Showing papers on "Electricity generation published in 1999"

Thermoelectric Cooling and Power Generation

Abstract: In a typical thermoelectric device, a junction is formed from two different conducting materials, one containing positive charge carriers (holes) and the other negative charge carriers (electrons). When an electric current is passed in the appropriate direction through the junction, both types of charge carriers move away from the junction and convey heat away, thus cooling the junction. Similarly, a heat source at the junction causes carriers to flow away from the junction, making an electrical generator. Such devices have the advantage of containing no moving parts, but low efficiencies have limited their use to specialty applications, such as cooling laser diodes. The principles of thermoelectric devices are reviewed and strategies for increasing the efficiency of novel materials are explored. Improved materials would not only help to cool advanced electronics but could also provide energy benefits in refrigeration and when using waste heat to generate electrical power.

Pitch-controlled variable-speed wind turbine generation

Abstract: Wind energy is a viable option to complement other types of pollution-free generation. In the early development of wind energy, the majority of wind turbines were operated at constant speed. Recently, the number of variable-speed wind turbines installed in wind farms has increased and more wind turbine manufacturers are making variable-speed wind turbines. This paper covers the operation of variable-speed wind turbines with pitch control. The system the authors considered is controlled to generate maximum energy while minimizing loads. The maximization of energy was only carried out on a static basis and only drive train loads were considered as a constraint. In medium wind speeds, the generator and power converter control the wind turbine to capture maximum energy from the wind. In the high wind speed region, the wind turbine is controlled to maintain the aerodynamic power produced by the wind turbine. Two methods to adjust the aerodynamic power were investigated: pitch control and generator load control, both of which are employed to control the operation of the wind turbine. The authors analysis and simulation shows that the wind turbine can be operated at its optimum energy capture while minimizing the load on the wind turbine for a wide range of wind speeds.

Dispersed generation impact on distribution networks

Abstract: The insertion of dispersed generation into existing electric power systems has a great impact on real-time operation and planning. Several uncertainties characterize the ability of the existing power system to integrate this form of generation, Hence, dispersed generation must be taken into consideration in power system performance so that operation and security are not disturbed. Dispersed generation increases the complexity of controlling, protecting and maintaining power distribution systems. This article focuses on some technical aspects, but not on the impact on the quality of supply and on tariff signals.

Life Cycle Assessment of Coal-fired Power Production

Abstract: Coal has the largest share of utility power generation in the US, accounting for approximately 56% of all utility-produced electricity (US DOE, 1998). Therefore, understanding the environmental implications of producing electricity from coal is an important component of any plan to reduce total emissions and resource consumption. A life cycle assessment (LCA) on the production of electricity from coal was performed in order to examine the environmental aspects of current and future pulverized coal boiler systems. Three systems were examined: (1) a plant that represents the average emissions and efficiency of currently operating coal-fired power plants in the US (this tells us about the status quo), (2) a new coal-fired power plant that meets the New Source Performance Standards (NSPS), and (3) a highly advanced coal-fired power plant utilizing a low emission boiler system (LEBS).

Wind speed and power forecasting based on spatial correlation models

Abstract: Wind energy conversion systems (WECS) cannot be dispatched like conventional generators. This can pose problems for power system schedulers and dispatchers, especially if the schedule of wind power availability is not known in advance. However, if the wind speed can be reliably forecasted up to several hours ahead, the generating schedule can efficiently accommodate the wind generation. This paper illustrates a technique for forecasting wind speed and power output up to several hours ahead, based on cross correlation at neighboring sites. The authors develop an artificial neural network (ANN) that significantly improves forecasting accuracy comparing to the persistence forecasting model. The method is tested at different sites over a year.

An axial-flux permanent-magnet generator for a gearless wind energy system

Abstract: The paper discuses the development of an axial-flux permanent-magnet generator for a gearless wind energy system which aims to demonstrate the feasibility of integrating wind and photovoltaic energy converters for the generation of electricity and to achieve optimum exploitation of the two energy sources. The merits of an axial-flux generator topology are discussed with reference to the particular requirements of an electrical generator for a direct-coupled wind turbine application. The design, construction and test results of a 5 kW, 200 rev/min permanent-magnet generator, to form a 10 kW pilot power plant with a 5 kW photovoltaic array, are presented.

