20.16: Geothermal Energy

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Why is there so much heat coming from below?

A visit to an active geothermal area is likely to be very interesting. Some of the most active ones in the U.S. are Yellowstone in Wyoming and Lassen Peak in California. These places are not available for energy production. But the Geysers Geothermal Resource Area in California is used for energy. A magma chamber deep below produces dry superheated steam. This steam can be harnessed.

Geothermal Energy

Geothermal energy stems from Earth's internal heat. Hot springs and geysers are produced by water that is heated by magma or hot rock below the surface.

At a geothermal power plant, engineers drill wells into the hot rocks. Hot water or steam may come up through the wells. Alternatively, water may be put down into the well to be heated. It then comes up. The hot water or steam makes a turbine spin. This makes electricity. Pictured below is an example of a geothermal power plant (Figure below).

A geothermal power plant in operation

A geothermal power plant in operation.

Geothermal Energy as a Resource

Because the hot water or steam can be used directly to make a turbine spin, geothermal energy can be used without processing. Geothermal energy is clean and safe. It is renewable. The earth's interior will be hot for the foreseeable future, and water can be pumped down into a well. There, the water can be heated again to make more steam.

Geothermal energy is an excellent resource in some parts of the world. Iceland gets about one fourth of its electricity from geothermal sources. In the United States, California leads all states in producing geothermal energy. Geothermal energy in California is concentrated in the northern part of the state. The largest plant is in the Geysers Geothermal Resource Area. Geothermal energy is not economical everywhere. Many parts of the world do not have underground sources of heat that are close enough to the surface for building geothermal power plants.

KQED: Geothermal Heats Up

Where Earth's internal heat gets close to the surface, geothermal power is a clean source of energy. In California, the Geysers supplies energy for many nearby homes and businesses.

Summary

Most geothermal energy being used now is in regions where hot material comes to the surface.
Hot rocks are everywhere below Earth's surface. Geothermal energy could be used anywhere with drilling.
Geothermal energy is clean and does not release greenhouse gases.

Review

How is geothermal energy harnessed?
What is the ultimate source of geothermal energy?
What is positive about geothermal energy?
What is not so good about geothermal energy?