France
Validation of Selected Optical Methods for Assessing Polyethylene (PE) Liners Used in High Pressure Vessels for Hydrogen Storage
Jun 2021
Publication
A polyethylene (PE) liner is the basic element in high-pressure type 4 composite vessels designed for hydrogen or compressed natural gas (CNG) storage systems. Liner defects may result in the elimination of the whole vessel from use which is very expensive both at the manufacturing and exploitation stage. The goal is therefore the development of efficient non-destructive testing (NDT) methods to test a liner immediately after its manufacturing before applying a composite reinforcement. It should be noted that the current regulations codes and standards (RC&S) do not specify liner testing methods after manufacturing. It was considered especially important to find a way of locating and assessing the size of air bubbles and inclusions and the field of deformations in liner walls. It was also expected that these methods would be easily applicable to mass-produced liners. The paper proposes the use of three optical methods namely visual inspection digital image correlation (DIC) and optical fiber sensing based on Bragg gratings (FBG). Deformation measurements are validated with finite element analysis (FEA). The tested object was a prototype of a hydrogen liner for high-pressure storage (700 bar). The mentioned optical methods were used to identify defects and measure deformations.
Experimental Challenges in Studying Hydrogen Absorption in Ultrasmall Metal Nanoparticles
Jun 2016
Publication
Recent advances on synthesis characterization and hydrogen absorption properties of ultrasmall metal nanoparticles (defined here as objects with average size ≤3 nm) are briefly reviewed in the first part of this work. The experimental challenges encountered in performing accurate measurements of hydrogen absorption in Mg- and noble metal-based ultrasmall nanoparticles are addressed. The second part of this work reports original results obtained for ultrasmall bulk-immiscible Pd–Rh nanoparticles. Carbon-supported Pd–Rh nanoalloys in the whole binary chemical composition range have been successfully prepared by liquid impregnation method followed by reduction at 300°C. EXAFS investigations suggested that the local structure of these nanoalloys is partially segregated into Rh-rich core and Pd-rich surface coexisting within the same nanoparticles. Downsizing to ultrasmall dimensions completely suppresses the hydride formation in Pd-rich nanoalloys at ambient conditions contrary to bulk and larger nanosized (5–6 nm) counterparts. The ultrasmall Pd90Rh10 nanoalloy can absorb hydrogen-forming solid solutions under these conditions as suggested by in situ X-ray diffraction (XRD). Apart from this composition common laboratory techniques such as in situ XRD DSC and PCI failed to clarify the hydrogen interaction mechanism: either adsorption on developed surfaces or both adsorption and absorption with formation of solid solutions. Concluding insights were brought by in situ EXAFS experiments at synchrotron: ultrasmall Pd75Rh25 and Pd50Rh50 nanoalloys absorb hydrogen-forming solid solutions at ambient conditions. Moreover the hydrogen solubility in these solid solutions is higher with increasing Pd content and this trend can be understood in terms of hydrogen preferential occupation in the Pd-rich regions as suggested by in situ EXAFS. The Rh-rich nanoalloys (Pd25Rh75 and Pd10Rh90) only adsorb hydrogen on the developed surface of ultrasmall nanoparticles. In summary in situ characterization techniques carried out at large-scale facilities are unique and powerful tools for in-depth investigation of hydrogen interaction with ultrasmall nanoparticles at local level.
Building an Optimal Hydrogen Transportation System for Mobility, Focus on Minimizing the Cost of Transportation via Truck
Jan 2018
Publication
The approach developed aims to identify the methodology that will be used to deliver the minimum cost for hydrogen infrastructure deployment using a mono-objective linear optimisation. It focuses on minimizing both capital and operation costs of the hydrogen transportation based on transportation via truck which represents the main focus of this paper and a cost-minimal pipeline system in the case of France and Germany. The paper explains the mathematical model describing the link between the hydrogen production via electrolysers and the distribution for mobility needs. The main parameters and the assumed scenario framework are explained. Subsequently the transportation of hydrogen via truck using different states of aggregation is analysed as well as the transformation and storage of hydrogen. This is used finally to build a linear programming aiming to minimize the sum of costs of hydrogen transportation between the different nodes and transformation/storage within the nodes.
