Abstract: In order to provide a fuel cell system (which ensures high proton conductivity and high energy conversion efficiency and, in addition, copes with an operating mode of the startup/shutdown type and which has excellent durability capable of effectively preventing a polymer electrolyte membrane from deterioration) and an operating method of such a fuel cell system, a fuel cell system (100) is provided with a fuel cell (11), a fuel gas supplier (16) and an oxidizing gas supplier (17), a temperature supplier (19) which controls the temperature of the fuel cell, and a humidifier unit (18) which humidifies oxidizing gas, wherein there is further provided a controller (20) which controls the dew point of fuel gas and the dew point of oxidizing gas as follow: during the generation of electric power, the fuel gas dew point is made higher than or equal to the temperature of the fuel cell while the oxidizing gas dew point is made less than the temperature of the fuel cell and, before interrupting the electric connection

Abstract: A membrane-membrane reinforcing member assembly includes: a polymer electrolyte membrane (1) having a substantially quadrilateral shape; a membrane-like first membrane reinforcing member (10a) disposed on a first main surface (F10) of the polymer electrolyte membrane (1) to bend at a substantially right angle at a corner of the polymer electrolyte membrane (1) and extend along sides forming the corner; and a membrane-like second membrane reinforcing member (10b) disposed on a second main surface (F20) of the polymer electrolyte membrane (1) to bend at a substantially right angle at a corner of the polymer electrolyte membrane (1) and extend along sides forming the corner, and the first membrane reinforcing member (10a) and the second membrane reinforcing member (10b) are disposed to extend along four sides of the polymer electrolyte membrane (1) as a whole.

Abstract: A membrane-membrane reinforcing member assembly includes: a polymer electrolyte membrane (1) having a substantially square shape; a pair of membrane-like first membrane reinforcing members (10a) disposed on one main surface of the polymer electrolyte membrane (1) so as to extend along a pair of opposed sides, respectively, of four sides of said one main surface; and a pair of membrane-like second membrane reinforcing members (10b) disposed on another main surface of the polymer electrolyte membrane (1) so as to extend along a pair of opposed sides, respectively, of four sides of said another main surface, wherein: portions of the polymer electrolyte membrane (1) at which portions the first membrane reinforcing members (10a, 10a) and the second membrane reinforcing members (10b, 10b) are disposed are concave; and the first membrane reinforcing members (10a, 10a) and the second membrane reinforcing members (10b, 10b) are disposed such that main surfaces thereof are exposed, and the first membrane reinforcing me

Abstract: The present invention includes a fuel cell (11), a fuel gas supplying device (16), an oxidizing gas supplying device (17) and a control apparatus (20) and further includes at least one of a temperature control device (19) which controls the temperature of the fuel cell (11) and a humidifying device (24) which humidifies at least one of the fuel gas and the oxidizing gas to be supplied to the fuel cell (11), wherein: the control apparatus (20) controls at least one of the temperature control device (19), the humidifying device (24), the fuel cell (11) and the fuel gas supplying device (16) to cause the temperature of the fuel cell (11) to be equal to at least one of the dew point of the fuel gas and the dew point of the oxidizing gas, before cutting off an electrical connection between the fuel cell (11) and a load; and then the control apparatus (20) cuts off the electrical connection between the fuel cell (11) and the load.