Canada

In this paper CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank to ambient through a Pressure Relieve Device (PRD) 6 mm (¼”) opening. The numerical simulations using the TOPAZ software developed by Sandia National Laboratory addressed the changes of pressure density and flow rate variations at the leak orifice during release while the PHOENICS software package predicted extents of various hydrogen concentration envelopes as well as the velocities of gas mixture for the dispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFD model implemented through the TOPAZ and PHOENICS software to accurately predict the real gas properties for hydrogen release and dispersion under high pressures. The numerical results were compared with those obtained from using the ideal gas law and it was found that the ideal gas law overestimates the hydrogen mass release rates by up to 35% during the first 25 seconds of release. Based on the findings the authors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRD releases.

This study outlines an approach to identifying the difficulties associated with the bench-marking of alkaline single cells under real electrolyzer conditions. A challenging task in the testing and comparison of different catalysts is obtaining reliable and meaningful benchmarks for these conditions. Negative effects on reproducibility were observed due to the reduction in conditioning time. On the anode side a stable passivation layer of NiO can be formed by annealing of the Ni foams which is even stable during long-term operation. Electrical contact resistance and impedance measurements showed that most of the contact resistance derived from the annealed Ni foam. Additionally analysis of various overvoltages indicated that most of the total overvoltage comes from the anode and cathode activation overpotential. Different morphologies of the substrate material exhibited an influence on the performance of the alkaline single cell based on an increase in the ohmic resistance.

A buoyant round vertical hydrogen jet is investigated using Large Eddy Simulations at low Mach number (M = 0.3). The influence of the transient concentration fields on the extent of the gas envelope with concentrations within the flammability limits is analyzed and their structure are characterized. The transient flammable region has a complex structure that extends up to 30% beyond the time-averaged flammable volume with high concentration pockets that persist sufficiently long for potential ignition. Safety envelopes devised on the basis of simplified time-averaged simulations would need to include a correction factor that accounts for transient incursions of high flammability concentrations.

Widespread uptake of battery electric plug-in hybrid and hydrogen fuel-cell vehicles (collectively zero-emissions vehicles or ZEVs) could help many regions achieve deep greenhouse gas mitigation goals. Using the case of Canada this study investigates the extent to which increasing ZEV charging and refuelling availability may boost ZEV sales relative to other ZEV-supportive policies. We adapt a version of the Respondent-based Preferences and Constraints (REPAC) model using 2017 survey data from 1884 Canadian new vehicle-buyers to simulate the sales impacts of increasing electric vehicle charging access at home work public destinations and on highways as well as increasing hydrogen refuelling station access. REPAC is built from a stated preference choice model and represents constraints in supply and consumer awareness as well as dynamics in ZEV policy out to 2030. Results suggest that new ZEV market share from 2020 to 2030 does not substantially benefit from increased infrastructure. Even when electric charging and hydrogen refuelling access are simulated to reach “universally” available levels by 2030 ZEV sales do not rise by more than 1.5 percentage points above the baseline trajectory. On the other hand REPAC simulates ZEV market share rising as high as 30% by 2030 with strong ZEV-supportive policies even without the addition of charging or refuelling infrastructure. These findings stem from low consumer valuation of infrastructure found in the stated preference model. Results suggest that achieving ambitious ZEV sale targets requires a comprehensive suite of policies beyond a focus on charging and refuelling infrastructure.

Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and commercially acceptable systems it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate risk mitigation strategies to handle unforeseen accidental events. To evaluate these materials and systems an IPHE sanctioned program was initiated in 2006 partnering laboratories from Europe North America and Japan. The objective of this international program is to understanding the physical risks involved in synthesis handling and utilization of solid state hydrogen storage materials and to develop methods to mitigate these risks. This understanding will support ultimate acceptance of commercially high density hydrogen storage system designs. An overview of the approaches to be taken to achieve this objective will be given. Initial experimental results will be presented on environmental exposure of NaAlH4 a candidate high density hydrogen storage compound. The tests to be shown are based on United Nations recommendations for the transport of hazardous materials and include air and water exposure of the hydride at three hydrogen charge levels in various physical configurations. Additional tests developed by the American Society for Testing and Materials were used to quantify the dust cloud ignition characteristics of this material which may result from accidental high energy impacts and system breach. Results of these tests are shown along with necessary risk mitigation techniques used in the synthesis and fabrication of a prototype hydrogen storage system.

The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using CFD numerical simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm PRD from 100 barg and 700 barg storage units are presented for horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes.

Computational fluid dynamics (CFD) is used to numerically solve the sudden release of hydrogen from a high pressure tank (up to 70MPa) into air. High pressure tanks increase the risk of failure of the joints and pipes connected to the tank which results in release of Hydrogen. The supersonic flow caused by high pressure ratio of reservoir to ambient generates a strong Mach disk. A three dimensional in-house code is developed to simulate the flow. High pressure Hydrogen requires a real gas law because it deviates from ideal gas law. Firstly Beattie-Bridgeman and Abel-Noble real gas equation of states are applied to simulate the release of hydrogen in hydrogen. Then Abel-Noble is implied to simulate the release of hydrogen in air. Beattie-Bridgeman has stability problems in the case of hydrogen in air. A transport equation is used to solve the concentration of Hydrogen-air mixture. The code is second order accurate in space and first order in time and uses a modified Van Leer limiter. The fast release of Hydrogen from a small rupture needs a very small mesh therefore parallel computation is applied to overcome memory problems and to decrease the solution time. The high pressure ratio of the reservoir to ambient causes a very fast release which is accurately modelled by the code and all the shocks and Mach disk happening are observed in the results. The results show that the difference between real gas and ideal gas models cannot be ignored.

Experiments with a hydrogen jet were performed at two different pressures 96 psig (6.6 bars) and 237 psig (16.3 bars). The hydrogen leak was generated at two different hole sizes 1/16 inch (1.6 mm) and 1/32 inch (0.79 mm). The flammable shape of the plume was characterised by numerous measurements of the hydrogen concentration inside of the jet. The effect of the nearby horizontal surface on the shape of the plume was measured and compared with results of CFD numerical simulations. The paper will present results and an interpretation on the nature of the plume shape.

