Thermal Energy Storage with Nanoparticle Embedded Phase Change Materials in Concentrated Solar Systems

In this study, a concentrated solar thermal system for water heating is coupled with latent heat storage utilizing nanoparticle embedded phase change materials (nano-PCM). The system consists of parabolic trough collector (PTC), pipes carrying the heat transfer fluid (HTF), water in this study, and a nano-PCM tank. The HTF transfers its thermal energy to nano-PCM via pipes passing through the tank. The main function of the storage system is the nighttime use of solar energy stored during the day. Numerous types of nanoparticles with different concentrations are investigated in the literature, and it is observed that while the nanoparticle addition improves some thermophysical properties, some others get negatively affected. For this reason, an optimization study is necessary. In our study, the effects of nanoparticle addition on thermal conductivity, heat storage capacity, and charge-discharge time are investigated. TiO₂, graphene, Al₂O₃, CuO, SiO₂ and carbon black are chosen as nanoparticles within the concentration range of 0-1% vol. RT42 and RT55 are used as PCMs. Among the considered cases, the addition of graphene nanoparticles into the PCM with 1% concentration yielded the highest effective thermal conductivity, 1% CuO addition resulted in the highest heat capacity, and 1% SiO₂ in RT55 provided the longest discharge time.