Lifetime Of Modules Research Articles

Influence of different vibration directions on the solder layer fatigue in IGBT modules

Insulated-gate bipolar transistor (IGBT) modules are extensively utilized in high-speed trains, ships, and electric vehicles. Compared to those used in power systems, IGBT modules in these applications are more susceptible to vibration effects on their reliability. This paper proposes a multi-physics field simulation method and a lifetime model for IGBT modules to assess the impact of different vibration directions on solder layer fatigue. Initially, a multi-physics field model of the IGBT module is developed, incorporating electrical, thermal, mechanical, and vibration coupling. The effectiveness of this multi-physics simulation model is verified by an experimental platform. Subsequently, the influence of different vibration directions on solder layer fatigue in the IGBT module is analysed, and a life model of the IGBT is proposed through simulation. Finally, a power cycling with a vibration environment experimental platform is established to validate the effect of vibration on solder layer fatigue in the IGBT module. The simulation and experimental results indicate that vertical vibration accelerates the solder layer fatigue of IGBT modules, and the lifetime of an IGBT module operating under vertical vibration at 30 Hz is about 15 % shorter than that of an IGBT module operating under power cycling alone. The error between the calculated results of the solder layer failure and the experimental result is <5 %.

Effect of module configurations on the performance of parallel-connected lithium-ion battery modules

To meet the power and energy of battery storage systems, lithium-ion batteries have to be connected in parallel to form various battery modules. However, different single module collector configurations (SCCs) and unavoidable interconnect resistances lead to inhomogeneous currents and state-of-charge (SoC) within the module, thereby significantly reducing the module lifetime and safety. Therefore, the correlation of SCCs to module inhomogeneous currents and SoC are worth investigating. Based on mathematical permutations and combinations calculations, all SCCs are firstly defined and obtained in this paper. Then, two parallel modules are developed in Matlab/Simscape based on fresh cell and degradation cell separately, which are used to quantify the influence of all SCCs. Furthermore, multiple module collector configurations (MCCs) and Urban Dynamometer Driving Schedule (UDDS) working condition are considered in the analysis. Results indicate that both module collectors connected to same edge cell of module cause the most inhomogeneity. The maximum SoC difference under the UDDS is only 46 % of the 0.5C. Moreover, MCCs can reduce inhomogeneous currents and SoC within the parallel module, while not all MCCs perform better homogeneous performance than SCCs. Finally, the effect of changes in SCCs on degradation module inhomogeneous currents and SoC is verified as same as for fresh cells parallel module. Based on the above results, the optimal single module collector configuration of the N cells parallel module is obtained through mathematical analysis, which can greatly improve the currents and SoC homogeneity of the module.

Soldering Pressure Effect on Lifetime of Thermoelectric Modules under Thermal Cycling.

For practical industrial applications, enhancing the longevity and the reliability of thermoelectric modules (TEMs) is equally as crucial as improving their conversion efficiency. This study proposes a strategy for extending the lifespan and introduces the quality evaluation criteria for the most extensively used commercial bismuth telluride TEM. By varying the soldering pressure during module assembly, its impact on the quality of the module's internal interfacial connections was investigated, via analyzing its contact resistivity, shear modulus, and antifatigue ability through thermal cycling tests. The findings reveal that increasing the soldering pressure leads to a slight reduction in interfacial contact resistivity and has no significant effect on the shear modulus but notably enhances the module's antifatigue ability during thermal cycling tests. According to the SEM results, it can be evidently deduced that the aforementioned phenomena are directly correlated with the size and quantity of voids distributed in the solder layer, which is regarded as the origin of antifatigue ability. Thus, it can be inferred that augmenting the soldering pressure represents an effective approach to prolonging the lifespan of TEMs assembled by using the soldering method. Furthermore, the existence of voids within the solder layer can serve as a criterion for an initial assessment of module longevity. This study provides a reference for both the industrial assembly and lifespan evaluation of commercial bismuth telluride TEMs.

