Impacts of intermittency on low-temperature electrolysis technologies: A comprehensive review

Photovoltaic-based integrated energy systems act as a possible modern technological solution for clean and affordable green hydrogen production. However, research attempts are required from the scientific community to develop power management, control, optimization algorithms, and new techniques for these integrated energy systems effective and economical operation. The integrated energy system considered in this work consists of a solar photovoltaic, battery, grid and proton exchange membrane (PEM) electrolyzer. PEM electrolyzer with a power rating of 100 kW is modelled as a controlled current sink to interfere with the DC bus directly. This work proposes a power management and control algorithm for the photovoltaic-based integrated energy system considering different parameters like availability of solar photovoltaic power, DC link voltage, battery state of charge (SOC), tariff and availability of grid power. Effective power-sharing among the different power sources increases system reliability and stability. Optimization is performed for optimal sizing and costing to achieve economical operation such that these photovoltaic-based integrated energy systems become affordable and are encouraged for wide use. The photovoltaic system operates at the maximum power point through a neural network-based control strategy; in addition to this, stacking in neural network topologies is also discussed for improving system accuracy in tracking the reference voltage for MPPT operation. The DC link voltage is controlled by interfacing the battery with the DC link via a bidirectional buck-boost power converter. The contribution of the work is to highlight the role of renewable energy sources for continuous green hydrogen production. Green hydrogen will be a critical driving force for the future transportation system, fuel cell-based power generation, and industries utilizing hydrogen in direct or indirect forms-that will help transition towards a carbon-free society. Optimization and time-domain simulation results indicated the economic and technical feasibility of the proposed photovoltaic-based integrated energy system for green hydrogen production with the best optimal configuration producing hydrogen at the cost of $ 4.806/kg and total net present cost of $749904.

The transition to carbon neutrality is critically dependent on the development of sustainable power sources and energy storage solutions. One of them is green hydrogen production via water electrolysis from renewable energy. Proton Exchange Membrane (PEM) electrolysis is recognized as one key technology in this domain due to its high efficiency, eligibility for transient operation and compact design. One primary development goal is to reduce the Levelized Cost of Hydrogen production (LCOH) by improving efficiency and durability while assuring safe operation at all conditions. This can only be achieved by a holistic approach on system level, optimizing every aspect of the technology, including cell design, material selection, stack configuration and its integration with all kinds of balance of plant components. In this context, the application of multi-scale and multi-domain system simulation, incorporating precise thermodynamic and electrochemical models, is a promising measure to reduce development time and cost. Simulation models account for the key processes such as cell polarization, reactant cross-diffusion, auxiliary power demands, and hydrogen purification with their related losses.This work employs a system simulation method for the thermodynamic and electrochemical optimization of a state-of-the-art PEM electrolysis system with a target hydrogen pressure of 70 bar and product purity of 99.999%. The baseline system operates at 30 bar stack pressure, with a two-bed Pressure Swing Adsorber (PSA) for hydrogen purification and a subsequent hydrogen compressor. The part-load limit, given the hydrogen in oxygen concentration due to reactant cross-diffusion is at 20%. The study first explores an increase in the stack operation temperature for reducing the activation overpotential and ohmic losses. Subsequently, it examines the potential of advanced membrane materials featuring lower hydrogen cross-diffusion characteristics. These materials allow for higher stack pressure, reduced membrane thickness, or for extended part-load operation, all while maintaining the hydrogen in oxygen safety limits. The results show that, on system level, increasing the stack pressure is more efficient than reducing the membrane thickness. The reduced power consumption for hydrogen compression and the reduced PSA losses more than compensate the effects of cell polarization characteristics. Finally, the system model serves to determine an optimal load profile for minimal LCOH at volatile electricity prices. Figure 1

Green Hydrogen is widely acknowledged as one of the important pillars for decarbonisation of hard-to-abate sectors and to transition the global economy to Net Zero. The current priority in the energy sector is to rapidly establish and scale a green Hydrogen based energy value chain that meets three core objectives: affordability, sustainability and security of supply, also referred to as ‘Energy Trinity’. Green hydrogen is produced from electrolysis of fresh water through technologies such as alkaline electrolyser, PEM (proton exchange membrane), and SOEC (solid oxide electrolyser). The production of green hydrogen from water is an energy intensive process, due to the high thermodynamic stability of water molecules. The cost of producing green hydrogen at scale is large proportional to the cost of renewable electricity. This requires green hydrogen production basins to be located close to regions/ geographies with access to surplus and low-cost renewable electricity, such as Australia, Middle East, Norway, Scotland and Chile. The current cost of green hydrogen in the UK has a 5-10 times cost premium as compared to fossil fuels. The primary inputs from green hydrogen production through electrolysis technologies are renewable electricity and freshwater. There has been an increasing concern globally on the availability and preservation of water resources. There are publications from water companies in the UK citing that the supply of constant fresh water supply for industrial applications such as green hydrogen production cannot be guaranteed under rapidly changing scenarios of climate change. There is a potential to set up large scale desalination plants to meet the fresh water for hydrogen production, however the large quantities of discharge water with high brine concentration might pose environmental hazards to marine habitat. This calls for alternate technologies to be developed which addresses the freshwater dependence for green hydrogen production and the significant green premium on cost structure. The paper describes a novel biocatalysis approach for production of green Hydrogen from wastewater, without requiring electricity input.

