Safety

In the course towards a safe future hydrogen based society one of the tasks to be considered is the investigation of the conditions under which the use or storage of hydrogen systems inside buildings becomes too dangerous to be accepted. One of the relevant scenarios which is expected to have a relatively high risk is a slow (and long lasting) hydrogen release from a vehicle stored in a closed private garage without any forced ventilation i.e. only with Read More

The modelling of Rayleigh–Taylor instability during premixed combustion scenarios is presented. Experimental data obtained from experiments undertaken by FM Global using their large-scale vented deflagration chamber was used to develop the modelling approach. Rayleigh–Taylor instability is introduced as an additional time-dependent combustion enhancing mechanism. It is demonstrated that prior to the addition of this mechanism the LES deflagration Read More

Experiments were carried out inside a 25 m3 vented combustion test facility (CVE) with a fixed vent area sealed by a plastic sheet vent. Inside the CVE a 0.64 m3 open vent box called RED-CVE was placed. The vent of the RED-CVE was left open and three different vent area were tested. Two different mixing fans one for each compartment were used to establish homogeneous H2 concentrations. This study examined H2 concentrations in the range between Read More

In the transition to a hydrogen economy it is likely that hydrogen will be used or stored in close proximity to other flammable fuels and gases. Accidents can occur that result in the release of two or more fuels such as hydrogen and natural gas that can mix and form a hazard. A series of five medium-scale semi-open-space deflagration experiments have been conducted with hydrogen natural gas and air mixtures. The natural gas consisted of 90% methan Read More

We present results from hydrogen dispersion simulations from a pressurized reservoir at constant flow rate in the presence and absence of a wall. The dispersion simulations are performed using a commercial finite volume solver. Validation of the approach is discussed. Constant concentration envelopes corresponding to the 2% 4% and 15% hydrogen concentration in air are calculated for a subcritical vertical jet and for an equivalent subcritical ho Read More

The development of hydrogen as energy carrier is promoted by the increasing in energy demand depletion of fossil resources and the global warming. However this issue relies primarily on the safety aspect which requires the knowledge in the case of gas release of the quantities such as the flammable cloud size release path and the location of the lower flammability limit of the mixture. The integral models for predicting the atmospheric dispersi Read More

Clarification of questions of safety represents a decisive contribution to the successful introduction of vehicles fuelled by hydrogen. At the moment the safety of hydrogen is being discussed and investigated by various bodies. The primary focus is on fuel-cell vehicles with hydrogen stored in gaseous form. This paper looks at the safety of hydrogen-fuelled vehicles with an internal combustion engine and liquefied hydrogen storage. The safety concept of BMW’s Read More

The first part of the present work is to validate a detailed kinetic mechanism for the oxidation of hydrogen – methane – air mixtures in a detonation waves. A series of experiments on auto-ignition delay times have been performed by shock tube technique coupled with emission spectrometry for H2 / CH4 / O2 mixtures highly diluted in argon. The CH4/H2 ratio was varied from 0 to 4 and the equivalence ratio from 0.4 up to 1. The temperature range was Read More

Hydrogen is not more dangerous than current fossil energy carriers but it behaves differently. Therefore hydrogen specific analyses and countermeasures will be needed to support the development of safe hydrogen technologies. A systematic step-by-step procedure for the mechanistic analysis of hydrogen behaviour and mitigation in accidents is presented. The procedure can be subdivided into four main parts:1) 3D modelling of the H2-air mixture ge Read More

The CEP (Clean Energy Partnership) – Berlin is one of the most diversified hydrogen demonstration projects at present. The first hydrogen fuelling station serving 16 cars is fully integrated in an ordinary highly frequented Aral service station centrally located at Messedamm in Berlin. Hydro has supplied and is the owner of the electrolyser with ancillary systems. This unit produces gaseous hydrogen at 12 bar with use of renewable energy presently servin Read More

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 fro Read More

Computational Fluid Dynamics codes are increasingly being considered for safety assessment demonstrations in many industrial fields as tools to model accidental phenomena and to design mitigation (risk reducing) systems. Thus they naturally complement experimental programmes which may be expensive to run or difficult to set up. However to trust numerical simulations the validity of the codes must be firmly established and a certain number of err Read More

