Transmission, Distribution & Storage
Evaluation Techniques of Hydrogen Permeation in Sealing Rubber Materials
Dec 2020
Publication
Three techniques for determining the hydrogen permeation properties of rubber samples were developed based on the volumetric and gravimetric measurements of released H2 gas after sample decompression. These methods include gas chromatography (GC) by thermal desorption analysis (TDA) volumetric collection (VC) measurement of hydrogen by graduated cylinder and gravimetric (GM) measurement by electronic balance. By measuring the released hydrogen against elapsed time after the decompression of pressure the charging amount (C0) and diffusivity (D) were obtained with the developed diffusion analysis program. From these values the solubility (S) and permeability (P) of polymers were evaluated through the relations of Henry's law and P=SD respectively. The developed techniques were applied to three kinds of spherically shaped sealing rubber materials. D S and P were analyzed as a function of pressure. The transport behaviors obtained in the three methods are discussed and compared with the characteristics of each measuring technique. The correlations between transport parameters and carbon black filler or density are discussed.
Current Research Trends and Perspectives on Solid-State Nanomaterials in Hydrogen Storage
Jan 2021
Publication
Hydrogen energy with environment amicable renewable efficiency and cost-effective advantages is the future mainstream substitution of fossil-based fuel. However the extremely low volumetric density gives rise to the main challenge in hydrogen storage and therefore exploring effective storage techniques is key hurdles that need to be crossed to accomplish the sustainable hydrogen economy. Hydrogen physically or chemically stored into nanomaterials in the solid-state is a desirable prospect for effective large-scale hydrogen storage which has exhibited great potentials for applications in both reversible onboard storage and regenerable off-board storage applications. Its attractive points include safe compact light reversibility and efficiently produce sufficient pure hydrogen fuel under the mild condition. This review comprehensively gathers the state-of-art solid-state hydrogen storage technologies using nanostructured materials involving nanoporous carbon materials metal-organic frameworks covalent organic frameworks porous aromatic frameworks nanoporous organic polymers and nanoscale hydrides. It describes significant advances achieved so far and main barriers need to be surmounted to approach practical applications as well as offers a perspective for sustainable energy research.
Micro-grid Design and Life-cycle Assessment of a Mountain Hut's Stand-alone Energy System with Hydrogen Used for Seasonal Storage
Dec 2020
Publication
Mountain huts as special stand-alone micro-grid systems are not connected to a power grid and represent a burden on the environment. The micro-grid has to be flexible to cover daily and seasonal fluctuations. Heat and electricity are usually generated with fossil fuels due to the simple on-off operation. By introducing renewable energy sources (RESs) the generation of energy could be more sustainable but the generation and consumption must be balanced. The paper describes the integration of a hydrogen-storage system (HSS) and a battery-storage system (BattS) in a mountain hut. The HSS involves a proton-exchange-membrane water electrolyser (PEMWE) a hydrogen storage tank (H2 tank) a PEM fuel cell (PEMFC) and a BattS consisting of lead-acid batteries. Eight micro-grid configurations were modelled using HOMER and evaluated from the technical environmental and economic points of view. A life-cycle assessment analysis was made from the cradle to the gate. The micro-grid configurations with the HSS achieve on average a more than 70% decrease in the environmental impacts in comparison to the state of play at the beginning but require a larger investment. Comparing the HSS with the BattS as a seasonal energy storage the hydrogen-based technology had advantages for all of the assessed criteria.
H21- Leeds City Gate Project Report
Jul 2016
Publication
The H21 Leeds City Gate project is a study with the aim of determining the feasibility from both a technical and economic viewpoint of converting the existing natural gas network in Leeds one of the largest UK cities to 100% hydrogen. The project has been designed to minimise disruption for existing customers and to deliver heat at the same cost as current natural gas to customers. The project has shown that:
The project has provided costs for the scheme and has modelled these costs in a regulatory finance model. In addition the availability of low-cost bulk hydrogen in a gas network could revolutionise the potential for hydrogen vehicles and via fuel cells support a decentralised model of combined heat and power and localised power generation.
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 gas network has the correct capacity for such a conversion
- It can be converted incrementally with minimal disruption to customers
- Minimal new energy infrastructure will be required compared to alternatives
- The existing heat demand for Leeds can be met via steam methane reforming and salt cavern storage using technology in use around the world today
The project has provided costs for the scheme and has modelled these costs in a regulatory finance model. In addition the availability of low-cost bulk hydrogen in a gas network could revolutionise the potential for hydrogen vehicles and via fuel cells support a decentralised model of combined heat and power and localised power generation.
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.
Metallurgical Model of Diffusible Hydrogen and Non-Metallic Slag Inclusions in Underwater Wet Welding of High-Strength Steel
Nov 2020
Publication
High susceptibility to cold cracking induced by diffusible hydrogen and hydrogen embrittlement are major obstacles to greater utilization of underwater wet welding for high-strength steels. The aim of the research was to develop gas–slag systems for flux-cored wires that have high metallurgical activity in removal of hydrogen and hydroxyl groups. Thermodynamic modeling and experimental research confirmed that a decrease in the concentration of diffusible hydrogen can be achieved by reducing the partial pressure of hydrogen and water vapor in the vapor–gas bubble and by increasing the hydroxyl capacity of the slag system in metallurgical reactions leading to hydrogen fluoride formation and ionic dissolution of hydroxyl groups in the basic fluorine-containing slag of a TiO2–CaF2–Na3AlF6 system.
Cohesive Zone Modelling of Hydrogen Assisted Fatigue Crack Growth: The Role of Trapping
Apr 2022
Publication
We investigate the influence of microstructural traps in hydrogen-assisted fatigue crack growth. To this end a new formulation combining multi-trap stress-assisted diffusion mechanism-based strain gradient plasticity and a hydrogen- and fatigue-dependent cohesive zone model is presented and numerically implemented. The results show that the ratio of loading frequency to effective diffusivity governs fatigue crack growth behaviour. Increasing the density of beneficial traps not involved in the fracture process results in lower fatigue crack growth rates. The combinations of loading frequency and carbide trap densities that minimise embrittlement susceptibility are identified providing the foundation for a rational design of hydrogen-resistant alloys.
Wood Cellulose as a Hydrogen Storage Material
Apr 2020
Publication
Hydrogen has become a strong candidate to be a future energy storage medium but there are technological challenges both in its production and storage. For storage a search for lightweight abundant and non-toxic materials is on the way. An abundant natural material such as wood cellulose would make an ideal storage medium from a sustainability perspective. Here using a combination of static DFT calculations and ab initio molecular dynamics simulations at different temperatures it is shown that wood cellulose has the ability to uptake H2 via a physisorption mechanism based on dispersion interactions of the van der Waals type involving the O-atoms of the d-glucose rings. The absorption causes little to no disturbances on the cellulose structure and H2 is highly mobile in the material. At an external pressure of H2(g) of 0.09 atm and T = 25 °C cellulose has a theoretical gravimetric density of hydrogen storage of ≈1%.
Hydrogen Embrittlement: The Game Changing Factor in the Applicability of Nickel Alloys in Oilfield Technology
Jun 2017
Publication
Precipitation hardenable (PH) nickel (Ni) alloys are often the most reliable engineering materials for demanding oilfield upstream and subsea applications especially in deep sour wells. Despite their superior corrosion resistance and mechanical properties over a broad range of temperatures the applicability of PH Ni alloys has been questioned due to their susceptibility to hydrogen embrittlement (HE) as confirmed in documented failures of components in upstream applications. While extensive work has been done in recent years to develop testing methodologies for benchmarking PH Ni alloys in terms of their HE susceptibility limited scientific research has been conducted to achieve improved foundational knowledge about the role of microstructural particularities in these alloys on their mechanical behaviour in environments promoting hydrogen uptake. Precipitates such as the γ′ γ′′ and δ-phase are well known for defining the mechanical and chemical properties of these alloys. To elucidate the effect of precipitates in the microstructure of the oil-patch PH Ni alloy 718 on its HE susceptibility slow strain rate tests under continuous hydrogen charging were conducted on material after several different age-hardening treatments. By correlating the obtained results with those from the microstructural and fractographic characterization it was concluded that HE susceptibility of oil-patch alloy 718 is strongly influenced by the amount and size of precipitates such as the γ′ and γ′′ as well as the δ-phase rather than by the strength level only. In addition several HE mechanisms including hydrogen-enhanced decohesion and hydrogen-enhanced local plasticity were observed taking place on oil-patch alloy 718 depending upon the characteristics of these phases when present in the microstructure.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Nonlinear Model Predictive Control of an Autonomous Power System Based on Hydrocarbon Reforming and High Temperature Fuel Cell
Mar 2021
Publication
The integration and control of energy systems for power generation consists of multiple heterogeneous subsystems such as chemical electrochemical and thermal and contains challenges that arise from the multi-way interactions due to complex dynamic responses among the involved subsystems. The main motivation of this work is to design the control system for an autonomous automated and sustainable system that meets a certain power demand profile. A systematic methodology for the integration and control of a hybrid system that converts liquefied petroleum gas (LPG) to hydrogen which is subsequently used to generate electrical power in a high-temperature fuel cell that charges a Li-Ion battery unit is presented. An advanced nonlinear model predictive control (NMPC) framework is implemented to achieve this goal. The operational objective is the satisfaction of power demand while maintaining operation within a safe region and ensuring thermal and chemical balance. The proposed NMPC framework based on experimentally validated models is evaluated through simulation for realistic operation scenarios that involve static and dynamic variations of the power load.
A Hybrid Energy Storage System Using Compressed Air and Hydrogen as the Energy Carrier
Feb 2020
Publication
In this paper an innovative concept of an energy storage system that combines the idea of energy storage through the use of compressed air and the idea of energy storage through the use of hydrogen (with its further conversion to synthetic natural gas) has been proposed. The thermal integration of two sub-systems allows for efficient storage of large amounts of energy based on the use of pressure tanks with limited volumes. A thermodynamic assessment of the integrated hybrid system was carried out. For the assumed operation parameters an energy storage efficiency value of 38.15% was obtained which means the technology is competitive with intensively developed pure hydrogen energy storage technologies. The results obtained for the hybrid system were compared to the results obtained for three reference systems each of which uses hydrogen generators. The first is a typical Power-to-H2-to-Power system which integrates hydrogen generators with a fuel cell system. The other two additionally use a compressed air energy storage installation. In the first case the compressed air energy storage system consists of a diabatic system. In the second case the compressed air energy storage system is adiabatic. The article has discussed the disadvantages and advantages of all the analyzed systems.
Freeze-dried Ammonia Borane-polyethylene Oxide Composites: Phase Behaviour and Hydrogen Release
Feb 2018
Publication
A solid-state hydrogen storage material comprising ammonia borane (AB) and polyethylene oxide (PEO) has been produced by freeze-drying from aqueous solutions from 0% to 100% AB by mass. The phase mixing behaviour of AB and PEO has been investigated using X-ray diffraction which shows that a new ‘intermediate’ crystalline phase exists different from both AB and PEO as observed in our previous work (Nathanson et al. 2015). It is suggested that hydrogen bonding interactions between the ethereal oxygen atom (–O–) in the PEO backbone and the protic hydrogen atoms attached to the nitrogen atom (N–H) of AB molecules promote the formation of a reaction intermediate leading to lowered hydrogen release temperatures in the composites compared to neat AB. PEO also acts to significantly reduce the foaming of AB during hydrogen release. A temperature-composition phase diagram has been produced for the AB-PEO system to show the relationship between phase mixing and hydrogen release.
Analysis of Environmentally Assisted Cracking Processes in Notched Steels Using the Point Method
Sep 2019
Publication
This paper proposes the use of the Point Method (PM) to analyse Environmentally Assisted Cracking (EAC) processes in steels containing U-shaped notches. The PM a methodology included within the Theory of Critical Distances (TCD) has been extensively validated by many authors for the analysis of fracture and fatigue phenomena of different types of materials containing notches. However it has never been applied to other critical or subcritical cracking processes such as EAC or creep crack propagation.<br/>This work provides a PM-based analysis of EAC emanating from notches which is validated by testing CT notched specimens of X80 and S420 steels subjected to aggressive environments under hydrogen embrittlement conditions.<br/>The results reveal that the PM accurately predicts the crack propagation onset condition as well as the evolution of the material’s apparent EAC resistance.
The Role of Hydrogen in Hydrogen Embrittlement of Metals: The Case of Stainless Steel
Apr 2019
Publication
Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen leading to formation of short-range order and a high number of planar dislocations in the 316 SS and causing its anisotropic lattice contraction. Hence hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase.
Hydrogen-Assisted Crack Growth in the Heat-Affected Zone of X80 Steels during in Situ Hydrogen Charging
Aug 2019
Publication
Herein the hydrogen embrittlement of a heat-affected zone (HAZ) was examined using slow strain rate tension in situ hydrogen charging. The influence of hydrogen on the crack path of the HAZ sample surfaces was determined using electron back scatter diffraction analysis. The hydrogen embrittlement susceptibility of the base metal and the HAZ samples increased with increasing current density. The HAZ samples have lower resistance to hydrogen embrittlement than the base metal samples in the same current density. Brittle circumferential cracks located at the HAZ sample surfaces were perpendicular to the loading direction and the crack propagation path indicated that five or more cracks may join together to form a longer crack. The fracture morphologies were found to be a mixture of intergranular and transgranular fractures. Hydrogen blisters were observed on the HAZ sample surfaces after conducting tensile tests at a current density of 40 mA/cm2 leading to a fracture in the elastic deformation stage.
