WO2021112276A1

WO2021112276A1 - Fuel cell system and control method thereof

Info

Publication number: WO2021112276A1
Application number: PCT/KR2019/016998
Authority: WO
Inventors: 백지숙; 오흥렬
Original assignee: 코오롱머티리얼(주)
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2021-06-10

Abstract

A fuel cell system of the present invention comprises: a compressor that sucks in and compresses air; a humidifier that humidifies the air compressed by the compressor; a fuel cell stack that receives humidified air from the humidifier; a humidity sensor installed at the inlet end of the fuel cell stack; a bypass flow path connected from the inlet end of the humidifier to the inlet end of the fuel cell stack; a bypass valve installed at the inlet end of the bypass flow path; and a control unit that controls the bypass valve according to a humidity value measured by the humidity sensor. According to the present invention, it is possible to prevent an anode flooding phenomenon of the fuel cell due to excessive humidification by controlling the humidification amount of the humidifier in a low flow rate or low power section.

Description

Fuel cell system and its control method

The present invention relates to a fuel cell system and a method for controlling the same.

A fuel cell is a power generation type cell that produces electricity by combining hydrogen and oxygen. Unlike general chemical cells such as dry cells and storage batteries, fuel cells can continuously produce electricity as long as hydrogen and oxygen are supplied, and there is no heat loss, so the efficiency is about twice that of an internal combustion engine.

In addition, since chemical energy generated by the combination of hydrogen and oxygen is directly converted into electrical energy, the emission of pollutants is small. Accordingly, the fuel cell has the advantage of being environmentally friendly and reducing concerns about resource depletion due to increased energy consumption.

These fuel cells are largely classified according to the type of electrolyte used: a Polymer Electrolyte Membrane Fuel Cell (PEMFC), a Phosphoric Acid Fuel Cell (PAFC), and a Molten Carbonate Fuel Cell (Molten Carbonate Fuel Cell). : MCFC), Solid Oxide Fuel Cell (SOFC), and Alkaline Fuel Cell (AFC).

Each of these fuel cells operates on the same fundamental principle, but the type of fuel used, operating temperature, catalyst, electrolyte, and the like are different from each other. Among them, the polymer electrolyte fuel cell (PEMFC) is known to be the most promising not only in small-scale stationary power generation equipment but also in transportation systems because it operates at a low temperature compared to other fuel cells and can be miniaturized due to its high power density.

One of the most important factors in improving the performance of a polymer electrolyte fuel cell (PEMFC) is a certain amount of a polymer electrolyte membrane (Polymer Electrolyte Membrane or Proton Exchange Membrane: PEM) of a membrane-electrode assembly (MEA). It is to maintain the moisture content by supplying more moisture. This is because when the polymer electrolyte membrane is dried, the power generation efficiency is rapidly reduced.

As a method of humidifying a polymer electrolyte membrane, 1) a bubbler humidification method in which water is supplied by passing a target gas through a diffuser after filling a pressure-resistant container with water, 2) the amount of supplied water required for fuel cell reaction There are a direct injection method in which moisture is calculated and directly supplying moisture to a gas flow pipe through a solenoid valve, and 3) a humidification membrane method in which moisture is supplied to a fluidized bed of gas using a polymer membrane.

Among them, the humidification membrane method for humidifying the polymer electrolyte membrane by providing water vapor to the gas supplied to the polymer electrolyte membrane using a membrane that selectively transmits only water vapor contained in the exhaust gas is advantageous in that the humidifier can be reduced in weight and size.

The selective permeable membrane used in the humidification membrane method is preferably a hollow fiber membrane having a large permeation area per unit volume when forming a module. In other words, when a membrane humidifier is manufactured using a hollow fiber membrane, the high integration of the hollow fiber membrane with a large contact surface area is possible, so that the fuel cell can be sufficiently humidified even with a small capacity, and low-cost materials can be used, and the high temperature in the fuel cell There is an advantage in that moisture and heat contained in the discharged unreacted gas can be recovered and reused through a humidifier.

Meanwhile, the dry air compressed by the compressor receives moisture from the wet air supplied from the fuel cell stack in the humidifier, becomes humidified air, and flows into the fuel cell stack.

However, in the anode of the fuel cell, water is generated by an electrochemical reaction, and when the balance with humidifying the electrolyte membrane is broken, a flooding phenomenon occurs in which moisture attaches to the electrode, which can lead to a decrease in the performance of the fuel cell voltage. have.

Moreover, if the flooding continues, the water positive ions that have passed through the polymer electrolyte membrane cannot combine with oxygen but with electrons, thereby becoming hydrogen and burning again, thereby damaging the electrodes of the fuel cell.

