Transmission, Distribution & Storage
Phase Field Modelling of Formation and Fracture of Expanding Precipitates
May 2017
Publication
It is a common belief that embedded expanding inclusions are subjected to an internal homogeneous compressive hydrostatic stress. Still cracks that appear in precipitates that occupy a larger volume than the original material are frequently observed. The appearance of cracks has since long been regarded as a paradox. In the present study it is shown that matrix materials that increases its volume even several percent during the precipitation process develop a tensile hydrostatic stress in the centre of the precipitate. This is the result of a complicated mechanical-chemical phase transformation process. The process is here studied using a Landau phase feld model. Before the material is transformed and incorporated in a precipitate it undergoes stretching beyond the elastic strain limit because of the presence of already expanded material. During the phase transformation the accompanying volumetric expansion cannot be fully accommodated which instead creates an internal compressive stress and adds tension in the surrounding material. As the growth of the precipitate proceeds a region with increasing tensile stress develops in the interior of the precipitate. This is suggested to be the most probable cause of the observed cracks. First the mechanics that lead to the tension is computed. The infuence of elastic-plastic properties is studied both for cases both with and without cracks. The growth history from microscopic to macroscopic precipitates is followed and the result is compared with observations of so called hydride blisters that are formed on surfaces of zirconium alloys in the presence of hydrogen. A common practical situation is when the zirconium is in contact with an object of lower temperature. Then the cooled spot attracts hydrogen that make the zirconium transform to a metal hydride with the shape of a blister. The simulations predicts a final size and position of the growing crack that compares well with the experimental observations.
Hydrogen Impacts on Downstream Installation and Appliances
Nov 2019
Publication
The report analyses the technical impacts to end-users of natural gas in Australian distribution networks when up to 10% hydrogen (by volume) is mixed with natural gas.
The full report can be found at this link.
The full report can be found at this link.
Advanced Hydrogen Storage of the Mg–Na–Al System: A Review
May 2021
Publication
A solid-state storage system is the most practical option for hydrogen because it is more convenient and safer. Metal hydrides especially MgH2 are the most promising materials that offer high gravimetric capacity and good reversibility. However the practical application of MgH2 is restricted by slow sorption kinetics and high stability of thermodynamic properties. Hydrogen storage performance of MgH2 was enhanced by introducing the Mg–Na–Al system that destabilises MgH2 with NaAlH4. The Mg–Na–Al system has superior performance compared to that of unary MgH2 and NaAlH4. To boost the performance of the Mg–Na–Al system the ball milling method and the addition of a catalyst were introduced. The Mg–Na–Al system resulted in a low onset decomposition temperature superior cyclability and enhanced kinetics performances. The Al12Mg17 and NaMgH3 that formed in situ during the dehydrogenation process modify the reaction pathway of the Mg–Na–Al system and alter the thermodynamic properties. In this paper the overview of the recent progress in hydrogen storage of the Mg–Na–Al system is detailed. The remaining challenges and future development of Mg–Na–Al system are also discussed. This paper is the first review report on hydrogen storage properties of the Mg–Na–Al system.
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.
Catalytic Hydrogen Production, Storage and Application
Jul 2021
Publication
Hydrogen is a clean fuel for transportation and energy storage. It has several attractive features including a higher energy content by weight use in fuel cells that produces only water as a by-product storage in small and large quantities by various methods and established transportation and infrastructures. A hydrogen economy consists of three steps i.e. hydrogen production storage and applications. All three steps involved in a hydrogen economy can be divided into catalytic and non-catalytic approaches. For catalytic processes the efficiency highly depends on the type and physico-chemical characteristics of the catalysts. Therefore for the improvement of these catalytic processes the development of highly efficient and stable catalysts is highly required.
Strain Rate Sensitivity of Microstructural Damage Evolution in a Dual-Phase Steel Pre-Charged with Hydrogen
Dec 2018
Publication
We evaluated the strain rate sensitivity of the micro-damage evolution behavior in a ferrite/martensite dual-phase steel. The micro-damage evolution behavior can be divided into three regimes: damage incubation damage arrest and damage growth. All regimes are associated with local deformability. Thus the total elongation of DP steels is determined by a combination of plastic damage initiation resistance and damage growth arrestability. This fact implies that hydrogen must have a critical effect on the damage evolution because hydrogen enhances strain localization and lowers crack resistance. In this context the strain rate must be an important factor because it affects the time for microstructural hydrogen diffusion/segregation at a specific microstructural location or at the damage tip. In this study tensile tests were carried out on a DP steel with different strain rates of 10− 2 and 10− 4 s−1. We performed the damage quantification microstructure characterization and fractography. Specifically the quantitative data of the damage evolution was analyzed using the classification of the damage evolution regimes in order to separately elucidate the effects of the hydrogen on damage initiation resistance and damage arrestability. In this study we obtained the following conclusions with respect to the strain rate. Lowering the strain rate increased the damage nucleation rate at martensite and reduced the critical strain for fracture through shortening the damage arrest regime. However the failure occurred via ductile modes regardless of strain rate.
Geomechanical Simulation of Energy Storage in Salt Formations
Oct 2021
Publication
A promising option for storing large-scale quantities of green gases (e.g. hydrogen) is in subsurface rock salt caverns. The mechanical performance of salt caverns utilized for long-term subsurface energy storage plays a signifcant role in long-term stability and serviceability. However rock salt undergoes non-linear creep deformation due to long-term loading caused by subsurface storage. Salt caverns have complex geometries and the geological domain surrounding salt caverns has a vast amount of material heterogeneity. To safely store gases in caverns a thorough analysis of the geological domain becomes crucial. To date few studies have attempted to analyze the infuence of geometrical and material heterogeneity on the state of stress in salt caverns subjected to long-term loading. In this work we present a rigorous and systematic modeling study to quantify the impact of heterogeneity on the deformation of salt caverns and quantify the state of stress around the caverns. A 2D fnite element simulator was developed to consistently account for the non-linear creep deformation and also to model tertiary creep. The computational scheme was benchmarked with the already existing experimental study. The impact of cyclic loading on the cavern was studied considering maximum and minimum pressure that depends on lithostatic pressure. The infuence of geometric heterogeneity such as irregularly-shaped caverns and material heterogeneity which involves diferent elastic and creep properties of the diferent materials in the geological domain is rigorously studied and quantifed. Moreover multi-cavern simulations are conducted to investigate the infuence of a cavern on the adjacent caverns. An elaborate sensitivity analysis of parameters involved with creep and damage constitutive laws is performed to understand the infuence of creep and damage on deformation and stress evolution around the salt cavern confgurations.
Hydrogen Accumulation and Distribution in Pipeline Steel in Intensified Corrosion Conditions
Apr 2019
Publication
Hydrogen accumulation and distribution in pipeline steel under conditions of enhanced corrosion has been studied. The XRD analysis optical spectrometry and uniaxial tension tests reveal that the corrosion environment affects the parameters of the inner and outer surface of the steel pipeline as well as the steel pipeline bulk. The steel surface becomes saturated with hydrogen released as a reaction product during insignificant methane dissociation. Measurements of the adsorbed hydrogen concentration throughout the steel pipe bulk were carried out. The pendulum impact testing of Charpy specimens was performed at room temperature in compliance with national standards. The mechanical properties of the steel specimens were found to be considerably lower and analogous to the properties values caused by hydrogen embrittlement.
Bayesian Inference and Uncertainty Quantification for Hydrogen-Enriched and Lean-Premixed Combustion Systems
May 2021
Publication
Development of probabilistic modelling tools to perform Bayesian inference and uncertainty quantification (UQ) is a challenging task for practical hydrogen-enriched and low-emission combustion systems due to the need to take into account simultaneously simulated fluid dynamics and detailed combustion chemistry. A large number of evaluations is required to calibrate models and estimate parameters using experimental data within the framework of Bayesian inference. This task is computationally prohibitive in high-fidelity and deterministic approaches such as large eddy simulation (LES) to design and optimize combustion systems. Therefore there is a need to develop methods that: (a) are suitable for Bayesian inference studies and (b) characterize a range of solutions based on the uncertainty of modelling parameters and input conditions. This paper aims to develop a computationally-efficient toolchain to address these issues for probabilistic modelling of NOx emission in hydrogen-enriched and lean-premixed combustion systems. A novel method is implemented into the toolchain using a chemical reactor network (CRN) model non-intrusive polynomial chaos expansion based on the point collocation method (NIPCE-PCM) and the Markov Chain Monte Carlo (MCMC) method. First a CRN model is generated for a combustion system burning hydrogen-enriched methane/air mixtures at high-pressure lean-premixed conditions to compute NOx emission. A set of metamodels is then developed using NIPCE-PCM as a computationally efficient alternative to the physics-based CRN model. These surrogate models and experimental data are then implemented in the MCMC method to perform a two-step Bayesian calibration to maximize the agreement between model predictions and measurements. The average standard deviations for the prediction of exit temperature and NOx emission are reduced by almost 90% using this method. The calibrated model then used with confidence for global sensitivity and reliability analysis studies which show that the volume of the main-flame zone is the most important parameter for NOx emission. The results show satisfactory performance for the developed toolchain to perform Bayesian inference and UQ studies enabling a robust and consistent process for designing and optimising low-emission combustion systems.
Continuum Level Simulation of the Grain Size and Misorientation Effects on Hydrogen Embrittlement in Nickel
Jul 2016
Publication
This paper addresses the size and misorientation effects on hydrogen embrittlement of a four grain nickel aggregate. The grain interior is modelled with orthotropic elasticity and the grain boundary with cohesive zone technique. The grain misorientation angle is parameterized by fixing the lower grains and rotating the upper grains about the out-of-plane axis. The hydrogen effect is accounted for via the three-step hydrogen informed cohesive zone simulation. The grain misorientation exerts an obvious weakening effect on the ultimate strength of the nickel aggregate which reaches its peak at misorientation angles around 20◦ but such effect becomes less pronounced in the case with a pre-crack. The misorientation could induce size effect in the otherwise size independent case without a pre-crack. The contribution of misorientation to the size effect is negligible compare to that caused by the existence of a pre-crack. These findings indicate that the misorientation effect in cases with a deep pre-crack is weaker than expected in shallow-pre-crack situations. Most of these conclusions hold for the hydrogen charging situation except that the ultimate strength is lowered in all the sub-cases due to hydrogen embrittlement. Interestingly it is observed that the size effect becomes less pronounced with hydrogen taken into account which is caused by the fact that hydrogen takes more time to reach the failure initiation site in larger grains.
Influence of Hydrogen for Crack Formation during Mechanical Clinching
Jan 2018
Publication
Hydrogen intrudes into the steel during pickling process which is a pre-processing before a joining process promoting crack formation. In a mechanical clinching which is one of joining method in the automotive industry cracks due to large strain sometimes forms. In order to guarantee reliability it is important to clarify the influence of hydrogen on crack formation of the joint. In this study we clarified the influence of hydrogen for the crack formation on the mechanical clinching. Hydrogen charge was carried out using an electrolytic cathode charge. After the charging mechanical clinching was performed. Mechanical clinching was carried out with steel plate and aluminium alloy plate. To clarify the influence of hydrogen mechanical clinching was conducted without hydrogen charring. To investigate the crack formation the test piece was cut and the cut surface was observed. When the joint was broken during the clinching the fracture surface was observed using an optical microscope and an electron microscope. The load-displacement diagram showed that without hydrogen charging the compressive load increased as the displacement increased. On the other hand the compressive load temporarily decreased with high hydrogen charging suggesting that cracks formed at the time. The cut surface observation showed that interlock was formed in both cases with low hydrogen charging and without hydrogen charging. With low hydrogen charging no cracks were formed in the joint. When high hydrogen charging was performed cracks were formed at the joining point. Fracture analysis showed brittle-like fracture surface. These results indicate that hydrogen induces crack formation in the mechanical clinching.
The Enhanced Hydrogen Storage Capacity of Carbon Fibers The Effect of Hollow Porous Structure and Surface Modification
Jul 2021
Publication
In this study highly porous carbon fiber was prepared for hydrogen storage. Porous carbon fiber (PCF) and activated porous carbon fiber (APCF) were derived by carbonization and chemical activation after selectively removing polyvinyl alcohol from a bi-component fiber composed of polyvinyl alcohol and polyacrylonitrile (PAN). The chemical activation created more pores on the surface of the PCF and consequently highly porous APCF was obtained with an improved BET surface area (3058 m2 g−1) and micropore volume (1.18 cm3 g−1) compare to those of the carbon fiber which was prepared by calcination of monocomponent PAN. APCF was revealed to be very efficient for hydrogen storage its hydrogen capacity of 5.14 wt% at 77 K and 10 MPa. Such hydrogen storage capacity is much higher than that of activated carbon fibers reported previously. To further enhance hydrogen storage capacity catalytic Pd nanoparticles were deposited on the surface of the APCF. The Pd-deposited APCF exhibits a high hydrogen storage capacity of 5.45 wt% at 77 K and 10 MPa. The results demonstrate the potential of Pd-deposited APCF for efficient hydrogen storage.
Prospecting Stress Formed by Hydrogen or Isotope Diffused in Palladium Alloy Cathode
Oct 2018
Publication
The objective of this project is to take into account the mechanical constraints formed by diffusion of hydrogen or tritium in watertight palladium alloy cathode. To know the origin of these it was necessary to discriminating the damaging effects encountered. Effectively hydrogen and isotope induce deformation embrittlement stress corrosion cracking and cathodic corrosion in different regions of cathode. Palladium can be alloyed with silver or yttrium to favourably increase diffusion and reduce these constraints. Effects of electrochemical factors temperature cathode structure adsorbed transient complex of palladium and porous material support are given to estimate and to limit possible damage.
Hydrogen Embrittlement: Future Directions—Discussion
Jun 2017
Publication
The final session of the meeting consisted of a discussion panel to propose future directions for research in the field of hydrogen embrittlement and the potential impact of this research on public policy.
This article is a transcription of the recorded discussion of ‘Hydrogen Embrittlement: Future Directions’ at the Royal Society Scientific Discussion Meeting Challenges of Hydrogen and Metals Jan 16th–18th 2017. The text is approved by the contributors. H.L. transcribed the session and drafted the manuscript. Y.C. assisted in the preparation of the manuscript.
