Publications
Helium Release in A Closed Enclosure- Comparisons Between Simple Models, CFD Calculations And Experimental Results
Sep 2011
Publication
In the prospect of a safe use of hydrogen in our society one important task is to evaluate under which conditions the storage of hydrogen systems can reach a sufficient level of safety. One of the most important issues is the use of such system in closed area for example a private garage or an industrial facility. In the scope of this paper we are mainly interested in the following scenario: a relatively slow release of hydrogen (around 5Nl/min) in a closed and almost cubic box representing either a fuel cell at normal scale or a private garage at a smaller scale. For practical reasons helium was used instead of hydrogen in the experiments on which are based our comparisons. This kind of situation leads to the fundamental problem of the dispersion of hydrogen due to a simple vertical source in an enclosure. Many numerical and experimental studies have already been conducted on this problem showing the formation of either a stably stratified distribution of concentration or the formation of a homogeneous layer due to high enough convective flows at the top of the enclosure. Nevertheless most of them consider the cases of accidental situation in which the flow rate is relatively important (higher than 10Nl/min). Numerical simulations carried out with the CEA code Cast3M and a LES turbulence model confirm the differences of results already observed in experimental helium concentration measurements for a same injection flow rate and two different injection nozzle diameters contradicting simple physical models used in safety calculations.
HIAD – Hydrogen Incident and Accident Database
Sep 2011
Publication
The Hydrogen Incident and Accident Database (HIAD) is being developed as a repository of systematic data describing in detail hydrogen-related undesired events (incidents or accidents). It is an open web-based information system serving various purposes such as a data source for lessons learnt risk communication and partly risk assessment. The paper describes the features of the three HIAD modules – the Data Entry Module (DEM) the Data Retrieval Module (DRM) and the Data Analysis Module (DAM) – and the potential impact the database may have on hydrogen safety. The importance of data quality assurance process is also addressed.
Dynamic Energy and Mass Balance Model for an Industrial Alkaline Water Electrolyzer Plant Process
Nov 2021
Publication
This paper proposes a parameter adjustable dynamic mass and energy balance simulation model for an industrial alkaline water electrolyzer plant that enables cost and energy efficiency optimization by means of system dimensioning and control. Thus the simulation model is based on mathematical models and white box coding and it uses a practicable number of fixed parameters. Zero-dimensional energy and mass balances of each unit operation of a 3 MW and 16 bar plant process were solved in MATLAB functions connected via a Simulink environment. Verification of the model was accomplished using an analogous industrial plant of the same power and pressure range having the same operational systems design. The electrochemical mass flow and thermal behavior of the simulation and the industrial plant were compared to ascertain the accuracy of the model and to enable modification and detailed representation of real case scenarios so that the model is suitable for use in future plant optimization studies. The thermal model dynamically predicted the real case with 98.7 % accuracy. Shunt currents were the main contributor to relative low Faraday efficiency of 86 % at nominal load and steady-state operation and heat loss to ambient from stack was only 2.6 % of the total power loss.
Experimental Investigation of Hydrogen Release and Ignition from Fuel Cell Powered Forklifts in Enclosed Spaces
Sep 2011
Publication
Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refuelling operations. Based on industry stakeholder input conducted experiments were devised to assess the utility of modelling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International's Corral Hollow Test Site. Moreover the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modelling approaches.
Experimental Results and Comparison with Simulated Data of a Low Pressure Hydrogen Jet
Sep 2011
Publication
Experiments with a hydrogen jet were performed at two different pressures 96 psig (6.6 bars) and 237 psig (16.3 bars). The hydrogen leak was generated at two different hole sizes 1/16 inch (1.6 mm) and 1/32 inch (0.79 mm). The flammable shape of the plume was characterised by numerous measurements of the hydrogen concentration inside of the jet. The effect of the nearby horizontal surface on the shape of the plume was measured and compared with results of CFD numerical simulations. The paper will present results and an interpretation on the nature of the plume shape.
