Seasonal yaw misalignment

Understanding "seasonality" or seasonal yaw misalignment

What is the purpose of the turbine issue check?

• Variability in yaw misalignment seasonally detected using one year of high-speed data
• WindESCo has observed this behavior on several wind farms with different terrains and locations leading to variation in yaw misalignment estimates throughout the year.

Could this be identified in 10-min data?

• No, to view the changes in the yaw misalignment over time high-frequency data is required.  For more on this see the knowledge base article on yaw misalignment

What does this look like / How do you identify this issue?

• The plot below shows 12 turbines with multiple years of data. The mean yaw misalignment has been subtracted from each turbine, leaving a “Delta yaw misalignment”, which is the change of the estimate from its average value. The yaw misalignment for optimal power changes by 10 degrees over the year.
• We will evaluate the plant to identify seasonal yaw misalignment and then recommend a yaw adjustment strategy that optimizes both AEP and effort requirements for implementation.

More Detail:

• Seasonal behavior can include any behavior that is repeatable year over year and typically shows up as a sinusoidal variation.  
  • If it has a low amplitude it has little to no impact on AEP.
  • If the amplitude is high it may be appropriate to have biannual yaw misalignment corrections.
• Sources of seasonality are complex and include turbine design, terrain, and weather patterns.  It is common for there to be variability within a site.  When present it is consistent - even if the root cause is not fully explainable.  
• WindESCo has on-going investigations on this topic and has discussed the topic with our customer’s meteorological teams.