Using the Earth's HEAT

Ground-source heat pumps use the stable temperature of the ground to heat, cool, and provide hot water for
homes and businesses.

Gary Prior, an avid follower of renewable energy, decided to tap into this source for both philosophical and economic
reasons. His family reduced its annual space and water heating expenses from $3,300 to less than $600. The 3-ton system also provides central air-conditioning and dehumidification that the home did not have previously.

How it Works

Ground-source heat pumps (GSHPs; sometimes termed “geothermal” by the heat pump industry) take advantage of the earth’s steady subsurface temperature year-round. No matter if you are in Alaska or Arizona, the temperature 6 feet underground remains fairly constant. In New England, for instance, the earth’s subsurface temperature is between 52 and 54°F. If you’ve ever gone into a cave on a warm day, you’ve probably noticed that the cave temperature is much cooler than outside. When the weather is cool, that same cave would be warmer than the outside air.

GSHPs use heat-transfer fluids (refrigerants) that have a low boiling temperature, so they can easily change from liquid to vapor and back again, transferring the energy from,or to, the earth’s subsurface. Pipes (called a loop) drilled or buried in the ground circulate the refrigerants to transfer the heat in the ground to the heat pump. There, the heat is extracted from vaporized refrigerants and sent to a heat

... read the entire article from home power 140 • december 2010 & january 2011