Performance design of high-temperature chloride salts as thermal energy storage material

Abstract

The chloride salts have great potential used as high-temperature thermal energy storage (TES) medium for the concentrated solar power system. In this study, LiCl, KCl and CaCl 2 were selected as energy storage materials in order to further broaden the working temperature of ternary chloride salt and improve its energy storage density. The new high-temperature energy storage ternary chloride composed of LiCl, KCl, and CaCl 2 was developed based on the phase diagram generated by FactSage. Three components of LiCl-KCl-CaCl 2 with the mass ratio of 37.85%-53.38%-8.77%, 30.90%-13.82%-55.28% and 1.78%-18.61%-79.61% were developed, of which the corresponding melting temperature (T m) 340.93, 433.57 and 626.85°C, respectively, was obtained either. Considering that T m of the third group of salts was too high, only the first two groups of salts were tested. DSC test showed that the actual melting point was only 0.46% and 1.64% different from the melting point predicted by Factsage. The thermal properties of the two ternary chloride salts were also compared. The solid and liquid-specific heat of ternary salts was determined by DSC using sapphire as the standard reference. The vapor pressure and decomposition temperature of ternary chloride salts were investigated. The results showed that the vapor pressure of salt 1 was almost constant below 650°C by FactSage. Meanwhile, the TG results showed that the upper working temperature of salt 1 was 650°C under the air atmosphere. In addition, the ternary chloride salts after short-term cycling still exhibited excellent thermal properties, which revealed that these good thermal properties make them have broad application prospects in high-temperature thermal energy storage systems.