Sage Geosystems will construct a first-of-its-kind 3-MW geothermal baseload energy and power storage system on land owned by San Miguel Electrical Cooperative (SMECI) in Christine, Texas. The corporate plans to start working the undertaking later this yr to produce the Electrical Reliability Council of Texas (ERCOT) grid.
The undertaking will mark the primary commercial-scale deployment of EarthStore, Sage’s proprietary Geopressured Geothermal System (GGS), the corporate mentioned on Aug. 13. Sage plans to function the undertaking as a service provider, shopping for and promoting electrical energy to the ERCOT South Load Zone.
“As soon as operational, our EarthStore facility in Christine would be the first geothermal power storage system to retailer potential power deep within the earth and provide electrons to an influence grid,” mentioned Cindy Taff, CEO of Sage Geosystems.
A Price-Efficient ‘Underground Battery’
The system basically makes use of mechanical power storage expertise to reap each the warmth and strain of subsurface fluids in geothermal wells. Like a standard enhanced geothermal system (EGS), Sage’s Earthstore makes use of a two-well fracking system. However as an alternative of harvesting solely the warmth from the working fluid, it additionally leverages the strain.
“We’re centered on the thermodynamics and the geomechanics of getting the warmth out of the properly,” Taff defined to POWER at CERAweek by S&P World in March. “We pump the water into the fracture so it opens up like a balloon. After we need the water again, we let Mom Nature shut the fracture, and that principally jettisons the water, so we don’t should pump it out, which signifies that we don’t should spend this enormous quantity of power to get power out.”
Sage’s expertise is suited to low-permeability rock formations, usually discovered under depths of 5,000 ft. The fractures, which function synthetic underground reservoirs, are created utilizing gravity fracking, she famous. When electrical energy demand is low, Sage will use grid energy to energy and electrical pump, which is able to inject water into the fracture, inflicting it to “balloon.”
“The rock formation has elasticity, in order the water is pumped in, the fracture opens up and shops the pressurized water,” Taff mentioned. “This pressurized water is actually the saved power.” When electrical energy is required, Sage will open the wellhead valve, which permits the pressurized water within the fracture to move again out quickly to spin a high-pressure Pelton turbine to generate energy.
“The important thing benefit of this ‘balloon’ method is that we will do load following. Or we will do peak load, the place you’re letting all of the water out,” she defined. “You are able to do that with the identical properly design and the identical energy plant design. The one distinction is, if you’d like it produced for 17 or 18 hours, and then you definately need to cost inside a 24-hour interval, like seven hours, you would want extra injection pumps, which implies your capital goes up. However aside from that, the entire design is identical.”
The undertaking in Christine, which will likely be constructed close to SMECI’s 391-MW lignite coal energy plant, will likely be able to power storage durations of six to 10 hours, with a round-trip effectivity (RTE) of between 70% and 75%, Sage mentioned in an announcement on Tuesday. “As well as, water losses are focused to be lower than 2%. At scale, this power storage system will likely be paired with renewable power to offer baseload and dispatchable energy to the electrical grid.” When mixed with solar energy, Sage’s EarthStore facility “permits 24/7 electrical energy technology at a blended Levelized Price of Power (LCOE) properly below $0.10/kWh,” it added.
Speedy Improvement for a Idea that Leans on Oil and Gasoline Experience
The business facility in Christine will likely be primarily based on a full-scale business pilot that Sage demonstrated over 5 weeks in an present oil properly on a ranch south of San Isidro in Starr County, Texas, beginning in March 2023. The pilot produced 200 kW for greater than 18 hours (long-duration) and 1 MW for half-hour (load-following) with Pelton generators, with a round-trip effectivity of as much as 75% and water losses of lower than 2%, Taff mentioned.
The pilot adopted solely 2.5 years of growth by Sage, an organization based in 2020 by a workforce that boasts a mixed 150 years within the oil and gasoline trade. That’s primarily as a result of the corporate has leaned closely on present oil and gasoline drilling gear and methods, which embody casing and perforation, Taff mentioned. “The one distinction is we use a heavier fluid after we fracture. It’s known as gravity fracking.”
