Showing papers on "Power station published in 1995"

Alkali deposits found in biomass power plants: A preliminary investigation of their extent and nature. Volume 1

Abstract: Alkali in the ash of annual crop biomass fuels creates serious fouling and slagging in conventional boilers. Even with the use of sorbents and other additives, power plants can only fire limited amounts of these fuels in combination with wood. The National Renewable Energy Laboratory (NREL), US Department of Energy, and the biomass power industry carried out eight full-scale firing tests and several laboratory experiments to study the nature and occurrence of deposits with the goal of increasing the quantities of these biofuels that can be used. This report describes the results of the laboratory and power plant tests that included: tracking and analyzing fuels and deposits by various methods; recording operating conditions; and extensive laboratory testing. The paper describes the occurrence of deposits, fuel and deposit analyses, boiler design and operation, fouling and slagging indicators, and recommendations. 37 refs., 41 figs., 17 tabs.

Enhancing gas turbine performance by intake air cooling using an absorption chiller

Abstract: The performance of gas turbines, operated either as a simple cycle or a combined cycle, is critically constrained by the prevailing ambient temperature, particularly in arid and tropical climates This paper investigates the option of cooling the intake air to the compressor of the gas-turbine system using an absorption chiller in order to increase the gas turbine capacity High-temperature waste heat from the exhaust gas may be utilized to produce steam in a recovery boiler Part of the steam produced could then be used to drive a lithium-bromide double-effect absorption chiller which in turn could cool the incoming air An analysis carried out by taking the weather data of Bangkok (Thailand) indicates that reducing the temperature from ambient condition to 15°C could help to increase the instantaneous power output between 8 and 13% As an outcome, as much as 11% additional electricity could be generated from the same gas turbine power plant A simple economic assessment indicates that the proposed scheme will require a minimal investment as compared to the commissioning cost of a new gas turbine unit to meet the corresponding capacity increment The latter will need nearly four times higher initial cost than the amount estimated for the proposed scheme Thus, implementation of such a system would significantly abate the negative impact of the ambient temperature, while providing an economically and environmentally attractive option for energy producers in most developing nations of the world which are located in arid and tropical zones

Combined Power Plants—Past, Present, and Future

Abstract: The early history of combined power plants is described, together with the birth of the CCGT plant (the combined cycle gas turbine). Sustained CCGT development in the 1970s and 1980s, based on sound thermodynamic considerations, is outlined. Finally more recent developments and future prospects for the combined gas turbine/steam turbine combined plant are discussed.

Integrated plasmatron-turbine system for the production and utilization of hydrogen-rich gas

Abstract: An integrated plasmatron-turbine system which is capable of producing and utilizing clean burning hydrogen-rich gas is provided. The system may be incorporated into vehicles, stationary turbines, and the like to reduce emissions. The system may also be used to generate electricity in a power generating station. The system includes a plasmatron which reforms fuel into a hydrogen-rich gas and a turbine driven by the hydrogen-rich gas jet from the plasmatron. The turbine converts the heat and kinetic energy of the hydrogen-rich gas into electricity using an alternator. The alternator provides electricity to the plasmatron and may also be used to charge a battery for plasmatron initiation. Additional electricity may be used for other needs of the vehicle or stationary turbine. The hydrogen-rich gas can then utilized as clean burning fuel in a combustor coupled into the same turbine, in a second turbine or in an internal combustion engine.

Compressor drive system for a natural gas liquefaction plant having an electric motor generator to feed excess power to the main power source

Abstract: In a compressor drive system for a natural gas liquefaction plant including a plurality of gas turbines each provided in an individual refrigeration cycle for pressurizing a different refrigerant, an electric motor is provided for each of the gas turbines so as to serve both as an auxiliary electric motor for generating a startup torque and as an AC generator, and the excess output power of the gas turbine is converted into electric power by this electric motor when the power requirement of the associated compressor is less than the power output of the gas turbine. Additionally, at least two of the gas turbines are of an identical make which is suitable for driving the compressor of one of the associated refrigeration cycles requiring a larger driving power. Therefore, the gas turbines can be operated at optimum conditions at all times without regard to seasonal changes of the operating conditions, and the efficient operation of the gas turbines will result in a significant reduction in the operation costs through a substantial saving of fuel consumption. Moreover, any excess power output of one of the gas turbines can be allocated so as to reduce the burden of the in-plant power station and/or to supplement the shortage of the power output of the other gas turbine, and the management of the stand-by units and spare parts can be simplified. These factors have a compounded effect in reducing the investment costs of the plant.

