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).
Hydrogen Release from a High-Pressure Gh2 Reservoir in Case of a Small Leak
Sep 2009
Publication
High-pressure GH2 systems are of interest for storage and distribution of hydrogen. The dynamic blow-down process of a high-pressure GH2 reservoir in case of a small leak is a complex process involving a chain of distinct flow regimes and gas states which needs to be understood for safety investigations.<br/>This paper presents models to predict the hydrogen concentration and velocity field in the vicinity of a postulated small leak. An isentropic expansion model with a real gas equation of state for normal hydrogen is used to calculate the time dependent gas state in the reservoir and at the leak position. The subsequent gas expansion to 0.1 MPa is predicted with a zero-dimensional model. The gas conditions after expansion serve as input to a newly developed integral model for a round free turbulent H2-jet into ambient air. The model chain was evaluated by jet experiments with sonic hydrogen releases from different reservoir pressures and temperatures.<br/>Predictions are made for the blow-down of hydrogen reservoirs with 10 30 and 100 MPa initial pressure. The evolution of the pressure in the reservoir and of the H2 mass flux at the orifice are presented in dimensionless form which allows scaling to other system dimensions and initial gas conditions. Computed hydrogen concentrations and masses in the jet are given for the 100 MPa case. A normalized hydrogen concentration field in the free jet is presented which allows for a given leak scenario the prediction of the axial and radial range of burnable H2-air mixtures.
Effects of Radiation on the Flame Front of Hydrogen-air Explosions
Oct 2015
Publication
The flame velocities of unconfined gas explosions depend on the cloud size and the distance from the initiating source. The mechanisms for this effect are not fully understood; a possible explanation is turbulence generated by the propagating flame front. The molecular bands in the flame front are exposed to continuously increasing radiation intensity of water bands in the interior of the reaction product ball. A first approach to verifying this assumption is described in this paper. The flame propagation was observed by high speed video techniques including time resolved spectroscopy in the UV-Vis-NIR spectral range with a time resolution up to 3000 spectra/s. Ignition flame head velocity flame contours reacting species and temperatures were evaluated. The evaluation used video brightness subtraction and 1-dimensional image contraction to obtain traces of the movements perpendicular to the direction of propagation. Flame front velocities are found to be between 16m/s and 25 m/s. Analysis focused in particular on the flame front which is not smooth. Salients emerge on the surface to result in the well-known cellular structures. The radiation of various bands from the fire ball on the reacting species is estimated to have an influence on the flame velocity depending on the distance from initiation. Evaluation of OH-band and water band spectra might indicate might indicate higher temperatures of the flame front induced by radiation of the fireball. But it is difficult to verify the effect relative to competing flame acceleration mechanisms.
Hyper Experiments on Catastrophic Hydrogen Releases Inside a Fuel Cell Enclosure
Sep 2009
Publication
As a part of the experimental work of the EC-funded project HYPER Pro-Science GmbH performed experiments to evaluate the hazard potential of a severe hydrogen leakage inside a fuel cell cabinet. During this study hydrogen distribution and combustion experiments were performed using a generic enclosure model with the dimensions of the fuel cell "Penta H2" provided by ARCOTRONICS (now EXERGY Fuel Cells) to the project partner UNIPI for their experiments on small foreseeable leaks. Hydrogen amounts of 1.5 to 15 g H2 were released within one second into the enclosure through a nozzle with an internal diameter of 8 mm. In the distribution experiments the effects of different venting characteristics and different amounts of internal enclosure obstruction on the hydrogen concentrations measured at fixed positions in- and outside the model were investigated. Based on the results of these experiments combustion experiments with ignition positions in- and outside the enclosure and two different ignition times were performed. BOS (Background-Oriented-Schlieren) observation combined with pressure and light emission measurements were performed to describe the characteristics and the hazard potential of the induced hydrogen combustions. The experiments provide new experimental data on the distribution and combustion behaviour of hydrogen that is released into a partly vented and partly obstructed enclosure with different venting characteristics.
Spontaneous Ignition Processes Due To High-Pressure Hydrogen Release in Air
Sep 2011
Publication
Spontaneous ignition processes due to the high-pressure hydrogen releases into air were investigated both experimentally and theoretically. Such processes reproduce accident scenarios of sudden expansion of pressurized hydrogen into the ambient atmosphere in cases of tube or valve rupture. High-pressure hydrogen releases in the range of initial pressures from 20 to 275 bar and with nozzle diameters of 0.5 – 4 mm have been investigated. Glass tubes and high-speed CCD camera were used for experimental study of self-ignition process. The problem was theoretically considered in terms of contact discontinuity for the case when spontaneous ignition of pressurized hydrogen due to the contact with hot pressurized air occurs. The effects of boundary layer and material properties are discussed in order to explain the minimum initial pressure of 25 bar leading to the self-ignition of hydrogen with air.
A New Technology for Hydrogen Safety: Glass Structures as a Storage System
Sep 2011
Publication
The storage of hydrogen poses inherent weight volume and safety obstacles. An innovative technology which allows for the storage of hydrogen in thin sealed glass capillaries ensures the safe infusion storage and controlled release of hydrogen gas under pressures up to 100 MPa. Glass is a non-flammable material which also guarantees high burst pressures. The pressure resistance of single and multiple capillaries has been determined for different glass materials. Borosilicate capillaries have been proven to have the highest pressure resistance and have therefore been selected for further series of advanced testing. The innovative storage system is finally composed of a variable number of modules. As such in the case of the release of hydrogen this modular arrangement allows potential hazards to be reduced to a minimum. Further advantage of a modular system is the arrangement of single modules in every shape and volume dependent on the final application. Therefore the typical locations of storage systems e.g. the rear of cars can be modified or shifted to places of higher safety and not directly involved in crashes. The various methods of refilling and releasing capillaries with compressed hydrogen the increase of burst pressures through pre-treatment as well as the theoretical analysis and experimental results of the resistance of glass capillaries will further be discussed in detail.
Hydrogen Combustion Experiments in a Vertical Semi-confined Channel
Sep 2017
Publication
Experiments in an obstructed semi-confined vertical combustion channel with a height of 6 m (cross-section 0.4 × 0.4 m) inside a safety vessel of the hydrogen test center HYKA at the Karlsruhe Institute of Technology (KIT) are reported. In the work homogeneous hydrogen-air-mixtures as well as mixtures with different well-defined H2-concentration gradients were ignited either at the top or at the bottom end of the channel. The combustion characteristics were recorded using pressure sensors and sensors for the detection of the flame front that were distributed along the complete channel length. In the tests slow subsonic and fast sonic deflagrations as well as detonations were observed and the conditions for the flame acceleration (FA) to speed of sound and deflagration-to-detonation transition (DDT) are compared with the results of similar experiments performed earlier in a larger semi-confined horizontal channel.
Visualisation of Jet Fires from Hydrogen Release
Sep 2009
Publication
In order to achieve a high level of safety while using hydrogen as a vehicle fuel the possible hazards must be estimated. Especially hydrogen release tests with defined ignition represent a very important way to characterize the basics of hydrogen combustion in a potential accident. So ICT participated on a hydrogen jet release campaign at HSL (Buxton) in 2008 to deploy their measurement techniques and evaluation methods to visualize jets ignition and subsequent flames. The following paper shows the application of high speed cinematography in combination with image processing techniques the Background Oriented Schlieren (BOS) and a difference method to visualize the shape of hydrogen jet. In addition these methods were also used to observe ignition and combustion zone after defined initiation. In addition the combustion zone was recorded by a fast spectral radiometer and a highspeed-IR-camera. The IR-camera was synchronized with a rotating filter wheel to generate four different motion pictures at 100Hz each on a defined spectral range. The results of this preliminary evaluation provide some detailed information that might be used for improving model predictions.
Evaluation of an Improved Vented Deflagration CFD Model Against Nine Experimental Cases
Sep 2019
Publication
In the present work a newly developed CFD deflagration model incorporated into the ADREA-HF code is evaluated against hydrogen vented deflagrations experiments carried out by KIT and FM-Global in a medium (1 m3) and a real (63.7 m3) scale enclosure respectively. A square vent of 0.5 m2 and 5.4 m2 respectively is located in the center of one of side walls. In the case of the medium scale enclosure the 18% v/v homogeneous hydrogen-air mixture and back-wall ignition case is examined. In the case of the real scale enclosure the examined cases cover different homogeneous mixture concentrations (15% and 18% v/v) different ignition locations (back-wall and center) and different levels of initial turbulence. The CFD model accounts for flame instabilities that develop as the flame propagates inside the chamber and turbulence that mainly develops outside the vent. Pressure predictions are compared against experimental measurements revealing a very good performance of the CFD model for the back-wall ignition cases. For the center ignition cases the model overestimates the maximum overpressure. The opening of the vent cover is identified as a possible reason for the overprediction. The analysis indicates that turbulence is the main factor which enhances external explosion strength causing the sudden pressure increase confirming previous findings.
HYDRIDE4MOBILITY: An EU HORIZON 2020 Project on Hydrogen Powered Fuel Cell Utility Vehicles Using Metal Hydrides in Hydrogen Storage and Refuelling Systems
Feb 2021
Publication
Volodymyr A. Yartys,
Mykhaylo V. Lototskyy,
Vladimir Linkov,
Sivakumar Pasupathi,
Moegamat Wafeeq Davids,
Gojmir Radica,
Roman V. Denys,
Jon Eriksen,
José Bellosta von Colbe,
Klaus Taube,
Giovanni Capurso,
Martin Dornheim,
Fahmida Smith,
Delisile Mathebula,
Dana Swanepoel,
Suwarno Suwarno and
Ivan Tolj
The goal of the EU Horizon 2020 RISE project 778307 “Hydrogen fuelled utility vehicles and their support systems utilising metal hydrides” (HYDRIDE4MOBILITY) is in addressing critical issues towards a commercial implementation of hydrogen powered forklifts using metal hydride (MH) based hydrogen storage and PEM fuel cells together with the systems for their refuelling at industrial customers facilities. For these applications high specific weight of the metallic hydrides has an added value as it allows counterbalancing of a vehicle with no extra cost. Improving the rates of H2 charge/discharge in MH on the materials and system level simplification of the design and reducing the system cost together with improvement of the efficiency of system “MH store-FC” is in the focus of this work as a joint effort of consortium uniting academic teams and industrial partners from two EU and associated countries Member States (Norway Germany Croatia) and two partner countries (South Africa and Indonesia).<br/>The work within the project is focused on the validation of various efficient and cost-competitive solutions including (i) advanced MH materials for hydrogen storage and compression (ii) advanced MH containers characterised by improved charge-discharge dynamic performance and ability to be mass produced (iii) integrated hydrogen storage and compression/refuelling systems which are developed and tested together with PEM fuel cells during the collaborative efforts of the consortium.<br/>This article gives an overview of HYDRIDE4MOBILITY project focused on the results generated during its first phase (2017–2019).
Modeling of the Flame Acceleration in Flat Layer for Hydrogen-air Mixtures
Sep 2011
Publication
The flame propagation regimes for the stoichiometric hydrogen-air mixtures in an obstructed semiconfined flat layer have been numerically investigated in this paper. Conditions defining fast or sonic propagation regime were established as a function of the main dimensions characterizing the system and the layout of the obstacles. It was found that the major dependencies were the following: the thickness of the layer of H2-air mixture the blockage ratio and the distance between obstacles and the obstacle size. A parametric study was performed to determine the combination of the above variables prone to produce strong combustions. Finally a criterion that separates experiments resulting in slow subsonic from fast sonic propagations regimes was proposed.