An Analysis of the Experiments Carried Out by HSL in the HyIndoor European Project Studying Accumulation of Hydrogen Released into a Semi-confined Enclosure
Oct 2015
Publication
Experimental work on hydrogen releases consequences in a 31-m3 semi-confined enclosure was performed in the framework of the collaborative European Hyindoor project. Natural ventilation effectiveness on hydrogen build-up limitation in a confined area was studied for several configurations of ventilation openings and of release conditions in real environmental conditions [1]; influence of wind on gas build-up was observed as well. This paper proposes a critical analysis of these experiments carried out by HSL and compares results with analytical approaches available in open scientific literature. The validity of these models in presence of wind was broached.
ISO 19880-1, Hydrogen Fueling Station and Vehicle Interface Safety Technical Report
Oct 2015
Publication
Hydrogen Infrastructures are currently being built up to support the initial commercialization of the fuel cell vehicle by multiple automakers. Three primary markets are presently coordinating a large build up of hydrogen stations: Japan; USA; and Europe to support this. Hydrogen Fuelling Station General Safety and Performance Considerations are important to establish before a wide scale infrastructure is established.
This document introduces the ISO Technical Report 19880-1 and summarizes main elements of the proposed standard. Note: this ICHS paper is based on the draft TR 19880 and is subject to change when the document is published in 2015. International Standards Organisation (ISO) Technical Committee (TC) 197 Working Group (WG) 24 has been tasked with the preparation of the ISO standard 19880-1 to define the minimum requirements considered applicable worldwide for the hydrogen and electrical safety of hydrogen stations. This report includes safety considerations for hydrogen station equipment and components control systems and operation. The following systems are covered specifically in the document as shown in Figure 1:
This document introduces the ISO Technical Report 19880-1 and summarizes main elements of the proposed standard. Note: this ICHS paper is based on the draft TR 19880 and is subject to change when the document is published in 2015. International Standards Organisation (ISO) Technical Committee (TC) 197 Working Group (WG) 24 has been tasked with the preparation of the ISO standard 19880-1 to define the minimum requirements considered applicable worldwide for the hydrogen and electrical safety of hydrogen stations. This report includes safety considerations for hydrogen station equipment and components control systems and operation. The following systems are covered specifically in the document as shown in Figure 1:
- H2 production / supply delivery system
- Compression
- Gaseous hydrogen buffer storage;
- Pre-cooling device;
- Gaseous hydrogen dispensers.
- Hydrogen Fuelling Vehicle Interface
High-Purity and Clean Syngas and Hydrogen Production From Two-Step CH4 Reforming and H2O Splitting Through Isothermal Ceria Redox Cycle Using Concentrated Sunlight
Jul 2020
Publication
The thermochemical conversion of methane (CH4) and water (H2O) to syngas and hydrogen via chemical looping using concentrated sunlight as a sustainable source of process heat attracts considerable attention. It is likewise a means of storing intermittent solar energy into chemical fuels. In this study solar chemical looping reforming of CH4 and H2O splitting over non-stoichiometric ceria (CeO2/CeO2−δ) redox cycle were experimentally investigated in a volumetric solar reactor prototype. The cycle consists of (i) the endothermic partial oxidation of CH4 and the simultaneous reduction of ceria and (ii) the subsequent exothermic splitting of H2O and the simultaneous oxidation of the reduced ceria under isothermal operation at ~1000°C enabling the elimination of sensible heat losses as compared to non-isothermal thermochemical cycles. Ceria-based reticulated porous ceramics with different sintering temperatures (1000 and 1400°C) were employed as oxygen carriers and tested with different methane flow rates (0.1–0.4 NL/min) and methane concentrations (50 and 100%). The impacts of operating conditions on the foam-averaged oxygen non-stoichiometry (reduction extent δ) syngas yield methane conversion solar-to-fuel energy conversion efficiency as well as the effects of transient solar conditions were demonstrated and emphasized. As a result clean syngas was successfully produced with H2/CO ratios approaching 2 during the first reduction step while high-purity H2 was subsequently generated during the oxidation step. Increasing methane flow rate and CH4 concentration promoted syngas yields up to 8.51 mmol/gCeO2 and δ up to 0.38 at the expense of enhanced methane cracking reaction and reduced CH4 conversion. Solar-to-fuel energy conversion efficiency namely the ratio of the calorific value of produced syngas to the total energy input (solar power and calorific value of converted methane) and CH4 conversion were achieved in the range of 2.9–5.6% and 40.1–68.5% respectively.
