Control method, control device, and power generation system

Abstract

Compared to conventional technology, this invention provides a control method for a fuel cell system that can perform appropriate control in response to the ratio of heat demand to electricity demand of a customer or changes in the customer's heat demand. [Solution] The control method is a control method for a fuel cell system including a plurality of fuel cell units, and switches between a first operating mode and a second operating mode in which the utilization rate of more deteriorated fuel cell units is higher than that of the first operating mode, based on the ratio of the heat demand to the power demand of the customer or the heat demand of the customer.

Description

Technical Field

[0001] The present disclosure relates to a control method for a fuel cell device, a control device for a fuel cell device, and a power generation system including a fuel cell device.

Background Art

[0002] In order not to waste the heat generated during power generation of a fuel cell, a power generation system that supplies not only the electricity generated by the fuel cell but also the heat energy to consumers has been devised. Regarding such technology, Patent Document 1 below discloses a method of setting the operating time of a fuel cell according to the ratio of the heat demand to the power demand of a consumer. In Patent Document 1, it is explained that when the ratio of the heat demand to the power demand is large, the fuel cell can be efficiently operated by shortening the daily operating time of the fuel cell, and a large amount of electric power and heat energy can be efficiently extracted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, appropriate control of the fuel cell with respect to changes in the ratio of the heat demand to the power demand of the consumer has not been sufficiently studied.

[0005] An object of the present disclosure is to provide a control method for a fuel cell device, a control device for a fuel cell device, and a power generation system that can perform appropriate control with respect to a change in the ratio of the heat demand to the power demand of a consumer or the heat demand of a consumer as compared with the prior art.

Means for Solving the Problems

[0006] To solve the above problems, a control method according to one aspect of the present disclosure is a control method for a fuel cell system including a plurality of fuel cell units, which switches between a first operating mode and a second operating mode in which the utilization rate of more degraded fuel cell units is higher than that of the first operating mode, based on the ratio of the heat demand to the power demand of the customer or the heat demand of the customer.

[0007] Furthermore, a control device according to one aspect of the present disclosure is a control device for a fuel cell system including a plurality of fuel cell units, comprising: a memory for storing the ratio of a customer's heat demand to their power demand or the customer's heat demand; and a controller for switching between a first operating mode and a second operating mode in which the utilization rate of more deteriorated fuel cell units is higher than that of the first operating mode, based on the ratio or the customer's heat demand.

[0008] Furthermore, a power generation system according to one aspect of the present disclosure comprises a fuel cell device including a plurality of fuel cell units and the control device described above. [Effects of the Invention]

[0009] One embodiment of the present disclosure provides the effect of enabling appropriate control to the ratio of a customer's heat demand to their electricity demand or to changes in their heat demand, compared to the prior art. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram of the power generation system. [Figure 2] Figure 2 is a graph showing the power generation efficiency curve and the heat recovery efficiency curve. [Figure 3] Figure 3 is a flowchart of the power generation control program. [Figure 4] Figure 4 is a table showing an example of fuel cell unit combinations. [Figure 5] Figure 5 is a flowchart of the power generation control program in a modified example. [Modes for carrying out the invention]

[0011] Fuel cell systems, which consist of multiple fuel cell units, generate electricity through a chemical reaction between a fuel such as hydrogen-containing gas or methanol and an oxidizing agent such as oxygen. This chemical reaction also generates heat. By supplying both the electricity and heat generated from the fuel cell system to consumers, and allowing consumers to utilize these energies, the overall energy utilization efficiency can be improved.

[0012] On the other hand, the amount of electricity and thermal energy required by consumers changes depending on the circumstances. Therefore, the ratio of heat demand to electricity demand also changes depending on the circumstances. If the ratio of heat output to generated power of the fuel cell system can be changed in response to this change in the ratio of heat demand to electricity demand, it becomes easier to reduce the surplus or deficit of electricity and thermal energy generated by the fuel cell system relative to the consumer's electricity and thermal demand.

[0013] Here, the inventors focused on the fact that the ratio of heat output to generated power differs depending on the degree of deterioration of each fuel cell unit in the fuel cell system, and realized that the ratio of heat output to generated power of the fuel cell system can be changed by changing the combination of fuel cell units that generate power, taking into account the degree of deterioration of each fuel cell unit.

[0014] Based on the above, the control method of the first aspect of this disclosure is a control method for a fuel cell system including a plurality of fuel cell units, which switches between a first operating mode and a second operating mode in which the utilization rate of more degraded fuel cell units is higher than that of the first operating mode, based on the ratio of the heat demand to the electricity demand of the customer or the heat demand of the customer.

