A Reverse Greenhouse Effect

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:

MODTRAN 375 ppmv

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:

photonic-radiator-i

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:

modtran-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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274 thoughts on “A Reverse Greenhouse Effect

  1. Hmmm … Sounds like a cousin of Maxwell’s Demon. Are they limbering up to mess with the Second Law of Thermodynamics?

    • It would have been valuable if Eschenbach had explained why it does not violate the laws of thermodynamics.

      • How does the material, as described, violate the laws of thermodynamics?
        The energy isn’t disappearing – it is simply photonic energy being redirected out as photonic energy rather than vibrational (heat).

      • ticketstopper:

        How does the material, as described, violate the laws of thermodynamics?
        The energy isn’t disappearing – it is simply photonic energy being redirected out as photonic energy rather than vibrational (heat).

        You are talking about the first law of thermodynamics, which concerns energy. But this invention seemingly raises issues about the 2nd law of thermodynamics, which concerns entropy.

      • Killer Marmot February 13, 2017 at 10:35 am

        It would have been valuable if Eschenbach had explained why it does not violate the laws of thermodynamics.

        Huh? I put it up there to discuss how it works and to ask questions, not to issue explanations.

        In any case, it’s been tested and it works, so obviously it doesn’t violate thermodynamical laws.

        w.

      • @Willis

        In any case, it’s been tested and it works, so obviously it doesn’t violate thermodynamical laws.

        The bumblebee of coated films!

      • Huh? I put it up there to discuss how it works and to ask questions, not to issue explanations.

        And here I thought “discussing how it works” was issuing explanations.

        My point is that anyone familiar with thermodynamics is going to immediately wonder why this invention does not violate the 2nd law of thermodynamics. It’s an obvious and foreseeable question.

        A journalist should attempt to identify what questions are likely to arise among the readership, and try to address them in the story.

      • How does reradiation of photons violate entropy?
        After all, this happens in nature all the time as via fluorescence, among other phenomena.

    • Does it cool or is it just a good thermal insulator that stops the sun from heating the surface.

      Acrid test. Put a sheet of this wunderfilm on a table down in the basement of a house in the dark, so no sunlight can shine on it. Then let’s see it cool the table to 10 deg. C below the basement temperature.

      I’m not saying this stuff might not be a good thermal insulator.

      But stopping something from getting hotter due to natural causes, is not the same as cooling something that is not being heated by natural causes.

      G

      • It is technically neither. Heat from light is photons hitting the surface and causing atoms in the surface to vibrate – which is heat. The material absorbs the light energy then re-radiates it out as light.
        It isn’t cooling so much as it is preventing the heating from starting. For materials that are already being “heated” by light, it cuts off the ongoing energy flow.

    • “””””…… Already, the new material, when combined with a mirror like silver film, has been shown to cool whatever it sits on by as much as 10°C. …..””””””

      There’s no such thing as a cheap silver film.

      Silver does have very high reflectance at visible wavelengths, but there is no assurance that it does at thermal wavelengths.

      And no johny come lately can just slap a cheap silver film on top of a solar panel and suddenly find extra light that decades of careful research hasn’t been able to capture to raise the conversion efficiency.

      Tell them to come back when they have their inexpensive silver enhanced solar panels available for immediate installation.

      G

      • but there is no assurance that it does at thermal wavelengths.

        You use gold for IR wavelengths.
        Why they use it on space stuff(plus even though it’s really heavy, it spreads very thin).

      • george e. smith February 13, 2017 at 12:17 pm
        “””””…… Already, the new material, when combined with a mirror like silver film, has been shown to cool whatever it sits on by as much as 10°C. …..””””””

        There’s no such thing as a cheap silver film.

        Silver does have very high reflectance at visible wavelengths, but there is no assurance that it does at thermal wavelengths.

        That’s just the point George, they want something that reflects visible but not IR.

      • george smith writes “There’s no such thing as a cheap silver film”. If you would read the pdf, you would find that they use an Aluminized Mylar film under their Photonic radiative cooler. Aluminized mylar is basically what we call space blankets. The actual radiative cooler consists of “seven layers of HfO2 and SiO2, whose thicknesses are defined by extensive
        numerical optimization (see Methods), on top of 200nm of Ag, a 20-nm-thick
        Ti adhesion layer, and a 750-mm-thick, 200-mm-diameter Si wafer substrate.”

        I note that the pdf is copyright 2014, so there should have been plenty of time for this to have been developed. Makes one wonder.

    • The Ozone absorption peak is at 9.6 microns wavelength so it is right in the middle of the so-called atmospheric window. According to Trenberth only 4% of the total surface emitted LWIR EM radiation escapes to spacen that atmospheric window.

      G

      • george e. smith February 13, 2017 at 2:16 pm

        The Ozone absorption peak is at 9.6 microns wavelength so it is right in the middle of the so-called atmospheric window.

        Thanks, george. You’re right, 9.6 microns wavelength is wavenumber 1042 (wavenumber = 10000 / wavelength). As I said in the head post,

        The “atmospheric window” is the area from wavenumber 750 to 1250, interrupted in the middle by the ozone absorption band just above wavenumber 1000

        However, I’m not sure about your claim that Trenberth said only 4% escapes through that window.

        This graphic from Trenberth’s 2008 puts the number at just over 10% …

        w.

      • From a typical average surface at about 15C (288K) the atmospheric window cover about 25% of the heat, But with a typical cloud cover of 60%, only about 10% goes directly to space, Trenberth shows 40 Wm-2 out of about 390, close to 10%. But in any event, this only effects what the atmosphere absorbs. It does not effect the surface heat loss. It is about 390 Wm-2 at 15C. Some other mechanism must cause the “cooling” if any.

      • Richard, I think but I am by no means sure, that the other mechanism is that the higher radiation from the glass beads, cools them faster than the surrounding material so heat is conducted from the film material to the beads and from the underlying surface to the film. Without the beads the radiation would be distributed differently across the spectrum and absorbed by the near air and would therefore be radiated or conducted back into the film. With the beads the absorption by the air is very much less and heat conducted from the surface into the film is still radiated by the beads so the temperature of the surface drops until a new equilibrium is reached when conduction from the top of the film through the film to the surface material balances conduction out from the surface material. That temperature will be lower than if the film were not in place. The silver foil greatly reduces any radiation from the air (and sun) impinging on the surface material. The limit is reached when the resonance of the beads is insufficient to radiate more energy then the net flows by other mechanisms, including from the ambient air through the film to the surface to be cooled.

        So it should work in the dark as well as in sunlight. Its effectiveness would be reduced if there is anything, solid, gas or liquid, nearby that absorbs the radiation at the resonant wavelength of the beads and has a radiative, conducting or convection path back to the film or the surface to be cooled. Basically, the beads, by changing the energy density distribution of the radiated energy short circuit the other energy paths through air.

    • Conduction of heat from surface to gas or vice versa is slow. I thought that emission at any wavelength would be sufficient if there was convection of air. I think that strong emission at a few discrete frequencies, even if random, would give the same effect if the air above the surface was moving.

  2. I think this could work, at a casual first glance. Frequency shifting is no big deal – any absorber that re-emits does that.

    Forget greenhouse gases: this thing also needs to punch through clouds.

    My physics is too rusty to get to grips with this completely, but I’d say that for now it’s one to watch.

    • First, is it possible-to frequency-shift infrared radiation in this manner?

      It seems that the principal effect is not one of shifting wavelength but of converting thermal energy into radiated energy. It is apparently used in contact with the object to be cooled.

    • Sure frequency shifting is no big deal; well so long as it only shifts to longer wavelengths.

      That is the whole reason why the Beer’s law thing doesn’t apply.

      Beer’s law only applies to the absorption versus path length or absorbing species amount, provided the absorbed photons stay dead.

      They don’t; any absorbed energy will raise the Temperature, and eventually that absorbed energy will be radiated away as thermal radiation (at a lower frequency).

      So the “transmitted” portion of the energy entering an absorbing medium, DOES NOT follow any logarithmic law.

      Sharp cut optical filter glasses that can attenuate by four or five orders of magnitude at quite close to the cutoff wavelength, might still transmit 75% of the incident energy; just at a different wavelength.

      You really have to go out of your way to stop materials from transmitting energy.

      G

    • Suppose someone was suffering heat prostration or heat stroke. Wrap in them in one of these blankets ASAP, every ambulance should carry a few in summertime. I’m also thinking of NASCAR drivers, some of this on the outside of their Nomex, but what would be the flammability of this material? Probably pretty nasty, but perhaps just the opposite? Intriguing.

    • in the article they say that in the solar application the silver layer that reflects light is removed.

      And without the silver backing, he adds, the plastic film could also increase the power generation from solar cells, which operate more efficiently at lower temperatures.

      • At what cost? Solar panels are already cost more than they are can produce, a small increase in efficiency at big cost does not help.

      • ” Solar panels are already cost more than they are can produce”

        How do you manage to get to that conclusion?

      • Steven Mosher February 13, 2017 at 8:49 am
        Steve, just because the materials are cheap does not mean actual production will be.
        Tiny glass beads, lots of them. They will get into the air. Workers will have to wear protective clothes.

