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Houston-based geothermal energy startup releases promising results of Texas pilot

Houston startup Sage Geosystems released the results of its pilot at a Shell-drilled oil well in the Rio Grande Valley’s Starr County. Photo via sagegeosystems.com

As it seeks an additional $30 million in series A funding, Houston startup Sage Geosystems has released promising results from a test of its technology for underground storage of geothermal energy.

Sage says the pilot project, conducted at a Shell-drilled oil well in the Rio Grande Valley’s Starr County, showed the company’s long-term energy storage can compete on a cost basis with lithium-ion battery storage, hydropower storage, and natural gas-powered peaker plants. Peaker plants supply power during periods of peak energy demand.

Furthermore, Sage’s geothermal technology will provide more power capacity at half the cost of other advanced geothermal systems, the company says.

Sage’s storage system retrofits oil and gas wells with the company’s geothermal technology. But the company says its technology “can be deployed virtually anywhere.”

The system relies on mechanical storage instead of battery storage. In mechanical storage, heat, water, or air works in tandem with compressors, turbines, and other machinery. By contrast, battery storage depends on chemistry to get the job done.

“We have cracked the code to provide the perfect complement to renewable energy. … The opportunities for our energy storage to provide power are significant — from remote mining operations to data centers to solving energy poverty in remote locations,” former Shell executive Cindy Taff, CEO of Sage, says in a September 12 news release.

Sage says its storage capacity can be connected to existing power grids, or it can develop microgrids that harness stored energy.

An August 2023 article in The New York Times explained that Sage “is pursuing fracked wells that act as batteries. When there’s surplus electricity on the grid, water gets pumped into the well. In times of need, pressure and heat in the fractures pushes water back up, delivering energy.”

The pilot project, a joint venture between Sage and the Bureau of Economic Ecology at the University of Texas at Austin, was performed as part of a feasibility study financed by the Air Force. Now that the test results are in, Sage plans to build a prototype geothermal project at the Air Force’s Ellington Field Joint Reserve Base in Houston.

Sage says another feasibility study is underway in the Middle East in partnership with an unnamed oil and gas company.

Founded in 2020, Sage plans to raise another $30 million to accompany its previous series A funding.

The Virya climate fund and Houston-based drilling contractor Nabors Industries helped finance the pilot project in Starr County.

Last year, Sage announced it received an undisclosed amount of equity from Houston-based Ignis H2 Energy, a geothermal exploration and development company, and Dutch energy company Geolog International. Also last year, Sage said Nabors and Virya had teamed up for a $12 million investment in the startup.

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A View From HETI

ERCOT plans to build a “super highway” of new transmission lines to boost grid reliability. Photo via Getty Images

The Electric Reliability Council of Texas, which manages the electric grid for 90 percent of Texans, is undertaking a $9.4 billion project to improve the reliability and efficiency of statewide power distribution. The initiative comes as ERCOT copes with escalating demand for electricity from data centers and cryptocurrency-mining facilities.

The project, approved Dec. 9 by ERCOT’s board, will involve building a 1,109-mile “super highway” of new 765-kilovolt transmission lines. One kilovolt equals 1,000 volts of electricity.

According to the Hoodline Dallas news site, the $9.4 billion project represents the five- to six-year first phase of ERCOT’s Strategic Transmission Expansion Plan (STEP). Hoodline says the plan, whose price tag is nearly $33 billion, calls for 2,468 miles of new 765-kilovolt power lines.

STEP will enable ERCOT to “move power longer distances with fewer losses,” Hoodline reports.

Upgrading the ERCOT grid is a key priority amid continued population growth in Texas, along with the state’s explosion of new data centers and cryptocurrency-mining facilities.

ERCOT says about 11,000 megawatts of new power generation capacity have been added to the ERCOT grid since last winter.

But in a report released ahead of the December board meeting, ERCOT says it received 225 requests this year from large power users to connect to its grid — a 270 percent uptick in the number of megawatts being sought by mega-users since last December. Nearly three-fourths (73 percent) of the requests came from data centers.

Allan Schurr, chief commercial officer of Houston-based Enchanted Rock, a provider of products and services for microgrids and onsite power generation, tells Energy Capital that the quickly expanding data center industry is putting “unprecedented pressure” on ERCOT’s grid.

“While the state has added new generation and transmission capacity, lengthy interconnection timelines and grid-planning limitations mean that supply and transmission are not keeping pace with this rapid expansion,” Schurr says. “This impacts both reliability and affordability.”

For families in Texas, this could result in higher energy bills, he says. Meanwhile, critical facilities like hospitals and grocery stores face a heightened challenge of preventing power outages during extreme weather or at other times when the ERCOT grid is taxed.

“I expect this trend to continue as AI and high-density computing grow, driving higher peak demand and greater grid variability — made even more complex by more renewables, extreme weather and other large energy users, like manufacturers,” Schurr says.

According to the Pew Research Center, data centers accounted for 4 percent of U.S. electricity use in 2024, and power demand from data centers is expected to more than double by 2030. Data centers that support the AI boom make up much of the rising demand.

In September, RBN Energy reported more than 10 massive data-center campuses had been announced in Texas, with dozens more planned. The Lone Star State is already home to roughly 400 data centers.

“Texas easily ranks among the nation’s top states for existing data centers, with only Virginia edging it out in both data-center count and associated power demand,” says RBN Energy.

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