Computational Fluid Dynamics (CFD) is applied to investigate the near exit jet behavior of high pressure hydrogen release into quiescent ambient air through different types of orifices. The size and geometry of the release hole can affect the possibility of auto-ignition. Therefore the effect of release geometry on the behavior and development of hydrogen jet issuing from non-axisymmetric (elliptical) and expanding orifices is investigated and compared with their equivalent circular orifices. A three-dimensional in-house code is developed using the MPI library for parallel computing to simulate the flow based on an inviscid approximation. Convection dominates viscous effects in strongly underexpanded supersonic jets in the vicinity of release exit justifying the use of the Euler equations. The transport (advection) equation is applied to calculate the concentration of hydrogen-air mixture. The Abel-Nobel equation of state is used because high pressure hydrogen flow deviates from the ideal gas assumption. This work effort is conducted to fulfill two objectives. First two types of circular and elliptic orifices with the same cross sectional area are simulated and the flow behavior of each case is studied and compared during the initial stage of release. Second the comparative study between expanding circular exit and its fixed counterpart is carried out. This evaluation is conducted for different sizes of nozzle with different aspect ratios.

In the current study a Large Eddy Simulation strategy is applied to model the dispersion of compressible turbulent hydrogen jets issuing from realistic pipe geometries. The work is novel as it explores the effect of jet densities and Reynolds numbers on vertical buoyant jets as they emerge from the outer wall of a pipe through a round orifice perpendicular to the mean flow within the pipe. An efficient Godunov solver is used and coupled with Adaptive Mesh Refinement to provide high resolution solutions only in areas of interest. The numerical results are validated against physical experiments of air and helium which allows a degree of confidence in analysing the data obtained for hydrogen releases. The results show that the jets investigated are always asymmetric. Thus significant discrepancies exist when applying conventional round jet assumptions to determine statistical properties associated with gas leaks from pipelines.

Hydrogen has the potential to be used by many countries as part of decarbonising the future energy system. Hydrogen can be used as a fuel ‘vector’ to store and transport energy produced in low-carbon ways. This could be particularly important in applications such as heating and transport where other solutions for low and zero carbon emission are difficult. To enable the safe uptake of hydrogen technologies it is important to develop the international scientific evidence base on the potential risks to safety and how to control them effectively. The International Association for Hydrogen Safety (known as IA HySAFE) is leading global efforts to ensure this. HSE hosted the 2018 IA HySAFE Biennial Research Priorities Workshop. A panel of international experts presented during nine key topic sessions: (1) Industrial and National Programmes; (2) Applications; (3) Storage; (4) Accident Physics – Gas Phase; (5) Accident Physics – Liquid/ Cryogenic Behaviour; (6) Materials; (7) Mitigation Sensors Hazard Prevention and Risk Reduction; (8) Integrated Tools for Hazard and Risk Assessment; (9) General Aspects of Safety.<br/>This report gives an overview of each topic made by the session chairperson. It also gives further analysis of the totality of the evidence presented. The workshop outputs are shaping international activities on hydrogen safety. They are helping key stakeholders to identify gaps in knowledge and expertise and to understand and plan for potential safety challenges associated with the global expansion of hydrogen in the energy system.

Hydrogen mixed natural gas for combustion can improve combustion characteristics and reduce carbon emission which has important engineering application value. A casing swirl burner model is adopted to numerically simulate and research the natural gas hydrogen mixing technology for combustion in gas boilers in this paper. Under the condition of conventional air atmosphere and constant air excess coefficient the six working conditions for hydrogen mixing proportion into natural gas are designed to explore the combustion characteristics and the laws of pollution emissions. The temperature distributions composition and emission of combustion flue gas under various working conditions are analyzed and compared. Further investigation is also conducted for the variation laws of NOx and soot generation. The results show that when the boiler heating power is constant hydrogen mixing will increase the combustion temperature accelerate the combustion rate reduce flue gas and CO2 emission increase the generation of water vapor and inhibit the generation of NOx and soot. Under the premise of meeting the fuel interchangeability it is concluded that the optimal hydrogen mixing volume fraction of gas boilers is 24.7%.

The rapid evolution of information related to hydrogen safety is multidimensional ranging from developing codes and standards to CFD simulations and experimental studies of hydrogen releases to a variety of risk assessment approaches. This information needs to be transformed into system design risk decision-making and first responder tools for use by hydrogen community stakeholders. The Canadian Transportation Fuel Cell Alliance (CTFCA) has developed HySTARtm an interactive Hydrogen Safety Training And Risk System. The HySTARtm user interacts with a Web-based 3-D graphical user interface to input hydrogen system configurations. The system includes a Codes and Standards Expert System that identifies the applicable codes and standards in a number of national jurisdictions that apply to the facility and its components. A Siting Compliance and Planning Expert System assesses compliance with clearance distance requirements in these jurisdictions. Incorporating the results of other CTFCA projects HySTARtm identifies stand-out hydrogen release scenarios and their corresponding release condition that serves as input to built-in consequence and risk assessment programs that output a variety of risk assessment metrics. The latter include on- and off-site individual risk probability of loss of life and expected number of fatalities. These results are displayed on the graphical user interface used to set up the facility. These content and graphical tools are also used to educate regulatory approval and permitting officials and build a first-responder training guide.

