Geothermal Energy

The Basics

Geothermal energy comes from the heat of the Earth’s interior. Reservoirs of steam or hot water with temperatures higher than about 225°F can generate electricity,^[1] while lower-temperature geothermal fluids are often used directly for heating and other applications.^[2] In western states like California and Nevada, hot rocks beneath the Earth’s surface create shallow hot water reservoirs. Scientists are developing enhanced geothermal systems to extract heat from hot, dry rocks in order to produce electricity.

Why does geothermal matter?

In 2017, only 0.4% of U.S. electricity came from geothermal energy sources,^[3] but the U.S. Geological Survey estimates that geothermal energy could generate more than 10% of the nation’s electricity.^[4] While geothermal has historically been limited to western states with shallow hot water reservoirs, enhanced geothermal systems may make it possible to extract geothermal energy from hot, dry rocks throughout the country.

How does geoscience help?

Geoscientists identify geothermal resources and estimate how much energy they can provide, including developing ways to create enhanced geothermal systems. They also investigate the environmental impacts of geothermal energy development and study how to manage existing geothermal systems.

References

¹ Geothermal - Electricity Generation, DOE, https://www.energy.gov/eere/geothermal/geothermal-electricity-generation

² Geothermal Heat Pumps, DOE, https://www.energy.gov/eere/geothermal/geothermal-heat-pumps

³ Use of Geothermal Energy, EIA, https://www.eia.gov/energyexplained/geothermal/use-of-geothermal-energy.php

⁴ Assessment of moderate- and high-temperature geothermal resources of the United States, U.S. Geological Survey, https://pubs.usgs.gov/fs/2008/3082/

Learn More

Introductory Resources

• Geothermal Explained, Energy Information Administration
  An overview of the source of geothermal energy, types of geothermal power plants, locations of geothermal energy, geothermal heat pumps, and brief discussion of geothermal energy and the environment.

• What You Need to Know About Energy: Renewable Sources, The National Academies
  An in-depth overview of the current role of each renewable energy source in the United States, the benefits and disadvantages of each energy source, and opportunities and challenges for using that energy source in the future. (Discusses geothermal, wind, solar, hydroelectric, biomass.)

• Learning About Renewable Energy, National Renewable Energy Laboratory
  Basic overview of renewable energy sources and technologies, including biomass, geothermal, hydrogen & fuel cells, hydropower, ocean, solar, and wind energy. Provides links to more information on each topic.

Resources for Educators

• Education GeoSource Network (EGS), AGI
  Search for geothermal energy resources related to professional resources, curricula & instruction, teaching media, outreach programs, and other EGS collections.

• NGSS Performance Expectations, Next Generation Science Standards
  K-ESS3-1, 4-ESS3-1, MS-ESS3-1, HS-ESS3-1, HS-ESS3-2

• NGSS Disciplinary Core Ideas, Next Generation Science Standards
  ESS3.A

Coal

Coal is a carbon-rich rock formed from plants that grew millions of years ago. Coal is a major source of electricity in the United States and the largest source of energy for electricity generation worldwide.

Energy

All of the energy we use comes from the Earth, its atmosphere, or the Sun. Some resources are mined or extracted, like coal, uranium, oil, and gas. Others, like wind, solar, tidal, biomass, and hydropower resources, are harnessed at the Earth’s surface. Geoscientists play an essential role in developing energy resources and evaluating their environmental impacts.

Groundwater

Groundwater is the water found underground in the cracks and spaces in soil, sand, and rock. Groundwater has been used by humans for thousands of years; today it provides 25% of the fresh water used in the United States, mostly for irrigation and public water supplies.

Hydraulic Fracturing

Hydraulic fracturing is a technique used in one step of the extraction of energy resources. Sometimes referred to as “fracking”, its wide application over the last decade has led to debate over its risks and benefits.

Hydropower

Hydropower uses the energy from moving water to power machines or generate electricity. Used for over two thousand years in water mills, today hydropower is more commonly associated with electricity generation.

Nuclear Energy

Nuclear energy is produced from fission, which splits the large atoms of heavy elements like uranium into smaller atoms, releasing enormous amounts of energy. Thirty U.S. states have nuclear power plants, and nuclear energy makes up around 20% of the U.S. electricity supply.

Oil and Gas

Petroleum (“oil”) and natural gas are hydrocarbons that formed over millions of years under heat and pressure deep in the Earth. Petroleum and natural gas are the largest sources of energy in the United States.

Renewable Energy

Renewable energy comes from sources that are constantly replenished, like running water, the heat of the Earth, the Sun’s light, or wind. Renewables account for around 11% of U.S. energy consumption and 17% of electricity production.

Solar Energy

Solar energy is energy from the Sun, which can be harnessed in several ways. Solar panels use the photovoltaic effect to generate electricity directly from sunlight. The Sun’s heat can be used directly to heat water or air, or it can be concentrated to boil water, driving steam turbines that generate electricity.

Wind Energy

Wind energy is harnessed by wind turbines, which convert the energy of the wind into electricity. Wind energy is one of the largest sources of renewable energy. Wind farms can now be found in more than 40 states.