CFD design of protective walls against the effects of vapor cloud fast deflagration of hydrogen
Oct 2015
Publication
Protective walls are a well-known and efficient way to mitigate overpressure effects of accidental explosions (detonation or deflagration). For detonation there are multiple published studies whereas for deflagration no well-adapted and rigorous method has been reported in the literature. This article describes the validation of a new modelling approach for fast deflagrations of H2. This approach includes two steps. At the first step the combustion phase of vapor cloud explosion (VCE) involving a fast deflagration is substituted by equivalent vessel burst problem. The purpose of this step is to avoid the reactive flow computations. At the second step CFD is used for computations of pressure propagation from the equivalent (non reactive) vessel burst problem. After verifying the equivalence of the fast deflagration and the vessel burst problem at the first step the capability of two CFD codes such as FLACS and Europlexus are examined for modelling of the vessel burst problem (with and without barriers). Finally the efficiency of finite and infinite barriers used for mitigation of the shock is investigated
An Extended Flamelet-based Presumed Probability Density Function for Predicting Mean Concentrations of Various Species in Premixed Turbulent Flames
Sep 2020
Publication
Direct Numerical Simulation (DNS) data obtained by Dave and Chaudhuri (2020) from a lean complex-chemistry hydrogen-air flame associated with the thin-reaction-zone regime of premixed turbulent burning are analyzed to perform a priori assessment of predictive capabilities of the flamelet approach for evaluating mean species concentrations. For this purpose dependencies of mole fractions and rates of production of various species on a combustion progress variable c obtained from the laminar flame are averaged adopting either the actual Probability Density Function (PDF) P (c) extracted from the DNS data or a common presumed β-function PDF. On the one hand the results quantitatively validate the flamelet approach for the mean mole fractions of all species including radicals but only if the actual PDF P (c) is adopted. The use of the β-function PDF yields substantially worse results for the radicals’ concentrations. These findings put modeling the PDF P (c) on the forefront of the research agenda. On the other hand the mean rate of product creation and turbulent burning velocity are poorly predicted even adopting the actual PDF. These results imply that in order to evaluate the mean species concentrations the flamelet approach could be coupled with another model that predicts the mean rate and turbulent burning velocity better. Accordingly the flamelet approach could be implemented as post-processing of numerical data yielded by that model. Based on the aforementioned findings and implications a new approach to building a presumed PDF is developed. The key features of the approach consist in (i) adopting a re-normalized flamelet PDF for intermediate values of c and (ii) directly using the mean rate of product creation to calibrate the presumed PDF. Capabilities of the newly developed PDF for predicting mean species concentrations are quantitively validated for all species including radicals.
LES Simulation of Buoyancy Jet From Unintended Hydrogen Release with GASFLOW-MPI
Sep 2017
Publication
Hydrogen leakage is a key safety issue for hydrogen energy application. For hydrogen leakage hydrogen releases with low momentum hence the development of the leakage jet is dominated by both initial momentum and buoyancy. It is important for a computational code to capture the flow characteristics transiting from momentum-dominated jet to buoyancy dominated plume during leakage. GASFLOW-MPI is a parallel computational fluid dynamics (CFD) code which is well validated and widely used for hydrogen safety analysis. In this paper its capability for small scale hydrogen leakage is validated with unintended hydrogen release experiment. In the experiment pure hydrogen is released into surrounding stagnant air through a jet tube on a honeycomb plate with various Froude numbers (Fr). The flow can be fully momentum-dominated at the beginning while the influence of buoyancy increases with the Fr decreases along the streamline. Several quantities of interest including velocity along the centerline radial profiles of the time-averaged H2 mass fraction are obtained to compare with experimental data. The good agreement between the numerical results and the experimental data indicates that GASFLOW-MPI can successfully simulate hydrogen turbulent dispersion driven by both momentum and buoyant force. Different turbulent models i.e. k-ε LES and DES model are analyzed for code performance the result shows that all these three models are adequate for hydrogen leakage simulation k-ε simulation is sufficient for industrial applications while LES model can be adopted for detail analysis for a jet/plume study like entrainment. The DES model possesses both characters of the former two model only the performance of its result depends on the grid refinement.
