Experimental investigation into the dynamics and power coupling effects of floating semi-submersible wind turbine combined with point-absorber array and aquaculture cage

This study presents an experimental investigation into the dynamics of an integrated offshore wind-wave-aquaculture (WWA) system, addressing the limited experimental studies of coupling effect. The coupling dynamics of the hybrid system under combined wind loads, wave loads, power take-off (PTO) forces, and mooring tensions are thoroughly examined. Through a 1:40 Froude similarity scaled model, the experimental setup integrated a point-absorber array and an aquaculture cage with a floating semi-submersible wind turbine (WT), incorporating a hydraulic PTO system for wave energy conversion. A semi-taut mooring system was designed to ensure the station-keeping of the hybrid model under the tested environments of rated and extreme winds, as well as regular and irregular waves. Specifically, the findings reveal the significant impact of the quasi-resonant state of the point-absorber array on the systems motion responses. The motion amplitudes are amplified by integrating a point-absorber array, whereas the average pitch responses are suppressed when exposed to irregular waves. The nuanced influence of the aquaculture cage, which dampens the oscillation under irregular waves, is also uncovered. Additionally, the quasi-resonance of the point-absorber array leads to a substantial increase in the power output of the wind turbine. Moreover, the integration of wave energy converters contributes an average of 5.2 % to overall power generation, resulting in a 1.5 % reduction in the Levelized Cost of Energy (LCOE). This investigation reveals that, despite the reduction in cost resulting from the combination, careful consideration should be given to the quasi-resonance of wave energy converters in the hybrid system. This is in order to safeguard the system from being damaged by excessive movement.