CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2019-0033525, filed on Mar. 25, 2019, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to a shutdown control method and a shutdown control system of a fuel cell, and more particularly, to a technique for controlling the shutdown of a fuel cell in the colder temperatures.

2. Description of the Prior Art

A fuel cell is a device that converts chemical energy into electrical energy using an oxidation-reduction reaction of hydrogen and oxygen respectively provided from a hydrogen supply device and an air supply device, and includes a fuel cell stack that produces electrical energy and a cooling system that cools the fuel cell stack. In other words, when hydrogen is supplied to an anode of the fuel cell stack, an oxidation reaction of hydrogen occurs at the anode to produce protons and electrons, which move to a cathode through an electrolyte membrane and a separation membrane. At the cathode, the protons and the electrons, which move from the anode, and oxygen in the air participate in an electrochemical reaction to form water. Through this flow of electrons, electrical energy is produced.

Generated water formed inside the fuel cell stack remains in the fuel cell stack. When the outside temperature is particularly cold, for example, in the winter season, there is the possibility that the generated water freezes when the fuel cell is in a shutdown state. When the generated water freezes inside the fuel cell stack, the water may cause a performance deterioration. Thus, it is important to discharge the generated water when the fuel cell is shut down. However, the process of discharging the generated water at shutdown generates a substantial amount of noise, causes a reduction in fuel efficiency due to the consumption of hydrogen, and increases the time for shutdown control. Thus, it is required to determine the possibility that generated water freezes and to limitedly discharge the generated water.

It should be noted that the foregoing description of the background art is made merely to enhance the understanding of the background of the present disclosure and is not to be construed as being acknowledged as the prior art already known to those skilled in the art.

SUMMARY

The present disclosure has been made to solve the above-mentioned problems in the prior art, and an aspect of the present disclosure provides shutdown control that determines the possibility that generated water freezes and limitedly discharges generated water from a fuel cell.

In accordance with an aspect of the present disclosure, a shutdown control method of a fuel cell may include: applying power to a controller in a shutdown state; determining, by the controller to which the power is applied, a possibility of moisture freezing based on an estimated outdoor temperature, a temperature of a fuel cell stack, or a measured outdoor temperature; and executing shutdown of the fuel cell by performing moisture removal from the fuel cell stack in response to determining the possibility of moisture freezing after restart.

The applying of the power to the controller may include activating the controller by applying power to the controller at preset wake-up time intervals in the shutdown state. The determining of the possibility of moisture freezing may include receiving the estimated outdoor temperature for a preset estimated time from an outside and determining that there is a possibility of moisture freezing when the estimated outdoor temperature decreases to below a preset first temperature within the preset estimated time. Additionally, the determining of the possibility of moisture freezing may include measuring the temperature of the fuel cell stack and determining that there is a possibility of moisture freezing when the measured temperature of the fuel cell stack decreases to below a preset second temperature.

The determining of the possibility of moisture freezing may further include determining that there is a possibility of moisture freezing when an outdoor temperature is reduced in the shutdown state based on the measured outdoor temperature and an outdoor temperature measured in the shutdown state. In addition, the determining of the possibility of moisture freezing may include determining that there is a possibility of moisture freezing when a temperature difference of the measured outdoor temperature minus an outdoor temperature measured in the shutdown state is less than a preset reference value. The preset reference value may be preset to increase as a change time, from the time of shutdown to a time of measurement of the outdoor temperature, increases.

The execution of the shutdown of the fuel cell may include omitting moisture removal control of the fuel cell stack in the shutdown state in response to determining that there is no possibility of moisture freezing. Additionally, the execution of the shutdown of the fuel cell may include discharging moisture out of the fuel cell stack by operating an air compressor configured to supply air to the fuel cell stack at a preset rotation speed when moisture removal control of the fuel cell stack is performed.

In accordance with an aspect of the present disclosure, a shutdown control system of a fuel cell may include: an input device configured to input an estimated outdoor temperature from an outside; a temperature sensor configured to measure a temperature of a fuel cell stack or an outdoor temperature; and a controller configured to determine a possibility of moisture freezing based on the estimated outdoor temperature input via the input device or the temperature of the fuel cell stack or the outdoor temperature measured by the temperature sensor when power is applied in a shutdown state and to execute shutdown of the fuel cell by performing moisture removal from the fuel cell stack in response to determining the possibility of moisture freezing after restart.

The shutdown control system of the fuel cell may further include a battery configured to apply power to the input device, the temperature sensor, or the controller to activate the input device, the temperature sensor, or the controller at preset wake-up time intervals in the shutdown state. The input device may be configured to receive the estimated outdoor temperature for a preset estimated time, and the controller may be configured to determine that there is a possibility of moisture freezing when the estimated outdoor temperature decreases to below a preset first temperature within the preset estimated time.

The controller may further be configured to determine that there is a possibility of moisture freezing when the temperature of the fuel cell stack, measured by the temperature sensor, decreases to below a preset second temperature. Additionally, the controller may be configured to determine that there is a possibility of moisture freezing when a temperature difference of the measured outdoor temperature minus an outdoor temperature measured in the shutdown state is less than a preset reference value, and the preset reference value may be preset to increase as a change time, from the time of shutdown to a time of measurement of the outdoor temperature, increases. The shutdown control system may further include: an air compressor configured to supply air to the fuel cell stack. The controller may be configured to execute moisture removal control of the fuel cell stack to discharge moisture out of the fuel cell stack by operate the air compressor configured to supply air to the fuel cell stack at a preset rotation speed in response to determining that there is a possibility of moisture freezing.

According to a shutdown control method and a shutdown control system of a fuel cell of the present disclosure, moisture removal control of a fuel cell stack may be limitedly included in shutdown control of the fuel cell to prevent unnecessary hydrogen consumption and power waste, thereby improving fuel efficiency. Further, when moisture removal control of a fuel cell stack is omitted, it may be possible to reduce the time consumed for the shutdown of a fuel cell and to reduce the occurrence of noise, thereby improving merchantable quality.

