France

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.

As part of the ongoing transition from fossil fuels to renewable energies advances are particularly expected in terms of safe and cost-effective solutions. Publicising instances of such advances and emphasising global safety considerations constitute the rationale for this communication. Knowing that high-strength steels can prove economically relevant in the foreseeable future for transporting hydrogen in pipelines by limiting the pipe wall thickness required to withstand high pressure one advance relates to a bench designed to assess the safe transport or renewableenergy-related buffer storage of hydrogen gas. That bench has been implemented at the technology readiness level TRL 6 to test initially intact damaged or pre-notched 500 mm-long pipe sections with nominal diameters ranging from 300 to 900 mm in order to appropriately validate or question the use of reputedly satisfactory predictive models in terms of hydrogen embrittlement and potential corollary failure. The other advance discussed herein relates to the reactivation of a previously fruitful applied research into safe mass solid-state hydrogen storage by magnesium hydride through a new public–private partnership. This latest development comes at a time when markets have started driving the hydrogen economy bearing in mind that phase-change materials make it possible to level out heat transfers during the absorption/melting and solidification/desorption cycles and to attain an overall energy efficiency of up to 80% for MgH2 -based compacts doped with expanded natural graphite.

Fuel cells and electric batteries are competing technologies for the energy transition in heavy transportation. We explore the conditions for the survival of a unique technology in the long term. Learning by doing suggests focusing on a single technology while differentiation and decreasing return to scale (cost convexity) favor diversification. Exogenous technical change also plays a role. The interaction between these factors is analyzed in a general model. It is proved that in absence of convexity and exogenous technical change only one technology is used for the whole transition. We then apply this framework to analyze the competition between fuel-cell electric buses (FCEBs) and battery electric buses (BEB) in the European bus sector. There are both learning by doing and exogenous technical change. The model is calibrated and solved. It is shown that the existence of a niche for FCEBs critically depends on the speed at which cost reductions are achieved. The speed depends both on the size of the niche and the rate of learning by doing for FCEBs. Public policies to decentralize the socially optimal trajectory in terms of taxes (carbon) and subsidies (learning by doing) are derived.

A growing share of renewable energy production in the energy supply systems is key to reaching the European political goal of zero CO2 emission in 2050 highlighted in the green deal. Linked to the irregular production of solar and wind energies which have the highest potential for development in Europe massive energy storage solutions are needed as energy buffers. The European project HyPSTER [1] (Hydrogen Pilot STorage for large Ecosystem Replication) granted by the Clean Hydrogen Partnership addresses this topic by demonstrating a cyclic test in an experimental salt cavern filled with hydrogen up to 3 tons using hydrogen that is produced onsite by a 1 MW electrolyser. One specific objective of the project is the assessment of the risks and environmental impacts of cyclic hydrogen storage in salt caverns and providing guidelines for safety regulations and standards. This paper highlights the first outcome of the task WP5.5 of the HyPSTER project addressing the regulatory and normative frameworks for the safety of hydrogen storage in salt caverns from some selected European Countries which is dedicated to defining recommendations for promoting the safe development of this industry within Europe.

This paper proposes a numerical setup for 3D-CFD in-cylinder simulations of H2-fuelled internal combustion engines. The flamelet G-equation model based on Verhelst and Damkohler-like ¨ correlations for laminar and turbulent flame speeds respectively is used to reproduce the flame propagation. The validation against experimental data from a homogeneous-mixture port-injection engine enables a focus on combustion simulation by minimising stratification uncertainties. Accurate flame propagation modelling is identified as the main challenge. The results on different operating conditions confirm the predictive capabilities of the framework thanks to the agreement with the experimental pressure traces combustion indicators and flame imaging. Notably combustion rate predictions remain accurate even without considering the flame thermo-diffusive instability as the turbulence effect dominates at the investigated conditions. The combustion regime is analysed by a modified Borghi-Peters diagram and it ranges from flamelet to thin reaction zones. This highlights the numerical setup flexibility which accurately simulates combustion across different regimes.

Ammonia a molecule that is gaining more interest as a fueling vector has been considered as a candidate to power transport produce energy and support heating applications for decades. However the particular characteristics of the molecule always made it a chemical with low if any benefit once compared to conventional fossil fuels. Still the current need to decarbonize our economy makes the search of new methods crucial to use chemicals such as ammonia that can be produced and employed without incurring in the emission of carbon oxides. Therefore current efforts in this field are leading scientists industries and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector moving through all of the steps in the production distribution utilization safety legal considerations and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes legal barriers that will be faced to achieve its deployment safety and environmental considerations that impose a critical aspect for acceptance and wellbeing and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein this work sets the principles research practicalities and future views of a transition toward a future where ammonia will be a major energy player.