Investigation of the Multi-Point Injection of Green Hydrogen from Curtailed Renewable Power into a Gas Network
Nov 2020
Publication
Renewable electricity can be converted into hydrogen via electrolysis also known as power-to-H2 (P2H) which when injected in the gas network pipelines provides a potential solution for the storage and transport of this green energy. Because of the variable renewable electricity production the electricity end-user’s demand for “power when required” distribution and transmission power grid constrains the availability of renewable energy for P2H can be difficult to predict. The evaluation of any potential P2H investment while taking into account this consideration should also examine the effects of incorporating the produced green hydrogen in the gas network. Parameters including pipeline pressure drop flowrate velocity and most importantly composition and calorific content are crucial for gas network management. A simplified representation of the Irish gas transmission network is created and used as a case study to investigate the impact on gas network operation of hydrogen generated from curtailed wind power. The variability in wind speed and gas network demands that occur over a 24 h period and with network location are all incorporated into a case study to determine how the inclusion of green hydrogen will affect gas network parameters. This work demonstrates that when using only curtailed renewable electricity during a period with excess renewable power generation despite using multiple injection points significant variation in gas quality can occur in the gas network. Hydrogen concentrations of up to 15.8% occur which exceed the recommended permitted limits for the blending of hydrogen in a natural gas network. These results highlight the importance of modelling both the gas and electricity systems when investigating any potential P2H installation. It is concluded that for gas networks that decarbonise through the inclusion of blended hydrogen active management of gas quality is required for all but the smallest of installations.
A Review of Cohesive Zone Modelling as an Approach for Numerically Assessing Hydrogen Embrittlement of Steel Structures
Jun 2014
Publication
Simulation of hydrogen embrittlement (HE) requires a coupled approach; on one side the models describing hydrogen transport must account for local mechanical fields while on the other side the effect of hydrogen on the accelerated material damage must be implemented into the model describing crack initiation and growth. This study presents a review of coupled diffusion and cohesive zone modelling as a method for numerically assessing HE of a steel structure. While the model is able to reproduce single experimental results by appropriate fitting of the cohesive parameters there appears to be limitations in transferring these results to other hydrogen systems. Agreement may be improved by appropriately identifying the required input parameters for the particular system under study.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Technologies and Infrastructures Underpinning Future CO2 Value Chains: A Comprehensive Review and Comparative Analysis
Feb 2018
Publication
In addition to carbon capture and storage efforts are also being focussed on using captured CO2 both directly as a working fluid and in chemical conversion processes as a key strategy for mitigating climate change and achieving resource efficiency. These processes require large amounts of energy which should come from sustainable and ideally renewable sources. A strong value chain is required to support the production of valuable products from CO2 . A value chain is a network of technologies and infrastructures (such as conversion transportation storage) along with its associated activities (such as sourcing raw materials processing logistics inventory management waste management) required to convert low-value resources to high-value products and energy services and deliver them to customers. A CO2 value chain involves production of CO2 (involving capture and purification) technologies that convert CO2 and other materials into valuable products sourcing of low-carbon energy to drive all of the transformation processes required to convert CO2 to products (including production of hydrogen syngas methane etc.) transport of energy and materials to where they are needed managing inventory levels of resources and delivering the products to customers all in order to create value (economic environmental social etc.).
Technologies underpinning future CO2 value chains were examined. CO2 conversion technologies such as urea production Sabatier synthesis Fischer-Tropsch synthesis hydrogenation to methanol dry reforming hydrogenation to formic acid and electrochemical reduction were assessed and compared based on key performance indicators such as: CAPEX OPEX electricity consumption TRL product price net CO2 consumption etc. Technologies for transport and storage of key resources are also discussed. This work lays the foundation for a comprehensive whole-system value chain analysis modelling and optimisation.
Technologies underpinning future CO2 value chains were examined. CO2 conversion technologies such as urea production Sabatier synthesis Fischer-Tropsch synthesis hydrogenation to methanol dry reforming hydrogenation to formic acid and electrochemical reduction were assessed and compared based on key performance indicators such as: CAPEX OPEX electricity consumption TRL product price net CO2 consumption etc. Technologies for transport and storage of key resources are also discussed. This work lays the foundation for a comprehensive whole-system value chain analysis modelling and optimisation.
Alloy Optimization for Reducing Delayed Fracture Sensitivity of 2000 MPa Press Hardening Steel
Jun 2020
Publication
Press hardening steel (PHS) is widely applied in current automotive body design. The trend of using PHS grades with strengths above 1500 MPa raises concerns about sensitivity to hydrogen embrittlement. This study investigates the hydrogen delayed fracture sensitivity of steel alloy 32MnB5 with a 2000 MPa tensile strength and that of several alloy variants involving molybdenum and niobium. It is shown that the delayed cracking resistance can be largely enhanced by using a combination of these alloying elements. The observed improvement appears to mainly originate from the obstruction of hydrogen-induced damage incubation mechanisms by the solutes as well as the precipitates of these alloying elements.
Dynamic Operation of Fischer-Tropsch Reactors for Power-to-liquid Concepts: A Review
Apr 2022
Publication
The Fischer-Tropsch synthesis (FTS) is considered as a power-to-X (PtX) storage concept for converting temporally available excess energy to fuels or chemical compounds without the need of fossil resources. Fluctuating energy supplies demand a load-flexible energy system and a dynamically operating FTS reactor might be beneficial compared to traditional steady-state operations which rely on expensive upstream buffer capacities. This review provides an overview of recent experimental and simulation studies dealing with dynamic FTS operation and summarizes the main findings. The results are presented the two categories process intensification and PtX application. The review further discusses the experimentally difficult task of wide-ranging product characterization with a high temporal resolution. While dynamic reactor operation is often related to a complicated process control which challenges a save and efficient reactor performance the literature findings indicate that for dynamic FTS operation such concerns might not be as critical as assumed at least within well-known boundaries. Researchers further agree that dynamic operation might be a tool for process intensification. Especially hydrogen pulsing seems to be a potentially beneficial operating technique to remove accumulated liquid products restore initial catalyst activity and increase diesel-range productivity. The main challenge in this context is the prevention of high methane selectivity. A lucid future engineering goal seems to be the combination of the two applications: a robust and reliable FTS reactor in a PtX scenario that not only handles a fluctuating feed but uses such variations for process enhancement.
Stress–Corrosion Cracking of AISI 316L Stainless Steel in Seawater Environments: Effect of Surface Machining
Oct 2020
Publication
To understand the effect of surface machining on the resistance of AISI 316L to SCC (stress–corrosion cracking) in marine environments we tested nuts surface-machined by different methods in a seawater-spraying chamber. Two forms of cracks were observed: on the machined surface and underneath it. On the surface cracks connected with the pitting sites were observed to propagate perpendicular to the hoop-stress direction identifying them as stress–corrosion cracks. Under the surface catastrophic transgranular cracks developed likely driven by hydrogen embrittlement caused by the chloride-concentrating level of humidity in the testing environment. Under constant testing conditions significantly different SCC resistance was observed depending on how the nuts had been machined. Statistical evaluation of the nut surface-crack density indicates that machining by a “form” tool yields a crack density one order of magnitude lower than machining by a “single-point” tool. Microstructural analysis of form-tool-machined nuts revealed a homogeneous deformed subsurface zone with nanosized grains leading to enhanced surface hardness. Apparently the reduced grain size and/or the associated mechanical hardening improve resistance to SCC. The nanograin subsurface zone was not observed on nuts machined by a single-point tool. Surface roughness measurements indicate that single-point-tool-machined nuts have a rougher surface than form-tool machined nuts. Apparently surface roughness reduces SCC resistance by increasing the susceptibility to etch attack in Cl--rich solutions. The results of X-ray diffractometry and transmission electron microscopy diffractometry indicate that machining with either tool generates a small volume fraction (< 0.01) of strain-induced martensite. However considering the small volume fraction and absence of martensite in regions of cracking martensite is not primarily responsible for SCC in marine environments.
Impact of Chemical Inhomogeneities on Local Material Properties and Hydrogen Environment Embrittlement in AISI 304L Steels
Feb 2018
Publication
This study investigated the influence of segregations on hydrogen environment embrittlement (HEE) of AISI 304L type austenitic stainless steels. The microstructure of tensile specimens that were fabricated from commercially available AISI 304L steels and tested by means of small strain-rate tensile tests in air as well as hydrogen gas at room temperature was investigated by means of combined EDS and EBSD measurements. It was shown that two different austenitic stainless steels having the same nominal alloy composition can exhibit different susceptibilities to HEE due to segregation effects resulting from different production routes (continuous casting/electroslag remelting). Local segregation-related variations of the austenite stability were evaluated by thermodynamic and empirical calculations. The alloying element Ni exhibits pronounced segregation bands parallel to the rolling direction of the material which strongly influences the local austenite stability. The latter was revealed by generating and evaluating two-dimensional distribution maps for the austenite stability. The formation of deformation-induced martensite was shown to be restricted to segregation bands with a low Ni content. Furthermore it was shown that the formation of hydrogen induced surface cracks is strongly coupled with the existence of surface regions of low Ni content and accordingly low austenite stability. In addition the growth behavior of hydrogen-induced cracks was linked to the segregation-related local austenite stability.
Concept of Hydrogen Fired Gas Turbine Cycle with Exhaust Gas Recirculation: Assessment of Process Performance
Nov 2019
Publication
High hydrogen content fuels can be used in gas turbine for power generation with CO2 capture IGCC plants or with hydrogen from renewables. The challenge for the engine is the high reactive combustion properties making dilution necessary to mitigate NOx emissions at the expense of a significant energy cost. In the concept analysed in this study high Exhaust Gas Recirculation (EGR) rate is applied to the gas turbine to generate oxygen depleted air. As a result combustion temperature is inherently limited keeping NOx emissions low without the need for dilution or unsafe premixing. The concept is analysed by process simulation based on a reference IGCC plant with CO2 Capture. Results with dry and wet EGR options are presented as a function EGR rate. Efficiency performance is assessed against the reference power cycle with nitrogen dilution. All EGR options are shown to represent an efficiency improvement. Nitrogen dilution is found to have a 1.3% efficiency cost. Although all EGR options investigated offer an improvement dry EGR is considered as the preferred option despite the need for higher EGR rate as compared with the wet EGR. The efficiency gain is calculated to be of 1% compared with the reference case.
Pressurized Hydrogen from Charged Liquid Organic Hydrogen Carrier Systems by Electrochemical Hydrogen Compression
Feb 2021
Publication
We demonstrate that the combination of hydrogen release from a Liquid Organic Hydrogen Carrier (LOHC) system with electrochemical hydrogen compression (EHC) provides three decisive advantages over the state-of-the-art hydrogen provision from such storage system: a) The EHC device produces reduced hydrogen pressure on its suction side connected to the LOHC dehydrogenation unit thus shifting the thermodynamic equilibrium towards dehydrogenation and accelerating the hydrogen release; b) the EHC device compresses the hydrogen released from the carrier system thus producing high value compressed hydrogen; c) the EHC process is selective for proton transport and thus the process purifies hydrogen from impurities such as traces of methane. We demonstrate this combination for the production of compressed hydrogen (absolute pressure of 6 bar) from perhydro dibenzyltoluene at dehydrogenation temperatures down to 240 °C in a quality suitable for fuel cell operation e.g. in a fuel cell vehicle. The presented technology may be highly attractive for providing compressed hydrogen at future hydrogen filling stations that receive and store hydrogen in a LOHC-bound manner.
Baking Effect on Desorption of Diffusible Hydrogen and Hydrogen Embrittlement on Hot-Stamped Boron Martensitic Steel
Jun 2019
Publication
Recently hot stamping technology has been increasingly used in automotive structural parts with ultrahigh strength to meet the standards of both high fuel efficiency and crashworthiness. However one issue of concern regarding these martensitic steels which are fabricated using a hot stamping procedure is that the steel is highly vulnerable to hydrogen delayed cracking caused by the diffusible hydrogen flow through the surface reaction of the coating in a furnace atmosphere. One way to make progress in understanding hydrogen delayed fractures is to elucidate an interaction for desorption with diffusible hydrogen behavior. The role of diffusible hydrogen on delayed fractures was studied for different baking times and temperatures in a range of automotive processes for hot-stamped martensitic steel with aluminum- and silicon-coated surfaces. It was clear that the release of diffusible hydrogen is effective at higher temperatures and longer times making the steel less susceptible to hydrogen delayed fractures. Using thermal desorption spectroscopy the phenomenon of the hydrogen delayed fracture was attributed to reversible hydrogen in microstructure sites with low trapping energy.
