Water Electrolysis Technology Research Articles

Life cycle environmental impacts and costs of water electrolysis technologies for green hydrogen production in the future

BackgroundTo limit climate change and reduce further harmful environmental impacts, the reduction and substitution of fossil energy carriers will be the main challenges of the next few decades. During the United Nations Climate Change Conference (COP28), the participants agreed on the beginning of the end of the fossil fuel era. Hydrogen, when produced from renewable energy, can be a substitute for fossil fuel carriers and enable the storage of renewable energy, which could lead to a post-fossil energy age. This paper outlines the environmental impacts and levelized costs of hydrogen production during the life cycle of water electrolysis technologies.ResultsThe environmental impacts and life cycle costs associated with hydrogen production will significantly decrease in the long term (until 2045). For the case of Germany, the worst-case climate change results for 2022 were 27.5 kg CO2eq./kg H2. Considering technological improvements, electrolysis operation with wind power and a clean heat source, a reduction to 1.33 kg CO2eq./kg H2 can be achieved by 2045 in the best case. The electricity demand of electrolysis technologies is the main contributor to environmental impacts and levelized costs in most of the considered cases.ConclusionsA unique combination of possible technological, environmental, and economic developments in the production of green hydrogen up to the year 2045 was presented.Based on a comprehensive literature review, several research gaps, such as a combined comparison of all three technologies by LCA and LCC, were identified, and research questions were posed and answered. Consequently, prospective research should not be limited to one type of water electrolysis but should be carried out with an openness to all three technologies. Furthermore, it has been shown that data from the literature for the LCA and LCC of water electrolysis technologies differ considerably in some cases. Therefore, extensive research into material inventories for plant construction and into the energy and mass balances of plant operation are needed for a corresponding analysis to be conducted. Even for today’s plants, the availability and transparency of the literature data remain low and must be expanded.

Pioneering Built-In Interfacial Electric Field for Enhanced Anion Exchange Membrane Water Electrolysis.

As a half-reaction in anion exchange membrane water electrolysis (AEMWE) technology, the hydrogen evolution reaction (HER) at the cathode is severely hindered by the sluggish reaction kinetics involved in additional water dissociation step, which results in large overpotentials and low energy conversion efficiency. Here, we develop a nano-heterostructure composed of ultra-thin W5N4 shells over Ni3N nanoparticles (Ni3N@W5N4) as efficient catalysts, in which built-in interfacial electric field (BIEF) is created owing to the distinct lattice arrangements and work functions of biphasic metal nitrides. The BIEF facilitates the electron localization around the interface and enables high valence W and more exposed binding sites in the surface W5N4 shell for accelerating the water dissociation step, ultimately leading to a remarkable reduction in the energy barriers of RDS from 1.40 eV to 0.26 eV. Theoretical calculations and operando X-ray absorption spectroscopy analysis results demonstrated that surface W5N4 serves as the active species for HER. Moreover, the ultra-thin shell characteristics enable the optimized W5N4 with enhanced intrinsic catalytic activity to be fully exposed as active sites. Consequently, the Ni3N@W5N4 exhibits exceptional performance in alkaline HER (60 mV@10 mA cm-2) and remarkable long-term stability (500 mA cm-2 for 100 hours). When employed as the cathode in the AEMWE device, the synthesized Ni3N@W5N4 demonstrates stable performance for 90 hours at a current density of 1 A cm-2.

Green hydrogen production by PEM water electrolysis up to the year 2050: Prospective life cycle assessment using learning curves

AbstractWater electrolysis technologies for producing green hydrogen are promising options for avoiding the use of fossil fuels and thus limiting climate change. Hydrogen can be used in a variety of sectors, enabling sector coupling, and strengthening the security of the energy supply through its storability. Environmental impacts provoked by green hydrogen production are comparatively low and improving manufacturing processes and technological advances will enable to further reduce the demand for raw materials and electricity and thus the environmental impacts. The objective of this study is to compare the status quo with prospective trends and target values. Learning curves of expected specific electricity demand and critical raw material (CRM) intensity are applied, and environmental impacts are subsequently analyzed via life cycle assessment. This study focuses on the polymer electrolyte membrane water electrolysis technology. As a result of the calculated learning curves, the CRM intensity could be reduced by more than 96% between 2022 and 2050. The specific electricity demand is projected to be reduced by 11.2%–22.5%. Combining the extrapolated reductions of electricity and CRM demand, a climate change impact decrease of 16.5%–28.5% is possible for green hydrogen production until the year 2050.

