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Prediction of the Lift-off, Blow-out and Blow-off Stability Limits of Pure Hydrogen and Hydrogen and Hydrocarbon Mixture Jet Flames
Sep 2007
Publication
The paper presented experimental studies of the liftoff and blowout stability of pure hydrogen hydrogen/propane and hydrogen/methane jet flam es using a 2 mm burner. Carbon dioxide and Argon gas were also used in the study for the comparison with hydrocarbon fuel. Comparisons of the stability of H 2/C3H8 H 2/CH4 H 2/Ar and H 2/CO2 flames showed that H 2/C3H8 produced the highest liftoff height and H 2/CH4 required highest liftoff and blowoff velocities. The non-dimensional analysis of liftoff height approach was used to correlate liftoff data of H 2 H2-C3H8 H 2-CO2 C 3H8 and H2-Ar jet flames tested in the 2 mm burner. The suitability of extending the empirical correlations based on hydrocarbon flames to both hydrogen and hydrogen/ hydrocarbon flames was examined.
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.
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.
Hydrogen Risk Assessment in Sao Paulo State, Brazil
Sep 2011
Publication
Sao Paulo State Environmental Protection Agency CETESB Brazil adopts a so called Reference Distance (RD) from hazardous substances storage facilities to populated places as a decision making tool for the application of a simplified or a full Risk Analysis (RA). As for hydrogen RD was set up based on instantaneous release scenarios where consequences reaching off-site population were estimated for delayed ignition ending up in vapor cloud explosion (VCE) with a 0.1 bar blast wave overpressure as a chosen endpoint corresponding to a 1%2of death probability range. Procedures for RD evaluation and further adoption by CETESB are presented in this paper.
Risk Analysis of the Storage Unit in Hydrogen Refuelling Station
Sep 2007
Publication
Nowadays consumer demand for local and global environmental quality in terms of air pollution and in particular greenhouse gas emissions reduction may help to drive to the introduction of zero emission vehicles. At this regard the hydrogen technology appears to have future market valuablepotential. On the other hand the use of hydrogen vehicles which requires appropriate infrastructures for production storage and refuelling stages presents a lot of safety problems due to the peculiar chemicophysical hydrogen characteristics. Therefore safe at the most practices are essential for the successful proliferation of hydrogen vehicles. Indeed to avoid limit hazards it is necessary to implement practices that if early adopted in the development of a fuelling station project can allow very low environmental impact safety being incorporated in the project itself. Such practices generally consist in the integrated use of Failure Mode and Effect Analysis (FMEA) HAZard OPerability (HAZOP) and Fault Tree Analysis (FTA) which constitute well established standards in reliability engineering. At this regard however a drawback is the lack of experience and the scarcity of the relevant data collection. In this work we present the results obtained by the integrated use of FMEA HAZOP and FTA analyses relevant for the moment the high-pressure storage equipment in a hydrogen gas refuelling station. The study that is intended to obtain elements for improving safety of the system can constitute a basis for further more refined works.
H21- Public Perceptions of Converting the Gas Network to Hydrogen - Social Sciences Sudy
Jun 2020
Publication
The next decade will see fundamental changes in how people heat their homes. The global energy system is changing in response to the need to transition away from fossil-based generation towards more environmentally sustainable alternatives.
Hydrogen offers one such alternative but currently there is limited understanding of public perceptions of hydrogen the information that people need in order to make an informed choice about using hydrogen in their homes and how misunderstandings could present barriers to the uptake of hydrogen technology. This is crucial to ensure the success of future policy and investment. The H21 concept is to convert the UK gas distribution network to 100% hydrogen over time thereby decarbonising heat and supporting decarbonisation of electric large industrials and transport. This would be achieved using the existing UK gas grid network and technology available across the world today whilst maintaining the benefits of gas and the gas networks in the energy mix for the long-term future. Additionally this would maintain choice of energy for customers i.e. they would be able to use both gas and electricity. The H21 project is being delivered by the UK gas distribution networks Northern Gas Networks Cadent Wales & West Utilities and SGN. As part of the H21 project Leeds Beckett University has been working with Northern Gas Networks to gain insight into public perceptions of hydrogen as a domestic fuel. Using innovative social science methods the research team has explored for the first time public perceptions of moving the UK domestic fuel supply to 100% hydrogen. We identify what people think and feel about a potential conversion the concerns and questions that they have and how to address them clearly. The findings presented in this report will ensure that issues around the current perception of hydrogen are identified and addressed prior to any large-scale technology rollout.
