New method to calibrate a spinner anemometer

The spinner anemometer is a wind sensor, based on three one dimensional sonic sensor probes, mounted on the wind turbine spinner, and an algorithm to convert the wind speeds measured by the three sonic sensors to horizontal wind speed, yaw misalignment and flow inclination angle. The conversion algorithm utilizes two constants k1 and k2 that are specific to the spinner and blade root design and to the mounting position of the sonic sensors on the spinner.

The two constants are calibrated by means of two different test and instrument set-ups. Both calibrations consider the rotor of the wind turbine to be stopped during calibration in order for the rotor induction not to influence on the calibration, so that the spinner anemometer measures ”free” wind values in stopped condition.

The calibration of flow angle measurements is made by calibration of the ratio of the two algorithm constants k2=k1 = k_. The calibration of k_ is made by relating the spinner anemometer yaw misalignment measurements to the yaw position when yawing the wind turbine in and out of the wind several times.

The calibration of the constant k1 is made by comparing the spinner anemometer wind speed measurement with a free metmast or lidar wind speed measurement at hub height. The present paper describes both procedures, exemplified and applied to a 500 kW wind turbine.