Germany

Green hydrogen is a cornerstone in the global quest for a carbon-neutral future offering transformative potential for decarbonizing transportation. This study investigates its role by assessing the feasibility of a large-scale hydrogen refueling station in Germany focusing on integrating renewable energy sources. A hydrogen demand model with a 10-min time resolution to refuel 30 trucks and 20 vans (1019 kg/day) is combined with a techno-economic optimization model to evaluate a hybrid energy system utilizing wind solar and grid electricity. Scenario-based analysis reveals that Levelized Cost of Hydrogen ranges from 13.92 to 18.12 €/kg primarily influenced by electricity costs. Excess electricity sales can reduce this cost to 13.34–16.92 €/kg. On-site wind energy reduces storage and grid reliance achieving the lowest hydrogen cost. Unlike prior studies this work combines temporally resolved hydrogen demand profiles with comprehensive techno-economic modeling offering unprecedented insights into decentralized green hydrogen systems for heavy-duty transport. By bridging critical gaps in the scalability and economic feasibility of Power-to-Hydrogen systems it provides viable strategies for advancing green hydrogen infrastructure.

An important component of the deep decarbonization of the worldwide energy system is to build up the large-scale utilization of hydrogen to substitute for fossil fuels in all sectors including industry the electricity sector transportation and heating. Hence apart from reducing hydrogen production costs establishing an efficient and suitable infrastructure for the storage transportation and distribution of hydrogen becomes essential. This article provides a technically detailed overview of the state-of-the-art technologies for hydrogen infrastructure including the physical- and material-based hydrogen storage technologies. Physical-based storage means the storage of hydrogen in its compressed gaseous liquid or supercritical state. Hydrogen storage in the form of liquid-organic hydrogen carriers metal hydrides or power fuels is denoted as material-based storage. Furthermore primary ways to transport hydrogen such as land transportation via trailer and pipeline overseas shipping and some related commercial data are reviewed. As the key results of this article hydrogen storage and transportation technologies are compared with each other. This comparison provides recommendations for building appropriate hydrogen infrastructure systems according to different application scenarios.

Wind power-to-gas concepts have a high potential to sustainably cover the increasing demand for hydrogen as an energy carrier and raw material as it has been shown in the past that there is an enormous potential in energy overproduction which currently remains unused due to the shutdown of wind turbines. Thus there is barely experience in maritime production offshore storage and transport of large quantities of liquid hydrogen (LH2) due to the developing market. Instead tank designs refer to heavy standard onshore storage and transport applications with vacuum insulated double wall hulls made from austenitic stainless steel and comparatively high thermal diffusivity and conductivity. This reduces cost effectiveness due to inevitable boil-off and disregards some other requirements such as mechanical and cyclic strength and high corrosion resistance. Hence new concepts for LH2 tanks are required for addressing these issues. Two innovative technical concepts from space travel and high-temperature applications were adopted combined and qualified for use in the wind-power-to-gas scenario. The focus was particularly on the high requirements for transport weight insulation and cryogenic durability. The first concept part consisted of the implementation of FRP (fiber-reinforced plastics)–steel hybrid tanks which have a high potential as a hull for LH2 tanks. However these hybrid tanks are currently only used in the space sector. Questions still arise regarding interactions with coatings production material temperature resilience and design for commercial use. Thermally sprayed thermal barrier coatings (TBC) in turn show promising potential for surfaces subject to high thermal and mechanical stress. However the application is currently limited to use at high temperatures and needed to be extended to the cryogenic temperature range. The research on this second part of the concept thus focused on the validation of standard MCrAlY alloys and innovative (partially) amorphous metal coatings with regard to mechanical-technological and insulating properties in the low temperature range. This article gives an overview regarding the achieved results including manufacturing and measurements on a small tank demonstrator.

The green hydrogen economy is evolving rapidly accompanied by the need to establish trading routes on a global scale. Currently several technologies arecompeting for a leadership role in future hydrogen value chains. Within thiscontext liquid organic hydrogen carrier (LOHC) technology represents an excellent solution for large-scale storage and safe transportation of hydrogen.This article presents LOHC technology recent progress as well as further potential of this technology with focus on benzyltoluene as the carrier material.Furthermore this contribution offers an insight into previous and ongoingproject development activities led by Hydrogenious LOHC Technologies togetherwith an evaluation of the economic viability and an overview of the regulatory aspects of LOHC technology.

