Reliability Of Photovoltaic Modules Research Articles

(Invited) Reliability Improvement and Remaining Issues on Photovoltaic Cells and Modules

Worldwide rapid growth of photovoltaics requires not only high-efficiency but also high-reliability and long-lifetime photovoltaic cells and modules. Reliability of photovoltaic modules is determined by module materials such as encapsulant, backsheet, etc. and, of course, also by photovoltaic cells themselves. There are some complicated phenomena concerning degradation of photovoltaic properties. Those physical and chemical degradation phenomena should be microscopically analyzed in detail in order to clarify degradation mechanism and also realize highly reliable photovoltaic cells and modules. Although such degradation phenomena are complicated and often related each other, degradation mechanism is classified into only three categories; 1) less incident light into solar cells, 2) less collection of photogenerated carriers, and 3) less photovoltaic ability itself. Less incident light often originates from soiling of cover glass; however, in some cases originates from browning of encapsulant or reduction of transparent conductive oxide electrode. Less correction of carriers originates from damage of electrodes on the cell or damage of interconnector ribbons between the cells. Less photovoltaic ability originates from surface or bulk recombination or shunting. These three categories are schematically shown in the attached figure. There are various degradation factors, for example, thermal or mechanical stress, high temperature, high humidity, UV irradiation, and potential difference. In particular, hygrothermal stress, UV irradiation, potential difference, and also their combination are considerable factors. For example, UV irradiation accelerates degradation by hygrothermal stress [1], on the other hand, delays degradation by potential difference [2].Both development of indoor acceleration test method and estimation of acceleration factor are also important for predicting the lifetime of photovoltaic modules. As mentioned above, although UV light irradiation much influences degradation phenomena, test method with UV light irradiation is not popular. The reason is that it is quite difficult to keep the module temperature under irradiation during test duration and also to realize uniform irradiation for large-size photovoltaic modules over 1.5 m. However, using acetic acid concentration in the encapsulant as the mediator between outdoor exposure and indoor acceleration test, it was elucidated that damp heat test at 85°C and 85% relative humidity for 4000 h corresponds to outdoor exposure at Japan for 30 years [3].Based on degradation mechanism clarified, highly reliable photovoltaic cells and modules should be developed. It is clarified that the most important key material is electrode of solar cells. Even when photocarriers are generated, if damage or degradation occurs in the electrodes, such carriers are not collected and photovoltaic performance is lowered. Problems in photocarrier collection occupy majority of origins for degradation observed outdoors. Degradation by potential difference has also attracted much attention in the last 10 years especially in mega-watt scale photovoltaic plant with high system voltage. Encapsulant materials and anti-reflection coating of solar cells are key materials for suppressing such kinds of degradation.There are some remaining issues on photovoltaic cells and modules for improving reliability and increasing lifetime. First, interaction between module materials and cells should be completely clarified. Photovoltaic modules are composed of various materials including polymers, metals, ceramics, and, of course, semiconductors. Complicated reactions should occur both at the interface and in the bulk of those materials by many stressors such as high temperature, high humidity, thermal cycle, UV irradiation, and potential difference. Many observations and knowledges have been obtained so far, however, we do not reach the complete understanding, and essential point is that materials with less change and less interaction with other materials should be employed. Second, acceleration test results should be always analyzed considering outdoor exposure results. Especially, climate conditions such as desert, tropical zone, etc. for outdoor exposure also should be employed for acceleration test conditions. Photovoltaic cells and modules appropriate to specific climate conditions should be developed. Third, high efficiency photovoltaic cells and modules should be developed always considering high reliability and long lifetime. Those are inseparable issues for development of photovoltaic cells and modules. Especially, reliability issues on high-efficiency perovskite cells and modules should be intensively studied and urgently solved for realizing high-efficiency and high-stable perovskite/silicon tandem solar cells and modules.The author is grateful to Professors Keisuke Ohdaira, Sachiko Jonai, Yasuaki Ishikawa, Yasushi Sobajima, Fumitaka Ohashi, Kentaro Iwami, Dr. Seira Yamaguchi, Mr. Yasushi Tachibana, and Ms. Yukiko Hara for their collaboration and fruitful discussion. This study was in part supported by the New Energy and Industrial Technology Development Organization.

