Fuel cell system

Abstract

This reduces the constraints on the utilization of heat generated in fuel cell systems. [Solution] The power generation system 1a comprises a fuel cell system 1a, at least one fuel cell unit 10, and a controller 20. The fuel cell unit 10 includes a fuel cell stack 11, a cooling water path 12, and a heat transfer medium path 13. The cooling water path 12 is a path that guides cooling water to the fuel cell stack 11. The heat transfer medium path 13 receives the heat recovered from the fuel cell stack 11 by the cooling water and guides the heat transfer medium to the outside of the fuel cell unit 10 toward a heat utilization device 2 outside the fuel cell unit 10. The controller 20 adjusts the temperature of the cooling water supplied to the fuel cell stack 11 according to the heat demand of the heat utilization device 2.

Description

[Technical Field]

[0001] This disclosure relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 describes a combined heat and power system equipped with a fuel cell system. This combined heat and power system comprises a hot water storage tank, a hot water storage means, and a control means. A water supply channel for supplying water to the tank is connected to the bottom of the hot water storage tank, and a hot water outlet channel for sending the hot water from the tank to an auxiliary heater is connected to the top of the hot water storage tank. The hot water storage means stores hot water in the hot water storage tank by heating the hot water taken from the bottom of the hot water storage tank with heat generated by the fuel cell system and then returning it to the top of the hot water storage tank. The combined heat and power system is equipped with a mixing means in the hot water outlet channel that mixes the hot water taken from the hot water storage tank with water supplied from a mixing water supply channel, and allows adjustment of the mixing ratio. The control means controls the mixing means to set the temperature of the hot water coming out of the hot water outlet channel to a specified target hot water temperature. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-004224 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventional technologies deserve re-examination from the perspective of reducing the constraints on the utilization of heat generated in fuel cell systems. [Means for solving the problem]

[0005] The fuel cell system in this disclosure is A fuel cell unit comprising a fuel cell stack, a cooling water path for supplying cooling water to the fuel cell stack, and a heat transfer medium path, Equipped with a controller, The heat medium path receives the heat recovered from the fuel cell stack by the cooling water by the heat medium, and is a path for guiding the heat medium outside the fuel cell unit toward heat utilization equipment outside the fuel cell unit. The controller adjusts the temperature of the cooling water supplied to the fuel cell stack according to the heat demand in the heat utilization equipment.

Advantages of the Invention

[0006] According to the present disclosure, the restrictions on the utilization of heat generated in the fuel cell system can be reduced.

Brief Description of the Drawings

[0007] [Figure 1] Configuration diagram of the fuel cell system in Embodiment 1 [Figure 2] Flowchart showing the control of the fuel cell system in Embodiment 1 [Figure 3] Flowchart showing another control of the fuel cell system in Embodiment 1 [Figure 4] Diagram schematically showing data including the change order of the cooling water temperature of a plurality of fuel cell units in the fuel cell system in Embodiment 1 [Figure 5A] Diagram schematically showing data indicating the deterioration state of the fuel cell stacks in a plurality of fuel cell units of the fuel cell system in Embodiment 1 [Figure 5B] Diagram schematically showing another data indicating the deterioration state of the fuel cell stacks in a plurality of fuel cell units of the fuel cell system in Embodiment 1

[0008] (Knowledge etc. on which the present disclosure is based) At the time the inventors conceived this disclosure, it was known that heat generated in a fuel cell system could be recovered and used for thermal utilization outside the fuel cell system. On the other hand, the temperature of the heat transfer medium that is recovered from the fuel cell system and supplied to the outside of the fuel cell system is determined from the standpoint of achieving temperature control inside the fuel cell system, and there were many constraints on thermal utilization using that heat transfer medium.

[0009] If the temperature of the heat transfer medium supplied to the outside of the fuel cell system can be adjusted to suit various heat utilization methods, the number of situations in which heat generated in the fuel cell system can be recovered and utilized will increase, thereby enhancing the value of the fuel cell system.

[0010] The inventors focused on the fact that by adjusting the temperature of the cooling water supplied to the fuel cell stack, the temperature of the heat transfer medium supplied to the outside of the fuel cell system can be adjusted over a wide range, and this constitutes the subject matter of this disclosure.

[0011] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0012] The attached drawings and the following description are provided to enable the parties to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0013] (Embodiment 1) Embodiment 1 will be described below with reference to Figures 1 to 5B.

