Publications

The cost reduction of electrolysers is critical for scaling up green hydrogen production and achieving decarbonization targets. This study presents a novel and comprehensive dataset of electrolyser projects in Europe. It includes full cost and capacity details for each project and capturing project-specific characteristics such as technology type location and project type for the period 2005–2030. We apply the learning curve methodology to assess cost reductions across different electrolyser technologies and project sizes. Our findings indicate a significant learning effect for PEM and AEL electrolysers in the last 20 years with learning rates of 32.1% and 22.9% respectively. While AEL cost reductions are primarily driven by scaling effects PEM electrolysers benefit from both technological advancements and economies of scale. Small-scale electrolysers exhibit a stronger learning effect (25%) whereas large-scale projects show no clear cost reductions due to their early stage of deployment. Projections based on our learning rates suggest that reaching Europe’s 2030 target of 40 GW electrolyser capacity would require an estimated total investment of 14 billion EUR. These results align closely with previous studies and such predictions are closed to estimates from other organization. The dataset is publicly available allowing for further analysis and periodic updates to track cost trends.

The growing energy crisis and increasing threat of climate change are driving the need to take action regarding the use of alternative fuels in transport including public transport. Hydrogen is undoubtedly a fuel which is environmentally friendly and constitutes an alternative to fossil fuels. The wider deployment of hydrogen-powered vehicles involves the need to adapt infrastructure to support the operation of these vehicles. Such infrastructure includes refuelling stations for hydrogen-powered vehicles. The widespread use of hydrogen-powered vehicles is dependent on the development of a network of hydrogen refuelling stations. The aim of this article is to propose the conceptual location of infrastructure for fuelling public transport vehicles with hydrogen in selected cities of the West Pomeranian Voivodeship in particular the cities of Szczecin and Koszalin. The methodology used to determine the number of refuelling stations is described and the concept of the location for the refuelling stations has been proposed. Based on a set assumptions it was stated that two stations may be located in the Voivodeship in 2025 and seven stations in 2040. The research results will be of interest to infrastructure developers public transport companies and municipalities involved in making decisions related to the purchase and operation of hydrogen-powered buses.

Hydrogen (H2) is emerging as a key alternative to fossil fuels in the global energy transition. This study presents a comparative techno-economic analysis of H2 and natural gas (NG) focusing on safety hazards energy output CO2 emissions and cost-effectiveness aspects. Our analysis showed that compared to NG and other highly flammable gases like acetylene (C2 H2) and propane (C3 H8) H2 has a higher hazard potential due to factors such as its wide flammability range low ignition energy and high flame speed. In terms of energy output 1 kg of NG produces 48.60 MJ while conversion to liquefied natural gas (LNG) grey H2 and blue H2 reduces energy output to 45.96 MJ 35.45 MJ and 31.21 MJ respectively. Similarly while unconverted NG emits 2.72 kg of CO2 per kg emissions increase to 3.12 kg for LNG and 3.32 kg for grey H2. However blue H2 significantly reduces CO2 emissions to 1.05 kg per kg due to carbon capture and storage. From an economic perspective producing 1 kg of NG yields a profit of $0.011. Converting NG to grey H2 is most profitable yielding a net profit of $0.609 per kg of NG while blue H2 despite higher production costs remains viable with a profit of $0.390 per kg of NG. LNG conversion also shows profitability with $0.061 per kg of NG. This analysis highlights the trade-offs between energy efficiency environmental impact and economic viability providing valuable insights for stakeholders formulating hydrogen and LNG implementation strategies.

Transitioning to renewable energy is vital to achieving decarbonization at the global level but energy storage is still a major challenge. This review discusses the role of energy storage in the energy transition and the blue economy focusing on technological development challenges and directions. Effective storage is vital for balancing intermittent renewable energy sources like wind solar and marine energy with the power grid. The development of battery technologies hydrogen storage pumped hydro storage and emerging technologies like sodium-ion and metal-air batteries is discussed for their potential for large-scale deployment. Shortages in critical raw materials environmental impact energy loss and costs are some of the challenges to large-scale deployment. The blue economy promises opportunities for offshore energy storage notably through ocean thermal energy conversion (OTEC) and compressed air energy storage (CAES). Moreover the capacity of datadriven optimization and artificial intelligence to enhance storage efficiency is discussed. Policy interventions and economic incentives are necessary to spur the development and deployment of sustainable energy storage technology. Education and workforce training are also important in cultivating future researchers engineers and policymakers with the ability to drive energy innovation. Merging sustainability training with an interdisciplinary approach can potentially establish an efficient workforce that is capable of addressing energy issues. Future work needs to focus on higher energy density efficiency recyclability and cost-effectiveness of the storage technologies without sacrificing their environmental sustainability. The study underlines the need for converging technological economic and educational approaches to enable a sustainable and resilient energy future.

Green hydrogen has become a core element of Europe’s energy transition to assist in lowering carbon emissions. However the transition to green hydrogen faces challenges including the cost of production availability of renewable energy sources public opposition and the need for supportive government policies and financial initiatives. While there are other alternatives for producing low-carbon hydrogen for example blue hydrogen German funding favours projects that involve hydrogen production via electrolysis. Beyond climate goals it is anticipated that a green hydrogen industry will create economic benefits and a wide-range of collaborative opportunities with key international partnerships increasing energy security if done appropriately. Germany a leader in green hydrogen technology will need to rely on imports to meet long-term demand due to limited renewable energy capacity. Despite the current obstacles to transitioning to green hydrogen it is felt that ultimately the benefits of this industry and reducing emissions will outweigh the associated costs of production. This study analyses the hydrogen transition in Germany by interviewing 37 European experts guided by the research question: What are the key perceived barriers and opportunities influencing the successful adoption and integration of hydrogen technologies in Germany’s hydrogen transition?

Injection timing in low-pressure hydrogen direct injection (H2LPDI) engines plays a critical role in optimising gas jet structure and mixture formation due to the complex and transient nature of ambient air flow and density inside the cylinder. This study systematically investigates the macroscopic characteristics of gas jet development at five distinct injection timings from 210 to 120 ◦CA bTDC with the intake valve closure (IVC) as a reference point in a motored inline four-cylinder spark-ignition engine at 2000 rpm and 160 Nm load using low-pressure injection of 3.5 MPa. Optical access was made with two endoscopes: one for high-speed imaging and the other for laser insertion to realise laser shadowgraph imaging of the gas jet delivered using a side-mounted outwardopening pintle nozzle injector. The experimental results reveal spatial and temporal variations in jet morphology penetration spreading angle and mixture dispersion as a function of injection timing. Pre-IVC injection (210 ◦CA bTDC) produced a narrow mean cone angle of ~40◦ and the highest penetration-rate proxy (0.49) whereas postIVC injection (120 ◦CA bTDC) retained a wider ~53◦ cone yet reduced the penetration rate to 0.28 while increasing the sheet-based mixing index from − 0.084 to − 0.106. Pre-IVC injection occurring under low ambient pressure and with active intake airflow was found to produce elongated jets with enhanced penetration and mixing rates though accompanied by substantial cyclic variations. Conversely post-IVC injection was strongly influenced by a fully developed tumble flow which redirected the jet trajectory towards the pent-roof and facilitated mixing through increased turbulence. However the elevated air density constrained the jet penetration. At-IVC injection resulted in a more uniform and stable jet structure. However the lack of convective flow constrained the overall mixing effectiveness. Quantitative analysis of jet spreading angle pixel intensity gradient and centroid movement using 100 consecutive cycles confirms the critical role of injection timing in shaping the gas jet development as suggested by the images.