To enable a sustainable and socially accepted hydrogen and methanol economy it is crucial to prioritize green and water-conscious production. In this review we reveal that there is a significant research gap regarding comprehensive assessments of such production methods. We present an innovative process chain consisting of adsorption-based direct air capture solid oxide electrolysis and methanol synthesis to address this issue. To allow future comprehensive techno-economic assessments we perform a systematic literature review and harmonization of the techno-economic parameters of the process chain’s technologies. Based on the conducted literature review we find that the long-term median specific energy demand of adsorption-based direct air capture is expected to decrease to 204 kWhel/tCO2 and 1257 kWhth/tCO2 while the capture cost is expected to decrease to 162 €2024/tCO2 with a relative high uncertainty. The evaluated sources expect a future increase in system efficiency of solid oxide electrolysis to 80% while the purchase equipment costs are expected to decrease significantly. Finally we demonstrate the feasibility of the process chain from a technoeconomic perspective and show a potential reduction in external heat demand of the DAC unit of up to 34% when integrated in the process chain.

The high potential of hydrogen as a key factor on the pathway towards a climate neutral economy leads to rising demand in technical applications where gaseous hydrogen is used. For several metals hydrogen-metal interactions could cause a degradation of the material properties. This is especially valid for low carbon and highstrength structural steels as they are commonly used in natural gas pipelines and analyzed in this work. This work provides an insight to the impact of hydrogen on the mechanical properties of an API 5L X65 pipeline steel tested in 60 bar gaseous hydrogen atmosphere. The analyses were performed using the hollow specimen technique with slow strain rate testing (SSRT). The nature of the crack was visualized thereafter utilizing μCT imaging of the sample pressurized with gaseous hydrogen in comparison to one tested in an inert atmosphere. The combination of the results from non-conventional mechanical testing procedures and nondestructive imaging techniques has shown unambiguously how the exposure to hydrogen under realistic service pressure influences the mechanical properties of the material and the appearance of failure.

Green hydrogen has the potential to decarbonize hard-to-abate sectors and processes and should therefore play an important role in the energy system in achieving climate goals. However the main hydrogen supply is still based on fossil fuels and only limited amounts of electrolyzers have been installed. Switching from fossil-based fuel sources to green hydrogen is highly dependent on when and at what price green hydrogen will become available which in turn is dependent on the technological development of electrolyzers. In this paper we apply the experience curve methodology to project the capital expenditure and electrical consumption developments of the three main electrolysis technologies: alkaline proton exchange membrane and solid oxide electrolysis. Based on our calculations we expect that both AEL and PEM will reach similar costs by 2030 of around 300 e per kW and SOEC will remain the most expensive technology with a considerable cost reduction down to 828 e per kW. The electrical consumptions will fall to 4.23 kWh per Nm3 for AEL 3.86 kWh per Nm3 for PEM and 3.05 kWh per Nm3 for SOEC. Based on this technological progress we calculate that the levelized cost of hydrogen will be reduced to 2.43–3.07 e per kg. To reach lower levelized cost of hydrogen notable reductions in electricity (purchase) cost are required.

