In 2023, Southwest Research Institute, GTI Energy, GE Vernova (GE) and the U.S. Department 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 a revolutionary new method of higher-efficiency, lower-cost electric power generation.
The STEP Demo pilot plant represents a shift toward more sustainable and efficient power generation and operated its main compressor with CO2 at supercritical fluid conditions for the first time in 2023.
Conventional power plants heat water to create steam that drives electricity-generating turbines. In contrast, the STEP pilot plant 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, or in a supercritical state, it can act like a gas while having a density near that of a liquid. The sCO2 power cycle technology can generate electricity from many heat sources including concentrating solar, geothermal, nuclear, and industrial waste heat. Supercritical CO2 systems are also being developed as industrial heat pumps.
Another 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.
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 dramatically improve the efficiency, economics, operational flexibility, space requirements and environmental performance of this new technology. SwRI, GTI Energy, and GE collaborated on the plant design, which was developed to evolve over time to keep pace with industry advancements. The facility’s skid-mounted components provide flexibility and a unique, reconfigurable design.
SwRI is an industry leader in the development of sCO2 power cycles. Staff members have conducted numerous DOE projects advancing the efficiency, reliability and commercial readiness of sCO2 power cycle turbomachinery, heat exchangers, cycles and systems. The team brings extensive experience with sCO2 technology and the key building blocks to make the STEP Demo project a success and a landmark demonstration.