JP2004207133A - Fuel cell system and fuel cell operation method - Google Patents

Abstract

An object of the present invention is to accurately control a supply amount of a gas serving as a fuel or an oxidant, and realize a stable power supply regardless of an outside air temperature.
A pump output calculation unit (5) converts a reference value (S) of a pump output control amount corresponding to a measured value (K) of a load current (I) of a fuel cell into a measured value of an outside air temperature near an intake of an air pump (6). Based on the temperature T), an output control amount P for controlling the air pump 6 is obtained by performing correction in consideration of the influence of a change in the volume of air, and is sent to the air pump 6. The air pump 6 controls the pump output based on the output control amount P to supply air A (oxidant) to the air electrode 11. Thus, the electric power required by the load is supplied stably without being affected by the outside air temperature near the intake of the air pump 6 or the like.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system and a fuel cell operation method.
[0002]
[Prior art]
2. Description of the Related Art In recent years, fuel cells have attracted attention as a power source that has high energy conversion efficiency and does not generate harmful substances due to power generation reactions. As one of such fuel cells, a polymer electrolyte fuel cell that operates at a low temperature of 100 ° C. or less is known.
[0003]
FIG. 3 is an explanatory diagram for explaining the principle of a conventional general polymer electrolyte fuel cell.
[0004]
As shown in FIG. 3, the polymer electrolyte fuel cell has a basic structure in which a polymer electrolyte membrane, which is an electrolyte membrane, is disposed between a fuel electrode and an air electrode. Is a device that generates electricity by the following electrochemical reaction.
[0005]
Fuel ^{_{electrode: H 2 → 2H + + 2e}} - (1)
Air electrode: 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
The fuel electrode and the air electrode have a structure in which a catalyst layer and a gas diffusion layer are stacked. The catalyst layers of the respective electrodes are opposed to each other with the solid polymer film interposed therebetween, and constitute a fuel cell. The catalyst layer is a layer formed by binding carbon particles carrying a catalyst with an ion exchange resin. The gas diffusion layer serves as a passage for oxygen and hydrogen. The power generation reaction proceeds at a so-called three-phase interface between the catalyst, the ion exchange resin, and hydrogen in the catalyst layer.
[0006]
At the fuel electrode, hydrogen contained in the supplied fuel is decomposed into hydrogen ions and electrons as shown in the above formula (1). Among them, hydrogen ions move inside the solid polymer electrolyte membrane toward the oxygen electrode, and electrons move to the oxidant electrode (air electrode) through an external circuit. On the other hand, in the oxidant electrode, oxygen contained in the oxidant (air) supplied to the oxygen electrode (air electrode) reacts with the hydrogen ions and electrons moved from the fuel electrode, and is expressed by the above equation (2). Water is produced. As described above, in the external circuit, the electrons move from the fuel electrode toward the air electrode, so that electric power is extracted.
[0007]
In recent years, cogeneration systems using such a solid polymer electrolyte fuel cell as a household power supply have been developed. Patent Literature 1 describes an example of such a home fuel cell cogeneration system. According to the document, a fuel cell power supply including a solid polymer electrolyte fuel cell is installed outdoors, supplies raw fuel gas such as city gas and generates electric power, and converts DC into AC by an inverter B to convert indoor power to indoor power. A system for supplying power to electrical equipment is described.
[0008]
In such a home fuel cell cogeneration system, the amount of fuel supplied from the reformer is usually controlled by flow rate measuring means capable of measuring the flow rate in terms of mass. Since the supply amount is controlled by measuring the mass-converted flow rate of the supplied fuel, the supply amount can be controlled accurately, and is not affected by the ambient temperature or the like. On the other hand, regarding the control method of the supply amount of the oxidant (that is, air) supplied to the air electrode, conventionally, it is only necessary to control the air supply amount corresponding to the load current of the fuel cell without considering the outside air temperature. I was done.
[0009]
FIG. 4 is a block diagram schematically showing a conventional fuel cell system. The conventional fuel cell system shown in FIG. 4 includes a fuel cell main body 1, a load current measuring section 2 for measuring a current value of a load current I output from the fuel cell main body 1, and a measured value of the load current I ( A reference value setting unit 3 for setting a reference pump output control amount (reference value S) corresponding to the load current measurement value K), and an air pump whose output is controlled based on the reference value S set by the reference value setting unit 3 6 is provided.
