A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

POWER PLANTS

DOI: 10.1615/AtoZ.p.power_plants

The adoption of electric power has a great significance for infrastructure and is a factor of primary importance for progress in science and technology and growth of labor productivity in all spheres of the economy. Output and structure of the production of primary energy resources are presented in Table 1 by key figures of the world energy consumption in 1990 in relation to 1973 and 1985 (1 ton of coal equivalent (t.c.e.) corresponds to 7 × 106 kcal or 29 GJ).

Table 2 presents the structure of consumption of primary energy resources within the period from 1980 to 2020 (on an average) according to the forecast of the International Power Commission.

In 1980, power plants (PP) generated over 11600 TW-hr of electric energy.

The total annual consumption of electric energy in the world at the end of the 20th century is estimated to range from 13000 to 16000 TW-hr. This corresponds to an annual average growth of 2.5 to 3.0% between 1990-2000. By 2020, electric energy consumption is estimated at 25000 TW-hr. Installed capacity of power plants in 2000 is estimated at 3.3-3.7 TW Production of electric energy in the industrialized nations accounts for up to 35% of energy resources consumed. In the future, it is anticipated that coal will be the predominant fuel for power plants (up to 50%), less than 10% from renewables, and from 15 to 18% from nuclear energy.

A power plant is an assemblage of equipment, and apparatus used directly for generation of electric energy and also the buildings and structures needed for it. Power plants are classified into those using traditional and nontraditional energy resources. The former type includes thermal power stations (TPS), nuclear power plants (NPP), hydraulic power plants (HPP), and hydro pumped storage power plants (HPSPP). The latter type includes solar power plants (SPP), geothermal power plants (GTPP), wind power stations (WPS), tidal power plants (TPP), magnetohydrodynamic power plants (MHDPP), etc.

Table 1. World power supply

Table 2. World energy supply

TPSs are the foundation of electric power industry, they generate electric energy by conversion of thermal energy released in burning of fossil fuel. Depending on the type of equipment they can be steam-turbine, gas-turbine, steam-gas, and diesel power plants. The basic items of equipment are boiler units, turbines, electric units, pumps, compressors, heat exchangers, electric switch-gears, etc. Steam-turbine TPSs are divided into condensation power plants (CPP) and combined heat and power generation plants (CHPP).

In an NPP the energy source is a nuclear reactor, in which thermal energy is generated as a result of a chain fission reaction of heavy elements. The removed heat is transferred from the reactor by a heat-carrying agent, which is admitted to a steam generator or a turbine. Depending on the type of neutrons used, thermal and fast reactors are distinguished. The former are most commonly encountered. Unlike TPSs, NPSs are furnished with biological shield, equipment for nuclear fuel recharging, systems of special ventilation and emergency cooling, and other systems. In the next century, electric energy will probably be generated in thermonuclear plants. The energy source at these plants is light nuclei fusion. Controlled thermonuclear fusion will make it possible for humankind to solve completely the problems of power supply.

In an HPP, hydraulic power is converted to electric energy. The HPP is a collection of water development works, power-generating plant, and machinery. The main components of an HPP in flat country are a dam across the river producing a concentrated drop of water level, the plant building in which hydroturbines are arranged, electric current generators, and other equipment. Navigation locks, water intake works for irrigation, water supply, and fish ladders are constructed if needed.

With pumped storage systems (HPSPPs) the system acts, during lower loading of the electric power systems, as a pumping plant consuming electric energy and pumping the water from a lower to an upper basin. With increasing electric power consumption in the system the water from the upper pool is passed via turbines to the lower pool. At this time the HPSPP works as a HPP, i.e., generates electric power. There are HPSPPs with 24-hour, weekly, and even seasonal power storage. Pumps and turbines or reversible hydraulic machines (pump-turbines), which can operate in turn as a pump or as a turbine are mounted in HPSPPs. An electric machine can also operate in a reversible regime, i.e., operate as either a motor or a generator.

