Publications

We have modelled sudden hydrogen expansion from a cryogenic pressure vessel. This model considers real gas equations of state single and two-phase flow and the specific “vessel within vessel” geometry of cryogenic vessels. The model can solve sudden hydrogen expansion for initial pressures up to 1210 bar and for initial temperatures ranging from 27 to 400 K. For practical reasons our study focuses on hydrogen release from 345 bar with temperatures between 62 K and 300 K. The pressure vessel internal volume is 151 L. The results indicate that cryogenic pressure vessels may offer a safety advantage with respect to compressed hydrogen vessels because i) the vacuum jacket protects the pressure vessel from environmental damage ii) hydrogen when released discharges first into an intermediate chamber before reaching the outside environment and iii) working temperature is typically much lower and thus the hydrogen has less energy. Results indicate that key expansion parameters such as pressure rate of energy release and thrust are all considerably lower for a cryogenic vessel within vessel geometry as compared to ambient temperature compressed gas vessels. Future work will focus on taking advantage of these favourable conditions to attempt fail-safe cryogenic vessel designs that do not harm people or property even after catastrophic failure of the inner pressure vessel.

Solid state materials such as metal and chemical hydrides have been proposed and developed for high energy density automotive hydrogen storage applications. As these materials are implemented into hydrogen storage systems developers must understand their behavior during accident scenarios or contaminated refueling events. An ability to predict thermal and chemical processes during contamination allows for the design of safe and effective hydrogen storage systems along with the development of appropriate codes and standards. A model for the transport of gases within an arbitrary-geometry reactive metal hydride bed (alane -AlH3) is presented in this paper. We have coupled appropriate Knudsen-regime permeability models for flow through packed beds with the fundamental heat transfer and chemical kinetic processes occurring at the particle level. Using experimental measurement to determine and validate model parameters we have developed a robust numerical model that can be utilized to predict processes in arbitrary scaled-up geometries during scenarios such as breach-in-tank or contaminated refueling. Results are presented that indicate the progression of a reaction front through a compacted alane bed as a result of a leaky fitting. The rate of this progression can be limited by; 1) restricting the flow of reactants into the bed through densification and 2) maximizing the rate of heat removal from the bed.

The development of an infrastructure for the future hydrogen economy will require the simultaneous development of a set of codes and standards. As part of the U.S. Department of Energy Hydrogen Fuel Cells & Infrastructure Technologies Program Sandia National Laboratories is developing the technical basis for assessing the safety of hydrogen-based systems for use in the development/modification of relevant codes and standards. This work includes experimentation and modelling to understand the fluid mechanics and dispersion of hydrogen for different release scenarios including investigations of hydrogen combustion and subsequent heat transfer from hydrogen flames. The resulting technical information is incorporated into engineering models that are used for assessment of different hydrogen release scenarios and for input into quantitative risk assessments (QRA) of hydrogen facilities. The QRAs are used to identify and quantify scenarios for the unintended release of hydrogen and to identify the significant risk contributors at different types of hydrogen facilities. The results of the QRAs are one input into a risk-informed codes and standards development process that can also include other considerations by the code and standard developers. This paper describes an application of QRA methods to help establish one key code requirement: the minimum separation distances between a hydrogen refuelling station and other facilities and the public at large. An example application of the risk-informed approach has been performed to illustrate its utility and to identify key parameters that can influence the resulting selection of separation distances. Important parameters that were identified include the selected consequence measures and risk criteria facility operating parameters (e.g. pressure and volume) and the availability of mitigation features (e.g. automatic leak detection and isolation). The results also indicate the sensitivity of the results to key modelling assumptions and the component leakage rates used in the QRA models.

The properties of hydrogen compared to conventional fuels such as gasoline and diesel are substantially different requiring adaptations to the design and layout of test cells for hydrogen fuelled engines and vehicles. A comparison of hydrogen fuel properties versus conventional fuels in this paper provides identification of requirements that need to be adapted to design a safe test cell. Design examples of actual test cells are provided to showcase the differences in overall layout and ventilation safety features fuel supply and metering and emissions measurements. Details include requirements for ventilation patterns the necessity for engine fume hoods as well as hydrogen specific intake and exhaust design. The unique properties of hydrogen in particular the wide flammability limits and nonvisible flames also require additional safety features such as hydrogen sensors and flame cameras. A properly designed and implemented fuel supply system adds to the safety of the test cell by minimizing the amount of hydrogen that can be released. Apart from this the properties of hydrogen also require different fuel consumption measurement systems pressure levels of the fuel supply system additional ventilation lines strategically placed safety solenoids combined with appropriate operational procedures. The emissions measurement for hydrogen application has to be expanded to include the amount of unburned hydrogen in the exhaust as a measurement of completeness of combustion. This measurement can also be used as a safety feature to avoid creation of ignitable hydrogen-air mixtures in the engine exhaust. The considerations provided in this paper lead to the conclusion that hydrogen IC engines can be safely tested however properly designed test cell and safety features have to be included to mitigate the additional hazards related to the change in fuel characteristics.

Storing a hydrogen fuel-cell vehicle in a garage poses a potential safety hazard because of the accidents that could arise from a hydrogen leak. A series of tests examined the risk involved with hydrogen releases and deflagrations in a structure built to simulate a one-car garage. The experiments involved igniting hydrogen gas that was released inside the structure and studying the effects of the deflagrations. The “garage” measured 2.72 m high 3.64 m wide and 6.10 m long internally and was constructed from steel using a reinforced design capable of withstanding a detonation. The front face of the garage was covered with a thin transparent plastic film. Experiments were performed to investigate extended-duration (20–40 min) hydrogen leaks. The effect that the presence of a vehicle in the garage has on the deflagration was also studied. The experiments examined the effectiveness of different ventilation techniques at reducing the hydrogen concentration in the enclosure. Ventilation techniques included natural upper and lower openings and mechanical ventilation systems. A system of evacuated sampling bottles was used to measure hydrogen concentration throughout the garage prior to ignition and at various times during the release. All experiments were documented with standard and infrared (IR) video. Flame front propagation was monitored with thermocouples. Pressures within the garage were measured by four pressure transducers mounted on the inside walls of the garage. Six free-field pressure transducers were used to measure the pressures outside the garage.

