Transmission, Distribution & Storage
Rechargeable Proton Exchange Membrane Fuel Cell Containing an Intrinsic Hydrogen Storage Polymer
Oct 2020
Publication
Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential transportation and portable applications. Currently a high-pressure tank is the state-of-the-art mode of hydrogen storage; however the energy cost safety and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP) which is a solid-state organic hydride as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylenebased PEM) enhances the operable time reaching up to ca. 10.2 s mgHSP −1 which is more than a factor of two longer than that (3.90 s mgHSP −1) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable at least up to 50 cycles. The features of this RCFC system including safety ease of handling and light weight suggest applications in mobile light-weight hydrogen-based energy devices.
European Hydrogen Backbone
Jul 2020
Publication
This paper authored by eleven gas infrastructure companies and supported by Guidehouse describes how a dedicated hydrogen infrastructure can be created in
a significant part of the EU between 2030 and 2040 requiring work to start during the 2020s. The hydrogen infrastructure as proposed in this paper fits well with the ambitions of the EU Hydrogen Strategy and the Energy System Integration Strategy plus it aligns well with the goals of the recently announced Clean Hydrogen Alliance to scale up hydrogen enabled by hydrogen transport. Hydrogen clearly gains momentum and this paper aims to provide a contribution towards accelerating a large scale-up of hydrogen by enabling its transport from supply to demand across Europe.
This paper analyses the likely routes across Europe by 2030 2035 and 2040. The included maps show the suggested topology of hydrogen pipelines in ten European countries: Germany France Italy Spain the Netherlands Belgium Czech Republic Denmark Sweden and Switzerland.
You can download the whole report by clicking this link
a significant part of the EU between 2030 and 2040 requiring work to start during the 2020s. The hydrogen infrastructure as proposed in this paper fits well with the ambitions of the EU Hydrogen Strategy and the Energy System Integration Strategy plus it aligns well with the goals of the recently announced Clean Hydrogen Alliance to scale up hydrogen enabled by hydrogen transport. Hydrogen clearly gains momentum and this paper aims to provide a contribution towards accelerating a large scale-up of hydrogen by enabling its transport from supply to demand across Europe.
This paper analyses the likely routes across Europe by 2030 2035 and 2040. The included maps show the suggested topology of hydrogen pipelines in ten European countries: Germany France Italy Spain the Netherlands Belgium Czech Republic Denmark Sweden and Switzerland.
You can download the whole report by clicking this link
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.
Quantification of Temperature Dependence of Hydrogen Embrittlement in Pipeline Steel
Feb 2019
Publication
The effects of temperature on bulk hydrogen concentration and diffusion have been tested with the Devanathan–-Stachurski method. Thus a model based on hydrogen potential diffusivity loading frequency and hydrostatic stress distribution around crack tips was applied in order to quantify the temperature’s effect. The theoretical model was verified experimentally and confirmed a temperature threshold of 320 K to maximize the crack growth. The model suggests a nanoscale embrittlement mechanism which is generated by hydrogen atom delivery to the crack tip under fatigue loading and rationalized the ΔK dependence of traditional models. Hence this work could be applied to optimize operations that will prolong the life of the pipeline.
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.
Optimal Operation of a Hydrogen Storage and Fuel Cell Coupled Integrated Energy System
Mar 2021
Publication
Integrated energy systems have become an area of interest as with growing energy demand globally means of producing sustainable energy from flexible sources is key to meet future energy demands while keeping carbon emissions low. Hydrogen is a potential solution for providing flexibility in the future energy mix as it does not emit harmful gases when used as an energy source. In this paper an integrated energy system including hydrogen as an energy vector and hydrogen storage is studied. The system is used to assess the behaviour of a hydrogen production and storage system under different renewable energy generation profiles. Two case studies are considered: a high renewable energy generation scenario and a low renewable energy generation scenario. These provide an understanding of how different levels of renewable penetration may affect the operation of an electrolyser and a fuel cell against an electricity import/export pricing regime. The mathematical model of the system under study is represented using the energy hub approach with system optimisation through linear programming conducted via MATLAB to minimise the total operational cost. The work undertaken showcases the unique interactions the fuel cell has with the hydrogen storage system in terms of minimising grid electricity import and exporting stored hydrogen as electricity back to the grid when export prices are competitive.
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.
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.
