Applications & Pathways

This paper presents an energy management system (EMS) based on a novel approach using model predictive control (MPC) for the optimized operation of power sources in a hybrid charging station for electric vehicles (EVs). The hybrid charging station is composed of a photovoltaic (PV) system a battery a complete hydrogen system based on a fuel cell (FC) electrolyzer (EZ) and tank as an energy storage system (ESS) grid connection and six fast charging units all of which are connected to a common MVDC bus through Z-source converters (ZSC). The MPC-based EMS is designed to control the power flow among the energy sources of the hybrid charging station and reduce the utilization costs of the ESS and the dependency on the grid. The viability of the EMS was proved under a long-term simulation of 25 years in Simulink using real data for the sun irradiance and a European load profile for EVs. Furthermore this EMS is compared with a simpler alternative that is used as a benchmark which pursues the same objectives although using a states-based strategy. The results prove the suitability of the EMS achieving a lower utilization cost (-25.3%) a notable reduction in grid use (-60% approximately) and an improvement in efficiency.

Hydrogen demand estimation for various transport modes supports policy and decision-making for the transition towards a sustainable low-carbon future transport system. It is one of the major factors that determine infrastructure construction production and distribution cost optimisation. Researchers have developed various methods for modelling hydrogen demand and its geographical distribution each based on different sets of predictor variables. This paper systematically reviews these methods and examines the key variables used in hydrogen demand estimation including the number of vehicles travel distance penetration rate and fuel economy. It emphasises the role of spatial analysis in uncovering the geographical distribution of hydrogen demand providing insights for strategic infrastructure planning. Furthermore the discussion underscores the significance of minimising uncertainty by incorporating multiple scenarios into the model thereby accommodating the dynamic nature of hydrogen adoption in transport. The necessity for multi-temporal estimation which accounts for the changing nature of hydrogen demand over time is also highlighted. In addition this paper advocates for a holistic approach to hydrogen demand estimation integrating spatiotemporal analysis. Future research could enhance the reliability of hydrogen demand models by addressing uncertainty through advanced modelling techniques to improve accuracy and spatial-temporal resolution.

This second edition of the European Maritime Transport Environmental Report (EMTER 2025) examines the progress made towards achieving Europe′s decarbonisation targets and environmental goals for the maritime sector while indicating the most important trends key challenges and opportunities. The objective was to update the indicators developed for the first report analyse new datasets and fill existing gaps to provide a data and knowledge-based assessment of the maritime transport sector′s transition to sustainability.

In this study Distribution of Relaxation Times (DRT) was successfully demonstrated in the analysis of the impedance spectra of High-Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC) doped with phosphoric acid. Electrochemical impedance spectroscopy (EIS) was performed and the quality of the recorded spectra was verified by Kramers-Kronig relations. DRT was then applied to the measured spectra and polarization losses were separated on the basis of their typical time constants. The main features of the distribution function were assigned to the cell’s polarization processes by selecting appropriate experimental conditions. DRT can be used to identify individual internal HT-PEMFC fuel cell phenomena without any a-priori knowledge about the physics of the system. This method has the potential to further improve EIS spectra interpretation with either equivalent circuits or physical models.

Aviation is one of the most important industries in the current global scenario but it has a significant impact on climate change due to the large quantities of carbon dioxide emitted daily from the use of fossil kerosene-based fuels (jet fuels). Although technological advancements in aircraft design have enhanced efficiency and reduced emissions over the years the rapid growth of the aviation industry presents challenges in meeting the environmental targets outlined in the “Flightpath 2050” report. This highlights the urgent need for effective decarbonisation strategies. Hydrogen propulsion via fuel cells or combustion offers a promising solution with the combustion route currently being more practical for a wider range of aircraft due to the limited power density of fuel cells. In this context this paper designs and models a nitrogen–hydrogen heat exchanger architecture for use in an innovative hydrogen-propelled aircraft fuel system where the layout was recently proposed by the same authors to advance sustainable aviation. This system stores hydrogen in liquid form and injects it into the combustion chamber as a gas making the cryogenic heat exchanger essential for its operation. In particular the heat exchanger enables the vaporisation and superheating of liquid hydrogen by recovering heat from turbine exhaust gases and utilising nitrogen as a carrier fluid. A pipe-in-pipe design is employed for this purpose which to the authors’ knowledge is not yet available on the market. Specifically the paper first introduces the proposed heat exchanger architecture then evaluates its feasibility with a detailed thermodynamic model and finally presents the calculation results. By addressing challenges in hydrogen storage and usage this work contributes to advancing sustainable aviation technologies and reducing the environmental footprint of air travel.

