Electric Power Plant


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electric power plant

[i¦lek·trik ′pau̇·ər ‚plant]
(mechanical engineering)
A power plant that converts a form of raw energy into electricity, for example, a hydro, steam, diesel, or nuclear generating station for stationary or transportation service.

Electric Power Plant

 

an aggregate of installations, and equipment directly involved in the production of electricity, together with the requisite buildings and structures located within a specified area. Depending on the energy source used, a distinction is made between fossil-fuel-fired steam power plants, hydroelectric power plants, pumped-storage hydroelectric power plants, atomic power plants, tidal electric power plants, wind-power plants, geothermal electric power plants, and electric power plants that use a magnetohydrodynamic generator.

Fossil-fuel-fired steam power plants are the foundation of a country’s energy industry; they produce electricity by converting the thermal energy released during the combustion of an organic fuel. They are classified according to the type of equipment as steam-turbine, gas-turbine, and diesel power plants.

The basic power equipment in modern steam-turbine power plants comprises a boiler unit, steam turbines, and turbine generators together with superheaters, feed pumps, condensate pumps, circulating pumps, condensers, air preheaters, and electrical distribution equipment. The plants are subdivided into condensation electric power plants and district heat and power plants.

In condensation electric power plants the heat obtained from the combustion of fuel converts water into steam in a boiler, from which the steam is fed into a condensing turbine; the internal energy of the steam is converted to mechanical energy in the turbine and then into electric current by an electric generator. The spent steam is bled off to a condenser, from which condensate is pumped back to the boiler. The condensation electric power plants operating in the energy systems of the USSR are also called state regional electric power plants.

Unlike condensation electric power plants, the superheated steam in district heat and power plants is not completely used up in the turbines but is partially diverted for district heat supply. The integrated use of the heat substantially increases the efficiency of fossil-fuel-fired steam power plants and significantly reduces the cost per kilowatt-hour of the electricity generated.

Between the 1950’s and 1970’s, gas turbines were introduced in electric power plants. Gas-turbine installations ranging from 25 to 100 megawatts (MW) are used as reserve power sources to meet loads during peak hours or to handle emergencies that may occur in energy systems. A promising application is the use of combination steam-gas installations, in which the combustion products and heated air are fed to a gas turbine and the heat of the exhaust gases is used to heat water or produce steam for low-pressure steam turbines.

Diesel power plants are equipped with one or more electric generators driven by diesel engines. Stationary diesel power plants have four-cycle diesel units with power ratings from 110 to 750 MW. Both stationary diesel power plants and diesel-equipped power trains (whose operating characteristics are similar to those of stationary power plants) may have several diesel engines with power ratings up to 10 MW. Mobile diesel electric power plants with ratings from 25 to 150 kilowatts (kW) are usually mounted in motor vehicles (semitrailers) or on a separate railroad chassis (at a railroad platform or in a car). Diesel electric power plants are also used in agriculture, the lumber industry, and prospecting as primary, reserve, and emergency sources for power and lighting networks. They are used in transportation as primary power plants in diesel-electric locomotives and ships.

Hydroelectric power plants produce electricity by converting the energy of a stream of water. Such plants include hydraulic engineering structures (such as a dam, water conduits, and water intakes), which provide the necessary concentration of water flow and create a pressure head, in addition to power equipment (hydroturbines, hydroelectric generators, and distribution equipment). The concentrated and directed flow of water rotates the hydroturbine and the hydroelectric generator coupled to it.

Depending on the design format for using the water resources and concentrating the pressure heads, hydroelectric power plants are usually classified as channel, dam, diversion, pumped-storage, and tidal types. Channel and dam power plants are situated on high rivers in plains areas and in narrow valleys on mountain streams. The pressure head is created by a dam, which partitions the river and raises the water level of the upper pond. In channel power plants the building housing the hydroelectric units is usually a part of the dam. In diversion power plants water is diverted from the river channel into a water conduit with a slope less than the average slope of the section of the river being tapped; the conduit leads to the power-plant building, where the water is fed to hydroturbines. The discharged water is either returned to the river or fed to the next diversion power plant. Such plants are usually constructed on rivers whose channels have a steep slope and, usually, according to an integrated plan for concentrating the flow (a dam and diversion together).

A pumped-storage hydroelectric power plant operates in two modes: a storage mode, in which energy obtained from other plants, mostly during the night, is used to pump water from a lower reservoir to an upper one; and a generating mode, in which water from the upper reservoir is fed through a pipeline to a hydroelectric unit. The electricity generated is delivered to a power system. High-capacity pumped-storage plants constructed close to centers of high demand are the most economical; their principal function is to accommodate peak loads when the power of a system is being completely used and to utilize the surplus electric power during the day, when other plants are not operating under full load.

Tidal electric power plants produce electricity by converting the energy in ocean tides. Because of the periodic nature of high and low tides, the electricity from such plants can only be used in conjunction with electricity from other systems, which make up any deficit within the day and the month.

The energy source in atomic power plants is a nuclear reactor, where energy is evolved in the form of heat as the result of the chain reaction of nuclear fission of heavy elements. The heat liberated is transported by a heat-transfer agent, which is fed to a heat exchanger (a boiler); the steam thus produced is used in the same way as in a steam-turbine electric power plant. Modern facilities and methods used for monitoring radiation completely eliminate the risk of radioactive irradiation for plant personnel.

Wind-power plants produce electricity from the conversion of wind energy. The primary equipment of such a plant comprises a wind-driven motor and an electric generator. Such plants are usually constructed in regions that have steady wind conditions.

Geothermal electric power plants are steam-turbine plants that use the heat of the earth’s interior. In volcanic regions subsurface waters are heated to more than 100°C at relatively shallow depths, from which they emerge through fissures in the earth’s crust. The mixture of steam and water is fed from boreholes to a separator in the plant, where the steam is extracted from the water and is fed to turbines. After chemical treatment the hot water is used for district heating. The absence of boiler units, a fuel supply, fly-ash collectors, and the like in geothermal plants reduces construction costs and simplifies plant operation.

Electric power plants that use magnetohydrodynamic generators produce electricity directly by converting the internal energy of a liquid or gaseous conducting medium.

V. A. RPOKUDIN

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