JP2013109888A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that the temperature of a heating medium is changed by rapid change in temperature of hot water to a heat exchanger.SOLUTION: A fuel cell system 1 comprises a hot water storage tank 5, a heating medium temperature detector 4, a stored hot water circulation passage 6, a circulation temperature detector 11, a bypass pathway 7, a switch 8 which switches water conduction from the bypass pathway 7 to the hot water storage tank 5 when the temperature detected by the circulation temperature detector 11 reaches or goes above a predetermined temperature, a circulator 9 for circulating the hot water in the stored hot water circulation passage 6 or the bypass pathway 7, and a controller 10 controlling the amount of hot water circulating the stored hot water circulation passage 6 or the bypass pathway 7 by controlling the output of the circulator 9 on the basis of the temperature detected by the heating medium temperature detector 4. The controller 10 changes the output of the circulator 9 by a predetermined amount, when the temperature detected by the circulation temperature detector 11 reaches or goes above a predetermined temperature.

Description

  The present invention relates to a fuel cell that generates power using fuel gas and air, and a fuel cell system that uses generated power and exhaust heat of the fuel cell.

  As a conventional fuel cell system intended to use exhaust heat for hot water supply, there is one as described below (for example, see Patent Document 1).

  FIG. 3 is a configuration diagram of a conventional fuel cell system. As shown in FIG. 3, the conventional fuel cell system includes a fuel cell unit 1 and a hot water storage unit 2. The fuel cell unit 1 and the hot water storage unit 2 are composed of circulation paths 3 and 4, a circulation path 6 that returns to the upper part of the hot water storage tank 5, and a bypass path 7 that is connected to the circulation path 4 without returning to the hot water storage tank 5. The water is circulated by the circulation pump 8. The water circulating through the fuel cell unit 1 and the hot water storage unit 2 passes through the circulation pump 8 from the lower part of the hot water storage tank 5 and the heat medium (for example, water) and heat recovered from the exhaust heat of the fuel cell 9 flowing through the heat medium path 20. Heat is exchanged by the exchanger 10 to become hot water.

  The hot water flowing through the circulation path 3 is detected by the temperature sensor 11 so as not to lower the upper temperature of the hot water storage tank 5. When the temperature is higher than the upper temperature of the hot water storage tank 5, It is conveyed to the upper part of the hot water storage tank 5 by the return circulation path 6. When the temperature of the heat recovery hot water heated here is lower than the temperature of the upper part of the hot water storage tank 5, it is conveyed to the bypass path 7 by the switching valve 12 and circulates in the circuit. Further, water is supplied through the water supply pipe 13, and hot water 14 used as hot water is discharged from the upper part of the hot water storage tank 5 by mixing hot water in the hot water supply pipe 15 and water in the water supply pipe 13 to a predetermined temperature by the mixing valve 16. .

  Further, as a conventional fuel cell cooling device, there is one that cools a fuel cell using a radiator (see, for example, Patent Document 2).

JP-A-11-223385 JP 2004-178826 A

  However, in the configuration of the conventional fuel cell system described above, the temperature of the hot water flowing into the heat exchanger 10 when the path is switched by the switching valve 12 varies depending on the temperature of the hot water recovered from the exhaust heat, whereby the heat medium path. 20 has a problem that the temperature of the heat medium flowing through 20 fluctuates and power generation of the fuel cell 1 becomes unstable. In particular, when the temperature of the hot water flowing through the bypass path 7 is higher than the temperature of the hot water in the lower part of the hot water storage tank 5, the temperature of the hot water flowing into the heat exchanger 10 when the path is switched changes rapidly. The amount of heat exchanged at 10 may change, and the temperature of the heat medium flowing through the heat medium path 20 may fluctuate. Along with this fluctuation, output fluctuation such as a voltage drop of the fuel cell 9 occurs, and there is a possibility that the operation of the fuel cell system becomes unstable.

