Operational implications of transporting hydrogen via a high-pressure gas network

Transporting hydrogen gas has long been identified as one of the key issues to scaling up the hydrogen economy. Among various means of transportation, many countries are considering using the existing natural gas pipeline networks for hydrogen transmission. This paper examines the implications of transporting hydrogen on the operational metrics of the high-pressure natural gas networks. A model of the GB high-pressure gas network was developed, which has a high granularity, with 294 nodes, 356 pipes, and 24 compressor stations. The model was developed using Synergi Gas, a hydraulic pipeline network simulation software. By performing unsteady-state analysis, pressure levels, linepack levels and compressor energy consumption were simulated with 10-minute time steps. Additionally, component tracing analysis was utilised to examine the variations in gas composition when hydrogen is injected into the gas network. Five scenarios were developed: one benchmark scenario representing the network transporting natural gas in 2018; one scenario where demand and supply levels are projected for 2035, but no hydrogen was transported by the network; two hydrogen injection scenarios in 2035 considering different geographical locations for hydrogen injection into the gas network; and lastly, one pure hydrogen transmission scenario for 2050. The studies found that the GB's high-pressure gas network could accept 20 % volumetric hydrogen injection without significantly impacting network operation. Pressure levels and compressor energy consumption remain within the operational range. The geographical distribution of hydrogen injection points would highly affect the percentage of hydrogen across the network. Pure hydrogen transportation will cause significant variations in network linepack and increase compressor energy consumption significantly compared to other case studies. The findings signal that operating a network with pure hydrogen is possible only when it is prepared for these changes.