Japan
Effect of High-pressure H2 Gas on Tensile and Fatigue Properties of Stainless Steel SUS316L by Means of the Internal High-pressure H2 Gas Method
Dec 2019
Publication
For prohibiting a global warming fuel-cell systems without carbon dioxide emissions are a one of the promising technique. In case of a fuel-cell vehicle (FCV) high-pressure H2 gas is indispensable for a long running range. Although there are lot of paper for studying a hydrogen embrittlement (HE) there are few paper referred to the effect of high-pressure H2on the HE phenomenon.
In this study an effect of high-pressure H2 gas on tensile & fatigue properties of stainless steel SUS316L were investigated by means of the internal high-pressure H2 gas technique. Main findings of this study are as follows;
In this study an effect of high-pressure H2 gas on tensile & fatigue properties of stainless steel SUS316L were investigated by means of the internal high-pressure H2 gas technique. Main findings of this study are as follows;
- Although there are almost no hydrogen embrittlement effect on the 0.2 % proof stress and tensile strength elongation and reduction of area decrease in H2 gas environment
- For case of low Nieq material fatigue life and fatigue limit decrease in H2 gas environment
- For case of low Nieq material not a few α’ martensitic phase generated on the fatigue fractured specimen.
Magnesium Based Materials for Hydrogen Based Energy Storage: Past, Present and Future
Jan 2019
Publication
Volodymyr A. Yartys,
Mykhaylo V. Lototskyy,
Etsuo Akiba,
Rene Albert,
V. E. Antonov,
Jose-Ramón Ares,
Marcello Baricco,
Natacha Bourgeois,
Craig Buckley,
José Bellosta von Colbe,
Jean-Claude Crivello,
Fermin Cuevas,
Roman V. Denys,
Martin Dornheim,
Michael Felderhoff,
David M. Grant,
Bjørn Christian Hauback,
Terry D. Humphries,
Isaac Jacob,
Petra E. de Jongh,
Jean-Marc Joubert,
Mikhail A. Kuzovnikov,
Michel Latroche,
Mark Paskevicius,
Luca Pasquini,
L. Popilevsky,
Vladimir M. Skripnyuk,
Eugene I. Rabkin,
M. Veronica Sofianos,
Alastair D. Stuart,
Gavin Walker,
Hui Wang,
Colin Webb,
Min Zhu and
Torben R. Jensen
Magnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures kinetics and thermodynamics of the systems based on MgH2 nanostructuring new Mg-based compounds and novel composites and catalysis in the Mg based H storage systems. Finally thermal energy storage and upscaled H storage systems accommodating MgH2 are presented.
Model of Local Hydrogen Permeability in Stainless Steel with Two Coexisting Structures
Apr 2021
Publication
The dynamics of hydrogen in metals with mixed grain structure is not well understood at a microscopic scale. One of the biggest issues facing the hydrogen economy is “hydrogen embrittlement” of metal induced by hydrogen entering and diffusing into the material. Hydrogen diffusion in metallic materials is difficult to grasp owing to the non-uniform compositions and structures of metal. Here a time-resolved “operando hydrogen microscope” was used to interpret local diffusion behaviour of hydrogen in the microstructure of a stainless steel with austenite and martensite structures. The martensite/austenite ratios differed in each local region of the sample. The path of hydrogen permeation was inferred from the time evolution of hydrogen permeation in several regions. We proposed a model of hydrogen diffusion in a dual-structure material and verified the validity of the model by simulations that took into account the transfer of hydrogen at the interfaces.
Assessing Uncertainties of Well-To-Tank Greenhouse Gas Emissions from Hydrogen Supply Chains
Jun 2017
Publication
Hydrogen is a promising energy carrier in the clean energy systems currently being developed. However its effectiveness in mitigating greenhouse gas (GHG) emissions requires conducting a lifecycle analysis of the process by which hydrogen is produced and supplied. This study focuses on the hydrogen for the transport sector in particular renewable hydrogen that is produced from wind- or solar PV-powered electrolysis. A life cycle inventory analysis is conducted to evaluate the Well-to-Tank (WtT) GHG emissions from various renewable hydrogen supply chains. The stages of the supply chains include hydrogen being produced overseas converted into a transportable hydrogen carrier (liquid hydrogen or methylcyclohexane) imported to Japan by sea distributed to hydrogen filling stations restored from the hydrogen carrier to hydrogen and filled into fuel cell vehicles. For comparison an analysis is also carried out with hydrogen produced by steam reforming of natural gas. Foreground data related to the hydrogen supply chains are collected by literature surveys and the Japanese life cycle inventory database is used as the background data. The analysis results indicate that some of renewable hydrogen supply chains using liquid hydrogen exhibited significantly lower WtT GHG emissions than those of a supply chain of hydrogen produced by reforming of natural gas. A significant piece of the work is to consider the impacts of variations in the energy and material inputs by performing a probabilistic uncertainty analysis. This suggests that the production of renewable hydrogen its liquefaction the dehydrogenation of methylcyclohexane and the compression of hydrogen at the filling station are the GHG-intensive stages in the target supply chains.
Development of Technical Regulations for Fuel Cell Motorcycles in Japan—Hydrogen Safety
Jul 2019
Publication
Hydrogen fuel cell vehicles are expected to play an important role in the future and thus have improved significantly over the past years. Hydrogen fuel cell motorcycles with a small container for compressed hydrogen gas have been developed in Japan along with related regulations. As a result national regulations have been established in Japan after discussions with Japanese motorcycle companies stakeholders and experts. The concept of Japanese regulations was proposed internationally and a new international regulation on hydrogen-fueled motorcycles incorporating compressed hydrogen storage systems based on this concept are also established as United Nations Regulation No. 146. In this paper several technical regulations on hydrogen safety specific to fuel cell motorcycles incorporating compressed hydrogen storage systems are summarized. The unique characteristics of these motorcycles e.g. small body light weight and tendency to overturn easily are considered in these regulations.
