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

window tinting?

[natron 2.0]

Sounds very similar to Ceramic window tinting film that is found on cars

Temperature of Glass

[Crazy Man on Fire]

My AC comes on way before 84F.

Looking at the article, it seems that it is the temperature of the glass that must reach 84F, not the temperature of the air inside the room. I would imagine that the glass reaches 84 much faster than the air inside, so your AC shouldn't be much of a factor unless it is cold enough to have a larger impact on the glass temp than the outside air and the solar energy.

Re:84 degrees is okay for some things.

[value_added]

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.

What amazes me to this day is that a less hi-tech approach would be to plant a frigging tree. Cities here in Southern California still insist on cutting them down (ostensibly to save money from the city maintenance budgets). Without the shade, you get roofs and attic spaces that easily heat up to over 100 degrees and don't cool until 6-7 hours after nightfall.

Trouble

[dr_dank]

Won't this interfere with the thermal imaging cameras fire departments use to find people in fires?

Re:can be used in cars

[misleb]

Ever notice how the inside of a car gets HOTTER than the outside air? That is from the sun's radiation, not conduction through the metal (or glass). If you could block the heat from the sun, cars would be much easier to cool and they might not get so damn hot when parked.

I thought visible light was the problem

[clone22]

Visible light comes through the window and is absorbed by materials which start radiating that energy as IR. Auto glass is better at transmission of visible light than IR, so inside of car gets hotter. If true, it would help to have better IR transmission than to limit IR transmission.

Re:Roof gardens.

[valkraider]

Here in Portland, OR - they try and implement things like this, but then people just complain about the extra cost up-front.

When will Americans learn - if we build stuff cheap up front it is more expensive long term. If we spend more money up front, we save LOTS of money in the long term...

Oh, wait. That would be smart...

Nature says you can't

[Engineer-Poet]

But why can't the consumptive tech be improved so solar collectors/transformers DO use ALL the heat (or the amount above xx Celsius)? Is this some law of nature where thermal can be blocked but not utilized?

Yes. It's called the second law of thermodynamics. You can't convert heat to more-useful forms without a heat "sink" at a lower temperature, and when your house is the thing at the lowest temperature and you want to cool it this is problematic. Just keeping the heat out is the easiest and most economical thing to do; heat that doesn't get in doesn't have to be pumped out again.