Geothermal energy is energy that is generated and stored within the earth. It takes advantage of the Earth’s core heat to produce usable energy. Learn more with this video from the Explore More: The Future of Energy series.
Geothermal energy is energy that is generated and stored within the earth. It takes advantage of the Earth’s core heat to produce usable energy.
How it Works and How it is Used
Geothermal power is accessed in two different ways, and the underground temperature where it is accessed determines how it used.
Heating and Cooling
At a certain depth, the underground temperature remains relatively constant. Using geothermal heat pumps, these stable temperatures (55-60° F) can be tapped, and used in heating and cooling applications. In heating mode, heat is extracted from the earth by the geothermal heat pump and distributed to the home or building—typically through a system of air ducts. Cooler air from the building is returned into the ground to be reheated. In cooling mode, the process is reversed.
In some regions, including the United States’ West Coast and the West Coast of South America, underground temperatures are much higher because magma or molten rock is much closer to the earth’s surface. These regions can use the extreme temperatures to actually generate electricity.
To produce electric power from geothermal resources, underground reservoirs of steam or hot water are tapped by wells, and this steam is used to rotate turbines that generate electricity. Typically, water is returned to the ground to recharge the reservoir and reheat, completing the renewable energy cycle.
In some areas, water is already in steam form when it’s extracted through the wells. The world’s largest geothermal area is called "The Geysers", an area north of Napa Valley, California. Steam wells fuel twenty-one separate electric plants in this region, pumping out a total of 1000 megawatt (MW) of electricity.
However geothermal is used, there are many benefits. Geothermal produces no emissions. The resource is naturally renewable. Using this resource can help reduce the demand for fossil fuels – the only outside energy source you would need for heating/cooling air is for energy to run the heat pumps.
Geography and Geology
The biggest limitations of using geothermal to generate electricity is related to geography and geology – there are relatively few places on earth that have magma close enough to the earth’s crust to create the conditions necessary for generating electricity in an economical way. These locations are in regions where there are young volcanoes, crustal shifts, and recent mountain building.
Like some other types of electrical generation, the costs of drilling the wells and building the plants can be very expensive. Once all that initial money is spent, the cost of producing geothermal electricity is quite competitive with other forms of electrical generation. A geothermal heating/cooling system is more expensive to install than other systems. Over time though, experts say the savings in heating and cooling costs more than pay for the system. People who live in extreme climates can see the return on their investment within three to five years.