Influence of hydraulic sequential tests on the burst strength of Type-4 compressed hydrogen containers
Sep 2019
Publication
One of the topics for the revision deliberation of GTR13 on hydrogen and fuel cell vehicles is the study of an appropriate initial burst pressure of the containers. The purpose of this study is to investigate the influence of the hydraulic sequential tests on the residual burst pressure in order to examine the appropriate initial burst pressure correlated with the provisions for the residual burst pressure at the Endof-Life (EOL). Specifically we evaluated any deterioration and variations of burst pressure due to hydraulic sequential tests on 70MPa compressed-hydrogen containers. When the burst pressure after the hydraulic sequential testing (EOL) was compared with the initial burst pressure at the beginning of life (BOL) the pressure proved to have decreased by a few percent while the variation increased. In the burst test it was observed that the rupture originated in the cylindrical part in all the BOL containers while in some of the EOL containers the rupture originated in the dome part. Since the dome part is a section that suffers an impact of vertical drop test it is conceivable that some sort of damage occurred in the CFRP. Therefore it was assumed that this damage was the main causal factor for the decrease in the burst pressure and the increase of the burst pressure variation at the dome part.
Catalytic Hydrogen Production, Storage and Application
Jul 2021
Publication
Hydrogen is a clean fuel for transportation and energy storage. It has several attractive features including a higher energy content by weight use in fuel cells that produces only water as a by-product storage in small and large quantities by various methods and established transportation and infrastructures. A hydrogen economy consists of three steps i.e. hydrogen production storage and applications. All three steps involved in a hydrogen economy can be divided into catalytic and non-catalytic approaches. For catalytic processes the efficiency highly depends on the type and physico-chemical characteristics of the catalysts. Therefore for the improvement of these catalytic processes the development of highly efficient and stable catalysts is highly required.
Strain Rate Sensitivity of Microstructural Damage Evolution in a Dual-Phase Steel Pre-Charged with Hydrogen
Dec 2018
Publication
We evaluated the strain rate sensitivity of the micro-damage evolution behavior in a ferrite/martensite dual-phase steel. The micro-damage evolution behavior can be divided into three regimes: damage incubation damage arrest and damage growth. All regimes are associated with local deformability. Thus the total elongation of DP steels is determined by a combination of plastic damage initiation resistance and damage growth arrestability. This fact implies that hydrogen must have a critical effect on the damage evolution because hydrogen enhances strain localization and lowers crack resistance. In this context the strain rate must be an important factor because it affects the time for microstructural hydrogen diffusion/segregation at a specific microstructural location or at the damage tip. In this study tensile tests were carried out on a DP steel with different strain rates of 10− 2 and 10− 4 s−1. We performed the damage quantification microstructure characterization and fractography. Specifically the quantitative data of the damage evolution was analyzed using the classification of the damage evolution regimes in order to separately elucidate the effects of the hydrogen on damage initiation resistance and damage arrestability. In this study we obtained the following conclusions with respect to the strain rate. Lowering the strain rate increased the damage nucleation rate at martensite and reduced the critical strain for fracture through shortening the damage arrest regime. However the failure occurred via ductile modes regardless of strain rate.
Hydrogen: A Reviewable Energy Perspective
Sep 2019
Publication
Hydrogen has emerged as an important part of the clean energy mix needed to ensure a sustainable future. Falling costs for hydrogen produced with renewable energy combined with the urgency of cutting greenhouse-gas emissions has given clean hydrogen unprecedented political and business momentum.
This paper from the International Renewable Energy Agency (IRENA) examines the potential of hydrogen fuel for hard-to-decarbonise energy uses including energy-intensive industries trucks aviation shipping and heating applications. But the decarbonisation impact depends on how hydrogen is produced. Current and future sourcing options can be divided into grey (fossil fuel-based) blue (fossil fuel-based production with carbon capture utilisation and storage) and green (renewables-based) hydrogen. Green hydrogen produced through renewable-powered electrolysis is projected to grow rapidly in the coming years.
Among other findings:
Important synergies exist between hydrogen and renewable energy. Hydrogen can boost renewable electricity market growth and broaden the reach of renewable solutions.
Trade of energy-intensive commodities produced with hydrogen including “e-fuels” could spur faster uptake or renewables and bring wider economic benefits.
This paper from the International Renewable Energy Agency (IRENA) examines the potential of hydrogen fuel for hard-to-decarbonise energy uses including energy-intensive industries trucks aviation shipping and heating applications. But the decarbonisation impact depends on how hydrogen is produced. Current and future sourcing options can be divided into grey (fossil fuel-based) blue (fossil fuel-based production with carbon capture utilisation and storage) and green (renewables-based) hydrogen. Green hydrogen produced through renewable-powered electrolysis is projected to grow rapidly in the coming years.
Among other findings:
Important synergies exist between hydrogen and renewable energy. Hydrogen can boost renewable electricity market growth and broaden the reach of renewable solutions.
- Electrolysers can add demand-side flexibility. In advanced European energy markets electrolysers are growing from megawatt to gigawatt scale.
- Blue hydrogen is not inherently carbon free. This type of production requires carbon-dioxide (CO2) monitoring verification and certification.
- Synergies may exist between green and blue hydrogen deployment given the chance for economies of scale in hydrogen use or logistics.
- A hydrogen-based energy transition will not happen overnight. Hydrogen use is likely to catch on for specific target applications. The need for new supply infrastructure could limit hydrogen use to countries adopting this strategy.
- Dedicated hydrogen pipelines have existed for decades and could be refurbished along with existing gas pipelines. The implications of replacing gas abruptly or changing mixtures gradually should be further explored.
Trade of energy-intensive commodities produced with hydrogen including “e-fuels” could spur faster uptake or renewables and bring wider economic benefits.
Influence of Hydrogen for Crack Formation during Mechanical Clinching
Jan 2018
Publication
Hydrogen intrudes into the steel during pickling process which is a pre-processing before a joining process promoting crack formation. In a mechanical clinching which is one of joining method in the automotive industry cracks due to large strain sometimes forms. In order to guarantee reliability it is important to clarify the influence of hydrogen on crack formation of the joint. In this study we clarified the influence of hydrogen for the crack formation on the mechanical clinching. Hydrogen charge was carried out using an electrolytic cathode charge. After the charging mechanical clinching was performed. Mechanical clinching was carried out with steel plate and aluminium alloy plate. To clarify the influence of hydrogen mechanical clinching was conducted without hydrogen charring. To investigate the crack formation the test piece was cut and the cut surface was observed. When the joint was broken during the clinching the fracture surface was observed using an optical microscope and an electron microscope. The load-displacement diagram showed that without hydrogen charging the compressive load increased as the displacement increased. On the other hand the compressive load temporarily decreased with high hydrogen charging suggesting that cracks formed at the time. The cut surface observation showed that interlock was formed in both cases with low hydrogen charging and without hydrogen charging. With low hydrogen charging no cracks were formed in the joint. When high hydrogen charging was performed cracks were formed at the joining point. Fracture analysis showed brittle-like fracture surface. These results indicate that hydrogen induces crack formation in the mechanical clinching.
