Multi-objective optimization of a time-delay compensated ventilation control system in a subway facility – A harmony search strategy

Abstract Meeting the high current demand for public mobility requires massive transportation systems with their corresponding infrastructures. An example of this is the subway transportation system with underground public commuting space. However, indoor air quality (IAQ) management in this space is challenging due to these environments' hostile conditions with high ventilation energy demand. This study introduces an adaptive ventilation control system that dynamically regulates the setpoint of the coarse particulate matter (PM10) concentration considering the IAQ level and the ventilation energy consumption through a multi-objective harmony search (MOHS) strategy. Additionally, a time-delay term affects the IAQ model in the subway station. Therefore, a time-delay compensator (TDC), i.e., the Smith predictor (S–P), was introduced into the feedback loop to address this dead-time response. The proposed ventilation control system was compared with two other systems. This comparison is conducted under different outdoor air quality (OAQ) conditions, i.e., good, moderate, and unhealthy. The proposed ventilation control system (SP-VS) yielded an energy-saving potential in the range of 4%–13% under good OAQ conditions compared to the conventional ventilation system. In contrast, the health risk level for the unhealthy OAQ case decreased from an unhealthy to a moderate health risk level.