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Smog-Sucking Electrostatic Vacuum Cleaners May Scrub Polluted Air

Residents of Beijing may enjoy pockets of fresh air, thanks to giant devices that remove particulates out of the city’s filthy sky
electrostatic air cleaner


An electrostatic air cleaner for Beijing might look like this rendering.
Credit: Courtesy of ENS

The murky brown smoke that hangs over Beijing and other industrial cities has long presented a health challenge to China. Unwilling to shut the factories and coal-burning plants that cause pollution, authorities instead are seeking novel solutions. Proposals have included seeding clouds to make rain to wash particulates out of the sky and equipping bicycles with pedal-powered generators that pump fresh air into riders’ helmets. The latest idea comes from Dutch artist Daan Roosegaarde, who hopes to create bubbles of clean air in various pockets around the Beijing.

Roosegaarde’s positive–ionization “vacuum cleaner” uses high-voltage, low-amp electricity to create an electrostatic field. Particles flowing across the field—enclosed in a box—become positively charged and attach themselves to a grounded electrode, which need to be scraped clean periodically. (Roosegaarde plans to turn the stuff into “diamond” rings, with a cubic-centimeter stone representing a cubic kilometer of smog.)

The system was actually invented by Delft University of Technology researcher Bob Ursem, who came up with the idea of ionizing smog particles after watching tiny bits of salt, dust and organic matter flow off the Atlantic Ocean onto a Dutch beach. “They floated into the dunes toward some bushes,” Ursem says, “and there was a lift effect, carrying them above the bushes.” The particles, negatively charged from friction, were avoiding contact with negatively charged foliage. “They floated above the bushes, indicating that the electrical force is greater than the gravity force,” Ursem says.

He replicated the phenomenon using dust in his lab, and he devised a way of reversing the charge on the particles using the electrostatic field. Under lab conditions, he says, his invention doesn't even require a ventilation system to draw air across the coils of electrified copper wire. The force of positively charged particles attaching themselves to a ground makes room for other particles to follow, soon creating an “ionic wind,” Ursem says.

But in reality, the Beijing air cleaner would require fans, say officials the research and development firm Environmental Nano Solutions (ENS) Europe, which bought the concept from Delft University and is developing it for commercial marketing. And it would not—as portrayed in Roosegaarde’s animated depiction of the device in action—produce an actual patch of blue sky above.

Roosegaarde, who uses technology to make big artistic statements about the environment, came up with the idea of using it to tackle the smog problem in Beijing, and he pitched it to then-Mayor Guo Jinlong last year. After a March trade meeting with Xi Jinping, China’s president, and two subsequent meetings with Beijing authorities—who have budgeted $2.4 billion to address the smog problem in various ways—Roosegaarde and ENS have agreed to install one of their smog-busting machines in a municipal park there sometime in the next year.

The outward appearance of the device is flexible, says Martin Pau, ENS’s business manager. Plans for the Beijing device center on a large octagonal structure eight meters tall with intake vents at the top and exhaust vents in the middle, out of which will flow smog-free air. The steel structure will weigh about nine metric tons. To demonstrate the absence of smog in the freshair zone, lasers will shoot out beams, which will be invisible in a particle-free environment. ENS Europe’s smog buster will clean a dome-shaped area 30 meters in diameter to a height of about five meters. The whole thing, Pau says, will “resemble a medieval Chinese palace.”

Demonstrations using prototype smog-collectors in a parking garage, a large pig barn and a highway tunnel have proved the machines’ ability to clear out up to 99 percent of particles as big as 15 micrometers and as small as 10 nanometers, Pau says. This range includes the particles—from 2.5 to 10 micrometers—that the World Health Organization deems as having the greatest potential for causing human health problems.

The ENS technology may sound similar to home ionizing devices, such as Sharper Image’s Ionic Breeze, which are marketed as air-cleansing machines. The Ionic Breeze has been roundly criticized by Consumer Reports and others not only for its ineffectiveness but also for its tendency to emit ozone, which harms the lungs. But that is a totally different situation, Roosegaarde and his technical advisers say. The trick is to create only positively charged ions—not negative ions, which latch onto oxygen molecules to form ozone.

ENS wants to persuade Chinese officials eventually to install their air-cleansing devices on the sides of Beijing buildings, thereby creating pockets of smog-free air around the city. The device may not be the permanent solution to Beijing’s smog problem, Roosegaarde notes. “But it’s an interesting way of using technology—not just in a purely scientific way but also creating an experience to engage people.”

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