Renewable energy : How Geothermal Energy Works
A thermal power plant that uses the internal heat of the Earth to generate electricity and heat. Virtually the only sources of geothermal energy are steam hydrotherms (fields of self-heating steam-air mixture or steam) and hydrotherms (deposits of self-pouring hot water), which are used to generate both electric energy (at a steam or air-vapor mixture temperature of more than 150 ° C) and thermal (at a temperature 30-150 ° C).
However, such steam-hydrothermal deposits are located only in areas of active volcanic activity. At geothermal power plants, a steam-air mixture from a natural source, drawn to the surface, as a rule, by specially drilled wells, is sent to separators where the steam separates from the water. Then, the separated steam enters a steam turbine, and hot water (at a temperature of about 120 ° C) is used for heat supply and other purposes. In some cases, before the turbine, devices are installed that purge steam from aggressive (highly corrosive) gases. Unlike other thermal power plants, geothermal power plants do not have a boiler plant, ash collectors and many other devices; almost a geothermal power plant consists only of a computer room and a room for electrical devices. The cost of electricity at such power plants is much lower than in thermal power plants.
Geothermal power plants - principles of operation
Currently, there are three schemes for generating electricity using hydrothermal resources: direct using dry steam, indirect using steam and a mixed production scheme (binary cycle). The type of conversion depends on the state of the medium (vapor or water) and its temperature. The first to be mastered power plants on dry steam. To produce electricity on them, steam coming from the well is passed directly through the turbine / generator. Power plants with indirect type of electricity generation are by far the most common. They use hot underground water (up to 182 ° C), which is pumped at high pressure into the generator sets on the surface. Geothermal power plants with a mixed production scheme differ from the two previous types of geothermal power plants in that steam and water never enter into direct contact with the turbine / generator.
Geothermal power plants operating on dry steam
Steam power plants operate primarily on a hydrothermal steam. The steam flows directly into the turbine, which feeds the generator that produces electricity. The use of steam makes it possible to avoid burning fossil fuels (there is also no need for transportation and storage of fuel). These are the oldest geothermal power plants. The first such power plant was built in Larderello (Italy) in 1904, it is still in effect. Steam technology is used at the Geysers power station in Northern California, the largest geothermal power plant in the world.
To produce electricity in such plants, superheated fluids (above 182 ° C) are used. The hydrothermal solution is pumped into the evaporator to reduce pressure, because of this a part of the solution evaporates very quickly. The resulting steam drives the turbine. If liquid remains in the tank, it can be evaporated in the next evaporator to obtain even more power.
Most geothermal regions contain water of moderate temperatures (below 200 ° C). In power plants with a binary production cycle, this water is used to generate energy. Hot geothermal water and a second, additional liquid with a lower boiling point than water have been passed through the heat exchanger. The heat of the geothermal water evaporates the second liquid whose vapors drive the turbines. Since this is a closed system, there are practically no emissions to the atmosphere. Temperate water is the most common geothermal resource, so most future geothermal power plants will work on this principle.
Reservoirs with steam and hot water are only a small part of geothermal resources. Earth magma and dry solid rock will provide cheap, clean, almost inexhaustible energy, as soon as appropriate technologies for their utilization are developed. Until then, the most common producers of geothermal power will be power plants with a binary cycle.
To make geothermal electricity a key element of the US energy infrastructure, it is necessary to develop methods to reduce the cost of obtaining it. The US Department of Energy works with representatives of the geothermal industry to reduce the cost of a kilowatt hour to $ 0.03-0.05. According to forecasts, in the coming decade, new geothermal power plants with a capacity of 15,000 MW.
Geothermal power plants are built (or constructed) in Italy (Tuscany, Larderello district), New Zealand (Taupo zone), USA (California - Valley of Great Geysers) and Japan.
In the Reykjavik region (Iceland), geothermal waters are used for heating. The total installed capacity of all geothermal power plants in the world in 1980 was 2.5 thousand MW, in 2000 - about. 17 thousand MW. The geothermal resources of the planet are practically unlimited.
References for further reading :
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Fantastic article; geothermal energy is overlooked quite often, yet we're basically sitting on a fire-ball, so it's very renewable. There are quite a few areas around the world that could take advantage of this and it allows us to diversify our energy sources.
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Love the post on how the working of geothermal technology have been explained and the data presented.
Given the renewable nature of geothermal, its only poised to increase in future having a total installed capacity of 12,635 MWe that gave a total production of 73,549 GWh in 2015 and a forcast of 21,443 MWe by 2021, key to it's scalability in potential regions is reducing costs.
Would really love to know other methods of producing electricity apart from the dry steam production, would make for a really good follow-up article.