Hydrogen Safety Research Articles

Disaster evaluation of hydrogen explosion leakage from industrial-scale non-metallic pipeline

This work is aimed at evaluating the disaster consequence of leaked hydrogen explosion from the industrial-scale non-metallic pipeline. The flame evolution and explosion overpressure are experimentally obtained. A standard k-ε turbulence model and a beta flame model is established to analyze the explosion overpressure generation. The results indicated that whether there is an external ignition source or not, the hydrogen explosion still occurs when the high-pressure hydrogen leaks from non-metal pipelines. The formation of three overpressure peaks could be attributed to the non-metallic pipeline rupture, leaked hydrogen explosion and sand soil spread. The explosion overpressure peaks continue to decrease with increasing monitoring point distance. The moving speed of explosion overpressure is between 349.34 m/s and 436.21 m/s. The leaked hydrogen concentration outside non-metallic pipeline could reach up to about 10% and the explosion overpressure generation is dependent on the concentration distribution.

Comparing hybrid method simulations to hydrogen dispersion and explosion tests

With an increase in the production and storage of hydrogen, it is likely that an increased number of explosions in which hydrogen plays a central role will occur unless a step change increase in safety is seen. Modelling releases of hydrogen and explosions arising from the delayed ignition of premixed gas clouds of hydrogen is carried out today using analytical and numerical approaches and most recently, using a hybrid methodology with the commercially available software exploCFD. Hybrid simulation methodology relies on the calculation of an analytically derived source term which is then used as an input for a 2D numerical simulation. In this paper we further our earlier validation work and test the ability of the hybrid methodology to predict flammable gas dispersion and subsequent explosions arising from hydrogen releases. Hydrogen has some particularly unique properties; it is the lightest of fuels – meaning masses involved are very small, and it has the highest laminar burning velocity – an order of magnitude greater than most hydrocarbons. The hybrid methodology is compared against previously documented 3D corner tests and dispersion tests. Excellent agreement between overpressure prediction and the reported experimental data for explosion against equivalence ratio is observed. The data from the hydrogen jet release simulations also compare extremely well to the previously reported experimental data. The results show that it is difficult to justify the use of far more laborious, time and cost-intensive purely numerical methods, or the use of largely uncertain more crude methods still widely used today.

Effects of hydrogen concentration, number of obstacles, and blockage ratio on vented hydrogen-air explosions and its consequence analysis

With the swift advancement of commercial hydrogen fuel cell vehicles (HFCVs), accident risks of hydrogen explosions are heightened, especially in enclosed or semi-enclosed areas such as tunnels and underground parking lots. To prevent and control these accidents, experiments are conducted in a 1 m-long cylindrical tube at 1 atm and 286 K to study the impacts of hydrogen concentration, number of obstacles, and blockage ratios on vented hydrogen-air explosions. As the number of obstacles rises, there is a gradual rise in the maximum internal overpressure for a hydrogen concentration of 20 vol%. However, a reverse trend is observed for hydrogen concentrations of 30 vol% and 50 vol%. The size of the external flame gradually expands as the hydrogen concentration increases, but diminishes gradually with increasing in the number of obstacles and blockage ratio. The maximum external overpressure decreases as the distance to the vent increases. The maximum temperature experiences an increase with increasing in hydrogen concentration and blockage ratio but undergoes a decrease with an increase in the number of obstacles. Furthermore, the safety radii are determined using thermal radiation criteria to ensure the absence of thermal radiation hazards for humans, and PROBIT equations to ensure the absence of overpressure and impulse hazards for humans and buildings. The safety radii for humans based on thermal radiation criteria are smaller compared to those based on the corresponding overpressure and impulse hazards.

