JP5482108B2 - Fuel cell system and operation method thereof - Google Patents

Description

  The present invention relates to a fuel cell system including a plurality of fuel cell stacks and an operation method thereof.

  A polymer electrolyte fuel cell (hereinafter referred to as “fuel cell stack”) has a structure in which cells called “unit cells” are stacked. In this unit cell, a membrane electrode assembly (hereinafter referred to as “MEA”) in which a polymer electrolyte is sandwiched between a positive electrode (anode) and a negative electrode (cathode) provided with a catalyst layer is sandwiched between separators. It is configured. Electric power is generated by supplying air as an oxidizing agent and fuel as a reducing agent for each unit cell.

  As an example using such a fuel cell stack, there is a so-called direct methanol fuel cell (hereinafter referred to as a direct fuel cell), which directly oxidizes a liquid methanol aqueous solution as fuel and extracts electricity. Can be mentioned. Since the direct fuel cell does not require a reformer or the like, there is an advantage that the system can be configured relatively easily. Therefore, direct fuel cells can be reduced in weight and size, and are currently used in automobiles, distributed power supplies, information electronic devices, etc., and are expected to be used in mobile devices such as mobile phones and laptop computers in the future.

  A fuel cell system that generates power by connecting fuel cell stacks in parallel has been proposed as a proposal for a form of use of the fuel cell stack. For example, in Patent Document 1, a fuel cell system includes a plurality of fuel cell stacks, and means for supplying fuel and an oxidant to each of the plurality of fuel cell stacks, and the fuel cell stack is driven in units of blocks. It is described that it is configured to be able to stop it. If comprised in this way, a some fuel cell stack can be driven efficiently, while suppressing the voltage fluctuation of the whole fuel cell system, it can supply required electric power easily.

  Here, if power generation of the fuel cell stack is stopped for a certain period of time, there is a problem that the fuel cell stack does not start immediately upon restart. The reason for this is that when the temperature of the fuel cell stack decreases, the activity of the chemical reaction in the fuel cell stack, that is, the oxidation-reduction reaction between hydrogen ions and oxygen ions decreases. Further, when power generation of the fuel cell stack is performed under such a condition, the unit cells are also inverted due to temperature variations in the fuel cell stack. Therefore, a fuel cell system has been proposed that can supply power immediately from a fuel cell stack that does not supply power for a certain period of time. For example, Patent Document 2 describes that an idling operation for reducing the fuel concentration or intermittently supplying fuel when there is no external load is described. Further, Patent Document 3 describes that even when power generation by the fuel cell stack is stopped, an intermittent operation mode in which the oxygen supply unit and the hydrogen supply unit are operated based on predetermined conditions is described. .

JP 2001-102074 A JP 2006-147486 A JP 2004-172028 A

  However, the idling operation and intermittent operation of the fuel cell stack do not stop the power generation of the fuel cell stack in the first place, but generate power by supplying air and fuel to the fuel cell stack under certain conditions. However, there is a problem that fuel is consumed even though power is not supplied to the load. For this reason, when power is not supplied from the fuel cell stack to the load for a long time, the fuel consumption efficiency is very poor.

  Further, by reducing the concentration of fuel supplied to the fuel cell stack, the voltage of the fuel cell stack can be lowered, but it takes a certain time for the voltage to drop. Therefore, it has been difficult to adjust the concentration of fuel supplied to the fuel cell stack to suppress voltage fluctuation of the entire fuel cell system due to load fluctuation.

  The present invention has been made in view of the above, and in a liquid supply type fuel cell system in which fuel cell stacks are connected in parallel, voltage fluctuation of the entire system due to load fluctuation is suppressed, and fuel consumption is suppressed and stopped. It is a technical subject to propose a liquid supply type fuel cell system that can immediately restart the fuel cell stack inside.

A first invention is a fuel cell system including a plurality of fuel cell stacks electrically connected in parallel . In the first aspect of the invention, the fuel cell stack is a liquid supply type fuel cell stack in which liquid fuel and an oxidant are reacted to generate electric power, and at least one fuel cell stack is independent of other fuel cell stacks. Then, a switching unit that enables switching between the power generation state / non-power generation state, and a heating unit that increases the temperature of the fuel cell stack in the non-power generation state or prevents temperature decrease . The heating unit includes a supply unit that supplies the fuel cell stack in a power generation state as a heat source and supplies heat from the heat source to the fuel cell stack in a non- power generation state , and the supply unit is discharged from the fuel cell stack in a power generation state. Liquid fuel is supplied to a fuel cell stack in a non-power generation state .

  The power generation state refers to a state where a fuel such as a liquid and an oxidant are supplied to the fuel cell stack. On the other hand, the non-power generation state refers to a state in which supply of at least one of fuel or oxidant to the fuel cell stack is stopped. The temperature of the fuel cell stack in the power generation state is about 65 [° C.] to 70 [° C.]. Here, in the present invention, the temperature of the fuel cell stack refers to the temperature measured by the thermistor for the single cell at the end of the fuel cell stack. The switching unit individually supplies and stops the fuel and the oxidant for each fuel cell stack.

  Any heating means may be used as long as it can supply the heat of the fuel cell stack in the power generation state to the fuel cell stack in the non-power generation state, and various types can be applied. In addition to the heat of the fuel cell stack in the power generation state, other heat sources, heaters, and the like can be used.

