Safety
Exploratory Numerical Study of Liquid Hydrogen Hazards
Sep 2023
Publication
Hydrogen is one of a handful of new low carbon solutions that will be critical for the transition to net zero. The upscaling of production and applications entails that hydrogen is likely to be stored in liquid phase (LH2) at cryogenic conditions to increase its energy density. Widespread LH2 use as an alternative fuel will require significant infrastructure upgrades to accommodate increased bulk transport storage and delivery. However current LH2 bulk storage separation distances are based on subjective expert recommendations rather than experimental observations or physical models. Experimental studies of large-scale LH2 release are challenging and costly. The existing large-scale tests are scarce and numerical studies are a viable option to investigate the existing knowledge gaps. Controlled or accidental releases of LH2 for hydrogen refueling infrastructure would result in high momentum two-phase jets or formation of liquid pools depending on release conditions. Both release scenarios lead to a flammable/explosive cloud posing a safety issue to the public.<br/>The manuscript reports exploratory study to numerically determine the safety zone resulting from cryogenic hydrogen releases related to LH2 storage and refueling using the in-house HyFOAM solver further modified for gaseous hydrogen releases at cryogenic conditions and the subsequent atmospheric dispersion and ignition within the platform of OpenFOAM V8.0. The current version of the solver neglects the flashing process by assuming that the temperature of the stored LH2 is equal to the boiling point at the atmospheric condition. Numerical simulations of dispersion and subsequent ignition of LH2 release scenarios with respect to different release orientations release rates release temperatures and weather conditions were performed. Both hydrogen concentration and temperature fields were predicted and the boundary of zones within the flammability limit was also defined. The study also considered the sensitivities of the consequences to the release orientation wind speed ambient temperature and release content etc. The effect of different barrier walls on the deflagration were also evaluated by changing the height and location.
Hydrogen Related Accidents and Lesson Learned from Events Reported in the East Continental Asia
Sep 2023
Publication
Hydrogen as an energy carrier plays an important role in carbon neutrality and energy transition. Hydrogen is the lightest element with a density of only 0.08375 kg/m3 in gaseous form at standard temperature and pressure (STP); as a result hydrogen is usually stored and transported in a highly compressed form. It is prone to leakage and has a very low ignition energy of 0.017 mJ. Safety remains a challenge in the use of hydrogen as an energy source. This paper examines approximately 20 hydrogen-related accidents in China over a 20-year period focusing on the root causes consequences of the accidents and responses to them. These accidents occurred in the production storage transport and application of hydrogen with different causes in different locations and resulting in losses at different scales. Some statistical evaluations were conducted to learn lessons from the accidents. The main objective of this paper is (i) to retrieve a set of hydrogen related incidents from a region which is under-represented in incident repositories (ii) to contribute to a generalised lesson learned from them and (iii) to assist the definition of realistic scenarios for commonly occurring hydrogen accidents.
Research Progress on Corrosion and Hydrogen Embrittlement in Hydrogen-Natural Gas Pipeline Transportation
Jun 2023
Publication
Hydrogen clean efficient and zero-carbon is seen as a most promising energy source. The use of existing gas pipelines for hydrogenenatural gas transportation is considered to be an effective way to achieve long-distance large-scale efficient and economical hydrogen transportation. However the pipelines for hydrogenenatural gas transportation contain lots of impurities (e.g. CH4 high-pressure H2 H2S and CO2) and free water which will inevitably lead to corrosion and hydrogen embrittlement. This paper presents a systematic review of research and an outlook for corrosion and hydrogen embrittlement in hydrogenenatural gas pipeline transportation. The results show that gasphase hydrogen charging is suitable for hydrogenenatural gas transportation but this technique lacks technical standards. By contrast the liquid-phase hydrogen charging technique is more mature but has large deviation from the engineering reality. In the hydrogenenatural gas transportation pipelines corrosion and hydrogen embrittlement are synergetic and competitive but the failure mechanism and change law when corrosion and hydrogen embrittlement coexist remain unclear which need to be further clarified by experiments. The failure mechanism is believed to be mainly sensitive to three key factors i.e. the H2S/CO2 partial pressure ratio the hydrogen blending ratio and material strength. The increase of the three factors will make the pipeline materials more corrosive and more sensitive to hydrogen embrittlement. The research findings can be used as a reference for research and development of long-distance hydrogenenatural gas transportation technology and will drive the high-quality development of the hydrogenenatural gas blending industry.
