Effects of Co-Located Floating Wind-Wave Systems on Fatigue Damage of Floating Offshore Wind Turbine Mooring Cables

Industrial realization of both floating offshore wind and wave energy technologies requires reductions in the current high levelized cost of energy. Reducing mooring fatigue loads could decrease levelized cost of energy, as mooring is expected to be a major cost of these systems. Previous work on improving mooring reliability and costs has focused on material and design. In this exploratory study, we quantify how placing WECs in front of a FOWT could reduce fatigue damage incurred by FOWT mooring cables in long-crested wave conditions. We use SWAN to quantify the WEC-induced sea state modifications and obtain wave spectra at the FOWT location. The spectra are then input into WEC-Sim and MooDy to model the mooring cable behavior. Fatigue analysis with Rainflow Counting is used to quantify the fatigue loading on the mooring cables. Results from this study show a 8% reduction in fatigue damage to mooring cables over the lifetime of the structure. These results indicate that co-location could have a beneficial effect on FOWT mooring cable fatigue. In future work, these results will be leveraged to perform optimal O&M planning and reliability-based design optimization of floating offshore wind turbines.