Link to document download on Royal Society Website
This article is a transcription of the recorded discussion of ‘Hydrogen Embrittlement: Future Directions’ at the Royal Society Scientific Discussion Meeting Challenges of Hydrogen and Metals Jan 16th–18th 2017. The text is approved by the contributors. H.L. transcribed the session and drafted the manuscript. Y.C. assisted in the preparation of the manuscript.
Link to document download on Royal Society Website
Hydrogen Storage in Depleted Gas Reservoirs: A Comprehensive Review
Nov 2022
Publication
Hydrogen future depends on large-scale storage which can be provided by geological formations (such as caverns aquifers and depleted oil and gas reservoirs) to handle demand and supply changes a typical hysteresis of most renewable energy sources. Amongst them depleted natural gas reservoirs are the most cost-effective and secure solutions due to their wide geographic distribution proven surface facilities and less ambiguous site evaluation. They also require less cushion gas as the native residual gases serve as a buffer for pressure maintenance during storage. However there is a lack of thorough understanding of this technology. This work aims to provide a comprehensive insight and technical outlook into hydrogen storage in depleted gas reservoirs. It briefly discusses the operating and potential facilities case studies and the thermophysical and petrophysical properties of storage and withdrawal capacity gas immobilization and efficient gas containment. Furthermore a comparative approach to hydrogen methane and carbon dioxide with respect to well integrity during gas storage has been highlighted. A summary of the key findings challenges and prospects has also been reported. Based on the review hydrodynamics geochemical and microbial factors are the subsurface’s principal promoters of hydrogen losses. The injection strategy reservoir features quality and operational parameters significantly impact gas storage in depleted reservoirs. Future works (experimental and simulation) were recommended to focus on the hydrodynamics and geomechanics aspects related to migration mixing and dispersion for improved recovery. Overall this review provides a streamlined insight into hydrogen storage in depleted gas reservoirs.
Effect of Cementite on the Hydrogen Diffusion/Trap Characteristics of 2.25Cr-1Mo-0.25V Steel with and without Annealing
May 2018
Publication
Hydrogen embrittlement (HE) is a critical issue that affects the reliability of hydrogenation reactors. The hydrogen diffusivity/trap characteristics of 2.25Cr-1Mo-0.25V steel are important parameters mainly used to study the HE mechanism of steel alloys. In this work the hydrogen diffusivity/trap characteristics of heat-treated (annealed) and untreated 2.25Cr-1Mo-0.25V steel were studied using an electrochemical permeation method. The microstructures of both 2.25Cr-1Mo-0.25V steels were investigated by metallurgical microscopy. The effect of cementite on the hydrogen diffusivity/trap mechanisms was studied using thermodynamics-based and Lennard–Jones potential theories. The results revealed that the cementite located at the grain boundaries and at the interfaces of lath ferrite served as a kind of hydrogen trap (i.e. an irreversible hydrogen trap). In addition hydrogen was transported from ferrite to cementite via up-hill diffusion thereby supporting the hypothesis of cementite acting as a hydrogen trap.
Hydrogen Effects on Progressively Cold-Drawn Pearlitic Steels: Between Donatello and Michelangelo
Sep 2017
Publication
This paper reviews previous research by the author in the field of hydrogen effects on progressively cold-drawn pearlitic steels in terms of hydrogen degradation (HD) hydrogen embrittlement (HE) or at the micro-level hydrogen-assisted micro-damage (HAMD) thus affecting their microstructural integrity and compromising the (macro-)structural integrity of civil engineering structures such as prestressed concrete bridges. It is seen that hydrogen effects in pearlitic microstructure (either oriented or not) are produced at the finest micro-level by plastic tearing in the form in general of hydrogen damage topography (HDT) with different appearances depending of the cold drawing degree evolving from the so-called tearing topography surface (TTS) in hot-rolled (not cold-drawn at all) or slightly cold-drawn pearlitic steels to a sort of enlarged and oriented TTS (EOTTS) in heavily drawn steels (the pronounced enlargement and marked orientation being along the wire axis or cold drawing direction). Whereas the pure TTS mode (null or low degree of cold drawing) resembles the Michelangello stone sculpture texture (MSST) the EOTTS mode does the same in relation to the Donatello wooden sculpture texture (DWST).
Hydrogen adsorption on transition metal carbides
Jan 2019
Publication
Transition metal carbides are a class of materials widely known for both their interesting physical properties and catalytic activity. In this work we have used plane-wave DFT methods to study the interaction with increasing amounts of molecular hydrogen on the low-index surfaces of four major carbides – TiC VC ZrC and NbC. Adsorption is found to be generally exothermic and occurs predominantly on the surface carbon atoms. We identify trends over the carbides and their surfaces for the energetics of the adsorption as a function of their electronic and geometrical characteristics. An ab initio thermodynamics formalism is used to study the properties of the slabs as the hydrogen coverage is increased.
Calibrating a Ductile Damage Model for Two Pipeline Steels: Method and Challenges
Dec 2020
Publication
This work is part of a project that aims to develop a micromechanics based damage law taking into account hydrogen assisted degradation. A 'vintage' API 5L X56N and a 'modern' API 5L X70M pipeline steel have been selected for this purpose. The paper focuses on an experimental calibration of ductile damage properties of the well known complete Gurson model for the two steels in absence of hydrogen. A basic microstructural characterization is provided showing a banded ferrite-pearlite microstructure for both steels. Charpy impact tests showed splits at the fracture surface for the X70 steel. Double-notched round bar tensile tests are performed aiming to provide the appropriate input for damage model calibration. The double-notched nature of the specimens allows to examine the material state at maximum load in the unfailed notch and the final material state in the failed notch. Different notch radii are used capturing a broad range of positive stress triaxialities. The notches are optically monitored for transverse necking in two perpendicular directions (transverse to rolling and through thickness) to reveal any anisotropy in plastic deformation and/or damage. It is explained how the occurrence of splits at the segregation zone and anisotropy complicate the calibration procedure. Calibration is done for each steel and acceptable results are obtained. However the occurrence of splits did not allow to evaluate the damage model for the highest levels of tested stress triaxiality.
Hydrogen Assisted Macrodelamination in Gas Lateral Pipe
Jul 2016
Publication
Hydrogen assisted macrodelamination in the pipe elbows of 40-year exploited lateral pipelines located behind the compressor station was studied. The crack on the external surface of the pipe elbow was revealed. Macrodelamination was occurred in the steel being influenced by the joined action of working loads and hydrogen absorbed by metal during long-term operation. The causes of the material degradation were investigated by non-destructive testing using ultrasound thickness meter observing microstructure hydrostatic pressure testing and mechanical properties testing of pipe steel.<br/>Intensive degradation of steel primarily essential reduction of plasticity was revealed. The degradation degree of the pipe elbow steel was higher than of the straight pipe steel regardless of a section was tensioned or compressed. Basing on the tensile tests carried out on cylindrical smooth and notched specimens from the pipe elbow steel it was established that the plasticity of the damaged steel could be measured correctly only on the specimens with a circular notch due to concentration of deformation in the cross section location only. The limitations in using elongation and reduction in area for characterisation of plasticity of the pipe steel with extensive delamination were defined. The diagnostic features of macrodelamination namely an abnormal thickness meter readings and a sharp decrease in hardness and plasticity of the pipe elbow steel were established.
Feature of Stress Corrosion Cracking of Degraded Gas Pipeline Steels
Aug 2019
Publication
Stress corrosion cracking (SCC) of steels can reduce the structural integrity of gas pipelines. To simulate in-service degradation of pipeline steels in laboratory the method of accelerated degradation consisted in subjecting specimens to electrolytic hydrogenation to loading up the certain plastic deformation and heating of specimen at 250°C was recently developed. The purpose of this paper was to analyse mechanical and SCC behaviour of in-service and in-laboratory degraded gas pipeline steels and to reveal some fractographic features of SCC. Three pipeline steels of the different strength (17H1S which is equivalent of API X52 API X60 and API X70) were investigated. The characteristics of the as-received pipeline steels with different strength were compared with the properties of pipeline steels after in-service and in-laboratory degradation. An influence of the NS4 solution on SCC resistance of 17H1S and API X60 steels in the as-received state and after the accelerated degradation using slow strain rate tension method was analysed. The noticeable decrease of plasticity for 17H1S and API X60 steels after long-term operation was shown. Deep microdelaminations revealed in the central part of fracture surfaces for the operated steels can be considered as the signs of dissipated damaging in the metal caused by texture and hydrogen absorbed by metal. Comparison of the SCC tests results showed that the characteristics of both steels in the as-received state were insignificantly changed under the influence of the environment. At the same time the degraded steels were characterized by a high sensitivity to SCC. It was shown fractographically that it associated with cracking along interfaces of ferrite and pearlite grains with secondary deep intergranular cracks formation and also by delamination between ferrite and cementite inside pearlite grains. The similar fracture mechanism at SCC tests was revealed for near the outer surface of the specimens and in the central part of the fracture surfaces of in-laboratory degraded specimens. These results demonstrated the key role of hydrogen during SCC and in-bulk cracking as well.
Effect of Hydrogen on Short Crack Propagation in SA508 Grade 3 Class I Low Alloy Steel Under Cyclic Loading
Aug 2019
Publication
The effect of hydrogen on short crack propagation under cyclic loading in SA508 Grade 3 Class I low alloy steel is investigated. This low alloy steel is used in manufacturing of pressure vessel installed in Indian nuclear power plants. During operation these pressure vessels are subjected to continuous supply of pressurized hot water at 600 K and hence are susceptible to hydrogen embrittlement. In past research has been conducted on the effect of hydrogen embrittlement on long fatigue crack propagation in this material but the mechanistic understanding and correlation of hydrogen embrittlement with microstructural features in the material can be understood well by studying the effect of hydrogen embrittlement on short fatigue crack propagation. Short fatigue cracks are of the order of 10 µm to 1 mm and unlike long cracks these short cracks strongly interact with the microstructural features in the material such as grain/phase boundaries. The effect of hydrogen embrittlement on short crack propagation is studied by artificial hydrogen charging of the material through electrochemical process. The single edge notch tension (SENT) specimens with an initial notch of the order of 85 to 90 µm are used to study the short crack propagation. The short cracks in hydrogen charged samples initiated from the notch at lower number of loading cycles as compared to the uncharged notched samples for the same value of applied stress range (Δσ). After initiation the short fatigue crack in hydrogen charged samples propagated at higher rate as compared to uncharged samples. This dissimilarity in crack propagation behavior is due to the difference in the interaction of short fatigue crack with the microstructural features for a hydrogen charged and uncharged samples.
Hydrogen Assisted Crack Initiation and Propagation in Nickel-cobalt Heat Resistant Superalloys
Aug 2019
Publication
It has been investigated the Ni-Co alloys (obtained from powder 0.1...0.3 mm under hot gaseous (in argon) isostatic pressure (up to 300 MPa) (Ni60Co15Cr8W8Al2Mo3) (Firth Rixon Metal Ltd Sheffield) and deformed (obtained by vacuum induced remealting) materials (Ni62Cr14Co10Mo5Nb3Al3Ti3) for gaseous turbine discs. Investigation has performed in the range of temperature 25…800°С and hydrogen pressure up to 70 MPa. By the 3D visualization of crack morphology it has been discovered the structure of fatigue crack surface and established the refer points on crack path including the boundary between the matrix and intermetallic particles (400×200 μm) crack opening structural elements distributions on the surface for selection of next local areas for more precision fracture surface and TEM examinations. Hydrogen influence on cyclic crack resistance parameters appears in the decreasing of loading cycles number (with amplitudes 15 MPa) in hydrogenated specimens of both alloys and increase with hydrogen concentration. At the highest hydrogen saturation regimes of Ni60Co15Cr8W8Al2Mo3 alloy (800°С 35 MPa Н2 36 hours СН = 32.7 ppm) number of cycles which necessary for crack initiation is 3 times less in comparison with specimen in initial state. At crack initiation step in hydrogenated Ni56Cr14Co15Mo5Al3Ti3 alloy it has been established that before intermetallic inclusion (400×200 μm) local stresses increased after its passing – has decreased. By fracture surface investigation it has been found the micro cracks up to 40 μm. Thin structure of heat resistant superalloys has characterises by disperse phase agglomeration with dimensions from 5 to 30 nm and crack propagation has a jumping character with no less then 50…70 nm steps.
Study on Flake Formation Behavior and Its Influence Factors in Cr5 Steel
Apr 2018
Publication
A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However according to recent studies the hydrogen leads to the decline of the mechanical properties of steel which is known as hydrogen embrittlement is another reason for flake formation. In addition the phenomenon of stress induced hydrogen uphill diffusion should not be neglected. All of the three behaviors are at work simultaneously. In order to further explore the formation mechanism of flakes in steel the process of flake initiation and growth were studied with the following three coupling factors: trap hydrogen pressure hydrogen embrittlement and stress induced hydrogen re-distribution. The analysis model was established using the finite element method and a crack whose radius is 0.5 mm was set in its center. The cohesive method and Bilinear Traction Separate Law (BTSL) were used to address the coupling effect. The results show that trap hydrogen pressure is the main driving force for flake formation. After the high hydrogen pressure was generated around the trap a stress field formed. In addition the trap is the center of stress concentration. Then hydrogen is concentrated in a distribution around this trap and most of the steel mechanical properties are reduced. The trap size is a key factor for defining the critical hydrogen content for flake formation and propagation. However when the trap size exceeds the specified value the critical hydrogen content does not change any more. As for the crack whose radius is 0.5 mm the critical hydrogen content of Cr5VMo steel is 2.2 ppm which is much closer to the maximum safe hydrogen concentration of 2.0 ppm used in China. The work presented in this article increases our understanding of flake formation and propagation mechanisms in steel.
