United States

A suitably trained emergency response force is an essential component for safe implementation of any type of fuel infrastructure. Because of the relative newness of hydrogen as a fuel however appropriate emergency response procedures are not yet well understood by responder workforces across the United States and around the world. A significant near-term training effort is needed to ensure that the future hydrogen infrastructure can be developed and operated with acceptable incident risk. Efforts are presently underway at the HAMMER site in Washington State to develop curricula related to hydrogen properties and behavior identification of problems (e.g. incorrect equipment installation) and appropriate response and other relevant information intended for classroom instruction. In addition a number of hands-on training props are planned for realistic simulation of hydrogen incidents in order to convey proper response procedures in high-pressure cryogenic high leakage or other high-risk accident situations. Surveys of emergency responders fire marshals regulatory authorities manufacturers and others are being undertaken to ensure that the capabilities developed and offered at HAMMER will meet the acknowledged need. This paper describes the training curricula and props anticipated at HAMMER and is intended to provide useful information to others planning similar training programs.

Energy storage is a promising approach to address the challenge of intermittent generation from renewables on the electric grid. In this work we evaluate energy storage with a regenerative hydrogen fuel cell (RHFC) using net energy analysis. We examine the most widely installed RHFC configuration containing an alkaline water electrolyzer and a PEM fuel cell. To compare RHFC's to other storage technologies we use two energy return ratios: the electrical energy stored on invested (ESOI_e) ratio (the ratio of electrical energy returned by the device over its lifetime to the electrical-equivalent energy required to build the device) and the overall energy efficiency (the ratio of electrical energy returned by the device over its lifetime to total lifetime electrical-equivalent energy input into the system). In our reference scenario the RHFC system has an ESOI_eratio of 59 more favorable than the best battery technology available today (Li-ion ESOI_e= 35). (In the reference scenario RHFC the alkaline electrolyzer is 70% efficient and has a stack lifetime of 100 000 h; the PEM fuel cell is 47% efficient and has a stack lifetime of 10 000 h; and the round-trip efficiency is 30%.) The ESOIe ratio of storage in hydrogen exceeds that of batteries because of the low energy cost of the materials required to store compressed hydrogen and the high energy cost of the materials required to store electric charge in a battery. However the low round-trip efficiency of a RHFC energy storage system results in very high energy costs during operation and a much lower overall energy efficiency than lithium ion batteries (0.30 for RHFC vs. 0.83 for lithium ion batteries). RHFC's represent an attractive investment of manufacturing energy to provide storage. On the other hand their round-trip efficiency must improve dramatically before they can offer the same overall energy efficiency as batteries which have round-trip efficiencies of 75–90%. One application of energy storage that illustrates the trade-off between these different aspects of energy performance is capturing overgeneration (spilled power) for later use during times of peak output from renewables. We quantify the relative energetic benefit of adding different types of energy storage to a renewable generating facility using [EROI]grid. Even with 30% round-trip efficiency RHFC storage achieves the same [EROI]grid as batteries when storing overgeneration from wind turbines because its high ESOI_eratio and the high EROI of wind generation offset the low round-trip efficiency.

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 of the development of risk identification and mitigation strategies is the development of rigorous environmental reactivity testing standards and procedures. This will allow for the identification of potential hazards and implementation of risk mitigation strategies. Modified testing procedures for shipping air and/or water sensitive materials as codified by the United Nations have been used to evaluate two potential hydrogen storage materials 2LiBH4·MgH2 and NH3BH3. The modified U.N. procedures include identification of self-reactive substances pyrophoric substances and gas-emitting substances with water contact. The results of these tests for air and water contact sensitivity will be compared to the pure material components where appropriate (e.g. LiBH4 and MgH2). The water contact tests are divided into two scenarios dependent on the hydride to water mole ratio and heat transport characteristics. Air contact tests were run to determine whether a substance will spontaneously react with air in a packed or dispersed form. Relative to 2LiBH4·MgH2 the chemical hydride NH3BH3 was observed to be less environmentally reactive.

One of the main benefits sought by including hydrogen in the alternative fuels mix is emissions reduction – eventually by 100%. However in the near term there is a very significant cost differential between fossil fuels and hydrogen. Hythane (a blend of hydrogen and natural gas) can act as a viable next step on the path to an ultimate hydrogen economy as a fuel blend consisting of 8−30 % hydrogen in methane can reduce emissions while not requiring significant changes in existing infrastructure. This work seeks to evaluate whether hythane may be safer than both hydrogen and methane under certain conditions. This is due to the fact hythane combines the positive safety properties of hydrogen (strong buoyancy high diffusivity) and methane (much lower flame speeds and narrower flammability limits as compared to hydrogen). For this purpose several different mixture compositions (e.g. 8 % 20 % and 30 % hydrogen) are considered. The evaluation of (a) dispersion characteristics (which are more positive than for methane) (b) combustion characteristics (which are closer to methane than hydrogen) and (c) Combined dispersion + explosion risk is performed. This risk is expected to be comparable to that of pure methane possibly lower in some situations and definitely lower than for pure hydrogen. The work is performed using the CFD software FLACS that has been well-validated for safety studies of both natural gas/methane and hydrogen systems. The first part of the work will involve validating the flame speeds and flammability limits predicted by FLACS against values available in literature. The next part of the work involves validating the overpressures predicted by the CFD tool for combustion of premixed mixtures of methane and hydrogen with air against available experimental data. In the end practical systems such as vehicular tunnels garages etc. is used to demonstrate positive safety benefits of hythane with comparisons to similar simulations for both hydrogen and methane.

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-stage buoyant turbulent entrainment model is developed to predict the properties (trajectory hydrogen concentration and temperature) of a jet emanating from the leak. Atmospheric hydrogen properties (temperature and quality) at the leak plane depend on the storage pressure and whether the leak occurs from the saturated vapor space or saturated liquid space. In the first stage of the entrainment model ambient temperature air (295 K) mixes with the leaking hydrogen (20–30 K) over a short distance creating an ideal gas mixture at low temperature (∼65 K). During this process states of hydrogen and air are determined from equilibrium thermodynamics using models developed by NIST. In the second stage of the model (also relatively short in distance) the radial distribution of hydrogen concentration and velocity in the jet develops into a Gaussian profile characteristic of free jets. The third and by far the longest stage is the part of the jet trajectory where flow is fully developed. Results show that flammability envelopes for cold hydrogen jets are generally larger than those of ambient temperature jets. While trajectories for ambient temperature jets depend solely on the leak densimetric Froude number results from the present study show that cold jet trajectories depend on the Froude number and the initial jet density ratio. Furthermore the flammability envelope is influenced by the hydrogen concentration in the jet at the beginning of fully developed flow.

