A comparison of anchor loads, planar displacement, and rotation for nylon and polyester moored systems for a 15 MW floating wind turbine in shallow water

Abstract

Renewable energy is crucial for addressing energy security and climate change challenges. Offshore wind energy presents a significant opportunity to generate renewable energy. Shallow water areas, between 50 and 70 m deep, are economically feasible for wind farms using shared anchor concepts and mooring line systems. However, choosing the appropriate type of system is critical. Previous studies have demonstrated that synthetic fiber ropes are more efficient than traditional chain catenary. In this paper we present the results of a dynamic analysis of a 15 MW Turbine and the VolturnUS-S reference platform deployed in the Celtic Sea. We compare the planar displacements, rotations, and loads acting on a shared anchor using nylon and polyester ropes, the latter as retrieved from the literature. An engineering procedure is used to simulate the behavior of the nylon rope, and a diffraction analysis is employed considering the stiffness of the mooring matrix. Our results show that using nylon rope reduces the peak resolved anchor load by 44% compared to polyester, but at the cost of a relatively larger displacements and rotations, which can be mitigated with improvements in mooring design. Since nylon is 10% cheaper than polyester rope with an identical minimum breaking load (MBL), and more cost-efficient anchor concepts are being investigated, the findings of this study encourage further research on nylon applications for wind farms in shallow water using shared anchors.