Applications & Pathways

Long-term reliability and accuracy of pressure valves are critical for hydrogen infrastructure and applications particularly in hydrogen-powered vehicles exposed to extreme weather conditions like cold winters and hot summers. This study evaluates such valves using the Endurance Test specified in European Commission Regulation (EU) No 406/2010 fulfilling Regulation (EC) No 79/2009 requirements for hydrogen vehicle type approval. A long short-term memory (LSTM) network accelerates valve development and validation by simulating endurance tests. The LSTM model with three inputs and one output predicts valve outlet pressure responses using experimental data collected at 25 ◦C 85 ◦C and − 40 ◦C simulating a 20-year lifecycle of 75000 cycles. At 25 ◦C the model achieves optimal performance with 40000 training cycles and an R2 of 0.969 with R2 values exceeding 0.960 across all temperatures. This efficient robust approach accelerates testing enabling realtime diagnostics and advancing hydrogen technologies for a sustainable future.

The study provides a study on energy storage technologies for photovoltaic and wind systems in response to the growing demand for low-carbon transportation. Energy storage systems (ESSs) have become an emerging area of renewed interest as a critical factor in renewable energy systems. The technology choice depends essentially on system requirements cost and performance characteristics. Common types of ESSs for renewable energy sources include electrochemical energy storage (batteries fuel cells for hydrogen storage and flow batteries) mechanical energy storage (including pumped hydroelectric energy storage (PHES) gravity energy storage (GES) compressed air energy storage (CAES) and flywheel energy storage) electrical energy storage (such as supercapacitor energy storage (SES) superconducting magnetic energy storage (SMES) and thermal energy storage (TES)) and hybrid or multi-storage systems that combine two or more technologies such as integrating batteries with pumped hydroelectric storage or using supercapacitors and thermal energy storage. These different categories of ESS enable the storage and release of excess energy from renewable sources to ensure a reliable and stable supply of renewable energy. The optimal storage technology for a specific application in photovoltaic and wind systems will depend on the specific requirements of the system. It is important to carefully evaluate these needs and consider factors such as power and energy requirements efficiency cost scalability and durability when selecting an ESS technology.

Proliferation of co-located petrol-hydrogen fueling stations is an effective solution for widespread deployment of hydrogen as a transportation fuel. Such combined fueling stations largely rely on existing infrastructure hence represent a low-cost option for setting up hydrogen fueling facilities. However optimizing the layout of dual petrol-hydrogen fueling stations and their rational site selection is critical for ensuring the efficient use of re sources. This paper investigates the site selection of combined hydrogen and petrol fueling stations at the ter minus of China’s "West-to-East Hydrogen Pipeline" project. A weighting model based on EWM-CRITIC-Game Theory is developed and the weight coefficients derived from game theory are used to perform the compre hensive ranking of potential sites. The combined evaluation results yield an overall ranking of A9 > A4 > A8 > A26 > A20 > A21 > A11. The effectiveness of this novel method is verified by comparing the results with those obtained from Copeland Borda Average and geometric mean methods. Considering the actual distance con straints the final site ranking is A9 > A4 > A8 > A20 > A21 > A11 > A14. This location offers optimal con ditions for infrastructure integration and hydrogen fueling service coverage. The reliability analysis indicates that the proposed game theory-based method delivers strong performance across various scenarios underscoring its reliability and versatility in consistently delivering accurate results.

Hydrogen is commonly perceived as the key player in the transition towards a low-carbon future. Nevertheless H2 low energy density hinders its easy storage and transportation. To address this issue different alternatives (liquefied hydrogen ammonia and liquid organic hydrogen carriers) are explored as hydrogen vectors. The techno-economic assessment of H2 transport through these carriers is strongly dependent on the basis of design adopted such that it is difficult to draw general conclusions. In this respect this work is aimed at performing a sensitivity analysis on the hypotheses introduced in the layout of H2 value chains. Different scenarios are discussed depending on harbour-to-harbour distances cost of utilities and raw materials and H2 application to the industrial or mobility sector. The most cost-effective carrier is selected for each case-study: NH3 is the most advantageous for industrial sector while LH2 holds promises for mobility. Critical issues are pointed out for future large-scale applications.

Adopting machine learning (ML) in hydrogen systems is a promising approach that enhances the efficiency reliability and sustainability of hydrogen power systems and revolutionizes the hydrogen energy sector to optimize energy usage/management and promote sustainability. This study explores hydrogen energy systems including production storage and applications while establishing a connection between machine learning solutions and the challenges these systems face. The paper provides an in-depth review of the literature examining not only ML techniques but also optimization algorithms evaluation methods explainability techniques and emerging technologies. By addressing these aspects we highlight the key factors of new technologies and their potential benefits across the three stages of the hydrogen value chain. We also present the advantages and limitations of applying ML models in this field offering recommendations for their optimal use. This comprehensive and precise work serves as the most current and complete examination of ML applications within the hydrogen value chain providing a solid foundation for future research across all stages of the hydrogen industry.

The utilization of “green” hydrogen in transportation areas gives rise to production- and supply infrastructure-related challenges; therefore its wider application in automotive transport would lead to higher demand with cost reduction and a faster expansion of the hydrogen refuelling network. This study presents energy and environmental performance indicators analyses of a Nissan Qashqai J10 engine during the Worldwide Harmonised Light Vehicles Test Cycle (WLTC) replacing conventional fossil gasoline with dual-fuel (D-F) gasoline and hydrogen. Numerical modelling was conducted using AVL Cruise™ (Version R2022.2) software utilizing the torque fuel consumption and environmental performance data of the HR16DE engine obtained through experimental testing across a wide range of loads and speeds on an engine test bench. The experimental investigation was carried out in two stages: using pure gasoline (G100); injecting a hydrogen additive into the intake air constituting 5% of the gasoline mass (G95H5). Following similar stages numerical modelling was conducted using the vehicle’s technical specifications to calculate engine load and speed throughout the WLTC range. Instant fuel consumption and pollutant emissions (CO CH NOx) were determined for various driving modes using experimental data maps. CO2 emissions were calculated considering fuel composition and consumption. By integrating the instant values the total and specific fuel consumption and emissions were calculated. As a result this study identified the effect of a 5% hydrogen additive in improving engine energy efficiency reducing incomplete combustion products and lowering greenhouse gas (CO2) emissions under various driving modes. Finally the results were compared with the requirements of EU standards.

This study conducts a thorough review of fuel cell technology including types economy applications and V2G scheme. Fuel cells have been considered for diverse applications namely electric vehicles specialty vehicles such as warehouse forklifts public transportation including buses trains and ferries. Other applications include grid-related stationary and portable applications. Among available five types of fuel cells PEMFC is presently the optimal choice for electric vehicle usage due to its low operating temperature and durability. Meanwhile high temperature fuel cells such as MCFC and SOFC currently remain the best choice for utility and grid related applications. The economy of fuel cells has been continuously improving and has been illustrated to only grow into a potential main source of sustainable energy soon. With the transportation sector as fuel cell electric ve hicles evolve V2G technology is beneficial towards energy efficiency and fuel cell economy. There is evidence for V2G using FCEV being more advantageous in comparison to conventional BEVs. The costs of the five types of fuel cell vary from US$1784 to US$4500 per kW capacity. The findings are beneficial for researchers and industry professionals who wish to gain comprehensive understanding of fuel cells for adoption and development of the emerging low-emission energy solutions.

