Coupled dynamics and energy conversion in a semi-submersible floating platform-point absorber WECs hybrid system: An experimental investigation

Integrating wave energy converters (WECs) with floating offshore structures provides a promising solution for advancing wave energy commercialisation. In this study, hybrid systems consisting of a semi-submersible platform and 3 or 6 WECs are investigated experimentally, with a geometric scale of λ = 50 adopted. The energy absorption of the WEC array, along with the motion response and mooring tension of the hybrid system is compared with those of an isolated WEC and a single semi-submersible platform. Results indicate that the platform improves WEC energy absorption at off-resonance periods and broadens the effective working bandwidth. Maximum energy output occurs under backward waves, with full-scale peak power of 574 kW and 1095 kW for the hybrid system with 3WEC and 6WEC arrays at an incident wave height of H = 2 m. The influence of WEC integration on platform motion responses and mooring tensions depends strongly on both wave period and incident direction. Platform motions are effectively suppressed under short-period waves but intensified under long-period waves. Meanwhile, mooring tension varies distinctly across different wave directions, with obvious increases observed under oblique and backward waves, which deserve careful consideration in practical design.