Degradation Of Photovoltaic Modules Research Articles

Effects of UV on power degradation of photovoltaic modules in combined acceleration tests

UV exposure and other factors such as high/low temperature, humidity and mechanical stress have been reported to degrade photovoltaic (PV) module materials. By focusing on the combined effects of UV stress and moisture on PV modules, two new acceleration tests of light irradiation and damp heat (DH) were designed and conducted. The effects of UV exposure were validated through a change in irradiation time (UV dosage) and a change of the light irradiation side (glass side vs backsheet side) in the UV-preconditioned DH and cyclic sequential tests, respectively. The chemical corrosion of finger electrodes in the presence of acetic acid generated from ethylene vinyl acetate used as an encapsulant was considered to be the main origin of degradation. The module performance characterized by electroluminescence images was confirmed to correlate with the measured acetic acid concentration and Ag finger electrode resistance.

Behavior of the potential-induced degradation of photovoltaic modules fabricated using flat mono-crystalline silicon cells with different surface orientations

This paper deals with the dependence of the potential-induced degradation (PID) of flat, p-type mono-crystalline silicon solar cell modules on the surface orientation of solar cells. The investigated modules were fabricated from p-type mono-crystalline silicon cells with a (100) or (111) surface orientation using a module laminator. PID tests were performed by applying a voltage of −1000 V to shorted module interconnector ribbons with respect to an Al plate placed on the cover glass of the modules at 85 °C. A decrease in the parallel resistance of the (100)-oriented cell modules is more significant than that of the (111)-oriented cell modules. Hence, the performance of the (100)-oriented-cell modules drastically deteriorates, compared with that of the (111)-oriented-cell modules. This implies that (111)-oriented cells offer a higher PID resistance.

Assessment of PV Modules Degradation based on Performances and Visual Inspection in Algerian Sahara

On-site measurement is a useful mean of diagnostic value and an important key for the assessment of electrical performances and the study of degradation of photovoltaic modules. This paper presents some findings of PV modules behaviour in Adrar (southernmost of Algeria). The study allowed assessing the long-term degradation of modules and detecting possibly defects by visual inspection method. The average annual power degradation rate of PV modules is around 1,5%. Such value tallies with several studies. The visual inspection let us to detect many types of failures in PV modules like delamination, burn marks, cracking but discoloration of encapsulant was the predominant modes of degradation. This study will provide useful information to the manufacturers and owners and helps to better understanding the degradation mechanisms and, therefore, improving the long-term reliability of photovoltaic modules in the Algerian Sahara.

An outdoor investigation of the absorption degradation of single-junction amorphous silicon photovoltaic module due to localized heat/hot spot formation

This paper investigates the absorbance degradation of single-junction amorphous silicon (a-Si:H) photovoltaic (PV) module, due to the presence of localized heat. The decrease in optical density is a huge challenge due to the long-term degradation of PV modules. The reduction in solar cell optical density causes a decline in its conversion efficiency. This decreases the photogenerating current, hence reduces the effective efficiency of the PV device. An infrared thermography was used for mapping the module temperature profile. Fourier transform infrared spectroscopy (FTIR) was used for the absorption characterization. The rationale behind the outdoor deployment was to deduce a practical effect of hot spot formation on the module’s absorption ability. The results show a direct correlation between localized heat and the absorption degradation.

The contribution of dust to performance degradation of PV modules in a temperate climate zone

