PEFC Separator Recess Overlap Reduction
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Solution Overview
Problem
Conventional polymer electrolyte fuel cells experience increased electrical contact resistance and membrane degradation when using reaction gases with low humidity, particularly at the turn portions with recesses and projections, leading to concentrated power generation and potential heat-related issues.
Innovation Solution
The design includes a polymer electrolyte fuel cell with reduced electrical contact resistance between separators and electrodes by optimizing the configuration of recesses and projections, where the overlap area between recesses in adjacent separators is minimized to less than 5% of the total area, and a fuel cell system that controls the dew point of reaction gases to be lower than the cooling medium temperature, facilitating better gas distribution and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If projections are arranged on the extension of channel grooves to mix power generation gas, then gas mixing is improved, but electrical contact resistance increases and membrane degradation occurs at turn portions
Solution Approach 1:
The patent applies local quality by making the recess depth non-uniform across different turn portions. Specifically, recesses at turn portions adjacent to the same gas diffusion layer have different depths, creating localized variations in contact area. This ensures that while gas mixing is maintained through the presence of recesses, the electrical contact resistance is managed by preventing excessive concentration of contact area at any single location, thereby protecting the membrane from degradation.
2Productivity
If reaction gases with low humidity are used to improve efficiency, then power generation efficiency increases, but electrical contact resistance increases and concentrated power generation occurs
Solution Approach 1:
The patent applies dynamics by making the recess depth variable rather than uniform. The recess depth is designed to differ depending on the specific turn portion and its adjacency relationship with gas diffusion layers. This dynamic variation in recess depth allows the separator structure to adapt to different operating conditions, including low humidity scenarios, by distributing contact areas appropriately to maintain stable electrical contact resistance while preserving power generation efficiency.
3Ease of operation
If recesses are provided at all turn portions to enhance gas distribution, then gas distribution is improved, but overlap of recesses between adjacent separators causes excessive contact concentration
Solution Approach 1:
The patent applies asymmetry by designing turn portions with asymmetric characteristics relative to adjacent separators. When a turn portion of a first separator is adjacent to a gas diffusion layer, the corresponding turn portion of the adjacent second separator is designed with different recess depth or configuration. This asymmetric design prevents symmetric overlap of recesses between adjacent separators, thereby avoiding excessive concentration of contact areas and the resulting heat generation problems, while still maintaining improved gas distribution.
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 configuration reduces electrical contact resistance and alleviates membrane degradation, ensuring stable power generation even under low-humidity conditions by minimizing the area of non-contact regions and ensuring consistent gas supply, thereby enhancing fuel cell performance and longevity.
Implementation Method 1
a polymer electrolyte membrane and a pair of gas diffusion electrodes (an anode and a cathode)
Implementation Method 2
configured to cause an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air, thereby generating electric power and heat at the same time
Data Source
Figure 1
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AI summary
A polymer electrolyte fuel cell according to the present invention includes: an electrolyte layer-electrode assembly (5); a first separator (6A) provided with a first reaction gas flowing region; and a second separator (6B) provided with a second reaction gas flowing region. In the first separator (6A), among one or more first turn portions (28), at least one first turn portion (28) is provided with a first recess (48) and first projections (58). In the second separator (6B), among one or more second turn portions (29), at least one second turn portion (29) is provided with a second recess (49) and second projections (59). When seen in the thickness direction of the first separator (6A), an overlap area is less than or equal to 5 % of a gross area, the overlap area being a total overlap area between the first and second recesses (48, 49), the gross area being the total of the following areas: the area of all the first recesses (48); and the area of all the second recesses (49).