Design and dynamic analysis of a co-existence solution between a semi-submersible offshore fish cage and a spar-type floating offshore wind turbine

Abstract Clean energy captured by offshore wind turbines have been widely used for supporting onshore activities. In the near future, facilities such as offshore wind turbines can also play an important role in energy transition of offshore activities. Offshore wind energy can be employed for electrifying the operations in offshore fish farms, which are traditionally supplied by diesel-engine barges/generators. Based on this motivation, this study focuses on a design of shared mooring system between a semi-submersible offshore fish cage and a spar-type floating wind turbine. A numerical model of the proposed shared-mooring system is implemented in a global response analysis software SIMA for performing fully coupled time domain simulations. The configuration of the shared mooring line is determined using an engineering approach which comprises Irvine's formulation, system eigenvalue analysis and cost estimation. Moreover, relevant case studies by altering the environmental conditions are performed. Extreme operational conditions that may give large relative motions are investigated thoroughly. The dynamic performance of the integrated system is compared with that of individual structures. The global motion of the floating wind turbine and its mooring line's tension behavior are obviously influenced by the existence of the shared line. In general, the present work investigates the feasibility of a shared-mooring system for these types of offshore structures and further gives insights about the engineering design procedure.