Selection of appropriate configuration for optimal cascaded thermal energy storage system under the effect of outlet threshold temperature constraint

Abstract

For analyzing the performance of the studied configuration, consideration of its application is highly crucial. Therefore, analyzing the amount of discharged energy against the temperature margin of the outlet is vital. A 2-D Numerical analysis was performed on various TES cases (under dynamic solar energy conditions). The type of storage media for each column was subject to choice and optimized using a genetic algorithm. The optimal distribution of the HTF rows altitude showed a variety of 12.3 mm (Center) to 29.1 mm (Sidewall) within the structure. The study objective is the selection of the best configuration to maximize the system discharge energy following two scenarios, first when there is no applied outlet threshold temperature constraint for the TES and second, when a specific outlet threshold temperature constraint is applied on the system. Generally, the cascaded structure showed a 14.7 % higher amount of stored energy in comparison with the average of cases with only one PCM, whereas the hybrid-cascaded configuration showed a 7.8 % higher stored energy compared to the same cases. At the first scenario (under no outlet temperature constraint) outputs, a higher figure of energy was discharged by the cascaded structure against the hybrid-cascaded one, however, the difference in the energy discharged amounts has decreased, describing the better thermal performance of hybrid cascaded setup while discharging. In the second scenario (with applied outlet temperature constraint), it was found that the useful discharged energy of the hybrid-cascaded structure is higher, meaning that more amount of energy is discharged in the required temperature range and thermal control is enhanced, and this is the most important result of this research and shows that the use of the sensible storage material as well as latent storage material will cause a very favorable change in the performance of the system.