Energy-efficient control strategy for air conditioning and mechanical ventilation system based on occupant distribution —— A case study on stratum ventilation

Existing operation methods of air conditioning and mechanical ventilation system ignore actual occupant distribution, resulting in energy waste due to overcooling and overventilation. To create an acceptable indoor environment while reducing energy consumption of operation, occupant-centric control (OCC) strategy has been proposed and developed. In this study, the proposed OCC strategy adjusts on/off of air supply vents and sub-zone air supply parameters according to sub-zone occupancy, involving two sub-zone air supply volume allocation methods, so as to prioritize thermal comfort and air quality in local occupied zone. Computational fluid dynamics was employed to evaluate the OCC strategy's performance in the case of applying stratum ventilation. The results show that the predicted mean vote at 0.6 m height is kept at 0.29–0.53, and the CO2 concentration at 1.1 m is controlled below 1100 ppm, which can achieve energy savings of 18–51 % (compared to Baseline 1) and 4–16 % (compared to Baseline 2). Moreover, the larger the difference in the number of occupants between sub-zones, the more energy savings the OCC strategy can achieve. It is suggested that sub-zone air supply volume should be allocated according to sub-zone cooling load and the outdoor air ratio in critical sub-zone should be employed to compensate for total outdoor air volume. This study provides an approach to combine the OCC strategy with non-uniform air distribution, offering insights into the balance of energy efficiency and occupied environmental comfort in system operation.