The marine industry being the backbone of world trade is under tremendous pressure to reduce its environmental impact mainly driven by reliance on fossil fuels and significant greenhouse gas emissions. This paper looks at hydrogen as a transformative energy vector for maritime logistics. It delves into the methods of hydrogen production innovative propulsion technologies and the environmental advantages of adopting hydrogen. The analysis extends to the economic feasibility of this transition and undertakes a comparative evaluation with other alternative fuels to emphasize the distinct strengths and weaknesses of hydrogen. Furthermore based on case studies and pilot projects this study elaborates on how hydrogen can be used in real-world maritime contexts concluding that the combination of ammonia and green hydrogen in hybrid propulsion systems presents increased flexibility with ammonia serving as the primary fuel while hydrogen enhances efficiency and powers auxiliary systems. This approach represents a promising solution for reducing the shipping sector’s carbon footprint enabling the industry to achieve greater sustainability while maintaining the efficiency and scalability essential for global trade. Overall this work bridges the gap between theoretical concepts and actionable solutions therefore offering valuable insights into decarbonization in the maritime sector and achieving global sustainability goals.

To achieve deep decarbonization in the transportation sector this study employs life cycle assessment (LCA) and the GREET model to construct baseline and low-carbon scenarios. It simulates the evolution of emissions and energy consumption within Inner Mongolia’s public transportation energy system (including diesel buses (DBs) electric buses (EBs) and hydrogen fuel cell buses (HFCBs)) from 2022 to 2035 while exploring synergistic pathways for its low-carbon transition. Results reveal that under the baseline scenario reliance on industrial by-product hydrogen causes fuel cell bus emissions to increase by 3.64% in 2025 compared to 2022 with system energy savings below 10% and decarbonization potential will be constrained by scale limitations and storage/transportation losses in cold regions. Under the low-carbon scenario deep grid decarbonization vehicle structure optimization and green hydrogen integration reduced system emissions and energy consumption by 66.86% and 40.44% respectively compared to 2022. The study identifies a 15% green hydrogen penetration rate as the critical threshold for resource misallocation and confirms grid decarbonization as the top-priority policy tool yielding marginal benefits 1.43 times greater than standalone hydrogen policies. This study underscores the importance of multipolicy coordination and ‘technology-supply chain’ synergy particularly highlighting the critical threshold of green hydrogen penetration and the primacy of grid decarbonization offering insights for similar coal-dominated cold-region transportation energy transitions.

Hydrogen is widely considered advantageous for long-duration storage applications however the conditions under which hydrogen outperforms batteries remain unclear. This study employs a novel load parameterisation approach to systematically examine the conditions under which integrating hydrogen significantly reduces the levelised cost of energy (LCOE). The study analyses a broad spectrum of 210 synthetic load profiles varying independently in duration frequency and timing at two Australian locations. This reveals that batteries dominate short frequent or wellaligned solar loads and that hydrogen becomes economically beneficial during prolonged infrequent or poorly aligned loads—achieving up to 122 % (Gladstone) and 97 % (Geelong) LCOE improvements under current fuel cell costs and even higher savings under reduced costs. This systematic method clarifies the load characteristics thresholds that define hydrogen’s advantage providing generalisable insights beyond individual case studies.

