Hydrodynamic performance of a novel WEC-breakwater integrated system consisting of triple dual-freedom pontoons

Abstract A breakwater consisting of three pontoon-type wave energy converters equipped with Power Take-Off (PTO) systems to extract wave energy from pitch and heave motions is proposed. The proposed integrated system has the potential to reduce the cost of the wave energy conversion system by sharing the essential infrastructure with the floating breakwater. In the model, the eigenfunction expansion matching method and technique of variables separation are used. The effects of the geometrical parameters (including pontoon width, draft and spacing) on the hydrodynamic performance characterized by the wave energy conversion efficiency, transmission and reflection coefficients are investigated, respectively. It is found that the effective bandwidth (transmission coefficient KT   0.3) and the peak efficiency are enhanced when the pitch and heave motions are considered simultaneously, compared with the single DoF motion system. The effective bandwidth increases with the decrease of width and draft of the front pontoon. And the variation of pontoon spacing affects significantly the distribution of the efficiency due to the Bragg-type reflection. Additionally, it is found that the variation of the geometrical parameters of the front pontoon on wave transmission is limited by changing the geometrical parameters of the front pontoon only.