Of all the alternatives to hydrocarbon fuels hydrogen offers the greatest long-term potential to radically reduce the many problems inherent in fuel used for transportation. Hydrogen vehicles have zero tailpipe emissions and are very efficient. If the hydrogen is made from renewable sources such as nuclear power or fossil sources with carbon emissions captured and sequestered hydrogen use on a global scale would produce almost zero greenhouse gas emissions and greatly reduce air pollutant emissions. The aim of this work is to realise a traceability chain for hydrogen flow metering in the range typical for fuelling applications in a wide pressure range with pressures up to 875 bar (for Hydrogen Refuelling Station - HRS with Nominal Working Pressure of 700 bar) and temperature changes from −40 °C (pre-cooling) to 85 °C (maximum allowed vehicle tank temperature) in accordance with the worldwide accepted standard SAE J2601. Several HRS have been tested in Europe (France Netherlands and Germany) and the results show a good repeatability for all tests. This demonstrates that the testing equipment works well in real conditions. Depending on the installation configuration some systematic errors have been detected and explained. Errors observed for Configuration 1 stations can be explained by pressure differences at the beginning and end of fueling in the piping between the Coriolis Flow Meter (CFM) and the dispenser: the longer the distance the bigger the errors. For Configuration 2 where this distance is very short the error is negligible.

The MultHyFuel Project funded by the Clean Hydrogen Partnership aims to achieve the effective and safe deployment of hydrogen as a carbon-neutral fuel by developing a common strategy for implementing Hydrogen Refueling Stations (HRS) in a multifuel context. The project hopes to contribute to the harmonisation of existing regulations codes and standards (RCS) by generating practical theoretical and experimental data related to HRS.<br/>This paper presents how a set of safety critical scenarios have been identified from the initial preliminary as well as detailed risk analysis of three different hydrogen refueling station configurations. To achieve this a detailed examination of each potential hazardous phenomenon (DPh) or major accident event at or near the hydrogen dispenser was carried out. Particular attention is paid to the scenarios which could affect third parties external to the refueling station.<br/>The paper presents a methodology subdivided into the following steps:<br/>♦ determination of the consequence level and likelihood of each hazardous phenomenon<br/>♦ the classification of major hazard scenarios for the 3 HRS configurations specifically those arising on the dispensing forecourt;<br/>♦ proposal of example preventative control and/or mitigation barriers that could potentially reduce the probability of occurrence and/ or consequences of safety critical scenarios and hence reducing risks to a tolerable level or to as low as reasonably practicable.

Green hydrogen generated from water through renewable energies like solar and wind is a key player in sus tainable energy. It only produces water when used making it a clean energy source. However the inconsistent nature of solar and wind energy highlights the need for storage solutions where green hydrogen is promising. This study uniquely combines green hydrogen (GH) and renewable energy (RE) domains using a comprehensive bibliometric approach covering 2018–2022. It identifies emerging trends collaboration networks and key contributors that shape the global landscape of GH research. Our findings show a significant yearly growth in this research field averaging 93.56 %. The study also identifies China Germany India and Italy as leaders among 76 countries involved in this area. Research trends have shifted from technical details to social and economic factors. Given the increasing global commitment to achieving carbon neutrality understanding the evolution and integration of GH within RE systems is essential for guiding future research policy-making and technology development. The analysis categorizes the research into seven main themes focusing on green hydrogen’s role in energy transition and storage. Other vital topics include improving hydrogen production methods assessing its climate impact examining its environmental benefits and exploring various production techniques like water electrolysis and photocatalysis. Our analysis reveals a 93.56 % annual growth rate in GH research highlighting key challenges in storage integration and policy development and offering a roadmap for future studies. The study highlights areas needing more exploration such as better storage methods integration with existing energy infrastructures risk management and policy development. The advancement of green hydrogen as a sustainable energy solution depends on innovative research international collaboration and supportive policy frameworks.

In the frame of hydrogen-powered aircraft Airbus wants to understand all the H2 physics and explore every scenario in order to develop and manufacture safe products operated in a safe environment. Within the framework of a Large Eddy Simulation (LES) methodology for modeling turbulence a comparative numerical study of free under-expanded jet H2/AIR flame is conducted. The investigated geometry consists of straight nozzles with a millimetric diameter fed with pure H2 at upstream pressures ranging from 2 to 10 bar. Numerical results are compared with available experimental measurements such as; temperature signals using thermocouples. LES confirms its prediction capability in terms of shock jet structure and flame length. A particular attention is paid for capturing experimental unstable flame when upstream pressure decreases. Furthermore flame stabilization and flame anchoring are analyzed. Mechanisms of flame stabilization are highlighted for case 1 and stabilization criteria are tested. Finally an ignition map to reach flame stabilization is proposed for each case regarding the literature.