Publications

Liquid hydrogen has attracted much attention due to its high energy storage density and suitability for long-distance transportation. An efficient hydrogen liquefaction process is the key to obtaining liquid hydrogen. In an effort to determine the parameter optimization of the hydrogen liquefaction process this paper employed process simulation software Aspen HYSYS to simulate the hydrogen liquefaction process. By establishing a dynamic model of the unit module this study carried out dynamic simulation optimization based on the steady-state process and process parameters of the hydrogen liquefaction process and analyzed the dynamic characteristics of the process. Based on the pressure drop characteristic experiment an equation for the pressure drop in the heat exchanger was proposed. The heat transfer of hydrogen conversion was simulated and analyzed and its accuracy was verified by comparison with the literature. The dynamic simulation of a plate-fin heat exchanger was carried out by coupling heat transfer simulation and the pressure drop experiment. The results show that the increase in inlet temperature (5 C and 10 C) leads to an increase in specific energy consumption (0.65 % and 1.29 % respectively) and a decrease in hydrogen liquefaction rate (0.63 % and 2.88 % respectively). When the inlet pressure decreases by 28.57 % the hydrogen temperature of the whole liquefaction process decreases and the specific energy consumption increases by 52.94 %. The research results are of great significance for improving the operating efficiency of the refrigeration cycle and guiding the actual liquid hydrogen production.

Disposing of plastic waste through burial or burning leads to air pollution issues while also contributing to gas emissions and plastic waste spreading underground into seas via springs. Henceforth this research aims at reducing plastic waste volume while simultaneously generating clean energy. Hydrogen energy is a promising fuel source that holds great value for humanity. However achieving clean hydrogen energy poses challenges including high costs and complex production processes especially on a national scale. This research focuses on Iran as a country capable of producing this energy examining the production process along with related challenges and the general supply chain. These challenges encompass selecting appropriate raw materials based on chosen technologies factory capacities storage methods and transportation flow among different provinces of the country. To deal with these challenges a mixed-integer linear programming model is developed to optimize the hydrogen supply chain and make optimal decisions about the mentioned problems. The supply chain model estimates an average cost—IRR 4 million (approximately USD 8)—per kilogram of hydrogen energy that is available in syngas during the initial period; however subsequent periods may see costs decrease to IRR 1 million (approximately USD 2) factoring in return-on-investment rates.

This paper describes a model of hydrogen blowdown dynamics for storage tanks needed for hydrogen safety engineering to accurately represent incident scenarios. Heat transfer through a tank wall affects the temperature and pressure dynamics inside the storage vessel and therefore the characteristics of the resulting hydrogen jet in case of loss of containment. Available non-adiabatic blowdown models are validated only against experiments on hydrogen storages at ambient temperature. Effect of heat transfer for cryo-compressed hydrogen can be more significant due to a larger temperature difference between the stored hydrogen and surrounding atmosphere especially in case of failure of equipment insulation. Previous work by the authors demonstrated that the heat transfer through a discharge pipe wall can significantly affect the mass flow rate of cryogenic hydrogen releases. To the authors’ knowledge thoroughly validated models of non-adiabatic blowdown dynamics for cryo-compressed hydrogen are currently missing. The present work further develops the non-adiabatic blowdown model at ambient temperature using the under-expanded jet theory developed at Ulster University to expand it to cryo-compressed hydrogen storages. The non-ideal behaviour of cryo-compressed hydrogen is accounted through the high-accuracy Helmholtz energy formulations. The developed model includes effect of heat transfer at both the tank and discharge pipe wall. The model is thoroughly validated against sixteen tests performed by Pro-Science on blowdown of hydrogen storage tanks with initial pressure 0.5-20 MPa and temperature 80-310 K through release nozzle of diameter 0.5-4.0 mm. The model well reproduces the experimental pressure and temperature dynamics during the entire blowdown duration.

Maritime and aviation transport are widely recognised as sectors where reducing greenhouse gas emissions is particularly challenging due to their reliance on energy-dense fuels and the challenges associated with direct electrification. These sectors face increasing pressure to defossilise and reduce emissions in line with global climate goals while simultaneously facing unique technological operational and economic uncertainties. This study addresses a key research gap by comparing the maritime and aviation sectors for common factors and sector-specific differences in their transition to green e-fuels produced from renewable electricity and sustainable CO2. A techno-economic assessment is conducted to evaluate alternative fuel and propulsion options using the levelised cost of mobility framework. The analysis also incorporates the pricing of non-CO2 greenhouse gases and air pollutant emissions. Results show that e-ammonia or e-LNG combustion is the most cost-effective option for maritime transport when emission costs are excluded whereas hydrogen fuel cells become more economical when these costs are internalised. In aviation e-kerosene use in conventional aircraft presents the lowest costs regardless of the year or emission pricing. The findings highlight the importance of considering unique characteristics of each sector and tailored defossilisation and decarbonisation strategies that consider sector-specific constraints. To sustainably meet the growing demand for transport fuels rapid investments in renewable electricity generation electrolysers and e-fuel synthesis are essential. Development of strong regulatory frameworks and financial instruments will be critical to support early deployment of e-fuels and minimise the risks.

In Southern Italy near the Mediterranean Sea mobility services like cars bicycles scooters and materialhandling forklifts are frequently required in addition to multimodal local transportation services such as trains ferry boats and airplanes. This research proposes an innovative concept of hydrogen valley virtually simulated in Matlab/Simulink environment located in Calabria. As a novelty hydrogen is produced centrally and delivered via fuel cell hybrid trains to seven hydrogen refueling stations serving various mobility hubs. The centralized production facility operates with a nominal capacity of about 4 tons/day producing hydrogen via PEM electrolysis and storing hydrogen at 200 bar with a hydrogen compressor. As the size of vehicle fleets and the cost of acquiring renewable energy through power purchase agreements vary the hydrogen valley is examined from both a technical and an economic perspective analyzing: the values of the levelized cost of hydrogen the energy consumption and the energy efficiency of the energy systems. Specifically the levelized cost of hydrogen reached competitive values close to 5 €/kg of hydrogen under the most optimistic scenarios with fleet conversions of more than 60 % and a power purchase agreement price lower than 150 €/MWh. Then the benefits of hydrogen rail transport in terms of emissions reduction and health from an economic standpoint are compared to conventional diesel trains and fully electric trains saving respectively 3.2 ktons/year and 0.4 ktons/year of carbon dioxide equivalent emissions and corresponding economic benefits of respectively 51 and 0.548 million euros.

As a clean and renewable energy carrier hydrogen is one of the most promising alternative fuels. Cryogenic compressed hydrogen can achieve high storage density without liquefying hydrogen which has good application prospects. Investigation of the safety problems of cryogenic compressed hydrogen is necessary before massive commercialization. The present study modeled the instantaneous flow field using the Large Eddy Simulation (LES) for cryogenic (50 and 100 K) underexpanded hydrogen jets released from a round nozzle of 1.5 mm diameter at pressures of 0.5-5.0 MPa. The simulation results were compared with the experimental data for validation. The axial and radial concentration and velocity distributions were normalized to show the self-similar characteristics of underexpanded cryogenic jets. The shock structures near the nozzle were quantified to correlate the shock structure sizes to the source pressure and nozzle diameter. The present study on the concentration and velocity distributions of underexpanded cryogenic hydrogen jets is useful for developing safety codes and standards.

