Effect of Complex Terrain on Vertical Wind Profile Measured by SODAR Technique

Abstract

This paper describes the effect of terrain configuration on the atmospheric boundary layer for siting large wind turbines, based on data from Doppler SODAR. Prior to installing large machines, standard meteorological anemometers, to about 30 m height, are cost effective and relatively easy to install for an approximate extrapolated wind assessment. However, if accurate wind assessment is needed, the wind condition at hub height of more than 50 m should be measured directly, especially in complex terrain. The data presented in this paper were collected from a measurement site located at the coast of the Japan Sea. Comparison is made between data measured at hub-height by Doppler SODAR and the data predicted from observation of the wind condition at lower height. A significant difference is noted between the extrapolated results from lower level measurements and the results directly measured by SODAR, especially when the wind is over complex terrain. Thus it is shown that wind speed measurement at low height is not satisfactory for assessing wind accurately at rotor height, but that Doppler SODAR measurement is satisfactory.