Patent Application
20050053815
1. Field of the Invention
The present invention relates generally to the field of fuel cells, and in particular to a device for regulating temperature and humidity of reaction gas of fuel cells, especially a fuel cell stack.
2. Description of the Prior Art
Fuel cells are an electro-chemical device that makes use of electro-chemical reaction between a fuel, such as hydrogen, and an oxidizer, such as oxygen contained in the surrounding air, to generate electrical power. The fuel cells are advantageous in low contamination, high efficiency and high power density. Thus, developments and researches are intensively devoted to the fuel cell field for exploitation of the utilization thereof. A variety of fuel cells are available, among which proton exchange membrane fuel cell, abbreviated as PEMFC, is the most prospective one due to the advantages of low operation temperature, fast activation and high power density with respect to unit weight and volume.
A typical fuel cell stack is comprised of a number of membrane electrode assemblies (MEA). Each MEA comprises an anode catalyst layer, a high molecular proton exchange membrane and a cathode catalyst layer. A basic cell can be formed by coupling the MEA with a gas diffuser and a bipolar plate in an overlapping and stacked manner.
The operation of the fuel cells is dependent upon the proton exchange membrane that functions to convey hydrogen ions between the cathode and the anode of the fuel cell for the progress of the electro-chemical reaction. The performance of the fuel cells is heavily dependent upon the reaction conditions, such as operation temperature, humidity, hydrogen flow rate, and air flow rate. For example, the proper humidity must be maintained for the high molecular proton exchange membrane in order to provide a fuel cell stack of high performance.
Currently, to maintain proper operation humidity for the fuel cell, a humidifier is added in a supply pipe of reaction gas, which increases the relative humidity of the reaction gas flowing through the supply pipe. Such a humidity-regulated reaction gas is then supplied to the fuel cell. For example, in an air supply conduit through which air containing oxygen is driven by a blower toward the fuel cell, a humidifier is arranged in the supply conduit to add water to and thus increasing relative humidity of the air supplied through the conduit. Thus, the air may reach the fuel cell with proper relative humidity and the performance of the fuel cell can be maintained/enhanced.
On the other hand, a substantial amount of heat is generated in the fuel cell during the operation of the fuel cell. Such heat must be removed properly. Conventionally, liquid coolant, such as water, is employed in a cooling circuit for removal of such heat. In other words, water flows through a cooling conduit inside the fuel cell and removes the heat. For a typical fuel cell, the temperature of the water at a coolant outlet of the fuel cell is around 60-70° C. Recycle of such heat is of great interest for the application of the fuel cell.
It is also known in the industry to regulate the relative humidity of reaction gas by using the cooling water to operate the humidifier. This inevitably consumes a portion of the cooling water and replenishment of the cooling water has to be done periodically.
Techniques that recycle the heat generated during the operation of the fuel cell for improving the performance of the fuel cell are currently known. For example, the heat that is generated during the operation of he fuel cell is commonly employed to heat canisters that store hydrogen and in order to regulate the temperature of hydrogen supplied to the fuel cell. Although the temperature of reaction gas (hydrogen) has been regulated by using by-product (heat) of the fuel cell, none of the known techniques deal with regulation of both temperature and relative humidity of the reaction gas with “by-product” of the fuel cell.
Thus, the present invention is aimed to solve the problems of temperature and humidity regulation of a fuel cell by means of “by-products” of the fuel cell in order to provide an optimum operation of the fuel cell.
Thus, a primary object of the present invention is to provide a fuel cell comprising a device for regulating temperature and humidity of reaction gas for the fuel cell whereby the fuel cell is operated at an optimum condition.
Another object of the present invention is to provide a device for properly regulating temperature and humidity of a reaction gas that is supplied to a fuel cell for maintaining optimum operation of the fuel cell.
A further object of the present invention is to provide a device that employs “by-products” of a fuel cell to regulate temperature and humidity of a reaction gas of the fuel cell whereby thermal energy of coolant of the fuel cell can be recycled and proper humidity of the fuel cell can be realized.
To achieve the above objects, in accordance with the present invention, there is provided a device for regulating temperature and humidity of a reaction gas to be supplied to a fuel cell stack, comprising a temperature regulation section comprised of a first gas guide board through which the reaction gas flows, a coolant guide board through which a coolant from the fuel cell stack flows and a first partition interposed between the first gas guide board and the coolant guide board for exchange of heat between the reaction gas and the coolant and a humidity regulation section coupled to the temperature regulation section with a second partition therebetween and comprised of a second gas guide board through which the temperature-regulated gas flows and a fluid guide board through which a fluid from the fuel cell stack and rich of water contents flows and a humidity exchange film interposed between the second gas guide board and fluid guide board to allow for exchange of water contents between the temperature-regulated gas and the fluid. The device allows for recycle and use of the thermal energy contained in the high temperature coolant discharged from the fuel cell stack and also allows for use of the water rich fluid from the chemical reaction of the fuel cell stack to regulate the temperature and humidity of the reaction gas so that an optimum operation of the fuel cell stack may be obtained without substantial additional expense for the conditioning the reaction gas. In addition, the coolant is guided back to the fuel cell through a closed loop and lose of the coolant can be neglected. No periodical replenishment of the coolant is necessary.