Numerical analysis of the reliability of photovoltaic modules based on the fatigue life of the copper interconnects

A typical photovoltaic (PV) module is composed of different layers bonded together, each with a different material and thus, a different coefficient of thermal expansion (CTE). While under operation, it is subjected to thermal loads due to continuous temperature variations. The CTE mismatch induces thermo-mechanical stresses, whose cyclic nature causes fatigue failure. Due to their relative small size, the copper interconnects are one of the most vulnerable constituents.In this work, the finite element (FE) analysis has been used to calculate these thermal stress/strain variations. To make the simulations more reliable, well-known material models have been adopted from the literature and used for each constituent of the PV module. Furthermore, to reduce computational time and complexity, a simplified modeling approach has been proposed in this work. In this approach, a 2-D FE global model was first used to identify the region that undergoes maximum strain. Then a 3-D FE local model was used for that particular region only. This approach helps calculate the maximum stress/strain variations. Thus, using the proposed modeling approach coupled with a fatigue criterion, one can calculate the fatigue life of the PV module, while significantly reducing the computational time. The initial conditions, in terms of residual stresses, due to the lamination process for the fabrications of the PV module are also accounted for in our approach. We applied our approach to silicon-based PV module under desert weather conditions of Doha (Qatar) and the results show a reduced life compared to the one provided by the manufacturer.

Photovoltaic module regional clustering in mainland China and application based on factors influencing field reliability

The field reliability of photovoltaic modules is important to make investment, design, operation and maintenance decisions in PV power generation projects. By minimizing the field reliability differences between the congeneric regions of PV modules, a regional clustering method based on the factors influencing field reliability is proposed, and a model to predict the field reliability or service lifetime by the clustering results is presented. Based on systematic analysis of the regional differences between workload and natural wear factors impacting field reliability, a comprehensive clustering model is constructed, and nine clustering indexes are accurately quantified. The Ward and entropy weight methods are adopted to objectively calculate index and time weights, respectively. The weighted Ward clustering algorithm is applied to cluster regions based on workload and natural wear factors. Two clustering results are integrated through comprehensive clustering to obtain the final result. Finally, this method is applied to the clustering of 31 provincial administrative regions in mainland China, and the result is applied to predict the average annual power degradation amount of the PV modules in the different regions, both of which validate the applicability and effectiveness of the proposed method.

Analysis of long-term performance and reliability of PV modules under tropical climatic conditions in sub-Saharan

Reliability assessment of Photovoltaic (PV) modules is very crucial to increase the service lifetime of PV systems. This study assesses the degradation rate and reliability of PV modules operated for twelve years under the tropical climatic condition in sub-Saharan. For this purpose, various characterization techniques, namely visual inspection, infrared (IR) thermography assessment, and current-voltage (I-V) characterization, have been employed to evaluate the performance of PV modules. Moreover, the functioning of bypass diodes has been tested under partial shading situations. The results demonstrate that after twelve years of outdoor operation, the short-circuit current (Isc) of modules have been degraded up to 16.4% with an average decrease of 11.7% compared to the nameplate values. The open-circuit voltages (Voc) were reduced from 11.4% to 17.1% with a mean of 14.8%. The decline in Fill Factor (FF) of the modules ranges from 11.3% to 24.2%, and the losses of power output were between 34.5% and 41.4%. Moreover, the visual and thermography assessment reveals that the PV modules are severely affected by various failures such as EVA browning, cell interconnects ribbons browning and the corrosion of solder bonds. The results show that averagely, the FF is the most significant factor influencing the loss in the power output of the modules.

