Publications

This article analyzes a power-to-hydrogen system designed to provide high-temperature heat to hard-to-abate industries. We leverage on a geospatial analysis for wind and solar availability and different industrial demand profiles with the aim to identify the ideal sizing of plant components and the resulting Levelized Cost of Hydrogen (LCOH). We assess the carbon intensity of the produced hydrogen especially when grid electricity is utilized. A methodology is developed to size and optimize the PV and wind energy capacity the electrolyzer unit and hybrid storage by combining compressed hydrogen storage with lithium-ion batteries. The hydrogen demand profile is generated synthetically thus allowing different industrial consumption profiles to be investigated. The LCOH in a baseline scenario ranges from 3.5 to 8.9 €/kg with the lowest values in wind-rich climates. Solar PV only plays a role in locations with high PV full-load hours. It was found that optimal hydrogen storage can cover the users’ demand for 2–3 days. Most of the considered scenarios comply with the emission intensity thresholds set by the EU. A sensitivity analysis reveals that a lower variability of the demand profile is associated with cost savings. An ideally constant demand profile results in a cost reduction of approximately 11 %.

Meeting climate targets requires profound transformations in the energy system. Most energy uses should be electrified but where this is not feasible hydrogen can be part of the solution. However 98% of global hydrogen production involves greenhouse gas emissions with an average of 12 kg CO2e/kg H2. Therefore new hydrogen production pathways are needed in order to make hydrogen production compatible with climate targets. In this work we fill this gap by systematically comparing the energy and emissions intensity of 173 hydrogen production pathways suitable for the UK. Scenarios include onshore and offshore pathways and the use of repurposed infrastructure. Unlike fossil-fuel based pathways the results show that electrolytic hydrogen powered by fixed offshore wind could align with proposed emissions standards either onshore or offshore. However the embodied and fugitive emissions are important to consider for electrolytic pathways as they result in 10–50% of the total emissions intensity.

This paper deals with the optimal scheduling of the resources of a renewable energy community whose coordination is aimed at providing flexibility services to the electrical distribution network. The available resources are renewable generation units battery energy storage systems dispatchable loads and power-to-hydrogen systems. The main purposes behind the proposed strategy are enhancement of self-consumption and hydrogen production from local resources and the maximization of the economic benefits derived from both the selling of hydrogen and the subsidies given to the community for the shared energy. The proposed approach is formulated as an economic problem accounting for the perspectives of both community members and the distribution system operator. In more detail a mixed-integer constrained non-linear optimization problem is formulated. Technical constraints related to the resources and the power flows in the electrical grid are considered. Numerical applications allow for verifying the effectiveness of the procedure. The results show that it is possible to increase self-consumption and the production of green hydrogen while providing flexibility services through the exploitation of community resources in terms of active and reactive power support. More specifically the application of the proposed strategy to different case studies showed that daily revenues of up to EUR 1000 for each MW of renewable energy generation installed can be obtained. This value includes the benefit obtained thanks to the provision of flexibility services which contribute about 58% of the total.

Battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) whose exhaust pipes emit nothing are examples of zero-emission automobiles. FCEVs should be considered an additional technology that will help battery-powered vehicles to reach the aspirational goal of zero-emissions electric mobility particularly in situations where the customers demand for longer driving ranges and where using batteries would be insufficient due to bulky battery trays and time-consuming recharging. This study stipulates a current evaluation of the status of development and challenges related to (i) research gap to promote fuel-cell based HEVs (ii) key barriers of fuel-cell based HEVs (iii) advancement of electric mobility and their power drive (iv) electrochemistry of fuel cell technology for FCEVs (v) power transformation topologies communication protocols and advanced charging methods (vi) recommendations and future prospects of fuel-cell HEVs and (vii) current research trends of EVs and FCEVs. This article discusses key challenges with fuel cell electric mobility such as low fuel cell performance cold starts problems with hydrogen storage cost-reduction safety concerns and traction systems. The operating characteristics and applications of several fuel-cell technologies are investigated for FCEVs and FCHEVs. An overview of the fuel cell is provided which serves as the primary source of energy for FCHEVs along with comparisons and its electrochemistry. The study of power transformation topologies communication protocols and enhanced charging techniques for FCHEVs has been studied analytically. Recent technology advancements and the prospects for FCHEVs are discussed in order to influence the future vehicle market and to attain the aim of zero emissions.

Hydrogen is envisaged to play a major role in decarbonizing our future energy systems. Hydrogen is ideal for storing renewable energy over longer durations strengthening energy security. It can be used to provide electricity renewable heat power long-haul transport shipping and aviation and in decarbonizing several industrial processes. The cost of green hydrogen produced from renewable via electrolysis is dominated by the cost of electricity used. Operating electrolyzers only during periods of low electricity prices will limit production capacity and underutilize high investment costs in electrolyzer plants. Hydrogen production from deep offshore wind energy is a promising solution to unlock affordable electrolytic hydrogen at scale. Deep offshore locations can result in an increased capacity factor of generated wind power to 60–70% 4–5 times that of onshore locations. Dedicated wind farms for electrolysis can use the majority >80% of the produced energy to generate economical hydrogen. In some scenarios hydrogen can be the optimal carrier to transport the generated energy onshore. This review discusses the opportunities and challenges in offshore hydrogen production using electrolysis from wind energy and seawater. This includes the impact of site selection size of the electrolyzer and direct use of seawater without deionization. The review compares overall electrolysis system efficiency cost and lifetime when operating with direct seawater feed and deionized water feed using reverse osmosis and flash evaporation systems. In the short to medium term it is advised to install a reverse osmosis plant with an ion exchanger to feed the electrolysis instead of using seawater directly.

The objective of the paper is to simulate the whole steelmaking process cycle based on Direct Reduced Iron and Electric Arc Furnace technologies by modeling for the first time the reduction furnace based on kinetic approach to be used as a basis for the environmental and techno-economic plant analysis by adopting different reducing gases. In addition the impact of carbon capture section is discussed. A complete profitability analysis has been conducted for the first time adopting a Monte Carlo simulation approach.<br/>In detail the use of syngas from methane reforming syngas and hydrogen from gasification of municipal solid waste and green hydrogen from water electrolysis are analyzed. The results show that the Direct Reduced Iron process with methane can reduce CO2 emissions by more than half compared to the blast furnace based-cycle and with the adoption of carbon capture greenhouse gas emissions can be reduced by an additional 40%. The use of carbon capture by amine scrubbing has a limited economic disadvantage compared to the scenario without it becoming profitable once carbon tax is included in the analysis. However it is with the use of green hydrogen from electrolyzer that greenhouse gas emissions can be cut down almost completely. To have an environmental benefit compared with the methane-based Direct Reduced Iron process the green hydrogen plant must operate for at least 5136 h per year (64.2% of the plant's annual operating hours) on renewable energy.<br/>In addition the use of syngas and separated hydrogen from municipal solid waste gasification is evaluated demonstrating its possible use with no negative effects on the quality of produced steel. The results show that hydrogen use from waste gasification is more economic with respect to green hydrogen from electrolysis but from the environmental viewpoint the latter results the best alternative. Comparing the use of hydrogen and syngas from waste gasification it can be stated that the use of the former reducing gas results preferable from both the economic and environmental viewpoint.