Pitfall on the interpretation of double layer capacitance increase after accelerated stress test of hydrogen evolution reaction on NiMo catalysts

Critical investigation of methods used to screen the catalytic activity of different electrocatalysts is crucial for the development of water electrolysis technology. One of such protocols to justify the catalytic activity trend among different catalysts involves determining their electrochemically active surface area (ECSA) which is usually estimated from non-Faradic double layered capacitance (Cdl) of the catalyst material. Furthermore, catalytic current normalized with ECSA is frequently used to gain insight into the intrinsic activity of a catalyst. Since not all the metallic catalysts are highly stable under the electrolysis conditions, it is highly important, though rarely explored, to investigate whether or not the adsorption/desorption of leached/dissolved multivalent metal ions influences the measurement of non-Faradic Cdl. Here, we explore the possible influence of Mo leached from NiMo alloy on the measured Cdl of NiMo. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), Cdl of NiMo alloy was measured before and after carrying out long term (chronopotentiometric and CV cycling) hydrogen evolution reaction (HER) in alkaline conditions. After extended HER testing, we observe a notable rise (∼22 % averaging all our experiments) in the Cdl of NiMo alloy when measured with traditional methods. Interestingly, only 8 % of this increase can be attributed to an expansion in surface area. We hypothesize that the majority of the increase in Cdl stems from the higher amount of charges stored through leached multivalent ions, which accumulate within surface cavities.

Synergistic Catalytic Sites in High-Entropy Metal Hydroxide Organic Framework for Oxygen Evolution Reaction.

The integration of multiple elements in a high-entropy state is crucial in the design of high-performance, durable electrocatalysts. High-entropy metal hydroxide organic frameworks (HE-MHOFs) are synthesized under mild solvothermal conditions. This novel crystalline metal-organic framework (MOF) features a random, homogeneous distribution of cations within high-entropy hydroxide layers. HE-MHOF exhibits excellent electrocatalytic performance for the oxygen evolution reaction (OER), reaching a current density of 100mA cm-2 at ≈1.64 VRHE, and demonstrates remarkable durability, maintaining a current density of 10mA cm-2 for over 100 h. Notably, HE-MHOF outperforms precious metal-based electrocatalysts despite containing only ≈60% OER active metals. Ab initio calculations and operando X-ray absorption spectroscopy (XAS) demonstrate that the high-entropy catalyst contains active sites that facilitate a multifaceted OER mechanism. This study highlights the benefits of high-entropy MOFs in developing noble metal-free electrocatalysts, reducing reliance on precious metals, lowering metal loading (especially for Ni, Co, and Mn), and ultimately reducing costs for sustainable water electrolysis technologies.

Techno-economic and life cycle assessment for the zero-carbon emission process of the production of methanol from VOCs

Volatile organic compounds (VOCs) are one of the major sources of air pollutants, and the efficient treatment technologies for VOCs have garnered significant attention. The conventional VOCs treatment system converts VOCs into CO2 and directly releases them into air, and it is one of the biggest challenges for carbon neutrality. This paper integrates emerging water electrolysis and carbon utilization technologies with traditional VOCs thermal conversion to produce methanol in a zero-emission approach, converting harmful hydrocarbon compounds into valuable fuel, methanol, without CO2 emission. This paper conducts a comprehensive techno-economic analysis (TEA) and life cycle assessment (LCA) to evaluate their economic and environmental impacts. The research demonstrates that under current market conditions, the treatment costs for this technology range between $5.8 and $8.8 per kilogram. However, when bio-methane is utilized as a VOCs accelerant in this project, it significantly reduces the project's carbon footprint compared to traditional VOCs treatment. It provides insight into the waste-to-worth process in a zero-carbon footprint approach

Strain Effects and Crystalline-Amorphous Interface of NiFe-LDH@S-NiFeOx/NF with Heterogeneous Structure for Enhancing Electrocatalytic Oxygen Evolution Reaction of Water-Electrolysis.

