JP4638132B2 - Fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell system, and more particularly to a fuel cell system in which durability is improved by switching an operation method according to a power load situation.
[0002]
[Prior art]
As a conventional fuel cell system of this type, the control device of the fuel cell system includes a storage battery, an operation schedule creation unit, and a control unit, and the operation schedule creation unit sets the time zone of the day as three time zones, It is divided into a high electricity bill time zone, an equivalent time zone, and a low electricity bill time zone. In the high electricity bill time zone, the fuel cell generates the amount of power consumed by the power load, and the fuel cell is not consumed in the equivalent time zone. The storage battery is charged with the electric power, and the fuel cell is stopped or operated with the first operating capacity in the low electricity bill period (see, for example, Patent Document 1).
[Patent Document 1]
JP 2002-198079 A (Claim 1, FIG. 1)
[0003]
[Problems to be solved by the invention]
By the way, in order to obtain the introduction effect (running cost reduction), the control device of the fuel cell system having the above structure adopts a method of changing the output following the power load. However, the power load varies greatly from moment to moment. Accordingly, the surrounding environment (temperature, humidity, etc.) of the fuel cell also fluctuates. For example, the fuel cell stack, particularly a polymer electrolyte membrane or MEA (an assembly of an electrolyte membrane and an electrode) due to thermal stress, etc. There was a risk of rapid deterioration.
[0004]
The present invention has been made in view of such problems, and the object of the present invention is to prevent the fuel cell stack from being subjected to large thermal stress, and to improve the durability of the polymer electrolyte membrane and the electrode assembly. An object of the present invention is to provide a fuel cell system that can improve the durability by delaying deterioration of peripheral devices.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a fuel cell system according to the present invention generates electricity and heat in a fuel cell unit, supplies this electricity to a commercial power source and outputs it to an electrical device, and heats the generated heat. a system for outputting to the device, the system is operated by switching the load following operation, a constant power operation operating at a low constant output than the rated output of the fuel cell unit regardless of the power load.
[0006]
With this configuration, the fuel cell system of the present invention does not always perform load following operation, but switches between load following operation and constant output operation according to the load condition at that time, so the load varies greatly. Thus, the fuel cell is frequently switched to a high load operation, so that no great thermal stress is applied to the fuel cell stack of the fuel cell unit, and the durability of the fuel cell stack can be improved. Further, compared with a system that switches between a stopped state and a load following operation, the start-up loss can be reduced, and the durability can be improved because the thermal stress at the time of switching is small.
[0007]
The fuel cell system according to the present invention includes power load measuring means, and performs a constant output operation when the power load measured by the power load measuring means is less than or equal to a predetermined value, and when the power load is greater than a predetermined value. It is characterized by performing load following operation. According to this configuration, when the power load is less than or equal to a predetermined value, a constant output operation is performed to reduce the energy used in the fuel cell unit, and the load following operation is performed only when the power load is greater than the predetermined value. It can be used and heat stress on the fuel cell stack can be reduced.
[0008]
Furthermore, as another preferable specific aspect of the fuel cell system according to the present invention, the system further includes a timer unit, and is characterized in that the load following operation and the constant output operation are switched according to a time zone. According to this configuration, it is possible to reduce the thermal stress on the fuel cell stack or the like by performing a constant output operation at a time when the power load is small such as nighttime and performing a load following operation at a time when the power load is large such as daytime. And durability can be improved. In addition, this can be achieved with a simple configuration.
[0009]
The system further includes a power load measuring unit and a time measuring unit, and normally performs load following operation, and is constant when the power load measured by the power load measuring unit is below a predetermined value for a predetermined time. It is preferable to switch to the output operation and control to return to the load following operation when the state in which the power load is equal to or higher than a predetermined value continues for a predetermined time. With this configuration, the operating state is not switched when the power load fluctuates momentarily or for a short period of time, so it is possible to prevent thermal stress on the fuel cell stack and influence on peripheral devices, and durability is improved. Can be improved.
