Evaluation of an optimal ventilation IAQ control strategy using control performance assessment and energy demand

• Finding an optimal IAQ control strategy of ventilation system in a subway station.
• Suggestion of CPA and cumulative healthy risk assessment index as an index.
• Evaluation of the four control structures by combining FB and FF controllers.
• Optimized S2 improved control performance by 70% with 36% energy saving.

The purpose of this study is to suggest an optimal indoor air quality (IAQ) strategy for ventilation systems based on the control performance assessment (CPA) technique, whereby the performance of a control system can be quantified by a performance index. Four control structures of the IAQ ventilation system are proposed using a combination of a proportional-integral-derivative (PID) controller which is employed to control the concentration of particulate matter (PM), and two feed-forward controllers which are used to reject the influence of the subway train schedule and the concentration of outdoor PM. The control structure with the highest control performance is selected as an optimal control structure and re-tuned by a line search algorithm. The control structure consisting of a PID controller and a feed-forward controller for rejecting the effect of the train schedule exhibited the best control performance as well as low energy demand and low healthy risk of IAQ. When compared to a conventional ventilation system, the optimized structure exhibited a 70% improvement in control performance and reduced almost healthy risk of IAQ while reducing energy demand by 36%.