X Международная студенческая научная конференция Студенческий научный форум - 2018

With the development of technology, man needed powerful sources of energy. These are the power stations that produce it from various sources. A power station, also referred to as a power plant or powerhouse and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Most power stations contain one or more generators, a rotating machine that converts mechanical power into electrical power. The relative motion between a magnetic field and a conductor creates an electrical current. The energy source harnessed to turn the generator varies widely. Most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate electricity. Others use nuclear power, but there is an increasing use of cleaner renewable sourcessuch a solar, wind, wave and hydroelectric.

Classification

By heat source

• Fossil-fuel power stations may also use a steam turbine generator or in the case of natural gas-fired plants may use a combustion turbine. A coal-fired power station produces heat by burning coal in a steam boiler. The steam drives a steam turbine and generator that then produces electricity. The waste products of combustion include ash, sulphur dioxide, nitrogen oxides and carbon dioxide. Some of the gases can be removed from the waste stream to reduce pollution.

• Nuclear power plants use the heat generated in a nuclear reactor's core (by the fission process) to create steam which then operates a steam turbine and generator. About 20 percent of electric generation in the USA is produced by nuclear power plants.

• Geothermal power plants use steam extracted from hot underground rocks. These rocks are heated by the decay of radioactive material in the Earth's crust.

• Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.

• In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.

• Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.

• Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.

By prime mover

• Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90 percent of all electric power produced in the world is through use of steam turbines.

• Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Princetown[7] being the world's first, commissioned in 1959.

• Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new baseload power plants are combined cycle plants fired by natural gas.

• Internal combustion reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas, and landfill gas.

• Microturbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.

By duty

Power plants that can be dispatched (scheduled) to provide energy to a system include:

• Base load power plants run nearly continually to provide that component of system load that doesn't vary during a day or week. Baseload plants can be highly optimized for low fuel cost, but may not start or stop quickly during changes in system load. Examples of base-load plants would include large modern coal-fired and nuclear generating stations, or hydro plants with a predictable supply of water.

• Peaking power plants meet the daily peak load, which may only be for one or two hours each day. While their incremental operating cost is always higher than base load plants, they are required to ensure security of the system during load peaks. Peaking plants include simple cycle gas turbines and sometimes reciprocating internal combustion engines, which can be started up rapidly when system peaks are predicted. Hydroelectric plants may also be designed for peaking use.

• Load following power plants can economically follow the variations in the daily and weekly load, at lower cost than peaking plants and with more flexibility than baseload plants.

Non-dispatchable plants include such sources as wind and solar energy; while their long-term contribution to system energy supply is predictable, on a short-term (daily or hourly) base their energy must be used as available since generation cannot be deferred. Contractual arrangements ("take or pay") with independent power producers or system interconnections to other networks may be effectively non-dispatchable.

Hydroelectric power station

In a hydroelectric power station water flows through turbines using hydropower to generate hydroelectricity. Power is captured from the gravitational force of water falling through penstocks to water turbines connected to generators. The amount of power available is a combination of height and flow. A wide range of Dams may be built to raise the water level, and create a lake for storing water. Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use.

Solar

Solar energy can be turned into electricity either directly in solar cells, or in a concentrating solar power plant by focusing the light to run a heat engine.

A solar photovoltaic power plant converts sunlight into direct current electricity using the photoelectric effect. Inverters change the direct current into alternating current for connection to the electrical grid. This type of plant does not use rotating machines for energy conversion.

Solar thermal power plants are another type of solar power plant. They use either parabolic troughs or heliostats to direct sunlight onto a pipe containing a heat transfer fluid, such as oil. The heated oil is then used to boil water into steam, which turns a turbine that drives an electrical generator. The central tower type of solar thermal power plant uses hundreds or thousands of mirrors, depending on size, to direct sunlight onto a receiver on top of a tower. Again, the heat is used to produce steam to turn turbines that drive electrical generators.

Wind

Wind turbines can be used to generate electricity in areas with strong, steady winds, sometimes offshore. Many different designs have been used in the past, but almost all modern turbines being produced today use a three-bladed, upwind design. Grid-connected wind turbines now being built are much larger than the units installed during the 1970s. They thus produce power more cheaply and reliably than earlier models. With larger turbines (on the order of one megawatt), the blades move more slowly than older, smaller, units, which makes them less visually distracting and safer for birds.

Osmosis

Salinity gradient energy is called pressure-retarded osmosis. In this method, seawater is pumped into a pressure chamber that is at a pressure lower than the difference between the pressures of saline water and fresh water. Freshwater is also pumped into the pressure chamber through a membrane, which increases both the volume and pressure of the chamber. As the pressure differences are compensated, a turbine is spun creating energy. This method is being specifically studied by the Norwegian utility Statkraft, which has calculated that up to 25 TWh/yr would be available from this process in Norway. Statkraft has built the world's first prototype osmotic power plant on the Oslo fiord which was opened on November 24, 2009.