[0014] [1-1. Structure] Figure 1 is a diagram of the configuration of a fuel cell system 1a in Embodiment 1. As shown in Figure 1, the fuel cell system 1a comprises at least one fuel cell unit 10 and a controller 20. The fuel cell system 1a comprises, for example, 10 fuel cell units 10, and includes fuel cell units 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, and 10j (10c to 10i are not shown). The fuel cell system 1a may comprise only one fuel cell unit 10, or it may comprise 2 to 9 or 11 or more fuel cell systems 1a.

[0015] The fuel cell unit 10 includes a fuel cell stack 11, a cooling water path 12, and a heat transfer medium path 13. The cooling water path 12 is a path that guides cooling water to the fuel cell stack 11. The cooling water path 12 is connected to the fuel cell stack 11 and is configured to circulate cooling water between the fuel cell stack 11 and the outside of the fuel cell stack 11. The heat transfer medium path 13 receives the heat recovered from the fuel cell stack 11 by the cooling water and guides the heat transfer medium to the outside of the fuel cell unit 10 toward the heat utilization equipment 2 outside the fuel cell unit 10.

[0016] As shown in Figure 1, the fuel cell system 1a is connected to the heat utilization device 2 by a first path 3a and a second path 3b. The first path 3a and the second path 3b are connected to the heat transfer medium path 13. Heat transfer medium is supplied from the heat utilization device 2 to the heat transfer medium path 13 through the first path 3a. In addition, heat transfer medium that has been led from the heat transfer medium path 13 to the outside of the fuel cell unit 10 is supplied to the heat utilization device 2 through the second path 3b. The first path 3a and the second path 3b are composed of at least one pipe. A pump for dispensing the heat transfer medium may be provided in either the first path 3a or the second path 3b.

[0017] The fuel cell unit 10 further includes, for example, a heat exchanger 15, a cooling water pump 16, and a supply unit 17. In the heat exchanger 15, the cooling water recovered from the heat generated in the fuel cell stack 11 exchanges heat with the heat transfer medium. The heat exchanger 15 is connected to a cooling water path 12 and a heat transfer medium path 13. The cooling water pump 16 is located in the cooling water path 12 and sends cooling water toward the fuel cell stack 11. The flow rate of the cooling water in the cooling water path 12 can be controlled by changing the rotational speed or other control variables of the cooling water pump 16. The supply unit 17 is located in the heat transfer medium path 13. An example of the supply unit 17 is a pump or a flow control valve. The flow rate of the heat transfer medium in the heat transfer medium path 13 can be controlled by changing the rotational speed or opening degree of the supply unit 17.

[0018] The heat exchanger 15 is a liquid-liquid heat exchanger such as a double-tube heat exchanger, a shell-and-tube heat exchanger, or a plate heat exchanger. The heat exchanger 15 is configured such that, for example, the flow of cooling water and the flow of the heat transfer medium are in a countercurrent.

[0019] The fuel cell unit 10 includes, for example, a temperature sensor 18. The temperature sensor 18 measures the temperature of the cooling water supplied to the fuel cell stack 11 in the cooling water path 12.

[0020] The fuel cell system 1a includes, for example, a temperature sensor 30. The temperature sensor 30 measures the ambient temperature around the fuel cell unit 10.

[0021] The temperature sensors 18 and 30 are, for example, contact-type temperature sensors and include thermocouples, platinum resistance thermometers, or thermistors.

[0022] The fuel used in the fuel cell system 1a is, for example, pure hydrogen gas. Pure hydrogen gas is, for example, a gas with a volume concentration of 99% or more. In this case, the fuel cell system 1a further includes a tank (not shown) in which pure hydrogen is stored. From this tank, hydrogen gas is supplied to the fuel cell stack 11 as fuel gas. Hydrogen gas may also be supplied to the fuel cell system 1a from a hydrogen gas infrastructure. The fuel used in the fuel cell system 1a may also include hydrocarbon gases such as methane gas, propane gas, and butane gas. In this case, the fuel cell system 1a includes a reformer (not shown). In the reformer, hydrogen-containing gas is produced from the hydrocarbon gas as fuel gas, and the hydrogen-containing gas is supplied to the fuel cell stack 11. Examples of fuels containing hydrocarbon gases are city gas and LPG.

[0023] The fuel cell stack 11 is, for example, a polymer electrolyte fuel cell (PEFC) stack.

