United States
Hydrogen Fueling Standardization: Enabling ZEVs with "Same as Today" Fueling and FCEV Range and Safety
Oct 2015
Publication
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.
Overview of the DOE Hydrogen Safety, Codes and Standards Program Part 3- Advances in Research and Development to Enhance the Scientific Basis for Hydrogen Regulations, Codes and Standards
Oct 2015
Publication
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.
Detection of Hydrogen Released In a Full-Scale Residential Garage
Sep 2011
Publication
Experiments were conducted to assess detectability of a low-level leak of hydrogen gas and the uniformity of hydrogen concentration at selected sensor placement locations in a realistic setting. A 5%2hydrogen/95%2nitrogen gas mixture was injected at a rate of 350 L/min for about 3/4 hour into a 93m3 residential garage space through a 0.09 m2 square open-top dispersion box located on the floor. Calibrated catalytic sensors were placed on ceiling and wall locations and the sensors detected hydrogen early in the release and continued to measure concentrations to peak and diminishing levels. Experiments were conducted with and without a car parked over the dispersion box. The results show that a car positioned over the dispersion box tends to promote dilution of the hydrogen cause a longer time for locations to reach a fixed threshold and produce lower peak concentrations than with no car present.
Component Availability Effects for Pressure Relief Valves Used at Hydrogen Fueling Stations
Sep 2017
Publication
There are times in engineering when it seems that safety and equipment cost reduction are conflicting priorities. This could be the case for pressure relief valves and vent stack sizing. This paper explores the role that component availability (particularly variety in flow and orifice diameters) plays in the engineer’s decision of a relief valve. This paper outlines the guidelines and assumptions in sizing and selecting pressure relief devices (PRDs) found in a typical high pressure hydrogen fueling station. It also provides steps in sizing the station common vent stack where the discharge gas is to be routed to prior being released into the atmosphere. This paper also explores the component availability landscape for hydrogen station designers and identifies opportunities for improvement in the supply chain of components as hydrogen fueling stations increase in number and size. American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section VIII (ASME BPVC Section VIII) Compressed Gas Association S-1.3 (CGA S-1.3) and American Petroleum Institute 520 (API 520) standards provide specific design criteria for hydrogen pressure relief valves. Results of these calculations do not match the available components. The available safety relief valves are 50 to 87 times larger than the required calculated flow capacities. Selecting a significantly oversized safety relief valve affects the vent stack design as the stack design requires sizing relative to the actual flowrate of the safety relief valve. The effect on the vent stack size in turn negatively affects site safety radiation threshold set back distances.
Empirical Profiling of Cold Hydrogen Plumes Formed from Venting of LH2 Storage Vessels
Sep 2017
Publication
Liquid hydrogen (LH2) storage is viewed as a viable approach to assure sufficient hydrogen capacity at commercial fuelling stations. Presently LH2 is produced at remote facilities and then transported to the end-use site by road vehicles (i.e. LH2 tanker trucks). Venting of hydrogen to depressurize the transport storage tank is a routine part of the LH2 delivery and site transfer process. The behaviour of cold hydrogen plumes has not been well characterized because of the sparsity of empirical field data which can lead to overly conservative safety requirements. Committee members of the National Fire Protection Association (NFPA) Standard 2 [1] formed the Hydrogen Storage Safety Task Group which consists of hydrogen producers safety experts and computational fluid dynamics modellers has identified the lack of understanding of hydrogen dispersion during LH2 venting of storage vessels as a critical gap for establishing safety distances at LH2 facilities especially commercial hydrogen fuelling stations. To address this need the National Renewable Energy Laboratory Sensor Laboratory in collaboration with the NFPA Hydrogen Storage Task Group developed a prototype Cold Hydrogen Plume Analyzer to empirically characterize the hydrogen plume formed during LH2 storage tank venting. The prototype analyzer was field deployed during an actual LH2 venting process. Critical findings included
- Hydrogen above the lower flammable limit (LFL) was detected as much as 2 m lower than the release point which is not predicted by existing models.
- Personal monitors detected hydrogen at ground level although at levels below the LFL.
- A small but inconsistent correlation was found between oxygen depletion and the hydrogen concentration.
- A negligible to non-existent correlation was found between in-situ temperature measurements and the hydrogen concentration.
Development of Uniform Harm Criteria for Use in Quantitative Risk Analysis of the Hydrogen Infrastructure
Sep 2009
Publication
This paper discusses the preliminary results of the Risk Management subtask efforts within the International Energy Agency (IEA) Hydrogen Implementing Agreement (HIA) Task 19 on Hydrogen Safety to develop uniform harm criteria for use in the Quantitative Risk Assessments (QRAs) of hydrogen facilities. The IEA HIA Task 19 efforts are focused on developing guidelines and criteria for performing QRAs of hydrogen facilities. The performance of QRAs requires that the level of harm that is represented in the risk evaluation be established using deterministic models. The level of harm is a function of the type and level of hazard. The principle hazard associated with hydrogen facilities is uncontrolled accumulation of hydrogen in (semi) confined spaces and consecutive ignition. Another significant hazard is combustion of accidentally released hydrogen gas or liquid which may or may not happen instantaneously. The primary consequences from fire hazards consist of personnel injuries or fatalities or facility and equipment damage due to high air temperatures radiant heat fluxes or direct contact with hydrogen flames. The possible consequences of explosions on humans and structures or equipment include blast wave overpressure effects impact from fragments generated by the explosion the collapse of buildings and the heat effects from subsequent fire balls. A harm criterion is used to translate the consequences of an accident evaluated from deterministic models to a probability of harm to people structures or components. Different methods can be used to establish harm criteria including the use of threshold consequence levels and continuous functions that relate the level of a hazard to a probability of damage. This paper presents a survey of harm criteria that can be utilized in QRAs and makes recommendations on the criteria that should be utilized for hydrogen-related hazards.
Mixing and Warming of Cryogenic Hydrogen Releases
Sep 2017
Publication
Laboratory measurements were made on the concentration and temperature fields of cryogenic hydrogen jets. Images of spontaneous Raman scattering from a pulsed planar laser sheet were used to measure the concentration and temperature fields from varied releases. Jets with up to 5 bar pressure with near-liquid temperatures at the release point were characterized in this work. This data is relevant for characterizing unintended leaks from piping connected to cryogenic hydrogen storage tanks such as might be encountered at a hydrogen fuel cell vehicle fuelling station. The average centerline mass fraction was observed to decay at a rate similar to room temperature hydrogen jets while the half-width of the Gaussian profiles of mass fraction were observed to spread more slowly than for room temperature hydrogen. This suggests that the mixing and models for cryogenic hydrogen may be different than for room temperature hydrogen. Results from this work were also compared to a one-dimensional (streamwise) model. Good agreement was seen in terms of temperature and mass fraction. In subsequent work a validated version of this model will be exercised to quantitatively assess the risk at hydrogen fuelling stations with cryogenic hydrogen on-site.
Modeling of Hydrogen Pressurization and Extraction in Cryogenic Pressure Vessels Due to Vacuum Insulation Failure
Sep 2017
Publication
We have analyzed vacuum insulation failure in an automotive cryogenic pressure vessel (also known as cryo-compressed vessel) storing hydrogen (H2). Vacuum insulation failure increases heat transfer into cryogenic vessels by about a factor of 100 potentially leading to rapid pressurization and venting to avoid exceeding maximum allowable working pressure (MAWP). H2 release to the environment may be dangerous if the vehicle is located in a closed space (e.g. a garage or tunnel) at the moment of insulation failure. We therefore consider utilization of the hydrogen in the vehicle fuel cell and electricity dissipation through operation of vehicle accessories or battery charging as an alternative to releasing hydrogen to the environment. We consider two strategies: initiating hydrogen extraction immediately after vacuum insulation failure or waiting until MAWP is reached before extraction. The results indicate that cryogenic pressure vessels have thermodynamic advantages that enable slowing down hydrogen release to moderate levels that can be consumed in the fuel cell and dissipated onboard the vehicle even in the worst case when the vacuum fails with a vessel storing hydrogen at maximum refuel density (70 g/L at 300 bar). The two proposed strategies are therefore feasible and the best alternative can be chosen based on economic and/or implementation constraints.
Metal Hydride Hydrogen Compressors
Feb 2014
Publication
Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine – the metal hydride material itself – should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage hydrogen sorption kinetics and effective thermal conductivity) the thermodynamics of the metal–hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimised to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors reduction of slope of the isotherms and hysteresis increase of cycling stability and life time together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation.<br/>The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal–hydrogen systems suitable for the hydrogen compression; and (b) applied aspects including their consideration from the applied thermodynamic viewpoint system design features and performances of the metal hydride compressors and major applications.
A Study of Barrier Walls for Mitigation of Unintended Releases of Hydrogen
Sep 2009
Publication
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.
Developing a Hydrogen Fuel Cell Vehicle (HFCV) Energy Consumption Model for Transportation Applications
Jan 2022
Publication
This paper presents a simple hydrogen fuel cell vehicle (HFCV) energy consumption model. Simple fuel/energy consumption models have been developed and employed to estimate the energy and environmental impacts of various transportation projects for internal combustion engine vehicles (ICEVs) battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs). However there are few published results on HFCV energy models that can be simply implemented in transportation applications. The proposed HFCV energy model computes instantaneous energy consumption utilizing instantaneous vehicle speed acceleration and roadway grade as input variables. The mode accurately estimates energy consumption generating errors of 0.86% and 2.17% relative to laboratory data for the fuel cell estimation and the total energy estimation respectively. Furthermore this work validated the proposed model against independent data and found that the new model accurately estimated the energy consumption producing an error of 1.9% and 1.0% relative to empirical data for the fuel cell and the total energy estimation respectively. The results demonstrate that transportation engineers policy makers automakers and environmental engineers can use the proposed model to evaluate the energy consumption effects of transportation projects and connected and automated vehicle (CAV) transportation applications within microscopic traffic simulation models.
Hydrogen Wide Area Monitoring of LH2 Releases
Sep 2019
Publication
The characterization of liquid hydrogen (LH2) releases has been identified as an international research priority to expand the safe use of hydrogen as an energy carrier. The elucidation of LH2 release behavior will require the development of dispersion and other models guided and validated by empirical field measurements such as those afforded by Hydrogen Wide Area Monitoring (HyWAM). HyWAM can be defined as the quantitative spatial and temporal three-dimensional monitoring of planned or unintentional hydrogen releases. With support provided through the FCH JU Prenormative Research for the Safe Use of Liquid Hydrogen (PRESLHY) program HSE performed a series of LH2 releases to characterize the dispersion and pooling behavior of cold hydrogen releases. The NREL Sensor Laboratory developed a HyWAM system based upon a distributed array of point sensors that is amenable for profiling cold hydrogen plumes. The NREL Sensor Laboratory and HSE formally committed to collaborate on profiling the LH2 releases. This collaboration included the integration of the NREL HyWAM into the HSE LH2 release hardware. This was achieved through a deployment plan jointly developed by the NREL and HSE personnel. Under this plan the NREL Sensor Laboratory provided multiple HyWAM modules that accommodated 32 sampling points for near-field hydrogen profiling during the HSE PRESLHY LH2 releases. The NREL HyWAM would be utilized throughout the LH2 release study performed under PRESLHY by HSE including Work Package 3 (WP3—Release and Mixing--Rainout) and subsequent work packages (WP4—Ignition and WP5—Combustion). Under the auspices of the PRESLHY WP6 (Implementation) data and findings from the HSE LH2 Releases are to be made available to stakeholders in the hydrogen community. Comprehensive data analysis and dissemination is ongoing but the integration of the NREL HyWAM into the HSE LH2 Release Apparatus and its performance as well as some key outcomes of the LH2 releases in WP3 are presented.
Localized Plasticity and Associated Cracking in Stable and Metastable High-Entropy Alloys Pre-Charged with Hydrogen
Dec 2018
Publication
We investigated hydrogen embrittlement in Fe20Mn20Ni20Cr20Co and Fe30Mn10Cr10Co (at.%) alloys pre-charged with 100 MPa hydrogen gas by tensile testing at three initial strain rates of 10−4 10−3 and 10−2 s−1 at ambient temperature. The alloys are classified as stable and metastable austenite-based high-entropy alloys (HEAs) respectively. Both HEAs showed the characteristic hydrogen-induced degradation of tensile ductility. Electron backscatter diffraction analysis indicated that the reduction in ductility by hydrogen pre-charging was associated with localized plasticity-assisted intergranular crack initiation. It should be noted as an important finding that hydrogen-assisted cracking of the metastable HEA occurred not through a brittle mechanism but through localized plastic deformation in both the austenite and ε-martensite phases.
Can the Addition of Hydrogen to Natural Gas Reduce the Explosion Risk?
Sep 2009
Publication
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.
Risk Quantification of Hydride Based Hydrogen Storage Systems for Automotive Applications
Sep 2009
Publication
For hydrogen fuelled vehicles to attain significant market penetration it is essential that any potential risks be controlled within acceptable levels. To achieve this goal on-board vehicle hydrogen storage systems should undergo risk analyses during early concept development and design phases. By so doing the process of eliminating safety-critical failure modes will help guide storage system development and be more efficient to implement than if undertaken after the design-freeze stage. The focus of this paper is the development of quantitative risk analyses of storage systems which use onboard reversible materials such as conventional AB5 metal hydrides the complex hydride NaAlH4 or other material candidates currently being researched. Collision of a vehicle having such a hydrogen storage system was selected as a dominant accident initiator and a probabilistic event tree model has been developed for this initiator. The event tree model contains a set of comprehensive mutually exclusive accident sequences. The event tree represents chronological ordering of key events that are postulated to occur sequentially in time during the accident progression. Each event may represent occurrence of a phenomenon (e.g. hydride chemical reaction and dust cloud explosion) or a hardware failure (e.g. hydride storage vessel rupture). Event tree branch probabilities can be quantified using fault tree models or basic events with probability distributions. A fault tree model for hydride dust cloud explosion is provided as an example. Failure probabilities assigned to the basic events in the fault tree can be estimated from test results published data or expert opinion elicitation. To account for variabilities in the probabilities assigned to fault tree basic events and hence to propagate uncertainties in event tree sequences Monte Carlo sampling and Latin Hypercube sampling were employed and the statistics of the results from both techniques were compared.
Overview of the DOE Hydrogen Safety, Codes and Standards Program part 2- Hydrogen and Fuel Cells, Emphasizing Safety to Enable Commercialization
Oct 2015
Publication
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.
Carbon Negative Transportation Fuels - A Techno-Economic-Environmental Analysis of Biomass Pathways for Transportation
Feb 2022
Publication
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.
Safety of Hydrogen Powered Industrial Trucks, Lessons Learned and Existing Codes and Standards Gaps
Sep 2011
Publication
This paper provides an introduction to the powered industrial truck application of fuel cell power systems the safety similarities with the automotive application and safety lessons learned. Fuel Cell niche markets have proven their value to many early adopters. How has the automotive market provided a springboard for these niche applications? How are niche markets revealing gaps in current safety approaches? What is different about the powered industrial truck application and what new codes and standards are needed to accommodate those differences?
Validated Equivalent Source Model for an Under-expanded Hydrogen Jet
Oct 2015
Publication
As hydrogen fuel cell vehicles become more widely adopted by consumers the demand for refuelling stations increases. Most vehicles require high-pressure (either 350 or 700 bar) hydrogen and therefore the refuelling infrastructure must support these pressures. Fast running reduced order physical models of releases from high-pressure sources are needed so that quantitative risk assessment can guide the safety certification of these stations. A release from a high pressure source is choked at the release point forming the complex shock structures of an under-expanded jet before achieving a characteristic Gaussian pro le for velocity density mass fraction etc. downstream. Rather than using significant computational resources to resolve the shock structure an equivalent source model can be used to quickly and accurately describe the ow in terms of velocity diameter and thermodynamic state after the shock structure. In this work we present correlations for the equivalent boundary conditions of a subsonic jet as a high-pressure jet downstream of the shock structure. Schlieren images of under-expanded jets are used to show that the geometrical structure of under-expanded jets scale with the square root of the static to ambient pressure ratio. Correlations for an equivalent source model are given and these parameters are also found to scale with square root of the pressure ratio. We present our model as well as planar laser Rayleigh scattering validation data for static pressures up to 60 bar.
From Research Results to Published Codes And Standards - Establishing Code Requirements For NFPA 55 Bulk Hydrogen Systems Separation Distances
Sep 2009
Publication
Performing research in the interest of providing relevant safety requirements is a valuable and essential endeavor but translating research results into enforceable requirements adopted into codes and standards a process sometimes referred to as codification can be a separate and challenging task. This paper discusses the process utilized to successfully translate research results related to bulk gaseous hydrogen storage separation (or stand-off) distances into code requirements in NFPA 55:Storage Use and Handling of Compressed Gases and Cryogenic Fluids in Portable and StationaryContainers Cylinders and Tanks and NFPA 2: Hydrogen Technologies. The process utilized can besummarized as follows: First the technical committees for the documents to be revised were engaged to confirm that the codification process was endorsed by the committee. Then a sub-committee referred to as a task group was formed. A chair must be elected or appointed. The chair should be a generalist with code enforcement or application experience. The task group was populated with several voting members of each technical committee. By having voting members as part of the task group the group becomes empowered and uniquely different from any other code proposal generating body. The task group was also populated with technical experts as needed but primarily the experts needed are the researchers involved. Once properly populated and empowered the task group must actively engage its members. The researchers must educate the code makers on the methods and limitations of their work and the code makers must take the research results and fill the gaps as needed to build consensus and create enforceable code language and generate a code change proposal that will be accepted. While this process seems simple there are pitfalls along the way that can impede or nullify the desired end result – changes to codes and standards. A few of these pitfalls include: wrong task group membership task group not empowered task group not supported in-person meetings not possible consensus not achieved. This paper focuses on the process used and how pitfalls can be avoided for future efforts.
Modeling of 2LiBH4+MgH2 Hydrogen Storage System Accident Scenarios Using Empirical and Theoretical Thermodynamics
Sep 2009
Publication
It is important to understand and quantify the potential risk resulting from accidental environmental exposure of condensed phase hydrogen storage materials under differing environmental exposure scenarios. This paper describes a modelling and experimental study with the aim of predicting consequences of the accidental release of 2LiBH4+MgH2 from hydrogen storage systems. The methodology and results developed in this work are directly applicable to any solid hydride material and/or accident scenario using appropriate boundary conditions and empirical data.
The ability to predict hydride behaviour for hypothesized accident scenarios facilitates an assessment of the risk associated with the utilization of a particular hydride. To this end an idealized finite volume model was developed to represent the behaviour of dispersed hydride from a breached system. Semi-empirical thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released energy release rates and to quantify the reaction products resulting from water and air exposure of a lithium borohydride and magnesium hydride combination.
The hydrides LiBH4 and MgH2 were studied individually in the as-received form and in the 2:1 “destabilized” mixture. Liquid water hydrolysis reactions were performed in a Calvet calorimeter equipped with a mixing cell using neutral water. Water vapor and oxygen gas phase reactivity measurements were performed at varying relative humidities and temperatures by modifying the calorimeter and utilizing a gas circulating flow cell apparatus. The results of these calorimetric measurements were compared with standardized United Nations (UN) based test results for air and water reactivity and used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems. Thermodynamic parameters obtained from these tests were then inputted into a computational fluid dynamics model to predict both the hydrogen generation rates and concentrations along with localized temperature distributions. The results of these numerical simulations can be used to predict ignition events and the resultant conclusions will be discussed.
The ability to predict hydride behaviour for hypothesized accident scenarios facilitates an assessment of the risk associated with the utilization of a particular hydride. To this end an idealized finite volume model was developed to represent the behaviour of dispersed hydride from a breached system. Semi-empirical thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released energy release rates and to quantify the reaction products resulting from water and air exposure of a lithium borohydride and magnesium hydride combination.
The hydrides LiBH4 and MgH2 were studied individually in the as-received form and in the 2:1 “destabilized” mixture. Liquid water hydrolysis reactions were performed in a Calvet calorimeter equipped with a mixing cell using neutral water. Water vapor and oxygen gas phase reactivity measurements were performed at varying relative humidities and temperatures by modifying the calorimeter and utilizing a gas circulating flow cell apparatus. The results of these calorimetric measurements were compared with standardized United Nations (UN) based test results for air and water reactivity and used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems. Thermodynamic parameters obtained from these tests were then inputted into a computational fluid dynamics model to predict both the hydrogen generation rates and concentrations along with localized temperature distributions. The results of these numerical simulations can be used to predict ignition events and the resultant conclusions will be discussed.
Overview of the DOE Hydrogen Safety, Codes and Standards Program part 4- Hydrogen Sensors
Oct 2015
Publication
Hydrogen sensors are recognized as a critical element in the safety design for any hydrogen system. In this role sensors can perform several important functions including indication of unintended hydrogen releases activation of mitigation strategies to preclude the development of dangerous situations activation of alarm systems and communication to first responders and to initiate system shutdown. The functionality of hydrogen sensors in this capacity is decoupled from the system being monitored thereby providing an independent safety component that is not affected by the system itself. The importance of hydrogen sensors has been recognized by DOE and by the Fuel Cell Technologies Office’s Safety and Codes Standards (SCS) program in particular which has for several years supported hydrogen safety sensor research and development. The SCS hydrogen sensor programs are currently led by the National Renewable Energy Laboratory Los Alamos National Laboratory and Lawrence Livermore National Laboratory. The current SCS sensor program encompasses the full range of issues related to safety sensors including development of advance sensor platforms with exemplary performance development of sensor-related code and standards outreach to stakeholders on the role sensors play in facilitating deployment technology evaluation and support on the proper selection and use of sensors.
Adapted Tube Cleaning Practices to Reduce Particulate Contamination at Hydrogen Fueling Stations
Sep 2017
Publication
The higher rate of component failure and downtime during initial operation in hydrogen stations is not well understood. The National Renewable Energy Laboratory (NREL) has been collecting failed components from retail and research hydrogen fuelling stations in California and Colorado and analyzing them using an optical zoom and scanning electron microscope. The results show stainless steel metal particulate contamination. While it is difficult to definitively know the origin of the contaminants a possible source of the metal particulates is improper tube cleaning practices. To understand the impact of different cleaning procedures NREL performed an experiment to quantify the particulates introduced from newly cut tubes. The process of tube cutting threading and bevelling which is performed most often during station fabrication is shown to introduce metal contaminants and thus is an area that could benefit from improved cleaning practices. This paper shows how these particulates can be reduced which could prevent station downtime and costly repair. These results are from the initial phase of a project in which NREL intends to further investigate the sources of particulate contamination in hydrogen stations.
Enhancing Safety of Hydrogen Containment Components Through Materials Testing Under In-service Conditions
Oct 2015
Publication
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.
Simulation of High-pressure Liquid Hydrogen Releases
Sep 2011
Publication
Sandia National Laboratories is working with stakeholders to develop scientific data for use by standards development organizations to create hydrogen codes and standards for the safe use of liquid hydrogen. Knowledge of the concentration field and flammability envelope for high-pressure hydrogen leaks is an issue of importance for the safe use of liquid hydrogen. Sandia National Laboratories is engaged in an experimental and analytical program to characterize and predict the behaviour of liquid hydrogen releases. This paper presents a model for computing hydrogen dilution distances for cold hydrogen releases. Model validation is presented for leaks of room temperature and 80 K high-pressure hydrogen gas. The model accounts for a series of transitions that occurs from a stagnate location in the tank to a point in the leak jet where the concentration of hydrogen in air at the jet centerline has dropped to 4% by volume. The leaking hydrogen is assumed to be a simple compressible substance with thermodynamic equilibrium between hydrogen vapor hydrogen liquid and air. For the multi-phase portions of the jet near the leak location the REFPROP equation of state models developed by NIST are used to account for the thermodynamics. Further downstream the jet develops into an atmospheric gas jet where the thermodynamics are described as a mixture of ideal gases (hydrogen–air mixture). Simulations are presented for dilution distances in under-expanded high-pressure leaks from the saturated vapor and saturated liquid portions of a liquid hydrogen storage tank at 10.34 barg (150 PSIG).
Application of Quantitative Risk Assessment for Performance-based Permitting of Hydrogen Fueling Stations
Oct 2015
Publication
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.
A Review on Advanced Manufacturing for Hydrogen Storage Applications
Dec 2021
Publication
Hydrogen is a notoriously difficult substance to store yet has endless energy applications. Thus the study of long-term hydrogen storage and high-pressure bulk hydrogen storage have been the subject of much research in the last several years. To create a research path forward it is important to know what research has already been done and what is already known about hydrogen storage. In this review several approaches to hydrogen storage are addressed including high-pressure storage cryogenic liquid hydrogen storage and metal hydride absorption. Challenges and advantages are offered based on reported research findings. Since the project looks closely at advanced manufacturing techniques for the same are outlined as well. There are seven main categories into which most rapid prototyping styles fall. Each is briefly explained and illustrated as well as some generally accepted advantages and drawbacks to each style. An overview of hydrogen adsorption on metal hydrides carbon fibers and carbon nanotubes are presented. The hydrogen storage capacities of these materials are discussed as well as the differing conditions in which the adsorption was performed under. Concepts regarding storage shape and materials accompanied by smaller-scale advanced manufacturing options for hydrogen storage are also presented.
The International Energy Agency Hydrogen Implementing Agreement Task on Hydrogen Safety
Sep 2009
Publication
The International Energy Agency’s Hydrogen Implementing Agreement (www.ieahia.org) initiated a collaborative task on hydrogen safety in 1994 and this has proved to an effective method of pooling expert knowledge to address the most significant problems associated with the barriers to the commercial adoption of hydrogen energy. Presently there are approximately 10 countries participating in the task and it has proven a valuable method of efficiently combining efforts and resources. The task is now in the fifth year of a six year term and will end in October 2010. This paper will describe the scope of the task the progress made and plans for future work. There are also a number of other tasks underway and this paper will give a brief summary of those activities. Because of the nature of the International Energy Agency which is an international agreement between governments it is intended that such collaboration will complement other efforts to help build the technology base around which codes and standards can be developed. This paper describes the specific scope and work plan for the collaboration that has been developed to date.
HYRAM: A Methodology and Toolkit for Quantitative Risk Assessment of Hydrogen Systems
Oct 2015
Publication
HyRAM is a methodology and accompanying software toolkit which is being developed to provide a platform for integration of state-of-the-art validated science and engineering models and data relevant to hydrogen safety. As such the HyRAM software toolkit establishes a standard methodology for conducting quantitative risk assessment (QRA) and consequence analysis relevant to assessing the safety of hydrogen fueling and storage infrastructure. The HyRAM toolkit integrates fast-running deterministic and probabilistic models for quantifying risk of accident scenarios for predicting physical effects and for characterizing the impact of hydrogen hazards (thermal effects from jet fires thermal and pressure effects from deflagrations and detonations). HyRAM incorporates generic probabilities for equipment failures for nine types of hydrogen system components generic probabilities for hydrogen ignition and probabilistic models for the impact of heat flux and pressure on humans and structures. These are combined with fast-running computationally and experimentally validated models of hydrogen release and flame behaviour. HyRAM can be extended in scope via user contributed models and data. The QRA approach in HyRAM can be used for multiple types of analyses including codes and standards development code compliance safety basis development and facility safety planning. This manuscript discusses the current status and vision for HyRAM.
Validation Testing In Support Of Hydrogen Codes and Standards Developments
Sep 2011
Publication
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.
Statistical Analysis of Electrostatic Spark Ignition of Lean H2-O2-Ar Mixtures
Sep 2009
Publication
Determining the risk of accidental ignition of flammable mixtures is a topic of tremendous importance in industry and aviation safety. The concept of minimum ignition energy (MIE) has traditionally formed the basis for studying ignition hazards of fuels. In recent years however the viewpoint of ignition as a statistical phenomenon has formed the basis for studying ignition as this approach appears to be more consistent with the inherent variability in engineering test data. We have developed a very low energy capacitive spark ignition system to produce short sparks with fixed lengths of 1 to 2 mm. The ignition system is used to perform spark ignition tests in lean hydrogen oxygen-argon test mixtures over a range of spark energies. The test results are analyzed using statistical tools to obtain probability distributions for ignition versus spark energy demonstrating the statistical nature of ignition. The results also show that small changes in the hydrogen concentration lead to large changes in the ignition energy and dramatically different flame characteristics. A second low-energy spark ignition system is also developed to generate longer sparks with varying lengths up to 10 mm. A second set of ignition tests is performed in one of the test mixtures using a large range of park energies and lengths. The results are analyzed to obtain a probability distribution for ignition versus the spark energy per unit spark length. Preliminary results show that a single threshold MIE value does not exist and that the energy per unit length may be a more appropriate parameter for quantifying the risk of ignition.
Quantifying the Potential Consequences of a Detonation in a Hydrogen Jet Release
Sep 2019
Publication
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.
Clean Energy and Fuel Storage
Aug 2019
Publication
Clean energy and fuel storage is often required for both stationary and automotive applications. Some of the clean energy and fuel storage technologies currently under extensive research and development are hydrogen storage direct electric storage mechanical energy storage solar-thermal energy storage electrochemical (batteries and supercapacitors) and thermochemical storage. The gravimetric and volumetric storage capacity energy storage density power output operating temperature and pressure cycle life recyclability and cost of clean energy or fuel storage are some of the factors that govern efficient energy and fuel storage technologies for potential deployment in energy harvesting (solar and wind farms) stations and on-board vehicular transportation. This Special Issue thus serves the need to promote exploratory research and development on clean energy and fuel storage technologies while addressing their challenges to a practical and sustainable infrastructure.
An Assessment on the Quantification of Hydrogen Releases Through Oxygen Displacement Using Oxygen
Sep 2013
Publication
Contrary to several reports in the recent literature the use of oxygen sensors for indirectly monitoring ambient hydrogen concentration has serious drawbacks. This method is based on the assumption that a hydrogen release will displace oxygen which is quantified using oxygen sensors. Despite its shortcomings the draft Hydrogen Vehicle Global Technical Regulation lists this method as a means to monitor hydrogen leaks to verify vehicle fuel system integrity. Experimental evaluations that were designed to impartially compare the ability of commercial oxygen and hydrogen sensors to reliably measure and report hydrogen concentration changes are presented. Numerous drawbacks are identified and discussed.
A Comparative Technoeconomic Analysis of Renewable Hydrogen Production Using Solar Energy
May 2016
Publication
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 (mS−2) $14.7 WH2P−1) and $260 MM ($371 mS−2 $18.8 WH2P−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 mS−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 WH2P−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.
Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues
Mar 2013
Publication
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.
Natural and Forced Ventilation of Buoyant Gas Released In a Full-Scale Garage, Comparison of Model Predictions and Experimental Data
Sep 2011
Publication
An increase in the number of hydrogen-fuelled applications in the marketplace will require a better understanding of the potential for fires and explosion associated with the unintended release of hydrogen within a structure. Predicting the temporally evolving hydrogen concentration in a structure with unknown release rates leak sizes and leak locations is a challenging task. A simple analytical model was developed to predict the natural and forced mixing and dispersion of a buoyant gas released in a partially enclosed compartment with vents at multiple levels. The model is based on determining the instantaneous compartment over-pressure that drives the flow through the vents and assumes that the helium released under the automobile mixes fully with the surrounding air. Model predictions were compared with data from a series of experiments conducted to measure the volume fraction of a buoyant gas (at 8 different locations) released under an automobile placed in the center of a full-scale garage (6.8 m × 5.4 m × 2.4 m). Helium was used as a surrogate gas for safety concerns. The rate of helium released under an automobile was scaled to represent 5 kg of hydrogen released over 4 h. CFD simulations were also performed to confirm the observed physical phenomena. Analytical model predictions for helium volume fraction compared favourably with measured experimental data for natural and forced ventilation. Parametric studies are presented to understand the effect of release rates vent size and location on the predicted volume fraction in the garage. Results demonstrate the applicability of the model to effectively and rapidly reduce the flammable concentration of hydrogen in a compartment through forced ventilation.
Polymer Behaviour in High Pressure Hydrogen, Helium and Argon Environments as Applicable to the Hydrogen Infrastructure
Sep 2017
Publication
Polymers for O-rings valve seats gaskets and other sealing applications in the hydrogen infrastructure face extreme conditions of high-pressure H2 (0.1 to 100 MPa) during normal operation. To fill current knowledge gaps and to establish standard test methods for polymers in H2 environments these materials can be tested in laboratory scale H2 manifolds mimicking end use pressure and temperature conditions. Beyond the influence of high pressure H2 the selection of gases used for leak detection in the H2 test manifold their pressures and times of exposure gas types relative diffusion and permeation rates are all important influences on the polymers being tested. These effects can be studied ex-situ with post-exposure characterization. In a previous study four polymers (Viton A Buna N High Density Polyethylene (HDPE) and Polytetrafluoroethylene (PTFE)) commonly used in the H2 infrastructure were exposed to high-pressure H2 (100 MPa). The observed effects of H2 were consistent with typical polymer property-structure relationships; in particular H2 affected elastomers more than thermoplastics. However since high pressure He was used for purging and leak detection prior to filling with H2 a study of the influence of the purge gas on these polymers was considered necessary to isolate the effects of H2 from those of the purge gas. Therefore in this study Viton A Buna N and PTFE were exposed to the He purge procedure without the subsequent H2 exposure. Additionally six polymers Viton A Buna N PTFE Polyoxymethylene (POM) Polyamide 11 (Nylon) and Ethylenepropylenediene monomer rubber (EPDM) were subjected to high pressure Ar (100 MPa) followed by high pressure H2 (100 MPa) under the same static isothermal conditions to identify the effect of a purge gas with a significantly larger molecular size than He. Viton A and Buna N elastomers are more prone to irreversible changes as a result of H2 exposure from both Ar and He leak tests as indicated by influences on storage modulus extent of swelling and increased compression set. EPDM even though it is an elastomer is not as prone to high-pressure gas influences. The thermoplastics are generally less influenced by high pressure regardless of the gas type. Conclusions from these experiments will provide insight into the influence of purging processes and purge gases on the subsequent testing in high pressure gaseous H2. Control for the influence of purging on testing results is essential for the development of robust test methods for evaluating the effects of H2 and other high-pressure gases on the properties of polymers.
Mapping of Hydrogen Fuel Quality in Europe
Nov 2020
Publication
As part of FCH-JU funded HyCoRA project running from 2014 to 2017 28 gaseous and 13 particulate samples were collected from hydrogen refuelling stations in Europe. Samples were collected with commercial sampling instruments and analysis performed in compliance with prevailing fuel quality standards. Sampling was conducted with focus on diversity in feedstock as well as commissioning date of the HRS. Results indicate that the strategy for sampling was good. No evidence of impurity cross-over was observed. Parallel samples collected indicate some variation in analytical results. It was however found that fuel quality was generally good. Fourteen analytical results were in violation with the fuel tolerance limits. Therefore eight or 29% of the samples were in violation with the fuel quality requirements. Nitrogen oxygen and organics were the predominant impurities quantified. Particulate impurities were found to be within fuel quality specifications. No correlation between fuel quality and hydrogen feedstock or HRS commissioning date was found. Nitrogen to oxygen ratios gave no indication of samples being contaminated by air. A comparison of analytical results between two different laboratories were conducted. Some difference in analytical results were observed.
Simulations of Hydrogen Releases from a Storage Tanks- Dispersion and Consequences of Ignition
Sep 2005
Publication
We present results from hydrogen dispersion simulations from a pressurized reservoir at constant flow rate in the presence and absence of a wall. The dispersion simulations are performed using a commercial finite volume solver. Validation of the approach is discussed. Constant concentration envelopes corresponding to the 2% 4% and 15% hydrogen concentration in air are calculated for a subcritical vertical jet and for an equivalent subcritical horizontal jet from a high pressure reservoir. The consequences of ignition and the resulting overpressure are calculated for subcritical horizontal and vertical hydrogen jets and in the latter case compared to available experimental data.
Everything About Hydrogen Podcast: Is This the End of the Diesel Train?
Jan 2020
Publication
For this show the team are taking a dive into the world of hydrogen trains and who better to speak to this space than Mike Muldoon Head of Business Development and Marketing for Alstom UK&I. Alstom have been the pioneers of hydrogen powered rail and in addition to two operating trains in Germany have secured over Eur500 million of orders for hydrogen trains. On the show we talk to Mike about why Alstom see hydrogen as a key part of the evolution of the rail industry towards zero emissions and why hydrogen today is such a compelling proposition for operators and investors.
The podcast can be found on their website
The podcast can be found on their website
Exchange Current Density of Reversible Solid Oxide Cell Electrodes
Mar 2022
Publication
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.
Deflagration Safety Study of Mixtures of Hydrogen and Natural Gas in a Semi-open Space
Sep 2007
Publication
In the transition to a hydrogen economy it is likely that hydrogen will be used or stored in close proximity to other flammable fuels and gases. Accidents can occur that result in the release of two or more fuels such as hydrogen and natural gas that can mix and form a hazard. A series of five medium-scale semi-open-space deflagration experiments have been conducted with hydrogen natural gas and air mixtures. The natural gas consisted of 90% methane 6% ethane 3% propane and 1% butane by volume. Mixtures of hydrogen and natural gas were created with the hydrogen mole fraction in the fuel varying from 1.000 to 0.897 and the natural gas mole fraction varying from 0.000 to 0.103. The hydrogen and natural gas mixture was then released inside a 5.27-m³ thin plastic tent. The stoichiometric fuel-air mixtures were ignited with a 40-J spark located at the bottom center of the tent. Overpressure and impulse data were collected using pressure transducers located within the mixture volume and in the free field. Flame front time-of-arrival was measured using fast response thermocouples and infrared video. Flame speeds relative to a fixed observer were measured between 36.2 m/s and 19.7 m/s. Average peak overpressures were measured between 2.0 kPa and 0.3 kPa. The addition of natural gas inhibited the combustion when the hydrogen mole fraction was less than or equal to 0.949. For these mixtures there was a significant decrease in overpressures. When the hydrogen mole fraction in the fuel was between 0.999 and 0.990 the overpressures were slightly higher than for the case of hydrogen alone. This could be due to experimental scatter or there may be a slight enhancement of the combustion when a very small amount of natural gas was present. From a safety standpoint variation in overpressure was small and should have little effect on safety considerations.
