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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

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

A View From UH

A Rice University professor studied the Earth's carbon cycle in the Rio Madre de Dios to shed light on current climate conditions. Photo courtesy of Mark Torres/Rice University

Carbon cycles through Earth, its inhabitants, and its atmosphere on a regular basis, but not much research has been done on that process and qualifying it — until now.

In a recent study of a river system extending from the Peruvian Andes to the Amazon floodplains, Rice University’s Mark Torres and collaborators from five institutions proved that that high rates of carbon breakdown persist from mountaintop to floodplain.

“The purpose of this research was to quantify the rate at which Earth naturally releases carbon dioxide into the atmosphere and find out whether this process varies across different geographic locations,” Torres says in a news release.

Torres published his findings in a study published in PNAS, explaining how they used rhenium — a silvery-gray, heavy transition metal — as a proxy for carbon. The research into the Earth’s natural, pre-anthropogenic carbon cycle stands to benefit humanity by providing valuable insight to current climate challenges.

“This research used a newly-developed technique pioneered by Robert Hilton and Mathieu Dellinger that relies on a trace element — rhenium — that’s incorporated in fossil organic matter,” Torres says. “As plankton die and sink to the bottom of the ocean, that dead carbon becomes chemically reactive in a way that adds rhenium to it.”

The research was done in the Rio Madre de Dios basin and supported by funding from a European Research Council Starting Grant, the European Union COFUND/Durham Junior Research Fellowship, and the National Science Foundation.

“I’m very excited about this tool,” Torres said. “Rice students have deployed this same method in our lab here, so now we can make this kind of measurement and apply it at other sites. In fact, as part of current research funded by the National Science Foundation, we are applying this technique in Southern California to learn how tectonics and climate influence the breakdown of fossil carbon.”

Torres also received a three-year grant from the Department of Energy to study soil for carbon storage earlier this year.

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