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Figure 112: Power curve met mast and umean method.
the 49 measurement points (Big-Cross). Even when reducing the measurement points the
standard deviation is still very small.
ubigcross = 1
5
ui. (183)
5
Figure 113: Five points out of 49 for the Big cross method (left) and calculated power curve
(right).
8.8.2 Rotor effective wind speed
In this case the six measurement points of a circle are measured at each of the five focus
distances(Figure 114(left)). Forquite goodwind fieldinformationahighspatial and temporal
resolution of the wind fields is needed. Therefore all of these thirty measurement points in
space are taken into account and are calculated to one single speed, which is further called
rotoreffective wind speed v0: In (Schlipf et al., 2012)one describes how to calculate this rotor
effective wind speed. The line-of-sight wind speeds are measured by the laser in six points at
five different fixed distances. By the use of assumptions the wind speeds are corrected and
averaged over the last trajectory at each focus distance. In a further step the resulting preview
DTU Wind Energy-E-Report-0029(EN) 167
i=1