Production & Supply Chain

Hydrogen produced via water electrolysis from renewable electricity is considered a key energy carrier to defossilize hard-to-electrify sectors. Solid oxide cells (SOC) based reactors can supply hydrogen not only in electrolysis but also in fuel cell mode when operating with (synthetic) natural gas or biogas at low conversion (polygeneration mode). However the scale-up of SOC reactors to the multi-MW scale is still a research topic. Strategies for transient operation depending on electricity intermittency still need to be developed. In this work a unique testing environment for SOC reactors allows reversible operation demonstrating the successful switching between electrolysis (− 75 kW) and polygeneration (25 kW) modes. Transient and steady state experiments show promising performance with a net hydrogen production of 53 kg day− 1 in SOEL operation with ca. − 75 kW power input. The experimental results validate the scaling approach since the reactor shows homogenous temperature profiles.

Hydrogen is increasingly recognized as a pivotal energy storage solution and a transformative alternative to conventional energy sources. This review summarizes the evolving landscape of global H2 production and consumption markets focusing on the crucial role of photothermal catalysts (PTCs) in driving Hydrogen evolution reactions (HER) particularly with regards to oxide selenide and telluride-based PTCs. Within this exploration the mechanisms of PTCs take center stage elucidating the intricacies of light absorption localized heating and catalytic activation. Essential optimization parameters ranging from temperature and irradiance to catalyst composition and pH are detailed for their paramount role in enhancing catalytic efficiency. This work comprehensively explores photothermal catalysts (PTCs) for hydrogen production by assessing their synthesis techniques and highlighting the current research gaps particularly in optimizing catalytic stability light absorption and scalability. The energy-efficient nature of oxide selenide and telluride-based PTCs makes them prime candidates for sustainable H2 production when compared to traditional materials. By analyzing a range of materials we summarize key performance metrics including hydrogen evolution rates ranging from 0.47 mmolh− 1 g− 1 for Ti@TiO2 to 22.50 mmolh− 1 g− 1 for Mn0.2Cd0.8S/NiSe2. The review concludes with a strategic roadmap aimed at enhancing PTC performance to meet the growing demand for renewable hydrogen as well as a critical literature review addressing challenges and prospects in deploying PTCs.

Disputed supply chains inappropriate weather and low investment followed by the Russian invasion of Ukraine has led to a phenomenal energy crisis especially in the Horn of Africa. Accordingly proposing eco-friendly and sustainable solutions to diversify the access of electricity in the Republic of Djibouti which has no conventional energy resources and is completely energy dependent on its neighboring countries has become a must. Therefore the implementation of sustainable renewable and energy storage systems is nationally prioritized. This paper deals for the first time with the exploitation of such an affordable and carbon-free resource to produce hydrogen from wind energy in the rural areas of Nagad and Bara Wein in Djibouti. The production of hydrogen and the relevant CO2 emission reduction using different De Wind D6 Vestas and Nordex wind turbines are displayed while using Alkaline and Proton Exchange Membrane (PEM) electrolyzers. The Bara Wein and Nagad sites had a monthly wind speed above 7 m/s. From the results the Nordex turbine accompanied with the alkaline electrolyzer provides the most affordable electricity production approximately 0.0032 $/kWh for both sites; this cost is about one per hundred the actual imported hydroelectric energy price. Through the ecological analysis the Nordex turbine is the most suitable wind turbine with a CO2 emission reduction of 363.58 tons for Bara Wein compared to 228.76 tons for Nagad. While integrating the initial cost of wind turbine implementation in the capital investment the mass and the levelized cost of the produced green hydrogen are estimated as (29.68 tons and 11.48 $/kg) for Bara Wein with corresponding values of (18.68 tons and 18.25 $/kg) for Nagad.

This review provides a comprehensive techno-economic assessment of four leading electrolyzer technologies such as the Alkaline Water Electrolyzers (AWE) Proton Exchange Membrane (PEM) electrolyzers Solid Oxide Electrolyzer Cells (SOEC) and Anion Exchange Membrane (AEM) systems for green hydrogen production. Drawing on more than 40 peer-reviewed studies and real-world deployment scenarios the analysis compares performance indicators such as levelised cost of hydrogen (LCOH) capital expenditure (CAPEX) operating expenditure (OPEX) efficiency stack durability and water treatment requirements. AWE is identified as the most cost-effective option for baseload power contexts while PEM offers superior dynamic response and gas purity at a higher cost. SOECs despite their high theoretical efficiency remain limited by thermal cycling and material degradation. AEMs though less mature hold promise for low-cost decentralized hydrogen production. Cost of electricity is more than 64 % of LCOH in all technologies so it is important to match electrolyzers with stable or hybrid renewable energy resources such as geothermal wind-solar or Concentrated Solar Power (CSP). Optimisation methods such as genetic algorithms and GIS-based siting also enhance system performance and economic value. The report also considers regional and policy dimensions of deployment underlining the need for site-specific solutions in the context of local energy portfolios water supply and infrastructure readiness. Recommendations are provided for advancing membrane longevity integrating smart control systems and optimizing techno-economic assessment models. This study is a policy decision-making tool for policymakers investors and researchers who are interested in accelerating the global scale-up of green hydrogen using contextrelevant and economically viable electrolyzer technologies.

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 optimizationbased 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 e/kg decreasing by 0.35 e/kg and 0.21 e/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.

The main purpose of this paper is the techno-economic analysis of hydrogen production from biogas via steam reforming in a pilot plant. Process flow modeling based on mass and energy balance is used to estimate the total equipment purchase and operating costs of hydrogen production. The pilot plant installation produced 250.67 kg/h hydrogen from 1260 kg/h biomethane obtained after purification of 4208 m3/h biogas using a heat and mass integration process. Despite the high investment cost the plant shows a great potential for biomethane reduction and conversion to hydrogen an attractive economic path with ecological possibilities. The conversion of waste into hydrogen is a possibility of increasing importance in the global energy economy. In the future such a plant will be expanded with a CO2 reduction module to increase economic efficiency and further reduce greenhouse gases in an economically viable manner.

This study introduces a method for identifying territories ideal for establishing photovoltaic (PV) plants for green hydrogen (GH2 ) production in the Antofagasta region of northern Chile a location celebrated for its outstanding solar energy potential. Assessing the viability of PV plant installation necessitates a balanced consideration of technical aspects and socio-environmental constraints such as the proximity to areas of ecological importance and indigenous communities to identify potential zones for solar and non-conventional renewable energy (NCRE)-based hydrogen production. To tackle this challenge we propose a methodology that utilizes geospatial analysis integrating Geographic Information System (GIS) tools with sensitivity analysis to determine the most suitable sites for PV plant installation in the Antofagasta region. Our geospatial analysis employs the QGIS software to identify these optimal locations while sensitivity analysis uses the Sørensen–Dice coefficient method to assess the similarity among chosen socio-environmental variables. Applying this methodology to the Antofagasta region reveals that a significant area within a 15 km radius of existing road networks and electrical substations is favorable for photovoltaic projects. Our sensitivity analysis further highlights the limiting effects of socio-environmental factors and their interactions. Moreover our research finds that enlarging areas of socio-environmental importance could increase the total hydrogen production by about 10% per commune indicating the impact of these factors on the potential for renewable energy production.

