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STEP Demo pilot plant makes new breakthrough for sCO2 power generation

January 22, 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 achieved an industry first during commissioning by firing its natural gas heater and operating its turbine up to an intermediate speed of 18,000 rpm.

“Operating the integrated system is a noteworthy accomplishment. It follows the team’s successful component-based commissioning activities and demonstrates combined operation of all equipment, including plant controls, compressor, heat exchangers, heater, turbine and CO2 inventory in addition to the facility’s electrical and gas supply and cooling water systems,” said Dr. Tim Allison, director of SwRI’s Department of Machinery.

The STEP Demo project developed in collaboration with SwRI, GTI Energy, GE Vernova, the U.S. Department of Energy/National Energy Technology Laboratory (U.S. DOE/NETL), and several industry participants. The project’s central goal is to dramatically improve the efficiency, economics, operational flexibility, space requirements and environmental performance of this new technology. The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCO2 technology, and achieved mechanical completion in October 2023, when major subsystems were installed and began commissioning.

System commissioning tests will continue over the next several months to achieve maximum power in its current configuration by increasing operating temperatures to 500 °C and ramping up the full turbine speed of 27,000 rpm. The turbine was developed jointly by SwRI and GE Vernova Research Center and is being tested in a simple recuperated configuration of the plant. The plant will eventually operate at 715 °C to achieve full 10 MWe output.

“This is an important step for our sCO2 demonstration plant,” said SwRI Project Manager Dr. Jeff Moore. “The STEP Demo team is thrilled to have achieved this significant milestone of integrated plant operation.”

STEP Demo is a unique facility designed to demonstrate high-temperature sCO2 power generation, which increases efficiency by as much as 10% due to its favorable thermodynamic properties. Carbon dioxide is nontoxic and nonflammable and, when it is held above a critical temperature and pressure, it can act like a gas while having the density near that of a liquid. The sCO2 turbomachinery is approximately one-tenth the size of conventional power plant components, which shrinks the physical footprint and construction cost of any new facilities. Additionally, the sCO2 power cycles are compatible with many heat sources including concentrating solar power, industrial waste heat, geothermal power and advanced nuclear power plants.

“I am excited that our team is now starting to demonstrate supercritical CO2 technology that can have a positive impact on the planet by making clean energy more affordable and efficient, and decarbonizing more challenging industrial applications through waste heat recovery,” said Bill Follett, STEP Demo program director at GTI Energy.

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 STEP Demo Pilot Plant or contact Joanna Quintanilla+1 210 522 2073, Communications Department, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166.