France

For safety issues related to the storage of hydrogen under high pressure it is necessary to determine how the gas is released in the case of failure. In particular there exist limited quantitative information on the near-field properties of the gas jets which are important for establishing proper decay laws in the far-field. This paper reports recent CFD results for air and helium obtained in the near-field of the highly under-expanded jets. The gas jets are released from a 30-bar tank with the same opening (orifice). The Reynolds number based on the diameter of the orifice and corresponding gas conditions at the exit was well beyond 106 . The 3D Compressible Multi-Component Navier-Stokes equations were solved directly without relying on the compressibility-corrected turbulence models. The numerical model was initially tested on a one-component (air-air) case where a few aerospace-driven data sets are available for validation. The shock geometry is characterized through the Mach disk position and diameter. These are compared to the results known from the literature and to the scaling laws developed based on the dimensional analysis. In the second two-component (helium-air) jet scenario the density field was validated and examined together with other fields in the attempt to suggest potential initial conditions for the forthcoming far-field simulations.

We present an experimental study on the dispersion of helium in an enclosure of 1 m3 with natural ventilation through one vent. Three vent geometries have been studied. Injection parameters have been varied so that the injection Richardson number ranges from 2·10−6 to 9 and the volume Richardson number which gives the ability of the release to mix the enclosure content ranges from 8·10−4 to 900. It has been found that the vertical distribution of helium volume fraction can exhibit significant gradient. Nevertheless the results are compared to the simple analytical model based on the homogenous mixture hypothesis which gives fairly good estimates of the maximum helium volume fraction.

The use of hydrogen as an energy carrier is a real perspective for Europe since a number of breakthroughs now enable to envision a deployment at the industrial scale. However some safety issues need to be further addressed but experimental data are still lacking especially about the explosion dynamics in realistic dimensions. A set of hydrogen-air vented explosions were thus performed in two medium scale chambers (1 m3 and 10 m3). Homogeneous mixtures were used (10% to 30% vol.). The explosion overpressure was measured inside the chamber and outside on the axis of the discharge from the vent. The incidence of the external explosion is clearly seen. All the results in this paper and the predictions from the standards differ greatly meaning that a significant effort is still required. It is the purpose of the French project DIMITRHY to help progressing.

During the synthesis of hydrogen by methane steam reforming mixtures composed of H2 CH4 CO and CO2 are produced in the process. In this work the explosion reactivity of these mixtures on the basis of detonation cell size and laminar flame speed is calculated using a reactant assimilation simplification and a kinetic approach. The detonation cells width are calculated using the Cell_CH Kurchatov institute method and the laminar flame velocities are calculated with Chemkin Premix using different detailed chemical kinetic mechanisms. These calculations are used to define if these mixtures could be considered having a medium or a high reactivity for risk assessment in case of leak in the hydrogen plants.

Computational fluid dynamic simulations have been performed in order to study the consequences of a hydrogen release from a pressure swing adsorption installation operating at 30 barg. The simulations were performed using FLACS-Hydrogen software from GexCon. The impact of obstruction partial confinement leak orientation and wind on the explosive cloud formation (size and explosive mass) and on explosion consequences is investigated. Overpressures resulting from ignition are calculated as a function of the time to ignition.

Hydrogen energy applications can be used outdoor and thus exposed to environmental varying conditions like wind. In several applications natural ventilation is the first mitigation means studied to limit hydrogen build-up inside a confined area. This study aims at observing and understanding the influence of wind on light gas build-up in addition. Experiments were performed with helium as releasing gas in a 1-m 3 enclosure equipped with ventilation openings varying wind conditions openings location release flow rate; obstructions in front of the openings to limit effects of wind were studied as well. Experimental results were compared together and with the available analytical models.

