Germany
Assessment of Hydrogen Quality Dispensed for Hydrogen Refuelling Stations in Europe
Dec 2020
Publication
The fuel quality of hydrogen dispensed from 10 refuelling stations in Europe was assessed. Representative sampling was conducted from the nozzle by use of a sampling adapter allowing to bleed sample gas in parallel while refuelling an FCEV. Samples were split off and distributed to four laboratories for analysis in accordance with ISO 14687 and SAE J2719. The results indicated some inconsistencies between the laboratories but were still conclusive. The fuel quality was generally good. Elevated nitrogen concentrations were detected in two samples but not in violation with the new 300 μmol/mol tolerance limit. Four samples showed water concentrations higher than the 5 μmol/mol tolerance limit estimated by at least one laboratory. The results were ambiguous: none of the four samples showed all laboratories in agreement with the violation. One laboratory reported an elevated oxygen concentration that was not corroborated by the other two laboratories and thus considered an outlier.
Hydrogen Fueling Standardization: Enabling ZEVs with "Same as Today" Fueling and FCEV Range and Safety
Oct 2015
Publication
Zero Emission Vehicles (ZEVs) are necessary to help reduce the emissions in the transportation sector which is responsible for 40% of overall greenhouse gas emissions. There are two types of ZEVs Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs) Commercial Success of BEVs has been challenging thus far also due to limited range and very long charging duration. FCEVs using H2 infrastructure with SAE J2601 and J2799 standards can be consistently fuelled in a safe manner fast and resulting in a range similar to conventional vehicles. Specifically fuelling with SAE J2601 with the SAE J2799 enables FCEVs to fill with hydrogen in 3-5 minutes and to achieve a high State of Charge (SOC) resulting in 300+ mile range without exceeding the safety storage limits. Standardized H2 therefore gives an advantage to the customer over electric charging. SAE created this H2 fuelling protocol based on modelling laboratory and field tests. These SAE standards enable the first generation of commercial FCEVs and H2 stations to achieve a customer acceptable fueling similar to today's experience. This report details the advantages of hydrogen and the validation of H2 fuelling for the SAE standards.
A Comparison Exercise on the CFD Detonation Simulation in Large Scale Confined Volumes
Sep 2009
Publication
The use of hydrogen as an energy carrier is going to widen exponentially in the next years. In order to ensure the public acceptance of the new fuel not only the environmental impact has to be excellent but also the risk management of its handling and storage must be improved. As a part of modern risk assessment procedure CFD modeling of the accident scenario development must provide reliable data on the possible pressure loads resulted from explosion processes. The expected combustion regimes can be ranged from slow flames to deflagration-to-detonation transition and even to detonation. In the last case the importance of the reliability of simulation results is particularly high since detonation is usually considered as a worst case state of affairs. A set of large-scale detonation experiments performed in Kurchatov Institute at RUT facility was selected as benchmark. RUT has typical industry-relevant characteristic dimensions. The CFD codes possibilities to correctly describe detonation in mixtures with different initial and boundary conditions were surveyed. For the modeling two detonation tests HYD05 and HYD09 were chosen; both tests were carried out in uniform hydrogen/air mixtures; first one with concentration of 20.0% vol. and the second one with 25.5% vol. In the present exercise three CFD codes using a number of different models were used to simulate these experiments. A thorough inter-comparison between the CFD results including codes models and obtained pressure predictions was carried out and reported. The results of this inter comparison should provide a solid basis for the further code development and detonation models’ validation thus improving CFD predictive capabilities.
Analysis of Transient Supersonic Hydrogen Release, Dispersion and Combustion
Sep 2017
Publication
A hydrogen leak from a facility which uses highly compressed hydrogen gas (714 bar 800 K) during operation was studied. The investigated scenario involves supersonic hydrogen release from a 10 cm2 leak of the pressurized reservoir turbulent hydrogen dispersion in the facility room followed by an accidental ignition and burn-out of the resulting H2-air cloud. The objective is to investigate the maximum possible flame velocity and overpressure in the facility room in case of a worst-case ignition. The pressure loads are needed for the structural analysis of the building wall response. The first two phases namely unsteady supersonic release and subsequent turbulent hydrogen dispersion are simulated with GASFLOW-MPI. This is a well validated parallel all-speed CFD code which solves the compressible Navier-Stokes equations and can model a broad range of flow Mach numbers. Details of the shock structures are resolved for the under-expanded supersonic jet and the sonic-subsonic transition in the release. The turbulent dispersion phase is simulated by LES. The evolution of the highly transient burnable H2-air mixture in the room in terms of burnable mass volume and average H2-concentration is evaluated with special sub-routines. For five different points in time the maximum turbulent flame speed and resulting overpressures are computed using four published turbulent burning velocity correlations. The largest turbulent flame speed and overpressure is predicted for an early ignition event resulting in 35–71 m/s and 0.13–0.27 bar respectively.
