ERCOT’s first geothermal electrons are coming to the grid

The Texas electric grid will play host to a first-of-a-kind geothermal energy storage facility thanks to a partnership between the startup Sage Geosystems and the San Miguel Electric Cooperative, the company announced today.

• The top line: The so-called “EarthStore” facility, set to launch later this year, will store up to three megawatts of excess renewable energy via pressurized water deep underground. The storage system will target six- to 10-hour durations, and Sage will essentially act as an ERCOT energy trader, buying and selling electricity. 
• The nuts and bolts: When electricity is cheap, Sage will buy it to power its pumps, injecting water into the ground for storage. When grid demand peaks, the company will open the well and allow the pressurized water to flow through a turbine to produce electricity that it will sell back to the grid. According to Sage, the project will deliver a roundtrip efficiency of between 70% and 75%, and enable electricity generation with a levelized cost of energy of under ten cents per kilowatt hour.
• The market grounding: Geothermal has been having something of a breakout moment. At least six geothermal companies (including Sage) have closed financing rounds in the last year. And geothermal companies are inking PPAs with utilities as well as pioneering rate structures and data center strategies with tech companies desperate for clean firm energy.

The ERCOT announcement comes roughly a year after Sage piloted its tech for 18-hour durations last fall. The key to that pilot, the company said, was proving not only duration capability, but showing that the system is “cost-competitive with lithium-ion batteries, pumped storage hydropower, and natural gas peaker plants.” That pilot, the company said, demonstrated a levelized cost of storage between 2 cents and 4 cents per kilowatt-hour.

The new Christine, Texas project, which relies on a land use agreement with the San Miguel Electric Cooperative, is funded by a $17 million Series A that Sage raised in February, and is the company’s first commercial energy storage facility. 

CEO Cindy Taff said that Texas was the clear choice for both the Christine project and the company’s first geothermal electricity generation project, which will come online mid-2025. 

“You can get a permit pretty quickly, in two or three weeks, in Texas,” Taff told Latitude Media. And the project’s levelized electricity costs can be competitive in ERCOT, she added, even though the region’s energy prices are generally low compared to some other parts of the country.

While of course the technology for next-gen geothermal is still in development, Taff said that getting the technology to commercial scale in short order is a primary focus for the company, in part because of the energy needs of the data center boom.

And that’s where Sage Geosystem’s long-duration capabilities will set it apart, she added: “I think it’s a great opportunity not only to advance next-gen geothermal but also to advance long-duration energy storage.”