The first stage of the project comprised a series of discovery interviews which explored how to talk to people about hydrogen and the H21 project. We interviewed 12 participants selected to ensure we included people with a range of experiences and domestic settings for example people who live in urban and rural areas those who live alone those who live with children or a partner those who live in their own home and those who rent. Most participants had given very little thought about where their gas and electric comes from and other than switching supplier to get a better tariff had very little interest in it. They had not previously considered their domestic heating as a source of carbon emissions and were surprised that there may be a need in the future to change their gas supply. From the discovery interviews we identified several key areas to explore in the next stage of the work:
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Hydrogen offers one such alternative but currently there is limited understanding of public perceptions of hydrogen the information that people need in order to make an informed choice about using hydrogen in their homes and how misunderstandings could present barriers to the uptake of hydrogen technology. This is crucial to ensure the success of future policy and investment. The H21 concept is to convert the UK gas distribution network to 100% hydrogen over time thereby decarbonising heat and supporting decarbonisation of electric large industrials and transport. This would be achieved using the existing UK gas grid network and technology available across the world today whilst maintaining the benefits of gas and the gas networks in the energy mix for the long-term future. Additionally this would maintain choice of energy for customers i.e. they would be able to use both gas and electricity. The H21 project is being delivered by the UK gas distribution networks Northern Gas Networks Cadent Wales & West Utilities and SGN. As part of the H21 project Leeds Beckett University has been working with Northern Gas Networks to gain insight into public perceptions of hydrogen as a domestic fuel. Using innovative social science methods the research team has explored for the first time public perceptions of moving the UK domestic fuel supply to 100% hydrogen. We identify what people think and feel about a potential conversion the concerns and questions that they have and how to address them clearly. The findings presented in this report will ensure that issues around the current perception of hydrogen are identified and addressed prior to any large-scale technology rollout.
The first stage of the project comprised a series of discovery interviews which explored how to talk to people about hydrogen and the H21 project. We interviewed 12 participants selected to ensure we included people with a range of experiences and domestic settings for example people who live in urban and rural areas those who live alone those who live with children or a partner those who live in their own home and those who rent. Most participants had given very little thought about where their gas and electric comes from and other than switching supplier to get a better tariff had very little interest in it. They had not previously considered their domestic heating as a source of carbon emissions and were surprised that there may be a need in the future to change their gas supply. From the discovery interviews we identified several key areas to explore in the next stage of the work:
- Beliefs about the environment
- Beliefs about inconvenience and cost
- Beliefs about safety
- Beliefs about the economic impact
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Using Solar Power Regulation to Electrochemically Capture Carbon Dioxide: Process Integration and Case Studies
Mar 2022
Publication
This work focuses on the use of solar photovoltaic energy to capture carbon dioxide by means of a combined electrolyzer–absorption system and compares operating results obtained in two cases studies (operation during one clear and one cloudy day in March) in which real integration of solar photovoltaics electrolyzer and absorption technologies is made at the bench-scale. The system is a part of a larger process (so-called EDEN⃝R Electrochemically-based Decarbonizing ENergy) which aims to regulate solar photovoltaic energy using a reversible chloralkaline electrochemical cell. Results demonstrate the feasibility of the sequestering technology which can produce chlorine and hydrogen but also the sequestration of CO2 and its transformation into a mixture of sodium chloride bicarbonate and carbonate useful as raw matter. Efficiencies over 70% for chlorine 60% for hydrogen and 90% for sodium hydroxide were obtained. The sequestration of carbon dioxide reached 24.4 mmol CO2/Ah with an average use of 1.6 mmol NaOH/mmol CO2. Important differences are found between the performance of the system in a clear and a cloudy day which point out the necessity of regulating the dosing of the electrochemically produced sodium hydroxide to optimize the sequestration of CO2.
H21- Strategic Modelling Major Urban Centres
Aug 2019
Publication
This report summarises the results of an independent audit carried out by DNV GL on the model conversions from natural gas to hydrogen for the models being used as a benchmark for the wider UK proposed hydrogen conversion of the natural gas network. The detailed model conversion process was derived from the H21 modelling meetings and the detailed notes were put together by NGN as a basic guide which has been included in Appendix A and is summarised as follows:
- Current 5 year planning model is updated and then used to generate a Replacement Expenditure (REPEX) natural gas model which would remove metallic pipes from the networks by insertion where possible
- Merging models together to form larger networks where required
- Preparation for conversion to hydrogen which would include the District Governor (DG) capacity increases to run the additional model flows
- Conversion of the models to hydrogen by changing demands to thermal and the gas characteristics to those of hydrogen
- Applying reinforcement to remove pressure failures.
Evaluation of Optical and Spectroscopic Experiments of Hydrogen Jet Fires
Sep 2009
Publication
This paper reports results of evaluating joint experiments under the work programme of Hysafe occurring at HSL who provided the test facilities and basic measurements to generate jet fires whereas Fraunhofer ICT applied their equipment to visualise the jet fires by fast video techniques IR-cameras and fast scanning spectroscopy in the NIR/IR spectral region. Another paper describes the experimental set up and main findings of flame structures and propagation resolved in time. The spatial distribution of species and temperate as well as their time history and fluctuations give a basis of the evaluation of effects caused by such jet fires. Fraunhofer ICT applied their comprehensive evaluation codes to model the radiation emission from 3-atomic species in the flame especially H2O in the Infrared spectral range. The temperatures of the hydrogen flame were about 2000 K as found by least squares fit of the measured molecular bands by the codes. In comparison with video and thermo camera frames these might enable to estimate on a qualitative level species distribution and air entrainment and temperatures to identify hot and reactive zones. The risk analysis could use this information to estimate heat transfer and the areas of risk to direct inflammation from the jet fires by semi-empirical approaches.
