Tapping the Earth for Home Heating and Cooling by Martin LaMonica

Ground-source heat pumps have been around for decades but every year seem to attract more homeowners and organizations who are looking for alternatives to traditional space heating and cooling. They can hook into existing forced hot air and hot water systems but not steam heat.
Starting in 2006, Harvard University installed six ground-source heat pumps as part of its Green Campus initiative. Administration buildings and athletic facilities are already online and two more buildings planned.



During the summer, the systems pump indoor heat underground and draw on the lower temperatures of the Earth to cool a building. In colder months, the same process works in reverse, with heat from the ground being used to warm indoor air.
Indoors are box-shaped heat pumps that pull and and push either water or a working fluid, such as antifreeze, in and out of the ground. Using the same compressor loop mechanism that a refrigerator has, a heat exchanger draws energy from the circulating liquid to either heat or cool a building.
The International Ground Source Heat Pump Association, based in Stillwater, Oklahoma, said geothermal is 50 percent to 70 percent more efficient for heating than other systems. The U.S. Department of Energy says that a ground-source heat pump uses 25 percent to 50 percent less electricity than conventional heating and cooling systems.  Maintenance costs for geothermal are half the cost of traditional heating and cooling systems. The payback on geothermal systems, which used to be about seven years, is now typically four years, she said. Recently passed federal renewable energy initiatives now include $2,000 per year tax credit.

Source:

LaMonica, Martin. "Tapping the Earth for Home Heating and Cooling | Green Tech - CNET News." Technology News - CNET News. CNet, 14 Jan. 2009. Web. 29 Nov. 2011. <http://news.cnet.com/8301-11128_3-10131539-54.html>.