Study Of Night Ventilation Application In North Office Buildings

Night ventilation system is a passive cooling system. It uses cold outdoor air during the night to cool the building's thermal mass (building internal partitions and structure). The thermal mass functions as a heat sink during the day, absorbing the internal heat gains. Night ventilation can reduce the indoor air temperature and effectively delay the starting time of active cooling. Compared with conventional air-conditioning system, night ventilation system consumes less energy, require less maintenance, have lower first costs and operation costs, and are environmentally friendly. Therefore, in-depth study of night ventilation characteristics is of great significance.In this paper, the whole energy-consumption analysis software EnergyPlus is applied to simulate indoor thermal environment and energy consumption in office buildings with night ventilation in the representative north city–Harbin, Beijing and Shenyang. This paper analyses impact factors of night ventilation and sum up ventilation principles. Through simulation results, energy consumption and indoor thermal comfort is analyzed and night ventilation potential forecasts of other cities are assessed.The results show that: first, ventilation time, night outdoor temperature, air change rate and envelope have different degrees of impact on night ventilation. Longer ventilation time, lower outdoor temperature, greater numbers of air change rate have better ventilation effects. Heavyweight construction is slightly more suitable for night ventilation than lightweight construction. Second, based on the analysis of impact factors, energy consumption, active cooling delay time, different principles are summed up with different areas. Third, this paper analyses night ventilation's energy consumption and economy in Harbin, Beijing and Shenyang. It turns out that night ventilation greatly reduce cooling load, save energy consumption and has a certain degree of economic significance. Fourth, night ventilation can meet thermal comfort standards. In active cooling stage, indoor thermal environment of night ventilation is much better than conventional air-conditioning mode's. And rooms with smaller ratio of volume to area of envelope can improve thermal comfort in active cooling stage. Finally, potential application of using night ventilation in other areas is estimated. It shows that it is suitable to use night ventilation in Urumqi and Lanzhou, but not in Shanghai, Guangzhou and Kunming.