Re: 13sq km of mirrors to heat 3 boilers to 560C
This really isn't the same thing at all. This is simply reflecting and focussing sunlight onto a salt tank, which heats up and uses that heat to drive a working fluid through turbines, generating electricity. Totally different principle.
Space solar uses photovoltaics panels to generate electricity from sunlight, converts that electiricy to microwaves of very specific frequency that is not absorbed by water molecules, and transmits that microwave energy to receiving rectennas spread across the ground. Those the microwave energy induces electrical current in those rectennas. Direct electrical conversion. No heating involved.
Same way that radio waves induces a tiny current in an antenna. Just on a much larger scale, and a very specific frequency.
Focal spot of the transmitter is deliberately spread out to avoid concentrating a large amount of energy in a small area. The frequency is chosen to not be absorbed by stuff. There's no way anything in the beam will catch fire. This won't kill any birds, down any planes, or anything else.
Oh, and people keep saying "what if this is hacked and used as a weapon?" It can't be used as a weapon because the beam cannot be focussed tightly enough. That's an aspect of how it is constructed. Not something you can hack in and tamper with. Worst thing hacking could do is move the transmitter (slowly, it's a satellite - it'll have reaction wheels and station keeping thrusters, but that its) or turn it off. It might use a phased array to keep the beam tracked to the receiver, so you could maybe redirect the bam that way, but the beam still can't do any damage.