How Geothermal Systems Work
Geothermal systems work by utilizing the earth beneath our feet. Heat is extracted from the earth in the winter and absorbed by the earth in the summer. This huge solar thermal battery averages about 47 degrees in Vermont. Low grade heat is collected from the ground and then using a refrigeration circuit, like your refrigerator, this heat is upgraded by an electrically driven compressor which then can be delivered at a useful temperature for heating. For cooling the system is simply reversed. This system can also heat the domestic hot water when it is running.
The geothermal system is highly efficient because for every unit of electrical energy used to run the compressor and pumps, the geothermal system can extract and upgrade 2 to 3 units of heat energy from the ground. Therefore the homeowner receives 3 to 4 units of heat for each energy unit put in, which makes the geothermal system 300 to 400 percent more efficient than baseboard electric heating. This efficiency can also be expressed as a Coefficient of Performance (COP) of 3.0 to 4.0. The homeowner who truly wants to have a carbon free heating system, can install sufficient solar PV or wind power with the energy returned to the grid to offset their annual usage. Such a system would be a zero net energy heating system!