Green Hydrogen Production: Advances and Challenges

This review focuses on the integration of renewable energy, advanced materials, and civil engineering to foster urban resilience in future cities. As urban populations continue to grow, the demand for sustainable solutions to mitigate environmental impact and enhance quality of life becomes increasingly urgent. This review explores how the convergence of renewable energy sources, innovative materials, and civil engineering practices can contribute to the development of resilient cities capable of meeting the challenges of the 21st century. The integration of renewable energy sources, such as solar, wind, and hydroelectric power, offers opportunities to reduce dependence on fossil fuels and mitigate greenhouse gas emissions. Advancements in renewable energy technologies allow for the generation of clean, reliable energy within urban environments, promoting energy independence and reducing carbon footprints. Additionally, the utilization of advanced materials in urban infrastructure can enhance durability, efficiency, and sustainability. Nanotechnology, for example, enables the development of high-performance materials with superior strength, flexibility, and resilience. These materials can be used in construction, transportation, and water management systems to improve infrastructure resilience and longevity. Furthermore, civil engineering plays a crucial role in designing and implementing sustainable urban infrastructure. From green building practices to resilient urban planning, civil engineers are instrumental in creating cities that can withstand environmental hazards and adapt to changing conditions. By integrating renewable energy, advanced materials, and innovative engineering solutions, cities can enhance their resilience to climate change, natural disasters, and other challenges. This review examines case studies and examples of successful integration of renewable energy, advanced materials, and civil engineering in urban development projects worldwide. It also discusses the challenges and opportunities associated with implementing these solutions, including technological barriers, financial considerations, and policy frameworks. The integration of renewable energy, advanced materials, and civil engineering is essential for building resilient and sustainable cities of the future. By embracing innovation and collaboration across disciplines, cities can enhance their capacity to thrive in the face of environmental, social, and economic challenges, ultimately improving the quality of life for urban residents while preserving the planet for future generations.

Electrolysis – Proton-exchange membrane electrolyzer | Proton exchange membrane water electrolysis: State-of-the-art technique and systems

Hydrogen is a potential energy vector and storage medium for achieving net-zero emissions on a large scale.Among the various methods of producing low-carbon hydrogen, water electrolysis is the most appropriate and promising.Despite the commercial implementation of technical and industrial hydrogen production via electrolysis, conducting a comprehensive economic analysis of its production using grid or micro grid renewable energy systems presents challenges.Accordingly, it's important to review the approaches in the literature on the performance and costs of water electrolysis systems.This critical review aims to identify key performance parameters of the main commercial water electrolysers.In particular, the review will highlight advances in materials and challenges of Alkaline and Polymer Electrolyte Membrane commercial water electrolysis technologies.A techno-economic analysis using Multi-Criteria Decision Making (MCDM) will be performed on these technologies.The review will present various MCDM analysis methods used for these analyses.Results obtained from these methods will be compared and discussed, including their technological issues and the cost of hydrogen prospects, will be shown.Additionally, the potential of using Multi-Criteria Decision Making (MCDM) as a tool for supporting appropriate decision-making in hydrogen production and identifying research and development gaps in water electrolysis will be presented.Also, the limitations and performance of commercial electrolysers while suggesting possible solutions for achieving cost-effective hydrogen production will be described.The goal of this critical review is to propose innovative ideas and solutions for driving cost-effective green hydrogen production for commercial applications.The manuscript clearly states its objective to provide a comprehensive review of the fundamental principles and challenges associated with Proton Exchange Membrane (PEM) and Alkaline Water Electrolysis (AWE).It aims to identify current trends in water electrolysis technology and evaluate the techno-economic feasibility of hydrogen production using Multi-Criteria Decision Making (MCDM) tools.This objective is directly aligned with the need for practical solutions in green hydrogen production, emphasizing the study's contribution towards promoting the adoption of green hydrogen as a critical technology for a low-carbon economy.The introduction discusses the significant challenges in adopting electrolysis technologies, such as high capital costs and the need for innovation in materials and design.It mentions ongoing research to find affordable alternatives to expensive materials like platinum, aiming to reduce the overall cost of electrolysis.

