The yaw system of wind turbines is the component responsible for the orientation of the wind turbine rotor towards the wind.
The task of orienting the rotor into the wind was a complicated issue already for historical windmills. The first windmills able to rotate in order to "face" the wind appeared in the mid-18th century. Their rotatable nacelles were mounted on the main structure of the windmill using primitive wooden gliding bearings lubricated with animal fat. The necessary yawing torque was created by means of animal power, human power or even wind power (implementation of an auxiliary rotor known as fantail).
Vertical-axis wind turbines (VAWTs) do not need a yaw system since their vertical rotors can face the wind from any direction and only their self rotation gives the blades a clear direction of the air flow. Horizontal-axis wind turbines (HAWTs), however, need to orient their rotors into and out of the wind and they achieve tha