Advanced radiative cooling through meta-materials

[Streetwind]

Okay, I know that "nano"-anything is a terrible industry buzzword. And perhaps some of you have heard of this particular application before. But it was new to me, and it just blew my mind:

 

 

TL;DW: You can, through creative material engineering, make a substance that rejects heat to the environment faster than even the sun can heat it up. As in: a surface that manages to stay cooler than ambient temperature, in direct sunlight, at noon, in the middle of summer. And manufacturing this material isn't even that complicated.

Potential applications abound:
- Spacecraft radiators that no longer care whether they are in sunlight or not
- Passive heat rejection installations for residential and industrial air conditioning systems, reducing global energy consumption for cooling
- Increasing solar cell efficiency through keeping them cold in direct sunlight
- Possibly even building a heat engine that can "generate electricity out of darkness", to produce power where solar panels don't work
- And so on and so forth

And the really mindblowing thing is: the very reason that this works (radiative heat rejection that bypasses the atmosphere) means the heat rejected by these materials just... vanishes into deep space. It doesn't get trapped in Earth's greenhouse bubble. We can literally shunt excess heat away from the planet for good.

Now I'm sure that there's a lot of R&D left to do on that stuff, and even when it's widely available it won't magically solve our climate change problem. But it's likely going to be a contributor to the solution - and the potential uses go beyond "merely" better managing humanity's waste heat.

Shut up and take my money!

[YNM]

It sounds interesting.

I looked up on the frost thing. I genuinely never saw it down here.

But then I thought : why do I never saw it down here ?

I don't know, but I smell this might not work well in my place.

[Xd the great]

So if i am not mistaken, the material can radiate heat really quickly?

Only by radiation?

So I cannot use this for heatshield?

That is sad.

[kerbiloid]

The heatshield will be working as a photonic engines without fuel!!11

Two pieces of this material put aside will heat each other without any source of energy!

Earth core is made of it. That's why volcanoes!

Edited June 23, 2018 by kerbiloid

[Xd the great]

59 minutes ago, kerbiloid said:

The heatshield will be working as a photonic engines without fuel!!11

Two pieces of this material put aside will heat each other without any source of energy!

Earth core is made of it. That's why volcanoes!

Sir, conservation of energy please. If anything happens, its like a beam of light bouncing between two mirrors.

[kerbiloid]

10 minutes ago, Xd the great said:

Sir, conservation of energy please.

You would address this to the speaker.

[Xd the great]

1 minute ago, kerbiloid said:

You would address this to the speaker.

Well, it would work as a photonic engine, you just need a light source...

[Xd the great]

Wait... this thingy will work best for giant aerospike engines!

[kerbiloid]

Can find: at what time does he demonstrate a boiling teapot heated by light of the ceiling lamps?

[MatterBeam]

It is a material tailored to re-emit absorbed heat as long-wavelength infrared, which is good at travelling through the atmosphere. It's not magical...

[wumpus]

3 hours ago, MatterBeam said:

It is a material tailored to re-emit absorbed heat as long-wavelength infrared, which is good at travelling through the atmosphere. It's not magical...

So it is turning sunlight into energy on the ground?  From the comments I was expecting somebody pitching the idea of building Maxwell's Demon out of nanotech...

Even starting to work out the math on high Isp interstellar engines, I've commented that the heatsinks would provide significant thrust (even if one side was black and the other white), possibly even more than the nominal engines.  Convincing matter to emit energy as  short-wavelength radiation would go a long way into building such a beast (so what if your cyclotron was inefficiently flinging mass at relativistic speeds, your heatsinks will take the "wasted" energy and turn it into "infinite Isp").

[kerbiloid]

A stupid question: how great is ratio between the re-emitted energy per second and thermal radiation of the piece itself?

I mean, https://en.wikipedia.org/wiki/Wien's_displacement_law

P.S.
"Meta-" is a safe-word in 99% of cases, speaking metaphilosophically. Once heard - make a stop.

Edited June 28, 2018 by kerbiloid

[Xd the great]

15 hours ago, wumpus said:

So it is turning sunlight into energy on the ground?  From the comments I was expecting somebody pitching the idea of building Maxwell's Demon out of nanotech...

