Axisymmetric reflectors in wave energy converter arrays: Harnessing scattering to increase energy extraction

Abstract

We elucidate the effect of non-extracting reflectors on the performance of wave energy converter (WEC) arrays. We consider an infinitely periodic row of converters parallel to an infinitely periodic row of discrete axisymmetric reflectors (C-R arrays), and we study how the spatial configuration affects energy extraction. Using a multiple-scattering algorithm for linear wave-array interactions, we conduct a series of simulations of C-R arrays for a range of spatial configuration parameters, wavenumbers, and wave incident angles. We find that C-R arrays can significantly increase energy extraction compared to a WEC array by itself. We offer a simplified theoretical model, based on the far-field response of periodic rows in isolation, which shows that the large increases in energy extraction result from the constructive Bragg and Laue interferences caused by wave interactions with the reflector row. For the pertinent case of incident waves of the WEC-resonant frequency, we find that optimized C-R arrays can achieve energy extraction gains of O(500%). Remarkably, the optimal C-R array extracts more energy than two rows of converters of optimal configuration even though the C-R array consists of only half as many WECs.