This paper is devoted to a benchmarking exercise of the EUROPLEXUS code against several large scale deflagration and detonation experimental data sets in order to improve its hydrogen combustion modeling capabilities in industrial settings. The code employs an algorithm for the propagation of reactive interfaces RDEM which includes a combustion wave as an integrable part of the Reactive Riemann problem propagating with a fundamental flame speed (being a function of initial mixture properties as well as gas dynamics parameters). An improvement of the combustion model is searched in a direction of transient interaction of flames with regions of elevated vorticity/shear in obstacle-laden channels and vented enclosures.

Since a few years hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous hazardous events like explosion could occur and some accidents like the Hindenburg disaster are still in the mind. Objectively hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method derived from ARAMIS method permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies.

The ADREA-HF CFD code is validated against a large scale liquefied helium release experiment on flat ground performed by INERIS in the past. The predicted release and dispersion behavior is evaluated against the experimental using temperature time histories at sensors deployed at various distances and heights downstream the source. For the selected sensors the temperature predictions are generally in good agreement with the experimental with a tendency to under-predict temperature as the source is approached.

In this work the validity of simplified mathematical models for predicting dispersion of turbulent buoyant jet or plume within a confined volume is evaluated. In the framework of the HYSAFE Network of Excellence CEA performed experimental tests in a full-scale Garage facility in order to reproduce accidental gas leakages into an unventilated residential garage. The effects of release velocities diameters durations mass flow rates and flow regimes on the vertical distribution of the gas concentration are investigated. Experimental data confirm the formation for the release conditions of an almost well-mixed upper layer and a stratified lower layer. The comparison of the measurements and the model predictions shows that a good agreement is obtained for a relatively long-time gas discharge for jet like or plume like flow behaviour.

In the prospect of a safe use of hydrogen in our society one important task is to evaluate under which conditions the storage of hydrogen systems can reach a sufficient level of safety. One of the most important issues is the use of such system in closed area for example a private garage or an industrial facility. In the scope of this paper we are mainly interested in the following scenario: a relatively slow release of hydrogen (around 5Nl/min) in a closed and almost cubic box representing either a fuel cell at normal scale or a private garage at a smaller scale. For practical reasons helium was used instead of hydrogen in the experiments on which are based our comparisons. This kind of situation leads to the fundamental problem of the dispersion of hydrogen due to a simple vertical source in an enclosure. Many numerical and experimental studies have already been conducted on this problem showing the formation of either a stably stratified distribution of concentration or the formation of a homogeneous layer due to high enough convective flows at the top of the enclosure. Nevertheless most of them consider the cases of accidental situation in which the flow rate is relatively important (higher than 10Nl/min). Numerical simulations carried out with the CEA code Cast3M and a LES turbulence model confirm the differences of results already observed in experimental helium concentration measurements for a same injection flow rate and two different injection nozzle diameters contradicting simple physical models used in safety calculations.

The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.

The thermal degradation of two epoxy resin/carbon fiber composites which differ by their volume fractions in carbon fiber (56 and 59 vol%.) was investigated in cone calorimeter under air atmosphere with a piloted ignition. The external heat flux of cone calorimeter was varied up to 75 kW.m-2 to study the influence of the carbon fiber amount on the thermal decomposition of those composites. Thus main parameters of the thermal decomposition of two different composites were determined such as: mass loss mass loss rate ignition time thermal response parameter ignition temperature critical heat flux thermal inertia and heat of gasification. As a result all the parameters that characterize the thermal resistance of composites are decreased when the carbon fiber volume fraction is increased.

The aim of the present work is to investigate the interaction between a water spray and a laminar hydrogen-air flame in the case of steam inerted mixture. A first work is devoted to study the thermodynamics involved in the phenomena via a lumped parameter code. The flow is two- phase and reactive the gas is multi-component the water spray is polydisperse and the droplet size has certainly an influence on the flame propagation. The energy released by the reaction between hydrogen and oxygen vaporizes suspended droplets. The next step of this study will be to consider a drift-flux model for the droplets and air under hypotheses that the velocity and thermal disequilibria are weak. The multi-component feature of the gas will be further taken into account by studying a gas mixture containing hydrogen air and water vapor. A second study concerns an experimental investigation of the effect of droplets on the flame propagation using a spherical vessel. A Schlieren system is coupled to the spherical vessel in order to record the flame propagation on a digital high speed camera. Both studies will help improve our knowledge of safety relevant phenomena.