[0010]
Further, the system further includes a power load measuring unit and a calculation unit thereof, and normally performs load following operation, and integrates the power load for a predetermined time until immediately before being measured by the power load measuring unit and integrated by the calculation unit. It is preferable to control to switch to a constant output operation when the amount or the power load average value is less than or equal to a predetermined value, and to return to the load following operation when the power load integrated amount or the power load average value is greater than a predetermined value during the constant output operation. With this configuration, instantaneous power load fluctuations and short-time power load fluctuations are averaged by the power load integration amount and the power load average value, so that the operation switching is not frequently performed and the fuel cell stack It is possible to prevent thermal stress and influence on peripheral devices, and improve the durability of the system. In addition, energy consumption can be reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a fuel cell cogeneration system according to a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram of a fuel cell cogeneration system according to the present embodiment, and FIG. 2 is a graph showing fluctuations of a daily power load of the system of FIG. 1 and an operation pattern diagram showing its switching state. is there.
[0012]
In FIG. 1, the fuel cell cogeneration system is such that a fuel gas 2 such as city gas is supplied to a fuel cell unit 10, electricity and heat are generated by the fuel cell unit 10, and electricity is supplied to a commercial power source 1 to generate electricity. In this system, the generated heat is output to the heat device 6 such as hot water supply as well as being output to the device 5. The fuel cell unit 10 includes a reformer 11 that reforms fuel, a fuel cell stack 12, an inverter 13, and a heat exchanger 14, which are controlled by a controller 15.
[0013]
The reforming device 11 is a device that obtains hydrogen by reforming the hydrocarbons of the fuel gas 2 by adding water vapor in a high temperature state. The fuel cell stack 12 is a polymer electrolyte fuel cell. Here, direct current electricity generated by reacting hydrogen and oxygen is supplied to an inverter 13, converted into alternating current, and output to the main line 4 of the commercial power source 1. The In addition to the reaction heat recovery of the fuel cell stack 12, the heat exchanger 14 recovers the exhaust heat of the reformer 11, circulates hot water, stores the exhaust heat in the hot water storage tank 16 into which the city water 3 is introduced, It is used as a heat source for the heat equipment 6 such as air conditioning and hot water supply. The main line 4 is connected to an electric load 5 such as various electric devices, and a hot water pipe is connected from the hot water storage tank 16 to a thermal device 6 such as a water heater or floor heating. The fuel gas 2 may be city gas, LPG, natural gas, or the like. Alternatively, an auxiliary heat source 7 may be installed in front of the heat device 6 to heat the hot water when the temperature is low.
[0014]
The control device 15 is composed of a microcomputer or the like, and starts and stops the fuel cell unit 10 in accordance with the usage status of the electric device 5 and the heat device 6, and generates required power and heat. A timer function may be provided. The program timer measures the time of the day and can start the system at a predetermined time and stop the system at another predetermined time, for example.
[0015]
This system further includes a power load measuring means 20 in the main line 4, and this power load measuring means measures a power load used in an electric device 6 used in a house, for example. Then, the control device 15 operates the system by switching between the load following operation and the constant output operation based on the signal output from the power load measuring means 20, and performs the constant output operation when the measured power load is a predetermined value or less. If the power load is greater than a predetermined value, load following operation is performed. The load following operation is performed by changing the output according to the amount of power load used. The constant output operation is an operation with a constant output lower than the rated output of the fuel cell unit 10 regardless of the power load.
[0016]
In the load following operation that follows the electric power load, the operation is performed regardless of the heat load such as hot water supply. Therefore, there is a possibility that the heat efficiency is generated in the warm season when the hot water supply load is small, and the overall efficiency is lowered. The constant output operation is an operation with an output smaller than the rated output of the fuel cell unit 10, and when the power load is increased, the power is supplied from the commercial power source 1 to cope with it. In this system, since intermittent operation (DSS operation or the like) for stopping the fuel cell unit 10 is not performed, there are few disadvantages due to startup loss when starting and stopping the system, and thermal stress applied to the fuel cell stack 12 can be reduced. .
