【Haichuan Quality Articles Sharing】Modular design method for large-scale electrolytic hydrogen production systems

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The 25th National \"Safety Production Month\" in 2026: Everyone should talk about safety and know how to handle emergencies; identify and address potential risks and hazards. -------------------------------------------------- Gigawatt-scale large-scale electrolytic hydrogen production is the key trend in the industrialization and scaling up of green hydrogen. Due to the limitations of individual electrolyzer stacks, it is not possible to build large-capacity electrolysis systems using single stacks alone; therefore, modular parallel integration design has become the core technical approach to overcoming the challenges associated with expanding large-scale hydrogen production. By analyzing the Process Flow Diagrams (PFD) and Piping and Instrumentation Diagrams (P&ID) of the three main types of water electrolysis technologies—alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and high-temperature solid oxide electrolysis (HTEL)—and taking into account the expert opinions from the German Mechanical Engineering Industry Association VDMA P2X4A, this paper establishes a standardized classification system for the functional modules of these three electrolysis technologies. At the same time, a comparative analysis is conducted on the technical parameters of major electrolysis equipment manufacturers in Europe and the United States; the expansion mechanism, process architecture, and control logic of modular design are examined, and material and energy balance calculations are carried out using a 3-megawatt alkaline electrolysis system as a model. The study identified the differences in module configurations and common units among various electrolysis technologies, providing systematic theoretical support and engineering references for the standardized integration, automated control, and lifecycle-based iterative expansion of gigawatt-scale electrolysis systems. I. Introduction: The global new energy industry is evolving at a rapid pace, and green hydrogen, as a zero-carbon energy storage medium, has become a key element in the transformation of the energy structure. Many countries have set targets for the development of the hydrogen energy industry; Germany, in particular, has outlined a plan to achieve an electrolytic hydrogen production capacity of 10 gigawatts by 2030. The development of large-scale, low-cost, and highly efficient electrolytic hydrogen production systems has become a key focus for this industry. Under the existing industrial technology framework, relying solely on increasing the size of individual equipment to boost hydrogen production capacity faces significant technical and economic barriers. From a technical perspective, increasing the size of individual electrolyzers exacerbates pressure fluctuations between the anode and cathode, making it difficult to achieve stable operation ； Proton exchange membrane electrolysis technology is also constrained by the scarcity of precious metal catalysts such as iridium and platinum, preventing a significant increase in production capacity through simply scaling up the size of the individual units. From an engineering application perspective, the manufacturing, transportation, and operation costs of ultra-large single-unit equipment rise significantly, and integral system designs struggle to meet the demands of large-scale production. Modular design effectively circumvents the performance limits of individual devices by breaking down system functional units, implementing standardized modules for parallel expansion, and thus represents the optimal solution for constructing gigawatt-scale electrolysis systems. The core idea is to reconcile the conflict between centralized and decentralized design of the functional units in an electrolysis system. By breaking down complex electrolysis systems into several independent, reusable, and parallelizable standardized functional modules, it is possible to increase production capacity on a larger scale through the replication and parallel connection of these modules. At the same time, process control and system integration frameworks tailored to this modular architecture are employed to ensure the stable and efficient operation of large-scale systems. The industry has currently begun to explore the modular application of electrolysis systems; existing research has enabled the parallel expansion of megawatt-class PEM electrolyzer stacks, and design plans have been developed for PEM electrolysis systems of various scales ranging from 100 kilowatts to 100 megawatts, as well as for hundred-megawatt-class AEL electrolysis systems. Overall, however, the modular application of electrolysis systems is still in the initial planning stage; traditional integrated designs remain the dominant approach in practical implementation, and the potential for adapting process control to a modular format as well as for systematic integration has not yet been fully explored. In accordance with the industry standards VDI 2776 and VDI VDE NAMUR 2658 issued by the German Engineers’ Association, a systematic modular design enables the integration of process engineering and automation technologies. Through standardized interfaces, modular function encapsulation, and hierarchical module organization, it facilitates the standardization of the entire process involved in the design, integration, and operation of electrolysis systems. Standardized modules for pre-testing and pre-automation can significantly reduce the difficulty of system deployment, eliminating the need to rewrite control code. This helps to simplify the system architecture and reduce operational complexity, while also facilitating scaling, modification, and upgrading throughout the system’s lifecycle. Based on this, this paper systematically reviews the process frameworks of three mainstream water electrolysis technologies, defines standardized and reusable electrolysis process functional modules, develops a modular classification scheme suitable for different technical approaches, and explores the mechanisms by which modular design supports process control and integrated operation and maintenance of electrolysis systems. It provides a theoretical basis and technical reference for the standardized and modular implementation of large-scale electrolytic hydrogen production systems.