JP2013016356A - Solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell that implements improved energy efficiency while stably maintaining an appropriate temperature in a fuel cell module.SOLUTION: A solid oxide fuel cell (1) includes: a fuel cell module (2); fuel supply means (38); generating oxidant gas supply means (45); a combustion section (18) for combusting residual fuel; a heat storage material (7); demand detection means (126); temperature detection means (142); heat storage estimation means (110a) for integrating temperatures to estimate a heat storage; and control means (110) for executing appropriate temperature control using a heating effect of fuel and a cooling effect of generating oxidant gas. The control means has fuel usage rate adjustment means (110b) for, when the fuel cell module is within an appropriate temperature range, correcting fuel and oxidant gas supplies such that a fuel usage rate increases while substantially keeping the appropriate temperature range.

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell that generates variable generated power according to demand power.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, attaches electrodes on both sides thereof, and supplies fuel gas on one side, The fuel cell operates at a relatively high temperature by supplying an oxidant (air, oxygen, etc.) to the other side.

  In this SOFC, water vapor or carbon dioxide is generated by the reaction between oxygen ions that have passed through the oxide ion conductive solid electrolyte and fuel, and electric energy and thermal energy are generated. Electric energy is taken out of the SOFC and used for various electrical applications. On the other hand, thermal energy is used to raise the temperature of fuel, reformer, water, oxidant and the like.

  Japanese Unexamined Patent Application Publication No. 2010-92836 (Patent Document 1) describes a fuel cell device. This fuel cell device is a solid oxide fuel cell of a type that changes generated power according to demand power, and in a low load region where the generated power is low, a fuel utilization rate is higher than in a high load region where the generated power is large. It is disclosed that the operation is performed with reduced pressure. That is, in Patent Document 1, when the generated power is low, the ratio of the supplied fuel used for power generation is reduced, but on the other hand, it is not used for power generation but used for heating the fuel cell module. The fuel cell module is configured so that a large proportion of fuel is used to heat the fuel cell module without causing a significant decrease in the fuel generated, so that the fuel cell module is thermally self-supported and maintained at a temperature capable of generating electricity. Is.

  Specifically, in the region where the generated power is low, the heat generated in the fuel cell unit decreases with the power generation, so the temperature inside the fuel cell module tends to decrease, so the region where the generated power is low However, if a constant fuel utilization rate is maintained, the temperature inside the fuel cell module will decrease, making it difficult to maintain the temperature at which power can be generated. This makes it possible to increase the amount of fuel used to enable thermal independence.

  However, lowering the fuel utilization rate means increasing the amount of fuel that does not contribute to power generation even if thermal independence can be achieved. Therefore, if the operation with reduced fuel utilization rate is performed, the solid oxide fuel cell There is a problem that it causes a decrease in energy efficiency. Thus, the longer the operation in a state where the fuel utilization rate is lowered, the lower the overall energy efficiency. Therefore, solid oxidation generally considered to be higher in energy efficiency than a polymer membrane fuel cell (PEFC). This leads to the loss of the superiority of the physical fuel cell (SOFC).

  In particular, assuming that a solid oxide fuel cell is used for home use, the fuel cell must be used with a small amount of generated power for a predetermined time of the day, such as late at night when a householder is sleeping. This will significantly reduce the overall energy efficiency of the solid oxide fuel cell. Therefore, even in such a low power generation state, the fuel efficiency is high and the efficiency is high. An excellent technology capable of realizing operation has been desired for a solid oxide fuel cell.

  On the other hand, if the heat insulation of the housing for storing the fuel cells and the like is increased, the heat insulation that maintains the temperature inside the housing raised by the remaining fuel that is supplied to the fuel cells and not used for power generation is maintained. Since the performance is increased, the input heat amount can be reduced and the fuel efficiency can be increased. However, in a situation where the residual fuel becomes excessive, another problem that the temperature inside the casing rises excessively occurs. If the temperature in the casing rises excessively, the fuel cell in the casing, the reformer, etc. may be damaged. In addition, the excessively raised temperature has a high heat insulating property and a very large heat capacity, so that it is not easy to lower the temperature to an appropriate temperature, and there is a problem that further excessive temperature rise is caused.

  Here, Japanese Unexamined Patent Application Publication No. 2010-205670 (Patent Document 2) describes a technique for increasing the fuel utilization rate by using the residual heat accumulated in the fuel cell system. The fuel cell system can be operated at a high temperature in a high load zone where the generated power is large, and when the generated power is small, the temperature can be lowered slightly. For this reason, after the load changes from a high load to a low load, the temperature in the high load region is maintained for a while, and the inside of the module is maintained at a temperature higher than the operation temperature in the low load region due to the accumulated heat. In the invention described in Patent Document 2, the remaining heat is used to increase the fuel utilization rate, and the amount of heat necessary for heat self-supporting is supplemented by consuming the remaining heat. In other words, it is an excellent technology that enables operation with an increased fuel utilization rate up to fuel that is less than the amount of fuel that can be thermally independent.

JP 2010-92936 A JP 2010-205670 A

  However, in the invention described in Patent Document 2, since the accumulated residual heat is estimated from the integrated value of the electric load, the above-described characteristic of excessive temperature rise caused by the surplus fuel remaining It was not possible to make this work well for the problem. Specifically, in the invention described in Patent Document 2, since the amount of fuel supply is indirectly grasped from the generated power and the residual heat is estimated based on this, the residual fuel remaining without being used for power generation is determined. It cannot be grasped, and overheating caused by this cannot be prevented. Therefore, the invention described in Patent Document 2 cannot be applied to solve the above specific problem.

  In addition, even if the operation is continued with the temperature inside the fuel cell module stabilized at an appropriate temperature, the energy efficiency in the operation state is necessarily high, even if the fuel utilization rate is increased by utilizing the residual heat. It is not possible. That is, an increase in the fuel supply amount leads to an increase in residual fuel, which raises the temperature in the fuel cell module. On the other hand, when the power supply air supply amount is increased, the heat taken from the fuel cell module is increased, so that the temperature in the fuel cell module is lowered. Accordingly, when the fuel cell module is heated by supplying an excessive amount of fuel to the generated power and heating the inside of the fuel cell module, the fuel cell module temperature is decreased. Even in a state where the temperature is stable at an appropriate temperature, the energy efficiency is low. However, there is a problem that control that simply stabilizes the temperature inside the fuel cell module to an appropriate temperature cannot escape from such a stable state with low energy efficiency and increase the efficiency.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid oxide fuel cell that can utilize the accumulated residual heat and increase the energy efficiency while stably maintaining the inside of the fuel cell module at an appropriate temperature. Yes.

  In order to solve the above-described problems, the present invention provides a solid oxide fuel cell that generates variable generated power according to demand power, a fuel cell module that generates power using supplied fuel, and the fuel cell. Fuel supply means for supplying fuel to the module, oxidant gas supply means for power generation for supplying oxidant gas for power generation to the fuel cell module, and residual fuel supplied by the fuel supply means and not used for power generation A combustion section that heats the inside of the fuel cell module, a heat storage material that accumulates heat generated in the fuel cell module, a demand power detection means that detects demand power, and a temperature that detects the temperature in the fuel cell module A heat storage amount estimating means for estimating the amount of heat stored in the heat storage material by integrating the temperature detected by the temperature detecting means; If the estimated heat storage amount is large based on the demand power detected by the heat storage amount and the heat storage amount estimated by the heat storage amount estimation means, the fuel utilization rate increases for the same generated power and the residual heat amount is used. As described above, the fuel supply means and the power generation oxidant gas supply means are controlled, and the heating effect by increasing the fuel supply amount and the cooling effect by increasing the power generation oxidant gas supply amount are utilized. And a control means for executing an appropriate temperature control for converging the temperature in the fuel cell module to a predetermined appropriate temperature range, and the control means, when the temperature in the fuel cell module is in the appropriate temperature range, Correct the fuel supply amount and / or oxidant gas supply amount for power generation set by the appropriate temperature control so that the fuel utilization rate becomes high without the temperature largely deviating from the appropriate temperature range. It is characterized by having a fuel utilization rate adjusting means that.

  In the present invention configured as described above, the fuel supply unit and the power generation oxidant gas supply unit respectively supply the fuel and the power generation oxidant gas to the fuel cell module. The fuel cell module generates electric power using the supplied fuel and oxidant gas for power generation, and the remaining fuel that is not used for power generation is burned in the combustion section, and the generated heat is accumulated in the heat storage material. When the estimated heat storage amount is large based on the demand power detected by the demand power detection means and the heat storage amount estimated by the heat storage amount estimation means, the control means uses the fuel utilization rate for the same generated power. The fuel supply means and the oxidant gas supply means for power generation are controlled so that the residual heat quantity is utilized. In addition, the control means uses the heating effect by increasing the fuel supply amount and the cooling effect by increasing the oxidant gas supply amount for power generation to bring the temperature in the fuel cell module into a predetermined appropriate temperature range. Execute the appropriate temperature control to converge. The fuel utilization rate adjusting means incorporated in the control means is designed to ensure that when the temperature in the fuel cell module is within the appropriate temperature range, the fuel utilization rate becomes high without the temperature largely deviating from the appropriate temperature range. The fuel supply amount and / or the oxidant gas supply amount for power generation set by the control are corrected.

  According to the present invention configured as described above, when the estimated heat storage amount is large, the fuel utilization rate is increased for the same generated power. The energy efficiency of the fuel cell can be improved. Further, according to the present invention configured as above, since the heat storage is used when the amount of heat storage is large, it is possible to maintain the temperature in the fuel cell module within an appropriate temperature range without reducing the energy efficiency. Temperature control can be performed. However, even if the fuel cell module is maintained at an appropriate temperature and is operated stably by appropriate temperature control, the energy efficiency in that state may be low. For example, if the heating with increased fuel supply and the cooling with increased oxidant gas supply for power generation coexist and are thermally stable, the supplied fuel is wasted and energy efficiency Is low. According to the solid oxide fuel cell of the present invention, in a state where the temperature is within the appropriate temperature range, the fuel utilization rate adjusting means is adjusted so as to increase the fuel utilization rate without substantially deviating from the appropriate temperature range. Since the fuel supply amount and / or the oxidant gas supply amount for power generation set by the control are corrected, it is possible to achieve both improvement of the appropriate temperature and energy efficiency.

In the present invention, preferably, the fuel utilization rate adjusting means does not perform the correction when the rate of change in temperature in the fuel cell module is equal to or greater than a predetermined correction prohibition change rate.
In general, since the fuel cell module has a large heat capacity, even if the fuel cell module is currently in the proper temperature range, the temperature may not be converged within the proper temperature range as it is, and may pass the proper temperature range. When the fuel utilization rate adjustment control is executed in such a thermally unstable state, the thermal balance of the fuel cell module may be greatly broken, leading to a rapid temperature drop or excessive temperature rise. According to the present invention configured as described above, even when the fuel cell module is in the proper temperature range, the correction is not executed when the temperature change rate is large. It is possible to prevent the descent and overheating.

In the present invention, preferably, the fuel supply amount and the oxidant gas supply amount for power generation both change as a result of the correction by the fuel utilization rate adjusting means.
According to the present invention configured as described above, the temperature decrease due to the fuel supply amount decrease and the temperature increase due to the power generation oxidant gas supply amount decrease are offset, and the thermal balance is maintained while the fuel supply amount is decreased. can do.

