Redox Flow Battery Array SOC Balancing by Electrolyte Flow Control
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Solution Overview
Problem
Existing redox flow battery arrays face challenges in efficiently and cost-effectively managing capacity balancing between flow battery units with shared common electrolyte supplies, particularly in large arrays, due to limitations in voltage, efficiency, and system complexity, making it difficult to integrate with high-voltage DC connections and increasing system costs.
Innovation Solution
The solution involves measuring the state of charge of common electrolyte pairs and regulating flow in anolyte and catholyte circuits using state-of-charge measuring devices, flow regulators, and controllers, eliminating the need for multiple bi-directional power converters and fluid interconnection subsystems, allowing for balanced state of charge within flow battery unit strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple bi-directional power converters are used to manage capacity balancing in flow battery arrays, then voltage control and power management capability is improved, but system cost and device complexity increase
Solution Approach 1:
The patent combines multiple power converter functions into a single bi-directional power converter that handles both charging and discharging operations for the flow battery array. This single converter manages capacity balancing by controlling electrolyte flow between series and parallel strings, eliminating the need for multiple separate converters and reducing system complexity while maintaining full power management capability
Solution Approach 2:
The single bi-directional power converter is designed to perform multiple functions: it can operate in forward mode to charge the flow battery from AC input, in reverse mode to discharge to AC output, and in bypass mode to manage electrolyte redistribution. This multi-functional design replaces what would traditionally require multiple specialized converters, reducing cost and complexity
2Power
If series connected cell voltage is increased to improve power output, then power delivery capability is improved, but system cost increases due to shunt mitigation measures and pumping power requirements
Solution Approach 1:
The patent implements dynamic voltage balancing by periodically switching between series and parallel string configurations. During charging, the system can operate in series mode for high voltage; during discharging or balancing, it switches to parallel mode to equalize states of charge. This dynamic reconfiguration allows the system to achieve high power delivery when needed while mitigating shunt effects and reducing pumping requirements through periodic balancing cycles
3Ease of manufacture
If flow battery units with shared common electrolyte supplies are used to reduce system complexity, then ease of manufacture is improved, but capacity balancing between units becomes difficult to manage
Solution Approach 1:
The patent incorporates state of charge sensing for each flow battery unit and uses this feedback information to control electrolyte redistribution. The system monitors individual unit states and dynamically adjusts flow paths to balance capacity across units sharing common electrolyte supplies. This feedback-controlled balancing mechanism maintains the manufacturing simplicity of shared supplies while solving the capacity balancing problem through intelligent control
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 simplifies the redox flow battery array, reduces costs, and enhances efficiency by enabling effective state of charge balancing within flow battery unit strings, improving energy storage capacity and integration with high-voltage AC/DC converters without the need for additional converters or complex interconnection systems.
Implementation Method 1
They convert electrical energy into chemical energy that can be stored and then converted into electrical energy which is released when there is a demand. In operation, liquid electrolytes are delivered to a flow battery to either convert electrical energy into chemical energy
Implementation Method 2
The separator can be a micro-porous separator or an ion exchange membrane and it separates the electrodes and prevents the electrolytes from mixing, but allows selected ions to pass through to complete the redox reactions
Data Source
AI summary
Designs of redox flow battery arrays and methods for balancing state of charge within the arrays are disclosed. Flow battery unit strings in the arrays which comprise strings of flow battery units (in which units share a common electrolyte pair) are balanced by measuring the states of charge of the common electrolyte pairs and appropriately regulating flow in one or more of the associated anolyte and catholyte circuits so as to balance the state-of charge in the flow battery unit strings. The apparatus required, i.e. state-of-charge measuring device, flow regulator, and controller, represents a substantial simplification to state of the art approaches.