Lindahl was contracted by a major developer/owner to provide power curve performance testing services for one of their operating projects. The wind farm, the name of which remains confidential, with an installed capacity of more than 100 MW represents a very large investment. Concerns of power curve under-performance were raised after deviations from budget expectations were mounting up.
Contractually, power curve performance testing was to be carried out by a specific third party using purpose-made testing equipment, including new temporary masts and high-quality power transducers. The costs of undertaking such a test would of course be very high. The project was already equipped with several permanent hub-height meteorological masts, all with high quality and well-maintained instrumentation, with one of the masts in a location well suited for power curve performance testing of three wind turbines.
Together with the owner, Lindahl developed an analysis scope based on the principle of following the guidelines defined in IEC61400-12-1 as closely as practical but utilising only readily available and existing data. Lindahl undertook data quality assurance and normalisation procedures, application of site calibration factors, wind speed to power correlations, extrapolation and AEP calculations. The analysis was undertaken for all three wind turbines, and for several different turbulence and wind shear conditions. From the results, significant performance variability was found to have been caused by flow conditions outside of the scope of the performance warranty. The conditions were known prior to construction, but the impact on the power curve had been underestimated.
While disappointing for the owner, they were relieved they hadn't spent 100s of thousands of dollars to find this out. They are now cooperating with the OEM on improving performance in the specific flow conditions.