[0024] The controller 20 is responsible for controlling the operation of the fuel cell unit 10. The controller 20 adjusts the temperature of the cooling water supplied to the fuel cell stack 11 according to the heat demand of the heat utilization equipment 2. The controller 20 is composed of a DSP (Digital Signal Processor) which includes, for example, input / output circuits, a processor, and memory. The controller 20 stores in an executable format the program necessary for the operation of the fuel cell unit 10.

[0025] Heat utilization equipment 2 is, for example, equipment for hot water supply, heating, or other heat utilization processes.

[0026] [1-2. Operation] The operation and function of the fuel cell system 1a, configured as described above, will be explained below.

[0027] Fuel is supplied to the anode of the fuel cell stack 11, and oxygen-containing gas is supplied to the cathode of the fuel cell stack 11, thereby generating electricity in the fuel cell stack 11. The generated electricity is supplied via power lines to loads (not shown) connected to the fuel cell system 1a.

[0028] The fuel cell stack 11 generates heat during power generation. The cooling water pump 16 is activated and cooling water is supplied to the fuel cell stack 11 through the cooling water path 12. As the cooling water passes through the fuel cell stack 11, the heat generated in the fuel cell stack 11 is recovered by the cooling water, and the fuel cell stack 11 is adjusted to a temperature suitable for the operation of the fuel cell unit 10. The cooling water that has passed through the fuel cell stack 11 exchanges heat with the heat medium supplied from the heat utilization equipment 2 to the heat medium path 13 through the first path 3a in the heat exchanger 15. As a result, the heat medium receives the heat recovered from the fuel cell stack 11 by the cooling water. The temperature of the cooling water decreases as it passes through the heat exchanger 15. The cooling water that has passed through the heat exchanger 15 returns to the cooling water pump 16 through the cooling water path 12 and is supplied to the fuel cell stack 11. The temperature of the heat medium increases as it passes through the heat exchanger 15. The heat medium that has passed through the heat exchanger 15 is led to the outside of the fuel cell unit 10 through the supply unit 17 and supplied to the heat utilization equipment 2 through the second path 3b.

[0029] Figure 2 is a flowchart illustrating the control of the fuel cell system 1a. As shown in Figure 2, in step S1, the controller 20 acquires data indicating the heat demand Q2 in the heat utilization equipment 2, for example. Alternatively, the controller 20 determines the heat demand Q2 by performing a predetermined calculation. The data indicating the heat demand Q2 can be acquired, for example, from the heat utilization equipment 2 or a control panel (not shown) that receives user instructions. The controller 20 may also predict the heat demand Q2 based, for example, on historical data of the heat demand in the heat utilization equipment 2.

[0030] In step S2, the controller 20 sets the target temperature T of the heat transfer medium corresponding to the heat demand Q2 obtained or predicted in step S1. 13is determined. The higher the heat demand Q2, the higher the target temperature T 13 is determined. The target temperature T 13 of the heat medium is, for example, the target temperature at the outlet of the second path 3b. The controller 20 may acquire information including the target temperature T 13 from the heat utilization device 2.

[0031] In step S3, the controller 20 acquires measurement data of the temperature around the fuel cell unit 10 from the temperature sensor 30.

[0032] In step S4, the controller 20 determines the deterioration state of the fuel cell stack 11. For example, the controller 20 may determine the deterioration state of the fuel cell stack 11 based on the power generation voltage of the fuel cell unit 10. For example, it can be determined that the higher the degree of deterioration of the fuel cell stack 11, the lower the power generation voltage of the fuel cell unit 10 during rated operation.

[0033] In step S5, the controller 20 determines the target temperature T 12 of the cooling water. The target temperature T 12 is the target temperature of the cooling water supplied to the fuel cell stack 11 in the cooling water path 12. The target temperature T 12 is determined based on the target temperature T 13 . The higher the target temperature T 13 , the higher the target temperature T 12 is determined.

[0034] In addition to the target temperature T 13 , the controller 20 may determine the target temperature T 12 based on the temperature around the fuel cell unit 10 acquired in step S3, the deterioration state of the fuel cell stack 11 determined in step S4, or both. For example, when the temperature around the fuel cell unit 10 is low, the heat dissipation amount tends to increase when supplying the heat medium to the heat utilization device 2. Therefore, the lower the temperature around the fuel cell unit 10, the higher the target temperature T 12 can be determined. The higher the degree of deterioration of the fuel cell stack 11, the higher the target temperature T 12This can be determined to be low. This makes it easier to suppress further degradation of the fuel cell stack 11.

[0035] In step S5, the target temperature T 12 The target temperature T 13 The decision may be based solely on this. In this case, steps S3 and S4 may be omitted.

