UTILISATION OF INLAND WIND POWER - Fist results of 200 m mast measurements in comparison to lidar measurements at a complex terrain site

摘要

At the end of the first half of 2011 a capacity of almost 27 GW of onshore wind power was installed in Germany. However, wind power onshore has still a huge potential for further growth. To assess this potential, especially in forested and complex terrain, new measurement techniques have to be established. With current tower technologies allowing the installation of turbines with hub heights up to 150 m, extrapolation methods for traditional mast based measurements are becoming increasingly unreliable particularly under consideration of today's large rotor diameters. Furthermore building measurement masts up to hub height tends to be uneconomic. Nowadays ground based remote sensing using lidar technique is a new option to complement or eventually even replace mast mounted measurements. Lidar measurements have shown a high accuracy in even, homogeneous terrain i.e. offshore or in flat lands. In contrast to that, applying these techniques in hilly or mountainous terrain results in considerable bias, due to the principle of the 3D wind vector reconstruction. Within the two years of project "Utilization of Inland Wind Power", ending in December 2011, a 200 m high met mast has been installed at a hilly, forested site in central Germany to survey the profiles, the wind resource and the design parameters relevant for the design of wind turbines, e.g. turbulence, extreme winds, etc. The met mast is equipped with up-to-date meteorological sensors observing a wide range of different meteorological parameters. In addition to that diverse lidar measurements are carried out, to analyze uncertainties and limits of those devices in this terrain. For this purpose the measured wind profiles will be compared to mast mounted measurements in several heights between 40 and 200 m. This allows to survey the dependency of the accuracy of the measurement on the height of the measurement. Additionally measurement results are to be evaluated under consideration of different atmospheric conditions, weather situations and time of day. Wind speed and direction sensors at least every 20 m up to 200 m height and multiple temperature difference, pressure and humidity sensors give detailed information about wind profiles for different atmospheric stabilities. As a first approach to correct the lidar measurements the method developed by Ferhat Bingol was applied to check if it improves the quality of the measurement. First calculation results show that (depending on wind direction) lidar measurement bias reaches values in the order of 10%. Due to the fact that for this site the highest errors occur at the main wind direction, the resulting impact on the energy yield assessment on basis of lidar technique will be considerably high. As expected there is a significant deviation between lidar and mast at all heights [1]. Neglecting the few outliers, the maximum absolute difference is about 2 m/s. Most values are located within an interval of -1 m/s to 1 m/s.