Preparation, characterization and performance of paraffin/sepiolite composites as novel shape-stabilized phase change materials for thermal energy storage

In this paper, the paraffin/sepiolite composites were fabricated as novel shape-stable phase change materials (SSPCMs) by vacuum impregnation for thermal energy storage. The structure-property relationships and comprehensive performance of sepiolite-based composite SSPCMs prepared with/without treatment of sepiolite from three mineral deposits were investigated. Compared with the natural sepiolite (SEP), the sepiolite after the purification and acidification treatment (TSEP) is a more suitable supporting carrier for paraffin wax. The prepared paraffin/TSEP composite SSPCM exhibits a significant promotion in absorption mass of paraffin and phase change latent heat. The maximum increase in latent heat of melt and crystallization is 78.32 % and 77.47 %. Simultaneously, the prepared sepiolite-based SSPCMs can reach up to 35.18 % paraffin loading. Its highest latent heat of melting and freezing is 60.12 J/g and 57.09 J/g, respectively, and the relative enthalpy efficiency is as high as 94.45 %. In addition, the sepiolite-based composite SSPCMs show good thermal stability and chemical stability according to the thermal cycling test. Moreover, it is demonstrated that sepiolite-based SSPCMs can slow down the spread of heat by absorbing heat energy and have reliable energy storage and temperature regulation performance. Therefore, the inexpensive and abundant sepiolite can be applied in phase change materials for waste heat recovery and temperature regulation.