Hydrogen Embrittlement and Notch Tensile Strength of Pearlitic Steel: A Numerical Approach
Dec 2020
Publication
This paper offers a numerical approach to the problem of hydrogen embrittlement and notch tensile strength of sharply notched specimens of high-strength pearlitic steel supplied in the form of hot rolled bars by using the finite element method in order to determine how the notch depth influences the concentration of hydrogen in the steady-state regime for different loading values. Numerical results show that the point of maximum hydrostatic stress (towards which hydrogen is transported by a mechanism of stress-assisted diffusion) shifts from the notch tip to the inner points of the specimen under increasing load with numerical evidence of an elevated inwards gradient of hydrostatic stress “pumping” hydrogen inside the sample.
Requirements for Hydrogen Resistance of Materials in CI Engine Toxic Substances Powered by Biofuels
Aug 2019
Publication
It has been described the conception of using platinum catalytic layer in multi hole fuel injector atomizer. The catalytic layer has been placed on not working part of atomizer needle. The aim of modification was activation of dehydrogenation reaction paraffin to olefin hydrocarbons with escape hydrogen molecule in CI engine bio fuel. The modification of atomizer with catalytic layer and reaction process leads to the presence of hydrogen and its influence on structural materials properties after the catalysis which requires the high hydrogen and crack resistance of used materials. There is used high speed steel as material. Article describes how hydrogen and combustion gases influence on thermal friction processes on this material. First of all the investigations were conduct 359 engine with biodiesel. During test had been observed nitrogen oxides carbon monoxide and particles emission. The obtained results show that there is possibility to lower toxic substances emission in exhaust gases CI engine powered by biodiesel. On the second it has been described the influence of biodiesel (including hydrogen) on fuel injector components and their influence on structural materials characteristics. There has been presented how biodiesel with hydrogen influences on precision elements and injection and return discharges. The investigation has been made by using engine test bench and fuel injector and pumps test equipment.
Effect of Hydrogen on Very High Cycle Fatigue Behavior of a Low-strength Cr-Ni-Mo-V Steel Containing Micro-defects
Dec 2017
Publication
The role of hydrogen in fatigue failure of low strength steels is not as well understood as of high strength steels in very high cycle fatigue regime. In this work axially cyclic tests on a low strength Cr-Ni-Mo-V steel with charged hydrogen were carried out up to the very high cycle fatigue regime under ultrasonic frequency to examine the degradation of fatigue strength and associated failure mechanisms. Results show that the S-N curves show a continuously decreasing mode and hydrogen-charged specimens have lower fatigue strength and shorter fatigue lifetime as compared with as-received specimens. It is concluded that the hydrogen trapped by inclusions drives interior micro-defects as dominant crack initiation site and has a clear link to the initiation and early growth of interior fatigue cracks.
Characterising Hydrogen Induced Cracking of Alloy 625+ Using Correlative SEM - EDX and NanoSIMS
Dec 2020
Publication
Hydrogen induced cracking behaviour of O&G nickel alloy 625+ (UNS N07716) was investigated. Deuterium was introduced electrochemically into samples by cathodic polarisation (3.5 wt.% NaCl.D2O) under different mechanical conditions. Subsequently deuterium distributions were mapped using NanoSIMS. Deuterium was used as an isotopic tracer instead of hydrogen to avoid the detection of hydrogen artefacts. Complimentary image analysis using scanning electron microscopy (SEM) and low voltage energy dispersive X-ray (EDX) allowed the identification of microstructural features corresponding to deuterium enrichments. The results provided experimental evidence of enrichments at dislocation slip bands (DSB) twin boundary and grain boundary features that include σ precipitates.
Hydrogen Enhanced Fatigue Crack Growth Rates in a Ferritic Fe-3wt%Si Alloy
Dec 2018
Publication
It is well known that ferrous materials can be damaged by absorption of hydrogen. If a sufficient quantity of hydrogen penetrates into the material static fracture and the material's fatigue performances can be affected negatively in particular causing an increase in the material crack growth rates. The latter is often referred as Hydrogen Affected-Fatigue Crack Growth Rate (HA-FCGR). It is therefore of paramount importance to quantify the impact in terms of hydrogen induce fatigue crack growth acceleration in order to determine the life of components exposed to hydrogen and avoid unexpected catastrophic failures. In this study in-situ fatigue crack growth rate testing on Compact Tension (CT) specimens were carried out to determine the fatigue crack growth behaviour for a Fe-3 wt%Si alloy and X70 pipeline steel. Tests were carried out in two environmental conditions i.e. laboratory air and in-situ electrochemically charged hydrogen and different mechanical conditions in terms of load ratio (R = 0.1 and R = 0.5 for the Fe-3 wt%Si R = 0.1 for the X70 steel) and test frequency (f = 0.1 Hz 1 Hz and 10 Hz) were adopted under electrochemically charged hydrogen conditions. The results show a clear detrimental effect of H for the specimens tested in hydrogen when compared to the specimens tested in air for both materials and that the impact of hydrogen is test frequency-dependent: the hydrogen induced acceleration is more prominent as the frequency is decreased. Post-mortem surface investigations consistently relate the global crack growth acceleration to a shift from transgranular to Quasi-cleavage fracture mechanism. Despite such consistency the acceleration factor strongly depends on the material: Fe-3wt%Si features acceleration up to 1000 times while X70 accelerates up to 76 times when compare to the material fatigue crack growth rate recorded in air. Observation of the deformation activities in the crack wake in relation to the transition into hydrogen accelerated regime in fatigue crack growth show a tendency toward restricted plastic activity in presence of hydrogen.
Review of Solid State Hydrogen Storage Methods Adopting Different Kinds of Novel Materials
Aug 2015
Publication
Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.
How To Transport and Store Hydrogen – Facts and Figures
Apr 2021
Publication
The EU has set a goal of achieving climate neutrality by 2050 and decided to raise its 2030 climate target to 55%. For this the EU needs to transform its energy system. It is of paramount importance that it will become more efficient affordable and interconnected. Hydrogen can play a pivotal role in the EU’s decarbonisation efforts and be at the centre of the energy system integration supporting transport of renewable energy over very long distances and facilitating renewables storage from one season to another.<br/><br/>ENTSOG GIE and Hydrogen Europe have joined forces on a factsheet that answers a number of fundamental questions about gaseous and liquid hydrogen transport and storage titled “How to transport and store hydrogen? Facts and figures”. This factsheet provides an objective and informative analysis on key concepts terminology and facts and figures from different public sources.<br/><br/>The factsheet illustrates the EU’s potential to enable a global hydrogen economy and to become a global technology leader due to its extensive gas infrastructure that can be used to transport blends of hydrogen or be converted to transport pure hydrogen.
Blue Hydrogen as an Enabler of Green Hydrogen: The Case of Germany
Jun 2020
Publication
In Germany decarbonization of the electricity sector by fostering renewables and now phasing out coal-fired power is on track to reach the 2050 de-carbonisation targets while decarbonising non-electric energy consumption is proving to be more difficult. The present discussion of a national hydrogen strategy has run into strong political opposition against carbon sequestration as a necessary element in the use of decarbonized natural gas (blue hydrogen) and is aiming at the use of green hydrogen only (from renewable electricity and electrolysis). This paper shows that as long as the power sector is not decarbonized – not likely before 2040 – only marginal volumes of renewable electricity will be available to produce green hydrogen. To meet the decarbonization target by 2050 blue hydrogen has to fill that gap paving the way for green hydrogen at a later stage. The paper discusses the elements needed for an expedient development of blue hydrogen. It also points at the need and instruments to decarbonize core industries like the steel and chemical industry so that they can become future proof in competition with the US which is more advanced with a decarbonization strategy for its industry based on carbon sequestration.
Shielded Hydrogen Passivation – A Novel Method for Introducing Hydrogen into Silicon
Sep 2017
Publication
This paper reports a new approach for exposing materials including solar cell structures to atomic hydrogen. This method is dubbed Shielded Hydrogen Passivation (SHP) and has a number of unique features offering high levels of atomic hydrogen at low temperature whilst inducing no damage. SHP uses a thin metallic layer in this work palladium between a hydrogen generating plasma and the sample which shields the silicon sample from damaging UV and energetic ions while releasing low energy neutral atomic hydrogen onto the sample. In this paper the importance of the preparation of the metallic shield either to remove a native oxide or to contaminate intentionally the surface are shown to be potential methods for increasing the amount of atomic hydrogen released. Excellent damage free surface passivation of thin oxides is observed by combining SHP and corona discharge obtaining minority carrier lifetimes of 2.2 ms and J0 values below 5.47 fA/cm2. This opens up a number of exciting opportunities for the passivation of advanced cell architectures such as passivated contacts and heterojunctions.
Hydrogen Assisted Cracking in Pearlitic Steel Rods: The Role of Residual Stresses Generated by Fatigue Precracking
May 2017
Publication
Stress corrosion cracking (SCC) of metals is an issue of major concern in engineering since this phenomenon causes many catastrophic failures of structural components in aggressive environments. SCC is even more harmful under cathodic conditions promoting the phenomenon known as hydrogen assisted cracking (HAC) hydrogen assisted fracture (HAF) or hydrogen embrittlement (HE). A common way to assess the susceptibility of a given material to HAC HAF or HE is to subject a cracked rod to a constant extension rate tension (CERT) test until it fractures in this harsh environment. This paper analyzes the influence of a residual stress field generated by fatigue precracking on the sample’s posterior susceptibility to HAC. To achieve this goal numerical simulations were carried out of hydrogen diffusion assisted by the stress field. Firstly a mechanical simulation of the fatigue precracking was developed for revealing the residual stress field after diverse cyclic loading scenarios and posterior stress field evolution during CERT loading. Afterwards a simulation of hydrogen diffusion assisted by stress was carried out considering the residual stresses after fatigue and the superposed rising stresses caused by CERT loading. Results reveal the key role of the residual stress field after fatigue precracking in the HAC phenomena in cracked steel rods as well as the beneficial effect of compressive residual stress.
A Manganese Hydride Molecular Sieve for Practical Hydrogen Storage Under Ambient Conditions
Dec 2018
Publication
A viable hydrogen economy has thus far been hampered by the lack of an inexpensive and convenient hydrogen storage solution meeting all requirements especially in the areas of long hauls and delivery infrastructure. Current approaches require high pressure and/or complex heat management systems to achieve acceptable storage densities. Herein we present a manganese hydride molecular sieve that can be readily synthesized from inexpensive precursors and demonstrates a reversible excess adsorption performance of 10.5 wt% and 197 kgH2 m-3 at 120 bar at ambient temperature with no loss of activity after 54 cycles. Inelastic neutron scattering and computational studies confirm Kubas binding as the principal mechanism. The thermodynamically neutral adsorption process allows for a simple system without the need for heat management using moderate pressure as a toggle. A storage material with these properties will allow the DOE system targets for storage and delivery to be achieved providing a practical alternative to incumbents such as 700 bar systems which generally provide volumetric storage values of 40 kgH2 m-3 or less while retaining advantages over batteries such as fill time and energy density. Reasonable estimates for production costs and loss of performance due to system implementation project total energy storage costs roughly 5 times cheaper than those for 700 bar tanks potentially opening doors for increased adoption of hydrogen as an energy vector.
A Review for Consistent Analysis of Hydrogen Permeability through Dense Metallic Membranes
Jun 2020
Publication
The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However the hydrogen permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper various methods for consistent analysis of hydrogen permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of hydrogen permeability are introduced: (1) prediction of hydrogen flux under given conditions (2) comparability of hydrogen permeability (3) understanding of the anomalous temperature dependence of hydrogen permeability of Pd-Ag alloy membrane and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high hydrogen permeability together with strong resistance to hydrogen embrittlement.
Comparing Exergy Losses and Evaluating the Potential of Catalyst-filled Plate-fin and Spiral-wound Heat Exchangers in a Large-scale Claude Hydrogen Liquefaction Process
Jan 2020
Publication
Detailed heat exchanger designs are determined by matching intermediate temperatures in a large-scale Claude refrigeration process for liquefaction of hydrogen with a capacity of 125 tons/day. A comparison is made of catalyst filled plate-fin and spiral-wound heat exchangers by use of a flexible and robust modelling framework for multi-stream heat exchangers that incorporates conversion of ortho-to para-hydrogen in the hydrogen feed stream accurate thermophysical models and a distributed resolution of all streams and wall temperatures. Maps of the local exergy destruction in the heat exchangers are presented which enable the identification of several avenues to improve their performances.<br/>The heat exchanger duties vary between 1 and 31 MW and their second law energy efficiencies vary between 72.3% and 96.6%. Due to geometrical constraints imposed by the heat exchanger manufacturers it is necessary to employ between one to four parallel plate-fin heat exchanger modules while it is possible to use single modules in series for the spiral-wound heat exchangers. Due to the lower surface density and heat transfer coefficients in the spiral-wound heat exchangers their weights are 2–14 times higher than those of the plate-fin heat exchangers.<br/>In the first heat exchanger hydrogen feed gas is cooled from ambient temperature to about 120 K by use of a single mixed refrigerant cycle. Here most of the exergy destruction occurs when the high-pressure mixed refrigerant enters the single-phase regime. A dual mixed refrigerant or a cascade process holds the potential to remove a large part of this exergy destruction and improve the efficiency. In many of the heat exchangers uneven local exergy destruction reveals a potential for further optimization of geometrical parameters in combination with process parameters and constraints.<br/>The framework presented makes it possible to compare different sources of exergy destruction on equal terms and enables a qualified specification on the maximum allowed pressure drops in the streams. The mole fraction of para-hydrogen is significantly closer to the equilibrium composition through the entire process for the spiral-wound heat exchangers due to the longer residence time. This reduces the exergy destruction from the conversion of ortho-hydrogen and results in a higher outlet mole fraction of para-hydrogen from the process.<br/>Because of the higher surface densities of the plate-fin heat exchangers they are the preferred technology for hydrogen liquefaction unless a higher conversion to heat exchange ratio is desired.
