Production & Supply Chain

The present study explores the potential of integrating the NET Zero Cycle (NZC) with hydrogen production by alkaline electrolyzers. To achieve this an Aspen Plus model was developed for the NZC and its accuracy was first confirmed by comparing it with literature data. The creation of a model for an alkaline electrolyzer was achieved using Aspen Custom Modeler and later imported into Aspen Plus. A comprehensive simulation was conducted in Aspen Plus to examine the synergies between the NZC and the alkaline electrolyzer. In this integration the oxygen demand of the NZC is met by a combination of an air separation unit (ASU) and the electrolyzer. The electrolyzer not only partially fulfills the oxygen requirements but also acts as an external heat supplier for the regenerator. Additionally the NZC supplies deionized water to the electrolyzer. A thermodynamic analysis in dicates that the integration of the NZC and alkaline electrolyzers results in a higher efficiency of 56.5 % compared to the stand-alone NZC an improvement of 2.3 %. Assuming that the NZC and alkaline electrolyzer operate at the same power production and input levels the alkaline electrolyzer can generate substantial oxygen to reduce the energy consumption of the ASU significantly. This aspect represents one of the primary reasons for the enhanced efficiency observed in this study. However the ASU still needs to be operated to provide the full oxygen demands of the process. To identify the key parameters influencing the integration of the NZC and alkaline electrolyzers a sensitivity analysis was performed. To enhance the system efficiency a comprehensive investigation was conducted to analyze the influence of key parameters such as combustor outlet temperature (COT) turbine outlet pressure (TOP) and combustor outlet pressure (COP) on the thermodynamic first law efficiency of the cycle. An increase in electrolyzer input power and a reduction in electrolyzer inlet feed were associated with a higher cycle effi ciency. The results also highlight that the TOP COT and the electrolyzer input power have a more significant impact on the cycle thermodynamic first law efficiency within the range of 5.7 4.0 and 2.6 % respectively while COP only causes a 0.4 % change in cycle efficiency. The integrated system demonstrates an impressive system first law thermodynamic efficiency of 62.5 % and exergy efficiency of 60.6 %.

Studies estimating the production cost of hydrogen-based fuels known as e-fuels often use renewable power profile time series obtained from open-source simulation tools that rely on meteorological reanalysis and satellite data such as Renewables.ninja or PVGIS. These simulated time series contain errors compared to real on-site measured data which are reflected in e-fuels cost estimates plant design and operational performance increasing the risk of inaccurate plant design and business models. Focusing on solar-powered e-fuels this study aims to quantify these errors using high-quality on-site power production data. A state-of-the-art optimization techno-economic model was used to estimate e-fuel production costs by utilizing either simulated or high-quality measured PV power profiles across four sites with different climates. The results indicate that in cloudy climates relying on simulated data instead of measured data can lead to an underestimation of the fuel production costs by 36 % for a hydrogen user requiring a constant supply considering an original error of 1.2 % in the annual average capacity factor. The cost underestimation can reach 25 % for a hydrogen user operating between 40 % and 100 % load and 17.5 % for a fully flexible user. For comparison cost differences around 20 % could also result from increasing the electrolyser or PV plant costs by around 55 % which highlights the importance of using high-quality renewable power profiles. To support this an open-source collaborative repository was developed to facilitate the sharing of measured renewable power profiles and provide tools for both time series analysis and green hydrogen techno-economic assessments.

Green hydrogen has recently gained importance as a key element in the transition to a low-carbon energy future sparking a boom in possible production regions. This article aims at situating incipient hydrogen production in the Argentine province of Río Negro within a global production network (GPN). The early configuration of the hydrogen-GPN includes several stakeholders and is contested in many ways. To explore the possible materialization of the hydrogen economy in Argentina this article links GPN literature to the concept of sociotechnical imaginaries. In so doing this study finds three energy imaginaries linked to hydrogen development: First advocates of green hydrogen (GH2) project a sociotechnical imaginary in which GH2 is expected to promote scientific and technological progress. Second proponents of blue hydrogen point to Vaca Muerta and the role of natural gas for energy autonomy. Third opponents of the GH2 project question the underlying growth and export model emphasizing conservation and domestic energy sovereignty. The competition between different capital fractions i.e. green and fossil currently poses the risk of pro-fossil path decisions and lock-in effects. Current power constellations have led to the replacement of green with low-emission resulting in the promotion of multi-colored hydrogen. This is particularly evident in the draft for the new national hydrogen law and the actors involved in defining the national hydrogen strategy. The conceptual combination of actors and their interests their current power relations and the sociotechnical imaginaries they deploy illustrates how Argentina's energy future is already being shaped today.

The updraft rotating bed gasifier (URBG) offers a sustainable solution for waste-to-energy conversion utilizing low-grade lignite and municipal solid waste (MSW) from metropolitan dumping sites. This study investigates the co-gasification of lignite with various MSW components demonstrating a significant enhancement in gasification efficiency due to the synergistic effects arising from their higher hydrogen-to-carbon (H/C) ratios. We find feedstock blending is key to maximizing gasification efficiency from 11% to 52% while reducing SO emissions from 739 mg/kg to 155 mg/kg. Increasing the combustion zone temperature to 1100 K resulted in a peak hydrogen yield which was 19% higher than at 800 K. However steam management is complicated as increasing it improves hydrogen fraction in produced gas but gasification efficiency is compromised. These findingsshowcase the URBG’s potential to address both energy production and waste management challenges guiding fossil-reliant regions toward a more sustainable energy future.

The need to reduce the carbon footprint of conventional energy sources has made green hydrogen a promising solution for the energy transition. The most environmentally friendly way to produce hydrogen is through water-based production using renewable energy. However the availability of fresh water is limited so switching to wastewater instead of fresh water is the key solution to this problem. In response to this issue the present review reports the main findings of the research studies dealing with the feasibility of hydrogen production from wastewater using various technologies including biological electrochemical and advanced oxidation routes. These methods have been studied in a large number of experiments with the aim of investigating and improving the potential of each method. On the other hand the maturity of solar energy technologies has led researchers to focus on the possibility of harnessing this source and combining it with wastewater treatment techniques for the production of green hydrogen. Therefore the present review pays special attention to solar driven hydrogen production from wastewater by highlighting the potential of several technologies for simultaneous water treatment and green hydrogen production from wastewater. Recent results limitations challenges possible improvements and techno-economic assessments reported by several authors as well as future directions of research and industrial implementation in this field are reported.

Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors measuring techniques and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis facilitating more competent inexpensive and feasible green hydrogen production.

As the most attractive energy carrier hydrogen production through electro-chemical water splitting (EWS) is promising for resolving the serious environ-mental problems derived from the rapid consumption of fossil fuels globally. Theproton exchange membrane water electrolyzer (PEMWE) is one of the mostpromising EWS technologies and has achieved great advancements. To offer atimely reference for the progress of the PEMWE system the latest advancementsand developments of PEMWE technology are systematically reviewed. The keycomponents including the electrocatalysts PEM and porous transport layer(PTL) as well as bipolar plate (BPP) are first introduced and discussed followedby the membrane electrode assembly and cell design. The highlights are put onthe design of the electrocatalyst and the relationship of each component on theperformance of the PEMWE. Moreover the current challenges and future per-spectives for the development of PEMWE are also discussed. There is a hope thatthis review can provide a timely reference for future directions in PEMWEchallenges and perspectives.