[0036] In step S6, the controller 20 receives the measured value T of the cooling water temperature. M The temperature is obtained from the temperature sensor 18.

[0037] In step S7, the controller 20 measures the measured value T M and target temperature T 12 is T M -T 12 >Determine whether the condition V1 is met. V1 is, for example, 1°C. If the determination result in step S7 is positive, proceed to step S8. In step S8, the controller 20 increases the flow rate F1. Then return to step S6. Flow rate F1 is the flow rate of cooling water in the cooling water path 12. For example, the controller 20 increases the flow rate F1 by sending a control signal to increase the rotational speed of the cooling water pump 16. When the flow rate F1 increases, the time required for the cooling water to pass through the fuel cell stack 11 decreases. This lowers the temperature of the cooling water. Therefore, the difference T M -T 12 As the temperature decreases, the temperature of the cooling water supplied to the fuel cell stack 11 reaches the target temperature T. 12 Approaching.

[0038] If the judgment result in step S7 is negative, proceed to step S9. In step S9, the controller 20 determines the measured value T M and target temperature T 12 is T M -T 12Determine whether the condition of V2 is satisfied. V2 is, for example, -1°C. If the determination result in step S9 is affirmative, proceed to step S10. In step S10, the controller 20 decreases the flow rate F1. Then return to step S6. For example, the controller 20 sends a control signal to increase the rotation speed of the cooling water pump 16 to decrease the flow rate F1. When the flow rate F1 decreases, the time required for the cooling water to pass through the fuel cell stack 11 becomes longer. As a result, the temperature of the cooling water increases. Therefore, the difference T M -T 12 becomes larger, and the temperature of the cooling water supplied to the fuel cell stack 11 approaches the target temperature T 12 approaches.

[0039] If the determination result in step S9 is negative, the measured value T M and the target temperature T 12 satisfy the condition of V2 ≤ T M -T 12 ≤ V1, and since the temperature of the cooling water supplied to the fuel cell stack 11 is the same as or close to the target temperature T 12 end a series of processes. According to steps S6 to S10, the temperature of the cooling water supplied to the fuel cell stack 11 approaches the target temperature T 12 approaches.

[0040] In steps S6 to S10, the temperature of the cooling water supplied to the fuel cell stack 11 may be made to approach the target temperature T 12 by changing the flow rate F2 instead of the flow rate F1. The flow rate F2 is the flow rate of the heat medium in the heat medium path 13. By changing the flow rate F2, the time required for the heat medium to pass through the heat exchanger 15 fluctuates. As a result, the temperature of the cooling water can be adjusted. In steps S6 to S10, the temperature of the cooling water supplied to the fuel cell stack 11 may be made to approach the target temperature T 12 by changing the flow rate F1 and the flow rate F2.

[0041] Figure 3 is a flowchart showing another control of the fuel cell system 1a. This control is performed, for example, to determine which fuel cell unit 10 is subject to a change in cooling water temperature when a change in the cooling water temperature is required in at least one of the multiple fuel cell units 10.

[0042] As shown in Figure 3, in steps S101 to S105, the target temperature T of the cooling water is set in the same manner as in steps S1 to S5. 12 The following is determined. Next, in step S106, the measured value T of the coolant temperature is determined. M The value T is obtained from the temperature sensor 18. Next, in step S107, the measured value T M and target temperature T 12 Based on this, it is determined whether or not the cooling water temperature needs to be changed in at least one of the multiple fuel cell units 10. In the determination in step S107, it is also determined how many fuel cell units 10 need to have their cooling water temperature changed in accordance with the heat demand Q2. For example, suppose in step S107 it is determined that two fuel cell units 10 need to have their cooling water temperature changed in accordance with the heat demand Q2. In this case, in step S108, the controller 20 determines which fuel cell units 10a to 10j will have their cooling water temperature changed.

[0043] For example, when it is necessary to change the cooling water temperature in at least one of the multiple fuel cell units 10, the controller 20 changes the cooling water temperature of the multiple fuel cell units 10 in a predetermined order.

