[Someone]

> You get about 40% more power/area in space vs on the ground. You need about ~22 TW to "power" humanity. So you need about 70,000 km^2 of space […]. So lets round it to 100,000 km^2. But thats a significantly smaller area than the terrestrial equivalent of about 500,000 km^2.

Those number are inconsistent with each other. Seems you calculated with 400% more power/area in space vs on the ground. That seems incorrect to me, as it would make space solar convert close to 100% of incident solar energy to electricity.

[choilive]

Ground based solar has a capacity factor of about ~25% depending on location, while a space based installation would have nearly a 100% capacity factor. So to generate the same amount of energy per year you need about 4x as many panels on the ground. I probably should not have said power but instead something like exajoules/year.

[pfdietz]

Another important issue is that in space, PV can be extremely thin. The actual active layer of semiconductor can be maybe 50 microns (for silicon) or less than 1 micron (for CdTe). This also suggests solar-powered electric propulsion in space can have high acceleration, limited by heat dissipation in the engine.