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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

The project would nearly eliminate the emissions associated with power and steam generation at the Dow plant in Seadrift, Texas. Getty Images

Dow, a major producer of chemicals and plastics, wants to use next-generation nuclear reactors for clean power and steam at a Texas manufacturing complex instead of natural gas.

Dow's subsidiary, Long Mott Energy, applied Monday to the U.S. Nuclear Regulatory Commission for a construction permit. It said the project with X-energy, an advanced nuclear reactor and fuel company, would nearly eliminate the emissions associated with power and steam generation at its plant in Seadrift, Texas, avoiding roughly 500,000 metric tons of planet-warming greenhouse gas emissions annually.

If built and operated as planned, it would be the first U.S. commercial advanced nuclear power plant for an industrial site, according to the NRC.

For many, nuclear power is emerging as an answer to meet a soaring demand for electricity nationwide, driven by the expansion of data centers and artificial intelligence, manufacturing and electrification, and to stave off the worst effects of a warming planet. However, there are safety and security concerns, the Union of Concerned Scientists cautions. The question of how to store hazardous nuclear waste in the U.S. is unresolved, too.

Dow wants four of X-energy's advanced small modular reactors, the Xe-100. Combined, those could supply up to 320 megawatts of electricity or 800 megawatts of thermal power. X-energy CEO J. Clay Sell said the project would demonstrate how new nuclear technology can meet the massive growth in electricity demand.

The Seadrift manufacturing complex, at about 4,700 acres, has eight production plants owned by Dow and one owned by Braskem. There, Dow makes plastics for a variety of uses including food and beverage packaging and wire and cable insulation, as well as glycols for antifreeze, polyester fabrics and bottles, and oxide derivatives for health and beauty products.

Edward Stones, the business vice president of energy and climate at Dow, said submitting the permit application is an important next step in expanding access to safe, clean, reliable, cost-competitive nuclear energy in the United States. The project is supported by the Department of Energy’s Advanced Reactor Demonstration Program.

The NRC expects the review to take three years or less. If a permit is issued, construction could begin at the end of this decade, so the reactors would be ready early in the 2030s, as the natural gas-fired equipment is retired.

A total of four applicants have asked the NRC for construction permits for advanced nuclear reactors. The NRC issued a permit to Abilene Christian University for a research reactor and to Kairos Power for one reactor and two reactor test versions of that company's design. It's reviewing an application by Bill Gates and his energy company, TerraPower, to build an advanced reactor in Wyoming.

X-energy is also collaborating with Amazon to bring more than 5 gigawatts of new nuclear power projects online across the United States by 2039, beginning in Washington state. Amazon and other tech giants have committed to using renewable energy to meet the surging demand from data centers and artificial intelligence and address climate change.

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