H2FC SUPERGEN- Delivering Negative Emissions from Biomass derived Hydrogen
Apr 2020
Publication
Bioenergy with carbon capture and storage (BECCS) removes carbon dioxide (CO2) from the atmosphere i.e. negative CO2 emissions. It will likely have an important role in the transition to a net-zero economy by offsetting hard-to-abate greenhouse gas emissions. However there are concerns about the sustainability of large scale BECCS deployment using bioenergy from predominantly primary biomass sources (i.e. dedicated energy crops). Secondary sources of biomass (e.g. waste biomass municipal solid wastes forest/agricultural residues) are potentially an economical and sustainable alternative resource. Furthermore supplementing primary biomass demand with secondary sources could enable the supply of biomass from solely indigenous sources (i.e. from the UK) which could provide economic advantages in a growing global bio-economy.<br/><br/>There is also a growing interest in biomass-derived hydrogen production with CCS (BHCCS) which generates hydrogen and removes CO2 from the atmosphere. Hydrogen could help decarbonise fuel-dependent sectors such as heat industry or transportation. The aim of this study was to determine whether BHCCS could possibly deliver net negative CO2 emissions making comparisons against the other BECCS technologies.
Laser-Induced Generation of Hydrogen in Water by Using Graphene Target
Jan 2022
Publication
A new method of hydrogen generation from water by irradiation with CW infrared laser diode of graphene scaffold immersed in solution is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high at about 80% and assisted by a small emission of O2 CO and CO2 gases.
Computational Modelling of Pressure Effects from Hydrogen Explosions
Sep 2007
Publication
The statement of the problem and algorithm of computational modelling of the processes of formation of the hydrogen-air mixture in the atmosphere its explosion (taking into account chemical interaction) and dispersion of the combustion materials in the open space with complex relief are presented. The finite-difference scheme was developed for the case of the three-dimensional system of gas dynamics equations complemented by the mass conservation laws of the gas admixture and combustion materials. The algorithm of the computation of thermal and physical parameters of the gas mixture appearing as a result of the instantaneous explosion taking into account chemical interaction was developed. The algorithm of computational solution of the difference scheme obtained on the basis of Godunov method was considered. The verification of the mathematical model showed its acceptable accuracy in comparison with known experimental data. It allows using the developed model for the modelling of pressure and thermal consequences of possible failures at the industrial enterprises which store and use hydrogen. The computational modelling of an explosion of the gas hydrogen cloud appearing as a result of instantaneous destruction of high pressure containers at the fuelling station was carried out. The analysis of different ways of protection of the surrounding buildings from destructive effects of the shock wave was conducted. The recommendations considering the choice of dimensions of the protection area around the fuelling station were worked out.
Numerical Studies of Dispersion and Flammable Volume of Hydrogen in Enclosures
Sep 2007
Publication
Hydrogen dispersion in an enclosure is numerically studied using simple analytical solutions and a large-eddy-simulation based CFD code. In simple calculations the interface height and temperature rise of the upper layer are obtained based on mass and energy conservation and the centreline hydrogen volume fraction is derived from similarity solutions of buoyant jets. The calculated centreline hydrogen volume fraction using the two methods agree with each other; however discrepancies are found for the calculated total flammable volume as a result of the inability of simple calculations in taking into account local mixing and diffusion. The CFD model in contrast is found to be capable of correctly reproducing the diffusion and stratification phenomena during the mixing stage.
CFD Study of the Unignited and Ignited Hydrogen Releases from TRPD Under a Fuel Cell Car
Oct 2015
Publication
This paper describes a CFD study of a scenario involving the vertical downward release of hydrogen from a thermally-activated pressure relief device (TPRD) under a fuel cell car. The volumetric source model is applied to simulate hydrogen release dynamics during the tank blowdown process. Simulations are conducted for both unignited and ignited releases from onboard storage at 35 MPa and 70 MPa with TPRD orifice 4.2 mm. Results show that after TPRD opening the hazards associated with the release of hydrogen lasts less than two minutes and the most hazardous timeframe occurs within ten seconds of the initiation of the release. The deterministic separation distances for unignited releases are longer than those for ignited releases indicating that the separation distances are dominated by delayed ignition events rather than immediate ignition events. The deterministic separation distances for both unignited and ignited hydrogen downward releases under the car are significantly shorter than those of free jets. To ensure the safety of people a deterministic separation distance of at least 10 m for 35 MPa releases is required. This distance should be increased to 12 m for the 70 MPa release case. To ensure that the concentration of hydrogen is always less than 4% at the location of the air intake of buildings the deterministic separation distance should be at least 11 m for 35 MPa releases and 13 m for 70 MPa releases.
LES Modelling Of Hydrogen Release and Accumulation Within a Non-Ventilated Ambient Pressure Garage Using The Adrea-HF CFD Code
Sep 2011
Publication
Computational Fluid Dynamics (CFD) has already proven to be a powerful tool to study the hydrogen dispersion and help in the hydrogen safety assessment. In this work the Large Eddy Simulation (LES) recently incorporated into the ADREA-HF CFD code is evaluated against the INERIS-6C experiment of hydrogen leakage in a supposed garage which provides detailed experimental measurements visualization of the flow and availability of previous CFD results from various institutions (HySafe SBEP-V3). The short-term evolution of the hydrogen concentrations in this confined space is examined and comparison with experimental data is provided along with comments about the ability of LES to capture the transient phenomena occurring during hydrogen dispersion. The influence of the value of the Smagorinsky constant on the resolved and on the unresolved turbulence is also presented. Furthermore the renormalization group (RNG) LES methodology is also tested and its behaviour in both highly-turbulent and less-turbulent parts of the flow is highlighted.
