Smog tower

Smog towers or smog free towers are structures designed as large-scale air purifiers to reduce air pollution particles (smog), the prototype for which was built in 2017 by Dutch artist Daan Roosegaarde, in Beijing. This approach to the problem of urban air pollution involves air filtration, and removal of suspended mechanical particulates such as soot, and requires energy or power. Another approach is to remove urban air pollution by a chimney effect in a tall stack, or updraft tower, which may be either filtered or simply released at altitude as with a solar updraft tower, and which may not require operating energy beyond what may be produced by the updraft.

Examples

Roosegaarde's 2017 prototype was later installed in Tianjin, China and Kraków, Poland .^[1] In 2018, a 100-metre (330 ft) tower has been built in Xi'an, Shaanxi to tackle the city's pollution.^[2] It is under testing by researchers at the Institute of Earth Environment of the Chinese Academy of Sciences.^[3]

In Delhi, India Kurin Systems is developing a 12-metre (40 ft) tall smog tower, called the "Kurin City Cleaner".^[4] It is claimed the tower will filter air for up to 75,000 people within a 3-kilometre (1.9 mi) radius.^[5] The Kurin City cleaner would be the strongest air purification tower, cleaning more than 32 million cubic metres of air every day.^[6] According to The Times, environmentalists "decried" the Delhi project on the grounds that "given the city's size and the scale of its pollution, 2.5 million smog towers would be needed to clean its air".^[7]

In Xian, central China, an experimental demonstration urban updraft tower is cleaning the air in a Chinese city with little external energy input.^[8][9] A 60-metre urban chimney with surrounding solar collector has significantly reduced urban air pollution. This demonstration project was led by Cao Jun Ji, a chemist at the Chinese Academy of Sciences' Key Laboratory of Aerosol Chemistry and Physics.^[10] This work has since been published on, with performance data and modelling.^[11][12]

Criticisms

Some air pollution experts view smog filtration tower projects with scepticism. For example, Alastair Lewis, Professor of Atmospheric Chemistry at the University of York, Science Director at the National Centre for Atmospheric Science, and chair of the Air Quality Expert Group, has argued that static air cleaners, like the prototypes in Beijing and Delhi, cannot process enough city air, quickly enough, to make a meaningful difference to urban pollution. Instead, Lewis argues that "it is far, far easier to come up with technologies and schemes that stop harmful emissions at source, rather than to try to capture the resulting pollution once it's free and in the air".^[13] Sunil Dahiya from India's Centre for Research on Energy and Clean Air has commented that "Installing smog towers has never been, and will never be a solution", noting that the Delhi tower would be powered by (mostly) coal-fired electricity, "so we will only be adding to pollution elsewhere in the country".^[14]

References

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