Optimal Design of Current Takeoff in Bus Bars for Tubular Solid Oxide Fuel Cells

The technology of tubular solid oxide fuel cells of cylindrical geometry has advanced enough such that several demonstration units are currently being tested. This paper presents a simple analytical model for the determination of the current density as a function of axial active cell length under idealized conditions. In addition, a current density axial profile under generator conditions obtained from modeling work is used and compared to the simpler approach. The resulting current density axial profiles are then used to design current takeoff in bus bars where the losses in the power leads are minimized. The result is an optimal scenario where bus bars can be considered to be surfaces that do not significantly affect the natural current density of the solid oxide fuel cell.