US20070196705A1 - Fuel cell system - Google Patents
Fuel cell system Download PDFInfo
- Publication number
- US20070196705A1 US20070196705A1 US10/592,671 US59267105A US2007196705A1 US 20070196705 A1 US20070196705 A1 US 20070196705A1 US 59267105 A US59267105 A US 59267105A US 2007196705 A1 US2007196705 A1 US 2007196705A1
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- Prior art keywords
- fuel cell
- gas
- passage
- airtightness
- fuel
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
- H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/0438—Pressure; Ambient pressure; Flow
- H01M8/04388—Pressure; Ambient pressure; Flow of anode reactants at the inlet or inside the fuel cell
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/0438—Pressure; Ambient pressure; Flow
- H01M8/04395—Pressure; Ambient pressure; Flow of cathode reactants at the inlet or inside the fuel cell
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04664—Failure or abnormal function
- H01M8/04679—Failure or abnormal function of fuel cell stacks
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04753—Pressure; Flow of fuel cell reactants
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04761—Pressure; Flow of fuel cell exhausts
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a fuel cell system adapted for use in portable power supplies, power supplies for electric vehicles, cogeneration systems and others. More particularly, the present invention relates to a fuel cell system equipped with a fuel cell having polymer electrolyte membranes.
- Fuel cells are designed to cause an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air, thereby simultaneously generating electric power and heat.
- a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air, thereby simultaneously generating electric power and heat.
- polymer electrolyte fuel cells having the following structure.
- a catalytic reaction layer containing carbon powder which carries a platinum group metal catalyst as a chief component is formed on both sides of a polymer electrolyte membrane, for selectively transporting hydrogen ions.
- a diffusion layer is formed which is made of, for example, carbon paper or carbon cloth having both fuel gas permeability and electronic conductive properties.
- this membrane electrode assembly is sandwiched by separators made from conductive materials such as glass-like carbon or metal. These separators are provided with gas passages that are formed so as to expose the aforesaid fuel gas and oxidizing gas to the membrane electrode assembly and with cooling fluid passages that are formed so as to control the temperature of the membrane electrode assembly, in other words, so as to recover the heat generated together with electric power.
- a gas sealing material or gasket is provided between the membrane electrode assembly and each separator, for preventing leakage of the supplied fuel gas and oxidizing gas to the outside and mingling of these gases.
- the membrane electrode assembly sandwiched between the separators serves as a basic unit.
- such membrane electrode assemblies are stacked in numbers corresponding to the design output of electric power or heat of the polymer electrolyte fuel cell.
- a fuel gas feeder for supplying the fuel gas and an oxidizing gas feeder for supplying the oxidizing gas are connected to the polymer electrolyte fuel cell (hereinafter abbreviated as PEFC).
- PEFC polymer electrolyte fuel cell
- an exhaust heat recovery system for recovering generated heat and a power converting system for making the electric power generated in the PEFC usable is provided.
- the fuel gas feeder includes a hydrogen generator for generating a hydrogen-rich gas (i.e., the fuel gas) by reforming hydrocarbon fuel such as natural gas, propane gas and gasoline to output to the PEFC.
- the oxidizing gas feeder consists of, for example, a blower or fan and supplies air to the PEFC as the oxidizing gas.
- the fuel gas feeder and oxidizing gas feeder are equipped with a humidifier for controlling the amount of moisture contained in the fuel gas or oxidizing gas to be supplied to the PEFC.
- the exhaust heat recovery system is composed of a heat exchanger and a hot water tank. The heat exchanger recovers the heat retained by, for instance, the cooling fluid flowing in the cooling fluid passage by means of water to produce hot water.
- the hot water tank stores this hot water.
- the power converting system includes an inverter for converting a dc power generated by the PEFC into an ac power and a transformer.
- the fuel gas or oxidizing gas flows in the route made by the gas passages formed in the gasket, polymer electrolyte membrane and separators.
- the constituents of the gas passages degrade causing, for instance, increases in the gas permeation of the polymer electrolyte membrane and hardening of the gasket, so that the airtightness of the gas passages decreases.
- This entails leakage of the fuel gas or oxidizing gas to the outside or mingling of these gases.
- the leakage of the fuel gas to the outside and the mingling of the fuel gas/the oxidizing gas may trigger off abnormal combustion or an explosion.
- a fuel cell system or detection method which enables detection of the airtightness of the passages in which the fuel gas or oxidizing gas flows.
- General type pressure vessels usually employ “escape probability detection” in which pressure gas is sealed in a vessel and the time taken for pressure to decrease or a decrease in pressure within a specified period of time is detected.
- the detection method in which pressurized gas is sealed in a fuel cell system and the progress of decreasing of pressure is observed, can not be practically applied to fuel cell systems, because they are operated as needed and therefore detection of the airtightness of the passages for the fuel gas or oxidizing gas in the PEFC has to be promptly performed so as not to hinder the operation of the PEFC.
- the consumption of the fuel gas is calculated based on the output current of the fuel cell and the pressure of the fuel gas within the fuel gas cylinder is calculated from the fuel gas consumption. Then, the presence/absence of fuel gas leakage is determined from a comparison between this calculated pressure value and a detected pressure value that is obtained from actual detection with a pressure sensor.
- a hydrogen-containing gas and an oxygen-containing gas are supplied to the fuel electrode and oxidant electrode, respectively, of the fuel cell and a rapid change in the generated voltage of the fuel cell caused by a decrease in the supply of the oxygen-containing gas is detected. Then, the leakage of hydrogen in the fuel cell is calculated from the relationship between the oxygen-containing gas and the generated voltage.
- Patent Document 3 discloses a PEFC operating method according to which a judgment is made to check whether the operational state of the PEFC is in a performance decreasing zone by analyzing impurity ions contained in the moisture of a fuel gas humidifying water or the like from the PEFC. If it is determined that the operational state is in the performance decreasing zone, the operation of the PEFC is brought to a stop or operating conditions for the PEFC are limited, thereby making the operational state of the PEFC get out of the performance decreasing zone.
- Patent Document 4 discloses a method of estimating the service life of a fuel cell. According to this method, a fuel cell is operated in several basic operating patterns and its service life is estimated based on the time taken for power generation and the change rate of output voltage in each basic operation pattern.
- Patent Document 1 Japanese Laid-Open Patent Application Publication No. Hei 11-224681
- Patent Document 2 Japanese Laid-Open Patent Application Publication No. Hei 9-27336
- Patent Document 3 Japanese Laid-Open Patent Application Publication No. 2004-127548
- Patent Document 4 Japanese Laid-Open Patent Application Publication No. Hei 11-97049
- the vapor contained in the gas supplied to the fuel cell becomes flocculated water in the oxidizing gas passage or fuel gas passage and this water dwells in the oxidizing gas passage or fuel gas passage, hampering a flow of the gas, which results in a decrease in the output of the fuel cell.
- it is usual to perform purging treatment in which the residual gas or moisture remaining in the fuel cell is purged in the course of the start-up, stop or operation of the fuel cell.
- a dried fuel gas for instance, is supplied to the fuel cell thereby forcing the flocculated water out of the fuel cell.
- Patent Document 1 has the disadvantage that where a fuel gas is used for the purging of the residual gas or water from the fuel cell, the consumption of the fuel gas used for the purging treatment is counted in the measurement of leakage so that the accuracy of the detection of leakage in the fuel cell decreases.
- the generated voltage of the fuel cell is measured while gradually reducing the amount of oxygen-containing gas supplied to the cathode, yet changes in the generated voltage measured according to changes in the supply of the gas are so small that this method has much to do with detection accuracy.
- various factors such as decreasing electrode performance are involved with fluctuations in the output electric power of a fuel cell.
- the method of estimating the leakage of the fuel gas based on voltage generation has left room for improvements in accuracy.
- fluoride ions are generated when the polymer electrolyte membrane decomposes. Fluoride ions are strongly acidic and therefore corrode metals.
- the PEFC operating method disclosed in Patent Document 3 utilizes this phenomena and determines deterioration of a PEFC by detecting ions such as metal ions in moisture such as produced water and humidifying water.
- physical damage to the polymer electrolyte membrane also causes a decrease in the airtightness of the passage for the fuel gas or oxidizing gas in a PEFC. When the polymer electrolyte membrane gets such damage, generation of metal ions or fluoride ions are unlikely to occur.
- the method of determining deterioration of a PEFC from detection of metal ions or fluoride ions is not suited for detection of the airtightness of a PEFC and, more precisely, the airtightness of the passage where the fuel gas or oxidizing gas flows.
- the catalytic power of the electrode catalyst (e.g., platinum) of a fuel cell is affected by various environmental conditions such as load fluctuations in the fuel cell, the gas components contained in the fuel cell, the partial pressure of the gas components of the fuel cell and temperature/humidity conditions during suspension.
- the electrode surface area of a fuel cell varies according to the history of the fuel cell and in fact, it is difficult to estimate the service life of a fuel cell with high accuracy from the operating patterns of the fuel cell. Therefore, the estimation of the service life of a fuel cell by approximating it from one or plural basic operation patterns of the fuel cell has left room for improvements.
- the prior art techniques have proved unsuccessful in providing satisfactory accuracy in quick detection of the airtightness of the passage of the fuel cell where the fuel gas or oxidizing gas flows and therefore left room for improvements.
- the acquisition of the basic operating patterns of a fuel cell requires much time and labor and the provision of a special apparatus such as a detector for detecting metal ions or fluoride ions incurs additional costs.
- the invention is directed to overcoming the above problems and a primary object of the invention is therefore to provide a fuel cell system that is constructed in simple structure and capable of promptly, accurately detecting the airtightness of a fuel cell as a deterioration information of a fuel cell.
- a fuel cell system comprising:
- a fuel cell having a fuel gas passage and an oxidizing gas passage which are so formed as to be in contact with an anode and a cathode respectively, the anode and the cathode being formed on opposed sides of a polymer electrolyte membrane respectively;
- a fuel gas feeder configured to feed a fuel gas to the fuel gas passage
- an oxidizing gas feeder configured to feed an oxidizing gas to the oxidizing gas passage
- a fuel gas exhaust passage configured to flow an excessive fuel gas discharged from the fuel gas passage
- an oxidizing gas exhaust passage configured to flow an excessive oxidizing gas discharged from the oxidizing gas passage
- test gas feeder configured to feed a test gas to either the fuel gas passage or the oxidizing gas passage
- a flow rate detector configured to detect a flow rate of the test gas
- a first passage blocking device configured to block off either the fuel gas exhaust passage or the oxidizing gas exhaust passage to which the test gas is fed
- the controller controls the first passage blocking device to block off the passage and controls the test gas feeder to feed the test gas to the fuel cell, thereby obtaining a detected value from the flow rate detector or an airtightness value that is numerical information into which the detected value is converted.
- the fuel cell system of the above structure can promptly, accurately detect the airtightness of the fuel cell as a deterioration information of the fuel cell by the simplified structure and operation of the flow rate detector, the passage blocking device and the test gas feeder.
- the test gas feeder of the fuel cell system may be either the fuel gas feeder or the oxidizing gas feeder.
- the test gas feeder can be eliminated, which enables prompt, accurate detection of the airtightness of the fuel cell with a more simplified structure and operation.
- the fuel cell system may further comprise a second passage blocking device configured to block off a gas passage connected to an outlet side of either the fuel gas passage or the oxidizing gas passage which is not fed with the test gas; and a third passage blocking device configured to block off a gas passage connected to an inlet side of either the fuel gas passage or the oxidizing gas passage which is not fed with the test gas, wherein the controller controls the first to third passage blocking devices to block off their associated passages, thereby obtaining a first airtightness value of the flow rate detector; controls the first passage blocking device to block off its associated passage while controlling the second and third passage blocking devices so as not to block off either of their associated passages, thereby obtaining a second airtightness value of the flow rate detector; and obtains a difference between the first airtightness value and the second airtightness value.
