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Pt/Al 2 O 3 -coated Al foams were tested for the passive autocatalytic recombination of H 2. The characterisation of the washcoat surface confirmed the uniform distribution of Pt and Al 2 O 3 over the entire washcoat surface. Transmission electron microscopy results revealed a slight increase in particle size from 3.8 to 6.2 nm after prolonged reaction. High H 2 conversions of 57–89% are achieved and the catalyst activity is maintained for >480 h on stream. The performance of the foam-based catalyst bed is similar to that of plates but surpasses that of catalyst pellets. Temperatures recorded at the hottest spots on the foam surface reach a maximum of only 393 °C at the highest H 2 inflow. Computational fluid dynamics simulations were performed on the actual foam geometry obtained using computed tomography. The simulations demonstrate the importance of thermal radiation in the model. There is good agreement between results of experimental H 2 conversions and maximum combustion temperatures. [Display omitted] • Efficiency of the foam-, plate-supported and pellet catalysts were compared experimentally. • Pt/Al₂O₃ foams demonstrated rapid start-up behaviour and high catalytic activity. • Computed tomography and CFD methods were combined and velidated. • CFD simulations revealed the importance of accounting for thermal radiation model. • Results showed high H₂ conversion rates within the catalytic foam region. [ABSTRACT FROM AUTHOR]

This article adopts a reduced size design to construct a medium-sized model (1/15) of a three-dimensional parking garage, and studies the hydrogen release concentration distribution characteristics of hydrogen fuel cell vehicles under different operating conditions. To ensure the safety of the experimental process, helium gas with similar density was used as a substitute for hydrogen gas. The objective was to study the gas concentration distribution in the garage under different leakage flow rates and leakage areas. The impact of leakage flow rate and leakage area on the spatiotemporal distribution of helium concentration in a three-dimensional garage was elucidated. The experimental results indicate that the initial release rate of helium is a significant parameter influencing the stratification of helium concentration in space. If the release flow rate is excessive, the helium concentration will exhibit three distinct phases throughout the entirety of the leakage diffusion process: an initial rapid growth stage, a subsequent rapid decline stage, and finally, a gradual decline stage. The spatial configuration of a three-dimensional garage exerts a discernible influence on the vertical diffusion of helium concentration. The findings of this study can inform the design, construction, and layout of three-dimensional hydrogen sensors in garages, thereby promoting the safe use of hydrogen fuel cell vehicles. • Studied the diffusion law of hydrogen leakage in a three-dimensional garage. • Explored the influence of leakage area on the distribution characteristics of hydrogen gas in a three-dimensional garage. • Explored the influence of leakage flow rate on hydrogen distribution characteristics in both horizontal and vertical directions. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising alternative fuel due to its high energy density and carbon-free combustion. However, safe and widespread adoption requires effective hazard identification, assessment, and mitigation, including rapid hydrogen dispersion modeling for early risk mitigation. Data-driven modeling offers rapid predictive capabilities; however, such approaches are costly due to the need for vast amounts of high-quality or high-fidelity (HF) data. To this end, multi-fidelity (MF) modeling can fuse scarce HF data with abundant low-fidelity (LF) data for rapid HF predictions. In this work, we used helium as a surrogate light gas of hydrogen and developed a Bayesian regression-based MF model to predict the gas concentration in a semi-confined dispersion chamber at multiple locations for various operating conditions. The MF model predicts distributions of potential concentration values, allowing for uncertainty quantification and a statistical assessment of leakage risk. Both experimental and numerical approaches are used to generate datasets used in the current study. The experiment is designated as the HF model, serving as the ground truth with fewer data points. The numerical approach employing computational fluid dynamics (CFD) is designated as the LF model, with more data sets generated at a relatively lower cost. The MF model was trained on all LF data and a subset of the HF data. Good predictive performance is observed on the testing HF data, indicated by an R 2 value of 0.9, particularly for physical locations away from the leakage point. This study provides new pathways to rapidly assess hydrogen safety and mitigate early-stage risk with minimal HF data. [Display omitted] • A probabilistic model was developed to predict helium concentration in a semi-confined space by fusing datasets from low and high-fidelity helium dispersion models. • The model achieves an R 2 value of 0.9, with excellent predictive capabilities for locations far from the helium leakage source. • This study provides new pathways to rapidly assess hydrogen safety with sparse high-fidelity data. [ABSTRACT FROM AUTHOR]

Hydrogen safety for fuel cell vehicles (FCVs) should not be limited to their use process and accident scenarios. Their transportation should be a typical scenario, since it is an enclosed space and the carried vehicle has few failures. In this study, the path of hydrogen diffusion and the effect of hydrogen venting during the container transportation have been explored. An experiment of hydrogen leakage from an FCV inside a 40-foot container has been conducted and 8 sensors were used to detect hydrogen concentrations. The leaking hydrogen mainly spreads along the nearest wall to the top, and then diffuses to the distant area. Although the amount of leaking hydrogen is small (5 MPa, 61 L), there still exists large volume of flammable cloud inside. To exhaust the leaking hydrogen, vents must be installed. A computational fluid dynamics (CFD) model for ventilating a 20-foot container was developed and well validated. It was found that under conditions of a fully loaded hydrogen storage tank (70 MPa), high efficiency and complete venting cannot be achieved by a single vent at the same time. The side-wall vents positioned low can exhaust hydrogen quickly, but make hydrogen remain at the top and maximum concentration will be over 40 vol%, while high-positioned vents have the opposite effects. The combined method with both upper and lower vents is considered most effective, particularly when the driving state is considered. Through this configuration, all internal hydrogen can be removed within 120 s, and the maximum concentration can be reduced by 71% compared to conditions without ventilation. • An full-scale experiment of hydrogen release in an container carrying FCVs has been conducted. • A simple path of hydrogen diffusion with the obstruction of vehicles inside the container is plotted. • Ventilation effects of different venting methods at both parking and driving states have been investigated, and optimal ventilation types are achieved. • An 'inlet + outlet' ventilation type can facilitate the hydrogen exhausting with 40 km/h longitudinal winds. [ABSTRACT FROM AUTHOR]

Significant and concerning discrepancies exist between the hydrogen ignition data reported in scientific literature and that obtained from practical observations of various real-world applications. This includes data regarding ignition temperatures, minimum ignition energies and flammability limits. These inconsistencies raise critical questions about the reliability and applicability of the existing data. This paper aims to thoroughly investigate these discrepancies, providing a comprehensive and balanced perspective about the underlying causes. By examining the differences between theoretical predictions and practical outcomes, we highlight these gaps' potential risks and challenges. Furthermore, actionable strategies are proposed to rectify these issues, emphasizing the need for improved research methodologies, enhanced data accuracy, and better communication between scientists and practitioners. Our goal is to ensure that hydrogen ignition data is both reliable and applicable, ultimately contributing to safer and more efficient hydrogen utilization in various industries. • It investigates the discrepancies in reported and observed hydrogen properties. • It provides a comprehensive and balanced perspective on the underlying causes. • It proposed actionable strategies to rectify data discrepancy issues. • The current work contributes to safer and more efficient hydrogen utilization. [ABSTRACT FROM AUTHOR]

