The Field Test of a Shallow-Water Mooring System for FOWT Using Nylon Synthetic Fiber Ropes

Abstract Japan Marine United Corporation (JMU) are currently developing substructures and mooring systems for floating offshore wind turbines (FOWT) With the cooperation of National Maritime Research Institute. Cost reduction technology is very important for the large-scale commercialization of FOWTs, and a low-cost mooring system as well as a floating foundation are required. Among these, mooring systems using nylon ropes have been attracting attention in recent years because they can reduce mooring costs in shallow waters. However, nylon rope has little experience in mooring large offshore structures. Therefore, there is insufficient durability data of nylon ropes under actual sea conditions. The authors conducted a field test of a mooring system using nylon ropes in shallow water to verify the durability of nylon ropes. The 1/9th scale semi-submersible floating structure designed for FOWT is moored, and the mooring system consists of two taut mooring lines and two catenary mooring lines, totaling four lines, was set up at a depth of about 20 m off Akita Prefecture in Japan for about one-year test. This paper introduces the field tests conducted and presents the results of the comparison between the design and measured values, as well as the results of the evaluation of the durability of the nylon rope.