Methane steam reforming is the most widely adopted hydrogen production technology. To address the challenges associated with the large radial thermal resistance and low mass transfer rates inherent in the tubular packed bed reactors during the MSR process this study proposes a structural design optimization that integrates annular metal foam gas channels along the inner wall of the reforming tubes. Utilizing multi-physics simulation methods and taking the conventional tubular reactor as a baseline a comparative analysis was performed on physical parameters that characterize flow behavior heat transfer and reaction in the reforming process. The integration of the annular channels induces a radially non-uniform distribution of flow resistance in the tubes. Since the metal foam exhibits lower resistance the fluid preferentially flows through the annular channels leading to a diversion effect that enhances both convective heat transfer and mass transfer. The diversion effect redirects the central flow toward the near-wall region where the higher reactant concentration promotes the reaction. Additionally the higher thermal conductivity of the metal foam strengthens radial heat transfer further accelerating the reaction. The effects of operating parameters on performance were also investigated. While a higher inlet velocity tends to hinder the reaction in tubes integrated with annular channels it enhances the diversion effect and convective heat transfer. This offsets the adverse impact maintaining high methane conversion with lower pressure drop and thermal resistance than the conventional tubular reactor does.

The effect of the initial state of ZrO2 on properties of Ni/ZrO2 catalysts for hydrogen production in steam reforming of glycerol was investigated. The catalysts were synthesized by impregnating the supports obtained by varying the treatment temperature of ZrO2‧nH2O and introducing Y2O3 as a promoter. All materials were characterized by thermal analysis X-ray diffraction N2 physisorption scanning electron microscopy H2-TPR NH3-TPD and transmission electron microscopy. The mutual influence of NiO and ZrO2 on the genesis of the phase composition pore structure and reducibility was demonstrated. Different catalytic behavior is explained by influence of the initial form of the support on the size morphology of Ni particles and the support thermal stability. The initial activity of Ni/ZrO2is proportional to the monoclinic phase content. The catalysts based on tetragonal ZrO2 displayed the best stability. For the first time the presence of the aldol condensation products in glycerol steam reforming was demonstrated.

The yield of photovoltaic hydrogen production systems is influenced by a number of factors including weather conditions the cleanliness of photovoltaic modules and operational efficiency. Temporal variations in weather conditions have been shown to significantly impact the output of photovoltaic systems thereby influencing hydrogen production. To address the inaccuracies in hydrogen production capacity predictions due to weather-related temporal variations in different regions this study develops a method for predicting photovoltaic hydrogen production capacity using the long short-term memory (LSTM) neural network model. The proposed method integrates meteorological parameters including temperature wind speed precipitation and humidity into a neural network model to estimate the daily solar radiation intensity. This approach is then integrated with a photovoltaic hydrogen production prediction model to estimate the region’s hydrogen production capacity. To validate the accuracy and feasibility of this method meteorological data from Lanzhou China from 2013 to 2022 were used to train the model and test its performance. The results show that the predicted hydrogen production agrees well with the actual values with a low mean absolute percentage error (MAPE) and a high coefficient of determination (R2 ). The predicted hydrogen production in winter has a MAPE of 0.55% and an R2 of 0.985 while the predicted hydrogen production in summer has a slightly higher MAPE of 0.61% and a lower R2 of 0.968 due to higher irradiance levels and weather fluctuations. The present model captures long-term dependencies in the time series data significantly improving prediction accuracy compared to conventional methods. This approach offers a cost-effective and practical solution for predicting photovoltaic hydrogen production demonstrating significant potential for the optimization of the operation of photovoltaic hydrogen production systems in diverse environments.

Nickel-based catalysts recognized for their cost-efficiency and availability play a critical role in advancing hydrogen production technologies. This study evaluates their optimization in water electrolysis to improve efficiency and system stability. Key findings highlight the enhancement of these catalysts with nickel-iron oxyhydroxide and nickel-molybdenum co-catalysts. Technological innovations such as Perovskite Solar Cells integration for solar-to-hydrogen conversion are explored. The use of nickel foam enhances electrode durability offering valuable insights into designing sustainable and efficient hydrogen production systems.

A holistic approach to decision-making in modern energy systems is vital due to their increase in complexity and interconnectedness. However decision makers often rely on narrowlyfocused strategies such as economic assessments for energy system strategy selection. The approach in this paper helps considers various factors such as economic viability technological feasibility environmental impact and social acceptance. By integrating these diverse elements decision makers can identify more economically feasible sustainable and resilient energy strategies. While existing focused approaches are valuable since they provide clear metrics of a potential solution (e.g. an economic measure of profitability) they do not offer the much needed system-as-a-whole understanding. This lack of understanding often leads to selecting suboptimal or unfeasible solutions which is often discovered much later in the process when a change may not be possible. This paper presents a novel evaluation framework to support holistic decision-making in energy systems. The framework is based on a systems thinking approach applied through systems engineering principles and model-based systems engineering tools coupled with a multicriteria decision analysis approach. The systems engineering approach guides the development of feasible solutions for novel energy systems and the multicriteria decision analysis is used for a systematic evaluation of available strategies and objective selection of the best solution. The proposed framework enables holistic multidisciplinary and objective evaluations of solutions and strategies for energy systems clearly demonstrates the pros and cons of available options and supports knowledge collection and retention to be used for a different scenario or context. The framework is demonstrated in case study evaluation solutions for a novel energy system of clean hydrogen generation.

The present study aims to conduct a thermodynamic analysis of a novel concept that synergistically integrates clean hydrogen and power production with a liquified natural gas (LNG) regasification system. The designed integrated energy system aims to achieve hydrogen production power production liquified natural gas regasification carbon capture storage and in situ recirculation. Hydrogen sulfide (H2S) from industrial waste streams is used as a major feedstock and filtration combustion of H2S is employed as a hydrogen production method. CO2 obtained from the combustion process is liquified and pumped at a high pressure to recirculated back to the CO2 cycle power generation combustion process. The flu gas obtained after expansion on the turbine is condensed and CO2 is captured and pressurized. The entire plant is simulated in the Aspen Plus simulation environment and a comprehensive thermodynamic assessment including the energy and exergy analysis is conducted. Additionally several parametric studies and assessments of various factors influencing the system's performance are conducted. From the sensitivity analyses it is found that at 20% CO2 recirculation the hydrogen production rate decreases by 31.81% when the operating pressure is increased from 0.05 bar to 3 bar. The adiabatic temperature is reduced by 39.72% 35.37% and 32.85% when 50% 60% and 70% CO2 is recirculated in the oxidant stream at an oxygen to natural gas (ONG) ratio of 0.5. The energy and exergy efficiencies of the system are found to be 71.48% and 60.69% respectively. The present system avoids 2571.94 tons/yr of CO2 emissions for clean hydrogen production and 1426.27 tons/yr of CO2 for clean power production which would otherwise be emitted from steam methane reforming and coal gasification.

