Estimation of consequence and damage caused by an organic hydride hydrogen refueling station

Organic hydride hydrogen refueling stations are currently being developed in Japan. For these stations, we estimate the consequence and damage caused by explosions and heat radiation after a hydrogen leak, and the acute toxicity caused by the leakage and dispersion of methylcyclohexane and toluene energy carriers. First, the organic hydride hydrogen refueling station is defined, and an accident scenario for four leak sizes of hydrogen and chemical leak accidents is set. Next, simulations of the blast wave pressure and heat radiation after the hydrogen leak and of atmospheric dispersion for the evaporation after liquid methylcyclohexane and toluene leaks are performed. Probit functions or threshold values are created for each type of effects caused by the explosion, heat and the inhalation effect on humans of toluene acute toxicity. Population data for the area surrounding the station are created in a 10-m mesh. The consequence and damage are estimated for each leak size. The results show that although the explosion and chemical leak affects the area around the refueling station, the effects are small in all of the accident scenarios. In contrast, although the area of the heat effect is limited to inside the refueling station, the burn damage is large, and there is a need for conducting quantitative risk assessment.     

Harm effect distances evaluation of severe accidents for gaseous hydrogen refueling station

With the development of large-scale fell cell vehicle demonstration project worldwide, the global number of hydrogen refueling stations has increased rapidly in recent years. The external safety of hydrogen refueling stations has always been a public concern for its further development. This paper examines the harm effect distances of severe accidents for a gaseous hydrogen refueling station. First, different accident scenarios are assumed and their subsequent consequences are calculated, including physical explosion, jet fire, flash fire and confined vapor cloud explosion. Results show that physical explosion and worst case of confined vapor cloud explosion produce the longest harm effect distances for instantaneous release and continuous release, respectively. This indicates that they may be used as decisive consequences to the determination of safe distances. Second, the influences of different factors on harm effect distances are investigated, including those of release inventory, release pressure, release height, release angle, release diameter and wind velocity. Then, based on these results, several potential hazard mitigation measures are proposed such as elevating hydrogen equipment, using smaller vessel and adopting smaller pipe work, if reasonably practicable.     

An advanced framework for leakage risk assessment of hydrogen refueling stations using interval-valued spherical fuzzy sets (IV-SFS)

The extensive population growth calls for substantial studies on sustainable development in urban areas. Thus, it is vital for cities to be resilient to new situations and adequately manage the changes. Investing in renewable and green energy, including high-tech hydrogen infrastructure, is crucial for sustainable economic progress and for preserving environmental quality. However, implementing new technology needs an effective and efficient risk assessment investigation to minimize the risk to an acceptable level or ALARP (As low as reasonably practicable). The present study proposes an advanced decision-making framework to manage the risk of hydrogen refueling station leakage by adopting the Bow-tie analysis and Interval-Value Spherical Fuzzy Sets to properly deal with the subjectivity of the risk assessment process. The outcomes of the case study illustrate the causality of hydrogen refueling stations' undesired events and enhance the decision-maker's thoughts about risk management under uncertainty. According to the findings, jet fire is a more likely accident in the case of liquid hydrogen leakage. Furthermore, equipment failure has been recognized as the most likely cause of hydrogen leakage. Thus, in order to maintain the reliability of liquid hydrogen refueling stations, it is crucial that decision-makers develop a trustworthy safety management system that integrates a variety of risk mitigation measures including asset management strategies.     

Quantitative risk assessment of a mobile hydrogen refueling station in Korea

Hydrogen infrastructure is expanding. Mobile hydrogen refueling stations are advantageous because they can be moved between locations to provide refueling. However, there are serious concerns over the risk of various accident scenarios as the refueling stations are transported. In this study, we conduct a quantitative risk assessment of a mobile hydrogen refueling station. Risks that may occur at two refueling locations and the transport path between them are analyzed. Our evaluation reveals that risks are mostly in an acceptable zone and to a lesser degree in a conditionally acceptable zone. The greatest single risk factor is an accident resulting from the rupture of the tube trailer at the refueling site. At sites with no tube trailer and during the transport, the risk is greatest from large leaks from the dispenser or compressed gas facility. The mobile hydrogen refueling station can be safely built within acceptable risk levels.     