DNV GL believes that the National Transmission System (NTS) will be central to the future of decarbonised energy in the UK. The future NTS could transmit natural gas hydrogen blends of the two and carbon dioxide. New pipelines will be built however a large cost-saving is available if the existing NTS assets can also be re-purposed. To move towards this future National Grid Gas Transmission wants to develop a project to trial injection hydrogen into the NTS. This is an opportunity to show that National Grid is part of the solution to achieving Net Zero. The trial will demonstrate to the Government and public that re-purposing the NTS is cost-effective safe and involves minimal disruption.

This report sets out a roadmap of projects to provide the knowledge needed for the trial. The roadmap was developed by assessing the knowledge required and how much of it already existed. The knowledge already available is summarised in this report with references to where further details can be found. Gaps in the knowledge are then described. The roadmap consists of projects to conduct work to close the knowledge gaps. The results are summarised in the figures below and in the box to the right.  

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.

Over the last century there have been reports of high pressure hydrogen leaks igniting for no apparent reason and several ignition mechanisms have been proposed. Although many leaks have ignited there are also reported leaks where no ignition has occurred. Investigations of ignitions where no apparent ignition source was present have often been superficial with a mechanism postulated which whilst appearing to satisfy the conditions prevailing at the time of the release simply does not stand up to rigorous scientific analysis. Some of these proposed mechanisms have been simulated in a laboratory under superficially identical conditions and appear to be rigorous and scientific but the simulated conditions often do not have the same large release rates or quantities mainly because of physical constraints of a laboratory. Also some of the release scenarios carried out or simulated in laboratories are totally divorced from the realistic situation of most actual leaks. Clearly there are gaps in the knowledge of the exact ignition mechanism for releases of hydrogen particularly at the high pressures likely to be involved in future storage and use. Mechanisms which have been proposed in the past are the reverse Joule-Thomson effect; electrostatic charge generation; diffusion ignition; sudden adiabatic compression; and hot surface ignition. Of these some have been characterized by means of computer simulation rather than by actual experiment and hence are not validated. Consequently there are discrepancies between the theories releases known to have ignited and releases which are known to have not ignited. From this postulated ignition mechanisms which are worthy of further study have been identified and the gaps in information have been highlighted. As a result the direction for future research into the potential for ignition of hydrogen escapes has been identified.

The largest known experiment on hydrogen-air deflagration in the open atmosphere has been analysed by means of the large eddy simulation (LES). The combustion model is based on the progress variable equation to simulate a premixed flame front propagation and the gradient method to decouple the physical combustion rate from numerical peculiarities. The hydrodynamic instability has been partially resolved by LES and unresolved effects have been modelled by Yakhot's turbulent premixed combustion model. The main contributor to high flame propagation velocity is the additional turbulence generated by the flame front itself. It has been modelled based on the maximum flame wrinkling factor predicted by Karlovitz et al. theory and the transitional distance reported by Gostintsev with colleagues. Simulations are in a good agreement with experimental data on flame propagation dynamics flame shape and outgoing pressure wave peaks and structure. The model is built from the first principles and no adjustable parameters were applied to get agreement with the experiment.

We have investigated hydrogen explosion risk and its mitigation focusing on compact hydrogen refuelling stations in urban areas. In this study numerical analyses were performed of hydrogen blast propagation and the structural behaviour of barrier walls. Parametric numerical simulations of explosions were carried out to discover effective shapes for blast-mitigating barrier walls. The explosive source was a prismatic 5.27 m3 volume that contained 30% hydrogen and 70% air. A reinforced concrete wall 2 m tall by 10 m wide and 0.15 m thick was set 2 or 4 m away from the front surface of the source. The source was ignited at the bottom centre by a spark for the deflagration case and 10 g of C-4 high explosive for two detonation cases. Each of the tests measured overpressures on the surfaces of the wall and on the ground displacements of the wall and strains of the rebar inside the wall. The blast simulations were carried out with an in-house CFD code based on the compressive Euler equation. The initial energy estimated from the volume of hydrogen was a time-dependent function for the deflagration and was released instantaneously for the detonations. The simulated overpressures were in good agreement with test results for all three test cases. DIANA a finite element analysis code released by TNO was used for the structural simulations of the barrier wall. The overpressures obtained by the blast simulations were used as external forces. The analyses simulated the displacements well but not the rebar strains. The many shrinkage cracks that were observed on the walls some of which penetrated the wall could make it difficult to simulate the local behaviour of a wall with high accuracy and could cause strain gages to provide low-accuracy data. A parametric study of the blast simulation was conducted with several cross-sectional shapes of barrier wall. A T-shape and a Y-shape were found to be more effective in mitigating the blast.

