Wave energy extraction by an oscillating water column with a gap on the fully submerged front wall

In this paper, the theoretical analysis of an alternative oscillating water column type wave energy converter is presented. The problem geometry differs from earlier two dimensional studies by a modification on the front wall where the surface piercing barrier is replaced with a fully submerged barrier with a gap. Linear Wave Theory is used to govern the fluid motion. Matched eigenfunction expansions and a Galerkin approximation are utilized and results are presented comparatively. Two optimization ideas for power conversion are discussed. First, optimization for all frequencies is considered with the usual assumption of linear, Wells-type air turbine characteristics. Next, results following the practical optimization idea of Lovas et al. [16] are obtained where it is found that only one value for the turbine parameter can be sufficient to obtain efficiency very close to theoretical maximum for any wave frequency. It is also shown that by choosing geometrical parameters of the current problem appropriately, it is possible to obtain improvements on the efficiency curve of the OWC with a surface piercing barrier type front wall where both problems have the same resonant frequency.

► Theoretical analysis of an alternative two dimensional oscillating water column is considered. ► Efficiency of the surface piercing type is improved by choosing parameters appropriately. ► Power optimization is discussed for both variable and fixed turbine parameter. ► Fixing turbine parameter appropriately gives efficiency close to theoretical maximum.