Validated Equivalent Source Model for an Under-expanded Hydrogen Jet
Oct 2015
Publication
As hydrogen fuel cell vehicles become more widely adopted by consumers the demand for refuelling stations increases. Most vehicles require high-pressure (either 350 or 700 bar) hydrogen and therefore the refuelling infrastructure must support these pressures. Fast running reduced order physical models of releases from high-pressure sources are needed so that quantitative risk assessment can guide the safety certification of these stations. A release from a high pressure source is choked at the release point forming the complex shock structures of an under-expanded jet before achieving a characteristic Gaussian pro le for velocity density mass fraction etc. downstream. Rather than using significant computational resources to resolve the shock structure an equivalent source model can be used to quickly and accurately describe the ow in terms of velocity diameter and thermodynamic state after the shock structure. In this work we present correlations for the equivalent boundary conditions of a subsonic jet as a high-pressure jet downstream of the shock structure. Schlieren images of under-expanded jets are used to show that the geometrical structure of under-expanded jets scale with the square root of the static to ambient pressure ratio. Correlations for an equivalent source model are given and these parameters are also found to scale with square root of the pressure ratio. We present our model as well as planar laser Rayleigh scattering validation data for static pressures up to 60 bar.
Study of a Post-fire Verification Method for the Activation Status of Hydrogen Cylinder Pressure Relief Devices
Oct 2015
Publication
To safely remove from its fire accident site a hydrogen fuel cell vehicle equipped with a carbon fiber reinforced plastic composite cylinder for compressed hydrogen (CFRP cylinder) and to safely keep the burnt vehicle in a storage facility it is necessary to verify whether the thermally-activated pressure relief device (TPRD) of the CFRP cylinder has already been activated releasing the hydrogen gas from the cylinder. To develop a simple post-fire verification method on TPRD activation the present study was conducted on the using hydrogen densitometer and Type III and Type IV CFRP cylinders having different linings. As the results TPRD activation status can be determined by measuring hydrogen concentrations with a catalytic combustion hydrogen densitometer at the cylinder's TPRD gas release port.
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.
Potential Hydrogen Market: Value-Added Services Increase Economic Efficiency for Hydrogen Energy Suppliers
Apr 2022
Publication
Hydrogen energy is a clean zero-carbon long-term storage flexible and efficient secondary energy. Accelerating the development of the hydrogen energy industry is a strategic choice to cope with global climate change achieve the goal of carbon neutrality and realize high-quality economic and social development. This study aimed to analyze the economic impact of introducing valueadded services to the hydrogen energy market on hydrogen energy suppliers. Considering the network effect of value-added services this study used a two-stage game model to quantitatively analyze the revenue of hydrogen energy suppliers under different scenarios and provided the optimal decision. The results revealed that (1) the revenue of a hydrogen energy supplier increases only if the intrinsic value of value-added services exceeds a certain threshold; (2) the revenue of hydrogen energy suppliers is influenced by a combination of four key factors: the intrinsic value of value-added services network effects user scale and the sales strategies of rivals; (3) the model developed in this paper can provide optimal decisions for hydrogen energy suppliers to improve their economic efficiency and bring more economic investment to hydrogen energy market in the future.
Influence of Initial Pressure in Hydrogen/Air flame Acceleration During Severe Accident in Nuclear Power Plant
Sep 2017
Publication
Flame acceleration (FA) and explosion of hydrogen/air mixtures remain key issues for severe accident management in nuclear power plants. Empirical criteria were developed in the early 2000s by Dorofeev and colleagues providing effective tools to discern possible FA or DDT (Deflagration-to-Detonation Transition) scenarios. A large experimental database composed mainly of middle-scale experiments in obstacle-laden ducts at atmospheric pressure condition has been used to validate these criteria. However during a severe accident the high release rate of steam and non-condensable gases into the containment can result in pressure increase up to 5 bar abs. In the present work the influence of the unburnt gas initial pressure on flame propagation mechanisms was experimentally investigated. Premixed hydrogen/air mixtures with hydrogen concentration close to 11% and 15% were considered. From the literature we know that these flames are supposed to accelerate up to Chapman-Jouguet deflagration velocity in long obstacle-laden tubes at initial atmospheric conditions. Varying the pressure in the fresh gas in the range 0.6–4 bar no effects on the flame acceleration phase were observed. However as the initial pressure was increased we observed a decrease in the flame velocity close to the end of the tube. The pressure increase due to the combustion reaction was found to be proportional to the initial pressure according to adiabatic isochoric complete combustion.
Numerical Study on the Influence of Different Boundary Conditions on the Efficiency of Hydrogen Recombiners Inside a Car Garage
Oct 2015
Publication
Passive auto-catalytic recombiners (PARs) have the potential to be used in the future for the removal of accidentally released hydrogen inside confined areas. PARs could be operated both as stand-alone or backup safety devices e.g. in case of active ventilation failure.
Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.
In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.
As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.
Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.
In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.
As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.
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.