[0015] As the fuel cell unit deteriorates, the ratio of the heat output to the generated power increases. Therefore, by switching between the first operation mode and the second operation mode as in the control method of the first aspect, the operating rate of the deteriorated fuel cell unit, that is, the ratio of the deteriorated fuel cell unit among the fuel cell units generating power can be changed, and the ratio of the heat output to the generated power of the fuel cell device can be changed.

[0016] Therefore, according to the control method of the first aspect, while maintaining power generation, the ratio of the heat output to the generated power of the fuel cell device can be changed with respect to the ratio of the heat demand to the power demand of the consumer or the change in the heat demand of the consumer.

[0017] In the control method of the second aspect of the present disclosure, in the control method of the first aspect, when the ratio increases, the switching is made from the first operation mode to the second operation mode.

[0018] Here, since the operating rate of the deteriorated fuel cell unit is higher in the second operation mode than in the first operation mode, the ratio of the heat output to the generated power of the fuel cell device is higher than in the first operation mode. Therefore, in the control method of the second aspect, when the ratio of the heat demand to the power demand of the consumer increases, the switching is made from the first operation mode to the second operation mode, and the ratio of the heat output to the generated power of the fuel cell device increases. Therefore, the ratio of the heat output to the generated power of the fuel cell device can be increased in response to the increase in the ratio of the heat demand to the power demand of the consumer. As a result, it becomes easier to reduce the excess or deficiency of the power and heat energy generated by the fuel cell device with respect to the power demand and heat demand of the consumer when the ratio of the heat demand to the power demand of the consumer increases.

[0019] In the control method of the third aspect of the present disclosure, in the control method of the first aspect, when the heat demand of the consumer increases, the switching is made from the first operation mode to the second operation mode.

[0020] In the control method of the second aspect described above, when the "ratio of heat demand to power demand of the consumer" increases, the operation mode is switched from the first operation mode to the second operation mode. In contrast, in the control method of the third aspect, when the "heat demand of the consumer" increases, the operation mode is switched from the first operation mode to the second operation mode. Also, when the heat demand of the consumer increases, the ratio of the heat demand to the power demand of the consumer also increases. Therefore, the control method of the third aspect has the same operational effects as the control method of the second aspect.

[0021] In the control method of the fourth aspect of the present disclosure, in the control method of the second aspect, after switching to the second operation mode, when the ratio decreases, the operation mode is switched from the second operation mode to the first operation mode.

[0022] In this control method, when the ratio of the heat demand to the power demand of the consumer decreases, the operation mode is switched from the second operation mode to the first operation mode, and the ratio of the heat output to the generated power of the fuel cell device decreases. Therefore, the ratio of the heat output to the generated power of the fuel cell device can be decreased in response to the decrease in the ratio of the heat demand to the power demand of the consumer. As a result, it becomes easier to reduce the excess or deficiency of the power and heat energy generated by the fuel cell device with respect to the power demand and heat demand of the consumer when the ratio of the heat demand to the power demand of the consumer increases.

[0023] In the control method of the fifth aspect of the present disclosure, in the control method of the third aspect, after switching to the second operation mode, when the heat demand of the consumer decreases, the operation mode is switched from the second operation mode to the first operation mode.

[0024] In the control method of the fourth aspect described above, when the "ratio of heat demand to power demand of the consumer" decreases, the operation mode is switched from the second operation mode to the first operation mode. In contrast, in the control method of the fifth aspect, when the "heat demand of the consumer" decreases, the operation mode is switched from the second operation mode to the first operation mode. Also, when the heat demand of the consumer decreases, the ratio of the heat demand to the power demand of the consumer also decreases. Therefore, the control method of the fifth aspect has the same operational effects as the control method of the fourth aspect.

[0025] A sixth aspect of the present disclosure is a control method in the second or third aspect of the present disclosure in which, when switching from the first operating mode to the second operating mode, at least one of the operating fuel cell units is stopped from generating power, and a degraded fuel cell unit is started to generate power in place of the fuel cell unit that has stopped generating power.

[0026] According to this control method, when switching from the first operating mode to the second operating mode, the number of fuel cell units that have not deteriorated significantly decreases, and the number of fuel cell units that have deteriorated significantly increases, thereby increasing the operating rate of the deteriorated fuel cell units.

[0027] The seventh aspect of the present disclosure is a control method in the second or third aspect of the present disclosure in which, when switching from the first operating mode to the second operating mode, a newly degraded fuel cell unit is started to generate power in addition to the multiple fuel cell units that are currently in operation.