Climate change is a major concern for the sustainable development of global energy systems. Hydrogen produced through water electrolysis offers a crucial solution by storing and generating renewable energy with minimal environmental impact thereby reducing carbon emissions in the energy sector. Our research evaluates current hydrogen production technologies such as alkaline water electrolysis (AWE) proton exchange membrane water electrolysis (PEMWE) solid oxide electrolysis (SOEC) and anion exchange membrane water electrolysis (AEMWE). We systematically review life cycle assessments (LCA) for these technologies analyzing their environmental impacts and recent technological advancements. This study fills essential gaps by providing detailed LCAs for emerging technologies and evaluating their scalability and environmental footprints. Our analysis outlines the strengths and weaknesses of each technology guiding future research and assisting stakeholders in making informed decisions about integrating hydrogen production into the global energy mix. Our approach highlights operational efficiencies and potential sustainability enhancements by employing comparative analyses and reviewing advancements in membrane technology and electrocatalysts. A significant finding is that PEMWE when integrated with renewable energy sources offers rapid response capabilities that are vital for adaptive energy systems and reducing carbon footprints.

The escalating urgency to address climate change has sparked unprecedented interest in green hydrogen as a clean energy carrier. The intermittent nature of Renewable Energy Sources (RES) like wind and solar can introduce unpredictability into the energy supply potentially causing mismatches in the power grid. To this end green hydrogen production can provide a solution by enhancing system flexibility thereby accommodating the fluctuations and stochastic characteristics of RES. Furthermore green hydrogen could play a pivotal role in decarbonizing hard-to-abate sectors and promoting sector coupling. This research article endeavors to delve into this subject by developing a dynamic techno-economic analysis tool capable of flexibly assessing the optimal setup of Alkaline (AEL) electrolysis coupled with RES in a specific region or hub. The focus lies on achieving costeffectiveness efficiency and sustainable production of green hydrogen. The tool leverages a comprehensive dataset covering a full year of hourly data on both renewable electricity production from intermittent RES and wholesale electricity market prices alongside customizable inputs from users. It can be applied across various scenarios including direct coupling with dedicated RES plants and hybrid configurations utilizing the electricity grid as a backup source. The model optimizes RES electrolyser and hydrogen storage capacities to minimize the Levelized Cost of Hydrogen (LCOH) and/or the operational Carbon Intensity (CI) of hydrogen produced. The tool is applied within a real-world application study in the framework of the TRIERES Hydrogen Valley Project which is taking shape in Peloponnese Greece. For the various configurations analysed the LCOH ranges from 7.75 to 12.68 €/kgH2. The cost-optimal system configuration featuring a hybrid RES power supply of 12 MW solar and 19 MW wind energy alongside with 3.5 tonnes of hydrogen storage leads to a minimum LCOH of 7.75 €/kgH2. Subsidies on electrolyser stack and balance of plant CAPEX can reduce LCOH by up to 0.6 €/kgH2.

Proposals for achieving net-zero emissions by 2050 include scaling-up electrolytic hydrogen production however this poses technical economic and environmental challenges. One such challenge is for policymakers to ensure a sustainable future for the environment including freshwater and land resources while facilitating low-carbon hydrogen production using renewable wind and solar energy. We establish a country-by-country reference scenario for hydrogen demand in 2050 and compare it with land and water availability. Our analysis highlights countries that will be constrained by domestic natural resources to achieve electrolytic hydrogen self-sufficiency in a net-zero target. Depending on land allocation for the installation of solar panels or wind turbines less than 50% of hydrogen demand in 2050 could be met through a local production without land or water scarcity. Our findings identify potential importers and exporters of hydrogen or conversely exporters or importers of industries that would rely on electrolytic hydrogen. The abundance of land and water resources in Southern and Central-East Africa West Africa South America Canada and Australia make these countries potential leaders in hydrogen export.

The article presents the application of the metalog family of probability distributions to predict the energy production of photovoltaic systems for the purpose of generating small amounts of green hydrogen in distributed systems. It can be used for transport purposes as well as to generate energy and heat for housing purposes. The monthly and daily amounts of energy produced by a photovoltaic system with a peak power of 6.15 kWp were analyzed using traditional statistical methods and the metalog probability distribution family. On this basis it is possible to calculate daily and monthly amounts of hydrogen produced with accuracy from the probability distribution. Probabilistic analysis of the instantaneous power generated by the photovoltaic system was used to determine the nominal power of the hydrogen electrolyzer. In order to use all the energy produced by the photovoltaic system to produce green hydrogen the use of a stationary energy storage device was proposed and its energy capacity was determined. The calculations contained in the article can be used to design home green hydrogen production systems and support the climate and energy transformation of small companies with a hydrogen demand of up to ¾ kg/day.

Installing multi-renewable energy (RE) power plants at designated locations known as RE parks is a promising solution to address their intermittent power. This research focuses on optimizing RE parks for three scenarios: photovoltaic (PV)-only wind-only and hybrid PV-wind with the aim of generating green hydrogen in locations with different RE potentials. To ensure rapid response to RE fluctuations a Proton Exchange Membrane (PEM) electrolyzer is employed. Furthermore this research proposes detailed models for manufacturer-provided wind power curves electrolyzer efficiency against its operating power and electrolyzer cost towards its capacity. Two optimization cases are conducted in MATLAB evaluating the optimum sizes of the plants in minimizing levelized cost of hydrogen (LCOH) using classical discrete combinatorial method and determining the ideal PV-to-wind capacity ratio for operating PEM electrolyzer within hybrid PV-wind parks using particle swarm optimization. Numerical simulations show that wind power-based hydrogen production is more cost-effective than PV-only RE parks. The lowest LCOH $4.26/kg H2 and the highest LCOH $14.378/kg H2 are obtained from wind-only and PV-only configurations respectively. Both occurred in Adum-Kirkeby Denmark as it has highest average wind speed and lowest irradiance level. Notably LCOH is reduced with the hybrid PV-wind configuration. The results suggest the optimum PV-to-wind capacity ratio is 65:35 on average and indicate that LCOH is more sensitive to electrolyzer’s cost than to electricity tariff variation. This study highlights two important factors i.e. selecting the suitable location based on the available RE resources and determining the optimum size ratio between the plants within the RE park.

The current transition to renewable energies has motivated research into energy storage using various techniques. Of these electrolysis for pure hydrogen production stands out as hydrogen is a crucial energy vector molecule capable of decarbonizing multiple sectors. However the low efficiency of the electrolysis process presents a major limitation. In this work an electrochemical evaluation of catalyst materials for water splitting under elevated temperature and pressure (ETP) conditions to replicate realistic electrolyzer operating environments is proposed. The NiFeP/Zn-coated nickel foam electrodes demonstrated a brain-like compact morphology with EDS revealing a composition of 62.20 at% Ni 13.90 at% Fe 1.60 at% Zn 7.65 at% P and 15.21 at% O2. Electrochemical performance tests revealed a significant reduction in overpotential for the hydrogen evolution reaction (HER) achieving 38 mV at 8 bar and 80 ◦C while the oxygen evolution reaction (OER) exhibited 119 mV at 1 bar and 80 ◦C both at |30| mAcm− 2 . Chronopotentiometry confirmed the stability of the coating for over 24 h at high current density of |400| mAcm− 2 . The bifunctional capability of the coating was validated in a fullcell test obtaining a remarkably low overpotential of 1.47 V at 30 mAcm− 2 for overall water splitting under 80 ◦C and 8 bar conditions.