With the increasingly severe climate change situation and the trend of green energy transformation the development and utilization of hydrogen energy has attracted extensive attention from government industry and academia in the past few decades. Renewable energy electrolysis stands out as one of the most promising hydrogen production routes enabling the storage of intermittent renewable energy power generation and supplying green fuel to various sectors. This article reviews the evolution and development of green hydrogen policies in the United States the European Union Japan and China and then summarizes the key technological progress of renewable energy electrolysis while introducing the progress of hydrogen production from wind and photovoltaic power generation. Furthermore the environmental social and economic benefits of different hydrogen production routes are analyzed and compared. Finally it provides a prospective analysis of the potential impact of renewable energy electrolysis on the global energy landscape and outlines key areas for future research and development.

Liquid hydrogen storage is an important way of hydrogen storage and transportation which greatly improves the storage and transportation efficiency due to the high energy density but at the same time brings new safety hazards. In this study the liquid hydrogen leakage in the storage area of a hydrogen production station is numerically simulated. The effects of ambient wind direction wind speed leakage mass flow rate and the mass fraction of gas phase at the leakage port on the diffusion behavior of the liquid hydrogen leakage were investigated. The results show that the ambient wind direction directly determines the direction of liquid hydrogen leakage diffusion. The wind speed significantly affects the diffusion distance. When the wind speed is 6 m/s the diffusion distance of the flammable hydrogen cloud reaches 40.08 m which is 2.63 times that under windless conditions. The liquid hydrogen leakage mass flow rate and the mass fraction of the gas phase have a greater effect on the volume of the flammable hydrogen cloud. As the leakage mass flow rate increased from 5.15 kg/s to 10 kg/s the flammable hydrogen cloud volume increased from 5734.31 m3 to 10305.5 m3 . The installation of a barrier wall in front of the leakage port can limit the horizontal diffusion of the flammable hydrogen cloud elevate the diffusion height and effectively reduce the volume of the flammable hydrogen cloud. This study can provide theoretical support for the construction and operation of hydrogen production stations.

In the latest OIES podcast from the Hydrogen Programme James Henderson talks to Abdurahman Alsulaiman about his latest paper entitled “Navigating Turbulence: Hydrogen’s Role in the Decarbonisation of the Aviation Sector.” In the podcast we discuss the current balance of fuels in the aviation sector the importance of increasing efficiency of aero-engines and the impact of increasing passenger miles travelled. The podcast then considers different decarbonisation options for the sector focussing on a change of engine technology to allow the use of alternative fuels such as hydrogen or electricity but also looking at the potential for hydrogen to play an important role in the development of Sustainable Aviation Fuels (SAFs) for use with current engine technology. We also look at Low Carbon Aviation Fuels which are essentially existing fuels derived from a significantly decarbonised supply chain and assess whether they have an important role to play as the aviation sector targets a net zero outcome.

The podcast can be found on their website.

The production of biohydrogen with negative CO2 emissions through the steam methane reforming of biomethane coupled with carbon capture and storage represents a promising technology particularly for industries that are difficult to electrify. In spite of the maturity of this technology which is currently employed in the production of grey and blue hydrogen a detailed cost model that considers the entire supply chain is lacking in the literature. This study addresses this gap by applying correlations derived from actual facilities producing grey and blue hydrogen to calculate the CAPEX while exploring various feedstock combinations for biogas generation to assess the OPEX. The analysis also includes logistic aspects such as decentralised biogas production and the transportation and storage of CO2 . The levelized cost of golden hydrogen is estimated to range from EUR 1.84 to 2.88/kg compared to EUR 1.47/kg for grey hydrogen and EUR 1.93/kg for blue hydrogen assuming a natural gas cost of EUR 25/MWh and excluding the CO2 tax. This range increases to between 3.84 and 2.92 with a natural gas cost of EUR 40/MWh with the inclusion of the CO2 tax. A comparison with conventional green hydrogen is performed highlighting both prices and potential thereby offering valuable information for decision-making.

Alternative fuels of low or zero carbon content can decarbonise the shipping operations. This study aims at assessing the lifetime environmental-economic sustainability of ammonia and hydrogen as alternatives to diesel fuel for short sea shipping cargo vessels. A model is employed to calculate key performance indicators representing the lifetime financial sustainability and environmental footprint of the case ship using a realistic operating profile and considering several scenarios with different diesel substitution rates. Scenarios meeting the carbon emissions reduction targets set by the International Maritime Organisation (IMO) for 2030 are identified whereas policy measures for their implementation including the emissions taxation are discussed. The derived results demonstrate that the future implementation of carbon emissions taxation in the ranges of 136–965 €/t for hydrogen and 356–2647 €/t for ammonia can support these fuels financial sustainability in shipping. This study provides insights for adopting zero-carbon fuels and as such impacts the de-risking of shipping decarbonisation.

Blending hydrogen with natural gas (NG) is an efficient method for transporting hydrogen on a large scale at a low cost. The manifold at the NG initial station is an important piece of equipment that enables the blending of hydrogen with NG. However there are differences in the components and component contents of imported NG from different countries. The components of hydrogen-blended NG can affect the safety and efficiency of transportation through pipeline systems. Therefore numerical simulations were performed to investigate the blending process and changes in the thermodynamic properties of four imported NGs and hydrogen in the manifold. The higher the heavy hydrocarbon content in the imported NG the longer the distance required for the gas to mix uniformly with hydrogen in the pipeline. Hydrogen blending reduces the temperature and density of NG. The gas composition is the main factor affecting the molar calorific value of a gas mixture and hydrogen blending reduces the molar calorific value of NG. The larger the content of high-molar calorific components in the imported NG the higher the molar calorific value of the gas after hydrogen blending. Increasing both the temperature and hydrogen mixing ratio reduces the Joule-Thomson coefficient of the hydrogen-blended NG. The results of this study provide technical references for the transport of hydrogen-blended NG.

The decarbonization of the energy sector has been a subject of research and of political discussions for several decades gaining significant attention in the last years. It is commonly acknowledged that the most obvious way to achieve decarbonization is the use of renewable energy sources. Within the context of the energy sector decarbonization many mainly industrialized countries recently started developing national plans to establish a hydrogen-based economy in the very near future. The plans for green hydrogen initially try to (a) target sectors that are difficult to decarbonize and (b) address issues related to the storage and transportation of CO2-free energy. To achieve almost complete decarbonization electric power must be generated exclusively from renewable sources. In so-called Power-to-X (PtX) technologies green hydrogen is generated from electricity and subsequently converted to another energy carrier which can be further stored transported and used. In PtX X stands for example for liquid hydrogen methanol or ammonia. The challenges associated with decarbonization include those associated with (a) the expansion of renewable energies (e.g. high capital demand political and social issues) (b) the production transportation and storage of hydrogen and the energy carriers denoted by X in PtX (e.g. high cost and low overall efficiency) and (c) the expected significant increase in the demand for electrical energy. The paper discusses whether and under which conditions the current national and international hydrogen plans of many industrialized countries could lead to a maximization of decarbonization in the world. It concludes that in general as long as the conditions for generating large excess amounts of green electricity are not met the quick establishment of a hydrogen economy could not only be very expensive but also counterproductive to the worldwide decarbonization efforts.

