Design optimisation of a funnel-shaped floating dock for installation of offshore wind turbines

Master's thesis in Civil and structural engineering (BYG508)Offshore wind power is a rapidly growing renewable energy industry and has a tremendous potentialof further expansion. Installation of offshore wind turbines is a challenging task. Floating windturbines are believed to be cost-effective solutions for deep water installation. This technologyis extremely sensitive to wave excitation during the installation process. As deep-water windfarms often are located in areas exposed to rough weather, innovative methods of installation areinvestigated. The floating dock concept has been proposed in recent studies in order to expand theweather window for installing spar floating wind turbines. The idea is for the dock to shield the sparfrom wave excitation. Previous studies show that a funnel-shaped dock potentially has a betterhydrodynamic performance compared to cylindrical and bottle-shaped docks. This master’s thesistakes the previous studies into consideration and investigates how a parametric design optimisationcan be carried out for a funnel-shaped dock intended for installation of floating wind turbines. Theoptimisation objective is defined as reduction of steel weight. While investigating how to bestpredict the operational constraint of piston-mode periods, the Gaussian process regression modelappeared to be the best predictor. The study revealed that the heights;T1,T2andT3, in additionto the diameters,Di1andDi2, are design parameters which significantly affect the piston-modeperiod. The optima found in this study deviate from the predictions from the GPR based model asthe geometry is outside the trained model-area. This can be solved with a new model which alsoincludes bottle-shaped and cylindrical docks

Design optimisation of a funnel-shaped floating dock for installation of offshore wind turbines

Offshore wind power is a rapidly growing renewable energy industry and has a tremendous potentialof further expansion. Installation of offshore wind turbines is a challenging task. Floating windturbines are believed to be cost-effective solutions for deep water installation. This technologyis extremely sensitive to wave excitation during the installation process. As deep-water windfarms often are located in areas exposed to rough weather, innovative methods of installation areinvestigated. The floating dock concept has been proposed in recent studies in order to expand theweather window for installing spar floating wind turbines. The idea is for the dock to shield the sparfrom wave excitation. Previous studies show that a funnel-shaped dock potentially has a betterhydrodynamic performance compared to cylindrical and bottle-shaped docks. This master’s thesistakes the previous studies into consideration and investigates how a parametric design optimisationcan be carried out for a funnel-shaped dock intended for installation of floating wind turbines. Theoptimisation objective is defined as reduction of steel weight. While investigating how to bestpredict the operational constraint of piston-mode periods, the Gaussian process regression modelappeared to be the best predictor. The study revealed that the heights;T1,T2andT3, in additionto the diameters,Di1andDi2, are design parameters which significantly affect the piston-modeperiod. The optima found in this study deviate from the predictions from the GPR based model asthe geometry is outside the trained model-area. This can be solved with a new model which alsoincludes bottle-shaped and cylindrical docks