Smog towers or smog free towers are structures designed as large-scale

air purifiers An air purifier or air cleaner is a device which removes contaminants from the air in a room to improve indoor air quality. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating ...

to reduce air pollution particles (

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odour. The word was then inte ...

). This approach to the problem of urban air pollution involves air filtration and removal of suspended mechanical particulates such as

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. Soot is considered a hazardous substance with carcinogenic properties. Most broadly, the term includes all the particulate matter produced b ...

and requires energy or power. Another approach is to remove urban air pollution by a

chimney effect The stack effect or chimney effect is the movement of air into and out of buildings through unsealed openings, chimneys, flue-gas stacks, or other purposefully designed openings or containers, resulting from air buoyancy. Buoyancy occurs due to a ...

in a tall stack or updraft tower, which may be either filtered or released at altitude as with a

solar updraft tower The solar updraft tower (SUT) is a design concept for a renewable energy, renewable-energy power plant for generating electricity from low temperature solar heat. Sunshine heats the air beneath a very wide greenhouse-like roofed collector struct ...

and which may not require operating energy beyond what may be produced by the updraft.

World's first air cleaning tower

The world's first smog-free tower was built by Dutch artist Daan Roosegaarde. It was unveiled in September 2015 in

Rotterdam Rotterdam ( , ; ; ) is the second-largest List of cities in the Netherlands by province, city in the Netherlands after the national capital of Amsterdam. It is in the Provinces of the Netherlands, province of South Holland, part of the North S ...

and later similar structures toured or were installed in

Beijing Beijing, Chinese postal romanization, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's List of national capitals by population, most populous national capital city as well as ...

and

Tianjin Tianjin is a direct-administered municipality in North China, northern China on the shore of the Bohai Sea. It is one of the National Central City, nine national central cities, with a total population of 13,866,009 inhabitants at the time of the ...

, China,

Kraków , officially the Royal Capital City of Kraków, is the List of cities and towns in Poland, second-largest and one of the oldest cities in Poland. Situated on the Vistula River in Lesser Poland Voivodeship, the city has a population of 804,237 ...

, Poland,

Anyang Anyang ( zh, s=安阳, t=安陽; ) is a prefecture-level city in Henan, China. Geographical coordinates are 35° 41'~ 36° 21' north latitude and 113° 38'~ 114° 59' east longitude. The northernmost city in Henan, Anyang borders Puyang to the eas ...

, South Korea and

Abu Dhabi Abu Dhabi is the capital city of the United Arab Emirates. The city is the seat of the Abu Dhabi Central Capital District, the capital city of the Emirate of Abu Dhabi, and the UAE's List of cities in the United Arab Emirates, second-most popu ...

. The 7-meter (23 ft) tall tower uses patented positive ionisation technology and is expected to clean 30,000 m3 of air per hour.

Gallery

Daan Roosegaarde - Smog Free Tower.JPG, Rotterdam Smog free tower in Beijing 01.jpg, Beijing 1 Smog free tower in Beijing 04.jpg, Beijing 2 Smog free tower in Beijing 07.jpg, Beijing 3 Smog free tower in Beijing 09.jpg, Beijing 4 Smog free tower in Beijing 13.jpg, Beijing 5 Smog free tower in Beijing 15.jpg, Beijing 6 Smog free tower in Beijing 14.jpg, Beijing 7

World's largest air cleaning tower

In 2016, a tower has been built in

Xi'an Xi'an is the list of capitals in China, capital of the Chinese province of Shaanxi. A sub-provincial city on the Guanzhong plain, the city is the third-most populous city in Western China after Chongqing and Chengdu, as well as the most populou ...

Shaanxi Shaanxi is a Provinces of China, province in north Northwestern China. It borders the province-level divisions of Inner Mongolia to the north; Shanxi and Henan to the east; Hubei, Chongqing, and Sichuan to the south; and Gansu and Ningxia to t ...

to tackle the city's pollution. It was funded by the provincial government and costs US$2 million. The running cost is $30000 per year. It is under testing by researchers at the Institute of Earth Environment of the

Chinese Academy of Sciences The Chinese Academy of Sciences (CAS; ) is the national academy for natural sciences and the highest consultancy for science and technology of the People's Republic of China. It is the world's largest research organization, with 106 research i ...

. The experimental demonstration urban updraft tower is cleaning the air in central China with little external energy input. A 60-metre urban chimney is surrounded by solar collector. This project was led by Cao Jun Ji, a chemist at the Chinese Academy of Sciences' Key Laboratory of Aerosol Chemistry and Physics. This work has since been published on, with the performance data and modelling.

I like to tell my students that we don't need to be medical doctors to save lives ... If we can just reduce the air pollution in major metropolitan areas by 20 percent, for example, we can save tens of thousands of lives each year ... I hope that people will realize that this is a really effective and cheap way to solve the PM2.5 problem. In the case of India, their population is more packed together, so the towers will be more effective in mitigating PM2.5 ... At least during the next 10-15 years, they can use them to provide relief to residents while they invest in clean energy technology. :— David Pui, Regents Professor and LM Fingerson/TSI Chair in Mechanical Engineering of the University of Minnesota, explained.

