Selection of high temperature materials for concentrated solar power systems: Property maps and experiments

Concentrated solar power systems are receiving increasing attention as electricity generating systems, whereby the sun's heat is focused onto a receiver heated to high temperatures. Systems operating today are generally limited to temperatures below about 600 °C, but there is considerable interest in increasing operating temperatures, with heat receivers generally constructed using refractory metallic alloys or ceramics. The present study compares the behaviour of a range of metallic or ceramic materials with advanced intermetallic alloys which have been developed for high-temperature aeronautic or power-generating systems. A few experiments are reported using intense solar heating to demonstrate the damage that may be sustained, depending on the material that is considered. Accelerated cyclic oxidation experiments further emphasize the sensitivity of the various materials to oxidation and thermal damage accumulation. The important characteristics required of the material to be used for the receiver are described and used to generate property maps where the suitability of different classes of materials (metal, intermetallic, ceramic) may be compared. Depending on the precise conditions of where the receiver will operate, and whether creep, fracture or oxidation/spalling is the most important damaging process, either refractory Ni-base alloys, Mo-silicides, or ceramics may be the best material for the application.