Design optimization of dynamic inter-array cable systems for floating offshore wind turbines

Despite its huge potential, floating offshore wind technology has not reached commercial maturity yet and numerous problems remain to be investigated. A major knowledge gap exists regarding the dynamic behavior of the freely moving inter-array cables, that link the floating turbines. This work presents a design approach based on a genetic algorithm. No publications on this topic were done before. The hybrid MATLAB-OrcaFlex tool considers fatigue life, performance in extreme weather events and economic evaluation criteria. Starting point for the dynamic analysis are cable configurations from hydrostatic optimization. Based on this hydrostatic optimization, a general design rule for lazy wave cables can be deduced in the depth range from 70 to 200 m. To the best knowledge of the authors, such a generalized design recommendation is unique in literature. The methodology and peculiarities of the fatigue life assessment are discussed. Recommendable parameters for the algorithm and the simulations are presented. The optimization tool is applied on a case study with the OC4-DeepCwind model located at Portugal's Agucadoura test site. In a parametric study, water depth and cable orientation are varied.