Geothermal energy is the energy left over from the Earth’s formation. Around the world, hot springs and volcanoes are used for heating. In Iceland, five power plants are run on geothermal energy, two of which supply hot water and electricity, three of which supply electricity only. Hot water is even piped under roads to melt ice! In the United States, the world’s geothermal leader, 83 geothermal power plants operate in 7 states. 1 But we don’t need to live near a volcano to utilize geothermal heating and cooling. Home systems have nothing to do with generating electricity or using heat from hot springs or volcanoes. They simply use the earth to heat and cool.
The premise is very simple. Dig deep enough into the earth, below the frost line, and the temperature remains a constant 50 degrees. Run water pipes into the ground in 4” to 6” wells to heat or cool the water to 50 degrees then pump that water through the geothermal unit.
As refrigerant in the geothermal unit and water in the pipes flow past one another, heat exchange occurs. The water in the pipes either transfers heat or absorbs heat, depending on the season and the temperature of the coolant.
The unit compresses or expands the refrigerant and air blows across coils to be heated or cooled; that air is then blown into the vent system in the house. The heat exchange from the water pipes greatly lowers the energy required to heat or cool the refrigerant, thus providing energy savings.
The systems are not cheap, but the U.S. government is willing to help. A stimulus bill allows a 30% tax credit for homeowners who install geothermal heat pump systems. 3 The great news is that the systems certainly pay for themselves over time by significantly cutting energy use.
1 Geothermal Energy Association
2 Sawyers, Harry, Popular Mechanics, The Guide to Home Geothermal Energy, October 2009
3 GeoExchange.org