High temperature fuel cells (MCFCs and SOFCs) can operate at atmospheric or pressurised conditions. In both cases, system performance can be significantly improved when the fuel cells are integrated with proper devices, which are designed to provide the necessary air inlet conditions and to recover the exhaust-gas energy. This paper presents a review of modelling and design issues for the integration of turbomachinery with the fuel cell system, because turbomachinery is the most promising technology for coping with the high temperature fuel cell requirements.Analytical approach is undertaken for properly modelling composition influence on expander performance, and results are presented to demonstrate the quantitative influence of the system parameters on the performance. The analysis covers the three main aspects of performance evaluation: the on-design, the off-design and, as a final mention, the control of the fuel cell hybrid systems.
