Offshore wind energy is experiencing rapid development and is expected to make up an even bigger part of the worlds future energy mix. New installation concepts for offshore wind farms involve lifting operations of wind turbine components from floating vessels. These installation concepts will only be economic if the lifting operations are performed safely at sea states with high significant wave heights. In this paper, we give an overview of current technical solutions, which could be used to lift the components tower, nacelle, hub and rotor blade from a floating vessel. We classify and analyze solutions found in patents and the academic literature and point out open problems, which need to be addressed to enable lifting operations at higher sea states than what is currently feasible. While enhancements on the vessel and crane can help to achieve this goal as well, this paper only deals with technical solutions concerning the interface between the vessel and the component as well as the interface between the component and the crane. Consequently, we analyze, classify and discuss solutions for the seafastening, the lifting gear as well as motion compensation systems. We find that there exists a large number of solutions, which are specific for a single component, but few solutions, which are applicable to all components without adaptations. Additionally, we miss hydraulic seafastening mechanisms, which are remotely controlled and synchronized with the lifting operation. Consequently, we argue that standardized interfaces between the component and the crane as well as remotely controlled and synchronized seafastening mechanisms are best suited to enhance the lifting process. |