Proactive Emergency Response Strategies for First Responders to Hydrogen Gas Leakages in Vehicles
Feb 2024
Publication
The widespread use of fossil fuels in automobiles has become a concern particularly in light of recent frequent natural disasters prompting a shift towards eco-friendly vehicles to mitigate greenhouse gas emissions. This shift is evident in the rapidly increasing registration rates of hydrogen vehicles. However with the growing presence of hydrogen vehicles on roads a corresponding rise in related accidents is anticipated posing new challenges for first responders. In this study computational fluid dynamics analysis was performed to develop effective response strategies for first responders dealing with high-pressure hydrogen gas leaks in vehicle accidents. The analysis revealed that in the absence of blower intervention a vapor cloud explosion from leaked hydrogen gas could generate overpressure exceeding 13.8 kPa potentially causing direct harm to first responders. In the event of a hydrogen vehicle accident requiring urgent rescue activities the appropriate response strategy must be selected. The use of blowers can aid in developing a variety of strategies by reducing the risk of a vapor cloud explosion. Consequently this study offers a tailored response strategy for first responders in hydrogen vehicle leak scenarios emphasizing the importance of situational assessment at the incident site.
Lessons Learned and Recommendations from Analysis of Hydrogen Incidents and Accidents to Support Risk Assessment for the Hydrogen Economy
Feb 2024
Publication
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.
Odorisation of Natural Gas/Hydrogen Mixure and Pure Hydrogen
Dec 2023
Publication
MARCOGAZ has prepared this document to provide comprehensive information on the odorisation of hydrogen and natural gas (H2-NG) mixtures as well as pure hydrogen. The primary goal is to assist in determining the crucial data to be taken into account when odorising gases containing hydrogen.
The document is structured into two main sections with the initial part focusing on the theoretical interactions between hydrogen and odorants. Subsequent sections delve into the existing data related to this subject. The conclusions section offers additional considerations on the topic.
The report can be found on their website.
The document is structured into two main sections with the initial part focusing on the theoretical interactions between hydrogen and odorants. Subsequent sections delve into the existing data related to this subject. The conclusions section offers additional considerations on the topic.
The report can be found on their website.
Design of Long-Life Wireless Near-Field Hydrogen Gas Sensor
Feb 2024
Publication
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.
Risk Analysis of Fire and Explosion of Hydrogen-Gasoline Hybrid Refueling Station Based on Accident Risk Assessment Method for Industrial System
Apr 2023
Publication
Hydrogen–gasoline hybrid refueling stations can minimize construction and management costs and save land resources and are gradually becoming one of the primary modes for hydrogen refueling stations. However catastrophic consequences may be caused as both hydrogen and gasoline are flammable and explosive. It is crucial to perform an effective risk assessment to prevent fire and explosion accidents at hybrid refueling stations. This study conducted a risk assessment of the refueling area of a hydrogen–gasoline hybrid refueling station based on the improved Accident Risk Assessment Method for Industrial Systems (ARAMIS). An improved probabilistic failure model was used to make ARAMIS more applicable to hydrogen infrastructure. Additionally the accident consequences i.e. jet fires and explosions were simulated using Computational Fluid Dynamics (CFD) methods replacing the traditional empirical model. The results showed that the risk levels at the station house and the road near the refueling area were 5.80 × 10−5 and 3.37 × 10−4 respectively and both were within the acceptable range. Furthermore the hydrogen dispenser leaked and caused a jet fire and the flame ignited the exposed gasoline causing a secondary accident considered the most hazardous accident scenario. A case study was conducted to demonstrate the practicability of the methodology. This method is believed to provide trustworthy decisions for establishing safe distances from dispensers and optimizing the arrangement of the refueling area.