Effect of Backsheet Properties on PV Encapsulant Degradation during Combined Accelerated Aging Tests

Long-term photovoltaic (PV) module reliability is highly determined by the durability of the polymeric components (backsheet and encapsulation materials). This paper presents the result of experiments on encapsulant degradation influenced by the backsheet permeation properties. Towards this goal, one type of ethylene/vinyl acetate copolymer (EVA) was aged in glass/EVA/backsheet laminates in accelerated aging tests (up to 4000 h for Damp-Heat (DH) and up to 480 kWh/m2 for UV and UV-DH combined). The samples contained three backsheets with different permeation properties to examine their impact on EVA degradation. Thermal and chemical characterization shows that the EVA degradation is stronger with the glass–EVA–polyamide (PA)-based backsheet than with the polyethylene terephthalate (PET)-based backsheets. The higher oxygen transmission rate (OTR) of the PA-based backsheet may increase photo-oxidation and aggravating the degradation of EVA in the laminates. Furthermore, FTIR results were used to demonstrate the effect of damp heat exposure on the EVA interfaces, showing an accelerated degradation at the glass–EVA interface. The comparison of accelerated aging stress factors reveals that EVA suffers the strongest chemical and optical degradation when high UV, high temperature and high relative humidity are combined simultaneously.

Crack initiation and growth in PV module interconnection

As the cost of PV (photovoltaic) solar panels drops, it is widely expected that solar energy will become the cheapest source of electricity in many parts of the world over the next two decades. To ensure that PV solar modules have a long service life and can meet the PV manufacturer’s warranty, the PV modules need to have high reliability. Solar PV module manufacturers typically provide two warranties: a performance warranty which guarantees 90% of original power output after 10 years and 80% of original output of at 25 years; and an equipment warranty which guarantees their PV module will have a minimum of 10–12 years operation before failure. A critical part of the solar PV module assembly is the ribbon interconnection between the solar cells (i.e. the solder joint interconnections), and failure of the ribbon interconnection can adversely affect the performance and reliability of whole PV module. Ribbon interconnection failures have been linked to the thermal cracks which are initiated in the solder joint material during the high temperature ribbon interconnection manufacturing process; and then the crack propagation and growth associated with the thermal cycling of the ribbon interconnections under higher than ambient temperature PV module operating conditions. This paper reports on the study of high temperature crack initiation and propagation in different PV Module interconnection configurations by using XFEM in ABAQUS software. It concerns a necessary, urgent and fundamental revision of the manufacturing process that lies at the heart of PV module ribbon interconnection manufacture.

A Novel Hot Spot Mitigation Circuit for Improved Reliability of PV Module

Generation of hot spot in photovoltaic (PV) cells, under mismatch condition, is a reliability and safety issue associated with PV systems since its very early applications in satellites. Some of the solutions to this long-standing problem, proposed by the researchers in the past, were though effective in reducing the hot spot temperature, but were not accepted widely in commercial scale, because of design complexity and significant cost implications. The main aim of this paper is to present a novel hot spot mitigation circuit (HSMC), which effectively reduces temperature of the cells under mismatch conditions through a modified bypass arrangement, and thereby increase the reliability of the complete PV system. Special attention is paid to ensure that the proposed solution does not increase complexity of the bypass circuit to restrict its impact on the project cost and system reliability. Experimental investigation is carried out to quantify the comparative performance of the proposed HSMC vis-a-vis standard bypass circuit (SBC). Thermographic images revealed that temperature of the cells, under mismatch condition, reduced by up to 10.3 °C when protected by the proposed HSMC, while the temperature increased by 6 °C under protection of the SBC under same ambient and operating conditions.

