| 17 Jun 2026
An Open-Access Integrated Hierarchical Optimization Framework applied to a 15 MW Medium-Speed Offshore Wind Turbine Drivetrain
Abstract. This work presents an open-access hierarchical, physics-based optimization framework for medium-speed wind turbine drivetrains. The methodology combines mixed-integer architecture exploration with continuous gradient-based refinement, enabling simultaneous optimization of gearbox topology, stage-ratio distribution, gear geometry, shaft sizing, and bearing selection under ISO 6336, ISO 281, and DIN 743 constraints.
Compared to previous design frameworks based on empirical scaling laws, such as WISDEM, the integrated stage-ratio optimization achieved drivetrain mass reductions of approximately 4–5 % while satisfying all design constraints.
Convergence studies demonstrated that the proposed hierarchical optimization strategy efficiently handles the complex mixed-integer design landscape, producing competitive gearbox solutions in <2.5 h on a desktop computer.
Applied to a 15 MW offshore wind turbine, the optimized medium-speed drivetrain achieved a total mass of 274.2 t, corresponding to a 31.5 % reduction relative to the direct-drive reference while maintaining comparable efficiency (97.2 %). The results demonstrate that integrated hierarchical optimization enables competitive drivetrain solutions for next-generation offshore wind turbines.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Wind Energy Science.
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