This research investigates the contribution of dust to the long-term performance degradation of various photovoltaic (PV) modules that have been operating for almost eighteen years without any cleaning procedures at the Renewable Energy Outdoor Testing Area (ROTA), Murdoch University, Perth, Australia. A solar module analyser was used to assess the PVs’ electrical performance, while a combination of spectrophotometer, scanning electron microscope, electron dispersive spectroscope and X-ray diffraction were used to exam the properties of the dust on the panels. The study found that the degradation of the PV modules’ power output, ranged from 19% to 33%. The degradation is mostly due to non-dust related factors such as corrosion, delamination, and discoloration, which account about 71–84%, although the contribution of dust is still significant at 16–29%. Anova analysis shows that the dust has a fairly uniform impact on the performance degradation of all PV technologies at ROTA. This is in line with the results of spectral transmittance curves for different dust density samples that essentially flat over the wavelength range of the PV modules. An investigation of the properties of dust revealed that dust particles deposited on PV modules’ surface at ROTA were dominated by fine particles built of large amounts of quartz (SiO2), followed by calcium oxide (CaO) and some minors of feldspars minerals (KAlSi3O8), which are the main factors in transmittance losses that affect PV module performance.

A Combined Experimental and Simulation Study on the Effects of Irradiance and Temperature on Photovoltaic Modules

Solar cell is one of the crucial components in photovoltaic systems. Silicon solar modules are widely used in the Photovoltaic (PV) industry. The silicon PV electrical performance is described by its current–voltage (I–V) characteristic, which is as function of the device used and material properties. This study provides a comparison between a simplified PV-cell and module model and its parameterization, guaranteeing that the I–V characteristic curves fit with the typical points given by manufacturers’ datasheets and experimental data. The PV performance study is carried out as function of the junction temperature and insolation. This contribution gives an overview over PV module defects and degradation.

Prediction of the Potential Induced Degradation of Photovoltaic Modules Based on the Leakage Current Flowing Through Glass Laminated With Ethylene-Vinly Acetate

In the potential induced degradation (PID) phenomenon, the output power of a photovoltaic (PV) module decreases due to the high potential difference between the PV system and the ground. This voltage forcefully moves the positive charge in the module to the surface of the solar cell. The accumulated charge leads to the performance deterioration of the module, namely, PID of the module. We conducted a study to accurately predict the output reduction of the module operating in various installation conditions coming from the PID phenomenon. We investigated the leakage current flowing through front glass laminated with encapsulation material simultaneously exposed to various performance conditions of the PV system, namely, relative humidity, temperature, and applied voltage, which have an important effect on the PID of the module. The degradation of the module coming from PID was calculated on the basis of the obtained leakage current. To confirm the calculated data, modules with one solar cell were manufactured and the power loss results of the modules' exposure to various PID generation experiments were compared with the expected results. The results showed that we could predict the degradation of the modules by PID within a 2% tolerance under the PV system installation conditions.

Relationship between cross-linking conditions of ethylene vinyl acetate and potential induced degradation for crystalline silicon photovoltaic modules

In this study, we investigated the relationship in crystalline silicon (c-Si) photovoltaic (PV) modules between the cross-linking level of copolymer of ethylene and vinyl acetate (EVA) as the encapsulant and the degree of degradation due to potential induced degradation (PID) phenomenon. We used three methods for the determination of cross-linking level of EVA: xylene method, which is one of the solvent extraction methods (SEM), curing degree by differential scanning calorimetry (DSC), and viscoelastic properties by dynamic mechanical analysis (DMA). The results indicate that degradation of PV modules by PID test depends on the cross-linking level of EVA. The PV modules encapsulated by EVA with higher cross-linking level show lower degradation degree due to PID phenomenon. Also we showed that EVA with higher cross-linking level tended to be higher volume resistivity. This tendency is similar to that for electrical resistance value during the PID test. The PID test was also done by changing thickness of EVA between front cover glass and c-Si with the same cross-linking level. The PV modules encapsulated by thicker EVA between front cover glass and c-Si cell show lower degradation by PID. From these results, the PV modules encapsulated by EVA with higher cross-linking level, higher volume resistivity and increased thickness would be tolerant of PID phenomenon.

