Tap into the million-year-old power source beneath our feet

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What does geothermal energy have to do with nuclear energy? There’s an abandoned coal-fired power plant in upstate New York that most people consider a useless relic. 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 are still connected to the grid. Using an approach he’s been working on for 14 years, he hopes it’ll be back online, completely carbon-free, within a decade.

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

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

The plan would be easier to dismiss as unrealistic if it were based on new and unproven technology. But Quaise’s drilling systems revolve around a microwave-emitting device called a gyrotron that’s been used in research and manufacturing for decades.

“That will happen quickly once we resolve the immediate engineering issues of transmitting a clean beam and operating it at high energy density without failure,” says Woskov, who is not officially affiliated. in Quaise but serves as an adviser. “It will go fast because the underlying technology, gyrotrons, is commercially available. You can place an order with a company and have a system delivered to you immediately. Admittedly, these beam sources have never been used 24/7, but they are designed to be operational for long periods of time. In five or six years, I think we will have a plant running if we solve these engineering problems. I am very optimistic.

Woskov and many other researchers have been using gyrotrons to heat materials in nuclear fusion experiments for decades. It wasn’t until 2008, however, after the MIT Energy Initiative (MITEI) issued a request for proposals on new geothermal drilling technologies, that Woskov thought of using gyrotrons for a new application.

“[Gyrotrons] haven’t been well publicized in the general science community, but those of us in fusion research have come to realize that these are very powerful beam sources – like lasers, but in a range of frequencies different,” says Woskov. “I thought, why not direct these high power beams, instead of into the fusion plasma, into the rock and vaporize the hole?”

While power from other renewable energy sources has exploded in recent decades, geothermal power has plateaued, primarily because geothermal power plants only exist in places where natural conditions allow extraction. energy at relatively shallow depths of up to 400 feet below the Earth’s surface. At a certain point, conventional drilling becomes impractical because the deeper crust is both hotter and harder, which wears down mechanical drill bits.

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

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

That year, Araque and Matt Houde, who were working with geothermal company AltaRock Energy, founded Quaise. Quaise soon received a grant from the Department of Energy to expand Woskov’s experiments using a larger gyrotron.

With the larger machine, the team hopes to vaporize a hole 10 times deeper than Woskov’s lab experiments. This should be accomplished by the end of this year. After that, the team will vaporize a hole 10 times deeper than the previous one – what Houde calls a 100 to 1 hole.

“It’s something [the DOE] is particularly interested, as they want to address the challenges of material removal over these longer lengths – in other words, can we show that we completely eliminate rock fumes? Houde explains. “We believe the 100-to-1 test also gives us the confidence to go out and mobilize a prototype gyrotron drill into the field for initial field demonstrations.”

Testing on the 100-to-1 hole is expected to be completed within the next year. Quaise also hopes to start vaporizing rock in field trials late next year. The short timeline reflects the progress Woskov has already made in his lab.

Although more engineering research is needed, the team expects to be able to drill and operate these geothermal wells safely. “We believe, through Paul’s work at MIT over the past decade, that most, if not all, of the fundamental questions in physics have been answered and resolved,” Houde says. “These are really engineering challenges that we have to meet, which doesn’t mean they’re easy to solve, but we’re not working against the laws of physics, to which there are no answers. It’s more about overcoming some of the more technical and cost considerations to make it work at scale.

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

“We believe that if we can dig down to 20 kilometers, we can access these extremely hot temperatures in over 90% of places around the world,” Houde said.

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

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

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

Transforming the world’s energy systems in such a short time is something the Founders consider essential to help avoid the most catastrophic global warming scenarios.

“There have been huge gains in renewable energy over the past decade, but the big picture today is that we are not moving fast enough to meet the milestones we need to limit the worst impacts. of climate change,” says Houde. “[Deep geothermal] is an energy resource that can scale anywhere and has the ability to tap into a large energy industry workforce to easily retrain their skills for a completely carbon-free energy source.

Related: Researchers launch new vision of deep rock fractures for geothermal energy


 


 

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