Simulation of hydrogen leak and explosion for the safety design of hydrogen fueling station in Korea

Hydrogen has been used as chemicals and fuels in industries for last decades. Recently, it has become attractive as one of promising green energy candidates in the era of facing with two critical energy issues such as accelerating deterioration of global environment (e.g. carbon dioxide emissions) as well as concerns on the depletion of limited fossil sources. A number of hydrogen fueling stations are under construction to fuel hydrogen-driven vehicles. It would be indispensable to ensure the safety of hydrogen station equipment and operating procedure in order to prevent any leak and explosions of hydrogen: safe design of facilities at hydrogen fueling stations e.g. pressurized hydrogen leak from storage tanks. Several researches have centered on the behaviors of hydrogen ejecting out of a set of holes of pressurized storage tanks or pipes. This work focuses on the 3D simulation of hydrogen leak scenario cases at a hydrogen fueling station, given conditions of a set of pressures, 100, 200, 300, 400 bar and a set of hydrogen ejecting hole sizes, 0.5, 0.7, 1.0 mm, using a commercial computational fluid dynamics (CFD) tool, FLACS. The simulation is based on real 3D geometrical configuration of a hydrogen fueling station that is being commercially operated in Korea. The simulation results are validated with hydrogen jet experimental data to examine the diffusion behavior of leak hydrogen jet stream. Finally, a set of marginal safe configurations of fueling facility system are presented, together with an analysis of distribution characteristics of blast pressure, directionality of explosion. This work can contribute to marginal hydrogen safety design for hydrogen fueling stations and a foundation on establishing a safety distance standard required to protect from hydrogen explosion in Korea being in the absence of such an official requirement.     

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.     

Security risk analysis of a hydrogen fueling station with an on-site hydrogen production system involving methylcyclohexane

Although many studies have looked at safety issues relating to hydrogen fueling stations, few studies have analyzed the security risks, such as deliberate attack of the station by threats such as terrorists and disgruntled employees. The purpose of this study is to analyze security risks for a hydrogen fueling station with an on-site production of hydrogen from methylcyclohexane. We qualitatively conducted a security risk analysis using American Petroleum Institute Standard 780 as a reference for the analysis. The analysis identified 93 scenarios, including pool fires. We quantitatively simulated a pool fire scenario unique to the station to analyze attack consequences. Based on the analysis and the simulation, we recommend countermeasures to prevent and mitigate deliberate attacks.     

Predicting demand for hydrogen station fueling

Full function hydrogen stations are a reality; fuel cell electric vehicle drivers can pull up to commercial fueling stations and receive 3–5 kg in less than 5 min, for an approximately 300-mile range. The demand for hydrogen is increasing, driven by an increase in the fueling of public and private fuel cell vehicles. This study describes the development and value of a model that simulates stochastic future demand at a hydrogen filling station. The predictive hydrogen demand model described in this article is trained from mathematical models constructed from actual hydrogen fill count, amount, and frequency data. Future fill probabilities inform the hour-by-hour demand profile and the station state of either “available, ready to fill” or “available, filling”. For example, a prediction for a station generally dispensing 5,000 kg a week on a Friday afternoon at 4 p.m. is 16 fills, totaling 48.7 kg, with a 0.52 proportion of time spent in “available, filling” state yielding 31 min of filling time. This is a first-of-its kind, published study on predicting future hydrogen demand by the time of day (e.g., hour-by-hour intervals) and day of week. This study can be used for hydrogen station requirements and operation and maintenance strategies and to assess the impact of demand variations and scenarios. This article presents the current status of hydrogen demand, the model development methods, a set of sample results. Discussion and conclusions concentrate on the value and use of the proposed model.     

