Safety

With the advancement of Fuel Cell Vehicles (FCVs) detecting hydrogen leaks is critically important in facilities such as hydrogen refilling stations. Despite its significance the dynamic response performance of hydrogen sensors in confined spaces particularly under ceilings has not been comprehensively assessed. This study utilizes a catalytic combustion hydrogen sensor to monitor hydrogen leaks in a confined area. It examines the effects of leak size and placement height on the distribution of hydrogen concentrations beneath the ceiling. Results indicate that hydrogen concentration rapidly decreases within a 0.5–1.0 m range below the ceiling and declines more gradually from 1.0 to 2.0 m. The study further explores the attenuation pattern of hydrogen concentration radially from the hydrogen jet under the ceiling. By normalizing the radius and concentration it was determined that the distribution conforms to a Gaussian model akin to that observed in open space jet flows. Utilizing this Gaussian assumption the model is refined by incorporating an impact reflux term thereby enhancing the accuracy of the predictive formula.

Lead–acid batteries are widely used in modern battery-powered ships. During the charging process of lead–acid batteries hydrogen gas is released which poses a potential hazard to ship safety. To address this this paper first establishes a turbulent flow model for hydrogen deflagration. Then using FDS6.7.9 software simulations of hydrogen deflagration are conducted and a simulation model of the ship’s cabin is constructed. The changes in temperature and pressure during the hydrogen deflagration process in the ship’s cabin are analyzed and the evolution process of hydrogen deflagration in the ship’s cabin is derived. Hydrogen deflagration poses a significant threat to the fire safety of battery-powered ships. Additionally a comparative analysis of hydrogen deflagration under different hydrogen concentrations is performed. It is concluded that battery-powered ships using lead–acid batteries should pay attention to controlling the hydrogen concentration below 4%.

As a clean and renewable energy carrier hydrogen is one of the most promising alternative fuels. Cryogenic compressed hydrogen can achieve high storage density without liquefying hydrogen which has good application prospects. Investigation of the safety problems of cryogenic compressed hydrogen is necessary before massive commercialization. The present study modeled the instantaneous flow field using the Large Eddy Simulation (LES) for cryogenic (50 and 100 K) underexpanded hydrogen jets released from a round nozzle of 1.5 mm diameter at pressures of 0.5-5.0 MPa. The simulation results were compared with the experimental data for validation. The axial and radial concentration and velocity distributions were normalized to show the self-similar characteristics of underexpanded cryogenic jets. The shock structures near the nozzle were quantified to correlate the shock structure sizes to the source pressure and nozzle diameter. The present study on the concentration and velocity distributions of underexpanded cryogenic hydrogen jets is useful for developing safety codes and standards.

Cryogenic liquid hydrogen offers a promising solution for achieving high-density hydrogen storage and efficient on-site distribution. However the potential hazards associated with hydrogen leakages necessitate thorough investigations. This research aims to model cryogenic hydrogen release from circular and high aspect ratio (HAR) nozzles tested by Sandia. The test conditions cover reservoir pressures and temperatures corresponding to cryogenic hydrogen storage. The study conducts computational simulations using OpenFOAM to examine hydrogen concentration temperature fields mass fraction and temperature distributions achieving good agreement with the experimental data. To further explore the study of velocity variations shows a consistent decay rate with room-temperature jets. The numerical data reveals comparable inverse centreline hydrogen mass fractions (0.254 for HAR and 0.26 for circular) and normalised centreline temperature decay rates (0.031 for HAR and 0.032 for circular). The present computational model holds the potential for further analysis of cryogenic hydrogen in large-scale facilities.

As a paradigm of clean energy hydrogen is gradually attracting global attention. However its unique characteristics of leakage and autoignition pose significant challenges to the development of high-pressure hydrogen storage technologies. In recent years numerous scholars have made significant progress in the field of high-pressure hydrogen leakage autoignition. This paper based on diffusion ignition theory thoroughly explores the mechanism of high-pressure hydrogen leakage autoignition. It reviews the effects of various factors such as gas properties burst disc rupture conditions tube geometric structure obstacles etc. on shock wave growth patterns and autoignition characteristics. Additionally the development of internal flames and propagation characteristics of external flames after ignition kernels generation are summarized. Finally to promote future development in the field of high-pressure hydrogen energy storage and transportation this paper identifies deficiencies in the current research and proposes key directions for future research.

