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A
100-metre high air purification tower in Xian in Shaanxi province has helped
reduce smog levels in the city, preliminary results suggest. Standing between
high-rises, the giant air purifier is capable of cleaning between 5 million and
18 million cubic meters of air each day, depending on the weather, season, and
level of pollution, according to South China Morning Post
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An experimental tower over 100 metres (328 feet)
high in northern China – dubbed the world’s biggest air purifier by its
operators – has brought a noticeable improvement in air quality, according to
the scientist leading the project, as authorities seek ways to tackle the
nation’s chronic smog problem.
The tower has been built in Xian in Shaanxi
province and is undergoing testing by researchers at the Institute of Earth
Environment at the Chinese Academy of Sciences.
The head of the research, Cao Junji, said
improvements in air quality had been observed over an area of 10 square
kilometres (3.86 square miles) in the city over the past few months and the
tower has managed to produce more than 10 million cubic metres (353 million
cubic feet) of clean air a day since its launch. Cao added that on severely
polluted days the tower was able to reduce smog close to moderate levels.
The system works through greenhouses covering
about half the size of a soccer field around the base of the tower. Polluted air is sucked into the glasshouses and
heated up by solar energy. The hot air then rises through the tower and passes
through multiple layers of cleaning filters.
“The tower has no peer in terms of size … the
results are quite encouraging,” said Cao.
Xian can experience heavy pollution in winter,
with much of the city’s heating relying on coal. The tower’s operators say, however, that the
system still works in the cold months as coatings on the greenhouses enable the
glass to absorb solar radiation at a much higher efficiency. Cao’s team set up more than a dozen pollution
monitoring stations in the area to test the tower’s impact.
The average reduction in PM2.5 – the fine particles
in smog deemed most harmful to health – fell 15% during heavy pollution.
Cao said the results were preliminary because the
experiment is still ongoing. The team plans to release more detailed data in
March with a full scientific assessment of the facility’s overall performance.
The Xian smog tower project was launched by the
academy in 2015 and construction was completed last year at a development zone
in the Chang’an district. The purpose of the project was to find an effective,
low cost method to artificially remove pollutants from the atmosphere. The cost
of the project was not disclosed.
What was previously thought to be the largest
smog tower in China was built last year by Dutch artist Daan Roosegaarde at
798, a creative park in Beijing.
The seven-metre (23-feet) tall tower produced
about eight cubic metres (282.5 cubic feet) of clean air per second. It was
entirely powered by electricity, most of which is generated by coal-fired power
plants in China.
Cao, however, said their tower in Xian required
little power to run. “It barely requires any power input throughout
daylight hours. The idea has worked very well in the test run,” he said.
Several people in Xian told the South China
Morning Post they had noticed the difference since the tower started
operating. A manager at a restaurant about 1km (0.62 miles)
northwest of the facility said she had noticed an improvement in air quality
this winter, although she was previously unaware of the purpose of the tower.
“I do feel better,” she said.
A student studying environmental science at
Shaanxi Normal University, also a few hundred metres from the tower, said the
improvement was quite noticeable. “I can’t help looking at the tower each time I
pass. It’s very tall, very eye-catching, but it’s also very quiet. I can’t hear
any wind going in or out,” she said. “The air quality did improve. I have no
doubt about that.”
However, a teacher at the Meilun Tiancheng
Kindergarten on the edge of the 10-square-kilometre (3.86-square-mile) zone
said she had felt no change. “It’s just as bad as elsewhere,” she said.
The experimental facility in Xian is a
scaled-down version of a much bigger smog tower that Cao and his colleagues
hope to build in other cities in China in the future. A full-sized tower would reach 500 metres (1,640
feet) high with a diameter of 200 metres (656 feet), according to a patent
application they filed in 2014. The
size of the greenhouses could cover nearly 30 square kilometres (11.6 square
miles) and the plant would be powerful enough to purify the air for a small
sized city.
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Here’s How
It Works: ØPolluted air is sucked up into greenhouses surrounding the
base of the tower; ØSolar power is used to heat the air; ØAs the hot air rises up through the tower, it’s cleaned by
multiple layers of filters; ØThe cleaner air exits through the top of the tower
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NEWS POST: China Fights
Big Smog With Big Air Purifier
China has a found a novel way to tackle its
massive air pollution problem: Putting up a giant air purifier the size of an
industrial smokestack in the middle of a smog-plagued city. Instead of pumping out billows of black smoke
like the chimneys rising from factories in the northern province of Shaanxi,
the 60-meter (197-foot) tall structure on the outskirts of the regional capital
Xian blasts clean air.
Standing between high-rises, the device is
capable of cleaning between five million and 18 million cubic meters of air
each day, depending on the weather, season, and level of pollution, according
to a report by the Chinese website Thecover.cn.
The tower can reduce the density of PM 2.5 -- the
tiny airborne particles considered most harmful to health -- by between 10 and
19 percent in a 10 square kilometer (3.9 square mile) area, the website said.
PM 2.5 can play a role in heart disease, stroke,
and lung ailments such as emphysema and cancer.
For now, the facility -- which was built in June
2016 -- is just an experiment. But its designers hope to build similar towers
across the city. Cao Junji, an environmental protection expert at
the Chinese Academy of Sciences, told reporters that it would take about 100
towers to cover the city of 1,000 square kilometres (385 square miles). A lot of people have questioned the device's
effectiveness, he said.
"I questioned it myself. But when we
finished, the results were quite good. They met our expectations."
China's government declared "war" on
pollution in 2014. Pollution is so bad in many regions that people
often wear masks on the street and buy expensive air purifiers for their homes. This past winter, China cut production for many
steel smelters, mills and factories.
The environment ministry imposed tough
anti-pollution targets on 28 cities around Beijing, with at least three million
homes expected to switch from coal to gas or electric heating.
China's air quality improved in 2017, with the
average level of PM 2.5 particles falling by 6.5% in 338 cities, according to
environmental authorities.
A University of Chicago study found last year
that air pollution in northern China had cut life expectancy by three years
compared with the south of the country. But a new study by the university in March found that China had made so much progress against smog that life expectancy could rise by more than two years.
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Giant
Air Purifier - The experimental facility in Xian is a scaled-down version of a
much bigger smog tower that Cao and his colleagues hope to build in other cities
in China in the future. A full-sized tower would reach 500 metres (1,640 feet)
high with a diameter of 200 metres (656 feet), according to a patent
application they filed in 2014. The size of the greenhouses could cover nearly
30 square kilometres (11.6 square miles) and the plant would be powerful enough
to purify the air for a small sized city.
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