Influence of Microstructural Anisotropy on the Hydrogen-assisted Fracture of Notched Samples of Progressively Drawn Pearlitic Steel
Dec 2020
Publication
In this study fracture surfaces of notched specimens of pearlitic steels subjected to constant extension rate tests (CERTs) are analyzed in an environment causing hydrogen assisted fracture. In order to obtain general results both different notched geometries (to generate quite distinct stress triaxiality distributions in the vicinity of the notch tip) and diverse loading rates were used. The fracture surfaces were classified in relation to four micromechanical models of hydrogen-assisted micro-damage. To this end fractographic analysis in each fracture surface was carried out with a scanning electron microscopy. Generated results increase the number of micromechanical models found in the scientific literature.
Assessment of the Contribution of Internal Pressure to the Structural Damage in a Hydrogen-charged Type 316L Austenitic Stainless Steel During Slow Strain Rate Tensile Test
Dec 2018
Publication
The aim of this study is to provide a quantification of the internal pressure contribution to the SSRT properties of H-charged Type-316L steel tested in air at room temperature. Considering pre-existing penny-shaped voids the transient pressure build-up has been simulated as well as its impact on the void growth by preforming JIc calculations. Several void distributions (size and spacing) have been considered. Simulations have concluded that there was no impact of the internal pressure on the void growth regardless the void distribution since the effective pressure was on the order of 1 MPa during the SSRT test. Even if fast hydrogen diffusion related to dislocation pipe-diffusion has been assessed as a conservative case the impact on void growth was barely imperceptible (or significantly low). The effect of internal pressure has been experimentally verified via the following conditions: (I) non-charged in vacuum; (II) H-charged in vacuum; (III) H-charged in 115-MPa nitrogen gas; (IV) non-charged in 115-MPa nitrogen gas. As a result the relative reduction in area (RRA) was 0.84 for (II) 0.88 for (III) and 1.01 for (IV) respectively. The difference in void morphology of the H-charged specimens did not depend on the presence of external pressure. These experimental results demonstrate that the internal pressure had no effect on the tensile ductility and void morphology of the H-charged specimen.
UV Assisted on Titanium Doped Electrode for Hydrogen Evolution from Artificial Wastewater
Jul 2018
Publication
Formaldehyde (H2CO) is the harmful chemical that used in variety of industries. However there are many difficulties to treat discharged H2CO in the wastewater. Hydrogen energy is arising as a one of the renewable energy that can replace fossil fuel. Many researches have been conducted on hydrogen production from electrolysis using expensive metal electrodes and catalysts such as platinum (Pt) and palladium (Pd). However they are expensive and have obstacles to directly use from the production. We used copper (Cu) as an electrode substrate because it has a good current density. To avoid corrosion issue of Cu substrate we used commercially available carbon (C) coated Cu substrate and synthesized titanium (Ti) on C/Cu substrate. We found that Ti was well synthesized and stayed on substrate after hydrogen evolution reaction (HER) in artificial wastewater. Moreover we quantified hydrogen production from the wastewater and compared it to pure water. Hydrogen production was enhanced in wastewater and H2CO was decomposed after reaction. We expected to use Ti-C/Cu electrode for hydrogen production of wastewater by electrolysis.
Highly Porous Organic Polymers for Hydrogen Fuel Storage
Apr 2019
Publication
Hydrogen (H2) is one of the best candidates to replace current petroleum energy resources due to its rich abundance and clean combustion. However the storage of H2presents a major challenge. There are two methods for storing H2 fuel chemical and physical both of which have some advantages and disadvantages. In physical storage highly porous organic polymers are of particular interest since they are low cost easy to scale up metal-free and environmentally friendly.
In this review highly porous polymers for H2 fuel storage are examined from five perspectives:
(a) brief comparison of H2 storage in highly porous polymers and other storage media;
(b) theoretical considerations of the physical storage of H2 molecules in porous polymers;
(c) H2 storage in different classes of highly porous organic polymers;
(d) characterization of microporosity in these polymers; and
(e) future developments for highly porous organic polymers for H2 fuel storage. These topics will provide an introductory overview of highly porous organic polymers in H2 fuel storage.
In this review highly porous polymers for H2 fuel storage are examined from five perspectives:
(a) brief comparison of H2 storage in highly porous polymers and other storage media;
(b) theoretical considerations of the physical storage of H2 molecules in porous polymers;
(c) H2 storage in different classes of highly porous organic polymers;
(d) characterization of microporosity in these polymers; and
(e) future developments for highly porous organic polymers for H2 fuel storage. These topics will provide an introductory overview of highly porous organic polymers in H2 fuel storage.
Internal and Surface Damage after Electrochemical Hydrogen Charging for Ultra Low Carbon Steel with Various Degrees of Recrystallization
Jul 2016
Publication
An ultra low carbon (ULC) steel was subjected to electrochemical hydrogen charging to provoke hydrogen induced damage in the material. The damage characteristics were analyzed for recrystallized partially recrystallized and cold deformed material. The goal of the study is to understand the effect of cold deformation on the hydrogen induced cracking behavior of a material which is subjected to cathodic hydrogen charging. Additionally charging conditions i.e. charging time and current density were varied in order to identify correlations between on the one hand crack initiation and propagation and on the other hand the charging conditions. The obtained hydrogen induced cracks were studied by optical microscopy scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Hydrogen induced cracks were observed to propagate transgranularly independently of the state of the material. Deformed samples were considerably more sensitive to hydrogen induced cracking which implies the important role of dislocations in hydrogen induced damage mechanisms.
Chemical Utilization of Hydrogen from Fluctuating Energy Sources- Catalytic Transfer Hydrogenation from Charged Liquid Organic Hydrogen Carrier Systems
Nov 2015
Publication
Liquid Organic Hydrogen Carrier (LOHC) systems offer a very attractive way for storing and distributing hydrogen from electrolysis using excess energies from solar or wind power plants. In this contribution an alternative high-value utilization of such hydrogen is proposed namely its use in steady-state chemical hydrogenation processes. We here demonstrate that the hydrogen-rich form of the LOHC system dibenzyltoluene/perhydro-dibenzyltoluene can be directly applied as sole source of hydrogen in the hydrogenation of toluene a model reaction for large-scale technical hydrogenations. Equilibrium experiments using perhydro-dibenzyltoluene and toluene in a ratio of 1:3 (thus in a stoichiometric ratio with respect to H2) yield conversions above 60% corresponding to an equilibrium constant significantly higher than 1 under the applied conditions (270 °C).
Paving the Way to the Fuel of the Future—Nanostructured Complex Hydrides
Dec 2022
Publication
Hydrides have emerged as strong candidates for energy storage applications and their study has attracted wide interest in both the academic and industry sectors. With clear advantages due to the solid-state storage of hydrogen hydrides and in particular complex hydrides have the ability to tackle environmental pollution by offering the alternative of a clean energy source: hydrogen. However several drawbacks have detracted this material from going mainstream and some of these shortcomings have been addressed by nanostructuring/nanoconfinement strategies. With the enhancement of thermodynamic and/or kinetic behavior nanosized complex hydrides (borohydrides and alanates) have recently conquered new estate in the hydrogen storage field. The current review aims to present the most recent results many of which illustrate the feasibility of using complex hydrides for the generation of molecular hydrogen in conditions suitable for vehicular and stationary applications. Nanostructuring strategies either in the pristine or nanoconfined state coupled with a proper catalyst and the choice of host material can potentially yield a robust nanocomposite to reliably produce H2 in a reversible manner. The key element to tackle for current and future research efforts remains the reproducible means to store H2 which will build up towards a viable hydrogen economy goal. The most recent trends and future prospects will be presented herein.
Hydrogen Embrittlement Susceptibility of Prestressing Steel Wires: The Role of the Cold-drawing Conditions
Jul 2016
Publication
Prestressing steel wires are highly susceptible to hydrogen embrittlement (HE). Residual stress-strain state produced after wire drawing plays an essential role since hydrogen damage at certain places of the material is directly affected by stress and strain fields. Changes in wire drawing conditions modify the stress and strain fields and consequently the HE susceptibility and life in service of these structural components in the presence of a hydrogenating environment. This paper analyzes the distributions of residual stress and plastic strain obtained after diverse drawing conditions (inlet die angle die bearing length varying die angle and straining path) and their influence on HE susceptibility of the wires. The conditions for industrial cold drawing can thus be optimized thereby producing commercial prestressing steel wires with improved performance against HE phenomena.
Effect of Corrosion-induced Hydrogen Embrittlement and its Degradation Impact on Tensile Properties and Fracture Toughness of (Al-Cu-Mg) 2024 Alloy
Jul 2016
Publication
In the present work the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA) Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.
Critical Assessment of the Effect of Atmospheric Corrosion Induced Hydrogen on Mechanical Properties of Advanced High Strength Steel
Dec 2020
Publication
Hydrogen absorption into steel during atmospheric corrosion has been of a strong concern during last decades. It is technically important to investigate if hydrogen absorbed under atmospheric exposure conditions can significantly affect mechanical properties of steels. The present work studies changes of mechanical properties of dual phase (DP) advanced high strength steel specimens with sodium chloride deposits during corrosion in humid air using Slow Strain Rate Test (SSRT). Additional annealed specimens were used as reference in order to separate the possible effect of absorbed hydrogen from that of corrosion deterioration. Hydrogen entry was monitored in parallel experiments using hydrogen electric resistance sensor (HERS) and thermal desorption mass spectrometry (TDMS). SSRT results showed a drop in elongation and tensile strength by 42% and 6% respectively in 27 days of atmospheric exposure. However this decrease cannot be attributed to the effect of absorbed hydrogen despite the increase in hydrogen content with time of exposure. Cross-cut analysis revealed considerable pitting which was suggested to be the main reason for the degradation of mechanical properties
Hydrogen Permeation Under High Pressure Conditions and the Destruction of Exposed Polyethylene-property of Polymeric Materials for High-pressure Hydrogen Devices (2)-
Feb 2021
Publication
Aiming to elucidate physical property affecting to hydrogen gas permeability of polymer materials used for liner materials of storage tanks or hoses and sealants under high-pressure environment as model materials with different free volume fraction five types of polyethylene were evaluated using two methods. A convenient non-steady state measurement of thermal desorption analysis (TDA) and steady-state high-pressure hydrogen gas permeation test (HPHP) were used both under up to 90 MPa of practical pressure. The limit of TDA method of evaluation for the specimens suffering fracture during decompression process after hydrogen exposure was found. Permeability coefficient decreased with the decrease of diffusion coefficient under higher pressure condition. Specific volume and degree of crystallinity under hydrostatic environment were measured. The results showed that the shrinkage in free volume caused by hydrostatic effects of the applied hydrogen gas pressure decreases diffusion coefficient resulting in the decrease of permeability coefficient with the pressure rise.
The Impact of Hydrogen on Mechanical Properties; A New In Situ Nanoindentation Testing Method
Feb 2019
Publication
We have designed a new method for electrochemical hydrogen charging which allows us to charge very thin coarse-grained specimens from the bottom and perform nanomechanical testing on the top. As the average grain diameter is larger than the thickness of the sample this setup allows us to efficiently evaluate the mechanical properties of multiple single crystals with similar electrochemical conditions. Another important advantage is that the top surface is not affected by corrosion by the electrolyte. The nanoindentation results show that hydrogen reduces the activation energy for homogenous dislocation nucleation by approximately 15–20% in a (001) grain. The elastic modulus also was observed to be reduced by the same amount. The hardness increased by approximately 4% as determined by load-displacement curves and residual imprint analysis.
Efficient Hydrogen Storage in Defective Graphene and its Mechanical Stability: A Combined Density Functional Theory and Molecular Dynamics Simulation Study
Dec 2020
Publication
A combined density functional theory and molecular dynamics approach is employed to study modifications of graphene at atomistic level for better H2 storage. The study reveals H2 desorption from hydrogenated defective graphene structure V222 to be exothermic. H2 adsorption and desorption processes are found to be more reversible for V222 as compared to pristine graphene. Our study shows that V222 undergoes brittle fracture under tensile loading similar to the case of pristine graphene. The tensile strength of V222 shows slight reduction with respect to their pristine counterpart which is attributed to the transition of sp2 to sp3-like hybridization. The study also shows that the V222 structure is mechanically more stable than the defective graphene structure without chemically adsorbed hydrogen atoms. The current fundamental study thus reveals the efficient recovery mechanism of adsorbed hydrogen from V222 and paves the way for the engineering of structural defects in graphene for H2 storage.
A Multi‐input and Single‐output Voltage Control for a Polymer Electrolyte Fuel Cell System Using Model Predictive Control Method
Mar 2021
Publication
Efficient and robust control strategies can greatly contribute to the reliability of fuel cell systems and a stable output voltage is a key criterion for evaluating a fuel cell system's reliability as a power source. In this study a polymer electrolyte fuel cell (PEFC) system model is developed and its performances under different operating conditions are studied. Then two different novel controllers—a proportional integral derivative (PID) controller and a model predictive control (MPC) controller—are proposed and applied in the PEFC system to control its output voltage at a desired value by regulating the hydrogen and air flow rates at the same time which features a multi‐input and single‐output control problem. Simulation results demonstrate that the developed PEFC system model is qualified to capture the system's behaviour. And both the developed PID and MPC controllers are effective at controlling the PEFC system's output voltage. While the MPC controller presents superior performance with faster response and smaller overshoot. The proposed MPC controller can be easily employed in various control applications for fuel cell systems.
