5 ms·

Energy-saving coating without pigment keeps the surface beneath cool

104 points by gumby 4y ago

mensetmanusman 4y ago
https://www.3m.com/3M/en_US/energy-conservation-us/applications/passive-radiative-cooling/ https://www.3m.com/3M/en_US/energy-conservation-us/applicati... 3M sells film that does this. Advantage for film over paint is that it doesn’t build up, as it can be removed, recycled, and replaced. This is especially important for things that move so as not to gain additional weight. Very cool material to experience in person. It’s black body emission is also tuned to exit the atmospheric IR window.
bilsbie 4y ago
Now how does this compare to this material that sends heat into space: https://www.scientificamerican.com/article/the-supercool-materials-that-send-heat-to-space1/ https://www.scientificamerican.com/article/the-supercool-mat...
smusamashah 4y ago
> "A raisin's worth of structural paint is enough to cover the front and back of a door," > Chanda uses a Boeing 747 as an example in his team's study. To cover these planes, approximately 500 kilograms of paint is needed. Chanda estimates that using structural paint, manufacturers could cover the plane with only 1.7 kilograms. Can someone explain how this will look like in real life? I have a hard time imagining painting something that big with such tiny supply of paint. Brushing can not possibly work, but even if its sprayed over, how can so little spread over such large area?
- goda90 4y ago
  I don't know, but maybe it has to do with the viscosity of the paint? If it sticks to the surface well, but not itself, then it could be easier to achieve a thinner layer.
- deleted 4y ago
  [deleted]
adamwong246 4y ago
I have always dreamed of a paint/pigment that you could flip from high absorbent to highly reflective and then connect it to a thermostat. When it is cold out, your house is vantablack and in the summer, it's bright white.
deleted 4y ago
[deleted]
firstlink 4y ago
> A raisin's worth of structural paint is enough to cover the front and back of a door. Ah, so this will never come to a home near you. Shame.
gumby 4y ago
The posted article makes the cooling claim (and quotes one of the paper's authors) but the paper itself is silent on this issue, except indirectly (this is reflective paint, not normal absorbent paint) Paper: https://www.science.org/doi/10.1126/sciadv.adf7207 https://www.science.org/doi/10.1126/sciadv.adf7207
- fnordpiglet 4y ago
  The real article is infinitely more interesting than the original article above. Painting with butterfly wings! The processes are super interesting and the result is remarkable. I’d love to get my hands on some, I hope they commercialize this.
cesaref 4y ago
The examples are weird in this article. Paint isn't applied to most structures to give the structure a colour, but to achieve some other effect, such as weatherproofing, or to make the surface more uniform. It just so happens that putting pigment into the paint achieves an aesthetic effect. It's cool tech though, but i'm not imagining how distracting driving along a street of iridescent houses will be!
- deleted 4y ago
  [deleted]
- pcl 4y ago
  The paper says: > “The optical response of these artificially engineered nanostructures can be spectrally tuned across the entire visible spectrum to form a full-color gamut by controlling the gap plasmon dispersion via the geometrical parameters. In the proposed architecture, the subwavelength optical cavity ensures a large degree of angle insensitivity, while the stochastic nature of the self-assembled layer results in polarization independence and near 100% absorption at selected spectral bands.” See https://news.ycombinator.com/item?id=35521006 https://news.ycombinator.com/item?id=35521006 for the link to the paper.
- TheSpiceIsLife 4y ago
  It's definitely both otherwise we wouldn't bother top coating half the structural steel we manufacture, everything could just be Zincanode 402 or similar, which is great if you love dull grey. https://www.duluxprotectivecoatings.com.au/products/ranges/zincanode/zincanode-402/ https://www.duluxprotectivecoatings.com.au/products/ranges/z...
slimsag 4y ago
Two YouTube researchers[0][1] (they make science content that is very much not in the traditional form of YouTube) have been working on Infrared Cooling Paint for almost a year now and have been detailing how individuals can make it at home (although a fairly involved/lengthy process today.) There's definitely something here, hopefully someone sells it pre-made, I'd love to try some. [0] https://www.youtube.com/watch?v=N3bJnKmeNJY https://www.youtube.com/watch?v=N3bJnKmeNJY [1] https://www.youtube.com/watch?v=dNs_kNilSjk https://www.youtube.com/watch?v=dNs_kNilSjk
- HopenHeyHi 4y ago
  These two, NightHawkInLight and TechIngredients are great and you should watch all their videos not just about this subject.
londons_explore 4y ago
Paint coatings can make a massive difference to temperatures in a home. People understand "black paint = hot", but that isn't even necessarily true, and there is far more to it. I believe building regulations should require specific performance from paint on new buildings, and that commercial painters be required to replace any paint on a 'same or better' basis. Performance would be measured on the basis of watts of absorption under sunlight, and watts of emissions to the night sky. It is possible to design paint that visually is any color, yet maximizes or minimizes each of those parameters independently - therefore allowing you to choose a coating to minimize energy use for the building in whatever climate surrounds it. I think if all buildings were painted with optimal paint tomorrow, we could probably shave more off the worlds energy consumption than all EV's have saved so far.
- detourdog 4y ago
  I wonder if it makes sense to work these formulas by region. When people discuss that roofs need to be white I would think that only applies when cooling dominates energy use. It seems where heating is dominate should have black roofs.
  - KiranRao0 4y ago
    While I agree, often times the places that need the most heat are those with snow. So it may still be better to optimize for cooling in many cases.
    - detourdog 4y ago
      Maybe but I can tell that is not my case. If I was to generalize my question beyond my circumstances it would. What coatings should be used for roof and exterior walls for a well insulated building in in the mid forties latitude. Snow has some insulating value so the heatloss is reduced. A highly absorbent roof might still be a plus. I'm currently trying to figure out the if I can put a thin layer of phase change material PCM on my exterior walls. The idea would be that the phase change would delay the reaction of the heat transmission through the walls. The building has a high thermal mass and it takes about 72 hours of a 15+ degree temperature difference to result in 4 degree temperature change of the interior of the building. Modern commercial buildings can't use open windows for ventilation. The ventilation has to be provided by a mechanical system. I'm trying to optimize the building to maintain a consistent overall temperature range of 72-78 degrees. The summer is not a problem the heat pumps and solar array mean I only get 5 electric bills a year. I think that I can do a lot of optimization of coatings and solar thermal to get to net zero.