3D Real Time Monitoring of H2 in FCV Applications
Sep 2019
Publication
In order to monitor a trace amount of Hydrogen in millisecond portable H2 sensor (Sx) was made by using mass spectrometer. The method of monitoring the hydrogen pulse of millisecond in exhaust gas is the increasing needed. Determining H2 concentration both inside and outside of the Fuel Cell Vehicle (FCV) for the optimized operations is becoming a critical issue. The exhaust gas of Fuel Cell Vehicle H2 consumption flushing and disposal around Fuel cell the real time monitoring of H2 in highly humid conditions is the problematic. To solve this issue the system volume of the sampling route was minimized with the heater and the dehumidifier to avoid condensation of water droplets. And also for an automatic calibration of H2 concentration the small cylinder of specific H2 concentration was mounted into the system.<br/>Our basic experiment started from a flow pattern analysis by monitoring H2 concentration in narrow tube. The flow patter analysis was carried out. When H2 gas was introduced in the N2 flow or air in the tube the highly concentrated H2 front phases were observed. This H2 sensor can provide the real time information of the hydrogen molecules and the clouds. The basic characterization of this sensor showed 0-100% H2 concentrations within milliseconds. Our observations showed the size of the high concentration phase of H2 and the low concentration phase after mixing process. The mixed and unmixed H2 unintended concentration of H2 cloud the high speed small cluster of H2 molecules in purged gas were explored by this system.
Exploring the Capability of Mayenite (12CaO·7Al2O3) as Hydrogen Storage Material
Mar 2021
Publication
We utilized nanoporous mayenite (12CaO·7Al2O3) a cost-effective material in the hydride state (H−) to explore the possibility of its use for hydrogen storage and transportation. Hydrogen desorption occurs by a simple reaction of mayenite with water and the nanocage structure transforms into a calcium aluminate hydrate. This reaction enables easy desorption of H− ions trapped in the structure which could allow the use of this material in future portable applications. Additionally this material is 100% recyclable because the cage structure can be recovered by heat treatment after hydrogen desorption. The presence of hydrogen molecules as H− ions was confirmed by 1H-NMR gas chromatography and neutron diffraction analyses. We confirmed the hydrogen state stability inside the mayenite cage by the first-principles calculations to understand the adsorption mechanism and storage capacity and to provide a key for the use of mayenite as a portable hydrogen storage material. Further we succeeded in introducing H− directly from OH− by a simple process compared with previous studies that used long treatment durations and required careful control of humidity and oxygen gas to form O2 species before the introduction of H−.
A Review for Consistent Analysis of Hydrogen Permeability through Dense Metallic Membranes
Jun 2020
Publication
The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However the hydrogen permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper various methods for consistent analysis of hydrogen permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of hydrogen permeability are introduced: (1) prediction of hydrogen flux under given conditions (2) comparability of hydrogen permeability (3) understanding of the anomalous temperature dependence of hydrogen permeability of Pd-Ag alloy membrane and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high hydrogen permeability together with strong resistance to hydrogen embrittlement.
A New Design Concept for Prevention of Hydrogen-induced Mechanical Degradation: Viewpoints of Metastability and High Entropy
Dec 2018
Publication
‟How crack growth is prevented” is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance type 304 austenitic steels show high hydrogen embrittlement susceptibility because of the high hydrogen diffusivity of bcc (α´) martensite. In contrast metastability in specific austenitic steels enables fcc (γ) to hcp (ε) martensitic transformation which decreases hydrogen diffusivity and increases strength simultaneously. As a result even if hydrogen-assisted cracking occurs during monotonic tensile deformation the ε-martensite acts to arrest micro-damage evolution when the amount of ε-martensite is limited. Thus the formation of ε-martensite can decrease hydrogen embrittlement susceptibility in austenitic steels. However a considerable amount of ε-martensite is required when we attempt to have drastic improvements of work hardening capability and strength level with respect to transformation-induced plasticity effect. Since the hcp structure contains a less number of slip systems than fcc and bcc the less stress accommodation capacity often causes brittle-like failure when the ε-martensite fraction is large. Therefore ductility of ε-martensite is another key when we maximize the positive effect of ε-martensitic transformation. In fact ε-martensite in a high entropy alloy was recently found to be extraordinary ductile. Consequently the metastable high entropy alloys showed low fatigue crack growth rates in a hydrogen atmosphere compared with conventional metastable austenitic steels with α´-martensitic transformation. We here present effects of metastability to ε-phase and configurational entropy on hydrogen-induced mechanical degradation including monotonic tension properties and fatigue crack growth resistance.
Role of Hydrogen-Charging on Nucleation and Growth of Ductile Damage in Austenitic Stainless Steels
May 2019
Publication
Hydrogen energy is a possible solution for storage in the future. The resistance of packaging materials such as stainless steels has to be guaranteed for a possible use of these materials as containers for highly pressurized hydrogen. The effect of hydrogen charging on the nucleation and growth of microdamage in two different austenitic stainless steels AISI316 and AISI316L was studied using in situ tensile tests in synchrotron X-ray tomography. Information about damage nucleation void growth and void shape were obtained. AISI316 was found to be more sensitive to hydrogen compared to AISI316L in terms of ductility loss. It was measured that void nucleation and growth are not affected by hydrogen charging. The effect of hydrogen was however found to change the morphology of nucleated voids from spherical cavities to micro-cracks being oriented perpendicular to the tensile axis.
Cost Optimization of a Stand-Alone Hybrid Energy System with Fuel Cell and PV
Mar 2020
Publication
Renewable energy has become very popular in recent years. The amount of renewable generation has increased in both grid-connected and stand-alone systems. This is because it can provide clean energy in a cost-effective and environmentally friendly fashion. Among all varieties photovoltaic (PV) is the ultimate rising star. Integration of other technologies with solar is enhancing the efficiency and reliability of the system. In this paper a fuel cell–solar photovoltaic (FC-PV)-based hybrid energy system has been proposed to meet the electrical load demand of a small community center in India. The system is developed with PV panels fuel cell an electrolyzer and hydrogen storage tank. Detailed mathematical modeling of this system as well as its operation algorithm have been presented. Furthermore cost optimization has been performed to determine ratings of PV and Hydrogen system components. The objective is to minimize the levelized cost of electricity (LCOE) of this standalone system. This optimization is performed in HOMER software as well as another tool using an artificial bee colony (ABC). The results obtained by both methods have been compared in terms of cost effectiveness. It is evident from the results that for a 68 MWh/yr of electricity demand is met by the 129 kW Solar PV 15 kW Fuel cell along with a 34 kW electrolyzer and a 20 kg hydrogen tank with a LPSP of 0.053%. The LCOE is found to be in 0.228 $/kWh. Results also show that use of more sophisticated algorithms such as ABC yields more optimized solutions than package programs such as HOMER. Finally operational details for FC-PV hybrid system using IEC 61850 inter-operable communication is presented. IEC 61850 information models for FC electrolyzer hydrogen tank were developed and relevent IEC 61850 message exchanges for energy management in FC-PV hybrid system are demonstrated.
