The SHIMMER project investigates the safe and efficient integration of hydrogen into European gas transmission and distribution networks. The study combines detailed simulations and operational analyses of two Transmission System Operator (TSO) networks in Italy and Spain, and two Distribution System Operator (DSO) networks in Italy and Spain. Results show that hydrogen blending is a viable short-term decarbonization pathway, while pipeline repurposing may enable larger-scale hydrogen transport where infrastructure conditions allow. However, hydrogen injection introduces dynamic gas-quality and hydraulic effects, requiring network-wide monitoring, transient modelling, and coordinated operation between TSOs and DSOs.
The analysis demonstrates that hydrogen concentrations depend strongly on network topology, flow conditions, and pressure-driven interactions, leading to spatial and temporal variations in gas quality. To support effective monitoring, a clustering-based methodology for optimal gas-quality sensor placement is proposed, enabling accurate estimation of gas quality while minimising deployment costs. The findings highlight the need for advanced modelling, real-time monitoring, optimised sensor deployment, and harmonised operational and regulatory frameworks. Together, these elements provide a foundation for the safe, reliable, and scalable integration of hydrogen into future European gas networks, supporting the transition toward a low-carbon energy system.