[0044] Figure 4 schematically shows data including the order in which the cooling water temperature of multiple fuel cell units 10 of the fuel cell system 1a is changed. This data is stored, for example, in the controller 20. According to this data, the change order of fuel cell unit 10a is "1", and the change order increases by 1 from fuel cell unit 10a to fuel cell unit 10j. In this data, a flag is placed in the part corresponding to the fuel cell unit 10 that has the highest change order among the fuel cell units 10 selected in the previous determination of which fuel cell units 10 will have their cooling water temperature changed. In the example shown in Figure 4, a flag is placed in the part corresponding to fuel cell unit 10c. In step S108, the controller 20 determines the fuel cell units 10 whose cooling water temperature will be changed in ascending order of this change order. According to Figure 4, fuel cell units 10a, 10b, and 10c have been determined in this order so far as fuel cell units 10 whose cooling water temperature will be changed. Therefore, this time, the controller 20 determines fuel cell units 10d and 10e as the two fuel cell units 10 whose cooling water temperature will be changed. Furthermore, the position of the flag is updated to the part corresponding to fuel cell unit 10e. If there is a flag in the part corresponding to fuel cell unit 10j, fuel cell unit 10a, which corresponds to change priority "1", is determined to be the fuel cell unit 10 whose cooling water temperature will be changed.

[0045] In step S109, the controller 20 changes at least one selected from the group consisting of flow rates F1 and F2 in the fuel cell units 10d and 10e. This changes the temperature of the cooling water supplied to the fuel cell stack 11 in the fuel cell units 10d and 10e to a target temperature T 12 To bring it closer to the target temperature T. In step S109, in the same manner as in steps S6 to S10, the temperature of the cooling water supplied to the fuel cell stack 11 is brought closer to the target temperature T. 12 It can be brought closer.

[0046] The controller 20 may, for example, change the temperature of the cooling water in at least one of the fuel cell units 10 based on the degree of degradation of the fuel cell stack 11 when it is necessary to change the temperature of the cooling water in at least one of the fuel cell units 10.

[0047] For example, when the controller 20 needs to raise the cooling water temperature in at least one of the multiple fuel cell units 10, it raises the cooling water temperature of the fuel cell unit 10 in which the degree of degradation of the fuel cell stack 11 is low.

[0048] Figure 5A schematically shows data indicating the degradation state of fuel cell stacks 11 in multiple fuel cell units 10. In this data, the degree of degradation of the fuel cell stacks 11 is shown in five stages from "0" to "4", with a higher numerical value indicating a more advanced degradation of the fuel cell stacks 11. This data is stored in the controller 20. The controller 20, for example, periodically or irregularly, acquires the generated voltage of the fuel cell unit 10 during rated operation and calculates the degree of degradation based on that generated voltage. A lower generated voltage results in a higher calculated degree of degradation. The degree of degradation of the fuel cell stacks 11 may also be calculated based on physical quantities that correlate with the degree of degradation of the fuel cell stacks 11, other than the generated voltage of the fuel cell unit 10.

[0049] For example, suppose in step S107, it is determined that the cooling water temperature needs to be increased in two fuel cell units 10 to meet the heat demand Q2. In this case, the controller 20 refers to the data shown in Figure 5A and determines that the fuel cell units 10c and 10d with the lowest degree of degradation are the fuel cell units 10 whose cooling water temperature should be increased.

[0050] For example, when the controller 20 needs to lower the cooling water temperature in at least one of the multiple fuel cell units 10, it lowers the cooling water temperature of the fuel cell unit 10 in which the fuel cell stack 11 is more degraded.

[0051] For example, suppose in step S107, it is determined that a decrease in the cooling water temperature is necessary in two fuel cell units 10 to match the heat demand Q2. In this case, the controller 20 refers to the data shown in Figure 5A and determines that the fuel cell units 10f and 10j with a higher degree of degradation are the fuel cell units 10 whose cooling water temperature will be lowered.

[0052] Consider a case where the cooling water temperature needs to be increased in at least one of the multiple fuel cell units 10, and the multiple fuel cell units 10 do not include any fuel cell stacks that have a degree of degradation exceeding a predetermined standard. In this case, the controller 20 increases the cooling water temperature of the multiple fuel cell units 10 in a predetermined order, for example.

[0053] Figure 5B is a schematic diagram showing other data indicating the degradation state of the fuel cell stack 11 in multiple fuel cell units 10. According to Figure 5B, the degree of degradation of the fuel cell stack 11 in multiple fuel cell units 10 is low. For example, no fuel cell units 10 with a degradation degree of fuel cell stack 11 exceeding "2" are included. Assume that in step S107, it is determined that an increase in the cooling water temperature is necessary in two fuel cell units 10 to match the heat demand Q2. The controller 20 first refers to the data shown in Figure 5B and confirms that no fuel cell units 10 with a degradation degree of fuel cell stack 11 exceeding "2" are included. Then, the controller 20 refers to the data shown in Figure 4 and determines that fuel cell units 10d and 10e are the two fuel cell units 10 for which the cooling water temperature will be increased.

