Metro AC set to go green with new tech
Times of India | 17 September 2025Contractors have been appointed for the Rs 500 crore project, which includes Rs 150 crore to replace 30 out of 46 water-cooled chillers with air-cooled ones and Rs 350 crore designated for modernising tunnel ventilation system.
"The transition from water-cooling chillers to air-cooling ones will reduce carbon footprint," a senior official said. The AC units will maintain a subsoil temperature of 28 degrees Celsius, facilitating survival of thousands of microbes.
Metro operations generate heat in the tunnels, and a temperature rise could threaten microbes essential to ecological balance.
Regarding the tunnel ventilation system revamp, the official said, "The non-AC rakes that ran through our underground tunnels have been replaced with AC ones. Accordingly, the system is being upgraded, so that passengers continue to get cool air after the train pulls in. The stations will be cooler with over-the-track exhaust.
The fans will start revolving automatically if there is the slightest deviation in the standard subsoil temperature (28 degrees).
A linear heat detector system will be installed across the tunnel to measure temperature. Sensors will gauge the CO2 concentration to help control fresh air's entry to the station. The advanced smoke emission feature will have fans, acting as exhausts as well as fans, to release smoke in right direction in case of fire, also providing oxygen to passengers during evacuation."
"Physical work can only be done in winter, after commercial hours. It will take three years to complete the upgrade, if we try replacing ACs in five stations at a time," an engineer said. A maximum 5% incentive is being offered for faster execution. "Tunnel temperatures can be monitored from Metro Bhavan," he added. The electrical panel of European standards will protect equipment in case of an earthquake.
