Towards minimising hazards in hydrogen and fuel cell stationary applications : key findings of modelling and experimental work in the HYPER project

There are a number of hazards associated with small stationary hydrogen and fuel cell applications. In order to reduce the hazards of such installations, and provide guidance to installers, consequence analysis of a number of potential accident scenarios has been carried out with the scope of the EC FP6 project HYPER. This paper summarises the modelling and experimental programme in the project and a number of key results are presented. The relevance of these findings to installation permitting guidelines (IPG) for small stationary hydrogen and fuel cell systems is discussed. A key aim of the activities was to generate newscientific data and knowledge in the field of hydrogen safety, and, where possible, use this data as a basis to support the recommendations in the IPG. The structure of the paper mirrors that of the work programme within HYPER in that the work is described in terms of a number of relevant scenarios as follows: 1. high pressure releases, 2. small foreseeable releases, 3. catastrophic releases, and 4. the effects of walls and barriers. Within each scenario the key objectives, activities and results are discussed. The work on high pressure releases sought to provide information for informing safety distances for high-pressure components and associated fuel storage, activities on both ignited and unignited jets are reported. A study on small foreseeable releases, which could potentially be controlled through forced or natural ventilation, is described. The aim of the study was to determine the ventilation requirements in enclosures containing fuel cells, such that in the event of a foreseeable leak, the concentration of hydrogen in air for zone 2 ATEX is not exceeded. The hazard potential of a possibly catastrophic hydrogen leakage inside a fuel cell cabinet was investigated using a generic fuel cell enclosure model. The rupture of the hydrogen feed line inside the enclosure was considered and both dispersion and combustion of the resulting hydrogen air mixture were examined for a range of leak rates, and blockage ratios. Key findings of this study are presented. Finally the scenario on walls and barriers is discussed; a mitigation strategy to potentially reduce the exposure to jet flames is to incorporate barriers around hydrogen storage equipment. Conclusions of experimental and modelling work which aim to provide guidance on configuration and placement of these walls to minimise overall hazards is presented