I can see one possible benefit of this set-up...the rider can pedal continuously with the same resistance and cadence regardless of terrain rather than the start-and-stop as a direct chain drive would require. Assuming the designer has enough power and gearing for hills, he's designed an electric scooter trike that allows a workout while traveling-whether this function allows a decent partial charge or jusy a trickle charge and Regen on hills-well, we'd have to quiz the builder on his results to date...
Here's a vaguely similar design:
SUNZEECAR
I'm assuming that the 100 watt pedal generator must be contributing enough charge to incorporate into the vehicle, otherwise the designer would probably ditch it for either additional solar panels or to trim the weight for a touch more range.