JP2005310429A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which efficient power generation by the energy of exhaust gas is attained while the pressure control of a cathode electrode of the fuel cell is carried out with high precision. <P>SOLUTION: An energy regenerating system 50 has a turbine generator 51 arranged in a cathode off-gas discharge passage 32 and a power generation controller 54 to control a power generation amount of the turbine generator 51. The turbine generator 51 is constituted of a turbine 52 driven by the cathode off-gas and a generator 53 coaxial with the turbine 52. Furthermore, the power generation controller 54 is constituted of a rectifying means and an magnetized current control means, converts alternate current electric power generated by the dynamo 53 into direct current electric power, and increases and decreases an electric load (power generation amount) of the generator 53 based on a direction from a control device 60. The direct current electric power generated by the power generation controller 54 is supplied to an electric compressor or the like of an air supply system 30 from an in-vehicle battery 70 after being stored in the in-vehicle battery 70. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that realizes efficient power generation by the energy of exhaust gas while performing pressure control of a cathode electrode of a fuel cell with high accuracy.

2. Description of the Related Art In recent years, fuel cell electric vehicles (FCEVs) have attracted attention from the standpoint of suppressing carbon dioxide emissions that cause global warming. The fuel cell electric vehicle is equipped with a fuel cell (FC) that generates electricity by electrochemically reacting hydrogen (H ₂ ) and oxygen (O ₂ ) in the air, and uses the fuel cell to generate electricity. A driving force is generated by supplying the traveling motor.

  In the fuel cell system, hydrogen (anode gas) from a high-pressure hydrogen tank is decompressed and then supplied to the anode electrode through the hydrogen supply line, while air (cathode gas) pressurized by an electric compressor is supplied to the air supply line. To be supplied to the cathode electrode. Hydrogen (anode offgas) that has not been consumed by the fuel cell is discharged from the anode electrode as exhaust gas through the anode offgas discharge passage, and air after reaction (cathode offgas) is discharged from the cathode electrode as cathode exhaust gas discharge passage. It is discharged through. Usually, an electric back pressure control valve is provided in the cathode offgas discharge passage, and the back pressure of the cathode electrode is controlled by adjusting the valve opening degree of the back pressure control valve.

Conventionally, the exhaust gas of a fuel cell has been released from the discharge path into the atmosphere via a diluting device or the like. However, the applicant of the present application has added VG ( In the past, a fuel cell system (see Patent Document 1) provided with a variable geometry (turbocapacity) type turbocharger has been proposed. In the fuel cell system of Patent Document 1, anode off-gas and cathode off-gas are combusted by a combustor, a turbine of a turbocharger is rotationally driven by the combustion gas, and cathode gas is compressed by a compressor coaxial with the turbine. Further, in the fuel cell system disclosed in Patent Document 1, the speed of the combustion exhaust gas that collides with the rotor of the turbine by adjusting the opening degree of the vane (capacity variable means) provided in the turbine housing (that is, the rotational speed of the turbine). Changes, and the supply amount of the cathode gas to the fuel cell is controlled. In the fuel cell system of Patent Document 1, the back pressure of the cathode electrode is controlled by opening and closing a pressure regulating valve (back pressure control valve) provided in the cathode offgas discharge passage.
JP 2000-315510 A (paragraphs 0014 and 0016, FIG. 1)

  In the fuel cell system of Patent Document 1, since the turbine and the compressor are coaxial, when the back pressure of the cathode electrode is set to a certain value, the supply amount (discharge amount) of the cathode gas by the compressor is uniquely determined. End up. Therefore, it is necessary to provide a back pressure control valve in the cathode offgas discharge passage as in the conventional device, and the back pressure control valve must be throttled at the time of mass power generation in which the amount of cathode gas required by the fuel cell increases. There was a problem that much of the cathode off-gas energy was discarded. Further, since the VG type turbocharger is an expensive device as compared with a normal turbocharger, there is a problem that the product cost of the fuel cell system becomes high.

  The present invention has been made in view of such a background, and provides a fuel cell system that realizes efficient power generation by the energy of exhaust gas while controlling the pressure of the cathode electrode of the fuel cell with high accuracy. With the goal.

In order to solve the above-described problem, the fuel cell system according to claim 1, wherein a fuel cell that generates electricity by chemically reacting a fuel gas supplied to an anode electrode and an oxidant gas supplied to a cathode electrode; An exhaust gas passage into which exhaust gas discharged from the fuel cell is introduced, and an energy conversion means that is provided in the exhaust gas passage and converts the energy of the exhaust gas into electric energy are provided.
In the fuel cell system according to claim 1, the kinetic energy and combustion energy of the exhaust gas of the fuel cell are converted into electric energy by the energy conversion means, and the electric energy is temporarily stored in, for example, an in-vehicle battery and then supplied for air supply. Supplied to electric compressors.

Further, the fuel cell system according to claim 2 is the fuel cell system according to claim 1, further comprising a back pressure control means for increasing or decreasing an electric load of the energy conversion means in order to control the pressure of the cathode electrode. It is characterized by having.
In the fuel cell system according to the second aspect, for example, the back pressure of the cathode electrode is determined from the target power generation amount or the like, and the back pressure control means increases or decreases the electric load of the energy conversion means so as to obtain this back pressure.