This study discusses energy management in thermal and electrical microgrids while taking heat pumps renewable sources thermal and hydrogen storages into account. The weighted total of the operating cost grid emissions level voltage and temperature deviation function and other factors makes up the objective function of the suggested method. The restrictions include the operationflexibility model of resources and storages micro-grid flexibility limits and optimum power flow equations. Point Estimation Method is used in this work to simulate load energy price and renewable phenomenon uncertainty. A fuzzy decision-making methodology is used to arrive at a compromise solution that satisfies network operators’ operational environmental and financial goals. The innovations of this paper include energy management of various smart microgrids simultaneous modeling of several indicators especially flexibility investigation of optimal performance of resources and storage devices and modeling of uncertainty considering low computational time and an accurate flexibility model. Numerical findings indicate that the fuzzy decision-making approach has the capability to reach a compromise point in which the objective functions approach their minimum values. The integration of the proposed uncertainty modeling with precise flexibility modeling results in a reduction in computational time when compared to stochastic optimization based on scenarios. For the compromise point and uncertainty modeling with PEM by efficiently managing resources and thermal and hydrogen storages scheme is capable of attaining high flexibility conditions. Compared to load flow studies the approach can enhance the operational environmental and economic conditions of smart microgrids by approximately 33–57% 68% and 33–68% respectively under these circumstances.

To enable climate-neutral aviation improving the energy efficiency of aircraft is essential. The research project Synergies of Highly Integrated Transport Aircraft investigates cross-disciplinary synergies in aircraft and propulsion technologies to achieve energy savings. This study examines a fuel cell electric powered configuration with distributed electric propulsion. For this a reverse-engineered ATR 72-500 serves as a reference model for calibrating the methods and ensuring accurate performance modeling. A baseline configuration featuring a state-of-the-art turboprop engine with the same entry-into-service is also introduced for a meaningful performance comparison. The analysis uses an enhanced version of the Stanford University Aerospace Vehicle Environment (SUAVE) a Python-based aircraft design environment that allows for novel energy network architectures. This paper details the preliminary aircraft design process including calibration presents the resulting aircraft configurations and examines the integration of a fuel cell-electric energy network. The results provide a foundation for higher fidelity studies and performance comparisons offering insights into the trade-offs associated with hydrogen-based propulsion systems. All fundamental equations and methodologies are explicitly presented ensuring transparency clarity and reproducibility. This comprehensive disclosure allows the broader scientific community to utilize and refine these findings facilitating further progress in hydrogen-powered aviation technologies.

Electricity access deficits remain acute in Sub-Saharan Africa (SSA) where more than 600 million people lack reliable supply. Green hydrogen produced through renewablepowered electrolysis is increasingly recognized as a transformative energy carrier for decentralized systems due to its capacity for long-duration storage sector coupling and near-zero carbon emissions. This review adheres strictly to the PRISMA 2020 methodology examining 190 records and synthesizing 80 peer-reviewed articles and industry reports released from 2010 to 2025. The review covers hydrogen production processes hybrid renewable integration techno-economic analysis environmental compromises global feasibility and enabling policy incentives. The findings show that Alkaline (AEL) and PEM electrolyzers are immediately suitable for off-grid scenarios whereas Solid Oxide (SOEC) and Anion Exchange Membrane (AEM) electrolyzers present high potential for future deployment. For Sub-Saharan Africa (SSA) the levelized costs of hydrogen (LCOH) are in the range of EUR5.0–7.7/kg. Nonetheless estimates from the learning curve indicate that these costs could fall to between EUR1.0 and EUR1.5 per kg by 2050 assuming there is (i) continued public support for the technology innovation (ii) appropriate flexible and predictable regulation (iii) increased demand for hydrogen and (iv) a stable and long-term policy framework. Environmental life-cycle assessments indicate that emissions are nearly zero but they also highlight serious concerns regarding freshwater usage land occupation and dependence on platinum group metals. Namibia South Africa and Kenya exhibit considerable promise in the early stages of development while Niger demonstrates the feasibility of deploying modular community-scale systems in challenging conditions. The study concludes that green hydrogen cannot be treated as an integrated solution but needs to be regarded as part of blended off-grid systems. To improve its role targeted material innovation blended finance and policies bridging export-oriented applications to community-scale access must be established. It will then be feasible to ensure that hydrogen

Amid escalating global climate crises and the urgent imperative to meet the Paris Agreement’s carbon neutrality targets the steel industry—a leading contributor to global greenhouse gas emissions—confronts unprecedented challenges in driving sustainable industrial transformation through innovative low-carbon steelmaking technologies. This paper examines decarbonization technologies across three stages (source process and end-of-pipe) for two dominant steel production routes: the long process (BF-BOF) and the short process (EAF). For the BF-BOF route carbon reduction at the source stage is achieved through high-proportion pellet charging in the blast furnace and high scrap ratio utilization; at the process stage carbon control is optimized via bottom-blowing O2-CO2-CaO composite injection in the converter; and at the end-of-pipe stage CO2 recycling and carbon capture are employed to achieve deep decarbonization. In contrast the EAF route establishes a low-carbon production system by relying on green and efficient electric arc furnaces and hydrogen-based shaft furnaces. At the source stage energy consumption is reduced through the use of green electricity and advanced equipment; during the process stage precision smelting is realized through intelligent control systems; and at the end-of-pipe stage a closed-loop is achieved by combining cascade waste heat recovery and steel slag resource utilization. Across both process routes hydrogen-based direct reduction and green power-driven EAF technology demonstrate significant emission reduction potential providing key technical support for the low-carbon transformation of the steel industry. Comparative analysis of industrial applications reveals varying emission reduction efficiencies economic viability and implementation challenges across different technical pathways. The study concludes that deep decarbonization of the steel industry requires coordinated policy incentives technological innovation and industrial chain collaboration. Accelerating large-scale adoption of low-carbon metallurgical technologies through these synergistic efforts will drive the global steel sector toward sustainable development goals. This study provides a systematic evaluation of current low-carbon steelmaking technologies and outlines practical implementation strategies contributing to the industry’s decarbonization efforts.

This study presents a techno-economic environmental risk analysis (TERA) of large-scale green hydrogen production using Alkaline Water Electrolysis (AWE) and Proton Exchange Membrane (PEM) systems. The analysis integrates commercial data market insights and academic forecasts to capture variability in capital expenditure (CAPEX) efficiency electricity cost and capacity factor. Using Libya as a case study 81 scenarios were modelled for each technology to assess financial and operational trade-offs. For AWE CAPEX is projected between $311 billion and $905.6 billion for 519 GW (gigawatts) of installed capacity equivalent to 600–1745 $/kW. PEM systems show a wider range of $612 billion to $1020 billion for 510 GW translating to 1200–2000 $/kW. Results indicate that AWE while requiring greater land use provides significant cost advantages due to lower capital intensity and scalability. In contrast PEM systems offer compact design and operational flexibility but at substantially higher costs. The five most economical scenarios for both technologies consistently feature low CAPEX and high efficiency while sensitivity analyses confirm these two parameters as the dominant cost drivers. The findings emphasise that technology choice should reflect context-specific priorities such as land availability budget and performance needs. This study provides actionable guidance for policymakers and investors developing cost-effective hydrogen infrastructure in emerging green energy markets.