The challenges and approaches of the safety and risk management for the hydrogen production with nuclear-based thermochemical water splitting have been far from sufficiently reported as the thermochemical technology is still at a fledgling stage and the linkage of a nuclear reactor with a hydrogen production plant is unprecedented. This paper focuses on the safety issues arising from the interactions between the nuclear heat source and thermochemical hydrogen production cycle as well between the proximate individual processes in the cycle. As steam is utilized in most thermochemical cycles for the water splitting reaction and heat must be transferred from the nuclear source to hydrogen production plant this paper particularly analyzes and quantifies the heat hazard for the scenarios of start-up and shutdown of the hydrogen production plant. Potential safety impacts on the nuclear reactor are discussed. It is concluded that one of the main challenges of safety and risk management is efficient rejection of heat in a shutdown accident. Several options for the measures to be taken are suggested. Copper-chlorine and sulphur-iodine thermochemical cycles are taken as two representative examples for the hazard analysis. It is expected that these newly reported challenges and approaches could help build the future safety and risk management codes and standards for the infrastructure of the thermochemical hydrogen production.

In order to facilitate the application of hydrogen energy and ensure its safety the compressed hydrogen storage tank on board needs to be full of hydrogen gas within 3 minutes. Therefore to meet this requirement the effects of refueling parameters on the filling time need to be investigated urgently. For the purpose of solving this issue a novel analytical solution of filling time is obtained from a lumped parameter model in this paper. According to the equation of state for real gas and dimensionless numbers Nu and Re the function relationships between the filling time and the refueling parameters are presented. These parameters include initial temperature initial pressure inflow temperature final temperature and final pressure. These equations are used to fit the reference data the results of fitting show good agreement. Then the values of fitting parameters are further utilized so as to verify the validity of these formulas. We believe this study can contribute to control the hydrogen filling time and ensure the safety during fast filling process.

Metal fuels as recyclable carriers of clean energy are promising alternatives to fossil fuels in a future low-carbon economy. Fossil fuels are a convenient and widely-available source of stored solar energy that have enabled our modern society; however fossil-fuel production cannot perpetually keep up with increasing energy demand while carbon dioxide emissions from fossil-fuel combustion cause climate change. Low-carbon energy carriers with high energy density are needed to replace the multiple indispensable roles of fossil fuels including for electrical and thermal power generation for powering transportation fleets and for global energy trade. Metals have high energy densities and metals are therefore fuels within many batteries energetic materials and propellants. Metal fuels can be burned with air or reacted with water to release their chemical energy at a range of power-generation scales. The metal-oxide combustion products are solids that can be captured and then be recycled using zero-carbon electrolysis processes powered by clean energy enabling metals to be used as recyclable zero-carbon solar fuels or electrofuels. A key technological barrier to the increased use of metal fuels is the current lack of clean and efficient combustor/reactor/engine technologies to convert the chemical energy in metal fuels into motive or electrical power (energy). This paper overviews the concept of low-carbon metal fuels and summarizes the current state of our knowledge regarding the reaction of metal fuels with water to produce hot hydrogen on demand and the combustion of metal fuels with air in laminar and turbulent flames. Many important questions regarding metal-fuel combustion processes remain unanswered as do questions concerning the energy-cycle efficiency and life-cycle environmental impacts and economics of metals as recyclable fuels. Metal fuels can be an important technology option within a future low-carbon society and deserve focused attention to address these open questions.

The study on temper embrittlement and hydrogen embrittlement of a test block from a 3Cr1Mo1/4V hydrogenation reactor after ten years of service was carried out by small punch test (SPT) at different temperatures. The SPT fracture energy Esp (derived from integrating the load-displacement curve) divided by the maximum load (Fm) of SPT was used to fit the Esp/Fm versus-temperature curve to determine the energy transition temperature (Tsp) which corresponded to the ductile-brittle transition temperature of the Charpy impact test. The results indicated that the ratio of Esp/Fm could better represent the energy of transition in SPT compared with Esp. The ductile-to-brittle transition temperature of the four different types of materials was measured using the hydrogen charging test by SPT. These four types of materials included the base metal and the weld metal in the as-received state and the base metal and the weld metal in the de-embrittled state. The results showed that there was a degree of temper embrittlement in the base metal and the weld metal after ten years of service at 390 °C. The specimens became slightly more brittle but this was not obvious after hydrogen charging. Because the toughness of the material of the hydrogenation reactor was very good the flat samples of SPT could not characterize the energy transition temperature within the liquid nitrogen temperature. Additionally there was no synergetic effect of temper embrittlement and hydrogen embrittlement found in 3Cr1Mo1/4V steel.

The potential benefits are examined of the “Power-to-Gas” (P2G) scheme to utilize excess wind power capacity by generating hydrogen (or potentially methane) for use in the natural gas distribution grid. A parametric analysis is used to determine the feasibility and size of systems producing hydrogen that would be injected into the natural gas grid. Specifically wind farms located in southwestern Ontario Canada are considered. Infrastructure requirements wind farm size pipeline capacity geographical dispersion hydrogen production rate capital and operating costs are used as performance measures. The model takes into account the potential production rate of hydrogen and the rate that it can be injected into the local gas grid. “Straw man” systems are examined centered on a wind farm size of 100 MW integrating a 16-MW capacity electrolysis system typically producing 4700 kg of hydrogen per day.

Unintended releases can occur during the production storage transportation and filling of liquid hydrogen which may cause devastating consequences. In the present work liquid hydrogen leak is modeled in ANSYS Fluent with the numerical model validated using the liquid hydrogen spill test data. A three-layer artificial neural network (ANN) model is built in which the wind speed ground temperature leakage time and leakage rate are taken as the inputs the horizontal diffusion distance and vertical diffusion distance of combustible gas as the outputs of the ANN. The representative sample data derived from the detailed calculation results of the numerical model are selected via the orthogonal experiment method to train and verify the back propagation (BP) neural network. Comparing the calculation results of the formula fitting with the sample data the results show that the established ANN model can quickly and accurately predict the horizontal and vertical diffusion distance of flammable vapor cloud relatively. The influences of four parameters on the horizontal hazard distance as well as vertical hazard height are predicted and analyzed in the case of continuous overflow of liquid hydrogen using the ANN model.