[0017]
The operation of the fuel cell cogeneration system of the present embodiment configured as described above will be described below. The rated output of the fuel cell cogeneration system is 1000 W, and the lower limit output is 200 W. FIG. 2a is a graph in which a daily power load in a general home is plotted every other hour.
[0018]
As shown in FIG. 2a, the power load is from 0 o'clock to 5 o'clock, and the fluctuation thereof is small. From 5 o'clock, the power load increases rapidly, and a time zone with large fluctuation continues until 0 o'clock the next day. Therefore, when the power load measured by the power load measuring means 20 is a predetermined value (for example, 200 W) or less, a constant output operation is performed, and when the power load is larger than the predetermined value (for example, 200 W), a load following operation is performed. Thus, the control device 15 controls the operation of the fuel cell unit 10.
[0019]
As a result, as shown in FIG. 2b, the electric load becomes 200 W or less, the time zone from about 0:30 to about 5 o'clock and the time zone from 14:00 to 15:00 perform constant output operation, and 200 W The load following operation is performed in the time zone from 5:00 to 14:00 and from 15:00 to 0:30. By controlling the operation of the system in this way, it is possible to perform an efficient operation that prevents excessive heat and reduces energy costs and prevents thermal stress on the fuel cell stack 12. In addition, the durability of the fuel cell unit 10 and peripheral devices associated therewith can be improved. The electric power generated by the constant output operation such as at night can be sold, and the heat generated at this time is stored in the hot water tank 16. Further, electric power that cannot be covered by the fuel cell unit 10 is purchased from a commercial power source.
[0020]
In the conventional load following operation, as shown in FIG. 7a, the output greatly fluctuates in accordance with the power load. Therefore, the thermal stress on the fuel cell stack may fluctuate greatly and the durability may be reduced. In this case, as shown in FIG. 2a, since the fuel cell (FC) output can be varied in the range of 200 to 1000 W to reduce thermal stress, durability can be improved. Further, in the conventional DSS operation, the fuel cell unit 10 is stopped during the night time period as shown in FIG. 7b. In this operation, the energy cost at night can be reduced to “0”, so that the cost can be reduced. However, there is a demerit that a heat loss due to starting and stopping and a large starting loss at the time of starting.
[0021]
Next, another embodiment of the present invention will be described in detail with reference to FIGS. FIG. 3 is a system configuration diagram of a second embodiment of the fuel cell cogeneration system according to the present invention, and FIG. 4 is an operation pattern diagram thereof. In addition, the system of this embodiment is characterized by further comprising a timer means for switching the load follow-up operation and the constant output operation depending on the time zone. Other substantially equivalent configurations are denoted by the same reference numerals, and detailed description thereof is omitted.
[0022]
In FIG. 4, the control device 15 is provided with a timer means 21, and the timer means is provided with a program timer function, which measures the time of the day and sends a switching signal to the control device 15 at a predetermined time, for example. The battery unit 10 can be operated to follow the load, and operation switching such as sending a switching signal to the control device 15 at another predetermined time to cause the fuel cell unit 10 to perform a constant output operation can be performed. Of course, it is possible to perform switching many times a day.
[0023]
In this embodiment, as shown in FIG. 4, a constant output operation of 200 W, which is the lower limit output of the fuel cell unit 10, is performed from 1 to 5 o'clock, and a load following operation is performed from 5 o'clock to 1 o'clock the next day. Control is performed by the control device 15 as described above. About this time slot | zone, a user may set arbitrarily and may set based on the measured value of the electric power load measurement means 20 with which the system was equipped. Further, for example, the load follow-up operation is performed from 5:00 am on weekdays, and the load follow-up operation is performed from 7:00 am on holidays. As a result, it is possible to perform an efficient operation while preventing thermal stress on the fuel cell stack 12, and it is possible to improve the durability of the fuel cell unit 10 and peripheral devices associated therewith.
