Integrated design and operation of offshore wind energy hubs: Multi-vector green hydrogen and ammonia networks

Decarbonizing hard-to-abate sectors in the UK will require scalable green hydrogen production derived from offshore wind energy, yet the optimal system configuration remains unclear due to fundamental trade-offs between economies of scale and transmission infrastructure costs. This study presents a superstructure optimisation framework for the integrated design and operation of multi-vector offshore wind energy hubs, providing a systematic comparison across twelve competing hydrogen and ammonia network configurations. Applied to the UK North Sea, the framework reveals that fixed-bottom offshore platform hubs with liquefied hydrogen delivered via seaborne vessels achieve the lowest cost at 0.0649 £/MJ (7.790 £/kg H₂), while turbine-integrated electrolysis with offshore Haber-Bosch synthesis achieves 0.0784 £/MJ (1.458 £/kg NH₃). Critically, turbine-integrated distributed electrolysis proves competitive at 0.0697 £/MJ (8.36 £/kg H₂), challenging conventional centralisation paradigms. Key findings demonstrate that liquefied hydrogen pathways consistently outperform compressed alternatives by 5.5–12% despite liquefaction penalties, floating platforms impose 33–35% cost premiums over fixed-bottom foundations, and onshore electrolysis with marine cable transmission incurs a 57% cost penalty relative to the optimal offshore configuration. The narrow performance range of 0.065–0.077 £/MJ across the six most economical hydrogen configurations confirms that multiple technology pathways can achieve commercial viability, emphasising site-specific optimisation over prescriptive technology mandates.