As Europe is gradually moving towards a hydrogen based society it has been acknowledged that adding certain amount of hydrogen as a clean energy carrier to the existing natural gas pipeline will help reduce the CO2 emissions which contribute to the greenhouse effect. On the other hand hydrogen has been demonstrated to be able to change the behaviour of the pipeline steel such as lower toughness and faster crack growth due to hydrogen em Read More

In searching for high gravimetric and volumetric density hydrogen storage systems it is inevitable that higher energy density materials will be used. In order to make safe and commercially acceptable condensed phase hydrogen storage systems it is important to understand quantitatively the hazards involved in using and handling these materials and to develop appropriate mitigation strategies to handle potential material exposure events. A crucial aspect Read More

Knowledge of the concentration field and flammability envelope from small-scale leaks is important for the safe use of hydrogen. These small-scale leaks may occur from leaky fittings or o-ring seals on liquid hydrogen-based systems. The present study focuses on steady-state leaks with large amounts of pressure drop along the leak path such that hydrogen enters the atmosphere at near atmospheric pressure (i.e. Very low Mach number). A three- Read More

Metallic hydrides represent a safe way of storing hydrogen minimising explosion and flammability risks. Nowadays there are several methods for the storage of hydrogen and the more conventional techniques are high-pressure tanks for gaseous hydrogen and cryogenic vessels for liquid hydrogen. However there are two main drawbacks in the storage of gaseous and liquid hydrogen. First as a fuel hydrogen in the gaseous and liquid states is very combustibl Read More

Discrete Event Simulation (DES) environments are rapidly developing and they appear to be promising tools for developing reliability and risk analysis models of safety-critical systems. DES models are an alternative to the conventional methods such as fault and event trees Bayesian networks and cause-consequence diagrams that could be used to assess the reliability of fuel supply. DES models can rather easily account for the dynamic dimension Read More

The temperature of the hydrogen cylinder needs to be carefully controlled during fuelling process. The maximum temperature should be less than 85℃ according to the ISO draft code. If the fuelling period is reduced the maximum temperature should increase. In this study temperature change of a Type IV cylinder was measured during the hydrogen fuelling process up to 35 MPa. Fuelling period was 3 to 5 minutes. Twelve thermocouples were installe Read More

The objectives of the presented experimental work were investigation of hydrogen release distribution and combustion modelling possible emergency situation at industry scale. Results of large scale experiments on distribution and combustion in an open and congested area are presented. The mass of hydrogen in experiments varied from 50g to 1000g with release rate from 180 to 220 g/s. Qualitative characteristics of high momentum hydrogen Read More

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 rele Read More

Results are given of experimental study of propagation of explosion waves in hydrogen-air mixtures of different compositions under conditions of cumulation. The investigations are performed in a setup consisting of two parts namely the upper part in the form of a metal cone and the lower part in the form of a rubber envelope hermetically attached to the cone. The upper and lower parts of the experimental setup are separated by a thin rubber film and Read More

Recent advances in optical sensors show promise for the development of new wide area monitoring and distributed optical network hydrogen detection systems. Optical hydrogen sensing technologies reviewed here are: 1) open path Raman scattering systems 2) back scattering from chemically treated solid polymer matrix optical fiber sensor cladding; and 3) schlieren and shearing interferometry imaging. Ultrasonic sensors for hydrogen release detec Read More

Hydrogen is being considered as a pathway to decarbonize large energy systems and for utility-scale energy storage. As these applications grow transportation infrastructure that can accommodate large quantities of hydrogen will be needed. Many millions of tons of hydrogen are already consumed annually some of which is transported in dedicated hydrogen pipelines. The materials and operation of these hydrogen pipeline systems however Read More

Numerical simulations have been carried out for pressurised hydrogen release through a nozzle in a simulated vehicle refilling environment of an experiment carried out in a joint industry project by Shell bp Exxon and the UK HSE Shirvill[1]. The computational domain mimics the experimental set up for a vertical downwards release in a vehicle refuelling environment. Due to lack of detailed data on pressure decay in the storage cylinder following the releas Read More

Considering the transition towards the hydrogen economy dependent on hydrogen penetration scenario the cost of a new hydrogen pipeline infrastructure in Europe may amount to several thousands of billions of EURO’s. Therefore the examination of the potential contribution of the existing natural gas assets is a practical and logical first step. As the physical and chemical properties of hydrogen differ significantly from those of natural gas it is not at all possi Read More