Hydrogen Production from Offshore Wind Parks: Current Situation and Future Perspectives
Jun 2021
Publication
With the increase in renewable energy connected to the grid new challenges arise due to its variable supply of power. Therefore it is crucial to develop new methods of storing energy. Hydrogen can fulfil the role of energy storage and even act as an energy carrier since it has a much higher energetic density than batteries and can be easily stored. Considering that the offshore wind sector is facing significant growth and technical advances hydrogen has the potential to be combined with offshore wind energy to aid in overcoming disadvantages such as the high installation cost of electrical transmission systems and transmission losses. This paper aims to outline and discuss the main features of the integration of hydrogen solutions in offshore wind power and to offer a literature review of the current state of hydrogen production from offshore wind. The paper provides a summary of the technologies involved in hydrogen production along with an analysis of two possible hydrogen producing systems from offshore wind energy. The analysis covers the system components including hydrogen storage the system configuration (i.e. offshore vs. onshore electrolyzer) and the potential uses of hydrogen e.g. Power to Mobility Power to Power and Power to Gas.
Optimal Operation of a Hydrogen Storage and Fuel Cell Coupled Integrated Energy System
Mar 2021
Publication
Integrated energy systems have become an area of interest as with growing energy demand globally means of producing sustainable energy from flexible sources is key to meet future energy demands while keeping carbon emissions low. Hydrogen is a potential solution for providing flexibility in the future energy mix as it does not emit harmful gases when used as an energy source. In this paper an integrated energy system including hydrogen as an energy vector and hydrogen storage is studied. The system is used to assess the behaviour of a hydrogen production and storage system under different renewable energy generation profiles. Two case studies are considered: a high renewable energy generation scenario and a low renewable energy generation scenario. These provide an understanding of how different levels of renewable penetration may affect the operation of an electrolyser and a fuel cell against an electricity import/export pricing regime. The mathematical model of the system under study is represented using the energy hub approach with system optimisation through linear programming conducted via MATLAB to minimise the total operational cost. The work undertaken showcases the unique interactions the fuel cell has with the hydrogen storage system in terms of minimising grid electricity import and exporting stored hydrogen as electricity back to the grid when export prices are competitive.
A New Design Concept for Prevention of Hydrogen-induced Mechanical Degradation: Viewpoints of Metastability and High Entropy
Dec 2018
Publication
‟How crack growth is prevented” is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance type 304 austenitic steels show high hydrogen embrittlement susceptibility because of the high hydrogen diffusivity of bcc (α´) martensite. In contrast metastability in specific austenitic steels enables fcc (γ) to hcp (ε) martensitic transformation which decreases hydrogen diffusivity and increases strength simultaneously. As a result even if hydrogen-assisted cracking occurs during monotonic tensile deformation the ε-martensite acts to arrest micro-damage evolution when the amount of ε-martensite is limited. Thus the formation of ε-martensite can decrease hydrogen embrittlement susceptibility in austenitic steels. However a considerable amount of ε-martensite is required when we attempt to have drastic improvements of work hardening capability and strength level with respect to transformation-induced plasticity effect. Since the hcp structure contains a less number of slip systems than fcc and bcc the less stress accommodation capacity often causes brittle-like failure when the ε-martensite fraction is large. Therefore ductility of ε-martensite is another key when we maximize the positive effect of ε-martensitic transformation. In fact ε-martensite in a high entropy alloy was recently found to be extraordinary ductile. Consequently the metastable high entropy alloys showed low fatigue crack growth rates in a hydrogen atmosphere compared with conventional metastable austenitic steels with α´-martensitic transformation. We here present effects of metastability to ε-phase and configurational entropy on hydrogen-induced mechanical degradation including monotonic tension properties and fatigue crack growth resistance.
Effect of Vanadium-alloying on Hydrogen Embrittlement of Austenitic High-nitrogen Steels
Dec 2018
Publication
The effect of hydrogen on tensile behavior and fracture mechanisms of V-alloying and V-free high-nitrogen austenitic steels was evaluated. Two steels with the chemical compositions of Fe-23Cr–17Mn–0.1C–0.6N (0V-HNS) and Fe-19Cr–22Mn–1.5V–0.3C–0.9N (1.5V-HNS) were electrochemically hydrogen-charged in NaCl water-solution for 100 hours. According to X-ray diffraction analysis and TEM researches V-alloying promotes particle strengthening of the 1.5V-HNS. Despite differences in chemical compositions namely carbon and nitrogen concentrations a solid solution hardening is similar for both steels because of precipitate-assisted depletion of austenite by interstitial atoms (carbon and nitrogen) in 1.5V-HNS. For hydrogen-free state the values of the yield stress and the tensile strength are higher for particle-strengthened 1.5V-HNS as compared to 0V-HNS. Hydrogen-charging increases both the yield stress and the tensile strength of the steels but hydrogen-assisted fracture micromechanisms are different for 0V-HNS and 1.5V-HNS. Hydrogen-charging drastically reduces a total elongation in 0V-HNS but provides insufficient embrittlement in 1.5V-HNS. Hydrogen-assisted brittle layers form on lateral surfaces of the specimens and the widths and fracture micromechanisms in them are different for two steels. For 0V-HNS surface layers of 84 μm in width possess transgranular brittle fracture mechanism (quasi-cleavage mode). For 1.5V-HNS the brittle surface layers (31 μm width) destroy in intergranular brittle fracture mode. The central parts of steel specimens show dimple fracture similar to hydrogen-free steels. The possible reasons for different hydrogen-induced effects in 0V-HNS and 1.5V-HNS are discussed.
Morphological, Structural and Hydrogen Storage Properties of LaCrO3 Perovskite-Type Oxides
Feb 2022
Publication
Recently perovskite-type oxides have attracted researchers as new materials for solid hydrogen storage. This paper presents the performances of perovskite-type oxide LaCrO3 dedicated for hydrogen solid storage using both numerical and experimental methods. Ab initio calculations have been used here with the aim to investigate the electronic mechanical and elastic properties of LaCrO3Hx (x = 0 6) for hydrogen storage applications. Cell parameters crystal structures and mechanical properties are determined. Additionally the cohesive energy indicates the stability of the hydride. Furthermore the mechanical properties showed that both compounds (before and after hydrogenation) are stable. The microstructure and storage capacity at different temperatures of these compounds have been studied. We have shown that storage capacities are around 4 wt%. The properties obtained from this type of hydride showed that it can be used for future applications. XRD analysis was conducted in order to study the structural properties of the compound. Besides morphological thermogravimetric analysis was also conducted on the perovskite-type oxide. Finally a comparison of these materials with other hydrides used for hydrogen storage was carried out.
Application of the Incremental Step Loading Technique to Small Punch Tests on S420 Steel in Acid Environments
Dec 2020
Publication
The Small Punch test has been recently used to estimate mechanical properties of steels in aggressive environments. This technique very interesting when there is shortage of material consists in using a small plane specimen and punch it until it fails. The type of tests normally used are under a constant load in an aggressive environment with the target to determine the threshold stress. However this is an inaccurate technique which takes time as the tests are quite slow. In this paper the Small Punch tests are combined with the step loading technique collected in the standard ASTM F1624 [1] to obtain the value of threshold stress of an S420 steel in a total time of approximately one week. The ASTM F1624 indicates how to apply constant load steps in hydrogen embrittlement environments increasing them subsequently and adapting their duration until the specimen fails. The environment is created by means of cathodic polarization of cylindrical tensile specimens in an acid electrolyte. A batch of standard tests are performed to validate the methodology.
Reversible Hydrogen Storage Using Nanocomposites
Jul 2020
Publication
In the field of energy storage recently investigated nanocomposites show promise in terms of high hydrogen uptake and release with enhancement in the reaction kinetics. Among several carbonaceous nanovariants like carbon nanotubes (CNTs) fullerenes and graphitic nanofibers reveal reversible hydrogen sorption characteristics at 77 K due to their van der Waals interaction. The spillover mechanism combining Pd nanoparticles on the host metal-organic framework (MOF) show room temperature uptake of hydrogen. Metal or complex hydrides either in the nanocomposite form and its subset nanocatalyst dispersed alloy phases illustrate the concept of nanoengineering and nanoconfinement of particles with tailor-made properties for reversible hydrogen storage. Another class of materials comprising polymeric nanostructures such as conducting polyaniline and their functionalized nanocomposites are versatile hydrogen storage materials because of their unique size high specific surface-area pore-volume and bulk properties. The salient features of nanocomposite materials for reversible hydrogen storage are reviewed and discussed.
Hydrogen Embrittlement in Super Duplex Stainless Steels
Nov 2019
Publication
In super duplex stainless steels (SDSSs) both austenite and ferrite are susceptible to hydrogen embrittlement however there is a lack of understanding into the effect of hydrogen in each phase. In this study in neutron diffraction was applied on hydrogen-charged (H-charged) samples to investigate the hydrogen embrittlement behaviour in super duplex stainless steels. The result reveals that austenite maintains good plasticity during tensile testing whilst a loss of it is realised in ferrite. Fractography analysis reveals the diffusion of hydrogen induced a brittle-to-ductile transition from the sample surface towards the centre; hydrogen embrittlement vanishes as the specimen’s centre is approached while it is demonstrated to disappear first in austenite but not in ferrite. This transition can be predicted by applying a physics-based hydrogen embrittlement model which incorporates the effects of hydrogen concentration hydrogen diffusivity residual stress loading state and temperature. The present work demonstrates the dissimilar susceptibility of austenite and ferrite to hydrogen embrittlement providing a tool to describe it.
Role of Hydrogen-Charging on Nucleation and Growth of Ductile Damage in Austenitic Stainless Steels
May 2019
Publication
Hydrogen energy is a possible solution for storage in the future. The resistance of packaging materials such as stainless steels has to be guaranteed for a possible use of these materials as containers for highly pressurized hydrogen. The effect of hydrogen charging on the nucleation and growth of microdamage in two different austenitic stainless steels AISI316 and AISI316L was studied using in situ tensile tests in synchrotron X-ray tomography. Information about damage nucleation void growth and void shape were obtained. AISI316 was found to be more sensitive to hydrogen compared to AISI316L in terms of ductility loss. It was measured that void nucleation and growth are not affected by hydrogen charging. The effect of hydrogen was however found to change the morphology of nucleated voids from spherical cavities to micro-cracks being oriented perpendicular to the tensile axis.
Hydrogen or Batteries for Grid Storage? A Net Energy Analysis
Apr 2015
Publication
Energy storage is a promising approach to address the challenge of intermittent generation from renewables on the electric grid. In this work we evaluate energy storage with a regenerative hydrogen fuel cell (RHFC) using net energy analysis. We examine the most widely installed RHFC configuration containing an alkaline water electrolyzer and a PEM fuel cell. To compare RHFC's to other storage technologies we use two energy return ratios: the electrical energy stored on invested (ESOIe) ratio (the ratio of electrical energy returned by the device over its lifetime to the electrical-equivalent energy required to build the device) and the overall energy efficiency (the ratio of electrical energy returned by the device over its lifetime to total lifetime electrical-equivalent energy input into the system). In our reference scenario the RHFC system has an ESOIeratio of 59 more favorable than the best battery technology available today (Li-ion ESOIe= 35). (In the reference scenario RHFC the alkaline electrolyzer is 70% efficient and has a stack lifetime of 100 000 h; the PEM fuel cell is 47% efficient and has a stack lifetime of 10 000 h; and the round-trip efficiency is 30%.) The ESOIe ratio of storage in hydrogen exceeds that of batteries because of the low energy cost of the materials required to store compressed hydrogen and the high energy cost of the materials required to store electric charge in a battery. However the low round-trip efficiency of a RHFC energy storage system results in very high energy costs during operation and a much lower overall energy efficiency than lithium ion batteries (0.30 for RHFC vs. 0.83 for lithium ion batteries). RHFC's represent an attractive investment of manufacturing energy to provide storage. On the other hand their round-trip efficiency must improve dramatically before they can offer the same overall energy efficiency as batteries which have round-trip efficiencies of 75–90%. One application of energy storage that illustrates the trade-off between these different aspects of energy performance is capturing overgeneration (spilled power) for later use during times of peak output from renewables. We quantify the relative energetic benefit of adding different types of energy storage to a renewable generating facility using [EROI]grid. Even with 30% round-trip efficiency RHFC storage achieves the same [EROI]grid as batteries when storing overgeneration from wind turbines because its high ESOIeratio and the high EROI of wind generation offset the low round-trip efficiency.
Investigation of Structure of AlN Thin Films Using Fourier-transform Infrared Spectroscopy
Feb 2020
Publication
This study focuses on structural imperfections caused by hydrogen impurities in AlN thin films obtained using atomic layer deposition method (ALD). Currently there is a severe lack of studies regarding the presence of hydrogen in the bulk of AlN films. Fourier-transform infrared spectroscopy (FTIR) is one of the few methods that allow detection bonds of light elements in particular - hydrogen. Hydrogen is known to be a frequent contaminant in AlN films grown by ALD method it may form different bonds with nitrogen e.g. amino (–NH2) or imide (–NH) groups which impair the quality of the resulting film. Which is why it is important to investigate the phenomenon of hydrogen as well as to search for the suitable methods to eliminate or at least reduce its quantity. In this work several samples have been prepared using different precursors substrates and deposition parameters and characterized using FTIR and additional techniques such as AFM XPS and EDS to provide a comparative and comprehensive analysis of topography morphology and chemical composition of AlN thin films.
Hydrogen Embrittlement Evaluation of Micro Alloyed Steels by Means of J-Integral Curve
Jun 2019
Publication
The aim of this work is the evaluation of the hydrogen effect on the J-integral parameter. It is well-known that the micro alloyed steels are affected by Hydrogen Embrittlement phenomena only when they are subjected at the same time to plastic deformation and hydrogen evolution at their surface. Previous works have pointed out the absence of Hydrogen Embrittlement effects on pipeline steels cathodically protected under static load conditions. On the contrary in slow strain rate tests it is possible to observe the effect of the imposed potential and the strain rate on the hydrogen embrittlement steel behavior only after the necking of the specimens. J vs. Δa curves were measured on different pipeline steels in air and in aerated NaCl 3.5 g/L solution at free corrosion potential or under cathodic polarization at −1.05 and −2 V vs. SCE. The area under the J vs. Δa curves and the maximum crack propagation rate were taken into account. These parameters were compared with the ratio between the reduction of area in environment and in air obtained by slow strain rate test in the same environmental conditions and used to rank the different steels.
