Production & Supply Chain

An exemplary techno-economic and environmental assessment of carbon-negative hydrogen (H2) production is carried out in this work. It is based on the so-called “dark photosynthesis” with carbon dioxide (CO2) capture and geological storage. As a special feature of the assessment the economic consequences due to the impact on the global climate are taken into account. The results indicate that the example project would be capable of generating negative GHG emissions under the assumptions made. The amount is estimated to be 17.72 kgCO2 to be removed from the atmosphere per kilogram of H2 produced. The levelized costs of carbon-negative hydrogen are obtained considering the economic impact of greenhouse gas emissions and removals. They are estimated to be 0.013 EUR/kWhH2. Compared to grey hydrogen from natural gas (0.12 EUR/kWhH2) and green hydrogen from electrolysis using renewable electricity (0.18 EUR/kWhH2) this shows a potential environmental-economic advantage of the considered example. Even without internalization of GHG impacts an economic advantage of the project (0.12 EUR/kWhH2) over green hydrogen (0.17 EUR/kWhH2) is indicated. Compared to other NETs the GHG removal efficiency is at the lower end of both BECCS and DACCS approaches.

As the commercialisation of two contrasting solar-powered water splitting devices with lower TRLs of proton exchange membrane (PEM) electrolyser systems and photoelectrochemical (PEC) systems gains momentum the path towards a sustainable H2 economy is taking shape. Ongoing pilot projects and demonstration plants are proving the feasibility and potential of these technologies in real-world applications. However to ensure their success we must confront the critical challenges of cost reduction and efficiency enhancement making green H2 economically competitive with traditional production methods. To achieve this a collaborative effort among academia industry and policymakers is paramount. This comprehensive review begins by examining traditional water electrolysis methods focusing on the production of green H2 through electrochemical splitting. It delves into crucial components and advancements in the PEM systems addressing challenges related to catalysts membranes gas diffusion layers and bipolar plates. The review also explores solar-driven PEC water splitting emphasizing the significance of efficient photoelectrodes and reactor design. Additionally it discusses the integration of photovoltaic cells with electrochemical or PEC systems for higher H2 yield. Commercialisation is underway and this endeavour necessitates a collaborative approach with active involvement from academia industry and policymakers. This collective effort not only propels us towards greener and more sustainable energy solutions but also represents a transformative step in the global journey towards a sustainable and environmentally conscious economy.

Hydrogen produced from electrolysis is an attractive carbon-free fuel and feedstock but potential benefits depend on the carbon intensity of electricity production. This study uses technoeconomic modeling to analyze the benefits of producing zero-carbon hydrogen through dynamically operated polymer electrolyte membrane electrolyzers connected to photovoltaic and wind variable renewable energy (VRE) sources. Dynamic operation is considered for current densities between 0 and 6 A cm2 and compared to a constant current density of 2 A cm2 for different combinations of VRE to electrolysis (VRE:E) capacity ratios and compositions of photovoltaic and wind energy in four locations across the United States. For optimal VRE:E and wind:photovoltaic capacity ratios dynamic operation is found to reduce the levelized cost of hydrogen by 5%–9% while increasing hydrogen production by 134%–173% and decreasing excess electrical power by 82%–95%. The framework herein may be used to determine the optimal VRE:E capacity and VRE mix for dynamically operated green hydrogen systems.

Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however it emits an enormous amount of CO2. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53% producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO2-free turquoise hydrogen. In practice methane pyrolysis reduces CO2 emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO2 energy source.

Hydrogen is an attractive clean sustainable energy source primarily produced via industry. At present most reviews on hydrogen mainly focus on the preparation and storage of hydrogen while the development and utilization of natural hydrogen will greatly reduce its cost. Natural hydrogen has been discovered in many geological environments. Therefore based on extensive literature research in this study the distribution and sources of natural hydrogen were systematically sorted and the identification method and occurrence state of natural hydrogen were examined and summarized. The results of this research show that hydrogen has been discovered in oceanic spreading centers transform faults passive margins convergent margins and intraplate settings. The primary sources of the hydrogen include alterations in Fe(II)-containing rocks the radiolysis of water degassed magma and the reaction of water- and silica-containing rocks during the mechanical fracturing. Hydrogen can appear in free gas it can be adsorbed and trapped in inclusions. Currently natural hydrogen exploration is in its infancy. This systematic review helps to understand the origin distribution and occurrence pattern of natural hydrogen. In addition it facilitates the exploration and development of natural hydrogen deposits thus enabling the production of low-cost hydrogen.

The Brazilian energy grid is considered as one of the cleanest in the world because it is composed of more than 80% of renewable energy sources. This work aimed to apply the levelized costs (LCOH) and environmental cost accounting techniques to demonstrate the feasibility of producing hydrogen (H2 ) by alkaline electrolysis powered by the Brazilian energy grid. A project of hydrogen production with a lifetime of 20 years had been evaluated by economical and sensitivity analysis. The production capacity (8.89 to 46.67 kg H2/h) production volume (25 to 100%) hydrogen sale price (1 to 5 USD/kg H2 ) and the MAR rate were varied. Results showed that at 2 USD/kg H2 all H2 production plant sizes are economically viable. On this condition a payback of fewer than 4 years an IRR greater than 31 a break-even point between 56 and 68% of the production volume and a ROI above 400% were found. The sensitivity analysis showed that the best economic condition was found at 35.56 kg H2/h of the plant size which generated a net present value of USD 10.4 million. The cost of hydrogen varied between 1.26 and 1.64 USD/kg and a LCOH of 37.76 to 48.71 USD/MWh. LCA analysis showed that the hydrogen production project mitigated from 26 to 131 thousand tons of CO2 under the conditions studied.

In the sustainability context the performance of energy-producing technologies using different energy sources needs to be scored and compared. The selective criterion of a higher level of useful energy to feed an ever-increasing demand of energy to satisfy a wide range of endo- and exosomatic human needs seems adequate. In fact surplus energy is able to cover energy services only after compensating for the energy expenses incurred to build and to run the technology itself. This paper proposes an energy sustainability analysis (ESA) methodology based on the internal and external energy use of a given technology considering the entire energy trajectory from energy sources to useful energy. ESA analysis is conducted at two levels: (i) short-term by the use of the energy sustainability index (ESI) which is the first step to establish whether the energy produced is able to cover the direct energy expenses needed to run the technology and (ii) long-term by which all the indirect energy-quotas are considered i.e. all the additional energy requirements of the technology including the energy amortization quota necessary for the replacement of the technology at the end of its operative life. The long-term level of analysis is conducted by the evaluation of two indicators: the energy return per unit of energy invested (EROI) over the operative life and the energy payback-time (EPT) as the minimum lapse at which all energy expenditures for the production of materials and their construction can be repaid to society. The ESA methodology has been applied to the case study of H2 production at small-scale (10–15 kWH2) comparing three different technologies: (i) steam-methane reforming (SMR) (ii) solar-powered water electrolysis (SPWE) and (iii) two-stage anaerobic digestion (TSAD) in order to score the technologies from an energy sustainability perspective.

