JP2009224293A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which effectively utilizes electric power obtained from the outside. <P>SOLUTION: Outside electric power 92 is distributed to a power storage device and an electrolysis apparatus with an electric power control part. The electric power control part, first, supplies all the outside electric power 92 to the power storage device as charging electric power 94. In the period from the time T0 for starting charge to the time Td, all the outside electric power 92 is supplied to the power storage device as charging electric power 94, to quickly charge the power storage device. When charging of the power storage device is advanced and full charge state is approached, charging electric power 94 starts to decrease. The electric power control part starts the supply of electric power to the electrolysis device from the time Td. In the period, starting from the time Td to the time Tm, the electric power control part supplies only the electric power portion equivalent to decrease of the charging electric power 94 to the electrolysis device. Hence, in the period, starting from the time Td to the time Tm, the maximum electric power (3 kW) of the outside electric power 92 is utilized effectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system having a water electrolysis function.

  2. Description of the Related Art A fuel cell system that generates power using a fuel gas such as hydrogen and an oxidizing gas such as air is known. The fuel cell system is mounted on, for example, a vehicle and used as a power source for a vehicle driving motor. Of course, the fuel cell system can be used other than the vehicle.

  In addition, in a fuel cell system, a system has been proposed in which water is electrolyzed using electric power obtained from outside the system, and hydrogen generated thereby is stored and used as fuel gas for the fuel cell. (See Patent Documents 1 and 2).

JP 2002-98009 A JP 2001-197790 A

  As described above, while there is a technique for storing hydrogen generated by using electric power, a secondary battery that stores electric power in an electrical state is also known.

  Under such circumstances, the inventor of the present application has repeatedly researched and developed a fuel cell system for storing electric power obtained from the outside as hydrogen and storing it in an electrical state. In particular, we focused on the usage of power obtained from outside the fuel cell system.

  The present invention has been made in the course of research and development, and an object of the present invention is to provide a fuel cell system that effectively uses electric power obtained from the outside.

  In order to achieve the above object, a fuel cell system according to a preferred embodiment of the present invention includes a fuel cell that functions as a first power source by generating electricity using hydrogen and oxygen, and is electrically charged by being charged. A rechargeable battery that stores electric power in the battery and functions as a second power source; an electrolysis unit that generates hydrogen used in the fuel cell by electrolyzing water; and external power obtained from the outside. And a control unit that distributes to the electrolysis unit, and the control unit controls a power supply amount to the electrolysis unit based on a state quantity reflecting a state of charge of the rechargeable battery. It is characterized by.

  In a preferred aspect, the control unit increases the power supply amount to the electrolysis unit in accordance with a decrease in the supply amount of charging power distributed to the rechargeable battery.

  In a preferred aspect, the control unit extends the period of maximum use of external power by increasing the power supply amount to the electrolysis unit by a decrease in the supply amount of the charging power. .

  In a preferred aspect, the control unit confirms the supply amount of the charging power from the charge amount of the rechargeable battery.

  According to the present invention, since the amount of power supplied to the electrolysis unit is controlled based on the state quantity reflecting the state of charge of the rechargeable battery, the electric power obtained from the outside is effectively used. For example, according to a preferred aspect of the present invention, the period of maximum use of external power is extended by increasing the power supply amount to the electrolysis unit by a decrease in the supply amount of charging power distributed to the rechargeable battery. And more energy can be stored more rapidly.

  FIG. 1 shows a preferred embodiment of a fuel cell system according to the present invention, and FIG. 1 is a functional block diagram showing the overall configuration thereof.

  The fuel cell system shown in FIG. 1 includes a fuel cell stack 10 that functions as a first power source and a power storage device 20 that functions as a second power source, and supplies power to the motor 40. The motor 40 is, for example, a vehicle travel motor. In this case, the fuel cell system is mounted on the vehicle and used as a power source for the vehicle travel motor. In addition, this fuel cell system may be utilized for apparatuses and systems other than a vehicle.

  The fuel cell stack 10 generates power by reacting a fuel gas containing hydrogen with an oxidizing gas containing oxygen. That is, fuel gas and oxidizing gas are supplied to the fuel cell stack 10, and electric energy is obtained by reacting the fuel gas and oxidizing gas in a plurality of battery cells (not shown) in the fuel cell stack 10. The battery cell is, for example, a substantially rectangular plate-shaped cell, and the fuel cell stack 10 is formed by stacking the plurality of plate-shaped battery cells. Each battery cell may be cylindrical, for example.