In this study a novel thermo-economic analysis on a membrane reactor adopted to generate hydrogen coupled to a carbon-dioxide capture system is proposed. Exergy destruction fuel and environmental as well as pur chased equipment costs have been accounted to estimate the cost of hydrogen production in the aforementioned integrated plant. It has been found that the integration of the CO2 capture system with the membrane reactor is responsible for the reduction of the hydrogen production cost by 12 % due to the decrease in environmental penalty cost. In addition the effects of operating parameters (steam-to-carbo ratio and biogas temperature) on the hydrogen production cost are investigated. Hence this work demonstrates that the latter can be decreased by approximately 2 $/kgH2 when steam to carbon ratio increases from 1.5 to 4. The analyses reveal that steam-tocarbo ratio increases exergy destruction cost affecting consequently also the hydrogen production cost. How ever from a thermodynamic point of view it enhances the hydrogen production in the membrane reactor mutually lowering the hydrogen production cost. It has been also estimated that a decrease in the biogas inlet temperature from 450 to 400◦C can reduce the hydrogen production cost by 7 %. This study demonstrates that the fuel cost is a major economic parameter affecting commercialization of hydrogen production while exergy destruction and environmental costs are also significant factors in determining the hydrogen production cost.

Transforming Europe into a climate neutral economy and society by 2050 requires extraordinary efforts and the mobilisation of all sectors and economic actors coupled with all the creative and brain power one can imagine. Each sector has to fundamentally rethink the way it operates to ensure it can be transformed towards this new net-zero paradigm without jeopardising other environmental and societal objectives both within the EU and globally. Given the scale of the transformation ahead our ability to meet climate neutrality targets directly depends on our ability to innovate. In this context Research & Innovation programmes have a key role to play and it is crucial to ensure they are fit for purpose and well equipped to support the next wave of breakthrough innovations that will be required to achieve climate neutrality in the EU and globally by 2050. The objective of this study is to contribute to these strategic planning discussions by not only identifying high-risk and high-impact climate mitigation solutions but most importantly look beyond individual solutions and consider how systemic interactions of climate change mitigation approaches can be integrated in the development of R&I agendas.

Hydrogen is experiencing a resurgence in energy transition debates. Before representing a solution however the existing hydrogen economy is still a climate change headache: over 99 % of production depends on fossil fuels oil refining accounts for 42 % of demand and its transportation is intertwined with fossil infrastructure like natural gas pipelines. This article investigates the path-dependent dynamics shaping the hydrogen economy and its interconnections with the oil and gas industry. It draws on the global production networks (GPN) approach and political economy research to provide a comprehensive review of current and prospective enduses of hydrogen modes of transport networks of industrial actors and state strategies along the major production facilities and holders of intellectual property rights. The results presented in this article suggest that the superimposition of private agendas may jeopardise the viability of future energy systems and requires counterbalancing forces to override the negative consequences of path-dependent energy transitions.

Carbon dioxide and hydrogen storage in geological formations at Gt scale are two promising strategies toward net-zero carbon emissions. To date investigations into underground hydrogen storage (UHS) remain relatively limited in comparison to the more established knowledge body of underground carbon dioxide storage (UCS). Despite their analogous physical processes can be used for accelerating the advancements in UHS technology the existing distinctions possibly may hinder direct applicability. This review therefore contributes to advancing our fundamental understanding on the key differences between UCS and UHS through multi-scale comparisons. These comparisons encompass key factors influencing underground gas storage including storage media trapping mechanisms and respective fluid properties geochemical and biochemical reactions and injection scenarios. They provide guidance for the conversion of our existing knowledge from UCS to UHS emphasizing the necessity of incorporating these factors relevant to their trapping and loss mechanisms. The article also outlines future directions to address the crucial knowledge gaps identified aiming to enhance the utilisation of geological formations for hydrogen and carbon dioxide storage.

Hydrogen energy is regarded as an ideal solution for addressing climate change issues and an indispensable part of future integrated energy systems. The most environmentally friendly hydrogen production method remains water electrolysis where the electrolyzer constructs the physical interface between electrical energy and hydrogen energy. However few articles have reviewed the electrolyzer from the perspective of power supply topology and control. This review is the first to discuss the positioning of the electrolyzer power supply in the future integrated energy system. The electrolyzer is reviewed from the perspective of the electrolysis method the market and the electrical interface modelling reflecting the requirement of the electrolyzer for power supply. Various electrolyzer power supply topologies are studied and reviewed. Although the most widely used topology in the current hydrogen production industry is still single-stage AC/DC the interleaved parallel LLC topology constructed by wideband gap power semiconductors and controlled by the zero-voltage switching algorithm has broad application prospects because of its advantages of high power density high efficiency fault tolerance and low current ripple. Taking into account the development trend of the EL power supply a hierarchical control framework is proposed as it can manage the operation performance of the power supply itself the electrolyzer the hydrogen energy domain and the entire integrated energy system.

As a clean energy source hydrogen not only helps to reduce the use of fossil fuels but also promotes the transformation of energy structure and sustainable development. This paper firstly introduces the development status of green hydrogen at home and abroad and then focuses on several advanced green hydrogen production technologies. Then the advantages and shortcomings of different green hydrogen production technologies are compared. Among them the future source of hydrogen tends to be electrolysis water hydrogen production. Finally the challenges and application prospects of the development process of green hydrogen technology are discussed and green hydrogen is expected to become an important part of realizing sustainable global energy development.

Modern energy conversion technologies with low or no emissions are needed to achieve sustainable development goals. This research examines the thermodynamic and exergy-economic features of a high-temperature proton exchange membrane fuel cell. A cutting-edge integrated energy system uses high-temperature proton exchange membrane fuel cells an organic Rankine cycle a proton exchange membrane electrolyzer and a multi-effect desalination unit. This setup generates electricity hydrogen and fresh water. Methanol-steam reformation produces hydrogen for the fuel cell. The recommended cycle drives an organic Rankine power producing cycle using 120-200 °C waste heat from hightemperature proton exchange membrane fuel cell to power water electrolysis and hydrogen generation. An integrated method incorporates energy and exergy balances and cost analysis to assess the proposed system's exergetic economic and environmental impacts. The suggested integration delivers high energy and exergy efficiency at an acceptable cost and environmental effect. According to parametric research boosting the fuel cell's working temperature decreases production costs and carbon dioxide emissions per mass. Raising current density has positive technical and environmental impacts. As the current density increases from 0.4 to 0.8 (A/cm2 ) the net power generation increases to 46.67% and the exergy efficiency increases from 64.5% to 68%. An increase in multi-effect distillation motivate steam pressure from 200 to 600 kPa results in an increase in the daily freshwater generated from 111.68 m3 to 116.41 m3 . For environmental protection and output optimization fuel utilization ratio must be reduced. The ideal system's exergy efficiency product unit cost and environmental impact are 65.78% 86.28 ($/h) and 4.33% respectively.

