Intercomparison of two offshore wind park sites using SAR data

Kurzfassung

Due to the shortage of suitable sites on land offshore Windfarming has grown rapidly in Europe over the last decade. For the optimal siting, building and operation of these wind parks remote sensing techniques can help in many different ways. In this study a special application of the well known windfield measurement technique based on synthetic aperture radar (SAR) data is presented. SAR scenes as acquired by the European satellites ERS-2 or ENVISAT permit the estimation of two-dimensional wind fields with a resolution of less than 1 km and a coverage of up to 500 km. With this capability SAR is an efficient instrument to obtain wind information on spatial scales relevant for offshore windfarming. In the analysis the two windparks sites "Horns Rev" and "Butendiek" in the north sea are intercompared. While "Horns Rev" is already in operation "Butendiek" is still in the planning stage. The objective is to assess the expected power yield in the new wind park in comparison to the existig wind farm. For the investigation ERS-2 image mode scenes of 100 by 100 km size were used, which are ideally suited for this application, because both wind farm sites are coverd by a single scene. Scatterplots of SAR derived windspeed and winddirection obtained for both windfarm sites are analyzed. The significance of differences are discussed based on the error statistics of the SAR wind measurement technique. Examples of low wind and high wind cases are discussed in detail in particular analyzing saturation effects. It is furthermore investigated how the expected wind errors depend on the spatial resolution of the wind field. The applicability of the method to other sites is discussed.