Dynamic modelling of Spar-Buoy oscillating water column wave energy converter

The main objective of this research is to develop an experimentally validated numerical wave power prediction tool for an offshore Spar-Buoy oscillating water column (OWC) wave energy converter (WEC). The numerical tool should be able to predict the spar heave motion and the water column oscillations inside the structure, in order to estimate the power absorber and evaluate the device performance. A two-degree-of-freedom mechanical oscillation model was adopted. The model considers the power take-off (PTO) damping and the stiffness due to air compressibility inside the pneumatic chamber. Experiments were performed in order to calculate the damping coefficients and to validate the predicted results. PTO mechanism was experimentally modelled by orifice plate located on top of the OWC model. Different orifice areas were used to allow the examination of the PTO damping effect on the hydrodynamic behaviour of the system.