An integrated optimization framework for coordinated maintenance and environment-aware routing in multi-farm offshore wind portfolios

The expansion of offshore wind farms into deeper waters poses significant challenges to system accessibility and reliability. Existing maintenance strategies usually optimize each wind farm independently, decouple vessel routing from task scheduling, and approximate vessel transit using simplified distances that ignore dynamic marine conditions. To address these limitations, this paper proposes a Neighbor-farm Environment-aware Location and Routing with Opportunistic Maintenance (NELROM) framework for coordinated maintenance in multi-farm offshore wind portfolios. NELROM introduces a cross-farm opportunistic maintenance mechanism, in which a mandatory maintenance requirement at one farm can create an opportunity to perform eligible maintenance tasks at the neighboring farm. Operationally, it formulates an integrated location-routing-scheduling problem under a daily rolling-horizon structure. Updating daily turbine-health and marine-environment information, the framework jointly determines service operation vessel anchorage selection, crew transfer vessel routing, task timing, and environment-aware sailing paths. Numerical case studies demonstrate that NELROM reduces total O&M costs by up to 14.6% compared to traditional approaches while ensuring operational safety and accessibility. It also shifts the maintenance strategy towards proactivity, significantly decreasing the share of corrective maintenance from 44.9 to 21.9%. By integrating cross-farm coordination, daily vessel scheduling, and environment-aware execution, NELROM enhances both reliability and cost-effectiveness in challenging offshore environments. © 2026 Elsevier Ltd.