Recent modeling efforts of non-equilibrium effects in detonations have suggested that hydrogen-based detonations may be affected by vibrational non-equilibrium of the hydrogen and oxygen molecules effects which could explain discrepancies of cell sizes measured experimentally and calculated without relaxation effects. The present study addresses the role of vibrational relaxation in 2H2/O2 detonations by considering two-bath gases argon and helium. These two gases have the same thermodynamic and kinetic effects when relaxation is neglected. However due to the bath gases differences in molecular weight and reduced mass differences which affect the molecular collisions relaxation rates can be changed by approximately 50-70%. Experiments were performed in a narrow channel in mixtures of 2H2/O2/7Ar and 2H2/O2/7He to evaluate the role of the bath gas on detonation cellular structures. The experiments showed differences in velocity deficits and cell sizes for experimental conditions keeping the induction zone length constant in each of the mixtures. These differences were negligible in sensitive mixtures but increased with the increase in velocity deficits while the cell sizes approaching the channel dimensions. Near the limits differences of cell size in two mixtures approached a factor of 2. These differences were however reconciled by accounting for the viscous losses to the tube walls evaluated using a modified version of Mirels' laminar boundary layer theory and generalized Chapman-Jouguet theory for eigenvalue detonations. The experiments suggest that there is an influence of relaxation effects on the cellular structure of detonations which is more sensitive to wall boundary conditions. However the previous works showed that the impact of vibrational non-equilibrium in a mixture of H2/Air is more visible due to the effects of N2 in the air slowest to relax. Previous discrepancies suggested to be indicative of relaxation effects should be reevaluated by the inclusion of wall loss effects.

A new spinelized Ni catalyst (Ni-UGSO) using Ni(NO₃)₂·6H₂O as the Ni precursor was prepared according to a less material intensive protocol. The support of this catalyst is a negative-value mining residue UpGraded Slag Oxide (UGSO) produced from a TiO2 slag production unit. Applied to dry reforming of methane (DRM) at atmospheric pressure T = 810 °C space velocity of 3400 mL/(h·g) and molar CO₂/CH₄ = 1.2 Ni-UGSO gives a stable over 168 h time-on-stream methane conversion of 92%. In this DRM reaction optimization study: (1) the best performance is obtained with the 10–13 wt% Ni load; (2) the Ni-UGSO catalysts obtained from two different batches of UGSO demonstrated equivalent performances despite their slight differences in composition; (3) the sulfur-poisoning resistance study shows that at up to 5.5 ppm no Ni-UGSO deactivation is observed. In steam reforming of methane (SRM) Ni-UGSO was tested at 900 °C and a molar ratio of H₂O/CH₄ = 1.7. In this experimental range CH4 conversion rapidly reached 98% and remained stable over 168 h time-on-stream (TOS). The same stability is observed for H₂ and CO yields at around 92% and 91% respectively while H₂/CO was close to 3. In mixed (dry and steam) methane reforming using a ratio of H₂O/CH₄ = 0.15 and CO2/CH4 = 0.97 for 74 h and three reaction temperature levels (828 °C 847 °C and 896 °C) CH₄ conversion remains stable; 80% at 828 °C (26 h) 85% at 847 °C (24 h) and 95% at 896 °C (24 h). All gaseous streams have been analyzed by gas chromatography. Both fresh and used catalysts are analyzed by scanning electron microscopy-electron dispersive X-ray spectroscopy (SEM-EDXS) X-ray diffraction (XRD) and thermogravimetric analysis (TGA) coupled with mass spectroscopy (MS) and BET Specific surface. In the reducing environment of reforming such catalytic activity is mainly attributed to (a) alloys such as FeNi FeNi3 and Fe3Ni2 (reduction of NiFe2O4 FeNiAlO4) and (b) to the solid solution NiO-MgO. The latter is characterized by a molecular distribution of the catalytically active Ni phase while offering an environment that prevents C deposition due to its alkalinity.

Currently hydrogen production is based on the reforming process leading to the emission of pollutants; therefore a substitute production method is imminently required. Water electrolysis is an ideal alternative for large-scale hydrogen production as it does not produce any carbon-based pollutant byproducts. The production of green hydrogen from water electrolysis using intermittent sources (e.g. solar and eolic sources) would facilitate clean energy storage. However the electrocatalysts currently required for water electrolysis are noble metals making this potential option expensive and inaccessible for industrial applications. Therefore there is a need to develop electrocatalysts based on earth-abundant and low-cost metals. Nickel-based electrocatalysts are a fitting alternative because they are economically accessible. Extensive research has focused on developing nickel-based electrocatalysts for hydrogen and oxygen evolution. Theoretical and experimental work have addressed the elucidation of these electrochemical processes and the role of heteroatoms structure and morphology. Even though some works tend to be contradictory they have lit up the path for the development of efficient nickel-based electrocatalysts. For these reasons a review of recent progress is presented herein.

When hydrogen flows through a small finite length constant exit area nozzle the viscous effects create a fluid throat which acts as a converging-diverging nozzle and lead to Mach number greater than one at the exit if the jet is under-expanded. This phenomenon influences the mass flow rate and the dispersion cloud size. In this study the boundary layer effect on the unsteady hydrogen sonic jet flow through a 1 mm diameter pipe from a high pressure reservoir (up to 70 MPa) is studied using computational fluid dynamics with a large eddy simulation turbulence model. This viscous flow simulation is compared with a non-viscous simulation to demonstrate that the velocity is supersonic at the exit of a small exit nozzle and that the mass flow is reduced.

The use of high-fidelity simulation methods based on large-eddy simulation (LES) are proving useful for understanding and mitigating the safety hazards associated with hydrogen releases from nuclear power plants. However accurate modelling of turbulent premixed hydrogen flames via LES can require very high resolution to capture both the large-scale turbulence and its interaction with the flame fronts. Standard meshing strategies can result in impractically high computational costs especially for the thin fronts of hydrogen flames. For these reasons the use of a recently formulated integral length scale approximation (ILSA) subfilter-scale model in combination with an efficient anisotropic block-based adaptive mesh refinement (AMR) technique is proposed and examined herein for performing LES of turbulent premixed hydrogen flames. The anisotropic AMR method allows dynamic and solution-dependent resolution of flame fronts and the grid-independent properties of the ILSA model ensure that numerical errors associated with implicitly-filtered LES techniques in regions with varying resolution are avoided. The combined approach has the potential to allow formally converged LES solutions (direct numerical simulation results are typically reached in the limit of very fine meshes with standard subgrid models). The proposed LES methodology is applied to combustion simulations of lean premixed hydrogen-air mixtures within closed vessels: a problem relevant to hydrogen safety applications in nuclear facilities. A progress variable-based method with a multi-phenomena burning velocity model is used as the combustion model. The present simulation results are compared to the available experiment data for several previously studied THAI vessel cases and the capabilities of the proposed LES approach are assessed.