Increased reliability of modified polyolefin backsheet over commonly used polyester backsheets for crystalline PV modules

ABSTRACTThe weathering stability of polymeric backsheets is very important for the reliability of photovoltaic (PV) modules. In addition to reliability, cost reduction and sustainability are upcoming challenges the PV backsheet industry is facing with. The most commonly used material for PV backsheets is poly(ethylene‐terephthalate)‐PET. However, PET is in general very sensitive to hydrolysis, which leads to chain scission and causes embrittlement, cracking, delamination, and dimensional instability of the backsheet. Compared to that newly developed modified polyolefin backsheets have favorable selective permeation properties and high mechanical flexibility, which could be key properties for backsheets in terms of higher PV module reliability. In this work, the weathering stability of PET/fluoropolymer backsheet and an alternative coextruded polyolefin‐backsheet was investigated in terms of thermal and mechanical stability. Both materials were artificially aged and the changes caused by aging were investigated. The polyester‐based backsheet showed embrittlement and reduced elongation at break for 70%. The polyolefin‐based backsheet retained its mechanical flexibility even after 2000 h of aging under damp‐heat conditions, with no significant physical or chemical aging processes occurring. The comparison of the results of both backsheets suggests that the polyolefin backsheet is a promising candidate for the reduction of cracks and delamination in the field. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48899.

Sol–gel processed silica based highly transparent self-cleaning coatings for solar glass covers

In order to enhance performance and reliability of photovoltaic modules (PV), it is very essential to keep the PV modules clean. Although there are good number of available technologies to clean the glass covers of solar panels, however, self-cleaning coatings, with extreme wettability, is emerging as one of the most reliable solution which can be easily applied and at the same time comes with low cost. Such coatings should be not only good at keeping the PV modules clean but at the same time should maintain the transparency of solar glass covers so as to allow maximum light to enter the surface of encapsulated solar panels. Most importantly such self-cleaning glazing structures have become very much useful in diverse field of solar energy application areas, such as solar radiation transmission, building integrated photovoltaics (BIPV), solar panels, concentrated solar power (CSP) systems. Here we havedeveloped a facile sol–gel based highly transparent and self-cleaning coatingwith tunable wetting property, by synthesizing single component silane modified base and acid catalyzed mixed silica sol. The sol is coated by following dip-coating approach on glass substrates. A static contact angle (WCA) as high as 150° and contact angle hysteresis (CAH) of ∼2° has been achieved with these coatings. The maximum transmission of glass used in solar glass cover has been found to increase from 91.8% to 95.5% and concomitantly minimum reflectance has been found to reduce from 8.7% to 3.2%. Such antireflection behavior has been further investigated by making ellipsometry studies, where we found the refractive index of the coating to be 1.35 and film thickness 103.54 nm.

Analysis of Field Degradation Rates Observed in All-India Survey of Photovoltaic Module Reliability 2018

The analysis of performance degradation in photovoltaic (PV) modules with c-Si technologies as observed in the All-India Survey of PV Module Reliability 2018 is presented in this article. The degradation rates are correlated with the module age, system size, mounting configuration, and climate of deployment. Key failure modes responsible for the higher degradation rates seen in certain sites are identified using visual, infrared, and electroluminescence imaging. Potential-induced degradation is found to be the key mechanism responsible for higher degradation rates seen in Young sites. Also, deployment in hot climates and rooftops is seen to accelerate degradation. Multipoint analysis of degradation rates is presented at sites inspected in prior All-India Surveys.

Global Climate Data Processing and Mapping of Degradation Mechanisms and Degradation Rates of PV Modules

