KR100988815B1 - Operating method in fuel cell system - Google Patents

Abstract

The present invention relates to a method of operating a system of a fuel cell including a fuel cell stack and a hydrogen supply control device, the first step of measuring a change in hydrogen pressure of a fuel cell stack due to external load fluctuations, the measured pressure value Is coupled to a fuel cell stack by providing a fuel cell operating method comprising a second step of comparing the pressure with a reference section pressure and a third step of turning on and off the hydrogen supply device according to the comparison result. By responding quickly to changes in the dynamic load, the life cycle of the fuel cell stack can be prevented and the overall safety can be improved. In addition, it is unnecessary to recover the hydrogen discharged from the fuel cell, and it is possible to efficiently use the hydrogen.

Hydrogen supply line on / off, relationship between load and output duration, hydrogen supply

Description

Operating method in fuel cell system

The present invention relates to a method of operating a fuel cell system, and more particularly, it is possible to effectively cope with dynamic loads by supplying hydrogen on the anode side of the fuel cell stack according to the output of the fuel cell when the required output is changed by the dynamic load. The present invention relates to a hydrogen supply control technique of a fuel cell system which enables efficient use of hydrogen and stability as the amount of hydrogen in the line is appropriate.

In general, a fuel cell is a power generation system that directly converts fuel energy into electrical energy, and has advantages of low pollution and high efficiency.

In particular, fuel cells are attracting attention as next-generation energy sources because they can generate electrical energy using energy sources such as petroleum energy, natural gas, and methanol, which are easy to store and transport.

These fuel cells are classified into phosphoric acid type, molten carbonate type, solid oxide type, polymer electrolyte type, and alkaline type fuel cell according to the type of electrolyte used, and each of these fuel cells basically operates on the same principle. However, the type of fuel used, the driving behavior, the catalyst and the electrolyte are different.

The polymer electrolyte fuel cell is a fuel cell that uses a polymer membrane having hydrogen ion exchange characteristics as an electrolyte, and has a high output characteristic with a higher current density than other types of fuel cells. In addition, since methanol and natural gas can be used as fuel in addition to hydrogen, it is suitable for various fields such as automobile power source, distributed on-site generator, military emergency power source and spacecraft power source.

1 is a view for explaining a fuel cell stack using a general polymer membrane as an electrolyte.

As shown in FIG. 1, the fuel cell stack basically includes a polymer electrolyte membrane and an anode electrode and a cathode electrode bonded to both surfaces of the electrolyte membrane. The electrolyte membrane, anode electrode and cathode electrode constitute a unit cell called a membrane-electrode assembly (MEA).

In order to improve performance on electrochemical reactivity, ion conductivity, electron conductivity, fuel or oxidant transfer, by-product transfer, interfacial stability, etc., the anode electrode and the cathode electrode preferably include a platinum catalyst layer and a diffusion layer, respectively.

In addition, the fuel cell stack includes a bipolar plate installed between the unit cells and a monopolar plate installed between one side of the unit cell and the end plate.

These plates have electrical insulation properties and one or both of them are provided with flow passages for fuel supply.

The stack of unit cells and plates is fixed while being pressed by a pair of end plates and fastening members.

The operating principle of the fuel cell stack described above is as follows.

First, when hydrogen is supplied to the anode electrode and oxygen or oxygen-containing air is supplied to the cathode electrode, the supplied hydrogen on the anode side is called electrons and hydrogen ions in the platinum catalyst layer so that the electrons move along the outer conductor and the hydrogen After the ions move through the electrolyte membrane, oxygen, electrons and hydrogen ions meet on the cathode side to generate water. At this time, electrical energy is obtained by electrons moving through an external circuit.

Referring to FIG. 1, a fuel cell stack is a portion in which electricity is generated, and a hydrogen supply control device is a device for controlling hydrogen supplied from a hydrogen storage tank to a fuel cell stack.

In a fuel cell system, the output can vary with external loads, so the hydrogen and oxygen consumption in the fuel cell stack also varies.

Oxygen supplied is important for fuel cell output, but it is possible to supply a sufficient amount through air pumps and other devices, but in the case of hydrogen, efficient use is needed due to the limitation of the storage tank.

The hydrogen supply control device is a control device for supplying the required amount of hydrogen according to the consumption of hydrogen according to the changing load.

On the other hand, if the amount of hydrogen supplied is less than the amount of hydrogen used, deterioration of fuel cell performance may occur due to fuel shortage, which may cause durability problems. Therefore, a plan for supplying sufficient hydrogen before deterioration occurs must be prepared. do. On the contrary, when the amount of hydrogen supplied is larger than the amount of hydrogen used, the pressure difference with the oxygen side occurs due to the increase in pressure on the hydrogen side, which may result in a decrease in performance.

The technical problem to be achieved by the present invention is to improve the above-described problems of the prior art, and to provide a method for supplying an appropriate level of hydrogen required by a fuel cell when an external load is changed.

