Thermodynamic evaluation of liquid metals as heat transfer fluids in concentrated solar power plants

Concentrated solar power, and in particular central receiver 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. While current commercial projects are dominated by direct steam generation and molten nitrate salt concepts, next-generation systems will require higher operating temperature and larger heat-flux densities in order to increase the efficiency and reduce costs. In that context, liquid metals are proposed in this work as advanced heat transfer fluids that can face those challenges. The main advantages, regarding higher temperature and improved heat transfer performance, are discussed and quantified using simplified models. Indirect thermal storage solutions are proposed for compensating their relatively small heat capacity. Overall, provided that some practical challenges can be overcome, liquid metals present large potential as efficient heat transfer fluids. -- Highlights: • Liquid metals (sodium and LBE) are studied as advanced HTFs. • Larger heat transfer rates lead to an improved receiver performance. • High operating temperature above 1000 °C is possible. • Advanced high-temperature power conversion cycles are investigated