An Investigation of Gaseous Hydrogen Storage Characterizations of Mg–Y–Ni–Cu Alloys Synthesized by Melt Spinning
Aug 2018
Publication
Melt spinning was successfully utilized to prepare Mg25−xYxNi9Cu (x = 0 1 3 5 7) alloys producing nanocrystalline and amorphous structures with improved hydrogenation and dehydrogenation performances. The influence of spinning rate on hydrogenation and dehydrogenation thermodynamics and kinetics was studied in detail. XRD and TEM were utilized to characterize the alloy structures. Hydrogenation and dehydrogenation performances were investigated by Sievert apparatus DSC and TGA connected to a H2 detector. Dehydrogenation activation energies were estimated using both Arrhenius and Kissinger methods. Results show that melt spinning significantly decreases thermodynamic parameters (ΔH and ΔS) and ameliorates desorption kinetics. Dehydrogenation activation energy markedly lowers with increase in spinning rate and is the real driver of amelioration of dehydrogenation kinetics caused by increasing Y content.
Specific Effects of Hydrogen Concentration on Resistance to Fracture of Ferrite-pearlitic Pipeline Steels
Aug 2019
Publication
The presented work is dedicated to evaluation of strain and fatigue behaviour of the ferrite-pearlite low-alloyed pipeline steels under known hydrogen concentration in a bulk of metal. Tensile test results have shown on the existence of some characteristic value of the hydrogen concentration CH at which the mechanism of hydrogen influence changes namely: below this value the enhanced plasticity (decreasing of the yield stress value) takes place and above – the hydrogen embrittlement occurs. The ambiguous relationship between fatigue crack growth rate and hydrogen concentration CH in the bulk of steels under their cyclic loading in hydrogen-contained environments has been found. There is a certain CH value at which the crack growth resistance of steel increases and the diagram of fatigue crack growth rate shifts to higher values of stress intensity factor. The generalised diagram of hydrogen concentration effect on strength behaviour of low-alloyed ferrite-pearlite pipeline steels is presented and discussed with the aim of evaluation of different mechanisms of hydrogen effect conditions of their realization and possible co-existence.
Effect of Gasoline Pool Fire on Liquid Hydrogen Storage Tank in Hybrid Hydrogen-gasoline Fueling Station
Nov 2015
Publication
Multiple-energy-fuelling stations which can supply several types of energy such as gasoline CNG and hydrogen could guarantee the efficient use of space. To guide the safety management of hybrid hydrogen–gasoline fuelling stations which utilize liquid hydrogen as an energy carrier the scale of gasoline pool fires was estimated using the hazard assessment tool Toxic Release Analysis of Chemical Emissions (TRACE). Subsequently the temperature and the stress due to temperature distribution were estimated using ANSYS. Based on the results the safety of liquid hydrogen storage tanks was discussed. It was inferred that the emissivity of the outer material of the tank and the safety distance between liquid hydrogen storage tanks and gasoline dispensers should be less than 0.2 and more than 8.5 m respectively to protect the liquid hydrogen storage tank from the gasoline pool fire. To reduce the safety distance several measures are required e.g. additional thermal shields such as protective intumescent paint and water sprinkler systems and an increased slope to lead gasoline off to a safe domain away from the liquid hydrogen storage tank
Hydrogen Embrittlement in Pipelines Transporting Sour Hydrocarbons
Sep 2017
Publication
Lamination-like defects in pipeline steels can be of both metallurgical and operational origin. In pipelines transporting hydrocarbon usually such defects are not a big challenge since they do not propagate under operating conditions. Nonetheless in presence of a corrosion phenomenon and sour gas (H2S) it is possible to observe blisters and cracks which may propagate in the steel. The observed damage mechanisms is Hydrogen Embrittlement and in spite of a huge amount of study and publications available it is quite difficult for a pipeline owner to get practical data (crack propagation rate for instance) allowing a reliable estimate of the fitness for service of a pipeline. Taking advantage of a pipeline spool containing internal defects that was in service for more than 10 years and recently removed a comprehensive study is underway to obtain a complete assessment of the pipeline future integrity. The program is comprehensive of study and comparison of ILI reports of the pipeline to determine the optimum interval between inspections assessment of inspection results via an accurate nondestructive (UT) and destructive examination of the removed section to verify ILI results lab tests program on specimens from the removed spool at operating conditions (75-80 bar and 30°-36° C) in presence of a small quantity of water H2S (5%) and CO2 (7%) in order to assess defect propagation and to obtain an estimate of crack growth rate and test in field of available methods to monitor the presence of Hydrogen and/or the growth of defects in in-service pipelines. This quite ambitious program is also expected to be able of offering a small contribution toward a better understanding of HE mechanisms and the engineering application of such complex often mainly academic studies.
Towards a Unified and Practical Industrial Model for Prediction of Hydrogen Embrittlement and Damage in Steels
Jul 2016
Publication
Bearing in mind the multiple effects of hydrogen in steels the specific mechanism of hydrogen embrittlement (HE) is active depending on the experimental conditions and numerous factors which can be grouped as environmental mechanical and material influences. A large number of contemporary studies and models about hydrogen environment assisted cracking and HE in steels are presented in the form of critical review in this paper. This critical review represent the necessary background for the development of a multiscale structural integrity model based on correlation between simultaneously active HE micro-mechanisms: the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE) - (HELP+HEDE) and macro-mechanical response of material unevenly enriched with hydrogen during service of boiler tubes in thermal fossil fuel power plant. Several different experimental methods and techniques were used to determine the boiler tube failure mechanism and afterwards also the viable HE mechanisms in the investigated ferritic-pearlitic low carbon steel grade 20 - St.20 (equivalent to AISI 1020). That represent a background for the development of a structural integrity model based on the correlation of material macro-mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces of Charpy specimens in the presence of confirmed and simultaneously active HE micro-mechanisms (HELP+HEDE) in steel. The aim of this paper is to show how to implement what we have learned from theoretical HE models into the field to provide industry with valuable data and practical structural integrity model.
Cross-regional Drivers for CCUS Deployment
Jul 2020
Publication
CO2 capture utilization and storage (CCUS) is recognized as a uniquely important option in global efforts to control anthropogenic greenhouse-gas (GHG) emissions. Despite significant progress globally in advancing the maturity of the various component technologies and their assembly into full-chain demonstrations a gap remains on the path to widespread deployment in many countries. In this paper we focus on the importance of business models adapted to the unique technical features and sociopolitical drivers in different regions as a necessary component of commercial scale-up and how lessons might be shared across borders. We identify three archetypes for CCUS development—resource recovery green growth and low-carbon grids—each with different near-term issues that if addressed will enhance the prospect of successful commercial deployment. These archetypes provide a framing mechanism that can help to translate experience in one region or context to other locations by clarifying the most important technical issues and policy requirements. Going forward the archetype framework also provides guidance on how different regions can converge on the most effective use of CCUS as part of global deep-decarbonization efforts over the long term.
Hydrogen-assisted Cracking Paths in Oriented Pearlitic Microstructures: Resembling Donatello Wooden Sculpture Texture (DWST) & Mantegna’s Dead Christ Perspective (MDCP)
Jun 2020
Publication
Progressive cold drawing in eutectoid steel produces a preferential orientation of pearlitic colonies and ferrite/cementite lamellae thus inducing strength anisotropy in the steel and mixed mode propagation. While in the hot rolled steel (not cold drawn) the pearlitic microstructure is randomly oriented and the crack progresses in hydrogen by breaking the ferrite/cementite lamellae in heavily drawn steels the pearlitic microstructure is fully oriented and the predominant mechanism of hydrogen assisted cracking is the delamination (or decohesion) at the ferrite/cementite interface.
Proposal and Verification of Novel Fatigue Crack Propagation Simulation Method by Finite Element Method.
Dec 2018
Publication
In this paper we propose and verify a novel method to simulate crack propagation without propagating a crack by finite element method. We propose this method for elastoplastic analysis coupled with convection-diffusion. In the previous study we succeeded in performing elastoplastic analysis coupled with convection-diffusion of hydrogen for a material with a crack under tensile loading. This research extends the successful method to fatigue crack propagation. In convection-diffusion analysis in order to simulate the invasion and release of elements through the free surface the crack tip is expressed by using a notch with a sufficiently small radius. Therefore the node release method conventionally used to simulate crack propagation cannot be applied. Hence instead of crack propagation based on an analytical model we propose a novel method that can reproduce the influence of the vicinity of the crack tip on a crack. We moved the stress field near the crack tip in the direction opposite to that of crack propagation by an amount corresponding to the crack propagation length. When we extend the previous method to fatigue crack propagation simulation we must consider the difference in strain due to loading and unloading. This problem was solved by considering the strain due to loading as a displacement. Instead of moving the strain due to loading we moved the displacement. First we performed a simple tensile load analysis on the model and output the displacement of all the nodes of the model at maximum load. Then the displacement was moved in the direction opposite to that of crack propagation. Finally the stress field was reproduced by forcibly moving all the nodes by the displacement amount. The strain due to unloading was reproduced by removing the displacement. Furthermore we verified the equivalence of the crack propagation simulation and the proposed method.
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.
Grand Canonical Monte Carlo Simulations of the Hydrogen Storage Capacities of Slit-shaped Pores, Nanotubes and Torusenes
Jan 2022
Publication
Grand Canonical Monte Carlo GCMC simulations are used to study the gravimetric and volumetric hydrogen storage capacities of different carbon nanopores shapes: Slit-shaped nanotubes and torusenes at room temperature 298.15 K and at pressures between 0.1 and 35 MPa and for pore diameter or width between 4 and 15 A. The influence of the pore shape or curvature on the storage capacities as a function of pressure temperature and pore diameter is investigated and analyzed. A large curvature of the pores means in general an increase of the storage capacities of the pores. While torusenes and nanotubes have surfaces with more curvature than the slit-shaped planar pores their capacities are lower than those of the slit-shaped pores according to the present GCMC simulations. Torusene a less studied carbon nanostructure has two radii or curvatures but their storage capacities are similar or lower than those of nanotubes which have only one radius or curvature. The goal is to obtain qualitative and quantitative relationships between the structure of porous materials and the hydrogen storage capacities in particular or especially the relationship between shape and width of the pores and the hydrogen storage capacities of carbon-based porous materials.
Towards Net-zero Smart System: An Power Synergy Management Approach of Hydrogen and Battery Hybrid System with Hydrogen Safety Consideration
May 2022
Publication
The building system is one of key energy consumption sector in the market and low-carbon building will make a significant contribution for the worldwide carbon emission reduction. The multiple energy systems including renewable generations hydrogen energy and energy storage is the perspective answer to the net-zero building system. However the research gap lies in the synergy power management among the renewable flexible loads batteries and hydrogen energy systems and at the same time taking the unique characteristic of different energy sectors into account by power managing. This paper proposed the power management approach based on the game theory by which the different characteristics of the energy players are described via creating the competing relationship against net-zero emission objective so that to achieve the power synergy. Under the proposed power management method the hydrogen and battery hybrid system including the fuel cell electrolyzer and battery is designed and investigated as to unlock the power management regions and control constraints within the building system. Particularly for the hydrogen system within the hybrid system the safe and long-lifetime operation is considered respectively by high-efficiency and pressure constraints within the power management. Simulation results show that providing the same energy storage services for the building system the fuel cell with the proposed power management method sustains for 9.9 years much longer than that of equivalent consumption minimization (4.98) model predictive control (4.61) and rule-based method (7.69). Moreover the maximum tank temperature of the hydrogen tank is reduced by 3.4 K and 2.9 K compared with consumption minimization strategy and model predictive control. Also the real-time of the proposed power management is verified by a scaled-down experiment platform.
Room Temperature Metal Hydrides for Stationary and Heat Storage Applications: A Review
Apr 2021
Publication
Hydrogen has been long known to provide a solution toward clean energy systems. With this notion many efforts have been made to find new ways of storing hydrogen. As a result decades of studies has led to a wide range of hydrides that can store hydrogen in a solid form. Applications of these solid-state hydrides are well-suited to stationary applications. However the main challenge arises in making the selection of the Metal Hydrides (MH) that are best suited to meet application requirements. Herein we discuss the current state-of-art in controlling the properties of room temperature (RT) hydrides suitable for stationary application and their long term behavior in addition to initial activation their limitations and emerging trends to design better storage materials. The hydrogen storage properties and synthesis methods to alter the properties of these MH are discussed including the emerging approach of high-entropy alloys. In addition the integration of intermetallic hydrides in vessels their operation with fuel cells and their use as thermal storage is reviewed.
Recent Progress in Hydrogen Storage
Nov 2008
Publication
The ever-increasing demand for energy coupled with dwindling fossil fuel resources make the establishment of a clean and sustainable energy system a compelling need. Hydrogen-based energy systems offer potential solutions. Although in the long-term the ultimate technological challenge is large-scale hydrogen production from renewable sources the pressing issue is how to store hydrogen efficiently on board hydrogen fuel-cell vehicles.
Tracking Hydrogen Embrittlement Using Short Fatigue Crack Behavior of Metals
Dec 2018
Publication
Understanding hydrogen embrittlement phenomenon that leads to deterioration of mechanical properties of metallic components is vital for applications involving hydrogen environment. Among these understanding the influence of hydrogen on the fatigue behaviour of metals is of great interest. Total fatigue life of a material can be divided into fatigue crack initiation and fatigue crack growth phase. While fatigue crack initiation can be linked with the propagation of short fatigue cracks the size of which is of the order of grain size (few tens of microns) that are generally not detectable by conventional crack detection techniques applicable for the long fatigue crack growth behaviour using conventional CT specimens. Extensive literature is available on hydrogen effect on long fatigue crack growth behaviour of metals that leads to the change in crack growth rate and the threshold stress intensity factor range (ΔKth). However it is the short fatigue crack growth behaviour that provides the fundamental understanding and correlation of the metallic microstructure with hydrogen embrittlement phenomenon. Short fatigue crack growth behaviour is characteristically different from long crack growth behaviour showing high propagation rate at much lower values than threshold stress intensity factor range as well as a strong dependency on the microstructural features such as grain boundaries phase boundaries and inclusions. To this end a novel experimental framework is developed to investigate the short fatigue crack behaviour of hydrogen charged materials involving in-situ observation of propagating short cracks coupled with image processing to obtain their da/dN vs a curves. Various metallic materials ranging from austenitic stainless steel (AISI 316L) to reactor pressure vessel steel (SA508 Grade 3 Class I low alloy steel) and line pipe steels (API 5L X65 & X80) are studied in this work.