Safety of Hydrogen and Natural Gas Mixtures by Pipelines- ANR French Project Hydromel
Sep 2011
Publication
In order to gain a better understanding of hazards linked with Hydrogen/Natural gas mixtures transport by pipeline the National Institute of Industrial Environment and Risks (INERIS) alongside with the Atomic Energy Commission (CEA) the industrial companies Air Liquide and GDF SUEZ and the French Research Institutes ICARE and PPRIME (CNRS) have been involved in a project called HYDROMEL. This project was partially funded by the French National Research Agency (ANR) in the framework of its PAN-H program aimed at promoting the R&D activities related to the hydrogen deployment. Firstly the project partners investigated how a NG/H2 mixture may influence the modelling of a hazard scenario i.e. how the addition of a quantity of hydrogen in natural gas can increase the potential of danger. Therefore it was necessary to build an experimental database of physics properties for mixtures. Secondly effect distances in accidental scenarios that could happen on pipelines have been calculated with existing models adapted to the mixtures. This part was preceded by a benchmark exercise between all partners models and experimental results found in the literature. Finally the consortium wrote a good practice guideline for modelling the effects related to the release of natural gas /hydrogen mixture?. The selected models and their comparison with data collected in the literature as well as the experimental results of this project and the main conclusions of the guidelines are presented in this paper.
Explosion Venting of Rich Hydrogen-air Mixtures in a Cylindrical Vessel with Two Symmetrical Vents
Oct 2015
Publication
The safety issues related to explosion venting of hydrogen-air mixtures are significant and deserve more detailed investigation. Vented hydrogen-air explosion has been studied extensively in vessels with a single vent. However little attention has been paid to the cases with more than one vent. In this paper experiments about explosion venting of rich hydrogen-air mixtures were conducted in a cylindrical vessel with two symmetrical vents to investigate the effect of vent area and distribution on pressure build up and flame behaviours. Venting accelerates the flame front towards the vent but has nearly no effect on the opposite side. The maximum internal overpressure decreases and the maximum external flame length increases with the increase of vent area. Two pressure peaks can be identified outside of vessel which correspond to the external explosion and the burnt gas jet respectively. Compared with single vent two vents with same total vent area leads to nearly unchanged maximum internal and external overpressure but much smaller external flame length.
Non-stoichiometric Methanation as Strategy to Overcome the Limitations of Green Hydrogen Injection into the Natural Gas Grid
Jan 2022
Publication
The utilization of power to gas technologies to store renewable electricity surpluses in the form of hydrogen enables the integration of the gas and electricity sectors allowing the decarbonization of the natural gas network through green hydrogen injection. Nevertheless the injection of significant amounts of hydrogen may lead to high local concentrations that may degrade materials (e.g. hydrogen embrittlement of pipelines) and in general be not acceptable for the correct and safe operation of appliances. Most countries have specific regulations to limit hydrogen concentration in the gas network. The methanation of hydrogen represents a potential option to facilitate its injection into the grid. However stoichiometric methanation will lead to a significant presence of carbon dioxide limited in gas networks and requires an accurate design of several reactors in series to achieve relevant concentrations of methane. These requirements are smoothed when the methanation is undertaken under non-stoichiometric conditions (high H/C ratio). This study aims to assess to influence of nonstoichiometric methanation under different H/C ratios on the limitations presented by the pure hydrogen injection. The impact of this injection on the operation of the gas network at local level has been investigated and the fluid-dynamics and the quality of gas blends have been evaluated. Results show that non-stoichiometric methanation could be an alternative to increase the hydrogen injection in the gas network and facilitates the gas and electricity sector coupling.
Single Step Compact Steam Methane Reforming Process for Hydrogen-Cng (H-Cng) Production from Natural Gas
Sep 2011
Publication
Compressed natural gas (CNG) is being increasingly used as a clean transportation fuel. However for further reduction in emissions particularly NOx H-CNG mixture with ~ 20 % hydrogen is recommended. Presently most of the H-CNG mixture is produced by blending hydrogen with CNG. For hydrogen production Steam Methane Reforming (SMR) is a major process accounting for more than 90% of hydrogen production by various industries. In this process natural gas is first reformed to syn gas under severe operating conditions (Pressure 20-30 bar temperature 850-950 deg C) followed by conversion of CO to hydrogen in the shift reactor. Other method of hydrogen production such as electrolysis of water is more expensive. Further there are issues of safety with handling of hydrogen its storage and transportation for blending. In order to overcome these problems a single step compact process for the production of H-CNG gaseous mixture through low severity steam methane reforming of natural gas has been developed. It employs a catalyst containing nickel nickel oxide magnesium oxide and silica and has the capability of producing H-CNG mixture in the desired proportion containing 15-20 vol % hydrogen with nil CO production. The process is flexible and rugged allowing H-CNG production as per the demand. The gaseous H-CNG product mixture can directly be used as automobile fuel after compression. The process can help as important step in safe transition towards hydrogen economy. A demonstration unit is being set up at IOC R&D Centre.