Risk Assessment of a Hydrogen Refueling Station in an Urban Area
May 2023
Publication
After the Paris Agreement was signed in 2015 many countries worldwide focused on the hydrogen economy aiming for eco-friendly and renewable energy by moving away from the existing carbon economy which has been the primary source of global warming. Hydrogen is the most common element on Earth. As a light substance hydrogen can diffuse quickly; however it also has a small risk of explosion. Representative explosion accidents have included the Muskingum River Power Plant Vapor Cloud Explosion accident in 2007 and the Silver Eagle Refinery Vapor Cloud Explosion accident in 2009. In addition there was an explosion in a hydrogen tank in Gangneung Korea in May 2019 and a hydrogen refueling station (HRS) in Norway exploded in 2018. Despite this risk Korea is promoting the establishment of HRSs in major urban centers including downtown areas and public buildings by using the Regulatory Sandbox to install HRSs. This paper employed the Hydrogen Risk Assessment Model (HyRAM) of Sandia National Laboratories (SNL) a quantitative risk assessment (QRA) program specialized in hydrogen energy for HRSs installed in major urban hubs. A feasibility evaluation of the site conditions of an HRS was conducted using the French land use planning method based on the results obtained through evaluation using the HyRAM and the overpressure results of PHAST 8.0. After a risk assessment we confirmed that an HRS would be considered safe even if it was installed in the city center within a radius of influence of jet fires and overpressure.
A Model for Assessing the Potential Impact Radius of Hydrogen Pipelines Based on Jet Fire Radiation
Jan 2024
Publication
The accurate determination of the potential impact radius is crucial for the design and risk assessment of hydrogen pipelines. The existing methodologies employ a single point source model to estimate radiation and the potential impact radius. However these approaches overlook the jet fire shape resulting from high-pressure leaks leading to discrepancies between the calculated values and real-world incidents. This study proposes models that account for both the mass release rate while considering the pressure drop during hydrogen pipeline leakage and the radiation while incorporating the flame shape. The analysis encompasses 60 cases that are representative of hydrogen pipeline scenarios. A simplified model for the potential impact radius is subsequently correlated and its validity is confirmed through comparison with actual cases. The proposed model for the potential impact radius of hydrogen pipelines serves as a valuable reference for the enhancement of the precision of hydrogen pipeline design and risk assessment.
Computational Fluid Dynamics Simulations of Hydrogen Releases and Vented Deflagrations in Large Enclosures
Nov 2019
Publication
This paper presents model predictions obtained with the CFD tool FLACS for hydrogen releases and vented deflagrations in containers and larger enclosures. The paper consists of two parts. The first part compares experimental results and model predictions for two test cases: experiments performed by Gexcon in 20-foot ISO containers (volume 33 m3 ) as part of the HySEA project and experiments conducted by SRI International and Sandia National Laboratories in a scaled warehouse geometry (volume 45.4 m3 ). The second part explores the use of the model system validated in the first part to accidental releases of hydrogen from forklift trucks inside a full-scale warehouse geometry (32 400 m3 ). The results demonstrate the importance of using realistic and reasonably accurate geometry models of the systems under consideration when performing CFD-based risk assessment studies. The discussion highlights the significant inherent uncertainty associated with quantitative risk assessments for vented hydrogen deflagrations in complex geometries. The suggestions for further work include a pragmatic approach for developing empirical correlations for pressure loads from vented hydrogen deflagrations in industrial warehouses with hydrogen-powered forklift trucks.
