Guidance on Sensor Placement was identified as the top research priority for hydrogen sensors at the 2018 HySafe Research Priority Workshop on hydrogen safety in the category Mitigation, Sensors, Hazard Prevention, and Risk Reduction. This paper discusses the initial steps (Phase 1) to develop such guidance for mechanically ventilated enclosures. This work was initiated as an international collaborative effort to respond to emerging market needs related to the design and deployment equipment for hydrogen infrastructure that is often installed in individual equipment cabinets or ventilated enclosures. The ultimate objective of this effort is to develop guidance for an optimal sensor placement such that, when integrated into a facility design and operation, will allow earlier detection at lower levels of incipient leaks, leading to significant hazard reduction. Reliable and consistent early warning of hydrogen leaks will allow for the risk mitigation by reducing or even eliminating the probability of escalation of small leaks into large and uncontrolled events. To address this issue, a study of a real-world mechanically ventilated enclosure containing GH2 equipment was conducted, where CFD modeling of the hydrogen dispersion (performed by AVT and UQTR, and independently by the JRC) was validated by the NREL Sensor laboratory using a Hydrogen Wide Area Monitor (HyWAM) consisting of a 10-point gas and temperature measurement analyzer. In the release test, helium was used as a hydrogen surrogate. Expansion of indoor releases to other larger facilities (including parking structures, vehicle maintenance facilities and potentially tunnels) and incorporation into QRA tools, such as HyRAM is planned for Phase 2. It is anticipated that results of this work will be used to inform national and international standards such as NFPA 2 Hydrogen Technologies Code, Canadian Hydrogen Installation Code (CHIC) and relevant ISO/TC 197 and CEN documents.

The actual engineering utilization of hydrogen energy technologies requires a series of best practices and regulations, codes, and standards (RCS) to be properly followed for safety, efficiency, and sustainability reasons. Metrology is a foundation and guarantor of high-quality technical RCS and is critically essential for conformity assessment of products and services that ensure public safety. In addition to that, the introduction of a new form of energy in the world energy matrix is very much dependent on the social acceptance of new technologies from safety and risk perspective. These themes should be reviewed and specified and have their introduction in the society evaluated by time-independent analyses.

The effect of an adjacent surface on the lower flammability limit cloud extents of high pressure horizontal and vertical unignited jets of both hydrogen and methane is studied using Computational Fluid Dynamics (CFD) simulations performed with FLACS Hydrogen. Two jet directions (horizontal and vertical) and two surface positions (horizontal or ground, vertical or side wall) were studied: horizontal jets along a horizontal surface, vertical and horizontal jets along a vertical surface or side wall. Results for constant flow rate through a 6.35 mm round leak orifice from 101 bar, 251 bar, 401 bar, 551 bar and 701 bar compressed gas systems are presented. The effect of the surface on the flammable extents is studied systematically by positioning the jet exit release at various distances from the surface ranging from 0.029 m to 10 m. Free jets simulations were performed for comparison purposes. Our results were quantified by establishing engineering correlations that could be used to predict the flammable extent of hydrogen and methane jet releases in the presence of surfaces. These correlations were validated using experiments conducted for horizontal hydrogen jets in the vicinity of horizontal surfaces, carried out at the facilities of Defence Research and Development Canada (DRDC) in Val-Belair, Quebec. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This chapter gives a brief overview of hydrogen safety and RCS (regulations, codes, and standards). From the safety perspective, the focus is given to hydrogen flammability and materials compatibility issues, and from the RCS perspective to key international activities.

There has been increasing interest in using Quantitative Risk Assessment (QRA) to help improve the safety of hydrogen infrastructure and applications. Hydrogen infrastructure for transportation (e.g. fueling fuel cell vehicles) or stationary (e.g. back-up power) applications is a relatively new area for application of QRA vs. traditional industrial production and use, and as a result there are few tools designed to enable QRA for this emerging sector. There are few existing QRA tools containing models that have been developed and validated for use in small-scale hydrogen applications. However, in the past several years, there has been significant progress in developing and validating deterministic physical and engineering models for hydrogen dispersion, ignition, and flame behavior. In parallel, there has been progress in developing defensible probabilistic models for the occurrence of events such as hydrogen release and ignition. While models and data are available, using this information is difficult due to a lack of readily available tools for integrating deterministic and probabilistic components into a single analysis framework. This paper discusses the first steps in building an integrated toolkit for performing QRA on hydrogen transportation technologies and suggests directions for extending the toolkit.

The Hydrogen Incident and Accident Database (HIAD) is being developed as a repository of systematic data describing in detail hydrogen-related undesired events (incidents or accidents). It is an open web-based information system serving various purposes such as a data source for lessons learnt, risk communication and partly risk assessment. The paper describes the features of the three HIAD modules – the Data Entry Module (DEM), the Data Retrieval Module (DRM) and the Data Analysis Module (DAM) – and the potential impact the database may have on hydrogen safety. The importance of data quality assurance process is also addressed.

The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using computer fluid dynamics simulations performed with FLAGS Hydrogen. Results for constant flow rate through a 6.35 mm diameter pressure relief Device (PRD) orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for both horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet, the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes. Also, for cross-validation purposes, a number of cases for 100 barg releases were simulated using proprietary models developed for hydrogen within commercial CFD software PHOENICS. It is found that the presence of a surface and its proximity to the jet centreline result in a pronounced increase in the extent of the flammable cloud compared to a free jet. (c) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm round leak orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for vertical jets. To quantify the effect of the surface on the jet, the jet exit is positioned at various distances from the surface ranging from 0.029 m to 12 m. Free jets simulations are performed for comparison purposes.

