Wake Effects when Estimating Residual Life of Wind Turbine Support Structures

Monitoring the structural state of support structures is key to reduce maintenance costs and extend the life-time of wind turbines. Different wind turbines in a farm experience different loading conditions, due to for example flow distortion from other turbines (i.e. wakes), different geotechnical and topographic conditions. The effects of wakes are known to impact power production and mechanical loads on the rotor. Thus components will wear differently within a wind farm. To what extend are the loads on the support structure influenced? Can we estimate tendencies and map fatigue across the wind farm with coarse models? Using a coarse resolution model of a wind farm that considers wake effects (wind speed deficit, wake expansion, and wake meandering), quasi-static aerodynamics, controls and state-space models of drive-train torsion and tower bending we observed that: loads on the support structure are affected by wakes, coarse resolution models of wakes can give trends that indicate which turbines suffer more within a farm; when designing a farm level SHM it is worth to consider wake effects to decide which turbines to instrument and how to extrapolate to other turbines. Next steps in this approach are to add fidelity by means of: larger set of load cases to reduce statistical uncertainty, and increase fidelity of physics and parametric models