Investigation of Sequential Enhancement of Onshore OWC Chamber in a Wave Energy Converter Using Experimental Process

Wave energy converters (WECs), particularly oscillating water column (OWC) systems, offer a range of economic and ecological benefits that make them an attractive and promising renewable energy source. To improve energy extraction in medium wave power regions, such as the Mediterranean beaches, the concept of an OWC device with an optimized oscillation chamber according to a sequential process is considered. In this regard, experimental tests, using sequential optimization procedure, are performed in this paper on an onshore OWC device focusing on its overall hydraulic effectiveness. Major emphasis is given to analyze the effects of the underwater front-wall vertical and angular positions, the oscillating chamber geometry, wave conditions and the power take-off (PTO) shape on hydrodynamic performances. The variation of the front-wall was studied according to two criteria: vertical type and angular type where the range of variation is between the angles 0° and 35° with a step of 5°. The chamber volume varying is ensured by inserting a pair of air-guide plates between the roof and the fluid free-surface. The obtained results revealed that changing the chamber front-wall direction affects the OWC oscillation energetic characteristics and the aerodynamic behavior of the turbine driving flow. Water elevation ratio “ η / h ”, absorbed power, hydraulic efficiency, inlet air velocity upstream of the turbine and turbine rotating speed showed a gradual growth with increasing the wall opening angle up to FWA = 20°. The dimensionless turbine coefficients exhibited also an improvement in their behavior with this angle value. The air-guide plates addition leads to a raise of inlet air velocity, turbine speed and device efficiency by 5.5%, 12.3% and 7.5%, respectively. The developed process can greatly help to enhance the performance of real-size OWCs.