The present document is part of a larger literature survey of this WP aiming to establish the current status of gas utilisation technologies in order to determine the impact of hydrogen (H₂) admixture on natural gas (NG) appliances. This part focuses on the non-combustion related aspects of injecting hydrogen in the gas distribution networks within buildings including hydrogen embrittlement of metallic materials chemical compatibility and leakage issues. In the particular conditions of adding natural gas and hydrogen (NG / H2) mixture into a gas distribution network hydrogen is likely to reduce the mechanical properties of metallic components. This is known as hydrogen embrittlement (HE) (Birnbaum 1979). This type of damage takes place once a critical level of stress / strain and hydrogen content coexist in a susceptible microstructure. Currently four mechanisms were identified and will be discussed in detail. The way those mechanisms act independently or together is strongly dependent on the material the hydrogen charging procedure and the mechanical loading type. The main metallic materials used in gas appliances and gas distribution networks are: carbon steels stainless steels copper brass and aluminium alloys (Thibaut 2020). The presented results showed that low alloy steels are the most susceptible materials to hydrogen embrittlement followed by stainless steels aluminium copper and brass alloys. However the relative pressures of the operating conditions of gas distribution network in buildings are low i.e. between 30 to 50 mbar. At those low hydrogen partial pressures it is assumed that a gas mixture composed of NG and up to 50% H2 should not be problematic in terms of HE for any of the metallic materials used in gas distribution network unless high mechanical stress / strain and high stress concentrations are applied. The chemical compatibility of hydrogen with other materials and specifically polyethylene (PE) which is a reference material for the gas industry is also discussed. PE was found to have no corrosion issues and no deterioration or ageing was observed after long term testing in hydrogen gas. The last non-combustion concern related to the introduction of hydrogen in natural gas distribution network is the propensity of hydrogen toward leakage. Indeed the physical properties of hydrogen are different from other gases such as methane or propane and it was observed that hydrogen leaks 2.5 times quicker than methane. This bibliographical report on material deterioration chemical compatibility and leakage concerns coming with the introduction of NG / H₂ mixture in the gas distribution network sets the basis for the upcoming experimental work where the tightness of gas distribution network components will be investigated (Task 3.2.3 WP3). In addition tightness of typical components that connect end-user appliances to the local distribution line shall be evaluated as well.

"This paper summarises the modelling and experimental programme in the EC FP6 project HYPER. A number of key results are presented and the relevance of these findings to installation permitting guidelines (IPG) for small stationary hydrogen and fuel cell systems is discussed. A key aim of the activities was to generate new scientific data and knowledge in the field of hydrogen safety and where possible use this data as a basis to support the recommendations in the IPG. The structure of the paper mirrors that of the work programme within HYPER in that the work is described in terms of a number of relevant scenarios as follows: 1. high pressure releases 2. small foreseeable releases 3. catastrophic releases and 4. the effects of walls and barriers. Within each scenario the key objectives activities and results are discussed.<br/>The work on high pressure releases sought to provide information for informing safety distances for high-pressure components and associated fuel storage activities on both ignited and unignited jets are reported. A study on small foreseeable releases which could potentially be controlled through forced or natural ventilation is described. The aim of the study was to determine the ventilation requirements in enclosures containing fuel cells such that in the event of a foreseeable leak the concentration of hydrogen in air for zone 2 ATEX is not exceeded. The hazard potential of a possibly catastrophic hydrogen leakage inside a fuel cell cabinet was investigated using a generic fuel cell enclosure model. The rupture of the hydrogen feed line inside the enclosure was considered and both dispersion and combustion of the resulting hydrogen air mixture were examined for a range of leak rates and blockage ratios. Key findings of this study are presented. Finally the scenario on walls and barriers is discussed; a mitigation strategy to potentially reduce the exposure to jet flames is to incorporate barriers around hydrogen storage equipment. Conclusions of experimental and modelling work which aim to provide guidance on configuration and placement of these walls to minimise overall hazards is presented. "