Proton exchange membrane (PEM) water electrolysis is a technology designed to produce H2 using only water and electricity as inputs; it has gained increased attention in industry and academia due to its advantages over incumbent H2 generation processes (of which the most widely used are steam reforming and coal gasification) namely, low temperature, carbon-neutral and intermittent operation. PEM electrolysis can be instrumental for creating a hydrogen economy, although still much research needs to be carried out before widespread industrial adoption is achieved. PEM water electrolyzers suffer energy losses associated with the chemical reactions and the transport of charge and mass; of these phenomena, mass transport in PEM electrolyzers is the least understood subject, given the complex nature of the interaction of multiphase flows (mainly consisting of liquid water and evolved gases) through micrometric pores. The subject of multiphase flow in water electrolysis and its relationship with the mass transport phenomena in PEM water electrolysis has been a prevalent subject in the literature. Despite numerous attempts at pinpointing the relationship between mass transport overpotential and the operating parameters, there is no clear consensus about which transport mechanisms dominate, nor about how the component design of PEM electrolyzers affects the mass transport. While the effect of temperature and current density on mass transport losses has been extensively studied and is well understood, there are significantly fewer studies that focus on the effect of water flow and pressure. Both water flow and pressure have a direct effect on mechanisms such as bubble nucleation and two-phase flows that occur in the porous structures within a PEM electrolyzer (electrodes and porous transport layers, PTLs). In this work, I studied the effect of water flow and pressure on the mass transport phenomena in PEM electrolyzers. Chapters 1 and 2 provide an introduction to the topic as well as a description of the materials and experimental setups used. Chapter 3 of this thesis depicts the visualization and modeling of bubble nucleation in an operating PEM electrolyzer. I discovered that bubble detachment radii are largely independent of water flow and I identified two types of bubbles: bubbles that detach after reaching a critical size, and bubbles that fill up the pores of a PTL before detaching. Chapter 3 consists of the measurements I carried out regarding the transport of evolved gas through the water-filled pores of a PTL, where I observed that water flow severely impedes the gas transport through the pores and that such impediment is related to a shear stress exerted by the water flow on the pores. Chapter 5 shows the measuring of mass transport losses using electrochemical impedance spectroscopy (EIS) on an operating PEM electrolyzer; the results indicate that pressure and water flow affect the diffusion of gas in the electrode and that the mass transport overpotential depends on design parameters of the PEM electrolyzer, such as electrode thickness and hydrophobicity. Overall, I derived a theoretical framework based on the assumption that the evolved gas in a PEM electrolyzer permeates through the PTL after diffusing from the active sites to the bubble nucleation sites. Such framework, constructed on the basis of the models regarding gas transport in porous media, can be used to explain the mass transport loses in a PEM electrolyzer that arise from operating with increased water flows and pressures. The model I derived can be used in future work as a guideline to optimize the components of a PEM electrolyzer, in particular regarding the hydrophobicity and pore size distribution of PTLs as well as the composition of the catalyst ink to produce the electrodes. Moreover, this work can also be used to further understand the mass transport losses and optimize the operation of PEM electrolyzers to decrease the energy consumption of H2 generation.

The integration of renewable energy sources into existing energy systems is imperative for enhancing climate resilience and mitigating the adverse impacts of climate change. This comprehensive review explores the multifaceted aspects of renewable energy integration for climate resilience, focusing on key challenges, strategies, and opportunities. By analyzing the latest research findings and case studies, this review offers insights into the diverse approaches to renewable energy integration and their implications for enhancing climate resilience at local, regional, and global scales. The review begins by examining the significance of renewable energy integration as a crucial component of climate resilience strategies. It delves into the interconnectedness between renewable energy deployment and climate adaptation, highlighting the potential of renewable energy systems to enhance energy security, reduce greenhouse gas emissions, and build community resilience to climate-related hazards. Subsequently, the review explores the challenges associated with renewable energy integration, including intermittency, grid stability, and socioeconomic considerations. It discusses innovative solutions and technological advancements aimed at overcoming these challenges, such as energy storage technologies, smart grid systems, and demand-side management strategies. Moreover, the review investigates the role of policy frameworks, regulatory mechanisms, and financial incentives in facilitating renewable energy integration for climate resilience. It assesses the effectiveness of various policy instruments and governance structures in promoting renewable energy deployment and fostering climate-resilient energy systems. Furthermore, the review highlights the importance of stakeholder engagement, community involvement, and capacity-building initiatives in ensuring the successful implementation of renewable energy projects. It emphasizes the need for inclusive and participatory approaches to renewable energy planning and decision-making, particularly in vulnerable and marginalized communities. Overall, this comprehensive review provides valuable insights into the complex dynamics of renewable energy integration for climate resilience. By synthesizing existing knowledge and identifying emerging trends, it informs policymakers, practitioners, and researchers about the opportunities and challenges associated with leveraging renewable energy as a key strategy for building climate resilience in a rapidly changing world. Keywords: Renewable Energy, Integration, Climate, Resilience, Policy.

