DOE OSTI2019
Southwest Research Institute® (SwRI®) has developed a novel, high-efficiency, supercritical carbon dioxide (sCO 2 ), hot gas turbo-expander optimized for the highly-transient, solar-powerplant, duty-cycle profile. This MW-scale sCO 2 turbo-expander design advances the state-of-theart of sCO 2 turbo-expanders from a current Technology Readiness Level (TRL) of three (initial, small-scale, laboratory, size testing) to a full TRL6 (MW-scale prototype demonstration). A secondary objective of this project was to optimize novel compact heat exchangers for sCO 2 applications to drastically reduce their manufacturing costs. Significant learning was achieved on how to design and fabricate a more cost effective, high performance recuperator, at the MWt capacity. The sCO 2 turbo-expander and novel sCO 2 heat exchanger have been tested in a 1- MWe sCO 2 test loop, fabricated to demonstrate component performance and the performance of the optimized sCO 2 Brayton cycle over a wide range of part load conditions and during transient operations representative of a typical Concentrating Solar Power (CSP) duty cycle. The scalable sCO 2 expander design and improved heat exchanger address and close two critical technology gaps required for an optimized CSP sCO 2 power plant and provide a major stepping stone on the pathway to achieving CSP power at $\$ $0.06/kW-hr Levelized Cost of Electricity (LCOE), increasing energy conversion efficiency to greater than 50% and reducing total power block cost to below $\$ $1,200/kW installed. Construction of the facility and testing has been completed. Test targets of 1,320°F, 27,000 rpm, and 3,500 psi were reached during separate tests. Overall, the turbine saw 37.5 hours of operation with many other hours of testing and troubleshooting all of the loop components. All the test data and troubleshooting is useful and applicable for future tests and operations with not only this loop but in any sCO2 application.