A composite member includes a base member and a covering layer. The base member includes a first surface not exposed to an oxidizing atmosphere and contains chromium. The covering layer covers the first surface and includes a first outer surface that is not exposed to the oxidizing atmosphere. At least one of the base member and the covering layer includes an exposed surface that is exposed to the oxidizing atmosphere. The surface roughness of the exposed surface is different from the surface roughness of the first surface or the first outer surface.

A composite member includes a base member and a covering layer. The base member includes a first surface not exposed to an oxidizing atmosphere and contains chromium. The covering layer covers the first surface and includes a first outer surface that is not exposed to the oxidizing atmosphere. At least one of the base member and the covering layer includes an exposed surface that is exposed to the oxidizing atmosphere. The surface roughness of the exposed surface is different from the surface roughness of the first surface or the first outer surface.

A SOC stack has interconnects with a maximum distance between the contact points which are designed to compensate for pressure difference between one side of the interconnect to the other side.

A SOC stack has interconnects with a maximum distance between the contact points which are designed to compensate for pressure difference between one side of the interconnect to the other side.

A metal support for an electrochemical element where the metal support includes a plate face, has a plate shape as a whole, and has a warping degree of 1.5×10.sup.−2 or less determined by calculating a least square value through the least squares method using at least three points in the plate face of the metal support, calculating a first difference between the least square value and a positive-side maximum displacement value on a positive side with respect to the least square value and a second difference between the least square value and a negative-side maximum displacement value on a negative side that is opposite to the positive side with respect to the least square value, and dividing the sum of the first difference and the second difference by a maximum length of the plate face of the metal support that passes through a center of gravity.

A method of operating a solid oxide fuel cell system may comprise contacting a cathode gas comprising oxygen with a heating element to produce a heated cathode gas, passing the heated cathode gas through a cathode of a solid oxide fuel cell stack to increase the temperature of the solid oxide fuel cell stack to an operation temperature and reduce the oxygen to oxygen anions, and passing an anode gas through an anode of the solid oxide fuel cell stack to initiate the electrochemical oxidation of the oxygen anions within the anode. The passing of the anode gas through the anode of the solid oxide fuel cell stack may be initiated when the solid oxide fuel cell stack is heated to an operational temperature.

A method of operating a solid oxide fuel cell system may comprise contacting a cathode gas comprising oxygen with a heating element to produce a heated cathode gas, passing the heated cathode gas through a cathode of a solid oxide fuel cell stack to increase the temperature of the solid oxide fuel cell stack to an operation temperature and reduce the oxygen to oxygen anions, and passing an anode gas through an anode of the solid oxide fuel cell stack to initiate the electrochemical oxidation of the oxygen anions within the anode. The passing of the anode gas through the anode of the solid oxide fuel cell stack may be initiated when the solid oxide fuel cell stack is heated to an operational temperature.

A contacting arrangement of solid oxide cells is disclosed, each solid oxide cell having at least two flow field plates to arrange gas flows in the cell, and an active electrode structure, which has an anode side, a cathode side, and an electrolyte element between the anode side and the cathode side. The contacting arrangement includes a gasket structure to perform sealing functions in the solid oxide cell and a contact structure located between the flow field plates and the active electrode structure, the contact structure being at least partly a gas permeable structure configured and adapted according to structures of the flow field plates and according to the active electrode structure.

A contacting arrangement of solid oxide cells is disclosed, each solid oxide cell having at least two flow field plates to arrange gas flows in the cell, and an active electrode structure, which has an anode side, a cathode side, and an electrolyte element between the anode side and the cathode side. The contacting arrangement includes a gasket structure to perform sealing functions in the solid oxide cell and a contact structure located between the flow field plates and the active electrode structure, the contact structure being at least partly a gas permeable structure configured and adapted according to structures of the flow field plates and according to the active electrode structure.

A method for operating a fuel cell system includes drawing a base level DC electric energy from a first fuel cell of a first type to a combined DC bus, measuring a DC voltage at the combined DC bus, determining whether the DC voltage at the combined DC bus falls short of a DC voltage threshold, and drawing a variable DC electric energy from a second fuel cell of a second type different from the first type in response to determining that the DC voltage at the combined DC bus falls short of the DC voltage threshold.