Fuel cell system and control method for fuel cell system

A fuel cell system comprising:

• a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• a temperature detector that detects a temperature of the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell, and
• wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than a temperature at which an oxidation-reduction reaction at the anode slows down.

A fuel cell system comprising:

• a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
• wherein the electrolyte membrane contains a compound represented by BaCe1-xMxO3-α, BaZr1-x-yCexMyO3-α, or BaZr1-xMxO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.

A fuel cell system comprising:

• a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
• wherein the electrolyte membrane contains a compound represented by BaZr1-xYbxO3-α, where x is 0<x<1, and α is an oxygen deficiency and is 0<α<0.5.

A method for controlling a fuel cell system including:

• a fuel cell that includes a membrane electrode assembly including a proton conducting electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• a temperature detector that detects a temperature of the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, in a shutdown process, the control program, when executed by the processing unit, causes the controller to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
• wherein the electrolyte membrane has hole conductivity, and
• wherein the control program, when executed by the processing unit, causes the controller to control the power source in the shutdown process such that the terminal voltage is equal to or higher than the open circuit voltage until the temperature detected by the temperature detector is determined to be equal to or lower than a temperature at which hole conduction in the electrolyte membrane decreases.

A fuel cell system comprising:

• a fuel cell that includes a membrane electrode assembly including a proton conducting ceramic electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, the control program, when executed by the processing unit, causes the controller, in a shutdown process, to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell, and
• wherein the electrolyte membrane contains a compound represented by BaCe1-xMxO3-α or BaZr1-x-yCexMyO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.

A method for controlling a fuel cell system including:

• a fuel cell that includes a membrane electrode assembly including a proton conducting electrolyte membrane, a cathode disposed on a first surface of the electrolyte membrane, and an anode disposed on a second surface of the electrolyte membrane, the fuel cell generating electric power through an electrochemical reaction using a fuel gas and an oxidant gas;
• a power source that applies a voltage to the fuel cell;
• and
• a controller including a processing unit and a memory circuit storing a control program,
• wherein, in a shutdown process, the control program, when executed by the processing unit, causes the controller to control the power source to apply the voltage to the fuel cell such that a terminal voltage of the fuel cell is equal to or higher than an open circuit voltage of the fuel cell,
• wherein the proton conducting electrolyte membrane is a ceramic electrolyte membrane,
• the ceramic electrolyte membrane contains a compound represented by BaCe1-xMxO3-α, or BaZr1-x-yCexMyO3-α, where M is a trivalent substituent element, x is 0<x<1, y is 0<y<1, and α is an oxygen deficiency and is 0<α<0.5.