[0054] Consider a case where the cooling water temperature needs to be increased in at least one of the multiple fuel cell units 10, and the multiple fuel cell units 10 include fuel cell stacks that have a degree of degradation exceeding a predetermined standard. In this case, the controller 20 increases the cooling water temperature of the multiple fuel cell units 10 in ascending order of degradation degree, for example.

[0055] In step S107, it is determined that the cooling water temperature of two fuel cell units 10 needs to be increased to match the heat demand Q2, and the data shown in Figure 5A is stored as data indicating the degradation state of the fuel cell stack 11. In this case, the controller 20 first refers to the data shown in Figure 5A and confirms that there are fuel cell units 10 in which the degradation degree of the fuel cell stack 11 exceeds "2". Then, the controller 20 increases the cooling water temperature of multiple fuel cell units 10 in ascending order of degradation degree, for example. The controller 20 refers to the data shown in Figure 5A and determines that fuel cell units 10c and 10d, which have a low degradation degree, are the fuel cell units 10 whose cooling water temperature should be increased.

[0056] Consider a case where a decrease in the cooling water temperature is necessary in at least one of the multiple fuel cell units 10, and the multiple fuel cell units 10 do not include any fuel cell stacks that have a degree of degradation exceeding a predetermined standard. In this case, the controller 20, for example, lowers the temperature of the cooling water in the multiple fuel cell units 10 in a predetermined order.

[0057] In step S107, it is determined that a decrease in the cooling water temperature is necessary in two fuel cell units 10 to match the heat demand Q2, and it is assumed that the data shown in Figure 5B is stored as data indicating the degradation state of the fuel cell stack 11. The controller 20 first refers to the data shown in Figure 5B and confirms that there are no fuel cell units 10 in which the degradation degree of the fuel cell stack 11 exceeds "2". Then, the controller 20 refers to the data shown in Figure 4 and determines that fuel cell units 10d and 10e are the two fuel cell units 10 in which the cooling water temperature will be decreased.

[0058] Consider a case where a decrease in the cooling water temperature is necessary in at least one of the multiple fuel cell units 10, and the multiple fuel cell units 10 include fuel cell stacks that have a degree of degradation exceeding a predetermined standard. In this case, the controller 20 lowers the cooling water temperature of the multiple fuel cell units 10 in descending order of degradation degree, for example.

[0059] In step S107, it is determined that a decrease in the cooling water temperature is necessary in two fuel cell units 10 to match the heat demand Q2, and the data shown in Figure 5A is stored as data indicating the degradation state of the fuel cell stack 11. In this case, the controller 20 first refers to the data shown in Figure 5A and confirms that there are fuel cell units 10 in which the degradation degree of the fuel cell stack 11 exceeds "2". Then, the controller 20 raises the cooling water temperature of multiple fuel cell units 10 in descending order of degradation degree, for example. The controller 20 refers to the data shown in Figure 5A and determines that fuel cell units 10f and 10j, which have a high degree of degradation, are the fuel cell units 10 whose cooling water temperature should be lowered.

[0060] In step S108, when determining which fuel cell unit 10 will change the cooling water temperature by referring to Figure 5A, it is conceivable that the determination may be difficult based solely on the degree of degradation. In this case, the fuel cell unit 10 that will change the cooling water temperature may be determined by referring to Figure 4. Alternatively, the fuel cell unit 10 that will change the cooling water temperature may be determined based on at least one selected from the group consisting of the cumulative operating time and the number of starts of the fuel cell unit 10. For example, a fuel cell unit 10 with a short cumulative operating time or a low number of starts may be determined as the fuel cell unit 10 that will raise the cooling water temperature. A fuel cell unit 10 with a long cumulative operating time or a high number of starts may be determined as the fuel cell unit 10 that will lower the cooling water temperature.

[0061] (Other embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, replaced, added, omitted, etc. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiments.

[0062] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the scope of the claims or equivalents thereof.

[0063] The fuel cell system 1a may be used in conjunction with a photovoltaic power generation device, or in conjunction with a photovoltaic power generation device and a storage battery. In this case, a heat utilization device 2 may be used to keep a predetermined part of the photovoltaic power generation device or storage battery warm.