  In the present invention, preferably, the fuel utilization rate adjusting means performs correction so that the fuel supply amount and the power generation oxidant gas supply amount are decreased, and the change rate of the power generation oxidant gas supply amount due to the correction is increased. Then, the fuel supply means and the power generating oxidant gas supply means are controlled so as to be larger than the change rate of the fuel supply amount.

  According to the present invention configured as described above, even when the fuel supply amount and the power generation oxidant gas supply amount are reduced by the fuel utilization rate adjusting means, the rate of change of the power generation oxidant gas supply amount is increased. Therefore, the risk of the fuel cell module deviating from the appropriate temperature range can be suppressed by the rapid correction of the fuel supply amount.

  In the present invention, preferably, the fuel utilization rate adjusting means controls only the oxidant gas supply means for power generation to reduce the supply amount of oxidant gas for power generation, and a fuel cell accompanying a decrease in the supply amount of oxidant gas for power generation. The fuel supply amount is reduced by appropriate temperature control corresponding to the temperature rise in the module.

  According to the present invention configured as described above, in the fuel utilization rate adjustment control, only the power generation oxidant gas supply amount is reduced, so that the fuel supply amount is not directly corrected by the fuel utilization rate adjustment control. For this reason, it is possible to prevent the thermal balance from being largely lost by correcting the fuel supply amount and changing it rapidly.

  In the present invention, preferably, the fuel utilization rate adjusting means decreases the fuel supply amount determined based on the integrated value by increasing / decreasing the integrated value of the temperature by the heat storage amount estimating means, and / or the integrated value. The oxidant gas supply amount for power generation determined based on the above is reduced.

  According to the present invention configured as described above, the fuel supply amount and / or the oxidant gas supply amount for power generation is decreased by increasing or decreasing the integrated value of the temperature. Therefore, compared with the case of directly correcting the supply amount, The fuel utilization rate can be increased gradually, and the risk that the temperature in the fuel cell module deviates from the appropriate temperature range can be further reduced.

  In the present invention, preferably, the fuel utilization rate adjusting means reduces the power generation oxidant gas supply amount by reducing only the integrated value used for determining the power generation oxidant gas supply amount.

  According to the present invention configured as described above, since only the power generation oxidant gas supply amount is decreased by reducing the integrated value, compared to the case where the integrated value for determining the fuel supply amount is changed, Since the fuel supply amount changes gradually, the temperature in the fuel cell module can be more reliably maintained within the appropriate temperature range.

  According to the solid oxide fuel cell of the present invention, harmful gas contained in exhaust gas can be reduced while improving energy efficiency by utilizing the accumulated residual heat.

1 is an overall configuration diagram showing a fuel cell device according to an embodiment of the present invention. It is front sectional drawing which shows the fuel cell module of the fuel cell apparatus by one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a fuel cell device by one embodiment of the present invention. It is a perspective view which shows the fuel cell stack of the fuel cell apparatus by one Embodiment of this invention. 1 is a block diagram showing a fuel cell device according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the fuel cell apparatus by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the stop of the fuel cell apparatus by one Embodiment of this invention. It is a graph which shows the relationship between the output electric current and fuel supply amount in the solid oxide fuel cell of 1st Embodiment of this invention. It is a graph which shows the relationship between the output electric current in the solid oxide fuel cell of 1st Embodiment of this invention, and the calorie | heat amount which generate | occur | produces with the supplied fuel. It is the graph which showed typically the relation of the change of demand electric power, the amount of fuel supply, and the current actually taken out from a fuel cell module. It is the graph which showed an example of the relationship of the electric current actually taken out from the air supply amount for power generation, the water supply amount, the fuel supply amount, and the fuel cell module. It is a flowchart which shows the procedure which determines the air supply amount for electric power generation, the water supply amount, and the fuel supply amount based on detection temperature Td. It is a graph which shows the temperature of the appropriate fuel cell stack with respect to a generated electric current. It is a graph which shows the fuel usage rate determined according to an integrated value. It is a graph which shows the range of the value of the fuel utilization factor which can be determined with respect to each generated current. It is a graph which shows the air utilization factor determined according to an integrated value. It is a graph which shows the range of the value of the air utilization factor which can be determined with respect to each generated electric current. It is a graph for determining water supply with respect to the determined air utilization rate. It is a graph which shows the electric power generation voltage of the fuel cell module appropriate with respect to electric power generation current. It is a flowchart of the subroutine for performing fuel utilization rate adjustment control called from the flowchart of FIG. It is a time chart which shows an example of the control by fuel utilization rate adjustment control.

Next, a solid oxide fuel cell (SOFC) according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell (SOFC) 1 according to an embodiment of the present invention includes a fuel cell module 2 and an auxiliary unit 4.

  The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed inside the housing 6 via a heat insulating material 7. A fuel cell assembly 12 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant (air) ) And combusted to generate exhaust gas.
Further, a reformer 20 for reforming the fuel gas is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which a reforming reaction can be performed by the combustion heat of the residual gas. ing. Further, an air heat exchanger 22 is disposed above the reformer 20 to heat the air by receiving heat from the reformer 20 and suppress a temperature drop of the reformer 20.

  Next, the auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as tap water and uses the filter to obtain pure water, and a water flow rate that adjusts the flow rate of the water supplied from the water storage tank. An adjustment unit 28 (such as a “water pump” driven by a motor) is provided. The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the flow rate of air, and a power generation air flow rate adjusting unit. 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

Next, a hot water production apparatus 50 to which exhaust gas is supplied is connected to the fuel cell module 2. The hot water production apparatus 50 is supplied with tap water from the water supply source 24, and the tap water is heated by the heat of the exhaust gas and supplied to a hot water storage tank of an external hot water heater (not shown).
The fuel cell module 2 is provided with a control box 52 for controlling the amount of fuel gas supplied and the like.
Furthermore, the fuel cell module 2 is connected to an inverter 54 that is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module to the outside.

Next, the internal structure of a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a side sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention, and FIG. 3 is a sectional view taken along line III-III in FIG. .
As shown in FIGS. 2 and 3, in the sealed space 8 in the housing 6 of the fuel cell module 2, as described above, the fuel cell assembly 12, the reformer 20, and the air heat exchange are sequentially performed from below. A vessel 22 is arranged.

  The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In the reformer 20, an evaporator 20a and a reformer 20b are formed in this order from the upstream side, and the evaporator 20a and the reformer 20b are filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 20 are reformed by the reforming catalyst filled in the reformer 20. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

  A fuel gas supply pipe 64 is connected to the downstream end side of the reformer 20, and the fuel gas supply pipe 64 extends downward and further in an manifold 66 formed below the fuel cell assembly 12. It extends horizontally. A plurality of fuel supply holes 64 b are formed in the lower surface of the horizontal portion 64 a of the fuel gas supply pipe 64, and the reformed fuel gas is supplied into the manifold 66 from the fuel supply holes 64 b.

  A lower support plate 68 having a through hole for supporting the fuel cell stack 14 described above is attached above the manifold 66, and the fuel gas in the manifold 66 flows into the fuel cell unit 16. Supplied.

  Next, an air heat exchanger 22 is provided above the reformer 20. The air heat exchanger 22 includes an air aggregation chamber 70 on the upstream side and two air distribution chambers 72 on the downstream side. The air aggregation chamber 70 and the air distribution chamber 72 include six air flow path tubes 74. Connected by. Here, as shown in FIG. 3, three air flow path pipes 74 form a set (74a, 74b, 74c, 74d, 74e, 74f), and the air in the air collecting chamber 70 is in each set. It flows into each air distribution chamber 72 from the air flow path pipe 74.

The air flowing through the six air flow path pipes 74 of the air heat exchanger 22 is preheated by exhaust gas that burns and rises in the combustion chamber 18.
An air introduction pipe 76 is connected to each of the air distribution chambers 72, the air introduction pipe 76 extends downward, and the lower end side communicates with the lower space of the power generation chamber 10, and the air that has been preheated in the power generation chamber 10. Is introduced.

Next, an exhaust gas chamber 78 is formed below the manifold 66. Further, as shown in FIG. 3, an exhaust gas passage 80 extending in the vertical direction is formed inside the front surface 6 a and the rear surface 6 b which are surfaces along the longitudinal direction of the housing 6, and the upper end of the exhaust gas chamber passage 80 is formed. The side communicates with the space in which the air heat exchanger 22 is disposed, and the lower end side communicates with the exhaust gas chamber 78. Further, an exhaust gas discharge pipe 82 is connected to substantially the center of the lower surface of the exhaust gas chamber 78, and the downstream end of the exhaust gas discharge pipe 82 is connected to the above-described hot water producing apparatus 50 shown in FIG.
As shown in FIG. 2, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.

Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 4 is a partial sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolyte layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

  Since the inner electrode terminal 86 attached to the upper end side and the lower end side of the fuel cell 16 has the same structure, the inner electrode terminal 86 attached to the upper end side will be specifically described here. The upper portion 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an upper end surface 90 c exposed to the electrolyte layer 94 and the outer electrode layer 92. The inner electrode terminal 86 is connected to the outer peripheral surface 90b of the inner electrode layer 90 through a conductive sealing material 96, and is further in direct contact with the upper end surface 90c of the inner electrode layer 90, thereby Electrically connected. A fuel gas passage 98 communicating with the fuel gas passage 88 of the inner electrode layer 90 is formed at the center of the inner electrode terminal 86.

  The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 94 is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 5 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 5, the fuel cell stack 14 includes 16 fuel cell units 16, and the lower end side and the upper end side of these fuel cell units 16 are a ceramic lower support plate 68 and an upper side, respectively. It is supported by the support plate 100. The lower support plate 68 and the upper support plate 100 are formed with through holes 68a and 100a through which the inner electrode terminal 86 can pass.

  Furthermore, a current collector 102 and an external terminal 104 are attached to the fuel cell unit 16. The current collector 102 includes a fuel electrode connection portion 102a that is electrically connected to an inner electrode terminal 86 attached to the inner electrode layer 90 that is a fuel electrode, and an entire outer peripheral surface of the outer electrode layer 92 that is an air electrode. And an air electrode connecting portion 102b electrically connected to each other. The air electrode connecting portion 102b is formed of a vertical portion 102c extending in the vertical direction on the surface of the outer electrode layer 92 and a plurality of horizontal portions 102d extending in a horizontal direction along the surface of the outer electrode layer 92 from the vertical portion 102c. Has been. The fuel electrode connection portion 102a is linearly directed obliquely upward or obliquely downward from the vertical portion 102c of the air electrode connection portion 102b toward the inner electrode terminal 86 positioned in the vertical direction of the fuel cell unit 16. It extends.

  Further, the inner electrode terminals 86 at the upper end and the lower end of the two fuel cell units 16 located at the ends of the fuel cell stack 14 (the far left side and the near side in FIG. 5) are external terminals, respectively. 104 is connected. These external terminals 104 are connected to the external terminals 104 (not shown) of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and as described above, the 160 fuel cell units 16 Everything is connected in series.

