A solid oxide fuel cell (SOFC) stack concept is described which comprises "condensed-tubes" like extruded honeycomb sections of ceramic electrolyte (ZrO2-based) and interconnectors of nickel sheet as key elements. According to this concept, well known and extensively tested construction principles can be realised in a low-cost production. The cells are self-supported with in-plane conduction. A demonstrator model stack of five honeycomb elements and six nickel sheet seals/interconnectors was built and operated for 860 h at 1000 degrees C. Volumetric power densities of 160 kW/m(3) were obtained with H-2 vs. air, of close to 200 kW/m(3) with H-2 VS. O-2.