JP6952248B2 - Fuel cell system - Google Patents

Description

The present disclosure relates to a fuel cell system.

Fuel cell systems capable of supplying both power and heat are well known. Waste heat is generated as the fuel cell system operates. Waste heat is used to generate hot water. Hot water is stored in a hot water storage tank and supplied to a bathtub or faucet as needed.

Recently, the development of a fuel cell system that can be operated even in an emergency such as a power outage is underway. As is known to those skilled in the art, the fuel cell system cannot continue to operate when hot hot water accumulates from the top to the bottom of the hot water storage tank. Operation can be continued by replenishing the hot water storage tank with cold city water by discarding the hot water in the hot water storage tank or transferring it to the bathtub, but there is a possibility that the water supply will be cut off at the same time in an emergency. In an apartment house, the pump may stop and the water may be cut off during a power outage.

In order to deal with this problem, the power generation system described in Patent Document 1 includes an auxiliary unit for cooling the hot water in the hot water storage tank. In an emergency, if the hot water in the hot water storage tank is cooled by the auxiliary unit, it is possible to prevent the power generation system from falling into a state where it cannot continue operation.

Japanese Unexamined Patent Publication No. 2010-262833

Cooling devices such as the auxiliary unit described in Patent Document 1 are often not used in normal times. Therefore, it is necessary to inspect the cooling device on a regular basis so that the cooling device operates reliably in an emergency.

The present disclosure provides a technique for facilitating inspection of a cooling device for cooling hot water with respect to a fuel cell system that can be operated even in an emergency.

This disclosure is
With the fuel cell unit
A hot water storage tank for storing hot water generated by the exhaust heat of the fuel cell unit, and
A heat recovery path having a first portion through which water to be supplied from the hot water storage tank to the fuel cell unit flows, and a second portion through which the hot water to be returned from the fuel cell unit to the hot water storage tank flows.
A bypass path connecting the first position of the first portion and the second position of the second portion,
A cooling device provided in the heat recovery path or provided in the bypass path on the downstream side of the first position and on the upstream side of the second position.
A flow path switching mechanism that selectively switches between a first state in which the hot water is guided from the fuel cell unit to the hot water storage tank and a second state in which the hot water is guided from the fuel cell unit to the bypass path.
Provide a fuel cell system equipped with.

According to the technique of the present disclosure, it is possible to easily inspect the cooling device in an emergency.

FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present disclosure. FIG. 2 is a flowchart showing an operation method of the fuel cell system. FIG. 3 is a flowchart showing an inspection method of the cooling device. FIG. 4 is a configuration diagram showing a modified example of the fuel cell unit. FIG. 5 is a configuration diagram showing a modified example of the cooling device. FIG. 6A is a configuration diagram showing a modified example of the flow path switching mechanism. FIG. 6B is a configuration diagram showing another modification of the flow path switching mechanism.

(Findings underlying this disclosure)
In fuel cell systems, water is used for treatments such as gas humidification and generation of fuel gas by steam reforming. Since the exhaust gas such as the anode off gas, the cathode off gas, and the combustion exhaust gas contains a large amount of water vapor, the condensed water can be recovered by cooling the exhaust gas with the water stored in the hot water storage tank. By reusing the condensed water, it is possible to continue the operation of the fuel cell system without supplying water from the outside. Condensed water also has the advantage of not containing impurities such as metal ions.

When high-temperature hot water accumulates from the top to the bottom of the hot water storage tank, the hot water in the hot water storage tank cannot sufficiently cool the exhaust gas. If the exhaust gas cannot be cooled sufficiently, the amount of condensed water recovered will decrease. As a result, the water inside the fuel cell system is depleted, and the fuel cell system cannot continue to operate. As described in Patent Document 1, it is certainly effective to cool the hot water in the hot water storage tank with the auxiliary unit. However, the use of a cooling device such as an auxiliary unit is disadvantageous from the viewpoint of energy efficiency of the fuel cell system. Therefore, the cooling device is often not used in normal times. On the other hand, it is necessary to inspect the cooling device on a regular basis so that the cooling device operates reliably in an emergency.

In the power generation system described in Patent Document 1, in order to inspect whether or not the auxiliary unit operates normally, it is necessary to prepare in advance a state in which operation cannot be continued or a state close to it. In other words, after storing hot water from the top to the bottom of the hot water storage tank, it is necessary to check whether the auxiliary unit operates normally and whether the power generation system can be prevented from falling into a state where it cannot continue operation. be. However, since the heat capacity of the water in the hot water storage tank is large, it may take a long time to store hot hot water from the upper part to the lower part of the hot water storage tank. This is a major obstacle to regular or easy inspection of the integrity of the cooling system.

(Summary of one aspect of the present disclosure)
The fuel cell system according to the first aspect of the present disclosure is
With the fuel cell unit
A hot water storage tank for storing hot water generated by the exhaust heat of the fuel cell unit, and
A heat recovery path having a first portion through which water to be supplied from the hot water storage tank to the fuel cell unit flows, and a second portion through which the hot water to be returned from the fuel cell unit to the hot water storage tank flows.
A bypass path connecting the first position of the first portion and the second position of the second portion,
A cooling device provided in the heat recovery path or provided in the bypass path on the downstream side of the first position and on the upstream side of the second position.
A flow path switching mechanism that selectively switches between a first state in which the hot water is guided from the fuel cell unit to the hot water storage tank and a second state in which the hot water is guided from the fuel cell unit to the bypass path.
It is equipped with.

