Something I haven't seen mentioned is that if you use mirrors made of layers with thickness matching the most useful wavelength, then almost all of the light re

Something I haven't seen mentioned is that if you use mirrors made of layers with thickness matching the most useful wavelength, then almost all of the light reflected onto your PV panels is converted to electricity, and so avoids heating up the panels. (The rest of the light goes right through the mirror.) Not heating is very important in space, where convective cooling does not work. This means you can focus a great deal of sunshine onto less of expensive panel area, from much broader, cheaper, lighter thin-film mirrors. You would actually keep the panels edge-on to the sun to keep them cool, lit only by the mirrors. I am betting that microwaves will not be the favored transmission medium. Lasers at optical wavelengths focus better. Maximum intensity could be limited to match natural insolation, for safety. In principle, by using those monochromatic mirrors focused onto an array of laser cavities, you could generate the laser beams directly, without the round trip through PV panels. The laser wavelength would be chosen for maximum conversion efficiency at the ground array, where you ought to be able to get above 80% conversion.