Wave power extraction analysis for an oscillating water column device with various surging lip-walls

The performance in extracting wave power from an offshore OWC device with a surging front lip-wall and back lip-wall is explored and according to the potential flow theory, the matched eigenfunction method is employed to establish a theoretical model to solve the boundary value problem. Effects from the variation of symmetry lipwall drafts, chamber breadth, and spring stiffness, on the optimal extraction efficiency and other parameters of the OWC with different moving components are compared and discussed. It is found that a relatively deeper wall draft is more beneficial for the power extraction when equipped with a surging front lip-wall within the interested wave frequency range. To improve the trapped energy and reduce the occurring of sloshing mode inside the pneumatic chamber for a surging front lip-wall, a medium chamber breadth is more desirable as it can significantly enhance the peak efficiency as well as the expansion of high-efficiency frequency bandwidth, while a surging back lip-wall model is inferior in this aspect. In addition, generally a relatively smaller spring stiffness and even stiffness of zero is more recommended for the front-wall than the back-wall surging motion as the former can make full use the positive effects of the surging mode.

Automated summary

The study explores the performance of extracting wave power from an offshore OWC device with different moving components. It is found that a deeper lip-wall draft is more beneficial for power extraction, and a medium chamber breadth is more desirable for a surging front lip-wall. Generally, a relatively smaller spring stiffness is recommended for the front-wall surging motion to make full use of the positive effects of the surging mode.