Abstract: An energy storage system includes at least one battery pack and a thermal management system. The battery pack includes a cooling plate and a battery cell. The cooling plate comes in contact with the battery cell to transfer heat energy. The thermal management system includes a control unit, a compressor, a heat exchanger, and at least one first control valve. The control unit is configured to: when a battery cell temperature of the battery pack is greater than or equal to a first temperature threshold, control the compressor to compress a thermal management medium, so that a thermal management medium flows into the heat exchanger; and control opening of the first control valve to control the thermal management medium to flow into the cooling plate in the battery pack to exchange heat with the battery cell, to decrease the battery cell temperature.