Detection, Characterization and Sizing of Hydrogen Induced Cracking in Pressure Vessels Using Phased Array Ultrasonic Data Processing
Jul 2016
Publication
Pressure vessels operating in sour service conditions in refinery environments can be subject to the risk of H₂S cracking resulting from the hydrogen entering into the material. This risk which is related to the specific working conditions and to the quality of the steel used shall be properly managed in order to maintain the highest safety at a cost-effective level.<br/>Nowadays the typical management strategy is based on a risk based inspection (RBI) evaluation to define the inspection plan used in conjunction with a fitness for service (FFS) approach in defining if the vessel although presenting dangerous defects such as cracks can still be considered “fit for purpose” for a given time window based on specific fracture mechanics analysis.<br/>These vessels are periodically subject to non-destructive evaluation typically ultrasonic testing. Phased Array (PA) ultrasonic is the latest technology more and more used for this type of application.<br/>This paper presents the design and development of an optimized Phased Array ultrasonic inspection technique for the detection and sizing of hydrogen induced cracking (HIC) type flaws used as reference for comparison. Materials used containing natural operational defects were inspected in “as-service” conditions.<br/>Samples have then been inspected by means of a “full matrix capture” (FMC) acquisition process followed by “total focusing method” (TFM) data post processing. FCM-TFM data have been further post-processed and then used to create a 3D geometrical reconstruction of the volume inspected. Results obtained show the significant improvement that FMC/TFM has over traditional PA inspection techniques both in terms of sensitivity and resolution for this specific type of defect. Moreover since the FMC allows for the complete time domain signal to be captured from every element of a linear array probe the full set of data is available for post-processing.<br/>Finally the possibility to reconstruct the geometry of the component from the scans including the defects present in its volume represents the ideal solution for a reliable data transferring process to the engineering function for the subsequent FFS analysis.
Is Direct Seawater Splitting Economically Meaningful?
Jun 2021
Publication
Electrocatalytic water splitting is the key process for the formation of green fuels for energy transport and storage in a sustainable energy economy. Besides electricity it requires water an aspect that seldomly has been considered until recently. As freshwater is a limited resource (<1% of earth's water) lately plentiful reports were published on direct seawater (around 96.5% of earth's water) splitting without or with additives (buffers or bases). Alternatively the seawater can be split in two steps where it is first purified by reverse osmosis and then split in a conventional water electrolyser. This quantitative analysis discusses the challenges of the direct usage of non-purified seawater. Further herein we compare the energy requirements and costs of seawater purification with those of conventional water splitting. We find that direct seawater splitting has substantial drawbacks compared to conventional water splitting and bears almost no advantage. In short it is less promising than the two-step scenario as the capital and operating costs of water purification are insignificant compared to those of electrolysis of pure water.
Environmentally-Assisted Cracking of Type 316L Austenitic Stainless Steel in Low Pressure Hydrogen Steam Environments
Aug 2019
Publication
A low pressure superheated hydrogen-steam system has been used to accelerate the oxidation kinetics while keeping the electrochemical conditions similar to those of the primary water in a pressurized water reactor. The initiation has been investigated using a Constant Extension Rate Tensile (CERT) test. Tests were performed on flat tapered specimens made from Type 316L austenitic stainless steel with strain rates of 2×10-6 and 2×10-8 ms-1 at room temperature and at an elevated temperature of 350 °C. R = 1/6 was chosen as a more oxidizing environment and R = 6 was selected as a more reducing environment where the parameter R represents the ratio between the oxygen partial pressure at the Ni/NiO transition and the oxygen partial pressure. Different exposures (1 day and 5 days) prior to loading were investigated post-test evaluation by scanning electron microscopy.
Hydrogen Induced Damage in Heavily Cold-Drawn Wires of Lean Duplex Stainless Steel
Sep 2017
Publication
The paper addresses the sensitivity to hydrogen embrittlement of heavily cold-drawn wires made of the new generation of lower alloyed duplex stainless steels often referred to as lean duplex grades. It includes comparisons with similar data corresponding to cold-drawn eutectoid and duplex stainless steels. For this purpose fracture tests under constant load were carried out with wires in the as-received condition and fatigue-precracked in air and exposed to ammonium thiocyanate solution. Microstructure and fractographic observations were essential means for the cracking analysis. The effect of hydrogen-assisted embrittlement on the damage tolerance of lean duplex steels was assessed regarding two macro-mechanical damage models that provide the upper bounds of damage tolerance and accurately approximate the failure behavior of the eutectoid and duplex stainless steels wires.
Features of the Hydrogen-Assisted Cracking Mechanism in the Low-Carbon Steel at Ex- and In-situ Hydrogen Charging
Dec 2018
Publication
Hydrogen embrittlement has been intensively studied in the past. However its governing mechanism is still under debate. Particularly the details of the formation of specific cleavage-like or quasi-cleavage fracture surfaces related to hydrogen embrittled steels are unclear yet. Recently it has been found that the fracture surface of the hydrogen charged and tensile tested low-carbon steel exhibits quasi-cleavage facets having specific smoothly curved surface which is completely different from common flat cleavage facets. In the present contribution we endeavor to shed light on the origin of such facets. For this purpose the notched flat specimens of the commercial low carbon steel were tensile tested using ex- and in-situ hydrogen charging. It is found that in the ex-situ hydrogen charged specimens the cracks originate primarily inside the specimen bulk and expand radially form the origin to the specimen surface. This process results in formation of “fisheyes” – the round-shape areas with the surface composed of curved quasi-cleavage facets. In contrast during tensile testing with in-situ hydrogen charging the cracks initiate from the surface and propagate to the bulk. This process results in the formation of the completely brittle fracture surface with the quasi-cleavage morphology - the same as that in fisheyes. The examination of the side surface of the in-situ hydrogen charged specimens revealed the straight and S-shaped sharp cracks which path is visually independent of the microstructure and crystallography but is strongly affected by the local stress fields. Nano-voids are readily found at the tips of these cracks. It is concluded that the growth of such cracks occurs by the nano-void coalescence mechanism and is responsible for the formation of fisheyes and smoothly curved quasi-cleavage facets in hydrogen charged low-carbon steel.
Comarine Derivatives Designed as Carbon Dioxide and Hydrogen Storage
Feb 2022
Publication
The growing of fossil fuel burning leads to increase CO2 and H2 emissions which cause increasing of global warming that has brought big attention. As a result enormous researches have been made to reduce CO2 and H2 build up in the environment. One of the most promising approaches for managing CO2 and H2 gases percentage in the atmosphere is capturing and storage them inside proper materials. Therefore the design of new materials for carbon dioxide and hydrogen storage has received increasing research attention. Four derivatives of coumarine linked to thiazolidinone were synthesized in good yields by reacting 3-(2-Phenylaminoacetyl)coumarine and 2-phenylimino thiazolidinone-4-one in a solution of anhydrous sodium acetate /glacial acetic acid at 120° for 5-6 hours. The synthesised organic compounds were identified by using different techniques such as 1H NMR 13C NMR FTIR and energy dispersive X-ray spectra. The agglomeration shape and porosity of the particles were determined utilizing scanning electron microscopy (SEM) and microscopy images analysis. The capacity of carbon dioxide (CO2) and hydrogen (H2) adsorption on the prepared organic materials at 323 K 50 bar ranged from 22 to 31 cm3 /g and hydrogen from 4 to 12 cm3 /g for the four synthesised compounds which contain phenyl substituted with chloro nitro and bromo groups was found to be the most active adsorbent surfaces for carbon dioxide and hydrogen storage.
Effects of Hydrogen Pressure, Test Frequency and Test Temperature on Fatigue Crack Growth Properties of Low-carbon Steel in Gaseous Hydrogen
Jul 2016
Publication
Fatigue crack growth (FCG) tests for compact tension (CT) specimens of an annealed low-carbon steel JIS-SM490B were performed under various combinations of hydrogen pressures ranging from 0.1 to 90 MPa test frequencies from 0.001 to 10 Hz and test temperatures of room temperature (RT) 363 K and 423 K. In the hydrogen pressures of 0.1 0.7 and 10 MPa at RT the FCG rate increased with a decrease in the test frequency; then peaked out. In the lower test frequency regime the FCG rate decreased and became nearly equivalent to the FCG rate in air. Also in hydrogen pressure of 45 MPa at RT the hydrogen-assisted FCG acceleration showed an upper limit around the test frequencies of 0.01 to 0.001 Hz. On the other hand in the hydrogen pressure of 90 MPa at RT the FCG rate monotonically increased with a decrease in the test frequency and eventually the upper limit of FCG acceleration was not confirmed down to the test frequency of 0.001 Hz. In the hydrogen pressure of 0.7 MPa at the test frequency of 1 Hz and temperatures of 363 K and 423 K the stress intensity factor range ΔK for the onset of the FCG acceleration in hydrogen gas was shifted to a higher ΔK with an increase in the test temperature. The laser-microscope observation at specimen surface revealed that the hydrogen-assisted FCG acceleration always accompanied a localization of plastic deformation near crack tip. These results infer that the influencing factor dominating the hydrogen-assisted FCG acceleration is not the presence or absence of hydrogen in material but is how hydrogen localizes near the crack tip. Namely a steep gradient of hydrogen concentration can result in the slip localization at crack tip which enhances the Hydrogen Enhanced Successive Fatigue Crack Growth (HESFCG) proposed by the authors. It is proposed that such a peculiar dependence of FCG rate on hydrogen pressure test frequency and test temperature can be unified by using a novel parameter representing the gradient of hydrogen concentration near crack tip.
On the Concept of Micro-fracture Map (MFM) and its Role in Structural Integrity Evaluations in Materials Science and Engineering: A Tribute to Jorge Manrique
Dec 2020
Publication
This paper deals with the concept of micro-fracture map (MFM) and its role in structural integrity evaluations in materials science and engineering on the basis of previous research by the author on notch-induced fracture and hydrogen embrittlement of progressively cold drawn pearlitic steels and 316L austenitic stainless steel. With regard to this some examples are provided of assembly of MFMs in particular situations.
Ammonia for Power
Sep 2018
Publication
A potential enabler of a low carbon economy is the energy vector hydrogen. However issues associated with hydrogen storage and distribution are currently a barrier for its implementation. Hence other indirect storage media such as ammonia and methanol are currently being considered. Of these ammonia is a carbon free carrier which offers high energy density; higher than compressed air. Hence it is proposed that ammonia with its established transportation network and high flexibility could provide a practical next generation system for energy transportation storage and use for power generation. Therefore this review highlights previous influential studies and ongoing research to use this chemical as a viable energy vector for power applications emphasizing the challenges that each of the reviewed technologies faces before implementation and commercial deployment is achieved at a larger scale. The review covers technologies such as ammonia in cycles either for power or CO2 removal fuel cells reciprocating engines gas turbines and propulsion technologies with emphasis on the challenges of using the molecule and current understanding of the fundamental combustion patterns of ammonia blends.
Interface Instabilities of Growing Hydrides
Jul 2016
Publication
Formation of metal hydrides is a serious complication that occur when hydride forming metals such as zirconium niobium vanadium and magnesium are exposed to long term hydrogen environment. The main concern is that the hydride as being a brittle material has very poor fracture mechanical properties. Formation of hydride is associated with transportation of hydrogen along the gradients of increasing hydrostatic stress which leads to crack tips and other stress concentrators where it forms the hydride. In the present study the thermodynamics of the evolving hydrides is studied. The process is driven by the release of free strain chemical and gradient energies. A phase field model is used to capture the driving forces that the release of the free energy causes. The study gives the conditions that lead to hydride advancement versus retreat and under which conditions the metal-hydride interface becomes unstable and develops a waviness. The spatial frequency spectrum leading to instability is found to depend on the ratio of the elastic strain energy density and parameters related to the interface energy.
The Energy Approach to the Evaluation of Hydrogen Effect on the Damage Accumulation
Aug 2019
Publication
The energy approach for determining the durability of structural elements at high temperature creep and hydrogen activity was proposed. It has been shown that the approach significantly simplifies research compared with the known ones. Approbation of the approach was carried out on the example of determining the indicators of durability of the Bridgman sample under conditions of creep and different levels of hydrogenation of the metal. It was shown that with an increase of hydrogen concentration in the metal from 2 to 10 ppm the durability of the test sample decreased from 22 to 58%.