The Spread of Fire from Adjoining Vehicles to a Hydrogen Fuel Cell Vehicle
Sep 2011
Publication
Two vehicle fire tests were conducted to investigate the spread of fire to adjacent vehicles from a hydrogen fuel cell vehicle (HFCV) equipped with a thermal pressure relief device (TPRD) : – 1) an HFCV fire test involving an adjacent gasoline vehicle 2) a fire test involving three adjoining HFCV assuming their transportation in a carrier ship. The test results indicated that the adjacent vehicles were ignited by flames from the interior and exterior materials of the fire origin HFCV but not by the hydrogen flames generated through the activation of TPRD.
Effect of Gasoline Pool Fire on Liquid Hydrogen Storage Tank in Hybrid Hydrogen-gasoline Fueling Station
Nov 2015
Publication
Multiple-energy-fuelling stations which can supply several types of energy such as gasoline CNG and hydrogen could guarantee the efficient use of space. To guide the safety management of hybrid hydrogen–gasoline fuelling stations which utilize liquid hydrogen as an energy carrier the scale of gasoline pool fires was estimated using the hazard assessment tool Toxic Release Analysis of Chemical Emissions (TRACE). Subsequently the temperature and the stress due to temperature distribution were estimated using ANSYS. Based on the results the safety of liquid hydrogen storage tanks was discussed. It was inferred that the emissivity of the outer material of the tank and the safety distance between liquid hydrogen storage tanks and gasoline dispensers should be less than 0.2 and more than 8.5 m respectively to protect the liquid hydrogen storage tank from the gasoline pool fire. To reduce the safety distance several measures are required e.g. additional thermal shields such as protective intumescent paint and water sprinkler systems and an increased slope to lead gasoline off to a safe domain away from the liquid hydrogen storage tank
Techno-economic Analysis on Renewable Energy Via Hydrogen, Views from Macro and Micro Scopes
Mar 2019
Publication
This paper addresses from both macro- and micro- areal coverage in introducing hydrogen system in terms of cost and performance where the produced hydrogen from surplus photovoltaic (PV) power is stored. Feed-in tariff in Japan had successful achievement for great expansion of renewable energy systems (RES) causing problematic operation due to excess power by overcapacity of RES. One of the candidate approaches to overcome this surplus energy by RES is Power to gas (P2G) system using electrolysis cells (ECs) fuel cells (FCs) or co-firing in gas turbines both for energy conversion as well as power balancing. Numerous studies had been investigated on P2G however within our knowledge no study had been addressed the system from both coverages with different capacity and scales. We investigate micro level (zero emission building in our university) and macro level (Kyushu one of big regions in Japan). We describe for macro side preliminary result on economic analysis of using surplus power of RES via production and storage of hydrogen while for micro side research design.
Proposal and Verification of Novel Fatigue Crack Propagation Simulation Method by Finite Element Method.
Dec 2018
Publication
In this paper we propose and verify a novel method to simulate crack propagation without propagating a crack by finite element method. We propose this method for elastoplastic analysis coupled with convection-diffusion. In the previous study we succeeded in performing elastoplastic analysis coupled with convection-diffusion of hydrogen for a material with a crack under tensile loading. This research extends the successful method to fatigue crack propagation. In convection-diffusion analysis in order to simulate the invasion and release of elements through the free surface the crack tip is expressed by using a notch with a sufficiently small radius. Therefore the node release method conventionally used to simulate crack propagation cannot be applied. Hence instead of crack propagation based on an analytical model we propose a novel method that can reproduce the influence of the vicinity of the crack tip on a crack. We moved the stress field near the crack tip in the direction opposite to that of crack propagation by an amount corresponding to the crack propagation length. When we extend the previous method to fatigue crack propagation simulation we must consider the difference in strain due to loading and unloading. This problem was solved by considering the strain due to loading as a displacement. Instead of moving the strain due to loading we moved the displacement. First we performed a simple tensile load analysis on the model and output the displacement of all the nodes of the model at maximum load. Then the displacement was moved in the direction opposite to that of crack propagation. Finally the stress field was reproduced by forcibly moving all the nodes by the displacement amount. The strain due to unloading was reproduced by removing the displacement. Furthermore we verified the equivalence of the crack propagation simulation and the proposed method.
Comparison of Regulations Codes and Standards for Hydrogen Refueling Stations in Japan and France
Sep 2019
Publication
The states of Regulations Codes and Standards (RCS) of hydrogen refueling stations (HRSs) in Japan and France are compared and specified items to understand correspondence and differences among each RCSs for realizing harmonization in RCS. Japan has been trying to reform its RCSs to reduce HRS installation and operation costs as a governmental target. Specific crucial regulatory items such as safety distances mitigation means materials for hydrogen storage and certification of anti-explosion proof equipments are compared in order to identify the origins of the current obstacles for disseminating HRS.
Tensile and Fatigue Properties of 17-4PH Martensitic Stainless Steels in Presence of Hydrogen
Dec 2019
Publication
Effects of hydrogen on slow-strain-rate tensile (SSRT) and fatigue-life properties of 17-4PH H1150 martensitic stainless steel having an ultimate tensile strength of ~1GPa were investigated. Smooth and circumferentially-notched axisymmetric specimens were used for the SSRT and fatigue-life tests respectively. The fatigue-life tests were done to investigate the hydrogen effect on fatigue crack growth (FCG) properties. The specimens tested in air at ambient temperature were precharged by exposure to hydrogen gas at pressures of 35 and 100 MPa at 270°C for 200 h. The SSRT properties of the H-charged specimens were degraded by hydrogen showing a relative reduction in area (RRA) of 0.31 accompanied by mixed fracture surfaces composed of quasi-cleavage (QC) and intergranular cracking (IG). The fatigue-life tests conducted under wide test frequencies ranging from 10-3 Hz to 10 Hz revealed three distinct characteristics in low- and high-cycle regimes and at the fatigue limit. The fatigue limit was not degraded by hydrogen. In the high-cycle regime the hydrogen caused FCG acceleration with an upper bound ratio of 30 accompanied by QC surfaces. In the low-cycle regime the hydrogen caused FCG acceleration with a ratio of ~100 accompanied by QC and IG. The ordinary models such as process competition and superposition models hardly predicted the H-assisted FCG acceleration; therefore an interaction model successfully reproducing the experimental FCG acceleration was newly introduced.