This study presents a hybrid power system comprising a fuel cell (FC) and a lithium-ion battery (LIB) for liquid hydrogen (LH2) carriers which is expected to increase globally due to the production cost gap of green hydrogen between renewable-rich and renewable-poor countries. The LH2 carrier has a key challenge in handling the inevitably considerable boil-off hydrogen (BOH). As a target ship of a 50000 m3 LH2 carrier with a boil-off rate (BOR) of 0.4% per day this study employs an optimization tool to determine the economic power dispatch between the FC and LIB aimed at minimizing the lifetime cost of the ship. The BOH is used as fuel for FC during the voyage. Moreover when the ship is under cargo loading and unloading operations at the port the considerable surplus BOH is utilized to generate electricity and then sold to the shore grid (StG). The results indicate that 45.2% of the BOH can be utilized as fuel for the FC and the StG system can effectively reduce the total lifetime cost by 32.0%. Further the paper presents the outcomes of a sensitivity analysis conducted on critical parameters. This study provides new insights into the BOH issue of LH2 carriers and helps to increase the international green hydrogen market.

Hydrogen plasma offers an emerging route for carbon-free iron oxide reduction but typical inert gas dilution limits industrial applicability. This study explores pure hydrogen and hydrogen–carbon dioxide plasma for in-flight hematite reduction in atmospheric elongated arc discharge. Pure hydrogen yields the lowest power consumption but reduced plasma stability and limited conversion. CO2 addition enhances stability increasing gas temperature from approximately 1900 K (pure H2 ) to 2900 K at 50% CO2 driven by exothermic H2 oxidation. Particle rapidly reach gas temperature (>2000 K within 5 ms). The highest metallization degree (≈37%) achieved at 30% CO2 corresponds to an optimal reductant gas composition balancing hydrogen carbon monoxide and atomic hydrogen availability. Higher dilution (50% CO2 ) significantly decreased the reductant gas availability lowering the degree of reduction despite higher temperatures. These insights demonstrate that controlled CO2 co-feeding and regeneration optimize plasma stability temperature and reductant gas chemistry presenting a promising approach towards scalable and energy-efficient hydrogen plasma smelting reduction for sustainable metallurgy with a CO2 closed loop.

Aviation is under increasing pressure to reduce carbon emissions in conventional transports and support the growth of low-altitude operations such as long-endurance eVTOLs. Hybrid-electric propulsion addresses these challenges by integrating the high specific energy of fuels or hydrogen with the controllability and efficiency of electrified powertrains. At present the field of hybrid-electric aircraft is developing rapidly. To systematically study hybrid-electric propulsion control in aviation this review focuses on practical aspects of system development including propulsion architectures system- and component-level modeling approaches and energy management strategies. Key technologies in the future are examined with emphasis on aircraft power-demand prediction multi-timescale control and thermal integrated energy management. This review aims to serve as a reference for configuration design modeling and control simulation as well as energy management strategy design of hybrid-electric propulsion systems. Building on this reference role the review presents a coherent guidance scheme from architectures through modeling to energy-management control with a practical roadmap toward flight-ready deployment.

Environmental pollution caused by shipping has always received great attention from the international community. Currently due to the difficulty of fully electrifying medium- and large-scale ships the hybrid energy ship power system (HESPS) will be the main type in the future. Considering the economic and long-term energy efficiency of ships as well as the uncertainty of the output power of renewable energy units this paper proposes an improved design for an integrated power system for large cruise ships combining renewable energy and a hybrid energy storage system. An energy management strategy (EMS) based on time-gradient control and considering load dynamic response as well as an energy storage power allocation method that considers the characteristics of energy storage devices is designed. A bi-level power capacity optimization model grounded in comprehensive scenario planning and aiming to optimize maximum return on equity is constructed and resolved by utilizing an improved particle swarm optimization algorithm integrated with dynamic programming. Based on a large-scale cruise ship the aforementioned method was investigated and compared to the conventional planning approach. It demonstrates that the implementation of this optimization method can significantly decrease costs enhance revenue and increase the return on equity from 5.15% to 8.66%.

The ongoing energy transition and decarbonization efforts have prompted the development of Hybrid Renewable Energy Systems (HRES) capable of integrating multiple generation and storage technologies to enhance energy autonomy. Among the available options hydrogen has emerged as a versatile energy carrier yet most studies have focused either on stationary applications or on mobility seldom addressing their integration withing a single framework. In particular the potential of Metal Hydride (MH) tanks remains largely underexplored in the context of sector coupling where the same storage unit can simultaneously sustain household demand and provide in-house refueling for lightduty fuel-cell vehicles. This study presents the design and analysis of a residential-scale HRES that combines photovoltaic generation a PEM electrolyzer a lithium-ion battery and MH storage intended for direct integration with a fuel-cell electric microcar. A fully dynamic numerical model was developed to evaluate system interactions and quantify the conditions under which low-pressure MH tanks can be effectively integrated into HRES with particular attention to thermal management and seasonal variability. Two simulation campaigns were carried out to provide both component-level and system-level insights. The first focused on thermal management during hydrogen absorption in the MH tank comparing passive and active cooling strategies. Forced convection reduced absorption time by 44% compared to natural convection while avoiding the additional energy demand associated with thermostatic baths. The second campaign assessed seasonal operation: even under winter irradiance conditions the system ensured continuous household supply and enabled full recharge of two MH tanks every six days in line with the hydrogen requirements of the light vehicle daily commuting profile. Battery support further reduced grid reliance achieving a Grid Dependency Factor as low as 28.8% and enhancing system autonomy during cold periods.

The transition to sustainable and smart urban energy systems requires combustion technologies that combine high efficiency with near-zero emissions. Moderate or intense low-oxygen dilution (MILD) combustion has emerged as a promising solution offering volumetric heat release reduced peak temperatures and strong NOX suppression ideal for integrating green hydrogen carriers such as ammonia and ammonia–hydrogen blends into stationary energy systems. While MILD combustion is well-studied for hydrocarbons its application to carbon-free fuels presents challenges including high ignition temperatures low reactivity and potential NOX formation. This review examines the behavior of ammonia-based fuels under MILD conditions mapping combustion regimes across reactor types and operating parameters. To address ignition and stability issues the review also explores plasma-assisted MILD combustion (PAMC). Non-equilibrium plasma (NEP) discharges promote radical generation reduce ignition delay times and enhance flame stability under lean highly diluted conditions. Recent experimental and numerical studies demonstrate that plasma activation can reduce ignition delay times by up to an order of magnitude lower flame lift-off heights by over 30 % in certain configurations and enhance OH radical concentrations and heat release intensity. The extent of these improvements depends on factors such as plasma energy input fuel type and dilution level. This review synthesizes key findings identifies technical gaps and highlights the potential of MILD and PAMC as clean flexible and scalable solutions for low-emission stationary energy generation in smart city environments.

