91. A Game-Changing Vision for Geothermal Energy

According to a report released in 2019 by the U.S. Department of Energy, geothermal electricity generation could increase more than 26-fold by 2050—reaching 60 GW of installed capacity. That may seem like a pipe dream to some power observers, but if new well-drilling techniques allow enhanced geothermal systems to become economical, the reality could be much greater. In fact, Quaise Energy, a company working to develop enabling technologies needed to expand geothermal on a global scale, claims as much as 30 TW of geothermal energy could be added around the world by 2050. Most of the geothermal systems that supply power to the grid today utilize hydrothermal resources. These tap into naturally occurring conditions in the Earth that include heat, groundwater, and rock characteristics (such as open fractures that allow fluid flow) for the recovery of heat energy, usually through produced hot water or steam. Enhanced geothermal systems contain heat similar to conventional hydrothermal resources but lack the necessary groundwater and/or rock characteristics to enable energy extraction without innovative subsurface engineering and transformation. The technology that Quaise Energy is working on would allow drilling down as far as 20 kilometers (12.4 miles) to utilize heat from dry rock formations, which are much hotter and available in almost all parts of the world. “The key thing is we’re going for hotter rock, because we want the water to get hotter,” Carlos Araque, CEO of Quaise Energy, said as a guest on The POWER Podcast. “We want it even to be supercritical, which is the fourth phase of water—when it goes above a certain temperature and pressure—that’s what we’re looking for.” But drilling to those depths is difficult. “It really boils down to temperature,” Araque said. “The state-of-the-art of drilling technologies is in the 200C neighborhood, and the reason for that is electronics that go with the drilling systems. Making higher-temperature electronics is a very, very difficult task.” Another problem is the hotter the rock gets, the faster drill bits wear out. “So, if you imagine drilling at five kilometers below the surface of the earth, your drill bit will only last a few hours, because the rock is so hot and so hard,” said Araque. He explained that pulling the drill string out of a five-kilometer-deep hole so that the drill bit can be changed, and then pushing it back into the hole can take a significant amount of time. “So, a week to pull out of the hole, a few hours to change the drill bit, a week to push down into the hole to drill a few more hours. It becomes exponentially impossible to do that,” he said. “That’s where the drilling technology that we’re proposing comes into play. We’re basically trying to do directed-energy drilling with millimeter waves,” Araque said. “Imagine a microwave source on the surface, it’s called a gyrotron. We beam this energy through a pipe into the hole. Together with this energy, we push a gas—could be nitrogen, could be air, could be argon, if necessary—and at the bottom of that pipe, this energy comes out, evaporates the rock, and the gas picks up the vapor of that rock and pulls it back out. What comes out of the hole looks like volcanic ash, and the hole actually burns its way down, you know, five, six, 10, 15, 20 kilometers, as needed, to get to the temperatures we’re looking at.”