Redox Flow Battery PWM Charging for Lower Ohmic Losses
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Solution Overview
Problem
Redox flow batteries face performance losses due to ohmic resistance and electrode inefficiencies, which are exacerbated by the aqueous nature of their electrolytes, leading to lower power and energy density compared to Li-ion batteries, and retrofitting to reduce these losses is complex and costly.
Innovation Solution
A method of operating redox flow batteries by supplying a pulse-width-modulated (PWM) charging voltage signal when the state of charge decreases below a threshold, which increases voltaic and energy efficiency while maintaining coulombic efficiency and reducing material costs, allowing for retrofitting of existing systems without increasing complexity or costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If operating temperature is increased to reduce ohmic resistance losses, then ohmic resistance losses are reduced, but material costs increase due to robustness requirements for system plumbing
Solution Approach 1:
The patent changes the electrical operating parameters by implementing pulsed voltage charging instead of continuous voltage charging. This parameter change allows the system to achieve lower ohmic losses through periodic high-voltage pulses followed by rest periods, avoiding the need for continuous high-temperature operation and its associated material cost increases.
2Loss of energy
If plating gap is reduced to increase redox flow battery efficiencies, then voltaic efficiency is improved, but system complexity and manufacturing cost increase due to retrofitting requirements
Solution Approach 1:
The patent changes the electrical charging parameters by using pulsed voltage signals with specific duty cycles and pulse widths. This approach improves voltaic efficiency by optimizing the charging process without requiring mechanical modifications to the plating gap, thereby avoiding increased system complexity and manufacturing costs.
3Productivity
If continuous charging is used to maintain battery operation, then productivity is maintained, but energy efficiency decreases due to continuous ohmic losses
Solution Approach 1:
The patent implements periodic charging action through pulsed voltage signals. The charging process operates in cycles with active charging pulses followed by rest periods, creating a periodic action pattern. This allows the battery to be charged effectively while reducing continuous ohmic losses, thereby improving energy efficiency while maintaining operational productivity.
Solution Approach 2:
The patent maintains continuous useful action by ensuring the battery remains in a charged state through periodic pulsing. The pulsed charging strategy keeps the battery charged and ready for operation without requiring continuous energy input, thus maintaining productivity while improving energy efficiency by eliminating continuous ohmic losses during rest periods.
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 enhances the efficiency of redox flow batteries by improving voltaic and energy efficiency while maintaining reliability and durability, facilitating retrofitting without additional hardware or complexity, thus bridging the power and energy density gap with Li-ion batteries.
Implementation Method 1
Redox flow batteries, such as all-iron redox flow batteries (IFBs)... due to the aqueous nature of the electrolytes
Implementation Method 2
charging the redox flow battery, including supplying a pulsed power signal to the redox flow battery
Implementation Method 3
supplying a pulse-width-modulated (PWM) charging voltage signal to the redox flow battery, the PWM charging voltage signal fluctuating between an upper threshold charging voltage and an open circuit voltage (OCV)
Data Source
AI summary
Systems and methods are provided for a redox flow battery. In one example, a method of operating a redox flow battery includes charging the redox flow battery, including supplying a pulsed power signal to the redox flow battery in response to the redox flow battery state of charge (SOC) decreasing below a lower threshold redox flow battery SOC, wherein supplying the pulsed power signal includes supplying a pulse-width-modulated (PWM) charging voltage signal to the redox flow battery, the PWM charging voltage signal fluctuating between an upper threshold charging voltage and an open circuit voltage (OCV).