Fuel Cell Stack Water Removal for Cold Start
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fuel cell systems in hydrogen fuel cell vehicles face challenges in completely removing water during shutdown at temperatures below freezing, leading to difficulties in cold startability due to frozen water in the fuel cell stack and components, which hinders the smooth supply of reactant gases and maintains voltage instability.
Innovation Solution
A method involving determining outside air temperature and using the fuel cell stack's power to warm up and maintain hydrogen supply, passing heated air through the stack to remove water, and then shutting down the system by cutting off air supply, with optional auxiliary power from an electricity storage means to further heat and dry the stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the fuel cell system is shut down at temperatures below freezing without water removal, then the shutdown process is simple and quick, but water freezes in the fuel cell stack and components, causing difficulty in cold startability
Solution Approach 1:
The patent applies preliminary action by removing water from the fuel cell stack before shutdown occurs. The control unit detects when the vehicle is parked for a predetermined time or when temperature drops below freezing, and automatically executes water removal operations (increasing air supply to the cathode, stopping humidifier operation) before the shutdown is finalized, preventing water freezing and ensuring reliable cold startability.
Solution Approach 2:
The fuel cell system performs self-service by using its own operational components (air blower, humidifier, cathode reaction) to remove water during the shutdown process. The system leverages the existing air supply and electrochemical reactions to drive water removal without requiring external equipment, making the process autonomous and integrated into the normal shutdown sequence.
2Reliability
If water removal operations are performed before shutdown at low temperatures, then cold startability is improved, but the shutdown process becomes more complex and time-consuming
Solution Approach 1:
The patent applies dynamics by making the shutdown process adaptive and conditional rather than fixed. The control unit dynamically adjusts the shutdown sequence based on detected conditions (parking duration, ambient temperature, stack temperature) - executing water removal operations only when necessary (below freezing temperatures or extended parking), and using different removal strategies (air supply adjustment, humidifier control) based on real-time temperature measurements.
Solution Approach 2:
The patent maintains continuity of useful action by integrating water removal into the existing shutdown sequence rather than adding separate discrete operations. The air supply system continues its useful action of supplying air to the cathode for electrochemical reactions, while simultaneously this same air flow removes water from the stack. The humidifier continues its useful action of humidifying air, while its operation is adjusted to prevent excessive water generation. This eliminates the need for separate water removal equipment or operations.
3Reliability
If rapid thawing is performed by heating coolant during cold start, then cold startability is improved, but the system requires additional heating devices and increased energy consumption
Solution Approach 1:
The patent converts the harmful effect of water accumulation during shutdown into a beneficial precondition for cold start. By removing water before shutdown at low temperatures, the system prevents water freezing that would otherwise block reactant gas flow during cold start. This eliminates the need for active heating devices during cold start, as the preventive water removal creates favorable conditions for immediate startup without requiring additional heating equipment or energy consumption.
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 complete water removal from the fuel cell stack, improving cold startability by preventing water freezing and ensuring stable system operation during subsequent start-ups without the need for additional heating devices.
Implementation Method 1
a fuel cell stack for generating electricity by an electrochemical reaction of reactant gases
Implementation Method 2
a thermal management system (TMS) for removing reaction heat from the fuel cell stack to the outside of the fuel cell system, controlling operation temperature
Implementation Method 3
the dry air supplied by the air blower 122 passes through the humidifier 123 to be humidified by absorbing water from the exhaust gas discharged from a cathode
Implementation Method 4
passing heated air through the stack to remove water
Implementation Method 5
removing water from the fuel cell stack
Data Source
AI summary
A method for shutting down a fuel cell system includes: determining whether an outside air temperature is below a first predetermined reference temperature when a shutdown of a fuel cell system is detected; warming up the fuel cell stack by operating balance of plant components of the fuel cell system and a stack load using the power of the fuel cell stack, while the supply of hydrogen to the fuel cell stack is normally maintained, when the outside air temperature is below the first reference temperature; removing water in the fuel cell stack by passing air supplied by an air supply system through the stack load to supply heated air to a cathode of the fuel cell stack; and shutting down the fuel cell system by cutting off the supply of air after the removal of water. The method can eliminate or reduce cold start failure.