Fuel cell system and method of reducing decrease in power generation efficiency of fuel cell

A fuel cell system including a fuel cell, comprising:

• a heater core used by a heating device;
• a first circulation circuit arranged to circulate a heat medium through the fuel cell;
• a second circulation circuit arranged to circulate the heat medium through the heater core;
• a connection channel arranged to connect the first circulation circuit with the second circulation circuit and thereby circulate the heat medium between the first circulation circuit and the second circulation circuit;
• a first temperature regulator located on the second circulation circuit and downstream of the heater core and configured to regulate temperature of the heat medium after flowing out of the heater core and before flowing into the fuel cell;
• a first temperature sensor located upstream of the fuel cell and configured to measure temperature of the heat medium before flowing into the fuel cell;
• a second temperature regulator located on the second circulation circuit and upstream of the heater core and configured to regulate temperature of the heat medium after flowing out of the fuel cell and before flowing into the heater core;
• a second temperature sensor located upstream of the heater core and configured to measure temperature of the heat medium before flowing into the heater core;
• and
• a controller configured to control the first temperature regulator based on the temperature of the heat medium measured by the first temperature sensor and to control the second temperature regulator based on the temperature of the heat medium measured by the second temperature sensor, wherein
• the first temperature regulator is a first electric heater that has a first heater capacity,
• the second temperature regulator is a second electric heater that has a second heater capacity, and
• the controller performs feedback-control of the first heater capacity of the first electric heater based on a target temperature of the heat medium allowable for the fuel cell, and performs feedback-control of the second heater capacity of the second electric heater based on a target temperature of the heat medium required by the heating device.