"If you want to go 'green' and not wait for batteries to improve, then what about considering a very lightweight Genset?"
Dave
No such thing as "Green". (in my opinion)
Even solar cells are made from huge amounts of coal used to refine the silicon.
(up to 25 times more energy than used to make steel, I think some professor calculated)
A genset design might just add more unneeded weight if you try to connect the main engine with various shafts, etc. I think a very small alternator would be enough and avoid some problems.