A Form Stable Composite Phase Change Material for Thermal Energy Storage Applications over 700 °C

Thermal energy storage (TES) is a highly effective approach for mitigating the intermittency and fluctuation of renewable energy sources and reducing industrial waste heat. We report here recent research on the use of composite phase change materials (PCM) for applications over 700 °C. For such a category of material, chemical incompatibility and low thermal conductivity are often among the main challenges. Our aims are to address these challenges through the formulation of form-stable composite PCMs and to understand their thermophysical properties. The eutectic K2CO3-Na2CO3 salt was used as a PCM with MgO as a form stabilizer. We found that such a formulation could maintain shape stability with up to 60 wt.% PCM. With a melting point of ~710.1 °C and an energy density as high as 431.2 J/g over a temperature range between 550 °C and 750 °C, the composite PCM was shown to be thermally stable up to 885 °C. An addition of 10 wt.% SiC enhanced the overall thermal conductivity from 1.94 W·m−1 K−1 to 2.28 W·m−1 K−1, giving an enhancement of 17.53%. Analyses of thermal cycling data also showed a high extent of chemical compatibility among the ingredients of the composite PCM.