Showing papers on "Electricity generation published in 1993"

Protection against loss of utility grid supply for a dispersed storage and generation unit

Abstract: The requirements of an islanding, or 'loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system. >

Constant voltage fuel cell with improved reactant supply and control system

Abstract: A method and apparatus for providing a substantially constant output voltage from a fuel cell, notwithstanding output current variations, is disclosed. The voltage and secondarily the current of the cell is determined at least periodically. The pressure of the reactant gas in the fuel cell is then regulated so substantially the nominal voltage is maintained. The temperature in the fuel cell may also be regulated to maintain the nominal output voltage. Also, a method and apparatus for minimizing the parasitic power drain in an electric power generation system is disclosed. The fuel cell is fed with a reactant gas by a compressor driven by parasitic power drawn from the fuel cell. The method is carried out by determining that the output current of the fuel cell has changed, and changing one or more or the pressure, the mass flow rate and the reactant utilization ratio of the reactant in the fuel cell, thereby changing the amount of the parasitic power drawn from the electrical power output to drive the compressor.

Directions of research on electric power quality

Abstract: Several important research areas in electric power quality are described. Aspects of electric power quality are categorized as fundamental concepts, modeling and analysis, measurement and instrumentation, sources, solutions, effects, and educational issues. The goals are to identify the high-priority research areas in electric power quality and to stimulate interest in this topic. >

Advanced gasification-based biomass power generation

Abstract: A promising strategy for modernizing bioenergy is the production of electricity or the cogeneration of electricity and heat using gasified biomass with advanced conversion technologies Major advances that have been made in coal gasification technology, to marry the gas turbine to coal, are readily adaptable to biomass applications Integrating biomass gasifiers with aeroderivative gas turbines in particular makes it possible to achieve high efficiencies and low unit capital costs at the modest scales required for bioenergy systems Electricity produced with biomass-integrated gasifier/gas turbine (BIG/GT) power systems not only offers major environmental benefits but also would be competitive with electricity produced from fossil fuels and nuclear energy under a wide range of circumstances Initial applications will be with biomass residues generated in the sugarcane, pulp and paper, and other agro- and forest-product industries Eventually, biomass grown for energy purposes on dedicated energy farms will also be used to fuel these gas turbine systems Continuing improvements in jet engine and biomass gasification technologies will lead to further gains in the performance of BIG/GT systems over the next couple of decades Fuel cells operated on gasified biomass offer the promise of even higher performance levels in the period beyond the turn of themore » century 79 refs, 21 figs, 11 tabs« less

Wave power conversion by a prototype wave power extracting caisson in sakata port

Abstract: Ocean wave energy is clean and inexhaustible. Repeated oil crises and the urgent need for environmental preservation on a global scale have made utilization of ocean wave energy increasingly important. The Japanese Ministry of Transport has been developing a wave power extracting caisson breakwater which can absorb wave power and convert it into electric power. The breakwater shown in Fig.l is a composite breakwater with a special caisson for absorption and conversion of wave power. The caisson has a so-called air chamber where wave power is converted into air power. The air power activates a turbine-generator in the machine room on the caisson. The use of the breakwater as a wave power converter will effectively cut down the power generation cost. This breakwater also aims at the improvement of the wave resisting stability and performance as a breakwater by absorbing the wave energy.

Variable-reluctance generators in wind-energy systems

Abstract: Two methods of incorporating the variable-reluctance generator (VRG) into advanced wind conversion systems at or above the 50-kW power level are presented. Operating through a power electronic interface to the electric utility, this generator offers simplifications of the utility/generator interface over adjustable-speed wind conversion systems based on the induction generator. In addition, analyses performed using experimentally based data show that the VRG system is as much as 6% more efficient and up to 13% less expensive than a comparably rated induction generator system. These analyses are based on a piecewise linearization of the nonlinear VRG characteristics. At comparable power levels, the VRG can offer superior utility power-quality relative to the induction generator systems presently under development, and also offers a reduction in the operating, maintenance, and energy costs associated with advanced wind-energy systems. >

Electric power distribution module for an electric power generation and distribution system

Abstract: This invention relates to an electric power generation and distribution system, and more particularly to an electric power distribution module for use in such systems, having an insulative support structure which includes integral therewith electrically conductive means which define a circuit for distributing electric power received from one or more power sources to one or more electrical loads, the insulative support structure also including integral therewith current sensing means for sensing a flow of electrical current in the electrically conductive means.

