JP6278339B2 - Solid oxide fuel cell device - Google Patents

Description

  The present invention relates to a solid oxide fuel cell device, and more particularly to a solid oxide fuel cell device that changes generated output 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 gas (air, oxygen, etc.) to the other side.

  Among solid oxide fuel cell devices, one that operates so that the amount of power generation follows the change in demand power is known (see, for example, Patent Document 1). In the solid oxide fuel cell device described in Patent Document 1, when demand power increases, an oxidant gas (air) supply amount, a water supply amount, and a fuel supply amount are sequentially increased according to a target power generation amount. Thus, the power generation amount can be increased to the target power generation amount with a predetermined time delay without deteriorating the fuel cell unit.

  That is, even if the supply amount of fuel or the like is increased according to the target power generation amount, for example, there is a time delay until the fuel reaches the fuel cell unit through the fuel supply path including the reformer, etc. If the power extraction from the fuel cell device is allowed to follow the increase in demand power without a time delay, excessive power extraction is performed, and the fuel cell unit is deteriorated or damaged.

  Therefore, in the solid oxide fuel cell device described in Patent Document 1, there is a time delay until the fuel corresponding to the extracted power reaches the fuel cell unit, or until the power generation reaction is actually possible after the fuel arrives. Corresponding to the time delay, delay control for delaying the increase timing of the extraction power is executed. Thus, the solid oxide fuel cell device can follow the output power with a predetermined time delay with respect to the change in the demand power. Therefore, when the time fluctuation of the demand power is small with respect to the above-described delay time, the output power can follow the change in the demand power relatively well.

JP 2013-69447 A

  However, when the time fluctuation of the demand power is large compared to the delay time and is accompanied by a rapid change, the solid oxide fuel cell device cannot follow the sudden change in the demand power. In addition, when the power demand fluctuates frequently in a short time, even if the fuel supply amount increases as the demand power increases, if the power demand decreases before the above-mentioned delay time elapses, it will increase. The remaining fuel cannot be used for the power generation reaction. For this reason, the portion not used for the power generation reaction becomes surplus fuel and is simply used for combustion in the fuel cell module.

  Therefore, if the time fluctuation of the demand power is repeated in a cycle shorter than such a delay time, the surplus fuel is increased and the temperature inside the fuel cell module is excessively increased due to the heat of combustion. was there. In particular, since the fuel cell module has good heat insulation to keep the interior at a high temperature, if the combustion with excess fuel is excessive, the internal temperature will rise too much.

  A specific example will be described below. In the home, power demand changes throughout the day. For example, a breakfast time zone and a dinner time zone are high load periods in which demand power is large, and a time zone from midnight to early morning or a specific time zone in the daytime is a low load period in which demand power is small. During the high load period, the period of demand power exceeding the rated power (for example, 700 W) of the solid oxide fuel cell device continues, so the shortage is supplemented by the system power. Therefore, even if there is a sudden fluctuation in demand power during such a high load period, the fluctuation in demand power can be dealt with by the grid power while the output power from the fuel cell device is kept constant.

  On the other hand, during the low load period, the solid oxide fuel cell device performs a low output operation of, for example, about 1 ampere (about several hundred watts) below the rated power. It covers electricity. In such a low load period, if the fluctuation of demand power in a short and short cycle is repeated, as described above, the solid oxide fuel cell device causes problems of generation of useless fuel and excessive temperature rise.

  For example, when a household electrical appliance operates using a timer function in the early morning hours during a low load period, the power demand increases rapidly and instantaneously exceeds 1,000 watts. Furthermore, many household electric appliances repeat simple power on / off control. For example, rice cookers are repeatedly turned on and off at intervals of about 1 minute during rice cooking. In this way, if the rapid power on / off control is repeatedly performed in the low load period, the fuel cell device tries to follow this rapid demand power fluctuation with a delay time, and therefore, excessive fuel or excessive increase of the fuel cell module is caused. Temperature will be generated.

  Accordingly, the present invention provides a solid oxide fuel cell device that follows fluctuations in demand power with a delay time, and can prevent overheating of the fuel cell module due to repeated sudden fluctuations in demand power. It aims at providing a type fuel cell device.

  In order to solve the above-described problems, the present invention includes a fuel cell module that accommodates a fuel cell, and a control unit that controls power generation by the fuel cell module so as to supply part or all of the demand power. In the solid oxide fuel cell device, the control means includes: a power generation amount determining means that determines a power generation amount based on demand power; a fuel supply amount determination means that determines a fuel supply amount according to the determined power generation amount; A load that causes the output power to follow the change in the demand power by executing delay control that extracts the output power corresponding to the fuel supply amount from the fuel cell module after a predetermined time delay from the start of fuel supply of the determined fuel supply amount Follow-up control execution means, and the control means further includes a demand power history storage means for storing a change in demand power over time, and a demand stored by the demand power history storage means. An upper limit value setting means for setting an upper limit value of the power generation amount based on the time change of the force, and a fuel supply exceeding the fuel supply amount according to the upper limit value set by the upper limit value setting means and taking out of output power are limited. Load follow-up limiting means.

  In the solid oxide fuel cell device, by performing load follow-up with respect to fluctuations in demand power, it is possible to supply the necessary amount of fuel when necessary and to perform efficient power generation operation. However, since solid oxide fuel cells have a delay time from fuel injection to power extraction, when the demand power fluctuates rapidly in a short cycle, the output power is converted to demand power by load following operation. The more faithful follow-up is, the more excess fuel is wasted as described above, and the fuel cell module may be overheated due to an increase in the amount of combustion heat. In order to suppress such an excessive temperature rise, the load follow-up may be performed slowly, but the efficiency of the power generation operation is reduced simply by slowing down.

  Therefore, in the present invention, attention is paid to the fact that there is regularity in the life patterns of ordinary households. For example, a home appliance (such as a rice cooker) at a specific time (early morning, evening, etc.) may be started every day and a large load fluctuation in a short cycle may be repeated. In such a case, if load follow-up control with a delay time is strictly performed, there is a high possibility that an excessive temperature increase due to combustion of surplus fuel occurs in the fuel cell module as described above. The solid oxide fuel cell system employs a power generation method that is not suitable for load following appliances (especially heating equipment such as rice cookers) that repeats on / off control of power with a short period of several minutes or less. Rather, such load following operation does not give a user's merit in terms of reduction in efficiency of power generation operation due to generation of useless fuel, and also reduces the durability of the fuel cell module itself. For this reason, in the present invention, in the specific time period as described above, based on the tendency of the demand power to change over time, the upper limit value is set by setting the upper limit value of power generation so as to suppress the generation of surplus fuel. By limiting the load following control that exceeds the limit, excessive temperature rise is suppressed and efficient power generation operation is enabled.

