In China, due to very thick silty soil top layers existed in many offshore wind farms, the self-elevated offshore wind turbine installation units are not versatile, and therefore the installation of the offshore wind turbine tower and nacelle by floating crane vessels is demanded recently. In this paper, a numerical approach, involves the floating body dynamic analysis and explicit dynamic analysis, is established for the evaluation on this new installation method. An offshore wind farm construction project is examined by this numerical approach, and the computational results reveals that this new installation method is feasible.
The offshore wind turbine (OWT) installation is commonly accomplished by a self-elevated wind turbine installation unit, which is the bottom-founded offshore structure. However, the self-elevated wind turbine installation unit may be unable to work when the top layer of the sea bed is the soft mud with a prominent depth, requiring a much large leg penetration depth which may exceeds the installation unit's capability. Under such situation, floating crane vessel is attractive because the sea bed condition will not impede its operation. However, installing offshore wind turbine component with floating crane vessel is one of the most challenging activities in offshore wind industry, since installing the offshore wind components requires an extremely benign work condition, such as a stable working platform and small hook movement induced by wind. Recently, Parkwind plan to install the offshore wind components with floating crane vessel in Arcadis Ost 1 Offshore Wind Farm due to the challenging sea bed condition in the wind farm. Their floating installation method is to assemble the nacelle and the rotor first on a dummy tower placed on board a crane vessel, and then lift the nacelle-rotor assembly onto the top of the pre-installed wind turbine tower.
This installation method is simple since it involves only vertical mating operation. Therefore, the critical event related to this installation method should be the jib top vertical motion, and a numerical approach could be established as the critical event is determined.
