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Professors Claim Passive Cooling Breakthrough Via Plastic Film (sciencemag.org)
What if you could cool buildings without using electricity? charlesj68 brings word of "the development of a plastic film by two professors at the University of Colorado in Boulder that provides a passive cooling effect."
The film contains embedded glass beads that absorb and emit infrared in a wavelength that is not blocked by the atmosphere. Combining this with half-silvering to keep the sun from being the source of infrared absorption on the part of the beads, and you have a way of pumping heat at a claimed rate of 93 watts per square meter.
The film is cheap to produce -- about 50 cents per square meter -- and could create indoor temperatures of 68 degrees when it's 98.6 outside. "All the work is done by the huge temperature difference, about 290C, between the surface of the Earth and that of outer space," reports The Economist.
The film is cheap to produce -- about 50 cents per square meter -- and could create indoor temperatures of 68 degrees when it's 98.6 outside. "All the work is done by the huge temperature difference, about 290C, between the surface of the Earth and that of outer space," reports The Economist.
You non-RTFA infidel! The article states the temperatures as 20C and 37C respectively.
Ask me how the Heisenberg Principle may or may not have saved my life.
Not as hardcore as an active cooling by a gas dynamic laser.
Most notable about this material is that it does not do heat pumping, just tricks with reflectivity and selective absorbtion, and emission bands
"Passive cooling on the order of what this article talks about would seem to be too good to be true. If it is true these guys should be filthy rich soon."
Don't forget to sell your Air Conditioning stock.
Its interesting that they have made the film, yet have not demonstrated it in a practical application. That makes me skeptical as they are relying on performance claims when they shouldn't have to. Why could they not take the film and cover a small structure (like a shed), and simply tell us the resulting cooling effect? And maybe compare against a simple reflective coating
Yeah, but how many is that in Kelvin?
Some people encrypt by using rot-13 twice. I prefer the more secure method of using rot-1 a total of twenty six times.
It's called physics, even if you don't find it interesting.
1) Letting visible light through in principle lets the PV work while keeping it cool. The increase in output with lower temperatures is quite significant, thus the presence on the market of combined PV/Thermal panels for example. (And absorbing more of the visible light and removing the energy as electricity rather than letting it turn into heat would be good too, natch, and that one is being worked on.)
2) Outer space is at ~3K/-270C: having that as your cold sink *day and night* is really quite significant. What I cannot work out is if clouds are transparent at the same wavelengths, eg if this could be used to make the cold end of a Seebeck device even under cloudy skies: that would allow a small amount of power generation day and night also, if so.
This looks plausible to me and and an astonishingly good thing if it works even a 1/10th as well as the researchers hope.
Sometimes the science is good before the marketing people get to it.
Rgds
Damon
http://m.earth.org.uk/
It's called physics.
Outer space is on average at about 3K/-270C. So if you can freely radiate energy away to it from a surface then that surface can nominally get to, or close to, that temperature. Having that that as the cold end of a Carnot heat engine, such as a thermal electricity generation plant, would do amazing things for efficiency in principle. Never mind aircon and PV.
So it's not crap.
And you can experience a similar effect in the opposite direction standing some distance from a bonfire on a cold night: you can feel the heat on your face even while the air around you is a very different temperature to your skin and the bonfire.
Rgds
Damon
http://m.earth.org.uk/
I wouldn't sell it just yet. Even if this film works, it's probably only in clear conditions when the IR radiation can escape to outer space. On muggy cloudy or hazy days, I doubt it would work. On top of that, it would do nothing to lower the humidity in the building.
A plain mirror could do that. The idea here is that infrared emitted by warm objects is absorbed and re-emitted at frequencies the atmosphere is transparent to, thus the heat escapes to space rather than warming the air.
Yeah, but WHEN? When will we see this available for consumer use?
I see news stories every damn day about some amazing breakthrough in this field or that field, but fuck all if it ever seems to make it to market.
I must have seen 100 stories in the last few years about more efficient and less expensive solar cells, but where the fuck are they?
