Posters

Abstract

Wind turbines are traditionally designed for 20 years of operation. By extending turbine operation beyond design lifetime both the return of investment and the climate benefit improve significantly. Most national guidelines and standards on wind turbine lifetime extension require both theoretical calculations and practical inspections. The theoretical calculations concern fatigue accumulation incurred during the operation period relative to the original design limits. Over time wind turbine fatigue accumulation is mainly driven by wind speed and turbulence. Hence, accurate data for wind speed and turbulence form an important basis for potential lifetime assessments. Here we present a method to accurately recover wind speed and turbulence data from time series of typical 10-minute SCADA operational statistics. The proposed method does not rely on the notoriously inaccurate nacelle mounted anemometers, nor does it require mounting of new sensors. The method relies on an accurate model for the interaction between a turbine rotor and a turbulent wind field to recover reliable wind speeds and turbulence from turbine SCADA data. As a four-dimensional phenomenon turbulence fluctuates both in space and time. The net effect of the rotor-turbulence interaction is that only the larger spatial scales of turbulence significantly result in fluctuations in power output. Hence, as wind turbine rotors become larger, their power output becomes increasingly insensitive to turbulence. This effect is an important component in the retrieval of reliable wind speed and turbulence from operational SCADA data. The presented method has the advantage that it recovers reliable time series of historical wind speed and turbulence as directly experienced by each individual wind turbine within a park. Not only does the recovered wind climate account for the ambient climate, but it also includes the effects of wakes within a park leading to reduced wind speeds and increased turbulence. This relieves the need for additional and uncertain models for wake deficit and turbulence. Theoretical fatigue lifetime calculations are the important first step when assessing the potential for wind turbine lifetime extension. Theoretical calculations are cheap relative to physical inspections and help identify the wind farms and individual turbines with the biggest potential for continued operation. This can ensure directing inspection investments towards farms and turbines where extension is most likely to be feasible.