Humidity Tolerant Hydrogen-oxygen Recombination Catalysts for Hydrogen Safety Applications
Sep 2017
Publication
Catalytic hydrogen-oxygen recombination is a non-traditional method to limit hydrogen accumulation and prevent combustion in the hydrogen industry. Outside of conventional use in the nuclear power industry this hydrogen safety technology can be applied when traditional hydrogen mitigation methods (i.e. active and natural ventilation) are not appropriate or when a back-up system is required. In many of these cases it is desirable for hydrogen to be removed without the use of power or other services which makes catalytic hydrogen recombination attractive. Instances where catalytic recombination of hydrogen can be utilized as a stand-alone or back-up measure to prevent hydrogen accumulation include radioactive waste storage (hydrogen generated from water radiolysis or material corrosion) battery rooms hydrogen-cooled generators hydrogen equipment enclosures etc.<br/>Water tolerant hydrogen-oxygen recombiner catalysts for non-nuclear applications have been developed at Canadian Nuclear Laboratories (CNL) through a program in which catalyst materials were selected prepared and initially tested in a spinning-basket type reactor to benchmark the catalyst’s performance with respect to hydrogen recombination in dry and humid conditions. Catalysts demonstrating high activity for hydrogen recombination were then selected and tested in trickle-bed and gas phase recombiner systems to determine their performance in more typical deployment conditions. Future plans include testing of selected catalysts after exposure to specific poisons to determine the catalysts’ tolerance for such poisons.
Estimation of Final Hydrogen Temperature From Refueling Parameters
Oct 2015
Publication
Compressed hydrogen storage is currently widely used in fuel cell vehicles due to its simplicity in tank structure and refuelling process. For safety reason the final gas temperature in the hydrogen tank during vehicle refuelling must be maintained under a certain limit e.g. 85 °C. Many experiments have been performed to find the relations between the final gas temperature in the hydrogen tank and refueling conditions. The analytical solution of the hydrogen temperature in the tank can be obtained from the simplified thermodynamic model of a compressed hydrogen storage tank and it serves as function formula to fit experimental temperatures. From the analytical solution the final hydrogen temperature can be expressed as a weighted average form of initial temperature inflow temperature and ambient temperature inspired by the rule of mixtures. The weighted factors are related to other refuelling parameters such as initial mass initial pressure refuelling time refuelling mass rate average pressure ramp rate (APRR) final mass final pressure etc. The function formula coming from the analytical solution of the thermodynamic model is more meaningful physically and more efficient mathematically in fitting experimental temperatures. The simple uniform formula inspired by the concept of the rule of mixture and its weighted factors obtained from the analytical solution of lumped parameter thermodynamics model is representatively used to fit the experimental and simulated results in publication. Estimation of final hydrogen temperature from refuelling parameters based on the rule of mixtures is simple and practical for controlling the maximum temperature and for ensuring hydrogen safety during fast filling process.
Hazard Distance Nomograms for a Blast Wave from a Compressed Hydrogen Tank Rupture in a Fire
Sep 2017
Publication
Nomograms for assessment of hazard distances from a blast wave generated by a catastrophic rupture of stand-alone (stationary) and onboard compressed hydrogen cylinder in a fire are presented. The nomograms are easy to use hydrogen safety engineering tools. They were built using the validated and recently published analytical model. Two types of nomograms were developed – one for use by first responders and another for hydrogen safety engineers. The paper underlines the importance of an international effort to unify harm and damage criteria across different countries as the discrepancies identified by the authors gave the expected results of different hazard distances for different criteria.
Numerical Simulation on Low-speed Hydrogen Jet Diffusion
Oct 2015
Publication
The numerical simulation for the hydrogen jet experiments performed by Schefer et al. is conducted using the compressible multicomponent Navier-Stokes equations with the preconditioning method. The simulated results for the hydrogen jet agree with the theoretical results of Tollmien. As far as comparing with the experiments by Schefer et al. the concentration profiles along the radial direction agree with the present numerical results and that along the centerline also agree well with the experimental results after the data are normalized by the equivalent nozzle diameter. It is confirmed that the spread of the jet width from the jet exit to downstream is affected by the Kelvin-Helmholtz instability. It is also confirmed that the jet flow field is formed alternately by the high pressure region and the low pressure one to cause the jet flow fluctuation.
Hydrogen Concentration Distribution in 2.25Cr-1Mo-0.25V Steel under the Electrochemical Hydrogen Charging and Its Influence on the Mechanical Properties
May 2020
Publication
The deterioration of the mechanical properties of metal induced by hydrogen absorption threatens the safety of the equipment serviced in hydrogen environments. In this study the hydrogen concentration distribution in 2.25Cr-1Mo-0.25V steel after hydrogen charging was analyzed following the hydrogen permeation and diffusion model. The diffusible hydrogen content in the 1-mm-thick specimen and its influence on the mechanical properties of the material were investigated by glycerol gas collecting test static hydrogen charging tensile test scanning electron microscopy (SEM) test and microhardness test. The results indicate that the content of diffusible hydrogen tends to be the saturation state when the hydrogen charging time reaches 48 h. The simulation results suggest that the hydrogen concentration distribution can be effectively simulated by ABAQUS and the method can be used to analyze the hydrogen concentration in the material with complex structures or containing multiple microstructures. The influence of hydrogen on the mechanical properties is that the elongation of this material is reduced and the diffusible hydrogen will cause a decrease in the fracture toughness of the material and thus hydrogen embrittlement (HE) will occur. Moreover the Young’s modulus E and microhardness are increased due to hydrogen absorption and the variation value is related to the hydrogen concentration introduced into the specimen.
