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New Spray-On Coating Can Make Buildings, Cars, and Even Spaceships Cooler (bgr.com)
Long-time Slashdot reader davidwr and Iwastheone both submitted this story about "a paint-like coating that facilitates what is known as 'passive daytime radiative cooling,' or PDRC for short...when a surface can efficiently radiate heat and reflect sunlight to a degree that it cools itself even if it's sitting in direct sunlight." BGR reports on research from the Columbia School of Engineering:
Their newly-invented coating has "nano-to-microscale air voids that acts as a spontaneous air cooler," which is a very technical and fancy way of saying that the coating is great at keeping itself cool all on its own. "The air voids in the porous polymer scatter and reflect sunlight, due to the difference in the refractive index between the air voids and the surrounding polymer," Columbia writes in a post. "The polymer turns white and thus avoids solar heating, while its intrinsic emittance causes it to efficiently lose heat to the sky."
It sounds great, but the best news is that it can be applied to just about anything, from cars to spaceships and even entire buildings. The team believes their invention would be an invaluable resource for developing countries in sweltering climates where air conditioning is impractical or unavailable.
It sounds great, but the best news is that it can be applied to just about anything, from cars to spaceships and even entire buildings. The team believes their invention would be an invaluable resource for developing countries in sweltering climates where air conditioning is impractical or unavailable.
FAKE NEWS! Retarded.
realized "cooler" was about temperature.
For example if someone is being a bit of a dick, you just spray some of this on them and they become cooler?
You'd be the life of the party.
My ism, it's full of beliefs.
Seriously, how much better is this than using plain old white paint?
I would think that this coating would be useful in the developed world where a coating like this would reduce air conditioning requirements for homes and buildings.
The biggest issue would be that the buildings/cars would become a lot more whiter and I suspect more blinding in direct sunlight.
Mimetics Inc. Twitter
I posted & now it's gone?
https://tech.slashdot.org/story/18/09/30/1122238/tim-berners-lee-announces-solid-an-open-source-project-which-would-aim-to-decentralize-the-web
Everyone already knows that if you paint flames on anything it instantly makes it look cooler.
Solid melted. Now it's called "Liquid" and thus must be revised.
Compressed Earth Blocks: Why and How, Here and There https://youtu.be/IuQB3x4ZNeA
"Tempers are wearing thin. Let's just hope some robot doesn't kill everybody." --Bender
Between this an solar freakin' roadways the world should just about be saved.
It's the best thing since spray-on shoes!
How well does this paint clump together? As a spray, it seems likely that some of the particles would linger in the air. Medical researchers are still trying to get a handle on the risks of nanoparticles to living beings -- we just aren't made to filter stuff at that level because its not common in the natural environment for there to be free-floating bits at the nanoscale. It might be safe, but we don't currently know. Here is one report from the UK government just listing the research unknowns about nanoparticle exposure. Before we start spraying whole buildings in stuff like this, we should know the environmental and health impacts. I hope the inventors of this stuff start working on those questions before they try to productize this.
This is a tricky point of physics which is seldom explained well, and I don't understand it much more than the basic idea. But in nearly everything emissivity at a given wavelength is the compliment (1-x) of the reflectance.
It's a frustrating idea because it says that while white can keep the sun off you (reflecting) it also doesn't radiate either keeping you hot.
Now the escape clause here is that if you are not as hot as the sun, then your black body emission is in the mid IR while the sun is peaked in the visible. Thus if you can make something white looking in the visible but black in the Mid IR it can beat the system and help cool by both reflection of the sun and thermal emission.
Now this device seems to be arguing for something different it sounds like they are saying they use a dark (emissive) material but then make it so granular and scattering that it looks white (which indeed is why clear crystals look white when you powderize them (e.g. sugar).