In rotating machinery unbalanced mass is one of the most common causes of system vibration. This paper presents an experimental investigation of the unbalance response of a gas foil bearing-rotor system based on a 30 kW-rated commercial hydrogen fuel cell vehicle air compressor. The study examines the response of the system to varying unbalanced masses at different rotational speeds. Experimental results show that after adding unbalanced mass subsynchronous vibration of the rotor is relatively slight while synchronous vibration is the main source of vibration; when unbalanced mass is added to one side of the rotor the synchronous vibration on that side initially decreases and then increases with speed while synchronous vibration on the opposite side continuously increases with speed; when unbalanced mass is added to both sides the synchronous vibration on each side increases with the phase difference of the unbalanced mass at low speed while the opposite trend occurs at high speed. The analysis of the gas foil bearingrotor system dynamics model established based on the dynamic coefficient of the bearing shows that the bending of the rotor offsets the displacement caused by the unbalanced mass which is the primary reason for the nonlinear behavior of the synchronous vibration of the rotor. These findings contribute to an improved understanding of GFB-rotor interactions under unbalanced conditions and provide practical guidance for optimizing dynamic balancing strategies in hydrogen fuel cell vehicle compressors.

The increase in power generation facilities from nonprogrammable renewable sources is posing several challenges for the management of electrical systems due to phenomena such as congestion and reverse power flows. In mitigating these phenomena Power-to-Gas plants can make an important contribution. In this paper a linear optimisation study is presented for the sizing of a Power-to-Hydrogen plant consisting of a PEM electrolyser a hydrogen storage system composed of multiple compressed hydrogen tanks and a fuel cell for the eventual reconversion of hydrogen to electricity. The plant was sized with the objective of minimising reverse power flows in a medium-voltage distribution network characterised by a high presence of photovoltaic systems considering economic aspects such as investment costs and the revenue obtainable from the sale of hydrogen and excess energy generated by the photovoltaic systems. The study also assessed the impact that the electrolysis plant has on the power grid in terms of power losses. The results obtained showed that by installing a 737 kW electrolyser the annual reverse power flows are reduced by 81.61% while also reducing losses in the transformer and feeders supplying the ring network in question by 17.32% and 29.25% respectively on the day with the highest reverse power flows.

Addressing the critical need for sustainable high-density hydrogen (H2) carriers to decarbonize the global energy landscape this paper presents a comprehensive critical review of ammonia’s pivotal role in the energy transition with a specific focus on its application in the transportation sector. While H2 is recognized as a future fuel its storage and distribution challenges necessitate alternative vectors. Ammonia (NH3) with its compelling advantages including high volumetric H2 density established global infrastructure and potential for near-zero greenhouse gas emissions emerges as a leading candidate. This review uniquely synthesizes the evolving landscape of sustainable NH3 production pathways (e.g. green NH3 from renewable electricity) with a systematic analysis of technological advancements to investigate its direct utilization as a transportation fuel. The paper critically examines the multifaceted challenges and opportunities associated with NH3-fueled vehicles refueling infrastructure development and comprehensive safety considerations alongside their environmental and economic implications. By providing a consolidated forward-looking perspective on this complex energy vector this paper offers crucial insights for researchers policymakers and industry stakeholders highlighting NH3’s transformative potential to accelerate the decarbonization of hard-to-abate transportation sectors and contribute significantly to a sustainable energy future.

As an efficient and low-carbon renewable energy source hydrogen plays a strategic role in the global energy transition particularly in the transportation sector. However the flammable and explosive nature of hydrogen makes leakage risks in enclosed environments a core challenge for the safe promotion of hydrogen fuel cell vehicles. Catalytic combustion sensors are ideal choices due to their high sensitivity and long lifespan. Nevertheless they face technical bottlenecks under vehicle operational conditions such as high-power consumption caused by elevated working temperatures slow response rates weak anti-interference capabilities and catalyst poisoning. This paper systematically reviews the research status of catalytic combustion hydrogen sensors for vehicle applications summarizes technical difficulties and development strategies from the perspectives of hydrogen-sensitive material design and integration processes and provides theoretical references and technical guidance for the development of catalytic combustion hydrogen sensors suitable for vehicle use.