With the rapid development of alternative fuel vehicles (AFVs) and renewable energy sources the increasing coordination between electric vehicles (EVs) and hydrogen vehicles (HVs) in urban coupled powertransportation networks (CPTNs) fosters optimized energy scheduling and enhanced system performance. This study proposes a two-level Stackelberg-Nash game framework for AFV-integrated microgrids in a CPTN to enhance the economic efficiency of microgrid. This framework employs a Stackelberg game model to define the leader-follower relationship between the microgrid operator and the vehicle-to-grid (V2G) aggregator. Nash equilibrium games are established to capture competitive interactions among charging stations (CSs) and among hydrogen refueling stations (HRSs). Furthermore an optimal scheduling model is proposed to minimize microgrid operation costs considering the spatiotemporal dynamics and user preferences of EVs and HVs supported by the proposed dynamic choice model. A game-theoretic pricing and incentive mechanism promotes AFV participation in V2G services enhancing the profitability of CSs and HRSs. Afterward a momentum-enhanced Stackelberg-Nash equilibrium algorithm is developed to address the bi-level optimization problem. Finally numerical simulations validate the effectiveness of the proposed method in improving economic efficiency and reducing operation costs. The proposed approach offers an effective solution for integrating large-scale AFV fleets into sustainable urban energy and transportation systems.

In recent years there has been an increasingly larger fraction of intermittent energy sources. In the northern parts of Europe the main source of intermittent power is wind power. This source of power is low inertia inconsistent and will always fluctuate with different magnitudes leaving a need for balancing. One source of balancing is to have the widespread non-zero inertia combined heat and power stations work as back-up sources. One way to boost the capability of these power sources is by adding an oxyfuel internal hydrogen combustor. To study the effects of this the steam generator was tested in four different positions within the power plant to test different possibilities with different levels of retrofits. The first was in the high- and lowpressure crossover the second was a reheat at a higher pressure the third was a superheat of the admission steam and finally the fourth was a superheat using the overload valves. The final results showed that the configurations of crossover reheat and superheat of admission steam were the best in terms of retrofit while the reheat at higher pressure was deemed the best in terms of backup capacity reaching a gain in power of 9.5 MW at a fuel efficiency of 30.93 %. The highest fuel efficiencies were shown by the latter two amounting to 45.19 % and 51.58 % in district heating mode respectively. There is great potential to be made from these power plants due to the possibility of increased capacity all across Sweden.

This study presents the conceptual design and evaluation of an HRS for light-duty FCEVs. The proposed system integrates wind turbines a water electrolyzer three-stage hydrogen compressor heat recovery and storage a two-stage Organic Rankine Cycle (TS-ORC) hydrogen storage tanks a Vapor Compression Refrigeration Cycle (VCRC) and a hydrogen dispenser. Waste heat from the hydrogen compression process is harnessed to power the TS-ORC where the first stage drives the VCRC and the second stage generates additional electricity. A comprehensive assessment of the system confirmed the system's compliance with the principles of thermodynamics. The results indicate an overall system efficiency of 25.4% and the wind turbines alone achieve 46.21% efficiency. The overall exergy destruction rate of the system is computed to be 2120 kW and the main exergy destruction occurs in wind turbines and water electrolyzer. The first and second stages of the ORC exhibit efficiencies of 14.45% and 6.05% respectively while the VCRC yields a Coefficient of Performance (COP) of 1.24. The specific energy consumption for electrolytic hydrogen production compression and pre-cooling are calculated as 58.83 1.99 and 0.29 kWh/kg respectively. The hydrogen dispenser fills an onboard hydrogen storage tank with a 4 kg capacity at 700 bar in 5.5 min.

The rapid development of fuel cell electric vehicles (FCEVs) has highlighted the critical importance of optimizing energy management strategies to improve vehicle performance energy efficiency durability and reduce hydrogen consumption and operational costs. However existing approaches often face limitations in real-time applicability adaptability to varying driving conditions and computational efficiency. This paper aims to provide a comprehensive review of the current state of FCEV energy management strategies systematically classifying methods and evaluating their technical principles advantages and practical limitations. Key techniques including optimization-based methods (dynamic programming model predictive control) and machine learning-based approaches (reinforcement learning deep neural networks) are analyzed and compared in terms of energy distribution efficiency computational demand system complexity and real-time performance. The review also addresses emerging technologies such as artificial intelligence vehicle-to-everything (V2X) communication and multi-energy collaborative control. The outcomes highlight the main bottlenecks in current strategies their engineering applicability and potential for improvement. This study provides theoretical guidance and practical reference for the design implementation and advancement of intelligent and adaptive energy management systems in FCEVs contributing to the broader goal of efficient and low-carbon vehicle operation.

This work proposes a new method to refill fuel cell electric vehicle hydrogen tanks from a storage system in hydrogen refueling stations. The new method uses the storage tanks in cascade to supply hydrogen to the refueling station dispensers. This method reduces the hydrogen compressor power requirement and the energy consumption for refilling the vehicle tank; therefore the proposed alternative design for hydrogen refueling stations is feasible and compatible with low-intensity renewable energy sources like solar photovoltaic wind farms or micro-hydro plants. Additionally the cascade method supplies higher pressure to the dispenser throughout the day thus reducing the refueling time for specific vehicle driving ranges. The simulation shows that the energy saving using the cascade method achieves 9% to 45% depending on the vehicle attendance. The hydrogen refueling station design supports a daily vehicle attendance of 9 to 36 with a complete refueling process coverage. The carried-out simulation proves that the vehicle tank achieves the maximum attainable pressure of 700 bars with a storage system of six tanks. The data analysis shows that the daily hourly hydrogen demand follows a sinusoidal function providing a practical tool to predict the hydrogen demand for any vehicle attendance allowing the planners and station designers to resize the elements to fulfill the new requirements. The proposed system is also applicable to hydrogen ICE vehicles.

The reliance on fossil fuels for electricity production in insular regions creates critical environmental economic and logistical challenges particularly for ecologically fragile islands. Transitioning to renewable energy is essential to mitigate these impacts enhance energy security and preserve unique ecosystems. This systematic review addresses key research questions: what practical strategies have proven effective in reducing fossil fuel dependency in island contexts and what barriers hinder their widespread adoption? By applying the PRISMA methodology this study examines a decade (2014–2024) of research on renewable energy systems highlighting successful initiatives such as the integration of solar and wind systems in Hawaii energy storage advancements in La Graciosa hybrid renewable grids in the Galápagos Islands and others. Specific barriers include high upfront costs regulatory challenges and technical limitations such as grid instability due to renewable energy intermittency. This review contributes by synthesizing lessons from diverse case studies and identifying innovative approaches like hydrogen storage predictive control systems and community-driven renewable projects. The findings offer actionable insights for policymakers and researchers to accelerate the transition towards sustainable energy systems in island environments.

