Capacitors do not actually have on/off switches. This is a bug that has been around for a LONG time. Log out and back in and they should work normally.
For days/weeks/months after I am swimming in promethium, I still convert lumber to biofuel with my left-over portable constructor. I find it comes in handy for topping fuel tanks, bailing out newbies who run into trouble, and given the inefficiency of the portable constructor, using it as a biofuel generator is one of the few post-new-game things it is actually good for anyways.
Solar power is useful but only in very specific circumstances. I set up a space base in a system that had a gas giant with moons really close to the sun. I think it was 0.4 AU, maybe even closer. With 15 panels and lots of capacitors to handle surges it can power 8 running constructors plus the other base stuff just fine. That said I had set up a ground base on a planet a bit further out and it was almost useless even for just powering the passive stuff.
I've gone a similar route - Portables are so cheap (3 steel!?!) that I make three of them at each base and stick them outside, fill 'em up with wood and let 'em be. Harvest each time I come back to a base.
instead of having a base around a planet, why not making a base directly around a sun .. you'll get 12k power ... enough to run a big base
