France

Introduction and commercialisation of hydrogen as an energy carrier of the future make great demands on all aspects of safety. Safety is a critical issue for innovations as it influences the economic attractiveness and public acceptance of any new idea or product. However research and safety expertise related to hydrogen is quite fragmented in Europe. The vision of a significant increased use of hydrogen as an energy carrier in Europe could not go ahead without strengthening and merging this expertise. This was the reason for the European Commission to support the launch on the first of March 2004 of a so-called Network of Excellence (NoE) on hydrogen safety: HySafe.

Climate change is one of today’s most pressing global challenges. Since the emission of greenhouse gases is often closely related to the use and supply of energy the goal to avoid emissions requires a fundamental restructuring of the energy system including all parts of the technology chains from production to end-use. Natural gas is today one of the most important primary energy sources in Europe with utilization ranging from power generation and industry to appliances in the residential and commercial sector as well as mobility. As natural gas is a fossil fuel gas utilization is thus responsible for significant emissions of carbon dioxide (CO₂ ) a greenhouse gas. However the transformation of the gas sector with its broad variety of technologies and end-use applications is a challenge as a fuel switch is related to changing physical properties. Today the residential and commercial sector is the biggest end user sector for natural gas in the EU both in terms of consumption and in the number of installed appliances. Natural gas is used to provide space heating as well as hot water and is used in cooking and catering appliances with in total about 200 million gas-fired residential and commercial end user appliances installed. More than 40 % of the EU gas consumption is accounted for by the residential and commercial sector. The most promising substitutes for natural gas are biogases and hydrogen. The carbon-free fuel gas hydrogen may be produced e.g. from water and renewable electricity; therefore it can be produced with a greatly lowered carbon footprint and on a very large scale. As a gaseous fuel it can be transported stored and utilised in all end-use sectors that are served by natural gas today: Power plants industry commercial appliances households and mobility. Technologies and materials however need to be suitable for the new fuel. The injection of hydrogen into existing gas distribution for example will impact all gas-using equipment in the grids since these devices are designed and optimized to operate safely efficiently and with low pollutant emissions with natural gas as fuel. The THyGA project1 focusses on all technical aspects and the regulatory framework concerning the potential operation of domestic and commercial end user appliances with hydrogen  / natural gas blends. The THyGA deliverables start with theoretical background from material science (D2.4) and combustion theory (this report) and extend to the project’s experimental campaign on hydrogen tolerance tests as well as reports on the status quo and potential future developments on rules and standards as well as mitigation strategies for coping with high levels of hydrogen admixture. By this approach the project aims at investigating which levels of hydrogen blending impact the various appliance technologies to which extent and to identify the regime in which a safe efficient and low-polluting operation is possible. As this is in many ways a question of combustion this report focuses on theoretical considerations about the impact of hydrogen admixture on combustion processes. The effects of hydrogen admixture on main gas quality properties as well as combustion temperatures laminar combustion velocities pollutant formation (CO NOx) safety-related aspects and the impact of combustion control are discussed. This overview provides a basis for subsequent steps of the project e.g. for establishing the testing program. A profound understanding of the impact on hydrogen on natural gas combustion is also essential for the development of mitigation strategies to reduce potential negative consequences of hydrogen admixture on appliances.

This is part one. Part two of this project can be found at this link

Explosion venting is a prevention/mitigation solution widely used in the process industry to protect indoor equipment or buildings from excessive internal pressure caused by an accidental explosion. Vented explosions are widely investigated in the literature for various geometries hydrogen/air concentrations ignition positions initial turbulence etc. In real situations the vents are normally covered by a vent panel. In the case of an indoor leakage the hydrogen/air cloud will be stratified rather than homogeneous. Nowadays there is a lack in understanding about the vented explosion of stratified clouds and about the influence of vent cover inertia on the internal overpressure. This paper aims at shedding light on these aspects by means of experimental investigation of vented hydrogen/air deflagration using an experimental facility of 1m3 and via numerical simulations using the computational fluid dynamics (CFD) code FLACS

Polymer electrolyte membrane (PEM) water electrolysis is an efficient and environmental friendly method that can be used for the production of molecular hydrogen of electrolytic grade using zero-carbon power sources such as renewable and nuclear. However market applications are asking for cost reduction and performances improvement. This can be achieved by increasing operating current density and lifetime of operation. Concerning performance safety reliability and durability issues the membrane-electrode assembly (MEA) is the weakest cell component. Most performance losses and most accidents occurring during PEM water electrolysis are usually due to the MEA. The purpose of this communication is to report on some specific degradation mechanisms that have been identified as a potential source of performance loss and membrane failure. An accelerated degradation test has been performed on a MEA by applying galvanostatic pulses. Platinum has been used as electrocatalyst at both anode and cathode in order to accelerate degradation rate by maintaining higher cell voltage and higher anodic potential that otherwise would have occurred if conventional Ir/IrOx catalysts had been used. Experimental evidence of degradation mechanisms have been obtained by post-mortem analysis of the MEA using microscopy and chemical analysis. Details of these degradation processes are presented and discussed.

In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking (KIH) constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2% proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa m1/2 to 44.5 MPa m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa m1/2 to 41.1 MPa m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material.

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.

This work deals with a comparative study of regulations codes and standards for hydrogen fuelling station dedicated for light duty land vehicles in the following countries: United States (California) United Kingdom Italy Germany Canada Sweden Norway Denmark and Spain.<br/>The following technical components of a hydrogen fuelling station are included in the scope of the study: the hydrogen storage systems (cryogenic or compressed gases) and buffer storage the compressor stations the high pressure buffer storage the cooling systems for hydrogen the dispensing equipments and the dispensing area. The hydride storage the pipelines on site production and the hydrogen vehicle have been excluded.<br/>The analysis performed in September 2014 in a report from INERIS DRA-14-141532-06227C BENCHMARK STATIONS-SERVICE HYDROGENE is based on documents collected by bibliographic review and information obtained through a questionnaire sent to authorities and IA HySafe members in the above mentioned countries.<br/>This paper gives a synthesis of the regulations and on permitting process in the different studied countries (including the new European Directive on the deployment of alternative fuels infrastructure in Europe) it develops the required safety barriers in the different parts of a fuelling station and specially for the dispensing area gives an overview of the different approaches for safety distances and processes to obtain licences to operate.

A methodology for explosion and fire risk analyses in enclosed rooms is presented. The objectives of this analysis are to accurately predict the risks associated with hydrogen leaks in maritime applications and to use the approach to provide decision support regarding design and risk-prevention and risk mitigating measures. The methodology uses CFD tools and simpler consequence models for ventilation dispersion and explosion scenarios as well as updated frequency for leaks and ignition. Risk is then efficiently calculated with a Monte Carlo routine capturing the transient behavior of the leak. This makes it possible to efficiently obtain effects of sensitivities and design options maintaining safety and reducing costs.

In order to improve risk analyses and influence the design of the future H2 systems an experimental study on “real” leaks qualification and quantification was performed. In H2 energy applications fittings appeared as a significant leakage potential and subsequently explosion and flame hazards. Thus as a part of the “Horizon Hydrogène Energie” French program four kinds of commercial fittings usually employed on H2 systems were tested thanks to a new high pressure test bench – designed setup and operated by INERIS – allowing experiments to be led for H2 pressures until 700 bar. The fittings underwent defined stresses representative of H2 systems lifetime and beyond. The associated leaks – when existing – are characterized in terms of flow rate.

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.