  In the first aspect of the invention, the heat in the heat source of the fuel cell stack in the power generation state is supplied to the fuel cell stack in the non-power generation state, so that the temperature in the fuel cell stack in the non-power generation state is higher than when the conventional power generation is stopped. Can be temperature. Therefore, an effect is obtained in that the fuel cell stack in the non-power generation state can be started immediately by simply supplying fuel or oxidant.

The first invention is a fuel cell system for a fuel cell stack, a fuel cell stack of the liquid supply type which generates electricity by reacting a liquid fuel oxidizer. The heating means supplies the liquid fuel discharged from the fuel cell stack in the power generation state to the fuel cell stack in the non-power generation state.

In the first invention, the liquid fuel discharged from the power generation state fuel cell stack and having the same temperature as that during power generation is supplied to the non-power generation state fuel cell stack. The temperature can be higher than that at the time of conventional power generation stoppage. In addition, when liquid fuel is always supplied to a fuel cell stack in a non-power generation state, a shortage of supply of fuel in the fuel cell stack can be resolved when the fuel cell stack generates power. Therefore, an effect is obtained in that the fuel cell stack in the non-power generation state can be started immediately only by supplying an oxidant.

A second aspect of the invention is to be et al., A liquid supply type fuel cell system including a fuel tank for storing the liquid fuel. The heating means stores the liquid fuel discharged from the fuel cell stack in the power generation state once in the fuel tank, and then supplies the liquid fuel to the fuel cell stack in the non-power generation state.

In the second invention, the temperature of the liquid fuel discharged from the fuel cell stack in the power generation state in the fuel tank can be adjusted. Therefore, the effect of the first invention and the effect that the temperature in the fuel cell stack in the non-power generation state can be adjusted to a predetermined value are obtained.

According to a third aspect of the present invention, in the fuel cell system of the second aspect , the heating means stores the liquid fuel discharged from the fuel cell stack in the power generation state in the fuel tank once in the fuel cell stack in the power generation state. It is characterized by supplying.

In the third invention, the temperature and concentration of the liquid fuel discharged from the fuel cell stack in the power generation state in the fuel tank can be adjusted. Therefore, the effects of the first and second aspects of the invention and the effect that the utilization efficiency of the liquid fuel can be increased by recirculating the liquid fuel are obtained. In addition, since the liquid fuel supply path between the fuel cell stack in the power generation state and the fuel cell stack in the non-power generation state can be integrated, the liquid fuel can be efficiently transferred to the fuel cell stack in the power generation state and the fuel cell stack in the non-power generation state. The effect that can be supplied is also obtained.

According to a fourth invention, in the fuel cell system according to any one of the first to third inventions, at least one fuel cell stack can be switched between a power generation state and a non-power generation state independently of the other fuel cell stacks. The switching means is characterized by including an oxidant supply valve for stopping the supply of the oxidant and a control means for controlling opening and closing of the oxidant supply valve.

In the fourth aspect of the invention, the power generation and non-power generation states of the fuel cell stack can be easily switched only by supplying and stopping the oxidant by opening and closing the oxidant supply valve. Therefore, the effects of the first to third aspects of the invention and the effect of easily starting the fuel cell stack in the non-power generation state can be obtained.

According to a fifth aspect of the present invention, there are provided a plurality of fuel cell stacks electrically connected in parallel, and switching that enables at least one fuel cell stack to be switched between a power generation state and a non-power generation state independently of other fuel cell stacks. And a fuel cell system operating method. The fuel cell stack is a liquid supply type fuel cell stack that reacts with liquid fuel and an oxidant to generate electric power, and the switching means switches the at least one fuel cell stack from a power generation state to a non-power generation state. Heat is supplied to the fuel cell stack in the non-power generation state using the fuel cell in the other power generation state as a heat source, and the liquid fuel discharged from the fuel cell stack in the other power generation state is supplied to the fuel cell stack in the non-power generation state and, thereafter, the fuel cell stack of the non-power generation state by the switching means, and switches from the non-power generation state in the power generation state.

  The timing of supplying heat from the heat source of the fuel cell in the power generation state to the fuel cell stack in the non-power generation state and the supply time may be appropriately changed.

In the fifth aspect of the invention, after the fuel cell stack that can be switched between the power generation state and the non-power generation state is switched from the power generation state to the non-power generation state, heat generated from the fuel cell stack in the other power generation state is supplied to the fuel cell stack. By supplying, even if a fuel cell stack becomes a non-power generation state, the temperature in the fuel cell stack can be maintained at a higher temperature than when the conventional power generation is stopped. Therefore, an effect is obtained in that the fuel cell stack in the non-power generation state can be started immediately by simply supplying fuel or oxidant.

  According to the present invention, fuel consumption can be suppressed, and the temperature in the fuel cell stack in the non-power generation state can be made higher than the temperature of the fuel cell stack in which conventional power generation is stopped. In addition, when the fuel passing through the fuel cell stack in the power generation state is supplied to the fuel cell stack in the non-power generation state, it is possible to eliminate a region where the fuel in the fuel cell stack is insufficient during power generation. Therefore, the fuel cell stack in the non-power generation state can be started immediately, and voltage fluctuations in the liquid supply type fuel cell system can be suppressed.