The aim of this study is to investigate the technical and economic potential of electricity and hydrogen production in Casablanca Morocco. For this reason we simulated the performance of a 4.2 MWp wind turbine if installed in Casablanca. The results show that the electricity and hydrogen production varies greatly through the year due to the high fluctuation in wind speed. The annual electricity and hydrogen production is 29.16 GWh and 555 Tons respectively. As for the levelized cost of production the LCOE was found to be 0.24 $/kWh and the H2 LCO were equal to 13.52 $/Kg.

Alkaline electrolyzers are the most widespread technology due to their maturity low cost and large capacity in generating hydrogen. However compared to proton exchange membrane (PEM) electrolyzers they request the use of potassium hydroxide (KOH) or sodium hydroxide (NaOH) since the electrolyte relies on a liquid solution. For this reason the performances of alkaline electrolyzers are governed by the electrolyte concentration and operating temperature. Due to the growing development of the water electrolysis process based on alkaline electrolyzers to generate green hydrogen from renewable energy sources the main purpose of this paper is to carry out a comprehensive survey on alkaline electrolyzers and more specifically about their electrical domain and specific electrolytic conductivity. Besides this survey will allow emphasizing the remaining key issues from the modeling point of view.

This study presents an enhancement to the Switch optimization model for hydrogen energy planning by integrating the capability to consider the construction and operation of hydrogen electrolysis plants and the operation of water distribution systems. This integration was achieved through the addition of two new modules and their effectiveness is demonstrated through their application in a case study for Durham region. The study highlights the significance of incorporating water distribution systems into energy planning demonstrating how optimal locations for hydrogen plants can significantly influence water and power demand as well as alter the total operating costs. The enhanced Switch model showcases its improved capability to assist policymakers and stakeholders in transitioning towards a sustainable energy future.

Water electrolysis is the most promising method for efficient production of high purity hydrogen (and oxygen) while the required power input for the electrolysis process can be provided by renewable sources (e.g. solar or wind). The thus produced hydrogen can be used either directly as a fuel or as a reducing agent in chemical processes such as in Fischer–Tropsch synthesis. Water splitting can be realized both at low temperatures (typically below 100 °C) and at high temperatures (steam water electrolysis at 500– 1000 °C) while different ionic agents can be electrochemically transferred during the electrolysis process (OH− H+ O2− ). Singular requirements apply in each of the electrolysis technologies (alkaline polymer electrolyte membrane and solid oxide electrolysis) for ensuring high electrocatalytic activity and long-term stability. The aim of the present article is to provide a brief overview on the effect of the nature and structure of the catalyst–electrode materials on the electrolyzer’s performance. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The current trends limitations and perspectives for future developments are summarized for the diverse electrolysis technologies of water splitting while the case of CO2/H2O co-electrolysis (for synthesis gas production) is also discussed.

The necessity of energy solutions that are economically viable ecologically sustainable and environmentally friendly has become fundamental to economic and societal advancement of nations. In this context renewable energy sources emerge as the most vital component. Furthermore hydrogen generation systems based on renewable energies are increasingly recognized as the most crucial strategies to mitigate global warming. In the present study a comparative analysis is conducted from an exergy-economic perspective to find the most efficient configuration among three different systems for renewable-based power to hydrogen production. These renewable sources are wind turbine salinity gradient solar pond (SGSP) and ocean thermal energy conversion (OTEC). SGSP and OTEC are coupled with a hydrogen production unit by a trilateral cycle (TLC) to improve the temperature match of the heating process. The heat waste energy within these systems is recovered by a thermoelectric generator (TEG) and a proton exchange membrane electrolyzer (PEME) is used for hydrogen production. Under base case input conditions the net power input of PEME is estimated to be approximately 327.8 kW across all configurations. Additionally the 3E (energy exergy and exergy-economic) performance of the three systems is evaluated by a parametric study and design optimization. The results of the best performance analysis reveal that the best exergy efficiency is achievable with the wind-based system in the range of 5.8–10.47% and for average wind speed of 8–12 m/s. Correspondingly the most favorable total cost rate is attributed to the wind-based system at a wind speed of 8 m/s equating to 66.08 USD/h. Subsequently the unit cost of hydrogen for the SGSP-based system is estimated to be the most economical ranging from 42.78 to 44.31 USD/GJ.

Environmental concerns regarding greenhouse gases have spurred research into alternative energy sources. One of the most prevalent waste products in the beverage industry is spent coffee grains (SCG) an estimated 60 million tons globally each year. These quantities justify the need to find effective ways to recycle this waste through the adoption of closed-loop circular economies (CE) and sustainable biofuel strategies. One promising approach is the conversion of SCG into biofuels particularly biohydrogen and biomethane through biological processes. However prior to commercialization it is critical to validate its potential profitability via technical and economic analyses such as techno-economic assessment (TEA). To this end in this study the profitability of two scenarios for biohydrogen and biomethane production has been assessed to explore feasible processing routes for SCG valorization. First a two-step dark fermentation and anaerobic digestion (DF-AD) process and second a two-step dark fermentation and photo fermentation (DF-PF) process. The profitability and sensitivity analysis results clarified that Scenario I should be chosen over Scenario II due to its higher net present value (NPV) of 138 million $ internal rate of return (IRR) of 15.3 % gross margin (GM) of 56.9 % return on investment (ROI) of 12.7 % and shorter payback period (PBP) of 6.2 years.

This study describes the optimization of a modelling process concerning biogas’ use to generate green hydrogen and electrical power. The Aspen Plus simulation tool is used to model the procedure and the approach employed to limit the emissions of gas from the hydrogen production process will be the CO2 capture method. This technique uses slack lime (Ca(OH)2) to absorb CO2 capture since it is readily available. The study analyzes many critical parameters in the process including the temperature and pressure in the steam reforming (SR) and the water gas shift (WGS) reactions along with the steam to carbon ratio (S/C) to determine how the production of green hydrogen and electrical power will be influenced. Electricity generation is achieved by taking the residual water from the SR WGS carbonation reactions and converting it to the vapour phase allowing the steam to pass through the turbine to generate electricity. To examine the effects of the synchronized critical parameters response surface methodology (RSM) was used thus allowing the optimal operational conditions to be determined in the form of an optimized zone for operation. The result of parameter optimization gave the maximum green hydrogen production of 211.46 kmol/hr and electric power production of 2311.68 kWh representing increases of 34.86% and 5.62% respectively when using 100 kmol/hr of biogas. In addition control structures were also built to control the reactors’ temperature in the dynamic section. The tuning parameters can control the SR and WGS system’s reactor to maintain the system in approximately 0.29 h and 0.32 h respectively.

