>vacuum is a fucking terrible heat convector
Yes we're talking about radiating not convection
And a kilowatt from one square meter is awful. You can do far more than that with access to an atmosphere, never mind water.
The fact that people aren’t using something isn’t evidence that it’s not possible or even a great idea, it could be that a practical application didn’t exist before or someone enterprising enough hasn’t come along yet.
Assuming that this is the right order of magnitude, a 8MW datacenter discussed upthread would require ~8000 m^2, plus a fancy way of getting the heat there.
A kilowatt is nothing. The workstation on my desk can sustain 1 kW.
Radiative cooling is great for achieving temperature a bit below ambient at night when you don’t have any modern refrigeration equipment. That’s about all. It’s used in space applications because it’s literally the only option.