Geothermal energy is a clean and renewable form of energy that can help reduce climate change.
Geothermal systems extract heat from the earth, which is then used to produce electricity or hot water for heating buildings or swimming pools. Geothermal power plants are not only environmentally friendly because they do not emit greenhouse gases like other fossil fuel-fired plants, but also because their waste products – mostly just steam and hot water – are benign.
Existing geothermal capacity worldwide totals about 10 gigawatts (GW), with an additional 20 GW under construction in various stages of development. The United States currently has about 3 GW of installed capacity, making it the world’s third largest producer behind Indonesia (6 GW) and Italy (4 GW). Countries such as Japan, China and the Philippines are all investing heavily to develop geothermal energy.
In producing electricity, geothermal power plants emit virtually no greenhouse gases. To understand why this is so, consider how a typical fossil fuel-fired plant works.
When coal or oil is burned to generate electricity, the thermal energy produced must first be converted into mechanical energy to run the turbine. The mechanical energy is then converted back into thermal energy by a cooling system before it heats water, which produces steam. And finally, the steam produced must be converted back into mechanical energy so that it can spin the turbine again.
Geothermal plants work in reverse order from fossil fuel-fired plants. Water is drawn from a hot geothermal resource and pumped through a steam generator to produce high-pressure, saturated steam that spins the turbine. The remaining liquid – which is actually quite warm, but not hot enough to generate electricity from – is simply re-injected into the reservoir.
Because this process does not release any carbon dioxide or other greenhouse gases into the atmosphere, geothermal energy does not contribute to climate change.
Even the power plants that burn fossil fuels for supplemental heat – a technique known as cogeneration – emit fewer greenhouse gases than do comparable coal-fired power plants.
Individual geothermal electricity generating plants range in size from about 125 kilowatts (kW) – enough to power a small hospital – to about 750 MW, about the same size as many coal-fired power plants (though there are some even larger).
The world’s largest geothermal generating plant is located at The Geysers in California and produces more than 20 percent of the state’s renewable energy. Since 1985, this complex has produced more than 7,000 billion kilowatt-hours (kWh) of electricity, enough to meet the annual power needs of a city the size of Seattle.
So geothermal energy does help reduce climate change, and it should be utilized in as many possible areas as possible.