The Effect of Hydrogen Content and Yield Strength on the Distribution of Hydrogen in Steel a Diffusion Coupled Micromechanical FEM Study
Mar 2021
Publication
In this study we investigate the effect of the heterogeneous micromechanical stress fields resulting from the grain-scale anisotropy on the redistribution of hydrogen using a diffusion coupled crystal plasticity model. A representative volume element with periodic boundary conditions was used to model a synthetic microstructure. The effect of tensile loading initial hydrogen content and yield strength on the redistribution of lattice (CL) and dislocation trapped (Cx) hydrogen was studied. It was found that the heterogeneous micromechanical stress fields resulted in the accumulation of both populations primarily at the grain boundaries. This shows that in addition to the well-known grain boundary trapping the interplay of the heterogeneous micromechanical hydrostatic stresses and plastic strains contribute to the accumulation of hydrogen at the grain boundaries. Higher yield strength reduced the amount of Cx due to the resulting lower plastic deformation levels. On the other side the resulting higher hydrostatic stresses increased the depletion of CL from the compressive regions and its diffusion toward the tensile ones. These regions with increased CL are expected to be potential damage initiation zones. This aligns with the observations that high-strength steels are more susceptible to hydrogen embrittlement than those with lower-strength.
Degradation Mechanisms in the Operation of Pressured Pipelines
Aug 2019
Publication
Many non-standard situations like subsoil slipping vibrations ... as well as degradation mechanisms of pipeline materials can occur in the operation of pressured pipelines. The article deals with the mechanisms of the degradation processes and their formation like corrosion brittleness and steel ageing that may occur in operation of pipeline systems. Material ageing of steels is documented on specimens created from pipeline materials and obtained by experimental measurements on these specimens after the multi-annual operation.
Advanced Hydrogen Storage of the Mg–Na–Al System: A Review
May 2021
Publication
A solid-state storage system is the most practical option for hydrogen because it is more convenient and safer. Metal hydrides especially MgH2 are the most promising materials that offer high gravimetric capacity and good reversibility. However the practical application of MgH2 is restricted by slow sorption kinetics and high stability of thermodynamic properties. Hydrogen storage performance of MgH2 was enhanced by introducing the Mg–Na–Al system that destabilises MgH2 with NaAlH4. The Mg–Na–Al system has superior performance compared to that of unary MgH2 and NaAlH4. To boost the performance of the Mg–Na–Al system the ball milling method and the addition of a catalyst were introduced. The Mg–Na–Al system resulted in a low onset decomposition temperature superior cyclability and enhanced kinetics performances. The Al12Mg17 and NaMgH3 that formed in situ during the dehydrogenation process modify the reaction pathway of the Mg–Na–Al system and alter the thermodynamic properties. In this paper the overview of the recent progress in hydrogen storage of the Mg–Na–Al system is detailed. The remaining challenges and future development of Mg–Na–Al system are also discussed. This paper is the first review report on hydrogen storage properties of the Mg–Na–Al system.
Role of Hydrogen-Charging on Nucleation and Growth of Ductile Damage in Austenitic Stainless Steels
May 2019
Publication
Hydrogen energy is a possible solution for storage in the future. The resistance of packaging materials such as stainless steels has to be guaranteed for a possible use of these materials as containers for highly pressurized hydrogen. The effect of hydrogen charging on the nucleation and growth of microdamage in two different austenitic stainless steels AISI316 and AISI316L was studied using in situ tensile tests in synchrotron X-ray tomography. Information about damage nucleation void growth and void shape were obtained. AISI316 was found to be more sensitive to hydrogen compared to AISI316L in terms of ductility loss. It was measured that void nucleation and growth are not affected by hydrogen charging. The effect of hydrogen was however found to change the morphology of nucleated voids from spherical cavities to micro-cracks being oriented perpendicular to the tensile axis.
Interfacial Fracture Strength Property of Micro-scale SiN/Cu Components
Jul 2016
Publication
The strength against fracture nucleation from an interface free-edge of silicon-nitride (SiN)/copper (Cu) micro-components is evaluated. A special technique that combines a nano-indenter specimen holder and an environmental transmission electron microscope (E-TEM) is employed. The critical load at the onset of fracture nucleation from a wedge-shaped free-edge (opening angle: 90°) is measured both in a vacuum and in a hydrogen (H2) environment and the critical stress distribution is evaluated by the finite element method (FEM). It is found that the fracture nucleation is dominated by the near-edge elastic singular stress field that extends about a few tens of nanometers from the edge. The fracture nucleation strength expressed in terms of the stress intensity factor (K) is found to be eminently reduced in a H2 environment.
