Iron-Based Flow Battery Decoupling Power and Energy
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Solution Overview
Problem
Conventional redox flow batteries are expensive and have coupled power and energy capacities, limiting their scalability and efficiency, while existing technologies lack a cost-effective solution for high cell voltages and efficient energy storage.
Innovation Solution
An iron-based flow battery system with external storage tanks, using electrolytes containing Fe 2+ and Fe 3+ ions, and electrodes with hydrogen evolution suppressing agents and Fe 3+ stabilizing agents, allowing for decoupled power and energy storage with improved coulombic and voltaic efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional redox flow batteries use vanadium or zinc-based electrolytes, then they achieve stable electrochemical performance, but the system cost increases significantly
Solution Approach 1:
The patent replaces expensive vanadium or zinc-based electrolytes with iron-based electrolytes, which are significantly cheaper and more abundant. The iron electrolyte uses common materials like iron sulfate or iron chloride, reducing the cost of materials while maintaining functional performance for the intended application lifecycle
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte from vanadium/zinc-based to iron-based, altering the fundamental chemical system to achieve lower cost. This includes adjusting pH levels, ion concentrations, and additive compositions to optimize iron-based electrolyte performance
2Adaptability or versatility
If flow batteries use external storage tanks for electrolytes, then energy capacity can be scaled independently, but the system complexity and pumping requirements increase
Solution Approach 1:
The patent extracts the energy storage function into external tanks while keeping the power generation function in compact flow cells. This separation allows independent scaling of energy capacity by simply adding or removing electrolyte volume in external tanks, without increasing the complexity of the electrochemical conversion system
Solution Approach 2:
The system is segmented into distinct functional modules: external storage tanks for energy capacity, flow cells for power generation, and pumping systems for electrolyte circulation. This modular segmentation enables independent optimization and scaling of each component
3Power
If flow batteries operate at higher cell voltages, then power output increases, but side reactions like hydrogen evolution increase reducing efficiency
Solution Approach 1:
The patent introduces pH buffer additives and complexing agents as intermediary substances that mediate between the high cell voltage operation and the electrolyte stability. These additives suppress hydrogen evolution reactions and prevent iron precipitation, enabling high voltage operation while maintaining high coulombic efficiency
Solution Approach 2:
The patent optimizes electrolyte composition parameters including pH control, ion concentration ratios, and additive compositions to shift the electrochemical window and suppress side reactions. By adjusting these parameters, the system achieves high cell voltage operation with minimal energy loss to hydrogen evolution
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
The iron-based flow battery provides high cell voltages, excellent efficiency, and significantly lower costs compared to traditional batteries, with a cost of $250/kW and $30/kWh, and achieves a round-trip storage efficiency of 75% or greater, decoupling power and energy storage effectively.
Implementation Method 1
Reduction-oxidation (redox) flow batteries store electrical energy in a chemical form and subsequently dispense the stored energy in an electrical form via a spontaneous reverse redox reaction
Implementation Method 2
electrodes with hydrogen evolution suppressing agents and Fe 3+ stabilizing agents
Data Source
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AI summary
An iron based redox flow cell. The redox flow cell comprises a first half-cell comprising a first electrolyte providing a source of Fe2+ ions and an electrode disposed within the first half-cell; a second half-cell comprising a second electrolyte providing a source of Fe2+ and Fe3+ ions and an electrode disposed within the second half-cell; and a separator between the first and second half- cells, where (a) the second electrolyte comprises a Fe3+ stabilizing agent; (b) the first electrolyte comprises a hydrogen evolution suppressing agent; or (c) the first electrolyte comprises a hydrogen evolution suppressing agent, and the second electrolyte comprises a Fe3+ stabilizing agent.