  The power storage device 20 functions as a rechargeable battery (secondary battery) that electrically stores power supplied to itself. The electric power stored in the power storage device 20 is supplied to the motor 40 via the power combining unit 30. The power combining unit 30 combines the power obtained from the power storage device 20 and the power obtained from the fuel cell stack 10 or selects the power obtained from either one and supplies it to the motor 40.

  The water electrolyzer 70 generates hydrogen by electrolyzing water. The water used in the water electrolyzer 70 is generated water discharged from the gas discharge port (OUT) of the fuel cell stack 10. The water electrolysis device 70 uses generated water stored in a pipe connecting the fuel cell stack 10 and the water electrolysis device 70. A tank for storing water such as generated water may be provided in the water electrolysis apparatus 70.

  Hydrogen generated in the water electrolyzer 70 is stored in the hydrogen tank 60. Hydrogen stored in the hydrogen tank 60 is supplied to a gas supply port (IN) of the fuel cell stack 10 via a pipe having valves 62 and 64 and used for power generation in the fuel cell stack 10. Note that the hydrogen tank 60 may be omitted, and the piping provided with the valves 62 and 64 may be thickened to store hydrogen in the piping so that the piping functions as the hydrogen tank 60. Moreover, when the pressure of hydrogen in the hydrogen tank 60 becomes a predetermined value or more, the electrolysis process in the water electrolysis apparatus 70 may be controlled to stop.

  The high-pressure tank 50 is a tank for storing hydrogen supplied from the outside of the fuel cell system, and hydrogen (hydrogen gas) is packed inside at a high pressure. Note that hydrogen stored in the hydrogen tank 60 may be stored in the high-pressure tank 50 via the pump 80. Hydrogen stored in the high-pressure tank 50 is supplied to the gas supply port (IN) of the fuel cell stack 10 via a pipe provided with the valve 52 and pipes provided with the valves 62 and 64. Used for power generation.

  In the present embodiment, external power is supplied from the outside of the fuel cell system. Then, using the external power, the water electrolyzer 70 electrolyzes water and stores energy as hydrogen, and the power storage device 20 electrically stores power and stores energy as electricity. For example, external power is supplied from the outside at night or the like, and energy is stored as hydrogen or electricity in the fuel cell system. The external power is distributed to the power storage device 20 and the water electrolysis device 70 by the power control unit 90.

  The power storage device 20 can be charged by receiving a relatively large amount of power. However, when the amount of charge (SOC) of the power storage device 20 increases, for example, when the state of charge reaches a fully charged state, the voltage of the power storage device 20 rises and a large current hardly flows.

  On the other hand, the water electrolyzer 70 cannot supply a large amount of electric power compared to the power storage device 20 due to a chemical change when water is electrolyzed, and rapidly accumulates (hydrogen generation). I can't do it.

  In consideration of the above-described properties of the power storage device 20 and the water electrolysis device 70, the power control unit 90 efficiently distributes external power to the power storage device 20 and the water electrolysis device 70.

  FIG. 2 is a diagram for explaining control by the power control unit 90. Hereinafter, the control by the power control unit 90 will be described with reference to FIG. In addition, about the part (structure) already shown in FIG. 1, the code | symbol of FIG. 1 is utilized also in the following description.

  FIG. 2 shows a graph in which the horizontal axis represents the time axis and the vertical axis represents the magnitude of power. In the graph, the time change of the external power 92 supplied from the outside to the fuel cell system of FIG. 1 is shown by a solid line, and the external power 92 is supplied (distributed) to the power storage device 20. The state of change in the charging power 94 over time is shown by a broken line.

  The external power 92 supplied from the outside is limited to the maximum power according to the specifications of the charging facility that generates the external power 92. In FIG. 2, as an example, the maximum power of the external power 92 is 3 kW. In order to rapidly capture a large amount of power in the fuel cell system, it is desirable to make the maximum power usage period of the external power 92 as long as possible.

  Therefore, in the present embodiment, the power control unit 90 first supplies more power to the power storage device 20 that can be charged by receiving a relatively large amount of power. For example, all of the external power 92 is supplied to the power storage device 20 as charging power 94. In FIG. 2, during the period from the charging start time T0 to the time Td, all of the external power 92 is supplied to the power storage device 20 as the charging power 94, and the power storage device 20 is rapidly charged.

