Geothermal power plant in Iceland. Credit: Scott Ableman/Flickr.
For decades, geothermal energy has been the shy cousin of the renewable energy family. While solar and wind power scaled up dramatically, geothermal has remained niche, delivering only a fraction of the world’s electricity. Its Achilles’ heel has always been geography — those pockets of underground heat are mostly found near volcanic regions.
But what if we could tap into Earth’s heat nearly anywhere? A new study out of Cornell University suggests we can. The answer may lie in something called superhot rock energy.
The Heat Beneath Our Feet
Diagram of a superhot rock system
In a superhot rock system, water is injected deep into hot rock, heated and returned to the Earth’s surface as steam that can be used to produce power in electric turbines or to generate hydrogen using a high-temperature process. See animation. Credit: Cornell University.
Imagine drilling deep into the Earth — much deeper than ever before — into rock heated to at least 374 degrees Celsius (over 700°F). At these extreme temperatures, water injected into the rock turns into a supercritical fluid, carrying immense energy back to the surface. And this energy could generate electricity, provide heat, or even produce hydrogen fuel.
Well, this isn’t just a pipe dream. Researchers believe superhot rock energy (SHR) could unlock enough power to meet the United States’ energy needs thousands of times over.
In their new series of reports, researchers from Cornell and the nonprofit Clean Air Task Force (CATF) lay out a clear roadmap for how we might get there. These reports analyze the technological challenges in drilling, well construction, heat extraction, and power production.
“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,” said Seth Saltiel, a research professor at Cornell and co-author of the siting report.
Saltiel and his team emphasize that a better understanding of the Earth’s subsurface — the fractures, fault lines, and rock structures — is critical. Success will require precision drilling and a detailed knowledge of how heat flows beneath our feet.
“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,” Saltiel explained.
The potential rewards are staggering. According to the CATF report, just 2% of geothermal energy within a few kilometers of the surface could theoretically meet the U.S.’s energy needs 2,000 times over. Superhot rock energy, if developed, could offer “an inexhaustible, always-available source of clean energy,” the report states, unlike solar and wind which are intermittent and unreliable year-round.
A Global Race for Superhot Rocks
Geothermal’s next frontier isn’t limited to the U.S. — and that’s part of the excitement. New research indicates that China, Russia, and the U.S. hold the largest potential reserves of superhot rock energy. Furthermore, according to CATF’s analysis, the U.S. alone could tap into 4 terawatts of power from SHR, the equivalent of burning 21 billion barrels of oil.
Nevada and California sit atop some of the best superhot rock resources. And, in a twist of energy irony, the oil and gas industry may play a pivotal role in bringing SHR to life. The technology needed for SHR — advanced drilling rigs, robust drill bits, and sensors that can withstand hellish temperatures — already exists, developed for oil and gas extraction. “It’s hard to imagine a group more well-positioned to push this up the commercialization curve,” said Terra Rogers, CATF’s program director for superhot rock energy.
Lauren Boyd, director of the Geothermal Technologies Office at the U.S. Department of Energy, put it bluntly. “We need investment, and we need people to get into this space.” The department estimates that the U.S. needs between $20 billion and $25 billion of investment by 2030 to bring next-generation geothermal technologies, including SHR, to market.
For oil and gas companies, SHR presents an opportunity to pivot toward clean energy while leveraging existing skills and infrastructure. Land leased for oil and gas drilling in the U.S. can often be used for geothermal exploration without new permits. “This decade is the decade of geothermal,” Rogers declared in an interview with the Financial Times.
Obstacles and Optimism
Still, as promising as SHR sounds, challenges remain. Drilling six miles into dense bedrock isn’t easy — or cheap. Early projects always carry high risks, and without substantial investment, SHR could remain trapped in the realm of ‘what if’. The Earth, after all, keeps its secrets well-guarded. But for some researchers, policymakers, and investors, those barriers seem increasingly surmountable.
Jennifer Granholm, the U.S. Energy Secretary, echoed this sentiment, telling energy executives gathered at the March 2024 CERAWeek conference, “If we can capture the ‘heat beneath our feet,’ it can be the clean, reliable baseload scalable power for everybody from industry to households.”
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