Thickness-Prediction Method Involving Tow Redistribution for the Dome of Composite Hydrogen Storage Vessels
Feb 2022
Publication
Traditional thickness-prediction methods underestimate the actual dome thickness at polar openings leading to the inaccurate prediction of the load-bearing capacity of composite hydrogen storage vessels. A method of thickness prediction for the dome section of composite hydrogen storage vessels was proposed which involved fiber slippage and tow redistribution. This method considered the blocking effect of the port on sliding fiber tows and introduced the thickness correlation to predict the dome thickness at polar openings. The arc length corresponding to the parallel circle radius was calculated and then the actual radius values corresponding to the bandwidth were obtained by the interpolation method. The predicted thickness values were compared with the actual measured thickness. The maximum relative error of the predicted thickness was 4.19% and the mean absolute percentage error was 2.04%. The results show that the present method had a higher prediction accuracy. Eventually this prediction method was used to perform progressive damage analysis on vessels. By comparing with the results of the cubic spline function method the analysis results of the present method approached the actual case. This showed that the present method improved the accuracy of the design.
Influence of Carbon Catalysts on the Improvement of Hydrogen Storage Properties in a Body-Centered Cubic Solid Solution Alloy
Jun 2021
Publication
Body-centered cubic (BCC) alloys are considered as promising materials for hydrogen storage with high theoretical storage capacity (H/M ratio of 2). Nonetheless they often suffer from sluggish kinetics of hydrogen absorption and high hydrogen desorption temperature. Carbon materials are efficient hydrogenation catalysts however their influence on the hydrogen storage properties of BCC alloy has not been comprehensively studied. Therefore in this paper composites obtained by milling of carbon catalysts (carbon nanotubes mesoporous carbon carbon nanofibers diamond powder graphite fullerene) and BCC alloy (Ti1.5V0.5) were extensively studied in the non-hydrogenated and hydrogenated state. The structure and microstructure of the obtained materials were studied by scanning and transmission electron microscopes X-ray diffraction (XRD) and Raman spectroscopy. XRD and Raman measurements showed that BCC alloy and carbon structures were in most cases intact after the composite synthesis. The hydrogenation/dehydrogenation studies showed that all of the used carbon catalysts significantly improve the hydrogenation kinetics reduce the activation energy of the dehydrogenation process and decrease the dehydrogenation temperature (by nearly 100 K). The superior kinetic properties were measured for the composite with 5 wt % of fullerene that absorbs 3.3 wt % of hydrogen within 1 min at room temperature.
Peculiarities of Bond Strength Degradation in Reinforced Concrete Induced by Accelerated Electrochemical Methods
Dec 2018
Publication
Reinforced concrete (RC) structures are long-term operated objects with service life of 50–100 years. During their operation they subject to continuous ambient effects (cyclic temperature changes acid rains de-icing salts) and service loads (e.g. traffic) which effect on structural integrity of the composite and lead to worsening of structures serviceability. One of the reasons for strength loss of RC members is bond degradation between rebar and concrete. It could be caused by two different factors: overprotection of RC and reinforcement corrosion. These effects were simulated in the laboratory conditions by the electrochemical methods applying of impressed cathodic current and accelerated corrosion tests respectively. It was shown that applied anode polarization causes not only concrete cracking due to internal pressure of corrosion products at the interface but also due to their expansion far from rebar for a distance comparative with a specimen thickness evidently into preliminary formed cracks. Since intensive corrosion of steel reinforcement decreases its diameter and corrosion products can migrate from the rebar surface into a depth of concrete these factors could weaken bond in RC installations up to a total loss of cohesion between rebar and concrete. The influence of cathodic polarization of steel embedded in concrete is commonly seemed to consist in its possible hydrogen embrittlement and ions redistribution in concrete matrix. In this paper the effect of hydrogen recombined at the rebar–concrete interface on bond weakening and concrete cracking is considered.
Towards Non-Mechanical Hybrid Hydrogen Compression for Decentralized Hydrogen Facilities
Jun 2020
Publication
The cost of the hydrogen value chain needs to be reduced to allow the widespread development of hydrogen applications. Mechanical compressors widely used for compressing hydrogen to date account for more than 50% of the CAPEX (capital expenditure) in a hydrogen refuelling station. Moreover mechanical compressors have several disadvantages such as the presence of many moving parts hydrogen embrittlement and high consumption of energy. Non-mechanical hydrogen compressors have proven to be a valid alternative to mechanical compressors. Among these electrochemical compressors allow isothermal and therefore highly efficient compression of hydrogen. On the other hand adsorption-desorption compressors allow hydrogen to be compressed through cooling/heating cycles using highly microporous materials as hydrogen adsorbents. A non-mechanical hybrid hydrogen compressor consisting of a first electrochemical stage followed by a second stage driven by adsorption-desorption of hydrogen on activated carbons allows hydrogen to be produced at 70 MPa a value currently required for the development of hydrogen automotive applications. This system has several advantages over mechanical compressors such as the absence of moving parts and high compactness. Its use in decentralized hydrogen facilities such as hydrogen refuelling stations can be considered
Tensile and Fatigue Properties of 17-4PH Martensitic Stainless Steels in Presence of Hydrogen
Dec 2019
Publication
Effects of hydrogen on slow-strain-rate tensile (SSRT) and fatigue-life properties of 17-4PH H1150 martensitic stainless steel having an ultimate tensile strength of ~1GPa were investigated. Smooth and circumferentially-notched axisymmetric specimens were used for the SSRT and fatigue-life tests respectively. The fatigue-life tests were done to investigate the hydrogen effect on fatigue crack growth (FCG) properties. The specimens tested in air at ambient temperature were precharged by exposure to hydrogen gas at pressures of 35 and 100 MPa at 270°C for 200 h. The SSRT properties of the H-charged specimens were degraded by hydrogen showing a relative reduction in area (RRA) of 0.31 accompanied by mixed fracture surfaces composed of quasi-cleavage (QC) and intergranular cracking (IG). The fatigue-life tests conducted under wide test frequencies ranging from 10-3 Hz to 10 Hz revealed three distinct characteristics in low- and high-cycle regimes and at the fatigue limit. The fatigue limit was not degraded by hydrogen. In the high-cycle regime the hydrogen caused FCG acceleration with an upper bound ratio of 30 accompanied by QC surfaces. In the low-cycle regime the hydrogen caused FCG acceleration with a ratio of ~100 accompanied by QC and IG. The ordinary models such as process competition and superposition models hardly predicted the H-assisted FCG acceleration; therefore an interaction model successfully reproducing the experimental FCG acceleration was newly introduced.
Unconventional Pearlitic Pseudocolonies Affecting Macro-, Micro- and Nano-structural Integrity of Cold-drawn Pearlitic Steel Wires: Resembling van Gogh, Bernini, Mantegna and Picasso
Dec 2020
Publication
Prestressing steel wires are manufactured by cold drawing during which a preferential orientation is achieved in the matter of pearlitic colonies and lamellae. In addition to this general trend special (unconventional) pearlitic pseudocolonies evolve during the heavy-drawing manufacture process affecting the posterior macro- micro- and nano-structural integrity of the material. This paper discusses the important role of such a special microstructural unit (the pearlitic pseudocolony) in the fracture process in air (inert) environment in the presence of crack-like defects as well as in the case of environmentally assisted cracking (stress corrosion cracking by localized anodic dissolution) or hydrogen embrittlement. Results clearly demonstrate the key role of pearlitic pseudocolonies in promoting crack deflection (and thus mixed-mode propagation) after a global mode I cracking especially in the case of fracture in air and stress corrosion cracking.
Environmental Degradation Effect of High-Temperature Water and Hydrogen on the Fracture Behavior of Low-Alloy Reactor Pressure Vessel Steels
Dec 2019
Publication
Structural integrity of reactor pressure vessel (RPV) in light water reactors (LWR) is of highest importance regarding operation safety and lifetime. The fracture behaviour of low-alloy RPV steels with different dynamic strain aging (DSA) & environmental assisted cracking (EAC) susceptibilities in simulated LWR environments was evaluated by elastic plastic fracture mechanics tests (EPFM) and by metallo- and fractographic post-test analysis. Exposure to high temperature water (HTW) environments at LWR temperatures revealed only moderated reductions in the fracture initiation and tearing resistance of low alloy RPV steels with high DSA or EAC susceptibility accompanied with a moderate but clear change in fracture morphology which indicates the potential synergies of hydrogen/HTW embrittlement with DSA and EAC under suitable conditions. The most pronounced degradation effects occurred in a) RPV steels with high DSA susceptibility where the fracture initiation and tearing resistance reduction increased with decreasing loading rate and were most pronounced in hydrogenated HTW and b) high sulphur steels with high EAC susceptibility in aggressive occluded crevice environment and with preceding fast EAC crack growth in oxygenated HTW. The moderate effects are due to the low hydrogen availability in HTW together with high density of fine-dispersed hydrogen traps in RPV steels. Stable ductile transgranular tearing by microvoid coalescence was the dominant failure mechanism in all environments with additional varying few % of secondary cracks macrovoids and quasi-cleavage in HTW. The observed behavior suggests a combination of plastic strain localisation by the Hydrogen-enhanced Local Plasticity (HELP) mechanism in synergy with DSA and Hydrogen-enhanced Strain-induced Vacancies (HESIV) mechanism with additional minor contributions of Hydrogen-enhanced Decohesion Embrittlement (HEDE) mechanism.
Hydrogen-Assisted Brittle Fracture Behavior of Low Alloy 30CrMo Steel Based on the Combination of Experimental and Numerical Analyses
Jul 2021
Publication
Compact-tension (CT) specimens made of low alloy 30CrMo steels were hydrogen-charged and then subjected to the fracture toughness test. The experimental results revealed that the higher crack propagation and the lower crack growth resistance (CTOD-R curve) are significantly noticeable with increasing hydrogen embrittlement (HE) indexes. Moreover the transition in the microstructural fracture mechanism from ductile (microvoid coalescence (MVC)) without hydrogen to a mixed quasi-cleavage (QC) fracture and QC + intergranular (IG) fracture with hydrogen was observed. The hydrogen-enhanced decohesion (HEDE) mechanism was characterized as the dominant HE mechanism. According to the experimental testing the coupled problem of stress field and hydrogen diffusion field with cohesive zone stress analysis was employed to simulate hydrogen-assisted brittle fracture behavior by using ABAQUS software. The trapezoidal traction-separation law (TSL) was adopted and the initial TSL parameters from the best fit to the load-displacement and J-integral experimental curves without hydrogen were calibrated for the critical separation of 0.0393 mm and the cohesive strength of 2100 MPa. The HEDE was implemented through hydrogen influence in the TSL and to estimate the initial hydrogen concentration based on matching numerical and experimental load-line displacement curves with hydrogen. The simulation results show that the general trend of the computational CTOD-R curves corresponding to initial hydrogen concentration is almost the same as that obtained from the experimental data but in full agreement the computational CTOD values being slightly higher. Comparative analysis of numerical and experimental results shows that the coupled model can provide design and prediction to calculate hydrogen-assisted fracture behavior prior to extensive laboratory testing provided that the material properties and properly calibrated TSL parameters are known.
Investigation of Certain Mechanical and Magnetic Properties of a Stressed Low-carbon steel after corrosion in NaCl-water solution
Jun 2020
Publication
Atomic hydrogen produced by corrosion of a low-carbon steel in NaCl – Water solution may markedly affect its certain tensile mechanical and magnetic properties in a complex and peculiar manner. This influence was investigated by employing the intrinsic micromagnetic emission (ME)-response as well as tensile mechanical response of this ferromagnetic material and also by introduction a relevant measurement parameter of specific micromagnetic emission response. In this fashion it was shown that an increase in the hydrogen accumulation with corrosion time leads to an associated increase in the pervasive and embrittling influence expressed by a marked loss in ductility of the material. It was also shown that the competitive interplay of cumulative hydrogen applied stress and plastic strain-induced microstructural damage was related to a specific ME-response parameter by which an increased magnetic hardening tendency of material with corrosion time was established. In general embrittlement and magnetic hardening are parallel products of stress- assisted hydrogen accumulation where magnetic hardening process seems to be in a time processing advance of embrittlement one. The above findings allow to estimate that the magnetic properties are more susceptible to hydrogen effects than the mechanical ones.
Study of the Microstructural and First Hydrogenation Properties of TiFe Alloy with Zr, Mn and V as Additives
Jul 2021
Publication
In this paper we report the effect of adding Zr + V or Zr + V + Mn to TiFe alloy on microstructure and hydrogen storage properties. The addition of only V was not enough to produce a minimum amount of secondary phase and therefore the first hydrogenation at room temperature under a hydrogen pressure of 20 bars was impossible. When 2 wt.% Zr + 2 wt.% V or 2 wt.% Zr + 2 wt.% V + 2 wt.% Mn is added to TiFe the alloy shows a finely distributed Ti2Fe-like secondary phase. These alloys presented a fast first hydrogenation and a high capacity. The rate-limiting step was found to be 3D growth diffusion controlled with decreasing interface velocity. This is consistent with the hypothesis that the fast reaction is likely to be the presence of Ti2Fe-like secondary phases that act as a gateway for hydrogen.
SimSES: A Holistic Simulation Framework for Modeling and Analyzing Stationary Energy Storage Systems
Feb 2022
Publication
The increasing feed-in of intermittent renewable energy sources into the electricity grids worldwide is currently leading to technical challenges. Stationary energy storage systems provide a cost-effective and efficient solution in order to facilitate the growing penetration of renewable energy sources. Major technical and economical challenges for energy storage systems are related to lifetime efficiency and monetary returns. Holistic simulation tools are needed in order to address these challenges before investing in energy storage systems. One of these tools is SimSES a holistic simulation framework specialized in evaluating energy storage technologies technically and economically. With a modular approach SimSES covers various topologies system components and storage technologies embedded in an energy storage application. This contribution shows the capabilities and benefits of SimSES by providing in-depth knowledge of the implementations and models. Selected functionalities are demonstrated with two use cases showing the easy-to-use simulation framework while providing detailed technical analysis for expert users. Hybrid energy storage systems consisting of lithium-ion and redox-flow batteries are investigated in a peak shaving application while various system topologies are analyzed in a frequency containment reserve application. The results for the peak shaving case study show a benefit in favor of the hybrid system in terms of overall cost and degradation behavior in applications that have a comparatively low energy throughput during lifetime. In terms of system topology a cascaded converter approach shows significant improvements in efficiency for the frequency containment reserve application.
