Hydrogen fuel cell vehicles are expected to come into widespread use in the near future. Accordingly, manyhydrogen carrying vehicles will begin to pass through tunnels. It is therefore important to predict whetherrisk from leaked hydrogen accidents in tunnels can be avoided. CFD simulation was carried out on diffusion of leaked hydrogen in tunnels. Three areas of tunnels were chosen for study. One is the typical longitudinal and lateral areas of tunnels, and the others are underground ventilation facilities and electrostatic dustcollectors which were simulated with an actual tunnel. The amount of hydrogen leaked was 60m3(approximately 5.08 kg), which corresponds to the amount necessary for future fuel cell vehicles to achieve their desired running distance. Analytical periods were the time after leaks began until regions of hydrogen above the low flammability limit had almost disappeared, or thirty minutes. We found that leaked hydrogen is immediately carried away from leaking area under existing ventilation conditions. We also obtained basic data on behavior of leaked hydrogen.

In the course towards a safe future hydrogen based society, one of the tasks to be considered is the investigation of the conditions under which the use or storage of hydrogen systems inside buildings becomes too dangerous to be accepted. One of the relevant scenarios, which is expected to have a relatively high risk, is a slow (and long lasting) hydrogen release from a vehicle stored in a closed private garage without any forced ventilation, i.e. only with natural ventilation. This scenario has been earlier investigated experimentally (by M. Swain), using He (helium) to simulate the hydrogen behavior. In the present work the CFD code ADREA-HF is used to simulate three of the abovementioned experiments, using the standard k- turbulence model. For each case modeled the predicted concentration (by vol.) time series are compared against the experimental at the given sensor locations. In addition the structure of the flow is investigated by presenting the helium concentration field.

It is necessary to investigate cylinder crush behavior for improvement of fuel cell vehicle crash safety. However, there have been few crushing behavior investigations of high pressurized cylinders subjected to external force. We conducted a compression test of pressurized cylinders impacted by external force. We also investigated the cylinder strength and crushing behavior of the cylinder. The following results were obtained. 1) The crush force of high pressurized cylinders is different from the direction of external force. The lateral crush force of high pressurized cylinders is larger than the external axial crush force. 2) Tensile stress occurs in the boundary area between the cylinder dome and central portion when the pressurized cylinder is subjected to axial compression force, and the cylinder is destroyed. 3) However, the high pressurized cylinders tested had a high crush force, which exceeded the assumed range of vehicle crash test procedures.

For decades risk assessment has been an important tool in risk management of activities in several industries world wide. It provides among others, authorities and stakeholders with a sound basis for creating awareness about existing and potential hazards and risks and making decisions related to how they can prioritise and plan expenditures on risk reduction. The overall goal of the ongoing HySafe project is to contribute to the safe transition to a more sustainable development in Europe by facilitating the safe introduction of hydrogen technologies and applications. An essential element in this is the demonstration of safety: that all safety aspects related to production, transportation and public use are controlled to avoid that introducing hydrogen as energy carrier should pose unacceptable risk to the society.

History has proven that introducing risk analysis to new industries is beneficial, e.g. in transportation and power production and distribution. However, this will require existing methods and standards to be adapted to the specific applications. Furthermore, when trying to quantify risk, it is of utmost importance to have access to relevant accident and incident information. Such data may in many cases not be readily available, and the utilisation of them will then require specific and long lasting data collection initiatives.

In this paper we will present the work that has been undertaken in the HySafe project in developing methodologies and collecting data for risk management of hydrogen infrastructure. Focus is laid on the development of risk acceptance criteria and on the demonstration of safety and benefits to the public. A trustworthy demonstration of safety will have to be based on facts, especially on facts widely known, and emphasis will thus be put on the efforts taken to establish and operate a database containing hydrogen accident and incident information, which can be utilised in risk assessment of hydrogen applications. A demonstration of safety will also have to include a demonstration of risk control measures, and the paper will also present work carried out on safety distances and ignition source control.

