Investigation of Concentration Stabilization Methods for Hydrogen-Blended Natural Gas Grid Based on Gas Supply Routes

Hydrogen is expected to be utilized for decarbonization of energy systems. One of the barriers to society's implementation of hydrogen use is transportation costs. One method proposed to reduce transportation costs is to inject hydrogen into the existing natural gas grid and transport it as a gas mixture. Since the characteristics of the blended gas vary depending on the hydrogen concentration, the deployment of mixed gas transportation requires concentration control in the gas grid and in the gas supplied to customers. More specifically, the distribution of hydrogen concentration in the grid will vary spatially and temporally depending on the facility layout and operating conditions of the gas grid, and that complicates management of the hydrogen concentration in the grid. Therefore, this study proposed an evaluation indicator that enables selection of robust pathways that can stabilize hydrogen concentration at demand points. To avoid gas merging from multiple supply points in the gas grid and to unify the supply sources, a consolidation path ratio was defined using the gas distribution ratio as an indicator. This indicator was applied to a simulated grid, and the mainstream pathway was identified, even if the supply pressure changed. By shutting off the non-mainstream pathway, a pathway with stable demand point concentrations was established. Use of the consolidation path ratio is expected to allow robust paths to be extracted for demand points connected to the mixed gas grid.