Critical components in supercritical CO2 Brayton cycle power blocks for solar power systems: Degradation mechanisms and failure consequences

This review presents an overview of the critical components in supercritical CO2 Brayton cycle power block systems along with their degradation mechanisms and possible consequences in Concentrated Solar Power (CSP) systems. Requirements for high strength, efficiency, and environmental compatibility are also discussed. sCO2 turbines are advantageous because of their small size and significantly reduced number of turbomachinery components. These components are exposed to a sCO2 environment with high pressures, temperatures, and thermal cycling that can result in premature failure due to fatigue, creep, corrosion, stress corrosion cracking, erosion, and carburization. Nickel and stainless steel candidate alloys have been proposed for sCO2 service and at these operational conditions their failures are discussed. The consequences of loss of containment for typical system designs are also explored with specific reference to potential exothermic reactions with other heat transfer media such as sodium.