The simulation and analysis of leakage and explosion at a renewable hydrogen refuelling station

The number of hydrogen refuelling stations (HRSs) is steadily growing worldwide. In China, the first renewable hydrogen refuelling station has been built in Dalian for nearly 3 years. FLACS software based on computational fluid dynamics approach is used in this paper for simulation and analysis on the leakage and explosion of hydrogen storage system in this renewable hydrogen refuelling station. The effects of wind speed, leakage direction and wind direction on the consequences of the accident are analyzed. The harmful area, lethal area, the farthest harmful distance and the longest lethal distance in explosion accident of different accident scenarios are calculated. Harmful areas after explosion of different equipments in hydrogen storage system are compared. The results show that leakage accident of the 90 MPa hydrogen storage tank cause the greatest harm in hydrogen explosion. The farthest harmful distance caused by explosion is 35.7 m and the farthest lethal distance is 18.8 m in case of the same direction of wind and leakage. Moreover, it is recommended that the hydrogen tube trailer should not be parked in the hydrogen refuelling station when the amount of hydrogen is sufficient.     

Numerical investigation of the leakage and explosion scenarios in China's first liquid hydrogen refueling station

Promoting fuel cells has been one of China's ambitious hydrogen policies in the past few years. Currently, several hydrogen fueling stations (HRSs) are under construction in China to fuel hydrogen-driven vehicles. In this regard, it is necessary to assess the risks of hydrogen leakage in HRSs. Aiming at conducting a comprehensive consequence assessment of liquid hydrogen (LH2) leakage on China's first liquid hydrogen refueling station (LHRS) in Pinghu, a pseudo-source model is established in the present study to simulate the LH2 leakage using a commercial CFD tool, FLACS. The effects of the layout of the LHRS, leakage parameters, and local meteorological conditions on the LH2 leakage consequence has been assessed from the perspectives of low-temperature hazards and explosion hazards. The obtained results reveal that considering the prevailing southeast wind in Pinghu city, the farthest low-temperature hazard distance and lower flammable limit (LFL) -distance occurs in the leakage scenario along the north direction. It is found that the trailer parking location in the current layout of the LHRS will worsen the explosion consequences of the LH2 leakage. Moreover, the explosion will completely destroy the control room and endanger people on the adjacent road when the leakage equivalent diameter is 25.4 mm. The performed analyses reveal that as the wind speed increases, the explosion hazard decreases.     

Quantitative risk assessment of an urban hydrogen refueling station

Hydrogen is one of important energy source in the next generation of renewable energy. It has powerful strength such as no emission from CO2 for fuel, Nevertheless, many countries have difficulties to expand hydrogen infra due to high risky from hydrogen. Especially, the hydrogen refueling station which is located in urban area has congested structure and high population around, it has higher risk than conventional refueling station. This paper presents a quantitative risk assessment (QRA) of a high pressure hydrogen refueling station in an urban area with a large population and high congestion between the instruments and equipment. The results show that leaks from the tube-trailer and dispenser as well as potential explosion of the tube-trailer are the main risks. For the safety of the station operator, customers and people surrounding the refueling station, additional mitigation plans such as adding additional safety barrier system have to be implemented on the compressor and dispenser in order to prevent continuous release of hydrogen from an accident.     

A study of hydrogen leak and explosion in different regions of a hydrogen refueling station

The consequences of hydrogen leaks and explosions are predicted for the sake of the safety in hydrogen refueling stations. In this paper, the effect of wind speed on hydrogen leak and diffusion is analyzed in different regions of a hydrogen refueling station, and the influence of delayed ignition time on hydrogen explosion after an accidental hydrogen leak is further studied by numerical simulation. Results show that the effect of wind speed on the probability of hydrogen fires is distinctive in different regions of hydrogen refueling station. The size of combustible clouds in the trailer front region and the outer region increases in the low wind speed case, and the front of combustible clouds is formed in a spherical shape in the outer region, which can greatly increase the probability of hydrogen explosion. However, the high wind speed may cause an increase of the risk of accidents in the near ground region. Moreover, a non-linear correlation is shown between the rate of combustible cloud dissipation and wind speed after the hydrogen stops leaking. In addition, it is found that an increase in delayed ignition time may lead to an increase in explosion intensity, which is related with the larger high temperature area and stronger explosion overpressure. Two flame fronts and the reverse propagation of the explosion overpressure can be observed, when the delayed ignition time is larger.     