In 1987, the annual output of electric power per capita on average was 2085 kW-hr all over the world, the maximum in Norway (24756 kW-hr), the minimum in Kampuchea (13 kW-hr). A total of 1790 GW was installed at TPSs in 1990. The most powerful blocks with a single-unit power 1365 MW and 1200 MW are installed in the USA (PP in Rockport) and in Russia (Kostroma TPS), respectively. In Western Europe the largest gas turbine, 135 MW, as a part of 600 MW steam-gas plant, is installed at the TPS in Amsterdam. In Japan TPS's work with 1000 MW steam-gas plant. In the USA the overall power of gas turbine and steam-gas plants exceeds 60 million kW (8% of installed power). Japan is planning to construct in mid-1990s a TPS with 2.6 million kW steam-gas plant (8 blocks). Siemens designed and constructed in Turkey a TPS with six steam-gas plants of 450 MW each.

Contribution of NPPs is about 12% of power, i.e., 334 GW as of the end of 1990. In 1990, 8.6 GW was put into operation and 3 GW was brought to a halt at NPPs all over the world. The most powerful NPPs are in Japan (9.0 GW), in Canada (9.4 GW), in France (5.5 GW). The installed power of NPPs in the USA is 106 GW, in France 55 GW, in Russia 20 GW, in Japan 32 GW, in Germany 24 GW. The most powerful nuclear block (1500 MW) is installed in Lithuania.

HPPs account for 24% of the total power, 550.5 GW in 1990. The biggest operative HPPs are in Venezuela (10.3 GW), in Brazil (12.6 GW, though not all the units in operation), in Grand Coulee (USA, 6.5 GW), and in the Sayano-Shushenskaya (6.4 GW), and Krasnoyarsk (6.0 GW) plants in Russia.

In 1990 there were 240 operative HPSPPs all over the world with the total power 70 GW. In addition, these were 16 HPSPPs, with total power of 13 GW, were under construction and 18, with total power 12 GW, were planned for construction. USA (36 HPSPPs, 15.1 GW), Japan (23 HPSPPs, 12.8 GW), Italy (32 HPSPPs, 11.8 GW), and Spain (36 HPSPPs, 8.3 GW) have the highest installed power.

In the latest forecasts for development of world power generation for the next 20-40 years, nontraditional energy sources are of minor importance. It is clear that, taking into account switching to systems using inexhaustible energy resourses such as thermonuclear, nuclear, and solar energy, there is no danger of energy shortage. However, fossil fuels will be of predominant importance in the world's energy balance up to the middle of the next century.

The total engineering potential of renewable energy sources is estimated to be 12 TW-yr a year (Table 3). Table 4 presents an approximate cost of electric power from traditional and renewable energy sources.

Table 3. Engineering potential of renewable resources

Table 4. Comparison of costs of power plants

It is commonly believed that nontraditional energy sources are advisable to use for decentralized energy supply. Until recently diesel electric power stations with the power from several kilowatts to several hundred kilowatts gained currency. However, even with the current expenditures the cost of electric power generated by them often turns out to be higher than from less powerful HPPs and WPSs. Heat supply from solar power plants even now can successfully compete with direct electric heating. If the cost of fossil fuel is doubled, solar power plants virtually appear to be more efficient than all the traditional heating systems.

Several powerful SPPs with the total power 145 MW are run in the USA. By 1995 the SPP power is planned to grow up to 590 MW and by 2000, up to 4000 MW. The highest single-unit powers are installed in the USA (15 MW), Ghana (6 MW), and Australia (2 MW). In addition, SPPs of small power are expected to increase in quantity on other countries too. In some states generation of power by SPPs increased considerably. For instance, in Israel SPPs generate 3.1% electric power.

Electric energy based on geothermal resources is produced in 16 countries, with the installed power in each country not exceeding a few tens or hundreds megawatts. There are extremely low values compared to the vast world geothermal energy resources. The total geothermal resources, including the three-kilometer continental shelf, are estimated at 4.1 × 1019 MJ of which 3.6 × 1015 MJ can be utilized by the present-day technologies of electric energy generation. This is equivalent to 1.2 TW of electric power used for 100 years. By the beginning of 1989 the total installed power of geothermal power plants amounted to 5.1 GW (233 units), including 2.02 GW in the USA, 0.89 GW in the Philippines, 0.645 GW in Mexico, and 0.519 GW in Italy. An annual growth in electric power output at these plants was 16.5% from 1978 to 1985. If this rate continued, then in 1990 the installed electric power must have attained 9.4 GW. Geothermal energy accounts for 20% of the entire electric power output in the Philippines and in Kenya, while in Mexico it is about 50%. The most powerful unit operates at a geothermal power plant in the USA (135 MW).

