China


How is electricity produced?


Water is injected into the geothermal reservoir via an injection well, and flows through the geothermal reservoir using the network of fractures. As the water passes through the reservoir it is rapidly heated - this is known as the underground heat exchanger. Under pressure the heated water is returned to the surface via a production well. On the surface Binary Cycle or Flash Steam power plants can be used to generate electricity from the superheated water. Binary Cycle power plants use a surface heat exchanger to extract heat. The heat exchanger is a series of pipes which allow the transfer of heat from the geothermal water to another liquid, without the liquids ever mixing. The second liquid is allowed to boil, producing high-pressure steam that is used to drive the electricity turbines. Once the heat has been removed from the geothermal water it can be re-injected into the reservoir to be heated and used again. Flash Steam power plants allow the geothermal water to turn to steam, and the steam is directly used to turn electricity turbines. Any remaining water is re-injected into the reservoir for re-use.

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