In the present invention, it is preferable that the load follow-up limiting unit sets an upper limit value at least in a time zone in which the time change of the demand power is large based on the stored time change of the demand power, and extracts output power exceeding the upper limit value. Limit.
According to the present invention configured as described above, the time when the power on / off is repeated at a high frequency with the same or shorter period than the delay time of the load following control as in the use time zone of the rice cooker or the like. Since the upper limit of the demand power is set in the belt, the temperature change of the fuel cell itself, the generation of surplus fuel caused by the delay time, and the excessive temperature rise caused by the combustion are suppressed. As a result, the durability of the fuel cell can be ensured, and user benefits such as improvement of fuel consumption can be obtained by suppressing the generation of useless fuel.

In the present invention, preferably, the load follow-up limiting means sets the minimum value of the demand power in the time zone as the upper limit value in the time zone based on the stored time change of the demand power.
According to the present invention configured as described above, in the time zone where the time change of the demand power is large, the minimum value of the demand power in that time zone is set to the upper limit value, so that the output power can be made constant, For this reason, it is possible to stabilize the power generation operation of the fuel cell device and improve the durability of the fuel cell module.

In the present invention, preferably, the load follow-up limiting unit prohibits the setting of the upper limit value or resets the upper limit value to a higher value when the demand power exceeds the upper limit value for a predetermined period in the time period.
According to the present invention configured as described above, there is a case where it is better to follow the actual power demand when the time change of the demand power is different from the tendency. That is, if the upper limit is fixed, power is supplied from the fuel cell device when the user uses different power than usual (usually when using a large amount of power during a time when only a small amount of power is used). Instead, power may be supplied from the grid power. If it does so, the merit which uses a fuel cell device will reduce. Therefore, in the present invention, when the demand power exceeds the upper limit value for a predetermined period, more output power can be supplied by prohibiting the setting of the upper limit value or resetting the upper limit value to a higher value.

  According to the solid oxide fuel cell device of the present invention, it is possible to prevent an excessive increase in temperature of the fuel cell module due to repeated rapid fluctuations in demand power.

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 an example of each supply_amount | feed_rate of fuel etc. in the starting process of the fuel cell apparatus by one Embodiment of this invention, and the temperature of each part. It is a graph which shows the daily change of the demand power in a household, and the output power of a fuel cell apparatus. 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 a graph which shows the time change of the upper limit of the output electric power of the fuel cell apparatus by one Embodiment of this invention. It is a flowchart of the process which sets the upper limit of the output electric power of the fuel cell apparatus by one Embodiment of this invention.

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 metal case 8 is built in the housing 6 via a heat insulating material 7. A fuel cell assembly 12 that performs a power generation reaction with fuel and oxidant gas (air) is disposed in a power generation chamber 10 that is a lower portion of the case 8 that is a sealed space. 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 that is a combustion section is formed above the above-described power generation chamber 10 of the case 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel and the remaining oxidant that have not been used for the power generation reaction. (Air) is combusted to generate exhaust gas. Further, the case 8 is covered with a heat insulating material 7 to suppress the heat inside the fuel cell module 2 from being diffused to the outside air.
Further, a reformer 20 for reforming the fuel 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. Yes. Further, an air heat exchanger 22, which is a heat exchanger for heating the power generation air with the remaining combustion gas and preheating the power generation air, is disposed above the reformer 20.

  Next, the auxiliary unit 4 stores pure water tank 26 that stores water condensed from moisture contained in the exhaust from the fuel cell module 2 and makes it pure water with a filter, and water supplied from the water storage tank. Is provided with a water flow rate adjusting unit 28 (such as a “water pump” driven by a motor). In addition, the auxiliary unit 4 adjusts the flow rate of the fuel gas, the gas shutoff valve 32 for shutting off the fuel supplied from the fuel supply source 30 such as city gas, the desulfurizer 36 for removing sulfur from the fuel gas, A fuel flow adjustment unit 38 (such as a “fuel pump” driven by a motor) and a valve 39 that shuts off fuel gas flowing out from the fuel flow adjustment unit 38 when power is lost. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant gas supplied from an 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 adjustment. A 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 first heater for heating the power generating air supplied to the power generation chamber 2 heaters 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, the case 8 in the housing 6 of the fuel cell module 2 has a fuel cell assembly 12, a reformer 20, and an air heat exchanger in order from the bottom as described above. 22 is arranged.

The reformer 20 is provided with a reformer introduction pipe 62 for introducing pure water, fuel gas to be reformed, and reforming air on the end side surface on the upstream end side.
The reformer introduction pipe 62 is a circular pipe extending from the side wall surface at one end of the reformer 20, is bent by 90 ° and extends in a substantially vertical direction, and penetrates the upper end surface of the case 8. The reformer introduction pipe 62 functions as a water introduction pipe for introducing water into the reformer 20. Further, a T-shaped tube 62a is connected to the upper end of the reformer introduction tube 62, and fuel gas and pure water are supplied to both ends of the T-shaped tube 62a extending in a substantially horizontal direction. Pipes for connecting are connected to each other. The water supply pipe 63a extends obliquely upward from one side end of the T-shaped pipe 62a. The fuel gas supply pipe 63b extends in the horizontal direction from the other side end of the T-shaped pipe 62a, then bends in a U shape, and extends substantially horizontally in the same direction as the water supply pipe 63a.

  On the other hand, an evaporation unit 20a, a mixing unit 20b, and a reforming unit 20c are formed in the reformer 20 sequentially from the upstream side, and the reforming unit 20c is filled with a reforming catalyst. The fuel gas mixed with the steam (pure water) introduced into the reformer 20 is 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. Further, in the middle of the vertical portion of the fuel gas supply pipe 64, a pressure fluctuation suppressing flow path resistance portion 64c having a narrow flow path is provided, and the flow path resistance of the fuel gas supply flow path is adjusted.