[0028] According to this control method, when switching from the first operating mode to the second operating mode, a degraded fuel cell unit is added to the multiple fuel cell units generating power, thereby increasing the operating rate of the degraded fuel cell unit.

[0029] The control method of the eighth aspect of the present disclosure, in the control method of the fourth or fifth aspect, when switching from the second operating mode to the first operating mode, stops power generation from at least one of the degraded fuel cell units and starts power generation from a fuel cell unit that is not degraded in place of the fuel cell unit that has stopped power generation.

[0030] According to this control method, when switching from the second operating mode to the first operating mode, the number of fuel cell units that have not deteriorated significantly increases, and the number of fuel cell units that have deteriorated significantly decreases, thereby reducing the operating rate of the deteriorated fuel cell units.

[0031] In the control method of the ninth aspect of this disclosure, in the control method of the fourth or fifth aspect, when switching from the second operating mode to the first operating mode, the power generation of the fuel cell unit that has deteriorated among the multiple operating fuel cell units is stopped.

[0032] According to this control method, when switching from the first operating mode to the second operating mode, the number of degraded fuel cell units among the multiple fuel cell units generating power is reduced, thereby reducing the operating rate of the degraded fuel cell units.

[0033] A control device according to a tenth aspect of the present disclosure is a control device for a fuel cell system including a plurality of fuel cell units, comprising: a memory for storing the ratio of a customer's heat demand to their power demand or the customer's heat demand; and a controller for switching between a first operating mode and a second operating mode in which the utilization rate of more degraded fuel cell units is higher than that of the first operating mode, based on the ratio or the customer's heat demand.

[0034] According to this control device, for the same reasons as the control method of the first embodiment, it is possible to change the ratio of heat output to generated power in response to a change in the ratio of heat demand to electricity demand of the customer or a change in the customer's heat demand, while maintaining power generation.

[0035] A power generation system according to the eleventh aspect of this disclosure comprises a fuel cell device including a plurality of fuel cell units and a control device according to the tenth aspect.

[0036] According to this power generation system, for the same reasons as the control method of the first embodiment, it is possible to change the ratio of heat output to generated power in response to changes in the ratio of heat demand to electricity demand of the customer or changes in the customer's heat demand, while maintaining power generation.

[0037] The following describes specific examples of the above embodiments of this disclosure with reference to the attached drawings. The specific examples described below are all examples of the above embodiments of this disclosure. Therefore, the shapes, numerical values, components, arrangement positions of components, and connection configurations shown below do not limit the scope of the claims unless they are described in the claims.

[0038] Furthermore, among the components described below, those not described in the independent claim representing the highest-level concept of this disclosure will be described as optional components. Also, in the drawings, components with the same reference numeral may not be described. The drawings are schematic representations of each component for ease of understanding, and the shape and dimensional ratios may not be accurately represented.

[0039] Furthermore, in the operation of the apparatus, the order of the processes may be changed or known processes may be added as needed.

[0040] (Power generation system configuration) First, the device configuration of the power generation system 100 according to this embodiment will be described. Figure 1 is a block diagram of the power generation system 100. The power generation system 100 according to this embodiment is a system that supplies electricity and thermal energy to a customer 101 in accordance with the customer's electricity demand and heat demand. The customer 101 is, for example, a house, a shop, a factory, etc.

[0041] As shown in Figure 1, the power generation system 100 includes a fuel cell device 10 and a control device 20. The fuel cell device 10 and the control device 20 will be described in detail below.

[0042] <Fuel cell device> The fuel cell device 10 is a device that generates electricity using a fuel cell. As shown in Figure 1, the fuel cell device 10 has a plurality of fuel cell units 11. The number of fuel cell units 11 that the fuel cell device 10 has is not limited, but the fuel cell device 10 may have, for example, several to several hundred fuel cell units 11.

[0043] In the fuel cell unit 11, electricity is generated by a chemical reaction between a fuel such as hydrogen-containing gas or methanol and an oxidizing agent such as oxygen, and heat is generated in conjunction with this chemical reaction. The electrical and thermal energy generated in the fuel cell unit 11 is supplied to the consumer 101. Figure 2 is a graph showing an example of the power generation efficiency curve and heat recovery efficiency curve of the fuel cell unit 11. In Figure 2, the horizontal axis represents the power generated by the fuel cell unit 11, and the vertical axis represents the power generation efficiency or heat recovery efficiency.

[0044] The thick solid line in Figure 2 represents the power generation efficiency curve. The power generation efficiency curve shows the relationship between the power generated by the fuel cell unit 11 and its power generation efficiency. In the power generation efficiency curve shown in Figure 2, when the power generated by the fuel cell unit 11 is small, the power generation efficiency increases as the power generated increases, and after the power generation efficiency reaches its peak, the power generation efficiency decreases as the power generated increases.