As the global transition to carbon neutrality accelerates hydrogen energy has emerged as a key alternative to fossil fuels due to its potential to reduce carbon emissions. Many countries including Korea are constructing hydrogen refueling stations; however safety concerns persist due to accidents caused by equipment failures and human errors. While various accident analysis models exist the application of the root cause analysis (RCA) technique to hydrogen refueling station accidents remains largely unexplored. This study develops an RCA modeling map specifically for hydrogen refueling stations to identify not only direct and indirect causes of accidents but also root causes and applies it to actual accident cases to provide basic data for identifying the root causes of future hydrogen refueling station accidents. The RCA modeling map developed in this study uses accident cause investigation data from accident investigation reports over the past five years which include information on the organizational structure and operational status of hydrogen refueling stations as well as the RCA handbook. The primary defect sources identified were equipment defect personal defect and other defects. The problem categories which were the substructures of the primary defect source “equipment defect” consisted of four categories: the equipment design problem the equipment installation/fabrication problem the equipment reliability program problem and the equipment misuse problem. Additionally the problem categories which were the substructures of the primary defect source “personal defect” consisted of two categories: the company employee problem and the contract employee problem. The problem categories which were the substructures of the primary defect source “other defects” consisted of three categories: sabotage/horseplay natural phenomena and other. Compared to existing accident investigation reports which identified only three primary causes the RCA modeling map revealed nine distinct causes demonstrating its superior analytical capability. In conclusion the proposed RCA modeling map provides a more systematic and comprehensive approach for investigating accident causes at hydrogen refueling stations which could significantly improve safety practices and assist in quickly identifying root causes more efficiently in future incidents.

Achieving global net-zero emissions by 2050 demands integrated and scalable strategies that unite decarbonization technologies across sectors. This review provides a forwardlooking synthesis of carbon capture and storage and hydrogen systems emphasizing their integration through artificial intelligence to enhance operational efficiency reduce system costs and accelerate large-scale deployment. While CCS can mitigate up to 95% of industrial CO2 emissions and hydrogen particularly blue hydrogen offers a versatile low-carbon energy carrier their co-deployment unlocks synergies in infrastructure storage and operational management. Artificial intelligence plays a transformative role in this integration enabling predictive modeling anomaly detection and intelligent control across capture transport and storage networks. Drawing on global case studies (e.g. Petra Nova Northern Lights Fukushima FH2R and H21 North of England) and emerging policy frameworks this study identifies key benefits technical and regulatory challenges and innovation trends. A novel contribution of this review lies in its AI-focused roadmap for integrating CCS and hydrogen systems supported by a detailed analysis of implementation barriers and policy-enabling strategies. By reimagining energy systems through digital optimization and infrastructure synergy this review outlines a resilient blueprint for the transition to a sustainable low-carbon future.

This study explores the safety problems of hydrogen leakage and explosion in hydrogen fuel cell buses through Computational Fluid Dynamics simulations. The research investigates the diffusion behavior of hydrogen in the passenger cabin depending on the leakage position and flow rates identifying a stratified constant-concentration layer formed at the top of the cabin. Leakage near the rear wall of the vehicle provided the highest hydrogen concentration while at higher flow rates the diffusive process accelerated the spreading of flammable hydrogen concentrations. Hydrogen ignition simulations showed a fast internal pressure increase and secondary explosions outside the vehicle. Thermal hazards in the cases were higher than overpressure. The research’s additional analysis of ignition timing and source location shows that overpressure peaked initially with delayed ignition but declined afterward while rear-ignited flames exhibited the farthest high-temperature hazard range at 10.88 m. These findings are fundamental for giving insight into hydrogen behavior in confined spaces and thus guiding risk assessment and emergency response planning for the development of safety protocols in hydrogen fuel cell buses contributing to the safer implementation of hydrogen energy in public transportation.

A simulation study was conducted on the hydrogen leakage diffusion process and influencing factors of fuel cell vehicles in enclosed spaces. The results indicate that when hydrogen leakage flows towards the rear of the vehicle it mainly flows along the rear wall of the space and diffuses to the surrounding areas. Setting ventilation openings of different areas on the top of the carriage did not significantly improve the spatial diffusion speed of the leaked hydrogen and the impact on the concentration of leaked hydrogen was limited to the vicinity of the ventilation openings. The ventilation opening at the rear can accelerate the diffusion of hydrogen gas to the external environment significantly reducing the concentration of hydrogen and rate of gas rise. When the leaked hydrogen gas flows towards the front of the vehicle and above the space the concentration of hydrogen mainly increases along the height direction of the space. The research results have significant safety implications for the use of fuel cell semi-trailer trucks.

As one of the most promising renewable green energies hydrogen power is a popularly accepted option to drive automobiles. Commercial application of fuel cell vehicles has been started since 2015. More and more hydrogen safety concerns have been considered for years. Tunnels are an important part of traffic infrastructure with a mostly confined feature. A hydrogen leak followed possibly by a hydrogen fire is a potential accident scenario which can be triggered trivially by a car accident while hydrogen-powered vehicles operate in a tunnel. Water spray is recommended traditionally as a mitigation measure against tunnel fires. The interaction between water spray and hydrogen fire is studied by way of numerical simulations. By using the computer program of Fire Dynamics Simulator (FDS) tunnel fires of released hydrogen in different scales are simulated coupled with water droplet injections featured in different droplet sizes or varying mass flow rates. The cooling effect of spray on hot gases of hydrogen fires is apparently observed in the simulations. However in some circumstances the turbulence intensified by the water injection can prompt hydrogen combustion which is a negative side effect of the spray.