Critical issues for the deployment of floating offshore hybrid energy systems comprising wind and solar: a case study analysis for the Mediterranean Sea

Floating offshore energy systems have seen rising attention in recent years. The massive deployment of these systems implies several challenges, especially in sea basins with moderate wind, making floating wind turbines alone not financially viable. In some cases, such as the Mediterranean Sea, the presence of high solar radiation and moderate waves suggests the installation of floating photovoltaic panels, but the integration between different generators with the grid must be carefully evaluated. This study investigates a floating offshore energy system situated near the Sicilian coast, Italy, with a target export capacity of 1 GW. The analysis explores various combinations of wind and solar power to maximize the net present value of the system and minimize the levelized cost of energy, while maximizing the utilization factor of the export cable. In the first scenario, the study considers hybrid farms with a total rated power capacity of 1 GW, varying the wind and solar share in the mix. In the second scenario, solar production is added to a fixed 1 GW wind farm, keeping the maximum power export to shore equal to 1 GW and curtailing the excess. When a high-industry price is considered for floating solar, its levelized cost of energy (137.7 €/MWh) is higher than the remuneration proposed in the 2025 Italian financing scheme (105 €/MWh), making it economically unfeasible in every situation. Results show that the installation cost of solar energy must be lower than 1.11 M€/MWp to be competitive in the current market scenario. Sensitivity analyses on the remuneration applied to both sources go beyond the Italian scenario to show that the hybridization of wind with solar energy in floating systems can improve the techno-economic outcome of the system by exploiting the synergy between the two sources and reducing the cost of the expensive export cable.