Electrochemical water-electrolysis for hydrogen generation often requires more energy due to the sluggish oxygen evolution reaction (OER). This work introduces a double-layered nanoflower catalyst, NiFe-LDH@S-NiFeOx/NF, featuring a crystalline NiFe-LDH coating on amorphous S-NiFeOx on nickel foam. Strategically integrating a crystalline-amorphous (c-a) heterostructure leverages strain engineering to enhance OER activity with low overpotentials (η100 = 220 and η500 = 245mV) and stability (135 h at η100 and 80 h at η500). Theoretical density functional theory (DFT) calculations reveal that the compressive strain can optimize the adsorption of oxygen-containing intermediates to reduce the reaction energy barrier, thus improving the reaction kinetics and performance of OER. Moreover, its phosphated derivative, NiFeP@S-NiFeOx/NF, exhibits high hydrogen evolution reaction (HER) performance (η10 = 64mV, η100 = 187mV). An alkaline water-electrolysis cell of NiFeP@S-NiFeOx/NF(-)||NiFe-LDH@S-NiFeOx/NF(+) requires only a cell voltage of 1.77V at 100 mA cm-2, demonstrating excellent stability over 110 h (at both 10 and 100mA cm-2). This work highlights the benefits of integrating crystal-amorphous interfaces and strain effects, offering insights into the understanding and optimizing catalytic OER mechanism and advancing water-electrolysis technology.

Control Structures for Combined H2/Electricity from Offshore Wind Turbines

Wind energy proves to be a highly favourable choice for electricity generation due to its clean and renewable nature, and is playing a significant role in reducing global greenhouse gas emissions. Offshore wind turbine systems have gained widespread popularity as they can capitalise on elevated and consistent wind speeds surpassing those found in onshore locations, resulting in increased energy efficiency. Furthermore, offshore wind power possesses the potential to emerge as a significant electricity source for the production of green hydrogen. As water electrolysis technology for hydrogen production continues to advance, utilizing offshore wind power for hydrogen generation is becoming more economically viable and practical. Offshore wind power with higher wind speeds in combination with efficient control structures presents an attractive option for electricity generation and hydrogen co-production. This paper aims to present and evaluate four different production structures for combined H2/energy generation from offshore wind turbines. Previous research studies in this area often overlook control structures and lack information on power converter operations. In contrast, this article studies control structures that enable proper functionality and ensure adequate interoperability, enhancing the reliability of renewable energy integration. Each structure, including both wind turbines and electrolyser, is described in detail, along with the corresponding controllers. Simulation results are presented for each structure and controller to demonstrate their effective operation.

Developing Practical Catalysts for High‐Current‐Density Water Electrolysis

AbstractHigh‐current‐density water electrolysis is considered a promising technology for industrial‐scale green hydrogen production, which is of significant value to energy decarbonization and numerous sustainable industrial applications. To date, substantial research advancements are achieved in catalyst design for laboratory‐based water electrolysis. While the designed catalysts demonstrate remarkable performance at laboratory‐based low current densities, they suffer from marked deteriorations in both activity and long‐term stability under industrial‐level high‐current‐density operations. To provide a timely assessment that helps bridge the gap between laboratory‐scale fundamental research and industrial‐scale practical water electrolysis technology, here the current advancements in various commercial water electrolyzers are first systematically analyzed, then the key parameters including work temperature, current density, lifetime of stacks, cell efficiency, and capital cost of stacks are critically evaluated. In addition, the impact of high current density on the electrocatalytic behavior of catalysts, including intrinsic activity, long‐term stability, and mass transfer, is discussed to advance the catalyst design. Therefore, by covering a range of critical issues from fundamental material design principles to industrial‐scale performance parameters, here the future research directions in the development of highly efficient and low‐cost catalysts are presented and a procedure for screening laboratory‐designed catalysts for industrial‐scale water electrolysis is outlined.

Activating and Stabilizing Lattice Oxygen via Self-Adaptive Zn-NiOOH Sub-Nanowires for Oxygen Evolution Reaction.

