Exergy analysis of cascaded encapsulated phase change material-High-temperature thermal energy storage systems

•Exergy Analysis of an encapsulated phase change material-based EPCM system.•Six different salt PCM system is considered.•System analysis of latent heat storage module containing 72 capsules.•Benefit to employing a cascaded multi-PCM system.•Study aids in designing and optimizing storage module for CSP.

The second law analysis of an example thermal energy storage (TES) system was conducted to determine the benefit of a system employing a multiple phase change materials. Six systems were considered: three single PCM systems (NaNO3, NaNO2, and KNO3), a 2-PCM system a 3-PCM system, and a sensible heat only system as a comparison. The latent heat-based systems were able to store more energy and exergy with comparable efficiencies than a system that relies on sensible heat only. Furthermore, when the overall cyclic performance was examined and showed that systems with multiple PCMs outperform their corresponding single PCM-based systems. While for the operating conditions and PCMs chosen the 2-PCM system (NaNO3/NaNO2) was superior, great care is required during the design of an EPCM-based TES system as the difference between the melting point of the PCMs and the inlet temperatures during charging and discharging greatly affect the performance of the system.