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Geothermal

Heat from below the earth's surface, or geothermal energy, can be used to heat and cool individual buildings and neighborhoods or produce utility scale electricity. Unlike fossil fuels, geothermal energy is a renewable resource that does not emit the greenhouse gases that cause climate change. In addition, once a geothermal system is built, the marginal costs are relatively low, because the “fuel” is free. Geothermal Heat Pumps

To heat and cool buildings, geothermal (or ground-source) heat pumps use the earth as a temperature exchange medium. The temperature underground is fairly constant (about 50 to 60 degrees Fahrenheit) and warmer than the outside air during the colder months in many climates. Water or another fluid runs through pipes buried 10 to 300 feet underground or underwater, to absorb the heat. The liquid then is compressed in a heat pump and its stored heat is released through air ducts in the building. The cooling process is just the reverse. Because the ground temperature is cooler than the air on hot days, the heat from the air is drawn from the building and carried off by the coolant in the pipes and back into the earth. Since underground temperatures are consistent almost everywhere, geothermal energy can be used for heating and cooling across the world. Iceland has been a major proponent of this clean energy source, with about 90 percent of its housing relying on geothermal heating systems as of 2013. Geothermal Power Plants

Geothermal power plants run continuously to provide a reliable form of base load power. To provide utility scale electricity, geothermal energy is accessed by drilling deep wells (sometimes over 5,000 feet) to tap steam and hot water from underground reservoirs. The steam drives turbines to generate electricity.