Next, sensors and the like attached to the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 6, the solid oxide fuel cell 1 includes a control unit 110, and the control unit 110 includes operation buttons such as “ON” and “OFF” for operation by the user. An operation device 112, a display device 114 for displaying various data such as a power generation output value (wattage), and a notification device 116 for issuing a warning (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 110.
First, the combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4.
The CO detection sensor 122 detects whether or not CO in the exhaust gas originally discharged to the outside through the exhaust gas passage 80 or the like leaks to an external housing (not shown) that covers the fuel cell module 2 and the auxiliary unit 4. Is to do.
The hot water storage state detection sensor 124 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 126 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown).
The power generation air flow rate detection sensor 128 is for detecting the flow rate of power generation air supplied to the power generation chamber 10.
The reforming air flow sensor 130 is for detecting the flow rate of the reforming air supplied to the reformer 20.
The fuel flow sensor 132 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

The water flow rate sensor 134 is for detecting the flow rate of pure water supplied to the reformer 20.
The water level sensor 136 is for detecting the water level of the pure water tank 26.
The pressure sensor 138 is for detecting the pressure on the upstream side outside the reformer 20.
The exhaust temperature sensor 140 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

As shown in FIG. 3, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14 to thereby detect the fuel cell stack. 14 (ie, the fuel cell 84 itself) is estimated.
The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20.
The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

  Signals from these sensors are sent to the control unit 110, and the control unit 110, based on data based on these signals, the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, A control signal is sent to the power generation air flow rate adjusting unit 45 to control each flow rate in these units.

Next, the operation at the time of start-up by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 7 is a time chart showing the operation at the start-up of the solid oxide fuel cell (SOFC) according to the embodiment of the present invention.
Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

First, reforming air is supplied from the reforming air flow rate adjustment unit 44 to the reformer 20 of the fuel cell module 2 via the first heater 46. At the same time, the power generation air is supplied from the power generation air flow rate adjustment unit 45 to the air heat exchanger 22 of the fuel cell module 2 via the second heater 48, and this power generation air is supplied to the power generation chamber 10 and the combustion chamber. Reach chamber 18.
Immediately after this, the fuel gas is also supplied from the fuel flow rate adjustment unit 38, and the fuel gas mixed with the reforming air passes through the reformer 20, the fuel cell stack 14, and the fuel cell unit 16, and It reaches the combustion chamber 18.

  Next, the ignition device 83 is ignited to burn the fuel gas and air (reforming air and power generation air) in the combustion chamber 18. Exhaust gas is generated by the combustion of the fuel gas and air, and the power generation chamber 10 is warmed by the exhaust gas, and when the exhaust gas rises in the sealed space 8 of the fuel cell module 2, The fuel gas containing the reforming air is warmed, and the power generation air in the air heat exchanger 22 is also warmed.

  At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction POX shown in FIG. Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. Further, the heated fuel gas is supplied to the lower side of the fuel cell stack 14 through the fuel gas supply pipe 64, whereby the fuel cell stack 14 is heated from below, and the combustion chamber 18 also has the fuel gas and air. The fuel cell stack 14 is also heated from above, and as a result, the fuel cell stack 14 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)

  When the reformer temperature sensor 148 detects that the reformer 20 has reached a predetermined temperature (for example, 600 ° C.) after the partial oxidation reforming reaction POX is started, the water flow rate adjustment unit 28 and the fuel flow rate adjustment unit 38 are detected. In addition, the reforming air flow rate adjusting unit 44 supplies a gas in which fuel gas, reforming air, and water vapor are mixed in advance to the reformer 20. At this time, in the reformer 20, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 20 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

  When the reformer temperature sensor 146 detects that the reformer 20 has reached a predetermined temperature (for example, 700 ° C.) after the start of the autothermal reforming reaction ATR shown in Formula (2), the reforming air flow rate The supply of reforming air by the adjustment unit 44 is stopped, and the supply of water vapor by the water flow rate adjustment unit 28 is increased. As a result, the reformer 20 is supplied with a gas that does not contain air and contains only fuel gas and water vapor, and the steam reforming reaction SR of formula (3) proceeds in the reformer 20.

_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (2)
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (3)

  Since the steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 18. At this stage, since the fuel cell module 2 is in the final stage of start-up, the power generation chamber 10 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 10 is greatly reduced in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 18.

  In this way, after the fuel cell module 2 is ignited by the ignition device 83, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the inside of the power generation chamber 10 The temperature gradually increases. Next, when the temperature in the power generation chamber 10 and the fuel cell 84 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module 2 is stably operated, the circuit including the fuel cell module 2 is closed, and the fuel cell Power generation by the module 2 is started, so that a current flows in the circuit. Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises. As a result, the rated temperature at which the fuel cell module 2 is operated becomes, for example, 600 ° C. to 800 ° C.

  Thereafter, in order to maintain the rated temperature, more fuel gas and air than the amount of fuel gas and air consumed in the fuel cell 84 are supplied, and combustion in the combustion chamber 18 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

Next, the operation when the operation of the solid oxide fuel cell (SOFC) according to the present embodiment is stopped will be described with reference to FIG. FIG. 8 is a time chart showing the operation when the solid oxide fuel cell (SOFC) is stopped according to this embodiment.
As shown in FIG. 8, when the operation of the fuel cell module 2 is stopped, first, the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28 are operated to supply fuel gas and water vapor to the reformer 20. Reduce the amount.

  Further, when the operation of the fuel cell module 2 is stopped, the amount of fuel gas and water vapor supplied to the reformer 20 is reduced, and at the same time, the fuel cell module for generating air by the reforming air flow rate adjusting unit 44 The supply amount into 2 is increased, the fuel cell assembly 12 and the reformer 20 are cooled by air, and these temperatures are lowered. Thereafter, when the temperature of the reformer 20 decreases to a predetermined temperature, for example, 400 ° C., the supply of fuel gas and steam to the reformer 20 is stopped, and the steam reforming reaction SR of the reformer 20 is ended. . This supply of power generation air continues until the temperature of the reformer 20 decreases to a predetermined temperature, for example, 200 ° C., and when this temperature is reached, the power generation air from the power generation air flow rate adjustment unit 45 is supplied. Stop supplying.

  As described above, in the present embodiment, when the operation of the fuel cell module 2 is stopped, the steam reforming reaction SR by the reformer 20 and the cooling by the power generation air are used in combination. The operation of the fuel cell module can be stopped.

Next, control of the solid oxide fuel cell 1 according to the first embodiment of the present invention will be described with reference to FIGS. 9 to 23.
FIG. 9 is a graph showing the relationship between the output current and the fuel supply amount in the solid oxide fuel cell 1 of the present embodiment. FIG. 10 is a graph showing the relationship between the output current in the solid oxide fuel cell 1 and the amount of heat generated by the supplied fuel.

  First, as shown by the solid line in FIG. 9, the solid oxide fuel cell 1 of the present embodiment is configured such that the output can be varied within 700 W (output current 7 A), which is the rated output power, according to the demand power. Has been. The fuel supply amount (L / min) required to output the required power is set as shown by the solid line in FIG. Note that the fuel supply amount shown in FIG. 9 is for the case where the heat amount accumulated in the heat insulating material 7 described later is not used. The control unit 110 as the control means determines the fuel supply amount according to the demand power detected by the power state detection sensor 126 as the demand power detection means and the estimated heat storage amount, and based on this, the fuel supply means The fuel flow rate adjustment unit 38 is controlled.

  The amount of fuel required for power generation is proportional to the output power (output current), but as shown by the solid line in FIG. 9, the set fuel supply amount is not proportional to the output current. This is because if the fuel supply amount is reduced in proportion to the output power, the fuel cell unit 16 in the fuel cell module 2 cannot be maintained at a temperature at which power can be generated. For this reason, in the example shown in FIG. 9, the fuel utilization rate is set to about 70% when the generated power is near the output current 7A, and the fuel utilization rate is set to about 50% when the generated power is about 2A. In this way, the fuel utilization rate in the small power generation region is reduced, the remaining fuel that is not used for power generation is burned and used for heating the reformer 20 and the like, thereby reducing the temperature of the fuel cell unit 16. And the temperature inside the fuel cell module 2 is maintained at a temperature at which power generation is possible.

  However, since the fuel that does not contribute to power generation is increased by reducing the fuel utilization rate, the energy efficiency of the solid oxide fuel cell 1 in the small power generation region is reduced. In the solid oxide fuel cell 1 of the present embodiment, the heat storage amount is estimated by the heat storage amount estimation means 110a (FIG. 6) built in the control unit 110. If the estimated heat storage amount is large, the fuel is used. Residual heat utilization control with a higher rate is executed. By the residual heat amount utilization control, the fuel supply amount indicated by the solid line in FIG. 9 is changed / corrected, and is decreased as shown by an example in the broken line in FIG. Thereby, the fuel utilization rate in the small power generation region is increased, and the energy efficiency of the solid oxide fuel cell 1 is improved.

  FIG. 10 is a graph schematically showing the relationship between the output current when the fuel is supplied without using the remaining heat amount and the heat amount of the supplied fuel in the solid oxide fuel cell 1 of the present embodiment. It is. As shown by the one-dot chain line in FIG. 10, the amount of heat necessary to make the fuel cell module 2 thermally independent and operate stably increases monotonically with an increase in output current. The graph shown by the solid line in FIG. 10 shows the amount of heat when the fuel is supplied without using the remaining amount of heat. In the present embodiment, in a region lower than the output current 5A corresponding to the medium power generation, the required amount of heat indicated by the alternate long and short dash line and the amount of heat of the basic fuel supply amount indicated by the solid line substantially coincide.

  Further, in a region higher than the output current 5A, the heat amount of the basic fuel supply amount indicated by the solid line exceeds the heat amount indicated by the one-dot chain line that is at least necessary for heat self-sustainment. The surplus heat amount between the solid line and the broken line is accumulated in the heat insulating material 7 that is a heat storage material provided in the fuel cell module 2. Further, the output current from the solid oxide fuel cell 1 is correlated with the temperature of the fuel cell unit 16 in the fuel cell module 2 when this current is constantly output, and the output current is increased. In order to do so, it is necessary to increase the temperature of the fuel cell unit 16, and therefore the temperature of the fuel cell unit 16 is high when the output current is large. In the solid oxide fuel cell 1 of the present embodiment, a larger amount of heat is accumulated in the heat insulating material 7 when the output current is 5 A or more.

  In the present embodiment, as will be described later, when the amount of heat that can be used in the heat insulating material 7 is accumulated, correction is made so as to decrease the fuel supply amount to improve the fuel utilization rate. On the other hand, the heat quantity deficient due to the reduction in the fuel supply quantity is supplemented by using the heat quantity accumulated in the heat insulating material 7 of the fuel cell module 2. In this embodiment, since the heat capacity of the heat insulating material 7 is very large, the heat insulating material is operated when the fuel cell module 2 is operated in a region where the generated power is small after being operated for a predetermined time with large generated power. The amount of heat stored in 7 can be used for 2 hours or more, and the fuel utilization rate is improved by performing correction to reduce the fuel supply amount during this period.

Next, with reference to FIG.11 and FIG.12, accumulation | storage of the calorie | heat amount to the heat insulating material 7 accompanying a load following is demonstrated.
FIG. 11 is a graph schematically showing the relationship between the change in demand power, the fuel supply amount, and the current actually taken out from the fuel cell module 2. FIG. 12 is a graph showing an example of the relationship between the power generation air supply amount, the water supply amount, the fuel supply amount, and the current actually extracted from the fuel cell module 2.

  As shown in FIG. 11, the fuel cell module 2 is controlled so as to be able to generate power corresponding to the demand power shown in the uppermost stage of FIG. 11. The control unit 110 sets the fuel supply current value If, which is a target current to be generated by the fuel cell module 2, based on the demand power as shown in the second graph of FIG. Although the fuel supply current value If is set so as to substantially follow the change in demand power, the response speed of the fuel cell module 2 is extremely slow with respect to the change in demand power. It is set so as to follow the demand power gently without following the change. In addition, when the demand power exceeds the maximum rated power of the solid oxide fuel cell, the fuel supply current value If follows the current value corresponding to the maximum rated power and is set to a current value higher than that. There is no.