Hydrogen is regarded as a promising energy source for the future due to its clean combustion products, remarkable efficiency and renewability. However, its characteristics of low-ignition energy, a wide flammable range from 4% to 75%, and a rapid flame speed may bring significant explosion risks. Typically, accidental release of hydrogen into confined enclosures can result in a flammable hydrogen–air mixture with concentration gradients, possibly leading to flame acceleration (FA) and deflagration-to-detonation transition (DDT). The current study focused on the evolutions of the FA and DDT of homogenous/inhomogeneous hydrogen–air mixtures, based on the open-source computational fluid dynamics (CFD) platform OpenFOAM and the modified Weller et al.'s combustion model, taking into account the Darrieus–Landau (DL) and Rayleigh–Taylor (RT) instabilities, the turbulence and the non-unity Lewis number. Numerical simulations were carried out for both homogeneous and inhomogeneous mixtures in an enclosed channel 5.4 m in length and 0.06 m in height. The predictions demonstrate good quantitative agreement with the experimental measurements in flame-tip position, speed and pressure profiles by Boeck et al. The characteristics of flame structure, wave evolution and vortex were also discussed. [ABSTRACT FROM AUTHOR]

The operational cabin of hydrogen tube bundle containers (HTBCs) is susceptible to vibration and fatigue loads during transportation, which may result in hydrogen leakage and deflagration accidents. In this paper, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed to simulate the effects of leakage diameter, leakage pressure, leakage direction and position on hydrogen leakage and diffusion in the operational cabin of HTBCs. The results demonstrate that the formation of vortex recirculation zones leads to the accumulation of flammable gas cloud (FGC) in the operational cabin. The medium leakage diameter (1.5 mm) and higher leakage pressure (20 MPa, 35 MPa) cause the operational cabin to be filled with FGC within 5 s, requiring the operational cabin to be designed with no possible ignition source inside. In addition, when hydrogen leaks from the +Z direction, the sensor responds within 0.31 s, which is 1.7 s earlier than the response time in the -Z direction, indicating that the existing sensor layout cannot meet the requirements of fast response. When the leak position (L 3) is close to the vent, the FGC volume proportion at 2 s is 19.3 % and 15.88 % lower than that of L 1 and L 2 , respectively, indicating that the leak position close to the vent can effectively slow down the accumulation of FGC. The research results have implications for the safety design of operational cabin of HTBCs, the layout of hydrogen sensors and vents, and the emergency response measures for hydrogen leakage. [Display omitted] • Numerical simulation reveals hydrogen leakage and diffusion behavior of tube bundle containers during transport. • Vortex recirculation zones cause flammable gas cloud accumulation in operational cabins. • Medium leakage (1.5 mm) and high pressure can fill the cabin with flammable gas cloud in 5 s. • Leakage direction and position affect hydrogen sensor response time. • The addition of hydrogen sensors and vents can reduce the risk of explosion. [ABSTRACT FROM AUTHOR]

Even for short space flights, such as manned flights to the Moon back in the 60s, it became extremely obvious that electric batteries are completely unsuitable because of their huge mass needed to store the required supply of onboard energy. Therefore, already in the 60s of the last century, the USA and the USSR took the path of using a hydrogen storage system using hydrogen fuel cells. Solar-hydrogen energy systems for spacecraft reliably provide energy for carrying out various kinds of unscheduled work on board and for eliminating emergency situations. Surplus energy is constantly accumulated on board in the form of the chemical energy of cryogenic hydrogen. The article presents too the result of the development of a solar-hydrogen power supply system for spacecraft, the onboard network of which provides slow and fast processes. This paper delves into designing digital control systems for power conditioning devices on the example of charging-discharging device based on a boost DC-DC converter. The device was implemented to condition a storage battery by properly charging and discharging it. A technique for constructing a small signal model of the converter has been developed. This involves constructing a block diagram using the discontinuous switching functions and analog models of electrical circuit components. The transfer functions of the analog controllers for the two-loop subordinate control system were derived. Then the procedure of a bilinear z-transform to the given transfer functions was applied. As a result, the discrete transfer functions of the digital controllers were obtained. Realization both analog and digital controllers in Matlab Simulink confirmed their identical behavior and stability within the power converter. Experimental studies of the static and dynamic waveforms of the digital control system showed controllability and stability of the charging-discharging device for the storage battery in typical operating modes. Thus, the method of synthesizing digital control systems for energy converters is proved valid and applicable for designing new power conditioning devices within modern power supplies. [ABSTRACT FROM AUTHOR]

In recent years, there has been a significant increase in research on hydrogen due to the urgent need to move away from carbon-intensive energy sources. This transition highlights the critical role of hydrogen storage technology, where hydrogen tanks are crucial for achieving cleaner energy solutions. This paper aims to provide a general overview of hydrogen treatment from a mechanical viewpoint, and to create a comprehensive review that integrates the concepts of hydrogen safety and storage. This study explores the potential of hydrogen applications as a clean energy alternative and their role in various sectors, including industry, automotive, aerospace, and marine fields. The review also discusses design technologies, safety measures, material improvements, social impacts, and the regulatory landscape of hydrogen storage tanks and safety technology. This work provides a historical literature review up to 2014 and a systematic literature review from 2014 to the present to fill the gap between hydrogen storage and safety. In particular, a fundamental feature of this work is leveraging systematic procedural techniques for performing an unbiased review study to offer a detailed analysis of contemporary advancements. This innovative approach differs significantly from conventional review methods, since it involves a replicable, scientific, and transparent process, which culminates in minimizing bias and allows for highlighting the fundamental issues about the topics of interest and the main conclusions of the experts in the field of reference. The systematic approach employed in the paper was used to analyze 55 scientific articles, resulting in the identification of six primary categories. The key findings of this review work underline the need for improved materials, enhanced safety protocols, and robust infrastructure to support hydrogen adoption. More importantly, one of the fundamental results of the present review analysis is pinpointing the central role that composite materials will play during the transition toward hydrogen applications based on thin-walled industrial vessels. Future research directions are also proposed in the paper, thereby emphasizing the importance of interdisciplinary collaboration to overcome existing challenges and facilitate the safe and efficient use of hydrogen. [ABSTRACT FROM AUTHOR]

The issue of spontaneous ignition has become a bottleneck for hydrogen applications. This comprehensive review delves into the intricate mechanisms governing the spontaneous ignition of pressurized hydrogen released through tubes. Beginning with an exploration of fundamental concepts, including the properties of hydrogen and various theoretical frameworks, the study meticulously examines the development of diffusion ignition theory. Methodologically, both experimental and simulation approaches are scrutinized for their contributions to understanding this complex phenomenon. Moving deeper into the core of the investigation, the review dissects the spontaneous ignition mechanisms occurring inside pipes, unraveling the influence of different initial conditions as well as the impact of varying pipe structures. Subsequently, the review shifts its focus to the flame morphology at the pipe exit, analyzing combustion behavior, shock wave dynamics, flow structures, and the formation of jet flames, while exploring influential factors affecting combustion. Through a comprehensive synthesis of findings, this review provides valuable insights into the spontaneous ignition dynamics of pressurized hydrogen within tube systems, offering a foundation for future research and engineering applications in safety and energy sectors. • Introduced theories of self-ignition and development of diffusion ignition theory. • Summarized ignition mechanisms of pressurized hydrogen released inside pipes. • Summarized flame morphology at pipe exit based on vortex position. • Identified deficiencies in reviewed studies and areas needing further research. [ABSTRACT FROM AUTHOR]