Dispersion Tests on Concentration and its Fluctuations for 40MPa Pressurized Hydrogen
Sep 2007
Publication
Hydrogen is one of the important alternative fuels for future transportation. At the present stage research into hydrogen safety and designing risk mitigation measures are significant task. For compact storage of hydrogen in fuel cell vehicles storage of hydrogen under high pressure up to 40 MPa at refuelling stations is planned and safety in handling such high-pressure hydrogen is essential. This paper describes our experimental investigation into dispersion of high-pressure hydrogen gas which leaks through pinholes in the piping to the atmosphere. First in order to comprehend the basic behaviour of the steady dispersion of high-pressure hydrogen gas from the pinholes the time-averaged concentrations were measured. In our experiments initial release pressures of hydrogen gas were set at 20 MPa or 40 MPa and release diameters were in the range from 0.25 mm to 2 mm. The experimental results show that the hydrogen concentration along the axis of the dispersion plume can be expressed as a simple formula which is a function of the downwind distance X and the equivalent release diameter. This formula enables us to easily estimate the axial concentration (maximum concentration) at each downstream distance. However in order for the safety of flammable gas dispersion to be analyzed comparisons between time-averaged concentrations evaluated as above and lower flammable limit are insufficient. This is because even if time-averaged concentration is lower than the flammability limit instantaneous concentrations fluctuate and a higher instantaneous concentration occasionally appears due to turbulence. Therefore the time-averaged concentration value which can be used as a threshold for assessing safety must be determined considering concentration fluctuations. Once the threshold value is determined the safe distance from the leakage point can be evaluated by the above-mentioned simple formula. To clarify the phenomenon of concentration fluctuations instantaneous concentrations were measured with the fast-response flame ionization detector. A small amount of methane gas was mixed into the hydrogen as a tracer gas for this measurement. The relationship between the time-mean concentration and the occurrence probability of flammable concentration was analyzed. Under the same conditions spark-ignition experiments were also conducted and the relationship between the occurrence probability of flammable concentration and actual ignition probabilities were also investigated. The experimental results show that there is a clear correlation between the time-mean concentration the occurrence probability of flammable concentration flame length and occurrence probability of hydrogen flame.
Phenomena of Dispersion and Explosion of High Pressurized Hydrogen
Sep 2005
Publication
To make “Hydrogen vehicles and refuelling station systems” fit for public use research on hydrogen safety and designing mitigative measures are significant. For compact storage it is planned to store under high pressure (40MPa) at the refuelling stations so that the safety for the handling of high-pressurized hydrogen is essential. This paper describes the experimental investigation on the hypothetical dispersion and explosion of high-pressurized hydrogen gas which leaks through a large scale break in piping and blows down to atmosphere. At first we investigated time history of distribution of gas concentration in order to comprehend the behaviour of the dispersion of high-pressurized hydrogen gas before explosion experiments. The explosion experiments were carried out with changing the time of ignition after the start of dispersion. Hydrogen gas with the initial pressure of 40MPa was released through a nozzle of 10mm diameter. Through these experiments it was clarified that the explosion power depends not only on the concentration and volume of hydrogen/air pre-mixture but also on the turbulence characteristics before ignition. To clarify the explosion mechanism the numerical computer simulation about the same experimental conditions was performed. The initial conditions such as hydrogen distribution and turbulent characteristics were given by the results of the atmospheric diffusion simulation. By the verification of these experiments the results of CFD were fully improved.
The New Facility for Hydrogen and Fuel Cell Vehicle Safety Evaluation
Sep 2005
Publication
For the evaluation of hydrogen and fuel cell vehicle safety a new comprehensive facility was constructed in our institute. The new facility includes an explosion resistant indoor vehicle fire test building and high pressure hydrogen tank safety evaluation equipment. The indoor vehicle fire test building has sufficient strength to withstand even an explosion of a high pressure hydrogen tank of 260 liter capacity and 70 MPa pressure. It also has enough space to observe vehicle fire flames of not only hydrogen but also other conventional fuels such as gasoline or compressed natural gas. The inside dimensions of the building are a 16 meter height and 18 meter diameter. The walls are made of 1.2 meter thick reinforced concrete covered at the insides with steel plate. This paper shows examples of hydrogen vehicle fires compared with other fuel fires and hydrogen high pressure tank fire tests utilizing several kinds of fire sources. Another facility for evaluation of high pressure hydrogen tank safety includes a 110 MPa hydrogen compressor with a capacity of 200 Nm3/h a 300 MPa hydraulic compressor for burst tests of 70 MPa and higher pressure tanks and so on. This facility will be used for not only the safety evaluation of hydrogen and fuel cell vehicles but also the establishment of domestic/international regulations codes and standards.
Safety Study of Hydrogen Supply Stations for the Review of High Pressure Gas Safety Law in Japan
Sep 2005
Publication
A safety study of gaseous hydrogen supply stations with 40MPa storage system is undertaken through a risk based approach. Accident scenarios are identified based on a generic model of hydrogen station. And risks of identified accident scenarios are estimated and evaluated comparing with risk acceptance criteria. Also safety measures for risk reduction are discussed. Especially for clearance distance it is proposed that the distance from high-pressurized equipment to site borders should be at least 6 meters. As a result of the study it is concluded that risks of accidental scenarios can be mitigated to acceptable level under the proposed safety measures with several exceptions. These exceptional scenarios are very unlikely to occur but expected to have extremely severe consequence once occurred.
Influence of Temperature on the Fatigue Strength of Compressed Hydrogen Tanks for Vehicles
Sep 2009
Publication
The influence of environmental temperatures on the fatigue strength of compressed-hydrogen tanks for vehicles was investigated. The fatigue strength of Type-3 tanks was found to decrease in a low temperature environment and increase in a high-temperature environment. The Type-3 tank has been subjected to autofrettage to improve fatigue strength. The investigation clarified that the effect of autofrettage changes according to the environmental temperature due to the difference between the coefficients of thermal expansion of carbon fiber reinforced plastic (CFRP) and aluminum alloy. This causes life strength to change with changes in temperature. These results indicate that the service life of the Type-3 tank is influenced by the environmental temperature. The Type-4 tank has a very long fatigue life and did not break after 45000 cycles in a room-temperature or low-temperature environment. In a high-temperature environment however the tank broke in fewer than 45000 cycles. The fatigue of CFRP was promoted in the high-temperature environment resulting in breakage of the tank.
