Bipolar Plate Branched Channels for Fuel Cell Membrane Hydration
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Solution Overview
Problem
Fuel cell systems require significant pre-humidification of reactants, particularly on the cathode side, leading to increased costs and reduced power density due to the large area of fresh cathode gas entering the inlet side, which can cause drying out of the membrane and necessitate large humidifiers.
Innovation Solution
The bipolar plate design features flow fields with inlet-side webs having a larger contact surface than outlet-side webs, creating a 'moisture storage' area and reducing the number of flow channels on the inlet side, allowing for more efficient reactant distribution and reduced need for pre-humidification, with channel divisions that double or triple flow channels downstream, ensuring reliable water discharge and humidification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the number of flow channels on the inlet side is increased to improve reactant distribution, then the reactant flow uniformity is improved, but the contact surface area of webs is reduced leading to membrane drying
Solution Approach 1:
The flow channels on the inlet side are segmented into multiple smaller sub-channels by dividing webs. This segmentation increases the contact surface area between the reactant stream and the membrane, improving humidification and preventing membrane drying while maintaining uniform reactant distribution across the active area.
Solution Approach 2:
The inlet-side webs are designed with larger contact surfaces compared to outlet-side webs, creating local quality differences. This allows the inlet region to provide enhanced humidification where needed most, while the outlet region maintains efficient water discharge with smaller web contact surfaces.
2Object-affected harmful factors
If pre-humidification is increased to prevent membrane drying, then membrane hydration is improved, but system cost and volume increase due to larger humidifiers
Solution Approach 1:
The bipolar plate flow field structure itself performs the humidification function through its web design. The inlet-side webs with larger contact surfaces create a self-humidifying effect as the reactant stream passes over them, eliminating the need for separate external humidification systems and reducing overall system complexity.
Solution Approach 2:
The flow channel design incorporates preliminary humidification action at the inlet side before the reactant reaches the membrane. The larger web contact surfaces at the inlet prepare the reactant stream with sufficient humidity in advance, preventing membrane drying without requiring post-processing humidification equipment.
3Object-affected harmful factors
If the web contact surface area is increased to improve humidification, then membrane hydration is improved, but the flow channel cross-section is reduced affecting reactant flow
Solution Approach 1:
By dividing the flow channels into multiple sub-channels with dividing webs, the patent increases the total web contact surface area while maintaining adequate flow capacity. The segmentation allows the reactant to be distributed across multiple smaller pathways, each with sufficient flow characteristics while collectively providing enhanced humidification surface area.
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 design reduces the need for pre-humidification, simplifies the distribution area, and maintains membrane hydration, thereby reducing costs and enhancing fuel cell system efficiency by minimizing drying out and optimizing reactant flow.
Implementation Method 1
The flow fields each comprise, in an active region, a plurality of flow channels delimited by webs for one of the two reactants participating in the fuel cell reaction
Implementation Method 2
the fuel, in particular hydrogen H2 or a hydrogen-containing gas mixture, is fed to the anode where an electrochemical oxidation of H2 to H+
Implementation Method 3
Fuel cell devices are used for the chemical conversion of a fuel with oxygen to water in order to generate electrical energy
Implementation Method 4
a cooling medium is also passed through the bipolar plates due to the heat generated during the fuel cell reaction
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a flow field plate (2) for a fuel cell, the first plate side of which is formed with a first reactant flow field (3) and the second plate side of which, opposite the first plate side, is formed with a second reactant flow field (3), wherein: the flow fields (3) in an active region (10) each comprise a plurality of flow channels (9), delimited by webs (7), for one of the two reactants involved in the fuel cell reaction; in each case the active region (10) is connected flow-mechanically on the inlet side via a distribution region (11) running outside the active region (10) to an inlet-side media port (4, 5) extending from the first plate side to the second plate side for one of the two reactants; and in each case the active region (10) is connected flow-mechanically on the outlet side via a collection region (16) running outside the active region (10) to an outlet-side media port (4, 5) extending from the first plate side to the second plate side. At least one of the flow fields (3, 54) is formed in its active region (10) on the inlet side with webs (7) which have a contact surface (12) for an adjacent layer of the fuel cell that is larger than a contact surface (13) of the outlet-side webs (7), resulting from a channel division (14) present in the active region (10) of at least some of the flow channels (9). The invention also relates to a fuel cell stack (1).