- a second passage blocking device configured to block off a gas passage connected to an outlet side of either the fuel gas passage or the oxidizing gas passage which is not fed with the test gas
- a third passage blocking device
- the fuel cell system of this structure can obtain leakage from the fuel gas passage to the oxidizing gas passage and therefore can perform prompt, accurate detection of the airtightness of the fuel cell and more particularly the degree of damage to the polymer electrolyte membrane with a more simplified structure and operation.
- the test gas feeder of the fuel cell system may be either the fuel gas feeder or the oxidizing gas feeder.
- the test gas feeder can be eliminated, which enables prompt, accurate detection of the airtightness of the fuel cell with a more simplified structure and operation.
- a fuel cell system in which the test gas may be composed of chemical components that do not cause a chemical reaction within the fuel cell. This prevents damages in the fuel cell such as decrease of the catalytic power by the test gas.
- test gas may contain at least one selected from a group consisting of fuel gas, oxidizing gas, inactive gas, carbon dioxide and methane mixed gas.
- the controller of the fuel cell system may have an output section for outputting the airtightness value to outside.
- the controller of the fuel cell system may have a memory section for prestoring reference airtightness values for evaluation of the airtightness value, and the controller makes a comparison between the airtightness value and the reference airtightness values thereby evaluating the airtightness of the fuel cell. This enables the fuel cell system to use the reference airtightness values as a criterion of judgment so that the condition of the fuel cell in terms of airtightness can be properly evaluated.
- the controller of the fuel cell system may have an output section for outputting the airtightness value which has been evaluated to outside.
- the controller of the fuel cell system may adjust operating conditions for the fuel cell based on the evaluated airtightness value. This makes the fuel cell system automatically prolong the service life of the fuel cell, using the reference airtightness values as a criterion of judgment.
- the controller of the fuel cell system may obtain the airtightness value at specified detection time intervals and accumulatively stores the obtained airtightness values in the memory section in relation to an operating time of the fuel cell; and wherein the controller obtains a transition line of the airtightness values relative to the operating time by a statistical approximation method and estimates a deterioration in the airtightness of the fuel cell based on a comparison between the transition line and the reference airtightness values.
- the controller of the fuel cell system may alter the detection time intervals according to a locus of the transition line. This makes it possible to eliminate operation for obtaining unnecessary detected airtightness values without affecting the acquisition of the transition line of detected airtightness values, so that the operation of the fuel cell system can be rationalized.
- the reference airtightness values stored in the memory section of the controller of the fuel cell system may include a limit airtightness value representative of a service limit of the fuel cell; and wherein the controller extrapolates the transition line to obtain an estimated remaining operation time of the fuel cell left before the transition line reaches the limit airtightness value. This enables the fuel cell system to estimate a service life of the fuel cell system based on concrete numerical information.
- the controller of the fuel cell system may have an output section for outputting the estimated remaining operation time to outside. This enables the user of the fuel cell system to obtain concrete numerical information on the remaining service life of the fuel cell, so that he can preliminarily consider countermeasures against damage to the fuel cell system and a decrease in its performance, can select a proper operation mode of the fuel cell and can make an operation schedule for the fuel cell.
- the controller of the fuel cell system may adjust operating conditions for the fuel cell based on the estimated remaining operation time.
- the service life of the fuel cell can be substantially automatically prolonged so that the burden imposed on the user of the fuel cell system in terms of operation management can be reduced.
- the controller of the fuel cell system may obtain the detected value or the airtightness value when starting up and/or stopping the operation of the fuel cell. This enables the fuel cell system to substantially automatically detect the airtightness of the fuel cell.
- the fuel cell system of the invention has the effect of promptly accurately detecting the airtightness of the fuel cell, with a simple structure.
- FIG. 1 is a schematic diagram illustrating a fuel cell system according to a first embodiment of the invention.
- FIG. 2 is graphs each conceptually showing a transition line of a detected airtightness value relative to the operating time of a PEFC, wherein FIG. 2 ( a ) is a graph showing a case where the detected airtightness value varies at a constant pace, FIG. 2 ( b ) is a graph showing a case where the detected airtightness value varies so as to gradually become stable, and FIG. 2 ( c ) is a graph showing a case where the change of the detected airtightness value gradually becomes significant.
- FIG. 3 is a schematic diagram illustrating a fuel cell system according to a second embodiment of the invention.
- FIG. 4 is a schematic diagram illustrating a fuel cell system according to a third embodiment of the invention.
- FIG. 5 is a schematic diagram illustrating a fuel cell system according to a fourth embodiment of the invention.
- FIG. 6 is a schematic diagram illustrating a fuel cell system according to a fifth embodiment of the invention.
- FIG. 7 is a schematic diagram illustrating a fuel cell system according to a sixth embodiment of the invention.
- PEFC polymer electrolyte fuel cell
- passage blocking device (first passage blocking device)
- FIG. 1 is a schematic diagram illustrating a fuel cell system according to a first embodiment of the invention.
- the fuel cell system 100 has a fuel gas feeder 2 and an oxidizing gas feeder 3 .
- the fuel gas feeder 2 is connected to a fuel gas feeding passage 6 whereas the oxidizing gas feeder 3 is connected to an oxidizing gas feeding passage 7 .
- the fuel gas feeding passage 6 is connected to a polymer electrolyte fuel cell (hereinafter referred to as “PEFC”) 1 , and a fuel gas is supplied from the fuel gas feeder 2 to the PEFC 1 .
- the oxidizing gas feeding passage 7 is connected to the PEFC 1 , and an oxidizing gas is supplied from the oxidizing gas feeder 3 to the PEFC 1 .
- the fuel gas feeding passage 6 is provided with a flow rate detector 5 .
- the flow rate detector 5 is constituted by, for instance, a flowmeter and detects the flow rate of a fluid that flows in a target passage that is the fuel gas feeding passage 6 herein.
- a membrane electrode assembly 1 A is sandwiched between a pair of separators, namely, an anode separator 1 B and a cathode separator 1 C.
- a fuel gas passage 1 D is defined by the membrane electrode assembly 1 A and a groove formed on the surface of the anode separator 1 B.
- an oxidizing gas passage 1 E is defined by the membrane electrode assembly 1 A and a groove formed on the surface of the cathode separator 1 C.
- the fuel gas passage 1 D and the oxidizing gas passage 1 E are accordingly separated from each other by the membrane electrode assembly 1 A having a polymer electrolyte membrane.
- the fuel gas feeding passage 6 is connected to one end of the fuel gas passage 1 D to supply the fuel gas to the fuel gas passage 1 D.
- the oxidizing gas feeding passage 7 is connected to one end of the oxidizing gas passage 1 E to supply the oxidizing gas to the oxidizing gas passage 1 E.
- the fuel gas and oxidizing gas which are supplied to the fuel gas passage 1 D and oxidizing gas passage 1 E respectively, cause a chemical reaction, thereby generating electric power and heat.
- a fuel gas exhaust passage 8 is connected to the other end of the fuel gas passage 1 D.
- the redundant fuel gas which has not chemically reacted in the anode, is discharged from the other end of the fuel gas passage 1 D to the fuel gas exhaust passage 8 .
- An oxidizing gas exhaust passage 9 is connected to the other end of the oxidizing gas passage 1 E.
- the redundant oxidizing gas which has not chemically reacted in the cathode, is discharged from the other end of the oxidizing gas passage 1 E to the oxidizing gas exhaust passage 9 .
- the fuel gas exhaust passage 8 is provided with a passage blocking device 4 .
- the passage blocking device 4 is configured to block off a flow of fluid in a target passage that is the fuel gas exhaust passage 8 herein.
- the passage blocking device 4 has an electric-operated valve whose valve disc blocks the passage.
- the fuel cell system 100 has a controller 10 .
- the controller 10 has a controlling section 10 A that is constituted by a controlling member such as micro computers; a memory section 10 B that is constituted by a storing member such as memories; an input section 10 C that is constituted by an input unit such as key boards and touch panels; and an output section 10 D that is constituted by an output unit such as monitors.
- the controller 10 controls the operation of the fuel cell system 100 . More particularly, the controller 10 controls the passage blocking device 4 and a raw material gas feeder 14 to obtain a detected value with the flow rate detector 5 .
- the memory section 10 B stores reference airtightness values used for evaluation of the airtightness of the PEFC 1 . Specifically, an initial airtightness value Q 100 of the PEFC 1 in the initial (starting) stage of the operation; a limit airtightness value Q 0 of the PEFC 1 in the stage where a functional disturbance appears in the PEFC 1 (i.e., in the service limit stage); and intermediate airtightness values Q 80 , Q 60 , Q 40 , Q 20 which are intermediate values between the initial airtightness value Q 100 and the limit airtightness value Q 0 are input through the input section 10 D and stored in the memory section 10 B beforehand.
- the airtightness value Q is numerical information such as a detected value (e.g., a current signal value and a voltage signal value) obtained by the flow rate detector 5 or numerical information such as a flow rate value obtained by converting the detected value.
- the airtightness value Q is used as deterioration information indicative of the degree of deterioration of the PEFC 1 .
- the controller 10 is not necessarily constituted by a single controller but may be constituted by a plurality of controllers that are disposed at discrete positions so as to control the operation of the fuel cell system 100 in cooperation with one another.
- the output section 10 D may be designed such that its output is transmitted by a data terminal so as to be displayed on a mobile device.
- This airtightness value detecting operation is performed, being controlled by the controller 10 .
- the controller 10 While the oxidizing gas feeder 3 is in a stopped state, the controller 10 first controls the passage blocking device 4 to block off the fuel gas exhaust passage 8 and controls the fuel gas feeder 2 to supply the fuel gas at constant pressure. For example, in either or both of the start-up operation and stop operation of the PEFC 1 , the controller 10 executes the airtightness value detecting operation of the fuel cell system 100 . Thereby, the airtightness of the PEFC 1 can be substantially automatically detected.
- the fuel gas feeder 2 will continue to supply the fuel gas to the PEFC 1 .
- the flow rate detector 5 detects the flow rate of the fuel gas.
- the controller 10 obtains an airtightness value based on a detected value of the flow rate detector 5 , i.e., a detected airtightness value Q. If no fuel gas leakage occurs, the flow of the fuel gas can be substantially shut off by blocking off the fuel gas exhaust passage 8 . Accordingly, the presence/absence of leakage of the fuel gas can be checked, in other words, the degree of airtightness can be evaluated within a short time. Since the precision of the flow rate detector 5 (flow rate detection capability) is high enough to detect fuel gas leakage in the PEFC 1 , high accuracy gas leakage detection can be ensured.
- the fuel cell system 100 can promptly, accurately detect the airtightness of the PEFC 1 with the simplified structure and operation of the flow rate detector 5 , the passage blocking device 4 and the fuel gas feeder 2 .
- the controller 10 displays the detected airtightness value Q on the output section 10 D. Thereby, the user of the fuel cell system 100 can promptly accurately grasp the airtightness condition of the PEFC 1 , i.e., the degree of deterioration, so that damage to the fuel cell system 100 and a decrease in its performance can be prevented beforehand.
- the controller 10 makes, in the controlling section 10 A, a comparison between the detected airtightness value Q and the reference airtightness values Q 100 to Q 0 stored in the memory section 10 B, thereby evaluating the condition of the airtightness of the PEFC 1 to display. More concretely, one of the reference airtightness values Q 100 to Q 0 that is the closest to the detected airtightness value Q and the difference between the detected airtightness value Q and the closest one of the reference airtightness values Q 100 to Q 0 are obtained and displayed on the output section 10 D. In such an evaluation, the fuel cell system 100 uses the reference airtightness values Q 100 to Q 0 as a criterion of judgment so that the condition of the fuel cell in terms of airtightness can be properly evaluated. Further, since the result of the evaluation of the airtightness of the PEFC 1 is displayed and therefore the user of the fuel cell system 100 is informed of it, the user can more easily take countermeasures against damage to the fuel cell system 100 and a decrease in its performance.