In order to achieve the above object, the present invention provides a fuel cell stack and a method of operating a fuel cell system including a hydrogen supply control device, the interior of the fuel cell stack for generating electrical energy by the electrochemical reaction of hydrogen and oxygen A pressure measuring device for monitoring the hydrogen pressure and measuring the pressure of the hydrogen inside the fuel cell is connected to the hydrogen side outlet of the fuel cell stack, comparing the measured pressure value with the reference section pressure, and turning on the hydrogen supply device (ON). Inputting to a central controller which transmits / OFF signals; Analyzing the hydrogen pressure data to extract the amount of hydrogen supplied based on the size and distribution of the hydrogen pressure data; In the pressure change according to the difference between the amount of hydrogen supplied and the amount of hydrogen used, when the pressure falls below the minimum reference pressure within the set period, the hydrogen supply device is turned on to start the hydrogen supply, and the pressure is higher than the maximum reference pressure. When up, it is characterized in that it comprises a hydrogen supply control step of shutting off the hydrogen supply by turning off the hydrogen supply device (OFF).

According to the present invention, when the required output is changed by the dynamic load, the anode side of the fuel cell stack is supplied with the output of the fuel cell according to the output of the fuel cell to effectively cope with the dynamic load, and the efficient use of hydrogen and the amount of hydrogen in the line This titration can have a wide range of advantages, such as stability.

Hereinafter, in accordance with an embodiment of the present invention based on the accompanying example drawings will be described in detail.

2 is a control flowchart illustrating a method of operating a fuel cell system according to an exemplary embodiment, and FIG. 3 is a block diagram showing a fuel cell configuration according to an embodiment of the present invention.

As illustrated in the drawings, according to an embodiment of the present invention, a method of operating a fuel cell system including a fuel cell stack and a hydrogen supply control device generates electric energy by an electrochemical reaction between hydrogen and oxygen. The internal hydrogen pressure of the fuel cell stack is monitored, and a pressure measuring device (P) for measuring the pressure of hydrogen in the fuel cell is connected to the hydrogen side outlet of the fuel cell stack, and the measured pressure value is compared with the reference section pressure. Inputting to the central control unit for transmitting an (ON) / off (OFF) signal to the hydrogen supply device; Analyzing the hydrogen pressure data to extract the amount of hydrogen supplied based on the size and distribution of the hydrogen pressure data; In the pressure change according to the difference between the amount of hydrogen supplied and the amount of hydrogen used, when the pressure falls below the minimum reference pressure within the set period, the hydrogen supply device is turned on to start the hydrogen supply, and the pressure is higher than the maximum reference pressure. When up, it comprises a hydrogen supply control step of shutting off the hydrogen supply by turning off the hydrogen supply device.

In addition, by periodically turning on / off hydrogen twice the amount of hydrogen required for the reference output in the hydrogen supply device and then turning it on based on the data measured according to the magnitude of the external load of the fuel cell. The technique of extracting a) / OFF time period and adjusting the hydrogen supply amount based on this is employed.

의 온/오프 제어 관계식으로 계산하는 것이 바람직하다.Wherein the output is:

It is preferable to calculate by the on / off control relation of.

In addition, the pressure measuring device (P) for real-time measurement of the fuel cell output value that increases with the change of the external load of the fuel cell, and the ON / OFF time calculated in real time based on the measured data according to the measured output value Through the central control unit to control the hydrogen supply, the cathode oxygen supply amount of the fuel cell stack is sufficiently supplied according to the controlled hydrogen supply amount, the anode and the cathode outlet side is normally closed structure, a predetermined time interval It is purged to make it easy to discharge the generated water and flow of oxygen and hydrogen.

According to an aspect of the present invention, a fuel cell including a fuel cell stack and a hydrogen supply control device includes: a control circuit unit configured to control a hydrogen supply according to a change in fuel cell output value due to an internal hydrogen pressure change and an external load change of the fuel cell stack; It provides a fuel cell comprising a.

In addition, the present invention is a fuel cell operating method including a fuel cell stack and a hydrogen supply control device, the first step of measuring the hydrogen pressure change of the fuel cell stack due to external load variation, based on the measured pressure value And a third step of comparing the section pressure and a third step of turning on and off the hydrogen supply device according to the comparison result.

In addition, the present invention provides a fuel cell operating method including a fuel cell stack and a hydrogen supply control device, the method comprising: a first cycle in which twice or more of an appropriate amount of hydrogen is repeatedly turned on or off for a predetermined time; And a second step of measuring a fuel cell output value due to external load variation, and a third step of controlling an OFF time according to the measured output value.

In this operation method, the central controller can be used to measure the fuel cell output and the hydrogen pressure in the stack, and perform off time control through comparison with reference values and calculation of relations.

4 is a graph showing the output duration at each load (1.0A, 2.6A) when hydrogen is supplied at 100 sccm for 10 seconds in one embodiment of the present invention. The time until the output started to decrease after the hydrogen supply was cut off was set as the output duration. The graph shows that the output duration decreases as the load increases. Based on the first experimental results, the on / off control relationship Equation 1 can be obtained as follows.

