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Power Demand (power + demand)
Selected AbstractsOptimal CBM of tie lines between control areas in a deregulated environmentELECTRICAL ENGINEERING IN JAPAN, Issue 1 2009Hideaki Kuraishi Abstract In order to keep power supply reliability at a certain level, electric power utilities have a certain amount of reserve capacity. When no generator outage or no unexpected large power demand occurs, however, the reserve capacity is regarded as surplus facility. To reduce the reserve capacity, some margin is reserved in tie lines between utilities. This margin is called the capacity benefit margin (CBM). In this study, a method of calculating optimal CBM in tie line under deregulated environment is described and two kinds of optimal CBM are proposed. As a result, it is shown how the deregulation affects the optimal CBM by using numerical simulation for the IEE Japan West 30 test system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 35, 48, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20654 [source] Analysis of GaInAsP laser diodes degraded by light absorption at an active layer of the facetELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2010Hiroyuki Ichikawa Abstract Electrostatic discharge-induced degradation is one of the serious reliability problems of GaInAsP/InP laser diodes. The authors have conducted an analysis of electrostatic discharge-induced degradation, and have elucidated the principal degradation mechanism. The main cause of degradation is heating by light absorption at the active layer of the facet. This phenomenon is similar to the catastrophic optical damage that occurs in GaAs-based high-power laser diodes. The problem has become more serious with the recent tendency to high power demand. Therefore, technology to suppress against degradation is extremely important. Focusing on facet coating, which is one of the key processes to suppress facet degradation, we demonstrated that facet degradation can be successfully suppressed by inserting an ultrathin aluminum layer between the semiconductor and the dielectric coaling films. This effect is caused by a reduction of surface recombination. This degradation suppression technology has the potential to be applied not only to GaInAsP/InP laser diodes, but to any InP-based laser diodes. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(2): 32,38, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10196 [source] Transmission pricing using the exact power and loss allocation method for bilateral contracts in a deregulated electricity supply industryEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2007Cattareeya Adsoongnoen Abstract This paper proposes a new method based on exact power and loss allocation for bilateral transactions under the enhanced single buyer model in the Thai electricity supply industry (Thai ESI). Generally, a transmission network is designed to transfer mainly active power. The transmission pricing for this active power charge in the Thai ESI comprises three components, namely the transmission use-of-system charge, the connection charge, and the common service charge. However, the calculation of transmission pricing, using marginal cost scheme, might not ensure revenue requirements of the transmission owner in case of a high reactive power demand in the network because a part of transmission line capacity is subsequently required for the reactive power transfer. Thus, the triangle method is used to segregate the transmission pricing by classifying active and reactive charges. The users are charged regarding their system usages by applying the exact power and loss allocation method. The proposed transmission pricing sends economic incentives to the users with fair charges. It ensures an investment recovery of the transmission owner in case of high reactive demand in the network. The Thai power 424-bus network demonstrates the method exemplarily. Copyright © 2006 John Wiley & Sons, Ltd. [source] Energy Conservation in Urban AreasIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2008Hideharu Sugihara Member Abstract This article outlines the energy conservation measures in the civilian sector from a few different viewpoint regarding energy conservation in cities. First, the energy consumption trends in the business and residential sectors are discussed, focusing the importance of energy conservation measures in applications such as home heating, water heating and specific power demand. Second, as a measure to reduce energy demand itself, energy conservation by way of applying heat insulating materials to buildings and changing the life style of residents is considered. And from the viewpoint of improving the energy system efficiency, additionally discussed here are the measures to improve the efficiency of each energy equipment such as air-conditioners and co-generation equipment, and the characteristics of District heating and cooling systems such as the local energy infrastructures. Lastly, from the knowledge obtained through model analyses by the authors, a scheme is recommended that would be one of the most efficient city-energy schemes where the energy systems including heat pumps, co-generators or equipment using solar power are utilized for their best-suited applications for business and residential customers. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] A comparative analysis of energy and CO2 taxes on the primary energy mix for electricity generationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2005Kris Voorspools Abstract In many countries, economies are moving towards internalization of external costs of greenhouse-gas (GHG) emissions. This can best be achieved by either imposing additional taxes or by using an emission-permit-trading scheme. The electricity sector is under scrutiny in the allocation of emission-reduction objectives, not only because it is a large homogeneous target, but also because of the obvious emission-reduction potential by decreasing power generation based on carbon-intensive fuels. In this paper, we discuss the impact of a primary-energy tax and a CO2 tax on the dispatching strategy in power generation. In a case study for the Belgian power-generating context, several tax levels are investigated and the impact on the optimal dispatch is simulated. The impact of the taxes on the power demand or on the investment strategies is not considered. As a conclusion, we find that a CO2 tax is more effective than a primary-energy tax. Both taxes accomplish an increased generation efficiency in the form of a promotion of combined-cycle gas-fired units over coal-fired units. The CO2 tax adds an incentive for fuel switching which can be achieved by altering the merit order of power plants or by switching to a fuel with a lower carbon content within a plant. For the CO2 tax, 13 ,/tonCO2 is withheld as the optimal value which results in an emission reduction of 13% of the electricity-related GHG emissions in the Belgian power context of 2000. A tax higher than 13 ,/tonCO2 does not contribute to the further reduction of GHGs. Copyright © 2005 John Wiley & Sons, Ltd. [source] Integrated model framework for the evaluation of an SOFC/GT system as a centralized power sourceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2004Michihisa Koyama Abstract New power generation technologies are expected to reduce various environmental impacts of providing electricity to urban regions for some investment cost. Determining which power generation technologies are most suitable for meeting the demand of a particular region requires analysis of tradeoffs between costs and environmental impacts. Models simulating different power generation technologies can help quantify these tradeoffs. An Internet-based modelling infrastructure called DOME (distributed object-based modelling environment) provides a flexible mechanism to create integrated models from independent simulation models for different power generation technologies. As new technologies appear, corresponding simulation models can readily be added to the integrated model. DOME was used to combine a simulation model for hybrid SOFC (solid oxide fuel cell) and gas turbine system with a power generation capacity and dispatch optimization model. The integrated models were used to evaluate the effectiveness of the system as a centralized power source for meeting the power demand in Japan. Evaluation results indicate that a hybrid system using micro-tube SOFC may reduce CO2 emissions from power generation in Japan by about 50%. Copyright © 2004 John Wiley & Sons, Ltd. [source] Stochastic unit commitment problemINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 1 2004Takayuki Shiina Abstract The electric power industry is undergoing restructuring and deregulation. We need to incorporate the uncertainty of electric power demand or power generators into the unit commitment problem. The unit commitment problem is to determine the schedule of power generating units and the generating level of each unit. The objective is to minimize the operational cost which is given by the sum of the fuel cost and the start-up cost. In this paper we propose a new algorithm for the stochastic unit commitment problem which is based on column generation approach. The algorithm continues adding schedules from the dual solution of the restricted linear master program until the algorithm cannot generate new schedules. The schedule generation problem is solved by the calculation of dynamic programming on the scenario tree. [source] Design and power management of a solar-powered "Cool Robot" for polar instrument networksJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 7 2007Laura E. Ray The Cool Robot is a four-wheel-drive, solar-powered, autonomous robot designed to support summertime science campaigns in Antarctica and Greenland over distances exceeding 500 km. This paper provides an overview of key features of the robot, including design for good mobility, high efficiency, and long-term deployment under solar power in harsh polar environments. The Cool Robot's solar panel box, comprising panels on four sides and a top panel, encounters insolation variations with a bandwidth of up to 1 Hz due to sastrugi. The paper details a unique photovoltaic control algorithm to accommodate these variations. We deployed the robot at Summit Camp, Greenland to validate its mobility and power