Conceptual Design of a Single-Point-Moored FOWT and Tank Test for Its Motion Characteristics

A new design concept of a semi-submersible type floating offshore wind turbine (FOWT) moored by a single-point mooring is proposed. The FOWT model adopting 5MW class wind turbine is designed. The motion characteristics of the FOWT are evaluated by a series of tank tests. To this end, a scaled model with a scale ratio 1/100 is fabricated. The scaled mode tests are performed under winds, waves, and combined winds and waves to check its fundamental feasibility. It is observed that the motion characteristics under wind and waves are acceptable in general, and the combination of the single point mooring and the down-wind type rotor is effective in terms of weathervane. It is also shown that the difference between the two transfer functions to wave loads, one with and the other without wind loads, is small except pitch response at low frequencies.