Experimental study on a novel form-stable phase change materials based on diatomite for solar energy storage

PCM has been investigated for solar energy storage in recent years. The magnesium nitrate hexahydrate was chosen as PCM due to the suitable melting temperature and high latent heat for solar thermal energy in this paper. In order to prevent the leakage during the phase transition, a novel form-stable composite PCM based on diatomite was prepared by the vacuum impregnation method. The micromorphology, chemical structure, crystalloid phase, thermal properties, supercooling degree, thermal conductivity and thermal reliability were investigated by SEM, XRD, FT-IR, DSC, self-designed device and hot-wire method. FT-IR spectra indicated that there was no chemical reaction during the preparation process. The supercooling tested by the self-designed device was just 0.3 °C which can be neglected. The melting and freezing temperature measured by DSC and step-cooling curve method were 88.89 °C and 83.5 °C, respectively. Furthermore, the latent heat was 69.39 J/g and the adsorptive capacity was 46.78% according the pure PCM used in this study. The thermal reliability test was performed and the results showed that the thermal properties basically unchanged after 2000 thermal cycles.