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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."
(sidenote: I guess there's a new geek test out on how to actually post to this story... the Read More link being wrong and everything...)
84 degrees actually is pretty comfortable for people in the south, especially if it's going to be a dry 84 degrees, which air conditioning can help with. This can be useful, if it's not as expensive as gold, and if it really works as advertised, for people living in dry climates (read: desert southwest) who don't want to run A/C bills through the roof.
That said, I recall that while a significant percentage of heat comes from solar energy through windows... when the house is sitting in a 110 degree plain, it may not be quite as good as first thought.
-Rob
Marriage doesn't have to suck!
It is called color compensating. You tint with complementary colors to neutralize a color cast. Yes it will make the window appear a bit tinted as less total light gets through, but it would be less yellow.
Beauty is truly in the eye of the tiger
Imagine living in Nevada, where you get sun for more than 300 days a year, and most of those days are high quality 90F or higher sun.
A solar home can only use so much.
A trombe wall can only absorb so much.
Even the new 10% transparent solar collectors can only do so much.
What do you do with the excess heat?
You run evaporative coolers and AC.
The only other way to shed the excess heat is to absorb it (ala these panes or burying the house underground) or redirect it, with things like geothermal heat pumps.
GPL Deconstructed
No, the point of activating it only when it's hot is for cold weather times. When it's cold outside, letting solar energy IN saves money; when it's hot outside, keeping it out saves money. Pumping in hot air would be a waste in three ways (heating the air, pumping the air, and negating the entire point of the treated glass).
No, you actually still want a light roof in winter. A black roof is a good absorber and a good radiator as well. In the winter, a black roof will radiate the heat out of your house more rapidly than it can heat up from the sun (since the radiant intensity is generally much lower in winter). You still want a light-colored, insulating roof, even in winter.
In areas of the world that receive snowfall in winter, the snow on the roof is actually helping, by reflecting heat back into the building.
In cold weather, it still wouldn't make sense since it would require you to remove the insulation layer which in turn would cause heat to escape from the house. Only solution I could think of is skylights but unless the insulation factor increases on them dramatically, they'll never have the insulation value of a foot fiberglass.
Have you ever been to a turkish prison?
Wrong. Solar gain from radiation is a significant factor in design. See for instance this, or this, or this, or this.
Convection/Conduction are certainly at issue when there isn't sun (say, Seattle or Syracuse), but when there is, the radiation transmission is a major factor. This new technology sounds very promising. And yes, deciduous trees planted in good spots are a good low-tech approach.
-dB
"It if was easy to do, we'd find someone cheaper than you to do it."
If the film is on the inside pane to prevent it from environmental damage, then there will be two passes through the outer pane, which can warm up the gas between the panes, leading ultimately to convection/conduction gain. Coating the outside would be most effective, if it weren't fragile.
-dB
"It if was easy to do, we'd find someone cheaper than you to do it."
One of the reasons rooms get so hot is that ordinary glass is already blocking a lot of infrared--from getting out. Non-infrared (ordinary visible) light comes through easily and strikes whatever is inside. In doing so, it heats it, so a portion of the visible light is converted to infrared. But, since the glass isn't very permeable to infrared, it can't get out, so the inside space heats up.
This innovation will make it even harder for infrared to get out, but it also reduces the infrared that gets in. So the question is whether the inside heats up more with visible light converted to infrared that can't get out at all, or visible plus some infrared converted to even more infrared that can get out a little bit.
I suppose they've done the experiment, but it's not obvious to me which one would be superior or by how much.
"Those who have never entered upon scientific pursuits know not a tithe of the poetry by which they are surrounded."
Not an ideal solution, but take a hose to your "hot" wall. The water evaporates and hopefully the heat blows away in the breeze instead of just baking your house and everything inside.
It works, even if not very well, and it's relatively cheap. Not something you want to do every day forever but on a couple of those screaming hot summer days it works well enough.
no, visible light turns into heat when it strikes and is absorbed by an object, as does IR. Transmitting more IR would just make the insides hotter.
Karma: Negative (Mostly affected by dorm trolling)
When you touch your bathroom tile, it typically feels colder than the surrounding air. This is not because the tile is somehow cooled with respect to its surroundings, but because the tile is much more efficient at carrying away heat from your body. An air temperature of 70 degrees F can feel very comfortable, since air is a very poor conductor of heat, but 70 F water feels decidedly cool to the skin. Having said that, it still may be the case that your window is cooler or hotter than the inside of your house since it is the boundary between zones --- in fact, this is very likely, since glass is a much better heat conductor than the surrounding walls.
You mean like Audi's "Warm Weather Package"?
Granted.
You're special forces then? That's great! I just love your olympics!
Vanadium is a common alloying element in steel. The two MSDS pages I found indicate that the powdered oxide isn't very good to breathe or eat, but the amount released by breaking a window is probably so small that you wouldn't notice. The biggest hazard would be to people working in the manufacture of such windows.
Sustainability and energy independence essay
Wrong. It blocks some IR. It certinaly doesn't block the IR nearer the red spectrum (rather than heat). If it did, I wouldn't be able to take IR photos with my camera.