What is yaw misalignment?

What is yaw misalignment in a wind turbine?

Yaw misalignment occurs when a wind turbine’s rotor and blades are not facing directly into the wind. Ideally, a wind turbine is positioned precisely perpendicular to the direction of the wind. In this position, the wind turbine receives the maximum amount of energy from the wind’s current. 

Most wind turbines have some degree of yaw misalignment, which results in lower power production. Eight degrees of yaw misalignment can decrease a wind turbine’s annual energy production (AEP) by approximately 2%. Yaw misalignment can also cause unnecessary strain and wear on the turbine mechanical systems, thereby reducing its lifespan.

What causes yaw misalignment?

There are multiple factors that can cause yaw misalignment. One common factor is inaccurate directional calibration of the windvane and yaw positioning system. Typically, this originates from a mechanical issue caused by wear and tear of the yaw system.

Another common factor is inaccurate wind direction sensing. This can happen when nacelle anemometers encounter turbulence triggered by the spinning wind turbine blades.

Finally, faulty control system settings that dictate when and how to yaw the turbine can contribute to misalignment. Many of these factors are rooted in aging systems.

How to detect yaw misalignment? 

Yaw misalignment is typically detected via one of two methods. The first method is to mount a LiDAR system on the wind turbine. This will provide an accurate reading of both the wind velocity and its direction prior to being ‘swirled’ by the rotating blades. However, this can be an expensive approach on a large wind farm. 

Another method utilizes an independent anemometer on a tower located near the targeted wind turbine, and then comparing readings with the unit’s sensor. 

Both methods are time consuming and only provide reference data. As such, the need to detect yaw misalignment is often superseded by advanced control algorithms that automatically find the correct yaw position to generate full power output.
 

How to correct yaw misalignment?

Modern turbine control system retrofits utilize advanced control logic to mitigate suboptimal turbine performance created by misalignment. Self-calibrating yaw control algorithms detect static yaw misalignment and provide continuous alignment to ensure the turbine is performing to its full potential.

Emerson includes a self-calibrating yaw control algorithm as part of its standard wind turbine control system retrofit. It requires no extra sensors. Consisting of machine-learning, the algorithm typically requires a brief, two-week period for auto-calibration after installation. If the windvane and yaw calibration shift or degrades further, it will adapt and autocorrect.

The result is a wind turbine with correct rotor-positioning, and power-performance optimization of the turbine generator. Emerson retrofits can extend turbine lifespans and typically deliver 3-5 percent more annual production, resulting in payback within a year. Visit our Wind Turbine Retrofit page to learn more.