Multi-timescale performance analysis of an offshore wind–solar–wave hybrid hydrogen production system for an energy island

Offshore hybrid renewable energy hydrogen production systems deployed on energy islands offer a promising pathway for large-scale utilization of marine renewable energy. Comprehensive performance analysis is necessary to quantify the performance of hydrogen production systems and to guide design and investment decisions. However, traditional analyses often focus on long timescale and therefore fail to account for the multi-timescale system performance of offshore renewable energy hydrogen production systems. To address this gap, this study proposes an offshore wind–solar–wave hybrid energy hydrogen production system and conducts a multi-timescale performance analysis based on a rigorous thermodynamic model, including annual-scale system 4E (energy, exergy, economic and environmental) analyses, sensitivity analyses, and hourly-scale system exergy analysis. Results indicate an annual hydrogen output of 2.17 × 10⁷ kg, energy and exergy efficiencies of 14.28 % and 20.56 %, respectively, a levelized cost of hydrogen of 8.23 $/kg, and a CO₂ emission reduction of 2.17 × 10⁸ kg for 2023 at the northern South China Sea (35.0° N, 123.0° E). At a hydrogen selling price of 10.0·$/kg, the net present value is 4.78 × 10⁸ $ and the payback period is 14.59 years. Furthermore, integrating wave energy increases annual hydrogen output by 12.0 %, reduces the levelized cost of hydrogen by 15.4 %, and improves hydrogen production stability. The PEM electrolyzer is the primary source of exergy destruction, accounting for over 70.0 % of the total, followed by the heat exchangers and the hydrogen compressor. Potential pathways to reduce exergy destruction in the PEM electrolyzer are proposed.