The Impact of Hydrogen on Mechanical Properties; A New In Situ Nanoindentation Testing Method
Feb 2019
Publication
We have designed a new method for electrochemical hydrogen charging which allows us to charge very thin coarse-grained specimens from the bottom and perform nanomechanical testing on the top. As the average grain diameter is larger than the thickness of the sample this setup allows us to efficiently evaluate the mechanical properties of multiple single crystals with similar electrochemical conditions. Another important advantage is that the top surface is not affected by corrosion by the electrolyte. The nanoindentation results show that hydrogen reduces the activation energy for homogenous dislocation nucleation by approximately 15–20% in a (001) grain. The elastic modulus also was observed to be reduced by the same amount. The hardness increased by approximately 4% as determined by load-displacement curves and residual imprint analysis.
Assessing the Environmental Impacts of Wind-based Hydrogen Production in the Netherlands Using Ex-ante LCA and Scenarios Analysis
Mar 2021
Publication
Two electrolysis technologies fed with renewable energy sources are promising for the production of CO2-free hydrogen and enabling the transition to a hydrogen society: Alkaline Electrolyte (AE) and Polymer Electrolyte Membrane (PEM). However limited information exists on the potential environmental impacts of these promising sustainable innovations when operating on a large-scale. To fill this gap the performance of AE and PEM systems is compared using ex-ante Life Cycle Assessment (LCA) technology analysis and exploratory scenarios for which a refined methodology has been developed to study the effects of implementing large-scale sustainable hydrogen production systems. Ex-ante LCA allows modelling the environmental impacts of hydrogen production exploratory scenario analysis allows modelling possible upscaling effects at potential future states of hydrogen production and use in vehicles in the Netherlands in 2050. A bridging tool for mapping the technological field has been created enabling the combination of quantitative LCAs with qualitative scenarios. This tool also enables diversity for exploring multiple sets of visions. The main results from the paper show with an exception for the “ozone depletion” impact category (1) that large-scale AE and PEM systems have similar environmental impacts with variations lower than 7% in all impact categories (2) that the contribution of the electrolyser is limited to 10% of all impact categories results and (3) that the origin of the electricity is the largest contributor to the environmental impact contributing to more than 90% in all impact categories even when renewable energy sources are used. It is concluded that the methodology was applied successfully and provides a solid basis for an ex-ante assessment framework that can be applied to emerging technological systems.
Calibration of Hydrogen Coriolis Flow Meters Using Nitrogen and Air and Investigation of the Influence of Temperature on Measurement Accuracy
Feb 2021
Publication
The performance of four Coriolis flow meters designed for use in hydrogen refuelling stations was evaluated with air and nitrogen by three members of the MetroHyVe JRP consortium; NEL METAS and CESAME EXADEBIT.<br/>A wide range of conditions were tested overall with gas flow rates ranging from (0.05–2) kg/min and pressures ranging from (20–86) bar. The majority of tests were conducted at nominal pressures of either 20 bar or 40 bar in order to match the density of hydrogen at 350 bar and 20 °C or 700 bar and −40 °C. For the conditions tested pressure did not have a noticeable influence on meter performance.<br/>When the flow meters were operated at ambient temperatures and within the manufacturer's recommended flow rate ranges errors were generally within ±1%. Errors within ±0.5% were achievable for the medium to high flow rates.<br/>The influence of temperature on meter performance was also studied with testing under both stable and transient conditions and temperatures as low as −40 °C.<br/>When the tested flow meters were allowed sufficient time to reach thermal equilibrium with the incoming gas temperature effects were limited. The magnitude and spread of errors increased but errors within ±2% were achievable at moderate to high flow rates. Conversely errors as high as 15% were observed in tests where logging began before temperatures stabilised and there was a large difference in temperature between the flow meter and the incoming gas.<br/>One of the flow meters tested with nitrogen was later installed in a hydrogen refuelling station and tested against the METAS Hydrogen Field Test Standard (HFTS). Under these conditions errors ranged from 0.47% to 0.91%. Testing with nitrogen at the same flow rates yielded errors of −0.61% to −0.82%.