[0045] On the other hand, the thick dashed line in Figure 2 represents the heat recovery efficiency curve. The heat recovery efficiency curve shows the relationship between the power generated by the fuel cell unit 11 and the heat recovery efficiency. In the heat recovery efficiency curve shown in Figure 2, the heat recovery efficiency increases as the power generated by the fuel cell unit 11 increases.

[0046] Thus, the power generation efficiency and heat recovery efficiency of the fuel cell unit 11 have a constant relationship with the generated power, and once the generated power is determined, the power generation efficiency and heat recovery efficiency are uniquely determined. Therefore, the ratio of the heat output to the generated power of the fuel cell unit 11 (hereinafter referred to as the "generated thermoelectric ratio") also has a constant relationship with the generated power, and once the generated power of the fuel cell unit 11 is determined, the generated thermoelectric ratio of the fuel cell unit 11 is also uniquely determined. Note that the relationship between the generated thermoelectric ratio and the generated power is specific to the fuel cell unit 11, but it changes as the fuel cell unit 11 deteriorates.

[0047] The thin solid line in Figure 2 represents the power generation efficiency curve of a degraded fuel cell unit 11. The thin dashed line in Figure 2 represents the heat recovery efficiency curve of a degraded fuel cell unit 11. As shown in Figure 2, when the fuel cell unit 11 degrades, the power generation efficiency curve shifts in the direction of decreasing power generation efficiency, and the heat recovery efficiency curve shifts in the direction of increasing heat recovery efficiency. Therefore, when the fuel cell unit 11 degrades, if the power generated by the fuel cell unit 11 remains the same, the power generation efficiency decreases and the heat recovery efficiency increases. In other words, when the fuel cell unit 11 degrades, the heat-to-electrical ratio of the fuel cell unit 11 increases.

[0048] As described above, the fuel cell device 10 of this embodiment has a plurality of fuel cell units 11. However, these plurality of fuel cell units 11 include fuel cell units 11 that have deteriorated and fuel cell units 11 that have not deteriorated. In other words, the fuel cell device 10 has a plurality of fuel cell units 11 with different heat and power ratios.

[0049] Furthermore, whether or not a fuel cell unit 11 is degraded may be determined based on criteria such as the voltage during power generation, cumulative power generation time, and cumulative number of power generation cycles. For example, if the voltage during power generation is used as the criterion, a fuel cell unit 11 whose voltage during power generation falls below a predetermined value may be determined to be a degraded fuel cell unit 11, or a fuel cell unit 11 whose voltage during power generation is lower than the average value of the fuel cell units 11 included in the fuel cell device 10 may be determined to be a degraded fuel cell unit 11.

[0050] Furthermore, for example, when using cumulative power generation time as a criterion, a fuel cell unit 11 whose cumulative power generation time exceeds a predetermined value may be determined to be a deteriorated fuel cell unit 11, and a fuel cell unit 11 whose cumulative power generation time is longer than the average value of the fuel cell units 11 included in the fuel cell device 10 may also be determined to be a deteriorated fuel cell unit 11.

[0051] Furthermore, for example, if the cumulative number of power generation cycles is used as a criterion, a fuel cell unit 11 whose cumulative number of power generation cycles exceeds a predetermined value may be determined to be a deteriorated fuel cell unit 11, or a fuel cell unit 11 whose cumulative number of power generation cycles is greater than the average value of the fuel cell units 11 included in the fuel cell device 10 may be determined to be a deteriorated fuel cell unit 11.

[0052] <Control device> The control device 20 is a device that controls the fuel cell device 10. The control device 20 includes a processor, volatile memory, non-volatile memory, and an I / O interface. Various programs, including the power generation control program described later, are stored in the non-volatile memory of the control device 20, and the processor performs calculations using the volatile memory based on each program. The control device 20 may consist of one device or multiple devices. The control device 20 may consist of multiple devices connected by a network, for example.

[0053] As shown in Figure 1, the control device 20 of this embodiment includes a controller 21 and a memory 22.

[0054] The controller 21 is a device that performs calculations. The controller 21 may be, for example, the processor of the control device 20. The controller 21 is communicatively connected to each fuel cell unit 11. The controller 21 can start power generation in a fuel cell unit 11 that is stopped by sending a power generation instruction signal to that fuel cell unit 11. The controller 21 can also stop power generation in a fuel cell unit 11 that is generating power by sending a stop instruction signal to that fuel cell unit 11. The power generation instruction signal or stop instruction signal from the controller 21 is received by a controller (not shown) installed in the fuel cell unit 11, and this controller executes the power generation and power generation stop of the fuel cell unit 11.

