Heat Balance of Long-term Supercooled Thermal Energy Storage

Abstract

The fundamental heat balance was evaluated by numerical simulation for a long-term latent heat thermal energy storage system using supercooled phenomena. The supercooled thermal energy storage (Super-TES) stores thermal energy at temperatures lower than the melting point of the phase-change material, which reduces heat loss from the storage system. The thermophysical properties of disodium hydrogenphosphate dodecahydrate were used for the calculation. From the results of the calculation, we found that Super-TES contributes for saving available energy (exergy) more than for saving energy. Although the exergy efficiency is generally lower than the energy efficiency, the relation reverses when the storage material is kept in the supercooled condition. Super-TES exceeds conventional latent heat thermal energy storage (LHTES) in both energy and exergy efficiencies. The difference in efficiency between Super-TES and LHTES increases with increasing period of the storage in the supercooled condition.