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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

Shell has entered a 15-year agreement to be the first offtaker to receive electrons from Fervo Energy's flagship geothermal development in Beaver County, Utah, known as Cape Station. Photo via fervoenergy.com

Beginning in 2026, Shell will be able to apply 31 megawatts of 24/7 carbon-free geothermal power to its customers thanks to a new 15-year power purchase agreement with Houston next-gen geothermal development company Fervo Energy.

“This agreement demonstrates that Fervo is stepping up to meet the moment,” Dawn Owens, VP, Head of Development & Commercial Markets at Fervo, said in a news release.

Shell will become the first offtaker to receive electrons from Fervo's flagship geothermal development in Beaver County, Utah’s Phase I of Cape Station. Cape Station is currently one of the world’s largest enhanced geothermal systems (EGS) developments, and the station will begin to deliver electricity to the grid in 2026.

Cape Station will increase from 400 MW to 500 MW, which is considered by the company a major accomplishment due to recent breakthroughs in Fervo’s field development strategy and well design. Fervo is now able to generate more megawatts per well by optimizing well spacing using fiber optic sensing, increasing casing diameter and implementing staggered bench development. This can allow for a 100 MW capacity increase without the need for additional drilling, according to the company.

With the addition of the new Shell deal, all 500 MW of capacity from Fervo’s Cape Station are now fully contracted. The deal also includes existing agreements, like Fervo’s PPAs with Southern California Edison and an expanded deal with Clean Power Alliance that adds 18 MW of carbon-free geothermal energy to the company’s existing PPA with Fervo.

“As customers seek out 24/7 carbon-free energy, geothermal is clearly an essential part of the solution,” Owens said in the release.

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