Nanomaterials enhanced heat storage in molten salts

Molten salts have great potentials as thermal energy storage (TES) media due to their many types and compositions, wide operating temperatures and relatively high values of specific heat capacity. The rapid development of TES technologies in recent years has triggered the modification of TES media to higher operating temperatures and hence larger heat capacities for capturing and storing heat from a wider range of sources, especially renewables and thermal wastes from industry. In doing so, many nanomaterials have been added to molten salts, particularly their eutectic mixtures, as heat storage enhancers as reported in the literature, achieving remarkable increases in specific heat capacity. To explain the mechanism of the resultant capacity variations, different factors of the nanomaterials including particle size, concentration and structure, as well as interaction between the nanomaterials and the molten salts have been investigated with divergent results. It has been speculated that the formation of nanolayers on the surface of the nanomaterials and the induced larger surface area may be responsible for the enhanced specific heat capacity of molten salts. Besides, the principle of formation of the nanostructures and the specific heat capacity prediction model were also proposed. More efforts are needed to systematically analyse and integrate previous findings, including those contradictions originated from the scattered methods and techniques applied, to facilitate more comparable and repeatable outputs in the further work.