Exfoliation of graphite by solar irradiation and investigate their thermal property on capric–myristic–palmitic acid/exfoliated graphite composite as phase change material (PCM) for energy storage

Abstract

Nowadays, the energy recruitment increased day-today life. The energy usage can be reduced by means storing or recycle process. This work is focused on developing ternary eutectic mixture based on organic compound fatty acid like capric–myristic–palmitic acid in the mass ratio of 64.8:22.6:12.6 and optimize their thermal property by inorganic compound like exfoliated graphite (CA–MA–PA/xG) composites as phase change material (PCM) for energy storage. In this process xG was prepared from flake graphite, initially the graphite has undergone a carburization process for increase carbon content, then in a second step carburized graphite were undergone exfoliation with the addition of potassium permanganate and nitric acid in a ratio of 1:1:2 were done in an open atmosphere under roof of short length focusing by a Fresnel lens. The exfoliation of graphite was produced rapidly and efficiently within 3min. The xG were dispersed into CA–MA–PA under the assistance of high speed ultra-sonication in the mass ratio of 5% and 10%. The structural, thermal energy storage properties, thermal stability and thermal conductivity of novel composite (CA–MA–PA/xG) PCM was investigated. The thermal conductivity and thermal energy storage property of composite PCM when doped with 10% of xG were increased from 0.149W/mK to 0.180W/mK which showed increased about 20.8%. TG analysis tests revealed that the prepared CA–MA–PA/xG composite PCM has a high thermal stability in the working temperature range. The thermal energy storage for CA–MA–PA/xG (Tm=17.1°C; ΔHm=142.2J/g) for melting, (Tf=9.7°C; ΔHf=139.5J/g) for freezing respectively, for 90:10. The prepared CA–MA–PA/xG composite as PCM have a great potential application for low thermal energy storage.