On the improved design of the buoy geometry on a two-body wave energy converter model

The motion of some geometries of a buoy in a two-body wave energy converter (WEC) system is studied under regular wave excitations. The buoy is coupled to a heave damping plate where the coupling system models a simplified power takeoff (PTO) system. A frequency-domain analysis is conducted on the two-body model to predict the wave-induced motion behavior of the bodies considering the mutual effects of two bodies and the PTO system. The designed buoys are axisymmetric and have an identical water-plane area and submerged volume. The model was analyzed in identical conditions for different buoys so that the effect of the buoy shape on its dynamic properties and the hydrodynamic coefficients, as well as the absorption efficiency of the two-body WEC model, could be evaluated. The impact of the buoy shape and its hydrodynamic coefficients on the optimal and suboptimal design of the PTO system is studied. The results indicate that a suitable geometry for the buoy can have beneficial effects on the improved efficiency of the two-body WEC model, increasing the relative displacement between the two bodies and, also, allowing an optimal design of the PTO system. Furthermore, the buoy shape can reduce the difference between the damping coefficients of the PTO system and the buoy in order to create the resonance condition in the WEC system.