Review of the Status and Prospects of Fiber Optic Hydrogen Sensing Technology
Aug 2023
Publication
With the unprecedented development of green and renewable energy sources the proportion of clean hydrogen (H2 ) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984 including: interferometer technology fiber grating technology surface plasma resonance (SPR) technology micro lens technology evanescent field technology integrated optical waveguide technology direct transmission/reflection detection technology etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands such as: high temperature resistance fast response speed fast recovery speed large concentration range low cross sensitivity excellent long-term stability etc. On the basis of palladium (Pd)-sensitive material alloy metals catalysts or nanoparticles are proposed to improve the performance of fiberoptic-based H2 sensors including gold (Au) silver (Ag) platinum (Pt) zinc oxide (ZnO) titanium oxide (TiO2 ) tungsten oxide (WO3 ) Mg70Ti30 polydimethylsiloxane (PDMS) graphene oxide (GO) etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review.
The Effect of Natural Ventilation through Roof Vents Following Hydrogen Leaks in Confined Spaces
Sep 2023
Publication
Hydrogen energy is gaining global popularity as a green energy source and its use is increasing. However hydrogen has a rapid diffusion rate and a broad combustion range; thus it is vital to take safety precautions during its storage. In this study we examined the change of hydrogen concentration in a confined space exposed to a hydrogen leak according to the size of the leakage hole and the leakage flow rate assuming an extreme situation. In addition we investigated rectangular vents (that serve as explosion panels in the event of an explosion) to assess their ventilation performance according to the area of the vent when used for emergency natural ventilation. The vent areas tested represented 12% 24% and 36% of the floor area and they were installed in the ceiling of the test enclosure. When exposed to a simulated hydrogen leak the enclosure acquired a hydrogen concentration of 1% which is 25% of the lower flammability limit (LFL) in less than 6 s across all test cases. The time to LFL varied from approximately 4–81 s. In an assessment of the emergency ventilation duration the ventilation time required to reach safe hydrogen concentrations decreased and showed less deviation as the vent size was increased. For the largest vent size tested the LFL was reached in <1 min; it took 145.6 s to acquire a 1 vol% of hydrogen which is relatively fast. However there were no significant differences between the performance of large and medium-sized vent areas. Therefore through the results we found that it is reasonable to apply the area Kv = 3.31 (24% of the floor area) or less when considering the design of a roof vent that can serve as both an emergency ventilation and an explosion vent. This suggests that it is difficult to expect an improvement in ventilation performance by simply increasing the area of the vent beyond a certain area. Through these results this study proposes a practical and novel method for future design and parameters of safety functions that protect areas where hydrogen is present.
Populating the Hydrogen Component Reliability Database (HYCRED) with Incident Data from Hydrogen Dispensing
Sep 2023
Publication
Safety risk and reliability issues are vital to ensure the continuous and profitable operation of hydrogen technologies. Quantitative risk assessment (QRA) has been used to enable the safe deployment of engineering systems especially hydrogen fueling stations. However QRA studies require reliability data which are essential to collect to make the studies as realistic and relevant as possible. These data are currently lacking and data from other industries such as oil and gas are used in hydrogen system QRAs. This may lead to inaccurate results since hydrogen fueling stations have differences in physical properties system design and operational parameters when compared to other fueling stations thus necessitating new data sources are necessary to capture the effects of these differences. To address this gap we developed a structure for a hydrogen component reliability database (HyCReD) [1] which could be used to generate reliability data to be used in QRA studies. In this paper we demonstrate populating the HyCReD database with information extracted from new narrative reports on hydrogen fueling station incidents specifically focused on the dispensing processes. We analyze five new events and demonstrate the feasibility of populating the database and types of meaningful insights that can be obtained at this stage.
