The global energy transition faces a significant technical hurdle: how to store hydrogen on an industrial scale in a safe and economically viable way. In February 2025, the HYBRIT consortium, formed by the steelmaker SSAB, the mining company LKAB, and the energy company Vattenfall, presented a compelling answer by successfully validating lined rock cavern (LRC) storage technology in Sweden.
The pilot project in Svartöberget, near Luleå, demonstrated that it is technically possible to store hydrogen under high pressure in prepared rock formations, with an operational horizon equivalent to five decades. More than an engineering achievement, this validation could redefine the economic viability of green steel production and other energy-intensive industrial processes.
Why does geological storage matter to industry?
Industrial hydrogen production via electrolysis depends on electricity, often sourced from intermittent renewable sources like wind and solar. This volatility creates a fundamental mismatch: energy generation fluctuates throughout the day and seasons, but continuous industrial processes, such as the direct reduction of iron ore, require a stable supply of hydrogen.
Storing large volumes of H₂ solves this equation. The HYBRIT pilot project demonstrated in practice how to adjust hydrogen production to periods of cheap energy in the spot market, resulting in savings of 26% to 31% in variable costs. Future simulations point to reductions of up to 40%.
Main advantages of LRC storage:
- Geographical flexibility in regions without salt formations.
- Ability to operate under high pressures (up to 250 bar on the pilot).
- Leveraging existing skills in excavation and geotechnics.
- Low cost per unit of energy stored on a large scale.
Compared to pressurized surface tanks, geological caverns offer superior energy density and a smaller physical footprint. Compared to salt dome caverns, a mature technology for natural gas storage, LRCs (Low-Cost Retaining Tanks) have a decisive advantage: they are not dependent on specific geology and can be implemented wherever competent rock is available.
Technical architecture and experimental validation
An LRC cave is not simply a hole in the rock. The system combines three critical layers: the rock mass provides structural confinement; an intermediate layer of reinforced concrete distributes stresses; and an inner lining of specially treated steel ensures sealing against hydrogen, a molecule notoriously difficult to contain due to its small atomic size.
The Svartöberget pilot plant has a usable capacity of 100 m³, excavated 30 meters deep in granite rock. Between 2022 and 2024, the installation accumulated 3,800 operating hours with 94% availability, storing up to 2 tons of H₂ under a pressure of 250 bar, equivalent to the force exerted by a 2,500-meter column of water.
What makes validation robust:
- Accelerated mechanical tests simulating pressure cycles equivalent to 50 years of commercial operation.
- Continuous monitoring with no leaks detected in the sealing layer.
- Real integration with hydrogen production by electrolysis and direct reduction pilot plant.
- Practical demonstration of arbitrage in the Nordic electricity market (Nordpool)
The claim of "50 years of service life" requires technical context. This refers to mechanical equivalence obtained through accelerated fatigue tests, not continuous operation for half a century. The tests subjected the metal coating to pressure variations that replicate the accumulated wear from decades of load and unload cycles.
Technical risks and knowledge gaps
Validating a 100 m³ pilot project differs substantially from operating commercial caverns of 50,000 to 120,000 m³. The geometry changes, flow rates scale, and construction logistics become exponentially more complex. Three areas of uncertainty deserve attention:
Hydrogen embrittlement: H₂ can penetrate the crystalline structures of steels, reducing ductility and accelerating crack propagation. Although HYBRIT has selected resistant materials, their behavior under prolonged exposure on a commercial scale remains a subject of research. Recent academic studies from KTH (Royal Institute of Technology) highlight that simplified models may underestimate risks in systems with very low fault tolerance.
Geomechanics and hydrogeology: Natural microcracks in the rock, groundwater flows, and thermal variations can alter stress distributions in the lining over decades. The pilot demonstrated performance in stable Scandinavian geology, but extrapolations to other rock formations require rigorous local characterization.
Public Data Gaps: There is no disclosure of round-trip efficiency (energy to compress versus recoverable energy), complete liner steel specifications, leak detection limits, or detailed operating costs. This information would be essential for a complete technical audit.
Strategic implications and potential for scale.
For the steel industry, LRC storage could be a key element in making green steel viable. SSAB plans to eliminate 10% of Sweden's total CO₂ emissions by replacing blast furnaces with direct hydrogen reduction. Without a robust energy buffer, this system would be at the mercy of variations in electricity supply.
The model makes geographical sense in regions with competent granitic or metamorphic rock, concentrated industrial demand, and an absence of saline formations. Scandinavia, parts of Canada, and Precambrian shields on other continents emerge as natural candidates.
In Brazil, the theoretical potential exists — the country possesses extensive areas of crystalline basement in the Brazilian Shield and significant industrial hubs — but conclusions depend on specific geological prospecting and local feasibility modeling. HYBRIT is extending its tests until 2026 to “improve commercial design conditions,” acknowledging that the leap to industrial scale still requires additional engineering.
Conclusion
The validation of HYBRIT represents concrete progress, not speculation. The consortium demonstrated that lined caverns can safely and reliably store hydrogen with measurable economic benefit. Accelerated testing supports the claim of long-term durability, although definitive confirmation requires prolonged commercial operation.
Three next steps seem inevitable for wider adoption: intermediate-scale demonstration (10,000 to 20,000 m³), publication of more granular technical data for independent validation, and development of specific regulatory standards for hydrogen LRC, which is still under construction in Europe.
For executives evaluating hydrogen storage, LRC technology has moved beyond being a concept and has become a viable option in appropriate geological contexts. The question is no longer "does it work?", but "where does it work best?" and "at what cost on a commercial scale?"
