Applications & Pathways

The use of green hydrogen can support the decarbonization of sectors which are difficult to electrify such as industry or heavy transport. Yet the wider power sector effects of providing green hydrogen are not well understood so far. We use an open-source electricity sector model to investigate potential power sector interactions of three alternative supply chains for green hydrogen in Germany in the year 2030. We distinguish between model settings in which Germany is modeled as an electric island versus embedded in an interconnected system with its neighboring countries as well as settings with and without technology-specific capacity bounds on wind energy. The findings suggest that large-scale hydrogen storage can provide valuable flexibility to the power system in settings with high renewable energy shares. These benefits are more pronounced in the absence of flexibility from geographical balancing. We further find that the effects of green hydrogen production on the optimal generation portfolio strongly depend on the model assumptions regarding capacity expansion potentials. We also identify a potential distributional effect of green hydrogen production at the expense of other electricity consumers of which policy makers should be aware.

Low-carbon ammonia has recently received interest as alternative fuel for the maritime sector. This paper presents a techno-economic analysis of the total cost of ownership (TCO) of a Post-Panamax vessel powered by low-carbon ammonia. We also calculate the annual increase in carbon tax needed to compensate for the increment in TCO compared to a vessel powered by very low sulfur fuel oil. The increment in TCO is calculated as function of propulsion efficiency to account for uncertainties in the thermodynamics of ammonia combustion for three different cost scenarios of low-carbon ammonia. We evaluate the benefits and drawbacks of hydrogen and diesel as dual fuel for three types of propulsion systems: a compression ignition engine a spark-ignition engine and a combination of a solid oxide fuel cell (SOFC) system and a spark-ignition engine. We incorporate three different cost levels for ammonia and a variable engine efficiency ranging from 35% to 55%. If the ammonia engine has the efficiency of a conventional marine engine the increment in TCO is 25% in the most optimistic cost scenario. SOFCs can reach a better efficiency and yield no pollutant emissions but the reduction in fuel expenses in comparison to conventional combustion engines only offsets their high investment costs at either low engine efficiency or high fuel prices. The increment in TCO and reduction in GHG emissions depend on whether high combustion efficiencies small dual fuel fractions and low NOx N2O and NH3 emissions can be simultaneously achieved.

Aviation is one of the most challenging sectors to electrify directly due to its high energy density demands. Hydrogen offers a pathway for indirect electrification in such sectors enabling sustainable aviation fuels (SAF) production when combined with a carbon source. SAF produced via methanol or Fischer-Tropsch (FT) synthesis (e-SAF) has higher volumetric density than hydrogen remains liquid under standard conditions and can be used as a direct drop-in fuel. Certain FT-based e-SAF pathways are already certified for use in blends enhancing their appeal for sustainable aviation. This study evaluates e-SAF pathways in terms of resource efficiency and costs for different carbon sources. The results from both a standalone and system-level perspective indicate that biomass gasification-sourced carbon is the most energy-efficient pathway given biomass availability. For point-source and direct air capture pathways electricity costs for renewable hydrogen dominate the overall costs comprising about 70 % of total e-SAF costs. Given cheap renewable electricity and by-product revenues e-SAF can achieve price levels of 0.5–1.1 €/litre which is cost-competitive with their fossil-based counterparts. A breakeven electricity price of 9–29 €/MWh is needed for e-SAF made via a point source-based CO2 pathway compared with a moderate aviation fossil fuel price of 0.5 €/litre.

Ammonia production currently contributesalmost 11% of global industrial carbon dioxide emissions or1.3% of global emissions. In the context of global emissiontargets and growing demand decarbonization of this processis highly desirable. We present a method to calculate a firstestimate for the optimum size of an ammonia productionplant (at the process level) the required renewable energy(RE) supply and the levelized cost of ammonia (LCOA) forislanded operation with a hydrogen buffer. A model wasdeveloped to quantitatively identify the key variables thatimpact the LCOA (relative to a ±10 GBP/tonne change inLCOA): levelized cost of electricity (±0.89 GBP/MWh) electrolyzer capital expenditure (±65 GBP/kW) minimum Haber−Bosch (HB) load (±12% of rated power) maximum rate of HB load ramping and RE supply mix. Using 2025/2030 estimatesresults in a LCOA of 588 GBP/tonne for Lerwick Scotland. The application of the model will facilitate and improve theproduction of carbon-free ammonia in the future.

The integration of renewable energy resources (RES) into microgrids (MGs) poses significant challenges due to the intermittent nature of generation and the increasing complexity of multi-energy scheduling. To enhance operational flexibility and reliability this paper proposes an intelligent energy management system (EMS) for MGs incorporating a hybrid hydrogen-battery energy storage system (HHB-ESS). The system model jointly considers the complementary characteristics of short-term and long-term storage technologies. Three conflicting objectives are defined: economic cost (EC) system response stability and battery life loss (BLO). To address the challenges of multi-objective trade-offs and heterogeneous storage coordination a novel deep-reinforcement-learning (DRL) algorithm termed MOATD3 is developed based on a dynamic reward adjustment mechanism (DRAM). Simulation results under various operational scenarios demonstrate that the proposed method significantly outperforms baseline methods achieving a maximum improvement of 31.4% in SRS and a reduction of 46.7% in BLO.

Financing sizing operating or upgrading a hydrogen refueling station (HRS) is challenging and may be complex much more so in today's rapidly changing and growing hydrogen industry. There is a significant information gap regarding experimental hydrogen station activities. A high-level perspective on such data and information may facilitate the transition between present and future HRS operations. To address the need for such high-level perspective this paper presents a comprehensive data set on the performance of the California State University Los Angeles Hydrogen Research and Fueling Facility based on multi-year operational data. The analysis of over 4500 refueling events and over 8800 kg of hydrogen dispensed as well as the operation of the facility electrolyzer and of both storage and refueling compressors from 2016 to 2020 reveals a comprehensive picture of HRS energy performance and the identification of useful key performance indicators. In 2016 the station's energy efficiency was 25% but in 2017 and the first three quarters of 2018 it dropped to 15%. Station-specific energy consumption increased during these quarters. The 2020 first quarter energy consumption was between 70 and 80 kWh/kg. At this time the energy efficiency of the station reached 40%.<br/>This research is based on an unprecedented and unique dataset of an HRS operating under real-world conditions with an approach that can be informative for modeling the performance of other stations providing a dataset that HRS designers operators and investors may utilize to make data-driven choices regarding HRS components and their specs and size as well as operating strategies.

With the deepening electrification of transportation hydrogen fuel cell electric vehicles (FCEVs) are emerging as a vital component of clean and electrified transportation systems. Nonetheless renewable-based hydrogen production–refueling stations (HPRSs) for FCEVs still need solid models for accurate simulations and a practical capacity optimization method for cost reduction. To address this gap this study leverages real operation data from China’s largest HPRS to establish and validate a comprehensive model integrating hydrogen production storage renewables FCEVs and the power grid. Building on this validated model a novel capacity optimization framework is proposed incorporating an improved Jellyfish Search Algorithm (JSA) to minimize the initial investment cost operating cost and levelized cost of hydrogen (LCOH). The results demonstrate the framework’s significant innovations and effectiveness: It achieves the maximum reductions of 29.31% in the initial investment 100% in the annual operational cost and 44.19% in LCOH while meeting FCEV demand. Simultaneously it reduces peak grid load by up to 43.80% and enables renewable energy to cover up to 89.30% of transportation hydrogen demand. This study contributes to enhancing economic performance and optimizing the design and planning of HPRS for FCEVs as well as promoting sustainable transportation electrification.

