Hey @robynE : some say the real area where advancing is need is more in the batteries that store the current that the solar panels...but I agree that for a vehcile, with limited footprint on to which to place such panels, efficiency gains would come in handy!Hey, I know, I can mount a wind turbine to the roof! hahaha
It's funny you mentioned a turbine on the roof. How's about one "below the fuselage."
It's call a RAT or ram air turbine, and it's tucked away on most commercial aircraft to be cranked down in an emergency, to supply electrical power to essential aircraft systems if both the primary and backup power systems fail.
The turbine adjusts its blades to spin at a constant spin independent of plane velocity, to supply power in just the right phase for the plane's needs.