Modeling and simulation of photovoltaic (PV) systems represents an essential task for the integration of PV panels in current power applications. At the present time, there are sizing tools of photovoltaic systems available on the market, taking into account the proposed energy consumption, site localization and system cost. this paper aims to simulation of a stand-alone system for two types: fixed system and non-fixed system in Alkhums city _ Libya using the PVsyst software. The sizing and simulations developed using PV modules based on two different technologies: Monocrystalline and polycrystalline silicon, Results show that the non-fixed system is more efficient than fixed system and the Monocrystalline silicon is more efficient than polycrystalline silicon where the solar fraction was 0.981,performance ratio was 0.653 and energy supplied to the user was 1259.8 kWh/year.