Simulation and Experimental Verification of Dispersion and Explosion of Hydrogen–Methane Mixture in a Domestic Kitchen

Hydrogen is a carbon-free energy source that can be obtained from various sources. The blending of hydrogen represents a transitional phase in the shift from natural gas systems to hydrogen-based systems. However, concerns about the safety implications of introducing hydrogen have led to extensive discussions. This paper utilizes Fluent 17.0 numerical simulation software to simulate the leakage of hydrogen-blended natural gas in a closed domestic kitchen and analyze the concentration distribution and its variation pattern after a leakage. An experimental platform is set up, and a mixture of nitrogen and helium gas is used as a substitute for hydrogen-blended natural gas for the simulations and experiments. The simulation results demonstrate that the leaked gas spreads and accumulates towards the top of the space, gradually filling the entire area as the leak persists. As the hydrogen content in the leaked gas increases, the dispersion capacity of the gas in the confined space also increases. Furthermore, as the flow rate of the leaked gas increases, the average concentration of the leaked gas rises, and the gas stratification in the confined kitchen diminishes. The concentration distribution observed in the experiments aligns with the simulation results. After establishing the feasibility conditions of the model, the dispersion of the hydrogen-blended natural gas in the kitchen is further simulated. The results suggest that blending hydrogen into the gas enhances the dispersion of the gas after a leak, leading to a wider distribution within the kitchen and an increased risk in the event of a leak. Additionally, this paper employs the CASD module of FLACS 11.0 software to construct a three-dimensional geometric model of the domestic kitchen for simulation studies on the explosion of hydrogen-blended natural gas in a confined space. By adjusting the hydrogen ratio in the combustible gases present in the space and examining the variations in hydrogen concentration and external conditions, such as opening or closing the door, the influence on parameters including the peak explosion pressure, explosion overpressure, explosion flame temperature, and explosion response time are examined. Furthermore, the extent of the explosion area is determined, and the effect of hydrogen on the blast is clarified.

Experimental study on the inhibition of hydrogen deflagration by flame-retardant compounded ultrafine dry powder fire extinguishing media containing zinc hydroxystannate

With the rapid development of global hydrogen energy industry, the issue of hydrogen energy safety has emerged, it is prone to cause a serious explosion accident once hydrogen leaks. Therefore, it is urgent to develop efficient suppression media to reduce the severity of hydrogen explosion accidents. In this paper, a new compounded powder composed of ordinary ultra-fine dry powder extinguishing agent (ODPEA) and zinc hydroxystannate (ZHS) is prepared. On the basis of material preparation, an experimental system of hydrogen explosive suppression is established to explore the inhibitory effect of ODPEA-ZHS. In terms of explosion overpressure, the results show that the peak overpressure suppression rates of ODPEA-ZHS are 90.12 %, 92.31 %, and 93.04 % for hydrogen release pressures of 2.0, 4.0, and 6.0 MPa, respectively. Besides, the flame front propagation velocity under the action of ODPEA-ZHS reaches a suppression rate of 40.55 %. Furthermore, the overpressure suppression efficiency of ODPEA-ZHS exceeds 90 % when ignites 1.0 m axially from leak port. Ultimately, the physicochemical synergistic inhibition mechanism of ODPEA-ZHS is revealed by combining material characterization and pyrolysis results. This study can provide effective countermeasures for accident prevention in hydrogen energy industry, and also contribute to the establishment of hydrogen energy safety standards and norms.

Industry R&D needs in hydrogen safety

Hydrogen's unique physicochemical and combustion properties make it stand out among fuels as new hydrogen production technologies, means of transportation, and consumers emerge. The future viability of these technological solutions will depend on numerous factors, including safety, environmental, regulatory, and economic considerations. Safe deployment of these technologies requires additional research and development activities. These range from an improved quantitative understanding of hydrogen leaks, material limitations due to embrittlement, very large-volume liquefied hydrogen storage and transport, to equipment- and usage-specific considerations as is the case for gas turbines and electrolyzers.

