Remote Sensing of Offshore Winds for Wind Energy Applications

Winds in the coastal zone are variable due to sudden changes of the meteorological conditions caused by the land-sea transition. Near-shore areas are, however, attractive for installation of offshore wind farms because of the shallow waters and the proximity to logistics on land. Accurate information about winds in the coastal zone is necessary for optimizing the positioning and layout of wind farms.

The PhD project explores the potential of new remote sensing techniques for mapping of coastal winds and wind resources. Wind fields retrieved from satellite observations represent the crosscutting research theme of the project because the maps are available anywhere in the world and for many years in the past.

The satellite wind fields are benchmarked against in situ observations, model simulations, and ground based remote sensing using lidars and Doppler radars in different configurations. The accuracy of individual wind speed estimates from satellites is quantified and it turns out that observations from different satellite missions and periods need to be carefully inter-calibrated before they can be combined.

A method for inter-calibration is developed and applied in different areas. The results show consistently that intercalibration removes most biases so that a better agreement with reference wind speeds is achieved. Wind resource estimates derived from the satellite wind speeds become more conservative.

Comparisons against spatial wind data from ground based remote sensing confirm for the first time that satellite winds are reliable as close as 1 km from the coastline. Wind speed gradients in the along-shore and cross-shore directions fit well with reference observations but the satellite imagery could provide smaller-scale wind variability, which modeling cannot capture.

The influence of large offshore wind farms on the wind flow is examined and the project shows how the interplay of wind farm effects and natural wind speed gradients lead to very complex wind conditions in coastal zone. The project has advanced our understanding of the wind farm interaction with the surrounding environment.

The project work has been carried out in collaboration with academic and industry partners from Denmark and abroad. The applicability of findings for the wind energy industry has been in focus and innovative efforts have been put into improving the ease of use in connection with novel remote sensing observations.