Hydrogen (H2) has been recognized as a promising solution to reduce carbon dioxide (CO2) emissions. H2 is considered a green energy carrier for energy storage transport and usage and it can be produced from renewable energy resources (such as solar hydropower and wind energy). However H2 is a highly diffusive compound compared to other natural gases raising concerns about the possibility of H2 loss in geo-storage (e.g. in underground geological formations such as depleted oil/gas reservoirs aquifers or shale formations) or H2 leak via pipelines when blending H2 with natural gas in existing pipeline systems. Thus understanding H2 diffusion in subsurface formations and pipeline systems is vital. However despite its importance only limited data is available to assess the above situations. Therefore in this study molecular dynamics simulations were used to predict the self-diffusion coefficients of H2 in water and cushion gases (CH4 and N2) at relevant geothermal conditions (i.e. 300 K–373 K and pressures up to 50 MPa). The findings showed that H2 self-diffusion in methane and nitrogen increases with increasing temperature but decreases with increasing pressure. However H2 selfdiffusion in water increases with increasing temperature but is not impacted by increasing or decreasing pres sure. The results also indicated that the rate of H2 self-diffusion in cushion gas is faster than in water about exceeding two-digit times. Furthermore the outcomes reported extended or new data on H2 self-diffusion for the binary system of H2–H2O H2–CH4 and H2–N2. This study is beneficial and contributes to assessing efficiency and safety for executing H2 transportation and underground hydrogen storage (UHS) schemes.

Healthcare facilities in isolated rural areas of sub-Saharan Africa face challenges in providing essential health services due to unreliable energy access. This study examines the use of hybrid renewable energy systems consisting of solar PV wind turbines batteries and hydrogen storage for the electrification of rural healthcare facilities in Nigeria and South Africa. The study deployed the efficacy of Hybrid Optimization of Multiple Energy Resources software for techno-economic analysis and the Evaluation based on the Distance from Average Solution method for multicriteria decision-making for sizing optimizing and selecting the optimal energy system. Results show that the optimal configurations achieve cost-effective levelized energy costs ranging from $0.336 to $0.410/kWh for both countries. For the Nigeria case study the optimal energy system includes 5 kW PV 10 kW fuel cell 10 kW inverter 10 kW electrolyzer and 16 kg hydrogen tank. South Africa's optimal configuration has 5 kW PV 10 kW battery 10 kW inverter and 7.5 kW rectifier. Solar PV provides more than 90% of energy with dual axis tracking yielding the highest output: 8889kWh/yr for Nigeria and 10470kWh/yr for South Africa. The multi-criteria decisionmaking analysis reveals that Nigeria's preferred option is the hybrid system without tracking. In contrast the horizontal axis weekly adjustment tracking configuration is optimal for South Africa considering technical economic and environmental criteria. The findings highlight the importance of context-specific optimization for hybrid renewable energy systems in rural healthcare facilities to accelerate Sustainable Development Goals 3 and 7.

This paper delves into the enhancement and optimization of on-grid renewable energy systems using a variety of renewable energy sources with a particular focus on large-scale applications designed to meet the energy demand of a certain load. As global concerns surrounding climate change continue to mount the urgency of replacing traditional fossil fuel-based power generation with cleaner more cost-effective and dependable alternatives becomes increasingly apparent. In this context a comprehensive investigation is conducted on grid connected hybrid energy system that combines photovoltaic wind and fuel cell technologies. The study employs three state-of-the-art optimization algorithms namely Walrus Optimization Algorithm (WaOA) Coati Optimization Algorithm (COA) and Osprey Optimization Algorithm (OOA) to determine the optimal system size and energy management strategies all aimed at minimizing the cost of energy (COE) for grid-based electricity. The results of the optimization process are compared with the results obtained from the utilization of the Particle swarm optimization (PSO) and Grey Wolf optimizer (GWO). The findings of this study underscore both the practical feasibility and the critical importance of adopting on-grid renewable energy systems to decrease the dependence on traditional energy sources within the grid. The proposed WaOA succeeded to reach the optimal solution of the optimal design process with a COE of 0.51758129611 $//kwh while keeping the loss of power supply probability (LPSP) the reliability index at 7.303681e-19. The practical recommendations and forwardlooking insights provided within this research hold the potential to foster sustainable development and effectively mitigate carbon emissions in the future.

Germany aligned with the European Union has set important targets for decreasing greenhouse gas emissions by 65% by 2030 and achieving climate neutrality by 2045. In this context Power-to-X fuels have emerged as promising solutions for defossilizing transport modes less suitable for electrification. However a significant challenge in developing Power-to-X fuels is the absence of a well-defined regulatory framework for their production and utilization. Thus this study investigates the regulatory landscapes of the EU and Germany aiming to comprehend objectives support schemes and advancements. A total of 25 legal frameworks from the EU and Germany with direct or indirect effects on Power-to-X fuels were identified. For a detailed and comprehensive policy analysis a qualitative inductive approach based on a coding scheme and policy content analysis was implemented. Findings indicate that several updates in the German and EU regulatory frameworks addressed Power-to-X fuels in the 2010s and 2020s. The RED III the REFuelEU Aviation and the FuelEU Maritime have shown to be turning points for Power-to-X fuels in the EU. In Germany the most relevant policies are the 37. BImSchV the National Hydrogen Strategy and the PtL Roadmap. Key challenges are identified related to the limited coherence among policies supporting the sustainable use of resources for the fuel production.

The industry is advancing decarbonization in hydrogen production through water splitting technologies like water electrolysis which involves the hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode. Alkaline water electrolyser (AWE) is particularly suited for industrial applications due to its use of cost-effective and abundant nickel-based electrodes. However AWE faces significant challenges including energy losses from gas bubble coverage and poor detachment known as “bubble resistance”. Recent research highlights the role of power ultrasound in mitigating these issues by leveraging Bjerknes forces. These forces facilitate the ejection of larger bubbles and the coalescence of smaller ones enhancing gas removal. Additionally ultrasound improves mass transfer from the electrolyte to electrodes and boosts heat transfer via acoustic streaming and acoustic cavitation which the latter also enhances electrocatalytic properties for both HER and OER. However employing ultrasonic fields presents both benefits and challenges for scaling the system.

This paper presents a techno-economic assessment of adding state-of-the-art solvent-based CO2 capture technologies to greenfield steam methane reforming (SMR)-based H2 production plants and quantifies the impacts of improvements in CO2 capture technology. Current conventional capture technologies are reviewed and future technologies in intermediate and long-term scenarios are analyzed. The results show that adding significantly more efficient solvent-based capture technologies leads to an equivalent rate of natural gas consumption as that of a conventional SMR plant without capture despite capturing most of the CO2 and producing the same amount of H2. Overall improvements in reboiler duty and reductions in capital costs can significantly reduce the cost of H2 production and cost of capture. Particularly the reboiler duty of pre-combustion capture and the capital cost of post-combustion capture have the greatest impact. Based on the results research goals are suggested. Solvent development is recommended—particularly pre-combustion solvents—for reducing the reboiler duties and process schemes to reduce the capital costs. Costlier but more efficient solvents can be considered. A sensitivity analysis using natural gas price shows that technological improvements can reduce the impacts of high natural gas prices. The degree of economic feasibility of CO2 capture increases with improvements to the capture technology.

The present study proposes and thoroughly examines a novel approach for the effective hybridization of solar and wind sources based on hydrogen storage to increase grid stability and lower peak load. The parabolic trough collector vanadium chloride thermochemical cycle hydrogen storage tank alkaline fuel cells thermal energy storage and absorption chiller make up the suggested smart system. Additionally the proposed system includes a wind turbine to power the electrolyzer unit and minimize the size of the solar system. A rule-based control technique establishes an intelligent two-way connection with energy networks to compensate for the energy expenses throughout the year. The transient system simulation (TRNSYS) tool and the engineering equation solver program are used to conduct a comprehensive techno-economic-environmental assessment of a Swedish residential building. A four-objective optimization utilizing MATLAB based on the grey wolf algorithm coupled with an artificial neural network is used to determine the best trade-off between the indicators. According to the results the primary energy saving carbon dioxide reduction rate overall cost and purchased energy are 80.6 % 219 % 14.8 $/h and 24.9 MWh at optimal conditions. From the scatter distribution it can be concluded that fuel cell voltage and collector length should be maintained at their lowest domain and the electrode area is an ineffective parameter. The suggested renewable-driven smart system can provide for the building’s needs for 70 % of the year and sell excess production to the local energy network making it a feasible alternative. Solar energy is far less effective in storing hydrogen over the winter than wind energy demonstrating the benefits of combining renewable energy sources to fulfill demand. By lowering CO2 emissions by 61758 kg it is predicted that the recommended smart renewable system might save 7719 $ in environmental costs equivalent to 6.9 ha of new reforestation.

