Fuel cell system

Abstract

To provide a fuel cell system capable of resolving an anode gas supply shortage without reducing power generation efficiency.SOLUTION: A fuel cell system includes a cell stack 2 in which a plurality of battery cells are stacked, first and second anode gas supply channels 8, 10 that supply anode gas to the cell stack, and a cathode gas supply channel 6 that supplies cathode gas to the cell stack. The first anode gas supply channel 8 supplies an anode gas to the center side portion of the cell stack 2 in the stacking direction, and the second anode gas supply channel 10 supplies anode gas to both ends of the cell stack 2 in the stacking direction. When the temperature of the central portion of the cell stack increases, the flow rate of anode gas supplied from the first anode gas supply channel 8 is increased, while the supply flow rate of anode gas from the second anode gas supply channel 10 is decreased, without changing the total supply flow rate of the anode gas, thereby avoiding fuel exhaustion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel cell system including a cell stack in which battery cells are stacked.

Background Art

[0002] As a fuel cell system, there is known one including a cell stack in which flat battery cells are stacked, an anode gas supply passage for supplying anode gas (fuel gas) to the anode chamber of the cell stack, a cathode gas supply passage for supplying cathode gas (oxidant gas) to the cathode chamber of the cell stack, anode gas supply means for supplying anode gas, and cathode gas supply means for supplying cathode gas. In such a fuel cell system, it is necessary to maintain the fuel utilization rate in the cell stack within a certain range. If the operation is continued in a state where the fuel utilization rate is excessively high (so-called shortage state of anode gas), the battery cells are damaged and it becomes difficult to continue the power generation operation.

[0003] In a cell stack in which a plurality of flat battery cells are stacked, a temperature distribution is formed in the stacking direction (i.e., the thickness direction), and heat tends to accumulate more in the central portion in the stacking direction (so-called central stage portion), and the temperature of this central portion tends to be higher than that of its both end portions (so-called end stage portions).

[0004] Also, generally, a fuel cell system deteriorates over time and the resistance of the battery cells increases, and the amount of heat generation tends to increase at a portion where this resistance becomes large. In particular, the central portion of the cell stack where the temperature is high has a faster deterioration progress, and thus the temperature becomes even higher compared to its both end portions.

[0005] In a cell stack consisting of stacked flat battery cells, the anode gas supplied through the anode gas supply channel is initially set to be evenly distributed to multiple battery cells. However, as the viscosity of the anode gas increases with temperature, the pressure drop increases. Therefore, as the cell stack deteriorates over time and its temperature distribution changes, the pressure drop at the inlet of the anode chamber of each battery cell also changes due to this temperature distribution. This fluctuation in pressure drop then changes the amount of anode gas distributed to each battery cell.

[0006] For example, in the high-temperature areas of the cell stack (the central areas), the pressure drop at the inlet of the anode chamber increases. This reduces the distribution flow rate of anode gas to the anode chamber, leading to a shortage of anode gas supply (so-called fuel depletion). If this shortage of anode gas supply continues, the battery cell will be damaged.

[0007] For these reasons, fuel cell systems have been proposed that address the issue of insufficient anode gas supply in the cell stack. For example, one system measures the resistance value of each battery cell to determine the fuel utilization rate in each cell and prevents insufficient anode gas supply based on the determined fuel utilization rate (see, for example, Patent Document 1); another system uses output current-fuel utilization rate data from the cell stack to adjust the anode gas supply flow rate so that the fuel utilization rate is below a predetermined value (see, for example, Patent Document 2); and yet another system uses the voltage change rate and resistance change rate of the cell stack as indicators to detect insufficient anode gas supply (fuel depletion) and adjusts the anode gas supply flow rate or the power output of the cell stack to prevent damage to the cell stack (see, for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2009-110666 [Patent Document 2] Japanese Patent Publication No. 2006-59550 [Patent Document 3] Japanese Patent Publication No. 2008-103198 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, these conventional fuel cell systems have the following problems. For example, in the fuel cell system of Patent Document 1, when a shortage of anode gas is detected, the anode gas supply flow rate is increased for all battery cells in the cell stack. However, with this type of anode gas supply control, the anode gas supply flow rate is also increased for battery cells that are not experiencing a shortage of anode gas, resulting in a decrease in power generation efficiency.

[0010] Furthermore, while the fuel cell system described in Patent Document 2 allows for the determination of the fuel utilization rate of the entire cell stack, it does not allow for the determination of the fuel utilization rate of some of the battery cells in the cell stack, and therefore cannot resolve the partial shortage of anode gas supply in the cell stack.

[0011] Furthermore, in the fuel cell system described in Patent Document 3, when a shortage of anode gas supply is detected in the cell stack, the anode gas supply flow rate is increased for all battery cells in the cell stack. However, as mentioned above, this type of anode gas supply control increases the anode gas supply flow rate even for battery cells that are not experiencing a shortage, resulting in a decrease in power generation efficiency.

[0012] The objective of the present invention is to provide a fuel cell system that can resolve the shortage of anode gas supply without reducing power generation efficiency. [Means for solving the problem]

[0013] The fuel cell system according to claim 1 of the present invention is a fuel cell system comprising: a cell stack in which a plurality of battery cells are stacked, each having an electrolyte layer that conducts ions, an anode disposed on one side of the electrolyte layer, and a cathode disposed on the other side of the electrolyte layer; an anode gas supply channel for supplying anode gas to the anode chamber of the cell stack; a cathode gas supply channel for supplying cathode gas to the cathode chamber of the cell stack; an anode gas supply means for supplying anode gas; and a controller for controlling the anode gas supply means, wherein The anode gas supply channel includes a first anode gas supply channel that supplies anode gas to the central portion of the cell stack in the stacking direction, and a second anode gas supply channel that supplies anode gas to both end portions of the cell stack in the stacking direction, wherein the cell stack is subject to a temperature tendency during electrochemical reactions. Central part Alternatively, a temperature sensing means is provided in the vicinity thereof, or on the anode inflow side of the battery cell in the central portion thereof. When the temperature detected by the temperature detection means exceeds a predetermined temperature threshold, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel, while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