Underground Hydrogen Storage (UHS) is a promising solution to maximize the use of hydrogen as an energy carrier. This study presents a standardized methodology for assessing UHS quality by introducing the Underground Hydrogen Storage Suitability Index (UHSSI) which integrates three sub-indices: the Caprock Potential Index (CPI) the Reservoir Quality Index (RQI) and the Site Potential Index (SPI). Parameters such as porosity permeability lithology caprock thickness depth temperature and salinity are evaluated and ranked from 0 (unsuitable) to 5 (excellent). The methodology was validated using data from six worldwide sites including salt caverns and aquifers. Sites like Moss Bluff Clemens Dome and Spindletop (USA) scored highly while Teesside (UK) Lobodice (Czech Republic) and Beynes (France) were classified as unsuitable due to shallow depths and microbial activity. A software tool the UHSSI Calculator was developed to automate site evaluations. This approach offers a cost-effective tool for preliminary screening and supports the safer development of UHS.

Emissions from fossil fuel extraction conveyance and combustion are among the most significant causes of air pollution and climate change leading to arguably the most acute crises mankind has ever faced. The transition from fossil fuel-based energy systems to hydrogen is essential for meeting a portion of global decarbonization goals. Hydrogen offers certain features such as high gravimetric energy density that is required for heavy-duty shipping and freight applications and chemical properties such as high temperature combustion and reducing capabilities that are required for steel chemicals and fertilizer industries. However hydrogen that leaks has indirect climate implications stemming from atmospheric interactions that are emerging as a critical area of research. This study reviews recent literature on hydrogen’s global warming potential (GWP) highlighting its indirect contributions to radiative forcing via methane’s extended atmospheric lifetime tropospheric ozone formation and stratospheric water vapor formation. The 100-year GWP (GWP100) of hydrogen estimated to range between 8 and 12.8 underscores the need to minimize leakage throughout the hydrogen supply chain to maximize the climate benefits of using hydrogen instead of fossil fuels. Comparisons with methane reveal hydrogen’s shorter atmospheric lifetime and reduced long-term warming effects establishing it as a viable substitute for fossil fuels in sectors such as steel cement and heavy-duty transport. The analysis emphasizes the importance of accurate leakage assessments robust policy frameworks and advanced infrastructure to ensure hydrogen realizes its potential as a sustainable energy carrier that displaces the use of fossil fuels. Future research is recommended to refine climate models better understand atmospheric sinks and hydrogen leakage phenomena and develop effective strategies to minimize hydrogen emissions paving the way for environmentally sound use of hydrogen.

The transportation sector is a significant contributor to global carbon emissions thus necessitating a transition toward renewable energy sources (RESs) and electric vehicles (EVs). Among EV technologies fuel-cell EVs (FCEVs) offer distinct advantages in terms of refueling time and operational efficiency thus rendering them a promising solution for sustainable transportation. Nevertheless the integration of FCEVs in rural areas poses challenges due to the limited availability of refueling infrastructure and constraints in energy access. In order to address these challenges this study proposes a multi-objective energy management model for a hydrogen refueling station (HRS) integrated with RESs a battery storage system an electrolyzer (EL) a fuel cell (FC) and a hydrogen tank serving diverse FCEVs in rural areas. The model formulated using mixed-integer linear programming (MILP) optimizes station operations to maximize both cost and load factor performance. Additionally bi-directional trading with the power grid and hydrogen network enhances energy flexibility and grid stability enabling a more resilient and self-sufficient energy system. To the best of the authors’ knowledge this study is the first in the literature to present a multi-objective optimal management approach for grid-interactive renewablesupported HRSs serving hydrogen-powered vehicles in rural areas. The simulation results demonstrate that RES integration improves economic feasibility by reducing costs and increasing financial gains while maximizing the load factor enhances efficiency cost-driven strategies that may impact stability. The impact of the EL on cost is more significant while RES capacity has a relatively smaller effect on cost. However its influence on the load factor is substantial. The optimization of RES-supported hydrogen production has been demonstrated to reduce external dependency thereby enabling surplus trading and increasing financial gains to the tune of USD 587.83. Furthermore the system enhances sustainability by eliminating gasoline consumption and significantly reducing carbon emissions thus supporting the transition to a cleaner and more efficient transportation ecosystem.

The safe removal transportation and long-term storage of fuel debris in the decommissioning of Fukushima Daiichi is the biggest challenge facing Japan. In the nuclear power field passive autocatalytic recombiners (PARs) have become established as a technology to prevent hydrogen explosions inside the containment vessel. To utilize PAR as a measure to reduce the concentration of hydrogen generated in the fuel debris storage canister which is currently an issue it is required to perform in a sealed environment with high doses of radiation low temperature and high humidity and there are many challenges different from conventional PAR. A honeycombshaped catalyst based on automotive catalyst technology has been newly designed as a PAR and research has been conducted to solve unique problems such as high dose radiation low temperature high humidity coexistence of hydrogen and low oxygen and catalyst poisons. This paper summarizes the challenges of hydrogen generation in a sealed container the results of research and a guide to how to use the PAR for fuel debris storage canisters.

Proton exchange membrane water electrolyzers (PEMWEs) are a promising technology for green hydrogen production. However the adoption of PEMWE-based hydrogen production systems remains limited due to several challenges including high material costs limited performance and durability and difficulties in scaling the technology. Computational modeling serves as a powerful tool to address these challenges by optimizing system design improving material performance and reducing overall costs thereby accelerating the commercial rollout of PEMWE technology. Despite this conventional models often oversimplify key components such as porous transport and catalyst layers by assuming constant porosity and neglecting the spatial heterogeneity found in real electrodes. This simplification can significantly impact the accuracy of performance predictions and the overall efficiency of electrolyzers. This study develops a mathematical framework for modeling variable porosity distributions—including constant linearly graded and stepwise profiles—and derives analytical expressions for permeability effective diffusivity and electrical conductivity. These functions are integrated into a three-dimensional multi-domain COMSOL simulation to assess their impact on electrochemical performance and transport behavior. The results reveal that although porosity variations have minimal effect on polarization at low voltages they significantly influence internal pressure species distribution and gas evacuation at higher loads. A notable finding is that reversing stepwise porosity—placing high porosity near the membrane rather than the channel—can alleviate oxygen accumulation and improve current density. A multi-factor comparison highlights this reversed configuration as the most favorable among the tested strategies. The proposed modeling approach effectively connects porous media theory and systemlevel electrochemical analysis offering a flexible platform for the future design of porous electrodes in PEMWE and other energy conversion systems.

Green hydrogen produced through renewable energy sources is emerging as a pivotal element in global energy transitions. Despite its potential public acceptance remains a critical barrier to its large-scale implementation. This study aims to identify the socio-political and demographic determinants of public acceptance of green hydrogen. Using advanced variable selection methods including ridge lasso and elastic net regression we analyzed perceptions of climate change trust in government policies and demographic characteristics. The findings reveal that individuals prioritizing climate change over economic growth perceiving its impacts as severe and recognizing it as South Korea’s most pressing issue are more likely to accept green hydrogen. Trust in the government’s climate change response also emerged as a key factor. Demographic characteristics such as younger age higher income advanced education smaller family size and conservative political ideology were significantly associated with greater acceptance. These results highlight the importance of raising public awareness about the urgency of climate change and enhancing trust in government policies to promote societal acceptance of green hydrogen. Policymakers should consider these factors when developing strategies to advance the adoption of green hydrogen technologies and foster sustainable energy transitions.