The release of gases heavier than air like propane at ground level or lighter than air like hydrogen close to a ceiling can both lead to fire and explosion hazards that must be carefully considered in safety analyses. Even if the simulation of accident scenarios in complex installations and long transients often appears feasible only using lumped parameter computer codes the phenomenon of denser or lighter gas dispersion is not implicitly accounted by these kind of tools. In the aim to set up an ad hoc model to be used in the computer code ECART fluid-dynamic simulations by the commercial FLUENT 6.0 CFD code are used. The reference geometry is related to cavities having variable depth (2 to 4 m) inside long tunnels filled with a gas heavier or lighter than air (propane or hydrogen). Three different geometrical configurations with a cavity width of 3 6 and 9 m are considered imposing different horizontal air stream velocities ranging from 1 to 5 m/s. A stably-stratified flow region is observed inside the cavity during gas shearing. In particular it is found that the density gradient tends to inhibit turbulent mixing thus reducing the dispersion rate. The obtained data are correlated in terms of main dimensionless groups by means of a least squares method. In particular the Sherwood number is correlated as a function of Reynolds a density ratio modified Froude numbers and in terms of the geometrical parameter obtained as a ratio between the depth of the air-dense gas interface and the length of the cavity. This correlation is implemented in the ECART code to add the possibility to simulate large installations during complex transients lasting many hours with reasonable computation time. An example of application to a typical case is presented.

The method of the numerical solution of a three-dimensional problem of atmospheric release dispersion and explosion of gaseous admixtures is presented. It can be equally applied for gases of different densities including hydrogen. The system of simplified Navie-Stocks equations received by truncation of viscous members (Euler equations with source members) is used to obtain a numerical solution. The algorithm is based on explicit finite-difference Godunov scheme of arbitrary parameters breakup disintegration. To verify the developed model and computer system comparisons of numerical calculations with the published experimental data on the dispersion of methane and hydrocarbons explosions have been carried out. Computational experiments on evaporation and dispersion of spilled liquid hydrogen and released gaseous hydrogen at different wind speeds have been conducted. The largest mass concentrations of hydrogen between the bottom and top limits of flame propagation and cloud borders have been determined. The problem of the explosion of a hydrogen-air cloud of the complex form generated by large-scale spillage of liquid hydrogen and instant release of gaseous hydrogen has been numerically solved at low wind speed. Shock-wave loadings affecting the buildings located on a distance of 52 m from a hydrogen release place have been shown.

A phenomenological approach is developed to calculate the velocity of flame propagation and to estimate the value of pressure peak when igniting gaseous combustible mixtures in a congested space. The basic idea of this model is afterburning of the remanent fuel in pockets of congested space behind the flame front. The estimation of probable overpressure peak is based on solution of one-dimensional problem of the piston (having corresponding symmetry) moving with given velocity in polytropic gas. Submitted work is the first representation of such phenomenological approach and is realized for the simplest situation close to one-dimensional.

To provide more practical data for safety assessments a systematic study of explosion and combustion processes which can take place in mixtures produced by jet releases in realistic environmental conditions is required. The presented work is aimed to make step forward in this direction binding three inter-connected tasks: (i) study of horizontal and vertical jets (ii) study of the burnable clouds formed by jets in different geometry configurations and (iii) examination of combustion and explosion processes initiated in such mixtures. Test matrix for the jet experiments included variation of the release pressure and nozzle diameter with the aim to study details of the resulting hydrogen concentration and velocity profiles depending on the release conditions. In this study the following parameters were varied: mass flow rate jet nozzle diameter (to alter gas speed) and geometry of the hood located on top of the jet. The carried out experiments provided data on detailed structure for under-expanded horizontal and buoyant vertical jets and data on pressure loads resulted from deflagration of various mixtures formed by jet releases. The data on pressures waves generated in the conditions under consideration provides conservative estimation of pressure loads for realistic leaks.

Based on the increasing need of energy for the future and the related risks to the environments due to burning of fossils fuels hydrogen is seen as an efficient and application related clean energy carrier that may be derived from renewable energy sources. A variety of applications connected with production and use of hydrogen and the related risks have been identified and a survey has been conducted among a number of experts as an internet exercise for unveiling the potential lack of necessary knowledge in order to handle hydrogen in a safe way concerning the various applications. The main results concern hazardous situations related to release and explosions of hydrogen in confined and semi-confined areas tunnels and garages and mitigation of hazardous situations i.e. preventions of accidents and reduction of consequences from accidents happening anyway.

Interest in the future is not new. Economic constraints and acceptability considerations of today compel decision-makers from industry and authorities to speculate on possible safety risks originating from a hydrogen economy developed in the future. Tools that support thinking about the long-term consequences of today's actions and resulting technical systems are usually prognostic based on data from past performance of past or current systems. It has become convention to assume that the performance of future systems in future environments can be accommodated in the uncertainties of such prognostic models resulting from sensitivity studies. This paper presents an alternative approach to modelling future systems based on narratives about the future. Such narratives based on the actions and interactions of individual "agents" are powerful means for addressing anxiety about engaging the imagination in order to prepare for events that are likely to occur detect critical conditions and to thus achieve desirable outcomes. This is the methodological base of Agent-Based Models (ABM) and this paper will present the approach discuss its strengths and weaknesses and present a preliminary application to modelling safety risks related to energy scenarios in a possible future hydrogen economy.

The future of hydrogen energy is wrapped up with the future of natural gas renewable energy and carbon capture and storage (CCS). This yields useful synergies but also political economic and technical complexity. Nevertheless our survey of more than 1000 senior oil and gas professionals suggests a more certain future for hydrogen and that the time is right to begin scaling the hydrogen economy.

In order to improve risk analyses and influence the design of the future H2 systems an experimental study on “real” leaks qualification and quantification was performed. In H2 energy applications fittings appeared as a significant leakage potential and subsequently explosion and flame hazards. Thus as a part of the “Horizon Hydrogène Energie” French program four kinds of commercial fittings usually employed on H2 systems were tested thanks to a new high pressure test bench – designed setup and operated by INERIS – allowing experiments to be led for H2 pressures until 700 bar. The fittings underwent defined stresses representative of H2 systems lifetime and beyond. The associated leaks – when existing – are characterized in terms of flow rate.

