Lifetime Of Modules Research Articles

FEA-Dominant Reliability and Lifetime Model of Double-Sided Cooling SiC Power Module

Owing to the low parasitic inductance, high power density, and excellent heat extraction performance, double-sided cooling (DSC) is regarded as a promising packaging solution for the silicon carbide (SiC) power module. Nevertheless, given the unclear failure mechanism and missed lifetime model, the reliability assessment and lifetime prediction of the DSC SiC power module remains a concern. Besides, the accelerated aging test generally used for the reliability assessment of the SiC power module is extremely time-consuming and costly. Therefore, the obstacles mentioned before limit the development and deployment of the DSC SiC power module. Aiming to fulfill these research gaps, based on the aging mechanism and failure criterion of packaging materials, the lifetime model of the DSC SiC power module is proposed in this paper. Comparative experiments show that the relative error of the FEA-dominated model is less than 6%. Moreover, the stress property and creep principle of the solder layer in SiC and Si power modules are assessed, respectively. Besides, the lifetime models of SiC and Si power modules applying different packaging materials are created. It is found that the lifetime of the DSC power module is twice that of the single-sided cooling (SSC) counterpart. Furthermore, applying the same packaging, the lifetime of the SiC power module decreases by 70% compared with the Si counterpart. In addition, the lifetime of the DSC SiC power module affected by different materials such as ceramic and spacer is studied in order to enhance its reliability.

Copper-Wire Stress Buffers for Extending Lifetime of Double-Sided Bidirectional SiC Modules

The mismatch of thermal expansion coefficients causes tremendous thermo-mechanical stress in die attachment of double-sided bi-directional modules (BMs), thus reducing the reliability of the module. The thermo-mechanical reliability of a double-sided power module is the most critical issue, which needs to be addressed. People proposed ways to improve the reliability by reducing the CTE mismatches using such as Moly spacer instead of copper or junction temperature rise using high conductive spacer. This work first proposed a composite buffer, namely copper-wire-spacer (CWS), with low elastic modulus, capable of reducing thermo-mechanical stress by >50%. The lifetime of the double-sided BM with the CWS buffer is 40.0% and 42.9% longer than that with the conventional solid copper buffer, and is only 6.67% and 6.25% shorter than that with the moly buffer under the thermal shocking tests and the power cycling tests, respectively. The novel method of reducing the elastic modulus of the spacer could be a novel and good concept to reduce the thermo-mechanical stresses as well as improving the reliability of double-sided power modules. It can provide new guidance to design and packaging reliable double-sided power modules.

Lab-to-Fab development and long-term greenhouse test of stable flexible semitransparent organic photovoltaic module

The Lab-to-Fab transfer from cell to large-area flexible semitransparent organic photovoltaic (OPV) module by the slot-die coating based on halogen-free host solvent and under ambient air environment is developed. The bulk heterojunction structure (BHJ) and formation mechanism of slot-die-coated active layer on flexible substrate are different from those usually reported. The relationship among processing, film thickness/BHJ morphology, transmittance and performance for the slot-die-coated module, and the optimum strategy are studied in this article. The flexible semitransparent modules with active areas of 45 and 22.5 cm2 have the average visible transmittance of 21.3%–16.7%. The corresponding average power conversion efficiency (PCE) values are 4%–6.2%. The highest PCE can achieve 7.8%. Compared to all large-area flexible semitransparent slot-die-coated OPV modules reported with PCEs (usually ≤5%), the modules prepared here have the best PCE. The electric behavior and stability of these OPV modules and a Si-PV panel under the greenhouse test are studied. Among the stability data (usual T80 lifetime ≤100 days) reported for semitransparent flexible OPV modules under greenhouse test, the T80 lifetime of the OPV modules prepared here can reach 200 days and also remain the highest PCE with the least burn-in loss.