Method and device for solar steam generation

Abstract: The invention concerns a method and device for solar steam generation. A medium is conveyed through pipes (1*), which are disposed in solar collectors (1), and from there it is guided to a turbine (3) after heating and evaporation. A medium whose enthalpy is greater than that of saturated water relative to the pressure in the pipe (1*) is fed, initially by a feed line (5, 5*, 5**), into said pipe (1*) in the solar collectors (1). In addition, the pressure of the medium to be fed in is greater than the pressure in the pipe (1*). The medium to be fed in can be high-pressure water or high-pressure steam. For this purpose, the feed line (5, 5*, 5**), for example, can emerge from a water-steam separator (9) or a high-pressure turbine (32) forming part of a power station.

A multiple objective linear programming model for power generation expansion planning

Abstract: SUMMARY The planning of new units for electrical power generation is a problem which involves different and conflicting aspects. Besides cost, security issues and environmental concerns must be explicitly incorporated into the models. In this way mathematical models become more realistic, and they enhance the decision maker’s comprehension of the complex and conflicting nature of the distinct aspects of the problem. A multiple objective linear programming model for power generation expansion planning is presented. The model considers three objective functions (net present cost of the expansion plans, reliability of the supply system, and environmental impacts) and three categories of constraints (load requirements, operational restrictions and budget). Three generating technologies are considered for power system expansion: oil, nuclear and coal.

Systems and control theory for power systems

Abstract: Bifurcation-theoretic issues in the control of voltage collapse.- Reduced-order modeling of electric machines using integral manifolds.- The BCU method for direct stability analysis of electric power systems: theory and applications.- New algorithms for slow coherency aggregation of large power systems.- Computational complexity results in parametric robust stability analysis with power systems applications.- Damping and resonance in a high power switching circuit.- Dynamic analysis of voltage collapse in power systems.- Exact convergence of a parallel textured algorithm for constrained economic dispatch control problems.- Variable structure regulation of power plant drum level.- Analysis of mechanisms of voltage instability in electric power systems.- Structural stability in power systems.- Power system load modeling.- Parallel solutions of linear equations by overlapping epsilon decompositions.- Insects, fish and computer-based super-agents.- Application of real-time phasor measurements in power system control.- On the dynamics of differential-algebraic systems such as the balanced large electric power system.- Robust stabilization of controls in power systems.

Integrated drying of feedstock feed to integrated combined-cycle gasification plant

Abstract: In a combined cycle gasification plant, high-pressure fuel gas from the gasification unit (16) is heated prior to combustion, and is then used to dry the feedstock (12). The moist fuel gas from the drying operation is combusted to drive the turbine in a power plant (22). Alternatively, high-pressure inert gas such as nitrogen is heated in the gasification unit (16) and is then used to dry the coal feed (12). Some of the moist inert gas is recycled, and some of it is passed to the combustion turbine in power plant (22).

Rotor heating as an indicator of system voltage instability

Abstract: Voltage stability hinges on the continuing control of the total power system's supply and demand of reactive power within the overall transmission, subtransmission and distribution networks which connects the power stations to the consumers. This is complicated by the elements interspersed within this extensive network that both supply and consume reactive power. Extensive collapses have followed disturbances more severe than considered at the planning stages, but there is a puzzling delay of minutes between the disturbance and collapse. By simulating the physical process, the critical factor has been found to be the action of rotor overcurrent protection in curtailing rotating unit reactive power output. The puzzling delay has been solved by the mathematical modelling of the generator rotor's thermal response which shows that above rated rotor current would take minutes to reach the rotor's temperature limit. The paper describes the heat run tests from which the parameters for mathematical rotor thermal models for 500 MW and 660 MW generators have been obtained. The algorithm that has been devised is both simple and reliable and allows computer evaluation, in a fraction of a second, of the time for rotor temperature limit to be reached. When integrated into SCADA, this information would give an early warning and so provide a valuable tool for the control system voltage stability. >