In the active venting process of the burn pond, the hydrogen diffusion behavior underwater directly affects their uniformity on the water surface and the stability of the safety burning. A series of visualization experiments are conducted to assess the influence of disposal structure, flow rate, and water seal depth on the diffusion area and fountain height for rising plume formation. Helium is used as a substitute for hydrogen in the experiments. The study demonstrates that the plume structure is notably smaller in bubble cap mode compared to the nozzle mode, regardless of the conditions. This mode minimizes water surface fluctuation efficiently, making it ideal for constructing a disposal-array burn pond with multiple bubble cap units. Additionally, through dimensionless analysis, the study quantifies the parameters related to water surface stability with various venting conditions, thus establishing a foundation for the underwater active venting of hydrogen and other combustible gases. • Transition mechanism of underwater diffusion behavior is altered by the bubble cap. • The bubble cap mode effectively controls the stability of underwater venting. • Fluctuation degree of the water surface affects the gas distribution uniformity. • Dimensionless analysis quantifies the underwater venting behavior of disposal unit. [ABSTRACT FROM AUTHOR]

CFD-based numerical wave tank models are valuable tools for analyzing the nonlinear interaction between waves and structures. This paper aims to examine the deformation of high-order free surfaces near a vertical, surface-piercing fixed cylinder with various cross-sections under regular head waves, assuming no wave breaking. Additionally, the study investigates the effects of wavelength on wave evolution, nonlinear wave amplification, and the harmonics around the cylinder. The numerical analysis is performed using the CFD toolbox OpenFOAM. The comparison of numerical results for different cross-sections reveals the influence of corner ratio on lateral edge waves and highlights its significant impact on the nonlinear wave field around the cylinder, particularly for short incident waves. The numerical results indicate the important contribution of the cross-section shape together with the corner effect on the lateral edge waves and accordingly the nonlinear wave field surrounding the given column, which involves high harmonics wave amplification up to fourth. The reduction in corner ratio results in a reduction in maximum run-up height from 2.57 to 2.2 in short waves, while for the long waves, it is from 1.61 to 1.45. This research not only enhances our understanding of fluid–structure interactions but also has implications for the design and safety of hydrogen storage and transportation systems. Understanding dynamic pressures and structural responses is crucial for these applications. CFD simulations of wave–cylinder interactions are essential for designing and optimizing offshore hydrogen infrastructure. These simulations model how waves interact with cylindrical structures, such as wind turbine foundations, hydrogen production platforms, and storage tanks. Understanding these interactions is vital for ensuring the structural integrity, efficiency, and sustainability of offshore hydrogen facilities. [ABSTRACT FROM AUTHOR]

The paper describes the new principle of passive NPP safety systems designing, in which the natural circulation of working fluid or gas is replaced by forced circulation in order to increase it’s capacity. The energy required by the system is converted from the emergency process itself, which this system resists when performing a given safety function. The goal is to expand the variety and capacity of passive NPP safety systems in order to optimize and reduce costs of NPP power units with various types of reactors while increasing the safety level. The proposed technical solutions are based on the use of direct non-mechanical conversion of the energy, comprised in emergency process, to electricity, and then to mechanical energy of hydraulic machine for working medium moving in a forced circulation mode. To demonstrate the proposed principles, the following technical solutions have been considered: • new passive electrochemical hydrogen recombiner for NPPs with light water reactors. Application of new techniques allowed increasing the performance by weight of the recommended hydrogen simultaneously with increasing the hydrogen torch threshold, as well as other important characteristics; • passive emergency core cooling system for heavy liquid metal cooled reactors. Application of new techniques allowed increasing the core remove heat capacity in order to scale down the main equipment; • passive system for in-vessel core melt retention of Pressurized Water Reactors of high thermal capacity (more than 3000 MWe). Application of new techniques allowed increasing the system thermal capacity in order to be able to apply to high thermal power reactors like VVER-1000 and more.

Cryogenic hydrogen circulation system is a critical infrastructure of the China Spallation Neutron Source phase II project. Safety considerations related to hydrogen are paramount for the stable operation of the system. This study focuses on the cryogenic hydrogen circulation system within the context of the China Spallation Neutron Source phase II project and conducts a detailed investigation of hydrogen safety issues throughout the process. The operational modes and fault occurrence mitigation strategies of the cryogenic hydrogen circulation system are analyzed and discussed. Additionally, employing centralized layout, zoning management, and multiple barrier layers as guiding concepts for hydrogen safety design, the study addresses physical and interlocking control designs concerning hydrogen distribution, hydrogen venting, vacuum, hydrogen circulation pressure control, and hydrogen leakage. Drawing upon the successful experiences of the first-phase project, the hydrogen safety design of the cryogenic hydrogen circulation system in the China Spallation Neutron Source phase II project provides valuable insights for the development and optimization of hydrogen safety designs across various industrial domains. • Cryogenic hydrogen circulation system of CSNS-Ⅱ is introduced. • Principles and concepts of hydrogen safety in CSNS-Ⅱ are elucidated. • Operational modes and fault analysis of hydrogen circulation system are presented. • Physical and interlock control designs of hydrogen-related system are illustrated. [ABSTRACT FROM AUTHOR]

A reduction in greenhouse gases has become an inescapable requirement. An effective scenario for achieving carbon neutrality is to develop a hydrogen economy. Its success, however, requires strict control of the different processes involved in planned hydrogen chains. The energy chain considered in this paper is a stationary application which involves the production of hydrogen by electrolysis (a power-to gas process) and its combustion in gas turbine combined cycles to generate electricity (a gas-to-power process). In such applications, the need is twofold: (i) to control the risk of explosive atmospheres by performing safe gas detection in the presence of hydrogen and (ii) to secure the reliability of all chain processes using hydrogen-rich gases by achieving reliable analyses of these gases. This paper is dedicated to the development of hydrogen energy to decarbonize the thermal production of electricity. We will first describe the hydrogen chain that would best suit the power generation sector. Then, we will highlight the properties of hydrogen that are critical for its reliable operation. Finally, we will review the sensing technologies suitable for hydrogen-containing fuels. This review paper was published as part of a Joint Industrial Project (JIP) aimed at enabling the safe and reliable deployment of hydrogen energy. [ABSTRACT FROM AUTHOR]