Notch-induced Anisotropic Fracture of Cold Drawn Pearlitic Steels and the Associated Crack Path Deflection and Mixed-mode Stress State: A Tribute to Masaccio
Jul 2018
Publication
This paper deals with notch-induced anisotropic fracture behavior of progressively cold drawn pearlitic steels on the basis of their microstructural evolution during manufacturing by multi-step cold drawing that produces slenderizing and orientation of the pearlitic colonies together with densification and orientation of the Fe/Fe3C lamellae reviewing previous research by the author. Results of fracture test using notched specimens of cold drawn pearlitic steels with different degrees of cold drawing (distinct levels of strain hardening) in air and hydrogen environment shows: (i) the key impact of the colonies and lamellae alignment and orientation on notch-induced fracture producing anisotropic fracture behavior with its related crack path deflection (or fracture path deviation); (ii) the necessity of both stress triaxiality (constraint) and microstructural orientation (colonies/lamellae) alignment to produce fracture path deflection; (iii) hydrogen presence (the circumstance) promotes crack path deviation in addition to the inherent microstructural anisotropy created by cold drawing; (iv) the anisotropic fracture path with a stepped profile in cold drawn pearlitic steel consisting of deflections and deviations from the initial transverse fracture path in mode I resembles Masaccio’s Tribute Money painting with its mountains at the background so that the present paper can be considered as a Tribute to Masaccio.
Catalytic Effect of MoS2 on Hydrogen Storage Thermodynamics and Kinetics of an As-milled YMg11Ni Alloy
Jul 2017
Publication
In this study YMg11Ni and YMg11Ni + 5 wt% MoS2 (named YMg11Ni–MoS2) alloys were prepared by mechanical milling to examine the effect of adding MoS2 on the hydrogen storage performance of a Y–Mg–Ni-based alloy. The as-cast and milled alloys were tested to identify their structures by X-ray diffraction and transmission electron microscopy. The isothermal hydrogen storage thermodynamics and dynamics were identified through an automatic Sieverts apparatus and the non-isothermal dehydrogenation performance was investigated by thermogravimetry and differential scanning calorimetry. The dehydrogenation activation energy was calculated by both Arrhenius and Kissinger methods. Results revealed that adding MoS2produces a very slight effect on hydrogen storage thermodynamics but causes an obvious reduction in the hydrogen sorption and desorption capacities because of the deadweight of MoS2. The addition of MoS2significantly enhances the dehydrogenation performance of the alloy such as lowering dehydrogenation temperature and enhancing dehydrogenation rate. Specifically the initial desorption temperature of the alloy hydride lowers from 549.8 K to 525.8 K. The time required to desorb hydrogen at 3 wt% H2 is 1106 456 363 and 180 s corresponding to hydrogen desorption temperatures at 593 613 633 and 653 K for the YMg11Ni alloy and 507 208 125 and 86 s at identical conditions for the YMg11Ni–5MoS2 alloy. The dehydrogenation activation energy (Ea) values with and without added MoS2are 85.32 and 98.01 kJ mol−1. Thus a decrease in Ea value by 12.69 kJ mol−1 occurs and is responsible for the amelioration of the hydrogen desorption dynamics by adding a MoS2 catalyst.
A Probabilistic Framework for the Techno-economic Assessment of Smart Energy Hubs for Electric Vehicle Charging
Apr 2022
Publication
Smart energy hubs (Smart Hubs) equipped with Vehicle-to-Grid (V2G) charging photovoltaic (PV) energy generation and hydrogen storage capabilities are an emerging technology with potential to alleviate the impact of electric vehicles (EV) on the electricity grid. Their operation however is characterised by intermittent PV energy generation as well as uncertainties in EV traffic and driver preference. These uncertainties when combined with the need to maximise their financial return while guaranteeing driver satisfaction yields a challenging decision-making problem. This paper presents a novel Monte-Carlo-based modelling and computational framework for simulating the operation of Smart Hubs — providing a means for a holistic assessment of their technical and financial viability. The framework utilises a compact and representative mathematical model accounting for power losses PV module degradation variability in EV uptake price inflation driver preference and diversity in charge points and EVs. It provides a comprehensive approach for dealing with uncertainties and dependencies in EV data while being built on an energy management algorithm that maximises revenue generation ensures driver satisfaction and preserves battery life. The energy management problem is formulated as a mixed-integer linear programming problem constituting a business case that includes an adequate V2G reward model for drivers. To demonstrate its applicability the framework was used to assess the financial viability of a fleet management site for various caps on vehicle stay at the site. From the assessment controlled charging was found to be more financially rewarding in all cases yielding between 1.7% and 3.1% more revenue than uncontrolled charging. The self-consumption of the site was found to be nearly 100% due mainly to local load shifting and dispatchable hydrogen generation. V2G injection was however negligible — suggesting its unattractiveness for sites that do not participate in the demand side response market. Overall the numerical results obtained validate the applicability of the proposed framework as a decision-support tool in the sustainable design and operation of Smart Hubs for EV charging.
The Hydrogen Storage Properties of MgH2–Fe7S8 Composites
Nov 2020
Publication
Nanostructured Fe7S8 was successfully synthesized and its catalytic effect on hydrogen absorption/desorption performance of MgH22 is systemically discussed. The MgH2 + 16.7 wt% Fe7S8 composite prepared by ball-milling method offers a striking catalytic activity for hydrogenation kinetics and also reduces the initial decomposition temperature for MgH22. The composite of MgH2–Fe7S8 can absorb 4.000 wt% of hydrogen within 1800 s at 473 K which is about twice that of pristine MgH2 (1.847 wt%) under the same conditions. The onset hydrogen release temperature of Fe7S8-modified MgH2 is 420 K which is 290 K lower than that of additive-free MgH2 (710 K). Meanwhile the doped sample could release 4.403 wt% of hydrogen within 1800 s at 623 K as compared to 2.479 wt% of hydrogen by MgH2. The activation energy for MgH2–Fe7S8 is about 130.0 kJ mol−1 approximately 36 kJ mol−1 lower than that of MgH2. The hydriding process of MgH2 + 16.7 wt% Fe7S8 follows the nucleation and growth mechanism. The prominent hydrogen storage performances are related to the reactions between MgH2 and Fe7S8. The newly formed MgS and Fe in the ball-milling process present a co-catalytic effect on the hydrogen storage performance of MgH22.
Hydrogen Energy
Feb 2007
Publication
The problem of anthropogenically driven climate change and its inextricable link to our global society’s present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century capable of assisting in issues of environmental emissions sustainability and energy security. Hydrogen has the potential to provide for energy in transportation distributed heat and power generation and energy storage systems with little or no impact on the environment both locally and globally. However any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Numerical Simulations of Cryogenic Hydrogen Cooling in Vortex Tubes with Smooth Transitions
Mar 2021
Publication
Improving efficiency of hydrogen cooling in cryogenic conditions is important for the wider applications of hydrogen energy systems. The approach investigated in this study is based on a Ranque-Hilsch vortex tube (RHVT) that generates temperature separation in a working fluid. The simplicity of RHVT is also a valuable characteristic for cryogenic systems. In the present work novel shapes of RHVT are computationally investigated with the goal to raise efficiency of the cooling process. Specifically a smooth transition is arranged between a vortex chamber where compressed gas is injected and the main tube with two exit ports at the tube ends. Flow simulations have been carried out using STAR-CCM+ software with the real-gas Redlich-Kwong model for hydrogen at temperatures near 70 K. It is determined that a vortex tube with a smooth transition of moderate size manifests about 7% improvement of the cooling efficiency when compared vortex tubes that use traditional vortex chambers with stepped transitions and a no-chamber setup with direct gas injection.
The Effects of Electrochemical Hydrogen Charging on Room-Temperature Tensile Properties of T92/TP316H Dissimilar Weldments in Quenched-and-Tempered and Thermally-Aged Conditions
Aug 2019
Publication
The influence of isothermal aging at 620 °C in combination with subsequent electrochemical hydrogen charging at room-temperature was studied on quenched-and-tempered T92/TP316H martensitic/austenitic weldments in terms of their room-temperature tensile properties and fracture behavior. Hydrogen charging of the weldments did not significantly affect their strength properties; however it resulted in considerable deterioration of their plastic properties along with significant impact on their fracture characteristics and failure localization. The hydrogen embrittlement plays a dominant role in degradation of the plastic properties of the weldments already in their initial material state i.e. before thermal aging. After thermal aging and subsequent hydrogen charging mutual superposition of thermal and hydrogen embrittlement phenomena had led to clearly observable effects on the welds deformation and fracture processes. The measure of hydrogen embrittlement was clearly lowered for thermally aged material state since the contribution of thermal embrittlement to overall degradation of the weldments has dominated. The majority of failures of the weldments after hydrogen charging occurred in the vicinity of T92 BM/Ni weld metal (WM) fusion zone; mostly along the Type-II boundary in Ni-based weld metal. Thus regardless of aging exposure the most critical failure regions of the investigated weldments after hydrogen charging and tensile straining at room temperature are the T92 BM/Ni WM fusion boundary and Type-II boundary acting like preferential microstructural sites for hydrogen embrittling effects accumulation
Hydrogen Embrittlement Behavior of 18Ni 300 Maraging Steel Produced by Selective Laser Melting
Jul 2019
Publication
A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density of 1 A m−2 and 50 A m−2 for 48 h at room temperature. Charged and uncharged specimens were subjected to tensile tests and the hydrogen concentration was eventually analysed using quadrupole mass spectroscopy. After tensile tests uncharged maraging samples showed fracture surfaces with dimples. Conversely in H-charged alloys quasi-cleavage mode fractures occurred. A lower concentration of trapped hydrogen atoms and higher elongation at fracture were measured in the H-charged samples that were subjected to solution treatment prior to hydrogen charging compared to the as-built counterparts. Isothermal aging treatment performed at 460 °C for 8 h before hydrogen charging increased the concentration of trapped hydrogen giving rise to higher hydrogen embrittlement susceptibility.
Hydrogen Effect on the Cyclic Behavior of a Superelastic NiTi Archwire
Mar 2019
Publication
In this work we are interested in examining the strain rate effect on the mechanical behavior of Ni–Ti superelastic wires after hydrogen charging and ageing for 24 h. Specimens underwent 50 cycles of loading-unloading reaching an imposed deformation of 7.6%. During loading strain rates from 10−4 s−1 to 10−2 s−1 were achieved. With a strain rate of 10−2 s−1 the specimens were charged by hydrogen for 6 h and aged for one day showed a superelastic behavior marked by an increase in the residual deformation as a function of the number of cycles. In contrast after a few number of cycles with a strain rate of 10−4 s−1 the Ni-Ti alloy archwire specimens fractured in a brittle manner during the martensite transformation stage. The thermal desorption analysis showed that for immersed specimens the desorption peak of hydrogen appeared at 320 °C. However after annealing the charged specimens by hydrogen at 400 °C for 1 h an embrittlement took place at the last cycles for the lower strain rates of 10−4 s−1. The present study suggests that the embrittlement can be due to the development of an internal stress in the subsurface of the parent phase during hydrogen charging and due to the creation of cracks and local zones of plasticity after desorption.
Optimal Operations for Hydrogen-based Energy Storage Systems in Wind Farms via Model Predictive Control
Feb 2021
Publication
Efficient energy production and consumption are fundamental points for reducing carbon emissions that influence climate change. Alternative resources such as renewable energy sources (RESs) used in electricity grids could reduce the environmental impact. Since RESs are inherently unreliable during the last decades the scientific community addressed research efforts to their integration with the main grid by means of properly designed energy storage systems (ESSs). In order to highlight the best performance from these hybrid systems proper design and operations are essential. The purpose of this paper is to present a so-called model predictive controller (MPC) for the optimal operations of grid-connected wind farms with hydrogen-based ESSs and local loads. Such MPC has been designed to take into account the operating and economical costs of the ESS the local load demand and the participation to the electricity market and further it enforces the fulfillment of the physical and the system's dynamics constraints. The dynamics of the hydrogen-based ESS have been modeled by means of the mixed-logic dynamic (MLD) framework in order to capture different behaviors according to the possible operating modes. The purpose is to provide a controller able to cope both with all the main physical and operating constraints of a hydrogen-based storage system including the switching among different modes such as ON OFF STAND-BY and at the same time reduce the management costs and increase the equipment lifesaving. The case study for this paper is a plant under development in the north Norway. Numerical analysis on the related plant data shows the effectiveness of the proposed strategy which manages the plant and commits the equipment so as to preserve the given constraints and save them from unnecessary commutation cycles.
Influence of Microstructural Morphology on Hydrogen Embrittlement in a Medium-Mn Steel Fe-12Mn-3Al-0.05C
Aug 2019
Publication
The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite achieving an extraordinary balance of mechanical properties and alloying cost. In the present work two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve comparable mechanical properties with different microstructural morphologies. One heat treatment was merely austenite-reverted-transformation (ART) annealing and the other one was a successive combination of austenitization (AUS) and ART annealing. The distinct responses to hydrogen ingression were characterized and discussed. The UFG martensite colonies produced by the AUS + ART process were found to be detrimental to ductility regardless of the amount of hydrogen which is likely attributed to the reduced lattice bonding strength according to the H-enhanced decohesion (HEDE) mechanism. With an increase in the hydrogen amount the mixed microstructure (granular + lamellar) in the ART specimen revealed a clear embrittlement transition with the possible contribution of HEDE and H-enhanced localized plasticity (HELP) mechanisms.
