Layout optimization of oscillating water column (OWC) wave energy converter (WEC) array coupled with a parabolic-wall energy concentrator

Using parabolic-type structure is feasible to achieve high wave energy concentration in the designated areas, thereby greatly enhancing the energy capture efficiency of wave energy converters (WECs) in those regions. The wave field surrounding the parabolic structures as well as the wave energy capture performance of oscillating water column (OWC) devices that are coupled with such structures are investigated in this study. Detailed numerical investigation is conducted using the numerical model based on a higher-order boundary element method (HOBEM). The findings of this study reveal that in the low-frequency region, there is a notable concentration of wave energy near the vertex of the parabolic structure, referred to as vertex concentration mode. As the wave frequency increases, significant wave energy concentration appears near the geometric focal point of the parabolic structure, referred to as focal concentration mode. The results also indicate that for an OWC device coupled with a parabolic structure, its wave energy capture is notably superior to that in open water. The combined effects of the substantial wave energy concentration and the resonant water-column motion within the chamber results in an optimal gain in the wave energy capture. This research also identifies that under the focal concentration mode, secondary energy concentration areas appear on both sides of the vertex of the parabolic structure. To optimize the wave energy utilization, this study explores the integration of arrays of 3 and 5 OWC devices with the parabolic structure. A methodology for optimizing the layout of the device array is developed, incorporating the wave field analysis, genetic algorithms, and iterative analysis techniques. The results suggest that to maximize the wave energy capture, the devices should be positioned in closer proximity as the wave frequency increases. In the case of the 5-device array, the optimal layout reveals a ‘W’-shaped configuration. Within a specific frequency range, this optimized layout enables the overall hydrodynamic efficiency of the OWC array surpasses 60 %.