Low-cost Backsheet Materials with Excellent Resistance to Chemical Degradation for Photovoltaic Modules

Low-cost Backsheet Materials with Excellent Resistance to Chemical Degradation for Photovoltaic Modules

Potential-induced degradation in photovoltaic modules based on n-type single crystalline Si solar cells

Potential-induced degradation (PID) in photovoltaic (PV) modules based on n-type single crystalline Si solar cell (front junction cell) was experimentally generated by applying negative voltage from an Al plate, which was attached on the front cover glass of the module, to the Si cell. The solar energy-to-electricity conversion efficiency of the standard n-type Si PV module decreased from 17.8% to 15.1% by applying −1000V at 85°C for 2h. The external quantum efficiency in the range from 400 to 600nm significantly decreased after the PID test, although no change was observed from 800 to 1100nm. PID in n-type Si PV modules can be basically explained by enhanced front surface recombination between electron and hole on the Si cell, whereas the polarity of voltage leading to PID depends on structure of Si cell. An ionomer encapsulant instead of EVA has significantly suppressed PID in n-type Si PV modules.

Quantification of photovoltaic module degradation using model based indicators

One of the most important characteristics of the photovoltaic (PV) modules is their long lifetime (around 25 years). However, recent investigations have shown that PV modules may suffer significant degradation before that time; that is why the development of diagnostic techniques is important for the customers of PV systems. In this paper two indicators to quantify the degradation of a PV module are presented. Such indicators use the single-diode model to represent a PV module without degradation and combine such information with the experimental measurements to estimate the increase in the series resistance and/or the decrease in the parallel resistance with respect to reference values. The estimation of those variations allows the quantification of the module degradation. Simulation results comparing the proposed indicators with the fill factor (a traditional indicator to quantify the electrical quality of a PV module), and other indicators to estimate the series resistance are presented to illustrate the advantages of the proposed indicators.

Yield predictions for photovoltaic power plants: empirical validation, recent advances and remaining uncertainties

AbstractYield predictions are performed to predict the solar resource, the performance and the energy production over the expected lifetime of a photovoltaic (PV) system. In this study, we compare yield predictions and monitored data for 26 PV power plants located in southern Germany and Spain. The monitoring data include in‐plane irradiance for comparison with the estimated solar resource and energy yield for comparison with predicted performance. The results show that because of increased irradiance in recent years (‘global brightening’) the yield predictions systematically underestimate the energy yield of PV systems by about 5%. Because common irradiance databases and averaging times were used for the yield predictions analysed in this paper, it is concluded that yield predictions for areas where the global brightening effect occurred in general underestimated the energy yield by the same magnitude. Using recent satellite‐derived irradiance time series avoids this underestimation. The observed performance ratio of the analysed systems decreases by 0.5%/year in average with a relatively high spread between individual systems. This decrease is a main factor for the combined uncertainty of yield predictions. It is attributed to non‐reversible degradation of PV cells or modules and to reversible effects, like soiling. Based on the results of the validation, the combined uncertainty of state of the art yield predictions using recent solar irradiance data is estimated to about 8%. Copyright © 2015 John Wiley & Sons, Ltd.

유무연 용융도금 리본에 따른 결정질 실리콘 태양전지 모듈 열화거동

Usage of heavy metal element (Pb, Hg and Cd etc.) in electronic devices have been restricted due to the environmental banning of the European Union, such as WEEE and RoHS. Therefore, it is needed to develop the Pb-free solder plated ribbon in photovoltaic (PV) module. This study described that degradation characteristics of PV module under damp heat (DH, 85 ℃ and 85% R.H.) condition test for 1,000 h. Solar cell ribbons were utilized to hot dipping plate with Pb-free solder alloys. Two types of Pb-free solder plated ribbons, Sn-3.0Ag-0.5Cu (SAC305) and Sn-48Bi-2Ag, and an electroless Sn-40Pb solder hot dipping plated ribbon as a reference sample were prepared to evaluate degradation characteristics. To detect the degradation of PV module with the eutectic and Pb-free solder plated ribbons, I-V curve, electro-luminescence (EL) and cross-sectional SEM analysis were carried out. DH test results show that the reason of maximum power (Pm) drop was mainly due to the decrease fill factor (FF). It was attributed to the crack or oxidation of interface between the cell and the ribbon. Among PV modules with the eutectic and Pb-free solder plated ribbon, the PV module with SAC305 ribbon relatively showed higher stability after DH test than the case of PV module with Sn-40Pb and Sn-48Bi-2Ag solder plated ribbons.