The permitting process for hydrogen fueling stations requires demonstration that the proposed facility meets certain safety requirements. Currently, many permitting authorities rely on compliance with well-known codes and standards as evidence of a safe design. To ensure that a hydrogen facility is indeed safe, the code and standard requirements should be identified using a risk-informed process that utilizes an acceptable level of risk. This paper describes an approach for risk-informing the permitting process for hydrogen fueling stations that relies primarily on the establishment of risk-informed codes and standards. Using accepted Quantitative Risk Assessment (QRA) techniques and the established risk criteria, the minimum code and standard requirements necessary to ensure the safe operation of hydrogen facilities can be identified. To facilitate consistent risk-informed approaches, the participants in the International Energy Agency (IEA) Task 19 on hydrogen safety are working to identify acceptable risk criteria, QRA models, and supporting data. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Hydrogen clearance or safety distance can be defined as the minimum distance between a hydrogen leak source and surrounding equipment, property or personnel beyond which the risk to the said recipients associated with existing hydrogen hazards is deemed acceptable. The same principal is applied to determine clearances to ignition sources and air intakes only the criteria in this case are the risk of ignition or the risk of intaking a flammable mixture. The study of effects of small barriers as means to reduce clearance distances for compressed hydrogen releases is important for the development of installation codes and risk mitigation requirements. In this paper, computational fluid dynamics (CFD) modeling techniques were applied to the numerical simulation of the effects of a protective wall of 1m by 1m on reducing the size of hydrogen cloud. The protective wall was 1m away from a 70MPa (700bar) 60L tank, from which an incidental hydrogen release impinged horizontally onto the wall, causing a complicated 3D dispersion of hydrogen cloud. In-house CFD codes first accurately estimated the non-linear hydrogen mass release rate decreasing with time. Then the effects of the wall on the propagation speed of the hydrogen cloud moving behind the wall were investigated using the PHOENICS software package, provided with both the ideal gas law and the real gas law expressed by the Abel-Nobel equation of state (AN-EOS). The distributions of lower flammability limit (LFL) and 50% of LFL hydrogen clouds were described in detail based on the numerical results. It was found that the 50% of LFL hydrogen clouds (2%vol) could propagate behind the wall in less than 0.2s after the onset of the release. The horizontal extents corresponding to 50% of LFL hydrogen cloud on the central vertical plane are 9.6m at 5s when they are predicted using the ideal gas law. When using the real gas law, the predicted extents decrease to 6.3m at 5s. The ideal gas law significantly overestimates the hypothetical hydrogen cloud volumes for LFL, or fractions of LFL, for different release times at the current initial stagnation pressure level (700bar). The current model codes and standards generally specify clearance distances for hydrogen based on the regulators’ experience in other flammable gases, like natural gas or propane, rather than on real hydrogen gas properties that particularly deviate from ideal gas law under high pressure. On the other hand, it is relatively more conservative to exploit the ideal gas law to predict the combustible hydrogen cloud extents than using the real gas law for industrial applications. The numerical results from the impingement release also confirm that a small protective wall, or a barrier, can reduce the hydrogen concentration behind the wall. The numerical results can be further applied for defining the zoning requirements for Canadian Electrical Code and clearance distances for Canadian Hydrogen Installation Code.

Hydrogen has the potential to be used by many countries as part of decarbonising the future energy system. Hydrogen can be used as a fuel ‘vector’ to store and transport energy produced in low-carbon ways. This could be particularly important in applications such as heating and transport where other solutions for low and zero carbon emission are difficult. To enable the safe uptake of hydrogen technologies, it is important to develop the international scientific evidence base on the potential risks to safety and how to control them effectively. The International Association for Hydrogen Safety (known as IA HySAFE) is leading global efforts to ensure this. HSE hosted the 2018 IA HySAFE Biennial Research Priorities Workshop. A panel of international experts presented during nine key topic sessions: (1) Industrial and National Programmes; (2) Applications; (3) Storage; (4) Accident Physics – Gas Phase; (5) Accident Physics – Liquid/ Cryogenic Behaviour; (6) Materials; (7) Mitigation, Sensors, Hazard Prevention and Risk Reduction; (8) Integrated Tools for Hazard and Risk Assessment; (9) General Aspects of Safety.This report gives an overview of each topic made by the session chairperson. It also gives further analysis of the totality of the evidence presented. The workshop outputs are shaping international activities on hydrogen safety. They are helping key stakeholders to identify gaps in knowledge and expertise, and to understand and plan for potential safety challenges associated with the global expansion of hydrogen in the energy system.

Wide spread deployment and use of hydrogen and fuel cell technologies can occur only if hydrogen safety issues have been addressed in order to ensure that hydrogen fuel presents the same or lower level of hazards and associated risk compared to conventional fuel technologies. To achieve this goal, hydrogen safety research should be directed to address the remaining knowledge gaps using risk-informed approaches to develop engineering solutions and Regulation Codes and Standards (RCS) requirements that meet individual and societal risk acceptance criteria, yet are cost-effective and market-competitive. IA HySafe and JRC IET partnered to organize a Research Priorities Workshop in Berlin on October 16-17, 2012 hosted by BAM (on behalf of IA HySafe) to address knowledge gaps in CFD modelling of hydrogen safety issues. The findings of the workshop are described in the report. The document aims to become a reference document for researchers/scientists and technical (including industry) experts working in the area worldwide. It is also a welcomed contribution for the Fuel Cell and Hydrogen Joint Undertaking (FCH JU) and for other funding bodies/organizations that must make decisions on research programmes and during the selection/choice of projects to be financially supported pursuing the safe use of hydrogen within Horizon 2020 framework.