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The word geothermal comes from the Greek words geo (earth) and therme (heat). So, geothermal energy is heat from within the earth.

Geothermal energy is a renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the earth. Geothermal energy can sometimes find its way to the surface in the form of volcanoes and fumaroles (holes where volcanic gases are released); hot springs and geysers. It may be used for heating as well as to generate electricity.


Did You Know?

  • If we could extract all the geothermal energy that exists underneath the United States to a depth of two miles, it would supply America’s power demands (at the current rate of usage) for the next 30,000 years!
  • 85 percent of Icelandic houses are heated geothermally, and five geothermal plants now provide almost a quarter of the country’s electricity.
  • When The Geysers in USA were discovered, the gigantic spouts of steam that emerged from them led the first visitors to believe that they had found the gates to Hell!
  • The amount of thermal energy under the ground available for heating — more than a million megawatts — dwarfs the amount available for electricity generation.

Extraction of Geothermal Energy


Typically, geothermal electricity is generated when hot water or steam under the ground is harvested to the surface of the Earth. This heat is used to power a turbine, which drives a dynamo that then produces electricity.

Probably the best example of a good Geothermal source is the The Geysers, 72 miles north of San Francisco in the United States. An elaborate array of gleaming metal pipes brings steam up from underground to drive turbines that generate 850 megawatts of electricity.

Using Geothermal Energy


Geothermal energy need not be only used to generate electricity. It may also be used for heating purposes. In fact, people have used hot water from natural geysers as an energy source since ancient times. The Romans, Chinese, and Native Americans used hot mineral springs for bathing, cooking and heating. Today, many hot springs are still used for bathing, and many people believe the hot, mineral-rich waters have natural healing powers.

Another common use of geothermal energy is for heating buildings through district heating systems. Geothermal sources that are not hot enough to be used for electricity generation may be better used to heat buildings through a network of hot water pipes. Such Geothermal Heat Pumps have the potential to provide nearly all US households with heat and hot water. A district heating system provides heat for 95 percent of the buildings in Reykjavik, Iceland. Examples of other direct uses include: growing crops, and drying lumber, fruits, and vegetables.


  • Geothermal Energy
  • The Great Forgotten Clean Energy Source
  • Geothermal Resources

See Also