This study presents results of numerical simulations on the effects of the presence of breakwaters on the OWC (Oscillating Water Column) performance. CFD (Computational Fluid Dynamics) simulations using a commercial code, Star-CCM+, are done for evaluating performances of the OWC without and with considering the breakwaters in regular waves. Flow fields of the OWC in regular waves are shown as continuous contours, and the effects of the breakwater on the performance of OWC are evaluated. Finally, the cause of the performance improvement and reduction of OWC due to breakwater is discussed.
Economic feasibility of the OWC (Oscillating Water Column) WEC (Wave Energy Converter) can be improved by combining it with existing or newly constructed breakwaters. The OWC WEC, which has a sloped chamber with same inclination as the breakwaters, has been developed for installation in a breakwater on isolated islands since 2016 by the R&D Project funded by the Korean government (Park et al., 2018). Demonstration tests of the developed breakwater OWC will be done in the future after completion of construction for the OWC with modifying the existing breakwater in Chuja Island, Korea, based on the design for the integrated system composed of OWC chamber, turbine, generator, controller, energy storage system, and micro-grid system. Fig. 1 shows a conceptual diagram of the present OWC system integrated with the breakwater.
The OWC chamber producing a reciprocating airflow that operates a turbine from ocean waves functions as the device for primary energy conversion. Earlier studies had performed experimental and numerical analysis for OWC chamber without considering the presence of the breakwater (Elhanafi et al., 2017; Vyzikas et al., 2017; López et al., 2015; 2014; Iturrioz et al., 2015; Kamath et al., 2015; 2015). They evaluated the performance of the independent OWC by measuring or calculating wave elevations in the chamber, the differential pressure between the inside of the chamber and atmosphere, and airflow speed through the duct. In addition, interactions between water surfaces in the chamber and the turbine were considered by modeling it as the orifice representing a damping effect for an impulse turbine of the present OWC system.