Instabilities in Underground Hydrogen Storage

The International Panel on Climate Change’s (IPCC) 1.5°C report emphasizes the need to significantly reduce carbon dioxide (CO₂) emissions by 2030, motivating many organizations to consider hydrogen gas (H₂) as a means of renewable energy. H₂ has significant application to fuel cells, agriculture, and as combustion for heat and power. One method of utilizing H₂ as an efficient energy source is underground storage. Renewable energy sources, such as wind and solar, are dependent on seasonal and environmental conditions. As a result, there are fluctuations in clean energy production. To bridge the gaps, H₂ can be stored and later retrieved when energy demand is higher than production. H₂ could be stored underground in depleted oil/natural gas reservoirs and aquifers. However, this process is complex and requires researchers to consider the effects of fluid instabilities that may arise due to physical differences between fluids stored underground. When injected underground, H₂ can physically interact with other gases already occupying underground regions, potentially leading to these instabilities. Evolution of instabilities between gases leads to mixing, resulting in contamination of H₂ such that it can no longer be used as an energy source. This risk is a contributing factor that prevents underground H₂ storage to be considered at a commercial scale. Using a Schlieren imaging system, we investigate the specific conditions under which instabilities form when H₂ is injected into other gasses and how to constrain their development.