  As shown in the third graph of FIG. 11, the control unit 110 controls the fuel flow rate adjustment unit 38 that is a fuel supply unit to generate a fuel supply amount at a flow rate that can generate power corresponding to the fuel supply current value If. Fr is supplied to the fuel cell module 2. If the fuel utilization rate, which is the ratio of the fuel actually used for power generation with respect to the fuel supply amount, is constant, the fuel supply current value If and the fuel supply amount Fr are proportional. The graph of FIG. 11 is drawn on the assumption that the fuel supply current value If and the fuel supply amount Fr are proportional, but as will be described later, the fuel utilization rate is actually not constant in this embodiment as well.

  Further, as shown in the lowermost graph of FIG. 11, the control unit 110 outputs a signal that instructs the inverter 54 about the extractable current Iinv that is a current value that can be extracted from the fuel cell module 2. The inverter 54 extracts current (electric power) from the fuel cell module 2 within the range of the extractable current Iinv according to the demand power that changes suddenly every moment. The portion where the demand power exceeds the extractable current Iinv is supplied from the grid power. Here, as shown in FIG. 11, when the current tends to increase, the extractable current Iinv instructed by the control unit 110 to the inverter 54 changes so as to be delayed by a predetermined time with respect to the change in the fuel supply amount Fr. Is set. For example, at time t10 in FIG. 11, after the fuel supply current value If and the fuel supply amount Fr start to increase, the increase of the extractable current Iinv is started with a delay. Also at time t12, after the fuel supply current value If and the fuel supply amount Fr increase, the increase of the extractable current Iinv is started with a delay. As described above, after the fuel supply amount Fr is increased, the timing at which the electric power actually extracted from the fuel cell module 2 is increased is delayed so that the fuel supplied to the fuel cell module 2 passes through the reformer 20 and the like. A time delay until the fuel cell stack 14 is reached and a time delay until the actual power generation reaction becomes possible after the fuel reaches the battery cell stack 14 are dealt with. This reliably prevents the fuel battery cell unit 16 from being depleted of fuel and damaging the fuel battery cell unit 16.

  FIG. 12 shows in more detail the relationship between the power supply air supply amount, the water supply amount, and the fuel supply amount, and the extractable current Iinv. Note that the graphs of the power supply air supply amount, the water supply amount, and the fuel supply amount shown in FIG. 12 are all converted into current values corresponding to the respective supply amounts. That is, if the supplied power generation air, water, and fuel are all set to supply amounts that are used for power generation, the graphs of the respective supply amounts overlap the graph of the extractable current Iinv. It has been converted. Therefore, the amount of deviation of each supply amount graph with respect to the extractable current Iinv corresponds to the surplus of each supply amount. The remaining fuel that is not used for power generation is burned in the combustion chamber 18 that is a combustion section above the fuel cell stack 14 and is used for heating in the fuel cell module 2.

  As shown in FIG. 12, the air supply amount for power generation, the water supply amount, and the fuel supply amount always exceed the extractable current Iinv, and the current exceeding the current that can be generated by each supply amount is greater than the fuel cell module 2. The fuel cell unit 16 is prevented from being damaged by fuel exhaustion, air exhaustion, and the like. Further, the water supply amount is set to a supply amount capable of steam reforming all of the supplied fuel with respect to the fuel supply amount supplied exceeding the extractable current Iinv. That is, the amount of water supplied is the ratio of the amount of water vapor necessary for steam reforming and the amount of carbon contained in the fuel, so that all of the supplied fuel is steam reformed. It is set in consideration. This prevents carbon deposition in the reformer. Further, in the region A and region C of FIG. 12 where the extractable current Iinv tends to increase with the increase in demand power, the margin of fuel supply amount and the like is greater than the region B where the extractable current Iinv is flat. Is set large (low fuel utilization). In addition, when the generated power is increased, the fuel supply amount supplied to the fuel cell module 2 is increased by a power extraction delay means (not shown) built in the control unit 110, and then the fuel cell is delayed. The generated power output from the module 2 is increased. That is, after the fuel supply amount is changed according to the change in demand power, the power actually output from the fuel cell module 2 is changed with a delay. Furthermore, when the extractable current Iinv is suddenly reduced according to the reduction in demand power (the initial period of the region C and the region D), each supply amount decreases with a predetermined time delay from the decrease of the extractable current Iinv. Is done. Therefore, a very large amount of residual fuel is generated during a predetermined time after the extractable current Iinv suddenly decreases. Such a rapid decrease in the extractable current Iinv is performed in order to prevent a reverse current flow when the demand power rapidly decreases. Thus, when the generated power is increased and when the generated power is decreased, more residual fuel is generated than when the generated power is constant, and this residual fuel is used for heating the fuel cell module 2. Will be. For this reason, the fuel cell module 2 is strongly heated not only when the fuel cell module 2 is operated for a long time with high generated power but also when the generated power is frequently increased or decreased, and a large amount of heat is accumulated in the heat insulating material 7. Is done.

  In the solid oxide fuel cell of this embodiment, after operating for a long time with high generated power, not only the heat storage is used when the generated power decreases, but also the amount of heat that is being accumulated due to the increase or decrease of the generated power, etc. Are used sequentially depending on the situation.

Next, a procedure for determining the power generation air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td will be described with reference to FIGS.
FIG. 13 is a flowchart showing a procedure for determining the power generation air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td. FIG. 14 is a graph showing the proper temperature of the fuel cell stack 14 with respect to the generated current. FIG. 15 is a graph showing the fuel utilization rate determined according to the integrated value. FIG. 16 is a graph showing a range of fuel utilization rate values that can be determined for each generated current. FIG. 17 is a graph showing the air utilization rate determined according to the integrated value. FIG. 18 is a graph showing a range of air utilization rate values that can be determined for each generated current. FIG. 19 is a graph for determining the water supply amount with respect to the determined air utilization rate. FIG. 20 is a graph showing an appropriate generated voltage of the fuel cell module 2 with respect to the generated current.

  As indicated by a one-dot chain line in FIG. 14, in the present embodiment, an appropriate temperature Ts (I) of the fuel cell stack 14 is defined for the current to be generated by the fuel cell module 2. The control unit 110 controls the fuel supply amount and the like so that the temperature of the fuel cell stack 14 approaches the appropriate temperature Ts (I). In other words, the control unit 110 roughly indicates that when the temperature of the fuel cell stack 14 is higher than the generated current (when the temperature of the fuel cell stack 14 is above the one-dot chain line in FIG. 14). The fuel utilization rate is increased, the amount of heat accumulated in the heat insulating material 7 and the like is actively consumed, and the temperature in the fuel cell module 2 is lowered. On the other hand, when the temperature of the fuel cell stack 14 is lower than the generated current, the fuel utilization rate is reduced so that the temperature in the fuel cell module 2 does not decrease. Specifically, the fuel utilization rate is not determined based on the simple detected temperature Td, but is calculated by adding the addition / subtraction values determined based on the detected temperature Td and the like to reflect the heat storage. The fuel utilization rate and the like are determined based on this amount. The estimated value of the heat storage amount by integrating the addition / subtraction values is calculated by the heat storage amount estimation means 110a built in the control unit.

  The flowchart shown in FIG. 13 determines the power generation air supply amount, the water supply amount, and the fuel supply amount based on the detected temperature Td and the like detected by the power generation chamber temperature sensor 142 serving as the temperature detection means. It is executed at the time interval.

First, in step S31 of FIG. 13, the first addition / subtraction value M1 is calculated based on the detected temperature Td and FIG. First, when the detected temperature Td is within a predetermined temperature range (between the two solid lines in FIG. 14) with respect to the appropriate temperature Ts (I) of the fuel cell stack 14, the first addition / subtraction value M1. Is set to zero.
That is, the detected temperature Td is
Ts (I) −Te ≦ Td ≦ Ts (I) + Te
Is within the range, the first addition / subtraction value M1 = 0. Here, Te is the first addition / subtraction value threshold temperature. In the present embodiment, the first addition / subtraction value threshold temperature Te is 3 ° C.

Further, the detected temperature Td is lower than the appropriate temperature Ts (I),
Td <Ts (I) −Te (4)
Is within the range (below the lower solid line in FIG. 14), the first addition / subtraction value M1 is
M1 = Ki × (Td− (Ts (I) −Te)) (5)
Calculated by At this time, the first addition / subtraction value M1 is a negative value (subtraction value). Ki is a predetermined proportionality constant.

Further, the detected temperature Td is higher than the appropriate temperature Ts (I),
Td> Ts (I) + Te (6)
Is within the range (above the upper solid line in FIG. 14), the first addition / subtraction value M1 is
M1 = Ki × (Td− (Ts (I) + Te)) (7)
Calculated by At this time, the first addition / subtraction value M1 is a positive value (addition value). As described above, the first addition / subtraction value M1 is determined based on the generated current in addition to the detected temperature Td, and the heat storage amount is estimated by integrating the value. That is, the appropriate temperature Ts (I) is set to be different depending on the generated current (electric power), and the value of (Ts (I) + Te) determined based on the appropriate temperature Ts (I) and (Ts Based on the value of (I) −Te), the first addition / subtraction value M1 is determined as a positive or negative value.

  If the detected temperature Td exceeds (Ts (I) + Te), the first addition / subtraction value M1 becomes a positive value, and the fuel supply amount is changed to increase the fuel utilization rate as will be described later. In the document, the temperature (Ts (I) + Te) for each generated power is referred to as the fuel utilization rate change temperature. Moreover, after the fuel utilization rate change temperature (Ts (I) + Te) is exceeded, after shifting to the high efficiency control in which the fuel utilization rate is increased, the target temperature range in which the amount of heat accumulated from the high efficiency control is not consumed. As will be described later, the timing for returning to control is when the integrated value N1id such as the first addition / subtraction value M1 has decreased to zero. For this reason, even after the detected temperature Td falls below the fuel utilization rate changing temperature (Ts (I) + Te), the integrated value N1id is maintained at a value larger than 0 for a while, and high efficiency control is performed.

  Next, in step S32 of FIG. 13, the second addition / subtraction value M2 is calculated based on the latest detected temperature Td and the detected temperature Tdb detected one minute ago. First, when the absolute value of the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is less than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is set to zero. In the present embodiment, the second addition / subtraction value threshold temperature is 1 ° C.

When the change temperature difference that is the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is equal to or higher than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is:
M2 = Kd × (Td−Tdb) (8)
Calculated by The second addition / subtraction value M2 becomes a positive value (addition value) when the detected temperature Td tends to increase, and becomes a negative value (subtraction value) when the detected temperature Td tends to decrease. Kd is a predetermined proportional constant. Therefore, when the detected temperature Td is increasing, the second addition / subtraction value M2, which is the quick response estimated value, is greatly increased in the region where the change temperature difference (Td−Tdb) is large compared to the region where the change temperature difference is small. Is done. On the other hand, when the detected temperature is low, the second addition / subtraction value M2 is greatly reduced in the region where the absolute value of the change temperature difference (Td−Tdb) is large than in the region where the absolute value of the change temperature difference is small. Is done.

  In the present embodiment, the proportionality constant Kd is a constant value, but as a modification, different proportionality constants Kd can be used depending on whether the change temperature difference is positive or negative. For example, the proportionality constant Kd can be set large when the change temperature difference is negative. As a result, when the detected temperature is lowered, the estimated quick response value is changed more rapidly with respect to the change temperature difference than when the detected temperature is increased. Alternatively, as a modification, the proportionality constant Kd can be set larger in the region where the absolute value of the change temperature difference is large than in the small region. As a result, in the region where the absolute value of the change temperature difference is large, the estimated quick response value is changed more rapidly than the region where the absolute value of the change temperature difference is small. Further, the change of the proportional constant Kd based on the sign of the change temperature difference and the change of the proportional constant Kd based on the magnitude of the absolute value of the change temperature difference can be combined.