[0055] The memory unit 22 is a device that stores various types of information. The memory unit 22 may be, for example, the volatile memory or non-volatile memory of the control device 20. The memory unit 22 is communicated with the customer 101 (more precisely, the control device or other equipment installed by the customer 101). In Figure 1, the memory unit 22 is directly connected to the customer 101, but the memory unit 22 may also be connected to the customer 101 via the controller 21.

[0056] The memory unit 22 can acquire and store the power demand and heat demand from the customer 101. It can also store the ratio of heat demand to power demand (hereinafter referred to as the "demand-heat-electricity ratio") calculated by the controller 21. Here, "power demand" is the amount of electricity requested by the customer 101, and "heat demand" is the amount of thermal energy requested by the customer 101. The power demand, heat demand, and demand-heat-electricity ratio of the customer 101 fluctuate depending on the customer 101's circumstances. In addition to the actual power demand and heat demand acquired from the customer 101, the memory unit 22 can also store predicted power demand and heat demand predicted by the controller 21 based on these actual values.

[0057] Furthermore, the memory unit 22 is connected to the controller 21 in a communicative manner. The controller 21 can obtain the power demand and heat demand of the customer 101 from the memory unit 22 and calculate the demand-thermoelectric ratio. As described above, in this embodiment, the memory unit 22 stores the demand-thermoelectric ratio calculated by the controller 21. However, the memory unit 22 may also obtain the demand-thermoelectric ratio from the customer 101 and store this value.

[0058] (Operation of the power generation system) Next, we will explain a specific example of the operation of the power generation system 100. Below, we will explain a specific example of the operation of the power generation system 100 by describing the flow of the power generation control program executed by the controller 21.

[0059] Figure 3 is a flowchart of the power generation control program. As shown in Figure 3, when the power generation control program starts, the controller 21 obtains the power demand and heat demand of customer 101 from the memory 22 (step S1). As mentioned above, the memory 22 stores the power demand and heat demand of customer 101. The memory 22 also stores the demand-to-heat ratio calculated by the controller 21 based on the power demand and heat demand. The power demand and heat demand of customer 101 described here may be measured values ​​or predicted values.

[0060] Next, the controller 21 calculates the demand-thermoelectric ratio of the customer 101 based on the power demand and heat demand stored in the memory 22, and determines whether this demand-thermoelectric ratio is less than the first threshold (step S2). The demand-thermoelectric ratio of the customer 101 calculated by the controller 21 is stored in the memory 22 as described above, and the controller 21 determines whether the demand-thermoelectric ratio stored in the memory 22 is less than the first threshold. The first threshold is a ratio that serves as a criterion for switching the operating mode. The first threshold may be set to any ratio between 0.8 and 1 (for example, 0.9) depending on the performance of the fuel cell device 10.

[0061] If the controller 21 determines in step S2 that the demand-heat-power ratio of the customer 101 is less than a first threshold (YES in step S2), it operates the fuel cell system 10 in a first operating mode (step S3). Specifically, the controller 21 operates the fuel cell system 10 by selecting a combination of fuel cell units 11 to generate electricity such that the electricity and thermal energy generated by the fuel cell system 10 each satisfy at least one of the electricity demand and thermal demand of the customer 101, and the operating rate of the degraded fuel cell units 11 (hereinafter referred to as "degraded operating rate") falls within a first degraded operating rate range. However, instead of "falling within the first degraded operating rate range," it may be written as "falling below the first degraded operating rate."

[0062] The "first degraded operating rate range" described above may be any range where the degraded operating rate is less than 50% (for example, 0 to 30%). However, the first degraded operating rate range may not be a fixed range, but may be set based on the demand-to-heat-electric ratio of customer 101 obtained in step S1. For example, the first degraded operating rate range may be set so that the median of the first degraded operating rate range decreases as the demand-to-heat-electric ratio of customer 101 decreases. Also, if "so that it is within the first degraded operating rate range" is replaced with "so that it is less than or equal to the first degraded operating rate," the "first degraded operating rate" may be any value where the degraded operating rate is less than 50% (for example, 20%). However, the first degraded operating rate may not be a fixed value, but may be set based on the demand-to-heat-electric ratio of customer 101 obtained in step S1. For example, the first degraded operating rate may be set so that it decreases as the demand-to-heat-electric ratio of customer 101 decreases. After executing step S3, the controller 21 returns to step S1 and repeats the steps from step S1 onward.

