Purdue University engineers have created white paint that can keep surfaces up to 18 degrees Fahrenheit cooler than their ambient surroundings – almost like a refrigerator does, but without consuming energy. Commercial “heat rejecting paints” currently on the market reflect only 80%-90% of sunlight and cannot achieve temperatures below their surroundings. The white paint that Purdue researchers created reflects 95.5% sunlight and efficiently radiates infrared heat.
Earth’s surface would actually get cooler with this technology if the paint were applied to a variety of surfaces including roads, rooftops and cars all over the world. The paint would not only send heat away from a surface, but also away from Earth into deep space.
In a paper published Wednesday (Oct. 21) in the journal Cell Reports Physical Science, the researchers show that compared with commercial white paint, the paint that they developed can maintain a lower temperature under direct sunlight and reflect more ultraviolet rays.
This paint would be both cheaper to produce than its commercial alternative and could save about a dollar per day that would have been spent on air conditioning for a one-story house of approximately 1,076 square feet. It would take about ten gallons to paint a 1,076 square foot house.
The world makes about ten billion gallons (55 million tons of paint a year). Saving a dollar a day would mean a payback for ten gallons of paint in 6-12 months.
If paint production was doubled and the new production was used for this superwhite paint then 100,000 square kilometers could be painted every year.
Highlights
Paint using CaCO3 fillers with high concentration and broad particle size
The paint shows a high solar reflectance of 95.5% and sky window emissivity of 0.94
Field test shows over 37 W/m2 cooling power and over 1.7°C below ambient at noon
Commercial-like paint offers a high standard figure of merit of 0.49
The new paint is compatible with regular commercial paint fabrication processes.
SOURCES Purdue University, Cell Reports Physical Science
Written By Brian Wang, Nextbigfuture.com
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
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White pigment is usually TiO2, aka Titanium Dioxide. Basically anything white uses it. Toothpaste, paint, whatever. Remember about 20 years ago, the marketing craze was “Titanium”. I remember titanium golf balls were popular. Basically meant the paint used had TiO2 in it.
How about mirrors?
Gee whiz you think technology has changed much from the 70s, grandpa? Lord…
Was the attic meant for storage?
The reason I ask is because my house in Canada has the insulation on the floor of the attic, and the entire attic isn't climate controlled. In an ideal scenario, the attic would be the same temperature/humidity as the outside air.
Problem with that idea is that you need very large volumes of water to cool a nuclear power plant, something that deserts are lacking.
Also, having a power plant in the middle of nowhere leads to massively increased infrastructure costs to transport the electricity to the populated centers, not to mention it would be difficult to get local workers if it is remotely located.
A few years back we visited people down in Sarasota FL and they all had white-ish roof tiles for heat reflection. It was a bit odd looking at first but you'd have to be pretty dumb to miss out on the savings just to keep a "traditional" roof.
The best thing I saw was that styrofoam stuff they spray up under the roof in your attic. I was at a party in a new development and one of the parents there was the guy who shows new houses. He asked some of if we wanted to see a new house. I'm always up so yes. The attic access was in a weird place so I pulled on the rope to see the ladder going up. I asked him about that stuff under the roof and he said it was insulation. He said it keeps the attic cold.
I didn't believe him, as it was August in Alabama. But I went up there and it was actually cool. Knock my socks off.
With the lights down it was still weird (a well-lit gloom?) and reading (at least back when everything was on paper) was somehow more difficult.
One of the reasons I wanted to locate nuclear power plants out in the deserts of the southwest US was that I figured cooling ponds would radiate waste heat into space at night. This is why if you have even been to a desert it can get very cold at night, even though everything was very hot in the day. The heat just radiates away into space. The lower moisture reduces the absorption/re-emission or reflection of the heat by water in the air.
That is because calcium carbonate is not that white to visible light. People want whiter whites. That means titanium oxide generally. I actually suspect paints made with it will wear well, as the ultraviolet light is a major reason paint deteriorates. And if it is reflecting that…seems plausible the paint would last longer. Limestone does not deteriorate with sunlight. It is acid that gets it…eventually.
Rain and smog stops you radiating heat away to space anyway.
They don't engineer the concrete formulas for traction, they just alter the texture. As long as the concrete holds together and it is not slick as snot in the rain, it will work fine. Calcium carbonate is not clay. And it is not hydrophobic.
It does erode with acid, but so does concrete.