Therefore, it is necessary to prevent a flooding phenomenon in the fuel cell stack due to excessive humidification in the low flow rate or low output section.

An object of the present invention is to provide a fuel cell system capable of preventing anode flooding of a fuel cell by adjusting the humidification amount of a humidifier, and a method for controlling the same.

The fuel cell system of the present invention for achieving the above object includes a compressor for sucking air and compressing it, a humidifier for humidifying the air compressed in the compressor, a fuel cell stack receiving the humidified air from the humidifier, and the fuel cell stack a humidity sensor installed at the inlet end of the humidifier, a bypass passage connected from the inlet end of the humidifier to the inlet end of the fuel cell stack, a bypass valve installed at the inlet end of the bypass passage, and the humidity sensor and a control unit for controlling the bypass valve according to the humidity value to be changed.

Preferably, the control unit opens the bypass valve when the humidity value measured by the humidity sensor is 50% or more.

Preferably, the control unit closes the bypass valve when the humidity value measured by the humidity sensor is less than 50%.

The control method of the fuel cell system of the present invention includes a compressor for sucking air and compressing it, a humidifier for humidifying the air compressed by the compressor, a fuel cell stack receiving humidified air from the humidifier, and the inlet of the humidifier. A control method of a fuel cell system including a bypass flow path connected to an inlet end of a fuel cell stack, the method comprising: measuring a humidity at an inlet end of the fuel cell stack; determining whether the measured humidity is 50% or more step, and controlling the air compressed in the compressor to flow to the humidifier or the bypass passage according to whether the measured humidity is 50% or more.

In the control step, when the measured humidity is 50% or more, the bypass valve is opened to allow the compressed air from the compressor to flow into the bypass flow path, and when the measured humidity is less than 50%, the bypass valve is closed. It is preferable to control the air compressed in the compressor to pass through the humidifier.

According to the fuel cell system and the control method of the present invention described above, it is possible to prevent the anode flooding of the fuel cell by adjusting the humidification amount of the humidifier.

1 is a view showing a fuel cell system according to an embodiment of the present invention.

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

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'comprising' or 'having' are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other It is to be understood that this does not preclude the possibility of addition or presence of features or numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that the same components in the accompanying drawings are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings.

As shown in FIG. 1 , the fuel cell system according to an embodiment of the present invention includes a compressor 10 that sucks and compresses air, a humidifier 30 that humidifies the air compressed in the compressor, and air humidified in the humidifier. The fuel cell stack 80 receiving the supply, the humidity sensor 70 installed at the inlet end of the fuel cell stack, the bypass flow path 50 connected from the inlet end of the humidifier to the inlet end of the fuel cell stack, and the bypass flow path It includes a bypass valve 40 installed at the inlet end, and a control unit 100 for controlling the bypass valve 40 according to a humidity value measured by the humidity sensor 70 .

The compressor 10 is for supplying air to the cathode of the fuel cell, and sucks in external air (hereinafter referred to as "dry air"), compresses the dry air, and supplies it to the humidifier 30 . A dry air supply passage 20 is connected between the compressor 10 and the humidifier 30 .

The humidifier 30 humidifies the dry air compressed in the compressor 10 and supplies it to the fuel cell stack 80 . The exhaust gas discharged from the cathode of the fuel cell (hereinafter referred to as "wet air") and the dry air supplied from the compressor 10 exchange gas-to-gas moisture in the humidifier 30 to moisten the dry air with a membrane. this is done

The fuel cell stack 80 has a membrane-electrode assembly (MEA) interposed therebetween, and an air electrode including a separator (commonly referred to as a “separator plate” or a bipolar plate) on both sides thereof and a fuel electrode are disposed. made up of aggregates

Hot and humid humid air is discharged from the cathode of the fuel cell, and hot and humid hydrogen as unreacted hydrogen is discharged from the anode of the fuel cell. The wet air is supplied from the fuel cell stack 80 through the wet air supply passage 90 connected to the humidifier 30 to exchange moisture with the dry air.

The humidified air discharged from the humidifier 30 after water exchange is supplied to the fuel cell stack 80 through the humidified air supply passage 60 .

A humidity sensor 70 is installed at the inlet end of the fuel cell stack 80 in the humidified air supply passage 60 . The humidity sensor 70 measures the humidity of the humidified air flowing into the fuel cell stack 80 .