        Cogs (cost of goods sold) -the materials are often the smallest percentage, pun intended.

        michael

      • Sure, the plastic film could increase the power generation from solar cells, but it probably wouldn’t.

        The film must “suck” heat from the solar panel through conduction first, and then through convection and emission to the surrounding environment. Plastic and glass are poor conductors of heat. A regular solar panel emits heat directly via convection and emission without having to conduct its heat through an insulating blanket first. I’m not buying the glass sphere snake oil. There’s a reason why the only boast about the film by itself without the mirror is based on the weasel word “could”. Nothing but smoke and mirrors.

        The reflective layer by itself is probably what accounts for the boasted 10°C of cooling. I’ll be cooler under a mirror on the beach than my mirror-less neighbour.

      • Steven,even a small cost, assuming it is as small as you wish, is still a problem.
        Greg, I get that by adding up all the costs and determining how much electricity a cell can produce over it’s expected lifetime.
        Basic math, try it some time.

      • PS, assuming these plastic sheets go on the top of the solar cells (They couldn’t radiate heat to space if they were on the bottom), they are going to cut down the total amount of visible light that gets to the cells. Nothing is 100% transparent.
        Beyond that, if they are plastic, they are going to weather over time, which will further reduce the amount of light reaching the solar cells.

      • Indeed – if the material can take photons at wavelengths not presently well converted by PV gates, then it would increase efficiency of solar PV dramatically – assuming the re-radiation is in the right direction.
        The concern I would have is just how durable a plastic based material can be for such an application.

      • I think everyone is missing the point here, they aren’t saying there is some magical transmission of energy to space that is causing cooling, they are saying because few things absorb energy at the wavelength they are radiating at there will be little local environmental heating (small e). meaning the surrounding air, structures or body of the object it is applied to, a typical heat sink would warm everything around it thus making it self and the device it is cooling less efficient the warmer it gets, this won’t.

      • MarkW said:

        “Steven,even a small cost, assuming it is as small as you wish, is still a problem.
        Greg, I get that by adding up all the costs and determining how much electricity a cell can produce over it’s expected lifetime.
        Basic math, try it some time.”

        OK, if you’ve actually got the necessary information and done these calculations, could you share them with us? I’ve asked time after time when people make these claims, for them to show their work, because I’d like to know if it is true or not. So, please do share you calculations and results with us.

      • Steve, usually when they say something like “the plastic film could also increase the power generation from solar cells” the word “could” means something like “in a perfect World where flying Unicorns fart rainbows”; but I’m sure this is different, so we’ll just jump into our hydrogen fusion powered flying car and cruise down to the local hardware store and pick up a roll next week.

    • It would have to be on the top. But with regard to solar cells, it might be better to make cells that convert a wider band of photon energies into electricity by creating a layer that converts out of band photons into photons that the solar cells are sensitive to.

      • Go for it.

        The current record for doing that is something like 43% conversion efficiency, according to NREL and that is with knowledgeable experts doing everything they damn well know how to achieve that result.

        Nothing is left lying around for some 4-H club project to find some extra that has been missed.

        And that was done irregardless of how much it might cost to make.

        When you only have one KW/m^2 to work with, the only thing that matters is efficiency.

        Non-imaging capture optics is much cheaper than exotic PV structures.

        So knock yourself out trying to improve the efficiency.

        G

    • Don’t need the solar panels or other “green energy” anymore. Just solve the AGW problem by putting out square miles of this stuff.

    • The planet does this by converting high energy photons emitted by the Sun into LWIR photons emitted by the surface and clouds. It then does this again, to a lesser extent, when water vapor that is not in the ground state condenses in the atmosphere and the state energy is converted into broad band Planck spectrum emitted by the water in the clouds. We see evidence of this in the emitted spectrum, where around 15u, the attenuation in the H2O absorption bands is slightly more than 3db where it would be exactly 3db without any subsequent conversion.

    • Even a perfect black body will emit a spectrum which depends upon it’s temperature. This is not directly connected to the temperature of the body which emitting the radiation it receives.

    • You may look at what a black body means, what black body radiation means, and what Plank’s law is. When you find out all the nasty details, you may find out that:

      – the atmosphere is NOT in thermal equilibrium (yeap, quite different temperatures all over the places)
      – the atmosphere is NOT absorbing all incident radiation (a nasty thing is that it’s actually transparent to some)
      – the emission spectrum (which is measured from satellites) is NOT the black body spectrum (really!)

      I don’t think I should detail it more. The differences from the black body are so huge that ex falso, quodlibet can be applied to prove anything you would like if you assume it true for the atmosphere. For example, you can prove that CO2 is God and it’s bringing Armageddon.

  3. If the glass beads do preferentially emit and absorb at wavelengths with a cooler “sky temperature”, then they will tend to be more like that “sky temperature”. However, it all depends on the emission/absorption spectrum of the glass beads – which isn’t obviously shown anywhere. If it’s very wide – then the effect will be small, but if it’s narrow enough to fit in the dip (and if there are no clouds) – and if you want to be cooler, then it would work.

    • My understanding of the process is as you described it. The flip side is that the beads have low emissivity and absorption at the wavelengths are opaque. In this case, the beads try to reach thermal equilibrium with the sky temperature in the “window” as opposed to the various GHG absorption lines are. Conversely, beads made to have high emissivity in the IR absorption wavelengths should be warmer than a black body.

      FWIW, the atmosphere is “clearest” on the order of 1 to a few GHz, sky temp there is 3K, but not much heat gets radiated there.

  4. First, is it possible-to frequency-shift infrared radiation in this manner?

    Yes, it’s possible to shift from higher energy excitement to lower energy emission. It’s how fluorescent bulbs work. Gas discharge generates ultraviolet light which excites phosphors which emit visible light. link

  5. If it works you could wrap patients running dangerously high temperatures in it to cool them down

    • The problem is to shift the low energy IR to higher energies. When you start with UV (invisible to the eye) and shift it with phosphors, the lost photon energy (Stokes Shift Loss) is converted to waste heat.

      That’s why blue pumped white LEDs are way more efficient that fluorescent tubes. The blue pump photons already contribute a part of the visible spectrum. UV photons contribute NOTHING to the visible light, so 100% of the visible light suffers from Stokes Shift loss.

      G

    • johnmarshall February 13, 2017 at 2:07 am

      No such thing as the greenhouse effect.

      Perhaps on your planet there isn’t, but on this planet there assuredly is.

      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…

      • One thing that is absolutely certain is that this planet is not a steel greenhouse.

        Very often mind experiments fall on basic premise. One may reasonably consider an analogy to be analogous but due to unknowns and/or lack of understanding, it turns out not to be analogous. The problem is that we have insufficient knowledge and understanding of Earth’s atmosphere, and the interaction with the oceans.

        Water, on the other hand is a very different beast to CO2 with its heat capacity, phase changes and latent heat.

        Whilst I am not suggesting that the GHE necessarily offends the laws of thermodynamics, as Einstein observed:

        A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended is its area of applicability. Therefore the deep impression which classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that within the framework of the applicability of its basic concepts, it will never be overthrown.

        There are multiple lines of evidence that suggest that in the Northern Hemisphere, the temperatures today are no warmer than they were in the 1940s, notwithstanding that some 95% of all manmade CO2 emissions have occurred since 1940. If that is so, then perhaps CO2 is not the GHG that it is claimed to be, or perhaps the GHE does not operate as it is claimed to operate.

        We have no good data on the Southern Hemisphere (too sparsely sampled) and since we have no data on the Southern Henisphere, we have no global data worth a pinch of salt. The only worthwhile data is that of the Northern Hemisphere and that is why I cite that as an example.

        Until we know and understand absolutely everything, everything is up for grabs including the GHE as postulated by the enhanced GHE theory which has given rise to (c)AGW. I would not limit anything from debate. A closed mind does not assist understanding. It is a dangerous tool in the box.

      • Willis Eschenbach February 13, 2017 at 10:33 am

        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.

        richard verney February 13, 2017 at 2:01 pm

        One thing that is absolutely certain is that this planet is not a steel greenhouse.

        One thing that is absolutely certain is that NOBODY ever said that this planet is a steel greenhouse. That is just your sick fantasy.

        And of course, what such a claim does is that it allows you to impugn an argument without actually engaging with it.

        I’ve shown quite clearly the basic principle upon which the “greenhouse effect” is based. I’ve shown that it works even if the atmosphere is replaced by a steel shell. This provides a deeper understanding of the effect, by removing extraneous questions of which gases and absorptivity and the like.

        And because you can find nothing wrong with the idea, you build a straw man and attack that instead.

        Nice try …

        w.

      • Willis

        The irony of your response is that you do unto me the very thing that you accuse me of doing unto you. You have not quoted any comment of mine that you join issue with, still less sought to explain why you join issue.

        I consider that you have misconstrued my comment. I did not make any observation on whether your article was correct or not, I merely made a general comment,a caveat that should always be placed on all thought experiments. Your article being, as in the second paragraph making clear:

        A thought experiment shows how a steel greenhouse would work.