The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3 upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.

Green hydrogen is considered to be one of the best candidates for fossil fuels in the near future. Bio-hydrogen production from the dark fermentation of organic materials including organic wastes is one of the most cost-effective and promising methods for hydrogen production. One of the main challenges posed by this method is the low production rate. Therefore optimizing the operating parameters such as the initial pH value operating temperature N/C ratio and organic concentration (xylose) plays a significant role in determining the hydrogen production rate. The experimental optimization of such parameters is complex expensive and lengthy. The present research used an experimental data asset adaptive network fuzzy inference system (ANFIS) modeling and particle swarm optimization to model and optimize hydrogen production. The coupling between ANFIS and PSO demonstrated a robust effect which was evident through the improvement in the hydrogen production based on the four input parameters. The results were compared with the experimental and RSM optimization models. The proposed method demonstrated an increase in the biohydrogen production of 100 mL/L compared to the experimental results and a 200 mL/L increase compared to the results obtained using ANOVA.

Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products such as off-gases currently used for the internal production of heat steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy namely polymer electrolyte membrane electrolysis solid oxide electrolyze cell electrolysis and biomass gasification. Aspen Plus® V11-based models were developed and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed

The depletion of fossil fuel reserves has resulted from their application in the industrial and energy sectors. As a result substantial efforts have been dedicated to fostering the shift from fossil fuels to renewable energy sources via technological advancements in industrial processes. Microalgae can be used to produce biofuels such as biodiesel hydrogen and bioethanol. Microalgae are particularly suitable for hydrogen production due to their rapid growth rate ability to thrive in diverse habitats ability to resolve conflicts between fuel and food pro duction and capacity to capture and utilize atmospheric carbon dioxide. Therefore microalgae-based bio hydrogen production has attracted significant attention as a clean and sustainable fuel to achieve carbon neutrality and sustainability in nature. To this end the review paper emphasizes recent information related to microalgae-based biohydrogen production mechanisms of sustainable hydrogen production factors affecting biohydrogen production by microalgae bioreactor design and hydrogen production advanced strategies to improve efficiency of biohydrogen production by microalgae along with bottlenecks and perspectives to over come the challenges. This review aims to collate advances and new knowledge emerged in recent years for microalgae-based biohydrogen production and promote the adoption of biohydrogen as an alternative to con ventional hydrocarbon biofuels thereby expediting the carbon neutrality target that is most advantageous to the environment.

Apart from many limitations the usage of hydrogen in different day-to-day applications have been increasing drastically in recent years. However numerous techniques available to produce hydrogen electrolysis of water is one of the simplest and cost-effective hydrogen production techniques. In this method water is split into hydrogen and oxygen by using external electric current. In this research a novel hydrogen production system incorporated with Photovoltaic – Thermal (PVT) solar collector is developed. The influence of different parameters like solar collector tilt angle thermal collector design and type of heat transfer fluid on the performance of PVT system and hydrogen production system are also discussed. Finally thermal efficiency electrical efficiency and hydrogen production rate have been predicted by using the Adaptive Neuro-Fuzzy Inference System (ANFIS) technique. Based on this study results it can be inferred that the solar collector tilt angle plays a significant role to improve the performance of the electrical and thermal performance of PVT solar system and Hydrogen yield rate. On the other side the spiral-shaped thermal collector with water exhibited better end result than the other hydrogen production systems. The predicted results ANFIS techniques represent an excellent agreement with the experimental results. In consequence it is suggested that the developed ANFIS model can be adopted for further studies to predict the performance of the hydrogen production system.

This study assesses the competitiveness of producing green hydrogen (H2) in Saudi Arabia and Germany using a power-to-carrier (P2X) model in PLEXOS for 2030 and beyond. The target amount of H2 to be produced serves as the only exogenous input allowing the model which runs on an hourly temporal resolution to endogenously optimize the electrolyzer technology (alkaline proton exchange membrane or solid oxide electrolyzer cell) the capacity of the electrolyzer to be built and the optimal carbon-free energy mix. Results suggest the overall investment needs in Saudi Arabia are approximately 25% lower than those for wind-based hydrogen production in Germany with the best-case scenario to produce 0.213 Mt of green H2 costing a net present value of $6.20 billion in Saudi Arabia compared to $8.11 billion in Germany. The findings indicate that alkaline electrolyzers dominate the production process favored for their low cost despite the higher efficiencies of other electrolyzer types. Moreover the model opts to dump excess energy rather than construct battery storage. Based on 16 scenarios the study determines a levelized cost of hydrogen of 2.34–3.08 $/kg for Saudi Arabia compared with 3.06–3.69 $/kg in Germany. Subsequently a detailed sensitivity analysis considers various discount rates for both countries. It is concluded that even when considering shipment costs from Saudi Arabia to Germany (~1 $/kg) green H2 can still be competitively delivered from Saudi Arabia to Germany.

This paper explores the opportunities for and progress in establishing a social licence to operate (SLO) for CCS in industrial clusters in the UK focusing on the perspectives of key stakeholders. The evolution of narratives and networks relating to geographical clusters as niches for CCS in industrial decarbonisation is evaluated in relation to seven pillars supporting SLO. Evidence is drawn from a combination of cluster mapping documentary analysis and stakeholder interviews to identify the wider contexts underpinning industrial decarbonisation stakeholder networks interaction and communication critical narratives the conditions for establishing trust and confidence different scales of social licence and maintaining a SLO. The delivery of a sustainable industrial decarbonisation strategy will depend on multiple layers of social licence involving discourses at different scales and potentially for different systems (heat transport different industrial processes). Despite setbacks as a result of funding cancellations and changes to government policy the UK is positioned to be at the forefront of CCS deployment. While there is a high ambition and a strong narrative from government of the urgency to accelerate projects involving CCS clear coordinated strategy and funding frameworks are necessary to build confidence that UK policy is both compatible with net zero and economically viable.

Solar H2 production is considered as a potentially promising way to utilizesolar energy and tackle climate change stemming from the combustion of fossil fuels.Photocatalytic photoelectrochemical photovoltaic−electrochemical solar thermochem-ical photothermal catalytic and photobiological technologies are the most intensivelystudied routes for solar H2 production. In this Focus Review we provide a comprehensivereview of these technologies. After a brief introduction of the principles and mechanisms ofthese technologies the recent achievements in solar H2 production are summarized with aparticular focus on the high solar-to-H 2 (STH) conversion efficiency achieved by eachroute. We then comparatively analyze and evaluate these technologies based on the metricsof STH efficiency durability economic viability and environmental sustainability aimingto assess the commercial feasibility of these solar technologies compared with currentindustrial H 2 production processes. Finally the challenges and prospects of future researchon solar H2 production technologies are presented.

