Wave absorber ballast optimization based on the analytical model for a pitching wave energy converter

The present paper considers pitching wave energy converters (WECs) integrated in a floating platform, e.g., floating foundation for a wind turbine. Each WEC consists of a partially submerged wave absorber that rotates about the hinge located above the still water level under the influence of waves. Each wave absorber contains separated ballast tanks that are used to ensure the desired initial tilting angle of the absorber with respect to the floating foundation (called the rest angle). The same rest angle can be achieved by filling different ballast compartments that impacts the inertia moment about the hinge, response amplitude operator (RAO), resonance frequency of the absorber, and the power absorption performance. The exhaustive search for a suitable ballast configuration can quickly become a computationally expensive task depending on the number of ballast tanks. In this paper, the ballast optimization algorithm based on an analytical model is developed. The algorithm is applied to investigate the impact of the ballasts on the rest angle, RAO and resonance frequency of the wave absorber. It provides a base for ballast design and location for improved power absorption performance. The proposed algorithm can be adapted to the ballast optimization of other pitching WECs.