Things To Know:  Geothermal energy is the heat energy springing from the core of the earth.  Radioactive decay, plate subduction, and pressure gradients are the primary reasons for these high temperatures.  New technologies are coming online all the time to harness this energy rich resource.  Icelanders are masters at harnessing geothermal: http://www.energy.rochester.edu/is/reyk/. Iceland has an amazing wealth of geothermal heat, and derives much of its electricity from steam turbines hooked up to geysers dotting the island.  The United States also has a great wealth of geothermal potential, which will only increase with better drilling technology in the future.  Much of our potential has not been exploited according to the GEO: http://geothermal.marin.org/pwrheat.html#Q11 home page: http://geothermal.marin.org/ .

In an effort to gain maximum energy from low-grade or residual heat from geothermal and other heat sources, Kalina cycle power may be employed.  This technology utilizes weak heat to vaporize a working fluid (usually ammonia water) forcing the vapor through a turbine and allowing the option of low-cost refrigeration.  http://www.state.hi.us/dbedt/ert/iesw2003/lerner/lerner-all.pdf.  Please see http://www.exergy.se/ftp/kalina.pdf and the Rankine cycle at: http://europa.eu.int/comm/energy_transport/atlas/htmlu/orcint.html.

New ground source heat pumps are no less fantastic.  These devices harness ground heat, even from relatively frigid ground water or soils or deposit surface heat into the same medium.  The mechanism has the potential to save enormous sums in energy costs in both cold and hot weather climates. 

Geothermal Electricity:  Currently the U.S. has an installed capacity of 2200 MW from Geothermal sources.  The following web sites will be able to provide more information: http://www.geothermal.org/.  One can find more information and statistics from http://www.consrv.ca.gov/dog/geothermal/index.htm, http://iga.igg.cnr.it/index.php and http://www.eere.energy.gov/geothermal/.

A fantastic virtual tour of a geothermal power plant is currently available from the website of Calenergy: http://www.calenergy.com/html/aboutus4.asp.  It is also important to note that the remaining heat in the fluid after the flash vaporizing stage could still be used to generate electricity by the Kalina cycle mentioned above.  One also wonders why the spent fluid returning back to the depths couldn't be passed through a small hydroelectric installation on the way back down? 

Heat Pumps:  Heat pumps are a fairly innovative solution to reducing the large amounts of energy necessary get the benefits from both the furnace and the air conditioner.  Energy savings of 4 to 5 times are achievable.  These devices condense either the heat or refrigeration from the ground or ground water.  If you have trouble envisioning this concept, just think of your house becoming a giant refrigerator with the radiator stuck in the ground, or using the same device but reversing the  process, the ground becomes a giant refrigerator with the radiator stuck in your house.  The following are some companies and web sites that will tell you more: Applied Energy Systems http://www.aers.com/, Architectural Residential Technologies Inc. http://www.arit.com/index.htm, and Tetco Geothermal Products: http://www.edwards-eng.com/geo/product.html.  An excellent source of information for people considering adapting their home's heating and cooling equipment can be found at http://www.geoexchange.org/.  This site includes both technology and financing options!