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An experimental air purifier more than 100m tall has cut pollution levels in a Chinese city, offering the possibility of reducing smog across the country.
The tower, the world’s largest purifier, improved air quality in a 10 sq km area over the past few months, according to the scientist leading the project.
It was the brainchild of China’s most respected science institute, whose researchers hope the technology, once proved effective, can be used in hospitals, schools and residential areas.
The tower aims to remove tiny pollutants, the fine particles known as PM2.5, and substances such as nitrates and sulphur dioxide. It draws air through four inlets into a system of greenhouses built around the base, that cover an area of about half a football pitch. The air is heated by solar energy, passes through a series of filters as it rises through the tower and emerges cleaned.
“The tower has no peer in terms of size,” Cao Junji, a researcher at the Chinese Academy of Sciences, said. “The results are quite encouraging.”
China’s smog tower, which went into operation last year, is in the central city of Xi’an in Shaanxi province. Much of the city’s heating comes from coal and it experiences heavy pollution in winter.
Mr Cao said that the tower produces more than ten million cubic metres of clean air each day. On severely polluted days, the tower was able to reduce the smog to close to moderate levels, he told the South China Morning Post.
More than a dozen monitoring stations are testing the tower’s impact. The average reduction in pollutants has been 15 per cent.
The tower requires little power to run during daylight hours, said Mr Cao, even in winter because coatings on the greenhouses enabled the glass to absorb solar radiation efficiently.
Several Xi’an residents contacted by the newspaper said that they had noticed air improvements since the tower started working, although a kindergarten teacher on the edge of the tower’s coverage said that she had felt no change.
Mr Cao said a full assessment of the project’s performance would be released in March with data collected from the dozen or so monitoring stations in the area. If successful, Mr Cao plans a series of even bigger towers of up to 500m high, one of which could purify a medium-sized city.
Until these results, a seven-metre tower built by the Dutch artist Daan Roosegaarde in 2015 in Beijing was regarded as the biggest air filter. Roosegaarde’s contraption, nicknamed the giant vacuum cleaner, uses positive ionisation technology to clean as much as 30,000 cubic metres of air per hour and its workings have been scientifically validated, according to the project’s official page.
(THE TIMES)
