Intermittent electrolytic hydrogen produced from renewable power sources, such as solar and wind farms, can fluctuate significantly. However, the synthesis of green ammonia and methanol in chemical processing plants requires steady hydrogen supplies. Designing a pipeline to deliver stable and large-scale hydrogen from renewable sources is a challenge. A large storage volume is often needed to buffer the gap between the intermittent supply and the steady demand. And a portion of volume is also required to make up for the lower design pressure and the thicker wall thickness of the pipe due to hydrogen embrittlement that negatively affects the mechanical properties of steel materials and for the more specific mass because of lower hydrogen density.
A pipeline design option for compressed hydrogen gas that can mitigate the supply challenge is by using an over-sized pipeline for both storage and transmission. This over-sized pipeline is widely used to meet peak demands and temporary transient operations in natural gas pipelines. A second option is pairing of a smaller transmission pipeline with an on-site hydrogen storage facility. The smaller pipeline utilizes the on-site storage to achieve a stable delivery. The on-site storage could be either an underground geological storage reservoir such as a salt cavern, a depleted oil or gas field, and an aquifer, or an aboveground storage container such as a pressure vessel(s) for low-pressure applications.
In this study, hydraulic models are utilized to demonstrate the feasibility of each pipeline design option based on one monthly hydrogen production profile from renewable wind farms as an example. A parametric study is carried out by varying the design and operation parameters. The feasibility of the over-sized pipeline option can be constrained by pipe length, pipe size, and pressures, while the feasibility of the smaller pipeline option is mainly dependent on the availability of the underground storage and the required hydraulics for the aboveground container. Technical analysis of the impact of the parameters for both design options are carried out to illustrate their advantages, applicability, and limitations.
