Unexplainable - One weird trick to get unlimited clean energy

Episode Date: July 23, 2025

Is a solution to climate change…pouring water on hot rocks? Guest: Dylan Matthews, Senior Correspondent at Vox's Future Perfect This episode was made in partnership with Vox's Future Perfect team. For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠[e-mail]⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠ Help us plan for the future of Unexplainable by filling out a brief survey: ⁠⁠⁠⁠⁠⁠⁠⁠voxmedia.com/survey⁠⁠⁠⁠⁠⁠⁠⁠. Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

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I'm at the Blue Lagoon in Iceland, which is this 100 degree almost fell into the Blue Lagoon. A while back, I went to Iceland, and I decided to check out this dreamy hot sprain. It's kind of like in Pirates of the Caribbean, where Jack Sparrow was like kind of slowly going through the fog. I actually got lost for 15 minutes. a couple minutes ago trying to find my way through this place because you can't see more than five or ten feet in front of you because it's so misty. The whole place is filled with this mineral-rich blue water.

It's this weird kind of thing where you can see your hand when it's at the top of the water and then you move it away and you basically can't see it at all because there's so much stuff in the water here. It's also filled with tons of tourists like me just hanging out, drinking cocktails, getting massages. And then there's just all this steam in the distance. I guess like from the power plant?

The power plant. And I am bathing in power plant, wastewater at the moment. This is not what I expected to be swimming in on vacation. But this is a power plant that's so incredibly clean, even its wastewater is a spa. And tourists like me, We love it. National Geographic even picked it as one of the 25 wonders of the world. But I got to say, I think National Geographic slept on the real wonder here.

What that wastewater does before it gets to the tourists. The water bubbles up from deep underground. It gets converted into steam. It spins a turbine, generates power. And then after that whole process, that's when it settles into this eerie blue pool. The Blue Lagoon. The reason I think this is the real wonder here is because of what this means for climate change.

By far, the biggest contributor to global warming is fossil fuels. But geothermal energy barely has any emissions. In a lot of ways, it's even better than solar wind because the inside of the earth doesn't turn off at night or stop making power when there's no breeze. And these plants are all over Iceland, A ridiculous sounding two-thirds of Iceland's energy is geothermal. The country basically runs off power from the Earth itself,

which makes sense. It's on a fault line, so all this hot water is just bubbling up to the surface all the time. But the fact is, no matter where you are on Earth, there's just tons of potential clean energy buried underneath you. We all just need to figure out how to get at it. I'm Noam, I'm Hassanfeld, and today I'm, unexplainable, why getting at all that unlimited energy is such a tough problem, and how we might

just be on the verge of cracking it. It's really tantalizing that we are sitting on this big mass of hot rocks just a few miles beneath us, and it's so hot that in theory it's more energy than we could ever need if we could maybe get at it. That's Dylan Matthews. He's a senior correspondent on Vox's Future Perfect team, and he writes about all kinds of big world-changing, ideas from global health to economics to energy. So I asked him just how possible all of this is. So if you aren't lucky enough to have that hot water kind of bubble all the way up like it does in Iceland, what do you do to get at it? So up to now, the answer has been that unless you're

on geysers or volcanoes or things, you don't. But there are efforts to make geothermal viable outside those areas. And the basic idea, which takes a bunch of forms, but all of them share the idea that you drill down really, really deep, and then you pour some kind of liquid down there, and you get steam or hot water coming up, and then you can either use the hot water directly, or you can use it to spin a turbine and make electricity. There's a few different companies trying this, but they're all variations on the same idea of, like, dig or blast really, really deep, pour some liquid in there, use that to spin a turbine or get some hot water. I mean, that seems like relatively straightforward to me.

It is a lot harder than it seems. The biggest barrier that I've heard from people is just that getting that deep into the earth is really tough. It's really expensive. And there's also been a concern about what happens when you pour liquid into rocks that deep. There was a demonstration project in South Korea that wound up causing a magnitude 5.5 earthquake. Whoa. Residents of the city of Pohang had to evacuate, as aftershocks from Korea's second largest earthquake on record

destroyed thousands of homes and injured dozens of people. Investigators confirmed it was man-made caused by a nearby geothermal power plant. I feel obliged to say that this was an unusual incident in most geothermal to date has not been associated with any significant seismic activity, but this was a concern people had about fracking that has, I think, held up to some degree. Yeah, I mean, you're kind of like weakening the ground, right? You're weakening the ground.

You're messing with the system deep in the earth, and you're putting liquid potentially in places where it hasn't been before. Yeah. This is part of the reason why some companies are building what they call a closed-loop system. So instead of just pumping liquid into the ground and it heating up, you actually place a pipe

all the way into the ground. And that way you're not leaking the liquid permanently. But that's really hard. You're actually placing in piping, potentially thousands of meters under the earth. And so it's more investment in a very difficult kind of drilling. And we don't have really good drill bits. It sounds like such a trivial or technical thing, but when I talk to people about geothermal, one of the things they bring up again and again is just like, we don't have good drill bits. That is crazy that like the thing that is standing, or at least one thing that is standing between us and kind of limitless, clean, constant energy is drill bits.