A wind power system (WPS) is a setup converting the kinetic energy of wind flow to electric energy. A WPS consists of a wind motor, electric current generator, automatic devices for controlling the wind motor and generator operation, and structures for their assembly and maintenance. WPSs are used as low power electric energy sources in areas with strong winds, where the annual average wind velocity exceeds 5 m/s, and far away from the centralized electric power supply systems. Wind possesses a tremendous energy (26.6 × 1015 kW-hr), which constitutes 2% of all energy of solar radiation incident on the earth.

In recent 15 years more than 10,000 WPSs with the power from 3 to 330 kW were constructed and run all over the world. The first WPS was put into operation in Great Britain (the power 3 MW) and another WPS in Denmark (2 MW).

Tidal energy attracts a considerable interest. It is commonly believed that technical reserves for electric energy generation at tidal power plants (TPP) are about one-third of potential tidal energy. Thus, under Russian conditions technical resources of tidal energy are 250 billion kW-hr per annum. Sea tide electric power plants use tidal fluctuations of the sea level, which, as a rule, occur twice in 24 hours.

At the end of the 1980s TPPs were constructed in a number of countries. In France a 240 MW TPP was constructed, in Russia, near Murmansk a pilot TPP was constructed. In addition, preliminary work was carried out on the possibility of full scale TPP construction in Russia. There is one TPP in the USA and a few in China. In Great Britain final plans and specifications are being prepared for construction of a tidal power plant with the power 7.2 GW. In Norway and Japan electric power stations using the sea wave energy have been run successfully.

The constant rise of prices for petroleum and natural gas gives impetus to search of new energy sources one of which is the energy of biomass. By composition it can be carbon-containing (plants, wood, seaweed, grain, paper, ets.) and sugar-containing (sugar beetroot, sugar cane, Chinese sugar cane). The sources of biomass are wood products, vegetable remnants, livestock breeding wastes, domestic garbage and industrial wastes, etc. Though the energy of biomass can meet only 6 to 10% of power demands of industrial states, its potential role is important because biomass is a renewable energy source.

Small gas turbines can use bioresources. At the end of 1992 in Great Britain, 24 biogas units operated, 8 were being constructed, and 18 were under design. It is expected that by 2000 the annual energy potential of this energy source will achieve 1 million t.c.e. In the state of Penjab, India, a 10 MW TPS has been constructed that will use straw as fuel. In 1987, by the data of the 14th Congress of the International Power Commission, the total of biomass used in power production was 1.8 billion t.c.e.

Further development of electric power plants is linked with using new cycles and working media. An analysis of various trends in developing electric power engineering shows that one of the most promising new power-generation technologies is the use of combined cycle steam-gas plants (SGP). In these plants, a gas turbine is used with the hot exhaust gases being used to generate steam, which is passed to a steam turbine (often on the same shaft as the steam turbine). The greatest part of operating SPGs in the world are the binary-type plants. Depending on the power ratio of steam to gas in the unit, on the initial temperature in combustion chamber, and the degree of air compression, the efficiency of such plants varies from 42% to 53%.

In recent years, considerable progress was achieved in solving the problem of cooling gas-turbine plant (GTP) elements. This allowed a substantial rise of the initial gas temperature in the combustion chamber, a change of power ratio of gas and turbine cycles and going over to a new version of SGP by the STIG cycle with admission of steam in the gas turbine. According to the data of the 14th Congress of the International Power Commission these plants are put into operation most actively in the USA, Japan, Western Europe, and other parts of the world. According to the data of the US Department of Energy as of the beginning of 1990 the total capacity of SGPs amounted to 5.3 GW. About 40 GW capacity is expected to be installed before 2000.

There exist real prospects of putting into operation of magneto-hydrodynamic power plants and hydrogen-based power generation. The efficiency of TPS can be sharply raised by a combined cycle with an MHD topping plant. MHD power plants use, as a working medium, plasma produced by high-temperature (about 2700°C) fuel burning. An increase in the upper temperature limit of the working medium even now can give efficiency up to 50% and higher.

