Thermal Performance of Erythritol-Based Biochar Composites for Medium-Temperature Energy Storage Applications

The present study focuses on the development of erythritol-based activated biochar composite phase change materials (PCMs) targeting medium-temperature energy storage applications, including waste heat recovery, solar desalination, and solar thermal energy storage. The activated biochar composites were produced from coconut shell using pyrolysis. The fabricated samples were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR) to evaluate the phase composition, thermal properties, and functional group analysis of the composites. Biochar composites exhibited enhanced thermal energy storage properties and thermal stability compared to pure PCM. TGA was employed to assess weight changes during controlled temperature increase to analyze thermal stability and decomposition. The degradation kinetics for both materials were evaluated to determine the activation energy needed for degradation processes using Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink models. The results indicate that the activation energies for pure PCM, determined using the KAS, FWO, and Starink methods, are 82.81, 88.04, and 83.54 kJ/mol, respectively. For PCM + 0.25% G + 20% BC, activation energies varied between 325.67 and 347.37 kJ/mol. For PCM + 0.5% G + 20% BC, activation energies varied between 235.05 and 256.94 kJ/mol. For PCM + 20% BC, activation energies varied between 13.83 and 24.10 kJ/mol. Overall, the findings highlight the impact of graphene with biochar on the thermal properties of both pure and composite biochar PCMs. The 20% biochar composite with 0.25% graphene demonstrated improved thermal stability, highlighting its potential for effective medium-temperature energy storage solutions.