A study of open literature was performed to determine the effects of high hydrogen purity and gas pressure (in the range of 700-1000 bar) on the hydrogen embrittlement of several metallic materials. A particular focus was given to carbon low-alloy and stainless steels but information on embrittlement of aluminum and copper was included in the study. Additionally the most common test methods were studied and results from similar tests are presented in a manner so as to simplify comparisons of materials. Finally suggestions are provided for future testing necessary to ensure the safety of hydrogen storage at 700 bar.

Recent studies of J.H. Song et al. and S.Y. Yang et al. have been concentrated on mitigation measures against hydrogen risk. The authors have proposed installation of quenching meshes between compartments or around the essential equipment in order to contain hydrogen flames. Preliminary tests were conducted which demonstrated the possibility of flame extinction using metallic meshes of specific size.<br/>Considerable amount of numerical and theoretical work on flame quenching phenomenon has been performed in the second half of the last century and several techniques and models have been proposed to predict the quenching phenomenon of the laminar flame system. Most of these models appreciated the importance of heat loss to the surroundings as a primary cause of extinguishment in particular the heat transfer by conduction to the containing wall. The supporting simulations predict flame-quenching structure either between parallel plates (quenching distance) or inside a tube of a certain diameter (quenching diameter).<br/>In the present study the flame quenching is investigated assuming the laminar hydrogen flame propagating towards a quenching mesh using two-dimensional configuration and the earlier developed models. It is shown that due to a heat loss to a metallic grid the flame can be quenched numerically.

The time and space evolution of the distribution of hydrogen in confined settings was investigated computationally and experimentally for permeation from typical compressed gaseous hydrogen storage systems for buses or cars. The work was performed within the framework of the InsHyde internal project of the HySafe NoE funded by EC. The main goal was to examine whether hydrogen is distributed homogeneously within a garage like facility or whether stratified conditions are developed under certain conditions. The nominal hydrogen flow rate considered was 1.087 NL/min based on the then current SAE standard for composite hydrogen containers with a non-metallic liner (type 4) at simulated end of life and maximum material temperature in a bus facility with a volume of 681m3. The release was assumed to be directed upwards from a 0.15m diameter hole located at the middle part of the bus cylinders casing. Ventilation rates up to 0.03 ACH were considered. Simulated time periods extended up to 20 days. The CFD simulations performed with the ADREA-HF code showed that fully homogeneous conditions exist for low ventilation rates while stratified conditions prevail for higher ventilation rates. Regarding flow structure it was found that the vertical concentration profiles can be considered as the superposition of the concentration at the floor (driven by laminar diffusion) plus a concentration difference between floor and ceiling (driven by buoyancy forces). In all cases considered this concentration difference was found to be less than 0.5%. The dispersion experiments were performed at the GARAGE facility using Helium. Comparison between CFD simulations and experiments showed that the predicted concentrations were in good agreement with the experimental data. Finally simulations were performed using two integral models: the fully homogeneous model and the two-layer model proposed by Lowesmith et al. (ICHS-2 2007) and the results were compared both against CFD and the experimental data.

The three years European MATHRYCE project dedicated to material testing and design recommendations for components exposed to hydrogen enhanced fatigue started in October 2012. Its main goal is to provide an “easy” to implement methodology based on lab-scale experimental tests under hydrogen gas to assess the service life of a real scale component taking into account fatigue loading under hydrogen gas. Dedicated experimental tests will be developed for this purpose. In the present paper the proposed approach is presented and compared to the methodologies currently developed elsewhere in the world.

