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Supercritical CO2 pilot plant generates electricity for the first time

The STEP Demo project team believes the project will “change how we approach power generation in the near future.”
Supercritical CO2 pilot plant generates electricity for the first time
(Courtesy of SwRI.)

The Supercritical Transformational Electric Power, or “STEP” Demo pilot plant generated electricity for the first time using supercritical carbon dioxide (sCO2) power cycles, Southwest Research Institute (SwRI) announced last month.

The $169 million, 10 MW sCO2 facility at the Institute in San Antonio is demonstrating the next- technology in a project led by GTI Energy. Partners include SwRI, GE Vernova, the U.S. Department of Energy/National Energy Technology Laboratory (U.S. DOE/NETL) and several other industry participants.

For the first time, SwRI said the pilot plant’s turbine achieved its full speed of 27,000 RPM at an operating temperature of 260°C and generated a small amount of power. The Insitute said the STEP team would slowly ramp up the operating temperature to 500°C and generate 5 MWe of power.

After completion of this first test configuration, the STEP Demo project would enter its final phase. The pilot plant would be reconfigured to boost its efficiency and overall energy output.

SwRI said this modification requires the installation of new equipment, as well as a new commission and test phase that would continue into 2025 until the pilot plant is running at full power. At the end of its final phase, the pilot plant would produce 10 MWe hourly.

SwRI Project Manager Dr. Jeff Moore said he believed this project would “change how we approach power generation in the near future.”

Unlike conventional steam power plants, which use water as the thermal medium in power cycles, STEP uses high-temperature sCO2 to increase efficiency by as much as 10% due to its favorable thermodynamic properties. Carbon dioxide is nontoxic and nonflammable, and when CO2 is held above a critical temperature and pressure, it can act like a gas while having the density near that of a liquid.

The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCO2 technology. However, the pilot plant’s 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.

SwRI, GTI Energy and GE broke ground on the STEP Demo site in 2018. The facility achieved mechanical completion in October 2023, when major subsystems began commissioning.