  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.

On the other hand, an air heat exchanger 22 is provided above the reformer 20.
Further, 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 that are caps respectively connected to both 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 84 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. At the center of the inner electrode terminal 86, a fuel gas channel capillary 98 that communicates with the fuel gas channel 88 of the inner electrode layer 90 is formed.

  The fuel gas passage narrow tube 98 is an elongated thin tube provided so as to extend in the axial direction of the fuel cell 84 from the center of the inner electrode terminal 86. For this reason, a predetermined pressure loss occurs in the flow of the fuel gas flowing from the manifold 66 (FIG. 2) into the fuel gas passage 88 through the fuel gas passage narrow tube 98 of the lower inner electrode terminal 86. . Accordingly, the fuel gas flow passage narrow tube 98 of the lower inner electrode terminal 86 acts as an inflow side flow passage resistance portion, and the flow passage resistance is set to a predetermined value. Further, a predetermined pressure loss also occurs in the flow of the fuel gas flowing out from the fuel gas flow path 88 to the combustion chamber 18 (FIG. 2) through the fuel gas flow path narrow tube 98 of the upper inner electrode terminal 86. Therefore, the fuel gas flow passage narrow tube 98 of the upper inner electrode terminal 86 acts as an outflow side flow passage resistance portion, and the flow passage resistance is set to a predetermined value.

  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 these fuel cell units 16 are arranged in two rows of 8 each.
Each fuel cell unit 16 is supported at its lower end by a rectangular lower support plate 68 (FIG. 2) made of ceramic, and at the upper end, four fuel cell units 16 at both end portions are provided, each having a generally square shape. It is supported by the upper support plate 100. The lower support plate 68 and the upper support plate 100 are formed with through holes 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 outer peripheral surface of the outer electrode layer 92 that is an air electrode. It is integrally formed so as to connect the air electrode connecting portion 102b that is electrically connected. In addition, a silver thin film is formed on the entire outer surface of the outer electrode layer 92 (air electrode) of each fuel cell unit 16 as an electrode on the air electrode side. When the air electrode connecting portion 102b contacts the surface of the thin film, the current collector 102 is electrically connected to the entire air electrode.

  Furthermore, two external terminals 104 are connected to the air electrode 86 of the fuel cell unit 16 located at the end of the fuel cell stack 14 (the far left side in FIG. 5). These external terminals 104 are connected to the inner electrode terminal 86 of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and as described above, all 160 fuel cell units 16 are connected in series. It has come to be.

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.
In addition, the control unit 110 incorporates a microprocessor, a memory, and a program (not shown) for operating these components, and thereby, based on input signals from the respective sensors, the auxiliary unit 4, The inverter 54 and the like are controlled. 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 flow of fuel, power generation air, and exhaust gas during power generation operation of the solid oxide fuel cell 1 will be described with reference to FIGS.
First, the fuel is introduced into the evaporation section 20a of the reformer 20 through the fuel gas supply pipe 63b, the T-shaped pipe 62a, and the reformer introduction pipe 62, and the pure water is supplied to the water supply pipe 63a, It is introduced into the evaporator 20a through the T-shaped tube 62a and the reformer introducing tube 62. Accordingly, the supplied fuel and water are merged in the T-shaped tube 62 a and introduced into the evaporation unit 20 a through the reformer introduction tube 62. During the power generation operation, since the evaporation unit 20a is heated to a high temperature, the pure water introduced into the evaporation unit 20a is evaporated relatively quickly to become water vapor. The evaporated water vapor and fuel are mixed in the mixing unit 20 b and flow into the reforming unit 20 c of the reformer 20. The fuel introduced into the reforming unit 20c together with the steam is steam reformed here and reformed into a fuel gas rich in hydrogen. The fuel reformed in the reforming unit 20c goes down through the fuel gas supply pipe 64 and flows into the manifold 66 which is a dispersion chamber.

  The manifold 66 is a rectangular parallelepiped space having a relatively large volume, which is disposed on the lower side of the fuel cell stack 14, and a plurality of holes provided on the upper surface thereof constitute each fuel cell constituting the fuel cell stack 14. It communicates with the inside of the unit 16. The fuel introduced into the manifold 66 flows out from the upper end of the fuel cell unit 16 through the many holes provided on the upper surface thereof, through the fuel electrode side of the fuel cell unit 16, that is, through the inside of the fuel cell unit 16. . Further, when hydrogen gas as a fuel passes through the inside of the fuel cell unit 16, it reacts with oxygen in the air passing outside the fuel cell unit 16 as an air electrode (oxidant gas electrode) to generate a charge. Is done. The remaining fuel that is not used for power generation flows out from the upper end of each fuel cell unit 16 and is combusted in a combustion chamber 18 provided above the fuel cell stack 14.

  On the other hand, the power generation air that is the oxidant gas is sent into the fuel cell module 2 through the power generation air introduction pipe 74 by the power generation air flow rate adjustment unit 45 that is a power generation oxidant gas supply device. The air sent into the fuel cell module 2 is introduced into the power generation air passage 72 of the air heat exchanger 22 via the power generation air introduction pipe 74 and preheated. The preheated air flows out to each communication channel 76 via each outlet port 76a (FIG. 3). The power generation air flowing into each communication channel 76 flows downward through the power generation air supply passages 77 provided on both side surfaces of the fuel cell module 2, and the fuel cell stack 14 from a number of outlets 77a. Toward the power generation chamber 10.

  The air injected into the power generation chamber 10 comes into contact with the outer surface of each fuel cell unit 16 on the air electrode side (oxidant gas electrode side) of the fuel cell stack 14, and a part of oxygen in the air is in contact with it. Used for power generation. Moreover, the air injected to the lower part of the power generation chamber 10 through the blower outlet 77a rises in the power generation chamber 10 while being used for power generation. The air rising in the power generation chamber 10 burns the fuel flowing out from the upper end of each fuel cell unit 16. The combustion heat generated by this combustion heats the evaporation section 20a, the mixing section 20b, and the reforming section 20c of the reformer 20 disposed above the fuel cell stack 14. The combustion gas generated by burning the fuel heats the upper reformer 20 and then flows into the upper side of the rectifying plate 21 through the opening 21 a above the reformer 20. The combustion gas that has flowed into the upper side of the rectifying plate 21 is guided to the communication opening 8 a that is the inlet of the air heat exchanger 22 through the exhaust passage 21 b formed by the rectifying plate 21. The combustion gas that has flowed into the air heat exchanger 22 from the communication opening 8 a flows into the open end of each combustion gas pipe 70 and flows through the power generation air flow path 72 outside each combustion gas pipe 70. Are exchanged with each other and collected in an exhaust gas collecting chamber 78. The exhaust gas collected in the exhaust gas collection chamber 78 is discharged to the outside of the fuel cell module 2 through the exhaust gas discharge pipe 82. As a result, the evaporation of water in the evaporation unit 20a and the steam reforming reaction, which is an endothermic reaction in the reforming unit 20c, are promoted, and the power generation air in the air heat exchanger 22 is preheated.