The bypass flow path 50 is connected from the inlet end of the humidifier 30 in the dry air supply passage 20 to the inlet end of the fuel cell stack 80 in the humidified air supply passage 60 . Compressed air supplied from the compressor 10 may be supplied directly to the fuel cell stack 80 without being humidified while selectively passing through the humidifier 30 through the bypass flow path 50 . That is, since there is no need to humidify the compressed dry air when the humidity is high, the dry air may bypass the humidifier 30 and be directly supplied to the fuel cell stack 80 . A bypass valve 40 is installed at the inlet end of the bypass flow passage 50 . The bypass valve 40 may be configured as a three-way valve provided in a connection portion of the dry air supply passage 20 to the bypass passage 50 .

When the bypass valve 40 installed at the inlet end of the bypass flow path 50 is closed, all of the dry air flows into the humidifier 30 . When the bypass valve 40 is opened, all of the dry air is supplied to the fuel cell stack 80 without being humidified through the bypass flow passage 50 .

The bypass valve 40 may be configured as an on/off valve, but may also be configured as a valve whose opening rate can be adjusted in stages. In the latter case, the opening degree of the bypass valve 40 may be adjusted according to the humidity of the humidified air flowing into the fuel cell stack 80 .

The controller 100 controls the bypass valve 40 according to the humidity value measured by the humidity sensor 70 . That is, the control unit 100 receives the measurement value of the humidity sensor 70 and controls the bypass valve 40 according to the humidity value. When the humidity value is low, the bypass valve 40 is closed, and when the humidity value is high, the bypass valve 40 is opened.

Specifically, the control unit 100 opens the bypass valve 40 when the humidity value measured by the humidity sensor 70 is 50% or more. That is, if the humidity value at the inlet end of the fuel cell stack 80 is 50% or more, there is no need to humidify the dry air.

In addition, when the humidity value measured by the humidity sensor 70 is less than 50%, the controller 100 closes the bypass valve 40 . That is, when the humidity value at the inlet end of the fuel cell stack 80 is less than 50%, the dry air is humidified while passing through the humidifier 30 , and then supplied to the fuel cell stack 80 .

A method of controlling the fuel cell system will be described with reference to FIG. 2 .

Here, the fuel cell system is as described above with reference to FIG. 1 .

First, when an operation command of the fuel cell system is input, the fuel cell system is operated ( S10 ).

Next, the humidity at the inlet of the fuel cell stack is measured (S20).

Next, it is determined whether the measured humidity is 50% or more (S30).

Finally, depending on whether the measured humidity is 50% or more, the air compressed in the compressor 10 is controlled to flow into the humidifier 30 or the bypass flow path 50 .

In the control step, when the measured humidity is 50% or more, the bypass valve 40 is opened to control the air compressed in the compressor 10 to flow into the bypass flow path 50 (S40).

In the control step, if the measured humidity is less than 50%, the bypass valve 40 is closed to control the air compressed in the compressor 10 to pass through the humidifier 30 (S50).

According to the present invention, the anode flooding of the fuel cell due to excessive humidification can be prevented by controlling the humidification amount of the humidifier in the low flow rate or low power section.

Above, an embodiment of the present invention has been described, but those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. It will be said that various modifications and changes of the present invention can be made by, and this is also included within the scope of the present invention.

Claims

Compressor that sucks air and compresses it;

a humidifier for humidifying the air compressed in the compressor;

a fuel cell stack receiving the humidified air from the humidifier; a humidity sensor installed at the inlet end of the fuel cell stack;

a bypass passage connected from the inlet end of the humidifier to the inlet end of the fuel cell stack;

a bypass valve installed at the inlet end of the bypass flow path; and

A control unit for controlling the bypass valve according to the humidity value measured by the humidity sensor

A fuel cell system comprising a.
According to claim 1,

The control unit opens the bypass valve when the humidity value measured by the humidity sensor is 50% or more.
3. The method of claim 2,

The control unit closes the bypass valve when the humidity value measured by the humidity sensor is less than 50%.
A compressor that sucks air and compresses it, a humidifier that humidifies the air compressed by the compressor, a fuel cell stack receiving the humidified air from the humidifier, and a bypass connected from an inlet end of the humidifier to an inlet end of the fuel cell stack In the control method of a fuel cell system including a flow path,

measuring the humidity at the inlet end of the fuel cell stack;

determining whether the measured humidity is 50% or more;

controlling the air compressed in the compressor to flow to the humidifier or the bypass passage according to whether the measured humidity is 50% or more

A control method of a fuel cell system comprising a.
5. The method of claim 4,

In the controlling step, when the measured humidity is 50% or more, the bypass valve is opened to allow the compressed air from the compressor to flow into the bypass flow path, and when the measured humidity is less than 50%, the bypass valve is closed. to control the air compressed in the compressor to pass through the humidifier.

A control method of a fuel cell system.