Hydrogen storage technologies are key enablers for the development of low-emission sustainable energy supply chains primarily due to the versatility of hydrogen as a clean energy carrier. Hydrogen can be utilized in both stationary and mobile power applications and as a lowenvironmental-impact energy source for various industrial sectors provided it is produced from renewable resources. However efficient hydrogen storage remains a significant technical challenge. Conventional storage methods such as compressed and liquefied hydrogen suffer from energy losses and limited gravimetric and volumetric energy densities highlighting the need for innovative storage solutions. One promising approach is hydrogen storage in metal hydrides which offers advantages such as high storage capacities and flexibility in the temperature and pressure conditions required for hydrogen uptake and release depending on the chosen material. However these systems necessitate the careful management of the heat generated and absorbed during hydrogen absorption and desorption processes. Thermal energy storage (TES) systems provide a means to enhance the energy efficiency and cost-effectiveness of metal hydride-based storage by effectively coupling thermal management with hydrogen storage processes. This review introduces metal hydride materials for hydrogen storage focusing on their thermophysical thermodynamic and kinetic properties. Additionally it explores TES materials including sensible latent and thermochemical energy storage options with emphasis on those that operate at temperatures compatible with widely studied hydride systems. A detailed analysis of notable metal hydride–TES coupled systems from the literature is provided. Finally the review assesses potential future developments in the field offering guidance for researchers and engineers in advancing innovative and efficient hydrogen energy systems.

Cryogenic liquid is often stored in a vacuum insulated Dewar vessel for a high efficiency of thermal insulation. Multi-layer insulation (MLI) can be further applied in the double-walled vacuum space to reduce the heat transfer from the environment to the stored cryogenic fluid. However in loss-of-vacuum accident (LOVA) scenarios heat flux across the MLI will raise to orders of magnitudes larger than with an intact vacuum shield. The cryogenic liquid will boil intensively and pressurize the vessel due to the heat ingress. The pressurization endangers the integrity of the vessel and poses an extra catastrophic risk if the vapor is flammable e.g. hydrogen. Therefore safety valves have to be designed and installed appropriately to make sure the pressure is limited to acceptable levels. In this work the dynamic process of the heat and mass transfers in the LOVA scenarios is studied theoretically. The mass deposition - desublimation of gaseous nitrogen on cryogenic surfaces is modeled as it provides the dominant contribution of the thermal load to the cryogenic fluid. The conventional heat convection and radiation are modeled too although they play only secondary roles as realized in the course of the study. The temperature dependent thermal properties of e.g. gaseous and solid nitrogen and stainless steel are used to improve the accuracy of calculation in the cryogenic temperature range. Presented methodology enabling the computation of thermodynamic parameters in the cryogenic storage system during LOVA scenarios provides further support for the future risk assessment and safety system design.

This study presents sector-coupled PyPSA-Earth: a novel global open-source energy system optimization model that incorporates major demand sectors and energy carriers in high spatial and temporal resolution to enable energy transition studies worldwide. The model includes a workflow that automatically downloads and processes the necessary demand supply and transmission data to co-optimize investment and operation of energy systems of countries or regions of Earth. The workflow provides the user with tools to forecast future demand scenarios and allows for custom user-defined data in several aspects. Sector-coupled PyPSA-Earth introduces novelty by offering users a comprehensive methodology to generate readily available sector-coupled data and model of any region worldwide starting from raw and open data sources. The model provides flexibility in terms of spatial and temporal detail allowing the user to tailor it to their specific needs. The capabilities of the model are demonstrated through two showcases for Egypt and Brazil. The Egypt case quantifies the relevant role of PV exceeding 35 GW and electrolysis in Suez and Damietta regions for meeting 16% of the EU hydrogen demand. Complementarily the Brazil case confirms the model’s ability in handling hydrogen planning infrastructure including repurposing of existing gas networks which results in 146 M€ lower costs than building new pipelines. The results prove the suitability of sector-coupled PyPSA-Earth to meet the needs of policymakers developers and scholars in advancing the energy transition. The authors invite the interested individuals and institutions to collaborate in the future developments of the model within PyPSA meets Earth initiative.

