The paint reflects 98.1% of solar radiation while also emitting infrared heat. Because the paint absorbs less heat from the sun than it emits, a surface coated with this paint is cooled below the surrounding temperature without consuming power.
Using this new paint to cover a roof area of about 1,000 square feet could result in a cooling power of 10 kilowatts.
Doyle Rice
September 17, 2021
Scientists created the world’s whitest paint. It could eliminate the need for air conditioning.
[Of course it will make the building cooler in the winter as well.
Still, I love living in the future.—Joe]
My spidey-sense tells me that the physics of this doesn’t hold up, for several reasons. Emission and absorption go together; a body can’t emit if it doesn’t also absorb. The other problem, of course, is that radiation is not the only heat transfer mechanism, and in fact it isn’t the major one. Conduction and especially convection are the others. Heat flow is from higher to lower temperature; if a body is cooler than its surroundings the heat flow will be into the body, not out of it.
Pkoning, I hear what you are saying. What I think is happening, at a physical level and the short blurb says/hints at this, is that the paint is absorbing heat from the surface it is on (conduction) and then radiating that heat. Thus pulling heat from the building.
So now we have the situation where the sun is not “cooling” the building, it just isn’t heating the building. And because of the ability of the paint to radiate heat efficiently and absorb it efficiently(?) we end up with the situation where it actual cools.
My issue with this as a magic solution is, what happens when it gets dirty? How often do you have to clean it? And how long does it last when it has to be cleaned?
Yup…that was my first reaction: What happens when it gets dirty? How hard is it to clean? How often will it need to be repainted?
Also, don’t forget the big one…how much is it going to cost?
The quote is, I think, a dumbed-down version for the general public.
Certainly emissivity can be wavelength dependent, so having a very low emissivity at the solar spectrum peak (at the Earth’s surface), while a higher emissivity at longer wavelengths, would let such a coating reflect the majority of the incoming light while allowing better “pass-through” of heat coming as longer wavelengths (IR) or conduction from the other side.
Beyond that I’d need to think about it some more … it’s been a long time since I played in this area of physics.
Re the heating question, 1000 sq ft is around 93 square meters. With an average solar flux of around 1.4 kW/m^2, reflecting 98% of the light rather than 90% would lower the heat load by ~10 kW.
Of course, what happens to the performance when the coating gets dirty…?
ETA: seems several of us are thinking on similar lines. 🙂
To the cleaning question: what can and cannot be used to clean it? And cleaning aside, how’s it perform over time just from exposure to (for instance) UV? Something like this would be nice for the high desert, say, much of New Mexico and Arizona; but the UV is pretty intense.
Now I need coffee.
Here’s a link to the journal paper.
https://pubs.acs.org/doi/10.1021/acsami.1c02368
Looks like it’s not open access, however.
https://sci-hub.st/https://doi.org/10.1021/acsami.1c02368
To describe this as cooling is pretty deceptive. If it is 100F outside, it won’t be cool in your house.
Two reasons: 1) the radiative power is on the wrong side of your insulation, 2) the far IR emission will be largely absorbed in the air around your house, creating a heat bubble.
That said painting the planet with high reflectivity paint would cool the world by raising the visible light albedo. Which is what clouds already do.
I’m betting that here in Florida, where it is 100 degrees with a dewpoint of 78, this paint won’t do shit.
Oh, winter is simple – that’s when you repaint with vantablack.
And once enough seasons and repaints go by, you can start selling Fordite tchotchkes.
The whole problem of heating and cooling stems from economics. And the way one builds one’s home, for where one lives.
Fancy paints are are nice. And might be a nice upgrade.( Aside from the problems already mentioned by several commenters.) Same as windows. Double thermal pane, with the right glaze, for how the window is positioned, will work wonders on a home.
All that being said. There’s just no replacement for mass. Mass reacts slower to the externals ones trying to mitigate.
The problem is mass in construction cost more than people want, or can spend.
If we as a people would could get passed the profit/fear complex that’s so much a part of our lives.
We could build better, open up our energy sector. (Quit fearing were going to run out of something that’s impossible to run out of.) And start making a more durable paint. Which keeps us from having to repaint every 10 years. Or replace your roof every 15.
For heating and cooling. One can’t get passed mass.( Unless you want to live in a vacuum.)
Or have walls / roof with internal vacuum chambers.
I see reporter ignorance here. It will reduce your heat load, but no way it passively cools unless the exterior air temp is lower than the interior temp.
Agreed.
“The paint reflects 98.1% of solar radiation…”
What percentage of solar radiation is reflected by the mirrored glass common in Texas office buildings?
As long as there are people inside the building it will gain heat; humans = 160 BTU/HR per, even LED lights generate some waste heat, and for goodness’ sake, don’t turn your computer on, use an electric vacuum cleaner, or run an elevator motor.
