Power Plant Engineering

 Fig. 2.34. Schematic of the Dry Steam Power Plant.
Flash Steam Power Plant (Liquid Domain System). Flash steam power plants are the most
common. They use geothermal reservoirs of water with temperatures greater than 182°C. This very hot
water flows up through wells in the ground under its own pressure. As it flows upward, the pressure
decreases and some of the hot water boils into steam. The steam is then separated from the water and
used to power a turbine/generator. Any leftover water and condensed steam are injected back into the
reservoir, making this a sustainable resource.
Turbine
Generator
Steam
Water
Waste Brine
Injection
Well
Brine
Production
Well
Steam
Air and
Water vapour
Air
Air
Cooling
Tower
Direct Heat
Uses
Water
Geothermal Zone
Fig. 2.35. Schematic of the Flash Steam Power Plant.
Flash-steam power plants built in the 1980s tapped into reservoirs of water with temperatures
greater than 182°C. The hot water flows up through wells in the ground under its own pressure. As it

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flows upward, the pressure decreases and some of the hot water “flashes” into steam. The Geysers in
northern California, which uses steam piped directly from wells, produces the world’s largest single
source of geothermal power.
Flash steam plants are the most common type of geothermal power generation plants in opera-
tion today. They use water at temperatures greater than 182°C that is pumped under high pressure to the
generation equipment at the surface. Upon reaching the generation equipment the pressure is suddenly
reduced, allowing some of the hot water to convert or “flash” into steam. This steam is then used to
power the turbine/generator units to produce electricity. The remaining hot water not flashed into steam,
and the water condensed from the steam is generally pumped back into the reservoir. An example of an
area using the flash steam operation is the Cal Energy Navy I flash geothermal power plant at the Coso
geothermal field.