Presentations

Abstract

ArcVera performed IEC-61400-12-1 power curve (PC) measurements on wind turbines at different projects. ArcVera used the Nacelle Transfer Function (NTF) to derive free wind speed and evaluate the impact on the AEP compared to 61400-12-1 procedures.  The average and standard deviation of the AEP difference between NTF and 61400-12-1 procedures vary with the Rayleigh wind speed. Average AEP deviations are 1% and standard deviation is 1.3% when Rayleigh wind speed is 8 m/s. Once an NTF is derived at a turbine, the free wind speeds at that turbine can be recreated with good accuracy. It is shown that the NTF within a site for turbines of the same OEM and rotor diameter are remarkably similar. When comparing NTFs of the same OEM and rotor diameter from different sites it is shown that the NTF from one site can be used at another site with reasonable uncertainty. However, a strong quality control program should identify outlier nacelle transfer functions. In fact, that is one of the advantages of testing all wind turbines in a wind farm using nacelle anemometer testing. Anomalous NTF could potentially be a result of improperly entered controller settings, yaw misalignment or physical flow conditions at the site such as the inflow angle.   This paper shows the importance of quality assurance when using the NTF derived from one site to apply to another site.   An example is given where the slope of the NTF from one site varied by 16% from the slope at another site.   By removing the outlier, standard deviation of slope is reduced to 1.25%.  If the outlier is not removed, standard deviation of the slopes can be reduced to 6% by using an ensemble approach using data from all turbines at several sites.  Careful quality assurance of the NTF will both reduce uncertainty and give an indication of the magnitude of the resulting uncertainty.  Future work will analyze NTF from additional projects and cross compare AEP using NTF from turbines at other sites.