Material and experimental issues related to the use of liquid metals as heat transfer media for CSP tower receivers

Abstract

Liquid metals are one of the promising heat transfer media for CSP that allow higher receiver temperatures and more efficient and cost effect electricity production. PbBi, Na and Sn are the liquid metals discussed, each with its specific issues regarding compatibility with structural materials in contact. Recently it was shown that even at 550°C liquid Na cooled CSP systems have beneficial LCOE compared to the state of the art molten salts used at time. All discussed liquid metals will allow even more efficient CSP systems at higher temperatures. To qualify materials, existing and advanced new types, KIT started a research program to bring in its expertise in liquid metal research to the CSP community. New corrosion and material test facilities are designed and constructed and build up. The general liquid metal corrosion phenomena are discussed for all three liquid metals and based on this material concepts for the different liquid metals are presented. Advanced alumina forming metals like FeCrAlY, AFA-steels and HEA can be employed for PbBi and possibly for Sn. Their use in Na at very high temperatures require further investigations. Ceramics and maxphases are further options to be investigated. Finally WCuW laminates are an interesting new option that is under development and investigation.