Abstract
In this paper, we investigate the performance of a linear array of five semi-immersed, oblate spheroidal heaving Wave Energy Converters (WECs) in front of a bottom-mounted, finite-length, vertical wall under perpendicular to the wall regular waves. The diffraction and radiation problems are solved in the frequency domain by utilizing the conventional boundary integral equation method. Initially, to demonstrate the enhanced absorption ability of this array, we compare results with the ones corresponding to arrays of cylindrical and hemisphere-shaped WECs. Next, we investigate the effect of the array’s distance from the wall and of the length of the wall on the physical quantities describing the array’s performance. The results illustrate that the array’s placement at successively larger distances from the wall, up to three times the WECs’ radius, induces hydrodynamic interactions that improve the array’s hydrodynamic behavior, and thus its power absorption ability. An increase in the length of the wall does not lead to any significant power absorption improvement. Compared to the isolated array, the presence of the wall affects positively the array’s power absorption ability at specific frequency ranges, depending mainly on the array’s distance from the wall. Finally, characteristic diffracted wave field patterns are presented to interpret physically the occurrence of the local minima of the heave exciting forces.
Highlights
Wave energy is a vast and powerful renewable energy source
The power absorption efficiency of single-unit heaving Wave Energy Converters (WECs) can be improved by adequately modifying its shape or its Power Take-Off (PTO) mechanism, the need to absorb significant amounts of wave power at a given location requires the deployment of multiple WECs arranged in
The BIE-based numerical model described in Section 2 is applied for an array of M = 5 identical, semi-immersed oblate spheroidal WECs (Figure 1) with semi-major axis a = 2.0 m and non-dimensional semi-minor axis b/a = 0.85
Summary
Wave energy is a vast and powerful renewable energy source. Its sustainable harnessing, directly associated with the European Unions’ energy strategies and priorities for the reduction of greenhouse emissions, can contribute to climate change effects’ mitigation and energy security enhancement, and at the same time it provides the potential for long-term economic growth through the creation of jobs and the generation of export opportunities for both technology and expertise [1,2,3]. WECs arrays in front of existing coastal structures, such as vertical (wall-type) breakwaters In these cases, the WECs’ hydrodynamic behavior and their power absorption efficiency can be improved by taking advantage of both the incident and the scattered from the wall boundary waves. The power absorption of a linear array of five cylindrical heaving WECs in front of a bottom-mounted vertical wall of infinite length was examined and evaluated in [20] in both frequency and time domain, by utilizing the method of images. The performance of nine cylindrical heaving WECs in the seaward side of a bottom-mounted vertical wall of finite length was examined in the frequency domain by [22], where emphasis was mainly given on the effect of the array’s distance from the wall on the WECs’ heave exciting forces and responses, as well as on the power absorption ability of the array.
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