Integrated planning method of green hydrogen supply chain for hydrogen fuel cell vehicles

To satisfy the growing refueling demand of hydrogen fuel cell vehicles (HFCVs) with carbon-free hydrogen supply, this paper proposes an integrated planning method of green hydrogen supply chain. First, the k-shorted path method is introduced to analyze HFCV refueling load considering vehicle travel habits and routing diversity. Second, based on it, a two-stage integrated planning model is established to minimize the total investment and operation cost. The construction of hydrogen refueling stations, electrolysis-based hydrogen generation stations and hydrogen pipelines are coordinated with their operating constraints, constituting the green hydrogen supply chain, in which hydrogen storage is also an important part for consideration to address variable renewable power. Then, the proposed model is reformulated as a mixed integer linear programing (MILP) problem solved efficiently. Finally, the case studies are carried out on an urban area in Xi'an China to verify the validity and correctness of the proposed method. The results show that the integrated planning can realize synergy benefits. The influence of electricity prices and k values is also discussed.     

Safety investigation of hydrogen charging platform package with CFD simulation

Hydrogen has been expected as one of the most promising green energy sources, especially in transportation section. Despite its great potential as a new source of energy, it is reluctant to build hydrogen charging stations for the fear of accidents such as hydrogen leakage, fire, and following explosion. To reduce those problems and promote the acceptance of hydrogen charging station, this study focuses on the hydrogen charging platform package (HCPP) which is a new type of the mobile hydrogen station. Hydrogen leakage cases are investigated using CFD (computational fluid dynamics) simulation. The simulation is performed with the whole configuration of the HCPP including main components, storage, compressor, and dispenser. Based on the risk assessment, hydrogen leak scenarios with high possibilities of accidents are simulated. The simulation results show the leak length of hydrogen gas, its dispersion, and the various ranges of volume ratios of leaked hydrogen gas. Based on the simulation results, it is clearly confirmed that the leaked hydrogen gas with high concentration stays inside the HCPP. Therefore, the effects of ventilation to reduce the possibility of the explosion are continuously considered to investigate the safety of the HCPP in the case of the leakage accident.     

How to finance for establishing hydrogen refueling stations in China? An analysis based on Fuzzy AHP and PROMETHEE

Fuel Cell Vehicles are considered as a promising alternative for future sustainable transportation, while the deployment of hydrogen refueling stations is one of the major barriers that blocking the commercial introduction of Fuel Cell Vehicles. Since the establishment of hydrogen infrastructures not only requires quite a large investment, but also needs efficient project management and operation. Therefore, how to finance and operate hydrogen infrastructures is a difficult question for decision makers. In this study, it introduced four business models for financing and operating hydrogen refueling stations: Build-Operate-Transfer, Transfer-Operate-Transfer, Public-Private-Partnership, and Asset- Backed Securitization, and identified six criteria for prioritizing them. Then, it employed Fuzzy Analytic Hierarchy Process to determine the weight for the criteria, and compared the performance of these models with respect each criterion. Finally, the method of Preference Ranking Organization Method for Enrichment Evaluations was used to determine the priority of each model for financing hydrogen refueling stations, and a Sensitivity Analysis was conducted to find the most appropriate model in different situations. The results indicated that financing difficulty, project risks, and financing costs are the most important factors for strategic investors to involve in financing hydrogen refueling stations. Among the four financing models, Public-Private-Partnership and Transfer-Operate-Transfer models are turned out to be more preferable for financing hydrogen infrastructure in China. Some policy implications have also been provided for the establishment of hydrogen refueling stations.     

