Concentrated solar power (CSP) systems can play a major role as a renewable energy source with the inherent possibility of including a thermal energy storage subsystem for improving the plant dispatchability. Next-generation CSP systems have to provide an increased overall efficiency at reduced specific costs and they will require higher operating temperatures and larger heat flux densities. In that context, liquid metals are proposed as advanced high temperature heat transfer fluids, particularly for central receiver systems. Their main advantages are chemical stability at temperatures up to 900 ℃ and even beyond, as well as largely improved heat transfer when compared to conventional fluids like oil or salt mixtures, primarily due to their superior thermal conductivity. However, major issues here are the corrosion protection of structural materials and the development of technology components and control systems, as well as the development of indirect storage solutions, to circumvent the relatively small heat capacity of liquid metals. On the other hand, using liquid metals might enable alternative technologies like direct thermal-electric conversion or use of solar high-tem­perature heat in chemical processes. This article aims at describing research areas and research needs to be addressed for fully evaluating and subsequently utilizing the potential of liquid metals in CSP systems. A second aim of the article is a brief overview of the liquid metal research capabilities of Karlsruhe Institute of Technology (KIT), their background and their relation to CSP and the aforementioned research pathways.

Liquid lead (Pb) is an attractive heat transfer fluid (HTF) for packed‐bed thermal energy storage (TES) systems aimed for high temperatures. However, liquid Pb is corrosive and its corrosivity increases with rising temperature. Therefore, compatibility tests of possible filler materials with Pb are mandatory. This study tested the corrosion and thermal alteration of seven ceramic materials (two alumina materials, one alumina zirconia composite material, two zirconia ceramics stabilized with either yttria or ceria, and two zirconium silicates in different compositions) in liquid Pb at 650°C and 750°C in a reducing environment for up to 5000 h. The results showed that the tested zirconium silicates are not suitable due to the high glass content and the ceria stabilized ZrO ₂ revealed a poor thermal shock resistance. In contrast, the yttria stabilized ZrO ₂ and the alumina zirconia composite showed a very good compatibility with a negligible reaction with Pb.