Traditional geothermal systems require rare sites like geysers where steam or very hot water (at least 350 degrees Fahrenheit) can be tapped to drive a turbine and generate electricity. Now binary geothermal technology can use 200 to 300 degree water, providing many more opportunities to harness underground energy. Binary cycle geothermal power plants pump hot water from a geothermal well, through a heat exchanger, and the cooled water is returned to the underground reservoir. A second fluid with a low boiling point is pumped through the heat exchanger where it is vaporized and then directed through a turbine.
Innovate | To Develop a Head of Steam from Sierra Magazine March/April 09
Raser’s Binary Geothermal Process Animation