[0014] Furthermore, in the fuel cell system according to claim 2 of the present invention, the anode gas supply means includes a first anode gas supply means disposed in the first anode gas supply channel and a second anode gas supply means disposed in the second anode gas supply channel, wherein when the temperature of the central portion of the cell stack rises, the controller increases the rotation speed of the first anode gas supply means while decreasing the rotation speed of the second anode gas supply means, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

[0016] Furthermore, the claims of the present invention 3The fuel cell system described herein is provided with an accumulating timing means for timing the cumulative operating time from the start of operation after installation, and when the accumulating timing means has timed a predetermined cumulative time, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel, while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

[0017] Furthermore, the present invention claims 4 The fuel cell system described herein comprises a cell stack in which a plurality of battery cells are stacked, each having an electrolyte layer that conducts ions, an anode disposed on one side of the electrolyte layer, and a cathode disposed on the other side of the electrolyte layer; an anode gas supply channel for supplying anode gas to the anode chamber of the cell stack; a cathode gas supply channel for supplying cathode gas to the cathode chamber of the cell stack; an anode gas supply means for supplying anode gas; and a controller for controlling the anode gas supply means. The anode gas supply channel includes a first anode gas supply channel that supplies anode gas to the central portion of the cell stack in the stacking direction, and a second anode gas supply channel that supplies anode gas to both end portions of the cell stack in the stacking direction. In relation to the cell stack, a voltage measuring means is provided for measuring the generated voltage of the battery cells in the central part of the cell stack. In a fuel depletion detection mode for detecting the fuel depletion state of the battery cells, the supply flow rate of anode gas supplied through the first anode gas supply channel is temporarily increased. When the comparison voltage difference between the measured voltage rise value and the reference voltage rise value of the voltage measured by the voltage measuring means exceeds a predetermined voltage threshold, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack. [Effects of the Invention]

[0018] According to the fuel cell system described in claim 1 of the present invention, the anode gas supply channel includes a first anode gas supply channel that supplies anode gas to the central portion of the cell stack in the stacking direction, and a second anode gas supply channel that supplies anode gas to both end portions of the cell stack in the stacking direction. When the temperature of the central portion of the cell stack rises, the supply flow rate of anode gas in the first anode gas supply channel is increased while the supply flow rate of anode gas in the second anode gas supply channel is decreased, without changing the total supply flow rate of anode gas supplied to the entire cell stack. This makes it possible to increase the supply flow rate of anode gas supplied to the central portion of the cell stack without reducing the power generation efficiency of the cell stack, thereby avoiding a shortage of anode gas (fuel depletion) in the central portion of the cell stack. Furthermore, a temperature sensing means is provided in the central part of the cell stack or its vicinity (or on the anode chamber inlet side of the battery cell in the central part) where a tendency for high temperatures to occur during electrochemical reactions. This temperature sensing means monitors the temperature of the central part of the cell stack, which is prone to high temperatures. When the temperature detected by this temperature sensing means exceeds a predetermined temperature threshold, the controller controls the supply flow rate of anode gas supplied through the first and second anode gas supply channels without reducing the power generation efficiency of the cell stack. This allows monitoring of the temperature of the central part of the cell stack to avoid a shortage of anode gas (fuel depletion).

[0019] Furthermore, according to the fuel cell system described in claim 2 of the present invention, the anode gas supply means includes a first anode gas supply means disposed in a first anode gas supply channel and a second anode gas supply means disposed in a second anode gas supply channel. Therefore, by controlling the rotation speed of the first anode gas supply means, the supply flow rate of anode gas supplied through the anode gas supply channel can be adjusted, and by controlling the rotation speed of the second anode gas supply means, the supply flow rate of anode gas supplied through the second anode gas supply channel can be adjusted.

[0021] Furthermore, the claims of the present invention 3According to the fuel cell system described in [reference], an integrated timing means for measuring the integrated operation time from the start of operation after installation is provided, and the degradation state of the cell stack is estimated based on the integrated time measured by this integrated timing means. When the integrated timing means measures a predetermined integrated time, it is estimated that the degradation of the central part of the cell stack has progressed and the temperature has risen. Then, without reducing the power generation efficiency of the cell stack, the controller controls the supply flow rate of the anode gas supplied through the first and second anode gas supply channels, thereby estimating the degradation state of the central part of the cell stack and avoiding insufficient supply of the anode gas (fuel depletion).

[0022] Furthermore, according to the claims of the present invention 4 According to the fuel cell system described in [reference], a voltage measurement means for measuring the power generation voltage of the battery cells in the central part of the cell stack is provided, and in the fuel depletion detection mode, the power generation voltage (output voltage) of the central part of the cell stack is measured by the voltage measurement means. When the supply flow rate of the anode gas is temporarily increased in the fuel depletion detection mode, the fuel utilization rate decreases, so the power generation voltage of the cell stack (central part) increases, and this increase in the power generation voltage is greater for the battery cells with a greater degree of fuel depletion. From this, when the comparison voltage difference between the measured increase voltage value of the measured voltage by the voltage measurement means in the fuel depletion detection mode and the reference increase voltage value exceeds a predetermined voltage threshold, it is estimated that the fuel depletion of the battery cells in the central part of the cell stack has progressed. Then, without reducing the power generation efficiency of the cell stack, the controller controls the supply flow rate of the anode gas supplied through the first and second anode gas supply channels, thereby avoiding insufficient supply of the anode gas (fuel depletion) in the central part of the cell stack.

Brief Description of the Drawings

[0023] [Figure 1] An overall view schematically showing a first embodiment of a fuel cell system according to the present invention. [Figure 2] A schematic perspective view schematically showing the cell stack of the fuel cell system of FIG. 1. [Figure 3] A cross-sectional view schematically showing the cell stack of FIG. 2. [Figure 4] A simplified block diagram showing the control system of the fuel cell system in Figure 1. [Figure 5] A flowchart showing the control flow by the control system in Figure 4. [Figure 6] A simplified block diagram showing the control system in a second embodiment of the fuel cell system according to the present invention. [Figure 7] A flowchart showing the control flow by the control system in Figure 6. [Figure 8] A simplified block diagram showing the control system in a third embodiment of the fuel cell system according to the present invention. [Figure 9] A diagram showing the relationship between the fuel utilization rate of a battery cell and the output voltage of the battery cell. [Figure 10] A flowchart showing the control flow by the control system in Figure 8. [Modes for carrying out the invention]

[0024] Hereinafter, various embodiments of the fuel cell system according to the present invention will be described with reference to the attached drawings.