Efficient and durable catalysts for the oxygen evolution reaction are essential for realizing the large-scale application of water electrolysis technologies. Here, we report a novel Zn-doped NiOOH subnanowires (Zn-NiOOH SNWs) catalyst synthesized via the electrochemical reconstruction of Zn-NiMoO4 SNWs. The inclusion of Zn triggers a transition in the oxygen evolution reaction mechanism of NiOOH from the adsorbate evolution mechanism to the lattice oxygen mechanism, resulted from Zn's adaptive adjustment of coordination types, which also improves the reaction energetics, thereby enhancing the stability and activity. Furthermore, the subnanowire structure provides further stabilization of the lattice oxygen in Zn-NiOOH, preventing its destructive dissolution. Remarkably, Zn-NiOOH SNWs display a current density of 10 mA cm-2 with an overpotential of only 179 mV and maintain stable operation at 200 mA cm-2 for 800 h with minimal changes in overpotential, establishing them as one of the most effective catalysts involving lattice oxygen for the alkaline oxygen evolution reaction. When utilized as the anode in an alkaline water electrolyzer, our Zn-NiOOH SNWs catalyst demonstrates stability exceeding 500 h under a water-splitting current of 200 mA cm-2, indicating promising potential for practical applications.

Lower-Carbon Hydrogen Production from Wastewater: A Comprehensive Review

Hydrogen has the capability of being a potential energy carrier and providing a long-term solution for sustainable, lower-carbon, and ecologically benign fuel supply. Because lower-carbon hydrogen is widely used in chemical synthesis, it is regarded as a fuel with no emissions for transportation. This review paper offers a novel technique for producing hydrogen using wastewater in a sustainable manner. The many techniques for producing hydrogen with reduced carbon emissions from wastewater are recognized and examined in detail, taking into account the available prospects, significant obstacles, and potential future paths. A comparison of the assessment showed that water electrolysis and dark fermentation technologies are the most effective methods for hydrogen generation from wastewater, with microbial electrolysis and photofermentation. Thus, the incorporation of systems that are simultaneously producing lower-carbon hydrogen and meant for wastewater treatment is important for the minimization of emissions from greenhouse gases and recovering the energy utilized in the treatment of wastewater.

Synergistic effects of feni bimetal-doped biochar on oxygen evolution reaction kinetics: A one-step, low-temperature pyrolysis approach

As the hydrogen energy sector progresses, water electrolysis technology played a crucial role in producing green hydrogen. A major challenge in this endeavor lied in the oxygen evolution reaction (OER), where the overpotential has consistently been high leading to an increase in the energy demand. This study developed a one-step pyrolysis technique to transform metal-supported biomass into FeNi/NC catalysts having enhanced crystallinity and defect sites. This process without activation step using strong acids or bases reduced the operational procedures and the treatment of intermediate products, which reduced the technical difficulty. As the pyrolysis temperature increases, the metal ions in the biochar gradually formed stable metal oxides, which catalyze the alkaline OER and markedly boosted catalytic efficiency. Crucially, the abundance of lattice oxygen and oxygen vacancies in the catalyst played a key role in enhancing the OER kinetics. Notably, the catalyst pyrolyzed at 750 °C demonstrated good performance, with an overpotential of 270 mV at a concentration of 10 mA cm−2 of the density of current, which was superior to RuO2(η10=315 mV) and IrO2(η10=300 mV). Overall, this study reported an approach for the fabrication of high-performance OER catalysts and the strategic utilization of biomass resources for application in clean energy technologies.

Micelle-assisted electrodeposition of mesoporous PtCo nodular films and their electrocatalytic activity towards the hydrogen evolution reaction in acidic media

Hydrogen has received extensive attention in the energy field due to its high energy density and environmental friendliness. However, the large overpotential and slow kinetics limit the development of green water electrolysis technology. Rational design and construction of efficient and economical electrocatalysts are essential for sustainable hydrogen production. In this work, mesoporous PtCo films are successfully prepared by micelle-assisted electrodeposition using Pluronic F127 as a soft template. The optimal electrodeposition conditions of the film such as temperature and potential are determined. The composition of the films can be adjusted with the deposition potential to a Co content up to 45 at.%. The mesoporosity is clearly present at T=45 °C and E= − 0.6 V with a pore diameter of around 5–10 nm. The mechanism for the mesoporous PtCo films is proposed and the electrocatalytic activity in H2SO4 is evaluated. Mesoporous PtCo film with 45 at.% Co exhibits excellent electrocatalytic hydrogen evolution performance over commercial Pt/C, with an overpotential of − 22 mV at a current density of − 10 mA cm−2, and exhibits remarkable durability in the 24 h long-term aging stability test.