According to the first aspect, the bypass path can be opened to guide the hot water to the cooling device. As a result, it is possible to inspect whether or not the cooling device operates normally without filling the hot water storage tank. The time spent on the inspection is short. Therefore, it is easy to regularly inspect the soundness of the cooling device, and the energy consumed in the inspection is small.

In the second aspect of the present disclosure, for example, in the fuel cell system according to the first aspect, the flow path switching mechanism includes a three-way valve arranged at the first position or the second position. According to the second aspect, hot water can be smoothly circulated in the heat recovery path.

In the third aspect of the present disclosure, for example, in the fuel cell system according to the first or second aspect, the cooling device includes a first heat exchanger arranged in the first portion of the heat recovery path. According to the third aspect, since the water or hot water passes through the first heat exchanger of the cooling device, the temperature of the water or hot water may decrease. When the temperature of water or hot water drops in the first heat exchanger, the temperature difference between the water or hot water and the object (exhaust gas) to be heat exchanged increases, so that the heat exchange efficiency in the fuel cell unit can be expected to improve.

In the fourth aspect of the present disclosure, for example, in the fuel cell system according to the third aspect, the cooling device supplies a refrigerant between the second heat exchanger, the first heat exchanger, and the second heat exchanger. Further includes a refrigerant circulation path for circulation. According to the fourth aspect, a liquid-liquid heat exchanger can be used as the first heat exchanger. Liquid-liquid heat exchangers have a dimensional advantage over air-cooled heat exchangers.

In the fifth aspect of the present disclosure, for example, in the fuel cell system according to the fourth aspect, the second heat exchanger is an air-cooled heat exchanger. When the second heat exchanger is an air-cooled heat exchanger, the cooling device can exhibit sufficient cooling capacity even when the water is cut off.

In the sixth aspect of the present disclosure, for example, the fuel cell system according to any one of the first to fifth aspects controls the flow path switching mechanism so that the hot water is guided to the bypass path when the water is cut off. It is equipped with more vessels. According to the sixth aspect, the condensed water can be sufficiently recovered in the fuel cell unit, and the operation of the fuel cell system can be continued for a long time even though the water supply is cut off.

In the seventh aspect of the present disclosure, for example, in the fuel cell system according to the sixth aspect, when the water is cut off, the controller guides the hot water to the hot water storage tank until the hot water storage tank reaches the full storage state. The flow path switching mechanism is controlled, and when the hot water storage tank reaches the full storage state, the flow path switching mechanism is controlled so that the hot water is guided to the bypass path. According to the seventh aspect, the power supplied to the outside is increased, so that the convenience of the user is increased.

In the eighth aspect of the present disclosure, for example, the fuel cell system according to any one of the first to seventh aspects is arranged in the heat recovery path or the bypass path and should be supplied to the fuel cell unit. It also has a temperature sensor that detects the temperature of the water. According to the eighth aspect, the temperature of the hot water before being cooled by the cooling device or the temperature of the hot water cooled by the cooling device can be accurately detected.

In the ninth aspect of the present disclosure, for example, in the fuel cell system according to the eighth aspect, the temperature sensor is arranged in the first portion of the heat recovery path on the downstream side of the first position. According to the ninth aspect, the temperature of the hot water before being cooled by the cooling device or the temperature of the hot water cooled by the cooling device can be accurately detected.

In the tenth aspect of the present disclosure, for example, in the fuel cell system according to the sixth aspect, the controller controls the flow path switching mechanism so that the hot water is guided to the bypass path, and inspects the cooling device. Is executed regularly. According to the tenth aspect, since the soundness of the cooling device can always be guaranteed, it is possible to provide a highly reliable fuel cell system that can be reliably operated in an emergency.

In the eleventh aspect of the present disclosure, for example, in the fuel cell system according to the tenth aspect, when a certain period of time has elapsed from the time when the previous inspection is completed and the fuel cell unit is generating power, the control The department executes the inspection this time. According to the eleventh aspect, since the soundness of the cooling device can always be guaranteed, it is possible to provide a highly reliable fuel cell system that can be reliably operated in an emergency.

In the twelfth aspect of the present disclosure, for example, in the fuel cell system according to the tenth or eleventh aspect, a certain period of time has passed from the time when the previous inspection was completed, and the fuel cell unit is stopped. , The control unit activates the fuel cell unit and executes the inspection this time. According to the twelfth aspect, even if the fuel cell unit does not generate electricity, the inspection of the cooling device can be reliably performed.

In the thirteenth aspect of the present disclosure, for example, in the fuel cell system according to any one of the tenth to twelfth aspects, when the operation of the cooling device is not normal, the controller generates electricity from the fuel cell unit. At least one process selected from the group consisting of stopping and notifying the outside that there is an abnormality in the cooling device is executed. According to the thirteenth aspect, since the repair of the cooling device can be started immediately, the soundness of the cooling device can always be guaranteed.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

(Embodiment)
The fuel cell system 100 of the present embodiment includes a fuel cell unit 10 and a hot water storage unit 30. The hot water storage unit 30 has a hot water storage tank 20. The fuel cell unit 10 and the hot water storage tank 20 are connected to each other by a heat recovery path 21. The hot water generated in the fuel cell unit 10 is stored in the hot water storage tank 20.

