Most manufacturers of solar modules guarantee the minimum performance of their modules for 20 to 25 years, and 30-year warranties have been introduced. The warranty typically guarantees that the modules will perform to at least 90% capacity in the first 10 years and to at least 80% in the following 10 -15 years. Early degradation resulting from design flaws, materials or processing issues is often apparent from startup to the first few years in service. Importantly, many module failures and performance losses are the result of gradual accumulated damage resulting from long-term outdoor exposure in harsh environments, referred. Many of these processes occur on relatively long time scales and the various degradation processes may be chemical, electrical, thermal or mechanical in nature. These are either initiated or accelerated by the combined stresses of the service environment, in particular solar radiation, temperature and moisture, and other stresses such as salt air, wind and snow. Accelerated Life Testing (ALT) test methodology is normally predicated on first being able to reproduce a specific degradation or failure mode without altering it (correlation); and, second, to produce that result in less than real-time acceleration. Degradation and failure may result when an applied stress exceeds material or product strength. This may be a one-time catastrophic event, the result of cyclic fatigue, or a gradual decline in requisite properties due to ageing mechanisms. Engineers in the manufacturing industries have used accelerated test (AT) experiments for many decades. The purpose of AT experiments is to acquire reliability information quickly. Test units of a material, component, subsystem or entire systems are subjected to higher-than-usual levels of one or more accelerating variables such as temperature or stress. Then the AT results are used to predict life of the units at use conditions. The extrapolation is typically justified (correctly or incorrectly) on the basis of physically motivated models or a combination of empirical model fitting with a sufficient amount of previous experience in testing similar units. The need to extrapolate in both time and the accelerating variables F. Dia et al. 50 generally necessitates the use of fully parametric models. Statisticians have made important contributions in the development of appropriate stochastic models for AT data [typically a distribution for the response and regression relationships between the parameters of this distribution and the accelerating variable(s)], statistical methods for AT planning (choice of accelerating variable levels and allocation of available test units to those levels) and methods of estimation of suitable reliability metrics. This paper provides a review of many of the AT models that have been used successfully in this area.

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In this paper, the electrical properties of heterojunction solar cells thin film n-CdS/p-CdTe from dielectric model have been studied. Based on the expression of the minority, carriers density in the p-CdTe base of solar cell, the photocurrent density and that of the photo voltage are determined according to the cell dimensions, doping levels, the absorption coefficient, the solar irradiance and the temperature, etc. Fitting using Mathcad and Origin Lab software on the photocurrent and the photovoltage of the n-CdS/p-CdTe enabled to determine the series, shunt resistance and the maximum power point. The results obtained, in good agreement with experimental results, allow operating simulations for optimizing maximum outputs parameters (I p , V p ). Thereafter, it is proposed a type of photovoltaic generator module with a good command of the design parameters for better efficiency.

To compare the performance of PV modules, it was required to translate the measured I-V characteristics, to use certain standard conditions. The International Electrotechnical Committee (IEC) has defined the standard test condition (STC) for PV modules with 1000 W/m 2 irradiance with AM 1.5 and 25°C module temperature. The IEC has also published some standard correction procedures (contained in IEC 60891) to translate irradiance and temperature values between different. IEC 60891 defines a procedure which helps to translate the measured I-V characteristics photovoltaic devices at standard test condition (STC). The IEC 60891 translation procedures can be applied only for the 20% variation in the irradiance, the irradiance should not be below 800 W/m 2 for translation at STC but also for limit temperatures (35 ° VS). In our study we will use crystal technology and the temperature measurements carried out at the study site show temperatures varying from 55°C to 65°C. Data from tests in the wild has been converted to standard test conditions (STC) using four methods proposed by AJ Anderson and G. Blaesser, the combination method and the equations from international standard IEC 60891. These methods are compared using data from one year and the correlation between the measured data and the standardized data. The results demonstrated that the combination method has good precision in the STC conversion of the performance of the PV module under different climatic and technological conditions. Then, based on the investigation results of the conversion equations, these translation methods are distinguished by the type of solar cell technology and the field of application. There is a difference between in situ and natural tests, attributed to various factors but mainly to the mismatch between the spectral responses of the PV module and the reference solar cell. The combination method uses irradiance data and temperature and performance parameters under STC conditions of PV modules to predict the maximum output power. Therefore, it is essential to provide reliable weather data before designing photovoltaic power systems.