Method and apparatus for controlling an air conditioner with a solar cell

Abstract: A DC power supply bus is used.to connect a solar cell to an outdoor unit of air conditioners. The output voltage of each outdoor unit is so controlled as to maximize the power generation efficiency of the solar cell and the DC power supplid to the air conditioner is regulated to predetermined value.

Solar-thermal electric technology

Abstract: Significant progress has been made in developing economically competitive solar-thermal electric technologies. During the early 1980s, several important pilot plants were constructed and successfully operated, thus establishing the technology`s feasibility. Today more than 350 mega-watts of electricity are generated by commercial solar-thermal plants in the US, and the experience gained from those plants, in addition to research and development activities, has helped reduce the cost of solar-thermal systems to one-fifth that of the early pilot plants. Continued technological improvements are likely to reduce costs further, while enhancing performance levels. These advances, along with cost reductions made possible by large-scale production, construction of a succession of power plants, and scale-up to plant sizes of 100 to 200 megawatts of electricity, promise to make solar-thermal systems cost-competitive with fossil-fuel plants. Solar-thermal technologies are appropriate for a wide range of applications, including central-station power plants, where they can meet peak utility and intermediate load needs, and modular power plants in both remote and grid-distributed areas. 101 refs., 34 figs., 13 tabs.

An assessment of ocean thermal energy conversion as an advanced electric generation methodology

Abstract: The history of ocean thermal energy conversion (OTEC), a process that employs the temperature difference between surface and deep ocean water to alternately evaporate and condense a working fluid, is reviewed. In the open-cycle OTEC configuration, the working fluid is seawater. In the closed-cycle configuration, a working fluid such as propane is used. OTEC is assessed for its practical merits for electric power generation. Because rather large amounts of seawater and working fluid are required, the energy requirements for pumping them may be greater than the energy recovered from the OTEC engine itself. The concept of net power production is discussed. The components of a typical OTEC plant are described with emphasis on the evaporator heat exchanger. Operation of an OTEC electric generating station is discussed, including transient operation. Recent experiments and efforts at the National Energy Laboratory-Hawaii (NELH) are summarized. Remarks are made on bottlenecks and the future of OTEC as an advanced electric generation methodology. >

Economical, PV maximum power point tracking regulator with simplistic controller

Abstract: A 30% cost reduction of photovoltaic generation can be brought about by the investment in a novel, highly efficient maximum power point tracker (MPPT). Such a power converter is currently under development, implementing a feedforward output current controller as tracking algorithm. The DC-DC power converter, typical of a MPPT, exploits the efficient high-frequency operation, associated with zero-transition switching. Thus the output filter only consists of the combination of a storage battery and its cabling. The resulting power converter is suitable for integration into standard PV panels during manufacturing. The efficiency of the MPPT is 96% for a range of output powers at a low battery voltage of 12.5 V and a component cost of US$21.00. >

Solar pond technology

Abstract: Solar pond technology has made substantial progress in the last fifteen years. This paper reviews the basic principles of solar ponds and the problems encountered in their operation and maintenance. The factors which influence the technical and economic viability of solar ponds for thermal applications and power generation have been discussed.