The fuel cell system according to claim 3 is the fuel cell system according to claim 1 or 2, wherein the energy conversion means is a turbine generator.
In the fuel cell system according to the third aspect, the turbine of the turbine generator is driven by the exhaust gas or the combustion gas of the fuel cell, and power is generated by the generator connected to the turbine coaxially or via a speed reducer.

  According to the fuel cell system of the first aspect, the energy conversion means can convert the energy of the exhaust gas into the electric energy regardless of the amount of cathode gas required by the fuel cell. improves. According to the fuel cell system of claim 2, the pressure control accuracy and responsiveness are improved by storing the relationship between the pressure of the cathode electrode and the electric load of the energy conversion means as a map or a calculation formula. be able to. According to the fuel cell system of claim 3, high power generation efficiency can be obtained with a relatively simple device configuration.

Hereinafter, two embodiments in which the present invention is applied to a fuel cell electric vehicle will be described in detail with reference to the drawings.
<< First Embodiment >>
FIG. 1 is a partially transparent side view of a vehicle on which the fuel cell system according to the first embodiment is mounted, and FIG. 2 is a schematic configuration diagram of the fuel cell system according to the first embodiment.

<Vehicle configuration>
First, the vehicle will be described. In the vehicle V shown in FIG. 1, the FC box FCB is mounted under the passenger seat, and the fuel cell 10 (see FIG. 2) is accommodated in the FC box FCB. A traveling motor M is mounted on the front portion of the vehicle V, and a high-pressure hydrogen tank CHT is mounted horizontally above the rear wheels of the vehicle V. Further, the vehicle V has a turbine generator 51 mounted on the rear of the vehicle body.

  The fuel cell 10 generates electricity by electrochemically reacting oxygen in the air and hydrogen supplied from the high-pressure hydrogen tank CHT, and the generated power is supplied to the traveling motor M to drive the vehicle V. Incidentally, the fuel cell 10 here is a solid polymer type PEM type fuel cell, and a membrane electrode structure (MEA) composed of an anode electrode, a cathode electrode, and the like is further sandwiched between separators with an electrolyte interposed therebetween. However, it has a laminated structure in which, for example, about several tens to several hundreds of single cells are laminated (not shown above). Here, PEM is an abbreviation for Proton Exchange Membrane, and MEA is an abbreviation for Membrane Electrode Assembly.

<Configuration of fuel cell system>
Next, the fuel cell system will be described with reference to FIG. The fuel cell system of the first embodiment includes a fuel cell 10, a hydrogen supply system 20, an air supply system 30, a cooling system 40, an energy regeneration system 50, and a control device 60.

  The fuel cell 10 is a PEM type fuel cell having the anode electrode 11, the cathode electrode 12, and the electrolyte 13 as described above. Hydrogen (anode gas), which is a fuel gas, is supplied from the hydrogen supply system 20 to the anode electrode 11. Then, the cathode 12 is supplied with air (cathode gas) as an oxidant gas from the air supply system 30 to generate power. The electric power generated by the fuel cell 10 is supplied to a load such as a traveling motor M (see FIG. 1) or an auxiliary machine.

  The hydrogen supply system 20 supplies hydrogen as an anode gas to the anode electrode 11 of the fuel cell 10, and includes a high-pressure hydrogen tank, a pressure reducing valve, and the like (not shown). The air supply system 30 supplies air as a cathode gas to the fuel cell 10 and includes an air cleaner, a humidifier, an electric compressor, and the like (not shown). The air supply system 30 is provided with a cathode pressure sensor 31 that detects the pressure of the cathode gas. The cooling system 40 releases heat generated by the fuel cell 10 accompanying power generation to the atmosphere, and includes a radiator, a thermostat valve, a water pump, and the like.

  The energy regeneration system 50 includes a turbine generator (energy conversion means) 51 installed in the cathode offgas discharge path 32 and a power generation controller (back pressure control means) 54 that controls the amount of power generated by the turbine generator 51. Yes. The turbine generator 51 includes a turbine 52 driven by a cathode off gas, and a generator (three-phase AC generator) 53 coaxial with the turbine 52. The power generation controller 54 is composed of rectification means and excitation current control means. The power generation controller 54 converts AC power generated by the generator 53 into DC power, and the electric load of the generator 53 based on a command from the control device 60. Increase or decrease (power generation). The DC power generated by the power generation controller 54 is stored in the in-vehicle battery 70 and then supplied from the in-vehicle battery 70 to the electric compressor of the air supply system 30.

<Operation of First Embodiment>
When the fuel cell system is activated, the control device 60 determines the amount of current taken out from the fuel cell 10 based on the depression amount θth of a throttle pedal (not shown) and the power consumption of various devices (lighting device, air conditioner, etc.) The hydrogen supply system 20 and the air supply system 30 are driven and controlled so as to supply the anode gas and the cathode gas corresponding to the extraction current amount to the fuel cell 10. As a result, in the fuel cell 10, a predetermined amount of anode gas and cathode gas are respectively supplied, and electric power is generated as hydrogen moves from the anode electrode 11 to the cathode electrode 12 and is not consumed from the anode electrode 11. Hydrogen is discharged as an anode off gas, and air after reaction is discharged from the cathode electrode 12 as a cathode off gas.

