Mechanical to electrical power conversion calculations
As usual, you need to understand your system. What generator do you use? Do you have any gear? What load is on your generator?
Basically, you will get all the power you have on input, minus the losses. The losses include friction, heat on the generator, and other parts. Probably for each point on the speed chart the losses will differ, which means you may be able to optimize.
For example, if you are charging a battery with your generator, you can use a circuit to adjust charging current to the rotor speed. Another loss would be the power of the circuit including any speed sensor, but it may pay off by reducing other inefficiencies.
Anyway, there is a lot to do to really understand this system.