Advances in phase change materials and nanomaterials for applications in thermal energy storage.

Phase-changing materials are nowadays getting global attention on account of their ability to store excess energy. Solar thermal energy can be stored in phase changing material (PCM) in the forms of latent and sensible heat. The stored energy can be suitably utilized for other applications such as space heating and cooling, water heating, and further industrial processing where low-temperature heat energy is required. The presented work attempts to evaluate past, present, and future trends in the development of energy storage materials and their encapsulation techniques for efficient utilization of the available energy. Hybrid PCM with nanoparticles has excellent potential to tailor thermo-physical properties and uplift the efficiency of energy storage systems. Synergistic use of PCM with nanomicromaterial can further improve the capacity of energy storage system along with the charging and discharging efficiencies of the system. Impacts of the size of particle, concentration ratio, and shape of particle have been studied to assess their effectiveness in enhancing storage efficiency of the systems. Waste heat recovered and stored in energy storage materials can undoubtedly improve the total energy availability of the source, thus enhancing the exergy efficiency with simultaneous reduction in the entropy generation rate. Core-shell nanoparticles can further improve the optical absorptance spectra towards an infrared region of thermal energy. Paraffin wax-based NEPCMs with graphene nanoplatelets achieve 2.14 W/(m·K) thermal conductivity, enabling faster and more efficient heat transmission and lowering charging and discharging times for thermal storage devices.