Fuel Cell Shutdown Control for Low-Temperature Purging
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Solution Overview
Problem
In fuel cell systems, low temperature conditions restrict the allowable charging power of electric power storage devices, leading to prolonged charging times and increased risk of moisture freezing within the fuel cell, especially during system shutdown.
Innovation Solution
The fuel cell system incorporates a control unit that executes a purging process to discharge excess moisture and adjusts the charging process by setting a smaller target remaining capacity for the electric power storage device when low temperature conditions are met, thereby shortening the charging time and preventing moisture freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system charges the electric power storage device to a larger amount of charge at low temperature, then the purging and restart reliability is improved, but the stopping time is prolonged
Solution Approach 1:
The control unit dynamically adjusts the target remaining capacity based on temperature conditions. At low temperature, it sets the target remaining capacity to a first value that ensures purging reliability, while at normal temperature, it sets it to a second value that allows faster stopping. This dynamic adjustment resolves the contradiction by adapting the charging target to environmental conditions.
Solution Approach 2:
The system changes the parameter of target remaining capacity based on temperature. When temperature is below the threshold, the target remaining capacity is set to a higher first value to ensure moisture discharge and purging reliability. When temperature is above the threshold, it is set to a lower second value to reduce stopping time. This parameter change strategy resolves the contradiction between reliability and time.
2Reliability
If the system executes purging process at low temperature, then moisture discharge is improved, but the charging time is prolonged
Solution Approach 1:
The control unit executes the purging process before the charging process when low temperature is detected. By performing moisture discharge first through purging, the system ensures that the fuel cell is properly prepared for subsequent charging, preventing moisture accumulation that would otherwise extend charging time. This preliminary action resolves the contradiction between moisture discharge effectiveness and charging time.
Solution Approach 2:
The control unit dynamically adjusts the sequence of operations based on temperature conditions. At low temperature, it prioritizes purging before charging to ensure moisture discharge. At normal temperature, it can proceed with charging directly. This dynamic sequencing resolves the contradiction by adapting the process order to environmental conditions.
3Loss of time
If the system sets target remaining capacity to a smaller value at low temperature, then the stopping time is shortened, but the purging reliability is reduced
Solution Approach 1:
The control unit performs the purging process as a preliminary action before charging when low temperature is detected. This ensures that moisture is discharged from the fuel cell before the charging process begins, maintaining purging reliability even when the target remaining capacity is set to a smaller value to shorten stopping time.
Solution Approach 2:
The system changes the target remaining capacity parameter based on temperature and process stage. At low temperature, it initially sets a higher target to ensure purging reliability, then adjusts to a smaller value after purging is complete to reduce stopping time. This staged parameter change resolves the contradiction between purging reliability and stopping time.
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 effectively reduces the time required for system shutdown and prevents moisture freezing in the fuel cell, even when environmental temperatures decrease after shutdown, by optimizing the purging and charging processes based on temperature conditions.
Implementation Method 1
a fuel cell 100, an air supply unit 140 configured to supply air to the fuel cell 100, an electric power storage device 172 capable of storing at least electric power generated by the fuel cell 100
Implementation Method 2
the control unit executes the purging process so as to discharge more of moisture stored in the fuel cell to an outside of the fuel cell
Implementation Method 3
an electric power storage device 172 capable of storing at least electric power generated by the fuel cell 100
Data Source
AI summary
A fuel cell system includes a fuel cell, a gas supply unit, an electric power storage device, a remaining capacity monitor, and a control unit. The control unit determines whether the temperature conditions are met, wherein the low temperature conditions include temperature related to a state of the fuel cell being equal to or lower than a predetermined threshold value set, when the control unit determines that the low temperature conditions are met, the control unit executes the purging process so as to discharge more of moisture stored in the fuel cell to an outside of the fuel cell, as compared with when the control unit determines that the low temperature conditions are not met, and the control unit executes the charging process with target remaining capacity of the electric power storage device set to a smaller value, as compared with when the control unit determines that the low temperature conditions are not met.