An experimental investigation is carried out to evaluate the effect of introducing hydrogen into natural gas flames on the combustion process (different temperature profiles flame locations and burning velocity) in glass melting furnaces. This work considers the fundamental changes in a non-premixed natural gas-oxygen flame (referred to as oxyfuel flame) with varying levels of hydrogen admixtures ranging from 0 to 100 vol%. To facilitate meaningful data comparisons the burner power output is maintained at a constant thermal power of 20 kW during the entire series of tests. At first the flow field of the oxyfuel burner is measured by using laser doppler anemometry (LDA). Then the burner is tested in a multi-segment combustion chamber with optical accesses. A camera system is employed to visually observe the combustion zone capturing signals in both the visible (VIS) and ultraviolet (UV) wavelengths. The chemiluminescence of the OH* radicals could be determined over the entire flame length. Notably the study reveals variations in flame position especially with higher hydrogen concentrations. Furthermore radial and axial flame temperature profiles are recorded at various po sitions. The analysis extends to major exhaust gas components (CO2 NOx O2) at different fuel compositions and multiple equivalence ratios. In addition a study is being carried out to investigate the influence of false air impacts. The obtained results indicate that the flame temperature increases slightly with pure hydrogen. The NOx values in the overall exhaust gas also show an increase with a higher hydrogen admixture. In particular the influence of false air can lead to a significant rise in NOx levels.

Côte d’Ivoire has substantially neglected crop residues from farms in rural areas so this study aimed to provide strategies for the sustainable conversion of these products to hydrogen. The use of existing data showed that in the Côte d’Ivoire there were up to 16801306 tons of crop residues from 11 crop types in 2019 from which 1296424.84 tons of hydrogen could potentially be derived via theoretical gasification and dark fermentation approaches. As 907497.39 tons of hydrogen is expected annually the following estimations were derived. The three hydrogen-project implementation scenarios developed indicate that Ivorian industries could be supplied with 9026635 gigajoules of heat alongside 17910 cars and 4732 buses in the transport sector. It was estimated that 817293.95 tons of green ammonia could be supplied to farmers. According to the study 5727992 households could be expected to have access to 1718.40 gigawatts of electricity. Due to these changes in the transport energy industry and agricultural sectors a reduction of 1644722.08 tons of carbon dioxide per year could theoretically be achieved. With these scenarios around 263276.87 tons of hydrogen could be exported to other countries. The conversion of crop residues to hydrogen is a promising opportunity with environmental and socio-economic impacts. Therefore this study requires further extensive research.

The increase of using hydrogen as a replacement for fossil fuels in power generation and mobility is expected to witness a huge leap in the next decades. However several safety issues arise due to the physical and chemical properties of hydrogen especially its wide range of flammability. In case of Hydrogen leakage in confined areas Hydrogen clouds can accumulate in the space and their concentration can build up quickly to reach the lower flammability limit (LFL) in case of not applying a proper ventilation system. As a part of the Living Lab Energy Campus (LLEC) project at Jülich Research Centre the use of hydrogen mixed with natural gas as a fuel for the central heating system of the campus is being studied. The current research aims to investigate the release dispersion and formation and the spread of a hydrogen cloud inside the central utility building at the campus of Jülich Research Centre in case of hypothetical accidental leakage. Such a leakage is simulated using the opensource containmentFoam package base on OpenFOAM CFD code to numerically simulate the behavior of the air-hydrogen mixture. The critical locations where hydrogen concentrations can reach the LFL values are shown.

The transition to renewable energy sources to mitigate climate change will require large-scale energy storage to dampen the fluctuating availability of renewable sources and to ensure a stable energy supply. Energy storage in the geological subsurface can provide capacity and support the cycle times required. This study investigates hydrogen storage methane storage and compressed air energy storage in subsurface porous formations and quantifies potential storage capacities as well as storage rates on a site-specific basis. For part of the North German Basin used as the study area potential storage sites are identified employing a newly developed structural geological model. Energy storage capacities estimated from a volume-based approach are 6510 TWh and 24544 TWh for hydrogen and methane respectively. For a consistent comparison of storage capacities including compressed air energy storage the stored exergy is calculated as 6735 TWh 25795 TWh and 358 TWh for hydrogen methane and compressed air energy storage respectively. Evaluation of storage deliverability indicates that high deliverability rates are found mainly in two of the three storage formations considered. Even accounting for the uncertainty in geological parameters the storage potential for the three considered storage technologies is significantly larger than the predicted demand and suitable storage rates are achievable in all storage formations.