Biomass gasification: Environmentally sound technology for decentralized power generation, a case study from India

Abstract: This study aims at understanding the need for decentralized power generation systems and to explore the potential, feasibility and environmental implications of biomass gasifier-based electricity generation systems for village electrification. Electricity needs of villages are in the range of 5–20 kW depending on the size of the village. Decentralized power generation systems are desirable for low load village situations as the cost of power transmission lines is reduced and transmission and distribution losses are minimised. A biomass gasifier-based electricity generation system is one of the feasible options; the technology is readily available and has already been field tested. To meet the lighting and stationary power needs of 500,000 villages in India the land required is only 16 Mha compared to over 100 Mha of degraded land available for tree planting. In fact all the 95 Mt of woody biomass required for gasification could be obtained through biomass conservation programmes such as biogas and improved cook stoves. Thus dedication of land for energy plantations may not be required. A shift to a biomass gasifier-based power generation system leads to local benefits such as village self reliance, local employment and skill generation and promotion of in situ plant diversity plus global benefits like no net CO2 emission (as sustainable biomass harvests are possible) and a reduction in CO2 emissions (when used to substitute thermal power and diesel in irrigation pump sets).

A novel approach to minimize line-current harmonics in interfacing power electronics equipment with 3-phase utility systems

Abstract: A novel approach is presented to achieve nearly sinusoidal line current rectification of three-phase utility voltages by DC link current modulation. Significant benefits of this approach are: only two transistor switches are required; a regulated DC voltage is provided at the output, thus simplifying the design of the rest of the power electronics equipment; the output DC voltage, which can be quite large, is automatically shared equally by two series-connected capacitors; and the usual disadvantages of passive filters are avoided. This approach can be applied to most of the power electronics equipment with three-phase utility input, as well as to interface generation using renewable energy resources such as wind and solar power. >

Utilization of interrupted energy assessment rates to evaluate reliability worth in electric power systems

Abstract: The adequacy assessment of electric power systems is discussed. Power system planning is concerned both with the level of predicted reliability and the investment/operation alternatives associated with satisfying the desired level. The total societal cost consists of costs associated with required investments and operation of the system and the customer unsupplied energy costs due to electric supply interruptions. The predicted system reliability in quantitative terms and the consumer costs associated with supply interruptions can be used to compute the customer unserved energy costs. This association is formed by the development of a reliability worth factor designated as the interrupted energy assessment rate (IEAR). The authors show how IEAR can be utilized in a generating capacity adequacy study, composite system adequacy study and at each individual customer load point and/or sectors within the overall electric power system in an assessment of the monetary worth of reinforcements. >

Multi-area analysis of small signal stability in large electric power systems by SMA

Abstract: The authors present an efficient methodology for the analysis of small signal stability in large electric power systems. It is based on the selective modal analysis approach and assumes a multi-area structure of the small signal behavior in large power systems. In the proposed procedure, the system modes are separated into two categories (the inter-area and the intra-area modes) and are independently determined. Results of the application to a realistic large power system with 266 generators and 1472 buses are discussed. >

Gas Turbine Topping Stage Based on Energy Exchangers: Process and Performance

Abstract: Power generation in gas turbines is facing three main challenges today:• Low pollution prescribed by legal requirements.• High efficiency to obtain low operating cost and low CO2 emissions.• High specific power output to obtain low product and installation cost.Unfortunately, some of these requirements are contradictory: high efficiency and specific power force the development towards higher temperatures and pressures which increase NOx emissions and intensify the cooling and material strength problems. A breakthrough can be achieved by applying an energy exchanger as a topping stage. Inherent advantages are the self-cooled cell-rotor which can be exposed to much higher gas temperature than a steady-flow turbine and a very short residence time at peak temperature which keeps NOx emissions under control.The basic idea has been proposed long time ago. Fundamental research has now led to a new energy exchanger concept. Key issues include symmetric pressure-wave processes, partial suppression of flow separation and fluid mixing, as well as quick afterburning in premixed mode. The concept has been proven in a laboratory-scale engine with very promising results. The application of an energy exchanger as a topping stage onto existing gas turbines would increase the efficiency by 17% (relative) and the power by 25%. Since the temperature level in the turbine remains unchanged, the performance improvement can also be fully utilized in combined cycle applications. This process indicates great potentials for developing advanced gas turbine systems as well as for retrofitting existing ones.Copyright © 1993 by ASME