The transition from fossil-based fuel to hydrogen combustion in steel reheating furnaces is a possible way to decrease the process-originated CO2 emissions significantly. This potential change alters the furnace gas atmo sphere’s composition impacting the oxide scale formation of the slab surface. Dynamic heating tests are per formed for three low-carbon steels using different simulated combustion atmospheres including natural gas coke oven gas and hydrogen combustion in air and hydrogen combustion in oxygen. Significant differences are found in the oxidation behavior of steel grades in the simulated hydrogen reheating scenario. A steel grade with low Mn content only has an 18% increase in oxidation between methane-air to hydrogen-oxygen methods while it is 41% for a high Mn and Si steel grade and 65% for a high-Mn steel grade. Thus in terms of material loss increase by oxidation the transition of the heating method causes the least problems for the low-Mn steel grade.

The decarbonization of the maritime sector represents a priority in the energy policy agendas of the majority of Countries worldwide and the International Maritime Organization (IMO) has recently revised its strategy aiming for an ambitious zero-emissions scenario by 2050. In these regards there is a broad consensus on hydrogen as one of the most promising clean energy vectors for maritime transport and a key towards that goal. However to date an international regulatory framework for the use of hydrogen on-board of ships is absent this posing a severe limitation to the adoption of hydrogen technologies in this sector. To cope with this issue this paper presents a preliminary gap assessment analysis for the International Code of Safety for Ship Using Gases or other Low-flashpoint Fuels (IGF Code) with relation to hydrogen as a fuel. The analysis is structured according to the IGF Code chapters and a bottom-up approach is followed to review the code content and assess its relevance to hydrogen. The risks related to hydrogen are accounted for in assessing the gaps and providing a first level set of recommendations for IGF Code updates. By this means this work settles the basis for further research over the identified gaps towards the identification of a final set of recommendations for the IGF Code update.

Ammonia (NH₃) presents a comprehensive energy storage solution for future energy demands. Its synthesis plays a pivotal role in the chemical industry acting as a fundamental precursor for fertilizers explosives and a wide range of industrial applications. In recent years there has been a growing interest in exploring novel catalyst materials to enhance the efficiency selectivity and sustainability of NH3 production technologies. Among these materials perovskite-based catalysts have emerged as promising candidates due to their unique properties. This review article aims to provide a sharp and short understanding of the role of perovskite-based catalysts in emerging NH3 production technologies and to stimulate further research and innovation in this rapidly evolving field. It provides an overview of recent advances in the synthesis and characterisation of perovskite-based cat alysts for NH3 production in terms of structural properties and catalytic performance of perovskite catalysts in NH3 synthesis. The review also discusses the underlying mechanisms involved in NH3 production on perovskite surfaces highlighting the role of surface chemistry and electronic structure. Furthermore the review examines the potential applications and prospects of perovskite-based catalysts in NH3 production technologies. It explores opportunities for integrating perovskite catalysts into existing NH3 synthesis processes as well as the develop ment of process configurations to maximise the efficiency and sustainability of NH3 production.