Influence of Thermal Treatment on SCC and HE Susceptibility of Supermartensitic Stainless Steel 16Cr5NiMo
Apr 2020
Publication
A 16Cr5NiMo supermartensitic stainless steel was subjected to different tempering treatments and analyzed by means of permeation tests and slow strain rate tests to investigate the effect of different amounts of retained austenite on its hydrogen embrittlement susceptibility. The 16Cr5NiMo steel class is characterized by a very low carbon content. It is the new variant of 13Cr4Ni. These steels are used in many applications for example compressors for sour environments offshore piping naval propellers aircraft components and subsea applications. The typical microstructure is a soft-tempered martensite very close to a body-centered cubic with a retained austenite fraction and limited δ ferrite phase. Supermartensitic stainless steels have high mechanical properties together with good weldability and corrosion resistance. The amount of retained austenite is useful to increase low temperature toughness and stress corrosion cracking resistance. Experimental techniques allowed us to evaluate diffusion coefficients and the mechanical behaviour of metals in stress corrosion cracking (SCC) conditions.
Effect of Hot Mill Scale on Hydrogen Embrittlement of High Strength Steels for Pre-Stressed Concrete Structures
Mar 2018
Publication
The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further electrochemical tests were performed on bars in as received surface conditions in order to evaluate pitting initiation. The adverse effect of mill scale was recognized.
The Effect of Hydrogen on the Nanoindentation Behavior of Heat Treated 718 Alloy
Oct 2020
Publication
In this study the effect of precipitates on the surface mechanical properties in the presence of hydrogen (H) is investigated by in situ electrochemical nanoindentation. The nickel superalloy 718 is subjected to three different heat treatments leading to different sizes of the precipitates: (i) solution annealing (SA) to eliminate all precipitates (ii) the as-received (AR) sample with fine dispersed precipitates and (iii) the over-aged (OA) specimen with coarser precipitates. The nanoindentation is performed using a conical tip and a new method of reverse imaging is employed to calculate the nano-hardness. The results show that the hardness of the SA sample is significantly affected by H diffusion. However it could be recovered by removing the H from its matrix by applying an anodic potential. Since the precipitates in the OA and AR samples are different they are influenced by H differently. The hardness increase for the OA sample is more significant in −1200mV while for the AR specimen the H is more effective in −1500mV. In addition the pop-in load is reduced when the samples are exposed to cathodic charging and it cannot be fully recovered by switching to an anodic potential.
Investigation of Mechanical Tests for Hydrogen Embrittlement in Automotive PHS Steels
Aug 2019
Publication
The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study slow strain rate four-point bending and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake in the case of automotive components can take place in many phases of the manufacturing process: during hot stamping due to the presence of moisture in the furnace atmosphere high-temperature dissociation giving rise to atomic hydrogen or also during electrochemical treatments such as cataphoresis. Moreover possible corrosive phenomena could be a source of hydrogen during an automobile’s life. This series of tests was performed here in order to characterize two press-hardened steels (PHS)—USIBOR 1500® and USIBOR 2000®—to establish a correlation between ultimate mechanical properties and critical hydrogen concentration.
Research of Nanomaterials as Electrodes for Electrochemical Energy Storage
Jan 2022
Publication
This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes a powerful exothermic reaction of atomic hydrogen recombination with a large energy release occurs. This exothermic reaction is the cause of thermal runaway in alkaline batteries. For the KSL-15 battery the gravimetric capacity of sintered nickel matrix of the oxide-nickel electrode as hydrogen storage is 20.2 wt% and cadmium electrode is 11.5 wt%. The stored energy density in the metal-ceramic matrix of the oxide-nickel electrode of the battery KSL-15 is 44 kJ/g and in the cadmium electrode it is 25 kJ/g. The similar values for the KPL-14 battery are as follows. The gravimetric capacity of the active substance of the pocket oxide-nickel electrode as a hydrogen storage is 22 wt% and the cadmium electrode is 16.9 wt%. The density of the stored energy in the active substance oxide-nickel electrode is 48 kJ/g and in the active substance of the cadmium electrode it is 36.8 kJ/g. The obtained results of the accumulation of hydrogen energy in the electrodes by the electrochemical method are three times higher than any previously obtained results using the traditional thermochemical method.
Linking Ab Initio Data on Hydrogen and Carbon in Steel to Statistical and Continuum Descriptions
Mar 2018
Publication
We present a selection of scale transfer approaches from the electronic to the continuum regime for topics relevant to hydrogen embrittlement. With a focus on grain boundary related hydrogen embrittlement we discuss the scale transfer for the dependence of the carbon solution behavior in steel on elastic effects and the hydrogen solution in austenitic bulk regions depending on Al content. We introduce an approximative scheme to estimate grain boundary energies for varying carbon and hydrogen population. We employ this approach for a discussion of the suppressing influence of Al on the substitution of carbon with hydrogen at grain boundaries which is an assumed mechanism for grain boundary hydrogen embrittlement. Finally we discuss the dependence of hydride formation on the grain boundary stiffness
Hydrogen Effects in Non-ferrous Alloys: Discussion
Jun 2017
Publication
This is a transcript of the discussion session on the effects of hydrogen in the non-ferrous alloys of zirconium and titanium which are anisotropic hydride-forming metals. The four talks focus on the hydrogen embrittlement mechanisms that affect zirconium and titanium components which are respectively used in the nuclear and aerospace industries. Two specific mechanisms are delayed hydride cracking and stress corrosion cracking.
This article is a transcription of the recorded discussion of the session ‘Hydrogen in non-ferrous alloys’ at the Royal Society Discussion Meeting Challenges of Hydrogen in Metals 16–18 January 2017. The text is approved by the contributors. M.P. transcribed the session. M.A.S. 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 the session ‘Hydrogen in non-ferrous alloys’ at the Royal Society Discussion Meeting Challenges of Hydrogen in Metals 16–18 January 2017. The text is approved by the contributors. M.P. transcribed the session. M.A.S. assisted in the preparation of the manuscript.
Link to document download on Royal Society Website
Hydrogen Diffusion Mechanism around a Crack Tip in Type 304L Austenite Stainless Steel Considering the Influence of the Volume Expansion of Strain-Induced Martensite Transformation
Sep 2019
Publication
Strain-induced martensite transformation (SIMT) commonly exists around a crack tip of metastable austenite stainless steels. The influence of the volume expansion of the SIMT on the hydrogen diffusion was investigated by hydrogen diffusion modelling around a crack tip in type 304L austenite stainless steel. The volume expansion changed the tensile stress state into pressure stress state at the crack tip resulting in a large stress gradient along the crack propagation direction. Compared to the analysis without considering the volume expansion effect this volume expansion further accelerated the hydrogen transport from the inner surface to a critical region ahead of the crack tip and further increased the maximum value of the hydrogen concentration at the critical position where the strain-induced martensite fraction approximates to 0.1 indicating that the volume expansion of the SIMT further increased the hydrogen embrittlement susceptibility.
Experimental Investigation of the Effect of Hydrogen on Fracture Toughness of 2.25Cr-1Mo-0.25V Steel and Welds after Annealing
Mar 2018
Publication
Hydrogen embrittlement (HE) is a critical issue that hinders the reliability of hydrogenation reactors. Hence it is of great significance to investigate the effect of hydrogen on fracture toughness of 2.25Cr-1Mo-0.25V steel and weld. In this work the fracture behavior of 2.25Cr-1Mo-0.25V steel and welds was studied by three-point bending tests under hydrogen-free and hydrogen-charged conditions. The immersion charging method was employed to pre-charge hydrogen inside specimen and the fracture toughness of these joints was evaluated quantitatively. The microstructure and grain size of the specimens were observed by scanning electron microscopy (SEM) and by metallurgical microscopy to investigate the HE mechanisms. It was found that fracture toughness for both the base metal (BM) and the weld zone (WZ) significantly decreased under hydrogen-charged conditions due to the coexistence of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms. Moreover the formation and growth of primary voids were observed in the BM leading to a superior fracture toughness. In addition the BM compared to the WZ shows superior resistance to HE because the finer grain size in the BM leads to a larger grain boundary area thus distributing more of the diffusive hydrogen trapped in the grain boundary and reducing the hydrogen content.
Large-scale Compressed Hydrogen Storage as Part of Renewable Electricity Storage Systems
Mar 2021
Publication
Storing energy in the form of hydrogen is a promising green alternative. Thus there is a high interest to analyze the status quo of the different storage options. This paper focuses on the large-scale compressed hydrogen storage options with respect to three categories: storage vessels geological storage and other underground storage alternatives. In this study we investigated a wide variety of compressed hydrogen storage technologies discussing in fair detail their theory of operation potential and challenges. The analysis confirms that a techno-economic chain analysis is required to evaluate the viability of one storage option over another for a case by case. Some of the discussed technologies are immature; however this does not rule out these technologies; rather it portrays the research opportunities in the field and the foreseen potential of these technologies. Furthermore we see that hydrogen would have a significant role in balancing intermittent renewable electricity production.
A Panoramic Analysis of Hydrogen Utilization Systems Using an Input-output Table for Next Generation Energy Systems
Apr 2017
Publication
The objective of this study is to analyze a government proposal from a panoramic perspective concerning the economic and environmental effects associated with the construction and operation of hydrogen utilization systems by the year 2030. We focused on a marine transport system for hydrogen produced offshore hydrogen gas turbine power generation fuel cell vehicles (FCVs) and hydrogen stations as well as residential fuel cell systems (RFCs). In this study using an Input-Output Table for Next Generation Energy Systems (IONGES) we evaluated the induced output labor and CO2 emissions from the construction and operation of these hydrogen technologies using a uniform approach. This may be helpful when considering future designs for the Japanese energy system. In terms of per 1 t-H2 of hydrogen use CO2 reductions from the use of FCVs are considerably higher than the additional CO2 emissions from foreign production and transportation of hydrogen. Because new construction of a hydrogen pipeline network is not considered to be realistic RFCs is assumed to consume hydrogen generated by refining town gas. In this case the CO2 reductions from using RFCs will decline under the electricity composition estimated for 2030 on the condition of a substantial expansion of electricity generation from renewable energy sources. However under the present composition of electricity production we can expect a certain amount of CO2 reductions from using RFCs. If hydrogen is directly supplied to RFCs CO2 reductions increase substantially. Thus we can reduce a significant amount of CO2 emissions if various unused energy sources dispersed around local areas or unharnessed renewable energies such as solar and wind power can be converted into hydrogen to be supplied to FCVs and RFCs.
Impact of Depth on Underground Hydrogen Storage Operations in Deep Aquifers
Mar 2024
Publication
Underground hydrogen storage in geological structures is considered appropriate for storing large amounts of hydrogen. Using the geological Konary structure in the deep saline aquifers an analysis of the influence of depth on hydrogen storage was carried out. Hydrogen injection and withdrawal modeling was performed using TOUGH2 software assuming different structure depths. Changes in the relevant parameters for the operation of an underground hydrogen storage facility including the amount of H2 injected in the initial filling period cushion gas working gas and average amount of extracted water are presented. The results showed that increasing the depth to approximately 1500 m positively affects hydrogen storage (flow rate of injected hydrogen total capacity and working gas). Below this depth the trend was reversed. The cushion gas-to-working gas ratio did not significantly change with increasing depth. Its magnitude depends on the length of the initial hydrogen filling period. An increase in the depth of hydrogen storage is associated with a greater amount of extracted water. Increasing the duration of the initial hydrogen filling period will reduce the water production but increase the cushion gas volume.
Location-dependent Effect of Nickel on Hydrogen Dissociation and Diffusion on Mg (0001) Surface: Insights into Hydrogen Storage Material Design
Apr 2021
Publication
Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.
HyUnder – Hydrogen Underground Storage at Large Scale: Case Study Spain
Aug 2015
Publication
Hydrogen as an energy carrier is understood as a system capable of storing energy for a later use in a controlled manner. Surplus electricity from renewable energy serves for green hydrogen generation via electrolysis. Once produced the hydrogen is stored for later consumption. This paper describes the Spanish Case Study of the HyUnder project which aims to evaluate the potential of underground hydrogen storage for large-scale energy storage along Europe analysing besides the Spanish Case France Germany the Netherlands Romania and the United Kingdom. This case study has considered for the assessment the competitiveness of hydrogen storage against other large scale energy storage concepts the geological potential for hydrogen storage in the region how to embed the hydrogen energy storage in the energy market and the possible business cases in four different applications: transport Power to Gas re-electrification and industry taking into account all the economic aspects such us the electrolyser OPEX and CAPEX or the cavern electricity and water costs. It is shown that the Spanish geology can provide four technical options for hydrogen underground storage. Results have shown the interest of the technology in short – medium term especially linked to certain conditions of high intermittent renewable energy penetration in the Spanish power grid that result in surplus or residual electricity. Hydrogen storage is interesting because it can integrate renewable energy systems in other sectors which do not have overcapacity and a high use of fossil fuels as the natural gas sector and the transport sector. Moreover all the economic issues have been analysed for two different horizons 2025 and 2050; concluding that the average price of electricity is the main cost. From the financial results transport application represents a business case which although in order has enough values of hydrogen demand to be stored combination of different applications must be needed in order to make sense to the development of the cavern.
