Techno-economic assessment of a U-shaped sloshing tank wave energy converter for Italian offshore applications

Wave energy converters (WECs) offer promising opportunities for supplying power to isolated grids and for synergistic co-location with offshore wind farms, particularly in moderate wave climates such as the Mediterranean Sea. This work presents a techno-economic assessment of a floating U-shaped sloshing tank Wave Energy Converter (U-WEC), which exploits the coupled motion of a floating hull and an internal U-tank to drive a Wells turbine-based power take-off. A two-stage optimisation framework is proposed. First, a bi-objective techno-economic optimisation is performed on the main system parameters governing displacement mass, used as a proxy for capital cost, and gross annual energy production. Second, an ad hoc optimisation of the Wells turbine is carried out for each optimal device, accounting for the strong coupling between hull size, resonance behaviour, and turbine operating conditions. The methodology is applied to a Mediterranean site in the Strait of Sicily and compared with a Northern European site to assess the impact of different wave climates. The results show that optimal solutions consistently converge towards asymmetric hull configurations, highlighting the importance of multi-degree-of-freedom hydrodynamic coupling and resonance tuning between the hull and the U-tank. A multi-site assessment across several Italian offshore locations, including offshore wind co-location areas and off-grid islands, confirms the suitability of the proposed U-WEC for Mediterranean offshore applications.