Improving efficiency of hydrogen cooling in cryogenic conditions is important for the wider applications of hydrogen energy systems. The approach investigated in this study is based on a Ranque-Hilsch vortex tube (RHVT) that generates temperature separation in a working fluid. The simplicity of RHVT is also a valuable characteristic for cryogenic systems. In the present work novel shapes of RHVT are computationally investigated with the goal to raise efficiency of the cooling process. Specifically a smooth transition is arranged between a vortex chamber where compressed gas is injected and the main tube with two exit ports at the tube ends. Flow simulations have been carried out using STAR-CCM+ software with the real-gas Redlich-Kwong model for hydrogen at temperatures near 70 K. It is determined that a vortex tube with a smooth transition of moderate size manifests about 7% improvement of the cooling efficiency when compared vortex tubes that use traditional vortex chambers with stepped transitions and a no-chamber setup with direct gas injection.

A technoeconomic analysis of photoelectrochemical (PEC) and photovoltaic-electrolytic (PV-E) solar-hydrogen production of 10 000 kg H₂ day⁻¹ (3.65 kilotons per year) was performed to assess the economics of each technology and to provide a basis for comparison between these technologies as well as within the broader energy landscape. Two PEC systems differentiated primarily by the extent of solar concentration (unconcentrated and 10× concentrated) and two PV-E systems differentiated by the degree of grid connectivity (unconnected and grid supplemented) were analyzed. In each case a base-case system that used established designs and materials was compared to prospective systems that might be envisioned and developed in the future with the goal of achieving substantially lower overall system costs. With identical overall plant efficiencies of 9.8% the unconcentrated PEC and non-grid connected PV-E system base-case capital expenses for the rated capacity of 3.65 kilotons H₂ per year were $205 MM ($293 per m² of solar collection area (m_S⁻²) $14.7 W_H2P⁻¹) and $260 MM ($371 mS−2 $18.8 W_H2P⁻¹) respectively. The untaxed plant-gate levelized costs for the hydrogen product (LCH) were $11.4 kg⁻¹ and $12.1 kg⁻¹ for the base-case PEC and PV-E systems respectively. The 10× concentrated PEC base-case system capital cost was $160 MM ($428 m_S−2 $11.5 WH₂P⁻¹) and for an efficiency of 20% the LCH was $9.2 kg−1. Likewise the grid supplemented base-case PV-E system capital cost was $66 MM ($441 _mS⁻² $11.5 W_H2P⁻¹) and with solar-to-hydrogen and grid electrolysis system efficiencies of 9.8% and 61% respectively the LCH was $6.1 kg⁻¹. As a benchmark a proton-exchange membrane (PEM) based grid-connected electrolysis system was analyzed. Assuming a system efficiency of 61% and a grid electricity cost of $0.07 kWh⁻¹ the LCH was $5.5 kg⁻¹. A sensitivity analysis indicated that relative to the base-case increases in the system efficiency could effect the greatest cost reductions for all systems due to the areal dependencies of many of the components. The balance-of-systems (BoS) costs were the largest factor in differentiating the PEC and PV-E systems. No single or combination of technical advancements based on currently demonstrated technology can provide sufficient cost reductions to allow solar hydrogen to directly compete on a levelized cost basis with hydrogen produced from fossil energy. Specifically a cost of CO₂ greater than ∼$800 (ton CO₂)−1 was estimated to be necessary for base-case PEC hydrogen to reach price parity with hydrogen derived from steam reforming of methane priced at $12 GJ⁻¹ ($1.39 (kg H₂)⁻¹). A comparison with low CO₂ and CO₂-neutral energy sources indicated that base-case PEC hydrogen is not currently cost-competitive with electrolysis using electricity supplied by nuclear power or from fossil-fuels in conjunction with carbon capture and storage. Solar electricity production and storage using either batteries or PEC hydrogen technologies are currently an order of magnitude greater in cost than electricity prices with no clear advantage to either battery or hydrogen storage as of yet. Significant advances in PEC technology performance and system cost reductions are necessary to enable cost-effective PEC-derived solar hydrogen for use in scalable grid-storage applications as well as for use as a chemical feedstock precursor to CO₂-neutral high energy-density transportation fuels. Hence such applications are an opportunity for foundational research to contribute to the development of disruptive approaches to solar fuels generation systems that can offer higher performance at much lower cost than is provided by current embodiments of solar fuels generators. Efforts to directly reduce CO₂ photoelectrochemically or electrochemically could potentially produce products with higher value than hydrogen but many as yet unmet challenges include catalytic efficiency and selectivity and CO₂ mass transport rates and feedstock cost. Major breakthroughs are required to obtain viable economic costs for solar hydrogen production but the barriers to achieve cost-competitiveness with existing large-scale thermochemical processes for CO₂ reduction are even greater.

Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. Depending on the leak diameter and source pressure the resulting consequence distances can be unacceptably large. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. An experimental and modeling program has been performed at Sandia National Laboratories to better characterize the effectiveness of barrier walls to reduce hazards. This paper describes the experimental and modeling program and presents results obtained for various barrier configurations. The experimental measurements include flame deflection using standard and infrared video and high-speed movies (500 fps) to study initial flame propagation from the ignition source. Measurements of the ignition overpressure wall deflection radiative heat flux and wall and gas temperature were also made at strategic locations. The modeling effort includes three-dimensional calculations of jet flame deflection by the barriers computations of the thermal radiation field around barriers predicted overpressure from ignition and the computation of the concentration field from deflected unignited hydrogen releases. The various barrier designs are evaluated in terms of their mitigation effectiveness for the associated hazards present. The results show that barrier walls are effective at deflecting jet flames in a desired direction and can help attenuate the effects of ignition overpressure and flame radiative heat flux.

