Development of high efficiency hot gas turbo-expander for optimized CSP supercritical CO2 power block operation

Abstract

GE Global Research in collaboration with Southwest Research Institute is working on development of a supercritical CO2 (sCO2) turbo-expander for application to a sCO2 based power cycle for concentrated solar power (CSP) conversion. The proposed cycle uses sCO2 as both the heat transfer fluid in the solar receiver and the working fluid in the power block. The lower thermal mass and increased power density of the sCO2 cycle, as compared to steam-based systems, enables the development of compact, high- efficiency power blocks that are compatible with sensible-heat thermal energy storage, and can respond quickly to transient environmental changes and frequent start-up/shut-down operations. These smaller, integrated power blocks are ideal for modular tower mounted CSP solutions in the 5-10 MW range. With funding under the Sunshot initiative, the authors are developing this high-efficiency sCO2 turbo-expander for the solar power plant duty cycle profile for the sCO2 Brayton cycle. The scalable sCO2 expander design closes a critical technology gap required for an optimized CSP sCO2 power plant and provides a major stepping stone on the pathway to achieving CSP power at $0.06/kW-hr levelized cost of electricity, increasing energy conversion efficiency to greater than 50%, and reducing total power block cost to below $1,200/kW installed. High power density of the sCO2 working and its impact on turbine design are presented in detail.