Wave Power Extraction from a Dual Oscillating-Water- Column System Composed of Heave-Only and Onshore Units

Abstract

With the aim of broadening the wave-frequency bandwidth of high-efficiency, a small-scaled dual oscillating-water-column (OWC) system consisting of two heave-only and onshore units was numerically investigated by a well-validated computational fluid dynamics (CFD) model. Based on the popular open source package OpenFOAM, the volume of fluid (VOF) method was employed to track the transformation of the air−water interface under the excitation of regular waves. The six degree of freedom (6DOF) solver was applied to duplicate the heaving motion of the floating device. The effects of the two chamber widths b 1 and b 2 , the vertical restraint force (represented by the dimensionless stiffness coefficient K), the back-lip draught d 2 of the floating device, and the gap Δ L between the two OWCs on the hydrodynamic characteristics and the wave energy conversion efficiencies were examined. The numerical results show that a larger width ratio b 2 / b 1 with a relatively shallow back-lip draught is more conducive to the high-performance over a broader frequency range. The floating device with a stronger vertical restraint force is more satisfactory for the high-performance of the system. Moreover, a relatively small gap is more recommended in the stage of design and construction.

Keywords

• marine energy
• oscillating water column
• dual OWC system
• wave energy extraction efficiency
• six degree of freedom (6DOF)
• dynamic mesh