Endurance Energy raises $54M to harness a massive untapped energy source

After you’ve worked on rockets that find their way to outer space, it can be hard to come up with a second act. For SpaceX alumni Andrew Redd, it meant looking deep in the ocean.

Redd, who grew up in the Pacific Northwest, a region affected by uncharacteristic heat waves and catastrophic fires in recent years, knew he wanted to tackle something in renewable energy.

“But the experience at a very hardcore company like SpaceX made me realize that I can’t just come up with an incremental solution. It actually has to be brand new and it has to be approached from first principles,” according to Redd, who was an engineer on Dragon and Starship at SpaceX.

Redd left SpaceX and founded Endurance Energy, a startup that has raised a $54 million Series A to eventually harness terawatts of geothermal energy deep in the ocean, TechCrunch has learned. Founders Fund led the round, with participation from Ascend, Construct Capital, Felicis Ventures, First Round Capital, Point72 Ventures, Riot Ventures, and Voyager Ventures. The new funding will allow the company to develop its plans for power plants at a time of surging energy demand from AI data centers, electric vehicles, and heavy industry.

Since founding the company last year, Redd has grown the team to 25 employees, 12 of whom used to work at SpaceX. The company’s vice president of engineering previously worked at Helion Energy, the fusion startup.

Geothermal energy isn’t a new idea — humans have been using the Earth’s heat for millennia, whether it be from spa-like hot springs or geothermal power plants. But Redd, drawing on his experience at SpaceX, figured there was another opportunity people were overlooking. 

Here’s how he distilled the problem: Any future energy source should be renewable, or at least non-polluting, in his opinion. “That’s my non-negotiable,” said Redd, who is CEO of Endurance. It should also be available 24/7 — or baseload power, as the industry calls it — and it should be quickly deployable and able to generate tens or hundreds of gigawatts of electricity, according to Redd. 

He quickly ruled out nuclear power because regulatory and construction timelines can stretch on for years. Solar and wind aren’t available 24/7 without batteries, and hydropower is limited in where it can be built (plus all the good spots have been taken). That left geothermal.

“Geothermal is the only real deployable, baseload renewable,” he said. “But why is it only 0.4% of U.S. energy?”

There are other startups pursuing geothermal, including Fervo and Zanskar. But those companies need to drill thousands of feet into the Earth’s crust to access temperatures hot enough to drive a power plant. So far, the best opportunities for many geothermal startups has been in the Western U.S., far from large population centers.

The best places to drill, where the crust is thin and magma flows close to the surface, like in Iceland or California, have long been claimed. More recently, startups like Fervo Energy, XGS Energy, and Sage Geosystems have found other sites, but to find rocks that are hot enough to drive a power plant, they need to drill thousands of feed deeper. Those locations have so far been away from large population centers.

But no one has tapped the oceans. 

At several points around the globe, the Earth’s tectonic plates are spreading apart, allowing hot magma to flow to the surface. The U.S. West Coast, Japan, and a good chunk of Southeast Asia are near the so-called Ring of Fire, the geologically active zone that encircles the Pacific Ocean.

Heading out to sea poses several challenges. Operating underwater, at the depths Endurance is proposing, isn’t easy. Robots will need to do much of the work. Saltwater is famously corrosive, so anything placed down there will have to be hardened against both water pressure and corrosion. 

But Redd said those are surmountable hurdles, pointing to the oil and gas industry’s decades of experience drilling in the ocean. Endurance’s work should pose less risk to the surrounding ocean, he points out. “If we have a blowout — quote unquote — you’re leaking hot water into the ocean, which is already leaking out in terawatts all over the Earth,” Redd said.

Some of the geothermal resources Endurance is eyeing are a few dozen miles from shore, while others are a few hundred. Which get developed will be the product of an optimization algorithm that balances the cost of the submarine cable with the scale of the resource and the size of the market on shore. (Redd says the company plans to avoid sensitive habitats like those near hydrothermal vents.)

If Endurance taps just a fraction of the geothermal potential out there, it could generate a significant amount of electricity. Redd estimates there’s about 6 terawatts that could be developed in the next five to 10 years around the Ring of Fire. To put that in perspective, the world uses an average of about 20 terawatts across all energy sources at any given moment. 

“The idea is that you could support any major coastal city on the Ring of Fire,” Redd said.