Optimal Energy Management for Battery Swapping Based Electric Bus Fleets With Consideration of Grid Ancillary Services Provision

In this paper, a novel optimization model is formulated to optimize the scheduling of battery swapping stations (BSS) operating electrified public bus transit fleets. The BSS consists of a number of battery modules that are combined together to create a MW-scale battery storage system. As such, the formulated optimization problem aims at minimizing the running costs of the BSS via i) exploiting the low electricity prices in the market (i.e., charging the battery modules at low prices), and ii) utilizing the BSS in the provision of grid ancillary services. The proposed model considers the operational requirements of the bus transit fleet to satisfy the energy needs of the battery electric buses (BEBs) and maintain their defined timetable. Also, the model integrates the power distribution network constraints such as bus voltages and line capacity limits to ensure its reliable operation. The impact of the BSS participation in the provision of ancillary grid services on the operation, degradation, and lifetime of the battery modules is investigated in this work by using a proposed saving cost index (SCI). It is demonstrated that the proposed model propels the economic viability of the BSS operation concept.

Sodium Diffuses from Glass Substrates through P1 Lines and Passivates Defects in Perovskite Solar Modules

Most thin‐film photovoltaic modules are constructed on soda‐lime glass (SLG) substrates containing alkali oxides, such as Na2O. Na may diffuse from SLG into a module's active layers through P1 lines, an area between a module's constituent cells where the substrate‐side charge transport layer (CTL) is in direct contact with SLG. Na diffusion from SLG is known to cause several important effects in II–VI and chalcogenide solar modules, but it has not been studied in perovskite solar modules (PSMs). In this work, we use complementary microscopy and spectroscopy techniques to show that Na diffusion occurs in the fabrication process of PSMs. Na diffuses vertically inside P1 lines and then laterally from P1 lines into the active area for up to 360 μm. We propose that this process is driven by the high temperatures the devices are exposed to during CTL and perovskite annealing. The diffused Na preferentially binds with Br, forming Br‐poor, I‐rich perovskite and a species rich in Na and Br (Na‐Br) close to P1 lines. Na‐Br passivates defect sites, reducing non‐radiative recombination in the perovskite and boosting its luminescence by up to 5×. Na‐Br is observed to be stable after 12 weeks of device storage, suggesting long‐lasting effects of Na diffusion. Our results not only point to a potential avenue to increase PSM performance but also highlight the possibility of unabated Na diffusion throughout a module's lifetime, especially if accelerated by the electric field and elevated temperatures achievable during device operation.

The intelligent modelling and optimization of an economic and ecosystem-friendly model for grid connected prosumer community.

The establishment of grid-connected prosumer communities to bridge the demand-supply gap in developing nations, especially in rural areas will assist to minimize the use of carbon enriched fossil fuels and the resulting economic pressure. In the promoted study, an economic and ecosystem-friendly hybrid energy model is proposed for grid-connected prosumer community of 147 houses in district Kotli, AJK. The grid search algorithm-based HOMER software is used to simulate and analyze the load demand and biomass sources-based onsite collected data through a survey for an optimal proposed design. The research objectives are to minimize the net present cost (USD) of design, the per unit cost of energy (USD/kWh), and the carbon emissions (kgs/year). A sensitivity analysis based on photovoltaic module lifetime is also performed. The simulations show that the per unit cost of energy is reduced from 0.1 USD/kWh to 0.001 USD/kWh for the annual energy demand (kWh/year) of the community. The number of carbon emissions is also minimized from 122056 kgs/year to 1628 kgs/year through the proposed optimal energy model.

