Geothermal energy is an enormous, underused heat and power resource that is emits very little greenhouse gas, provides reliable energy, and is fully homegrown, helping to makeus less dependent on foreign oil.
Geothermal resources range from shallow ground to hot water and rock several miles below the Earth’s surface, and even farther down to the extremely hot molten rock called magma. In some places—most famously Yellowstone National Park—geothermal activity occurs at the earth’s crust, and the ability to tap these sources for utility-scale power is viable. But almost everywhere, the upper 10 feet of Earth’s surface maintains a nearly constant temperature between 50 and 60°F, making residential and commercial-scale geothermal a possibility for anyone.
Geothermal Power Plants are built on technologies that drill into rock up to 5 kilometers deep, creating reservoirs for water to be heated by the activity in the rock. This activity is widespread around the United States but is most viable in the West. The installed domestic capacity of geothermal power plants is nearly 3,000 megawatts in five western states. These power plants use hot water and steam from hydrothermal reservoirs as their energy source. DOE estimates there are prodigious amounts of heat at depths from 3 to 10 km, and cites it as a key resource for future energy production.
Geothermal heat pumps leverage the consistent temperature of shallow ground to provide heating and cooling for an adjacent structure. These are built on a simple system of looped coils filled with fluid that help to transit heat to and from a heat pump that regulates indoor temperature.
HOW IT WORKS
A geothermal heat pump system consists of pipes buried in the shallow ground near the building, a heat exchanger, and ductwork into the building. In winter, heat from the relatively warmer ground goes through the heat exchanger into the house. In summer, hot air from the house is pulled through the heat exchanger into the relatively cooler ground. Heat removed during the summer can be used as no-cost energy to heat water.
They may be used in combination with solar photovoltaic systems to form geosolar systems, further reducing the electricity demand of a household.