Outdoor thermal condition based-segmented intermittent demand-controlled ventilation for constant-air-volume system

Abstract

The outdoor air supply is mandatory for healthy built environments but consumes a large amount of building energy. The demand-controlled ventilation method adjusts the outdoor air supply for both indoor air quality and high energy efficiency. However, the conventional demand-controlled ventilation method does not apply to the constant-air-volume ventilation system. Since the constant-air-volume ventilation system is widely used in practice for outdoor air supply, this study proposes a novel demand-controlled ventilation method, i.e., the segmented intermittent demand-controlled ventilation, to improve the energy efficiency of the constant-air-volume ventilation system with indoor air quality. The proposed method intermittently supplies outdoor air to reduce the amount of outdoor air supply for energy saving of ventilation fan while satisfying indoor air quality. Moreover, the proposed method divides the working time into segments and adjusts the outdoor air supply of each segment according to the outdoor weather for cooling/heating energy saving. This study reveals the detailed mechanisms of energy saving of the proposed method and develops an optimization algorithm to maximize the energy saving of the proposed method with indoor air quality. The proposed method is tested for both cooling and heating scenarios in different climate zones. The results show that compared with the conventional methods and the existing intermittent demand-controlled ventilation, the proposed method achieves weekly energy savings of 18.0%–62.4% and 4.3%–6.8% respectively. The proposed method can contribute to the development of low-carbon and healthy built environments.