This study presents a technoeconomic analysis of renewables-based hydrogen production in Queensland Australia under Optimistic Reference and Pessimistic scenarios to address uncertainty in cost predictions. The goal of the work was to ascertain if the target fam-gate cost of AUD 3/kg (approx. USD 2/kg) could be reached. Economies of scale and the learning rate concept were factored into the economic model to account for the effect of scale-up and cost reductions as electrolyser manufacturing capacity grows. The model assumes that small-scale to large-scale wind turbine (WT)-based and photovoltaic (PV)-based power generation plants are directly coupled with an electrolyser array and utilises hourly generation data for the Gladstone hydrogen-hub region. Employing first a commonly used simplified approach the electrolyser array was sized based on the maximum hourly power available for hydrogen production. The initial results indicated that scale-up is very beneficial: the levelised cost of green hydrogen (LCOH) could decrease by 49% from $6.1/kg to $3.1/kg when scaling PV-based plant from 10 MW to 1 GW and for WT-based plant by 36% from $5.8/kg to $3.7/kg. Then impacts on the LCOH of incorporating curtailment of ineffective peak power and electrolyser overload capacity were investigated and shown to be significant. Also significant was the beneficial effect of recognising that electrolyser efficiency depends on input power. The latter two factors have mostly been overlooked in the literature. Incorporating in the model the influence on the LCOH of real-world electrolyser operational characteristics overcomes a shortcoming of the simplified sizing method namely that a large portion of electrolyser capacity is under-utilised leading to unnecessarily high values of the LCOH. It was found that AUD 3/kg is achievable if the electrolyser array is properly sized which should help to incentivise large-scale renewable hydrogen projects in Australia and elsewhere.

Thanks to investments in diversifying the supply of natural gas Poland did not encounter any gas supply issues in 2022 when gas imports from Russia were ceased due to the Russian Federation’s armed intervention in Ukraine. Over the past few years the supply of gas from routes other than the eastern route has substantially grown particularly the supplies of liquefied natural gas (LNG) via the LNG terminal in Swinouj´scie. The growing proportion of LNG in Poland’s gas supply ´ leads to a rise in ethane levels in natural gas as verified by the review of data taken at a specific location within the gas system over the years 2015 2020 and 2022. Using measurements of natural gas composition the effectiveness of the steam hydrocarbon reforming process was simulated in the Gibbs reactor via Aspen HYSYS. The simulations confirmed that as the concentration of ethane in the natural gas increased the amount of hydrogen produced and the heat required for reactions in the reformer also increased. This article aims to analyze the influence of the changes in natural gas quality in the Polish transmission network caused by changes in supply structures on the mass and heat balance of the theoretical steam reforming reactor. Nowadays the chemical composition of natural gas may be significantly different from that assumed years ago at the plant’s design stage. The consequence of such a situation may be difficulties in operating especially when controlling the quantity of incoming natural gas to the reactor based on volumetric flow without considering changes in chemical composition.

To address climate change energy security and waste management new sustainable energy sources must be developed. This study uses Aspen Plus software to extract bio-H2 from food waste with the goal of efficiency and environmental sustainability. Anaerobic digestion optimised to operate at 20-25°C and keep ammonia at 3% greatly boosted biogas production. The solvent [Emim][FAP] which is based on imidazolium had excellent performance in purifying biogas. It achieved a high level of methane purity while consuming a minimal amount of energy with a solvent flow rate of 13.415 m³/h. Moreover the utilization of higher temperatures (600-700°C) during the bio-H2 generation phase significantly enhanced both the amount and quality of hydrogen produced. Parametric and sensitivity assessments were methodically performed at every stage. This integrated method was practicable and environmentally friendly according to the economic assessment. H2 generation using steam reforming results in a TCC of 1.92×106 USD. The CO2 separation step has higher costs (TCC of 2.15×107 USD) due to ionic liquid washing and CO2 liquefaction. Compressor electricity consumption significantly impacts total operating cost (TOC) totaling 4.73×108 USD. showing its ability to reduce greenhouse gas emissions optimize resource utilization and promote energy sustainability. This study presents a sustainable energy solution that addresses climate and waste challenges.

The global energy demand is expected to increase by 30% within the next two decades. Plastic thermochemical recycling is a potential alternative to meet this tremendous demand because of its availability and high heating value. Polypropylene (PP) and polyethylene (PE) are considered in this study because of their substantial worldwide availability in the category of plastic wastes. Two cases were modeled to produce hydrogen from the waste plastics using Aspen Plus®. Case 1 is the base design containing three main processes (plastic gasification syngas conversion and acid gas removal) where the results were validated with the literature. On the other hand case 2 integrates the plastic gasification with steam methane reforming (SMR) to enhance the overall hydrogen production. The two cases were then analyzed in terms of syngas heating values hydrogen production rates energy efficiency greenhouse gas emissions and process economics. The results reveal that case 2 produces 5.6% more hydrogen than case 1. The overall process efficiency was enhanced by 4.13%. Case 2 reduces the CO2 specific emissions by 4.0% and lowers the hydrogen production cost by 29%. This substantial reduction in the H2 production cost confirms the dominance of the integrated model over the standalone plastic gasification model.

This work develops a novel optimisation approach to determine the optimal installed capacities of wind solar and hydrogen storage systems for the continuous production of green hydrogen targeting the lowest "True Cost of Hydrogen" (TCOH). TCOH is a metric that combines both costs and life cycle environmental impacts facilitating decision-making and supporting project design. Two hypothetical scenarios were evaluated using evolutionary optimisation of the TCOH namely the “Slow” or “Fast” technology developments projected for 2030. Results show that optimising TCOH (for both cost and environmental impacts) may reduce a large range of environmental impact categories by up to 37% while increasing cost by up to 0.23€/kg H2. Overall the proposed method allows for a cost-effective hydrogen production but also contributes to the mitigation of relevant environmental impacts. Our approach has the potential to add to the current carbon footprint requirements towards truly sustainable pathways for green hydrogen production.

The production of green hydrogen requires significant water usage making the economic evaluation of different water sources crucial for optimizing the Levelized Cost of Hydrogen (LCOH). This study examines the economic impact of using seawater groundwater grid water industrial wastewater and rainwater for hydrogen production through PEM electrolysis considering the water abstraction transport treatment and storage costs across various plant sizes (1 MW 10 MW 20 MW 50 MW and 100 MW) were assessed and a sensitivity analysis on electricity prices was conducted. Findings reveal that while water-related costs are minimal.

