Guest Post By Willis Eschenbach [See two Updates at the end]
Here’s an oddity. Some very clever folks have invented a plastic film that cools surfaces by as much as 10°C. From Science magazine:
Cheap plastic film cools whatever it touches up to 10°C
Here’s the innovative part, according to the article. The tiny glass spheres act as resonators for the infrared emitted by the underlying surface. By choosing the right size spheres, the frequency of the resonators is tuned to be that of the so-called “atmospheric window”. This is the band of frequencies that is not significantly absorbed by any of the greenhouse gases. Infrared (IR) at that frequency pretty much slides right past the water vapor, the carbon dioxide, the methane, the ozone, it misses everyone and goes straight out to space.
In other words, it dodges the greenhouse effect …
Now, I’m left with some questions.
First, is it possible-to frequency-shift infrared radiation in this manner?
Next, what does the emission curve for this material look like? As an example, here’s a typical curve from MODTRAN showing the absorption of upwelling longwave radiation:
The smooth colored lines in the upper right panel show the Planck blackbody emission curves for various temperatures. The uppermost green curve is the warmest, 300 kelvin. The lowest yellow curve is 22oK. The “atmospheric window” is the area from wavenumber 750 to 1250, interrupted in the middle by the ozone absorption band just above wavenumber 1000.
As you can see, the warmer it is, the more the peak of the Planck curves (smooth colored lines) is shifted to the right. Now, with the resonator the peak radiation is supposed to be shifted by the resonators to a wavenumber of around 1000. That’s just below the ozone absorption band.
So I’m very curious about the shape of that curve. If the peak shifts towards the right it would have the characteristics of a warmer surface … can you mess with the Planck curve like that, shift the peak? Not saying it’s impossible, metamaterials have bizarre properties, I’m just out of my wheelhouse here.
Finally, what can this be used for? Well, I had a scheme a while ago for solar distillation of water. This would have been very useful to cool the condensing side of the still.
More directly it seems like it could cool buildings. A coating that could cool a large building by even one degree would translate into big savings in air conditioning. Ten degrees would be marvelous.
Anyhow, that’s what I’m calling a reverse greenhouse effect … it concentrates the radiation on the band where there is minimum atmospheric absorption by greenhouse gases.
Best to all,
w.
My Usual Request: If you comment please QUOTE THE EXACT WORDS YOU ARE DISCUSSING. That way we can all understand your subject.
[UPDATE] Thanks to a tip from the commenter Johanus, the underlying paper is here. It has what I asked for above, the actual emissivity curve in the thermal IR range. Fascinating. Here’s a preview, a graph of the temperatures throughout the day:
Now, that is a beautiful thing for a couple of reasons.
One is that I love real data. It is so much more interesting that a computer model of the same thing. Facts. Observations. If I stick to the facts I know I can’t go far wrong.
Next, look at the photonic radiative cooler. Throughout the day it is running cooler than the ambient air temperature by something on the order of 5°C … so for all the folks who said it was impossible, there’s an old Soviet joke about a Political Commissar berating someone and saying “Yes, yes, Comrade, you’ve proven that it works in practice … but it will never work in theory!” …
[UPDATE 2] After many helpful comments I’m finally understanding what’s happening. It’s not so much related to the selective emission of longwave radiation (thermal infrared). Instead, Kirchoff’s law says that frequency by frequency, emissivity equals absorptivity. So selective emission in a narrow band also means selective absorption in the same band.
The selective absorption is important because the “atmospheric window” also means that there is very little downwelling radiation in that window. Here’ MODTRAN again, showing the downwelling radiation from the viewpoint of the surface looking up:
Now, we can see that as expected, we have a lot of downwelling radiation. With the given parameters shown at the left, it’s shown at the top right as “Iout”, about 260 W/m2.
But notice … almost none of that is in the atmospheric window. The photonic material selectively absorbs mainly in that window … but there’s almost nothing in that window to absorb.
This is how they get the large temperature differences shown in the underlying papers. The material simply absorbs poorly where the incoming longwave radiation is, and absorbs well in the window where there’s little radiation.
At least that’s my current understanding …
w.
