Assessing the Feasibility of Repurposing the Existing Natural Gas Pipelines for Hydrogen Transport—A Comprehensive Review

In a bid to investigate the optimum transportation method for offshore wind-produced hydrogen (H2) and assess the feasibility of repurposing the existing oil and gas infrastructure for H2 transmission, this paper assesses the existing H2 transportation methods with a comprehensive review of the H2 impact on the existing natural gas pipeline infrastructure. To establish the possibility of repurposing the existing natural gas (NG) pipelines for H2 gas transport, this paper reviews the influential technical measures—composition, pressure, temperature, volumetric energy density, density, and pressure drop—to assess whether the characteristics of hydrogen gas are compatible with the natural gas pipeline infrastructure. Based on these reviews, it was found that the current NG pipeline pressure exacerbates the H2 embrittlement; for the existing NG pipelines to be repurposed, the operating pressure should be reduced, and the pipeline material should be revised. It was found that higher strength steels can be re-used with major modifications, or the pipeline should be constructed from material grade X52 or below. Nevertheless, the fitness of the existing NG pipelines for H2 transmission should be assessed on a case-by-case basis and other factors such as erosion, leakage, pressure cycling, monitoring (e.g., distributed fiber-optic sensing technology) and a rigorous assessment of welds and joints should also be considered.