JPH0325861A - Operation of hybrid fuel cell - Google Patents

Abstract

PURPOSE:To prevent the overcharge of a storage battery without use of an automatic voltage controller by comparing the terminal voltage of a storage battery with allowable upper limit voltage which is previously set and controlling at least one of hydrogen supply amount and air supply amount to a fuel cell to maintain the terminal voltage to the allowable upper limit voltage or lower. CONSTITUTION:In operation of a hybrid fuel cell, the terminal voltage of a storage battery 3 detected with a voltage sensor 27 is compared with the upper limit voltage V set in a memory in a computing unit of a controller 32. When the terminal voltage exceeds the upper limit voltage, a revolution number decrease signal based on voltage difference is outputted to a fuel pump 13 and/or a blower 22 and supply amount of hydrogen and/or air to a fuel cell 2 is controlled. Output of the fuel cell 2 is decreased and the terminal voltage of the storage battery 3 is maintained so as to come near the upper limit voltage. Overcharge is prevented and charging efficiency is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of operating a hybrid fuel cell equipped with a storage battery, and more particularly to a method of operating a hybrid fuel cell that prevents overcharging of the storage battery.

[Prior art]

A fuel cell is a device that generates water and electricity by reacting hydrogen and air (oxygen). When such a fuel cell is connected to a load and operated, there are some that are equipped with a storage battery as an auxiliary power source during startup, etc., and the storage battery can be charged by the fuel cell. In such a hybrid fuel cell equipped with a storage battery, overcharging of the storage battery will shorten the life of the storage battery, so it is necessary to protect the battery from overcharging. Vehicles equipped with a magneto as a power source for power generation, such as automobiles, are generally equipped with an automatic voltage regulator to prevent overcharging of storage batteries serving as auxiliary power sources. However, as is well known, this automatic voltage regulator has the drawbacks of being large-sized and having large electrical losses.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for operating a hybrid fuel cell that makes it possible to prevent overcharging of a storage battery without increasing the size of the device or using an automatic voltage regulator that causes electrical loss. [Means for Solving the Problems] The present invention, which achieves the above object, provides a hybrid system in which a storage battery is attached to a fuel cell that generates electricity by reacting hydrogen and air, and the storage battery can be charged by the fuel cell. During operation of the fuel cell, detecting the terminal voltage of the storage battery, comparing the detected terminal voltage with a preset allowable upper limit voltage to adjust at least one of the hydrogen supply amount and the air supply amount to the fuel cell, The present invention is characterized in that the terminal voltage is maintained close to or below the allowable upper limit voltage. Hereinafter, the operating method of the present invention will be explained with reference to the embodiments shown in the figures.

FIG. 1 schematically shows a hybrid fuel cell in which the operating method of the present invention is implemented.

1 is a reformer that generates hydrogen; 2 is a fuel cell that generates electricity by reacting hydrogen with air; 3 is a storage battery that is attached to the fuel cell 2 so that it can be charged; 4 is a system that combines the fuel cell 2 and the storage battery 3. This is the load connected to both batteries. The reformer 1 has an evaporator 5 for vaporizing liquid raw material and a reaction layer 6 for reacting the vaporized raw material gas, and below the evaporator 5 there are two types of burners 7m for heating. It has 7h. In this embodiment, in addition to the burner 7m that uses methanol as fuel, a burner 7h that uses excess hydrogen as fuel is provided, but of course it is also possible to use only 111!1. In addition, a blower 1 is installed at the bottom of the reactor to supply air.
1 is connected. 8 is a fuel tank that stores fuel for combustion (methanol). Fuel is supplied from this fuel tank 8 to the burner 7■ via a valve 10 by a supply bomb 9, and the blower 1
It is combusted by the air supplied from 1 and becomes heated gas. The heated gas heats the evaporator 5 and the reaction layer 6.

On the other hand, 12 is a raw material tank that stores a liquid raw material for reaction (mixture of methanol and water).

The liquid raw material is supplied to the evaporator 5 by the supply bomb 13 via the valve 14, and after being vaporized in the evaporator 5, it is transferred to the reaction layer 6.
It reacts and is converted into a hydrogen-based reformed gas.