Hydrogen Storage in Pure and Boron-Substituted Nanoporous Carbons—Numerical and Experimental Perspective
Aug 2021
Publication
Nanoporous carbons remain the most promising candidates for effective hydrogen storage by physisorption in currently foreseen hydrogen-based scenarios of the world’s energy future. An optimal sorbent meeting the current technological requirement has not been developed yet. Here we first review the storage limitations of currently available nanoporous carbons then we discuss possible ways to improve their storage performance. We focus on two fundamental parameters determining the storage (the surface accessible for adsorption and hydrogen adsorption energy). We define numerically the values nanoporous carbons have to show to satisfy mobile application requirements at pressures lower than 120 bar. Possible necessary modifications of the topology and chemical compositions of carbon nanostructures are proposed and discussed. We indicate that pore wall fragmentation (nano-size graphene scaffolds) is a partial solution only and chemical modifications of the carbon pore walls are required. The positive effects (and their limits) of the carbon substitutions by B and Be atoms are described. The experimental ‘proof of concept’ of the proposed strategies is also presented. We show that boron substituted nanoporous carbons prepared by a simple arc-discharge technique show a hydrogen adsorption energy twice as high as their pure carbon analogs. These preliminary results justify the continuation of the joint experimental and numerical research effort in this field.
Graphene Oxide/metal Nanocrystal Multilaminates as the Atomic Limit for Safe and Selective Hydrogen Storage
Mar 2016
Publication
Interest in hydrogen fuel is growing for automotive applications; however safe dense solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material protected from oxygen and moisture by the rGO layers exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin this approach minimizes inactive mass in the composite while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.
Tetrahydroborates: Development and Potential as Hydrogen Storage Medium
Oct 2017
Publication
The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative hydrogen is widely regarded as a key element for a potential energy solution. However differently from fossil fuels such as oil gas and coal the production of hydrogen requires energy. Alternative and intermittent renewable energy sources such as solar power wind power etc. present multiple advantages for the production of hydrogen. On the one hand the renewable sources contribute to a remarkable reduction of pollutants released to the air and on the other hand they significantly enhance the sustainability of energy supply. In addition the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of renewable energy sources. In this regard hydrogen storage technology is a key technology towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen solid-state storage is the most attractive alternative from both the safety and the volumetric energy density points of view. Because of their appealing hydrogen content complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review the progresses made over the last century on the synthesis and development of tetrahydroborates and tetrahydroborate-based systems for hydrogen storage purposes are summarized.
Evaluation of Hydrogen-induced Cracking in High-strength Steel Welded Joints by Acoustic Emission Technique
Feb 2020
Publication
Hydrogen-induced cracking behavior in high-strength steel mainly composed of martensite was analyzed by acoustic emission (AE) technique and finite element method (FEM) in slow strain-rate tensile (SSRT) tests and welding tests. The crack initiation was detected by the AE signals and the time evolution of stress concentration and hydrogen diffusion were calculated by FEM. The effect of hardness and plastic strain on the hydrogen diffusion coefficientwas explicitly introduced into the governing equation in FEM. The criterion and indicator parameter for the crack initiation were derived as a function of maximum principal stress and locally accumulated hydrogen concentration. The results showed that the cracking criterion derived by AE and FEM is useful for predicting the cold cracking behavior and determining the critical preheat temperature to prevent hydrogeninduced cracking.
Effect of the Strain Rate on the Fracture Behaviour of High Pressure Pre-Charged Samples
Dec 2018
Publication
The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then fracture tests of the pre-charged specimens were performed using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.
Molecular Dynamics Studies of Hydrogen Effect on Intergranular Fracture in α-Iron
Nov 2020
Publication
In the current study the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure and a theoretical model is then developed to predict the intergranular cracking rate
The Use of Metal Hydrides in Fuel Cell Applications
Feb 2017
Publication
This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.
Hydrogen Storage: Thermodynamic Analysis of Alkyl-Quinolines and Alkyl-Pyridines as Potential Liquid Organic Hydrogen Carriers (LOHC)
Dec 2021
Publication
The liquid organic hydrogen carriers (LOHC) are aromatic molecules which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum coal processing and wood preservation or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems provided they have favorable thermodynamic properties which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected evaluated and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines calculated using the quantum-chemical G4 methods agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.
Energy Storage as Part of a Secure Energy Supply
Mar 2017
Publication
Florian Ausfelder,
Christian Beilmann,
Martin Bertau,
Sigmar Bräuninger,
Angelika Heinzel,
Renate Hoer,
Wolfram Koch,
Falko Mahlendorf,
Anja Metzelthin,
Marcell Peuckert,
Ludolf Plass,
Konstantin Räuchle,
Martin Reuter,
Georg Schaub,
Sebastian Schiebahn,
Ekkehard Schwab,
Ferdi Schüth,
Detlef Stolten,
Gisa Teßmer,
Kurt Wagemann and
Karl-Friedrich Ziegahn
The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However it affects all areas of the energy system albeit with different results. Within the energy system various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers and the demand-oriented supply ensures that energy demands are met at all times. However renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly.<br/>Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy store it in a storage medium for a suitable period of time and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations.<br/>These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage various technologies are currently in various stages of research development and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat exploitation of phase transitions adsorption/desorption processes and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus they are in direct economic competition with established (fossil fuel) supply routes. The key technology here – now and for the foreseeable future – is the electrolysis of water to produce hydrogen and oxygen.<br/>Hydrogen can be transformed by various processes into other energy carriers which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector it also creates new opportunities for increased flexibility novel synergies and additional optimization.<br/>Several examples of specific energy utilization are discussed and evaluated with respect to energy storage applications. The article describes various technologies for energy storage and their potential applications in the context of Germany’s Energiewende i.e. the transition towards a more sustainable energy system. Therefore the existing legal framework defines some of the discussions and findings within the article specifically the compensation for renewable electricity providers defined by the German Renewable Energy Sources Act which is under constant reformation. While the article is written from a German perspective the authors hope this article will be of general interest for anyone working in the areas of energy systems or energy technology.
Application of DFT Simulation to the Investigation of Hydrogen Embrittlement Mechanism and Design of High Strength Low Alloy Steel
Dec 2022
Publication
In this work first-principles methods were performed to simulate interactions between hydrogen and common alloying elements of high strength low alloy (HSLA) steel. The world has been convinced that hydrogen could be one of the future clean energy sources. HSLA steel with a balance of strength toughness and hydrogen embrittlement susceptibility is expected for application in large-scale hydrogen storage and transportation. To evaluate the property deterioration under a hydrogen atmosphere hydrogen embrittlement (HE) of HSLA steel attracts attention. However due to the small size of hydrogen atoms the mechanism of HE is challenging to observe directly by current experimental methods. To understand the HE mechanism at an atomic level DFT methods were applied to simulate the effects of alloying elements doping in bcc-Fe bulk structure and grain boundary structure. Furthermore the potential application of DFT to provide theoretical advice for HSLA steel design is discussed.
Heat Transfer Analysis for Fast Filling of On-board Hydrogen Tank
Mar 2019
Publication
The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature hydrogen pressure tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.
Injecting Hydrogen into the Gas Network- A Literature Search
Jan 2015
Publication
Hydrogen injection into the GB gas network is a likely consequence of using excess offshore wind generated electricity to power large-scale onshore electrolysis plants. Government and DECC in particular now have a keen interest in supporting technologies that can take advantage of the continued use of the gas networks. HSE can contribute to the government’s Growth and Green agendas by effectively regulating and safely enabling this technology.
This report will allow HSE to regulate effectively by pulling together scientific and engineering knowledge regarding the hazards of conveying hydrogen/methane mixtures in network pipes and its use in consumer appliances into a single ‘state-of-play’ report. It enables Energy Division to consider and assess submissions for ‘gas quality’ exemptions to the Gas Safety (Management) Regulations 1996 (GSMR).
In particular the report has examined the following hazards:
This report will allow HSE to regulate effectively by pulling together scientific and engineering knowledge regarding the hazards of conveying hydrogen/methane mixtures in network pipes and its use in consumer appliances into a single ‘state-of-play’ report. It enables Energy Division to consider and assess submissions for ‘gas quality’ exemptions to the Gas Safety (Management) Regulations 1996 (GSMR).
In particular the report has examined the following hazards:
- conveyance of H2/CH4 mixtures in network pipes
- use of H2/CH4 mixtures in consumer appliances (domestic/commercial/industrial)
- explosion and damage characteristics (and ignition likelihood) of H2/CH4 mixtures
- effects on odourisation
Hydrogen Storage Performance of the Multi-principal-component CoFeMnTiVZr Alloy in Electrochemical and Gas–solid Reactions
Jun 2020
Publication
The single-phase multi-principal-component CoFeMnTiVZr alloy was obtained by rapid solidification and examined by a combination of electrochemical methods and gas–solid reactions. X-ray diffraction and high-resolution transmission electron microscopy analyses reveal a hexagonal Laves-phase structure (type C14). Cyclic voltammetry and electrochemical impedance spectroscopy investigations in the hydrogen absorption/desorption region give insight into the absorption/desorption kinetics and the change in the desorption charge in terms of the applied potential. The thickness of the hydrogen absorption layer obtained by the electrochemical reaction is estimated by high-resolution transmission electron microscopy. The electrochemical hydrogen storage capacity for a given applied voltage is calculated from a series of chronoamperometry and cyclic voltammetry measurements. The selected alloy exhibits good stability for reversible hydrogen absorption and demonstrates a maximum hydrogen capacity of ∼1.9 wt% at room temperature. The amount of hydrogen absorbed in the gas–solid reaction reaches 1.7 wt% at 298 K and 5 MPa evidencing a good correlation with the electrochemical results.
A Study on the Influential Factors of Stress Corrosion Cracking in C110 Casing Pipe
Jan 2022
Publication
In this paper we analyze the potential factors affecting the hydrogen sulfide type of stress corrosion cracking in C110 casing pipes. In order to further study these cracking factors the methods of material property testing scanning electron microscopy XRD TEM and 3D ultra-depth-of-field were applied in the experiments. Besides that an HTHP autoclave was independently designed by the laboratory to simulate the actual corrosion environment and the potential factors affecting the stress corrosion cracking of C110 casing pipes were determined. The test results showed that the chemical composition metallographic structure hardness and non-metallic inclusions of the two types of C110 casing pipes were all qualified. In fact there remains a risk of stress corrosion cracking when the two kinds of C110 casing pipes serve under long-term field-working conditions. It is considered in this paper that the precipitates on the material surface stress damage and pitting corrosion are all critical factors affecting the stress corrosion cracking of casing pipes.
Understanding Composition–property Relationships in Ti–Cr–V–Mo Alloys for Optimisation of Hydrogen Storage in Pressurised Tanks
Jun 2014
Publication
The location of hydrogen within Ti–Cr–V–Mo alloys has been investigated during hydrogen absorption and desorption using in situ neutron powder diffraction and inelastic neutron scattering. Neutron powder diffraction identifies a low hydrogen equilibration pressure body-centred tetragonal phase that undergoes a martensitic phase transition to a face-centred cubic phase at high hydrogen equilibration pressures. The average location of the hydrogen in each phase has been identified from the neutron powder diffraction data although inelastic neutron scattering combined with density functional theory calculations show that the local structure is more complex than it appears from the average structure. Furthermore the origin of the change in dissociation pressure and hydrogen trapping on cycling in Ti–Cr–V–Mo alloys is discussed.
Hydrogen Concentration Distribution in 2.25Cr-1Mo-0.25V Steel under the Electrochemical Hydrogen Charging and Its Influence on the Mechanical Properties
May 2020
Publication
The deterioration of the mechanical properties of metal induced by hydrogen absorption threatens the safety of the equipment serviced in hydrogen environments. In this study the hydrogen concentration distribution in 2.25Cr-1Mo-0.25V steel after hydrogen charging was analyzed following the hydrogen permeation and diffusion model. The diffusible hydrogen content in the 1-mm-thick specimen and its influence on the mechanical properties of the material were investigated by glycerol gas collecting test static hydrogen charging tensile test scanning electron microscopy (SEM) test and microhardness test. The results indicate that the content of diffusible hydrogen tends to be the saturation state when the hydrogen charging time reaches 48 h. The simulation results suggest that the hydrogen concentration distribution can be effectively simulated by ABAQUS and the method can be used to analyze the hydrogen concentration in the material with complex structures or containing multiple microstructures. The influence of hydrogen on the mechanical properties is that the elongation of this material is reduced and the diffusible hydrogen will cause a decrease in the fracture toughness of the material and thus hydrogen embrittlement (HE) will occur. Moreover the Young’s modulus E and microhardness are increased due to hydrogen absorption and the variation value is related to the hydrogen concentration introduced into the specimen.