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With the rapid development and application of hydrogen in the chemical and energy industry, the safety of hydrogen industrial facilities has been widely concerned. In this study, the safety of hydrogen accidently released from a high-pressure tube storage system (tube diameter:10 mm, storage tank volume:4 L) was explored experimentally. The combustion behavior of the transient hydrogen jet and explosion overpressure under self-ignition and electric spark induction were investigated. Besides, the explosion overpressure and jet flame evolution laws of the hydrogen cloud induced by the release of unsteady turbulent hydrogen jets into the open environment were analyzed. The results revealed that the peak value of hydrogen self-ignition explosion overpressure was higher than that of electric spark ignition overpressure. Compared with spark ignition, hydrogen self-ignition flame structures can be maintained for longer time. However, spark ignition at low release pressures was more likely to cause hydrogen ignition and explosion compared to self-ignition. Finally, the combustion behavior and potential hazards of the ignited free transient hydrogen jet under different ignition modes were analyzed. This study can provide a reference for the prevention and control of hydrogen explosion accidents in practice. • Hydrogen jet explosion can be induced by spark within 5D of the nozzle axis. • Comparing with spark ignition, self-ignition explosion had higher overpressure peak. • Self-ignition process was stable, but spark ignition was sensitive to the spark position. [ABSTRACT FROM AUTHOR]

HyResponder is a European Hydrogen Train the Trainer programme for responders. This paper describes the key outputs of the project and the steps taken to develop and implement a long-term sustainable train the trainer programme in hydrogen safety for responders across Europe and beyond. This FCH2 JU (now Clean Hydrogen Joint Undertaking) funded project has built on the successful outcomes of the previous HyResponse project. HyResponder has developed further and updated educational, operational, and virtual reality training for trainers of responders to reflect the state-of-the-art in hydrogen safety, including liquid hydrogen, and expand the programme across Europe and specifically within the 10 countries represented directly within the project consortium: Austria, Belgium, the Czech Republic, France, Germany, Italy, Norway, Spain, Switzerland, and the United Kingdom. For the first time, four levels of educational materials from fire fighter through to specialist have been developed. The digital training resources are available on the e-Platform (https://hyresponder.eu/e-platform/). The revised European Emergency Response Guide is now available to all stakeholders. The resources are intended to be used to support national training programs. They are available in 8 languages: Czech, Dutch, English, French, German, Italian, Norwegian and Spanish. Through the HyResponder activities, trainers from across Europe have undertaken joint actions which are in turn being used to inform the delivery of regional and national training both within and beyond the project. The established pan-European network of trainers is shaping the future in the important for inherently safer deployment of hydrogen systems and infrastructure across Europe and enhancing the reach and impact of the programme. • Responders across 10 European countries have been trained in hydrogen safety. • Translated teaching materials are available in 8 languages. • A unique operational training platform for responders has been extended. • Operational, virtual reality and educational training materials have been revised. • A revised European Emergency Response guide is available on an e-Platform. [ABSTRACT FROM AUTHOR]

An accurate determination of minimum ignition energy (MIE) is essential for assessing electrostatic hazards and characterising potential for occurrence of combustion in flammable mixtures. This is of utmost importance for hydrogen-air mixtures characterised by a MIE equal to 0.017 mJ, whereas conventional flammable gases are characterised by MIE typically higher than 0.1 mJ. The study aims at developing and validating a CFD three-dimensional model capable to simulate complex unsteady physical and chemical phenomena underlying capacitive discharge spark. The model accounts for the experimental apparatus details, including the effect of electrodes' gap and associated heat losses. The numerical approach accurately reproduced the experimental measurements of MIE for mixtures of hydrogen with air at initial temperature ranging from ambient (T = 288 K) to cryogenic (T = 123 K). Hydrogen concentration in air was included in the range 10–55% for tests at T = 288 K, and 20–60% for tests at T = 173 K and 123 K respectively. Simulations assess the impact of experimental characteristics and design, such as the electrodes' dimension, and numerical features on process dynamics, growth of the flame kernel and MIE predictions. • Development of a CFD 3D model simulating the phenomena underlying a discharge spark. • Inclusion of effect of conductive and radiative heat losses on the MIE predictions. • Validation against tests on H 2 -air mixtures at ambient and cryogenic temperatures. • Simulations provide insights into the process dynamics and flame kernel development. [ABSTRACT FROM AUTHOR]

Based on the hydrogen-helium similarity theory, the leakage experiments using helium instead of hydrogen can effectively reduce the risk of hydrogen deflagration, but the experimental results show that there is a large difference between the concentration of hydrogen and helium in initial period of leakage base on this theory. This paper focuses on leakage experiments under turbulent conditions in enclosed spaces. Based on the hydrogen-helium similarity theory, helium is used to replace hydrogen to find out the concentration of helium at multiple leakage speeds. A comparison is made between helium concentration values and hydrogen concentration values, and a polynomial correction algorithm is used to shrink the difference. The results show that this correction method can reduce the concentration average error between the helium and the hydrogen from 14.06% to 7.94% for the Reynolds number range of 3500–9500. Therefore, a polynomial fitting algorithm based on this theory can improve the accuracy of experiment using helium instead of hydrogen. • Analyzed the accuracy of the hydrogen helium similarity theory under some working conditions in the experiment. • Proposed a correction method for helium concentration, which can improve the accuracy of using helium instead of hydrogen in experiments. • The improvement effect of using this correction method is significant. • This study can offer support in the formulation of regulations pertaining to hydrogen safety development. [ABSTRACT FROM AUTHOR]

Safety issues such as unintentional hydrogen releases in confined spaces limit the widespread promotion of hydrogen terminal applications, especially hydrogen fuel cell vehicles (HFCVs). This paper aims to perform a systematical numerical investigation of hydrogen leakage and dispersion in a full-scale underground garage, and the effects of smoke barriers are also considered. Four sets of smoke barriers with different heights, 0.1–0.7 m with 0.2 m increment, are installed below the ceiling, and three different partition types are set. The results show that smoke barriers can reduce flammable areas but increase local hydrogen concentrations. As the height of the smoke barrier increases, its obstruction to hydrogen dispersion on the ceiling is enhanced, making it easier for hydrogen to accumulate in the area and increasing the hydrogen cloud thickness. The hydrogen concentration in the horizontal direction showed a stair-like stratification phenomenon and decreased with increasing horizontal distance from the leak point. When the height of the smoke barrier is below 0.7 m, a larger partition area is safer. This study can provide new insights into the accidental hydrogen leakage and dispersion issues in confined spaces, in particular the effects of smoke barriers, and lay a theoretical foundation for the safety design of enclosed garages for HFCVs. [Display omitted] • Typical H 2 dispersion in a full-scale underground garage is numerical investigated. • Effects of smoke barriers on hydrogen dispersion is studied. • Smoke barriers can reduce flammable areas but increase local hydrogen concentrations. • Higher smoke barriers result in thicker flammable hydrogen clouds. • Larger partition area is found to be safer for 0.5 m barrier height. [ABSTRACT FROM AUTHOR]