[0025] [First embodiment of a fuel cell system] First, a first embodiment of a fuel cell system according to the present invention will be described with reference to Figures 1 to 5. In Figure 1, the fuel cell system of the first embodiment includes a cell stack 2 that generates electricity by an electrochemical reaction between an anode gas (e.g., hydrogen as a fuel gas) and a cathode gas (e.g., air as an oxidizing gas). An anode gas supply channel 4 for supplying anode gas (fuel gas) and a cathode gas supply channel 6 for supplying cathode gas (oxidizing gas) are provided on the inlet side of the cell stack 2. In this embodiment, the anode gas supply channel 4 consists of a first anode gas supply channel 8 that supplies anode gas to the central part (central stage) of the cell stack 2 and a second anode gas supply channel 10 that supplies anode gas to the end part (end stage) of the cell stack 2. Furthermore, an anode off-gas discharge channel 11 for discharging anode off-gas and a cathode off-gas discharge channel 13 for discharging cathode off-gas are provided on the discharge side of the cell stack 2.

[0026] The anode gas supply means 12 for supplying anode gas includes, for example, a first fuel pump 14 as a first anode gas supply means and, for example, a second fuel pump 16 as a second anode gas supply means, with the first fuel pump 14 being located in the first anode gas supply passage 8 and the second fuel pump 16 being located in the second anode gas supply passage 10. The upstream sides of the first and second anode gas supply passages 8 and 10 are connected to, for example, an anode gas cylinder 18 as an anode gas supply source, and anode gas from the anode gas cylinder 18 is supplied through the first and second anode gas supply passages 8 and 10. In addition, a cathode gas supply means, for example, an air blower 20, is located in the cathode gas supply passage 6.

[0027] With this configuration, anode gas from the anode gas cylinder 18 (anode gas supply source) is supplied by the first fuel pump 14 through the first anode gas supply channel 8 to the anode chamber 22 (22a) (see Figure 2) of the battery cell 20 (20a) in the central part of the cell stack 2, and also supplied by the second fuel pump 16 through the second anode gas supply channel 10 to the anode chamber (22b) of the battery cells 20 (20b) at both ends of the cell stack 2. In addition, air as an oxidizing gas is supplied by the air blower 20 through the cathode gas supply channel 6 to the cathode chambers 24 (24a, 24b) of the battery cells 20 (20a, 20b) in the cell stack 2.

[0028] The cell stack 2 will be described primarily with reference to Figures 2 and 3. The illustrated cell stack 2 comprises a plurality of battery cells 20 (20a, 20b) stacked vertically in Figures 2 and 3, and each battery cell 20 is composed of substantially the same shape of flat cell. Each battery cell 20 (20a, 20b), although not specifically shown, comprises, for example, a solid oxide electrolyte layer that conducts ions, an anode (fuel electrode) disposed on one side of this electrolyte layer (the lower side in Figure 3), and a cathode (air electrode) disposed on the other side of this electrolyte layer (the upper side in Figure 3). An interconnector 26 is disposed between each battery cell 20, and the battery cells 20 (20a, 20b) are electrically connected via this interconnector 26. Furthermore, current collector plates 28 are provided at both ends of the cell stack 2.

[0029] In this embodiment, the cell stack 2 is provided with a first inlet manifold 32 and a second inlet manifold 34 extending in the stacking direction of the multiple battery cells 20 (20a, 20b). The first inlet manifold 32 is connected to a first anode gas supply channel 8, and the anode gas supplied through the first anode gas supply channel 8 is distributed by the first inlet manifold 32 and delivered to the anode chamber 22a of the battery cells 20a in the central part of the cell stack 2, as shown by the dashed arrow in Figure 3. The second inlet manifold 34 is connected to a second anode gas supply channel 10, and the anode gas supplied through the second anode gas supply channel 10 is distributed by the second inlet manifold 34 and delivered to the anode chamber 22b of the battery cells 20b at both ends of the cell stack 2, as shown by the double-dash arrow in Figure 3.

[0030] Furthermore, the cell stack 2 is provided with a third inflow-side manifold 36 that extends in the stacking direction of the multiple battery cells 20 (20a, 20b). The third inflow-side manifold 36 is connected to a cathode gas supply channel 6, and the cathode gas supplied through the cathode gas supply channel 6 is distributed by this third inflow-side manifold 36 and delivered to the cathode chambers 24 (24a, 24b) of all the battery cells 20 (20a, 20b) in the cell stack 2, as shown by the solid arrows in Figure 3.

[0031] The cell stack 2 is further provided with a first outlet-side manifold 38 and a second outlet-side manifold 40 that extend in the stacking direction of the multiple battery cells 20 (20a, 20b). The first outlet-side manifold 38 is connected to the anode off-gas discharge channel 11, and the anode off-gas from the anode chambers 22 (22a, 22b) of the multiple battery cells 20 (20a, 20b) of the cell stack 2 is collected in the first outlet-side manifold 38 and supplied to the combustor 42 (see Figure 1) through this first outlet-side manifold 38. Furthermore, the second outlet manifold 40 is connected to the cathode-off gas discharge channel 13, and the cathode-off gas from the cathode chambers 24 (24a, 24b) of the multiple battery cells 20 (20a, 20b) of the cell stack 2 is collected in the second outlet manifold 40 and supplied to the combustor 42 (see Figure 1) through this second outlet manifold 40.

[0032] Returning to Figure 1, in this fuel cell system, the cell stack 2 and combustor 42 are housed in a high-temperature space 46 defined by a high-temperature module 44 whose inner surface is covered with insulating material. Anode off-gas from the anode chambers 22 (22a, 22b) (see Figure 2) of the battery cells 20 (20a, 20b) and cathode off-gas from the cathode chambers 24 (24a, 24b) (see Figure 2) are supplied to the combustion section 42, where the anode off-gas is burned. This combustion heat maintains a high temperature inside the high-temperature module 44, and the combustion exhaust gas after combustion is discharged to the outside through a combustion exhaust gas discharge channel 48.