In Poland hydrogen production should be carried out using renewable energy sources particularly wind energy (as this is the most efficient zero-emission technology available). According to hydrogen demand in Poland and to ensure stability as well as security of energy supply and also the realization of energy policy for the EU it is necessary to use offshore wind energy for direct hydrogen production. In this study a centralized offshore hydrogen production system in the Baltic Sea area was presented. The goal of our research was to explore the possibility of producing hydrogen using offshore wind energy. After analyzing wind conditions and calculating the capacity of the proposed wind farm a 600 MW offshore hydrogen platform was designed along with a pipeline to transport hydrogen to onshore storage facilities. Taking into account Poland’s Baltic Sea area wind conditions with capacity factor between 45 and 50% and having obtained results with highest monthly average output of 3508.85 t of hydrogen it should be assumed that green hydrogen production will reach profitability most quickly with electricity from offshore wind farms.

Current climate crisis makes the need for reducing carbon emissions more than evident. For this reason renewable energy sources are expected to play a fundamental role. However these sources are not controllable but depend on the weather conditions. Therefore green hydrogen (hydrogen produced from water electrolysis using renewable energies) is emerging as the key energy carrier to solve this problem. Although different properties of hydrogen have been widely studied some key aspects such as the water and energy footprint as well as the technological development and the regulatory framework of green hydrogen in different parts of the world have not been analysed in depth. This work performs a data-driven analysis of these three pillars: water and energy footprint technological maturity and regulatory framework of green hydrogen technology. Results will allow the evaluation of green hydrogen deployment both the current situation and expectations. Regarding the water footprint this is lower than that of other fossil fuels and competitive with other types of hydrogen while the energy footprint is higher than that of other fuels. Additionally results show that technological and regulatory framework for hydrogen is not fully developed and there is a great inequality in green hydrogen legislation in different regions of the world.

Plastics have become integral to modern life playing crucial roles in diverse industries such as agriculture electronics automotive packaging and construction. However their excessive use and inadequate management have had adverse environmental impacts posing threats to terrestrial and marine ecosystems. Consequently researchers are increasingly searching for more sustainable ways of managing plastic wastes. Pyrolysis a chemical recycling method holds promise for producing valuable fuel sustainably. This study explores the process of the pyrolysis of plastic and incorporates recent advancements. Additionally the study investigates the integration of reforming into the pyrolysis process to improve hydrogen production. Hydrogen a clean and eco-friendly fuel holds significance in transport engines power generation fuel cells and as a major commodity chemical. Key process parameters influencing the final products for pyrolysis and in-line reforming are evaluated. In light of fossil fuel depletion and climate change the pyrolysis and in-line reforming strategy for hydrogen production is anticipated to gain prominence in the future. Amongst the various strategies studied the pyrolysis and in-line steam reforming process is identified as the most effective method for optimising hydrogen production from plastic wastes.

The present study investigates the feasibility of coupling the intermittent electric power generation from a wind farm with alkaline electrolyzers to produce green hydrogen. A physically accurate model of commercial elec trolytic modules has been first developed accounting for conversion efficiency drop due to modules’ cool down effects of shutdowns due to the intermittence of wind power and voltage degradation over the working time frame. The model has been calibrated on real modules for which industrial data were available. Three com mercial module sizes have been considered i.e. 1 2 and 4 MW. As a second step the model has been coupled with historical power datasets coming from a real wind farm characterized by a nominal installed power of 13.8 MW. Finally the model was implemented within a sizing algorithm to find the best combination between the actual wind farm power output and the electrolyzer capacity to reach the lowest Levelized Cost Of Hydrogen (LCOH) possible. To this end realistic data for the capital cost of the whole system (wind farm and electrolyzers) have been considered based on industrial data and market reports as well as maintenance costs including both periodic replacements of degraded components and periodic maintenance. Simulations showed that if the right sizing of the two systems is made competitive hydrogen production costs can be achieved even with current technologies. Bigger modules are less flexible but by now considerably cheaper than smaller ones. A future economy of scale in alkaline electrolyzers is then needed to foster the diffusion of the technology.

The increase in industrial production and energy consumption has led to excessive exploitation of non-renewable resources resulting in serious environmental problems such as greenhouse gas emissions. In response there’s a growing investment in renewable energies such as hydroelectric wind and solar power. However these sources are unable to fully meet demand leading to imbalances between consumption and production. An emerging solution to this challenge is green hydrogen produced from clean sources reducing dependence on fossil fuels and mitigating greenhouse gas emissions. The S-LCA methodology presented in the UNEP/SETAC Guidelines for the Social Life Cycle Assessment is applied to the production of green hydrogen via the electrolytic separation of water using a proton exchange electrolyser. The process involves the extraction and processing of raw materials from the electrolyser BOP and reverse osmosis system the manufacture of the systems and the production of green hydrogen. The data from each stage is inventoried and entered into the PSILCA v.3.1 and SHDB 2022FV5 databases integrated into the SimaPro software version 9.3.0.2 enabling a complete analysis of the social im pacts associated with the production of green hydrogen. The data was evaluated considering 4 stakeholder categories: workers value chain actors society and local community. The results indicate that the extraction and processing of raw materials for the electrolyser was the primary stage responsible for the social impacts in both databases. However the electrolyser manufacturing stage was the main contributor to the indicators “weekly working hours per employee” and “union density” in the PSILCA database. Nafion® and Iridium were identified as the major contributors among components in both databases. The study highlights the significant role played by countries like China and South Africa in social impacts particularly in the extraction and processing of raw materials. Despite this Portugal emerged as the largest contributor to five out of fourteen indicators in the PSILCA database while its contributions in the SHDB database were less than 7 %. Moreover a comparison between the two databases revealed that PSILCA exhibited a greater distribution of results across various stages components and countries assessed whereas SHDB showed more centralized results. The observed discrepancies between the results obtained from different databases can be attributed to three main factors: the input-output database utilized in each S-LCA tool the assumed risk levels for each indicator and the equivalence between indicators and subcategories. This exploratory study offers valuable insights for guiding strategic decisions regarding the social component of sustainability providing a detailed understanding of the social impacts associated with the specific case of green hydrogen production in a planned hub in Portugal.

Low-cost green hydrogen production will be key in reaching net zero carbon emissions by 2050. Green hydrogen can be produced by electrolysis using renewable energy including wind energy. However the configuration of offshore wind-to-hydrogen systems is not yet standardised. For example electrolysis can take place onshore or offshore. This work presents a framework to assess and quantify which configuration is more resilient so that security of hydrogen supply is incorporated in strategic decisions with the following key findings. First resilience should be assessed according to hydrogen supply rather than hydrogen production. This allows the framework to be applicable for all identified system configurations. Second resilience can be quantified according to the quantity ratio and lost revenue of the unsupplied hydrogen.