Recent targets have increased pressure for the maritime sector to accelerate the uptake of clean fuels. A potential future fuel for shipping is hydrogen however there is a common perception that the volume requirements for this fuel are too large for deep sea shipping. This study has developed a range of techniques to accurately simulate the fuel requirements of hydrogen for a case study vessel. Hydrogen can use fuel cells which achieve higher efficiencies than combustion methods but may require a battery hybrid system to meet changes in demand. A series of novel models for different fuel cell types and other technologies have been developed. The models have been used to run dynamic simulations for different energy system setups. Simulations tested against power profiles from real-world shipping data to establish the minimum viable setup capable of meeting all the power demand for the case study vessel to a higher degree of accuracy than previously achieved. Results showed that the minimum viable setup for hydrogen was with liquid storage a 105.6 MW PEM fuel cell stack and 6.9 MWh of batteries resulting in a total system size of 8934 m3 . Volume requirement results could then be compared to other concepts such as systems using ammonia and methanol 8970 m3 and 6033 m3 respectively.

Global warming is an accepted fact of life on Earth posing grave consequences in the form of weather patterns with life-threatening outcomes for inhabitants and their cultures especially those of island countries. These wild and unpredictable weather patterns have persuaded authorities governments and industrial leaders to adapt a range of solutions to combat the temperature rise on Earth. One such solution is to abandon fossil fuels (hydrocarbons) for energy generation and employ renewable energy sources or at least use energy sources that do not generate greenhouse gases. One such energy carrier is hydrogen which is expected to slowly replace natural gas and will soon be pumped into the energy distribution pipeline network. Since the current energy distribution network was designed for hydrocarbons its use for hydrogen may pose some threat to the safety of urban society. This is the first time an overview article has examined the replacement of hydrocarbons by hydrogen from a totally different angle by incorporating material science viewpoints. This article discusses hydrogen properties and warns about the issue of hydrogen embrittlement in the current pipeline network if hydrogen is to be pumped through the current energy distribution network i.e. pipelines. It is recommended that sufficient study and research be planned and carried out to ensure the safety of using the current energy distribution network for hydrogen distribution and to set the necessary standards and procedures for future design and construction.

As part of executing 25 hydrogen-based Power to X (PtX) projects our team of Safety consultants has completed safety and risk assessments for a number of hydrogen production developments. Drawing on this experience we will present the importance of making comparisons between hydrogen specific data sources such as HyRAM and conventional oil and gas data sets and calculation methods to ensure that project design is carried out to the most appropriate data and provides a robust solution to demonstrate risks are managed. This presentation will be based on case studies where Fire and Explosion Risk Assessments (FERA) and Quantitative Risk Assessments (QRA) were conducted. The frequency calculations for these assessments used the release frequencies and ignition probabilities provided in HyRAM. However it is noted that the HyRAM ignition probabilities are derived from a correlation from oil and gas assessments in the 1990s. The oil and gas approach has moved on from this data source and now derives ignition probabilities based on the type of facility and fluid characteristics. To address this evolution a comparison was made between the leak frequencies for equipment in hydrogen service and established oil and gas release frequencies from IOGP. In addition a comparison between the HyRAM recommended ignition probabilities and the correlations used for oil and gas (from OEUK formerly UKOOA) was conducted. By taking this approach it was confirmed that the UKOOA data was more conservative and sensitivity calculations were carried out. It was also noted that as hydrogen technologies are emerging there is a level of uncertainty around the data and comparisons must be regularly made to ensure the most appropriate basis for calculations is used.

Quantitative Risk Assessment (QRA) is a risk-informed approach that considers past performances and the likelihood of events and distinguishes must-haves from nice-to-haves. Following the approach applied for the HyRAM code developed by the Sandia National Laboratories a QRA toolkit for hydrogen systems was developed using MATLAB by Canadian Nuclear Laboratories (CNL). Based on user inputs for system components and their operating parameters the toolkit calculates the consequence of a hydrogen leak from the system. The fatality likelihood can be estimated from the severity of a person’s exposure to radiant heat flux (from a jet fire) and overpressure (from an explosion). This paper presents a verification and validation exercise by comparing the CNL model predictions with the HyRAM code and available experimental data including a QRA case study for a locomotive. The analysis produces risk contours recommending personnel (employees/public) numbers time spent and safe separation distances near the incident (during maintenance or an accident). The case study demonstrated the importance of hydrogen leak sensors’ reliability for leak detection and isolation. The QRA toolkit calculates a more practical value of the safe separation distance for hydrogen installations and provides evidence to support communication with authorities and other stakeholders for decision-making.

The European Union aims to increase its climate ambition and achieve climate neutrality by 2050. This necessitates expanding offshore wind energy and green hydrogen production especially for hard-to-abate industrial sectors. A study examines the impact of green hydrogen on offshore wind projects specifically focusing on a potential future North Sea offshore grid. The study utilizes data from the TYNDP 2020 Global Ambition scenario 2040 considering several European countries. It aims to assess new transmission and generation capacity utilization and understand the influencing factors. The findings show that incorporating green hydrogen production increases offshore wind utilization and capture prices. The study estimates that by 2040 the levelized cost of hydrogen could potentially decrease to e1.2-1.6/kg H2 assuming low-cost electricity supply and declining capital costs of electrolysers. These results demonstrate the potential benefits and cost reductions of integrating green hydrogen production into North Sea offshore wind projects.

Hydrogen is emerging as one of the most promising energy carriers for a decarbonised global energy system. Transportation and storage of hydrogen are critical to its large-scale adoption and to these ends liquid hydrogen is being widely considered. The liquefaction and storage processes must however be both safe and efficient for liquid hydrogen to be viable as an energy carrier. Identifying the most promising liquefaction processes and associated transport and storage technologies is therefore crucial; these need to be considered in terms of a range of interconnected parameters ranging from energy consumption and appropriate materials usage to considerations of unique liquid-hydrogen physics (in the form of ortho–para hydrogen conversion) and boil-off gas handling. This study presents the current state of liquid hydrogen technology across the entire value chain whilst detailing both the relevant underpinning science (e.g. the quantum behaviour of hydrogen at cryogenic temperatures) and current liquefaction process routes including relevant unit operation design and efficiency. Cognisant of the challenges associated with a projected hydrogen liquefaction plant capacity scale-up from the current 32 tonnes per day to greater than 100 tonnes per day to meet projected hydrogen demand this study also reflects on the next-generation of liquid-hydrogen technologies and the scientific research and development priorities needed to enable them.

South Korea has drawn up plans to reduce greenhouse gases by 29.7 million tons by supplying 4.5 million electric and hydrogen cars by 2030 to implement the “2050 carbon neutrality” goal. This article gathers data on public preferences for electric cars (ECs) over hydrogen cars (HCs) in the commercial vehicle transportation sector through a survey of 1000 people. Moreover the strength of the preference was evaluated on a five-point scale. Of all respondents 60.0 percent preferred ECs and 21.0 percent HCs the former being 2.86 times greater than the latter. On the other hand the strength of the preference for HCs was 1.42 times greater than that for ECs. Factors influencing the preference for ECs over HCs were also explored through adopting the ordered probit model which is useful in examining ordinal preference rather than cardinal preference. The analyzed factors which are related to respondents’ characteristics experiences and perceptions can be usefully employed for developing strategies of promoting carbon neutrality in the commercial vehicle transportation sector and preparing policies to improve public acceptance thereof.

