1. Field of the Invention
The present invention generally relates to a fuel supplying and controlling method and a fuel cell apparatus using the same and, more particularly, to a fuel supplying and controlling method and a fuel cell apparatus using the fuel supplying and controlling method, in which a fuel sensor-less control method and a fuel concentration sensor are combined together to stabilize the operation of the fuel cell apparatus.
2. Description of the Prior Art
A fuel cell is a power generating device that uses electro-chemical reactions to transform chemical energy into electrical energy. In a fuel cell, fuel comprising hydrogen and an oxidant (such as the air or oxygen) are introduced respectively to the anode and the cathode of the cell. At the anode, oxidation takes place to ionize the fuel into hydrogen ions and electrons. The hydrogen ions travel from the anode through a proton exchange membrane (PEM) to the cathode to combine with the electrons traveling through the external load circuit to the cathode to cause reduction reaction with oxygen to produce water. Accordingly, as long as the fuel is kept supplied, the fuel cell is capable of generating power continuously with high efficiency and low pollution.
Among currently available fuel cells, the direct methanol fuel cell (DMFC) is widely used as a power supply in various portable electronic appliances such as notebooks, personal digital assistants (PDA's) and global positioning systems (GPS's). The DMFC is advantageous over other fuel cells such as the proton exchange membrane fuel cell (PEMFC) in that liquid-phase methanol is used as fuel to significantly improve security and safety in storage and transportation of fuel.
However, in the supply of fuel for the DMFC, which is well known to those with ordinary skills in the art, the methanol fuel concentration is a key factor. Over-supply of fuel (such as methanol) leads to serious fuel (methanol) crossover, which results from direct reaction between methanol and oxygen to cause a mixed potential at the cathode, to lower the cell performance and even worse, to damage the fuel cell due to a negative voltage. Moreover, the control of the supply of fuel is important to meet the requirement of the load of the fuel cell.
Therefore, there is demand in providing a fuel supplying and controlling method and a fuel cell apparatus using the fuel supplying and controlling method to overcome the aforementioned problems.
It is an object of the present invention to provide a fuel supplying and controlling method and a fuel cell apparatus using the method, in which a fuel sensor-less control method is used to control the fuel concentration in fuel cell apparatus, and a fuel concentration range is pre-determined so that whether the fuel concentration exceeds the fuel concentration range is monitored using the fuel concentration sensor as a second line of defense.
It is another object of the present invention to provide a fuel supplying and controlling method and a fuel cell apparatus using the method, in which the fuel sensor-less control method is used as a first line of defense for monitoring whether the fuel cell apparatus operates within the optimum range of fuel concentration or not and determining an optimum range of fuel concentration, while whether the fuel concentration exceeds the optimum range of fuel concentration is monitored using the fuel concentration sensor as a second line of defense for monitoring the fuel concentration.
In one embodiment, the present invention provides a fuel supplying and controlling method, comprising steps of: determining an operation concentration range of a fuel cell module; and using a fuel concentration sensor with a monitoring process to monitor a fuel concentration in the fuel cell module according to the operation concentration range to determine the timing for fuel injection. The operation of the fuel cell module is controlled using a fuel sensor-less control method to replace the abnormal or damaged fuel concentration sensor when the characteristic value for the fuel cell module is abnormal.
In another embodiment, the present invention further provides a fuel supplying and controlling method, comprising steps of; determining an operation concentration range of a fuel cell module; using a fuel sensor-less control method to control the operation of the fuel cell module within the operation concentration range to supply power to a load; and using a fuel concentration sensor with a monitoring process to monitor a fuel concentration in the fuel cell module according to the operation concentration range to determine the timing for fuel injection.
In still another embodiment, the present invention further provides a fuel cell apparatus, comprising: a fuel cell module, being coupled to a load to provide the load with power required for operation; a fuel supplying unit, being coupled to the fuel cell module to provide the fuel cell module with fuel; a fuel concentration sensor, being coupled to the fuel cell module to detect a fuel concentration in the fuel cell module to generate a detection signal; and a measurement control unit, being coupled to the fuel cell module, the fuel supplying unit and the fuel concentration sensor to determine an operation concentration range of the fuel cell module and to determine the timing for fuel injection according to the detection signal.
The objects, spirits and advantages of the preferred embodiments of the present invention will be readily understood by the accompanying drawings and detailed descriptions, wherein:
The present invention can be exemplified but not limited by the preferred embodiment as described hereinafter.
