Fuel cell channeled distribution of hydration water

Details Fuel cell channeled distribution of hydration water Fuel cell channeled distribution of hydration water

1999-08-27

2001-10-16

Brouillette, Gabrielle (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S006000, C429S006000, C429S006000

Reexamination Certificate

active

06303245

ABSTRACT:

This invention relates generally to fuel cells and more specifically to humidifying the ion exchange membrane in such cells.
BACKGROUND OF THE INVENTION
A fuel cell is a device which converts chemical energy of a fuel into electrical energy, typically by oxidizing the fuel. In general a fuel cell includes an anode and a cathode fluid flow plate separated by an electrolyte. When fuel is supplied to the anode and oxidant is supplied to the cathode, the electrolyte electrochemically generates a useable electric current which is passed through an external load. The fuel typically supplied is hydrogen and the oxidant typically supplied is oxygen. In such cells, the electrolyte combines the oxygen and hydrogen to form water and to release electrons. The chemical reaction of a fuel cell using hydrogen as the fuel and oxygen as the oxidant is shown in equation (1).
H
2
+½O
2
→H
2
O  (1)
This process occurs through two redox or separate half-reactions which occur at the electrodes:
Anode Reaction
H
2
→2H
+
+2e
−
  (2)
Cathode Reaction
½O
2
+2H
+
+2e
−
→H
2
O  (3)
In the anode half-reaction, hydrogen is consumed at the fuel cell anode releasing protons and electrons as shown in equation (2). The protons are injected into the fuel cell electrolyte and migrate to the cathode. The electrons travel from the fuel cell anode to cathode through an external electrical load. In the cathode half-reaction, oxygen, electrons from the load, and protons from the electrolyte combine to form water as shown in equation (3). The directional flow of protons, such as from anode to cathode, serves as a basis for labeling an “anode” side and a “cathode” side of the fuel cell.
The anode and cathode fluid flow plates are made of an electrically conductive material, typically metal or compressed carbon, in various sizes and shapes. Fluid flow plates act as current collectors, provide paths for access of the fuels and oxidants to the cell, and provide a path for removal of waste products formed during operation of the cell. Each fuel cell includes a catalyst, such as platinum, for promoting the chemical reaction(s) that take place on the electrodes in the fuel cells. Additionally, the fluid flow plates include a fluid flow field of channels for directing fluids within the cell.
Fluid flow plates are commonly produced by any of a variety of processes. For example, one technique for plate construction, referred to as “monolithic” style, includes compressing carbon powder into a coherent mass which is subjected to high temperature processes to bind the carbon particles together, and to convert a portion of the mass into graphite for improved electrical conductivity. The mass is then cut into slices, which are formed into the fluid flow plates. Typically, each fluid flow plate is subjected to a sealing process (e.g., resin impregnation) in order to decrease gas permeation therethrough and reduce the risk of uncontrolled reactions.
Fuel cells are classified into several types according to the electrolyte used to accommodate ion transfer during operation. Examples of electrolytes include aqueous potassium hydroxide, concentrated phosphoric acid, fused alkali carbonate, stabilized zirconium oxide, and solid polymers, e.g., a solid polymer ion exchange membrane.
An example of a solid polymer ion exchange membrane is a Proton Exchange Membrane (hereinafter “PEM”) which is used in fuel cells to convert the chemical energy of hydrogen and oxygen directly into electrical energy. A PEM is a solid polymer electrolyte which when used in a PEM-type fuel cell permits the passage of protons (i.e.,H
+
ions) from the anode side of a fuel cell to the cathode side of the fuel cell while preventing passage of reactant fluids such as hydrogen and oxygen gases.
Typically, a PEM-type fuel cell includes an electrode assembly disposed between two fluid flow plates. The electrode assembly usually includes five components: two gas diffusion layers; two catalysts; and an electrolyte. The electrolyte is located in the middle of the five-component electrode assembly. On one side of the electrolyte (the anode side), a gas diffusion layer (the anode gas diffusion layer) is disposed adjacent the anode layer, and a catalyst (the anode catalyst) is disposed between the anode gas diffusion layer and the electrolyte. On the other side of the electrolyte (the cathode side), a gas diffusion layer (the cathode gas diffusion layer) is disposed adjacent the cathode layer, and a catalyst (the cathode catalyst) is disposed between the cathode gas diffusion layer and the electrolyte.
Several PEM-type fuel cells usually are arranged as a multi-cell assembly or “stack.” In a multi-cell stack, multiple single PEM-type cells are connected together in series. The number and arrangement of single cells within a multi-cell assembly are adjusted to increase the overall power output of the fuel cell. Typically, the cells are connected in series with one side of an fluid flow plate acting as the anode for one cell and the other side of the fluid flow plate acting as the cathode for an adjacent cell.
Fluid flow plates also have holes therethrough for alignment and for formation of fluid manifolds that service fluids for the stack. Some of the fluid manifolds distribute fuel (such as hydrogen) and oxidant (such as air or oxygen) to, and remove unused fuel and oxidant as well as product water from, the fluid flow fields of the plates. Additionally, other fluid manifolds circulate coolant. Furthermore, other cooling mechanisms such as cooling plates are commonly installed within the stack between adjacent single cells to remove heat generated during fuel cell operation.
Typically, the PEM works more effectively if it is wet. Conversely, once any area of the PEM dries out, the electrochemical reaction in that area stops. Eventually, the dryness can progressively march across the PEM until the fuel cell fails completely. As a result, the fuel and oxidant fed to each fuel cell are usually humidified, e.g., with steam.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention is a fluid flow element for a fuel cell. The fluid flow element includes a plate made at least in part of a conductive material. The plate has a front surface in which there is formed a first plurality of open-faced channels and a second plurality of open-faced channels. The second plurality of channels is interleaved among the first plurality of channels. Each of the channels of said first plurality of channels has an inlet end and an outlet end and each of the channels of the second plurality of channels has an inlet end. The plate further includes a first supply opening, a first exhaust opening, and a second supply opening which is separate from the first supply opening. The inlet ends of the first plurality of channels are connected to the first supply opening and the inlet ends of the second plurality of channels are connected to the second supply opening.
In another aspect, a fuel cell plate has reactant channels, lands, and hydration channels formed in at least a portion of the lands.
In another aspect, a solid polymer fuel cell includes a solid polymer electrolyte, an anode fluid flow plate, and a cathode fluid flow plate. At least one of the plates has a front surface in which there is formed a first plurality of open-faced channels and a second plurality of open-faced channels interleaved among the first plurality of channels. Each of the channels of the first plurality of channels has an inlet end and an outlet end and each of the channels of the second plurality of channels have an inlet end. Each plate further includes a first supply opening, a first exhaust opening, and a second supply opening which is separate from the first supply opening. The inlet ends of the first plurality of channels are connected to the first supply opening and the inlet ends of the second plurality of channels are connected to the second supply opening.
In other embodiments, the second supply opening re

Affiliated with

Also associated with

Rating

Fuel cell channeled distribution of hydration water does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Fuel cell channeled distribution of hydration water, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel cell channeled distribution of hydration water will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2600943