Geothermal energy’s champions point to enormous amounts of energy locked in hot rocks under the ground: we drill down, pipe hot water down into the rocks to make steam, and collect the steam to spin turbines and generate electricity.

Problem: there aren’t that many places where those hot rocks are near the surface—Iceland and New Zealand are two of them—and barely half of geothermal wells pan out. As an energy source, the world’s hot rocks contribute just a fraction of a percent to the global mix of renewable energy.

Fervo Energy, based in the oil capital of Houston, TX, thinks it can fix that by drilling for geothermal energy the way shale oil companies drilled and made the U.S. the world’s leading petroleum producer.

Instead of poking down strictly vertical wells as geothermal ventures typically do, shale drillers use “horizontal drilling.” Wells begin vertically but gradually snake out to become horizontal tunnels reaching a mile or more through oil-bearing rocks.

Fervo found a good stretch of hot rocks in Nevada and drilled a horizontal shaft a little more than half a mile long. It pumped water through the pipe, the heat in the rocks turned it to steam, and another vertical well on the other end brought the steam to the surface to spin a turbine.

The steam condenses back to water and is pumped back down into the horizontal well to make more steam.

In a 30-day test, Fervo’s well accommodated 63 liters of water—about 16 gallons—per second and the rocks heated it as high as 376°F. The steam generated 3.4 megawatts of electricity, enough to power about 500 typical U.S. homes. 

Fervo has raised $187 million, data service Crunchbase reported, and plans to test its method on deeper layers of rock.

TRENDPOST: The company believes it can drill horizontal wells as far as 2.8 miles underground. At that depth, hot rocks are not only hotter but also more plentiful and could justify the cost of drilling so deep.

When in widespread commercial use—which will take at least a decade—Fervo’s technology could deliver hundreds of gigawatts of electricity annually into the world’s electric grids.