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Influence of nanoparticle type on the heat storage performance of solar salt for thermal energy storage applications
Han Thi Thu, Tsogtbilegt Boldoo, Seongmin Choi and Honghyun Cho

Solar salt is widely used as a high-temperature thermal energy storage (TES) material; however, its relatively low specific heat limits its heat-storage density. In this study, solar salt nanofluids containing 1 wt% Al₂O₃, graphene nanoplatelets (GNPs), and SiO₂ nanoparticles, were prepared using an aqueous-assisted dispersion method to investigate the influence of nanoparticle type on thermal storage performance. Differential scanning calorimetry (DSC) was employed to evaluate phase-transition behavior, specific heat, and total TES capacity. The results showed that the specific heat of the base salt was increased with the addition of nanoparticles, and the degree of enhancement was strongly dependent on the type of nanoparticles. The Al₂O₃ nanocomposite showed the greatest improvement, with specific heat increases of 30.5% and 40.4% in the solid and liquid phases, respectively, while SiO₂ produced a moderate enhancement and GNPs a comparatively limited one. The TES capacity, calculated from both sensible and latent heat contributions over the temperature range of 150-300°C, reached a maximum of 341.3 kJ·kg^-1 for the Al₂O₃ nanocomposite, an increase of 17.3% over the base solar salt. The results suggest that nanoparticle-dependent morphology and particle-salt interfacial effects may contribute to the observed differences in TES performance.

Keywords: Nanocomposites, Nanoparticle dispersion, Solar salt, Specific heat, Thermal energy storage (TES)