Outdoor degradation of thin film amorphous silicon based PV modules

One of the main problems in thin film silicon based modules is the deterioration of their performance upon exposure to light. The presented work focuses on a methodology for evaluation of thin-film photovoltaic module degradation behavior under real operating conditions. The outdoor degradation of double junction a-Si:H/a-Si:H modules was investigated using automated measurement setup for a period of two years. A deterioration of the module's maximum power was observed due to the well known Staebler-Wronski effect, which main causes are the decrease of open circuit voltage and the fill factor of the module. The obtained results can be correlated to the technology and construction of the thin film silicon based modules.

Power Optimization for Photovoltaic Microconverters Using Multivariable Newton-Based Extremum Seeking

Extremum seeking (ES) is a real-time optimization technique that has been applied to maximum power point tracking (MPPT) design for photovoltaic (PV) microconverter systems, where each PV module is coupled with its own dc/dc converter. Most of the existing MPPT designs are scalar, i.e., employ one MPPT loop around each converter, and all designs, whether scalar or mutivariable, are gradient based. The convergence rate of gradient-based designs depends on the Hessian, which in turn is dependent on environmental conditions, such as irradiance and temperature. Therefore, when applied to large PV arrays, the variability in environmental conditions and/or PV module degradation results in nonuniform transients in the convergence to the maximum power point (MPP). Using a multivariable gradient-based ES algorithm for the entire system instead of a scalar one for each PV module, while decreasing the sensitivity to the Hessian, does not eliminate this dependence. We present a recently developed Newton-based ES algorithm that simultaneously employs estimates of the gradient and Hessian in the peak power tracking. The convergence rate of such a design to the MPP is independent of the Hessian, with tunable transient performance that is independent of environmental conditions. We present simulation as well as the experimental results that show the effectiveness of the proposed algorithm in comparison with the existing scalar designs, and also to multivariable gradient-based ES.

Visual Degradation in Field-Aged Crystalline Silicon PV Modules in India and Correlation With Electrical Degradation

This paper presents the analysis of visual degradation data collected during an All-India Survey of Photovoltaic Module Degradation conducted in 2013, in which 57 crystalline silicon modules were inspected in the five different climatic zones of India. Analysis of the data indicates that the highest percentage of modules suffered discoloration in the Hot and Dry climatic zone, with the Hot and Humid zone coming in second in the list. A higher percentage of modules have suffered corrosion in the Hot and Humid zone, as compared with other zones. The modules installed in the Cold climate suffered the least degradation. Both discoloration and corrosion have been seen in modules across all age groups, even in some of the modules installed less than five years ago. On the other hand, delamination and backsheet degradation have been seen only in modules more than a decade old. The visual degradation data have been correlated with the electrical performance data and reaffirm the direct relation between encapsulant discoloration and reduction in short-circuit current and output power, as well as that of series resistance with metal corrosion.

Assessing the early degradation of photovoltaic modules performance in the Saharan region

In this study, the electrical performance degradation of photovoltaic modules (UDTS-50) functioning for a period of 11years in a region of the Sahara (URER-MS ADRAR) is analyzed. This paper is devoted to an experimental study of current–voltage characteristics of several PV modules exposed to the extreme weather conditions in desert area. The electrical performance degradation and failure modes are estimated from series of current–voltage characteristics performed in the field. Experimental results show that some PV modules degrade up to 12% compared to their initial state. The performance analysis of the others tested modules revealed some defects, such as cracked cells and physical material defects. The identification of the origin of degradation and failure modes and how they affect the photovoltaic modules is necessary to improve the reliability of photovoltaic installations.