  Next, in step S33 of FIG. 13, the first addition / subtraction value M1 calculated in step S31 and the second addition / subtraction value M2 calculated in step S32 are integrated into the first integration value N1id. In the first integrated value N1id, the available heat storage amount accumulated in the heat insulating material 7 and the like is reflected by the first addition / subtraction value M1, and the latest change in the detected temperature Td is reflected by the second addition / subtraction value M2. . That is, the first integrated value N1id can be used as an estimated value of the available heat storage amount accumulated in the heat insulating material 7 or the like. Further, the integration is performed every time the flowchart of FIG. 13 is executed continuously after the operation of the solid oxide fuel cell is started. The first addition value N1id and the first addition / subtraction value M1 are added to the previously calculated first integration value N1id. The 2 addition / subtraction value M2 is added or subtracted and updated to a new first integrated value N1id. The first integrated value N1id is limited to take a value between 0 and 4, and when the first integrated value N1id reaches 4, the value is held at 4 until the next subtraction is performed. When the first integrated value N1id decreases to 0, the value is held at 0 until the next addition is performed.

  In step S33, in addition to the first integrated value N1id, the value of the second integrated value N2id is also calculated. The second integrated value N2id is calculated in the same manner as the first integrated value N1id when no voltage drop occurs in the fuel cell module 2, and takes the same value as the first integrated value N1id. Further, when a voltage drop occurs in the fuel cell module 2, the integration of the first integrated value N1id is stopped, and the first integrated value N1id and the second integrated value N2id take different values. The first and second integrated values will be described later.

As described above, in the present embodiment, the integrated value is calculated by integrating the sum of the first addition / subtraction value M1 and the second addition / subtraction value M2 to the first integration value N1id. That is,
N1id = N1id + M1 + M2 (9)
Thus, the first integrated value N1id is calculated. Here, as a modification, the integrated value may be calculated by integrating the product of the first addition / subtraction value M1 and the second addition / subtraction value M2. That is, in this modification, the first integrated value N1id is
N1id = N1id + Km × M1 × M2 (10)
Is calculated by Here, Km is a variable coefficient that is changed according to a predetermined condition. In this modified example, when the absolute value of the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago is less than a predetermined second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is 1. Is done.

  Next, in step S34, a fuel usage rate adjustment subroutine (FIG. 21) for optimally adjusting the fuel usage rate and reducing the fuel supply amount is executed. As will be described later, in the subroutine shown in FIG. 21, when the detected temperature Td is within the appropriate temperature range shown in FIG. 14, the value of the second integrated value N2id is manipulated under a predetermined condition. Increase fuel utilization and reduce fuel supply. The subroutine shown in FIG. 21 is not called every time the flowchart shown in FIG. 13 is executed, but is called once every predetermined number of times. In the present embodiment, the subroutine of FIG. 21 is executed about once every 20 seconds.

Further, in step S35 of FIG. 13, the fuel utilization rate is determined using the graphs of FIGS. 15 and 16 based on the calculated first integrated value N1id.
FIG. 15 is a graph showing a set value of the fuel utilization rate Uf with respect to the calculated first integrated value N1id. As shown in FIG. 15, when the first integrated value N1id is 0, the fuel utilization rate Uf is set to the minimum fuel utilization rate Ufmin, which is the minimum value. Further, as the first integrated value N1id increases, the fuel utilization rate Uf also increases, and becomes the maximum fuel utilization rate Ufmax that is the maximum value at the first integrated value N1id = 1. During this time, the fuel utilization rate Uf has a small slope in the region where the first integrated value N1id is small, and the slope increases as the first integrated value N1id approaches 1. That is, in the region where the estimated heat storage amount is large, the fuel utilization rate Uf is significantly changed with respect to the change in the estimated heat storage amount, compared to the region where the estimated heat storage amount is small. In other words, the fuel supply amount is decreased so that the fuel utilization rate Uf is significantly increased as the estimated heat storage amount is larger. Further, when the first integrated value N1id is larger than 1, the fuel usage rate Uf is fixed to the maximum fuel usage rate Ufmax. Specific values of the minimum fuel utilization rate Ufmin and the maximum fuel utilization rate Ufmax are determined by the graph shown in FIG. 16 based on the generated current. Thus, when it is estimated that the amount of heat that can be used is accumulated in the heat insulating material 7 and the like, the fuel utilization rate is higher for the same generated power than in the case where the amount of available heat is not accumulated. The fuel supply is reduced to be higher.

  FIG. 16 is a graph showing a range of values that the fuel utilization rate Uf can take for each generated current, and shows the maximum value and the minimum value of the fuel utilization rate Uf for each generated current. As shown in FIG. 16, the minimum fuel utilization rate Ufmin for each generated current is set so as to increase as the generated current increases. That is, the fuel utilization rate is set high when the generated power is large, and the fuel utilization rate is set low when the generated power is small. The straight line of the minimum fuel utilization rate Ufmin corresponds to the solid line in FIG. 9, and when set to the fuel utilization rate on this straight line, the amount of heat accumulated in the heat insulating material 7 or the like is not used. The fuel cell module 2 can be thermally independent.

  On the other hand, the maximum fuel utilization rate Ufmax is set so as to change in a polygonal line with respect to each generated current. Here, the range of values that the fuel utilization rate Uf can take for each generated current (the difference between the maximum fuel utilization rate Ufmax and the minimum fuel utilization rate Ufmin) is the narrowest at the maximum generated current, and as the generated current decreases. Become wider. This is because, in the vicinity of the maximum generated current, the minimum fuel utilization rate Ufmin that can be thermally independent is high, and there is little room for increasing the fuel utilization rate Uf (reducing the fuel supply amount) even when using heat storage. Furthermore, since the minimum fuel utilization rate Ufmin that can be thermally self-sustained decreases as the generated current decreases, there is room for reducing the amount of fuel supplied by using heat storage, and when there is a large amount of heat storage, fuel use The rate Uf can be significantly increased. For this reason, in the region where the generated power is small, the fuel utilization rate is changed in a wider range than in the region where the generated power is large.

  Further, in a region where the generated current is very small and is less than or equal to the predetermined utilization rate suppressed power generation amount IU, the range of possible values of the fuel utilization rate Uf is set to be narrower as the generated power is reduced. This is because in the region where the generated current is small, the minimum fuel utilization rate Ufmin that can be thermally independent is low, and there is much room for improvement. However, in the region where the generated current is small, the temperature in the fuel cell module 2 is low. Therefore, if the fuel utilization rate Uf is significantly improved in this state and the amount of heat accumulated in the heat insulating material 7 or the like is consumed rapidly, There is a risk of causing an excessive temperature drop in the battery module 2. For this reason, in the area | region below the utilization factor suppression electric power generation amount IU in which an electric power generation current is very small, the change amount which raises the fuel utilization factor Uf is significantly suppressed, so that generated electric power becomes small. That is, the amount of change to decrease the fuel supply amount decreases as the power generation amount of the fuel cell module 2 decreases. This avoids the risk of a sudden temperature drop and makes it possible to use the accumulated heat for a long time.

  In the present embodiment, the fuel supply amount is reduced by the fuel supply amount changing means (not shown) built in the control unit 110 so that the fuel usage rate Uf is higher than the minimum fuel usage rate Ufmin. This fuel supply amount changing means (not shown) acts to increase the fuel utilization rate by changing the base fuel supply amount.

  In step S35 of FIG. 13, specific values of the minimum fuel utilization rate Ufmin and the maximum fuel utilization rate Ufmax are determined based on the generated current, using the graph of FIG. Next, the determined minimum fuel utilization rate Ufmin and maximum fuel utilization rate Ufmax are applied to the graph of FIG. 15, and the fuel utilization rate Uf is determined based on the first integrated value N1id calculated in step S33.

Next, in step S36 of FIG. 13, the air utilization rate is determined using the graphs of FIGS. 17 and 18 based on the second integrated value N2id.
FIG. 17 is a graph showing a set value of the air utilization rate Ua with respect to the calculated second integrated value N2id. As shown in FIG. 17, when the second integrated value N2id is 0 to 1, the air utilization rate Ua is set to the maximum air utilization rate Uamax that is the maximum value. Further, as the second integrated value N2id increases beyond 1, the air utilization rate Ua decreases, and becomes the minimum air utilization rate Uamin that is the minimum value at the second integrated value N2id = 4. Thus, since the increased amount of air due to the reduction in the air utilization rate Ua acts as a cooling fluid, the setting of the air utilization rate Ua shown in FIG. 17 acts as a forced cooling means. Specific values of the minimum air utilization rate Uamin and the maximum air utilization rate Uamax are determined by the graph shown in FIG. 18 based on the generated current.

  FIG. 18 is a graph showing a range of values that the air utilization rate Ua can take for each generated current, and shows the maximum value and the minimum value of the fuel utilization rate Ua for each generated current. As shown in FIG. 18, the maximum air utilization rate Uamax for each generated current is set to be slightly increased with an increase in the generated current. On the other hand, the minimum air utilization rate Uamin decreases as the generated current increases. Reducing the air utilization rate Ua below the maximum air utilization rate Uamax (increasing the air supply amount) introduces more air into the fuel cell module 2 than is necessary for power generation. The temperature in the fuel cell module 2 is lowered. Therefore, when the temperature in the fuel cell module 2 rises excessively and the temperature needs to be lowered, the air utilization rate Ua is lowered. In this embodiment, when the minimum air utilization rate Uamin is decreased (the air supply amount is increased) as the generation current is increased, the air supply amount corresponding to the minimum air utilization rate Uamin is generated for power generation at a predetermined generation current. The maximum air supply amount of the air flow rate adjustment unit 45 will be exceeded. For this reason, the air utilization rate Ua set by the graph of FIG. 17 may not be realized in a region where the minimum air utilization rate Uamin is equal to or greater than a predetermined generated current indicated by a broken line in FIG. In this case, the actually supplied air supply amount is fixed to the maximum air supply amount of the power generation air flow rate adjustment unit 45 regardless of the set air utilization rate Ua. Along with this, the minimum air utilization rate Ua actually realized increases above a predetermined generated current. Further, when a power generation air flow rate adjustment unit having a large maximum air supply amount is used, the minimum air utilization rate Uamin of the portion indicated by the broken line in FIG. 18 can be realized. The air utilization rate Ua defined by reaching the maximum air supply amount of the power generation air flow rate adjustment unit 45 is referred to as a limit minimum air utilization rate ULamin.

  In step S36 of FIG. 13, specific values of the minimum air utilization rate Uamin and the maximum air utilization rate Uamax are determined based on the generated current using the graph of FIG. Next, the determined minimum air utilization rate Uamin and maximum air utilization rate Uamax are applied to the graph of FIG. 17, and the air utilization rate Ua is determined based on the second integrated value N2id calculated in step S33. If the value of the second integrated value N2id has been changed by the subroutine called in step S34, that value is used.

Next, in step S37 of FIG. 13, based on the air utilization rate Ua determined in step S36, S / C which is the ratio of the water vapor amount and the carbon amount is determined using FIG.
FIG. 19 is a graph in which the horizontal axis represents the air utilization rate Ua, and the vertical axis represents the ratio S / C between the amount of supplied water vapor and the amount of carbon contained in the fuel.