[0010]
Inside the fuel cell body 1, an air electrode 11 and a fuel electrode 12 are formed. The path of the load current between the two electrodes correctly takes the same path as the path of the load current shown in FIG. 3, but is schematically shown in FIG.
[0011]
The load current measuring unit 2 measures the current value of the load current I flowing between the air electrode 11 and the fuel electrode 12 (measured load current value K), and sends the measured load current value K to the reference value setting unit 3. I do.
[0012]
The reference value setting unit 3 sets a reference value S of the pump output control amount corresponding to the load current measurement value K. The correspondence between the load current measurement value K and the reference value S can be determined, for example, by setting a table in which the value of the reference value S is recorded in an appropriate section of the load current measurement value K in advance, and as needed. Achieved by reference.
[0013]
The air pump 6 refers to the reference value S as a pump output control amount, supplies the air A (oxidizing agent) to the air electrode 11, and adjusts the supply amount based on the reference value S.
[0014]
[Patent Document 1]
JP-A-2002-216810
[Problems to be solved by the invention]
By the way, in the conventional fuel cell, as described above, the supply amount of the air A supplied to the air electrode 11 shown in FIG. 4 is controlled by controlling the air amount corresponding to the load current I of the fuel cell. Therefore, there is a problem that an error occurs in the required supply amount in terms of mass due to the influence of the outside air temperature such as the air intake port. That is, the volume of supplied air changes depending on the outside air temperature of the air intake port. For example, if there is a temperature difference between 30 ° C. and 0 ° C. in the summer and winter seasons, the volume changes by about 10%. (Volume expansion occurs in summer). Therefore, the amount of oxygen per unit volume is also changed by about 10%. The output of the air pump 6 of the fuel cell, that is, the amount of air supplied to the air electrode 11 corresponding to the measured value K of the load current I is conventionally corrected for the change in the amount of oxygen per unit volume. There was no air volume.
[0016]
The present invention has been made in view of the above-described conventional problems, and has an object to accurately control a supply amount of a gas serving as a fuel or an oxidizing agent and to realize a stable power supply regardless of an outside air temperature. Aim.
[0017]
Another object of the present invention is to make the supply amount of the gas constant irrespective of the outside air temperature and to operate the fuel cell stably under optimum conditions.
[0018]
[Means for Solving the Problems]
According to the present invention, a fuel cell, gas supply means for supplying a fuel or oxidant gas to the fuel cell, outside air temperature measurement means for measuring an outside air temperature, and current for measuring an output current of the fuel cell Measuring means, and the gas supply means is configured to adjust the supply amount of the gas based on an outside air temperature measured by the outside air temperature measuring means and an output current measured by the current measuring means. A fuel cell system is provided.
[0019]
In the fuel cell system according to the aspect of the invention, the gas supply unit may include an output current and data on a relationship between a supply amount of the gas required in accordance with the output current and an output current measured by the current measurement unit. A calculating unit for calculating a gas amount required in accordance with the output current, and a correcting unit for correcting the gas amount in consideration of a volume change due to the outside air temperature measured by the outside air temperature measuring means. , May be included.
[0020]
In the fuel cell system of the present invention, the gas may be air serving as an oxidant, and the gas supply unit may supply the air to an oxidant electrode of the fuel cell.
[0021]
Further, according to the present invention, there is provided a method of operating a fuel cell while controlling an amount of supplying a gas serving as a fuel or an oxidizing agent, the method comprising: measuring an outside air temperature; and measuring an output current of the fuel cell. And a step of supplying the gas to the fuel cell while adjusting a supply amount based on the outside air temperature and the output current.
[0022]
In the method for operating a fuel cell according to the present invention, the step of supplying the gas is performed by measuring the output current and data relating to a relationship between the supply amount of the gas required in accordance with the output current and the current measurement unit. Calculating a gas amount necessary for the output current based on the output current; correcting the gas amount in consideration of a volume change due to the outside air temperature; and Supplying an amount to the fuel cell.
[0023]
In the fuel cell operating method of the present invention, the gas may be air serving as an oxidant, and the air may be supplied to an oxidant electrode of the fuel cell.
[0024]
According to the present invention, since the supply amount of the fuel or the gas serving as the oxidant is corrected in accordance with the fluctuation of the outside air temperature, a stable power supply can be obtained regardless of the outside air temperature. Further, the fuel cell can be stably operated under optimal conditions regardless of the outside air temperature.
