Naturally stratified chilled-water storage is widely used to offset the peak electrical demand caused by air-conditioning, but the mixing between cold and warm water greatly influences its thermal performance, especially for a low aspect ratio tank. In this study, a novel physically separated chilled water storage tank is proposed to take place traditional membrane tanks. The thermal performance of this novel tank is evaluated by static and dynamic experiments. The temperature distribution, outlet temperature, figure of merit (FOM1/2/FOM), and percent cold recoverable (PCR) are analyzed when the cold water temperature is approximately 2 °C and 4 °C, and the temperature difference ranges from 7.91 to 13.86 °C. The results demonstrate the excellent thermal performance of the novel tank under a large temperature difference. Compared with conventional temperature conditions, the stability of the outlet temperature under low-temperature conditions is better during the discharging process with the dimensionless temperature increasing by 10% at the end of the process. The full-cycle FOM increases significantly and the PCR decreases slightly with increasing temperature difference. When the FOM reaches its maximum of 93.2%, the PCR exceeds 91%. Therefore, this research work exhibits great application potential of this novel tank due to its ability to improve the thermal performance for a low aspect ratio tank, which provides a new direction for chilled water storage tank design.