It is the schematic which shows an example of the basic composition of a fuel cell system. It is a schematic block diagram which shows an example of a direct methanol type fuel cell system. It is a schematic block diagram which shows accommodation of the fuel cell stack of a power generation state, and the fuel cell stack of a non-power generation state in the same case. It is a schematic block diagram which shows an example which fixes the fuel cell stack of a power generation state, and the fuel cell stack of a non-power generation state by an end plate. It is a schematic block diagram which shows an example of the fuel cell system which supplies the warm air of a radiator to a fuel cell stack. It is a schematic block diagram which shows an example of a part of fuel cell stack of FIG. It is a figure which shows the image of an example of the fuel cell stack by which fuel piping was wound. It is a schematic block diagram which shows an example which provided the through-hole in the end plate. It is a figure which shows an example of the procedure of the operating method of the fuel cell system which starts a fuel cell stack immediately. It is a graph which shows the result of an example of an experiment. It is a graph which shows the result of a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. However, from the second embodiment to the seventh embodiment, a direct methanol fuel cell system that is a liquid supply type will be described as an example. However, since the effect can be obtained regardless of whether the fuel is liquid or not, in the fuel cell systems from the third embodiment to the seventh embodiment that are not specialized for liquid fuel, other than the liquid supply type It can also be applied to other fuel cells.

(First embodiment)
FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a fuel cell system. In FIG. 1, solid arrows indicate fuel flow, broken arrows indicate oxidant flow, solid lines indicate electric wires, and broken lines indicate signal lines. The fuel cell system 10 includes a fuel cell stack 1 and 2, a fuel pump 4, an oxidant pump 5, an oxidant supply valve 6 and 7, a heating unit 9, a control unit 11, and fuel supply valves 16 and 17. With. The fuel cell stacks 1 and 2 are connected in parallel to a voltage converter 8 that supplies electricity to an external load (not shown) as shown by the solid line in FIG. In FIG. 1, the fuel and oxidant discharge paths of the fuel cell stacks 1 and 2 are omitted.

  The control means 11 includes a central processing unit (CPU), a storage device that stores a program and the like, and a program that controls each device such as the fuel pump 4 and the fuel supply valves 16 and 17. The control means 11 is connected to each device by signal lines, as shown by broken lines in FIG. 1, and operates the fuel pump 4 and the oxidant pump 5, the oxidant supply valves 6 and 7, the fuel supply valve 16 and By controlling the opening / closing of the fuel cell stack 17, the power generation of the fuel cell stacks 1 and 2 and the stop thereof are performed. If the fuel cell system is configured as shown in FIG. 1, the fuel cell stacks 1 and 2 can be switched between the power generation state and the non-power generation state only by opening and closing each supply valve, even if the fuel cell stack 1 is in the non-power generation state. However, if the other fuel cell stack 2 is in the power generation state, electricity can be supplied to the external load via the voltage converter 8.

  When either one of the fuel cell stacks 1 or 2 is in the power generation state, the heating means 9 supplies the heat of the fuel cell stack in the power generation state to the other fuel cell stack. The timing for supplying the heat and the time for supplying the heat can be arbitrarily set. The supply of heat may be started several minutes before the start of the operation of the fuel cell stack in the non-power generation state, or the heat may be supplied constantly. The heating means 9 may be any means as long as it can supply the heat of the fuel cell stack in the power generation state, and may be in any form or method.

The heating means 9 will be described in detail in the second to seventh embodiments described later, and examples thereof include the following (A) to (F).
(A) A configuration in which high-temperature liquid fuel discharged from a fuel cell stack in a power generation state is supplied to a fuel cell stack in a non-power generation state that is a target for temperature increase.
(B) A case for storing the fuel cell stack of both the fuel cell stack in the power generation state and the fuel cell stack in the non-power generation state.
(C) A thermally conductive end plate that contacts both the fuel cell stack in the power generation state and the fuel cell stack in the non-power generation state.
(D) A configuration in which air discharged from a fuel cell stack in a power generation state is connected to a radiator, and warm air heated by the radiator is blown to a fuel cell stack in a non-power generation state to be heated. In particular, it is preferable to provide a through hole for allowing outside air to pass through the separator of the fuel cell stack in a non-power generation state, and to allow hot air heated by a radiator to pass through the through hole.
(E) A configuration in which the fuel pipe after passing through the fuel cell stack in the power generation state is wound around the fuel cell stack to be heated.
(F) A configuration in which high-temperature liquid fuel discharged from a fuel cell stack in a power generation state is brought into contact with a thermally conductive end plate of a fuel cell stack to be heated.

  In any of the above (A) to (F), the heat of the fuel cell stack in one power generation state can be supplied to the other fuel cell stack to warm the other fuel cell stack.

  In the first embodiment, the heat of the fuel cell stack in the power generation state is supplied to the fuel cell stack in the non-power generation state, thereby suppressing a decrease in the temperature of the fuel cell stack in the non-power generation state and maintaining a constant temperature. The fuel cell stack in the non-power generation state can be started immediately.

  In the first embodiment, two fuel cell stacks are described, but the same applies to three or more fuel cell stacks.