Photovoltaic (PV) systems are the cheapest source of electricity in sunny locations and nearly all European countries. However, the fast deployment of PV systems around the world is bringing uncertainty to the PV community in terms of the reliability and long-term performance of PV modules under different climatic stresses, such as irradiation, temperature changes, and humidity. Methodologies and models to estimate the annual degradation rates of PV modules have been studied in the past, yet, an evaluation of the issue at global scale has not been addressed so far. Hereby, we process the ERA5 climate re-analysis dataset to extract and model the climatic stresses necessary for the calculation of degradation rates. These stresses are then applied to evaluate three degradation mechanisms (hydrolysis-degradation, thermomechanical-degradation, and photo- degradation) and the total degradation rate of PV modules due to the combination of temperature, humidity, and ultraviolet irradiation. Further on, spatial distribution of the degradation rates worldwide is computed and discussed proving direct correlation with the Köppen-Geiger-Photovoltaic climate zones, showing that the typical value considered for the degradation rate on PV design and manufacturer warranties (i.e., 0.5%/a) can vary ± 0.3%/a in the temperate zones of Europe and rise up to 1.5%/a globally. The mapping of degradation mechanisms and total degradation rates is provided for a monocrystalline silicon PV module. Additionally, we analyze the temporal evolution of degradation rates, where a global degradation rate is introduced and its dependence on global ambient temperature demonstrated. Finally, the categorization of degradation rates is made for Europe and worldwide to facilitate the understanding of the climatic stresses.

Quantitative Estimation of Shunt Resistance in Crystalline Silicon Photovoltaic Modules by Electroluminescence Imaging

Ohmic shunts in crystalline silicon (c-Si) solar cells and modules are of critical concern as these affect the open-circuit voltage, fill factor, and the net output power. In modules, such shunts create a mismatch and can lead to hotspot formation that can thermally destroy the module. It is essential to estimate the shunt resistance value in a nondestructive manner in order to prioritize the removal of shunts on the basis of severity. In this paper, an approach to estimate the quantitative shunt resistance values in crystalline silicon photovoltaic (PV) modules by electroluminescence (EL) imaging has been presented. The quantitative properties of EL emission from the solar cell has been correlated with shunt resistive effects, which has led to the estimation of the voltage and current across the shunts, and hence the shunt resistance values. The approach has been experimentally supported by externally introducing shunt resistances of different values in a solar cell. The estimated shunt resistances have been found to be in a good agreement with the actual shunt values. This work can be helpful in detailed quantitative analysis of ohmic shunts, which can be further used to improve the performance and reliability of PV modules.

Experimental study of observed defects in mini-modules based on crystalline silicone solar cell under damp heat and thermal cycle testing

In this study, consumer type multicrystalline modules are investigated. To assess the long-term reliability of photovoltaic (PV) multicrystalline modules, extended thermal cycling and damp heat testing were performed. This study focused on four multicrystalline modules. Two modules were subjected to 85 °C/85% damp heat testing at 1000 h and 1300 h, respectively. The other two modules were subjected to thermal cycle test of 55 cycles and 66 cycles, respectively. After testing, all 4 solar panels were investigated with the help of visual inspection, thermography, electroluminescence and IV-curve measurements. The main degradations observed were corrosion, hot spot and delamination.

Bonding Strengths and Thermal Degradation of Photovoltaic Module Ribbon Solder Joints

In this study, solar ribbon solder joints were investigated to ensure the reliability of photovoltaic (PV) modules. Ribbon joints comprising two different solder compositions (wt. %: 60Sn40Pb, 62Sn36Pb2Ag) were used to perform thermal aging tests at three different temperatures (150 °C, 120 °C, and 90 °C) during a 1000-h period to analyze the resultant thermal degradation; shear tests were also performed to measure bond strengths. Initial bond strengths were 271.3 MPa and 241.3 MPa for 62Sn36Pb2Ag and 60Sn40Pb solder joints, respectively. Bonding strength decreased as a result of thermal aging, but was maintained at a value of around 130 MPa regardless of solder composition. Fracture surfaces from the shear test were observed to analyze for the constant bond strength phenomenon. It was verified that the shear fracture surface changed from the solder/sintered Ag interface and the sintered silver (Ag)/silicon (Si) wafer interface during thermal aging. Thus, the bond strengths and bonding characteristics of PV ribbon solder joints decreased under a thermal load, which could be attributed to a weakening of the bonding characteristics for sintered Ag silicon interfaces as opposed to a degradation of solder metallurgy.