        At the heart of any thought experiment is the projection of assumptions that underpin and upon which the thought experiment is made. Hopefully, those assumptions are based upon the best state of our knowledge and understanding at the time when the thought experiment is made.

        However, over time our knowledge and/or understanding may change, and if so, it may be the case that the thought experiment becomes inapposite since it is not describing the real world as we later know and/or understand it to be,

    • It’s unfortunately named, but it does exist, CO2 and water vapor does scatter LWIR, Long Wave InfraRed light radiated from the Earth’s surface and results in the Earth being warmer than it would be without the scattering; this is settled science. What is poorly understood is how much of the warming is natural and how much is anthropogenic, how much more warming additional CO2 would cause, and what negative (cooling) forcings will occur and by how much.
      It’s very much a matter of “Past Performance Does Not Guarantee Future Results” as the investment community would say.

  6. Good simple thing.
    Does not absorb visible and radiates IR. Very useful to cool down smth. Important that it is cheap.
    Does not have to “shift” anything.

  7. Just plant trees-

    “The extent of the effect varies in space and in time, which complicates the issue, but large parks or tracts of urban trees can cool daytime summer air temperatures by about 10°F”

    • Yes, and if you live out in the country, be sure to plant deciduous for shade in the summer and coniferous for wind break in the winter. Properly sited trees can have an enormous effect on energy usage year round.

  8. A mirror like film would cool, or prevent much heat from reaching what ever it covered anyway. What it reflects away heats the atmosphere. This new stuff seems to/must reflect as well, with its silver film/surface but also absorb heat from what it is in contact with. It turns any heat it picks up into an emission that will not heat the atmosphere. Even a silver or white surface will reach ‘too hot to touch’ temps, just touch a stainless steel surface that’s been in the hot sun for a while. So I think I get it – ten degrees Celsius lower temps on things in the sun AND the reflected heat goes on a space mission. Frequency shifting is common technology now. I used to work on ruby lasers, 80’s, basically ruby crystals in a highly reflective chamber, water cooled, with high wattage light bulbs. A high fraction of the light, of a wide range of frequencies, from the bulbs, was absorbed by the ruby and re-emitted out of the end of the ruby into a light channel and directed, as a laser beam, onto thin film resistors, to cut until resistor value came into tolerance required.

    I’m not sure we want to cool the planet – some warmer will be suggesting we have roads and fields, roofs and mountains covered in this stuff to stop CAGW.
    I’m hopeful that warmth and extra CO2 will soon be welcomed, especially when the powers that be realise there is nothing they can do to stop it.

    • I think you’ve got the right take on it. The film absorbs heat by contact with its substrate, then in turn warms up the glass spheres that emit preferentially in a band that has a clear shot to outer space. Wavelength absorption and frequency shifting by the spheres don’t come into play.

    • Probably can’t use it on buildings in areas will cooler seasons. It seems most practical for areas near deserts or near the equator where it rarely gets cold.

  9. Here’s the innovative part, according to the article. The tiny glass spheres act as resonators for the infrared emitted by the underlying surface.

    So it’s an IR laser?
    Could this how glassy volcanic aerosols cool earth’s climate?

    • Lasers are coherent light. All these beads vibrating independently would not create a coherent beam.
      The glassy stuff doesn’t stay in the atmosphere long enough to make a difference. Beyond that, they would only have this effect if the glassy beads were of the correct size.

    • ptolemy2,

      “So it’s an IR laser?
      Could this how glassy volcanic aerosols cool earth’s climate?”

      There is something about clear spherical objects I’ve asked about a few time around here, that involves reflectance of light . I “discovered” some years ago that tiny glass beads are added to the line paint on roads, which causes it to preferentially reflect light right back toward the source (headlights in this case).

      My interest in the beads was to use them in conjunction regular liquid plastic coating, for creating a durable clear non-skid surface for the flooring of the small wooden boat I was designing (worked perfectly), but it occurred to me when pondering this global warming stuff that water vapor particles that were tiny, would (owing to the dominance of surface tension at that scale) be spherical.

      Hence, tiny water droplets would (I highly suspect) also tend to preferentially reflect light directly back at the source . . and this effect might play a role in either or both; the slowing of nighttime cooling, and possibly some small variation in global temps due to solar cycles, owing to variation in cosmic rays reaching the atmosphere, which effect small water droplet formation, as I understand it.

      It’s not a laser effect, but is a sort of synchronized directional light emission effect I’m imagining . . and I’m pondering how it might play a role in this film’s (apparently) unusual properties . .

  10. 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?

    In a word, no. There is no process to mess with the Plank Curve, shifting it around.
    BUT: That is not what is going on here. This is spectral absorption and emission. So you can absorb and emit at certain frequencies characteristic of the molecule. The question now becomes:
    Can you absorb energy at one frequency, then emit that energy at a higher frequency (energy)?
    Again, no

    For people not familiar with spectra outside the Plank Curve, here is a link to the IR spectrum of methane. Not because it is a GHG, just a random example of an organic molecule with an unremarkable spectra.
    http://webbook.nist.gov/cgi/cbook.cgi?ID=C74828&Type=IR-SPEC&Index=1
    (scroll down)
    Note that it is utterly different from the Plank Curve.

    Note:
    commieBob says yes, above. He is right for the question he answers, which is about spectral absorption and emission, with the emission at a *longer* wavelength (lower energy) than the absorption.

    The problem here is shifting around the Plank Curve which is a completely different animal. Also, we have the case where we need to absorb at a longer wavelength (lower energy) and emit at a shorter wavelength (higher energy). There is no way to do that at all. (Outside of a 2-photon process which is terribly inefficient, vis. RAMAN spectroscopy.)

    • What about the fact that it is absorbing heat energy, I presume, from what it is in contact with. Wouldn’t this make more energy available for the higher energy wavelength? Also, there could be the evaporative cooling principle, analogue, going on somehow – as in a few water molecules at the surface receive K.E. from other molecules hitting it just right, they lose energy, the one gains most and has enough energy to leave the surface and evaporate. Ave speed of air molecule 500m/s, some, just a few, have, at any one time, a velocity as much as 10,000m/s! A similar principle could be going on here, where electromagnetic wave emission occurs at higher frequency when two or more lower frequency w/ls give up their energy.

      • One thing to look at is the Top MODTRAN graph Willis posted. The uppermost Green line for 300K corresponds to about room temperature. You can see that the peak emission is at 600/cm, and falls to about 30% of peak at 1250/cm. That, in short, is what this system has to work with at room temp. The authors claim they radiate at 10 microns, or 1000/cm. So anything below that level (in 1/cm) will not play a part. So they are only working with the right hand corner of that plot. They say they use 8 micron beads acting as resonators, so that would be 1250/cm. That means they absorb at 1250 and emit at 1000. (Maxwell’s Demon goes back to his corner.)
        The whole thing looks like it would be more efficient at higher temperatures like 50C or 100C, where the peak of the Plank Curve is shifted to higher wavenumbers. This would provide more source IR at 1250 for the system to work with.
        But that is an unremarkable outcome because hot things lose heat more rapidly than warm things anyway.

        “where electromagnetic wave emission occurs at higher frequency when two or more lower frequency w/ls give up their energy.”
        No! That is a two photon process, which is ungerate, or forbidden.

    • If you have a material, which can absorb 90% at wave length smaller than say, 1 micron, and absorb only 10% at longer wave length, this material will heat up in sunlight and can not emit the heat as good as receiving it. This is used for wave length sensitive receivers. So if this material is at night without incoming light in the short wave length, but has a certain temperature it can emit energy proportional to the Plank Curve with 90% in the short and 10% in the long wave length region. If you now radiate heat of long wave length on this surface, it will absorb 10% of it and heat up. But most of the emission will be in the short wave length. There is no transformation of photon with long to photon with short wave length, but only energy exchange between the body of the material to the environment via radiation. This has nothing to do with a 2-photon process.
      Suppose now, the absorption characteristic is just opposite to the one mentioned above.
      Good absorption and emission at longer wave length and bad at short wave length. This material can emit heat better than absorb the incoming energy from the sun, which is mostly in the short wave length. These materials have long been used for coatings of radiators. They look white, but radiate very good in the IR. It’s name is ZnO.
      Mother nature has made such materials long time ago. Every leave from a potato plant cools down in night more than the surrounding air. By this the surface is colder than the air and water vapor condenses on it.

  11. There is no such thing as a greenhouse effect in the atmosphere. So-called “greenhouse gases” cannot trap heat and they cannot transfer heat from a cold atmosphere to a warmer earth. To believe otherwise is to believe in fake physics. What is happening here (if it works) is radiative heat transfer from a hot surface to space. To call it a “reverse greenhouse effect” is just dumb and is pandering to alarmism.

    • What greenhouse gases do is slow down loss of heat from the earth. The 2nd Law only puts a requirement on the direction of net flow. The surface loses heat less when it is facing greenhouse gases than it does when facing deep space through a GHG-free atmosphere. Slowing heat loss from the surface (which is outgoing IR minus downwelling IR) makes the surface warmer than it would otherwise be.