Equation 1 above applies 70% of the equation obtained by converting the experimental data to the least-square method in consideration of the operation delay of the solenoid valve and the stability of the output duration as part of the hydrogen supply device.

As a result of applying the on / off control time using this equation, the pressure change and the flow rate change in the fuel cell when a constant load occurs, and the pressure change and the flow rate change in the fuel cell when the load changes, In all cases, hydrogen was constantly supplied at 100 sccm for 10 seconds. As a result of controlling the time during which hydrogen was not supplied to the line by using the above relation Equation 1, the output was stable.

By using this invention, it is possible to cope with the change of load and to use hydrogen efficiently. In addition, it is possible to prevent the deterioration of durability by preventing the deterioration of the fuel cell stack due to the lack of hydrogen.

2 is a flowchart illustrating a method of operating a fuel cell system according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the fuel cell apparatus of the present embodiment first includes a fuel cell stack, a hydrogen tank, an oxygen tank, a hydrogen supply control device, and a control factor measuring device. When the required power increases, the central controller responds to the load without degrading the fuel cell performance by controlling the hydrogen supply.

In order to measure the output of the fuel cell and the internal hydrogen pressure, as shown in FIG. 3, a pressure gauge for measuring the hydrogen pressure may be provided at the hydrogen outlet side to which the current and voltage measuring device is attached and closed. The central control unit operates the hydrogen supply unit based on the measured hydrogen pressure inside the fuel cell and the fuel cell current and voltage.

The flow regulator as a hydrogen supply device shown in FIG. 2 can be replaced with a general manual solenoid valve type, and unlike the hydrogen whose input is controlled, the oxygen supply is sufficient.

The operating method using the internal pressure of the fuel cell uses a pressure change according to the hydrogen consumption inside the fuel cell as a main agent for turning on and off the hydrogen supply device as shown in FIG. 2.

On the other hand, the operation method using the output change according to the fuel cell load is supplied to the inside of the fuel cell by first supplying more than twice the amount of hydrogen required for the fuel cell output, and by periodically turning on and off time It is a form that balances the amount of hydrogen consumed by hydrogen production with the power generation.

When the output changes according to the load fluctuation, it is possible to control the supply according to the hydrogen demand as the supply time (flow x on time) is maintained and then the off time is reduced and increased.

In the above two hydrogen supply control methods, it is preferable to use about 80% of the limit section in consideration of the stability of the system when determining the appropriate hydrogen pressure section and the appropriate OFF time according to the load.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. The scope of the invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

As described above, according to the present invention, stable output can be maintained by controlling hydrogen supplied to the fuel cell stack by the above-described method even when the dynamic load is changed.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawing.

Although the present invention has been described as a specific preferred embodiment, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above-described embodiments without departing from the gist of the present invention as claimed in the claims. Anyone with a variety of variations will be possible.

Brief description of the drawings

1 is a view showing the structure of a fuel cell stack according to the prior art.

2 is a control flowchart of a method of operating a fuel cell system according to an exemplary embodiment.

3 is a block diagram showing a configuration of a fuel cell according to an embodiment of the present invention.

4 is a control graph using a relationship between load and output duration.

Claims (4)

In a method of operating a fuel cell system including a fuel cell stack and a hydrogen supply control device, the internal hydrogen pressure of a fuel cell stack generating electric energy by an electrochemical reaction between hydrogen and oxygen is monitored. A pressure measuring device for measuring the pressure of the fuel cell stack is connected to the outlet of the hydrogen side of the fuel cell stack, and compares the measured pressure value with the reference section pressure, and transmits the ON / OFF signal to the hydrogen supply device. Inputting to a control device; Analyzing the hydrogen pressure data to extract the amount of hydrogen supplied based on the size and distribution of the hydrogen pressure data; In the pressure change according to the difference between the amount of hydrogen supplied and the amount of hydrogen used, when the pressure falls below the minimum reference pressure within the set period, the hydrogen supply device is turned on to start the hydrogen supply, and the pressure is higher than the maximum reference pressure. And a hydrogen supply control step of shutting off the hydrogen supply by turning off the hydrogen supply device. The method of claim 1, After twice or more hydrogen of the amount of hydrogen required for the reference output is periodically turned on / off from the hydrogen supply device, on / off based on the measured data according to the magnitude of the external load of the fuel cell. A method of operating a fuel cell system which extracts an OFF time period and adjusts the hydrogen supply amount based on this. The method of claim 2, The output is

A method of operating a fuel cell system comprising calculating with the on / off control relationship of. The method of claim 3, wherein Controls the hydrogen supply by measuring the fuel cell output value that increases according to the external load of the fuel cell in real time and on / off time calculated in real time based on the data measured according to the measured output value. Through the central controller, the cathode oxygen supply amount of the fuel cell stack is sufficiently supplied according to the hydrogen supply amount to be controlled, and the anode and cathode outlet sides are normally closed, and are purged at regular time intervals to generate the generated water. A method of operating a fuel cell system, characterized by facilitating discharge and flow of oxygen and hydrogen.

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