Biomass

Biomass energy can be produced from combustion of waste green material to heat water into steam and drive a steam turbine. Bioenergy can also be processed through a range of temperatures and pressures in gasification, pyrolysis or torrefaction reactions. Depending on the desired end product, these reactions create more energy-dense products (syngas, wood pellets, biocoal) that can then be fed into an accompanying engine to produce electricity at a much lower emission rate when compared with open burning.

The largest hydroelectric power stations

THREE GORGES: The world’s largest hydroelectric power station is about to be built in China. It is located on the Yangtze River. The design capacity of the station is 22.4 GW. The station is located in Yichang County, Hubei Province. Having begun to build this large-scale project in 1992, China seemed to have continued the communist tradition of giant construction projects. The idea of ​​erecting a dam in these lands was put forward as far back as 1918. The height of the constructed dam was 185 meters. The resulting reservoir is an area of ​​more than 1,000 square kilometers. The erection of this station led to the relocation of more than 1.2 million people. Under the water were 2 cities and many villages. HPP not only generates electricity needed for China’s growing economy, but also regulates the Yangtze’s water regime. Previously, the floods of the river led to great cataclysms. In this part of the river, shipping has improved, and cargo turnover has increased tenfold!

ITAIPU: This station is located in Brazil on the Parana River, 20 kilometers from the city of Foss do Iguaçu. The power of the station is 14 GW. The first work on designing the station and preparing for construction began in 1971, the first generators were launched in 1984, and the last ones – in 2007. The total length of the combined dam was more than 7 kilometers, and its height was 196 meters. To carry out the construction, a 150-meter canal was even cut in the rocks. The value of HPP is very high – it produces about 16% of electricity consumed by Brazil and 71% of Paraguay. Although the power of the “Three dams” and above, the total annual electricity volume of Itaipu produces more because of the more uniform hydrological regime of the Parana compared to the Yangtze.

GURI: Officially, this station bears the name of Simon Bolivar, although it used to be Raoul Leoni until 2000. The building is located in Venezuela, Bolivar state on the Caroni River. From here 100 kilometers to its confluence with Orinoco. The station’s capacity is 10.2 GW. Construction of Guria began in 1963, the last stage of construction was completed only in 1986. Since 2000, the reconstruction is under way here – turbines and components are being changed. The total length of the dam is 1300 meters, its height is 162 meters. Guri forms a reservoir with a length of 175 kilometers and a width of 48. It is located at an altitude of 272 meters above sea level. The value of the station for the country is great – it produces 82% of all electricity. Curiously, the walls of the second engine room are decorated with the Venezuelan artist Carlos Cruz-Deez.This makes it possible to reduce the psychological pressure on the workers of the responsible facility.

The largest nuclear power stations.

Kashiwazaki-Kariwa nuclear power plant: Tokyo Electric Power Co.’s (TEPCO) Kashiwazaki-Kariwa plant in Japan is currently the world’s largest nuclear power plant, with a net capacity of 7,965MW.Kashiwazaki-Kariwa has seven boiling water reactors (BWR) with a gross installed capacity of 8,212MW.The first five units have a gross capacity of 1,100MW each, whereas the sixth and seventh units have a capacity of 1,356MW each.The first unit began commercial operation in September 1985 and the last unit became commercially operational in July 1997.Operations have seized at present but will resume after a safety assessment due for completion in 2013. TEPCO is currently implementing safety measures at the plant to meet the new safety guidelines set forth by Japan’s Nuclear Regulatory Authority.

Bruce Nuclear Generating Station: Bruce Nuclear Generating Station, located in Bruce County, Ontario, Canada, is the second largest nuclear power plant in the world.The 6,234MW (net) nuclear facility is owned by Ontario Power Generation (OPG) and operated by Bruce Power.The plant is made up of eight pressurised heavy water reactors (PHWR) with gross capacities varying from 786MW to 891MW. The last reactor of the Canadian NPP became commercially operational in May 1987Bruce 1 witnessed a long-term shut down in 1997 and was reopened in September 2012. Bruce 2 was restarted in October 2012, also after a long-term shut down which occurred in 1995.

Hanul Nuclear Power Plant: Ulchin Nuclear Power Plant, which was renamed Hanul Nuclear Power Plant in 2013, is the largest South Korean nuclear power plant.The plant currently has a gross installed capacity of 6,189MW and net design capacity of 5,908MW ranking as the fourth largest NPP in the world.Phase one of the Hanul NPP was completed in 2005 with six pressurised water reactor (PWR) units. Two more reactors are being added to Hanul as part of the second phase of plant development.The two new reactors will have a net capacity of 1,350MW each and will increase the plant’s total net capacity to 8,608MW when completed in 2018. The gross capacity of the plant will increase to 8,989MW upon completion of phase two.

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