The European Union's Ecodesign Directive – Analysis of Carbon Footprint Assessment Methodology and Implications for Photovoltaic Module Manufacturers

With an increasing shift away from fossil fuels toward renewable energy sources within the European Union (EU), photovoltaics (PV) are projected to see substantial growth with estimates of nearly 600 GWp of capacity by 2030. As the use of PV technology continues to expand, the European Commission has introduced various policy instruments, enabling consumers to make informed choices. Among those, the Ecodesign directive 2009/125/EC sets a carbon footprint threshold as a minimum qualification for the European market to cut out the least sustainable PV modules. For this directive, the methodological guidelines for the complex carbon footprint calculation of PV modules are under development. To this end, this analysis compares the two methodologies, namely Electronic Product Environmental Assessment Tool (EPEAT) and the Ecodesign adaptation of Product Environmental Footprint Category Rules (PEFCR), emphasizing the implications of choosing one over the other for the PV industry. This study illustrates how varying parameters, like module lifetime, degradation rate, and purchased renewable electricity certificate allowance limit, stemming from the differing methodological approaches can influence the carbon footprint calculation. Apart from the strengths and weaknesses of each methodology, this article emphasizes the need for globally harmonized standards to ensure consistency in evaluating the carbon footprint of PV modules. The observations made in this study should be considered not just for Ecodesign directive but for any such market regulation policy like the recently passed EU Net Zero Industry Act or the EU Ecolabel for PV modules. It underlines the significance of choosing a transparent and fair approach to ensure the credibility of carbon footprint labels and meet the EU's decarbonization objectives successfully, propelling the transition toward a more sustainable energy landscape.

Light-activated surface passivation for more efficient silicon heterojunction solar cells: Origin, physics and stability

Silicon heterojunction (HJT) solar cells have world-leading efficiencies due to outstanding surface passivation. Yet, maintaining their performance during the lifetime of a photovoltaic module requires excellent quality and stability of the surface regions. It is well known that HJT solar cells can show an increase or reduction in performance under illumination, and this instability has been related to changes in the surface regions. This work investigates the stability of surface passivation in HJT solar cells by modelling the injection-dependent minority carrier lifetime of a range of symmetrically a-Si passivated silicon wafers. Fixed charges and defects at the interface are varied in the model to find the best fit to the injection-dependent lifetime before and after a high-intensity illumination treatment. The results indicate that the laser process induces an increase in field effect passivation at the surface, which is then reduced upon storage in the dark. The results show that lifetime spectroscopy is a useful tool to investigate the nature of a-Si passivation degradation.

Lifetime Prediction Method of the Traction Converter IGBT Based on Plastic Strain Energy Density

Insulated gate bipolar transistor (IGBT) is the most important power electronic component in the traction converters of trains. During the operation of the IGBT, the solder layer is continuously subjected to alternating stress, which eventually leads to the fatigue failure of the solder layer. Therefore, an accurate assessment of the lifetime of the IGBT module solder layer is of great importance for the safe and reliable operation of the trains. Firstly, the micromechanism of the plastic deformation of the base solder layer of the IGBT module is introduced, as well as the lifetime model based on the plastic strain energy density. Then the total plastic strain energy density of the base solder layer is determined by conducting the accelerated aging tests on the IGBT module and combining the finite element simulation results. Meanwhile, the relationship between different aging degrees of the base solder layer of the IGBT module and the plastic strain energy density is studied by finite element simulation. Then, the lifetime of the base solder layer at different aging stages is calculated based on the above results so that the total lifetime of the IGBT module is obtained. Finally, the predicted lifetime of the IGBT module by the proposed method is compared with the lifetime obtained by the accelerated aging test and compared with the traditional lifetime prediction method based on the Coffin-Manson-Arrhenius model. The comparison results verify the accuracy of the proposed lifetime prediction method in this paper.

Thin-Film Transistor-Based Sensor Interface Circuits Enabling Distributed Local In-Module Solar Cell Temperature Monitoring

Accurate efficiency prediction, improved reliability, and extended lifetime of solar modules are the key driving factors for investment and research in photovoltaic (PV) systems. Enhanced performance and more refined models are realized by incorporating data derived from localized monitoring of solar modules. This work combines interface circuits designed in flexible thin-film transistors (TFTs) with distributed temperature sensors integrated into solar cell lamination enabling in-module within-cell PV monitoring. A TFT multiplexer selects between sensors and is commanded through a serial peripheral interface (SPI) to reduce the IO connections, while the low offset unity-gain TFT buffer enables precise signal transfer. The in-cell sensors together with TFT read-out circuitry demonstrate accurate outdoor temperature monitoring, comparable to silicon integrated circuits.