Dynamic risk assessment of hybrid hydrogen-gasoline fueling stations using complex network analysis and time-series data

Since hybrid hydrogen-gasoline fueling stations store two types of hazardous chemicals, the number of victims might be substantially higher than at gas or hydrogen fueling stations during a leakage or explosion. Therefore, it is crucial to conduct an in-depth analysis and risk assessment of hybrid hydrogen-gasoline fueling stations. We establish a time series risk assessment model and use complex network analysis to analyze potential fire and explosion events in hybrid hydrogen-gasoline fueling stations. The complex network model is used to assess the structural characteristics of the complex hybrid hydrogen-gasoline fueling stations, extract the accident causal chain, and explain the relationship between the accident causal factors and the system's risk from a multi-dimensional perspective. Subsequently, time-ordered weighted averaging (TOWA) and time-ordered weighted geometric averaging (TOWGA) operators are incorporated into the complex network model. The TOWA-TOWGA hybrid operator combines the evaluation values of the summer and winter periods to obtain the dynamic risk assessment results. The static and dynamic assessment results are used to determine the degree of influence of the accident causal factors on the system risk in different periods and dimensions. The information is suitable for developing highly targeted measures to prevent/control high-risk disaster events in hybrid hydrogen-gasoline fueling stations.     

Addition of hydrogen refueling for fuel cell bus fleet to existing natural gas stations: A case study in Wuhan,China

Hydrogen refueling is an essential infrastructure for fuel cell vehicles, and currently, it appears to be a critical service needed to initiate the highly anticipated hydrogen economy in China. A practical selecting procedure of adding hydrogen refueling service to existing natural gas (NG) stations is proposed in this study. A case study in Wuhan, China, is established to assess the feasibility and future planning. The demand for hydrogen fuel and initial supply chain of hydrogen in Wuhan are estimated based on the deployment objective of fuel cell buses. The existing NG stations are evaluated based on 300 kg/day to determine whether they meet the hydrogen safety requirement using Google map or field investigation. The safety space requirement of the hydrogen refueling area on existing NG station is determined as 25.9 × 27.1 m². The optimal hydrogen refueling plan for fuel cell buses is calculated with multi‐objective analysis in economic, environmental, and safety aspects from the view of the hydrogen refueling supply chain. It is shown that adding hydrogen refueling stations to existing NG stations is feasible in technology, economics, regulation, and operation considerations. This study provides guidelines for building the hydrogen infrastructure for fuel cell buses at their early stage of commercial operation.     

Trade-off study between risk and benefit in safety devices for hydrogen refueling stations using a dynamic physical model

As hydrogen refueling stations become increasingly common, it is clear that a high level of economic efficiency and safety is crucial to promoting their use. One way to reduce costs is to use a simple orifice instead of an excess flow valve, which Japanese safety regulations have identified as a safety device. However, there is concern about its effect on refueling time and on risk due to hydrogen leakage. To clarify the effect, we did a study of model-based refueling time evaluation and quantitative risk assessment for a typical refueling station. This study showed that an orifice is an effective alternative safety device. The increase in refueling time was less than 10%, based on simulations using a dynamic physical model of the station. Neither was there a significant difference in the risk between a configuration with excess flow valves and one with an orifice.     

Development of a Hydrogen Refueling Station Design Tool

In the last couple of decades, there has been a growing concern in what effects fossil fuels are having on the environment, resulting in governments and governing organizations issuing stringent emission standards in an effort to curve their environmental damage. To meet these new standards, the transportation industry has been conducting research into alternative fuels, such as hydrogen, but one critical problem utilizing hydrogen is that there is almost no infrastructure. A network of hydrogen refueling stations similar to modern gasoline stations will be required to be constructed to meet future demand. The hydrogen refueling station model was created to aid in designing hydrogen facilities, thus accelerating their development while reducing design cost. A model was created using Simulink consisting of an electrolyzer that generates hydrogen, a compressor, numerous storage tanks, a dispensing unit that transfers hydrogen, and a vehicle component that consumes hydrogen fuel. The model was validated using data from existing hydrogen refueling stations, and the data obtained from testing the previous version of the hydrogen refueling station model to determine model accuracy and if the model has improved. The model has demonstrated that it can produce reasonable results for a station's performance and has improved compared to the previous version.     

