Experimental Study on the Effects of Hydrogen in Gas Distribution Customer Service Lines: Stratification in Risers and Meter Aging

The injection of hydrogen into the existing gas networks, known as hydrogen blending, has been widely proposed as a transitional solution to reduce carbon emissions while rapidly facilitating the integration of hydrogen-based technologies. The current natural gas infrastructure can accommodate modest hydrogen volume concentrations (cv,H2 < 10%) without significant alterations to thermo-fluid dynamic properties or natural gas quality. Nonetheless, several studies have reported functional limitations on components and equipment in high and medium-pressure infrastructure. Conversely, detailed research on the operational impact of hydrogen blending on low-pressure distribution network equipment, particularly in customer service lines, remains limited. This lack is particularly relevant not only due to potential safety risks but also because of the fiscal implications related to legal metrology in domestic gas meters (GMs). In light of this context, two key aspects must be addressed across different hydrogen blends: the stability of the mixture in gas risers and the metrological integrity of gas meters. In gas risers, stratification effects due to hydrogen’s lower density must be analyzed to prevent localized hydrogen enrichment when gas is withdrawn. Existing studies offer conflicting results on hydrogen stratification, with some reporting significant separation in stagnant conditions, while others suggest the effect does not persist over long periods [1] [2]. These discrepancies highlight the need for further experimental studies to clarify hydrogen behavior in real-world distribution networks. Meanwhile, GMs must ensure accurate billing measurements: since natural gas is metered volumetrically rather than based on energy content that is not inherently conserved, measurement errors can become significant when gas meters operate with gas mixtures they were not originally calibrated for. This issue is particularly pronounced with a high presence of hydrogen in the mixture, as certain metering technologies may exhibit accuracy drift over time when exposed to varying gas compositions [3] [4].