ABSTRACT
The Spar-buoy is an axisymmetric floating Oscillating Water Column (OWC) wave energy converter. Minimizing the cost of energy requires an efficient power conversion while limiting costs and ensuring survivability. A critical and challenging design problem is the parsimonious definition of a compliant mooring system, assuring sea-keeping but with small impact on energy extraction. The mathematical model should be able to articulate parametric resonance (detrimental for power extraction and threatening survivability) and compute fast enough to extensively investigate the design space for the mooring layout optimization. Considering a three-line mooring system, alternative design solutions based on different fairlead attachment points are investigated with a computationally efficient nonlinear Froude-Krylov hydrodynamic model and a quasi-static inelastic line model. Results discuss the impact of mooring configurations on inducing parametric resonance (roll&pitch and yaw), on power extraction, and on the peak tension in the mooring lines. From the tested configurations, the most convenient appears to be with the attachment point close to the centre of gravity.
