Geothermal Energy
    Geothermal energy is when heat from the earth is used to create energy. It has
been used for thousands of years; however only in recent years has it been used
to do more than simply cook or heat. The energy inside the earth is an estimated
6000 degrees. Geothermal energy uses this heat to create an electricity resource.

    To reach a temperature that is over 100 degrees in order to boil water, one
must drill over 3 kilometers into the earth. An easier way to reach this high of a
temperature is to locate a geothermal “hotspot”. A “hotspot” is an area that is
less dense than the surrounding mantle. Heat moves through this area more
easily, so heat can be transmitted from the center earth into the outer crust.
Hotspots are located closer to the earth’s surface which makes them easier to
access than other areas.

    There are 3 main ways that geothermal energy can be used to convert heat into
electricity.
  •  Dry steam plants - use steam piped directly from a geothermal reservoir to
    turn the generator turbines. These plants can only be built at a place where
    natural steam is erupting from the earth.
  •   Flash steam plants - take high-pressure hot water from deep inside the
    earth and convert it to steam to drive the generator turbines. When the
    steam cools, it condenses to water and is injected back into the ground to
    be used over and over again. Most geothermal power plants are flash plants.
  •  Binary power plants - transfer the heat from geothermal hot water to
    another liquid. The heat causes the second liquid to turn to steam which is
    used to drive a generator turbine.

    Geothermal energy produces less than 3% of greenhouse gas emissions than
a fossil fuel plant. The steam and water used by the plant is injected back into the
earth once it has been used. One major concern surrounding geothermal energy
is that it is not a permanent resource. The hotspots will loose too much of their
heat if used for too long and the plant will not continue to produce energy.





Sources

"Energy Resources: Geothermal." Energy Resources. 12 Feb. 2008. 03 July 2008 <http://home.clara.net/darvill/altenerg/geothermal.htm>.

"Geothermal Energy." Energy Page. July 2007. 03 July 2008 <http://www.eia.doe.gov/kids/energyfacts/sources/renewable/geothermal.html>.