But my understanding of this, possibly wrong which is why I'm asking, is that it doesn't matter why something looks white to the emissivity/reflectance relation. If a nominally black material "looks" white to the eye then it's going to act identically to an object that is actually pigmented white. It doesn't matter if its refraction, reflection of pigment that causes it to be white. White is white.
THus the explanation seems like B.S. However it still might be working just fine for the old boting reason of being a mid IR black object. that just would not be news.
The reason I'm wobbly on this is when you think about absorbption down at the atomic transition scale then the whole emissivity, reflectance thing gets confusing. It becomes unclear how discrete spectral lines actually add up to that. It's much easier to treat the relation at the macroscopic black body level.
SO is it really possible for this nano scale voodoo to do something other than white paint does?
Some drink at the fountain of knowledge. Others just gargle.
The air conditioner in the master bedroom of my house in the Philippines runs constantly from mid-March to Mid-June. It's their version of summer. The sun heats up one side of the house and that's all it takes. I need this product there as soon as I can get it. Somehow, I think it will be years from now.
I see a black door and I want to paint it white.
This is just the usually white paint keeps it cool. They just use $10 adjectives and make up some fancy sounding nouns.
Here's what actually is useful, though not new, in their system.
1. They can take a black (emissive) material and make it white in the short wavelength band by foaming it at a certain length scale so it scatters a lot in the short wavelength range but looks homogenously dark in the long wavelength. This isn't a new idea but is a new material and manufacturing approach
2. using scattering rather than pigment means that it will be white everywhere since it's physics not chemical spectroscopy. Hence it's uniformly white. Pigments can age or have dark spectral regions making them less white.
That is exactly what you said! I used $5 adjectives and you used $1 ones. But we both just said the same thing as the article did.
However the reason we use paint isn't jest because it's white. We use paint because holds up to the UV and rain and bonds to the surface. Paint is basically titanium dioxide, glue, and some rubbery sealant. Those mechanical and spectral properties are what give it durability. Many polymers degrade when exposed to UV or acid rain.
Additionally when this stuff gets dirty it's no better than white paint! but since it's tectured it might not clean up as well as white paint. So it may be ruined by acidic soot found in cities
How long before those pores get clogged up ?
passphrase : monotony
I'd love to see what crap the HOA comes up with when I paint my house white.
I should use this sig to advertise my book ISBN-13 : 978-1501515132.
they tried cooling tall buildings by making them semi-reflective. Obviously, this was not thought thru well. I remember one skyscraper near I35 (which was practically already a death trap) that would blind you at certain times while driving. Like rush hour. Gawd only knows what it cost to fix these buildings.
I thought graffiti artists have been doing this for years. It doesn't take special paint just special skillz. Girls like guys with skillz!
... it is carcinogenic.
What the inventors don't want you to think about is that this is essentially a consumable product. Polymers de-polymerize and lose their beneficial properties over time, especially when exposed to solar radiation... which is the intended point of this stuff. It will have to be replaced repeatedly as it fails.
This solution to the problem is akin to Big Pharma's tactics: rather than develop one-time permanent solutions, they concoct band-aids that require a lifetime subscription to get any benefit.
Trumplestiltskin needs all the help he can get. Come to think of it I was told by my GF's 14 year old that while I wasn't terminal, like her mother, just because I could board or inline skate did not make me cool anymore :(
errr....umm...*whooosh* *whoosh* Is this thing on ?
Is there any way this technology could be integrated into clothing?
J
If you painted "The Fonz" with this paint, would he become even more cooler or would it be impossible for The Fonz to be any cooler than he already is? This question of course applies only to "pre-shark" Fonzie.
Can we have spray-on paint to make builders and cars warmer please?
Don't worry about spaceships, mine is at the right temperature already.
Since the claim is that it cools a surface to below ambient, I wonder if it could be used to passively extract useful heat energy from the environment, on the hot side of a stirling engine or a thermoelectric generator. Shouldn't be a thermodynamic lawbreaker, since it would essentially be only collecting ambient energy and passively radiating IR into space?