Justification of Pore Configuration of Metal-Foam-Filled Thermal Energy Storage Tank: Optimization of Energy Performance

Thermal energy storage (TES) is a crucial technology for mitigating energy supply–demand mismatches and facilitating the integration of renewable energy. This study proposes a novel horizontal phase change TES unit integrated with partially filled metal foam (MF) and fins, divided into six sub-regions (ε1–ε6) with graded pore parameters. A comprehensive numerical model is developed to investigate the synergistic heat exchange mechanism and energy storage performance. The results demonstrate that porosity in Porosity-1 (ε1) and Porosity-2 (ε2) regions dominates melting dynamics. Through multi-objective optimization, targeting both minimal energy storage time and maximal energy storage rate, an optimal configuration (Case TD) is derived after technical design. Case TD features porosity values ε1 = ε2 = ε3 = ε5 = ε6 = 0.97 and ε4 = 0.98, where the graded porosity distribution balances heat conduction efficiency and energy storage capacity. Compared to the uniform MF case (Case 1) and the fin-only case (Case 6), Case TD reduces TES time by 51.75% and 17.39%, respectively, while increasing the mean TES rate by 102.55% and 19.12%, respectively. This design minimizes the TES capacity loss (only decreasing by 2.14% compared to Case 1) while maximizing the energy storage density and improving the efficiency–cost trade-off of the phase-change material-based system. It provides a scalable solution for rapid-response TES applications in solar thermal power plants and industrial waste heat recovery.