More specifically, when switching the path from the circulation path 6 to the bypass path 7, the temperature of hot water flowing into the heat exchanger 10 may increase, and the temperature of the heat medium supplied to the fuel cell 9 increases. There was a fear. As a result, the temperature of the fuel cell 9 rises, the polymer electrolyte membrane is not sufficiently wetted, and the output of the fuel cell 9 may be reduced. Further, when switching the path from the bypass path 7 to the circulation path 6, the temperature of the hot water flowing into the heat exchanger 10 may decrease, and the temperature of the heat medium supplied to the fuel cell 9 may decrease. It was. As a result, the temperature of the fuel cell 9 is lowered, moisture in the reaction gas is condensed and flooding occurs, and the reaction gas is not sufficiently supplied to the membrane electrode assembly, which may reduce the output of the fuel cell 9. It was.

  Further, the conventional fuel cell cooling device technology described in Patent Document 2 still has room for improvement from the viewpoint of using exhaust heat for hot water supply.

  An object of the present invention is to solve the above-described problems of the conventional fuel cell system, and to provide a fuel cell system capable of suppressing the fluctuation of the temperature of the heat medium supplied to the fuel cell and capable of stable operation. To do.

  In order to solve the above-described conventional problems, the fuel cell system of the present invention is controlled when the temperature sensor becomes equal to or higher than a predetermined temperature and is switched from the bypass path to the hot water storage tank by the switch configured on the circulation path. The output of the circulator is changed by a predetermined amount by the vessel.

  That is, when the path is switched by the switch, the amount of hot water flowing through the circulation path is changed by the circulator, and the amount of hot water flowing into the heat exchanger is changed.

  According to the fuel cell system of the present invention, fluctuations in the amount of heat supplied to the heat exchanger can be suppressed, and fluctuations in the temperature of the heat medium supplied to the fuel cell can be suppressed. Therefore, the power generation state of the fuel cell becomes stable, and the fuel cell system can be stably operated.

1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. Flowchart of controller output determination processing procedure in Embodiment 1 of the present invention Configuration diagram of conventional fuel cell system

  A first invention includes a polymer electrolyte fuel cell that generates power using fuel gas and air, a heat exchanger that recovers exhaust heat of the fuel cell, and a heat medium between the fuel cell and the heat exchanger. A heat medium circulation path for circulating the heat medium, a heat medium temperature detector for detecting the temperature of the heat medium, a hot water storage tank for collecting exhaust heat recovered by the heat exchanger, and water below the hot water storage tank as the fuel A hot water circulating path in which the hot water storage tank and the heat exchanger are annularly connected so as to return the hot water to the upper part of the hot water storage tank by using exhaust heat of the battery, and hot water flowing through the hot water storage circulating path A circulating temperature detector for detecting the temperature of the hot water, a bypass path connected to the hot water storage circulation path to bypass the hot water storage tank, and a temperature detected by the circulating temperature detector is equal to or higher than a first predetermined temperature. If the bypass path Switching from passing water to passing through the hot water storage tank, and switching from passing water through the hot water storage tank to passing through the bypass path when the temperature falls below a second predetermined temperature lower than the first predetermined temperature. A switch, a circulator for circulating hot water in the hot water storage circulation path or the bypass path, and an output of the circulator when the temperature detected by the circulation temperature detector is equal to or higher than the first predetermined temperature. And a controller that decreases the first predetermined amount and increases the output of the circulator by a second predetermined amount when the temperature falls below the second predetermined temperature.

That is, when the temperature detected by the circulation temperature detector becomes equal to or higher than the first predetermined temperature and the switch is switched to the hot water storage circulation path from the water passing through the bypass path to the hot water storage tank, the hot water flowing through the circulation path by the circulator The amount of hot water flowing into the heat exchanger is reduced. In addition, when the temperature detected by the circulation temperature detector becomes equal to or lower than the second predetermined temperature and the switching device switches the water flow from the hot water storage tank to the bypass route, the hot water flowing through the circulation route is circulated by the circulator. Increase the amount and increase the amount of hot water flowing into the heat exchanger.

  Thereby, the fluctuation | variation of the calorie | heat amount supplied to a heat exchanger can be suppressed by this, the heat transfer amount in a heat exchanger can be stabilized, and the fluctuation | variation of the temperature of a heat medium can be reduced. As a result, it is possible to realize a fuel cell system in which the power generation state of the fuel cell is stable and stable operation is possible.

  In a second aspect of the invention, particularly in the first aspect of the invention, the controller changes the first predetermined amount and the second predetermined amount according to the amount of power generated by the fuel cell.