Random thought: The Left would like it if there were zero humans on the planet because that “will save Gaia” (interesting, though, that they’re never among the humans whom they say need to disappear…); were that to be suddenly accomplished, what’s the BTU per pound per hour rate for decomposition of high fat biological material?
My father came from Missouri where he was the son of a farmer/carpenter (once the planting is in, it’s all fix, fix, fix, or work for others to bring in the cash without interest). There was a thing in the old days called Hotbeds. They were essentially ditches dug and partially filled with horse manure and soil for the plants that couldn’t take a winter. The horse manure produced heat as it decomposed and kept the plants warm or warmer than the surrounding land. Somewhere there is likely a table or formula that could calculate just that heat emission.
So, does that mean that Leftists believe that they aren’t actually humans?
Because that’s what it sounds like from the above.
If they are not humans, and we are, then what are they? Isn’t this a very dangerous line of thought for all concerned? I don’t like the implications of any of this.
Leftists believe that they are gods. They bend reality to their whim.
This isn’t that new. And the claim on A/C is for sure overblown.
In my experience with this stuff, it won’t get *as* hot as something painted with conventional pigments. But it will still get plenty hot inside.
Depends on the application, but most likely you are talking 10-20 degrees cooler inside.
It’ll cut the air conditioning bill significantly but I wouldn’t expect miracles.
I should also point out that barium sulphate has been used in the industry since forever as an extender for titanium dioxide (normal white pigment).
It has very little opacity to begin with.
Add into that the fact that they are making the particles finer, and it will have even less opacity. This will also increase the oil absorption, which will make it difficult to load up a paint with enough pigment to make it useful.
In my expert opinion, this article is highly misleading and should be discounted without further proof.
This relates directly to my line of work.
What’s the cost and how long does it last? Ya’ gotta beat my air conditioning cost and monthly bill to be worthwhile.
this all sounds great on paper and the green weenies are probably having little orgasms all over themselves because evil air conditioners will go away but all the white paint in the world won’t stop the humidity from kicking your ass in the south…these people are fucking morons…
If you don’t like this idea, you might prefer a cold fusion system to power your bunker. Just contact Pons and Fleischmann. Maybe they’d sell you their plans for $24.99 and even throw in a free, secret decoder ring.
Of course if they didn’t make fantastic claims they wouldn’t have a shot at the lucrative world-wide climate-scam subsidies. By that reasoning then, the release of fantastic claims (passive cooling paint) to the Ignoratti (the rulers of ignorance) would become the norm, being as its now incentivized.
Call me in 20 years and we’ll see if this ever panned out and became a viable consumer product. Also, yes; how about a mirror? Let’s reflect our solar heat over to the neighbors and let them deal with it.
Hey, I came up with a revolutionary new idea; trees. They provide shade, evaporative cooling, and oxygen, and they’re beautiful, and they automatically drop their leaves in winter so you can get more sun, and then you can pelletize the leaves and branch trimmings and use them for fuel. Some trees even provide food. Can I get my government grant to study the feasibility of trees? Where’s my start-up capital?
Lyle,
I think this is more about what happens when researchers find something cool, which goes through the university press office and dumbed down, together with an attempt by someone (who has never held a real job in their life) to translate it into real world terms/implications.
My academic publication record barely exists, but much of my work since leaving academia has actually been sold, and the odds are very high that you’ve seen the downstream results somewhere.
I don’t think it’s their fault exactly, they don’t know, they don’t know that they don’t know, and they probably don’t know where to start looking.
I only learned anything that was actually useful for anything after getting a job in industry. It’s a big jump for STEM people, I honestly have no idea how humanities people ever amount to anything.
“I only learned anything that was actually useful for anything after getting a job in industry.”
This.
Retired now, but for years it was fun watching brand-new engineering grads get introduced to the Real World where the textbook-and-lecture stuff had developed teeth.
May have been fun for you, but those of us who had to deal with the stupidity they brought to work found it very frustrating. My experience was that positions for those newbies should have been as an intern, as in no way did they actually add value to the company.
One I had to work with cost the company millions, and that started due to some dept idiot deciding that the FNG should be the person to evaluate his own design vs mine. They eventually ended up tossing his and resurrecting mine, but the damage to the market was extensive, and contributed to the eventual sale to their biggest competitor.
The only ones I saw hit the road running were gearheads in their private lives. Hotrods and motorcycles seemed to add some bedrock to their thinking.
Thanks Will. You should try building some of their ignorant ideas out of concrete.
The only fun part was pointing out the problems and glaring mistakes to the fatheads.
Lyles spot on with the trees.
Thick walls and firewood work wonderfully, and have for thousands of years.
I wish high schools taught the laws of thermodynamics…..
Time will tell if this is an actual “miracle product” or just another boondoggle
that will make someone rich but NOT do what it’s advertised as doing.
Odds are good this will end up in that category of new miracle inventions
that include the 400 MPG carburetor…..