Next, control in the starting process of the solid oxide fuel cell device 1 will be described with reference to FIG.
FIG. 7 is a time chart showing an example of each supply amount of fuel and the temperature of each part in the starting process. In addition, the scale of the vertical axis | shaft of FIG. 7 has shown temperature, and each supply amount of fuel etc. has shown those increase / decrease roughly.

In the starting process shown in FIG. 7, the temperature of the fuel cell stack 14 at room temperature is raised to a temperature at which power generation is possible.
First, at time t0 in FIG. 7, supply of power generation air and reforming air is started. Specifically, the control unit 110 that is a controller sends a signal to the power generation air flow rate adjustment unit 45 that is a power generation oxidant gas supply device to operate it. As described above, the power generation air is introduced into the fuel cell module 2 through the power generation air introduction pipe 74 and flows into the power generation chamber 10 through the air heat exchanger 22 and the power generation air supply path 77. . In addition, the control unit 110 sends a signal to the reforming air flow rate adjustment unit 44 which is a reforming oxidant gas supply device to operate it. The reforming air introduced into the fuel cell module 2 flows into the interior of each fuel cell unit 16 through the reformer 20 and the manifold 66, and flows out from the upper end thereof. Note that at time t0, no reforming reaction occurs in the reformer 20 because fuel has not yet been supplied. In the present embodiment, the supply amount of power generation air started at time t0 in FIG. 7 is about 100 L / min, and the supply amount of reforming air is about 10.0 L / min.

  Next, the fuel supply is started at time t1 after a predetermined time from time t0 in FIG. Specifically, the control unit 110 sends a signal to the fuel flow rate adjustment unit 38 which is a fuel supply device to operate it. In the present embodiment, the fuel supply amount started at time t1 is about 5.0 L / min. The fuel introduced into the fuel cell module 2 flows into the interior of each fuel cell unit 16 through the reformer 20 and the manifold 66, and flows out from the upper end thereof. At time t1, the reformer reaction is not generated in the reformer 20 because the temperature of the reformer is still low.

  Next, at time t2 when a predetermined time has elapsed from time t1 in FIG. 7, an ignition process for the supplied fuel is started. Specifically, in the ignition process, the control unit 110 sends a signal to an ignition device 83 (FIG. 2) that is an ignition means, and ignites the fuel flowing out from the upper end of each fuel cell unit 16. The ignition device 83 repeatedly generates a spark in the vicinity of the upper end of the fuel cell stack 14 and ignites the fuel flowing out from the upper end of each fuel cell unit 16.

When ignition is completed at time t3 in FIG. 7, supply of reforming water is started. Specifically, the control unit 110 sends a signal to the water flow rate adjustment unit 28 (FIG. 6), which is a water supply device, to activate it. In the present embodiment, the supply amount of water started at time t3 is 2.0 cc / min. At time t3, the fuel supply amount is maintained at about 5.0 L / min. Further, the supply amounts of the power generation air and the reforming air are also maintained at the previous values. At this time t3, the ratio O ₂ / C of oxygen O ₂ in the reforming air and carbon C in the fuel becomes about 0.32.

  After being ignited at time t3 in FIG. 7, the supplied fuel flows out from the upper end of each fuel cell unit 16 as off-gas and is burned here. This combustion heat heats the reformer 20 disposed above the fuel cell stack 14. Here, an evaporating chamber heat insulator 23 is disposed above the reformer 20 (above the case 8), so that immediately after the start of fuel combustion, the temperature of the reformer 20 suddenly increases from room temperature. To rise. Since the outside air is introduced into the air heat exchanger 22 disposed on the heat insulating material 23 for the evaporation chamber, the air heat exchanger 22 has a low temperature, particularly immediately after the start of combustion, and serves as a cooling source. Cheap. In the present embodiment, the evaporation chamber heat insulating material 23 is disposed between the upper surface of the case 8 and the bottom surface of the air heat exchanger 22, so that the reformer 20 disposed in the upper portion of the case 8 The movement of heat to the air heat exchanger 22 is suppressed, and heat is easily trapped in the vicinity of the reformer 20 in the case 8. In addition, the space above the rectifying plate 21 above the evaporation unit 20a is configured as a gas retention space 21c (FIG. 2) in which the flow of combustion gas is slow, so that the vicinity of the evaporation unit 20a is double insulated. And the temperature rises more rapidly.

  As described above, the temperature of the evaporation unit 20a rapidly increases, so that water vapor can be generated in a short time after the start of off-gas combustion. In addition, since the reforming water is supplied to the evaporation unit 20a little by little, it is possible to heat the water to the boiling point with a slight amount of heat compared to the case where a large amount of water is stored in the evaporation unit 20a. The supply of water vapor can be started immediately. Furthermore, since water flows in immediately after the start of the operation of the water flow rate adjustment unit 28, it is possible to avoid an excessive increase in temperature of the evaporation unit 20a and a delay in supply of water vapor due to a delay in supply of water.

  When a certain amount of time elapses after the start of off-gas combustion, the temperature of the air heat exchanger 22 also rises due to the exhaust gas flowing from the combustion chamber 18 into the air heat exchanger 22. The evaporation chamber heat insulating material 23 that insulates between the reformer 20 and the air heat exchanger 22 is a heat insulating material provided inside the heat insulating material 7. Therefore, the heat insulating material 23 for the evaporation chamber does not suppress the dissipation of heat from the fuel cell module 2, but immediately increases the temperature of the reformer 20, particularly the evaporation section 20a immediately after the start of off-gas combustion. Let

In this way, at time t4 when the temperature of the reformer 20 rises, the fuel and the reforming air that have flowed into the reforming unit 20b through the evaporation unit 20a undergo the partial oxidation reforming reaction represented by the equation (1). Get up.
_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)
Since this partial oxidation reforming reaction is an exothermic reaction, when the partial oxidation reforming reaction occurs in the reforming part 20b, the ambient temperature rapidly rises locally.

