Abstract:
Efficient and economical thermal energy storage (TES) system can effectively reduce mismatch between seasonal energy supply and demand. The single tank type thermocline TES has been investigated as economical alternative for medium temperature applications. However, key disadvantages of this design are quick degradation of thermocline thickness, thermal ratcheting and drop of temperature at outlet section during discharging. To overcome these issues, a new type of structured hybrid sensible-latent design is developed in this research. The focus of the present work is to experimentally investigate the charge and discharge performance of the proposed TES system and it is designed by incorporating the sensible heat concrete block with axial holes placed in between multilayers of PCMs (D- mannitol and adipic acid). Charge and discharge experiments are performed to study the effect of hybrid structured concrete and multilayer PCM’s configuration on thermocline temperature profiles, stratification number, total energy stored and retained by storage medium, effective charge and discharge efficiency, utilization ratio. The relative experimental study is developed for four configurations, i.e., multilayered sensible heat concrete with PCM (MLSPCM), two uni-layered sensible concrete with PCM (SLSPCM-1 and SLSPCM-2) arrangements and single sensible heat concrete block (SSCB) arrangement. The results show that effective discharge efficiency and storage capacity of MLSPCM, SLSPCM-1, SLSPCM-2 and SSCB are 87%, 85%, 86%, 79% and 12.53kWhr, 10.37kWhr, 9.96kWhr, 6.23kWhr, respectively. Moreover, the charging and discharging behavior of MLSPCM is further characterized at different mass flow rates to study the effect on thermocline thickness formation, effective discharge time and amount of energy extracted from storage medium. The present study shows that use of multilayers of PCM with suitable melting and solidification temperature together with low-cost sensible concrete, is viable and economical TES solution for medium temperature applications.