Research on performance optimization of electrolytic cell: Non-parameter topology and parameter optimization

The technology of water electrolysis for hydrogen production converts renewable energy into hydrogen, enabling efficient storage and utilization of clean energy. The key to enabling the large-scale development of water electrolysis technology lies in enhancing the performance of electrolytic cells and minimizing energy consumption. The mastoid process structure obviously influences the electrolytic cell's flow and electrochemical performance. Therefore, this paper studied the sensitivity of the mastoid process structure to the optimization target, designed the shape topology and the parameter optimization structure, and further analyzed the influence of the two optimization methods on the flow and electrochemical performance of the electrolytic cell based on the multi-physics coupling model. The results show that under the same deformation area, the pressure drop of the topology and the parameter optimization structure is reduced by 17.17 % and 11.89 % compared with that of the original structure. The electrochemical properties were almost unaffected, and the change value was less than 0.1 %. Topology optimization design can achieve optimal performance within limited deformation constraints, and parameter optimization design is more conducive to industrial processing.

The strong metal-support interaction at Ni–O–Pt interface facilitates rapid electrocatalytic hydrogen production

Electrocatalytic water splitting technology, as an essential method for storing and converting renewable energy, has garnered significant attention. However, traditional electrolytic water splitting is hampered by issues such as noble metal catalysts are expensive and unstable, limiting its widespread application. To address this challenge, this study proposes an innovative method that utilizes nickel metal-organic framework (Ni-MOF) as a support to firmly anchor platinum (Pt) nanoparticles on its surface. This approach not only overcomes the high cost and instability associated with traditional noble metal catalysts but also leverages the strong chelation effect of ethylenediaminetetraacetic acid disodium salt (EDTA·2Na) and the strong metal-support interaction (SMSI) at the Ni–O–Pt interface, prompting catalysts to possess excellent stability and catalytic activity. The catalyst exhibits excellent performance in promoting the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall electrolysis of water, maintaining stability throughout the entire electrochemical process. At a current density of 10 mA cm−2, the overpotentials for HER and OER with Pt1·5/Ni-MOF are only 29 mV and 234 mV, respectively. When Pt1·5/Ni-MOF serves as both the cathode and anode for overall water splitting, only a low voltage of 1.557 V is needed. This study offers fresh insights into the development of stable, efficient, and low-budget dual-functional catalysts for water electrolysis, with the potential to drive the commercialization of water electrolysis technology and make significant contributions to the advancement of clean energy.

Feasibility of Placing Large-Scale Electrolyzers in Domestic Power Plants

The aim of the article is to verify the feasibility of placing large-scale (up to 100 MWe) water electrolysis technology unit inside, or in the proximity of a domestic nuclear power plant. The possible location is investigated from technological, logistic and nuclear-safety points of view.

Boosting alkaline hydrogen evolution via in-plane heterostructure construction with Ultra-Exposed heterointerfaces

Enhancing the catalytic efficiency of molybdenum disulfide (MoS2) towards the hydrogen evolution reaction (HER) is valuable for water electrolysis technology. This study fabricated a novel Co2P@1T-MoS2 “in-plane” heterostructure as a catalyst for alkaline HER. In this heterostructure, the Co2P nanoclusters are dispersed within the 1 T-MoS2 nanosheet. Remarkably, the coexistence of Co2P and 1 T-MoS2 phases within the same plane maximizes the exposure of interfacial active sites. The interfacial interaction between Co2P and 1 T-MoS2 facilitates water dissociation and hydrogen adsorption. This results in outstanding catalytic activity with a small overpotential of 37 mV at a current density of 10 mA cm−2 in 1.0 M KOH. Intriguingly, the Co2P@1T-MoS2 heterostructure exhibits higher activity in alkaline electrolytes compared to acidic ones. The difference in active sites for hydrogen adsorption (Co versus S) in distinct electrolytes is believed to be the underlying reason for this “abnormality”.

Enhancing hydrogen evolution reaction performance through defect engineering in WTeX (X= S, Se) monolayers: A first-principles study

Finding a novel material to substitute the existing noble metal catalysts for the hydrogen evolution reaction (HER) is essential for the further advancement of water electrolysis technology. Herein, we investigated the feasibility of using defect engineering to improve the hydrogen evolution reaction (HER) catalytic performance of WTeX (X = Se, S) materials in the 2H, 1 T, and 1 T′ phases. The results demonstrate that the introduction of defects significantly enhances WTeX monolayers’ HER performance. As exemplary cases, the Gibbs free energy changes for 2H WTeSe with a Te vacancy (2H WTeSe–VTe) and 2H WTeS with a Te vacancy (2H WTeS–VTe) are 0.029 eV and −0.002 eV, respectively. It was found that the active sites in 2H WTeSe–VTe and 2H WTeS–VTe have a substantial number of empty anti-bonding states, which increases the bond strength between H and the catalyst, leading to exceptional catalytic performance. This work demonstrates the feasibility of defect-engineered WTeX structures as electrocatalysts and provides a reliable reference for the study of non-precious metal catalysts.

