The downwind turbine has its rotor on the back of the turbine. The nacelle typically is designed to seek the wind, thus negating the need for a separate yaw mechanism.

downwind turbine

Advantage: The rotor blades can be flexible since there is no danger of a tower strike. The flexing blade has two advantages: 1) less expensive; 2) They can relieve stress on the tower during high or gusty wind conditions since the flexing allows some wind load to be transferred directly to the blades instead of tower.

Disadvantage: The flexible blade advantage can also be a disadvantage as the flexing may fatigue the blades. Tower shadow is problem with a downwind machine since the rotor blade actually passed behind the tower. This can cause turbulence and increased fatigue on the unit.

References & Resources