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'Whitest ever' paint reflects 98% of sunlight

bbc.com

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Re: 'Whitest ever' paint reflects 98% of sunlight

#181

Post by theluketaylor »

quercusa wrote: post #101
beauzero wrote: post #38

Earlier quoted context omitted.

If you look at old architecture in rural Georgia and Alabama. Houses are on rocks raised above the ground (air circulates underneath), 10 ft ceilings, a huge attic fan to pull cool air in in the evening, tall trees planted next to the house for shade (we have 4 pecan trees), and reflective tin roofs (if still shiny). This helped significantly to cooling in the summer. Winters aren't cold enough to warrant more than a…

Wide eaves help as well to keep summer sun off windows and to provide a place for a porch. A gentle rain on a tin roof is a sure ticket to sleep; a strong one not so much. I'd never thought about ceiling height - that makes a lot of sense.

Well designed buildings for passive cooling/heating in the higher latitudes can also take advantage of wide eaves. Since the sun is lower in the sky during winter you can design a home with eaves that block the summer midday intensity but allow sunlight to flood in throughout the winter with some careful calculations and site placement. Houses built to suit their location can slash the amount of energy required to regulate the temperature.

Re: 'Whitest ever' paint reflects 98% of sunlight

#182

Post by m463 »

Duralias wrote: post #134
TorKlingberg wrote: post #118

Earlier quoted context omitted.

This makes me wonder, does "anti-flash white" reflect more than polished mirror-like metal?

Maybe not more, but different wavelengths. The Wikipedia page does say "The purpose of the colour was to reflect some of the thermal radiation from a nuclear explosion", as far as my experience goes polished metal can still get extremely hot.

wouldn't it just be different directions?

A mirror would reflect light directionally, but white paint would seem to be diffuse.

Or said in another way, seeing a laser in a mirror might cause retinal damage, but on a white wall you would just see a dot. (although probably a speckly coherent dot)

Re: 'Whitest ever' paint reflects 98% of sunlight

#183

Post by samatman »

quickthrowman wrote: post #64
FredPret wrote: post #45

Earlier quoted context omitted.

Speaking of joining the dots, did you know that both the train and steam power (albeit a toy version of it) were invented in ancient Egypt? Think what could have been had we joined those two dots in 2000BC instead of 17-1800 AD. I should note that their train was of course pulled by slaves and not a locomotive.

You need machine tools capable of tight tolerances and quality metals/alloys to make useable (for work) steam engines. The Egyptians, Greeks, Romans, Abbasid, Persians, Europeans, etc all lacked these, thus no usable steam engines in antiquity/Middle Ages. Usable engines followed consistent quality metal production and machine tools pretty closely, it’s not like older people were just stupid, they didn’t have the tec…

That's a conventional response with a lot of merit to it.

But then I watch Clickspring recreating the Antikythera mechanism, and I wonder.

Yes, there is a big leap between what is effectively clockwork and, say, making a pressure boiler. But I wonder: if Francis Bacon had been a student of Euclid and derived the scientific method in 3rd century BC Alexandria, and Rome had been better governed, devoting more energy to science and less to war, speed-walking the tech tree 1500 years early isn't impossible to contemplate.

Fun to think about anyway!

Re: 'Whitest ever' paint reflects 98% of sunlight

#184

Post by djoldman »

"And we estimate we would only need to paint 1% of the Earth's surface with this paint - perhaps an area where no people live that is covered in rocks - and that could help fight the climate change trend."

"...only need to paint 1% of the Earth's surface..."

https://postimg.cc/fJ2TJHqh

Re: 'Whitest ever' paint reflects 98% of sunlight

#185

Post by trhway »

quickthrowman wrote: post #64
FredPret wrote: post #45

Earlier quoted context omitted.

Speaking of joining the dots, did you know that both the train and steam power (albeit a toy version of it) were invented in ancient Egypt? Think what could have been had we joined those two dots in 2000BC instead of 17-1800 AD. I should note that their train was of course pulled by slaves and not a locomotive.

You need machine tools capable of tight tolerances and quality metals/alloys to make useable (for work) steam engines. The Egyptians, Greeks, Romans, Abbasid, Persians, Europeans, etc all lacked these, thus no usable steam engines in antiquity/Middle Ages. Usable engines followed consistent quality metal production and machine tools pretty closely, it’s not like older people were just stupid, they didn’t have the tec…

Romans had copper and that would be enough to run the Empire using the telegraph. They just didn't know about the electricity and how to make a voltaic pile in particular even though they had the sufficient technology.

