Hydrodynamic optimization of the geometry of a sloped-motion wave energy converter

Abstract

This paper presents the hydrodynamic optimization study of CECO, a point absorber wave energy converter (WEC) with sloped motion. To maintain the overall costs, the characteristic dimensions of the optimized solution were not allowed to change significantly. Instead, different geometrical shapes have been generated and numerically investigated based on the exhaustive search method with a heuristic approach. The assessment of the different geometries was based on a new index - the hydrodynamic capacity for wave energy conversion - which considers that the theoretical maximum WEC's absorbed power from irregular waves is obtained assuming that for each individual wave component of the sea spectrum, the PTO system can operate with its optimum damping coefficient. The optimum geometry obtained is able to harvest twice as much wave energy than the original design of CECO. The numerical outcomes have been validated with the results of experimental tests with the new geometry. Unlike “pure” heaving WECs, a sloped-motion WEC can achieve natural oscillation periods within a broad range by controlling the inclination of the motion path, the submergence level or the shape of its floaters. Therefore, CECO can be tuned to any given sea state and avoid the need for active complex control strategies.