A novel real-time method for HVAC system operation to improve indoor environmental quality in meeting rooms

For indoor environmental quality (IEQ), previous studies only focused on one-sided aspect (e.g. monitoring, diagnostic, or intervention), and have not fully considered excessive pollutants and dew condensation in meeting rooms. Based on a real-time sensor network, this study newly implemented a three-phase cyclic process (i.e. monitoring-diagnostic-intervention process), with which a novel real-time method for HVAC system operation was developed to improve IEQ in meeting rooms. In particular, this study conducted two kinds of analyses and controls: (i) basic analysis and control for excessive pollutants by utilizing temperature and CO2 concentration; and (ii) advanced analysis and control for dew condensation on the diffuser of HVAC system by utilizing temperature, humidity, and CO2 concentration. The main findings were summarized as follows. For the "basic analysis", the CO2 concentration was estimated to exceed 1000 ppm at 14.8% and 31.7% in two meeting rooms. To avoid it, a real-time "basic control" strategy was developed: if the CO2 concentration would exceed 1000 ppm, the ventilation volume of the outdoor air could increase in real time. For the "advanced analysis", dew condensation on the diffuser was estimated to happen at 40.7% and 82.6% in two meeting rooms. To avoid it, a real-time "advanced control" strategy was developed: if the estimated supply air temperature would be lower than the calculated dew-point temperature, the supply-air temperature and ventilation volume of HVAC system could increase. The novel real-time method can be easily applied to HVAC system operation in existing buildings where events are hard to be predicted and recognized.