Renewable hydrogen is a promising energy carrier that facilitates greater renewable energy integration while supporting the decarbonization of the industrial and transportation sectors. This study investigates the optimal design and operation of two hydrogen-based energy systems. The first energy system comprises an electrolyser compressor and hydrogen storage system. It aims to supply hydrogen as a drop-in fuel for a future potential hydrogen fleet. The electrolyser provides excess heat and oxygen for a combined heat and power (CHP) plantand ancillary services to the grid for frequency support. In the second energy system the hydrogen stored in the hydrogen tank is used by a fuel cell or gas turbine to sell electricity to the grid following price signals. The optimisation algorithm developed in this study finds the optimal capacities for the hydrogen production and storage systems and optimizes the hourly dispatch of the electrolyser. The profitability of the first investigated hydrogen-based energy system is closely connected to the hydrogen production cost which fluctuates depending on the average electricity price. The profitability is also affected by the average compensation of the ancillary services and to a lesser extent by the value of excess heat and oxygen produced during the electrolysis. Only 2020 marked out by the lowest average electricity price among the investigated years could lead to a profitable investment for the first studied energy system. The breakeven hydrogen selling price varied between 24.13 SEK/kg in 2020 to 65.63 SEK/kg in 2022 while considering the extra revenues of the grid service compensation and heat and oxygen sale. If only hydrogen sale was considered the breakeven hydrogen selling prices varied between 31.28 SEK/kg in 2020 to 86.08 SEK/kg in 2022. For the second investigated hydrogen-based energy system if the threshold electricity price for activating the hydrogen consumption system is the 90th percentile of the electricity prices every week the profitability is never attained. The fuel cell system leads to lower electrolyser and hydrogen tank capacities to meet the targeted power supply given the higher assumed efficiency as compared to the gas turbine. Nevertheless the fuel cell system shows in all the investigated subcases lower net present values as compared to the gas turbine subcases due to the higher investment and running costs. The fuel cell system shows better performances in terms of net present values than the gas turbine only in an optimistic sub case marked out by higher conversion efficiencies and lower investment and running costs for the fuel cell. The profitability of the second investigated hydrogen-based energy system is guaranteed only at an annual average electricity price above 2.7 SEK/kWh.

Eco-design is an innovative design methodology that focuses on minimizing the environmental footprint of industries including aviation right from the conceptual and development stages. However rising industrial demand calls for a more comprehensive strategy wherein beyond environmental considerations competitiveness becomes a critical factor supported by additional pillars of sustainability such as economic viability circularity and social impact. By incorporating sustainability as a primary design driver at the initial design stages this study suggests a shift from eco-driven to sustainability-driven design approaches for aircraft components. This expanded strategy considers performance and safety goals environmental impact costs social factors and circular economy considerations. To provide the most sustainable design that balances all objectives these aspects are rigorously quantified and optimized during the design process. To efficiently prioritize different variables methods such as multi-criteria decision-making (MCDM) are employed and a sustainability index is developed in this framework to assess the overall sustainability of each design alternative. The most sustainable design configurations are then identified through an optimization process. A typical aircraft component namely a hat-stiffened panel is selected to demonstrate the proposed approach. The study highlights how effectively sustainability considerations can be integrated from the early stages of the design process by exploring diverse material combinations and geometric configurations. The findings indicate that the type of fuel used and the importance given to the sustainability pillars—which are ultimately determined by the particular requirements and goals of the user—have a significant impact on the sustainability outcome. When equal prioritization is given across the diverse dimensions of sustainability the most sustainable option appears to be the full thermoplastic component when kerosene is used. Conversely when hydrogen is considered the full aluminum component emerges as the most sustainable choice. This trend also holds when environmental impact is prioritized over the other aspects of sustainability. However when costs are prioritized the full thermoplastic component is the most sustainable option whether hydrogen or kerosene is used as the fuel in the use phase. This innovative approach enhances the overall sustainability of aircraft components emphasizing the importance and benefits of incorporating a broader range of sustainability factors at the conceptual and initial design phases.

In order to improve energy utilization efficiency and the flexibility of resource transfer in oceanic-island-group microgrids a water–electricity–hydrogen flexible scheduling strategy based on a multi-rate hydrogen-powered ship is proposed. First the characteristics of the seawater desalination unit (SDU) proton exchange membrane electrolyzer (PEMEL) and battery system (BS) in consuming surplus renewable energy on resource islands are analyzed. The variable-efficiency operation characteristics of the SDU and PEMEL are established and the effect of battery life loss is also taken into account. Second a spatiotemporal model for the multi-rate hydrogen-powered ship is proposed to incorporate speed adjustment into the system optimization framework for flexible resource transfer among islands. Finally with the goal of minimizing the total cost of the system a flexible water–electricity–hydrogen hybrid resource transfer model is constructed and a certain island group in the South China Sea is used as an example for simulation and analysis. The results show that the proposed scheduling strategy can effectively reduce energy loss promote renewable energy absorption and improve the flexibility of resource transfer.

