Minimising risk of hydrogen technologies

Hydrogen fuel cell (HFC) technology will first be commercialised for market-ready applications such as backup power supply, portable power generation and powering of materials handling vehicles. These applications generally require, by nature or for security reasons, that hydrogen systems be used indoors. Yet, existing regulations, codes and standards (RCSs) are very incomplete regarding the practical specification of safety requirements indoors.

Addressing the safe indoor use of HFC systems for early markets was the main objective of the EU-funded project 'Pre-normative research on safe indoor use of fuel cells and hydrogen systems' (HYINDOOR). The project sought to provide scientific and engineering knowledge for specifying cost-effective means to control hazards, and to develop state-of-the-art safety guidelines.

HYINDOOR addressed knowledge gaps regarding indoor hydrogen accumulation, vented deflagration and under-ventilated jet fire. The generated knowledge should be translated into safety guidelines, including contemporary engineering tools supporting their implementation. Recommendations should be formulated for advancements in the EU and international RCS frameworks to support the safe introduction of HFC in early markets.

Project partners sought to enhance understanding of hydrogen dispersion and accumulation in confined spaces. Work focused on a room-like enclosure of typically a few tens of cubic metres with natural ventilation. Based on existing and new analytical and numerical models, partners worked on identifying characteristic regimes of hydrogen dispersion. Parameters such as the size of the venting area, the size of the enclosure area and the leak flow rates were taken into account.

A number of experiments were conducted to study vented hydrogen–air deflagrations and the interplay between hydrogen–air and enclosure parameters with regard to overpressure effects. Another task was to conduct experimental and numerical studies on hydrogen jet fire dynamics. Focus was placed on parameters such as self-extinction, re-ignition, radiation and flame length from external hydrogen jet fires.

Possible safety strategies should be given in a guidelines document with important rules for indoor hydrogen use in the configurations addressed by HYINDOOR. Additional safety devices should be proposed when sizing methods are not sufficient to respect the safety rules.