Testing floating LiDARs offshore - as a prerequisite for a cost-efficient wind resource assessment: Paper presented at EWEA Offshore Conference 2015, Copenhagen, Denmark, 10-12 March 2015

Floating LiDAR systems gain more and more in importance for the realisation of cost-efficient offshore wind resource assessments (WRA). These kinds of systems may not only offer measurement data that are more complete than those from present offshore meteorological masts (by adding e.g. further measurement heights due to the used LiDAR technology) but have also significant advantages in terms of the associated costs for the provision, installation and final removal of the devices. Before applying a floating LiDAR system within an offshore WRA campaign, its performance needs to be tested and verified according to a well-defined scheme. In addition to the measurement accuracy the expectable system and data availability is a crucial outcome of a test preliminary to the final application. Guidelines for such testing are underway – with an early document initiated by the Carbon Trust and already presented in 2013, and a more detailed draft document presently prepared within the IEA Wind Annex 32. To illustrate the guidelines we consider here a particular case study with the Fraunhofer IWES Wind LiDAR Buoy that was first introduced in 2013 and since then tested in two offshore measurement campaigns. Both campaigns confirm a very good measurement accuracy – in terms of correlation to the reference measurements – of the system. We present in detail how the arranged tests follow the drafted guidelines and how the measurement performance of the investigated system is deduced from the collected system and reference data. As test site we have used the FINO1 measurement mast and infrastructure in the German North Sea that has proven to be a suitable reference site for floating LiDAR offshore tests.