On The Kinetics of Alh3 Decomposition and the Subsequent Al Oxidation
Sep 2011
Publication
Metal hydrides are used for hydrogen storage. AlH3 shows a capacity to store about 10 wt% hydrogen. Its hydrogen is split-off in the temperature interval of 400–500 K. On dehydrogenation a nano-structured Al material emerges with specific surfaces up to 15–20 m2/g. The surface areas depend on the heating rate because of a temperature dependent crystallite growth. The resulting Al oxidizes up to 20–25% weight on air access forming an alumina passivation layer of 3–4 nm thickness on all exposed surfaces. The heat released from this Al oxidation induces a high risk to this type of hydrogen storage if the containment might be destroyed accidentally. The kinetics of the dehydrogenation and the subsequent oxidation is investigated by methods of thermal analysis. A reaction scheme is confirmed which consists of a starting Avrami-Erofeev mechanism followed by formal 1st order oxidation on unlimited air access. The kinetic parameters activation energies and pre-exponentials are evaluated and can be used to calculate the reaction progress. Together with the heat of the Al oxidation the overall heat release and the related rate can be estimated.
Measurements of Effective Diffusion Coefficient of Helium and Hydrogen Through Gypsum
Sep 2011
Publication
An experimental apparatus which was based on the ¼-scale garage previously used for studying helium release and dispersion in our laboratory was used to obtain effective diffusion coefficients of helium and hydrogen (released as forming gas for safety reasons) through gypsum panel. Two types of gypsum panel were used in the experiments. Helium or forming gas was released into the enclosure from a Fischer burner1 located near the enclosure floor for a fixed duration and then terminated. Eight thermal-conductivity sensors mounted at different vertical locations above the enclosure floor were used to monitor the temporal and spatial gas concentrations. An electric fan was used inside the enclosure to mix the released gas to ensure a spatially uniform gas concentration to minimize stratification. The temporal variations of the pressure difference between the enclosure interior and the ambience were also measured. An analytical model was developed to extract the effective diffusion coefficients from the experimental data.
Introduction to Hydrogen Safety Engineering
Sep 2011
Publication
The viability and public acceptance of the hydrogen and fuel cell (HFC) systems and infrastructure depends on their robust safety engineering design education and training of the workforce regulators and other stakeholders in the state-of-the-art in the field. This can be provided only through building up and maturity of the hydrogen safety engineering (HSE) profession. HSE is defined as an application of scientific and engineering principles to the protection of life property and environment from adverse effects of incidents/accidents involving hydrogen. This paper describes a design framework and overviews a structure and contents of technical sub-systems for carrying out HSE. The approach is similar to British standard BS7974 for application of fire safety engineering to the design of buildings and expanded to reflect on specific for hydrogen safety related phenomena including but not limited to high pressure under-expanded leaks and dispersion spontaneous ignition of sudden hydrogen releases to air deflagrations and detonations etc. The HSE process includes three main steps. Firstly a qualitative design review is undertaken by a team that can incorporate owner hydrogen safety engineer architect representatives of authorities having jurisdiction e.g. fire services and other stakeholders. The team defines accident scenarios suggests trial safety designs and formulates acceptance criteria. Secondly a quantitative safety analysis of selected scenarios and trial designs is carried out by qualified hydrogen safety engineer(s) using the state-of-the-art knowledge in hydrogen safety science and engineering and validated models and tools. Finally the performance of a HFC system and/or infrastructure under the trial safety designs is assessed against predefined by the team acceptance criteria. This performance-based methodology offers the flexibility to assess trial safety designs using separately or simultaneously three approaches: deterministic comparative or combined probabilistic/deterministic.
Catalysis of Oxides in Hydrogen Generation by the Reaction of Al with Water
Sep 2013
Publication
Hydrogen generation by the reaction of pure Al powder in water with the addition of Al(OH)3 γ- Al2O3 α-Al2O3 or TiO2 at mild temperatures was investigated. It was found that the reaction of Al with water is promoted and the reaction induction time decreases greatly by the above hydroxide and oxides. X-ray diffraction analyses revealed that the hydroxide and oxide phases have no any change during the Al-water reaction indicating that they are just as catalysts to assist the reaction of Al with water. A possible mechanism was proposed which shows that hydroxide and oxides could dissociate water molecules and promote the hydration of the passive oxide film on Al particle surfaces.