The increasing depletion of fossil fuels and their environmental impact have led to the development of fuel cell hybrid electric vehicles. By combining fuel cells with batteries these vehicles offer greater efficiency and zero emissions. However their energy management remains a challenge requiring advanced strategies. This paper presents a comparative study of two developed energy management strategies: a deterministic rule-based approach and a fuzzy logic approach. The proposed system consists of a proton exchange membrane fuel cell (PEMFC) as the primary energy source and a lithium-ion battery as the secondary source. A comprehensive model of the hybrid powertrain is developed to evaluate energy distribution and system behaviour. The control system includes a model predictive control (MPC) method for fuel cell current regulation and a PI controller to maintain DC bus voltage stability. The proposed strategies are evaluated under standard driving cycles (UDDS and NEDC) using a simulation in MATLAB/Simulink. Key performance indicators such as fuel efficiency hydrogen consumption battery state-of-charge and voltage stability are examined to assess the effectiveness of each approach. Simulation results demonstrate that the deterministic strategy offers a structured and computationally efficient solution while the fuzzy logic approach provides greater adaptability to dynamic driving conditions leading to improved overall energy efficiency. These findings highlight the critical role of advanced control strategies in improving FCHEV performance and offer valuable insights for future developments in hybrid-vehicle energy management.

This study investigates potential solutions for low-carbon power generation with hydrogen firing and carbon capture. Multi-dimensional system modeling was used to assess the effects on plant performance size and cost. The examined cycles include advanced dry- wet- bottoming- oxyfuel cycles with air-separation units and post-combustion carbon capture with exhaust gas recirculation. The results identify three distinct lowcarbon technology pathways. While conventional combined-cycle plants are suitable for hydrogen retrofits hydrogen firing (both blue and green) results in levelized costs of electricity 50%–300% higher than carbon capture solutions making carbon capture more attractive for long-term energy storage. When carbon capture is applied to conventional combined cycles they become suboptimal compared to alternative solutions. The intercooled-recuperated (ICR) gas turbine cycle integrated with post-combustion carbon capture offers superior performance: over 3% higher efficiency 12% lower capital costs and 70% smaller physical footprint compared to conventional combined cycles with carbon capture. The Allam cycle represents a third pathway achieving 100% CO2 capture with efficiency comparable to combined cycles at 90% capture. Gas separation units emerge as the dominant source of both capital costs and efficiency penalties across all carbon capture configurations representing the key area for future optimization to reduce overall electricity costs.

Underground hydrogen storage in porous rocks is a promising method to stabilize renewable energy fluctuations. However data on the geochemical reactivity of hydrogen with reservoir rocks and its potential effects on reservoir performance are limited. This study investigates the geochemical reactivity of hydrogen with Bunt sandstein reservoir sandstones from northern Germany collected at a depth of about 2.5 km. Experiments were performed at 100 ◦C and 150 bar hydrogen partial pressure for four weeks examining scenarios with dry hydrogen synthetic saline fluid with hydrogen synthetic saline fluid with helium (as a control) and an oxidation environment (air). We measured permeability porosity magnetic susceptibility and fluid element concentration before and after the experiments. Results showed no significant mineral changes attributed to hydrogen. Mag netic susceptibility indicated no formation of magnetic minerals such as magnetite and pyrrhotite. Minor var iations in permeability and porosity were attributed to anhydrite dissolution from fluid chemistry nonequilibrium. Overall our findings suggest hydrogen interactions with Buntsandstein sandstone (no pyrite content) at temperatures up to 100 ◦C do not risk hydrogen loss or reservoir performance degradation.

This work discusses the current scenario and future growth of electrochemical energy devices such as water electrolyzers and fuel cells. It is based on the pivotal role that hydrogen can play as an energy carrier to replace fossil fuels. Moreover it is envisaged that the scaled-up and broader deployment of the technologies can hold the potential to address the challenges associated with intermittent renewable energy generation. From a sustainability perspective this synergy between hydrogen and electricity from renewable sources is particularly attractive: electrolyzers convert the excess energy from renewables into green hydrogen and fuel cells use this hydrogen to convert it back into electricity when it is needed. Although this transition endorses the ambitious goal to supply greener energy for all it also entails increased demand for the materials that are essential for developing such cleaner energy technologies. Herein several economic and environmental issues are highlighted besides a critical overview regarding each technology. The aim is to raise awareness and provide the reader (a non-specialist in the field) with useful resources regarding the challenges that need to be overcome so that a green hydrogen energy transition and a better life can be fully achieved.

Solar hydrogen production technology is a key technology for building a clean low-carbon safe and efficient energy system. At present the intermittency and volatility of renewable energy have caused a lot of “wind and light.” By combining renewable energy with electrolytic water technology to produce high-purity hydrogen and oxygen which can be converted into electricity the utilization rate of renewable energy can be effectively improved while helping to improve the solar hydrogen production system. This paper summarizes and analyzes the research status and development direction of solar hydrogen production technology from three aspects. Energy supply mode: the role of solar PV systems and PT systems in this technology is analyzed. System control: the key technology and system structure of different types of electrolytic cells are introduced in detail. System economy: the economy and improvement measures of electrolytic cells are analyzed from the perspectives of cost consumption efficiency and durability. Finally the development prospects of solar hydrogen production systems in China are summarized and anticipated. This article reviews the current research status of photovoltaic-photothermal coupled electrolysis cell systems fills the current research gap and provides theoretical reference for the further development of solar hydrogen production systems.

The transport sector heavily relies on the use of fossil fuels which are causing major environmental concerns. Solutions relying on the direct or indirect use of electricity through efuel production are emerging to power the transport sector. To ensure environmental benefits are achieved over this transition an accurate estimation of the impact of the use of electricity is needed. This requires a high temporal resolution to capture the high variability of electricity. This paper presents a previously unseen temporal analysis of the carbon intensity of e-fuels using grid electricity in countries that are members of the European Network of Transmission System Operators (ENTSO-E). It also provides an estimation of the potential load factor for producing low-carbon e-fuels according to the European Union legislative framework. This was achieved by building on top of the existing EcoDynElec tool to develop EcoDynElec_xr a python tool enabling—with an hourly time resolution—the calculation visualisation and analysis of the historical time-series of electricity mixing from the ENTSO-E. The results highlight that in 2023 very few European countries were reaching low carbon intensity for electricity that enables the use of grid electricity for the production of green electrolytic hydrogen. The methodological assumptions consider the consumption of the electricity mix instead of the production mix and the considered time step is of paramount importance and drastically impacts the potential load factor of green hydrogen production. The developed tools are released under an open-source license to ensure transparency result reproducibility and reuse regarding newer data for other territories or for other purposes.

