Fuel Cell Shutdown Method Preventing Membrane Deterioration
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Solution Overview
Problem
Fuel cell systems face complexity and high costs due to the need for complex structures and large sizes when shutting down, as fuel gas and oxygen-containing gas can mix and cause electrochemical reactions, leading to membrane deterioration.
Innovation Solution
A method involving controlled supply of oxygen-containing gas and fuel gas, where the fuel gas supply is stopped while maintaining oxygen supply at a low stoichiometry, allowing the fuel cell to generate electricity until the anode pressure reaches a preset limit, thereby preventing hydrogen from crossing the membrane and reducing oxygen concentration, and using a coolant to prevent temperature-related deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the fuel cell is shut down by stopping supply of both fuel gas and oxygen-containing gas, then the shutdown process is simple, but the fuel gas and oxygen-containing gas may pass through the electrolyte membrane and mix, causing membrane deterioration
Solution Approach 1:
The patent applies preliminary action by continuing to supply oxygen-containing gas to the cathode after shutting down fuel gas supply to the anode. This creates a nitrogen-rich environment in the cathode that prevents hydrogen from crossing the membrane by maintaining a concentration gradient that blocks hydrogen permeation, thereby protecting the membrane during shutdown
Solution Approach 2:
The patent creates an inert atmosphere by using nitrogen (from air) to fill the cathode side of the fuel cell during shutdown. The nitrogen-rich environment prevents harmful electrochemical reactions by displacing oxygen and creating a barrier that stops hydrogen from reaching the cathode side of the membrane, thus protecting the membrane from deterioration
2Reliability
If the cathode outlet gas is circulated upstream and nitrogen gas is used to purge the fuel cell, then the membrane deterioration is prevented, but the system becomes complex and large in size
Solution Approach 1:
The patent extracts the essential protective function (preventing membrane deterioration) from the complex circulation and purge system. By simply continuing oxygen-containing gas supply to the cathode after anode shutdown, the patent achieves membrane protection without requiring separate circulation lines, tanks, or active purge mechanisms, thereby eliminating the need for complex additional components
Solution Approach 2:
The patent makes the oxygen-containing gas supply device perform multiple functions: during normal operation it supplies oxygen for electrochemical reaction, and during shutdown it creates a protective nitrogen-rich atmosphere to prevent membrane deterioration. This multi-functionality eliminates the need for separate protective systems, simplifying the overall system structure
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 simplifies the shutdown process, reduces membrane deterioration, and maintains a compact system by ensuring hydrogen concentration is lowered, preventing excessive hydrogen passage and maintaining nitrogen-rich environments within the fuel cell, thus minimizing damage and maintaining efficiency.
Implementation Method 1
a fuel cell for generating electricity from an electrochemical reaction between an oxygen-containing gas and a fuel gas
Implementation Method 2
a membrane electrode assembly (MEA) including an anode and a cathode disposed on respective sides of an electrolyte membrane
Data Source
AI summary
A method of shutting down a fuel cell system includes a first step of supplying hydrogen gas and air to a fuel cell stack to thereby cause the fuel cell stack to generate electricity, and a second step of stopping supply of the hydrogen gas, and then supplying air to the fuel cell stack so as to cause the fuel cell stack to generate electricity upon detection of a command to shut down the fuel cell stack. In the second step, when the pressure of the hydrogen gas is lowered to a preset lower-limit value based on an anode pressure, which actually is measured, the fuel cell stack is caused to stop generating electricity.