Production & Supply Chain

Green hydrogen produced by water electrolysis using renewable energy sources (RES) is an emerging technology that aligns with sustainable development goals and efforts to address climate change. In addition to energy electrolyzers require ultrapure water to operate. Although seawater is abundant on the Earth it must be desalinated and further purified to meet the electrolyzer’s feeding water quality requirements. This paper reviews seawater purification processes for electrolysis. Three mature and commercially available desalination technologies (reverse osmosis multiple-effect distillation and multi-stage flash) were examined in terms of working principles performance parameters produced water quality footprint and capital and operating expenditures. Additionally pretreatment and post-treatment techniques were explored and the brine management methods were investigated. The findings of this study can help guide the selection and design of water treatment systems for electrolysis.

Hydrogen is expected to play a critical role in future energy systems projected to have an annual demand of 401–660 Mt by 2050. With large-scale green hydrogen projects advancing in water-scarce regions like Australia Chile and the Middle East and North Africa understanding water requirements for large-scale green hydrogen production is crucial. Meeting this future hydrogen demand will necessitate 4010 to 6600 GL of demineralised water annually for electrolyser feedwater if dry cooling is employed or an additional 6015 to 19800 GL for cooling water per year if evaporative cooling is employed. Using International Panel of Climate Change 2050 climate projections this work evaluated the techno-economic implications of dry vs. evaporative cooling for large-scale electrolyser facilities under anticipated higher ambient temperatures. The study quantifies water demands costs and potential operational constraints showing that evaporative cooling is up to 8 times cheaper to implement than dry cooling meaning that evaporative cooling can be oversized to accommodate increased cooling demand of high temperature events at a lower cost. Furthermore of the nations analysed herein Chile emerged as having the lowest cost of hydrogen owing to the lower projected ambient temperatures and frequency of high temperature events.

The global push for sustainable energy has heightened the demand for green hydrogen which is crucial for decarbonizing heavy industry. However current electrolysis plant capacities are insufficient. This research addresses the challenge through optimizing large-scale electrolysis construction via standardization modularization process optimization and automation. This paper introduces H2Giga a project for mass-producing electrolyzers and HyPLANT100 investigating largescale electrolysis plant structure and construction processes. Modularizing electrolyzers enhances production efficiency and scalability. The integration of AutomationML facilitates seamless information exchange. A digital twin concept enables simulations optimizations and error identification before assembly. While construction site automation provides advantages tasks like connection technologies and handling cables tubes and hoses require pre-assembly. This study identifies key tasks suitable for automation and estimating required components. The Enapter Multicore electrolyzer serves as a case study showcasing robotic technology for tube fittings. In conclusion this research underscores the significance of standardization modularization and automation in boosting the electrolysis production capacity for green hydrogen contributing to ongoing efforts in decarbonizing the industrial sector and advancing the global energy transition.

Hydrogen energy the cleanest fuel presents extensive applications in renewable energy technologies such as fuel cells. However the transition process from carbon-based (fossil fuel) energy to desired hydrogen energy is usually hindered by inevitable scientific technological and economic obstacles which mainly involves complex hydrocarbon reforming reactions. Hence this paper provides a systematic and comprehensive analysis focusing on the hydrocarbon reforming mechanism. Accordingly recent related studies are summarized to clarify the intrinsic difference among the reforming mechanism. Aiming to objectively assess the activated catalyst and deactivation mechanism the rate-determining steps of reforming process have been emphasized summarized and analyzed. Specifically the effect of metals and supports on individual reaction processes is discussed followed by the metalsupport interaction. Current tendency and research map could be established to promote the technology development and expansion of hydrocarbon reforming field. This review could be considered as the guideline for academics and industry designing appropriate catalysts.

Green hydrogen is gaining prominence as a sustainable fuel to decarbonize hard-to-electrify industries and complement renewable energy growth. Among clean hydrogen production technologies seawater-based PEM electrolysis systems hold substantial promise. However implementing offshore PEM electrolysis systems faces significant challenges in ensuring long-term availability due to technological infancy and harsh environmental conditions. Ensuring safe and reliable operation is therefore critical to advancing global sustainability goals. While existing research has primarily focused on component-level techno-economic feasibility limited attention has been given to system-level safety and availability analysis particularly for offshore renewable-powered seawater-based PEM electrolysis systems. This study addresses this gap by conducting a comprehensive availability analysis of containerized plug-and-play PEM systems in offshore environments. A Bayesian Network model is employed incorporating Fault Tree Analysis and Reliability Block Diagram approaches for failure and availability analysis at the system level. A maintenance decision support tool using Influence diagram is developed to analyse different maintenance planning strategies impact on system availability improvement. A case study incorporating industrial modular PEM model is utilised to analyse the developed model effectiveness. The study identifies 81 availability states with the hydrogen generation subsystem being the most critical to system performance. Comparative analysis shows that applying redundancy across all subsystems improves availability by 18.54% but reduces Expected Utility by 4.94%. The optimal strategy involves redundancy for seawater purification cooling and monitoring subsystems with preventive maintenance for hydrogen generation achieving a maximum EU of 5.29 × 106. This framework supports decision-makers in evaluating system availability under uncertain offshore conditions optimizing maintenance strategies and ensuring resilience for large-scale H2 production.