Element One Inc. is developing novel indicators for hydrogen gas for applications as a complement to conventional electronic hydrogen sensors or as a low-cost alternative in situations where an electronic signal is not needed. The indicator consists of a thin film coating or a pigment of a transition metal oxide such as tungsten oxide or molybdenum oxide with a catalyst such as platinum or palladium. The oxide is partially reduced in the presence of hydrogen in concentrations as low as 300 parts per million and changes from transparent to a dark colour. The colour change is fast and easily seen from a distance. In air the colour change reverses quickly when the source of hydrogen gas is removed in the case of tungsten oxide or is nearly irreversible in the case of molybdenum oxide. A number of possible implementations have been successfully demonstrated in the laboratory including hydrogen indicating paints tape cautionary decals and coatings for hydrogen storage tanks. These and other implementations may find use in vehicles stationary appliances piping refuelling stations and in closed spaces such as maintenance and residential garages for hydrogen-fuelled vehicles. The partially reduced transition metal oxide becomes semi conductive and increases its electrical conductivity by several orders of magnitude when exposed to hydrogen. The integration of this electrical resistance sensor with an RFID tag may extend the ability of these sensors to record and transmit a history of the presence or absence of leaked hydrogen over long distances. Over long periods of exposure to the atmosphere the indicator’s response may slow due to catalyst degradation. Our current emphasis is on controlling this degradation. The kinetics of the visual indicators is being investigated along with their durability in collaboration with the NASA Kennedy Space Center.

We have modelled sudden hydrogen expansion from a cryogenic pressure vessel. This model considers real gas equations of state single and two-phase flow and the specific “vessel within vessel” geometry of cryogenic vessels. The model can solve sudden hydrogen expansion for initial pressures up to 1210 bar and for initial temperatures ranging from 27 to 400 K. For practical reasons our study focuses on hydrogen release from 345 bar with temperatures between 62 K and 300 K. The pressure vessel internal volume is 151 L. The results indicate that cryogenic pressure vessels may offer a safety advantage with respect to compressed hydrogen vessels because i) the vacuum jacket protects the pressure vessel from environmental damage ii) hydrogen when released discharges first into an intermediate chamber before reaching the outside environment and iii) working temperature is typically much lower and thus the hydrogen has less energy. Results indicate that key expansion parameters such as pressure rate of energy release and thrust are all considerably lower for a cryogenic vessel within vessel geometry as compared to ambient temperature compressed gas vessels. Future work will focus on taking advantage of these favourable conditions to attempt fail-safe cryogenic vessel designs that do not harm people or property even after catastrophic failure of the inner pressure vessel.

The H2@Scale program of the U.S. Department of Energy (DOE) Fuel Cell Technologies Office is supporting work on the hydrogen compatibility of polymers to improve the durability and reliability of materials for hydrogen infrastructure. The hydrogen compatibility program (H-Mat) seeks “to address the challenges of hydrogen degradation by elucidating the mechanisms of hydrogen-materials interactions with the goal of providing science-based strategies to design materials (micro)structures and morphology with improved resistance to hydrogen degradation.” This research has found hydrogen and pressure interactions with model rubber-material compounds demonstrating volume change and compression-set differences in the materials. The research leverages state-of-the-art capabilities of the DOE national labs. The materials were investigated using helium-ion microscopy which revealed significant morphological changes in the plasticizer incorporating compounds after exposure as evidenced by time-of-flight secondary ion mass spectrometry. Additional studies using transmission electron microscopy and nuclear magnetic resonance revealed that nanosized inclusions developed after gas decompression in rubber- and plasticizer-only materials; this is an indication of void formation at the nanometer level.

The hourly operation of Thermal Hydrogen electricity markets is modelled. The economic values for all applicable chemical commodities are quantified (syngas ammonia methanol and oxygen) and an hourly electricity model is constructed to mimic the dispatch of key technologies: bi-directional power plants dual-fuel heating systems and plug-in fuel-cell hybrid electric vehicles. The operation of key technologies determines hourly electricity prices and an optimization model adjusts the capacity to minimize electricity prices yet allow all generators to recover costs. We examine 12 cost scenarios for renewables nuclear and natural gas; the results demonstrate emissionsfree ‘energy-only’ electricity markets whose supply is largely dominated by renewables. The economic outcome is made possible in part by seizing the full supply-chain value from electrolysis (both hydrogen and oxygen) which allows an increased willingness to pay for (renewable) electricity. The wholesale electricity prices average $25–$45/ MWh or just slightly higher than the assumed levelized cost of renewable energy. This implies very competitive electricity prices particularly given the lack of need for ‘scarcity’ pricing capacity markets dedicated electricity storage or underutilized electric transmission and distribution capacity.

On October 16-17 2012 the International Association for Hydrogen Safety (HySafe) in cooperation with the Institute for Energy and Transport of the Joint Research Centre of the European Commission (JRC IET Petten) held a two-day workshop dedicated to Hydrogen Safety Research Priorities. The workshop was hosted by Federal Institute for Materials Research and Testing (BAM) in Berlin Germany. The main idea of the Workshop was to bring together stakeholders who can address the existing knowledge gaps in the area of the hydrogen safety including identification and prioritization of such gaps from the standpoint of scientific knowledge both experimental and theoretical including numerical. The experience highlighting these gaps which was obtained during both practical applications (industry) and risk assessment should serve as reference point for further analysis. The program included two sections: knowledge gaps as they are addressed by industry and knowledge gaps and state-of-the-art by research. In the current work the main results of the workshop are summarized and analysed.

The United States has 11 distinct natural gas pipeline corridors: five originate in the Southwest four deliver natural gas from Canada and two extend from the Rocky Mountain region. This study assesses the potential to deliver hydrogen through the existing natural gas pipeline network as a hydrogen and natural gas mixture to defray the cost of building dedicated hydrogen pipelines.

Studying thermal ignition mechanisms is a key step for evaluating many ignition hazards. In the present work two-dimensional simulations with detailed chemistry are used to study the reaction pathways of the transient flow and ignition of a stoichiometric hydrogen-air mixture by moving hot spheres. For temperatures above the ignition threshold ignition takes place after a short time between the front stagnation point and separation location depending upon the sphere's surface temperature. Closer to the threshold the volume of gas adjacent to the separation region ignites homogeneously after a longer time. These results demonstrate the importance of boundary layer development and flow separation in the ignition process.

Just in line with any emerging alternative transportation fuel incidents involving hydrogen used as transportation fuel are learning opportunities for this new and growing industry. This paper includes discussion of many topics in hydrogen safety surrounding the installation operation and maintenance of commercial hydrogen stations or compression storage and dispensing systems.