The same with medications and advances in medical technology....lots of news and hype and excitement but rarely does anything ever appear.
FFS, all I want is to be buried in a casket made of an advanced polymer plastic film that eliminates diabetes and has a 98% solar conversion efficiency rate, and that can autonomously pilot itself down I-5 during rush hour. Is that too fucking much to ask?? Oh, and the battery has to last for a full week without a charge.
Just cruising through this digital world at 33 1/3 rpm...
Mao's political method was to enter a village and kill every leader who didn't agree with him. Get a new set of leaders, kill every leader who didn't agree with him. Repeat until purified.
The words "nuance and subtlety" do not apply. His central committee was thugs and murderers like himself.
Just WTF are people being taught these days?
Contribute to civilization: ari.aynrand.org/donate
Outer space is at ~3K/-270C: having that as your cold sink *day and night* is really quite significant.
Radiative cooling doesn't work that way: all that matters is your temperature. You don't radiate more into a cold area than a hot (a hot area sends more thermal radiation to warm you up, but that's orthogonal). It would be different if the atmosphere reflected IR, but that's not the case.
Socialism: a lie told by totalitarians and believed by fools.
Unless you are furry.
Part of your air conditioner's load is removing heat that has been conducted inwards through roof and walls. Coat your house with this stuff and the heat flow will be outwards. Perhaps it won't be enough to remove the heat coming through windows and air leaks, and generated internally, but it should lessen your AC load substantially..
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It would be different if the atmosphere reflected IR, but that's not the case.
Not in the sense of a mirror, but yes, it does, nondirectionally. More importanty, it tends to radiate at frequencies not absorbed by the material.
Someone had to do it.
But, can it cool a Beowulf Cluster?
-Unresolved symbol? Byte me!
Just WTF are people being taught these days?
Apparently they're not taught the difference between a real comment and trolling
lucm, indeed.
in order to sink heat you must have something to heat, and vacuum just ain't that.
If you can get heat into radiative form (which this gadget can) and it doesn't get reflected back at you, effectively, it is sunk.
Second - I don't suppose there is some kind of magic involved in this discover, that magically allows IR radiation to bypass the several kilometers of atmosphere you have before outer space.
It's called an absorption spectrum. In this case, specifically it's called the Infrared Atmospheric Window.
Someone had to do it.
This sounds almost like Maxwell's Demon -- which makes me very skeptical.
The Web is packed with thousands of great inventions and solutions that you never will see.
Wrong. The Web is packed with conspiracy theorists who don't understand why some "great inventions" are not practical. We've heard this bullshit for decades about electric cars and it took a billionaire with balls of steel and no fear of bankruptcy to make it happen. And yet they're barely making a profit nowadays after years of losing money to the tune of 1 billion per year.
Get real. There's no mysterious stash of brilliant inventions that got "scrubbed" from the web by nefarious agents. There's tons of unrealistic, not cost-effective ideas and only one Elon Musk, that's the real problem.
lucm, indeed.
> Did you get your biofuel from you local landfill yet? No?? Why not? All it takes ...
> to convert almost anything in a landfill into biofuel, is a high pressure tank,
> heat and time. Because they've been doing it for almost 2 decades now
> in Canada. (It's been mostly scrubbed off of the Web.) Latin people laugh
> at you when you don't believe they can make gasoline out of tires.
Yes you can make biofuel. Yes it does work in Latin America, aka the tropics. Other areas of the planet have this thing called "winter". Biofuel congeals when temperatures drop near zero. Back in 2009 https://wattsupwiththat.com/20...
> "All schools in the Bloomington School District (Minnesota) will be closed today
> after state-required biodiesel fuel clogged in school buses Thursday morning and
> left dozens of students stranded in frigid weather, the district said late Thursday.
>
> Rick Kaufman, the district's spokesman, said elements in the biodiesel fuel that
> turn into a gel-like substance at temperatures below 10 degrees clogged
> about a dozen district buses Thursday morning. Some buses weren't able to
> operate at all and others experienced problems while picking up students, he said.
