Objective As nearshore wind resources approach saturation, the development of deep-sea wind power is facing a critical opportunity of scalable growth. Concurrently, the urgent need for low-carbon transformation in international shipping has driven a substantial increase in de-mand for green methanol fuel. In response, this paper proposes the concept of integrated energy islands with electrici-ty-carbon-hydrogen-methanol synergy.

Method First, this paper delineated the form of the integrated energy islands with electricity-carbon-hydrogen-methanol synergy and identified key technologies in the form. Second, a capacity planning model of the integrated energy islands with electrici-ty-carbon-hydrogen-methanol synergy was developed to optimize unit configurations, aiming to minimize the levelized unit cost of methanol production. Finally, sensitivity analyses on wind speed, carbon price, and oxygen price were conducted, alongside cost pres-sure testing, to clarify future cost reduction pathways.

Result The results show that: (1) For a typical 700 MW off-grid floating offshore wind farm, the integrated energy island requires a 235 MW/470 MWh electrochemical energy storage, 44 tons of hydrogen storage tanks, and a 264 MW PEM electrolysis to stabilize opera-tion of methanol synthesis system; (2) The current green methanol production cost is 12.36 CNY/kg, exceeding the market price of 5.95 CNY/kg; (3) The integrated energy island achieves an annual green methanol production of 221.6 kilotons, sufficient to power large methanol-fueled container ships for 800000 nautical miles while reducing CO₂ emissions by 980 kilotons annually.

Conclusion Integrated energy islands with electricity-carbon-hydrogen-methanol synergy demonstrate significant effect in consuming deep-sea wind power, meeting maritime green methanol demand, and assisting in carbon emission reduction. With anticipated technological advance-ments in PEM electrolysis cell, floating wind turbines, and direct air carbon capture, green methanol production is projected to achieve cost parity by 2035.