During the early phase of the transient process following a hydrogen leak into the atmosphere a contact surface appears separating air heated by the leading shock from hydrogen cooled by expansion. Locally the interface is approximately planar. Diffusion leads to a temperature decrease on the air side and an increase in the hydrogen-filled region and mass diffusion of hydrogen into air and of air into hydrogen potentially resulting in ignition. This process was analyzed by Li ˜nan and Crespo [1] for unity Lewis number and Li ˜nan and Williams [2] for Lewis number less than unity. We included in the analysis the effect of a slow expansion [3 4] leading to a slow drop in temperature which occurs in transient jets. Chemistry being very temperature-sensitive the reaction rate peaks close to the hot side of the interface where only a small fuel concentration present close to the warm air-rich side which depends crucially upon the fuel Lewis number. For Lewis number unity the fuel concentration due to diffusion is comparable to the rate of consumption by chemistry. If the Lewis number is less than unity diffusion brings in more fuel than temperature-controlled chemistry consumes. For a Lewis number greater than unity diffusion is not strong enough to bring in as much fuel as chemistry would burn; combustion is controlled by fuel diffusion. If the temperature drop due to expansion associated with the multidimensional jet does not lower significantly the reaction rate up to that point analysis shows that ignition in the jet takes place. For fuel Lewis number greater than unity chemistry does not lead to a defined explosion so that eventually expansion will affect the process; ignition does not take place [3 4]. In the current paper these results are extended to consider multistep chemical kinetics but for otherwise similar assumptions. High activation energy is no longer applicable. Instead results are obtained in the short time limit still as a perturbation superimposed to the self-similar solution to the chemically frozen diffusion solution. In that approximation the initiation step which consumes fuel and oxidant is taken to be slow compared with steps that consume one of the reactants and an intermediate species. The formulation leads to a two point boundary value problem for set of coupled rate equations plus an energy equation for perturbations. These equations are linear with variable co-effcients. The coupled problem is solved numerically using a split algorithm in which chemical reaction is solved for frozen diffusion while diffusion is solved for frozen chemistry. At each time step the still coupled linear problem is solved exactly by projecting onto the eigenmodes of the stiff matrix so that the solution is unaffected by stiffness. Since in the short time limit temperature is only affected at the perturbation level the matrix depends only on the similarity variable x t but it is otherwise time-independent. As a result determination of the eigenvalues and eigenvectors is only done once (using Maple) for the entire range of discretized values of the similarity variable. The diffusion problem consists of a set of independent equations for each species. Each of these is solved using orthogonal decomposition onto Hermite polynomials for the homogeneous part plus a particular solution proportional to time for the non-homogeneous (source) terms. That approach can be implemented for different kinetic schemes.

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

The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature hydrogen pressure tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

This paper describes experimental and numerical modelling results from an investigation into the flammability profiles associated with high pressure hydrogen jets released in close proximity to surfaces. This work was performed under a Transnational Access Agreement activity funded by the European Research Infrastructure project H2FC.<br/>The experimental programme involved ignited and unignited releases of hydrogen at pressures of 150 and 425 barg through nozzles of 1.06 and 0.64 mm respectively. The proximity of the release to a ceiling or the ground was varied and the results compared with an equivalent free-jet test. During the unignited experiments concentration profiles were measured using hydrogen sensors. During the ignited releases thermal radiation was measured using radiometers and an infra-red camera. The results show that the flammable volume and flame length increase when the release is in close proximity to a surface. The increases are quantified and the safety implications discussed.<br/>Selected experiments were modelled using the CFD model FLACS for validation purposes and a comparison of the results is also included in this paper. Similarly to experiments the CFD results show an increase in flammable volume when the release is close to a surface. The unstable atmospheric conditions during the experiments are shown to have a significant impact on the results.

The current study addresses the spontaneous ignition of hydrogen jets released into a confined oxidizer environment experimentally. The experiments are conducted in a shock tube where hydrogen gas is shock-accelerated into oxygen across a perforated plate. The operating conditions and hole dimension of the plate were varied in order to identify different flow field and ignition scenarios. Time resolved Schlieren visualization permitted to reconstruct the gasdynamic evolution of the release and different shock interactions. Time resolved self-luminosity records permitted us to record whether ignition was achieved and also to record the dimension of the turbulent mixing layer. The ignition limits determined experimentally in good agreement with the 1D diffusion ignition model proposed by Maxwell and Radulescu. Nevertheless the experiments demonstrated that the mixing layer is two to three orders of magnitude thicker than predicted by molecular diffusion which can be attributed to the observed mixing layer instabilities and shock-mixing layer interactions which provide a much more intense mixing rate than anticipated from previous and current numerical predictions. These observations further clarify why releases through partly confined geometries are more conducive to jet ignition of the jets.

