Performance investigation of outdoor air supply and indoor environment related to energy consumption in two subway stations

On-site measurements of the outdoor air supply and indoor environment in the public area (hall and platform) in two subway stations have been conducted in cooling season in this study. The result revealed that the outdoor air intake through entrances was enormous and played an important role in outdoor air supply. Influencing factors have been discussed and negative effects of mechanical outdoor air supply and train interval are revealed. The total outdoor air involved in by both infiltration and mechanical ventilation was far greater than the demand of occupants in public area under the normal condition, with indoor CO2 concentration only 399∼670 ppm. Return air alone (RAA) condition for ventilation with no mechanical outdoor air supply was then proposed, utilizing the air infiltration through entrances to meet outdoor air demand and reduce the cooling load in public area. Under the proposed condition, similar indoor thermal performance could be realized, and enough outdoor air could be supplied through entrances even for expected maximum passengers. Electricity consumption of VAC systems reduced by 10%∼20% compared with the normal operation condition in cooling season.