  First, in the region of generated current where the air utilization rate Ua set in step S36 is not defined by the maximum air supply amount of the power generation air flow rate adjustment unit 45 (between Uamax and ULamin in FIG. 19), the amount of water vapor and carbon The value of the quantity ratio S / C is fixed at 2.5. The ratio of the amount of water vapor to the amount of carbon S / C = 1 means that the total amount of carbon contained in the supplied fuel is chemically steam-reformed by the supplied water (steam). means. Therefore, the ratio S / C = 2.5 of the amount of steam and the amount of carbon is 2.5 times the amount of steam (water) that is 2.5 times the minimum amount of steam that is chemically necessary for steam reforming the fuel. Means the state. Actually, carbon precipitation occurs in the reformer 20 at the amount of steam at which S / C = 1, so that the amount of steam at which S / C = 2.5 is for steam reforming the fuel. Appropriate amount.

  Next, in the region of the generated current in which the air utilization rate Ua set in step S36 is limited by the maximum air supply amount of the power generation air flow rate adjustment unit 45, the water vapor amount and the carbon amount using the graph of FIG. The ratio S / C is determined. In FIG. 19, the horizontal axis is the air utilization rate Ua, the air utilization rate Ua is larger, and the closer to the maximum air utilization rate Uamax, the smaller the air supply amount. On the other hand, when the air utilization rate Ua is lowered and approaches the minimum air utilization rate Uamin (broken line in FIG. 18), the air supply amount reaches the limit, and the air utilization rate Ua becomes the limit minimum air utilization rate ULamin. As shown in FIG. 19, when the air utilization rate Ua is larger than the limit minimum air utilization rate ULamin (the air supply amount is small), the ratio S / C = 2.5 of the water vapor amount and the carbon amount is set. . Furthermore, when the air utilization rate Ua determined in step S36 is smaller than the limit minimum air utilization rate ULamin (the air supply amount is large) (between Uamin and ULamin in FIG. 19), the air utilization rate Ua decreases. The ratio S / C between the water vapor amount and the carbon amount is increased, and S / C = 3.5 is set at the minimum air utilization rate Uamin. That is, when the air utilization rate Ua determined in step S36 cannot be realized by the limit minimum air utilization rate ULamin (when the air utilization rate Ua is determined within the hatched range in FIG. 18), the water vapor amount and carbon Increase the quantity ratio S / C and increase the water supply. Thereby, the temperature of the reformed fuel gas flowing out from the reformer 20 is lowered, and the temperature in the fuel cell module 2 tends to be lowered. As described above, when the water supply amount is increased after decreasing the air utilization rate Ua and increasing the air supply amount, the increased amount of water (water vapor) acts as a cooling fluid. The water supply setting shown acts as a forced cooling means.

  In step S38, specific fuel supply is performed based on the fuel utilization rate Uf, air utilization rate Ua, the ratio S / C of the water vapor amount and the carbon amount determined in steps S35, S36, and S37, and the generated current. Determine the volume, air supply, and water supply. That is, the actual fuel supply amount is calculated by dividing the fuel supply amount when the total amount is used for power generation by the determined fuel utilization rate Uf, and the total amount is used for power generation. The actual air supply amount is calculated by dividing the air supply amount by the determined air utilization rate Ua. Further, the water supply amount is calculated based on the calculated fuel supply amount and the ratio S / C of the water vapor amount and the carbon amount determined in step S37.

  Next, in step S39, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38, the power generation air flow rate adjustment unit 45, and the water flow rate adjustment unit 28 that is the water supply means, and the amount of fuel calculated in step S38. , Air and water are supplied, and one process of the flowchart of FIG. 13 is completed.

  Next, the time interval for executing the flowchart of FIG. 13 will be described. In the present embodiment, when the output current is large, the flowchart of FIG. 13 is executed every 0.5 seconds. As the output current decreases, it is doubled for 1 second, 4 times for 2 seconds, and 8 times. It is executed every 4 seconds. Thus, when the first and second addition / subtraction values are constant values, the change in the first or second integrated value per time becomes gentler as the output current is smaller. That is, the heat storage amount estimation means 110a changes the estimated value of the heat storage amount rapidly with respect to time as the output current (generated power) increases. Thereby, the estimation of the heat storage amount by the integrated value well reflects the actual heat storage amount.

  Next, a procedure for determining the fuel supply amount, the air supply amount, and the water supply amount when the output voltage of the fuel cell stack 14 decreases will be described with reference to FIG. FIG. 20 is a diagram illustrating a generated voltage with respect to a generated current by the fuel cell module 2. In general, since an internal resistance exists in the fuel cell stack 14, as shown in FIG. 20, when the current output from the fuel cell module 2 increases, the voltage decreases. The dashed-dotted line shown in FIG. 20 has shown the relationship between the electric power generation electric current and electric power generation voltage in case the fuel cell module 2 is drive | operating appropriately. In addition, depending on the operating state of the fuel cell module 2, the power generation voltage is temporarily lower than the relationship between the power generation current and the power generation voltage indicated by the one-dot chain line. Or when degradation has arisen in the fuel cell module 2, since the internal resistance of the fuel cell stack 14 increases, the generated voltage for the same generated current constantly decreases.

  In the solid oxide fuel cell of the present embodiment, when the generated voltage decreases by 10% or more with respect to the initial generated voltage, and the generated voltage enters a region below the solid line in FIG. The fuel supply amount, the air supply amount, and the water supply amount are determined by processing corresponding to the decrease.

  That is, when the generated voltage is in a region below the solid line in FIG. 20, in step S33 in FIG. 13, the integration of the first integrated value N1id is stopped and only the integration of the second integrated value N2id is continued. . Accordingly, the value of the first integrated value N1id used when referring to the graph of FIG. 15 for determining the fuel utilization rate Uf is fixed to a constant value. As a result, the fuel utilization rate Uf is fixed until the generated voltage deviates from the region below the solid line in FIG. As described above, when a large voltage drop is generated in the power generation voltage of the fuel cell module 2, changes to increase the fuel utilization rate Uf are reduced. On the other hand, the value of the second integrated value N2id used when referring to the graph of FIG. 17 for determining the air utilization rate Ua is increased or decreased as before, and the increase or decrease in the air utilization rate Ua is continued. Thus, the fuel utilization rate Uf is changed based on the output voltage of the fuel cell module 2 in addition to the first and second integrated values corresponding to the estimated heat storage amount and the demand power.

Next, fuel utilization rate adjustment control will be described with reference to FIG.
FIG. 21 is a flowchart of a subroutine for performing fuel utilization rate adjustment control, which is called in step S34 of FIG.

  As described above, in the flowchart shown in FIG. 13, the first addition / subtraction value M1 and the second addition / subtraction value M2 are determined based on the detected temperature Td, and the first addition value is an estimated value of the heat storage amount by integrating these values. The second integrated values N1id and N2id were calculated (FIG. 13, step S33). Further, based on the first and second integrated values N1id and N2id, the fuel usage rate Uf, the air usage rate Ua, and the like were calculated, and fuel and power generation air were supplied. By determining the fuel supply amount and the power generation air supply amount in this way, when the heat quantity available in the heat insulating material 7 in the fuel cell module 2 is accumulated, this is utilized, and the fuel utilization rate is increased. However, the temperature in the fuel cell module 2 is maintained within the appropriate temperature range (FIG. 14). In a state where the fuel cell module 2 is stable at an appropriate temperature, the heating effect by the heat generated by the fuel cell stack 14 and the combustion heat of the remaining fuel not used for power generation, and the cooling effect by the power generation air are obtained. Balanced.

  In this state, the values of the first and second integrated values N1id and N2id do not change until the detected temperature Td deviates from the appropriate temperature range (Ts (I) −Te ≦ Td ≦ Ts (I) + Te) (however, The second addition / subtraction value M2 is 0), and the fuel utilization rate Uf and the air utilization rate Ua are maintained at the previous values. Here, when the values of the first integrated value N1id and the second integrated value N2id are the same, and the fuel usage rate Uf is not the maximum fuel usage rate (N1id = 0 to 1), the air usage rate Ua is The maximum air utilization rate (minimum air supply amount, N2id = 0 to 1).

  On the other hand, when the power generation voltage decreases (FIG. 20), the first integrated value N1id and the second integrated value N2id are different. For example, when the first integrated value N1id = 0.5 and the second integrated value N2id = 2.0, neither the fuel utilization rate Uf nor the air utilization rate Ua takes a maximum value. In such a state, the remaining fuel is increased by reducing the fuel utilization rate Uf, and heating is performed. At the same time, the air utilization rate Ua is decreased, so the amount of power generation air is also increased. The inside of the fuel cell module 2 is cooled. That is, in such a state, the heating by increasing the fuel supply amount and the cooling by increasing the power generation air supply amount are performed at the same time, and the heat balance is achieved. Therefore, as a result of the appropriate temperature control shown in FIG. 13, this state is thermally balanced within the appropriate temperature range and has low energy efficiency even in a stable operation state. Further, in this state, since the fuel cell module 2 is within the appropriate temperature range, the values of the first and second integrated values N1id and N2id do not change, and the operation state changes greatly due to a large change in generated power. Until then, the inefficient stable state will continue for a relatively long time. The fuel utilization rate adjusting means 110b (FIG. 6) incorporated in the control unit 110 executes the fuel utilization rate adjustment control so as to escape from such an inefficient stable state at an early stage while maintaining a thermal balance. Act on. This fuel utilization rate adjustment control is executed according to the flowchart shown in FIG.

  First, in step S41 of FIG. 21, it is determined whether or not the detected temperature Td is within an appropriate temperature range (Ts (I) −Te ≦ Td ≦ Ts (I) + Te). When the detected temperature Td is within the appropriate temperature range, the process proceeds to step S42, and when it is not within the appropriate temperature range, the process proceeds to step S46. In step S46, it is determined not to execute the fuel utilization rate adjustment control, and one process of the flowchart of FIG. 21 is terminated. That is, when the detected temperature Td is not within the proper temperature range, priority is given to the proper temperature control (FIG. 13) for converging the temperature in the fuel cell module 2 within the proper temperature range, and the fuel utilization rate adjustment control is executed. Not. As a result, the fuel utilization rate adjustment control is applied to the fuel cell module 2 that is not thermally balanced, and the risk of sudden temperature drop and excessive temperature rise is avoided.

  On the other hand, in step S42, it is determined whether or not the absolute value of the change temperature difference, which is the difference between the latest detected temperature Td and the detected temperature Tdb one minute ago, is less than a predetermined second addition / subtraction value threshold temperature. If the absolute value of the change temperature difference is less than the second addition / subtraction value threshold temperature, the process proceeds to step S43. If the absolute value of the change temperature difference is greater than or equal to the second addition / subtraction value threshold temperature, the process proceeds to step S46, and one process of the flowchart is terminated. Thus, even when the detected temperature Td is within the appropriate temperature range, if the change temperature difference is large and the temperature change rate is equal to or greater than the predetermined correction prohibition change rate, a sudden temperature drop or excessive temperature rise Therefore, the fuel utilization rate adjustment control is not executed. Further, as described above, in the present embodiment, the second addition / subtraction value threshold temperature is 1 ° C.