Hydrogen is experiencing an unprecedented global hype. Hydrogen is globally discussed as a possible future energy carrier and regarded as the urgently needed building block for the much needed carbon-neutral energy transition of hard-to-abate sectors to mitigate the effects of global warming. This article provides synthesised measurable sustainability criteria for analysing green hydrogen production proposals and strategies. Drawn from expert interviews and an extensive literature review this article proposes that a sustainable hydrogen production should consider six impact categories; Energy transition Environment Basic needs Socio-economy Electricity supply and Project planning. The categories are broken down into sixteen measurable sustainability criteria which are determined with related indicators. The article concludes that low economic costs can never be the only decisive criterion for the hydrogen production; social aspects must be integrated along the entire value chain. The compliance with the criteria may avoid social and ecological injustices in the planning of green hydrogen projects and increases inter alia the social welfare of the affected population.

A huge amount of organic waste is generated annually around the globe. The main sources of solid and liquid organic waste are municipalities and canning and food industries. Most of it is disposed of in an environmentally unfriendly way since none of the modern recycling technologies can cope with such immense volumes of waste. Microbiological and biotechnological approaches are extremely promising for solving this environmental problem. Moreover organic waste can serve as the substrate to obtain alternative energy such as biohydrogen (H2 ) and biomethane (CH4 ). This work aimed to design and test new technology for the degradation of food waste coupled with biohydrogen and biomethane production as well as liquid organic leachate purification. The effective treatment of waste was achieved due to the application of the specific granular microbial preparation. Microbiological and physicochemical methods were used to measure the fermentation parameters. As a result a four-module direct flow installation efficiently couples spatial succession of anaerobic and aerobic bacteria with other micro- and macroorganisms to simultaneously recycle organic waste remediate the resulting leachate and generate biogas.

This paper presents an analysis of a treatment system selection for municipal wastewater stream based on the DuPont Water Solutions WAVE software. The results obtained based on an analysis of 7 different processing cases studies (ultrafiltration and reverse osmosis) confirmed that the application of 2-pass membrane systems enables the reclamation of water from municipal wastewater that fulfills the requirements concerning the quality of water intended as electrolyzer feedstock as the obtained water exhibited a conductivity of < 5 µS/cm. Depending on the analyzed case study the attainable level of water reclamation ranged from 68.8 to 84.1 % at an energy consumption of 606.1 – 2 694 kWh/d. The results of this work not only confirm that the selected pro cessing solutions make it possible to reclaim water from municipal wastewater but also confirm the necessity of using software to simulate the membrane system operation to select the most economic and cost-effective solution.

Hydrogen has a key role to play in decarbonising industry and other sectors of society. It is important to develop low-carbon hydrogen production technologies that are cost-effective and energy-efficient. Sorption-enhanced steam methane reforming (SE-SMR) is a developing low-carbon (blue) hydrogen production process which enables combined hydrogen production and carbon capture. Despite a number of key benefits the process is yet to be fully realised in terms of efficiency. In this work a sorption-enhanced steam methane reforming process has been intensified via exergy analysis. Assessing the exergy efficiency of these processes is key to ensuring the effective deployment of low-carbon hydrogen production technologies. An exergy analysis was performed on an SE-SMR process and was then subsequently used to incorporate process improvements developing a process that has theoretically an extremely high CO2 capture rate of nearly 100 % whilst simultaneously demonstrating a high exergy efficiency (77.58 %) showcasing the potential of blue hydrogen as an effective tool to ensure decarbonisation in an energy-efficient manner.

Actually green hydrogen is viewed as a fundamental component in accelerating energy transition and empowering a sustainable future. The current study focuses on the estimation of green hydrogen generation by using wind energy via electrolysis in four sites located in Saudi Arabia. Results showed that the yearly amount of hydrogen that could be generated by using wind turbine ranges between 2542877 kg in Rafha and 3676925 kg in Dhahran. The hydrogen generated could be used to fuel vehicles and decrease the amount of GHG emission from vehicles in KSA. Also hydrogen may be used to store the excess of wind energy and to support the achievement of vision 2030 of the Kingdom. An economic assessment is carried out also in this paper. Results showed that the LCOH by using wind energy in KSA ranges from 2.82 $/kg to 3.81 $/kg.

Climatic changes are reaching alarming levels globally seriously impacting the environment. To address this environmental crisis and achieve carbon neutrality transitioning to hydrogen energy is crucial. Hydrogen is a clean energy source that produces no carbon emissions making it essential in the technological era for meeting energy needs while reducing environmental pollution. Abundant in nature as water and hydrocarbons hydrogen must be converted into a usable form for practical applications. Various techniques are employed to generate hydrogen from water with solar hydrogen production—using solar light to split water—standing out as a cost-effective and environmentally friendly approach. However the widespread adoption of hydrogen energy is challenged by transportation and storage issues as it requires compressed and liquefied gas storage tanks. Solid hydrogen storage offers a promising solution providing an effective and low-cost method for storing and releasing hydrogen. Solar hydrogen generation by water splitting is more efficient than other methods as it uses self-generated power. Similarly solid storage of hydrogen is also attractive in many ways including efficiency and cost-effectiveness. This can be achieved through chemical adsorption in materials such as hydrides and other forms. These methods seem to be costly initially but once the materials and methods are established they will become more attractive considering rising fuel prices depletion of fossil fuel resources and advancements in science and technology. Solid oxide fuel cells (SOFCs) are highly efficient for converting hydrogen into electrical energy producing clean electricity with no emissions. If proper materials and methods are established for solar hydrogen generation and solid hydrogen storage under ambient conditions solar light used for hydrogen generation and utilization via solid oxide fuel cells (SOFCs) will be an efficient safe and cost-effective technique. With the ongoing development in materials for solar hydrogen generation and solid storage techniques this method is expected to soon become more feasible and cost-effective. This review comprehensively consolidates research on solar hydrogen generation and solid hydrogen storage focusing on global standards such as 6.5 wt% gravimetric capacity at temperatures between −40 and 60 ◦C. It summarizes various materials used for efficient hydrogen generation through water splitting and solid storage and discusses current challenges in hydrogen generation and storage. This includes material selection and the structural and chemical modifications needed for optimal performance and potential applications.

In this work we report the preparation of Nafion membranes containing two different nanocomposite MF-4SC membranes modified with polyaniline (PANI) by the casting method through two different polyaniline infiltration procedures. These membranes were evaluated as a polymer electrolyte membrane for water electrolysis. Operating conditions were optimized in terms of current density stability and methanol concentration. A study was made on the effects on the cell performance of various parameters such as methanol concentration water and cell voltage. The energy required for pure water electrolysis was analyzed at different temperatures for the different membranes. Our experiments showed that PEM electrolyzers provide hydrogen production of 30 mL/min working at 160 mA/cm2 . Our composite PANI membranes showed an improved behavior over pristine perfluorinated sulfocationic membranes (around 20% reduction in specific energy). Methanol–water electrolysis required considerably less (around 65%) electrical power than water electrolysis. The results provided the main characteristics of aqueous methanol electrolysis in which the power consumption is 2.34 kW h/kg of hydrogen at current densities higher than 0.5 A/cm2 . This value is ~20-fold times lower than the electrical energy required to produce 1 kg of hydrogen by water electrolysis.

