Energy consumption and indoor thermal environment of night mechanical ventilation in an office building in Harbin

Simulates indoor thermal environment and energy consumption in a typical office building with night mechanical ventilation and conventional air conditioning system in Harbin with EnergyPlus software. The results show that the periods when the maximum outdoor temperatures are higher than 24 ℃ are suitable for night ventilation, the corresponding length is about 60 days, taking 72.3 percent of the summer cooling season. When the air conditioning system is used in Harbin, this night ventilation system would offer a 1.15 kilowatthour per square metre per annum reduction in energy consumption for cooling and a 1.02 yuan per square metre per annum reduction in electricity cost. It can improve the indoor thermal comfort significantly in the air conditioning system operating stage during the daytime with night mechanical ventilation. The smaller the ratio of the room volume to its surface area is, the more effective the improvement of thermal comfort is. The higher the indoor design temperature is, the more quickly the indoor temperature drops. Therefore, the start time of the air conditioning system can be delayed. However, thd energy saved may not be more than that with the lower design temperature.