  That is, when the water flow is switched by the switch, the output of the circulator is changed by a change amount corresponding to the power generation amount of the fuel cell. As a result, the amount of hot water flowing through the circulation path can be changed, the amount of heat exchanged in the heat exchanger can be stabilized, and fluctuations in the temperature of the heat medium can be reduced, so that the operation of the fuel cell can be stabilized. .

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the same reference numerals are given to the same configurations as those of the conventional examples or the embodiments described above, and detailed description thereof will be omitted. The present invention is not limited to the embodiments.

(Embodiment 1)
The fuel cell system according to Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel cell system according to the present embodiment includes a polymer electrolyte fuel cell 1 that generates power using fuel gas and air, a heat exchanger 2 that recovers exhaust heat from the fuel cell 1, The heat medium circulation path 3 for circulating the heat medium (for example, water) between the fuel cell 1 and the heat exchanger 2, the heat medium temperature detector 4 for detecting the temperature of the heat medium, and the heat exchanger 2 collect the heat medium. The hot water storage tank 5 for storing the exhausted heat and the water in the lower part of the hot water storage tank 5 are converted into hot water using the exhaust heat of the fuel cell 1 and the hot water is returned to the upper part of the hot water storage tank 5 so as to exchange heat. A hot water storage circulation path 6 connected in a ring shape, a circulation temperature detector 11 for detecting the temperature of hot water flowing through the hot water storage circulation path 6, and a bypass connected to the hot water storage circulation path 6 so as to bypass the hot water storage tank 5 Temperature detected by path 7 and circulating temperature detector 11 A switching valve 8 that is a switch for switching between water flow to the bypass path 7 and water flow to the hot water storage tank 5 when the temperature reaches a predetermined temperature, and a circulator that circulates hot water in the hot water storage circulation path 6 or the bypass path 7. A hot water storage pump 9 and a controller 10 that controls the amount of hot water circulating in the hot water storage circulation path 6 or the bypass path 7 by controlling the output of the hot water storage pump 9 based on the temperature detected by the heat medium temperature detector 4. I have.

  In the fuel cell 1, power generation is performed by an electrochemical reaction between a fuel gas such as a hydrogen-containing gas supplied from the fuel gas supply device 30 and an oxidant gas such as air supplied from the oxidant gas supply device 31. Further, since the fuel cell 1 generates heat as power is generated, the fuel cell 1 is cooled by the heat medium circulating through the heat medium circulation path 3 via the fuel cell 1 by the heat medium pump 13. As the heat medium pump 13, a centrifugal pump, a mixed flow pump, a reciprocating pump or the like is mainly used, and as the heat exchanger 2, a plate heat exchanger or a double pipe heat exchanger is mainly used. The heat medium whose temperature has risen due to the recovery of heat in the fuel cell 1 is exchanged with the hot water in the heat exchanger 2 and supplied again to the fuel cell 1 by the heat medium pump 13.

  The hot water storage circulation path 6 is connected to the lower part of the hot water storage tank 5 and the suction port of the hot water storage pump 9 which is a circulator, and the discharge port of the hot water storage pump 9 is connected to the hot water storage water inlet of the heat exchanger 2. Hot water stored at a low temperature is taken out from the lower part of the hot water storage tank 5 and supplied to the heat exchanger 2.

  The circulation temperature detector 11 detects the temperature of the hot water circulation path water from the hot water outlet side of the heat exchanger 2. When the detected temperature is higher than the first predetermined temperature (for example, 43 ° C.), the hot water is returned to the upper part of the hot water storage tank 5, and when the detected temperature is lower than the second predetermined temperature (for example, 40 ° C.), it passes through the bypass path 7. In this way, hot water having a predetermined temperature or higher is stored from the upper part of the hot water storage tank 5 by switching the switching valve 8 which is a switching device. Further, when the tank lower temperature detector 14 reaches a predetermined temperature (for example, 43 ° C.), the power generation of the fuel cell 1 is stopped.