  When the charging of the power storage device 20 progresses and the amount of charge (SOC) of the power storage device 20 increases, for example, when the state approaches a fully charged state, the voltage of the power storage device 20 rises and a large current hardly flows. That is, the charging power 94 starts to decrease. For example, during the period from time Td to time Tf in FIG. 2, the charging power 94 decreases as indicated by a broken line.

  In the present embodiment, the amount of power supplied to the water electrolyzer 70 is increased by a decrease in the charging power 94, thereby extending the period of maximum use of the external power 92. That is, in FIG. 2, the power control unit 90 starts supplying (distributing) power to the water electrolyzer 70 from time Td. The electric power control unit 90 supplies electric power to the water electrolyzer 70 by the decrease of the charging electric power 94 during the period from the time Td to the time Tm. Therefore, the maximum power (3 kW) of the external power 92 is used in the period from time Td to time Tm.

  The power control unit 90 confirms the supply amount of the charging power 94 from the charging amount of the power storage device 20. For example, the magnitude (supply amount) of the charging power 94 is confirmed from the detection value of the charging amount with reference to a table in which the charging amount (SOC) of the power storage device 20 and the magnitude of the charging power 94 are determined in advance. Then, when the charging power 94 starts to decrease from 3 kW, power is supplied to the water electrolyzer 70 by the reduced amount.

  The power control unit 90 may check the magnitude of the charging power 94 using, for example, the output voltage of the power storage device 20, or may determine the charging power 94 based on the time change (differential value) of the charging amount (SOC). May be calculated. Further, the magnitude of the charging power 94 may be confirmed directly by an ammeter or the like.

  The water electrolyzer 70 cannot supply larger electric power than the power storage device 20. In FIG. 2, as an example, the maximum power that can be supplied to the water electrolyzer 70 is 1 kW. Therefore, when charging power 94 further decreases after time Tm, the power supplied to power storage device 20 and water electrolysis device 70 becomes smaller than the maximum power (3 kW) of external power 94. Therefore, in FIG. 2, the external power 92 decreases during the period from time Tm to time Tf.

  When charging of the power storage device 20 is completed at time Tf, the charging power 94 is not supplied, and the external power 92 is only 1 kW of power for the water electrolyzer 70. Furthermore, when the generation of hydrogen is continued in the water electrolyzer 70 and, for example, the pressure of stored hydrogen increases, the power supplied to the water electrolyzer 70 starts to gradually decrease from 1 kW, which is the maximum power. In FIG. 2, in the period after time Tf, the electric power supplied to the water electrolyzer 70 gradually decreases, and the external electric power 92 also gradually decreases from 1 kW.

  As described above, in the present embodiment, the external power 92 is maximized by increasing the power supply amount to the water electrolyzer 70 by the decrease in the supply amount of the charging power 94 supplied to the power storage device 20. The period to do is extended. For example, in FIG. 2, when power is supplied only to the power storage device 20, the period of maximum use of the external power 92 is from time T0 to time Td, whereas in this embodiment, from time T0. It is extended by time Tm. Therefore, in the present embodiment, the external power 92 is effectively used, and a lot of energy can be stored more rapidly.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

1 is a functional block diagram showing an overall configuration of a fuel cell system according to the present invention. It is a figure for demonstrating control by an electric power control part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell stack, 20 Electric power storage apparatus, 30 Electric power synthesis part, 50 High pressure tank, 60 Hydrogen tank, 70 Water electrolysis apparatus, 90 Electric power control part.

Claims (4)

A fuel cell that functions as a first power source by generating electricity using hydrogen and oxygen;
A rechargeable battery that functions as a second power source by electrically storing power by being charged;
An electrolysis unit that generates hydrogen used in the fuel cell by electrolyzing water;
A control unit for distributing external power obtained from the outside to the rechargeable battery and the electrolysis unit;
Have
The control unit controls the amount of power supplied to the electrolysis unit based on a state quantity reflecting a state of charge of the rechargeable battery;
A fuel cell system. The fuel cell system according to claim 1,
The control unit increases a power supply amount to the electrolysis unit according to a decrease in a supply amount of charging power distributed to the rechargeable battery.
A fuel cell system. The fuel cell system according to claim 2, wherein
The control unit extends a period of maximum use of external power by increasing a power supply amount to the electrolysis unit by a decrease in a supply amount of the charging power,
A fuel cell system. The fuel cell system according to claim 3, wherein
The control unit confirms the supply amount of the charging power from the charge amount of the rechargeable battery,
A fuel cell system.

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