I would surmise that the losses due to the transfer of energies via a belt or gearbox would make wind-generated power too inefficient to be financially feasible.

Consider that hydro-electric generators are coupled to the water and transfer energy in the same manner but don't have the physical challenges.

If you've ever looked at a dyno sheet demonstrating the HP output of an engine at the crank versus output at the drivetrain, there is a pronounced reduction of power due to the losses of energy transfer (friction, additional weight of the drivetrain, heat, etc.)

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