Characterization and stability study of a form-stable erythritol/expanded graphite composite phase change material for thermal energy storage

Abstract

A form-stable erythritol/expanded graphite (EG) composite phase change material (PCM) for mid-temperature thermal energy storage (TES) was successfully developed by an “impregnation, compression and sintering” three-step method. Five composite samples were prepared with EG contents of 5, 8, 10, 12 and 15 wt%, respectively. After measuring the thermal properties, it is shown that with the increase of EG content, the thermal conductivity and the freezing temperature are increased, while the melting temperature, the supercooling degree, and the latent heat of the composite PCMs are reduced. Furthermore, the 40 times charging-discharging performance of the form-stable composite PCMs was also tested on a supercooling test platform from room temperature to 130 °C. The charging time and the supercooling degree can be significantly reduced with the increase of the EG content. The present work shows that the 10 wt% EG content of form-stable composite PCM exhibits an optimal overall performance with a high thermal conductivity of 12.51 W/(m·K) (17.38 times higher than the pure erythritol) a low supercooling degree of 19.5 °C (11 °C lower than that of pure erythritol) and a good cyclic stability after 140 cycles. Therefore, it is proposed in this study as a promising PCM for mid-temperature TES.