Optimal night mechanical Ventilation control strategy in office buildings

Overheating in buildings during summertime, especially in office buildings is emerging as a challenge. Night mechanical ventilation (NMV) seems to be an energy-efficient technique by inducing the cold ambient air with a fan to cool the exposed building thermal mass and save air-conditioner energy for the following day. However, as sufficient cooling energy should be stored in thermal mass at night, the minimum indoor air temperature setpoint is relatively low, which may cause an overcooling penalty. Moreover, the NMV energy consumption may outweigh the energy saved for the air-conditioner at next daytime. Therefore, a multi-objective optimization was conducted to explore the optimal NMV control strategy to improve the building energy performance and indoor thermal comfort concurrently, based on a typical office building with three thermal mass levels in three climate regions. The final optimal NMV control strategies under different scenarios are presented in this study. The results show that the total cooling energy consumption of the final optimal NMV control strategies reduces 0%-8.6%, while the Predicted Percentage of Dissatisfied (PPD) during occupied hours decreases 0%-59.4%, compared to the base NMV control strategy in different scenarios. The benefit of the night cooling control strategy optimization is obvious in cold and medium climate region.