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Earth Science

World's Whitest Paint Sets Guinness Record, Could Reduce Need For Air Conditioning (usatoday.com) 139

Posted by EditorDavid from the brightest-whites dept.
"The whitest paint in the world has been created in a lab at Purdue University," reports USA Today, "a paint so white that it could eventually reduce or even eliminate the need for air conditioning, scientists say.

"The paint has now made it into the Guinness World Records book as the whitest ever made."

Long-time Slashdot reader phalse phace shared their report: "When we started this project about seven years ago, we had saving energy and fighting climate change in mind," said Xiulin Ruan, a professor of mechanical engineering at Purdue, in a statement. The idea was to make a paint that would reflect sunlight away from a building, researchers said. Making this paint really reflective, however, also made it really white, according to Purdue University. 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. "That's more powerful than the air conditioners used by most houses," Ruan said. Typical commercial white paint gets warmer rather than cooler. Paints on the market that are designed to reject heat reflect only 80% to 90% of sunlight and can't make surfaces cooler than their surroundings...

Researchers at Purdue have partnered with a company to put this ultra-white paint on the market, according to a news release.
"This white paint is the result of research building on attempts going back to the 1970s," adds a statement from Purdue University, "to develop radiative cooling paint as a feasible alternative to traditional air conditioners.

"Ruan's lab had considered over 100 different materials, narrowed them down to 10 and tested about 50 different formulations for each material..." Two features make this paint ultra-white: a very high concentration of a chemical compound called barium sulfate — also used in photo paper and cosmetics — and different particle sizes of barium sulfate in the paint. What wavelength of sunlight each particle scatters depends on its size, so a wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun.
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World's Whitest Paint Sets Guinness Record, Could Reduce Need For Air Conditioning More

World's Whitest Paint Sets Guinness Record, Could Reduce Need For Air Conditioning

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  • When can I buy it and more importantly when can I (Score:5, Insightful)

    by Pierre Pants ( 6554598 ) on Sunday September 19, 2021 @09:37AM (#61810319)
    afford it?

    • Re: (Score:3)

      by MrL0G1C ( 867445 )

      And is it toxic to the environment? The amount of fancy but toxic chemicals we use in household products is absurd.

    • Re:When can I buy it and more importantly when can (Score:5, Interesting)

      by Joce640k ( 829181 ) on Sunday September 19, 2021 @10:20AM (#61810435) Homepage

      Never mind that: Who wants to live in a refrigerator in winter?

      The harder the sun shines, the colder your house gets? No thanks.

    • afford it?

      Even if I could afford it, the HOA committee would not allow that particular shade of white, and definitely not on the roof.

      • afford it?

        Even if I could afford it, the HOA committee would not allow that particular shade of white, and definitely not on the roof.

        The reason the house I just purchased was not in a HOA. I've had houses in HOAs. I've been president of a HOA. I've learned that they attract all the worst people that want a forum in which they can control other people.

    • How does this compare to the NASA studies of highly-reflective surfaces, which are 99.9% reflective in the solar spectrum?
        https://www.nasa.gov/feature/c... [nasa.gov]
        https://tfaws.nasa.gov/wp-cont... [nasa.gov]

  • You'll have to keep it clean (Score:5, Insightful)

    by ZorinLynx ( 31751 ) on Sunday September 19, 2021 @09:39AM (#61810325) Homepage

    Will the effort and cost to keep it clean be less than the energy saved? I wonder.

    • It's a good point. However, the numbers listed in the summary seem to refer to residential housing, which has sloped roofs. So that could stay clean reasonably well. How often do rooftop solar collectors need to be cleaned? Given the margins on solar power, it can't be that often.
      • There is a big difference between a sloped glass surface and a sloped painted surface, the only reason roofs mostly don't look dirty is because we don't use lighter colors that would show all the dirt and grime that builds up between significant rain events.

        I can see it now: HOA requires all white roofs and complaining about being blinded while driving by is forbidden.

        • Re: (Score:3)

          by MikeMo ( 521697 )
          Here in Florida, with mostly tile roofs, we have to pressure-wash them every two years or so, anyway. If that’s all it takes to maintain this paint, it would be a winner down here.

