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Numerical study on multi-buoy-type wave energy converter platform with hydraulic PTO system

This study examined the hydrodynamic performance of a multi-point absorber with a hydraulic power take-off (PTO) system and estimated the optimal conditions for maximum power extraction. The multi-point absorber is composed of two hemispheric buoys with a hydraulic PTO system. The hydrodynamic interactions between the two buoys were evaluated by modeling the buoys together with the PTO system. First, parametric studies of the distance between the two buoys and the angle of the incident wave were carried out to determine the optimal distance and incident angles in the frequency domain. Because the hydraulic PTO system has strong nonlinearity, an approximate coulomb damping force, as a suitable numerical model, was introduced. The heave motion and the extraction power of the buoy were calculated for various hydraulic PTO pressures. Furthermore, as the real sea-state condition, irregular waves were applied to the present wave energy converter model to predict the generated power for various PTO conditions. The relationships between the peak wave period and the PTO conditions with various wave angles were investigated to determine the optimal buoy position and hydraulic pressure for maximum energy extraction.