The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:
With reference to the drawings and in particular to
Also referring to
Also referring to
The hydrogen supply comprises a hydrogen source of any suitable form, such as a hydrogen canister that store hydrogen in solid form. Hydrogen from the canister is directly supplied to the fuel cell stack 1 through a hydrogen inlet 13. Excessive hydrogen is discharged from the fuel cell stack 1 through a hydrogen outlet 14.
The fuel cell stack 1 also comprises an outlet 12 through which a fluid, which can be a reaction product, is discharged from the fuel cell stack 1. Such a fluid is rich of water contents and is conducted to the second inlet fitting 23 of the regulating device 2, serving as a humidity source for regulating the humidity of the air flowing through regulating device 2. This constitutes the gas circulation loop.
In the coolant circulation loop, coolant that cools the fuel cell stack 1 flows out of the fuel cells stack 1 through a cell-side coolant outlet 15 of the fuel cell stack 1. The coolant that flows out of the cell-side coolant outlet 15 is at a high temperature around 60-70° C. The high temperature coolant is guided to the device-side coolant inlet 25 and enters the regulating device 2 for regulating the temperature of the air flowing through the regulating device 2. When the coolant flows through the regulating device 2, the coolant, serving as a heat source, exchanges heat with the air and thus the temperature of the coolant is lowered down. The coolant that flows through the regulating device 2 is discharged to a pump 32 through the device-side coolant outlet 26. The pump 32 forces the coolant through a heat dissipation device 33, such a heat radiator, through which heat is further removed from the coolant to bring the temperature of the coolant down to a desired low value. Such a low temperature coolant is then fed back into the fuel cell stack 1 through a cell-side coolant inlet 16 for once again removing heat from the fuel cell stack 1.
Particularly referring to
The temperature regulation section 4 comprises the first end board 41 that is arranged opposite to the central partition board 6 with a first gas guide board 42, a temperature regulation side partition board 43 and a coolant guide board 44 interposed in sequence therebetween. The first gas guide board 42 forms at least one first gas channel 421, which in the embodiment illustrated comprises three U-shaped channels that are spaced by isolation ribs 422 and are of segments substantially parallel to each other. The U-shaped channels 421 have a first end 421a and a second end 421b. The gas guide board 42 also defines two coolant passages 423, 424.
The temperature regulation side partition board 43 forms two coolant passages 432, 433 corresponding to the coolant passages 423, 424 of the gas guide board 42 and a gas passage 431 corresponding to the second end 421b of the gas channels 421. The temperature regulation side partition board 43 is made of a thermally conductive material, such as an aluminum board.
The coolant guide board 44 forms at least one coolant channel 441, which in the embodiment illustrated comprises three U-shaped channels that spaced by isolation ribs 442 and are of segments substantially parallel to each other. The U-shaped channels 441 have a first end 441a and a second end 441b. The coolant guide board 44 also defines a gas passage 443 corresponding in position to the gas passage 431 of the temperature regulation side partition board 43. The coolant guide board 44 is isolated from the gas guide board 42 by the temperature regulation side partition board 43 that is in physical engagement with both the coolant guide board 44 and the gas guide boards 42 for heat transfer purposes.
Air that is supplied from the blower 31 is conducted into the temperature regulation section 4 through the first inlet fitting 21 and the first entry opening 411 of the first end board 41. The air then enters the first end 421a of the gas channels 421 of the first gas guide board 42, and moves along the gas channels 421 to the second end 421b, where air passes, in sequence, through the gas passage 431 of the partition board 43 and the gas passage 443 of the coolant guide board 44. Eventually, air passes through an opening 61 defined in the central partition board 6 that is in physical engagement with the coolant guide board 44.
On the other hand, the coolant discharged from the fuel cell stack 1 is supplied to the device-side coolant inlet 25 and flows into the regulating device 2 sequentially through the coolant passage 423 of the gas guide board 42 and the coolant passage 432 of the partition board 43 to reach the first end 441a of the coolant channels 441 of the coolant guide board 44. The coolant then moves along the coolant channels 441 to the second end 441b, where the coolant flows in sequence through the coolant passage 433 of the partition board 43 and the coolant passage 424 of the gas guide board 42. The coolant returns through the device-side coolant outlet 26 and is guided to the cell-side coolant inlet 16 for cooling the fuel cell stack 1 again.
