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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

Blackstone Infrastructure, an affiliate of Blackstone Inc., will acquire a major Texas electricity provider. Photo via Shutterstock

Blackstone Infrastructure, an investment giant with $600 million in assets under management, has agreed to buy publicly traded TXNM Energy in a debt-and-stock deal valued at $11.5 billion.

TXNM Energy is the parent company of Lewisville-based Texas New Mexico Power (TNMP), which supplies electricity to more than 270,000 homes and businesses throughout Texas. Its Houston-area service territory includes Alvin, Angleton, Brazoria, Dickinson, Friendswood, La Marque, League City, Sweeny, Texas City and West Columbia.

Once Blackstone Infrastructure wraps up the deal in the second half of 2026, Albuquerque, New Mexico-based TXNM will no longer be a public company. But TNMP’s headquarters will remain in Texas and its rates will continue to be set by the Public Utility Commission of Texas. TNMP was founded in 1934.

Blackstone Infrastructure is affiliated with investment powerhouse Blackstone Inc., which has $1.2 trillion in assets under management and is the world’s largest investment manager.

“TNMP has done an excellent job of meeting its customers’ growing demand for electricity and supporting the communities it serves,” Sean Klimczak, Blackstone’s global head of infrastructure, said in a news release. “We look forward to utilizing our long-term investment commitments to support TNMP as they continue on this path of high-demand growth across Texas.”

During TXNM’s fourth-quarter earnings call in February, Chairwoman and CEO Patricia Vincent-Collawn said the company’s five-year Texas capital investment plan had grown by more than $1 billion.

“Our future is so bright with these increased investment levels that we are now targeting earnings growth of 7 percent to 9 percent through 2029,” Vincent-Collawn said.

“Our financial expectations are driven by the continued expansion of grid infrastructure supporting growth and reliability in our Texas service territory,” she added.

In 2024, TXNM reported revenue of $1.96 billion, up 1.7 percent from the previous year.

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