On the other hand, in the present embodiment, the supply of the reforming water is started from time t3 immediately after the ignition is confirmed, and the temperature of the evaporation unit 20a is rapidly increased. At time t4, water vapor has already been generated in the evaporator 20a and supplied to the reformer 20b. That is, after the off-gas is ignited, the supply of water is started a predetermined time before the temperature of the reforming unit 20b reaches the temperature at which the partial oxidation reforming reaction occurs, and reaches the temperature at which the partial oxidation reforming reaction occurs. At that time, a predetermined amount of water is stored in the evaporation unit 20a, and water vapor is generated. For this reason, when the temperature rapidly rises due to the occurrence of the partial oxidation reforming reaction, a steam reforming reaction occurs in which the reforming steam supplied to the reforming unit 20b reacts with the fuel. This steam reforming reaction is an endothermic reaction shown in Formula (2), and occurs at a higher temperature than the partial oxidation reforming reaction.
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (2)

As described above, when the time t4 in FIG. 7 is reached, the partial oxidation reforming reaction occurs in the reforming unit 20b, and the steam reforming is caused by the temperature rise caused by the partial oxidation reforming reaction. Reaction will also occur at the same time. Therefore, the reforming reaction that occurs in the reforming unit 20b after time t4 is an autothermal reforming reaction (ATR) shown in Formula (3) in which the partial oxidation reforming reaction and the steam reforming reaction are mixed. That is, the ATR1 process is started at time t4.
_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (3)

Thus, in the solid oxide fuel cell device 1 according to the embodiment of the present invention, water is supplied during the entire start-up process, and the partial oxidation reforming reaction (POX) does not occur alone. In the time chart shown in FIG. 12, the reformer temperature at time t4 is about 200.degree. The reformer temperature is lower than the temperature at which the partial oxidation reforming reaction occurs, but the temperature detected by the reformer temperature sensor 148 (FIG. 6) is the average temperature of the reforming unit 20b.
Actually, even at time t4, the reforming unit 20b partially reaches the temperature at which the partial oxidation reforming reaction occurs, and the steam reforming reaction is performed by the reaction heat of the generated partial oxidation reforming reaction. Is also triggered. As described above, in this embodiment, after the ignition, the supply of water is started before the reforming unit 20b reaches the temperature at which the partial oxidation reforming occurs, and the partial oxidation reforming reaction is performed independently. Will not occur.

Next, when the temperature detected by the reformer temperature sensor 148 reaches about 500 ° C. or higher, the process moves from the ATR1 process to the ATR2 process at time t5 in FIG. At time t5, the water supply amount is changed from 2.0 cc / min to 3.0 cc / min. Further, the fuel supply amount, the reforming air supply amount, and the power generation air supply amount are maintained at the previous values. As a result, the steam / carbon ratio S / C in the ATR2 step is increased to 0.64, while the reforming air / carbon ratio O ₂ / C is maintained at 0.32. Thus, by maintaining the ratio of reforming air and carbon O ₂ / C constant, the ratio S / C of steam and carbon is increased, so that the amount of carbon that can be partially oxidized and reformed is not reduced. In addition, the amount of carbon that can be steam reformed is increased. This makes it possible to increase the amount of carbon subjected to steam reforming as the temperature of the reforming unit 20b increases while reliably avoiding the risk of carbon deposition in the reforming unit 20b.

Furthermore, when the temperature detected by the power generation chamber temperature sensor 142 reaches about 400 ° C. or higher at time t6 in FIG. 7, the process proceeds from the ATR2 process to the ATR3 process. Accordingly, the fuel supply amount is changed from 5.0 L / min to 4.0 L / min, and the reforming air supply amount is changed from 9.0 L / min to 6.5 L / min. Also, the previous values are maintained for the water supply amount and the power generation air supply amount. This increases the steam / carbon ratio S / C in the ATR3 step to 0.80, while the reforming air to carbon ratio O ₂ / C is reduced to 0.29.

Furthermore, when the temperature detected by the power generation chamber temperature sensor 142 reaches about 550 ° C. or higher at time t7 in FIG. 7, the process proceeds to the SR1 process. Along with this, the fuel supply amount is changed from 4.0 L / min to 3.0 L / min, and the water supply amount is changed from 3.0 cc / min to 7.0 cc / min.
Further, the supply of the reforming air is stopped, and the power supply air supply amount is maintained at the previous value. Thus, in the SR1 process, steam reforming occurs exclusively in the reforming unit 20b, and the steam / carbon ratio S / C is 2 which is appropriate for steam reforming the entire amount of supplied fuel. .49. At time t7 in FIG. 12, since the temperature of both the reformer 20 and the fuel cell stack 14 is sufficiently increased, the steam reforming is performed even if the partial oxidation reforming reaction has not occurred in the reforming unit 20b. The reaction can be generated stably.

Next, when the temperature detected by the power generation chamber temperature sensor 142 reaches about 600 ° C. or higher at time t8 in FIG. 7, the process proceeds to the SR2 step. Accordingly, the fuel supply amount is changed from 3.0 L / min to 2.5 L / min, and the water supply amount is changed from 7.0 cc / min to 6.0 cc / min.
In addition, the previous value of the power supply air supply amount is maintained. Thereby, in the SR2 step, the ratio S / C of water vapor to carbon is set to 2.56.

  Further, after executing the SR2 process for a predetermined time, the process proceeds to the power generation process. In the power generation process, power is extracted from the fuel cell stack 14 to the inverter 54 (FIG. 6), and power generation is started. In the power generation process, the reforming unit 20b reforms the fuel exclusively by steam reforming. Further, during the power generation operation, the fuel supply amount, the power generation air supply amount, and the water supply amount are changed in accordance with the output power required for the fuel cell module 2. Further, during the power generation operation, the control unit 110 sets the fuel supply amount, the power generation air supply amount, and the water supply amount so that they are within an appropriate temperature range in which the temperature of the fuel cell stack 14 is within a predetermined power generation temperature range. Is controlling.

