International Journal of Energy

ISSN: 1998-4316
Volume 7, 2013

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Issue 1, Volume 7, 2013

Title of the Paper: A New Method to Optimize Reactive Power with Hybrid Network Equations


Authors: Yi Tao, Wang Cheng-min, Sun Wei-qing, Gao Yang

Pages: 1-7

Abstract: Electric power network components can be simulated with equivalent circuit. Establish the hybrid node voltage and branch current electricity network analysis model based on it, and then form the hybrid electric power network equations to research the reactive power optimization of power system. Firstly, define the node voltages and branch currents as the state variables in this model. The network flow is explicitly expressed along with the branch currents introduced, and they play a key role for the simplification of the calculation. Then, in the process of reactive optimization the optimal objective has been broken down into two sub-objectives: one is a network loss minimization objective augmented Lagrange function, forming the Kuhn-Tucker conditions, and the other is a linear equation. The calculated results of IEEE 30-bus system show that the complexity and high dimension of the model have been significantly reduced, the solving process becomes easier, and the solution is close to the global optimal solution. Compared with traditional optimal power flow algorithm, this algorithm can improve the computational efficiency of reactive power optimization.

Title of the Paper: Localized O2 Starvation Threat Estimation and Rapid O2 Compensation Technique in Air PEMFC


Authors: Saurav Mitra, Ramesh P., Siddhartha P. Duttagupta

Pages: 8-18

Abstract: Air breathing proton exchange membrane fuel cells (PEMFC) have now found its use in wide range of domestic and commercial energy based applications. Minimum carbon footprint, low maintenance, low heat operation, and higher energy efficiency at partial and full load conditions have made PEMFC one of the most sought after green energy sources for future. Optimization of PEMFC system parameters and its safer operation under dynamic load conditions ensure higher system output and longer device lifetime. Ensuring safety against oxygen starvation during transient load variation reduces the degradation of membrane electrode assembly (MEA). PEMFC performance optimization and safety against oxygen starvation requires efficient estimation and precise control of air supply subsystem state variables. This paper proposes a Kalman filter based estimation technique that helps estimate the fuel cell air supply subsystem performance parameters. Some parameters that are otherwise non-measurable under industrial environment are also estimated using the proposed estimation technique. The FEM based fuel cell modeling gives further insight regarding the degree of oxygen starvation in PEMFC. The qualitative membrane degradation threat occurring during oxygen starvation under fluctuating load at varying environmental humidity is also estimated here. Finally, a rapid oxygen compensation technique is proposed which helps mitigate the permanent PEMFC health damage. The proposed oxygen compensation technique ensures safe operation, longer life, higher energy efficiency, and reduced per unit energy cost obtained from the renewable energy source.

Title of the Paper: A New Arrangement with Time-Varying Capacitance for Power Generation


Authors: Takuya Hirata, Ichijo Hodaka, Masanori Ushimizu

Pages: 19-22

Abstract: Ocean wave energy is enormous and there are many methods for power generation from the wave energy. Our method also is for power generation from the wave energy, but we utilize a capacitor for power generation instead of using the electric generator for any conventional method. Our method is one way of power generation which utilizes a phenomenon that capacitance of a capacitor is changed by wave energy.

Issue 2, Volume 7, 2013

Title of the Paper: Simulation-Based Aggregate Installation Planning of Offshore Wind Farms


Authors: Abderrahim Ait-Alla, Moritz Quandt, Michael Lütjen

Pages: 23-30

Abstract: The offshore wind energy is considered as one of the main sources for renewable and sustainable energy for the future. In addition, it can contribute to the decrease of greenhouse gas emissions and pollution caused by fossil energy. Therefore, the construction and utilization of offshore wind farms (OWF) will increase within the next years [1]. However, during the installation process of a wind farm, the installation planning has to deal with harsh weather conditions and limited vessel availability. This makes the installation of wind farms to a complex planning problem. Furthermore the offshore installation process requires not only short-time scheduling but also medium-term planning. In general, the term of aggregate planning is characterized by its medium-term character, which ranges from months to years. This paper addresses the problem of aggregate installation planning of OWF and proposes a mathematical model in order to generate an aggregated schedule. The objective of the optimization is to minimize the total installation costs by considering different vessel types as well as constraints, like e.g. chartering costs, travel times and weather restrictions for operations.