    • Molecules in the air absorb radiation and emit it in every direction without knowing if there is a hotter body in the direction they emit half of the energy. They effectively reflect half of the energy, which comes from the surface of the earth back to it. Certainly they are colder than the surface temperature of the earth, but the energy loss of the earth is lowered down, and so more energy stays here, heating up the mean temperature of the atmosphere. This effect is named “Greenhouse effect”. It has nothing to do with a real greenhouse. There is no glass window, but molecules which reflect radiation back to earth. This is real physics. You have not to believe, but can prove it yourself.
      You can make a simple experiment yourself. Put your hands in ice water and take them out, when they are cold enough. With a thermometer you will measure a temperature lower than the temperature of your face. Now hold your hands very close, but without touching, in front of your face. You will certainly feel a warmth, because the surface of the hands reflect part of the emitted radiation from the face back to your face. So the skin can not cool down as fast as it would without holding the hands in front of the face. This is very similar to the earth’ reduced energy loss by reflecting radiation back from some matter above it.

      • The CO2 molecules that have absorbed IR photons don’t always lose that energy by radiative emission. Mostly they lose it by kinetic collision with other molecules. The ratio between these two forms of energy loss can be described by the mean time it takes to re-radiate an absorbed quanta versus the mean time it takes to collide with another molecule. But the mean time to collision in the zone where CO2 is absorbing IR in the atmosphere is far shorter than the mean time to re-emission. Which just means that most of the energy collected by CO2 becomes kinetic energy of the other molecules around it [heat]. [this process is not the full AGW theory because it alone wouldn’t account for the claimed temperature rise. For that some sort of amplification is tacked on].

    • Phillip,

      If what you say were true, then the climate debate would have been over long ago in favour of us climate sceptics.

      Experiments with radiating/absorbing gases such as water vapour and CO2 show that your assertion is simply not correct. Furthermore, empirical laboratory conclusions conform exactly with standard thermodynamic theory.

      Assuming steady state energy flow, any gases (e.g. atmospheric water vapour and CO2) that absorb radiation from a warmer source (e.g. the earth’s surface) and emit radiation to a cooler sink (e.g. space), will cause the intermediate radiative/absorptive gases (and also, by thermal equilibration, any non-radiative/absorptive gases) to have a higher temperature than otherwise.

      Strong evidence: The earth’s lower atmosphere has an empirically measured near-ground mean temperature of around 288K (15C). The Moon, at the same average distance from the Sun as the Earth, has a measured mean surface temperature of around 200K (-73C).

      The battle you should be fighting is the one that most climate sceptics nowadays pursue – to point out that the additional warming effect due to man-made CO2 is negligible. This is clearly evidenced by the data, namely a rise in lower atmospheric temperatures of under 1C per century, with no significant environmental consequences, despite the best (and increasingly desperate) efforts of climate alarmists to argue otherwise.

  12. bubblewrap on windows keeps heat IN rather well in winter, and keeps cool air IN in summer.
    simply spray water from a mister to make it tick OR bluetack a few spots on edges.
    you still get light in, bonus privacy;-) and saves a bit on powerbills;-)

  13. I call BS on this article because it claims to work by “pulling” heat from the surfaces it touches:

    The film absorbed only about 4% of incoming photons. At the same time, the film sucked heat out of whatever surface it was sitting on and radiated that energy at a mid-IR frequency of 10 micrometers. Because few air molecules absorb IR at that frequency…

    Imagine what these surface molecules experience when the plastic film draws near. (Let’s assume it’s daytime in a very hot climate, T=35C). So they’re all just minding their own business and emitting long-wave IR (because it’s hot, remember?). Suddenly, they feel this giant suction force, from above, trying to suck the heat out of them. But resistance is futile, they finally give up and start emitting long-wave IR (because it’s hot).

    Wait a minute, they were already emitting long-wave IR (because it’s hot), at the “earthshine” wavelengths (~10u), in accordance with the laws of physics. So what did the film do? (besides get slightly warmer from absorbing all those photons and rebroadcast them isotropically).

    So, is the film acting like a “Planck Amplifier”, remotely signalling the surface molecules to release more heat? But there is no such thing.

    Pure BS.
    :-|

    • Totally agree. Absolute BS. I’m too busy laughing about it to come up with a list that shows this is wrong and unworkable. Effin ‘resonating glass balls’. Give me a break.

    • It’s not as simple as a fairy tale.

      Different bodies have different emissivity in IR and they might not be ‘black bodies’. As a curiosity, a sheet of a shiny metal can become hotter when exposed to the Sun than the same sheet painted… black (to not be confused with the already mentioned ‘black body’, though). The secret is in the IR emissivity, despite the painted black one having a visible (sic) disadvantage in the visible spectrum.

      The ‘heat sucking’ is indeed hilarious, though.

    • No BS at all, it’s simply emissive cooling, the exact same property that makes deserts cool down rapidly at night.

  14. This might help explain what is going on.

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

    The unfortunate use of “greenhouse effect” label should be discouraged.

    It doesn’t work for real greenhouses (or glasshouses).
    The ‘atmospheric’ greenhouse effect likewise is too small to be measured.

    Sure CO2 absorbs around 15um and this energy is partially lost to neighbouring molecules by collision and less by re-emission .
    These other molecules include H2O which numerically swamp CO2 and also have preferential emission at lower excitation wavelengths.
    Then any overall local heating is swept away by convection which is a much more efficient heat transfer mechanism.

    So the ‘atmospheric’ greenhouse effect is too small to be measured.

    • The fact that about 1% of the outgoing radiation is absorbed by water vapor and CO2 molecules is enough to heat up this zone in the atmosphere. If this energy is partly radiated back to the earth, the heat loss of the earth will be smaller and it will heat up a little. The radiation laws say, that the emitted energy is proportional to the fourth power of the absolute temperature. So if the earth has to emit 101% of the formerly emitted energy, the temperature has to rise about 0,25% of 288K. That is 0.72 degrees. This effect has been measured. If CO2-concentration will rise further, it is very likely, that more radiation will be absorbed and emitted back to the earth. What will happen, if 5% comes back and shall be emitted to the outer space? The temperature will go up 1,22% of 288K, that is 3,5 degrees. If you are young enough you will probably fell this climate change before you die. Your children and grandchildren will ask you, why you didn’t act?

      • Because of this:

        I want my grandchildren to be able to have enough food to eat. More CO2 means more food for them.

        Would you like your children and grandchildren to starve to death?

        Bad, bad grandpa.

      • “The temperature will go up 1,22% of 288K, that is 3,5 degrees.”

        No, it could go up, if there were no other changes. But, there are always countervailing reactions which tend to oppose a shift in state from a given equilibrium condition. Always.

        “Your children and grandchildren will ask you, why you didn’t act?”

        They will look upon it as we look upon Lord Kelvin’s prediction that the Earth’s supply of oxygen would be exhausted in 400 years, as a naive prediction based upon faulty and incomplete knowledge. They will ask, “how did you ever fall for this?”

    • “So the ‘atmospheric’ greenhouse effect is too small to be measured.”

      That’s why they have to constantly adjust global temperature data. Otherwise, the effect would be too small to scare anyone (other than a few snowflakes and pajama boys who are afraid of their own shadows).

      • ” Your children and grandchildren will ask you, why you didn’t act?”
        Because grandchild, we love you and are making sure there is food on the table. For me and granny and your and your brother, sisters and Mom and Dad!

  15. 1. Haven’t they just re-invented retro-reflective material – as what traffic signs are typically made of?

    2.0 Maybe I missed it but they always seem to be talking about ‘radiating to the sky’ and hence being outside, So why not just paint your object white? Or if they want to radiate more, follow the example of camel-riding Arabs in the desert and wear (paint it) black?

    2.1 They say ‘cooling’ But again as in 2.0, the ‘cooled’ object is simply not getting as hot by virtue of the incoming solar being reflected. Cause and effect hit the blender yet again.

    3. Resonance is resonance, it is *very* frequency selective. 8u beads will resonate at half-lambda (16u wavelength or about minus 92degC, 1 lambda (plus 89degC), 1.5 lambda (plus 273degC) So you make different sized beads but you can easily see that quality control of the size is critical.

    4. Every time a (heat) photon interacts with matter, you can regard it as being frequency shifted. All these interactions are basically heat to mechanical conversions, a-la Carnot. Those conversions are not 100% efficient because the exhaust of the engine can never be 0 Kelvin. Such a heatsink doesn’t exist. What happens is that the original short (ish) photon is shattered into a myriad of longer wavelength photons. Energy is conserved but not photons

    5. They say their glass beads are great emitters (hence coolers) because they resonate. Haven’t they just shot down the entire theory of Global Warming. Carbon dioxide molecules (and water) are great resonators, great absorbers and hence great emitters. If their film works as the imagine it does and cools by being a great resonator, so do (extra) CO2 and water molecules in the atmosphere.
    GHG molecules absorb energy just like the shredder in your office absorbs sheets of paper, reasonable quality stuff goes in and scrambled garbage comes out.