Growth of an Ag3Sn Intermetallic Compound Layer Within Photovoltaic Module Ribbon Solder Joints

In this study, the characteristics of growing an intermetallic compound(IMC) layer at solder joint in photovoltaic (PV) ribbon solder joint were investigated through the thermal ageing test. Also, the growth rate of IMC in the ribbon solder joint, which depend on the temperature and time, was predicted through the ageing test. That the ageing test were performed under three different conditions: 90 °C, 120 °C and 150 °C. Also, we prepare the two type solder composition(60Sn40Pb, 62Sn2Ag36Pb) to analyze Ag addition effect in solder to forming IMC layer. Following testing, the IMC layer formed Ag3Sn in Ag sintered layer by Sn diffusion phenomena at high temperature. The thickness of Ag3Sn in solder joint was measured by cross-section images during the thermal ageing test. The Ag3Sn IMC layer was filled in sintered Ag layer in 70 h under the harshest conditions of 150 °C and 750 h at 120 °C. The Ag3Sn thicknesses were calculated to activation energies forming IMC layer in solder joints. The results, the Ag3Sn growth rates under the various temperatures were predicted for long-term reliability of PV modules.

Fault diagnosis of Photovoltaic Modules

AbstractFault diagnosis and condition monitoring are important to increase the efficiency and reliability of photovoltaic modules. This paper reviews the challenges and limitations associated with fault diagnosis of solar modules. A thorough analysis of various faults responsible for failure of solar modules has been discussed. After reviewing relevant work, a monitoring tool is designed using thermography and artificial intelligent systems that allows the detection of various types of faults in PV modules and at the same time the designed tool aims to filter the nonsignificant anomalies. A neural network (NN) classifier is applied to the transfer characteristics (I‐V data) of the faulty PV module for the diagnosis which adapts multilayer perceptron (MLP) networks to identify the type and location of occurring faults. The Discrete wavelet transform (DWT) based signal processing technique is utilized in the feature extraction process to reduce the NN input size. The developed detection algorithm is adapted for 24/7 automated surveillance. For a given fault condition, the average fault detection time is observed to be <9 seconds, which is lower than the previous work done. The developed algorithm achieved 100% accuracy when tested on a predetermined fault data set.

Non-destructive approach for severity investigation of shunts in crystalline silicon photovoltaic modules by combination of electroluminescence imaging and lock-in thermography

The characterization of localized shunts in photovoltaic (PV) modules is of major concern due to its impact on the performance and reliability of the modules. Generally, lock-in thermography has been used as an effective non-destructive technique for the characterization of shunts in solar cells; however, it has limited applicability in PV modules. Electroluminescence (EL) imaging is another non-destructive technique for the investigation of shunts, which can be employed in both cells and modules in a much faster and inexpensive way. However, it suffers from a limitation in differentiating shunts from other defects. In this paper, a novel non-destructive approach is presented by combining both techniques, which systematically overcomes the limitations of an individual technique for the characterization of shunts in commercial crystalline silicon PV modules. The dark lock-in thermography technique has been utilized to locate shunts in cells and combined with different aspects of EL imaging applications for the spatial severity analysis of individual shunts. The proposed approach has been successfully employed to investigate the severity of different shunts in modules. This approach can be helpful in locating shunts on the basis of severity, which can be related to the performance, degradation and reliability of PV modules.

