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Geothermal energy is a form of renewable energy obtained from the heat coming from the Earth's interior.
It is based on the use of heat stored underground to generate electricity or to provide heating and hot water in different applications.
A geothermal power plant harnesses heat from underground to produce electricity.
The process is generally divided into three stages: extraction, conversion and generation.
In the extraction stage, boreholes are drilled into the ground to reach the hot water or geothermal steam reservoirs.
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These deposits are found in geologically active regions, such as volcanic or tectonically active areas. The hot water or steam is extracted through wells and brought to the surface.
In the conversion stage, the hot water or geothermal steam is directed to a geothermal power plant. There, the hot water is used to heat a secondary fluid, such as an organic working fluid or a coolant. The secondary fluid evaporates due to the heat and expands in a turbine.
The turbine, in the generation stage, converts the kinetic energy of the fluid into mechanical energy. As the turbine rotates, so does the shaft of the generator, which is connected to it. This generates electricity in the generator.
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After passing through the turbine, the cooled secondary fluid is condensed and returned to the geothermal well to repeat the cycle.
Some geothermal plants use binary cycle systems, where the secondary fluid does not come into direct contact with the hot water or geothermal steam, which minimises the environmental impact.
Some countries, such as Iceland, the Philippines and New Zealand, are known for their extensive use of geothermal energy to generate electricity. Iceland, in particular, obtains most of its electricity from geothermal sources.
In the United States, California is one of the leading states in geothermal electricity generation. It has several geothermal fields in operation, such as The Geysers, which is the largest geothermal field in the world.
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Other countries such as Mexico, Kenya, Indonesia and Japan also have geothermal plants in operation. These plants take advantage of the geothermal resources available in their respective regions.