A novel dual-chamber oscillating water column system with dual lip-wall pitching motions for wave energy conversion

The topic focusing on the dual-chamber Oscillating Water Column (OWC) system is still in its infancy. To improve energy extraction within a wider wave frequency regime, the concept of a dual-chamber OWC device with pitching front and mid lip-walls simultaneously is proposed. Its performance in wave energy capturing is analytical investigated based on potential flow theory. The matching conditions in terms of the pressure and velocity continuity along the adjacent interfaces are employed, and the power take-off model and the motion response of pitching lip-walls are incorporated into the procedure for solving a set of linear matrix equations. Factors, including the lip-wall drafts and the angle spring stiffness are explored to analyze the influences on the interested parameters. Results show that an intermediate lip-wall drafts condition is of more benefit for improving power extraction. There exists a certain range of angle spring stiffness determining the optimal power extraction performance. Most predominantly, the inclusion of dual pitching motions provides the possibility of making full use of the both chambers in absorbing wave power, and the supplement function by the rear chamber can be greatly strengthened. In addition, the extension of the novel offshore model to an onshore device illustrates the necessity and superiority of including the lip-wall pitching motions for a land-based structure as well, as remarkable improvement can be achieved especially excited by short-period waves under relatively deeper drafts.