The European Union promotes decarbonization in energy-intensive industries like glass manufacturing. Collaboration between industry and researchers focuses on reducing CO2 emissions through hydrogen (H2) integration as a natural gas substitute. However to the best of the authors’ knowledge no updated real-world case studies are available in the literature that consider the on-site implementation of an electrolyzer for autonomous hydrogen production capable of meeting the needs of a glass manufacturing plant within current technological constraints. This study examines a representative hollow glass plant and develops various decarbonization scenarios through detailed process simulations in Aspen Plus. The models provide consistent mass and energy balances enabling the quantification of energy demand and key cost drivers associated with H2 integration. These results form the basis for a scenario-specific techno-economic assessment including both on-grid and off-grid configurations. Subsequently the analysis estimates the levelized costs of hydrogen (LCOH) for each scenario and compares them to current and projected benchmarks. The study also highlights ongoing research projects and technological advancements in the transition from natural gas to H2 in the glass sector. Finally potential barriers to large-scale implementation are discussed along with policy and infrastructure recommendations to foster industrial adoption. These findings suggest that hybrid configurations represent the most promising path toward industrial H2 adoption in glass manufacturing.

The maritime sector’s transition to sustainable energy is critical for achieving global carbon neutrality with container terminals representing a key focus due to their high energy consumption and emissions. This study explores the potential of hydrogen energy as a decarbonization solution for port operations using the Chuanshan Port Area of Ningbo Zhoushan Port (CPANZP) as a case study. Through a comprehensive analysis of hydrogen production storage refueling and consumption technologies we demonstrate the feasibility and benefits of integrating hydrogen systems into port infrastructure. Our findings highlight the successful deployment of a hybrid “wind-solar-hydrogen-storage” energy system at CPANZP which achieves 49.67% renewable energy contribution and an annual reduction of 22000 tons in carbon emissions. Key advancements include alkaline water electrolysis with 64.48% efficiency multi-tier hydrogen storage systems and fuel cell applications for vehicles and power generation. Despite these achievements challenges such as high production costs infrastructure scalability and data integration gaps persist. The study underscores the importance of policy support technological innovation and international collaboration to overcome these barriers and accelerate the adoption of hydrogen energy in ports worldwide. This research provides actionable insights for port operators and policymakers aiming to balance operational efficiency with sustainability goals.

To address global CO2 emissions and the intermittency of renewables hydrogen is emerging as a promising carbon-free fuel for micro gas turbines (MGTs) offering potential for grid stability and decarbonization. However its high flame speed and adiabatic temperature present challenges including flashback and elevated NOx emissions. Conventional combustors often lack the compactness and NOx control needed for MGT-scale systems. This study numerically investigates pure hydrogen combustion in a compact MGT combustor using a secondary air dilution strategy. Based on the experimental setup of Tanneberger et al. simulations were conducted in ANSYS Fluent using steady-state RANS equations a CRECK-based chemical mechanism and the Flamelet Generated Manifold (FGM) model. The parametric study explores three design variables swirler blockage (B) central fuel tube length (C) and fuel injection split (S) along with five secondary air configurations (T1–T5). Results show that the secondary air hole pattern significantly affects flow structure and temperature uniformity. Configuration T1 provided the most uniform exhaust and lowest NOx emissions due to better air penetration and earlier dilution. Higher B and S increased local flame temperature intensifying thermal NOx via the Zeldovich mechanism. The findings offer design guidance for stable low-emission hydrogen combustors suitable for compact MGT applications.

In response to increasingly stringent emission regulations low-carbon fuels have received significant attention as sustainable energy sources for internal combustion engines. This study investigates four representative low-carbon fuels methane methanol hydrogen and ammonia by systematically summarizing their combustion characteristics and emission profiles along with a review of existing after-treatment technologies tailored to each fuel type. For methane engines unburned hydrocarbon (UHC) produced during lowtemperature combustion exhibits poor oxidation reactivity necessitating integration of oxidation strategies such as diesel oxidation catalyst (DOC) particulate oxidation catalyst (POC) ozone-assisted oxidation and zoned catalyst coatings to improve purification efficiency. Methanol combustion under low-temperature conditions tends to produce formaldehyde and other UHCs. Due to the lack of dedicated after-treatment systems pollutant control currently relies on general-purpose catalysts such as three-way catalyst (TWC) DOC and POC. Although hydrogen combustion is carbon-free its high combustion temperature often leads to elevated nitrogen oxide (NOx) emissions requiring a combination of optimized hydrogen supply strategies and selective catalytic reduction (SCR)-based denitrification systems. Similarly while ammonia offers carbon-free combustion and benefits from easier storage and transportation its practical application is hindered by several challenges including low ignitability high toxicity and notable NOx emissions compared to conventional fuels. Current exhaust treatment for ammonia-fueled engines primarily depends on SCR selective catalytic reduction-coated diesel particulate filter (SDPF). Emerging NOx purification technologies such as integrated NOx reduction via hydrogen or ammonia fuel utilization still face challenges of stability and narrow effective temperatures.

Fossil fuels have been the conventional source of energy that has driven economic growth and industrial development for a long time. However their extensive use has led to immense environmental problems especially concerning the emission of greenhouse gases. These problems have stimulated researchers to turn their attention to renewable alternative fuels. Hydrogen has risen in recent years as a prospective energy carrier because it is possible to produce it in an environmentally friendly manner and because it is the most common element. Hydrogen may be used in diesel engines in a dual-fuel mode. Hydrogen has a higher heating value flame speed and diffusivity in air. These superior fuel properties can enhance performance and combustion efficiency. Hydrogen can decrease carbon monoxide unburned hydrocarbons and soot emissions due to the absence of carbon in hydrogen. However hydrogen-fuelled diesel engines have problems such as engine knocking and high nitrogen oxide emission. This paper presents a comprehensive review of the recent literature on the performance combustion and emission characteristics of hydrogen-fuelled diesel engines. Moreover this paper discusses the long-term sustainability of hydrogen production methods nitrogen oxide emission reduction techniques challenges to the large-scale use of hydrogen economic implications of hydrogen use safety issues in hydrogen applications regulations on hydrogen safety conflicting NOx emission results in the literature and material incompatibility issues in hydrogen applications. This study highlights state-of-the-art developments along with critical knowledge gaps that will be useful in guiding future research. These findings can support researchers and industry professionals in the integration of hydrogen into both existing and future diesel engine technologies. According to the literature the use of hydrogen up to 46% decreased smoke emissions by over 75% while CO2 and CO emissions significantly decreased. Moreover hydrogen addition improved thermal efficiency up to 7.01% and decreased specific fuel consumption up to 7.19%.

Energy management in hybrid fuel cell ship systems faces the dual challenges of optimizing hydrogen consumption and ensuring power quality. This study proposes an Improved Weighted Antlion Optimization (IW-ALO) algorithm for multi-objective problems. The method incorporates a dynamic weight adjustment mechanism and an elite-guided strategy which significantly enhance global search capability and convergence performance. By integrating IW-ALO with the Equivalent Consumption Minimization Strategy (ECMS) an improved weighted ECMS (IW-ECMS) is developed enabling real-time optimization of the equivalence factor and ensuring efficient energy sharing between the fuel cell and the lithium-ion battery. To validate the proposed strategy a system simulation model is established in Matlab/Simulink 2017b. Compared with the rule-based state machine control and optimization-based ECMS methods over a representative 300 s ferry operating cycle the IW-ECMS achieves a hydrogen consumption reduction of 43.4% and 42.6% respectively corresponding to a minimum total usage of 166.6 g under the specified load profile while maintaining real-time system responsiveness. These reductions reflect the scenario tested characterized by frequent load variations. Nonetheless the results highlight the potential of IW-ECMS to enhance the economic performance of ship power systems and offer a novel approach for multi-objective cooperative optimization in complex energy systems.

