A dynamic model of a (portable) polymer electrolyte fuel cell system including the heat transfer between stack and periphery - here stack and metal hydride storage - has been developed within MATLAB-Simulink. The implemented equations describe the steady-state as well as the dynamic operation of the PEFC system with sufficient accuracy, although considerable simplifications have been made to keep model complexity and computing time low. As simulations are performed in 100-fold real time, different operating conditions and control strategies for PEFCs can be analyzed and evaluated in short-time. Here, emphasis is given to the operation limits of the PEFC system, i.e. the conditions for trouble-free operation at different loads and high or low ambient temperature are established. The model has been validated by experiments on a home-made portable system. (c) 2005 Published by Elsevier B.V.