Hydrogen Injection into Gas Grids as a Flexibility Option for Renewable Energy Integration and Storage

The integration of renewable energy sources, particularly photovoltaic (PV) solar, is increasingly challenged by the limited flexibility and storage capacity of existing ener-gy systems. Hydrogen produced via renewable-powered electrolysis offers a promising pathway to address these constraints. Among the various utilization options, hydrogen injection into natural gas grids represents a technically feasible and strategically rele-vant solution in the medium term. The paper develops a methodological framework aimed at interpreting hydrogen injection as a flexibility option for renewable energy integration and storage. The approach focuses on identifying those gas network seg-ments where flow fluctuations are minimal, conditions more suitable for hydrogen blending, and on quantifying the potential contribution of this strategy to PV expan-sion. The methodology is applied to the Italian energy system, a paradigmatic case characterized by strong PV growth and extensive natural gas utilization. Results indi-cate that, under current regulatory constraints (up to 5% hydrogen blending), the ad-ditional PV capacity that could be effectively integrated remains limited, and the overall decarbonization impact modest. Nonetheless, the analysis highlights the con-ceptual and methodological value of considering gas networks as dynamic compo-nents of an integrated energy system. In this perspective, hydrogen injection emerges less as an immediate large-scale solution and more as a framework for coupling power and gas systems, paving the way for future assessments under evolving technical, economic, and regulatory conditions.