[0025]
Further, when the present invention is applied to the supply of air to the air electrode, the oxidant utilization rate of the air electrode can be kept constant, so that the durability of the fuel cell body can be improved.
[0026]
The present invention is particularly effective when applied to a fuel cell system used as a household fuel cell cogeneration system and a method of operating a fuel cell.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the fuel cell system of the present invention will be described in detail with reference to the drawings.
[0028]
FIG. 1 is a block diagram schematically showing a configuration of a fuel cell system according to an embodiment of the present invention. In the figure, the same reference numerals are given to portions overlapping with FIG. 4 (conventional example).
[0029]
In FIG. 1, the fuel cell system according to the present embodiment includes a fuel cell main body 1, a load current measuring unit 2 for measuring a current value of a load current I output from the fuel cell main body 1, and a measurement of the load current I. A reference value setting unit 3 for setting a reference pump output control amount (reference value S) corresponding to the value (load current measurement value K), and an outside air temperature measurement unit 4 for measuring the outside air temperature of the air intake port and the like. A pump output calculation unit 5 for correcting the reference value S set by the reference value setting unit 3 based on the outside air temperature T measured by the outside air temperature measurement unit 4, and an output control amount P corrected for displacement caused by the outside air temperature T. And an air pump 6 whose output is controlled based on the
[0030]
In the fuel cell body 1, a plurality of membrane electrode assemblies each including an air electrode 11 and a fuel electrode 12 are generally integrated (in FIG. 1, one is schematically shown). The path of the load current between the two electrodes correctly takes the same path as the path of the load current shown in FIG. 3, but is schematically shown in FIG.
[0031]
The load current measuring unit 2 measures the current value of the load current I flowing between the air electrode 11 and the fuel electrode 12 (measured load current value K), and sends the measured load current value K to the reference value setting unit 3. I do.
[0032]
The reference value setting unit 3 sets a reference value S of the pump output control amount corresponding to the load current measurement value K. The correspondence between the measured load current value K and the reference value S is set, for example, in advance by setting a table in which the value of the reference value S is recorded in an appropriate section of the measured load current value K, and as needed. Can be achieved. A storage unit may be provided in the reference value setting unit 3, and the table may be stored in this storage unit.
[0033]
The outside air temperature measuring unit 4 measures the outside air temperature near the air intake port of the air pump and sends the measured value (outside air temperature T) to the pump output calculation unit 5.
[0034]
The pump output calculation unit 5 corrects the reference value S set by the reference value setting unit 3 based on the outside air temperature T measured by the outside air temperature measurement unit 4. Hereinafter, the procedure of this correction will be described.
[0035]
FIG. 2 is a graph showing a relationship between a load current of the fuel cell and a pump output corresponding to the load current. FIG. 2A shows a relationship between a load current of the fuel cell and a pump output required to supply a predetermined mass-converted air amount required corresponding to the load current, and FIG. FIG. 2 (c) conceptually shows the relationship between the load current of the fuel cell and the pump output for each season required to obtain an air amount corresponding to the above-mentioned mass-converted predetermined air amount. And the pump output values (p ₁ , p ₂ , p ₃ ) for each required season (winter, spring, summer) corresponding to the current value a obtained from the graph. As shown, the amount of air required to obtain a certain load current varies with the season. This is because the volume of the supplied air changes depending on the outside air temperature.
[0036]
In consideration of such a volume change, the pump output calculation unit 5 corrects the reference value S based on the gas state equation. That is, the outside air temperature when the reference value S is calculated is T _0, and the outside air temperature during fuel cell operation is T ₁ ,
S ′ = S × (T ₁ / T ₀ )
The correction is performed by the following equation. Here, T ₀ and T ₁ are absolute temperatures.
[0037]
As a correction method, another method can be adopted. For example, the relationship between the load current and the required pump output as shown in FIG. 2 is recorded in advance in the pump output calculator 5 for each specific value or range of the outside air temperature T, and the pump output calculator 5 In 5, the output control amount P can be obtained by referring to this record.
[0038]
The air pump 6 refers to the output control amount P as a pump output control amount, adjusts the output, and supplies air A (oxidizing agent) to the air electrode 11.
