Design of an overtopping wave energy converter: the role of the seaward outflow

Overtopping Breakwaters for Energy Conversion (OBREC) typically route overtopped water into a basin landward of the structure, protected from large sea-level fluctuations. Considering that numerous coastal structures suitable for OBREC integration are incompatible with the construction of a protected basin, we study an alternative configuration that releases the stored water seaward, introducing the influence of the open sea on the available hydraulic power along the conveyance system. The approach aims to expand OBREC applicability to natural shorelines by enabling installation on shore-connected breakwaters, structures that are widely deployed, for example, along the Italian coast of the Adriatic Sea. The study presents an integrated design workflow, including offshore and nearshore wave characterization, port-scale wave modelling, ramp slope, device orientation, and turbine assessment, to characterize the wave structure interaction and performance of OBRECs integrated into typical Adriatic coastal protections. This framework serves to optimize a full-scale prototype that will be deployed at the Port of Ancona, Italy. In particular, the effect of wave conditions and related sea-level fluctuation on the extractable power is examined, showing that for seaward discharge without waves and landward discharge, the highest mean energy is available next to the outlet discharge system, where flow velocities are maximal. On the other hand, for seaward discharge with waves and increased sea-level, the location of maximum available energy shifts progressively toward the basin, with a significant reduction in available power up to about 90%.