Thermomechanical residual stress evaluation in multi-crystalline silicon solar cells of photovoltaic modules with different encapsulation polymers using synchrotron X-ray microdiffraction

Photovoltaic (PV) module reliability issues, due to silicon cell cracking, are gaining more and more attention due to increasing demand for solar power and reduction of cell thickness to reduce cost. Recent reports show significant effect of encapsulation polymer material on cell cracks leading to the idea of tailoring encapsulation materials for more reliable PV modules. This paper investigates the effect of encapsulation modulus on the cell residual stress using Synchrotron scanning X-ray microdiffraction (µSXRD), which has been proven to be an effective technique to probe the stress in silicon solar cells, especially once they are encapsulated. The post lamination residual stress in the encapsulated multi-crystalline silicon (mc-Si) solar cells was reported for the first time using µSXRD in this manuscript and provide quantitative evaluation of the effect of encapsulation modulus on the cell residual stress. Further, simple approximate finite element (FE) model was also developed to evaluate the effect of the encapsulation polymer on the cell stress. The FE simulations predict the trend of the stress variation with encapsulation polymer modulus very well. Dynamic mechanical analysis and rheological testing of the encapsulation polymers was also performed to correlate the polymer behaviour with the experimental and simulated stresses. Both experimental and simulation results show a similar trend of significant cell stress variation with encapsulation polymer modulus. In the case of external loading, the temperature of load application is observed to be very significant as it dictates the elastic state of the encapsulant, leading to critical conclusion that the encapsulant needs to be selected based on elastic behaviour over the temperature history of the encapsulant during module fabrication and operation. The results and discussion presented are expected to be very useful for development of more reliable PV modules.

Performance, energy loss, and degradation prediction of roof-integrated crystalline solar PV system installed in Northern India

This article predicts the performance, energy loss, and degradation of a 200 kW roof-integrated crystalline photovoltaic (PV) system installed at IRB Complex-5, Chandigarh in the Northern part of India. PVsyst simulation tool is used for predicting the energy generation, and energy loss. Analysis of the energy generation and various input parameters are carried out for evaluating the capacity factor (CF), performance ratio (PR), and efficiencies. For a detailed analysis of the energy losses, a three-stage approach (sunlight reaching onto the PV array, sunlight into DC electricity conversion, and DC to AC electricity conversion) is used. The light-induced degradation (LID), which is possible in the PV modules in the second stage (sunlight into DC electricity conversion) is predicted using the PVsyst simulation modeling. Apart from this, the possible degradation rate (DR) in the crystalline PV systems is considered based on the All-India survey of PV module reliability reports. The predicted results show that 292954 kWh of energy generation is possible on an annual basis from the planned PV system. The system is estimated to operate with a yearly CF, PR, and energy losses as 16.72%, 77.27%, and −26.5% respectively. The estimated DR of the PV system would lie between −0.6 to −5%/year, and the possible LID is −2.5%/year. Finally, the energy losses due to LID, and DR are predicted as −8109.99 kWh/year, and −1757.724 to −14647.7 kWh/year respectively.

Thermo-mechanical behavior assessment of smart wire connected and busbarPV modules during production, transportation, and subsequent field loading stages

Thermo-mechanical loads induce stresses in photovoltaic (PV) modules, leading to crack formation. In this context, the understanding of module's thermo-mechanical behavior is important. To investigate the thermo-mechanical behavior of smart wire connected technology (SWCT) and busbarPV modules throughout their entire life, the present study is conducted that probes the stress distribution and deformation during production, transportation, and subsequent mechanical and thermal loading stages in a consecutive step-by-step manner using finite element modellingapproach. Pre-stresses and non-linearitiesare considered in simulation models. Stresses and displacements experienced by different parts/layers are examined, and crack sensitive regions are identified. In addition, the SWCTand busbarmodules are compared, and it is found that SWCTinterconnection is relatively a less stress inducing process and less susceptible to thermal and dynamic affects. During production stage, stresses of 39.3 MPaand 40.4 MPaare generated in SWCTcells and copper wires respectively; while, stresses of 60 MPaand 87 MPaare generated in busbarcells and busbarrespectively. Similarly, lower stresses are induced in SWCTPV modules during subsequent stages. The comparison results show advantages of SWCTmodule in terms of mechanical stability which can lead to improve the performance and reliability of PV modules.