D3a.2 Realistic hydrogen specifications in hydrogen distribution grids

Key Takeaways: If the hydrogen from the Hydrogen Network Netherlands is already contaminated, it could be difficult for some sections of a repurposed distribution network to adhere to the 99.5% purity level set in the EZK-proposed (KGG) hydrogen specification in distribution grids (especially under <1 bar). If the purity level specification (the >99.5 vol% H2) is relaxed under a specific distribution pressure (e.g. somewhere between 1-4 bar), and the Wobbe index limit is used instead, some more contamination can be tolerated. This would facilitate distribution in re-used pipelines or lower pressure pipelines. The amount of contamination tolerable by the installed combustion equipment is determined by the type of contamination. The Wobbe Index can be used to evaluate this. Since end-users of pipelines under ~1 bar are predominately combustion end-users, the Wobbe Index is a more relevant limit than the purity specification alone. However, the rate of change in hydrogen purity should be limited. Specific hazardous contaminants (ammonia etc.) should always be limited, regardless of the pressure level.