Solid oxide fuel cell unit
Provided is a solid oxide fuel cell unit comprising an insulating support, and a power generation element comprising, at least, a fuel electrode, an electrolyte and an air electrode, which are sequentially laminated one another, the power generation element being provided on the insulating support, wherein an exposed insulating support portion, an exposed fuel electrode portion, and an exposed electrolyte portion are provided in an fuel electrode cell end portion.
1. A solid oxide fuel cell unit comprising:
an insulating support having a gas flow path running therein; and
a first power generation element provided on a surface of the insulating support in a first end of the insulating support,
wherein the first power generation element comprises a fuel electrode, an electrolyte and an air electrode, the fuel electrode, the electrolyte and the air electrode being sequentially laminated one over another in this order from inner most to outer most, the fuel electrode including a first surface and a second surface, the first surface being located between the fuel electrode and the electrolyte, the second surface being located between the fuel electrode and the insulating support, the insulating support being made of a porous material comprising an oxide, and the electrolyte being made of an oxide having a smaller coefficient of thermal expansion than a coefficient of thermal expansion of the insulating support,
the solid oxide fuel cell unit further comprises an exposed electrolyte portion, which is a portion of the electrolyte exposed, uncovered by the air electrode, an exposed fuel electrode portion, which is a portion of the fuel electrode exposed on the first surface, uncovered by either the electrolyte or the air electrode, and an exposed insulating support portion, which is a portion of the insulating support located in the first end thereof that is exposed, uncovered by any of the fuel electrode, the electrolyte and the air electrode, and
the exposed insulating support portion, the exposed fuel electrode portion, and the exposed electrolyte portion are arranged one next to another in this order along the gas flow path from the first end of the insulating support.
2. The solid oxide fuel cell unit according to claim 1 , wherein
the gas flow path runs in a direction perpendicular to a lamination direction of the fuel electrode, the electrolyte and the air electrode,
the solid oxide fuel cell comprises a second power generation element comprising a fuel electrode, an electrolyte and an air electrode, the fuel electrode, the electrolyte and the air electrode being sequentially laminated one over another in this order from inner most to outer most, the insulating support being made of a porous material comprising an oxide, and the electrolyte being made of an oxide having a smaller coefficient of thermal expansion than a coefficient of thermal expansion of the insulating support, and
the solid oxide fuel cell unit further comprises:
an interconnector electrically connecting the fuel electrode of the second power generation element to the air electrode of the first power generation element; and
an exposed insulating electrolyte portion, which is a portion of the electrolyte of the second power generation element exposed, uncovered by the air electrode of the second power generation element, provided to separate the interconnector and the air electrode of the second power generation element for electrical insulation therebetween and separate the air electrodes of the first and second power generation elements for electrical insulation therebetween, wherein
a relationship of L 3 >L 4 is satisfied, where L 4 represents a length of the exposed insulating electrolyte portion along the gas flow path, and L 3 represents a length of the exposed electrolyte portion along the gas flow path.
3. The solid oxide fuel cell unit according to claim 1 , wherein a relationship of L 3 >L 2 is satisfied, where L 2 represents a length of the exposed fuel electrode portion along the gas flow path, and L 3 represents a length of the exposed electrolyte portion along the gas flow path.
4. A solid oxide fuel cell stack comprising:
the solid oxide fuel cell unit according to claim 1 ; and
a fuel gas tank, wherein the fuel gas tank is gas-tightly joined around the exposed electrolyte portion.
5. The solid oxide fuel cell stack according to claim 4 , wherein a relationship of T<(L 1 +L 2 )×2 is satisfied, where L 1 represents a length of the exposed insulating support portion along the gas flow path, L 2 represents a length of the exposed fuel electrode portion along the gas flow path, and T is a thickness of the fuel gas tank along the gas flow path measured at a location where the fuel gas tank and the solid oxide fuel cell unit are gas-tightly joined to each other.
6. The solid oxide fuel cell stack according to claim 1 , further comprising a third power generation element provided in a second end of the insulating support, wherein the third power generation element comprises a fuel electrode, an electrolyte and an air electrode all of which are configured similarly in a mirror image with the fuel electrode, the electrolyte and the air electrode of the first power generation element.