The effect of lip extrusion on performance of a Breakwater Integrated Bent Duct OWC WEC

Oscillating Water Column (OWC) Wave Energy Converters (WECs) are one of the most studied, developed and tested devices associated with Ocean Renewable Energy (ORE) today. Variations in concept design and hydrodynamic characteristics have been researched extensively, however the main issue associated with ORE is the high Levelised Cost of Energy (LCOE). One of the most promising applications devised to potentially decrease the LCOE is maritime structure integration by sharing the costs associated with construction, and lowering the costs of maintenance. This paper investigates physical model experimentation into the effect that lip extrusion of a breakwater integrated bent duct type OWC has on the performance. The importance of the investigation has implications regarding tuning of the device for site-specific breakwater integration and constructability. It is documented that a bent duct OWC observes change in its natural resonance frequency through variation in length of the swept path of the geometrical cross-section. Subsequently, lip extrusion could present a way of tuning the device to suit a site-specific sea state, and is a design consideration that will affect both optimal power absorption and constructability. It was found that the longer the lip extrusion the lower the performance and that the no lip extrusion case resulted in the maximum non-dimensional capture width of 2.2 compared to the maximum lip extrusion considered in this paper corresponding to 1.4. This is a positive result for construction consideration as less materials are required, however, using lip extrusion to tune OWC resonance might come at the cost of performance.