About Geothermal

Geothermal heating is best defined as the use of the Earth's thermal energy for space and water heating. This energy can be heat that was stored in the ground's thermal mass during the summer, or it can come from the radioactive decay of minerals deep within the Earth. The latter form has been used since the time of the Roman Empire as a way of heating buildings and spas by utilizing sources of hot water and steam that exist near the Earth's surface. Some areas, including substantial portions of many western states (U.S.), are underlain by relatively shallow geothermal resources. Similar conditions exist in Iceland, parts of Japan, and other geothermal hot spots around the world. These resources can be classified as low temperature (less than 90°C or 194°F), moderate temperature (90°C - 150°C or 194 - 302°F), and high temperature (greater than 150°C or 302°F).
Where such geological geothermal resources are available, it is possible to distribute hot water or steam to multiple buildings. This technique, long practiced throughout the world in locations such as Reykjavik, Iceland, Boise, Idaho, and Klamath Falls, Oregon is known as geothermal district heating. Heat is extracted from the ground with earth tubes or downhole heat exchangers.

source: wikipedia.org

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