The time and space evolution of the distribution of hydrogen in confined settings was investigated computationally and experimentally for permeation from typical compressed gaseous hydrogen storage systems for buses or cars. The work was performed within the framework of the InsHyde internal project of the HySafe NoE funded by EC. The main goal was to examine whether hydrogen is distributed homogeneously within a garage like facility or whether stratified conditions are developed under certain conditions. The nominal hydrogen flow rate considered was 1.087 NL/min based on the then current SAE standard for composite hydrogen containers with a non-metallic liner (type 4) at simulated end of life and maximum material temperature in a bus facility with a volume of 681m3. The release was assumed to be directed upwards from a 0.15m diameter hole located at the middle part of the bus cylinders casing. Ventilation rates up to 0.03 ACH were considered. Simulated time periods extended up to 20 days. The CFD simulations performed with the ADREA-HF code showed that fully homogeneous conditions exist for low ventilation rates while stratified conditions prevail for higher ventilation rates. Regarding flow structure it was found that the vertical concentration profiles can be considered as the superposition of the concentration at the floor (driven by laminar diffusion) plus a concentration difference between floor and ceiling (driven by buoyancy forces). In all cases considered this concentration difference was found to be less than 0.5%. The dispersion experiments were performed at the GARAGE facility using Helium. Comparison between CFD simulations and experiments showed that the predicted concentrations were in good agreement with the experimental data. Finally simulations were performed using two integral models: the fully homogeneous model and the two-layer model proposed by Lowesmith et al. (ICHS-2 2007) and the results were compared both against CFD and the experimental data.

When introducing hydrogen-fuelled vehicles an evaluation of the potential change in risk level should be performed. It is widely accepted that outdoor accidental releases of hydrogen from single vehicles will disperse quickly and not lead to any significant explosion hazard. The situation may be different for more confined situations such as parking garages workshops or tunnels. Experiments and computer modelling are both important for understanding the situation better. This paper reports a simulation study to examine what if any is the explosion risk associated with hydrogen vehicles in tunnels. Its aim was to further our understanding of the phenomena surrounding hydrogen releases and combustion inside road tunnels and furthermore to demonstrate how a risk assessment methodology developed for the offshore industry could be applied to the current task. This work is contributing to the EU Sixth Framework (Network of Excellence) project HySafe aiding the overall understanding that is also being collected from previous studies new experiments and other modelling activities. Releases from hydrogen cars (containing 700 bar gas tanks releasing either upwards or downwards or liquid hydrogen tanks releasing only upwards) and buses (containing 350 bar gas tanks releasing upwards) for two different tunnel layouts and a range of longitudinal ventilation conditions have been studied. The largest release modelled was 20 kg H2 from four cylinders in a bus (via one vent) in 50 seconds with an initial release rate around 1000 g/s. Comparisons with natural gas (CNG) fuelled vehicles have also been performed. The study suggests that for hydrogen vehicles a typical worst-case risk assessment approach assuming the full gas inventory being mixed homogeneously at stoichiometry could lead to severe explosion loads. However a more extensive study with more realistic release scenarios reduced the predicted hazard significantly. The flammable gas cloud sizes were still large for some of the scenarios but if the actual reactivity of the predicted clouds is taken into account very moderate worst-case explosion pressures are predicted. As a final step of the risk assessment approach a probabilistic QRA study is performed in which probabilities are assigned to different scenarios time dependent ignition modelling is applied and equivalent stoichiometric gas clouds are used to translate reactivity of dispersed nonhomogeneous clouds. The probabilistic risk assessment study is based on over 200 dispersion and explosion CFD calculations using the commercially available tool FLACS. The risk assessment suggested a maximum likely pressure level of 0.1-0.3 barg at the pressure sensors that were used in the study. Somewhat higher pressures are seen elsewhere due to reflections (e.g. under the vehicles). Several other interesting observations were found in the study. For example the study suggests that for hydrogen releases the level of longitudinal tunnel ventilation has only a marginal impact on the predicted risk since the momentum of the releases and buoyancy of hydrogen dominates the mixing and dilution processes.

This paper presents a compilation of the results supplied by HySafe partners participating in the Standard Benchmark Exercise Problem (SBEP) V2 which is based on an experiment on hydrogen combustion that is first described. A list of the results requested from participants is also included. The main characteristics of the models used for the calculations are compared in a very succinct way by using tables. The comparison between results together with the experimental data when available is made through a series of graphs. The results show quite good agreement with the experimental data. The calculations have demonstrated to be sensitive to computational domain size and far field boundary condition.

This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow the simulation of hydrogen releases from a pipeline with or without ignition of the hydrogen-air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However in the opinion of the Group the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.

This Energy Insight examines the current regulatory framework and challenges facing the natural gas industry (producers transporters suppliers and consumers) during the transition to a zero-carbon economy.  The EU has declared its intention to be climate neutral by 2050 which means that the current level of natural gas usage will no longer be possible. However natural gas is a crucial component of energy supply representing 24 per cent of primary energy supply for the EU27+UK and 36 per cent of residential energy consumption. In some countries the use of natural gas is much higher – around 40 per cent of primary energy supply in Netherlands UK and Italy. The current framework impacting gas addresses two different market failures – natural monopolies for gas transportation and the externalities of Greenhouse Gas Emissions. The framework will not deliver decarbonisation of gas as it does not stimulate either supply or demand for alternatives such as hydrogen nor create the conditions to enable gas networks to transition to a decarbonised future. Policy makers need to prioritise their objectives to take account of the trade-offs involved in designing a new framework. Exclusion of certain low carbon technologies risks driving away investors and reduces the chances of targets being met whilst “picking winners” involves risks because of the many uncertainties involved such as future costs and time required to build new value chains.

Link to Document on Oxford Institute for Energy Studies website

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.