Prediction of hydrogen production in proton exchange membrane water electrolysis via neural networks

Advancements in water electrolysis technologies are crucial for green hydrogen production. Proton exchange membrane water electrolysis (PEMWE) is characterized by its efficiency and environmental benefits. The prediction and optimization of hydrogen production rates (HPRs) in PEMWE systems is difficult and still challenging because of the complexity of the system as well as the operational parameters. The integration of artificial intelligence (AI) and machine learning (ML) appears to be effective in optimization within the energy sector. Hence, this work employs the artificial neural network (ANN) to develop a model that accurately predicts HPR in PEMWE setups. A novel approach is introduced by employing the Levenberg–Marquardt backpropagation (LMBP) algorithm for training the ANN. This model is designed to predict HPR based on critical operational parameters, including anode and cathode areas (mm2), cell voltage (V) and current (A), water flow rate (mL/min), power (W), and temperature (K). The optimized ANN configuration features an architecture with 7 input nodes, two hidden layers of 64 neurons each, and a single output node. The performance of the ANN model was evaluated against conventional regression models using key metrics: mean squared error (MSE), coefficient of determination (R2), and mean absolute error (MAE). The findings of this study reveal that the developed ANN model significantly outperforms traditional models, achieving an R2 value of 0.9989 and an MAE of 0.012. In comparison, random forest (R2 = 0.9795), linear regression (R2 = 0.9697), and support vector machines (R2 = − 0.4812) show lower predictive accuracy, underscoring the ANN model's superior performance. This work demonstrates the efficiency of the LMBP in enhancing hydrogen production forecasts and sets a foundation for future improvements in PEMWE efficiency. By enabling precise control and optimization of operational parameters, this study contributes to the broader goal of advancing green hydrogen production as a viable and scalable alternative to fossil fuels, offering both immediate and long-term benefits to sustainable energy initiatives.

Hydrogen production from non-potable water resources: A techno-economic investment and operation planning approach

The production of hydrogen through water electrolysis facilitates large-scale energy storage, provides ancillary services, and supports the decarbonization of industries with hard-to-reduce emissions. As renewable energy adoption expands, the demand for these applications is increasing. However, water electrolysis currently faces challenges in cost competitiveness compared to other hydrogen production methods. Additionally, its reliance on potable water sources places additional strain on freshwater reserves. This study addresses these issues by exploring the economically optimal investment and operational strategy for hydrogen production using non-potable water sources. The goal is to maximize net profit through mathematical optimization, utilizing three advanced electrolysis technologies: alkaline electrolysis, proton exchange membrane electrolysis, and solid oxide electrolysis. The study examines three non-potable water sources: seawater, urban wastewater effluent, and rainwater. The model takes into account electricity market values from day-ahead and balancing markets, as well as the market values for hydrogen, oxygen, freshwater, and mixed solid salt. Two scenarios are analysed, reflecting varying levels of uncertainty in electricity price forecasts. Each scenario includes nine case studies, representing various combinations of water sources and electrolysis technologies. The results indicate that alkaline electrolysis and proton exchange membrane electrolysis are financially viable technologies, with potential annual net profits of up to 6.4 and 6.2 million euros, respectively. In contrast, solid oxide electrolysis incurs a negative net profit across all scenarios and is not economically viable under the given conditions. The main revenue sources are hydrogen sales and combined up-balancing and down-balancing services in electricity markets. Participation in the balancing market constitutes a significant portion (35 to 61%) of the total revenue in all cases with positive net profits, making it critical for economic viability. Rainwater is identified as the most cost-effective water source for hydrogen production. However, the costs associated with water treatment and brine management are minimal, contributing only 0.7 to 3.7% to the total cost of hydrogen production. Thus, differences in net profit are primarily attributed to the type of electrolysis technology used.