Energy-efficient fresh air system with pressure-independent dampers for nearly zero energy buildings

Fresh air volume control is of great significance in reducing energy consumption in nearly zero energy buildings. Previous studies have shown that the operating fresh air volume often deviates significantly from the design value, resulting in unnecessary energy consumption. To overcome this problem, this study proposes an energy efficiency fresh air system for NEBs by using pressure-independent dampers to balance system resistance and control the operating fresh air volume accurately. A typical fresh air system used in a typical NZEB was tested both in laboratory and on site for a whole heating season. Based on the test data, the energy consumption model of the proposed fresh air system was established and validated. The energy performance of the proposed system was analyzed comprehensively. Results show that using the pressure-independent damper in the fresh air system to control the fresh air flow rate can significantly reduce the fresh air load by 39.2%, 49.4%, 52.3% and 45.5% in Harbin, Beijing, Shanghai and Guangzhou, respectively; The annual energy saving rates in these cities are approximately 29.3%, 28.7%, 27.0% and 19.1%, respectively. These energy saving rates are smaller than the corresponding fresh air load reductions due to the additional energy consumption caused by the pressure-independent damper; Furthermore, replacing the pressure-independent damper with an ideal variable speed ventilator for fresh air flow rate control can further increase the energy saving rate by 12%similar to 16%. This study identifies the energy saving potential of fresh air systems and contributes to achieving sustainable development in nearly zero energy buildings.