France

The development of hydrogen as energy carrier is promoted by the increasing in energy demand depletion of fossil resources and the global warming. However this issue relies primarily on the safety aspect which requires the knowledge in the case of gas release of the quantities such as the flammable cloud size release path and the location of the lower flammability limit of the mixture. The integral models for predicting the atmospheric dispersion were extensively used in previous works for low pressure releases such as pollutant and  flammable gas transport. In the present investigation this approach is extended to the high pressure gas releases. The model is developed in the non-Boussinesq approximation and is based on Gaussian profiles for buoyant variable density jet or plume in stratified atmosphere with a crossflow. Validations have been performed on a broad range of hydrogen methane and air dispersion cases including vertical or horizontal jets or plumes into a quiescent atmosphere or with crosswind.

The first part of the present work is to validate a detailed kinetic mechanism for the oxidation of hydrogen – methane – air mixtures in a detonation waves. A series of experiments on auto-ignition delay times have been performed by shock tube technique coupled with emission spectrometry for H2 / CH4 / O2 mixtures highly diluted in argon. The CH4/H2 ratio was varied from 0 to 4 and the equivalence ratio from 0.4 up to 1. The temperature range was from 1250 K to 2000 K and the pressure behind reflected shock waves was between 0.15 and 1.6 MPa. A correlation was proposed between temperature (K) concentration of chemical species (mol m-3) and ignition delay times. The experimental auto-ignition delay times were compared to the modelled ones using four different mechanisms from the literature: GRI [22] Marinov et al. [23] Hughes et al. [24] Konnov [25]. A large discrepancy was generally found between the different models. The Konnov’s model that predicted auto-ignition delay times close to the measured ones has been selected to calculate the ignition delay time in the detonation waves. The second part of the study concerned the experimental determination of the detonation properties namely the detonation velocity and the cell size. The effect of the initial composition hydrogen to methane ratio and the amount of oxygen in the mixture as well as the initial pressure on the detonation velocity and on the cell size were investigated. The ratio of methane / (methane + hydrogen) varied between 0 and 0.6 for 2 different equivalence ratio (0.75 and 1) while the initial pressure was fixed to 10 kPa. A correlation was established between the characteristic cell size and the ignition delay time behind the leading shock of the detonation. It was clearly showed that methane has an important inhibitor effect on the detonation of these combustible mixtures.

This paper presents a compilation of the results supplied by HySafe partners participating in the Standard Benchmark Exercise Problem (SBEP) V2 which is based on an experiment on hydrogen combustion that is first described. A list of the results requested from participants is also included. The main characteristics of the models used for the calculations are compared in a very succinct way by using tables. The comparison between results together with the experimental data when available is made through a series of graphs. The results show quite good agreement with the experimental data. The calculations have demonstrated to be sensitive to computational domain size and far field boundary condition.

Abatement of greenhouse gas emissions and diversification of energy sources will probably lead to an economy based on hydrogen. In order to evaluate safety conditions during transport and distribution experimental data is needed on the detonation of Hydrogen/Natural gas blend mixtures. The aim of this study is to constitute detonation and deflagration to detonation transition (DDT) database of H2/CH4-air mixtures. More precisely the detonability of such mixtures is evaluated by the detonation cell size and the DDT run up distance measurements. Large experimental conditions are investigated (i) various equivalence ratios from 0.6 to 3 (ii) various H2 molar fraction x ( ( )2 2 4x H H CH= + ) from 0.5 to 1 (iii) different initial pressure P0 from 0.2 to 2 bar at fixed ambient temperature T0=293 K. Detonation pressures P velocities D and cell sizes ? were measured in two smooth tubes with different i.d. d (52 and 106 mm). For DDT data minimum DDT run up distances LDDT were determined in the d=52 mm tube containing a 2.8 m long Schelkin spiral with a blockage ratio BR = 0.5 and a pitch equal to the diameter. Measured detonation velocities D are very close to the Chapman Jouguet values (DCJ). Concerning the effect of detonation cell size ? follows a classical U shaped- curve with a minimum close to =1 and concerning the effect of x ? decreases when x increases. The ratio ik L?= obtained from different chemical kinetics (Li being the ZND induction length) is well approximated by the value 40 in the range 0.5 < x < 0.9 and 50 for x 0.9. Minimum DDT run up distance LDDT varies from 0.36 to 1.1m when x varies from 1 to 0.8. The results show that LDDT obeys the linear law LDDT ~ 30-40? previously validated in H2/Air mixtures. Adding Hydrogen in Natural Gas promotes the detonability of the mixtures and for x 0.65 these mixtures are considered more sensitive than common heavy Alkane-Air mixtures.

