On the other hand, I wonder if anyone's ever built a 100m placebo before. It could be a really interesting university study on the placebo effect in disguise.
Let's do the math.
Guidelines state that the limit on PM2.5 particulates is approximately 10 micrograms per cubic meter for an annual average. Xian, where the tower was installed, is currently (http://aqicn.org/city/xian/) under 231 ug/m^3 of pollution. The tower is supposed to process 10 million cubic meters of air per day.
10^7 m^3 x 231 x 10^-6 g/m^3 x 10^-3 g/kg x 0.15 = 231 x 0.15 x 10^-2 =>
Let's also check the amount of air it should be processing. It's about 100 meters tall, and intended to cover 10 square kilometers. We'll conservatively assume that this volume represents the total quantity of air it needs to process. Ihe volume is:
10 km^2 x 10^3 m/km x 10^3 m/km x 10 ^ 2 m = 10^8 m^3
The math still seems low. Micrograms per cubic meter are hard to intuit.
There's the issue that it's probably removing nearly all of the particulates from the air it actually processes, say over 90%, which works out to 2.1 kg. It doesn't reduce the PM2.5 level in the area by 90%, but only by 15%, because it's only able to process some 16% of the air in its area during whatever the relevant time interval is, which seems like a good match to your 10%-per-day.
However, you got the volume of that area wrong: it's 10⁹ m³, not 10⁸ m³. That suggests that the natural lifetime of PM2.5 particulates is closer to a week than a day.
As for jhugg's question about how the filters are cleaned, a common way to remove particulates from flue gas or indoor spaces is using electrostatic precipitators, which are flat plates at a high voltage. The voltage sticks the particulates to the plates, and when the coating is thick enough, you close the valves to stop the gas flow and vibrate the plates to unstick the dust, and it falls out the bottom of the filter into a bucket (or, say, a truck). Other systems clean the plates with water (either spray or immersion) and possibly soap or lye.
That's what I get for interweaving a mantissa of 10 with scientific notation! Too late to edit now, but people should see this comment thread.
Three are alternative chemical processes to clean up such filters.
The microgram is a very small unit :) I mean, a gram is already pretty dinky, a millionth of it is even tinier! The whole point of these particles is that they're miniscule and can pass through tissue other particles can't, so maybe it's not so surprising that it's not a massive amount when you pile them up.
As for the volume of air, I'm most curious where the 15% measurement was taken and how consistent it was. How far from the tower? How many different places were measured? How many days are in the sample? What's the P-Value?
But still, thanks. Makes this interesting to think about.
I agree, this is very surprising. Before I saw LeifCarrotson's calculation, I would have thought "tons" was the right unit as well. There's so much polluted air, you'd think that it would add up to some significant amount of matter, but apparently not.
So it's still a lot of pollution, just much less actual mass than I would have guessed.
EDIT: In 2016, the United States burned roughly 728 million tons of coal, enough to fill a typical railroad car every 4 seconds
See the protests that erupt over mobile(Cell) phone towers. People claiming towers that weren't even on made them sick etc.
"Facebook is generous by storing your posts and friend lists on their own servers."
For a project this big, they should be able to quantify the results instead of just relying on what people say about the air :/
EDIT: I'm a dummy, although the article leaves with an anecdotal, there are some nuggets of stats "The average reduction in PM2.5 – the fine particles in smog deemed most harmful to health – fell 15 per cent 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."
Perhaps this will help:
...especially if my uncle manufactures air filter membranes and needs to get rid of some extra inventory
That’s what it is in China, with the added benefit of it actually supporting their local and hindering foreign businesses.
In a lot of areas it’s us in the west who are stuck behind a hopelessly inefficient bureaucracy, but on the upside, you’re less likely to drop through a poorly constructed escalator or have your local lake filled with industrial waste (well, unless you’re American I guess).
Taihu lake, near Suzhou, is practically radioactive. Fish in pretty much any freshwater within the entire country is toxic. I lived in China for 3 years or so and as soon as my son was born, we got the hell out -- it's a fun place, but no "modern, advanced" civilization operates like China. It's a country of mostly uneducated, superstitious peasants who suddenly got a lot of money and are kept in line with the threat of "re-education" or death. Even an artist has to fear for his life. http://aiweiwei.com
Then there's Lui Xiaobo.
Remember, this "modern, advanced" civilization still has Traditional Chinese Medicine as a "thing." It's a complete fraud with zero scientific basis: https://sciencebasedmedicine.org/retconning-traditional-chin...
This "modern, advanced" civilization is responsible for massive worldwide poaching to satisfy demand for quack TCM remedies: https://www.forbes.com/sites/jamesconca/2014/08/08/extinctio...
Really, powdered rhino horn? That's has the chemical composition of human fingernails -- and works just as "effectively."
They still do "postpartum confinement" http://edition.cnn.com/2015/08/11/china/chinese-postpartum-c... -- based on pretty much nothing but old wives tales and dangerous superstition.
Then there's the atrocious human rights record: https://www.hrw.org/world-report/2017/country-chapters/china...
I actually like China -- but the CCP isn't running a "modern, advanced civilization." They're the Beverly Hillbillies.
And a short time ago Americans were electro-shocking homosexuals to try and make them straight.
> Remember, this "modern, advanced" civilization still has Traditional Chinese Medicine as a "thing." It's a complete fraud with zero scientific basis: https://sciencebasedmedicine.org/retconning-traditional-chin....
America has chiropractors covered under insurance, people who believe in homeopathy, and a growing culture of vaccine denial.
No culture is perfect. Not too long ago we had horribly polluted waters, and in a lot of places we still do. Have you seen the impact of pollution from pig farms?
I'm not trying to play what-about-ism here, I am just saying that "modern, advanced civilizations" do all the things you listed.
The Chinese government is capable of undertaking massive infrastructure projects, and they do an incredible job of picking industries for government protectionism, allowing for growth of local talent. Multiple areas of technology and advanced automation are both areas where China has invested heavily in education and building a huge local talent pool. Pulling off multi-decade economic growth plans is impressive, they plotted a path from basic industry all the way to an advanced technology sector, and then executed on that plan.
That more than qualifies them as an advanced modern society.
Haha you're funny... It's us in the West stuck with bureaucracy. China's growth is unprecedented, with a labor force that's becoming more educated and has always been very hungry for work (no beer or foosball needed). We're finally starting to see engineers and scientists trained here going back after they graduate. For a startup, China potentially has all the following advantages:
- Lower operating costs
- Less regulations
- Bigger market
Those are pretty huge.
Of course there's the big authoritarian elephant in the room, but in practice this is less detrimental to most startups than one would think.
Despite that the HN consensus saying otherwise - I'll say yes, China is innovating just fine. Just a few days back, I got downvoted for stating that DJI was forcing competitors to exit the drone market by out-innovating them.
> If yes, how come in such a regime?
Perhaps because innovation and governance model aren't as coupled as some would assume/like?
More brains, more dreams, more ideas.
This FastCompany article from 2013 (https://www.fastcompany.com/2682151/5-imaginative-buildings-...) had some additional concepts that could be added.
Have they tried to filter directly the air at the source of pollution? For instance, placing filters on the coal heating facilities. It should be more efficient, as you wouldn't release as many particles in the air in the first place.
If I understand correctly this "air purifier" is just shooting polluted air up, bringing cleaner air from above.
That sounds like a very short term solution, but it's interesting
>"The hot air then rises through the tower and passes through multiple layers of cleaning filters."
Meaning you just have to clean the filters