Cao fuel cell stack with large specific reactive surface area

A polymer electrolyte membrane (PEM) fuel cell stack having a plurality of micro fuel cell units, wherein each micro fuel cell unit comprises a micro electric conductive tube defining an inner axial flow path for the fuel cell unit, said tube including a porous section, an inner electrode being disposed coaxially around and in intimidate contact with a peripheral surface of the porous section, a solid polymer electrolyte member being disposed coaxially around and in intimate contact with the inner electrode, and an outer electrode being disposed coaxially around and in intimate contact with the electrolyte, said inner electrode, polymer electrolyte and outer electrode defining a reactive zone and generally covering the peripheral surface of the porous section of the micro tube,

• said fuel cell stack comprising a plurality of fuel cell modules, wherein each fuel cell module comprises an electric conductive planar sheet, and the plurality of micro fuel cell units being laid side by side on the electric conductive planar sheet in a generally parallel arrangement, with the inner electrodes of said micro fuel cell units being electrically interconnected and being electrically isolated from the conductive planar sheet,
• wherein said fuel cell modules being are stacked one over another with an electrical insulating material being sandwiched between the outer electrodes of the micro fuel cell units of a first fuel cell module and the conductive planar sheet of a second fuel cell module overlying the outer electrodes of the first module, and wherein the stacked fuel cell modules are electrically connected in series.