Improving the efficiency of solar thermal storage systems using TPMS: A pore-scale simulation

The thermal efficiency of latent heat thermal energy storage (LHTES) systems based on phase change materials (PCMs) remains a significant barrier to their widespread adoption in solar energy and industrial processes. LHTES systems incorporating triply periodic minimal surface (TPMS) lattice within PCMs exhibited excellent heat storage performance. However, the influence of model height, a key structural parameter, on heat storage behavior of LHTES systems had not been quantitatively analyzed, hindering further optimization. This study used a simplified central column model to evaluate the heat storage behavior of two TPMS structures (I-WP and Primitive) at three heights (15, 30, and 45 mm), comparing them with traditional metal foams (BCC). The results revealed a significant reduction in thermal conduction with increasing model height, with I-WP exhibiting the largest decrease (49.4 % from 15 mm to 45 mm), followed by Primitive (46.2 %) and BCC (45.7 %). Convective heat transfer in both Primitive and BCC initially increased and then decreased with model height, whereas in I-WP, the effect of model height was less pronounced. Additionally, the study quantitatively analyzed how the performance advantage of the two TPMS structures over BCC changed with model height. I-WP's advantage over BCC decreased with increasing height (26.7 %–16.7 %), while Primitive showed an opposite trend, with its advantage increasing from 18.1 % to 21.4 %. At a model height of 15 mm, I-WP was the most efficient structure, whereas Primitive outperformed at 30 mm and 45 mm. These findings enhanced LHTES efficiency, supporting their application in solar thermal storage.