The unconfined release of high-pressure hydrogen can create a large flammable jet with the potential to generate significant damage. To properly understand the separation distances necessary to protect the immediate surroundings it is important to accurately assess the potential consequences. In these events the possibility for a detonation cannot be excluded and would generally result in the worst case scenario from the standpoint of damaging overpressure. The strong concentration gradients created by a jet release however raises the question of what portion of the flammable cloud should be considered. Often all of the fuel within the limits of fast-flame acceleration or even all of the fuel within the flammability range is considered which typically comprises the majority of the flammable cloud. In this work prior detonation studies are reviewed to illustrate the inherently unstable nature of detonations with a focus on the critical dimensions and concentration gradients that can support a propagating detonation wave. These criteria are then applied to the flammable cloud concentration distributions generated by an unconfined jet release of hydrogen. By evaluating these limits it is found that the portion of the flammable cloud that is likely to participate is significantly reduced. These results are compared with existing experimental data on the ignition of unconfined hydrogen releases and the peak pressures that were measured are consistent with a detonation of a mass of fuel that is equivalent to the model prediction for the mass of fuel within the detonable limits. This work demonstrates how the critical conditions for detonation propagation can be used to estimate the portion of a hydrogen release that could participates in a detonation and how these criteria can be readily incorporated into existing dispersion modelling approaches.

Demonstrated safety in the production distribution and use of hydrogen will be critical to successful implementation of a hydrogen infrastructure. Recognizing the importance of this issue the U.S. Department of Energy has established the Hydrogen Safety Program to ensure safe operations of its hydrogen research and development program as well as to identify and address needs for new knowledge and technologies in the future hydrogen economy. Activities in the Safety Program range across the entire safety spectrum including: R&D devoted to investigation of hydrogen behaviour physical characteristics materials compatibility and risk analysis; inspection and investigation into the safety procedures and practices of all hydrogen projects supported by DOE funds; development of critical technologies for safe hydrogen systems such as sensors and design techniques; and safety training and education for emergency responders code inspectors and the general public. Throughout its activities the Safety Program encourages the open sharing of information to enable widespread benefit from any lessons learned or new information developed.



This paper provides detailed descriptions of the various activities of the DOE Hydrogen Safety Program and includes some example impacts already achieved from its implementation.

A simple approximate method for evaluation of blast effects and safety distances for unconfined hydrogen explosions is presented. The method includes models for flame speeds hydrogen distribution blast parameters and blast damage criteria. An example of the application of this methodology for hydrogen releases in three hypothetical obstructed areas with different levels of congestion is presented. The severity of the blast effect of unconfined hydrogen explosions is shown to depend strongly on the level of congestion for relatively small releases. Extremely large releases of hydrogen are predicted to be less sensitive to the congestion level.

Hydrogen is seen as an ideal energy carrier for stationary and mobile applications. However the use of high energy density materials such as hydrides comes with the drawback of risks associated to their high reactivity towards air and water exposure. We have developed novel strategies to mitigate these risks. These strategies were evaluated using standard UN tests and isothermal calorimetric measurements. Cycling experiments were conducted to assess the impact of the mitigants on the modified materials derived from 8LiH•3Mg(NH2)2 system. In some cases our results show an improvement in kinetics when compared to the unmodified material.  Effective mitigants were also discovered for aluminium hydride (alane) and lithium borohydride completely inhibiting ignition.

Large-scale experiments examining spherical-flame acceleration in lean hydrogen-air mixtures were performed in a 64 m3 constant-pressure enclosure. Equivalence ratios ranging from 0.33 to 0.57 were examined using detailed front tracking for flame diameters up to 1.2 m through the use of a Background Oriented Schlieren (BOS) technique. From these measurements the critical radii for onset of instability for these mixtures on the order of 2–3 cm were obtained. In addition the laminar burning velocity and rate of flame acceleration as a function of radius were also measured.

Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refuelling operations. Based on industry stakeholder input conducted experiments were devised to assess the utility of modelling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International's Corral Hollow Test Site. Moreover the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modelling approaches.

Sandia National Laboratories has worked with stakeholders and original equipment manufacturers (OEMs) to develop scientific data that can be used to create risk-informed hydrogen codes and standards for the safe operation of indoor hydrogen fuel-cell forklifts. An important issue is the possibility of an accident inside a warehouse or other enclosed space where a release of hydrogen from the high-pressure gaseous storage tank could occur. For such scenarios computational fluid dynamics (CFD) simulations have been used to model the release and dispersion of gaseous hydrogen from the vehicle and to study the behavior of the ignitable hydrogen cloud inside the warehouse or enclosure. The overpressure arising as a result of ignition and subsequent deflagration of the hydrogen cloud within the warehouse has been studied for different ignition delay times and ignition locations. Both ventilated and unventilated warehouses have been considered in the analysis. Experiments have been performed in a scaled warehouse test facility and compared with simulations to validate the results of the computational analysis.

New codes and standards are being developed to facilitate the safe deployment of emerging hydrogen technologies. Hydrogen markets will benefit from standards that address the specific properties of hydrogen hydrogen effects on strength of materials and hydrogen compressed gas storage at pressures up to 70 MPa. The need for validation of new hydrogen requirements has been identified by codes and standards technical committees. The US Department of Energy (DOE) office of Energy Efficiency and Renewable Energy (EERE) has tasked the National Renewable Energy Laboratory (NREL) with the role of supporting hydrogen codes and standards research and development needs. NREL has provided validation test support to several new standards development efforts including pressure testing of 70 MPa on board vehicle storage systems flaw testing of stationary hydrogen tanks fill protocols for hydrogen fuel dispensing and hydrogen compatibility testing for hydrogen pressure relief devices (HPRD’s). Validation test results are presented for these four specific standards development needs.

This paper provides a detailed technical description of the United Nations Global Technical Regulation No. 13 (UN GTR #13) 1998 Agreement and contracting party obligations phase 2 activity and safety provisions being discussed and developed for heavy duty hydrogen fuel cell vehicles.