The hydrogen-based reformed gas recovered in the reaction layer 6 is fed to the supply pipe 15.
The fuel is supplied to the fuel cell 2 via the storage tank 16 and valve 17. The storage tank 16 temporarily stores the reformed gas and supplies a predetermined amount to the fuel cell 2 . Excess reformed gas is returned to the burner 7h via the relief valve 18 and/or the bypass valve 19, and is consumed for combustion. Also,
Excess hydrogen gas exhausted unreacted by the fuel cell 2 is also supplied to this burner 7h via a reclaimer 20 and a valve 2l. In the fuel cell 2, air to be reacted with the hydrogen is supplied from a blower 22 via a valve 23. A four-way valve 24 is connected to the upstream side of the blower 22 so that either low-temperature air in the atmosphere or high-temperature air from the reformer 1 is appropriately selected and introduced. Excess air that is not used in the reaction in the fuel cell 2 is discharged to the outside air via the valve 25. The fuel cell 2 is connected to supply generated power to an external load 4, and a storage battery 3 is connected in parallel as an auxiliary power source for charging the storage battery 3.
Furthermore, a system auxiliary device 26 is connected to the fuel cell 2 and the storage battery 3. The auxiliary equipment 26 is not limited to the case where a special device is provided as shown in the figure, but may also be a drive unit for an internal load such as a bomb 9 or a valve 10 provided within the system. 30 is a manual load switch that turns on and off the current to the load 4, and 31 is a protection switch that turns on and off the charging current to the storage battery 3. Furthermore, the above electric circuit includes a current sensor 28 for detecting the output current I of the fuel cell 2, and a terminal voltage (I) of the storage battery 3.
, a voltage sensor 27 that detects charging current I, a current sensor 29 that also detects charging current I, and the like are connected.

32 is a micro ? This is a control unit consisting of a computer, and outputs a rotation speed control signal to the liquid raw material supply pump 13 and the blower 22. This control section 32 controls other bombs 9 in addition to those mentioned above.
, blower 11, valve 10.14.17.19.21,
Control signals are output to 23, 24, 25, switch 31, etc. The control unit 32 also receives detection signals of the terminal voltage of the storage battery, charging current, and output current of the fuel cell from the voltage sensor 27 and current sensor 29.28, and the reaction layer temperature and temperature from the temperature sensors 41.42 and 43.44. Detection signals such as burner temperature, fuel cell reaction temperature, and ambient temperature are input. In the control unit 32 of the hybrid fuel cell, an upper limit voltage V l/+sax that allows charging of the storage battery 3 is preset in its storage unit. This upper limit voltage Vl/■8 is the value before the gassing phenomenon that occurs at the end of charging (approximately 7
For example, in the case of a normal lead-acid battery, the voltage is 2.5 volts per single cell. The position will be chosen. In operation of such a hybrid fuel cell, the terminal voltage V of the storage battery 3 detected by the voltage sensor 27 is compared with the upper limit voltage Vm/wax set in the storage section in the calculation section of the control section 32, and the terminal voltage vl is the upper limit voltage v
．． 7. When exceeds (2), a signal is output to the fuel pump 13 and/or the blower 22 to reduce the rotational speed based on the differential pressure, and the amount of hydrogen and/or air supplied to the fuel cell 2 is adjusted. Through such adjustment, the output of the fuel cell 2 decreases, and the terminal voltage vl of the storage battery 3 is lowered to the upper limit voltage Vl/
■Maintain it near 8. Therefore, overcharging is prevented and charging efficiency is improved. In addition, there is no water loss due to gassing, and the amount of water replenishment is small, making maintenance easier. FIGS. 2A and 2B show overcharge prevention control when the above-described hybrid fuel cell is operated while the load switch 30 is turned on and off. Figure 2 A is the output current of the fuel cell! .

? Output voltage■. 2B shows the relationship between the charging current L of the storage battery and the terminal voltage Vm corresponding to the output of the fuel cell. As shown in FIG. 2B, as charging from the fuel cell 2 progresses, the terminal voltage V of the storage battery 3,
As the amount of charge increases, the charging current! ．． gradually decreases. The terminal voltage Vl is the upper limit voltage Vl/
When @■ is reached, hydrogen and/or
Alternatively, the output of the fuel cell may be reduced by reducing the amount of air supplied, and the charging current I. The terminal voltage vl is maintained near the upper limit voltage while gradually decreasing the voltage. On the other hand, the second
As shown in Figure A, the output current of the fuel cell! . and the output voltage VC are the charging current of the storage battery mentioned above, and the terminal voltage V. The terminal voltage VI changes almost in proportion to the change in the upper limit voltage V. /． ■When the output voltage VC reaches the upper limit voltage VC/+
The output current ■ maintains the vicinity of m■. decrease.

