U.S. startups are developing proprietary technologies based on hydraulic fracturing to drill wells for storing renewable energy from solar and wind in underground pressurized water reservoirs.
As the share of renewable energy in electricity generation in the top American oil state, Texas, grows – so does the need for energy storage, which ensures clean energy is available when needed.
The new pressurized storage technology could be an alternative to lithium-ion batteries if it proves commercially feasible and cost-effective in the new pressurized energy storage systems.
Grid-connected batteries in California and Texas, for example, have started to play a significant role in helping to balance the system, Ed Crooks, Vice-chair, Americas at Wood Mackenzie, wrote earlier this year.
Now, at least three startups based in Houston are working on and piloting projects to store water under pressure in underground reservoirs and release it to turn a turbine when needed to generate power.
“Zero-carbon energy storage harnessing oil and gas technology is here, because we can store renewable solar and wind underground,” Mike Eros, Chief Geoscientist at Sage Geosystems, said earlier this year, when the company—founded in 2020—announced the first close of $17 million in Series A funding, led by Chesapeake Energy, for a commercial facility.
The 3 MW facility, called EarthStore, will use Sage Geosystems’ technology that harvests energy from pressurized water stored deep underground. The facility will be able to store energy for short and long periods and can be paired with intermittent renewable energy sources, including wind and solar, to provide baseload, dispatchable power, and inertia to the electric grid.
Last year, the company successfully demonstrated the EarthStore system in a full-scale commercial pilot project in Texas. The pilot produced 200 kW for more than 18 hours (long-duration) and 1 MW for 30 minutes (load-following), generating electricity with Pelton turbines to run equipment on location. The system has a roundtrip efficiency of 70-75% and water losses of less than 2%, Sage Geosystems said in February.
Earlier this month, the company announced the location of the project after entering into a land use agreement with San Miguel Electric Cooperative Inc. (SMECI) for the Geopressured Geothermal System energy storage facility. The EarthStore system will be in Christine, Texas, near the SMECI lignite coal power plant. Sage will operate as a merchant, buying and selling electricity to the ERCOT grid.
“Geothermal energy storage is a viable solution for long-duration storage and an alternative for short-duration lithium-ion batteries,” said Sage Geosystems CEO Cindy Taff.
Sage will also utilize its proprietary Geopressured Geothermal System to provide carbon-free power to Meta’s data centers, the company said this week.
Other companies pioneering pressurized storage systems include Fervo Energy and Quidnet Energy.
Fervo Energy boasts it has developed proprietary geothermal technology called FervoFlex, which can deliver in-reservoir energy storage and dispatchable generation attributes. Fervo’s horizontal well design connects subsurface wells with a set of hydraulically conductive fractures surrounded by impermeable rock. The company says that its technology “effectively enables Fervo to operate their assets to achieve multi-day energy storage attributes in addition to the traditional benefits of clean, firm geothermal power.”
Fervo Energy is also backed by a U.S. shale firm. Last year, it announced a $10 million strategic investment from Devon Energy.
Fervo said back then that it was the first geothermal company to successfully drill and complete a horizontal well pair for commercial geothermal production, using technologies, skills, and processes pioneered by Devon for oil and gas production.
Quidnet Energy, for its part, aims to develop a modified pumped hydro energy storage system that stores energy via high-pressure water in the subsurface. To charge, the team will pump water into confined rock underground, creating high pressures.
Quidnet Energy is calling the technology Geomechanical Pumped Storage and says that it is widely deployable at very low cost.
“Subsurface rock layers are converted into energy storage reservoirs for large-scale renewables integration and grid management,” the company says.
The fracking process in these technologies is less intensive than in oil and gas production.
Sage’s chief geoscientist, Mike Eros, told Inside Climate News that the company’s fracking process is about a tenth of the scale and intensity.
“We call it an Earth battery,” he added.
