A passive airflow regulation system for controlling temperature of a heat-absorbing subassembly is disclosed. The passive airflow regulation system includes a duct configured to provide a conduit for an incident ambient airflow to the heat-absorbing subassembly. The duct is arranged proximate to the heat-absorbing subassembly. The airflow regulation system includes a valve configured to control passage of the incident ambient airflow through the duct. The airflow regulation system also includes an actuator employing a phase-change element configured to selectively store and release energy in response to changes in temperature and stress. The actuator is arranged at the heat-absorbing subassembly and configured to select a position for the valve between and inclusive of fully-opened and fully-closed in response to a temperature of the heat-absorbing subassembly. The airflow regulation system can be arranged on a vehicle having a vehicle body including a first body end configured to face the incident ambient airflow.