Southwest Research Institute (SwRI), GTI Energy, GE Vernova (GE) and the USDepartment of Energy celebrated the ribbon-cutting of the Supercritical Transformational Electric Power (STEP) Demo pilot plant. The $155-million, 10-megawatt supercritical carbon dioxide (sCO2) test facility at SwRI’s headquarters in San Antonio will demonstrate an innovative new method of higher-efficiency, lower-cost electric power generation. (Earlier post.)

Unlike conventional power plants, which use water as the thermal medium in power cycles, STEP is designed to use high-temperature sCO₂, which increases 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 sCO₂ power cycle technology is also compatible with concentrated solar power and industrial waste heat.

One advantage to using sCO₂ as a working fluid is that STEP Demo’s turbomachinery is approximately one-tenth the size of conventional power plant components, making it possible to shrink the footprint and construction cost of any new facilities. For example, STEP Demo’s desk-sized sCO₂ turbine could power up to 10,000 homes.

SwRI’s John Klaerner, lead turbine engineer, and Dr. Jeff Moore, the principal investigator of the STEP Demo project, are pictured with the sCO₂ turbine developed by SwRI for the 10 MWe demonstration plant.

SwRI, GTI Energy, and GE broke ground on the STEP Demo site on 15 October 2018, and building construction was completed in 2020. The pilot plant achieved its first operation of its compressor with CO₂ at supercritical fluid conditions earlier this year. Commissioning of the facility will continue through early next year.

The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCO₂ technology. The project’s central goal is to improve the efficiency, economics, operational flexibility, space requirements and environmental performance of this new technology. SwRI, GTI Energy, and GE collaborated on the design of the plant, which is specially conceived to evolve over time to keep pace with industry advancements. The facility’s skid-mounted components provide flexibility and a unique, reconfigurable design.