Next, with reference to FIG. 8, the time fluctuation of demand power and output power is demonstrated. FIG. 8A is a graph showing daily changes in demand power and output power by the fuel cell device in one day in the home, and FIG. 8B shows daily changes in demand power and output power in another day. It is a graph.
The power demand at home varies depending on the season and differences such as weekdays or weekends. However, although the life cycle of each household varies depending on the family structure, there is a certain pattern, so there is a certain pattern in demand power. For example, there are many cases where there is almost no power demand in the bedtime, and there is often a large demand power in the morning and evening meal time zones and the time zone after going to dinner after going to dinner.

  In the example of FIG. 8A, the household power demand is between 6:30 and 9:30, between 14:30 and 19:30, between 20:30 and 21:30, and 22:00 24:30 is a high load period, and the other time zone is a low load period. On the other hand, in the example of FIG. 8B, since it is the same household demand power but different days of the week, the period between 6:30 and 9:30 and between 20:30 and 24:00 is a high load period. The other time zones are low load periods. In this way, even in the same home, there are differences as shown in FIG. 8A and FIG. 8B on different days, but for example, high power demand before bedtime or bedtime, It can be seen that there is a common pattern in terms of low power demand in the time zone.

  During a high load period (for example, between 6:30 and 9:30 in FIG. 8A), the fuel cell device 1 operates at the maximum output (rated output of about 700 W), and the demand power reaches the rated output. Therefore, the shortage is compensated by the grid power. Therefore, if there is a change in demand power in the range exceeding the rated power during the high load period, the change is covered by the grid power.

  On the other hand, in the low load period (for example, between 0:30 and 6:30 in FIG. 8A), since the demand power is lower than the rated power, in principle, all the demand power is supplied from the fuel cell device 1. It is possible to supply. When the demand power increases during such a low load period, the fuel cell device 1 tries to increase the output power following the increase. However, as will be described later, since there is a delay time in the response of the fuel cell device 1 to the increase in demand power, the increase in demand power cannot be supplied immediately, and the demand power during the delay time cannot be supplied. The increase will be covered by grid power. Furthermore, if the demand power rapidly increases in a short period during the low load period, the fuel cell device 1 cannot immediately follow the rapid increase. For example, in FIG. 8 (A) and FIG. 8 (B), the power demand rapidly increases around 6 o'clock and exceeds 1000 watts. This is because certain electrical products are activated by a timer.

  In addition, when the electric product is controlled to be turned on / off in a short cycle during a low load period, the demand power repeatedly increases and decreases rapidly in a short cycle. The fuel cell device 1 tries to follow such a rapid increase and decrease in demand power in a short period. However, even if the fuel supply amount is increased in order to cope with the sudden increase in demand power, the output power increases due to the delay control after a predetermined delay time. If the fuel consumption is rapidly decreasing, the power generation reaction and the power extraction corresponding to the increased fuel supply amount cannot be performed, and the increased fuel cannot be consumed by the power generation reaction. For this reason, fuel that cannot be consumed becomes surplus fuel and is wasted, and this surplus fuel is consumed by combustion. And if the combustion of the surplus fuel accompanying the increase / decrease of the short period of such demand power is repeated, the internal temperature of the fuel cell module 2 will rise too much.

  In this way, when the demand power repeatedly increases and decreases at short intervals in the low load period, in the control that simply follows the load with a delay time, there is a possibility that waste of fuel and excessive temperature rise inside the fuel cell module 2 may occur. There is. If it is only to suppress such excessive temperature rise, the response speed of the delay control may be further slowed down, but the reduction in the response speed sacrifices the power generation operation efficiency. Therefore, in the present embodiment, in order to prevent such an inconvenience, a time change pattern of demand power is learned, and a target power generation amount (target output power) at the time of following the load based on the learned pattern is currently calculated. It is configured to limit the power to less than the required power. Thereby, in the low load period, when there is a change in the short time interval of the demand power, it is possible to limit the extent to which the fuel cell device 1 follows the load (demand power). The occurrence of problems such as wasteful fuel and excessive temperature rise can be suppressed without sacrificing.

Next, control of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described with reference to FIGS. 9 to 11.
FIG. 9 is a graph schematically showing the relationship between the change in power demand, the amount of fuel supplied, and the current actually taken from the fuel cell module. FIG. 10 is a graph showing the time change of the upper limit value of the output power. FIG. 11 is a flowchart of a process of setting an upper limit value of output power.

First, referring to FIG. 9, load follow-up control with delay time control in the present embodiment will be described.
As shown in FIG. 9, 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. The power generation amount determination unit 110a of the control unit 110, which is a control unit, displays the fuel supply current value If, which is a target current to be generated by the fuel cell module 2, on the second graph of FIG. Set as shown. The fuel supply current value If is generally set so as to follow a change in power demand. That is, by outputting the fuel supply current value If, it is possible to substantially supply the demand power.

However, since the response speed of the fuel cell module 2 is slow with respect to the change in the demand power, the fuel supply current value If is not allowed to completely follow the rapid change in the short-term cycle of the demand power. It is set to gently follow the demand power. In addition, when the demand power exceeds the rated generated power of the solid oxide fuel cell, the fuel supply current value If follows the current value corresponding to the rated generated power and is set to a current value higher than that. There is no.
In the present embodiment, the power generation amount determination unit 110a sets the target output current as the target power generation amount, but is not limited thereto, and the target output power may be set as the target power generation amount.

  The fuel supply amount determination means 110b of the control unit 110 determines the fuel supply amount Fr at a flow rate that can generate electric power corresponding to the fuel supply current value If, as shown in the third graph of FIG. The fuel flow rate adjusting unit 38 is controlled to supply fuel to the fuel cell module 2 with the determined fuel supply amount Fr. 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. In the graph of FIG. 9, the fuel supply current value If and the fuel supply amount Fr are drawn as being proportional to each other, but actually, the fuel utilization rate is changed according to the operating state.

  Further, as shown in the lowermost graph of FIG. 9, the load follow-up control execution unit 110c of the control unit 110 takes out from the fuel cell module 2 according to the fuel supply amount Fr determined by the fuel supply amount determination unit 110b. A signal for instructing the inverter 54 of the extractable current Iinv that is a current value that can be output is output. 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, and this is the purchased power.