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http://www.colorado.edu/today/2017/02/09/newly-engineered-material-can-cool-roofs-structures-zero-energy-consumption
Looks like they have their prototype machine up and running producing this material.
I note they have had a 3 million dollar grant to do this, perhaps some good can come out of this taxpayer funding?
The link does not mention climate change at all, that was just hype from the ‘Science Mag’.
My reading was that it was a grant for development, not production
Nobody tells me in my other business and scientific activities to quote exactly what I disagree with. It sounds like some kind of pedant trying to drag everyone else down in grammatical argument. Real science doesn’t have many grammatical arguments because by the time we flew the first 50 probes around the universe we have names for everything in real science.
Like the words “scamming pseudo-science fakes” for the people who tried to tell the world there’s a Green House Effect.
We elected a president who feels the same way and knows what an alarmist profiteer sounds like.
And acts like.
They act like if we all just used the right words, they wouldn’t be promoting fraudulent scam as sound science.
Trevor A February 13, 2017 at 4:18 am
Nobody told you that here either. Since you’re too much of an arrogant unpleasant fellow to actually quote what I said, here it is.
It was a POLITE REQUEST, so you’re totally misrepresenting what I said. And you’ve just given us a wonderful demonstration of exactly why I put the request in there
As your reward for totally misrepresenting what I said, you can now be today’s poster boy for why I make the request—to keep nasty folks like yourself from claiming I said something I didn’t say.
As to whether a greenhouse effect exists, you’re denying basic physics and exposing your abysmal ignorance through your foolish claims.
w.
The Steel Greenhouse 2009-11-17
There is a lot of misinformation floating around the web about the greenhouse effect works. It is variously described as a “blanket” that keeps the Earth warm, or a “mirror” that reflects part of the heat back to Earth, or “a pane of glass” that somehow keeps energy from escaping. It is none of these things.
People Living in Glass Planets 2010-11-27
Dr. Judith Curry notes in a posting at her excellent blog Climate Etc. that there are folks out there that claim the poorly named planetary “greenhouse effect” doesn’t exist. And she is right, some folks do think that. I took a shot at explaining that the “greenhouse effect” is a…
The R. W. Wood Experiment 2013-02-06
Pushed by a commenter on another thread, I thought I’d discuss the R. W. Wood experiment, done in 1909. Many people hold that this experiment shows that CO2 absorption and/or back-radiation doesn’t exist, or at least that the poorly named “greenhouse effect” is trivially small. I say it doesn’t show…
So much warmist drivel you have there in those three posts, Esch. Nobody can fake having a real scientific education for long, because the laws of thermodynamics are so simple, so inviolable. You never were destined to go down in the history of science as anyone but a darkener and obfuscator: a massage therapist trying to pass himself off as a physicist and mathematician. You’re neither.
Wander off the reservation and get caught in a 1 to 1 side-by-side debate on whether the
fraud
you have been ”teaching” for the past 10 years
is real.
You have a new mandate from the real scientists if you wondered, whether we were talking to you:
It’s fraud.
End of your [pruned].
Those three articles are disgraceful is what they are and you should be ashamed to have tried to [pruned] such worthless quack-0-pseud-0-dynamics onto the face of humanity and scientific discourse.
You will most definitely be remembered as one of the
frauds
who trashed the name of science, Esch. That’s just all there is to that. If people thought you were a legitimate scientific thinker, they’d be asking you for your opinion.
Real scientists cover the earth: we’re everywhere, we make the world run. None of us will touch you with a stick long enough to drag carrion from a roadway.
Specifically because you claim you thought you were speaking intelligently in those three addled attacks on science.
You can’t have two shells whose diameters are identical,
and the inner one and outer one, and have free radiant transfer you ignorant clod.
Free radiant can’t occur in such conditions: it’s conduction at that point.
You’re an idiot.
And it’s fraud.
Get used to hearing it.
You’re the idiot who owns it.
You’re gonna take the giant [pruned] science pours on it right between your thermodynamically befuddled ears.
Would you like for some people to put you in touch with President Trumps science fraud staff as another one of the Quack-0-Dynamics barking FRAUDS,
darkening science?