Liquid hydrogen storage is an important way of hydrogen storage and transportation, which greatly improves the storage and transportation efficiency due to the high energy density but at the same time brings new safety hazards. In this study, the liquid hydrogen leakage in the storage area of a hydrogen production station is numerically simulated. The effects of ambient wind direction, wind speed, leakage mass flow rate, and the mass fraction of gas phase at the leakage port on the diffusion behavior of the liquid hydrogen leakage were investigated. The results show that the ambient wind direction directly determines the direction of liquid hydrogen leakage diffusion. The wind speed significantly affects the diffusion distance. When the wind speed is 6 m/s, the diffusion distance of the flammable hydrogen cloud reaches 40.08 m, which is 2.63 times that under windless conditions. The liquid hydrogen leakage mass flow rate and the mass fraction of the gas phase have a greater effect on the volume of the flammable hydrogen cloud. As the leakage mass flow rate increased from 5.15 kg/s to 10 kg/s, the flammable hydrogen cloud volume increased from 5734.31 m3 to 10,305.5 m3. The installation of a barrier wall in front of the leakage port can limit the horizontal diffusion of the flammable hydrogen cloud, elevate the diffusion height, and effectively reduce the volume of the flammable hydrogen cloud. This study can provide theoretical support for the construction and operation of hydrogen production stations. [ABSTRACT FROM AUTHOR]

This review explores recent advancements in hydrogen gas (H2) safety through the lens of artificial intelligence (AI) techniques. As hydrogen gains prominence as a clean energy source, ensuring its safe handling becomes paramount. The paper critically evaluates the implementation of AI methodologies, including artificial neural networks (ANN), machine learning algorithms, computer vision (CV), and data fusion techniques, in enhancing hydrogen safety measures. By examining the integration of wireless sensor networks and AI for real-time monitoring and leveraging CV for interpreting visual indicators related to hydrogen leakage issues, this review highlights the transformative potential of AI in revolutionizing safety frameworks. Moreover, it addresses key challenges such as the scarcity of standardized datasets, the optimization of AI models for diverse environmental conditions, etc., while also identifying opportunities for further research and development. This review foresees faster response times, reduced false alarms, and overall improved safety for hydrogen-related applications. This paper serves as a valuable resource for researchers, engineers, and practitioners seeking to leverage state-of-the-art AI technologies for enhanced hydrogen safety systems.

This study compares four computational fluid dynamics (CFD) models, i.e. k-ε, RSM, SAS, and LES, to simulate temperature non-uniformity during hydrogen tank refuelling. Three grids with a total number of control volumes of 64k, 363k, and 2.9 M were used. The maximum dimensionless wall distances, y + , were 80, 5 and 2.5, respectively. The predictive capability of the models was assessed by recommended statistical indicators using ten thermocouple locations during 620 s of the experiment. The comparative analysis demonstrated a better predictive capability of temperature non-uniformity and stratification by the LES model and a shorter simulation time. It is concluded that meshes with y + larger than 80 would overpredict the average hydrogen temperature while meshes with y + < 5 provide a good simulation accuracy. The results underline the importance of the turbulence model choice and the numerical grid resolution for proper prediction of temperature non-uniformity during hydrogen tank refuelling. • Comparative analysis of k-ε, RSM, SAS, and LES models in refuelling simulations. • Three meshes are studied to understand their effect on model predictive capability. • The performance of the models is evaluated by recommended statistical indicators. • LES model is the fastest and most accurate in predicting temperature non-uniformity. [ABSTRACT FROM AUTHOR]

This review explores recent advancements in hydrogen gas (H2) safety through the lens of artificial intelligence (AI) techniques. As hydrogen gains prominence as a clean energy source, ensuring its safe handling becomes paramount. The paper critically evaluates the implementation of AI methodologies, including artificial neural networks (ANN), machine learning algorithms, computer vision (CV), and data fusion techniques, in enhancing hydrogen safety measures. By examining the integration of wireless sensor networks and AI for real-time monitoring and leveraging CV for interpreting visual indicators related to hydrogen leakage issues, this review highlights the transformative potential of AI in revolutionizing safety frameworks. Moreover, it addresses key challenges such as the scarcity of standardized datasets, the optimization of AI models for diverse environmental conditions, etc., while also identifying opportunities for further research and development. This review foresees faster response times, reduced false alarms, and overall improved safety for hydrogen-related applications. This paper serves as a valuable resource for researchers, engineers, and practitioners seeking to leverage state-of-the-art AI technologies for enhanced hydrogen safety systems. [ABSTRACT FROM AUTHOR]

The global transition toward decarbonization and the Paris Agreement's zero-carbon target has led to increased interest in secondary energy sources. Hydrogen, with its high efficiency, cleanliness, and diverse storage forms, has emerged as a promising alternative fuel. However, the flammability and explosiveness of hydrogen pose safety concerns, limiting its widespread development. This study focuses on hydrogen distribution and application safety issues, aiming to identify gaps and propose recommendations. A comprehensive document review of safety standards and best practices was conducted, highlighting the need for tailored RCS and safety measures. The paper focuses on maritime and land-based hydrogen transportation, as well as its application in Hydrogen Refuelling Stations. By analyzing accident cases and existing literature, this research provides insights into the regulatory landscape and suggests measures to enhance safety practices in the hydrogen energy sector. The findings serve as a valuable reference for establishing a robust legal framework to promote the growth and safety of the hydrogen industry. [ABSTRACT FROM AUTHOR]

As the construction of hydrogen stations and other hydrogen-related facilities progresses, it becomes increasingly crucial for safety designs to account for scenarios where leaked hydrogen might ignite. Since a hydrogen flame is usually invisible, detection must rely on radiative heat or temperature. While it is possible to predict accurate radiative heat flux from a high pressure hydrogen jet flame through detailed numerical calculations of hydrogen combustion with its radiation, the objective of this study is to provide a simpler and more accurate prediction method. Previous experimental data of radiative heat flux, Q r from high pressure hydrogen jet flames were compiled, and a simple experimental equation Q r = 1463.3 (L o / L f) − 2.32 was derived, where L f and L o represent the flame length and the distance perpendicular to the flame axis from the midpoint of the flame length to the observer, respectively. Radiative heat fluxes were computed through detailed numerical simulations using three types of water vapor radiation models: Goody's narrow random band model, the exponential broad band model by Edward and Elsasser's narrow regular band model. The temperature and water vapor partial pressure distributions obtained from numerical simulations were used as input conditions. The results were found to be in good agreement with the experimental equation. Moreover, a simple diagram representing the radiative heat flux from a hydrogen flame was derived using the method of cylinder-like approximation. The results of this study show that if the hydrogen pressure and leakage aperture diameter are given, the radiative heat flux at a certain distance can be predicted with high accuracy. Additionally, the average value of emissivity for the hydrogen diffusion flame was found to be on the order of 0.03. • Experimental data of radiative heat from hydrogen flame. • Wide range of hydrogen release conditions of Pressure 0.5–82 MPa, aperture 0.2–10 mm. [ABSTRACT FROM AUTHOR]

