Given the headline, I expected this to be about passive radiative cooling. Infrared rays between 8–13-µm are not blocked by the atmosphere and leave earth, turning space into a heat sink. There have been some advances in materials science, with new materials that reflect a broad spectrum (like a mirror or white paint), but in that 8–13-µm gap, they strongly absorb and then emit radiation. I’ve seen results indicating a 10C differential in temps, which might make lower-power / passive A/C possible, was hoping someone had figured out how to turn that temp differential into energy.

Still, reducing the power needed for A/C and — not dumping the resultant heat back into the atmosphere — is something of a big deal.