Title of the Paper: Study and Simulation of Direct Torque Control (DTC) for a Six Phase Induction Machine (SPIM)


Authors: Radhwane Sadouni, Abdelkader Meroufel, Salim Djriou

Pages: 31-37

Abstract: This paper presents a performances study of a Direct Torque and Flux Control (DTC) for a Six Phase Induction Machine (SPIM) dedicated to electrical drives using a two level voltage source inverter (VSI). This method has become one of the high performance control strategies for AC machine to provide a very fast torque and flux control. The simulation results show the effectiveness of the proposed method in both dynamic and steady state response.

Title of the Paper: Multiple Employed Artificial Bees Colony Algorithm for Allocating Reactive Power Losses in Deregulated Power System


Authors: Abdul Rahman Minhat, Mohd Wazir Mustafa, Ismail Musirin

Pages: 38-46

Abstract: The extensive use of heuristic technique for solving problem given in various field, not the least in power system analysis, has provided a source of inspiration in the determination of reactive power losses that occur along transmission the reactive power from source to consumer in deregulated power system. Based on the original idea of honeybees perform foraging activity from their colony to food source that available in their confines, it has been adopted as proposed in this paper to solve the allocation of reactive power losses to generators in the system by optimization approach. However for allocating the reactive power losses in deregulated power system purpose, multiple numbers of employed bees has been used in performing the Artificial Bees Colony algorithm. The results showed that performance and quality of the experiment is better compared to original ABC algorithm. Meanwhile, a comparative experiment is also performed on conventional method to observe the contribution of generators to power losses that occurs in the system with both methods. IEEE 30-bus Reliability Test System was chosen as a test system in this study.

Title of the Paper: Computational Research of Burning Coal in the Real Boiler of Almaty CHP


Authors: Askarova A. S., Bolegenova S. A., Maximov V. Yu., Bekmukhamet A., Beketayeva M. T.

Pages: 47-58

Abstract: The tendency of development of fuel-energy sector of Kazakhstan at the present stage imposes strict requirements for the use of energy sources. In this case the important thing is the development of the "clean" coal combustion with the smallest possible emission of harmful substances, and therefore it is need to optimize all the constructive and operational parameters of the process.

Issue 3, Volume 7, 2013

Title of the Paper: Dilemma in Estonian Renewable Energy Policy: Do State Subsidies Meet Public Preferences?


Authors: Ü. Ehrlich, M. Roodi

Pages: 59-65

Abstract: Estonia has assumed with the EU the obligation to produce by 2020 25% of the electricity from renewable sources. For the achievement of this objective a surcharge has been imposed on electricity generated from renewable sources, which shall be paid by consumers of electricity. In connection with the Estonian electricity market opening in January 2013, the electricity price for end users rose, which has increased discontent with the surcharge on renewable energy based electricity for consumers. The paper attempts to find out the attitude of Estonian consumers toward the electricity produced from renewable sources and demand for electricity produced from renewable sources. Using the Contingent Valuation method the Estonian population’s willingness to pay a surcharge on renewable sources based electricity is identified and it is compared to the mandatory renewable energy charge. The study shows that the main criterion for selecting an electricity package under the open energy market has been the electricity price and the willingness to pay of approximately 80% of the consumers for electricity from renewable sources is smaller than the obligatory renewable energy charge.

Title of the Paper: Experimental Approach on Degradation Process during Anaerobic Fermentation for Different Agricultural Biomass Properties


Authors: A. E. Cioablă, G. A. Dumitrel, F. Popescu, D. G. Călinoiu, A. Ţenchea

Pages: 66-71

Abstract: Relative to the existing technologies for using renewable sources in order to produce clean energy, the use of biomass for biogas production is one of the means to replace at least partially the existing natural gas which represents a fossil fuel. There will be presented the influence of degradation process, during anaerobic digestion on agricultural materials in terms of process indicators during the process and chemical parameters evolution before and after the anaerobic fermentation.

