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Thread: This Ultra-White Paint May Someday Replace Air Conditioning

  1. Top | #11
    Fair dinkum thinkum bilby's Avatar
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    Quote Originally Posted by Jimmy Higgins View Post
    And as soon as we paint roofs this’ll be a game changer.
    Almost every house in Brisbane has a painted roof. Mine certainly does - and it's overdue for a repaint. There's some rust starting to show through.

  2. Top | #12
    Fair dinkum thinkum bilby's Avatar
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    Quote Originally Posted by ZiprHead View Post
    Developed by researchers at Purdue University, the paint reflects 98.1 percent of sunlight

    A new coat of paint is an easy way to freshen up your home’s curb appeal. Soon, it may also help keep your house cool.

    Researchers at Purdue University have developed a new ultra-white paint that reflects 98.1 percent of sunlight and can keep surfaces up to 19 degrees Fahrenheit cooler than their ambient surroundings. This new paint, which may become available for purchase in the next year or two, could someday help combat global warming and reduce our reliance on air conditioners.

    The team of scientists in Purdue’s mechanical engineering department recently published the findings of their paint research, funded by the university’s cooling technologies research center and the Air Force’s scientific research office, in the journal ACS Applied Materials & Interfaces.

    “Our paint only absorbs 1.9 percent of the sunlight, whereas commercial paint absorbs 10 to 20 percent of sunlight,” says Xiulin Ruan, a Purdue mechanical engineering professor and one of the study’s co-authors.
    19°F seems oddly specific, particularly for a figure described as "up to". Why not 20°?

    Oh, wait. I bet you dollars to donuts it's 10°C, and the writer converted to °F with spurious accuracy. Because a) Americans have no clue what a °C is, and b) Journalists have no clue what spurious accuracy is.

  3. Top | #13
    the baby-eater
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    Quote Originally Posted by bilby View Post
    Quote Originally Posted by ZiprHead View Post
    Developed by researchers at Purdue University, the paint reflects 98.1 percent of sunlight

    A new coat of paint is an easy way to freshen up your home’s curb appeal. Soon, it may also help keep your house cool.

    Researchers at Purdue University have developed a new ultra-white paint that reflects 98.1 percent of sunlight and can keep surfaces up to 19 degrees Fahrenheit cooler than their ambient surroundings. This new paint, which may become available for purchase in the next year or two, could someday help combat global warming and reduce our reliance on air conditioners.

    The team of scientists in Purdue’s mechanical engineering department recently published the findings of their paint research, funded by the university’s cooling technologies research center and the Air Force’s scientific research office, in the journal ACS Applied Materials & Interfaces.

    “Our paint only absorbs 1.9 percent of the sunlight, whereas commercial paint absorbs 10 to 20 percent of sunlight,” says Xiulin Ruan, a Purdue mechanical engineering professor and one of the study’s co-authors.
    19°F seems oddly specific, particularly for a figure described as "up to". Why not 20°?

    Oh, wait. I bet you dollars to donuts it's 10°C, and the writer converted to °F with spurious accuracy. Because a) Americans have no clue what a °C is, and b) Journalists have no clue what spurious accuracy is.
    Kinda disappointed that they wrote 98.1 percent of sunlight instead of "over 49 out of every 50 rays of sunlight".

  4. Top | #14
    Elder Contributor barbos's Avatar
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    In places where it is a problem roofs should be covered by solar panels.

  5. Top | #15
    Veteran Member
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    Quote Originally Posted by barbos View Post
    In places where it is a problem roofs should be covered by solar panels.
    You sure that’d be better than reflecting the light back to space?

  6. Top | #16
    Content Thief Elixir's Avatar
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    Quote Originally Posted by bigfield View Post
    Kinda disappointed that they wrote 98.1 percent of sunlight instead of "over 49 out of every 50 rays of sunlight".
    "more than 980,000,000,000 out of every 1,000,000,000,000 photons" would have been more impressive.

  7. Top | #17
    Elder Contributor barbos's Avatar
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    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by barbos View Post
    In places where it is a problem roofs should be covered by solar panels.
    You sure that’d be better than reflecting the light back to space?
    Direct effect of black roofs is minimal. They don't heat the air inside the house, the heat air around in the city creating heat island.
    So you need to paint white everything which is reached by the sunlight - roads, building walls.
    Better solution is to have more trees and solar panels.

  8. Top | #18
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    So a house in space will not heat up from solar radiation?

    It is cooler in the shade ten in direct sunlight.

    Flat smooth shiny surfaces reflect more than rough surfaces. In high power laser systems optics can heat up from absorption.

    So called 'cold' mirrors reflect the IR spectrum with low absorption.

  9. Top | #19
    Elder Contributor barbos's Avatar
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    Quote Originally Posted by steve_bank View Post
    So a house in space will not heat up from solar radiation?

    Depends what's underneath of paint. If there is a layer of good insulation then color of the roof will have no effect.
    Of course having white surface reduces requirements on insulation.

  10. Top | #20
    Contributor skepticalbip's Avatar
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    Quote Originally Posted by barbos View Post
    Quote Originally Posted by steve_bank View Post
    So a house in space will not heat up from solar radiation?

    Depends what's underneath of paint. If there is a layer of good insulation then color of the roof will have no effect.
    Of course having white surface reduces requirements on insulation.
    Temperature control in space is different than on Earth. On Earth most heat transfer is through conduction and convection and not so much through radiation. In space the only method of transferring heat is through radiation.

    The black body radiation curve is also an absorption curve so an object in space will reach thermal equilibrium at the point where its absorption equals its radiation. So (assuming solar radiation is the only heat source) the black body radiation curve tells us that a black object in space will reach thermal equilibrium at a lower temperature than a white or silvered object. Having only lived on Earth in a dense atmosphere, this is rather counter intuitive.

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