The scenario of detonative ignition in shocked mixture is significant because it is a contributor to deflagration to detonation transition for example following shock reflections. However even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into a combustible mixture is difficult because of the singular nature of the initial conditions. Initially as the shock starts moving into reactive mixture the region filled with reactive mixture has zero thickness. On a fixed grid the number of grid points between the shock and the contact surface increases as the shock moves away from the latter. Due to initial lack of resolution in the region of interest staircasing may occur whereby the resulting plots consist of jumps between few values a few grid points and these numerical artifacts are amplified by the chemistry which is very sensitive to temperature leading to unreliable results. The formulation is transformed replacing time and space by time and space over time as the independent variables. This frame of reference corresponds to the self-similar formulation in which the non-reactive problem remains stationary and the initial conditions are well-resolved. Additionally a solution obtained from short time perturbation is used as initial condition at a time still short enough for the perturbation to be very accurate but long enough so that there is sufficient resolution. The numerical solution to the transformed problem is obtained using an essentially non-oscillatory algorithm which is adequate not only for the early part of the process but also for the latter part when chemistry leads to appearance of a shock and eventually a detonation wave is formed. A validation study was performed and the results were compared with the literature for single step Arrhenius chemistry. The method and its implementation were found to be effective. Results are presented for values of activation energy ranging from mild to stiff.

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.

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.

In close cooperation with their Canadian counterparts United States public safety authorities are taking the first steps towards creating a proper infrastructure to ensure the safe use of the new hydrogen fuel cells now being introduced commercially. Currently public safety officials are being asked to permit hydrogen fuel cells for stationary power and as emergency power backups for the telecommunications towers that exist everywhere. Consistent application of the safety codes is difficult – in part because it is new – yet it is far more complex to train emergency responders to deal safely with the inevitable hydrogen incidents. The US and Canadian building and fire codes and standards are similar but not identical. The US and Canadian rules are unlikely to be useful to other nations without modification to suit different regulatory systems. However emergency responder safety training is potentially more universal. The risks strategies and tactics are unlikely to differ much by region. The Hydrogen Executive Leadership Panel (HELP) made emergency responder safety training its first priority because the transition to hydrogen depends on keeping incidents small and inoffensive and the public and responders safe from harm. One might think that advising 1.2 million firefighters and 800000 law enforcement officers about hydrogen risks is no more complicated than adding guidance to a website. One would be wrong. The term “training” has specific legal implications which may vary by state. For hazardous materials federal requirements apply. Insurance companies place training requirements on the policies they sell to fire departments including the thousands of small all-volunteer departments which may operate as private corporations. Union contracts may define training and promotions may be based on satisfactorily completed certain levels of training. Emergency responders could no sooner learn how to extinguish a<br/>hydrogen fire by reading a webpage than a person could learn to ride a bicycle by reading a book. Procedures must be learned by listening reading and then doing. Regular practice is necessary. As new hydrogen applications are commercialized additional responder training may be necessary. This highlights another obstacle emergency responders’ ability to travel distances and take the time to undergo training. Historically fire academies established adjunct instructor programs and satellite academies to bring the training to firefighters. The large well-equipped academies are typically used for specialized training. States rarely have enough instructors and instructors often must take the time to create a course outline research each point and produce a program that is informative useful and holds the attention of responders. The challenge of training emergency responders seems next to impossible but public safety authorities are asked to tackle the impossible every day and a model exists to move forward in the U.S. Over the past few years the National Association of State Fire Marshals and U.S. Department of Transportation enlisted the help of emergency responders and industry to create a standardized approach to train emergency responders to deal with pipeline incidents. A curriculum and training materials were created and more than 26000 sets have been distributed for free to public safety agencies nationwide. More than 8000 instructors have been trained to use these materials that are now part of the regular training in 23 states. Using this model HELP intends to ensure that all emergency responders are trained to address hydrogen risks. The model and the rigorous scenario analysis and review used to developing the operational and technical training is addressed in this paper.

Computational fluid dynamics is used to simulate the release of high pressure Hydrogen from a reservoir with an exit of increasing diameter. Abel-Noble real gas equation of state is used to accurately simulate this high pressure release. Parallel processing based on Message Passing Interface for domain decomposition is employed to decrease the solution time. The release exit boundary is increased in time to simulate a scenario when the exit area increases during the release. All nodes and elements are moved accordingly at each time step to maintain the quality of the mesh. Different speeds of increasing diameter are investigated to see the impact on this unsteady flow.

An accident modelling approach is used to assess the safety of a hydrogen station as part of a ground transportation network. The method incorporates prevention barriers associated to human factors management and organizational failures in a risk assessment framework. Failure probabilities of these barriers and end-states events are predicted using Fault Tree Analysis and Event Tree Analysis respectively. Results from the case study considered revealed the capability of the proposed method in estimating the likelihood of various outcomes as well as predicting the future probability. In addition the scheme offers opportunity to provide dynamic adjustment by updating the failure probability with actual plant data. Results from the analysis can be used to plan maintenance and management of change as required by the plant condition.

The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm round leak orifice from 100 barg 250 barg 400 barg 550 barg and 700 barg compressed gas systems are presented for vertical jets. To quantify the effect of the surface on the jet the jet exit is positioned at various distances from the surface ranging from 0.029 m to 12 m. Free jets simulations are performed for comparison purposes.

CFD simulations investigating the effect of ventilation airflow on hydrogen release behaviour in an underground mining tunnel were performed using FLACS hydrogen. Both dispersion and combustion scenarios of a hydrogen release coming from a severed distribution pipeline were investigated. Effects on the hydrogen dispersion such as ventilation strength and the mechanism of air flow supply (a pull or push fan) and mine opening surface roughness surface cavities and obstructions were explored. Results showing the effect of changing the position of the leak adding a cavity on the ceiling of the tunnel and changing the roughness of the walls are given. Overpressure sensitivity to the ignition delay was also considered. From the results for the varied ventilation regimes and spatial scenarios it is difficult to identify the optimal ventilation strategy giving the safest conditions for hydrogen distribution and refuelling in an underground mine.

We have implemented a portable large-scale shadowgraph system for use in flow visualization relating to hydrogen safety. Previous large-scale shadowgraph and schlieren implementations have often been limited to background- oriented techniques which are subject to noise. The system built is based on a large-scale shadowgraph technique developed by Settles which allows for high-quality visualization. We have applied the shadowgraph system to complex phenomena and current issues in hydrogen safety including DDT in long channels jet releases and unconfined deflagrations. Shadowgrams taken are compared to a Z-schlieren system. This shadowgraph system allows analysis of these phenomena at longer length scales.