(Second Embodiment)
The second embodiment is a direct methanol fuel cell system which is a liquid fuel supply type in which the heating means 9 is the above (A) in the first embodiment. The main configuration of the second embodiment is the same as that of the first embodiment. Hereinafter, the second embodiment will be described in detail.

  FIG. 2 is a schematic configuration diagram showing an example of a direct methanol fuel cell system. 2 indicate the flow of the aqueous alcohol solution, the broken arrow indicates the air flow, the solid line indicates the electric wire, and the broken line indicates the signal line. The fuel cell stacks 1 and 2 in the system 20 are direct methanol fuel cells (DMFC) that generate electricity by directly contacting air as an oxidant and a liquid fuel such as an alcohol aqueous solution as a reducing agent. It consists of The fuel tank 3 that stores the aqueous alcohol solution is connected to the inlet of the fuel pump 4 that sucks and discharges the aqueous alcohol solution through a distribution path such as a pipe. The outlet of the fuel pump 4 is connected to the fuel inlet of the fuel cell stack 1 and the fuel inlet of the fuel cell stack 2 by branching a pipe connected to the outlet. The fuel outlet of the fuel cell stack 1 and the fuel outlet of the fuel cell stack 2 are connected to the fuel tank 3 through a distribution path. Accordingly, the aqueous alcohol solution is branched by the fuel pump 4 from the fuel tank 3 via the fuel pump 4 and then supplied to the fuel cell stack 1 and the fuel cell stack 2. Then, the alcohol aqueous solution is recovered from the outlet to the fuel tank 3 through the fuel flow path in the fuel cell stack. Then, the recovered aqueous alcohol solution is supplied to the fuel cell stack 1 and the fuel cell stack 2 again. In this way, the aqueous alcohol solution circulates between the fuel cell stacks 1 and 2 and the fuel tank 3.

  Since heat is generated when the fuel cell stack generates power, the alcohol aqueous solution passing through the fuel cell stack is warmed. Therefore, by circulating the warmed aqueous alcohol solution to the fuel cell stacks 1 and 2, even when either one of the fuel cell stacks 1 or 2 is not generating power, the fuel cell stack not generating power is not generated. Is maintained at a constant temperature. Further, by supplying the alcohol aqueous solution to the fuel cell stacks 1 and 2 constantly, the shortage of fuel supply in the fuel cell stacks 1 and 2 is solved.

  In FIG. 2, the number of the fuel pumps 4 is one, but a plurality of fuel pumps 4 may be provided in consideration of fuel supply efficiency. For example, the fuel pumps 4 may be provided for each fuel cell stack. In the fuel tank 3, the temperature of the alcohol aqueous solution may be measured and the temperature may be adjusted by a heater or a cooler (not shown). Further, due to the power generation of the fuel cell stacks 1 and 2, the concentration thereof decreases during circulation of the aqueous alcohol solution. Therefore, in the fuel tank 3, the concentration of the alcohol aqueous solution may be adjusted by measuring the concentration of the alcohol aqueous solution and mixing the water and the alcohol aqueous solution having a high concentration.

  The air pump 5 a is connected to the fuel cell stack 1 via the oxidant supply valve 6 and to the fuel cell stack 2 via the oxidant supply valve 7. A plurality of air pumps 5 a may be provided similarly to the fuel pump 4. The oxidant supply valves 6 and 7 open and close to supply and stop air to the fuel cell stacks 1 and 2.

  The output terminals of the fuel cell stacks 1 and 2 are electrically connected in parallel. The output terminals of the fuel cell stacks 1 and 2 are connected to an external load (not shown), auxiliary equipment such as the fuel pump 4 and the air pump 5a, a storage battery (not shown), and the like via the voltage converter 8. Yes.

  The control means 11 operates the air pump 5a and opens / closes the oxidant supply valves 6 and 7 in a state where the aqueous alcohol solution is circulated via the fuel cell stacks 1 and 2. As a result, the fuel cell stacks 1 and 2 can be switched between power generation and stoppage.

  In the second embodiment, an alcohol aqueous solution, which is a liquid fuel discharged from a fuel cell stack that is generating electricity, is circulated, and the alcohol aqueous solution is supplied to a fuel cell stack that is not generating electricity. It is possible to suppress a decrease in the temperature of a fuel cell stack that is not maintained and maintain a constant temperature, and to immediately start the fuel cell stack that is not generating power.

(Third embodiment)
The third embodiment is a direct methanol fuel cell system which is a liquid fuel supply type in which the heating means 9 is the above (B) in the first embodiment. The main configuration of the third embodiment is the same as that of the first embodiment. Hereinafter, the third embodiment will be described in detail.

  FIG. 3 is a schematic configuration diagram showing another example of a direct methanol fuel cell system, and in particular, a schematic configuration showing storage of a fuel cell stack in a power generation state and a fuel cell stack in a non-power generation state in the same case. FIG. In addition, the solid line arrow in FIG. 3 shows the flow of alcohol aqueous solution and water, and the broken line arrow shows the flow of air, respectively.

