The world’s biggest air purifier has been constructed in the city of Xian in Shaanxi province, which is located in the northern part of the country. Standing 100 meters high, the tower uses heat from the sun to create an upward flow of air which passes through multiple filters inside. Cao Junji, the scientist in charge of the project, says the tower has made the air within 10 kilometers of the tower noticeably cleaner.
The tower has processed more than 10 million cubic meters of air every day since it began operating a few months ago. Data collected at a dozen test sites confirm that the concentration of fine particulates has dropped by 15% since the tower went into service. The effectiveness of the tower is the subject of ongoing research by the Institute of Earth Environment at the Chinese Academy of Sciences. “The tower has no peer in terms of size … the results are quite encouraging,” Cao tells the South China Morning Post.
The tower is surrounded by a collection of greenhouses. Polluted air is sucked into them and heated by the sun before being ducted into the tower and through the filters inside. The purified air then exits at the top of the tower. “It barely requires any power input throughout daylight hours. The idea has worked very well in the test run,” Cao reports. A special coating on the glass increases the ability of the greenhouses to absorb solar energy in the winter.
A student at Shaanxi Normal University told the press, “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.”
Cao and his colleagues have big plans for the future. They want to build a tower 500 meters tall and 200 meters in diameter in several Chinese cities, according to a patent application filed in 2014. The greenhouses needed to support such projects would cover an area of nearly 12 square miles. The fact that these sorts of air purifying towers operate with little need for electrical power is a big factor in their favor as China struggles to separate itself from the pollution caused by decades of making electricity in coal-fired generating stations.
Hat tip: Leif Hansen