Comparative Study of Embrittlement of Quenched and Tempered Steels in Hydrogen Environments
Mar 2022
Publication
The study of steels which guarantee safety and reliability throughout their service life in hydrogen-rich environments has increased considerably in recent years. Their mechanical behavior in terms of hydrogen embrittlement is of utmost importance. This work aims to assess the effects of hydrogen on the tensile properties of quenched and tempered 42CrMo4 steels. Tensile tests were performed on smooth and notched specimens under different conditions: pre-charged in high pressure hydrogen gas electrochemically pre-charged and in-situ hydrogen charged in an acid aqueous medium. The influence of the charging methodology on the corresponding embrittlement indexes was assessed. The role of other test variables such as the applied current density the electrolyte composition and the displacement rate was also studied. An important reduction of the strength was detected when notched specimens were subjected to in-situ charging. When the same tests were performed on smooth tensile specimens the deformation results were reduced. This behavior is related to significant changes in the operative failure micromechanisms from ductile (microvoids coalescence) in absence of hydrogen or under low hydrogen contents to brittle (decohesion of martensite lath interfaces) under the most stringent conditions.
Effects of Purity and Pressure on the Hydrogen Embrittlement of Steels and Other Metallic Materials
Sep 2009
Publication
A study of open literature was performed to determine the effects of high hydrogen purity and gas pressure (in the range of 700-1000 bar) on the hydrogen embrittlement of several metallic materials. A particular focus was given to carbon low-alloy and stainless steels but information on embrittlement of aluminum and copper was included in the study. Additionally the most common test methods were studied and results from similar tests are presented in a manner so as to simplify comparisons of materials. Finally suggestions are provided for future testing necessary to ensure the safety of hydrogen storage at 700 bar.
Evaluation of Steels Susceptibility to Hydrogen Embrittlement: A Thermal Desorption Spectroscopy-Based Approach Coupled with Artificial Neural Network
Dec 2020
Publication
A novel approach has been developed for quantitative evaluation of the susceptibility of steels and alloys to hydrogen embrittlement. The approach uses a combination of hydrogen thermal desorption spectroscopy (TDS) analysis with recent advances in machine learning technology to develop a regression artificial neural network (ANN) model predicting hydrogen-induced degradation of mechanical properties of steels. We describe the thermal desorption data processing artificial neural network architecture development and the learning process beneficial for the accuracy of the developed artificial neural network model. A data augmentation procedure was proposed to increase the diversity of the input data and improve the generalization of the model. The study of the relationship between thermal desorption spectroscopy data and the mechanical properties of steel evidences a strong correlation of their corresponding parameters. A prototype software application based on the developed model is introduced and is openly available. The developed prototype based on TDS analysis coupled with ANN is shown to be a valuable engineering tool for steel characterization and quantitative prediction of the degradation of steel properties caused by hydrogen.
Measurement of Fatigue Crack Growth Rates for Steels in Hydrogen Containment Components
Sep 2009
Publication
The objective of this work was to enable the safe design of hydrogen pressure vessels by measuring the fatigue crack growth rates of ASME code-qualified steels in high-pressure hydrogen gas. While a design framework has recently been established for high-pressure hydrogen vessels a material property database does not exist to support the design calculations. This study addresses such voids in the database by measuring the fatigue crack growth rates of three different heats of ASME SA-372 Grade J steel in 100 MPa hydrogen gas. Results showed that the fatigue crack growth rates were similar for all three steel heats although the highest-strength steel appeared to exhibit the highest growth rates. Hydrogen accelerated the fatigue crack growth rates of the steels by as much as two orders of magnitude relative to anticipated crack growth rates in inert environments. Despite such dramatic effects of hydrogen on the fatigue crack growth rates measurement of these properties enables reliable definition of the design life of steel hydrogen containment vessels.
Carbon Capture and Storage in the USA: The Role of US Innovation Leadership in Climate-technology Commercialization
Nov 2019
Publication
To limit global warming and mitigate climate change the global economy needs to decarbonize and reduce emissions to net-zero by mid-century. The asymmetries of the global energy system necessitate the deployment of a suite of decarbonization technologies and an all-of-the-above approach to deliver the steep CO2 -emissions reductions necessary. Carbon capture and storage (CCS) technologies that capture CO2 from industrial and power-plant point sources as well as the ambient air and store them underground are largely seen as needed to address both the flow of emissions being released and the stock of CO2 already in the atmosphere. Despite the pressing need to commercialize the technologies their large-scale deployment has been slow. Initial deployment however could lead to near-term cost reduction and technology proliferation and lowering of the overall system cost of decarbonization. As of November 2019 more than half of global large-scale CCS facilities are in the USA thanks to a history of sustained government support for the technologies. Recently the USA has seen a raft of new developments on the policy and project side signalling a reinvigorated push to commercialize the technology. Analysing these recent developments using a policy-priorities framework for CCS commercialization developed by the Global CCS Institute the paper assesses the USA’s position to lead large-scale deployment of CCS technologies to commercialization. It concludes that the USA is in a prime position due to the political economic characteristics of its energy economy resource wealth and innovation-driven manufacturing sector.
Effect of Hydrogen on the Tensile Behavior of Austenitic Stainless Steels 316L Produced by Laser-Powder Bed Fusion
Apr 2021
Publication
Hydrogen was doped in austenitic stainless steel (ASS) 316L tensile samples produced by the laser-powder bed fusion (L-PBF) technique. For this aim an electrochemical method was conducted under a high current density of 100 mA/cm2 for three days to examine its sustainability under extreme hydrogen environments at ambient temperatures. The chemical composition of the starting powders contained a high amount of Ni approximately 12.9 wt.% as a strong austenite stabilizer. The tensile tests disclosed that hydrogen charging caused a minor reduction in the elongation to failure (approximately 3.5% on average) and ultimate tensile strength (UTS; approximately 2.1% on average) of the samples using a low strain rate of 1.2 × 10−4 s−1. It was also found that an increase in the strain rate from 1.2 × 10−4 s−1 o 4.8 ×10−4 s−1 led to a reduction of approximately 3.6% on average for the elongation to failure and 1.7% on average for UTS in the pre-charged samples. No trace of martensite was detected in the X-ray diffraction (XRD) analysis of the fractured samples thanks to the high Ni content which caused a minor reduction in UTS × uniform elongation (UE) (GPa%) after the H charging. Considerable surface tearing was observed for the pre-charged sample after the tensile deformation. Additionally some cracks were observed to be independent of the melt pool boundaries indicating that such boundaries cannot necessarily act as a suitable area for the crack propagation.
The Role of Hydrogen on the Behavior of Intergranular Cracks in Bicrystalline α-Fe Nanowires
Jan 2021
Publication
Hydrogen embrittlement (HE) has been extensively studied in bulk materials. However little is known about the role of H on the plastic deformation and fracture mechanisms of nanoscale materials such as nanowires. In this study molecular dynamics simulations are employed to study the influence of H segregation on the behavior of intergranular cracks in bicrystalline α-Fe nanowires. The results demonstrate that segregated H atoms have weak embrittling effects on the predicted ductile cracks along the GBs but favor the cleavage process of intergranular cracks in the theoretically brittle directions. Furthermore it is revealed that cyclic loading can promote the H accumulation into the GB region ahead of the crack tip and overcome crack trapping thus inducing a ductile-to-brittle transformation. This information will deepen our understanding on the experimentally-observed H-assisted brittle cleavage failure and have implications for designing new nanocrystalline materials with high resistance to HE.
Hydrogen in Aluminium-Coated Steels Exposed to Synthetic Seawater
Jul 2020
Publication
Thermally sprayed aluminium (TSA) coatings provide protection to offshore steel structures without the use of external cathodic protection (CP) systems. These coatings provide sacrificial protection in the same way as a galvanic anode and thus hydrogen embrittlement (HE) becomes a major concern with the use of high strength steels. The effect of TSA on the HE of steel seems to remain largely unknown. Further the location of hydrogen in TSA-coated steel has not been explored. To address the above knowledge gap API 5L X80 and AISI 4137 steel coupons with and without TSA were prepared and the amount of hydrogen present in these steels when cathodically polarised to −1.1 V (Ag/AgCl) for 30 days in synthetic seawater was determined. One set of TSA-coated specimens was left at open circuit potential (OCP). The study indicates that the amount of hydrogen present in TSA-coated steel is ~100 times more than the amount found in uncoated steel and that the hydrogen seems to be largely localised in the TSA layer.
Influence of Temperature on the Fatigue Strength of Compressed Hydrogen Tanks for Vehicles
Sep 2009
Publication
The influence of environmental temperatures on the fatigue strength of compressed-hydrogen tanks for vehicles was investigated. The fatigue strength of Type-3 tanks was found to decrease in a low temperature environment and increase in a high-temperature environment. The Type-3 tank has been subjected to autofrettage to improve fatigue strength. The investigation clarified that the effect of autofrettage changes according to the environmental temperature due to the difference between the coefficients of thermal expansion of carbon fiber reinforced plastic (CFRP) and aluminum alloy. This causes life strength to change with changes in temperature. These results indicate that the service life of the Type-3 tank is influenced by the environmental temperature. The Type-4 tank has a very long fatigue life and did not break after 45000 cycles in a room-temperature or low-temperature environment. In a high-temperature environment however the tank broke in fewer than 45000 cycles. The fatigue of CFRP was promoted in the high-temperature environment resulting in breakage of the tank.
SGN Aberdeen Vision Project: Final Report
May 2020
Publication
The Aberdeen Vision Project could deliver CO2 savings of 1.5MtCO2/y compared with natural gas. A dedicated pipeline from St Fergus to Aberdeen would enable the phased transfer of the Aberdeen regional gas distribution system to 20% then 100% hydrogen.
The study has demonstrated that 2% hydrogen can be injected into the National Transmission System (NTS) at St Fergus and its distribution through the system into the gas distribution network. Due to unique regional attributes the Aberdeen region could lead the UK in the conversion to largescale clean hydrogen. A 200MW hydrogen generation plant is planned to suit 2% blend into the NTS followed by a build out to supply the Aberdeen gas networks and to enable low cost hydrogen transport applications.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
The study has demonstrated that 2% hydrogen can be injected into the National Transmission System (NTS) at St Fergus and its distribution through the system into the gas distribution network. Due to unique regional attributes the Aberdeen region could lead the UK in the conversion to largescale clean hydrogen. A 200MW hydrogen generation plant is planned to suit 2% blend into the NTS followed by a build out to supply the Aberdeen gas networks and to enable low cost hydrogen transport applications.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Effect of Relative Humidity on Mechanical Degradation of Medium Mn Steels
Mar 2020
Publication
Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles medium Mn steels look forward to a highly promising future. However hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40% 60% 80% and 100%). Under normal relative humidity (about 40%) at 25 °C the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity the hydrogen concentration in steel increases slowly and reaches a stable value about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions the tensile strength changed the hydrogen concentration increased and the elongation decreased as well thereby increasing the hydrogen embrittlement sensitivity. In other words the smaller the tensile rate applied the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions the threshold value of the delayed cracking of M7B (‘M’ referring to Mn ‘7’ meaning the content of Mn ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80% the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.
Alloy and Composition Dependence of Hydrogen Embrittlement Susceptibility in High-strength Steel Fasteners
Jun 2017
Publication
High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Additionally inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. HE susceptibility is a function of the material condition which is comprehensively described by the metallurgical and mechanical properties. Material strength has a first-order effect on HE susceptibility which increases significantly above 1200 MPa and is characterized by a ductile--brittle transition. For a given concentration of hydrogen and at equal strength the critical strength above which the ductile–brittle transition begins can vary due to second-order effects of chemistry tempering temperature and sub-microstructure. Additionally non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. Below 1200 MPa non-conforming quality is often the root cause of real-life failures.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Health & Safety Laboratory - Gas Detection for Hydrogen Enriched Gas Distribution Networks
Jul 2019
Publication
The UK has committed to significantly reduce greenhouse gas emissions by 2050 to help address climate change. Decarbonising heating is a key part of this and using hydrogen (H2) as a replacement to natural gas (NG) can help in achieving this. The objective of current research including HyDeploy is to demonstrate that NG containing levels of H2 beyond those currently allowed of 0.1 vol% (1000 ppm) [1] can be distributed and utilised safely and efficiently. Initial projects such as HyDeploy are studying the effects of introducing up to 20 vol% H2 in NG but later projects are considering using up to 100 vol% H2.
A key element in the safe operation of a modern gas distribution system is gas detection. However the addition of hydrogen to NG will alter the characteristics of the gas and the impact on gas detection must be considered. It is important that sensors remain sufficiently sensitive to the presence of hydrogen natural gas carbon monoxide (CO) and oxygen (O2) deficiency and that they don’t lead to false positive or false negative readings. The aim of this document is to provide a summary of the requirements for gas detection of hydrogen enriched natural gas for the gas distribution industry and other potentially interested parties. As such it is based on gas detectors presently used by the industry with the only major differences being the effects of hydrogen on the sensitivity of flammable gas sensors and the cross sensitivity of carbon monoxide gas sensors to hydrogen.
There is further information of gas detector concepts and technologies in the appendices.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
A key element in the safe operation of a modern gas distribution system is gas detection. However the addition of hydrogen to NG will alter the characteristics of the gas and the impact on gas detection must be considered. It is important that sensors remain sufficiently sensitive to the presence of hydrogen natural gas carbon monoxide (CO) and oxygen (O2) deficiency and that they don’t lead to false positive or false negative readings. The aim of this document is to provide a summary of the requirements for gas detection of hydrogen enriched natural gas for the gas distribution industry and other potentially interested parties. As such it is based on gas detectors presently used by the industry with the only major differences being the effects of hydrogen on the sensitivity of flammable gas sensors and the cross sensitivity of carbon monoxide gas sensors to hydrogen.