In addition to conventional elements installed at TPSs, MHD power plants possess compressor plants, high-temperature oxidizer heaters, combustion chambers, MHD channel, a superconduction magnetic system, inverter substantions, the cooling system of high-temperature elements, the system of additive inlet and outlet. These elements substantially raise the cost of the plant and complicate its operation. At the same time the higher efficiency of MHD power plants, the consequential reduction of environmental pollution, the possibility of producing high-power units, and their greater flexibility speak in favor of MHD power plant construction. Experience gained in these plants will form the basis for the adoption of high efficiency solid-fuel plants in power engineering.

A key problem in development of hydrogen-based power engineering is production of low-cost hydrogen. Different processes exist for this, such as using coal, water electrolysis, and plasma chemistry. It seems promising to use hydrogen in power-chemistry, power-metallurgy, and other systems. The economic benefit turns out to be the highest if both power and technological problems are solved simultaneously.

In the USA a pilot hydrogen power plant with a power of 1 MW was constructed in 1977. Then the demonstration station with a 4.5 MW hydrogen-air electrochemical generator began to be constructed. Tests of the different systems of this station were carried out in 1981. By the end of 1990s commercial stations of this type are planned to be put into practice. In Germany, an experimental hydrogen-oxygen "steam generator with the thermal power 15 MW is being designed with steam parameters: temperature 850°C, pressure 8 MPa. Fuel systems for such power stations are still being improved. The power single units is rising. In Japan and USA 4 MW units have already been put into operation.

Electric power plants are a source of disturbance to environmental equilibrium. The interaction of energy generation and the biosphere in the majority of cases has a negative environmental consequence, primarily due to the generation of wastes such as noxious gases, solid and liquid pollutants, radioactive substances and waste heat (Figure 1). They pollute the atmosphere and water basins. Operation of electric power plants changes the regime of river run-off and withdraws valuable land from agricultural rotation. For instance, a TPS of the power 1 GW consumes 8 million tons of coal a year, ejecting about 10 million tons of CO2 find hundreds of thousands of tons of ash. By the way, the dust radioactivity of TPSs is about twice as high as the radiation from all NPP. TPSs are not only the source of heavy pollution, but consume much oxygen from the air.

Currently more than 2.5 billion tons per annum of various substances are ejected in to the earth atmosphere. One of the most harmful components is sulfur dioxide SO2. In 1970 about 90 million tons of SO2 were ejected into the atmosphere, in 1980 the total ejections of SO2 in developed countries amounted to 111.9 million tons incrising by 1990 by about 15%. Other harmful components in waste gases are nitrogen oxides. In practice, nitrogen oxide NO and dioxide NO2 whose sum is denoted as NOx pose a problem of atmospheric air protection. Globally the quantity of naturally formed nitrogen oxides by far exceeds its creation as a result of human activities. According to estimates made in 1990, 80 million tons of NOx was generated annually. However, it should be taken into account that anthropogenic ejections of nitrogen oxides virtually grow twice every 20-25 years.

NPPs are environmently less dangerous compared to TPS, particularly TPP's using low-grade solid fuels with a high content of ash and sulfur and a high-sulfur content, but NPP's need strict observance of the radiation safety rules. Ensuring safety in nuclear power generation involves many technical aspects, but nuclear safety and removal of decay-heat in the active reactor zone are decisive due to their influence on general safety. Burial of radioactive waste and decommissioning NPPs present a number of grave problems.

In the coming years we cannot expect that nontraditional renewable energy sources can significantly improve the condition of the environment in a global scale because their share in the world energy production is small. The efficiency of technological measures taken to reduce the harmful effect of electric power plants, using traditional energy resources, on the environment is substantially higher than going over to using nontraditional renewable energy sources.

Figure 1. 

The reduction of negative effect on the environment is possible owing to (1) improvement of the structure of traditional energy resources, (2) lowering of total utilization energy resources by improving efficiency, (3) improvement of engineering and technological design of electric power plants.

A more intensive use of renewable energy resources for energy generation will also contribute to improvement of environment.

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