Hydrogen blending in the Italian scenario: Effects on a real distribution network considering natural gas origin

Blending hydrogen into the natural gas network can help decarbonize the energy sector by supporting the penetration of renewables. Italy is an importer of natural gas whose composition and properties depend on its origin. Previous literature simulates gas networks using a set of hydrogen molar fractions regardless of the natural gas composition variability. Instead, this paper defines the maximum mixable percentage of hydrogen as a function of the gas composition underlining the importance of not adopting a single hydrogen limit. Furthermore, the paper investigates whether guaranteeing gas quality also guarantees compliance with fluid dynamic constraints on a real network. The test case consists of seven gases imported in Italy in 2019 and an urban distribution network, meshed and consisting of more than 2000 elements with medium and several low-pressure levels. A steady-state simulation of the network is performed using each of the seven gases for a winter day in the case of pure natural gas and natural gas blended with hydrogen. The results show that the highest hydrogen molar fraction mixable in these gases can range between 5.3% and 14.8% and considering the lowest percentage can reduce the decarbonization potential of the network by 1463 kg of CO2,eq. The simulations show that fluid-dynamic standards are not always met in the low-pressure networks and safety limits on pressure and velocity are exceeded at peak demand. The results also lead the authors to suggest that a modulation of pressure setpoints as a function of gas composition should be investigated.