This article examines the growing potential of low-emission hydrogen as an innovative solution supporting the decarbonization of the agricultural sector. It discusses its potential applications on farms including as an energy source for powering agricultural machinery producing fertilizers and storing energy from renewable sources. Within the European context it considers actions arising from the European Green Deal and the “Fit for 55” strategy which promote the development of hydrogen infrastructure and support research into low-emission technologies. The article also discusses global initiatives and trends in the development of the hydrogen economy pointing to international cooperation investment and the need for technology standardization. It highlights the challenges related to cost infrastructure and scalability as well as the opportunities hydrogen offers for a sustainable and energy-efficient agriculture of the future.

The power-to-methanol (PtMeOH) will play a crucial role as a form of renewable chemical energy storage. In this paper PtMeOH techno-economics are assessed using the promising configuration from the previous work (Mbatha et al. [1]). This study evaluated the effect of parameters such as the CO2 emission tax electricity price and CAPEX reduction on the product methanol economic parity with respect to a reference case. Superior to previous economic studies a scenario where an existing methanol synthesis infrastructure is 100 % retrofitted with the promising electrolyser is assessed in terms of its economics and the associated economic parity. The volatile South African electricity market is considered as a case study. The sensitivity of the PtMeOH and green H2 profitability are checked. Grid-connected and standalone renewable energy PtMeOH scenarios are assessed. Foremost generalisable effect trends of these parameters on the net present value (NPV) and the levelized cost of methanol(LCOMeOH) and H2 (LCOH2) are discussed. The results show that economic parity of H2 (LCOH2 = current selling price = 4.06 €/kg) can be reached with an electricity price of 30 €/MWh and 70 % of the CAPEX. While the LCOMeOH will still be above 2 €/kg at 80 % of the CAPEX and electricity price of 20 €/MWh. This indicates that even if the CAPEX reduces to 20 % of its original in this study and the electricity price reduces to about 20 €/MWh the LCOMEOH will still not reach economic parity (LCOMeOH > current selling price = 0.44 €/kg). The results show that to make the retrofitted plant with a minimum of 20 years of life span profitable a feasible reduction in the electricity price to below 10 €/MWh along with favourable incentives such as CO2 credit and reduction in CAPEX particularly that of the electrolyser and treatment of the PtMeOH as a multiproduct plant will be required.

In the context of renewable energy systems microgrids (MG) are a solution to enhance the reliability of power systems. In the last few years there has been a growing use of energy storage systems (ESSs) such as hydrogen and battery storage systems because of their environmentally-friendly nature as power converter devices. However their short lifespan represents a major challenge to their commercialization on a large scale. To address this issue the control strategy proposed in this paper includes cost functions that consider the degradation of both hydrogen devices and batteries. Moreover the proposed controller uses scenarios to reflect the stochastic nature of renewable energy resources (RESs) and load demand. The objective of this paper is to integrate a stochastic model predictive control (SMPC) strategy for an economical/environmental MG coupled with hydrogen and battery ESSs which interacts with the main grid and external consumers. The system's participation in the electricity market is also managed. Numerical analyses are conducted using RESs profiles and spot prices of solar panels and wind farms in Abu Dhabi UAE to demonstrate the effectiveness of the proposed controller in the presence of uncertainties. Based on the results the developed control has been proven to effectively manage the integrated system by meeting overall constraints and energy demands while also reducing the operational cost of hydrogen devices and extending battery lifetime.

For centuries fossil fuels have been the primary energy source but their unchecked use has led to significant environmental and economic challenges that now shape the global energy landscape. The combustion of these fuels releases greenhouse gases which are critical contributors to the acceleration of climate change resulting in severe consequences for both the environment and human health. Therefore this article examines the potential of hydrogen as a sustainable alternative energy source capable of mitigating these climate impacts. It explores the properties of hydrogen with particular emphasis on its application in industrial burners and furnaces underscoring its clean combustion and high energy density in comparison to fossil fuels and also examines hydrogen production through thermochemical and electrochemical methods covering green gray blue and turquoise pathways. It discusses storage and transportation challenges highlighting methods like compression liquefaction chemical carriers (e.g. ammonia) and transport via pipelines and vehicles. Hydrogen combustion mechanisms and optimized burner and furnace designs are explored along with the environmental benefits of lower emissions contrasted with economic concerns like production and infrastructure costs. Additionally industrial and energy applications safety concerns and the challenges of large-scale adoption are addressed presenting hydrogen as a promising yet complex alternative to fossil fuels.

Hydrogen price significantly impacts its potential as a viable alternative in the sustainable energy transition. This study introduces a synergy-based Hydrogen Pricing Mechanism (HPM) within an integrated framework. The HPM leverages synergy between a Renewable-Penetrated Electric Power System (RP-EPS) and a Hydrogen Energy System (HES). Utilizing the Alternating Direction Method of Multipliers (ADMM) it facilitates data exchange quantifying integration levels and simplifying the complexities. The study assesses the HPM’s operational sensitivity across various scenarios of hydrogen generation transportation and storage. It also evaluates the benefits of synergy-based versus stand-alone HPMs. Findings indicate that the synergy-based HPM effectively integrates infrastructure and operational improvements from both EPS and HES leading to optimized hydrogen pricing.

The transition from traditional petrol-based combustion engines to hydrogen-powered systems represents a promising advancement in sustainable and clean energy solutions. This review paper explores the intricacies of converting a conventional internal combustion engine to operate on hydrogen gas. Key topics include the performance limitations of hydrogen engines the role of water injection in combustion modulation and the investigation of direct injection and port injection systems. This review also examines challenges associated with lean and rich mixtures risks of backfire and pre-ignition and the conversion’s overall impact on engine performance and longevity. Additionally this paper discusses hydrogen lubrication to prevent mechanical wear and addresses emission-related considerations.

Hydrogen valleys are encompassed within a defined geographical region with various technologies across the entire hydrogen value chain. The scope of this study is to analyze and assess the different hydrogen technologies for their application within the hydrogen valley context. Emphasizing on the coupling of renewable energy sources with electrolyzers to produce green hydrogen this study is focused on the most prominent electrolysis technologies including alkaline proton exchange membrane and solid oxide electrolysis. Moreover challenges related to hydrogen storage are explored alongside discussions on physical and chemical storage methods such as gaseous or liquid storage methanol ammonia and liquid organic hydrogen carriers. This article also addresses the distribution of hydrogen within valley operations especially regarding the current status on pipeline and truck transportation methods. Furthermore the diverse applications of hydrogen in the mobility industrial and energy sectors are presented showcasing its potential to integrate renewable energy into hard-to-abate sectors.

