Note4Students

From UPSC perspective, the following things are important :

Prelims level: Smog Tower

Mains level: Air quality issue in New Delhi

Ahead of its infamous smog season, Delhi has got a ‘smog tower’, a technological aid to help combat air pollution.

Smog towers are structures designed to work as large-scale air purifiers. They are fitted with multiple layers of air filters and fans at the base to suck the air.
After the polluted air enters the smog tower, it is purified by the multiple layers before being re-circulated into the atmosphere.

The structure is 24 m high, about as much as an 8-storey building — an 18-metre concrete tower, topped by a 6-metre-high canopy. At its base are 40 fans, 10 on each side.
Each fan can discharge 25 cubic metres per second of air, adding up to 1,000 cubic metres per second for the tower as a whole. Inside the tower in two layers are 5,000 filters.
The filters and fans have been imported from the United States.

The tower uses a ‘downdraft air cleaning system’ developed by the University of Minnesota.
Polluted air is sucked in at a height of 24 m, and filtered air is released at the bottom of the tower, at a height of about 10 m from the ground.
When the fans at the bottom of the tower operate, the negative pressure created sucks in air from the top.
The ‘macro’ layer in the filter traps particles of 10 microns and larger, while the ‘micro’ layer filters smaller particles of around 0.3 microns.
The downdraft method is different from the system used in China, where a tower uses an ‘updraft’ system — air is sucked in from near the ground, and is propelled upwards by heating and convection.
Filtered air is released at the top of the tower.

Computational fluid dynamics modelling suggests the tower could have an impact on the air quality up to 1 km from the tower.
The actual impact will also determine how the tower functions under different weather conditions, and how levels of PM2.5 vary with the flow of air.

Delhi’s new Smog Tower

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