Superhot rock energy could power geothermal systems anywhere

Geothermal energy holds the potential to provide abundant renewable energy at equivalent cost to fossil fuels, and targeted investments could quickly speed its development, according to a new report from Cornell researchers and the nonprofit Clean Air Task Force (CATF).

The “Gaps, Challenges, and Pathways Forward for Superhot Rock Energy” reports explore current and emerging technologies to expand geothermal energy and identify priority areas for research investments.

Subject experts explore technology gaps and strategies to overcome them in drilling, well construction, heat extraction, power production and siting. The siting report is co-authored by Seth Saltiel, assistant research professor of earth and atmospheric sciences, a shared department in the College of Engineering and the College of Agriculture and Life Sciences; Chanmaly Chhun, a postdoctoral associate in Saltiel’s lab; Pascal Caraccioli Salinas, a doctoral student in Saltiel’s lab, and colleagues at Cascade Institute.

Conventional geothermal energy systems are limited to regions where concentrated heat exists near the Earth’s surface, especially near the boundaries of tectonic plates where the crust is thinner and volcanic activity provides heat. However, next-generation technologies seek to make geothermal energy possible almost anywhere.

By drilling deeper into the Earth, geothermal systems could access superhot rock energy (SHR), where rock is heated to 374 degrees Celsius or hotter—temperatures high enough to carry significantly more energy and produce electricity more efficiently.

Safely accessing these energy sources will require careful siting and understanding of key subsurface features, such as rock structures, locations of fractures and fault lines, heat flow and heat sources, the researchers found. This is because geothermal project designs rely heavily on detailed characterizations of a proposed site’s temperatures, stress, hydrologic conditions and rock properties—conditions that can change over time as fluids are injected and heat is extracted, Saltiel said.

“Unlike other readily scalable renewable energy technologies, the highly site-specific aspects of geothermal power production introduce risk that has been a major obstacle to commercial development,” he said.

“By identifying state-of-the-art technologies and opportunities for research and development to improve and validate characterization methods, we hope to help overcome these obstacles and speed commercial development of this technology.”

The CATF reports stem from partnerships with multidisciplinary teams, including nonprofit organizations, drilling companies, surface equipment companies, academics and other stakeholders. Saltiel’s collaboration with Terra Rogers, program director for Superhot Rock Energy at CATF, was supported in part by an Innovation for Impact Fund award from the Cornell Atkinson Center for Sustainability.

“This report series and its insights were made possible through collaboration across academia, government and industry—a vital element in advancing SHR to commercialization at a meaningful pace,” Rogers said. “By sharing knowledge, resources and investments today, we can meet the clean energy needs of tomorrow.”

To access superhot dry rocks, boreholes must be drilled into hard, dense bedrock. Technological innovations developed for current geothermal systems and for hydraulic fracturing for oil and gas extraction already exist to support this concept; however, “significant innovations” are needed to decrease risk and increase efficiency, including advancements in drill rigs, drill bits, sensors and temperature management equipment, the reports find.

Cornell drilled a 2-mile-deep exploratory borehole on its Ithaca campus in 2022 to study the capacity for deep geothermal energy to provide Earth-source heat. However, that facility is not expected to delve deep enough to access superhot rocks, which would require drilling at least 6 miles below Earth’s surface in low heat flow areas like the eastern US.

Existing research suggests that 2% of the geothermal energy within 3 to 10 kilometers of the Earth’s surface could provide the equivalent of 2,000 times the current energy demand of the United States, according to the CATF report.

“Geothermal energy can offer an inexhaustible, always-available source of clean energy,” the report states. “With innovation, superhot rock energy could have the potential to provide long-term, scalable, renewable baseload power in many more places around the world at a scale and cost equivalent to fossil fuels.”