Numerical Study of the Detonation Benchmark using GASFLOW-MPI
Sep 2019
Publication
Hydrogen has been widely used as an energy carrier in recent years. It should a better understand of the potential hydrogen risk under the unintended release of hydrogen scenario since the hydrogen could be ignited in a wide range of hydrogen concentrations in the air and generate a fast flame speed. During the accidental situation the hydrogen-air detonation may happen in the large-scale space which is viewed as the worst case state of affairs. GASFLOW-MPI is a powerful CFD-based numerical tool to predict the complicated hydrogen turbulent transport and combustion dynamics behaviours in the three-dimensional large-scale industrial facility. There is a serious of well-developed physical models in GASFLOW-MPI to simulate a wide spectrum of combustion behaviours ranging from slow flames to deflagration-to-detonation transition and even to detonation. The hydrogen–air detonation experiment which was carried out at the RUT tunnel facility is a well-known benchmark to validate the combustion model. In this work a numerical study of the detonation benchmark at RUT tunnel facility is performed using the CFD code GASFLOW-MPI. The complex shock wave structures in the detonation are captured accurately. The experimental pressure records and the simulated pressure dynamics are compared and discussed.
Experiments on the Combustion Behaviour of Hydrogen-Carbon Monoxide-Air Mixtures
Sep 2019
Publication
As a part of a German nuclear safety project on the combustion behaviour of hydrogen-carbon monoxide-air mixtures small scale experiments were performed to determine the lower flammability limit and the laminar burning velocity of such mixtures. The experiments were performed in a spherical explosion bomb with a free volume of 8.2 litre. The experimental set-up is equipped with a central spark ignition and quartz glass windows for optical access. Further instrumentation included pressure and temperature sensors as well as high-speed shadow-videography. A wide concentration range for both fuel gases was investigated in numerous experiments from the lower flammability limits up to the stoichiometric composition of hydrogen carbon monoxide and air (H2-CO-air) mixtures. The laminar burning velocities were determined from the initial pressure increase after the ignition and by using high-speed videos taken during the experiments.
Prevention of Hydrogen Accumulation Inside the Vacuum Vessel Pressure Suppression System of the ITER Facility by Means of Passive Auto-catalytic Recombiners
Sep 2017
Publication
Hydrogen safety is a relevant topic for both nuclear fission and fusion power plants. Hydrogen generated in the course of a severe accident may endanger the integrity of safety barriers and may result in radioactive releases. In the case of the ITER fusion facility accident scenarios with water ingress consider the release of hydrogen into the suppression tank (ST) of the vacuum vessel pressure suppression system (VVPSS). Under the assumption of additional air ingress the formation of flammable gas mixtures may lead to explosions and safety component failure.<br/>The installation of passive auto-catalytic recombiners (PARs) inside the ST which are presently used as safety devices inside the containments of nuclear fission reactors is one option under consideration to mitigate such a scenario. PARs convert hydrogen into water vapor by means of passive mechanisms and have been qualified for operation under the conditions of a nuclear power plant accident since the 1990s.<br/>In order to support on-going hydrogen safety considerations simulations of accident scenarios using the CFD code ANSYS-CFX are foreseen. In this context the in-house code REKO-DIREKT is coupled to CFX to simulate PAR operation. However the operational boundary conditions for hydrogen recombination (e.g. temperature pressure gas mixture) of a fusion reactor scenario differ significantly from those of a fission reactor. In order to enhance the code towards realistic PAR operation a series of experiments has been performed in the REKO-4 facility with specific focus on ITER conditions. These specifically include operation under sub-atmospheric pressure (0.2–1.0 bar) gas compositions ranging from lean to rich H2/O2 mixtures and superposed flow conditions.<br/>The paper gives an overview of the experimental program presents results achieved and gives an outlook on the modelling approach towards accident scenario simulation.
