Salt Cavern Hydrogen Storage Boundary Formation
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Solution Overview
Problem
Storing very high purity hydrogen in underground salt caverns is challenging due to permeation issues, as hydrogen's small atomic radius allows it to escape through the salt, posing safety risks and requiring high pressures to confine it effectively, which is beyond the current technological limit of 1 psi per foot of cavern depth.
Innovation Solution
A method to form and maintain a fundamentally impervious boundary within a salt cavern by introducing compressed very high purity hydrogen and maintaining it at pressures between 1.0 and 4.0 psi per linear foot, using a domed roof formed through solution mining under an inert blanket, with specific parameters for leaching water velocity, inert gas selection, and cavern geometry to reduce permeability and enhance storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen is stored at high pressure to prevent permeation through salt walls, then hydrogen retention is improved, but the risk of cavern roof failure and structural damage increases
Solution Approach 1:
The patent employs a domed roof geometry instead of a flat roof, creating a curved structural form that better distributes internal hydrogen pressure throughout the salt cavern. This curvature allows the structure to withstand higher pressures without roof failure, enabling improved hydrogen retention while managing structural risk.
Solution Approach 2:
The patent changes the pressure parameter from the conventional limit of 1 psi per foot to a higher range of 1.0-4.0 psi per foot. This parameter change is made possible by the domed roof design, which alters the stress distribution and allows safe operation at elevated pressures that improve hydrogen containment while preventing permeation losses.
2Ease of manufacture
If conventional flat roof design is used, then construction is simpler, but maximum storage pressure is limited to 1 psi per foot
Solution Approach 1:
The domed roof design replaces the conventional flat roof, transforming the structural geometry to achieve better pressure distribution. While slightly more complex than flat roof construction, the domed design enables storage pressures up to 4 times higher, providing a favorable trade-off between construction complexity and operational capability.
3Quantity of substance
If salt cavern is used for hydrogen storage, then large volume storage is achieved, but hydrogen permeation through salt occurs
Solution Approach 1:
The patent increases the storage pressure parameter to 1.0-4.0 psi per foot, which enhances hydrogen retention by reducing the relative driving force for permeation. The high pressure confining force counteracts hydrogen's tendency to migrate through the salt formation, maintaining large-volume storage capacity while minimizing losses.
Solution Approach 2:
The patent converts the harmful effect of high pressure (which could cause structural failure) into a beneficial force by using it to prevent hydrogen permeation. The elevated pressure that might otherwise be dangerous is instead utilized to keep hydrogen confined, turning a potential hazard into a protective mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly exceeds the conventional pressure limit for hydrogen storage, allowing for over 99% retention of very high purity hydrogen over 72 hours, thereby improving storage efficiency and safety while reducing the risk of leakage.
Implementation Method 1
hydrogen is the smallest and lightest element within the periodic table of elements, having an atomic radius measuring 25 pm+/−5 pm... salt caverns consist of salt that have various ranges of permeability (e.g., 0-23×10^−6 Darcy) that if not controlled properly could easily allow gaseous hydrogen to permeate through the salt and escape to the surface
Implementation Method 2
the process of solution mining the salt and forming the cavern, even though continuously filled with pressurized fluid, is known to introduce fractures of various sizes in the crystal structure of the salt
Implementation Method 3
pressures in excess of 1.0 psi per linear foot within salt caverns (Hcavern) is the technological pressure limit... pressures in excess of 1.0 psi per linear foot of cavern depth... cracks are sufficiently large to allow hydrogen to leak therethrough
Data Source
AI summary
A system for forming and/or maintaining a fundamentally impervious boundary within a salt cavern for storing very high purity hydrogen is provided. The system includes a salt cavern comprising a salt cavern wall; a conduit configured to introduce a compressed very high purity hydrogen gas into a salt cavern, thereby producing a stored very high purity hydrogen gas; the conduit also configured to remove the compressed very high purity hydrogen gas from the salt cavern, wherein the stored very high purity hydrogen gas is maintained at a pressure greater than about 1.0 psi per linear foot of height within the cavern, and less than about 4.0 psi per linear foot of height within the cavern.