[0024]
Furthermore, another embodiment of the present invention will be described in detail with reference to FIG. FIG. 5 is a system configuration diagram of a third embodiment of the fuel cell cogeneration system according to the present invention. In addition, the system of this embodiment is further provided with a power load measuring means and a time measuring means with respect to the first embodiment described above, and normally performs a load following operation and is measured by the power load measuring means. When the state where the power load is below the predetermined value continues for a predetermined time, the operation is switched to the constant output operation, and when the state where the power load is equal to or higher than the predetermined value continues for a predetermined time in that state, the operation is returned to the load following operation.
[0025]
In FIG. 5, the control device 15 includes a timer means 21 similar to that of the second embodiment as a time measuring means, which can start and stop the fuel cell unit 10 and measure a time interval. is there. That is, the timer unit 21 can measure the state of change of the power load for a time, and has a function of measuring, for example, how long the power load is 200 W or less or 200 W or more.
[0026]
In this embodiment, the timer means 21 switches to a constant output operation when the power load is 200 W or less for 10 minutes, for example, and when the power load is 200 W or more for 10 minutes in that state, the load follow-up is performed. A switching signal is sent to the control device 15 so as to return to operation. When the control for switching the operation is performed in this way, for example, a power load fluctuation of 200 W or less for less than 10 minutes can be ignored, so the switching to the constant output operation is not performed and the thermal stress on the fuel cell stack 12 is prevented. it can. Of course, the measurement time interval can be set arbitrarily. Also in this operation pattern, since the fuel cell unit 10 is not started and stopped, it is possible to prevent thermal stress from being applied to the fuel cell stack 12 and to improve durability.
[0027]
Furthermore, another embodiment of the present invention will be described in detail with reference to FIG. FIG. 6 is a system configuration diagram of a fourth embodiment of the fuel cell cogeneration system according to the present invention. In addition, the system of this embodiment is further provided with a power load measuring means and its calculation means, and normally performs load following operation, and is measured and calculated by the power load measurement means, as compared with the first embodiment described above. When the power load integrated amount or power load average value for a predetermined time until immediately before being integrated by the means is equal to or less than the predetermined value, the operation is switched to the constant output operation, and during the constant output operation, the power load integrated amount or power load average value is more than the predetermined value. When it is larger, it is returned to the load following operation.
[0028]
In FIG. 6, the system includes a calculation unit 22 that integrates the power load measured by the power load measurement unit 20, and the output of the calculation unit 22 is input to the control device 15. The calculation means 22 can calculate the power load integrated amount for a predetermined time until immediately before the calculation, and can calculate the average power load by dividing by the predetermined time. Then, the control device 15 can switch the operation of the fuel cell unit 10 based on the integrated power load amount or the average power load value calculated by the arithmetic device 22.
[0029]
That is, the control device 15 normally performs control so as to perform load following operation, and for example, when the integrated amount of power load for 30 minutes or the average value of power load calculated by the arithmetic device 22 is 200 W or less per hour, for example, a constant output The operation is switched to the operation, and the control is performed so as to return to the load following operation when it becomes larger than 200 W per hour during the constant output operation.
[0030]
For this reason, instantaneous power load reduction and power load reduction for less than 30 minutes are averaged, no signal is output from the arithmetic unit 22, and switching to constant output operation is not performed. The time setting is not limited to 30 minutes and can be set to any time. As described above, the operation is not frequently switched due to a momentary or extremely short time electric power fluctuation, and it is possible to prevent the fuel cell stack 12 from being frequently subjected to thermal stress. And deterioration of a peripheral device can be delayed.