[0033] In this fuel cell system, as can be seen from Figures 2 and 3, anode gas from the first anode gas supply channel 8 is supplied to the anode chamber 22a of the battery cell 20a in the central part of the cell stack 2, anode gas from the second anode gas supply channel 10 is supplied to the anode chamber 22b of the battery cells 20b at both ends of the cell stack 2, and cathode gas from the cathode supply channel 6 is supplied to the cathode chambers 24a and 24b of all the battery cells 20 (20a and 20b) in the cell stack 2. Electricity is generated by the electrochemical reaction between the anode gas in anode chamber 22 (22a and 22b) and the cathode gas in cathode chamber 24 (24a and 24b).

[0034] The power generated by each battery cell 26 is collected by the current collector plate 30, and the collected power is output through the power output line 50. After being converted from DC current to AC current by the inverter 52, it is supplied to a power load (not shown), such as a lighting device or home appliance.

[0035] In such fuel cell systems, prolonged operation can lead to degradation of the cell stack over time, causing the temperature of the cell stack 2, particularly the battery cells 20a in the central part, to rise. This rise in temperature of the battery cells 20a increases the viscosity of the anode gas flowing into the anode chamber 22a, reducing the flow rate of anode gas into the anode chamber 22a and potentially leading to a shortage of anode gas (so-called fuel depletion).

[0036] Therefore, in this embodiment, the temperature of the battery cells 20a in the central part of the cell stack 2, where the temperature tends to rise, is detected, and the supply flow rate of anode gas supplied through the first and second anode gas supply channels 8 and 10 is controlled.

[0037] Referring further to Figure 4 in addition to Figure 1, in this embodiment, a temperature sensing means 62 is provided in or near the central part of the cell stack 2. This temperature sensing means 62 can be made up of, for example, a thermocouple and detects the temperature of the battery cell 20a in the central part of the cell stack 2. This temperature sensing means 62 may also be provided on the anode chamber inflow side of the battery cell 20a in the central part of the cell stack 2, for example, in the first inflow side manifold 32 (see Figures 2 and 3).

[0038] The detection signal from the temperature sensing means 62 is sent to the controller 64 that controls the fuel cell system, and the controller 64 controls the first and second fuel pumps 14 and 16 based on this detection signal as described later.

[0039] The controller 64 is composed of, for example, a microprocessor, and in this example includes a fuel utilization rate setting means 66, a fuel supply flow rate calculation means 68, an air supply flow rate calculation means 70, a temperature determination means 72, a fuel increase / decrease signal generation means 74, a control means 76, and a memory means 78. The fuel utilization rate setting means 66 sets the fuel utilization rate of the anode gas consumed in power generation in the cell stack 2, the fuel supply flow rate setting means 68 calculates the fuel supply flow rate (anode gas supply flow rate) to achieve the set fuel utilization rate, and the air supply flow rate calculation means 70 calculates the air supply flow rate (cathode gas supply flow rate) at this time.

[0040] In this embodiment, the anode gas supply flow rate calculated by the fuel supply flow rate calculation means 68 is the total supply flow rate supplied to the cell stack 2 through the first and second anode gas supply passages 8 and 10. In addition to this total supply flow rate, the fuel supply flow rate calculation means 68 also calculates the supply flow rate supplied through the first anode gas supply passage 8 (i.e., the supply flow rate supplied to the battery cells 20a in the central part of the cell stack 2) and the supply flow rate supplied through the second anode gas supply passage 10 (i.e., the supply flow rate supplied to the battery cells 20b at both ends of the cell stack 2).

[0041] For example, when the number of battery cells 20a in the central section and the number of battery cells 20b in both end sections are equal, the supply flow rate through the first anode gas supply channel 8 and the supply flow rate through the second anode gas supply channel 10 are calculated to be equal. Also, for example, when the ratio of the number of battery cells 20a in the central section to the number of battery cells 20b in both end sections is 1:2, the ratio of the supply flow rate through the first anode gas supply channel 8 and the supply flow rate through the second anode gas supply channel 10 is calculated to be 1:2. In this embodiment, for the sake of ease of understanding, the case in which the number of battery cells 20a in the central section and the number of battery cells 20b in both end sections are equal will be explained.

[0042] Furthermore, the temperature determination means 72 determines whether the temperature t0 detected by the temperature detection means 62 has risen above the first temperature rise threshold T1 (e.g., 10°C) from the initial detection temperature T0, or above the second temperature rise threshold T2 (e.g., 20°C) from the initial detection temperature T0. The fuel increase / decrease signal generation means 74 generates a first increase / decrease signal when the detected temperature t0 rises above the first temperature rise threshold T1 from the initial detection temperature T0 (t0>(T0+T1)), and generates a second increase / decrease signal when the detected temperature t0 rises above the second temperature rise threshold T2 from the initial detection temperature T0 (t0>(T0+T2)). The control means 76 controls the first and second fuel pumps 14 and 16 as described later, and the memory means 78 stores the first temperature rise threshold T1 (10°C), the second temperature rise threshold T2 (20°C), the initial detection temperature T0, etc.

[0043] Next, the control flow of the fuel cell system described above will be explained, mainly with reference to Figures 1, 4, and 5. When the operation of the fuel cell system is started (step S1), the fuel utilization rate setting means 66 of the controller 64 sets the fuel utilization rate of power generation by the cell stack 2 (for example, a value of about 80-85%) (step S2). Once the fuel utilization rate is set in this way, the fuel supply flow rate calculation means 68 calculates the total supply flow rate of anode gas to be supplied to the cell stack 2 (step S3), and also calculates the supply flow rate supplied through the first anode gas supply channel 8 and the supply flow rate supplied through the second anode gas supply channel 10 (step S4). In addition, the air supply flow rate calculation means 70 calculates the supply flow rate of cathode gas to be supplied to the cell stack 2 (step S5).

[0044] Once calculated in this manner, the control means 76 controls the rotation speed of the first fuel pump 14 so that the supply flow rate of anode gas supplied to the battery cells 20a in the central part of the cell stack 2 becomes the calculated supply flow rate, controls the rotation speed of the second fuel pump 16 so that the supply flow rate of anode gas supplied to the battery cells 20b at both ends of the cell stack 2 becomes the calculated supply flow rate, and controls the rotation speed of the air blower 20 so that the supply flow rate of cathode gas supplied to the cell stack becomes the calculated supply flow rate (step S6). In this way, the supply flow rates of anode gas and cathode gas supplied to the cell stack 2 are controlled.

