Development of new molten salts with LiNO3 and Ca(NO3)2 for energy storage in CSP plants

•The joint study of the two additives, LiNO3 and Ca(NO3)2, present a working range between 132 and 571°C.•The synergistic effect between both additives shows a higher heat capacity of the individual proposed mixtures.•These mixtures would allow a direct use as storage material in parabolic trough solar power plants. In this study, the effect of the addition of LiNO3 and/or Ca(NO3)2 to the solar salt NaNO3/KNO3, which is used as a storage material in CSP plants, on the physicochemical properties thereof was studied. Thermal analyses were performed by differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA), obtaining the phase transitions, melting points, heat capacities and thermal stability of the materials studied. In addition, viscosity measurements were carried out at different temperatures close to the melting point of the salt mixtures to determine their flowability. The study of these low-melting-point mixtures was executed through the synergistic effect exerted by a 30% LiNO3+60% KNO3+10% Ca(NO3)2 mixture, and it was observed that the addition of LiNO3 increases the thermal stability of the tested salts, whereas the addition of Ca(NO3)2 reduces the melting points and improves the economic cost of these mixtures These mixtures were designed such that the melting point of the molten nitrates would be reduced, allowing for the mixtures’ direct use as storage materials in parabolic-trough solar power plants, therefore replacing the synthetic oil currently used as a heat transfer fluid (HTF) and heat exchanger oil. The use of these mixtures is intended to reduce the economic costs and improve the thermal storage of current solar technology.