The masseuse going around science forums calling everyone else abysmally ignorant, when YOUR STEEL SHELLS CAN’T HAVE FREE RADIANT TRANSFER WHEN THEIR OUTER/INNER DIAMETERS ARE IDENTICAL.
You’re so stupid you can’t fathom the conditions necessary for free radiation, Willis. You thought you were talking about SIGHNTZ! the whole time.. You can’t HAVE free radiant transfer with identical diameters.
You can’t HAVE the total energy be MORE than that stated initially as output.
Any [pruned] time
you ignorant [pruned]
you show up off the reservation somewhere and start telling everyone you’re going to explain your
steel shells of abysmal stupidity from the masseuse who thought he was a physicist.
You dumb-assed [pruned] loser. THEY’RE THE SAME DIAMETER.
Your TOTAL ENERGY is MORE than ALLOWED. That’s just scanning through the [pruned]-for-brains garbage.
No telling how many more bombasitic idiocies are hidden in all that fud/mud/dud physics.
*shakes head* YOU are the MASSEUSE screaming at REAL SCIENTISTS that your FRAUD is the REAL stuff, and
WE’RE all JUST MISLED and… DON’T KNOW WHAT WE’RE DOING.
No, you’re a mentally ill street musician, with a masseuse certificate and MAYBE a degree in psychology in 1976.
[Well, that “interesting” rant was an revelation of the mindset and patience and communication ability of (some of) those who disagree with Willis, wasn’t it? …. .mod]
[The amazing thing to me was that he could rant for that long and never say one thing about the science. I’ve put out a simple thought experiment. If he disagrees, he is free to point out just where I’m wrong … instead, he killed all those poor electrons in a science-free ad hominem attack. Man … guys like that are not good for the skeptical side of the discussion. Real scientists just point and laugh when they see that. Well, I gave it my shot, he’s obviously beyond my poor power to add or detract … -w.]
It is typical of the sort of attack on science you find here. He objects to the spheres being the same size. He (I am assuming a he) does not acknowledge that Willis explained (several times, almost to the extent of laboring the point one might have thought) that the spheres were not in reality exactly the same size, but the difference in area was very small and could be neglected for simplicity. One could of course do the calculations accounting for the difference in areas, and the result would be almost the same.
However, having spotted this simplification is not a totally accurate representation (for good and well explained reasons), he is like a dog with a bone. Aha! I have spotted this problem! That means Willis must be an idiot and I must be clever! This is not untypical of the sorts of arguments one sees.
Everybody needs to read the actual article, its not some kind of magic, it reflects incoming sunlight while still allowing radiation of the heat from the body its applied to. Cleaver and probably works.
Begs a question that has popped up to me from time to time, does a degrease in solar radiation allow for an increase in geothermal transmission to space?
In principle.
I don’t think geothermal has any practical meaning whatsoever, it is smaller than any small CO2 ghg effect and smaller than the variation in top-of-atmosphere radiation. Oceans are cold from below, and they don’t much warm in 1000 years it takes for them to circulate.
Does it only work outside on a cloud-free day?
It probably works best with a cold object like clear sky. It probably works to some extent even if there are clouds.
I don’t think it has anything to do with the wave length of radiating IR, I think it is simply reflecting all in coming energy while at the same time not blocking any out going radiation from the object it is covering. If the emission spectrum was relevant then it would have a cooling effect at night as well, I don’t see them make such a claim anywhere.
@ur momisugly Bob Boder, from the article:That helps the materials cool back down, particularly at night when they are no longer absorbing visible light but are still radiating IR photons.: “
Asybot
Everything cools at night, that doesn’t mean if I put it on an object at night that it will be 10c cooler than everything else before the sun comes up
Hmmm. Robert F Service? There was a Robert W Service (1874-1958) who wrote a rather well known poem called The Cremation of Sam McGee. You don’t suppose …
I don’t really think the article is a hoax although the thermodynamics seem a bit unintuitive. But … it is an odd coincidence
Have to go now and remove a foot or so of snow (definitely not a thing of the past) from the driveway so I can pick up my wife and son who got themselves stranded yesterday in Dallas and Montreal respectively when all public transportation to and from BTV shut down.
Willis, you are confusing wavenumber with wavelength. Wavenumber is the inverse of wavelength and the curve looks a lot different.