[0045] During this power generation operation, the temperature sensing means 62 detects the temperature of the central part of the cell stack 2 (step S7), and the detection signal is sent to the controller 64. Then, the temperature determination means 72 of the controller 64 determines whether the temperature t0 detected by the temperature sensing means 62 has risen above the first temperature rise threshold T1 (10°C) from the initial detection temperature, or above the second temperature rise threshold T2 (20°C) from the initial detection temperature.

[0046] When the increase in the detected temperature t0 is, for example, not more than the first temperature increase threshold value T1 (10 °C) (t0≤T0 + T1), the process returns from step S8 to step S7, the power generation operation described above is continuously performed, and the temperature detection by the temperature detection means 62 is repeatedly performed.

[0047] When the detected temperature t0 rises beyond the first temperature increase threshold value T1 from the initial detected temperature T0 (t0>(T0 + T1)), the process proceeds from step S8 to step S9. When the temperature increase of the detected temperature t0 is not more than the second temperature increase threshold value T2 from the initial detected temperature T0 ((T0 + T1)<t0≤(T0 + T2)), the process proceeds to step S10. When the process proceeds to step 10, based on this determination result of the temperature determination means 72, the fuel increase / decrease signal generation means 74 generates a first fuel increase / decrease signal, and the control means 76 controls the supply flow rate of the anode gas in one step based on this first fuel increase / decrease signal (step S11).

[0048] In this first-stage control, in the operation state where the fuel utilization rate in the cell stack 2 is maintained as it is (that is, the supply state where the total supply flow rate of the anode gas is maintained), the control means 76 increases the rotation speed of the first fuel pump 14 by, for example, 2% to increase the supply flow rate of the anode gas supplied through the first anode gas supply passage 8. On the other hand, in order to decrease the increased supply flow rate, the control means 76 decreases the rotation speed of the second fuel pump 16 by, for example, 2% to decrease the supply flow rate of the anode gas supplied through the second anode gas supply passage 10 (step S12). By controlling in this way, without increasing or decreasing the total supply flow rate of the anode gas supplied to the cell stack 2, the supply flow rate of the anode gas supplied to the cell stack 2 (the battery cell 20a at the central side part) through the first anode gas supply passage 8 can be increased. Therefore, since there is no increase or decrease in the total supply flow rate of the anode gas, the power generation efficiency does not decrease, the supply flow rate of the anode gas to the cell stack 2, particularly to the battery cell 20a at the central side part where the temperature tends to be high, can be increased, and the supply shortage of the anode gas (so-called fuel depletion) in the battery cell 20a at this central side part can be avoided.

[0049] Furthermore, when the detected temperature t0 rises above the second temperature rise threshold T2 from the initial detected temperature T0 (t0 > (T0 + T2)), the process proceeds from step S8 through step S9 to step S13. Based on this determination result from the temperature determination means 72, the fuel increase / decrease signal generation means 74 generates a second fuel increase / decrease signal, and the control means 76 controls the anode gas supply flow rate in two stages based on this second fuel increase / decrease signal (step S14).

[0050] During this second stage of control, while maintaining the fuel utilization rate in the cell stack 2, the control means 76 increases the rotational speed of the second fuel pump 14 by, for example, 4%, to further increase the supply flow rate of anode gas supplied through the first anode gas supply passage 8. Simultaneously, to reduce this increased supply flow rate, the control means 76 decreases the rotational speed of the second fuel pump 16 by, for example, 4%, to further decrease the supply flow rate of anode gas supplied through the second anode gas supply passage 10 (step S15). In this way, without increasing or decreasing the total supply flow rate of anode gas supplied to the cell stack 2, the control means 76 further increases the supply flow rate of anode gas supplied to the cell stack 2 (the battery cells 20a in the central part) through the first anode gas supply passage 8. Therefore, without increasing or decreasing the total supply flow rate of anode gas, the power generation efficiency can be reduced, and the supply flow rate of anode gas to the cell stack 2, especially the battery cells 20a in the central part, can be further increased, thus avoiding a shortage of anode gas supply to the battery cells 20a in the central part.

[0051] In this embodiment, the supply flow rate of the anode gas supplied to the cell stack 2 is controlled in two stages based on the temperature detected by the temperature sensing means 62. However, the control is not limited to this, and the supply flow rate of the anode gas can also be controlled in one stage or three or more stages based on the detected temperature.

[0052] [Second embodiment of the fuel cell system] Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to Figures 6 and 7. The basic configuration of the fuel cell system of this second embodiment is substantially the same as that of the first embodiment described above, and its basic configuration can be seen in Figure 1. In the following embodiments, parts that are substantially the same as those of the first embodiment will be given the same numbers, and their descriptions will be omitted.

[0053] In Figure 6, in this second embodiment, instead of directly measuring the temperature of the battery cells in the central part of the cell stack, operational data is acquired showing the relationship between the cumulative operating time from the start of operation after the installation of the fuel cell system and the temperature of the battery cells in the central part of the cell stack. Using this operational data, a first cumulative operating time U1 (e.g., 20,000 hours) corresponding to a first temperature rise threshold T1 (e.g., 10°C), a second cumulative operating time U2 (e.g., 40,000 hours) corresponding to a second temperature rise threshold T2 (e.g., 15°C), and a third cumulative operating time U3 (e.g., 60,000 hours) corresponding to a third temperature rise threshold T3 (e.g., 20°C) are set, and these first to third cumulative operating times U1 to U3 are registered in the memory means 78A.

[0054] In the control system of the fuel cell system of this second embodiment, an integrating timekeeping means 82 is provided instead of a temperature sensing means. For example, the controller 64A includes this integrating timekeeping means 82, and when a start signal is sent from the system start button 83, the integrating timekeeping means 82 is activated based on this start signal to measure the cumulative operating time from the start of operation after the installation of the fuel cell system. This cumulative timekeeping time u0 is stored in the memory means 78A.

[0055] The controller 64A of this embodiment differs from the first embodiment in that it includes an integrated operating time determination means 84 instead of a temperature determination means, and includes an integrated timing means 82 and an integrated operating time determination means 84, but the other configurations are the same as those of the first embodiment described above.

[0056] In this second embodiment, control is performed, for example, as follows: When the start button 83 is activated (step S21), the start signal is sent to the controller 64A to start the operation of the fuel cell system (step S22), and the cumulative timing means 82 is activated to measure the cumulative operating time since the start of operation after installation (step S23).

