Renewable Energy - Geothermal Energy
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Geothermal Energy
Geothermal energy ultimately comes from radioactive decay in the core of the Earth, which heats the Earth from the inside out, and from the sun, which heats the surface. It can be used in three ways:
Geothermal electricity
Geothermal heating, through deep Earth pipes
Geothermal heating, through a heat pump.
Usually, the term 'geothermal' is reserved for the thermal energy from the
core of the Earth. Geothermal electricity is created by pumping a fluid (oil
or water) into the Earth, allowing it to evaporate and using the hot gases
vented from the earth's crust to run turbines linked to electrical generators.
The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Iceland, New Zealand, United States, the Philippines and Italy. The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.
Geothermal heat from the surface of the Earth can be used on most of the globe directly to heat and cool buildings. The temperature of the crust a few feet below the surface is buffered to a constant 7-14C (45-58F), so a liquid can be pre-heated or pre-cooled in underground pipelines, providing free cooling in the summer and, via a heat pump, heating in the winter. Other direct uses are in agriculture (greenhouses), aquaculture and industry.
Drawbacks
Although geothermal sites are capable of providing heat for many decades, eventually specific locations cool down. Some interpret this as meaning a specific geothermal location can undergo depletion. Others see such an interpretation as an inaccurate usage of the word depletion because the overall supply of geothermal energy on Earth, and its source, remain nearly constant. Geothermal energy depends on local geological instability, which, by definition, is unpredictable, and might stabilise.
The general public considers geothermal energy to be renewable.
From Wikipedia.