Mechanism of Action of Polytetrafluoroethylene Binder on the Performance and Durability of High-temperature Polymer Electrolyte Fuel Cells
Feb 2021
Publication
In this work new insights into impacts of the polytetrafluoroethylene (PTFE) binder on high temperature polymer electrolyte fuel cells (HT-PEFCs) are provided by means of various characterizations and accelerated stress tests. Cathodes with PTFE contents from 0 wt% to 60 wt% were fabricated and compared using electrochemical measurements. The results indicate that the cell with 10 wt% PTFE in the cathode catalyst layer (CCL) shows the best performance due to having the lowest mass transport resistance and cathode protonic resistance. Moreover cyclic voltammograms show that Pt (100) edge and corner sites are significantly covered by PTFE and phosphate anions when the PTFE content is higher than 25 wt%. Open-circuit and low load-cycling conditions are applied to accelerate degradation processes of the HT-PEFCs. The PTFE binder shows a network structure in the pores of the catalyst layer which reduces phosphoric acid leaching during the aging tests. In addition the high binder HT-PEFCs more easily suffer from a mass transport problem leading to more severe performance degradation.
Experiments on Flame Acceleration and DDT for Stoichiometric Hydrogen/Air Mixture in a Thin Layer Geometry
Sep 2017
Publication
A series of experiments in a thin layer geometry performed at the HYKA test site of the KIT. The experiments on different combustion regimes for lean and stoichiometric H2/air mixtures were performed in a rectangular chamber with dimensions of 20 x 90 x h cm3 where h is the thickness of the layer (h = 1 2 4 6 8 10 mm). Three different layer geometries:
- a smooth channel without obstructions;
- the channel with a metal grid filled 25% of length and
- a metal grid filled 100% of length.
Numerical Study on the Influence of Different Boundary Conditions on the Efficiency of Hydrogen Recombiners Inside a Car Garage
Oct 2015
Publication
Passive auto-catalytic recombiners (PARs) have the potential to be used in the future for the removal of accidentally released hydrogen inside confined areas. PARs could be operated both as stand-alone or backup safety devices e.g. in case of active ventilation failure.
Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.
In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.
As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.
Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.
In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.
As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.
Hydrogen Storage Using a Hot Pressure Swing Reactor
Jun 2017
Publication
Our contribution demonstrates that hydrogen storage in stationary Liquid Organic Hydrogen Carrier (LOHC) systems becomes much simpler and significantly more efficient if both the LOHC hydrogenation and the LOHC dehydrogenation reaction are carried out in the same reactor using the same catalyst. The finding that the typical dehydrogenation catalyst for hydrogen release from perhydro dibenzyltoluene (H18-DBT) Pt on alumina turns into a highly active and very selective dibenzyltoluene hydrogenation catalyst at temperatures above 220 °C paves the way for our new hydrogen storage concept. Herein hydrogenation of H0-DBT and dehydrogenation of H18-DBT is carried out at the same elevated temperature between 290 and 310 °C with hydrogen pressure being the only variable for shifting the equilibrium between hydrogen loading and release. We demonstrate that the heat of hydrogenation can be provided at a temperature level suitable for effective dehydrogenation catalysis. Combined with a heat storage device of appropriate capacity or a high pressure steam system this heat could be used for dehydrogenation.
The Slow Burst Test as a Method for Probabilistic Quantification of Cylinder Degradation
Sep 2013
Publication
"The current practise of focusing the periodic retesting of composite cylinders primarily on the hydraulic pressure test has to be evaluated as critical - with regard to the damage of the specimen as well as in terms of their significance. This is justified by micro damages caused to the specimen by the test itself and by a lack of informative values. Thus BAM Federal Institute of Materials Research and Testing (Germany) uses a new approach of validation of composite for the determination of re-test periods. It enables the description of the state of a population of composite cylinders based on destructive tests parallel to operation.<br/>An essential aspect of this approach is the prediction of residual safe service life. In cases where it cannot be estimated by means of hydraulic load cycle tests as a replacement the creep or burst test remains. As a combination of these two test procedures BAM suggests the ""slow burst test SBT"". On this a variety of about 150 burst test results on three design types of cylinders with plastic liners are presented. For this purpose both the parameters of the test protocol as well as the nature and intensity of the pre-damage artificially aged test samples are analysed statistically. This leads first to an evaluation of the different types of artificial ageing but also to the clear recommendation that conventional burst tests be substituted totally if indented for assessment of composite pressure receptacles."
Review and Assessment of the Effect of Hydrogen Gas Pressure on the Embrittlement of Steels in Gaseous Hydrogen Environment
Apr 2021
Publication
Hydrogen gas pressure is an important test parameter when considering materials for high-pressure hydrogen applications. A large set of data on the effect of hydrogen gas pressure on mechanical properties in gaseous hydrogen experiments was reviewed. The data were analyzed by converting pressures into fugacities (f) and by fitting the data using an f|n| power law. For 95% of the data sets |n| was smaller than 0.37 which was discussed in the context of (i) rate-limiting steps in the hydrogen reaction chain and (ii) statistical aspects. This analysis might contribute to defining the appropriate test fugacities (pressures) to qualify materials for gaseous hydrogen applications.
Safety Criteria for the Transport of Hydrogen in Permanently Mounted Composite Pressure Vessels
Sep 2019
Publication
The recent growth of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by battery vehicles or tube-trailers both in composite pressure vessels. As a transport regulation the ADR is applicable in Europe and adjoined regions and is used for national transport in the EU. This regulation provides requirements based on the behaviour of each individual pressure vessel regardless of the pressure of the transported hydrogen and relevant consequences resulting from generally possible worst case scenarios such as sudden rupture. In 2012 the BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national transport requirements concerning the “UN service life checks” etc. to consider the transported volume and pressure of gases. This results in a requirement that becomes more restrictive as the product of pressure and volume increases. In the studies presented here the safety measures for hydrogen road transport are identified and reviewed through a number of safety measures from countries including Japan the USA and China. Subsequently the failure consequences of using trailer vehicles the related risk and the chance are evaluated. A benefit-related risk criterion is suggested to add to regulations and to be defined as a safety goal in standards for hydrogen transport vehicles and for mounted pressure vessels. Finally an idea is given for generating probabilistic safety data and for highly efficient evaluation without a significant increase of effort.
Single-catalyst High-weight% Hydrogen Storage in an N-heterocycle Synthesized from Lignin Hydrogenolysis Products and Ammonia
Oct 2016
Publication
Large-scale energy storage and the utilization of biomass as a sustainable carbon source are global challenges of this century. The reversible storage of hydrogen covalently bound in chemical compounds is a particularly promising energy storage technology. For this compounds that can be sustainably synthesized and that permit high-weight% hydrogen storage would be highly desirable. Herein we report that catalytically modified lignin an indigestible abundantly available and hitherto barely used biomass can be harnessed to reversibly store hydrogen. A novel reusable bimetallic catalyst has been developed which is able to hydrogenate and dehydrogenate N-heterocycles most efficiently. Furthermore a particular N-heterocycle has been identified that can be synthesized catalytically in one step from the main lignin hydrogenolysis product and ammonia and in which the new bimetallic catalyst allows multiple cycles of high-weight% hydrogen storage.
Optimizing Mixture Properties for Accurate Laminar Flame Speed Measurement from Spherically Expanding Flame: Application to H2/O2/N2/He Mixtures
Sep 2019
Publication
The uncertainty on the laminar flame speed extracted from spherically expanding flames can be minimized by using large flame radius data for the extrapolation to zero stretch-rate. However at large radii the hydrodynamic and thermo-diffusive instabilities induce the formation of a complex cellular flame front and limit the range of usable data. In the present study we have employed the flame stability theory of Matalon to optimize the properties of the initial mixture so that transition to cellularity may occur at a pre-determined large radius. This approach was employed to measure the laminar flame speeds of H2/O2/N2/He mixtures with equivalence ratios from 0.6 to 2.0 at pressures of 50/80/100 kPa and a temperature of 300 K. For all the performed experiments the uncertainty related to the extrapolation to zero stretch-rate (performed with the linear curvature model) was below 2% as shown by the position of the data points in the (Lb/Rf;U Lb/Rf;L) plan where Lb is the burned Markstein length; and Rf;L and Rf;U are the flame radii at the lower and upper bounds of the extrapolation range. Comparison of the predictions of four chemical mechanisms with the present unstretched laminar flame speed data indicated an error below 10% for most conditions. In addition unsteady 1-D simulations performed with A-SURF demonstrated that the flame dynamical response to stretch rate could not be captured by the mechanisms. The present work indicates that although the stability theory of Matalon provides a well defined framework to optimize the mixture properties for improved flame speed measurement the uncertainty of some of the required parameters can result in largely over-estimated critical radius for cellularity onset which compromise the accuracy of the optimization procedure.
Modelling and Optimization of a Flexible Hydrogen-fueled Pressurized PEMFC Power Plant for Grid Balancing Purposes
Feb 2021
Publication
In a scenario characterized by an increasing penetration of non-dispatchable renewable energy sources and the need of fast-ramping grid-balancing power plants the EU project GRASSHOPPER aims to setup and demonstrate a highly flexible PEMFC Power Plant hydrogen fueled and scalable to MW-size designed to provide grid support.<br/>In this work different layouts proposed for the innovative MW-scale plant are simulated to optimize design and off-design operation. The simulation model details the main BoP components performances and includes a customized PEMFC model validated through dedicated experiments.<br/>The system may operate at atmospheric or mild pressurized conditions: pressurization to 0.7 barg allows significantly higher net system efficiency despite the increasing BoP consumptions. The additional energy recovery from the cathode exhaust with an expander gives higher net power and net efficiency adding up to 2%pt and reaching values between 47%LHV and 55%LHV for currents between 100% and 20% of the nominal value.
Anchoring of Turbulent Premixed Hydrogen/Air Flames at Externally Heated Walls
Oct 2020
Publication
A joint experimental and numerical investigation of turbulent flame anchoring at externally heated walls is presented. The phenomenon has primarily been studied for laminar flames and micro-combustion while this study focuses on large-scale applications and elevated Reynolds number flows. Therefore a novel burner design is developed and examined for a diverse set of operating conditions. Hydroxyl radical chemiluminescence measurements are employed to validate the numerical method. The numerical investigation evaluates the performance of various hydrogen/air kinetics Reynolds-averaged turbulence models and the eddy dissipation concept (EDC) as a turbulence-chemistry interaction model. Simulation results show minor differences between detailed chemical mechanisms but pronounced deviations for a reduced kinetic. The baseline k-ω turbulence model is assessed to most accurately predict flame front position and shape. Universal applicability of EDC modelling constants is contradicted. Conclusively the flame anchoring concept is considered a promising approach for pilot flames in continuous combustion devices.
Hydrogen Risk Analysis for a Generic Nuclear Containment Ventilation System
Oct 2015
Publication
Hydrogen safety issue in a ventilation system of a generic nuclear containment is studied. In accidental scenarios a large amount of burnable gas mixture of hydrogen with certain amount of oxygen is released into the containment. In case of high containment pressure the combustible mixture is further ventilated into the chambers and the piping of the containment ventilation system. The burnable even potentially detonable gas mixture could pose a risk to the structures of the system once being ignited unexpectedly. Therefore the main goal of the study is to apply the computational fluid dynamics (CFD) computer code – GASFLOW to analyze the distribution of the hydrogen in the ventilation system and to find how sensitive the mixture is to detonation in different scenarios. The CFD simulations manifest that a ventilation fan with sustained power supply can extinguish the hydrogen risk effectively. However in case of station blackout with loss of power supply to the fan hydrogen/oxygen mixture could be accumulated in the ventilation system. A further study proves that steam injection could degrade the sensitivity of the hydrogen mixture significantly.
