Underground storage of hydrogen is a key research area associated with NETL’s overall contribution to the U.S. Department of Energy’s (DOE) Hydrogen Shot.

Renewable energy sources like wind, hydroelectric, solar, biomass and geothermal are an increasing portion of the total energy supply mix and helping to reduce carbon dioxide (CO₂) in the atmosphere. However, dealing with the intermittent supply associated with those energy sources and varying demand for energy is a key challenge.

Converting energy produced by renewable sources into hydrogen and then storing it for future demand is seen by energy experts as an answer to the challenge and NETL researchers are at work independently and as members of a unique multi-national laboratory team to make that approach feasible.

Use of hydrogen as a fuel source has been identified by DOE as a critical step toward transitioning to a net-zero carbon emissions society if storage issues can be resolved. Large-scale geological hydrogen storage offers the capacity to balance inter-seasonal supply/demand discrepancies, de-couple energy generation from demand, and decarbonize heating, transportation, and other difficult-to-decarbonize industrial processes.

Natural gas has been stored in depleted oil and gas fields, saline aquifers and salt caverns for decades. However, the impacts of underground hydrogen storage on reservoirs, hydrogen leakage risks, and flow behavior of hydrogen and blended mixtures are not well understood. The new demand for widely available hydrogen sources and opportunities to use hydrogen blended with natural gas will require storage reservoirs at locations across the United States.

“Underground storage of hydrogen is less costly than storage in above-ground vessels,”  Angela Goodman of NETL’s Biogeochemistry and Water Team explained. “But the technical challenges must be addressed. We are teaming with other national laboratories to focus on quantifying materials compatibility and investigating potential microbial interactions.”

She said NETL researchers are working with colleagues at the Pacific Northwest National Laboratory and the Lawrence Livermore National Laboratory under a research umbrella known as SHASTA —Subsurface Hydrogen Assessment, Storage, and Technology Acceleration — to generate knowledge leading to effective widespread use of underground storage for the nation’s hydrogen and the energy it can bring to bear on decarbonization efforts.

SHASTA was organized by the DOE’s Office of Fossil Energy and Carbon Management. SHASTA researchers are determining the viability, safety, and reliability of storing pure hydrogen or hydrogen-natural gas blends in subsurface environments.

Goodman said at NETL, experts are supporting the SHASTA initiative by addressing a range of challenges including:

• Hydrogen storage feasibility in a variety of underground systems.
• Hydrogen gas behavior during storage.
• Hydrogen loss through biogeochemical reactions.
• Risks of loss of containment from storage reservoirs, through caprock, faults. fractures, or leaky wells.
• Development of real-time monitoring technologies to assure storage integrity and safety.
• Levels of support from key stakeholders and the public.
• Expected regulatory environment.

Hydrogen is currently stored in salt caverns in locations around the world, but those geologic formations are not widely available throughout the U.S. The SHASTA work seeks to address that problem by exploring hydrogen storage in saline formations and depleted oil & gas wells that are more geographically disbursed throughout the U.S.

“Our work builds on existing subsurface capabilities that were designed to study wellbore and subsurface reactions,” Goodman said. “The Lab’s capabilities will also be used to assess the geochemistry and microbiology of reservoir types targeted for storage and to develop optic fiber sensors needed to monitor underground storage.”

In addition to expert personnel, NETL brings a collection of technical research tools to the SHASTA effort including equipment that examines wellbore cement integrity, microbial characterization, sensors, testing and many other technical aspects of hydrogen storage.

Goodman said the SHASTA initiative “can accelerate and expand the use of hydrogen by using existing natural gas facilities at storage sites across the United States, by addressing critical technical hurdles, demonstrating the feasibility of emergent technology, and developing tools and technologies to support industry and by enabling the advancement of subsurface hydrogen storage.”