[0064] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0065] (Technology 1) A fuel cell unit comprising a fuel cell stack, a cooling water path for supplying cooling water to the fuel cell stack, and a heat transfer medium path, Equipped with a controller, The heat transfer medium path is a path that receives heat recovered from the fuel cell stack by the cooling water through the heat transfer medium and guides the heat transfer medium to the outside of the fuel cell unit toward heat utilization equipment outside the fuel cell unit. The controller adjusts the temperature of the cooling water supplied to the fuel cell stack in accordance with the heat demand of the heat utilization equipment. Fuel cell system.

[0066] According to the fuel cell system of Technology 1, the temperature of the cooling water supplied to the fuel cell stack is adjusted according to the heat demand of the heat utilization equipment, thereby reducing the constraints on the utilization of heat generated in the fuel cell system.

[0067] (Technology 2) The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand. The fuel cell system described in Technology 1.

[0068] According to the fuel cell system described in Technology 2, the temperature of the cooling water is adjusted according to the target temperature of the heat transfer medium that corresponds to the heat demand, making it easier to supply a heat transfer medium that has the temperature corresponding to the heat demand. Therefore, the constraints on the utilization of heat generated in the fuel cell system can be reduced.

[0069] (Technology 3) The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand and the deterioration state of the fuel cell stack. A fuel cell system as described in Technology 1 or 2.

[0070] According to the fuel cell system described in Technology 3, the temperature of the cooling water is adjusted according to the target temperature of the heat transfer medium corresponding to the heat demand, making it easier to supply a heat transfer medium with a temperature that meets the heat demand. Therefore, the constraints on the utilization of heat generated in the fuel cell system can be reduced. In addition, since the temperature of the cooling water is adjusted according to the degradation state of the fuel cell stack, the fuel cell stack is more easily suppressed.

[0071] (Technology 4) The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand and the ambient temperature around the fuel cell unit. A fuel cell system as described in any one of the three technical specifications.

[0072] According to the fuel cell system described in Technology 4, the temperature of the cooling water is adjusted according to the target temperature of the heat transfer medium corresponding to the heat demand, making it easier to supply a heat transfer medium with a temperature that meets the heat demand. This reduces the constraints on the utilization of heat generated in the fuel cell system. In addition, since the temperature of the cooling water is adjusted according to the ambient temperature around the fuel cell unit, the temperature of the heat transfer medium is more likely to reach a desirable temperature that matches the ambient temperature around the fuel cell unit.

[0073] (Technology 5) The controller determines a target temperature of the heat transfer medium corresponding to the heat demand, or obtains information including the target temperature from the heat utilization equipment and adjusts the temperature of the cooling water. A fuel cell system as described in any one of the technologies described in items 1 to 4.

[0074] According to the fuel cell system described in Technology 5, the target temperature of the heat transfer medium can be determined or obtained depending on the type of heat utilization equipment, and then the temperature of the cooling water can be adjusted.

[0075] (Technology 6) The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to change the temperature of the cooling water in at least one of the plurality of fuel cell units, changes the temperature of the cooling water in the plurality of fuel cell units in a predetermined order. A fuel cell system as described in any one of the technical items 1 to 5.

[0076] According to the fuel cell system described in Technology 6, the fuel cell unit in which the cooling water temperature is changed is not limited to a specific fuel cell unit, and the durability of the fuel cell system tends to be higher.

[0077] (Technology 7) The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, raises the temperature of the cooling water in the fuel cell unit in which the degree of deterioration of the fuel cell stack is low among the plurality of fuel cell units. A fuel cell system as described in any one of the technical items 1 to 6.

[0078] According to the fuel cell system described in Technology 7, the temperature of the cooling water in fuel cell units with a low degree of fuel cell stack degradation can be increased, which tends to increase the durability of the fuel cell system.

[0079] (Technology 8) The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, lowers the temperature of the cooling water in the fuel cell unit in which the degree of deterioration of the fuel cell stack is high among the plurality of fuel cell units. A fuel cell system as described in any one of the technologies described in items 1 to 7.

[0080] According to the fuel cell system described in Technology 8, the temperature of the cooling water in fuel cell units with a high degree of fuel cell stack degradation can be lowered, which tends to increase the durability of the fuel cell system.

[0081] (Technology 9) The at least one fuel cell unit includes a plurality of such fuel cell units, The controller raises the temperature of the cooling water in the plurality of fuel cell units in a predetermined order when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units do not include a fuel cell stack that has a degree of deterioration exceeding a predetermined standard. The controller increases the temperature of the cooling water in the plurality of fuel cell units in ascending order of the degree of deterioration when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units include a fuel cell stack having a degree of deterioration exceeding a predetermined standard. A fuel cell system as described in any one of the technologies described in items 1 through 8.