[0063] On the other hand, if the controller 21 determines in step S2 that the demand-thermoelectric ratio is not below the first threshold (i.e., it is above the first threshold) (NO in step S2), it operates the fuel cell system 10 in the second operating mode (step S4). Specifically, the controller 21 operates the fuel cell system 10 by selecting a combination of fuel cell units 11 that generate electricity so that the electricity and thermal energy generated by the fuel cell system 10 satisfy at least one of the electricity demand and heat demand of the consumer 101, and so that the degradation operating rate is within the second degradation operating rate range. However, "so that it is within the second degradation operating rate range" may be replaced with "so that it is above the second degradation operating rate."

[0064] The "second degraded operating rate range" described above is a range where the lower limit is higher than the upper limit of the first degraded operating rate range. The second degraded operating rate range may be any range where the degraded operating rate is 50% or higher (for example, 70-100%). However, the second degraded operating rate range may not be a fixed range, but may be set based on the demand-to-heat-electric ratio of customer 101 obtained in step S1. For example, the second degraded operating rate range may be set so that the median value of the second degraded operating rate range increases as the demand-to-heat-electric ratio of customer 101 increases. Also, if "so that it is within the range of the second degraded operating rate" is replaced with "so that it is above the second degraded operating rate," the "second degraded operating rate" may be any value where the degraded operating rate is 50% or higher (for example, 80%). However, the second degraded operating rate may not be a fixed value, but may be set based on the demand-to-heat-electric ratio of customer 101 obtained in step S1. For example, the second degraded operating rate may be set so that it increases as the demand-to-heat-electric ratio of customer 101 increases. After executing step S4, the controller 21 returns to step S1 and repeats the steps from step S1 onward.

[0065] As described above, the first degradation operating rate range of the first operating mode has an upper limit that is lower than the lower limit of the second degradation operating rate range of the second operating mode. Therefore, when the demand-to-thermal-electric ratio of the customer 101 increases and changes from a state below the first threshold to a state above the first threshold, the system switches from the first operating mode to the second operating mode. At this time, the degradation operating rate of the fuel cell device 10 increases, and thus the generation-to-thermal-electric ratio of the fuel cell device 10 increases. Thus, according to this embodiment, the generation-to-thermal-electric ratio of the fuel cell device 10 can be increased in accordance with the increase in the demand-to-thermal-electric ratio of the customer 101, thereby reducing the surplus or deficit of the power and thermal energy generated by the fuel cell device 10 in relation to the power and heat demands of the customer 101.

[0066] On the other hand, when the demand-to-heat-coefficient ratio of customer 101 decreases and changes from being above the first threshold to below the first threshold, the system switches from the second operating mode to the first operating mode. However, this reduces the degradation operating rate of the fuel cell device 10, thus decreasing the generation-to-heat-coefficient ratio of the fuel cell device 10. Therefore, according to this embodiment, the generation-to-heat-coefficient ratio of the fuel cell device 10 can be reduced in accordance with the decrease in the demand-to-heat-coefficient ratio of customer 101, thereby reducing the surplus or deficit of power and energy generated by the fuel cell device 10 in relation to the power and heat demands of customer 101.

[0067] Furthermore, when switching from the first operating mode to the second operating mode, at least one of the fuel cell units 11 that are not significantly degraded may be stopped from generating power, and a fuel cell unit 11 that is significantly degraded may be started to generate power in its place. This reduces the number of fuel cell units 11 that are not significantly degraded and increases the number of fuel cell units 11 that are significantly degraded, thereby increasing the degradation operating rate of the fuel cell system 10. Furthermore, the number of fuel cell units 11 that are stopped from generating power and the number of fuel cell units 11 that are started to generate power do not have to match, as long as it is possible to satisfy at least one of the electricity demand and heat demand of the customer 101 by adjusting the power generated by each fuel cell unit 11.

[0068] Furthermore, when switching from the first operating mode to the second operating mode, the deteriorated fuel cell unit 11 may be started to generate power without stopping any of the currently generating fuel cell units 11. This adds a deteriorated fuel cell unit 11 to the multiple fuel cell units 11 generating power, thereby increasing the deterioration operating rate of the fuel cell system 10.

[0069] Furthermore, when switching from the second operating mode to the first operating mode, at least one of the fuel cell units 11 that are deteriorating may be stopped from generating power, and a fuel cell unit 11 that is not deteriorating may be started to generate power in its place. This reduces the number of deteriorating fuel cell units 11 and increases the number of non-deteriorating fuel cell units 11 among the multiple fuel cell units 11 generating power, thereby reducing the degradation rate of the fuel cell system 10. Note that the number of fuel cell units 11 that are stopped from generating power and the number of fuel cell units 11 that are started to generate power do not have to match, as long as it is possible to satisfy at least one of the electricity demand and heat demand of the customer 101 by adjusting the power generated by each fuel cell unit 11.