Environmental concerns such as global warming and human health damage are intensifying and the transportation sector significantly contributes to carbon and harmful emissions. This review examines the life cycle assessment (LCA) of alternative fuels (AF) evaluating current research on fuel types LCA framework development life cycle inventory (LCI) and impact selection. The objectives of this paper are: (1) to compare various AF LCA frameworks and develop a comprehensive framework for the transportation sector; (2) to identify emission hotspots of different AFs through simulations and real-world cases; (3) to review AF LCA research; (4) to extract valuable information for potential future research directions. The analysis reveals that all stages except for hydrogen use have an environmental impact. LCA boundaries and LCIs vary considerably depending on the raw materials production processes and products involved leading to different emission hotspots. Due to knowledge or data limitations some stages remain uncalculated in the current study emphasizing the need for further refinement of the AF LCI. Future research should also explore the various impacts of widespread adoption of alternative fuels in transportation encompassing social economic and environmental aspects. Lastly the review provides structured recommendations for future research directions.

Canada’s commitment to be net-zero by 2050 combined with ATCO’s own Environmental Social and Governance goals has led ATCO to pursue hydrogen blending within the existing natural gas system to reduce CO2 emissions while continuing to provide safe reliable energy service to customers. Utilization of hydrogen in the distribution system is the least-cost alternative for decarbonizing the heating loads in jurisdictions like Alberta where harsh winter climates are encountered and low-carbon hydrogen production can be abundant. ATCO’s own Fort Saskatchewan Hydrogen Blending Project began blending 5% hydrogen by volume to over 2100 customers in the Fall of 2022 and plans to increase the blend rates to 20% hydrogen in 2023. Prior to blending ATCO worked together with DNV to examine the impact of hydrogen blended natural gas to twelve Canadian appliances: range/stove oven garage heater high and medium efficiency furnaces conventional and on demand hot water heaters barbeque clothes dryer radiant heater and two gas fireplaces. The tests were performed not only within the planned blend rates of 0-20% hydrogen but also to higher percentages to determine how much hydrogen can be blended into a system before appliance retrofits would be required. The testing was designed to get insights on safety-related combustion issues such as flash-back burner overheating flame detection and other performance parameters such as emissions and burner power. The experimental results indicate that the radiant heater is the most sensitive appliance for flashback observed at 30 vol% hydrogen in natural gas. At 50% hydrogen the range and the radiant burner of the barbeque tested were found to be sensitive to flashback. All other 9 appliances were found to be robust for flashback with no other short-term issues observed. This paper will detail the findings of ATCO and DNV’s appliance testing program including results on failure mechanisms and sensitivities for each appliance.

Hydrogen Fuel Cell Electric Vehicles (HFC EVs) represent an alternative to replace current internal combustion engine vehicles. The use of these vehicles with storage of compressed gaseous hydrogen (CGH2) in confined spaces such as tunnels underground car parks etc. creates new challenges to ensure the protection of people and property and to keep the risk at an acceptable level. The HYTUNNEL-CS project sponsored by the FCH-JU was launched to develop validated hazard and risk assessment tools for the behavior of hydrogen leaks in tunnels. Among the experiments carried out in support of the validation tools the CEA has conducted tests on gas dispersion in a full-scale tunnel geometry. In the tests carried out hydrogen is replaced by helium under a pressure of 70 MPa in a 78 liter tank. The car is simulated by a flat plate called chassis and the discharges are made either downwards under the chassis or upwards to take into account a rollover of the car during the accident. Different thermally activated pressure relief device (TPRD) diameters are examined as well as different orientations of the discharge. Finally the mixing transient of helium with air is measured for distances between -50 and +50m from the release. Performing CFD simulations of such an under-expanded jet in an environment as large as a road tunnel demands a compressible flow solver and so a large computational cost. To optimize this cost a notional nozzle approach is generally used to replace the under-expanded jet by a subsonic jet that has the same concentration dilution behavior. The physics at the injection point is then not resolved and a model of these boundary conditions has to be implemented. This article first reviews the main experimental results. Then a model of boundary conditions is proposed to have a subsonic hydrogen jet that matches the dilution characteristics of an under-expanded jet. Furthermore this model is implemented in the TRUST LES computer code and in the Neptune-CFD RANS computer code in order to simulate some helium dispersion experiments. Finally results from the CFD simulations are compared to the experimental results and the effect of the exact shape of the tunnel is also assessed by comparing simulations with idealized flat walls and real scanned walls.

Offshore renewables are expected to play a significant role in achieving the ambitious emission targets set by the North Sea countries. Among other factors energy technology costs and their cost reduction potential determine their future role in the energy system. While fixed-bottom offshore wind is well-established and competitive in this region generation costs of other emerging offshore renewable technologies remain high. Hence it is vital to better understand the future role of offshore renewables in the North Sea energy system and the impact of technological learning on their optimal deployments which is not well-studied in the current literature. This study implements an improved framework of integrated energy system analysis to overcome the stated knowledge gap. The approach applies detailed spatial constraints and opportunities of energy infrastructure deployment in the North Sea and also technology cost reduction forecasts of offshore renewables. Both of these parameters are often excluded or overlooked in similar analyses leading to overestimation of benefits and technology deployments in the energy system. Three significant conclusions are derived from this study. First offshore wind plays a crucial role in the North Sea power sector where deployment grows to a maximum of 498 GW by 2050 (222 GW of fixed-bottom and 276 GW of floating wind) from 100 GW in 2030 contributing up to 51% of total power generation and declining cumulative system cost of power and hydrogen system by 4.2% (approx. 40 billion EUR in cost savings) when compared with the slow learning and constrained space use case. Second floating wind deployment is highly influenced by its cost reduction trend and ability to produce hydrogen offshore; emphasizing the importance of investing in floating wind in this decade as the region lacks commercial deployments that would stimulate its cost reduction. Also the maximum floating wind deployment in the North Sea energy system declined by 70% (162 GW from 276 GW) when offshore hydrogen production was avoided while fixed-bottom offshore wind deployment remains unchanged. Lastly the role of other emerging offshore renewables remains limited in all scenarios considered as they are expensive compared to other technology choices in the system. However around 8 GW of emerging technologies was observed in Germany and the Netherlands when the deployment potential of fixed-bottom offshore wind became exhausted.

The analysis of Carbon Footprint (CF) for technology of hydrogen production from cleaned coke oven gas was performed. On the basis of real data and simulation calculations of the production process of hydrogen from coke gas emission indicators of carbon dioxide (CF) were calculated. These indicators are associated with net production of electricity and thermal energy and direct emission of carbon dioxide throughout a whole product life cycle. Product life cycle includes: coal extraction and its transportation to a coking plant the process of coking coal purification and reforming of coke oven gas carbon capture and storage. The values were related to 1 Mg of coking blend and to 1 Mg of the hydrogen produced. The calculation is based on the configuration of hydrogen production from coke oven gas for coking technology available on a commercial scale that uses a technology of coke dry quenching (CDQ). The calculations were made using ChemCAD v.6.0.2 simulator for a steady state of technological process. The analysis of carbon footprint was conducted in accordance with the Life Cycle Assessment (LCA).