The electric–hydrogen coupled integrated energy system (EHCS) is a critical pathway for the low-carbon transition of energy systems. However the inherent uncertainties of renewable energy sources present significant challenges to optimal energy management in the EHCS. To address these challenges this paper proposes an energy management method for the EHCS based on an improved proximal policy optimization (IPPO) algorithm. This method aims to overcome the limitations of traditional heuristic algorithms such as low solution accuracy and the inefficiencies of mathematical programming methods. First a mathematical model for the EHCS is established. Then by introducing the Markov decision process (MDP) this mathematical model is transformed into a deep reinforcement learning framework. On this basis the state space and action space of the system are defined and a reward function is designed to guide the agent to learn to the optimal strategy which takes into account the constraints of the system. Finally the efficacy and economic viability of the proposed method are validated through numerical simulation.

Hydrogen use is increasing in transportation including within the railway sector. In collaboration with a governmental institution in the Netherlands we study how to design an efficient hydrogen fueling infrastructure for a railway system. The problem involves selecting yards in a network for hydrogen fueling assigning trains to these yards locating hydrogen storage and fueling stations and connecting them via pipelines. This key planning phase must avoid oversizing costly fueling infrastructure while accounting for track availability at yards and costs due to fueling operations. We formulate this novel problem which has the structure of a nested facility location problem as a mixed-integer linear program to minimize total annualized investment and operational costs. Due to the complexity of real-sized instances we propose a matheuristic that estimates the infrastructural costs for each yard and train assignment by combining a constructive algorithm with a set covering model. It then solves a single-stage facility location problem to select yards and assign trains followed by a yard-level improvement phase. Numerical experiments on a real Dutch case show that our approach delivers high-quality solutions quickly and offer insights into the optimal infrastructure design depending on the discretization of yard areas number of trains and other parameters.

Microgrids enable the integration of renewable energy sources; however managing electricity from intermittent wind and solar power remains a significant challenge. This study investigates two storage strategies for managing surplus renewable electricity in an IEEE 84-Bus microgrid with wind turbines and photovoltaic units. The first option involves producing hydrogen via electrolyzers which is stored for later electricity generation through fuel cells. The second option involves converting surplus electricity into heat using heat pumps which is then stored in thermal energy storage systems to efficiently meet the microgrid's thermal load requirements. A scenariobased day-ahead scheduling model is proposed to optimize the microgrid's electrical and thermal load management while considering uncertainties in market prices wind speeds and solar irradiance. The resulting large-scale optimization challenge is effectively tackled using the self-adaptive charge system search algorithm. The results indicate that for the optimal utilization of excess renewable electricity heat generation via heat pumps is more cost-effective than hydrogen production primarily due to the inefficiencies in hydrogen conversion and the ability of heat pumps to produce several units of heat for each unit of electricity consumed. Moreover heat pumps prove to be more economical than natural gas combustion in boilers for meeting the thermal demands across a wide range of gas prices. These findings highlight the economic benefits of integrating heat pumps and thermal energy storage systems into renewable energy microgrids.

As one of the most promising clean energy sources hydrogen power has gradually emerged as a viable alternative to traditional energy sources. However hydrogen safety remains a significant concern due to the potential for explosions and the associated risks. This review systematically examines hydrogen explosions with a focus on high-pressure and low-temperature storage transportation and usage processes mostly based on the published papers from 2020. The fundamental principles of hydrogen explosions classifications and analysis methods including experimental testing and numerical simulations are explored. Key factors influencing hydrogen explosions are also discussed. The safety issues of hydrogen power on railway applications are focused and finally recommendations are provided for the safe application of hydrogen power in railway transportation particularly for long-distance travel and heavy-duty freight trains with an emphasis on storage safety considerations.