Water photoelectrolysis cells based on photoelectrochemical water splitting seem to be an interesting alternative to other traditional green hydrogen generation processes (e.g. water electrolysis). Unfortunately the practical application of this technology is currently hindered by several difficulties: low solar-to-hydrogen (STH) efficiency expensive electrode materials etc. A novel concept based on a tandem photoelectrolysis cell configuration with an anion-conducting membrane separating the photoanode from the photocathode has already been proposed in the literature. This approach allows the use of low-cost metal oxide electrodes and nickel-based co-catalysts. In this paper we conducted a study to evaluate the economic and environmental sustainability of this technology using the environmental life cycle cost. Preliminary results have revealed two main interesting aspects: the negligible percentage of externalities in the total cost.

To address the collaborative optimization challenge in multi-microgrid systems with significant renewable energy integration this study presents a dual-layer optimization model incorporating power-hydrogen coupling. Firstly a hydrogen energy system coupling framework including photovoltaics storage batteries and electrolysis hydrogen production/fuel cells was constructed at the architecture level to realize the flexible conversion of multiple energy forms. From a modeling perspective the upper-layer optimization aims to minimize lifecycle costs by determining the optimal sizing of distributed PV systems battery storage hydrogen tanks fuel cells and electrolyzers within the microgrid. At the lower level a distributed optimization framework facilitates energy sharing (both electrical and hydrogen-based) across microgrids. This operational layer maximizes yearly system revenue while considering all energy transactions—both inter-microgrid and grid-to-microgrid exchanges. The resulting operational boundaries feed into the upper-layer capacity optimization with the optimal equipment configuration emerging from the iterative convergence of both layers. Finally the actual microgrid in a certain area is taken as an example to verify the effectiveness of the proposed method.

Hydrogen production from gasification of biowaste generates large volumes of CO2 due to endothermic biowaste decomposition. Alternatively the Sun can provide that energy. To evaluate the yield and performance of solarbased gasifiers at country scale a multi-scale approach is required. First the operation of a solar gasifier is analyzed by developing a two-phase model validated and scaled to industrial level. Next the performance and yield of such technology as a function of the radiation received is studied taking Spain as a case study. The results were promising obtaining a syngas rich in H2. However tar and char were not reduced due to insufficient temperature. Scale-up studies revealed energy losses to the environment in the industrial-scale gasifier which suggested the use of segmented heating. In turn diameters no larger than 0.8 m and biomass feeding rates below 0.85 kg/s highlight the deployment of a modular design due to particle size limitations. Finally the large-scale waste valorization showed that the gasifier can only operate in Spain in the summer months. It can run over 180 h/month and more than 250 days/year only in C´ adiz and Santa Cruz de Tenerife which also showed the highest yearly production capacities.

Water management is crucial for the performance of anion exchange membrane water electrolyzers (AEM-WEs) to maintain membrane hydration and enable phase separation between hydrogen gas and liquid water. Therefore careful material selection for the anode and cathode is essential to enhance reactant/product transport and optimize water management under ‘dry cathode’ conditions. This study investigates the wetting characteristics of two commercially available porous transport layers (PTLs) used in AEM-WE: carbon paper and carbon paper with a microporous layer (MPL). Wettability was measured under static quasi-static and dynamic conditions to assess the effect of water and electrolytes (NaOH KOH K2CO3) across concentrations (up to 1 M) and operational temperatures (20 °C to 92 °C). Carbon paper exhibits mild hydrophobicity (advancing contact angles of ∼120° however with receding contact angle ∼0°) whereas carbon paper with MPL demonstrates superhydrophobicity (advancing and receding contact angles >145° and low contact angle hysteresis) maintaining a stable Cassie-Baxter wetting state. Dynamic wetting experiments confirmed the robustness of the superhydrophobicity in carbon paper with MPL facilitating phase separation between hydrogen gas and liquid water. The presence of supporting electrolytes did not significantly affect wettability and the materials retained hydrophobic properties across different temperatures. These findings highlight the importance of MPLs in optimizing water transport and gas rejection within AEM-WEs ensuring efficient and stable operation under “dry cathode” conditions. These PTLs (with and without the addition of the MPL) were integrated into AEM-WE and polarization curves were run. Preliminary data in a specific condition suggested the presence of the MPL within the PTL enhance AEM-WE performance.

Within energy system analysis there is discourse regarding the role and economic benefits of nuclear energy in terms of overall system costs. The reported findings range from considerable drawbacks to substantial benefits depending on the chosen models scenarios and underlying assumptions. This article addresses existing gaps by demonstrating how subtle variations in model assumptions significantly impact analysis outcomes. Historically uncertainties associated with nuclear energy costs have been well documented whereas renewable energy costs have steadily declined and have been relatively predictable. However as land availability increasingly constrains future renewable expansion development is shifting from onshore to offshore locations where cost uncertainties are greater and anticipated cost reductions are less reliable. This study emphasizes this fundamental shift highlighting how uncertainties in future renewable energy costs could strengthen the economic case of nuclear energy within fully integrated sector-coupled energy systems especially when the costs of all technologies and weather conditions are set in the moderate range. Focusing specifically on Denmark this article presents a thorough sensitivity analysis of renewable energy costs and weather conditions within anticipated future ranges providing a nuanced perspective on the role of nuclear energy. Ultimately the findings underscore that when examining total annual system costs the differences between scenarios with low and high nuclear energy shares are minimal and are within ±5 % for the baseline assumptions while updated adjustments reduce this variation to ±1 %.

Hydrogen production from water electrolysis can not only reduce greenhouse gas emissions but also has abundant raw materials which is one of the ideal ways to produce hydrogen from new energy. The hydrogen production power supply is the core component of the new energy electrolytic water hydrogen production device and its characteristics have a significant impact on the efficiency and purity of hydrogen production and the service life of the electrolytic cell. In essence the DC/DC converter provides the large current required for hydrogen production. For the converter its input still needs the support of a DC power supply. Given the maturity and technical characteristics of new energy power generation integrating energy storage into offshore energy systems enables stable power supply. This configuration not only mitigates energy fluctuations from renewable sources but also further reduces electrolysis costs providing a feasible pathway for large-scale commercialization of green hydrogen production. First this paper performs a simulation analysis on the wind–solar hybrid energy storage power generation system to demonstrate that the wind–solar–storage system can provide stable power support. It places particular emphasis on the significance of hydrogen production power supply design—this focus stems primarily from the fact that electrolyzers impose specific requirements on high operating current levels and low current ripple which exert a direct impact on the electrolyzer’s service life hydrogen production efficiency and operational safety. To suppress the current ripple induced by high switching frequency and high output current traditional approaches typically involve increasing the output inductor. However this method substantially increases the volume and weight of the device reduces the rate of current change and ultimately results in a degradation of the system’s dynamic response performance. To this end this paper focuses on developing a virtual impedance control technology aiming to reduce the ripple amplitude while avoiding an increase in the filter inductor. Owing to constraints in current experimental conditions this research temporarily relies on simulation data. Specifically a programmable power supply is employed to simulate the voltage output of the wind–solar–storage hybrid system thereby bringing the simulation as close as possible to the actual operating conditions of the wind–solar–storage hydrogen production system. The experimental results demonstrate that the proposed method can effectively suppress the ripple amplitude maintain high operating efficiency and ultimately meet the expected research objectives. That makes it particularly suitable as a high-quality power supply for offshore hydrogen production systems that have strict requirements on volume and weight.