This article analyzes and compares three methodologies for identifying suitable regions for solar hydrogen production using photovoltaic panels: AHP (Analytic Hierarchy Process) FAHP (Fuzzy Analytic Hierarchy Process) and MC-FAHP (Monte Carlo FAHP) integrated with GIS (Geographic Information Systems). The study employs ten criteria across technical (Global Horizontal Irra diance temperature slope elevation orientation) economic (distance from transportation and electrical networks) and social (population density proximity to residential areas) factors. Environmental and exclusion criteria define restrictive zones. The analysis reveals that while all three methods agree on areas of low suitability they diverge in their classification of "Suitable" "Highly Suitable" and "Most Suitable" regions. FAHP identifies 229.573 km2 as "Highly Suitable" compared to AHP’s 222.048 km2 and MC-FAHP’s 230.299 km2 for "Suitable" areas. Despite these differences the energy potential is consistent across methods totaling around 79000 TWh/year with MC-FAHP estimating the highest hydrogen production potential at 1.51 billion tons/year. The study concludes that fuzzy-based methods (FAHP and MC-FAHP) better handle uncertainties than traditional AHP. The MC-FAHP method in particular performs well in managing stochastic variability and yielding more reliable results. The findings are validated through a case study in Guider and Maroua highlighting the importance of socio-economic and environmental criteria in decision-making. A sensitivity analysis reveals that economic and social criteria significantly influence land suitability underscoring the importance of criteria selection in decision-making.

Green hydrogen represents a critical underpinning technology for achievingcarbon neutrality. Although researchers often fixate on its energy inputs atruly ‘green’ hydrogen production process would also be sustainable in termsof water and materials inputs. To address this holistic challenge we demon-strate a new green hydrogen production system which can utilize secondarywastewater as the input (preserving scarce fresh water supplies for drinkingand sanitation). The enabling feature of the proposed system is a self-grownbifunctional CoNi electrode which consists of ultrathin spontaneously depos-ited CoNi nanosheets on a three-dimensional nickel foam. As such a greensynthesis process was developed using an immersion procedure at room-temperature with zero net energy input. Testing revealed that the synthesizedCoNi electrodes can reach a current density of 10 mA cm2 at a small overpo-tential of 197 mV for the hydrogen evolution reaction and 315 mV for the oxy-gen evolution reaction in alkalified wastewater. The values are 16.5%and 6.5% smaller than that from precious catalysts (20 wt% Pt/C and RuO 2 respectively). Importantly this CoNi catalyst offers outstanding durability foroverall wastewater splitting. A prototype solar-energy-powered rooftop waste-water splitting system was constructed and can produce more than 100 Lhydrogen on a sunny day in Sydney Australia. Taken together these resultsindicate that it is promising to unlock holistically green routes for hydrogenproduction by wastewater uplifting with regards to water energy and mate-rials synthesis.

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 pre diction 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 in telligence (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 pa rameters 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.

The energy sector constitutes a dynamic and complex system indicating that its actions are influenced not just by its individual components but also by the emergent behavior resulting from interactions among them. Moreover there are crucial limitations of previous approaches for addressing the sustainability challenge of the energy sector. Changing transforming and integrating paradigms are the most relevant leverage points for transforming a given system. In other words nowadays the integration of new predominant paradigms in order to provide a unified framework could aim at this actual transformation looking for a sustainable future. This research aims to develop a new unified framework for the integration of the following three paradigms: (1) Sustainability (2) Complexity and (3) Systems Thinking which will be applied to achieving sustainable energy production (using hydrogen production as a case study). The novelty of this work relies on providing a holistic perspective through the integration of the aforementioned paradigms considering the multiple and complex interdependencies among the economy the environment and the economy. For this purpose an integrated seven-stage approach is introduced which explores from the starting point of the integration of paradigms to the application of this integration to sustainable energy production. After applying the Three-Paradigm approach for sustainable hydrogen production as a case study 216 feedback loops are identified due to the emerged complexity linked to the analyzed system. Additionally three system dynamics-based models are developed (by increasing the level of complexity) as part of the application of the Three-Paradigm approach. This research can be of interest to a broad professional audience (e.g. engineers policymakers) as looks into the sustainability of the energy sector from a holistic perspective considering a newly developed Three-Paradigm model considering complexity and using a Systems Thinking approach.

In response to the European Union’s initiative toward achieving carbon neutrality the utilization of water electrolysis for hydrogen production has emerged as a promising avenue for decarbonizing current energy systems. Among the various approaches Solid Oxide Electrolysis Cell (SOEC) presents an attractive solution especially due to its potential to utilize impure water sources. This study focuses on modeling a SOEC supplied with four distinct streams of treated municipal wastewaters using the Aspen Plus software. Through the simulation analysis it was determined that two of the wastewater streams could be effectively evaporated and treated within the cell without generating waste liquids containing excessive pollutant concentrations. Specifically by evaporating 27% of the first current and 10% of the second it was estimated that 26.2 kg/m3 and 9.7 kg/m3 of green hydrogen could be produced respectively. Considering the EU’s target for Italy is to have 5 GW of installed power capacity by 2030 and the mass flowrate of the analyzed wastewater streams this hydrogen production could meet anywhere from 0.4% to 20% of Italy’s projected electricity demand.

Hydrogen is envisaged to play a major role in decarbonizing our future energy systems. Hydrogen is ideal for storing renewable energy over longer durations strengthening energy security. It can be used to provide electricity renewable heat power long-haul transport shipping and aviation and in decarbonizing several industrial processes. The cost of green hydrogen produced from renewable via electrolysis is dominated by the cost of electricity used. Operating electrolyzers only during periods of low electricity prices will limit production capacity and underutilize high investment costs in electrolyzer plants. Hydrogen production from deep offshore wind energy is a promising solution to unlock affordable electrolytic hydrogen at scale. Deep offshore locations can result in an increased capacity factor of generated wind power to 60–70% 4–5 times that of onshore locations. Dedicated wind farms for electrolysis can use the majority >80% of the produced energy to generate economical hydrogen. In some scenarios hydrogen can be the optimal carrier to transport the generated energy onshore. This review discusses the opportunities and challenges in offshore hydrogen production using electrolysis from wind energy and seawater. This includes the impact of site selection size of the electrolyzer and direct use of seawater without deionization. The review compares overall electrolysis system efficiency cost and lifetime when operating with direct seawater feed and deionized water feed using reverse osmosis and flash evaporation systems. In the short to medium term it is advised to install a reverse osmosis plant with an ion exchanger to feed the electrolysis instead of using seawater directly.