Degradation evaluation of crystalline-silicon photovoltaic modules after a few operation years in a tropical environment

This paper presents an evaluation of the performance degradation of Photovoltaic modules after few operation years in a tropical environment. To this end, the International Center for Research and Training in solar energy at Dakar University and the Lasquo-ISTIA laboratory of Angers University have put in place a research project in order to investigate the impact of the tropical climatic conditions on the PV modules characteristics. Accordingly, two monocrystalline-silicon (mc-Si) PV modules and two polycrystalline- silicon (pc-Si) PV modules are installed at Dakar in Senegal and monitored during a few operation years: Module A (16 months), Module B (41 months), Module C (48 months) and Module D (48 months). After few operation years under tropical environment, the global degradation and the degradation rate of electrical characteristics such as I-V and P-V curves, open-circuit voltage (Voc), short-circuit current (Isc), maximum ouput current (Imax), maximum output voltage (Vmax), maximum power output (Pmax) and fill factor (FF) are evaluate at standard test conditions (STC). This study reports on data collected from 4 distinct mono- and poly-crystalline modules deployed at Dakar University in Senegal. The study has shown that Pmax, Imax, Isc and FF are the most degraded performance characteristics for all PV modules. The maximum power output (Pmax) presents the highest loss that can be from 0.22%/year to 2.96%/year. However, the open-circuit voltage (Voc) is not degraded after these few exposition years for all studied PV modules.

Statistical and Domain Analytics Applied to PV Module Lifetime and Degradation Science

A better understanding of the degradation modes and rates for photovoltaic (PV) modules is necessary to optimize and extend the lifetime of these modules. Lifetime and degradation science (L&DS) is used to understand degradation modes, mechanisms and rates of materials, components and systems to predict lifetime of PV modules. A PV module lifetime and degradation science (PVM L&DS) model is an essential component to predict lifetime and mitigate degradation of PV modules using reproducible open data science. Previously published accelerated testing data from Underwriter Laboratories on PV modules with fluorinated polyester backsheets, which included eight modules that were exposed up to 4000 hrs of damp heat (85% relative humidity at 85°C) and eight exposed up to 4000 hrs of ultraviolet light (80 W/m2 of 280-400 nm wavelengths at 60°C) (UV preconditioning) were used to determine statistically significant relationships between the applied stresses and measured responses. There were 15 different variables tracking aspects of system performance, degradation mechanisms, component metrics and time. Modules were analyzed for three system performance metrics (fill factor, peak power, and wet insulation). The results were statistically analyzed to identify variable transformations, statistically significant relationships (SSRs) and to develop the PVM L&DS model informed by a generalization of structural equation modeling techniques. The SSRs and significant model coefficients, combined with domain analytics, incorporating materials science, chemistry, and physics expertise, produced a pathway diagram ranking the variables' impact on the system performance, which were iteratively examined using sound statistical analysis and diagnostics. The SSRs determined from the damp heat exposure for the system response of Pmax corresponded to the degradation pathway of polyester terephthalate (PET) and ethylene vinyl acetate (EVA) hydrolysis. A linear change point for the damp heat exposure with the system response of Pmax was determined to be 1890 hrs. The UV preconditioning exposure did not induce sufficient degradation shown by the quality of the R2 values for many of the best fitting models. This exemplifies the development of a methodology to determine rank ordered lifetime and degradation pathways present in modules and their effects on module performance over lifetime.

Experimental investigation of the mechanical behavior of photovoltaic modules at defined inflow conditions

The mechanical behavior of a photovoltaic (PV) module induced by aerodynamic loads is analyzed in a wind tunnel for three different wind velocities at varied azimuthal and inclination angles. The deformations and flow-induced vibrations of the PV module have been monitored by a displacement sensor. The frequencies of the monitored vibrations are analyzed by Fourier transformation. Finally, the damage potential at cell level caused by wind loads is investigated by electroluminescence. The aim of this work was to study the mechanical transfer behavior of the coupled fluid-structure interaction between the aerodynamic loads and the deformations and vibrations of the module, which is one aspect of the mechanically induced degradation of PV modules.