Development and characterization of NaCl-KCl/Kaolin composites for thermal energy storage

Abstract Molten chloride salts are considered a promising thermal storage materials because of their high energy storage density and thermal stability. However, the application of molten chloride salts is districted by its the corrosion behavior with metal containers. Encapsulation is one viable method for corrosion prevention. In this study, molten chloride salts as phase change materials (PCMs) were combined with encapsulation materials to form stable shape phase change materials (SSPCMs). The PCM was the mixture of NaCl and KCl eutectic salts, and the encapsulation material was kaolin. The SSPCMs were prepared by direct mixing and sintering, and the morphology and the thermal behaviors of the SSPCMs were investigated. The results showed that PCMs were uniformly distributed in kaolin, and the kaolin was compatible with NaCl-KCl. With the increase of the ratio of NaCl-KCl eutectic salt, the latent heat and energy storage density of SSPCMs increased. Meanwhile, the results indicated that the NaCl-KCl/kaolin composite with salt content of 80 wt% demonstrated the best performance with the phase change enthalpy of 178 J/g and the energy storage density of 171.32 J/cm3. Besides, it could maintain intact shape after 400 thermal cycling tests from 600 to 700 °C.