The THOTH2 project, under the Clean Hydrogen JU framework, addresses a critical challenge in the energy transition: the accurate and safe metering of hydrogen and hydrogen-natural gas (H2NG) mixtures. As hydrogen becomes a key vector in decarbonizing hard-to-electrify sectors—such as heavy industry, long-distance transport, and high-temperature processes—its integration into existing gas infrastructures demands a fundamental revision of metering standards.
This deliverable D4.1 provides a comprehensive technical assessment of the limitations of current European gas metering standards (EN, ISO, OIML) when applied to hydrogen and H2NG blends. It proposes preliminary guidelines and recommendations for updating existing standards or developing new ones, with the aim of ensuring metrological accuracy, operational safety, and regulatory compliance in hydrogen-rich environments.
The key technical challenges identified are the physical and chemical properties of hydrogen. Hydrogen differs significantly from natural gas in terms of energy density, diffusivity, viscosity, and combustion characteristics. These differences impact:
− Meter sizing and flowrate calibration: Hydrogen’s lower calorific value (~3.54 kWh/Std.m3 vs. ~10.5–12.5 kWh/Std.m3 for NG) requires higher volumetric flow to deliver equivalent energy.
− Leak tightness: Hydrogen’s small molecular size increases the risk of leakage through seals and materials not originally designed for it.
− Material compatibility: Hydrogen can cause embrittlement and degradation in metals and polymers, affecting long-term durability.
These differences affect not only gas meters but the entire measurement chain, including leak detectors, pressure and temperature sensors, and gas analysers. Regulatory frameworks, such as the Measuring Instruments Directive (MID 2014/32/EU), lack hydrogen-specific performance criteria, creating ambiguity in certification and conformity assessment.
This deliverable provides preliminary guidelines and recommendations to bridge these gaps across all critical components:
- Gas Meters
- Leak Detectors
- Pressure Sensors
- Temperature Sensors
- Gas Analysers
- Water dew point sensors
Implementing these recommendations will ensure metrological integrity, operational safety, and regulatory clarity for hydrogen deployment. It will accelerate Europe’s hydrogen roadmap, foster international harmonization, and enable a secure, efficient, and sustainable energy future.
