In just 12 months, Sage Geosystems and San Miguel Electric Cooperative built the world's first pressure geothermal system. It is now poised to deliver long-duration, dispatchable storage for the Electric Reliability Council of Texas (ERCOT) as variable generation and data center demand surge.
In Christine, Texas a town of barely 365 people an hour south of San Antonio San Miguel Electric Cooperative Inc. (SMECI) is pulling off a transformation that will redefine rural generation. Borne out of efforts to bring reliable, affordable power to South Texas's overlooked ranchlands and small towns, the member-owned cooperative built and commissioned a 391-MW mine-mouth lignite power plant at the Atascosa County site, tapping deposits from its own San Miguel Mine. For more than 40 years, that plant, the entity's only unit, provided baseload power to 47 counties through a wholesale contract with member-customer South Texas Electric Cooperative (STEC), and functioning as a critical anchor in the Electric Reliability Council of Texas's (ERCOT's) South Load Zone.
While coal, fueled by locally mined lignite, has long been SMECI's backbone, the cooperative has been working to ensure it can sustain its baseload responsibility while transitioning to cleaner resources, easing the early retirement of the lignite plant ahead of STEC's 2037 contract expiry. "Unlike investor-owned utilities, we are operated by and for the people of South Texas in predominantly rural areas regions that had historically been overlooked," the cooperative notes on its website. "We have one simple goal: reliable power, not making a profit."
That mission drove two landmark efforts last year: a first-of-its-kind geothermal partnership with Sage Geosystems to launch a Pressure Geothermal pilot and an application to the U.S. Department of Agriculture's New Empowering Rural America (New ERA) program which in December secured over $1.4 billion in grants and low-interest loans to replace the lignite unit with 400 MW of solar and 200 MW of battery storage by 2027.
The geothermal pilot, SMECI Well #1, is the first piece of that vision to materialize. Moving from funding approval to "ready to store" in just 12 months, Sage completed drilling, fracture stimulation, surface-facility installation, and commissioning by August 2025. Leveraging innovative design, existing oilfield expertise, and streamlined permitting, the 3-MW/4-6-hour system has transformed a pioneering underground energy storage concept into a fully built asset in record time. While the project is still awaiting grid interconnection currently slated for December 2025 the pioneering project has showcased a new model for firm, dispatchable capacity in ERCOT's evolving grid, and is well worthy of this POWERTop Plant award.