- the controller 10 adjusts operating conditions for the fuel cell system 100 according to the comparative evaluation of the detected airtightness value Q by use of the reference airtightness values Q 100 to Q 0 . For instance, whenever the detected airtightness value Q sequentially reaches the intermediate airtightness values Q 80 , Q 60 , Q 40 , Q 20 , starting from the initial airtightness value Q 100 , the controller 10 lowers the upper limit of the loss of the supply pressure of the oxidizing gas and fuel gas between the outlet and inlet of the PEFC 1 during the operation period of the fuel cell system 100 , thereby controlling the oxidizing gas feeder 3 and the fuel gas feeder 2 so as to operate, restricting the pressure loss. Thereby, the fuel cell system 100 can substantially automatically prolong its service life, using the reference airtightness values Q 100 to Q 0 as a threshold, that is, a criterion of judgment.
- the controlling section 10 A of the controller 10 controls the fuel cell system 100 , using a built-in clock so as to perform the airtightness value detecting operation at specified detecting time intervals ⁇ t.
- the specified detecting time interval ⁇ t is a time interval based on the operating time of the PEFC 1 .
- the controller 10 accumulatively stores the detected airtightness values Q in correspondence with the operating time T of the PEFC 1 that elapses before the airtightness value detecting operation is done. If the fuel cell 1 is in operation at the scheduled time of the airtightness value detecting operation, the controller 10 performs the airtightness value detecting operation in the nearest stop operation of the fuel cell 1 .
- the controller 10 A obtains a transition line of the detected airtightness value Q relative to the operating time T based on the accumulated detected airtightness values Q, using a statistical approximation method. For example, this transition line may be obtained by making use of a statistical processing method such as a least square method.
- the controller section 10 A estimates future changes in the detected airtightness value Q. The future changes may be estimated, for instance, by extrapolating the transition line.
- FIG. 2 is graphs each conceptually showing a transition line of the detected airtightness value relative to the operating time of the PEFC, wherein FIG. 2 ( a ) is a graph showing a case where the detected airtightness value varies at a constant rate, FIG. 2 ( b ) is a graph showing a case where the detected airtightness value varies so as to gradually become stable, and FIG. 2 ( c ) is a graph showing a case where the change of the detected airtightness value gradually becomes significant.
- the controller 10 A compares this transition line with the limit airtightness value Q 0 to calculate an estimated remaining operating time ⁇ T 0 , that is, an estimated time left before the PEFC 1 reaches the limit airtightness value Q 0 .
- the airtightness of the PEFC 1 can be promptly accurately detected with the simplified structure and operation of the flow rate detector 5 , the passage blocking device 4 and the fuel gas feeder 2 and the service life of the fuel cell system 100 can be estimated.
- the controller 10 displays the estimated remaining operating time ⁇ T 0 on the output section 10 D. Since this enables the user of the fuel cell system 100 to obtain an evaluated value of the remaining service life of the PEFC 1 in the form of concrete numerical information, the user can preliminarily consider countermeasures against damage to the fuel cell system 100 and a decrease in its performance, can select a proper operation mode of the PEFC 1 and can make an operation schedule for the PEFC 1 .
- the controlling section 10 A of the controller 10 adjusts operating conditions for the PEFC 1 based on the estimated remaining operating time ⁇ T 0 . For example, a life prolongation operation mode is selected and the oxidizing gas feeder 3 , the fuel gas feeder 2 and the output power of the PEFC 1 are controlled. In the life prolongation operation mode for instance, the controlling section 10 A controls the oxidizing gas feeder 3 and the fuel gas feeder 2 such that the pressure loss of the oxidizing gas and the pressure loss of the fuel gas are equalized between the inlet and outlet of the PEFC 1 , or alternatively such that the supply pressure of the oxidizing gas and the fuel gas is suppressed thereby restricting the pressure losses of these gases between the inlet and outlet of the PEFC 1 . This enables substantially automatic prolongation of the service life of the fuel cell system 100 with the result that the burden imposed on the user of the fuel cell system 100 in terms of operation management can be reduced.
- the controlling section 10 A of the controller 10 alters the detecting time interval At according to the locus of the transition line of the detected airtightness value Q relative to the operating time T. For example, as shown in FIG. 2 ( a ), where the detected airtightness value Q transitions at a constant pace, ⁇ t is kept constant. As shown in FIG. 2 ( b ), where the detected airtightness value Q changes so as to gradually become stable, ⁇ t is changed so as to increase gradually. As shown in FIG. 2 ( c ), where the change of the detected airtightness value Q gradually becomes significant, ⁇ t is changed so as to decrease gradually. This makes it possible to eliminate operation for obtaining unnecessary detected airtightness values without affecting the acquisition of the transition line of the detected airtightness value Q, so that the operation of the fuel cell system 100 can be rationalized.
- FIG. 3 is a schematic diagram illustrating a fuel cell system according to a second embodiment of the invention.
- the parts that are substantially equivalent or function similarly to those of FIG. 1 are identified with the same reference numerals as in FIG. 1 , and an explanation of them is omitted in this embodiment.
- the structure of the fuel cell system 101 of the second embodiment does not differ from that of the fuel cell system 100 of the first embodiment except that the flow rate detector 5 is provided not in the fuel gas feeding passage 6 but in the oxidizing gas feeding passage 7 and the passage blocking device 4 is provided not in the fuel gas exhaust passage 8 but in the oxidizing gas exhaust passage 9 .
- the airtightness value detecting operation of the fuel cell system 101 of the second embodiment does not differ from that of the fuel cell system 100 of the first embodiment except that the controller 10 controls the oxidizing gas feeder 3 in place of the fuel gas feeder 2 .
- the passage blocking device 4 is controlled to block off the oxidizing gas feeder 9 and the oxidizing gas feeder 3 is controlled to supply the fuel gas at constant pressure. Then, the controller 10 obtains the detected airtightness value Q based on the detected value of the flow rate detector 5 .
- the controller 10 controls the fuel cell system 101 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment.
- the airtightness of the PEFC 1 is accordingly detected using not the fuel gas but the oxidizing gas, so that the risk of damage to the fuel cell system 101 owing to abnormal combustion of the fuel gas during the airtightness value detecting operation can be avoided.
- FIG. 4 is a schematic diagram illustrating a fuel cell system according to a third embodiment of the invention.
- the parts that are substantially equivalent or function similarly to those of FIG. 1 are identified with the same reference numerals as in FIG. 1 , and an explanation of them is omitted in this embodiment.
- the structure of the fuel cell system 102 of the third embodiment does not differ from that of the fuel cell system 100 of the first embodiment except that the fuel cell system 102 is provided with a test gas feeder 20 , a test gas passage 22 through which a test gas is supplied from the test gas feeder 20 , and a switching device 21 disposed in the fuel gas feeding passage 6 in the vicinity of the inlet of the PEFC 1 , for switching a gas supply source and that the flow rate detector 5 is provided not in the fuel gas passage 6 but in the test gas passage 22 .
- the test gas feeder 20 is composed of a steel cylinder charged with the test gas under pressure and a pressure regulating valve attached to the vent of the steel cylinder.
- the test gas may be any gases having chemical compositions that do not cause a chemical reaction with the membrane electrolyte assembly 1 A.
- the test gas contains at least one kind of gas selected from the group consisting of, for example, fuel gas, oxidizing gas, inactive gas, carbon dioxide, and methane mixed gas.
- the methane mixture gas is a natural-gas-basis gas containing methane as a chief component, ethane, propane, and butane.
- the methane mixture gas may be “13A gas” used in the gas supply infrastructure in Japan.
- the inactive gas is a gas composed of chemically stable components such as nitrogen, argon and helium. Such a test gas does not cause damage to the inside of the fuel cell such as deterioration in catalytic power.
- the switching device 21 is composed of a three-way valve. Alternatively, it may be composed of a plurality of electric-operated valves. That is, the switching device 21 should just be constructed such that it selectively connects the test gas feeder 22 and a fuel gas feeder side portion 6 A of the fuel gas feeding passage 6 to a PEFC 1 side portion 6 B of the fuel gas feeding passage 6 .
- the airtightness value detecting operation of the fuel cell system 102 of the third embodiment does not differ from that of the fuel cell system 100 of the first embodiment except that the controller 10 controls the switching device 21 and the test gas feeder 20 in place of the fuel gas feeder 2 . More specifically, when the oxidizing gas feeder 3 is in its stop state, the passage blocking device 4 is controlled to block off the fuel gas exhaust passage 8 and the switching device 21 is controlled to disconnect the fuel gas feeder 2 from the PEFC 1 while connecting the test gas passage 22 to the PEFC 1 . Then, the test gas feeder 20 is controlled to supply the test gas to the PEFC 1 at constant pressure. Thereafter, the controller 10 obtains the detected airtightness value Q based on the detected value of the flow rate detector 5 .
- the controller 10 controls the fuel cell system 102 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment.
- the fuel cell system 102 can detect the airtightness of the PEFC 1 without use of a special power source for test gas supply. As a result, the airtightness of the PEFC 1 can be promptly, accurately detected while the fuel gas feeder 2 and the oxidizing gas feeder 3 being stopped, with a simplified structure and operation.
- FIG. 5 is a schematic diagram illustrating a fuel cell system according to a fourth embodiment of the invention.
- the parts that are substantially equivalent or function similarly to those of FIG. 4 are identified with the same reference numerals as in FIG. 4 , and an explanation of them is omitted in this embodiment.
- the structure of the fuel cell system 103 of the fourth embodiment does not differ from those of the fuel cell systems 101 , 102 of the second and third embodiments except that the fuel cell system 103 is provided with the test gas feeder 20 , the test gas passage 22 through which the test gas is supplied from the test gas feeder 20 , and the switching device 21 disposed in the oxidizing gas feeding passage 7 in the vicinity of the inlet of the PEFC 1 , and that the flow rate detector 5 is provided not in the oxidizing gas passage 7 but in the test gas passage 22 .
- the airtightness value detecting operation of the fuel cell system 103 of the fourth embodiment does not differ from that of the fuel cell system 101 of the second embodiment except that the controller 10 controls the switching device 21 and the test gas feeder 20 instead of the oxidizing gas feeder 3 .
- the passage blocking device 4 is controlled to block off the oxidizing gas exhaust passage 9 and the switching device 21 is controlled to disconnect the oxidizing gas feeder 3 from the PEFC 1 while connecting the test gas feeder 22 to the PEFC 1 .
- the test gas feeder 20 is controlled to supply the test gas to the PEFC 1 at constant pressure.
- the controller 10 obtains the detected airtightness value Q based on the detected value of the flow rate detector 5 .
- the controller 10 controls the fuel cell system 103 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment.
- the airtightness of the PEFC 1 is accordingly detected without use of a special power source for test gas supply similarly to the fuel cell system 102 of the third embodiment.
- the airtightness of the PEFC 1 can be promptly, accurately detected while the fuel gas feeder 2 and the oxidizing gas feeder 3 being stopped, with a simplified structure and operation.
- FIG. 6 is a schematic diagram illustrating a fuel cell system according to a fifth embodiment of the invention.
- the parts that are substantially equivalent or function similarly to those of FIG. 1 are identified with the same reference numerals as in FIG. 1 , and an explanation of them is omitted in this embodiment.
