Joined: Mar 04, 2005 Posts: 2250 Location: New Zealand
Posted: Tue May 13, 2008 12:22 am Post subject: Geothermal Energy Sources 101
This is one area where I have some expertise. I think this is a good summary and introduction to this important energy source.
Geothermal Energy Sources 101
Quote:
Geothermal power plants are an almost pollution free source of electricity. Typically they are installed near shallow subsurface sources of steam and / or hot water characterized by faults, seismic activity, earthquakes and volcanoes.
The source of geothermal power generation is steam at a temperature of ~300 degree C. To access geothermal steam involves drilling a vertical well to the source. A second well is drilled to the lower water level of the steam source. The steam is directed into a steam turbine which in turn generates electricity. The condensed turbine exhaust is re-injected back into the underground reservoir.
There are essentially three types of geothermal power plants used depending on the source.
On dry land and free of volcanic activity, the temperature is typically 41 degrees C higher for every 1.6 km below the surface. With a well drilled to a depth of 3 to 10 kms, steam can be successfully produced from water upon contact with subsurface rock. Steam produced in this manner is known as an Enhanced Geothermal System [EGS] and sometimes referred to as a Hot Dry Rock [HDR] system.
A 2006 MIT report suggests that there is enough hard {hot} rock at a 10 km depth in the United States subsurface, to supply the entire world's energy requirements for 30,000 years.
To produce a sustainable source of steam, the HDR system requires sufficient heat at a subsurface depth, a hard rock layer capable of being fractured, an insulating layer above it and a source of water.
seekingalpha _________________ Human history becomes more and more a race between education and catastrophe. H. G. Wells.
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