A. Saikiran

This study presents a novel, cost‐effective composite phase change material (PCM) using cetyl alcohol (CAL) and shape‐stabilizing biochar derived from industrial waste wood carbon (WWC) for low‐temperature thermal energy storage, and the simultaneous use of Kissinger and Ozawa techniques to assess the kinetics and activation energies of PCM samples. Biochar content was varied from 0 to 3 g per 10 g CAL to synthesize various composite PCM samples. The morphological studies confirmed the encapsulation of molten PCM into biochar. FTIR and XRD investigations confirmed the chemical stability of the synthesized PCM samples, ascribing to the absence of extra peaks/bands. TGA studies divulged the enhanced thermal stability of the CAL4 sample. CAL4 sample has exhibited suitable thermal properties comprising a latent heat of 184.83 J/g, an encapsulation efficiency of 76.76%, and a thermal energy storage capacity of 99.62%. The activation energy of CAL4 calculated by both models, i.e., 551.118 and 531.827 kJ/mol, is superior compared to that of the pure PCM, which is due to the porous matrix of the CAL4 sample. Even after 100 thermal cycles, CAL4 showed negligible thermal property changes and zero leakage, proving it as a cost‐effective leak‐proof solution for long‐term low‐temperature thermal 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.