Based on the current models of solid oxide fuel cells and two-heat-source heat engines
consisting of two isothermal and two polytropic processes, a general model of a class of
fuel cell/heat engine hybrid systems is established, in which multi-irreversibilities existing
in real hybrid systems are taken into account. Expressions for the efficiency and power
output of the hybrid systems are analytically derived from the model. The curves of the
efficiency and power output of the hybrid systems varying with the current density and
the efficiency versus power output curves are represented through numerical calculation.
The general performance characteristics of the hybrid systems are revealed and the
optimum criteria of the main performance parameters are determined. The effects of some
key irreversibilities existing in the fuel cell, regenerator and two-heat-source heat engine
on the performance of the hybrid systems are discussed in detail. The results obtained here
are very general and may be directly used to derive the various interesting conclusions of
the hybrid systems which are operated under different special cases