Multidisciplinary Control Codesign of a Spar–Torus Hybrid Wind-Wave Energy System

Abstract In response to the growing global demand for sustainable energy and the need to reduce greenhouse gas emissions, advanced offshore renewables—particularly floating wind and wave systems—are poised to play an important role in future power grids. This study develops an integrated control codesign (CCD) framework to optimize a hybrid floating platform that couples a spar-type offshore wind turbine with a torus-shaped wave energy converter (WEC). The framework automates geometry generation, applies boundary element method (BEM) analyses to compute hydrostatic and frequency-dependent hydrodynamic coefficients, and uses interpolation-based surrogates to avoid repeated costly BEM calls during optimization. High-speed dynamic simulations are then run via WEC-Sim (leveraging its MOST module), enabling rapid time-domain analysis of the coupled WEC–wind turbine system. A sensitivity analysis quantifies each design variable’s impact on the mass-to-power objective and on key structural and dynamic constraint margins, focusing optimization on the most influential parameters. The resulting CCD minimizes total system mass to power under structural and dynamic limits—achieving a 13% reduction versus a standalone spar turbine and demonstrating clear synergy beyond independent designs. The wave energy converter contributes approximately 11.29% of the total annual energy production, complementing wind generation and underscoring the hybrid system’s viability. In addition, a comparison study is conducted, demonstrating that full CCD reduces the mass-to-power ratio by an additional 3.33% compared to sequential design.