Coastal regions have abundant off-shore wind energy resources and surrounding areas have large-scale liquefied natural gas (LNG) receiving stations. From the engineering perspectives there are limitations in unstable off-shore wind energy and fluctuating LNG loads. This article offers a new energy scheme to combine these 2 energy units which uses surplus wind energy to produce hydrogen and use LNG cold energy to liquefy and store hydrogen. In addition in order to improve the efficiency of utilizing LNG cold energy and reduce electricity consumption for liquid hydrogen (LH2) production at coastal regions this article introduces the liquid air energy storage (LAES) technology as the intermediate stage which can stably store the cold energy from LNG gasification. A new scheme for LNG-LAES-LH2 hybrid LH2 production is built. The case study is based on a real LNG receiving station at Hainan province China and this article presents the design of hydrogen production/liquefaction process and carries out the optimizations at key nodes and proves the feasibility using specific energy consumption and exergy analysis. In a 100 MW system the liquid air storage round-trip efficiency is 71.0% and the specific energy consumption is 0.189 kWh/kg and the liquid hydrogen specific energy consumption is 7.87 kWh/kg and the exergy efficiency is 46.44%. Meanwhile the corresponding techno-economic model is built and for a LNGLAES-LH2 system with LH2 daily production 140.4 tons the shortest dynamic payback period is 9.56 years. Overall this novel hybrid energy scheme can produce green hydrogen using a more efficient and economical method and also can make full use of surplus off-shore wind energy and coastal LNG cold energy.

Proton exchange membrane (PEM) electrolyser stands as a promising candidate for sustainable hydrogen pro duction from renewable energy sources (RESs). Given the fluctuating nature of RESs accurate modelling of the PEM electrolyser is crucial. Nonetheless complex models of the PEM electrolyser demand substantial time and resource investments when integrating them into a large-scale power system. The majority of introduced models in the literature are either overly intricate or fail to effectively reproduce the dynamic behaviour of the PEM electrolyser. To this end this article aims to develop a model that not only captures the dynamic response of the PEM electrolyser crucial for conducting flexibility studies in the power system but also avoids complexity for seamless integration into large-scale simulations without comprising accuracy. To verify the model it is vali dated against static and dynamic experimental data. Compared to the investigated experimental cases the model exhibited an average error of 0.66% and 3.93% in the static and dynamic operation modes respectively.

The cost of polymer electrolyte water electrolysis (PEWE) is dominated by the price of electricity used to power the water splitting reaction. We present a liquid water fed polymer electrolyte water electrolyzer cell operated at a cell temperature of 100 °C in comparison to a cell operated at state-of-the-art operation temperature of 60 °C over a 300 h constant current period. The hydrogen conversion efficiency increases by up to 5% at elevated temperature and makes green hydrogen cheaper. However temperature is a stress factor that accelerates degradation causes in the cell. The PEWE cell operated at a cell temperature of 100 °C shows a 5 times increased cell voltage loss rate compared to the PEWE cell at 60 °C. The initial performance gain was found to be consumed after a projected operation time of 3500 h. Elevated temperature operation is only viable if a voltage loss rate of less than 5.8 μV h−1 can be attained. The major degradation phenomena that impact performance loss at 100 °C are ohmic (49%) and anode kinetic losses (45%). Damage to components was identified by post-test electron-microscopic analysis of the catalyst coated membrane and measurement of cation content in the drag water. The chemical decomposition of the ionomer increases by a factor of 10 at 100 °C vs 60 °C. Failure by short circuit formation was estimated to be a failure mode after a projected lifetime 3700 h. At elevated temperature and differential pressure operation hydrogen gas cross-over is limiting since a content of 4% hydrogen in oxygen represents the lower explosion limit.

The research motivation of this paper is to utilize the large amount of energy wasted during the LNG (liquefied natural gas) gasification process and proposes a synergistic liquefied hydrogen (LH2) production and storage process scheme for LNG receiving station and methane reforming hydrogen production process - SMR-LNG combined liquefied hydrogen production system which uses the cold energy from LNG to pre-cool the hydrogen and subsequently uses an expander to complete the liquefaction of hydrogen. The proposed process is modeled and simulated by Aspen HYSYS software and its efficiency is evaluated and sensitivity analysis is carried out. The simulation results show that the system can produce liquefied hydrogen with a flow rate of 5.89t/h with 99.99% purity when the LNG supply rate is 50t/h. The power consumption of liquefied hydrogen is 46.6kWh/kg LH2; meanwhile the energy consumption of the HL subsystem is 15.9kWh/kg LH2 lower than traditional value of 17~19kWh/kg LH2. The efficiency of the hydrogen production subsystem was 16.9%; the efficiency of the hydrogen liquefaction (HL) subsystem was 29.61% which was significantly higher than the conventional industrial value of 21%; the overall energy efficiency (EE1) of the system was 56.52% with the exergy efficiency (EE2) of 22.2% reflecting a relatively good thermodynamic perfection. The energy consumption of liquefied hydrogen per unit product is 98.71 GJ/kg LH2.

Offshore green hydrogen emerges as a guiding light in the global pursuit of environmental sustainability and net-zero objectives. The burgeoning expansion of offshore wind power faces significant challenges in grid integration. This avenue towards generating offshore green hydrogen capitalises on its ecological advantages and substantial energy potential to efficiently channel offshore wind power for onshore energy demands. However a substantial research void exists in efficiently integrating offshore wind electricity and green hydrogen. Innovative designs of offshore hydrogen platforms present a promising solution to bridge the gap between offshore wind and hydrogen integration. Surprisingly there is a lack of commercially established offshore platforms dedicated to the hydrogen industry. However the wealth of knowledge from oil and gas platforms contributes valuable insights to hydrogen platform design. Diverging from the conventional decentralised hydrogen units catering to individual turbines this study firstly introduces a pioneering centralised Offshore Green Hydrogen Platform (OGHP) which seamlessly integrates modular production storage and offloading modulars. The modular design of facilitates scalability as wind capacity increases. Through a detailed case study centred around a 100-Megawatt floating wind farm the design process of offshore green hydrogen modulars and its floating sub-structure is elucidated. Stability analysis and hydrodynamic analysis are performed to ensure the safety of the OGHP under the operation conditions. The case study will enhance our understanding OGHP and its modularised components. The conceptual design of modular OGHP offers an alternative solution to ‘‘Power-to-X’’ for offshore renewable energy sector.