Hydrogen Storage: Recent Improvements and Industrial Prospective
Oct 2015
Publication
Efficient storage of hydrogen is crucial for the success of hydrogen energy markets (early markets as well as transportation market). Hydrogen can be stored either as a compressed gas a refrigerated liquefied gas a cryo-compressed gas or in hydrides. This paper gives an overview of hydrogen storage technologies and details the specific issues and constraints related to the materials behaviour in hydrogen and conditions representative of hydrogen energy uses. It is indeed essential for the development of applications requiring long-term performance to have good understanding of long-term behaviour of the materials of the storage device and its components under operational loads.
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.
Effect of Relative Humidity on Mechanical Degradation of Medium Mn Steels
Mar 2020
Publication
Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles medium Mn steels look forward to a highly promising future. However hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40% 60% 80% and 100%). Under normal relative humidity (about 40%) at 25 °C the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity the hydrogen concentration in steel increases slowly and reaches a stable value about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions the tensile strength changed the hydrogen concentration increased and the elongation decreased as well thereby increasing the hydrogen embrittlement sensitivity. In other words the smaller the tensile rate applied the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions the threshold value of the delayed cracking of M7B (‘M’ referring to Mn ‘7’ meaning the content of Mn ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80% the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.
Engineering Safety in Hydrogen-Energy Applications
Oct 2015
Publication
Since a few years hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous hazardous events like explosion could occur and some accidents like the Hindenburg disaster are still in the mind. Objectively hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method derived from ARAMIS method permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies.
Full Scale Experimental Campaign to Determine the Actual Heat Flux Produced by Fire on Composite Storages - Calibration Tests on Metallic Vessels
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it’s important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
Syngas Explosion Reactivity in Steam Methane Reforming Process
Sep 2013
Publication
During the synthesis of hydrogen by methane steam reforming mixtures composed of H2 CH4 CO and CO2 are produced in the process. In this work the explosion reactivity of these mixtures on the basis of detonation cell size and laminar flame speed is calculated using a reactant assimilation simplification and a kinetic approach. The detonation cells width are calculated using the Cell_CH Kurchatov institute method and the laminar flame velocities are calculated with Chemkin Premix using different detailed chemical kinetic mechanisms. These calculations are used to define if these mixtures could be considered having a medium or a high reactivity for risk assessment in case of leak in the hydrogen plants.
State of the Art of Hydrogen Production via Pyrolysis of Natural Gas
Jul 2020
Publication
Fossil fuels have to be substituted by climate neutral fuels to contribute to CO2 reduction in the future energy system. Pyrolysis of natural gas is a well-known technical process applied for production of e. g. carbon black.
In the future it might contribute to carbon dioxide-free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by-product of this process can be used for material production or can be sequestrated the produced hydrogen has a low carbon footprint.
This article reviews literature on the state of the art of methane/ natural gas pyrolysis process developments and at-tempts to assess the technology readiness level (TRL).
In the future it might contribute to carbon dioxide-free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by-product of this process can be used for material production or can be sequestrated the produced hydrogen has a low carbon footprint.
This article reviews literature on the state of the art of methane/ natural gas pyrolysis process developments and at-tempts to assess the technology readiness level (TRL).
Feasibility of Renewable Hydrogen Based Energy Supply for a District
Sep 2017
Publication
Renewable generation technologies (e.g. photovoltaic panels (PV)) are often installed in buildings and districts with an aim to decrease their carbon emissions and consumption of non-renewable energy. However due to a mismatch between supply and demand at an hourly but also on a seasonal timescale; a large amount of electricity is exported to the grid rather than used to offset local demand. A solution to this is local storage of electricity for subsequent self-consumption. This could additionally provide districts with new business opportunities financial stability flexibility and reliability.<br/>In this paper the feasibility of hydrogen based electricity storage for a district is evaluated. The district energy system (DES) includes PV and hybrid photovoltaic panels (PVT). The proposed storage system consists of production of hydrogen using the renewable electricity generated within the district hydrogen storage and subsequent use in a fuel cell. Combination of battery storage along with hydrogen conversion and storage is also evaluated. A multi-energy optimization approach is used to model the DES. Results of the model are optimal battery capacity electrolyzer capacity hydrogen storage capacity fuel cell capacity and energy flows through the system. The model is also used to compare different system design configurations. The results of this analysis show that both battery capacity and conversion of electricity to hydrogen enable the district to decrease its carbon emissions by approximately 22% when compared to the reference case with no energy storage.
Technical and Economic Analysis of One-Stop Charging Stations for Battery and Fuel Cell EV with Renewable Energy Sources
Jun 2020
Publication
Currently most of the vehicles make use of fossil fuels for operations resulting in one of the largest sources of carbon dioxide emissions. The need to cut our dependency on these fossil fuels has led to an increased use of renewable energy sources (RESs) for mobility purposes. A technical and economic analysis of a one-stop charging station for battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV) is investigated in this paper. The hybrid optimization model for electric renewables (HOMER) software and the heavy-duty refueling station analysis model (HDRSAM) are used to conduct the case study for a one-stop charging station at Technical University of Denmark (DTU)-Risø campus. Using HOMER a total of 42 charging station scenarios are analyzed by considering two systems (a grid-connected system and an off-grid connected system). For each system three different charging station designs (design A-hydrogen load; design B-an electrical load and design C-an integrated system consisting of both hydrogen and electrical load) are set up for analysis. Furthermore seven potential wind turbines with different capacity are selected from HOMER database for each system. Using HDRSAM a total 18 scenarios are analyzed with variation in hydrogen delivery option production volume hydrogen dispensing option and hydrogen dispensing option. The optimal solution from HOMER for a lifespan of twenty-five years is integrated into design C with the grid-connected system whose cost was $986065. For HDRSAM the optimal solution design consists of tube trailer as hydrogen delivery with cascade dispensing option at 350 bar together with high production volume and the cost of the system was $452148. The results from the two simulation tools are integrated and the overall cost of the one-stop charging station is achieved which was $2833465. The analysis demonstrated that the one-stop charging station with a grid connection is able to fulfil the charging demand cost-effectively and environmentally friendly for an integrated energy system with RESs in the investigated locations.