Civil aviation provides an essential transportation network that connects the world and supports global economic growth. To maintain these benefits while meeting environmental goals next-generation aircraft must have drastically reduced climate impacts. Hydrogen-powered aircraft have the potential to fly existing routes with no carbon emissions and reduce or eliminate other emissions. This paper is a comprehensive guide to hydrogen-powered aircraft that explains the fundamental physics and reviews current technologies. We discuss the impact of these technologies on aircraft design cost certification and environment. In the long term hydrogen aircraft appear to be the most compelling alternative to today’s kerosene-powered aircraft. Using hydrogen also enables novel technologies such as fuel cells and superconducting electronics which could lead to aircraft concepts that are not feasible with kerosene. Hydrogen-powered aircraft are technologically feasible but require significant research and development. Lightweight liquid hydrogen tanks and their integration with the airframe is one of the critical technologies. Fuel cells can eliminate in-flight emissions but must become lighter more powerful and more durable to make large fuel cell-powered transport aircraft feasible. Hydrogen turbofans already have these desirable characteristics but produce some emissions albeit much less damaging than kerosene turbofans. Beyond airframe and propulsion technologies the viability of hydrogen aircraft hinges on low-cost green hydrogen production which requires massive investments in the energy infrastructure.

This paper evaluates the potential impacts of introducing low-carbon intensity hydrogen technologies in two oil refineries with different complexity levels emphasizing the role of hydrogen production in reducing CO2 emissions. The novelty of this work lies in three key aspects: Comprehensive system analysis of refinery complexity using real site data integration of low-carbon Hydrogen technologies long-term and short-term strategies. Two Colombian refineries serve as case studies with technological solutions adapted to their complexity levels. The methodology involves evaluating different options for hydrogen production accounting for improvement in technological efficiency over time.<br/>The refinery systems were evaluated in a cost-optimization model built in Linny-r. Three different scenarios were considered Business-As-Usual (BAU) high and low-ambitions decarbonization scenarios focusing on the time horizons of 2030 and 2050.<br/>When comparing the two case studies the preferred decarbonization strategy for both facilities involves the substitution of SMR technology with water electrolyzers powered by renewable electricity. Post-2030 biomass-based hydrogen technology is still a costly alternative; however to achieve CO2 neutrality negative emissions storage of biogenic CO2 emerges as an achievable alternative.<br/>Our results indicate the achievability of CO2 reduction objectives in both refineries. Our results show that achieving long-term CO2 neutrality requires both refineries to increase renewable electricity production by 5 to 6 times for powering water electrolyzers steam production by 2 to 2.5 times for CO2 capture and supply of dry biomass by 2.6 to 4.5 kt/d.<br/>The two most significant factors influencing the refining net margin in the decarbonization scenarios are primarily the CO2 and the renewable electricity prices. The short-term horizon emerges as the pivotal period particularly within the high-ambition decarbonization scenarios. In this context the medium complexity refinery demonstrates economic viability until a CO2 price of 140 €/t CO2 while the high complexity refinery endures up to 205 €/t CO2.<br/>The high complexity refinery is better prepared to face the challenges of decarbonization and the impacts generated on the refining margin. Compared to the BAU scenario the high complexity refinery shows a negative impact on the net margin that corresponds to a 40% and 5% reduction in the short and long term respectively. Meanwhile for the medium complexity refinery the impact on net margin amounts to a 52% reduction in the short term and a 27% improvement in the long term.<br/>Furthermore our research highlights the significant potential for reducing CO2 emissions by fully eliminating the use of refinery gas as fuel providing alternative applications for it beyond combustion.

Electrofuels fuels produced from electricity water and carbon or nitrogen are of interest as substitutes for fossil fuels in all energy and chemical sectors. This paper focuses on electrofuels for transportation where some can be used in existing vehicle/vessel/aircraft fleets and fueling infrastructure. The aim of this study is to review publications on electrofuels and summarize costs and environmental performance. A special case denoted as bio-electrofuels involves hydrogen supplementing existing biomethane production (e.g. anaerobic digestion) to generate additional or different fuels. We use costs identified in the literature to calculate harmonized production costs for a range of electrofuels and bio-electrofuels. Results from the harmonized calculations show that bio-electrofuels generally have lower costs than electrofuels produced using captured carbon. Lowest costs are found for liquefied bio-electro-methane bio-electro-methanol and bio-electro-dimethyl ether. The highest cost is for electro-jet fuel. All analyzed fuels have the potential for long-term production costs in the range 90–160 € MWh−1 . Dominant factors impacting production costs are electrolyzer and electricity costs the latter connected to capacity factors (CFs) and cost for hydrogen storage. Electrofuel production costs also depend on regional conditions for renewable electricity generation which are analyzed in sensitivity analyses using corresponding CFs in four European regions. Results show a production cost range for electro-methanol of 76–118 € MWh−1 depending on scenario and region assuming an electrolyzer CAPEX of 300–450 € kWelec −1 and CFs of 45%–65%. Lowest production costs are found in regions with good conditions for renewable electricity such as Ireland and western Spain. The choice of system boundary has a large impact on the environmental assessments. The literature is not consistent regarding the environmental impact from different CO2 sources. The literature however points to the fact that renewable energy sources are required to achieve low global warming impact over the electrofuel life cycle.

The decarbonization of the building stock in this paper focusing the single-family house sector in Germany is essential to achieve the climate goals. In fact as the largest part of the building stock it represents more than 65 % of the entire German residential building stock. Current strategies and regulations have demonstrated low impact on carbon emission reduction due to poor renovation rates particularly in the single-family house typology. The present study analyzes the potential of carbon emission reduction prioritizing local renewable energy generation and storage in combination with improved building energy systems. Through a simulation-based approach it considers reference buildings of different age classes and formulates variants for improving strategies with different levels of retrofit under the premise of a fully renewable locally generated energy supply. Based on the potential for solar energy supply the variants consider the seasonal shift that needs to be stored and particularly the role of hydrogen as an energy storage medium. The study´s goal is quantifying the impacts of the local renewable energy production its required storage capacity depending on the retrofit depth both for estimating the potential of transforming the single-family house stock to net zero carbon emissions.

Hydrogen flight is one important part of the way to net zero aviation. However safety challenges around refuelling are not well understood but are paramount to enable airports to be more comfortable with using hydrogen in the airport environment. This study investigates safety considerations of hydrogen aircraft refuelling at airports. Technical and human factor risks are explored as well as risk assessment models. Two focus groups were conducted in 2022. Data was analysed using NVivo revealing major themes including the mental and physical performance of refuellers technical aspects of refuelling stations environmental factors and the use of risk assessment models. These findings contribute significantly to an understanding of hydrogen refuelling challenges in busy airport environments. Recommendations help airports preparing for hydrogen as a fuel source further supporting the transition towards net zero aviation. Future research could focus on carrying out experiments analysing chemical reactions between kerosene and hydrogen vapours and testing the identified risk assessment tools in different airport environments.