The present study examines the effect of storage conditions on the characteristics of cryogenic hydrogen jets released into the atmosphere, relevant to an accidental leakage scenario during storage or transportation. The compressible Reynolds-Averaged Navier–Stokes equations, coupled with the Peng–Robinson equation of state for hydrogen-air mixtures, are solved for a range of operating conditions (storage pressures from 3 – 7 bar and storage temperatures of 50 – 70 K). Flow structures in the near-orifice and self-similar regions are analysed, showing that the presence of shock waves creates conditions favourable for possible condensation of hydrogen and air. In the self-similar region, decay laws based on the shock exit conditions are proposed, demonstrating a slower decay of centreline temperature in comparison to hydrogen concentration and velocity. Additionally, a universal relationship between the centreline mole fraction of hydrogen and temperature is observed, explained using an adiabatic mixing model. [Display omitted] • Numerical simulations of cryogenic hydrogen jet dispersion are performed. • Shock waves in the near-orifice region create conditions conducive to condensation of air. • Scaling of far-field flow quantities using shock exit conditions is more appropriate than using orifice exit conditions. • A universal relationship between the centreline mole fraction of hydrogen and temperature is found. • The found universal relationship can be explained by considering adiabatic mixing between hydrogen and air. [ABSTRACT FROM AUTHOR]

Hydrogen, as a promising energy vector, can cause an explosion or even a detonation due to its unique physical and chemical properties. Water spray is an ideal mitigant for detonations, because of its multiple benefits. The one-dimensional Zel'dovich–von Neumann–Döring (ZND) structure and multi-dimensional detonation cellular structure are introduced. Effectiveness of explosion inhibition by water sprays is linked with the droplet characteristics (diameter, concentration, spray or cloud size) and shock intensity (pressure or Mach No). The mitigation effect can be characterized by the momentum or heat transfer by quasi-steady drag. Moreover, gas-droplet two-phase detonation structures are clarified. Analyses of the mean structures show that mass, momentum, and energy transfer alter the hydrodynamic thickness. Droplet breakup and evaporation occur behind the leading shock. The peak pressure trajectories of the detonation wave are influenced by the gas equivalence ratio, water droplet concentration, and droplet size. Parametric studies on the water spray detonation further provide a guidance for the detonation inhibition. Finally, transferring mass, heat, and momentum between phases can mitigate explosions and detonations, reducing flame reaction rates and shock intensity. • Parametric studies on mitigating explosions and detonations are discussed. • Detonation front structures of gas-droplet mixtures are initially clarified. • Peak pressure trajectories of the unsteady detonations are analyzed. • Hydrogen hazard mitigation mechanisms are first summarized. • Indications of research gaps for future investigations are presented. [ABSTRACT FROM AUTHOR]

In recent literature, aqueous formate/bicarbonate has been proposed as a safer alternative hydrogen storage system under normal operating conditions. In the present work, a preliminary quantitative risk assessment is presented for the first time on a standard tank for hydrogen storage containing aqueous formate mixture invested by an external fire. The results are compared to compressed hydrogen tanks at 350 bar as a benchmark. Frequency and consequence analysis were used to build risk maps. Results show that aqueous formate storage is intrinsically safer in the case of catastrophic failure of the vessel, due to the presence of water in the system as well as in the case of continuous release from safety valves, because of the lower operating pressure required in the storage vessel. [Display omitted] • Aqueous formate mixtures are an intrinsically safer hydrogen storage technology. • Water can prevent ignition and reduce thermal radiation in case of fires. • Smaller areas are affected by accidents compared to traditional pressurized H 2. • Water can also drastically reduce risks in the case of confined explosions. [ABSTRACT FROM AUTHOR]

The paper is devoted to the comparative analysis of different CFD techniques used to solve the problem of high-pressure hydrogen release into the air. Three variations of a contemporary low-dissipation numerical technique (CABARET) are compared with each other and a conventional first-order numerical scheme. It is shown that low dissipation of the numerical scheme defines better resolution of the contact surface between released hydrogen and ambient air. As a result, the spatial structures of the jet and the reaction wave that arise during self-ignition are better resolved, which is useful for predicting the local effects of high-pressure hydrogen release. At the same time, the dissipation has little effect on the induction delay, so critical conditions of self-ignition can be reliably reproduced even via conventional numerical schemes. The test problem setups formulated in the paper can be used as benchmarks for compressible CFD solvers. [ABSTRACT FROM AUTHOR]

A reasonable inflating strategy must be developed for filling an onboard hydrogen storage tank with hydrogen gas. The inflow hydrogen temperature has always been a constant value in filling cases. However, in our opinion, the optimal inflow hydrogen temperature is not supposed to be a fixed value but a value that constantly changes and adjusts with filling time, i.e., the inflow hydrogen temperature is a function of the filling time. How to determine this functional relationship is a critical problem to be addressed. Herein, an approach is introduced. A dual-zone model is presented to research the thermal effect during the process of charging hydrogen storage tanks. Based on the numerical results of the dual-zone model, the charging process was divided into three stages, allowing us to obtain data for 1331 filling cases. Then, a back propagation (BP) neural network model was built to analyze the data, and the implicit relationship between the inflow hydrogen temperatures and maximum hydrogen temperature pressure could be deduced. With this implicit relationship, the critical values of the inflow hydrogen temperatures can be obtained from the critical situation. Suppose the inflow hydrogen temperatures in a practical case are higher than the critical values. In that case, the highest hydrogen temperature in the tank will exceed the limited safety value of 358 K. In contrast, if the inflow hydrogen temperatures are lower than the critical values, then more energy will be needed to precool the inlet hydrogen temperature. Thus, theoretically, the critical inflow hydrogen temperatures should be at their optimal values. [ABSTRACT FROM AUTHOR]

Objective In order to improve the infrastructure of the hydrogen energy industry chain and identify the causes of fire and explosion accidents in vehicle hydrogen refueling stations, the prevention and control measures are put forward for fire and explosion accidents so as to ensure the safe and sustainable development of vehicle hydrogen refueling stations and improve the public's trust in their safety prevention and control. Methods Using the theory of accident causation the essence of the accident is revealed. The hazard sources of fire and explosion accidents in vehicle hydrogen refueling stations are systematically analyzed from the perspective of unsafe state of energy substances energy carriers, things and unsafe behaviors of people. An accident tree map is established with the fire and explosion accidents of hydrogen refueling stations as the top event and targeted prevention and control strategies are proposed. Results Firstly, the proportion of basic events in the unsafe state of fire and explosion in the hydrogen refueling stations is the largest (52%). Secondly. The minimum set of 350 sets that may cause fire and explosion in hydrogen refueling stations and 4 minimum sets to avoid fire and explosion accidents are obtained. Thirdly, without considering the probability of basic event occurrences, five basic events are revealed to have high structural importance including poor ventilation alarm device failure, detector failure, safety valve failure and automatic brake system failure. Conclusions The theory of accident causes can be used to identify the hazard sources of hydrogen refueling stations scientifically and comprehensively. Accident tree system is adopted to analyze the importance of the basic event structure, and the normal operation of protective measures is the key control point to reduce fire and explosion accidents, which can serve as a theoretical basis for the formulation of relevant risk prevention and control measures for the construction and operation of hydrogen refueling stations. [ABSTRACT FROM AUTHOR]