Performances of the sandwich panel structures under fire accident due to hydrogen leaks: Consideration of structural design and environment factor using FE analysis

Abstract This study presents a comprehensive analysis using the finite element method (FEM) to examine and evaluate the behavior of fuel carrier ship structure. Sandwich panels are effective structures for use in ship structures due to their lightweight yet robust nature. Sandwich panels used in ship structures have various core shapes, such as hexagonal, circular, and square, as needed. The sandwich panel structure can be widely implemented in ship construction, for example, on the deck, hull, and bulkhead of the ship’s cabin. Hydrogen is an alternative fuel that can replace fossil fuels. In this modern era, hydrogen is high valuable energy commodity, so accidents involving carrier ships could have significant consequences. Hydrogen is produced from liquefied natural gas (LNG), so if a leak occurs, for instance, in a storage tank or fuel tank, it has the potential to lead to accidents such as fires. Corrosion is a significant concern for the maritime industry, as it can jeopardize the structural integrity of these vessels and pose substantial safety and environmental risks. In this research, FEM was utilized to model and simulate the effects of corrosion on hydrogen carrier ships when exposed to fire, considering various environmental and operational factors. Through a systematic investigation, it is aimed to gain insights into the impact of corrosion on ship structural components during fires, such as hulls and storage tanks. The result of this study will contribute to improving corrosion and fire mitigation strategies, ensuring the safety and longevity of hydrogen and LNG carrier ships, and supporting the sustainable transportation of hydrogen to meet global energy demands. No research has been conducted on the structural behavior resulting from hydrogen fires and corrosion simultaneously. To achieve this, it is assumed to use the corrosion properties of steel in heavily traveled ship routes such as the Panama Canal Zone, Barent Sea, North Sea, and Suez Canal Zone. This study utilized an approach by modeling corrosion using shell thickness in Abaqus Quasi-Static and applying boundary conditions in the form of temperature increase up to 800°C and subsequent cooling back to the initial temperature. At the maximum temperature, the most significant mid-span displacement occurred in the circular core sandwich panel, with a value of 4 mm. The axial force in the structure was inversely proportional to the mid-span displacement. In the case of the circular core sandwich panel, the axial force was 96 kN. The most resilient core type was hexagonal because it experiences the least deformation when compared to circular and square cores.

Quaternary conducting Cs/GO/PANi hydrogel composites: A smart material for room temperature hydrogen sensing

Hydrogen sensors are essential for hydrogen energy technology development and safety monitoring. However, hydrogen sensing is difficult because it requires effective and fast detection of tiny quantities of hydrogen. In situ oxidative radical polymerization is used in this study to combine polyaniline (PANi) with a chitosan/graphene oxide (Cs/GO) hydrogel, which is very good at conducting electricity, to make it sensor. FTIR, XRD, SEM, and UV were used to evaluate the material's functional groups, crystal structure, morphology, and bandgap. This work shows that Cs/GO/PANi can synthesise a hydrogel-based sensor. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry (CA) were used to evaluate electron transfer mobility, redox behaviour, and hydrogen sensing. Using a hydrogen source with a concentration of 0.5–2.5 M KOH, the hydrogen sensor's response time, recovery sensitivity, and limit of detection were found to be 0.4 s, 0.8 s, 54.3748 μAM, and 3.5520 μM, respectively. Under conventional conditions, the experiment demonstrated significant sensing capabilities at ambient temperature. According to the research, the sensor works so well because of the π-π stacking interaction, the irregular structure, and the way the GO-based hydrogel and PANi work together.

Consequence analysis of a small-scale hydrogen leakage from the overhead hydrogen piping based on machine learning and physical modeling

Leakage from the overhead hydrogen piping (OHP) must be contained because of the wide flammability range and low minimum ignition energy of hydrogen; rapid leakage detection and appropriate emergency responses are necessary to ensure safe OHP operation. Consequence analysis after leakage detection is useful for hazardous-area estimation and assists operators in emergency-response planning. However, consequence analysis and leakage-detection methods have not been combined so far, and an integrated method has not yet been developed. This study aimed to develop a method based on machine learning (ML), physical modeling, and consequence analyses for rapid and appropriate decision-making after hydrogen leakage. Initially, an OHP model was constructed using physical modeling; this is a method that models target systems based on fundamental physical equations. Subsequently, an ML model for leakage detection was constructed based on various pressure or flow-rate profiles obtained from the OHP model. Regression models were constructed to estimate the leakage diameter. In addition, consequence analyses were conducted to estimate the effects of hydrogen explosions and fires using the leakage diameters predicted by the regression model. We confirmed that the ML model could distinguish between leakage and non-leakage conditions, and the estimated consequences could be used to visualize the risk level of hazardous areas near the leakage points in the case studies. The results of the case studies demonstrated the effectiveness of the proposed method for rapid decision making when hydrogen leaks from OHP. This method enables improved emergency responses in post-leakage situations.