  In the third embodiment, in addition to the first embodiment, a case 12 for storing the fuel cell stack 1 and the fuel cell stack 2, a fuel tank 3 for storing fuel, and a water tank 13 for storing water are provided. A water pump 14 for supplying water from the water tank 13 to the fuel tank 3, radiators 18 and 19 for cooling the exhaust from the fuel cell stack, and a path such as a pipe connecting them are provided. In the third embodiment, a case 12 is provided in a conventional direct methanol fuel cell system.

  The concentration and temperature of the aqueous alcohol solution stored in the fuel tank 3 are adjusted with the water stored in the water tank 13. Then, the alcohol aqueous solution is supplied to the fuel cell stacks 1 and 2 by the fuel pump 4 with the fuel supply valves 16 and 17 opened, circulated through the fuel cell stack, and returned to the fuel tank 3.

  Further, air is supplied to the fuel cell stacks 1 and 2 by the air pump 5 a with the oxidant supply valves 6 and 7 being opened, and is circulated through the fuel cell stack and sent to the radiators 18 and 19. The air is cooled by the radiators 18 and 19, then sent to the water tank 13, and discharged outside the direct fuel cell system.

  When the fuel cell stack generates power, heat is generated, and the fuel cell stack housed in the same case is warmed by the heat. Therefore, even when either one of the fuel cell stacks 1 or 2 is not generating power, the temperature of the fuel cell stack that is not generating power is maintained at a constant temperature.

  The case 12 is preferably hermetically sealed without providing holes other than the path through which the aqueous alcohol solution or air passes. Further, the case 12 may be configured to cover the entire case with a heat insulating material in order to cut off the temperature of the outside air.

  In the third embodiment, since the inside of the case is warmed by the heat of the fuel cell stack that is generating power, the fuel cell stack that is housed together in the case and not generating power is also warmed, and the fuel that is not generating power The battery stack can be activated immediately.

(Fourth embodiment)

  The fourth embodiment is a direct methanol fuel cell system that is a liquid fuel supply type in which the heating means 9 is the above (C) in the first embodiment. The main configuration of the fourth embodiment is the same as that of the first embodiment. Hereinafter, the fourth embodiment will be described in detail.

  FIG. 4 is a schematic configuration diagram showing an example in which a fuel cell stack in a power generation state and a fuel cell stack in a non-power generation state are fixed by end plates. The fuel cell stacks 1 and 2 are fixed at both ends by two thermally conductive end plates 21. In the fourth embodiment, the end plate 21 shown in FIG. 4 is used in the first embodiment.

  Since heat is generated when the fuel cell stack generates power, the end plate of the fuel cell stack is heated. Therefore, by bringing the end plate of the fuel cell stack that is not generating power into contact with this warmed end plate, even if either one of the fuel cell stacks 1 or 2 is not generating power, the generated power is generated. No fuel cell stack temperature is maintained at a constant temperature.

  In the fourth embodiment, by heating the end plate with the heat of the fuel cell stack that is generating power, the fuel cell stack that is fixed to the end plate and not generating power is also warmed, and the power generation is not performed. The fuel cell stack can be started immediately.

(Fifth embodiment)

  The fifth embodiment is a direct methanol fuel cell system that is a liquid fuel supply type in which the heating means 9 is the above (D) in the first embodiment. The main configuration of the fifth embodiment is the same as that of the first embodiment. Hereinafter, the fifth embodiment will be described in detail.

  FIG. 5 is a schematic configuration diagram illustrating another example of the direct methanol fuel cell system, and is a schematic configuration diagram illustrating an example of a fuel cell system that supplies warm air of a radiator to the fuel cell stack. In addition, the arrow of the broken line in FIG. 5 shows the flow of air.

  In the fifth embodiment, the first embodiment further includes radiators 22 and 23 for cooling the exhaust from the fuel cell stack, and a route such as a pipe connecting them. The radiator 22 is arranged so that the hot air F1 can be blown against the fuel cell stack 1, and the radiator 23 is blown against the fuel cell stack 2 so as to blow hot air F2. The air discharge port of the fuel cell stack 1 is connected to the radiator 23 and the air discharge port of the fuel cell stack 2 is connected to the radiator 22 by piping.

  The air is supplied to the fuel cell stacks 1 and 2 by the air pump 5a with the oxidant supply valves 6 and 7 opened, and the air passing through the fuel cell stack 1 passes through the radiator 23 and the fuel cell stack 2. Air is sent to the radiator 22 respectively. The air is cooled by the radiators 22 and 23, then sent to the water tank 13 and discharged outside the direct fuel cell system. At this time, the radiators 22 and 23 take the heat of the air discharged from the fuel cell stacks 1 and 2 and generate hot air.

  Since heat is generated when the fuel cell stack generates power, the air passing through the fuel cell stack is warmed. Then, by supplying this warmed air to the radiator, warm air is generated from the radiator. Therefore, by blowing this warm air on the fuel cell stack in the non-power generation state, even if either one of the fuel cell stacks 1 or 2 is not generating power, the temperature of the fuel cell stack not generating power is A constant temperature is maintained.

  FIG. 6 is a schematic configuration diagram showing an example of a part of the fuel cell stack of FIG. The fuel cell stacks 1 and 2 are configured by sandwiching the MEA 25 between the separators 24 to form a single cell and stacking the single cells. In FIG. 6, the part which laminated | stacked three single cells is shown. The separator 24 is provided with a plurality of through holes 24a near the center. If it does in this way, warm air can be sent in into each single cell of a fuel cell stack, the heat of the warm air can be efficiently transmitted in a fuel cell stack, and the fuel cell stack can be warmed.

