Generator to motor to propeller
 

Something I have been thing about lately and may very well do, if I can figure out the particulars...I wanted to buy a paramotor frame and use a 2000W generator to provide a direct A/C current to a 80kv brushless motor. I am not sure if I need to "step-down" the voltage, since the motor is rated at 70v, using a step-down device (power supply) or if I can just use a heavy duty ESC to do this for me, along with a servo to meter the power and thus the speed to the motor. Any thoughts on how I could accomplish this or is it even possible? I am looking to extend the flight time by mounting a "super-quiet" or some other variety of generator to the paramotor frame rather than a standard gas engine to power the prop. is there a supply and demand law I am violating or some other reason people resort to using batteries in this sort of an application rather than a generator?