Patent Application
20140212781
The technical field relates to a stacked type fuel cell.
With the rapid development of industry, the consumption of conventional energy source, such as coal, petroleum, and natural gas, is increasingly high, and the limited natural energy sources necessitate the development of novel alternative energy sources in replacement of the conventional energy sources. A fuel cell, one of the alternative energy sources, is taken as an important and practical choice.
In brief, the fuel cell is basically a power generator that converts chemical energy into electrical energy through a reverse reaction of water electrolysis. For instance, a proton exchange membrane fuel cell is mainly composed of a membrane electrode assembly (MEA) and two electrode plates. The MEA often includes a proton exchange membrane, an anode catalyst layer, a cathode catalyst layer, an anode gas diffusion layer (GDL), and a cathode GDL. The anode catalyst layer and the cathode catalyst layer are respectively located at two sides of the proton conducting membrane, and the anode GDL and the cathode GDL are respectively located on the anode catalyst layer and the cathode catalyst layer. Besides, the two electrode plates include an anode and a cathode that are respectively located on the anode GDL and the cathode GDL.
Currently, the common proton exchange membrane fuel cell is the direct methanol fuel cell (DMFC) that uses the methanol aqueous solution as the fuel supply source and generates currents through the relevant electrode reaction between methanol and oxygen. The reaction formulas of the DMFC are shown below:
Anode: CH3OH+H2O→CO2+6H++6e−
Cathode: 3/2O2+6H++6e−→3H2O
During reaction, the concentration of methanol and water in the anode must be kept to a proper level. In theory, the concentration ratio of methanol to water is 1 mole: 1 mole. However, the MEA is unable to prevent such a high concentration methanol aqueous solution from crossing over to the cathode; therefore, in the conventional fuel cell system, the cathode water is collected from the cathode with a condenser, and the collected cathode water is delivered back to the fuel mixing tank at the anode. With a fuel concentration detector, a fuel cycle pump, a high concentration methanol replenishment pump, and other devices, the concentration of the methanol aqueous solution in the anode is controlled to fall within a range from 2% to 6%. Such fuel cell system is referred to as an active fuel cell system.
In recent years, a passive fuel cell system has been developed. Specifically, the moisture at the cathode is adjusted to differentiate the concentration gradient of water at the anode from the concentration gradient of water at the cathode, and thus the cathode water penetrates the MEAs and is delivered back to the anode for further recycling. Such a technique has been proven feasible. In said passive fuel cell system, neither a condenser nor other water recycling devices are required to be set at the cathode, and complicated devices (e.g., a fuel mixing tank) are not required to be set at the anode. What is required is a micro pump for timely supplying the proper amount of high concentration methanol to the anode. Although the structure of said passive fuel system is rather simple, such a fuel cell system can operate in a stable manner. Unfortunately, the required concentration of fuel supplied to the anode of the passive fuel cell is rather high, i.e., at least 50%, and the fuel supplied to the anode is not recycled and thus cannot be re-used. Hence, the flow rate of the fuel supply is low, approximately 0.5 μL/min per square centimeter of reaction area, and thus it is difficult to evenly distribute such a small amount of fuel onto the entire reaction area, especially in the multi-module system with high power output. Besides, in the passive fuel cell system, material layers with different characteristics are utilized for evenly distributing the fuel at the anode end and facilitating the water recycling at the cathode end. These material layers in the passive fuel cell system complicate the process of assembling the electricity generating modules, and the incapability of effectively utilizing space in the passive fuel cell system may also be attributed to the material layers. Thereby, the passive fuel cell system is difficult to be applied in case of the high power output.
A conventional fuel cell often has the bipolar plates stacked together, i.e., flow field plates not only provide the fuel channels at the anode and the cathode but also serve as collectors after plural membrane electrode assemblies (MEAs) are serially connected. Said design of stacked bipolar plates allows the MEAs to be assembled compactly. Nevertheless, in the passive fuel cell system, the non-conductive material layers prevent the MEAs from being directly connected in series along a direction that the MEAs are stacked. Additionally, at the anode end, the liquid fuel with an extremely small flow rate cannot be well spread onto the fuel channels along said direction. As a result, the conventional design of stacked bipolar plates cannot be adopted in the passive fuel cell system.
In a passive DMFC, plural MEAs are arranged in array, as disclosed in patent applications Nos. WO2008105272 and TW201228085, wherein the design of the fuel channel allows the fuel at the anode end to be evenly distributed onto a reaction plane. Such design is applicable to the fuel cell with one single reaction plane. However, in a fuel cell system with high power output requirements, more space for accommodating plural fuel cells with one single reaction plane is required; what is more, the issue as how to evenly deliver the fuel with the low flow rate into the fuel channels remains unresolved.
One of exemplary embodiments provides a stacked type fuel cell having a common anode flow field plate.
In an exemplary embodiment, a stacked type fuel cell that includes at least two electricity generating modules, at least two cathode flow field plates, and at least one common anode flow field plate is provided. Each of the electricity generating modules includes an anode collector, a cathode collector, a membrane electrode assembly (MEA) between the anode collector and the cathode collector, a fuel diffusion layer, and a cathode moisture layer. The fuel diffusion layer and the cathode moisture layer are respectively located at two sides of the MEA. The anode collector is located between the fuel diffusion layer and the MEA, and the cathode collector is located between the cathode moisture layer and the MEA. The common anode flow field plate is located between two fuel diffusion layers in two adjacent electricity generating modules. The common anode flow field plate and two electricity generating modules located at two sides of the common anode flow field plate are sandwiched between the cathode flow field plates.
Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details.
The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure.
In the present exemplary embodiment, the common anode flow field plate 130 allows the space utilization rate of the stacked type fuel cell 100 to be increased. Besides, each common anode flow field plate 130 may supply fuel simultaneously to the electricity generating modules 110 located at two sides of the common anode flow field plate 130, and thus the fuel supplied to the electricity generating modules 110 is not distributed in an uneven manner.
In addition to the electricity generating modules 110, the cathode flow field plates 120, and the common anode flow field plate 130, the stacked type fuel cell 100 described in the present exemplary embodiment may further include a fuel supply unit 140 that includes a fuel storage tank 142, a pump 144, and a main channel 146. The fuel storage tank 142 is adapted to store a fuel, and the main channel 146 is connected between two common anode flow field plates 130. The fuel stored in the fuel storage tank 142 is supplied to the two common anode flow field plates 130 through the pump 144 and the main channel 146. Note that the main channel 146 is filled with a filler 148, and a capillary force provided by the filler 148 may lessen the impact of gravity on fuel with the low flow rate, such that the fuel in the main channel 146 may be evenly supplied to the two common anode flow field plates 130. According to the present exemplary embodiment, the filler 148 is, for instance, a capillary material (e.g., a woven fiber, a non-woven fiber, paper, foam, foamed PE, foamed PU, etc.) or any other “fuel-philic” material. For instance, the contact angle between the filler 148 and the fuel (e.g., methanol) is less than 90 degrees, i.e., the filler 148 has “fuel-philic” properties.
Since the main channel 146 is filled with the filler 148, the fuel flowing into the main channel 146 can be easily introduced into the common anode flow field plate 130 through the filler 148.
As shown in
The stacked type fuel cell 100 described in the present exemplary embodiment is a passive fuel cell; hence, fuel introduced to the stacked type fuel cell 100 is required to have high concentration, and the flow rate of fuel in the common anode flow field plate 130 is rather low. In the present exemplary embodiment, the concentration of the fuel is greater than 50%, for instance; in other feasible exemplary embodiments, the concentration of the fuel introduced into the stacked type fuel cell 100 is greater than 70%. Besides, the flow rate of fuel in the common anode flow field plate 130 is proportional to the reaction area of the MEAs 111. For instance, the fuel supplied to each of the MEAs 111 has a flow rate per square centimeter of reaction area, and the flow rate is between 3 μL/min and 0.1 μL/min; in other feasible exemplary embodiments, said flow rate is between 2 μL/min to 0.1 μL/min, for instance.
In most cases, if the total area of the MEAs 111 increases, it is rather difficult for the common anode flow field plate 130 to evenly distribute the fuel. An area of the common anode flow field plate 130 is frequently smaller than 250 cm2, preferably smaller than 100 cm2. According to the present exemplary embodiment, one common anode flow field plate 130 is able to evenly distribute the fuel to two neighboring MEAs 111, and therefore the flow rate of the fuel in the common anode flow field plate 130 is smaller than 1500 μL/min, preferably smaller than 600 μL/min.
As shown in
The stacked type fuel cell 100 described herein may further include a heat sink 160 that is located on outer surfaces of the cathode flow field plates 120, so as to dissipate the heat of the stacked type fuel cell 100.
Several designs of different common anode flow field plates 130 are described hereinafter with reference to
The capillary force provided by the filler 136 may lessen the impact of gravity on fuel with the low flow rate. According to the present exemplary embodiment, the filler 136 is, for instance, a capillary material (e.g., a woven fiber, a non-woven fiber, paper, foam, foamed PE, foamed PU, etc.) or any other appropriate material. For instance, the contact angle between the filler 136 and the fuel (e.g., methanol) is less than 90 degrees, i.e., the filler 136 has “fuel-philic” properties. Besides, since the patterned channel CH is filled with the filler 136, the fuel flowing into the common anode flow field plate 130 can be easily introduced into the electricity generating modules 110 through the filler 136.
In the present exemplary embodiment, the filler 136 filling the patterned channel CH may be the same as the filler 148 filling the main channel 146. Certainly, people having ordinary skill in the pertinent art may, according to the actual design requirements, differentiate the filler 136 from the filler 148.
Note that the location of the filler 136 may be modified according to actual design requirements of the stacked type fuel cell 100. For instance, people having ordinary skill in the pertinent art may fill the entire patterned channel CH with the filler 136; thus, parts of the patterned channel CH corresponding to the first and second fuel outlets 132a and 134b are filled with the filler 136 as well, and the filler 136 are exposed by the first and second fuel outlets 132a and 134b. In another embodiment, people having ordinary skill in the pertinent art may fill only parts of the patterned channel CH filled with the filler 136, specifically, the other parts of the patterned channel CH corresponding to the first and second fuel outlets 132a and 134b are not filled with the filler 136.
As shown in
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of the disclosure provided they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 99144306 | Dec 2010 | TW | national |
| 102148015 | Dec 2013 | TW | national |
This application is a continuation-in-part application of and claims the priority benefit of a prior application Ser. No. 13/030,149, filed on Feb. 18, 2011, now pending. The prior application Ser. No. 13/030,149 claims the priority benefit of Taiwan application serial no. 99144306, filed on Dec. 16, 2010. This continuation-in-part also claims the priority benefit of Taiwan application serial no. 102148015, filed on Dec. 24, 2013. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13030149 | Feb 2011 | US |
| Child | 14243897 | US |