On the Efficiency of Electric Power Generation With Piezoelectric Ceramic

Abstract: This paper analyzes the efficiency of piezoelectric ceramic for purposes of electric power generation. An analytical model is presented which suggests that the primary problem of using PZT for electric power generation is that most energy is stored in the ceramic and returned to the mechanical port. The efficiency as a function of force input frequency and resistive load are derived based upon a linearized model of a commercially available PZT stack. The analysis yields counterintuitive results in that maximum efficiency occurs in a low frequency region, several orders of magnitude below the structural resonance of the stack. The analytical results are followed by presentation of experimental data that substantiate the model. The model is then utilized to show that. due to hysteresis in the ceramic, the efficiency of energy transfer is dependent on the amplitude of force input, and that greatest efficiencies can be achieved with maximum input forces.

High efficiency and high concentration in photovoltaics

Abstract: In this paper, we present the state-of-the-art of multijunction solar cells and the future prospects of this technology. Their use in terrestrial applications will likely be for concentrators operating at very high concentrations. Some trends are also discussed and we present a cost calculation showing that highly efficient cells under very high concentration would be able to produce electricity at costs competitive with electricity generation costs for some utilities.

An overview of thermophotovoltaic generation of electricity

Abstract: This paper provides an overview of the developments in thermophotovoltaic (TPV) generation of electricity that have occurred relatively recently-from about 1994 to October 1998. The components considered are the semiconductor converter; the radiator; and the means of recirculating unusable, long-wavelength photons. A short account of the functions and performance of each of these components is given. Also discussed are operational systems and progress in modeling TPV systems.

The design of high-efficiency line-start motors

Abstract: In this paper, techniques for improving the efficiency of small line-start motors are investigated. Through a combination of formal optimization methods and standard design techniques, the efficiency of an induction motor is increased by 4%. This motor is then used as a basis for the design of a line-start permanent-magnet (LSPM) motor. Steady-state and dynamic finite-element analysis of the LSPM motor indicate that significant efficiency improvements are obtained and that the motor will start when fully loaded.

Development of vanadium redox flow battery for electricity storage

Abstract: There is serious demand today for superior technology for load levelling placed on power generation and transmission facilities. The vanadium battery, developed by Kashima-Kita, uses vanadium compounds as an electrolyte, recovered from boiler soot in Orimulsion-fired power stations to provide a solution to this problem. This battery is eminently suitable for load levelling, being operable at room temperature and normal pressure, easily convertible to a large scale and is environmentally friendly. In September 1997, Kashima-Kita built a 200 kW/spl times/4 hour-rate battery after having built both 2 kW and 10 kW prototype units. The battery is interconnected to the company's power plant grid system and has to date achieved 650 cycle continuous operation at the rated efficiency. This success has proved that a high-efficiency heat power station system equipped with such an electricity storage battery reusing byproducts of the power plant can be commercially viable.

Electricity generation from solid biomass via co-combustion with coal

Abstract: The environmental effects of electricity production from different biofuels by means of co-combustion with hard coal in existing coal fired power plants are analysed and compared to electricity production from hard coal alone based on Life Cycle Analysis (LCA). The use of straw and residual wood at a 10% blend with coal in an existing power plant in the southern part of Germany shows that all investigated environmental effects are significantly lower if biomass is used instead of coal. Thus based on the available and proven technology of co-combustion of hard coal and biomass in existing power plants a significant contribution could be made to a more environmentally sound energy system compared to using coal alone.

A method for simulation and analysis of reactive power market

Abstract: This paper presents a method for the simulation and analysis of alternative reactive power market arrangements based on combined reactive power capacity and energy payments. The value of reactive power support, in terms of both capability and utilisation, of each particular generator is quantified using a developed security constrained reactive optimal power flow. The relative competitiveness of participating generators is also assessed for a spectrum of arrangements between a reactive capacity and a reactive utilisation based market. Also, the conflicting objectives of the system operator, as a purchaser of reactive power service, and generators, as suppliers of the services, are analysed.

Communications processor remote host and multiple unit control devices and methods for micropower generation systems

Abstract: A communications processor is disclosed for a power generation system that permits data and control signals to be communicated to and from the power generation system and a host computer. The control signals include a power level command and power factor that are sent from a remote host to the power generation system which responds by delivering the requested power level having the desired power factor to a grid. The remote host receives performance data that permits an operator to accurately gauge the performance of the power generation system including the performance and any fault conditions of a line power unit, generator, and engine driving the generator. The communications processor unburdens the line power unit controller that is responsible for controlling power generation from the task of processing input data and driving local displays. The host may also be provided at a location remote from the power generation system. The host, local or remote, preferably includes a graphical user interface that permits an operator to monitor and control the power generation system in an efficient and highly effective manner. A dedicated serial bus connects the communications processors of multiple power generation systems. By utilizing a round-robbin polling of each power generation system across the dedicated serial bus, real-time control can be achieved.