  Next, in step S43, it is determined whether or not the state where the absolute value of the change temperature difference is less than the second addition / subtraction value threshold temperature continues for a predetermined fuel utilization rate adjustment control standby time. If the fuel usage rate adjustment control standby time has continued for more than the time, the process proceeds to step S44, and if not, the process proceeds to step S46, and one process of the flowchart is terminated. As described above, even if the absolute value of the change temperature difference is less than the second addition / subtraction value threshold temperature, if the second addition / subtraction value threshold temperature is recently exceeded, the temperature in the fuel cell module 2 is still sufficient. Therefore, the execution of the fuel utilization rate adjustment control is suspended. Preferably, as the fuel utilization rate adjustment control standby time, for example, a time suitable for the thermal response performance of the fuel cell module 2 is selected from 0.5 minutes to 20 minutes.

  On the other hand, in step S44, it is determined whether or not the value of the first integrated value N1id is not less than 0 and less than 1.0. If the value of the first integrated value N1id is not less than 0 and less than 1.0, the process proceeds to step S45, and if the value of the first integrated value N1id is not less than 1.0, the process proceeds to step S46. End the process. That is, when the value of the first integrated value N1id is 1.0 or more, the fuel utilization rate Uf has already been operated at the maximum value (FIG. 15), so the fuel utilization rate Uf is improved (fuel supply amount). The fuel utilization rate adjustment control is not executed.

  Next, in step S45, it is determined whether or not the value of the second integrated value N2id is greater than 1.0. When the value of the second integrated value N2id is larger than 1.0, the process proceeds to step S47, and when the value of the second integrated value N2id is 1.0 or less, the process proceeds to step S46, and one process of the flowchart is performed. Exit. That is, when the value of the second integrated value N2id is 1.0 or less, the power generation air utilization rate Ua has already been operated at the maximum value (FIG. 17), so the power generation air supply amount is further reduced. The fuel utilization rate adjustment control is not executed.

  In step S47, it is determined that the detected temperature Td is within the appropriate temperature range and the temperature state is sufficiently stable, and heating by the remaining fuel and cooling by increasing the amount of air for generating power are performed. The fuel utilization rate adjustment control is executed because it is performed at the same time. Specifically, as the fuel utilization rate adjustment control, the value of the second integrated value N2id is forcibly changed to 0. By changing the value of the second integrated value N2id to 0, the power generation air supply amount is reduced to a value corresponding to the maximum air utilization rate (FIG. 17). That is, the process in step S47 functions as a fuel utilization rate adjusting means for correcting the power generation air supply amount set by the appropriate temperature control according to the flowchart of FIG.

  When the power generation air supply amount is decreased from the state of being thermally balanced by the heating by the remaining fuel and the cooling due to the increase in the power generation air supply amount, the temperature in the fuel cell module 2 tends to increase. When the temperature in the fuel cell module 2 tends to increase, the addition / subtraction value, in particular, the second addition / subtraction value M2 becomes a positive value, and the value of the first integrated value N1id increases (the second integrated value N2id also increases). When the value of the first integrated value N1id increases, the appropriate temperature control (FIG. 13) functions, and as a result, the value of the fuel utilization rate Uf is increased and the fuel supply amount is decreased. Due to the decrease in the fuel supply amount, the temperature in the fuel cell module 2 tends to decrease, and the fuel cell module 2 is in a state where the fuel utilization rate Uf and the power generation air utilization rate Ua are higher than before the fuel utilization rate adjustment control is executed. The thermal balance in 2 is restored. Further, as described above, the fuel utilization rate adjustment control is executed in a state where the temperature in the fuel cell module 2 is extremely stable. For this reason, even when the thermal balance in the fuel cell module 2 is positively lost by the fuel utilization rate adjustment control, the detected temperature Td is maintained within the appropriate temperature range, and the fuel cell module 2 A new thermal balance is restored.

Next, with reference to FIG. 13, FIG. 21, and FIG. 22, the operation of appropriate temperature control and fuel utilization rate adjustment control in the solid oxide fuel cell 1 will be described. FIG. 22 is a time chart showing an example in which the fuel usage rate is improved by the fuel usage rate adjustment control.
First, when the value of the first integrated value N1id calculated in step S33 of FIG. 13 is 0, the fuel utilization rate Uf determined in step S34 is the minimum fuel utilization rate Ufmin (fuel supply) in the generated current. The maximum amount). As a result, even when the value of the first integrated value N1id is 0 and the amount of heat accumulated in the heat insulating material 7 or the like is small, sufficient fuel is supplied so that the fuel cell module 2 can be thermally independent. When the value of the second integrated value N2id calculated in step S33 is 0 as in the case of the first integrated value N1id, the air utilization rate Ua determined in step S35 is the maximum air in the generated current. The utilization rate Uafmax (air supply amount minimum) is set. For this reason, the effect | action which cools the fuel cell stack 14 with the air for electric power generation introduced into the fuel cell module 2 is minimized, and the temperature of the fuel cell stack 14 can be made to rise.

  Next, when the detected temperature Td is higher than the appropriate temperature Ts (I) and the fuel cell module 2 is operated in a state of Td> Ts (I) + Te, the value of the first addition / subtraction value M1 becomes a positive value, The value of 1 integrated value N1id becomes larger than 0. Accordingly, in FIG. 15, a fuel utilization rate Uf higher than the minimum fuel utilization rate Ufmin is set, the fuel supply amount is reduced, and the amount of residual fuel that remains without being used for power generation is reduced. The fuel utilization rate Uf is significantly increased by the fuel supply amount changing unit 110a as the value of the first integrated value N1id corresponding to the estimated heat storage amount increases. By increasing the fuel utilization rate Uf, the fuel supply amount is made smaller than the supply amount capable of self-sustaining heat, and high-efficiency control using the heat amount accumulated in the heat insulating material 7 or the like is executed. Since the amount of residual fuel is reduced and the amount of heat accumulated in the heat insulating material 7 or the like is used, the fuel supply amount changing means 110a suppresses the temperature rise in the fuel cell module 2 while continuing power generation. When the operation is continued in the state of Td> Ts (I) + Te, the integration of the positive first addition / subtraction value M1 is repeated, and the value of the first integration value N1id also increases. When the first integrated value N1id reaches 1, the fuel usage rate Uf is set to the maximum fuel usage rate Uafmax (fuel supply amount minimum). Thus, the fuel supplied to the fuel cell module 2 is determined based on the past history of the detected temperature Td reflecting the amount of heat accumulated in the heat insulating material 7 and the like.

  Even when the first integrated value N1id further increases and exceeds 1, the fuel utilization rate Uf is maintained at the maximum fuel utilization rate Uafmax (minimum fuel supply amount) as shown in FIG. On the other hand, since the value of the second integrated value N2id that takes the same value as the first integrated value N1id (when the output voltage of the fuel cell module 2 is not lowered) also exceeds 1, the air utilization rate based on FIG. Ua is reduced (air supply amount increased). Thereby, the inside of the fuel cell module 2 tends to be cooled due to an increase in supplied air.

  On the other hand, when the detected temperature Td is lower than the appropriate temperature Ts (I) and the fuel cell module 2 is operated in a state where Td <Ts (I) −Te, the value of the first addition / subtraction value M1 is a negative value. Thus, the value of the first integrated value N1id is decreased. Thus, the fuel utilization rate Uf is maintained (first integrated value N1id> 1) or decreased (first integrated value N1id ≦ 1). Further, the air utilization rate Ua is increased (second integrated value N2id> 1) or maintained (second integrated value N2id ≦ 1). Thereby, the temperature in the fuel cell module 2 can be increased.

  The above is the operation of the solid oxide fuel cell focusing only on the first addition / subtraction value M1 calculated based on the history of the detected temperature Td. The first integrated value N1id and the second integrated value N2id are It is also affected by the addition / subtraction value M2. The fuel cell module 2, particularly the fuel cell stack 14, has a very large heat capacity, and the change in the detected temperature Td is extremely slow. For this reason, once the detected temperature Td starts to increase, it is difficult to suppress the temperature increase in a short time, and when the detected temperature Td starts to decrease, this is returned to the upward trend. Takes a long time. For this reason, when the detected temperature Td tends to increase or decrease, it is necessary to react quickly to correct the first and second integrated values.

  That is, when the latest detected temperature Td is higher than the detected temperature Tdb one minute ago by the second addition / subtraction value threshold temperature, the second addition / subtraction value M2 becomes a positive value, and the first and second integrated values increase. Is done. Thereby, it can reflect in the 1st, 2nd integrated value that the detected temperature Td entered into the upward tendency. Similarly, when the latest detected temperature Td is lower than the detected temperature Tdb one minute ago by the second addition / subtraction value threshold temperature, the second addition / subtraction value M2 is a negative value, and the first and second integrated values are Will be reduced. In other words, the second addition / subtraction value M2, which is a rapid response estimated value, is calculated based on the change temperature difference that is the difference between the latest detected temperature Td detected by the power generation chamber temperature sensor 142 and the past detected temperature Tdb. Therefore, when the detected temperature Td is drastically reduced, the amount of change that increases the fuel utilization rate Uf is greatly suppressed, and the generated power is reduced by the utilization rate-suppressed power generation amount, compared with the case where the detected temperature Td is gradually decreasing. Since the maximum fuel utilization rate Ufmax is also set low in the region below IU, the amount of change is more greatly suppressed. Thereby, it can reflect in the 1st, 2nd integrated value that detected temperature Td entered into the fall tendency. Thus, in the present embodiment, the difference based on the integrated value of the first addition / subtraction value M1 determined based on the detected temperature Td and the difference between the newly detected detected temperature Td and the detected temperature Tdb detected in the past. The amount of heat storage is estimated based on the value. That is, in the present embodiment, the integrated value of the first addition / subtraction value M1, which is a basic estimated value calculated based on the history of the detected temperature Td, and the detected temperature Td in a period shorter than the history of calculating the basic estimated value. Based on the second addition / subtraction value M2 that is a speed response estimated value calculated based on the rate of change, the heat storage amount is estimated by the heat storage amount estimation means 110a. Thus, in this embodiment, the heat storage amount is estimated based on the sum of the basic estimated value and the quick response estimated value.

  Note that the temperature change of the fuel cell module 2 is extremely slow compared to 1 minute, which is the interval at which the detected temperatures Td and Tdb are detected, so the second addition / subtraction value M2 is often zero. For this reason, the first and second integrated values are mainly governed by the first addition / subtraction value M1, and when the detected temperature Td increases or decreases, the second addition / subtraction value M2 becomes the first and second integration values. Acts to correct the value of. Thus, in addition to the detected temperature history, the most recent change in the detected temperature Td is added to the estimated value of the heat storage amount by the second addition / subtraction value M2. For this reason, when the most recent change in detected temperature Td is large (change greater than or equal to the second addition / subtraction value threshold temperature), since the second addition / subtraction value M2 has a value, the estimated value of the heat storage amount is corrected, and the fuel utilization rate Uf is significantly changed.

  As described above, the residual heat amount utilization control realized by the flowchart shown in FIG. 13 reduces the temperature in the fuel cell module 2 by increasing the fuel utilization rate when the heat amount accumulated in the heat insulating material 7 is large, When the accumulated amount of heat is small, the temperature in the fuel cell module 2 is maintained in an appropriate range by increasing the temperature in the fuel cell module 2 by lowering the fuel utilization rate. To do.

