Fuel Cell Shutdown Drying via Impedance Monitoring
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Solution Overview
Problem
Fuel cell systems face inefficiencies due to uneven drying of power generation cells during shutdown, leading to potential freezing issues when temperatures drop, as cells at the ends of the stack may not dry sufficiently before operation cessation.
Innovation Solution
A method involving a power generation at shutdown step, where the fuel cell stack generates power until an impedance value is reached, followed by a continuous power generation step to ensure uniform drying of all cells, including those at the ends, by maintaining power generation for a specified period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power generation is stopped immediately when shutdown is commanded, then the system responds quickly, but water remains in the cells causing freezing issues at low temperatures
Solution Approach 1:
The patent implements preliminary action by executing a power generating process during the shutdown phase, before the system fully stops operation. This intermediate drying action removes water from the cells while the system is still generating power, preventing freezing issues that would occur if shutdown were immediate, while avoiding the need for extended idle drying time.
2Reliability
If the fuel cell stack operates continuously to dry all cells uniformly, then all cells are dried evenly including ends, but the shutdown time is extended
Solution Approach 1:
The patent applies periodic action by using alternating flow directions during the shutdown power generating process. The inlet and outlet are swapped compared to normal operation, creating a periodic reversal pattern that systematically addresses different regions of the cell stack. This ensures uniform drying across all cells including the difficult-to-reach end cells, while maintaining a controlled and optimized shutdown duration.
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 method ensures more uniform drying of the fuel cell stack, preventing freezing and reducing startup time, thereby enhancing operational efficiency and reliability.
Implementation Method 1
an impedance measuring unit for measuring an impedance of the fuel cell stack
Implementation Method 2
a fuel cell stack having a stack of a plurality of power generation cells that generate electric power through a reaction between an anode gas and a cathode gas
Data Source
AI summary
A fuel cell system includes a fuel cell stack of a plurality of power generation cells and an impedance measuring device for measuring the impedance in the fuel cell stack. When stopping the operation of the fuel cell system, a method for stopping the operation of the fuel cell system operates the plurality of power generation cells to generate electric power, until the impedance value becomes equal to or greater than an objective impedance value. After the impedance value has become equal to or greater than the objective impedance value, the operation stopping method still continues the power generation of the multiple power generation cells for a given period of time.