Open-source Simulation of the Long-term Diffusion of Alternative Passenger Cars on the Basis of Investment Decisions of Private Persons
Feb 2021
Publication
Numerous studies have shown that a full electrification of passenger cars is needed to stay within the 1.5° C temperature rise. This article deals with the question of how the required shares of alternative vehicles can be achieved by the year 2050. In literature the preferred technology are battery electric vehicles as these are more energy efficient than hydrogen vehicles. To be able to demonstrate how alternative vehicles diffuse into the German market the passenger car investment behavior of private persons was investigated. For this purpose a discrete choice experiment (DCE) with 1921 participants was carried out empirically. The results of the DCE show that the investment costs in particular are important when choosing a vehicle. This is followed by the driving range fuel costs and vehicle type. Less important are the charging infrastructure and CO2 emissions of the vehicle. A CO2 tax is of least importance. The utility values of the DCE were used to simulate future market shares. For this purpose the open-source software Invest was developed and different scenarios were defined and calculated. This paper shows that conservative assumptions on attribute development leave a large gap until full electrification as conventional vehicles still account for around 62% of market shares in 2050. In order to achieve full electrification extreme efforts must be made targeting the technical and economic characteristics of the vehicles but also addressing person-related characteristics such as level of information the subjective norm or the technological risk attitude. A ban on new registrations of combustion engines from 2030 could also lead to a full electrification by 2050. An average annual increase in the market share of alternative vehicles of 2.4 percentage points is needed to achieve full electrification. Other important factors are measures that address the modal shift to other modes of transport (rail public transport car-sharing).
A Homogeneous Non-equilibrium Two-phase Critical Flow Model
Sep 2011
Publication
A non-equilibrium two-phase single-component critical (choked) flow model for cryogenic fluids is developed from first principle thermodynamics. Modern equations-of-state (EOS) based upon the Helmholtz free energy concepts are incorporated into the methodology. Extensive validation of the model is provided with the NASA cryogenic data tabulated for hydrogen methane nitrogen and oxygen critical flow experiments performed with four different nozzles. The model is used to develop a hydrogen critical flow map for stagnation states in the liquid and supercritical regions.
Decentral Hydrogen
Apr 2022
Publication
This concept study extends the power-to-gas approach to small combined heat and power devices in buildings that alternately operate fuel cells and electrolysis. While the heat is used to replace existing fossil heaters on-site the power is either fed into the grid or consumed via heatcoupled electrolysis to balance the grid power at the nearest grid node. In detail the power demand of Germany is simulated as a snapshot for 2030 with 100% renewable sourcing. The standard load profile is supplemented with additional loads from 100% electric heat pumps 100% electric cars and a fully electrified industry. The renewable power is then scaled up to match this demand with historic hourly yield data from 2018/2019. An optimal mix of photovoltaics wind biomass and hydropower is calculated in respect to estimated costs in 2030. Hydrogen has recently entered a large number of national energy roadmaps worldwide. However most of them address the demands of heavy industry and heavy transport which are more difficult to electrify. Hydrogen is understood to be a substitute for fossil fuels which would be continuously imported from non-industrialized countries. This paper focuses on hydrogen as a storage technology in an all-electric system. The target is to model the most cost-effective end-to-end use of local renewable energies including excess hydrogen for the industry. The on-site heat coupling will be the principal argument for decentralisation. Essentially it flattens the future peak from massive usage of electric heat pumps during cold periods. However transition speed will either push the industry or the prosumer approach in front. Batteries are tried out as supplementary components for short-term storage due to their higher round trip efficiencies. Switching the gas net to hydrogen is considered as an alternative to overcome the slow power grid expansions. Further decentral measures are examined in respect to system costs.
Local Degradation Effects in Automotive Size Membrane Electrode Assemblies Under Realistic Operating Conditions
Dec 2019
Publication
In automotive applications the operational parameters for fuel cell (FC) systems can vary over a wide range. To analyze their impact on fuel cell degradation an automotive size single cell was operated under realistic working conditions. The parameter sets were extracted from the FC system modelling based on on-road customer data. The parameter variation included simultaneous variation of the FC load gas pressures cell temperature stoichiometries and relative humidity. Current density distributions and the overall cell voltage were recorded in real time during the tests. The current densities were low at the geometric anode gas outlet and high at the anode gas inlet. After electrochemical tests post mortem analysis was conducted on the membrane electrode assemblies using scanning electron microscopy. The ex-situ analysis showed significant cathode carbon corrosion in areas associated with low current densities. This suggests that fuel starvation close to the anode outlet is the origin of the cathode electrode degradation. The results of the numerical simulations reveal high relative humidity at that region and therefore water flooding is assumed to cause local anode fuel starvation. Even though the hydrogen oxidation reaction has low kinetic overpotentials “local availability” of H2 plays a significant role in maintaining a homogeneous current density distribution and thereby in local degradation of the cathode catalyst layer. The described phenomena occurred while the overall cell voltage remained above 0.3 V. This indicates that only voltage monitoring of fuel cell systems does not contain straightforward information about this type of degradation.
Combustion Features of CH4/NH3/H2 Ternary Blends
Mar 2022
Publication
The use of so-called “green” hydrogen for decarbonisation of the energy and propulsion sectors has attracted considerable attention over the last couple of decades. Although advancements are achieved hydrogen still presents some constraints when used directly in power systems such as gas turbines. Therefore another vector such as ammonia can serve as a chemical to transport and distribute green hydrogen whilst its use in gas turbines can limit combustion reactivity compared to hydrogen for better operability. However pure ammonia on its own shows slow complex reaction kinetics which requires its doping by more reactive molecules thus ensuring greater flame stability. It is expected that in forthcoming years ammonia will replace natural gas (with ~ 90% methane in volume) in power and heat production units thus making the co-firing of ammonia/methane a clear path towards replacement of CH4 as fossil fuel. Hydrogen can be obtained from the precracking of ammonia thus denoting a clear path towards decarbonisation by the use of ammonia/hydrogen blends. Therefore ammonia/methane/hydrogen might be co-fired at some stage in current combustion units hence requiring a more intrinsic analysis of the stability emissions and flame features that these ternary blends produce. In return this will ensure that transition from natural gas to renewable energy generated e-fuels such as so-called “green” hydrogen and ammonia is accomplished with minor detrimentals towards equipment and processes. For this reason this work presents the analysis of combustion properties of ammonia/methane/hydrogen blends at different concentrations. A generic tangential swirl burner was employed at constant power and various equivalence ratios. Emissions OH*/NH*/NH2*/CH* chemiluminescence operability maps and spectral signatures were obtained and are discussed. The extinction behaviour has also been investigated for strained laminar premixed flames. Overall the change from fossils to e-fuels is led by the shift in reactivity of radicals such as OH CH CN and NH2 with an increase of emissions under low and high ammonia content. Simultaneously hydrogen addition improves operability when injected up to 30% (vol) an amount at which the hydrogen starts governing the reactivity of the blends. Extinction strain rates confirm phenomena found in the experiments with high ammonia blends showing large discrepancies between values at different hydrogen contents. Finally a 20/55/25% (vol) methane/ammonia/hydrogen blend seems to be the most promising at high equivalence ratios (1.2) with no apparent flashback low emissions and moderate formation of NH2/OH radicals for good operability.
A Concept to Support the Transformation from a Linear to Circular Carbon Economy: Net Zero emissions, Resource Efficiency and Conservation Through a Coupling of the Energy, Chemical and Waste Management Sectors
Dec 2017
Publication
Coal and carbon-containing waste are valuable primary and secondary carbon carriers. In the current dominant linear economy such carbon resources are generally combusted to produce electricity and heat and as a way to resolve a nation’s waste issue. Not only is this a wastage of precious carbon resources which can be chemically utilized as raw materials for production of other value-added goods it is also contrary to international efforts to reduce carbon emissions and increase resource efficiency and conservation. This article presents a concept to support the transformation from a linear ‘one-way cradle to grave manufacturing model’ toward a circular carbon economy. The development of new and sustainable value chains through the utilization of coal and waste as alternative raw materials for the chemical industry via a coupling of the energy chemical and waste management sectors offers a viable and future-oriented perspective for closing the carbon cycle. Further benefits also include a lowering of the carbon footprint and increasing resource efficiency and conservation of primary carbon resources. In addition technological innovations and developments that are necessary to support a successful sector coupling will be identified. To illustrate our concept a case analysis of domestic coal and waste as alternative feedstock to imported crude oil for chemical production in Germany will be presented. Last but not least challenges posed by path dependency along technological institutional and human dimensions in the sociotechnical system for a successful transition toward a circular carbon economy will be discussed.
Electrochemical and Mechanical Stability of Catalyst Layers in Anion Exchange Membrane Water Electrolysis
Dec 2021
Publication
Anion exchange membrane (AEM) water electrolysis is considered a promising solution to future cost reduction of electrochemically produced hydrogen. We present an AEM water electrolyzer with CuCoOx as the anode catalyst and Aemion as membrane and electrode binder. Full cell experiments in pure water and 0.1 M KOH revealed that the optimum binder content depended on the type of electrolyte employed. Online dissolution measurements suggested that Aemion alone was not sufficient to establish an alkaline environment for thermodynamically stabilizing the synthesized CuCoOx in a neutral electrolyte feed. A feed of base is thus indispensable to ensure the thermodynamic stability of such non-noble catalyst materials. Particle loss and delamination of the catalyst layer during MEA operation could be reduced by employing a heat treatment step after electrode fabrication. This work summarizes possible degradation pathways for low-cost anodes in AEMWE and mitigation strategies for enhanced system durability and performance.
Statistics, Lessons Learned and Recommendations from Analysis of HIAD 2.0 Database
Mar 2022
Publication
The manuscript firstly describes the data collection and validation process for the European Hydrogen Incidents and Accidents Database (HIAD 2.0) a public repository tool collecting systematic data on hydrogen-related incidents and near-misses. This is followed by an overview of HIAD 2.0 which currently contains 706 events. Subsequently the approaches and procedures followed by the authors to derive lessons learned and formulate recommendations from the events are described. The lessons learned have been divided into four categories including system design; system manufacturing installation and modification; human factors and emergency response. An overarching lesson learned is that minor events which occurred simultaneously could still result in serious consequences echoing James Reason's Swiss Cheese theory. Recommendations were formulated in relation to the established safety principles adapted for hydrogen by the European Hydrogen Safety Panel considering operational modes industrial sectors and human factors. This work provide an important contribution to the safety of systems involving hydrogen benefitting technical safety engineers emergency responders and emergency services. The lesson learned and the discussion derived from the statistics can also be used in training and risk assessment studies being of equal importance to promote and assist the development of sound safety culture in organisations.
Challenges and Important Considerations When Benchmarking Single-cell Alkaline Electrolyzers
Nov 2021
Publication
This study outlines an approach to identifying the difficulties associated with the bench-marking of alkaline single cells under real electrolyzer conditions. A challenging task in the testing and comparison of different catalysts is obtaining reliable and meaningful benchmarks for these conditions. Negative effects on reproducibility were observed due to the reduction in conditioning time. On the anode side a stable passivation layer of NiO can be formed by annealing of the Ni foams which is even stable during long-term operation. Electrical contact resistance and impedance measurements showed that most of the contact resistance derived from the annealed Ni foam. Additionally analysis of various overvoltages indicated that most of the total overvoltage comes from the anode and cathode activation overpotential. Different morphologies of the substrate material exhibited an influence on the performance of the alkaline single cell based on an increase in the ohmic resistance.
