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."

Comments

84 degrees is okay for some things.

[lpangelrob2]

First poster brought up good points about toxicity... I'll address the temperature question.

(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.

Re:84 degrees is okay for some things.

[hummassa]

Where I live (Belo Horizonte, southwestern Brasil) 84F (29C) is room temperature 9 out of the 12 months of the year. In the northern states, it's 11/12. We usually only turn our ACs on at home when it's 37C (100F) and above.

Notwithstanding, this is _great_ (if the yellow tint and the toxicity when broken issues are solved) for car windows. AC won't kick in as often (less gas spent), seats/steering wheel won't get ultra-hot when the vehicle is left under the sun (the beach!!), baby-left-in-the-car dehidration deaths won't happen.

Re:Dye to change the color?

[CapnGib]

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.

Except in areas with exceptional solar exposure

[2nd Post!]

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.

Re:solution

[redJag]

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).

Re:Temperature of Glass

[wanerious]

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.

Re:can be used in cars

[rjstanford]

For example: I would LOVE to have a cartop solar cell harnessed to a fan helping to cool the car

You mean like Audi's "Warm Weather Package"?

• Solar sunroof (operates fresh air fan when parked in sun)
• Power rear window and manual rear side window sunshades

Granted.

It's safe

[Engineer-Poet]

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.