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Geothermal energy, a lesser known form of clean energy scored a big win this week


Enhanced geothermal energy is one of the lesser-known forms of clean renewable power, and it hit a milestone last week. The utility company Southern California Edison signed a 15-year purchasing agreement for 320 megawatts of electricity from geothermal wells in Utah. That's enough electricity to power 350,000 homes. It's the largest deal for enhanced geothermal energy in the world so far, and that makes it a real win for the industry. Jesse Jenkins is an assistant professor of mechanical and aerospace engineering at Princeton University. He leads the Princeton ZERO lab, which, we should say, has a research partnership with Fervo Energy, the developer of the Utah project. Welcome to the program.

JESSE JENKINS: Thanks for having me.

RASCOE: So tell us what is enhanced geotherermal energy?

JENKINS: Well, the deeper you go into the Earth's crust, the hotter it gets, and if you drill down deep enough, you can access temperatures that are hot enough to generate steam and spin a turbine, which can be used to generate electricity just like we might in, say, a coal-fired power plant or a natural gas plant, except this energy is renewable and clean and doesn't produce any air pollution or CO2 emissions.

RASCOE: What's the advantage of enhanced geotherermal over, say, wind or solar power?

JENKINS: Well, wind and solar power, as is inherent in the name, are variable weather-dependent resources, and so as the sun comes and goes or the wind comes and goes, the output that we get from those clean renewable resources varies over time. And that means we need to pair those resources with what I call firm resources, technologies that are, you know, there whenever you need them for as long as you need them. And so today, we depend on natural gas and coal and our existing nuclear power plants for that role. But as we want to clean up the grid and stop using less polluting fossil fuels, we need clean firm resources, and enhanced geothermal is one of the most promising options for that. It's the fastest-growing at the moment, although it's just one of several other options that are coming down the line and kind of turning from science fiction into reality over the next few years.

RASCOE: And you don't need any dirty chemicals or a whole lot of energy, you know, to get this geotherermal power out of the ground.

JENKINS: No, you don't. What you do need to do in the case of enhanced geothermal is create a fracture system, a network of cracks within the hot portion of the rock. That's usually several kilometers deep into the ground. Then if you intersect two of those fracture networks, one from one horizontal well and one from another, you basically create a big heat exchanger or radiator in the ground that you can pump water into and extract heat by pumping it back up to the surface, and that's all done in a closed loop. So there's no release of, you know, chemicals or dirty water. It just circulates through that closed loop, you know, over and over, producing clean electricity.

RASCOE: Is there a concern about, like, earthquakes 'cause I know with hydraulic fracturing, there was always a concern that they could cause earthquakes? Could this cause earthquakes?

JENKINS: Yeah, that is one important concern, and it may limit the areas in which we can develop enhanced geotherermal energy systems. But there are large portions of the Western United States where it is safe to operate and to develop these resources. We've been doing that to extract dirty fossil fuel resources in a way that has not triggered earthquakes in, you know, most of the areas where that occurs. And so, you know, like most resources, we have to be careful about where we develop and where we don't, but there's a broad chunk of the country - Utah, Nevada, New Mexico, Idaho, Oregon - where this is a resource that could generate tens of thousands of megawatts of clean renewable energy. Each thousand megawatts is enough to power a city the size of San Francisco. So these are real significant resources that could, you know, ultimately play as large a role in our electricity grid as our existing nuclear power plants do today, maybe by sometime around 2040 or 2050.

RASCOE: OK, so let's talk about this agreement between Southern California Edison and the Texas company doing the drilling, Fervo Energy. It's enough to power 350,000 homes. In the grand scheme of things, you know, that's not a huge amount. So why do experts think this is a big deal?

JENKINS: Well, what's exciting about it is this is the first, like, large-scale commercial power plant scale project in this class. Just last year, Fervo Energy started generating power at its first demonstration project, which produces just 4 megawatts of power, at a site in Nevada. You know, to go from 4 megawatts to over 500 megawatts of projects in development that will be online before 2030, you know, in the next couple of years is a pretty big development. That means that Fervo Energy is delivering projects on the scale of, you know, conventional coal-fired power plants or natural gas plants that as they scale up and build more and more, these can play a really central role in the energy mix.

RASCOE: That's Jesse Jenkins. He is an assistant professor of mechanical and aerospace engineering at Princeton University. Thank you so much for being with us.

JENKINS: It's my pleasure. Thank you.

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Ayesha Rascoe is a White House correspondent for NPR. She is currently covering her third presidential administration. Rascoe's White House coverage has included a number of high profile foreign trips, including President Trump's 2019 summit with North Korean leader Kim Jong Un in Hanoi, Vietnam, and President Obama's final NATO summit in Warsaw, Poland in 2016. As a part of the White House team, she's also a regular on the NPR Politics Podcast.