Hydrogen (H2) offers a green medium for storing the excess from renewables production instead of dumping it thus being crucial to decarbonisation efforts. Hydrogen also offers a storage medium for the grid’s cheap electricity to be used during grid peak demand or grid power cutoffs. Funded by the Scottish Government’s Emerging Energy Technologies this paper presents the design and performance analysis of a hydrogen uninterruptible power supply (H2GEN) for Cygnas Solutions Ltd. which is intended to enable continuity of supply in the residential sector while eradicating the need for environmentally and health risky lead–acid batteries and diesel generator backup. This paper presents the design optimal sizing and analysis of two H2Gen architectures one powered by the grid alone and the other powered by both the grid and a renewable (PV) source. By developing a model of each architecture in the HOMER space and using residential location weather data the home yearly load–demand profile and the grid yearly power outages profile in the developed models the optimal sizing of each H2Gen design was realised by minimising the costs while ensuring the H2Gen meets the home power demand during grid outages To enable HOMER to optimise its selection the sizes technical specifications and costs of all the market-available H2GEN components were added in the HOMER search space. Moreover the developed models were also used in assessing the sensitivity of the simulation outputs to several changes in the modelled system design and settings. Using a residential home with frequent power outages in New Delhi India as a case study it was found that the optimal sizing of H2Gen Architecture 1 is comprised of a 2 kW electrolyser a 0.2 kg type-I tank and a 2 kW water-cooled fuel cell directly connected to the AC bus offering an operational lifetime of 14.3 years. It was also found that the optimal sizing of Architecture 2 is comprised of a 1 kV PV utilised with the same 2 kW electrolyser 0.2 kg type-I tank and 2 kW water-cooled fuel cell connected to the AC bus. While the second design was found to have a higher capital cost due to the added PV it offered a more cost-effective and environmentally friendly architecture which contributes to the ongoing energy transition. This paper further investigated the capacity expansion of each H2GEN architecture to meet higher load demands or increased grid power outages. From the analysis of the simulation results it has been concluded that the most feasible and cost-effective H2GEN system expansion for meeting increased power demands or increased grid outages can be realised by using the developed models for optimally sizing the expanded H2Gen on a case-by-case basis because the increase in these profiles is highly time-dependent (for example an increased load demand or increased grid outage in the morning can be met by the PV while in the evening it must be met by the H2GEN). Finally this paper investigated the impact of other environmental variables such as the temperature and relative humidity on the H2GEN’s performance and provided further insights into increasing the overall system efficiency and cost benefit through utilising the H2GEN’s exhaust heat in the home space for heating/cooling and selling the electrolyser exhaust’s O2 as a commodity.

To reduce carbon dioxide emissions from the steel industry efforts are made to introduce a steelmaking route based on hydrogen reduction of iron ore instead of the commonly used cokebased reduction in a blast furnace. Changing fundamental pieces of steelworks affects the functions of most every system unit involved and thus warrants the question of how such a transition could optimally take place over time and no rigorous attempts have until now been made to tackle this problem mathematically. This article presents a steel plant optimization model written as a mixed-integer non-linear programming problem where aging blast furnaces and basic oxygen furnaces could potentially be replaced with shaft furnaces and electric arc furnaces minimizing costs or emissions over a long-term time horizon to identify possible transition pathways. Example cases show how various parameters affect optimal investment pathways stressing the necessity of appropriate planning tools for analyzing diverse cases.

Fuel cell electric vehicles are getting deployed exponentially in Europe. Hydrogen fuel quality regulations are getting into place in order to protect customers and ensure end-users satisfactory experiences. It became critical to have the capability to sample and analyse accurately hydrogen fuel delivered by hydrogen refuelling stations in Europe. This study presents two separate comparisons: the first bilateral comparison between two sampling systems (H2 Qualitizer) and (“H2 Sampling System” of Air Liquide) and the interlaboratory comparison between NPL and Air Liquide on hydrogen fuel quality testing according to EN 17124. The two sampling systems showed equivalent results for all contaminants for sampling at 70 MPa hydrogen refuelling stations. The two laboratories showed good agreement at 95% confidence level. Even if the study is limited due to the low number of samples it demonstrates the equivalence of two sampling strategies and the ability of two laboratories to perform accurate measurement of hydrogen fuel quality.

This paper aims at the development and validation of a computational fluid dynamic (CFD) model for simulations of the refuelling process through the entire equipment of the hydrogen refuelling station (HRS). The absence of such models hinders the design of inherently safer refuelling protocols for an arbitrary combination of HRS equipment hydrogen storage parameters and environmental conditions. The CFD model is validated against the complete process of refuelling lasting 195s in Test No.1 performed by the National Renewable Energy Laboratory (NREL). The test equipment includes high-pressure tanks of HRS pressure control valve (PCV) valves pipes breakaway hose and nozzle all the way up to three onboard tanks. The model accurately reproduced hydrogen temperature and pressure through the entire line of HRS equipment. A standout feature of the CFD model distinguishing it from simplified models is the capability to predict temperature non-uniformity in onboard tanks a crucial factor with significant safety implications.

Optimal design and performance analysis of renewable energy system to serve the cruise ship main and auxiliary power in Stockholm Sweden is presented in this paper. The goal is to integrate renewable energy systems in small and large ships for greener and sustainable marine transport. The power load for the cruise ship was determined and modeling and simulation analysis was used to investigate the daily and annual performance of the power system architectures including the efficiency and capacity factors of the energy conversion systems. The total electrical power generated from the solar PV PEM fuel cell and Diesel generator; the cost of electricity; and the greenhouse gas and particulate matter PM emissions were determined. The proposed renewable energy system offers a good penetration of renewable energy system (13.83%) and greenhouse gas and particulate emissions reduction (9.84% emissions reduction compared to baseline system using Diesel engines). The integration of renewable and clean power systems such as solar PV and PEM fuel cell (high electrical efficiency) is very attractive solution for onboard ship power generation. They are economically viable (reduce the cost of Diesel fuel) cleaner than the conventional gas turbine and internal combustion engines and reduce the dependency on fossil fuel.

Nowadays integrating renewable energy sources (RESs) poses significant challenges due to the deterioration of performance indices especially in cold-climate unbalanced microgrids. Beyond network unbalance harsh conditions with low irradiance weak wind speeds and low temperatures necessitate hydrogen storage systems (HSSs) to address seasonal mismatches between RES generation and demand. This paper proposes a two-stage multi-timescale planning framework that integrates RESs plug-in electric vehicles (PEVs) battery energy storage systems (BESSs) seasonal HSSs and a dynamic demand response (DDR) program. In the short term BESSs are coordinated under slow and fast charging/discharging modes for responding to daily load shifting and peak shaving or sudden demand fluctuations. Smart converters with active/reactive power control are equipped with RES and BESS for local voltage regulation. Furthermore the proposed DDR program which combines load reduction and valley filling strategies enables consumer flexibility based on real-time market signals across seasonal variations. Seasonal HSSs are designed to store excess hydrogen produced from RESs for long-term use across different seasons. The proposed strategy is validated in two stages. The first stage guarantees multitimescale coordination of BESSs seasonal HSSs and the DDR. In turn the second stage optimally plans RESs BESSs and HSSs in a unified manner to reduce voltage unbalance and line congestion while maximizing microgrid RES hosting capacity. Simulation results for six interconnected microgrids demonstrate a 12.5% reduction in voltage unbalance 21% alleviation of line congestion and a 108% increase in hosting capacity highlighting the effectiveness of the proposed planning approach for unbalanced RES-rich microgrids.