A Coupled Transient Gas Flow Calculation with a Simultaneous Calorific-value-gradient Improved Hydrogen Tracking
Apr 2022
Publication
Gas systems can provide considerable flexibility in integrated energy systems to accommodate hydrogen produced from Power-to-Hydrogen units using excess volatile renewable energy generation. To use the flexibility in integrated energy systems while ensuring a secure and reliable system operation gas system operators need to accurately and easily analyze the effects of varying hydrogen levels on the dynamic gas behavior and vice versa. Existing methods for hydrogen tracking however either solve the hydrogen propagation and dynamic gas behavior separately or must cope with a large inaccuracy. Hence existing methods do not allow an accurate and coupled analysis of gas systems in integrated energy systems considering varying hydrogen levels. This paper proposes a calorific-value-gradient method which can accurately track the propagation of varying hydrogen levels in a gas system even with large simulation time increments of up to one hour. The new method is joined and simultaneously solved with an implicit finite difference scheme describing the transient gas behavior in a single equation system in a coupled Newton–Raphson gas flow calculation. As larger simulation time increments can be chosen without reducing the accuracy the computation time can be strongly reduced compared to existing Euler-based methods. With its high accuracy and its coupled approach this paper provides gas system operators a method to accurately analyze how the propagation of hydrogen affects the entire gas system. With its coupled approach the presented method can enhance the investigation of integrated energy systems as the transient gas behavior and varying hydrogen propagation of the gas system can be easily included in such analyses.
Integration of Experimental Facilities: A Joint Effort for Establishing a Common Knowledge Base in Experimental Work on Hydrogen Safety
Sep 2009
Publication
With regard to the goals of the European HySafe Network research facilities are essential for the experimental investigation of relevant phenomena for testing devices and safety concepts as well as for the generation of validation data for the various numerical codes and models. The integrating activity ‘Integration of Experimental Facilities (IEF)’ has provided basic support for jointly performed experimental work within HySafe. Even beyond the funding period of the NoE HySafe in the 6th Framework Programme IEF represents a long lasting effort for reaching sustainable integration of the experimental research capacities and expertise of the partners from different research fields. In order to achieve a high standard in the quality of experimental data provided by the partners emphasis was put on the know-how transfer between the partners. The strategy for reaching the objectives consisted of two parts. On the one hand a documentation of the experimental capacities has been prepared and analysed. On the other hand a communication base has been established by means of biannual workshops on experimental issues. A total of 8 well received workshops has been organised covering topics from measurement technologies to safety issues. Based on the information presented by the partners a working document on best practice including the joint experimental knowledge of all partners with regard to experiments and instrumentation was created. Preserving the character of a working document it was implemented in the IEF wiki website which was set up in order to provide a central communication platform. The paper gives an overview of the IEF network activities over the last 5 years.
Multistage Risk Analysis and Safety Study of a Hydrogen Energy Station
Sep 2017
Publication
China has plenty of renewable energy like wind power and solar energy especially in the northwest part of the country. Due to the volatile and intermittent characters of the green powers high penetration level of renewable resources could arise grid stabilization problem. Therefore electricity storage is considered as a solution and hydrogen energy storage is proposed. Instead of storing the electricity directly it converts electricity into hydrogen and the energy in hydrogen will be released as needed from gas to electricity and heat. The transformed green power can be fed to the power grid and heat supply network. State Grid Corporation of China carried out its first hydrogen demonstration project. In the demonstration project an alkaline electrolyzer and a PEM hydrogen fuel cell stack are decided as the hydrogen producer and consumer respectively. Hydrogen safety issue is always of significant importance to secure the property. In order to develop a dedicated safety analysis method for hydrogen energy storage system in power industry the risk analysis for the power-to-gas-topower&heat facility was made. The hazard and operability (HAZOP) study and the failure mode and effects analysis (FMEA) are performed sequentially to the installation to identify the most problematic parts of the system in view of hydrogen safety and possible failure modes and consequences. At the third step the typical hydrogen leak accident scenarios are simulated by using computational fluid dynamics (CFD) computer code. The resulted pressure loads of the possibly ignited hydrogen-air mixture in the facility container are estimated conservatively. Important safeguards and mitigation measures are proposed based on the three-stage risk and safety studies.
Flammability Limits and Laminar Flame Speed of Hydrogen–air Mixtures at Sub-atmospheric Pressures
Sep 2011
Publication
Hydrogen behavior at elevated pressures and temperatures was intensively studied by numerous investigators. Nevertheless there is a lack of experimental data on hydrogen ignition and combustion at reduced sub-atmospheric pressures. Such conditions are related to the facilities operating under vacuum or sub-atmospheric conditions for instance like ITER vacuum vessel. Main goal of current work was an experimental evaluation of such fundamental properties of hydrogen–air mixtures as flammability limits and laminar flame speed at sub-atmospheric pressures. A spherical explosion chamber with a volume of 8.2 dm3 was used in the experiments. A pressure method and high-speed camera combined with schlieren system for flame visualization were used in this work. Upper and lower flammability limits and laminar flame velocity have been experimentally evaluated in the range of 4–80% hydrogen in air at initial pressures 25–1000 mbar. An extraction of basic flame properties as Markstein length overall reaction order and activation energy was done from experimental data on laminar burning velocity.
Addressing H-Material Interaction in Fast Diffusion Materials—A Feasibility Study on a Complex Phase Steel
Oct 2020
Publication
Hydrogen embrittlement (HE) is one of the main limitations in the use of advanced high-strength steels in the automotive industry. To have a better understanding of the interaction between hydrogen (H) and a complex phase steel an in-situ method with plasma charging was applied in order to provide continuous H supply during mechanical testing in order to avoid H outgassing. For such fast-H diffusion materials only direct observation during in-situ charging allows for addressing H effects on materials. Different plasma charging conditions were analysed yet there was not a pronounced effect on the mechanical properties. The H concentration was calculated while using a simple analytical model as well as a simulation approach resulting in consistent low H values below the critical concentration to produce embrittlement. However the dimple size decreased in the presence of H and with increasing charging time the crack propagation rate increased. The rate dependence of flow properties of the material was also investigated proving that the material has no strain rate sensitivity which confirmed that the crack propagation rate increased due to H effects. Even though the H concentration was low in the experiments that are presented here different technological alternatives can be implemented in order to increase the maximum solute concentration.
Best Practice in Numerical Simulation and CFD Benchmarking. Results from the SUSANA Project
Sep 2017
Publication
Correct use of Computational Fluid Dynamics (CFD) tools is essential in order to have confidence in the results. A comprehensive set of Best Practice Guidelines (BPG) in numerical simulations for Fuel Cells and Hydrogen applications has been one of the main outputs of the SUSANA project. These BPG focus on the practical needs of engineers in consultancies and industry undertaking CFD simulations or evaluating CFD simulation results in support of hazard/risk assessments of hydrogen facilities as well as on the needs of regulatory authorities. This contribution presents a summary of the BPG document. All crucial aspects of numerical simulations are addressed such as selection of the physical models domain design meshing boundary conditions and selection of numerical parameters. BPG cover all hydrogen safety relative phenomena i.e. release and dispersion ignition jet fire deflagration and detonation. A series of CFD benchmarking exercises are also presented serving as examples of appropriate modelling strategies.
Composite Gas Cylinders Probabilistic Analysis of Minimum Burst and Load Cycle Requirements
Oct 2015
Publication
Gas cylinders made of composite materials receive growing popularity in light-weight applications. Current standards are mostly based on safety determination relying on minimum amounts of endured load cycles and a minimum burst pressure of a small number of specimens. This paper investigates the possibilities of a probabilistic strength assessment for safety improvements as well as cost and weight savings. The probabilistic assessment is based on destructive testing of small sized samples. The influence of sample size on uncertainty of the assessment is analysed. Furthermore methods for the assessment of in-service ageing (degradation) are discussed and displayed in performance charts.
State of the Art of Hydrogen Production via Pyrolysis of Natural Gas
Jul 2020
Publication
Fossil fuels have to be substituted by climate neutral fuels to contribute to CO2 reduction in the future energy system. Pyrolysis of natural gas is a well-known technical process applied for production of e. g. carbon black.
In the future it might contribute to carbon dioxide-free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by-product of this process can be used for material production or can be sequestrated the produced hydrogen has a low carbon footprint.
This article reviews literature on the state of the art of methane/ natural gas pyrolysis process developments and at-tempts to assess the technology readiness level (TRL).
In the future it might contribute to carbon dioxide-free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by-product of this process can be used for material production or can be sequestrated the produced hydrogen has a low carbon footprint.
This article reviews literature on the state of the art of methane/ natural gas pyrolysis process developments and at-tempts to assess the technology readiness level (TRL).
On the Use of Hydrogen in Confined Spaces: Results from the Internal Project InsHyde
Sep 2009
Publication
Alexandros G. Venetsanos,
Paul Adams,
Inaki Azkarate,
A. Bengaouer,
Marco Carcassi,
Angunn Engebø,
E. Gallego,
Olav Roald Hansen,
Stuart J. Hawksworth,
Thomas Jordan,
Armin Keßler,
Sanjay Kumar,
Vladimir V. Molkov,
Sandra Nilsen,
Ernst Arndt Reinecke,
M. Stöcklin,
Ulrich Schmidtchen,
Andrzej Teodorczyk,
D. Tigreat,
N. H. A. Versloot and
L. Boon-Brett
The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.
Fundamental Safety Testing and Analysis of Solid State Hydrogen Storage Materials and Systems
Sep 2007
Publication
Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and commercially acceptable systems it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate risk mitigation strategies to handle unforeseen accidental events. To evaluate these materials and systems an IPHE sanctioned program was initiated in 2006 partnering laboratories from Europe North America and Japan. The objective of this international program is to understanding the physical risks involved in synthesis handling and utilization of solid state hydrogen storage materials and to develop methods to mitigate these risks. This understanding will support ultimate acceptance of commercially high density hydrogen storage system designs. An overview of the approaches to be taken to achieve this objective will be given. Initial experimental results will be presented on environmental exposure of NaAlH4 a candidate high density hydrogen storage compound. The tests to be shown are based on United Nations recommendations for the transport of hazardous materials and include air and water exposure of the hydride at three hydrogen charge levels in various physical configurations. Additional tests developed by the American Society for Testing and Materials were used to quantify the dust cloud ignition characteristics of this material which may result from accidental high energy impacts and system breach. Results of these tests are shown along with necessary risk mitigation techniques used in the synthesis and fabrication of a prototype hydrogen storage system.
Polymer Composites for Tribological Applications in Hydrogen Environment
Sep 2007
Publication
In the development of hydrogen technology special attention is paid to the technical problems of hydrogen storage. One possible way is cryogenic storage in liquid form. Generally cryo-technical machines need components with interacting surfaces in relative motion such as bearings seals or valves which are subjected to extreme conditions. Materials of such systems have to be resistant to friction-caused mechanical deformation at the surface low temperatures and hydrogen environment. Since materials failure can cause uncontrolled escape of hydrogen new material requirements are involved for these tribo-systems in particular regarding operability and reliability. In the past few years several projects dealing with the influence of hydrogen on the tribological properties of friction couples were conducted at the Federal Institute for Materials Research and Testing (BAM) Berlin. This paper reports some investigations carried out with polymer composites. Friction and wear were measured for continuous sliding and analyses of the worn surfaces were performed after the experiments. Tests were performed at room temperature in hydrogen as well as in liquid hydrogen.