Anaerobic digestion (AD) is a biotechnological process in which the microorganisms degrade complex organic matter to simpler components under anaerobic conditions to produce biogas and fertilizer. This process has many environmental benefits such as green energy production organic waste treatment environmental protection and greenhouse gas emissions reduction. It has long been known that the two main species (acidogenic bacteria and methanogenic archaea) in the community of microorganisms in AD differ in many aspects and the optimal conditions for their growth and development are different. Therefore if AD is performed in a single bioreactor (single-phase process) the optimal conditions are selected taking into account the slow-growing methanogens at the expense of fast-growing acidogens affecting the efficiency of the whole process. This has led to the development of two-stage AD (TSAD) in recent years where the processes are divided into a cascade of two separate bioreactors (BRs). It is known that such division of the processes into two consecutive BRs leads to significantly higher energy yields for the two-phase system (H2 + CH4) compared to the traditional single-stage CH4 production process. This review presents the state of the art advantages and disadvantages and some perspectives (based on more than 210 references from 2002 to 2024 and our own studies) including all aspects of TSAD—different parameters’ influences types of bioreactors microbiology mathematical modeling automatic control and energetical considerations on TSAD processes.

Hydrogen has been receiving a lot of attention in the last few years since it is seen as a viable yet not thoroughly dissected alternative for addressing climate change issues namely in terms of energy storage and therefore great investments have been made towards research and development in this area. In this context a study about the main options for hydrogen production along with the analysis of a variety of the main power electronics converter topologies for such applications is presented as the purpose of this paper. Much of the analyzed available literature only discusses a few types of hydrogen production methods so it becomes crucial to include an analysis of all known types of methods for producing hydrogen according to their production type along with the color code associated with each type and highlighting the respective contextualization as well as advantages and disadvantages. Regarding the topologies of power electronics converters most suitable for hydrogen production and more specifically for green hydrogen production a list of them was analyzed through the available literature and a discussion of their advantages and disadvantages is presented. These topologies present the advantage of having a low ripple current output which is a requirement for the production of hydrogen.

Water electrolysis is considered as an important technology for an increased renewable energy penetration. This perspective on low-temperature water electrolysis joins the dots between the interdisciplinary fields of fundamental science describing physicochemical processes engineering for the targeted design of cell components and the development of operation strategies. Within this aim the mechanisms of ion conduction gas diffusion corrosion and electrocatalysis are reviewed and their influence on the optimum design of separators electrocatalysts electrodes and other cell components are discussed. Electrocatalysts for the water splitting reactions and metals for system components are critically accessed towards their stability and functionality. On the basis of the broad scientific analysis provided challenges for the design of water electrolyzers are elucidated with special regard to the alkaline or acidic media of the electrolyte.

Combining electrolytic hydrogen production with wind–photovoltaic power can effectively smooth the fluctuation of power and enhance the schedulable wind–photovoltaic power which provides an effective solution to solve the problem of wind–photovoltaic power accommodation. In this paper the optimization operation strategy is studied for the wind–photovoltaic power-based hydrogen production system. Firstly to make up for the deficiency of the existing research on the multi-state and nonlinear characteristics of electrolyzers the three-state and power-current nonlinear characteristics of the electrolyzer cell are modeled. The model reflects the difference between the cold and hot starting time of the electrolyzer and the linear decoupling model is easy to apply in the optimization model. On this basis considering the operation constraints of the electrolyzer hydrogen storage tank battery and other equipment the optimization operation model of the wind–photovoltaic power-based hydrogen production system is developed based on the typical scenario approach. It also considers the cold and hot starting time of the electrolyzer with the daily operation cost as the goal. The results show that the operational benefits of the system can be improved through the proposed strategy. The hydrogen storage tank capacity will have an impact on the operation income of the wind–solar hydrogen coupling system and the daily operation income will increase by 0.32% for every 10% (300 kg) increase in the hydrogen storage tank capacity.

The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for largescale production. In this review we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts with a focus on their synthetic methods and the role of the so-called “co-catalysts”. Then a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications.