Safety
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.
Development of High-pressure Hydrogen Gas Barrier Materials
Oct 2015
Publication
We prepared several gas barrier resins based on amorphous PVA derivative that has the T1C (13C spin-lattice relaxation time) of a long time component in amorphous phase. We confirmed it was important to control state in amorphous phase of gas barrier resin in order to achieve both moldability and good gas barrier property. Polymer alloy was designed to improve flexibility. Polymer alloy made of amorphous PVA and elastomer resin showed good hydrogen resistance. Even after its polymer alloy were repeatedly exposed to 70MPa hydrogen gas the influence on higher-order structure in amorphous phase was in negligible level.
Rayleigh-Taylor Instability: Modelling and Effect on Coherent Deflagrations
Sep 2013
Publication
The modelling of Rayleigh–Taylor instability during premixed combustion scenarios is presented. Experimental data obtained from experiments undertaken by FM Global using their large-scale vented deflagration chamber was used to develop the modelling approach. Rayleigh–Taylor instability is introduced as an additional time-dependent combustion enhancing mechanism. It is demonstrated that prior to the addition of this mechanism the LES deflagration model under-predicted the experimental pressure transients. It is confirmed that the instability plays a significant role throughout the coherent deflagration process. The addition of the mechanism led to the model more closely replicating the pressure peak associated with the external deflagration.
Statistics, Lessons Learned and Recommendations from Analysis of HIAD 2.0 Database
Mar 2022
Publication
The manuscript firstly describes the data collection and validation process for the European Hydrogen Incidents and Accidents Database (HIAD 2.0) a public repository tool collecting systematic data on hydrogen-related incidents and near-misses. This is followed by an overview of HIAD 2.0 which currently contains 706 events. Subsequently the approaches and procedures followed by the authors to derive lessons learned and formulate recommendations from the events are described. The lessons learned have been divided into four categories including system design; system manufacturing installation and modification; human factors and emergency response. An overarching lesson learned is that minor events which occurred simultaneously could still result in serious consequences echoing James Reason's Swiss Cheese theory. Recommendations were formulated in relation to the established safety principles adapted for hydrogen by the European Hydrogen Safety Panel considering operational modes industrial sectors and human factors. This work provide an important contribution to the safety of systems involving hydrogen benefitting technical safety engineers emergency responders and emergency services. The lesson learned and the discussion derived from the statistics can also be used in training and risk assessment studies being of equal importance to promote and assist the development of sound safety culture in organisations.
CFD Modeling for Helium Releases in a Private Garage Without Forced Ventilation.
Sep 2005
Publication
In the course towards a safe future hydrogen based society one of the tasks to be considered is the investigation of the conditions under which the use or storage of hydrogen systems inside buildings becomes too dangerous to be accepted. One of the relevant scenarios which is expected to have a relatively high risk is a slow (and long lasting) hydrogen release from a vehicle stored in a closed private garage without any forced ventilation i.e. only with natural ventilation. This scenario has been earlier investigated experimentally (by M. Swain) using He (helium) to simulate the hydrogen behavior. In the present work the CFD code ADREA-HF is used to simulate three of the abovementioned experiments using the standard k- turbulence model. For each case modeled the predicted concentration (by vol.) time series are compared against the experimental at the given sensor locations. In addition the structure of the flow is investigated by presenting the helium concentration field.
Vertical Turbulent Buoyant Helium Jet - CFD Modelling and Validation
Sep 2005
Publication
In this paper a vertical turbulent round jet of helium was studied numerically using the PHOENICS software package. The flow was assumed to be steady incompressible and turbulent. The jet discharge Froude number was 14000 and the turbulent Schmidt number was 0.7. The incompressible Reynolds average Navier-Stokes equations and helium transport equation expressed in 2-D axisymmetric domain were applied to model the underlying helium release. The k-e RNG turbulence model was used for the calculations of the corresponding turbulent viscosity diffusivity velocity and concentration fields in the domain. The simulation results are compared with the experimental measurements from the earlier published studies on helium jets in non-buoyant jet region (NBJ) intermediate region (I) and buoyant plume region (BP). The numerical results show that the radial profiles of mean velocity and mean concentration are consistent with the empirical data scaled by the effective diameter and density-ratio dependence. The mean velocity and concentration fields along the axis of the jet agree with the decay laws correlated from the previous experiments. The discrepancy between the numerical and experimental data is within 10% proving that the current CFD model for gas release and dispersion is robust accurate and reliable and that the CFD technique can be used as an alternative to the experiments with similar helium jets. The authors believe that the current CFD model is well validated through this study and can be further extended to predict similar hydrogen releases and dispersion if the model is properly applied with hydrogen properties.
Hydrogen Fuelling Station, CEP-Berlin – Safety Risk Assessment and Authority Approval Experience and Lessons Learned
Sep 2005
Publication
The CEP (Clean Energy Partnership) – Berlin is one of the most diversified hydrogen demonstration projects at present. The first hydrogen fuelling station serving 16 cars is fully integrated in an ordinary highly frequented Aral service station centrally located at Messedamm in Berlin. Hydro has supplied and is the owner of the electrolyser with ancillary systems. This unit produces gaseous hydrogen at 12 bar with use of renewable energy presently serving 13 of the cars involved. The CEP project is planned to run for a period of five years and is supported by the German Federal Government and is part of the German sustainability strategy. During the planning and design phase there have been done several safety related assessments and analyses:
- Hydro has carried out a HAZOP (HAZard and OPerability) analysis of the electrolyser and ancillary systems delivered by Hydro Electrolysers.
- Hydro arranged with support from the partners a HAZOP analysis of the interface between the electrolyser and the compressor an interface with two different suppliers on each side.
- A QRA (Quantitative Risk Assessment) of the entire fuelling station has been carried out.
- Hydro has carried out a quantitative explosion risk analysis of the electrolyser container supplied by Hydro Electrolysers.
Explosion Characteristics of Hydrogen Gas in Varying Ship Ventilation Tunnel Geometries: An Experimental Study
Apr 2022
Publication
Hydrogen is widely regarded as a key element of prospective energy solutions for alleviating environmental emission problems. However hydrogen is classified as a high-risk gas because of its wide explosive range high overpressure low ignition energy and fast flame propagation speed compared with those of hydrocarbon-based gases. In addition deflagration can develop into detonation in ventilation or explosion guide tunnels if explosion overpressure occurs leading to the explosion of all combustible gases. However quantitative evidence of an increase in the explosion overpressure of ventilation tunnels is unavailable because the explosive characteristics of hydrogen gas are insufficiently understood. Therefore this study investigated an explosion chamber with the shape of a ventilation pipe in a ship compartment. The effect of tunnel length on explosion overpressure was examined experimentally. For quantitative verification the size of the hydrogen gas explosion overpressure was analyzed and compared with experimental values of hydrocarbon-based combustible gases (butane and LPG (propane 98%)). The experimental database can be used for explosion risk analyses of ships when designing ventilation holes and piping systems and developing new safety guidelines for hydrogen carriers and hydrogen-fueled ships.
Safety Demands for Automotive Hydrogen Storage Systems
Sep 2005
Publication
Fuel storage systems for vehicles require a fail-safe design strategy. In case of system failures or accidents the control electronics have to switch the system into a safe operation mode. Failure Mode and Effect Analysis (FMEA) or Failure Tree Analysis (FTA) are performed already in the early design phase in order to minimize the risk of design failures in the fuel storage system. Currently the specifications of requirements for pressurized and liquid hydrogen fuel tanks are based on draft UN-ECE Regulations developed by the European Integrated Hydrogen Project (EIHP). Used materials and accessories shall be compatible with hydrogen. A selection of metallic and non-metallic materials will be presented. Complex components have to be optimised by FEM simulations in order to determine weak spots in the design which will be overstressed in case of pressure thermal expansion or dynamic vibrations. According to automotive standards the performance of liquid hydrogen fuel tank systems has to be verified in various destructive and non-destructive tests.
Requirements for the Safety Assessment for the Approval of a Hydrogen Refueling Station
Sep 2007
Publication
The EC 6th framework research project HyApproval will draft a Handbook which will describe all relevant issues to get approval to construct and operate a Hydrogen Refuelling Station (HRS) for hydrogen vehicles. In WP3 of the HyApproval project it is under investigation which safety information competent authorities require to give a licence to construct an operate an HRS. The paper describes the applied methodology to collect the information from the authorities in 5 EC countries and the USA. The results of the interviews and recommendations for the information to include in the Handbook are presented.
A field explosion test of hydrogen-air mixtures
Sep 2005
Publication
This paper shows the experimental results and findings of field explosion tests conducted to obtain fundamental data concerning the explosion of hydrogen-air mixtures. A tent covered with thin plastic sheets was filled with hydrogen/air mixed gas and subsequently ignited by an electric-spark or explosives to induce deflagration and/or detonation. Several experiments with different concentrations and/or volumes of mixture were carried out. The static overpressure of blast waves was measured using piezoelectric pressure sensors. The recorded data show that the shape of the pressure-time histories of the resulting blast waves depends on the difference in the ignition method used. The pictures of the explosion phenomenon (deflagration and/or detonation) were taken by high-speed cameras.
Experimental Study of Vented Hydrogen Deflagration with Ignition Inside and Outside the Vented Volume
Sep 2013
Publication
Experiments were carried out inside a 25 m3 vented combustion test facility (CVE) with a fixed vent area sealed by a plastic sheet vent. Inside the CVE a 0.64 m3 open vent box called RED-CVE was placed. The vent of the RED-CVE was left open and three different vent area were tested. Two different mixing fans one for each compartment were used to establish homogeneous H2 concentrations. This study examined H2 concentrations in the range between 8.5% vol. to 12.5% vol. and three different ignition locations (1) far vent ignition (2) inside the RED-CVE box ignition and (3) near vent ignition (the vent refers to the CVE vent). Peak overpressures generated inside the test facility and the smaller compartment were measured. The results indicate that the near vent ignition generates negligible peak overpressures inside the test facility as compared to those originated by far vent ignition and ignition inside the RED-CVE box. The experiments with far vent ignition showed a pressure increase with increasing hydrogen concentration which reached a peak value at 11% vol. concentration and then decreased showing a non-monotonic behaviour. The overpressure measured inside the RED-CVE was higher when the ignition was outside the box whereas the flame entered the box through the small vent.
Risk Modelling of a Hydrogen Refuelling Station Using a Bayesian Network
Sep 2009
Publication
Fault trees and event trees have for decades been the most commonly applied modelling tools in both risk analysis in general and the risk analysis of hydrogen applications including infrastructure in particular. It is sometimes found challenging to make traditional Quantitative Risk Analyses sufficiently transparent and it is frequently challenging for outsiders to verify the probabilistic modelling. Bayesian Networks (BN) are a graphical representation of uncertain quantities and decisions that explicitly reveal the probabilistic dependence between the variables and the related information flow. It has been suggested that BN represent a modelling tool that is superior to both fault trees and event trees with respect to the structuring and modelling of large complex systems. This paper gives an introduction to BN and utilises a case study as a basis for discussing and demonstrating the suitability of BN for modelling the risks associated with the introduction of hydrogen as an energy carrier. In this study we explore the benefits of modelling a hydrogen refuelling station using BN. The study takes its point of departure in input from a traditional detailed Quantitative Risk Analysis conducted by DNV during the HyApproval project. We compare and discuss the two analyses with respect to their advantages and disadvantages. We especially focus on a comparison of transparency and the results that may be extracted from the two alternative procedures.
CFD Simulation Study to Investigate the Risk from Hydrogen Vehicles in Tunnels
Sep 2007
Publication
When introducing hydrogen-fuelled vehicles an evaluation of the potential change in risk level should be performed. It is widely accepted that outdoor accidental releases of hydrogen from single vehicles will disperse quickly and not lead to any significant explosion hazard. The situation may be different for more confined situations such as parking garages workshops or tunnels. Experiments and computer modelling are both important for understanding the situation better. This paper reports a simulation study to examine what if any is the explosion risk associated with hydrogen vehicles in tunnels. Its aim was to further our understanding of the phenomena surrounding hydrogen releases and combustion inside road tunnels and furthermore to demonstrate how a risk assessment methodology developed for the offshore industry could be applied to the current task. This work is contributing to the EU Sixth Framework (Network of Excellence) project HySafe aiding the overall understanding that is also being collected from previous studies new experiments and other modelling activities. Releases from hydrogen cars (containing 700 bar gas tanks releasing either upwards or downwards or liquid hydrogen tanks releasing only upwards) and buses (containing 350 bar gas tanks releasing upwards) for two different tunnel layouts and a range of longitudinal ventilation conditions have been studied. The largest release modelled was 20 kg H2 from four cylinders in a bus (via one vent) in 50 seconds with an initial release rate around 1000 g/s. Comparisons with natural gas (CNG) fuelled vehicles have also been performed. The study suggests that for hydrogen vehicles a typical worst-case risk assessment approach assuming the full gas inventory being mixed homogeneously at stoichiometry could lead to severe explosion loads. However a more extensive study with more realistic release scenarios reduced the predicted hazard significantly. The flammable gas cloud sizes were still large for some of the scenarios but if the actual reactivity of the predicted clouds is taken into account very moderate worst-case explosion pressures are predicted. As a final step of the risk assessment approach a probabilistic QRA study is performed in which probabilities are assigned to different scenarios time dependent ignition modelling is applied and equivalent stoichiometric gas clouds are used to translate reactivity of dispersed nonhomogeneous clouds. The probabilistic risk assessment study is based on over 200 dispersion and explosion CFD calculations using the commercially available tool FLACS. The risk assessment suggested a maximum likely pressure level of 0.1-0.3 barg at the pressure sensors that were used in the study. Somewhat higher pressures are seen elsewhere due to reflections (e.g. under the vehicles). Several other interesting observations were found in the study. For example the study suggests that for hydrogen releases the level of longitudinal tunnel ventilation has only a marginal impact on the predicted risk since the momentum of the releases and buoyancy of hydrogen dominates the mixing and dilution processes.
European Hydrogen Safety Panel (EHSP)
Sep 2019
Publication
Inaki Azkarate,
Marco Carcassi,
Francesco Dolci,
Alberto Garcia-Hombrados,
Stuart J. Hawksworth,
Thomas Jordan,
Georg W. Mair,
Daniele Melideo,
Vladimir V. Molkov,
Pietro Moretto,
Ernst Arndt Reinecke,
Pratap Sathiah,
Ulrich Schmidtchen,
Trygve Skjold,
Etienne Studer,
Tom Van Esbroeck,
Elena Vyazmina,
Jennifer Xiaoling Wen,
Jianjun Xiao and
Joachim Grüne
The FCH 2 JU launched the European Hydrogen Safety Panel (EHSP) initiative in 2017. The mission of the EHSP is to assist the FCH 2 JU both at programme and at project level in assuring that hydrogen safety is adequately managed and to promote and disseminate H2 safety culture within and outside of the FCH 2 JU programme. The EHSP is composed of a multidisciplinary pool of safety experts grouped in ad-hoc working groups (task forces) according to the tasks to be performed and to expertise. The scope and activities of the EHSP are structured around four main areas:
TF.1. Support at project level The EHSP task under this category includes the development of measures to avoid any accident by integrating safety learnings expertise and planning into FCH 2 JU funded projects and by ensuring that all projects address and incorporate the state-of-the-art in hydrogen safety appropriately. To this end a Safety guidance document for hydrogen and fuel cell projects will be produced.
TF.2. Support at programme level Activities under this category include answering questions related to hydrogen safety in an independent coordinated and consolidated way via hotline-support or if necessary via physical presence of safety representative at the FCH 2 JU. It could also include a short introduction to hydrogen safety and the provision of specific guidelines for the handling storage and use of hydrogen in the public domain. As a start a clear strategy on this should be developed and therefore related M ulti-annual work plan 2018-2020.
TF.3. Data collection and assessment The EHSP tasks include the analysis of existing events already introduced in the European Hydrogen Safety Reference Database (HIAD) and of new information from relevant mishaps incidents or accidents. The EHSP should therefore derive lessons learned and provide together with the involved parties further general recommendations to all stakeholders based on these data. For 2018 the following deliverables should be produced: methodology to collect inputs from projects and to provide lessons learned and guidelines assessment and lessons learned from HIAD and a report on research progress in the field of hydrogen safety.
TF.4. Public outreach Framed within the context of the intended broad information exchange the EHSP tasks under this category include the development of a regularly updated webpage hosted on the FCH 2 JU website.
The Effect of Vacancy Concentration on Hydrogen Diffusion in Alpha-Fe by Molecular Dynamic
Sep 2017
Publication
Diffusion coefficient is in significant dependence on vacancy concentration due to that migration of vacancy is the dominant mechanism of atom transport or diffusion in processes such as void formation dislocation movement and solid phase transformation. This study aims to investigate the effect of vacancy concentration on hydrogen diffusion in alpha-Fe by molecular dynamics simulations especially at low temperatures and with loading. Comparisons of the diffusion coefficients between alpha-Fe with a perfect structure and different-concentration vacancies as well as comparisons between experimental and theoretical results had been made to characterize and summarize the effect of vacancy on hydrogen diffusion coefficient.
Experimental Results and Comparison with Simulated Data of a Low Pressure Hydrogen Jet
Sep 2011
Publication
Experiments with a hydrogen jet were performed at two different pressures 96 psig (6.6 bars) and 237 psig (16.3 bars). The hydrogen leak was generated at two different hole sizes 1/16 inch (1.6 mm) and 1/32 inch (0.79 mm). The flammable shape of the plume was characterised by numerous measurements of the hydrogen concentration inside of the jet. The effect of the nearby horizontal surface on the shape of the plume was measured and compared with results of CFD numerical simulations. The paper will present results and an interpretation on the nature of the plume shape.
Safe Operation of Natural Gas Appliances Fuelled with Hydrogen & Natural Gas Mixtures (Progress Obtained in the Naturalhy-Project)
Sep 2007
Publication
Considering the transition towards the hydrogen economy dependent on hydrogen penetration scenario the cost of a new hydrogen pipeline infrastructure in Europe may amount to several thousands of billions of EURO’s. Therefore the examination of the potential contribution of the existing natural gas assets is a practical and logical first step. As the physical and chemical properties of hydrogen differ significantly from those of natural gas it is not at all possible to simply exchange natural gas by hydrogen in the existing infrastructure. In this paper first a brief overview will be given of the NATURALHY-project. Further the focus will be on the impact of added hydrogen on the performance of existing natural gas domestic end user appliances which is related to the operation of the natural gas grid connecting the different types of appliance. The application of the fundamental insights and carefully designed experiments comparing the behaviour of gases using justified reference conditions have been shown to offer essential progress. The Wobbe index limits of the natural gas distributed pose a first limiting factor upon the maximum allowable hydrogen concentration. Constant-Wobbe index and decreasing-Wobbe index options of H2 admixture have been studied. Considering the appliance light back H2 limiting factor for domestic appliances fuel-rich appliances are the critical ones. Also taking into account stationary gas engines gas turbines industrial applications and natural gas grid management it is not yet justified to present statements on what level of hydrogen concentration could be safely allowed in which specific natural gas distribution region. But more clarity has been obtained on combustion safety aspects of existing domestic appliances on the connection with Wobbe distribution conditions and on the bottlenecks still to be handled.
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
Characterising the Performance of Hydrogen Sensitive Coatings for Nuclear Safety Applications
Sep 2017
Publication
The detection of hydrogen gas is essential in ensuring the safety of nuclear plants. However events at Fukushima Daiichi NPP highlighted the vulnerability of conventional detection systems to extreme events where power may be lost. Herein chemochromic hydrogen sensors have been fabricated using transition metal oxide thin films sensitised with a palladium catalyst to provide passive hydrogen detection systems that would be resilient to any plant power failures. To assess their viability for nuclear safety applications these sensors have been gamma-irradiated to four total doses (0 5 20 50 kGy) using a Co-60 gamma radioisotope. Optical properties of both un-irradiated and irradiated samples were investigated to compare the effect of increased radiation dose on the sensors resultant colour change. The results suggest that gamma irradiation at the levels examined (>5 kGy) has a significant effect on the initial colour of the thin films and has a negative effect on the hydrogen sensing abilities.
Integration of Experimental Facilities: A Joint Effort for Establishing a Common Knowledge Base in Experimental Work on Hydrogen Safety
Sep 2009
Publication
With regard to the goals of the European HySafe Network research facilities are essential for the experimental investigation of relevant phenomena for testing devices and safety concepts as well as for the generation of validation data for the various numerical codes and models. The integrating activity ‘Integration of Experimental Facilities (IEF)’ has provided basic support for jointly performed experimental work within HySafe. Even beyond the funding period of the NoE HySafe in the 6th Framework Programme IEF represents a long lasting effort for reaching sustainable integration of the experimental research capacities and expertise of the partners from different research fields. In order to achieve a high standard in the quality of experimental data provided by the partners emphasis was put on the know-how transfer between the partners. The strategy for reaching the objectives consisted of two parts. On the one hand a documentation of the experimental capacities has been prepared and analysed. On the other hand a communication base has been established by means of biannual workshops on experimental issues. A total of 8 well received workshops has been organised covering topics from measurement technologies to safety issues. Based on the information presented by the partners a working document on best practice including the joint experimental knowledge of all partners with regard to experiments and instrumentation was created. Preserving the character of a working document it was implemented in the IEF wiki website which was set up in order to provide a central communication platform. The paper gives an overview of the IEF network activities over the last 5 years.
Mixed E-learning and Virtual Reality Pedagogical Approach for Innovative Hydrogen Safety Training for First Responders
Oct 2015
Publication
Within the scope of the HyResponse project the development of a specialised training programme is currently underway. Utilizing an andragogy approach to teaching distance learning is mixed with classroom instructors-led activities while hands-on training on a full-scale simulator is coupled with an innovative virtual reality based experience. Although the course is dedicated mainly to first responders provision has been made to incorporate not only simple table-top and drill exercises but also full-scale training involving all functional emergency response organisations at multi-agency cooperation level. The developed curriculum includes basics of hydrogen safety first responders' procedures and incident management expectations
Multistage Risk Analysis and Safety Study of a Hydrogen Energy Station
Sep 2017
Publication
China has plenty of renewable energy like wind power and solar energy especially in the northwest part of the country. Due to the volatile and intermittent characters of the green powers high penetration level of renewable resources could arise grid stabilization problem. Therefore electricity storage is considered as a solution and hydrogen energy storage is proposed. Instead of storing the electricity directly it converts electricity into hydrogen and the energy in hydrogen will be released as needed from gas to electricity and heat. The transformed green power can be fed to the power grid and heat supply network. State Grid Corporation of China carried out its first hydrogen demonstration project. In the demonstration project an alkaline electrolyzer and a PEM hydrogen fuel cell stack are decided as the hydrogen producer and consumer respectively. Hydrogen safety issue is always of significant importance to secure the property. In order to develop a dedicated safety analysis method for hydrogen energy storage system in power industry the risk analysis for the power-to-gas-topower&heat facility was made. The hazard and operability (HAZOP) study and the failure mode and effects analysis (FMEA) are performed sequentially to the installation to identify the most problematic parts of the system in view of hydrogen safety and possible failure modes and consequences. At the third step the typical hydrogen leak accident scenarios are simulated by using computational fluid dynamics (CFD) computer code. The resulted pressure loads of the possibly ignited hydrogen-air mixture in the facility container are estimated conservatively. Important safeguards and mitigation measures are proposed based on the three-stage risk and safety studies.
Cautiously Optimistic: Understanding the Australian Public’s Response to the Hydrogen Opportunity
Sep 2019
Publication
The increased activity across the technical world for developing hydrogen has not gone unnoticed at the political level. However there remains a gap in understanding of how the general public will respond to the development of such an emergent industry. Recognising this gap we undertook ten focus groups (N=92) and a nationally representative online survey (N=2785) with the Australian public to better understand their response to hydrogen and the opportunities it presents for export and domestic use. In both focus groups and the national survey when Australians first heard the word hydrogen they were most likely to respond with a neutral response. For example in the survey 81% responded with words such as gas energy water; with only 13% giving negative associations (e.g. bomb explosion Hindenburg); and 3% positive (e.g. clean future). Males were more likely to be supportive of hydrogen than females. Those who answered more knowledge questions correctly were also more supportive. The main benefits associated with the use of hydrogen technologies centred around the environment - reduced greenhouse gas emissions and climate change mitigation potential were key benefits. With safety cost and environmental impacts - particularly concerns around pollution emissions and water use - being the most frequently cited concerns about the production and use of hydrogen. This presentation focuses on Australian attitudes to the developing hydrogen export opportunity and also for domestic use. Implications for industry and policy makers will be discussed in light of these Australians responses.
Testing Safety of Hydrogen Components
Sep 2007
Publication
Hydrogen as a new and ecologic energy source is tempting though it creates the challenge of ensuring the safe use of hydrogen for all future consumers. Making sure that a hydrogen vehicle can be simply and safely used by anyone while performing as expected requires that the car be light with built-in safety features. This is achieved by combining high pressure composite cylinders with strict test procedures. Composite cylinders of up to 150 L operated to a maximum of 700 bar are required for vehicle applications. Air Liquide has developed test benches to hydraulically cycle such cylinders at 1400 bar and up to 3500 bar for burst tests. These tests are performed under controlled temperature conditions at ambient and extreme temperatures in order to simulate cylinder aging. Components in gas service such as valves hoses and other pressure devices are tested up to 1400 bars with hydrogen to simulate actual usage conditions. Hydrogen is used as a testing gas instead of nitrogen which is commonly used for such tests because hydrogen interacts with materials (e.g. hydrogen embrittlement) and because hydrogen has a special thermodynamic behaviour ( pressure drop velocity heat exchange…)
Hazid for CO2-free Hydrogen Supply Chain Feed (Front End Engineering Design)
Oct 2015
Publication
We at Kawasaki have proposed a “CO2 free H2 chain” using the abundant brown coal of Australia as a hydrogen source. We developed the basic design package and finished the Front End Engineering Design (FEED) in 2014. There are not only the hazards of the processing plant system but also the characteristic hazards of a hydrogen plant system. We considered and carried out Hazard Identification (HAZID) as the most appropriate approach for safety design in this stage. This paper describes the safety design and HAZID which we practiced for the CO2-Free Hydrogen Supply Chain FEED.
Flammability Limits and Laminar Flame Speed of Hydrogen–air Mixtures at Sub-atmospheric Pressures
Sep 2011
Publication
Hydrogen behavior at elevated pressures and temperatures was intensively studied by numerous investigators. Nevertheless there is a lack of experimental data on hydrogen ignition and combustion at reduced sub-atmospheric pressures. Such conditions are related to the facilities operating under vacuum or sub-atmospheric conditions for instance like ITER vacuum vessel. Main goal of current work was an experimental evaluation of such fundamental properties of hydrogen–air mixtures as flammability limits and laminar flame speed at sub-atmospheric pressures. A spherical explosion chamber with a volume of 8.2 dm3 was used in the experiments. A pressure method and high-speed camera combined with schlieren system for flame visualization were used in this work. Upper and lower flammability limits and laminar flame velocity have been experimentally evaluated in the range of 4–80% hydrogen in air at initial pressures 25–1000 mbar. An extraction of basic flame properties as Markstein length overall reaction order and activation energy was done from experimental data on laminar burning velocity.
Security Risk Analysis of a Hydrogen Fueling Station with an On-site Hydrogen Production System Involving Methylcyclohexane
Sep 2017
Publication
Although many studies have looked at safety issues relating to hydrogen fuelling stations few studies have analyzed the security risks such as deliberate attack of the station by threats such as terrorists and disgruntled employees. The purpose of this study is to analyze security risks for a hydrogen fuelling station with an on-site production of hydrogen from methylcyclohexane. We qualitatively conducted a security risk analysis using American Petroleum Institute Standard 780 as a reference for the analysis. The analysis identified 93 scenarios including pool fires. We quantitatively simulated a pool fire scenario unique to the station to analyze attack consequences. Based on the analysis and the simulation we recommend countermeasures to prevent and mitigate deliberate attacks.
Risk Analysis of Complex Hydrogen Infrastructures
Oct 2015
Publication
Building a network of hydrogen refuelling stations is essential to develop the hydrogen economy within transport. Additional hydrogen is regarded a likely key component to store and convert back excess electrical power to secure future energy supply and to improve the quality of biomass-based fuels. Therefore future hydrogen supply and distribution chains will have to address several objectives. Such a complexity is a challenge for risk assessment and risk management of these chains because of the increasing interactions. Improved methods are needed to assess the supply chain as a whole. The method of “Functional modelling” is discussed in this paper. It will be shown how it could be a basis for other decision support methods for comprehensive risk and sustainability assessments.
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.
Mixing of Dense or Light Gases with Turbulent Air- a Fast-Running Model for Lumped Parameter Codes
Sep 2005
Publication
The release of gases heavier than air like propane at ground level or lighter than air like hydrogen close to a ceiling can both lead to fire and explosion hazards that must be carefully considered in safety analyses. Even if the simulation of accident scenarios in complex installations and long transients often appears feasible only using lumped parameter computer codes the phenomenon of denser or lighter gas dispersion is not implicitly accounted by these kind of tools. In the aim to set up an ad hoc model to be used in the computer code ECART fluid-dynamic simulations by the commercial FLUENT 6.0 CFD code are used. The reference geometry is related to cavities having variable depth (2 to 4 m) inside long tunnels filled with a gas heavier or lighter than air (propane or hydrogen). Three different geometrical configurations with a cavity width of 3 6 and 9 m are considered imposing different horizontal air stream velocities ranging from 1 to 5 m/s. A stably-stratified flow region is observed inside the cavity during gas shearing. In particular it is found that the density gradient tends to inhibit turbulent mixing thus reducing the dispersion rate. The obtained data are correlated in terms of main dimensionless groups by means of a least squares method. In particular the Sherwood number is correlated as a function of Reynolds a density ratio modified Froude numbers and in terms of the geometrical parameter obtained as a ratio between the depth of the air-dense gas interface and the length of the cavity. This correlation is implemented in the ECART code to add the possibility to simulate large installations during complex transients lasting many hours with reasonable computation time. An example of application to a typical case is presented.
Numerical Investigation of Hydrogen-air Deflagrations in a Repeated Pipe Congestion
Sep 2019
Publication
Emerging hydrogen energy technologies are creating new avenues for bring hydrogen fuel usage into larger public domain. Identification of possible accidental scenarios and measures to mitigate associated hazards should be well understood for establishing best practice guidelines. Accidentally released hydrogen forms flammable mixtures in a very short time. Ignition of such a mixture in congestion and confinements can lead to greater magnitudes of overpressure catastrophic for both structure and people around. Hence understanding of the permissible level of confinements and congestion around the hydrogen fuel handling and storage unit is essential for process safety. In the present study numerical simulations have been performed for the hydrogen-air turbulent deflagration in a well-defined congestion of repeated pipe rig experimentally studied by [1]. Large Eddy Simulations (LES) have been performed using the in-house modified version of the OpenFOAM code. The Flame Surface Wrinkling Model in the LES context is used for modelling deflagrations. Numerical predictions concerning the effects of hydrogen concentration and congestion on turbulent deflagration overpressure are compared with the measurements [1] to provide validation of the code. Further insight about the flame propagation and trends of the generated overpressures over the range of concentrations are discussed.
Defining Hazardous Zones – Electrical Classification Distances
Sep 2005
Publication
This paper presents an analysis of computational fluid dynamic models of compressed hydrogen gas leaks into the air under different conditions to determine the volume of the hydrogen/air mixture and the extents of the lower flammable limit. The necessary hole size was calculated to determine a reasonably expected hydrogen leak rate from a valve or a fitting of 5 and 20 cfm under 400 bars resulting in a 0.1 and 0.2 mm effective diameter hole respectively. The results were compared to calculated hypothetical volumes from IEC 60079-10 for the same mass flowrate and in most cases the CFD results produced significantly smaller hydrogen/air volumes than the IEC standard. Prescriptive electrical classification distances in existing standards for hydrogen and compressed natural gas were examined but they do not consider storage pressure and there appears to be no scientific basis for the distance determination. A proposed table of electrical classification distances incorporating hydrogen storage volume and pressure was produced based on the hydrogen LFL extents from a 0.2 mm diameter hole and the requirements of existing standards. The PHOENICS CFD software package was used to solve the continuity momentum and concentration equations with the appropriate boundary conditions buoyancy model and turbulence models. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment typical for a hydrogen refuelling or energy station.<br/><br/>
Quantitative Risk Analysis Of Gaseous Hydrogen Storage Unit
Sep 2005
Publication
A quantitative risk analysis to a central pressurized storage tank for gaseous hydrogen has been performed to attend requirements of licensing procedures established by the State Environment Agency of São Paulo State Brazil. Gaseous hydrogen is used to feed the reactor to promote hydrogenation at the surfactant unit. HAZOP was the hazard identification technique selected. System components failures were defined by event and fault tree analysis. Quantitative risk analysis was complied to define the acceptability concepts on societal and individual risks required by the State Environmental Agency to approve the installation operation license. Acceptable levels to public society from the analysis were reached. Safety recommendations to the gaseous hydrogen central were proposed to assure minimization of risk to the near-by community operators environment and property.
Fire Protection Strategy for Compressed Hydrogen-Powered Vehicles
Sep 2007
Publication
Virtually all major automotive companies are currently developing hydrogen-powered vehicles. The vast majority of them employ compressed hydrogen tanks and components as a means of storing the fuel onboard. Compressed hydrogen vehicle fuel systems are designed in the same way as compressed natural gas vehicles (NGV) i.e. the high pressure (up to 70 MPa) fuel is always contained within the system under all conditions with the exception of vehicular fire. In the event of a vehicle fire the fuel system is protected using a non-reclosing thermally activated pressure relief device (PRD) which safely vents the contents. Hydrogen fuel system PRDs are presently qualified to the performance requirements specified in draft hydrogen standards such ANSI/CSA HPRD 1 and EIHP Rev. 12b. They are also qualified with individual fuel tank designs in accordance with the engulfing bonfire requirements in various published/draft tank standards such as CSA B51 Part 2 JARI S001 SAE TIR J2579 ANSI/CSA HGV 2 ISO DIS 15869.2 and EIHP Rev. 12b. Since 2000 there have been over 20 documented NGV tank failures in service 11 of which have been attributed to vehicle fires. This paper will examine whether currently proposed hydrogen performance standards and installation requirements offer suitable fuel system protection in the event of vehicular fires. A number of alternative fire protection strategies will be discussed including:
- The requirement of an engulfing and/or localized fire test for individual tanks fuel systems and complete vehicles;
- The advantages/disadvantages of point source- surface area- and/or fuse-based PRDs
- The use of thermal insulating coatings/blankets for fire protection resulting in the NONventing of the fuel
- The specification of appropriate fuel system installation requirements to mitigate the effect of vehicular fires.
Numerical Simulation of Hydrogen Release From High-Pressure Storage Vessel
Sep 2009
Publication
In this paper the deflagration region and characteristics of the hydrogen flow which was generated by high-pressure hydrogen discharge from storage vessels were studied. A 3-D analytic model is established based on the species transfer model and the SST k −ω turbulence model. The established model is applied to the research of the flow characteristics of the hydrogen under-expanded jet under different filling pressures of 30 MPa 35 MPa and 40 MPa respectively. The evolution process of hydrogen combustible cloud is analyzed under the filling pressure of 30 MPa. It is revealed that a supersonic jet is formed after the high-pressure hydrogen discharge outlet In the vicinity of the Mach disk the hydrogen jet velocity and temperature reach the maximum values and the variation of filling pressure has little effect on the peak values of the hydrogen jet flow velocity and temperature during the considered pressure range. In the rear of the Mach disk the variation rates of the hydrogen flow velocity and temperature are in inversely proportional to the hydrogen filling pressure. At the preliminary stage the discharged hydrogen is apple-shaped which expands along the radial and then the axial growth rate of the hydrogen cloud increases with the passage of time.
Hydrogen Deflagrations in Stratified Flat Layers in the Large-scale Vented Combustion Test Facility
Sep 2019
Publication
This paper examines the flame dynamics of vented deflagration in stratified hydrogen layers. It also compares the measured combustion pressure transients with 3D GOTHIC simulations to assess GOTHIC’s capability in simulating the associated phenomena. The experiments were performed in the Large-Scale Vented Combustion Test Facility at the Canadian Nuclear Laboratories. The stratified layer was formed by injecting hydrogen at a high elevation at a constant flow rate. The dominant parameters for vented deflagrations in stratified layers were investigated. The experimental results show that significant overpressures are generated in stratified hydrogen–air mixtures with local high concentration although the volume-averaged hydrogen concentration is non-flammable. The GOTHIC predictions capture the overall pressure dynamics of combustion very well but the peak overpressures are consistently over-predicted particularly with higher maximum hydrogen concentrations. The measured combustion overpressures are also compared with Molkov’s model prediction based on a layer-averaged hydrogen concentration.
The Effect of Polyurethane Sponge Blockage Ratio on Premixed Hydrogen-air Flame Propagation in a Horizontal Tube
Oct 2015
Publication
The effects of sponge blockage ratio on flame structure evolution and flame acceleration were experimentally investigated in an obstructed cross-section tube filled with stoichiometric hydrogen-air mixture. Experimental results show that the mechanisms responsible for flame acceleration can be in terms of the positive feedback of the unburned gas field generated ahead of the flame the area change of the gap between the sponge and the tube and the interaction between the flame and the shear layer appearing at the sponge left top corner. Especially the last one dominates the flame acceleration and causes its speed to be sonic. Then both the second and third contribute to the violent flame acceleration. In addition the unburned gas pockets can be found in both upstream and downstream regions of the sponge. With increasing blockage ratio the unburned gas pockets disappear easier and the flame acceleration is more pronounced. Moreover the sponge tilts more evidently and resultantly the maximum tilt angle increases.
Characteristics of Hydrogen Leakage Sound from a Fuel-cell Vehicle by Hearing
Oct 2015
Publication
Fuel-cell vehicle run on hydrogen is known that it has better energy efficiency than existing gasoline cars. The vehicles are designed so that hydrogen leaks from the tank are stopped automatically upon detection of hydrogen leakage or detection of impact in a collision. However we investigated the characteristics of hydrogen leakage sound from a hydrogen-leaking vehicle and the threshold of discrimination of hydrogen leakage from noise at a crossing with much traffic to examine a method to rescue people safely depending on the sense of hearing in the event of a continuous hydrogen leak. Here in the discrimination threshold test we conducted the test by using helium which is alternative gas of hydrogen leakage sound. We clarified that hydrogen leakage sound from vehicles has directivity height dependence and distance dependence. Furthermore we confirmed the threshold flow rate for distinguishing hydrogen gas when hydrogen leakage is heard at a distance of 5–10 m from the center of the hydrogen leaking vehicle in a 74 dB traffic noise environment.
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.
Numerical and Experimental Investigation of Buoyant Gas Release
Sep 2009
Publication
Buoyant round vertical jet had been investigated using Large Eddy Simulations at low Mach number. For the purpose of comparison with in-house experimental data in the present work helium has been used as a substitute for hydrogen. The influence of the transient concentration fields on the volume of gas with concentration within flammability limits has been investigated and their evolution and relation with average fields ad been characterized. Transient concentration fields created during initial jet development had been considered. Numerical results have been compared with in-house experiments and data published in the literature.
Numerical Investigation of a Vertical Surface on the Flammable Extent of Hydrogen and Methane Vertical Jets
Sep 2011
Publication
The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm round leak orifice from 100 barg 250 barg 400 barg 550 barg and 700 barg compressed gas systems are presented for vertical jets. To quantify the effect of the surface on the jet the jet exit is positioned at various distances from the surface ranging from 0.029 m to 12 m. Free jets simulations are performed for comparison purposes.
Best Practice in Numerical Simulation and CFD Benchmarking. Results from the SUSANA Project
Sep 2017
Publication
Correct use of Computational Fluid Dynamics (CFD) tools is essential in order to have confidence in the results. A comprehensive set of Best Practice Guidelines (BPG) in numerical simulations for Fuel Cells and Hydrogen applications has been one of the main outputs of the SUSANA project. These BPG focus on the practical needs of engineers in consultancies and industry undertaking CFD simulations or evaluating CFD simulation results in support of hazard/risk assessments of hydrogen facilities as well as on the needs of regulatory authorities. This contribution presents a summary of the BPG document. All crucial aspects of numerical simulations are addressed such as selection of the physical models domain design meshing boundary conditions and selection of numerical parameters. BPG cover all hydrogen safety relative phenomena i.e. release and dispersion ignition jet fire deflagration and detonation. A series of CFD benchmarking exercises are also presented serving as examples of appropriate modelling strategies.
An Experimental Study on Mechanism of Self-ignition of High-pressure Hydrogen
Oct 2015
Publication
In the present study the self-ignition of high-pressure hydrogen released in atmospheric air through a diaphragm is visualized under various test conditions. The experimental results indicate that the hydrogen that jets through the rupturing diaphragm is mixed with the heated air near the tube wall. The self-ignition event originated from this mixing. The self-ignition was strongly dependent on the strength of an incident shock wave generated at the diaphragm rupture. As a result a cylindrical flame that formed after the self-ignition shows a tendency to become longer as it propagates in the downstream direction. The head velocities of the hydrogen-air mixture and the cylindrical flame are consistent with that of a contact surface calculated from the measured shock speed. A modified self-ignition mechanism is proposed based on the experimental observations.
Composite Gas Cylinders Probabilistic Analysis of Minimum Burst and Load Cycle Requirements
Oct 2015
Publication
Gas cylinders made of composite materials receive growing popularity in light-weight applications. Current standards are mostly based on safety determination relying on minimum amounts of endured load cycles and a minimum burst pressure of a small number of specimens. This paper investigates the possibilities of a probabilistic strength assessment for safety improvements as well as cost and weight savings. The probabilistic assessment is based on destructive testing of small sized samples. The influence of sample size on uncertainty of the assessment is analysed. Furthermore methods for the assessment of in-service ageing (degradation) are discussed and displayed in performance charts.
Numerical Analysis of Detonation Propensity of Hydrogen-air Mixtures with Addition of Methane, Ethane or Propane
Oct 2015
Publication
The detonation propensity of hydrogen-air mixtures with addition of methane ethane or propane in wide range of compositions is analyzed. The analysis concerned the detonation cell width ignition delay time RSB and parameters. Results are presented as a function of hydrogen molar fraction. Computations were performed with the use of three Cantera 2.1.1. scripts in the Matlab R2010b environment. The validated mechanisms of chemical reactions based on data available in the literature were used. Six mechanisms were assessed: GRI-Mech 3.0 LLNL SanDiego Wang POLIMI and AramcoMech. In conclusion the relation between detonation propensity parameters is discussed.
CFD Investigation of Filling and Emptying of Hydrogen Tanks
Oct 2015
Publication
During the filling of hydrogen tanks high temperatures can be generated inside the vessel because of the gas compression while during the emptying low temperatures can be reached because of the gas expansion. The design temperature range goes from −40 °C to 85 °C. Temperatures outside that range could affect the mechanical properties of the tank materials. CFD analyses of the filling and emptying processes have been performed in the HyTransfer project. To assess the accuracy of the CFD model the simulation results have been compared with new experimental data for different filling and emptying strategies. The comparison between experiments and simulations is shown for the temperatures of the gas inside the tank for the temperatures at the interface between the liner and the composite material and for the temperatures on the external surface of the vessel.
Development of an Italian Fire Prevention Technical Rule For Hydrogen Pipelines
Sep 2011
Publication
This paper summarizes the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use of hydrogen. From the experimental point of view an apparatus has been designed and installed at the University of Pisa; this apparatus has allowed the simulation of hydrogen releases from a pipeline with and without ignition of hydrogen-air mixture. The experimental data have helped the completion of the above-mentioned draft document with the instructions about the safety distances. The document has been improved for example pipelines above ground (not buried) are allowed due to the knowledge acquired by means of the experimental campaign. The safety distances related to this kind of piping has been chosen on the base of risk analysis. The work on the text contents is concluded and the document is currently under discussion with the Italian stakeholders involved in the hydrogen applications.
Hydrogen Refuelling Stations for Public Transport Quality and Safety in the User-interface
Sep 2007
Publication
Hydrogen stations and supply systems for public transport have been demonstrated in a number of European cities during the last four years. The first refuelling facility was put into operation in Reykjavik in April 2003. Experience from the four years of operation shows that safety related incidents are more frequent in the user interface than in the other parts of the hydrogen refuelling station (HRS). This might be expected taking into account the fact that the refuelling is manually operated and that according to industrial statistics human failures normally stand for more than 80% of all safety related incidents. On the other hand the HRS experience needs special attention since the refuelling at the existing stations is carried out by well trained personnel and that procedures and systems are followed closely. So far the quality and safety approach to hydrogen refuelling stations has been based on industrial experience. This paper addresses the challenge related to the development of safe robust and easy to operate refuelling systems. Such systems require well adapted components and system solutions as well as user procedures. The challenge to adapt the industrial based quality and safety philosophy and methodologies to new hydrogen applications and customers in the public sector is addressed. Risk based safety management and risk acceptance criteria relevant to users and third party are discussed in this context. Human factors and the use of incident reporting as a tool for continuous improvement are also addressed. The paper is based on internal development programmes for hydrogen refuelling stations in Hydro and on participation in international EU and IPHE projects such as CUTE HyFLEET:CUTE HySafe and HyApproval.
Fire Tests Carried Out in FCH JU FIRECOMP Project, Recommendations and Application to Safety of Gas Storage Systems
Sep 2017
Publication
In the event of a fire composite pressure vessels behave very differently from metallic ones: the material is degraded potentially leading to a burst without significant pressure increase. Hence such objects are when necessary protected from fire by using thermally-activated devices (TPRD) and standards require testing cylinder and TPRD together. The pre-normative research project FireComp aimed at understanding better the conditions which may lead to burst through testing and simulation and proposed an alternative way of assessing the fire performance of composite cylinders. This approach is currently used by Air Liquide for the safety of composite bundles carrying large amounts of hydrogen gas.
Hydrogen Tank Filling Experiments at the JRC-IE Gastef Facility
Sep 2011
Publication
Storage of gases under pressure including hydrogen is a well-known technique. However the use in vehicles of hydrogen at pressures much higher than those applicable in natural gas cars still requires safety and performance studies with respect to the verification of the existing standards and regulations. The JRC-IE has developed a facility GasTeF for carrying out tests on full-scale high pressure vehicle’s tanks for hydrogen or natural gas. Typical tests performed in GasTeF are static permeation measurements of the storage system and hydrogen cycling in which tanks are fast filled and slowly emptied using hydrogen pressurised up to 70 MPa for at least 1000 times according to the requirements of the EU regulation on type-approval of hydrogen-powered motor vehicles. Moreover the temperature evolution of the gas inside and outside the tank is monitored using an ad-hoc designed thermocouples array system. This paper reports the first experimental results on the temperature distribution during hydrogen cycling tests.
On the Use of Hydrogen in Confined Spaces: Results from the Internal Project InsHyde
Sep 2009
Publication
Alexandros G. Venetsanos,
Paul Adams,
Inaki Azkarate,
A. Bengaouer,
Marco Carcassi,
Angunn Engebø,
E. Gallego,
Olav Roald Hansen,
Stuart J. Hawksworth,
Thomas Jordan,
Armin Keßler,
Sanjay Kumar,
Vladimir V. Molkov,
Sandra Nilsen,
Ernst Arndt Reinecke,
M. Stöcklin,
Ulrich Schmidtchen,
Andrzej Teodorczyk,
D. Tigreat,
N. H. A. Versloot and
L. Boon-Brett
The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.
Comparison of Convective Schemes in Hydrogen Impinging Jet CFD Simulation
Oct 2015
Publication
Hydrogen impinging jets can be formed in the case of an accidental release indoors or outdoors. The CFD simulation of hydrogen impinging jets suffers from numerical errors resulting in a non-physical velocity and hydrogen concentration field with a butterfly like structure. In order to minimize the numerical errors and to avoid the butterfly effect high order schemes need to be used. The aim of this work is to give best practices guidelines for hydrogen impinging jet simulations. A number of different numerical schemes is evaluated. The number of cells which discretize the source is also examined.
Hysafe SBEP-V20: Numerical Predictions of Release Experiments Inside a Residential Garage With Passive Ventilation
Sep 2009
Publication
This work presents the results of the Standard Benchmark Exercise Problem (SBEP) V20 of Work Package 6 (WP6) of HySafe Network of Excellence (NoE) co-funded by the European Commission in the frame of evaluating the quality and suitability of codes models and user practices by comparative assessments of code results. The benchmark problem SBEP-V20 covers release scenarios that were experimentally investigated in the past using helium as a substitute to hydrogen. The aim of the experimental investigations was to determine the ventilation requirements for parking hydrogen fuelled vehicles in residential garages. Helium was released under the vehicle for 2 h with 7.200 l/h flow rate. The leak rate corresponded to a 20% drop of the peak power of a 50 kW fuel cell vehicle. Three double vent garage door geometries are considered in this numerical investigation. In each case the vents are located at the top and bottom of the garage door. The vents vary only in height. In the first case the height of the vents is 0.063 m in the second 0.241 m and in the third 0.495 m. Four HySafe partners participated in this benchmark. The following CFD packages with the respective models were applied to simulate the experiments: ADREA-HF using k–ɛ model by partner NCSRD FLACS using k–ɛ model by partner DNV FLUENT using k–ɛ model by partner UPM and CFX using laminar and the low-Re number SST model by partner JRC. This study compares the results predicted by the partners to the experimental measurements at four sensor locations inside the garage with an attempt to assess and validate the performance of the different numerical approaches.
HIAD 2.0 – Hydrogen Incident and Accident Database
Sep 2019
Publication
Hydrogen technologies are expected to play a key role in implementing the transition from a fossil fuel- based to a more sustainable lower-carbon energy system. To facilitate their widespread deployment the safe operation and hydrogen systems needs to be ensured together with the evaluation of the associated risk.<br/>HIAD has been designed to be a collaborative and communicative web-based information platform holding high quality information of accidents and incidents related to hydrogen technologies. The main goal of HIAD was to become not only a standard industrial accident database but also an open communication platform suitable for safety lessons learned and risk communication as well as a potential data source for risk assessment; it has been set up to improve the understanding of hydrogen unintended events to identify measures and strategies to avoid incidents/accidents and to reduce the consequence if an accident occurs.<br/>In order to achieve that goal the data collection is characterized by a significant degree of detail and information about recorded events (e.g. causes physical consequences lesson learned). Data are related not only to real incident and accidents but also to hazardous situations.<br/>The concept of a hydrogen accident database was generated in the frame of the project HySafe an EC co-funded NoE of the 6th Frame Work Programme. HIAD was built by EC-JRC and populated by many HySafe partners. After the end of the project the database has been maintained and populated by JRC with publicly available events. The original idea was to provide a tool also for quantitative risk assessment able to conduct simple analyses of the events; unfortunately that goal could not be reached because of a lack of required statistics: it was not possible to establish a link with potential event providers coming from private sector not willing to share information considered confidential. Starting from June 2016 JRC has been developing a new version of the database (i.e. HIAD 2.0); the structure of the database and the web-interface have been redefined and simplified resulting in a streamlined user interface compared to the previous version of HIAD. The new version is mainly focused to facilitate the sharing of lessons learned and other relevant information related to hydrogen technology; the database will be public and the events will be anonymized. The database will contribute to improve the safety awareness fostering the users to benefit from the experiences of others as well as to share information from their own experiences.
Experimental Study of the Spontaneous Ignition of Partly Confined Hydrogen Jets
Sep 2011
Publication
The current study addresses the spontaneous ignition of hydrogen jets released into a confined oxidizer environment experimentally. The experiments are conducted in a shock tube where hydrogen gas is shock-accelerated into oxygen across a perforated plate. The operating conditions and hole dimension of the plate were varied in order to identify different flow field and ignition scenarios. Time resolved Schlieren visualization permitted to reconstruct the gasdynamic evolution of the release and different shock interactions. Time resolved self-luminosity records permitted us to record whether ignition was achieved and also to record the dimension of the turbulent mixing layer. The ignition limits determined experimentally in good agreement with the 1D diffusion ignition model proposed by Maxwell and Radulescu. Nevertheless the experiments demonstrated that the mixing layer is two to three orders of magnitude thicker than predicted by molecular diffusion which can be attributed to the observed mixing layer instabilities and shock-mixing layer interactions which provide a much more intense mixing rate than anticipated from previous and current numerical predictions. These observations further clarify why releases through partly confined geometries are more conducive to jet ignition of the jets.
Deflagration-to-detonation Transition in Highly Reactive Combustible Mixtures
Sep 2011
Publication
High resolution numerical simulations used to study the mechanism of deflagration-to-detonation transition (DDT). The computations solved two-dimensional time-dependent reactive Navier-Stokes equations including the effects of compressibility molecular diffusion thermal conduction viscosity and detailed chemical kinetics for the reactive species with subsequent chain branching production of radicals and energy release. It is shown that from the beginning the flame accelerates exponentially producing shock waves far ahead. On the next stage the flame acceleration decreases and the shocks are formed close ahead of the flame front. The final stage is the actual transition to detonation. During the second stage a compressed unreacted mixture of increased density enters the flame producing a high pressure pulse which enhances reaction rate and the heat release in the reaction zone with a positive feedback coupling between the pressure pulse and the reaction rate. As a result the peak of the pressure pulse grows exponentially steepens into a strong shock which is coupled with the reaction zone forming the overdriven detonation. This new mechanism of DDT is different from the Zel’dovich’s gradient mechanism. The temperature gradients which appear in the form of hot spots and the like are not suitable to initiate detonation.
Temperature Change of a Type IV Cylinder During Hydrogen Fuelling Process
Sep 2009
Publication
The temperature of the hydrogen cylinder needs to be carefully controlled during fuelling process. The maximum temperature should be less than 85℃ according to the ISO draft code. If the fuelling period is reduced the maximum temperature should increase. In this study temperature change of a Type IV cylinder was measured during the hydrogen fuelling process up to 35 MPa. Fuelling period was 3 to 5 minutes. Twelve thermocouples were installed to measure inside gas temperature and seven were attached on the outside of the cylinder. An infrared camera was also used for measuring temperature distribution of outside of cylinder. The maximum gas temperature was higher than 85℃ inside of the cylinder. Significant temperature difference between the upper and lower part of the vessel was observed. Temperature near the plug and the valve was quickly increased and maintained higher than that of the other region. Temperature increases for the partial refuelling process were also discussed.
Study on the Harm Effect of Liquid Hydrogen Release by Consequence Modeling
Sep 2011
Publication
In this paper the accidental release of hydrogen from cryogenic liquid storage tank and the subsequent consequences are studied including hydrogen cold cloud fire ball jet fire flash fire and vapor cloud explosion. The cold effect thermal effects and explosion overpressures from the above consequences are evaluated using IGC and TNO harm criteria. Results show that for instantaneous releases of liquid hydrogen the sequence of harm effect distances is that vapor cloud explosion>flash fire>cold cloud> fireball. For continuous releases of liquid hydrogen the sequence of harm effect distances is that vapor cloud explosion>jet fire>flash fire>cold cloud. The vapor cloud explosion is the leading consequence of both instantaneous and continuous releases and may be used for the determination of safety distances of a liquid hydrogen tank. Besides the harm effect distances of liquid hydrogen tank are compared with those of compressed hydrogen storages with equivalent mass. Results show that the liquid hydrogen storage may be safer than 70MPa gaseous storage in case of leak scenario but may be more dangerous than 70MPa storage in case of catastrophic rupture. It is difficult to tell which storage is safer from a consequence perspective. Further investigation need to be made from a standpoint of risk which combined both consequences and the likelihood of scenarios.
Update on Regulation Review for HRS Construction and Operations in Japan
Oct 2015
Publication
In 2005 the Japanese High-pressure Gas Safety Act the Fire Service Act and the Building Standards Act were revised to establish the requirements for 35 MPa hydrogen stations. And in 2012-2014 revisions were made to the High-pressure Gas Safety Act and the Fire Service Act to provide the regulatory requirements for 70 MPa hydrogen stations. We conducted a study on materials that may contribute to prepare technical standards concerning the major 4 items 12 additional items and 13 new items which may affect the costs from the point of view of promoting the hydrogen infrastructure.
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.
Estimation of an Allowable Hydrogen Permeation Rate From Road Vehicle Compressed Gaseous H2 Storage Systems In Typical Garages, Part 2: CFC Dispersion Calculations Using the ADREA-HF Code and Experimental Validation Using Helium Tests at the Garage Facility
Sep 2009
Publication
The time and space evolution of the distribution of hydrogen in confined settings was investigated computationally and experimentally for permeation from typical compressed gaseous hydrogen storage systems for buses or cars. The work was performed within the framework of the InsHyde internal project of the HySafe NoE funded by EC. The main goal was to examine whether hydrogen is distributed homogeneously within a garage like facility or whether stratified conditions are developed under certain conditions. The nominal hydrogen flow rate considered was 1.087 NL/min based on the then current SAE standard for composite hydrogen containers with a non-metallic liner (type 4) at simulated end of life and maximum material temperature in a bus facility with a volume of 681m3. The release was assumed to be directed upwards from a 0.15m diameter hole located at the middle part of the bus cylinders casing. Ventilation rates up to 0.03 ACH were considered. Simulated time periods extended up to 20 days. The CFD simulations performed with the ADREA-HF code showed that fully homogeneous conditions exist for low ventilation rates while stratified conditions prevail for higher ventilation rates. Regarding flow structure it was found that the vertical concentration profiles can be considered as the superposition of the concentration at the floor (driven by laminar diffusion) plus a concentration difference between floor and ceiling (driven by buoyancy forces). In all cases considered this concentration difference was found to be less than 0.5%. The dispersion experiments were performed at the GARAGE facility using Helium. Comparison between CFD simulations and experiments showed that the predicted concentrations were in good agreement with the experimental data. Finally simulations were performed using two integral models: the fully homogeneous model and the two-layer model proposed by Lowesmith et al. (ICHS-2 2007) and the results were compared both against CFD and the experimental data.
Safe Processing Route for the Synthesis of MG Based Metallic Hydrides
Sep 2009
Publication
Metallic hydrides represent a safe way of storing hydrogen minimising explosion and flammability risks. Nowadays there are several methods for the storage of hydrogen and the more conventional techniques are high-pressure tanks for gaseous hydrogen and cryogenic vessels for liquid hydrogen. However there are two main drawbacks in the storage of gaseous and liquid hydrogen. First as a fuel hydrogen in the gaseous and liquid states is very combustible and the related law imposes strict regulations on its utilization storage and transportation. Secondly even under a high pressure hydrogen gas is not dense enough for compact storage. Moreover the gas storage at high pressure involves significant safety risks. Hydrogen storage in the metal hydrides does not have such deficiencies. Metal hydrides are safe and can be easily store and transported. For that reason it should be stressed that metallic hydrides represent a safe way of storing hydrogen minimising explosion and flammability risks. Among metallic hydrides one of the most promising hydrides in terms of absorbed hydrogen content is Mg2NiH4. However it is difficult to obtain Mg2Ni by the conventional melting method because of the large difference in vapour pressure and melting point between magnesium and nickel. This paper presents an alternative and safe method for obtaining such hydride: HCS (Hydriding Combustion Synthesis). This method presents some interesting advantages over its conventional counterpart: the process is carried out at lower reaction process which means safer process and the alloy stoichiometry is closer to the nominal (Mg2Ni) which allow better hydrogen absorption behaviour. The aim of this work is to investigate the formation mechanism of this compound and to study some parameters of the process.
Gas Build-up in a Domestic Property Following Releases of Methane/Hydrogen Mixtures
Sep 2007
Publication
The EC funded Naturalhy project is investigating the possibility of promoting the swift introduction of hydrogen as a fuel by mixing hydrogen with natural gas and transporting this mixture by means of the existing natural gas pipeline system to end-users. Hydrogen may then be extracted for use in hydrogen fuel cell applications or the mixture may be used directly in conventional gas-fired equipment. This means that domestic customers would receive a natural gas (methane)/hydrogen mixture delivered to the home. As the characteristics of hydrogen are different from natural gas there may be an increased risk to end-users in the event of an accidental release of gas from internal pipe work or appliances. Consequently part of the Naturalhy project is aimed at assessing the potential implications on the safety of the public which includes end-users in their homes. In order to understand the nature of any gas accumulation which may form and identify the controlling parameters a series of large scale experiments have been performed to study gas accumulations within a 3 m by 3 m by 2.3 m ventilated enclosure representing a domestic room. Gas was released vertically upwards at a pressure typical of that experienced in a domestic environment from hole sizes representative of leaks and breaks in pipe work. The released gas composition was varied and included methane and a range of methane/hydrogen mixtures containing up to 50% hydrogen. During the experiments gas concentrations throughout the enclosure and the external wind conditions were monitored with time. The experimental data is presented. Analysis of the data and predictions using a model developed to interpret the experimental data show that both buoyancy and wind driven ventilation are important.
Towards a Set of Design Recommendations for Pressure Relief Devices On-board Hydrogen Vehicles
Oct 2015
Publication
Commercial use of hydrogen on-board fuel cell vehicles necessitates the compression of hydrogen gas up to 700 bar raising unique safety challenges. Potential hazards to be addressed include jet fires from high-pressure hydrogen on-board storage. Previous studies investigated effects of jet fires that occur when pressure relief devices (PRDs) on hydrogen fuel cell vehicles activate. This investigation examines plane jets’ axis switching and flame length accounting for compressibility effects and turbulent combustion near the point of release. Comparison with experimental data and previous plane jet simulation results reveal that combustion process does not affect flow dynamics in compressible region of jet flow. Furthermore a theoretical design of a variable aperture pressure relief device is examined which would enable the blow-down time to be minimized while reducing deterministic separation distances is examined using Computational Fluid Dynamics (CFD) techniques. Design recommendations are suggested for a novel PRD design.
An Overview of Hydrogen Safety Sensors and Requirements
Sep 2009
Publication
There exists an international commitment to increase the utilization of hydrogen as a clean and renewable alternative to carbon-based fuels. The availability of hydrogen safety sensors is critical to assure the safe deployment of hydrogen systems. Already the use of hydrogen safety sensors is required for the indoor fueling of fuel cell powered forklifts (e.g. NFPA 52 Vehicular Fuel Systems Code [1]). Additional Codes and Standards specific to hydrogen detectors are being developed [2 3] which when adopted will impose mandatory analytical performance metrics. There are a large number of commercially available hydrogen safety sensors. Because end-users have a broad range of sensor options for their specific applications the final selection of an appropriate sensor technology can be complicated. Facility engineers and other end-users are expected to select the optimal sensor technology choice. However some sensor technologies may not be a good fit for a given application. Informed decisions require an understanding of the general analytical performance specifications that can be expected by a given sensor technology. Although there are a large number of commercial sensors most can be classified into relatively few specific sensor types (e.g. electrochemical metal oxide catalytic bead and others). Performance metrics of commercial sensors produced on a specific platform may vary between manufacturers but to a significant degree a specific platform has characteristic analytical trends advantages and limitations. Knowledge of these trends facilitates the selection of the optimal technology for a specific application (i.e. indoor vs. outdoor environments). An understanding of the various sensor options and their general analytical performance specifications would be invaluable in guiding the selection of the most appropriate technology for the designated application.
Vented Confined Explosions Involving Methane/Hydrogen Mixtures
Sep 2009
Publication
The EC funded Naturalhy project is assessing the potential for using the existing gas infrastructure for conveying hydrogen as a mixture with natural gas (methane). The hydrogen could then be removed at a point of use or the natural gas/hydrogen mixture could be burned in gas-fired appliances thereby providing reduced carbon emissions compared to natural gas. As part of the project the impact on the safety of the gas system resulting from the addition of hydrogen is being assessed. A release of a natural gas/hydrogen mixture within a vented enclosure (such as an industrial housing of plant and equipment) could result in a flammable mixture being formed and ignited. Due to the different properties of hydrogen the resulting explosion may be more severe for natural gas/hydrogen mixtures compared to natural gas. Therefore a series of large scale explosion experiments involving methane/hydrogen mixtures has been conducted in a 69.3 m3 enclosure in order to assess the effect of different hydrogen concentrations on the resulting explosion overpressures. The results showed that adding up to 20% by volume of hydrogen to the methane resulted in a small increase in explosion flame speeds and overpressures. However a significant increase was observed when 50% hydrogen was added. For the vented confined explosions studied it was also observed that the addition of obstacles within the enclosure representing congestion caused by equipment and pipework etc. increased flame speeds and overpressures above the levels measured in an empty enclosure. Predictions of the explosion overpressure and flame speed were also made using a modified version of the Shell Global Solutions model SCOPE. The modifications included changes to the burning velocity and other physical properties of methane/hydrogen mixtures. Comparisons with the experimental data showed generally good agreement.
Novel Safe Method Of Manufacturing Hydrogen Metallic Hydrides
Sep 2005
Publication
The present work proposes a novel safe method for obtaining metallic hydrides. The method is called SHS (Self-Propagating High temperature synthesis). A novel high pressure gas reactor governed by an electromechanical control device has been designed and built up in order to synthesise metallic hydrides. This system is provided with a control system that allows calculating the amount of gas coming into the reaction vessel at every stage of the process. The main feature of this method is that metallic hydrides can be safely synthesised using low gas reaction pressures. In order to validate the assessing system the main kinetic regularities of SHS in Ti-H2 system were studied. In addition phase analysis (by means of X ray diffraction) as well as chemical analysis have been performed.
Numerical Modelling of Hydrogen Release, Mixture and Dispersion in Atmosphere.
Sep 2005
Publication
The method of the numerical solution of a three-dimensional problem of atmospheric release dispersion and explosion of gaseous admixtures is presented. It can be equally applied for gases of different densities including hydrogen. The system of simplified Navie-Stocks equations received by truncation of viscous members (Euler equations with source members) is used to obtain a numerical solution. The algorithm is based on explicit finite-difference Godunov scheme of arbitrary parameters breakup disintegration. To verify the developed model and computer system comparisons of numerical calculations with the published experimental data on the dispersion of methane and hydrocarbons explosions have been carried out. Computational experiments on evaporation and dispersion of spilled liquid hydrogen and released gaseous hydrogen at different wind speeds have been conducted. The largest mass concentrations of hydrogen between the bottom and top limits of flame propagation and cloud borders have been determined. The problem of the explosion of a hydrogen-air cloud of the complex form generated by large-scale spillage of liquid hydrogen and instant release of gaseous hydrogen has been numerically solved at low wind speed. Shock-wave loadings affecting the buildings located on a distance of 52 m from a hydrogen release place have been shown.
A Reappraisal of Containment Safety Under Hydrogen Detonation
Sep 2005
Publication
The response of a typical steel-lined reinforced concrete nuclear reactor containment to postulated internal hydrogen detonations is investigated by detailed axisymetric non-linear dynamic finite element analysis. The wall pressure histories are calculated for hydrogen detonations using a technique that reproduces the sharp discontinuity at the shock front. The pressure results can be applied to geometrically similar vessels. The analysis indicates that the response is more sensitive to the point of initiation than to the strength of the detonation. Approximate solutions based on a pure impulse assumption where the containment is modelled as a single-degree-of freedom (SDOF) system may be seriously unconservative. This work becomes relevant because new nuclear reactors are foreseen as a primary of source of hydrogen supply.<br/><br/>
Fire Prevention Technical Rule for Gaseous Hydrogen Transport in Pipelines
Sep 2007
Publication
This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow the simulation of hydrogen releases from a pipeline with or without ignition of the hydrogen-air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However in the opinion of the Group the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.
Experimental and Numerical Investigation of Hydrogen Gas Auto-ignition
Sep 2007
Publication
This paper describes hydrogen self-ignition as a result of the formation of a shock wave in front of a high-pressure hydrogen gas propagating in the tube and the semi-confined space for which the numerical and experimental investigation was done. An increase in the temperature behind the shock wave leads to the ignition on the contact surface of the mixture of combustible gas with air. The required condition of combustible self-ignition is to maintain the high temperature in the mixture for a time long enough for inflammation to take place. Experimental technique was based on a high-pressure chamber inflating with hydrogen burst disk failure and pressurized hydrogen discharge into tube of round or rectangular cross section filled with air. A physicochemical model involving the gas dynamic transport of a viscous gas the detailed kinetics of hydrogen oxidation k-ω differential turbulence model and the heat exchange was used for calculations of the self-ignition of high-pressure hydrogen. The results of our experiments and model calculations show that self-ignition in the emitted jet takes place. The stable development of self-ignition naturally depends on the orifice size and the pressure in the vessel a decrease in which leads to the collapse of the ignition process. The critical conditions are obtained.
Safety-Barrier Diagrams for Documenting Safety of Hydrogen Applications
Sep 2007
Publication
Safety-barrier diagrams have proven to be a useful tool in documenting the safety measures taken to prevent incidents and accidents in process industry. In Denmark they are used to inform the authorities and the nonexperts on safety relevant issues as safety-barrier diagrams are less complex compared to fault trees and are easy to understand. Internationally there is a growing interest in this concept with the use of so-called “bowtie” diagrams which are a special case of safety-barrier diagrams. Especially during the on-going introduction of new hydrogen technologies or applications as e.g. hydrogen refueling stations this technique is considered a valuable tool to support the communication with authorities and other stakeholders during the permitting process. Another advantage of safety-barrier diagrams is that there is a direct focus on those system elements that need to be subject to safety management in terms of design and installation operational use inspection and monitoring and maintenance. Safety-barrier diagrams support both quantitative and qualitative or deterministic approaches. The paper will describe the background and syntax of the methodology and thereafter the use of such diagrams for hydrogen technologies are demonstrated.
Consequence Assessment of the BBC Hydrogen Refuelling Station, Using The Adrea-Hf Code
Sep 2009
Publication
Within the framework of the internal project HyQRA of the HYSAFE Network of Excellence (NoE) funded by the European Commission (EC) the participating partners were requested to apply their Quantitative Risk Assessment (QRA) methodologies on a predefined hypothetical gaseous H2 refuelling station named BBC (Benchmark Base Case). The overall aim of the HyQRA project was to perform an inter-comparison of the various QRA approaches and to identify the knowledge gaps on data and information needed in the QRA steps specifically related to H2. Partners NCSRD and UNIPI collaborated on a common QRA. UNIPI identified the hazards on site selected the most critical ones defined the events that could be the primary cause of an accident and provided to NCSRD the scenarios listed in risk order for the evaluation of the consequences. NCSRD performed the quantitative analysis using the ADREA-HF CFD code. The predicted risk assessment parameters (flammable H2 mass and volume time histories and maximum horizontal and vertical distances of the LFL from the source) were provided to UNIPI to analyze the consequences and to evaluate the risk and distances of damage. In total 15 scenarios were simulated. Five of them were H2 releases in confined ventilated spaces (inside the compression and the purification/drying buildings). The remaining 10 scenarios were releases in open/semi-confined spaces (in the storage cabinet storage bank and refuelling hose of one dispenser). This paper presents the CFD methodology applied for the quantitative analysis of the common UNIPI/NCSRD QRA and discusses the results obtained from the performed calculations.
Hydrogen Safety and Permitting Hydrogen Fueling Stations
Sep 2007
Publication
Two key aspects of hydrogen safety are (1) incorporating data and analysis from research development and demonstration (RD&D) into the codes and standards development process; and (2) adopting and enforcing these codes and standards by state and local permitting officials. This paper describes work that the U.S. Department of Energy (DOE) is sponsoring to address these aspects of hydrogen safety. For the first DOE is working with the automobile and energy industries to identify and address high priority RD&D to establish a sound scientific basis for requirements that are incorporated in hydrogen codes and standards. The high priority RD&D needs are incorporated and tracked in an RD&D Roadmap adopted by the Codes and Standards Technical Team of the FreedomCAR and Fuel Partnership. DOE and its national laboratories conduct critical RD&D and work with key standards and model code development organizations to help incorporate RD&D results into the codes and standards process. To address the second aspect DOE has launched an initiative to facilitate the permitting process for hydrogen fueling stations (HFS). A key element of this initiative will be a Web-based information repository a toolkit that includes information fact sheets networking charts to encourage information exchange among code officials who have permitted or are in the process of permitting HFS templates to show whether a proposed station footprint conforms to requirements in the jurisdiction and a database of requirements incorporated in key codes and standards. The information repository will be augmented by workshops for code officials and station developers in jurisdictions that are likely to have HFS in the near future.
Risk-Informed Process and Tools for Permitting Hydrogen Fueling Stations
Sep 2007
Publication
The permitting process for hydrogen fueling stations varies from country to country. However a common step in the permitting process is the demonstration that the proposed fueling station meets certain safety requirements. Currently many permitting authorities rely on compliance with well known codes and standards as a means to permit a facility. Current codes and standards for hydrogen facilities require certain safety features specify equipment made of material suitable for hydrogen environment and include separation or safety distances. Thus compliance with the code and standard requirements is widely accepted as evidence of a safe design. However to ensure that a hydrogen facility is indeed safe the code and standard requirements should be identified using a risk-informed process that utilizes an acceptable level of risk. When compliance with one or more code or standard requirements is not possible an evaluation of the risk associated with the exemptions to the requirements should be understood and conveyed to the Authority Having Jurisdiction (AHJ). Establishment of a consistent risk assessment toolset and associated data is essential to performing these risk evaluations. This paper describes an approach for risk-informing the permitting process for hydrogen fueling stations that relies primarily on the establishment of risk-informed codes and standards. The proposed risk-informed process begins with the establishment of acceptable risk criteria associated with the operation of hydrogen fueling stations. Using accepted Quantitative Risk Assessment (QRA) techniques and the established risk criteria the minimum code and standard requirements necessary to ensure the safe operation of hydrogen facilities can be identified. Risk informed permitting processes exist in some countries and are being developed in others. To facilitate consistent risk-informed approaches the participants in the International Energy Agency (IEA) Task 19 on hydrogen safety are working to identify acceptable risk criteria QRA models and supporting data.
H2 High Pressure On-board Storage Considering Safety Issues
Sep 2007
Publication
The present paper reviews the state-of-the-art of integrated structural integrity monitoring systems applicable to hydrogen on-board applications. Storage safety and costs are key issues for the success of the hydrogen technology considered for replacing the conventional fuel systems in transport applications. An in-service health monitoring procedure for high pressure vessels would contribute to minimize the risks associated to high pressure hydrogen storage and to improve the public acceptance. Such monitoring system would also enable a reduction on design burst criteria enabling savings in material costs and weight. This paper reviews safety and maintenance requirements based on present standards for high pressure vessels. A state-of-the-art of storage media and materials for onboard storage tank is presented as well as of current European programmes on hydrogen storage technologies for transport applications including design safety and system reliability. A technological road map is proposed for the development and validation of a prototype within the framework of the Portuguese EDEN project. To ensure safety an exhaustive test procedure is proposed. Furthermore requirements of a safety on-board monitoring system is defined for filament wound hydrogen tanks.
Fundamental Safety Testing and Analysis of Solid State Hydrogen Storage Materials and Systems
Sep 2007
Publication
Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and commercially acceptable systems it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate risk mitigation strategies to handle unforeseen accidental events. To evaluate these materials and systems an IPHE sanctioned program was initiated in 2006 partnering laboratories from Europe North America and Japan. The objective of this international program is to understanding the physical risks involved in synthesis handling and utilization of solid state hydrogen storage materials and to develop methods to mitigate these risks. This understanding will support ultimate acceptance of commercially high density hydrogen storage system designs. An overview of the approaches to be taken to achieve this objective will be given. Initial experimental results will be presented on environmental exposure of NaAlH4 a candidate high density hydrogen storage compound. The tests to be shown are based on United Nations recommendations for the transport of hazardous materials and include air and water exposure of the hydride at three hydrogen charge levels in various physical configurations. Additional tests developed by the American Society for Testing and Materials were used to quantify the dust cloud ignition characteristics of this material which may result from accidental high energy impacts and system breach. Results of these tests are shown along with necessary risk mitigation techniques used in the synthesis and fabrication of a prototype hydrogen storage system.
Polymer Composites for Tribological Applications in Hydrogen Environment
Sep 2007
Publication
In the development of hydrogen technology special attention is paid to the technical problems of hydrogen storage. One possible way is cryogenic storage in liquid form. Generally cryo-technical machines need components with interacting surfaces in relative motion such as bearings seals or valves which are subjected to extreme conditions. Materials of such systems have to be resistant to friction-caused mechanical deformation at the surface low temperatures and hydrogen environment. Since materials failure can cause uncontrolled escape of hydrogen new material requirements are involved for these tribo-systems in particular regarding operability and reliability. In the past few years several projects dealing with the influence of hydrogen on the tribological properties of friction couples were conducted at the Federal Institute for Materials Research and Testing (BAM) Berlin. This paper reports some investigations carried out with polymer composites. Friction and wear were measured for continuous sliding and analyses of the worn surfaces were performed after the experiments. Tests were performed at room temperature in hydrogen as well as in liquid hydrogen.
Processes of the Formation of Large Unconfined Clouds Following a Massive Spillage of Liquid Hydrogen on the Ground
Sep 2007
Publication
Because of hydrogen low volumetric energy content under its gaseous form transport and storage of liquid hydrogen will certainly play a major role in any future hydrogen economy. One of the obstacles to the expected development use of hydrogen is the poor state of knowledge on explosion risks in the event of an extensive spillage. INERIS set up a large-scale experiment to study the mechanisms of the formation of the gas cloud resulting from such a spillage and the associated mixing process and turbulence effects. Dispersion tests have been performed with cryogenic helium presenting similar dispersion characteristics than liquid hydrogen (buoyancy). Flowrates up to 3 kg/s have been investigated and the instrumentation allowed the observation and quantification of bouyancy effects including internal turbulence. Those results constitute an originals et of data which can be used as a basis for the development of dispersion software and reinterpretation of other existing databases ([10 11])
Simulation of Detonation after an Accidental Hydrogen Release in Enclosed Environments
Sep 2007
Publication
An accidental hydrogen release in equipment enclosures may result in the presence of a detonable mixture in a confined environment. Numerical simulation is potentially a useful tool for damage assessment in these situations. To assess the value of CFD techniques numerical simulation of detonation was performed for two realistic scenarios. The first scenario starts with a pipe failure in an electrolyzer resulting in a leak of 42 g of hydrogen. The second scenario deals with a failure in a reformer where 84 g of hydrogen is released. In both cases dispersion patterns were first obtained from separate numerical simulation and were then used as initial condition in a detonation simulation based upon the reactive Euler's equations. Energy was artificially added in a narrow region to simulate detonative ignition. In the electrolyzer ignition was assumed to occur 500 ms after beginning of the release. Results show a detonation failing on the top and bottom side but propagating left and right before eventually failing also. Average impulse was 500 Ns/m². For the reformer three cases were simulated with ignition 1.0 1.4 and 2.0 seconds after the beginning of the release. In two cases the detonation wave failed everywhere except in the direction of the release in which it continued propagating until reaching the side wall. In the third the detonation failed everywhere at first but later a deflagration to detonation transition occurred resulting in a strong wave that propagated rapidly toward the side wall. In all three cases the consequences are more serious than in the electrolyzer.
High Pressure Hydrogen Jets in the Presence of a Surface
Sep 2009
Publication
The effect of surfaces on the extent of high pressure vertical and horizontal unignited jets is studied using CFD numerical simulations performed with FLACS Hydrogen and Phoenics. For a constant flow rate release of hydrogen from a 284 bar storage unit through a 8.5 mm orifice located 1 meter from the ground the maximum extent of the flammable cloud is determined as a function of time and compared to a free vertical hydrogen jet under identical release conditions. The results are compared to methane numerical simulations and to the predictions of the Birch correlations for the size of the flammable cloud. We find that the maximum extent of the flammable clouds of free jets obtained using CFD numerical simulations for both hydrogen and methane are in agreement with the Birch predictions. For hydrogen horizontal free jets there is strong buoyancy effect observed towards the end of the flammable cloud thus noticeably reducing its centreline extent. For methane horizontal free jets this effect is not observed. For methane the presence of the ground results in a pronounced increase in the extent of the flammable cloud compared to a free jet. The effects of a surface on vertical jets are also studied.
Flame Characteristics of High-Pressure Hydrogen Gas Jet
Sep 2005
Publication
It is expected that hydrogen will serve as a nonpolluting carrier of energy for the next generation of vehicles and guidelines for its safe use are required. Hydrogen-gas service stations for supplying fuel cell vehicles will have to handle high-pressure hydrogen gas but safety regulations for such installations have not received much investigation. In this study we experimentally investigated the flame characteristics of a rapid leakage of high-pressure hydrogen gas. A hydrogen jet diffusion flame was injected horizontally from convergent nozzles of various diameters between 0.1 and 4 mm at reservoir over pressures of between 0.01 and 40 MPa. The sizes of the flame were measured and experimental equations were obtained for the length and the width of the flame. Flame sizes depend not only on the nozzle diameter but also on the spouting pressure. Blow-off limits exists and are determined by the nozzle diameter and the spouting pressure. Furthermore the radiation from a hydrogen flame can be predicted from the flow rate of the gas and the distance from the flame.
Analysis of the Environmental Degradation Effects on the Cables of “La Arena” Bridge (Spain)
Sep 2017
Publication
After nearly 25 years of service some of the wires of the tendons of “La Arena” bridge (Spain) started to exhibit the effects of environmental degradation processes. “La Arena” is cable-stayed bridge with 6 towers and a reference span between towers of about 100 meters. After a maintenance inspection of the bridge evidences of corrosion were detected in some of the galvanized wires of the cables. A more in-deep analysis of these wires revealed that many of them exhibited loss of section due to the corrosion process. In order to clarify the causes of this degradation event and to suggest some remedial actions an experimental program was designed. This program consisted of tensile and fatigue tests on some strand samples of the bridge together with a fractographic analysis of the fracture surfaces of the wires its galvanized layer thickness and some hydrogen measurements (hydrogen embrittlement could be another effect of the environmental degradation process).Once the type and extension of the flaws in the wires was characterized a structural integrity assessment of the strands was performed with the aim of quantifying the margins until failure and establishing some maintenance recommendations.
Validation of Leading Point Concept in RANS Simulations of Highly Turbulent Lean Syngas-air Flames with Well-pronounced Diffusional-thermal Effects
Jan 2021
Publication
While significant increase in turbulent burning rate in lean premixed flames of hydrogen or hydrogen-containing fuel blends is well documented in various experiments and can be explained by highlighting local diffusional-thermal effects capabilities of the vast majority of available models of turbulent combustion for predicting this increase have not yet been documented in numerical simulations. To fill this knowledge gap a well-validated Turbulent Flame Closure (TFC) model of the influence of turbulence on premixed combustion which however does not address the diffusional-thermal effects is combined with the leading point concept which highlights strongly perturbed leading flame kernels whose local structure and burning rate are significantly affected by the diffusional-thermal effects. More specifically within the framework of the leading point concept local consumption velocity is computed in extremely strained laminar flames by adopting detailed combustion chemistry and subsequently the computed velocity is used as an input parameter of the TFC model. The combined model is tested in RANS simulations of highly turbulent lean syngas-air flames that were experimentally investigated at Georgia Tech. The tests are performed for four different values of the inlet rms turbulent velocities different turbulence length scales normal and elevated (up to 10 atm) pressures various H2/CO ratios ranging from 30/70 to 90/10 and various equivalence ratios ranging from 0.40 to 0.80. All in all the performed 33 tests indicate that the studied combination of the leading point concept and the TFC model can predict well-pronounced diffusional-thermal effects in lean highly turbulent syngas-air flames with these results being obtained using the same value of a single constant of the combined model in all cases. In particular the model well predicts a significant increase in the bulk turbulent consumption velocity when increasing the H2/CO ratio but retaining the same value of the laminar flame speed.
Risk Identification for the Introduction of Advanced Science and Technology: A Case Study of a Hydrogen Energy System for Smooth Social Implementation
May 2020
Publication
A method of risk identification is developed by comparing existing and advanced technologies from the viewpoint of comprehensive social risk. First to analyze these values from a multifaceted perspective we constructed a questionnaire based on 24 individual values and 26 infrastructural values determined in a previous study. Seven engineering experts and six social science experts were then asked to complete the questionnaire to compare and analyze a hydrogen energy system (HES) and a gasoline energy system (GES). Finally the responses were weighted using the analytic hierarchy process. Three important points were identified and focused upon: the distinct disadvantages of the HES compared to the GES judgments that were divided between experts in the engineering and social sciences fields and judgments that were divided among experts in the same field. These are important risks that should be evaluated when making decisions related to the implementation of advanced science and technology.
The Effect of Hydrogen Enrichment, Flame-flame Interaction, Confinement, and Asymmetry on the Acoustic Response of a Model Can Combustor
Apr 2022
Publication
To maximise power density practical gas turbine combustion systems have several injectors which can lead to complex interactions between flames. However our knowledge about the effect of flame-flame interactions on the flame response the essential element to predict the stability of a combustor is still limited. The present study investigates the effect of hydrogen enrichment flame-flame interaction confinement and asymmetries on the linear and non-linear acoustic response of three premixed flames in a simple can combustor. A parametric study of the linear response characterised by the flame transfer function (FTF) is performed for swirling and non-swirling flames. Flame-flame interactions were achieved by changing the injector spacing and the level of hydrogen enrichment by power from 10 to 50%. It was found that the latter had the most significant effect on the flame response. Asymmetry effects were investigated by changing one of the flames by using a different bluff-body to alter both the flame shape and flow field. The global flame response showed that the asymmetric cases can be reconstructed using a superposition of the two symmetric cases where all three bluff-bodies and flames are the same. Overall the linear response characterised by the flame transfer function (FTF) showed that the effect of increasing the level of hydrogen enrichment is more pronounced than the effect of the injector spacing. Increasing hydrogen enrichment results in more compact flames which minimises flame-flame interactions. More compact flames increase the cut-off frequency which can lead to self-excited modes at higher frequencies. Finally the non-linear response was characterised by measuring the flame describing function (FDF) at a frequency close to a self-excited mode of the combustor for different injector spacings and levels of hydrogen enrichment. It is shown that increasing the hydrogen enrichment leads to higher saturation amplitude whereas the effect of injector spacing has a comparably smaller effect.
A Study of Decrease Burst Strength on Compressed-hydrogen Containers by Drop Test
Sep 2019
Publication
We investigate an appropriate initial burst pressure of compressed hydrogen containers that correlates with a residual burst pressure requirement at the end of life (EOL) and report an influence of hydraulic sequential tests on residual burst pressure. Results indicate that a container damage caused by a drop test during hydraulic sequential tests has a large influence on burst pressure. The container damage induced through hydraulic sequential tests is investigated using non-destructive evaluations to clarify a strength decreasing mechanism. An ultrasonic flaw detection analysis is conducted before and after the drop test and indicated that the damage occurred at the cylindrical and dome parts of the container after the drop test. An X-ray computed tomography imaging identifies a delamination inside laminated structure made of carbon fiber reinforced plastics (CFRP) layer with some degree of delamination reaching the end boss of the container. Results suggest that a load profile fluctuates in the CFRP layer at the dome part and that a burst strength of the dome part decreases. Therefore an observed decreasing in drop damage at the dome part can be used to prevent a degradation of EOL container burst strength.
Hydrogen Dispersion in a Closed Environment
Sep 2017
Publication
The highly combustible nature of hydrogen poses a great hazard creating a number of problems with its safety and handling. As a part of safety studies related to the use of hydrogen in a confined environment it is extremely important to have a good knowledge of the dispersion mechanism.<br/>The present work investigates the concentration field and flammability envelope from a small scale leak. The hydrogen is released into a 0.47 m × 0.33 m x 0.20 m enclosure designed as a 1/15 – scale model of a room in a nuclear facility. The performed tests evaluates the influence of the initial conditions at the leakage source on the dispersion and mixing characteristics in a confined environment. The role of the leak location and the presence of obstacles are also analyzed. Throughout the test during the release and the subsequent dispersion phase temporal profiles of hydrogen concentration are measured using thermal conductivity gauges within the enclosure. In addition the BOS (Background Oriented Schlieren) technique is used to visualise the cloud evolution inside the enclosure. These instruments allow the observation and quantification of the stratification effects.
Some Fundamental Combustion Properties of "Cryogenic" Premixed Hydrogen Air Flames
Sep 2021
Publication
Because of the emergence of the U.E. “green deal” and because of the significant implication of national and regional authorities throughout Europe the “hydrogen” economy is emerging. And with it numerous questions and experimentations. One of them perhaps a key point is the storage and transport of hydrogen. Liquid hydrogen in cryogenic conditions is a possibility already used in the space industry but under a lot of constrains. What may be acceptable in a well-controlled and restrained domain may not be realistic in a wider application closer to the public. Safety should be ensured and there is a need for a better knowledge of the flammable and ignition properties of the “cold” hydrogen mixtures following a cryogenic spillage for instance to select adequate ATEX equipment. The purpose of PRESLHY project [4] is to investigate the ignition fire and explosion characteristics of cryogenic hydrogen spillages and to propose safety engineering methods. The present work is part of it and addresses the measurement of the laminar burning velocity (Sl) flammability limits (FL) minimum ignition energy (MIE)… of hydrogen air mixtures at atmospheric pressure but down to -150°C. To do this a special burner was designed with details given inside this paper together with the experimental results. It is found that the FL domain is reduced when the temperature drops that MIE increases slightly and Sl decreases.
Evaluating Uncertainty in Accident Rate Estimation at Hydrogen Refueling Station Using Time Correlation Model
Nov 2018
Publication
Hydrogen as a future energy carrier is receiving a significant amount of attention in Japan. From the viewpoint of safety risk evaluation is required in order to increase the number of hydrogen refuelling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability which increases over long operation period due to decrease in number of stations. In this paper a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.
3D Quantitative Risk Assessment on a Hydrogen Refuelling Station in Shanghai
Sep 2019
Publication
The number of hydrogen refuelling stations worldwide is growing rapidly in recent years. The first large capacity hydrogen refuelling station in China is under construction. A 3D quantitative risk assessment QRA)is conducted for this station. Hazards associated with hydrogen systems are identified. Leakage frequency of hydrogen equipment are analyzed. Jet flame explosion scenarios and corresponding accident consequences are simulated. Risk acceptance criteria for hydrogen refuelling stations are discussed. The results show that the risk of this refuelling station is acceptable. And the maximum lethality frequency is 6.3*10-6. The area around compressors has the greatest risk. People should be avoided as far as possible from the compressor when the compressor does not need to be maintained. With 3D QRA the visualization of the evaluation results will help stakeholders to observe the hazardous areas of the hydrogen refuelling station at a glance.
Performance Tests of Catalysts for the Safe Conversion of Hydrogen Inside the Nuclear Waste Containers in Fukushima Daiichi
Sep 2019
Publication
The safe decommissioning as well as decontamination of the radioactive waste resulting from the nuclear accident in Fukushima Daiichi represents a huge task for the next decade. At present research and development on long-term safe storage containers has become an urgent task with international cooperation in Japan. One challenge is the generation of hydrogen and oxygen in significant amounts by means of radiolysis inside the containers as the nuclear waste contains a large portion of sea water. The generation of radiolysis gases may lead to a significant pressure build-up inside the containers and to the formation of flammable gases with the risk of ignition and the loss of integrity.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
Modelling and Numerical Simulation of Hydrogen Jet Fires for Industrial Safety Analyses – Comparison with Large-scale Experiments
Sep 2019
Publication
Reliable predictive tools for hydrogen safety engineering are needed to meet increased and more widespread use of hydrogen in the society. Industrial models and methods used to establish thermal radiation hazard safety distances from hydrogen jet fires are often based on models previously developed for hydrocarbon jet fires. Their capability of predicting radiative heat fluxes from hydrogen jet fires has often only been validated against small-scale or medium-scale jet flame experiments. However large-scale hydrogen jet fire experiments have shown that thermal radiation levels can be significantly higher than one might expect from extrapolation of experience on smaller hydrogen flames. Here two large-scale horizontal hydrogen jet fires (from a 20.9 mm and a 52.5 mm diameter release respectively) have been modelled and simulated with the advanced industrial CFD code KAMELEON FIREEX KFX® based on the Eddy Dissipation Concept by Magnussen for turbulent combustion modelling. The modelling of the high-pressure hydrogen gas releases is based on a pseudo-source concept using real-gas thermodynamic data for hydrogen. The discrete transport method of Lockwood and Shah is used to calculate the radiative heat transfer and radiative properties of water vapour are modelled according to Leckner. The predicted thermal radiation is compared to data from large-scale hydrogen jet fire experiments and discussed. This work was conducted as part of a KFX-H2 R&D project supported by the Research Council of Norway.
Study of the Effects of Changes in Gas Composition as Well as Ambient and Gas Temperature on Errors of Indications of Thermal Gas Meters
Oct 2020
Publication
Thermal gas meters represent a promising technology for billing customers for gaseous fuels however it is essential to ensure that measurement accuracy is maintained in the long term and in a broad range of operating conditions. The effect of hydrogen addition to natural gas will change the physicochemical properties of the mixture of natural gas and hydrogen. Such a mixture will be supplied through the gas system to consumers including households where the amounts of received gas will be metered. The physicochemical properties of hydrogen including the specific density or viscosity differ significantly from those of the natural gas components such as methane ethane propane nitrogen etc. Therefore it is of utmost importance to establish the impact of the changes in the gas composition caused by the addition of hydrogen to natural gas on the metrological properties of household gas meters including thermal gas meters. Furthermore since household gas meters can be installed outdoors and taking into account the fact that household gas meters are good heat exchangers the influence of ambient and gas temperature on the metrological properties of those meters should be investigated. This article reviews a test bench and a testing method concerning errors of thermal gas meter indicators using air and natural gas including the type containing hydrogen. The indication errors for thermal gas meters using air natural gas and natural gas with an addition of 2% 4% 5% 10% and 15% hydrogen were determined and then subjected to metrological analysis. Moreover the test method and test bench are discussed and the results of tests on the impact of ambient and gas temperatures (-25 ◦C and 55 ◦C respectively) on the errors of indications of thermal gas meters are presented. Conclusions for distribution system operators in terms of gas meter selection were drawn based on the test results.
Advanced Polymeric/inorganic Nanohybrids: An Integrated Platform for Gas Sensing Applications
Jan 2022
Publication
Rapid industrial development vehicles domestic activities and mishandling of garbage are the main sources of pollutants which are destroying the atmosphere. There is a need to continuously monitor these pollutants for the safety of the environment and human beings. Conventional instruments for monitoring of toxic gases are expensive bigger in size and time-consuming. Hybrid materials containing organic and inorganic components are considered potential candidates for diverse applications including gas sensing. Gas sensors convert the information regarding the analyte into signals. Various polymeric/inorganic nanohybrids have been used for the sensing of toxic gases. Composites of different polymeric materials like polyaniline (PANI) poly (4-styrene sulfonate) (PSS) poly (34-ethylene dioxythiophene) (PEDOT) etc. with various metal/metal oxide nanoparticles have been reported as sensing materials for gas sensors because of their unique redox features conductivity and facile operation at room temperature. Polymeric nanohybrids showed better performance because of the larger surface area of nanohybrids and the synergistic effect between polymeric and inorganic materials. This review article focuses on the recent developments of emerging polymeric/inorganic nanohybrids for sensing various toxic gases including ammonia hydrogen nitrogen dioxide carbon oxides and liquefied petroleum gas. Advantages disadvantages operating conditions and prospects of hybrid composites have also been discussed.
Experimental Investigations Relevant for Hydrogen and Fission Product Issues Raised by the Fukushima Accident
Jan 2015
Publication
The accident at Japan's Fukushima Daiichi nuclear power plant in March 2011 caused by an earthquake and a subsequent tsunami resulted in a failure of the power systems that are needed to cool the reactors at the plant. The accident progression in the absence of heat removal systems caused Units 1-3 to undergo fuel melting. Containment pressurization and hydrogen explosions ultimately resulted in the escape of radioactivity from reactor containments into the atmosphere and ocean. Problems in containment venting operation leakage from primary containment boundary to the reactor building improper functioning of standby gas treatment system (SGTS) unmitigated hydrogen accumulation in the reactor building were identified as some of the reasons those added-up in the severity of the accident. The Fukushima accident not only initiated worldwide demand for installation of adequate control and mitigation measures to minimize the potential source term to the environment but also advocated assessment of the existing mitigation systems performance behavior under a wide range of postulated accident scenarios. The uncertainty in estimating the released fraction of the radionuclides due to the Fukushima accident also underlined the need for comprehensive understanding of fission product behavior as a function of the thermal hydraulic conditions and the type of gaseous aqueous and solid materials available for interaction e.g. gas components decontamination paint aerosols and water pools. In the light of the Fukushima accident additional experimental needs identified for hydrogen and fission product issues need to be investigated in an integrated and optimized way. Additionally as more and more passive safety systems such as passive autocatalytic recombiners and filtered containment venting systems are being retrofitted in current reactors and also planned for future reactors identified hydrogen and fission product issues will need to be coupled with the operation of passive safety systems in phenomena oriented and coupled effects experiments. In the present paper potential hydrogen and fission product issues raised by the Fukushima accident are discussed. The discussion focuses on hydrogen and fission product behavior inside nuclear power plant containments under severe accident conditions. The relevant experimental investigations conducted in the technical scale containment THAI (thermal hydraulics hydrogen aerosols and iodine) test facility (9.2 m high 3.2 m in diameter and 60 m3 volume) are discussed in the light of the Fukushima accident.
Improved Monitoring and Diagnosis of Transformer Solid Insulation Using Pertinent Chemical Indicators
Jul 2021
Publication
Transformers are generally considered to be the costliest assets in a power network. The lifetime of a transformer is mainly attributable to the condition of its solid insulation which in turn is measured and described according to the degree of polymerization (DP) of the cellulose. Since the determination of the DP index is complex and time-consuming and requires the transformer to be taken out of service utilities prefer indirect and non-invasive methods of determining the DP based on the byproduct of cellulose aging. This paper analyzes solid insulation degradation by measuring the furan concentration recently introduced methanol and dissolved gases like carbon oxides and hydrogen in the insulating oil. A group of service-aged distribution transformers were selected for practical investigation based on oil samples and different kinds of tests. Based on the maintenance and planning strategy of the power utility and a weighted combination of measured chemical indicators a neural network was also developed to categorize the state of the transformer in certain classes. The method proved to be able to improve the diagnostic capability of chemical indicators thus providing power utilities with more reliable maintenance tools and avoiding catastrophic failure of transformers.
Hy4Heat Safety Assessment: Conclusions Report (Incorporating Quantitative Risk Assessment) - Work Package 7
May 2021
Publication
The Hy4Heat Safety Assessment has focused on assessing the safe use of hydrogen gas in certain types of domestic properties and buildings. The summary reports (the Precis and the Safety Assessment Conclusions Report) bring together all the findings of the work and should be looked to for context by all readers. The technical reports should be read in conjunction with the summary reports. While the summary reports are made as accessible as possible for general readers the technical reports may be most accessible for readers with a degree of technical subject matter understanding. All of the safety assessment reports have now been reviewed by the HSE.<br/><br/>A comparative risk assessment of natural gas versus hydrogen gas including a quantitative risk assessment; and identification of control measures to reduce risk and manage hydrogen gas safety for a community demonstration.
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