The integration of wind and solar energy with green hydrogen technologies represents an innovative approach toward achieving sustainable energy solutions. This review examines state-ofthe-art strategies for synthesizing renewable energy sources aimed at improving the efficiency of hydrogen (H2 ) generation storage and utilization. The complementary characteristics of solar and wind energy where solar power typically peaks during daylight hours while wind energy becomes more accessible at night or during overcast conditions facilitate more reliable and stable hydrogen production. Quantitatively hybrid systems can realize a reduction in the levelized cost of hydrogen (LCOH) ranging from EUR 3.5 to EUR 8.9 per kilogram thereby maximizing the use of renewable resources but also minimizing the overall H2 production and infrastructure costs. Furthermore advancements such as enhanced electrolysis technologies with overall efficiencies rising from 6% in 2008 to over 20% in the near future illustrate significant progress in this domain. The review also addresses operational challenges including intermittency and scalability and introduces system topologies that enhance both efficiency and performance. However it is essential to consider these challenges carefully because they can significantly impact the overall effectiveness of hydrogen production systems. By providing a comprehensive assessment of these hybrid systems (which are gaining traction) this study highlights their potential to address the increasing global energy demands. However it also aims to support the transition toward a carbon-neutral future. This potential is significant because it aligns with both environmental goals and energy requirements. Although challenges remain the promise of these systems is evident.

The advancement of sustainable solutions through renewable energy sources is crucial to mitigate carbon emissions. This study reports a novel system for an airport utilizing geothermal biomass and PV solar energy sources. The proposed system is capable of producing five useful outputs including electrical power hot water hydrogen kerosene and space heating. In open literature there has been no system reported with these combination of energy sources and outputs. The system is considered for Vancouver Airport using the most recent statistics available. The geothermal sub-system introduced is also unique which utilizes carbon dioxide captured as the heat transfer medium for power generation and heating. The present system is considered using thermodynamic analysis through energetic and exergetic approaches to determine the variation in system performance based on different annual climate conditions. Biomass gasification and kerosene production are evaluated based on the Aspen Plus models. The efficiencies of the geothermal system with the carbon dioxide reservoir are found to have energetic and energetic efficiencies of 78 % and 37 % respectively. The total hydrogen production projection is obtained to be 452 tons on an annual basis. The kerosene production mass flow rate is reported as 0.112 kg/s. The overall energetic and exergetic efficiencies of the system are found to be 41.8 % and 32.9 % respectively. This study offers crucial information for the aviation sector to adopt sustainable solutions more effectively.

Hydrogen has emerged as a promising alternative to meet the growing demand for sustainable and renewable energy sources. Underground hydrogen storage (UHS) in depleted gas reservoirs holds significant potential for large-scale energy storage and the seamless integration of intermittent renewable energy sources due to its capacity to address challenges associated with the intermittent nature of renewable energy sources ensuring a steady and reliable energy supply. Leveraging the existing infrastructure and well-characterized geological formations depleted gas reservoirs offer an attractive option for large-scale hydrogen storage implementation. However significant knowledge gaps regarding storage performance hinder the commercialization of UHS operation. Hydrogen deliverability hydrogen trapping and the equation of state are key areas with limited understanding. This literature review critically analyzes and synthesizes existing research on hydrogen storage performance during underground storage in depleted gas reservoirs; it then provides a high-level risk assessment and an overview of the techno-economics of UHS. The significance of this review lies in its consolidation of current knowledge highlighting unresolved issues and proposing areas for future research. Addressing these gaps will advance hydrogen-based energy systems and support the transition to a sustainable energy landscape. Facilitating efficient and safe deployment of UHS in depleted gas reservoirs will assist in unlocking hydrogen’s full potential as a clean and renewable energy carrier. In addition this review aids policymakers and the scientific community in making informed decisions regarding hydrogen storage technologies.

Tunisia's rapid industrial expansion and population growth have created a pressing energy deficit despite the country's significant yet largely untapped renewable energy potential. This study addressed this challenge by developing a comprehensive framework to identify and evaluate strategies for promoting green hydrogen production from renewable energy sources in Tunisia. A Strength Weakness Opportunity and Threat (SWOT) analysis incorporating social economic and environmental dimensions was conducted to formulate potential solutions. The Step-wise Weight Assessment Ratio Analysis (SWARA) method facilitated the weighting of SWOT factors and subfactors. Subsequently a multi-criteria decision-making approach employing the gray technique for order preference by similarity to ideal solution (TOPSIS-G) method (validated by gray additive ratio assessment (ARAS-G) gray complex proportional assessment (COPRAS-G) and gray multi-objective optimization by ratio analysis (MOORA-G) was used to rank the identified strategies. The SWOT analysis revealed "Strengths" as the most influential factor with a relative weight of 47.3% followed by "Weaknesses" (26.5%) "Threats" (15.6%) and "Opportunities" (10.6%). Specifically experts emphasized Tunisia's renewable energy potential (21.89%) and robust power system (12.11%) as primary strengths. Conversely high investment costs (11.2%) and political instability (7.77%) posed substantial threat. Positive socio-economic impacts represented a key opportunity with a score of 5.2%. As for the strategies prioritizing criteria production cost ranked first with a score of 13.5% followed by environmental impact (12.8%) renewable energy potential (12.0%) and mitigation costs (11.3%). The gray TOPSIS analysis identified two key strategies: leveraging Tunisia's wind and solar resources and fostering regional cooperation for project implementation. The robustness of these strategies is confirmed by the strong correlation between TOPSIS-G ARAS-G COPRAS-G and MOORA-G results. Overall the study provides a comprehensive roadmap and expert-informed decision-support tools offering valuable insights for policymakers investors and stakeholders in Tunisia and other emerging economies facing similar energy challenges.

The use of hydrogen as an energy carrier within the scope of the decarbonisation of the world’s energy production and utilisation is seen by many as an integral part of this endeavour. However the discussion around hydrogen technologies often lacks some perspective on the currently available technologies their Technology Readiness Level (TRL) scope of application and important performance parameters such as energy density or conversion efficiency. This makes it difficult for the policy makers and investors to evaluate the technologies that are most promising. The present study aims to provide help in this respect by assessing the available technologies in which hydrogen is used as an energy carrier including its main challenges needs and opportunities in a scenario in which fossil fuels still dominate global energy sources but in which renewables are expected to assume a progressively vital role in the future. The production of green hydrogen using water electrolysis technologies is described in detail. Various methods of hydrogen storage are referred including underground storage physical storage and material-based storage. Hydrogen transportation technologies are examined taking into account different storage methods volume requirements and transportation distances. Lastly an assessment of well-known technologies for harnessing energy from hydrogen is undertaken including gas turbines reciprocating internal combustion engines and fuel cells. It seems that the many of the technologies assessed have already achieved a satisfactory degree of development such as several solutions for high-pressure hydrogen storage while others still require some maturation such as the still limited life and/or excessive cost of the various fuel cell technologies or the suitable operation of gas turbines and reciprocating internal combustion engines operating with hydrogen. Costs below 200 USD/kWproduced lives above 50 kh and conversion efficiencies approaching 80% are being aimed at green hydrogen production or electricity production from hydrogen fuel cells. Nonetheless notable advances have been achieved in these technologies in recent years. For instance electrolysis with solid oxide cells may now sometimes reach up to 85% efficiency although with a life still in the range of 20 kh. Conversely proton exchange membrane fuel cells (PEMFCs) working as electrolysers are able to sometimes achieve a life in the range of 80 kh with efficiencies up to 68%. Regarding electricity production from hydrogen the maximum efficiencies are slightly lower (72% and 55% respectively). The combination of the energy losses due to hydrogen production compression storage and electricity production yields overall efficiencies that could be as low as 25% although smart applications such as those that can use available process or waste heat could substantially improve the overall energy efficiency figures. Despite the challenges the foreseeable future seems to hold significant potential for hydrogen as a clean energy carrier as the demand for hydrogen continues to grow particularly in transportation building heating and power generation new business prospects emerge. However this should be done with careful regard to the fact that many of these technologies still need to increase their technological readiness level before they become viable options. For this an emphasis needs to be put on research innovation and collaboration among industry academia and policymakers to unlock the full potential of hydrogen as an energy vector in the sustainable economy.