In this paper, a direct cooling pipe for hydrogen inside the marine hydrogen storage cylinder (HSC) was designed, and the cooling pipe was simulated and analyzed under different cooling structures and different cooling fluids using ANSYS(Fluent) 2022 R2. The simulation results show that the effect of different cooling fluids on the temperatures were nearly the same. The heat transfer coefficients, however, of various fluids were different, and the cooling temperature was also different after cooling for the same time. The cooling structures mainly affect the cooling rate of the hydrogen due to the contact area with hydrogen inside the HSC. Among the three structures investigated in this study, the cooling capacity of the spiral layout was increased by 0.85 % and 0.63 %, respectively, compared to the rectangular and wavy layout. The rectangular layout has the certain cooling effect, however, in comparison to the spiral tube structure, it has too many corners, which increases the hindering effect on the flow of cooling medium inside the tubes and affects the cooling efficiency. The wavy layout has the largest contact area, but it has the problems of uneven cooling and occupying a large amount of hydrogen storage space. Among the three structures, comprehensively speaking, the spiral layout is considered to be the optimal. The optimal performance parameters were determined by comparing the simulation results of the three layouts during cooling process with hydrogen charging being performed. The results show that the cooling pipe can achieve the hydrogen temperature to be controlled within 358 K before the hydrogen pressure in the HSC reaches 70 MPa, and the maximum temperature is 336.07 K was obtained after the completion of hydrogen filling. This paper gives technical information for optimizing the thermal performance and safety of the hydrogen fueling system.

The development of reliable and longevous infrastructures and structural components is the key for the implementation of a hydrogen economy that is currently enjoying unprecedented political and research momentum due to the globally strong demand for clean energy. This is, however, strongly impeded by the risk and concerns of hydrogen embrittlement (or hydrogen-induced degradation in mechanical properties) that generally exists in almost all metallic materials. Structural components and materials operated in the hydrogen production-transport-storage-usage chain can be subjected to a very wide range of temperature, environmental and loading scenarios, which will essentially trigger different hydrogen embrittlement responses and even different embrittling mechanisms. It is thus important to have a systematic assessment and discussion of hydrogen embrittlement behavior of different materials at different testing conditions, which is the focus of the presented review. Here we cover the typical materials (mainly metallic materials) that have been used or planned to be used in the fields of hydrogen energy. We first briefly summarize the current understanding of fundamental hydrogen embrittlement mechanisms in metallic materials and the research progress in recent years. Then we analyze and discuss the hydrogen -induced damage phenomenon in typical materials used in the field of high-pressure hydrogen transport and storage. In addition to room-temperature hydrogen embrittlement behavior, the hydrogen embrittlement phenomenon of some alloys at elevated and cryogenic temperatures is also reviewed, with the aim to provide some guidelines of material selection and design in developing fields such as hydrogen gas turbines and long-flight-duration hydrogen powered aircraft. Finally, the current challenges in the study of hydrogen embrittlement are identified and discussed to guide future research efforts.

Hydrogen is regarded as a promising energy source for the future due to its clean combustion products, remarkable efficiency and renewability. However, its characteristics of low-ignition energy, a wide flammable range from 4% to 75%, and a rapid flame speed may bring significant explosion risks. Typically, accidental release of hydrogen into confined enclosures can result in a flammable hydrogen–air mixture with concentration gradients, possibly leading to flame acceleration (FA) and deflagration-to-detonation transition (DDT). The current study focused on the evolutions of the FA and DDT of homogenous/inhomogeneous hydrogen–air mixtures, based on the open-source computational fluid dynamics (CFD) platform OpenFOAM and the modified Weller et al.’s combustion model, taking into account the Darrieus–Landau (DL) and Rayleigh–Taylor (RT) instabilities, the turbulence and the non-unity Lewis number. Numerical simulations were carried out for both homogeneous and inhomogeneous mixtures in an enclosed channel 5.4 m in length and 0.06 m in height. The predictions demonstrate good quantitative agreement with the experimental measurements in flame-tip position, speed and pressure profiles by Boeck et al. The characteristics of flame structure, wave evolution and vortex were also discussed.

In recent years, there has been a significant increase in research on hydrogen due to the urgent need to move away from carbon-intensive energy sources. This transition highlights the critical role of hydrogen storage technology, where hydrogen tanks are crucial for achieving cleaner energy solutions. This paper aims to provide a general overview of hydrogen treatment from a mechanical viewpoint, and to create a comprehensive review that integrates the concepts of hydrogen safety and storage. This study explores the potential of hydrogen applications as a clean energy alternative and their role in various sectors, including industry, automotive, aerospace, and marine fields. The review also discusses design technologies, safety measures, material improvements, social impacts, and the regulatory landscape of hydrogen storage tanks and safety technology. This work provides a historical literature review up to 2014 and a systematic literature review from 2014 to the present to fill the gap between hydrogen storage and safety. In particular, a fundamental feature of this work is leveraging systematic procedural techniques for performing an unbiased review study to offer a detailed analysis of contemporary advancements. This innovative approach differs significantly from conventional review methods, since it involves a replicable, scientific, and transparent process, which culminates in minimizing bias and allows for highlighting the fundamental issues about the topics of interest and the main conclusions of the experts in the field of reference. The systematic approach employed in the paper was used to analyze 55 scientific articles, resulting in the identification of six primary categories. The key findings of this review work underline the need for improved materials, enhanced safety protocols, and robust infrastructure to support hydrogen adoption. More importantly, one of the fundamental results of the present review analysis is pinpointing the central role that composite materials will play during the transition toward hydrogen applications based on thin-walled industrial vessels. Future research directions are also proposed in the paper, thereby emphasizing the importance of interdisciplinary collaboration to overcome existing challenges and facilitate the safe and efficient use of hydrogen.

This study addresses challenges associated with hydrogen's physio-chemical characteristics and the need for safety and public acceptance as a precursor to the emerging hydrogen economy. It highlights the gap in existing literature regarding lessons learned from events in the green hydrogen production value chain. The study aims to use the documented lessons learned from previous hydrogen-related events to assist in enhancing safety measures and to guide stakeholders on how to avoid and mitigate future hydrogen-related events. Given the potential catastrophic consequences, robust safety systems are essential for hydrogen economy development. The work underscores the importance of human and operational factors as root causes of these events. The paper recommends establishing a specialized hydrogen-related event database to support risk assessment and risk mitigation, thus catering to the growing hydrogen industry's needs, and facilitating quick access to critical information for stakeholders in the private and public sectors. • 82 hydrogen-only events were identified from available databases. • From the identified hydrogen events, lessons learned are defined and recommendations provided. • Cause identification of events that could result in damaging consequences. • Maintenance operations, poor process management and human error are major causes of events. • Main value chain components related to hydrogen events are identified. [ABSTRACT FROM AUTHOR]

