United States

Stationary pressure vessels for the storage of large volumes of gaseous hydrogen at high pressure (>70 MPa) are typically manufactured from Cr-Mo steels. These steels display hydrogen-enhanced fatigue crack growth but pressure vessels can be manufactured using defect-tolerant design methodologies. However storage volumes are limited by the wall thickness that can be reliably manufactured for quench and tempered Cr-Mo steels typically not more than 25-35 mm. High-hardenability steels can be manufactured with thicker walls which enables larger diameter pressure vessels and larger storage volumes. The goal of this study is to assess the fracture and fatigue response of high hardenability Ni-Cr-Mo pressure vessel steels for use in high-pressure hydrogen service at pressure in excess of 1000 bar. Standardized fatigue crack growth tests were performed in gaseous hydrogen at frequency of 1Hz and for R-ratios in the range of 0.1 to 0.7. Elastic-plastic fracture toughness measurements were also performed. The measured fatigue and fracture behavior is placed into the context of previous studies on fatigue and fracture of Cr-Mo steels for gaseous hydrogen.

The method of Computational Fluid Dynamics is used to predict the process parameters and select the optimum operating regime of a methanol reformer for on-board production of hydrogen as fuel for a 3 kW High-Temperature Proton Exchange Membrane Fuel Cell power system. The analysis uses a three reactions kinetics model for methanol steam reforming water gas shift and methanol decomposition reactions on Cu/ZnO/Al₂O₃ catalyst. Numerical simulations are performed at single channel level for a range of reformer operating temperatures and values of the molar flow rate of methanol per weight of catalyst at the reformer inlet. Two operating regimes of the fuel processor are selected which offer high methanol conversion rate and high hydrogen production while simultaneously result in a small reformer size and a reformate gas composition that can be tolerated by phosphoric acid-doped high temperature membrane electrode assemblies for proton exchange membrane fuel cells. Based on the results of the numerical simulations the reactor is sized and its design is optimized.

CO₂ capture utilization and storage (CCUS) is recognized as a uniquely important option in global efforts to control anthropogenic greenhouse-gas (GHG) emissions. Despite significant progress globally in advancing the maturity of the various component technologies and their assembly into full-chain demonstrations a gap remains on the path to widespread deployment in many countries. In this paper we focus on the importance of business models adapted to the unique technical features and sociopolitical drivers in different regions as a necessary component of commercial scale-up and how lessons might be shared across borders. We identify three archetypes for CCUS development—resource recovery green growth and low-carbon grids—each with different near-term issues that if addressed will enhance the prospect of successful commercial deployment. These archetypes provide a framing mechanism that can help to translate experience in one region or context to other locations by clarifying the most important technical issues and policy requirements. Going forward the archetype framework also provides guidance on how different regions can converge on the most effective use of CCUS as part of global deep-decarbonization efforts over the long term.

Quantitative Risk Assessment (QRA) can help to establish a set of design and operational requirements in hydrogen codes and standards that will ensure safe operation of hydrogen facilities. By analyzing a complete set of possible accidents in a QRA the risk drivers for these facilities can be identified. Accident prevention and mitigation features can then be analyzed to determine which are the most effective in addressing these risk drivers and thus reduce the risk from possible accidents. Accident prevention features/methods such as proper material selection and preventative maintenance are included in the design and operation of facilities. Accident mitigation features are included to reduce or terminate the potential consequences from unintended releases of hydrogen. Mitigation features can be either passive or active in nature. Passive features do not require any component to function in order to prevent or mitigate a hydrogen release. Examples of passive mitigation features include the use of separation distances barriers and flow limiting orifices. Active mitigation features initiate when specific conditions occur during an accident in order to terminate an accident or reduce its consequences. Examples of active mitigation features include detection and isolation systems fire suppression systems and purging systems. A concept being pursued by the National Fire Protection Association (NFPA) hydrogen standard development is to take credit for prevention and mitigation features as a means to reduce separation distances at hydrogen facilities. By utilizing other mitigation features the risk from accidents can be decreased and risk-informed separation distances can be reduced. This paper presents some preliminary QRA results where the risk reduction potential for several active and passive mitigation features was evaluated. These measures include automatic leak detection and isolation systems the use of flow limiting orifices and the use of barriers. Reducing the number of risk-significant components in a system was also evaluated as an accident prevention method. In addition the potential reduction in separation distances if such measures were incorporated at a facility was also determined.

An experimental apparatus which was based on the ¼-scale garage previously used for studying helium release and dispersion in our laboratory was used to obtain effective diffusion coefficients of helium and hydrogen (released as forming gas for safety reasons) through gypsum panel. Two types of gypsum panel were used in the experiments. Helium or forming gas was released into the enclosure from a Fischer burner1 located near the enclosure floor for a fixed duration and then terminated. Eight thermal-conductivity sensors mounted at different vertical locations above the enclosure floor were used to monitor the temporal and spatial gas concentrations. An electric fan was used inside the enclosure to mix the released gas to ensure a spatially uniform gas concentration to minimize stratification. The temporal variations of the pressure difference between the enclosure interior and the ambience were also measured. An analytical model was developed to extract the effective diffusion coefficients from the experimental data.