An all-weather energy management scheme for island DC microgrid based on hydrogen energy storage is proposed. A dynamic model of a large-scale wind–solar hybrid hydrogen-generation power generation system was established using a quasi-proportional resonance (QPR). We used the distributed Nautilus vertical axis wind power generation system as the main output of the system and it used the photovoltaic and hydrogen energy storage systems as alternative energy sources. Based on meeting the load power requirements and controlling the bus voltage stability we can convert the excess energy of the microgrid to hydrogen energy. With a shortage of load power we can convert the stored hydrogen into electrical energy for the load. Based on the ANSYS FLUENT software platform the feasibility and superiority over large-scale distributed Nautilus vertical axis wind power generation systems are verified. Through the MATLAB/Simulink software platform the effectiveness of the energy management method is verified. The results show that the large-scale distributed Nautilus vertical axis wind power generation system runs well in the energy system produces stable torque produces energy better than other types of wind turbines and has less impact on the power grid. The energy management method can ensure the normal operation of the system 24 h a day under the premise of maintaining the stable operation of the electric hydrogen system without providing external energy.

Photoelectrochemical reforming of plastic waste offers an environmentally-benign and sustainable route for hydrogen generation. Nonetheless little attention was paid to develop electrocatalysts that can efficiently and selectively catalyze oxidative transformation of valueless plastic wastes into valued chemicals. Herein we report on facile electrosynthesis of nickel-phosphorus nanospheres (nanoNi-P) and their versatility in catalyzing hydrogen generation water oxidation and reforming of polyethylene terephthalate (PET). Notably composite of nanoNi-P with carbon nanotubes (CNT/nanoNi-P) requires −180 mV overpotential to drive hydrogen generation at -100 mA cm⁻². Besides CV-activated nanoNi-P (nanoNi-P(CV)) was shown to be capable of reforming PET into formate with high selectivity (Faradic efficiency= ∼100 %). Efficient and selective generation of hydrogen and formate from PET reforming is realized utilizing an Earth-abundant photoelectrochemical platform based on nanoNi-P(CV)-modified TiO2 nanorods photoanode and CNT/nanoNi-P cathode. This work paves a path for developing artificial leaf for simultaneous environmental mitigation and photosynthesis of renewable fuels and valued chemicals.

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.

Long-haul heavy-duty vehicles including trucks and coaches contribute to a substantial portion of the modern-day European carbon footprint and pose a major challenge in emissions reduction due to their energy-intensive usage. Depending on the hydrogen fuel source the use of fuel cell electric vehicles (FCEV) for long-haul applications has shown significant potential in reducing road freight CO2 emissions until the possible maturity of future long-distance battery-electric mobility. Fuel cell heavy-duty (HD) propulsion presents some specific characteristics advantages and operating constraints along with the notable possibility of gains in powertrain efficiency and usability through improved system design and intelligent onboard energy and thermal management. This paper provides an overview of the FCEV powertrain topology suited for long-haul HD applications their operating limitations cooling requirements waste heat recovery techniques state-of-the-art in powertrain control energy and thermal management strategies and over-the-air route data based predictive powertrain management including V2X connectivity. A case study simulation analysis of an HD 40-tonne FCEV truck is also presented focusing on the comparison of powertrain losses and energy expenditures in different subsystems while running on VECTO Regional delivery and Long-haul cycles. The importance of hydrogen fuel production pathways onboard storage approaches refuelling and safety standards and fleet management is also discussed. Through a comprehensive review of the H2 fuel cell powertrain technology intelligent energy management thermal management requirements and strategies and challenges in hydrogen production storage and refuelling this article aims at helping stakeholders in the promotion and integration of H2 FCEV technology towards road freight decarbonisation.

The aim of this work is to study the influence of the sulphur source (elemental sulphur thiourea and L-cysteine) in the solvothermal synthesis of Ag-CdS over its growth structuration and state of Ag and how these changes influence on its photoactivity. The differences in the generation rate of the S²⁻ from the sulphur sources during the solvothermal synthesis determine the nucleation and growth pathways of CdS affecting to the silver state and its incorporation into the CdS lattice. The hydrogen production on Ag-CdS photocatalysts decreases according the sequence: thiourea > elemental sulphur >> L-cysteine. The changes in the photoactivity of Ag-CdS samples are analysed in terms of the differences in the insertion of Ag⁺ into the CdS lattice the formation of composites between CdS and Ag₂S and the formation of CdS crystalline domains with strong confinement effect derived from the different sulphur source used in the solvothermal synthesis

Hydrogen is recognized as the “future fuel” and the most promising alternative of fossil fuels due to its remarkable properties including exceptionally high energy content per unit mass (142 MJ/kg) low mass density and massive environmental and economical upsides. A wide spectrum of methods in H₂ production especially carbon-free approaches H2purification and H2storage have been investigated to bring this energy source closer to the technological deployment. Hydrogen hydrates are among the most intriguing material paradigms for H₂storage due to their appealing properties such as low energy consumption for charge and discharge safety cost-effectiveness and favorable environmental features. Here we comprehensively discuss the progress in understanding of hydrogen clathrate hydrates with an emphasis on charging/discharging rate of H₂ (i.e. hydrate formation and dissociation rates) and the storage capacity. A thorough understanding on phase equilibrium of the hydrates and its variation through different materials is provided. The path toward ambient temperature and pressure hydrogen batteries with high storage capacity is elucidated. We suggest that the charging rate of H₂ in this storage medium and long cyclic performance are more immediate challenges than storage capacity for technological translation of this storage medium. This review and provided outlook establish a groundwork for further innovation on hydrogen hydrate systems for promising future of hydrogen fuel.