Development of a Model Evaluation Protocol for CFD Analysis of Hydrogen Safety Issues – The SUSANA Project
Oct 2015
Publication
The “SUpport to SAfety aNAlysis of Hydrogen and Fuel Cell Technologies (SUSANA)” project aims to support stakeholders using Computational Fluid Dynamics (CFD) for safety engineering design and assessment of FCH systems and infrastructure through the development of a model evaluation protocol. The protocol covers all aspects of safety assessment modelling using CFD from release through dispersion to combustion (self-ignition fires deflagrations detonations and Deflagration to Detonation Transition - DDT) and not only aims to enable users to evaluate models but to inform them of the state of the art and best practices in numerical modelling. The paper gives an overview of the SUSANA project including the main stages of the model evaluation protocol and some results from the on-going benchmarking activities.
Experimental Measurements, CFD Simulations and Model for a Helium Release in a Two Vents Enclosure
Sep 2017
Publication
The present work proposes improvements on a model developed by Linden to predict the concentration distribution in a 2 vented cavities. Recent developments on non constant entrainment coefficient from Carazzo et al as well as a non constant pressure distribution at the vents-the vents being vertical-are included in the Linden approach. This model is compared with experimental results from a parametric study on the influence of the height of the release source on the helium dispersion regimes inside a naturally ventilated 2 vents enclosure. The varying parameters of the study were mainly the height of the release the releasing flow rate and the geometry of the vents. At last Large Eddy Simulations of the flow and Particle Image Velocimetry measurements performed on a small 2 vented cavity are presented. The objective is to have a better understanding of the flow structure which is at the origin of the 2 layers concentration distribution described by Linden.
The Impact of Hydrogen Admixture into Natural Gas on Residential and Commercial Gas Appliances
Jan 2022
Publication
Hydrogen as a carbon-free fuel is commonly expected to play a major role in future energy supply e.g. as an admixture gas in natural gas grids. Which impacts on residential and commercial gas appliances can be expected due to the significantly different physical and chemical properties of hydrogen-enriched natural gas? This paper analyses and discusses blends of hydrogen and natural gas from the perspective of combustion science. The admixture of hydrogen into natural gas changes the properties of the fuel gas. Depending on the combustion system burner design and other boundary conditions these changes may cause higher combustion temperatures and laminar combustion velocities while changing flame positions and shapes are also to be expected. For appliances that are designed for natural gas these effects may cause risk of flashback reduced operational safety material deterioration higher nitrogen oxides emissions (NOx) and efficiency losses. Theoretical considerations and first measurements indicate that the effects of hydrogen admixture on combustion temperatures and the laminar combustion velocities are often largely mitigated by a shift towards higher air excess ratios in the absence of combustion control systems but also that common combustion control technologies may be unable to react properly to the presence of hydrogen in the fuel.
Effect of the Time Dependent Loading of Type IV Cylinders Using a Multi-scalemodel
Sep 2019
Publication
The current requirements for composite cylinders are still based on an arbitrary approach derived from the behaviour of metal structures that the designed burst pressure should be at least 2.5 times the maximum in-service pressure. This could lead to an over-designed composite cylinder for which the weight saving would be less than optimum. Moreover predicting the lifetime of composite cylinders is a challenging task due to their anisotropic characteristics. A federal research institute in Germany (BAM) has proposed a minimum load-cycle requirement that mitigates this issue by using a MonteCarlo analysis of the burst test results. To enrich this study more experiments are required however they are normally limited by the necessity of long duration testing times (loading rate and number of cylinders) and the design (stacking sequence of the composite layer). A multi-scale model incorporating the micromechanical behaviour of composite structures has been developed at Mines ParisTech. The model has shown similar behaviour to that of composite cylinders under different loading rates. This indicates that the model could assist the Monte-Carlo analysis study. An evaluation of the multi-scale model therefore has been carried out to determine its limitations in predicting lifetimes of composite cylinders. The evaluation starts with the comparison of burst pressures with type IV composite cylinders under different loading rates. A μCT-Scan of a type IV cylinder has been carried out at the University of Southampton. The produced images were analysed using the Fast-Fourier Transform (FFT) technique to determine the configuration of the composite layers which is required by the model. Finally the time dependent effect studied by using the multi scale model has been described. In the long-term this study can be used to conduct a parametric study for creating more efficient design of type IV cylinders.