      • Solar panels usually have a glass surface that is coated with an anti dirt paint. Except for snow, nothing really sticks to it.

    • Re:You'll have to keep it clean (Score:5, Funny)

      by Nkwe ( 604125 ) on Sunday September 19, 2021 @10:00AM (#61810383)

      Will the effort and cost to keep it clean be less than the energy saved? I wonder.

      You just have to whitewash it. Perhaps talk your friend into helping you?

    • Will the effort and cost to keep it clean be less than the energy saved? I wonder.

      No, because you'll have to repaint it twice per year - black in winter and white in summer.

      • With insulation it will make almost no difference regardless, it needs to be applied to an uninsulated roof to help significantly with cooling costs.

        In a static situation it only makes sense in hot climates where there's a need for air-conditioning year round. Otherwise you need some way to increase insulation during winter, probably with forced air circulation under the roof during summer, with the vent holes covered up by insulation during winter.

        • The latest technique in building is to put the insulation in the roof. Seems crazy, but I think works well. I went into a attic TX mid-summer of a new house I was contemplating and found it around 80. One plus is the air handler and ducting losses are practically zero.

          • I know insulation works well to prevent heat flow, but the paint can cool the roof below ambient, if there is insulation under it that won't do much for the building.

            • Re: (Score:2)

              by jbengt ( 874751 )
              TFA said "surrounding temperatures" not "ambient air temperature". I doubt the paint can actually reduce the surface temperature below ambient temperatures when sunlit in real life. That would require the roof to absorb heat from the air and radiate it to the sky. I don't doubt it can reduce the roof temperature below adjacent surface temperatures. And, anyway, on a roof it will get dirty enough to perform similarly to other whites.

        • probably with forced air circulation under the roof during summer, That is how a "traditional" house in Thailand looks like.
          Most of the time with cheap tin roofs. Painting those white would cool the house significantly during the hot season, and would not harm during the dry season. Those houses have no air con though.

        • Re: (Score:2)

          by jbengt ( 874751 )

          With insulation it will make almost no difference regardless, it needs to be applied to an uninsulated roof to help significantly with cooling costs.

          The more insulation used, the less the color of the roof matters. (Even better is to add mass to the roof between the insulation and the air-conditioned space for a "flywheel" effect that reduces the peak load.) But the color of the roof still makes a significant difference. When winds are calm in the summer, a dark, sunlit roof surface can be 30F hotter th

      • Against popular believe: there are places on earth that actually do not have a winter. Especially those places that have officially only three seasons anyway: dry season, rain season, hot season :P

    • I have a high reflectivity white metal roof on an A-frame. It needs to be sprayed about once every 3 months with a fungicide and cleaned about once a year. That is about the same as what I used to do when the roof was a brick red metal.
  • Oh great, now we're going to have a barium shortage.

    • Re: (Score:2)

      by Entrope ( 68843 )

      Barium? I just met 'im!

      I'll be here through Thursday. Try the veal! Don't forget to tip your waitperson.

      • That's what Khrushchev said: "We will bury you!" And then he turned to his comrades and said "Bury'em." In Russian, of course.

        • Re: (Score:2)

          by cstacy ( 534252 )

          That's what Khrushchev said: "We will bury you!" And then he turned to his comrades and said "Bury'em." In Russian, of course.

          In Soviet Russia, rats use barium carbonate to poison YOU! (It wasn't the KGB, no sir....)

    • There are about a billion tonnes of barium sulfate reserves.

      Barium can also be extracted from seawater.

      China is, by far, the biggest producer.

  • This paint is so white⦠(Score:3)

    by drewsup ( 990717 ) on Sunday September 19, 2021 @09:54AM (#61810367)

    It whiter than my cousin Larry from Minnesota!

  • Killer app (Score:5, Interesting)

    by AlanObject ( 3603453 ) on Sunday September 19, 2021 @09:56AM (#61810371)

    Wouldn't this be a major boon to spacecraft? Getting rid of heat in a vacuum is quite a problem.

    • Re: (Score:2)

      by redback ( 15527 )

      I don't see why not.

