How to air condition with much less electricity.

https://youtu.be/jUrF_Sme7YI

Ok this is pretty cool - a mirrored surface that not only reflects incoming sunlight but also radiates heat thanks to nanotechnology. (The part I don't understand is why they need to restrict wavelengths radiating out through the panels. Maybe it blocks infra-red in both directions - allows wavelengths both in and out that are not prevalent in sunlight but are more predominant in the infra-red emission of the object being cooled.)

Here's an article from the Washington Post: 

"developed a thin, mirror-like film engineered to maximize radiative cooling on a molecular level. The film sends heat into space while absorbing almost no radiation, lowering the temperature of objects by more than 10 degrees, even in the midday sun.

"radiative cooling... Most researchers saw the phenomenon as an interesting physical fact with few practical applications.

"The trick was to develop a material so perfectly reflective it absorbed almost no energy...On top of that, Raman wanted to maximize the amount of radiation the film sent into space.

"Earth's atmosphere blocks some outgoing infrared radiation — and it's blocking even more now that it's chock full of carbon. But there are "windows" that electromagnetic waves of just the right length can slip through...crafting a film from many microscopic layers. The thickness and composition of these layers were designed to interfere with the way different wavelengths of light travel. Incoming solar radiation would rebound right back into space. Outgoing thermal radiation would bounce around between the layers, like a pinball in a machine; only the desired infrared wavelengths would be able to escape.

https://www.washingtonpost.com/climate-solutions/2020/10/07/radiative-cooling-climate-change/

At 7:35 in this second video, he explains the cooling material a little more. 

This still doesn't explain it fully - it must have to do with absorbing less incoming (greenhouse effect) reflected heat from the sky while allowing the one outgoing wavelength emanating from the warm object underneath it that passes through the atmosphere unimpeded.