Inkstone
    Mar
    14
    2018
    Mar
    14
    2018
    A giant tower is scrubbing the smog from China’s skies
    A giant tower is scrubbing the smog from China’s skies
    SCIENCE

    A giant tower is scrubbing the smog from China’s skies

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    by
    Stephen Chen
    Stephen Chen
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    The South by Southwest (SXSW) festival, a week-long deep-dive into cutting-edge film, music and tech, is still buzzing with excitement about the latest global innovations.

    We’re using the chance to explore China’s own innovation. In this installment in our series on how Chinese scientists could revolutionize global technology, we look at what has been dubbed the world’s biggest air purifier. 

    This 328-foot-tall tower in the northern Chinese city of Xian could be vital in the battle against the country’s notorious smog problem.

    Scientists from the Institute of Earth Environment at the Chinese Academy of Sciences started testing the tower earlier this year and have found it has generated a noticeable improvement in air quality over a 3.9 square mile area.

    The tower pictured under construction.
    The tower pictured under construction. Photo: Handout
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    Xian has an urban area of 934.6 square miles, so the tower is just a start. But on severely polluted days the tower was able to reduce smog to almost moderate levels. On average the amount of PM2.5 – the fine particles most harmful to health – fell by 15% during periods of heavy pollution.

    The tower uses greenhouses that cover an area about half the size of a football field around the base of the tower. They suck up polluted air, which is then heated using solar power and rises through multiple layers of cleaning filters.

    Like many Chinese cities, Xian suffers from heavy pollution in winter, as much of the city’s heating requires burning coal.

    “The tower has no peer in terms of size,” said Cao Junji, the project's lead. “The results are quite encouraging.”

    Visitors stroll along the ancient city walls of Xian. No, it’s not fog.
    Visitors stroll along the ancient city walls of Xian. No, it’s not fog. Photo: Xinhua/Liu Xiao

    A student studying environmental science at Shaanxi Normal University, a few hundred yards away from the tower, said the improvement was 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.”

    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 23-foot-tall tower produced about 282.5 cubic feet of clean air per second. But, somewhat counterproductively, it was powered by electricity, which is mostly generated by coal-fired power plants in China.

    Dutch artist Daan Roosegaarde’s Smog Free Tower in 798 Art Zone, Beijing.
    Dutch artist Daan Roosegaarde’s Smog Free Tower in 798 Art Zone, Beijing. Photo: Daan Roosegaarde/Derrick Wang

    Cao, however, said the tower in Xian required little power.

    Full results will be released sometime this month and, if the findings are positive, then the team is planning to build a much bigger tower – 1,640 feet high – that could be powerful enough to purify the air of a small city.

    But others are more skeptical.

    Ian Colbeck, a professor of biological sciences at the University of Essex in the UK, said the available data did not show that the smog tower was making much of a difference to air quality, estimating that only around 1% of the air within the touted 3.9 square mile area could theoretically be “cleaned.”

    For it to work, he explained, the tower would have to "clean" a significantly larger volume, and replace its filters often.

    “It's better to stop the emissions at source, rather than trying to remove them once emitted into the atmosphere,” Colbeck said.

    STEPHEN CHEN
    STEPHEN CHEN
    Stephen is a contributor to Inkstone. He covers science and its impact on society, as well as the environment, military, geopolitics and business for the South China Morning Post.

    STEPHEN CHEN
    STEPHEN CHEN
    Stephen is a contributor to Inkstone. He covers science and its impact on society, as well as the environment, military, geopolitics and business for the South China Morning Post.

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