[Suicide Junkie]

Actually, the solar collectors already provide more than you're suggesting there.

1 engine's fuel for 1 mp = 10 supplies.

Of course, 6 engines going 1 mp use 60 supplies,
and 6 engines going 6 mp use 360 supplies.

For P&N PBW, I've gone with making the quantum reactor a giant supply storage bay.
3x the supplies per KT compared to the best "standard" supply tank, but 3x the cost, and its BIG so it needs to be on a dedicated supplyship until you get the really big hulls.