Every few decades or so, geothermal energy seems to be rediscovered as a promising U.S. renewable technology. So far it has remained restricted to Western states, where the most accessible resources are concentrated. 

There, in areas typically located near surface geysers, developers tap heat directly from trapped hot water to create steam to turn turbines. Now, a new renaissance is underway, but with a literal twist that could expand development well beyond previous boundaries. Several startups are borrowing fracking knowledge used to dramatically boost energy production over the last 20 years, except now those techniques are being adopted to tap the earth’s heat rather than its oil and gas.

One proof of concept for these new approaches is now supplying a Google data center with 3.5 megawatts (MW) of electricity near the northern Nevada city of Winnemucca. The search engine giant, which already has agreements in place for 10 gigawatts (GW) of carbon-free power globally, is working to match its specific energy needs more directly to individual facilities.

Like other tech leaders have done, the company may direct its current investments to projects constructed several states away from any Google data centers, with the idea that the carbon-free electricity those remote installations generate will offset emissions produced by the power plants directly serving their facilities. That model is starting to shift, though, with the recognition that those distant renewable resources can’t completely offset 24/7 data center operations that need to keep running even when the sun isn’t shining or winds aren’t blowing.

Fracking techniques in play

The new Google geothermal plant was built by Fervo Energy, a Houston-based company drawing on oil and gas expertise to create new geothermal resources, instead of simply relying on the heat of naturally occurring subsurface hot water. The company drilled two parallel wells 3,000 feet apart and down about 8,000 feet. It then turned the drilling equipment so the wells continued horizontally toward each other, with one line, called the injection well, running below and parallel to the second line, called the production well. A fracking process was used to create cracks in the ground formations surrounding the horizontal portions of both lines.

Now, water pumped through the injection well flows through these cracks absorbing heat, which it carries up through the production well at 375ºF. The scalding water creates the steam used to drive a generator turbine. Fiber optic cables inside the wells collect real-time operating data to help optimize operations. This process is called enhanced geothermal and, while it uses fracking techniques perfected by the oil and gas industry, it doesn’t use the chemicals petrochemical companies employ to extract fossil fuels. 

In September 2023, Fervo broke ground on the 400 MW Cape Station project in Beaver County, Utah, and in February 2024, the company announced that drilling is proceeding 70% faster than it did during the Google project. Cape Station is expected to begin producing electricity in 2026, with full power capacity expected in 2028. The company has also announced numerous power purchase agreements with several California utilities to buy the electricity produced by this plant and others.

Storing geothermal energy

Sage Geosystems, another Houston-based firm with oil and gas roots, has developed a different, closed-loop approach to create a new form of long-duration energy storage called EarthStore. The company successfully demonstrated a proof-of-concept installation at an abandoned oil well in Texas. There, it pumped dense drilling mud down the well at high pressure, forcing slim fractures apart. Water was then pumped in at high pressure to keep the fractures separated, a process that could be powered in the future using surplus renewable energy. A valve kept the pumped water in place until energy was needed, and then the valve opened to release the energy back through the same pump and motor, which acted as a turbine and generator to deliver electricity to the grid.

Sage said a single well could generate 3 MW in a fast-output scenario, or up to 200 kilowatts over an 18-hour period for longer grid support when renewables aren’t producing. Costs were estimated to be competitive with pumped-storage hydropower and lithium-ion batteries. Construction of a commercially operating system is expected to begin in Texas in mid-2024.

The possibilities for systems such as Fervo’s and Sage Geosystems’ have caught the imagination of the U.S. Department of Energy (DOE), which has launched the Enhanced Geothermal Shot initiative to reduce the cost of electricity produced by enhanced geothermal systems by 90% by 2035. In addition to producing clean energy, the technology could provide good jobs for former oil and gas workers, with their highly transferable skills.

Because they don’t require the high temperatures of conventional geothermal systems, these new approaches could work across much more of the country. DOE estimates installed enhanced geothermal could reach 90 GW of installed capacity by 2050—enough to power 65 million U.S. homes.

Header image: The method might have originated in oil fields, but the new Google geothermal plant in Winnemucca, Nev., is pumping heat, not petroleum.

fervo Energy