Photovoltaic (PV) and wind energy generation result in low greenhouse gas footprints and can supply electricity to the grid or generate hydrogen for various applications including seasonal energy storage. Designing integrated wind–PV–electrolyzer underground hydrogen storage (UHS) projects is complex due to the interactions between components. Additionally the capacities of PV and wind relative to the electrolyzer capacity and fluctuating electricity prices must be considered in the project design. To address these challenges process modelling was applied using cost components and parameters from a project in Austria. The hydrogen storage part was derived from an Austrian hydrocarbon gas field considered for UHS. The results highlight the impact of the renewable energy source (RES) sizing relative to the electrolyzer capacity the influence of different wind-to-PV ratios and the benefits of selling electricity and hydrogen. For the case study the levelized cost of hydrogen (LCOH) is EUR 6.26/kg for a RES-to-electrolyzer capacity ratio of 0.88. Oversizing reduces the LCOH to 2.61 €/kg when including electricity sales revenues or EUR 4.40/kg when excluding them. Introducing annually fluctuating electricity prices linked to RES generation results in an optimal RES-to-electrolyzer capacity ratio. The RES-to-electrolyzer capacity can be dynamically adjusted in response to market developments. UHS provides seasonal energy storage in areas with mismatches between RES production and consumption. The main cost components are compression gas conditioning wells and cushion gas. For the Austrian project the levelized cost of underground hydrogen storage (LCHS) is 0.80 €/kg with facilities contributing EUR 0.33/kg wells EUR 0.09/kg cushion gas EUR 0.23/kg and OPEX EUR 0.16/kg. Overall the analysis demonstrates the feasibility of integrated RES–hydrogen generation-seasonal energy storage projects in regions like Austria with systems that can be dynamically adjusted to market conditions.

Bioenergy with carbon capture and storage (BECCS) technology is expected to support net-zero targets by supplying low carbon energy while providing carbon dioxide removal (CDR). BECCS is estimated to deliver 20 to 70 MtCO2 annual negative emissions by 2050 in the UK despite there are currently no BECCS operating facility. This research is modelling and demonstrating the flexibility scalability and attainable immediate application of BECCS. The CDR potential for two out of three BECCS pathways considered by the Intergovernmental Panel on Climate Change (IPCC) scenarios were quantified (i) modular-scale CHP process with post-combustion CCS utilising wheat straw and (ii) hydrogen production in a small-scale gasifier with pre-combustion CCS utilising locally sourced waste wood. Process modelling and lifecycle assessment were used including a whole supply chain analysis. The investigated BECCS pathways could annually remove between − 0.8 and − 1.4 tCO2e tbiomass− 1 depending on operational decisions. Using all the available wheat straw and waste wood in the UK a joint CDR capacity for both systems could reach about 23% of the UK’s CDR minimum target set for BECCS. Policy frameworks prioritising carbon efficiencies can shape those operational decisions and strongly impact on the overall energy and CDR performance of a BECCS system but not necessarily maximising the trade-offs between biomass use energy performance and CDR. A combination of different BECCS pathways will be necessary to reach net-zero targets. Decentralised BECCS deployment could support flexible approaches allowing to maximise positive system trade-offs enable regional biomass utilisation and provide local energy supply to remote areas.

The aviation industry is facing challenges related to its environmental impact and thus the pressing need to develop aircraft technologies aligned with the society climate goals. Hydrogen is emerging as a potential clean fuel for aviation as it offers several advantages in terms of supply potential and weight specific energy. One of the key factors enabling the use of H2 in aviation is the development of reliable and safe storage technologies to be integrated into aircraft design. This work provides an overview of the technologies currently being investigated or developed for the storage of hydrogen within the aircraft which would enable the use of hydrogen as a sustainable fuel for aviation with emphasis on tanks material and structural aspects. The requirements dictated by the need of integrating the fuel system within existing or ex-novo aircraft architectures are discussed. Both the storage of gaseous and liquid hydrogen are considered and the main challenges related to the presence of either high internal pressures or cryogenic conditions are explored in the background of recent literature. The materials employed for the manufacturing of hydrogen tanks are overviewed. The need to improve the storage tanks efficiency is emphasized and issues such as thermal insulation and hydrogen embrittlement are covered as well as the reference to the main structural health monitoring strategies. Recent projects dealing with the development of onboard tanks for aviation are eventually listed and briefly reviewed. Finally considerations on the tank layout deemed more realistic and achievable in the near future are discussed.

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid large-scale implementation of hydrogen energy with pipeline transportation being the principal method of conveyance. However pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased the influence of impurity gases on the hydrogen embrittlement of the material diminished.

The strategic importance of hydrogen has gained significant recognition as nations across the world have committed to achieving net zero. Here in the UK there’s a widespread consensus that hydrogen is critical to achieving our net zero target. This commitment culminated in the launch of the UK’s first Hydrogen Strategy and has been reaffirmed by Chris Skidmore’s Independent Review of Net Zero. Both these documents highlight hydrogen’s importance not only to net zero but growing the UK industrial base1 . Analysis by Hydrogen UK estimates up to 20000 jobs could be created by 2030 contributing £26bn in cumulative GVA2. These economic benefits flow from all areas of the value chain ranging from production storage network development and off-taker markets. However with large scale projects still to take final investment decisions current volumes of low-carbon hydrogen produced and consumed fall well below the government’s 2030 ambitions. Encouragingly the UK has a positive track record of deploying low carbon technologies. The combination of the UK’s world leading policies and incentive schemes alongside our vibrant RD&I and engineering environment has enabled rapid deployment of technologies like offshore wind and electric vehicles. Yet despite being world leaders in deployment early opportunities for regional supply chain growth and job creation were not fully realised and taken advantage of from inception. The hydrogen sector is therefore at a tipping point. To capitalise on the economic opportunity hydrogen offers the UK must learn from prior technology deployments and build a strong domestic hydrogen supply chain in parallel to championing deployment. This report delivers on a recommendation from the Hydrogen Champion Report which encouraged industry to create an industry led supply chain strategy3 . With Hydrogen UK steering the work on behalf of the UK hydrogen industry this study focusses on identifying the actions needed to mature a local supply chain that can support the initial deployment of hydrogen technologies across the value chain. The report is segmented into two sections. The first section outlines a voluntary ambition for local content from industry alongside the potential intervention mechanisms needed to achieve the ambition. The second section exploresthe challenges companies across the hydrogen value chain face in maximising UK supply chain opportunities.

This report can be found on Hydrogen UK's website.

Hydrogen is one of the most popular alternatives for energy storage. Because of its low volumetric energy density hydrogen should be compressed for practical storage and transportation purposes. Recently electrochemical hydrogen compressors (EHCs) have been developed that are capable of compressing hydrogen up to P = 1000 bar and have the potential of reducing compression costs to 3 kWh/kg. As EHC compressed hydrogen is saturated with water the maximum water content in gaseous hydrogen should meet the fuel requirements issued by the International Organization for Standardization (ISO) when refuelling fuel cell electric vehicles. The ISO 14687−2:2012 standard has limited the water concentration in hydrogen gas to 5 μmol water per mol hydrogen fuel mixture. Knowledge on the vapor liquid equilibrium of H2O−H2 mixtures is crucial for designing a method to remove H2O from compressed H2. To the best of our knowledge the only experimental high pressure data (P > 300 bar) for the H2O−H2 phase coexistence is from 1927 [J. Am. Chem. Soc. 1927 49 65−78]. In this paper we have used molecular simulation and thermodynamic modeling to study the phase coexistence of the H2O−H2 system for temperatures between T = 283 K and T = 423 K and pressures between P = 10 bar and P = 1000 bar. It is shown that the Peng-Robinson equation of state and the Soave Redlich-Kwong equation of state with van der Waals mixing rules fail to accurately predict the equilibrium coexistence compositions of the liquid and gas phase with or without fitted binary interaction parameters. We have shown that the solubility of water in compressed hydrogen is adequately predicted using force-field-based molecular simulations. The modeling of phase coexistence of H2O−H2 mixtures will be improved by using polarizable models for water. In the Supporting Information we present a detailed overview of available experimental vapor−liquid equilibrium and solubility data for the H2O−H2 system at high pressures.