Hydrogen fuel cell electric trucks and battery electric trucks can significantly contribute to the decarbonisation of the heavy-duty vehicles transport segment. Nonetheless a paucity of hydrogen refuelling and fast-charging stations can represent a hindrance to the development of zero-emission vehicles. This work aims to provide a techno-economic analysis with a view to comparing the costs of hydrogen refuelling and electric charging and evaluating their effects on the total cost of ownership of zero-emission trucks. Thus a comprehensive analysis has been conducted on off-site compressed (CH2) cryo-compressed subcooled hydrogen refuelling stations in conjunction with a fast-charging station. The resulting levelized costs of hydrogen and charging have been incorporated into the total cost of ownership analysis. Thus it has been demonstrated that battery electric trucks are more costeffective than hydrogen-fuel cell electric trucks. The findings of this study indicate that the costs associated with electric charging and hydrogen refuelling are comparable and the economic profitability is contingent upon a number of techno-economic variables. Therefore it is not possible to determine a priori whether one solution is more economically competitive than the other. A mixed infrastructure can represent an opportunity for the transport sector decarbonisation whereby electric-charging and hydrogen-refuelling are not mutually exclusive.

Proton exchange membrane fuel cells (PEMFCs) present great potential for the decarbonization of the maritime sector but their durability in harsh marine environments remains a critical challenge. This review focuses on post-mortem analysis techniques as a tool to understand the degradation mechanisms of PEMFCs under stressors relevant to marine applications. In further detail the application of various imaging (SEM TEM) structural (XRD) electrochemical (CV) and elemental analysis (EDS) methods to characterize the effects of key stressors such as salt spray mechanical vibration and operational cycling was examined. By analyzing degraded PEMFC components post-mortem analysis reveals critical insights into catalyst layer degradation membrane damage and the impact of impurities enabling the identification of failure modes and the development of effective mitigation strategies for the establishment of PEMFCs in the maritime sector.

This work aims to study the technical and economical feasibility of a new hydrogen transport network by 2035 in France. The goal is to furnish charging stations for fuel cell electrical vehicles with hydrogen produced by electrolysis of water using low-carbon energy. Contrary to previous research works on hydrogen transport for road transport we assume a more realistic assumption of the demand side: we assume that only drivers driving more than 20000 km per year will switch to fuel cell electrical vehicles. This corresponds to a total demand of 100 TWh of electricity for the production of hydrogen by electrolysis. To meet this demand we primarily use surplus electricity production from wind power. This surplus will satisfy approximately 10% of the demand. We assume that the rest of the demand will be produced using surplus from nuclear power plants disseminated in regions. We also assume a decentralized production namely that 100 MW electrolyzers will be placed near electricity production plants. Using an optimization model we define the hydrogen transport network by considering decentralized production. Then we compare it with more centralized production. Our main conclusion is that decentralized production makes it possible to significantly reduce distribution costs particularly due to significantly shorter transport distances.

The fuel cell electric vehicle (FCEV) is a promising transportation technology for resolving the air pollution and climate change issues in the United States. However a large-scale penetration of FCEVs would require a sustained supply of hydrogen which does not exist now. Water electrolysis can produce hydrogen reliably and sustainably if the electricity grid is clean but the impacts of FCEVs on the electricity grid are unknown. In this paper we develop a comprehensive framework to model FCEV-driving and -refueling behaviors the water electrolysis process and electricity grid operation. We chose the Western Electricity Coordinating Council (WECC) region for this case study. We modeled the existing WECC electricity grids and accounted for the additional electricity loads from FCEVs using a Production Cost Model (PCM). Additionally the hydrogen need for five million FCEVs leads to a 3% increase in electricity load for WECC. Our results show that an inflexible hydrogen-producing process leads to a 1.55% increase to the average cost of electricity while a flexible scenario leads to only a 0.9% increase. On the other hand oversized electrolyzers could take advantage of cheaper electricity generation opportunities thus lowering total system costs.

The shift to renewable energy sources requires systems that are not only environmentally sustainable but also cost-effective and reliable. Mitigating the inherent intermittency of renewable energy optimally managing the hybrid energy storage efficiently integrating the microgrid with the power grid and maximizing the lifespan of system components are the significant challenges that need to be addressed. With this aim the paper proposes an economic viability assessment framework with an optimized dynamic operation approach to determine the most stable cost-effective and environmentally sound system for a specific location and demand. The green integrated hybrid microgrid combines photovoltaic (PV) generation battery storage an electrolyzer a hydrogen tank and a fuel cell tailored for deployment in remote areas with limited access to conventional infrastructure. The study’s control strategy focuses on managing energy flows between the renewable energy resources battery and hydrogen storage systems to maximize autonomy considering real-time changes in weather conditions load variations and the state of charge of both the battery and hydrogen storage units. The core system’s components include the interlinking converter which transfers power between AC and DC grids and the decentralized droop control approach which adjusts the converter’s output to ensure balanced and efficient power sharing particularly during overload conditions. A cloud-based Internet of Things (IoT) platform has been employed allowing continuous monitoring and data analysis of the green integrated microgrid to provide insights into the system's health and performance during the dynamic operation. The results presented in this paper confirmed that the proposed framework enabled the strategic use of energy storage particularly hydrogen systems. The optimal operational control of green hydrogen-integrated microgrid can indeed mitigate voltage and frequency fluctuations caused by variable solar input ensuring stable power delivery without reliance on the main grid or fossil fuel backups.

Adverse climate change has forced a deeper reflection on the scale of pollution related to human activity including in the aviation industry. As a result fundamental questions have arisen about the characteristics of these pollutants the mechanisms of their formation and potential strategies for reducing them. This paper provides a comprehensive overview of key technical solutions to minimize the environmental impact of aircraft engines. The solutions presented range from fuel innovations to advanced design changes and drive concepts. Particular attention was paid to sustainable aviation fuels (SAFs) which are currently an important element of the environmental strategy regulated by the European Union. It also discusses the potential use of hydrogen as a potential alternative fuel to replace traditional aviation fuels in the long term. The analysis in the article made it possible to characterize in detail possible modifications in the functioning of aircraft engines based both on the current state of technical knowledge and on the anticipated directions of its development which has not been a frequent issue in comprehensive research so far. The analysis shows that the type of raw material used to create SAF has a strong impact on its physical and chemical parameters and the degree of greenhouse gas emissions. This necessitates a broader analysis of the legitimacy of using a given type of fuel from the SAF group in the direction of selected air operations and areas with a higher risk of severe atmospheric pollution. These results provide the basis for further research into sustainable solutions in the aviation sector that can contribute to significantly reducing its impact on climate change.