One of the emerging and environmentally friendly technologies is the photoelectrochemical generation of green hydrogen; however the cheap cost of production and the need for customizing photoelectrode properties are thought to be the main obstacles to the widespread adoption of this technology. The primary players in hydrogen production by photoelectrochemical (PEC) water splitting which is becoming more common on a worldwide basis are solar renewable energy and widely available metal oxide based PEC electrodes. This study attempts to prepare nanoparticulate and nanorod-arrayed films to better understand how nanomorphology can impact structural optical and PEC hydrogen production efficiency as well as electrode stability. Chemical bath deposition (CBD) and spray pyrolysis are used to create ZnO nanostructured photoelectrodes. Various characterization methods are used to investigate morphologies structures elemental analysis and optical characteristics. The crystallite size of the wurtzite hexagonal nanorod arrayed film was 100.8 nm for the (002) orientation while the crystallite size of nanoparticulate ZnO was 42.1 nm for the favored (101) orientation. The lowest dislocation values for (101) nanoparticulate orientation and (002) nanorod orientation are 5.6 × 10−4 and 1.0 × 10−4 dislocation/nm2 respectively. By changing the surface morphology from nanoparticulate to hexagonal nanorod arrangement the band gap is decreased to 2.99 eV. Under white and monochromatic light irradiation the PEC generation of H2 is investigated using the proposed photoelectrodes. The solar-to-hydrogen conversion rate of ZnO nanorod-arrayed electrodes was 3.72% and 3.12% respectively under 390 and 405 nm monochromatic light which is higher than previously reported values for other ZnO nanostructures. The output H2 generation rates for white light and 390 nm monochromatic illuminations were 28.43 and 26.11 mmol.h−1 cm−2 respectively. The nanorod-arrayed photoelectrode retains 96.6% of its original photocurrent after 10 reusability cycles compared to 87.4% for the nanoparticulate ZnO photoelectrode. The computation of conversion efficiencies H2 output rates Tafel slope and corrosion current as well as the application of low-cost design methods for the photoelectrodes show how the nanorod-arrayed morphology offers low-cost high-quality PEC performance and durability.

The production of synthetic fuels and chemicals from solar energy and abundant reagents offers a promising pathway to a sustainable fuel economy and chemical industry. For the production of hydrogen photoelectrochemical or integrated photovoltaic and electrolysis devices have demonstrated outstanding performance at the lab scale but there remains a lack of larger-scale on-sun demonstrations (>100 W). Here we present the successful scaling of a thermally integrated photoelectrochemical device—utilizing concentrated solar irradiation— to a kW-scale pilot plant capable of co-generation of hydrogen and heat. A solar-to-hydrogen device-level efficiency of greater than 20% at an H2 production rate of >2.0 kW (>0.8 g min−1) is achieved. A validated model-based optimization highlights the dominant energetic losses and predicts straightforward strategies to improve the system-level efficiency of >5.5% towards the device-level efficiency. We identify solutions to the key technological challenges control and operation strategies and discuss the future outlook of this emerging technology.

The use of green hydrogen as a high-energy fuel of the future may be an opportunity to balance the unstable energy system which still relies on renewable energy sources. This work is a comprehensive review of recent advancements in green hydrogen production. This review outlines the current energy consumption trends. It presents the tasks and challenges of the hydrogen economy towards green hydrogen including production purification transportation storage and conversion into electricity. This work presents the main types of water electrolyzers: alkaline electrolyzers proton exchange membrane electrolyzers solid oxide electrolyzers and anion exchange membrane electrolyzers. Despite the higher production costs of green hydrogen compared to grey hydrogen this review suggests that as renewable energy technologies become cheaper and more efficient the cost of green hydrogen is expected to decrease. The review highlights the need for cost-effective and efficient electrode materials for large-scale applications. It concludes by comparing the operating parameters and cost considerations of the different electrolyzer technologies. It sets targets for 2050 to improve the efficiency durability and scalability of electrolyzers. The review underscores the importance of ongoing research and development to address the limitations of current electrolyzer technology and to make green hydrogen production more competitive with fossil fuels.

Electrolytic hydrogen from renewable sources is central to many nations' net-zero emission strategies serving as a low-carbon alternative for traditional uses and enabling decarbonisation across multiple sectors. Current stringent policies in the EU and US are set to soon require hourly time-matching of renewable electricity generation used by electrolysers aimed at ensuring that hydrogen production does not cause significant direct or indirect emissions. Whilst such requirements enhance the “green credentials” of hydrogen they also increase its production costs. A modest relaxation of these requirements offers a practicable route for scaling up low-carbon hydrogen production optimising both costs and emission reductions. Moreover in jurisdictions with credible and near-to-medium-term decarbonisation targets immediate production of electrolytic hydrogen utilising grid electricity would have a lifetime carbon intensity comparable to or even below blue hydrogen and very significantly less than that of diesel emphasising the need to prioritise rapid grid decarbonisation of the broader grid.

Biohydrogen a low-carbon footprint technology can play a significant role in decarbonizing the energy system. It uses existing infrastructure is easily transportable and produces no greenhouse gas emissions. Four technologies can be used to produce biohydrogen: photosynthetic biohydrogen dark fermentation (DF) photo-fermentation and microbial electrolysis cells (MECs). DF produces more biohydrogen and is flexible with organic substrates making it a sustainable method of waste repurposing. However low achievable biohydrogen yields are a common issue. To overcome this catalytic mechanisms including enzymatic systems such as [Fe-Fe]- and [Ni-Fe]-hydrogenases in DF and electroactive microbial consortia in MECs alongside advanced electrode catalysts which collectively surmount thermodynamic and kinetic constraints and the two stage system such as DF connection to photo-fermentation and anaerobic digestion (AD) to microbial electrolysis cells (MECs) have been investigated. MECs can generate biohydrogen at better yields by using sugars or organic acids and combining DF and MEC technologies could improve biohydrogen production. As such this review highlights the challenges and possible solutions for coupling DF–MEC while also offering knowledge regarding the technical and microbiological aspects.

The article discusses a regenerative heat exchange system for a solid oxide electrolyzer cell (SOEC) used in the production of green hydrogen. The heating system comprises four heat exchangers one condenser heat exchanger and a mixer evaporator. A pump and two throttle valves have been added to separate the hydrogen at an elevated steam condensation temperature. Assuming steady flow a thermodynamic analysis was performed to validate the design and to predict the main parameters of the heating system. Numerical optimization was then used to determine the optimal temperature distribution ensuring the lowest possible additional external energy requirement for the regenerative system. The proportions of energy gained through heat exchange were determined and their distribution analyzed. The calculated thermal efficiency of the regenerative system is 75% while its exergy efficiency is 73%. These results can be applied to optimize the design of heat exchangers for hydrogen production systems using SOECs.

