When I am in a factory building run out of power with my solar-powered robots frequently can I can power for personal robots for free when in a building that is powered?

Factory lighting isn't sunlight, and I won't change that (otherwise people would put all their solar in factory buildings). If you want to charge your power armor using your power grid, I recommend the Localized Charging mod (an up-to-date version is here). It should work in factory buildings.