Data requirements for improving the Quantitative Risk Assessment of liquid hydrogen storage systems

Quantitative Risk Assessment (QRA) supports the development of risk-informed safety codes and standards which are employed to enable the safe deployment of hydrogen technologies essential to decarbonize the transportation sector. System reliability data is a necessary input for rigorous QRA. The lack of reliability data for bulk liquid hydrogen (LH₂) storage systems located on site at fueling stations limits the use of QRAs. In turn, this hinders the ability to develop the necessary safety codes and standards that enable worldwide deployment of these stations. Through a QRA-based analysis of a LH₂ storage system, this work focuses on identifying relevant scenario and probability data currently available and ascertaining future data collection requirements regarding risks specific to liquid hydrogen releases. The work developed consists of the analysis of a general bulk LH₂ storage system design located at a hydrogen fueling station. Failure Mode and Effect Analysis (FMEA) and traditional QRA modeling tools such as Event Sequence Diagrams (ESD) and Fault Tree Analysis (FTA) are employed to identify, rank, and model risk scenarios related to the release of LH₂. Based on this analysis, scenario and reliability data needs to add LH₂-related components to QRA are identified with the purpose of improving the future safety and risk assessment of these systems.     

Development of Korean hydrogen fueling station codes through risk analysis

When hydrogen fueling stations were constructed first time in Korea in 2006, there were no standards for hydrogen fueling stations. Hence the CNG (Compressed Natural Gas) station codes were temporarily adopted. In last three years, from 2006 to 2009, the studies for the development of hydrogen fueling station standards were carried out, with the support of the Korean government. In this study, three research groups cooperated to develop optimized hydrogen fueling station codes through risk analysis of hydrogen production and filling systems. Its results were integrated to develop the codes. In the first step to develop the codes, the standards for CNG stations and hydrogen fueling station were compared with each other and analyzed. By referring to foreign hydrogen fueling station standards, we investigated the potential problems in developing hydrogen fueling station codes based on the CNG station standards. In the second, the results of the high-pressure hydrogen leakage experiment were analyzed, and a numerical analysis was performed to establish the safety distance from the main facilities of a hydrogen fueling station to the protection facilities. In the third, HAZOP (Hazard and Operability) and FTA (Fault Tree Analysis) safety assessments were carried out for the on-site and off-site hydrogen fueling stations—currently being operated in Korea— to analyze the risks in existing hydrogen fueling stations. Based on the study results of the above three groups, we developed one codes for off-site type hydrogen fueling stations and another codes for on-site type hydrogen fueling stations. These were applied from September 2010.     

Dynamic simulation of the effect of vehicle-side pressure loss of hydrogen fueling process

This study explains the fundamental mathematical equations used for the main component models that are implemented in freely available library for hydrogen fueling station. The paper provides a background to the model formulation and theory, useful for the further investigations of hydrogen fueling stations. The model was verified against a specific manufacturer model, and it was validated by using test data from an actual fueling station. The study works as documentation and validation of the model formulation. The simulation library is used to make a model for investigating how the pressure loss in the vehicle affects the fueling process. Keeping the temperature out of the station constant and fueling to 80 MPa in the compressed hydrogen storage system, the pressure loss in the compressed hydrogen storage system directly correlates to the final temperature. The final temperature increases with increasing pressure losses. It is also shown that with no pressure loss in the vehicle the fueling has no limit in fueling speed as the heat of compression depends on the mass filled and the enthalpy of the mass, and not the filling time.     

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.     

BIM与RFID集成技术在水利工程施工作业安全管理中的应用

为减少水利工程安全事故的发生,加强对施工作业的安全管理,通过BIM与RFID集成技术,将施工现场作业人员及机械设备的属性信息、坐标信息存储于RFID标签中,通过信息采集传输到BIM 4D模型中;根据不同危险因素的安全计算规则,确定危险区域及作业人员的安全状态,并对作业人员实施安全预警;以水闸工程的施工仿真为例,运用集成BIM和RFID技术对施工现场的危险因素和作业人员进行实时监控,快速高效计算出危险区域的范围,完成工人安全状态的判定并进行安全预警,以降低施工现场安全生产事故发生的概率,提高安全管理的效率。研究成果对于水利水电工程施工管理有指导和借鉴意义。     