Achieving net-zero emissions requires major changes across a nation’s economy energy and land systems particularly due to sectors where emissions are difficult to eliminate. Here we adapt two global scenarios from the International Energy Agency—the net-zero emissions by 2050 and the Stated Policies Scenario—using an integrated numerical economic-energy model tailored to Australia. We explore how emissions may evolve by sector and identify key technologies for decarbonisation. Our results show that a rapid shift to near-zero emissions electricity is central to reducing costs and enabling wider emissions reductions. From 2030 onwards carbon removal through land management and engineered solutions such as direct air capture and bioenergy with carbon capture and storage becomes critical. Australia is also well-positioned to become a global supplier of clean energy such as hydrogen made using renewable electricity helping reduce emissions beyond its borders.

Hydrogen (H2) has the potential to become a cleaner fuel alternative to increase energy mix versatility as part of a low-carbon economy. Geological H2 storage represents a key component of the emerging H2 value chain since large-scale energy generation linked to energy generation and large-scale industrial applications will require significant upscaling of geological storage. Geological H2 storage can take place in both salt domes and bedded salt formations. Bedded salt formations offer a significant advantage for H2 storage over salt domes because of their widespread availability. This research focuses on evaluating the H2 storage potential of the Salado Formation a bedded salt deposit in the Permian Basin of West Texas in the United States. Using data from 3268 well logs this study analyzes an area of 136100 km2 to identify suitable depth and net halite thickness for H2 storage in salt caverns. In addition this work applies a novel geostatistical workflow to quantify the uncertainty in the formation’s storage potential. The H2 working gas potential of the Salado Formation ranges from 0.62 to 17.53 Tsm3 (1.75–49.68 PWh of stored energy) across low-risk to high-risk scenarios with a median potential of 1.19 Tsm3 (3.37 PWh). The counties with the largest storage potential are: Lea in New Mexico and Gaines and Andrews in Texas. These three counties account for more than 75 % of the formation’s total storage potential. This is the first study to quantify uncertainty in H2 storage estimates for a bedded salt formation while providing a detailed breakdown of results by county and 1 km2 grid sections. The findings of this work offer critical insights for developing H2 infrastructure in the Permian Basin. The Permian Basin of West Texas has the potential to become an important hub for H2 production from both natural gas and/or renewable energy. Estimating H2 storage potential is an important contribution to assess the feasibility of the entire H2 value chain in Texas. An interactive map accompanies this work allowing the readers to explore the results visually.

Hydrogen is increasingly recognized as a clean energy alternative offering effective storage solutions for widespread adoption. Advancements in storage electrolysis and fuel cell technologies position hydrogen as a pathway toward cleaner more efficient and resilient energy solutions across various sectors. However challenges like infrastructure development cost-effectiveness and system integration must be addressed. This review comprehensively examines above-ground hydrogen storage technologies and their applications. It highlights the importance of established hydrogen fuel cell infrastructure particularly in gaseous and LH2 systems. The review favors material-based storage for medium- and long-term needs addressing challenges like adverse thermodynamics and kinetics for metal hydrides. It explores hydrogen storage applications in mobile and stationary sectors including fuel-cell electric vehicles aviation maritime power generation systems off-grid stations power backups and combined renewable energy systems. The paper underscores hydrogen’s potential to revolutionize stationary applications and co-generation systems highlighting its significant role in future energy landscapes.

This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development the MEC system was progressively adapted to winery wastewater enabling long-term electrochemical stability and high organic matter degradation. Upon winery wastewater addition (5% v/v) the system achieved a sustained hydrogen production rate of (0.7 ± 0.3) L H2 L −1 d −1 with an average current density of (60 ± 4) A m−3 and COD removal efficiency exceeding 55% highlighting the system’s resilience despite the presence of inhibitory compounds. Coulombic efficiency and cathodic hydrogen recovery reached (75 ± 4)% and (87 ± 5)% respectively. Electrochemical impedance spectroscopy provided mechanistic insight into charge transfer and biofilm development correlating resistive parameters with biological adaptation. These findings demonstrate the potential of MECs to simultaneously treat agro-industrial wastewaters and recover energy in the form of hydrogen supporting circular resource management strategies.

This study presents the application of a new sustainability assessment methodology. It aims to improve the information that can be obtained from a sustainability assessment including the concept of alternative usage impact. To prove the effectiveness of this methodology three different hydrogen production methodologies considering its consumption in transportation sector is the case of study. The methodologies considered are Steam Methane Reform using natural gas Proton Exchange Membrane electrolysis one using grid electricity and the other study case using central tower solar power plant electricity from the PS10 facility. While separately green hydrogen is the technology with less environmental impact when considering the full system and the impact of the green hydrogen on the rest of the resources the integration of green hydrogen technology is not the most environmentally sustainable. Similar behavior is observed in the economic and technical fields. The different accounting of combinations of technologies and the impact on the resource which is not used provides the sustainability performance of the overall system. These results show that in order to account the all impacts taking place in a energy technology integration its impact on the rest of resources and uses provide more valuable information.

Export-oriented green-hydrogen projects (EOGH2P) are being developed in regions with optimal renewableenergy resources. Their reliance on economies of scale makes them land-intensive and object of spatial planning policies. However the impact of spatial planning on the development of EOGH2P remains underexplored. Drawing on the spatial planning and megaproject literatures the analysis of planning documents and expert interviews this paper analyzes how spatial planning influences the development of EOGH2P in Chile Namibia and South Africa. The three countries have developed different spatial planning approaches for EOGH2Ps and are analyzed by employing a comparative case-study design. Our findings reveal that Namibia pursues a restrictive approach South Africa a facilitative approach whereas Chile is shifting from a market-based to a restrictive approach. The respective approaches reflect different political priorities and stakeholder interests and imply diverse effects on the development of EOGH2Ps in terms of their number size shared infrastructure socioenvironmental impact and acceptance. This study underscores the need for well-designed spatial planning frameworks and provides insights for planners and stakeholders on their potential effects.

Hydrogen is increasingly recognized as a key energy vector for achieving deep decarbonization across urban and industrial sectors. Supporting global efforts to reduce greenhouse gas (GHG) emissions and achieve the Sustainable Development Goals (SDGs) it is essential to understand the multi-sectoral role of the hydrogen value chain spanning production storage and end-use applications with particular emphasis on smart city systems and industrial processes. Green hydrogen production technologies including alkaline water electrolysis (AWE) proton exchange membrane (PEM) electrolysis anion exchange membrane (AEM) electrolysis and solid oxide electrolysis cells (SOECs) are evaluated in terms of efficiency scalability and integration potential. Storage pathways are examined across physical storage (compressed gas cryo-compressed and liquid hydrogen) material-based storage (solid-state absorption in metal hydrides and chemical carriers such as LOHCs and ammonia) and geological storage (salt caverns depleted gas reservoirs and deep saline aquifers) highlighting their suitability for urban and industrial contexts. In the smart city domain hydrogen is analyzed as an enabler of zero-emission transportation low-carbon residential and commercial heating and renewable-integrated smart grids with long-duration storage capabilities. System-level studies demonstrate that coordinated integration of these applications can deliver higher overall energy efficiency deeper reductions in life-cycle GHG emissions and improved resilience of urban energy systems compared with sector-specific approaches. Policy frameworks safety standards and digitalization strategies are reviewed to illustrate how hydrogen infrastructure can be embedded into interconnected urban energy systems. Furthermore industrial applications focus on hydrogen’s potential to decarbonize energy-intensive processes and enable sector coupling between electricity heat and manufacturing. The environmental implications of hydrogen deployment are also considered including resource efficiency life-cycle emissions and ecosystem impacts. In contrast to reviews addressing isolated aspects of hydrogen technologies this study synthesizes technological infrastructural and policy dimensions integrating insights from over 400 studies to highlight the multifaceted role of hydrogen in sustainable urban development and industrial decarbonization and the added benefits achievable through coordinated cross-sector deployment strategies.