  In this way, by using a stacked boiling system that stores hot water from the upper part of the hot water storage tank 5, hot water having a required temperature is stored from the upper part of the hot water storage tank 5 in a shorter time than when the entire hot water storage tank 5 is heated simultaneously. It is done. A water supply path is connected to the bottom of the hot water storage tank 5, and a hot water path for supplying hot hot water stored in the hot water storage tank 5 to a heat load such as a kitchen, a washroom, and a bath is connected to the top of the hot water storage tank 5. When the hot water stored in the tank 5 is supplied to the heat load and the stored hot water decreases, the hot water stored in the tank 5 is supplied to the bottom of the hot water storage tank 5 from the water supply path.

  The hot water storage pump 9 controls the output by the controller 10 so that the temperature detected by the heat medium temperature detector 4 is constant (for example, 57 ° C.). For example, if the temperature detected by the heat medium temperature detector 4 is higher than a target temperature (for example, 57 ° C.), the amount of water flowing through the hot water storage circulation path 6 is increased by increasing the output of the hot water storage pump 9, and the heat exchanger By controlling the amount of heat exchanged at 2 to be stable, the temperature detected by the heat medium temperature detector 4 is controlled to be the target temperature.

  Further, when the temperature detected by the circulating temperature detector 11 becomes equal to or higher than a first predetermined temperature (for example, 43 ° C. or higher), the controller 10 decreases the output of the hot water storage pump 9 by a first predetermined amount. That is, when the temperature detected by the circulating temperature detector 11 is equal to or higher than the first predetermined temperature, the output of the hot water storage pump 9 is reduced simultaneously with the operation of switching the switch 8. Further, when the temperature detected by the circulating temperature detector 11 becomes equal to or lower than the second predetermined temperature, the controller 10 increases the output of the hot water storage pump 9 by a second predetermined amount. That is, when the temperature detected by the circulating temperature detector 11 becomes equal to or lower than the second predetermined temperature, the output of the hot water storage pump 9 is increased simultaneously with the operation of switching the switch 8.

  The controller may set the first predetermined amount and the second predetermined amount to a constant ratio with respect to the output magnitude before the output change. As a result, the output of the circulator can be changed by a change amount corresponding to the flow rate of the heat medium immediately before the change, the heat exchange amount in the heat exchanger can be stabilized, and the fluctuation of the temperature of the heat medium can be reduced. As a result, the operation of the fuel cell can be stabilized.

  FIG. 2 is a flowchart showing an output determination process procedure of the hot water storage pump 9 in the controller 10. The controller 10 determines whether the temperature detected by the circulating temperature detector 11 is equal to or higher than a first predetermined temperature (for example, 43 ° C.) (step S50). If the temperature detected by the circulating temperature detector 11 is not equal to or higher than the first predetermined temperature, it is next determined whether it is equal to or lower than the second predetermined temperature (for example, 40 ° C.) (step 52). At this time, if the temperature is equal to or higher than the first predetermined temperature, the output of the hot water storage pump 9 is operated with the output decreased by the first predetermined amount (step 51, step 55). Is operated with the output increased by the second predetermined amount (step 52, step 53, step 55).

In step 52, if not below the second predetermined temperature, the circulating temperature detector 11 decreases or increases the first predetermined amount or the second predetermined amount determined by the temperature at the previous detection. For example, the temperature detected by the circulating temperature detector 11 last time is equal to or higher than a first predetermined temperature, and the temperature detected by the circulating temperature detector 11 this time is lower than the first predetermined temperature and higher than the second predetermined temperature. When it is high, the hot water storage pump 9 is operated with an output obtained by reducing the first predetermined amount. By doing so, the hot water storage pump 9 can operate without chattering at the temperature detected by the circulating temperature detector 11, and the flow rate of hot water flowing through the hot water storage circulation path 6 or the bypass path 7 can be stabilized. Heat medium According to the present embodiment, the amount of hot water flowing through the hot water circulation path 6 or the bypass path 7 is changed when the switch 8 switches between water flow to the bypass path 7 and water flow to the hot water storage tank 5. As a result, fluctuations in the amount of heat exchanged in the heat exchanger 2 can be suppressed and temperature fluctuations of the heat medium can be reduced, so that the operation of the fuel cell 1 can be stabilized.

(Embodiment 2)
The fuel cell system according to the second embodiment of the present invention has the same configuration as the fuel cell system of the first embodiment, and is operated in the same manner as in the first embodiment. It is different from Form 1.