Laser Powder Bed Fusion of WE43 in Hydrogen-argon-gas Atmosphere
Sep 2020
Publication
Growing demand for individual and especially complex parts with emphasis on biomedical or lightweight applications enhances the importance of laser powder bed fusion. Magnesium alloys offer both biocompatibility and low density but feature a very high melting point of oxide layers while the evaporation temperature of pure magnesium is much lower. This impedes adequate part quality and process reproducibility. To weaken this oxide layer and enhance processability a 2 %-hydrogen-argon-gas atmosphere was investigated. A machine system was modified to the use of the novel inert gas to determine the influence of gas atmosphere on hollow cuboids and solid cubes. While processing a 20.3 % decrease in structure width and 20.6 % reduction in standard deviation of the cuboids was determined. There was no significate influence on relative density of solid cubes although eight of the ten highest density specimen were fabricated with the hydrogen addition.
Experimental Study of Ignited Unsteady Hydrogen Jets into Air
Sep 2009
Publication
In order to simulate an accidental hydrogen release from the low pressure pipe system of a hydrogen vehicle a systematic study on the nature of transient hydrogen jets into air and their combustion behaviour was performed at the FZK hydrogen test site HYKA. Horizontal unsteady hydrogen jets with an amount of hydrogen up to 60 STP dm3 and initial pressures of 5 and 16 bar have been investigated. The hydrogen jets were ignited with different ignition times and positions. The experiments provide new experimental data on pressure loads and heat releases resulting from the deflagration of hydrogen-air clouds formed by unsteady turbulent hydrogen jets released into a free environment. It is shown that the maximum pressure loads occur for ignition in a narrow position and time window. The possible hazard potential arising from an ignited free transient hydrogen jet is described.
Ignition of Hydrogen Jet Fires from High Pressure Storage
Sep 2013
Publication
Highly transient jets from hydrogen high pressure tanks were investigated up to 30 MPa. These hydrogen jets might self-initiate when released from small orifices of high pressure storage facilities. The related effects were observed by high speed video technics including time resolved spectroscopy. Ignition flame head jet velocity flame contours pressure wave propagation reacting species and temperatures were evaluated. The evaluation used video cross correlation method BOS brightness subtraction and 1 dimensional image contraction to obtain traces of all movements. On burst of the rupture disc the combustion of the jet starts close to the nozzle on the outer shell of it at the boundary layer to the surrounding air. It propagates with a deceleration approximated by a drag force of constant value which is obtained by analysing the head velocity. The burning at the outer shell develops to an explosion converting a nearly spherical volume at the jet head the movement of the centroid is nearly unchanged and follows the jet front in parallel. The progress of the nearly spherical explosion could be evaluated on an averaged flame ball radius. An apparent flame velocity could be derived to be about 20 m/s. It seems to increase slightly on the pressure in the tank or the related initial jet momentum. Self-initiation is nearly always achieved especially induced the interaction of shock waves and their reflections from the orifice. The results are compared to thermodynamic calculations and radiation measurements. The combustion process is composed of a shell combustion of the jet cone at the bases with a superimposed explosion of the decelerating jet head volume.
Influence of Hydrogen-Based Storage Systems on Self-Consumption and Self-Sufficiency of Residential Photovoltaic Systems
Aug 2015
Publication
This paper analyzes the behavior of residential solar-powered electrical energy storage systems. For this purpose a simulation model based on MATLAB/Simulink is developed. Investigating both short-time and seasonal hydrogen-based storage systems simulations on the basis of real weather data are processed on a timescale of 15 min for a consideration period of 3 years. A sensitivity analysis is conducted in order to identify the most important system parameters concerning the proportion of consumption and the degree of self-sufficiency. Therefore the influences of storage capacity and of storage efficiencies are discussed. A short-time storage system can increase the proportion of consumption by up to 35 percentage points compared to a self-consumption system without storage. However the seasonal storing system uses almost the entire energy produced by the photovoltaic (PV) system (nearly 100% self-consumption). Thereby the energy drawn from the grid can be reduced and a degree of self-sufficiency of about 90% is achieved. Based on these findings some scenarios to reach self-sufficiency are analyzed. The results show that full self-sufficiency will be possible with a seasonal hydrogen-based storage system if PV area and initial storage level are appropriate.