Hydrogen is widely recognized as a key component of a decarbonized global energy system serving as both a fuel source and an energy storage medium. While current hydrogen production relies almost entirely on emissionsintensive processes two low-emissions production pathways – natural-gas-derived production combined with carbon capture and storage and electrolysis using carbon-free electricity – are poised to change the global supply mix. Our study assesses the financial conditions under which natural-gas-based hydrogen production combined with carbon capture and storage would be available at a cost lower than hydrogen produced through electrolysis and the degree to which these conditions are likely to arise in a transition to a net-zero world. We also assess the degree to which emissions reduction policies namely carbon pricing and carbon capture and storage tax credits affect the relative costs of hydrogen production derived from different pathways. We show that while carbon pricing can improve the relative cost of both green and blue hydrogen production compared with unabated grey hydrogen targeted tax credits favouring either blue or green hydrogen explicitly may increase emissions and/or increase the costs of the energy transition.

Hydrogen as a clean energy carrier is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies has ignited much attention in the past decades based on the high current density greater energy efficiency small mass-volume characteristic easy handling and maintenance. To date substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review we firstly compare the alkaline water electrolysis (AWE) solid oxide electrolysis (SOE) and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly current collector and bipolar plate). Finally the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.

The present study comprehensively examines the application of hydro wave tidal undersea current and geothermal energy sources of Canada for green hydrogen fuel production. The estimated potential capacity of each province is derived from official data and acceptable assumptions and is subject to discussion and evaluation in the context of a viable hydrogen economy. According to the findings the potential for green hydrogen generation in Canada is projected to be 48.86 megatons. The economic value of the produced green hydrogen results in an equivalent of 21.30 billion US$. The top three provinces with the highest green hydrogen production potential using hydro resources including hydro wave tidal undersea current and geothermal are Alberta Quebec and British Columbia with 26.13 Mt 7.34 Mt and 4.39 Mt respectively. Quebec is ranked first by only considering the marine sources including 4.14 Mt with hydro 1.46 Mt with wave 0.27 Mt underwater current and 1.45 Mt with tidal respectively. Alberta is listed as the province with the highest capacity for hydrogen production from geothermal energy amounting up to 26.09 Mt. The primary objective is to provide comprehensive hydrogen maps for each province in Canada which will be based on the identified renewable energy potential and the utilization of electrolysers. This may further be examined within the framework of the prevailing policies implemented by local communities and officials in order to develop a sustainable energy plan for the nation.

Energy transition is a key driver to combat climate change and achieve zero carbon future. Sustainable and costeffective hydrogen production will provide valuable addition to the renewable energy mix and help minimize greenhouse gas emissions. This study investigates the performance of in-situ hydrogen production (IHP) process using a full-field compositional model as a precursor to experimental validation The reservoir model was simulated as one geological unit with a single point uniform porosity value of 0.13 and a five-point connection type between cell to minimize computational cost. Twenty-one hydrogen forming reactions were modelled based on the reservoir fluid composition selected for this study. The thermodynamic and kinetic parameters for the reactions were obtained from published experiments due to the absence of experimental data specific to the reservoir. A total of fifty-four simulation runs were conducted using CMG STARS software for 5478 days and cumulative hydrogen produced for each run was recorded. Results generated were then used to build a proxy model using Box-Behnken design of experiment method and Support Vector Machine with RBF kernel. To ascertain accuracy of the proxy models analysis of variance (ANOVA) was conducted on the variables. The average absolute percentage error between the proxy model and numerical simulation was calculated to be 10.82%. Optimization of the proxy model was performed using genetic algorithm to maximize cumulative hydrogen produced. Based on this optimized model the influence of porosity permeability well location injection rate and injection pressure were studied. Key results from this study reveals that lower permeability and porosity reservoirs supports more hydrogen yield injection pressure had a negligible effect on hydrogen yield and increase in oxygen injection rate corelated strongly with hydrogen production until a threshold value beyond which hydrogen yield decreased. The framework developed in the study could be used as tool to assess candidate reservoirs for in-situ hydrogen production.

Low temperature water electrolysers such as Proton Exchange Membrane Water Electrolysers (PEMWEs) Alkaline Water Electrolysers (AWEs) and Anion Exchange Membrane Water Electrolysers (AEMWEs) are known to be sensitive to water quality with a range of common impurities impacting performance hydrogen quality and device lifetime. Purification of feed water adds to cost operational complexity and design limitations while failure of purification equipment can lead to degradation of electrolyser materials and components. Increased robustness to impurities will offer a route to longer device lifetimes and reduced operating costs but understanding of the impact of impurities and associated degradation mechanisms is currently limited. This critical review offers for the first time a comprehensive overview of relevant impurities in operating electrolysers and their impact. Impurity sources degradation mechanisms characterisation techniques water purification technologies and mitigation strategies are identified and discussed. The review generalises already reported mechanisms proposes new mechanisms and provides a framework for consideration of operational implications.

This study presents a new three-step Cu-Cl cycle that can operate with heat input without electrolysis. While the sensitivity analyses of the system are performed to evaluate the system performance through the Aspen Plus thermodynamic analyses of the system are performed with energetic and exergetic approaches. The highest exergy destruction among the components in the system was the decomposition reactor with a rate of 50.6%. Furthermore the energy and exergy values for the simulated system to produce 1 mol of hydrogen were determined by calculating the energy requirements of all components in the system. The total energy required for the system to generate 1 mol of hydrogen is calculated to be 997.81 kJ/mol H2. It was found that the component that required the most energy 504.76 kJ/mol H2 in the system was the decomposition reactor. Moreover the overall energy and exergy efficiencies are calculated to be 72.50% and 46.70% respectively.

Hydrogen plays a pivotal role in transitioning to CO2-free energy systems yet challenges regarding costs and sourcing persist in supplying Europe with renewable hydrogen. Our paper proposes a simulation-based approach to determine cost-optimal combinations of electrolyser power and renewable peak power for off-grid hydrogen production considering location and energy source dependencies. Key findings include easy estimation of Levelized Costs of Hydrogen (LCOH) and optimal plant sizing based on the regional energy yield and source. Regional investment risks influence the LCOH by 7.9 % per 1 % change of the Weighted Average Cost of Capital. In Central Europe (Austria) hydrogen production costs range from 7.4 €/kg to 8.6 €/kg whereas regions like Chile exhibit cheaper costs at 5.1 €/kg to 6.8 €/kg. Despite the favourable energy yields in regions like Chile or the UAE domestically produced hydrogen can be cost-competitive when location-specific risks and transport costs are taken into account. This underlines the critical role of domestic hydrogen production and cost-effective hydrogen transport for Europe’s future hydrogen supply.

Solar hydrogen and electricity are promising high energy-density renewable sources. Although photochemistry or photovoltaics are attractive routes special challenge arises in sunlight conversion efficiency. To improve efficiency various semiconductor materials have been proposed with selective sunlight absorption. Here we reported a hybrid system synergizing photo-thermochemical hydrogen and photovoltaics harvesting full-spectrum sunlight in a cascade manner. A simple suspension of Au-TiO2 in water/methanol serves as a spectrum selector absorbing ultraviolet-visible and infrared energy for rapid photo-thermochemical hydrogen production. The transmitted visible and near-infrared energy fits the photovoltaic bandgap and retains the high efficiency of a commercial photovoltaic cell under different solar concentration values. The experimental design achieved an overall efficiency of 4.2% under 12 suns solar concentration. Furthermore the results demonstrated a reduced energy loss in full-spectrum energy conversion into hydrogen and electricity. Such simple integration of photo-thermochemical hydrogen and photovoltaics would create a pathway toward cascading use of sunlight energy.