Freeze of Nozzle & Receptacle During Hydrogen Fueling
Oct 2015
Publication
We conducted a fuelling test with hydrogen gas for a safety evaluation of the nozzle/receptacle at a controlled temperature and humidity. Test results confirmed that the nozzle/receptacle froze under specific conditions. However freezing did not cause apparatus damage nor hydrogen leakage. The nozzle/receptacle is thus able to fuel safely even if the nozzle/receptacle is stuck due to ice. In addition we quantified the water volume that causes freezing.
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.
A Safety Assessment of Hydrogen Supply Piping System by Use of FDS
Sep 2017
Publication
At least once air filling a piping from main hydrogen pipe line to an individual home end should be replaced with hydrogen gas to use the gas in the home. Special attention is required to complete the replacing operation safely because air and supplied hydrogen may generate flammable/explosive gas mixture in the piping. The most probable method to fulfill the task is that at first an inert gas is used to purge air from the piping and then hydrogen will be supplied into the piping. It is easily understood that the amount of the inert gas consumed by this method is much to purge whole air especially in long piping system. Hence to achieve more economical efficiency an alternative method was considered. In this method previously injected nitrogen between air and hydrogen prevents them from mixing. The key point is that how much nitrogen is required to prevent the dangerous mixing and keep the condition in the piping safe. The authors investigated to find the minimum amount of nitrogen required to keep the replacing operation safe. The main objective of this study is to assess the effect of nitrogen and estimate a pipe length that the safety is maintained under various conditions by using computational fluid dynamic (CFD). The effects of the amount of injected nitrogen hydrogen-supply conditions and the structure of piping system are discussed.
Mach 4 Simulating Experiment of Pre-Cooled Turbojet Engine Using Liquid Hydrogen
Jan 2022
Publication
This study investigated a pre-cooled turbojet engine for a Mach 5 class hypersonic transport aircraft. The engine was demonstrated under takeoff and Mach 2 flight conditions and a Mach 5 propulsion wind tunnel test is planned. The engine is composed of a pre-cooler a core engine and an afterburner. The engine was tested under simulated Mach 4 conditions using an air supply facility. High-temperature air under high pressure was supplied to the engine components through an airflow control valve and an orifice flow meter and liquid hydrogen was supplied to the pre-cooler and the core engine. The results confirmed that the starting sequence of the engine components was effective under simulated Mach 4 conditions using liquid hydrogen fuel. The pre-cooling effect caused no damage to the rotating parts of the core engine in the experiment.
Combined Dehydrogenation and Hydrogen-based Power Generation
Jan 2018
Publication
An energy production from the combination of dehydrogenation and combined cycle power generation is proposed. The delivered system is established from three main modules: dehydrogenation combustion and combined cycle. The heat in the system is circulated thoroughly to enhance the energy efficiency due to optimum energy recovery. The Pt/Al2O3 catalyst is applied in the dehydrogenation module due to superior activity to accelerate the dehydrogenation of MCH. The toluene emitted from the MCH is recirculated to the hydrogenation plant while the hydrogen is further utilized as the fuel in the combustion. Although the high-temperature condition is necessary to perform high yield dehydrogenation the proposed system is capable of carrying out self-heating mechanism with no external heat. With the optimum configuration the delivered system can produce 100.0 MW of electricity from 100 t/h of MCH with 50.19% of energy efficiency.
Blast Wave from Bursting Enclosure with Internal Hydrogen-air Deflagration
Oct 2015
Publication
Most studies on blast waves generated by gas explosions have focused on gas explosions occurring in open spaces. However accidental gas explosions often occur in confined spaces and the blast wave generates from a bursting vessel as a result of an increase in pressure caused by the gas explosion. In this study blast waves from bursting plastic vessels in which gas explosions occurred are investigated. The flammable mixtures used in the experiments were hydrogen-air mixtures at several equivalence ratios and a stoichiometric methane-air mixture. The overpressures of the blast waves were generated by venting high-pressure gas in the enclosure and volumetric expansion with a combustion reaction. The measured intensities of the blast waves were greater than the calculated values resulting from high-pressure bursting without a combustion reaction. The intensities of the blast waves resulting from the explosions of hydrogen-air mixtures were much greater than those of the methane-air mixture.
Mechanism of High Pressure Hydrogen Auto-Ignition When Spouting Into Air
Sep 2009
Publication
High pressure hydrogen leak is one of the top safety issues presently. This study elucidates the physics and mechanism of high pressure hydrogen jet ignition when the hydrogen suddenly spouts into the air. The experimental work was done elsewhere while we did the numerical work on this high pressure hydrogen leak problem. The direct numerical simulation based on the compressible fluid dynamics considering viscous effect was carried out with the two-dimensional axisymmetric coordinate system A detailed model of hydrogen reaction is applied and a narrow tube attached to a high pressure reservoir is assumed in the numerical simulation. The exit of the tube is opened in the atmosphere. When high pressure hydrogen is passing through the tube filled by atmospheric air a strong shock wave is formed and heats up hydrogen behind the shock wave by compression effect. The leading shock wave is expanded widely after the exit hydrogen then mixed with air by several vortices generated around the exit of the tube. As a result a couple of auto-ignitions of hydrogen occur. It is found that there is a certain relationship between the auto-ignition and tube length. When the tube becomes longer the tendency of auto-ignition is increased. Additionally other type of auto-ignitions is predicted. An explosion is also occurred in the tube under a certain condition. Vortex is generated behind the shock wave in the long tube. There is a possibility of an auto-ignition induced by vortices.
Safety Design of Compressed Hydrogen Trailers with Composite Cylinders
Sep 2013
Publication
Compressed hydrogen is delivered by trailers in steel cylinders at 19.6 MPa in Japan. Kawasaki Heavy Industries Ltd. developed two compressed hydrogen trailers with composite cylinders in collaboration with JX Nippon Oil in a project of the New Energy and Industrial Technology Development Organization (NEDO).<br/>The first trailer which was the first hydrogen trailer with composite cylinder in Japan has 35 MPa cylinders and the second trailer has 45 MPa cylinders. These trailers have been operated transporting hydrogen and feedstock to hydrogen refuelling stations without the accident. This paper describes the safety design including compliance with regulations the influence of vibrations and safety verification in case of a collision.
