Fuel Cell Shutdown Cooling and Air Admission for Carbon Corrosion
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Solution Overview
Problem
Fuel cell systems face carbon corrosion issues during shutdown, leading to reduced useful life due to oxygen-hydrogen fronts, which existing methods attempt to mitigate by maintaining a hydrogen atmosphere but result in high hydrogen consumption and inefficient resource use.
Innovation Solution
A method that extends hydrogen protection time by metering hydrogen as needed and actively terminates the hydrogen protection state by cooling and exposing the cathode chamber to air, reducing carbon corrosion by controlling the hydrogen and oxygen levels within the fuel cell system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hydrogen is continuously metered into the anode chamber to maintain hydrogen atmosphere during shutdown, then carbon corrosion is prevented, but hydrogen consumption becomes excessively high
Solution Approach 1:
The patent implements periodic hydrogen metering instead of continuous supply. Hydrogen is metered into the anode chamber at specific intervals (e.g., every 4-6 hours) during shutdown periods. This periodic action maintains sufficient hydrogen atmosphere to prevent carbon corrosion while dramatically reducing overall hydrogen consumption compared to continuous metering approaches.
Solution Approach 2:
The patent applies preliminary cooling of the fuel cell stack before shutdown to extend the hydrogen protection time. By cooling the stack to lower temperatures (e.g., below 50°C) before initiating shutdown procedures, the residual hydrogen remains effective for longer periods, reducing the frequency and amount of hydrogen metering required during the shutdown period.
2Loss of substance
If air is supplied to the cathode chamber during shutdown to extend hydrogen protection time, then hydrogen consumption is reduced, but carbon corrosion increases due to oxygen-hydrogen fronts
Solution Approach 1:
The patent implements periodic air supply to the cathode chamber during shutdown, alternating between air supply periods and hydrogen-rich periods in the anode chamber. This periodic action allows oxygen to enter the cathode chamber to displace hydrogen and extend protection time, while preventing continuous oxygen-hydrogen front formation that would cause carbon corrosion.
Solution Approach 2:
The patent changes the temperature parameter by cooling the fuel cell stack before and during shutdown. Lower temperatures slow down the chemical reactions and diffusion processes, reducing the rate of carbon corrosion when air is supplied to the cathode chamber, while still allowing the hydrogen protection mechanism to function effectively.
3Loss of substance
If the fuel cell stack is cooled to extend hydrogen protection time, then hydrogen consumption is reduced, but the system requires additional cooling infrastructure and energy
Solution Approach 1:
The patent utilizes the fuel cell stack's existing cooling infrastructure and thermal management system to perform the cooling function, rather than requiring separate dedicated cooling equipment. The same cooling system used during normal operation is leveraged to cool the stack during shutdown, making the system self-sufficient and avoiding additional infrastructure requirements.
Solution Approach 2:
The patent makes the cooling system multi-functional by using it for both normal operational temperature control and for pre-cooling/extending hydrogen protection during shutdown periods. This universal use of the cooling infrastructure eliminates the need for separate cooling systems while achieving the dual benefits of operational control and shutdown protection.
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 significantly reduces carbon corrosion, conserves hydrogen, and extends the fuel cell's useful life by minimizing hydrogen consumption and oxidation processes, achieving a hydrogen protection time of up to 15 hours with minimal hydrogen usage.
Implementation Method 1
various publications propose adding more hydrogen, for example from time to time or based on other criteria, and thus to maintain the hydrogen atmosphere basically during the entire shutdown of the fuel cell
Implementation Method 2
the fuel cell system is actively cooled before the hydrogen protection time is actively terminated
Implementation Method 3
the hydrogen protection time is actively terminated in that the cathode chamber is actively exposed to air
Data Source
AI summary
A method for shutting down a fuel cell system (2) having at least one fuel cell (3), which fuel cell comprises an anode chamber (10) and a cathode chamber (6), wherein after the shut-down hydrogen remains in the anode chamber (10) of the fuel cell (3) in order to prevent carbon corrosion and to ensure a hydrogen protection time. The invention is characterized in that when the hydrogen in the anode chamber (10) is largely used up directly or after a specified number of subsequent meterings of hydrogen at least into the anode chamber (10), the hydrogen protection time is actively terminated by air being actively admitted into the cathode chamber (6), the fuel cell (3) being actively cooled before air is actively admitted into the cathode chamber (6).