Abstract
The effect of mechanical night ventilation on thermal comfort and electricity use for cooling of a typical historic office building in north-central Sweden was assessed. IDA-ICE simulation program was used to model the potential for improving thermal comfort and electricity savings by applying night ventilation cooling. Parametric study comprised different outdoor climates, flow rates, cooling machine’s coefficient of performance and ventilation units’ specific fan power values. Additionally, the effect of different door schemes (open or closed) on thermal comfort in offices was investigated. It was shown that night ventilation cannot meet the building’s total cooling demand and auxiliary active cooling is required, although the building is located in a cold climate. Night ventilation had the potential in decreasing the percentage of exceedance hours in offices by up to 33% and decreasing the total electricity use for cooling by up to 40%. More electricity is saved with higher night ventilation rates. There is, however, a maximum beneficial ventilation rate above which the increase in electricity use in fans outweighs the decrease in electricity use in cooling machine. It depends on thermal mass capacity of the building, cooling machine´s coefficient of performance, design ventilation rate, and available night ventilation cooling potential (ambient air temperature).
Highlights
The European Union (EU) has set an objective to be climate neutral by 2050
The time is during the period defined for Night ventilation (NV) schedule; The ventilation unit’s return air temperature is over 18 ◦ C; The ambient temperature is over 10 ◦ C; The ambient temperature is at least 2 ◦ C lower than the return air temperature
specific fan power (SFP) values for ventilation rates below the design flow rate were calculated based on data of part-load performance for VAV fan systems according to ASHRAE standard 90.1 [41]
Summary
The European Union (EU) has set an objective to be climate neutral by 2050. This implies that. Many parametric studies, using BES, investigated the influence of NV strategy on both improvement of thermal comfort and reduction of energy use for active cooling in office buildings. Some studies have shown the potential of NV in the form of determining the optimal NV flow rate over which further increase in ventilation rate, produces marginal improvements in thermal comfort in the building; dependent on the thermal mass capacity of the building [4,5,17] These studies, afterward, calculated the amount of saved energy for active cooling based on this maximum beneficial ventilation rate. Lain and Hensen [21] performed a parametric study on the optimization of mechanical NV system in an office building, including two NV rates and the mechanical cooling system’s coefficient of performance (COP) 2.5 They illustrated that due to the relatively high COP value, the electrical energy use in the fans can outweigh even the large cooling energy savings by NV. The effect of different door schemes (i.e., open doors or closed doors) on thermal comfort in the offices was investigated
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