Someone mentioned that generators produce more power the faster they go but this is putting the horse before the cart, so to speak.
Generators are governed, and their speed does not vary much, as the load increases there is a change in current and voltage which is detected and the strength of he magnetic fields of the rotor are increased(assuming an alternator) this causes a much larger increase in the magnetic field produced by the static windings and slows the generator down.
The governor detects this change in speed and more fuel/air mixture is added.
This means IRL that generators actually run faster under low load and produce less power(but the differance in speed is usually very small), diesel engines used like this are used at their most economic speed.