I've always wondered (especially after a Dr Hossenfelder video about it). Even if we figured out all of the tech to get such a solar cell satellite into orbit for a reasonable cost, they still need a giant ground station to accept the power. How much power would that ground station generate if it was simply a bunch of solar cells instead of microwave receiver? A space cell might get power 24/7, but if 75% is lost in the conversion, how is that better than a ground based cell that gets power for only 6 hours a day?
Putting cells over the area: You get intermittent power. Putting antennas over the area: You get continuous power. And that's the achillies heel of solar--you can't have things shutting down every time a cloud comes over.
Furthermore, microwave antennas are mesh, not solid. You won't have full sun under it, but neither will it be dark.
That being said, there's a fundamental issue here that without huge improvements in launch costs it's simply not viable unless made out of lunar materials.
And note that it doesn't have to be in a synchronous orbit so long as you permit some movement of the antennas. Put say 25 stations out there and 24 ground stations--they keep hopping to the next station as the Earth rotates underneath, the 25th station is offline because it's in shadow.
The real magic is not putting all the cells in one place. It's distributing them over the land mass.
A single solar power station can be taken out by a cloudy day.
A million little solar power stations spread across an continent average together into an even power source that provides power for longer than daylight hours.
There's a practical limit on how far you can ship power. Some while ago I tried to model what it would take to maintain continuous power worldwide with just looking at day/night. Nope, couldn't be done even if your cells were free. Just the wires became impossible--I was looking at the best wires to date and that still translated into a number of nines (I forget how many) on the loss percentage--and some mechanical bottlenecks were you simply didn't have enough land to run the wires.
The higher you run the voltage the more corona loss, the higher you run the current the more resistance loss. And there's a limit to how close you can put the wires to each other before they interfere. The band of land required for the massive power bus is gargantuan.
Secondary usage as an impromptu death ray is the only way that pencils out for me. Even if you could cut the receiving area to 1/10 the equivalent solar panel area, the economics of launching a huge space array seem really difficult to ever make economic sense vs fully land based system.
Microwaves don't absorb uniformly into materials. You can have a potentially deadly amount of energy, but if you can't actually interact with it then it's harmless.
The proposal for rectenna arrays was grids over farmland which could be used for cattle grazing with illeffects to the cattle - simply not enough EM can be absorbed by them for it to matter.