  In the fifth embodiment, the air passing through the fuel cell stack is heated by the heat of the fuel cell stack that is generating power, and the air is used to generate hot air in the radiator, which does not generate power. By spraying the battery stack, the fuel cell stack not generating electricity is also warmed, and the fuel cell stack not generating electricity can be started immediately.

(Sixth embodiment)
The sixth embodiment is a direct methanol fuel cell system that is a liquid fuel supply type in which the heating means 9 is the above (E) in the first embodiment. The main configuration of the sixth embodiment is the same as that of the first embodiment. Hereinafter, the sixth embodiment will be described in detail.

  FIG. 7 is a diagram showing an image of an example of a fuel cell stack around which fuel piping is wound. The fuel cell stack 31 is configured by winding a fuel pipe 32 around the cell stacking direction. The form and method of winding this pipe are not limited to an example of this embodiment, and can be changed as appropriate. In the sixth embodiment, the fuel cell stack shown in FIG. 7 is used in the first embodiment. Specifically, the fuel pipe connected to the fuel discharge port of the fuel cell stack 1 is connected to the fuel cell stack 2, the fuel pipe connected to the fuel discharge port of the fuel cell stack 2 is connected to the fuel cell stack. 1 is wound around each.

  Since heat is generated when the fuel cell stack generates power, the alcohol aqueous solution passing through the fuel cell stack is warmed. Therefore, the temperature of the fuel cell stack that does not generate electricity is fixed by wrapping the pipe through which the heated aqueous alcohol solution circulates around the fuel cell stack that is not generating power and allowing fuel to flow through the pipe. Maintained at temperature.

  In the sixth embodiment, an alcohol aqueous solution that passes through a fuel cell stack that is generating power is circulated through a pipe wound around the fuel cell stack that is not generating power to heat the fuel cell stack. It can be started immediately.

(Seventh embodiment)
The seventh embodiment is a direct methanol fuel cell system which is a liquid fuel supply type in which the heating means 9 is the above (F) in the first embodiment. The main configuration of the seventh embodiment is the same as that of the first embodiment. Hereinafter, the seventh embodiment will be described in detail.

  FIG. 8 is a schematic configuration diagram illustrating an example in which a through hole is provided in an end plate of a fuel cell stack. The fuel cell stack 41 includes a plurality of single cells 42 and two end plates 43 (one not shown). The end plate 43 is provided with a through hole 43a through which an aqueous alcohol solution discharged from the fuel cell stack that is generating electric power is circulated. This through-hole 43a is not limited to an example of this embodiment, and can be changed as appropriate. In the seventh embodiment, the fuel cell stack shown in FIG. 8 is used in the first embodiment. Specifically, the fuel pipe connected to the fuel discharge port of the fuel cell stack 1 is connected to the through hole 43 a of the end plate 43 of the fuel cell stack 2 and the fuel discharge port of the fuel cell stack 2. The fuel pipes are connected to the through holes 43a of the end plate 43 of the fuel cell stack 2, respectively.

  Since heat is generated when the fuel cell stack generates power, the alcohol aqueous solution passing through the fuel cell stack is warmed. Therefore, the temperature of the fuel cell stack not generating electricity is maintained at a constant temperature by bringing the heated aqueous alcohol solution into contact with the end plate of the fuel cell stack not generating electricity.

  In the seventh embodiment, the non-power-generating fuel is obtained by circulating the alcohol aqueous solution passing through the power-generating fuel cell stack through the through holes provided in the end plate of the fuel cell stack that is not generating power. The battery stack can be activated immediately.

(Eighth embodiment)
FIG. 9 is a diagram illustrating an example of the procedure of the operation method of the fuel cell system that immediately starts the fuel cell stack. During power generation of a plurality of fuel cell stacks, first, the target fuel cell stack is changed from the power generation state to the non-power generation state by closing the fuel supply valve and the oxidant supply valve corresponding to the fuel cell stack (step S1). ). Next, the heat of the fuel cell stack in the power generation state is supplied to the fuel cell stack in the non-power generation state (step S2). For example, the fuel passing through the fuel cell stack in the power generation state is supplied to the fuel cell stack in the non-power generation state. The heat supply timing and supply time may be arbitrarily set. When the operation of the fuel cell stack in the non-power generation state is resumed, the fuel supply valve and the oxidant supply valve corresponding to the fuel cell stack in the non-power generation state are opened to change from the non-power generation state to the power generation state (step S3). According to the above steps (Step S1) to (Step S3), the fuel cell stack in the non-power generation state is warmed and maintained at a constant temperature before generating power, so that the fuel cell stack is immediately put into the power generation state. Can supply electricity.

  In the eighth embodiment, a plurality of fuel cell stacks including a fuel cell stack that can be switched between a power generation state and a non-power generation state are in a power generation state, and one fuel cell stack in the power generation state is in a non-power generation state for a long time. When the fuel cell stack is restarted after being turned on, the fuel cell stack in the non-power generation state can be started immediately.