We report the development of new tools and methods for facile integration and meaningful representation of high throughput data generated by genome-wide analyses of the model cyanobacterium Synechocystis PCC6803 for future genetic engineering aiming at increasing its level of hydrogen photoproduction. These robust tools comprise new oligonucleotide DNA microarrays to monitor the transcriptomic responses of all 3725 genes of Synechocystis and the SVGMapping method and custom-made templates to represent the metabolic reprogramming for improved hydrogen production. We show for the first time that the AbrB2 repressor of the hydrogenase-encoding operon also regulates metal transport and protection against oxidative stress as well as numerous plasmid genes which have been overlooked so far. This report will stimulate the construction and global analysis of hydrogen production mutants with the prospect of developing powerful cell factories for the sustainable production of hydrogen as well as investigations of the probable role of plasmids in this process.

The lack of experimental data on hydrogen dispersion led to the experimental project DRIVE (Experimental Data for Hydrogen Automotive Risks Assessment for the validation of numerical tools and for the Edition of guidelines) that involves the CEA (French Atomic Energy Commission) the National Institute of Industrial Environment and Risks (INERIS) the French car manufacturer PSA PEUGEOT CITROËN and the Research Institute on Out of Equilibrium Phenomena (IRPHE). The CEA has developed an experimental setup named GARAGE in order to analyze the condition of formation of an explosive atmosphere in an enclosure. This is a full scale facility in which a real car can be parked. Hydrogen releases were simulated with helium which volume fraction was measured with mini-katharometers. These thermal conductivity probes allow spatial and time volume fraction variations measurements. We present experimental results on the dispersion of helium in the enclosure due to releases in a typical car. The tested parameters are the location of the source (engine bottom of the car storage) and the flow rate. Emphasis is put on the influence of these parameters on the time evolution of the volume fraction in the enclosure as well as on the vertical distribution of helium.

Since the rapid development of hydrogen stationary and vehicle fuel cells the last decade it is of importance to improve the prediction of overpressure generated during an accidental explosion which could occur in a confined part of the system. To this end small-scale vented hydrogen–air explosions were performed in a transparent cubic enclosure with a volume of 3375 cm3. The flame propagation was followed with a high speed camera and the overpressure inside the enclosure was recorded using high frequency piezoelectric transmitters. The effects of vent area and ignition location on the amplitude of pressure peaks in the enclosed volume were investigated. Indeed vented deflagration generates several pressures peaks according to the configuration and each peak can be the dominating pressure. The parametric study concerned three ignition locations and five square vent sizes.

In case of severe accidents in Pressurized Water Reactors a great amount of hydrogen can be released the resulting heterogeneous gaseous mixture (hydrogen-air-steam) can be flammable or inert and the pressure effects could alter the confinement of the reactor. Water spray systems have been designed in order to reduce overpressures in the containment but the presence of water droplets could enhance flame propagation through turbulence or generate flammable mixtures since the steam present in the vessel could condense on the droplets and could not inert the mixture anymore. However beneficial effects would be heat sinks and homogenization of mixtures. On-going work is devoted to the modelling of the interaction between fine water droplets and a hydrogen-air flame. We present in this paper an unsteady Lumped Parameter model in detail with a special focus on hydrogen-air flame propagation in the presence of water droplets. The effects of the initial concentration of droplets steam and hydrogen concentrations on flame propagation are discussed in the paper and a comparison between this model and our previous steady Lumped-Parameter model highlights the features of the unsteady approach. This physical model can serve as a validation tool for a CFD modelling. The results will be further validated against experimental data.

Energy Technology Perspectives 2020 is a major new IEA publication focused on the technology needs and opportunities for reaching international climate and sustainable energy goals. This flagship report offers vital analysis and advice on the clean energy technologies the world needs to meet net-zero emissions objectives.

The report’s comprehensive analysis maps out the technologies needed to tackle emissions in all parts of the energy sector including areas where technology progress is still lacking such as long-distance transport and heavy industries. It shows the amount of emissions reductions that are required from electrification hydrogen bioenergy and carbon capture utilisation and storage. It also provides an assessment of emissions from existing infrastructure and what can be done to address them.

Link to Document on IEA website

Photoanodes comprising a transparent glass substrate coated with a thin conductive film of fluorine-doped tin oxide (FTO) and a thin layer of a photoactive phase have been fabricated and tested with regard to the photo-electro-oxidation of water into molecular oxygen. The photoactive layer was made of a mat of TiO₂ nanorods (TDNRs) of micrometric thickness. Individual nanorods were successfully photosensitized with nanoparticles of a metal–organic framework (MOF) of nickel and 12-benzene dicarboxylic acid (BDCA). Detailed microstructural information was obtained from SEM and TEM analysis. The chemical composition of the active layer was determined by XRD XPS and FTIR analysis. Optical properties were determined by UV–Vis spectroscopy. The water photooxidation activity was evaluated by linear sweep voltammetry and the robustness was assessed by chrono-amperometry. The OER (oxygen evolution reaction) photo-activity of these photoelectrodes was found to be directly related to the amount of MOF deposited on the TiO₂ nanorods and was therefore maximized by adjusting the MOF content. The microscopic reaction mechanism which controls the photoactivity of these photoelectrodes was analyzed by photo-electrochemical impedance spectroscopy. Microscopic rate parameters are reported. These results contribute to the development and characterization of MOF-sensitized OER photoanodes.