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews and compares software tools for the planning and design of small hydropower (SHP) plants. The main emphasis is on small scale hydropower resource assessment computer tools and methodologies for the development of SHP plants corresponding to a preliminary or prefeasibility
[...] Read more.
This paper reviews and compares software tools for the planning and design of small hydropower (SHP) plants. The main emphasis is on small scale hydropower resource assessment computer tools and methodologies for the development of SHP plants corresponding to a preliminary or prefeasibility study level. The paper presents a brief evaluation of the historic software tools and the current tools used in the small hydro industry. The reviewed tools vary from simple initial estimates to quite sophisticated software. The integration of assessment tools into Geographic Information System (GIS) environments has led to a leap forward in the strengthening of the evaluation of the power potential of water streams in the case of the spatial variability of different factors affecting stream power. A number of countries (e.g., Canada, Italy, Norway, Scotland and the US) have re-assessed their hydropower capacities based on spatial information of their water stream catchments, developing tools for automated hydro-site identification and deploying GIS-based tools, so-called Atlases, of small-scale hydropower resources on the Internet. However, a reliable assessment of real SHP site feasibility implies some “on the ground” surveying, but this traditional assessment can be greatly facilitated using GIS techniques that involve the spatial variability of catchment characteristics. Full article
(This article belongs to the Special Issue Advances in Hydroelectric Power Generation)
Open AccessReview Available Resources for Algal Biofuel Development in China
Energies 2011, 4(9), 1321-1335; doi:10.3390/en4091321
Received: 27 June 2011 / Revised: 17 August 2011 / Accepted: 23 August 2011 / Published: 31 August 2011
Cited by 6 | PDF Full-text (386 KB) | HTML Full-text | XML Full-text
Abstract
Microalgal biofuel research in China has made noticeable progress, and algae cultivation for biofuel production is considered to be an important contribution to Greenhouse Gas (GHG) mitigation and energy security. In this paper, the algal biofuel potentiality in China was reviewed from the
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Microalgal biofuel research in China has made noticeable progress, and algae cultivation for biofuel production is considered to be an important contribution to Greenhouse Gas (GHG) mitigation and energy security. In this paper, the algal biofuel potentiality in China was reviewed from the points of view of algal biodiversity, algal culture collection, GHGs (especially CO2) mitigation, and the availability of the required sunlight, wastewater and land resources. The cultivation of microalgae utilizing power plants gas with large amounts of CO2 and wastewaters from urban households, industry and animal husbandry are suitable for large scale production in China. Land is hardly a limitation for algae cultivation. Full article
(This article belongs to the Special Issue Biomass and Biofuels)

Other

Jump to: Research, Review

Open AccessRetraction Retraction: Manivannan, V.; Chennabasappa, M.; Garrett, J. Optimization and Characterization of Lithium Ion Cathode Materials in the System (1 – x – y)LiNi0.8Co0.2O2 • xLi2MnO3 • yLiCoO2. Energies 2010, 3, 847-865.
Energies 2011, 4(9), 1336; doi:10.3390/en4091336
Received: 26 August 2011 / Published: 31 August 2011
PDF Full-text (33 KB) | HTML Full-text | XML Full-text
Abstract
It has been brought to our attention by an official faculty committee at Colorado State University that portions of the data of this article [1] are not derived from experimental activities. In particular, the ICP-AES data in Table 1 for Compound 6, and
[...] Read more.
It has been brought to our attention by an official faculty committee at Colorado State University that portions of the data of this article [1] are not derived from experimental activities. In particular, the ICP-AES data in Table 1 for Compound 6, and the cycle data plotted at cycle 15 and greater in Figure 9b represent projected rather than actual data. After confirming this case with the authors, we have determined that indeed this manuscript clearly violates our editorial policy as well as the generally accepted ethics of scientific publication. Consequently, the Editorial Team and Publisher have determined that it should be retracted. We apologize for any inconvenience this may cause. Full article

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