The fuel cell unit 10 includes a fuel cell 11, a reformer 12, a heat exchanger 13, and a pump 14.

The fuel cell 11 uses the fuel gas and the oxidant gas to generate electric power. The reformer 12 produces fuel gas by reforming a raw material gas such as city gas. The fuel gas includes hydrogen gas. The oxidant gas is typically air. The model of the fuel cell 11 is not particularly limited. The fuel cell 11 is a solid polymer fuel cell, a solid oxide fuel cell, a phosphoric acid fuel cell, or a molten carbonate fuel cell. When pure hydrogen gas is supplied to the fuel cell 11, the reformer 12 may be omitted.

The heat exchanger 13 may be a cooler that cools at least one gas selected from the anode off gas of the fuel cell 11, the cathode off gas of the fuel cell 11, and the combustion exhaust gas to generate condensed water. The heat exchanger 13 may be divided into a plurality of parts so that the plurality of gases can be individually cooled. The heat exchanger 13 is connected to the hot water storage tank 20 so that the water stored in the lower part of the hot water storage tank 20 can flow to the heat exchanger 13 as a cooling medium. Condensed water is stored in a condensed water tank (not shown). The water stored in the condensed water tank is supplied to the reformer 12 and used to generate fuel gas. The combustion exhaust gas is the combustion exhaust gas of the burner for raising the temperature of the reformer 12. As the fuel for the burner, the anode off gas of the fuel cell 11 can be used. The heat exchanger 13 is, for example, a gas-liquid heat exchanger such as a fin tube type heat exchanger or a plate type heat exchanger.

The heat recovery path 21 includes a first portion 21a and a second portion 21b. The first portion 21a connects the lower part of the hot water storage tank 20 and the inlet of the heat exchanger 13. The second portion 21b connects the outlet of the heat exchanger 13 and the upper part of the hot water storage tank 20. The first portion 21a constitutes an upstream portion of the heat recovery path 21. The second portion 21b constitutes a downstream portion of the heat recovery path 21. The first portion 21a is a flow path for guiding the water to be heated in the heat exchanger 13 to the heat exchanger 13. Water to be supplied from the hot water storage tank 20 to the fuel cell unit 10 flows through the first portion 21a. The second portion 21b is a flow path for guiding the water (hot water) heated in the heat exchanger 13 to the hot water storage tank 20. Hot water to be returned from the fuel cell unit 10 to the hot water storage tank 20 flows through the second portion 21b.

The pump 14 is arranged in the heat recovery path 21. Water is supplied from the hot water storage tank 20 to the heat exchanger 13 by the action of the pump 14, and the generated hot water is returned from the heat exchanger 13 to the hot water storage tank 20. In this embodiment, the pump 14 is arranged in the first portion 21a of the heat recovery path 21. The pump 14 may be located in the second portion 21b.

Each of the pumps used in the fuel cell system 100 of the present embodiment is a positive displacement pump such as a piston pump, a plunger pump, a gear pump, and a vane pump.

The fuel cell system 100 further includes a bypass path 22, a three-way valve 23, and a cooling device 24. The bypass path 22, the three-way valve 23, and the cooling device 24 are used to lower the temperature of the hot water to be supplied to the fuel cell unit 10 when the water is cut off.

The bypass path 22 connects the first portion 21a of the heat recovery path 21 and the second portion 21b of the heat recovery path 21. Specifically, the bypass path 22 extends from the first position P1 of the first portion 21a to the second position P2 of the second portion 21b. The bypass path 22 is a path for circulating the hot water generated by the fuel cell unit 10 in the heat recovery path 21 without returning it to the hot water storage tank 20.

The three-way valve 23 is arranged in the heat recovery path 21. In the present embodiment, the three-way valve 23 is arranged at a connection position between the heat recovery path 21 and the bypass path 22. The three-way valve 23 is an example of a flow path switching mechanism for switching the flow path of hot water. Specifically, the three-way valve 23 selectively switches between the first state in which hot water is guided from the fuel cell unit 10 to the hot water storage tank 20 and the second state in which hot water is guided from the fuel cell unit 10 to the bypass path 22. Be done. In the example shown in FIG. 1, the three-way valve 23 is arranged at the second position P2, which is the connection position between the bypass path 22 and the second portion 21b of the heat recovery path 21. However, the three-way valve 23 may be arranged at the first position P1. By the action of the three-way valve 23, hot water can be smoothly circulated in the heat recovery path 21. However, the three-way valve 23 may be replaced by a plurality of on-off valves. The three-way valve 23 may have a distribution function or a mixing function.

When the water is cut off, the user can use the hot water in the hot water storage tank 20. When the user uses hot water, the city water is not replenished, so that a space is created above the hot water storage tank 20. Therefore, when the three-way valve 23 is arranged only in the first position P1, there is a possibility that the hot water does not go to the bypass path 22 and returns to the hot water storage tank 20. An additional on-off valve is required to prevent hot water from returning to the hot water storage tank 20. However, when the three-way valve 23 is arranged at the second position P2, hot water can be reliably guided to the bypass path 22 regardless of the amount of water in the hot water storage tank 20. As long as the hot water storage tank 20 is not emptied, water can be circulated through the heat recovery path 21 to continue the operation of the fuel cell system 100.

