Investigation into the Potential Use of Damping Plates in a Spar-Type Floating Offshore Wind Turbine

Abstract

Spar is one of the promising floating platforms to support offshore wind turbines. Wind heeling moment is large in the case of floating offshore wind turbines and, therefore, it is important to reduce the pitch motion of the floating platform. To address this issue, a spar platform with damping plates is proposed and investigated in this study. (i) Type-A, (ii) Type-B, and (iii) Type-C models of 1/120 scale were fabricated with similar stability parameters. Type-A is a classic spar, Type-B and Type-C are spar with damping plates by replacing the ballast water part with horizontal plates and vertical plates, respectively. The rotor model consists of (i) no disk and (ii) with disk conditions. A series of model scale experiments were carried out in the water tank in regular waves, and motion response was measured. A calculation method based on classic frequency-domain was developed to incorporate damping plates and validated with the experiment results in no disk and with disk conditions. When pitch response of Type-B and Type-C were compared with respect to Type-A, it was found that the spar platform with damping plates reduced the pitch response in most wave frequencies.

Keywords

• floating offshore wind turbines
• spar platform
• damping plates
• added mass
• wave radiation damping
• wave excitation force