The concept of the “hydrogen economy” was first coined by Prof. John Bockris during a talk he gave in 1970 at the General Motors Technical Center. Bockris’s talk introduced the vision of a world economy in which energy was carried in the form of hydrogen resulting in zero emissions at its point of use—be that as a chemical feedstock or as a fuel for industrial or domestic heating for power generation in a gas turbine or in a fuel cell “engine” for transport applications. Despite several waves of significant interest and investment however due to the relative costs and technological immaturity of hydrogen technologies the hydrogen economy was never delivered at scale nor was there sufficient motivation to create the technology needed to overcome these hurdles.<br/>But today as the world seeks to transition to a truly net-zero carbon economy hydrogen has returned to the fore as a key energy carrier—not as a hydrogen economy but as “hydrogen in the economy” synergistically working alongside low- to zero-carbon electricity to decarbonize those parts of the economy that are too expensive or too difficult to be directly decarbonized with electricity. These include:<br/>♦ Transport applications in which large amounts of energy are needed on the vehicle such as planes trains shipping long-distance trucks and heavy-duty vehicles;<br/>♦ Industrial applications such as steelmaking and cement manufacturing;<br/>♦ Long-term energy storage for days to weeks at a time;<br/>♦ The production of green chemicals such as green ammonia and green methanol;<br/>♦ Industrial (and potentially residential) heating.

Japan has formulated a net-zero emissions target by 2050. Existing scenarios consistent with this target generally depend on carbon dioxide removal (CDR). In addition to domestic mitigation actions the import of low-carbon energy carriers such as hydrogen and synfuels and negative emissions credits are alternative options for achieving net-zero emissions in Japan. Although the potential and costs of these actions depend on global energy system transition characteristics which can potentially be informed by the global integrated assessment models they are not considered in current national scenario assessments. This study explores diverse options for achieving Japan's net-zero emissions target by 2050 using a national energy system model informed by international energy trade and emission credits costs estimated with a global energy system model. We found that demand-side electrification and approximately 100 Mt-CO2 per year of CDR implementation equivalent to approximately 10% of the current national CO2 emissions are essential across all net-zero emissions scenarios. Upscaling of domestically generated hydrogen-based alternative fuels and energy demand reduction can avoid further reliance on CDR. While imports of hydrogen-based energy carriers and emission credits are effective options annual import costs exceed the current cost of fossil fuel imports. In addition import dependency reaches approximately 50% in the scenario relying on hydrogen imports. This study highlights the importance of considering global trade when developing national net-zero emissions scenarios and describes potential new roles for global models.

Hydrogen has emerged as a critical energy carrier for achieving global decarbonization and supporting a sustainable energy future. This review explores key advancements in hydrogen production technologies including electrolysis biomass gasification and thermochemical processes alongside innovations in storage methods like metal hydrides and liquid organic hydrogen carriers (LOHCs). Despite its promise challenges such as high production costs scalability issues and safety concerns persist. Biomass gasification stands out for its dual benefits of waste management and carbon neutrality yet hurdles like feedstock variability and energy efficiency need further attention. This review also identifies opportunities for improvement such as developing cost-effective catalysts and hybrid storage systems while emphasizing future research on improving storage efficiency and tackling production bottlenecks. By addressing these challenges hydrogen can play a central role in the global transition to cleaner energy systems.

This paper examines the crucial elements of pipeline-based hydrogen transportation highlighting the particular difficulties and technical developments required to guarantee the sustainable effective and safe supply of hydrogen. This study lists the essential phases of hydrogen pipeline management from design to repair as the relevance of hydrogen infrastructure in the worldwide energy transition continues to rise. It discusses the upkeep monitoring operation and rehabilitation procedures for aged pipelines with an emphasis on the cutting-edge techniques and technology used to mitigate the dangers related to hydrogen’s unique features such as leakage and embrittlement. Together with highlighting the legislative and regulatory frameworks that enable the infrastructure this paper also discusses the material economic and environmental difficulties related to hydrogen pipelines. Lastly it emphasizes how crucial it is to fund research create cutting-edge materials and implement sophisticated monitoring systems to guarantee the long-term dependability and safety of hydrogen pipelines. These initiatives will be crucial in allowing hydrogen’s contribution to the future of renewable energy together with international collaboration on regulatory standards.

The work carried out in this paper focused on “Machine learning models for the prediction of turbulent combustion speed for hydrogen-natural gas spark ignition engines”. The aim of this work is to develop and verify the ability of machine learning models to solve the problem of estimating the turbulent flame speed for a spark-ignition internal combustion engine operating with a hydrogen-natural gas mixture then evaluate the relevance of these models in relation to the usual approaches. The novelty of this work is the possibility of a direct calculation of turbulent combustion speed with a good precision using only machine learning model. The obtained models are also compared to each other by considering in turn as a comparison criterion: the precision of the result calculation time and the ability to assimilate original data (which has not undergone preprocessing). An important particularity of this work is that the input variables of the machine learning models were chosen among the variables directly measurable experimentally based on the opinion of experts in combustion in internal combustion engines and not on the usual approaches to dimensionality reduction on a dataset. The data used for this work was taken from a MINSEL 380 a 380-cc single-cylinder engine. The results show that all the machine learning models obtained are significantly faster than the usual approach and Random Forest (R2: R-squared = 0.9939 and RMSE: Root Mean Square Error = 0.4274) gives the best results. With a forecasting accuracy of over 90 % both approaches can make reasonable predictions for most industrial applications such as designing engine monitoring and control systems firefighting systems simulation and prototyping tools.

Reversible solid oxide cells (rSOC) enable the efficient cyclic conversion between electrical and chemical energy in the form of fuels and chemicals thereby providing a pathway for longterm and high-capacity energy storage. Amongst the different fuels under investigation hydrogen methane and ammonia have gained immense attention as carbon-neutral energy vectors. Here we have compared the energy efficiency and the energy demand of rSOC based on these three fuels. In the fuel cell mode of operation (energy generation) two different routes have been considered for both methane and ammonia; Routes 1 and 2 involve internal reforming (in the case of methane) or cracking (in the case of ammonia) and external reforming or cracking respectively. The use of hydrogen as fuel provides the highest round-trip efficiency (62.1%) followed by methane by Route 1 (43.4%) ammonia by Route 2 (41.1%) methane by Route 2 (40.4%) and ammonia by Route 1 (39.2%). The lower efficiency of internal ammonia cracking as opposed to its external counterpart can be attributed to the insufficient catalytic activity and stability of the state-of-the-art fuel electrode materials which is a major hindrance to the scale-up of this technology. A preliminary cost estimate showed that the price of hydrogen methane and ammonia produced in SOEC mode would be ~1.91 3.63 and 0.48 $/kg respectively. In SOFC mode the cost of electricity generation using hydrogen internally reformed methane and internally cracked ammonia would be ~52.34 46.30 and 47.11 $/MWh respectively.