  The fuel cell system of the present embodiment is characterized in that when the temperature detected by the circulating temperature detector 11 reaches a predetermined temperature, the output of the hot water storage pump 9 is changed by a predetermined amount based on the power generation amount of the fuel cell. To do. That is, when the temperature detected by the circulating temperature detector 11 is equal to or higher than the first predetermined temperature, the output based on the temperature detected by the heat medium temperature detector 4 is added to the first output based on the power generation amount of the fuel cell 1. When the temperature detected by the circulating temperature detector 11 is equal to or lower than the second predetermined temperature, the hot water storage pump 4 is detected. The hot water storage pump 9 is controlled with an output obtained by increasing the second predetermined amount based on the power generation amount of the fuel cell 1 to the output based on the temperature.

  Normally, the exhaust heat generated by the power generation of the fuel cell 1 increases or decreases with the amount of power generation. By changing the output of the hot water storage pump 9 based on the power generation amount of the fuel cell 1, the hot water storage circulation path 6 or the bypass The amount of hot water flowing through the path 7 can be stabilized earlier.

  According to the present embodiment, the amount of hot water flowing through the hot water storage circulation path 6 or the bypass path 7 is changed to the fuel cell 1 when switching between the water flow to the bypass path 7 and the water flow to the hot water storage tank 5 by the switch 8. Since the variation in the amount of heat exchanged in the heat exchanger 2 can be suppressed and the variation in the temperature of the heat medium can be reduced by changing the amount based on the amount of power generated, the operation of the fuel cell 1 can be stabilized.

  In this embodiment, water is used as the heat medium. However, the present invention is not limited to this. For example, oil or antifreeze may be used. As the antifreeze, for example, ethylene glycol, propylene glycol, and an aqueous solution thereof can be used.

  According to the fuel cell system of the present invention, the amount of heat exchanged by the heat exchanger is changed by changing the amount of hot water flowing through the hot water storage circulation path or the bypass path when switching between the water passing through the bypass path and the water passing through the hot water storage tank. Therefore, the operation of the polymer electrolyte fuel cell can be stabilized.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Heat exchanger 3 Heat medium circulation path 4 Heat medium temperature detector 5 Hot water storage tank 6 Hot water storage circulation path 7 Bypass path 8 Switching valve (switch)
9 Hot water storage pump (circulator)
DESCRIPTION OF SYMBOLS 10 Controller 11 Circulating temperature detector 12 Fuel cell system 13 Heat medium pump 14 Tank lower temperature detector 30 Fuel gas supply 31 Oxidant gas supply

Claims (2)

A polymer electrolyte fuel cell that generates power using fuel gas and air; and
A heat exchanger for recovering exhaust heat of the fuel cell;
A heat medium circulation path for circulating a heat medium between the fuel cell and the heat exchanger;
A heat medium temperature detector for detecting the temperature of the heat medium;
A hot water storage tank for collecting exhaust heat recovered by the heat exchanger;
Hot water circulation in which the hot water storage tank and the heat exchanger are connected in an annular shape so that the water in the lower part of the hot water storage tank is converted into hot water using the exhaust heat of the fuel cell, and the hot water is returned to the upper part of the hot water storage tank. Route,
A circulating temperature detector for detecting the temperature of hot water flowing through the hot water circulation path;
A bypass path connected to the hot water circulation path to bypass the hot water storage tank;
When the temperature detected by the circulating temperature detector becomes equal to or higher than a first predetermined temperature, the water is switched from passing through the bypass path to passing through the hot water storage tank, and the second lower than the first predetermined temperature. A switch for switching from passing water to the hot water storage tank to passing water to the bypass path when the temperature is below a predetermined temperature of
A circulator for circulating hot water in the hot water storage circulation path or the bypass path;
When the temperature detected by the circulating temperature detector is equal to or higher than the first predetermined temperature, the output of the circulator is decreased by a first predetermined amount, and when the temperature is equal to or lower than the second predetermined temperature, the A controller for increasing the output of the circulator by a second predetermined amount;
A fuel cell system comprising:   The fuel cell system according to claim 1, wherein the controller changes the first predetermined amount and the second predetermined amount according to a power generation amount of the fuel cell.