- the structure of the fuel cell system 110 of the fifth embodiment does not differ from that of the fuel cell system 100 of the first embodiment except that the fuel cell system 110 is provided with a second passage blocking device 31 disposed in the oxidizing gas exhaust passage 9 and a third passage blocking device 32 disposed in the oxidizing gas feeding passage 7 in addition to the passage blocking device (the first passage blocking device) 4 disposed in the fuel gas exhaust passage 8 .
- the controller 10 obtains two kinds of airtightness values, that is, a first detected airtightness value Qa and a second detected airtightness value Qb when the oxidizing gas feeder 3 is in its stop state. More concretely, the controller 10 controls the first passage blocking device 4 to block off the fuel gas exhaust passage 8 ; controls the second passage blocking device 31 to block off the oxidizing gas exhaust passage 9 ; and controls the third passage blocking device 32 to block off the oxidizing gas feeding passage 7 . Then, the controller 10 controls the fuel gas feeder 2 thereby supplying the fuel gas at constant pressure. If gas leakage occurs in the PEFC 1 , the fuel gas feeder 2 will continuously supply the fuel gas to the PEFC 1 . Meanwhile, the controller 10 obtains the first detected airtightness value Qa based on the detected value of the flow rate detector 5 .
- the controller 10 controls the first passage blocking device 4 to block off the fuel gas exhaust passage 8 ; controls at least either the second passage blocking device 31 or the third passage blocking device 32 to open at least either the oxidizing gas feeding passage 7 or the oxidizing gas exhaust passage 9 . Then, the controller 10 controls the fuel gas feeder 2 to supply the fuel gas at constant pressure while obtaining the second detected airtightness value Qb based on the detected value of the flow rate detector 5 .
- the first detected airtightness value Qa may be obtained after obtaining the second detected airtightness value Qb.
- the first detected airtightness value Qa represents the leakage from the PEFC 1 to the outside
- the differential detected airtightness value Qc represents the leakage from the fuel gas passage 1 D to the oxidizing gas passage 1 E, that is, cross-leakage. Since this cross leakage varies mainly depending on the degree of damage to the polymer electrolyte membrane of the membrane electrode assembly 1 A, the fluctuation of the differential airtightness value Qc precisely reflects the degree of damage to the polymer electrolyte membrane. Therefore, the fuel cell system 110 can detect the degree of damage to the polymer electrolyte membrane with high accuracy.
- the controller 10 controls the fuel cell system 110 based on the differential airtightness value Qc so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment.
- the fuel gas was supplied under a pressure of 2 kPa after blocking off the fuel gas exhaust passage 8 , the oxidizing gas exhaust passage 9 and the oxidizing gas feeding passage 7 .
- the differential airtightness value Qc was 18 ml/min.
- the output voltage of the PEFC 1 when connected to a general-type electric load was 0.6V.
- Another test was conducted by use of a PEFC 1 having one membrane electrode assembly 1 A in which the polymer electrolyte membrane has no holes through which the fuel gas can pass.
- the fuel gas was supplied under a pressure of 2 kPa after blocking off the fuel gas exhaust passage 8 , the oxidizing gas exhaust passage 9 and the oxidizing gas feeding passage 7 .
- the differential airtightness value Qc was 0 ml/min.
- the output voltage of the PEFC 1 when connected to a general-type electric load was 0.8V.
- a further test was conducted by use of a PEFC 1 having 52 membrane electrode assemblies 1 A stacked therein.
- the fuel gas was supplied under a pressure of 2 kPa after blocking off the fuel gas exhaust passage 8 , the oxidizing gas exhaust passage 9 and the oxidizing gas feeding passage 7 .
- the differential airtightness value Qc was 0 ml/min.
- the invention was able to detect the degree of damage to the polymer electrolyte membrane with high accuracy.
- the decrease in the output voltage is about 0.2V. Since the PEFC 1 generally has about 50 membrane electrode assemblies 1 A stacked therein, the output voltage of the PEFC 1 is several tens of volts. In view of this, the decrease (about 0.2V) in the output voltage is minute. In addition, it is assumable that other various factors than damage to the polymer electrolyte membrane may cause decreases in the output voltage.
- the method of detecting damage to the polymer electrolyte membrane from the differential airtightness value Qc has higher accuracy compared to the method of detecting it from changes in the output voltage.
- the invention was able to detect the degree of damage to the polymer electrolyte membrane quickly. Specifically, it took about 3 minutes to obtain the differential airtightness value Qc after blocking off the fuel gas exhaust passage 8 , the oxidizing gas exhaust passage 9 and the oxidizing gas feeding passage 7 .
- FIG. 7 is a schematic diagram illustrating a fuel cell system according to a sixth embodiment of the invention.
- the parts that are substantially equivalent or function similarly to those of FIG. 6 are identified with the same reference numerals as in FIG. 6 , and an explanation of them is omitted in this embodiment.
- the structure of the fuel cell system 111 of the sixth embodiment does not differ from that of the fuel cell system 110 of the fifth embodiment except that the flow rate detector 5 is provided not in the fuel gas feeding passage 6 but in the oxidizing gas feeding passage 7 and the third passage blocking device 32 is provided not in the oxidizing gas feeding passage 7 but in the fuel gas feeding passage 6 .
- the airtightness value detecting operation of the fuel cell system 111 of the sixth embodiment does not differ from that of the fuel cell system 110 of the fifth embodiment except that the controller 10 controls the oxidizing gas feeder 3 instead of the fuel gas feeder 2 .
- the controller 10 controls the first passage blocking device 4 to block off the oxidizing gas exhaust passage 9 ; controls the second passage blocking device 31 to block off the oxidizing gas exhaust passage 8 ; and controls the third passage blocking device 32 to block off the fuel gas feeding passage 6 . Then, the controller 10 controls the oxidizing gas feeder 3 to supply the oxidizing gas at constant pressure and obtains the first detected airtightness value Qa similarly to the fuel cell system 110 .
- the controller 10 controls the first passage blocking device 4 to block off the oxidizing gas exhaust passage 9 and controls at least either the second passage blocking device 31 or the third passage blocking device 32 to open at least either the fuel gas feeding passage 6 or the fuel gas exhaust passage 8 . Then, the controller 10 controls the oxidizing gas feeder 3 to supply the oxidizing gas at constant pressure while obtaining the second detected airtightness value Qb based on the detected value of the flow rate detector 5 .
- the controller 10 controls the fuel cell system 111 based on the differential airtightness value Qc so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment.
- the fuel cell system 111 can promptly, accurately detect the airtightness of the PEFC 1 and more particularly the degree of damage to the polymer electrolyte membrane with a simplified structure and operation.
- the risk of damage to the fuel cell system 101 caused by abnormal combustion of the fuel gas during the airtightness value detecting operation can be avoided.
- the fuel cell system of the invention is suitably used in a wide range of applications as it enables prompt, accurate detection of the airtightness of a fuel cell with a simple arrangement.
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Abstract
Description
- The present invention relates to a fuel cell system adapted for use in portable power supplies, power supplies for electric vehicles, cogeneration systems and others. More particularly, the present invention relates to a fuel cell system equipped with a fuel cell having polymer electrolyte membranes.
- Fuel cells are designed to cause an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air, thereby simultaneously generating electric power and heat. As an example of fuel cells, there are known polymer electrolyte fuel cells having the following structure.
- A catalytic reaction layer containing carbon powder which carries a platinum group metal catalyst as a chief component is formed on both sides of a polymer electrolyte membrane, for selectively transporting hydrogen ions. On the outer face of each catalytic reaction layer, a diffusion layer is formed which is made of, for example, carbon paper or carbon cloth having both fuel gas permeability and electronic conductive properties. These diffusion layers and catalytic reaction layers are combined thereby forming a membrane electrode assembly.
- For power collection, this membrane electrode assembly is sandwiched by separators made from conductive materials such as glass-like carbon or metal. These separators are provided with gas passages that are formed so as to expose the aforesaid fuel gas and oxidizing gas to the membrane electrode assembly and with cooling fluid passages that are formed so as to control the temperature of the membrane electrode assembly, in other words, so as to recover the heat generated together with electric power. Generally, a gas sealing material or gasket is provided between the membrane electrode assembly and each separator, for preventing leakage of the supplied fuel gas and oxidizing gas to the outside and mingling of these gases.
- The membrane electrode assembly sandwiched between the separators serves as a basic unit. In a polymer electrolyte fuel cell, such membrane electrode assemblies are stacked in numbers corresponding to the design output of electric power or heat of the polymer electrolyte fuel cell.
- In a fuel cell system, a fuel gas feeder for supplying the fuel gas and an oxidizing gas feeder for supplying the oxidizing gas are connected to the polymer electrolyte fuel cell (hereinafter abbreviated as PEFC). In addition, there are provided, according to need, an exhaust heat recovery system for recovering generated heat and a power converting system for making the electric power generated in the PEFC usable. Further, a control unit for controlling these systems is provided.
- The fuel gas feeder includes a hydrogen generator for generating a hydrogen-rich gas (i.e., the fuel gas) by reforming hydrocarbon fuel such as natural gas, propane gas and gasoline to output to the PEFC. The oxidizing gas feeder consists of, for example, a blower or fan and supplies air to the PEFC as the oxidizing gas. In some cases, the fuel gas feeder and oxidizing gas feeder are equipped with a humidifier for controlling the amount of moisture contained in the fuel gas or oxidizing gas to be supplied to the PEFC. The exhaust heat recovery system is composed of a heat exchanger and a hot water tank. The heat exchanger recovers the heat retained by, for instance, the cooling fluid flowing in the cooling fluid passage by means of water to produce hot water. The hot water tank stores this hot water. The power converting system includes an inverter for converting a dc power generated by the PEFC into an ac power and a transformer.
- As described earlier, within the PEFC, the fuel gas or oxidizing gas flows in the route made by the gas passages formed in the gasket, polymer electrolyte membrane and separators. However, the constituents of the gas passages degrade causing, for instance, increases in the gas permeation of the polymer electrolyte membrane and hardening of the gasket, so that the airtightness of the gas passages decreases. This entails leakage of the fuel gas or oxidizing gas to the outside or mingling of these gases. The leakage of the fuel gas to the outside and the mingling of the fuel gas/the oxidizing gas may trigger off abnormal combustion or an explosion. Even if they do not result in abnormal combustion or an explosion, the leakage to the outside causes an insufficient supply of the fuel gas or oxidizing gas to the catalyst reaction layer and, in consequence, insufficient exposure of the gas to the membrane electrode assembly. As a result, the polarization resistance of the electrode reaction increases with a decrease in the output of the PEFC.
- To prevent damage to the PEFC and a decrease in the performance of the fuel cell, a fuel cell system or detection method is required which enables detection of the airtightness of the passages in which the fuel gas or oxidizing gas flows. General type pressure vessels usually employ “escape probability detection” in which pressure gas is sealed in a vessel and the time taken for pressure to decrease or a decrease in pressure within a specified period of time is detected. However, the detection method, in which pressurized gas is sealed in a fuel cell system and the progress of decreasing of pressure is observed, can not be practically applied to fuel cell systems, because they are operated as needed and therefore detection of the airtightness of the passages for the fuel gas or oxidizing gas in the PEFC has to be promptly performed so as not to hinder the operation of the PEFC. Apart from the above method, there have been heretofore proposed several fuel cell systems and methods for detecting the airtightness of a fuel cell. Typical techniques are as follows.
