A House bill that directs research, development, demonstration, and commercial application activities in support of enhanced geothermal systems (EGS), also known as supercritical geothermal systems and closed-loop geothermal systems (CLGS), has rare bipartisan support among lawmakers.
Supercritical geothermal is an experimental technology that requires deep drilling to access dry rocks at temperatures around 400 Celsius or greater, at which point water or other liquids are injected at depths of four kilometers or deeper and, utilizing natural heat deep within the Earth’s crust, returned to the surface at supercritical conditions to power a turbine and generate energy, according to the subcommittee.
The Department of Energy (DOE) describes supercritical geothermal systems as follows:
EGS is a man-made reservoir created where there is hot rock but insufficient or little natural permeability or fluid saturation. In an EGS, fluid is injected into the subsurface, which causes pre-existing fractures in the hot rock to re-open to heat the liquid and turn it to stream, which then turns generators to create electricity.
CLGS continuously circulates a heat transfer solution through buried or submerged plastic pipes. The loop is filled just once and requires only a moderate amount of solution. That is used again and again in a closed loop.
The bill supporting those systems is H.R. 8665, the Supercritical Geothermal Research and Development Act, which was introduced by Rep. Frank Lucas (R-Okla.). A hearing on the bill, along with three other bills, was held on July 23, 2024 by the Subcommittee on Energy and Mineral Resources.
At that hearing, lawmakers on both sides of the aisle praised H.R. 8665, including Subcommittee Chairman Pete Stauber (R-Minn.), who said, “As global demand for energy continues to rise, it’s important that we prioritize policies that boost domestic energy production and advance American energy independence, rather than relying on adversarial nations for our energy supply. We must support our domestic energy sector, which will, in turn, lower costs for consumers, provide good-paying jobs, and produce the cleanest forms of energy found anywhere in the world.”
Subcommittee Ranking Member Alexandria Ocasio-Cortez (D-N.Y.) also praised H.R. 8665, saying the bill supports much-needed research “to power up the deployment of these experimental forms of geothermal energy” and thereby “presents one important move towards a clean energy future. Supercritical geothermal is a reason that allows massive potential to produce reliable, always-available clean energy using the heat from the Earth’s core.”
If commercialized, supercritical geothermal has the potential to produce energy at significantly higher capacities compared to conventional geothermal systems, with the DOE estimating that next-generation geothermal technologies could provide 90 gigawatts (GW) or more of clean power to the U.S. grid by 2050.
Policies to increase the use of geothermal are supported by the Geothermal Steam Act of 1970, which directs the U.S. Geological Survey (USGS) to conduct national scale assessments of geothermal resources, the most recent of which was published in 2008. USGS currently operates several programs that support the research and development of geothermal energy resources. In addition, the USGS’ Earth Mapping Resources Initiative coordinates priorities with DOE’s Geothermal Technologies Office to collect useful data for both critical mineral and geothermal resources.
EGS and CLGS are rapidly enhancing the scalability of geothermal energy in the U.S., Rogers said. “While early movers in this industry are targeting, and will continue to target, regions in which the heat is closer to the surface, innovations in deep drilling are expected to unlock this resource at a global scale,” said Terra Rogers, director of the Clean Air Task Force's superhot rock energy program, who testified before the subcommittee.
Recent advancements in engineering have made commercialization of new forms of geothermal energy possible; Those engineering advances are operating somewhere, on average, between two and three miles deep, enabling the harvesting of the Earth’s heat without the need to locate rare and naturally occurring underground sources of water, Rogers told The Driller. Because those systems leave aquifers miles above, “there is very little concern of groundwater contamination,” she added.
U.S. demand for clean, baseload power is expected to rise significantly in the next decade. Still, traditional geothermal systems currently in operation only work in regions where hot water naturally exists near the surface. As a result, traditional geothermal potential represents less than three percent of utility-scale electric generation capacity in the U.S., according to Rogers.
EGS and CLGS are rapidly enhancing the scalability of geothermal energy in the U.S., Rogers said. “While early movers in this industry are targeting, and will continue to target, regions in which the heat is closer to the surface, innovations in deep drilling are expected to unlock this resource at a global scale,” she said.
“When deployed in belowground rock formations that exceed the supercritical temperature of water, these systems could significantly boost power potential and reduce costs, enabling geothermal energy to become cost-competitive with the lowest-cost energy,” she said. Because EGS and CLGS systems are demonstrating how cost effective they are, investment to develop geothermal projects is growing, she said. “I see this ripe for entrepreneurship,” she added.
