Household Appliances Wasted Heat Storage by means of a Packed bed TES with Encapsulated PCM

This study aims at developing a thermal energy storage (TES) system to store the low-temperature waste heat produced by the most common household appliances. Given the requirements of system integration into a kitchen environment, a latent TES system, based on a packed bed of macro-encapsulated phase change material (PCM), was selected as most suitable solution. Air was exploited as heat transfer fluid (HTF) for transferring the waste heat from the appliances to the TES system where, percolating through the packed bed from top, it delivers the thermal energy to the capsules allowing the PCM to melt. The energy stored may be recovered by reversing the air-flow direction. Typical household appliances were analyzed evaluating the waste heat produced on the basis of the average user habits at European level. Based upon the results obtained, the TES system was designed and analyzed. A real-scale experimental prototype was built and exploited to evaluate its performance under different conditions of charge, discharge and storage time. The TES prototype was also analyzed by means of transient 3D computational fluid dynamics (CFD) simulations with the aim of evaluating its thermo-fluid dynamics behaviour under different working conditions. The numerical model developed was satisfactorily validated with experimental data gathered from the TES prototype.