Experimental and Numerical Study on the Motion Response of a Hybrid Wind-Wave Energy Platform with Different WEC Arrangements

Floating offshore wind turbines (FOWTs) enable large-scale power generation in favorable wind conditions but require platform stability in harsh sea states. A hybrid wind-wave energy platform, combining wave energy converters (WECs) with a FOWT, can enhance motion stability and improve power efficiency through structural interactions. This study investigated experimentally and numerically the motion responses of a hybrid platform with four wave-star type WECs in different arrangements. The FOWT was modeled as a 5 MW Spar-type platform with a taut mooring system. Two-dimensional wave tank experiments and ANSYS AQWA simulations, which accounted for wall effects, showed that the walls had minimal influence on the platform motions. Compared to a single FOWT, the hybrid platform exhibited a lower heave natural frequency and increased pitch response. The maximum mooring line tension occurred near the heave resonance frequency but was lower in the hybrid platform. The changes in incident wave direction had little effect on overall motion. When a power take-off (PTO) system was applied, the WEC angular velocity decreased near its natural frequency range, resulting in a reduction of the surge and pitch responses of the hybrid platform. Moreover, rigidly fixing the WECs to the platform significantly altered motion characteristics, highlighting the importance of WEC dynamics in combined platform behavior.