[0057] Once operation is started in this manner, the fuel utilization rate setting means 66 sets the fuel utilization rate (step S24), and the fuel supply flow rate calculation means 68 calculates the total supply flow rate of anode gas to be supplied to the cell stack 2 (step S25), and further calculates the supply flow rate supplied through the first anode gas supply passage 8 and the supply flow rate supplied through the second anode gas supply passage 10 (step S26). In addition, the air supply flow rate calculation means 70 calculates the supply flow rate of cathode gas to be supplied to the cell stack 2 (step S26). Once the supply flow rates of anode gas and cathode gas are calculated in this manner, the control means 76A controls the rotational speeds of the first and second fuel pumps 14, 16 and the air blower 20 so that the supply of anode gas and cathode gas to the cell stack is at the calculated flow rates (step S28). These controls from steps S24 to S28 are performed in the same manner as the controls from steps S2 to S6 in the first embodiment.

[0058] During this power generation operation, the cumulative timing means 82 measures the cumulative operating time from the start of operation after installation (step S29), and the cumulative operating time determination means 84 of the controller 64A determines whether the cumulative operating time u0 of the cumulative timing means 82 has exceeded a first cumulative operating time U1 (for example, 20,000 hours), a second cumulative operating time U2 (for example, 40,000 hours), or a third cumulative operating time U3 (for example, 60,000 hours).

[0059] When this accumulated operating time u0 is less than or equal to the first accumulated operating time U1 (u0 ≤ U1), the process returns from step S30 to step S29, and the power generation operation described above continues.

[0060] When the integrated operation time u0 exceeds the first integrated operation time U1 (for example, 20,000 hours) (u0 > U1), the process proceeds from step S30 to step S31. When the integrated operation time u0 is less than or equal to the second integrated operation time U2 (for example, 40,000 hours) (U1 < u0 ≤ U2), the process proceeds to step S32. Thus, based on this determination result of the integrated operation time determination means 84, it is presumed that the cell stack has been operated beyond the first integrated operation time U1 and the temperature of the battery cells in the central part thereof has risen beyond the first temperature rise threshold value T1, and the fuel increase / decrease signal generation means 74A generates a first fuel increase / decrease signal (step S32).

[0061] When the integrated operation time u0 exceeds the second integrated operation time U2 (for example, 40,000 hours) (u0 > U2), the process proceeds from step S31 to step S33. When the integrated operation time u0 is less than or equal to the third integrated operation time U3 (for example, 60,000 hours) (U2 < u0 ≤ U3), the process proceeds to step S34. Thus, based on this determination result of the integrated operation time determination means 84, it is presumed that the cell stack has been operated beyond the second integrated operation time U2 and the temperature of the battery cells in the central part thereof has risen beyond the second temperature rise threshold value T2, and the fuel increase / decrease signal generation means 74A generates a second fuel increase / decrease signal (step S36).

[0062] Furthermore, when the integrated operation time u0 exceeds the third integrated operation time U3 (for example, 60,000 hours) (u0 > U3), the process proceeds from step S33 to step S35. Thus, based on this determination result, the integrated operation time determination means 84 presumes that the cell stack has been operated beyond the third integrated operation time U3 and the temperature of the battery cells in the central part thereof has risen beyond the third temperature rise threshold value T34, and the fuel increase / decrease signal generation means 74A generates a third fuel increase / decrease signal.

[0063] When the fuel increase / decrease signal generation means 74A generates a first fuel increase / decrease signal (or a second fuel increase / decrease signal, a third fuel increase / decrease signal) in this way, the process proceeds to step S36 (or step S37, step S38), and the control means 76A controls the fuel supply flow rate supplied to the cell stack in one step (or two steps, three steps).

[0064] For example, during the first stage control (or second stage control, third stage control) of the fuel supply flow rate, in step S39 (or step S40, step S41), while maintaining the fuel utilization rate in the cell stack, the control means 76A increases the rotational speed of the first fuel pump 14 by, for example, 2% (or 4%, 6%) to increase the supply flow rate of anode gas supplied through the first anode gas supply passage. Conversely, to reduce this increased supply flow rate, the rotational speed of the second fuel pump 16 is decreased by, for example, 2% (or 4%, 6%) to decrease the supply flow rate of anode gas supplied through the second anode gas supply passage. In this way, the anode gas supplied to the battery cells in the central part of the cell stack 2 through the first anode gas supply passage is increased without increasing or decreasing the total supply flow rate of anode gas supplied to the cell stack. Therefore, even when controlled in this manner, as described above, there is no increase or decrease in the total supply flow rate of anode gas, so power generation efficiency is not reduced, and the supply flow rate of anode gas to the cell stack 2, especially the battery cells in the central part where temperatures tend to be high, can be increased, thereby avoiding a supply shortage (so-called fuel depletion) in the battery cells in this central part.

[0065] In this second embodiment, the supply flow rate of anode gas supplied to the cell stack is controlled in three stages based on the cumulative operating time. However, the control is not limited to this, and the supply flow rate of anode gas may be controlled in one or two stages, or in four or more stages, based on the cumulative operating time.

[0066] [Third embodiment of the fuel cell system] Next, a third embodiment of the fuel cell system according to the present invention will be described with reference to Figures 8 to 10. The basic configuration of the fuel cell system of this third embodiment is substantially the same as that of the second embodiment described above.

[0067] In Figure 8, in this third embodiment, instead of directly measuring the temperature of the battery cells in the central part of the cell stack, the output voltage of the battery cells changes when the supply flow rate of anode gas is temporarily increased during power generation of the cell stack, and this change in output voltage is larger for battery cells that are more depleted of fuel. Based on this, a first voltage difference threshold V1 and a second voltage difference threshold V2 are set, and these first and second voltage difference thresholds V1 and V2 are registered in the memory means 78B.

[0068] In the control system of this third embodiment of the fuel cell system, a voltage measuring means 90 is provided instead of a temperature sensing means, and the measurement signal from this voltage measuring means 90 is sent to the controller 64B.

[0069] Furthermore, the controller 64B includes a comparison voltage difference determination means 98 instead of a temperature determination means, and in relation to this comparison voltage difference determination means 98, it further includes a fuel depletion detection mode setting means 91, a fuel increase signal generation means 92, a rising voltage calculation means 94, and a rising voltage comparison calculation means 96. In this respect, it differs from the second embodiment, but the other configurations are the same as those of the second embodiment described above.

