Department of Energy

Top 10 Things You Didn't Know about Enhanced Geothermal Systems

April 28, 2015

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Check out the infographic above to learn how Enhanced Geothermal Systems work. | Graphic by <a href="/node/379579"">Sarah Gerrity</a>.

Check out the infographic above to learn how Enhanced Geothermal Systems work. | Graphic by Sarah Gerrity.

This article is part of the series highlighting the "Top Things You Didn't Know About..." series. Be sure to check back for more entries soon.

10. Geothermal technologies use the naturally occurring heat located in shallow ground, hot water and rock below the earth’s surface to generate electricity. Geothermal is considered a renewable source of energy because the earth’s core generates nearly unlimited heat.

9. The United States generates more electricity through geothermal energy than any other country in the world. The leading state -- California -- generates 79 percent of the nation’s geothermal electricity.

8. With current geothermal technologies, electricity can be generated only where three key conditions are met: heat, fluid and natural permeability at depth. Small underground pathways conduct fluids through the hot rocks, carrying energy in the form of heat through wells to Earth’s surface, driving turbines and generating electricity.

7.  Breakthrough technology called Enhanced Geothermal Systems -- or EGS -- can generate electricity anywhere there is hot rock at depth, greatly expanding the potential for geothermal power in the United States.

6. EGS are man-made reservoirs created by drilling wells thousands of feet below the earth to access hot rock at the earth’s crust. Highly pressurized cold water is pumped through the wells to cause pre-existing fractures of the hot rock to open up, increasing permeability. This enables the water to flow through the cracked rock and pick up heat. The resulting hot water pumps back to the surface where it is depressurized to make steam, which spins a turbine to generate electricity. The water is then cooled and pumped through the wells again, repeating the same process and creating a closed-loop system. Check out this infographic to learn more about how EGS works.

5. The Energy Department supports research and development at five active EGS demonstration projects in Nevada, Idaho, Oregon and California.

4. The U.S. Geological Survey estimates that EGS could provide 100 gigawatts of geothermal resource capacity in the United States -- enough to power about 100 million homes.

3.  EGS provides power around the clock and emits little to no greenhouse gases. The technology also allows for geothermal development outside of the western United States, where most hydrothermal resources are located.

2. The Energy Department’s future Frontier Observatory for Research in Geothermal Energy, called FORGE, will be the first-of-its-kind field laboratory that will enable scientists and researchers to develop, test and accelerate breakthroughs in EGS technologies.

1. When it is fully implemented in 2020, FORGE will also allow researchers to collect and disseminate data in real time and identify low-risk, replicable pathways to commercial EGS development.

Learn more about FORGE and the Energy Department’s work related to EGS. Also, watch this animation to see how EGS works.