1 INTRODUCTION Photovoltaic (PV) systems are installed all around the world to produce electricity from solar energy. However, photovoltaic modules and systems life- time and availability have not been received great at- tention from researchers. These estimates are impor- tant to insure the performance (MTBF, number of outage days per year and steady state availability) of such a system over its life cycle. Reliability and the availability of a stand-alone pho- tovoltaic system are discussed by Díaz et al. (2007) using exponential law for different components. They use operational photovoltaic systems data de- duced from feedback record by Jahn & Nasse (2003) and Maish et al. (1997). In this paper, we propose a methodology using Petri networks to estimate the reliability and availability of a photovoltaic system. The main advantage of Pe- tri networks is the ability to simulate large systems with a complex configuration of its components, while considering many types of lifetime distribu- tions. Laronde et al. (2010a) studied a photovoltaic system using Petri networks assuming constant fail- ure rate for each component. The main objective of this paper is to take into account the components’ degradation and the power evolution of the photo- voltaic system. We first present the photovoltaic system under study, and then an overview of Petri networks, fol- lowed by modeling of the system as a Petri network. Finally, a simulation using several photovoltaic ar- rays is carried out and reliability and availability are estimated. The influence of the installation parame- ters and the capacity of the repair facility on system power output and availability are investigated. 2 PHOTOVOLTAIC SYSTEM The system under study is a grid-connected photo- voltaic system as shown in Figure 1. This system consists of a photovoltaic array with modules con- nected in a series-parallel configuration and balance- of-system (BOS) components which are not photo- voltaic components: there are an inverter which transforms the direct current from photovoltaic array to alternating current and wires which transmit the continuous energy from PV modules to an inverter (DC wires) and a wire which transmits the alternat- ing energy from the inverter to the electric grid (AC wire). Figure 1. Photovoltaic system under study. Photovoltaic modules are connected in a series- parallel configuration in order to obtain significant power by balancing the voltage and amperage deli- vered to the inverter. Generally, two DC wires are used to connect photovoltaic modules to the inverter. Reliability and availability estimation of a photovoltaic system using Petri networks R. Laronde, A. Charki, D. Bigaud LASQUO Laboratory, ISTIA, University of Angers, Angers, France E.A. Elsayed Rutgers University, New Jersey, USA P. Excoffier GINGER CEBTP, Elancourt, France ABSTRACT: Many photovoltaic (PV) systems are nowadays installed all around the world. However, the re- liability and the availability estimation of photovoltaic systems have not been received great attention from researchers. Reliability and availability are important consideration in the life-cycle of such systems. This pa- per presents a methodology for estimating the reliability and the availability of a photovoltaic system using Petri networks. Each component - module, wires and inverter - is detailed in Petri networks and several laws are used in order to determine the reliability and system availability. The degradation function of each com- ponent has been taken into account. Results show that Petri networks simplify the reliability and availability modeling and analysis.