Hydrogen is a key energy carrier for decarbonizing multiple sectors particularly when produced via water electrolysis powered by renewable energy. Proton exchange membrane (PEM) electrolyzers are well suited for this application due to their ability to rapidly adjust to fluctuating power inputs. Despite being conventionally operated at high temperatures and pressures to reduce heating and compression needs recent studies suggest that under partial loads lower operating conditions may enhance efficiency. This study introduces a novel optimization framework for dynamically adjusting pressure and temperature in PEM electrolyzers. The model integrates an efficiency map within a Mixed-Integer Linear Programming (MILP) formulation and applies McCormick tightening to address nonlinearities. A one-week case study demonstrates operational cost reductions of up to 12.5 % through optimal control favoring lower temperatures and pressures at low current densities and higher temperatures near rated load while maintaining moderate pressures. The results show improved efficiency and reduced hydrogen crossover enhancing safety and enabling scalable application over extended time horizons. These insights are valuable for long-term planning and evaluation of hydrogen production and storage systems.

This study evaluates the feasibility of repurposing produced water—an abundant byproduct of hydrocarbon extraction—for green hydrogen production in Wyoming USA. Analysis of geospatial distribution and production volumes reveals that there are over 1 billion barrels of produced water annually from key basins with a general total of dissolved solids (TDS) ranging from 35000 to 150000 ppm though Wyoming’s sources are often at the lower end of this spectrum. Optimal locations for hydrogen production hubs have been identified particularly in high-yield areas like the Powder River Basin where the top 2% of fields contribute over 80% of the state’s produced water. Detailed water-quality analysis indicates that virtually all of the examined sources exceed direct electrolyzer feed requirements (e.g. 10% LCOH) are notable electricity pricing (50–70% LCOH) and electrolyzer CAPEX (20–40% LCOH) are dominant cost factors. While leveraging produced water could reduce freshwater consumption and enhance hydrogen production sustainability further research is required to optimize treatment processes and assess economic viability under real-world conditions. This study emphasizes the need for integrated approaches combining water treatment renewable energy and policy incentives to advance a circular economy model for hydrogen production.

This research models a 20 MW PEM hydrogen plant. PEM units operate in the 60 to 80 ◦C range based on their location and size. This study aims to recover the waste heat from PEM modules to enhance the efficiency of the plant. In order to recover the heat two systems are implemented: (a) recovering the waste heat from each PEM module; (b) recovering the heat from hot water to produce electricity utilizing an organic refrigerant cycle (ORC). The model is made by ASPEN® V14. After modeling the plant and utilizing the ORC the module is optimized using Python to maximize the electricity produced by the turbine therefore enhancing the efficiency. The system is a closed-loop cycle operating at 25 ◦C and ambient pressure. The 20 MW PEM electrolyzer plant produces 363 kg/hr of hydrogen and 2877 kg/hr of oxygen. Based on the higher heating value of hydrogen the plant produces 14302.2 kWh of hydrogen energy equivalents. The ORC is maximized by increasing the electricity output from the turbine and reducing the pump work while maintaining energy conservation and mass balance. The results show that the electricity power output reaches 555.88 kW and the pump power reaches 23.47 kW.

In an effort to bridge the gap between academic research and industrial application this study investigates the integration potential of steam methane reforming and Co-electrolysis for the efficient conversion of refinery offgases into high-purity syngas. Experimental work was conducted under conditions representative of industrial environments using platinum- and nickel-based catalysts in steam reforming to assess methane conversion and H2 /CO ratio at varying temperatures and gas hourly space velocities (GHSV). Co-electrolysis was evaluated in solid oxide electrolysis cells (SOECs) across a range of gas compositions (H2O/CO2 /H2 /CO) including pure CO2 electrolysis as a strategy for pre-electrolysis hydrogen removal. Electrochemical performance was analyzed using impedance spectroscopy distribution of relaxation times (DRT) and current–voltage characterization. Results confirm the superior stability and performance of the Pt catalyst under high-throughput conditions while Ni-based systems were more sensitive to operational fluctuations. In the SOEC increased H2O content accelerated reaction kinetics whereas CO2 concentration governed polarization resistance. To enable optimal SOEC operation the addition of steam downstream of the reformer is proposed as a means of adjusting the reformate composition. The findings demonstrate that tuning reforming and electrolysis conditions in tandem offers a promising route for sustainable syngas production using renewable electricity. This work establishes a foundation for further development of integrated thermo-electrochemical systems tailored to industrial gas streams.

In this study the electrolysis of water by using ammonium chloride (NH4Cl) as an electrolyte was investigated for the production of hydrogen gas. The assembled electrochemical cell consists mainly of twenty-one stainless-steel electrodes and a direct current from a battery ammonium chloride solution. In the electrolysis process hydrogen and oxygen are developed at the same time and collected as a mixture to be used as a fuel. This study explores a technic regarding the matching of oxyhydrogen (HHO) electrolyzers with photovoltaic (PV) systems to make HHO gas. The primary objective of the present research is to enable the electrolyzer to operate independently of other energy origins functioning as a complete unit powered solely by PV. Moreover the impact of using PWM on cell operation was investigated. The experimental data was collected at various time intervals NH4Cl concentrations. Additionally the hydrogen unit consists of two cells with a shared positive pole fixed between them. Some undesirable anodic reaction affects the efficiency of hydrogen gas production because of the corrosion of anode to ferrous hydroxide (Fe(OH)2). Polyphosphate Inhibitor was used to minimize the corrosion reaction of anode and keep the efficiency of hydrogen gas flow. The optimal concentration of 3M for ammonium chloride was identified balancing a gas flow rate of 772 ml/min with minimal anode corrosion. Without PWM conversion efficiency ranges between 93% and 96%. Therefore PWM increased conversion efficiency by approximately 5% leading to a corresponding increase in hydrogen gas production.

