Comment by card_zero
5 days ago
There's PDRC, but we can't mass produce the "photonic metamaterials" that make it good.
https://en.wikipedia.org/wiki/Passive_daytime_radiative_cool...
It ought to be great. Takes no energy, sends heat through the infrared window back out into space where it came from.
I researched the topic and produced a short video on it: https://youtu.be/NVAcSgLZues
Purdue University produced a barium sulfate nanocomposite paint that has 98% reflectance in the desired band using a 150μm layer, cooling surfaces by 4.5C.