[0070] In this embodiment, the voltage measuring means 90 may measure the output voltage of the battery cells in the central part of the cell stack and measure the output voltage of the entire set of battery cells in the central part, or it may measure the output voltage of each battery cell in the central part.

[0071] Furthermore, the fuel depletion detection mode setting means 91 of the controller 64B sets a fuel depletion detection operation mode while the cell stack is generating power, and the fuel boost signal generation means 92 generates a fuel boost signal that temporarily increases the supply flow rate of anode gas (i.e., anode gas supplied through the first anode gas supply channel) supplied to the battery cells in the central part of the cell stack. In addition, the rise voltage calculation means 94 calculates the rise voltage value of the battery cells (in this form, the reference rise voltage value and the measured rise voltage value) when the supply flow rate of anode gas is temporarily increased.

[0072] Furthermore, the rising voltage comparison calculation means 96 compares the voltage difference between the reference rising voltage value V0 in the initial fuel depletion detection operation mode and the measured rising voltage value in the subsequent fuel depletion detection operation mode, and the comparison voltage difference determination means 98 determines whether the comparison voltage difference calculated by the rising voltage comparison calculation means 96 exceeds the first voltage difference threshold V1 or the second voltage difference threshold V2.

[0073] Referring to Figure 9, the relationship between fuel utilization rate and the output voltage (generated voltage) of the battery cell can be explained as follows: As shown in Figure 9, when the anode gas is temporarily increased and the fuel utilization rate decreases, the output voltage (generated voltage) of the battery cell changes and rises as shown in Figure 9.

[0074] As can be seen from Figure 9, in a battery cell with an anode gas supply condition where the fuel utilization rate exceeds, for example, 85%, the change in the output voltage of the battery cell (i.e., the voltage increase) when the anode gas is temporarily increased is large, and this change in output voltage becomes even larger as the fuel depletion progresses in the battery cell.

[0075] Therefore, if the change in output voltage in the initial state of the cell stack is taken as the reference rise voltage value, and the change in output voltage measured and calculated thereafter is taken as the measured rise voltage value, and the voltage difference calculated by comparing this reference rise voltage value with the subsequent measured rise voltage value becomes larger, it indicates that the battery cell's fuel depletion is progressing.

[0076] In this embodiment, since the comparative voltage difference is related to the depletion of the battery cell's fuel, a first voltage difference threshold V1 and a second voltage difference threshold V2 are set based on the degree of fuel depletion in the cell stack.

[0077] In this third embodiment, control is performed, for example, as follows: Referring to Figures 8 and 10, the start button 83 is activated (step S51), the start signal is sent to the controller 64B, and the operation of the fuel cell system begins (step S52), and the cumulative timing means 82 is activated to measure the cumulative operating time since the start of operation after installation (step S53).

[0078] Once operation is started in this manner, steps S54 to S57 are performed, and the control from steps S54 to S58 is carried out in the same way as the control from steps S24 to S28 in the second embodiment.

[0079] During this power generation operation, once an initial period (for example, 5,000 hours) has elapsed, the process proceeds from step S59 to step S60, where the fuel depletion detection mode setting means 91 sets the fuel depletion detection mode, and operation in fuel depletion detection mode begins. In this fuel depletion detection mode, the fuel increase signal generation means 92 generates a fuel increase signal (step S61), and based on this fuel increase signal, the control means 76B increases the rotational speed of the first fuel pump 14, thereby temporarily increasing the supply flow rate of anode gas supplied by the first fuel pump 14 (step S62).

[0080] At this time, the voltage measuring means 90 measures the output voltage of the battery cells in the central part of the cell stack before and after temporarily increasing the supply flow rate of the anode gas (step S63), and the rise voltage calculation means 74 calculates the voltage difference between the output voltage before and after increasing the supply flow rate of the anode gas, that is, the rise voltage value when the supply flow rate of the anode gas is increased (step S64), and this rise voltage value is registered in the memory means 78B as the reference rise voltage value.

[0081] Then, when the accumulating timekeeping means 82 has measured a predetermined time (for example, every 5,000 hours), the process proceeds from step S65 to step S66, where the fuel depletion detection mode setting means 91 sets the fuel depletion detection mode again, and the fuel depletion detection mode is operated. In this fuel depletion detection mode, as described above, the fuel increase signal generation means 92 generates a fuel increase signal (step S67), and based on this fuel increase signal, the control means 76B increases the rotational speed of the first fuel pump 14, thereby temporarily increasing the supply flow rate of anode gas supplied by the first fuel pump 14 (step S68).

[0082] In this case as well, the voltage measuring means 90 measures the output voltage of the battery cells in the central part of the cell stack before and after temporarily increasing the supply flow rate of the anode gas (step S69), and the voltage rise calculation means 94 calculates the voltage difference between the output voltage before and after increasing the supply flow rate of the anode gas, i.e., the measured voltage rise value.

[0083] Then, the voltage rise comparison calculation means 96 compares the reference voltage rise value registered in the memory means 78B with the measured voltage rise value calculated by the measured voltage rise calculation means 94 to calculate a comparison voltage difference value (voltage difference value between the reference voltage rise value and this measured voltage rise value) (step S70). A determination is made regarding this calculated comparison voltage difference value V0 (step S71), and the comparison voltage difference determination means 98 determines whether the comparison voltage difference value V0 calculated by the voltage rise comparison calculation means 96 exceeds the first voltage difference threshold V1 or the second voltage difference threshold V2.

[0084] When this comparative voltage difference value V0 is less than or equal to the first voltage difference threshold value V1 (V0≦V1), the process returns from step S72 to step S65. However, when this comparative voltage difference value V0 exceeds the first voltage difference threshold value V1 (V0>V1), the process proceeds from step S72 to step S73. When this comparative voltage difference value V0 is less than or equal to the second voltage difference threshold value V2 (V1<V0≦V2), the process proceeds to step S74. Thus, based on this determination result of the comparative voltage difference determination means 98, assuming that there is a slight fuel depletion in the cell stack, the fuel increase / decrease signal generation means 74B generates a first fuel increase / decrease signal, and the control means 76B controls the fuel supply flow rate supplied to the cell stack in one step (step S75). In the operating state where the fuel utilization rate in the cell stack is maintained as it is, the control means 76B increases the rotational speed of the first fuel pump 14 by, for example, 2% to increase the supply flow rate of the anode gas supplied through the first anode gas supply passage, and at the same time, to decrease the increased supply flow rate, decreases the rotational speed of the second fuel pump 16 by, for example, 2% to decrease the supply flow rate of the anode gas supplied through the second anode gas supply passage (step S76).

