UC Irvine

A global interest to increase the use of renewable resources has spurred an interest in hydrogen (H2) gas as an energy carrier. Natural gas (NG) infrastructure has been proposed as a potential storage, transmission and distribution system for renewably produced gaseous H2 fuel. Introducing H2 to the NG system has raised concerns about H2 leakage from the system. In this thesis, the leakage of H2, NG and H2/NG blends is theoretically and experimentally examined. Experimental evidence that suggests 100% H2 gas leaks at the same rate as H2/ NG mixtures and 100% NG in typical existing low-pressure NG infrastructure on the customer-side of the meter is provided. Additionally, a review of the classical leak analysis literature resulted in the discovery of similar results, though not mentioned in the literature. The efficacy of a commercial mitigation measure to reduce gaseous fuel leakage from piping system known to leak is assessed. Finally, a two-step leakage mechanism theory that involves molecular dynamics and a tortuous leakage path with significant wall interactions is proposed to explain the results that suggest H2 leaks at the same rate as NG in typical low-pressure gas infrastructure.