Power-to-gas is a promising option for storing interment renewables nuclear baseload power and distributed energy and it is a novel concept for the transition to increased renewable content of current fuels with an ultimate goal of transition to a sustainable low-carbon future energy system that interconnects power transportation sectors and thermal energy demand all together. The aim of this paper is to introduce different Power-to-gas “pathways” including Power to Hydrogen Power to Natural Gas End-users Power to Renewable Content in Petroleum Fuel Power to Power Seasonal Energy Storage to Electricity Power to Zero Emission Transportation Power to Seasonal Storage for Transportation Power to Micro grid Power to Renewable Natural Gas (RNG) to Pipeline (“Methanation”) and Power to Renewable Natural Gas (RNG) to Seasonal Storage. In order to compare the different pathways the review of key technologies of Power-to-gas systems are studied and the qualitative efficiency and benefits of each pathway is investigated from the technical points of view. Moreover different Power-to-gas pathways are discussed as an energy policy option that can be implemented to transition towards a lower carbon economy for Ontario’s energy systems

This brief explores recent momentum on hydrogen and evaluates potential implications for subsidies for fossil fuel-based hydrogen given the government's commitments on fossil fuel subsidies.

Spending on hydrogen has the potential to significantly influence the direction taken by the world’s energy systems. In December 2020 Canada unveiled a national hydrogen strategy following the announcement of a strengthened climate plan. The strategy emphasized both blue and green hydrogen. As the government considers whether to provide subsidies for hydrogen we recommend government:

• Ensure that any subsidies for hydrogen are in line with the government’s commitments to phase out inefficient fossil fuel subsidies by 2025 and meet net-zero by 2050.
• Thoroughly evaluate the potential efficiency of subsidies for hydrogen against robust social environmental and economic criteria. • Improve transparency by publicly reporting on direct spending and tax expenditures for hydrogen production.
• Follow international best practices being set by Canada’s peers. For example Germany and Spain have laid out hydrogen strategies prioritizing green hydrogen.

Based on IISD's analysis subsidies for hydrogen based on natural gas without significant levels of carbon capture and storage (CCS) should not be eligible for government assistance. Subsidies for blue hydrogen should only occur if blue hydrogen can meet the same level of environmental performance (including emission intensity) and is at or below the cost of green hydrogen.

This brief is one of three International Institute for Sustainable Development (IISD) policy briefs in its Recovery Through Reform series which assesses how efforts to achieve a green recovery from COVID-19 in Canada rely on—and can contribute to—fossil fuel subsidy reform.

Governments around the world are leveraging unprecedented amounts of capital to respond to the pandemic and bailing out struggling industries. Trends in energy-related spending indicate that despite the green push the world’s largest economies have still favoured fossil energy over clean energy.<br/><br/>We evaluate energy-related spending in Canada in 2020 (since the onset of COVID-19) using data from the Energy Policy Tracker. Trends in Canada are then compared to flagship policies in key jurisdictions with recent progressive climate policy announcements including France Germany and the United Kingdom. The brief ends with broad recommendations on how Canada can better align its recovery funding with climate action and fossil fuel subsidy reform.<br/><br/>This brief is one of three International Institute for Sustainable Development (IISD) policy briefs in its Recovery Through Reform series which assesses how efforts to achieve a green recovery from COVID-19 in Canada rely on—and can contribute to—fossil fuel subsidy reform.

This paper presents an analysis of computational fluid dynamic models of compressed hydrogen gas leaks into the air under different conditions to determine the volume of the hydrogen/air mixture and the extents of the lower flammable limit. The necessary hole size was calculated to determine a reasonably expected hydrogen leak rate from a valve or a fitting of 5 and 20 cfm under 400 bars resulting in a 0.1 and 0.2 mm effective diameter hole respectively. The results were compared to calculated hypothetical volumes from IEC 60079-10 for the same mass flowrate and in most cases the CFD results produced significantly smaller hydrogen/air volumes than the IEC standard. Prescriptive electrical classification distances in existing standards for hydrogen and compressed natural gas were examined but they do not consider storage pressure and there appears to be no scientific basis for the distance determination. A proposed table of electrical classification distances incorporating hydrogen storage volume and pressure was produced based on the hydrogen LFL extents from a 0.2 mm diameter hole and the requirements of existing standards. The PHOENICS CFD software package was used to solve the continuity momentum and concentration equations with the appropriate boundary conditions buoyancy model and turbulence models. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment typical for a hydrogen refuelling or energy station.<br/><br/>

Power- and biomass-to-liquid fuel processes (PBtL) can utilize renewable energy and residual forestry waste to produce liquid synthetic fuels which have the potential to mitigate the climate impacts of the current transportation infrastructure including the long-haul aviation sector. In a previous study we demonstrated that implementing a solid oxide electrolysis cell (SOEC) in the PBtL process can significantly increase the energy efficiency of fuel production by supplying the produced hydrogen to a reverse water gas shift (RWGS) reactor to generate syngas which is then fed downstream to a Fischer–Tropsch (FT) reactor. The tail gas emitted from the FT reactor consists primarily of a mixture of hydrogen carbon monoxide and methane and is often recycled to the entrained flow gasifier located at the beginning of the process. In this analysis we investigate the efficiency gains of the PBtL process as a result of redirecting the tail gas of the FT reactor to the anode of an SOEC to serve as fuel. Supplying fuel to an SOEC can lower the electrical work input required to facilitate steam electrolysis when reacting electrochemically with oxide ions in the anode which in turn can reduce oxygen partial pressures and thus alleviate material degradation. Accordingly we develop a thermodynamic framework to reveal the performance limits of fuel-assisted SOECs (FASOECs) and provide strategies to minimize oxygen partial pressures in the SOEC anode. Additionally we elucidate how much fuel is required to match the heating demands of a cell when steam is supplied to the cathode over a broad range of inlet temperatures and demonstrate the influence of a set of reaction pathways of the supplied fuel on the operating potential of an FASOEC and the corresponding efficiency gain of the PBtL process. Based on preliminary calculations we estimate that implementing an FASOEC in the PBtL process can increase the energy efficiency of fuel production to more than 90% depending on the amount of FT tail gas available to the system.