CFD Analysis of Hydrogen Leakage from a Small Hole in a Sloping Roof Hydrogen Refueling Station
Sep 2023
Publication
As a key link in the application of hydrogen energy hydrogen refueling stations are significant for their safe operation. This paper established a three-dimensional 1:1 model for a seaport hydrogen refueling station in Ningbo City. In this work the CFD software FLUENT was used to study the influence of leakage angles on the leakage of high-pressure hydrogen through a small hole. Considering the calculation accuracy and efficiency this paper adopted the pseudo-diameter model. When the obstacle was far from the leakage hole it had almost no obstructive effect on the jet's main body. Still it affected the hydrogen whose momentum in the outer layer of the jet has been significantly decayed. In this condition there would be more hydrogen in stagnation. Thus the volume of the flammable hydrogen cloud was hardly affected while there was a significant increase in the volume of the hazardous hydrogen cloud. When the obstacle was close to the leakage hole it directly affected the jet's main body. Therefore the volume of the flammable hydrogen cloud increased. However the air impeded the hydrogen jet relatively less because the hydrogen jet contacted the obstacle more quickly. The hydrogen jet blocked by the obstacle still has some momentum. Therefore there was no more hydrogen in stagnation and no significant increase in the volume of the hazardous hydrogen cloud.
The NREL Sensor Laboratory: Hydrogen Leak Detection for Large Scale Deployments
Sep 2023
Publication
The NREL Hydrogen Sensor Laboratory was commissioned in 2010 as a resource for sensor developers end-users and regulatory agencies within the national and international hydrogen community. The Laboratory continues to provide as its core capability the unbiased verification of hydrogen sensor performance to assure sensor availability and their proper use. However the mission and strategy of the NREL Sensor Laboratory has evolved to meet the needs of the growing hydrogen market. The Sensor Laboratory program has expanded to support research in conventional and alternative detection methods as hydrogen use expands to large-scale markets as envisioned by the DOE National Clean Hydrogen Strategy and Roadmap. Current research encompasses advanced methods of hydrogen leak detection including stand-off and wide area monitoring approaches for large scale and distributed applications. In addition to safety applications low-level detection strategies to support the potential environmental impacts of hydrogen and hydrogen product losses along the value chain are being explored. Many of these applications utilize detection strategies that supplement and may supplant the use of traditional point sensors. The latest results of the hydrogen detection strategy research at NREL will be presented.
Detailed Assessment of Dispersion for High-pressure H2 in Multi-fuel Environment
Sep 2023
Publication
The MultHyFuel project notably aims to produce the data missing for usable risk analysis and mitigation activity for Hydrogen Refuelling Stations (HRS) in a multi-fuel context. In this framework realistic releases of hydrogen that could occur in representative multi-fuel forecourts were studied. These releases can occur inside or outside fuel dispensers and they can interact with a complex environment notably made of parked cars and trucks. This paper is focused on the most critical scenarios that were addressed by a sub-group through the use of Computational Fluid Dynamics (CFD) modelling. Once the corresponding source terms for hydrogen releases were known two stages are followed:<br/>♦ Model Validation – to evaluate the CFD models selected by the task partners and to evaluate their performance through comparison to experimental data.<br/>♦ Realistic Release Modelling – to perform demonstration simulations of a range of critical scenarios.<br/>The CFD models selected for the Model Validation have been tested against measured data for a set of experiments involving hydrogen releases. Each experiment accounts for physical features that are encountered in the realistic cases. The selected experiments include an under-expanded hydrogen jet discharging into the open atmosphere with no obstacles or through an array of obstacles. Additionally a very different set-up was studied with buoyancy-driven releases inside a naturally ventilated enclosure. The results of the Model Validation exercise show that the models produce acceptable solutions when compared to measured data and give confidence in the ability of the models and the modellers to capture the behaviour of the realistic releases adequately. The Realistic Release Modelling phase will provide estimation of the flammable gas cloud volume for a set of critical scenarios and will be described at the second stage.
