Lidar Wind Resource Assessment in Simple and Complex Terrain

Wind Resource Assessment using lidar has been gaining pace during the last few years. The lidars are mainly mono-static backscatter profilers which measure wind speed and direction between some 40 m and 200 m agl. Lidars are usually compared to mechanical anemometry (cup and vane) which is the current standard in wind energy industry. A significant body of positive feedback in simple terrain – where lidar's volume measurement and mechanical anemometry's point measurement are easily correlated – has been reported. However, lidar measurement in complex terrain remains a real challenge.

Building upon existing literature and based on measurements in simple, complex and very complex terrains, tall met tower data and lidar data were gathered and analyzed. Both linear (WAsP) and RANS flow models were used to investigate how topography and land-use affect lidar readings as compared to mechanical anemometry. It is shown that the modeling is highly sensitive to the quality of digitized maps. Moreover, it is found that comparing lidar and met tower data is delicate and requires detailed data filtering. In a number of instances the discrepancies are due to the actual set up of the mechanical anemometer or its accuracy in complex flow. In such cases, lidar may not necessarily be more questionable than conventional mechanical anemometry.

Presented results provide insight on how to quantify precision and accuracy of lidar measurements in complex terrain when using it for Annual Energy Production estimations. The paper contributes to the advancement of the use of remote sensing in wind energy industry.