Wave power extraction for an oscillating water column device consisting of a surging front and back lip-wall: An analytical study

Abstract

Traditional oscillating water column (OWC) devices are mostly fixed with almost no components allowed to move. To complement the research of OWC consisting of moving components, the capability in extracting wave energy for a device with a surging front and back lip-wall restricted by different spring stiffness values is investigated. A theoretical model is developed based on potential flow theory and solved by the matched eigenfunction method, and the pros and cons between the proposed model and the traditional fixed model are compared. The influential factors, including the wall drafts and chamber breaths, are explored to study their effects on the interested hydrodynamic parameters. To make full use of the inclusion of surging motion of lip-walls, a progressive optimized process for the combination of spring stiffness values is proposed to obtain a superior efficiency curve. The results show that a relatively larger lip-wall draft and wider chamber for the dual-surging-motion model is more beneficial for wave energy absorption compared with the stationary model. In addition, an appropriate combination of the employed two spring stiffness values can expand the high-efficiency frequency bandwidth, with the peak efficiency improved to a more preferable extent in contrast to the maximum value 0.5 for a traditional fixed device. Moreover, through tuning the adopted spring stiffness, the performance enhancement can be attained by triggering multiple peak values within the efficiency curves for the mdoel allowed dual surging motions.