Hydrogen station siting optimization based on multi-source hydrogen supply and life cycle cost

Hydrogen station siting plays an important role in hydrogen-energy infrastructure construction, and it's different from gas station siting. A gas station has a unitary way of fuel transport and a unitary fuel supplier, hence no consideration given to factors like fuel supplier and way of fuel transport at the time of siting it. However, hydrogen for a hydrogen fueling station can be supplied jointly from a couple of different sources nearby. Since there is a diversity of hydrogen price and productivity between different sources, hydrogen fueling station siting also entails consideration of the effect of the proportions of hydrogen supplied by the sources on hydrogen's life cycle cost. With the purpose of minimizing hydrogen's life cycle cost, this paper creates a mathematical model for station siting, largely for the case that each station can get hydrogen supply from combined multiple sources, and considers the effect of geographical information factors on station siting. The effect of geographical information factors on such siting is described herein in two cases to avoid selecting a must-not-build location and rebuilding into a gasoline-hydrogen fueling station at an existing gas station location. The latter can reduce station construction and operating costs. By creating a particle swarm optimization (PSO) example for station siting with Shanghai-Nanjing Expressway and constructing a position particle swarm in the form of 5D vector in order to optimize 5 station locations at the same time as well a weight particle swarm in the form of 2D matrix in order to optimize the multi-source hydrogen supply programs, the paper works out optimal station construction locations on condition of multi-source hydrogen supply, multi-source hydrogen supply programs, ways of storage and transport and corresponding hydrogen's optimal life cycle cost.     

Safety Watchdog for universally safe gaseous high pressure hydrogen fillings

The fast filling time for hydrogen fuel cell vehicles makes them a user-friendly zero emission alternative to fossil fuel powered vehicles. The filling, by compressing gas into the vehicle tanks, produces heat that can be damaging. There are different protocols, standardized or the intellectual property of station operators, dedicated for different specific applications taking into account the specificity of the vessel and customer requirements. Standard protocols are developed for worst case conditions across a broad range of vehicle tank sizes and configurations. These worst case conditions do not result in the most economical equipment solution for hydrogen fueling. To ensure safety for different existing and future potential protocols a new “Safety Watchdog” approach is suggested in the current paper. This “Safety Watchdog” monitors the fueling process boundary conditions independently from the main process controls. The decoupling between the watchdog and the protocol allows use of protocols that are more economically beneficial while ensuring full safety conditions. The current paper provides a mathematical formulation of the Safety Watchdog as well as its validation versus modeling and field experimental data.     

Safety studies of a hydrogen refuelling station: Determination of the occurrence frequency of the accidental scenarios

At present, the hydrogen vehicles technology appears to have future prospective for reduction in greenhouse gas emissions. Nevertheless, the development of such a technology requires appropriate infrastructures for production, storage and refuelling stages in a refuelling station. This one presents safety challenges due to the hydrogen chemicophysical characteristics. So, to avoid hazards, it is necessary to implement safety practices that, if early adopted in the development of a fuelling station project, can allow very low impact, safety being incorporated in the project itself. However, a drawback is the not sufficient experience and the scarcity of the relevant data collection. To deepen studies about the risk in the above mentioned field, in this paper, for the moment, safety analyses of a high-pressure storage equipment in hydrogen gas refuelling station have been carried out by the integrated use of FMEA, HAZOP and FTA techniques. The work is intended to assess if the refuelling station design taken into consideration is safe enough, at least from the occurrence frequency point of view, as well to constitute a basis for further more refined studies which also consider the consequences aspects, allowing the plant risk assessment.     

