Coconut shell waste based activated carbon as a scaffolding of biobased phase change material for enhanced thermal energy storage: Sustainable waste recycling for renewable energy source

The utilization of cleaner products in the energy sector to promote renewable energy is essential for achieving sustainable development goals. This research investigates the formulation of a biobased phase change material (PCM) composed of a eutectic mixture of capric acid (CA) and myristic acid (MA), using activated carbon derived from waste coconut shells (AC cs ) as a porous scaffold. The main goal of this investigation is twofold: (a) to obtain a biobased PCM with enhanced thermal conductivity and leakage resistance, and (b) to contribute to minimizing the significant environmental burden and waste management concern associated with coconut shell waste. It is shown that the developed composite has the following properties. FTIR and XRD analyses confirm that PCM is physically incorporated within the AC cs matrix without chemical interaction. Meanwhile, SEM reveals a homogeneous impregnation of the PCM within the activated carbon porous structure. A DSC analysis yields a melting enthalpy of 32.5 J/g and a phase transition temperature of 21.8 °C for the composite with the ratio of AC cs to PCM equal to 80 wt%. A TGA analysis further demonstrates the thermal stability of the composite up to 155 °C. The thermal conductivity of AC cs , eutectic PCM (EPCM) and proposed composite PCM (AC cs /EPCM) were determined to be 0.49, 0.17 and 0.30 W/mK, respectively. Thus, the incorporation of the EPCM into the AC cs leads to a 43% enhancement in thermal conductivity. Further, the melting time for EPCM and AC cs /EPCM was determined to be 648 sec and 417 sec, respectively, showing a 35% reduction in time for the proposed composite. After 1000 thermal cycles, the reduction in the latent heat of the composite is marginal, implying its good thermal reliability. These results establish the proposed AC cs /EPCM as a sustainable thermal energy storage material with potential applications in passive temperature regulation for the building sector. • Coconut shell waste recycled for renewable energy source to promote sustainability • Novel Biobased PCM composite with good thermal conductivity and leakage resistance • Coconut Shell based activated Carbon scaffold improves PCM thermal stability. • 43% increase in thermal conductivity via composite PCM incorporation. • Minimal latent heat loss after 1000 thermal cycles ensures reliability. • Sustainable PCM composite suitable for passive building temperature control.