Quantifying Hydrogen Storage Risks to Potable Groundwater and Climate Change

University Of Texas At Austin, Austin TX

Investigators

Abstract

Hydrogen is becoming an important source of energy in the United States, and underground salt caverns are being considered for hydrogen storage. However, hydrogen is a highly reactive gas that can interact with natural microorganisms and minerals in the environment, potentially creating harmful chemicals like hydrogen sulfide or methane. These chemicals could contaminate drinking water supplies, damage wells, or escape into the atmosphere. This project will use experiments and mathematical modeling to advance scientific understanding of underground reactions of hydrogen in salt storage caverns. The project will study the extent of the reactions, the products formed, and the implications of the reactions on leaks into shallow aquifers. The project results will lead to improved efficiency, performance, and scalability of hydrogen storage, and protection of groundwater resources. The project team will train undergraduate and graduate students in research. The team will also create educational outreach programs to teach high school students about energy storage and the hydrogen economy. The United States is on the verge of a hydrogen (H2) revolution. Candidate storage reservoirs for H2 are mainly dissolution caverns in salt formations (either bedded or domal salts) and saline aquifers. However, H2 is an especially mobile and reactive molecule; it can embrittle metal, promote iron corrosion, and pass through nanofractures, leading to concerns that it will compromise well and/or formation materials and escape to overlying aquifers or to the atmosphere. This is especially concerning in salt caverns mined in shallow bedded salt formations or salt domes that are within several hundred meters of the ground surface with only thin beddings of overlying anhydrite or halite serving as caprock. An even greater concern is that stored H2 will transform to harmful by-products (such as hydrogen sulfide and methane) that reduce the quality and quantity of stored H2, more rapidly compromise well materials, harm drinking water aquifers, or escape into the atmosphere. The potential for such transformations has been identified, but the extent of these reactions under realistic biogeochemical conditions in salt caverns remains an open scientific question. This project will advance fundamental understanding of biogeochemical conditions that drive microbial-driven H2 consumption in salt caverns, and the risks that such reactions present to overlying potable-water aquifers and the atmosphere. This project comprises four objectives: (1) determine the biogeochemical conditions that promote H2 reduction with alternative electron acceptors; (2) determine shifts in microbial community dynamics and gene expression associated with H2 reduction coupled to alternative electron acceptors; (3) identify H2 reduction hotspots in salt caverns and the risk to H2 storage wells and seals; and (4) quantify and extend experimental results by using a biogeochemical model to simulate H2 reactions under a wider range of potential salt cavern conditions. Microbially-driven H2 consumption, reaction rates, and alternative acceptor consumption in evaporite materials will be measured. Microbial community dynamics and gene expression will be evaluated. Water transport, hydrogen consumption hotspots, and effects on storage security will be determined. A biogeochemical model will be developed and applied to a broad set of storage conditions. The project will train undergraduate and graduate students, and will create educational outreach programs to teach high school students about energy storage and the hydrogen economy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.