The cooling device 24 plays a role of cooling the hot water flowing through the heat recovery path 21. The cooling device 24 is provided in the heat recovery path 21 on the downstream side of the first position P1 and on the upstream side of the second position P2. In this embodiment, the cooling device 24 has a first heat exchanger 40. The first heat exchanger 40 is arranged in the first portion 21a of the heat recovery path 21. The first heat exchanger 40 is, for example, a liquid-liquid heat exchanger such as a double tube heat exchanger or a plate heat exchanger. In the first heat exchanger 40, heat exchange is performed between the hot water and the refrigerant so that the hot water is cooled. The type of refrigerant is not particularly limited. The refrigerant is a liquid refrigerant such as water, brine, oil, and alcohol.

During normal operation of the fuel cell system 100, the function of the cooling device 24 is off. However, since the water or hot water passes through the first heat exchanger 40 of the cooling device 24, the temperature of the water or hot water may drop. When the temperature of water or hot water drops in the first heat exchanger 40, the temperature difference between the water or hot water and the object (exhaust gas) to be heat exchanged increases, so it is expected that the heat exchange efficiency in the fuel cell unit 10 will be improved. can. It is also possible to prevent the temperature of the hot water generated by the fuel cell unit 10 from dropping in the first heat exchanger 40 during normal operation of the fuel cell system 100. Of course, the cooling device 24 may be provided in the second portion 21b of the heat recovery path 21.

The cooling device 24 may be provided in the bypass path 22. In this case, the hot water flowing through the bypass path 22 can be cooled by the cooling device 24. During normal operation of the fuel cell system 100, hot water does not flow through the bypass path 22, so that water stays in the bypass path 22. The shorter the bypass path 22, the less water stays. When the cooling device 24 is arranged in the heat recovery path 21, the bypass path 22 can be sufficiently shortened. On the other hand, when the cooling device 24 is provided in the bypass path 22, the length of the first portion 21a or the second portion 21b of the heat recovery path 21 can be shortened, so that the pressure loss during normal operation of the fuel cell system 100 can be shortened. Can be suppressed.

In the present embodiment, the cooling device 24 further includes a second heat exchanger 41 and a refrigerant circulation path 45. The second heat exchanger 41 plays a role of cooling the refrigerant heated by the hot water in the first heat exchanger 40. The refrigerant circulation path 45 is a path for circulating the refrigerant between the first heat exchanger 40 and the second heat exchanger 41.

According to the cooling device 24 of the present embodiment, a liquid-liquid heat exchanger can be used as the first heat exchanger 40. Liquid-liquid heat exchangers have a dimensional advantage over air-cooled heat exchangers. It is also possible to house the first heat exchanger 40 in the housing of the hot water storage unit 30. As a result, it is possible to prevent the water in the heat recovery path 21 from freezing when the outside air temperature is low.

The second heat exchanger 41 may be an air-cooled heat exchanger such as a fin tube heat exchanger or a plate heat exchanger. When the second heat exchanger 41 is an air-cooled heat exchanger, the cooling device 24 can exhibit a sufficient cooling capacity even when the water is cut off. The second heat exchanger 41 may be arranged outside the housing of the hot water storage unit 30.

A system turn tank 42 and a pump 43 are provided in the refrigerant circulation path 45. Refrigerant is stored in the systurn tank 42. By the action of the pump 43, the refrigerant circulates between the first heat exchanger 40 and the second heat exchanger 41. If the fan of the second heat exchanger 41 is rotated while circulating the refrigerant, the cooling device 24 exhibits a predetermined cooling capacity. An overflow pipe 44 may be attached to the systurn tank 42.

The fuel cell system 100 further includes temperature sensors 26, 27 and 28. The temperature sensors 26, 27 and 28 detect the temperature of water flowing through the heat recovery path 21. The temperature sensor 26 is arranged in the first portion 21a of the heat recovery path 21 on the downstream side of the first position P1. Specifically, the temperature sensor 26 is arranged in the first portion 21a of the heat recovery path 21 between the first position P1 and the cooling device 24. According to the temperature sensor 26, the temperature of hot water at the inlet of the first heat exchanger 40 of the cooling device 24 can be accurately detected. The temperature sensor 27 is arranged in the second portion 21b of the heat recovery path 21 on the upstream side of the second position P2. Specifically, the temperature sensor 27 is arranged in the second portion 21b of the heat recovery path 21 between the fuel cell unit 10 and the second position P2. According to the temperature sensor 27, the temperature of the hot water generated by the fuel cell unit 10 can be accurately detected. The temperature sensor 28 is arranged in the first portion 21a of the heat recovery path 21 between the cooling device 24 and the heat exchanger 13. The temperature sensor 28 may be included in the fuel cell unit 10 or the hot water storage unit 30. The temperature sensor 28 may be located inside the housing of the fuel cell unit 10 or may be located inside the housing of the hot water storage unit 30. According to the temperature sensor 28, it is the temperature of the hot water at the outlet of the first heat exchanger 40 of the cooling device 24, and the temperature of the hot water to be supplied to the heat exchanger 13 can be accurately detected. As will be described later, the detected values of the temperature sensors 26, 27 and 28 can also be effectively used in the inspection of the cooling device 24.