Prioritizing circular economy strategies for sustainable PV deployment at the TW scale

Global decarbonization requires an unprecedented scale-up of photovoltaic (PV) manufacturing and deployment. The material demand and eventual end of life management associated with multi-TW scale deployment poses many challenges. Circular Economy (CE) and it's associated R-Actions (Reduce, Reuse, Recycle) have been proposed to mitigate end of life management and material sourcing concerns. However, CE metrics typically focus on a single product and only consider mass, excluding energy flows. This work leverages the PV in Circular Economy (PV ICE) tool to quantify the deployment, mass, and energy impacts of R-Actions and proposed sustainable PV designs in the context of achieving energy transition deployment goals (75 TW in 2050). 13 module scenarios are established and evaluated across 6 capacity, mass and energy metrics to identify tradeoffs and priorities. We find that increasing module efficiency can reduce near-term material demands up to 30% and improve energy metrics by up to 9%. Material circularity (recycling) can minimize lifecycle wastes and reduce material demands at the cost of higher energy demands. Increasing module lifetime, including reliability improvements and reuse strategies, is effective at reducing both material (&gt;10%) and energy demands (24%). Uniquely, lifetime improvements maximize benefits and minimize the harms across all six metrics while achieving multi-TW scale deployment.

A field-function methodology predicting the service lifetime of photovoltaic modules

The service lifetime of photovoltaic (PV) modules is an essential basis for the business investment and operation in PV power generation systems, with continuous distribution in specific geographical areas. To accurately predict the service lifetime of PV modules operated at a specific location, a continuous quantitative field-function methodology based on geographical clustering of influencing factors is proposed in this research. Firstly, failure mode and effects analysis technology is applied to systematically analyze the relevant factors affecting the performance degradation of PV modules, where eight key factors are extracted and quantitatively described. Secondly, the fuzzy c-means algorithm clusters the geographical regions to identify the areas with continuously distributed service lifetimes of PV modules. Finally, the continuous quantitative field-function model with latitude and longitude as variables is designed to describe each clustering category's service lifetime distribution characteristics. The model uses Pearson correlation coefficient to quantitatively describe the differences in performance degradation influencing factors at different latitude and longitude positions, and the model parameters are determined by fitting analysis of the known service life data of PV modules at specific latitude and longitude positions. Based on this model, the PV module field degradation rates in Guangzhou, Shenzhen, and Zhuhai in mainland China are estimated with relative errors to be 3.7149 %, 8.1525 %, and 6.6753 %, respectively. Compared to the existing approach, not only are the relative errors reduced by 1.4783 %, 5.1455 %, and 4.485 %, but the variations of service lifetime with geographic latitude and longitude are also visually and clearly described.

Interfacial Crack Growth-Based Fatigue Lifetime Prediction of Thermoelectric Modules under Thermal Cycling.

As a result of the complexity and difficulty of the lifetime assessment of the thermoelectric (TE) module, the related research is still immature. In this work, to predict the lifetime of the Bi2Te3-based TE module from the perspective of cyclic thermal stress leading to interface cracking, the viscoplastic behavior of the solder layer is first described by the Anand material ontology model, and then the sprouting and expansion of interface cracking of the module are simulated by combining the Darveaux model and the viscoplastic dissipation energy accumulated during the thermal stress cyclic loading. After that, the complete lifetime prediction model of the TE module is established on the basis of the thermal cycling experiments and the finite element simulation calculation data, which can simply and efficiently predict the cycle number of the module resistance rise and its rise rate. The prediction deviations are 6.1 and 6.7%, respectively, verifying the feasibility of the model. The work in this paper can provide a reference for the life evaluation of TE modules.

Precise estimation of dynamic junction temperature of SiC transistors for lifetime prediction of power modules used in three-phase inverters

Precise transient temperature measurement is fundamental to estimate lifetime of power modules, especially those made with SiC transistors having very low thermal capacitance. This paper shows a precise method to estimate dynamic temperature of SiC components composing a power module used in three-phase inverters. This method is based on the use of a fast thermal camera to precisely measure thermal impedance of each die. Results of thermal camera measurements are validated by comparison with classical on-state resistance measurements to estimate junction temperature. Thermal impedance model is then coupled with precise loss calculation in order to predict dynamic die temperature during operation in a three-phase inverter. Measurements of the temperature variation of SiC dies conducting typical currents of a 540 V/7.5 kW three-phase inverter for aeronautical applications show the accuracy of the developed model for dynamic junction temperature estimation.