An energy source transition is necessary to realize carbon neutrality emphasizing the importance of a hydrogen economy. The transportation sector accounted for 27% of annual carbon emissions in 2019 highlighting the increasing importance of transitioning to hydrogen vehicles and establishing hydrogen refueling stations (HRSs). In particular HRSs need to be prioritized for deploying hydrogen vehicles and developing hydrogen supply chains. Thus research on HRS is important for achieving carbon neutrality in the transportation sector. In this study we improved the efficiency and scaled up the capacity of an on-site HRS (based on steam methane reforming with a hydrogen production rate of 30 Nm3/h) in Seoul Korea. This HRS was a prototype with low efficiency and capacity. Its efficiency was increased through thermodynamic analysis and heat exchanger network synthesis. Furthermore the process was scaled up from 30 Nm3/h to 150 Nm3/h to meet future hydrogen demand. The results of exergy analysis indicated that the exergy destruction in the reforming reactor and heat exchanger accounted for 58.1% and 19.8% respectively of the total exergy destruction. Thus the process was improved by modifying the heat exchanger network to reduce the exergy losses in these units. Consequently the thermal and exergy efficiencies were increased from 75.7% to 78.6% and from 68.1% to 70.4% respectively. The improved process was constructed and operated to demonstrate its performance. The operational and simulation data were similar within the acceptable error ranges. This study provides guidelines for the design and installation of low-carbon on-site HRSs.

As new sources of energy and advanced technologies are used there is a continuous evolution in energy supply demand and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies elucidating their respective merits and challenges. Furthermore this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.

With a limited global carbon budget it is imperative that decarbonisation decisions are based on accurate holistic accounts of all greenhouse gas (GHG) emissions produced to assess their validity. Here the upstream GHG emissions of potential UK offshore Green and Blue hydrogen production are compared to GHG emissions from hydrogen produced through electrolysis using UK national grid electricity and the ‘business-as-usual’ case of continuing to combust methane. Based on an operational life of 25 years and producing 0.5MtH2 per year for each hydrogen process the results show that Blue hydrogen will emit between 200-262MtCO2e of GHG emissions depending on the carbon capture rates achieved (39%–90%) Green hydrogen produced via electrolysis using 100% renewable electricity from offshore wind will emit 20MtCO2e and hydrogen produced via electrolysis powered by the National Grid will emit between 103-168MtCO2e depending of the success of its NetZero strategy. The ‘business-as-usual’ case of continuing to combust methane releases 250MtCO2e over the same lifetime. This study finds that Blue hydrogen at scale is not compatible with the Paris Agreement reduces energy security and will require a substantial GHG emissions investment which excludes it from being a ‘low carbon technology’ and should not be considered for any decarbonisation strategies going forward.

Blue hydrogen is gaining attention as an intermediate step toward achieving eco-friendly green hydrogen production. However the general blue hydrogen production requires an energy-intensive process for carbon capture and storage resulting in low process efficiency. Additionally the hydrogen production processes steam methane reforming (SMR) and electrolysis emits waste heat and byproduct oxygen respectively. To solve these problems this study proposes an oxy-fuel combustion-based blue hydrogen production process that integrates fossil fuel-based hydrogen production and electrolysis processes. The proposed processes are SMR + SOEC and SMR + PEMEC whereas SMR solid oxide electrolysis cell (SOEC) and proton exchange membrane electrolysis cell (PEMEC) are also examined for comparison. In the proposed processes the oxygen produced by the electrolyzer is utilized for oxy-fuel combustion in the SMR process and the resulting flue gas containing CO2 and H2O is condensed to easily separate CO2. Additionally the waste heat from the SMR process is recovered to heat the feed water for the electrolyzer thereby maximizing the process efficiency. Techno-economic sensitivity and greenhouse gas (GHG) analyses were conducted to evaluate the efficiency and feasibility of the proposed processes. The results show that SMR + SOEC demonstrated the highest thermal efficiency (85.2%) and exergy efficiency (80.5%) exceeding the efficiency of the SMR process (78.4% and 70.4% for thermal and exergy efficiencies respectively). Furthermore the SMR + SOEC process showed the lowest levelized cost of hydrogen of 6.21 USD/kgH2. Lastly the SMR + SOEC demonstrated the lowest life cycle GHG emissions. In conclusion the proposed SMR + SOEC process is expected to be a suitable technology for the transition from gray to green hydrogen.

Hydrogen production from sunlight using innovative photocatalytic and photoelectrochemical systems offers decentralized sustainable energy solutions with potential applications in remote off-grid locations.<br/>Photocatalytic hydrogen production has the potential to transform clean cooking by reducing dependency on wood and charcoal in low-resource settings addressing significant health and environmental challenges.<br/>Photocatalytic reactors could also be used to capture atmospheric carbon dioxide and perform artificial photosynthesis mimicking processes found in nature producing green energy molecules.

Rural mini-grids in Ghana often experience substantial midday solar PV generation surpluses due to mismatches between peak production and local demand with excess energy (redundant energy) frequently curtailed once batteries are fully charged. This underutilisation limits the socio-economic benefits of renewable electrification and highlights the need for alternative long-duration storage solutions. This study investigated the technoeconomic feasibility of converting excess PV energy from a 54 kWp mini-grid in Aglakope Ghana into hydrogen via electrolysis storing it and reconverting it to electricity using fuel cells. Redundant energy generation was quantified using measured PV output and load consumption and validated using statistical error metrics (R2 = 0.955). Hydrogen production and recovery potential were modelled for different electrolyser technologies and system performance was evaluated using round-trip efficiency (RTE) levelized cost of hydrogen (LCOH) and levelized cost of storage (LCOS) with comparative analysis against additional battery capacity. The results yielded an average monthly excess energy of about 2250 kWh convertible into 43–53 kg per month of hydrogen depending on electrolyser type. The proposed hydrogen-fuel cell pathway yielded a RTE of 44.4 % LCOH of $4.97/kg and LCOS of $0.249/kWh which is about 13 % higher than lithium-ion storage benchmarks. The study findings demonstrate that hydrogen storage can complement batteries offer seasonal and multi-day storage capability and reduce renewable curtailment. Therefore wider adoption could be supported by cost reductions efficiency improvements and enabling policies positioning hydrogen-based storage as a viable pathway for resilient low-carbon rural electrification in off-grid contexts.

Hydrogen produced from renewable sources is crucial for decarbonizing hard-to-abate sectors and achieving netzero targets. This study examines hydrogen production through the novel thermo-catalytic reforming (TCR) process using agricultural and forestry residues. The research aims to develop and optimize regression models that integrate feedstock properties (ash hydrogen-to-carbon molar ratio and lignin) and process parameters (reactor and reformer temperatures) to predict yields of hydrogen (H2) syngas methane (CH4) and carbon dioxide (CO2). Three biomass feedstocks – softwood pellets (SWPs) hardwood pellets (HWPs) and wheat straw pellets (WSPs) – were analyzed at reactor temperatures of 400–550 ◦C and reformer temperatures of 500–700 ◦C. Predictive models for H2 (R2 = 0.9642 RMSE = 1.0639) and syngas (R2 = 0.9894 RMSE = 0.0140) yields show strong agreement and accuracy between the predicted and experimental values. In contrast the models for CH4 and CO2 yields show higher variability in the predictions. Reformer temperature was the most significant parameter influencing the yields of H2 and syngas. The optimal H2 yields predicted for the model were obtained for HWPs at 550/700 ◦C (26.67 g H2/kg dry biomass) followed by SWPs at 550/700 ◦C (24.11 g H2/kg dry biomass) and WSPs at 550/685.2 ◦C (18.78 g H2/kg dry biomass). The volumetric syngas yields were highest for HWPs at 550/700 ◦C (0.831 Nm3 /kg dry biomass) followed by SWPs (0.777 Nm3 /kg dry biomass) and WSPs (0.634 Nm3 /kg dry biomass). This study demonstrates that regression modelling accurately predicts H2 and syngas yields which would help to expand the applicability of TCR technology for large-scale hydrogen production contributing to the decarbonization of the energy sector.

