This study analyses hybrid systems combining a molten carbonate fuel cell (MCFC) operating at ambient pressure and a gas turbine. Various possible system layouts, with the major difference among these layouts being the heating method of the turbine inlet gas, are proposed and their design performances are simulated and comparatively analyzed. Power of the MCFC in the hybrid system is explained in terms of the cathode inlet air temperature. Power of the gas turbine differs among various layouts because of large difference in the turbine inlet temperature. The direct firing in front of the turbine allows far higher turbine inlet temperature, and thus greater gas turbine power than the indirect heating of the inlet gas. The optimum pressure ratio of the directly fired system is higher than that of the indirectly fired system. The directly fired system allows not only much larger system power and higher optimum efficiency but also greater flexibility in the selection of the design pressure ratio of the gas turbine. In addition, the directly fired system can better accommodate the specifications of both current micro gas turbines and advanced gas turbines than the indirectly fired system. (c) 2005 Elsevier B.V. All rights reserved.