PRD Hydrogen Release and Dispersion, a Comparison of CFD Results Obtained from Using Ideal and Real Gas Law Properties.
Sep 2005
Publication
In this paper CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank to ambient through a Pressure Relieve Device (PRD) 6 mm (¼”) opening. The numerical simulations using the TOPAZ software developed by Sandia National Laboratory addressed the changes of pressure density and flow rate variations at the leak orifice during release while the PHOENICS software package predicted extents of various hydrogen concentration envelopes as well as the velocities of gas mixture for the dispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFD model implemented through the TOPAZ and PHOENICS software to accurately predict the real gas properties for hydrogen release and dispersion under high pressures. The numerical results were compared with those obtained from using the ideal gas law and it was found that the ideal gas law overestimates the hydrogen mass release rates by up to 35% during the first 25 seconds of release. Based on the findings the authors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRD releases.
Hydrogen Embrittlement of Medium Mn Steels
Feb 2021
Publication
Recent research efforts to develop advanced–/ultrahigh–strength medium-Mn steels have led to the development of a variety of alloying concepts thermo-mechanical processing routes and microstructural variants for these steel grades. However certain grades of advanced–/ultrahigh–strength steels (A/UHSS) are known to be highly susceptible to hydrogen embrittlement due to their high strength levels. Hydrogen embrittlement characteristics of medium–Mn steels are less understood compared to other classes of A/UHSS such as high Mn twinning–induced plasticity steel because of the relatively short history of the development of this steel class and the complex nature of multiphase fine-grained microstructures that are present in medium–Mn steels. The motivation of this paper is to review the current understanding of the hydrogen embrittlement characteristics of medium or intermediate Mn (4 to 15 wt pct) multiphase steels and to address various alloying and processing strategies that are available to enhance the hydrogen-resistance of these steel grades.
Recent Progress and Approaches on Transition Metal Chalcogenides for Hydrogen Production
Dec 2021
Publication
Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis photovoltaic and energy storage due to their quantum confinement effect optoelectronic behavior and their stability. In particular TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein the methods used for the fabrication of TMCs characterization techniques employed and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.
Continuous Codes and Standards Improvement (CCSI)
Oct 2015
Publication
As of 2014 the majority of the Codes and Standards required to initially deploy hydrogen technologies infrastructure in the US have been promulgated1. These codes and standards will be field tested through their application to actual hydrogen technologies projects. CCSI is process of identifying code issues that arise during project deployment and then develop codes solutions to these issues. These solutions would typically be proposed amendments to codes and standards. The process is continuous because of technology and the state of safety knowledge develops there will be a need for monitoring the application of codes and standards and improving them based on information gathered during their application. This paper will discuss code issues that have surfaced through hydrogen technologies infrastructure project deployment and potential code changes that would address these issues. The issues that this paper will address include:
- Setback distances for bulk hydrogen storage
- Code mandated hazard analyses
- Sensor placement and communication
- The use of approved equipment
- System monitoring and maintenance requirements
Comparison of NFPA and ISO Approaches for Evaluating Separation Distances
Sep 2011
Publication
The development of a set of safety codes and standards for hydrogen facilities is necessary to ensure they are designed and operated safely. To help ensure that a hydrogen facility meets an acceptable level of risk code and standard development organizations (SDOs) are utilizing risk-informed concepts in developing hydrogen codes and standards. Two SDOs the National Fire Protection Association (NFPA) and the International Organization for Standardization (ISO) through its Technical Committee (TC) 197 on hydrogen technologies have been developing standards for gaseous hydrogen facilities that specify the facilities have certain safety features use equipment made of material suitable for a hydrogen environment and have specified separation distances. Under Department of Energy funding Sandia National Laboratories (SNL) has been supporting efforts by both of these SDOs to develop the separation distances included in their respective standards. Important goals in these efforts are to use a defensible science-based approach to establish these requirements and to the extent possible harmonize the requirements. International harmonization of regulations codes and standards is critical for enabling global market penetration of hydrogen and fuel cell technologies.
Environmental Reactivity of Solid State Hydride Materials
Sep 2009
Publication
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.
Predictions of Solid-State Hydrogen Storage System Contamination Processes
Sep 2009
Publication
Solid state materials such as metal and chemical hydrides have been proposed and developed for high energy density automotive hydrogen storage applications. As these materials are implemented into hydrogen storage systems developers must understand their behavior during accident scenarios or contaminated refueling events. An ability to predict thermal and chemical processes during contamination allows for the design of safe and effective hydrogen storage systems along with the development of appropriate codes and standards. A model for the transport of gases within an arbitrary-geometry reactive metal hydride bed (alane -AlH3) is presented in this paper. We have coupled appropriate Knudsen-regime permeability models for flow through packed beds with the fundamental heat transfer and chemical kinetic processes occurring at the particle level. Using experimental measurement to determine and validate model parameters we have developed a robust numerical model that can be utilized to predict processes in arbitrary scaled-up geometries during scenarios such as breach-in-tank or contaminated refueling. Results are presented that indicate the progression of a reaction front through a compacted alane bed as a result of a leaky fitting. The rate of this progression can be limited by; 1) restricting the flow of reactants into the bed through densification and 2) maximizing the rate of heat removal from the bed.
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