Preparation and thermal properties of shape-stabilized composite phase change materials based on polyethylene glycol and porous carbon prepared from potato

Abstract

A shape-stabilized composite phase change material (ss-CPCM) comprising polyethylene glycol (PEG) and porous carbon was prepared by absorbing PEG into porous carbon, assisted by ultrasound. In the composite, PEG served as a phase change material for thermal energy storage, and the porous carbon, which was prepared from fresh potato via freeze drying followed by heat treatment, was used as an absorbent that also acted as the supporting material. Various analytical techniques were used to investigate the chemical composition, microstructure, and thermal properties of the prepared PEG/porous carbon ss-CPCMs. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopic results indicated that PEG was well absorbed and encapsulated in the porous structure of the carbon and that there was no chemical reaction between them during the phase change process. The shape and exudation stability test results indicated that the PEG/porous carbon ss-CPCMs have excellent shape stability, compared to pristine PEG. The contact angle test suggested that the melting PEG has good level of wettability on the carbon so that melting PEG could be well protected from exudation in the porous carbon by surface tension effects, even if the temperature is higher than the melting point of PEG. Differential scanning calorimetric results showed that the PEG/porous carbon ss-CPCMs have considerable phase change enthalpies and thermal storage capabilities. In addition to this, the latent heats of ss-CPCMs increased with increasing contents of PEG in the composites, and the highest value was achieved when the amount of PEG was 50%. Moreover, the thermogravimetric analysis results showed that the composites had excellent thermal stabilities. Based on the above analyses, the prepared ss-CPCM with 50% PEG content proved to be a promising candidate for thermal energy storage applications.