San Miguel Electric Cooperative is preparing to harness the future from the ground up.

The Christine, Texas-based generation and transmission cooperative has partnered with Sage Geosystems Inc. to develop EarthStore, a first-of-its-kind underground geothermal operation.

The project, near the G&T’s mine-mouth lignite plant, is expected to store and dispatch up to 200 megawatt-hours of energy and bolster supply for the Electric Reliability Council of Texas.

“Long-duration energy storage is crucial for the ERCOT utility grid, especially with the increasing integration of intermittent wind and solar power generation,” SMECI General Manager and CEO Craig Courter says. “Sage’s technology offers a reliable and resilient power source independent of weather conditions and not reliant on wind or sunshine. We are excited to be part of this innovative project that showcases the potential of geothermal energy storage.”

Geothermal energy generation traditionally involves steam from hot water located miles beneath the Earth’s surface. This new project will create an underground reservoir by pumping water into a high-pressure well.

With the turn of a valve, the water will be released up to a surface reservoir to activate a Pelton turbine to generate electricity when needed.

Like battery storage, the well will be filled or “charged” when excess power is available on the grid at a low cost, and water will be released to produce energy when demand and power prices escalate.

“Independent power producers would use this method to profit from the differential, and cooperatives would hedge against high-cost power during peak demand,” Courter says. “The ability to capitalize on storage is instrumental to managing cost avoidance.”

The underground geothermal system is expected to reap further savings by surpassing the lifetime of traditional batteries.

“The unique quality of this storage method is that it has a longer duration at a lower cost than battery storage,” he says. “The longer duration is key to solving dispatch needs when renewables are unavailable.”

Courter met Sage Geosystems CEO Cindy Taff and President Lev Ring last year in South Texas, where the geothermal tech company had repurposed an abandoned oil well as a pilot project.

“The project was successful, so we started discussing how to proceed to the next step of commercial operation of a storage well,” he says.

SMECI agreed to lease the company a tract in its coal mining area to drill a well 8,500 feet deep.

The underground reservoir will be far below the water table and outside harmful hydrocarbon-bearing formations, he says. It is also expected to improve water quality as the well is cycled and create no waste stream as clean energy is produced.

The G&T also recently received a $1.4 billion investment from the federal goverment to develop 400 MW of solar power and 200 MWh of battery storage.

Over the next 30 years, SMECI estimates these projects to deliver $1 billion in financial benefits to its nine distribution co-ops that serve more than 340,000 consumer-members across 47 rural Texas counties.

“We are immensely proud of these recent historic developments,” says Courter.