Dynamic life prediction of pitch and yaw bearings for wind turbine

The design guideline of the National Renewable Energy Laboratory (NREL) is a standard for designing and verifying pitch and yaw bearings of wind turbines. The usability of the guideline was evaluated by comparing with analytical results obtained by a commercial software. Results from calculation equations of the NREL guideline and from a commercial software were compared in terms of the main design evaluation items of pitch and yaw bearings, such as dynamic life, static load factor, and case-core interface models. Calculation and analysis were conducted using specifications and loading conditions for the yaw bearing of a 2.5 MW wind turbine. Results showed that the values computed using the NREL guideline were more conservative than those derived using the commercial software. Although the guideline showed some differences from the analytical results obtained using the software, they can be used in the initial design of pitch and yaw bearings because of the advantage of the simplicity and the characteristics of conservative output.