This is not pie in the sky. Limestone (calcium carbonate) is already used as a filler in concrete. It is just one choice of many including fly ash and other crud. file:///C:/Users/N/AppData/Local/Temp/materials-12-00781.pdf
Calcium carbonate is not really that white for visible spectrum. I just pulverized a calcium carbonate supplement with a hammer. I'd say it is gypsum white, if that. Definitely not super bright white. Only slightly whiter than ordinary concrete.
And in that picture, I believe it is the dull square on the left, not the brighter one on the right. If calcium carbonate were whiter than titanium dioxide, it would already be used instead, as calcium carbonate is much cheaper and whiter whites sell better.
And if it makes people's brights turn down, then I am definitely for it. I am tired of being blinded. But I highly doubt that would happen. Headlights would just be slightly better at illuminating the road at night. This is definitely not snow white. Much less white than white plastic plumbing. Do you go running in terror, "Oh my eyes. Oh my eyes" over white plastic pluming pipes? And if you do, they have these things called sunglasses.
This makes the rounds every few years. Same issue nukes it each time. As soon as it get dirty once, it becomes no better than normal white paint, and after cleaning it becomes less effective each time you clean it, generally as effective as normal white paint after the first cleaning. That dust and grime have normal emissivity properties. Cleaning abrades the surface. Dust, dirt ,etc., sticks to the surface. I'm not saying you can't clean the paint off, but that when you do the damage has already been done to the insanely good properties, and its no better than good old ultracheap white paint. These researchers are just trying to hype their work to get more funding, nothing irrational about that. Or their PR department is just misrepresenting their work due to technical misunderstanding. Work to keep dust off surfaces has been a near constant search by DOE EERE since like, forever, so solar cells can keep their high efficiencies. Tough nut to crack.
I had better clean up my parkour skills if all the cities are going to look like the city from Mirror's Edge.
We've seen this idea be proudly announced every couple of years since at least the 1970s. It's hard not to be a little bit cynical.
Admittedly, the real breakthrough here is making it cheap.
I am confused by someone saying that adding CaCO3 to paint makes it cheaper than normal white paint. What were they using before when making cheap white paint if they didn't go directly to chalk as the cheapest white pigment you would choose? Wouldn't that be the obvious choice?
Are we seeing any harm from existing white surfaces?
Aside from snow blindness…
The surface of a highway also needs a good friction coefficient with rubbber tyres. It needs a balance of properties.
Black bonnets to radiate heat are a common feature on modified performance cars.
But what sprang to my mind is the car roof. Because air conditioning of the cabin is a significant contributor to automotive energy consumption.
(In cold climates you can turn it around. Instead of a paint that's white in the visible spectrum but black in infrared, you get one that's black in visible (absorbs the sun's energy) but white in infrared (radiates less heat).
So you're saying you would not only save on cooling, you'd save on lighting too?
SeXiSt!!!! MuSt Be RaInBoW!!!!
When I was 12 or so, Dad decided that he was sick of the house being hot in summer (tropical north Queensland), so he bought a bunch of paint and we all painted the roof (children not allowed to paint the front of the roof where it was over a two storey drop onto concrete).
The result was very significant. The house was much cooler on hot days.
The people living further up the hill complained about being blinded by the glare, but …
Yeah, but when the article speculates that
you have to allow for a lot more painting and repainting than we do at present.
(And roads will wear out VERY quickly. Not to mention requiring other properties such as a high levels of grip.)
Houses are repainted that often, so what? That's minimal cost, since you'd likely be repainting anyway. Dirty, (formerly) ultrawhite paint is still going to reflect more light than dirty regular paint, so it's still a saving.
Silvered roofs have been common in cities for more than a decade, so I see no problem in accepting this new paint at least for that application.
I wonder how this paint would effect an air cooled engine. Some old motorcycles would have the upper part of the engine painted black to increase emissivity.
Why would it be harmful ?, those solar rays were already coming down, now they would had just switched direction.
Shouldn't be rejecting the power. You should be embracing it. Capture the light to make electricity and capture the waste heat to power your HVAC system.
So, perhaps make nano diffraction grating that would similarly bend the light a little, but also let the wind thru?
True, the solar wind is still 100% force, but that is smallish compared to full light pressure. But changing the direction of a photon 1 degree, so it barely misses the Earth, is far less momentum transfer, light pressure, than refection back would be. Maybe we can put a factory to make the glass *there*, as an anchor, and then continue with solar cells and light sails? Also, the glass could perhaps be tilted to steer into stable position?
it would just blow away in the solar wind without some heroic measures
Maybe the ground under solar panels should be covered with something like this. Bifacial panels can absorb reflected light, and there could be some credit mechanism for their direct cooling effect.