Design and development of vehicle cryo-compressed hydrogen storage vessel

Compared with other hydrogen storage methods, cryo-compressed hydrogen storage has significant advantages in terms of mass hydrogen storage density, volume hydrogen storage density, hydrogen storage cost, safety and evaporation loss. The key component of cryo-compressed hydrogen storage is cryo-compressed hydrogen storage vessel. In order to reasonably design and optimize the performance of cryo-compressed hydrogen storage tank, the author uses carbon fiber and low temperature resin to prepare composite one-way plate from the material, and then makes the one-way plate into relevant splines for testing. The relevant parameters of the spline are tested in the liquid nitrogen temperature zone, such as elastic modulus, Poisson’s ratio, thermal conductivity, etc. Using the relevant mechanical properties of the carbon fiber composite one-way plate obtained from the experiment, the target storage tank is designed to provide the actual storage tank for the subsequent low temperature and high pressure storage tank experiment.

Weight‐Reconfigurable Neuromorphic Computing Systems for Analog Signal Integration

AbstractOwing to the necessity of high computation amounts has emerged, interest in a neuromorphic computing system has significantly increased as a compelling alternative to conventional CMOS technology. This paper presents a neuromorphic hardware algorithm to finely reconfigure multi‐input signal processing, which can be implemented as an advanced processor for diverse external information, and the hydrogen explosion risk assessment system is demonstrated as a proof of concept. Hydrogen concentration and temperature are used as sensory inputs for the signal integration and the precise values of them are determined by offsetting the effect of temperature on the electrical signal from the hydrogen sensor through a sensor circuit. Each signal is then updated by the weight control circuit and converted into a postsynaptic current to represent the hydrogen explosion risk using a multi‐input artificial synapse. This simplicity of the circuitry renders the fabrication of all components and circuits compatible with simple inkjet printing methods, enabling cost‐effective and high‐throughput manufacturing. Additionally, the real‐time demonstration of the neuromorphic computing system is successfully conducted, offering insights into the practical application of neuromorphic computing.

Deep learning-driven analysis for cellular structure characteristics of spherical premixed hydrogen-air flames

The extraction of cellular structure feature on the spherical premixed flame surface faces accuracy challenges. The Schlieren technique was employed to obtain the hydrogen-air premixed spherical flames images in a constant volume vessel at room temperature and atmospheric pressure under an equivalent ratio of 0.8 in this work. A bio-inspired Cellpose 2.0, driven by deep learning, is innovatively introduced to train the cell segmentation model in the combustion field. After labeling and training cells of different shapes and sizes, an efficient and accurate model suitable for cell feature extraction was finally obtained to identify and quantify various cells characteristics, such as number, size, and distribution. Results show that the average precision (AP) during the model online pre-training process reaches 0.625. Meanwhile, the critical flame radius of transition acceleration obtained is 36 mm and the crack length tends to grow linearly after the flame radius exceeds this critical point. Additionally, the average cell area gradually converges to a stable value after the flame radius exceeds the uniform cellularity critical radius. The cell segmentation model obtained in this work can be further used to train different spherical flames under various conditions, helping to develop hydrogen combustion and explosion modelling.

