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Figure 49: A ground based ZephIR 300 system compared to the industry-certified met mast at
Pershore, demonstrating strong correlation and a gradient very close to unity. In this example,
comparison was carried out at a height of 70.5 m. From (Rutherford et al., 2012).
Figure 50: Graph showing results from routine re-calibration of four cups to be used at an
accreditedmetmastsite.Theverticalaxisshowsdifferenceswhenthesamecupwascalibrated
at two independent wind tunnel standards facilities. The tunnel-to-tunnel calibrations of the
same cups show variability of the order of 1%.
4.8 Turbine mounted continuous wave lidar
An application that has recently generated much interest is the use of remote sensors, such
as lidar, to measure the wind field ahead of an operating wind turbine generator. Since, for a
correctlyyawedturbine,thelidarisalwayspointingintotheincidentwindfield;thiscanbevery
useful for power curve measurement as no sectors need to be eliminated for turbine shadow,
as is the case when using a fixed meteorologicalmast and cup anemometers (of course sectors
affected by the wakes of adjacent turbines will still need to be filtered). Providing advance
wind data to the turbine control system also has many potential advantages such as reducing
stress loads by warning of incoming gusts or optimising rotor pitch control. The lidar can
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