Constant-Pressure Gas Storage With Stepped Hydraulic Compensation
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Solution Overview
Problem
Hydraulic compensation systems for isobaric gas storage suffer from significant gas loss due to dissolution of gas in the liquid, particularly in compressed air energy storage systems, leading to reduced efficiency and potential environmental impact.
Innovation Solution
The system divides the pressure difference in the continuous liquid line into multiple steps with settling volumes, allowing gas to dissolve into the liquid during emptying and bubble out during refilling, with small gas compressors extracting gas at intermediate pressures to maintain constant pressure storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If hydraulic compensation liquid is used to achieve isobaric gas storage, then constant pressure storage is achieved, but gas loss occurs due to dissolution of gas in the liquid
Solution Approach 1:
The system segments the continuous liquid line into multiple discrete settling volumes arranged in series, each operating at a different discrete intermediate pressure between the constant raised pressure and the lower pressure. This segmentation allows gas to be separated and removed at each pressure stage, preventing complete dissolution and reducing overall gas loss while maintaining the isobaric storage function.
2Volume of stationary object
If gas is stored in isochoric containment, then containment volume remains constant, but pressure varies during charge-discharge cycles
Solution Approach 1:
The patent introduces hydraulic compensation liquid as an intermediary substance between the gas storage containment and the external environment. This liquid mediator absorbs pressure variations by expanding and contracting in response to gas volume changes, thereby maintaining constant pressure within the gas containment while allowing volume flexibility through the liquid's compressibility and phase change capabilities.
3Stress or pressure
If hydraulic compensation liquid flows continuously, then pressure equalization is achieved, but gas dissolves and is carried away from the storage system
Solution Approach 1:
The system performs preliminary gas separation at each settling volume before the liquid continues its flow path. By providing settling volumes where gas can escape from the liquid at each pressure stage, the system preemptively removes dissolved gas before it can be carried away by the continuous liquid flow, thus preventing gas loss while maintaining pressure equalization.
Solution Approach 2:
The system employs feedback mechanisms where gas compressors detect and remove accumulated gas from each settling volume, and control systems monitor pressure differentials to regulate liquid flow rates. This feedback ensures that gas dissolution is minimized by adjusting operational parameters in real-time based on actual system conditions.
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 reduces gas loss during the charge-discharge cycle, improving the overall efficiency of gas storage systems and minimizing environmental impact by maintaining constant storage pressure and temperature.
Implementation Method 1
gas to dissolve into the liquid during emptying and bubble out during refilling
Implementation Method 2
Water at atmospheric pressure and 10° C. contains roughly 23×10−6 air by mass. That is to say, every litre of water (1 litre weighs 1 kg) contains 0.023 g of air. This is equivalent to approximately 18.4 ml of air at standard conditions. The amount of air dissolved in water increases linearly with pressure. Henry's law expresses this fact.
Data Source
AI summary
Disclosed herein is a system for storing gas at almost constant pressure, which involves the injection and withdrawal of a liquid in a process known as hydraulic compensation. This disclosure teaches a way to minimize that dissolution by ensuring that, as the gas containment is charged up, the hydraulic compensation liquid emerges from the containment at the gas storage pressure and the pressure of that liquid is caused to fall in a number of discrete steps with settling volumes present at the nodes between these steps. These settling volumes enable some gas to come out of solution at each node having lost relatively small amounts of pressure. The gas is compressed back up to storage pressure and re-injected into the main storage containment without significant use of energy.