Re: 'Whitest ever' paint reflects 98% of sunlight

#186

Post by SamBam »

yetihehe wrote: post #16
SamBam wrote: post #11

I assume this could be useful to shield something in space with extremely specific temperature tolerances. I'm not sure about the suggestion that people are going to paint their roofs with it. People already have the opportunity to paint their roofs with cheap white paint which would provide nearly all the benefits this would, and still choose not to do it.

Not as much benefits as their paint > Commercially available white paints reflect between 80% and 90% of sunlight, according to lead researcher Prof Xiulin Ruan from Purdue, in West Lafayette, Indiana. "It's a big deal, because every 1% of reflectance you get translates to 10 watts per metre squared less heat from the Sun," he explained.

Yes, sure, but if you painted just two roofs white with regular paint, you're already doing much better than painting a single roof white with super-fancy paint.

And yet it's hard enough even to do that.

Re: 'Whitest ever' paint reflects 98% of sunlight

#187

Post by jonny_eh »

djoldman wrote: post #184

"And we estimate we would only need to paint 1% of the Earth's surface with this paint - perhaps an area where no people live that is covered in rocks - and that could help fight the climate change trend." "...only need to paint 1% of the Earth's surface..." https://postimg.cc/fJ2TJHqh

The area gets smaller if it can be somehow raised, perhaps in orbit? (See: https://en.wikipedia.org/wiki/Who_Shot_Mr._Burns%3F)

Re: 'Whitest ever' paint reflects 98% of sunlight

#188

Post by dmoo »

duxup wrote: post #75
cyberlab wrote: post #4

Someone needs to compile a list of all this fringe tech that I see popping up in my feeds, almost daily now. I know there are techpress blogs that pump out articles like this, but there doesn't seem to be an authoritative compendium of such tech anywhere on the net. I could curate this by hand with 3 hours of free time and some Red Bull I suppose. The reason I want this is because we seem to be swimming in innovation…

I think ultimately what you want is some measure of say it's practicality / viability to really make change? I think the catch is that if you really knew that... you'd be out making an insane amount of money as you'd be able to pick and choose winners / make them work ;) I'm reminded of the old TV series "Connections" where lots of individual innovations are cobbled together over surprisingly long periods of time to…

For those that haven’t seen it I would highly recommend it.

https://youtu.be/XetplHcM7aQ

Re: 'Whitest ever' paint reflects 98% of sunlight

#189

Post by diggernet »

throwaway0a5e wrote: post #41
ebiester wrote: post #22

Earlier quoted context omitted.

What we really need is white paint in the summer, black paint in the winter - reversible roofs, if you will. That said, in the desert southwest and many places in the world, white roofs are common. I wish it were more common in the southeast...

Corrugated material could provide a white surface to the mid-day sun in the summer and a black surface to the mid-day sun in the winter. Of course you'd need to take latitude and roof slope into your calculations but I bet if you made the materials in 10-deg increments you could get something "good enough" for most use cases. Or you could just make the material change color based on temperature. This is all known sci…

Oh, nice, a lenticular roof. Make it show white from summer sun angle, black from winter sun angle, tile roof images from ground level, and a "Pull Up" sign for aircraft overhead.

Re: 'Whitest ever' paint reflects 98% of sunlight

#190

Post by ouid »

quickthrowman wrote: post #64
FredPret wrote: post #45

Earlier quoted context omitted.

Speaking of joining the dots, did you know that both the train and steam power (albeit a toy version of it) were invented in ancient Egypt? Think what could have been had we joined those two dots in 2000BC instead of 17-1800 AD. I should note that their train was of course pulled by slaves and not a locomotive.

You need machine tools capable of tight tolerances and quality metals/alloys to make useable (for work) steam engines. The Egyptians, Greeks, Romans, Abbasid, Persians, Europeans, etc all lacked these, thus no usable steam engines in antiquity/Middle Ages. Usable engines followed consistent quality metal production and machine tools pretty closely, it’s not like older people were just stupid, they didn’t have the tec…

Also worth mentioning that a lot of what is considered technology is actually mathematics.
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