Effect of the cooling rate on encapsulant's crystallinity and optical properties, and photovoltaic modules' lifetime

Since the renewable energy thrive, performances and lifetime of photovoltaic (PV) modules have been one of the big international concern. The mechanical bonding between the different components and the materials' choice can significantly improve both performances and lifetime of PV modules. The manufacturing process plays also a significant part in the modules lifetime [G. Oreski, B. Ottersböck, A. Omazic, Degradation Processes and Mechanisms of Encapsulants, in Durability and Reliability of Polymers and Other Materials in Photovoltaic Modules (Elsevier, 2019), pp. 135–152]. This work deals with the controlled cooling part of the manufacturing process. The aim is to characterize its influence on an encapsulant properties, and its influences on modules degradation. This work is a part of improving both performances and lifetime of PV modules. First, the work focuses on describing the real temperature seen by a thermoplastic polyolefin encapsulant during the lamination process. A multi-chamber R&D laminator is used and studied in order to better know the industrial equipment. Results show that the cooling process reduces the time to cool down by a factor of ∼5 compared to natural air convection. Secondly, the material's micro-structure is analysed by Differential Scanning Calorimetry (DSC). The impact of the process is quantified. It does have an influence on the encapsulant crystallites' size distribution without modifying the total crystallinity. Thirdly, the impact of the cooling process on optical properties is investigated. Using spectrophotometry and haze-metry optical characterization, coupled with a known light spectrum, the light intensity coming out from the material is analysed. Results show that the cooling process does not have any influence on transmittance nor reflectance. However, a 34% reduction in the haze factor is recorded when using the industrial laminator cooling process. Fourthly, mechanical bond strength between glass and encapsulant is characterized over ageing. Normalized 10 mm width strips are used to estimate the bond strength. It demonstrates that applying pressure during cooling does not influence the bond strength between glass and encapsulant after 1000 h of damp heat ageing. Finally, impact of the cooling process over ageing on PV modules is discussed. Two accelerating ageing methods, 300 Thermal Cycles and 1000 h damp heat, are used to speed up ageing processes. The electrical components of the PV modules are analysed and used to assess the modules' degradation. Modules manufactured with the cooling process are more sensitive to damp heat after 500 h than modules cooled by natural convection. No significant differences were found in thermal cycling ageing.

Design of Reference Junction Temperature Swing of Power Module for Thermal Management

Thermal management is a cost-effective means to improve the lifetime of power module, but it also brings negative influence to the converter. To alleviate the negative effect, this article proposes a strategy to design the reference junction temperature swing based on the distribution characteristics of consumed lifetime and the thermal control efficiency. We show that the selected reference temperature swing, including its type and amplitude, allows each application of thermal control to reduce as much consumed lifetime as possible and, at the same time, to guarantee the performance of the converter. Moreover, this approach does not need to obtain the junction temperature swing in real time, which makes the thermal management simple and efficient. The experimental results are presented to verify the merits of the proposed strategy. This article also evaluates the impact of uncertainties due to the semiconductor parameter variations and performs the error analysis of junction temperature estimation.

Effects of light, heat and relative humidity on the accelerated testing of photovoltaic degradation using Arrhenius model

Energy demands in Nigeria has increased tremendously over the past decade due to the increasing levels of industrialization and population size. This has led to a higher reliance on solar photovoltaic (PV) modules for power generation since Nigeria receives abundant solar energy. However, no information exists on the lifetime and reliability of PV modules operating in the Nigerian climate. The information on how long PV modules will last when operated in the Nigerian weather becomes necessary since many private and Government parastatals are heavily investing in installing and relying on PV generated electricity. The objective of this study is to compute the acceleration factor and effective temperatures in different strategic locations in Nigeria by considering the combined effects of light, heat and irradiation. The analysis is conducted for different PV module configurations (glass-cell-polymer) and (glass-cell-glass) using the Arrhenius model. A 13-year (2005–2017) climatic data of seven strategic locations that encompass the six climatic zones in Nigeria including the National Capital was used. Results are that when relative humidity was neglected, the acceleration factors for the seven states ranged from 1 to 4. However, when relative humidity was considered, Northern states with relative humidity of about 50% had the highest acceleration factors of up to 50, while other regions with relative humidity above 80% had peak acceleration factors of about 14. The results obtained from this study should provide useful guidelines on the lifespan testing of PV modules operating in Nigeria as a case study and other geographical regions as well.