Validation and Recommendations for CFD and Engineering Modeling of Hydrogen Vented Explosions: Effects of Concentration, Stratification, Obstruction and Vent Area
Oct 2015
Publication
Explosion venting is commonly used in the process industry as a prevention solution to protect equipment or buildings against excessive internal pressure caused by an explosion. This article is dedicated to the validation of FLACS CFD code for the modelling of vented explosions. Analytical engineering models fail when complex cases are considered for instance in the presence of obstacles or H2 stratified mixtures. CFD is an alternative solution but has to be carefully validated. In this study FLACS simulations are compared to published experimental results and recommendations are suggested for their application.
Beyond Haber-Bosch: The Renaissance of the Claude Process
Apr 2021
Publication
Ammonia may be one of the energy carriers in the hydrogen economy. Although research has mostly focused on electrochemical ammonia synthesis this however remains a scientific challenge. In the current article we discuss the feasibility of single-pass thermochemical ammonia synthesis as an alternative to the high-temperature high-pressure Haber-Bosch synthesis loop. We provide an overview of recently developed low temperature ammonia synthesis catalysts as well as an overview of solid ammonia sorbents. We show that the low temperature low pressure single-pass ammonia synthesis process can produce ammonia at a lower cost than the Haber-Bosch synthesis loop for small-scale ammonia synthesis (<40 t-NH3 d−1).
Safe Hydrogen Fuel Handling and Use for Efficient Implementation – SH2IFT
Sep 2019
Publication
The SH2IFT project combines social and technical scientific methods to address knowledge gaps regarding safe handling and use of gaseous and liquid hydrogen. Theoretical approaches will be complemented by fire and explosion experiments with emphasis on topics of strategic importance to Norway such as tunnel safety maritime applications etc. Experiments include Rapid Phase Transition Boiling Liquid Expanding Vapour Explosion and jet fires. This paper gives an overview of the project and preliminary results.
Comparison of Liquid Hydrogen, Methylcyclohexane and Ammonia on Energy Efficiency and Economy
Mar 2019
Publication
Among several candidates of hydrogen storage liquid hydrogen methylcyclohexane (MCH) and ammonia are considered as potential hydrogen carriers in terms of their characteristics application feasibility and economic performance. In addition as a main motor in the hydrogen introduction Japan has focused and summarized the storage methods for hydrogen into these three methods. Each of them has advantages and disadvantages compared to each other. This study focuses on the effort to analyze and clarify the potential of these three hydrogen storages especially in terms of physical characteristics energy efficiency and economic cost. Liquid hydrogen faces challenges in huge energy consumption during liquefaction and boil-off during storage. MCH has main obstacles in largely required energy in dehydrogenation. Lastly ammonia encounters high energy demand in both synthesis and decomposition (if required). In terms of energy efficiency ammonia is predicted to have the highest total energy efficiency (34–37%) followed by liquid hydrogen (30–33%) and MCH (about 25%). In addition from cost calculation ammonia with direct utilization (without decomposition) is considered to have the highest feasibility for being massively adopted as it shows the lowest cost (20–22 JPY/Nm3-H2 in 2050). However in case that highly pure hydrogen (such as for fuel cell) is demanded liquid hydrogen looks to be promising (24–25 JPY/Nm3-H2 in 2050) compared to MCH and ammonia with decomposition and purification.
Hydrogen Fast Filling to a Type IV Tank Developed for Motorcycles
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it's important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
Metal Hydride Hydrogen Compressors
Feb 2014
Publication
Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine – the metal hydride material itself – should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage hydrogen sorption kinetics and effective thermal conductivity) the thermodynamics of the metal–hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimised to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors reduction of slope of the isotherms and hysteresis increase of cycling stability and life time together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation.<br/>The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal–hydrogen systems suitable for the hydrogen compression; and (b) applied aspects including their consideration from the applied thermodynamic viewpoint system design features and performances of the metal hydride compressors and major applications.
Communicating Leakage Risk in the Hydrogen Economy: Lessons Already Learned from Geoenergy Industries
Sep 2019
Publication
Hydrogen may play a crucial part in delivering a net zero emissions future. Currently hydrogen production storage transport and utilisation are being explored to scope opportunities and to reduce barriers to market activation. One such barrier could be negative public response to hydrogen technologies. Previous research around socio-technical risks finds that public acceptance issues are particularly challenging for emerging remote technical sensitive uncertain or unfamiliar technologies - such as hydrogen. Thus while the hydrogen value chain could offer a range of potential environmental economic and social benefits each will have perceived risks that could challenge the introduction and subsequent roll-out of hydrogen. These potential issues must be identified and managed so that the hydrogen sector can develop adapt or respond appropriately. Geological storage of hydrogen could present challenges in terms of perceived safety. Valuable lessons can be learned from international research and practice of CO2 and natural gas storage in geological formations (for carbon capture and storage CCS and for power respectively). Here we explore these learnings. We consider the similarities and differences between these technologies and how these may affect perceived risks. We also reflect on lessons for effective communication and community engagement. We draw on this to present potential risks to the perceived safety of - and public acceptability of – the geological storage of hydrogen. One of the key lessons learned from CCS and natural gas storage is that progress is most effective when risk communication and public acceptability is considered from the early stages of technology development.
