INSTALLATION OF PRE-ASSEMSBLED OFFSHORE WIND TURBINES USING A CATAMARAN VESSEL AND AN ACTIVE GRIPPER MOTION CONTROL METHOD

抄録

To increase the competitiveness of offshore wind industry, cost-effective and time-efficient installation methods are needed. This work examines a novel installation concept using a catamaran vessel, which is specially designed to carry up to four tower-nacelle-rotor assemblies and perform offshore installation. The main challenge is to reduce the tower bottom motions induced by the vessel motions when it is placed on top of the foundation. A bottom fixed wind turbine foundation is considered in this study. An onboard gripper system is used to move the tower assembly along the vessel and perform the installation of turbine assembly onto turbine foundation. 1) Vessel is first positioned with its stern connected to the foundation through another gripper system, allowing only relative heave motions. 2) The turbine assembly is then transported to the vessel stern and it is hold right above the foundation. 3) Before the actual lowering and installation, the gripper and assembly are under active motion control so that they are kept steady in the vertical direction relative to the foundation top. 4) Once 3) is realized, the actual lowering and installation can start with active motion control on, to avoid unnecessary contact between assembly and foundation. The 3rd phase of the installation is numerically simulated. In the numerical simulation, an active force in vertical direction is added to control the assembly's vertical motion. The numerical simulation is performed using SIMO and RIFLEX under the SIMA environment.