The temperature sensor 26 or the temperature sensor 27 may be arranged in the bypass path 22. In this case, the temperature of the hot water flowing through the bypass path 22 can be accurately detected.

When the temperature of the water detected by the temperature sensor 28 is equal to or lower than the threshold temperature (for example, 45 ° C. or lower), there is no possibility that the fuel cell unit 10 will run out of water, and the operation of the fuel cell 11 can be continued. When the temperature of water detected by the temperature sensor 28 is higher than the threshold temperature, the fuel cell unit 10 may run out of water. When there is a risk that the fuel cell unit 10 will run out of water, the hot water in the hot water storage tank 20 may be partially discarded or discharged into the bathtub, and city water may be replenished in the hot water storage tank 20. Power generation may be stopped according to the power demand.

Each of the temperature sensors used in the fuel cell system 100 of the present embodiment is, for example, a temperature sensor using a thermistor or a temperature sensor using a thermocouple.

The hot water storage tank 20 is a container for storing hot water generated by waste heat generated by the operation of the fuel cell 11. The hot water storage tank 20 is composed of a container having heat insulation and pressure resistance. The hot water storage tank 20 is provided with a plurality of temperature sensors 25a to 25e. The temperature sensors 25a to 25e are arranged at substantially equal intervals along the vertical direction. The temperature sensors 25a to 25e may be arranged inside the hot water storage tank 20 or may be arranged on the surface of the hot water storage tank 20.

The temperature sensors 25a to 25e detect the temperature of the hot water stored in the hot water storage tank 20. Hot hot water is stored in the upper part of the hot water storage tank 20. When hot water is used, city water is replenished to the lower part of the hot water storage tank 20. Therefore, a temperature stratification of hot water is formed inside the hot water storage tank 20. The heat storage state of the hot water storage tank 20 can be grasped from the detected values of the temperature sensors 25a to 25e.

A water supply path 47 for city water is connected to the lower part of the hot water storage tank 20. When the hot water in the hot water storage tank 20 is consumed, city water is replenished to the hot water storage tank 20 through the water supply route 47. Therefore, the water supply pressure of city water is applied to the hot water storage tank 20.

A hot water supply path 60 is connected to the upper part of the hot water storage tank 20. The hot water supply route 60 is a flow path for supplying hot water stored in the hot water storage tank 20 to a use point such as a bathtub or a faucet, and extends from the hot water storage tank 20 to the use point.

The water supply path 47 is provided with a flow rate sensor 51, a temperature sensor 52, a pressure sensor 53, a pressure reducing valve 54, and a check valve 55. A branch path 57 branches from the water supply path 47 between the check valve 55 and the pressure sensor 53. The branch path 57 joins the hot water supply path 60 (not shown). A mixing valve 58 is arranged in the branch path 57. If the mixing valve 58 is controlled to mix the hot water in the hot water storage tank 20 and the city water in an appropriate ratio, hot water at an appropriate temperature can be supplied to the use point.

The pressure sensor 53 is, for example, a semiconductor pressure sensor that utilizes the piezoresistive effect. In a normal state, the pressure of city water (for example, 0.15 to 0.5 MPa) is applied to the pressure sensor 53. When the water is cut off, the value detected by the pressure sensor 53 is significantly lower than the value at the normal time. Based on the detected value of the pressure sensor 53, it is possible to identify whether or not the water is cut off. The position of the pressure sensor 53 is not particularly limited as long as the pressure of the city water can be detected.

A drainage path 62 is connected to the lower part of the hot water storage tank 20. The drainage path 62 is provided with an on-off valve 63. The on-off valve 63 may be a manual type. For example, when absent for a long period of time, all the water in the hot water storage tank 20 can be drained through the drainage path 62. A branch drainage route 64 is connected to the drainage route 62. The branch drainage route 64 is, for example, a route connected to a bathtub or the like. The water in the hot water storage tank 20 can be transferred to a bathtub or the like in a short time through the branch drainage path 64. The water intake path 65 branches from the heat recovery path 21, and a faucet 61 is attached to the tip of the water intake path 65. Since the heat recovery path 21 and the water intake path 65 are narrow paths, the water in the hot water storage tank 20 can be slowly transferred to a container such as a PET bottle through the water intake path 65 and the faucet 61.

The heat recovery path 21, the bypass path 22, the refrigerant circulation path 45, the water supply path 47, the hot water supply path 60, the drainage path 62, the branch drainage path 64, and the water intake path 65 are each composed of at least one pipe. The pipe may be a metal pipe such as a stainless steel pipe or a resin pipe. If necessary, components such as a filter, a check valve, a flow rate sensor, and an on-off valve may be provided in each flow path.

The fuel cell system 100 further includes a controller 70. The controller 70 is, for example, a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an arithmetic circuit, a storage device, and the like. Detection signals of measuring devices such as the temperature sensor 26, the temperature sensor 27, the temperature sensor 28, and the pressure sensor 53 are input to the controller 70. The controller 70 controls the controlled objects such as the three-way valve 23, the second heat exchanger 41, and the pump 43 based on the measurement results of various measuring devices. The controller 70 stores a program for properly operating the fuel cell system 100.