Green hydrogen will play a key role in the transition to a carbon-neutral energy system. This study addresses the challenge of supplying baseload green hydrogen through an integrated off-grid alkaline water electrolyzer (AWE) plant wind and solar photovoltaic (PV) power a battery energy storage system (BESS) and a hydrogen storage system based on salt and rock cavern geologies. The capacities of the components and the hydrogen storage size are optimized simultaneously with the control of the AWE plant to minimize the levelized cost of hydrogen (LCOH2) of the gas supplied. The operation of the system is simulated over 30 years with a 15 min time resolution considering degradation operating expenses and component replacements. Power generation data collected from a wind farm and a solar PV installation both located in southeastern Finland are used for system simulation. A sensitivity analysis exploring different hydrogen demand rates discount rates and installation years is conducted for both systems considering rock and salt caverns providing the optimal configuration for each case. It is found that for the price scenario of the year 2025 for a combined 100 MW AWE and compressor the optimal hydrogen demand rate is 12 kg/min with an LCOH2 of 3.14 e/kg and 2.77 e/kg in systems including rock and salt caverns respectively.

The transition towards clean and economically viable hydrogen production is crucial for ensuring energy sustainability and mitigating climate change. This transition can be effectively facilitated by using renewable energy sources and advanced hydrogen production methods. Methane pyrolysis and water electrolysis emerge as crucial techniques for achieving hydrogen production with minimal carbon intensity. Recognizing the unique opportunity presented by solar energy for both processes this study presents a comparative techno-economic analysis between solar-based molten salt methane pyrolysis (SMSMP) and solar-based solid oxide electrolyzer cell (SSOEC). This study offers a guideline for selecting SMSMP vs SSOEC for cities across theworld. In particular a comprehensive case study including five cities worldwide—San Antonio Edmonton Auckland Seville and Lyon—is conducted utilizing their dynamic solar data and localized prices of methane and electricity to provide a realistic comparison. The results indicate the superior economic feasibility of SMSMP across all case studies. Among different case studies San Antonio and Auckland have the lowest hydrogen costs for SMSMP (2.31 $/kgH2) and SSOEC (5.19 $/kgH2) respectively. It was also concluded that SMSMP is preferred over SSOEC in average to ideal solar conditions given its full dependency on solar thermal energy. However the SSOEC has the potential to achieve better economic feasibility by incorporating clean hydrogen tax incentives and reducing the costs associated with renewable energy infrastructure in the future.

This review presents a broad exploration of the techno economic evaluation of different technologies utilized in the production of hydrogen from both renewable and non-renewable sources. These encompass methods ranging from extracting hydrogen from fossil fuels or biomass to employing microbial processes electrolysis of water and various thermochemical cycles. A rigorous techno-economic evaluation of hydrogen production technologies can provide a critical cost comparison for future resource allocation priorities and trajectory. This evaluation will have a great impact on future hydrogen production projects and the development of new approaches to reduce overall production costs and make it a cheaper fuel. Different methods of hydrogen production exhibit varying efficiencies and costs: fast pyrolysis can yield up to 45% hydrogen at a cost range of $1.25 to $2.20 per kilogram while gasification operating at temperatures exceeding 750°C faces challenges such as limited small-scale coal production and issues with tar formation in biomass. Steam methane reforming which constitutes 48% of hydrogen output experiences cost fluctuations depending on scale whereas auto-thermal reforming offers higher efficiency albeit at increased costs. Chemical looping shows promise in emissions reduction but encounters economic hurdles and sorptionenhanced reforming achieves over 90% hydrogen but requires CO2 storage. Renewable liquid reforming proves effective and economically viable. Additionally electrolysis methods like PEM aim for costs below $2.30 per kilogram while dark fermentation though cost-effective grapples with efficiency challenges. Overcoming technical economic barriers and managing electricity costs remains crucial for optimizing hydrogen production in a low-carbon future necessitating ongoing research and development efforts.

This scientific article presents a developed model for optimising the scheduling of hydrogen production processes addressing the growing demand for efficient and sustainable energy sources. The study focuses on the integration of advanced scheduling techniques to improve the overall performance of the hydrogen electrolyser. The proposed model leverages constraint programming and satisfiability (CP-SAT) techniques to systematically analyse complex production schedules considering factors such as production unit capacities resource availability and energy costs. By incorporating real-world constraints such as fluctuating energy prices and the availability of renewable energy the optimisation model aims to improve overall operational efficiency and reduce production costs. The CP-SAT was applied to achieve more efficient control of the electrolysis process. The optimisation of the scheduling task was set for a 24 h time period with time resolutions of 1 h and 15 min. The performance of the proposed CP-SAT model in this study was then compared with the Monte Carlo Tree Search (MCTS)-based model (developed in our previous work). The CP-SAT was proven to perform better but has several limitations. The model response to the input parameter change has been analysed.

The analysis of Carbon Footprint (CF) for technology of hydrogen production from cleaned coke oven gas was performed. On the basis of real data and simulation calculations of the production process of hydrogen from coke gas emission indicators of carbon dioxide (CF) were calculated. These indicators are associated with net production of electricity and thermal energy and direct emission of carbon dioxide throughout a whole product life cycle. Product life cycle includes: coal extraction and its transportation to a coking plant the process of coking coal purification and reforming of coke oven gas carbon capture and storage. The values were related to 1 Mg of coking blend and to 1 Mg of the hydrogen produced. The calculation is based on the configuration of hydrogen production from coke oven gas for coking technology available on a commercial scale that uses a technology of coke dry quenching (CDQ). The calculations were made using ChemCAD v.6.0.2 simulator for a steady state of technological process. The analysis of carbon footprint was conducted in accordance with the Life Cycle Assessment (LCA).

Hydrogen is seen as a key element for the transition from a fossil fuel based economy to a renewable sustainable economy. Hydrogen can be used either directly as an energy carrier or as a feedstock for the reduction of CO2 to synthetic hydrocarbons. Hydrogen can be produced by electrolysis decomposing water in oxygen and hydrogen. This paper presents an overview of the three major electrolysis technologies: acidic (PEM) alkaline (AEL) and solid oxide electrolysis (SOEC). An updated list of existing electrolysers and commercial providers is provided. Most interestingly the specific prices of commercial devices are also given when available. Despite tremendous development of the PEM technology in the past decades the largest and most efficient electrolysers are still alkaline. Thus this technology is expected to play a key role in the transition to the hydrogen society. A detailed description of the components in an alkaline electrolyser and an analytical model of the process are provided. The analytical model allows investigating the influence of the different operating parameters on the efficiency. Specifically the effect of temperature on the electrolyte conductivity—and thus on the efficiency—is analyzed. It is found that in the typical range of operating temperatures for alkaline electrolysers of 65˚C - 220˚C the efficiency varies by up to 3.5 percentage points increasing from 80% to 83.5% at 65˚C and 220˚C respectively.

