Safety

The viability and public acceptance of the hydrogen and fuel cell (HFC) systems and infrastructure depends on their robust safety engineering design education and training of the workforce regulators and other stakeholders in the state-of-the-art in the field. This can be provided only through building up and maturity of the hydrogen safety engineering (HSE) profession. HSE is defined as an application of scientific and engineering principles to the protection of life property and environment from adverse effects of incidents/accidents involving hydrogen. This paper describes a design framework and overviews a structure and contents of technical sub-systems for carrying out HSE. The approach is similar to British standard BS7974 for application of fire safety engineering to the design of buildings and expanded to reflect on specific for hydrogen safety related phenomena including but not limited to high pressure under-expanded leaks and dispersion spontaneous ignition of sudden hydrogen releases to air deflagrations and detonations etc. The HSE process includes three main steps. Firstly a qualitative design review is undertaken by a team that can incorporate owner hydrogen safety engineer architect representatives of authorities having jurisdiction e.g. fire services and other stakeholders. The team defines accident scenarios suggests trial safety designs and formulates acceptance criteria. Secondly a quantitative safety analysis of selected scenarios and trial designs is carried out by qualified hydrogen safety engineer(s) using the state-of-the-art knowledge in hydrogen safety science and engineering and validated models and tools. Finally the performance of a HFC system and/or infrastructure under the trial safety designs is assessed against predefined by the team acceptance criteria. This performance-based methodology offers the flexibility to assess trial safety designs using separately or simultaneously three approaches: deterministic comparative or combined probabilistic/deterministic.

High-order perturbation solutions have been obtained for the simple physical model describing the LH2 spreading with a continuous spill and are shown to improve over the first-order perturbation solutions. The non-dimensional governing equations for the model are derived to obtain more general solutions. Non-dimensional parameters are sought as the governing parameters for the non-dimensional equations and the non-dimensional evaporation rate is used as the perturbation parameter. The results show that the second-order solutions exhibit an improvement over the first-order solutions with respect to the pool volume; however there is still a difference between numerical solutions and second-order solutions in the late stage of spread. Finally it is revealed that the third-order solutions almost agree with numerical solutions.

This paper describes a series of explosion experiments in inhomogeneous hydrogen air clouds in a standard 20′ ISO container. Test parameter variations included nozzle configuration jet direction reservoir back pressure time of ignition after release and degree of obstacles. The paper presents the experimental setup resulting pressure records and high speed videos. The explosion pressures from the experiments without obstacles were in the range of 0.4–7 kPa. In the experiments with obstacles the gas exploded more violently producing pressures in order of 100 kPa.

The Department of Energy the Department of Defense's Defense Logistics Agency and the Department of Transportation's Federal Transit Administration have funded learning demonstrations and early market deployments to provide insight into applications of hydrogen technologies on the road in the warehouse and as stationary power. NREL's analyses validate the technology in real-world applications reveal the status of the technology and facilitate the development of hydrogen and fuel cell technologies manufacturing and operations. This paper presents the maintenance safety and operation data of fuel cells in multiple applications with the reported incidents near misses and frequencies. NREL has analyzed records of more than 225000 kilograms of hydrogen that have been dispensed through more than 108000 hydrogen fills with an excellent safety record.

In the accident of Fukushima Daiichi nuclear power plants hydrogen was accumulated in the reactor buildings and exploded. To prevent such explosions hydrogen venting from reactor buildings is considered. When the gas mixture is released to a reactor building through a reactor containment together with the hydrogen some amount of steam might also be released. The steam condenses if the building atmosphere is below the saturation temperature and it affects the hydrogen behaviour. In this study the condensation effect to the hydrogen venting is evaluated using CFD analyses by comparing the case where a hydrogen-nitrogen mixture is released and the case where a hydrogen-steam mixture is released.

The flame propagation regimes for the stoichiometric hydrogen-air mixtures in an obstructed semiconfined flat layer have been numerically investigated in this paper. Conditions defining fast or sonic propagation regime were established as a function of the main dimensions characterizing the system and the layout of the obstacles. It was found that the major dependencies were the following: the thickness of the layer of H2-air mixture the blockage ratio and the distance between obstacles and the obstacle size. A parametric study was performed to determine the combination of the above variables prone to produce strong combustions. Finally a criterion that separates experiments resulting in slow subsonic from fast sonic propagations regimes was proposed.

The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.

GASFLOW is a finite-volume computer code that solves the time-dependent two-phase homogeneous equilibrium model compressible Navier–Stokes equations for multiple gas species with turbulence. The fluid-dynamics algorithm is coupled with conjugate heat and mass transfer models to represent walls floors ceilings and other internal structures to describe complex geometries such as those found in nuclear containments and facilities. Recent applications involve simulations of cryogenic hydrogen tanks at elevated pressures. These applications which often have thermodynamic conditions near the critical point require more accurate real-gas Equations-of-State (EoS) and transport properties than the standard ideal gas EoS and classical kinetic-theory transport properties. This paper describes the rigorous implementation of the generalized real-gas EoS into the GASFLOW CFD code as well as the specific implementation of respective real-gas models (Leachman's NIST hydrogen EoS a modified van der Waals EoS and a modified Nobel-Abel EoS); it also includes a logical testing procedure based upon a numerically exact benchmark problem. An example of GASFLOW simulations is presented for an ideal cryo-compressed hydrogen tank of the type utilized in fuel cell vehicles.

Sandia National Laboratories is working with stakeholders to develop scientific data for use by standards development organizations to create hydrogen codes and standards for the safe use of liquid hydrogen. Knowledge of the concentration field and flammability envelope for high-pressure hydrogen leaks is an issue of importance for the safe use of liquid hydrogen. Sandia National Laboratories is engaged in an experimental and analytical program to characterize and predict the behaviour of liquid hydrogen releases. This paper presents a model for computing hydrogen dilution distances for cold hydrogen releases. Model validation is presented for leaks of room temperature and 80 K high-pressure hydrogen gas. The model accounts for a series of transitions that occurs from a stagnate location in the tank to a point in the leak jet where the concentration of hydrogen in air at the jet centerline has dropped to 4% by volume. The leaking hydrogen is assumed to be a simple compressible substance with thermodynamic equilibrium between hydrogen vapor hydrogen liquid and air. For the multi-phase portions of the jet near the leak location the REFPROP equation of state models developed by NIST are used to account for the thermodynamics. Further downstream the jet develops into an atmospheric gas jet where the thermodynamics are described as a mixture of ideal gases (hydrogen–air mixture). Simulations are presented for dilution distances in under-expanded high-pressure leaks from the saturated vapor and saturated liquid portions of a liquid hydrogen storage tank at 10.34 barg (150 PSIG).

In this study we conducted hydrogen gas filling and discharging cycling tests to examine the thermal behaviour in hydrogen storage tanks under actual use conditions. As a result it was confirmed that the gas temperature in the tank varied depending on the initial test conditions such as the ambient temperature of the tank and the filling gas temperature and that the gas temperature tended to stabilize after several gas filling and discharging cycles.