[0085] Also, when this comparative voltage difference value V0 exceeds the second voltage difference threshold value V2 (V0>V2), the process proceeds from step S73 to step S77. Based on this determination result of the comparative voltage difference determination means 98, assuming that there is fuel depletion in the cell stack, the fuel increase / decrease signal generation means 74B generates a second fuel increase / decrease signal, and the control means 76B controls the fuel supply flow rate supplied to the cell stack in two steps (step S78). In the operating state where the fuel utilization rate in the cell stack is maintained as it is, the control means 76B increases the rotational speed of the first fuel pump 14 by, for example, 4% to further increase the supply flow rate of the anode gas supplied through the first anode gas supply passage, and at the same time, to decrease the increased supply flow rate, decreases the rotational speed of the second fuel pump 16 by, for example, 4% to further decrease the supply flow rate of the anode gas supplied through the second anode gas supply passage (step S79).

[0086] Thus, in this third embodiment as well, the anode gas supply flow rate to the battery cells in the central part of the cell stack is increased without increasing or decreasing the total supply flow rate of anode gas supplied to the cell stack. Therefore, a shortage of anode gas supply (so-called fuel depletion) can be avoided without reducing the power generation efficiency of the cell stack.

[0087] In this third embodiment, the supply flow rate of anode gas supplied to the cell stack is controlled in two stages based on the comparison voltage difference. However, the control is not limited to this, and the supply flow rate of anode gas may be controlled in one stage or in three or more stages.

[0088] Although various embodiments of the solid oxide fuel cell system according to the present invention have been described above, the present invention is not limited to these embodiments, and various changes and modifications are possible without departing from the scope of the present invention.

[0089] For example, in the embodiments described above, the present invention was applied to a solid oxide type (SOFC) as the cell stack, but it is not limited to this form and can be similarly applied to molten carbonate type (MCFC), phosphoric acid type (PAFC), and others. [Explanation of Symbols]

[0090] 2-cell stack 4 Anode gas supply channel 6. Cathode gas supply channel 8. First anode gas supply channel 10. Second anode gas supply channel 12. Fuel blower (anode gas supply means) 14. No. 1 Fuel Blower 16. Second fuel blower 20, 20a, 20b battery cells 22, 22a, 22b Anode Room 24, 24a, 24b Cathode chamber 62 Temperature detection means 64, 64A, 64B controllers 72 Temperature determination means 74, 74A, 74B Fuel increase / decrease signal generation means 82. Accumulation Timekeeping Means 84. Means for determining cumulative operating time 90 Voltage measurement means 91 Fuel depletion detection mode setting means 92 Fuel Increase Signal Generation Means 96 Voltage Increase Comparison Calculation Means 98. Means for determining the comparative voltage difference

Claims

1. A fuel cell system comprising: a cell stack in which a plurality of battery cells are stacked, each having an electrolyte layer that conducts ions, an anode disposed on one side of the electrolyte layer, and a cathode disposed on the other side of the electrolyte layer; an anode gas supply channel for supplying anode gas to the anode chamber of the cell stack; a cathode gas supply channel for supplying cathode gas to the cathode chamber of the cell stack; an anode gas supply means for supplying anode gas; and a controller for controlling the anode gas supply means, The anode gas supply channel includes a first anode gas supply channel that supplies anode gas to the central portion of the cell stack in the stacking direction, and a second anode gas supply channel that supplies anode gas to both end portions of the cell stack in the stacking direction, and a temperature sensing means is provided in the central portion of the cell stack or its vicinity where a high temperature tendency occurs during the electrochemical reaction, or on the anode inlet side of the battery cell in the central portion. A fuel cell system characterized in that, when the temperature detected by the temperature detection means exceeds a predetermined temperature threshold, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel, while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

2. The fuel cell system according to claim 1, wherein the anode gas supply means includes a first anode gas supply means disposed in the first anode gas supply channel and a second anode gas supply means disposed in the second anode gas supply channel, and when the temperature of the central portion of the cell stack rises, the controller increases the rotation speed of the first anode gas supply means while decreasing the rotation speed of the second anode gas supply means without changing the total supply flow rate of anode gas supplied to the entire cell stack.

3. The fuel cell system according to claim 1 or 2, wherein a cumulative timing means is provided in relation to the cell stack for timing the cumulative operating time from the start of operation after installation, and when the cumulative timing means has timed a predetermined cumulative time, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel, while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

4. A fuel cell system comprising: a cell stack in which a plurality of battery cells are stacked, each having an electrolyte layer that conducts ions, an anode disposed on one side of the electrolyte layer, and a cathode disposed on the other side of the electrolyte layer; an anode gas supply channel for supplying anode gas to the anode chamber of the cell stack; a cathode gas supply channel for supplying cathode gas to the cathode chamber of the cell stack; an anode gas supply means for supplying anode gas; and a controller for controlling the anode gas supply means, The anode gas supply channel includes a first anode gas supply channel that supplies anode gas to the central portion of the cell stack in the stacking direction, and a second anode gas supply channel that supplies anode gas to both end portions of the cell stack in the stacking direction. A fuel cell system characterized in that, in relation to the cell stack, a voltage measuring means is provided for measuring the generated voltage of the battery cells in the central part of the cell stack, and in a fuel depletion detection mode for detecting the fuel depletion state of the battery cells, the supply flow rate of anode gas supplied through the first anode gas supply channel is temporarily increased, and when the comparison voltage difference between the measured voltage rise value and the reference voltage rise value of the voltage measured by the voltage measuring means at this time exceeds a predetermined voltage threshold, the controller increases the supply flow rate of anode gas supplied through the first anode gas supply channel while decreasing the supply flow rate of anode gas supplied through the second anode gas supply channel, without changing the total supply flow rate of anode gas supplied to the entire cell stack.

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