Every five years as mandated in its founding regulation the European Environment Agency (EEA) publishes a state of the environment report. Europe's environment 2025 provides decision makers at European and national levels as well as the general public with a comprehensive and cross-cutting assessment on environment climate and sustainability in Europe. Europe's environment 2025 is the 7th state of the environment report published by the EEA since 1995. Europe's environment 2025 has been prepared in close collaboration with the EEA’s European Environment Information and Observation Network (Eionet). The report draws on the Eionet’s vast expertise of leading experts and scientists in the environmental field across the EEA’s 32 member countries and six cooperating countries.

Hydrogen recirculation is essential for maintaining fuel efficiency and durability in Proton Exchange Membrane Fuel Cell (PEMFC) systems particularly in automotive range extender applications. This study presents the design simulation and experimental validation of a dry all-metal scroll pump developed for hydrogen recirculation in a 5 kW PEMFC system. The pump operates without oil or polymer seals offering long-term compatibility with dry hydrogen. Two prototypes were fabricated: SP1 incorporating PTFE-bronze tip seals and SP2 a fully metallic seal-free design. A fully deterministic one-dimensional (1D) model was developed to predict thermodynamic performance including leakage and heat transfer effects and validated against experimental results. SP1 achieved higher flow rates due to reduced axial leakage but experienced elevated friction and temperature. In contrast SP2 provided improved thermal stability and lower friction with slightly reduced flow performance. The pump demonstrated a maximum flow rate of 50 l/min and an isentropic efficiency of 82.2 % at 2.5 bara outlet pressure. Simulated performance showed strong agreement with experimental results with deviations under 5 %. The findings highlight the critical role of thermal management and manufacturing tolerances in dry scroll pump design. The seal-free liquid-cooled scroll architecture presents a promising solution for compact oil-free hydrogen recirculation in low-power fuel cell systems.

For reaching the European greenhouse gas emission targets the phase-in of alternative technologies and energy carriers is crucial for all sectors. For the transport sector synthetic fuels are–next to electromobility–a promising option especially for long-distance shipping and air transport. Within this context the import of synthetic fuels from the Middle East and Northern Africa (MENA) region seems attractive due to low costs for renewable electricity in this region and low transport costs of synthetic fuels at the same time. Against this background this paper analyzes the role of the MENA region in meeting the future synthetic fuel demand in Europe using a cost-optimizing energy supply model. In this model the production storage and transport of electricity hydrogen and synthetic fuels by various technologies in both European and MENA countries in the period up to 2050 are explicitly modeled. Thereby different scenarios are analyzed to depict regional differences in investment risks: a base scenario that does not take into account regional differences in investments risks and three risk scenarios with different developments of regional investment risks. Sensitivity analyses are also carried out to derive conclusions about the robustness of results. Results show that meeting the future synthetic fuel demand in Europe to a large extent by imports from the MENA region can be an attractive option from an economic point of view. If investment risks are incorporated however lower import quotas of synthetic fuels are economically attractive for Europe: the higher generation costs are outweighed by the lower investments risks in Europe to a certain extent. Thereby investment risks outweigh other factors such as transport distance or renewable electricity generation costs in terms of exporting MENA regions and a synthetic fuel import is especially attractive from MENA countries with low investment risks. Concluding within this paper detailed export relations between MENA and EU considering investment risks were modeled for the first time. These model results should be complemented by a more in-depth analysis of the MENA countries including evaluating opportunities for local value chain development sustainability concerns (including social factors) and optimal site selection.

The urgent need to mitigate climate change and reduce greenhouse gas emissions has accelerated the search for sustainable and scalable energy carriers. Among the different alternatives ammonia stands out as a promising carbon-free fuel thanks to its high energy density efficient storage and compatibility with existing infrastructure. Moreover it can be produced through sustainable green processes. However its application in internal combustion engines is limited by several challenges including low reactivity narrow flammability limits and high ignition energy. These factors can compromise combustion efficiency and contribute to increased unburned ammonia emissions. To address these limitations hydrogen has emerged as a complementary fuel in dual-fuel configurations with ammonia. Hydrogen’s high reactivity enhances flame stability ignition characteristics and combustion efficiency while reducing emissions of unburned ammonia. This review examines the current status of dual-fuel ammonia and hydrogen combustion strategies in internal combustion engines and summarizes the experimental results. It highlights the potential of dual-fuel systems to optimize engine performance and minimize emissions. It identifies key challenges knowledge gaps and future research directions to support the development and widespread adoption of ammonia–hydrogen dual-fuel technologies.

Hydrogen offers a promising solution to reduce emissions in the energy sector with the growing need for decarbonisation. Despite its environmental benefits the use of hydrogen presents significant challenges in storage and transport. Many studies have focused on the different types of hydrogen production and analysed the pros and cons of each technique for different applications. This study focuses on techno-economic analysis of onsite hydrogen production through ammonia decomposition by utilising the heat from exhaust gas generated by hydrogen-fuelled gas turbines. Aspen Plus simulation software and its economic evaluation system are used. The Siemens Energy SGT-400 gas turbine’s parameters are used as the baseline for the hydrogen gas turbine in this study together with the economic parameters of the capital expenditure (CAPEX) and operating expenditure (OPEX) are considered. The levelised cost of hydrogen (LCOH) is found to be 5.64 USD/kg of hydrogen which is 10.6% lower than that of the conventional method where a furnace is used to increase the temperature of ammonia. A major contribution of the LCOH comes from the ammonia feed cost up to 99%. The price of ammonia is found to be the most sensitive parameter of the contribution to LCOH. The findings of this study show that the use of ammonia decomposition via heat recovery for onsite hydrogen production with ammonic recycling is economically viable and highlight the critical need to further reduce the prices of green ammonia and blue ammonia in the future.

Decarbonizing ammonia production is critical to meeting global climate targets in agriculture. This study evaluates two hydrogen pathways plasmalysis and electrolysis at Ontario’s Courtright Complex using detailed techno-economic modeling. The natural gas–based plasma system achieves the lowest hydrogen cost ($1.35/kg) but incurs high annual fuel expenses ($297.7 M/y) and shows strong sensitivity to natural gas prices. Electrolysis powered by 110 MW PV 1700 MW wind 60 MW biomass 95 MWh battery storage and a 2.0 GW electrolyzer produces hydrogen at $2.07/kg with lower fuel costs ($29.7 M/y) and significant grid interaction (2.67 TWh/y imports and 1.89 TWh/y exports) enhancing operational flexibility. Over a 15-year horizon both pathways deliver substantial CO2 reductions (plasmalysis: 27000 kt; electrolysis: 26045 kt). Extending plant lifetimes from 10 to 30 y reduces the levelized cost of hydrogen from $2.25 to $1.91/kg in the plasmalysis case and from $1.52 to $1.18/kg in the electrolysis case while increasing overall net present cost. Although electrolysis requires higher capital investment ($5.53 B compared with $1.79 B) it demonstrates resilience to fuel price volatility and provides additional grid revenue. In contrast plasmalysis offers near-term cost advantages but remains dependent on fossil gas underscoring its role as a transitional rather than fully green option for ammonia decarbonization.