-Experimental example-
In order to evaluate this embodiment, the following <Experimental example 1>, <Comparative example>, and <Experimental example 2> were performed. Here, the temperature of the fuel cell stack is measured by a thermistor for the single cell at the end of the fuel cell stack.

1. Experiment In order to evaluate the output characteristics of the direct methanol fuel cell system of the second embodiment, the following <Experimental example 1> and <Comparative example> were performed. And the relationship between time and the voltage or temperature of the fuel cell stack of a comparison object was confirmed, respectively. The following <Experimental example 1> and <Comparative example> were both carried out at room temperature of about 26 [° C.].
<Experimental example 1>
The following procedures (1) to (3) are performed with the same configuration as that of the second embodiment in FIG.
(1) The fuel cell stacks 1 and 2 connected to the load are supplied with an alcohol aqueous solution as the fuel and air as the oxidant, and the fuel cell stacks 1 and 2 are generated for one minute.
(2) The supply of air to the fuel cell stack 1 is stopped while reducing the load and continuing the supply of the aqueous alcohol solution and air of the fuel cell stack 2. That is, the fuel cell stack 1 stops power generation, and the fuel cell stack 2 continues power generation.
(3) One hour after stopping the power generation of the fuel cell stack 1, the load is increased and the supply of air to the fuel cell stack 1 is resumed.

<Comparative example>
The following is performed in a configuration in which the output terminals of the fuel cell stacks 1 and 2 are connected in parallel, fuel and air are supplied to each of the fuel cell stacks 1 and 2, and the fuel is not circulated. Specifically, in the first embodiment of FIG. 1, the following procedures (1) to (3) are performed with the same configuration as the conventional direct methanol fuel cell system except for the heating means 9. To do.
(1) The fuel cell stacks 1 and 2 connected to the load are supplied with an alcohol aqueous solution as the fuel and air as the oxidant, and the fuel cell stacks 1 and 2 are generated for one minute.
(2) The supply of fuel to the fuel cell stack 1 is stopped while the load is lightened and the fuel and air supply of the fuel cell stack 2 is continued. That is, the fuel cell stack 1 stops power generation, and the fuel cell stack 2 continues power generation.
(3) One hour after stopping the power generation of the fuel cell stack 1, the load is increased and the supply of fuel to the fuel cell stack 1 is resumed.

Further, as confirmation of the activation of the liquid supply type fuel cell system from the second embodiment to the seventh embodiment, the following <Experimental example 2> has a room temperature of about 10 [° C.] and a configuration similar to each embodiment. It carried out in. For comparison, as a conventional example, in the third embodiment of FIG. 3, a case 12 that is provided with anti-freezing means for supplying the air cooled by the radiator to the fuel cell stack in a non-power generation state and is a heating means. The same start-up confirmation was also performed for the direct methanol fuel cell system except for.
<Experimental example 2>
(1) First, only the fuel cell stack 1 is generated for 8 hours. A current of 10 [A] is supplied to the load only from the fuel cell stack 1.
(2) Thereafter, the power generation of the fuel cell stack 1 is stopped, and only the fuel cell stack 2 is generated for 8 hours. A current of 10 [A] is supplied to the load only from the fuel cell stack 2. At this time, except for the conventional example, the heat of the fuel cell stack 2 is supplied to the fuel cell stack 1 by the heating means.
(3) Thereafter, power generation of the fuel cell stack 2 is stopped, and power generation of only the fuel cell stack 1 is performed. At this time, it is confirmed whether or not a current of 10 [A] can be immediately supplied from only the fuel cell stack 1 to the load. Thereby, confirmation of activation is determined.

2. Experimental Results FIG. 10 is a graph showing the results of <Experimental Example 1>. In FIG. 10, the vertical axis represents the voltage [V] of the fuel cell stack 1 and the temperature [° C.] of the fuel cell stack, and the horizontal axis represents time [minute]. From FIG. 10, the temperature T1 of the fuel cell stack 1 is about 70 ° C. during power generation and decreases after the supply of air to the fuel cell stack 1 is stopped, but the temperature at the middle of 60 ° C. is maintained. I understand that. It can also be seen that the voltage V1 of the fuel cell stack 1 is about 21 V during power generation, and is 0 V or less when the supply of air to the fuel cell stack 1 is stopped. Further, when the supply is resumed one hour after the supply of air is stopped, it can be seen that the voltage V1 of the fuel cell stack 1 is immediately about 15V.

  FIG. 11 is a graph showing the results of <Comparative Example>. In FIG. 11, the vertical axis represents the voltage [V] of the fuel cell stack 1 and the temperature [° C.] of the fuel cell stack, and the horizontal axis represents time [minutes]. FIG. 11 shows that the temperature T2 of the fuel cell stack 1 is about 68 ° C. during power generation, and gradually decreases to about 26 ° C. after the supply of fuel to the fuel cell stack 1 is stopped. . Further, it can be seen that the voltage V2 of the fuel cell stack 1 is about 21 V for a while even after the fuel supply is stopped, and gradually decreases. It can be seen that the voltage V2 of the fuel cell stack 1 one hour after the fuel supply is stopped is about 11V. It can also be seen that when the fuel supply is resumed one hour after the fuel supply is stopped, the voltage V2 of the fuel cell stack 1 immediately decreases to about 0V. When the supply of fuel to the fuel cell stack 1 was resumed, several cells of the unit cells constituting the fuel cell stack 1 had a reversal.