Highly Resolve Large Eddy Simulations of a Transitional Air-helium Buoyant Jet in a Two Vented Enclosure: Validation Against Particle Image Velocimetry Experiments
Sep 2017
Publication
The article deals with LES simulations of an air-helium buoyant jet in a two vented enclosure and their validation against particle image velocimetry experiments. The main objective is to test the ability of LES models to simulate such scenarios. These types of scenarios are of first interest considering safety studies for new hydrogen systems. Three main challenges are identified. The two first are the ability of the LES model to account for a rapid laminar-to-turbulence transition mainly due to the buoyancy accelerations and the Rayleigh-Taylor instabilities that can develop due to sharp density gradients. The third one is the outlet boundary conditions to be imposed on the vent surfaces. The influence of the classical pressure boundary condition is studied by comparing the simulations results when an exterior region is added in the simulations. The comparisons against particle image velocimetry experiments show that the use of an exterior domain gives more accurate results than the classical pressure boundary condition. This result and the description of the phenomena involved are the main outlets of the article.
Risk Informed Separation Distances For Hydrogen Refuelling Stations
Sep 2011
Publication
The lay-out requirements developed for hydrogen systems operated in industrial environment are not suitable for the operating conditions specific to hydrogen refuelling stations (service pressure of up to 95 MPa facility for public use). A risk informed rationale has been developed to define and substantiate separation distance requirements in ISO 20100 Gaseous hydrogen – refuelling stations [1]. In this approach priority is given to preventing escalation of small incidents into majors ones with a focus on critical exposures such as places of occupancy (fuelling station retail shop) while optimizing use of the available space from a risk perspective a key objective for being able to retrofit hydrogen refuelling in existing stations.
Numerical and Experimental Investigation of H2-air and H2-O2 Detonation Parameters in a 9 m Long Tube, Introduction of a New Detonation Model
Sep 2017
Publication
Experimental and numerical investigation of hydrogen-air and hydrogen-oxygen detonation parameters was performed. A new detonation model was introduced and validated against the experimental data. Experimental set-up consisted of 9 m long tube with 0.17 m in diameter where pressure was measured with piezoelectric transducers located along the channel. Numerical simulations were performed within OpenFoam code based on progress variable equation where the detonative source term accounts for autoignition effects. Autoignition delay times were computed at a simulation run-time with the use of a multivariate regression model where independent variables were: pressure temperature and fuel concentration. The dependent variable was the autoignition delay time. Range of the analyzed gaseous mixture composition varied between 20% and 50% of hydrogen-air and 50%–66% of hydrogen in oxygen. Simulations were performed using LES one-equation eddy viscosity turbulence model in 2D and 3D. Calculations were validated against experimental data.
Development of a Realistic Hydrogen Flammable Atmosphere Inside a 4-m3 Enclosure
Sep 2017
Publication
To define a strategy of mitigation for containerized hydrogen systems (fuel cells for example) against explosion the main characteristics of flammable atmosphere (size concentration turbulence…) shall be well-known. This article presents an experimental study on accidental hydrogen releases and dispersion into an enclosure of 4 m3 (2 m x 2 m x 1 m). Different release points are studied: two circular releases of 1 and 3 mm and a system to create ring-shaped releases. The releases are operated with a pressure between 10 and 40 bars in order to be close to the process conditions. Different positions of the release inside the enclosure i.e. centred on the floor or along a wall are also studied. A specific effort is made to characterize the turbulence in the enclosure during the releases. The objectives of the experimental study are to understand and quantify the mechanisms of formation of the explosive atmosphere taking into account the geometry and position of the release point and the confinement. Those experimental data are analyzed and compared with existing models and could bring some new elements to improve them.
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