Mechanical Model of a Floating Oscillating Water Column Wave Energy Conversion Device

The study of floating oscillating water column (OWC) wave energy conversion (WEC) device performance includes analysis of the dynamic coupling of the water column and the floating structure. In the present investigation, a mechanical oscillator model was proposed in order to examine this relationship for the heave motion of a floating wave energy conversion device. Characterisation of the dynamic system optimal behaviour was performed by examining the effect of relative OWC and floating structure natural frequencies, the phase relationships of the various system components and the optimal power take-off damping of the system. It was determined that separation of the natural frequencies results in significant increases in maximum power capture. When the OWC and structure natural frequencies are coincident the motions are essentially in phase and limited power capture is achieved. For optimal power capture the separation of the natural frequencies should be such that the floating structure has the lower natural frequency. This should also generally result in improved alignment of the system resonant response with the available wave power. The model also provides evidence of the capacity of power take-off damping control to improve the nonresonant performance ofthe OWC WEC device in a spectrally distributed wave environment.