Publishers version - DTU Orbit

Table 7: Combined results from 28 ZephIR 300 units. The mean and standard deviation of
the mast comparison parameters, gradient and R 2 , were calculated from the first batch of 28
ZephIR 300 units. These results confirm the consistency of the lidars’ performance.
Height [m]
Gradient R 2 Laser sensitivity
Mean Std. Dev. Mean Std. Dev. Mean Std. Dev.
91 1.0039 0.0072 0.9894 0.0059
70 1.0033 0.0072 0.9928 0.0059
45 1.005 0.0050 0.9924 0.0050
20 0.9967 0.0045 0.9925 0.0048
1.0350 0.0893
be mounted on the nacelle roof, within the rotor spinner (Figure 51) or built into the rotor
blades.
Figure 51: Continuous wave dual mode ZephIR 300 lidars mounted on a nacelle roof (left)
and within a wind turbine spinner (right).
The high sensitivity and hence fast data rates of circular scanning CW lidar make it very
well suited to turbine mounted applications. By adopting different signal processing and data
analysis strategies; hub height wind speed, direction, shear exponent and turbulence can be
measured,orspeed,directionandturbulenceatdiscreteheightsacrosstherotorcancalculated
(or both). The latter technique can be used to generate rotor equivalent wind data which has
been shown to produce more precise and representative wind turbine power curves, especially
for large rotor diameters (Wagner et al., 2008; Wharton and Lundquist, 2012).By measuring
the inclination of the lidar in real-time, the circular scan CW approach allows the effects of
nacelle motion on both line-of-sight velocity and measurement height to be negated.
4.8.1 Least-squares fitting routine for horizontal scanning (turbine mounted) operation
The use of a CW lidar for turbine mounted applications is fundamentally a quite different
arrangement when compared to a ground based, vertical scanning configuration. Unlike the
latter, the scan axis is approximately horizontal, and the lidar is almost always predominantly
staring into the wind. A consequence of this is that the polar plot (of the measured line-ofsight
wind speeds as a function of scan angle) is no longer a figure-of-eight shape, but instead
takes on a more circular appearance (Figure 52).
DTU Wind Energy-E-Report-0029(EN) 93