Wednesday, March 17, 2010

Jumbo Size Vacuum Cleaners to Purify Urban Air?

See the cartoon by Marc Roberts - "Waiting to Exhale" in response to our blog piece below (3rd, April, 2010) on installation of a giant vacuum cleaner in Delhi.


Recently, at the entrance of the Palika Bazaar in Connaught place, the Delhi officials unveiled a giant air purifier. The European manufacturer, System Life, and their Indian business counterparts claim that this is the next innovative approach to clean the air and it is here for the better health of Delhites. See Hindustan Times, and UK Telegraph.

For an ordinary person, who is breathing the polluted air at any of the junctions and along the major road corridors, while stuck in the congested traffic, this sounds like a miracle solution. The machine is here to suck bad air and spew out clean air, with a freshener.

Are the officials suggesting that it is OK to pollute, because we are testing an innovative vacuum cleaner to clean the air we breathe, instead of acting on the technical and policy options, which might even be cheaper and faster to implement?

Air pollution is rising problem in Delhi and the sources are many – inside and outside the city. Growing motorization, coupled with an absence of appropriate road traffic reduction strategy on major corridors, an ageing and ill-maintained public vehicle stock, a sizeable share of two-stroke engine technologies, absence of an efficient public transport system, and inadequate separation between working, living, and moving space, have all led to traffic congestion resulting in longer travel times, extra fuel consumption, discomfort to road users, degradation of the urban environment, and high-level of air pollution in Delhi.

The particulate matter with aerodynamic diameter less than 10 micron (PM10) (and the lesser sizes like PM2.5) is considered the most harmful and routinely average above 150 micro-gm/m3 during the day, when the national standard is 100 micro-gm/m3 and the international health standard is 50 micro-gm/m3 for PM10.

In Delhi, the largest gain in the air quality was observed at the peak of the CNG conversions of buses. And since, the air quality levels have declined gradually over the years, in the residential areas and along the major corridors. The slow moving traffic during rush-hours puts the environment and lives in high danger and consequently stretches the health facilities beyond their capacities. In 2009, the Central Pollution Control Board (CPCB) announced that Delhi is now the “Asthma Capital” of India.

The machine acts as a vacuum cleaner, with an air intake capacity of 10,000 cubic meters per hour and the manufacturer demonstrates that the machine is capable of trapping the harmful PM (for three size fractions) by approximately 70 percent of the air flow. The machine costs ~2.5 crores plus the maintenance.

10,000 cubic meters of air per hour..?

The energy budget needed to reach a significant level of clean air is huge and not realistic.

Air flow, even in study conditions, for a distance of 100m (the operating zone for the machine), a height of 10m (the air we breathe), and an average wind speed of 1 m/sec, translates to 100*10*1*3600= 3,600,000 cubic meters per hour !!

Of this, at a point, 10,000 cubic meters of air is purified per hour. Now, think of a city which is 30km x 30km, at least. How many of these do we need and how effective are they really going to be?

Is this a realistic solution or giving false hopes of doing something?

The air pollution studies in Delhi have shown that the road dust is a major culprit, due to active re-suspension of the dust along the roads. Most often, the dust along the major corridors is swept and piled up, which over the day, makes its way back on the road and adds to the re-suspension. Plus all the vehicular exhaust.

Why aren't the city officials responding by taking measures to reduce the dust? An immediate and cheap option is to cut the road dust. Instead of a vacuum cleaner, get some of the vacuum trucks with water sprinklers in the back to suck dust off the roads, sprinkle some water, so we reduce the re-suspension effects. A truck can cover as much as 40 km in two hours, especially in the morning hours, and might effectively reduce the exposure levels during the rush hour.

While this is an innovative and effective solution for indoor settings like tunnels and subway stations, I have my doubts for using a vacuum station in an outdoor setting like Delhi.

There is no silver bullet for improving air quality, which is a growing problem in a number of cities.

Mitigation is probably the best solution, if the goal is to reduce air pollution quickly and effectively. What Beijing officials did for Olympics was unorthodox, closing down industries and cutting down traffic for the two months, but the series of measures and the event itself gave a reason to think back and realize what is the footprint of the human activities (transport and industries) that we are experiencing in the form of air pollution and related health impacts. Same is true in case of Delhi and the coming commonwealth games.

We need to try everything from promoting the use of public transport, clearing the dust on the roads, changing fuel characteristics at the refineries, curbing garbage burning in the residential areas, and controlling emissions at the industrial stacks, before we can think of vacuum cleaners for outdoors !!

Also see


Sunita Purushottam said...

Sarath this was a good article. Must say you are a relentless crusader.

Suvrat Kher said...

a fancy piece of tech catches the attention of a higher up and it gets pushed as the solution.

you should expand your calculations to show how much it might cost the city to have a large scale implementation of this.

makepurple said...

Having air purifier, can prevent us from many illnesses.

Sarath Guttikunda said...

Dear Makepurple,

thank you for your comment. Yes, having a purifier helps in a indoor setting or in a subway tunnel, but does it make sense, technically and financially, to have in the middle of the road?

Parthaa Bosu said...

The basic principle and its cost are questionable. Further we cannot overlook the fact that in India the power source is not that cleaning, meaning that maximum power generation is thru' coal! So what is it, pullute more to arrest pollution!

Sarath Guttikunda said...

Dear Partha,

this is where we have to differentiate between the local and regional priorities.

1. Yes, we have to reduce the pollution at the local level, even more specifically, along the road corridors and residential areas, where people tend to spend more time and get exposed more often to the harmful levels of pollution. In an open environment like this, does it make sense to operate a vacuum cleaner to reduce pollution? Irrespective of the power source to run the equipment.

2. Irrespective of the where the power is coming from - as a local regulator, does it matter where the power is coming from? For example, Metro is considered a clean mode of transport when compared a number of cars or diesel buses on the road. It doesn't mean that the metro are not polluting. If one does a life cycle assessment based on the electricity used, yes, then metro also pollute; but are they polluting in the city. Point being, as far as the city limits are concerned, metro rail, irrespective of the power source, is a clean mode of transport.

3. Similarly, if there is a magical vacuum to suck all the dirt in the air and clear up the blue skies, then so be it. But, technically, this is not possible in an open environment. As I mentioned in the blog, in a closed environment like a tunnel or a building, having a fancy equipment like this makes sense, but not in the middle of the road, where everything is dynamic in nature.

4. We have to start differentiating between the local evaluations and the life cycle evaluations.

5. India's power source is still majority thermal and it is not going to change, at least not in the next 20-30 years. Question is, given this scenario and given that the power plants are inherently getting efficient and controlled, what are we going to do about controlling air pollution in the cities.

Vacuum cleaner is not an answer :-)

Vlad said...

A very interesting concept. But is it really possible to implement this in places that need it more. House Clearance Glasgow

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roger said...
This comment has been removed by a blog administrator.
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