It seems really dumb, but also, I don't know, like, rocks are really hard. It makes sense that that can be a real technical limitation. The more you learn about industries like this, it all becomes, like, incredibly complex to do something seemingly simple. In the most closed-loop systems that people are trying to build right now, it is still at a point where you could generate electricity, but it won't do so super efficiently. So even if you nail all this, it might be hard for it to be cost competitive with something like solar or wind. So then why do it at all? So right now it's inefficient, and we can't make that much energy from it relative to the cost. But the ultimate dream is that you can get four kilometers or even deeper into the ground. And

this is where we get into what is super technically known as super hot rock energy. Oh, all right. We've so far been talking about hot rocks. Now we're going to talk about super hot rocks. Hot and hard rocks. Hot, hard rocks. Super hot, hard rocks. And at that point, the rocks are going to be over 752 degrees Fahrenheit.

And a special thing happens then, which is that water, H2O, becomes super critical, which is a phenomenon where it acts both like a liquid. and a gas. The pressure sort of liquefies that the heat, like, is pushing it toward being a gas. It's stuck in this sort of mysterious in-between state. But that means it can hold a lot more energy. The heat in the water is easier for turbines to turn into electricity. And you can get more electricity from the heat you're taking out of the earth than if you were sort of digging a little shallower and not getting to the supercritical level. Okay. The hard part is getting four kilometers into the earth.

Yeah. And so once you start asking that question, you start to hear ideas, like this one company wants to fire a word called millimeter waves into the ground, vaporize the rock. Vaporize the rock? Just like fully vaporize it. Like things get more and more sci-fi sounding in this. And the best part about this is you could just hook into a pre-existing power grid. So we've got all these coal plants.

They're already hooked up to the grid. They already have the transmission you need. and you could just replace the sort of coal burning that goes into the turbines with geothermal. So once you get this to work, it's kind of plug and play. It's a pretty easy transition. But once we get this to work is a huge caveat. So given what we know we need to do here and even the vision that we have of it working efficiently someday, why isn't this happening?

Is it the drill bits? I mean, there's, yeah, there's a lot of ways to look at. the causes. Some degree it's about the drill bits, but why don't we have better drill bits? We've gotten better mining technology and other things. We've gotten better solar. Why haven't we invested in this? And I think some of that is that we need a lot for this to go right. You need a lot of technical innovations, especially if you want super hot rocks. And often when we're trying to develop early-stage technologies like this, you need a lot of government help and subsidy. It requires a ton of just like physical investment up front. Yeah, they're like these huge complexes. Right. And

And we're at a time when administrations differ really profoundly on energy issues. Politics is really unpredictable. With Trump, it's not always clear what he feels about stuff day to day. So if you're one of these projects that's like a multi-year, hundreds of millions of dollars, physical infrastructure project, one thing you want is consistency. You just want to know that the support you're relying on from the government is always going to be there. And one thing our government has not been recently is consistent. All that said, the geothermal people I talk to are kind of optimistic, cautiously optimistic at this point for some maybe surprising reasons.

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This year, geothermal has been everywhere. That geothermal is so hot right now. In the first few months of 2025, there's been almost as much geothermal investment as there was all of last year. And there's also been a lot of progress on the ground, or not under the ground. One company in Utah has drilled 15,000 feet down to a point where the temperature's over 500 degrees Fahrenheit. So almost to that supercritical stage. There's a company that does closed-loop geothermal, so the kind where the water is always in an underground pipe and it doesn't leak. They're on track to generate actual electricity this year.

The rock vaporization guys just made their first real-world demonstration. And then even though Trump's big old bill made huge cuts to wind, and solar investment, there was a specific carve-out for geothermal, in large part due to the current energy secretary, Chris Wright. Will you pick up the phone and push congressional Republicans to maintain the energy tax credits for geothermal? I have been doing just that. Wright has founded multiple fracking companies, and he's been a big investor and backer of geothermal

for years. It's just an enormous, abundant energy resource below everyone's feet. Geothermal energy crosses partisan lines. It's renewable energy just for people that like oil and gas, because it's all about drilling. And fracking is a big reason geothermal has even gotten this far. The fracking revolution has dramatically improved the technology for drilling deep into the earth.

And it's been a big boon to geothermal sort of accidentally that natural gas has invested many, many billions of dollars, into getting better at drilling deep. And so you have this very skilled workforce and these new drilling technologies that can make it easier than it would have been 15 years ago before fracking had made all this progress. That's interesting.

Yeah, this is something you hear a lot from geothermal people of what does a just transition away from a fossil fuel economy look like? And one of the questions they want to ask is, what happens to the people who are doing all the drilling who are producing all this oil and gas right now? And one potential answer is, well, they keep drilling, but they drill geothermal wells rather than oil and gas wells. This all sounds great. It sounds even, you know, dreamily bipartisan. But we do know there are downsides. There's the earthquake, you mentioned, even if it's maybe a rare event.