[0082] According to the fuel cell system described in Technology 9, the temperature of the cooling water in multiple fuel cell units can be increased according to the degree of degradation of the fuel cell stack, which tends to increase the durability of the fuel cell system.

[0083] (Technology 10) The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, and when none of the plurality of fuel cell units include a fuel cell stack that has deteriorated beyond a predetermined standard, lowers the temperature of the cooling water in the plurality of fuel cell units in a predetermined order. The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units include a fuel cell stack having a degree of deterioration exceeding a predetermined standard, lowers the temperature of the cooling water in the plurality of fuel cell units in descending order of the degree of deterioration. A fuel cell system as described in any one of the technologies described in items 1 through 8.

[0084] According to the fuel cell system described in Technology 10, the temperature of the cooling water in multiple fuel cell units can be lowered according to the degree of degradation of the fuel cell stack, which tends to increase the durability of the fuel cell system. [Industrial applicability]

[0085] The technology disclosed herein is applicable to fuel cell systems that supply heat to heat utilization equipment, and is also applicable to power generation systems that supply electricity by linking solar power generation equipment, fuel cell equipment, battery storage equipment, and commercial power sources. The technology disclosed herein is also applicable to environmental protection initiatives such as RE100 (Renewable Energy 100%). [Explanation of Symbols]

[0086] 1a Fuel cell system 2 Heat utilization equipment 10 Fuel Cell Units 11 Fuel cell stack 12 Cooling water pathways 13 Heat transfer medium pathway 20 Controllers

Claims

1. A fuel cell unit comprising a fuel cell stack, a cooling water path for supplying cooling water to the fuel cell stack, and a heat transfer medium path, Equipped with a controller, The heat transfer medium path is a path that receives heat recovered from the fuel cell stack by the cooling water through the heat transfer medium and guides the heat transfer medium to the outside of the fuel cell unit toward heat utilization equipment outside the fuel cell unit. The controller adjusts the temperature of the cooling water supplied to the fuel cell stack in accordance with the heat demand of the heat utilization equipment. Fuel cell system.

2. The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand. The fuel cell system according to claim 1.

3. The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand and the deterioration state of the fuel cell stack. The fuel cell system according to claim 1.

4. The controller adjusts the temperature of the cooling water by changing at least one selected from the group consisting of the flow rate of the cooling water in the cooling water path and the flow rate of the heat transfer medium in the heat transfer medium path, according to the target temperature of the heat transfer medium corresponding to the heat demand and the ambient temperature around the fuel cell unit. The fuel cell system according to claim 1.

5. The controller determines a target temperature of the heat transfer medium corresponding to the heat demand, or obtains information including the target temperature from the heat utilization equipment and adjusts the temperature of the cooling water. The fuel cell system according to claim 1.

6. The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to change the temperature of the cooling water in at least one of the plurality of fuel cell units, changes the temperature of the cooling water in the plurality of fuel cell units in a predetermined order. The fuel cell system according to claim 1.

7. The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, raises the temperature of the cooling water in the fuel cell unit in which the degree of deterioration of the fuel cell stack is low among the plurality of fuel cell units. The fuel cell system according to claim 1.

8. The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, lowers the temperature of the cooling water in the fuel cell unit in which the degree of deterioration of the fuel cell stack is high among the plurality of fuel cell units. The fuel cell system according to claim 1.

9. The at least one fuel cell unit includes a plurality of such fuel cell units, The controller raises the temperature of the cooling water in the plurality of fuel cell units in a predetermined order when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units do not include a fuel cell stack that has a degree of deterioration exceeding a predetermined standard. The controller increases the temperature of the cooling water in the plurality of fuel cell units in ascending order of the degree of deterioration when it is necessary to raise the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units include a fuel cell stack having a degree of deterioration exceeding a predetermined standard. The fuel cell system according to claim 1.

10. The at least one fuel cell unit includes a plurality of such fuel cell units, The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, and when none of the plurality of fuel cell units include a fuel cell stack that has deteriorated beyond a predetermined standard, lowers the temperature of the cooling water in the plurality of fuel cell units in a predetermined order. The controller, when it is necessary to lower the temperature of the cooling water in at least one of the plurality of fuel cell units, and when the plurality of fuel cell units include a fuel cell stack having a degree of deterioration exceeding a predetermined standard, lowers the temperature of the cooling water in the plurality of fuel cell units in descending order of the degree of deterioration. The fuel cell system according to claim 1.

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