  In the present embodiment, the cathode offgas flows from the cathode electrode 12 into the cathode offgas discharge path 32 and is introduced into the turbine 52 of the turbine generator 51. The turbine 52 is driven by the cathode off gas to rotate, and the generator 53 also rotates together with the turbine 52 to start power generation. The AC power output from the generator 53 is converted into DC by the rectifying means of the power generation controller 54 and then stored in the in-vehicle battery 70.

  After determining the target pressure of the cathode electrode 12 based on the power generation state of the fuel cell 10 and the like, the control device 60 increases and decreases the electrical load (power generation amount) of the turbine generator 51 to obtain this target pressure, and the cathode pressure. Feedback control is performed using the measured pressure value of the cathode gas detected by the sensor 31. Thereby, in the turbine generator 51, the rotational resistance of the turbine 52 coaxial with the generator 53 increases and decreases, and the exhaust resistance (that is, the back pressure) of the cathode off gas that determines the pressure of the cathode electrode 12 changes. Incidentally, in the turbine generator 51, when the amount of power generated by the generator 53 increases, the rotational resistance of the turbine 52 also increases, and the back pressure of the cathode 12 increases. In the present embodiment, the relationship between the pressure of the cathode 12 and the electric load of the turbine generator 51 is stored as a map in the storage means of the control device 60, and the control device 60 determines the electric load with respect to the target pressure. Search from this map.

  In the present embodiment, by adopting such a configuration, the turbine generator 51 can be driven with a relatively large electric load (power generation amount) even during large-scale power generation in which the amount of cathode gas required by the fuel cell 10 increases. The kinetic energy of cathode off gas can be used with high efficiency. Further, since the turbine generator 51 is used in place of the expensive VG type turbocharger, the back pressure control valve becomes unnecessary, and the product cost of the fuel cell system can be reduced. .

<< Second Embodiment >>
FIG. 3 is a schematic configuration diagram of a fuel cell system according to the second embodiment. The fuel cell system of the second embodiment includes a combustor that burns anode off-gas and cathode off-gas, and differs from the first embodiment in that the combustion gas generated by the combustor is introduced into the turbine generator. ing.

  As shown in FIG. 3, in the fuel cell system according to the second embodiment, the energy regeneration system 50 performs combustion in which the anode offgas from the anode offgas discharge passage 21 and the cathode offgas from the cathode offgas discharge passage 32 flow in and burn. The combustion gas generated by the combustor 80 is introduced into the turbine generator 51 via the combustion gas flow path 81.

  Also in the second embodiment, the operation of the fuel cell system is substantially the same as in the first embodiment, but the anode off gas and the cathode off gas are burned in the combustor 80, and the turbine generator 51 is driven by the combustion gas. Therefore, the amount of discharged hydrogen can be reduced, and at the same time, the chemical energy of the anode off gas can be effectively utilized.

  The present invention is not limited to the above embodiment, and can be widely modified. For example, in the above embodiment, a turbine generator having a coaxial turbine and generator is used as the energy conversion means. However, a turbine generator in which a speed reduction mechanism is provided between the turbine and the generator, a reciprocating engine, and a rotary You may make it employ | adopt the generator which uses an engine as a drive side element. In the above-described embodiment, the fuel cell electric vehicle has been described as an example. However, the present invention can be applied to a fuel cell system for a ship or a stationary power generator. Moreover, although the fuel cell system provided with the PEM type fuel cell was taken up in the said embodiment, this invention is a fuel cell system provided with other types of fuel cells, such as an alkaline fuel cell and a phosphoric acid fuel cell. Is also applicable naturally. Further, the layout and the like of each device constituting the fuel cell system can be appropriately changed without departing from the gist of the present invention.

1 is a partially transparent side view of a vehicle on which a fuel cell system according to a first embodiment is mounted. 1 is a block configuration diagram of a fuel cell system according to a first embodiment. FIG. It is a block block diagram of the fuel cell system which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 11 Anode pole 12 Cathode pole 32 Cathode off-gas discharge path 50 Energy regeneration system 51 Turbine generator (energy conversion means)
54 Power generation controller (back pressure control means)
60 Control device 80 Combustor

Claims (3)

A fuel cell that generates electricity by chemically reacting the fuel gas supplied to the anode electrode and the oxidant gas supplied to the cathode electrode;
An exhaust gas passage through which exhaust gas discharged from the fuel cell is introduced;
A fuel cell system comprising: energy conversion means provided in the exhaust gas passage for converting the energy of the exhaust gas into electric energy.   2. The fuel cell system according to claim 1, further comprising back pressure control means for increasing or decreasing an electric load of the energy conversion means in order to control the back pressure of the cathode electrode.   The fuel cell system according to claim 1 or 2, wherein the energy conversion means is a turbine generator.

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