- In the fuel cell system disclosed in
Patent Document 1, the consumption of the fuel gas is calculated based on the output current of the fuel cell and the pressure of the fuel gas within the fuel gas cylinder is calculated from the fuel gas consumption. Then, the presence/absence of fuel gas leakage is determined from a comparison between this calculated pressure value and a detected pressure value that is obtained from actual detection with a pressure sensor. - According to the diagnosis method disclosed in
Patent Document 2, a hydrogen-containing gas and an oxygen-containing gas are supplied to the fuel electrode and oxidant electrode, respectively, of the fuel cell and a rapid change in the generated voltage of the fuel cell caused by a decrease in the supply of the oxygen-containing gas is detected. Then, the leakage of hydrogen in the fuel cell is calculated from the relationship between the oxygen-containing gas and the generated voltage. - There have been proposed fuel cell systems that make a judgment on deterioration of a fuel cell. According to this technique, the condition of a fuel cell is detected in various ways thereby determining whether or not the fuel cell has deteriorated and the result of the determination is fed back to the control mechanism for the fuel cell to restrain the progression of the deterioration so that the durability and service life of the fuel cell and the fuel cell system are increased.
- For instance,
Patent Document 3 discloses a PEFC operating method according to which a judgment is made to check whether the operational state of the PEFC is in a performance decreasing zone by analyzing impurity ions contained in the moisture of a fuel gas humidifying water or the like from the PEFC. If it is determined that the operational state is in the performance decreasing zone, the operation of the PEFC is brought to a stop or operating conditions for the PEFC are limited, thereby making the operational state of the PEFC get out of the performance decreasing zone. -
Patent Document 4 discloses a method of estimating the service life of a fuel cell. According to this method, a fuel cell is operated in several basic operating patterns and its service life is estimated based on the time taken for power generation and the change rate of output voltage in each basic operation pattern. - Patent Document 1: Japanese Laid-Open Patent Application Publication No. Hei 11-224681
- Patent Document 2: Japanese Laid-Open Patent Application Publication No. Hei 9-27336
- Patent Document 3: Japanese Laid-Open Patent Application Publication No. 2004-127548
- Patent Document 4: Japanese Laid-Open Patent Application Publication No. Hei 11-97049
- Incidentally, in a fuel cell, the vapor contained in the gas supplied to the fuel cell becomes flocculated water in the oxidizing gas passage or fuel gas passage and this water dwells in the oxidizing gas passage or fuel gas passage, hampering a flow of the gas, which results in a decrease in the output of the fuel cell. To prevent this, it is usual to perform purging treatment in which the residual gas or moisture remaining in the fuel cell is purged in the course of the start-up, stop or operation of the fuel cell. In a purging technique, a dried fuel gas, for instance, is supplied to the fuel cell thereby forcing the flocculated water out of the fuel cell. Therefore, the fuel cell system disclosed in
Patent Document 1 has the disadvantage that where a fuel gas is used for the purging of the residual gas or water from the fuel cell, the consumption of the fuel gas used for the purging treatment is counted in the measurement of leakage so that the accuracy of the detection of leakage in the fuel cell decreases. - In the diagnosis method disclosed in
Patent Document 2, the generated voltage of the fuel cell is measured while gradually reducing the amount of oxygen-containing gas supplied to the cathode, yet changes in the generated voltage measured according to changes in the supply of the gas are so small that this method has much to do with detection accuracy. In addition, various factors such as decreasing electrode performance are involved with fluctuations in the output electric power of a fuel cell. In view of this, the method of estimating the leakage of the fuel gas based on voltage generation has left room for improvements in accuracy. - In a PEFC, fluoride ions are generated when the polymer electrolyte membrane decomposes. Fluoride ions are strongly acidic and therefore corrode metals. The PEFC operating method disclosed in
Patent Document 3 utilizes this phenomena and determines deterioration of a PEFC by detecting ions such as metal ions in moisture such as produced water and humidifying water. However, physical damage to the polymer electrolyte membrane also causes a decrease in the airtightness of the passage for the fuel gas or oxidizing gas in a PEFC. When the polymer electrolyte membrane gets such damage, generation of metal ions or fluoride ions are unlikely to occur. Therefore, the method of determining deterioration of a PEFC from detection of metal ions or fluoride ions is not suited for detection of the airtightness of a PEFC and, more precisely, the airtightness of the passage where the fuel gas or oxidizing gas flows. - The catalytic power of the electrode catalyst (e.g., platinum) of a fuel cell is affected by various environmental conditions such as load fluctuations in the fuel cell, the gas components contained in the fuel cell, the partial pressure of the gas components of the fuel cell and temperature/humidity conditions during suspension. Specifically, the electrode surface area of a fuel cell varies according to the history of the fuel cell and in fact, it is difficult to estimate the service life of a fuel cell with high accuracy from the operating patterns of the fuel cell. Therefore, the estimation of the service life of a fuel cell by approximating it from one or plural basic operation patterns of the fuel cell has left room for improvements.
- As described above, the prior art techniques have proved unsuccessful in providing satisfactory accuracy in quick detection of the airtightness of the passage of the fuel cell where the fuel gas or oxidizing gas flows and therefore left room for improvements. Regarding the judgment on the deterioration of a fuel cell, the acquisition of the basic operating patterns of a fuel cell requires much time and labor and the provision of a special apparatus such as a detector for detecting metal ions or fluoride ions incurs additional costs.
- The invention is directed to overcoming the above problems and a primary object of the invention is therefore to provide a fuel cell system that is constructed in simple structure and capable of promptly, accurately detecting the airtightness of a fuel cell as a deterioration information of a fuel cell.
- In accomplishing the above object, there has been provided, in accordance with a first aspect of the invention, a fuel cell system comprising:
- a fuel cell having a fuel gas passage and an oxidizing gas passage which are so formed as to be in contact with an anode and a cathode respectively, the anode and the cathode being formed on opposed sides of a polymer electrolyte membrane respectively;
- a fuel gas feeder configured to feed a fuel gas to the fuel gas passage;
- an oxidizing gas feeder configured to feed an oxidizing gas to the oxidizing gas passage;
- a fuel gas exhaust passage configured to flow an excessive fuel gas discharged from the fuel gas passage;
- an oxidizing gas exhaust passage configured to flow an excessive oxidizing gas discharged from the oxidizing gas passage;
- a test gas feeder configured to feed a test gas to either the fuel gas passage or the oxidizing gas passage;
- a flow rate detector configured to detect a flow rate of the test gas;
- a first passage blocking device configured to block off either the fuel gas exhaust passage or the oxidizing gas exhaust passage to which the test gas is fed; and
- a controller;
- wherein the controller controls the first passage blocking device to block off the passage and controls the test gas feeder to feed the test gas to the fuel cell, thereby obtaining a detected value from the flow rate detector or an airtightness value that is numerical information into which the detected value is converted. The fuel cell system of the above structure can promptly, accurately detect the airtightness of the fuel cell as a deterioration information of the fuel cell by the simplified structure and operation of the flow rate detector, the passage blocking device and the test gas feeder.
- According to a second aspect of the invention, the test gas feeder of the fuel cell system may be either the fuel gas feeder or the oxidizing gas feeder. In this arrangement, the test gas feeder can be eliminated, which enables prompt, accurate detection of the airtightness of the fuel cell with a more simplified structure and operation.
- According to a third aspect of the invention, the fuel cell system may further comprise a second passage blocking device configured to block off a gas passage connected to an outlet side of either the fuel gas passage or the oxidizing gas passage which is not fed with the test gas; and a third passage blocking device configured to block off a gas passage connected to an inlet side of either the fuel gas passage or the oxidizing gas passage which is not fed with the test gas, wherein the controller controls the first to third passage blocking devices to block off their associated passages, thereby obtaining a first airtightness value of the flow rate detector; controls the first passage blocking device to block off its associated passage while controlling the second and third passage blocking devices so as not to block off either of their associated passages, thereby obtaining a second airtightness value of the flow rate detector; and obtains a difference between the first airtightness value and the second airtightness value. The fuel cell system of this structure can obtain leakage from the fuel gas passage to the oxidizing gas passage and therefore can perform prompt, accurate detection of the airtightness of the fuel cell and more particularly the degree of damage to the polymer electrolyte membrane with a more simplified structure and operation.
- According to a fourth aspect of the invention, the test gas feeder of the fuel cell system may be either the fuel gas feeder or the oxidizing gas feeder. In this arrangement, the test gas feeder can be eliminated, which enables prompt, accurate detection of the airtightness of the fuel cell with a more simplified structure and operation.
- According to a fifth aspect of the invention, there is provided a fuel cell system in which the test gas may be composed of chemical components that do not cause a chemical reaction within the fuel cell. This prevents damages in the fuel cell such as decrease of the catalytic power by the test gas.
- With a view to ensuring the effects of the invention described above, there is provided a fuel cell system according to a sixth aspect of the invention in which the test gas may contain at least one selected from a group consisting of fuel gas, oxidizing gas, inactive gas, carbon dioxide and methane mixed gas.
- According to a seventh aspect of the invention, the controller of the fuel cell system may have an output section for outputting the airtightness value to outside. With this arrangement, the user of the fuel cell system can quickly accurately obtain the degree of airtightness of the fuel cell so that a damage to the fuel cell system and a decrease in its performance can be prevented beforehand.
- According to an eighth aspect of the invention, the controller of the fuel cell system may have a memory section for prestoring reference airtightness values for evaluation of the airtightness value, and the controller makes a comparison between the airtightness value and the reference airtightness values thereby evaluating the airtightness of the fuel cell. This enables the fuel cell system to use the reference airtightness values as a criterion of judgment so that the condition of the fuel cell in terms of airtightness can be properly evaluated.
- According to a ninth aspect of the invention, the controller of the fuel cell system may have an output section for outputting the airtightness value which has been evaluated to outside. With this arrangement, the user of the fuel cell system can obtain the result of the evaluation of the airtightness of the fuel cell so that he can easily consider and implement measures to prevent damage to the fuel cell system and a decrease in its performance.
- According to a tenth aspect of the invention, the controller of the fuel cell system may adjust operating conditions for the fuel cell based on the evaluated airtightness value. This makes the fuel cell system automatically prolong the service life of the fuel cell, using the reference airtightness values as a criterion of judgment.
- According to an eleventh aspect of the invention, the controller of the fuel cell system may obtain the airtightness value at specified detection time intervals and accumulatively stores the obtained airtightness values in the memory section in relation to an operating time of the fuel cell; and wherein the controller obtains a transition line of the airtightness values relative to the operating time by a statistical approximation method and estimates a deterioration in the airtightness of the fuel cell based on a comparison between the transition line and the reference airtightness values. This enables the fuel cell system to promptly accurately detect the airtightness of the fuel cell and predict the service life of the fuel cell system, with a simplified structure and operation.
- According to a twelfth aspect of the invention, the controller of the fuel cell system may alter the detection time intervals according to a locus of the transition line. This makes it possible to eliminate operation for obtaining unnecessary detected airtightness values without affecting the acquisition of the transition line of detected airtightness values, so that the operation of the fuel cell system can be rationalized.
- According to a thirteenth aspect of the invention, the reference airtightness values stored in the memory section of the controller of the fuel cell system may include a limit airtightness value representative of a service limit of the fuel cell; and wherein the controller extrapolates the transition line to obtain an estimated remaining operation time of the fuel cell left before the transition line reaches the limit airtightness value. This enables the fuel cell system to estimate a service life of the fuel cell system based on concrete numerical information.
- According to a fourteenth aspect of the invention, the controller of the fuel cell system may have an output section for outputting the estimated remaining operation time to outside. This enables the user of the fuel cell system to obtain concrete numerical information on the remaining service life of the fuel cell, so that he can preliminarily consider countermeasures against damage to the fuel cell system and a decrease in its performance, can select a proper operation mode of the fuel cell and can make an operation schedule for the fuel cell.
- According to a fifteenth aspect of the invention, the controller of the fuel cell system may adjust operating conditions for the fuel cell based on the estimated remaining operation time. In this fuel cell system, the service life of the fuel cell can be substantially automatically prolonged so that the burden imposed on the user of the fuel cell system in terms of operation management can be reduced.
- According to a sixteenth aspect of the invention, the controller of the fuel cell system may obtain the detected value or the airtightness value when starting up and/or stopping the operation of the fuel cell. This enables the fuel cell system to substantially automatically detect the airtightness of the fuel cell.