  Here, as shown in FIG. 9, 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. Set (delay control). For example, at time t10 in FIG. 9, 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, the control unit 110 increases the fuel supply amount Fr, and then performs the delay control for delaying the timing for actually increasing the power to be extracted from the fuel cell module 2, while obtaining the extractable current Iinv or the extractable power as demand power. The time delay until the fuel supplied to the fuel cell module 2 reaches the fuel cell stack 14 through the reformer 20 or the like, or after the fuel reaches the fuel cell stack 14, The time delay until the actual power generation reaction becomes possible is addressed. This reliably prevents the fuel battery cell unit 16 from being depleted of fuel and damaging the fuel battery cell unit 16.
In the present embodiment, the load follow-up control execution unit 110c takes out the current Iinv that can be taken out in correspondence with the electric power that can be taken out (of which, the electric power output from the inverter 54 in accordance with the actual demand power at the time of taking out). However, the present invention is not limited to this, and the extractable power itself may be set.

  The demand power history storage means 110d of the control unit 110 is configured to store the time change of the demand power shown in FIG. 8 and the time change of the output power actually output from the inverter 54 to the load side. . The demand power history storage means 110d stores the demand power time data received from the outside and the output power time data received from the power state detection sensor 126 in the memory. Further, the demand power history storage unit 110d stores a predetermined cycle (this time) based on demand power and output power time data for the most recent predetermined period (eg, 3 days, 1 week, 2 weeks, 1 month, 3 months, etc.). In the embodiment, average data of demand power and output power for 1 day) is calculated, and the updated average data is stored. In the present embodiment, an average value is calculated for each predetermined time segment (2 hours in the present embodiment) in a predetermined cycle.

The upper limit value setting unit 110e of the control unit 110 sets and updates the upper limit value (upper limit power) of demand power using the average power demand data stored by the demand power history storage unit 110d.
FIG. 10 is an example of the set upper limit value. In the example of FIG. 10, the upper limit value of demand power is set as a time change (daily change in FIG. 10) with a predetermined period as a unit for every predetermined time segment (every 2 hours in FIG. 10). However, the present invention is not limited to this, and for example, the length of the time segment may be any time length such as 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours, or the like. Further, the time change may be a change in an arbitrary period such as a week change or a seasonal change instead of a daily change.
FIG. 10 is set based on the data including the power time change data shown in FIG. 8, and the inactive time zone (such as from midnight to early morning) in a general home is the upper limit value of the output power. On the other hand, the upper limit value of the output power is set high in the activity time zone (breakfast time zone or evening to midnight, etc.).

  The load follow-up limiting unit 110f of the control unit 110 limits the fuel supply amount and the extractable power that will exceed the upper limit value according to the upper limit value determined by the upper limit value setting unit 110e. Specifically, when the target power generation amount (calculated based on the fuel supply current value If which is the target output current) set by the power generation amount determination unit 110a according to the demand power does not exceed the upper limit value, the load follow-up restriction is performed. The means 110f sequentially outputs the fuel supply amount Fr determined by the fuel supply amount determination means 110b and the extractable current Iinv (or the extractable current Iinv instructed by the load following control execution means 110c) according to the target power generation amount. Is not limited.

  However, when the demand power exceeds the upper limit value, the load follow-up limiting means 110f outputs the upper limit value to the power generation amount determination means 110a instead of the demand power, so that it is based on the upper limit value instead of the demand power. The target power generation amount (fuel supply current value If) is set by the power generation amount determination means 110a, and as a result, the fuel supply amount Fr is determined by the fuel supply amount determination means 110b and the power that can be taken out by the load following control execution means 110c ( An extractable current value Iinv) is indicated. As a result, the target power generation amount set by the power generation amount determination means 110a, the fuel supply amount determined by the fuel supply amount determination means 110b, and the extractable power instructed by the load following control execution means 110c are limited.

In the present embodiment, the upper limit value setting unit 110e sets and updates the upper limit value of the power generation amount shown in FIG. 10 based on the flowchart of FIG. This process is repeatedly executed every predetermined time.
At the upper limit value setting process of the power generation amount, first, upper limit setting unit 110e reads the current demand power value T _n and the output power value U _n stored by the power demand history storage unit 110d (step S1).

Next, the upper limit value setting unit 110e reads the average value TO _n-1 of the demand power in the current time section from the average data of the demand power stored by the demand power history storage unit 110d (Step S2). it based on the power demand values T _n and demand electric power mean value tO _n-1, calculates and updates the latest demand power averages tO _n at the current time segment (step S3).
In the present embodiment, a plurality of demand power values T _n are read as time elapses within one time segment, and a plurality of updates are performed. For this reason, each demand electric power value _Tn is weighted and an average value is calculated | required. For example, if the demand power value T _n is read N times in one time segment and updated N times, one demand power value T _n is used for calculating the average value with a weight of 1 / N. It is done.

Next, the upper limit value setting unit 110e reads the average value UO _n-1 of the output power in the current time segment from the average data of the output power stored by the demand power history storage unit 110d (Step S4). I based on the output power value U _n and the output electric power mean value UO _n-1, it calculates and updates the latest output power averages UO _n at the current time segment (step S5).
In the present embodiment, a plurality of output power values _Un are read over time within one time segment, and a plurality of updates are performed. For this reason, each output power value _Un is weighted to obtain an average value. For example, reading of N times the output power value U _n is performed in one time segment, if it is assumed that N times updates are performed, one output power value U _n uses the average value calculated by the weight of 1 / N It is done.

Then, upper limit value setting means 110e on the basis of the updated latest output power averages UO _n and demand electric power mean value TO _n, calculates and updates the upper limit value of the power generation amount in the current time segment (step S6 ), The process is terminated. In the present embodiment, the upper limit value setting unit 110e calculates the upper limit value by “upper limit value = output power average value UO _n × 0.7 + demand power average value TO _n × 0.3”. Thus, the upper limit value is determined by adding the average demand power to the average value (output power average value) of the results in the current time segment.