Since the coolant and the air are simultaneously flowing through the coolant channels 441 of the coolant guide board 44 and the gas channels 421 of the first gas guide board 42 and since the coolant guide board 44 and the gas guide board 42, which correspond in position to each other, are both in physical and tight engagement with the temperature regulation side partition board 43 that is made of thermally conductive material to allow for physical contact of the air and the coolant with the partition board 43, heat exchange occurs between the coolant and the air flowing through the first gas guide board 42. Thermal energy flows from the coolant that is of a high temperature around 60-70° C. to the air that is of a lower temperature. Thus, the air is heated and the temperature of the air is increased.
Since the coolant circulation loop is a closed one, the total amount of the coolant flowing through the coolant circulation loop can be substantially preserved. Replenishment of the coolant due to lose in regulating the temperature and humidity of the air supplied to the fuel cell stack 1 is no longer necessary.
The humidity regulation section 5 comprises the second end board 51 opposing the central partition board 6 with a second gas guide board 52, a humidity exchange section 53, and a fluid guide board 54 interposed in sequence therebetween. The second gas guide board 52 forms at least one gas channel 521, which in the embodiment illustrated comprises three U-shaped channels that are spaced by isolation ribs 522 and are of segments substantially parallel to each other. The U-shaped channels 521 have a first end 521a and a second end 521b. The second gas guide board 42 also defines two gas passages 523, 524.
The fluid guide board 54 forms at least one fluid channel 541, which in the embodiment illustrated comprises three U-shaped channels that are spaced by isolation ribs 542 and are of segments substantially parallel to each other. The U-shaped channels 541 have a first end 541a and a second end 541b. The fluid guide board 54 also defines an air passage 543 corresponding in position to the opening 61 of the central partition board 6 and the first end 521a of the gas channels 521 of the second gas guide board 52. The fluid guide board 54 is isolated from the second gas guide board 52 by the humidity exchange section 43 that is interposed between and in physical engagement with both the fluid guide board 54 and the second gas guide board 52.
The humidity exchange section 53 is water permeable but does not allow air or gas to transmit therethrough, comprising a humidity exchange film 531 interposed between gas diffusion layers 532, 533, which are respectively in physical and tight engagement with the second gas guide board 52 and the fluid guide board 54 to allow physical contact of the air flowing through the gas channels 521 and the fluid flowing through the fluid channels 541. The humidity exchange section 53 is of a size that is sufficient to cover the fluid channels 541 of the fluid guide board 54 and the gas channels 521 of the second gas guide board 52. However, the first and second end 521a, 521b of the second gas guide board 521 are shielded by the humidity exchange section 53 and thus air that flows through the openings 61 of the central partition board 6 is allowed to freely flow into the first end 521a of the second gas guide board 52. The humidity exchange section 53 does not shield the gas passages 523, 524 of the second gas guide board 52.
Air of which temperature has been regulated in the temperature regulation section 4 flows through the openings 61 of the central partition board 6, and the air passage 543 of the fluid guide board 54 to reach the first ends 521a of the second gas guide board 52. The air then moves along the gas channels 521 to the second end 521b, where air passes through the first exit opening 511 and the first outlet 22 for supply to the fuel cell stack 1 through the air inlet 11 of the fuel cell stack 1.
On the other hand, the fluid rich of water contents that is discharged from the outlet 12 of the fuel cell stack 1 is supplied to the second inlet fitting 23 of the regulating device 23 and flows into the first end 541a of the fluid guide board 54 sequentially through the second entry opening 512 of the second end board 51 and the gas passage 523 of the second gas guide board 52. The fluid then moves along the fluid channels 541 to the second end 541b, where the fluid flows in sequence through the gas passage 524 of the second gas guide board 52 and the second exit opening 513 of the second end board 53 and is then discharged out of the regulating device 2 via the second outlet fitting 24.
The air of which the temperature has been regulated by the temperature regulation section 4 enters the humidity regulation section 5 in which the air is subject to regulation of humidity thereof by exchange of humidity with the fluid from the fuel cell stack 1, which is rich of water contents, whereby the air may absorb water from the fluid and the relative humidity of the air may be increased to a desired range for enhancing the chemical reaction inside the fuel cell stack 1.
Thus, air that is drawn in a fuel cell system comprised of the regulating device of the present invention, such as the one illustrated in
Also referring to
Similarly, the humidity regulation section 5 can server as a basic unit for constitute a humidity regulation unit and a number of humidity regulation units may be combined as a compound multi-unit humidity regulation means for a reaction gas temperature and humidity regulating device embodying the present invention.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 92124547 | Sep 2003 | TW | national |