This study investigates the techno-economic feasibility of a Power-to-X (PtX) system by integrating solarpowered hydrogen electrolysis with carbon capture and Fischer-Tropsch (FT) synthesis processes for e-fuel production in Basra Iraq. To this aim a comprehensive modeling framework is developed to cover the detailed simulation of E-fuel production along with the system cost analysis. The proposed PtX system is supposed to be located near the Hartha power plant which is one of the main sources of electricity in the Basra region allowing for the utilization of captured CO2 from the power plant’s exhaust gas. The PtX plant design shows significant potential producing 2.44 tonnes of (C12-C20) hydrocarbons and 3.36 tonnes of (C21-C40) heavy oils annually. This is achieved by utilizing 7.5 and 74.2 tonnes per year of hydrogen generated from solar electrolysis and captured CO2 respectively. A cash flow analysis covering 25 years shows that an E-fuel market price of $10 per liter is needed to achieve a positive cash flow within 15 years. The study also indicates that implementing a $200 per tonne carbon tax improves the economic feasibility of the project by allowing for earlier positive cash flows from 6 years and a quicker break-even point at the current E-fuel market price of $2 per liter with a NPV of $ 464 million. Sensitivity analysis reveals that higher carbon taxes and e-fuel prices enhance profitability by reducing payback periods and increasing the NPV. However an increase in hydrogen production costs introduces substantial risk with higher costs decreasing economic viability. The feasibility assessment suggests that despite the substantial initial investment needed for various system components the long-term advantages include reduced CO2 emissions and the potential for Iraq to emerge as a leader in renewable fuel production. Stable policies robust carbon taxes and cost-efficient hydrogen production are essential for the successful implementation of PtX project.

Hydrogen technologies are evolving to decarbonise the transport sector. The present work focuses on the technical design of a Hydrogen Refueling Station to supply hydrogen to five buses in the city of Valencia Spain. The study deals with the technical selection of the components from production to consumption setting an efficient standardisation method. Different calculation are used to size the storage systems for 70.8 kg of hydrogen produced by the elecrolyser daily. For the high-pressure storage system massive and cascade methods are proposed being the last one more efficient (1577.53 Nm3 non usable volume compared to 9948.95 Nm3 of the massive method).

This study addresses the challenge of decarbonizing highly energy-intensive Industrial Port Areas (IPA) focusing on emissions from various sources like ship traffic warehouses buildings cargo handling equipment and hardto-abate industry typically hosted in port areas. The analysis and proposal of technological solutions and their optimal integration in the context of IPA is a topic of growing scientific interest with considerable social and economic implications. Representing the main novelties of the work this study introduces (i) the development of a novel IPA energy and green hydrogen hub located in a tropical region (Singapore); (ii) a multi-objective optimization approach to analyse synthesize and optimize the design and operation of the hydrogen and energy hub with the aim of supporting decision-making for decarbonization investments. A sensitivity analysis identifies key parameters affecting optimization results indicating that for large hydrogen demands imported ammonia economically outperforms other green hydrogen carriers. Conversely local hydrogen production via electrolysis becomes economically viable when the capital cost of alkaline electrolyser drops by at least 30 %. Carbon tax influences the choice of green hydrogen but its price variation mainly impacts system operation rather than design. Fuel cells and batteries are not considered economically feasible solutions in any scenario.

Hydrogen-enabled Integrated Energy Systems (H-IES) stand out as a promising solution with the potential to replace current non-renewable energy systems. However their development faces challenges and has yet to achieve widespread adoption. These main challenges include the complexity of demand and supply balancing dynamic consumer demand and challenges in integrating and utilising hydrogen. Typical energy management strategies within the energy domain rely heavily on accurate models from domain experts or conventional approaches such as simulation and optimisation approaches which cannot be satisfied in the real-world operation of H-IES. Artificial Intelligence (AI) or Advanced Data Analytics (ADA) especially Machine Learning (ML) has the ability to overcome these challenges. ADA is extensively used across several industries however further investigation into the incorporation of ADA and hydrogen for the purpose of enabling H-IES needs to be investigated. This paper presents a systematic literature review to study the research gaps research directions and benefits of ADA as well as the role of hydrogen in H-IES.

The transition to green energy in the transport sector is becoming a priority in the context of global climate challenges and the European Green Deal. This paper investigates the development of alternative fuelling stations particularly electric vehicle (EV) charging infrastructure and hydrogen stations across EU countries with a focus on Poland. It combines a policy and technology overview with a quantitative scientific analysis offering a multidimensional perspective on green infrastructure deployment. A Pearson correlation analysis reveals significant links between charging station density and both GDP per capita and the share of renewable energy. The study introduces an original Infrastructure Accessibility Index (IAI) to compare infrastructure availability across EU member states and models Poland’s EV charging station demand up to 2030 under multiple growth scenarios. Furthermore the article provides a comprehensive overview of biofuels including first- second- and third-generation technologies and highlights recent advances in hydrogen and renewable electricity integration. Emphasis is placed on life cycle considerations energy source sustainability and economic implications. The findings support policy development toward zero-emission mobility and the decarbonisation of transport systems offering recommendations for infrastructure expansion and energy diversification strategies.

Until recently electrified aircraft propulsion (EAP) technology development has been driven by the dual objectives of reducing greenhouse gas (GHG) emissions and addressing the depletion of fossil fuels. However the increasing severity of climate change posing a significant threat to all life forms has resulted in the global consensus of achieving net-zero GHG emissions by 2050. This major shift has alerted the aviation electrification industry to consider the following: What is the clear path forward for EAP technology development to support the net-zero GHG goals for large commercial transport aviation? The purpose of this paper is to answer this question. After identifying four types of GHG emissions that should be used as metrics to measure the effectiveness of each technology for GHG reduction the paper presents three significant categories of GHG reduction efforts regarding the engine evaluates the potential of EAP technologies within each category as well as combinations of technologies among the different categories using the identified metrics and thus determines the path forward to support the net-zero GHG objective. Specifically the paper underscores the need for the aviation electrification industry to adapt adjust and integrate its EAP technology development into the emerging new engine classes. These innovations and collaborations are crucial to accelerate net-zero GHG efforts effectively.

Hydrogen-fueled engines require large values of the excess air ratio in order to achieve high thermal efficiency. A low value of this coefficient promotes knocking combustion. This paper analyzes the conditions for the occurrence of knocking combustion in an engine with a turbulent jet ignition (TJI) system with a passive pre-chamber. A single-cylinder engine equipped with a TJI system was running with an air-to-fuel equivalence ratio λ in the range of 1.25–2.00 and the center of combustion (CoC) was regulated in the range of 2–14 deg aTDC (top dead center). Such process conditions made it possible to fully analyze the ascension of knock combustion until its disappearance with the increase in lambda and CoC. Measures of knock in the form of maximum amplitude pressure oscillation (MAPO) and integral modulus of pressure oscillation (IMPO) were used. The absolute values of these indices were pointed out which can provide the basis for the definition of knock combustion. Based on our own work the MAPO index > 1 bar was defined determining the occurrence of knocking (without indicating its quality). In addition taking into account MAPO it was concluded that IMPO > 0.13 bar·deg is the quantity responsible for knocking combustion.