    6. Not least, how long is a sheet of plastic going to last exposed to the sun, especially clear plastic. Plastic can only be protected (to a limited extent) from UV damage by making it opaque.
    So just like Global Warming Theory, these guys have utterly utterly bamboozled themselves.

    • “They say ‘cooling’ But again as in 2.0, the ‘cooled’ object is simply not getting as hot by virtue of the incoming solar being reflected. ”

      Not according to the papers, if my understanding is correct. The material does reflect most of the incoming radiation, which prevent it heating. However the key aspect is that it also emits IR radiation because it is warm. If it is not absorbing radiation and it is emitting radiation it must be losing energy, which is cooling.

      The insight must lie in the “tuning” to wavelengths in which the atmosphere is transparent.

      1)Trying to think this through, if we placed an object in space it would be warmed by the sun. If we could cause all the incident energy to be reflected, then this object would not be warmed by the sun. It would emit IR black body radiation, so would cool.

      2)Now we surround this object with a layer that absorbs the IR black body radiation emitted by the object. This would cause the layer to heat up. This would necessarily at least slow down the heat loss, as some of that energy would come back to the object.

      3)If we can get the object to emit at wavelengths not absorbed by the layer, it will cool faster.

      The above is a way of thinking about it that seems helpful to me. If you think it is in error please let me know where you think I have gone wrong.

      • Shame they did not provide a thermal camera view of the effect. That I would think would make the description a lot easier to decode.
        I wonder why they did think of doing that?

  16. Just noting that your Modtran display is from 70 kms up “looking down” (with no clouds). So it is showing emissions upward in a clear sky environment from the surface and from the atmosphere below 70 kms height.

    The CO2 emission spectrum is at an intensity of -50C which means it is emissions from CO2 in the stratosphere (probably going to space eventually). Others are emissions from water vapor and atmospheric windows (probably also going to space).

    Run it from 0 metres surface “looking up” and now you are seeing absorption of long-wave emission. Put some clouds in there too and now it is a pure blackbody curve.

  17. Thinking abut the intuition of this. Thermodynamics says that heat will flow from the hotter to the cooler, or source to sink. For an object sitting in the atmosphere we normally think of the sink as the atmosphere in which it sits. But if we can connect the source to outer space we can “allow” heat to flow from source to sink and cool below the temperature of the atmosphere.

    Energy will flow then from atmosphere to object, but I guess this process is very slow.

    • A good way of looking at it.

      This also means it cant/wont work indoors and wont work well outside on say vertical building walls/windows where there are other nearby buildings. To maximise the effect the emission path to space should be as unimpeded as possible.

  18. 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 tells me in my other business and scientific activities to quote exactly what I disagree with.

      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.

      My Usual Request: If you comment please QUOTE THE EXACT WORDS YOU ARE DISCUSSING. That way we can all understand your subject.

      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.

      Like the words “scamming pseudo-science fakes” for the people who tried to tell the world there’s a Green House Effect.

      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.

  19. 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?

    • does a de[c]rease 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.

    • 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.

      • @ 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

  20. 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 …

    There are strange things done in the midnight sun,
    by the men who moil for gold;
    The Arctic trails have their secret tales
    That would make your blood run cold;
    The Northern Lights have seen queer sights,
    But the queerest they ever did see
    Was that night on the marge of Lake Lebarge
    I cremated Sam McGee.

    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.

  21. 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.

  22. “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.

  23. 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.

  24. 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

  25. 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.

      • 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.

  26. 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.

  27. 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.

  28. 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 :

    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 ae ratio 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.

  29. 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. \frac{\epsilon_{Thermal}}{\alpha_{Solar}}

    • 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.

  30. 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]

  31. 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.

  32. 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.

  33. 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.

  34. “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?”

  35. 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.”

  36. It seems to be a very efficient reflector of incident sunlight. That stops it from being heated up like its surroundings.

    It seems to be an efficient IR emitter, too. It reminds me of the way some clear plastics with parallel sides trap incident light by internal reflection and the light is emitted at the edge of the plastic.

    I suspect that in this case the IR gets trapped inside the glass beads by internal reflection then preferentially emits at the “top” of each bead where the covering of encapsulating plastic is minimum. This may be fortuitous rather than by design, but it means that the photons are mostly emitted away from the material.

    So it seems to work by reflecting incoming energy very efficiently and emitting outgoing energy directionally rather than in all directions.

    I don’t think that greenhouse gases, atmospheric windows or phase shifts have anything to do with it.

      • I also don’t see why the IR must be at the “window” wavelengths. Although on the face of it it seems to make sense that the energy is “dumped” in outer space, but why would it make any difference to the object if it were “dumped” into the atmosphere? As long as it emits IR would it not cool, whatever the wavelength.

        On directionality, it would not matter if the balls emitted downwards as well as upwards as long as some of the photons were emitted away from the object.

      • “I also don’t see why the IR must be at the “window” wavelengths.”

        Because IR radiation at other frequencies is blocked by the atmosphere. 8-13um is called the sky window is it is one of the few frequency ranges where IR does not get bounced back by the atmosphere.

      • Chris, thanks for the reply, but it is not quite the answer. Say the photon from the box was intercepted by “the air” 100m from the surface. The box does not know this and it has still lost a photon, so would still have cooled. It would not “bounce back” to the box. Why does it matter that the photon travels all the way to space? I mean, if it were absorbed by the ozone layer we would not expect that to be re-emitted back to the box.

        Update 2 seems to have answered this point. There is little downwelling radiation at these wavelengths (the window), so because emissivity = absorptivity (for a given wavelength), the frequencies where the material is a good emitter (and hence absorber) there is no incoming radiation to absorb.

        This means the “escape to space” argument is a bit of a red herring, although possibly related to the reason why there is little downwelling radiation at this wavelength.

  37. Some people don’t seem to understand the principle behind this.
    I will try to explain:
    First of all, forget about the resonating balls thing because it is science speak to dazzle the ignorant,whatever effect of the size of the balls will be lost because of their inclusion in the TPX (film). Some may disagree.
    The principle is quite clever. Over a highly reflective surface (Au, Ag, Al), really poor emitters, you place SiO2 (glass), which is quite transparent to SW radiation. At longer waves , glass is quite poor at transmission, which makes it an excellent emitter (Kirchoff’s Law).
    The metal backing picks up the ‘heat’ and passes it to the glass because it can’t emit but the glass can. It’s not a conspiracy, it’s just basic science. The glass then emits.Glass balls wil ,of course, make the film more flexible than a glass sheet.
    Practical application for domestic use:
    Check your bank about applying for a second mortgage.
    For the film to be effective it has to be in intimate contact with the area it is cooling.
    Good luck doing that with your tile or corrugated roof.
    It would need massive preparation before application, think film on your smooth car windows.
    As a tradesman, I would tell you to go f@ck yourself.
    If I took the job I would only give you a 3 month guarantee that most of the film would stay on the roof.
    Willis and I could make millions on instalation of this stuff but we would need some south pacific hideaway.

    • Alex,

      I like your humour. Just one small point…

      Whether or not the device is viable, I don’t think you are correct to say that the cooled object under the shield has to be in intimate contact with it. If the device works at all it would also cool the air below by convection. Thus it could (in principle!) be used to cool a (sealed) room to below ambient.

    • Alex February 13, 2017 at 8:21 am
      Some people don’t seem to understand the principle behind this.
      I will try to explain:
      First of all, forget about the resonating balls thing because it is science speak to dazzle the ignorant,whatever effect of the size of the balls will be lost because of their inclusion in the TPX (film). Some may disagree.

      I disagree, the size of the balls will have an effect if the refractive index difference between the media is non-zero, the Mie scattering pattern of the beads in the paper clearly shows a significant difference.

      The principle is quite clever. Over a highly reflective surface (Au, Ag, Al), really poor emitters, you place SiO2 (glass), which is quite transparent to SW radiation. At longer waves , glass is quite poor at transmission, which makes it an excellent emitter (Kirchoff’s Law).

      The paper is about plastic not glass.

      The metal backing picks up the ‘heat’ and passes it to the glass because it can’t emit but the glass can.

      The metal backing reflects visible but transmits IR, and the thermal IR from the surface interacts with the beads which then emit in the ‘window’ region.

  38. There is already a reverse greenhouse on the surface of water, its called surface tension and it works a treat.

  39. Well you still have convection to deal with. The surrounding air will warm the surface to air temperature.
    And now that I think about it I don’t think this thing can work. A black body will radiate more heat than any other surface. Whether the atmosphere radiates it back or not doesn’t matter much. Since most of the re-radiation would occur high in the atmosphere and would not make it back to the this surface.

  40. It’s possible this same effect is what causes the decrease in net radiation, only instead of little glass sphere’s, it’s little water sphere’s.
    As the condensing water becomes later and larger collections of molecules, at some time they will cross the proper dimension to radiate at 15u, a large increase in emitted IR during the middle of the night would be one explanation for the drop in this graph.

    • Very interesting plot. However, I doubt that CO2 has anything to do with it. The high cooling rate is due to heat leaving through the atmospheric window. When the relative humidity reaches 100%, a very thin fog forms and closes the window. (Fog is a full spectrum radiator.)

