Scientists make thin material that acts as air conditioner

Scientists have invented a new kind of thin material that can cool a surface against the heat of the sun without using energy or typical air conditioning, a study said Thursday.

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Tau.Neutrino said:

Scientists make thin material that acts as air conditioner

Scientists have invented a new kind of thin material that can cool a surface against the heat of the sun without using energy or typical air conditioning, a study said Thursday.

More…

So the wind farms can bugger off back to the north sea?

Tau.Neutrino said:

Scientists make thin material that acts as air conditioner

Scientists have invented a new kind of thin material that can cool a surface against the heat of the sun without using energy or typical air conditioning, a study said Thursday.

More…

Sort of like the “Dew Collectors” of Frank Herbert’s “Dune”?
A photochromic material that is white during the day to stay cool and turns black at night to cool off even faster.

Yes, very like that, but not the same.
The new material is even simpler, it has low absorptivity/emissivity over the visible spectrum and high absorptivity/emissivity in the thermal infrared.

Here’s a better explanation.
http://science.sciencemag.org/content/early/2017/02/08/science.aai7899

“We embedded resonant polar dielectric microspheres randomly in a polymeric matrix, resulting in a metamaterial that is fully transparent to the solar spectrum while having an infrared emissivity greater than 0.93 across the atmospheric window. When backed with silver coating, the metamaterial shows a noon-time radiative cooling power of 93 W/m² under direct sunshine. More critically, we demonstrated high-throughput, economical roll-to-roll manufacturing of the metamaterial, vital for promoting radiative cooling as a viable energy technology.”

That’s simple enough, they use scattering off density changes (in this case the interface between glass and plastic) to scatter visible light (wavelength 0.4 to 0.7 microns), but because the glass chunks are of the order of a micron across they don’t scatter thermal infrared with a longer wavelength of 2.5 to 14 microns.

This invention is long overdue. The need for it was apparent probably more than 100 years ago, and manufacturing methods have been available for … well probably for more than 50 years. It’s not more difficult to make these microspheres than it is to make lead shot, and that has been around for more than 200 years, and this sort of plastic has been around for more than 70 years (polyethylene began mass production in 1939). All that’s needed for the microspheres is to superheat glass to keep the viscosity very low, blow bubbles through it, and collect the droplets.

But is that how they do it? Let me check. They do use glass. “A 50-μm-thick film containing 6% of microspheres by volume in the matrix material of
polymethylpentene (TPX). We used TPX due to its excellent solar transmittance. Other visibly transparent polymers such as Poly(methyl methacrylate) and polyethylene can be used but would slightly increase solar absorption. “. They don’t say how they produce the microspheres or what the microsphere diameter is, they probably don’t even know, idiots.

So how does the efficiency of this stuff, in keeping the inside of a building cool, compare with:

1) A mirror
2) White paint
3) Any outside surface you like + lots of insulation
?

The Rev Dodgson said:

So how does the efficiency of this stuff, in keeping the inside of a building cool, compare with:

1) A mirror
2) White paint
3) Any outside surface you like + lots of insulation
?

Much better than all. The problem with all those it that they have similar absorptivity/emissivity in the visible and thermal infrared parts of the spectrum, so all they can do is add a time delay to the temperature vs time curve. This new material cools during the night as well as during the day, darn useful for hot nights. Everything else either cools during the day and heats at night or visa versa.