Fuel cell system and method of operating fuel cell system

A fuel cell system including:

• unit cells each having an MEA, a pair of an anode separator plate and a cathode separator plate which are disposed to sandwich said MEA, an anode gas passage which is provided between said MEA and said anode separator plate to connect an anode gas inlet to an anode gas outlet, and a cathode gas passage which is provided between said MEA and said cathode separator plate to connect a cathode gas inlet to a cathode gas outlet;
• and
• a fuel cell stack having said unit cells stacked and being provided with a heat transmission medium passage which is provided between surfaces of said stacked unit cells to connect a heat transmission medium inlet to a heat transmission medium outlet;
• wherein said anode gas passage, said cathode gas passage, and said heat transmission medium passage have a structure in which inlet-side regions of said anode gas passage, said cathode gas passage, and said heat transmission medium passage substantially overlap with each other and outlet-side regions of said anode gas passage, said cathode gas passage, and said heat transmission medium passage substantially overlap with each other as viewed from a direction in which said unit cells are stacked, and the anode gas, the cathode gas, and the heat transmission medium are flowed in a forward direction from the anode gas inlet to the anode gas outlet in said anode gas passage, from the cathode gas inlet to the cathode gas outlet in said cathode gas passage, and from the heat transmission medium inlet to the heat transmission medium outlet in said heat transmission medium passage, respectively;
• said fuel cell system comprising:
• at least one of an anode gas flow inverting device for inverting a flow direction of the anode gas in said anode gas passage from the forward direction to a reverse direction which is opposite to the forward direction, and a cathode gas flow inverting device for inverting a flow direction of the cathode gas in said cathode gas passage from the forward direction to the reverse direction;
• a heat transmission medium flow inverting device for inverting a flow direction of the heat transmission medium in said heat transmission medium passage from the forward direction to the reverse direction;
• and
• a control system configured to control inversion of said heat transmission medium flow inverting device after controlling inversion of at least one of said anode gas flow inverting device and said cathode gas flow inverting device, according to deterioration of said fuel cell stack.

A method of operating a fuel cell system including:

• unit cells each having an MEA, a pair of an anode separator plate and a cathode separator plate which are disposed to sandwich said MEA, an anode gas passage which is provided between said MEA and said anode separator plate to connect an anode gas inlet to an anode gas outlet, and a cathode gas passage which is provided between said MEA and said cathode separator plate to connect a cathode gas inlet to a cathode gas outlet;
• and
• a fuel cell stack having said unit cells stacked and being provided with a heat transmission medium passage which is provided between surfaces of said stacked unit cells to connect a heat transmission medium inlet to a heat transmission medium outlet;
• wherein said anode gas passage, said cathode gas passage, and said heat transmission medium passage have a structure in which inlet-side regions of said anode gas passage, said cathode gas passage, and said heat transmission medium passage substantially overlap with each other and outlet-side regions of said anode gas passage, said cathode gas passage, and said heat transmission medium passage substantially overlap with each other as viewed from a direction in which said unit cells are stacked, and the anode gas, the cathode gas, and the heat transmission medium are flowed in a forward direction from the anode gas inlet to the anode gas outlet in said anode gas passage, from the cathode gas inlet to the cathode gas outlet in said cathode gas passage, and from the heat transmission medium inlet to the heat transmission medium outlet in said heat transmission medium passage, respectively;
• said method comprising:
• inverting a flow direction of the heat transmission medium in said heat transmission medium passage from the forward direction to a reverse direction which is opposite to the forward direction, after inverting at least one of a flow direction of the anode gas in said anode gas passage and a flow direction of the cathode gas in said cathode gas passage from the forward direction to the reverse direction.