      Using a green laser, it is possible to see the nearly invisible fog several feet above your head.

      Unfortunately, the blue curve does not have a scale and there is no information on where, or how, the “net radiation” is determined.

      • First, the scale is the same, just W/m^2. And it’s not just the optical window at high speed, it’s much wider (though without a spectrometer..), because when the cooling rate has dropped, the temp in the window is still about the same delta to ground. https://micro6500blog.files.wordpress.com/2015/08/july31th2015-8_00am_cleardryuhi-annotated.png
        I suspect something very much like the magic foil. Except instead of silica, it’s water blobs floating mid-air. As air temps bang into dew point, you get that slight fog (visible or not, I’ve just taken pic’s of galaxies during the slow rate many times).
        I note co2, as it’s radiative forcing would still be embedded into either rates, it’s just that doesn’t matter in switching regulators, though as also noted it will leave a little of the residual energy until the nights get longer. And generally, co2 has minimal impact on morning minimum temps, the warming of the last 40 years is maybe 5% co2, the rest is just changes to global water vapor distribution.

  41. The only way to cool a surface exposed to direct sunlight is to make the surface more reflective. The silver does that. These people have invented “The Mirror.” Wow.

    There is mention made of a grant for dry cooling of power plants. So, some fool at the DOE got run by these clowns. Down with DOE! Up with Perry! Up with Trump!!!

    • Thanks, Kip.

      There is also a free review article from 2016 on this technology area here-

      onlinelibrary.wiley.com/doi/10.1002/advs.201500360/epdf

      Also, this is an old idea in general. US Patent 3043112 was issued in 1962- “Method and means for producing refrigeration by selective radiation”.

  42. Willis,

    “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 …”

    I don’t see any reason to think a small area would be significantly cooler because the IR from it was not intercepted by the atmosphere . . I don’t think that’s the “trick” involved here . .

  43. Can I order 45 squares of shingles, and posibly some opaque windows please? I would also like a canopy/tent to use at the beach made from this also. TIA

  44. If I understand it right, it does not cool the object down. it reflects incoming IR. Tuning to the atmospheric IR window has the only sense – it reflects preferably the band where sun can warm the object up directly. So where it helps is preventing objects in direct sunlight to warm up.

  45. So…what happens when it gets dark, will the miracle blanket allow the object it has been protecting from the heat to cool down? Nope? Dang!

  46. The first clue this BS:

    “Cooling is a significant end-use of energy globally and a major driver of peak electricity demand. Air conditioning, for example, accounts for nearly fifteen per cent of the primary energy used by buildings in the United States. A passive cooling strategy….”

    Everyplace I can think of ‘air conditioning’ includes heating. In Virginia we hand a mild winter climate with a 30 degree differential temperature (70 inside, 40 outside) for heating but some places could 60 degree differential temperature. On a hot humid summer 15 degree differential temperature on average.

    So, the first thing you need is insulation to reduce energy use. Then you have to account for moisture. Moisture condensing on colder surfaces will reduce efficiency of insulation and cause mold. In other words, it is important to do it correctly.

    We bought our split level house in Virginia in the spring but did not move in July when we discovered the old system could not keep up. I found that the attic was not properly vented and 130 degrees. The vertical wall were not insulated either. You feel the heat going upstairs. First I installed a thermostatically controlled power vent. Next I installed reflective covered foam insulation board on the vertical walls that is also a fire barrier. Then I put a reflective barrier on top the insulation over the ceiling joist. After completing the project, the a/c could keep up and upstairs felt cooler.

    Reflective heat barrier material were developed for space suits. Think of shiny aluminium foil with bubble wrap in between. For the attic get the kind that lets moisture escape. Added to existing insulation, it is more effective for summer than winter based on test results.

    The bottom line is that there are products that already serve the same purpose. Nothing to see here folks, keep moving.

  47. I am failing to see the mystery here… The material is absorbing mechanical energy (heat) from the material it touches, and emitting the energy as IR photons tuned to a narrow range. The reflective surface keeps the IR photons from being reabsorbed by the underlying material, hence improving the “cooling effect”. Why is this violating any natural laws? You are converting mechanical heat (vibrating matter) into radiant heat (IR photons), and then directing (reflecting) the photons away.

    • It would seem, at first glance, to violate the 2nd law of thermodynamics.

      It doesn’t, of course, but that’s the way the Science article kind of reads when it says that the material is capable of cooling the underlying surface by up to 10 C. At a minimum, an explanation is needed.

  48. “Cheap plastic film cools whatever it touches up to 10°C”

    I think a more useful metric would be maximum BTU/hr over a given surface area.

    • In the underlying paper:
      “and has a cooling power of 40.1 watts per square metre”
      That’s about 136 BTU/hr, 30 or 40 square meters of the stuff and you’ve put a 5,000 BTU window AC out of work. I’m impressed (if it does work that well).

  49. Willis,

    This is a very interesting post. The ‘magic sheet’ looks to me like a scam. But whether it is or not, it is a neat challenge in the application of thermodynamic principles. So let’s assume that it really works…

    If I read it correctly, the underlying assumption is that some object X situated at or near the ground is at some steady-state temperature T1. This steady-state is maintained by a balance between the incoming energy flow to the object (convection from the surrounding atmosphere + direct absorption of the Sun’s SW radiation) and the outgoing energy flow (convection from the object + LW radiation towards the atmosphere).

    We now interpose the Magic Sheet between the object and the Sun.

    The silver coating on the underside of the sheet cuts out all the Sun’s direct radiation. So the energy flow into the object X reduces its steady-state temperature significantly to some lower level T2. That’s great – so far. It’s called a sunshade.(I will need a grant to pursue the idea of a silver surfaced sunshade further…)

    But there is more…because this is no ordinary silver-surfaced sunshade. Instead of radiating across a broad spectrum it radiates more efficiently through the atmospheric window directly to space. So T2 is somewhat lower than it would be if the sunshade consisted just of an ordinary silver sheet.

    My problem is: how much lower? I strongly suspect that in any practical application the convection effects (which remain the same in both cases) would considerably outweigh the differing radiation effects. Because (as usual in most real situations) convection effects tend to dominate.

  50. Willis,
    I found the paper. It was on the lead author’s (Shanhui Fan) website at Standford:
    “Passive radiative cooling below ambient air temperature under direct sunlight”, Aaswath P. Raman, Marc Abou Anoma, Linxiao Zhu, Eden Rephaeli & Shanhui Fan

    web.stanford.edu/group/fan/publication/Raman_Nature_515_540_2014.pdf

    A quick scan revealed no claim of “pulling heat” from objects, so that particular phrasing was apparently invented by the journalist, otherwise it does indeed seem to work as described, by using a “phototonic radiative cooler” which optimizes solar reflectance and IR transmittance.

    On page 3 is a picture of the device, equipped with a 200mm photonic cooler disc, sitting a on Stanford rooftop. As a scientific control (page 4) they built two more devices, identical to the first except the cooler disc was replaced by plain 200mm discs covered with black paint and aluminum resp.

    Not surprisingly the black disc reached temperatures about 40C higher than the ambient air temperatures. The aluminum disc was 20C higher than the ambient air temperatures, while the unit with the photonic device was 4-5C cooler than the ambient air temperatures.

    I have to say I’m impressed by these results.

    • Johanus, you are THE MAN!

      The paper is everything I’d hoped for, including just what I’d asked—the planck emission curve in the thermal IR region.

      I’ll add it to the head post, credited to you.

      w.

    • johanus-

      Thanks for the link to the stanford paper.

      “As a scientific control (page 4) they built two more devices, identical to the first except the cooler disc was replaced by plain 200mm discs covered with black paint and aluminum resp.”

      It is unfortunate that they did not use as a control a silicon wafer coated with a state of the art white roof paint which both reflects highly in the visible and also has high emissivity in the infrared. The aluminum they used has good reflectance in the visible but an absorption band in the near infrared (dropping to 75% R at 800 nm) and poor emissivity (0.01 – 0.2) in the infrared. Also, why not use a silicon wafer coated with the same silver film but not the photonic layers? That would have about the same solar absorption but have a much lower infrared emissivity compared with the photonic structure.

      The white roofing paint reference sample would have been a much better comparison to determine the effect of narrowing the emissivity band to coincide with the atmospheric window, as compared with a conventional solution that can be purchased at your local hardware store.

  51. From the paper –

    “Further, the cold darkness of the Universe can be used as a renewable thermodynamic resource, even during the hottest hours of the day.”

    Yeah. Right. A couple of years have passed. Still no wondrous avoidance of thermodynamic laws.

    Amateurish experimental setup. By now, I expect these “researchers” to realise where they made their mistakes.

    Oh well, on to the next piece of silliness. Maybe someone could try to heat a thermometer using CO2!

    Cheers.

