Complementary Spanish photovoltaic and Danish offshore wind pathways to cost-competitive renewable hydrogen

• A techno-economic model for hydrogen export from Spain and Denmark is developed. • Seasonal PV–wind complementarity reduces hydrogen cost variability. • LOHC storage enables low-cost hydrogen in regions without underground options. • Storage type impacts LCOH more than local renewable energy characteristics. • Hybrid Spain–Denmark strategy supports EU hydrogen corridor development. This paper evaluates the techno-economic feasibility of large-scale green hydrogen production and export from Spain and Denmark by optimising renewable generation, electrolyser capacity, and hydrogen storage. We develop an integrated framework that minimizes the levelized cost of hydrogen (LCOH) while considering three storage technologies: liquid organic hydrogen carriers (LOHCs), salt caverns, and pressurised tanks. The approach combines country-specific optimisation with comparative technology assessment under future deployment assumptions and dual uncertainty (techno-economic and interannual). Results show that storage technology is the dominant cost driver, outweighing location-specific renewable energy characteristics. LOHC systems and salt caverns achieve comparably low LCOH values, offering competitive solutions depending on local geological constraints. In contrast, pressurised tanks entail substantially higher costs, making them suitable only for niche or short-term applications. A key finding is the seasonal complementarity between Spanish PV and Danish offshore wind: PV peaks in spring and summer, while offshore wind provides higher output in autumn and winter. Coordinating production and storage across both countries can reduce seasonal cost swings and improve export competitiveness under the European Hydrogen Backbone initiative. The proposed framework and sensitivity analysis offer strategic insights for designing hybrid hydrogen export systems and selecting appropriate storage technologies in regions with contrasting renewable profiles.