Industrial alkaline water electrolysis systems face challenges in maintaining hydrogenin-oxygen impurity within safe limits under fluctuating operating conditions. This study aims to characterize the dynamic response of hydrogen-in-oxygen concentration in an industrial 10 kW alkaline water electrolysis test platform (2 Nm3/h hydrogen output at 1.6 MPa and 90 ◦C) and to identify how operating parameters influence hydrogen-inoxygen behavior. We systematically varied the cell current system pressure and electrolyte flow rate while monitoring real-time hydrogen-in-oxygen levels. The results show that hydrogen-in-oxygen exhibits significant inertia and delay: during startup hydrogen-inoxygen remained below the 2% safety threshold and stabilized at 0.9% at full load whereas a step decrease to 60% load caused hydrogen-in-oxygen to rise to 1.6%. Furthermore reducing the pressure from 1.4 to 1.0 MPa lowered the hydrogen-in-oxygen concentration by up to 15% and halving the alkaline flow rate suppressed hydrogen-in-oxygen by over 20% compared to constant conditions. These findings provide new quantitative insights into hydrogen-in-oxygen dynamics and offer a basis for optimizing control strategies to keep gas purity within safe limits in industrial-scale alkaline water electrolysis systems.

The coupling of renewable energy sources with electrolyzers under standalone conditions significantly enhances the operational efficiency and improves the costeffectiveness of electrolyzers as a technologically viable and sustainable solution for green hydrogen production. To address the configuration optimization challenge in hybrid electrolyzer systems integrating alkaline water electrolysis (AWE) and proton exchange membrane electrolysis (PEME) this study proposes an innovative methodology leveraging the morphological analysis of Pareto frontiers to determine the optimal solutions under multi-objective functions including the hydrogen production cost and efficiency. Then the complementary advantages of AWE and PEME are explored. The proposed methodology demonstrated significant performance improvements compared with the single-objective optimization function. When contrasted with the economic optimization function the hybrid system achieved a 1.00% reduction in hydrogen production costs while enhancing the utilization efficiency by 21.71%. Conversely relative to the efficiency-focused optimization function the proposed method maintained a marginal 5.22% reduction in utilization efficiency while achieving a 6.46% improvement in economic performance. These comparative results empirically validate that the proposed hybrid electrolyzer configuration through the implementation of the novel optimization framework successfully establishes an optimal balance between the economy and efficiency of hydrogen production. Additionally a discussion on the key factors affecting the rated power and mixing ratio of the hybrid electrolyzer in this research topic is provided.

Hydrogen production via water electrolysis and renewable electricity is expected to play a pivotal role as an energy carrier in the energy transition. This fuel emerges as the most environmentally sustainable energy vector for non-electric applications and is devoid of CO2 emissions. However an electrolyzer´s infrastructure relies on scarce and energyintensive metals such as platinum palladium iridium (PGM) silicon rare earth elements and silver. Under this context this paper explores the exergy cost i.e. the exergy destroyed to obtain one kW of hydrogen. We disaggregated it into non-renewable and renewable contributions to assess its renewability. We analyzed four types of electrolyzers alkaline water electrolysis (AWE) proton exchange membrane (PEM) solid oxide electrolysis cells (SOEC) and anion exchange membrane (AEM) in several exergy cost electricity scenarios based on different technologies namely hydro (HYD) wind (WIND) and solar photovoltaic (PV) as well as the different International Energy Agency projections up to 2050. Electricity sources account for the largest share of the exergy cost. Between 2025 and 2050 for each kW of hydrogen generated between 1.38 and 1.22 kW will be required for the SOEC-hydro combination while between 2.9 and 1.4 kW will be required for the PV-PEM combination. A Grassmann diagram describes how non-renewable and renewable exergy costs are split up between all processes. Although the hybridization between renewables and the electricity grid allows for stable hydrogen production there are higher non-renewable exergy costs from fossil fuel contributions to the grid. This paper highlights the importance of nonrenewable exergy cost in infrastructure which is required for hydrogen production via electrolysis and the necessity for cleaner production methods and material recycling to increase the renewability of this crucial fuel in the energy transition.

As a result of international agreements on the reduction of CO2 emissions new technologies using hydrogen are being developed. Hydrogen despite being the most abundant element in Nature cannot be found in its pure state. Water is one of the most abundant sources of hydrogen on the planet. The proposal here is to use energy from the sea in order to obtain hydrogen from water. If plants to obtain hydrogen were to be placed in the ocean the impact of long submarines piping to the coast will be reduced. Further this will open the way for the development of ships propelled by hydrogen. This paper discusses the feasibility of an offshore installation to obtain hydrogen from the sea using ocean wave energy.

Today hydrogen (H2) is overwhelmingly produced through steam methane reforming (SMR) of natural gas which emits about 12 kg of carbon dioxide (CO2) for 1 kg of H2 (∼12 kg-CO2/kg-H2). Water electrolysis offers an alternative for H2 production but today’s electrolyzers consume over 55 kWh of electricity for 1 kg of H2 (>55 kWh/kg-H2). Electric grid-powered water electrolysis would emit less CO2 than the SMR process when the carbon intensity for grid power falls below 0.22 kg-CO2/kWh. Solar- and wind-powered electrolytic H2 production promises over 80% CO2 reduction over the SMR process but large-scale (megawatt to gigawatt) direct solar- or wind-powered water electrolysis has yet to be demonstrated. In this paper several approaches for solar-powered electrolysis are analyzed: (1) coupling a photovoltaic (PV) array with an electrolyzer through alternating current; (2) direct-current (DC) to DC coupling; and (3) direct DC-DC coupling without a power converter. Co-locating a solar or wind farm with an electrolyzer provides a lower power loss and a lower upfront system cost than long-distance power transmission. A load-matching PV system for water electrolysis enables a 10%–50% lower levelized cost of electricity than the other systems and excellent scalability from a few kilowatts to a gigawatt. The concept of maximum current point tracking is introduced in place of maximum power point tracking to maximize the H2 output by solarpowered electrolysis.

This study investigates the potential for establishing a self-sufficient renewable hydrogen production facility utilising a floating photovoltaic (FPV) system on an artificial irrigation reservoir located in a small municipality in southern Italy. The analysis examines the impact of different system configurations and operating conditions on the technical economic and environmental performance with a particular focus on hydrogen production and water conservation resulting from reduced evaporation. Different sizes of the FPV plant are considered with and without a tracking system. The electrolyser performance is evaluated under both fixed and variable load conditions also considering the integration of battery storage to ensure consistent operation. The findings indicate that the adoption of the largest FPV plant can result in the conservation of approximately 1.87 million m3 of water annually while simultaneously producing up to 4199 tons of hydrogen per year in variable load mode—more than twice the output compared to fixed load conditions. Although battery integration increases hydrogen production it also leads to higher investment and maintenance costs. Therefore the variable load operation emerges as the most economically viable option reducing the levelized cost of hydrogen (LCOH) to €13.18/kg a 26 % reduction compared to fixed load operation. Moreover the implementation of a vertical axis tracking system leads to only marginal LCOH reductions (maximum 2.2 %) and does not justify the additional complexity. In all tested scenarios the system proves to be self-sustaining. Given the case study’s location in southern Italy—where a pilot project for fuel cell–battery hybrid trains is underway—the hydrogen produced is assumed to be used for railway applications as a possible offtaker. The analysis shows that the potential of the system in terms of hydrogen production is much higher (tens of times) than the estimated demand of the present hydrogen railway configuration thus suggesting that a significant expansion of the number of trains and routes served could be considered. Although this work is based on a specific case study its key findings are potentially replicable in other contexts—particularly in Mediterranean or semi-arid regions where water scarcity may otherwise act as a limiting factor for the deployment of hydrogen production systems.