Low Energy Hydrogen Sensor
Sep 2011
Publication
A new silicon-based hydrogen sensor for measurements at high concentrations near the lower flammable limit of hydrogen (40000 ppm) is presented. Due to operation at room temperature the power consumption of the sensor is smaller than that of other sensors on the market by several orders magnitude. Further development of the sensor system could lead to battery powered or even energy-independent operation. As sensor fabrication is based on semiconductor technology low-cost production can be achieved for the mass market. The sensor investigated showed good long-term stability combined with a fast response on the basis of cyclic thermal activations. This was demonstrated by a stress test that simulated the activation and measurement cycles experienced by the sensor in one year. Finite element method was used to further reduce the power consumption of the thermal activation. This resulted in an average power consumption of 2 × 10−6 W for the sensor activation.
Status of the Pre-normative Research Project PRESLHY for the Safe Use of LH2
Sep 2019
Publication
Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large scale transport and storage of hydrogen with higher densities and potentially better safety performance. Although the gas industry has good experience with LH2 only little experience is available for the new applications of LH2 as an energy carrier. Therefore the European FCH JU funded project PRESLHY conducts pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The work program consists of a preparatory phase where the state of the art before the project has been summarized and where the experimental planning was adjusted to the outcome of a research priorities workshop. The central part of the project consists of 3 phenomena oriented work packages addressing Release Ignition and Combustion with analytical approaches experiments and simulations. The results shall improve the general understanding of the behavior of LH2 in accidents and thereby enhance the state-of-the-art what will be reflected in appropriate recommendations for development or revision of specific international standards. The paper presents the status of the project at the middle of its terms.
Membrane Based Purification of Hydrogen System (MEMPHYS)
Feb 2019
Publication
A hydrogen purification system based on the technology of the electrochemical hydrogen compression and purification is introduced. This system is developed within the scope of the project MEMPHYS. Therefore the project its targets and the different work stages are presented. The technology of the electrochemical purification and the state of the art of hydrogen purification are described. Early measurements in the project have been carried out and the results are shown and discussed. The ability of the technology to recover hydrogen from a gas mixture can be recognized and an outlook into further optimizations shows the future potential. A big advantage is the simultaneous compression of the purified hydrogen up to 200 bar therefore facilitating the transportation and storage.
Hytunnel Project to Investigate the Use of Hydrogen Vehicles in Road Tunnels
Sep 2009
Publication
Hydrogen vehicles may emerge as a leading contender to replace today’s internal combustion engine powered vehicles. A Phenomena Identification and Ranking Table exercise conducted as part of the European Network of Excellence on Hydrogen Safety (HySafe) identified the use of hydrogen vehicles in road tunnels as a topic of important concern. An internal project called HyTunnel was duly established within HySafe to review identify and analyse the issues involved and to contribute to the wider activity to establish the true nature of the hazards posed by hydrogen vehicles in the confined space of a tunnel and their relative severity compared to those posed by vehicles powered by conventional fuels including compressed natural gas (CNG). In addition to reviewing current hydrogen vehicle designs tunnel design practice and previous research a programme of experiments and CFD modelling activities was performed for selected scenarios to examine the dispersion and explosion hazards potentially posed by hydrogen vehicles. Releases from compressed gaseous hydrogen (CGH2) and liquid hydrogen (LH2) powered vehicles have been studied under various tunnel geometries and ventilation regimes. The findings drawn from the limited work done so far indicate that under normal circumstances hydrogen powered vehicles do not pose a significantly higher risk than those powered by petrol diesel or CNG but this needs to be confirmed by further research. In particular obstructions at tunnel ceiling level have been identified as a potential hazard in respect to fast deflagration or even detonation in some circumstances which warrants further investigation. The shape of the tunnel tunnel ventilation and vehicle pressure relief device (PRD) operation are potentially important parameters in determining explosion risks and the appropriate mitigation measures.
Hydrogen Onboard Storage: An Insertion of the Probabilistic Approach Into Standards & Regulations?