Despite the number of works on the techno-economics of offshore green hydrogen production there is a lack of research on the design of floating platforms to concomitantly support hydrogen production facilities and wind power generation equipment. Indeed previous studies on offshore decentralised configuration for hydrogen production implicitly assume that a floating platform designed for wind power generation (FOWT) can be also suitable as a floating wind hydrogen system (FWHS). This work proposes a novel design for an offshore decentralised FWHS and analyses the effects of the integration of the hydrogen facilities on the platform’s dynamics and how this in turn affects the performances of the wind turbine and the hydrogen equipment. Our findings indicate that despite the reduction in platform’s stability the performance of the wind turbine is barely affected. Regarding the hydrogen system our results aim at contributing to further assessment and design of this equipment for offshore conditions.

The iron and steel industry is a major emitter of carbon dioxide globally. To reduce their carbon footprint the iron and steel industry pursue different decarbonization strategies including deploying bio-based materials and energy carriers for reduction carburisation and/or energy purposes along their value-chains. In this study two potential roles for biomass were analysed: (a) substituting for fossil fuels in iron-ore pellets induration and (b) carburisation of DRI (direct reduced iron) produced via fully hydrogen-based reduction. The purpose of the study was to analyse the regional demand-driven price and allocative effects of biomass assortments under different biomass demand scenarios for the Swedish iron and steel industry. Economic modelling was used in combination with spatial biomass supply assessments to predict the changes on relevant biomass markets. The results showed that the estimated demand increases for forest biomass will have significant regional price effects. Depending on scenario the biomass demand will increase up to 25 percent causing regional prices to more than doubling. In general the magnitude of the price effects was driven by the volumes and types of biomasses needed in the different scenarios with larger price effects for harvesting residues and industrial by-products compared to those of roundwood. A small price effect of roundwood means that the incentives for forest-owners to increase their harvests and thus also the availability of harvest residues are small. Flexibility in the feedstock sourcing (both regarding quality and geographic origin) will thus be important if forest biomass is to satisfy demands in iron and steel industry.

This paper proposes a technical and cost analysis model to assess the change in costs of a zeroemission high-speed ferry when retrofitting from diesel to green hydrogen. Both compressed gas and liquid hydrogen are examined. Different scenarios explore energy demand energy losses fuel consumption and cost-effectiveness. The methodology explores how variation in the ferry's total weight and equipment efficiency across scenarios impact results. Applied to an existing diesel high-speed ferry on one of Norway's longest routes the study under certain assumptions identifies compressed hydrogen gas as the current most economical option despite its higher energy consumption. Although the energy consumption of the compressed hydrogen ferry is slightly more than the liquid hydrogen counterpart its operating expenses are considerably lower and comparable to the existing diesel ferry on the route. However constructing large hydrogen liquefaction plants could reduce liquid hydrogen's cost and make it competitive with both diesel and compressed hydrogen gas. Moreover liquid hydrogen allows the use of a superconducting motor to enhance efficiency. Operating the ferry with liquid hydrogen and a superconducting motor besides its technical advantages offers promising economic viability in the future comparable to diesel and compressed hydrogen gas options. Reducing the ferry's speed and optimizing equipment improves fuel efficiency and economic viability. This research provides valuable insights into sustainable zero-emission high-speed ferries powered by green hydrogen.

The urgency to mitigate greenhouse gas emissions from maritime vessels has intensified due to the increasingly stringent directives set forth by the International Maritime Organization (IMO). These directives specifically address energy efficiency enhancements and emissions reduction within the shipping industry. In this context hydrogen is the much sought after fuel for all the global economies and its applications for transportation and propulsion in particular is crucial for cutting down carbon emissions. Nevertheless the realization of hydrogen-powered vessels is confronted by substantial technical hurdles that necessitate thorough examination. This study undertakes a comprehensive analysis encompassing diverse facets including distinct variations of hydrogen fuel cells hydrogen internal combustion engines safety protocols associated with energy storage as well as the array of policies and commercialization endeavors undertaken globally for the advancement of hydrogen-propelled ships. By amalgamating insights from these multifaceted dimensions this paper adeptly encapsulates the myriad challenges intrinsic to the evolution of hydrogen-fueled maritime vessels while concurrently casting a forward-looking gaze on their prospective trajectory.

Hydrogen and methane as secondary fuels in diesel engines can be promising solutions to meet energy demand. The current study investigated the effect of the specialty gases of different compositions on diesel engine performance and exhaust gases. Four gases with various compositions of exhaust gas recirculation (Carbon monoxide Carbon dioxide and Nitrogen) and fuels (Hydrogen and Methane) were used at various mass flow rates of 10 20 and 25 LPM (liter per minute) and various engine speeds of 2000 2500 3000 and 3500 rpm (revolutions per minute). The procured results revealed that adding specialty gases improved brake thermal efficiency and power. Similarly the brake-specific fuel consumption was also massively retarded compared to diesel due to the influence of the hydrogen and methane composition. However the fuel with the higher nitrogen reported less BTE (brake thermal efficiency) and comparatively higher exhaust gas temperature owing to the higher presence of nitrogen in their composition. Regarding emissions including exhaust gas recirculation dropped the formation of pollutants efficiently compared to diesel. Among various fuels Case 1 (30 % H2 5 % CH4 5 CO2 and 60 % CO) reported the lowest emission of NOx and Case 2 (25 % H2 5 % CH4 5 CO2 30 % CO and 35 % N2) of CO and CO2 emissions. Generally specialty gases with a variable composition of exhaust gas recirculation gases can be a promising sustainable replacement for existing fossil fuels.

In recent years the use of alternative fuels in thermal engine power plants has gained more and more attention becoming of paramount importance to overcome the use of fuels from fossil sources and to reduce polluting emissions. The present work deals with the analysis of the response to two different gas fuels—i.e. hydrogen and a syngas from agriculture product—of a 30 kW micro gas turbine integrated with a solar field. The solar field included a thermal storage system to partially cover loading requests during night hours reducing fuel demand. Additionally a Heat Recovery Unit was included in the plant considered and the whole plant was simulated by Thermoflex® code. Thermodynamics analysis was performed on hour-to-hour basis for a given day as well as for 12 months; subsequently an evaluation of cogeneration efficiency as well as energy saving was made. The results are compared against plant performance achieved with conventional natural gas fueling. After analyzing the performance of the plant through a thermodynamic analysis the study was complemented with CFD simulations of the combustor to evaluate the combustion development and pollutant emissions formation particularly of NOx with the two fuels considered using Ansys-Fluent code and a comparison was made.

This study proposes four kinds of hybrid source–grid–storage systems consisting of pho‐ tovoltaic and wind energy and a power grid including different batteries and hydrogen storage systems for Sanjiao town. HOMER‐PRO was applied for the optimal design and techno‐economic analysis of each case aiming to explore reproducible energy supply solutions for China’s industrial clusters. The results show that the proposed system is a fully feasible and reliable solution for in‐ dustry‐based towns like Sanjiao in their pursuit of carbon neutrality. In addition the source‐side price sensitivity analysis found that the hydrogen storage solution was cost‐competitive only when the capital costs on the storage and source sides were reduced by about 70%. However the hydro‐ gen storage system had the lowest carbon emissions about 14% lower than the battery ones. It was also found that power generation cost reduction had a more prominent effect on the whole system’s NPC and LCOE reduction. This suggests that policy support needs to continue to push for genera‐ tion‐side innovation and scaling up while research on different energy storage types should be en‐ couraged to serve the needs of different source–grid–load–storage systems.