There is further information of gas detector concepts and technologies in the appendices.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Hydrogen Embrittlement at Cleavage Planes and Grain Boundaries in Bcc Iron—Revisiting the First-Principles Cohesive Zone Model
Dec 2020
Publication
Hydrogen embrittlement which severely affects structural materials such as steel comprises several mechanisms at the atomic level. One of them is hydrogen enhanced decohesion (HEDE) the phenomenon of H accumulation between cleavage planes where it reduces the interplanar cohesion. Grain boundaries are expected to play a significant role for HEDE since they act as trapping sites for hydrogen. To elucidate this mechanism we present the results of first-principles studies of the H effect on the cohesive strength of α-Fe single crystal (001) and (111) cleavage planes as well as on the Σ5(310)[001] and Σ3(112)[11¯0] symmetrical tilt grain boundaries. The calculated results show that within the studied range of concentrations the single crystal cleavage planes are much more sensitive to a change in H concentration than the grain boundaries. Since there are two main types of procedures to perform ab initio tensile tests different in whether or not to allow the relaxation of atomic positions which can affect the quantitative and qualitative results these methods are revisited to determine their effect on the predicted cohesive strength of segregated interfaces
A Microstructure Informed and Mixed-mode Cohesive Zone Approach to Simulating Hydrogen Embrittlement
Mar 2022
Publication
Hydrogen induced failure under uniaxial tension is simulated in a duplex stainless steel considering microstructural feature of the material. There are three key ingredients in the modelling approach: image processing and finite element representation of the experimentally observed microstructure stress driven hydrogen diffusion and diffusion coupled cohesive zone modelling of fracture considering mixed failure mode. The microstructure used as basis for the modelling work is obtained from specimens cut in the transverse and longitudinal directions. It is found that the microstructure significantly influences hydrogen diffusion and fracture. The austenite phase is polygonal and randomly distributed in the transverse direction where a larger effective hydrogen diffusion coefficient and a lower hydrogen fracture resistance is found compared to the specimen in the longitudinal direction where the austenite phase is slender and laminated. This indicates that the proper design and control of the austenite phase help improve hydrogen resistance of duplex stainless steel. The strength of the interface in the shear direction is found to dominate the fracture mode and initiation site which reveals the importance of considering mixed failure mode and calibrating the hydrogen induced strength reduction in shear.
The Techno-economics Potential of Hydrogen Interconnectors for Electrical Energy Transmission and Storage
Dec 2021
Publication
This research introduces a ‘Hydrogen Interconnector System’ (HIS) as a novel method 7 for transporting electrical energy over long distances. The system takes electricity from 8 stranded renewable energy assets converts it to hydrogen in an electrolyser plant transports 9 hydrogen to the demand centre via pipeline where it is reconverted to electricity in either a 10 gas turbine or fuel cell plant. This paper evaluates the competitiveness of the technology with 11 High Voltage Direct Current (HVDC) systems calculating the following techno-economic 12 indicators; Levelised Cost Of Electricity (LCOE) and Levelised Cost Of Storage (LCOS). The 13 results suggest that the LCOE of the HIS is competitive with HVDC for construction in 2050 14 with distance beyond 350km in case of all scenarios for a 1GW system. The LCOS is lower 15 than an HVDC system using large scale hydrogen storage in 6 out of 12 scenarios analysed 16 including for construction from 2025. The HIS was also applied to three case studies with 17 the results showing that the system outperforms HVDC from LCOS perspectives in all cases 18 and has 15-20% lower investment costs in 2 studies analysed.
Insight into Anomalous Hydrogen Adsorption on Rare Earth Metal Decorated on 2 Dimensional Hexagonal Boron Nitride a Density Functional Theory Study
Mar 2020
Publication
Hydrogen interaction with metal atoms is of prime focus for many energy related applications like hydrogen storage hydrogen evolution using catalysis etc. Although hydrogen binding with many main group alkaline and transition metals is quite well understood its binding properties with lanthanides are not well reported. In this article by density functional theory studies we show how a rare earth metal cerium binds with hydrogen when decorated over a heteropolar 2D material hexagonal boron nitride. Each cerium adatom is found to bind eight hydrogen molecules which is a much higher number than has been reported for transition metal atoms. However the highest binding energy occurs at four hydrogen molecules. This anomaly therefore is investigated in the present article using first-principles calculations. The number density of hydrogen molecules adsorbed over the cerium adatom is explained by investigating the electronic charge volume interactions owing to a unique geometrical arrangement of the guest hydrogen molecules. The importance of geometrical encapsulation in enhancing electronic interactions is explained.
Fatigue Crack Growth of Electron Beam Melted Ti-6Al-4V in High-Pressure Hydrogen
Mar 2020
Publication
Titanium-based alloys are susceptible to hydrogen embrittlement (HE) a phenomenon that deteriorates fatigue properties. Ti-6Al-4V is the most widely used titanium alloy and the effect of hydrogen embrittlement on fatigue crack growth (FCG) was investigated by carrying out crack propagation tests in air and high-pressure H2 environment. The FCG test in hydrogen environment resulted in a drastic increase in crack growth rate at a certain Δ K with crack propagation rates up to 13 times higher than those observed in air. Possible reasons for such behaviour were discussed in this paper. The relationship between FCG results in high-pressure H2 environment and microstructure was investigated by comparison with already published results of cast and forged Ti-6Al-4V. Coarser microstructure was found to be more sensitive to HE. Moreover the electron beam melting (EBM) materials experienced a crack growth acceleration in-between that of cast and wrought Ti-6Al-4V
Hydrogen Trapping in bcc Iron
May 2020
Publication
Fundamental understanding of H localization in steel is an important step towards theoretical descriptions of hydrogen embrittlement mechanisms at the atomic level. In this paper we investigate the interaction between atomic H and defects in ferromagnetic body-centered cubic (bcc) iron using density functional theory (DFT) calculations. Hydrogen trapping profiles in the bulk lattice at vacancies dislocations and grain boundaries (GBs) are calculated and used to evaluate the concentrations of H at these defects as a function of temperature. The results on H-trapping at GBs enable further investigating H-enhanced decohesion at GBs in Fe. A hierarchy map of trapping energies associated with the most common crystal lattice defects is presented and the most attractive H-trapping sites are identified.
Effect of Hydrogen on Fatigue Limit of SCM435 Low-Alloy Steel
Dec 2019
Publication
The objective of this study is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was a low-alloy steel modified to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The hydrogen gas pressure was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in the hydrogen gas than that in air although the material showed severe hydrogen embrittlement during the SSRT (Slow Strain Rate Test). The fatigue limit of the deep-notched specimen in the hydrogen gas was the same as that in air. For the smooth specimen the fatigue limit was determined by whether or not a crack was initiated. For the deep-notched specimen the fatigue limit was determined by whether or not a crack propagated. The results can be interpreted as that hydrogen has no significant effect on crack initiation in the high-cycle fatigue regime and affected the threshold of the crack propagation.
Fast Synthesis of TiNi by Mechanical Alloying and its Hydrogenation Properties
Mar 2019
Publication
Mechanical alloying is widely used for the synthesis of hydrogen storage materials. However amorphization and contamination triggered by long-time milling are serious drawbacks for obtaining efficient hydrogen storage. In this work short-time ball milling synthesis is explored for a representative hydride forming compound: TiNi. Through structural morphological and chemical characterizations we evidence that formation of TiNi is complete in only 20 min with minor Fe contamination (0.2 wt%). Cross-sectional analysis of powder stuck on milling balls reveals that alloy formation occurs through the interdiffusion between thin layers of co-laminated pure elements. Hydrogenation thermodynamics and kinetics of short-time mechanically alloyed TiNi are similar to those of coarse-grained compounds obtained by classical high-temperature melting. Mechanical alloying is a suitable method for fast and energy-efficient synthesis of intermetallic compounds such as TiNi.
Hydrogen Generation from Methanol at Near-room Temperature
Sep 2017
Publication
As a promising hydrogen storage medium methanol has many advantages such as a high hydrogen content (12.5 wt%) and low-cost. However conventional methanol–water reforming methods usually require a high temperature (>200 °C). In this research we successfully designed an effective strategy to fully convert methanol to hydrogen for at least 1900 min (∼32 h) at near-room temperature. The strategy involves two main procedures which are CH3OH →HCOOH → H2 and CH3OH → NADH → H2. HCOOH and the reduced form of nicotinamide adenine dinucleotide (NADH) are simultaneously produced through the dehydrogenation of methanol by the cooperation of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Subsequently HCOOH is converted to H2 by a new iridium polymer complex catalyst and an enzyme mimic is used to convert NADH to H2 and nicotinamide adenine dinucleotide (NAD+). NAD+ can then be reconverted to NADH by repeating the dehydrogenation of methanol. This strategy and the catalysts invented in this research can also be applied to hydrogen production from other small organic molecules (e.g. ethanol) or biomass (e.g. glucose) and thus will have a high impact on hydrogen storage and applications.
Understanding the Interaction between a Steel Microstructure and Hydrogen
Apr 2018
Publication
The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels i.e. high-strength low-alloy (HSLA) transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase i.e. ferrite bainite pearlite or martensite and with carbon contents of approximately 0 0.2 and 0.4 wt % are further considered to simplify the microstructure. Finally the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction a comparison of the available H trapping sites the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis.
Analysis of Stand-Alone Photovoltaic—Marine Current Hybrid System and the Influence on Daily and Seasonal Energy Storage
Jan 2022
Publication
Stand-alone systems in remote regions require the utilization of renewable resources; however their natural intermittence requires the implementation of energy-storage systems that allow a continuous power supply. More than one renewable source is usually available at the same site. Thus the choice of a hybrid system seems viable. It is relevant to study hybrid systems as they could reduce energy storage; however sizing the hybrid system might have several implications not only for the available daily energy but also for the required daily energy storage and surplus seasonal energy. In this work we present a case study of a stand-alone conventional household powered by photovoltaic and marine-current-energy systems in Cozumel Mexico. The analysis of different hybridization degrees serves as a guidance tool to decide whether hybrid systems are required for a specific situation; in contrast to previous approaches where ideal consumption and generation profiles have been utilized yearlong profiles were utilized here. The renewable potential data were obtained on site at an hourly resolution; requirements such as size of and cycles in the daily and seasonal energy storage were analyzed according to the degree of participation or hybridization of the proposed renewable systems through an algorithm that evaluates power generation and daily consumption throughout the year. A further analysis indicated that marine-current-energy implementation reduces the size of the daily energy-storage system by 79% in comparison to the use of only a photovoltaic system due to the similarity between the energy-demand profile and the marine-current-energy production profile. The results indicate that a greater participation of marine currents can help decrease daily storage while increasing seasonal storage by 16% compared to using only solar energy. On the other hand hybridization enabled a reduction in the number of daily charge and discharge cycles at 0.2 hybridization degrees. It also allowed us to reduce the seasonal energy storage by 38% at 0.6 hybridization degrees with respect to only using energy from marine currents. Afterwards energy-storage technologies were evaluated using the TOPSIS Multi-Criteria Decision Analysis to validate the best-suited technology for the energy-storage system. The evaluation considered the characteristics of the technology and the periods of energy storage. In this work hybrid storage systems were mandatory since for daily storage lithium-ion batteries are better suited while for seasonal storage hydrogen-producing systems are more suitable to manage the amount of energy and the storage duration due to the high seasonal renewable-energy variations.
Non-stoichiometric Methanation as Strategy to Overcome the Limitations of Green Hydrogen Injection into the Natural Gas Grid
Jan 2022
Publication
The utilization of power to gas technologies to store renewable electricity surpluses in the form of hydrogen enables the integration of the gas and electricity sectors allowing the decarbonization of the natural gas network through green hydrogen injection. Nevertheless the injection of significant amounts of hydrogen may lead to high local concentrations that may degrade materials (e.g. hydrogen embrittlement of pipelines) and in general be not acceptable for the correct and safe operation of appliances. Most countries have specific regulations to limit hydrogen concentration in the gas network. The methanation of hydrogen represents a potential option to facilitate its injection into the grid. However stoichiometric methanation will lead to a significant presence of carbon dioxide limited in gas networks and requires an accurate design of several reactors in series to achieve relevant concentrations of methane. These requirements are smoothed when the methanation is undertaken under non-stoichiometric conditions (high H/C ratio). This study aims to assess to influence of nonstoichiometric methanation under different H/C ratios on the limitations presented by the pure hydrogen injection. The impact of this injection on the operation of the gas network at local level has been investigated and the fluid-dynamics and the quality of gas blends have been evaluated. Results show that non-stoichiometric methanation could be an alternative to increase the hydrogen injection in the gas network and facilitates the gas and electricity sector coupling.
A Review of the Impact of Hydrogen Integration in Natural Gas Distribution Networks and Electric Smart Grids
Apr 2022
Publication
Hydrogen technologies have been rapidly developing in the past few decades pushed by governments’ road maps for sustainability and supported by a widespread need to decarbonize the global energy sector. Recent scientific progress has led to better performances and higher efficiencies of hydrogen-related technologies so much so that their future economic viability is now rarely called into question. This article intends to study the integration of hydrogen systems in both gas and electric distribution networks. A preliminary analysis of hydrogen’s physical storage methods is given considering both the advantages and disadvantages of each one. After examining the preeminent ways of physically storing hydrogen this paper then contemplates two primary means of using it: integrating it in Power-to-Gas networks and utilizing it in Power-to-Power smart grids. In the former the primary objective is the total replacement of natural gas with hydrogen through progressive blending procedures from the transmission pipeline to the domestic burner; in the latter the set goal is the expansion of the implementation of hydrogen systems—namely storage—in multi-microgrid networks thus helping to decarbonize the electricity sector and reducing the impact of renewable energy’s intermittence through Demand Side Management strategies. The study concludes that hydrogen is assumed to be an energy vector that is inextricable from the necessary transition to a cleaner more efficient and sustainable future.
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