Fuel Cell Stack Control Using SoH-Based Module Switching
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Solution Overview
Problem
Fuel cell systems face challenges in controlling single cell voltage at low loads, leading to inefficiency and degradation of catalysts and support materials due to excessive power generation and increased single cell potential, which is not effectively addressed by existing methods.
Innovation Solution
A control system that activates and deactivates fuel cell stacks based on the State of Health (SoH) and power demand, limiting single cell voltage to below 0.8V by sequentially deactivating stacks with lower SoH when power demand decreases and activating those with higher SoH when power demand increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the fuel cell system operates at higher power levels, then the power output is improved, but the single cell potential increases leading to catalyst degradation
Solution Approach 1:
The fuel cell system is divided into multiple independent stacks, each capable of being individually controlled. This segmentation allows the system to distribute power generation across multiple stacks, preventing any single stack from operating at excessively high power levels that would cause catalyst degradation. The control system can selectively activate or deactivate specific stacks based on power demand and individual stack health status.
2Reliability
If the fuel cell system operates at lower power levels, then the single cell potential decreases protecting the catalyst, but the system efficiency decreases due to excess power generation
Solution Approach 1:
The system dynamically adjusts the number of active stacks based on real-time power demand and individual stack performance. When power demand is low, fewer stacks are activated to match the demand, preventing excessive power generation. When demand increases, additional stacks are activated to meet the requirement. This dynamic adjustment optimizes both efficiency and catalyst protection at all operating levels.
Solution Approach 2:
The control system monitors and adjusts operational parameters including the number of active stacks, power distribution among stacks, and response to load changes. By changing these parameters dynamically, the system maintains optimal operating conditions for catalyst health while maximizing efficiency at each power level.
3Power
If multiple stacks are operated simultaneously, then the power output is improved, but the complexity of controlling single cell voltage increases
Solution Approach 1:
Each stack is monitored and controlled individually based on its specific state of health, performance characteristics, and operational status. The control system applies local quality management by treating each stack as a distinct unit with unique requirements, allowing for customized control strategies for each stack while maintaining overall system coordination.
4Reliability
If stacks are deactivated to reduce power generation, then the single cell voltage is maintained below threshold, but the risk of uneven degradation among stacks increases
Solution Approach 1:
The control system implements periodic rotation of active and inactive stack assignments. Stacks that have been deactivated are given periodic opportunities to rest and recover, while other stacks take turns being deactivated. This periodic rotation ensures that all stacks experience similar degradation patterns over time, maintaining uniformity in the degradation process rather than creating significant disparities between stacks.
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 balances degradation risk among stacks, improving durability and performance by maintaining single cell voltage below 0.8V, thereby extending the fuel cell system's lifetime and enhancing efficiency.
Implementation Method 1
generate electric power or energy via electrochemical reaction between fuel, such as hydrogen gas received at the anode or anode side, and oxidant, such as oxygen or air received at the cathode or cathode side
Implementation Method 2
metals such as e.g. palladium and platinum are used as catalysts to promote the electrochemical reaction between the hydrogen gas and the oxidizing gas
Data Source
Figure 1
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Figure 3A
AI summary
A system and method for controlling operation of a fuel cell system for a vehicle are provided. The fuel cell system comprises a fuel cell unit comprising a plurality of fuel cell stacks and an electrical circuit arranged to selectively connect the fuel cells stacks to a load. A control system comprises processing circuitry that is configured to obtain an actual or predicted value of requested power output that is requested from the fuel cell system; monitor a State of Health (SoH) of each of the plurality of fuel cell stacks; when the value of the requested power output is below a first threshold power level and at least two stacks out of the plurality of stacks are currently active, deactivate at least one first stack from the at least two currently active fuel cell stacks in an order of increasing SoH; and, when the value of the requested power output is above a second threshold power level, activate at least one second stack from the plurality of fuel cell stacks in an order of decreasing SoH.