budget and to assess the photovoltaic control system. The 61 kg robot drove continuously at 0.78 m/s on soft snow, its 160 W average power demand met by solar power alone under clear skies above 16° sun elevation. The power-control system reliably matched input with demand as insolation varied during testing. A simple GPS waypoint-following algorithm provides low-bandwidth path planning and course correction and demonstrated reliable autonomous navigation during testing over periods of 5,8 h. Field data validate the Cool Robot design models and indicate that it will exceed its design goal of carrying a 15 kg payload 500 km across Antarctica in 2 weeks. A brief description of instrument payloads and scientific studies aided by networks of such autonomous solar robots is provided. © 2007 Wiley Periodicals, Inc. [source] Designing man-portable power generation systems for varying power demandAICHE JOURNAL, Issue 5 2008Mehmet Yunt Abstract Portable electronic devices operate at varying power demand levels. This variability of power demand must be considered explicitly in the design of man-portable power generation systems for acceptable performance and portability. In this regard, a mathematical programming based design method is proposed. The method transcribes optimal operation of the system at a given power demand into a mathematical program. The power demand specific programs are incorporated into another upper level mathematical program encoding design requirements to form a final two-stage formulation. The design and operational parameters of the power generation system comprise a solution of the formulation. Unlike designs, based on a nominal power demand, the design guarantees that each power demand and all operational requirements can be satisfied. A detailed study of a microfabricated fuel-cell based system is performed. The proposed method produces smaller designs with significantly better performances than nominal power demand based approaches. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] The efficiency of natural gas futures marketsOPEC ENERGY REVIEW, Issue 2 2003Ahmed El Hachemi Mazighi Recent experience with the emergence of futures markets for natural gas has led to many questions about the drivers and functioning of these markets. Most often, however, studies lack strong statistical support. The objective of this article is to use some classical statistical tests to check whether futures markets for natural gas (NG) are efficient or not. The problem of NG market efficiency is closely linked to the debate on the value of NG. More precisely, if futures markets were really efficient, then: 1) spot prices would reflect the existence of a market assessment, which is proof that speculation and the manipulation of prices are absent; 2) as a consequence, spot prices could give clear signals about the value of NG; and 3) historical series on spot prices could serve as "clean" benchmarks in the pricing of NG in long-term contracts. On the whole, since the major share of NG is sold to power producers, the efficiency of futures markets implies that spot prices for NG are driven increasingly by power prices. On the other hand, if futures markets for natural gas fail the efficiency tests, this will reflect: 1) a lack of liquidity in futures markets and/or possibilities of an excess return in the short term; 2) a pass-through of the seasonality of power demand in the gas market; 3) the existence of a transitory process, before spot markets become efficient and give clear signals about the value of NG. Using monthly data on three segments of the futures markets, our findings show that efficiency is almost completely rejected on both the International Petroleum Exchange in London (UK market) and the New York Mercantile Exchange (US market). On the NYMEX, the principle of "co-movement" between spot and forward prices seems to be respected. However, the autocorrelation functions of the first differences in the price changes show no randomness of price fluctuations for three segments out of four. Further, both the NYMEX and the IPE fail, with regard to the hypothesis that the forward price is an optimal predictor of the spot price. Consequently, unless we have an increase in the liquidity of spot markets and an increase in the relative share of NG spot trading, futures markets cannot be considered as efficient. [source] Anwendung von massiv paralleler Berechnung mit Grafikkarten (GPGPU) für CFD-Methoden im BrandschutzBAUPHYSIK, Issue 4 2009Hendrik C. Belaschk Dipl.