The controller 70 may be composed of a single microcomputer or a plurality of microcomputers. Further, the fuel cell system 100 may have a plurality of controllers.

Next, the operation of the fuel cell system 100 will be described. The controller 70 periodically executes each process shown in the flowchart of FIG.

In step S1, it is determined whether or not the water supply is cut off. Specifically, it is determined whether or not the detected value of the pressure sensor 53 is equal to or less than the threshold value. Since the water pressure drops significantly when the water is cut off, it can be easily determined from the detection value of the pressure sensor 53 whether or not the water is cut off. The threshold can be set to a value that can reliably detect that a water outage has occurred, taking into account the normal water pressure.

Next, in step S2, it is determined whether or not the hot water storage tank 20 has reached the full storage state. Specifically, it is determined whether or not the detected value of the temperature sensor 26 or the detected value of the temperature sensor 28 is equal to or lower than the threshold temperature (for example, 45 ° C. or lower).

When the hot water storage tank 20 has reached the full state, in step S3, the fans of the pump 43 and the second heat exchanger 41 are moved to start the cooling device 24. In step S4, the three-way valve 23 is controlled so that the hot water is guided to the bypass path 22. Since the hot water is cooled in the first heat exchanger 40 of the cooling device 24, low temperature hot water (for example, less than 40 ° C.) is supplied to the heat exchanger 13 of the fuel cell unit 10. As a result, the condensed water can be sufficiently recovered, and the operation of the fuel cell system 100 can be continued for a long time even though the water is cut off. The order of the processing in step S3 and the processing in step S4 may be reversed from the order shown in FIG.

When the hot water storage tank 20 has not reached the full storage state, the three-way valve 23 is controlled so that the hot water is guided to the hot water storage tank 20 in step S5. In step S6, the cooling device 24 is stopped. The order of the processing in step S5 and the processing in step S6 may be reversed from the order shown in FIG.

According to the present embodiment, even if the water is cut off, hot water is stored in the hot water storage tank 20 until the full storage state is reached. In this way, when a power failure and a water outage occur at the same time, the cooling device 24 does not consume electric power. When the power is not consumed by the cooling device 24, the power supplied to the outside increases. This increases user convenience.

However, hot water may be circulated between the hot water storage tank 20 and the fuel cell unit 10 even after the livestock state is reached. It is not mandatory to use the bypass route 22. By the action of the cooling device 24, low temperature hot water can be supplied to the fuel cell unit 10.

Next, a method of inspecting the cooling device 24 will be described. The controller 70 inspects whether or not the cooling device 24 operates normally according to the flowchart of FIG.

In step S11, it is determined whether or not the inspection of the cooling device 24 is the first time. When the inspection of the cooling device 24 is the first time, that is, when the inspection has not been performed at all in the past, the inspection of the cooling device 24 is performed in step S12. The inspection begins by creating the same situation as when the water was cut off. That is, the three-way valve 23 is controlled so that the hot water is guided to the bypass path 22. The fans of the pump 43 and the second heat exchanger 41 are operated to start the cooling device 24. In this way, the inspection of the cooling device 24 can be immediately performed regardless of the heat storage state of the hot water storage tank 20. Even if the entire hot water storage tank 20 is filled with cold water, the inspection can be performed when the fuel cell unit 10 reaches a predetermined operating state. The “time when a predetermined operating state is reached” is, for example, a time when the temperature of hot water (detected value of the temperature sensor 26) at the inlet of the first heat exchanger 40 reaches a predetermined temperature (50 ° C.). The process of step S12 is performed together with, for example, a trial run of the fuel cell system 100.

According to this embodiment, the cooling device 24 is inspected fully automatically. However, it is also possible for the maintenance person or the system administrator to execute the inspection of the cooling device 24 at an arbitrary timing by giving a command to the controller 70 from the outside.

Next, in step S13, it is determined whether or not the operation of the cooling device 24 is normal. Specifically, it is determined whether or not the operation of the cooling device 24 is normal from the detected value of the temperature sensor 26 and the detected value of the temperature sensor 28. The detected value of the temperature sensor 26 substantially matches the water temperature at the inlet of the first heat exchanger 40. The detected value of the temperature sensor 28 substantially matches the water temperature at the outlet of the first heat exchanger 40. Based on the difference between the detected value of the temperature sensor 26 and the detected value of the temperature sensor 28, it can be determined whether or not the operation of the cooling device 24 is normal. Specifically, the temperature drop of the hot water in the cooling device 24 is calculated by subtracting the detected value of the temperature sensor 26 from the detected value of the temperature sensor 28. For example, when the lowered temperature is equal to or higher than the threshold temperature (for example, 10 ° C. or higher), the operation of the cooling device 24 is normal. When the lowered temperature is less than the threshold temperature, the operation of the cooling device 24 is not normal.

The method for determining whether or not the operation of the cooling device 24 is normal is not limited to the above method. For example, if the detected value of the temperature sensor 28 is below the upper limit temperature (for example, 40 ° C.) for a predetermined time after the fuel cell system 100 is started, it can be said that the operation of the cooling device 24 is normal. Further, it may be added that the detected value of the temperature sensor 28 is below the upper limit temperature (for example, 40 ° C.).