Development of a Pneumatic Actuated Low-pressure Direct Injection Gas Injector for Hydrogen-fueled Internal Combustion Engines
Dec 2022
Publication
Mixture formation is one of the greatest challenges for the development of robust and efficient hydrogen-fueled internal combustion engines. In many reviews and research papers authors pointed out that direct injection (DI) has noteworthy advantages over a port fuel injection (PFI) such as higher power output higher efficiency the possibility of mixture stratification to control NOx-formation and reduce heat losses and above all to mitigate combustion abnormalities such as back-firing and pre-ignitions. When considering pressurized gas tanks for on-vehicle hydrogen storage a low-pressure (LP) injection system is advantageous since the tank capacity can be better exploited accordingly. The low gas density upstream of the injector requires cross-sectional areas far larger than any other injectors for direct injection in today's gasoline or diesel engines. The injector design proposed in this work consists of a flat valve seat to enable the achievement of lifetime requirements in heavy-duty applications. The gas supply pressure is used as the energy source for the actuation of the valve plate by means of a pneumatic actuator. This article describes the design and the performed tests carried out to prove the concept readiness of the new LP-DI-injector.
Free Stream Behavior of Hydrogen Released from a Fluidic Oscillating Nozzle
May 2021
Publication
The H2 internal combustion engine (ICE) is a key technology for complete decarbonization of the transport sector. To match or exceed the power density of conventional combustion engines H2 direct injection (DI) is essential. Therefore new injector concepts that meet the requirements of a H2 operation have to be developed. The macroscopic free stream behavior of H2 released from an innovative fluidic oscillating nozzle is investigated and compared with that of a conventional multi-hole nozzle. This work consists of H2 flow measurements and injection tests in a constant volume chamber using the Schlieren method and is accompanied by a LES simulation. The results show that an oscillating H2 free stream has a higher penetration velocity than the individual jets of a multi-hole nozzle. This behavior can be used to inject H2 far into the combustion chamber in the vertical direction while the piston is still near bottom dead center. As soon as the oscillation of the H2 free stream starts the spray angle increases and therefore H2 is also distributed in the horizontal direction. In this phase of the injection process spray angles comparable to those of a multi-hole nozzle are achieved. This behavior has a positive effect on H2 homogenization which is desirable for the combustion process.
Hydrogen Refueling Station Networks for Heavy-duty Vehicles in Future Power Systems
May 2020
Publication
A potential solution to reduce greenhouse gas (GHG) emissions in the transport sector is to use alternatively fuelled vehicles (AFV). Heavy-duty vehicles (HDV) emit a large share of GHG emissions in the transport sector and are therefore the subject of growing attention from global regulators. Fuel cell and green hydrogen technologies are a promising option to decarbonize HDVs as their fast refuelling and long vehicle ranges are consistent with current logistic operational requirements. Moreover the application of green hydrogen in transport could enable more effective integration of renewable energies (RE) across different energy sectors. This paper explores the interplay between HDV Hydrogen Refuelling Stations (HRS) that produce hydrogen locally and the power system by combining an infrastructure location planning model and an electricity system optimization model that takes grid expansion options into account. Two scenarios – one sizing refuelling stations to support the power system and one sizing them independently of it – are assessed regarding their impacts on the total annual electricity system costs regional RE integration and the levelized cost of hydrogen (LCOH). The impacts are calculated based on locational marginal pricing for 2050. Depending on the integration scenario we find average LCOH of between 4.83 euro/kg and 5.36 euro/kg for which nodal electricity prices are the main determining factor as well as a strong difference in LCOH between north and south Germany. Adding HDV-HRS incurs power transmission expansion as well as higher power supply costs as the total power demand increases. From a system perspective investing in HDV-HRS in symbiosis with the power system rather than independently promises cost savings of around seven billion euros per annum. We therefore conclude that the co-optimization of multiple energy sectors is important for investment planning and has the potential to exploit synergies.
Production of H2-rich Syngas from Excavated Landfill Waste through Steam Co-gasification with Biochar
Jun 2020
Publication
Gasification of excavated landfill waste is one of the promising options to improve the added-value chain during remediation of problematic old landfill sites. Steam gasification is considered as a favorable route to convert landfill waste into H2-rich syngas. Co-gasification of such a poor quality landfill waste with biochar or biomass would be beneficial to enhance the H2 concentration in the syngas as well as to improve the gasification performance. In this work steam co-gasification of landfill waste with biochar or biomass was carried out in a lab-scale reactor. The effect of the fuel blending ratio was investigated by varying the auxiliary fuel content in the range of 15e35 wt%. Moreover co-gasification tests were carried out at temperatures between 800 and 1000°C. The results indicate that adding either biomass or biochar enhances the H2 yield where the latter accounts for the syngas with the highest H2 concentration. At 800°C the addition of 35 wt% biochar can enhance the H2 concentration from 38 to 54 vol% and lowering the tar yield from 0.050 to 0.014 g/g-fuel-daf. No apparent synergetic effect was observed in the case of biomass co-gasification which might cause by the high Si content of landfill waste. In contrast the H2 production increases non-linearly with the biochar share in the fuel which indicates that a significant synergetic effect occurs during co-gasification due to the reforming of tar over biochar. Increasing the temperature of biochar co-gasification from 800 to 1000°C elevates the H2 concentration but decreases the H2/CO ratio and increases the tar yield. Furthermore the addition of biochar also enhances the gasification efficiency as indicated by increased values of the energy yield ratio.
The Limitations of Hydrogen Blending in the European Gas Grid
Jan 2022
Publication
In recent years various studies have put forward the prospect of relying on low-carbon or renewable gases such as green hydrogen (H2) or biomethane to replace the supply of natural gas. Hydrogen in particular is receiving much attention as a versatile energy carrier that could complement direct electrification in a plethora of end-uses and questions over its production and deployment play an important part in the ongoing discussions around the energy chapters of the European Commission’s Green Deal agenda.
The aim of the short study was to assess the technical feasibility emission savings and cost impacts of the addition of hydrogen to the existing gas transport network the so-called practice of “hydrogen blending” which is currently being discussed as a deployment pathway in the context of the review of the EU Gas Market Regulation (GMR) and the Trans-European Networks for Energy (TEN-E) regulation.
The document can be downloaded from their website
The aim of the short study was to assess the technical feasibility emission savings and cost impacts of the addition of hydrogen to the existing gas transport network the so-called practice of “hydrogen blending” which is currently being discussed as a deployment pathway in the context of the review of the EU Gas Market Regulation (GMR) and the Trans-European Networks for Energy (TEN-E) regulation.
The document can be downloaded from their website
A Study on Electrofuels in Aviation
Feb 2018
Publication
With the growth of aviation traffic and the demand for emission reduction alternative fuels like the so-called electrofuels could comprise a sustainable solution. Electrofuels are understood as those that use renewable energy for fuel synthesis and that are carbon-neutral with respect to greenhouse gas emission. In this study five potential electrofuels are discussed with respect to the potential application as aviation fuels being n-octane methanol methane hydrogen and ammonia and compared to conventional Jet A-1 fuel. Three important aspects are illuminated. Firstly the synthesis process of the electrofuel is described with its technological paths its energy efficiency and the maturity or research need of the production. Secondly the physico-chemical properties are compared with respect to specific energy energy density as well as those properties relevant to the combustion of the fuels i.e. autoignition delay time adiabatic flame temperature laminar flame speed and extinction strain rate. Results show that the physical and combustion properties significantly differ from jet fuel except for n-octane. The results describe how the different electrofuels perform with respect to important aspects such as fuel and air mass flow rates. In addition the results help determine mixture properties of the exhaust gas for each electrofuel. Thirdly a turbine configuration is investigated at a constant operating point to further analyze the drop-in potential of electrofuels in aircraft engines. It is found that electrofuels can generally substitute conventional kerosene-based fuels but have some downsides in the form of higher structural loads and potentially lower efficiencies. Finally a preliminary comparative evaluation matrix is developed. It contains specifically those fields for the different proposed electrofuels where special challenges and problematic points are seen that need more research for potential application. Synthetically-produced n-octane is seen as a potential candidate for a future electrofuel where even a drop-in capability is given. For the other fuels more issues need further research to allow the application as electrofuels in aviation. Specifically interesting could be the combination of hydrogen with ammonia in the far future; however the research is just at the beginning stage.
Performance Tests of Catalysts for the Safe Conversion of Hydrogen Inside the Nuclear Waste Containers in Fukushima Daiichi
Sep 2019
Publication
The safe decommissioning as well as decontamination of the radioactive waste resulting from the nuclear accident in Fukushima Daiichi represents a huge task for the next decade. At present research and development on long-term safe storage containers has become an urgent task with international cooperation in Japan. One challenge is the generation of hydrogen and oxygen in significant amounts by means of radiolysis inside the containers as the nuclear waste contains a large portion of sea water. The generation of radiolysis gases may lead to a significant pressure build-up inside the containers and to the formation of flammable gases with the risk of ignition and the loss of integrity.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
Decarbonizing Copper Production by Power-to-Hydrogen A Techno-Economic Analysis
Apr 2021
Publication
Electrifying energy-intensive processes is currently intensively explored to cut greenhouse gas (GHG) emissions through renewable electricity. Electrification is particularly challenging if fossil resources are not only used for energy supply but also as feedstock. Copper production is such an energy-intensive process consuming large quantities of fossil fuels both as reducing agent and as energy supply.
Here we explore the techno-economic potential of Power-to-Hydrogen to decarbonize copper production. To determine the minimal cost of an on-site retrofit with Power-to-Hydrogen technology we formulate and solve a mixed-integer linear program for the integrated system. Under current techno-economic parameters for Germany the resulting direct CO2 abatement cost is 201 EUR/t CO2-eq for Power-to-Hydrogen in copper production. On-site utilization of the electrolysis by-product oxygen has a substantial economic benefit. While the abatement cost vastly exceeds current European emission certificate prices a sensitivity analysis shows that projected future developments in Power-to-Hydrogen technologies can greatly reduce the direct CO2 abatement cost to 54 EUR/t CO2-eq. An analysis of the total GHG emissions shows that decarbonization through Power-to-Hydrogen reduces the global GHG emissions only if the emission factor of the electricity supply lies below 160 g CO2-eq/kWhel.
The results suggest that decarbonization of copper production by Power-to-Hydrogen could become economically and environmentally beneficial over the next decades due to cheaper and more efficient Power-to-Hydrogen technology rising GHG emission certificate prices and further decarbonization of the electricity supply.
Here we explore the techno-economic potential of Power-to-Hydrogen to decarbonize copper production. To determine the minimal cost of an on-site retrofit with Power-to-Hydrogen technology we formulate and solve a mixed-integer linear program for the integrated system. Under current techno-economic parameters for Germany the resulting direct CO2 abatement cost is 201 EUR/t CO2-eq for Power-to-Hydrogen in copper production. On-site utilization of the electrolysis by-product oxygen has a substantial economic benefit. While the abatement cost vastly exceeds current European emission certificate prices a sensitivity analysis shows that projected future developments in Power-to-Hydrogen technologies can greatly reduce the direct CO2 abatement cost to 54 EUR/t CO2-eq. An analysis of the total GHG emissions shows that decarbonization through Power-to-Hydrogen reduces the global GHG emissions only if the emission factor of the electricity supply lies below 160 g CO2-eq/kWhel.
The results suggest that decarbonization of copper production by Power-to-Hydrogen could become economically and environmentally beneficial over the next decades due to cheaper and more efficient Power-to-Hydrogen technology rising GHG emission certificate prices and further decarbonization of the electricity supply.