长三角地区加氢站发展现状、障碍分析及对策建议

目的  为促进我国实现碳达峰、碳中和目标,深入推进生产和消费革命,构建清洁低碳、安全高效的能源体系,发展氢能产业有着重要意义。加速发展加氢站是实现氢能源全链条的关键,是实现氢能产业健康、迅速发展的重要保障。由于长三角地区石化和化工企业氢能消费规模大,氢燃料电池汽车等发展迅速,促进加氢站发展及网络建设是氢能推广的重中之重。 方法  通过文献研究法、个案研究法、调查研究法、经济性测算等研究方法分析长三角地区加氢站建站审批流程、政策环境等现状,识别制约长三角地区加氢站建设发展的障碍。 结果  由于氢的能源属性缺乏法律支撑,建设标准缺乏指导性,多部门协作机制不健全等因素制约了加氢站的建设,阻碍了氢能产业的发展。 结论  应健全氢能有关法律法规,明确氢能“危化品”与“能源”的边界条件,完善加氢站建设标准及审批流程,集中力量攻关核心技术,增加财政补贴扶持力度,加速推广燃料电池汽车,促进氢能产业发展。     

Improved safety by crossanalyzing quantitative risk assessment of hydrogen refueling stations

With the goal of building 310 hydrogen refueling stations (HRSs) in Korea by 2022, restrictions, such as location restrictions and separation distances, are being eased, so developing ways to improve technology and safety. As HRSs contain major facilities such as compressors, storage tanks, dispenser, and priority control panels, and a leakage could result in a large fire or explosion caused by an ignition source. To perform quantitative risk assessment, programs, namely, Hy-KoRAM and Phast/Safeti were used in this study. It could determine the damage range and effect on radiant heat and flame length, as well as personal and societal risks, using these programs. The crossanalysis of the two programs also improves the facility's safety and the reliability of the results.     

On optimal investment strategies for a hydrogen refueling station

The uncertainty and cost of changing from a fossil-fuel-based society to a hydrogen-based society are considered to be extensive obstacles to the introduction of fuel cell vehicles (FCVs). The absence of existing profitable refueling stations has been shown to be one of the major barriers. This paper investigates methods for calculating an optimal transition from a gasoline refueling station to future methane and hydrogen combined use with an on site small-scale reformer for methane. In particular, we look into the problem of matching the hydrogen capacity of a single refueling station to an increasing demand. Based on an assumed future development scenario, optimal investment strategies are calculated. First, a constant utilization of the hydrogen reformer is assumed in order to find the minimum hydrogen production cost. Second, when considerations such as periodic maintenance are taken into account, optimal control is used to concurrently find both a short term equipment variable utilization for one week and a long term strategy. The result is a minimum hydrogen production cost of $4–6/kg, depending on the number of reinvestments during a 20 year period. The solution is shown to yield minimum hydrogen production cost for the individual refueling station, but the solution is sensitive to variations in the scenario parameters.     

GASFLOW-MPI: A new 3-D parallel all-speed CFD code for turbulent dispersion and combustion simulations Part II: First analysis of the hydrogen explosion in Fukushima Daiichi Unit 1

The core-melt in Fukushima-Daiichi Unit 1 represents a new class of severe accidents in which combustible gas from core degradation leaked from the containment into the surrounding air-filled reactor building, formed there a highly reactive gas mixture, and exploded 25 h after begin of the station black-out. Since TMI-2 hydrogen safety research and management has focussed on processes and counter-measures inside the containment but the reactor building remained unprotected against hydrogen threats. The code GASFLOW-MPI is currently under development to simulate hydrogen behaviors, including distribution and combustion, for scenarios with containment leakage.This paper describes a first analysis of the hydrogen explosion in Unit 1. It investigates gas dispersion in the reactor building, assuming a leak at the drywell head flange, shows the evolution of a stratified, inhomogeneous H₂–O₂–N₂–steam mixture in the refueling bay, simulates the combustion of the reactive gas mixture, and predicts pressure loads to walls and internal structures of the reactor building. The blast wave propagated essentially sideways, which explains why all side walls were blown out and the ceiling just collapsed onto the floor of the refueling bay. The blast wave propagation into the free environment was also simulated. The over-pressure amplitudes are sufficiently high to cause damage to adjacent buildings and to injure people. The hitherto existing presumption that the blow-out panel of Unit 2 was removed by the Unit 1 explosion can be confirmed which likely prevented a hydrogen explosion in the Unit 2.GASFLOW-MPI provides validated models for the integral simulations of leakage related core-melt scenarios. Furthermore, the code contains extensively tested submodels for catalytic recombiners, igniters and burst foils, which allow design of new hydrogen risk mitigation systems for currently unprotected spaces in reactor buildings.