Thermal characterization of solar salts from north of Chile and variations of their properties over time at high temperature

The current study has conducted a wide-ranging characterization, under high-temperature conditions, of a new ternary and quaternary heat transfer fluid, with the addition of Ca(NO₃)₂ and LiNO₃, two of the solar salt additives with a greater potential for being included in these new formulations proposed for the new generation of concentrated solar power (CSP) plants. In this direction, the present research is focused on viscosity and thermal stability since these salts try to increase the work temperature range in CSP plants. Viscosity tests were analyzed each 10 °C from 130 to 300 °C in order to check the variation in this parameter close to their melting points. Isothermal analysis at 450 and 500 °C was also performed through thermal gravimetric (TG) analysis, measuring any resulting loss of mass in the sample at these temperatures. Results were compared with the behavior in binary solar salt. These tests showed a progressive thermal degradation of salts over the time and the maximum temperature for operation in CSP has been corrected regarding the use of ternary and quaternary molten salts.