This review critically examines hydrogen energy systems highlighting their capacity to transform the global energy framework and mitigate climate change. Hydrogen showcases a high energy density of 120 MJ/kg providing a robust alternative to fossil fuels. Adoption at scale could decrease global CO2 emissions by up to 830 million tonnes annually. Despite its potential the expansion of hydrogen technology is curtailed by the inefficiency of current electrolysis methods and high production costs. Presently electrolysis efficiencies range between 60 % and 80 % with hydrogen production costs around $5 per kilogram. Strategic advancements are necessary to reduce these costs below $2 per kilogram and push efficiencies above 80 %. Additionally hydrogen storage poses its own challenges requiring conditions of up to 700 bar or temperatures below −253 °C. These storage conditions necessitate the development of advanced materials and infrastructure improvements. The findings of this study emphasize the need for comprehensive strategic planning and interdisciplinary efforts to maximize hydrogen's role as a sustainable energy source. Enhancing the economic viability and market integration of hydrogen will depend critically on overcoming these technological and infrastructural challenges supported by robust regulatory frameworks. This comprehensive approach will ensure that hydrogen energy can significantly contribute to a sustainable and low-carbon future.

In order to reduce carbon emissions the effects of gas composition and initial turbulence on the premixed flame dynamics of hydrogen-blended natural gas were investigated. The results show that an increase in hydrogen content leads to earlier formation of flame wrinkles. When the equivalence ratio is 1 and hydrogen blending ratio is below 20% Tulip flames appear approximately 2.25 m away from the ignition point. When hydrogen blending ratio exceeds 20% Tulip flames appear approximately 1.3 m away from the ignition point and twisted Tulip flames appear approximately 2.5 m away from the ignition position. During the 0.05 m process of flame propagation downstream from ignition point flame propagation velocity increases by about 2 m/s for every 10% increase in hydrogen content. The increase in hydrogen content has the most significant impact on the flame propagation velocity during the ignition stage. The average flame propagation velocity increases with the increase of hydrogen blending ratio. The greater the initial turbulence the more obvious the stretching deformation of flame front structure. With the increase of wind speed the flame propagation velocity first increases and then decreases. At a wind speed of 3 m/s the flame propagation velocity reaches its maximum value.

Hydrogen (2 ) has a big role to play in energy transition to achieve net-zero carbon emissions by 2050. For 2 to compete with other fuels in the energy market more research is required to mitigate key issues like greenhouse gas (GHG) emissions safety and end-use costs. For these reasons a software-supported technical overview of 2 production storage transportation and utilisation is introduced. Drawbacks and mitigation approaches for 2 technologies were highlighted. The recommended areas include solar thermal or renewable-powered plasma systems for feedstock preheating and oxy-hydrogen combustion to meet operating temperatures and heat duties due to losses; integration of electrolysis of 2 into hydrocarbon reforming methods to replace air separation unit (ASU); use of renewable power sources for electrical units and the introduction of thermoelectric units to maximise the overall efficiency. Furthermore a battolyser system for small-scale energy storage; new synthetic hydrides with lower absorption and desorption energy; controlled parameters and steam addition to the combustor/cylinder and combustors with fitted heat exchangers to reduce emissions and improve the overall efficiency are also required. This work also provided detailed information on any of these systems implementations based on location factors and established a roadmap for 2 production and utilisation. The proposed 2 production technologies are hybrid pyrolysis-electrolysis and integrated AD-MEC and DR systems using renewable bioelectrochemical and low-carbon energy systems. Production and utilisation of synthetic natural gas (NG) using renewablepowered electrolysis of 2 oxy-fuel and direct air capture (DAC) is another proposed 2 energy system for a sustainable 2 economy. By providing these factors and information researchers can work towards pilot development and further efficiency enhancement.

In this study we employ an optimization model to optimally design a self-sufficient independent of any imports and exports hydrogen infrastructure for Austria by 2030. Our approach integrates key hydrogen technologies within a detailed spatial investment and operation model – coupled with a European scale electricity market model. We focus on optimizing diverse infrastructure componentsincluding trailers pipelines electrolyzers and storages to meet Austria's projected hydrogen demand. To accurately estimate this demand in hourly resolution we combine existing hydrogen strategies and projections to account for developments in various industrial sectors consider demand driven by the transport sector and integrate hydrogen demand arising from its use in gas-powered plants. Accounting for the inherent uncertainty linked to such projections we run the analysis for two complementary scenarios. Our approach addresses the challenges of integrating large quantities of renewable hydrogen into a future energy system by recognizing the critical role of domestic production in the early market stages. The main contribution of this work is to address the gap in optimizing hydrogen infrastructure for effective integration of domestic renewable hydrogen production in Austria by 2030 considering sector coupling potentials optimal electrolyzer placement and the design of local hydrogen networks.

Clean energy vehicles (CEVs) e.g. battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) are being adopted gradually to substitute for internal combustion engine vehicles (ICEVs) around the world. The fueling infrastructure is one of the key drivers for the development of the CEV market. When the government develops funding policies to support the fueling infrastructure development for FCEVs and BEVs it has to assess the effectiveness of different policy options and identify the optimal policy combination which is very challenging in transportation research. In this paper we develop a system dynamics model to study the feedback mechanism between the fueling infrastructure funding policies and the medium- to long-term diffusion of FCEVs and BEVs and the competition between FCEVs and BEVs based on relevant policy and market data in Guangzhou China. The results of the modeling analysis are as follows. (1) Funding hydrogen refueling stations and public charging piles has positive implications for achieving the substitution of CEVs for ICEVs. (2) Adjusting the funding ratio of hydrogen refueling stations and public charging piles or increasing the funding budget and extending the funding cycle does not have a significant impact on the overall substitution of CEVs for ICEVs but only impacts the relative competitive advantage between FCEVs and BEVs. (3) An equal share of funding for hydrogen refueling stations and public charging piles would have better strategic value for future net-zero-emissions urban transportation. (4) Making a moderate-level full investment in hydrogen refueling stations coupled with hydrogen refueling subsidies can provide the ideal conditions for FCEV diffusion.

Hydrogen (H2 ) is positioned as a key solution to the decarbonization challenge in both the energy and transportation sectors. While hydrogen is a clean and versatile energy carrier it poses significant safety risks due to its wide flammability range and high detonation potential. Hydrogen leaks can occur throughout the hydrogen value chain including production storage transportation and utilization. Thus effective leak detection systems are essential for the safe handling storage and transportation of hydrogen. This review aims to survey relevant codes and standards governing hydrogen-leak detection and evaluate various sensing technologies based on their working principles and effectiveness. Our analysis highlights the strengths and limitations of the current detection technologies emphasizing the challenges in achieving sensitive and specific hydrogen detection. The results of this review provide critical insights into the existing technologies and regulatory frameworks informing future advancements in hydrogen safety protocols.

