The objective of this paper is to mathematically model a stand-alone renewable power system, referred to as "Photovoltaic-Fuel Cell (PVFC) hybrid system", which maximizes the use of a renewable energy source it comprises a photovoltaic generator (PV), a water electrolyzer, a hydrogen tank, and a proton exchange membrane (PEM) fuel cell generator A multi-domain simulation platform Simplorer is employed to model the PVFC hybrid systems Electrical power from the PV generator meets the user loads when there is sufficient solar radiation. The excess power from the PV generator is then used for water electrolysis to produce hydrogen. The fuel cell generator works as a backup generator to supplement the load demands when the PV energy is deficient during a period of low solar radiation, which keeps the system's reliability at the same level as for the conventional system. Case studies using the present model have shown that the present hybrid system has successfully tracked the daily power consumption in a typical family It also verifies the effectiveness of the proposed management approach for operation of a stand-alone hybrid system, which is essential for determining a control strategy to ensure efficient and reliable operation of each part of the hybrid system. The present model scheme can be helpful in the design and performance analysis of a complex hybrid-power system prior to practical realization (C) 2009 Professor T. Nejat Veziroglu Published by Elsevier Ltd All rights reserved