Comparative design space exploration of centred and off-centred semisubmersible configurations for floating offshore wind turbines

Achieving net-zero carbon goals demands an accelerated energy transition, with offshore wind energy emerging as a key contributor due to its vast potential. While floating offshore wind turbines (FOWTs) have seen significant progress through demonstrators, scaling up turbine capacities and deploying large-scale wind farms require further research and innovation. This study explores the design trade-offs between centred and off-centred semisubmersible configurations in FOWTs, using the UMaine and WindFloat designs as base for representative case studies. Parametric analyses were conducted to evaluate key aspects such as dimensioning, mass properties, equilibrium, intact stability, natural periods, and wave-induced loads, applied to the 15-MW IEA reference wind turbine at Scotland's NE8 offshore site. The findings reveal that off-centred semisubmersible configurations face significant challenges due to stringent ballast distribution constraints, which restrict the feasible design space. Conversely, centred semisubmersible configurations demonstrated better overall performance across key design metrics, achieving these outcomes with notably less hull steel mass. These results highlight the critical influence of tower placement on floating substructure design, emphasising the importance of refining and optimising proven configurations to support the development of efficient, large-scale floating wind energy systems.