From lidar scans to roughness maps for wind resource modelling in forested areas

Rogier Ralph Floors*, Peter Enevoldsen, Neil Davis, Johan Arnqvist, Ebba Dellwik

*Corresponding author for this work

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Applying erroneous roughness lengths can have a large impact on the estimated performance of wind turbines, particularly in forested areas. In this study, a new method called the objective roughness approach (ORA), which converts tree height maps created using airborne lidar scans to roughness maps suitable for wind modelling, is evaluated via cross predictions among different anemometers at a complex forested site with seven tall meteorological masts using the Wind Atlas Analysis and Application Program (WAsP). The cross predictions were made using ORA maps created at four spatial resolutions and from four freely available roughness maps based on land use classifications. The validation showed that the use of ORA maps resulted in a closer agreement with observational data for all investigated resolutions compared to the land use maps. Further, when using the ORA maps, the risk of making large errors (> 25 %) in predicted power density was reduced by 40–50 % compared to satellite-based products with the same resolution. The results could be further improved for high-resolution ORA maps by adding the displacement height. The improvements when using the ORA maps were both due to a higher roughness length and due to the higher resolution.
Original languageEnglish
JournalWind Energy Science
Issue number1
Pages (from-to)353-370
Number of pages18
Publication statusPublished - 2018

Bibliographical note

© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License

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