Hydrogen mobility is one option for reducing local emissions avoiding greenhouse gas (GHG) emissions and moving away from a mainly oil-based transport system towards a diversification of energy sources. As hydrogen production can be based on a broad variety of technologies already existing or under development a comprehensive assessment of the different supply chains is necessary regarding not only costs but also diverse environmental impacts. Therefore in this paper a broad variety of hydrogen production technologies using different energy sources renewable and fossil are exemplarily assessed with the help of a Life Cycle Assessment and a cost assessment for Germany. As environmental impacts along with the impact category Climate change five more advanced impact categories are assessed. The results show that from an environmental point of view PEM and alkaline electrolysis are characterized by the lowest results in five out of six impact categories. Supply chains using fossil fuels in contrast have the lowest supply costs; this is true e.g. for steam methane reforming. Solar powered hydrogen production shows low impacts during hydrogen production but high impacts for transport and distribution to Germany. There is no single supply chain that is the most promising for every aspect assessed here. Either costs have to be lowered further or supply chains with selected environmental impacts have to be modified.

This paper summarizes a series of the authors’ research in the field of assessing the operational degradation of oil and gas transit pipeline steels. Both mechanical and electrochemical properties of steels are deteriorated after operation as is their resistance to environmentally-assisted cracking. The characteristics of resistance to brittle fracture and stress corrosion cracking decrease most intensively which is associated with a development of in-bulk dissipated microdamages of the material. The most sensitive indicators of changes in the material’s state caused by degradation are impact toughness and fracture toughness by the J-integral method. The degradation degree of pipeline steels can also be evaluated nondestructively based on in-service changes in their polarization resistance and potential of the fracture surface. Attention is drawn to hydrogenation of a pipe wall from inside as a result of the electrochemical interaction of pipe metal with condensed moisture which facilitates operational degradation of steel due to the combined action of operating stresses and hydrogen. The development of microdamages along steel texture was evidenced metallographically as a trend to the selective etching of boundaries between adjacent bands of ferrite and pearlite and fractographically by revealing brittle fracture elements on the fracture surfaces namely delamination and cleavage indicating the sites of cohesion weakening between ferrite and pearlite bands. The state of the X52 steel in its initial state and after use for 30 years was assessed based on the numerical simulation method.

The currently used bulk analysis and depth profiling methods for hydrogen in inorganic materials and inorganic coatings are reviewed. Bulk analysis of hydrogen is based on fusion of macroscopic samples in an inert gas and the detection of the thereby released gaseous H2 using inert gas fusion (IGF) and thermal desorption spectroscopy (TDS). They offer excellent accuracy and sensitivity. Depth profiling methods involve glow discharge optical emission spectroscopy and mass spectrometry (GDOES and GDMS) laser-induced breakdown spectroscopy (LIBS) secondary ion mass spectrometry (SIMS) nuclear reaction analysis (NRA) and elastic recoil detection analysis (ERDA). The principles of all these methods are explained in terms of the methodology calibration procedures analytical performance and major application areas. The synergies and the complementarity of various methods of hydrogen analysis are described. The existing literature about these methods is critically evaluated and major papers concerning each method are listed.

One of the most important requirements concerning the quality of natural gases guaranteeing their safe use involves providing the proper level of their odorization. This allows for the detection of uncontrolled leakages of gases from gas networks installations and devices. The concentration of an odorant should be adjusted in such a manner that the gas odor in a mixture with air would be noticeable by users (gas receivers). A permanent odor of gas is guaranteed by the stability of the odorant molecule and its resistance to changes in the composition of odorized gases. The article presents the results of experimental research on the impact of a hydrogen additive on the stability of tetrahydrothiophene (THT) mixtures in methane and in natural gas with a hydrogen additive. The objective of the work was to determine the readiness of measurement infrastructures routinely used in monitoring the process of odorizing natural gas for potential changes in its composition. One of the elements of this infrastructure includes the reference mixtures of THT used to verify the correctness of the readings of measurement devices. The performed experimental tests address possible changes in the composition of gases supplied via a distribution network resulting from the introduction of hydrogen. The lack of interaction between hydrogen and THT has been verified indirectly by assessing the stability of its mixtures with methane and natural gas containing hydrogen. The results of the presented tests permitted the identification of potential hazards for the safe use of gas from a distribution network resulting from changes in its composition caused by the addition of hydrogen.

To become climate-neutral by 2050 Europe needs to transform its energy system which accounts for 75% of the EU's greenhouse gas emissions.  The EU strategies for energy system integration and hydrogen adopted today will pave the way towards a more efficient and interconnected energy sector driven by the twin goals of a cleaner planet and a stronger economy.<br/><br/>The two strategies present a new clean energy investment agenda in line with the Commission's Next Generation EU recovery package and the European Green Deal. The planned investments have the potential to stimulate the economic recovery from the coronavirus crisis. They create European jobs and boost our leadership and competitiveness in strategic industries which are crucial to Europe's resilience.

Automated and electric mass transit will play a significant role in the connectivity of our cities and regions. But automated mass transit must be placed within the wider context of the optimum transport needs of those cities and regions— transport networks based on shared and multi-modal mobility. Realising the full potential of these networks will require sustained policy development and investment.<br/>This report examines current and future developments in the use of automation and new energy sources in land-based mass transit including rail and road mass transit point-to-point transport using automated vehicles and the role and responsibilities of the Commonwealth in the development of these technologies. It will analyse the opportunities and challenges presented by automation and new energy sources and the role the Australian Government has to play in managing this transport revolution.