Please refer to
The fuel cell module 10 comprises a pipeline for supplying methanol and air or oxygen and a pipeline for exhausting water and carbon dioxide. There are disposed a cathode plate 100, an anode plate 101 and a proton exchange membrane 102 disposed in the fuel cell apparatus 1 and a load 11 disposed between the anode plate 100 and the cathode plate 101 so that a loop is formed by the cathode plate 100, the anode plate 101 and the load 11. The load 11 is coupled to a meter 12. The meter 12 can be a voltmeter or an Ampere meter. In the present embodiment, the meter 12 is a voltmeter connected with the load in parallel. Alternatively, if the meter 12 is an Ampere meter, the load 11 is connected with the load in series.
The fuel cell apparatus 1 further comprises a fuel supplying unit 14, a fuel concentration sensor 15 and a measurement control unit 13. The fuel supplying unit 14 is coupled to the fuel cell module 10 to provide the fuel cell module 10 with fuel. The fuel concentration sensor 15 is coupled to the fuel cell module 10 to detect a fuel concentration in the fuel cell module 10 to generate a detection signal to be transmitted to the measurement control unit 13. In the present embodiment, the fuel concentration sensor 15 is a hydrogen-rich fuel concentration sensor. The hydrogen-rich fuel concentration sensor can be a methanol fuel concentration sensor, an ethanol fuel concentration sensor, a boron hydride fuel concentration sensor or a hydrogen fuel concentration sensor. Since the fuel cell uses a variety of types of fuels, the fuel concentration sensor is selected according to practical demands and is not limited to the aforesaid example. The measurement control unit 13 is coupled to the fuel cell module 10, the fuel supplying unit 14 and the fuel concentration sensor 15 to determine an operation concentration range of the fuel cell module 10 and to determine the timing for fuel injection according to the detection signal.
Please refer to
In order to describe the fuel supplying and controlling method of the present invention, the fuel cell apparatus in
First, in Step 20, an operation concentration range of a fuel cell module 10 is determined corresponding to a load. Please refer to
Referring to
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Returning to
In the monitoring process, if the detected fuel concentration exceeds the upper limit of the operation concentration range, the measurement control unit 13 stops the fuel supplying unit 14 from supplying the fuel cell module 10 with fuel even though it is the time for fuel injection. Otherwise, if the detected fuel concentration is smaller than the lower limit of the operation concentration range, the measurement control unit 13 forces the fuel supplying unit 14 to supply the fuel cell module 10 with fuel to keep the operation of the fuel cell module 10. During the monitoring process, if the load changes due to being turned on/off for example so that the operation concentration range has be to re-determined as in Step 20, the measurement control unit 13 will perform Step 20. In other words, the operation concentration range will be re-determined when the load of the fuel cell module fluctuates. The operation concentration range can be re-determined using steps as described in
At last, in Step 32, a fuel concentration sensor 15 with a monitoring process is used to monitor a fuel concentration in the fuel cell module 10 according to the operation concentration range to determine the timing for fuel injection. One object of Step 32 is to improve the security of the fuel sensor-less control method in Step 31. With the use of the fuel concentration sensor 15, incorrect fuel injection can be avoided. Therefore, in Step 32, the monitoring process is used to monitor the fuel concentration in the fuel cell module 10 to keep the fuel cell operating normally.
In the present embodiment, the monitoring process in Step 32 is performed to monitor whether the fuel concentration in the fuel cell module exceeds the upper limit or is lower than the lower limit. In other words, when the fuel concentration exceeds the upper limit, the measurement control unit 13 stops the fuel supplying unit 14 from supplying the fuel cell module 10 with fuel according to the fuel concentration sensor 15 even though it is determined in the fuel supplying method in Step 21 that it is the time for fuel injection. Otherwise, when the fuel concentration is smaller than the lower limit, the measurement control unit 13 forces the fuel supplying unit 14 to supply the fuel cell module 10 with fuel according to the fuel concentration sensor 15 to keep the operation of the fuel cell module 10 even though it is determined in the fuel supplying method in Step 21 that fuel injection is not required.
According to the above discussion, it is apparent that the present invention discloses a fuel supplying and controlling method and a fuel cell apparatus using the fuel supplying and controlling method, in which a fuel sensor-less control method and a fuel concentration sensor are combined together to stabilize the operation of the fuel cell apparatus. Therefore, the present invention is novel, useful and non-obvious.
Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments that will be apparent to persons skilled in the art. This invention is, therefore, to be limited only as indicated by the scope of the appended claims.
Number | Date | Country | Kind |
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096133798 | Sep 2007 | TW | national |