Someone tell me why I shouldn’t be ordering some this morning to test for a cube SAT
A reflective surface with glass beads “pulls in heat” and cools almost any surface? It apparently doesn’t get “hot” so your delta-T remains to transfer heat from the cooling surface? If the description was prevents heating rather than cools, it might be believable. Otherwise, it seems to have some strange heat transfer. Or are we supposed to believe that these glass beads have magic properties?
Does it work any better than a reflective foil with a layer of insulation between it and the surface to be cooled? I doubt it.
“And because it can be made cheaply at high volumes…” Whoa there, Skippy. Yes, we get the idea that raising production volume tends to lower per-unit cost. Beyond that though, how cheap? Compared to what? Someone’s trying to pull the wool.
Ok. I’ve stopped laughing about the resonating balls.
It’s, frankly , a good idea. A reflective surface (Al, Au, Ag) covered by a layer of Silicon Dioxide balls( a sheet would be useless because it’s not flexible). SiO2 is crap if you want to make a spectrum with IR output because it has a horrible property of absorbing IR. Which, therefore, makes it an excellent emitter of IR.
Throw this all together and encapsulate it in a tpx sheet and what do you have? A flexible sheet (cooling) that is useful for components etc
I will now put on my builder’s hat.
You would need the same techniques as a window glass film installer. The installer may need to do some preparation on your roof to make it like glass before he can proceed. At this point I would suggest you enquire with your bank wether you can take out a second mortgage.
If I was doing it for you, I would give a 3 month guarantee that the film would stay on your roof.
Further thoughts. Emissivity is the ability to emit photons – usually IR at “normal” temperatures. It is related to absorbtivity (wiki) “There is a fundamental relationship (Gustav Kirchhoff’s 1859 law of thermal radiation) that equates the emissivity of a surface with its absorption of incident radiation (the “absorptivity” of a surface).”
Basically, if is a good emitter it is a good absorber. So how can we cause cooling? Simple, we need to be a good emitter (and absorber) at wavelengths where there is no incoming radiation. And a very poor emitter (and absorber) at wavelengths where there are lots of incoming photons.
If our objective is to cool, then being a good absorber at wavelengths where there is no incoming radiation does not matter, because there are no photons to absorb. Being a very poor emitter at wavelengths where there is little emission does not matter, because there would not be many photons to emit anyway.
This you must emit at wavelengths where there is no incoming radiation.
So is there no incoming radiation at the atmospheric window?
Aluminium , Silver are poor emitters but because they are in intimate contact with SiO2, THE glass does the emitting for them
I think this is what the researchers are doing-
Start with a surface sitting in the sun. If you cover it with a reflective coating, then it will be cooler.
Use a highly reflective silver coating. This is a broadband reflector (visible through infrared).
The problem with silver is that it has a low emissivity in the infrared (0.01 or 0.02).
Coat the silver film with a material that has a high emissivity in the infrared, but is also broadband transparent.
The transparent coating is in thermal contact with the silver, which is in thermal contact with the original surface.
Now, if the emissivity spectrum of the transparent top coating can be tailored so that it has high emissivity in the atmosphere’s optical window, then the thermal radiation can be transported more effectively up through the atmosphere.
However, by reducing the emissivity of the top coating outside of the atmospheric window, you also reduce the total emissivity of the coating, which will reduce the total infrared radiative power of the coating.
The important thing to watch is, when the researchers say the surface temperature is reduced by 10 C, which two situations are being compared? There are a lot of choices here.
I suspect that a high quality white roofing paint (broadband reflective and high broadband emissivity) would do just as well as this approach.
Note that coating the silver with a layer of almost any clear plastic would give the same result. The novelty in this research seems to be tailoring of the emissivity spectrum. So the comparison in delta T should be between a silver coated plastic sheet without the resonant spheres, versus the silver coated plastic sheet with the resonant spheres added. I don’t know if they did this, and don’t want to pay Science for the privilege.
They are comparing the object with the surrounding air. From the earlier paper in Nature:
Title: “Passive radiative cooling below ambient air temperature under direct sunlight.”