Development of Pump Turbine for Seawater Pumped- Storage Power Plant

Abstract: Acquiring a pumped-storage power generation site utilizing river water recently faces several restrictions due to environmental assess- ment. On the other hand, there are many sites favorable for constructing a pumped-storage power plant utilizing seawater in Japan, which is surrounded by the sea. Seawater pumped-storage power plants have several advantages such as lower civil construction cost and lower power distribution cost due to their proximity to nuclear or steam turbine power plants. Seawater pump turbines are used under the condition where the corrosion environment is noticeably severe, rather than conventional river water pump turbines. In addition, pump turbines have many narrow spaces between parts and their major parts are embedded, so that it would be very difficult to apply proper corrosion prevention measures. This problem cannot be solved only by conventional corrosion-preventive engineering. The Agency of Natural Resources and Energy of the Ministry of International Trade and Industry entrusted Electric Power Development Co., Ltd. with the construction of the world's first seawater pumped-storage pilot plant in Kunigami Village in Okinawa Prefecture, Japan, to execute verification tests for five years after the completion of construction in March, 1999. This paper will deal with materials, structure, and corrosion-preventive engineering of the pump turbine for the seawater pumped-storage power plant.

Footwear with hydroelectric generator assembly

Abstract: A hydroelectirc generator assembly for use in footwear includes a pair of fluid filled sacs contained in the sole of the footwear. The sacs are connected by conduits whereby, when the footwear is used for walking, fluid is transferred between the sacs, via the conduits. A turbine positioned between the conduits is rotated by the moving fluid thereby resulting in the generation of electricity.

Improved power plant with carbon dioxide capture

Abstract: Method for low pollution power generation by combusting a fuel with a supply of highly concentrated oxygen in a combustion chamber (714), to which recirculated combustion products are introduced for temperature control, characterized in that all or parts of the combustion products are cooled (727) to an appropriate temperature which keeps all or most of the water vapor from condensing from said products, before said products are compressed and recirculated to the combustion chamber.

A neural-based redispatch approach to dynamic generation allocation

Abstract: A redispatch approach based on the Hopfield neural network is proposed for solving the dynamic generation allocation problem. This paper considers the dynamic dispatch problem that involve the allocation of system generation optimally among dispatchable generating units while tracking a load curve and observing power ramping response rate limits of the units, system spinning reserve requirements. The solution algorithm for solving the dynamic economic dispatch problem is divided into two major stages. First, the lambda-iteration method is employed to obtain the static economic dispatch as the base case. Then, the dynamic economic dispatch problem is linearized about this base case and is solved using the Hopfield neural network redispatch approach. This method has been successfully applied to a utility system. The results are given to show the efficiency of the proposed method.

Power conditioning apparatus with energy conversion and storage

Abstract: A method and apparatus for power conditioning and for storing electrical energy, fossil fuel energy, or both in the form of a compressed gas which may then be used in combination with a fossil fuel to generate conditioned electrical power is disclosed. The present invention provides a method wherein the energy so stored is used as a back-up power source to assure uninterrupted conditioned electrical power in the event of a failure of a primary electrical power source. Turbine rotors are maintained in rotation to provide a spinning reserve in that the inertia of the turbines can be used to generate power in the event of minor power disruptions, and the turbines can be powered for producing power in the event of greater power disruptions. The present invention provides an apparatus that enhances the flexibility and efficiency of a power consumer and the internconnected power providing system by allowing the user to have an efficient spinning reserve of power, by providing the capability of a user to shape the load, thereby reducing the spinning reserve requirement of the interconnected system, and to sell excess power and to control transportation costs. Since the present invention allows a user to purchase power from the most efficient source, the present invention promotes efficiency throughout the power generation and power transportation industry.

Flexible inorganic electrolyte fuel cell design

Abstract: Fuel cell designs (25) incorporating non-planar inorganic electrolyte membranes offer improved mechanical and thermal shock resistance for mobile power generation systems, e.g., for high temperature fuel cell applications using liquid fuel (diesel and gasoline) and air for automobile power plants and other power systems requiring only intermittent high-temperature fuel cell operation.