Nevertheless, as Taff underscored, GGS has been in steady discipline testing. “After getting our funding in mid-2021, we bought to the sphere, and we wished to check two of our applied sciences for geothermal. One was gravity fracking, the place we will frack downward towards the warmth,” she mentioned. “However then after we created the fracture, we truly spent about 5 months within the discipline working that fracture.” The five-week pilot in March 2023 was centered on Sage’s power storage resolution, an initiative that allowed it to display load following and long-duration storage, she famous.
For efficient power storage, Taff urged drilling ought to attain between 8,000 ft and 12,000 ft, which represents “90% of the U.S.” It means “you possibly can put power storage nearly wherever,” she mentioned. For geothermal energy, “We’re actually on the lookout for the temperature of the formation, 150C or better,” which geographically limits growth to about 35% of the U.S.
Engineering a Extra Highly effective Pelton Turbine
Nonetheless, for now, Sage can be engaged on re-engineering the Pelton turbine, a extensively used impulse water turbine, as a crucial part for the GGS. “As you possibly can think about, the very best mountain that’s at present getting used for pumped hydro is 3,000 ft, and we’re happening to 7,000, 8,000, 10,000 ft, so we’d like a 5000 PSI Pelton turbine” for a 3-MW system, Taff famous. The corporate is at present working with a associate on engineering the part for supply by October 2024, she mentioned.
The corporate has additionally developed a 3-MW supercritical carbon dioxide (sCO2) turbine that it plans to make use of in its geothermal purposes. “The benefit of that is that it’s smaller,” she mentioned. “So it’s going to be cheaper to construct, however extra importantly, it makes use of a hybrid Brayton cycle, that means that you just get extra electrical energy out per unit of warmth that you just put in.”
Whereas Sage’s first business undertaking, the Christine undertaking, will comprise a single properly, an injection pump, and a single Pelton turbine, scaling as much as 30 MW will likely be a “techno-economic resolution” primarily based on future undertaking wants, mentioned Taff.
Presently, Sage is focusing on a number of key markets suited to the expertise’s capabilities, corresponding to for microgrid, distant grid, and business and industrial purposes. Nevertheless, the expertise can be properly suited to grid balancing in markets like ERCOT. “Lengthy-duration power storage is essential for the ERCOT utility grid, particularly with the rising integration of intermittent wind and solar energy technology,” mentioned Craig Courter, CEO of San Miguel Electrical, on Tuesday.
Taff mentioned that GGS is already displaying value competitiveness with a number of present applied sciences. “We’re not focusing on to beat lithium-ion batteries for lower than two hours, but when it’s a must to begin stacking lithium-ion batteries for 4 hours or extra, then we will beat lithium-ion batteries, and we will beat pump storage hydropower proper now, each on the upfront capital and on the [levelized cost of storage (LCOS)].”
Geothermal energy prices pose a unique problem, she famous. “Our aim for a one-off pre-scale is to ship 9 cents/kWh LCOE,” she mentioned. “That’s thrilling in Germany and in California, however what we actually need to do is construct geothermal in order that it may be cost-competitive in Texas and different locations.” Scaling up will likely be essential, she famous.
Tasks Within the Pipeline
Sage mentioned it’s now gearing as much as apply for a drilling allow in Atascosa County for the EarthStore facility in Christine. Nevertheless, the corporate mentioned it’ll additionally apply for a second allow is in Starr County, adjoining to the corporate’s present take a look at properly.
Sage is already additionally fielding curiosity overseas. On July 24, Sage mentioned it could associate with Romanian generator Electrocentrale Bucuresti S.A. (ELCEN) to discover how geothermal power expertise might be applied throughout the metropolis of Bucharest to interchange a fossil-fuel-based thermal plant. ELCEN at present produces 40% of Romania’s and 90% of Bucharest’s thermal power for district heating, and implementing a renewable power supply like geothermal would considerably cut back carbon emissions all through town and the nation, Sage mentioned. “The primary undertaking will generate as much as 70 MW thermal energy for a district in Bucharest and, upon its success, will likely be expanded to different Romanian tasks and cities,” it mentioned. “A feasibility examine will likely be carried out in partnership with the Nationwide Renewable Power Laboratory (NREL).”
Earlier this yr, Sage additionally got down to discover the potential to deploy its proprietary GGS expertise at Fort Bliss for the U.S. Military and the Protection Innovation Unit (DIU). “Moreover, the corporate will consider the potential synergies of hybrid applied sciences corresponding to direct thermal use, power storage, and dispatchable energy to help cost-effective power resilience,” the corporate mentioned.
—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).