“When exposed to direct sunlight exceeding 850 watts per square metre on a rooftop, the photonic radiative cooler cools to 4.9 degrees Celsius below ambient air temperature, and has a cooling power of 40.1 watts per square metre at ambient air temperature.”
This is genuine cooling, not just saying that it is cooler than it would have been without the layer.
is it? Any perfectly insulate box would be cooler than ambient air in direct sunlight. Is it cooler at night would be the question, my guess is no.
Bob – yes, it works at night. It was demonstrated at night before the daytime. The problem seems to be to get the high IR emissivity at the same time as the very low UV/Vis absorptivity.
Seaice
Next question, does it only work outside?
Bob, I would guess it does only work outside – but not sure. Inside, the IR would be absorbed by the walls, and thus heat them, causing more IR to be transmitted back to the box.
It is the same reason why frost forms in areas open to the sky but not in places shielded from the sky.
Similar to nano-coatings that a friend of mine, Chhiu Tsu Lin at Northern Illinois University, has patented. HIs coating is used to cool CPU’s and LED electronic packages. Links to patent and presentation in Taiwan.
https://www.google.com/patents/US7931969
http://ord.ncku.edu.tw/ezfiles/3/1003/img/467/20080425.pdf
Presentation has information on the chemical and physical processes involved.
I was over at ScienceofDoom reading their defense of the K-T diagram using a 3m thick PVC shell thought experiment.
https://scienceofdoom.com/2010/07/26/do-trenberth-and-kiehl-understand-the-first-law-of-thermodynamics/
With 30,000 W radiating from surface 2 out into space per S-B & ε = 0.8 GB equation result is T2 of 132.8 K.
Check.
Using Q = U * A * dT and the 3m thick PVC conductivity of 0.19 W/m-K T1 = 413 K. (U = k/x & averaged areas 1 & 2. SoD got 423 K, used 43% of ave? Temp diff = 290 or 280 C.)
Check.
Insert T1 of 423 K in S-B 0.8 GB equation to get new current radiative flux from inner surface 1.
“Internal Radiation
Therefore, the radiated energy from the inner surface will be 1,452 W/m2 or a total of 1,824,900W (= εσT14.4πr12).” (413 K = 1,319)
Hold on. You can’t do that! Over 60 times the 30 kW input? Yeah, that’s energy out of nowhere!! All 100% of the 30,000 W have been transferred from surface 1 to surface 2 by conduction, there are ZERO W left for radiation.
BTW PVC is opaque so twice zero radiation.
Radiation from surface 1 is simply NOT possible no matter the surface temperature or S-B theory!!
Now 100% radiation heat transfer between surfaces 1 & 2 requires a vacuum between surface 1 and surface 2, i.e. no molecules, no conduction, convection, latent, etc. for a S-B 0.8 GB T1 of 151.5 K, a difference of 18.6 C. Energy moves, i.e heat flows, from high to low with little dT when there’s no insulative crap in the way.
Any media placed between the two surfaces that impedes energy/heat flow will increase the surface T1 temperature. This is what warms the earth, not down/“back” radiation. Placing any media between the surfaces, e.g. air, CO2, water, clouds, lucite, glass, wood, concrete, etc. will all have their unique combination of conduction, convection and radiation and inner surface 1 T1 earth warming consequences.
K-T diagram Trenberth et al 2011jcli24 Figure 10
Method A balance, mixed:
Incoming:
240 ASR at 100 km = 80 atmos + 160 surface
Outgoing:
17 convec + 80 latent + 63 LWIR = 160 surface + 80 atmos = 240 OLR at 100 km
Incoming = outgoing. That’s it, all balanced, nothing left for more radiation, certainly not up/down/back of 333.
Method B balance, 100% radiation:
15 C, 288 K, S-B BB = 390 W/m^2 with emissivity of 0.615 upwards = 240 W/m^2 OLR
You can use Method A OR Method B, you may NOT use BOTH!!!!!
And neither method A or B makes the surface warm/er. Q = U * A * dT does that as so clearly explained above by SoD.
Mr. Schroeder: You say “Hold on. You can’t do that! Over 60 times the 30 kW input? Yeah, that’s energy out of nowhere!! All 100% of the 30,000 W have been transferred from surface 1 to surface 2 by conduction, there are ZERO W left for radiation.”