This study outlines an approach to identifying the difficulties associated with the bench-marking of alkaline single cells under real electrolyzer conditions. A challenging task in the testing and comparison of different catalysts is obtaining reliable and meaningful benchmarks for these conditions. Negative effects on reproducibility were observed due to the reduction in conditioning time. On the anode side a stable passivation layer of NiO can be formed by annealing of the Ni foams which is even stable during long-term operation. Electrical contact resistance and impedance measurements showed that most of the contact resistance derived from the annealed Ni foam. Additionally analysis of various overvoltages indicated that most of the total overvoltage comes from the anode and cathode activation overpotential. Different morphologies of the substrate material exhibited an influence on the performance of the alkaline single cell based on an increase in the ohmic resistance.

The manuscript firstly describes the data collection and validation process for the European Hydrogen Incidents and Accidents Database (HIAD 2.0) a public repository tool collecting systematic data on hydrogen-related incidents and near-misses. This is followed by an overview of HIAD 2.0 which currently contains 706 events. Subsequently the approaches and procedures followed by the authors to derive lessons learned and formulate recommendations from the events are described. The lessons learned have been divided into four categories including system design; system manufacturing installation and modification; human factors and emergency response. An overarching lesson learned is that minor events which occurred simultaneously could still result in serious consequences echoing James Reason's Swiss Cheese theory. Recommendations were formulated in relation to the established safety principles adapted for hydrogen by the European Hydrogen Safety Panel considering operational modes industrial sectors and human factors. This work provide an important contribution to the safety of systems involving hydrogen benefitting technical safety engineers emergency responders and emergency services. The lesson learned and the discussion derived from the statistics can also be used in training and risk assessment studies being of equal importance to promote and assist the development of sound safety culture in organisations.

As governments focus on dealing with the Covid-19 health emergency they are increasingly turning their attention to the impact of shutting down their economies and how to revive them quickly through stimulus measures. Economic recovery packages offer a unique opportunity to create jobs while supporting clean energy transitions around the world.

Energy efficiency and renewable energy like wind and solar PV – the cornerstones of any clean energy transition – are good places to start. Those industries employ millions of people across their value chains and offer environmentally sustainable ways to create jobs and help revitalise the global economy.

But more than just renewables and efficiency will be required to put the world on track to meet climate goals and other sustainability objectives. IEA analysis has repeatedly shown that a broad portfolio of clean energy technologies will be needed to decarbonise all parts of the economy. Batteries and hydrogen-producing electrolysers stand out as two important technologies thanks to their ability to convert electricity into chemical energy and vice versa. This is why they also deserve a place in any economic stimulus packages being discussed today.

Link to Document on IEA Website

At the request of the government of Japan under its G20 presidency the International Energy Agency produced this landmark report to analyse the current state of play for hydrogen and to offer guidance on its future development.

The report finds that clean hydrogen is currently enjoying unprecedented political and business momentum with the number of policies and projects around the world expanding rapidly. It concludes that now is the time to scale up technologies and bring down costs to allow hydrogen to become widely used. The pragmatic and actionable recommendations to governments and industry that are provided will make it possible to take full advantage of this increasing momentum.

Hydrogen and energy have a long shared history – powering the first internal combustion engines over 200 years ago to becoming an integral part of the modern refining industry. It is light storable energy-dense and produces no direct emissions of pollutants or greenhouse gases. But for hydrogen to make a significant contribution to clean energy transitions it needs to be adopted in sectors where it is almost completely absent such as transport buildings and power generation.

The Future of Hydrogen provides an extensive and independent survey of hydrogen that lays out where things stand now; the ways in which hydrogen can help to achieve a clean secure and affordable energy future; and how we can go about realising its potential.

Link to Document on IEA Website

A phenomenological approach is developed to calculate the velocity of flame propagation and to estimate the value of pressure peak when igniting gaseous combustible mixtures in a congested space. The basic idea of this model is afterburning of the remanent fuel in pockets of congested space behind the flame front. The estimation of probable overpressure peak is based on solution of one-dimensional problem of the piston (having corresponding symmetry) moving with given velocity in polytropic gas. Submitted work is the first representation of such phenomenological approach and is realized for the simplest situation close to one-dimensional.