The present study describes hydrogen generation from N_aBH₄ in the presence of acid accelerator boric oxide or  B₂O₃ using seawater as a reactant. Reaction times and temperatures are adjusted using various delivery methods: bulk addition funnel and metering pump. It is found that the transition metal catalysts typically used to generate hydrogen gas are poisoned by seawater. B₂O₃ is not poisoned by seawater; in fact reaction times are considerably faster in seawater using  B₂O₃. Reaction times and temperatures are compared for pure water and seawater for each delivery method. It is found that using B2O3 with pure water bulk addition is 97% complete in 3 min; pump metering provides a convenient method to extend the time to 27 min a factor of 9 increase above bulk addition. Using  B₂O₃ with seawater as a reactant bulk addition is 97% complete in 1.35 min; pump metering extends the time to 23 min a factor of 17 increase above bulk. A second acid accelerator sodium bisulfate or NaHSO4 is investigated here for use with NaBH4 in seawater. Because it is non-reactive in seawater i.e. no spontaneous H₂ generation NaHSO₄ can be stored as a solution in seawater; because of its large solubility it is ready to be metered into NaBH₄. With N_aHSO₄ in seawater pump metering increases the time to 97% completion from 3.4 min to 21 min. Metering allows the instantaneous flow rate of H₂ and reaction times and temperatures to be tailored to a particular application. In one application the seawater hydrogen generator characterized here is ideal for supplying H₂ gas directly to Proton Exchange Membrane fuel cells in sea surface or subsea environments where a reliable source of power is needed.

Radiative heat fluxes from small to medium-scale hydrogen jet flames (<10 m) compare favorably to theoretical predictions provided the product species thermal emittance and optical flame thickness are corrected for. However recent heat flux measurements from two large-scale horizontally orientated hydrogen flames (17.4 and 45.9 m respectively) revealed that current methods underpredicted the flame radiant fraction by 40% or more. Newly developed weighted source flame radiation models have demonstrated substantial improvement in the heat flux predictions particularly in the near-field and allow for a sensible way to correct potential ground surface reflective irradiance. These updated methods are still constrained by the fact that the flame is assumed to have a linear trajectory despite buoyancy effects that can result in significant flame deformation. The current paper discusses a method to predict flame centerline trajectories via a one-dimensional flame integral model which enables optimized placement of source emitters for weighted multi-source heat flux prediction methods. Flame shape prediction from choked releases was evaluated against flame envelope imaging and found to depend heavily on the notional nozzle model formulation used to compute the density weighted effective nozzle diameter. Nonetheless substantial improvement in the prediction of downstream radiative heat flux values occurred when emitter placement was corrected by the flame integral model regardless of the notional nozzle model formulation used.

The ignition limits of hydrogen/air mixtures in turbulent jets are necessary to establish safety distances based on ignitable hydrogen location for safety codes and standards development. Studies in turbulent natural gas jets have shown that the mean fuel concentration is insufficient to determine the flammable boundaries of the jet. Instead integration of probability density functions (PDFs) of local fuel concentration within the quiescent flammability limits termed the flammability factor (FF) was shown to provide a better representation of ignition probability (PI). Recent studies in turbulent hydrogen jets showed that the envelope of ignitable gas composition (based on the mean hydrogen concentration) did not correspond to the known flammability limits for quiescent hydrogen/air mixtures. The objective of this investigation is to validate the FF approach to the prediction of ignition in hydrogen leak scenarios. The PI within a turbulent hydrogen jet was determined using a pulsed Nd:YAG laser as the ignition source. Laser Rayleigh scattering was used to characterize the fuel concentration throughout the jet. Measurements in methane and hydrogen jets exhibit similar trends in the ignition contour which broadens radially until an axial location is reached after which the contour moves inward to the centerline. Measurements of the mean and fluctuating hydrogen concentration are used to characterize the local composition statistics conditional on whether the laser spark results in a local ignition event or complete light-up of a stable jet flame. The FF is obtained through direct integration of local PDFs. A model was developed to predict the FF using a presumed PDF with parameters obtained from experimental data and computer simulations. Intermittency effects that are important in the shear layer are incorporated in a composite PDF. By comparing the computed FF with the measured PI we have validated the flammability factor approach for application to ignition of hydrogen jets.

The properties of hydrogen compared to conventional fuels such as gasoline and diesel are substantially different requiring adaptations to the design and layout of test cells for hydrogen fuelled engines and vehicles. A comparison of hydrogen fuel properties versus conventional fuels in this paper provides identification of requirements that need to be adapted to design a safe test cell. Design examples of actual test cells are provided to showcase the differences in overall layout and ventilation safety features fuel supply and metering and emissions measurements. Details include requirements for ventilation patterns the necessity for engine fume hoods as well as hydrogen specific intake and exhaust design. The unique properties of hydrogen in particular the wide flammability limits and nonvisible flames also require additional safety features such as hydrogen sensors and flame cameras. A properly designed and implemented fuel supply system adds to the safety of the test cell by minimizing the amount of hydrogen that can be released. Apart from this the properties of hydrogen also require different fuel consumption measurement systems pressure levels of the fuel supply system additional ventilation lines strategically placed safety solenoids combined with appropriate operational procedures. The emissions measurement for hydrogen application has to be expanded to include the amount of unburned hydrogen in the exhaust as a measurement of completeness of combustion. This measurement can also be used as a safety feature to avoid creation of ignitable hydrogen-air mixtures in the engine exhaust. The considerations provided in this paper lead to the conclusion that hydrogen IC engines can be safely tested however properly designed test cell and safety features have to be included to mitigate the additional hazards related to the change in fuel characteristics.

Hydrogen Infrastructures are currently being built up to support the initial commercialization of the fuel cell vehicle by multiple automakers. Three primary markets are presently coordinating a large build up of hydrogen stations: Japan; USA; and Europe to support this. Hydrogen Fuelling Station General Safety and Performance Considerations are important to establish before a wide scale infrastructure is established.

This document introduces the ISO Technical Report 19880-1 and summarizes main elements of the proposed standard. Note: this ICHS paper is based on the draft TR 19880 and is subject to change when the document is published in 2015. International Standards Organisation (ISO) Technical Committee (TC) 197 Working Group (WG) 24 has been tasked with the preparation of the ISO standard 19880-1 to define the minimum requirements considered applicable worldwide for the hydrogen and electrical safety of hydrogen stations. This report includes safety considerations for hydrogen station equipment and components control systems and operation. The following systems are covered specifically in the document as shown in Figure 1:

• H2 production / supply delivery system
• Compression
• Gaseous hydrogen buffer storage;
• Pre-cooling device;
• Gaseous hydrogen dispensers.
• Hydrogen Fuelling Vehicle Interface

The draft TR 19880-1 (and current plan for the standard) also gives guidance for the fueling validation with safety considerations relevant to the interaction between the hydrogen station and hydrogen road vehicles (during fuelling).. Through a cross-industry risk assessment carried out between OEMs Hydrogen Suppliers and existing vehicle fuelling station providers & operators (e.g. oil and industrial gas companies) the hydrogen fueling protocol SAE J2601 and associated dispenser hardware was evaluated."

