The air quality in Xi’an, in northwestern China’s Shaanxi Province, improved significantly after researchers initiated testing of a massive experimental tower, dubbed by its operators as the “World’s Biggest Air Purifier.”
The tower stands tall at 100 meters (328 feet) high, and covers an area of 10 square kilometers (3.86 square miles) in the city, according to South China Morning Post.
Cao Junji, head of research at the Institute of Earth Environment at the Chinese Academy of Sciences, which is conducting the test, noted that the tower has managed to produce more than 10 million cubic meters (353 million cubic feet) of clean air since its launch in 2015.
The construction of Xi’an’s smog tower finished last year at a developmental zone in Chang’an District. With the project, researchers aim to find a cost-effective way to get rid of the smog from the atmosphere.
Beijing had already developed its own large air filter — about 7 meters (23 feet) tall — which produces 8 cubic meters (282.5 cubic feet) of clean air per second. The smog tower, built by Dutch artist Daan Roosegaarde at 798, a creative park in Beijing, runs entirely on electricity mostly generated by coal-fired power plants.
The tower in Xi’an, however, does not require much power compared to the one in Beijing.
“It barely requires any power input throughout daylight hours. The idea has worked very well in the test run,” Cao said.
The system works through greenhouses around the base of the tower. The polluted air is sucked into the glasshouses, then heated up by solar energy. Hot air rises up through the tower, and passes through multiple layers of cleaning filters.
Cao and his team set up several pollution monitoring stations near the smog tower to test out the system. The tower helped reduce PM2.5 — fine particles considered to be the most harmful to health — by an average of 15% in heavy pollution.
“The tower has no peer in terms of size … the results are quite encouraging,” Cao said.
Xi’an reportedly has a tendency to experience heavy pollution during the winter season, which is caused by the city’s heating of burning coal. Luckily, the tower remains operational even in this weather condition as the coatings on the greenhouses enable the glass to absorb radiation from the sun more efficiently.
Cao said that these results are in the preliminary stage, but the researchers are planning to release more detailed data in March to show full scientific assessment of the Xi’an smog tower’s overall performance.
People within the radius of the smog tower have all expressed positive comments about the project, saying that they’ve felt the improvement in air quality.
“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. The air quality did improve. I have no doubt about that,” a student from Shaanxi Normal University, located a few hundred meters from the tower, told SCMP.
Those outside the radius have a different story to tell, however. A teacher at the Meilun Tiancheng Kindergarten, which is located at the edge of the 10-square-kilometer (3.86-square-mile) zone, told the publication that nothing much has changed in terms of air quality.
Fortunately, the tower in Xi’an is just the beginning of the bigger project that Cao and his colleagues initially planned. According to a patent filed in 2014, the full-sized tower would be about 500 meters (1,640 feet) high, with a diameter of 200 meters (656 feet). It could cover nearly 30 square kilometers (11.6 square miles), and would be powerful enough to actually purify the air of a small sized city.
Cao and his team hope to build a similar tower such as this one in other cities throughout China in the future.
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