Abstract
Abstract The Ostend Declaration commits North Sea countries to installing 300 GW of offshore wind (OW) capacity by 2050, a development that will reshape Europe’s decarbonised energy system. This study assesses how such large-scale OW deployment affects the European energy mix, transmission needs, and OW project profitability. Using the open energy system model GENeSYS-MOD with a 47-node spatial resolution, including 19 offshore nodes, we evaluate scenarios with different offshore grid layouts and OW investment requirements, and conduct a sensitivity analysis on OW capital costs. Results show that meeting the Ostend targets increases total system costs by only about 1%, while OW primarily displaces onshore wind, solar PV, and nuclear power. Achieving the targeted OW levels endogenously requires roughly a 50% reduction in OW CAPEX. The choice of offshore grid layout has little impact on overall system cost or average OW return on investment, but it does shift the geographic distribution of investments; notably, radial grid layouts reduce the need for onshore wind in Norway. Enforcing early OW buildout raises OW profitability due to higher electricity prices in earlier periods. The findings highlight trade-offs between cost efficiency, infrastructure design, and regional policy priorities for North Sea energy development.