The water held underground in a geothermal system is under high temperature and pressure. Are pumps used to raise the very hot underground water to the surface or does the water rise under its own pressure? One source says that the water is pumped up: https://energy.gov/eere/geothermal/electricity-generation while another says that it rises on its own: https://www.youtube.com/watch?v=kjpp2MQffnw I am not sure if I am just misunderstanding the wording. Does anyone know which is correct?
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2$\begingroup$ Both can be correct - it depends on the details of the systems and what needs to be achieved. $\endgroup$– Solar MikeDec 14, 2017 at 22:04
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2$\begingroup$ I think you will find most, if not all, practical systems recirculate the water and so require some active pumping system. $\endgroup$– agentpDec 15, 2017 at 19:21
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They are both correct. There are actually a number of different types of geothermal power plant with the most common being, dry steam, flash steam, and binary cycle.
Dry steam plants require pumps to draw from underground resources of steam. This is piped directly from underground wells to the power plant.
Flash steam plants (most common) use geothermal reservoirs that have naturally high temperatures (180 Celsius +). The hot water from the reservoir flows up through a well under its own pressure. As it reaches the surface the pressure decreases and the water begins to boil and turn in to steam. Any water left over from this process is then pumped back in to the reservoir.
Binary cycle power plants are more complex but are capable of operating at much lower temperatures (100-180 Celsius). These use hot water pumped from an underground reservoir to heat an organic fluid with a low boiling point. This organic fluid is vaporised in a heat exchanger which turns a turbine. The leftover water is "injected" back in to the reservoir.
If you want to read up more on the specific types of geothermal plant, this website has more information: https://www.conserve-energy-future.com/geothermalpowerplanttypes.php
Hope that helps!
