Off-grid wind/hydrogen systems with multi-electrolyzers: Optimized operational strategies

Optimized operation of wind/hydrogen systems can increase the system efficiency and further reduce the hydrogen production cost. In this regard, extensive research has been done, but there is a lack of detailed electrolyzer models and effective management of multiple electrolyzers, considering their physical restrictions. This work proposes electrolyzer models that integrate the efficiency variation caused by load level change, start-stop cycle (including hot and cold start), thermal management, and degradation caused by frequent starts. Based on the proposed models, three operational strategies are considered in this paper: two traditionally utilized methods, simple start-stop and cycle rotation strategies, and a newly proposed rolling optimization-based strategy. The results from daily operation show that the new strategy results in a more balanced load level among the electrolyzers and a more stable temperature. Besides, from a yearly operation perspective, it is found that the proposed rolling optimization method results in more hydrogen production, higher system efficiency, and lower LCOH. The new method leads to hydrogen production of 311297 kg, compared to 289278 kg and 303758 kg for simple start-stop and cycle rotation methods. Correspondingly, the system efficiencies for the new, simple start-stop and cycle rotation methods are 0.613, 0.572, and 0.587. The resulting LCOH from the new method is 3.89 euro/kg, decreasing by 0.35 euro/kg and 0.21 euro/kg compared to the simple start-stop and cycle rotation methods. Finally, the proposed model is compared with two conventional models to show its effectiveness in revealing more operational details and reliable results.