If this is kind of relying on a lot of fracking technology, is there a possibility that this is going to lead to a lot of the problems that fracking led to? I mean, I think there's any time you're drilling into the earth, there are risks, especially, regarding sort of the liquid, you're using potential contamination of groundwater, and I think there have been fracking projects in the U.S. that have had fairly minimal impacts in that regard. They're ones that have had very bad impacts. And so I would hope that if we're doing this with geothermal, we would try to emulate best practices and avoid that. But at the end of the day, geothermal and natural gas are very different technologies. One of the big concerns with natural gas is that methane leaks from either the drilling site or from pipelines. And that just doesn't

happen to any significant degree with geothermal. Yeah, we're not trying to get at methane in the ground here. Right, right. Natural gas, like, sort of is methane. Yeah, yeah, that's strange rebranding. Yeah, it's a fairly specific problem to them. And I think with any new technology like this, the thing that everyone developing is afraid of is that people will get spooked about it, the way people got spooked about nuclear, and we'll shut it down before it has a chance to prove itself.

And so I would say that the attitude is one of an abundance of caution. So if this does work, you know, and we do end up doing it safely and responsibly, it feels like this has the potential to really stick. Yeah, I think that's the dream. The asterix is always like, it needs to work. Right, right. The thing about fracking is that it provided all these jobs for people in drilling, but it also, like, provided a really cheap and reliable source of energy.

And it worked. It worked, and it was cost-competitive. And the challenge for geothermal is, okay, you have this attention, you have government regulators that are paying attention, you have the Trump administration that is pretty positive on all kinds of drilling, both oil and gas and geothermal. So now can you do it? And I don't know. I think the nuclear industry has had a lot of innovation and big ideas in the last 15 years, and it's just kept getting more expensive. And ultimately, the proof is in the

The drilling? The proof is in the drilling. I was going to say something about the levelized cost of energy, but the proof is in the drilling is pithier. I'm curious if you can just paint me a picture of what the world might look like if we do get this right. Like, what would a world with fully tapped geothermal potential look like? Yeah, there was a report from these two energy experts. I like a lot.

Austin Vernon and Eli Dorado that was trying to like really give a kind of blue sky. almost sci-fi picture of what you could do if you just like didn't need to worry about scarcity of energy. And I think part of the point of the exercise is to sort of highlight ways in which not having enough energy for stuff kind of structures our worlds even as we don't realize it. Like vertical farming, people have been trying to do farming in a way that makes better use of land and takes up less of our landscape. The real problem is that you need tons of energy for it. If you had abundant geothermal, you could have skyscraper farms.

You could have desalination plants that obviate the need for these huge aqueduct systems in places like California. You would have more than enough energy to get all the drinking water you need from the ocean. I think the point of this is not like draws some sci-fi utopia, but just a lot of our world is structured by what we don't have. And we definitely don't have enough energy to do all the things that we want to do. And an appealing thing about geothermal is that there's way more heat in the earth crust than humans would ever know how to use in a million years. And that can be pretty exciting. So then to get to our sci-fi energy abundant future, we just need to have consistent politics that we all agree on, massive government spending and really, really good drill bits. Yeah, but other than that, yeah, very easy.

So what do you think ends up happening here? How optimistic are you in the end? So I want to sort of distinguish kinds of optimism here. Like, do I think there will be one company or two that is doing geothermal, the kind that you can do almost anywhere, and doing that at a reasonable scale? I say I'm pretty optimistic. I think that's more likely than not. There's a difference, though, between that and this is a major source of energy in the U.S.

And I'm a lot less certain on this will get to a point fast enough that it can sort of win the race with wind and solar and batteries and that kind of thing. And it's just a matter of what works fastest, best, and cheapest in the end. Yeah. For better or worse, the U.S. energy system is run by rapaciously bottom line-oriented capitalists. And so, like, if the cheapest way to provide electricity in Texas, the state that produces more oil, in any other state is to use solar, they'll use solar. Right. And sure enough, like, they build a lot more solar than states that you would think of as more pro-solar.

And I think that's been driving a lot of progress toward renewables lately. And that can be pretty ruthless for young technologies. So I don't want to, I think there's totally a world where this is a cool idea that gets some adoption, but does not take the world by storm. But there's also a world where it works better than we thought it would, and it kind of surprises everybody. And yeah, in that world, maybe you come back and you re-listen to this and think, yeah, maybe those guys were on to something. All right, Dellen, thanks so much for coming on the show. Thanks for having me.

This episode was produced by me, Noam Hassenfeld. We had editing from Jorge Just, mixing and sound design from Christian Ayala, music from me, production support from Thomas Liu, and fact-checking from Melissa Hirsch. Meredith Haudenot runs the show. Julia Longoria is our editorial director, and Bird Pinkerton stared at the... platypus who look down and sighed. They have the babies, the puggles. The birds said, if we didn't help them. Thanks as always to Brian Resnick for co-creating the show.

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