Steam methane reforming (SMR) is a leading technology for hydrogen production. However this technology is still carbon-intensive since in current SMR units the PSA tail gas containing H2 CO and CH4 is burned at the reformer with air and exits the stack at a CO2 purity of less than 5% which is not feasible to capture. In this paper we aim to either harness the energy content of this gas to generate power in a solid oxide fuel cell (SOFC) or burn it via chemical looping combustion (CLC) or oxy-combustion process to produce off-gas with high CO2 purity ready to storage. Therefore an industrial-scale PSA with 72000 Nm3/h feed capacity was modelled to obtain the tail gas flow rate and composition. Then CLC SOFC and oxy-combustion were modelled to use tail gas. Finally a techno-economic analysis was conducted to calculate each technology's levelised cost of hydrogen (LCOH). It was observed that CO2 purity for CLC meets the criteria for storage (>95%) without further purification. On the other hand from the economic point of view all three technologies show a promising performance with an LCOH of 1.9 €/kg.

The goal of achieving a zero-emission energy system by 2050 requires accurate energy planning to minimise the overall cost of the energy transition. Long-term energy models based on cost-optimal solutions are extremely dependent on the cost forecasts of different technologies. However such forecasts are inherently uncertain. The aim of the present work is to identify a cost-optimal pathway for the Italian energy system decarbonisation and assess how renewable cost scenarios can affect the optimal solution. The analysis has been carried out with the H2RES model a single-objective optimisation algorithm based on Linear Programming. Different cost scenarios for photovoltaics on-shore and off-shore wind power and lithium-ion batteries are simulated. Results indicate that a 100% renewable energy system in Italy is technically feasible. Power-to-X technologies are crucial for balancing purposes enabling a share of non-dispatchable generation higher than 90%. Renewable cost scenarios affect the energy mix however both on-shore and off-shore wind saturate the maximum capacity potential in almost all scenarios. Cost forecasts for lithium-ion batteries have a significant impact on their optimal capacity and the role of hydrogen. Indeed as battery costs rise fuel cells emerge as the main solution for balancing services. This study emphasises the importance of conducting cost sensitivity analyses in long-term energy planning. Such analyses can help to determine how changes in cost forecasts may affect the optimal strategies for decarbonising national energy systems.

Hydrogen has become a key enabler for decarbonization as countries pledge to reach net zero carbon emissions by 2050. With hydrogen infrastructure expanding rapidly beyond its established applications there is a requirement for robust safety practices solutions and regulations. Since the 1980s considerable efforts have been undertaken by the nuclear community to address hydrogen safety issues because in severe accidents of water-cooled nuclear reactors a large amount of hydrogen can be produced from the oxidation of metallic components with steam. As evidenced in the Fukushima accident hydrogen combustion can cause severe damage to reactor building structures promoting the release of radioactive fission products to the environment. A great number of large-scale experiments have been conducted in the framework of national and international projects to understand the hydrogen dispersion and combustion behavior under postulated accidental conditions. Empirical engineering models and computer codes have been developed and validated for safety analysis. Hydrogen recombiners known as Passive Autocatalytic Recombiners (PARs) were developed and have been widely installed in nuclear containments to mitigate hydrogen risk. Complementary actions and strategies were established as part of severe accident management guidelines to prevent or limit the consequences of hydrogen explosions. In addition hydrogen monitoring systems were developed and have been implemented in nuclear power plants. The experience and knowledge gained from the nuclear community on hydrogen safety is valuable and applicable for other industries involving hydrogen production transport storage and use.

Nowadays several technologies based on powertrain electrification and the exploitation of hydrogen represent valuable options for decarbonizing the on-road public transport sector. The considered alternatives should exhibit an effective benchmark between CO2 reduction potential and production/operational costs. Conducting a comprehensive Total Cost of Ownership (TCO) analysis coupled with a thorough Life Cycle Assessment (LCA) is therefore crucial in shaping the future for cleaner urban mobility. From this perspective this study compares different powertrain configurations for a 12 m urban bus: a conventional diesel Internal Combustion Engine Vehicle (ICEV) a series hybrid diesel two hydrogen-based series hybrid vehicles: a Hydrogen Hybrid Electric Vehicle featuring an H2-ICE (H2-HEV) or a Fuel Cell Electric Vehicle (FCEV) and a Battery Electric Vehicle (BEV). Moreover a sensitivity analysis has been conducted on the carbon footprint for power generation considering also the marginal electricity mix. In addition prospective LCA and TCO elements are introduced by addressing future technological projections for the 2030 horizon. The research reveals that as of today the BEV and hydrogen-fueled vehicles have comparable environmental impacts when the marginal electricity mix is considered. The techno-economic analysis indicates that under current conditions FCEVs and H2-HEVs are not cost-effective for CO₂ reduction unless powered by renewable energy sources. However considering future technological advancements and market evolution FCEVs offer the most promising balance between economic and environmental benefits particularly if hydrogen prices reach €4 per kilogram. If hydrogen-powered vehicles remain a niche market BEVs will be the most viable option for decarbonizing the transport sector in most European countries.

The refining industry is shifting from decarbonization to hydrogenation for processing heavy fractions to reduce pollution and improve efficiency. However the carbon footprint of hydrogen production presents significant environmental challenges. This study couples refinery linear programming models with life cycle assessment to evaluate from a long-term perspective the role of low-carbon hydrogen in promoting sustainable and profitable hydrogenation refining practices. Eight hydrogen-production pathways were examined including those based on fossil fuels and renewable energy providing hydrogen for three representative refineries adopting hydrogenation decarbonization and co-processing routes. Learning curves were used to predict future hydrogen cost trends. Currently hydrogenation refineries using fossil fuels benefit from significant cost advantages in hydrogen production demonstrating optimal economic performance. However in the long term with increasing carbon taxes hydrogenation routes will be affected by the high carbon emissions associated with fossil-based hydrogen losing economic advantages compared to decarbonization pathways. With increasing installed capacity and technological advancements low-carbon hydrogen is anticipated to reach cost parity with fossil-based hydrogen before 2060. Coupling renewable hydrogen is expected to yield the most significant economic advantages for hydrogenation refineries in the long term. Renewable hydrogen drives the transition of refining processing routes from a decarbonization-oriented approach to a hydrogenation-oriented paradigm resulting in cleaner refining processes and enhanced competitiveness under emission-reduction pressures.

Green hydrogen production and storage are vital in mitigating carbon emissions and sustainable transition. However the high investment cost and management requirements are the bottleneck of utilizing hybrid hydrogen-based systems in microgrids. Given the necessity of cost-effective and optimal design of these systems the present study examines techno-economic feasibility of integrating hybrid hydrogen-based systems into an outdoor test facility. With this perspective several solar-driven hybrid scenarios are introduced at two energy storage levels namely the battery and hydrogen energy storage systems including the high-pressure gaseous hydrogen and metal hydride storage tanks. Dynamic simulations are carried out to address subtle interactions in components of the hybrid system by establishing a TRNSYS model coupled to a Fortran code simulating the metal hydride storage system. The OpenStudio-EnergyPlus plugin is used to simulate the building load validate against experimental data according to the measured data and monitored operating conditions. Aimed at enabling efficient integration of energy storage systems a techno-enviro-economic optimization algorithm is developed to simultaneously minimize the levelized cost of the electricity and maximize the CO2 mitigation in each proposed hybrid scenario. The results indicate that integrating the gaseous hydrogen and metal hydride storages into the photovoltaic-alone scenario enhances 22.6% and 14.4% of the annual renewable factor. Accordingly the inclusion of battery system to these hybrid scenarios gives a 30.4% and 20.3 % boost to the renewable factor value respectively. Although the inclusion of battery energy storage into the hybrid systems increases the renewable factor the results imply that it reduces the hydrogen production rate via electrolysis. The optimized values of the levelized cost of electricity and CO2 emission for different scenarios vary in the range of 0.376–0.789 $/kWh and 6.57–9.75 ton respectively. The multi-criteria optimizations improve the levelized cost of electricity and CO2 emission by up to 46.2% and 11.3% with respect to their preliminary design.