In the United States requirements for liquid motor vehicle fuelling stations have been in place for many years. Requirements for motor vehicle fuelling stations for gaseous fuels including hydrogen are relatively new. These requirements have in the United States been developed along different code and standards paths. The liquid fuels have been addressed in a single document and the gaseous fuels have been addressed in documents specific to an individual gas. The result of these parallel processes is that multi-fuel stations are subject to requirements in several fuelling regulations codes and standards (RCS). This paper describes a configuration of a multi-fuel motor vehicle fuelling station and provides a detailed breakdown of the codes and standards requirements. The multi-fuel station would dispense what the U.S. Department of Energy defines as the six key alternative fuels: biodiesel electricity ethanol hydrogen natural gas and propane. The paper will also identify any apparent gaps in RCS and potential research projects that could help fill these gaps.

The availability of repair garage infrastructure for hydrogen fuel cell vehicles is becoming increasingly important for future industry growth. Ventilation requirements for hydrogen fuel cell vehicles can affect both retrofitted and purpose-built repair garages and the costs associated with these requirements can be significant. A hazard and operability (HAZOP) study was performed to identify key risk-significant scenarios related to hydrogen vehicles in a repair garage. Detailed simulations and modeling were performed using appropriate computational tools to estimate the location behaviour and severity of hydrogen release based on key HAZOP scenarios. This work compares current fire code requirements to an alternate ventilation strategy to further reduce potential hazardous conditions. It is shown that position direction and velocity of ventilation have a significant impact on the amount of flammable mass in the domain.

The NREL Sensor Laboratory has been developing an analyzer that can verify compliance to the international United Nations Global Technical Regulation number 13 (GTR 13--Global Technical Regulation on Hydrogen and Fuel Cell Vehicles) prescriptive requirements pertaining to allowable hydrogen levels in the exhaust of fuel cell electric vehicles (FCEV) [1]. GTR 13 prescribes that the FCEV exhaust shall remain below 4 vol% H2 over a 3-second moving average and shall not at any time exceed 8 vol% H2 as verified with an analyzer with a response time (t90) of 300 ms or faster. GTR 13 has been implemented and is to serve as the basis for national regulations pertaining to hydrogen powered vehicle safety in the United States Canada Japan and the European Union. In the U.S. vehicle safety is overseen by the Department of Transportation (DOT) through the Federal Motor Vehicle Safety Standards (FMVSS) and in Canada by Transport Canada through the Canadian Motor Vehicle Safety Standard (CMVSS). The NREL FCEV exhaust analyzer is based upon a low-cost commercial hydrogen sensor with a response time (t90) of less than 250 ms. A prototype analyzer and gas probe assembly have been constructed and tested that can interface to the gas sampling system used by Environment and Climate Change Canada’s (ECCC) Emission Research and Measurement Section (ERMS) for the exhaust gas analysis. Through a partnership with Transport Canada ECCC will analyze the hydrogen level in the exhaust of a commercial FCEV. ECCC will use the NREL FCEV Exhaust Gas analyzer to perform these measurements. The analyzer was demonstrated on a FCEV operating under simulated road conditions using a chassis dynamometer at a private facility.

Hydrogen is seen as an ideal energy carrier for stationary and mobile applications. However the use of high energy density condensed hydrogen storage materials such as NH3BH3 comes with risks associated with their high reactivity with water exposure and their decomposition products reactivity in air. To predict their behaviour under these circumstances idealized finite element models of hypothetical accident scenarios have been developed. Empirical thermodynamic calculations based on precise thermal gravimetric analysis (TGA) and calorimetric experiments have been performed in order to quantify the energy and hydrogen release rates and to quantify the reaction products resulting from water and air exposure.

Zero Emission Vehicles (ZEVs) are necessary to help reduce the emissions in the transportation sector which is responsible for 40% of overall greenhouse gas emissions. There are two types of ZEVs Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs) Commercial Success of BEVs has been challenging thus far also due to limited range and very long charging duration. FCEVs using H2 infrastructure with SAE J2601 and J2799 standards can be consistently fuelled in a safe manner fast and resulting in a range similar to conventional vehicles. Specifically fuelling with SAE J2601 with the SAE J2799 enables FCEVs to fill with hydrogen in 3-5 minutes and to achieve a high State of Charge (SOC) resulting in 300+ mile range without exceeding the safety storage limits. Standardized H2 therefore gives an advantage to the customer over electric charging. SAE created this H2 fuelling protocol based on modelling laboratory and field tests. These SAE standards enable the first generation of commercial FCEVs and H2 stations to achieve a customer acceptable fueling similar to today's experience. This report details the advantages of hydrogen and the validation of H2 fuelling for the SAE standards.

A total of 12 ventilation experiments with various combinations of hydrogen release rates and ventilation speeds were performed in order to study how ventilation speed and release rate effect the hydrogen concentration in a closed system. The experiential facility was constructed out of steel plates and beams in the shape of a rectangular enclosure. The volume of the test facility was about 60m3. The front face of the enclosure was covered by a plastic film in order to allow visible and infrared cameras to capture images of the flame. The inlet and outlet vents were located on the lower front face and the upper backside panel respectively. Hydrogen gas was released toward the ceiling from the center of the floor. The hydrogen gas was released at constant rate in each test. The hydrogen release rate ranged from 0.002 m3/s to 0.02 m3/s. Ventilation speeds were 0.1 0.2 and 0.4 m3/s respectively. Ignition was attempted at the end of the hydrogen release by using multiple continuous spark ignition modules on the ceiling and next to the release point. Time evolution of hydrogen concentration was measured using evacuated sample bottles. Overpressure and impulse inside and outside the facility were also measured. The mixture was ignited by a spark ignition module mounted on the ceiling in eight of eleven tests. In the other three tests the mixture was ignited by spark ignition modules mounted next to the nozzle. Overpressures generated by the hydrogen deflagration in most of these tests were low and represented a small risk to people or property. The primary risk associated with the hydrogen deflagrations studied in these tests was from the fire. The maximum concentration is proportional to the ratio of the hydrogen release rate to the ventilation speed within the range of parameters tested. Therefore a required ventilation speed can be estimated from the assumed hydrogen leak rate within the experimental conditions described in this paper.

