Molten salts in the light of corrosion mitigation strategies and embedded with nanoparticles to enhance the thermophysical properties for CSP plants

Abstract

Solar power has prominently been showing potential as a means to sustainable, dispatchable and affordable source of energy while attracting huge attention for scientists as a viable alternative for next-generation energy usage. Solar Salt, KNO3-NaNO3 (40–60 wt%) mixture, has been considered indispensable as it is the most technologically mature molten salt for CSP plants. However, molten salt-based heat transfer fluids (HTF) and/or thermal energy storage (TES) media have been facing critical challenging issues of severe corrosion and lower specific heat capacity. Considering these problems, more effective studies should be conducted to explore the alternative nitrate salt mixtures, chlorides, fluorides and carbonates focusing on the widening thermal stability range, and to enhance thermal properties and to lower corrosion rate. Thereafter, scientists and engineers would be able to incorporate these variations of molten salts with an economical industrial way into CSP applications. In this context, the present review thoroughly investigates the Solar Salt, HitecXL, Hitec, LiNaKNO3, NaKMg chloride, NaKZn chloride, LiNaK fluoride and (LiNaK)2CO3 salts in terms of their basic thermal properties, corrosion rate and their contingent behaviour on nanoparticles; regardless of discrepancies and incompatibilities. Moreover, this article highlighted some corrosion mitigation approaches that could enhance the efficacy of molten salts for next-generation CSP plants. Also, there is a still need to further investigate the long-term thermal stability of molten salt-based nanofluids by researchers on an urgent basis.