The energy has not come from nowhere. You will notice that there is a long time delay between switching on the light bulb and the whole apparatus reaching its steady state temperatures. That enormous surface flux within the cavity is energy delayed by being stored in cavity radiation during that transient period. Yes, cavity radiation, a photon gas, has thermal capacity. All of the mis-understanding here is the result of leaving out the time dependence in the problem. I don’t know who blogs Science of Doom, but he didn’t clarify the issue much.
“Radiation from surface 1 is simply NOT possible no matter the surface temperature or S-B theory!!”
It is fairly fundamental that bodies emit radiation, so unless the inner surface is at 0K it will emit some radiation.
As K. Kilty says, we are talking about steady state, considerable time after the bulb is turned on. The inner wall emit 1834900W, but where does this go? It is also absorbed by the walls, as there is nowhere else for it to go. It receives an extra 30,000W from the bulb, which it loses through conduction to the outer surface.
A Watt is a unit of joules per second. You must include that time part of the unit.
I’m calling BS on this. The material will emit regardless of any frequency hole in the sky. It has no knowledge of the sky and the sky cannot focus the return back to the specific material.
Haven’t looked at the details , but it’s kind of the inverse of TiNOX which may be the material with the highest “solar heat gain” of any material yet constructed :
http://cosy.com/Science/AGWpptTiNOX.jpg
I cited TiNOX as a disproof that Venus’s extreme surface temperature could be explained as a spectral green house effect because that would require an even higher
aeratio of about 2.25 but starting with the highest reflectivity in the visible spectrum of any planet , about 0.9 versus TiNOX’s 0.05 .Indeed it is. Invert your ratio and you have a solar cooling material, if it were only that easy to produce. At almost the moment you posted this–I posted the inverse idea below.
While I won’t dispute this as innovative, essentially the same thing has been done for a long time with spacecraft surfaces to aid in flushing excess heat to space. Some of the white coatings for this purpose are pricey, but just an aluminum substrate covered with white epoxy appliance paint does a fair job. It may feel cool in broad daylight. The figure of merit for such a surface is its emissivity at thermal IR divided by solar absorptivity.
Kip Hansen and I are involved in “debates” over on Mark Boslough’s post at http://www.realclimate.org/index.php/archives/2017/01/non-condensable-cynicism-in-santa-fe/ .
I’ve just been trying to get an agreement to the most fundamental calculations of radiative equilibrium starting with the fact that gray , ie : flat spectrum , bodies , no matter how dark or light , come to the same temperature as that calculated for a black body — and in our orbit that’s about 279K , ~ 5c . I’d think for most purposes a broad spectrum “white” would be best to slow heat both in and out .
I haven’t yet gotten agreement on the generalized expression for the equilibrium for arbitrary spectra , ie : colored balls , and seem to be riding the edge of being censored . The arrogant mediocrity is appalling . The cowardice of Boslough who posted the challenge which prompted my taking up this particular battle is nakedly apparent .
Oh, THAT Mark Boslough. I had a look and I do not plan to go that way often if ever. Good luck with the debate.
The title of your article reminded me of an article on the “anti-greenhouse” effect on Titan.
http://science.sciencemag.org/content/253/5024/1118
http://www.lpl.arizona.edu/~griffith/pdf/Icarus_129_498.pdf
The haze containing organic molecules in Titan’s upper atmosphere absorbs 90% of the solar radiation reaching Titan, but is inefficient at trapping infrared radiation generated by the surface. l., Tthe anti-greenhouse effect on Titan reduces the surface temperature by 9 K whereas the greenhouse effect increases it by 21 K. The net effect is that the surface temperature is 12 K warmer than the effective temperature 82 K. [i.e., the equilibrium that would be reached in the absence of any atmosphere]
The grant providers suggest a 100W/m2 cooling effect. To be targeted at dry cooling of power stations:
https://arpa-e.energy.gov/?q=slick-sheet-project/radiative-cooling-and-cold-storage
As for “protecting buildings from heat, unless the plastic can be removed and then replaced season by season, you probably would lose at higher latitudes, where heating is most important and the most energy intensive requirement for maintaining a 72 degree interior. In cold weather, the difference between the external amd desired internal temps are far greater than the difference betweein those temps in hot weather, almost never exceeding 20 degrees, while cold interior/exterior temps can differ by twice that amount.
