All-Iron Flow Battery Rebalancing Cell for pH and Charge Balance
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Solution Overview
Problem
All-iron redox flow batteries face challenges in maintaining state of charge balance and pH control due to hydrogen generation during charging, leading to inefficiencies and potential battery failure from Fe(OH)3 precipitation, requiring additional fluids and downtime for acid flushing.
Innovation Solution
An all-iron redox flow battery system with a third electrolyte tank and rebalancing cell that selectively provides fluid communication to rebalance state of charge and pH, using hydrogen gas to lower the pH of the third electrolyte solution, which is then used to rebalance the first and second electrolyte tanks, eliminating the need for additional acids and reducing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acid flushing is used to remove deposited Fe(OH)3, then the Fe(OH)3 deposits are removed, but additional liquid and downtime are required
Solution Approach 1:
The system uses the hydrogen gas generated during normal charging operations to perform the cleaning function. The hydrogen is consumed in situ to generate low pH conditions that dissolve Fe(OH)3 deposits, eliminating the need for external acid flushing operations and reducing downtime
Solution Approach 2:
The hydrogen gas, which is a byproduct of charging that must be managed, is converted into a useful cleaning agent. The hydrogen consumption process creates low pH conditions that actively remove Fe(OH)3 deposits, turning a waste product into a beneficial cleaning mechanism
2Reliability
If acid flushing is used to remove deposited Fe(OH)3, then the Fe(OH)3 deposits are removed, but additional liquid and complexity are required
Solution Approach 1:
The cleaning function is merged with the existing charging process. The hydrogen generated during charging is redirected to consume protons and create low pH conditions for cleaning, combining two previously separate operations (charging and cleaning) into a unified process that eliminates the need for separate acid flushing equipment
Solution Approach 2:
The hydrogen gas serves multiple functions: it maintains charge balance during charging and acts as a cleaning agent for removing Fe(OH)3 deposits. This multi-functionality eliminates the need for separate cleaning systems and reduces overall device complexity
3Productivity
If state of charge balance is not maintained, then charging continues, but pH control deteriorates and Fe(OH)3 precipitation occurs
Solution Approach 1:
The system continuously monitors the state of charge balance and uses this information to control hydrogen consumption. When imbalance is detected, hydrogen is consumed to adjust pH and prevent Fe(OH)3 precipitation, creating a closed-loop feedback system that maintains both charge balance and pH control during continuous operation
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 solution maintains the state of health of the electrolyte, prevents Fe(OH)3 precipitation, and maintains optimal performance by continuously monitoring and controlling pH and charge balance, ensuring efficient operation without additional acids and downtime.
Implementation Method 1
the rebalancing cell is configured to lower a pH of the third electrolyte solution... transferring protons from the negative rebalancing half-cell to the third electrolyte solution passing through the positive rebalancing half-cell
Implementation Method 2
all-iron redox flow battery which has the advantage of being cost efficient due to using only iron in different oxidation states as the electrolyte... During charging of an all-iron redox flow battery, molecular hydrogen H2 is generated from protons H+
Data Source
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AI summary
The invention relates to an all-iron redox flow battery comprising a first electrolyte tank configured to contain a first electrolyte solution and a second electrolyte tank configured to contain a second electrolyte solution; a flow cell comprising a negative flow half-cell configured for passing through first electrolyte solution and a positive flow half-cell configured for passing through second electrolyte solution; a third electrolyte tank, distinct from the first and second electrolyte tanks, configured to contain a third electrolyte solution, wherein the battery is configured to selectively provide fluid communication of the third electrolyte tank with at least one of the first electrolyte tank and the second electrolyte tank; and a rebalancing cell comprising a negative rebalancing half-cell and a positive rebalancing half-cell, wherein the negative rebalancing half-cell is configured to receive hydrogen gas from the first electrolyte tank and/or from a separate hydrogen source, and wherein the positive rebalancing half-cell is configured for passing through third electrolyte solution, whereby the rebalancing cell is configured to lower a pH of the third electrolyte solution.