Two, simple, solid-oxide fuel-cell (SOFC) power systems fed by hydrogen and methane, respectively, are examined, While other models available in the literatures focus on complicated hybrid SOFC and gas-turbine (GT) power systems. this study focuses on simple SOFC power systems with detailed thermodynamic modeling of the SOFC. All performance-related parameters of the fuel-cell such as respective resistivity of the components, anode and cathode exchange current density. limiting current density. flow diffusivity, etc. are all expressed as a function of temperature, while the flow through of each nodes of the system is described as a function of thermodynamic state. Full analysis of the energy and exergy at each node of the system is conducted and their respective values are normalized by the lower heating value (LHV) of the fuel and its chemical exergy, respectively. Thus, the normalized electrical energy outputs directly indicate the first law and second law efficiencies, respectively, of the fuel-cell power systems.