The increasing demand for sustainable air mobility has led to the development of innovative aircraft designs necessitating a balance between environmental responsibility and profitability. However despite technological advancements there is still limited understanding of the maintenance implications for hydrogen systems in aviation. The aim of this study is to estimate the maintenance costs of replacing the hydrogen storage system in an aircraft as part of its life cycle costs. To achieve this we compared conventional and hydrogenpowered aircraft. As there is insufficient data for new aircraft concepts typical probabilistic methods are not applicable. However by combining global sensitivity analysis with Dempster–Shafer Theory of Evidence and discrete event simulation it is possible to identify key uncertainties that impact maintenance costs and economic efficiency. This innovative framework offers an early estimate of maintenance costs under uncertainty enhancing understanding and assisting in decision-making when integrating hydrogen storage systems and new aviation technologies.

Hydrogen and its derivatives are important components to achieve climate policy goals especially in terms of greenhouse gas neutrality. There is an ongoing controversial debate about the applications in which hydrogen and its derivatives should be used and to what extent. Typically the estimation of hydrogen demand relies on scenario-based analyses with varying underlying assumptions and targets. This study establishes a new framework consisting of existing energy system simulation and optimisation models in order to assess the long-term price-elastic demand of hydrogen. The aim of this work is to shift towards an analysis of the hydrogen demand that is primarily driven by its price. This is done for the case of Germany because of the expected high hydrogen demand for the years 2025–2045. 15 wholesale price pathways were established with final prices in 2045 between 56 €/MWh and 182 €/MWh. The results suggest that – if climate targets are to be achieved - even with high hydrogen prices (252 €/MWh in 2030 and 182 €/MWh in 2045) a significant hydrogen demand in the industry sector and the energy conversion sector is expected to emerge (318 TWh). Furthermore the energy conversion sector has a large share of price sensitive hydrogen demand and therefore its demand strongly increases with lower prices. The road transportation sector will only play a small role in terms of hydrogen demand if prices are low. In the decentralised heating for buildings no relevant demand will be seen over the considered price ranges whereas the centralised supply of heat via heat grids increases as prices fall.

One of the significant safety concerns in large-scale storage and transportation of liquefied (cryogenic) hydrogen (LH2) is the formation of flammable hydrogen/air mixtures after leakages during storage or transportation. Especially in maritime transportation hydrogen accumulations could occur within large and congested geometries. The installation of passive auto-catalytic recombiners (PARs) is a suitable mitigation measure for local areas where venting is insufficient or even impossible. Numerical models describing the operational behavior of PARs are required to allow for optimizing the location and assessing the efficiency of the mitigation measure. In the present study the operational behavior of a PAR with a compact design has been experimentally investigated. In order to obtain data for model validation an experimental program has been performed in the REKO-4 facility a 5.5 m³ vessel. The test procedure includes two phases steady-state and dynamic. The results provide insights into the hydrogen recombination rates and catalyst temperatures under different boundary conditions.

This research conducted a probabilistic life-cycle assessment (pLCA) into the greenhouse gas (GHG) emissions performance of nine combinations of truck size and powertrain technology for a recent past and a future (largely decarbonised) situation in Australia. This study finds that the relative and absolute life-cycle GHG emissions performance strongly depends on the vehicle class powertrain and year of assessment. Life-cycle emission factor distributions vary substantially in their magnitude range and shape. Diesel trucks had lower life-cycle GHG emissions in 2019 than electric trucks (battery hydrogen fuel cell) mainly due to the high carbon-emission intensity of the Australian electricity grid (mainly coal) and hydrogen production (mainly through steam–methane reforming). The picture is however very different for a more decarbonised situation where battery electric trucks in particular provide deep reductions (about 75–85%) in life-cycle GHG emissions. Fuel-cell electric (hydrogen) trucks also provide substantial reductions (about 50–70%) but not as deep as those for battery electric trucks. Moreover hydrogen trucks exhibit the largest uncertainty in emissions performance which reflects the uncertainty and general lack of information for this technology. They therefore carry an elevated risk of not achieving the expected emission reductions. Battery electric trucks show the smallest (absolute) uncertainty which suggests that these trucks are expected to deliver the deepest and most robust emission reductions. Operational emissions (on-road driving and vehicle maintenance combined) dominate life-cycle emissions for all vehicle classes. Vehicle manufacturing and upstream emissions make a relatively small contribution to life-cycle emissions from diesel trucks (

