Juan José Trujillo

Arrangements for enhanced measurements of a large turbine near-wake using LiDAR from the nacelle

New LiDAR techniques are being tested and developed to support the development of large offshore wind turbines. Our interest in this paper is concentrated in wake measurements; therefore, a pulsed standard LiDAR is adapted for fullscale wind field measurements from the nacelle of a large wind turbine. We show the conceptual framework for planned adaptations to a Windcube® LiDAR for operation at the nacelle of a 5 MW wind turbine. The standard scanning mode is to be modified to properly obtain downstream and also upstream wind speeds. The wind field measurements are intended for verification of models for near-wake wind speed, wake meandering and new predictive control estrategies.

Comparing measurements of the horizontal wind speed of a 2D Multi-Lidar and a cup anemometer

Wind measurements of a 2D Multi-Lidar and a mast mounted cup anemometer are compared in this study. Average wind speed and direction as well as the turbulence intensity of the wind speed are considered. Data analysis is mainly performed using standard regression analysis on 10 minute average data and the calculation of the power spectral density. The results show a good agreement regarding wind speed and direction and the turbulence intensity of the horizontal wind.

Orientation correction of wind direction measurements by means of staring lidar

In spite of the efforts made at the time of installation of wind vanes or ultrasonic anemometers (Sonic), there is always a remaining uncertainty of several degrees in the absolute north of such sensors. In this research a method is presented to reduce the azimuthal orientation error of wind direction sensors by means of Doppler Lidar measurements. The method is based on the comparison between the conventional sensor and a distant long range lidar pointing to it in staring mode. By comparing their line-of-sight wind speeds any misalignment between both systems can be estimated more accurately. This method was applied in an measurement campaign in the offshore wind farm alpha ventus next to the meteorological mast FINO 1. The maximum alignment error of a Sonic was reduced to below ±1°. This accurate alignment has asserted, that no bias exists between Lidar and Sonic wind speed measurements.

Lidar Simulations to Study Measurements of Turbulence in Different Atmospheric Conditions

Modern lidar technology promises a fundamental enhancement of wind velocity measurements for site assessment. Previous studies have shown good agreements between lidars and mast mounted sonic anemometers concerning measurements of the 10 minute average horizontal wind velocity in flat terrain but have shown substantial differences concerning the measurement of turbulence intensity. One of the main reasons for poor turbulence measurements is assumed to lie in the scanning technique called VAD, applied by lidars. In contrast to a sonic anemometer, a VAD-scanning lidar senses the wind field at different positions along a circle. This is centred at the target point, and with a radius three orders of magnitude larger than the typical size of an anemometer. The resulting temporal and spatial averaging by the VAD scan influences the turbulence measurements. To understand the effects of different VAD scanning configurations and of the atmospheric condition on measuring turbulence, a numerical lidar scanner simulator was used. The influence of the VAD cone angle and the stability of the used LES generated wind fields were studied. The results show a high dependency on the used cone angle and the atmospheric stability.