The applications and need for large-scale long-duration electrical energy storage are growing as both the share of renewable energy in energy systems and the demand for flexibility increase. One potential application is the renewable hydrogen industry where temporal matching of renewable electricity generation and hydrogen production will be required in the future according to the new European Union regulations. In this paper a case study of electrical energy storage utilization in hydrogen production is conducted in the Nordic context with a high share of wind production. The storage is used in the hydrogen production process for temporal matching. The levelized cost of storage of three medium- to long-term storage technologies is assessed using an Excel-based model with four case approaches. In the first case approach the electrolyzer load is inflexible while the other approaches explore how the flexibility of the electrolyzer and the increase in renewable production capacity affect the size and cost of the storage. Electro-thermal energy storage based on sand as storage material presented the lowest levelized cost of storage (114-198 €/MWh) due to its low energy-related investment cost. However the results show that additional usage purposes for all examined storage technologies are required to avoid high investment costs. Additionally flexibility from the electrolyzer load and over-investing in renewable capacity is required. In conclusion storage should not be the only component providing flexibility in the studied system and it should be used to integrate multiple assets in the wider energy system to reach cost-effectiveness. This paper brings novelty by expanding on the storage technology options considered in previous literature and deepening the perspective of storage as a component in renewable hydrogen production. Future research should assess the effect of electricity prices and emissions allowance prices from the regulatory perspective which could further reduce the storage investment.

Hydrogen will be an integral component for the transition to sustainable energy generation and storage due to its favourable characteristics and versatility in its application. This research provides a greater understanding of the potential light energy has to increase water electrolysis efficiency by examining the effects that light energy fields have on the molecular and electrochemical dynamics during electrolysis. The results indicate that light energy increased efficiency by ~10% while enhancing the molecular dynamics regardless of application. The application of a line laser generated the highest gains in efficiency with a maximum of ~15%. Furthermore the application of a line laser with a linear magnetic field resulted in a synergistic effect which generated higher increases in molecular dynamics as well as an ~18% increase in efficiency and a ~58% increase in hydrogen gas production. As such the application of light energy fields presents a promising method for enhancing water’s molecular dynamics and electrolysis efficiency.

The deployment of large installed power capacities from intermittent renewable energy sources requires balancing to ensure the steady and safe operation of the electrical grid. New methods of energy storage are essential to store excess electrical power when energy is not needed and later use it during high-demand periods both in the short and long term. Power-to-Gas (P2G) is an energy storage solution that uses electric power produced from renewables to generate gas fuels such as hydrogen which can be stored for later use. Hydrogen produced in this manner can be utilized in energy storage systems and in transportation as fuel for cars trams trains or buses. Currently most hydrogen is produced from fossil fuels. Solid-oxide electrolysis (SOE) offers a method to produce clean hydrogen without harmful emissions being the most efficient of all electrolysis methods. The objective of this work is to determine the optimal operational parameters of an SOE system such as lower heating value (LHV)-based efficiency and total input power based on calculations from a mathematical model. The results are provided for three different operating temperature levels and four different steam utilization ratios. The introductory chapter outlines the motivation and background of this work. The second chapter explains the basics of electrolysis and describes its different types. The third chapter focuses on solid-oxide electrolysis and electrolyzer systems. The fourth chapter details the methodology including the mathematical formulations and software used for simulations. The fifth chapter presents the results of the calculations with conclusions. The final chapter summarizes this work.

The production of green hydrogen the cleanest energy source plays a crucial role in enhancing the efficiency of renewable energy systems by utilizing surplus energy that would otherwise be wasted. With the global shift towards sustainability and the rising adoption of renewable energy sources green hydrogen is gaining significant importance as both an energy carrier and a storage solution. However determining the optimal locations for green hydrogen production facilities remains a complex challenge due to the interplay of technical economic logistical and environmental factors. This study introduces the City Location Evaluation Optimization for Green Hydrogen (CELO_GH) algorithm a novel heuristic approach designed to address this challenge. Unlike conventional multi-criteria decision-making (MCDM) models CELO_GH dynamically evaluates cities by considering renewable energy surplus proximity to industrial hydrogen demand port and pipeline accessibility and economic viability. A case study conducted in Turkey demonstrates the effectiveness of the approach by identifying optimal cities for green hydrogen production based on real-world energy and infrastructure data. The problem was also solved with the genetic algorithm and the results were compared and it was seen that the proposed heuristic provides the lowest cost location selection. A geographically flexible methodology as the proposed algorithm can be applied globally to regions with high renewable energy potential ensuring scalability and adaptability for future energy transition strategies. The results provide valuable insights for policy-makers energy investors and industrial planners aiming to optimize green hydrogen infrastructure while ensuring cost efficiency and sustainability.

This review paper presents an overview of fuel cell electrochemical systems that can be used for clean large-scale power generation and energy storage as global energy concerns regarding emissions and greenhouse gases escalate. The fundamental thermochemical and operational principles of fuel cell power generation and electrolyzer technologies are discussed with a focus on high-temperature solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) that are best suited for grid scale energy generation. SOFCs and SOECs share similar promising characteristics and have the potential to revolutionize energy conversion and storage due to improved energy efficiency and reduced carbon emissions. Electrochemical and thermodynamic foundations are presented while exploring energy conversion mechanisms electric parameters and efficiency in comparison with conventional power generation systems. Methods of converting hydrocarbon fuels to chemicals that can serve as fuel cell fuels are also presented. Key fuel cell challenges are also discussed including degradation thermal cycling and long-term stability. The latest advancements including in materials selection research design and manufacturing methods are also presented as they are essential for unlocking the full potential of these technologies and achieving a sustainable near zero-emission energy future.

