Improving O&M simulations by integrating vessel motions for floating wind farms

This study introduces an integrated methodology that incorporates vessel motion dynamics 1 into the evaluation of operations and maintenance (O&M) costs for floating offshore wind turbines 2 (FOWTs). By combining UWiSE, a discrete-event simulation tool, with SafeTrans, a voyage simulation 3 software, the methodology accounts for vessel motion effects during offshore operations. The 4 approach was demonstrated through a numerical case study at two wind farm sites, Marram Wind 5 and Celtic Sea C, with a fictive wind farm layout of 100 × 15 MW NREL turbine on a UMaine 6 VolturnUS-S platform. Three Major Component Replacement (MCR) strategies were assessed: Tow- 7 to-Port (T2P), Floating-to-Floating (FTF), and Self-Hoisting Crane (SHC). The T2P strategy resulted in 8
the highest O&M costs—94 k€/MW/year at Marram Wind and 97 k€/MW/year at Celtic Sea C—due 9 to extended MCR durations (90-180 days), leading to lower availability (90%-94%). In contrast, the 10 FTF and SHC strategies, which are still under development, demonstrate significantly lower costs 11 and reduced downtime. The SHC strategy, in particular, has proven to be the most cost-effective, 12 achieving up to a 64% reduction in costs while increasing availability to 97%-98%. The integrated 13 approach incorporates vessel dynamics, accounting for factors such as wave direction, wave period, 14 and vessel response to varying sea states. This allows for greater flexibility in setting operational 15 limits, potentially permitting higher limits in favorable conditions where vessel motion impact is 16 reduced. However, in scenarios where dynamic vessel responses lead to increased motions—such 17 as when waves approach from the side or when the wave period is close to the vessel’s natural roll 18 period—more restrictive limits may be necessary, even if significant wave heights (Hs) are lower. 19 This flexibility or restriction highlights the importance of incorporating motion-based dynamics for 20 emerging technologies in the evolving FOWT O&M market.