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| Renewable Energy Information: Geothermal Energy What is Geothermal Energy?  Geothermal energy is heat from the earth. Usable geothermal energy resources range from the constant 50 to 60 degree Fahrenheit temperatures found in the upper ten feet of earth's crust to very hot rock and water up to several miles below the surface. Hot rock and water resources are available predominantly in the western United States, Alaska, and Hawaii, but the constant temperatures in shallow ground can be tapped almost anywhere.
Like the energy of the sun, the energy within the earth is immense and has a lifetime measured in billions of years. However, unlike the sun, geothermal resources can be depleted by drawing energy out of them at a faster rate than they are replenished, resulting in a decrease in the local amount of available energy. If depleted, geothermal resources can take tens or hundreds of years to recover, so it is important to take measures that prolong the useful life of the resource.1 Geothermal fields produce only about one-sixth of the carbon dioxide that a natural-gas-fueled power plant produces, and very little, if any, nitrous oxide or sulfur-bearing gas. 1. The Status and Future of Geothermal Electric Power, Charles F. Kutscher, presented at the ASES conference, June 16–21, 2000. |