Validation of a balancing model based on master-slave battery management system architecture

The battery management system (BMS) performs the monitoring and control of the charging/discharging process of the cell, state of charge estimation, battery safety and protection, state of health estimation, cell balancing, and thermal management. These control operations ensure accurate, safe, and reliable operating conditions, individual cell damage on battery string, and increase the cell life. Battery balancing is one of the key technologies in the BMS, which affects the actual usable capacity range, performance, and lifetime of the entire battery module. However, it is difficult to evaluate or compare the performance of the overall BMS under the multi-series battery module structure. Most of the proposed battery energy storage system (ESS) models focus on energy distribution and system estimation (microgrid or renewable energy). This study develops a balancing model for estimating the balancing performance of the BMS. A Master-Slave BMS (MS-BMS) is proposed to validate the balancing model. The Master and Slaves of the BMS employed a traditional flyback converter with a MOSFET switching array and bidirectional flyback converters with photoMOS arrays, respectively, to perform the balancing behavior. The balancing skill, balancing circuit power, equalization speed, control simplicity, modularization simplicity, and cost has been considered in designing the proposed BMS. The simulation results are verified with the experimental results, which are then compared with the balancing model's results under the five balancing conditions, and the average absolute error of the balancing duration results is 3.12%. The performance of the proposed BMS is also compared with the existing modular BMS architecture, which validates the advantages of the proposed BMS including equalization speed, control simplicity, modularization simplicity, and cost.

Surface Maintenance Analysis of Module PV To Improve Solar PV Performance

The performance and reliability of the SPP module plays an important role in increasing the lifetime of the SPP module, together with the investment period, as an indicator that directly reduces the electricity cost or Levelized Cost of Energy (LCOE) of each SPP installation. In this study the aim was to analyze the effect, relationship and differences in changes in surface dirtiness of the module on the performance of the 50 kWp SPP UPDL Makassar both through frequency intervention and maintenance methods. The results showed that the most optimal maintenance method was the rubbing method with optimal time and cost maintenance in a period of 2 weeks, besides that if maintenance was carried out before entering the rainy season, the module cleanliness pattern was in accordance with previous conditions, even though the amount of output produced was smaller due to reduced radiation values. This study also shows that one of the significant factors on the output of SPP is the impact of shadows on the surface of the module.

A Review on Investigation of PV Solar Panel Surface Defects and MPPT Techniques

Abstract: The lifetime of PV modules is reduced due to a variety of degradation modes. Failure modes that contribute significantly to PV module output power losses include snail trails, hotspots, micro cracks, bubbles or delamination, and dust accumulation. The correlations between these phenomena, like those between corrosive environment and potential-induced breakdown, are not well understood. As a result, in this review, we will try to explain the relationship between snail trails, hotspots, microcracks, bubbles or delamination, and dust accumulation on photovoltaic module components in order to ensure the PV modules' reliability. This paper in the Photovoltaic literature gives an overview of several Maximum Point Tracking (MPPT) techniques that have been recently designed, simulated and/or experimentally validated. The main objective of every MPPT technology is to maximize the output of a photovoltaic array with shade or unshade conditions. The characteristics presented in this paper are unique, and they provide researchers with a starting point for choosing and implementing an appropriate MPPT technique.

Future‐proofing photovoltaics module reliability through a unifying predictive modeling framework

AbstractSolar energy, especially photovoltaics (PV), plays a significant role in the global energy transition required for decarbonization. Technological advancements in increasing efficiencies coupled with cost reductions through economies of scale made PV a cost‐competitive energy source set to exceed the milestone of 1 TW globally deployed capacity in 2022. However, ongoing downward price pressure coupled with increasing service life expectations creates tremendous challenges for reliability engineers in ensuring the safe and reliable operation of PV modules and systems over the anticipated service life. Today's reliability research efforts aim for module lifetimes of up to 50 years. Still, our current tools fall short in accurately assessing degradation mechanisms and failure modes over such extended periods. We argue that the well‐established PV reliability learning cycle needs to be accelerated to keep up with the rapid technological advancements and high expectations that are put on PV and its role in the global energy transition. In this article, we explore the evolution of the PV reliability learning cycle and highlight the significance that predictive modeling capabilities will have on future PV module reliability. We propose creating a unifying modeling framework—which once established will enable the holistic assessment of PV module reliability, accelerate the PV reliability learning cycle, and bring us closer to quantitative service life predictions of PV modules.

