Lifetime assessment of a photovoltaic system using stochastic Petri nets

The lifetime estimation of photovoltaic (PV) systems is an important consideration in their life cycle. This paper presents a multi-level methodology to estimate the availability and the lifetime of a PV system using stochastic Petri networks and taking into account the time distribution to failure and to repair. The following components – module, wires, and inverter – are modeled with a Petri network. The evolution of the MTBF, availability, and outages over a 30-year period is simulated for different series/parallel configurations of connected PV modules. Findings are in agreement with reported experimental results, namely the evolution of the availability which tends to be near 96% for long times. Numerical results show that the highest MTBF is 3.2 years and the lowest outage is of 11.84 days/year, which are both obtained for the string configuration. The approach is interesting for the dimensioning of a PV plant or an installation

Impact of the aging of a photovoltaic module on the performance of a grid-connected system

Photovoltaic systems belong to the green energy dynamics which is an ambitious program based on energy efficiency and sustainable development. In this study, the impact of the aging of a photovoltaic module is investigated on the electrical performance of a grid-connected system. A photovoltaic conversion chain with MPPT (Maximum Power Point Tracking) control and LC (Inductor-Capacitor) filter is modeled and dimensioned according to the grid constraints. A method of hybridation detection of the MPPT coupling long-time aging evolution and short-time determination is proposed. Aging laws for the electrical and optical degradations of the photovoltaic module are introduced for the long-time evolution. Results display the lowering of the maximal power point with a rate of 1%/year and a slight augmentation of the THD over time even though it remains inferior to the IEEE standard STD 19-1992 maximum value of 5% for a usage of 20 years. Moreover, an equivalent scheme for the additional electrical resistance engendered by the aging of the photovoltaic module regarding other resistances of the photovoltaic system is given. Finally, the elevation of this resistance by 12.8% in 20 years may have non-negligible consequences on the power production of a large-scale installation. © 201

Evaluation performance of photovoltaic modules after a long time operation in Saharan environment

Reliability and lifetime of photovoltaic (PV) systems depend mainly on the energy performance of modules and on their different degradation modes. Accordingly, research must be focused on degradations of PV modules. This paper presents the results of investigations carried out on the degradation mechanisms of PV modules of the Melouka central in the area of Adrar in Algeria after 28 years of exposure in the Saharan environment. Main degradation modes are observed through visual inspection of PV modules: discoloration of encapsulant, broken and abrasion of glass, delamination, discoloration and hot spot of cells, oxidation of front grid fingers and thermal shocks. The current-voltage (I-V) characteristics are acquired with outdoor measurements in the site. The experimental results permit to detect both hot spots and thermal shocks which are the most detrimental total defects visually observable in the site, and to quantify the reduction of electrical performance data correlated with visual degradation data. A maximum power (Pmax) degradation rate of 1.22%/year is found which is closely related to short-circuit current (Isc) of 0.78 %/year, followed by fill factor (FF) of 0.57%/year and finally short-circuit voltage (Voc) of 0.1%/year. Akin results are reported in literature for PV modules exploited under desert climate for long duration