Performance assessment of a novel energy system integrating both biomass gasification and fuel cell systems is performed thermodynamically through energy and exergy efficiencies. Steam gasification for rich hydrogen gas production as a useful gasification output is considered. Energy and exergy thermodynamics model of the gasification process is introduced. A thermal model of bubbling fluidized bed gasifier, operating at atmospheric pressure, is also considered to investigate the temperature profile through the gasifier. Direct internal reforming solid oxide fuel cell model is introduced and it is integrated with the system for power production. The presented models are validated, and the effects of different operating parameters on the system performance are studied under various conditions. Different values of gasification operating temperature and moisture content of the supplied fuel are also considered in parametric studies. The results show that steam biomass ratio has a significant effect on the hydrogen production efficiency and optimal value of 0.677 is calculated for maximum exergy efficiency at the base case condition. Copyright (c) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.