Growing expectations are being placed on green hydrogen-based steel for decarbonising the global steel industry. However the scale of the expected demand is dispersed across numerous case studies resulting in a fragmented picture. This study examines 28 existing scenarios to provide a cohesive view of future global demand. In the short term the demand for green hydrogen-based steel is expected to be limited constituting 2% of current total steel production by 2030. However a transformation phase is expected around 2040 marked by accelerated growth. By 2050 global demand is projected to reach 660 Mt (with an interquartile range of 368–1000 Mt) equivalent to 35% (19%–53%) of current total steel production. To meet such growing demand green hydrogen supply and electrolyser capacity will need to increase to more than 1000 times current levels by 2050. These trends highlight both short-term limitations and long-term potential. Decarbonisation efforts will therefore require immediate emission reductions with already scalable options while simultaneously building the enabling infrastructure for green hydrogen-based steelmaking to ensure long-term impacts.

Global warming’s major cause is the emission of greenhouse-effect gases (GHG) especially carbon dioxide (CO2) whose main source is the combustion of fossil fuels. Fossil fuels serve as the primary energy source in many industries including shipping which is the focus of this study. One of the measures proposed to tackle GHG emissions is the development of green shipping corridors - carbon-free shipping routes that require the transition to alternative fuels which are gaining competitiveness. One of the reasons for that is carbon pricing which taxes CO2 emissions. However the lack of consensus on the most cost-advantageous alternative fuel in the long run results in the delay of the implementation of green shipping corridors. To make it more accessible for stakeholders to conduct an economic analysis of the various options a framework to determine and minimize the costs of transitioning from fossil fuels to any alternative fuel is proposed over the period of one voyage considering the lost opportunity cost the deployment cost of bunkering vessels at the necessary call ports the cost of converting the vessel the car-bon emissions tax cost and the fuel cost. This will allow stakeholders to choose the most economical alternative fuel accelerating the development of green shipping corridor initiatives. To validate the effectiveness of the framework it was applied in a case study involving a shipowner seeking to transition from heavy fuel oil (HFO) to Ammonia Hydrogen Liquefied Natural Gas (LNG) or Methanol. This study faced limitations due to the unknown costs of installing bunkering vessels for Ammonia and Hydrogen. However it evaluates the cost-effectiveness of alternative fuels providing insights into their short-term economic viability. The results showed that Hydrogen is the most costadvantageous fuel until a deployment cost per bunkering vessel of 1990285$ for a sailing speed of 22 knots and 2190171$ for a sailing speed of 18 knots is reached after which LNG becomes the most economical option regardless of variations in the carbon tax. Moreover a sensitivity analysis was conducted to determine the effects of variations in parameters such as carbon tax fuel prices and vessel conversion costs in the total cost of each fuel option. Results highlighted that even though HFO remains the most economical fuel option even when considering a high increase in carbon tax the cost gap between HFO and alternative fuels narrows significantly with the increase in carbon tax. Furthermore the sailing speed impacts the fuels’ competitiveness as the cost difference between HFO and alternative fuels decreases at higher speeds.

Integrated hydrogen energy systems (IHESs) have attracted extensive attention in miti-gating climate problems. As a kind of large-scale hydrogen storage device undergroundhydrogen storage (UHS) can be introduced into IHES to balance the seasonal energy mis-match while bringing challenges to optimal operation of IHES due to the complex geolog-ical structure and uncertain hydrodynamics. To address this problem a deep deterministicpolicy gradient (DDPG)-based optimal scheduling method for underground space basedIHES is proposed. The energy management problem is formulated as a Markov decisionprocess to characterize the interaction between environmental states and policy. Based onDDPG theory the actor-critic structure is applied to approximate deterministic policy andactor-value function. Through policy iteration and actor-critic network training the oper-ation of UHS and other energy conversion devices can be adaptively optimised which isdriven by real-time response data instead of accurate system models. Finally the effective-ness of the proposed optimal scheduling method and the benefits of underground spaceare verified through time-domain simulations.

In the future steel products will be reheated for hot working using hydrogen instead of natural gas. This study investigated the differences in oxide scale formation between natural gas/air and hydrogen/air combustion at constant air-fuel-ratio. Samples of a hypo-eutectoid eutectoid and hyper-eutectoid steel grade (dimensions: 30 x 30 x 50 mm W x H x L) were exposed to the two atmospheres in a semi-industrial scale furnace for 180 min at three sample core temperatures (1100 1200 and 1280 °C). Specific mass gain was calculated and the samples were metallographically examined. Switching the fuel increased scale formation depending on the steel. The exponential correlation between temperature and scale formation is more pronounced for the eutectoid and the hyper-eutectoid steel grade. Metallographic investigations revealed similar scale morphologies in both atmospheres but with significant temperature dependence. The decarburization depth is atmosphere-independent. Thus switching fuel does not negatively impact the properties of the steel substrate; it only increases scale formation during reheating.

As a paradigm of clean energy hydrogen is gradually attracting global attention. However its unique characteristics of leakage and autoignition pose significant challenges to the development of high-pressure hydrogen storage technologies. In recent years numerous scholars have made significant progress in the field of high-pressure hydrogen leakage autoignition. This paper based on diffusion ignition theory thoroughly explores the mechanism of high-pressure hydrogen leakage autoignition. It reviews the effects of various factors such as gas properties burst disc rupture conditions tube geometric structure obstacles etc. on shock wave growth patterns and autoignition characteristics. Additionally the development of internal flames and propagation characteristics of external flames after ignition kernels generation are summarized. Finally to promote future development in the field of high-pressure hydrogen energy storage and transportation this paper identifies deficiencies in the current research and proposes key directions for future research.

An analysis of the turbulent premixed combustion speed in an internal combustion engine using natural gas hydrogen and intermediate mixtures as fuels is carried out with different air-fuel ratios and engine speeds. The combustion speed has been calculated by means of a two-zone diagnosis thermodynamic model combined with a geometric model using a spherical flame front hypothesis. 48 operating conditions have been analyzed. At each test point the pressure record of 200 cycles has been processed to calculate the cycle averaged turbulent combustion speed for each flame front radius. An expression of turbulent combustion speed has been established as a function of two parameters: the ratio between turbulence intensity and laminar combustion speed and the second parameter the ratio between the integral spatial scale and the thickness of the laminar flame front increased by instabilities. The conclusion of this initial study is that the position of the flame front has a great influence on the expression to calculate the combustion speed. A unified correlation for all positions of the flame front has been obtained by adding one correction term based on the expansion speed as a turbulence source. This unified correlation is thus valid for all experimental conditions of fuel types air–fuel ratios engine speeds and flame front positions. The correlation can be used in quasi-dimensional predictive models to determine the heat released in an ICE.