Master thesis : Development and Technical Feasibility of a Dry Dock System for a Floating Wind Turbine Installation Platform

Abstract

To achieve the goal of the sustainable development of the environment, floating offshore wind turbines (FOWT) will play a major role in enabling the green shift and achieving renewable energy goals. FOWTs have many advantages, therefore many large-scale floating offshore wind farms are being planned. At the same time, the capacity and size of the actual wind turbines grow rapidly. There have been many concept studies and pilot projects exploring different designs of FOWTs and their functionality. However, in the current stage, the turbine integration and heavy maintenance have so far been assumed to be done at a port. Considering the size of the FOWTs, this presupposes that there are ports nearby with sufficient water depth in the channel and at the quayside, with no air draft restrictions due to bridges or power lines, and sufficient bearing capacity for onshore cranes. Integrating the turbine on a floating foundation by making use of state-of-the-art heavy lift vessels as an alternative to being dependent on suitable base ports is extremely challenging due to the relative motions between the two floating objects. To overcome this limitation, KONGSTEIN contributed to developing a new concept for turbine integration and heavy maintenance of FOWTs offshore. A FOWT installation platform consisting of dry dock systems can be beneficial for executing this goal with the ability to assemble and install the FOWTs offshore without mobilizing a base harbor ashore. The idea is to lock the floating foundation inside the dry dock, thus there will be no relative motion between the vessel and the floating foundation and the lifting operation will be significantly safer and easier to control.

This feasibility study aims to evaluate the technical feasibility of the dry dock gate design for the dry dock system of a floating wind turbine installation platform. The concept design of the dry dock for wind turbine generators that have a capacity of 18+ MW is based on an exemplary wind energy area with high water depth, and harsh wave, and swell conditions. The market research is done afterward for choosing and ranking the most suitable gate design for the objective. The second phase of this study is the technical feasibility study. After the properest gate type is chosen, the modeling and load analysis for the structure is performed. The hydrodynamic load case for the target area is used as the input for the gate deformation simulation. The global and local model structure with the chosen gate type is analyzed in the next steps. Finally, the suitability of chosen gate design for this specific application will be evaluated based on market research and technical analysis. According to the evaluated result, it can be said that the gate design for this study is relatively conservative, the improved suggestion for the present design gate would be the following provided.