Development and In-situ validation of a multi-zone demand-controlled ventilation strategy using a limited number of sensors

This paper presents a new strategy using a limited number of sensors for demand-controlled ventilation (DCV) of multi-zone office buildings. The conventional CO2-based demand-controlled ventilation strategy for multi-zone offices requires CO2 sensors and supply airflow meters being installed in all zones. However, in many practical cases, CO2 sensors might not be available or not necessary. To control the outdoor airflow based on actual occupancy variations in such cases, a DCV strategy with two implementing schemes is developed for different sensor availabilities. The first scheme is used for the situation when CO2 sensors in individual zones are not available but the airflow meters for individual zones are installed. The second scheme is used for the conditions when CO2 sensors and airflow meters in individual zones are not available. These two schemes use two different approaches to estimate the outdoor airflow fraction of the critical zone approximately. Both schemes only require the CO2 sensor in the main return air to dynamically detect the total occupancy number. The developed strategy is implemented and validated in a high-rise office building in Hong Kong. The site test results show that the strategy can achieve significant energy saving while maintaining acceptable IAQ in the situations where only limited sensors are available.