Therefore, when there is no short-term fluctuation and the demand power is stable in the low load time, the demand power average value does not change day by day and the output power is constant at a value that matches the demand power. It becomes. Therefore, in such a stable state, the upper limit value matches the average value of output power and demand power.
However, even in the low load time zone, there is a small but short period fluctuation in demand power, so the average value of demand power is slightly less than the average value of output power due to the delay time due to delay control. Become bigger. Therefore, the upper limit value is set larger than the average value of the output power in the low load time zone.

  In addition, since demand power is also affected by seasonal changes and lifestyle changes, in this embodiment, by adding the average value of demand power as a factor for determining the upper limit value, The upper limit value can be set and updated in response to a change in style.

Next, control of the solid oxide fuel cell 1 according to the embodiment of the present invention based on the setting of the upper limit value will be described.
As described above, for example, as shown in FIG. 8, the electric appliance is operated using a timer at a fixed time (6:00 am), and the demand power is repeatedly increased and decreased repeatedly in a low load time period. Variations may occur. Even in a low load time zone, there is a slight increase or decrease in demand power, but if a large load fluctuation occurs that exceeds the rated power, fuel is wasted or excessively increased due to the power generation delay time of the fuel cell device 1. Problems such as temperature arise.

  When such a large load fluctuation occurs, the rapidly increased demand power exceeds the upper limit value, so that the load follow-up limiting means 110f of the control unit 110 can output the target power generation amount so that the output power up to the upper limit value can be taken out. (Fuel supply current value), fuel supply amount and extractable power (extractable current value) are limited. As a result, the power generation amount determining means 110a, the fuel supply amount determining means 110b, and the load follow-up control executing means 110c do not try to follow the actual increase in demand power, but are reduced so that the available power becomes the upper limit value. Follow-up control is performed. As a result, problems such as fuel waste and excessive temperature rise as described above can be suppressed.

  In addition, even when large fluctuations in demand power are started on time by using the timer, the upper limit value is determined based on the average value of output power and the average value of demand power. It is not set extremely large compared to the low load level until just before the start. In addition, since the large fluctuation of the demand power is based on the power on / off control, the demand power does not increase when averaged over time. Even during a large fluctuation in demand power, the output power does not become extremely large even if the target power generation amount is set large due to delay control. Therefore, as in this embodiment, the upper limit value is determined based on the average value of the output power and the average value of the demand power, and further, by setting the time segment, immediately before the start of a large fluctuation in the demand power. The upper limit value is not set to be significantly larger than the low load level until, but rather, a value close to the low load level is set.

  In the above embodiment, the upper limit value is set in all time segments in a predetermined cycle (for example, daily change). However, the present invention is not limited to this, and the upper limit value may be set only in a specific time segment. Good. For example, in a low load time zone, the upper limit is limited only to the time segment in which large demand power exceeding a predetermined power value (for example, rated output) occurs, or the time segment in which output power can be provided only at a predetermined ratio or less with respect to the demand power. A value may be set. By configuring in this way, it is possible to suppress the occurrence of the above problem in a time zone or a time segment in which there is a risk of waste of fuel or excessive temperature rise due to delay control.

  In the above embodiment, the upper limit value is determined based on the average value of the output power and the average value of the demand power. However, the present invention is not limited to this, and the minimum value of the demand power is set as the upper limit value in each time segment. You may comprise. By configuring in this way, fluctuations in output power due to fluctuations in demand power are suppressed, stable supply of output power becomes possible, and more efficient operation and longer life of the fuel cell module 2 are achieved. Can be planned.

  In the above-described embodiment, control is performed so that the output power does not exceed the upper limit value when there is a fluctuation in demand power that exceeds the set upper limit value. When the upper limit value is exceeded for a predetermined period, the upper limit value is reset to a larger value, or the upper limit value is not set temporarily, so that the degree of follow-up to fluctuations in demand power is reduced. May be raised. For example, when a period exceeding an upper limit value continues for a predetermined period in a certain time segment on a certain day, it can be determined that there is exceptional demand power. The setting of the upper limit value decreases the power supply by the fuel cell device 1 and increases the purchased power. Therefore, when there is exceptional demand power as described above, there is a merit that the purchased power is reduced and the power supply amount from the fuel cell device 1 is increased by resetting the upper limit value or temporarily stopping it.

DESCRIPTION OF SYMBOLS 1 Solid oxide type fuel cell 2 Fuel cell module 4 Auxiliary machine unit 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit 18 Combustion chamber 28 Water flow rate adjustment unit 38 Fuel flow rate adjustment unit 44 Reformation Air flow rate adjustment unit 45 Power generation air flow rate adjustment unit 54 Inverter 110 Control unit 110a Power generation amount determination means 110b Fuel supply amount determination means 110c Load follow-up control execution means 110d Demand power history storage means 110e Upper limit value setting means 110f Load follow-up restriction means 126 Power state detection sensor

Claims (4)

In a solid oxide fuel cell device comprising: a fuel cell module that accommodates fuel cells; and a control unit that controls power generation by the fuel cell module so as to supply part or all of the demand power.
The control means includes
A power generation amount determining means for determining a power generation amount based on demand power;
Fuel supply amount determination means for determining a fuel supply amount according to the determined power generation amount;
By executing delay control for extracting output power corresponding to the fuel supply amount from the fuel cell module after a predetermined time delay from the start of fuel supply of the determined fuel supply amount, the output power follows the change in demand power. Load follow-up control execution means,
The control means further includes
Demand power history storage means for storing changes in demand power over time;
Upper limit value setting means for setting an upper limit value of the amount of power generation based on a temporal change in the demand power stored by the demand power history storage means;
A solid oxide fuel cell device comprising: load follow-up limiting means for limiting fuel supply exceeding the fuel supply amount according to the upper limit value set by the upper limit value setting means and extraction of output power. .   The load follow-up limiting unit sets the upper limit value at least in a time zone in which the time change in demand power is large based on the stored time change in demand power, and limits the extraction of output power exceeding the upper limit value. The solid oxide fuel cell device according to claim 1.   3. The load follow-up limiting unit sets a minimum value of demand power in the time zone to the upper limit value in the time zone based on the time change of the stored demand power. The solid oxide fuel cell device described.   The load follow-up limiting means prohibits the setting of the upper limit value or resets the upper limit value to a higher value when demand power exceeds the upper limit value for a predetermined period in the time period. The solid oxide fuel cell device according to claim 2.

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