Green hydrogen is emerging as a pivotal energy carrier in the global transition toward decarbonization offering a sustainable alternative to fossil fuels in sectors such as heavy industry transportation power generation and long-duration energy storage. Despite its potential large-scale deployment remains hindered by significant economic technological and infrastructure challenges. Current production costs for green hydrogen range from USD 3.8 to 11.9/kg H2 significantly higher than gray hydrogen at USD 1.5–6.4/kg H2 due to high electricity prices and electrolyzer capital costs exceeding USD 2000 per kW. This review critically examines the key bottlenecks in green hydrogen production focusing on water electrolysis technologies electrocatalyst limitations and integration with renewable energy sources. The economic viability of green hydrogen is constrained by high electricity consumption capital-intensive electrolyzer costs and operational inefficiencies making it uncompetitive with fossil fuel-based hydrogen. Infrastructure and supply chain challenges including limited hydrogen storage transport complexities and critical material dependencies further restrict market scalability. Additionally policy and regulatory gaps disparities in financial incentives and the absence of a standardized certification framework hinder international trade and investment in green hydrogen projects. This review also highlights market trends and global initiatives assessing the role of government incentives and cross-border collaborations in accelerating hydrogen adoption. While technological advancements and cost reductions are progressing overcoming these challenges requires sustained innovation stronger policy interventions and coordinated efforts to develop a resilient scalable and cost-competitive green hydrogen sector.

Dual-fuel engines are a way of transitioning the marine sector to carbon-neutral fuels like hydrogen and methanol. For the development of these engines accurate simulation of the combustion process is needed for which calculating the pilot’s ignition delay is essential. The present work investigates novel methodologies for calculating this. This involves the use of chemical kinetic schemes to compute the ignition delay for various operating conditions. Machine learning techniques are used to train models on these data sets. A neural network model is then implemented in a dual-fuel combustion model to calculate the ignition delay time and is compared using a lookup table or a correlation. The numerical results are compared with experimental data from a dual-fuel medium-speed marine engine operating with hydrogen or methanol from which the method with best accuracy and fastest calculation is selected.

The present investigation aims to provide a comparative assessment of using hydrogen-enriched wood waste-derived producer gas (PG) for a dual-fuel diesel engine fueled with a 20% Jatropha biodiesel/80% diesel blend (BD20) with the traditional mode. The experiments were conducted at 23°bTDC of injection timing 240 bar of injection pressure 17.5:1 of compression ratio and 1500 rpm of engine speed under various engine loads. Gas carburetor induction (GCI) port injection (PI) and inlet manifold injection (IMI) methods were used to supply H2-enriched PG while B20 is directly injected into the combustion chamber. Among all the combinations the IMI method provided the highest brake thermal efficiency of 30.91% the lowest CO emission of 0.08% and smoke opacity discharge of 49.26 HSU while NOx emission reached 1744.32 ppm which was lower than that of the PI mode. Furthermore the IMI method recorded the highest heat release rate of 91.17 J/°CA and peak cylinder pressure of 83.29 bar reflecting superior combustion quality. Finally using the IMI method for H2-enriched PG in dual-fuel diesel engines could improve combustion efficiency reduce greenhouse gas emissions and improve fuel economy showing that the combination of BD20 with H2-enriched PG offers a cleaner more sustainable and economically viable technology.

Renewable energy systems are at the core of global efforts to reduce greenhouse gas (GHG) emissions and to combat climate change. Focusing on the role of energy storage in enhancing dependability and efficiency this paper investigates the design and optimization of a completely sustainable hybrid energy system. Furthermore hybrid storage systems have been used to evaluate their viability and cost-benefits. Examined under a 100% renewable energy microgrid framework three setup configurations are as follows: (1) photovoltaic (PV) and Battery Storage System (BSS) (2) Hybrid PV/Wind Turbine (WT)/BSS and (3) Integrated PV/WT/BSS/Electrolyzer/ Hydrogen Tank/Fuel Cell (FC). Using its geographical solar irradiance and wind speed data this paper inspires on an industrial community in Neom Saudi Arabia. HOMER software evaluates technical and economic aspects net present cost (NPC) levelized cost of energy (COE) and operating costs. The results indicate that the PV/ BSS configuration offers the most sustainable solution with a net present cost (NPC) of $2.42M and a levelized cost of electricity (LCOE) of $0.112/kWh achieving zero emissions. However it has lower reliability as validated by the provided LPSP. In contrast the PV/WT/BSS/Elec/FC system with a higher NPC of $2.30M and LCOE of $0.106/kWh provides improved energy dependability. The PV/WT/BSS system with an NPC of $2.11M and LCOE of $0.0968/kWh offers a slightly lower cost but does not provide the same level of reliability. The surplus energy has been implemented for hydrogen production. A sensitivity analysis was performed to evaluate the impact of uncertainties in renewable resource availability and economic parameters. The results demonstrate significant variability in system performance across different scenarios

In recent years the utilization of aluminium (Al) Al alloys and their composite powder and anode encourages the generation of green hydrogen through hydrolysis and water splitting electrolysis with zero emissions. As such in this study the development and characterization of Al Al alloys and Al-based composite powder and compacted Al composites for clean hydrogen production using hydrolysis and water splitting processes were reviewed. Herein based on the available literature it is worth mentioning that the incorporation of active additives such as h-BN Bi@C g-C3N4 MoS2 Ni In Fe and BiOCl@CNTs in the Al-based composites using ball milling melting smelting casting and spark plasma sintering technique remarkably improved the rate of hydrogen evolution and hydrogen gas conversion yield particularly during hydrolysis of Al-water reaction. Again Al-based electrodes with improved electrical conductivity notably results in better water splitting electrolysis as well as fast chemical reaction in achieving hydrogen gas production at low energy consumption with efficiency. Though notwithstanding the significance of Al Al alloy and Al-based composite hydrogen generation performances there are still some challenges associated with the Al-based materials for hydrogen production via hydrolysis and water electrolysis. For example the low current density and poor electrochemical properties of Al which on the other hand results in long induction time high overpotential and cost remains a gap to bridge. Hence the authors concluded the review study with recommendations for future improvement of Al-based composite electrodes on hydrogen production and sustainability via hydrolysis and water electrolysis. Thus the study will pave the way for further research on clean hydrogen energy generation.

Electricity in rural Alaska is provided by more than 200 standalone microgrid systems powered predominantly by diesel generators. Incorporating renewable energy generation and storage to these systems can reduce their reliance on costly imported fuel and improve sustainability; however uncertainty remains about optimal grid architectures to minimize cost including how and when to incorporate long-duration energy storage. This study implements a novel multi-pronged approach to assess the techno-economic feasibility of future energy pathways in the community of Kotzebue which has already successfully deployed solar photovoltaics wind turbines and battery storage systems. Using real community load resource and generation data we develop a series of comparison models using the HOMER Pro software tool to evaluate microgrid architectures to meet over 90% of the annual community electricity demand with renewable generation considering both battery and hydrogen energy storage. We find that near-term planned capacity expansions in the community could enable over 50% renewable generation and reduce the total cost of energy. Additional build-outs to reach 75% renewable generation are shown to be competitive with current costs but further capacity expansion is not currently economical. We additionally include a cost sensitivity analysis and a storage capacity sizing assessment that suggest hydrogen storage may be economically viable if battery costs increase but large-scale seasonal storage via hydrogen is currently unlikely to be cost-effective nor practical for the region considered. While these findings are based on data and community priorities in Kotzebue we expect this approach to be relevant to many communities in the Arctic and Sub-Arctic regions working to improve energy reliability sustainability and security.