Use of biomass in electric power generation: the california experience

Abstract: This paper considers the performance and operating characteristics of the 46 power plants in central and northern California presently generating electric power using wood wastes and/or agricultural residues to fire steam turbines. The paper is a synopsis of an assessment of the more than 750 MW of biomass-fueled capacity providing power to the PG&E grid which came on line during the past decade, following the passage of the federal Public Utility Regulatory Policies Act. The plants are fueled by sawdust or pulp process wastes, hog fuel, in-forest thinnings, clean landfilled wood, orchard and vineyard wastes, and other agricultural residues. The challenges associated with combustion of agricultural residues have proved to be much greater than had been anticipated. The smallest plant provides less than 3 MW of power to the utility grid and the largest nearly 50 MW. Overall they consume more than 7 million bone dry tons (BDT) of fuel each year, using about 1 BDT to generate 1 MWh, an overall efficiency of about 20%. Lack of a fuels supply infrastructure resulted in a very tight fuels market and resultant high spot market prices during 1989 and 1990. Nevertheless, most of the plants have had a capacity factor of greater than 80%, though there have been problems associated with design, management and fuels procurement at some others. Some of the plants were constructed from rehabilitated boilers and turbines and have minimal environmental controls; others reflect the best of fluidized bed combustion technologies, with non-catalytic deNOx and “zero-discharge” water treatment capability. Future research should include work on harvesting and collection technologies, better characterization of the fuel resources and integrated programs to produce and use biomass to fuel advanced generation technologies, such as gas turbines and fuel cells.

The opportunities for electricity production from biomass by advanced thermal conversion technologies

Abstract: The opportunities for biomass exploitation in Europe as an energy crop to replace food production are described. Annual energy crops could offer farmers a financial return similar to that from food production, where benefits from the higher productivity of the C4 crops are available. These crops can be converted to a variety of fuel products of which bio-oil, generated by flash pyrolysis of biomass, is particularly attractive due to its high energy density. The bio-oil can be used as a fossil fuel substitute for combustion and electricity generation. The range of possibilities for electricity production in centralised and decentralised facilities are summarised and cost estimates provided for a number of the main products.

Optimal operation of photovoltaic/diesel power generation system by neural network

Abstract: An artificial neural network is applied to the operation control of the photovoltaic/diesel hybrid power generation system. The optimal operation patterns of the diesel generator are calculated by dynamic programming (DP) under the known insolation and load demand, which minimize the fuel consumption of the diesel generator. These optimal patterns are learned by the three layer neural network, and it is tested for the different insolation and demand data from those used in the learning. Two kinds of neural networks are examined, and the results are compared with each other. >

Utility strategies for using renewables

Abstract: Electric utilities will play a key role in determining the contribution renewables will make in electric markets. Utility investment in renewables will be considered in the context of investment portfolios that will include a range of new technologies for generating electricity as well as new technologies for increasing the efficiency of energy use, for electric transmission and distribution, and for storing electric energy. If public policy encourages utilities to invest in ways that minimize energy service costs and environmental costs, renewable electric generation could play a major role. Renewable equipment likely to be available early in the 21st century could provide more than 80% of the energy inputs of modern utilities at prices no higher than those charged for electricity today. The appropriate mix of hydroelectric, biomass, and intermittent (wind, photovoltaics, solar thermal) systems depends on local resources. Intermittent resources should be able to meet at least one third of the utility`s energy needs without adverse effects on costs. The value of each type of renewable technology is strongly affected by its scale, location and the characteristics of other generating equipment operating in the region. Advanced natural-gas turbine systems, for example, make a good match with renewables. It is possiblemore » that advanced, fossil-powered equipment capable of very high efficiencies may be able to produce electricity at a slightly lower cost than advanced renewable equipment (both could be producing at prices below current electricity costs), but renewable equipment may still be preferred because of its environmental benefits.« less

Photovoltaic electricity generation by solar cells

Abstract: The electricity generation uses photovoltaic solar modules whose cells are cooled by air flow, wind, or pref. liq. or gaseous coolants, or by movement for the temp. control. The waste heat from cooling is pref. used for heating via heat pumps or similar cold-hot machines. If the solar cells are exposed to snow or front they are quickly heated, pref. by their own energy generation. The photovoltaic cells are mounted in physical contact on or within a plate-shaped base which is temp. controlled, i.e. gas or liq. cooled.