Current standards and configurations for the permitting and operation of hydrogen refueling stations

The literature lacks a systematic analysis of HRS equipment and operating standards. Researchers, policymakers, and HRS operators could find this information relevant for planning the network's future expansion. This study is intended to address this information need by providing a comprehensive strategic overview of the regulations currently in place for the construction and maintenance of hydrogen fueling stations.A quick introduction to fundamental hydrogen precautions and hydrogen design is offered. The paper, therefore, provides a quick overview of hydrogen's safety to emphasize HRS standards, rules, and regulations. Both gaseous and liquid safety issues are detailed, including possible threats and installation and operating expertise.After the safety evaluation, layouts, equipment, and operating strategies for HRSs are presented, followed by a review of in-force regulations: internationally, by presenting ISO, IEC, and SAE standards, and Europeanly, by reviewing the CEN/CENELEC standards. A brief and concise analysis of Italy's HRS regulations is conducted, with the goal of identifying potential insights for strategic development and more convenient technology deployment.     

Impact of hydrogen SAE J2601 fueling methods on fueling time of light-duty fuel cell electric vehicles

Hydrogen fuel cell electric vehicles (HFCEVs) are zero-emission vehicles (ZEVs) that can provide drivers a similar experience to conventional internal combustion engine vehicles (ICEVs), in terms of fueling time and performance (i.e. power and driving range). The Society of Automotive Engineers (SAE) developed fueling protocol J2601 for light-duty HFCEVs to ensure safe vehicle fills while maximizing fueling performance. This study employs a physical model that simulates and compares the fueling performance of two fueling methods, known as the “lookup table” method and the “MC formula” method, within the SAE J2601 protocol. Both the fueling methods provide fast fueling of HFCEVs within minutes, but the MC formula method takes advantage of active measurement of precooling temperature to dynamically control the fueling process, and thereby provides faster vehicle fills. The MC formula method greatly reduces fueling time compared to the lookup table method at higher ambient temperatures, as well as when the precooling temperature falls on the colder side of the expected temperature window for all station types. Although the SAE J2601 lookup table method is the currently implemented standard for refueling hydrogen fuel cell vehicles, the MC formula method provides significant fueling time advantages in certain conditions; these warrant its implementation in future hydrogen refueling stations for better customer satisfaction with fueling experience of HFCEVs.     

Design of a hydrogen community

This paper discusses the conceptual design of a scalable and reproducible hydrogen fueling station at Santa Monica, California. Hydrogen production using renewable energy sources such as biogas, which accounts for 100% of the total production, has been discussed. The fueling station consists of a direct fuel cell (DFC) 300 fuel cell for on-site generation of 136 kg/day of hydrogen and 300 kW of electric power, five hydrogen storage tanks (storage capacity of 198 kg of H₂ at 350 and 700 bar), four compressors which assist in dispensing 400 kg of hydrogen in 14 h, two hydrogen dispensers operating at 350 bar and 700 bar independently and a SAE J2600 compliant hydrogen nozzle. Potential early market customers for hydrogen fuel cells and their daily fuel requirements have been computed. The safety codes, potential failure modes and the methods to mitigate risks have been explained. A well-to-wheel analysis is performed to compare the emissions and the total energy requirements of conventional gasoline and fuel cell vehicles.     

Review of transportation hydrogen infrastructure performance and reliability

Hydrogen infrastructure for fueling vehicles has progressed in the last decade from stations with restricted access and limited operating hours to customer-friendly retail stations open to the public. There are now 121 retail hydrogen stations around the world. In California, the number of public retail hydrogen stations has increased from zero to more than 30 in less than two years, and the annual amount of hydrogen dispensed by retail stations has grown from 27,400 kg in 2015 to nearly 105,000 kg in 2016 and more than 440,000 kg in 2017—an increase of about four times year over year. For more than a decade, government, industry, and academia have studied many aspects of hydrogen infrastructure, from renewable hydrogen production to retail hydrogen station performance. This paper reviews the engineering and deployment of modern hydrogen infrastructure, including the costs, benefits, and operational considerations (including safety, reliability, availability), as well as challenges to the scale-up of hydrogen infrastructure. The results identify hydrogen station reliability as a key factor in the expense of operating hydrogen systems, placing it in the context of the larger reliability engineering field.     

