I guess you can have both positive and negative externalities.
I went back to re-read reflectorbital.com, indeed if you're only lighting a solar farm in the middle of nowhere maybe the light pollution is not so bad outside of the targeted zone.
Still fells like a complicated solution to me. Imo we need more storage innovation and investment, a lot more. We know we'll have more and more intermittent renewables electricity production, we just have to store it.
Oh, absolutely. The space mirror idea might be a net terrible idea; more panels and better batteries could simply be it.
I just don't see why, if this turns out to work, the benefits would not diffuse (principally because I don't see a line of previous innovations where this was not the case, electricity being a prime example of an extremely potent and well diffused commodity).