NOVELTY - A tubular cell element comprises an inner electronically conductive layer (3), an outer electronically conductive layer (1), an electronically insulating layer (2), and an ion conductive layer. The tubular cell element further comprises at least one of an inner current collector layer and an outer current collector layer. The tubular cell element comprises a catalyst.    USE - As a tubular cell element including a tubular fuel cell or an electrolyzer cell which are used in cell tube and stack (claimed).    ADVANTAGE - The tubular cell element has convenient set-up; is easy to repair; exhibits high current densities due to the macroporous electrodes with high surface area; has an open structure with relatively large passages to allow for the formed gases to escape and be collected; exhibits low internal resistance to reduce or minimize energy losses in the electrolysis process; provides highly catalytic electrode surfaces to reduce electrode over-potential; and exhibits a robust structure that can withstand the generation of gas bubbles continuously.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a cell tube comprising the multiplicity of tubular cell elements, where the tubular cell elements are assembled end to end in electrical connection, where the assembly of the multiplicity of tubular cell elements forms a tubular structure with a shell side and a bore side, where a first agent in the shell side of the cell tube can be prevented from mixing with a second agent on the bore side of the cell tube;    (2) a stack comprising the cell tubes, where the ends of the cell tubes are sealed into at least a first sealing plate, where the first sealing plate divides the stack into at least a first section and a second section, where the shell side of the cell tubes are open to the first section, where the bore side of the cell tubes are open to the second section;    (3) method of manufacturing the tubular cell element involving forming a tube structure using a first electronically conductive material to form an inner electronically conductive layer, winding a sheet of ion conductive material around the tube structure comprising the inner electronically conductive layer, and wrapping a second electronically conductive material to form an outer electronically conductive layer;    (4) method of manufacturing the cell tube;    (5) method of manufacturing the stack; and    (6) method of using the stack involving providing a first agent to the first section, where the first agent enters the shell side of the cell tubes, and providing a second agent to the second section, where the second agent enters the bore side of the cell tubes.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of an exemplary tubular cell element.    Outer electronically conductive layer (1)    Electronically insulating layer (2)    Inner electronically conductive layer (3)