An insight into a combined effect of backsheet and EVA encapsulant on field degradation of PV modules

AbstractPolymer components, in particular, backsheets (BSs) and ethylene‐vinyl acetate (EVA) encapsulants, play a crucial role in the degradation of commercial silicon photovoltaic (PV) modules. Degradation mechanisms depend in a complex way on the composition and properties of all involved polymers. In this study, we demonstrate that differences in the composition of EVA encapsulants, in particular, the presence of additives, such as UV blockers, affect the degradative processes in a decisive way, even for modules with identical BSs. A combination of spectral, imaging, and electrical characterization techniques applied in a mixed lab/field study showed that the field aging of PV modules with the same BSs and different encapsulant components results in the development of different degradation signs, such as insulation resistance loss, corrosion of metal interconnects, water ingress, oxidation depth in the encapsulant, and potential‐induced degradation, depending on the presence of additives in the encapsulant. The present study provides an outlook on the complex influence of polymer components on the lifetime and performance of silicon PV modules.

TIMs for transfer molded power modules: Characterization, reliability, and modeling

This work presents an integrated experimental–numerical method to characterize, model, and experimentally study the properties of transfer molded power modules, considering two different thermal interface materials (TIMs). More specifically, a thermal grease and a phase change material are considered. The aim is to select the most reliable solution by making analytical characterization and power cycling tests on the modules equipped with the two kinds of TIMs. Then, further reliability study is accomplished, in order to estimate the lifetime of the power module equipped with the best TIM, that is the phase change one. Finally, a finite-element numerical model is developed and correlated with experimental data.

Degradation and energy performance evaluation of mono-crystalline photovoltaic modules in Egypt

Degradation reduces the capability of solar photovoltaic (PV) production over time. Studies on PV module degradation are typically based on time-consuming and labor-intensive accelerated or field experiments. Understanding the modes and methodologies of degradation is critical to certifying PV module lifetimes of 25 years. Both technological and environmental conditions affect the PV module degradation rate. This paper investigates the degradation of 24 mono-crystalline silicon PV modules mounted on the rooftop of Egypt's electronics research institute (ERI) after 25 years of outdoor operation. Degradation rates were determined using the module's performance ratio, temperature losses, and energy yield. Visual inspection, I–V characteristic measurement, and degradation rate have all been calculated as part of the PV evaluation process. The results demonstrate that the modules' maximum power ({P}_{max}) has decreased in an average manner by 23.3% over time. The degradation rates of short-circuit current ({I}_{sc}) and maximum current ({I}_{m}) are 12.16% and 7.2%, respectively. The open-circuit voltage ({V}_{oc}), maximum voltage ({V}_{m}), and fill factor (FF) degradation rates are 2.28%, 12.16%, and 15.3%, respectively. The overall performance ratio obtained for the PV system is 85.9%. After a long time of operation in outdoor conditions, the single diode model's five parameters are used for parameter identification of each module to study the effect of aging on PV module performance.

On-Site Estimation of Thermal Resistance Degradation of Double-Sided Cooling (DSC) Power Modules Under Power Cycling Conditions

Double-sided cooling (DSC) power modules are increasingly used due to their superior cooling capability and low parasitic inductance. However, the DSC modules have multiple interconnections for heat dissipation, so it is challenging to accurately monitor the thermal resistance degradation of each interconnection under power cycling conditions. An estimation method considering the self-heating and thermal coupling effects of DSC power modules is proposed based on a traditional lumped RC thermal impedance network. The proposed method combining a recursive least squares algorithm with a thermal network model can well evaluate the thermal resistance of each interconnection and their variations on-site during power cycling tests. The lifetime of DSC power modules for power cycling tests could be overestimated if using the 20% increment in overall thermal resistance of DSC modules as a failure criterion.

Changes in ohmic shunts in Cu(In,Ga)Se2 devices during damp heat

To increase the bankability of photovoltaics (PV), a more accurate prediction of the lifetime and degradation-rate of PV modules is required. In past studies, average degradation rates for different technologies have been derived from field data. However, in Cu(In,Ga)Se2 (CIGS) based PV, localized shunts are commonly found in modules coming out of the factory. Although the impact of such localized defects on initial module performance has been studied in the past, their evolution and impact on module performance upon aging remain mostly unknown. In this paper, it is demonstrated that exposure of CIGS devices to elevated temperatures and humidity can result in the partial or complete recovery of localized ohmic shunts. This was observed for three types of shunting defects, each on a different CIGS device characterized before and after damp heat exposure. In each device, the reduction in shunting after damp heat could be observed in illuminated lock-in thermography, photoluminescence and current-voltage measurements. For two of the devices, the positive effect of shunt reduction was counteracted by other degradation mechanisms, such as increase in series resistance of TCO or back contact, while a 4% absolute efficiency increase was observed in the third device. Our data suggests that the shunting is mainly reduced due to oxidation of the materials initially forming the shunting path. The combined effects of moisture degradation and shunt reduction may limit detectability of moisture ingress in electrical performance data. These results illustrate the added value of regular visual inspection and luminescence in quality control.

