Development of a Prosopis Juliflora -derived biochar composite for energy storage applications

Phase change materials (PCMs) have great potential for thermal energy storage; however, their practical use is often limited by low thermal conductivity and the risk of leakage during phase transitions. This study aimed to develop a low-cost, form-stable composite PCM utilising biochar derived from the invasive weed Prosopis Juliflora as a sustainable support matrix to improve thermal performance and suppress leakage during phase-change processes. To create the composite PCM, Prosopis Juliflora biochar was incorporated into paraffin wax using a straightforward impregnation method. Leakage tests revealed that the optimal weight ratio of paraffin wax to biochar was 6:4, which demonstrated negligible leakage and good structural stability. The composite PCM was characterised using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). DSC analysis indicated a melting temperature of 66 °C, very close to that of pure paraffin wax (65.93 °C), suggesting that the addition of biochar had minimal impact on the phase transition temperature. The latent heat of fusion was 166.92 J/g. Furthermore, the addition of biochar increased thermal conductivity by 64% when 5 wt.-% was incorporated. Aluminium powders further increased it to 94%. The composite also exhibited improved thermal stability and delayed thermal degradation compared to pure paraffin wax. These findings confirm that Prosopis Juliflora biochar effectively serves as a support matrix for developing form-stable composite PCMs with enhanced thermal performance, providing a cost-effective and environmentally friendly solution for thermal energy storage applications.