Sunlight-driven water splitting allows renewable hydrogen to be produced from abundant and environmentally benign water. Large-scale societal implementation of this green fuel production technology within energy generation systems is essential for the establishment of sustainable future societies. Among various technologies photocatalytic water splitting using particulate semiconductors has attracted increasing attention as a method to produce large amounts of green fuels at low cost. The key to making this technology practical is the development of photocatalysts capable of splitting water with high solar-to-fuel energy conversion efficiency. Furthermore advances that enable the deployment of water-splitting photocatalysts over large areas are necessary as is the ability to recover hydrogen safely and efficiently from the produced oxyhydrogen gas. This lead article describes the key discoveries and recent research trends in photosynthesis using particulate semiconductors and photocatalyst sheets for overall water splitting via one-step excitation and two-step excitation (Z-scheme reactions) as well as for direct conversion of carbon dioxide into renewable fuels using water as an electron donor. We describe the latest advances in solar watersplitting and carbon dioxide reduction systems and pathways to improve their future performance together with challenges and solutions in their practical application and scalability including the fixation of particulate photocatalysts hydrogen recovery safety design of reactor systems and approaches to separately generate hydrogen and oxygen from water.

This study engineered seabed sediment with microwave-assisted Ni2+ -substitution to enhance its composition and properties. The catalytic activity of microwave-assisted Ni2+ - substituted seabed sediment (Mwx%Ni-SB) was investigated in the two-stage pyrolysis of plastic waste for hydrogen production. The characterization reveals microwave irradiation synergistically modifies the physical properties (increasing functional groups reducing crystallinity) and electronic properties (modulating bandgap energy increasing electron density) of the Mwx%Ni-SB thereby improving methane reforming performance. Microwave treatment compresses and rearranges Ni2+ ions within the sediment lattice resulting in increased order and density and creating defects that enhance catalytic activity. GC-TCD analysis demonstrates that the use of catalysts in the first and second stages more than doubled hydrogen production (109.74%) compared to not using catalysts. Therefore increased Ni2+ substitution significantly reduced methane production by 49.04% while simultaneously boosting hydrogen production by 23.00%.

Microbial electrolysis cells (MECs) have garnered significant attention as a promising solution for industrial wastewater treatment enabling the simultaneous degradation of organic compounds and biohydrogen production. Developing efficient and cost-effective cathodes to drive the hydrogen evolution reaction is central to the success of MECs as a sustainable technology. While numerous lab-scale experiments have been conducted to investigate different cathode materials the transition to pilot-scale applications remains limited leaving the actual performance of these scaled-up cathodes largely unknown. In this study nickel-foam and stainless-steel wool cathodes were employed as catalysts to critically assess hydrogen production in a 150 L MEC pilot plant treating sugar-based industrial wastewater. Continuous hydrogen production was achieved in the reactor for more than 80 days with a maximum COD removal efficiency of 40 %. Nickel-foam cathodes significantly enhanced hydrogen production and energy efficiency at non-limiting substrate concentration yielding the maximum hydrogen production ever reported at pilot-scale (19.07 ± 0.46 L H2 m− 2 d− 1 and 0.21 ± 0.01 m3 m− 3 d− 1 ). This is a 3.0-fold improve in hydrogen production compared to the previous stainless-steel wool cathode. On the other hand the higher price of Ni-foam compared to stainless-steel should also be considered which may constrain its use in real applications. By carefully analysing the energy balance of the system this study demonstrates that MECs have the potential to be net energy producers in addition to effectively oxidize organic matter in wastewater. While higher applied potentials led to increased energy requirements they also resulted in enhanced hydrogen production. For our system a conservative applied potential range from 0.9 to 1.0 V was found to be optimal. Finally the microbial community established on the anode was found to be a syntrophic consortium of exoelectrogenic and fermentative bacteria predominantly Geobacter and Bacteroides which appeared to be well-suited to transform complex organic matter into hydrogen.

Excessive reliance on traditional energy sources such as coal petroleum and gas leads to a decrease in natural resources and contributes to global warming. Consequently the adoption of renewable energy sources in power systems is experiencing swift expansion worldwide especially in offshore areas. Floating solar photovoltaic (FPV) technology is gaining recognition as an innovative renewable energy option presenting benefits like minimized land requirements improved cooling effects and possible collaborations with hydropower. This study aims to assess the levelized cost of electricity (LCOE) associated with floating solar initiatives in offshore and onshore environments. Furthermore the LCOE is assessed for initiatives that utilize floating solar PV modules within aquaculture farms as well as for the integration of various renewable energy sources including wind wave and hydropower. The LCOE for FPV technology exhibits considerable variation ranging from 28.47 EUR/MWh to 1737 EUR/MWh depending on the technologies utilized within the farm as well as its geographical setting. The implementation of FPV technology in aquaculture farms revealed a notable increase in the LCOE ranging from 138.74 EUR/MWh to 2306 EUR/MWh. Implementation involving additional renewable energy sources results in a reduction in the LCOE ranging from 3.6 EUR/MWh to 315.33 EUR/MWh. The integration of floating photovoltaic (FPV) systems into green hydrogen production represents an emerging direction that is relatively little explored but has high potential in reducing costs. The conversion of this energy into hydrogen involves high final costs with the LCOH ranging from 1.06 EUR/kg to over 26.79 EUR/kg depending on the complexity of the system.

This study presents a scientometric analysis of renewable energy applications in low-temperature regions focusing on green hydrogen production carbon storage and emerging trends. Using bibliometric tools such as RStudio and VOSviewer the research evaluates publication trends from 1988 to 2024 revealing an exponential growth in renewable energy studies post-2021 driven by global policies promoting carbon neutrality. Life cycle assessment (LCA) plays a crucial role in evaluating the environmental impact of energy systems underscoring the need to integrate renewable sources for emission reduction. Hydrogen production via electrolysis has emerged as a key solution in decarbonizing hardto-abate sectors while carbon storage technologies such as bioenergy with carbon capture and storage (BECCS) are gaining traction. Government policies including carbon taxes fossil fuel phase-out strategies and renewable energy subsidies significantly shape the energy transition in cold regions by incentivizing low-carbon alternatives. Multi-objective optimization techniques leveraging artificial intelligence (AI) and machine learning are expected to enhance decision-making processes optimizing energy efficiency reliability and economic feasibility in renewable energy systems. Future research must address three critical challenges: (1) strengthening policy frameworks and financial incentives for largescale renewable energy deployment (2) advancing energy storage hydrogen production and hybrid energy systems and (3) integrating multi-objective optimization approaches to enhance cost-effectiveness and resilience in extreme climates. It is expected that the research will contribute to the field of knowledge regarding renewable energy applications in low-temperature regions.