Thermodynamic parametric analysis of refueling heavy-duty hydrogen fuel-cell electric vehicles

Reliable design and safe operation of heavy-duty hydrogen refueling stations are essential for the successful deployment of heavy-duty fuel cell electric vehicles (FCEVs). Fueling heavy-duty FCEVs is different from light-duty vehicles in terms of the dispensed hydrogen quantities and fueling rates, requiring tailored fueling station design for each vehicle class. In particular, the selection and design of the onboard hydrogen storage tank system and the fueling performance requirements influence the safe design of hydrogen fueling stations. A thermodynamic modeling and analysis are performed to evaluate the impact of various fueling parameters and boundary conditions on the fueling performance of heavy-duty FCEVs. We studied the effect of dispenser pressure ramp rate and precooling temperature, initial tank temperature and pressure, ambient temperature, and onboard storage design parameters, such as onboard storage pipe diameter and length, on the fueling rate and final vehicle state-of-charge, while observing prescribed tank pressure and temperature safety limits. An important finding was the sensitivity of the temporal fueling rate profile and the final tank state of charge to the design factors impacting pressure drop between the dispenser and vehicle tank, including onboard storage pipe diameter selection, and flow coefficients of nozzle, valves, and fittings. The fueling rate profile impacts the design and cost of the hydrogen precooling unit upstream of the dispenser.     

熔盐塔式光热电站仿真机设计与开发

[目的]为了解决熔盐塔式光热电站建设和运维过程中,控制逻辑难以验证以及运行人员缺乏操作经验的问题.[方法]开发了一套用于塔式熔盐光热电站的仿真机.逻辑组态方面采用了虚拟DPU技术与软件化对象配置技术,采用了与实际电站完全相同的数值模型和设计参数.[结果]仿真试验结果表明该仿真机能够很好的实现电站生产过程中的工况模拟和仿...     

An integrated quantitative-qualitative study to monitor the utilization and assess the perception of hydrogen fueling stations

Zero-emission vehicle (ZEV) adoption is one of the critical solutions to decarbonize the transportation sector. Among the ZEV fleet in the US, battery electric vehicles (BEV) have been leading the market penetration. However, hydrogen fuel cell electric vehicles (FCEV) have also been increasingly adopted in recent years. Although both technologies have challenges with infrastructure, unlike BEVs that have multiple venues for charging (home, work or public), FCEVs rely solely on fueling at public hydrogen stations, and their availability is a significant factor before the vehicle purchase. Therefore, for the success of FCEV adoption, a need to monitor and understand the driver satisfaction of these stations is extremely critical. This research project introduces a quantitative-qualitative approach for continuous monitoring of hydrogen stations based on the station utilization patterns and to assess their preferability based on driver experiences. To illustrate a proof-of-concept, we collected the hourly utilization data of all the hydrogen fueling stations in California for three months. The time-series data was used to develop a capacity-independent term called “Normalized Relative Utilization Index” (NRUI) that encapsulates the utilization pattern of each station to a single metric. We spatially regressed this metric over the number of FCEVs present in the neighborhood to deduce the relationship. We designed a survey to obtain the refueling experiences of FCEV drivers, where about 100 participants responded with their station preferences. Their answers were used to validate the quantitative approach and identify a “Satisfactory Utilization Range” (SUR) of stations which are preferred by most drivers. Though this project illustrates the analysis of data collected over a small period, this approach is easily scalable with new station installations and can be implemented as a continuous monitoring system with real-time station utilization data. We believe this demand-focused approach could complement the existing supply-side monitoring methods on station performance to provide a smoother fueling experience to drivers. We are also releasing the hourly station capacity dataset that was collected as a part of this study to the research community.