Principles of Hydrogen Safety Engineering

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Numerical analysis of accidental hydrogen releases from high pressure storage at low temperatures

Evaluations of the performance of simplified engineering and CFD models are important to improve risk assessment tools e.g. to predict accurately releases from various types of hydrogen storages. These tools have to predict releases from a wide range of storage pressures (up to 80 MPa) and temperatures (down to 20 K), e.g. cryogenic compressed gas storage covers pressures up to 35 MPa and temperatures between 33 K and 338 K. Accurate calculations of high pressure releases require real gas EOS. This paper compares a number of EOS to predict hydrogen properties typical in different storage types. The vessel dynamics are modeled using a simplified engineering and a CFD model to evaluate the performance of various EOS to predict vessel pressures, temperatures mass flow rates and jet flame lengths. It is shown that the chosen EOS and the chosen specific heat capacity correlation are important to model accurately hydrogen releases at low temperatures.JRC.F.2-Cleaner energ

Benchmark Exercise on Risk Assessment Methods Applied to a Virtual Hydrogen Refuelling Station

A benchmarking exercise on quantitative risk assessment (QRA) methodologies for hydrogen safety has been conducted within the project HyQRA, under the framework of the European Network of Excellence (NoE), HySafe. The aim of the exercise was twofold: (i) to identify the differences and similarities in approaches in a QRA and their results for a hydrogen installation and (ii) to identify knowledge gaps in the various steps and parameters underlying the risk quantification of hydrogen safety. First, a reference case was defined for the benchmark: a virtual hydrogen refuelling station (HRS) in virtual surroundings comprising housing, school, shops and other vulnerable objects. For the study, a two phase approach was followed. In phase 1, all nine partners were requested to conduct a QRA according to their usual approach and experience. Basically, participants were free to define representative release cases, to apply models and frequency assessments according their own methodology, and to present risk according to their usual format. To enable inter-comparison, a required set of results data was prescribed, like distances to specific thermal radiation levels from fires and distances to specific overpressure levels. Moreover, complete documentation of assumptions, base data and references was to be reported. It was not surprising that a wide range of results was obtained, both in the applied approaches as well as in the quantitative outcomes and conclusions. This made it difficult to identify exactly which assumptions and parameters were responsible for the differences in results. These results provided the basis for a more guided QRA, the second phase. This phase 2 was defined in which the QRA was determined by a more limited number of release cases (scenarios). The partners in the project agreed to assess specific scenarios in order to identify the differences in consequence assessment approaches. The results of this phase provide a better understanding of the influence of modelling assumptions and limitations on the eventual conclusions with regard to risk to on-site people and to the off-site public.JRC.DDG.F.2-Cleaner energ

Benchmark exercise on risk assessment methods applied to a virtual hydrogen refuelling station

A benchmarking exercise on quantitative risk assessment (QRA) methodologies for hydrogen safety has been conducted within the project HyQRA, under the framework of the European Network of Excellence (NoE), HySafe. The aim of the exercise was twofold: (i) to identify the differences and similarities in approaches in a QRA and their results for a hydrogen installation and (ii) to identify knowledge gaps in the various steps and parameters underlying the risk quantification of hydrogen safety. First, a reference case was defined for the benchmark: a virtual hydrogen refuelling station (HRS) in virtual surroundings comprising housing, school, shops and other vulnerable objects. For the study, a two phase approach was followed. In phase 1, all nine partners were requested to conduct a QRA according to their usual approach and experience. Basically, participants were free to define representative release cases, to apply models and frequency assessments according their own methodology, and to present risk according to their usual format. To enable inter-comparison, a required set of results data was prescribed, like distances to specific thermal radiation levels from fires and distances to specific overpressure levels. Moreover, complete documentation of assumptions, base data and references was to be reported. It was not surprising that a wide range of results was obtained, both in the applied approaches as well as in the quantitative outcomes and conclusions. This made it difficult to identify exactly which assumptions and parameters were responsible for the differences in results. These results provided the basis for a more guided QRA, the second phase. This phase 2 was defined in which the QRA was determined by a more limited number of release cases (scenarios). The partners in the project agreed to assess specific scenarios in order to identify the differences in consequence assessment approaches. The results of this phase provide a better understanding of the influence of modelling assumptions and limitations on the eventual conclusions with regard to risk to on-site people and to the off-site public. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Benchmark Exercise on Risk Assessment Methods Applied to a Virtual Hydrogen Refuelling Station

A benchmarking exercise on quantitative risk assessment (QRA) methodologies has been conducted within the project HyQRA, under the framework of the European Network of Excellence (NoE), HySafe. The aim of the exercise was basically twofold: (i) to identify the differences and similarities in approaches in a QRA and their results for a hydrogen installation, between nine participating partners representing a broad spectrum of background in QRA culture and history, and (ii) to identify knowledge gaps in the various steps and parameters underlying the risk quantification. In the first step, a reference case was defined: a virtual hydrogen refuelling station (HRS) in virtual surroundings comprising housing, school, shops and other vulnerable objects. All partners were requested to conduct a QRA according to their usual approach and experience. Basically, participants were free to define representative release cases, to apply models and frequency assessments according their own methodology, and to present risk according to their usual format. To enable inter-comparison, a required set of results data was prescribed, like distances to specific thermal radiation levels from fires and distances to specific overpressure levels. Moreover, complete documentation of assumptions, base data and references was to be reported. It was not surprising that a wide range of results was obtained, both in the applied approaches as well as in the quantitative outcomes and conclusions. This made it difficult to identify exactly which assumptions and parameters were responsible for the differences in results, as the paper will show. A second phase was defined in which the QRA was determined by a more limited number of release cases (scenarios). The partners in the project agreed to assess specific scenarios in order to identify the differences in consequence assessment approaches. The results of this phase provide a better understanding of the influence of modelling assumptions and limitations on the eventual conclusions with regard to risk to on-site people and to the off-site public. This paper presents the results and conclusions of both stages of the exercise.JRC.F.2-Cleaner energ