Form-stable oxalic acid dihydrate/glycolic acid-based composite PCMs for thermal energy storage

Abstract

The development of high efficient materials for storage and utilization of sustainable thermal energy is very meaningful. Herein, in this research, an oxalic acid dihydrate/glycolic acid (OG) binary eutectic mixtures with the ratio of 80 wt%/20 wt% was prepared as phase change material (PCM), hydrothermal carbon (HTC) and poly (acrylamide-co-acrylic acid) copolymer (PAAAM) were separately and together used as support materials to solve liquid-state leakage problem and improve thermal conductivity. Three form-stable PCM composites (OG/PAAAM, OG/HTC/PAAAM and OG/HTC) were synthesized. The prepared composites were studied by XRD and FT-IR spectra, their thermophysical properties and PCM storage properties were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The OG/PAAAM, OG/HTC/PAAAM and OG/HTC showed the high loading rate to OG content, which are 1718 wt%, 1329 wt% and 1150 wt%, and the latent heat are 289.6, 313.2 and 318.8 J/g, respectively. In addition, the composites possess excellent recyclability after 101 times melting-freezing cycles. Compared to pure OG, OG/PAAAM and OG/HTC/PAAAM (0.2766, 0.3125 and 0.8538 W/m K), the OG/HTC exhibit a higher thermal conductivity of 1.3867 W/m K.