Autonomous underwater vehicles (AUVs) are programmable robotic vehicles that can drift drive or glide through the ocean without real-time control by human operators. AUVs that also can follow a planned trajectory with a chosen depth profile are used for geophysical surveys subsea pipeline inspection marine archaeology and more. Most AUVs are followed by a mother ship that adds significantly to the cost of an AUV mission. One pathway to reduce this need is to develop long-endurance AUVs by improving navigation autonomy and energy storage. Long-endurance AUVs can open up for more challenging mission types than what is possible today. Fuel cell systems are a key technology for increasing the endurance of AUVs beyond the capability of batteries. However several challenges exist for underwater operation of fuel cell systems. These are related to storage or generation of hydrogen and oxygen buoyancy and trim and the demanding environment of the ambient seawater. Protecting the fuel cell inside a sealed container brings along more challenges related to condensation cooling and accumulation of inert gases or reactants. This paper elaborates on these technical challenges and describes the solutions that the Norwegian Defence Research Establishment (FFI) has chosen in its development of a fuel cell system for long-endurance AUVs. The reported solutions enabled a 24 h demonstration of FFI's fuel cell system under water. The remaining work towards a prototype sea trial is outlined.

Electric bus transit is crucial in reducing greenhouse gas (GHG) emissions decreasing fossil fuel reliance and combating climate change. However the transition to electric-powered buses demands a comprehensive plan for optimal resource allocation technology choice infrastructure deployment and component sizing. This study develops system configuration optimization models for battery electric buses (BEBs) and hydrogen fuel cell buses (HFCBs) minimizing all related costs (i.e. capital and operational costs). These models optimize component sizing of the charging/refueling stations fleet configuration and energy/fuel management system in three operational schemes: BEBs opportunity charging BEBs overnight charging and electrolysis-powered HFCBs overnight refueling. The results indicate that the BEB opportunity system is the most economically viable choice. Meanwhile HFCB requires a higher cost (134.5%) and produces more emissions (215.7%) than the BEB overnight charging system. A sensitivity analysis indicates that a significant reduction in the HFCB unit and electricity costs is required to compete economically with BEB systems.

Under the background of energy interconnection and low-carbon electricity integrated energy systems (IES) play an important role in energy conservation and emission reduction. To further promote the low-carbon transition of energy this paper proposes a distributed robust optimal control strategy for IESs based on energy trading. Firstly an IES model that includes an electric hydrogen module and gas hydrogen doping combined heat and power is established and ladder-type carbon trading is introduced to reduce carbon emissions. Secondly for the energy trading issues between photovoltaic (PV) prosumers and IES a bi-level model is constructed using Stackelberg game method where the IES acts as the leader and the PV prosumers as the followers. Noteworthy a distributed robust optimization method is used to address the uncertainty of renewable energy and load. Additionally the Nash bargaining method ensures an equitable balance of benefits among the various IESs and encourages them to participate in market transactions. On this basis an intermediary transaction mode is proposed to address cheating behaviors in trading. Finally the simulation results demonstrate that the proposed strategy not only effectively promotes cooperative operation among multiple IESs but also significantly reduces the system’s operating costs and carbon emissions.

The production of hydrogen from renewable sources could play a significant role in supporting the transition toward a decarbonized energy system. This study has involved investigating optimization strategies − mixedinteger linear programming (MILP) a hybrid particle swarm optimization (PSO)-MILP framework and PSO combined with a rule-based energy management strategy (EMS) − applied to a power-to-hydrogen system for industrial applications. The analysis evaluates the levelized cost of hydrogen production (LCOH) carbon emissions and the impact of key factors such as battery degradation electrolyzer efficiency real-time pricing and hydrogen load management. The obtained results indicated that the MILP-based models achieved moderate LCOH values (10.1–10.7 €/kg) but incurred higher CO2 emissions (20.2–24.6 kt/y). Instead the PSO model combined with the rule-based EMS lowered emissions to 14.3 kt/y (a 27–45% reduction) albeit with a higher LCOH (11.6 €/kg). The hybrid PSO-MILP models struck a balance achieving LCOH values of between 9.2 and 9.7 €/kg with CO2 emissions of 19.7–20.3 kt/y as they benefited from the integration of piecewise affine linearization for modeling electrolyzer efficiency and battery degradation. In terms of computational efforts the MILP-based models required more than 48 h to converge while the PSO-MILP models completed within 27–35 h and the PSO model with rule-based EMS achieved results in 1.5 h. These findings offer guidance that can be used to select the most suitable optimization method on the basis of the desired performance targets resource constraints and computational complexity thereby contributing to the design of more sustainable energy systems.

This paper investigates the temperature control problem in hydrogen fuel cells based on the improved sliding mode control method specifically within the context of multirotor drone applications. The study focuses on constructing a control-oriented nonlinear thermal model which serves as a foundation for the subsequent development of a practical temperature regulation approach. Initially a novel sliding mode control strategy is proposed which significantly enhances the precision and stability of temperature control by reducing the impact of sensor errors and environmental disturbances. Subsequently the effectiveness and robustness of this control method under various dynamic loads and environmental conditions are demonstrated. The simulation results demonstrate that the improved sliding mode controller is effective in managing and regulating the fuel cell temperature ensuring optimal performance and stability.

This study investigates the effect of Oxygen-Enriched Combustion on hydrogen-enriched natural gas (H2 -NG) fuel mixtures at a semi-industrial scale (up to 60 kW). The analysis focuses on flame structure temperature distribu tion in the furnace NOx emissions and potential fuel savings. A multi-fuel multi-oxidizer jet burner was used to compare two oxygen enrichment configurations: premixed with air (PM) and air-pure O2 (AO) independent feed. The O2 -enriched flames remained stable across the entire fuel range. OH* chemiluminescence imaging for the H2 -NG fuel mixture delivering 50 concentration kW revealed that higher O2 increases the OH* intensity narrows and elongates the flame transitions from buoyancy- to momentum-driven shape and relocates the reaction zone. At 50 % oxygen enrichment level (OEL) flame shape OH* intensity and temperature profiles resembled pure O combustion. Up to 29 % OEL furnace temperature profiles were similar to those 2 of air-fuel combustion. The power required to maintain 1300 ± 25 ◦C at the reference position decreases with O2 enrichment. Higher OELs resulted in a sharp increase in NOx emissions. The effect of hydrogen enrichment on NOx levels was significantly less pronounced than that of oxygen enrichment. The rise in NOx emissions correlates with increased OH* in tensities. For a 50 % H2 2 blend increasing the O concentration in the oxidizer from 21 % to 50 % resulted in a 27 % reduction in flue gas heat losses. Utilizing O2 co-produced with H2 could be strategic for reducing fuel consumption facilitating the adoption of hydrogen-based energy systems.

The rapid growth in natural gas consumption by gas-fired generators and the emergence of power-to-hydrogen (P2H) technology have increased the interdependency of natural gas and power systems presenting new challenges to energy system operators due to the heterogeneous uncertainties associated with power loads renewable energy sources (RESs) and gas loads. These uncertainties can easily spread from one infrastructure to another increasing the risk of cascading outages. Given the erratic nature of RESs P2H technology provides a valuable solution for large-scale energy storage systems crucial for the transition to economic clean and secure energy systems. This paper proposes a new approach for the co-optimized operation of gas and electric power systems aiming to reduce combined operating costs by 10–15% without jeopardizing gas and energy supplies to customers. A mixed integer non-linear programming (MINLP) model is developed for the optimal day-ahead operation of these integrated systems with a case study involving the IEEE 24-bus power system and a 20-node natural gas system. Simulation results demonstrate the model’s effectiveness in minimizing total costs by up to 20% and significantly reducing renewable energy curtailment by over 50%. The proposed approach supports UN Sustainable Development Goals by ensuring sustainable energy (SDG 7) fostering innovation and resilient infrastructure (SDG 9) enhancing energy efficiency for resilient cities (SDG 11) promoting responsible consumption (SDG 12) contributing to climate action (SDG 13) and strengthening partnerships (SDG 17). It promotes clean energy technological innovation resilient infrastructure efficient resource use and climate action supporting the transition to sustainable energy systems.