Title of the Paper: Research on Transformer Interaction Caused by Inrush Current and Parametric Study of this Phenomenon


Authors: P. Heretík, M. Kovác, M. Smitková, A. Belán, V. Volcko, P. Heretík

Pages: 72-81

Abstract: The phenomenon of sympathetic interaction between transformers is discussed in this paper. The phenomenon of sympathetic interaction between transformers, which is very likely to occur when a transformer is energised on to a system where are other transformers already connected, changes significantly the duration and the magnitude of the transient magnetising currents in the transformers involved and in the line supplying transformers. At the same time, its characteristics are further analyzed by numerical simulation in Matlab-Simulink Program. The sympathetic inrush current could influence the transformer differential protection and even cause mal-operation differential protection of switching and already energized transformer. Based on simplified equivalent circuit of two shunt-wound transformers, the magnetic analytical expression and rule of bias magnetic attenuation are analyzed. After that, the reasons of sympathetic inrush current generation are illustrated. The effects parameters of supplying system and transformers, such as load, system resistance, manners of connections of windings and manners of transformer grounding to sympathetic inrush current are then analyzed deeply by analytical analysis. The conclusion is validated by using emulate program.

Issue 4, Volume 7, 2013

Title of the Paper: Loss of Wind Power for Wind Turbines Due to an Upstream Hill


Authors: B. Ruck, R. Boes, M. Gruber

Pages: 83-93

Abstract: In advance of the implementation of wind tur-bines, a profitability forecast must be performed allowing an economical assessment of the project. For a detailed analysis of the wind potential, wind climate data of the site are required. In most cases, however, these data do not exist and it is necessary to rely on data from remote stations, which are 'extrapolated' numerically to the site. This numerical extrapolation is critical and in debate, especially, when orographically structured ter-rain is present. In order to complement and to validate existing numerical programs, an experimental investigation in an at-mospheric boundary layer tunnel has been carried out, deliver-ing detailed information on the influence of upstream hills on the wind power potential for wind turbines. Special emphasis was laid on the case where wind turbine height and hill height are in the same order of magnitude. Depending on factors of influence, exposure coefficients could be determined, which account for the loss of wind power due to the upstream hill.

Title of the Paper: Power Quality Improvement Using Hardware Implementation of PI Controlled Three-Phase Shunt Active Power Filter


Authors: Ismail Ghadbane , Mohamed Toufik Benchouia

Pages: 94-101

Abstract: The simulation and experimental study of Proportional Integrator controlled DC bus voltage of three phase shunt active power filter (APF), to improve power quality by compensating harmonics and reactive power required by nonlinear load is proposed. The algorithm used to identify the reference currents is based on the Self Tuning Filter (STF). PWM signal generation is based on hysteresis control comparators to obtain the switching signals. Various simulation and experimental results show the feasibility and the effectiveness of the designed active filter.

Title of the Paper: Heat Distribution and Consumption Model with Continuous Consumption Part


Authors: Vasek Lubomir, Dolinay Viliam

Pages: 102-109

Abstract: This article describes the design and preparation of discrete model for heat distribution and consumption in city agglomeration. The model takes into account the basic rules of consumption and relations in the district heating systems (centralized location for residential and commercial heating requirements) and can be applied for heat distribution from heating plant to individual heat exchange station or distribution and consumption of heat energy from exchange station to single buildings (house stations). A combination of these two parts is also allowed. Model has been introduced in the previous articles;however it is still in progress and tested in real situations. The introductory part of this article will presents the proposed model, algorithms used for the calculations, principles and practices for each step of the simulation process. This article also shows recent improvement introduces two fundamental changes. The heat consumer as an essential part of the model, were modified to work more continuously and thereby it more corresponds to real consumption equipment. Second improvement is the addition of influence of internal temperature in heated objects. Originally consumption was solely dependent on heating water temperature and outside temperature, which has its undeniable logic – colder weather means more demand for heating, however it appears to be more appropriate to consider the heat transferred as a productof mass flow and temperature difference between heating water in inlet pipe and temperature of the heated media, i.e. the desired room temperature or temperature of the inlet water in secondary part of the heat exchanger. Binding to the outdoor temperature is however still present in relation to amount of heat requirement.The final part of the article shows comparison of simulation results for original and newly introduced modifications.