Hard to miss a thousand sloped roofs when driving.
So you look at roofs all day long?
Excellent. What is missing in the equation, that is hard to quantify, is the longevity of the roof. When a typically black roof made of some petroleum derivative is exposed to direct sun light and heats up (200F or more), it essentially cooks and the suns UV directly hits the material. This breaks down the material shortening the life of the roof. Lets say that the typical flat roof lasts 13 years but with this material it can last 15-17 years. That is an savings that is hard to estimate and sell. Environmental temperature reduction is another indirect savings for roofs in highly populated areas. Reducing the average urban temperature by 2F could have huge impacts on average cooling needs for an urban environment. Another saving is global warming reduction given large areas are reflecting the sun into space.
Yes this is s a great product if the cost is reasonable.
Prior to showing up at a new job. They decided to paint my office.
I walked in, turned on the lights, and wham! The silly painters had used ceiling paint on the walls. That stuff is way whiter than you may realize. I had to unscrew every other fluorescent light before I could work in there and until I could get it repainted.
If this paint catches on I think it might be time to buy stock in companies that make sunglasses.
What happens when it gets dirty?
But that would be RAciSt, YoU MuSt PaINt at LeAst 50% bLaCk.
As long as it is stark white.
Do you know how quickly white paint stains under the best conditions? Try it in rainy weather of a smog filled city.
This is more than that, as it cools efficiently to the dark IR sky even during the day. A local math prof refused to accept the idea, har! The problem is the place where the sunlight is encountered. In Space, between the Earth and the Sun, a thin sheet of transparent Moon glass will disperse rays that would otherwise hit the Earth so that they miss the Earth. This is better than reflecting as the light pressure is far less, so the verrrry thin stuff is not *shined* away. The Earth's surface is a bad place to try to coat.
I don't see everyone deciding to to have a pure white house. But I don't see why we can't have pure white rooftops, at least in desert areas.
Sadly, that was true and would have been a good idea even before this particular paint was developed, and yet in places with 100+ degree summers I still see a lot of black asphalt shingles, and very few white rooftops.
Who mocked you was very ignorant: many ancient cities in southern Italy, Greece and north Africa have white buildings for that very reason
I wonder if this could be more harmful to life as solar rays are reflected rather than absorbed.
I am surprised by all the negative comments here. This paint is cheap. As it is paint it can be applied to a large variety of surfaces and applications. It should not be expected to last any longer than any other paint before reapplication is needed however I would like to see, if left exposed to the elements for a year or 3, what kind of degradation in performance there is.
That's racist. 😉
Don't think I want to paint the vinyl siding on my house. The point of the siding investment was to get out of the painting cycle. Mindbreaker's comment below is on the right track, multiple colors and multiple substances need to be developed with this capability in order to achieve the over the top benefit's promised in the article.
I remember being mocked years ago for suggesting that white roofs and paving would moderate the urban heat island effect.
https://www.technologyreview.com/2017/09/12/149205/a-material-that-throws-heat-into-space-could-soon-reinvent-air-conditioning/
These mirrors that can emit a narrow band of infared radiation that passes through the lower atmosphere do better. But still have to be kept clean. Personally I think the best solution is just much cheaper electricity from 4th Generation nuclear.
They won't stop at walls, they'll use the windows too – in glass/metal skyscrapers that would be vital.
If every tall building in a city like New York had photovoltaics in the windows they could probably power the city (or at least those buildings) during the day, if not even store some extra power at basement level for night too, it's not like most places run at full power at night anyway.
You can just imagine a future where people are not completely dependent on exterior power companies doing their jobs properly to maintain essential power.
Increasing the reflectivity of highways is a bad idea unless you can guarantee that human drivers and driving AI fed by sensors will not be adversely effected by it.
Uhuh.
It will also cause record breaking numbers of snow blindness on even relatively sunny days.
I get serious headaches from looking at regular white paint on sunny days as it is, this sounds like a bad idea.
What you want are normal colored paints that reflect that infrared and ultraviolet.
Shipping containers seems like a good application…especially refrigerated ones.
The pigment they are using is calcium carbonate. That is limestone. They use that to make cement. Though it is cooked first changing it. But it should not be difficult to grind up some limestone and put that uncooked into concrete to improve the reflectivity of highways. Or it may work to just spread the powdered calcium carbonate on the wet concrete before it sets.
I haven't seen any paint that last for much more than a decade or two outdoors. Also, it doesn't stay clean without maintenance.
Walls in the future will be used in the future to generate electricity, that will be their best use environmentally when generating electricity from them will get low enough.