104 points by gumby 4y ago

https://www.3m.com/3M/en_US/energy-conservation-us/applications/passive-radiative-cooling/ https://www.3m.com/3M/en_US/energy-conservation-us/applicati... 3M sells film that does this. Advantage for film over paint is that it doesn’t build up, as it can be removed, recycled, and replaced. This is especially important for things that move so as not to gain additional weight. Very cool material to experience in person. It’s black body emission is also tuned to exit the atmospheric IR window.

bilsbie 4y ago

Now how does this compare to this material that sends heat into space: https://www.scientificamerican.com/article/the-supercool-materials-that-send-heat-to-space1/ https://www.scientificamerican.com/article/the-supercool-mat...

smusamashah 4y ago

> "A raisin's worth of structural paint is enough to cover the front and back of a door," > Chanda uses a Boeing 747 as an example in his team's study. To cover these planes, approximately 500 kilograms of paint is needed. Chanda estimates that using structural paint, manufacturers could cover the plane with only 1.7 kilograms. Can someone explain how this will look like in real life? I have a hard time imagining painting something that big with such tiny supply of paint. Brushing can not possibly work, but even if its sprayed over, how can so little spread over such large area?

goda90 4y ago
I don't know, but maybe it has to do with the viscosity of the paint? If it sticks to the surface well, but not itself, then it could be easier to achieve a thinner layer.
deleted 4y ago
[deleted]

adamwong246 4y ago

I have always dreamed of a paint/pigment that you could flip from high absorbent to highly reflective and then connect it to a thermostat. When it is cold out, your house is vantablack and in the summer, it's bright white.

deleted 4y ago

[deleted]

firstlink 4y ago

> A raisin's worth of structural paint is enough to cover the front and back of a door. Ah, so this will never come to a home near you. Shame.