This study investigates the integration of green hydrogen into building energy systems using local solar power with the electricity grid serving as a backup plan. A comprehensive bottom-up analysis compares six energy system configurations: the natural gas grid boiler system all-electric heat pump system natural gas and hydrogen blended system hydrogen microgrid boiler system cogeneration hydrogen fuel cell system and hybrid hydrogen heat pump system. Energy efficiency evaluations were conducted for 25 homes within one block in a neighborhood across five typological house stocks located in Stoke-on-Trent UK. This research was modeled using a spreadsheet-based approach. The results highlight that while the all-electric heat pump system still demonstrates the highest energy efficiency with the lowest consumption the hybrid hydrogen heat pump system emerges as the most efficient hydrogen-based solution. Further optimization through the implementation of a peak-shaving strategy shows promise in enhancing system performance. In this approach hybrid hydrogen serves as a heating source during peak demand hours (evenings and cold seasons) complemented by a solar energy powered heat pump during summer and daytime. An hourly operational configuration is recommended to ensure consistent performance and sustainability. This study focuses on energy performance excluding cost-effectiveness analysis. Therefore the cost of the energy is not taken into consideration requiring further development for future research in these areas.

Dual fuel combustion has gained attention as a cost-effective solution for reducing the pollutant emissions of internal combustion engines. The typical approach is combining a conventional high-reactivity fossil fuel (diesel fuel) with a sustainable low-reactivity fuel such as bio-methane ethanol or green hydrogen. The last one is particularly interesting as in theory it produces only water and NOx when it burns. However integrating hydrogen into stock diesel engines is far from trivial due to a number of theoretical and practical challenges mainly related to the control of combustion at different loads and speeds. The use of 3D-CFD simulation supported by experimental data appears to be the most effective way to address these issues. This study investigates the hydrogen-diesel dual fuel concept implemented with minimum modifications in a light-duty diesel engine (2.8 L 4-cylinder direct injection with common rail) considering two operating points representing typical partial and full load conditions for a light commercial vehicle or an industrial engine. The numerical analysis explores the effects of progressively replacing diesel fuel with hydrogen up to 80% of the total energy input. The goal is to assess how this substitution affects engine performance and combustion characteristics. The results show that a moderate hydrogen substitution improves brake thermal efficiency while higher substitution rates present quite a severe challenge. To address these issues the diesel fuel injection strategy is optimized under dual fuel operation. The research findings are promising but they also indicate that further investigations are needed at high hydrogen substitution rates in order to exploit the potential of the concept.

CO2 emission reduction of sectors such as aviation maritime shipping road haulage and chemical production is challenging but necessary. Although these sectors will most likely continue to rely on carbonaceous energy carriers they are expected to gradually shift away from fossil fuels. In order to do so the prominent option is to utilize alternative carbon sources—like biomass and CO2 originating from carbon capture—for the production of non-fossil carbonaceous vectors (biofuels and e-fuels). However the limited availability of biomass and the varying nature of other carbon sources necessitate a comprehensive evaluation of trade-offs between potential carbon uses and existing sources. Then it is primordial to understand the origin of carbon used in sustainable aviation fuel (SAF) to understand the implications of defossilizing aviation for the energy system. Moreover the production of SAF implies deep changes to the energy system that are quantified in this work. This study utilizes the linear programming cost optimization tool EnergyScope TD to analyze the holistic French energy system encompassing transport industry electricity and heat sectors while ensuring net greenhouse gas neutrality. A novel method to model and quantify carbon flows within the system is introduced enabling a comprehensive assessment of greenhouse gas neutrality. This study highlights the significance of fulfilling clean energy requirements and implementing carbon dioxide removal measures as crucial steps toward achieving climate neutrality. Indeed to reach climate neutrality a production of 1046 TWh of electricity by non-fossil sources is needed. Furthermore the findings underscore the critical role of efficient carbon and energy valorization from biomass providing evidence that producing fuels by combining biomass and hydrogen is optimal. The study also offers valuable insights into the future cost and impact of SAF production for air travel originating from France. That is the European law ReFuelEU would increase the price of plane tickets by +33% and would require 126 TWh of hydrogen and 50 TWh of biomass to produce the necessary 91 TWh of jet fuel. Finally the implications of the assumption behind the production of SAF are discussed.

Decarbonizing long-haul heavy-duty transport in Europe focuses on batteryelectric trucks with high-power chargers or electric road systems and fuel-cell-electric vehicles with hydrogen refueling stations. We present a comparative life cycle assessment and total cost of ownership analysis of these technologies for 20% of Germany’s heavy-duty long-haul transport alongside internal combustion engine vehicles. The results show that fuel cell vehicles with on-site hydrogen have the highest life cycle emissions (65 Mt CO2e) followed by internal combustion engine vehicles (55 Mt CO2e). Battery-electric vehicles using electric road systems achieve the lowest emissions (21 Mt CO2e) and the lowest costs (EUR 45 billion). In contrast fuel cell vehicles with on-site hydrogen have the highest costs (EUR 69 billion). Operational costs dominate total expenses making them a compelling target for subsidies. The choice between battery and fuel cell technologies depends on the ratio of vehicles to infrastructure transport performance and range. Fuel cell trucks are better suited for remote areas due to their longer range while integrating electric road systems with high-power charging could offer synergies. Recent advancements in battery and fuel cell durability further highlight the potential of both technologies in heavy-duty transport. This study provides insights for policymakers and industry stakeholders in the shift towards sustainable transport. The greenhouse gas emission savings from adopting battery-electric trucks are 54% in our high-power charging scenario and 62% in the electric road system scenario in comparison to the reference scenario with diesel trucks.

The integration of hydrogen technologies is widely regarded as a transformative step in the energy transition. Recently the German government unveiled a Power Plant Strategy to promote H2-Ready Combined-Cycle Gas Turbines (H2-CCGT) which are intended to initially run on natural gas and transition to green hydrogen by 2040 at the latest. This study assesses the role of H2-Ready power plants in a low-carbon transition and explores plausible pathways using a capacity expansion model for Germany. This topic is particularly relevant for other countries aiming to deploy a large share of renewables and considering H2-CCGT as a flexible backup solution to ensure system flexibility and achieve deep decarbonization. Our results indicate that H2-CCGT enhance system flexibility and significantly alleviate the investments need for additional flexibility and renewable generation capacity and reduce renewable-energy curtailment by more than 35 %. Moreover our results also demonstrate that allowing hydrogen in CCGT does not entirely reduce the need for fossil fueled power plants as hydrogen becomes economically viable only with deep decarbonization or direct subsidies. We show that policy interventions can alter the transition pathways for achieving a decarbonized energy system. Our research challenges a prevailing narrative that financial support for hydrogen is needed to ensure a cost-efficient system decarbonization. More straightforward market-based policy instruments such as intensified CO2 pricing or regulatory frameworks such as earlier mandatory hydrogen shifts in H2-CCGT prove more efficient at cutting emissions and costs.

