A comprehensive study of properties of paraffin phase change materials for solar thermal energy storage and thermal management applications

Paraffins are useful as phase change materials (PCMs) for thermal energy storage (TES) via their melting transition, Tmpt. Paraffins with Tmpt between 30 and 60 °C have particular utility in improving the efficiency of solar energy capture systems and for thermal buffering of electronics and batteries. However, there remain critical knowledge gaps concerning the properties of paraffin PCMs, including their long-term reliability and chemical compatibility. Therefore, we have undertaken a thorough, comprehensive study of the thermophysical properties, long-term stability and chemical compatibility of six widely useful paraffin PCMs. The PCMs investigated include three pure alkanes, nonadecane, eicosane, docosane, and three commercial blends of paraffin waxes. For each PCM, we accurately determined Tmpt, the latent heat of fusion, the density of the solid phase and the temperature dependences of the heat capacity and thermal conductivity. For the first time, we show the thermal stability of the PCMs after 3000 melt-freeze cycles, and their chemical compatibilities with 17 different metallic and plastic materials used for encapsulation and in composites and fillers. These results provide necessary information to improve energy modeling and analysis for existing and emerging TES applications, and guide the selection of reliable paraffin PCMs and encapsulation materials for such applications.