  52. I may be wrong but I don’t think the claim is to frequency-shift infrared radiation. Rather it is to change the shape of the energy distribution wrt wavelength. The report doesn’t say, at least in the one I read, what the temperature of the surface was when the film was laid on top and statements like “the radiation drifts away into space” and the film “sucks heat from the surface” are just daft. It does seem possible, however, that resonance at a particular wavelength will cause faster cooling at the point of resonance (a glass bead) to which heat will then be transferred from its surroundings (the plastic film and surface underneath). I suspect this film only has any effect when it is applied to a surface already hotter than the air. Obviously the silver foil reduces absorption of solar energy by the surface under the film but the sunlight also stimulates the resonance. The film would only work if more energy is radiated by the resonant beads than is absorbed from the sun, stated to be 4%. I wonder whether it works in the dark.

  53. I bought a flower vase at a second hand shop. Nice round belly with a thin neck, fitting perfectly for one red rose. Put in some water and set it on the living room table. In the afternoon, the sun shone in through the window, through the vase and a spot about 20cm behind the vase started smoking.
    So, whenever I see round glass things, I see lenses. The area behind this material may well be 10° C cooler, until the plastic stuff starts melting or burning.

  54. Yes this can work, See Pictet’s experiment of 1800. Which also explains why the cold gases in the atmosphere cannot warm the surface of the Earth permanently.

    See here;

    http://www.tech-know-group.com/papers/Pictet-Apparent_Radiation_and_Reflection_of_Cold.pdf

    Willis, with all due respect, you have simply disproved the “Radiative Greenhouse Effect”.

    This new film is merely optimized for maximum emission at a wavelength band that is most transparent.

    This film is also optimized to block transmission of incoming radiation.

    Thus it allows minimal radiative heating and maximum radiative cooling, much like the mirrors in Pictet’s experiment.

    The practical problem is durability, any plastic that is expected to see long term exposure to sunlight and is specifically designed to be an excellent absorber of sunlight will fade.

    Cheers, KevinK

    • KevinK,

      You say “See Pictet’s experiment of 1800. Which also explains why the cold gases in the atmosphere cannot warm the surface of the Earth permanently.”

      On the contrary, the document you refer to is a wonderful description of the thermodynamic work of the 17th/18th century on the physics of electromagnetic radiation that culminated in showing that when two radiating objects at different temperatures face one another, the only flow of energy between them is equal to the DIFFERENCE between their two facing radiative potentials – and is ALWAYS in the direction from the warmer to the cooler object.

      This is exactly the situation in the atmosphere, where the higher temperature of the ground compared with the air above causes a net flow of radiative energy upwards, but at a reduced rate compared with the rate that would occur if there were no atmosphere, but only space at a temperature of 3K.

      So just because the air exerts a radiative potential downwards, you don’t have to believe that any energy flows backwards towards the ground from colder to hotter.

      • This is exactly the situation in the atmosphere, where the higher temperature of the ground compared with the air above causes a net flow of radiative energy upwards, but at a reduced rate compared with the rate that would occur if there were no atmosphere,

        it’s more fun than that, it’s active :)

    • KevinK,

      Pictet’s experiment led the way to under standing that the rate of energy transfer between a hotter and a cooler radiating body is the difference between the radiative potential exerted by each body in the direction of the other. Because the radiative potential from the hotter body is greater than that from the cooler body, it follows that energy transfer is ALWAYS from hotter to cooler in full conformance with the 2nd law of thermodynamics.

      In the case of the ground-atmosphere interface, the energy flow from the warmer ground to the cooler atmosphere will be less than would be the case if there were no atmosphere. There is no need to postulate that energy flows from the atmosphere to the ground, only that there is a POTENTIAL exerted in that direction which is overcome by the larger POTENTIAL exerted by the ground towards the atmosphere, the difference representing the magnitude of the energy flow.

      So Willis has in no way “disproved the greenhouse effect” due to radiative atmospheric gases (which is real but most probably of negligible amplitude).

  55. Killer Marmot February 13, 2017 at 10:35 am

    It would have been valuable if Eschenbach had explained why it does not violate the laws of thermodynamics.

    See the update to the head post … I see no violation of the laws of thermo.

    w.

    • You don’t see violation of the laws of thermo in a thought experiment where more energy comes out of a steel shell than is in it.

      • I fear you’ve misunderstood something. The steel greenhouse example is balanced at all levels—the same amount of energy enters the steel shell as leaves the steel sheel. The difference is that the shell has ~ twice the surface area as does the planetary surface, so the shell radiates at half the intensity per square metre.

        Take a careful look, and multiply the emission in W/m2 by the areas. You’ll se it all balances exactly.

        w.

  56. At first glance, this material would appears to violate the 2nd law of thermodynamics. Of course it doesn’t, and after some thought I believe I understand why.

    Imagine a house with photovoltaic cells on its roof. The electricity from these cells is used to power an air conditioner, which cools the interior of the house.

    Obviously this is perfectly doable, and does not violate any law.

    This material might do something analogous, in that it uses energy from photons to pump heat. It uses a completely different mechanism — it does not generate electricity or run an A/C — but the end result is the same.

    How is this material not an example of Maxwell’s demon? This material needs photons to work. As soon as the sun goes down, it stops cooling the underlying material. Maxwell’s imp required vanishingly little energy to sort fast particles from slow, and thus was a thermodynamics scoff law.

    • Killer Marmot February 13, 2017 at 6:39 pm
      How is this material not an example of Maxwell’s demon? This material needs photons to work. As soon as the sun goes down, it stops cooling the underlying material.

      Not true, read the paper, it continues to cool even at night time, the photons it uses are IR photons from the surface.

    • “As soon as the sun goes down, it stops cooling the underlying material. ”
      Not necessarily. If the film allows radiation from the underlying surface to excite the resonance of the glass beads then, overall, radiation through the air is increased compared with the surface in the absence of the film. However, the silver film might well prevent that occurring. It needs numbers to find out. Clearly, there are limits to the conditions over which it works.

  57. “can you mess with the Planck curve like that, shift the peak?”

    Yes by changing the temperature of the emitter you change the curve. It is the plastic film that’s emitting IR not the original surface. Presumably the film has different temperature than the surface.

    Painting a surface white will change its emissivity and reflect all the spectra of visible light. It has cooling effect.

  58. I have a chance to read the paper thanks to Johanus. As an academic paper I am impressed with the use of computer models. As an engineer, I can not see any practical application. It is Standford after all.

    Quotes are from the paper.

    “We demonstrate the performance of the photonic radiative cooler on a clear winter day in Stanford, California…”

    With a few wind leaps of logic we put it on a roof in Phoenix.

    “We assume a twenty-year lifespan,…”

    On a roof in Phoenix?

    “similar multilayer coatings for low-emissivity windows and other surfaces. ”

    Window are different than roofs.

    “which are below aggressive levelized cost projections for both rooftop and utility-scale photovoltaics”

    Everything is better than PV.

    When comes to saving energy, there is clearly a case of diminishing returns. After doing all the cheap things, there is not much saving left. For example, reducing AC energy consumption $500/month to 100/month leaves only $100/month to work with. The materials for my do it yourself project cost $200 and saved 10% of $10/month. Less than a two year payback period.

    A couple years ago, I researched metal roof coating material. I selected a more expensive white coating not to save energy but to seal pin hole leaks in a storage shed. It still is not leaking. I used the same coating on an old camping trailer that is used a few weeks a year. I could have saved $100 using the product I used on my camping trailer 30 years ago. While clearly I will not save enough on energy to make up the difference. Now I just have to live long enough to see if last as long as claime.

    The point is a roof is a sturdy structure in a harsh environment to prevent expensive water damage. Saving relatively small amounts of energy is only important to idiots at places like Stanford.

    • The academics do the research then other people make something of it. No reason to think these academics have the best ideas on how to use it. Look at lasers. (No, on second thoughts, don’t look at lasers – bad for the eyes!)

  59. Ice cream scoops are made with some sort of aluminum alloy that are the opposite of this. – i.e. the scoop warms the ice cream as it cuts through more easily than a scoop made of some other material.

  60. Just good materials science. Seems there is still room for improvement. If they can dope the mix to skew the peak of absroptivity/emissivity out of the ozone bands, it will work even better. The cross section of the material in the paper is far more elaborate (and expensive) and bears no resemblance to the “pop culture” headline image.

    • gymnosperm February 14, 2017 at 8:41 am
      Just good materials science. Seems there is still room for improvement. If they can dope the mix to skew the peak of absroptivity/emissivity out of the ozone bands, it will work even better. The cross section of the material in the paper is far more elaborate (and expensive) and bears no resemblance to the “pop culture” headline image.

      That headline image is from the actual paper, it’s figure 4, as is the second image shown in the original post (Figure 1A). I suspect you are reading the wrong paper, the link given by Johanus is not the paper referred to in the Science article but a precursor to it from a couple of years ago, the actual material is described at the link I gave above at
      https://wattsupwiththat.com/2017/02/13/a-reverse-greenhouse-effect/#comment-2425306

  61. I’ve seen papers that compare satellite equilibrium temperatures when painted or covered with various materials and the coating or covering does affect operating temperature and this effect depends on the balance between albedo and IR emissivity. So an increase in IR emissivity in “clear window” wavelengths while preserving high albedo should have an effect.