- These objects as well as other objects, features and advantages of the invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings.
- The fuel cell system of the invention has the effect of promptly accurately detecting the airtightness of the fuel cell, with a simple structure.
- [
FIG. 1 ]FIG. 1 is a schematic diagram illustrating a fuel cell system according to a first embodiment of the invention. - [
FIG. 2 ]FIG. 2 is graphs each conceptually showing a transition line of a detected airtightness value relative to the operating time of a PEFC, whereinFIG. 2 (a) is a graph showing a case where the detected airtightness value varies at a constant pace,FIG. 2 (b) is a graph showing a case where the detected airtightness value varies so as to gradually become stable, andFIG. 2 (c) is a graph showing a case where the change of the detected airtightness value gradually becomes significant. - [
FIG. 3 ]FIG. 3 is a schematic diagram illustrating a fuel cell system according to a second embodiment of the invention. - [
FIG. 4 ]FIG. 4 is a schematic diagram illustrating a fuel cell system according to a third embodiment of the invention. - [
FIG. 5 ]FIG. 5 is a schematic diagram illustrating a fuel cell system according to a fourth embodiment of the invention. - [
FIG. 6 ]FIG. 6 is a schematic diagram illustrating a fuel cell system according to a fifth embodiment of the invention. - [
FIG. 7 ]FIG. 7 is a schematic diagram illustrating a fuel cell system according to a sixth embodiment of the invention. - 1: polymer electrolyte fuel cell (PEFC)
- 1A: membrane electrode assembly
- 1B: anode separator
- 1C: cathode separator
- 1D: fuel gas passage
- 1E: oxidizing gas passage
- 2: fuel gas feeder
- 3: oxidizing gas feeder
- 4: passage blocking device (first passage blocking device)
- 5: flow rate detector
- 6: fuel gas feeding passage
- 6A: fuel gas feeder side portion
- 6B: PEFC1 side portion
- 7: oxidizing gas feeding passage
- 8: fuel gas exhaust passage
- 9: oxidizing gas exhaust passage
- 10: controller
- 10A: controlling section
- 10B: memory section
- 10C: input section
- 10D: output section
- 20: test gas feeder
- 21: switching device
- 22: test gas passage
- 31: second passage blocking device
- 32: third passage blocking device
- 100, 101: fuel cell system
- T: operating time
- Q: airtightness value
- Δt: detection time interval
- Δt0: estimated remaining operating time
- Q0: limit airtightness value
- Q100: initial airtightness value
- Referring now to the accompanying drawings, the fuel cell system and operation method of the invention will be hereinafter described in detail according to preferred embodiments. In the following description, those parts that are substantially equivalent or function substantially similarly to one another are indicated by the same numerals and redundant explanations are avoided.
-
FIG. 1 is a schematic diagram illustrating a fuel cell system according to a first embodiment of the invention. - First of all, there will be explained the structure of the
fuel cell system 100 according to the first embodiment. - The
fuel cell system 100 has afuel gas feeder 2 and an oxidizinggas feeder 3. Thefuel gas feeder 2 is connected to a fuelgas feeding passage 6 whereas the oxidizinggas feeder 3 is connected to an oxidizinggas feeding passage 7. - The fuel
gas feeding passage 6 is connected to a polymer electrolyte fuel cell (hereinafter referred to as “PEFC”) 1, and a fuel gas is supplied from thefuel gas feeder 2 to the PEFC1. The oxidizinggas feeding passage 7 is connected to thePEFC 1, and an oxidizing gas is supplied from the oxidizinggas feeder 3 to the PEFC1. - The fuel
gas feeding passage 6 is provided with aflow rate detector 5. Theflow rate detector 5 is constituted by, for instance, a flowmeter and detects the flow rate of a fluid that flows in a target passage that is the fuelgas feeding passage 6 herein. - In the PEFC1, a
membrane electrode assembly 1A is sandwiched between a pair of separators, namely, ananode separator 1B and acathode separator 1C. Afuel gas passage 1D is defined by themembrane electrode assembly 1A and a groove formed on the surface of theanode separator 1B. Similarly, an oxidizinggas passage 1E is defined by themembrane electrode assembly 1A and a groove formed on the surface of thecathode separator 1C. Within the PEFC1, thefuel gas passage 1D and the oxidizinggas passage 1E are accordingly separated from each other by themembrane electrode assembly 1A having a polymer electrolyte membrane. - The fuel
gas feeding passage 6 is connected to one end of thefuel gas passage 1D to supply the fuel gas to thefuel gas passage 1D. The oxidizinggas feeding passage 7 is connected to one end of the oxidizinggas passage 1E to supply the oxidizing gas to the oxidizinggas passage 1E. The fuel gas and oxidizing gas, which are supplied to thefuel gas passage 1D and oxidizinggas passage 1E respectively, cause a chemical reaction, thereby generating electric power and heat. - A fuel
gas exhaust passage 8 is connected to the other end of thefuel gas passage 1D. The redundant fuel gas, which has not chemically reacted in the anode, is discharged from the other end of thefuel gas passage 1D to the fuelgas exhaust passage 8. An oxidizinggas exhaust passage 9 is connected to the other end of the oxidizinggas passage 1E. The redundant oxidizing gas, which has not chemically reacted in the cathode, is discharged from the other end of the oxidizinggas passage 1E to the oxidizinggas exhaust passage 9. - The fuel
gas exhaust passage 8 is provided with apassage blocking device 4. Thepassage blocking device 4 is configured to block off a flow of fluid in a target passage that is the fuelgas exhaust passage 8 herein. In this embodiment, thepassage blocking device 4 has an electric-operated valve whose valve disc blocks the passage. - The
fuel cell system 100 has acontroller 10. Thecontroller 10 has a controllingsection 10A that is constituted by a controlling member such as micro computers; amemory section 10B that is constituted by a storing member such as memories; aninput section 10C that is constituted by an input unit such as key boards and touch panels; and anoutput section 10D that is constituted by an output unit such as monitors. Thecontroller 10 controls the operation of thefuel cell system 100. More particularly, thecontroller 10 controls thepassage blocking device 4 and a raw material gas feeder 14 to obtain a detected value with theflow rate detector 5. - The
memory section 10B stores reference airtightness values used for evaluation of the airtightness of the PEFC1. Specifically, an initial airtightness value Q100 of the PEFC1 in the initial (starting) stage of the operation; a limit airtightness value Q0 of the PEFC1 in the stage where a functional disturbance appears in the PEFC 1 (i.e., in the service limit stage); and intermediate airtightness values Q80, Q60, Q40, Q20 which are intermediate values between the initial airtightness value Q100 and the limit airtightness value Q0 are input through theinput section 10D and stored in thememory section 10B beforehand. - The airtightness value Q is numerical information such as a detected value (e.g., a current signal value and a voltage signal value) obtained by the
flow rate detector 5 or numerical information such as a flow rate value obtained by converting the detected value. The airtightness value Q is used as deterioration information indicative of the degree of deterioration of the PEFC1. - The meaning of the controller as stated herein does not only indicate a single controller but includes a controller group consisting of a plurality of controllers that cooperate with one another to execute control. Therefore, the
controller 10 is not necessarily constituted by a single controller but may be constituted by a plurality of controllers that are disposed at discrete positions so as to control the operation of thefuel cell system 100 in cooperation with one another. For instance, theoutput section 10D may be designed such that its output is transmitted by a data terminal so as to be displayed on a mobile device. - Next, the airtightness value detecting operation of the
fuel cell system 100, which is one of the features of the invention, will be explained. This airtightness value detecting operation is performed, being controlled by thecontroller 10. - While the oxidizing
gas feeder 3 is in a stopped state, thecontroller 10 first controls thepassage blocking device 4 to block off the fuelgas exhaust passage 8 and controls thefuel gas feeder 2 to supply the fuel gas at constant pressure. For example, in either or both of the start-up operation and stop operation of the PEFC1, thecontroller 10 executes the airtightness value detecting operation of thefuel cell system 100. Thereby, the airtightness of the PEFC1 can be substantially automatically detected. - If gas leakage occurs in the PEFC1, the
fuel gas feeder 2 will continue to supply the fuel gas to the PEFC1. Then, theflow rate detector 5 detects the flow rate of the fuel gas. In accordance with a detected value of theflow rate detector 5, thecontroller 10 obtains an airtightness value based on a detected value of theflow rate detector 5, i.e., a detected airtightness value Q. If no fuel gas leakage occurs, the flow of the fuel gas can be substantially shut off by blocking off the fuelgas exhaust passage 8. Accordingly, the presence/absence of leakage of the fuel gas can be checked, in other words, the degree of airtightness can be evaluated within a short time. Since the precision of the flow rate detector 5 (flow rate detection capability) is high enough to detect fuel gas leakage in the PEFC1, high accuracy gas leakage detection can be ensured. - As a result, the
fuel cell system 100 can promptly, accurately detect the airtightness of the PEFC1 with the simplified structure and operation of theflow rate detector 5, thepassage blocking device 4 and thefuel gas feeder 2. - The
controller 10 displays the detected airtightness value Q on theoutput section 10D. Thereby, the user of thefuel cell system 100 can promptly accurately grasp the airtightness condition of the PEFC1, i.e., the degree of deterioration, so that damage to thefuel cell system 100 and a decrease in its performance can be prevented beforehand. - The
controller 10 makes, in the controllingsection 10A, a comparison between the detected airtightness value Q and the reference airtightness values Q100 to Q0 stored in thememory section 10B, thereby evaluating the condition of the airtightness of the PEFC1 to display. More concretely, one of the reference airtightness values Q100 to Q0 that is the closest to the detected airtightness value Q and the difference between the detected airtightness value Q and the closest one of the reference airtightness values Q100 to Q0 are obtained and displayed on theoutput section 10D. In such an evaluation, thefuel cell system 100 uses the reference airtightness values Q100 to Q0 as a criterion of judgment so that the condition of the fuel cell in terms of airtightness can be properly evaluated. Further, since the result of the evaluation of the airtightness of thePEFC 1 is displayed and therefore the user of thefuel cell system 100 is informed of it, the user can more easily take countermeasures against damage to thefuel cell system 100 and a decrease in its performance. - Additionally, the
controller 10 adjusts operating conditions for thefuel cell system 100 according to the comparative evaluation of the detected airtightness value Q by use of the reference airtightness values Q100 to Q0. For instance, whenever the detected airtightness value Q sequentially reaches the intermediate airtightness values Q80, Q60, Q40, Q20, starting from the initial airtightness value Q100, thecontroller 10 lowers the upper limit of the loss of the supply pressure of the oxidizing gas and fuel gas between the outlet and inlet of the PEFC1 during the operation period of thefuel cell system 100, thereby controlling the oxidizinggas feeder 3 and thefuel gas feeder 2 so as to operate, restricting the pressure loss. Thereby, thefuel cell system 100 can substantially automatically prolong its service life, using the reference airtightness values Q100 to Q0 as a threshold, that is, a criterion of judgment. - Next, there will be explained the service life estimation operation of the
fuel cell system 100 in which the airtightness value Q is used as deterioration information. - First, the controlling
section 10A of thecontroller 10 controls thefuel cell system 100, using a built-in clock so as to perform the airtightness value detecting operation at specified detecting time intervals Δt. The specified detecting time interval Δt is a time interval based on the operating time of the PEFC1. Thecontroller 10 accumulatively stores the detected airtightness values Q in correspondence with the operating time T of the PEFC1 that elapses before the airtightness value detecting operation is done. If thefuel cell 1 is in operation at the scheduled time of the airtightness value detecting operation, thecontroller 10 performs the airtightness value detecting operation in the nearest stop operation of thefuel cell 1. - The
controller 10A obtains a transition line of the detected airtightness value Q relative to the operating time T based on the accumulated detected airtightness values Q, using a statistical approximation method. For example, this transition line may be obtained by making use of a statistical processing method such as a least square method. Thecontroller section 10A estimates future changes in the detected airtightness value Q. The future changes may be estimated, for instance, by extrapolating the transition line. - Herein,