gumby 4y ago

The posted article makes the cooling claim (and quotes one of the paper's authors) but the paper itself is silent on this issue, except indirectly (this is reflective paint, not normal absorbent paint) Paper: https://www.science.org/doi/10.1126/sciadv.adf7207 https://www.science.org/doi/10.1126/sciadv.adf7207

fnordpiglet 4y ago
The real article is infinitely more interesting than the original article above. Painting with butterfly wings! The processes are super interesting and the result is remarkable. I’d love to get my hands on some, I hope they commercialize this.

cesaref 4y ago

The examples are weird in this article. Paint isn't applied to most structures to give the structure a colour, but to achieve some other effect, such as weatherproofing, or to make the surface more uniform. It just so happens that putting pigment into the paint achieves an aesthetic effect. It's cool tech though, but i'm not imagining how distracting driving along a street of iridescent houses will be!

deleted 4y ago
[deleted]
pcl 4y ago
The paper says: > “The optical response of these artificially engineered nanostructures can be spectrally tuned across the entire visible spectrum to form a full-color gamut by controlling the gap plasmon dispersion via the geometrical parameters. In the proposed architecture, the subwavelength optical cavity ensures a large degree of angle insensitivity, while the stochastic nature of the self-assembled layer results in polarization independence and near 100% absorption at selected spectral bands.” See https://news.ycombinator.com/item?id=35521006 https://news.ycombinator.com/item?id=35521006 for the link to the paper.
TheSpiceIsLife 4y ago
It's definitely both otherwise we wouldn't bother top coating half the structural steel we manufacture, everything could just be Zincanode 402 or similar, which is great if you love dull grey. https://www.duluxprotectivecoatings.com.au/products/ranges/zincanode/zincanode-402/ https://www.duluxprotectivecoatings.com.au/products/ranges/z...

slimsag 4y ago

Two YouTube researchers[0][1] (they make science content that is very much not in the traditional form of YouTube) have been working on Infrared Cooling Paint for almost a year now and have been detailing how individuals can make it at home (although a fairly involved/lengthy process today.) There's definitely something here, hopefully someone sells it pre-made, I'd love to try some. [0] https://www.youtube.com/watch?v=N3bJnKmeNJY https://www.youtube.com/watch?v=N3bJnKmeNJY [1] https://www.youtube.com/watch?v=dNs_kNilSjk https://www.youtube.com/watch?v=dNs_kNilSjk

HopenHeyHi 4y ago
These two, NightHawkInLight and TechIngredients are great and you should watch all their videos not just about this subject.

londons_explore 4y ago

Paint coatings can make a massive difference to temperatures in a home. People understand "black paint = hot", but that isn't even necessarily true, and there is far more to it. I believe building regulations should require specific performance from paint on new buildings, and that commercial painters be required to replace any paint on a 'same or better' basis. Performance would be measured on the basis of watts of absorption under sunlight, and watts of emissions to the night sky. It is possible to design paint that visually is any color, yet maximizes or minimizes each of those parameters independently - therefore allowing you to choose a coating to minimize energy use for the building in whatever climate surrounds it. I think if all buildings were painted with optimal paint tomorrow, we could probably shave more off the worlds energy consumption than all EV's have saved so far.

detourdog 4y ago
I wonder if it makes sense to work these formulas by region. When people discuss that roofs need to be white I would think that only applies when cooling dominates energy use. It seems where heating is dominate should have black roofs.
- KiranRao0 4y ago
  While I agree, often times the places that need the most heat are those with snow. So it may still be better to optimize for cooling in many cases.
  - detourdog 4y ago
    Maybe but I can tell that is not my case. If I was to generalize my question beyond my circumstances it would. What coatings should be used for roof and exterior walls for a well insulated building in in the mid forties latitude. Snow has some insulating value so the heatloss is reduced. A highly absorbent roof might still be a plus. I'm currently trying to figure out the if I can put a thin layer of phase change material PCM on my exterior walls. The idea would be that the phase change would delay the reaction of the heat transmission through the walls. The building has a high thermal mass and it takes about 72 hours of a 15+ degree temperature difference to result in 4 degree temperature change of the interior of the building. Modern commercial buildings can't use open windows for ventilation. The ventilation has to be provided by a mechanical system. I'm trying to optimize the building to maintain a consistent overall temperature range of 72-78 degrees. The summer is not a problem the heat pumps and solar array mean I only get 5 electric bills a year. I think that I can do a lot of optimization of coatings and solar thermal to get to net zero.