PNNL

Abstract

On the path to a net-zero-carbon economy, large-scale energy storage will be an essential part of a renewable energy system. Hydrogen generated from renewable or zero-carbon sources has significant potential as an energy storage medium, by allowing for long-duration and high-capacity energy storage. At the volumes anticipated, however, underground storage systems will likely be essential. Much like the current natural gas system, hydrogen underground storage would provide a safe and cost-effective complement to smaller surface storage infrastructure. Recently, there has been significant interest in the possibility of converting existing gas storage systems to hydrogen storage. This paper explores the reservoir dynamics of natural gas / hydrogen gas mixtures and the resulting impacts on storage design and gas deliverability. Two specific topics are addressed. First, a novel viscosity model for hydrogen-containing gas mixtures is developed, to better simulate experimental measurements. Second, detailed reservoir simulations are used to investigate strategies for converting a natural gas storage system to hydrogen storage of blends. The critical role of gravity override is described, and recommendations are made regarding key reservoir characteristics and injection strategies for managing this behavior.