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.