Hydrogen energy is very promising, as it ensures a high efficiency and ecological cleanliness of energy conversion. The goal of the present work is to provide the analysis of hydrogen safety aspects and to prescribe methods of safety operation with hydrogen. The authors conducted a hazard analysis of hydrogen operation and storage in comparison with other fuels. Good ventilation is the main hydrogen operation requirement. Besides, an effective way of protection against propagation of hazards (for instance, leaks) is neutralization of dangerous hydrogen-air mixtures by a method of controlled catalytic combustion inside special devices, so-called recombiners [1-3]. The basis of these devices is a high porosity cell material (HPCM), activated by platinum deposition. Apart from recombiners, HPCM was also applied for development of hydrogen detectors intended for measurement and analysis of hydrogen concentration for hydrogen-driven transport and objects of hydrogen infrastructure (including vapor-air media at high pressure and temperatures). A system of hydrogen safety based on hydrogen detectors and hydrogen catalytic recombiners was developed. Experimental and theoretical studies of hydrogen combustion processes, heat- and mass transfer, and also gas flows in catalytic-activated HPCM, allowed for a design optimization of recombiners and their location. Pilot hydrogen detectors and hydrogen catalytic recombiners were fabricated and their laboratory tests were successfully performed. Thus, it was indicated that on condition of following the appropriate passive and active safety measures, hydrogen is just as safe as the other fuels. This conclusion represents another incentive for a transition to the hydrogen energy.

This paper discusses the results of computational fluid dynamics (CFD) modeling of hydrogen releases and dispersion outdoors during venting of hydrogen storage in real environment and geometry of a hydrogen refueling or energy station for a given flow rate and dimensions of vent stack. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy model and turbulence models. Also, thermal effects resulting from potential ignition of flammable hydrogen clouds were assessed using TNO "Yellow Book" recommended approaches. The obtained results were then applied to determine appropriate clearance distances for venting of hydrogen storage for contribution to code development and station design considerations. CFD modeling of hydrogen concentrations and TNO-based modeling of thermal effects have proven to be reliable, effective and relatively inexpensive tools to evaluate the effects of hydrogen releases.

This paper presents an analysis of computational fluid dynamic models of compressed hydrogen gas leaks into the air under different conditions to determine the volume of the hydrogen/air mixture and the extents of the lower flammable limit. The necessary hole size was calculated to determine a reasonably expected hydrogen leak rate from a valve or a fitting of 5 and 20 cfm under 400 bars, resulting in a 0.1 and 0.2 mm effective diameter hole respectively. The results were compared to calculated hypothetical volumes from IEC 60079-10 for the same mass flowrate and in most cases the CFD results produced significantly smaller hydrogen/air volumes than the IEC standard. Prescriptive electrical classification distances in existing standards for hydrogen and compressed natural gas were examined but they do not consider storage pressure and there appears to be no scientific basis for the distance determination. A proposed table of electrical classification distances incorporating hydrogen storage volume and pressure was produced based on the hydrogen LFL extents from a 0.2 mm diameter hole and the requirements of existing standards. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy model and turbulence models. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment, typical for a hydrogen refueling or energy station.

In October 2004, the International Energy Agency Hydrogen Implementing Agreement (www.ieahia.org) approved the initiation of a collaborative task on hydrogen safety. During the past twelve months a work plan has been established and several member countries have committed to participate. Because of the nature of the International Energy Agency, which is an international agreement between governments, it is hoped that such collaboration will complement other cooperative efforts to help build the technology base around which codes and standards can be developed. In this way the new task on hydrogen safety will further the IEA Hydrogen Agreement in fulfilling its mission to accelerate the commercial introduction of hydrogen energy. This paper describes the specific scope and work plan for the collaboration that has been developed to date.

Under government funded project: " Development for Safe Utilization and Infrastructure of Hydrogen" entrusted by New Energy and Industrial Technology Development Organization (NEDO), special material testing equipment with heavy walled pressure vessel under 45MPa gaseous hydrogen is facilitated. Tensile properties, strain controlled, low-cycle and high-cycle fatigue and fatigue crack growth tests on CrMo steel (SCM435 (JIS G 4105)) which will be applied for the storage gas cylinders in Japanese hydrogen fuel stations are investigated. The results of the tensile tests under 45MPa ultra high purity hydrogen gas (O2

Experimental studies were carried out to examine the lift-off and blow-out stability of H2/CO2, H2/Ar, H2/C3H8 and H2/CH4 jet flames. The experiments were carried out using a burner with a 2mm inner diameter. The flame structures were recorded by direct filming and also by a schlieren apparatus. The experiments showed that the four gases affected the lift-off and blow-out stability of the hydrogen differently. The experiments showed that propane addition to an initially attached flame always produced lifted flame and the flame was blown out at higher jet velocity. The blow-out velocity decreased as the increasing in propane concentration. Direct blow-off of hydrogen/propane was never observed. Methane addition resulted in a relatively stable flame comparing with the carbon dioxide and propane addition. Comparisons of the stability of H2/C3H8, H2/CH4 and H2/CO2 flames showed that H2/C3H8 produced the highest lift-off height. Propane is much more effective in lift-off and blow out hydrogen flames. The study carried out a chemical kinetic analysis of H2/CO2, H2/Ar, H2/C3H8 and H2/CH4 flames for a comparison of effect of chemical kinetics on flame stability.