Underground Redox Flow Battery Electrolytes for High-Temperature Storage
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Solution Overview
Problem
Redox flow batteries (RFBs) face limitations in operating at elevated temperatures due to electrolyte decomposition, especially with organic redox-active compounds, which reduces their capacity and stability, and require multiple storage tanks and membranes, increasing complexity and cost.
Innovation Solution
The use of underground storage means, such as caverns, with high salt concentration electrolytes containing specific redox-active compounds that are stable at elevated temperatures, allowing for a single storage device and optional membrane-less operation, enhancing temperature stability and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If organic redox-active compounds are used in RFBs, then capacity and energy storage are improved, but electrolyte decomposition occurs at elevated temperatures reducing stability
Solution Approach 1:
The patent changes the temperature parameter by operating the RFB at elevated temperatures (30-90°C) and modifies the chemical composition parameter by using specific inorganic redox couples (Fe2+/Fe3+, Mn2+/Mn3+, Zn/Zn2+) that maintain stability across this temperature range, resolving the contradiction between capacity and temperature stability
Solution Approach 2:
The patent employs composite electrolyte systems combining inorganic redox-active compounds with conductive salts (e.g., LiCl, NaCl, KCl) in aqueous solutions, creating a composite material that achieves both high energy capacity and thermal stability, overcoming the limitations of pure organic systems
2Quantity of substance
If multiple storage tanks and membranes are used in RFBs, then energy storage capacity is improved, but system complexity and cost increase
Solution Approach 1:
The patent merges the storage tank and reaction chamber into a single integrated underground cavern system. The cavern serves dual functions as both storage reservoir and electrochemical reactor, eliminating the need for separate tanks and reducing system complexity while maintaining large-scale energy storage capacity
Solution Approach 2:
The patent extracts and eliminates the membrane component from the system by using hybrid RFB configurations where one half-cell contains a solid electrode (e.g., Zn anode) that naturally provides separation functionality, or by using immiscible electrolyte systems that require no membrane barrier
3Adaptability or versatility
If RFBs are designed for high temperature operation, then applicability to geothermal and industrial applications is improved, but electrolyte decomposition increases
Solution Approach 1:
The patent systematically changes the chemical composition parameters by selecting inorganic redox couples with high thermal decomposition temperatures and adjusting electrolyte concentration and pH to optimize stability in the 30-90°C operating range, enabling high-temperature applicability without decomposition losses
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 configuration enables RFBs to operate reliably at high temperatures with increased stability and capacity, reducing complexity and cost by utilizing underground storage and specific redox-active compounds, making them suitable for high-temperature applications.
Implementation Method 1
Such systems are used to store electrical energy based on electrochemical redox reactions
Implementation Method 2
During the charging or discharging process, (non-redox active) ions in the electrolyte enable a charge exchange across the membrane
Data Source
AI summary
A redox flow battery for storing electrical energy is described, comprising a reaction cell with two electrode chambers for catholyte and anolyte, each of which is connected to at least one liquid reservoir, the electrode chambers being separated by a membrane, being equipped with electrodes, and each being filled with electrolyte solutions which contain redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conducting salts dissolved therein and possibly further additives. A second embodiment relates to a redox flow battery for storing electrical energy, comprising a reaction cell with an electrode chamber for an electrolyte solution, which is connected to at least one liquid reservoir, the electrode chamber being equipped with a cathode and an anode, and being filled with electrolyte solution which contains redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conductive salts dissolved therein and possibly further additives. The redox flow cells are characterized in that the at least one liquid reservois is an underground storage means in which temperatures of at least 30° C. prevail, in that the concentration of the salts dissolved in the electrolyte solutions is at least 10% by weight, and in that the catholyte or the electrolyte solution contains selected redox-active and temperature-stable components. In the first embodiment, the anolyte contains a water-soluble redox-active component and in the second embodiment, the anolyte or the electrolyte solution contains a zinc salt.