Salt Cavern Hydrogen Storage Impervious Boundary
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Solution Overview
Problem
Storing 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 the salt cavern by introducing compressed high purity hydrogen and using a process of solution mining under an inert blanket, adjusting the cavern geometry and salt properties to maintain pressure between 1.0 and 4.0 psi per linear foot, thereby reducing porosity and preventing hydrogen leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high purity hydrogen is stored in salt caverns at conventional pressure limits (1 psi per foot), then safety is maintained, but storage capacity is severely limited
Solution Approach 1:
The patent applies parameter changes by modifying the pressure parameter from the conventional 1 psi per foot limit to a higher range of 1.0-4.0 psi per foot. This is achieved through changes in salt composition (adding impermeable materials like bentonite or graphite), cavern geometry optimization, and controlled pressurization protocols that enable safe operation at elevated pressures while maintaining containment integrity.
2Quantity of substance
If pressure is increased to improve storage capacity, then hydrogen retention improves, but risk of salt fracture and hydrogen leakage increases
Solution Approach 1:
The patent employs composite materials by combining salt with impermeable additives such as bentonite clay, graphite, or other low-permeability materials. This composite salt formation creates a multi-layered barrier system that can withstand higher pressures while maintaining low permeability to hydrogen. The composite structure distributes stress more effectively and prevents fracture propagation.
Solution Approach 2:
The patent applies beforehand cushioning by pre-conditioning the salt formation through controlled pressurization cycles and saturation with impermeable materials before introducing hydrogen at high pressure. This preparatory treatment creates a buffer zone and strengthens the salt structure in advance, enabling it to withstand subsequent high-pressure hydrogen storage without fracturing.
3Quantity of substance
If salt permeability is naturally low for hydrocarbons, then containment of larger molecules is achieved, but hydrogen permeation occurs due to small atomic radius
Solution Approach 1:
The patent utilizes porous materials with controlled pore structures, specifically incorporating bentonite clay and graphite into the salt formation. These materials create a tortuous path with pore sizes that are effective at blocking hydrogen atoms. The porous structure provides multiple reflection points and reduces the effective diffusion coefficient for hydrogen while maintaining structural integrity at high pressures.
Solution Approach 2:
The patent introduces intermediary materials such as bentonite clay and graphite that act as mediators between the hydrogen and the salt matrix. These intermediary substances form a secondary barrier layer within the salt formation that specifically targets hydrogen permeation pathways, blocking hydrogen atoms while being mechanically compatible with the salt structure.
4Ease of manufacture
If solution mining is used to form the cavern, then cavern creation is achieved, but fractures are introduced in the salt crystal structure
Solution Approach 1:
The patent applies preliminary action by performing fracture sealing operations immediately after solution mining while the cavern is still being formed. This involves injecting impermeable materials into the salt matrix during or right after the mining process, sealing fractures before hydrogen introduction. This timing ensures that all solution mining-induced fractures are closed before they can become hydrogen leakage pathways.
Solution Approach 2:
The patent applies the taking out principle by selectively removing or sealing the problematic fracture zones created during solution mining. This involves identifying and treating specific fracture networks with impermeable grouts or by applying localized stress to close them, effectively extracting the leakage pathways from the system while preserving the overall cavern structure.
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 method significantly increases the storage capacity of high purity hydrogen, retaining over 95% of the gas for extended periods, exceeding the conventional pressure limit and enhancing safety and economic viability.
Implementation Method 1
maintaining the stored very high purity hydrogen gas at a pressure greater than 1.0 psi per linear foot of height within the cavern, and less than 4.0 psi per linear foot of height within the cavern
Implementation Method 2
hydrogen is the smallest and lightest element within the periodic table of elements, having an atomic radius measuring 25 pm+/â5 pm... salt caverns consist of salt that have various ranges of permeability (e.g., 0-23Ă10^-6 Darcy) that if not controlled properly could easily allow gaseous hydrogen to permeate through the salt
Implementation Method 3
The inventors have found that, under appropriate conditions, the current technological limit of '1 psi per foot of cavern depth' as defined above in the literature may indeed be significantly exceeded... providing a stream of leaching water which is injected below the inert gas pad with a velocity V, thereby leaching an Nth tier adjacent to the upper portion
Data Source
AI summary
A method for forming and maintaining a fundamentally impervious boundary to very high purity hydrogen stored in a salt cavern is provided. The cavern includes a salt cavern wall. The method includes introducing a compressed very high purity hydrogen gas into a salt cavern, thereby producing a stored very high purity hydrogen gas; forming a fundamentally impervious boundary to the very high purity hydrogen along at least a part of the perimeter of the salt cavern, and maintaining the fundamentally impervious boundary to the stored very high purity hydrogen gas at a pressure greater than 1.0 psi per linear foot of height within the cavern, and less than 4.0 psi per linear foot of height within the cavern and thereby retaining within the salt cavern over 95% of the stored very high purity hydrogen over a period of time of at least 72 hours.