A Material That Throws Heat into Space Could Soon Reinvent Air-Conditioning

https://www.technologyreview.com/s/608840/a-material-that-throws-heat-into-space-could-soon-reinvent-air-conditioning/

by rbanffy • 9 years ago

52 25 9 years ago

technologyreview.com

mannigfaltig• 9 years ago

So we're going to shoot these precious entropy differentials away into space?

knieveltech• 9 years ago

You prefer the current approach, consuming excess fossil fuels to inefficiently dissipate them into the atmosphere?

yetihehe• 9 years ago

No, we're gonna shoot some heat to space to gain some of those precious entropy differentials.

linarism• 9 years ago

Low quality energy. Also, not sure how precious it really is. A car has a better entropy differential at the exhaust pipe.

tristanj2• 9 years ago

http://sites.gsu.edu/geog1112/files/2012/10/Energy_Balance.p...

The earth already emits massive amounts of energy back into space. Nearly all the energy received from the sun is reemitted back into space, if this didn't happen the earth would quickly burn up. Adding reflectors won't make a huge difference as this energy would go back into space anyway.

prestonh• 9 years ago

In equilibrium that's true, but the whole problem is that we're not in equilibrium at the moment. That's what climate change is all about. If we can increase the albedo (reflectance coefficient, basically) of the planet, we can push the Earth down into an equilibrium position at lower temperature.

EDIT: Of course, we would have to significantly alter the albedo, which is probably not possible with rooftop panels alone.

ChuckMcM3• 9 years ago

Same guys as the IEEE article : https://news.ycombinator.com/item?id=15176721 but a bit more on the practicality of hooking it into existing systems.

One of the interesting side effects of putting a bunch of solar panels on my roof was the shade they provide (they sit about 4" above the roof) and that small gap of air made the attic significantly cooler than before the panels were installed. With these on the 'north side' of the roof (not with water plumbing, just providing a 5 degree C temperature difference) that would be helpful in the Bay Area.

Xeoncross• 9 years ago

When we built our house we put the actual metal roof several inches above the roof. The actual roof decking NEVER gets hotter than the ambient air temperature (115F max here in Texas). Solar panels or any form of shade structure (including trees) accomplish the same thing.

http://tinyhousemansion.com

Shingles or metal directly on a roof heats the house substantially but is cheaper (costs less in labor). That is why we still do it. (Just like dark roofs look "nice" so we still do that too).

ChuckMcM3• 9 years ago

Great link, and with this material you would get 5 degrees C below ambient on their underside, so nearly 9 degrees F lower.

Putting the shingles directly on the roof has benefits like keeping water out, and a floating roof (like my panels) is much more susceptible to wind damage (either to create a sail out of them). The 'old school' fix was of course sod roofs. If you put enough thermal mass between the roof and the interior you avoid significant heating.

gyrgtyn• 9 years ago

Will it zap birds?

x3n0ph3n3• 9 years ago

My thought was blinding pilots...

mark-r2• 9 years ago

Infrared, no blinding.

mark-r2• 9 years ago

I don't believe it's radiated in a focused beam, so no chance of zapping. Worst case would be like stepping in front of a mirror I think. I can definitely feel it when I step into the reflection of my house windows.

Synaesthesia• 9 years ago

If this is feasible, the great thing about it is it’a entirely passive, basically getting cooling for “free”. (I suppose you still pump a coolant through it but that’s fairly negligible energy cost.)

smsm42• 9 years ago

From the article:

The point of jackets, mittens, and scarves is to retain as much of that radiant heat as possible, keeping us warm on winter days.

This is AFAIK not how clothing works - excepting special ones like space suits, firemen suits, etc. Clothes are primary to prevent convective cooling, not radiative cooling.

5C cooling in Bay area may be enough for most of the summer outside of top heat days in Jul-Sep. If that is substantially cheaper than installing AC, it could be a good solution for most homes and save lots of energy.

lordnacho• 9 years ago

I don't get why there's a magic band that lets the heat escape? Does it happen to be a gap in the spectra of the atmospheric gases?

Also I was wondering what the effect of plain old mirrors on people's roofs would be. The point being to reflect the sunlight of course.

tryingagainbro• 9 years ago

Also I was wondering what the effect of plain old mirrors on people's roofs would be. The point being to reflect the sunlight of course.

The sun can hit the roof all day and it will not heat a normal house...so many layers in between and the heat will not reach below.

IMO it's just a matter of time before we use the sun to offset its effects on homes and offices. A super sunny day gives us a lot of power we could use to cool what the sun is heating. They coincide perfectly for a lot of hours.

djrogers2• 9 years ago

The sun can hit the roof all day and it will not heat a normal house

This is completely false. An attic that's heated up to 130+* will have a significant impact on the temperature of the house it's attached to unless you use an uncommonly ridiculous amount of insulation. This is why things like attic fans are so effective in reducing AC load...

milesvp• 9 years ago

Because physics is full of magic! Sadly I don't have enough physics background to google this phenomenon in a way that provides good results results, so I can't find other sources, but the way I understand it is there is a small band of radiative frequency that the atmosphere (at least on a non cloudy day) is almost completely incapable of absorbing, and so the energy is essentially easy to radiate into space. If I had to guess, it's probably related to the chemical makeup of our atmosphere, and a different gas and particulate makeup would create a different frequency band.

Mirrors don't work in the way you're suggesting because they don't provide enough of a shift in frequency in the energy they rebound (though they would act as an effective shade). For active cooling strategies, what you want is a material that can take the infrared frequencies from a heatpump, and shift them to the specific frequencies that make it hard for the atmostphere to absorb (similar to the use of phosphors in lighting for the visible spectrum).

Edit: I clearly didn't read this particular article closely enough, and the process they're measuring is actually a passive cooling system, which shows the material, or at least it's shade to be cooler than ambient temps. You could still use this material in conjunction with simple radiators to get better performance from a heat pump though.

ScottBurson2• 9 years ago

Does it happen to be a gap in the spectra of the atmospheric gases?

Yes.

djrogers2• 9 years ago

I could see people in hot climates using these as reverse solar panels for cooling their pools. Nothing refreshing about jumping into a 95* pool on a 100*/90% humidity day...

A Material That Throws Heat into Space Could Soon Reinvent Air-Conditioning

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