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Smart Glass Blocks Infrared - But Only When It's Hot
klevin writes "New Scientist has an article about a new way of making sheets of glass so they block infrared energy at temperatures above 29C (84.2F). Just so long as it doesn't have to get that hot on both sides of the glass. My AC comes on way before 84F. I suppose that with double or triple paned glass, you'd only treat the exterior pane."
How's that yellow tint going to look where indoor light is already greenish from fluorescent lighting? Will we walk outside and everything will look pink or purple? Fun!
Hopefully in three years they'll give some answers to these questions and more. I've got a couple windows, but we've got no air conditioning and the heat reflects off an earthen bank, most of the heat comes through the walls.
A feeling of having made the same mistake before: Deja Foobar
If this technology comes out, a good application is to use it in cars (especially in hot areas).
I don't see how you *add* dye to get the coating to let in the light that the coating is currently blocking...
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when was the last time one of these "we'll have a commercial product ready in.." came true
The yellow tint issue would have to be definitively solved before this stuff could be used on vehicles, due to some states not allowing certain colors of window tinting (red and yellow, probably reasoning that that would lower the visibility of emergency vehicles and caution lights).
How about some electronics grounding that vanadium dioxide? If set up right, when the VO2 transitions to "metallic" above 29C, the panel's photoelectric effect could harness the solar power now more highly available. That in turn could power other devices, like awnings, vent covers, or even fans, to mitigate the heat, using the sun's power against itself.
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three panes of glass, separated by a short distance each. pump warm air into the two gaps. The middle glass is this infrared blocker dealy.
Or, if only one side needed to be warmed, use two panes instead of three with a small gap. The exterior pane is the infrared blocker. When it's cool outside or the window is shaded, pump warm air into the gap between panes.
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An interesting combination would be to incorporate it into a photosentive dye (photogrey?) like sunglasses. When it gets brighter, it gets darker. It would be useful in keeping rooms or cars from getting too bright.
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This is wonderful, and a step in the right direction to be sure. I was actually just pondering if this kind of thing was possible the other day. Unfortunatly, buildings are still made like huge heat syncs. This is because a flat surface has a very poor surface area to volume ratio, other sky scraper shapes, such as cylinders, are even worse. R. Buckminster Fuller explains this in his Critical Path. What really elucidates this is he says if we theoretically covered all the buildings from 20th to 80th St, I think it was, in Manhatten with one large dome we would decrease the surface area exposed to the elements by a factor of 84. Consequently, it would take 1/84th of the energy to heat and cool the environment.
~Anztac
These university folks are taking credit for a discovery made by Dr. Ouderkirk at 3M. As usual the actual scientist who makes the ground breaking discovering that was considered to prove "known" physcial laws false, gets no credit.
Most of the heat that comes into your house will do so by conduction from the air by the window to the glass to the air by the window, then get carried around by convection. It won't get in by radiation, so IR-proof glass will have only a small effect. If you have double glazing then you have a hefty heat buffer between your house and your environment anyway, and the buffering effect is large enough to render any conduction heat exchange negligible. What it *might* do, however, is stop your neighbours from changing the channel on your TV.
It seems to me that it would make more sense to come up with a roofing material that blocked infrared above a certain temperature. For example, I'm sure that my house gains far more heat from having the dark roof sitting out in the hot sun all day than it does from the windows. It would be *really* cool if someone set something up that would absorb IR in the winter (like a dark roof) but not in the summer (light roof). Still, I guess windows are better than nothing.
What happens to all that infrared energy that isn't being absorbed by the interior of the building anymore? Is it absorbed by the glass/film iteself and then dissapated by conduction or convection with other nearby materials like air, glass and steel or is it reflected back outside to make other buildings and surfaces and stuff even hotter?
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Actually everything else in the room hit by the sunlight get way beyond 84F before either the window glass or the air inside the room. They start to radiate and heating up the air, much sooner than glass. And a typical window glass has neligible surface connection with other material than air and air has poor heat conduction and storage (sorry I don't know the exact English name of these physic attributes) capabilities, I think it is an educated guess that glass gets hot slower than air, thus this temperature boundary can be a real issue. (Though I have never made such measurements.)
I've worked in the glass industry for over three years, acutally for one of the direct competitors of the people (Pilkington) who came up with this. Coating glass almost always (90% of the time) requires an insulated (two lites of glass) unit. The coating goes on the inner surface because it is easy to scratch the coating off, and since its a near vaccum inside insulated units they don't have to worry about what ambient conditions will do to the coating. Now the yellow tint will be a non-issue come production time. It realy will be either applying it to glass that is already tinted to cancel out the yellow or they'll modify the formula to get it to appear clear. And the fact that it eventually wears out will either be adjusted for in the R&D process (not likely, too expensive), or offering some kind of warranty on it. It is cheaper to re-produce because of the scale of glass plants, than it would be for the R&D to get another year or two of useful life. The process of coating itself is very very interesting. They pretty much ionize particles to bond at a molecular level to the glass. It's a niche field, but one that is very lucrative because there are not that many people in it. And as far as costs are concerned, it should be rather cheap. Glass itself costs around 1-5 cents (US) per squarefoot. A float glass plant produces around 650 tons of glass a day. The process is really really efficient.
In Tokyo, law requires large buildings to have roof gardens to prevent the roofs from getting so hot. Plants will use that energy to grow, instead of letting that energy hit concrete, metal, etc and become heat. Its estimated that tokyo would be 10 degrees hotter on average without the roof gardens.
The article just says "blocks" If the glass blocks by absorbing IR then this would be a problem in double pane windows. The outer pane (or is it lite?) would become dramatically hotter and would expand more than inner one. This could break the seal between the two sheets and release any enclosed gas (argon fill is commonly used to reduce convective currents that transfer heat) as well as allow moisture in causing fogging. This was apparently a problem with some do it some do-it-yourself window tints. I don't know much chemistry but they say it's metal-like above transition temp so maybe that means it reflects. BTW I have now idea why Argon would reduce convective currents. Anyone know? I just know that lower convection is a property of heavy gasses
Of course, red tinting limits little, if any, red. It could make it harder to distinguish red from white. BLUE light is attenuated; green might look kinda dull yellowish.
OTOH, A sharp blue tint could make red and yellow (emergency) lights difficult to see... up to invisible if one got legalistic about the wording I saw on a Kansas website. If I were to ban any color for safety reasons, it'd surely be blue.
Perhaps Kansas's lawmakers reasoned that we'd evolve our way around their apparent stupidity. =^>
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First off light will still get through, but, onto the the main problem of the parent's post (not really a problem, it was modded funny): anyone who has ever played with the keychain ring of tinted plastic in kindergarden knows that with the parent's solution, you get green. The appropriate color to achieve a colorless tint would be purple, as it, not blue, is the "opposite" color of yellow.
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