Enhanced energy harvesting of wave energy converters in site-specific wave climates: A hybrid approach by geometric shape optimization and power take-off control

Abstract

Wave energy converters are devices that capture the energy carried by ocean waves and convert it into electricity, and their performance is significantly influenced by the geometric shapes of harvesters and the control strategies of power take-off systems. This paper presents a hybrid methodology to improve conversion efficiency in realistic sea states measured from an intended deployment site, taking into account the full coupling of ocean waves, geometric shapes of wave energy harvesters, and control strategies of power take-off systems. The proposed hybrid approach employs a control-strategy-informed optimization routine to select optimal/suboptimal geometries at the design stage, then employs different control strategies for the power take-off system at the operation stage. In numerical case studies, the proposed hybrid methodology is applied to a direct-driven point-absorber type wave energy converter, where its geometric shape is optimized, informing an optimal linear passive control strategy at the design phase. Simulation results indicate that the concave shape has the best energy harvesting performance. A high capture width ratio of 428% is achieved for the found optimum concave shape that employs an optimal linear active control strategy, in a sea state with a significant wave height of 1.6 m and an average period of 5.5 s.