Operation optimization and configuration of a novel wide-power hybrid electrolytic water-to‑hydrogen system in response to fluctuations in renewable energy sources

Alkaline (ALK) electrolyzers face challenges adapting to the high volatility and variability of renewable energy generation for green hydrogen production. To address this issue, a novel hybrid hydrogen production system is developed, enabling structural coupling between ALK and proton exchange membrane (PEM) electrolyzer arrays by sharing balance-of-plant (BOP) units such as water replenishment, hydrogen condensation, purification and compression. This configuration efficiently regulates hydrogen production power while avoiding redundant BOP components. Based on the start-stop characteristics, power-regulation capabilities, and energy-efficiency profiles of the two electrolyzer types, we propose an operation-optimization strategy that prioritizes equipment startup. Aiming to maximize overall system benefit, the optimal capacity configuration of both electrolyzers is determined. Furthermore, through multi-scenario operation analysis, the influence of renewable energy output characteristics on the performance of the hybrid hydrogen production system is revealed. The proposed capacity allocation method identifies a 6:2 ALK-to-PEM ratio as the optimal equilibrium between cost investment and efficiency enhancement, maximizing net project benefits to $3.14 million while minimizing total installed capacity. The prioritization strategy enables flexible hydrogen power allocation, achieving a renewable energy utilization rate of 92.17 % under Typical Day 4 PV output, surpassing equalization and rotation strategies by 19.63 % and 6.95 %, respectively, and increasing to 95.52 % under Typical Day 1. The strategy is also well suited to extreme conditions such as high-frequency power fluctuations and prolonged low-power periods. By reducing ALK start-stop frequency, input power variability and downtime, the method lowers energy losses and equipment wear and improves operational continuity and economic efficiency. Overall, the findings provide theoretical and engineering support for structural design, capacity configuration, and operational control of hybrid hydrogen production systems, promoting their large-scale and efficient deployment.