Take of on batteries and when you get above 5000 feet you connect the little Jet-A powered jet-generator which tops up the battery again.
How big a gen would you need and how big a jet power system to run it?
Personally, I use repulsion as a power system. My plane is so ugly that the earth repels it! I believe that the Chevron microlight has a similar system.
E
Blue Up
G-BMMF