Premixed hydrogen-air laminar flames with equivalence ratios ranging from 0.32 to 2.68 adopt different shapes during propagation in a gap (from 1. 5 mm to 4. 2 mm) between two plates. Thermodiffusive and Darrieus–Landau instabilities are visible for lean mixture while Darrieus–Landau is visible at higher equivalent ratio. Using for the first time simultaneous schlieren visualisation in this configuration, we were able to make two important observations: (i) either symmetric or asymmetric shapes are observed and quantified within the gap as a function of equivalence ratio and gap thickness; (ii) 3D flame surface for unstable laminar flame was estimated. These results validate (or invalidate) the quasi-2D assumptions made in Hele-Shaw cells. Linear stability analysis allowed us to find an a priori criteria differentiating symmetric and asymmetric cases. Finally, curvature effect on flame speed enhancement relative to surface amplification is estimated for unstable hydrogen-air laminar flames. This experimental 3D amplification factor provides means to take into account instabilities effect on large scale turbulent models. • The first quantification of the asymmetry factor in Hele-Shaw cells is presented. • Asymmetric cases may occur when the channel gap exceeds the cut-off wavelength. • The curvature between the plates results in an increase of the 2D flame surface by 25%–50% • For the first time, we have estimated the 3D wrinkling factor for unstable flames. • Amplification factor measurements show values greater than one for lean H2 mixture. [ABSTRACT FROM AUTHOR]

This study evaluates an open-source explosion solver, PDRFoam, which is based on the Porosity/Distributed Resistance (PDR) approach. In this approach, only large-scale effects are numerically resolved, and small-scale effects are modelled semi-analytically—making explosion modelling at large scales economical. We evaluate the PDRFoam against experiments from the Hydrogen Safety in Energy Applications (HySEA) project. We consider different types of obstacles and different concentrations of hydrogen for the evaluation. PDRFoam predicts quantities like maximum overpressure, time trace of overpressure, impulse, and average rate of pressure rise—these are compared with experimental observations. We examine the external domain influence and sensitivity of the results to the different grid sizes. In general, PDRFoam gives conservative results, and it significantly overpredicts overpressure for 24% hydrogen concentration. It can model various stages of flame development, including flame folding and wrinkling; thus can become an open-source alternative in explosion modelling studies. • Evaluation of an open source CFD solver PDRFoam for modelling hydrogen explosions. • Predictions are compared to venting-through-the-doors experiments from HySEA. • Overpressure, mean pressure rise rate, impulse and flame arrival time are reported. • Sensitivity of the results to the different numerical mesh and domain are studied. • Following model evaluation protocol, predictions are in agreement with experiments. [ABSTRACT FROM AUTHOR]

Existing natural gas pipelines can facilitate low-cost, large-scale hydrogen transportation and storage, but hydrogen may entail safety challenges. These challenges stem from hydrogen's different properties compared to natural gas, such as higher ignition probability, different flame behavior, and potential for hydrogen embrittlement. Although risk assessments for hydrogen pipelines are increasing, the impact of hydrogen on the risk of third-party excavation damage (TPD), the major cause of pipeline incidents in the U.S., has received little attention. This work presents the SHyTERP model for Safe Hydrogen Transportation and Excavation Risk Prevention for Pipelines. The model incorporates causal models, excavation damage and pipeline failure statistics, and validated physical models of hydrogen and natural gas release and jet flame behavior. Through four case studies, the model compares the TPD risks of hydrogen and natural gas pipelines, offering insights and recommendations for the safe implementation of hydrogen in existing pipelines. • Presents a new model, SHyTERP, which assesses excavation risk in hydrogen pipelines via Bayesian networks. • SHyTERP integrates multi-source data relevant to modeling natural gas and hydrogen pipeline excavation risk. • SHyTERP identifies key risk drivers for excavation damage in hydrogen and natural gas pipelines. • SHyTERP offers timely safety insights and recommendations for managing risk for hydrogen and natural gas pipelines. • SHyTERP provides a baseline for future pipeline risk assessments. [Display omitted] [ABSTRACT FROM AUTHOR]

The technology for obtaining bio hydrogen from the micro algae Chlorella vulgaris is described, the stage of biomass accumulation is intensified, the effect of copper addition on the growth of Chlorella is studied, a new, optimized composition of the Tamiya medium was developed using mathematical modeling, the effect of the light spectrum, carbon dioxide content in the gas-air mixture and Chlorella cultivation was carried out in a continuous mode, which made it possible to greatly accelerate the accumulation of cells. Despite significant achievements in the field of biotechnology, hydrogen accumulation with the help of algae is still economically inexpedient, although the need for research in this direction is associated with the depletion of renewable energy sources, environmental problems and the increase in energy prices. Briefly, the main directions for the competitiveness of the technology are given; one of the vectors for solving this problem is obtaining bio-hydrogen during the metabolism of Chlorella, the cultivation of which is characterized by a number of advantages. The attractiveness of using Chlorella biomass for bio fuels is due to the high rate of biomass reproduction, ease of cultivation, and the use of carbon dioxide and small amounts of mineral salts, agricultural waste or sewage to ensure the growth of Chlorella. Chlorella vulgaris is able to increase the amount of its biomass dozens of times per day, while it takes months or even years for terrestrial plants. [ABSTRACT FROM AUTHOR]

A compact wireless near-field hydrogen gas sensor is proposed, which detects leaking hydrogen near its source to achieve fast responses and high reliability. A semiconductor-type sensing element is implemented in the sensor, which can provide a significant response in 100 ms when stimulated by pure hydrogen. The overall response time is shortened by orders of magnitude compared to conventional sensors according to simulation results, which will be within 200 ms, compared with over 25 s for spatial concentration sensors under the worst conditions. Over 1 year maintenance intervals are enabled by wireless design based on the Bluetooth low energy protocol. The average energy consumption during a single alarm process is 153 μJ/s. The whole sensor is integrated on a 20 × 26 mm circuit board for compact use. [ABSTRACT FROM AUTHOR]

There has been an increase in environmental degradation associated with the use of fossil fuels in an attempt to meet the ever-increasing demand for electricity. Therefore, alterative renewable energy sources have garnered the attention of many researchers globally; hydrogen is an important example due to its eco-friendly nature. For hydrogen to be used as an energy source, it has to first be compressed. The explosion of high-pressure hydrogen vessels has been the driver of most accidents associated with its use. To prevent explosions, thermally activated pressure relief devices (TPRDs) are used to release hydrogen. The TPRD release orientations in a tunnel, which is a confined space, were investigated in this study based on a high-pressure release of hydrogen. In addition, we also propose an evacuation and safety protocol in the event of such an accident. In addition, the dynamics associated with the release of hydrogen were analyzed based on vehicle type. We found that in passenger cars and buses, hydrogen is released from the bottom and top, respectively. The dispersion range in this study was simulated based on a hydrogen concentration of 4%, in which air currents, including those from jet fans in the tunnel, are considered. The results confirm that passenger cars are barely affected by the jet fan airflow, and backward release facilitates evacuation and secures a safety zone more effectively compared with vertical emission. Meanwhile, upward releases were significantly affected by the jet fan. Overall, release in the airflow direction, regardless of the tunnel location, was confirmed to be effective in the context of evacuation and securing safety zones for buses. • Consequence analysis for Thermally-activated Pressure Relief Devices of HFCVs. • Thorough CFD simulations to help the decision-making for emergency responders. • Open space and confined space hazards comparison for different vehicle types. • Open space and confined space hazards comparison for different TPRD release angles. [ABSTRACT FROM AUTHOR]