Fuel Cell Stack Transient Control for Durability
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Solution Overview
Problem
Fuel cell stacks experience damage and reduced longevity due to rapid pressure differentials and low relative humidity during downward transients in power demand, caused by sudden changes in current flow and temperature responses.
Innovation Solution
A method to temper the power output reduction by routing excess power to parasitic components, gradually reducing the power output while maintaining a controlled pressure differential and relative humidity within predetermined ranges, thereby smoothing the transition during power demand changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the quantity of anode reactant is rapidly reduced to meet decreased power demand, then the power output matches the power demand quickly, but the pressure differential between anode and cathode spikes causing damage to fuel cell stack
Solution Approach 1:
The control system applies preliminary anti-action by detecting the downward transient in power demand and preemptively adjusting the anode reactant flow reduction rate before the pressure differential can spike. The controller limits the rate of change of anode reactant quantity to prevent harmful pressure differentials from developing, thus counteracting the potential damage before it occurs.
Solution Approach 2:
The system dynamically adjusts the anode reactant flow based on real-time operating conditions. During downward transients, the control method dynamically limits the reduction rate of anode reactant quantity to maintain pressure differential within safe bounds, while allowing faster response during steady-state or upward transient conditions.
2Temperature
If the coolant flow is rapidly reduced to match decreased power demand, then the temperature regulation responds quickly, but the relative humidity drops causing membranes to become dry and damaged
Solution Approach 1:
The control system performs preliminary action by anticipating the humidity drop that would result from rapid coolant flow reduction. It preemptively limits the reduction rate of coolant flow during downward transients to maintain relative humidity above the minimum threshold, preventing membrane drying before it can occur.
Solution Approach 2:
The control method uses feedback from temperature and flow rate sensors to continuously monitor the state of the fuel cell stack. Based on this feedback, the controller adjusts the coolant flow reduction rate in real-time to maintain both temperature regulation effectiveness and adequate humidity levels during power demand transitions.
Data Source
AI summary
The present invention is a method of operating a fuel cell stack and system that minimizes the potential for having a large pressure differential between the anode and cathode flow fields and a low relative humidity occurrence within the cathode flow fields. This is accomplished by tempering the downward transient in power demand seen by the fuel cell stack. The downward transient in power demand on the fuel cell stack is tempered by reducing the rate at which the power generated by the fuel cell stack is decreased and providing the excess power generated by the fuel cell stack to other parasitic components of the fuel cell system.