Miles below ground, where pressures are intense and temperatures far exceed the boiling point of water, dense layers of super-hot rocks offer the promise of a natural, inexhaustible supply of clean energy.
Environmentalists have long dreamed of a way to reach those depths to tap the potential geothermal energy in those rocks, but the technological and financial barriers have been too great.
Now, officials at an MIT spinoff say they believe they’ve figured out how to drill as deep as 12 miles into the Earth’s crust, using a special laser that they say is powerful enough to blast through granite and basalt.
In the coming years, Quaise Energy, named for a section of Nantucket, plans to dig some of the deepest boreholes in history to reach rocks that can exceed temperatures of 1,000 degrees and surface a kind of heavy steam that has the potential to provide enormous quantities of energy. By the end of the decade, their hope is to capture the steam and use it to run turbines at power plants.
“By drilling deeper, hotter, and faster than ever before possible, Quaise aspires to provide abundant and reliable clean energy for all humanity,” said Carlos Araque, a former MIT student and employee, whose new company has raised $63 million to prove its technology. “This could provide a path to energy independence for every nation and enable a rapid transition off fossil fuels.”
Like nuclear fusion, a perennially elusive effort to harness the energy that powers stars, deep geothermal wells have long been viewed as a panacea for those hoping to displace our dependence on oil and gas with the energy from super-hot rocks. Shallower geothermal wells, which rely on the consistent heat underground, have long been a source of energy.
But the challenges of mining such subterranean energy remain great — and risky. Previous efforts to dig such deep holes have even triggered earthquakes.
The deepest borehole ever dug began in the 1970s, when the Soviets launched a two-decade-long drilling project on the Kola Peninsula, near the Russian border with Norway, that ultimately reached a depth of more than 7½ miles.
That long, expensive scientific experiment, as well as similar efforts in the United States and Germany, revealed the challenges of digging so deeply. Conventional drills had difficulty cutting through dense rock at such depths, where the pressure increases immensely and temperatures are scorching. The heat and density of the rocks required frequent replacement of drill bits, prolonging the effort and jacking up the costs.
Now, relying on technology developed to produce fusion power at MIT, Araque and others say they’ve solved many of those problems, making even deeper boreholes appear technically and financially feasible. If all goes well, they say, they’ll be able to dig to greater depths than the Russians reached in as few as 100 days.
The key advance came in recent years when Paul Woskov, a research engineer at MIT’s Plasma Science and Fusion Center, realized it might be possible to use an especially intense laser, one designed to generate a fusion reaction, to blast through rock.
After a series of tests at his lab in Cambridge, Woskov found that their gyrotron, a sophisticated device that creates electromagnetic beams of millimeter waves powerful enough to heat plasma to more than 100 million degrees, easily burned through granite and other dense rock found deep underground. In laboratory tests, the high-powered, high frequency waves can melt and vaporize the rocks.
In addition to the power of the laser to cut through dense rock, it could also retain its intensity over long distances, meaning a beam produced at the surface could, in theory, maintain its power miles underground. There’s also no need to replace drill bits, allowing the digging to proceed much more quickly. Another advantage is that the lasers vitrify boreholes, meaning that their heat encases the blasted rock in glass and makes the holes less likely to collapse.
“This is game-changing,” Woskov said. “We now have the potential to exploit an energy source that . . . could unleash the virtually limitless supply of energy beneath our feet.”
He added: “I haven’t found any fundamental physics reason why this can’t be done.”
Still, Woskov acknowledged that there remain significant engineering challenges to proving the technology can live up to its promise.
For example, it’s unclear whether the lasers will be as effective deep below ground, where there’s much greater atmospheric pressure, as they are at the surface. It also remains to be seen how easy or difficult it will be to remove the vaporized rock from the boreholes, how injected water will react with the hot rocks at such depths, and whether the resulting “supercritical fluid” will retain its ability to create efficient energy once it reaches the surface.
There are other larger concerns.
Previous efforts that relied on deep boreholes to produce geothermal energy ended after the drilling appeared to trigger seismic activity, in ways similar to how hydraulic fracking for natural gas has resulted in tremors.
After a 5.4-magnitude earthquake struck the South Korea city of Pohang in 2017, a government panel there determined that the likely cause was the result of fluid injected at high pressure into boreholes. The panel found the pressure sparked tremors that destabilized nearby faults, eventually leading to the 2017 earthquake — the second largest in South Korean history — which injured 135 people and caused an estimated $290 million in damage. The plant was eventually dismantled.
Earthquakes have been linked to geothermal plants elsewhere, including a 3.4-magnitude quake after fluids were injected into the ground at a similar facility in Basel, Switzerland, in 2006. That plant was also shut down.
“New technologies that may enable deep drilling are exciting, but they will likely encounter surprises as they go deeper than we have been before,” said William Ellsworth, a seismologist who studies earthquakes at Stanford University.
Others have raised concerns about the potential for ground water to be polluted, as has occurred with fracking. There’s the possibility that arsenic, mercury, and iron, as well as different salts, could be elevated from deep below ground and infiltrate drinking water supplies.
There’s also the possibility that toxic elements, such as boron, as well as greenhouse gases could be released into the atmosphere during the drilling and extraction process.
“There are unknowns, and we might not understand some of the risks,” said Jody Robins, a senior geothermal engineer at the National Renewable Energy Laboratory in Golden, Colo. “But until we do this, we won’t know.”
Despite the potential risks, Robins and others remain enthusiastic about deep geothermal, insisting that significant lessons have been learned from previous efforts to generate energy from super-hot rocks.
The risks from seismic activity are low, they said, because most of the intense drilling would occur below active fault lines in more stable rock. Moreover, surveys would be done before any drilling to ensure that boreholes wouldn’t be dug in active fault zones.
Emissions and ground water pollution could also be prevented with proper systems in place, as well as strict regulations ensuring their containment, they said.
“Super-hot rock has some formidable engineering challenges,” said Bruce Hill, chief geoscientist at the Clean Air Task Force in Boston. “It’s a high-risk, high-reward situation.”
Given the alternatives — and with the growing threats from climate change — he urged the federal government to spend much more for research and development for deep geothermal, calling the emphasis on solar, wind, and other smaller-scale forms of renewable energy “myopic.”
“This is a really important energy resource for the long-term future,” Hill said. “It’s hard to imagine that this doesn’t become one of the most dominant forms of energy.”
Dennis Whyte, director of MIT’s Plasma Science and Fusion Center, is also enthusiastic about the prospects of deep geothermal, saying “the basic science of this works.”
“There are some technical and scaling hurdles, but I think this has a pretty good chance,” he said. “There would be a beautiful irony if we could use the same tools to dig up carbon to replace them.”
Carlos Araque is betting on that promise.
With $40 million raised just last month, he vows his company will complete a prototype of its drilling machines within two years, prove it can dig miles-deep boreholes two years later somewhere on the West Coast, and build a power plant by 2028.
As the global population increases by billions of people in the coming decades, it’s critical to find a new source of clean power to meet increasing energy demands, he said.
“Geothermal can do that,” he said. “It doesn’t require any fuels and doesn’t produce any waste. It’s truly renewable, abundant, and equitable for all, even in the most challenging energy environments.”