Simultaneous Solar-Thermal Energy Harvesting and Storage via Shape Stabilized Salt Hydrate Phase Change Material

Abstract The intermittent nature of solar radiation for solar driven applications providing the vast opportunity for phase change materials(PCMs) to reduce the gap between supply and demand of energy. Nevertheless, the widespread utilization of PCMs is limited due to the flow of liquid PCMs during melting, phase separation, supercooling and low heat transfer rate. The ongoing progression of research in this field reveals that there is a high demand for shape stabilized PCMs (SSPCMs) with high energy storage capacity and fast charging and discharging rates. Here, we demonstrated the facile route to synthesize novel salt hydrate based SSPCMs via incorporation of the functionalized graphene nanoplatelets (GNPs). The hydrophilic GNPs not only prevented the PCM leakage but also improved the thermal conductivity and proffered the low supercooling degree. The resultant SSPCMs exhibited a high transition enthalpy (248.3 J/g) with low supercooling degree of 0.1 °C. The addition of graphene nanosheets significantly enhanced the solar absorption characteristics of pure PCM and simultaneously offered the high photo-thermal efficiency of 92.6%. This strategy concurrently enhanced the thermal conductivity of pure salt by 114% that accelerates solar-thermal energy storage rates while maintaining the high energy storage capacity. These novel SSPCMs have shown great thermal cycling reliability make them very promising materials for solar-to-thermal conversion and storage.