>
> We had students at bus stops longer than we think is acceptable, and
> that's too dangerous in these types of temperatures," Kaufman said."
Other school districts avoided these problems by either idling their buses all night long, or using heated parking garages. Not exactly "green solutions". And finally, the biodiesel stuff was forced down people's throats in Minnesota. If it's so cost effective and wonderful, why does it need to be mandatory? And the cold-weather problems are not exactly unkown. http://www.startribune.com/min... because "essential services" are exempt from the mandate.
> First, key industries have been permanently exempted from the requirement to use
> any biodiesel whatsoever. The state's nuclear power industry was given an indefinite
> exemption. A temporary exemption for railroads; taconite and copper mining;
> logging, and the U.S. Coast Guard was changed to a lifetime pass. Through
> such action, legislators acknowledged that biodiesel is not reliable enough
> to ensure that these vital industries would not suffer serious disruptions.
I'm not repeating myself
I'm an X window user; I'm an ex-Windows user
That's lacist!
I'm an American. I love this country and the freedoms that we used to have.
It doesn't work like that. Radiative heating/cooling works via exchange of IR. You're not just giving it up; everything you're radiating at is proportionally radiating back at you. So you cool the most when you're radiatively exchanging with something that's very cold. Aka, you want to be radiatively exchanging with the cosmic microwave background, not with low-altitude clouds. That's the whole point of radiating at low absorption frequencies in the atmosphere: so that you're exchanging with space, not with atmospheric air.
I'll never forget the last thing grandma said to me before she died: "What are you doing in here with that knife?!?"
Not in the sense of a mirror, but yes, it does, nondirectionally. More importanty, it tends to radiate at frequencies not absorbed by the material.
Look, "reflection" is a specific concept, OK? It's a different thing than absorption and emission. They are two different effects, which is why we use different words to describe them. There is some refraction by clouds, and I'm sure some trivial percentage is refracted multiple times to end up headed back towards the surface, but that's about it.
Why does the distinction matter? Actual reflection of IR nearly blocks radiative cooling (at some point the reflective surface, not being perfect, heats up and starts radiating). This is why a really good thermos needs a reflective layer in addition to a vacuum gap. If IR were being reflected close to the emitter, which it's not, changing the frequency to one not reflected would make a huge difference.
Absorption is very different. Sure, the atmosphere absorbs IR and becomes warmer as a result, but it's not like that happens meaningfully within a few yards of the ground! Changing the frequency of your thermal radiation a bit will not make a meaningful difference in cooling. OTOH, covering something sitting in the sun with a reflective surface makes a significant difference.
Socialism: a lie told by totalitarians and believed by fools.
Not so much. In fact, it is a bullshit lie. It is not providing cooling, as is claimed. It is preventing heat transfer. There is no cooling involved and this is bullshit.
How did you get a thermodynamics lab to fit under that bridge?
Changing the frequency of your thermal radiation a bit will not make a meaningful difference in cooling.
It is a bit backwards to phrase this as "beaming heat into cold space" rather than "reflecting most incoming ambiently-produced IR radiation while selectively emitting radiation in a same band we absorb" This doesn't seem to be the fault of journalists, it's phrased that way in the paper. This article avoids using that semantic.
Were they to allow the wavelengths re-emitted by the general environment outside, you'd get an offsetting absorptive heat gain. They could likely get the same effect at different wavelengths, but choosing this wavelength means basically no heat gain from atmospheric emission. There could even very well be a better choice of wavelength based on whatever materials the ground is made up of, but that could vary.
Someone had to do it.
No you couldn't embed them in glass, because the glass beads work by being resonate at a frequency that atmosphere is transparent to. The beads aren’t normal glass, they are transparent infra-red, most glass is rather opaque in infra-red. what you could do is apply it like a window tint, but I suspect it would have a lot of distortion and possibly an opalescent effect.
The film unsilvered is highly transparent to visible light, so the ideal application, would be to apply it to PV solar cells to help cool them and prolong their live span.
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