Geothermal Power and The Geysers

         Geothermal energy

Geothermal energy is the name given to heat energy pouring from deep within the Earth. Geothermal is generally considered a clean and sustainable form of energy, though limited supplies allow it to be sustainable only on a relatively small scale. Resources range from shallow ground water to hot water and hot rock found a few miles beneath the surface to high temperatures of molten rock called magma.  Most U.S. geothermal reservoirs are located in the western states.  

          The Geysers Geothermal Field in Northern California

Geothermal energy was first tapped commercially in the 1920s.  Full-scale commercial development began by 1955.

 Since 1987, however, The Geysers has experienced a decline in steam pressure and electricity production. Initial pressure was 500 psi, but by the mid-1990s pressure fell to 200 psi. Pressure determines production rate, so it is no longer practical to drill new wells in most areas of the Geysers.

 Reservoir heat in the Geysers remains near its original temperature. Injecting water into the reservoirs can result in the recovery of additional heat.

 Field life at The Geysers is expected to exceed 50 years.

The Geysers is the world’s largest geothermal source, with a peak capability of 1100 MW. Enough electricity to supply a city of over a million Californians is produced at the Geysers continuously. Calpine has emerged as the nation’s largest geothermal power producer after purchasing these geothermal steam fields from Unocal and Pacific Gas & Electric.  

To foster higher steam production, the Geysers are now operated at lower turbine inlet pressures. This increases the amount of steam recovered by lowering field abandonment pressure.