Thermal performance of sensible and latent heat thermal energy storage systems

The thermal energy storage is an essential subsystem for solar thermal energy systems. Few experimental studies are available to compare the performance of sensible and latent thermal energy storage systems for the same storage configurations. The comparison can provide guidance in selecting the storage system for particular solar thermal applications. The present work focuses on the experimental investigation of sensible and latent thermal storage systems with different mass flow rates. Concrete spheres and paraffin-encapsulated metal capsules having a uniform diameter of 38 mm were taken as the packing elements and air as a heat transfer fluid for both the storage systems. The performance characteristics of both the storage systems have been evaluated in terms of charging time, instantaneous/cumulative energy absorption and energy storage under different flow rate conditions. Thermal mass, conductivity and flow rate has a substantial impact on temperature difference in the storage system. The charging time and energy storage capacity of the sensible thermal storage system was found to be lesser than the latent thermal storage system for all the flow rates. Based on the study, it is recommended that the latent thermal storage system is preferable for higher energy storage capacity, while for better charging and medium storage capacities sensible storage may be a good option.