Table 1 below shows the results of <Experimental example 2>. However, in the column of whether the fuel cell stack 1 can be activated, ◯ indicates that the fuel cell stack 1 has been activated immediately, and x indicates that the fuel cell stack 1 has not been activated immediately.

  From Table 1, it can be seen that in the direct methanol fuel cell systems from the second embodiment to the seventh embodiment, the fuel cell stack 1 that is not generating electricity can be started immediately after the generation of electricity is stopped for 8 hours. Further, the temperature of the fuel cell stack 1 that is not generating power in the procedure of <Experimental example 2> (2) is from 60 [° C.] to 63 in the second embodiment, the fourth embodiment, and the seventh embodiment. It can be seen that the temperature is maintained at a high [° C.]. On the other hand, the direct methanol fuel cell system of the conventional example cannot be started immediately, and the temperature of the fuel cell stack 1 not generating power in the procedure of <Experimental example 2> (2) is 25 [° C.] It turns out that it has fallen significantly compared with embodiment.

(Summary)
When fuel is circulated in the fuel cell stack and the temperature of the fuel cell stack is close to the temperature at the time of power generation, if air is supplied to the fuel cell stack, the fuel cell stack may cause inversion. However, it was confirmed that power was generated immediately. In Experimental Example 2, it was also confirmed that the fuel cell stack can be started immediately by maintaining the temperature of the fuel cell stack at 46 [° C.] or higher. Therefore, by supplying the heat generated by the fuel cell stack in the power generation state to the fuel cell stack in the non-power generation state, the fuel cell stack in the non-power generation state can be set in an idling state without generating power. Therefore, even when the fuel cell stack is in the non-power generation state for a long time, the fuel cell stack in the non-power generation state can be immediately generated. Preferably, the second embodiment, the fourth embodiment, and the seventh embodiment can maintain the temperature of the fuel cell stack in the non-power generation state high.

  According to the present invention, it is possible to efficiently start and stop a plurality of fuel cell stacks. Therefore, it is expected that the operation efficiency of the liquid supply type fuel cell system including a plurality of fuel cell stacks will be improved, and the fields of use of the fuel cell system will be expanded in various ways. Therefore, expansion of demand is also expected, and industrial applicability is extremely large.

1, 2, 31, 41 Fuel cell stack 3 Fuel tank 4 Fuel pump 5 Oxidant pump 5a Air pump 6, 7 Oxidant supply valve 8 Voltage converter 9 Heating means 10 Fuel cell system 11 Control means 12 Case 13 Water tank 14 Water pump 16, 17 Fuel supply valve 18, 19, 22, 23 Radiator 20 Liquid supply fuel cell system 21, 43 End plate 24 Separator 24a Through hole 25 MEA
32 Fuel piping 43a Through holes F1, F2 Hot air T1, T2 Fuel cell stack temperature V1, V2 Fuel cell stack voltage

Claims (5)

In a fuel cell system comprising a plurality of fuel cell stacks electrically connected in parallel ,
The fuel cell stack is a liquid supply type fuel cell stack that generates electric power by reacting a liquid fuel and an oxidant,
Switching means for enabling at least one fuel cell stack to switch between a power generation state and a non-power generation state independently of other fuel cell stacks;
Heating means for raising the temperature of the fuel cell stack in a non-power generation state or preventing temperature drop ,
The heating means includes
Using the power generation fuel cell stack as a heat source,
Comprising a supply means for supplying heat from the heat source to the fuel cell stack of the non-power generation state,
The fuel cell system, wherein the supply means supplies the liquid fuel discharged from the fuel cell stack in the power generation state to the fuel cell stack in the non-power generation state . A fuel tank for storing liquid fuel;
The heating means, the fuel discharged from the fuel cell stack in the power generation state,
2. The fuel cell system according to claim 1, wherein the fuel cell system is supplied to a fuel cell stack in a non-power generation state after being temporarily stored in the fuel tank . The heating means according to claim 2 comprises:
Also the fuel cell stack of the power generation state, the fuel cell system according to claim 2, wherein the providing of supplying the fuel discharged from the fuel cell stack power generation state after once stored in the fuel tank. The switching means is
The fuel cell system according to any one of claims 1 to 3, wherein the oxidizing agent supply valve for supplying stopping of the oxidizing agent and including control means for controlling the opening and closing of said oxidant supply valve. A plurality of fuel cell stacks electrically connected in parallel;
Switching means for enabling at least one fuel cell stack to switch between a power generation state and a non-power generation state independently of other fuel cell stacks;
A method for operating a fuel cell system comprising:
The fuel cell stack is a liquid supply type fuel cell stack that generates electric power by reacting a liquid fuel and an oxidant,
By the switching means, the at least one fuel cell stack is
After switching from the power generation state to the non-power generation state,
In the fuel cell stack in the non-power generation state,
Supply heat from fuel cells in other power generation states as heat sources,
Supply the liquid fuel discharged from the other fuel cell stack in the power generation state to the fuel cell stack in the non-power generation state,
Thereafter, the non-power generation fuel cell stack is switched by the switching means.
A method for operating a fuel cell system , wherein the non-power generation state is switched to the power generation state .

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