STEP Demo Pilot Plant Achieves Supercritical CO2 Fluid Conditions


The Supercritical Transformational Electric Power (STEP) Demo pilot plant, a $155 million, 10-megawatt supercritical carbon dioxide (sCO2) test facility at Southwest Research Institute (SwRI) in San Antonio, developed in partnership with GTI Energy and GE Research and sponsored by the U.S. Department of Energy, has successfully achieved its first operation with COat supercritical fluid conditions in its compressor section. This accomplishment represents significant progress toward readying the facility for system-level testing.

“This exciting milestone represents a significant advancement for a truly transformational project,” said Dr. Tim Allison, director of SwRI’s Department of Machinery. “STEP Demo is laying the groundwork for power generation that is more efficient, with a smaller footprint.”

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 held above a critical temperature and pressure can act like a gas while having the density near that of a liquid.

The efficiency of sCOas 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. For example, a desk-sized sCOturbine can power up to 10,000 homes. The technology is also compatible with concentrated solar power and industrial waste heat.

“The sCO2 power cycle is a breakthrough clean, compact, and high-efficiency power generation technology that can deliver significant environmental performance. We look forward to continued operation of the current test to demonstrate control and operability of this power cycle while validating system performance over long periods of time,” notes Bhima Sastri, Director of Energy Asset Transformation, DOE Office of Fossil Energy and Carbon Management.

The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCOtechnology to dramatically improve the efficiency, economics, operational flexibility, space requirements and environmental performance of this new technology. The facility’s turbine is currently being installed and will be tested later this year.

SwRI is an industry leader in the development of sCOpower cycles. Staff members have conducted numerous related U.S. Department of Energy projects advancing the efficiency, reliability and commercial readiness of sCOpower 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.

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