Copper cobalt oxide nanoparticles (CCO NPs) were synthesized as an oxygen evolution electrocatalyst via a simple co-precipitation method with the composition being controlled by altering the precursor ratio to 1:1 1:2 and 1:3 (Cu:Co) to investigate the effects of composition changes. The effect of the ratio of Cu2+/Co3+ and the degree of oxidation during the co-precipitation and annealing steps on the crystal structure morphology and electrocatalytic properties of the produced CCO NPs were studied. The CCO1:2 electrode exhibited an outstanding performance and high stability owing to the suitable electrochemical kinetics which was provided by the presence of sufficient Co3+ as active sites for oxygen evolution and the uniform sizes of the NPs in the half cell. Furthermore single cell tests were performed to confirm the possibility of using the synthesized electrocatalyst in a practical water splitting system. The CCO1:2 electrocatalyst was used as an anode to develop an anion exchange membrane water electrolyzer (AEMWE) cell. The full cell showed stable hydrogen production for 100 h with an energetic efficiency of >71%. In addition it was possible tomass produce the uniform highly active electrocatalyst for such applications through the co-precipitation method.

Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide researchers and companies are continuously working on this matter taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content but a somewhat elusive one for being a gas with low molecular weight. This review examines the current electrolysis processes for obtaining hydrogen with an emphasis on alkaline water electrolysis. This process is far from being new but research shows that there is still plenty of room for improvement. The efficiency of an electrolyzer mainly relates to the overpotential and resistances in the cell. This work shows that the path to better electrolyzer efficiency is through the optimization of the cell components and operating conditions. Following a brief introduction to the thermodynamics and kinetics of water electrolysis the most recent developments on several parameters (e.g. electrocatalysts electrolyte composition separator interelectrode distance) are highlighted.

This study was aimed to define a methodology based on existing literature and evaluate the levelized cost of hydrogen (LCOH) for a decentralized hydrogen refueling station (HRS) in Halle Belgium. The results are based on a comprehensive data collection along with real cost information. The main results indicated that a LCOH of 10.3 €/kg at the HRS can be reached over a lifetime of 20 years if an average electricity cost of 0.04 €/kWh could be achieved and if the operating hours are maximized. Furthermore if the initial capital costs can be reduced by 80% in the case of direct subsidy the LCOH could even fall to 6.7 €/k

Renewable methanol obtained from CO₂ and hydrogen provided from renewable energy was proposed to close the CO₂ loop. In industry methanol synthesis using the catalyst CuO/ZnO/Al₂O₃ occurs at a high pressure. We intend to make certain modification on the traditional catalyst to work at lower pressure maintaining high selectivity. Therefore three heterogeneous catalysts were synthesized by coprecipitation to improve the activity and the selectivity to methanol under mild conditions of temperature and pressure. Certain modifications on the traditional catalyst Cu/Zn/Al₂O₃ were employed such as the modification of the synthesis time and the addition of Pd as a dopant agent. The most efficient catalyst among those tested was a palladium-doped catalyst 5% Pd/Cu/Zn/Al₂O₃. This had a selectivity of 64% at 210 °C and 5 bar.

Due to the low efficiency and high pollution of conventional internal combustion engine vehicles the fuel cell hybrid electric vehicles are expected to play a key role in the future of clean energy transportation attributed to the long driving range short hydrogen refueling time and environmental advantages. The development of energy management strategies has an important impact on the economy and durability but most strategies ignore the aging of fuel cells and the corresponding impact on hydrogen consumption. In this paper a rule-based fuzzy control strategy is proposed based on the constructed data-driven online estimation model of fuel cell health. Then a genetic algorithm is used to optimize this fuzzy controller where the objective function is designed to consider both the economy and durability by combining the hydrogen consumption cost and the degradation cost characterized by the fuel cell health status. Considering that the rule-based strategy is more sensitive to operating conditions this paper uses an artificial neural network for predictive control. The results are compared with those obtained from the genetic algorithm optimized fuzzy controller and are found to be very similar where the prediction accuracy is assessed using MAPE RMSE and 10-fold cross-validation. Experiments show that the developed strategy has a good generalization capability for variable driving cycles.

Steam methane (CH4–H2O) reforming in the presence of a catalyst usually nickel is the most common technology for generating synthesis gas as a feedstock in chemical synthesis and a source of pure H2 and CO. What is essential from the perspective of further gas use is the parameter describing a ratio of equilibrium concentration of hydrogen to carbon monoxide (/ = 2/). The parameter is determined by operating temperature and the initial ratio of steam concentration to methane = 2 0 /4 0 . In this paper the author presents a thermodynamic analysis of the effect of green hydrogen addition to a fuel mixture on the steam methane reforming process of gaseous phase (CH4/H2)–H2O. The thermodynamic analysis of conversion of hydrogen-enriched methane (CH4/H2)–H2O has been performed using parametric equation formalism allowing for determining the equilibrium composition of the process in progress. A thermodynamic condition of carbon precipitation in methane reforming (CH4/H2) with the gaseous phase of H2O has been interpreted. The ranges of substrate concentrations creating carbon deposition for temperature T = 1000 K have been determined based on the technologies used. The results obtained can serve as a model basis for describing the properties of steam reforming of methane and hydrogen mixture (CH4/H2)– H2O.

Flame propagation and acceleration in unobstructed channels/tubes is usually assumed as symmetric. A fully optically accessible narrow channel that allows to perform simultaneous high-speed schlieren visualization from two mutually perpendicular directions was built to asses the validity of the aforementioned assumption. Here we provide experimental evidence of the interesting three-dimensional structures and asymmetries that develop during the acceleration phase and show how these may control detonation onset in N2-diluted stoichiometric H2-O2 mixtures.