The report addresses the environmental challenges faced by European sea ports and aims to provide guidance to smaller ports for improving their environmental performance while achieving sustainability goals through experiences gained by implementing noteworthy green initiatives in practice. Larger ports possess significant advantages in terms of financial resources risk tolerance and organisational capacity. They often have the means to invest in innovative solutions and actively participate in research and development projects leading to co-funded pilot implementation of green initiatives. They typically have more skilled personnel stronger influence and stakeholder leverage which position them better to lead the way in sustainability efforts. Finally larger ports often form robust collaborations to drive collective action towards sustainable goals. Smaller ports face unique challenges stemming from typically limited resources and risk aversion. They often prioritise mature solutions relying on tested practices to mitigate potential risks. They may lack internal expertise requiring guidance and capacity-building programmes to navigate the selection and implementation of green practices. Also they require financial and technical support particularly as they may underutilise available funding mechanisms and have limited participation in R&D programmes. They may benefit from partnerships with other ports and stakeholders to create synergies and gain experience from their lessons learned to boost their capacity to implement green practices

Offshore wind power construction has seen significant development due to the high density of offshore wind energy and the minimal terrain restrictions for offshore wind farms. However integrating this energy into the grid remains a challenge. The scientific community is increasingly focusing on hydrogen as a means to enhance the integration of these fluctuating renewable energy sources. This paper reviews the research on renewable energy power generation water electrolysis for hydrogen production and large-scale hydrogen storage. By integrating the latest advancements we propose a system that couples offshore wind power generation seawater electrolysis (SWE) for hydrogen production and salt cavern hydrogen storage. This coupling system aims to address practical issues such as the grid integration of offshore wind power and large-scale hydrogen storage. Regarding the application potential of this coupling system this paper details the advantages of developing renewable energy and hydrogen energy in Jiangsu using this system. While there are still some challenges in the application of this system it undeniably offers a new pathway for coastal cities to advance renewable energy development and sets a new direction for hydrogen energy progress.

The availability of conventional fuels such as gasoline and methane which are used in spark-ignition (SI) engines is increasingly limited by the finite nature of fossil fuel reserves. The inefficiencies in combustion are associated with reduced engine effectiveness as incomplete combustion heightens the emissions of harmful pollutants including CO2 and CO while also negatively impacting fuel economy. The objective of this research is to undertake a comparative study of engine performance and emissions for a selection of conventional fuels and hydrogen while considering varying equivalence ratios and operational speeds. To accomplish this an extensive 3-dimensional numerical simulation was carried out using CONVERGE 3.0 simulation software to model a portfueled SI engine with the SI8 Engine Premix SAGE model facilitating the simulations. The performance metrics assessed in this research include cylinder pressure specific heat ratio heat rate thermal efficiency and mean temperature. The emission characteristics are analyzed in cases of NOx CO CO2 and HC emissions. The simulation results are obtained by varying the equivalence ratios of hydrogen (0.4 0.6 and 0.9) at different engine speeds (2000 2500 and 3000 rpm). The engine setup mesh creation boundary conditions turbulence combustion and species transport models were meticulously outlined to ensure accurate simulation results. Hydrogen fuel when operated at an equivalence ratio of 0.4 and an engine speed of 3000 rpm showcases the best overall performance among all tested conditions. It achieves the highest thermal efficiency of 40.94% optimal cylinder pressure and specific heat ratio a favorable mean temperature and the lowest fuel consumption. Additionally this configuration results in zero emissions of CO and HC along with a significant reduction in CO2 emissions due to the absence of carbon in the fuel structure. However due to the high combustion temperatures associated with hydrogen NOx emissions remained present and require further mitigation strategies.

To improve the energy utilization rate and realize the low-carbon emission of a park integrated energy system (PIES) this paper proposes an optimal operation strategy for multiple PIESs. Firstly the electrical power cooperative trading framework of multiple PIESs is constructed. Secondly the hydrogen blending mechanism and carbon capture system and power-to-gas system joint operation model are introduced to establish the model of each PIES. Then based on the Nash bargaining game theory a multi-PIES cooperative trading and operation model with electrical power cooperative trading is constructed. Then the alternating direction method of multipliers algorithm is used to solve the two subproblems. Finally case studies analysis based on scene analysis is performed. The results show that the cooperative operation model reduces the total cost of a PIES more effectively compared with independent operation. Meanwhile the efficient utilization and production of hydrogen are the keys to achieve carbon reduction and an efficiency increase in a PIES.

Hydrogen fuel cells are gaining attention as an eco-friendly propulsion system for ships but the structural safety of storage tanks which store hydrogen at high pressure and supply it to the fuel cell is a critical concern. Marine liquid hydrogen storage tanks typically designed as rotationally symmetric structures face challenges when subjected to asymmetric wave-induced sloshing loads that break geometric symmetry and induce localized stress concentrations. This study conducted a fluid–structure interaction (FSI) analysis of a rotationally symmetric liquid hydrogen storage tank for marine applications to evaluate the impact of asymmetric liquid sloshing induced by wave loads on the tank structure and propose symmetry-guided structural improvement measures to ensure fatigue life. Sensitivity analysis using the finite difference method (FDM) revealed the asymmetric influences of design variables on stress distribution: increasing the thickness of triangular mounts (T1) reduced stress 3.57 times more effectively than circular ring thickness (T2) highlighting a critical symmetry-breaking feature in support geometry. This approach enables rapid and effective design modifications without complex optimization simulations. The study demonstrates that restoring structural symmetry through targeted reinforcement is essential to mitigate fatigue failure caused by asymmetric loading.

To advance the hydrogen energy-driven low-altitude aviation sector it is imperative to establish sophisticated risk assessment frameworks tailored for hydrogen-powered aircraft. Such methodologies will deliver fundamental guidelines for the preliminary design phase of onboard hydrogen systems by leveraging rigorous risk quantification and scenario-based analytical models to ensure operational safety and regulatory compliance. In this context this study proposes a comprehensive hazard and operability analysis-fuzzy dynamic Bayesian network (HAZOP-FDBN) framework which quantifies risk without relying on historical data. This framework systematically maps the risk factor relationships identified in HAZOP results into a dynamic Bayesian network (DBN) graphical structure showcasing the risk propagation paths between subsystems. Expert knowledge is processed using a similarity aggregation method to generate fuzzy probabilities which are then integrated into the FDBN model to construct a risk factor relationship network. A case study on low-altitude aircraft hydrogen storage systems demonstrates the framework’s ability to (1) visualize time-dependent failure propagation mechanisms through bidirectional probabilistic reasoning and (2) quantify likelihood distributions of system-level risks triggered by component failures. Results validate the predictive capability of the model in capturing emergent risk patterns arising from subsystem interactions under low-altitude operational constraints thereby providing critical support for safety design optimization in the absence of historical failure data.