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.

The International Energy Agency’s Hydrogen Implementing Agreement (www.ieahia.org) initiated a collaborative task on hydrogen safety in 1994 and this has proved to an effective method of pooling expert knowledge to address the most significant problems associated with the barriers to the commercial adoption of hydrogen energy. Presently there are approximately 10 countries participating in the task and it has proven a valuable method of efficiently combining efforts and resources. The task is now in the fifth year of a six year term and will end in October 2010. This paper will describe the scope of the task the progress made and plans for future work. There are also a number of other tasks underway and this paper will give a brief summary of those activities. Because of the nature of the International Energy Agency which is an international agreement between governments it is intended that such collaboration will complement other efforts to help build the technology base around which codes and standards can be developed. This paper describes the specific scope and work plan for the collaboration that has been developed to date.

A series of experiments are described in which helium was released at a constant rate into a 1.5 m × 1.5 m × 0.75 m enclosure designed as a ¼-scale model of a two car garage. The purpose was to provide reference data sets for testing and validating computational fluid dynamics (CFD) models and to experimentally characterize the effects of a number of variables on the mixing behaviour within an enclosure and the exchange of helium with the surroundings. Helium was used as a surrogate for hydrogen and the total volume released was scaled as the amount that would be released by a typical hydrogen fuelled automobile with a full tank. Temporal profiles of helium were measured at seven vertical locations within the enclosure during and following one hour and four hour releases. Idealized vents in one wall sized to provide air exchange rates typical of actual garages were used. The effects of vent size number and location were investigated using three different vent combinations. The dependence on leak location was considered by releasing helium from three different points within the enclosure. It is shown that the National Institute of Standards and Technology (NIST) CFD code Fire Dynamics Simulator (FDS) provides time resolved predictions for helium concentrations that agree well with the experimental measurements.

This paper discusses the preliminary results of the Risk Management subtask efforts within the International Energy Agency (IEA) Hydrogen Implementing Agreement (HIA) Task 19 on Hydrogen Safety to develop uniform harm criteria for use in the Quantitative Risk Assessments (QRAs) of hydrogen facilities. The IEA HIA Task 19 efforts are focused on developing guidelines and criteria for performing QRAs of hydrogen facilities. The performance of QRAs requires that the level of harm that is represented in the risk evaluation be established using deterministic models. The level of harm is a function of the type and level of hazard. The principle hazard associated with hydrogen facilities is uncontrolled accumulation of hydrogen in (semi) confined spaces and consecutive ignition. Another significant hazard is combustion of accidentally released hydrogen gas or liquid which may or may not happen instantaneously. The primary consequences from fire hazards consist of personnel injuries or fatalities or facility and equipment damage due to high air temperatures radiant heat fluxes or direct contact with hydrogen flames. The possible consequences of explosions on humans and structures or equipment include blast wave overpressure effects impact from fragments generated by the explosion the collapse of buildings and the heat effects from subsequent fire balls. A harm criterion is used to translate the consequences of an accident evaluated from deterministic models to a probability of harm to people structures or components. Different methods can be used to establish harm criteria including the use of threshold consequence levels and continuous functions that relate the level of a hazard to a probability of damage. This paper presents a survey of harm criteria that can be utilized in QRAs and makes recommendations on the criteria that should be utilized for hydrogen-related hazards.

Determining the risk of accidental ignition of flammable mixtures is a topic of tremendous importance in industry and aviation safety. The concept of minimum ignition energy (MIE) has traditionally formed the basis for studying ignition hazards of fuels. In recent years however the viewpoint of ignition as a statistical phenomenon has formed the basis for studying ignition as this approach appears to be more consistent with the inherent variability in engineering test data. We have developed a very low energy capacitive spark ignition system to produce short sparks with fixed lengths of 1 to 2 mm. The ignition system is used to perform spark ignition tests in lean hydrogen oxygen-argon test mixtures over a range of spark energies. The test results are analyzed using statistical tools to obtain probability distributions for ignition versus spark energy demonstrating the statistical nature of ignition. The results also show that small changes in the hydrogen concentration lead to large changes in the ignition energy and dramatically different flame characteristics. A second low-energy spark ignition system is also developed to generate longer sparks with varying lengths up to 10 mm. A second set of ignition tests is performed in one of the test mixtures using a large range of park energies and lengths. The results are analyzed to obtain a probability distribution for ignition versus the spark energy per unit spark length. Preliminary results show that a single threshold MIE value does not exist and that the energy per unit length may be a more appropriate parameter for quantifying the risk of ignition.