In situ hydrogen production from Al–BiCl3 hydrolysis for small-sized fuel cell

Small-sized fuel cell has tremendous potential and broad market prospect in the field of portable devices, but its hydrogen source with compact structure and stable and high purity hydrogen supply remains an issue for commercialization. In this research, a novel in situ hydrogen production material Al–BiCl3 composite is developed via ball milling method, and its hydrogen production performance is evaluated in terms of induction time, storage stability, hydrogen production rate and hydrogen yield. The results demonstrate that Al–BiCl3 has excellent hydrogen production performance and its hydrogen yield can reach 85 % within 2.3 h. During ball milling process, many surface cracks and active surface are produced and some BiCl3 is reduced to metal Bi by Al, resulting in the high hydrolysis activity of Al–BiCl3. Prolonging milling time can promote the formation of surface cracks and Bi, enhancing the activity of Al–BiCl3. The hydrogen production mechanisms of Al–BiCl3 are attributed to pitting and microgalvanic effect between Al and Bi. Taking into account hydrogen production performance, cost and safety, Al-10 wt% BiCl3 milled for 1 h is a suitable and potential in situ hydrogen production material for small-sized fuel cells.

Numerical Study on the Effects of Ventilation System on Hydrogen Dispersion in an Underground Garage with Smoke Barriers

The promotion of hydrogen fuel cell vehicles (HFCVs) has been hindered by hydrogen safety issues. In this paper, hydrogen leakage in an underground garage with smoke barriers is numerically simulated. Nine vents are arranged for the distribution of smoke barriers, and the effects of the ventilation mode and ventilation opening time on hydrogen dispersion and hydrogen removal efficiency are discussed. It is found that ventilation can effectively inhibit the formation of flammable hydrogen clouds. The hydrogen removal efficiency of mechanical ventilation is much higher than that of natural ventilation, and the effect becomes more significant as the ventilation time increases. Reducing the opening time of ventilation can improve the overall ventilation effect and the efficiency of removing high concentration hydrogen, while reducing the time required for hydrogen concentrations to drop below the safety limit.

Study on the Effect of Bifurcation Position on Spontaneous Ignition and Shock Wave Propagation Characteristics in High-pressure Hydrogen Leakage Tubes

Hydrogen safety issues constrain the development and diffusion of hydrogen energy technologies. The current research on tube types in high-pressure hydrogen storage and transportation links is insufficient. In this paper, the spontaneous combustion law and the propagation characteristics of the shock wave in the tube after accidental leakage of high-pressure hydrogen in a bifurcated tube with a blocking structure are investigated by experimental means. By changing the relative position of the bifurcation structure, it is found that moving the bifurcation position upstream can effectively reduce the intensity of the shock wave at the nozzle of the tube, the propagation velocity of the shock wave inside the tube and the critical ignition pressure. There are three ignition possibilities in the bifurcated tube with blocking structure, and quenching can be realized in the tube under lower pressure.

Social media sentiment of hydrogen fuel cell vehicles in China: Evidence from artificial intelligence algorithms

Hydrogen energy is significant in the energy consumption, especially in Hydrogen Fuel Cell Vehicles(HFCVs) market. Social media data is critical for exploring public perceptions of HFCVs. To find hot topics and understand the public sentiment of HFCVs, we employ a computational model, which combines Kmeans algorithm, Latent Dirichlet Allocation (LDA), and SnowNLP. The training data consists of 42,063 comments sourced from Bilibili-a popular Chinese social media platform. The analysis has identified 12 clusters, each with distinct topics and sentiments. The results reveal that the Chinese public generally holds a neutral stance on the hydrogen energy market, while some stakeholders maintain a positive on the technology and development of HFCVs, but some concerns about the transportation and safety of hydrogen fuel. Furthermore, this study offers suggestions for the technological, operational, and strategic advancement of HFCVs.

Assessing the Role of Hydrogen in Sustainable Energy Futures: A Comprehensive Bibliometric Analysis of Research and International Collaborations in Energy and Environmental Engineering

