Impact of hydrogen blending on a real-world gas distribution network with a non-uniform elevation profile

The ongoing energy transition, characterized by the increasing integration of renewable energy sources, has amplified the demand for hydrogen as a clean energy carrier. Hydrogen requires not only efficient generation but also effective distribution. Utilizing the extensive natural gas infrastructure offers a practical solution, leveraging its widespread network and cost-effective capacity to transport large volumes of gas. Nevertheless, hydrogen blending causes significant alterations in gas quality and the fluid dynamic behavior of the whole network. This study aims to investigate the effects of hydrogen blending on the main fluid dynamic parameters, flow rate balancing, and gas quality in a multi-pressure gas distribution network with a non-uniform elevation profile. The proposed real test case leverages and validates the actual geometrical, altitudinal, and topological characteristics. Steady-state simulations with different mixtures, ranging from 2% to 20% hydrogen by volume, were performed. The results show that in the medium-pressure network, it is possible to operate with hydrogen mixtures while remaining within the normative fluid dynamic limits, and a marginal benefit can even be obtained on the minimum recorded pressure. In low-pressure subnetworks, the margin of pressure safety is greatly reduced, and with off-peak demand, even small elevation changes establish the most critical withdrawal node. However, due to the different distribution of gas flows, a decrease in maximum velocity is observed. The analysis shows some new fluid dynamic aspects to be considered to support feasibility analyses for hydrogen blending on gas infrastructure laid over areas with uneven elevations.