While not in play across the U.S. like solar or wind, another abundant renewable energy courses—literally—beneath the country’s surface, is geothermal heat. But there are few commercial deployments of it at this point and only one commercial-scale enhanced geothermal system (EGS). Desert Peak 2, a 1.7 megawatt EGSsystem, located in Churchill County, Nev., near the existing geothermal Desert Peak Power Plant, is the nation’s first commercial-scale EGS system.
Ormat Technologies’ Desert Peak previously generated 11 megawatts of electricity. The recently commissioned Desert Peak 2 EGS increased the power output of the overall system by nearly 38 percent.
While more homeowners and businesses are starting to use geothermal energy for heating and cooling, use geothermal energy to generate electricity is a lot different. First off, the temperature of the water must reach over 350 degrees Fahrenheit. In some places those temperatures are reached close to land, like at the original Desert Peak project, but in others wells must be dug much deeper to access heated rock to extract the heat.
The Department of Energy, which supported the project with $5.4 million—matched by $2.6 million in private sector funding, essentially uses fracking technologies. “To deploy EGS, production wells are drilled to depths of 10,000 feet and beyond to access the hot rock that makes up the earth’s crust,” DOE said.
“Pressurized water is injected into the wells to open pre-existing fractures along the surface of the rock—creating permeability. This increased permeability allows the water to flow through the openings in the rock—capturing the rock’s heat. The heated water is then pumped back to the surface and the resulting steam is used to power a turbine to generate electricity,” DOE said. After the steam is converted back to water it repeats the cycle, creating a closed-loop energy generation system.
"The Churchill County geothermal project represents a critical investment to ensure America leads in this growing global industry, helping to create new manufacturing, construction, and operation jobs across the country while diversifying our energy portfolio and reducing pollution," said Assistant Secretary for Energy Efficiency and Renewable Energy David Danielson.
EGS could prove to be a powerful form of renewable energy in the future. Since it uses existing drilling and steam generation technologies like concentrating solar power and provides a stable source of electricity, it can provide electricity at rates cost-competitive with coal and natural gas generation—and even cheaper after the plant’s construction costs are paid off, since it never needs any outside fuel source. There’s also plenty of it available in the U.S. The U.S. Geological Survey estimates that EGS in the United States has the potential to enable development of 100 to 500 gigawatts of new energy.