This paper presents a preliminary feasibility study for integrating hydro-pneumatic energy storage (HPES) with off-grid offshore wind turbines and green hydrogen production facilities—a concept termed HydroGenEration (HGE). This study compares the performance of this innovative concept system with an off-grid direct wind-to-hydrogen plant concept without energy storage both under central Mediterranean wind conditions. Numerical simulations were conducted at high temporal resolution capturing 10-min fluctuations of open field measured wind speeds at an equivalent offshore wind turbine (WT) hub height over a full 1-year seasonal cycle. Key findings demonstrate that the HPES system of choice namely the Floating Liquid Piston Accumulator with Sea Water under Compression (FLASC) system significantly reduces Proton Exchange Membrane (PEM) electrolyser (PEMEL) On/Off cycling (with a 66% reduction in On/Off events) while maintaining hydrogen production levels despite the integration of the energy storage system which has a projected round-trip efficiency of 75%. The FLASC-integrated HGE solution also marginally reduces renewable energy curtailment by approximately 0.3% during the 12-month timeframe. Economic analysis reveals that while the FLASC HPES system does introduce an additional capital cost into the energy chain it still yields substantial operational savings exceeding EUR 3 million annually through extended PEM electrolyser lifetime and improved operational efficiency. The Levelized Cost of Hydrogen (LCOH) for the FLASC-integrated HGE system which is estimated to be EUR 18.83/kg proves more economical than a direct wind-to-hydrogen approach with a levelized cost of EUR 21.09/kg of H2 produced. This result was achieved through more efficient utilisation of wind energy interfaced with energy storage as it mitigated the natural intermittency of the wind and increased the lifecycle of the equipment especially that of the PEM electrolysers. Three scenario models were created to project future costs. As electrolyser technologies advance cost reductions would be expected and this was one of the scenarios envisaged for the future. These scenarios reinforce the technical and economic viability of the HGE concept for offshore green hydrogen production particularly in the Mediterranean and in regions having similar moderate wind resources and deeper seas for offshore hybrid sustainable energy systems.

Urban Air Mobility (UAM) is gaining attention as a solution to urban population growth and air pollution. Hydrogen fuel cells are applied to overcome the limitations of battery-based UAM utilizing a PEMFC (Polymer Electrolyte Membrane Fuel Cell) with batteries in a hybrid system to enhance responsiveness. Power management improves efficiency through effective power distribution under varying loads while thermal management maintains optimal stack temperatures to prevent degradation. This study developed a hydrogen fuel cell–battery hybrid multicopter system using AMESim consisting of a 138 kW fuel cell stack 60 kW battery DC–DC converters and thrust motors. A rule-based power management system was implemented to define power distribution strategies based on SOC and load demand. The system’s operating range was designed to allocate power according to battery SOC and load variations. For an initial SOC of 45% the power management system distributed power for flight and the results showed that the state machine control system reduced hydrogen consumption by 5.85% and parasitic energy by 1.63% compared to the rule-based system.

The high volumetric capacity (53 g H2/L) and its low toxicity and flammability under ambient conditions make formic acid a promising hydrogen energy carrier. Particularly in the past decade significant advancements have been achieved in catalyst development for selective hydrogen generation from formic acid. This Perspective highlights the advantages of this approach with discussions focused on potential applications in the transportation sector together with analysis of technical requirements limitations and costs.

This study proposes the SMR Smart Net-Zero City (SSNC) framework—a scalable model for achieving carbon neutrality by integrating Small Modular Reactors (SMRs) renewable energy sources and sector coupling within a microgrid architecture. As deploying renewables alone would require economically and technically impractical energy storage systems SMRs provide a reliable and flexible baseload power source. Sector coupling systems—such as hydrogen production and heat generation—enhance grid stability by absorbing surplus energy and supporting the decarbonization of non-electric sectors. The core contribution of this study lies in its real-time data emulation framework which overcomes a critical limitation in the current energy landscape: the absence of operational data for future technologies such as SMRs and their coupled hydrogen production systems. As these technologies are still in the pre-commercial stage direct physical integration and validation are not yet feasible. To address this the researchers leveraged real-time data from an existing commercial microgrid specifically focusing on the import of grid electricity during energy shortfalls and export during solar surpluses. These patterns were repurposed to simulate the real-time operational behavior of future SMRs (ProxySMR) and sector coupling loads. This physically grounded simulation approach enables highfidelity approximation of unavailable technologies and introduces a novel methodology to characterize their dynamic response within operational contexts. A key element of the SSNC control logic is a day–night strategy: maximum SMR output and minimal hydrogen production at night and minimal SMR output with maximum hydrogen production during the day—balancing supply and demand while maintaining high SMR utilization for economic efficiency. The SSNC testbed was validated through a seven-day continuous operation in Busan demonstrating stable performance and approximately 75% SMR utilization thereby supporting the feasibility of this proxy-based method. Importantly to the best of our knowledge this study represents the first publicly reported attempt to emulate the real-time dynamics of a net-zero city concept based on not-yet-commercial SMRs and sector coupling systems using live operational data. This simulation-based framework offers a forward-looking data-driven pathway to inform the development and control of next-generation carbon-neutral energy systems.

This study explores the performance and emissions characteristics of a dual-fuel internal combustion engine operating on a blend of hydrogen and gasoline. This research began with a baseline simulation of a conventional gasoline engine which was subsequently validated through experimental testing on an AVL testbed. The simulation results closely matched the testbed data confirming the accuracy of the model with deviations within 5%. Building on this validated model a hydrogen–gasoline dual-fuel engine simulation was developed. The predictive simulation revealed an approximately 5% increase in overall engine efficiency at the optimal operating point primarily due to hydrogen’s combustion properties. Additionally the injected gasoline mass and CO2 emissions were reduced by around 30% across the RPM range. However the introduction of hydrogen also resulted in a slight reduction (~10%) in torque attributed to the lower volumetric efficiency caused by hydrogen displacing intake air. While CO emissions were significantly reduced NOx emissions nearly doubled due to the higher combustion temperatures associated with hydrogen. This research demonstrates the potential of hydrogen–gasoline dual-fuel systems in reducing carbon emissions while highlighting the need for further optimization to balance performance with environmental impact.

As the pursuit of greener energy solutions continues industries worldwide are turning away from fossil fuels and exploring the development of sustainable alternatives to meet their energy requirements. As a signatory to the Paris Agreement Australia has committed to reducing greenhouse gas emission by 43% by 2030 and reaching net-zero emissions by 2050. Australia’s domestic maritime sector should align with these targets. This paper aims to contribute to ongoing efforts to achieve these goals by examining the technical and commercial considerations involved in retrofitting conventional vessels with hydrogen power. This includes but is not limited to an analysis of cost risk and performance and compliance with classification society rules international codes and Australian regulations. This study was conducted using a small domestic commercial vessel as a reference to explore the feasibility of implementation of hydrogen-fuelled vessels (HFVs) across Australia. The findings indicate that Australia’s existing hydrogen infrastructure requires significant development for HFVs to meet the cost risk and performance benchmarks of conventional vessels. The case study identifies key determining factors for feasible hydrogen retrofitting and provides recommendations for the success criteria.