Japan aims for net-zero greenhouse gas emissions by 2050, with hydrogen playing a crucial role. Currently, Japan relies heavily on imported fossil fuels, accounting for 87% of its primary energy consumption. The ambitious target of 20 Mt year⁻¹ of low-carbon hydrogen consumption by 2050 (with an interim goal of 3 Mt year⁻¹ by 2030) requires a substantial and affordable hydrogen supply. Domestic green hydrogen production in Japan is projected to be costly ($6 kg⁻¹ by 2030), making imports essential. Import sources are explored, including Australia, New Zealand, and the Middle East, but these also face significant cost challenges relative to Japan's target of $3 kg⁻¹ by 2030, decreasing to $2 kg⁻¹ by 2050. This study investigates a potential alternative: leveraging China's substantial offshore wind resources to generate cost-competitive green hydrogen for export to Japan.

Existing literature highlights the challenges of achieving Japan's ambitious hydrogen goals due to the high costs of domestic renewable energy and the considerable expenses associated with importing hydrogen from other countries. Studies show that current and projected import costs from various regions would not meet Japan's price targets. This study builds upon previous work analyzing the potential of China's offshore wind resources for domestic energy use, extending the analysis to explore the potential for exporting green hydrogen to Japan.

This study performs a detailed techno-economic analysis of a potential China-Japan green hydrogen supply chain. The analysis is conducted on an hourly basis for each Chinese coastal province, considering various factors: 1. **Offshore Wind Resource:** Uses MERRA-2 wind data for 30 years (1990-2019) to assess the available wind power. It employs power curves for 8 MW and 9.5 MW offshore wind turbines, accounting for water depth and distance from shore limitations in assessing potential installed capacity. Three scenarios (high, moderate, low) for future capital costs are considered, based on NREL projections. 2. **Water Electrolysis:** Three electrolysis technologies (AEC, PEMEC, SOEC) are evaluated, considering their capital costs, operational costs, and efficiency. The analysis incorporates freshwater needs and the potential revenue from oxygen byproduct sales. 3. **Hydrogen Conversion & Transport:** Three transport mechanisms are considered: liquid hydrogen, MCH (methylcyclohexane), and ammonia. The analysis includes costs for compression, liquefaction, ammonia synthesis, hydrogenation/dehydrogenation (with waste heat, hydrogen/ammonia combustion, or natural gas combustion as heat sources), and shipping. Costs associated with storage (pressurized tanks, salt caverns), port buffering, and return transport of carriers are also incorporated. 4. **Economic Modeling:** A least-cost hydrogen delivery model, using MATLAB and Simulink, optimizes investment decisions and hourly operations, taking into account wind power volatility. The model considers different scenarios for offshore wind investment, electrolysis technologies, and transport mechanisms. 5. **Cost Normalization:** All costs are normalized to 2020 US dollars, and a 7% interest rate is used in the economic analysis. Electricity prices in China and Japan are also considered.

The analysis reveals that significant quantities of cost-competitive green hydrogen could be produced in China and delivered to Japan. * **Cost Competitiveness:** The levelized cost of hydrogen (LCOH) using the MCH transport mechanism can be as low as $2.0/kg in 2030 and $1.8/kg in 2050, significantly below Japan's target prices. Even with alternative transport mechanisms (ammonia, liquid hydrogen), the costs remain relatively competitive. Using salt caverns for storage reduces the overall costs further, making liquid hydrogen a more competitive option in 2050. * **Supply Capacity:** The potential hydrogen supply from offshore wind in China is substantial, potentially exceeding Japan's projected demands even under ambitious scenarios (up to 40 Mt year⁻¹). Individual provinces, such as Fujian, could single-handedly meet Japan's projected demands. * **Geographic Variation:** The LCOH varies geographically in China, with Fujian identified as the most cost-effective source, followed by Liaoning, Zhejiang, and Shandong. Water depth, distance from shore, and average capacity factors are key cost drivers. Interannual wind variability also plays a role. * **Cost Breakdown:** Hydrogen production represents the largest cost component (47-70%), followed by conversion (19-35%), with storage and transport contributing less. * **Sensitivity Analysis:** The results are robust to varying assumptions about future offshore wind costs and electrolysis technology choices. Even under high-cost scenarios for wind deployment, the Chinese source remains cost-competitive for supplying hydrogen to Japan in 2030.

The findings demonstrate the potential for a significant and cost-effective green hydrogen supply chain from China to Japan. The LCOH is substantially lower than projections for domestic production or imports from other locations. This strategic partnership could significantly advance both countries' decarbonization goals, reducing reliance on fossil fuel imports for Japan and offering a major export opportunity for China. The study highlights the potential for increased trade relationships and mutual benefits between the two nations, advancing their "3E+S" objectives (Energy security, Economic affordability, Environment, and Safety). The abundance of offshore wind resources in China presents a significant opportunity for large-scale green hydrogen production and export, contributing to a global transition towards a low-carbon future. The potential for similar export opportunities to South Korea is also noted.

This study demonstrates the feasibility and cost-competitiveness of supplying green hydrogen to Japan from China's offshore wind resources. The findings highlight the potential for a substantial and mutually beneficial trade relationship, contributing significantly to both countries' carbon neutrality goals. Future research should further refine cost projections, explore alternative transport options (e.g., pipelines), and investigate the policy implications of such large-scale international hydrogen trade.

The study relies on modeled projections of future technology costs and wind resource availability, which involve inherent uncertainties. The analysis focuses on a specific set of technologies and transport mechanisms, and other possibilities could be explored in further studies. Geopolitical factors and potential regulatory hurdles related to international hydrogen trade are not explicitly considered but could affect the feasibility of this supply chain.