Geothermal electricity power plants use hydrothermal resources to generate electricity. Hydrothermal resources include hydro (water) and thermal (heat). Geothermal electricity plants use extremely high temperature (300°F to 700°F) hydrothermal resources procured from hot water wells or dry steam wells. These hydrothermal resources are collected by drilling wells into the earth and streamed through piping. The steam or hot water powers a turbine that generates electricity. Geothermal electricity wells can be up to two miles deep.
The United States is the leader in geothermal electricity generation. Predominantly from the Western part of the country is enough geothermal electricity generated to power nearly 3.5 million homes.
Geothermal Electricity Power Plants
There are three types of geothermal power plant technologies used to convert hydrothermal fluids into electricity – binary cycle, dry steam, and flash steam. Here is a video overview of geothermal energy from the U.S. Department of Energy.
Curious about #geothermal power? Check out three different technologies that produce it!Posted by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy on Sunday, November 26, 2017
Binary Cycle Power Plant
Binary cycle geothermal electricity plants are different than dry steam and flash steam systems because the geothermal reservoir never encounters the turbine units. The binary cycle uses two types of fluid, hence its name. Hot fluid from underground heats a second fluid called, a heat-transfer fluid in a large heat exchanger. The second fluid has a much lower boiling point than the first fluid, and so it flashes into vapor at a lower temperature. When the second fluid flashes, it spins a turbine which drives a generator and creates electricity.
Binary plants emit virtually nothing into the atmosphere, except for water vapor, thanks to its closed-loop system design. Geothermal resources under 300°F are most commonly available and could result in more geothermal electricity from binary-cycle plants.
Dry Steam Power Plant
Dry steam power plants primarily use steam as its hydrothermal fluid. Underground steam travels directly to a generator that produces electricity. Steam from the earth is always accessible and eliminates the need to burn, store, or transport fossil fuels. Dry steam power plants emit only unused steam and very small amounts of gasses.
Dry steam power plants were the first type of geothermal electricity generation and date back to 1904. Steam technology is still widely used and effective. The Geysers in northern California power the world’s largest single source of geothermal dry steam power.
Flash Steam Power Plant
Flash steam power plants are currently the most common geothermal electricity generation plants. A pump pushes hot fluid under high pressure into a tank at the surface, where it cools. As it cools, the fluid flashes and turns into a vapor which drives a turbine and powers a generator that creates electricity.
If any fluid remains in the tank, it can be flashed again in a second tank to create even more electricity.
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