The Hygrid Project - a Hydrogen Blending Demonstration in a Gas Distribution Network - Design Considerations for Safe Operation

To meet the goals for decarbonization around the world and in the US, gas distribution utilities are developing plans to blend green hydrogen into their networks. Utility companies are supporting research, preparing for the transition, and implementing demonstration projects. These projects will produce store, and blend hydrogen using electrolysis powered with renewable electricity either delivered or produced local. National Grid and the Town of Hempstead, NY are developing a novel demonstration project that includes the expansion of an existing hydrogen vehicle fueling station to both upgrade its fueling performance in accordance with SAE standards and to expand its capacity. The additional capacity will be used for blending into an adjacent gas distribution network that was recently upgraded with HDPE pipelines. The system will be a single facility that will include a combination of vehicle fueling with pure compressed hydrogen, at or above 350 Bar, and blending up to 20% hydrogen into a 60 psig natural gas distribution system for delivery to residential buildings. Both systems are expected to operate simultaneously at times. Each application has different performance requirements such as utilization profiles, storage requirements and hydrogen purity standards. The potential for offsite impacts, such as emissions as well as the safety profile are of paramount concern in the design of the systems. The design will limit noise, discharges of gases and water and also to minimize the risk level while both uses are partially subject to different industry standards. The safety principles and the current or anticipated codes and standards to be applied at this facility as well as the application of the National Grid’s process safety program and the unique aspects to the Qualitative Risk Assessment will be discussed. The safety features anticipated at this facility will also be discussed including the various fault detection, alarm and notification functions