If the operation of the cooling device 24 is normal, the inspection ends. If the operation of the cooling device 24 is not normal, in step S14, an abnormality is notified to the outside of the cooling device 24. The method of notifying the abnormality to the outside is not particularly limited. For example, the abnormality lamp may be turned on, a message notifying the input / output device such as a touch panel may be displayed, or the presence of the abnormality may be notified by voice. Further, when the controller 70 is connected to a communication network such as the Internet, the terminal of the maintenance person may be notified that there is an abnormality in the cooling device 24. Instead of the process of notifying the outside that there is an abnormality in the cooling device 24, or together with the process of notifying the outside that there is an abnormality in the cooling device 24, the power generation of the fuel cell unit 10 may be stopped. In this way, the repair of the cooling device 24 can be started immediately, so that the soundness of the cooling device 24 can always be guaranteed. However, even if there is an abnormality in the cooling device 24, there is no problem in the normal operation of the fuel cell system 100. Therefore, after automatically stopping the power generation, it is possible to restart the power generation by the user's operation.

When the inspection of the cooling device 24 is performed for the second time or later, it is determined in step S15 whether or not an instruction to inspect the cooling device 24 is input. For example, after an abnormality is found in the cooling device 24 and the repair is completed, a trial run is required. In such a case, a command can be given to the controller 70 from the outside, and the inspection of the cooling device 24 can be performed immediately.

Next, in step S16, it is determined whether or not the condition 1 is satisfied. If condition 1 is satisfied, the current inspection of the cooling device 24 is performed in step S17. Condition 1 is, for example, that a certain period of time has passed from the time when the previous inspection was completed, and the fuel cell unit 10 is generating electricity. The "fixed period" is not particularly limited, and is, for example, 25 to 30 days. That is, according to the present embodiment, the cooling device 24 is inspected periodically according to a predetermined schedule. In this way, since the soundness of the cooling device 24 can always be guaranteed, it is possible to provide a highly reliable fuel cell system 100 that can be reliably operated in an emergency.

If the condition 1 is not satisfied, it is determined in step S18 whether or not the condition 2 is satisfied. When the condition 2 is satisfied, the fuel cell system 100 is started in step S19, and the current inspection of the cooling device 24 is carried out in step S17. Condition 2 is, for example, that a certain period of time has passed from the time when the previous inspection was completed and the fuel cell unit 10 is stopped. The "fixed period" is not particularly limited, and is, for example, 30 days. In this way, even if the fuel cell unit 10 is not generating electricity, the inspection of the cooling device 24 can be reliably performed.

If neither condition 1 nor condition 2 is satisfied, it is not the inspection timing, and the current operation (operation or stop) is continued (step S20).

As described above, according to the present embodiment, the bypass path 22 can be opened to guide the hot water to the cooling device 24. As a result, it is possible to inspect whether or not the cooling device 24 operates normally without having to fill the hot water storage tank 20 in a fully stored state. The time spent on the inspection is short. Therefore, it is easy to regularly inspect the soundness of the cooling device 24, and the energy consumed in the inspection is small.

(Modification example)
As shown in FIG. 4, when the fuel cell 11 is a solid polymer fuel cell, the fuel cell unit 10 may further include a heat exchanger 15 and a cooling water circuit 16. The heat exchanger 15 plays a role of heating the water in the hot water storage tank 20 by the exhaust heat of the fuel cell 11. The heat exchanger 15 causes heat exchange between the cooling water of the fuel cell 11 and the water of the hot water storage tank 20. The heat exchanger 15 is, for example, a liquid-liquid heat exchanger such as a double tube heat exchanger or a plate heat exchanger.

The cooling water circuit 16 is a flow path for circulating cooling water between the fuel cell 11 and the heat exchanger 15, and connects the fuel cell 11 and the heat exchanger 15. The cooling water circuit 16 can efficiently cool the fuel cell 11 and take out the waste heat of the fuel cell 11 to the outside of the fuel cell 11 in the form of hot water. The cooling water circuit 16 is provided with a pump 17 and a cooling water tank 18.

The heat recovery path 21 may include a third portion 21c that connects the heat exchanger 13 and the heat exchanger 15. In the heat recovery path 21, the heat exchanger 13 is located on the upstream side and the heat exchanger 15 is located on the downstream side. According to such an arrangement, the water in the hot water storage tank 20 is heated in the order of the heat exchanger 13 and the heat exchanger 15. Water at a lower temperature is supplied by the heat exchanger 13. In the heat exchanger 13, at least one gas can be sufficiently cooled, so that the condensed water can be sufficiently recovered. The third portion 21c connects the outlet of the heat exchanger 13 and the inlet of the heat exchanger 15.

As shown in FIG. 5, the cooling device 74 according to the modified example includes a cooling path 75, a heat exchanger 76, and a flow path switching mechanism 77. The cooling path 75 branches from the first portion 21a of the heat recovery path 21 and joins the first portion 21a. The cooling path 75 may branch from the second portion 21b of the heat recovery path 21 and join the second portion 21b. The heat exchanger 76 is arranged in the cooling path 75. The heat exchanger 76 may be an air-cooled heat exchanger such as a fin tube type heat exchanger or a plate type heat exchanger. The flow path switching mechanism 77 is, for example, a three-way valve arranged at a connection position between the cooling path 75 and the heat recovery path 21. The flow path switching mechanism 77 may be composed of a plurality of on-off valves. According to this modification, only one heat exchanger is required, which is inexpensive. The flow path switching mechanism 77 can selectively take the state A and the state B. When the flow path switching mechanism 77 is in the state A, hot water is guided to the cooling path 75. When the flow path switching mechanism 77 is in the state B, hot water is prohibited from flowing through the cooling path 75.