Numerical Investigation of Hydrogen Leakage from a High Pressure Tank and its Explosion
Oct 2015
Publication
We numerically investigated the initial behaviour of leakage and diffusion from high-pressure hydrogen storage tank assumed in hydrogen station. First calculations are carried out to validate the present numerical approach and compare with the theoretical distribution of hydrogen mass fraction to the direction which is vertical to the jet direction in the case of hydrogen leaking out from the circular injection port whose diameter is 0.25 mm. Then performing calculations about hydrogen leakage and diffusion behaviour on different tank pressures the effects are examined to reduce damage by gas explosion assumed in the hydrogen station. There is no significant difference in the diffusion distance to the jet direction from a start to 0.2 ms. After 0.2 ms it is seen the difference in the diffusion distance to the jet direction in different pressure. As tank pressures become large the hydrogen diffusion not only to the jet direction but also to the direction which is vertical to the jet direction is remarkably seen. Then according to histories of the percentage of the flammable mass to total one in the space it drastically increases up to 30%2between 0 and 0.05 ms. After 0.05 ms it uniformly increases so it is shown that the explosion risk becomes high over time. The place where mass within flammability range distributes at a certain time is shown. Hydrogen widely diffuses to jet direction and distributes in each case and time. Therefore it is found that when it is assumed that ignition occurs by some sources in place where high-pressure hydrogen is leaked and diffused the magnitude of the explosion damage can be predicted when and where ignition occurs.
Prediction of Pressure Reduction Rate in 30 m3 Liquid Hydrogen Tank Based on Experimental and Numerical Analysis
Sep 2019
Publication
Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large scale transport and storage of hydrogen with higher densities and potentially better safety performance. Although the gas industry has good experience with LH2 only little experience is available for the new applications of LH2 as an energy carrier. Therefore the European FCH JU funded project PRESLHY conducts pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The work program consists of a preparatory phase where the state of the art before the project has been summarized and where the experimental planning was adjusted to the outcome of a research priorities workshop. The central part of the project consists of 3 phenomena oriented work packages addressing Release Ignition and Combustion with analytical approaches experiments and simulations. The results shall improve the general understanding of the behaviour of LH2 in accidents and thereby enhance the state-of-the-art what will be reflected in appropriate recommendations for development or revision of specific international standards. The paper presents the status of the project at the middle of its terms.
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.
Effect of Hydrogen on Fatigue Limit of SCM435 Low-Alloy Steel
Dec 2019
Publication
The objective of this study is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was a low-alloy steel modified to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The hydrogen gas pressure was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in the hydrogen gas than that in air although the material showed severe hydrogen embrittlement during the SSRT (Slow Strain Rate Test). The fatigue limit of the deep-notched specimen in the hydrogen gas was the same as that in air. For the smooth specimen the fatigue limit was determined by whether or not a crack was initiated. For the deep-notched specimen the fatigue limit was determined by whether or not a crack propagated. The results can be interpreted as that hydrogen has no significant effect on crack initiation in the high-cycle fatigue regime and affected the threshold of the crack propagation.
Strong and Mild Ignition Mechanism behind Reflected Shock Waves in Hydrogen Mixture
Sep 2013
Publication
A reflected shock wave in two-dimensional shock tube is studied numerically using Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. The results show detailed process of mild ignition. The interaction between the reflected shock wave and the boundary layer yielded behind the incident shock wave produces clockwise and counter-clockwise vortices. These vortices generate compression waves. The future study related wall conditions (adiabatic or isothermal) will be shown at the conference site.
Fast Synthesis of TiNi by Mechanical Alloying and its Hydrogenation Properties
Mar 2019
Publication
Mechanical alloying is widely used for the synthesis of hydrogen storage materials. However amorphization and contamination triggered by long-time milling are serious drawbacks for obtaining efficient hydrogen storage. In this work short-time ball milling synthesis is explored for a representative hydride forming compound: TiNi. Through structural morphological and chemical characterizations we evidence that formation of TiNi is complete in only 20 min with minor Fe contamination (0.2 wt%). Cross-sectional analysis of powder stuck on milling balls reveals that alloy formation occurs through the interdiffusion between thin layers of co-laminated pure elements. Hydrogenation thermodynamics and kinetics of short-time mechanically alloyed TiNi are similar to those of coarse-grained compounds obtained by classical high-temperature melting. Mechanical alloying is a suitable method for fast and energy-efficient synthesis of intermetallic compounds such as TiNi.
Effectiveness of a Blower in Reducing the Hazard of Hydrogen Leaking from a Hydrogen-fueled Vehicle
Sep 2013
Publication
To handle a hydrogen fuel cell vehicle (HFCV) safely after its involvement in an accident it is necessary to provide appropriate emergency response information to the first responder. In the present study a forced wind of 10 m/s or faster with and without a duct was applied to a vehicle leaking hydrogen gas at a rate of 2000 NL/min. Then hydrogen concentrations were measured around the vehicle and an ignition test was conducted to evaluate the effectiveness of forced winds and the safety of emergency response under forced wind conditions. The results: 1) Forced winds of 10 m/s or faster caused the hydrogen concentrations in the vicinity of the vehicle to decline to less than the lower flammability limit and the hydrogen gas in the various sections of the vehicles were so diluted that even if ignition occurred the blast-wave pressure was moderate. 2) When the first responder had located the hydrogen leakage point in the vehicle it was possible to lower the hydrogen concentrations around the vehicle by aiming the wind duct towards the leakage point and blowing winds at 10 m/s from the duct exit.
Numerical Investigation of Vented Hydrogen-air Deflagration in a Chamber
Oct 2015
Publication
This paper shows numerical investigation related to hydrogen-air deflagration venting. The aim of this study is to clarify the influence of concentration gradient on the pressure histories and peak pressures in a chamber. The numerical analysis target is a 27 m3 cubic chamber which has 2.6 m2 vent area on the sidewall. The vent opening pressure is set to be gauge 10 kPa. Two different conditions of the hydrogen concentration are assumed which are uniform and gradient. In the uniform case 15 20 25 30 and 35 vol.% concentrations are assumed. In the gradient case the concentration linearly increases from 0 vol.% (at the ground) to 30 40 50 60 70 vol.% (at the ceiling). The initial total mass of hydrogen inside the chamber is the same as the uniform case. Moreover three different ignition points are assumed: on the rear center and the front of the chamber relative to the vent. The deflagrations are initiated by a single ignition source. In most gradient cases the highest peak is lower than in the uniform case though the initial total mass of hydrogen inside the chamber is the same as in the uniform case. This is because the generated burned gas per time is smaller in the gradient case than in the uniform case. In 15 vol.% gradient case however the peak pressure gets higher than in the uniform case. This is because in 15 vol.% gradient case the burning velocity around the ignition point gets faster and the flame surface gets larger which induces larger amount of burned gas per time.