System separation equipment to minimize power system instability using generator's angular-velocity measurements

Abstract: The purpose of the equipment described is to separate the power system when an out-of-step between two groups of generators within it is predicted. The out-of-step prediction method is based on the generator's angular-velocity data measured by electromagnetic sensors and gears that are fastened directly to the rotors. The equipment was tested by the large-scale power system simulator APSA (Advanced Power System Analyzer) and was also field tested. The results are presented. >

Proceedings of the sixth international symposium on environmental degradation of materials in nuclear power systems - water reactors

Abstract: The operation of water reactor nuclear power plants provides a significant fraction of the world's electric power generation. At the end of 1992, approximately 360 such plants were in operation, representing a total generating capacity of 320 GWe. As these plants age, and as new designs evolve, the impact of environmental degradation of reactor materials on reliability and power plants economics is receiving increasing recognition. The Sixth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors was organized to provide a forum for exchange of the results of research and plant operating experience associated with material degradation.

Comparative Evaluation of Combined Cycles and Gas Turbine Systems With Water Injection, Steam Injection and Recuperation

Abstract: Combined cycles have gained widespread acceptance as the most efficient utilization of the gas turbine for power generation, particularly for large plants. A variety of alternatives to the combined cycle that recover exhaust gas heat for re-use within the gas turbine engine have been proposed and some have been commercially successful in small to medium plants. Most notable has been the steam injected, high-pressure aero-derivatives in sizes up to about 50 MW. Many permutations and combinations of water injection, steam injection, and recuperation, with or without intercooling, have been shown to offer the potential for efficiency improvements in certain ranges of gas turbine cycle design parameters.A detailed, general model that represents the gas turbine with turbine cooling has been developed. The model is intended for use in cycle analysis applications. Suitable choice of a few technology description parameters enables the model to accurately represent the performance of actual gas turbine engines of different technology classes. The model is applied to compute the performance of combined cycles as well as that of three alternatives. These include the simple cycle, the steam injected cycle and the dual-recuperated intercooled aftercooled steam injected cycle (DRIASI cycle). The comparisons are based on state-of-the-art gas turbine technology and cycle parameters in four classes: large industrial (123–158 MW), medium industrial (38–60 MW), aeroderivatives (21–41 MW) and small industrial (4–6 MW). The combined cycle’s main design parameters for each size range are in the present work selected for computational purposes to conform with practical constraints.For the small systems, the proposed development of the gas turbine cycle, the DRIASI cycle, are found to provide efficiencies comparable or superior to combined cycles, and superior to steam injected cycles. For the medium systems, combined cycles provide the highest efficiencies but can be challenged by the DRIASI cycle. For the largest systems, the combined cycle was found to be superior to all of the alternative gas turbine based cycles considered in this study.Copyright © 1993 by ASME

Propulsion powered electric guns-a comparison of power system architectures

Abstract: Alternative power system architectures and interface technologies for driving high-energy pulsed loads from the propulsion equipment of naval surface combatants are compared. Gas turbine mechanical and gas turbine integrated electric drive propulsion trains are considered as prime power sources. Focus is on the energy path between the ship's prime power and the pulsed load, comparing system candidates on a size, weight, and component cost basis. A capacitor-based pulse forming network (PFN) supplying an electrothermal chemical gun is utilized as the common load for all configurations. Results indicate that dedicated auxiliary generators driven from propulsion gas turbine engines are the preferred method of powering electric gun PFNs from ship drive-train equipment. Auxiliary generator-based systems are compact and lightweight over a wide power range, are equally attractive with both electric and mechanical drive trains, and demonstrate retrofit potential to the current fleet. >