Assessing performance of an external compound parabolic concentrator solar collector with cascaded latent heat thermal storage

This study presents quantitative results of charging experiments conducted on cascaded thermal energy storage system (CTESS) integrated with external compound parabolic concentrator solar collector (XCPCSC). Increasing mass flow rate in 2-stage CTESS integrated with XCPCSC resulted in a 30% reduction in initiation time of phase change materials (PCMs) during charging, with a higher mass flow rate of 0.025 kg/s. However, due to disparate melting point temperatures of PCMs, phase transition in the two-stage CTESS did not occur simultaneously, leading to poor heat transfer rates within the CTESS. To address this, study extended number of phases from two to three, resulting in a 1.5-fold increase in rate of heat transfer compared to 2-stage PCM system. The simultaneous melting processes at various stages in the CTESS maximized energy absorption, leading to a 25% increase in system efficiency. Notably, the values of energy stored efficiency and over-all efficiency reached their peak values of 95% and 60%, respectively, between t = 12.00 h and t = 13.00 h. This time period also saw a significant increase in collector efficiency to 72%. These quantitative findings highlight importance of mass flow rate and PCM arrangement in achieving efficient heat transfer and system performance in a CTESS integrated with XCPCSC.