Harnessing the wind

Abstract: Wind power is now recognized as the one renewable-energy source on the verge of being economically viable. For developing countries, in fact, the technology is already practical for bringing pollution-free electricity to areas off the power grid. The author discusses the economic benefits of wind power and then discusses the basic principle involved in generating electricity from wind. The use of wind power by developing countries is outlined with particular reference to projects in Mexico and Indonesia. >

Feasibility of power production with pyrolysis and gasification systems

Abstract: The objective of the study was to evaluate the development potential of advanced power production systems based on biomass pyrolysis and gasification. Several alternative process configurations and power plant types (diesel, gas turbine, combined cycle) were compared to conventional steam cycle power plants. Electricity production capacities between 5 to 60 MWe were included. It was shown that although presently more expensive than conventional alternatives, all the new options have potential for further development. The biomass to power projects are most likely at sites, where low cost side products are available in countries, which have a favourable electricity tariff or subsidies for renewables. These projects are often small scale. Under these extreme circumstances capital intensive, high efficiency thermal biomass power technologies have difficulties in competing with conventional technology with lower investment cost and lower efficiency. However, environmental taxes and increasing fuel costs will improve the competitiveness of new biomass fuelled power plant concepts.

Electromagnetic heat engines and method for cooling a system having predictable bursts of heat dissipation

Abstract: Magnetic heat engines directly converting heat to electricity, using emf induced by demagnetization. Generated power manifests as negative resistance, and almost any kind and shape of magnetic medium can be used. Electromagnetic engines are also tolerant to non-uniform heating, inherently non-contact and non-mechanical, easy to model and design, and operable at high frequencies. The engines are suitable for augmenting local heating, refrigeration without fluid refrigerants, efficient cooling of cryogenic components, synchronous cooling of digital circuits, completely solid-state power generation, and improvement of power plant efficiency and control.

Power plant topping cycle repowering

Abstract: Traditionally, power plant repowering is defined as the replacement of a worn-out steam generator with a new steam generator meeting the original steam requirements so that the remaining life in the steam turbine and balance-of-plant equipment can be used. Because it is also possible to upgrade older power plants with a variety of technology improvements that have become available since the original plants were built, a number of power plant upgrade technologies are now included in the definition of power plant repowering. Another change, besides equipment wear-and-tear and technology advancements, that has overtaken older power plants is more restrictive environmental regulations. Repowering technologies are available for economically meeting more stringent mission standards while concomitantly improving power plant performance. Technology upgrades can be used to achieve a variety of improvements over the original power plant. These include low-cost capacity increases, lower heat rates, improved fuel flexibility, greater plant operating flexibility, reduced O and M costs, increased availability and reliability, along with achieving and maintaining environmental compliance. A figure provides ranges for the value of the savings available from the many identified repowering technologies. In many cases it will be necessary to identify many distinct savings to fully capture the benefits ofmore » a competitive repowering opportunity. The various repowering technologies will each have their own potential benefits; the size of these benefits will also depend on the existing site, power plant equipment, and competitive business environment.« less

A Mathematical Model of a Tubular Solid Oxide Fuel Cell

Abstract: The solid oxide fuel cell shows great potential as an efficient energy conversion system for use in central power stations. These cells can reform most hydrocarbon fuels with air to produce electricity and provide a heat source at 1,000 C while maintaining an efficiency of 60--75 percent. This paper describes a steady-state model for the prediction of voltage, current, and power from a single-cell tube. The model is a distributed parameter electrical network that includes the effects of mass transfer resistance (concentration polarization), chemical kinetic resistance (activation polarization), as well as relevant electrical resistance (ohmic losses). A finite-difference heat transfer model is also incorporated to allow for radial and axial temperature variations. The model computes the fuel and oxidant stream compositions as functions of axial length from energy and mass balances performed on each cell slice. The model yields results that compare favorably with the published experimental data from Westinghouse.