Wind speed measurement for absolute power curve determination from induction zone lidar measurements

Abstract

There is growing interest in turbine performance assessment using nacelle mounted lidars. In the past, this has involved measuring the free stream wind speed, on the periphery of the operating turbine’s induction zone. As turbines increase in size, measuring at correspondingly longer ranges can start to introduce uncertainties in the wind speed, especially in complex terrain or when a turbine is part of an array. One way of reducing these uncertainties is to measure wind speeds inside the turbine’s induction zone, closer to the turbine’s rotor, then use various techniques to adjust these measurements to generate free stream equivalent windspeeds. This paper describes the application of both induction zone model and transfer function approaches. The results from various campaigns are presented and the two methods are compared using correlations. Both yield good results in terms of accuracy (usually gradients of 1.00 ± 0.004) and coefficients of determination (typically 0.99).