Even starting to work out the math on high Isp interstellar engines, I've commented that the heatsinks would provide significant thrust (even if one side was black and the other white), possibly even more than the nominal engines.  Convincing matter to emit energy as  short-wavelength radiation would go a long way into building such a beast (so what if your cyclotron was inefficiently flinging mass at relativistic speeds, your heatsinks will take the "wasted" energy and turn it into "infinite Isp").

Ah photonic propulsion. Why not just use this material to emit photons?

Might be great for solar sails.

[K^2]

4 hours ago, kerbiloid said:

A stupid question: how great is ratio between the re-emitted energy per second and thermal radiation of the piece itself?

It radiates as a black body at wavelength matching its temperature. The fancy bits here are that it's reflective to incident sunlight, transparent in the same wavelengths as air, and is a good thermal insulator to conducted heat. That allows the opaque "inner" layer to cool relative to transparent/reflective "outer" layer that's in contact with ambient air.

[YNM]

4 hours ago, kerbiloid said:

how great is ratio between the re-emitted energy per second and thermal radiation of the piece itself?

Some normal materials can reflect photon at their "peak" emission wavelengths, like metal at room temperature.

 

Still, as the whole thing don't work under cloud shade, I think we're still going to be a sauna.

Edited June 28, 2018 by YNM

[K^2]

11 minutes ago, YNM said:

Still, as the whole thing don't work under cloud shade, I think we're still going to be a sauna.

It still works. Clouds are considerably colder than the surface, and thermal radiation is 4th power in temperature. Roughly speaking, under clouds, you'd be at half efficiency. Ballpark, as that will vary quite a bit. But that's far from useless either way. Your worst case is fog or a dust storm, actually.

[kerbiloid]

Greenhouse effect in a solid body?

[YNM]

17 minutes ago, K^2 said:

Your worst case is fog or a dust storm, actually.

Fog... I haven't heard of warm fog XD

You'd be lucky to survive a dust storm !

 

But yeah, we'll see. We are often overcast and it's actually waay worse when it's overcast or cloudy compared to when it's hot.

[kerbiloid]

2 minutes ago, YNM said:

I haven't heard of warm fog

https://en.wikipedia.org/wiki/Smog

[YNM]

24 minutes ago, kerbiloid said:

Smog

Oh. Yeah.

Well, won't help too much then ?

[kerbiloid]

1 minute ago, YNM said:

Well, won't help too much then ?

_{(If it really works, then)}  It would, if make them stop doing smog.

Coercion and progress together work miracles.

[K^2]

46 minutes ago, YNM said:

Fog... I haven't heard of warm fog XD

Compared to interstellar space? Definitely. Compared to clouds? Typically. It's all relative.

But the main point of the device is to bring it to temperatures bellow these of ambient air. If you were happy with how cool the fog is, you don't need fancy materials. Sheet of aluminum will work just as well. The challenge is to do better than that. And for clear or cloudy days, you can. For foggy days, no luck.

[YNM]

12 minutes ago, K^2 said:

Sheet of aluminum will work just as well.

We often wet the ground (or road) in front of the house to alleviate the heat.

[K^2]

2 hours ago, YNM said:

We often wet the ground (or road) in front of the house to alleviate the heat.

That's mostly evaporative, though. Also doesn't work that well in the fog. 

[p1t1o]

Theres some odd phrases here which tickle my BS meter. For instance, radiation does not "bypass the atmosphere" and a super efficient radiator cannot extract "energy from darkness". Im also generally skeptical of science news that first reaches my ears via Youtube and not some more sober avenue. Theres no links to papers or research etc.

I'll file this away next to the EM drive for now.

If I had to guess, and if I was being generous, this seems more of a "What if we could..." rather than a "Look what we did!"

Or more likely, its a discovery of some far more banal effect, and they've dressed it up in language to make it seem like they can break previously unassailable physics. Like all those "This research could let us build lightsabers!" "discoveries".

Edited July 2, 2018 by p1t1o