    • Re:Killer app (Score:4, Informative)

      by thegarbz ( 1787294 ) on Sunday September 19, 2021 @02:38PM (#61811213)

      Doubt it. In a vacuum nothing will radiate heat better than a black body. The only requirement is to keep it away from sunlight meaning that painting a heatsink black and then blocking the sun with a mirror reflector will be far better than simply painting it with this new material.

      • Probably not. Spacecraft do use "space paint" with a similar design goal of reflecting most light, but it has very different constraints. The harsh radiation environment, vacuum, and extreme temperature ranges will discolour or otherwise damage most coatings. Conversely, it doesn't need to be cheap, non-toxic, or easy to apply. So what's best for one environment is unlikely to be suitable for the other.

      • So this paint is useful only for realistic spacecraft, that not only have to operate in sunlight but also may depend on sunlight for e.g. solar power.

        • Have you ever noticed that houses with solar panels on their roofs have cooler roof spaces? Heatshields are very effective. A realistic spacecraft would balance heat in and out using clever engineering, one way of doing that would be using solar panels as a sunshade to protect a black body radiator.

          Maybe there are scenarios where this white paint compromise could have a technical benefit, but it certainly isn't a superior coating for radiating parts, which may I add are already protected from sunlight on ex

  • As far as I know, a white body radiates less heat that a black body, so maybe a really white paint could be more effective than cavity wall insulation. Mind you, it would make my bit of Birmingham a bit more dazzling than an Englishman is accustomed to.

    • You're right about the basics, but it will only reduce radiative/absorptive transfer and not any form of conductive transfer. It probably won't change the rate of radiation much as compared to ordinary flat white paint, though it will reduce absorption, but you're still going to need insulation to reduce conduction.

      • This reminds me of what it is like doing thermal design on power electronics. Radiation is only part of it. Conduction to the air, and subsequent air circulation, is probably more important. As far as I know, the colour of a surface, black or white, has no effect on conduction of heat from an enclosure wall to the surrounding air. If I use a finned heatsink on a power semiconductor, I can get a reasonable guess at the semiconductor temperature, at a given power input. But nowadays, common practice is to rel

  • An excellent explanation (Score:5, Informative)

    by redback ( 15527 ) on Sunday September 19, 2021 @10:03AM (#61810397)

    This video is an excellent explanation of how it works. https://www.youtube.com/watch?... [youtube.com]

  • This is great technology, but the first time it rains, the paint will be dirty enough to completely negate any benefit over traditional white paint.

    It would be impossible/impractical to keep clean enough so that the touted benefits are meaningful.

    • Ironically ICE cars are not cool, heat from engines and sun spring to early fall. Light color paint more practical. Northern icy winters perhaps a dark vehicle better. Not sure how big a difference dust n dirt will affect bs regular paint. Anyway the ultra white probably useful in some cases. Hats?
      • I had a 1989 Ford that recently had a weak air conditioner, even after cleaning, charging, and plugging vacuum leaks. Painting the roof with flat white interior(works better) paint, the car was much cooler most days. Looked like a factory vinyl roof from a few feet away.

    • Re:Cool but impractical (Score:5, Interesting)

      by Pinky's Brain ( 1158667 ) on Sunday September 19, 2021 @11:04AM (#61810557)

      Companies have done multiyear trials with the Australian version of this already, unless they are lying it seems it works :
      http://www.skycool.com.au/wool... [skycool.com.au]

    • but the first time it rains, the paint will be dirty enough to completely negate any benefit over traditional white paint.
      Depends on air pollution. Believe it or not: there are plenty of places that have none :P

  • This gets rediscovered every year.

    Skycool in Australia has been selling paint which is emissive in the IR window for decades. Skycool in the US used the same name to sell panels which do it and now there's another one ... I have a good idea for a name!

  • I wonder how it does in space. (Score:5, Insightful)

    by spiritplumber ( 1944222 ) on Sunday September 19, 2021 @10:35AM (#61810487) Homepage
    I wonder how it does in space. Good radiative cooling that you don't have to spend power on would help with a lot of stuff.

