Study of effect of Al and Cu microparticles dispersed in D-Mannitol PCM for effective solar thermal energy storage

Abstract

A practical use of phase change material (PCM)-based thermal energy storage (TES) system is effectively employed for mitigating the imbalance between energy demand and energy supply. Technological development of TES is essential to overcome the drawback of the poor thermo-physical property of many PCM’s. Otherwise, the PCM-based TES system would exhibit poor thermal management. In this work, D-Mannitol (DM) sugar alcohol is considered as PCM and experimental attempts were made to accelerate the phase change behaviour of the chosen PCM by adding 1 and 2% mass fraction of micron-sized copper and aluminium metal powders. The phase change temperature and enthalpy of fusion of the plain DM and composite DM were determined by differential scanning calorimetry (DSC) measurements, and the thermal stability of composite PCM was analysed using thermogravimetric analysis (TGA). Further, charging and discharging processes were conducted for plain DM and composite DM using Therminol 55 heat transfer fluid (HTF) to study their thermal energy storage performance. The DSC results indicated superior enthalpy of fusion and phase transition temperature and TGA results depicted extended decomposition temperature with an increase of about 2 °C to 32 °C for composite DM, respectively, over plain DM. Further, from charge–discharge studies, it was identified that the total time taken for a complete phase change process for the case of DM-Cu 2% during charging process was 22% and 11% lesser compared to plain DM and DM-Al 2%, respectively. Similarly during discharging process, the total time taken for a complete phase change process of DM-Cu 2% was 16% and 10% lesser compared to plain DM and DM-Al 2%, respectively, indicating superior phase change behaviour of composite DM compared to the plain DM. Thus, when compared to plain DM and Al microparticle in DM, Cu microparticle added DM was found to be more suitable to store thermal energy at a medium temperature range.