Fuel Cell Idle Stop Control via Intermittent Cathode Gas
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Solution Overview
Problem
Conventional fuel cell systems fail to precisely control the wet/dry state of electrolyte membranes during idle stop operations, leading to instability in fuel cell output and potential hydrogen deficiency upon returning to normal power generation.
Innovation Solution
A control method for fuel cell systems that intermittently supplies cathode gas, sets upper and lower voltage limits, detects the wet/dry state, and adjusts the voltage limits to maintain an appropriate range, ensuring the fuel cell membranes remain within a suitable wet/dry state during idle stop and upon return to normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cathode gas is intermittently supplied to the fuel cell stack during idle stop operation, then power generation efficiency is improved and membrane deterioration is prevented, but the wet/dry state of the electrolyte membranes cannot be precisely controlled
Solution Approach 1:
The system continuously monitors the wet/dry state of the electrolyte membranes using sensors and adjusts the intermittent cathode gas supply timing and duration based on this feedback. The control unit modifies the gas supply pattern to maintain the membranes within an appropriate wet/dry range, thereby achieving precise control while preserving power generation efficiency improvements.
Solution Approach 2:
The cathode gas supply timing and duration are made dynamic rather than fixed. The system adjusts the supply pattern in real-time based on the detected wet/dry state of the electrolyte membranes, allowing the control parameters to adapt to changing conditions and achieve precise control of the membrane state.
2Productivity
If the fuel cell system returns from idle stop state to normal power generation state, then power supply is restored, but hydrogen deficiency may occur causing output instability
Solution Approach 1:
Before transitioning from idle stop to normal power generation mode, the system performs preliminary actions including adjusting the cathode gas supply pattern and pre-conditioning the electrolyte membranes to an appropriate wet/dry state. This preliminary preparation prevents hydrogen deficiency during the transition, ensuring stable output when full power supply is restored.
Solution Approach 2:
The system takes preliminary counter-actions to prevent hydrogen deficiency before it occurs. By adjusting the cathode gas supply timing and maintaining appropriate membrane wetness before the transition to normal operation, the system preemptively counteracts the conditions that would lead to hydrogen deficiency and output instability.
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 stabilizes the fuel cell output, prevents membrane deterioration, and reduces the risk of hydrogen deficiency, enhancing the fuel cell system's efficiency and reliability during idle stop and restart conditions.
Implementation Method 1
anode gas (fuel gas) and cathode gas (oxidant gas) are supplied to fuel cells (fuel cell stack) to generate power by an electrochemical reaction
Implementation Method 2
air (cathode gas) is intermittently supplied during an idle stop operation (idle stop state), thereby causing an output voltage or cell voltage of a fuel cell stack to pulsate within a predetermined range
Implementation Method 3
residual anode gas leaking from anode gas flow passages in the fuel cell stack and cathode gas in cathode gas flow passages react by the intermittent supply of the cathode gas during the idle stop operation
Data Source
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AI summary
A control method for fuel cell system capable of executing an idle stop operation is provided, in which operation power generation of a fuel cell is selectively stopped according to a required output of a load and cathode gas is intermittently supplied to the fuel cell during an operation stop. An upper limit value and a lower limit value of an output voltage of the fuel cell during the idle stop operation is set, the cathode gas is intermittently supplied with the output voltage of the fuel cell set at a value between the upper limit value and the lower limit value, a wet/dry state of the fuel cell is detected, a wet/dry appropriate range in which the wet/dry state of the fuel cell during the idle stop operation is appropriate is set, and it is determined whether or not the detected wet/dry state of the fuel cell is within the set wet/dry appropriate range. If the wet/dry state of the fuel cell is determined to be outside the set wet/dry appropriate range, the output voltage of the fuel cell is reset, and the cathode gas is intermittently supplied with the output voltage of the fuel cell set at a value between the upper limit value and lower limit value of the reset output voltage.