In a sagebrush valley full of wind turbines and solar panels in western Utah, Tim Latimer gazed up at a very different device he believes could be just as powerful for fighting climate change — maybe even more.

It was a drilling rig, of all things, transplanted from the oil fields of North Dakota. But the softly whirring rig wasn’t searching for fossil fuels. It was drilling for heat.

Mr. Latimer’s company, Fervo Energy, is part of an ambitious effort to unlock vast amounts of geothermal energy from Earth’s hot interior, a source of renewable power that could help displace fossil fuels that are dangerously warming the planet.

“There’s a virtually unlimited resource down there if we can get at it,” said Mr. Latimer. “Geothermal doesn’t use much land, it doesn’t produce emissions, it can complement wind and solar power. Everyone who looks into it gets obsessed with it.”

Traditional geothermal plants, which have existed for decades, work by tapping natural […]