Several methods for power curve measurement with various deviations from the current standard requirements will be investigated.
Task 4.1 Evaluation of power curve measurement with profiling nacelle lidars
The wind speed and direction profiles measured by the nacelle lidars will be analyzed using normalization methods such as the rotor equivalent wind speed for power curve measurements. Comparison will be made between the power performance assessment obtained with the lidar profile measurements, the lidar hub height measurements and the mast measurements.
Task 4.2 Power curve verification based on near flow wind speed
Two power curves will be derived from near rotor speed measurements, with the continuous lidar for identical turbines: one offshore in MC2 and one in complex terrain in MC3. The wind field and the power curves measured in these two cases will be analysed; and, with the input from WP1, the effect of the terrain topography on the turbine inflow, and consequently on the power curve, will be assessed. A method for power performance verification of wind turbines in any type of terrain, without the need for site calibration, will be derived.
Task 4.3 Absolute power curve measurement based on near flow wind speed
The method from task 4.2 provides a ‘near field’ power curve, which whilst sufficient for verification purposes, cannot be used for resource assessment since estimation of the annual energy production requires a power curve relating the turbine power output to the free wind speed. Using the inflow modelling results from WP1, and measurements from MC2 and MC4, a method will be developed to relate the wind speed measured near the rotor to the free wind speed, to make it possible to map a short range power curve to an “absolute” measured power curve, and the associated uncertainties will be estimated.