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MAIN Arrow to Going Green Guides Society Arrow to Going Green Guides Go Green Guides Arrow to Geothermal Energy Geothermal Energy

The Geysers, northwest CA
Calpine operates 15 plants at The Geysers in
northwest California, which generate enough
clean energy daily to power a city the size of
San Francisco. Photo Courtesy of Calpine


Geothermal power is power derived from the heat stored within the earth. Geothermal power accounts for less than one percent of the world's energy production, despite the fact that there is huge potential in geothermal power.

In fact, using certain geothermal technologies, the ground below the United States alone could satisfy the entire world's energy needs for as much as 30 thousand years.

Feeling the heat

Geothermal technologies have come a long way since 1904, when the technology was first proven. Today, there are three basic types of geothermal technology.

One is based on the fact that on nearly every land surface on Earth, the top ten feet of surface soil remains at a constant temperature of fifty to sixty degrees Fahrenheit, regardless of the season.

So by circulating air through pipes buried at this depth, the air in a building above can be either warmed in the winter or cooled in the summer.

Another common geothermal technology is the pumping of warm water from deep below the Earth's surface to the ground level, where it is used to heat roads, buildings, and even whole communities.

Geothermal power pros and cons

The most powerful form of geothermal power is hot dry rock geothermal technology, wherein wells are drilled as deep as 10 kilometers into the Earth's surface, piercing through very hot rock.

Iceland geyser
Volcanically active Iceland
sits atop a huge & powerful
geothermal energy source.


Next, water other another liquid is pumped in to the well where it is heated by the rocks and used to generate power. This is a form of geothermal technology which shows a great deal of potential, and could provide huge amounts of power if properly implemented.

However, to get to a geothermal source, pumps and compressors run on electricity may negate any advantages geothermal energy may have on the environment. It may also indirectly contribute to harmful emissions, depending on the extraction power source used.

Land subsidence is another issue -- brought about by tapping into geothermal sources. Hydraulic fracturing can even trigger earthquakes resulting, for example, in the complete abandonment of a geothermal project below the city of Basel, Switzerland in 2006.

Geothermal success stories

Today, the United States is the country that produces the most geothermal power, with 14 plants in Nevada, one each in Hawaii and Utah, and 33 plants in California - home to the world's largest geothermal plant at the Geysers Geothermal Resource Area.

However, other countries like the Philippines and Iceland generate a far greater percentage of their power from geothermal technology. The tiny island of Nevis in the Caribbean is notable because when its geothermal projects are completed it will generate all of its power needs from geothermal power, with enough left over to export to neighboring islands, which makes it a fine example for the rest of the world.

More information about geothermal energy around the Web:

Geothermal power
- Excellent overview from Wikipedia including its history and development, a discussion on its pros and cons, with related photos, references & resources.

Geothermal Basics - Informative fact sheet from the Geothermal Energy Association including information on the various ways it can be used, a comparison of geothermal electric power plants types, geothermal facts and myths, with a guide to related resources around the Web.

Geothermal Energy Basics - Kid-friendly information including diagrams explaining geothermal energy and applications, with related resources.

EIA Energy Kids - Geothermal - Information and fun facts including a brief definition, where geothermal energy comes from and how it is harnessed with related maps and illustrations, from the US Energy Information Administration..


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