[0070] Furthermore, when switching from the second operating mode to the first operating mode, the fuel cell unit 11 that has deteriorated may be stopped from generating power without starting power generation from the fuel cell unit 11 that has not deteriorated. As a result, the number of deteriorated fuel cell units 11 among the multiple fuel cell units 11 generating power is reduced, thereby reducing the deterioration rate of the fuel cell system 10.

[0071] (An example of a fuel cell unit combination) Next, we will describe an example of a fuel cell unit 11 combination in the first and second operating modes. Figure 4 is a table showing an example of a fuel cell unit 11 combination in the first and second operating modes. The "Pattern 1" column in Figure 4 shows the fuel cell unit 11 combination in the first operating mode, and the "Pattern 2" column shows the fuel cell unit 11 combination in the second operating mode.

[0072] Here, as shown in the margin of Figure 4, the power generation capacity per unit of a degraded fuel cell unit 11 is 9 kW, and the thermal output is 9.1 kW. The power generation capacity per unit of a fuel cell unit 11 that has not degraded is 10 kW, and the thermal output is 7.5 kW.

[0073] As shown in Figure 4, in Pattern 1, the electricity demand of customer 101 is 400 kW and the heat demand is 300 kW. In this case, the demand-thermoelectric ratio is 0.75 (300 kW / 400 kW). Therefore, assuming the first threshold is 0.90, the demand-thermoelectric ratio will be less than the first threshold, so in Pattern 1, as shown below the arrow in Figure 4, the controller 21 will operate the fuel cell device 10 in the first operating mode (see steps S2 and S3 in Figure 3).

[0074] Furthermore, in the example shown in Pattern 1 of Figure 4, the controller 21 selects 0 degraded fuel cell units 11 and 40 undegraded fuel cell units 11 as the combination of fuel cell units 11 that generate power. The degradation rate at this time is 0%. With the 40 undegraded fuel cell units 11 generating power, the total power generated by the fuel cell system 10 becomes 400 kW (10 kW / unit × 40 units), and the thermal output becomes 300 kW (7.5 kW / unit × 40 units). At this time, the heat-power ratio of the fuel cell system 10 is 0.75 (300 kW / 400 kW).

[0075] Thus, in the example shown in Pattern 1 of Figure 4, the power generated by the fuel cell device 10 matches the power demand of the customer 101, the thermal output of the fuel cell device 10 matches the heat demand of the customer 101, and the heat-to-electrical ratio of the fuel cell device 10 matches the heat-to-electrical ratio of the customer 101. Therefore, in the example shown in Pattern 1 of Figure 4, the power generation system 100 can supply the power and thermal energy generated by the fuel cell device 10 to the customer 101 without any surplus or deficit in relation to the customer 101's power and heat demands.

[0076] Furthermore, as shown in Figure 4, in Pattern 2, the electricity demand of customer 101 is 350 kW and the heat demand is 350 kW. In this case, the demand-thermoelectric ratio is 1.00 (350 kW / 350 kW). Therefore, assuming the first threshold is 0.90, the demand-thermoelectric ratio will be greater than or equal to the first threshold, so in Pattern 2, as shown below the arrow in Figure 4, the controller 21 will operate the fuel cell device 10 in the second operating mode (see steps S2 and S4 in Figure 3).

[0077] Furthermore, in the example shown in Pattern 2 of Figure 4, the controller 21 selects 39 degraded fuel cell units 11 and 0 undegraded fuel cell units 11 as the combination of fuel cell units 11 that generate power. The degradation rate at this time is 100%. With the 39 degraded fuel cell units 11 generating power, the total power generated by the fuel cell system 10 becomes 351 kW (9 kW / unit × 39 units), and the thermal output becomes 355 kW (9.1 kW / unit × 39 units). At this time, the heat-power ratio of the fuel cell system 10 is 1.01 (355 kW / 351 kW).

[0078] Thus, in the example shown in Pattern 2 of Figure 4, the power generated by the fuel cell device 10 satisfies the electricity demand of the customer 101, the thermal output of the fuel cell device 10 also satisfies the heat demand of the customer 101, and the heat-to-electricity ratio of the fuel cell device 10 is close to the heat-to-electricity ratio of the customer 101's demand. Therefore, in the example shown in Pattern 2 of Figure 4, the power generation system 100 can reduce the surplus or deficit of the power and thermal energy generated by the fuel cell device 10 in relation to the electricity and heat demands of the customer 101.

