Tapping into the million-year energy source beneath our feet | MIT News

There is an abandoned coal plant in upstate New York that most people consider a useless leftover. But Paul Woskov of MIT sees things differently.

Woskov, a research engineer at MIT’s Plasma Science and Fusion Center, notes that the plant’s power turbine is still intact and the transmission lines still run to the grid. With an approach he’s been working on for the past 14 years, he hopes it will be completely carbon-free online again within a decade.

In fact, Quaise Energy, the company that commercializes Woskov’s work, believes that if it can retrofit one power plant, the same process will work on virtually every coal and gas power plant in the world.

Quaise hopes to achieve those lofty goals by harnessing the energy source beneath our feet. The company plans to vaporize enough rock to create the world’s deepest holes and harvest geothermal energy at a scale that could cover human energy consumption for millions of years. They haven’t solved all the related technical challenges yet, but the founders of Quaise have set an ambitious timeline to start harvesting energy from a pilot well by 2026.

The plan could more easily be dismissed as unrealistic if it were based on a new and unproven technology. But Quaise’s drilling systems revolve around a microwave-emitting device called a gyrotron, which has been used in research and manufacturing for decades.

“This will happen quickly once we have solved the immediate technical problems of transmitting a clean beam and having it with a high energy density without interference,” explains Woskov, who is not formally affiliated with Quaise but acts as a consultant. “It’s moving fast because the underlying technology, gyrotrons, is commercially available. You could place an order with a company and have a system delivered now – admittedly, these bundle sources have never been used 24/7, but they are designed to be operational for long periods of time. I think we’ll have a factory up and running in five or six years if we solve these technical problems. I am very optimistic.”

Woskov and many other researchers have been using gyrotrons to heat material in nuclear fusion experiments for decades. However, it wasn’t until 2008, after the MIT Energy Initiative (MITEI) was published A request for proposals for new geothermal drilling technologies, that Woskov came up with the idea of ​​using gyrotrons for a new application.

†[Gyrotrons] are not well publicized in the general scientific community, but those of us in fusion research understood that they were very powerful beam sources — like lasers, but in a different frequency range,” Woskov says. “I thought, why don’t we focus these powerful beams, instead of in fusion plasma, in rock and vaporize the hole?”

As the flow of other renewable energy sources has exploded in recent decades, geothermal energy has exploded, especially since geothermal plants only exist in places where natural conditions allow energy extraction at relatively shallow depths up to 120 meters below the earth’s surface. At some point, conventional drilling becomes impractical because deeper crust is both hotter and harder, which wears out mechanical drilling.

Woskov’s idea of ​​using gyrotron beams to vaporize rock sent him on a research journey that never really stopped. With some money from MITEI, he began conducting tests, quickly filling his office with small rock formations that he had shelled with millimeter waves from a small gyrotron at MIT’s Plasma Science and Fusion Center.

Around 2018, Woskov’s rocks caught the attention of Carlos Araque ’01, SM ’02, who had spent his career in the oil and gas industry and was the technical director of MIT’s investment fund The Engine at the time.

That year, Araque and Matt Houde, who had worked at geothermal company AltaRock Energy, founded Quaise. Quaise soon secured a grant from the Department of Energy to scale up Woskov’s experiments with a larger gyrotron.

With the larger machine, the team hopes to vaporize a hole 10 times as deep as Woskov’s lab experiments. This is expected to be completed by the end of this year. After that, the team will vaporize a hole 10 times as deep as the previous one — what Houde calls a 100-to-1 hole.

“That is something [the DOE] is particularly interested in, because they want to address the challenges of material removal over those greater lengths — in other words, can we show that we completely flush out the rock fumes?” Houde explains. “We believe the 100-to-1 test also gives us the confidence to mobilize a prototype gyrotron drill rig in the field for the first field demonstrations.”

Testing on the 100-to-1 gap is expected to be completed sometime next year. Quaise also hopes to start vaporizing rock in field tests by the end of next year. The short timeline reflects the progress Woskov has already made in his lab.

While more technical research is needed, the team expects to eventually be able to drill and operate these geothermal wells safely. “We believe that, because of Paul’s work at MIT over the past ten years, most, if not all, of the core physics questions have been answered and addressed,” says Houde. “They are really technical challenges that we have to answer, which doesn’t mean they are easy to solve, but we are not working against the laws of physics, to which there is no answer. It’s more a matter of overcoming some of the more technical and cost considerations to make this work at scale.”

The company plans to start harvesting energy from geothermal pilot wells that reach rock temperatures of up to 500C by 2026. From there, the team hopes to begin reusing coal and natural gas plants using its system.

“We believe that if we can drill up to 20 kilometers, we can access these super-hot temperatures in more than 90 percent of locations around the world,” says Houde.

Quaise’s work with the DOE addresses what it sees as the biggest remaining questions about drilling holes of unprecedented depth and pressure, such as material removal and determining the best casing to keep the hole stable and open. For the latter problem of well stability, Houde believes additional computer modeling is needed and expects to complete that modeling by the end of 2024.

Drilling the holes in existing power plants will allow Quaise to move faster than if it had to get permits to build new plants and transmission lines. And by making their millimeter wave drilling equipment compatible with the existing global fleet of rigs, the company can also take advantage of the global workforce of the oil and gas industry.

“At these high temperatures [we’re accessing], we produce steam that is very close to the temperature, if not higher than the temperature at which today’s coal and gas-fired power plants operate,” says Houde. “So we can go to existing power plants and say, ‘We can replace 95 to 100 percent of your coal use by developing a geothermal field and producing steam from the Earth, at the same temperature you burn coal to run your turbine,’ which directly replaces CO2 emissions.”

Transforming the world’s energy systems in such a short space of time is something the founders consider crucial to help prevent the most catastrophic global warming scenarios.

“Huge gains have been made in renewable energy over the past decade, but the big picture today is that we are not nearly fast enough to reach the milestones we need to mitigate the worst impacts of climate change,” says Houde. †[Deep geothermal] is an energy source that can be scaled anywhere and is able to tap into a large workforce in the energy industry to easily repackage their skills for a completely carbon-free energy source.”

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