Laboratory Method for Simulating Hydrogen Assisted Degradation of Gas Pipeline Steels
Aug 2019
Publication
Integrity of natural gas transmission systems is of great importance for energy and environmental security. Deterioration occurs in gas transit pipelines due to operational conditions and action of corrosion and hydrogenating media and leads to changes in microstructure and mechanical properties of pipeline steels which influences on pipeline performance. Hydrogenation of metal during corrosion process together with working stresses facilitates a development of in-bulk damaging at nano- and microscales. Reducing brittle fracture resistance of pipeline steels under operation increases significantly a failure risk of gas pipelines associated with in-bulk material degradation. Therefore hydrogen assisted degradation of pipelines steels under operation calls for effective methods for in-laboratory accelerated degradation. The present study is devoted to the development of the procedure of laboratory simulation of in-service degradation of pipeline steels. The role of hydrogen in degradation of pipeline steels was analysed. The procedure of accelerated degradation of pipeline steels under the combined action of axial loading and hydrogen charging was developed and induced in the laboratory. The procedure was consisted in consistently subjecting of specimens to electrolytic hydrogen charging to an axial loading up and to an artificial aging. Pipeline steels in the different states (as-received post-operated aged and after in-laboratory degradation) were investigated. The tensile mechanical behaviour of steels and impact toughness were experimentally studied. It was definitely concluded that the applied procedure caused the changes in the metal mechanical properties at the same level compared to the properties degradation due to operation. The developed procedure enables on a laboratory scale simulating of pipeline steel degradation during long-term operation under simultaneous action of hydrogenation and working loading and it makes possible to predict the mechanical behaviour of pipeline steels during service.
Open-cathode PEMFC Heat Utilisation to Enhance Hydrogen Supply Rate of Metal Hydride Canisters
Mar 2019
Publication
In this paper the hydrogen supply to an open-cathode PEM fuel cell (FC) by using metal hydride (MH) storage and thermal coupling between these two components are investigated theoretically. One of the challenges in using MH hydrogen storage canisters is their limited hydrogen supply rate as the hydrogen release from MH is an endothermic reaction. Therefore in order to meet the required hydrogen supply rate high amounts of MH should be employed that usually suggests storage of hydrogen to be higher than necessary for the application adding to the size weight and cost of the system. On the other hand the exhaust heat (i.e. that is usually wasted if not utilised for this purpose) from open-cathode FCs is a low-grade heat. However this heat can be transferred to MH canisters through convection to heat them up and increase their hydrogen release rate. A mathematical model is used to simulate the heat transfer between PEMFC exhaust heat and MH storage. This enables the prediction of the required MH for different FC power levels with and without heat supply to the MH storage. A 2.5-kW open-cathode FC is used to measure the exhaust air temperature at different output powers. It was found that in the absence of heat supply from the FC to the MH canisters significantly higher number of MH canisters are required to achieve the required rate of hydrogen supply to the FC for sustained operation (specially at high power outputs). However using the exhaust hot air from the FC to supply heat to the MH storage can reduce the number of the MH canisters required by around 40% to 70% for power output levels ranging from 500 W to 2000 W.
A Review on Underground Hydrogen Storage: Insight into Geological Sites, Influencing Factors and Future Outlook
Dec 2021
Publication
Without remorse fossil fuels have made a huge contribution to global development in all of its forms. However the recent scientific outlooks are currently shifting as more research is targeted towards promoting a carbon-free economy in addition to the use of electric power from renewable sources. While renewable energy sources may be a solution to the anthropogenic greenhouse gas (GHG) emissions from fossil fuel they are yet season-dependent faced with major atmospheric drawbacks which when combined with annually varying but steady energy demand results in renewable energy excesses or deficits. Therefore it is essential to devise a long-term storage medium to balance their intermittent demand and supply. Hydrogen (H2) as an energy vector has been suggested as a viable method of achieving the objectives of meeting the increasing global energy demand. However successful implementation of a full-scale H2 economy requires large-scale H2 storage (as H2 is highly compressible). As such storage of H2 in geological formations has been considered as a potential solution where it can be withdrawn again at the larger stage for utilization. Thus in this review we focus on the potential use of geological formations for large-scale underground hydrogen storage (UHS) where both conventional and non-conventional UHS options were examined in depth. Also insights into some of the probable sites and the related examined criteria for selection were highlighted. The hydrodynamics of UHS influencing factors (including solid fluid and solid–fluid interactions) are summarized exclusively. In addition the economics and reaction perspectives inherent to UHS have been examined. The findings of this study show that UHS like other storage systems is still in its infancy. Further research and development are needed to address the significant hurdles and research gaps found particularly in replaceable influencing parameters. As a result this study is a valuable resource for UHS researchers.
Hydrogen Deblending in the GB Network - Feasibility Study Report
Nov 2020
Publication
The UK government has committed to reducing greenhouse gas emissions to net zero by 2050. All future energy modelling identifies a key role for hydrogen (linked to CCUS) in providing decarbonised energy for heat transport industry and power generation. Blending hydrogen into the existing natural gas pipeline network has already been proposed as a means of transporting low carbon energy. However the expectation is that a gas blend with maximum hydrogen content of 20 mol% can be used without impacting consumers’ end use applications. Therefore a transitional solution is needed to achieve a 100% hydrogen future network.
Deblending (i.e. separation of the blended gas stream) is a potential solution to allow the existing gas transmission and distribution network infrastructure to transport energy as a blended gas stream. Deblending can provide either hydrogen natural gas or blended gas for space heating transport industry and power generation applications. If proven technically and economically feasible utilising the existing gas transmission and distribution networks in this manner could avoid the need for investment in separate gas and hydrogen pipeline networks during the transition to a future fully decarbonised gas network.
The Energy Network Association (ENA) “Gas Goes Green” programme identifies deblending could play a critical role in the transition to a decarbonised gas network. Gas separation technologies are well-established and mature and have been used and proven in natural gas processing for decades. However these technologies have not been used for bulk gas transportation in a transmission and distribution network setting. Some emerging hydrogen separation technologies are currently under development. The main hydrogen recovery and purification technologies currently deployed globally are:
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.
Deblending (i.e. separation of the blended gas stream) is a potential solution to allow the existing gas transmission and distribution network infrastructure to transport energy as a blended gas stream. Deblending can provide either hydrogen natural gas or blended gas for space heating transport industry and power generation applications. If proven technically and economically feasible utilising the existing gas transmission and distribution networks in this manner could avoid the need for investment in separate gas and hydrogen pipeline networks during the transition to a future fully decarbonised gas network.
The Energy Network Association (ENA) “Gas Goes Green” programme identifies deblending could play a critical role in the transition to a decarbonised gas network. Gas separation technologies are well-established and mature and have been used and proven in natural gas processing for decades. However these technologies have not been used for bulk gas transportation in a transmission and distribution network setting. Some emerging hydrogen separation technologies are currently under development. The main hydrogen recovery and purification technologies currently deployed globally are:
- Cryogenic separation
- Membrane separation
- Pressure Swing Adsorption (PSA)
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.
Mn-based Borohydride Synthesized by Ball-milling KBH4 and MnCl2 for Hydrogen Storage
Dec 2013
Publication
In this work a mixed-cation borohydride (K2Mn(BH4)4) with P21/n structure was successfully synthesized by mechanochemical milling of the 2KBH4–MnCl2 sample under argon. The structural and thermal decomposition properties of the borohydride compounds were investigated using XRD Raman spectroscopy FTIR TGA-MS and DSC. Apart from K2Mn(BH4)4 the KMnCl3 and unreacted KBH4 compounds were present in the milled 2KBH4–MnCl2. The two mass loss regions were observed for the milled sample: one was from 100 to 160 °C with a 1.6 ± 0.1 wt% loss (a release of majority hydrogen and trace diborane) which was associated with the decomposition of K2Mn(BH4)4 to form KBH4 boron and finely dispersed manganese; the other was from 165 to 260 °C with a 1.9 ± 0.1 wt% loss (only hydrogen release) which was due to the reaction of KBH4 with KMnCl3 to give KCl boron finely dispersed manganese. Simultaneously the formed KCl could dissolve in KBH4 to yield a K(BH4)xCl1−x solid solution and also react with KMnCl3 to form a new compound K4MnCl6.
Isotopic Tracing of Hydrogen Transport and Trapping in Nuclear Materials
Jun 2017
Publication
Some illustrations of the use of deuterium or tritium for isotopic tracing of hydrogen absorption transport and trapping in nuclear materials are presented. Isotopic tracing of hydrogen has been shown to be successful for the determination of the boundaries conditions for hydrogen desorption or absorption in a material exposed to a hydrogen source. Also the unique capabilities of isotopic tracing and related techniques to characterize H interactions with point defects and dislocations acting as moving traps has been demonstrated. Such transport mechanisms are considered to play a major role in some stress corrosion cracking and hydrogen embrittlement mechanisms.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Numerical Solution for Thermodynamic Model of Charge-discharge Cycle in Compressed Hydrogen Tank
Mar 2019
Publication
The safety and convenience of hydrogen storage are significant for fuel cell vehicles. Based on mass conservation equation and energy conservation equation two thermodynamic models (single zone model and dual zone model) have been established to study the hydrogen gas temperature and tank wall temperature for compressed hydrogen storage tank. With two models analytical solution and Euler solution for single zone (gas zone) charge-discharge cycle have been compared Matlab/Simulink solution and Euler solution for dual zone (gas zone wall zone) charge-discharge cycle have been compared. Three charge-discharge cycle cases (Case 1 constant inflow temperature; Case 2 variable inflow temperature; Case 3 constant inflow temperature variable outflow temperature) and two compressed hydrogen tanks (Type III 25L Type IV 99L) charge-discharge cycle are studied by Euler method. Results show Euler method can well predict hydrogen temperature and tank wall temperature.
Comparison of Liquid Hydrogen, Methylcyclohexane and Ammonia on Energy Efficiency and Economy
Mar 2019
Publication
Among several candidates of hydrogen storage liquid hydrogen methylcyclohexane (MCH) and ammonia are considered as potential hydrogen carriers in terms of their characteristics application feasibility and economic performance. In addition as a main motor in the hydrogen introduction Japan has focused and summarized the storage methods for hydrogen into these three methods. Each of them has advantages and disadvantages compared to each other. This study focuses on the effort to analyze and clarify the potential of these three hydrogen storages especially in terms of physical characteristics energy efficiency and economic cost. Liquid hydrogen faces challenges in huge energy consumption during liquefaction and boil-off during storage. MCH has main obstacles in largely required energy in dehydrogenation. Lastly ammonia encounters high energy demand in both synthesis and decomposition (if required). In terms of energy efficiency ammonia is predicted to have the highest total energy efficiency (34–37%) followed by liquid hydrogen (30–33%) and MCH (about 25%). In addition from cost calculation ammonia with direct utilization (without decomposition) is considered to have the highest feasibility for being massively adopted as it shows the lowest cost (20–22 JPY/Nm3-H2 in 2050). However in case that highly pure hydrogen (such as for fuel cell) is demanded liquid hydrogen looks to be promising (24–25 JPY/Nm3-H2 in 2050) compared to MCH and ammonia with decomposition and purification.
Formation and Dissociation Behaviour Studies of Hydrogen Hydrate in the Presence of Tetrahydrofuran by using High Pressure DSC
Mar 2019
Publication
Significant challenges still remain in the development of suitable materials for storing hydrogen for practical applications. Clathrate hydrates as a special inclusion compounds could be tailored by changing the storage pressure and temperature to adapt ambient conditions. In this work the hydrates were adopted to encage hydrogen in tetrahydrofuran (THF) aqueous solution with concentration of 3.0 mol%. The formation and dissociation behaviours were investigated by a high pressure micro-differential scanning calorimeter at the operating pressure of 18 MPa 25 MPa and 34 MPa. Experimental results show that the memory water only affects the hydrate formation behaviour instead of the hydrate dissociation behaviour. The dissociation temperature of the THF-H2 hydrate increases with the increase of the operating pressure and its dissociation equilibrium data can be obtained. The dissociation temperatures of the THF-H2 hydrate are 9.26 ℃ 10.94 ℃ and 12.67 ℃ at the operating pressure of 18 MPa 25 MPa and 34 MPa respectively. It is fundamental for performing the kinetics and microscopic experiments.
The Effect of Electrolytic Hydrogenation on Mechanical Properties of T92 Steel Weldments under Different PWHT Conditions
Aug 2020
Publication
In the present work the effects of electrolytic hydrogen charging of T92 steel weldments on their room-temperature tensile properties were investigated. Two circumferential weldments between the T92 grade tubes were produced by gas tungsten arc welding using the matching Thermanit MTS 616 filler material. The produced weldments were individually subjected to considerably differing post-welding heat treatment (PWHT) procedures. The first-produced weldment was conventionally tempered (i.e. short-term annealed below the Ac1 critical transformation temperature of the T92 steel) whereas the second one was subjected to its full renormalization (i.e. appropriate reaustenitization well above the T92 steel Ac3 critical transformation temperature and subsequent air cooling) followed by its conventional subcritical tempering. From both weldments cylindrical tensile specimens of cross-weld configuration were machined. The room-temperature tensile tests were performed for the individual welds’ PWHT states in both hydrogen-free and electrolytically hydrogen-charged conditions. The results indicated higher hydrogen embrittlement susceptibility for the renormalized-and-tempered weldments compared to the conventionally tempered ones. The obtained findings were correlated with performed microstructural and fractographic observations.
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