In the introduction to this article a brief overview of the generated energy and the power produced by the photovoltaic systems with a peak power of 3 MWp and different tilt and orientation of the photovoltaic panels is given. The characteristics of the latest systems generating energy by wind turbines with a capacity of 3.45 MW are also presented. In the subsequent stages of the research the necessity of balancing the energy in power networks powered by a mix of renewable energy sources is demonstrated. Then a calculation algorithm is presented in the area of balancing the energy system powered by a photovoltaic–wind energy mix and feeding the low-emission hydrogen production process. It is analytically and graphically demonstrated that the process of balancing the entire system can be influenced by structural changes in the installation of the photovoltaic panels. It is proven that the tilt angle and orientation of the panels have a significant impact on the level of power generated by the photovoltaic system and thus on the energy mix in individual hourly intervals. Research has demonstrated that the implementation of planned design changes in the assembly of panels in a photovoltaic system allows for a reduction in the size of the energy storage system by more than 2 MWh. The authors apply actual measurement data from a specific geographical context i.e. from the Lublin region in Poland. The calculations use both traditional statistical methods and probabilistic analysis. Balancing the generated power and the energy produced for the entire month considered in hourly intervals throughout the day is the essence of the calculations made by the authors.

A pivotal ambition to aid global decarbonisation efforts is green electrolytic hydrogen produced with renewable energy. Prolonged operation of water electrolysers induces cell degradation decreasing production efficiency and gas yield over the lifespan of the electrolyser stack. Considerations for degradation modelling is seen to a varying extent in previous literature. This work shows the effects of including degradation modelling within existing system scenarios and new ones to demonstrate the impact of inclusion on key techno-economic parameters. A fundamental Anion Exchange Membrane electrolyser model is constructed validated and utilised into a broader hydrogen and oxygen co-production system powered by solar-PV. A second scenario tests the compatibility of the no-degradation trend with reference material and then investigates the effects of including degradation modelling showing only a 1.47% increase in levelised cost of hydrogen (LCOH). Subsequent scenarios include determining that byproduct oxygen utilisation becomes beneficial for a scenario with rated electrolyser power of above 35 MW and the observations related to stack replacement strategies are discussed. Under hypothetically higher degradation rates detriment to gas yield and LCOH is around 5% for average operational degradation rates of 15–20 μV/hr and around 10% for 30–40 μV/hr compared to around 2% for the model baseline average rate of 5.23–5.26 μV/hr.

The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction comparing its performance with other reactors including packed bed membrane reactors (PBMR) fluidized bed reactors (FBR) and packed bed reactors (PBR). For this purpose a two-dimensional axisymmetric numerical model was developed using computational fluid dynamics (CFD) to simulate the reactor performances. Model accuracy was validated by comparing the simulation results for PBMR and PB with experimental data showing an accurate agreement within them. The model was then employed to examine the effects of key operating parameters including reaction temperature pressure steam-to-methanol molar ratio and gas volumetric space velocity on reactor performance in terms of methanol conversion hydrogen yield hydrogen recovery and selectivity. At 573 K 1 bar a feed molar ratio of 3/1 and a space velocity of 9000 h−1 the PBMR reached the best results in terms of methanol conversion hydrogen yield hydrogen recovery and hydrogen selectivity such as 67.6% 69.5% 14.9% and 97.1% respectively. On the other hand the FBMR demonstrated superior performance with respect to the latter reaching a methanol conversion of 98.3% hydrogen yield of 95.8% hydrogen recovery of 74.5% and hydrogen selectivity of 97.4%. These findings indicate that the FBMR offers significantly better performance than the other reactor types studied in this work making it a highly efficient method for hydrogen production through methanol steam reforming and a promising pathway for clean energy generation.

The biological production of hydrogen offers a renewable and potentially sustainable alternative for clean energy generation. In Northeast Brazil depleted oil reservoirs (DORs) present a unique opportunity to integrate biotechnology with existing fossil fuel infrastructure. These subsurface formations rich in residual hydrocarbons (RH) and native H2 producing microbiota can be repurposed as bioreactors for hydrogen production. This process often referred to as “Gold Hydrogen” involves the in situ microbial conversion of RH into H2 typically via dark fermentation and is distinct from green blue or grey hydrogen due to its reliance on indigenous subsurface biota and RH. Strategies include nutrient modulation and chemical additives to stimulate native hydrogenogenic genera (Clostridium Petrotoga Thermotoga) or the injection of improved inocula. While this approach has potential environmental benefits such as integrated CO2 sequestration and minimized surface disturbance it also presents risks namely the production of CO2 and H2S and fracturing which require strict monitoring and mitigation. Although infrastructure reuse reduces capital expenditures achieving economic viability depends on overcoming significant technical operational and biotechnological challenges. If widely applied this model could help decarbonize the energy sector repurpose legacy infrastructure and support the global transition toward low-carbon technologies.

This review article provides a comprehensive overview of the pivotal role that nanomaterials particularly graphene and its derivatives play in advancing hydrogen energy technologies with a focus on storage production and transport. As the quest for sustainable energy solutions intensifies the use of nanoscale materials to store hydrogen in solid form emerges as a promising strategy toward mitigate challenges related to traditional storage methods. We begin by summarizing standard methods for producing modified graphene derivatives at the nanoscale and their impact on structural characteristics and properties. The article highlights recent advancements in hydrogen storage capacities achieved through innovative nanocomposite architectures for example multi-level porous graphene structures containing embedded nickel particles at nanoscale dimensions. The discussion covers the distinctive characteristics of these nanomaterials particularly their expansive surface area and the hydrogen spillover effect which enhance their effectiveness in energy storage applications including supercapacitors and batteries. In addition to storage capabilities this review explores the role of nanomaterials as efficient catalysts in the hydrogen evolution reaction (HER) emphasizing the potential of metal oxides and other composites to boost hydrogen production. The integration of nanomaterials in hydrogen transport systems is also examined showcasing innovations that enhance safety and efficiency. As we move toward a hydrogen economy the review underscores the urgent need for continued research aimed at optimizing existing materials and developing novel nanostructured systems. Addressing the primary challenges and potential future directions this article aims to serve as a roadmap to enable scientists and industry experts to maximize the capabilities of nanomaterials for transforming hydrogen-based energy systems thus contributing significantly to global sustainability efforts.

Due to concerns regarding fossil greenhouse gas emissions biogenic material such as forest residues is viewed nowadays as a valuable source of carbon atoms to produce syngas that can be used to synthesise biofuels such as methanol. A great challenge in using gasified biomass for methanol production is the large excess of carbon in the syngas as compared to the H2 content. The water–gas shift (WGS) reaction is often used to add H2 and balance the syngas. CO2 is also produced by this reaction. Some of the CO2 has to be removed from the gaseous mixture thus decreasing the process carbon yield and maintaining CO2 emissions. The WGS reaction also decreases the overall process heat output. This paper demonstrates the usefulness of using an extra source of renewable H2 from steam electrolysis instead of relying on the WGS reaction for a much higher performance of syngas production from gasification of wood in a simple system with a fixed-bed gasifier. A commercial process simulation software is employed to predict that this approach will be more efficient (overall energy efficiency of about 67%) and productive (carbon conversion yield of about 75%) than relying on the WGS reaction. The outlook for this process that includes the use of the solid oxide electrolyser technology appears to be very promising because the electrolyser has the dual function of providing all of the supplemental H2 required for syngas balancing and all the O2 required for the production of a suitable hot raw syngas. This process is conducive to biomethanol production in dispersed small plants using local biomass for end-users from the same geographical area thus contributing to regional sustainability.