Global warming and fossil fuel depletion have necessitated alternative sources of energy. Biomass is a promising fuel source because it is renewable and can be carbon negative even without carbon capture and storage. This study considers biomass as a clean renewable source for transportation fuels. An Aspen Plus process simulation model was built of a biomass gasification biorefinery with Fischer-Tropsch (FT) synthesis of liquid fuels. A GaBi life cycle assessment model was also built to determine the environmental impacts using a cradle-to-grave approach. Three different product pathways were considered: Fischer-Tropsch synthetic diesel hydrogen and electricity. An offgas autothermal reformer with a recycle loop was used to increase FT product yield. Different configurations and combinations of biorefinery products are considered. The thermal efficiency and cost of production of the FT liquid fuels are analyzed using the Aspen Plus process model. The greenhouse gas emissions profitability and mileage per kg biomass were compared. The mileage traveled per kilogram biomass was calculated using modern (2019-2021) diesel electric and hydrogen fuel cell vehicles. The overall thermal efficiency was found to be between 20-41% for FT fuels production between 58-61% for hydrogen production and around 25-26% for electricity production for this biorefinery. The lowest production costs were found to be $3.171/gal of FT diesel ($24.304/GJ) $1.860/kg of H2 ($15.779/GJ) and 13.332¢/kWh for electricity ($37.034/GJ). All configurations except one had net negative carbon emissions over the life cycle of the biomass. This is because carbon is absorbed in the trees initially and some of the carbon is sequestered in ash and unconverted char from the gasification process furthermore co-producing electricity while making transportation fuel offsets even more carbon emissions. Compared to current market rates for diesel hydrogen and electricity the most profitable biorefinery product is shown to be hydrogen while also having net negative carbon emissions. FT diesel can also be profitable but with a slimmer profit margin (not considering government credits) and still having net negative carbon emissions. However our biorefinery could not compete with current commercial electricity prices in the US. As oil hydrogen and electricity prices continue to change the economics of the biorefinery and the choice product will change as well. For our current biorefinery model hydrogen seems to be the most promising product choice for profit while staying carbon negative while FT diesel is the best choice for sequestering the most carbon and still being profitable. All code and data are given.

The Hydrogen Safety Panel brings a broad cross-section of expertise from the industrial government and academic sectors to help advise the U.S. Department of Energy's (DOE) Fuel Cell Technologies Office through its work in hydrogen safety codes and standards. The Panel's initiatives in reviewing safety plans conducting safety evaluations identifying safety-related technical data gaps and supporting safety knowledge tools and databases cover the gamut from research and development to demonstration. The Panel's recent work has focused on the safe deployment of hydrogen and fuel cell systems in support of DOE efforts to accelerate fuel cell commercialization in early market applications: vehicle refuelling material handling equipment backup power for warehouses and telecommunication sites and portable power devices. This paper summarizes the work and learnings from the Panel's early efforts the transition to its current focus and the outcomes and conclusions from recent work on the deployment of hydrogen and fuel cell systems.

We are going to focus our discussion on “Explosions” its definitions from a scientific regulatory and societal perspective. We will point out that as defined these definitions are not consistent and lead to ambiguity. Of particular interest to this work is how this current ambiguity affects the emerging Regulation Codes and Standards (RCS) as applied to hydrogen technologies. While this manuscript has its roots in combustion science with extension to both the standard development and regulatory communities for hazards at large the unique behavior of hydrogen in many configurations motivates examining the relevant definitions and language used in these communities. We will point out the ambiguities how this leads to confusion in supporting definitions and how it leads to overly restrictive RCS for hydrogen applications. We will then suggest terminology which is not ambiguous internally self-consistent and allows appropriate RCS to be promulgated to ensure the safety of the public and capital to ensure the correct response of first responders and allow cost effective development of hydrogen technologies in our infrastructure.

The United Nations Economic Commission for Europe Global Technical Regulation (GTR) Number 13 (Global Technical Regulation on Hydrogen and Fuel Cell Vehicles) is the defining document regulating safety requirements in hydrogen vehicles and in particular fuel cell electric vehicles (FCEVs). GTR Number 13 has been formally adopted and will serve as the basis for the national regulatory standards for FCEV safety in North America (led by the United States) Japan Korea and the European Union. The GTR defines safety requirements for these vehicles including specifications on the allowable hydrogen levels in vehicle enclosures during in-use and post-crash conditions and on the allowable hydrogen emissions levels in vehicle exhaust during certain modes of normal operation. However in order to be incorporated into national regulations that is to be legally binding methods to verify compliance with the specific requirements must exist. In a collaborative program the Sensor Laboratories at the National Renewable Energy Laboratory in the United States and the Joint Research Centre Institute for Energy and Transport in the Netherlands have been evaluating and developing analytical methods that can be used to verify compliance with the hydrogen release requirements as specified in the GTR.

This document summarizes current hydrogen technologies and communicates the U.S. Department of Energy (DOE) Office of Fossil Energy's (FE's) strategic plan to accelerate research development and deploymnet of hydrogen technologies in the United States. It also describes ongoing FE hydrogen-related research and development (R&D). Hydrogen from fossil fuels is a versatile energy carrier and can play an important role in the transition to a low-carbon economy.

The deployment of hydrogen technologies particularly the deployment of hydrogen dispensing systems for passenger vehicles requires that hydrogen components perform reliably in environments where they have to meet the following performance parameters:

• Perform safely where the consumer will be operating the dispensing equipment
• Dispense hydrogen at volumes comparable to gasoline dispensing stations in timeframes comparable to gasoline stations
• Deliver a fueling performance that is within the boundaries of consumer tolerance
• Perform with maintenance/incident frequencies comparable to gasoline dispensing systems

This paper will describe the typical components of a hydrogen dispensing and storage system describe the hazards associated with these systems and components describe safety measures currently in place in codes and standards identify outstanding areas of safety concern and measures to address the outstanding areas of concern.

The paper will use incident frequency data from NREL’s Technology Validation project to more quantitatively identify safety concerns in hydrogen dispensing and storage systems.

