New Spray-On Coating Can Make Buildings, Cars, and Even Spaceships Cooler (bgr.com) 86
Long-time Slashdot reader davidwr and a reader 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.
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Tell me more about the vacuum of space, and how it prevents heat radiation.
Include, if you could, how your explanation applies to that small yellow thing in the sky that blinds me when I look at it.
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Actually, that's probably the best use of this kind of coating that I've seen mentioned in this discussion. It would mean not having to shield your radiators from sunlight. This is a good argument for white spaceships.
Does it work on people? (Score:5, Funny)
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.
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For example if someone is being a bit of a dick, you just spray some of this on them and they become cooler?
They have that already, although it's only really suitable for extreme cases. It's called pepper spray.
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It's called pepper spray.
lols!
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Ha! That headline was just begging for a comment like yours. I know some people who'd have to be dipped in it.
It's called "white paint" (Score:2)
Re:It's called "white paint" (Score:5, Informative)
Seriously, how much better is this than using plain old white paint?
It's better in that a white surface doesn't radiate much, so even though it reflects most of the energy that strikes it, it still heats up. It's worse in every other way. These nanoscale structures are always fragile and turn into nanoscale dust, and which don't break down easily (because of what they're made of) which makes them persist in the environment. Auto paint is expected to last for decades in harsh conditions, but they gave that as an example anyway.
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reciprocity, emissivity reflectance (Score:3)
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 th
Re:reciprocity, emissivity reflectance (Score:5, Informative)
I've been reading about this daytime cooling through infra-red emissivity to space stuff for a while now. The biggest benefit isn't the color (or the reflective value), but that it will absorb heat from whatever the source and radiate that energy away in the mid-IR band that will allow it to leave Earth's atmosphere without being re-absorbed by anything nearby. That makes it effectively a way to remove heat from the surface of the earth by emitting that energy into space.... heat that would otherwise be trapped by our atmosphere's greenhouse effect.
This is the first time I've seen this expressed as a coating for everyday consumer items rather than as a heat sink layer added to an exterior A/C unit or a potential roofing material, though.
My understanding is that generally these coatings are white in the visible spectrum to reflect sunlight, but emit light in the mid-IR range. There's a startup company for using this to improve efficiency in A/C units I read a while back, and they tested the material in the hot sun on a roof in India -- you could put your hand on it after it had been baking in the sun, and it was cool to the touch. That's relative term, though. I don't recall the actual temperature readings.
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In thermal properties it's not different from most other white materials or white paint: they absorb and emit well in the thermal infrared range (5 to 15 micrometers) and reflect well in the visible and near-IR (400 nm to 1500 nm). Even plain white paper would do the job. The effect of this fancy coating is possibly a marginal improvement in the 1500-2500 nm range, but sunlight does not carry that much energy in that range.
The opposite is much harder: absorb sunlight but don't emit or absorb thermal infrare
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Seriously, if you read TFA, you'll find out that:
1. It's more reflective than plain white paint
2. It emits IR which can actually bring the surface temperature BELOW ambient.
Re: It's called "white paint" (Score:2)
How does it get below ambient? Can I power a steaming engine with that?
Re: It's called "white paint" (Score:2)
Maybe.
It emits IR
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In essence, the temperature of an object depends on the heat transfer between itself and its surroundings. This transfer can be of conduction, convection, or radiation. For objects that are not fluids, that is limited to conduction and radiation. Now, a
Useful in the Developed World (Score:2)
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.
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This.
Replacing original windows (which were *all* tenant damaged anyway) with doublepane and non-metal frames made a *huge* difference in the desert summer . . . and when winter rolled around, my ife started claling them "you stupid windows" because the house didn't warm as fast in the morning . . . ..if it were trying to radiate away heat, it would have taken evne longer . . .
hawk
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and when winter rolled around, my ife started claling them "you stupid windows" because the house didn't warm as fast in the morning
There are two separate considerations when selecting windows, R-rating and E-rating. Multiple panes raise the R-rating. Coatings lower the E-rating. The E-rating measures how much non-visible light passes through the glass. Passive solar designs use glass with a high R-rating and a low E-rating, meaning that they don't let as much heat energy escape by conduction, but they let solar energy enter via radiation. And they use overhangs or awnings to prevent that from happening in the season when the sun is ove
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Sounds like a crude, reverse-engineered Starlite.. White paint's got nothing on this seemingly revolutionary product... what a history of what never became.
Note: I just became aware of this chemical marvel via a recent /. post remembering its history. Here's the BBC video that's referenced in the synopsis.
https://www.bbc.com/reel/video... [bbc.com]
or use better building materials (Score:1)
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The part you missed about the story of the three little piggies; their economy wouldn't support a brick house for all three. It isn't a story about smarts, it is a story about the difference in outcomes according to resource access.
The thing about "compressed earth blocks" is, they're not bricks. As you noticed when talking about clay. Instead, they're something that can be made from a much wider range of input materials. That means that production can be scaled without boosting the price by competing for r
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Earth bags can use an even wider range of soils, and use minimal materials. They do require that you come up with some burlap, and ideally barbed wire as well (to run between the courses) but they don't require compaction, just bag-filling.
alrighty (Score:2)
Any concerns about nanoscale particles? (Score:3)
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Spraying it on buildings would be out of the question until those questions can be answered, inside paint booths where air is run through filters and respirators are required would be the only place it could be used.
I Need this Yesterday (Score:1)
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While I can not give you a solution to your problem with paint, I do have a fun solution which is working with sunlight heat reduction. I use a thin cheesecloth over my plants in my garden with. it's slightly cooler by 4C to 7C. I've tried it for myself and it's very nice to read in this type of shade. just an idea, that's all nothing tech about his.
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https://www.amazon.com/Tobacco... [amazon.com]
this is the concept you need, 180ft x 36 inch,
find it at Divisoria Market in Manila
hope you get lucky
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They only claim to do it better, they are not the first. Skycool in Australia has been selling their wavelength selective reflecting/absorbing paint for over a decade now. Unfortunately they don't seem to want to get into the consumer or even small contractor supply chain, or at least they don't hint at it on their latest website. On their old website they had a link to a contractor, but that one is dead now.
https://www.skycool.com.au/ [skycool.com.au]
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HOAs! (Score:3)
I'd love to see what crap the HOA comes up with when I paint my house white.
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I have. I'm on the board (to keep a crazy rule nazi off the board).
We're good with solar panels. That's a fed thing as are the antenna rules.
We're good with painting the roof - They're flat and not visible from the street
Painting the front - there's no local ordinance for that.
Back inthe '70's or so... (Score:1)
And... (Score:1)
Keyword: POLYMER (Score:2)
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.
Can we quickly paint our president ? (Score:2)
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 :(
Make ME cooler (Score:2)