Gas Crossover Predictive Modelling Using Artificial Neural Networks Based on Original Dataset Through Aspen Custom Modeler for Proton Exchange Membrane Electrolyte System
Sep 2023
Publication
Proton exchange membrane electrolyzer cell (PEMEC) will play a central role in future power-to-H2 plants. Current research focuses on the materials and operation parameters. Setting up experiments to explore operational accident scenarios about safety feasibility is not always practical. This paper focuses on building mathematical and prediction models of hydrogen and oxygen mixing scenarios of PEMEC. A mathematical model of the PEMEC device was customized in the Aspen Custom Model (ACM) software and integrated various critical Physico-chemical phenomena as the original data set for the prediction model. The results of the mathematical simulation verified the experimental results. The prediction model proposes an artificial neural network (ANN) framework to predict component distribution in the gas stream to prevent hydrogen-oxygen explosion scenarios. The presented approach by training ANN to 1000 sets of hydrogen-oxygen mixing simulation data from ACM is applicable to bypass tedious and non-smooth systems of equations for PEMEC.
Hydrogen Jet Fires in a Full-scale Road Tunnel: Experimental Results
Sep 2023
Publication
Hydrogen Fuel Cell Electric Vehicles (HFC EVs) represent an alternative to replace current internal combustion engine vehicles. The use of these vehicles with storage of compressed gaseous hydrogen (CGH2) or cryogenic liquid hydrogen (LH2) in confined spaces such as tunnels underground car parks etc. creates new challenges to ensure the protection of people and property and to keep the risk at an acceptable level. Several studies have shown that confinement or congestion can lead to severe accidental consequences compared to accidents in an open atmosphere. It is therefore necessary to develop validated hazard and risk assessment tools for the behaviour of hydrogen in tunnels. The HYTUNNEL-CS project sponsored by the FCH-JU pursues this objective. Among the experiments carried out in support of the validation of the hydrogen safety tools the CEA conducted tests on large-scale jet fires in a full-scale tunnel geometry.<br/>The tests were performed in a decommissioned road tunnel in two campaigns. The first one with 50 liters type II tanks under a pressure of 20 MPa and the second one with 78 liters type IV tanks under 70 MPa. In both cases a flate plate was used to simulate the vehicle. Downward and upward gas discharges to simulate a rollover have been investigated with various release diameters. For the downward discharge the orientation varied from normal to the road to a 45° rearward inclination. The first campaign took place under a concrete vault while the second under a rocky vault. Additional tests with the presence of a propane fire simulating a hydrocarbon powered vehicle fire were performed to study the interaction between the two reactive zones.<br/>In the paper all the results obtained during the second campaign for the evolution of the hydrogen jet-fire size the radiated heat fluxes and the temperature of the hot gases released in the tunnel are reported. Comparisons with the classical correlations from open field tests used in engineering models are also presented and conclusions are given as to their applicability.
Explosion Free in Fire Self-venting (TPRD-less) Composite Tanks: Performance Under Fire Intervention Conditions
Sep 2023
Publication
This paper describes the performance of explosion free in fire self-venting (TPRD-less) composite tanks of Type IV in fires of realistic intensity HRR/A=1 MW/m2 in conditions of first responders’ intervention. This breakthrough safety technology does not require the use of thermally activated pressure relief devices (TPRD). It provides microleaks-no-burst (LNB) performance of high-pressure hydrogen storage tanks in a fire. Two fire intervention strategies are investigated one is the removal of a vehicle with LNB tank from the fire and another is the extinction of the fire. The removal from the fire scenario is investigated for one carbon-carbon and one carbon-basalt double-composite wall tank prototype. The fire extinction scenario is studied for four carbon-basalt prototypes. All six prototypes of 7.5 L volume and nominal working pressure of 70 MPa demonstrated safe release of hydrogen through microchannels of the composite wall after melting a liner. The technology allows fire brigades to apply standard intervention strategies and tactics at the fire scene with hydrogen vehicles if LNB tanks are used in the vehicle.
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