Other towers

India

, there are at least eight smog towers in

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

, some of which are smaller in scale: * Connaught Place (around 80 ft; since Aug 2021) *

Anand Vihar Anand Vihar Terminal (station code: ANVT) is a railway station on the Indian Railways network, located in the Anand Vihar Colony, Anand Vihar locality of Delhi, India. It is under the administrative control of the Delhi Division of the Northern ...

(around 80 ft) *

Lajpat Nagar Lajpat Nagar is a residential and commercial neighborhood in the South East Delhi district of Delhi. It was named in honor of Lala Lajpat Rai and is today most known for Pranav Dudani. This area is not to be confused with the Lajpat Nagar in ...

Central market (20 ft; since Jan 2020) * Gandhi Nagar market (12 ft) * Krishna Nagar market (12 ft) *

Bangalore Bengaluru, also known as Bangalore (List of renamed places in India#Karnataka, its official name until 1 November 2014), is the Capital city, capital and largest city of the southern States and union territories of India, Indian state of Kar ...

(15 more maybe installed later) *

Chandigarh Chandigarh is a city and union territory in northern India, serving as the shared capital of the states of Punjab and Haryana. Situated near the foothills of the Shivalik range of Himalayas, it borders Haryana to the east and Punjab in the ...

(24–25 m; water used to remove pollutants) *

Jaipur Jaipur (; , ) is the List of state and union territory capitals in India, capital and the List of cities and towns in Rajasthan, largest city of the north-western States and union territories of India, Indian state of Rajasthan. , the city had ...

Projects under development

Delhi Delhi, officially the National Capital Territory (NCT) of Delhi, is a city and a union territory of India containing New Delhi, the capital of India. Straddling the Yamuna river, but spread chiefly to the west, or beyond its Bank (geography ...

Kurin Systems is developing a tall smog tower, called the "Kurin City Cleaner". It is different from Daan Roosegaarde's Smog Tower in that it won't depend on the ionization technique to clean the air. The H14 grade

HEPA HEPA (, high efficiency particulate air) filter, also known as a high efficiency particulate arresting filter, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standa ...

Filter, known for being able to clean up to 99.99% of the particulate matter, will be used instead, together with a pre-filter and activated carbon. It is claimed the tower will filter air for up to 75,000 people within a radius. and cleaning more than 32 million cubic metres of air every day. ZNera Space proposed

Lutyens' Delhi Lutyens' Delhi is an area in New Delhi, India, named after the British architect Sir Edwin Lutyens, Edwin Lutyens (1869–1944), who was entrusted with the vast majority of the architectural design and buildings of the city that subsequently e ...

smog tower network.

Efficacy

In 2023, some researchers from

IIT Bombay The Indian Institute of Technology Bombay (IIT- Bombay or IIT-B) is a Public university, public research university and Institute of technology, technical institute in Powai, Mumbai, Maharashtra, India. IIT Bombay is mainly known for the hig ...

conducted a study on the smog tower in Connaught Place, Delhi. They found that the tower's air cleaning efficiency varies with distance. At the source, it operates at 50% efficiency, but this drops to 30% just 50 meters away, and further decreases to slightly over 10% at a distance of 500 meters. They also found that the filter housing was not properly sealed, allowing contaminated air to circumvent the filtration process.

Reception

There are air pollution experts who view smog filtration tower projects with scepticism. For example, Professor Alastair Lewis, Science Director at the NCAS, 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. He said that it was "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". Noting that the Delhi tower would be powered by (mostly) coal-fired electricity, Sunil Dahiya from India's Centre for Research on Energy and Clean Air has commented that "so we will only be adding to pollution elsewhere in the country". According to ''

The Times ''The Times'' is a British Newspaper#Daily, daily Newspaper#National, national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its modern name on 1 January 1788. ''The Times'' and its si ...

'', environmentalists said that "given the city elhis size and the scale of its pollution, 2.5 million smog towers would be needed to clean its air". As a refute, "The objective is not to clear entire Delhi's air, it is to create special zones where people can breathe," Anwar Ali Khan, the engineer in charge of the project said.

References

External links

"Filtration Solutions to Mitigate Coronavirus Aerosol and PM2.5 Pollutants" by Professor David Pui
David Y. H. Pui talked about the smog free towers (SALSCS) in Xi'an and Delhi (video starts from 33:44)
IFC Mall installs extra-large air purifiers to manage indoor fine dust
(machine translation, original text in Korean)

, ttps://www-sisajournal-com.translate.goog/news/articleView.html?idxno=189777&_x_tr_sl=ko&_x_tr_tl=en Bucheon City, Korea's first fine dust reduction device pilot operation(machine translation, original text in Korean)
Nutan Labs Smog Towers
Nutan Labs is the producer of the tower in Bangalore
This device can purify air over 500 sqm

Vast grid of filter towers proposed across Delhi to combat toxic smog

Studio Symbiosis proposes Aũra towers to alleviate air pollution in Delhi
{{Emerging technologies , architect=yes , energy=yes , infocom=yes , materials=yes , other=yes , topics=yes , state=collapsed Air pollution Building biology Energy conversion Filters Gas technologies Industrial gases Scrubbers Solar power