H2/Br2 Flow Battery Crossover Return System
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Solution Overview
Problem
Flow batteries, such as the H2/Br2 system, face efficiency losses and capacity reduction due to reactant crossover, where materials like H2, Br2, and HBr migrate through the cell membrane, leading to non-electrochemical reactions and reduced usable work.
Innovation Solution
A crossover return system is implemented, comprising a vessel connected to the H2 feed and return system, with separate return lines for hydrogen and bromine electrolytes, and optional components like a sump, heat exchanger, compressor, and gas-separation membrane to separate and return bromine electrolytes to their respective tanks, reducing crossover effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a membrane is used to separate H2 and Br2 in the flow battery, then electrochemical reactions are enabled, but reactant crossover occurs leading to efficiency losses
Solution Approach 1:
The patent extracts the harmful crossover reactants (H2 and Br2) that have migrated through the membrane from the electrolyte stream before it returns to the battery cell. A separation unit removes these crossed-over species, preventing them from causing harmful side reactions and energy losses, thereby resolving the contradiction between enabling electrochemical reactions and preventing energy loss.
Solution Approach 2:
The patent introduces an intermediary system between the membrane and the electrolyte tank that actively manages reactant crossover. This intermediary separation unit acts as a mediator that captures and removes crossed-over reactants, allowing the membrane to perform its primary function of enabling electrochemical reactions while preventing the harmful effects of reactant mixing.
2Productivity
If reactants are allowed to cross the membrane, then material transport occurs, but non-electrochemical reactions reduce usable work
Solution Approach 1:
The patent implements a feedback mechanism where the electrolyte stream is continuously monitored for crossed-over reactants, and the separation unit actively removes these reactants before the electrolyte returns to the battery. This feedback loop prevents reactant loss by continuously correcting the crossover problem, allowing rapid reaction rates while minimizing substance loss.
Solution Approach 2:
The patent converts the harmful effect of reactant crossover into a manageable process by capturing the crossed-over reactants in the separation unit. Instead of allowing these reactants to cause non-electrochemical reactions and energy losses, the system recovers and returns them to their proper compartments, transforming a harmful phenomenon into a controlled process.
3Power
If H2 and Br2 are separated by a membrane, then electrochemical work is enabled, but reactant mixing reduces battery capacity
Solution Approach 1:
The patent extracts crossed-over reactants from the electrolyte stream using a separation unit, preventing them from mixing and causing capacity reduction. This extraction process maintains the reliability and capacity of the battery while allowing the membrane to enable high power density electrochemical reactions.
Solution Approach 2:
The separation unit acts as an intermediary between the membrane separation function and the battery capacity maintenance. It captures crossed-over reactants that would otherwise reduce battery capacity, allowing the system to maintain high power density while protecting battery reliability and capacity.
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 system effectively reduces energy efficiency losses and battery capacity fade by separating and returning bromine electrolytes to their tanks, maintaining high power density and reducing reactant mixing, thereby enhancing the overall performance of the H2/Br2 flow battery.
Implementation Method 1
a heat exchanger configured to remove heat from the effluent to condense the second portion of the bromine electrolyte into a liquid form
Implementation Method 2
a compressor configured to increase a gas pressure of the effluent in the vessel
Data Source
AI summary
A flow battery system includes a first tank having a hydrogen reactant, a second tank having a bromine electrolyte, at least one cell including a hydrogen reactant side operably connected to the first tank through an ¾ feed and return system and a bromine electrolyte side operably connected to the second tank, and a crossover return system. The crossover return system includes a vessel operably connected to the ¾ feed and return system and configured to receive an effluent containing a first portion of the hydrogen reactant and a second portion of the bromine electrolyte, the vessel configured to separate the first portion from the second portion. A first return line returns the first portion of the hydrogen reactant to the first tank and a second return line returns the bromine electrolyte to the second tank.