This paper investigates innovative solutions to enhance the performance and lifespan of standalone photovoltaic (PV)-based microgrids with a particular emphasis on off-grid communities. A major challenge in these systems is the limited lifespan of batteries. To overcome this issue researchers have created hybrid energy storage systems (HESS) along with advanced power management strategies. This study introduces innovative multi-level HESS approaches and a related energy management strategy designed to alleviate the charge/discharge stress on batteries. Comprehensive Matlab Simulink models of various HESS topologies within standalone PV microgrids are utilized to evaluate system performance under diverse weather conditions and load profiles for rural site. The findings reveal that the proposed HESS significantly extends battery life expectancy compared to existing solutions. Furthermore the paper presents a novel energy management strategy based on the Reduced Fractional Gradient Descent (RFGD) algorithm optimization tailored for hybrid systems that include photovoltaic fuel cell battery and supercapacitor components. This strategy aims to minimize hydrogen consumption of Fuel Cells (FCs) thereby supporting the production of green ammonia for local industrial use. The RFGD algorithm is selected for its minimal user-defined parameters and high convergence efficiency. The proposed method is compared with other algorithms such as the Lyrebird Optimization Algorithm (LOA) and Osprey Optimization Algorithm (OOA). The RFGD algorithm exhibits superior accuracy in optimizing energy management achieving a 15% reduction in hydrogen consumption. Its efficiency is evident from the reduced computational time compared to conventional algorithms. Although minor losses in computational resources were observed they were substantially lower than those associated with traditional optimization techniques. Overall the RFGD algorithm offers a robust and efficient solution for enhancing the performance of hybrid energy systems.

The derivation of an efficient operational strategy for storing intermittent renewable energies using a hybrid battery-hydrogen energy storage system is a difficult task. One approach for deriving an efficient operational strategy is using mathematical optimization in the context of model predictive control. However mathematical optimization derives an operational strategy based on a non-exact mathematical system representation for a specified prediction horizon to optimize a specified target. Thus the resulting operational strategies can vary depending on the optimization settings. This work focuses on evaluating potential improvements in the operational strategy for a hybrid batteryhydrogen energy storage system using mathematical optimization. To investigate the operation a simulation model of a hybrid energy storage system and a tailor-made mixed integer linear programming optimization model of this specific system are utilized in the context of a model predictive control framework. The resulting operational strategies for different settings of the model predictive control framework are compared to a rule-based controller to show the potential benefits of model predictive control compared to a conventional approach. Furthermore an in-depth analysis of different factors that impact the effectiveness of the model predictive controller is done. Therefore a sensitivity analysis of the effect of different electricity demands and resource sizes on the performance relative to a rule-based controller is conducted. The model predictive controller reduced the energy consumption by at least 3.9 % and up to 17.9% compared to a rule-based controller. Finally Pareto fronts for multi-objective optimizations with different prediction and control horizons are derived and compared to the results of a rule-based controller. A cost reduction of up to 47 % is achieved by a model predictive controller with a prediction horizon of 7 days and perfect foresight. Keywords: Model Predictive Control Optimization Mixed Integer Linear Programming Hybrid Battery-Hydrogen Energy Storage System

With the question of ‘can short messages be effective in increasing public support for a complex new technology (hydrogen)?‘ this study uses a representative national survey in Australia to analyze the differences and variations in subjective support for hydrogen in response to four differently framed short messages. The findings of this study show that short messages can increase social acceptance but the effects depend on how strongly the message is framed in terms of its alignment with either an economic or environmental values framework. Furthermore the effects depend on the social and cultural context of the receiver of the message.

This paper presents the application of an active energy management strategy to a hybrid system consisting of a proton exchange membrane fuel cell (PEMFC) battery and supercapacitor. The purpose of energy management is to control the battery and supercapacitor states of charge (SOCs) as well as minimizing hydrogen consumption. Energy management should be applied to hybrid systems created in this way to increase efficiency and control working conditions. In this study optimization of an existing model in the literature with different meta-heuristic methods was further examined and results similar to those in the literature were obtained. Ant lion optimizer (ALO) moth-flame optimization (MFO) dragonfly algorithm (DA) sine cosine algorithm (SCA) multi-verse optimizer (MVO) particle swarm optimization (PSO) and whale optimization algorithm (WOA) meta-heuristic algorithms were applied to control the flow of power between sources. The optimization methods were compared in terms of hydrogen consumption and calculation time. Simulation studies were conducted in Matlab/Simulink R2020b (academic license). The contribution of the study is that the optimization methods of ant lion algorithm moth-flame algorithm and sine cosine algorithm were applied to this system for the first time. It was concluded that the most effective method in terms of hydrogen consumption and computational burden was the sine cosine algorithm. In addition the sine cosine algorithm provided better results than similar meta-heuristic algorithms in the literature in terms of hydrogen consumption. At the same time meta-heuristic optimization algorithms and equivalent consumption minimization strategy (ECMS) and classical proportional integral (PI) control strategy were compared as a benchmark study as done in the literature and it was concluded that meta-heuristic algorithms were more effective in terms of hydrogen consumption and computational time.

This study develops a semi-empirical model of an alkaline water electrolyzer (AWE) based on thermodynamic and electrochemical principles to investigate cell voltage behavior during electrolysis. By importing polarization curve test data under specific operational conditions eight undefined parameters are precisely fitted demonstrating the model’s high accuracy in describing the voltage characteristics of alkaline electrolyzers. Additionally an AWE system model is introduced to examine the influence of various operational parameters on system efficiency. This innovative approach not only provides detailed insights into the operational dynamics of AWE systems but also offers a valuable tool for optimizing performance and enhancing efficiency advancing the understanding and optimization of AWE technologies.

The global trend towards decarbonization and the demand for energy security have put hydrogen energy into the spotlight of industry politics and societies. Numerous governments worldwide are adopting policies and strategies to facilitate the transition towards hydrogen-based economies. To assess the determinants of such transition this study presents a comparative analysis of the technological innovation systems (TISs) for hydrogen technologies in Germany and South Korea both recognized as global front-runners in advancing and implementing hydrogen-based solutions. By providing a multi-dimensional assessment of pathways to the hydrogen economy our analysis introduces two novel and crucial elements to the TIS analysis: (i) We integrate the concept of ‘quality infrastructure’ given the relevance of safety and quality assurance for technology adoption and social acceptance and (ii) we emphasize the social perspective within the hydrogen TIS. To this end we conducted 24 semi-structured expert interviews applying qualitative open coding to analyze the data. Our results indicate that the hydrogen TISs in both countries have undergone significant developments across various dimensions. However several barriers still hinder the further realization of a hydrogen economy. Based on our findings we propose policy implications that can facilitate informed policy decisions for a successful hydrogen transition.

This article presents a novel approach to the analysis of heat release in a hydrogen-fueled internal combustion spark-ignition engine with exhaust gas recirculation (EGR). It also discusses aspects of thermodynamic analysis common to modeling and empirical analysis. This new approach concerns a novel method of calculating the specific heat ratio (cp/cv) and takes into account the reduction in the number of moles during combustion which is characteristic of hydrogen combustion. This reduction in the number of moles was designated as a molar contraction. This is particularly crucial when calculating the average temperature during combustion. Subsequently the outcomes of experimental tests including the heat-release rate the initial combustion phase (denoted CA0- 10) and the main combustion phase (CA10-90) are presented. Furthermore the impact of exhaust gas recirculation on the combustion process in the engine is also discussed. The efficacy of the proposed measures was validated by analyzing the heat-release rate and calculating the mean combustion temperature in the engine. The application of EGR in the range 0-40% resulted in a notable prolongation of both the initial and main combustion phases which consequently influenced the mean combustion temperature.