The safety and convenience of hydrogen storage are significant for fuel cell vehicles. Based on mass conservation equation and energy conservation equation two thermodynamic models (single zone model and dual zone model) have been established to study the hydrogen gas temperature and tank wall temperature for compressed hydrogen storage tank. With two models analytical solution and Euler solution for single zone (gas zone) charge-discharge cycle have been compared Matlab/Simulink solution and Euler solution for dual zone (gas zone wall zone) charge-discharge cycle have been compared. Three charge-discharge cycle cases (Case 1 constant inflow temperature; Case 2 variable inflow temperature; Case 3 constant inflow temperature variable outflow temperature) and two compressed hydrogen tanks (Type III 25L Type IV 99L) charge-discharge cycle are studied by Euler method. Results show Euler method can well predict hydrogen temperature and tank wall temperature.

The paper will present results of hydrogen/oxygen mixtures ignited by using electric sparks electrostatic discharges a heating element and a flame. Measurements of the lower flammability limit (LFL) was done for each ignition method. The hydrogen mixtures of different concentrations were ignited at the bottom of a combustion chamber leading to an upward propagation of the resulting flame. At some level of concentration the combustion was partial due to the limited upward propagation. The complete combustion of the whole mixture was observed at concentration limits higher than the known LFL of 4% vol. for hydrogen in air. The paper will describe the test facilities and the resulting ignition probabilities for different ignition methods.

Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.

The effects of temperature on bulk hydrogen concentration and diffusion have been tested with the Devanathan–-Stachurski method. Thus a model based on hydrogen potential diffusivity loading frequency and hydrostatic stress distribution around crack tips was applied in order to quantify the temperature’s effect. The theoretical model was verified experimentally and confirmed a temperature threshold of 320 K to maximize the crack growth. The model suggests a nanoscale embrittlement mechanism which is generated by hydrogen atom delivery to the crack tip under fatigue loading and rationalized the ΔK dependence of traditional models. Hence this work could be applied to optimize operations that will prolong the life of the pipeline.

The valorization of biomass-based solid wastes for both geotechnical engineering purposes and energy needs has been reviewed to achieve eco-friendly eco-efficient and sustainable engineering and reengineering of civil engineering materials and structures. The objective of this work was to review the procedure developed by SWI-NaOH-OCE Model for the valorization of biomass through controlled direct combustion and the sequestration of hydrogen gas for energy needs. The incineration model gave a lead to the sequestration of emissions released during the direct combustion of biomass and the subsequent entrapment of oxides of carbon and the eventual release of abundant hydrogen gas in the entrapment jar. The generation of geomaterials ash for the purpose of soil stabilization concrete and asphalt modification has encouraged greenhouse emissions but eventually the technology that has been put in place has made it possible to manage and extract these emissions for energy needs. The contribution from researchers has shown that hydrogen sequestration from other sources requires high amount of energy because of the lower energy states of the compounds undergoing thermal decomposition. But this work has presented a more efficient approach to release hydrogen gas which can easily be extracted and stored to meet the energy needs of the future as fuel cell batteries to power vehicles mobile devices robotic systems etc. More so the development of MXene as an exfoliated two-dimensional nanosheets with permeability and filtration selectivity properties which are connected to its chemical composition and structure used in hydrogen gas extraction and separation from its molecular combination has presented an efficient procedure for the production and management of hydrogen gas for energy purposes.

This paper presents experiments performed at Canadian Nuclear Laboratories (CNL) to examine the dispersion behaviour of helium in a polycarbonate enclosure that was representative of a residential parking garage. The purpose was to gain a better understanding of the effect of buoyancy- or winddriven natural ventilation on hydrogen dispersion behaviour. Although hydrogen dispersion studies have been reported extensively in the literature gaps still exist in predictive methods for hazard analysis. Helium a simulant for hydrogen was injected near the centre of the floor with a flow rate ranging from 5 to 75 standard litres per minute through an upward-facing nozzle resulting in an injection Richardson number ranging between 10-1 and 102. The location of the nozzle varied from the bottom of the enclosure to near the ceiling to examine the impact of the nozzle elevation on the development of a stratified layer in the upper region of the enclosure. When the injection nozzle was placed at a sufficiently low elevation the vertical helium profile always consisted of a homogenous layer at the top overlaying a stratified layer at the bottom. To simulate outdoor environmental conditions a fan was placed in front of each vent to examine the effect of opposing or assisting wind on the dispersion. The helium transients in the uniform layer predicted with analytical models were in good agreement with the measured transients for the tests with injection at lower elevations or with no wind. Model improvements are required for adequately predicting transients with significantly stratified profiles or with wind.

In this paper a new gasification system is developed for the three useful outputs of electricity heat and hydrogen and reported for practical energy applications. The study also investigates the composition of syngas leaving biomass gasifier. The composition of syngas is represented by the fractions of hydrogen carbon dioxide carbon monoxide and water. The integrated energy system comprises of an entrained flow gasifier a Cryogenic Air Separation (CAS) unit a double-stage Rankine cycle Water Gas Shift Reactor (WGSR) a combined gas–steam power cycle and a Proton Exchange Membrane (PEM) electrolyzer. The whole integrated system is modeled in the Aspen plus 9.0 excluding the PEM electrolyzer which is modeled in Engineering Equation Solver (EES). A comprehensive parametric investigation is conducted by varying numerous parameters like biomass flow rate steam flow rate air input flow rate combustion reactor temperature and power supplied to the electrolyzer. The system is designed in a way to supply the power produced by the steam Rankine cycle to the PEM electrolyzer for hydrogen production. The overall energy efficiency is obtained to be 53.7% where the exergy efficiency is found to be 45.5%. Furthermore the effect of the biomass flow rate is investigated on the various system operational parameters.