  • A whitewash (Score:3)

    by Kitkoan ( 1719118 ) on Sunday September 19, 2021 @10:36AM (#61810489)
    All this is doing is trying to whitewash the real issue....

    • Attention... all grammer nazi"s! Is they're anything; wrong with: my post,

      Yes, but most spelling mistaking & punctuation they has. No much grammar wrong go.

  • Incident light on a smooth surface (as are most painted surfaces) is reflected specularly [wikipedia.org], so light from up above (where the sun is) will get reflected to down below. This means that although the painted surface might not heat whatever objects where the light ends up will get warmer. So: unless the sun light is reflected back into space the planet will still get warmer. So it might work with close to horizontal surfaces, eg flat roofs.

    Can anyone come up with an argument that shows that I am wrong ?

    • Presumably the story is oversimplified bullshit. Skycool (both the Australian and US versions) are reflective in the visible spectrum and absorbing/emissive in the infrared window (so it's actually a black body in the IR window, not white). So ideally it absorbs nothing, while emitting IR, thus cooling down.

      https://en.wikipedia.org/wiki/... [wikipedia.org]

    • Oh, sorry I misunderstood what you're getting at.

      Sure, if the light gets reflected onto the ground the ground will heat up ... but who cares? You don't need to air-condition outside.

    • First, note it can be diagonal and the light will most likely reflect into the upper atmosphere. Merely being at say a 45 degree angle won't change anything.

      But the problem is the upper atmosphere absorbs light and heat. So even if most of the light is reflected upwards, the energy will be mostly be absorbed and not make it into space.

      That said, this will still be a net positive for global warming as electricity production and transmission is really inefficient and for every degree an air conditioner coo

    • Re: (Score:2)

      by Junta ( 36770 )

      Even at a typical slope, the amount of reflection destined to return back to space is presumably still more than natural surface would be for most of the earth (dirt, sand, vegetation) and certainly more than the traditional dark roof. Being described as 'white' suggests the reflection would be pretty diffuse and not so specular as to direct the light in a particular direction.

      The theoretical comparison would be a 'default' roof plus air conditioning to overcome the heat and what does the energy generation

    • Reflecting any of the light back to space is better than all the black surfaces we usually have converting it to heat on the ground. The overall albedo of an area is important to temperatures in that area. This is why there are efforts in many of our major heat islands, like Phoenix, to switch to lighter surfaces.

      But the real gain with using this material to replace cooling is in the reduction of power used. Power generation is still a large CO2 contributor.

  • It's n
    • It's nice to have all white roofs/buildings, but do they give the people who live around those roofs and have windows above them sunglasses? Due to construction we have a flat all concrete (which isn't full white) slab near the office window, but when the sun is shining we have to close the blinds otherwise you'll go blind by the reflected sunlight. Have they kept the blinding aspect of all white roofs to higher floors in mind?

  • Old news (Score:4, Informative)

    by mcswell ( 1102107 ) on Sunday September 19, 2021 @11:08AM (#61810561)

    1) This is old news, the story came out back in April (see e.g. https://www.popularmechanics.c... [popularmechanics.com]).
    2) It works well at night, and surprisingly well in the day--but only in dry air. So great for Phoenix, Tucson, Las Vegas and so forth, but not much good for Seattle.

    I get all the news I need in the weather report
          --Simon and Garfunkle

  • Cannot eliminate the need for air-conditioning (Score:3, Insightful)

    by mysidia ( 191772 ) on Sunday September 19, 2021 @11:22AM (#61810605)

    "a paint so white that it could eventually reduce or even eliminate the need for air conditioning, scientists say.

    This is basically like claiming better insulation on food storage boxes would make electric refrigeration unnecessary. Utterly unrealistic, or maybe possible only in climates that are cool to begin with. Even if we can stop 100% radiant heat transfer into buildings through the walls - air still needs to circulate and air still comes in that is already hot when it's 90 degrees 80% humidity outside. We also got these things called windows, And the paint does nothing to take the moisture out of the air like A/C does, so under hot humid conditions outdoors, you're not going to be able to make an environment comfortable to humans with just a little paint.

