Advances in Model Scale Testing of Floating Offshore Wind Turbines Utilizing the W2 Wind/Wave Basin

Abstract Increased interest in floating offshore wind turbine (FOWT) technology has stimulated the development of new testing facilities and techniques to support the design of these structures. This paper presents some specific challenges of testing FOWTs and how these requirements have driven the development of wind/wave basins capable of providing both high quality wind and wave environments necessary to test these structures. Previous experience by the University of Maine (UMaine) and others as part of the DeepCwind Consortium in testing 1/50th-scale FOWTs at the Maritime Research Institute Netherlands (MARIN) Offshore Basin has supported the development of UMaine's Harold Alfond W2 Ocean Engineering Laboratory (W2), which includes a movable, open-jet wind machine specifically designed to provide a high quality wind field for testing FOWTs. A calibration testing campaign of this newly constructed facility will recreate a subset of the tests performed at MARIN. The new test campaign will contain system identification, wind turbine performance characterization, wave only, wind only, and combined wind/wave test cases utilizing both regular and irregular wave specifications. This paper will focus on the initial phase of this campaign which includes select system identification and regular wave tests. The test specimen is the same used in the original test program performed at MARIN and consists of the 1/50th-scale model semi-submersible along with the 1/50th-scale model version of the National Renewable Energy Laboratory (NREL) 5MW Reference Wind Turbine. Results from the new test campaign are studied and compared with the data from the 2011 MARIN test. Differences in data collection methods, basin geometry, model specifics and test methods were expected and are discussed for this initial phase. In particular, differences in the basin geometry necessitate development of a truncated mooring system to emulate the response of the full mooring system used at MARIN. The implications of utilizing this method are discussed as well as additional areas of future work to be completed in subsequent phases of the validation test campaign.