A Comparative Study of Detonability and Propensity to Sustain High-speed Turbulent Deflagrations in Hydrogen and Methane Mixtures
Sep 2013
Publication
We’ve studied the conditions enabling a detonation to be quenched when interacting with an obstruction and the propensity for establishing subsequent fast-flame. Oxy-hydrogen detonations were found quench more easily than oxy-methane detonations when comparing the ratio of gap size and the detonation cell size. High-speed turbulent deflagrations that re-accelerate back to a detonation were only observed in methane-oxygen mixtures. Separate hot-spot ignition calculations revealed that the higher detonability of methane correlates with its stronger propensity to develop localized hot-spots. The results suggest that fast-flames are more difficult to form in hydrogen than in methane mixtures.
Understanding the Interaction between a Steel Microstructure and Hydrogen
Apr 2018
Publication
The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels i.e. high-strength low-alloy (HSLA) transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase i.e. ferrite bainite pearlite or martensite and with carbon contents of approximately 0 0.2 and 0.4 wt % are further considered to simplify the microstructure. Finally the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction a comparison of the available H trapping sites the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis.
Hydrogen Economy Roadmap of Korea
Jan 2019
Publication
Hydrogen economy" refers to an economy where hydrogen is an important environmentally-friendly energy source brings out radical changes to the national economy and society as a whole and is a driving force behind economic growth.<br/>As hydrogen is not only a driver of innovative growth but also a means of using energy in a more eco-friendly way a hydrogen economy refers to the pursuit of a society that realizes the unlimited potential of hydrogen.<br/>This document summarises Korea's roadmap towards a hydrogen economy the expected benefits for both economic and environmental factors and the potential limitations. It also emphasises Korea's vision going forward on fuel cells hydrogen production hydrogen storage and transport and the hydrogen ecosystem as a whole.
H2FC SUPERGEN- Delivering Negative Emissions from Biomass derived Hydrogen
Apr 2020
Publication
Bioenergy with carbon capture and storage (BECCS) removes carbon dioxide (CO2) from the atmosphere i.e. negative CO2 emissions. It will likely have an important role in the transition to a net-zero economy by offsetting hard-to-abate greenhouse gas emissions. However there are concerns about the sustainability of large scale BECCS deployment using bioenergy from predominantly primary biomass sources (i.e. dedicated energy crops). Secondary sources of biomass (e.g. waste biomass municipal solid wastes forest/agricultural residues) are potentially an economical and sustainable alternative resource. Furthermore supplementing primary biomass demand with secondary sources could enable the supply of biomass from solely indigenous sources (i.e. from the UK) which could provide economic advantages in a growing global bio-economy.<br/><br/>There is also a growing interest in biomass-derived hydrogen production with CCS (BHCCS) which generates hydrogen and removes CO2 from the atmosphere. Hydrogen could help decarbonise fuel-dependent sectors such as heat industry or transportation. The aim of this study was to determine whether BHCCS could possibly deliver net negative CO2 emissions making comparisons against the other BECCS technologies.
High-Order Perturbation Solutions to a Lh2 Spreading Model With Continuous Spill
Sep 2011
Publication
High-order perturbation solutions have been obtained for the simple physical model describing the LH2 spreading with a continuous spill and are shown to improve over the first-order perturbation solutions. The non-dimensional governing equations for the model are derived to obtain more general solutions. Non-dimensional parameters are sought as the governing parameters for the non-dimensional equations and the non-dimensional evaporation rate is used as the perturbation parameter. The results show that the second-order solutions exhibit an improvement over the first-order solutions with respect to the pool volume; however there is still a difference between numerical solutions and second-order solutions in the late stage of spread. Finally it is revealed that the third-order solutions almost agree with numerical solutions.
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.
Hydrogen Explosions in 20’ ISO Container
Oct 2015
Publication
This paper describes a series of explosion experiments in inhomogeneous hydrogen air clouds in a standard 20′ ISO container. Test parameter variations included nozzle configuration jet direction reservoir back pressure time of ignition after release and degree of obstacles. The paper presents the experimental setup resulting pressure records and high speed videos. The explosion pressures from the experiments without obstacles were in the range of 0.4–7 kPa. In the experiments with obstacles the gas exploded more violently producing pressures in order of 100 kPa.
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