image: The Supercritical Transformational Electric Power (STEP) Demo pilot plant, a $169 million, 10-megawatt supercritical carbon dioxide (sCO2) test facility at Southwest Research Institute (SwRI) in San Antonio, has completed its first phase of testing after achieving its full power for simple cycle configuration.
Credit: Southwest Research Institute
SAN ANTONIO — October 16, 2024 —The Supercritical Transformational Electric Power (STEP) Demo pilot plant, a $169 million, 10-megawatt supercritical carbon dioxide (sCO2) test facility at Southwest Research Institute (SwRI) in San Antonio, has completed its first phase of testing, having achieved its full operational speed of 27,000 rpm and operating at a target turbine inlet temperature of 500 degrees Celsius. As STEP achieved this milestone, it was synchronized with the electrical grid, generating approximately four megawatts of net power.
“Achieving full operating conditions while connected to the grid is a major advancement of the commercial maturity of these transformative power systems,” said Dr. Tim Allison, director of SwRI’s Machinery Department. “This accomplishment represents many technical ‘firsts’ due to the combination of power and operating temperatures and showcases the tenacity and perseverance of STEP’s engineering and project teams.”
The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCO2 technology. It achieved mechanical completion in October 2023, when major subsystems were installed and began commissioning. In May 2024, it generated electricity for the first time.
The completion of Phase 1 has shown the commercial readiness of sCO2 technology and confirmed its ability to meet initial performance targets. In 2025, the plan is to reconfigure the pilot plant into a recompression Brayton cycle, a variation of the power cycle that will boost power output and efficiency. At this point, the project plans to enter a new phase of testing to achieve its full 10-megawatt net power capacity — enough to power 10,000 homes.
“I could not be prouder of the STEP team achieving this major milestone, including reaching the greatest amount of power ever generated using sCO2 as the working fluid,” said SwRI Project Manager Dr. Jeff Moore.
The pilot plant differs greatly from conventional power plants because it uses high-temperature sCO2 instead of water as a thermal medium in its power cycles, increasing efficiency by as much as 10% due to its favorable thermodynamic properties. Carbon dioxide is nontoxic and nonflammable, and sCO2’s efficiency as a working fluid allows for STEP turbomachinery to be approximately one-tenth the size of conventional power plant components, providing the opportunity to shrink the environmental footprint and construction cost of any new facilities. The technology is also compatible with many heat sources including concentrated solar power, advanced nuclear reactors, industrial waste heat, thermal energy storage and geothermal heat.
The STEP Demo project is led by GTI Energy in collaboration with SwRI, GE Vernova Advanced Research, the U.S. Department of Energy/National Energy Technology Laboratory (U.S. DOE/NETL) and several industry participants. New collaborators are welcome to join the STEP Demo pilot project to gain deep technical insight into the technology and actual operating data.
SwRI is an industry leader in the development of sCO2 power cycles. Staff members have conducted numerous U.S. Department of Energy projects advancing the efficiency, reliability and commercial readiness of sCO2 power cycle turbomachinery, heat exchangers, cycles and systems. The team’s extensive experience with sCO2 technology is key to making the STEP Demo project a successful landmark demonstration.
For more information, visit https://www.swri.org/industry/advanced-power-systems/supercritical-transformational-electric-power-pilot-plant.