Refueling infrastructure for use in gaseous hydrogen powered vehicles requires extensive manifolding for delivering the hydrogen from the stationary fuel storage at the refueling station to the vehicle as well as from the mobile storage on the vehicle to the fuel cell or combustion engine. Manifolds for gas handling often use welded construction (as opposed to compression fittings) to minimize gas leaks. Therefore it is important to understand the effects of hydrogen on tubing and tubing welds. This paper provides a brief overview of on-going studies on the effects of hydrogen precharging on the tensile properties of austenitic stainless tubing and orbital tube welds of several austenitic stainless steels.

Hydrogen fuels are being deployed around the world as an alternative to traditional petrol and battery technologies. As with all fuels regulations codes and standards are a necessary component of the safe deployment of hydrogen technologies. There has been a focused effort in the international hydrogen community to develop codes and standards based on strong scientific principles to accommodate the relatively rapid deployment of hydrogen-energy systems. The need for science-based codes and standards has revealed the need to advance our scientific understanding of hydrogen in engineering environments. This brief review describes research and development activities with emphasis on scientific advances that have aided the advancement of hydrogen regulations codes and standards for hydrogen technologies in four key areas: (1) the physics of high-pressure hydrogen releases (called hydrogen behaviour); (2) quantitative risk assessment; (3) hydrogen compatibility of materials; and (4) hydrogen fuel quality.

Safety is of paramount importance in all facets of the research development demonstration and deployment work of the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Program. The Safety Codes and Standards sub-program (SC&S) facilitates deployment and commercialization of fuel cell and hydrogen technologies by developing and disseminating information and knowledge resources for their safe use. A comprehensive safety management program utilizing the Hydrogen Safety Panel to raise safety consciousness at the project level and developing/disseminating a suite of safety knowledge resources is playing an integral role in DOE and SC&S efforts. This paper provides examples of accomplishments achieved while reaching a growing and diverse set of stakeholders involved in research development and demonstration; design and manufacturing; deployment and operations. The work of the Hydrogen Safety Panel highlights new knowledge and the insights gained through interaction with project teams. Various means of collaboration to enhance the value of the program’s safety knowledge tools and training resources are illustrated and the direction of future initiatives to reinforce the commitment to safety is discussed.

RCS for hydrogen technologies were first developed approximately sixty years ago when hydrogen was being sold as an industrial commodity. The advent of new hydrogen technologies such as Fuel Cell Electric Vehicles (FCEVs) created a need for new RCS. These RCS have been developed with extensive support from the US DOE. These new hydrogen technologies are approaching commercial deployment and this process will produce information on RCS field performance that will create more robust RCS.

NFPA 2 Hydrogen Technologies Code allows the use of risk-informed approaches to permitting hydrogen fuelling installations through the use of performance-based evaluations of specific hydrogen hazards. However the hydrogen fuelling industry in the United States has been reluctant to implement the performance-based option because the perception is that the required effort is cost prohibitive and there is no guarantee that the Authority Having Jurisdiction (AHJ) would accept the results. This report provides a methodology for implementing a performance-based design of an outdoor hydrogen refuelling station that does not comply with specific prescriptive separation distances. Performance-based designs are a code-compliant alternative to meeting prescriptive requirements. Compliance is demonstrated by evaluating a compliant prescriptive-based refuelling station design with a performance-based design approach using Quantitative Risk Assessment (QRA) methods and hydrogen risk tools. This template utilizes the Sandia-developed QRA tool Hydrogen Risk Analysis Model (HyRAM) to calculate risk values when developing risk-equivalent designs. HyRAM combines reduced-order deterministic models that characterize hydrogen release and flame behaviour with probabilistic risk models to quantify risk values. Each project is unique and this template is not intended to cover unique site-specific characteristics. Instead example content and a methodology are provided for a representative hydrogen refuelling site which can be built upon for new hydrogen applications.

Reversible solid oxide cells (r-SOCs) can be operated in either solid oxide fuel cell or solid oxide electrolysis cell mode. They are expected to become important in the support of renewable energy due to their high efficiency for both power generation and hydrogen generation. The exchange current density is one of the most important parameters in the quantification of electrode performance in solid oxide cells. In this study four different fuel electrodes and two different air electrodes are fabricated using different materials and the microstructures are compared. The temperature fuel humidification and oxygen concentration at the air electrode are varied to obtain the apparent exchange current density for the different electrode materials. In contrast to ruthenium-and-gadolinia-doped ceria (Rh-GDC) as well as nickel-and-gadolinia-doped ceria (Ni-GDC) electrodes significant differences in the apparent exchange current density were observed between electrolysis and fuel cell modes for the nickel-scandia-stabilized zirconia (Ni-ScSZ) cermet. Variation of gas concentration revealed that surface adsorption sites were almost completely vacant for all these electrodes. The apparent exchange current densities obtained in this study are useful as a parameter for simulation of the internal properties of r-SOCs.

The capabilities in the Hydrogen Effects on Materials Laboratory (HEML) at Sandia National Laboratories and the related materials testing activities that support standards development and technology deployment are reviewed. The specialized systems in the HEML allow testing of structural materials under in-service conditions such as hydrogen gas pressures up to 138 MPa temperatures from ambient to 203 K and cyclic mechanical loading. Examples of materials testing under hydrogen gas exposure featured in the HEML include stainless steels for fuel cell vehicle balance of plant components and Cr-Mo steels for stationary seamless pressure vessels.

Reliable methods are needed to predict ignition boundaries that result from compressed hydrogen bulk storage leaks without complex modelling. To support the development of these methods a new high-pressure stagnation chamber has been integrated into Sandia National Laboratories’ Turbulent Combustion Laboratory so that relevant compressed gas release scenarios can be replicated. For the present study a jet with a 10:1 pressure ratio issuing from a small 0.75 mm radius nozzle has been examined. Jet exit shock structure was imaged by Schlieren photography while quantitative Planar Laser Rayleigh Scatter imaging was used to measure instantaneous hydrogen mole fractions downstream of the Mach disk. Measured concentration statistics and ignitable boundary predictions compared favorably to analytic reconstructions of downstream jet dispersion behaviour. Model results were produced from subsonic jet dispersion models and by invoking self-similarity jet scaling arguments with length scaling by experimentally measured effective source radii. Similar far field reconstructions that relied on various notional nozzle models to account for complex jet exit shock phenomena failed to satisfactorily predict the experimental findings. These results indicate further notional nozzle refinement is needed to improve the prediction fidelity. Moreover further investigation is required to understand the effect of different pressure ratios on measured virtual origins used in the jet dispersion model.