FIG. 2 is graphs each conceptually showing a transition line of the detected airtightness value relative to the operating time of the PEFC, whereinFIG. 2 (a) is a graph showing a case where the detected airtightness value varies at a constant rate,FIG. 2 (b) is a graph showing a case where the detected airtightness value varies so as to gradually become stable, andFIG. 2 (c) is a graph showing a case where the change of the detected airtightness value gradually becomes significant. - As seen from FIGS. 2(a) to 2(c), the
controller 10A compares this transition line with the limit airtightness value Q0 to calculate an estimated remaining operating time ΔT0, that is, an estimated time left before the PEFC1 reaches the limit airtightness value Q0. - Accordingly, in the
fuel cell system 100, the airtightness of the PEFC1 can be promptly accurately detected with the simplified structure and operation of theflow rate detector 5, thepassage blocking device 4 and thefuel gas feeder 2 and the service life of thefuel cell system 100 can be estimated. - The
controller 10 displays the estimated remaining operating time ΔT0 on theoutput section 10D. Since this enables the user of thefuel cell system 100 to obtain an evaluated value of the remaining service life of the PEFC1 in the form of concrete numerical information, the user can preliminarily consider countermeasures against damage to thefuel cell system 100 and a decrease in its performance, can select a proper operation mode of the PEFC1 and can make an operation schedule for the PEFC1. - The controlling
section 10A of thecontroller 10 adjusts operating conditions for the PEFC1 based on the estimated remaining operating time ΔT0. For example, a life prolongation operation mode is selected and the oxidizinggas feeder 3, thefuel gas feeder 2 and the output power of the PEFC1 are controlled. In the life prolongation operation mode for instance, the controllingsection 10A controls the oxidizinggas feeder 3 and thefuel gas feeder 2 such that the pressure loss of the oxidizing gas and the pressure loss of the fuel gas are equalized between the inlet and outlet of the PEFC1, or alternatively such that the supply pressure of the oxidizing gas and the fuel gas is suppressed thereby restricting the pressure losses of these gases between the inlet and outlet of the PEFC1. This enables substantially automatic prolongation of the service life of thefuel cell system 100 with the result that the burden imposed on the user of thefuel cell system 100 in terms of operation management can be reduced. - The controlling
section 10A of thecontroller 10 alters the detecting time interval At according to the locus of the transition line of the detected airtightness value Q relative to the operating time T. For example, as shown inFIG. 2 (a), where the detected airtightness value Q transitions at a constant pace, Δt is kept constant. As shown inFIG. 2 (b), where the detected airtightness value Q changes so as to gradually become stable, Δt is changed so as to increase gradually. As shown inFIG. 2 (c), where the change of the detected airtightness value Q gradually becomes significant, Δt is changed so as to decrease gradually. This makes it possible to eliminate operation for obtaining unnecessary detected airtightness values without affecting the acquisition of the transition line of the detected airtightness value Q, so that the operation of thefuel cell system 100 can be rationalized. -
FIG. 3 is a schematic diagram illustrating a fuel cell system according to a second embodiment of the invention. InFIG. 3 , the parts that are substantially equivalent or function similarly to those ofFIG. 1 are identified with the same reference numerals as inFIG. 1 , and an explanation of them is omitted in this embodiment. - The structure of the
fuel cell system 101 of the second embodiment does not differ from that of thefuel cell system 100 of the first embodiment except that theflow rate detector 5 is provided not in the fuelgas feeding passage 6 but in the oxidizinggas feeding passage 7 and thepassage blocking device 4 is provided not in the fuelgas exhaust passage 8 but in the oxidizinggas exhaust passage 9. - The airtightness value detecting operation of the
fuel cell system 101 of the second embodiment does not differ from that of thefuel cell system 100 of the first embodiment except that thecontroller 10 controls the oxidizinggas feeder 3 in place of thefuel gas feeder 2. - When the
fuel gas feeder 2 is in a stop state, thepassage blocking device 4 is controlled to block off the oxidizinggas feeder 9 and the oxidizinggas feeder 3 is controlled to supply the fuel gas at constant pressure. Then, thecontroller 10 obtains the detected airtightness value Q based on the detected value of theflow rate detector 5. - The
controller 10 controls thefuel cell system 101 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment. - In the
fuel cell system 101, the airtightness of the PEFC1 is accordingly detected using not the fuel gas but the oxidizing gas, so that the risk of damage to thefuel cell system 101 owing to abnormal combustion of the fuel gas during the airtightness value detecting operation can be avoided. -
FIG. 4 is a schematic diagram illustrating a fuel cell system according to a third embodiment of the invention. InFIG. 4 , the parts that are substantially equivalent or function similarly to those ofFIG. 1 are identified with the same reference numerals as inFIG. 1 , and an explanation of them is omitted in this embodiment. - The structure of the
fuel cell system 102 of the third embodiment does not differ from that of thefuel cell system 100 of the first embodiment except that thefuel cell system 102 is provided with atest gas feeder 20, atest gas passage 22 through which a test gas is supplied from thetest gas feeder 20, and aswitching device 21 disposed in the fuelgas feeding passage 6 in the vicinity of the inlet of the PEFC1, for switching a gas supply source and that theflow rate detector 5 is provided not in thefuel gas passage 6 but in thetest gas passage 22. - Herein, the
test gas feeder 20 is composed of a steel cylinder charged with the test gas under pressure and a pressure regulating valve attached to the vent of the steel cylinder. The test gas may be any gases having chemical compositions that do not cause a chemical reaction with themembrane electrolyte assembly 1A. Preferably, the test gas contains at least one kind of gas selected from the group consisting of, for example, fuel gas, oxidizing gas, inactive gas, carbon dioxide, and methane mixed gas. The methane mixture gas is a natural-gas-basis gas containing methane as a chief component, ethane, propane, and butane. For example, the methane mixture gas may be “13A gas” used in the gas supply infrastructure in Japan. The inactive gas is a gas composed of chemically stable components such as nitrogen, argon and helium. Such a test gas does not cause damage to the inside of the fuel cell such as deterioration in catalytic power. - The switching
device 21 is composed of a three-way valve. Alternatively, it may be composed of a plurality of electric-operated valves. That is, the switchingdevice 21 should just be constructed such that it selectively connects thetest gas feeder 22 and a fuel gas feeder side portion 6A of the fuelgas feeding passage 6 to a PEFC1 side portion 6B of the fuelgas feeding passage 6. - The airtightness value detecting operation of the
fuel cell system 102 of the third embodiment does not differ from that of thefuel cell system 100 of the first embodiment except that thecontroller 10 controls theswitching device 21 and thetest gas feeder 20 in place of thefuel gas feeder 2. More specifically, when the oxidizinggas feeder 3 is in its stop state, thepassage blocking device 4 is controlled to block off the fuelgas exhaust passage 8 and theswitching device 21 is controlled to disconnect thefuel gas feeder 2 from the PEFC1 while connecting thetest gas passage 22 to the PEFC1. Then, thetest gas feeder 20 is controlled to supply the test gas to the PEFC1 at constant pressure. Thereafter, thecontroller 10 obtains the detected airtightness value Q based on the detected value of theflow rate detector 5. - The
controller 10 controls thefuel cell system 102 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment. - Thereby, the
fuel cell system 102 can detect the airtightness of the PEFC1 without use of a special power source for test gas supply. As a result, the airtightness of the PEFC1 can be promptly, accurately detected while thefuel gas feeder 2 and the oxidizinggas feeder 3 being stopped, with a simplified structure and operation. -
FIG. 5 is a schematic diagram illustrating a fuel cell system according to a fourth embodiment of the invention. InFIG. 5 , the parts that are substantially equivalent or function similarly to those ofFIG. 4 are identified with the same reference numerals as inFIG. 4 , and an explanation of them is omitted in this embodiment. - The structure of the
fuel cell system 103 of the fourth embodiment does not differ from those of thefuel cell systems fuel cell system 103 is provided with thetest gas feeder 20, thetest gas passage 22 through which the test gas is supplied from thetest gas feeder 20, and theswitching device 21 disposed in the oxidizinggas feeding passage 7 in the vicinity of the inlet of the PEFC1, and that theflow rate detector 5 is provided not in the oxidizinggas passage 7 but in thetest gas passage 22. - The airtightness value detecting operation of the
fuel cell system 103 of the fourth embodiment does not differ from that of thefuel cell system 101 of the second embodiment except that thecontroller 10 controls theswitching device 21 and thetest gas feeder 20 instead of the oxidizinggas feeder 3. - Specifically, when the
fuel gas feeder 2 is in its stop state, thepassage blocking device 4 is controlled to block off the oxidizinggas exhaust passage 9 and theswitching device 21 is controlled to disconnect the oxidizinggas feeder 3 from the PEFC1 while connecting thetest gas feeder 22 to the PEFC1. Then, thetest gas feeder 20 is controlled to supply the test gas to the PEFC1 at constant pressure. Thereafter, thecontroller 10 obtains the detected airtightness value Q based on the detected value of theflow rate detector 5. - The
controller 10 controls thefuel cell system 103 based on the detected airtightness value Q so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment. - In the
fuel cell system 103, the airtightness of the PEFC1 is accordingly detected without use of a special power source for test gas supply similarly to thefuel cell system 102 of the third embodiment. As a result, the airtightness of the PEFC1 can be promptly, accurately detected while thefuel gas feeder 2 and the oxidizinggas feeder 3 being stopped, with a simplified structure and operation. -
FIG. 6 is a schematic diagram illustrating a fuel cell system according to a fifth embodiment of the invention. InFIG. 6 , the parts that are substantially equivalent or function similarly to those ofFIG. 1 are identified with the same reference numerals as inFIG. 1 , and an explanation of them is omitted in this embodiment. - The structure of the
fuel cell system 110 of the fifth embodiment does not differ from that of thefuel cell system 100 of the first embodiment except that thefuel cell system 110 is provided with a secondpassage blocking device 31 disposed in the oxidizinggas exhaust passage 9 and a thirdpassage blocking device 32 disposed in the oxidizinggas feeding passage 7 in addition to the passage blocking device (the first passage blocking device) 4 disposed in the fuelgas exhaust passage 8. - Next, the airtightness value detecting operation of the
fuel cell system 110 of the fifth embodiment will be explained. - The
controller 10 obtains two kinds of airtightness values, that is, a first detected airtightness value Qa and a second detected airtightness value Qb when the oxidizinggas feeder 3 is in its stop state. More concretely, thecontroller 10 controls the firstpassage blocking device 4 to block off the fuelgas exhaust passage 8; controls the secondpassage blocking device 31 to block off the oxidizinggas exhaust passage 9 ; and controls the thirdpassage blocking device 32 to block off the oxidizinggas feeding passage 7. Then, thecontroller 10 controls thefuel gas feeder 2 thereby supplying the fuel gas at constant pressure. If gas leakage occurs in the PEFC1, thefuel gas feeder 2 will continuously supply the fuel gas to the PEFC1. Meanwhile, thecontroller 10 obtains the first detected airtightness value Qa based on the detected value of theflow rate detector 5. - The
controller 10 controls the firstpassage blocking device 4 to block off the fuelgas exhaust passage 8; controls at least either the secondpassage blocking device 31 or the thirdpassage blocking device 32 to open at least either the oxidizinggas feeding passage 7 or the oxidizinggas exhaust passage 9. Then, thecontroller 10 controls thefuel gas feeder 2 to supply the fuel gas at constant pressure while obtaining the second detected airtightness value Qb based on the detected value of theflow rate detector 5. - It does not matter which of the first and second detected airtightness values Qa, Qb is firstly obtained. That is, the first detected airtightness value Qa may be obtained after obtaining the second detected airtightness value Qb.