-Ing. Berechnungsverfahren; Brandschutz; calculation methods; fire protection engineering Abstract Der Einsatz von Brandsimulationsprogrammen, die auf den Methoden der Computational Fluid Dynamics (CFD) beruhen, wird in der Praxis immer breiter. Infolge der Zunahme von verfügbarer Rechenleistung in der Computertechnik können heute die Auswirkungen möglicher Brandszenarien nachgebildet und daraus nützliche Informationen für den Anwendungsfall gewonnen werden (z. B. Nachweis der Zuverlässigkeit von Brandschutzkonzepten). Trotz der erzielten Fortschritte reicht die Leistung von heute verfügbaren Computern bei weitem nicht aus, um einen Gebäudebrand mit allen beteiligten physikalischen und chemischen Prozessen mit der höchstmöglichen Genauigkeit zu simulieren. Die in den Computerprogrammen zur Berechnung der Brand- und Rauchausbreitung implementierten Modelle stellen daher immer einen Kompromiss zwischen der praktischen Recheneffizienz und dem Detailgrad der Modellierung dar. Im folgenden Aufsatz wird gezeigt, worin die Ursachen für den hohen Rechenbedarf der CFD-Methoden liegen und welche Problemstellungen und möglichen Fehlerquellen sich aus den getroffenen Modellvereinfachungen für den Ingenieur ergeben. Darüber hinaus wird ein neuer Technologieansatz vorgestellt, der die Rechenleistung eines Personalcomputers unter Verwendung spezieller Software und handelsüblicher 3D-Grafikkarten massiv erhöht. Hierzu wird am Beispiel des Fire Dynamics Simulator (FDS) demonstriert, dass sich die erforderliche Berechnungszeit für eine Brandsimulation auf einem Personalcomputer um den Faktor 20 und mehr verringern lässt. Application of general-purpose computing on graphics processing units (GPGPU) in CFD techniques for fire safety simulations. The use of fire simulation programs based on computational fluid dynamics (CFD) techniques is becoming more and more widespread in practice. The increase in available computing power enables the effects of possible fire scenarios to be modelled in order to derive useful information for practical applications (e.g. analysis of the reliability of fire protection concepts). However, despite the progress in computing power the performance of currently available computers is inadequate for simulating a building fire including all relevant physical and chemical processes with maximum accuracy. The models for calculating the spread of fire and smoke implemented in the computer programs therefore always represent a compromise between practical computing efficiency and level of modelling detail. This paper illustrates the reasons for the high computing power demand of CFD techniques and describes potential problems and sources of error resulting from simplifications applied in the models. In addition, the paper presents a new technology approach that significantly increases the computing power of a PC using special software and standard 3D graphics cards. The Fire Dynamics Simulator (FDS) is used as an example to demonstrate how the required calculation time for a fire simulation on a PC can be reduced by a factor of 20 and more. [source] Carbon Monoxide Mass Transfer for Syngas Fermentation in a Stirred Tank Reactor with Dual Impeller ConfigurationsBIOTECHNOLOGY PROGRESS, Issue 3 2007Andrew J. Ungerman This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding. [source] Power generation expansion planning with emission control: a nonlinear model and a GA-based heuristic approachINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2006Jiraporn Sirikum Abstract This paper presents an application of genetic algorithms (GA) for solving the long-term power generation expansion planning (PGEP) problem, a highly constrained nonlinear discrete optimization problem. The problem is formulated into a mixed integer nonlinear programming (MINLP) program that determines the most economical investment plan for additional thermal power generating units over a planning horizon, subject to the requirements of power demands, power capacities, loss of load probability (LOLP) levels, locations, and environmental limitations. Computational results show that the GA-based heuristic method can solve the PGEP problem effectively and more efficiently at a significant saving in runtime, when compared with a commercial optimization package. Copyright © 2005 John Wiley & Sons, Ltd. [source] SAR and power implications of different RF shimming strategies in the pelvis for 7T MRIJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009Bob van den Bergen MSc Abstract Purpose To determine the best radiofrequency (RF) shimming method for 7 T body imaging that provides sufficient B1+ excitation inside the target region while energy deposition (SAR) and power demands are as low as possible and that does not incorporate anatomy specific electric field information inside the patient models, as this information is not available in practice. Materials and Methods Finite difference time domain (FDTD) simulations were used to evaluate five RF shimming strategies for the pelvis inside a body coil. The results were compared to the theoretical best solution that could be achieved if the electric field inside the patient was known. Results Most of the RF shimming strategies were successful. However, between the different strategies a factor of two difference in average SAR reduction, a factor of three difference in local maximum SAR reduction, and a factor of 20 difference in power efficiency was observed. Phase matching was found to be the most promising RF shimming method for the body coil used and patient models. Conclusion RF shimming can reduce the SAR and improve power efficiency in an accurate patient model without knowing the electric field. However, choosing the right method is critical to prevent unexpected behavior in local SAR deposition. J. Magn. Reson. Imaging 2009;30:194,202. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||