Material Degradation Mechanisms Relevant to the Next Generation of Concentrated Solar Power Plants

The higher working temperature of future Concentrated Solar Power (CSP) plants requires careful selection of containment materials (high-strength alloys) to meet the challenging high-temperature and corrosive environments within the plant. This is also true of high-temperature thermochemistry derived from renewables. For CSP, the receiver will operate at ~800 ^oC with liquid salt or sodium, all fluid piping systems allowing the transport of the heat transfer fluids, heat exchangers that permit the heat to flow through the CSP plant, storage tanks (with phase-change materials) operating in excess of 700 ^oC storing the thermal energy collected for later use, and the supercritical CO₂ power block operating in excess of 600 ^oC are critical components that need to survive harsh, high-temperature, pressurized environments that have thermal cycles designed into their ongoing operation. Thermo-mechanical fatigue, transient creep, (cyclic) corrosion, carburization, embrittlement and erosion have been recognized as general degradation mechanisms for all containment (metallic material) sections of the system as well as degradation of the heat transfer and storage fluids (sodium, phase change materials, supercritical CO₂). Accordingly, and for the purpose of improving compatibility, characterising the various and significant degradation mechanisms for a matrix of candidate materials has been developed and is currently being evaluated through specific and targeted testing to validate their appropriateness for these future and challenging CSP applications. Candidate metallic materials selected, the testing being conducted and preliminary results for the degradation of these materials in the various heat-transfer fluids will be presented and a summary of ongoing/future work.