[0039]
According to this embodiment, the pump output calculation unit 5 determines the reference value S of the pump output control amount corresponding to the measured value K of the load current I of the fuel cell as the outside air temperature near the intake of the air pump 6. The output control amount P for controlling the air pump 6 is sent to the air pump 6 by performing correction based on the measured outside air temperature T. The air pump 6 adjusts the pump output based on the output control amount P to supply air A (oxidant) to the air electrode 11. Thus, the air amount (oxygen amount) capable of generating the electric power required by the load can be stably supplied to the air electrode 11 without being affected by the outside air temperature near the intake of the air pump 6 or the like. it can.
[0040]
As described above, since the pump output value is corrected based on the outside air temperature, a change in the supply air amount due to a change in outside air temperature can be suppressed. As a result, stable operation of the fuel cell system can be performed throughout the year. Further, since the oxidant utilization rate of the air electrode can be kept constant, the durability of the fuel cell body can be improved.
[0041]
The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and that such modifications are also within the scope of the present invention. is there. For example, in the above embodiment, the system is applied to the air electrode side, but may be applied to the fuel electrode side. Further, as a method of correcting the reference value S, various methods other than the above can be adopted.
[0042]
【The invention's effect】
As described above, according to the present invention, the supply amount of the gas serving as the fuel or the oxidant is corrected in accordance with the fluctuation of the outside air temperature, so that a stable power supply can be performed regardless of the outside air temperature. Obtainable. Further, the fuel cell can be stably operated under optimal conditions regardless of the outside air temperature. Specifically, stable operation of the fuel cell system can be performed throughout the year. Further, when the present invention is applied to the supply of air to the air electrode, the oxidant utilization rate of the air electrode can be kept constant, so that the durability of the fuel cell body can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a configuration of a fuel cell system according to an embodiment of the present invention.
FIG. 2 is a graph showing a relationship between a load current of a fuel cell and a pump output corresponding to the load current.
FIG. 3 is an explanatory diagram for explaining the principle of a conventional general polymer electrolyte fuel cell.
FIG. 4 is a block diagram schematically showing a conventional fuel cell system.
[Explanation of symbols]
1 fuel cell main unit, 2 load current measuring unit, 3 reference value setting unit, 4 outside air temperature measuring unit, 5 pump output calculation unit, 6 air pump, 11 air electrode, 12 fuel electrode, A air, I load current, K load Current measurement value, P output control amount, S reference value, T Outside air temperature T.

Claims (6)

A fuel cell, gas supply means for supplying gas to be a fuel or an oxidant to the fuel cell, outside air temperature measurement means for measuring outside air temperature, and current measurement means for measuring an output current of the fuel cell,
The fuel, wherein the gas supply unit is configured to adjust a supply amount of the gas based on an outside air temperature measured by the outside air temperature measurement unit and an output current measured by the current measurement unit. Battery system. The fuel cell system according to claim 1,
Said gas supply means;
Based on the output current and the data on the relationship between the supply amount of the gas required corresponding to the output current and the output current measured by the current measuring means, the gas required corresponding to the output current is determined. A calculation unit for calculating the amount;
A correction unit that corrects the gas amount in consideration of a volume change due to the outside air temperature measured by the outside air temperature measurement unit,
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
The gas is air serving as an oxidizing agent,
The fuel cell system according to claim 1, wherein the gas supply unit supplies the air to an oxidant electrode of the fuel cell. A method of operating a fuel cell while controlling an amount of gas supplied as a fuel or an oxidant,
Measuring the outside air temperature;
Measuring the output current of the fuel cell;
Supplying the gas to the fuel cell while adjusting a supply amount based on the outside air temperature and the output current;
A method for operating a fuel cell, comprising: The method for operating a fuel cell according to claim 4,
Supplying the gas,
Based on the output current and the data on the relationship between the supply amount of the gas required corresponding to the output current and the output current measured by the current measuring means, the gas required corresponding to the output current is determined. Calculating the quantity;
Correcting the gas amount in consideration of a volume change due to the outside air temperature;
Supplying the corrected gas amount to the fuel cell;
A method for operating a fuel cell, comprising: The method for operating a fuel cell according to claim 4 or 5,
The method of operating a fuel cell, wherein the gas is air serving as an oxidant, and the air is supplied to an oxidant electrode of the fuel cell.

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