Magnesium Based Materials for Hydrogen Based Energy Storage: Past, Present and Future
Jan 2019
Publication
Volodymyr A. Yartys,
Mykhaylo V. Lototskyy,
Etsuo Akiba,
Rene Albert,
V. E. Antonov,
Jose-Ramón Ares,
Marcello Baricco,
Natacha Bourgeois,
Craig Buckley,
José Bellosta von Colbe,
Jean-Claude Crivello,
Fermin Cuevas,
Roman V. Denys,
Martin Dornheim,
Michael Felderhoff,
David M. Grant,
Bjørn Christian Hauback,
Terry D. Humphries,
Isaac Jacob,
Petra E. de Jongh,
Jean-Marc Joubert,
Mikhail A. Kuzovnikov,
Michel Latroche,
Mark Paskevicius,
Luca Pasquini,
L. Popilevsky,
Vladimir M. Skripnyuk,
Eugene I. Rabkin,
M. Veronica Sofianos,
Alastair D. Stuart,
Gavin Walker,
Hui Wang,
Colin Webb,
Min Zhu and
Torben R. Jensen
Magnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures kinetics and thermodynamics of the systems based on MgH2 nanostructuring new Mg-based compounds and novel composites and catalysis in the Mg based H storage systems. Finally thermal energy storage and upscaled H storage systems accommodating MgH2 are presented.
Impact of Hydrogen Admixture on Combustion Processes – Part II: Practice
Dec 2020
Publication
The Fuel Cells & Hydrogen Joint Undertaking (FCH JU) project ""Testing Hydrogen admixture for Gas Appliances"" aka THyGA is proud to release the second deliverable about the impact of hydrogen admixture on combustion processes. This time the report explores the expected impact of H2NG on a range of appliance designs installed in the EU.
After the deliverable D2.2 dedicated to the theorical estimation of the impact of H2 admixture THyGA reviews results from the litterature to evaluate available knowledge on CO and NOx formation overheating flame temperature flashback H2 leakage operational implications and efficiency of appliances supplied with H2NG blends. Learn more and read deliverable D2.3.
Climate change is one of today’s most pressing global challenges. Since the emission of greenhouse gases is often closely related to the use and supply of energy the goal to avoid emissions requires a fundamental restructuring of the energy system including all parts of the technology chains from production to end-use. Natural gas is today one of the most important primary energy sources in Europe with utilization ranging from power generation and industry to appliances in the residential and commercial sector as well as mobility. As natural gas is a fossil fuel gas utilization is thus responsible for significant emissions of carbon dioxide (CO2) a greenhouse gas.
This is part two. Part one of this project can be found at this link
After the deliverable D2.2 dedicated to the theorical estimation of the impact of H2 admixture THyGA reviews results from the litterature to evaluate available knowledge on CO and NOx formation overheating flame temperature flashback H2 leakage operational implications and efficiency of appliances supplied with H2NG blends. Learn more and read deliverable D2.3.
Climate change is one of today’s most pressing global challenges. Since the emission of greenhouse gases is often closely related to the use and supply of energy the goal to avoid emissions requires a fundamental restructuring of the energy system including all parts of the technology chains from production to end-use. Natural gas is today one of the most important primary energy sources in Europe with utilization ranging from power generation and industry to appliances in the residential and commercial sector as well as mobility. As natural gas is a fossil fuel gas utilization is thus responsible for significant emissions of carbon dioxide (CO2) a greenhouse gas.
This is part two. Part one of this project can be found at this link
Potential of New Business Models for Grid Integrated Water Electrolysis
Feb 2018
Publication
Grid integrated water electrolysers have the potential of coupling electric power systems subjected to high shares of renewable energy sources with sectors of hydrogen demand thus contributing to European decarbonization goals in future. We therefore investigate the business potential of future electrolyser applications in cross-commodity arbitrage trading by applying a complex power market simulation method for future scenarios and different European countries. Based on this we evaluate the potential of additional provision of grid services towards grid operators in order to increase the electrolyser utilization ratio. For this we use a method that identifies measures of transmission grid operators in order to ensure secure grid operation. In this context uncertain hydrogen prices and different sectors of hydrogen demand are addressed through sensitivities of different hydrogen sales prices. The analysis shows a high dependency of business model efficiency on the hydrogen price. While cross-commodity arbitrage trading can achieve profitability for the transportation sector applications for the industry sector and natural gas system are less efficient. The results however indicate that for these less efficient applications grid service provision can be an option of increasing the electrolyser utilization ratio thus increasing its profitability.
Options for Multilateral Initiatives to Close the Global 2030 Climate Ambition and Action Gap - Policy Field Synthetic E-fuels
Jan 2021
Publication
Achieving the goals of the Paris Agreement requires increased global climate action especially towards the production and use of synthetic e-fuels. This paper focuses on aviation and maritime transport and the role of green hydrogen for indirect electrification of industry sectors. Based on a sound analysis of existing multilateral cooperation the paper proposes four potential initiatives to increase climate ambition of the G20 countries in the respective policy field: a Sustainable e-Kerosene Alliance a Sustainable e-fuel Alliance for Maritime Shipping a Hard-to-Abate Sector Partnership and a Global Supply-demand-partnership.
The full report can be found here on the Umweltbundesamt website
The full report can be found here on the Umweltbundesamt website
Review on the Influence of Temperature upon Hydrogen Effects in Structural Alloys
Mar 2021
Publication
It is well-documented experimentally that the influence of hydrogen on the mechanical properties of structural alloys like austenitic stainless steels nickel superalloys and carbon steels strongly depends on temperature. A typical curve plotting any hydrogen-affected mechanical property as a function of temperature gives a temperature THEmax where the degradation of this mechanical property reaches a maximum. Above and below this temperature the degradation is less. Unfortunately the underlying physico-mechanical mechanisms are not currently understood to the level of detail required to explain such temperature effects. Though this temperature effect is important to understand in the context of engineering applications studies to explain or even predict the effect of temperature upon the mechanical properties of structural alloys could not be identified. The available experimental data are scattered significantly and clear trends as a function of chemistry or microstructure are difficult to see. Reported values for THEmax are in the range of about 200–340 K which covers the typical temperature range for the design of structural components of about 230–310 K (from −40 to +40 °C). That is the value of THEmax itself as well as the slope of the gradient might affect the materials selection for a dedicated application. Given the current lack of scientific understanding a statistical approach appears to be a suitable way to account for the temperature effect in engineering applications. This study reviews the effect of temperature upon hydrogen effects in structural alloys and proposes recommendations for test temperatures for gaseous hydrogen applications
Experimental Investigations Relevant for Hydrogen and Fission Product Issues Raised by the Fukushima Accident
Jan 2015
Publication
The accident at Japan's Fukushima Daiichi nuclear power plant in March 2011 caused by an earthquake and a subsequent tsunami resulted in a failure of the power systems that are needed to cool the reactors at the plant. The accident progression in the absence of heat removal systems caused Units 1-3 to undergo fuel melting. Containment pressurization and hydrogen explosions ultimately resulted in the escape of radioactivity from reactor containments into the atmosphere and ocean. Problems in containment venting operation leakage from primary containment boundary to the reactor building improper functioning of standby gas treatment system (SGTS) unmitigated hydrogen accumulation in the reactor building were identified as some of the reasons those added-up in the severity of the accident. The Fukushima accident not only initiated worldwide demand for installation of adequate control and mitigation measures to minimize the potential source term to the environment but also advocated assessment of the existing mitigation systems performance behavior under a wide range of postulated accident scenarios. The uncertainty in estimating the released fraction of the radionuclides due to the Fukushima accident also underlined the need for comprehensive understanding of fission product behavior as a function of the thermal hydraulic conditions and the type of gaseous aqueous and solid materials available for interaction e.g. gas components decontamination paint aerosols and water pools. In the light of the Fukushima accident additional experimental needs identified for hydrogen and fission product issues need to be investigated in an integrated and optimized way. Additionally as more and more passive safety systems such as passive autocatalytic recombiners and filtered containment venting systems are being retrofitted in current reactors and also planned for future reactors identified hydrogen and fission product issues will need to be coupled with the operation of passive safety systems in phenomena oriented and coupled effects experiments. In the present paper potential hydrogen and fission product issues raised by the Fukushima accident are discussed. The discussion focuses on hydrogen and fission product behavior inside nuclear power plant containments under severe accident conditions. The relevant experimental investigations conducted in the technical scale containment THAI (thermal hydraulics hydrogen aerosols and iodine) test facility (9.2 m high 3.2 m in diameter and 60 m3 volume) are discussed in the light of the Fukushima accident.
The Role of κ-Carbides as Hydrogen Traps in High-Mn Steels
Jul 2017
Publication
Since the addition of Al to high-Mn steels is known to reduce their sensitivity to hydrogen-induced delayed fracture we investigate possible trapping effects connected to the presence of Al in the grain interior employing density-functional theory (DFT). The role of Al-based precipitates is also investigated to understand the relevance of short-range ordering effects. So-called E21-Fe3AlC κ-carbides are frequently observed in Fe-Mn-Al-C alloys. Since H tends to occupy the same positions as C in these precipitates the interaction and competition between both interstitials is also investigated via DFT-based simulations. While the individual H–H/C–H chemical interactions are generally repulsive the tendency of interstitials to increase the lattice parameter can yield a net increase of the trapping capability. An increased Mn content is shown to enhance H trapping due to attractive short-range interactions. Favorable short-range ordering is expected to occur at the interface between an Fe matrix and the E21-Fe3AlC κ-carbides which is identified as a particularly attractive trapping site for H. At the same time accumulation of H at sites of this type is observed to yield decohesion of this interface thereby promoting fracture formation. The interplay of these effects evident in the trapping energies at various locations and dependent on the H concentration can be expressed mathematically resulting in a term that describes the hydrogen embrittlement
Greenhouse Gas Abatement in EUROPE—A Scenario-Based, Bottom-Up Analysis Showing the Effect of Deep Emission Mitigation on the European Energy System
Feb 2022
Publication
Greenhouse gas emissions need to be drastically reduced to mitigate the environmental impacts caused by climate change and to lead to a transformation of the European energy system. A model landscape consisting of four final energy consumption sector models with high spatial (NUTS-3) and temporal (hourly) resolution and the multi-energy system model ISAaR is extended and applied to investigate the transformation pathway of the European energy sector in the deep emission mitigation scenario solidEU. The solidEU scenario describes not only the techno-economic but also the socio-political contexts and it includes the EU27 + UK Norway and Switzerland. The scenario analysis shows that volatile renewable energy sources (vRES) dominate the energy system in 2050. In addition the share of flexible sector coupling technologies increases to balance electricity generation from vRES. Seasonal differences are balanced by hydrogen storage with a seasonal storage profile. The deployment rates of vRES in solidEU show that a fast profound energy transition is necessary to achieve European climate protection goals.
Liquid Organic Hydrogen Carriers - A Technology to Overcome Common Risks of Hydrogen Storage
Sep 2021
Publication
In transport and storage of hydrogen the risks are mainly seen in its volatile nature its ability to form explosive mixtures with air and the harsh conditions (high pressure or low temperature) for efficient storage. The concept of Liquid Organic Hydrogen Carriers (LOHC) offers a technology to overcome the above mentioned threats. The present submission describes the basics of the LOHC technology. It contains a comparison of a selection of common LOHC materials with a view on physical properties. The advantages of a low viscosity at low temperatures and a high flash point are expressed. LOHCs are also discussed as a concept to import large amounts of energy/hydrogen. A closer look is taken on the environmental and safety aspects of hydrogen storage in LOHCs since here the main differences to pressurized and cryo-storage of hydrogen can be found. The aim of this paper is to provide an overview of the principles of the LOHC technology the different LOHC materials and their risks and opportunities and an impression of a large scale scenario on the basis of the LOHC technology.