The decarbonization of the global ship traffic is one of the industry’s greatest challenges for the next decades and will likely only be achieved with the introduction of synthetic fuels. Until now however not one single best technology solution emerged to ideally fit this task. Instead different energy carriers including hydrogen ammonia methanol methane and synthetic diesel are subject of discussion for usage in either internal combustion engines or fuel cells. In order to drive the selection procedure a case study for the year 2030 with all eligible combinations of power technologies and fuels is conducted. The assessment quantifies the technologies’ economic performances for cost-optimized system designs and in dependence of a ship’s mission characteristics. Thereby the influence of trends for electrofuel prices and shipboard volume opportunity costs are examined. Even if gaseous hydrogen is often considered not suitable for large ship applications due to its low volumetric energy density both the comparatively small fuel price and the high efficiency of fuel cells lead to the overall smallest system costs for passages up to 21 days depending on assumed cost parameters. Only for missions longer than seven days fuel cells operating on methanol or ammonia can compete with gaseous hydrogen economically.

Limiting global warming to 1.5 ◦C is crucial to prevent the worst effects of climate change. This entails also the decarbonization of the aviation sector which is considered to be a “hard-to-abate” sector and thus requires special attention regarding its sustainability transition. However transition pathways to a potentially climateneutral aviation sector are unclear with different stakeholders having diverse imaginations of the sector's future. This paper aims to analyze socio-technical imaginaries of climate-neutral aviation as different perceptions of various stakeholders on this issue have not been sufficiently explored so far. In that sense this work contributes to the current scientific debate on socio-technical imaginaries of energy transitions for the first time studying the case of the aviation sector. Drawing on six decarbonization reports composed by different interest groups (e.g. industry academia and environmental associations) three imaginaries were explored following the process of a thematic analysis: rethinking travel and behavioral change (travel innovation) radical modernization and technological progress (fleet innovation) and transition to alternative fuels and renewable energy sources (fuel innovation). The results reveal how different and partly conflicting socio-technical imaginaries are co-produced and how the emergence and enforceability of these imaginaries is influenced by the situatedness of their creators indicating that the sustainability transition of aviation also raises political issues. Essentially as socio-technical imaginaries act as a driver for change policymakers should acknowledge the existence of alternative and counter-hegemonic visions created by actors from civil society settings to take an inclusive and equitable approach to implementing pathways towards climate-neutral aviation.

Power-to-gas technology can be used to convert excess power from renewable energies to hydrogen by means of water electrolysis. This hydrogen can serve as “chemical energy storage” and be converted back to electricity or fed into the natural gas grid. In the presented study a leak in a household pipe in a single-family house with a 13 KW heating device was experimentally investigated. An admixture of up to 40% hydrogen was set up to produce a scenario of burning leakage. Due to the outflow and mixing conditions a lifted turbulent diffusion flame was formed. This led to an additional examination point and expanded the aim and novelty of the experimental investigation. In addition to the fire safety experimental simulation of a burning leakage the resulting complex properties of the flame namely the lift-off height flame length shape and thermal radiation have also been investigated. The obtained results of this show clearly that as a consequence of the hydrogen addition the main properties of the flame such as lifting height flame temperature thermal radiation and total heat flux densities along the flame have been changed. To supplement the measurements with thermocouples imaging methods based on the Sobel gradient were used to determine the lifting height and the flame length. In order to analyze the determined values a probability density function was created.

HyCARE project supported by the Clean Hydrogen Partnership of the European Union deals with a prototype of hydrogen storage tank using a solid-state hydrogen carrier. Up to 40 kilograms of hydrogen are stored in twelve tanks at less than 50 barg and less than 100 °C. The innovative design is based on a standard twenty-foot container including twelve TiFe-based metal hydride (MH) hydrogen storage tanks coupled with a thermal energy storage in phase change materials (PCM). This article aims at showing the main risks related to hydrogen storage in a MH system and the safety barriers considered based on HyCARE’s specific risk analysis.<br/>Regarding the TiFe MH material used to store hydrogen experimental tests showed that the exposure of the MH to air or water did not cause spontaneous ignition. Furthermore an explosion within the solid MH cannot propagate due to internal pore size. Additionally in case of leakage the speed of hydrogen desorption from the MH is self-limited which is an important safety characteristic since it reduces the potential consequences from the hydrogen release scenario.<br/>Regarding the integrated system the critical scenarios identified during the risk analysis were: explosion due to release of hydrogen inside or outside the container internal explosion inside MH tanks due to accidental mix of hydrogen and air and asphyxiation due to inert gas accumulation in the container. This identification phase of the risk analysis allowed to pinpoint the most relevant safety barriers already in place and recommend additional ones if needed to further reduce the risk that were later implemented.<br/>The main safety barriers identified were: material and component selection (including the MH selected) safety interlocks safety valves ventilation gas detection and safety distances.<br/>The risk management process based on risk identification and assessment contributed to coherently integrate inherently safe design features and safety barriers.

Renewable hydrogen is widely considered a key technology to achieve net zero emissions in industrial production processes. This paper presents a structured bibliometric analysis examining current and future applications of hydrogen as feedstock and fuel across industries quantifying demand for different industrial processes and identifying greenhouse gas emissions reduction potential against the context of current fossil-based practices. The findings highlight significant focus on hydrogen as feedstock for steel ammonia and methanol production and its use in high-to medium-temperature processes and a general emphasis on techno-economic and technological evaluations of hydrogen applications across industries. However gaps exist in research on hydrogen use in sectors like cement glass waste pulp and paper ceramics and aluminum. Additionally the analysis reveals limited attention in the identified literature to hydrogen supply chain efficiencies including conversion and transportation losses as well as geopolitical and raw material challenges. The analysis underscores the need for comprehensive and transparent data to align hydrogen use with decarbonization goals optimize resource allocation and inform policy and investment decisions for strategic deployment of renewable hydrogen.

Hydrogen energy is recognized by many European governments as an important part of the development to achieve a more sustainable energy infrastructure. Great efforts are spent to build up a hydrogen supply chain to support the increasing number of hydrogen-powered vehicles. Naturally these vehicles will use the common traffic infrastructure. Thus it has to be ensured these infrastructures are capable to withstand the hazards and associated risks that may arise from these new technologies. In order to have an appropriate assessment tool for hydrogen vehicles transport through tunnels a new QRA methodology is developed and presented here. In Europe the PIARC is a very common approach. It is therefore chosen as a starting point for the new methodology. It provides data on traffic statistics accident frequencies tunnel geometries including certain prevention and protection measures. This approach is enhanced by allowing better identification of hazards and their respective sources for hydrogen vehicles. A detailed analysis of the accident scenarios that are unique for hydrogen vehicles hereunder the initiating events severity of collision types that may result in a release of hydrogen gas in a tunnel and the location of such an accident are included. QRA enables the assessment and evaluation of scenarios involving external fires or vehicles that burst into fire because of an accident or other fire sources. Event Tree Analysis is the technique used to estimate the event frequencies. The consequence analysis includes the hazards from blast waves hydrogen jet fires DDT.

Discussions about the transition to hydrogen in various applications have become an important topic in recent years. A key factor for an effective transition is public acceptance of hydrogen technologies. However the increase in acceptance depends among other things on individual knowledge about the hydrogen colors and the linked hydrogen production pathways currently under discussion. In communications colors such as green grey and blue are used to distinguish hydrogen sources. With new research additional colors have become necessary. Unfortunately there is no unified definition for the colors. The aim of this perspective is to identify the most frequent hydrogen colors used by scientists and the public derive open definitions and propose a solution to a representation problem. The general use of hydrogen colors in communication and the implications on public acceptance are briefly outlined. We then identified definitions for colors associated with a specific pathway and discussed some discrepancies between science and media use. To make better use of the existing colors more open definitions were formulated. We point out the representation problem with shades of a color and provide a connection between the assigned color and a view-independent RGB color code as proposal. The derived definitions can be used to unify communication in science and public media.