Non-contact measurement of wind turbine rotor blade pitch angle deviations from 150 m distance

Wind power is an important source of energy in Germany. The shape and position of the rotor blades of wind turbines have a major influence on the efficiency and service life of the turbine. Geometric characteristics of rotor blades are recorded using blade stencils, photogram-metric or interferometric measurement methods. For this purpose, however, the turbine must be stopped and, furthermore, provided with patterns or markers. For inprocess measurements without manipulation of the wind turbine, the principle of time-of-flight measurement, on which so-called terrestrial laser scanners are based, is suitable. However, the achievable measurement uncertainty for the determination of rotor blade pitch angles is unknown so far. In this paper, the measurement uncertainties of rotor blade surface sensing for distances > 100 m are investigated experimentally and propagated to determine the uncertainty of rotor blade pitch angle using Monte Carlo simulation. For the consideration of the pitch angle uncertainty it is distinguished whether the nominal geometry of the rotor blades is known and absolute statements about the rotor blade position can be made, or whether the nominal geometry is unknown and only relative differences between the rotor blades can be evaluated.