This paper presents an advanced Adaptive Sliding Mode Control (ASMC) strategy specifically developed for a hydrogen production system based on a Proton Exchange Membrane electrolyzer (PEM electrolyzer). This work utilized a static model of the PEM electrolyzer characterized by its V-I electrical characteristic which was approximated by a linear equation. The ASMC was designed to estimate the coefficients of this equation which are essential for designing an efficient controller. The primary objective of the proposed control strategy is to ensure the overall stability of the integrated system comprising both an interleaved buck converter (IBC) and PEM electrolyzer. The control framework aims to maintain the electrolyzer voltage at its reference value despite the unknown coefficients while ensuring equal current distribution among the three parallel legs of the IBC. The effectiveness of the proposed approach was demonstrated through numerical simulations in MATLAB-SIMULINK and was validated by the experimental results. The results showed that the proposed ASMC achieved a voltage tracking error of less than 2% and a current distribution imbalance of only 1.5%. Furthermore the controller exhibited strong robustness to parameter variations effectively handling fluctuations in the electrolyzer’s ohmic resistance (Rohm) (from ±28.75% to ±40.35%) and in the reversible voltage (Erev) (from ±28.67% to ±40.19%) highlighting its precision and reliability in real-world applications.

Different photoelectrochemical (PEC) artificial-leaf systems have been proposed for green hydrogen production. However their sustainability is not well understood in comparison to conventional hydrogen technologies. To fill this gap this study estimates cradle-to-grave life cycle environmental impacts and costs of PEC hydrogen production in different provinces in China using diverse tandem solar cells: Ge/GaAs/GaInP (Ge-PEC) GaAs/ GaInAs/GaInP (GaAs-PEC) and perovskite/silicon (P-PEC). These systems are benchmarked against conventional hydrogen production technologies − coal gasification (CG) and steam methane reforming (SMR) − across 18 environmental categories life cycle costs and levelised cost of hydrogen (LCOH). P-PEC emerges as the best options with 36–95 % lower impacts than Ge-PEC and GaAs-PEC across the categories including the climate change impact (0.38–0.52 t CO2 eq./t H2) which is 77–79 % lower. Economically P-PEC shows 81–84 % lower LCOH (2.51–3.81 k$/t). Compared to SMR and CG P-PEC reduces the impacts by 23–98 % saving 3.67–38.5 Mt of CO2 eq./yr. While its LCOH is 5 % higher than that of conventional hydrogen it could be economically competitive with both SMR and CG at 10 % higher solar-to-hydrogen efficiency and 25 % lower operating costs. In contrast Ge-PEC and GaAs-PEC while achieving much lower (81–91 %) climate change and some other impacts than the conventional technologies face significant economic challenges. Their LCOH (21.51–32.82 k$/t for Ge-PEC and 16.96–25.89 k$/t for GaAs-PEC) is 7–9 times higher than that of the conventional hydrogen due to the high solar cell costs. Therefore despite their environmental benefits these technologies require substantial cost reductions to become economically viable.

With the growing global focus on hydrogen as a key solution for achieving decarbonization understanding the most cost-effective and environmentally sustainable production methods is crucial. The objective of this study is to evaluate the economic and environmental performance of different renewable energy sources for hydrogen production while also considering the impact of geographic location system sizing and technological efficiency. This study compares the production of green hydrogen powered by onshorewind offshore-wind and solar PV with that of yellow hydrogen (grid-based hydrogen) in terms of cost and environmental impact for a large sample of publicly announced green hydrogen projects in Europe. Using geographic renewable energy data project-specific details and prevailing technological standards we derive each country’s weighted average cost of capital (WACC) to calculate market-based levelized cost of hydrogen. We find onshore-wind projects to have the lowest average levelized cost of green hydrogen followed by offshore-wind and then by solar PV . The costs for yellow hydrogen depend on the price of electricity. Excluding 2022 yellow hydrogen had lower mean costs than solar PV but higher costs than both types of wind. The environmental impact assessment finds significant decarbonization potential for green hydrogen particularly in regions with substantial renewable resources and carbon-intensive energy mixes. The study aggregates the project data at the country level then clusters the analyzed countries based on economic and environmental metrics to derive specific hydrogen strategies. It concludes that substantial governmental support is essential for the large-scale integration of green hydrogen into the energy system to achieve meaningful decarbonization.

Solid oxide electrolysis (SOEL) has emerged as a promising technology for efficient hydrogen production. Its main advantages lie in the high operating temperatures which enhance thermodynamic efficiency and in the ability to supply part of the required energy in the form of heat. Nevertheless improving the long-term durability of stack materials remains a key challenge. Thermal energy can be supplied by dedicated integration with different industrial processes where the main challenge lies in the elevated stack operating temperature (700–900 ◦C). This review provides a comprehensive analysis of the integration of solid oxide electrolysis cells (SOECs) into different industrial applications. Main processes cover methanol production methane production Power-to-Hydrogen systems or the use of reversible solid oxide electrolysis cell (rSOEC) stacks that can operate in both electrolysis and fuel cell mode. The potential of co-electrolysis to increase process flexibility and broaden application areas is also analyzed. The aim is to provide a comprehensive analysis of the integration strategies identify the main technical and economic challenges and highlight recent developments and future trends in the field. A detailed comparison assessment of the different processes is being discussed in terms of electrical and thermal efficiencies and operating parameters as well as Key Performance Indicators (KPIs) for each process. Technical-economic challenges that are currently a barrier to their implementation in industry are also analyzed.

To achieve energy transition hydrogen and carboxylic acids have attracted much attention due to their cleanliness and renewability. Anaerobic fermentation technology is an effective combination of waste biomass resource utilization and renewable energy development. Therefore the utilization of anaerobic fermentation technology is expected to achieve efficient co-production of hydrogen and carboxylic acids. However this process is fundamentally affected by gas–liquid mass transfer kinetics bubble behaviors and system partial pressure. Moreover the related studies are few and unfocused and no systematic research has been developed yet. This review systematically summarizes and discusses the basic mathematical models used for gas–liquid mass transfer kinetics the relationship between gas solubility and mass transfer and the liquid-phase product composition. The review analyzes the roles of the headspace gas composition and partial pressure of the reaction system in regulating co-production. Additionally we discuss strategies to optimize the metabolic pathways by modulating the gas composition and partial pressure. Finally the feasibility of and prospects for the realization of hydrogen and carboxylic acid co-production in anaerobic fermentation systems are outlined. By exploring information related to gas mass transfer and system pressure this review will surely provide an important reference for promoting cleaner production of sustainable energy.