Difference Between the PWM and Standard DC Power Cycling Tests Based on the Finite-Element Simulation

PWM power cycling, which has complex control strategies and high testing costs, received a lot of attention in recent years due to the test conditions are closer to the application of power modules than standard DC power cycling. Therefore, the root difference of the failure modes and lifetime of IGBT power modules between DC and PWM power cycling is the concern in this paper, based on the finite element simulation. For stimulating the PWM power cycling with high accuracy and fast speed, an IPWM power cycling is proposed and verified by a simple model. Then an electro-thermo-mechanical coupled model of a single chip is established for comparison. Mainly focus on the current distribution, temperature distribution and stress distribution. The current distribution comparison results show no difference while a higher temperature gradient is shown in PWM power cycling due to the additional switching losses. However, the stress distribution results show chip solder layer is still the main failure mechanism both in DC and IPWM power cycling. Therefore, a conclusion can be obtained that there is no difference in failure mechanism and lifetime between DC and PWM power cycling. And the same bond wire failure and similar lifetime of DC and PWM power cycling tests further verify this conclusion.

Understanding Multiple Stressors Which Degrade Antisoiling Coatings: Combined Effect of Rain, Abrasion, and UV Radiation

Antisoiling coatings (ASCs) are nano or microlayer coatings which reduce the settlement of dust on the surface of the PV module and are extensively investigated as a dust mitigation strategy. Since the coating is applied on the outer surface of the PV module, they are exposed to various environmental stressors, and the durability of these coatings is essential. Various studies have reported the effect of individual stressors that degrade ASCs. However, there are very few reports on the impact of the combination of stressors relevant to outdoor field conditions. In this article, we investigate the impact of the combination of the following stressors that degrade ASCs: 1) the combination of the impact of raindrops and acidic water, 2) the combination of UV radiation, the impact of raindrops, and acidic water, and 3) the combination of abrasion, UV radiation, the impact of raindrops and acidic water. The key takeaways from this study are 1) coating life reduced by 21× (average of all coatings) when exposed to the rainy season compared with those exposed to the nonrainy season. 2) All coated samples show lower coating life varying from 10× to 48× when exposed to the impact of raindrops with pH 7 water than those exposed to water immersion/water contact test with pH 7 water. This indicates that, during a rain event, the impact of raindrops hitting the coated surface causes more significant damage than water contact. This study shows that coatings A, B, C, and D are unreliable for long-term use in warm and humid climate zones, considering 25-year module lifetime. However, other chemistries of hydrophobic and hydrophilic solutions could be effective if they exhibit long-term reliability.

Investigation of the crack propensity of co-extruded polypropylene backsheet films for photovoltaic modules

Co-extruded backsheets based on polypropylene (PP) are an interesting alternative to laminated backsheets based on polyester films (PET). Backsheet cracking has become a frequent aging induced failure mode in the last years, causing not only safety issues but also reducing the lifetime of PV modules on the long term. In this work the crack susceptibility of four different backsheet types was investigated using solder bump coupon specimens: two co-extruded backsheets based on polyamide (PA) and PP, two laminated backsheet containing a PET core layer and polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF) outer layers. The solder bump coupons were exposed to an accelerated stress test sequence of repeated exposure to UV light followed by thermal cycles (TC). Overall, the PP as well as the PVF-PET backsheet showed excellent stability and no susceptibility to material embrittlement or cracking. By comparison, the PA based backsheets showed next to significant discoloration also strong cracking after a few UV-TC test cycles. The PET-PVDF backsheet exhibited cracking after the same number of test cycles as the PA-based backsheets. Overall, the study confirms that co-extruded PP backsheets show great potential to be a valid replacement of standard PET based backsheets in PV modules.

P‐136: Simulation study on the lifetime of Rollable AMOLED Module

Different materials and stacking structures of multi‐layer will be arranged and combined when AMOLED panels are in rollable form. Many problems such as residual stress of deformation recovery, peeling of multi‐layer are usually happen during dynamic process and repeat motion, which can influence module lifetime directly. In this paper, we standardize the method of rollable simulation modeling, and then analyze related equivalent strain data of different multi‐layer structure in rollable form, derive the whole lifetime mapping of single material, predict the fatigue lifetime of rollable module after using kriging fitting. At last, we find that the accuracy of lifetime prediction is more than 80% by using these ways, which can greatly improve design efficiency.