Friend of mine who’s done some pretty heavy duty structural welding has one, says they’re terrific. 10 CFM at 90 PSI isn’t efficient cooling by any means, but when you’re welding on plate steel in confined spaces efficiency isn’t what you’re after. Interesting where the uses for these things come up.
I know that effect can be put to good use at night to generate dozens or hundreds of mW of power between “ground” and “exposed to space,” but using it to chill cooling water for heat rejection is really neat! Plus the general “cool shade panels for the building” thing.
One advantage of rooftop solar is that you get shade, often on the sunniest roof panes - I prefer ground mount for a variety of reasons, but a layer over the roof (with airflow under) can really help reduce cooling loads too. I wonder if I can buy some of these panels to stick on my roof anywhere…
For hot water heating, the engineered black surfaces on the high absorption water heating systems is really unique. It absorbs IR, heats the water, but the emissivity is actually super low, which prevents the captured heat from re-radiating away. It’s not just paint, it’s not just dark, but they figured out how to do that. I read this years and years ago, but don’t recall any of the details. but it’s interesting to think about. Clearly the opposite can be true too; you can engineer a surface that’s really good at emitting IR (black body radiation) at your desired object temperature.