Fuel Cell Stack Bypass Control for Freeze-Safe Power Stop
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Solution Overview
Problem
Fuel cell systems in moving bodies face challenges in preventing freezing and membrane deterioration when power generation is stopped during operation, due to the flow of cathode gas through the fuel cell stack and potential freezing of stop valves at low temperatures.
Innovation Solution
A fuel cell system with a bypass passage and control device that manages cathode gas flow, stopping power generation by closing stop valves and opening a bypass valve when temperatures exceed a threshold, and generating reduced power when temperatures are below the threshold to prevent freezing and membrane deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cathode gas is caused to flow through the fuel cell stack each time a request to stop power generation is received during operation, then power generation can be stopped quickly, but deterioration of the electrolyte membrane of the power generation cell inside the fuel cell stack progresses
Solution Approach 1:
The patent extracts the harmful flow path of cathode gas through the fuel cell stack by introducing a bypass passage that allows cathode gas to flow from the cathode supply path to the cathode discharge path without passing through the fuel cell stack, thereby stopping power generation quickly while preventing electrolyte membrane deterioration
Solution Approach 2:
The bypass passage acts as an intermediary flow path that mediates between the need for quick power generation stop and the need to protect the electrolyte membrane, allowing cathode gas to bypass the fuel cell stack during stop conditions
2Speed
If the power generation of the fuel cell stack is stopped by closing the stop valve of the cathode path every time a power generation stop request is received, then power generation can be stopped quickly, but there is a possibility that the stop valve is frozen while being closed when the temperature of the surrounding environment becomes low
Solution Approach 1:
The patent extracts the stop valve from the critical flow path by routing cathode gas through a bypass passage that does not require closing the stop valve, thereby achieving quick power generation stop while eliminating the risk of stop valve freezing in low temperature environments
Solution Approach 2:
The bypass passage provides an alternative flow path that is activated under specific conditions (power generation stop requests), allowing partial flow through the bypass while maintaining the ability to close the stop valve when necessary for other operational requirements
3Stability of the object's composition
If the air pump continues to operate at full power during power generation stop, then cathode gas can be supplied continuously, but electric power consumption increases
Solution Approach 1:
The patent implements dynamic control of the air pump operation, adjusting the air pump's operating state based on system conditions and power generation requirements, thereby maintaining adequate cathode gas supply continuity while optimizing electric power consumption by avoiding unnecessary full-power operation during power generation stop
Data Source
AI summary
An ECU of a fuel cell system determines whether or not temperature information exceeds a temperature threshold for determination when receiving a signal related to power generation stop of a fuel cell stack during operation of a moving body. When the temperature information exceeds the determination temperature threshold, the ECU performs a stop control for stopping power generation of the fuel cell stack. On the other hand, when the temperature information is equal to or lower than the determination temperature threshold, the ECU performs an idle control for generating electric power smaller than electric power consumed by the air pump.