Scientists created the world's whitest paint. It could eliminate the need for air conditioning.
The world's whitest paint has been created in a lab at Purdue, a paint so white that it could eventually reduce the need for air conditioning.
White paint... wasnt expecting those results!
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That is nice; it absorbs less than it emits in the IR. I.e. it reflects visible (hence white), but whatever gets absorbed anyway gets redshifted to IR and emitted. (i.e. it gets hotter than only the IR load from the sun would make it).
However, they don't comment on making sure it emits it *to one side only* - because you'd have to make sure it does not emit on the back side (noting IR is low energy light that goes through a lot of materials).
Also, how to keep it clean...? Add TiO2 (or other) particles to catalyze oxidation of any grime adsorbing? (I know in Japan they have tests with TiO2-coated walls that stay nice and white.) Though TiO2 does absorb visible light (and uses the excited electrons to catalyze chemical reactions). So maybe not a good idea. "keeping it white" is, however, crucial for this to be a candidate for useful real-life utilization.
I like these approaches in general; there is much we can do with our homes (roofs, walls) to prevent the need for energy to heat or cool. Passive efficiency.
However, they don't comment on making sure it emits it *to one side only* - because you'd have to make sure it does not emit on the back side (noting IR is low energy light that goes through a lot of materials).
Also, how to keep it clean...? Add TiO2 (or other) particles to catalyze oxidation of any grime adsorbing? (I know in Japan they have tests with TiO2-coated walls that stay nice and white.) Though TiO2 does absorb visible light (and uses the excited electrons to catalyze chemical reactions). So maybe not a good idea. "keeping it white" is, however, crucial for this to be a candidate for useful real-life utilization.
I like these approaches in general; there is much we can do with our homes (roofs, walls) to prevent the need for energy to heat or cool. Passive efficiency.
I had my roof replaced a couple years ago. I chose a grey 1 shade darker than the energy star white. My wife wasn't thrilled. She thought it was too light. I forgot about the roof.
Then the world locked down and my wife was working from home. I saw my bills go up.
Then my energy company sent me a notice congratulating me on lowering my energy usage 11 or 12%. I couldn't figure out why that was the case until i remembered the roof the previous summer.
If my wife wasn't running a few computers all day long, the change would have been greater.
There's huge potential for something as simple as a white roof. Across a city, that could make a huge difference.
Then the world locked down and my wife was working from home. I saw my bills go up.
Then my energy company sent me a notice congratulating me on lowering my energy usage 11 or 12%. I couldn't figure out why that was the case until i remembered the roof the previous summer.
If my wife wasn't running a few computers all day long, the change would have been greater.
There's huge potential for something as simple as a white roof. Across a city, that could make a huge difference.
Back in the 1980s I had the roof coated white for a large facility to reduce the AC load. The effect was definitely noticeable and saved us from installing a larger AC unit.
We went from the black tar roof to a white EPDM roof at work and it made a huge difference in our electric bill, I was really surprised but I could tell a difference when I had to run cat6 up in the rafters, before I had to wait till after the sun went down in the summer to even think about doing cable runs, now I can do it most days in the afternoon, but this year those most days have been less and less with the 100F+ days.
Would this only benefit in summer? No one wants to be "emitting more heat than it is absorbing" in January.
One article claims a surface painted with this would actually be a lower temperature than its surroundings. Again, that's no benefit in winter.
One article claims a surface painted with this would actually be a lower temperature than its surroundings. Again, that's no benefit in winter.
I'd argue that once covered in snow that would add quite a bit of insulation. No ice dams either.
I used to have to replace industrial flat roofs and my preference were the with white Firestone TPO product. It made a quite a difference in hot weather. These were insulated roofs so they tended to hold snow so I did not notice any heating impacts. The biggest issue was everyone needed sunglasses from walking on the roof even in cool weather.
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