- The
controller 10 calculates a differential airtightness value (difference value) Qc that is the difference between the first and second detected airtightness values Qa and Qb (i.e., Qc=Qb−Qa). - Herein, the first detected airtightness value Qa represents the leakage from the PEFC1 to the outside, and the differential detected airtightness value Qc represents the leakage from the
fuel gas passage 1D to the oxidizinggas passage 1E, that is, cross-leakage. Since this cross leakage varies mainly depending on the degree of damage to the polymer electrolyte membrane of themembrane electrode assembly 1A, the fluctuation of the differential airtightness value Qc precisely reflects the degree of damage to the polymer electrolyte membrane. Therefore, thefuel cell system 110 can detect the degree of damage to the polymer electrolyte membrane with high accuracy. - The
controller 10 controls thefuel cell system 110 based on the differential airtightness value Qc so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment. - This enables the
fuel cell system 110 to promptly, accurately detect the airtightness of the PEFC1 and, especially, the degree of damage to the polymer electrolyte membrane with a simplified structure and operation. - Using a PEFC1 having one
membrane electrode assembly 1A in which the polymer electrolyte membrane has a hole of about 3 mm in diameter, the fuel gas was supplied under a pressure of 2 kPa after blocking off the fuelgas exhaust passage 8, the oxidizinggas exhaust passage 9 and the oxidizinggas feeding passage 7. In this case, the differential airtightness value Qc was 18 ml/min. The output voltage of the PEFC1 when connected to a general-type electric load was 0.6V. - Another test was conducted by use of a PEFC1 having one
membrane electrode assembly 1A in which the polymer electrolyte membrane has no holes through which the fuel gas can pass. In this test, the fuel gas was supplied under a pressure of 2 kPa after blocking off the fuelgas exhaust passage 8, the oxidizinggas exhaust passage 9 and the oxidizinggas feeding passage 7. In this case, the differential airtightness value Qc was 0 ml/min. The output voltage of the PEFC1 when connected to a general-type electric load was 0.8V. A further test was conducted by use of a PEFC1 having 52membrane electrode assemblies 1A stacked therein. The fuel gas was supplied under a pressure of 2 kPa after blocking off the fuelgas exhaust passage 8, the oxidizinggas exhaust passage 9 and the oxidizinggas feeding passage 7. In this case, the differential airtightness value Qc was 0 ml/min. - It was found from the above tests that the invention was able to detect the degree of damage to the polymer electrolyte membrane with high accuracy. Specifically, the decrease in the output voltage is about 0.2V. Since the PEFC1 generally has about 50
membrane electrode assemblies 1A stacked therein, the output voltage of thePEFC 1 is several tens of volts. In view of this, the decrease (about 0.2V) in the output voltage is minute. In addition, it is assumable that other various factors than damage to the polymer electrolyte membrane may cause decreases in the output voltage. The method of detecting damage to the polymer electrolyte membrane from the differential airtightness value Qc has higher accuracy compared to the method of detecting it from changes in the output voltage. - Further, it was found that the invention was able to detect the degree of damage to the polymer electrolyte membrane quickly. Specifically, it took about 3 minutes to obtain the differential airtightness value Qc after blocking off the fuel
gas exhaust passage 8, the oxidizinggas exhaust passage 9 and the oxidizinggas feeding passage 7. -
FIG. 7 is a schematic diagram illustrating a fuel cell system according to a sixth embodiment of the invention. InFIG. 7 , the parts that are substantially equivalent or function similarly to those ofFIG. 6 are identified with the same reference numerals as inFIG. 6 , and an explanation of them is omitted in this embodiment. - The structure of the
fuel cell system 111 of the sixth embodiment does not differ from that of thefuel cell system 110 of the fifth embodiment except that theflow rate detector 5 is provided not in the fuelgas feeding passage 6 but in the oxidizinggas feeding passage 7 and the thirdpassage blocking device 32 is provided not in the oxidizinggas feeding passage 7 but in the fuelgas feeding passage 6. - The airtightness value detecting operation of the
fuel cell system 111 of the sixth embodiment does not differ from that of thefuel cell system 110 of the fifth embodiment except that thecontroller 10 controls the oxidizinggas feeder 3 instead of thefuel gas feeder 2. - Specifically, when the
fuel gas feeder 2 is in its stop state, two kinds of airtightness values, i.e., the first detected airtightness value Qa and the second detected airtightness value Qb are obtained. More concretely, thecontroller 10 controls the firstpassage blocking device 4 to block off the oxidizinggas exhaust passage 9; controls the secondpassage blocking device 31 to block off the oxidizinggas exhaust passage 8; and controls the thirdpassage blocking device 32 to block off the fuelgas feeding passage 6. Then, thecontroller 10 controls the oxidizinggas feeder 3 to supply the oxidizing gas at constant pressure and obtains the first detected airtightness value Qa similarly to thefuel cell system 110. - Further, the
controller 10 controls the firstpassage blocking device 4 to block off the oxidizinggas exhaust passage 9 and controls at least either the secondpassage blocking device 31 or the thirdpassage blocking device 32 to open at least either the fuelgas feeding passage 6 or the fuelgas exhaust passage 8. Then, thecontroller 10 controls the oxidizinggas feeder 3 to supply the oxidizing gas at constant pressure while obtaining the second detected airtightness value Qb based on the detected value of theflow rate detector 5. - The
controller 10 calculates that differential airtightness value Qc that is the difference between the first airtightness value Qa and the second airtightness value Qb (i.e., Qc=Qb−Qa). - The
controller 10 controls thefuel cell system 111 based on the differential airtightness value Qc so as to perform the airtightness value detecting operation and the service life estimating operation similarly to the first embodiment. - Thereby, the
fuel cell system 111 can promptly, accurately detect the airtightness of the PEFC1 and more particularly the degree of damage to the polymer electrolyte membrane with a simplified structure and operation. In addition, the risk of damage to thefuel cell system 101 caused by abnormal combustion of the fuel gas during the airtightness value detecting operation can be avoided. - Although the preferred embodiments of the invention have been discussed hereinabove, it is apparent that the invention is not necessarily limited to them. Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. Further, it should be noted that the details of the construction and/or functions of the invention may be modified within the scope of the invention. For instance, the effects of the invention can be achieved by applying the
test gas feeder 20, switchingdevice 21 andtest gas passage 22 of the third or fourth embodiment to the fuel cell system of the fifth or sixth embodiment. - The fuel cell system of the invention is suitably used in a wide range of applications as it enables prompt, accurate detection of the airtightness of a fuel cell with a simple arrangement.
Claims (16)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US13/113,868 US8268494B2 (en) | 2004-12-28 | 2011-05-23 | Fuel cell system |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2004378967 | 2004-12-28 | ||
JP2004-378967 | 2004-12-28 | ||
PCT/JP2005/022746 WO2006070587A1 (en) | 2004-12-28 | 2005-12-12 | Fuel cell system |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2005/022746 A-371-Of-International WO2006070587A1 (en) | 2004-12-28 | 2005-12-12 | Fuel cell system |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/113,868 Division US8268494B2 (en) | 2004-12-28 | 2011-05-23 | Fuel cell system |
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US20070196705A1 true US20070196705A1 (en) | 2007-08-23 |
Family
ID=36614708
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
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US10/592,671 Abandoned US20070196705A1 (en) | 2004-12-28 | 2005-12-12 | Fuel cell system |
US13/113,868 Active US8268494B2 (en) | 2004-12-28 | 2011-05-23 | Fuel cell system |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
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US13/113,868 Active US8268494B2 (en) | 2004-12-28 | 2011-05-23 | Fuel cell system |
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US (2) | US20070196705A1 (en) |
JP (1) | JP4907343B2 (en) |
CN (1) | CN100466352C (en) |
WO (1) | WO2006070587A1 (en) |
Cited By (3)
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US20120070755A1 (en) * | 2010-03-01 | 2012-03-22 | Panasonic Corporation | Fuel cell power generation system |
US10985388B2 (en) * | 2016-12-14 | 2021-04-20 | Hyundai Motor Company | Method and apparatus for estimating hydrogen crossover loss of fuel cell system |
US11031612B2 (en) | 2017-12-03 | 2021-06-08 | Volkswagen Ag | Fuel cell system having integrated gas connections for connection to an external test gas supply |
Families Citing this family (4)
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JP6432745B2 (en) * | 2016-06-09 | 2018-12-05 | トヨタ自動車株式会社 | Power supply system |
CN108933269B (en) * | 2018-06-25 | 2021-06-25 | 武汉船用电力推进装置研究所(中国船舶重工集团公司第七一二研究所) | Device and method for detecting stack blow-by gas flow of proton exchange membrane fuel cell |
JP7120039B2 (en) * | 2019-01-21 | 2022-08-17 | トヨタ自動車株式会社 | Inspection device and inspection method |
CN112604454B (en) * | 2021-01-08 | 2021-12-28 | 山东一然环保科技有限公司 | Flue gas denitration device capable of automatically replacing activated carbon |
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JPH11224681A (en) | 1998-02-06 | 1999-08-17 | Sanyo Electric Co Ltd | Fuel cell system |
JP4464474B2 (en) * | 1998-06-25 | 2010-05-19 | トヨタ自動車株式会社 | FUEL CELL SYSTEM, FUEL CELL VEHICLE, AND FUEL CELL CONTROL METHOD |
CN1172392C (en) * | 1998-09-14 | 2004-10-20 | 探索空气技术公司 | Electrical current generation system |
JP4459518B2 (en) | 2002-09-30 | 2010-04-28 | 株式会社豊田中央研究所 | Method and system for operating polymer electrolyte fuel cell |
JP2004139842A (en) * | 2002-10-17 | 2004-05-13 | Nissan Motor Co Ltd | Hydrogen leakage detecting system of fuel cell vehicle |
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2005
- 2005-12-12 CN CNB2005800088882A patent/CN100466352C/en not_active Expired - Fee Related
- 2005-12-12 WO PCT/JP2005/022746 patent/WO2006070587A1/en not_active Application Discontinuation
- 2005-12-12 JP JP2006520431A patent/JP4907343B2/en active Active
- 2005-12-12 US US10/592,671 patent/US20070196705A1/en not_active Abandoned
-
2011
- 2011-05-23 US US13/113,868 patent/US8268494B2/en active Active
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US6492043B1 (en) * | 1998-12-23 | 2002-12-10 | Ballard Power Systems Inc. | Method and apparatus for detecting a leak within a fuel cell |
US20030008185A1 (en) * | 2001-07-04 | 2003-01-09 | Honda Giken Kogyo Kabushiki Kaisha | Fuel cell operation method |
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US20120070755A1 (en) * | 2010-03-01 | 2012-03-22 | Panasonic Corporation | Fuel cell power generation system |
US10985388B2 (en) * | 2016-12-14 | 2021-04-20 | Hyundai Motor Company | Method and apparatus for estimating hydrogen crossover loss of fuel cell system |
US11031612B2 (en) | 2017-12-03 | 2021-06-08 | Volkswagen Ag | Fuel cell system having integrated gas connections for connection to an external test gas supply |
Also Published As
Publication number | Publication date |
---|---|
JPWO2006070587A1 (en) | 2008-06-12 |
WO2006070587A1 (en) | 2006-07-06 |
CN1934738A (en) | 2007-03-21 |
US20110223504A1 (en) | 2011-09-15 |
US8268494B2 (en) | 2012-09-18 |
CN100466352C (en) | 2009-03-04 |
JP4907343B2 (en) | 2012-03-28 |
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