Specialists from the Austrian company RAG Austria AG, together with colleagues from Axiom Angewandte Prozesstechnik and the University of Natural Resources and Life Sciences in Vienna, have for the first time in the world tested the technology of storing pure hydrogen in a depleted gas field. During the experiment, 450,000 cubic meters of hydrogen were injected underground, and after several months, it was extracted with a purity exceeding 98%. According to the authors, the technology already corresponds to Technology Readiness Level (TRL) 7, meaning it has successfully passed tests in real‑world conditions and is now close to industrial implementation.
One of the main challenges for the future hydrogen economy is the accumulation of large fuel reserves. In summer, solar and wind power plants can produce more electricity than consumers need, while in winter a shortage arises. Excess electricity can be used to produce hydrogen via electrolysis, but the hydrogen then needs to be stored somewhere for several months. Surface tanks are too expensive for this purpose, so researchers are looking at depleted gas fields, which already account for about 80% of all underground gas storage facilities worldwide and can store energy on a regional scale for several months. However, it remained unclear whether hydrogen would leak through the rock, react with minerals, or be consumed by subsurface microorganisms, leading to fuel losses.
To test this assumption, the researchers created a pilot underground hydrogen storage facility based on the small depleted Rubensdorf field in Upper Austria. Hydrogen was produced directly on site using a 2 MW electrolyzer and then compressed and injected at a depth of 1,100 meters into a sandstone formation. Before the experiment began, the scientists spent several years testing rock samples and equipment for exposure to hydrogen and checking the sealing integrity of the rocks. The storage facility itself was prepared by creating a so‑called gas cushion: first, about 1 million cubic meters of natural gas were injected to maintain pressure, followed by another 0.5 million cubic meters of hydrogen to reduce mixing with residual natural gas during subsequent withdrawals. Two storage cycles were then carried out, with the second achieving a reserve of about 450,000 cubic meters of hydrogen.
The experiment showed that the underground storage facility operated almost identically to when it was used for natural gas. Rock permeability did not change, no signs of leakage were detected, while the formation temperature varied by less than one degree. Even after long‑term storage, the hydrogen concentration in the extracted gas exceeded 98%, and after additional purification — more than 99.99%, making it suitable even for fuel cells. Hydrogen sulphide was not detected throughout the experiment, while analysis of groundwater showed that microorganisms living in the formation consumed virtually no hydrogen and did not affect its quality.
The estimated storage cost was 30‑40 euros per megawatt‑hour, which increases the price of hydrogen by a mere 0.25‑0.4 euros per kilogram.
Thus, the results of the world’s first full‑scale experiment showed that depleted gas fields can be safely used for seasonal hydrogen storage. The next steps should be testing the technology at other fields and implementing it in larger projects.
