Development of novel form-stable PCM-biochar composites and detailed characterization of their morphological, chemical and thermal properties

Storing heat with phase change materials has the potential for several modern-day applications such as building thermal regulation, isothermal solar drying, electronic cooling, etc. However, to suitably incorporate latent heat energy storage systems, the challenges of leakage and low thermal conductivity of these materials need to be addressed. In this direction, biochar derived from abundantly available biomass feedstocks has been explored to develop form-stable, environmentally compatible energy storage materials. Biochar has been derived from wheat straw and softwood and has been analysed for their surface structure and utilised in the preparation of form-stable phase change material. The biochar derived from softwood was found to have a superior porous structure with a surface area of 441 m2/g compared to wheat straw. Biochar and phase change material Rubitherm 28 (RT28) were blended at various wt% and tested for leakage. The composite with 50 wt% of softwood biochar and RT28 had the lowest leakage rate. The developed green phase change-bio composite with minimum leakage has been thoroughly evaluated for its chemical and thermal properties. The latent heat of fusion has been found to be 228.6 J/g, 132.3 J/g and 51.6 J/g, for the RT28, softwood biochar composite, and wheat straw biochar composite respectively. Thermal conductivity was also higher for the composites than that of RT28. The thermal cycling reliability is suitable for thermal storage applications as there is a minimal alteration in the thermal properties observed after 200 cycles. The melting enthalpy of the new and aged composites after 200 cycles has been found to be 136.6 J/g and 132.42 J/g, respectively. The composite with minimal leakage and high thermal conductivity can potentially revolutionise the area of low temperature latent heat storage. The properties of the form-stable phase change-bio composite synthesised in this work make it suitable for application in the field of thermal management of photovoltaic modules, electronic devices, and buildings.