More ways of providing power

Add antimatter - an EXTREMELY rare substance, available at labs.
AM engine - practically infinite power, needs to be refilled with M/AM (Matter/Antimatter) cartridges.

Fusion reactor - essentially a mini-reactor taken a step further, now it generates power from nuclear fusion (combining of lighter particles in order to make heavier ones), various fuel modes, e.g. p-p (proton-proton (hydrogen-hydrogen)), D-T (Deuterium-Tritium), D-D (Deuterium-Deuterium), just to name a few.