However, according to the embodiment shown in FIG. 1, water does not stay in the first heat exchanger 40 when the cooling device 24 is off, which is advantageous in terms of hygiene.

As shown in FIG. 6A, when the three-way valves 23 are arranged at both ends (first position P1 and second position P2) of the bypass path 22, the user uses the hot water of the hot water storage tank 20 to use the hot water storage tank 20. Even if the fuel cell system 100 is emptied, the operation of the fuel cell system 100 can be continued. In this modification, the flow path switching mechanism is configured by the two three-way valves 23.

As shown in FIG. 6B, in this modification, the flow path switching mechanism is configured by the three on-off valves 78a to 78c. The three-way valve 78a is arranged in the heat recovery path 21 between the hot water storage tank 20 and the first position P1. The three-way valve 78b is arranged in the heat recovery path 21 between the second position P2 and the hot water storage tank 20. The three-way valve 78c is arranged in the bypass path 22.

The technique of the present disclosure is useful for cogeneration systems such as fuel cell systems.

10 Fuel cell unit 11 Fuel cell 12 Reformer 13 Heat exchanger 14 Pump 20 Hot water storage tank 21 Heat recovery path 21a 1st part 21b 2nd part 21c 3rd part 22 Bypass path 23 Three-way valve 24 Cooling device 25a to 25e, 26 , 27, 28 Temperature sensor 30 Hot water storage unit 40 1st heat exchanger 41 2nd heat exchanger 42 Systurn tank 43 Pump 44 Overflow pipe 45 Coolant circulation path 47 Water supply path 51 Flow sensor 52 Temperature sensor 53 Pressure sensor 54 Pressure reducing valve 55 Reverse Stop valve 57 Branch path 58 Mixing valve 60 Hot water supply path 62 Drainage path 63 On-off valve 70 Controller 74 Cooling device 75 Cooling path 76 Heat exchanger 77 Flow switching mechanism 78a, 78b, 78c On-off valve 100 Fuel cell system P1 1st position P2 2nd position

Claims (12)

With the fuel cell unit
A hot water storage tank for storing hot water generated by the exhaust heat of the fuel cell unit, and
A heat recovery path having a first portion through which water to be supplied from the hot water storage tank to the fuel cell unit flows, and a second portion through which the hot water to be returned from the fuel cell unit to the hot water storage tank flows.
A bypass path connecting the first position of the first portion and the second position of the second portion,
A cooling device provided in the heat recovery path or provided in the bypass path on the downstream side of the first position and on the upstream side of the second position.
A flow path switching mechanism that selectively switches between a first state in which the hot water is guided from the fuel cell unit to the hot water storage tank and a second state in which the hot water is guided from the fuel cell unit to the bypass path.
A controller that controls the flow path switching mechanism so that the hot water is guided to the bypass path when the inspection of the cooling device is performed and at least one case selected from the group consisting of when the water is cut off.
A fuel cell system equipped with. The fuel cell system according to claim 1, wherein the flow path switching mechanism includes a three-way valve arranged at the first position or the second position. The fuel cell system according to claim 1 or 2, wherein the cooling device includes a first heat exchanger arranged in the first portion of the heat recovery path. The third aspect of claim 3, wherein the cooling device further includes a second heat exchanger and a refrigerant circulation path for circulating a refrigerant between the first heat exchanger and the second heat exchanger. Fuel cell system. The fuel cell system according to claim 4, wherein the second heat exchanger is an air-cooled heat exchanger. When the water is cut off, the controller controls the flow path switching mechanism so that the hot water is guided to the hot water storage tank until the hot water storage tank reaches the full state, and when the hot water storage tank reaches the full state, the controller controls the flow path switching mechanism. The fuel cell system according to any one of claims 1 to 5, wherein the flow path switching mechanism is controlled so that hot water is guided to the bypass path. The fuel cell according to any one of claims 1 to 6 , further comprising a temperature sensor arranged in the heat recovery path or the bypass path and detecting the temperature of the water to be supplied to the fuel cell unit. system. The fuel cell system according to claim 7 , wherein the temperature sensor is arranged in the first portion of the heat recovery path on the downstream side of the first position. The fuel cell system according to any one of claims 1 to 8, wherein the controller periodically performs the inspection. Certain period has elapsed from when the last of the inspection is completed, and if the fuel cell unit is in the power generation, the controller executes the time of the inspection, either one of claims 1 to 9 1 The fuel cell system described in the section. Certain period has elapsed from when the last of the inspection is completed, and if the fuel cell unit is stopped, the controller executes the time of the inspection by activating the fuel cell unit, wherein Item 2. The fuel cell system according to any one of Items 1 to 10. At least selected from the group consisting of stopping the power generation of the fuel cell unit and notifying the outside that there is an abnormality in the cooling device when the operation of the cooling device is not normal. The fuel cell system according to any one of claims 1 to 11 , wherein one process is performed.

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