Is Iridium Demand a Potential Bottleneck in the Realization of Large-Scale PEM Water Electrolysis?
Jul 2021
Publication
Proton exchange membrane water electrolysis (PEMWE) is a key technology for future sustainable energy systems. Proton exchange membrane (PEM) electrolysis cells use iridium one of the scarcest elements on earth as catalyst for the oxygen evolution reaction. In the present study the expected iridium demand and potential bottlenecks in the realization of PEMWE for hydrogen production in the targeted GW a−1 scale are assessed in a model built on three pillars: (i) an in-depth analysis of iridium reserves and mine production (ii) technical prospects for the optimization of PEM water electrolyzers and (iii) PEMWE installation rates for a market ramp-up and maturation model covering 50 years. As a main result two necessary preconditions have been identified to meet the immense future iridium demand: first the dramatic reduction of iridium catalyst loading in PEM electrolysis cells and second the development of a recycling infrastructure for iridium catalysts with technical end-of-life recycling rates of at least 90%.
Low-Cost and Durable Bipolar Plates for Proton Exchange Membrane Electrolyzers
Mar 2017
Publication
Cost reduction and high efficiency are the mayor challenges for sustainable H2 production via proton exchange membrane (PEM) electrolysis. Titanium-based components such as bipolar plates (BPP) have the largest contribution to the capital cost. This work proposes the use of stainless steel BPPs coated with Nb and Ti by magnetron sputtering physical vapor deposition (PVD) and vacuum plasma spraying (VPS) respectively. The physical properties of the coatings are thoroughly characterized by scanning electron atomic force microscopies (SEM AFM); and X-ray diffraction photoelectron spectroscopies (XRD XPS). The Ti coating (50μm) protects the stainless steel substrate against corrosion while a 50- fold thinner layer of Nb decreases the contact resistance by almost one order of magnitude. The Nb/ Ti-coated stainless steel bipolar BPPs endure the harsh environment of the anode for more than 1000h of operation under nominal conditions showing a potential use in PEM electrolyzers for large-scale H2 production from renewables.
A Novel Emergency Gas-to-Power System Based on an Efficient and Long-Lasting Solid-State Hydride Storage System: Modeling and Experimental Validation
Jan 2022
Publication
In this paper a gas-to-power (GtoP) system for power outages is digitally modeled and experimentally developed. The design includes a solid-state hydrogen storage system composed of TiFeMn as a hydride forming alloy (6.7 kg of alloy in five tanks) and an air-cooled fuel cell (maximum power: 1.6 kW). The hydrogen storage system is charged under room temperature and 40 bar of hydrogen pressure reaching about 110 g of hydrogen capacity. In an emergency use case of the system hydrogen is supplied to the fuel cell and the waste heat coming from the exhaust air of the fuel cell is used for the endothermic dehydrogenation reaction of the metal hydride. This GtoP system demonstrates fast stable and reliable responses providing from 149 W to 596 W under different constant as well as dynamic conditions. A comprehensive and novel simulation approach based on a network model is also applied. The developed model is validated under static and dynamic power load scenarios demonstrating excellent agreement with the experimental results.
Kinetic Parameters Estimation via Dragonfly Algorithm (DA) and Comparison of Cylindrical and Spherical Reactors Performance for CO2 Hydrogenation to Hydrocarbons
Oct 2020
Publication
Climate change and global warming as well as growing global demand for hydrocarbons in industrial sectors make great incentives to investigate the utilization of CO2 for hydrocarbons production. Therefore finding an in-depth understanding of the CO2 hydrogenation reactors along with simulating reactor responses to different operating conditions are of paramount importance. However the reaction mechanisms for CO2 hydrogenation and their corresponding kinetic parameters have been disputable yet. In this regard considering the previously proposed Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism which considered CO2 hydrogenation as a combination of reverse water gas shift (RWGS) and Fischer-Tropsch (FT) reactions and using a one-dimensional pseudo-homogeneous non-isothermal model kinetic parameters of the rate expressions are estimated via fitting experimental and modelling data through a novel swarm intelligence optimization technique called dragonfly algorithm (DA). The predicted reactants conversion using DA algorithm are closer to the experimental data (with about 4% error) comparing to those obtained by the artificial bee colony (ABC) algorithm and are in significant agreement with available literature data. The proposed model is used to assess the effect of reactor configuration on the performance and temperature fluctuations. Results show that axial flow spherical reactor (AFSR) and radial flow spherical reactor (RFSR) exhibiting the same surface area with that of the cylindrical reactor (CR) i.e. AFSR-2 and RFSR-2-i are the most efficient exhibiting hydrocarbons selectivity of 40.330% and 40.286% at CO2 conversion of 53.763% and 53.891%. In addition it is revealed that the location of the jacket has an essential role in controlling the reactor temperature.
Hydrogen-assisted Cracking of GMA Welded 960 & A Grade High-strength Steels
Jan 2020
Publication
High-strength steels with yield strength of 960 MPa are susceptible to hydrogen-assisted cracking (HAC) during welding processing. In the present paper the implant test is used to study HAC in a quenched and tempered steel S960QL and a high-strength steel produced by thermo-mechanical controlled process S960MC. Welding is performed using the gas-metal arc welding process. Furthermore diffusible hydrogen concentration (HD) in arc weld metal is determined. Based on the implant test results lower critical stress (LCS) for complete fracture critical implant stress (σkrit) for crack initiation and embrittlement index (EI) are determined. At HD of 1.66 ml/100 g LCS is 605 MPa and 817 MPa for S960QL and S960MC respectively. EI is 0.30 and 0.46 for S960QL and S960MC respectively. Fracture surfaces of S960QL show higher degradation with reduced deformation. Both higher EI of S960MC and fractography show better resistance to HAC in the HAZ of S960MC compared to S960QL.
Blind-prediction: Estimating the Consequences of Vented Hydrogen Deflagrations for Homogeneous Mixtures in a 20-foot ISO Container
Sep 2017
Publication
Trygve Skjold,
Helene Hisken,
Sunil Lakshmipathy,
Gordon Atanga,
Marco Carcassi,
Martino Schiavetti,
James R. Stewart,
A. Newton,
James R. Hoyes,
Ilias C. Tolias,
Alexandros G. Venetsanos,
Olav Roald Hansen,
J. Geng,
Asmund Huser,
Sjur Helland,
Romain Jambut,
Ke Ren,
Alexei Kotchourko,
Thomas Jordan,
Jérome Daubech,
Guillaume Lecocq,
Arve Grønsund Hanssen,
Chenthil Kumar,
Laurent Krumenacker,
Simon Jallais,
D. Miller and
Carl Regis Bauwens
This paper summarises the results from a blind-prediction study for models developed for estimating the consequences of vented hydrogen deflagrations. The work is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The scenarios selected for the blind-prediction entailed vented explosions with homogeneous hydrogen-air mixtures in a 20-foot ISO container. The test program included two configurations and six experiments i.e. three repeated tests for each scenario. The comparison between experimental results and model predictions reveals reasonable agreement for some of the models and significant discrepancies for others. It is foreseen that the first blind-prediction study in the HySEA project will motivate developers to improve their models and to update guidelines for users of the models.
Economic Analysis of Improved Alkaline Water Electrolysis
Feb 2017
Publication
Alkaline water electrolysis (AWE) is a mature hydrogen production technology and there exists a range of economic assessments for available technologies. For advanced AWEs which may be based on novel polymer-based membrane concepts it is of prime importance that development comes along with new configurations and technical and economic key process parameters for AWE that might be of interest for further economic assessments. This paper presents an advanced AWE technology referring to three different sites in Europe (Germany Austria and Spain). The focus is on financial metrics the projection of key performance parameters of advanced AWEs and further financial and tax parameters. For financial analysis from an investor’s (business) perspective a comprehensive assessment of a technology not only comprises cost analysis but also further financial analysis quantifying attractiveness and supply/market flexibility. Therefore based on cash flow (CF) analysis a comprehensible set of metrics may comprise levelised cost of energy or respectively levelized cost of hydrogen (LCH) for cost assessment net present value (NPV) for attractiveness analysis and variable cost (VC) for analysis of market flexibility. The German AWE site turns out to perform best in all three financial metrics (LCH NPV and VC). Though there are slight differences in investment cost and operation and maintenance cost projections for the three sites the major cost impact is due to the electricity cost. Although investment cost is slightly lower and labor cost is significantly lower in Spain the difference can not outweigh the higher electricity cost compared to Germany. Given the assumption that the electrolysis operators are customers directly and actively participating in power markets and based on the regulatory framework in the three countries in this special case electricity cost in Germany is lowest. However as electricity cost is profoundly influenced by political decisions as well as the implementation of economic instruments for transforming electricity systems toward sustainability it is hardly possible to further improve electricity price forecasts.
A Direct Synthesis of Platinum/Nickel Co-catalysts on Titanium Dioxide Nanotube Surface from Hydrometallurgical-type Process Streams
Aug 2018
Publication
Solutions that simulate hydrometallurgical base metal process streams with high nickel (Ni) and minor platinum (Pt) concentrations were used to create Pt/Ni nanoparticles on TiO2 nanotube surfaces. For this electrochemical deposition – redox replacement (EDRR) was used that also allowed to control the nanoparticle size density and Pt/Ni content of the deposited nanoparticles. The Pt/Ni nanoparticle decorated titanium dioxide nanotubes (TiO2 nanotubes) become strongly activated for photocatalytic hydrogen (H2) evolution. Moreover EDRR facilitates nanoparticle formation without the need for any additional chemicals and is more effective than electrodeposition alone. Actually a 10000-time enrichment level of Pt took place on the TiO2 surface when compared to Pt content in the solution with the EDRR method. The results show that hydrometallurgical streams offer great potential as an alternative raw material source for industrial catalyst production when coupled with redox replacement electrochemistry.
Results of the Pre-normative Research Project PRESLHY for the Safe Use of Liquid Hydrogen
Sep 2021
Publication
Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large-scale transport and storage of hydrogen with higher densities. 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 conducted pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The central research consisted of a broad experimental program combined with analytical work modelling and simulations belonging to the three key phenomena of the accident chain: release and mixing ignition and combustion. The presented results improve the general understanding of the behavior of LH2 in accidents and provide some design guidelines and engineering tools for safer use of LH2. Recommendations for improvement of current international standards are derived.
Expected Impacts on Greenhouse Gas and Air Pollutant Emissions Due to a Possible Transition Towards a Hydrogen Economy in German Road Transport
Nov 2020
Publication
Transitioning German road transport partially to hydrogen energy is among the possibilities being discussed to help meet national climate targets. This study investigates impacts of a hypothetical complete transition from conventionally-fuelled to hydrogen-powered German transport through representative scenarios. Our results show that German emissions change between −179 and +95 MtCO2eq annually depending on the scenario with renewable-powered electrolysis leading to the greatest emissions reduction while electrolysis using the fossil-intense current electricity mix leads to the greatest increase. German energy emissions of regulated pollutants decrease significantly indicating the potential for simultaneous air quality improvements. Vehicular hydrogen demand is 1000 PJ annually requiring 446–525 TWh for electrolysis hydrogen transport and storage which could be supplied by future German renewable generation supporting the potential for CO2-free hydrogen traffic and increased energy security. Thus hydrogen-powered transport could contribute significantly to climate and air quality goals warranting further research and political discussion about this possibility.
