An energy storage system for an aircraft includes an enclosure having at least one vent hole, a plurality of energy storage devices arranged in the enclosure, and a ventilation system. The ventilation system includes an electrical circuit having at least one conductor arranged across the plurality of energy storage devices, a power source electrically coupled to and powering the electrical circuit, and a thermal vent mechanism positioned adjacent to the vent hole. During normal operation, the electrical circuit is open, and the thermal vent mechanism covers the vent hole. During a thermal event, the thermal event causes the electrical circuit to close such that the power source activates the thermal vent mechanism to expose the at least one vent hole to vent fumes outside of the aircraft.