‘Geo’ = ‘from the earth’ and ‘thermal’ = ‘heat’, so this type of energy is found under the earth. Here's how it works: about four feet underground, the temperature of the earth stays the same all year long, about 55 degrees.
A geothermal heating system uses pipes buried deeper than four feet down – so you have to watch out if you’re planting a tree anywhere near the pipes. The system pumps a liquid through the pipes to absorb the heat and brings it back indoors. A device called a ‘heat exchanger’ takes the heat from the liquid and uses it to heat the air inside the home.
A geothermal system can cool your house during the summer, too! It just works in reverse, absorbing the heat from the air inside your home and moves it back into the earth.
A geothermal heater is also very energy-efficient. Almost none of the energy used is wasted, so it helps keep heating bills low during the winter.
Only problem is, there are very few examples of geothermal heating systems in this country. A few civic buildings in Southampton are supplied with heat this way and the Eden Project in Cornwall has been granted permission to start drilling a Hot Rock Geothermal Plant which should produce up to 4 megawatts of electricity for use by Eden with a surplus, enough for about 5,000 houses, going in to the National Grid.
Alternatively, geothermal energy can be used to make electricity. A geothermal power plant works by tapping into steam or hot water reservoirs underground and the heat is used to drive an electrical generator.