Market Segmentation of Domestic and Commercial Natural Gas Appliances
Jan 2021
Publication
The main goal of the project is to enable the wide adoption of H2NG (hydrogen in natural gas) blends by closing knowledge gaps regarding technical impacts on residential and commercial gas appliances. The project consortium will identify and recommend appropriate codes and standards that should be adapted to answer the needs and develop a strategy for addressing the challenges for new and existing appliances.<br/>This deliverable on market segmentation is part of work package 2 and provides a quantitative segmentation of the gas appliance market in terms of appliance population numbers. It therefore prepares the project partners to perform the subsequent selection of the most representative product types to be tested in the laboratories of the THyGA partners.<br/>The classification is developed to categorise appliances installed in the field based on available statistics calculation methods and estimations. As a result appliance populations are provided for each technology segment that draw a representative picture of the installed end-use appliances within the European Union in 2020.
Origin of the Catalytic Activity at Graphite Electrodes in Vanadium Flow Batteries
Jun 2021
Publication
For many electrochemical devices that use carbon-based materials such as electrolyzers supercapacitors and batteries oxygen functional groups (OFGs) are considered essential to facilitate electron transfer. Researchers implement surface-active OFGs to improve the electrocatalytic properties of graphite felt electrodes in vanadium flow batteries. Herein we show that graphitic defects and not OFGs are responsible for lowering the activation energy barrier and thus enhance the charge transfer properties. This is proven by a thermal deoxygenation procedure in which specific OFGs are removed before electrochemical cycling. The electronic and microstructural changes associated with deoxygenation are studied by quasi in situ X-ray photoelectron and Raman spectroscopy. The removal of oxygen groups at basal and edge planes improves the activity by introducing new active edge sites and carbon vacancies. OFGs hinder the charge transfer at the graphite–electrolyte interface. This is further proven by modifying the sp2 plane of graphite felt electrodes with oxygen-containing pyrene derivatives. The electrochemical evolution of OFGs and graphitic defects are studied during polarization and long-term cycling conditions. The hypothesis of increased activity caused by OFGs was refuted and hydrogenated graphitic edge sites were identified as the true reason for this increase.
The New Oil? The Geopolitics and International Governance of Hydrogen
Jun 2020
Publication
While most hydrogen research focuses on the technical and cost hurdles to a full-scale hydrogen economy little consideration has been given to the geopolitical drivers and consequences of hydrogen developments. The technologies and infrastructures underpinning a hydrogen economy can take markedly different forms and the choice over which pathway to take is the object of competition between different stakeholders and countries. Over time cross-border maritime trade in hydrogen has the potential to fundamentally redraw the geography of global energy trade create a new class of energy exporters and reshape geopolitical relations and alliances between countries. International governance and investments to scale up hydrogen value chains could reduce the risk of market fragmentation carbon lock-in and intensified geo-economic rivalry.
Using the Jet Stream for Sustainable Airship and Balloon Transportation of Cargo and Hydrogen
Jul 2019
Publication
The maritime shipping sector is a major contributor to CO2 emissions and this figure is expected to rise in coming decades. With the intent of reducing emissions from this sector this research proposes the utilization of the jet stream to transport a combination of cargo and hydrogen using airships or balloons at altitudes of 10–20 km. The jet streams flow in the mid-latitudes predominantly in a west–east direction reaching an average wind speed of 165 km/h. Using this combination of high wind speeds and reliable direction hydrogen-filled airships or balloons could carry hydrogen with a lower fuel requirement and shorter travel time compared to conventional shipping. Jet streams at different altitudes in the atmosphere were used to identify the most appropriate circular routes for global airship travel. Round-the-world trips would take 16 days in the Northern Hemisphere and 14 in the Southern Hemisphere. Hydrogen transport via the jet stream due to its lower energy consumption and shorter cargo delivery time access to cities far from the coast could be a competitive alternative to maritime shipping and liquefied hydrogen tankers in the development of a sustainable future hydrogen economy.
Renewable Power and Heat for the Decarbonisation of Energy-Intensive Industries
Dec 2022
Publication
The present review provides a catalogue of relevant renewable energy (RE) technologies currently available (regarding the 2030 scope) and to be available in the transition towards 2050 for the decarbonisation of Energy Intensive Industries (EIIs). RE solutions have been classified into technologies based on the use of renewable electricity and those used to produce heat for multiple industrial processes. Electrification will be key thanks to the gradual decrease in renewable power prices and the conversion of natural-gas-dependent processes. Industrial processes that are not eligible for electrification will still need a form of renewable heat. Among them the following have been identified: concentrating solar power heat pumps and geothermal energy. These can supply a broad range of needed temperatures. Biomass will be a key element not only in the decarbonisation of conventional combustion systems but also as a biofuel feedstock. Biomethane and green hydrogen are considered essential. Biomethane can allow a straightforward transition from fossil-based natural gas to renewable gas. Green hydrogen production technologies will be required to increase their maturity and availability in Europe (EU). EIIs’ decarbonisation will occur through the progressive use of an energy mix that allows EU industrial sectors to remain competitive on a global scale. Each industrial sector will require specific renewable energy solutions especially the top greenhouse gas-emitting industries. This analysis has also been conceived as a starting point for discussions with potential decision makers to facilitate a more rapid transition of EIIs to full decarbonisation.
The Merit and the Context of Hydrogen Production from Water and Its Effect on Global CO2 Emission
Feb 2022
Publication
For a green economy to be possible in the near future hydrogen production from water is a sought-after alternative to fossil fuels. It is however important to put things into context with respect to global CO2 emission and the role of hydrogen in curbing it. The present world annual production of hydrogen is about 70 million metric tons of which almost 50% is used to make ammonia NH3 (that is mostly used for fertilizers) and about 15% is used for other chemicals [1]. The hydrogen produced worldwide is largely made by steam CH4 reforming (SMR) which is one of the most energy-intensive processes in the chemical industry [2]. It releases based on reaction stoichiometry 5.5 kg of CO2 per 1 kg of H2 (CH4+ 2 H2O → CO2 + 4 H2). When the process itself is taken into account in addition the production [3] becomes about 9 kg of CO2 per kg of H2 and this ratio can be as high as 12 [4]. This results in the production of about one billion tons/year of CO2. The world annual CO2 emission from fossil fuels is however much larger: it is about 36 billion tons of which roughly 25% is emitted while generating electricity and heat 20% due to transport activity and 20% from other industrial processes. Because of the link between global warming and CO2 emissions there is an increasing move towards finding alternative approaches for energy vectors and their applications.
International Association for Hydrogen Safety ‘Research Priorities Workshop’, September 2018, Buxton, UK
Sep 2018
Publication
Hydrogen has the potential to be used by many countries as part of decarbonising the future energy system. Hydrogen can be used as a fuel ‘vector’ to store and transport energy produced in low-carbon ways. This could be particularly important in applications such as heating and transport where other solutions for low and zero carbon emission are difficult. To enable the safe uptake of hydrogen technologies it is important to develop the international scientific evidence base on the potential risks to safety and how to control them effectively. The International Association for Hydrogen Safety (known as IA HySAFE) is leading global efforts to ensure this. HSE hosted the 2018 IA HySAFE Biennial Research Priorities Workshop. A panel of international experts presented during nine key topic sessions: (1) Industrial and National Programmes; (2) Applications; (3) Storage; (4) Accident Physics – Gas Phase; (5) Accident Physics – Liquid/ Cryogenic Behaviour; (6) Materials; (7) Mitigation Sensors Hazard Prevention and Risk Reduction; (8) Integrated Tools for Hazard and Risk Assessment; (9) General Aspects of Safety.<br/>This report gives an overview of each topic made by the session chairperson. It also gives further analysis of the totality of the evidence presented. The workshop outputs are shaping international activities on hydrogen safety. They are helping key stakeholders to identify gaps in knowledge and expertise and to understand and plan for potential safety challenges associated with the global expansion of hydrogen in the energy system.
Review of Power-to-Gas Projects in Europe
Nov 2018
Publication
Core of the Power-to-Gas (PtG) concept is the utilization of renewable electricity to produce hydrogen via water electrolysis. This hydrogen can be used directly as final energy carrier or can be converted to e.g. methane synthesis gas liquid fuels electricity or chemicals. To integrate PtG into energy systems technical demonstration and systems integration is of mayor importance. In total 128 PtG research and demonstration projects are realized or already finished in Europe to analyze these issues by May 2018. Key of the review is the identification and assessment of relevant projects regarding their field of application applied processes and technologies for electrolysis type of methanation capacity location and year of commissioning. So far main application for PtX is the injection of hydrogen or methane into the natural gas grid for storing electricity from variable renewable energy sources. Producing fuels for transport is another important application of PtX. In future PtX gets more important for refineries to lower the carbon food print of the products.
Hybrid Hydrogen Home Storage for Decentralized Energy Autonomy
May 2021
Publication
As the share of distributed renewable power generation increases high electricity prices and low feed-in tariff rates encourage the generation of electricity for personal use. In the building sector this has led to growing interest in energy self-sufficient buildings that feature battery and hydrogen storage capacities. In this study we compare potential technology pathways for residential energy storage in terms of their economic performance by means of a temporal optimization model of the fully self-sufficient energy system of a single-family building taking into account its residential occupancy patterns and thermal equipment. We show for the first time how heat integration with reversible solid oxide cells (rSOCs) and liquid organic hydrogen carriers (LOHCs) in high-efficiency single-family buildings could by 2030 enable the self-sufficient supply of electricity and heat at a yearly premium of 52% against electricity supplied by the grid. Compared to lithium-ion battery systems the total annualized cost of a self-sufficient energy supply can be reduced by 80% through the thermal integration of LOHC reactors and rSOC systems.
Improving the Efficiency of PEM Electrolyzers through Membrane-Specific Pressure Optimization
Feb 2020
Publication
Hydrogen produced in a polymer electrolyte membrane (PEM) electrolyzer must be stored under high pressure. It is discussed whether the gas should be compressed in subsequent gas compressors or by the electrolyzer. While gas compressor stages can be reduced in the case of electrochemical compression safety problems arise for thin membranes due to the undesired permeation of hydrogen across the membrane to the oxygen side forming an explosive gas. In this study a PEM system is modeled to evaluate the membrane-specific total system efficiency. The optimum efficiency is given depending on the external heat requirement permeation cell pressure current density and membrane thickness. It shows that the heat requirement and hydrogen permeation dominate the maximum efficiency below 1.6 V while above the cell polarization is decisive. In addition a pressure-optimized cell operation is introduced by which the optimum cathode pressure is set as a function of current density and membrane thickness. This approach indicates that thin membranes do not provide increased safety issues compared to thick membranes. However operating an N212-based system instead of an N117-based one can generate twice the amount of hydrogen at the same system efficiency while only one compressor stage must be added.
A Review of Recent Developments in Molecular Dynamics Simulations of the Photoelectrochemical Water Splitting Process
Jun 2021
Publication
In this review we provide a short overview of the Molecular Dynamics (MD) method and how it can be used to model the water splitting process in photoelectrochemical hydrogen production. We cover classical non-reactive and reactive MD techniques as well as multiscale extensions combining classical MD with quantum chemical and continuum methods. Selected examples of MD investigations of various aqueous semiconductor interfaces with a special focus on TiO2 are discussed. Finally we identify gaps in the current state-of-the-art where further developments will be needed for better utilization of MD techniques in the field of water splitting.
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