Deliverable D1.2 of THOTH2 project aims to investigate technical barriers and limitations of hydrogen injection in existing gas grids with a focus on measuring devices. Injecting hydrogen into existing gas networks requires several actions to assess the content of hydrogen in the H2NG mixture that can be transported through gas pipelines. One of the areas that needs to be evaluated is the field of gas quality and quantity measurements.

The Task 1.2 "Technical and performance barriers and limitations" aimed to identify barriers and gaps related to measurement devices such as gas meters, volume converters, pressure and temperature transducers, process gas chromatographs, dew point transducers, and leak detectors. By defining this measurement area, it allows identifying gaps and barriers concerning custody transfer measurements (gas volume and heating value).

Due to the different physicochemical properties of hydrogen and methane, the identification of barriers and considerations includes not only the measurement capabilities of devices for H2NG mixtures but also the resistance of design solutions to the effects of hydrogen. The assessment of the state-of-the-art technology was conducted based on a literature review, including the outcomes of projects such as "HyDeploy 2 Project" and "HyWay 27: hydrogen transmission using the existing natural gas grid?". The literature review was complemented by feedback gathered from surveys sent to manufacturers of measurement devices, selected based on the results of Task 1.1. The analyses conducted allowed identifying the following gaps and barriers:

• In the area of gas composition analyzers: there are solutions available that allow measuring the composition of H2NG mixtures with up to 100% hydrogen content. However, these solutions are not currently utilized by Transmission System Operators (TSOs) and Distribution System Operators (DSOs), since they entered in the market recently.
• In the area of dew point transducers: there are solutions resistant to hydrogen up to 20% content, and they are partially used by TSOs and DSOs.
• In the area of leak detectors: there are solutions that can be used by operational services on gas networks transporting H2NG mixtures. These detectors allow measuring hydrogen content in the air from 0 to 100% of the lower explosive limit. This range is sufficient to ensure safe network operation. However, such leak detectors are not currently employed by TSOs and DSOs.