It is believed that hydrogen will play an essential role in energy transition and achieving the net-zero target by 2050. Currently global hydrogen production mostly relies on processing fossil fuels such as coal and natural gas commonly referred to as grey hydrogen production while releasing substantial amounts of carbon dioxide (CO2). Developing economically and technologically viable pathways for hydrogen production while eliminating CO2 emissions becomes paramount. In this critical review we examine the common grey hydrogen production techniques by analyzing their technical characteristics production efficiency and costs. We further analyze the integration of carbon capture utilization and storage (CCUS) technology establishing the zero-carbon strategy transiting from grey to blue hydrogen production with CO2 capture and either utilized or permanently stored. Today grey hydrogen production exhibits technological diversities with various commercial maturities. Most methods rely on the effectiveness of catalysts necessitating a solution to address catalyst fouling and sintering in practice. Although CCUS captures utilizes or stores CO2 during grey hydrogen production its wide application faces multiple challenges regarding the technological complexity cost and environmental benefits. It is urgent to develop technologically mature low-cost and low-energy-consumption CCUS technology implementing extensive large-scale integrated pilot projects.

The study presents the development of a novel integrated wind-biomass energy system designed for sustainable urban development leveraging municipality waste and wind power energy sources. This innovative system is capable of producing multiple forms of energy including electricity cooling heat and hydrogen addressing the diverse energy needs of urban communities. It integrates advanced thermodynamic cycles like Kalina and water electrolysis via an alkaline electrolyzer. In addition the system uniquely combines power and refrigeration while utilizing landfills as an energy source. The designed system is thermodynamically modeled using the Engineering Equation Solver and process wise simulated by the Aspen Plus software to ensure better performance. By integrating advanced thermodynamic cycles such as the Kalina and combined power and refrigeration system the overall system is designed to maximize the utilization of biomass energy content and enhances overall performance. The thermodynamic analysis results reveal that the system achieved remarkable results with an energy efficiency of 67.60% and an exergy efficiency of 59.7% demonstrating its tangible performance compared to other standalone energy systems. The refrigeration system itself achieves an energetic COP of 5.41 and an exergetic COP of 1.7. Additionally the system's hydrogen production facilitated by an alkaline electrolyzer reaches a rate of 5.38 kg/h highlighting its potential to contribute to clean hydrogen energy solutions. Moreover the exergo-environmental assessment shows that the system is environmentally friendly. The cost assessment shows that the system reaches profitability in 7 years and demonstrates growth achieving a substantial NPV of 192.39 million by 30 years highlighting its long-term financial viability.

The transition to a hydrogen-based economy presents a promising solution to the challenges posed by unsus tainable energy systems and reliance on fossil fuels. This comprehensive review explores various hydrogen production methods emphasizing their technological advancements sustainability implications and future prospects. Beginning with an overview of hydrogen’s significance as a clean energy carrier the review examines key production methods such as Steam Methane Reforming Electrolysis (Proton Exchange Membrane alkaline solid oxide) Biomass Gasification Photoelectrochemical Water Splitting and Thermochemical Processes. Each method is scrutinized for its efficiency environmental impact and scalability providing valuable insights into their roles in advancing the hydrogen economy. The review highlights the transformative potential of hydrogen production to replace fossil fuels due to its ability to store renewable energy long-term and its zero emissions. It also discusses potential technological advancements including high-efficiency solid-state electrolysis and advanced catalysts for water splitting highlighting avenues for innovation in hydrogen production. Additionally policy recommendations aimed at promoting the hydrogen economy and fostering collaboration between academia industry and governments are elucidated. Through a detailed analysis of hydrogen production technologies and future prospects this review contributes to shaping the trajectory of sustainable energy sys tems advancing the adoption of hydrogen as a key energy vector and underscoring the importance of alternative and sustainable energy sources.

Alternative fuel opportunities can satisfy energy security and reduce carbon emissions. In this regard the hydrogen fuel is derived from the source of environmental pollutants like sewage and algae wastewater through hydrothermal gasification technique using a KOH catalyst with varied gasification process parameters of duration and temperature of 6–30 min and 500-800 ◦C. The novelty of the work is to identify the optimum gasification process parameter for obtaining the maximum hydrogen yield using a KOH catalyst as an alternative fuel for agricultural engine applications. Influences of gasification processing time and temperature on H2 selectivity Carbon gasification efficiency (CE) Lower heating value (LHV) Hydrogen yield potential (HYP) and gasification efficiency (GE) were studied. Its results showed that the gasifier operated at 800 ◦C for 30 min offering maximum hydrogen yield (26 mol/kg) and gasification efficiency (58 %). The synthesized H2 was an alternative fuel blended with diesel fuel/TiO2 nanoparticles. It was experimentally studied using an internal combustion engine. Influences of H2 on engine perfor mance like brake-specific fuel consumption brake thermal efficiency and emission performances were measured and compared with diesel fuel. The results showed that DH20T has the least (420g/kWh) brake-specific fuel consumption (BSFC) and superior brake thermal efficiency of about 25.2 %. The emission results revealed that the DH20T blend showed the NOX value increased by almost 10.97 % compared to diesel fuel whereas the CO UHC and smoke values reduced by roughly 31.25 28.34 and 42.35 %. The optimum fuel blend (DH20T) result is rec ommended for agricultural engine applications.

Conventional hydrogen production processes which often involve fossil raw materials emit significant amounts of carbon dioxide into the atmosphere. This study critically evaluates the feasibility of using sugarcane biomass as an energy source to produce green hydrogen. In the 2023/2024 harvest Brazil the world’s largest sugarcane producer processed approximately 713.2 million metric tons of sugarcane. This yielded 45.68 million metric tons of sugar and 29.69 billion liters of first-generation ethanol equivalent to approximately 0.0416 liters of ethanol per kilogram of sugarcane. A systematic literature review was conducted using Scopus and Clarivate Analytics Web of Science resulting in the assessment of 335 articles. The study has identified seven potential biohydrogen production methods including two direct approaches from second-generation ethanol and five from integrated bioenergy systems. Experimental data indicate that second-generation ethanol can yield 594 MJ per metric ton of biomass with additional energy recovery from lignin combustion (1705 MJ per metric ton). Moreover advances in electrocatalytic reforming and plasma-driven hydrogen production have demonstrated high conversion efficiencies addressing key technical barriers. The results highlight Brazil’s strategic potential to integrate biohydrogen production within its existing bioenergy infrastructure. By leveraging sugarcane biomass for green hydrogen the country can contribute significantly to the global transition to sustainable energy while enhancing its energy security.

The article provides a short review on catalyst-based processes for the production of hydrogen starting from methane both of fossil origin and from sustainable processes. The three main paths of steam- and dry-reforming partial oxidation and thermo-catalytic decomposition are briefly introduced and compared above all with reference to the latest publications available and to new catalysts which obey the criteria of lower environmental impact and minimize the content of critical raw materials. The novel strategies based on chemical looping with CO2 utilization membrane separation electrical-assisted (plasma and microwave) processes multistage reactors and catalyst patterning are also illustrated as the most promising perspective for CH4 reforming especially on small and medium scale. Although these strategies should only be considered at a limited level of technological readiness research on these topics including catalyst development and process optimization represents the crucial challenge for the scientific community