[0031]
Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention described in the claims. Design changes can be made. For example, the fuel cell is an example of a solid polymer fuel cell, but it is of course possible to use a phosphoric acid type, a molten carbonate type, a solid electrolyte type, or the like.
[0032]
Further, the timer means of the second embodiment is not limited to being installed in the control device, but may be outside the control device. The timer means of the third embodiment may be installed between the control device and the power load measuring means. The computing means of the fourth embodiment may be installed so as to be included in the control device. Furthermore, although the fuel cell cogeneration system has been described in each of the above-described embodiments, it is needless to say that the fuel cell cogeneration system may not be used.
[0033]
【The invention's effect】
As can be understood from the above description, the fuel cell system of the present invention can be operated by switching between the load following operation and the constant output operation, so that the thermal stress on the fuel cell stack can be reduced. The durability of peripheral devices can be improved. Further, since the fuel cell unit is not stopped, the start-up loss can be reduced and the energy efficiency can be increased.
[0034]
Furthermore, if the power load measuring means is provided and the constant output operation and the load following operation are switched according to the power load, the energy efficiency can be further improved. Energy efficiency can be increased with a simple configuration by switching the operating state by determining the time zone by the timer means. When the operation state is switched by providing the power load measuring means and the time measuring means, the operation is not switched due to an instantaneous or short-time power load fluctuation, so that the durability can be further improved. Further, if the operation state is switched by providing the power load measuring means and the calculation means, the operation is not switched due to the momentary or short-time power load fluctuation, so that the durability can be further improved.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a first embodiment of a fuel cell cogeneration system according to the present invention.
2A is a graph showing fluctuations of a daily power load of the system of FIG. 1, and FIG. 2B is an operation pattern diagram showing a switching state according to the first embodiment.
FIG. 3 is a system configuration diagram showing a second embodiment of a fuel cell cogeneration system according to the present invention.
4 is an operation pattern diagram showing a switching state according to the second embodiment of FIG. 3;
FIG. 5 is a system configuration diagram showing a third embodiment of a fuel cell cogeneration system according to the present invention.
FIG. 6 is a system configuration diagram showing a fourth embodiment of a fuel cell cogeneration system according to the present invention.
7A is an operation pattern diagram of conventional load following operation, and FIG. 7B is an operation pattern diagram of conventional DSS operation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Fuel gas, 10 ... Fuel cell unit, 12 ... Fuel cell stack, 15 ... Control apparatus, 20 ... Electric power load measurement means, 21 ... Timer means, 22 ... Calculation means

Claims (4)

A fuel cell system that generates electricity and heat in a fuel cell unit, supplies the electricity to a commercial power source, outputs the electricity, and outputs the heat,
The system operates by switching between load following operation and constant output operation that operates at a constant output lower than the rated output of the fuel cell unit regardless of the power load ,
The system includes a power load measuring unit, and performs the constant output operation when the power load measured by the power load measuring unit is a predetermined value or less, and performs the load following operation when the power load is larger than a predetermined value. The fuel cell system characterized by performing .   2. The fuel cell system according to claim 1, wherein the system further includes timer means, and switches between the load following operation and the constant output operation according to a time period.   The system further includes a power load measuring means and a time measuring means, normally performing the load following operation, and when the power load measured by the power load measuring means continues for a predetermined time or less. 2. The fuel cell system according to claim 1, wherein the fuel cell system is switched to a constant output operation, and is returned to the load following operation when the state in which the power load is equal to or higher than a predetermined value continues for a predetermined time.   The system further includes a power load measuring unit and a calculation unit thereof, and normally performs the load following operation, and a power load for a predetermined time until immediately before being measured by the power load measuring unit and integrated by the calculation unit. When the integrated amount or the power load average value is less than or equal to a predetermined value, the operation is switched to the constant output operation, and when the power load integrated amount or the power load average value is larger than the predetermined value during the constant output operation, the load following operation is restored. The fuel cell system according to claim 1, wherein

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