Organic-inorganic hybrid phase change materials with high energy storage density based on porous shaped paraffin/hydrated salt/expanded graphite composites

Latent heat thermal energy storage based on phase change materials (PCM) is considered to be an effective method to solve the contradiction between solar energy supply and demand in time and space. The development of PCM composites with high solar energy absorption efficiency and high energy storage density is the key to solar thermal storage technology. In this paper, a green and simple method is proposed to fabricate a porous PCM with stable shape, low supercooling degree and excellent photo-thermal conversion performance. The novel PCM which combine porous expanded graphite as the carrier material, n-eicosane as the stabilizer and sodium acetate trihydrate (SAT) as phase change energy storage material are designed and prepared by melt blending method. The expanded graphite contributes to the stable shape of the composites, and provides excellent thermal conductivity channels and light absorption properties as well. The composite PCM sample containing 3.3 wt% expanded graphite achieves excellent performance, phase change enthalpy of 266.54 J/g and a photothermal conversion efficiency of 91.14 %, and shows low supercooling degree of 2.2 °C with almost no leakage at 90 °C.