Steam Condensation Effect in Hydrogen Venting from a BWR Reactor Building
Oct 2015
Publication
In the accident of Fukushima Daiichi nuclear power plants hydrogen was accumulated in the reactor buildings and exploded. To prevent such explosions hydrogen venting from reactor buildings is considered. When the gas mixture is released to a reactor building through a reactor containment together with the hydrogen some amount of steam might also be released. The steam condenses if the building atmosphere is below the saturation temperature and it affects the hydrogen behaviour. In this study the condensation effect to the hydrogen venting is evaluated using CFD analyses by comparing the case where a hydrogen-nitrogen mixture is released and the case where a hydrogen-steam mixture is released.
Public Perception on Hydrogen Infrastructure in Japan
Oct 2015
Publication
A public survey was conducted in March 2015 in Japan asking public awareness knowledge perception and acceptance regarding hydrogen hydrogen infrastructure and fuel cell vehicle adopting the same key questions contained in the public surveys conducted six and seven years ago. Changes in answers between two different times of survey implementation were analyzed by comparing results of current survey to those of the previous surveys. Regression analyses were conducted and revealed influence of respondents’ awareness knowledge and perception about hydrogen hydrogen infrastructure and fuel cell vehicle on their acceptance on hydrogen station. We found a large increase in the awareness and relatively a small improvement on knowledge on hydrogen energy hydrogen infrastructure and fuel cell vehicle from the previous surveys. In contrast we did not find much changes in perception of risk and benefit perception on hydrogen society and hydrogen station and public acceptance of hydrogen infrastructure. Through the regression analyses we found large influences of negative risk perception of hydrogen itself and technology of hydrogen station and perception of necessity of hydrogen station on public acceptance of hydrogen station and the small influence of time background on the acceptance. Through the results of analyses implications to public communication in building public infrastructure are presented.
Low-carbon Energy Transition With the Sun and Forest: Solar-driven Hydrogen Production from Biomass
Nov 2021
Publication
There is a need to derive hydrogen from renewable sources and the innovative stewardship of two natural resources namely the Sun and forest could provide a new pathway. This paper provides the first comparative analysis of solar-driven hydrogen production from environmental angles. A novel hydrogen production process proposed in this paper named Solar-Driven Advanced Biomass Indirect-Gasification (SABI-Hydrogen) shows promise toward achieving continuous operation and scalability the two key challenges to meet future energy needs. The calculated Global Warming Potential for 1 kg of solar-driven hydrogen production is 1.04 kg CO2-eq/kg H2 less than half of the current biomass gasification process which emits 2.67 kg CO2-eq/kg H2. Further SABI-Hydrogen demonstrates the least-carbon intensive pathway among all current hydrogen production methods. Thus solar-driven hydrogen production from biomass could lead to a sustainable supply essential for a low-carbon energy transition.
A Study on Dispersion Resulting From Liquefied Hydrogen Spilling
Oct 2015
Publication
For massive utilization of hydrogen energy it is necessary to transport a large quantity of hydrogen by liquefied hydrogen carriers. However the current rule on ships carrying liquefied hydrogen in bulks do not address the maritime transport of liquefied hydrogen and the safety assessment of liquefied hydrogen carriage is thus very important. In the present study we spilled liquefied hydrogen and LNG (Liquefied Natural Gas) on the surface of various materials and compared the difference of their spread and dispersion. Liquefied hydrogen immediately dispersed upward compared to LNG. Furthermore we also measured the flammability limit of low temperature hydrogen gas. Its range at low temperature was narrower than the range at normal temperature.
Visualization of Auto-ignition Phenomenon Under the Controlled Burst Pressure
Oct 2015
Publication
A high-pressure hydrogen jet released into the air has the possibility of igniting in a tube without any ignition source. The mechanism of this phenomenon called spontaneous ignition is considered to be that hydrogen diffuses into the hot air caused by the shock wave from diaphragm rupture and the hydrogen-oxidizer mixed region is formed enough to start chemical reaction. Recently flow visualization studies on the spontaneous ignition process have been conducted to understand its detailed mechanism but such ignition has not yet been well clarified. In this study the spontaneous ignition phenomenon was observed in a rectangular tube. The results confirm the presence of a flame at the wall of the tube when the shock wave pressure reaches 1.2–1.5 MPa in more than 9 MPa burst pressure and that ignition occurs near the wall followed by multiple ignitions as the shock wave propagates with the ignitions eventually combining to form a flame.
Numerical Simulations of Spontaneous Ignition of High-pressure Hydrogen Based on Detailed Chemical Kinetics
Sep 2013
Publication
A two-dimensional (2-D) simulation of spontaneous ignition of high-pressure hydrogen in a length of duct is conducted in order to explore its underlying ignition mechanisms. The present study adopts a 2-D rectangular duct (i.e. not axisymmetric geometry) and focuses on the effects of initial diaphragm shape on the spontaneous ignitions. The Navier-Stokes equations with a detailed chemical kinetics mechanism are solved in a manner of direct numerical simulation. The detailed mechanisms of spontaneous ignition are discussed for each initial diaphragm shape. For a straight diaphragm shape it is found that the ignition occurs only near the wall due to the adiabatic wall condition while the three ignition events: ignitions due to leading shock wave reflection at the wall hydrogen penetration into shock-heated air near the wall and deep penetration of hydrogen into shock-heated air behind the leading shock wave are identified for a largely deformed diaphragm shape.
Numerical Study on Detailed Mechanism of H2-Air Flame Jet Ignition
Sep 2013
Publication
Jet ignition was recognized in the 1970s and has since been applied to automobile engines such as the Honda CVCC. In the 1990s jet ignition was observed in explosions and was seen as a problem that may relate to jet ignition. Our group presented jet ignition experimentally and numerically in 1999 and later using LIF measurements with the same experimental vessel as used in 1999. However the detailed mechanism of jet ignition was not clarified at that time. The target of this study is to clarify how jet ignition happens and to understand the detailed mechanism of flame jet ignition.
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