The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H2 Production with Inherent CO2 Capture
May 2021
Publication
The hydrogen economy has received resurging interest in recent years as more countries commit to net-zero CO2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO2 capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO2 capture imposes a large energy penalty advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR) which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO2 capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points with the upper bound only achievable by large power and H2 co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO2 capture by more than 10%-points both in terms of efficiency and CO2 avoidance.
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.
Water Removal from LOHC Systems
Oct 2020
Publication
Liquid organic hydrogen carriers (LOHC) store hydrogen by reversible hydrogenation of a carrier material. Water can enter the system via wet hydrogen coming from electrolysis as well as via moisture on the catalyst. Removing this water is important for reliable operation of the LOHC system. Different approaches for doing this have been evaluated on three stages of the process. Drying of the hydrogen before entering the LOHC system itself is preferable. A membrane drying process turns out to be the most efficient way. If the water content in the LOHC system is still so high that liquid–liquid demixing occurs it is crucial for water removal to enhance the slow settling. Introduction of an appropriate packing can help to separate the two phases as long as the volume flow is not too high. Further drying below the rather low solubility limit is challenging. Introduction of zeolites into the system is a possible option. Water adsorbs on the surface of the zeolite and moisture content is therefore decreased.
Micro and Macro Mechanical Analysis of Gas Pipeline Steels
Sep 2017
Publication
The actual safety margins of gas pipelines depend on a number of factors that include the mechanical characteristics of the material. The evolution with time of the metal properties can be evaluated by mechanical tests performed at different scales seeking for the best compromise between the simplicity of the experimental setup to be potentially employed in situ and the reliability of the results. Possible alternatives are comparatively assessed on pipeline steels of different compositions and in different states.
Complex Methods of Estimation Technological Strength of Welded Joints in Welding at Low Temperatures
Feb 2021
Publication
A comprehensive methodology for estimating the technological strength of welded joints are developed based on parameters reflecting the welding technology weldability hydrogen force and deformation conditions for welding and other informative parameters that correlate with the characteristics of the welded joint as well as improving existing methods for estimating the technological strength of welded joints connections through the introduction of modern equipment and non-destructive testing systems. It has been established that the proposed comprehensive estimation methodology will allow reaching a new qualitative level in assessing the technological strength of a welded joint using modern equipment and measuring instruments. According to the results of the experimental work it was found that when welding at low temperatures the increase in the probability of the formation and development of cold cracks is mainly determined by the critical content of diffusible hydrogen in the weld metal depending on the structural and force parameters of the welded joints.
Application of the Incremental Step Loading Technique to Small Punch Tests on S420 Steel in Acid Environments
Dec 2020
Publication
The Small Punch test has been recently used to estimate mechanical properties of steels in aggressive environments. This technique very interesting when there is shortage of material consists in using a small plane specimen and punch it until it fails. The type of tests normally used are under a constant load in an aggressive environment with the target to determine the threshold stress. However this is an inaccurate technique which takes time as the tests are quite slow. In this paper the Small Punch tests are combined with the step loading technique collected in the standard ASTM F1624 [1] to obtain the value of threshold stress of an S420 steel in a total time of approximately one week. The ASTM F1624 indicates how to apply constant load steps in hydrogen embrittlement environments increasing them subsequently and adapting their duration until the specimen fails. The environment is created by means of cathodic polarization of cylindrical tensile specimens in an acid electrolyte. A batch of standard tests are performed to validate the methodology.
Characterising Hydrogen Induced Cracking of Alloy 625+ Using Correlative SEM - EDX and NanoSIMS
Dec 2020
Publication
Hydrogen induced cracking behaviour of O&G nickel alloy 625+ (UNS N07716) was investigated. Deuterium was introduced electrochemically into samples by cathodic polarisation (3.5 wt.% NaCl.D2O) under different mechanical conditions. Subsequently deuterium distributions were mapped using NanoSIMS. Deuterium was used as an isotopic tracer instead of hydrogen to avoid the detection of hydrogen artefacts. Complimentary image analysis using scanning electron microscopy (SEM) and low voltage energy dispersive X-ray (EDX) allowed the identification of microstructural features corresponding to deuterium enrichments. The results provided experimental evidence of enrichments at dislocation slip bands (DSB) twin boundary and grain boundary features that include σ precipitates.
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