Renewable energy-based water electrolysis for hydrogen production is an effective pathway to achieve green energy transition. However the intermittency and randomness of renewable energy pose numerous challenges to the safe and stable operation of hydrogen production systems with the wide power fluctuation adaptability and economic efficiency of electrolyzers being prominent issues. Hybrid electrolyzers combine the operational characteristics of proton exchange membrane (PEM) and alkaline electrolyzers leveraging the advantages of both to improve adaptability to wide power fluctuations and economic efficiency thereby enhancing the overall system efficiency. To ensure coordinated operation of hybrid electrolyzers it is essential to consider their startstop characteristics and the impact of hydrogen to oxygen (HTO) concentration on the hydrogen production system. To achieve this we first discuss the operating characteristics of both types of electrolyzers and the in fluence of system parameters on HTO concentration. A control scheme for hybrid electrolyzer systems consid ering HTO content is proposed. By analyzing the electrolyzer efficiency curve the optimal efficiency point under low power operation is identified enabling the electrolyzers to operate at this optimal efficiency thus enhancing the efficiency of the hybrid electrolyzer system. The implementation of a dual-layer rotation control strategy effectively balances the lifecycle loss of the electrolyzers. Additionally reducing the pressure during startup broadens the startup range of the hybrid electrolyzer.

The integration of water electrolyzers and photovoltaic (PV) solar technology is a potential development in renewable energy systems offering new avenues for sustainable energy generation and storage. This coupling consists of using PV-generated electricity to power water electrolysis breaking down water molecules into hydrogen and oxygen. While oxygen is a useful byproduct the created hydrogen is used as a clean storable energy carrier or feedstock for numerous businesses. It is possible to operate the device with or without battery storage. When solar energy is combined with batteries excess solar energy may be stored for later use maximizing energy efficiency and guaranteeing a steady supply of electricity even in the absence of direct sunlight. On the other hand battery-free systems depend on the electrolyzer’s continuous power generation to convert solar energy into hydrogen during the day. In addition to allowing for the production of renewable hydrogenthis hybrid PV-solar and water electrolyzer setup contributes to grid stability by offering demand-side flexibility. Moreover the modularity of these systems enables scalability to meet diverse energy requirements spanning from residential to industrial applications thereby fostering a cleaner and more sustainable energy landscape. This review delves into various topologies for PV-driven electrolysis and conducts a thorough exploration of the dynamics of low-temperature water electrolyzers. Specifically it examines their integration with three primary technologies: Proton Exchange Membrane Alkaline and Anion Exchange Membrane shedding light on their implications for the broader integration landscape. Through detailed analysis and insights this study enriches the understanding of the potential and challenges inherent in the convergence of PV solar water electrolysis and renewable energy systems.

The commercialization of hydrogen as a fuel faces severe technological economic and environmental challenges. As a method to overcome these challenges microalgal biohydrogen production has become the subject of growing research interest. Microalgal biohydrogen can be produced through different metabolic routes the economic considerations of which are largely missing from recent reviews. Thus this review briefly explains the techniques and economics associated with enhancing microalgae-based biohydrogen production. The cost of producing biohydrogen has been estimated to be between $10 GJ-1 and $20 GJ−1 which is not competitive with gasoline ($0.33 GJ−1 ). Even though direct biophotolysis has a sunlight conversion efficiency of over 80% its productivity is sensitive to oxygen and sunlight availability. While the electrochemical processes produce the highest biohydrogen (>90%) fermentation and photobiological processes are more environmentally sustainable. Studies have revealed that the cost of producing biohydrogen is quite high ranging between $2.13 kg−1 and 7.24 kg−1 via direct biophotolysis $1.42kg−1 through indirect biophotolysis and between $7.54 kg−1 and 7.61 kg−1 via fermentation. Therefore low-cost hydrogen production technologies need to be developed to ensure long-term sustainability which requires the optimization of critical experimental parameters microalgal metabolic engineering and genetic modification.

Meeting climate targets requires profound transformations in the energy system. Most energy uses should be electrified but where this is not feasible hydrogen can be part of the solution. However 98% of global hydrogen production involves greenhouse gas emissions with an average of 12 kg CO2e/kg H2. Therefore new hydrogen production pathways are needed in order to make hydrogen production compatible with climate targets. In this work we fill this gap by systematically comparing the energy and emissions intensity of 173 hydrogen production pathways suitable for the UK. Scenarios include onshore and offshore pathways and the use of repurposed infrastructure. Unlike fossil-fuel based pathways the results show that electrolytic hydrogen powered by fixed offshore wind could align with proposed emissions standards either onshore or offshore. However the embodied and fugitive emissions are important to consider for electrolytic pathways as they result in 10–50% of the total emissions intensity.

Seawater electrolysis represents a promising green energy technology with significant potential for efficient energy conversion. This study provides an in-depth examination of the key scientific challenges inherent in the seawater-electrolysis process and their potential solutions. Initially it analyzes the potential issues of precipitation and aggregation at the cathode during hydrogen evolution proposing strategies such as self-cleaning cathodes and precipitate removal to ensure cathode stability in seawater electrolysis. Subsequently it addresses the corrosion challenges faced by anode catalysts in seawater introducing several anti-corrosion strategies to enhance anode stability including substrate treatments such as sulfidation phosphidation selenidation and LDH (layered double hydroxide) anion intercalation. Additionally this study explores the role of regulating the electrode surface microenvironment and forming unique coordination environments for active atoms to enhance seawater electrolysis performance. Regulating the surface microenvironment provides a novel approach to mitigating seawater corrosion. Contrary to the traditional understanding that chloride ions accelerate anode corrosion certain catalysts benefit from the unique coordination environment of chloride ions on the catalyst surface potentially enhancing oxygen evolution reaction (OER) performance. Lastly this study presents the latest advancements in the industrialization of seawater electrolysis including the in situ electrolysis of undiluted seawater and the implementation of three-chamber dual anion membranes coupled with circulating electrolyte systems. The prospects of seawater electrolysis are also explored.

While fossil fuels continue to be used and to increase air pollution across the world hydrogen gas has been proposed as an alternative energy source and a carrier for the future by scientists. Water electrolysis is a renewable and sustainable chemical energy production method among other hydrogen production methods. Hydrogen production via water electrolysis is a popular and expensive method that meets the high energy requirements of most industrial electrolyzers. Scientists are investigating how to reduce the price of water electrolytes with different methods and materials. The electrolysis structure equations and thermodynamics are first explored in this paper. Water electrolysis systems are mainly classified as high- and low-temperature electrolysis systems. Alkaline PEM-type and solid oxide electrolyzers are well known today. These electrolyzer materials for electrode types electrolyte solutions and membrane systems are investigated in this research. This research aims to shed light on the water electrolysis process and materials developments.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper recent developments in R&D on waste gasification (municipal solid waste tires plastic waste) are summarised and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However regulations like frame conditions or subsidies are necessary to bring the technology into the market.