De-risking utilising a floating crane for floating offshore wind turbine maintenance

The growing deployment of floating offshore wind turbines (FOWTs) presents new challenges in maintenance operations, particularly concerning in-situ component replacement. This study builds upon prior research into the feasibility of using a floating crane for generator exchange on a semi-submersible FOWT, specifically the UMaine VolturnUS-S supporting a 15 MW reference turbine. Utilising a marine simulation environment at NDC, the dynamic responses of the generator, nacelle, and crane barge were evaluated under various sea states. The results highlight that while generator accelerations are a significant operational factor, the primary constraint is the risk of collision between the generator and turbine structure during lifting operations. Parametric studies revealed critical wave periods that exacerbate generator motions and collisions, and while modifications to the lifting methodology proved ineffective, reorienting the crane barge parallel to incoming waves showed a modest reduction in collisions. These findings underline the importance of vessel selection, wave direction, and sea state limitations in ensuring the viability of in-situ maintenance using floating cranes for FOWTs. • Expanded analysis of floating crane lifts for offshore wind in higher sea states. • Developed novel collision detection using generator accelerations and jolts. • Identified barge motions as key constraint in floating-to-floating lifting operations. • Recommended crane barge orientation vs wave direction to reduce collision risk. • Provided first integrated study of offshore crane dynamics for in-situ maintenance for floating offshore wind applications.