Hydrogen storage in underground geological formations is a critical component of large-scale energy systems, offering solutions for long-term, high-capacity energy storage. Among the most promising options are salt caverns, which can be formed in salt domes or bedded salt formations. These two geological structures differ in their formation, stability, storage capacity, and regional distribution, influencing their suitability for hydrogen storage.

Salt domes are vertical, dome-shaped structures formed by the upward movement of salt due to its lower density compared to surrounding rock layers. These formations are highly stable, with thick salt layers providing excellent sealing properties to prevent hydrogen leakage. The Gulf Coast region of the United States is a prime example, hosting numerous salt domes that have been used for natural gas and oil storage for decades. The homogeneity and structural integrity of salt domes make them ideal for creating large, single-cavern storage facilities with capacities often exceeding hundreds of thousands of cubic meters.

In contrast, bedded salt formations consist of horizontal layers of salt interspersed with other sedimentary rocks. These formations are more geologically complex, with varying salt purity and thickness. Europe relies heavily on bedded salt for hydrogen and natural gas storage, particularly in Germany and the Netherlands. While bedded salt formations may not offer the same cavern size as salt domes, they are more widely distributed, providing regional flexibility. However, their layered structure introduces higher risks of irregularities, requiring careful site selection and engineering to ensure stability.

Geological stability is a key factor in hydrogen storage. Salt domes benefit from their massive, homogeneous salt bodies, which minimize the risk of fractures or leakage pathways. The plastic nature of salt allows it to self-heal under stress, further enhancing containment security. Bedded salt formations, while still stable, face greater challenges due to interbedded non-salt layers that may introduce weaknesses. These layers can lead to uneven stress distribution, increasing the risk of cavern deformation over time.

Storage capacity varies significantly between the two types. Salt domes typically support fewer but much larger caverns, with individual caverns capable of holding over 500,000 cubic meters of hydrogen at high pressures. Bedded salt formations generally host smaller, multiple caverns due to thinner salt layers, limiting individual cavern sizes but allowing for distributed storage networks. The total storage potential in bedded salt regions can still be substantial when aggregated across multiple sites.

Regional availability plays a major role in determining which type of storage is feasible. The U.S. Gulf Coast has an abundance of salt domes, making it a global leader in underground storage. Europe, lacking extensive salt dome formations, has turned to bedded salt, particularly in northern Germany, where salt layers are well-documented and accessible. Other regions, such as parts of Asia and Australia, are still evaluating their salt formations for hydrogen storage potential.

Case studies highlight the differences in implementation. In the U.S., the Strategic Petroleum Reserve utilizes salt domes for liquid fuel storage, demonstrating their reliability. For hydrogen, projects like the HyStorage initiative in Europe are exploring bedded salt caverns, focusing on adapting existing natural gas storage infrastructure. Each region faces unique engineering challenges. In salt domes, the primary concerns include ensuring uniform cavern shape during leaching and managing high-pressure injection cycles. Bedded salt projects must address interlayer slippage and ensure long-term cavern integrity despite heterogeneous geology.

Engineering challenges also extend to hydrogen-specific considerations. Hydrogen’s small molecular size increases the risk of permeation through salt, though studies indicate that well-designed caverns can mitigate this. Both salt domes and bedded salt formations require rigorous monitoring for micro-leaks and pressure changes. Additionally, hydrogen’s reactivity with certain minerals necessitates thorough geochemical analysis before cavern construction.

In summary, salt domes offer superior geological stability and larger storage capacities but are geographically limited. Bedded salt formations provide broader regional availability but require more complex engineering solutions. The choice between the two depends on local geology, infrastructure needs, and long-term energy strategies. As hydrogen economies expand, both types of storage will play crucial roles in enabling large-scale, sustainable energy systems.