Smart energy systems can be used to generate additional financial value by providing flexibility to the electricity network. It is fundamental to the effective economic implementation of these systems that an assessment can be made in advance to determine available value in comparison with any additional costs. The basic premise is that there is a distinct advantage in using similar algorithms to an actual smart energy system implementation for value assessment and that this is practical in this context which is confirmed in comparison with simpler modelling methods. Analysis has been undertaken using a ‘green’ hydrogen system case study of the impact of various simplifications to the value assessment algorithms used to speed computation time without sacrificing the decisionmaking potential of the output. The results indicate that for localised energy systems with a small number of controllable assets an rolling horizon optimisation model with a significant degree of temporal and component complexity is viable for planning phase value assessment requirements and would be a similar level of complexity to a computationally suitable implementation algorithm for actual asset control decision making.

The environmentally vulnerable Arctic’s harsh climate and remote geography demand innovative green energy solutions. This study introduces a hybrid off-grid system that integrates wave and wind energy with hydrogenelectricity conversion technologies. Designed to power cruise ships at berth fuel-cell hybrid electric vehicles and residential heating the system tackles the challenge of energy variability through dual optimization schemes. External optimization identifies a cost-effective architecture achieving a net present cost of $1.1M and a levelized hydrogen cost of $20.1/kg without a fuel cell. Internal optimizations employing multi-objective game theory and HYBRID algorithms further improve performance reducing the net present cost to $666K with a levelized hydrogen cost of $13.74/kg (game theory) and $729K with a levelized hydrogen of $15.63/kg (HYBRID). A key innovation is hydrokinetic turbines which streamline the design by cutting cumulative cash flow requirements by $470K from $1.85M to $1.38M. This approach prioritizes intelligent energy management shifting reliance from variable wind and wave inputs to optimized electrolyzer and battery operations. These results underscore the feasibility of cost-effective and scalable renewable energy systems and provide a compelling blueprint for addressing energy challenges in remote and resource-constrained environments.

Hydrogen fuel cell vehicles (HFCVs) are vital for advancing the hydrogen economy and decarbonizing the transportation sector. However research on HFCV market dynamics in passenger vehicles is limited especially incorporating both market competition from other vehicle types and the comprehensive supply–demand market dynamics. To bridge this gap our study proposed a spatial agent-based model to simulate the HFCV market evolution with the aim of finding effective strategies and policy implications for breaking the diffusion dilemma of the HFCV market. We calibrated the model using survey data (N=1065) collected from Beijing and evaluated its performance across five “What-If” scenarios. Results indicate that HFCVs and hydrogen stations are difficult to penetrate under the current conditions despite HFCV applicants and market share growing by 37.5% and 15.63% respectively. Consumer perceptions on cost social and environment have greater impacts on HFCV proliferation than facility availability. The HFCV purchase subsidy has much greater impact than the technological learning rate greatly accelerating its market emergence timing. Finally HFCVs’ diffusion significantly influences the market of battery electric vehicles.

The widespread adoption of hydrogen-fueled vehicles (HFVs) and the deployment of Hydrogen Refueling Stations (HRS) hinge on the ability to accurately predict system performance and ensure operational reliability. This study proposes a novel predictive framework integrating mathematical modeling state-space analysis and advanced data mining techniques supported by reliability analysis to evaluate the performance of HFVs and their associated refueling infrastructure. Utilizing a public dataset of 500 real-time operational data points key performance indicators are statistically analyzed. A significant negative correlation (r = −0.56) between hydrogen consumption and maximum vehicle range is identified highlighting that improved hydrogen efficiency directly extends travel range. The average maximum range is 555.21 km with a standard deviation of 87.09 km and a median of 563.65 km indicating strong consistency across vehicles. These findings underscore the importance of optimizing fuel efficiency to enhance system sustainability and inform the design and operation of next-generation hydrogen mobility solutions. The proposed approach offers a robust foundation for performance forecasting infrastructure planning and policy development in hydrogen-based transportation systems.

This study introduces the Smart Grid Hybrid Electrolysis-and-Combustion System (SGHE-CS) designed to seamlessly integrate hydrogen production storage and utilization within smart grid operations to maximize renewable energy use and maintain grid stability. The system achieves a hydrogen production efficiency of 98.5% indicating the effective conversion rate of electrical energy to hydrogen via PEM electrolysis. Combustion efficiency reaches 98.1% reflecting the proportion of hydrogen energy successfully converted into usable power through advanced staged combustion. Storage and transportation efficiency is 96.3% accounting for energy losses during hydrogen compression storage and delivery. Renewable integration efficiency is 97.3% representing the system’s capacity to utilize variable renewable energy inputs without curtailment. Operational versatility is 99.3% denoting the system’s ability to maintain high performance across load demands and grid conditions. Real-time monitoring and adaptive control strategies ensure reliability and resilience positioning SGHE-CS as a promising solution for sustainable low-carbon energy infrastructure.

In response to the global need to reduce greenhouse gas emissions and advance the decarbonization of thermal energy systems this study evaluates the performance of a tankless water heater operating with hydrogen–natural gas blends. The objective is to improve thermal efficiency and reduce pollutant emissions without requiring major modifications to existing equipment. Experimental tests were conducted at three thermal power levels (35 40 and 45 kW) and four hydrogen volume fractions (0% 20% 40% and 60%) analyzing operational variables such as temperatures flow rates efficiency and NOx emissions. Results show that efficiency increases with hydrogen content particularly at lower power levels reaching a maximum of 56%. NOx emissions tend to rise with both power and hydrogen fraction although this effect can be mitigated by controlling the water flow rate. In addition machine learning models were trained to predict efficiency and emissions with the scaled Support Vector Regression (SVR) model achieving R² values above 90% for both outputs. This approach not only enables system optimization but also represents a step toward the implementation of digital twins and opens the door to monitoring indirect variables offering broad potential for predictive applications in thermal equipment.

Accurate and efficient prediction of thermal radiant of hydrogen jet fire is important to schedule safety design and emergency rescue program for hydrogen pipelines. In response this paper proposes a novel Optuna-improved back propagation neural network (Optuna-BPNN) to estimate hydrogen jet flame radiation. A linear integral approach incorporating leakage rate and jet flame length is theoretically derived to establish dataset for machine learning. Then the Optuna tool is employed to optimize the initial weights and thresholds of the BP neural network. Input matrix of the Optuna-BPNN model includes pipeline diameter leakage aperture size and hydrogen pressure. 8 sets of experimental data are employed to verify its correctness. When the abnormal data is excluded the predicted thermal radiation of hydrogen jet fire agrees quite well with experimental results with average and maximum deviations being 12.4% and 24.4% respectively. Using the linear integral approach 32670 thermal radiation data points are generated to train and test the Optuna-BPNN model. The maximum deviation between predicted and theoretical radiant heat flux for training and testing sets are only 4.5% and 6.2% respectively. Parallel comparison trials using 6 different machine learning algorithms show that the Optuna-BPNN model gives the best mean absolute error root mean square error and determination coefficient which proves the effectiveness and feasibility of the developed OptunaBPNN model in predicting thermal radiation of hydrogen pipeline jet fires.

As a continuation of part 1 which examined the development status and system foundations of sustainable energy systems (SES) in the context of German energy transition this paper provides a comprehensive review of the core technologies enabling the development of SES. It covers recent advances in photovoltaic (PV) wind energy geo‑ thermal energy hydrogen and energy storage. Key trends include the evolution of high-efficiency solar and wind technologies intelligent control systems sector coupling through hydrogen integration and the diversification of electrochemical and mechanical storage solutions. Together these innovations are fostering a more flexible resil‑ ient and low-carbon energy infrastructure. The review further highlights the importance of system-level integration by linking generation conversion and storage to address the intermittency of renewable energy and support longterm decarbonization goals.