Note that the output voltage V of the fuel cell and the terminal voltage V of the storage battery.
Is there a potential drop between the diode and the diode? Let v0 be,
There is a relationship between Vc-V, +V, and cD. Depending on the characteristics of the diode, VD is approximately 0.6-0.7 volts. Therefore, the terminal voltage of the storage battery V. By checking , you can control the output voltage of the fuel cell. Also,
When stopping the operation of the above hybrid fuel cell, it can be done as follows. First, load switch 3
0 is turned off, the above charging operation continues, and when the terminal voltage V of the storage battery 3 reaches the upper limit voltage Vl/■8, the upper limit voltage Vl/■ is increased while decreasing the amount of hydrogen and/or air supplied to the fuel cell. Maintain 8. And charging current ■. When the charging current decreases to the preset minimum charging current Il/sin, the following termination process is executed. When performing this termination process, the fuel cell 2 is cut off from the external load 4, but is connected to the storage battery 3 and the auxiliary equipment 26. In this state, first the supply of hydrogen to the fuel cell 2 is stopped, but the reaction air continues to be supplied to generate electricity. This further reduces the hydrogen partial pressure. Then, the supply of air is stopped after the output current value becomes equal to or less than a predetermined value. By continuously supplying only air in this manner, water vapor generated at the cathode can be carried out of the system.

Further, since the storage battery 3, the auxiliary equipment 26, etc. remain connected, the catalyst does not deteriorate due to the fuel cell 2 having an open potential. When the supply of hydrogen and air is stopped, the hydrogen and air supply valves and exhaust valves are closed to cut off contact with the outside air, and the products are then stored to cool naturally.

Furthermore, in the operation of the hybrid fuel cell according to the present invention,
As mentioned above, the terminal voltage V. of the storage battery. is the upper limit voltage Vl/■
8, when the terminal voltage Vl is maintained near the upper voltage while reducing the flow rate of hydrogen and/or air to the fuel cell, the current sensor 29 detects the charging voltage. Current II
is detected, and when the charging current I3 decreases to a predetermined value, the output current Ic of the fuel cell is supplemented? It is also possible to control the output to 26. In this control, the charging current (2) of the storage battery is controlled to 0 or less than 0 (discharge). That is, when the current to the auxiliary equipment is IA,
It is controlled to have a relationship of Ie=In+Ig, 1g≦0.

When the output current of the fuel cell is supplied to the auxiliary equipment as described above, the charging current I of the storage battery is set to O or O.
The charging current I detected by the current sensor 29 is controlled to be as follows. This may be done using a signal.

In addition, in the above operation, the terminal voltage V, is the upper limit voltage V.
/． When reaching ■, the protection switch 3l is turned off and the amount of hydrogen and/or air supplied to the fuel cell is reduced to bring the output current I of the fuel cell to the level required for the auxiliary equipment 26. It may be supplied as follows.

In the case of such control, no output current is supplied to the supplementary cell 26, and the flow rate of hydrogen and/or air is reduced, and finally the fuel cell 4. Control may also be used to stop the . [Effects of the Invention] As described above, in the method of operating a hybrid fuel cell according to the present invention, the terminal voltage of the storage battery is detected, and the detected terminal voltage is compared with a preset allowable upper limit voltage to determine the hydrogen supply to the fuel cell. Since the terminal voltage is maintained near or below the allowable upper limit voltage by adjusting at least one of the air supply amount and the air supply amount, it is no longer necessary to use a conventional automatic voltage regulator that is large and has a large electrical loss. Therefore, overcharging of the storage battery can be prevented. Furthermore, since charging is performed while maintaining the voltage close to the allowable upper limit voltage, charging efficiency can be improved, and maintenance is facilitated because the amount of water replenishment is reduced.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a hybrid fuel cell that implements the operating method of the present invention, and Fig. 2 A shows the output current of the fuel cell! , and the output voltage V, FIG. 2B shows the charging current of the M battery corresponding to the output of the fuel cell. FIG. 3 is a diagram showing the relationship between DESCRIPTION OF SYMBOLS 1... Reformer, 2... Fuel cell, 3... Storage battery, 4... Load, 13... (Liquid raw material) supply pump, 22... (Air) blower, 27 . . . Voltage sensor, 32 . . . Control unit.

Claims (1)

[Claims] In operation of a hybrid fuel cell in which a storage battery is attached to a fuel cell that generates electricity by reacting hydrogen and air, and the storage battery can be charged by the fuel cell, a terminal voltage of the storage battery is detected, and the terminal voltage of the detected terminal is A hybrid fuel cell wherein at least one of hydrogen supply amount and air supply amount to the fuel cell is adjusted by comparing the voltage with a preset allowable upper limit voltage, and the terminal voltage is maintained near or below the allowable upper limit voltage. how to drive.