Within the framework of “dual carbon” intending to enhance the use of green energies and minimize the emissions of carbon from energy systems this study suggests a cost-effective low-carbon scheduling model that accounts for stepwise carbon trading for an integrated electricity heat gas cooling and hydrogen energy system. Firstly given the clean and low-carbon attributes of hydrogen energy a refined two-step operational framework for electricity-to-gas conversion is proposed. Building upon this foundation a hydrogen fuel cell is integrated to formulate a multi-energy complementary coupling network. Second a phased carbon trading approach is established to further explore the mechanism’s carbon footprint potential. And then an environmentally conscious and economically viable power dispatch model is developed to minimize total operating costs while maintaining ecological sustainability. This objective optimization framework is effectively implemented and solved using the CPLEX solver. Through a comparative analysis involving multiple case studies the findings demonstrate that integrating electrichydrogen coupling with phased carbon trading effectively enhances wind and solar energy utilization rates. This approach concurrently reduces the system’s carbon emissions by 34.4% and lowers operating costs by 58.6%.

Hydrogen is recognized as a key alternative fuel for mitigating greenhouse-gas emissions owing to its high fuel efficiency and carbon-free combustion. In the stratified charge combustion (SCC) mode ensuring optimal air-fuel mixing in the combustion chamber is crucial because the local equivalence ratio has a dominant influence on combustion characteristics. Therefore this study aims to build a detailed understanding of stratified hydrogen combustion under various local equivalence ratios. Laser-induced breakdown spectroscopy (LIBS) was used to measure the local equivalence ratios in hydrogen jets at different mixture-formation times (MFTs) and laserignition points (LIPs). The results showed that shorter MFTs induced highly stratified mixtures with elevated local equivalence ratios exceeding 2.0 enhancing the laminar flame speed and maximizing the conversion of chemical energy into pressure gain resulting in a representative total heat release over three times higher compared to longer MFTs. Furthermore ignition near the injector tip produced leaner mixtures with equivalence ratios around 0.3 whereas downstream LIPs generated peak local equivalence ratios around 2.0 facilitating rapid flame propagation and increased heat release by 25 %.

Hydrogen-based steelmaking using green hydrogen can achieve above 95 % CO2 emission reductions. Low-cost renewable electricity is a prerequisite and research has found that access to renewable energy resources could pull energy-intensive industry to new locations the “renewables pull”-effect. However previous studies on hydrogen-based steel differ on key assumptions and analyse a wide range of energy costs (10–105 EUR/MWh) making conclusions hard to compare. In this paper we assess techno-economic and strategic drivers for and against such a pull-effect by calculating the levelized cost of green hydrogen-based steel across five archetypical new value chain configurations. We find that the strength of the pull-effect is sensitive to assumptions and that the cost of hydrogen-based steel vary across geographies and value chain configurations to a similar degree as conventional steel. Other geographically varying factors such as labour costs can be as important for relocation and introducing globally varying cost of capital moderates the effect. The renewables pull effect can enable faster access to low-cost renewables and export of green iron ore is an important option to consider. However it is not clear how strong a driver the pull-effect will actually be compared to other factors and polices implemented for strategic reasons. A modest “strategic push“ implemented through various subsidies such as lowering the cost of hydrogen or capital will reduce the pull-effect. In addition focusing on the renewables pull effect as enabling condition risk slowing innovation and upscaling by 2030 in line with climate goals which is currently initiated in higher cost regions.

The large-scale utilization of hydrogen energy is currently hindered by challenges in lowcost production storage and transportation. This study focused on investigating the impact of the diaphragm cavity profile on the movement behavior and stress distribution of a dual-stage diaphragm compressor. Firstly an experimental platform was established to test the gas mass flowrate and fluid pressures under various preset conditions. Secondly a simulation path integrating the finite element method simulation theoretical stress model and movement model was developed and experimentally validated to analyze the diaphragm stress distribution and deformation characteristics. Finally comparative optimization analyses were conducted on different types of diaphragm cavity profiles. The results indicated that the driving pressure differences at the top dead center position reached 85.58 kPa for the first-stage diaphragm and 75.49 kPa for the second-stage diaphragm. Under experimental conditions of 1.6 MPa suction pressure 8 MPa second-stage discharge pressure and 200 rpm rotational speed the first-stage and second-stage diaphragms reached the maximum center deflections of 4.14 mm and 2.53 mm respectively at the bottom dead center position. Moreover the cavity profile optimization analysis indicated that the double-arc profile (DAP) achieved better cavity volume and diaphragm stress characteristics. The first-stage diaphragm within the optimized DAP-type cavity exhibited 173.95 MPa maximum principal stress with a swept volume of 0.001129 m3 whereas the second-stage optimized configuration reached 172.57 MPa stress with a swept volume of 0.0003835 m3 . This research offers valuable insights for enhancing the reliability and performance of diaphragm compressors.

Rail transit as a high-energy consumption field urgently requires the adoption of clean energy innovations to reduce energy consumption and accelerate the transition to new energy applications. As an energy-saving fluid machinery the ejector exhibits significant application potential and academic value within this field. This paper reviewed the recent advances technical challenges research hotspots and future development directions of ejector applications in rail transit aiming to address gaps in existing reviews. (1) In waste heat recovery exhaust heat is utilized for propulsion in vehicle ejector refrigeration air conditioning systems resulting in energy consumption being reduced by 12~17%. (2) In vehicle pneumatic pressure reduction systems the throttle valve is replaced with an ejector leading to an output power increase of more than 13% and providing support for zero-emission new energy vehicle applications. (3) In hydrogen supply systems hydrogen recirculation efficiency exceeding 68.5% is achieved in fuel cells using multi-nozzle ejector technology. (4) Ejector-based active flow control enables precise ± 20 N dynamic pantograph lift adjustment at 300 km/h. However current research still faces challenges including the tendency toward subcritical mode in fixed geometry ejectors under variable operating conditions scarcity of application data for global warming potential refrigerants insufficient stability of hydrogen recycling under wide power output ranges and thermodynamic irreversibility causing turbulence loss. To address these issues future efforts should focus on developing dynamic intelligent control technology based on machine learning designing adjustable nozzles and other structural innovations optimizing multi-system efficiency through hybrid architectures and investigating global warming potential refrigerants. These strategies will facilitate the evolution of ejector technology toward greater intelligence and efficiency thereby supporting the green transformation and energy conservation objectives of rail transit.

Aviation is of crucial importance for the transportation sector and fundamental for the economy as it facilitates trade and private travel. Nonetheless this sector is responsible for a great amount of global carbon dioxide emissions exceeding 920 million tonnes annually. Alternative energy fuels (AEFs) can be considered as a promising solution to tackle this issue with the potential to lower greenhouse gas emissions and reduce reliance on fossil fuels in the aviation industry. A life cycle analysis is performed considering an aircraft running on conventional jet fuel and various alternative fuels (biojet methanol and DME) including hydrogen and ammonia. The comparative assessment investigates different fuel production pathways including the following: JETA-1 and biojet fuels via hydrotreated esters and fatty acids (HEFAs) as well as hydrogen and ammonia employing water electrolysis using wind and solar photovoltaic collectors. The outputs of the assessment are quantified in terms of carbon dioxide equivalent emissions acidification eutrophication eco-toxicity human toxicity and carcinogens. The life cycle phases included the following: (i) the construction maintenance and disposal of airports; (ii) the operation and maintenance of aircrafts; and (iii) the production transportation and utilisation of aviation fuel in aircrafts. The results suggest that hydrogen is a more environmentally benign alternative compared to JETA-1 biojet fuel methanol DME and ammonia.