Coupled Mooring Systems for Floating Wind Farms
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In this work the feasibility of an integrated catenary loose mooring system for offshore floating wind turbines is investigated. The dynamic behavior of different wind farm layouts is analyzed employing the equation of motion. It will be especially sought after potential resonance problems. The equation is solved in frequency domain, using a linearized stiffness matrix, as well as in time domain. Time-domain simulation is done by using a quasi-static model, where the catenary equation is used to determine the non-linear mooring restoring forces. The most important forces to evaluate the station keeping performance of mooring systems are applied. Namely irregular wave forces, using the Morison equation, simplified mean drift and slow varying drift forces employing Newman’s approximation, and a wind-force represented by a wind thrust force time series. Load cases representing different operational conditions and a 50-year extreme event is applied. The potential cost savings are analyzed and an overview of different floating wind turbine concepts is given. The results are showing the general feasibility of integrated mooring systems. No response peaks appear that would indicate resonance problems. Also it shown that significant cost reductions of up to 80% in mooring system and 20% in total system costs could be achieved using integrated mooring systems.