This paper summarizes our research on modeling of metal hydride systems, examines the fundamental limitations imposed by geometrical and thermodynamic considerations, and presents a theoretical model for a complete system throughout an entire cycle. Apart from the assumption of local thermodynamic equilibrium no major simplifying assumptions are made and the non-ideal behavior of the hydrides is included. The nature of the heat and mass transfer processes as two coupled reactors are optimized is elucidated. The consequences for future metal hydride heat pump design are investigated. (C) 1997 Elsevier Science Ltd.