Liquefied Hydrogen Tank Pressure Control Using Boil-Off Gas Compression
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Solution Overview
Problem
Existing liquefied hydrogen storage technologies face challenges in maintaining low pressure and controlling irregular boil-off gas generation due to ortho-para conversion, leading to increased tank thickness and reduced efficiency.
Innovation Solution
A system with multiple liquefied hydrogen storage tanks operating in low-temperature and high-temperature modes, combined with a compressor and heat transfer medium circulation, controls boil-off gas generation by solidifying a portion of hydrogen and utilizing boil-off gas for power generation, maintaining tanks at low pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If liquefied hydrogen is stored using conventional LNG storage technology, then storage capacity is increased, but storage pressure increases to 3 bar or more requiring thicker tank walls
Solution Approach 1:
The patent changes the temperature parameter of stored hydrogen to below the ortho-para conversion temperature (below -259°C), which fundamentally alters the physical and chemical properties of hydrogen. This temperature parameter change suppresses ortho-para conversion, stabilizes vapor pressure, and enables storage at low pressure (0.03-0.36 bar) while maintaining large storage capacity
Solution Approach 2:
The system performs preliminary cooling of hydrogen to extremely low temperatures before storage, and pre-establishes temperature control systems that maintain this low temperature regime throughout storage. This preliminary action prevents ortho-para conversion from occurring, thereby preventing pressure buildup before it becomes a problem
2Reliability
If storage temperature is lowered to suppress ortho-para conversion, then boil-off gas generation is controlled, but energy consumption for cooling increases
Solution Approach 1:
The patent implements a self-service cooling system where boil-off gas that would normally be wasted is instead captured, compressed, and reused as a cooling medium. The system automatically maintains low temperature through this closed-loop process without requiring external energy input for cooling, making the system self-sufficient
Solution Approach 2:
The patent converts the harmful effect of ortho-para conversion (which generates boil-off gas and heat) into a beneficial cooling effect. By allowing controlled ortho-para conversion and using the generated heat exchange to cool incoming hydrogen, the system transforms what was previously a problem into a useful cooling mechanism that reduces external energy requirements
3Reliability
If multiple storage tanks are used with temperature control units, then boil-off gas generation is controlled, but system complexity increases
Solution Approach 1:
The patent merges multiple functions into integrated components: the temperature control unit combines refrigeration, heat exchange, and temperature monitoring functions; the boil-off gas treatment system integrates compression, cooling, and reuse functions. This functional integration reduces the number of separate components while maintaining sophisticated control capabilities
Solution Approach 2:
The temperature control unit and boil-off gas treatment system are designed as multi-functional components that perform multiple operations. The same equipment used for cooling also serves for heat exchange during ortho-para conversion, and the boil-off gas system simultaneously handles pressure control and cooling, reducing overall system complexity
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
Stabilizes liquefied hydrogen storage by reducing pressure, suppressing sloshing, and enhancing energy efficiency through controlled boil-off gas management, allowing safe and efficient long-term storage and supply.
Implementation Method 1
a first temperature control unit controlling an internal temperature of the at least one liquefied hydrogen storage tank to maintain an inside of the at least one liquefied hydrogen storage tank at a low pressure; and a densification unit maintaining at least a portion of stored liquefied hydrogen at a first temperature which is a densification temperature
Implementation Method 2
a second temperature control unit maintaining at least a portion of stored liquefied hydrogen at a second temperature higher than the first temperature
Implementation Method 3
a compressor compressing boil-off hydrogen gas generated in the liquefied hydrogen storage tanks and supplying the compressed boil-off hydrogen gas to the pressure tanks to generate a pressure required for delivery of liquefied hydrogen from the pressure tanks to the liquefied hydrogen demand site
Implementation Method 4
a heat transfer medium circulation unit recovering thermal energy from the low-temperature tank and supplying the recovered thermal energy to the high-temperature tank
Implementation Method 5
solidifying a portion of hydrogen and utilizing boil-off gas for power generation, maintaining tanks at low pressure
Data Source
AI summary
A system for supplying liquefied hydrogen includes: liquefied hydrogen storage tanks each comprising a temperature control unit controlling an internal temperature of the liquefied hydrogen storage tank to maintain an inside of the liquefied hydrogen storage tank at a low pressure; pressure tanks receiving and storing liquefied hydrogen to be supplied to a liquefied hydrogen demand site from the liquefied hydrogen storage tanks, the pressure tanks having a smaller capacity than the liquefied hydrogen storage tanks and maintained at a higher pressure than the liquefied hydrogen storage tanks; a liquefied hydrogen supply line through which liquefied hydrogen is transferred from the pressure tanks to the liquefied hydrogen demand site; and a compressor compressing boil-off hydrogen gas generated in the liquefied hydrogen storage tanks and supplying the compressed boil-off hydrogen gas to the pressure tanks to generate a pressure required for delivery.