Patent ID: 8715879

Claim:
A fuel cell system comprising: a hot zone chamber having an exterior chamber wall with a thickness T, the exterior chamber wall defining a hot zone therein adapted to be heated; one or more fuel cell devices each comprising an elongate rectangular or tubular substrate having a length that is the greatest dimension whereby the elongate rectangular or tubular substrate exhibits thermal expansion along a dominant axis that is coextensive with the length, a first portion of the length positioned in the hot zone chamber and comprising an electrolyte disposed between an opposing anode and cathode for undergoing a fuel cell reaction when heated in the hot zone, a second portion of the length lacking the opposing anode and cathode and positioned outside and shielded by the exterior chamber wall of the hot zone chamber and extending away from the hot zone without being heated so as to dissipate heat and thereby remain at a lower temperature than the first portion of the length when heated in the hot zone, and a third portion of the length equal to thickness T positioned within the exterior chamber wall, the third portion having a maximum dimension L in a plane transverse to the direction of the length wherein T≧½L.