Popcorn-derived porous carbon based adipic acid composite phase change materials for direct solar energy storage systems

As typical absorbing solar energy collectors, direct absorption solar collectors (DASCs) have shown great potentials in solar energy utilization. However, due to the instability and discontinuities of solar energy, it is difficult for the heat source output sustainably. Fabrication of direct solar energy storage system is appealing, which can combine the DASCs system and the phase change materials (PCMs) storage system in one unit. In our current work, using biomass-derived porous carbons (PC) as solar energy absorbance materials and adipic acid (AA) as PCMs in a direct solar storage system, integrations of solar energy collection, photo-thermal conversion and long-term energy storage have been achieved. The photothermal conversion efficiency of AA+7 wt% PC is as high as 93.83%. The thermal conductivity of the AA+7 wt% PC is 1.18 W/(m·K), which is 149% higher than pure AA (0.45 W/(m·K)). The PC-CPCMs have the advantages of no subcooling, and the energy storage density can reach 195.05 J/g. The environmental benign and cheap biomass porous carbons based composite PCMs encapsulated in direct solar energy storage systems pave a new avenue for high utilization of solar energy. It can meet thermal energy demands independent of weather conditions and time effects. • A novel direct solar energy storage system is designed and fabricated. • The system integrates the solar thermal collection with the PCMs storage systems. • Environmental benign biomass-derived carbons are used as light-capturing materials. • PC-CPCMs possess good solar energy absorption and energy storage. • AA+7wt%PC has photothermal conversion efficiency as high as 93.83%.