[0079] (Variable example of a power generation system) Next, a modified version of the power generation system 100 will be described. In the power generation system 100 described above, the controller 21 selects the operating mode in the power generation control program based on the "demand-heat-power ratio" of the customer 101 (see steps S2, S3, and S4 in Figure 3). In contrast, in the modified power generation system 100, the operating mode is selected based on the "heat demand" of the customer 101. In all other respects, it is the same as the power generation system 100 described above. Here, the power generation control program in the modified version will be described, and other explanations will be omitted.

[0080] Figure 5 is a flowchart of the power generation control program in the modified example. As shown in Figure 5, when the power generation control program in the modified example is started, the controller 21 obtains the power demand and heat demand from the memory 22 (step S11). The power demand and heat demand of the customer 101 described here may be measured values ​​or predicted values.

[0081] Next, the controller 21 determines whether the heat demand is below a second threshold (step S12). The second threshold is the heat demand value that serves as the criterion for switching the operating mode. The second threshold is set based on the size of the customer 101 and the capacity of the fuel cell device 10.

[0082] If the controller 21 determines in step S12 that the heat demand of customer 101 is less than the second threshold (YES in step S12), it operates the fuel cell device 10 in the first operating mode (step S13). On the other hand, if the controller 21 determines in step S12 that the heat demand of customer 101 is not less than the second threshold (is greater than or equal to the second threshold) (NO in step S12), it operates the fuel cell device 10 in the second operating mode (step S14). The first and second operating modes are the same as in the embodiment described above. After executing step S13 or step S14, the controller 21 returns to step S11 and repeats the steps from step S11 onward.

[0083] The above is a description of the modified power generation system 100. In the modified power generation system 100, the operating mode is selected based on heat demand, not on the heat-to-power ratio. Even in this case, the same effects and advantages as the power generation system 100 according to the embodiment described above can be achieved.

[0084] From the above description, many improvements and other embodiments of the disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. The details of its structure and / or function can be substantially modified without departing from the spirit of the disclosure. [Industrial applicability]

[0085] One aspect of this disclosure can be used in a control method for a fuel cell device, a control device for a fuel cell device, and a power generation system, which can perform appropriate control to the ratio of heat demand to electricity demand of a customer or to changes in the heat demand of a customer, compared to the prior art. [Explanation of symbols]

[0086] 10:Fuel cell device 11: Fuel cell unit 20: Control device 21: Controller 22:Memory 100: Power generation system 101: Consumer

Claims

1. A control method for a fuel cell system including multiple fuel cell units, A control method for switching between a first operating mode and a second operating mode in which the utilization rate of a more degraded fuel cell unit is higher than that of the first operating mode, based on the ratio of the customer's heat demand to electricity demand or the customer's heat demand.

2. The control method according to claim 1, wherein when the ratio increases, the system switches from the first operating mode to the second operating mode.

3. The control method according to claim 1, wherein when the heat demand of the customer increases, the control method switches from the first operating mode to the second operating mode.

4. The control method according to claim 2, wherein after switching to the second operating mode, if the ratio decreases, the system switches from the second operating mode to the first operating mode.

5. The control method according to claim 3, wherein, after switching to the second operating mode, if the heat demand of the customer decreases, the control method switches from the second operating mode to the first operating mode.

6. The control method according to claim 2 or 3, wherein when switching from the first operating mode to the second operating mode, at least one of the operating fuel cell units is stopped from generating power, and a degraded fuel cell unit is started to generate power in place of the fuel cell unit that has been stopped from generating power.

7. The control method according to claim 2 or 3, wherein when switching from the first operating mode to the second operating mode, a newly degraded fuel cell unit is started to generate power in addition to the multiple fuel cell units that are currently in operation.

8. The control method according to claim 4 or 5, wherein when switching from the second operating mode to the first operating mode, at least one of the degraded fuel cell units is stopped from generating power, and a fuel cell unit that is not degraded is started to generate power in place of the fuel cell unit that has stopped generating power.

9. The control method according to claim 4 or 5, wherein when switching from the second operating mode to the first operating mode, power generation is stopped for fuel cell units that have deteriorated among the multiple operating fuel cell units.

10. A control device for a fuel cell system including multiple fuel cell units, A memory device that stores the ratio of a customer's heat demand to their electricity demand, or the customer's heat demand. A control device comprising a controller that switches between a first operating mode and a second operating mode in which the utilization rate of a more deteriorated fuel cell unit is higher than that of the first operating mode, based on the aforementioned ratio or the heat demand of the customer.

11. A fuel cell system including multiple fuel cell units, A power generation system comprising the control device described in claim 10.

Images