An annular micro-stack array consisting of four fuel cells has been fabricated and operated successfully in single-chamber conditions using a nitrogen-diluted oxygen-methane mixture as the operating gas. The single cells consist of a state-of-the-art porous NiO/Y2O3-stabilized ZrO2 (YSZ) anode support, a YSZ electrolyte membrane and a modified La0.7Sr0.3MnO3 (LSM) cathode. The annular configuration of the array is favorable for utilizing the heating effect. The maximum power output of the annular stack decreases with increasingCH(4)/O-2 ratio. Its performance increases with increasing CH4 flow rate and decreases with increasing N-2 flow rate. The power output of the stack is similar to 380 mW at CH4/O-2=1 and an N-2 flow rate of 100 sccm and the average maximum power density of each cell is similar to 190 mW cm(-2). The average performance of each cell in the annular micro-stack array is higher than that of an additional single cell placed next to the stack. (C) 2010 Elsevier B.V. All rights reserved.