The type of generator that is best for wind turbines is an induction generator.
You can make a 12 volt wind generator out of a car alternator or you can make a larger generator that supplies AC power by attaching a small generator head to a wind turbine.
My neighbor had a harbor freight gas generator that worked great but then the engine stopped working so he repurposed the generator head and made a wind turbine out of it that produces both 12 volts and 110 volts.
If we analyze the commercially available wind turbine generators, it is found that direct drive, grid connected generators indicate a future trend in the wind generation.
The system reliability will increase by elimination of the gear boxes and the power electronic converters.
Also the system efficiency will increase because the losses in the gear box and power electronic converters are eliminated.
Permanent Magnet Synchronous Generator(PMSG), Field excited synchronous generator (FESG) and the Induction Generator(IG) are three candidate for such application.
As permanent magnet excitation eliminates the excitation losses of a FESG hence PMSG will be more favored option.
The direct drive, grid connected IG and PMSG generators are intended for fixed speed operations. When the PMSG generator is connected to the grid, the speed is determined by the grid frequency and is constant so, if the torque to the generator is increased (sudden blow of wind), the generator will produce electromagnetic force to resist an increase in speed.
So, a blow of wind leads to large stresses on the wind turbine’s drive train.
However IG allows a small change of speed with the change of torque going to the generator and lower stresses/tear and wear of the drive train.
As the IG and the PMSG machine have similar Stator, the cost difference is mainly due to the rotor.
The PM’s cost is always going to be more than that of aluminum and one can see that the cost of the induction generator is expected to be much lower than the PMSG generators for the same power rating.
But PMSG generators have higher efficiency so the higher material cost may be somewhat compensated for the extra electricity generated.
Also, inductive power factor of the induction generators require capacitors for power factor correction and may increases the overall cost of the IG.
So, a trade-off analysis is needed for case by case basis before declaring any one machine best for an application or an Installation.