The main results highlighted in this article underline the critical significance of hydrogen technologies in the move towards carbon neutrality. This research focuses on several key areas including the production, storage, safety, and usage of hydrogen, alongside innovative approaches for assessing hydrogen purity and production-related technologies. This study emphasizes the vital role of hydrogen storage technology for the future utilization of hydrogen as an energy carrier and the advancement of technologies that facilitate effective, safe, and cost-efficient hydrogen storage. Furthermore, bibliometric analysis has been instrumental in identifying primary research fields such as hydrogen storage, hydrogen production, efficient electrocatalysts, rotary engines utilizing hydrogen as fuel, and underground hydrogen storage. Each domain is essential for realizing a sustainable hydrogen economy, reflecting the significant research and development efforts in hydrogen technologies. Recent trends have shown an increased interest in underground hydrogen storage as a method to enhance energy security and assist in the transition towards sustainable energy systems. This research delves into the technical, economic, and environmental facets of employing geological formations for large-scale, seasonal, and long-term hydrogen storage. Ultimately, the development of hydrogen technologies is deemed crucial for meeting sustainable development goals, particularly in terms of addressing climate change and reducing greenhouse gas emissions. Hydrogen serves as an energy carrier that could substantially lessen reliance on fossil fuels while encouraging the adoption of renewable energy sources, aiding in the decarbonization of transport, industry, and energy production sectors. This, in turn, supports worldwide efforts to curb global warming and achieve carbon neutrality.

Analysis of hydrogen control in a Small Modular Reactor during TLOFW severe accident

During the Fukushima Daiichi nuclear accident in 2011, hydrogen explosions occurred in all units from Unit 1 to Unit 3. Consequently, one of the lessons learned from the Fukushima Daiichi accident is the necessity of implementing hydrogen control and mitigation strategies for most Nuclear Power Plants (NPPs). This paper focuses on the incorporation of Passive Autocatalytic Recombiners (PARs) during the design phase of a small modular Pressurized Water Reactor (SMR-PWR) project. The numerical analyses are conducted using the MELCOR v. 2.2 code. Two scenarios are compared: the Total Loss of Feed Water (TLOFW) severe accident with and without PARs. Saphiro’s diagram is utilized to investigate whether the mixture's composition (hydrogen, air, steam) is flammable for both scenarios. It has been observed that the inclusion of PARs leads to a reduction in hydrogen risk (detonative or deflagrative) as the final hydrogen concentration values fall below the flammability limit. This study is preliminary, and further research is required.

Real-time data acquisition inside high-pressure PEM water electrolyzer

This study used the micro-electro-mechanical systems (MEMS) technology to develop a high-pressure resistant flexible 7-in-1 microsensor (voltage, current, humidity, temperature, pressure, flow, and hydrogen). The microsensor is integrated with a flexible printed circuit (FPC) for real-time data acquisition of local voltage, current, humidity, temperature, pressure, flow, and hydrogen variations in different positions inside a high-pressure proton exchange membrane water electrolyzer (PEMWE). The goal of developing such microsensor is to observe the influence of temperature and pressure on the PEMWE. The operational safety of hydrogen is ensured by using a micro hydrogen sensor.

Towards a uniform description of recombiners performance by a consistent CFD approach with the use of a detailed mechanism of hydrogen oxidation

For a consistent CFD substantiation of the recombiner performance, a detailed mechanism of hydrogen and oxygen recombination is used. The detailed mechanism of chemical kinetics (multi-step recombination reaction) makes it possible to claim universality, both in the numerical justification of the recombiner performance and in the justification of the flameless recombination threshold and makes it possible to justify the method for optimizing the recombiner to improve its characteristics. The models developed based on this approach were applied to both flat and cylindrical catalytic elements, which are used in FR and RVK recombiners, respectively. As part of the numerical studies, the detailed recombination mechanism was verified, namely the temperature distribution along the catalytic elements was compared and the performance of catalytic elements was compared as well. Good agreement was obtained between the calculated and experimental data. The approach considers not only the mechanism of surface recombination of hydrogen and oxygen on platinum, but also the mechanism of recombination in the gas phase. This makes it possible to calculate the onset of intense combustion outside the catalytic plates, which is a sign of volumetric ignition of the hydrogen-air environment. The concentrations at which such ignition is possible were obtained at different contents of water vapor in the medium. Thus, the proposed approach and the created models make it possible to fully describe the performance of recombiners of distinct designs without the use of additional experimental data, which is extremely necessary when justifying the hydrogen explosion safety of nuclear power plants.