Green hydrogen has emerged as a promising energy vector for the decarbonisation of heavy industry. The EU and national governments have recently introduced incentives to address the high costs of green hydrogen production and accelerate the economic development of hydrogen. This study investigates the local production of green hydrogen to decarbonise the high-temperature process heat demand of a heavy industry located in Italy. The hydrogen generation is powered by PV electricity and from the electric grid. We have optimised the sizes of the energy system components including battery storage and hydrogen tanks. The Levelised Cost of Hydrogen (LCOH) was found to be 7.7 EUR/kg in the unincentivised base scenario but this amount significantly reduced to 3.3 EUR/kg when incentives on hydrogen production in abandoned industrial areas were considered. Thanks to such incentives the greenhouse gas emissions decreased by as much as 85 % with respect to the non-incentivised base case. Our results show that the effect of the incentives on the design and economics of the system is comparable with the expected reductions in equipment costs over the next decade. Importantly our findings reveal a linear relationship between Capital Costs and LCOH thereby enabling precise cost estimations to be made for the considered location without any further simulations. A side effect of the size optimisation in the presence of incentives is an increase of the plant footprint. However the limited availability of land could lead to non-optimal configurations with important impacts on emission intensity and LCOH.

This study compares hydrogen ammonia-hydrogen fuel blends and Jet-A2 fuel in gas turbine combustors using a well-stirred reactor model and validated MATLAB library H2ools to assess flame temperature pollutant generation combustion stability and thermal efficiency. The aim is to address a significant deficiency in existing research which frequently lacks standardized turbine-related comparisons among new zero-carbon fuels. Quantitative data indicate that pure hydrogen attains the maximum adiabatic flame temperature (2552 Kelvin) laminar flame speed (7.73 meters per second) and heat generation (9.02 × 1010 watts per cubic meter) while also demonstrating increased nitrogen oxide emissions (up to 6400 parts per million). Jet-A2 exhibits reduced flame temperatures (2429 Kelvin) and minimal nitrogen oxide emissions (1308 parts per million) whereas a 50% ammonia-hydrogen blend yields the maximum nitrogen oxide output (7022 parts per million) attributable to the nitrogen content in ammonia. Hydrogen generates the minimal nitrogen oxide emissions per unit of energy output—approximately 0.1 grams per kilowatt-hour at a residence time of five milliseconds. This study integrates reactor-level study with a high-fidelity modeling tool providing insights for combustor design fuel selection and emissions control strategies in low-carbon aircraft and power systems.

Hydrogen-based mobility solutions could offer viable technology for sustainable transportation. Current research often examines single pathways leaving broader comparisons unexplored. This comparative life cycle assessment (LCA) evaluates which vehicle type achieves the best environmental performance when using hydrogen from grey blue and green production pathways the three dominant carbon-intensity variants currently deployed. This study examines seven distinct vehicle configurations that rely on hydrogen-derived energy sources across various propulsion systems: a hydrogen fuel cell electric vehicle (H2FCEV) hydrogen internal combustion engine vehicle (H2ICEV) methanol flexible fuel vehicle (MeOH FFV) ethanol flexible vehicle (EtOH FFV) Fischer-Tropsch (FT) diesel internal combustion vehicle (FTD ICEV) and renewable compressed natural gas vehicle (RNGV). Via both grey and blue hydrogen production H2 FCEVs are the best options from the viewpoint of GWP but surprisingly in the green category FT-fueled vehicles take over both first and second place as they produce nearly half the lifetime carbon emissions of purely hydrogen-fueled vehicles. RNGV also emerges as a promising alternative offering optimal engine properties in a system similar to H2ICEVs enabling parallel development and technological upgrades. These findings not only highlight viable low-carbon pathways but also provide clear guidance for future targeted detailed applied research.