A thermodynamic model is developed to determine the fuels that Would yield all identical maximum cell voltage (MCV) for solid oxide Net cells (SOFCs) at a given operating condition. These fuels make a continuous Curve in the ternary coordinate system. A fuel map) is established by developing the continuous fuel curves for different MCVs at the same operating condition and representing them in the carbon-hydrogen-oxygen (C-H-O) ternary diagram. Using the fuel map, the effect of the composition of a fuel containing carbon, hydrogen, oxygen, and inert gas atoms on the MCV of SOFCs can be easily studied. In addition to the effect of the fuel composition, the graphical representation of fuel maps call be applied to study the effect of the fuel processors on the MCV of SOFCs. As a general results, among fuels that call be directly Utilized ill SOFCs, all the same temperature and pressure, the one located at the intersection of the H-C axis and the carbon deposition boundary (CDB) curve in the C-H-O ternary diagram, provides (lie highest MCV for SOFCs. The results also show that for the fuels that cannot be directly utilized in SOFC, the steam reforming fuel processor always yields a higher MCV than the autothermal reforming or the partial oxidation fuel processors at (lie same inlet fuel temperature. (C) 2009 Elsevier B.V. All rights reserved.