<p>A thermal energy storage (TES) system employing a cooling–heating dual–purpose hybrid PCM configuration was investigated in this study, in which the TES is charged with an equal amount of cooling and heating type PCM mixed at a 1:1 ratio. Numerical simulations were performed in ANSYS Fluent to examine the effects of PCM capsule diameter and flow velocity. Two capsule diameters, 65 mm and 130 mm, were examined. Although the larger capsules can reduce flow resistance and shell material cost, they required 18.9–25.6 times longer charging and discharging times, resulting in severely reduced thermal performance. Therefore, the 65 mm capsules were identified as the more suitable option for efficient TES operation. Changing the flow velocity from 2 to 4 and 6 m/s had no significant influence on the overall charging and discharging times, implying that flow velocity plays a minor role in the performance of PCM-based TES under the present conditions. Compared with a conventional water-based TES of the same tank volume, the hybrid PCM-TES stored about 40 % more thermal energy despite a longer charging period, demonstrating its higher energy density and potential for integrated cooling–heating operation.</p>