On the slopes of an Oregon volcano, engineers are building the hottest geothermal power plant on Earth.
The plant will tap into the infernal energy of Newberry Volcano, “one of the largest and most hazardous active volcanoes in the United States,” according to the U.S. Geological Survey. It has already reached temperatures of 629 degrees Fahrenheit, making it one of the hottest geothermal sites in the world, and next year it will start selling electricity to nearby homes and businesses.
But the start-up behind the project, Mazama Energy, wants to crank the temperature even higher — north of 750 degrees — and become the first to make electricity from what industry insiders call “superhot rock.”
“Geothermal has been mostly inconsequential,” said Vinod Khosla, a venture capitalist and one of Mazama Energy’s biggest financial backers. “To do consequential geothermal that matters at the scale of tens or hundreds of gigawatts for the country, and many times that globally, you really need to solve these high temperatures.”
Today, geothermal produces less than 1 percent of the world’s electricity. But tapping into superhot rock, along with other technological advances, could boost that share to 8 percent by 2050, according to the International Energy Agency (IEA). Geothermal using superhot temperatures could theoretically generate 150 times more electricity than the world uses, according to the IEA.
“We believe this is the most direct path to driving down the cost of geothermal and making it possible across the globe,” said Terra Rogers, program director for superhot rock geothermal at the Clean Air Task Force, an environmentalist think tank. “The [technological] gaps are within reason. These are engineering iterations, not breakthroughs.”
Mazama Energy is bringing its own water to the volcano, using a method called “enhanced geothermal energy.”
Historically, people have been able to use geothermal energy only in rare locations that have hot rocks and underground water, creating natural pockets of steam. That limits conventional geothermal to a handful of hot spots in countries such as Japan, Iceland, Kenya and the American West.
But over the past few decades, pioneering projects have started to make energy from hot dry rocks by cracking the stone and pumping in water to make steam, borrowing fracking techniques developed by the oil and gas industry. The geothermal start-up Fervo Energy and the U.S. Department of Energy have built pilot projects in Nevada and Utah, and international researchers have demonstrated the technology in France, Germany, Switzerland and Japan, among others.
Drilling into 750-degree rock presents some devilish challenges. Conventional geothermal plants can use off-the-shelf gear developed by the oil and gas industry, which can stand up to lower temperatures. But in superhot rock, standard drills die as their electronic components fail.
“To put it very technically, they get fried,” said Vasantharajan.
Mazama engineers cooled their drilling rigs by pumping in a constant stream of liquid carbon dioxide. That allowed them to burrow two miles into the flank of the volcano to find 629-degree rock earlier this year.
Other experimental wells have hit even higher temperatures, but none has survived for long. Drilling experiments in Iceland and Hawaii were called off after they unexpectedly hit magma, which broke their drill bits. Wells in Japan and Italy reached rock hotter than 900 degrees — approaching the region of Earth’s crust where rigid rock starts behaving more like putty — but were abandoned after facing problems with their drilling equipment and cement casings.