Cathode Liquid Circulation for PEM Hydration in Hydrogen Expanders
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrochemical hydrogen expanders (EHEs) suffer from PEM drying due to electro-osmotic drag, leading to reduced proton conductivity and power density, despite efforts to maintain hydration through high-pressure hydrogen streams and humidified gas delivery, which are insufficient in maintaining optimal liquid levels.
Innovation Solution
A system with a liquid reservoir and pump or gravity feed mechanism maintains hydration by circulating deionized liquid to the cathode electrode, adjusted by a controller based on sensor data to manage pressure differentials and concentration gradients, ensuring optimal liquid levels within the proton exchange membrane (PEM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-pressure hydrogen streams and humidified gas delivery are used to maintain hydration, then proton conductivity is improved, but the mass fraction of water being brought in is less than that leaving through the low-pressure stream, causing PEM drying
Solution Approach 1:
A liquid water delivery system introduces liquid water as an intermediary substance to the cathode side, which then migrates through the PEM to the anode side via electro-osmotic drag, providing additional water to compensate for water loss and maintain hydration without disrupting the pressure differential
Solution Approach 2:
The system changes the physical state of water delivery from vapor phase (humidified gas) to liquid phase, enabling higher water content delivery to the cathode side while maintaining the same pressure differential across the PEM, thereby improving the water mass fraction balance
2Power
If pressure differential across anode and cathode is increased to increase power density, then power output is improved, but water management becomes more difficult leading to PEM drying
Solution Approach 1:
The liquid water delivery system targets the cathode side locally, providing water precisely where needed to counteract the effects of high pressure differential, allowing the system to maintain high power density while preserving local hydration conditions at the cathode-PEM interface
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
Prevents PEM drying by maintaining optimal liquid levels, enhancing proton conductivity and power density in EHEs through controlled liquid circulation.
Implementation Method 1
As the protons generated at the anode through HOR move through the PEM during operation, they drag surrounding water molecules with them, depleting the amount of available water at the anode side
Implementation Method 2
the pressure differential across the anode and cathode can be increased
Implementation Method 3
a liquid concentration gradient across the MEA
Data Source
AI summary
An electrochemical cell includes a membrane electrode assembly having a first electrode operating at a first pressure, a second electrode operating at a second pressure that is lower than the first pressure, and a proton exchange membrane disposed between the first and second electrodes. The first and second electrodes are electrically connected to an external load. The second electrode has a liquid inlet and a liquid outlet. A first conduit is in communication with the first electrode and supplies a dry or humidified gas to the first electrode. A second conduit is in communication with the second electrode. The second conduit provides an outlet for gas products produced by electrochemical reactions across the MEA. A liquid reservoir contains a liquid and is in fluid communication with the second electrode via the liquid inlet and the liquid outlet to enable circulation of the liquid within the second electrode.