Publishers version - DTU Orbit

in Eastern Jutland between January and April, 2012 (Slinger et al., 2013). The lidar, a dual
mode ZephIR 300, was mounted on the nacelle roof of a NEG-Micon 2 MW wind turbine
with a 72 m rotor diameter. There was no meteorological mast data from the site - the trial
was intended to measure relative, rather than absolute power curves, in order to demonstrate
and quantify turbine performance improvements after turbine tuning.
Lidar data from the first part of the trial, before wind turbine tuning was carried out,
identified a turbine yaw error of between 14 ◦ and 16 ◦ (Figure 53). This was remedied by a
nacelle vane recalibration before the second phase of the trial was undertaken. The effects on
the lidar measured power curve (at a measurement range of 180 m or 2.5 rotor diameters)
are clearly visible (Figure 53). ROMO Wind estimated an improved annual energy production
(AEP) of approximately 5% after yaw recalibration.
Figure 53: (a) Measured turbine yaw misalignmentbefore and after nacelle vane recalibration.
(b)Wind turbinepowercurvesmeasuredbynacellemountedlidarbefore andafternacellevane
recalibration at a measurement range of 180 m.
Measurements were also made at a series of other ranges between 10 m and 180 m and
are shown in Figure 54). While the measurements at close range ”flatter” the power curve
due to the rotor induction effect, they demonstrate that high quality power curves can be
obtained very close to the rotor. While these would have to be corrected to be quantitative,
they are very representative of the true wind field incident on the turbine rotor and can be
expected to be immune to say, the effects of complex terrain, as compared to more remote
measurements.
Figure 54: (a) time series of wind speed measurements taken at a series of measurement
ranges. The measurements are highly correlated, but rotor induction (blockage) effect is
clearlyvisible.(b) Series of wind turbine powercurves generated from measurements at several
ranges. The upper curve is from the closest range (10 m), the lower curves were measured at
30, 50, 100 and 180 m respectively.
The second study reported here took place on a DTU test turbine situated at Roskilde,
DTU Wind Energy-E-Report-0029(EN) 95