Latent heat thermal energy storage in a modular flat plate energy storage with wedge fins

Flat plate latent heat thermal energy storage (LHTES) units can store a notable amount of thermal energy in a compact, modular space, offering efficient energy access through mini-channels. This study aims to investigate the charging and discharging behavior of phase change material (PCM) in a flat plate LHTES unit. Wedge-shaped (triangular) fins were employed to enhance heat transfer on the PCM side. Periodic boundary conditions were applied to account for the modular stacking effect. The impact of fin shape and arrangement on the average charging and discharging power was examined. Furthermore, the influence of the convective heat transfer coefficient in the heat transfer fluid channels and thermal boundary conditions was investigated. The results show that LHTES performance is highly sensitive to fin geometry, boundary conditions, and heat transfer coefficients. A moderate fin height ratio of 0.5 yielded the fastest melting times, outperforming both lower and higher ratios by approximately 8%. Using insulated boundaries instead of periodic ones increased melting times by around 1.6%. Enhancing the convective heat transfer coefficient from 50 to 150 W/m 2 ·K reduced melting duration by 44.9%. Increasing the fin tooth shape ratio from 0.75 to 1.5 led to a 39% reduction in melting time and nearly 50% shorter solidification time. At MVF = 0.7 and equal tooth ratios, top-fin configurations reduced melting time by 12.5–26.2% relative to bottom-only configurations. Configurations without fins required up to 327% longer charging (melting) time than the best-performing configuration; equivalently, the best-performing evaluated case reduced melting time by about 76.6% relative to the finless insulated case, identifying the best case within the tested parameter set rather than a formal optimum. Using the initial-to-target energy change divided by the corresponding elapsed time, increasing the convective coefficient from 50 to 150 W/m 2 ·K for the matched T3/T8 geometry raised average charging power from approximately 0.060 to 0.112 kW/m and average discharging power from approximately 0.055 to 0.086 kW/m.