In the present paper the two-stage model of detonative combustion of hydrogen is presented. The following improvements are described: accurate description of the heat release stage of combustion; the clear physics-based procedure for calculation of the parameters of the proposed model; sample calculations of the detonation wave in hydrogen/air mixtures in wide range of conditions showing that the proposed model performs well in a wide Read More

The report summarizes experimental results on the mechanisms and kinetics of hydrogen-air flammable gas cloud formation and evolution due to foreseeable (less than 10-3 kg/sec) hydrogen leaks into confined spaces with different shapes sizes and boundary conditions. The goals were - 1) to obtain qualitative information on the basic gas-dynamic patterns of flammable cloud formation at different leak velocities (between 935 and 905 m/sec) f Read More

In the present work release and ignition experiments with horizontal cryogenic hydrogen jets at temperatures of 35–65 K and pressures from 0.7 to 3.5 MPa were performed in the ICESAFE facility at KIT. This facility is specially designed for experiments under steady-state sonic release conditions with constant temperature and pressure in the hydrogen reservoir. In distribution experiments the temperature velocity turbulence and concentration distributio Read More

Within the scope of the French national project DRIVE and European project HyPER high pressure jet flames of hydrogen were produced and instrumented.The experimental technique and measurement strategy are presented. Many aspects are original developments like the direct measurement of the mass flow rate by weighing continuously the hydrogen container the image processing to extract the flame geometry the heat flux measurem Read More

In this paper safety considerations related to the operation of proton-exchange membrane (PEM) water electrolysers (hydrogen production capacity up to 1 Nm3/h and operating pressure up to 130 bars) are presented. These results were obtained in the course of the GenHyPEM project a research program on high-pressure PEM water electrolysis supported by the European Commission. Experiments were made using a high-pressure electrolysis stack de Read More

The issue of spontaneous ignition of highly pressurized hydrogen release is of important safety concern e.g. in the assessment of risk and design of safety measures. This paper reports on recent numerical investigation of this phenomenon through releases via a length of tube. This mimics a potential accidental scenario involving release through instrument line. The implicit large eddy simulation (ILES) approach was used with the 5th-order weighted essen Read More

Spontaneous ignition processes due to the high-pressure hydrogen releases into air were investigated both experimentally and theoretically. Such processes reproduce accident scenarios of sudden expansion of pressurized hydrogen into the ambient atmosphere in cases of tube or valve rupture. High-pressure hydrogen releases in the range of initial pressures from 20 to 275 bar and with nozzle diameters of 0.5 – 4 mm have been investigated. Glass tube Read More

Hydrogen behavior at elevated pressures and temperatures was intensively studied by numerous investigators. Nevertheless there is a lack of experimental data on hydrogen ignition and combustion at reduced sub-atmospheric pressures. Such conditions are related to the facilities operating under vacuum or sub-atmospheric conditions for instance like ITER vacuum vessel. Main goal of current work was an experimental evaluation of such fundamental Read More

The growing attention being paid by car manufacturers and the general public to hydrogen as a middle and long term energy carrier for automotive purpose is giving rise to lively discussions on the advantages and disadvantages of this technology – also with respect to safety. In this connection the focus is increasingly and justifiably so on the possibilities offered by a probabilistic approach to loads and component characteristics: a lower weight oblige Read More

Fuel storage systems for vehicles require a fail-safe design strategy. In case of system failures or accidents the control electronics have to switch the system into a safe operation mode. Failure Mode and Effect Analysis (FMEA) or Failure Tree Analysis (FTA) are performed already in the early design phase in order to minimize the risk of design failures in the fuel storage system. Currently the specifications of requirements for pressurized and liquid hydrogen fue Read More

This paper discusses the results of computational fluid dynamics (CFD) modelling of hydrogen releases and dispersion outdoors during venting of hydrogen storage in real environment and geometry of a hydrogen refuelling or energy station for a given flow rate and dimensions of vent stack. The PHOENICS CFD software package was used to solve the continuity momentum and concentration equations with the appropriate boundary conditions buoyancy Read More

Hydrogen is one of the important alternative fuels for future transportation. At the present stage research into hydrogen safety and designing risk mitigation measures are significant task. For compact storage of hydrogen in fuel cell vehicles storage of hydrogen under high pressure up to 40 MPa at refuelling stations is planned and safety in handling such high-pressure hydrogen is essential. This paper describes our experimental investigation into disper Read More

Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and co Read More

In this document after a review of the accidents/incidents are described the different interactions between hydrogen gas and the most commonly used materials including the influence of "internal" and "external" hydrogen the phenomena occurring in all ranges of temperatures and pressures and Hydrogen Embrittlement (HE) created by gaseous hydrogen. The principle of all the test methods used to investigate this phenomenon are presented and di Read More

The transition period towards the situation in which hydrogen will become an important energy carrier will be lengthy (decades) costly and needs a significant R&D effort. It’s clear therefore that the development of a hydrogen system requires a practical strategy within the context of the existing assets. Examining the potential of the existing extensive natural gas chain (transmission - distribution - end user infrastructures and appliances) is a logical first step Read More

A review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials hydrogen embrittlement low temperature effects material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials the hydride formation of titanium alloys is considered. Alpha titanium alloys are c Read More

Hydrogen technology requires efficient and safe hydrogen storage systems. For this purpose storage in solid materials such as high capacity complex hydrides is studied intensely. Independent from the actual material to be used eventually any tank design will combine nanoscale powders of highly reactive material with pressurized hydrogen gas and so far little is known about the behaviour of these mixtures in case of incidents. For a first evaluation Read More

Experiments were performed to investigate the radiative heat emission of small scale hydrogen/air explosions also impurified by minor amounts of inert particles and organic fuels. A volume of 1.5 dm3 hydrogen was injected into ambient air as free-jet and ignited. In further experiments simultaneously inert Aerosil and combustible fuels were injected into the blasting hydrogen/air gas cloud. Fuels were a spray of a solvent (Dipropyleneglycol-methyleth Read More

INERIS has set up large-scale fully instrumented experiments to study the formation of flammable clouds resulting from a finite duration spillage of hydrogen in a quiescent room (80 m3 chamber). Concentration temperature and mass flow measurements were monitored during the release period and several hours after. Experiments were carried out for mass flow rates ranging from 02 g/s to 1 g/s. The instrumentation allowed the observation and quan Read More

This paper is concerned with predicting the impact on the probability of failure of adding hydrogen to the natural gas distribution network. Hydrogen has been demonstrated to change the behaviour of crack like defects which may affect the safety of pipeline or make it more expensive to operate. A tool has been developed based on a stochastic approach to assess the failure probability of the gas pipeline due to the existence of crack-lie defects includ Read More

The BMW Hydrogen 7 is the world’s first premium sedan with a bi-fuelled internal combustion engine concept that has undergone the series development process. This car also displays the BMW typical driving pleasure. During development the features of the hydrogen energy source were emphasized. Engine tank system and vehicle electronics were especially developed as integral parts of the vehicle for use with hydrogen. The safety-oriented develop Read More

Underground or partial underground tunnels form a very important part of modern road transportation systems. As the development of hydrogen cars advancing into the markets it is unavoidable in the near future that hydrogen cars would become the users of ordinary road tunnels. This paper discusses potential fire scenarios and fire hazards of hydrogen cars in road tunnels and implications on the fire safety measures and ventilation systems in e Read More

The paper presents an overview of the main results of the EC NOE HySafe activity to estimate an allowable hydrogen permeation rate for automotive legal requirements and standards. The work was undertaken as part of the HySafe internal project InsHyde.A slow long term hydrogen release such as that due to permeation from a vehicle into an inadequately ventilated enclosed structure is a potential risk associated with the use of hydrogen in automotive Read More

A series of experiments are described in which helium was released at a constant rate into a 1.5 m × 1.5 m × 0.75 m enclosure designed as a ¼-scale model of a two car garage. The purpose was to provide reference data sets for testing and validating computational fluid dynamics (CFD) models and to experimentally characterize the effects of a number of variables on the mixing behaviour within an enclosure and the exchange of helium with the Read More

It has been suggested that separation or safety distances for pressurised hydrogen storage can be reduced by the inclusion of walls or barriers between the hydrogen storage and vulnerable plant or other items. Various NFPA codes (1) suggest the use of 60° inclined fire barriers for protection against jet flames in preference to vertical ones.This paper describes a series of experiments performed in order to compare the performance of 60° barriers with tha Read More