    You aren't eliminating the necessity of air conditioning... you might be able to reduce the intrusion of heat thus lowering the energy costs to maintain a lower temperature.

    • Re: (Score:3)

      by swell ( 195815 )

      Need?

      I can't speak for you, but my ancestors lived thousands of years without air-conditioning. Come to think of it, they didn't have central heating either even in the time of the ice age. This new generation is so soft. AC? Next you'll be wanting refrigerated beer!

    • The theoretical design of using this for air conditioning would be to have some system to circulate heat to the roof, and then this paint on the roof would emit that heat via the IR window.

      Much like the design of a current air conditioner is to circulate heat to a condenser outside the house, and dump the heat to the air.

      So it wouldn't just be "paint the house, get free A/C", but it could remove the energy required to run a compressor, which is most of the power consumption of an air conditioner.

    • Re: (Score:2)

      by jezwel ( 2451108 )
      One of the trials of a similar technology (Skycool) on shopping centre roofs showed ~47% less electricity use on average for AC requirements across summer and winter, with winter days requiring only air circulation/removal fans (for public safety/regulations).

      I would like to see residential trials including where there's solar on the roof and local battery storage, to see how feasible off-grid could be.

    • Why is the alternative of no air conditioning equal to nothing at all, so warm moist air gets to enter just like that? We don't have an air conditioning system with cooling, but our apartment building does have a heat exchange system. Very power efficient, keeps the inside temperature steady for wide temperature ranges outside. We need only minimal heating when it's freezing outside. Granted, when it's hot around here, it's rarely over 25ÂC at night. So getting in fresh air at 6am and then letting the

  • Can You Keep It Clean? (Score:3, Interesting)

    by careysub ( 976506 ) on Sunday September 19, 2021 @11:33AM (#61810649)

    The Achilles heel of super-black and super-white materials is that anything that gets on it destroys the "super" property quickly. However the problem is not quite as bad for this stuff - 98.1% reflective - compared to VantaBlack that is said to "absorb up to 99.965% of visible light". A 1% contamination with something grey (50% black say) on that white surface knocks its reflectivity down to 97.6% and increase in absorption from 1.9% to 2.4%, whereas with the VantaBlack it increases its reflection from 0.035% to 0.5%, and only 1% surface contamination in the environment is pretty darn clean.

    Still, a really white paint that gets little dirty is still whiter than one that start out lower.

  • Third law of moronics (Score:5, Funny)

    by groobly ( 6155920 ) on Sunday September 19, 2021 @12:32PM (#61810837)

    Any incremental improvement in efficiency is immediately negated by the actions of morons.

    Fourth law of moronics: When a moron and an anti-moron collide, the anti-moron is annihilated, and two morons emerge.

  • What does it do with humidity, which a lot of research indicates is important to comfort and often more important than temperature. Aside from the comfort factor, it also is important in high humidity areas.

    • Same thing the compressor in a current air conditioner does: Nothing.

      A large surface painted with this would theoretically replace the compressor in a system similar to a current A/C system (Along with a different heat transfer medium, since there wouldn't be a reason to use refrigerant). Dehumidification would be exactly the same as in the evaporator coil in a current system.

  • And it'll probably work for a week, until micro algae and such will start to grow on it and negate any benefit over "normal" white paint again?

    As anyone who has ever owned a white car can tell you, they don't stay white very long.

  • UNITS (Score:3)

    by Forty Two Tenfold ( 1134125 ) on Sunday September 19, 2021 @01:15PM (#61810931)
    Square feet and kilowatts?
  • None. None more white.

  • Blending shades of grey (Score:3)

    by dwywit ( 1109409 ) on Sunday September 19, 2021 @05:41PM (#61811707)

    So if I mix it with vantablack, will it be the greyest grey ever?

  • "a paint so white that it could eventually reduce or even eliminate the need for air conditioning, scientists say."

    Yeah, sounds great in a mild climate, bring that 'super white' paint down to Texas and turn off your A/C...

    If painting the roof of a Google data center would eliminate the need for A/C, they would be putting it on the roof of every data center they own.

  • Is Anish Kapoor allowed to use it?

  • What happens if you mix this with Vanta Black?

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