It pulls heat from everything it touches, so it concentrates that heat and it will finally blow up.
Down with Physics!
If this material takes heat from touching bodies, it can emit it, but its own temperature will fall only some degrees, than taking heat from the air too. This will go to an equilibrium, where incoming and emitting energy will cancel. But this contradicts the 2nd laws of thermodynamics. It is impossible to make a temperature difference without providing exergy to the system.
Certainly it is meant, that the plastic cover can cool down a body faster than this body would cool down without it. For this it has to reflect incoming radiation in the short wave region and to emit better in the long wave region, say IR.
The emitted radiation will be absorbed somewhere and heat this up again. Only part of the emitted radiation can be in the spectral region to go out from earth without absorption from molecules in the air. The rest will be absorbed.
This very special material will work only in thermal non-equilibrium, where short wave light will be reflected and long wave light absorbed. Because of its own temperature it can emit more IR than is absorbed.
I did not read the whole thing carefully enough. They claim to radiate the heat into space in one of the “atmospheric windows”, meaning frequency bands where the atmosphere is transparent. So it needs an unobstructed view of the sky in a wide angle. Won’t work under clouds. The space around us is filled with a useless thermal radiation 300 K, 300 w/m2, so I doubt the usefulness of this invention. Those glass spheres seem to be resonators, rather than emitters.
In order for this plastic film to cool a surface while passing incoming radiation to the surface (as it would have to for solar cells), it would have to have an emissivity greater than that of the surface it is placed on. Most surfaces other than bare metal have emissivity of ~room-temperature thermal IR being over .9.
If this plastic film has fluorescence, then it could shift its emissions to have effective emissivity greater than 1 at wavelengths longer than the normal peak emission wavelength for its temperature. But I don’t see fluorescence being mentioned in the article, only being brought up in comments, and I have yet to see a clear statement (as opposed to speculation) that this film actually has fluorescence.
Fluorescence has nothing to do with it, totally different physics
I am trying to post an answer to everyone about the physics behind this but seem unable to do so
“First, is it possible-to frequency-shift infrared radiation in this manner?”
The phenomenon birefringence, is used to make mineral identifications in rock thin sections under a microscope and between two polarizing lenses at right angles (crossed Nichols) to one another. It manifests itself in converting transmitted white light into colours (depending on differing indices of refraction of the minerals). The refractive index of a given mineral rotates the polarized light from below to a certain degree so that a component makes it through the second polarizer. These different colors are, of course, different wavelengths of light.
Perhaps this is totally unrelated to the phenomenon of this thread, but it suggests that shifting wavelength is an everyday experience.
The phenomenon birefringence is not shifting wavelength, but only absorbing all other frequencies without the one you see as color. This color was in the white light like all other colors. The other colors are erased by interference and reflected to an absorbing place.
You are correct. I’m guilty of an incomplete statement. Interference causes a phase shift. If you slide a tapering wedge of calcite into the field of view of the said minerals under examinaton, the colours change. This is used to count the “order” of the birefringence color but also, it can simply shift the phase, which for mineralogy is not a useful thing to do but it does.
https://www.physics.wisc.edu/undergrads/courses/spring08/208/Handouts/InterferenceFAQ.pdf
The post’s question was “First, is it possible-to frequency-shift infrared radiation in this manner?”
In other words, it dodges the greenhouse effect …
Now, I’m left with some questions.
First, is it possible-to frequency-shift infrared radiation in this manner?
Yes. It exploits the phenomenon of Fröhlich resonance.
The paper explains it well:
http://science.sciencemag.org.ezproxy.princeton.edu/content/early/2017/02/08/science.aai7899.full
“Our hybrid metamaterial is extremely emissive across the entire atmospheric transmission window (8-13 μm) due to phonon-enhanced Fröhlich resonances of the microspheres.”
Your link is useless
It’s the link to the paper, why do you believe it’s useless?
It has nothing to do with frequency shifting.. It’s simple physics
Something is not quite right on this website. I can make short comments but am unable to post long ones
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