Ammonia is considered to be a potential medium for hydrogen storage facilitating CO2-free energy systems in the future. Its high volumetric hydrogen density low storage pressure and stability for long-term storage are among the beneficial characteristics of ammonia for hydrogen storage. Furthermore ammonia is also considered safe due to its high auto ignition temperature low condensation pressure and lower gas density than air. Ammonia can be produced from many different types of primary energy sources including renewables fossil fuels and surplus energy (especially surplus electricity from the grid). In the utilization site the energy from ammonia can be harvested directly as fuel or initially decomposed to hydrogen for many options of hydrogen utilization. This review describes several potential technologies in current conditions and in the future for ammonia production storage and utilization. Ammonia production includes the currently adopted Haber–Bosch electrochemical and thermochemical cycle processes. Furthermore in this study the utilization of ammonia is focused mainly on the possible direct utilization of ammonia due to its higher total energy efficiency covering the internal combustion engine combustion for gas turbines and the direct ammonia fuel cell. Ammonia decomposition is also described in order to give a glance at its progress and problems. Finally challenges and recommendations are also given toward the further development of the utilization of ammonia for hydrogen storage.

This study discusses the potential of H₂ production by proton exchange membrane water electrolysis as an effective option to reduce greenhouse gas emissions in the hydrogen sector. To address this topic a life cycle assessment is conducted to compare proton exchange membrane water electrolysis versus the reference process - steam methane reforming. As a relevant result we show that hydrogen production via proton exchange membrane water electrolysis is a promising technology to reduce CO₂ emissions of the hydrogen sector by up to 75% if the electrolysis system runs exclusively on electricity generated from renewable energy sources. In a future (2050) base-load operation mode emissions are comparable to the reference system.

The results for the global warming potential show a strong reduction of greenhouse gas emissions by 2050. The thoroughly and in-depth modelled components of the electrolyser have negligible influence on impact categories; thus emissions are mainly determined by the electricity mix. With 2017 electricity mix of Germany the global warming potential corresponds to 29.5 kg CO₂ eq. for each kg of produced hydrogen. Referring to the electricity mix we received from an energy model emissions can be reduced to 11.5 kg CO₂ eq. in base-load operation by the year 2050. Using only the 3000 h of excess power from renewables in a year will allow for the reduction of the global warming potential to 3.3 kg CO₂ eq. From this result we see that an environmentally friendly electricity mix is crucial for reducing the global warming impact of electrolytic hydrogen.

Carbon capture and storage (CCS) continues to make significant progress around the world against a backdrop of greater climate action from countries and private companies. The Global Status of CCS 2021 demonstrates the critical role of CCS as nations and industry accelerate to net-zero.<br/>The report provides detailed analyses of the global project pipeline international policy finance and emerging trends. In addition four regional overviews highlight the rapid development of CCS across North America Asia Pacific Europe and nearby regions and the Gulf Cooperation Council states.

This work discusses the design and demonstration of an in-situ test setup for testing pipeline steels in a high pressure gaseous hydrogen (H2 ) environment. A miniature hollow pipe-like tensile specimen was designed that acts as the gas containment volume during the test. Specific areas of the specimen can be forced to fracture by selective notching as performed on the weldment. The volume of H2 used was minimised so the test can be performed safely without the need of specialised equipment. The setup is shown to be capable of characterising Hydrogen Embrittlement (HE) in steels through testing an X60 pipeline steel and its weldment. The percentage elongation (%El) of the base metal was found to be reduced by 40% when tested in 100 barg H2 . Reduction of cross-sectional area (%RA) was found to decrease by 28% and 11% in the base metal and weld metal respectively when tested in 100 barg H2 . Benchmark test were performed at 100 barg N2 pressure. SEM fractography further indicated a shift from normal ductile fracture mechanisms to a brittle transgranular (TG) quasi-cleavage (QC) type fracture that is characteristic of HE.

The growing consumption of global energy has posed serious challenges to environmental protection and energy supplies. A promising solution is via introducing clean and sustainable energy sources including photoelectrochemical hydrogen fuel production. 2D materials such as transition metal trichalcogenphosphites (MPCh₃) are gaining more and more interest for their potential as photocatalysts. Crystals of transition metal selenophosphites namely MnPSe₃ FePSe₃ and ZnPSe₃ were tested as photocatalysts for the hydrogen evolution reaction (HER). ZnPSe3 is the one that exhibited the lowest overpotential and the higher response to the light during photocurrent experiments in acidic media. For this reason among the crystals in this work it is the most promising for the photocatalyzed production of hydrogen.

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+ Mg2+ and Ca2+ while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.

Hydrogenation technology is an indispensable chemical upgrading process for converting the heavy feedstock into favorable lighter products. In this work a new kinetic model containing four hydrocarbon lumps (feedstock diesel gasoline cracking gas) was developed to describe the coal tar hydrogenation process the Levenberg–Marquardt’s optimization algorithm was used to determine the kinetic parameters by minimizing the sum of square errors between experimental and calculated data the predictions from model validation showed a good agreement with experimental values. Subsequently an adiabatic reactor model based on proposed lumped kinetic model was constructed to further investigate the performance of hydrogenation fixed-bed units the mass balance and energy balance within the phases in the reactor were taken into accounts in the form of ordinary differential equation. An application of the reactor model was performed for simulating the actual bench-scale plant of coal tar hydrogenation the simulated results on the products yields and temperatures distribution along with the reactor are shown to be good consistent with the experimental data.

Human health is a key pillar of modern conceptions of sustainability. Humanity pays a considerable price for its dependence on fossil-fueled energy systems which must be addressed for sustainable urban development. Public hospitals are focal points for communities and have an opportunity to lead the transition to renewable energy. We have reimagined the healthcare energy ecosystem with sustainable technologies to transform hospitals into networked clean energy hubs. In this concept design hydrogen is used to couple energy with other on-site medical resource demands and vanadium flow battery technology is used to engage the public with energy systems. This multi-generation system would reduce harmful emissions while providing reliable services tackling the linked issues of human and environmental health.