Thermal Energy Storage Based on Phase Change Material Composites

Composite stearic acid (SA) and powder of activated carbon (AC) obtained from olive pomace charged with graphite (Gr) was prepared as thermal energy storage material, using impregnation methods. In the composites, the activated carbon powder acted as a supporting matrix and stearic acid (SA) is selected as the phase change material (PCM), due to its appreciable thermal properties to the thermal storage by latent heat. Nevertheless, this PCM presents a major disadvantage which is its low thermal conductivity. In order to improve the thermal conductivity of the composite, the graphite (Gr) is chosen to be added it in the composite which also improves the stability of composite. The environmental scanning electronic microscopy (ESEM) was used to determine microstructure of SA/AC composites. The thermal properties, such as latent heat and phase change temperature, are investigated by a differential scanning calorimeter (DSC). Thermal conductivity is determined by a hot disk method. The results of ESEM analysis show that the SA is well dispersed in the porosity of AC. The DSC results indicate that the composites solidify at 52.34 °C with a latent heat of 99.93 J g−1 and melt at 52.70 °C with a latent heat of 89.93  J g−1 when the mass percentage of SA in the composites was 43%. The thermal conductivity results show that the addition of Gr improved considerably the thermal conductivity of SA/AC/Gr composite when the mass percentage of Gr in the composite was 8%.