Green hydrogen production from industrial effluent electrolysis: A brief bibliometric analysis and literature review

Mathematical modeling of an integrated photovoltaic-assisted PEM water electrolyzer system for hydrogen production

Green hydrogen production by proton exchange membrane water electrolysis (PEMWE) powered by clean energy is a promising and environmentally friendly technology. However, it relies on a high‐purity water source, which is limited in regions facing water scarcity. Here, a coupled self‐sustaining solar‐enabled system is reported that couples atmospheric water harvesting with PEM water electrolysis (AWH‐PEMWE), offering a novel pathway for clean water generation and green hydrogen production. The atmospheric water harvester (AWH) component utilizes N and O co‐doped hydrophilic ordered porous carbon, engineered with an interconnected hierarchical porous structure with prosperous channels for efficient mass transport. It enables effective interfacial solar evaporation for water release, achieving a record‐high water harvesting capacity of 0.49 L kg−1 h−1 at 40% relative humidity (RH). During outdoor tests, the AWH‐PEMWE system reaches a peak green hydrogen production rate of 204 mL h−1 at midday using only atmospheric water as feedstock. Remarkably, the system remains operational under ultra‐low humidity conditions down to 20% RH, addressing the challenge of water availability in arid environments. Importantly, the system operates without the need for carrier gases or external energy input accessories, enabling a fully solar‐driven process with zero carbon emission throughout the hydrogen production cycle.

The integration of variable wind and photovoltaic generation with proton exchange membrane (PEM) water electrolysis is a key enabler for green hydrogen production in smart multi-energy systems, but it exposes coupled multi-physics dynamics, conflicting operational objectives, and strict safety constraints. This paper proposes a hierarchical data–model hybrid scheduling framework for grid-connected PEM green hydrogen production. At the modeling layer, a physics-informed representation with six governing equations in the main text and twenty-two supporting equations in Appendix A defines explicit “red-line” constraints for electrochemical efficiency, thermal safety, and equipment degradation. At the coordination layer, a high-level module—designed with the aid of a large language model during a 90 day design phase—maps heterogeneous operational context (renewable forecasts, electricity prices, stack health indicators) into adaptive multi-objective preference weights and operating bounds. At the execution layer, Takagi–Sugeno fuzzy controllers provide real-time set-point tracking for multiple PEM units. Numerical studies using European wind, photovoltaic, and day-ahead price data over a 7 day test period demonstrate that the proposed framework achieves ∼4.9% power tracking root mean square error [compared with 7.8% for proportional-integral-derivative (PID) control], thermal safety margins approximately 174% larger than conventional baselines, and roughly 11.8% faster fault recovery. These results indicate that the proposed physics-informed, data–model hybrid architecture effectively supports the integration of green hydrogen into smart multi-energy systems.

Green hydrogen production via electrolysis from renewables is a promising method to achieve deep integration of renewable energy sources (RES) and boost decarbonisation of the whole energy system. Current studies mainly focus on low penetration levels, where both RES and electrolysers are treated as price-taker in the market. Here we develop an integrated hydrogen-electricity market simulation and investment tool, based on a mixed integer linear programming unit commitment with flexible hydrogen demand, with the aim of studying the techno-economic performance of a system with large-scale adoption of RES and electrolysis. We show how in a RES-dominated electricity market the marginal price could be set by the willingness-to-pay (WTP) price and installed capacity of electrolysers. The payback time or RES and electrolysers varies significantly for different resource portfolios and WTP prices of electrolysers. The results demonstrate how win-win RES and electrolyser economic equilibria can be achieved to produce large volumes of green hydrogen in low-carbon power systems.

This work explores the integration of Proton Exchange Membrane (PEM) electrolysis waste heat with district heating networks (DHN), aiming to enhance the overall energy efficiency and economic viability of hydrogen production systems. PEM electrolysers generate substantial amounts of low-temperature waste heat during operation, which is often dissipated and left unutilised. By recovering such thermal energy and selling it to district heating systems, a synergistic energy pathway that supports both green hydrogen production and sustainable urban heating can be achieved. The study investigates how the electrolyser’s operating temperature, ranging between 50 and 80 °C, influences both hydrogen production and thermal energy availability, exploring trade-offs between electrical efficiency and heat recovery potential. Furthermore, the study evaluates the compatibility of the recovered heat with common heat emission systems such as radiators, fan coils, and radiant floors. Results indicate that valorising waste heat can enhance the overall system performance by reducing the electrolyser’s specific energy consumption and its levelized cost of hydrogen (LCOH) while supplying carbon-free thermal energy for the end users. This integrated approach contributes to the broader goal of sector coupling, offering a pathway toward more resilient, flexible, and resource-efficient energy systems.