Germany

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.