Upwind, downwind, what's the best?

Upwind is the name given to wind turbines when their rotor faces the wind, so when in operation the rotor stays in a front position. In the same way, downwind means that the rotor adopts a rear position, so wind reaches first the turbine body and then the rotor. As seen before Aerotek is upwind and Skystream is downwind.

 

Which is best? As usual it depends on several questions. Upwind generators have turning axis near the rotor, thus allowing the rudder to apply enough torque to properly orient the turbine. Downwind generators accordingly have a turning axis not so close to the rotor, which acts as orienting device by its own air drag, thus getting rid of any rudder. Upwind turbines are more common than downwind, because of its simplicity. But getting rid of the rudder is a desirable feature not so easy to achieve.