Sep 2005
Publication
The growing attention being paid by car manufacturers and the general public to hydrogen as a middle and long term energy carrier for automotive purpose is giving rise to lively discussions on the advantages and disadvantages of this technology – also with respect to safety. In this connection the focus is increasingly and justifiably so on the possibilities offered by a probabilistic approach to loads and component characteristics: a lower weight obliged with a higher safety level basics for an open minded risk communication the possibility of a provident risk management the conservation of resources and a better and not misleading understanding of deterministic results. But in the case of adequate measures of standards or regulations completion there is a high potential of additional degrees of freedom for the designers obliged with a further increasing safety level. For this purpose what follows deals briefly with the terminological basis and the aspects of acceptance control conservation of resources misinterpretation of deterministic results and the application of regulations/standards.<br/>This leads into the initial steps of standards improvement which can be taken with relatively simple means in the direction of comprehensively risk-oriented protection goal specifications. By this it’s not focused on to provide to much technical details. It’s focused on the context of different views on probabilistic risk assessment. As main result some aspects of the motivation and necessity for the currently running pre-normative research studies within the 6th frame-work program of the EU will be shown.
Pool Spreading and Vaporization of Liquid Hydrogen
Sep 2005
Publication
An essential part of a safety analysis to evaluate the risks of a liquid hydrogen (LH2) containing system is the understanding of cryogenic pool spreading and its vaporization. It represents the initial step in an accident sequence with the inadvertent spillage of LH2 e.g. after failure of a transport container tank or the rupture of a pipeline. This stage of an accident scenario provides pertinent information as a source term for the subsequent analysis steps of atmospheric dispersion and at presence of an ignition source the combustion of the hydrogen-air vapor cloud. A computer model LAUV has been developed at the Research Center Juelich which is able to simulate the spreading and vaporization of a cryogenic liquid under various conditions such as different grounds (solid water). It is based on the so-called shallow-layer differential equations taking into account physical phenomena such as ice formation if the cryogen is spilled on a water surface. The presentation will give a description of the computer model and its validation against existing experimental data. Furthermore calculational results will be analyzed describing the prediction and quantification of the consequences of an LH2 spill for different cases. They also include the comparison of an LH2 spillage versus the corresponding release of other cryogens such as liquid natural gas liquid oxygen and liquid nitrogen.
Analysis of the Parametric-Acoustic Instability for Safety Assessment of Hydrogen-Air Mixtures in Closed Volumes
Sep 2011
Publication
The acoustic to the parametric instability has been studied for H2-air mixtures at normal conditions. Two approaches for the investigation of the problem have been considered. The simplified analytical model proposed by Bychkov was selected initially. Its range of applicability resulted to be very restricted and therefore numerical solutions of the problem were taken into account. The results obtained were used to study the existence of spontaneous transition from the acoustic to the parametric instability for different fuel concentrations. Finally the growth rate of the instabilities was numerically calculated for a set of typical mixtures for hydrogen safety.
Characterization of Materials in Pressurized Hydrogen Under Cyclic Loading at Service Conditions in Hydrogen Powered Engines
Sep 2005
Publication
A new testing device for cyclic loading of specimens with a novel shape design is presented. The device was applied for investigations of fatigue of metallic specimens under pressurized hydrogen up to 300 bar at temperatures up to 200 °C. Main advantage of the specimen design is the very small amount of medium here hydrogen used for testing. This allows experiments with hazardous substances at lower safety level. Additionally no gasket for the load transmission is required. Woehler curves which show the influence of hydrogen on the fatigue behaviour of austenitic steel specimens at relevant service conditions in hydrogen powered engines are presented. Material and test conditions are in agreement with the cooperating industry.
Venting Deflagrations of Local Hydrogen-air Mixture
Oct 2015
Publication
The paper describes a lumped-parameter model for vented deflagrations of localised and layered fuel air mixtures. Theoretical model background is described to allow insight into the model development with focus on lean mixtures and overpressures significantly below 0.1 MPa for protection of low strength equipment and buildings. Phenomena leading to combustion augmentation was accounted based on conclusions of recent CFD studies. Technique to treat layered mixtures with concentration gradient is demonstrated. The model is validated against 25 vented deflagration experiments with lean non-uniform and layered hydrogen-air mixtures performed in Health and Safety Laboratory (UK) and Karlsruhe Institute of Technology (Germany).
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