  62. It can work, but only with clear sky. Clouds would stop the effect. To work it needs a clear wiev to the cold space. The bottom of clouds would be only slightly colder than the roof and would radiate too much energy back in the same wavelenths.
    Play with that http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/radfrac.html#c1
    The sun would dissipate ~10W/m2 in the active band (5 to 10um), and in the same band at 293K it would radiate ~100W/m2.
    It is not exotic except that the material is very wavelenth selective.

  63. The part that I misunderstood at first was I thought that it was cooling by radiating more in the range where it’s not absorbed by the atmosphere.

    But I see now that it is the other way around. Emissivity equals absorptivity on a line-by-bline bases. So in addition to selectively radiating in the frequency band of the atmospheric window, it also ABSORBS SELECTIVELY in the atmospheric window …

    … and under a clear sky, there’s very, very little in that window to absorb. So it is radiating the same amount of IR … but it is absorbing much less IR.

    Best to you all, it’s a sunny bright day here, I can only wish the same for everyone. Well, unless you need rain …

    w.

    • Willis,
      I got and read the original paper. You are correct that it is the use of a film that absorbs/emits strongly in the 8-13 micron range, but not in the cisible range which is key. Turns out the polymer film they used just happens itself to have pretty strong absorbance in that wavelength range while perfectly transparent at visible wavelengths. Still, at 50 microns film thickness the plain film would have some transmission between 8 and 13 microns, and so less than perfect emissivity. The added “glass microspheres” (actually amorphous SiO2, or silica) have tremendously strong absorbance in the same wavelength range, so adding these (independent of their size) increases net emissivity. The only ‘interesting’ thing about the paper is the selection of the size of the particles. In general, interaction of particulate materials at or near the wavelenght of incident light maximizes the interaction of the light with the particles. The claim made by the paper is that the selected size of the silica particles is key to the emissive properties of the film. But neither the paper itself nor the supplimental information provides any real evidence of the importance of the particle size. They do provide a spectrum showing high emissivity in the 8-13 micron range for the film with ‘resonant’ particles, but provide no reasonable ‘control samples’ for comparison. The specific data they should provide but fail to:
      1) No measured infrared spectrum of the plain film (without particles)
      2) No measured infrared spectra of the same type of film with silica particles at a few different ‘non-resonant’ sizes.

      In other words, they don’t actually measure the contribution of ‘resonant particles’ to the emissivity of the film, they only do calculations. Had I been a reviewer, I would have asked for these measurements.

      Based on the published infrared spectrum for the polymer they used, along with the IR spectrum of silica, my guess is that you could accomplish exactly the same result without using ‘resonant’ particles, even if there is a significant contribution due to ‘resonance’, by just increasing the volume fraction of silica, increasing the thickness of the film, or both. A commercially produced film that is twice as thick actually is less expensive… probably because calendaring a very thin film is more difficult.

      The University of Colorado says the group is applying for a patent… it will be interesting to see what the patent looks like, because this is a pretty well plowed field.

      • That was my reaction as well. Without a control test of shiny film without “resonance spheres” the results are not very interesting.

  64. When solar radiation, with a 5800 K blackbody spectrum encounters the device, the device first reflects most of the incoming solar (albedo) and thermalizes the rest at ambient temperature, heating it. But instead of re-radiating as a blackbody which would be mostly reflected downward by greenhouse gases, it modifies the spectrum via a resonance so more can escape to space via the “radiation clear window,” hence the cooling effect.

    Of course, the device will not work inside because in an enclosure such as an interior room or an oven or under dense clouds, all objects come to the same equilibrium temperature (Kirchoff’s radiation law) regardless of albedo, emissivity absorptivity. You need a high temperature source to activate the effect.

    • pochas94 February 14, 2017 at 2:31 pm

      Thanks, Pochas. I was with you up to the last sentence, viz:

      You need a high temperature source to activate the effect.

      Actually, it will also work at night. Remember that it emits the same amount of IR … but it absorbs less. So all it needs is an unobstructed view of the sky to end up cooler than the surroundings.

      The underlying principle is quite old. In the desert areas of the US Southwest, back in the day people would put shallow flat trays of water on a low rack on the flat adobe roofs common in that area. Even though night-time air temperatures don’t go below freezing, In the morning the trays are filled with ice.

      This utilizes the same idea of an “atmospheric window” to get the water below air temperature, but in this case the “window” is due to the dry desert air. With no water and a clear sky, you’re basically exposed to outer space … add to that a slight bit of evaporative cooling (not a lot because of low temperature) and you get ice. Take it off the roof, bury it in sawdust to keep it frozen … old school.

      Regards,

      w.

      • As the paper shows the cooling effect is stronger at night. See Fig 4:
        ” (C) The continuous measurement of radiative cooling power over three days shows an average cooling power > 110 W/m2 and a noon-time cooling power of 93 W/m2 between 11am – 2pm.”

  65. ============
    Even though night-time air temperatures don’t go below freezing, In the morning the trays are filled with ice.
    This utilizes the same idea of an “atmospheric window” to get the
    water below air temperature, but in this case the “window” is due to the dry desert air. With no water and a clear sky, you’re basically exposed to outer space …
    ============

    Why does the ice drop below zero, but not the dry desert air?

    Evaporate cooling potential is maximum when air is dry.
    Could that be part of the equation that produces ice when ari temperature is above zero?

  66. One of the most important lessons I learned from my tutors as a grad student, was when they chose to say nothing to a speaker with grand claims.

    • michael hart February 15, 2017 at 11:20 am Edit

      One of the most important lessons I learned from my tutors as a grad student, was when they chose to say nothing to a speaker with grand claims.

      Thanks, Michael, but I don’t understand this. It seems that you think someone is making “grand claims” … who is making said claims, and where? Me? The authors of the first paper? The authors of the press release? Some random commenter? The comment immediately above yours? WHO ARE YOU MUMBLING ABOUT AND WHAT DID THEY SAY???

      This is why I ask people to QUOTE WHAT THEY ARE DISCUSSING.

      In this case, you appear to be saying that you have some special insight that lets you divide the world into something you call “grand claims” and some other category. Since you have not identified the other category, I’ll call them the “not-so-grand claims”.

      Then, bizarrely, you seem to think that the proper response to “grand claims” (whatever they may be) is to “say nothing”, but apparently you’re willing to discuss “not-so-grand claims” … say what? How on earth does staying schtumm help anyone? How does that improve understanding? How does that move science forwards?

      I have no clue what you are referring to in this post as being a “grand claim”, or what a “grand claim” is on your planet, or why you think allowing them to render you speechless is the best way to deal with them …

      Sorry, but you are making no sense at all. What am I missing?

      w.

  67. Won’t work for buildings, too much mass, the interior temperature change would be undetectably small at the new equilibrium.

    Might be fun for humans, if it’s flexible.

    • At the very least, the contribution from the resonant spheres (as opposed to the film) is probably undetectably small due to insulation beneath the alleged “100W cooling effect.” Think about it for a minute: would you heat your house by putting a heater on top of the roof?

      Also, the whole “beams IR directly to space, saving YOU big $$$ on cooling!” doesn’t really make any sense. What do you care if the IR is absorbed a hundred feet away or a million? It’s still not coming back.

  68. @Willis @Micro6500 @Killer Marmot @George E. Smith

    There is a fluorescence phenomenon known as anti-stokes radiation.
    It can be used for cooling since it extracts phonons from its matrix, and essentially adds the phonon energy to the absorbed radiation for re-radiation as fluorescence. It can be observed with aggregates of dyes that efficiently fluoresce.

    https://www.rp-photonics.com/optical_refrigeration.html
    http://www.sciencedirect.com/science/article/pii/S0022231306000214

  69. talldave2 February 15, 2017 at 1:14 pm

    Also, the whole “beams IR directly to space, saving YOU big $$$ on cooling!” doesn’t really make any sense. What do you care if the IR is absorbed a hundred feet away or a million? It’s still not coming back.

    Thanks, Dave. Let me repeat what I said above.

    The part that I misunderstood at first was I thought that it was cooling by radiating more in the range where it’s not absorbed by the atmosphere.

    But I see now that it is the other way around. Emissivity equals absorptivity on a line-by-bline bases. So in addition to selectively radiating in the frequency band of the atmospheric window, it also ABSORBS SELECTIVELY in the atmospheric window …

    … and under a clear sky, there’s very, very little in that window to absorb. So it is radiating the same amount of IR … but it is absorbing much less IR.

    Average downwelling longwave radiation on a 24/7 basis is on the order of 340 W/m2. This film ABSORBS LESS of that downwelling radiation.

    I’ll add another update to the head post explaining this,

    Best regards,

    w.

    • Thanks Willis, I did see that, and I agree, and I was pretty sure you understood too — my comment was directed more at the many commenters who did seem to think beaming IR to space was key.

      The absorption claim is more plausible, but I won’t believe the effect is actually measurable until they do the control with just the shiny film. It just seems unlikely that equilibrium condition is going to change much, nature abhors a non-Maxwellian thermal distribution.

  70. I’ve added the following to the head post:

    [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” at about 260 watts per square metre (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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