mostly you'd be floating them on the oceans (ideally the currently-nutrient-depleted parts of the oceans that aren't teeming with algae), but yeah, that's roughly the limit for solar, and as you're approaching that limit, you need to be thinking about space-based solar power, nuclear power, geothermal power, etc. maybe when you're at 64× of current energy consumption, say
since 02000, total solar installed capacity has gone from a gigawatt to 1.6 terawatts (see https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... and https://en.wikipedia.org/wiki/Swanson%27s_law#/media/File:19...), which is roughly 10 doublings, one doubling every 2.3 years. but that's peak capacity, and 1.6 terawatts peak is only 220 gigawatts of actual production at a presumed capacity factor of 21% (see https://en.wikipedia.org/wiki/Solar_power_by_country). that's 6 doublings away from world marketed energy consumption; adding the other 6 doublings to get to 64× gives you 12 doublings, and thus about 28 years before this starts to be a concern
probably we should think of this as a lower bound, though; adoption is likely to slow down as solar moves into application areas that are not already electrified or indeed yet done at all by humans, and the last 24 years have been, historically speaking, unusually peaceful