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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

Six companies have joined Greentown Houston, focused on long-duration energy storage systems, 3D solar towers and more. Photo courtesy Greentown Labs.

Greentown Labs announced the six startups to join its Houston community in Q2 of 2025.

The companies are among a group of 13 that joined the climatetech incubator, which is co-located in Houston and Boston, in the same time period. The companies that joined the Houston-based lab specialize in a number of clean energy applications, from long-duration energy storage systems to 3D solar towers.

The new Houston members include:

  • Encore CO2, a Louisiana-based company that converts CO2 into ethanol, acetate, ethylene and other sustainable chemicals through its innovative electrolysis technology
  • Janta Power, a Dallas-based company with proprietary 3D-solar-tower technology that deploys solar power vertically rather than flatly, increasing power and energy generation
  • Licube, an Austin-based company focused on sustainable lithium recovery from underutilized sources using its proprietary and patented electrodialysis technology
  • Newfound Materials, a Houston-based company that has developed a predictive engine for materials R&D
  • Pix Force, a Houston-based company that develops AI algorithms to inspect substations, transmission lines and photovoltaic plants using drones
  • Wattsto Energy, a Houston-based manufacturer of a long-duration-energy-storage system with a unique hybrid design that provides fast, safe, sustainable and cost-effective energy storage at the microgrid and grid levels

Seven other companies will join Greentown Boston's incubator. See the full list here.

Greentown Houston also added five startups to its local lab in Q1. Read more about the companies here.

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