Fuel Cell System
a fuel cell and system technology, applied in the field can solve the problems of high cost of gas concentration detection instruments, poor reliability of fuel cell systems, and inefficiency of fuel cell operating and waste of expensive fuel gas, so as to improve the reliability and durability of the fuel cell system, improve the efficiency of operation, and reduce the cost
Inactive Publication Date: 2008-01-10
NISSAN MOTOR CO LTD
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- Summary
- Abstract
- Description
- Claims
- Application Information
AI Technical Summary
Benefits of technology
[0012] According to the present disclosure, the gas replacement completion time is estimated based on the voltage information determined by a voltage detection means (e.g. a voltage sensor) connected to and monitoring the electric power generation of the fuel cell stack. Therefore, without using a gas concentration sensor, the deterioration of the catalyst layer resulting from exposure to a mixture of fuel gas and oxidizer gas during fuel cell start-up can be controlled, and the reliability and durability of the fuel cell system improved.
[0013] Certain aspects of the invention may provide fuel cell systems exhibiting improved operating efficiency. Other aspects of the invention may provide lower cost fuel cell systems that may not require gas concentration sensors to monitor fuel conversion efficiency. In other aspects, the invention may provide improved fuel cell system operating and control methods that reduce deterioration of the fuel cell electrode catalyst layers resulting from exposure to the mixture of fuel gas and oxidizer gas during fuel cell start-up.
Problems solved by technology
However, since only a portion of the oxidizing gas and the fuel gas supplied to the fuel cell generally reacts within the respective oxidizing electrode chamber and fuel electrode chamber, the gas exhausted from a fuel cell stack may be rich in unreacted fuel gas and / or oxidizer gas.
This leads to fuel cell operating inefficiency and waste of expensive fuel gas.
Although various methods have been developed to monitor the exit concentration of the exhaust gas from an operating fuel cell and adjust the operating parameters of the fuel cell system to achieve higher fuel gas conversion, these methods generally require expensive gas concentration detection instrumentation that adds substantially to the cost of a fuel cell system.
Moreover, the existing gas concentration monitoring systems may suffer from operating instability and gas detection interferences.
This may provide a false indication of the fuel gas concentration in the fuel cell system exhaust and lead to selection of improper fuel cell operating parameters.
Selection of improper fuel cell operating parameters can seriously degrade fuel cell operating efficiency, long term cycling performance and fuel cell life.
Method used
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Experimental program
Comparison scheme
Effect test
first embodiment
[0021]FIG. 1 is a schematic diagram of a fuel cell system 1A. FIG. 2 is a characteristic line graph showing voltage of fuel cell stack 2 upon start of the fuel cell and illustrates an estimation procedure of the gas replacement completion time.
[0022] In FIG. 1, fuel cell system 1A is equipped with fuel cell stack 2. Fuel cell stack 2 is equipped with fuel electrode 3 facing the fuel chamber and oxidizer electrode 4 facing the oxidizer gas chamber. In fuel cell stack 2, the voltage detection means 30 (for example, a voltage sensor) is electrically connected to the fuel cell system 1A and detects a voltage produced by the electric power generation of fuel electrode 3 and oxidizer electrode 4. The voltage detected by the voltage detection means 30 is output to a controller 40.
[0023] With respect to fuel gas supply conduit (e.g. fuel gas supply means) 5, one end is connected to fuel tank 6, and the other end is connected to the entry of the fuel chamber of the fuel cell stack 2. Fuel g...
second embodiment
[0054] Also, since circulation compressor 20 utilized as in the second embodiment, the fuel gas is more effectively circulated in fuel gas recirculation conduit 11. The fuel gas vent valve 10 is closed at the estimated gas replacement completion time T, but the valve for the fuel gas recirculation conduit 21 is closed sooner.
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Abstract
The disclosure describes fuel cell systems including a fuel cell stack that generates electricity, an exhaust valve that externally vents a fuel gas from a fuel chamber of the fuel cell stack, and a controller that computes an estimated time to replace an oxidant gas in at least the fuel chamber with a newly supplied fuel gas, wherein at a time of starting-up the fuel cell system the controller maintains the exhaust valve in an open position for the estimated time. In some embodiments, the controller computes the estimated time as a summation of a first time T1 measured from the fuel cell start-up time to a time when contents of a supply conduit are replaced with fuel gas, a second time T2 measured from the when contents of a supply conduit are replaced with fuel gas to a time when contents of the fuel chamber are replaced with fuel gas, and a third time T3 measured from time when contents of the fuel chamber are replaced with fuel gas to a time when contents of the exhaust conduit are replaced with fuel gas. The disclosure further describes methods of operating a fuel cell system, particularly during fuel cell start-up.
Description
TECHNICAL FIELD [0001] The present disclosure relates to fuel cell systems, more particularly, controlling fuel cell system operation. BACKGROUND [0002] In a fuel cell system, a fuel gas such as hydrogen and an oxidizer gas containing oxygen are electrochemically reacted across an electrolyte to produce electrical energy. Conventional fuel cell systems contain one or more unit fuel cells including generally a fuel electrode coated with a redox catalyst layer, an oxidizing electrode coated with a redox catalyst layer, and an electrolyte film separating the electrodes and having a gas passage formed to supply oxidizer gas (e.g. air) to the oxidizing electrode (e.g. cathode) in an oxidizer electrode chamber, and fuel gas (e.g. hydrogen) to the fuel electrode (e.g. anode) in a fuel electrode chamber. [0003] Conventional fuel cell systems may include pipes for supplying and exhausting oxidizing gas and fuel gas to and from the fuel cell stack. However, since only a portion of the oxidizi...
Claims
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IPC IPC(8): H01M8/04
CPCH01M8/04097H01M8/04223Y02E60/50H01M8/04753H01M8/04761H01M8/04559H01M8/24H01M8/04302H01M8/04225
Inventor SHIMOI, RYOICHIMASHIO, TETSUYA
Owner NISSAN MOTOR CO LTD
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