This article discusses possible strategies for decarbonizing the energy systems of an existing port. The approach consists in creating a complete superstructure that includes the use of renewable and fossil energy sources the import or local production of hydrogen vehicles and other equipment powered by Diesel electricity or hydrogen and the associated refuelling and storage units. Two substructures are then identified one including all these options the other considering also the addition of the energy demand of an adjacent steel industry. The goal is to select from each of these two substructures the most cost-effective configurations for 2030 and 2050 that meet the emission targets for those years under different cost scenarios for the energy sources and conversion/storage units obtained from the most reliable forecasts found in the literature. To this end the minimum total cost of all the energy conversion and storage units plus the associated infrastructures is sought by setting up a Mixed Integer Linear Programming optimization problem where integer variables handle the inclusion of the different generation and storage units and their activation in the operational phases. The comprehensive picture of possible solutions set allows identifying which options can most realistically be realized in the years to come in relation to the different assumed cost scenarios. Optimization results related to the scenario projected to 2030 indicate the key role played by Diesel hybrid and electric systems while considering the most stringent or much more stringent scenarios for emissions in 2050 almost all vehicles energy demand and industry hydrogen demand is met by hydrogen imported as ammonia by ship.

A wide range of aircraft propulsion technologies is being investigated in current research to reduce the environmental impact of commercial aviation. As the implementation of purely hydrogenpowered aircraft may encounter various challenges on the airport and vehicle side combined hydrogen and kerosene energy sources may act as an enabler for the first operations with liquid hydrogen propulsion technologies. The presented studies describe the conceptual design of such a dual-fuel regional aircraft featuring a retrofit derived from the D328eco under development by Deutsche Aircraft. By electrically assisting the sustainable aviation fuel (SAF) burning conventional turboprop engines with the power of high-temperature polymer-electrolyte fuel cells the powertrain architecture enables a reduction of SAF consumption. All aircraft were modeled and investigated using the Bauhaus Luftfahrt Aircraft Design Environment. A description of this design platform and the incorporated methods to model the hydrogen-hybrid powertrain is given. Special emphasis was laid on the implications of the hydrogen and SAF dual-fuel system design to be able to assess the potential benefits and drawbacks of various configurations with the required level of detail. Retrofit assumptions were applied particularly retaining the maximum takeoff mass while reducing payload to account for the propulsion system mass increase. A fuel cell power allocation of 20% led to a substantial 12.9% SAF consumption decrease. Nonetheless this enhancement necessitated an 18.1% payload reduction accompanied by a 34.5% increment in propulsion system mass. Various additional studies were performed to assess the influence of the power split. Under the given assumptions the design of such a retrofit was deemed viable.

As new sources of energy and advanced technologies are used there is a continuous evolution in energy supply demand and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies elucidating their respective merits and challenges. Furthermore this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.

Updates to the separation distances between different exposures and bulk liquid hydrogen systems are included in the 2023 version of NFPA 2: Hydrogen Technologies Code. This work details the models and calculations leading to those distances. The specific models used including the flow of liquid hydrogen through an orifice within the Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HyRAM+) toolkit are described and discussed to emphasize challenges specific to liquid hydrogen systems. Potential hazards and harm affecting individual exposures (e.g. ignition sources air intakes) for different unignited concentrations overpressures and heat flux levels were considered and exposures were grouped into three bins. For each group the distances to a specific hazard criteria (e.g. heat flux level) for a characteristic leak size informed by a risk-analysis led to a hazard distance. The maximum hazard distance within each group was selected to determine a table of separation distances based on internal pressure and pipe size rather than storage volume similar to the bulk gaseous separation distance tables in NFPA 2. The new separation distances are compared to the previous distances and some implications of the updated distances are given.

Growing renewable energy deployment worldwide has sparked a shift in the energy landscape with far-reaching geopolitical ramifications. Hydrogen’s role as an energy carrier is central to this change facilitating global trade and the decarbonisation of hard-to-abate sectors. This analysis offers a new method for optimally sizing solar/wind-to-hydrogen systems in specifically suitable locations. These locations are limited to the onshore and offshore regions of selected countries as determined by a bespoke geospatial analysis developed to be location-agnostic. Furthermore the research focuses on determining the best configurations for such systems that minimise the cost of producing hydrogen with the optimisation algorithm expanding from the detailed computation of the classic levelised cost of hydrogen. One of the study’s main conclusions is that the best hybrid configurations obtained provide up to 70% cost savings in some areas. Such findings represent unprecedented achievements for Italy and Portugal and can be a valuable asset for economic studies of this kind carried out by local and national governments across the globe. These results validate the optimisation model’s initial premise significantly improving the credibility of this work by constructively challenging the standard way of assessing large-scale green hydrogen projects.

With the aim of reducing carbon emissions and seeking independence from Russian gas in the wake of the conflict in Ukraine the use of hydrogen in the European Union is expected to rise in the future. In this regard hydrogen transport via pipeline will become increasingly crucial either through the utilization of existing natural gas infrastructure or the construction of new dedicated hydrogen pipelines. This study investigates the effects of hydrogen blending in existing pipelines on the European energy system by the year 2050 by introducing hydrogen blending sensitivities to the Global Energy System Model (GENeSYS-MOD). Results indicate that hydrogen demand in Europe is inelastic and limited by its high costs and specific use cases with hydrogen production increasing by 0.17% for 100%-blending allowed compared to no blending allowed. The availability of hydrogen blending has been found to impact regional hydrogen production and trade with countries that can utilize existing natural gas pipelines such as Norway experiencing an increase in hydrogen and synthetic gas exports from 44.0 TWh up to 105.9 TWh in 2050 as the proportion of blending increases. Although the influence of blending on the overall production and consumption of hydrogen in Europe is minimal the impacts on the location of production and dependence on imports must be thoroughly evaluated in future planning efforts.

Hydrogen plays an important role in the global transition towards Net-Zero emission. While pipelines are a viable option to transport large quantities of compressed hydrogen over long distances it is not always practical in many applications. In such situations a viable option is to transport and deliver large quantities of hydrogen as cryogenic liquid. The liquefaction process cools hydrogen to cryogenic temperatures below its boiling point of -259.2 0C. Such extreme low temperature implies specific hazards and risks which are different from those associated with the relatively well-known compressed gaseous hydrogen. Managing these specific issues brings new challenges for the stakeholders.<br/>Furthermore the transfer of liquid hydrogen (LH2) and its technical handling is relatively well known for industrial gas or space applications. Experience with LH2 in public and populated areas such as truck and aircraft refuelling stations or port bunkering stations for example is limited or non-existent. Safety requirements in these applications which involve or are in proximity of untrained public are different from rocket/aerospace industry.<br/>The manuscript reviews knowhow already gained by the international hydrogen safety community; and on such basis elucidate the gaps which are yet to be filled to meet industry needs to design and operate inherently safe LH2 operations including the implications for regulations codes and standards (RCS). Where relevant the associated gaps in some underpinning sciences will be mentioned; and the need to contextualise the information and safety practices from NASA1/ESA2/JAXA3 to inform risk adoption will be summarised.