Vented Hydrogen Deflagrations in Containers: Effect of Congestion for Homogeneous Mixtures
Sep 2017
Publication
This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foot ISO containers. The scenarios investigated include 14 tests with explosion venting through the doors of the containers and 20 tests with venting through openings in the roof. The parameters investigated include hydrogen concentration vent area type of venting device and the level of congestion inside the containers. All tests involved homogeneous and initially quiescent hydrogen-air mixtures. The results demonstrate the strong effect of congestion on the maximum reduced explosion pressures which typically is not accounted for in current standards and guidelines for explosion protection. The work is a deliverable from work package 2 (WP2) in the project “Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations” or HySEA which receives funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) under grant agreement no. 671461.
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.
Hazard Identification Study for Risk Assessment of a Hybrid Gasoline-hydrogen Fueling Station with an Onsite Hydrogen Production System Using Organic Hydride
Oct 2015
Publication
Hydrogen infrastructures are important for the commercialization of fuel cell vehicles. Hydrogen storage and transportation are significant topics because it is difficult to safely and effectively treat large amounts of hydrogen because of hydrogen hazards. An organic chemical hydride method keeps and provides hydrogen using hydrogenation and dehydrogenation chemical reactions with aromatic compounds. This method has advantages in that the conventional petrochemical products are used as a hydrogen carrier and petrochemicals are more easily treated than hydrogen because of low hazards. Hydrogen fueling stations are also crucial infrastructures for hydrogen supply. In Japan hybrid gasoline-hydrogen fuelling stations are needed for effective space utilization in urban areas. It is essential to address the safety issues of hybrid fueling stations for inherently safer station construction. We focused on a hybrid gasoline-hydrogen fuelling station with an on-site hydrogen production system using methylcyclohexane as an organic chemical hydride. The purpose of this study is to reveal unique hybrid risks in the station with a hazard identification study (HAZID study). As a result of the HAZID study we identified 314 accident scenarios involving gasoline and organic chemical hydride systems. In addition we suggested improvement safety measures for uniquely worst-case accident scenarios to prevent and mitigate the scenarios.
Design of an Efficient, High Purity Hydrogen Generation Apparatus and Method for a Sustainable, Closed Clean Energy Cycle
Jul 2015
Publication
In this paper we present a detailed design study of a novel apparatus for safely generating hydrogen (H2) on demand according to a novel method using a controlled chemical reaction between water (H2O) and sodium (Na) metal that yields hydrogen gas of sufficient purity for direct use in fuel cells without risk of contaminating sensitive catalysts. The apparatus consists of a first pressure vessel filled with liquid H2O with an overpressure of nitrogen (N2) gas above the H2O reactant and a second pressure vessel that stores solid Na reactant. Hydrogen gas is generated above the solid Na when H2O reactant is introduced using a regulator that senses when the downstream pressure of H2 gas above the solid Na reactant has dropped below a threshold value. The sodium hydroxide (NaOH) byproduct of the hydrogen producing reaction is collected within the apparatus for later reprocessing by electrolysis to recover the Na reactant.
Threshold Stress Intensity Factor for Hydrogen Assisted Cracking of Cr-Mo Steel Used as Stationary Storage Buffer of a Hydrogen Refueling Station
Oct 2015
Publication
In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking (KIH) constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2% proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa m1/2 to 44.5 MPa m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa m1/2 to 41.1 MPa m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material.
Alloy and Composition Dependence of Hydrogen Embrittlement Susceptibility in High-strength Steel Fasteners
Jun 2017
Publication
High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Additionally inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. HE susceptibility is a function of the material condition which is comprehensively described by the metallurgical and mechanical properties. Material strength has a first-order effect on HE susceptibility which increases significantly above 1200 MPa and is characterized by a ductile--brittle transition. For a given concentration of hydrogen and at equal strength the critical strength above which the ductile–brittle transition begins can vary due to second-order effects of chemistry tempering temperature and sub-microstructure. Additionally non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. Below 1200 MPa non-conforming quality is often the root cause of real-life failures.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Development of Hydrogen Behavior Simulation Code System
Oct 2015
Publication
In the Fukushima Daiichi Nuclear Power Station (NPS) accident hydrogen generated by oxidation reaction of the cladding and water etc. was leaked into the NPS building and finally led to occurrence of hydrogen explosion in the building. This resulted in serious damage to the environment. To improve the safety performance of the NPS especially on the hydrogen safety under severe accident conditions a simulation code system has been developed to analyze hydrogen behaviour including diffusion combustion explosion and structural integrity evaluation. This developing system consists of CFD and FEM tools in order to support various hydrogen user groups consisting of students researchers and engineers. Preliminary analytical results obtained with above mentioned tools especially with open source codes including buoyancy turbulent model and condensation model agreed well with the existing test data.
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