Further, according to the flowchart shown in FIG. 21 called from the flowchart of FIG. 13, the fuel usage rate adjustment control is executed for the fuel cell module 2 in the proper temperature state, and the fuel usage rate is improved.
First, at time t100 in FIG. 22, the detected temperature Td is lower than the appropriate temperature range. For this reason, the power generation air utilization rate is increased by the appropriate temperature control, and thereby the power generation air supply amount is reduced (FIG. 22, times t100 to t101). Even after the detected temperature Td converges within the appropriate temperature range, the fuel utilization rate adjustment control is not immediately executed, and the fuel utilization rate adjustment control standby time (FIG. 22, times t102 to t103) is waited. During this time, the fuel cell module 2 is in a thermally balanced and stable state, but the fuel utilization rate and the power generation air utilization rate are not the maximum values, and the heating by the remaining fuel and the cooling by the excessive power generation air coexist. The power generation efficiency is low. Next, after the fuel utilization rate adjustment control standby time has elapsed, the fuel utilization rate adjustment system is executed at time t103. When the fuel utilization rate adjustment system is executed, the value of the second integrated value N2id is forcibly changed to 0. As a result, the power generation air utilization rate is raised to the maximum value (FIG. 17), and the power generation air supply amount is reduced accordingly (FIG. 22, time t103-). By executing this fuel utilization rate adjustment system, the thermal balance state at times t102 to t103 is positively canceled, and the state becomes excessively heated.

  After the power generation air utilization rate is improved, the temperature in the fuel cell module 2 begins to rise with a delay (from time t104 in FIG. 22). When the temperature in the fuel cell module 2 rises, appropriate temperature control is activated to increase the fuel utilization rate to the maximum fuel utilization rate, thereby reducing the fuel supply amount. As described above, as a result of the correction by the fuel utilization rate adjusting means 110b, the fuel supply amount changes in addition to the power generation air supply amount. That is, the fuel supply amount is reduced by the appropriate temperature control corresponding to the temperature rise in the fuel cell module 2 accompanying the decrease in the power generation air supply amount. At this time, the increase in the fuel utilization rate is indirectly caused by an increase in the power generation air utilization rate (decrease in cooling by the power generation air). The rate of change (supply rate) is more gradual (small rate of change). In addition, as the fuel utilization rate increases, power generation efficiency also increases. Here, since the fuel cell module 2 has a large heat capacity, the temperature continues to rise even after the fuel utilization rate is increased. However, the detected temperature Td starts to decrease at time t105, and then stabilizes within an appropriate temperature range. As described above, the fuel usage rate adjustment system is executed in a state where the detected temperature Td is within the appropriate temperature range and is thermally stable, and the fuel usage rate does not deviate from within the appropriate temperature range. Be improved.

  According to the solid oxide fuel cell 1 of the embodiment of the present invention, when the estimated heat storage amount is large, the fuel utilization rate is increased for the same generated power (FIGS. 15 and 16). The energy efficiency of the solid oxide fuel cell 1 can be improved by using the accumulated amount of heat. Further, according to the present embodiment, since the heat storage is used when the amount of heat storage is large, the temperature in the fuel cell module 2 can be maintained in an appropriate temperature range without reducing the energy efficiency. However, even if the fuel cell module 2 is maintained at an appropriate temperature and is operated stably by appropriate temperature control, the energy efficiency in that state may be low. For example, in the case where the heating with the increased fuel supply amount and the cooling with the increased air supply amount for power generation coexist and are thermally stable (t101 to t103 in FIG. 22), the supplied fuel Is wasted and energy efficiency is low. According to the solid oxide fuel cell 1 of the present embodiment, in a state where the temperature is within the appropriate temperature range, the fuel utilization rate adjusting means 110b increases so that the fuel utilization rate does not substantially deviate from the appropriate temperature range. Since the fuel supply amount and / or the power generation air supply amount set by the appropriate temperature control are corrected, both the appropriate temperature and the energy efficiency can be improved.

  In general, since the fuel cell module 2 has a large heat capacity, even if the fuel cell module 2 is currently in the proper temperature range, the temperature does not converge to the proper temperature range as it is and may pass the proper temperature range. is there. When the fuel utilization rate adjustment control is executed in such a thermally unstable state, the thermal balance of the fuel cell module 2 is greatly disrupted, which may lead to a sudden temperature drop or excessive temperature rise. According to the solid oxide fuel cell 1 of the present embodiment, even if the fuel cell module 2 is in the appropriate temperature range, no correction is performed if the rate of change in temperature is large (FIG. 21, steps S42 and S43). Therefore, it is possible to prevent a sudden temperature drop or an excessive temperature rise from being caused by the fuel utilization rate adjustment control.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, as a result of the correction by the fuel utilization rate adjusting means 110b, both the fuel supply amount and the power generation air supply amount change (t103 to t105 in FIG. 22). The temperature decrease due to the decrease in the fuel supply amount and the temperature increase due to the decrease in the air supply amount for power generation are offset, and the thermal balance is maintained while the fuel supply amount is decreased (fuel utilization rate is improved) (from t104 in FIG. 22). )can do.

  Further, according to the solid oxide fuel cell 1 of the present embodiment, even when the fuel supply rate and the power generation air supply amount are reduced by the fuel usage rate adjusting means 110b, the power generation air supply amount (air usage rate). 22 (t103 to t104 in FIG. 22) is corrected to be larger than the change rate (t104 to t105 in FIG. 22) of the fuel supply amount (fuel utilization rate). Thus, the risk that the fuel cell module 2 deviates from the appropriate temperature range can be suppressed.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, in the fuel utilization rate adjustment control, only the power generation air supply amount is reduced (FIG. 21, step S47). It is not directly corrected by the control. For this reason, it is possible to prevent the thermal balance from being largely lost by directly correcting and rapidly changing the fuel supply amount.

  In addition, according to the solid oxide fuel cell 1 of the present embodiment, the temperature supply value N2id is decreased (FIG. 21, step S47), thereby reducing the power generation air supply amount determined based on this. Therefore, the fuel utilization rate can be increased gradually as compared with the case where the supply amount is directly corrected, and the risk that the temperature in the fuel cell module 2 deviates from the appropriate temperature range can be further reduced.

  Furthermore, according to the solid oxide fuel cell 1 of the present embodiment, only the integrated value N2id used for determining the power supply air supply amount is decreased (FIG. 21, step S47), thereby generating power air. Since only the supply amount is decreased, the fuel supply amount changes more slowly than when the integrated value N1id for determining the fuel supply amount is changed (t104 to t105 in FIG. 22), so the fuel cell module can be more reliably performed. The temperature in 2 can be maintained in an appropriate temperature range.

As mentioned above, although preferable embodiment of this invention was described, a various change can be added to embodiment mentioned above.
In particular, in the above-described embodiment, the integrated value N2id is decreased to 0 in the fuel utilization rate adjustment control (FIG. 21, step S47). However, as a modified example, the integrated value N2id can be gradually changed. . For example, in the fuel utilization rate adjustment control, the present invention can be configured to reduce the integrated value N2id to about 70% (multiply by 0.7). According to this modification, the fuel utilization rate can be adjusted more gradually.

In the embodiment described above, in the fuel utilization rate adjustment control, only the integrated value N2id for determining the power generation air utilization rate is reduced. However, as a modified example, the integrated values N1id and N2id are changed, Alternatively, the present invention can be configured to change only the integrated value N1id. When changing the integrated value N1id for determining the fuel usage rate, the fuel usage rate is increased by increasing the integrated value N1id.
Furthermore, in the above-described embodiment, the value of the integrated value is corrected in order to change the fuel usage rate and the power generation air usage rate. However, as a modification, the fuel usage rate and / or the power generation air usage rate are changed. The present invention can also be configured to change directly.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Fuel cell module 4 Auxiliary machine unit 7 Heat insulation material (heat storage material)
8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide fuel cell)
18 Combustion chamber (combustion section)
20 Reformer 22 Heat exchanger for air 24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit (water supply means)
30 Fuel supply source 38 Fuel flow rate adjustment unit (fuel supply means)
40 Air supply source 44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit (power generation oxidizing gas supply means)
46 1st heater 48 2nd heater 50 Hot water production apparatus 52 Control box 54 Inverter 83 Ignition apparatus 84 Fuel cell 110 Control part (control means)
110a Heat storage amount estimation means 110b Fuel utilization rate adjustment means 112 Operating device 114 Display device 116 Alarm device 126 Power state detection sensor (demand power detection means)
132 Fuel flow sensor (fuel supply detection sensor)
138 Pressure sensor (reformer pressure sensor)
140 Exhaust temperature sensor (temperature detection means)
142 Power generation chamber temperature sensor (temperature detection means)
148 Reformer temperature sensor (temperature detection means)
150 Outside temperature sensor

Claims (7)

A solid oxide fuel cell that generates variable generation power according to demand power,
A fuel cell module for generating electricity from the supplied fuel;
Fuel supply means for supplying fuel to the fuel cell module;
Power generation oxidant gas supply means for supplying power generation oxidant gas to the fuel cell module;
A combustion section that is supplied by the fuel supply means and burns the remaining fuel that is not used for power generation, and heats the inside of the fuel cell module;
A heat storage material for accumulating heat generated in the fuel cell module;
Demand power detection means for detecting demand power;
Temperature detecting means for detecting the temperature in the fuel cell module;
A heat storage amount estimation means for estimating the heat storage amount accumulated in the heat storage material by integrating the temperatures detected by the temperature detection means;
When the estimated heat storage amount is large based on the demand power detected by the demand power detection means and the heat storage amount estimated by the heat storage amount estimation means, the fuel utilization rate is high for the same generated power. The fuel supply means and the power generation oxidant gas supply means are controlled so that the remaining heat amount is utilized, and the heating effect by increasing the fuel supply amount and the power generation oxidant gas supply amount are increased. Control means for performing appropriate temperature control for converging the temperature in the fuel cell module to a predetermined appropriate temperature range using a cooling effect by
The control means is set by the appropriate temperature control so that when the temperature in the fuel cell module is within the appropriate temperature range, the fuel utilization rate is increased without substantially deviating from the appropriate temperature range. A solid oxide fuel cell comprising a fuel utilization rate adjusting means for correcting the fuel supply amount and / or the power generation oxidant gas supply amount.   2. The solid oxide fuel cell according to claim 1, wherein the fuel utilization rate adjusting means does not perform correction when the rate of change in temperature in the fuel cell module is equal to or greater than a predetermined correction prohibition change rate.   2. The solid oxide fuel cell according to claim 1, wherein both the fuel supply amount and the power generation oxidant gas supply amount change as a result of the correction by the fuel utilization rate adjusting means.   The fuel utilization rate adjusting means performs correction so that the fuel supply amount and the power generation oxidant gas supply amount are decreased, and the change rate of the power generation oxidant gas supply amount due to the correction is a change in the fuel supply amount. 4. The solid oxide fuel cell according to claim 3, wherein the fuel supply means and the power generating oxidant gas supply means are controlled so as to be larger than a rate.   The fuel utilization rate adjusting means controls only the power generation oxidant gas supply means to reduce the power generation oxidant gas supply amount, and also reduces the temperature in the fuel cell module as the power generation oxidant gas supply amount decreases. 4. The solid oxide fuel cell according to claim 3, wherein the fuel supply amount is reduced by appropriate temperature control corresponding to the rise.   The fuel utilization rate adjusting means decreases the fuel supply amount determined based on the integrated value by increasing / decreasing the integrated value of temperature by the heat storage amount estimating means, and / or is determined based on the integrated value. 2. The solid oxide fuel cell according to claim 1, wherein the supply amount of the oxidizing gas for power generation is reduced.   7. The solid oxide according to claim 6, wherein the fuel utilization rate adjusting means reduces the power generation oxidant gas supply amount by reducing only the integrated value used for determining the power generation oxidant gas supply amount. Type fuel cell.

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