In-situ characterizations and mechanism analysis of mechanical inhomogeneity in a prismatic battery module

Inhomogeneity can accelerate performance degradation and reduce the lifetime of large-format batteries and battery modules. It is necessary to in-situ monitor the internal heterogeneous information and investigate the mechanical inhomogeneity of the batteries and modules. In this study, an in-situ measurement platform based on the integrating sensors and optical methods is developed. The internal stress and strain evolutions at the module-level are characterized and related to the deformation evolution at the cell-level. Both levels are suffering the serious mechanical inhomogeneity, which is quantitatively analyzed by the in-situ experiments and corresponding simulations, significantly affecting the long-term cyclic performance and consistency of the module. A new concept of mechanical consistency is introduced to correlate the mechanical inhomogeneity with module aging. This study can provide a basis for analyzing the aging mechanism and optimizing the structure of battery modules.

Lightweight Flexible Polyimide-Derived Laser-Induced Graphenes for High-Performance Thermal Management Applications

Laser pyrolysis of polyimide (PI) is a promising approach for preparing porous graphenes with hierarchical structures. In this study, we used a dual-focusing lens with a collimator to generate a highly concentrated CO2 laser beam with a high focal energy density. The resulting PI-derived graphene (PIDG) obtained under high-intensity laser irradiation possessed a high degree of graphitization, a low sheet resistance (27.4 Ω/sq.), and a large surface area (240.4 m2/g). Through optimization of the high-intensity laser parameters, we obtained a hierarchical PIDG possessing a fiber-like structure. We used this PIDG as a flexible heater and efficient heat sink for Si photovoltaic (PV) and light-emitting diode (LED) modules. The developed heater could reach a temperature of 202.6 °C under an applied voltage of 16 V, with rapid responses and remarkable flexibility. As a result of improved convective and radiative heat dissipation, the PIDG-based heat sink lowered the operating temperatures of the Si PV and LED modules efficiently. Accordingly, the power conversion efficiency of the Si PV and the lifetime of the LED module both increased dramatically.

A Log-Logistic Predictor for Power Generation in Photovoltaic Systems

Photovoltaic (PV) systems are dependent on solar irradiation and environmental temperature to achieve their best performance. One of the challenges in the photovoltaic industry is performing maintenance as soon as a system is not working at its full generation capacity. The lack of a proper maintenance schedule affects power generation performance and can also decrease the lifetime of photovoltaic modules. Regarding the impact of environmental variables on the performance of PV systems, research has shown that soiling is the third most common reason for power loss in photovoltaic power plants, after solar irradiance and environmental temperature. This paper proposes a new statistical predictor for forecasting PV power generation by measuring environmental variables and the estimated mass particles (soiling) on the PV system. Our proposal was based on the fit of a nonlinear mixed-effects model, according to a log-logistic function. Two advantages of this approach are that it assumes a nonlinear relationship between the generated power and the environmental conditions (solar irradiance and the presence of suspended particulates) and that random errors may be correlated since the power generation measurements are recorded longitudinally. We evaluated the model using a dataset comprising environmental variables and power samples that were collected from October 2019 to April 2020 in a PV power plant in mid-west Brazil. The fitted model presented a maximum mean squared error (MSE) of 0.0032 and a linear coefficient correlation between the predicted and observed values of 0.9997. The estimated average daily loss due to soiling was 1.4%.

A Monitoring System Based on NB-IoT and BDS/GPS Dual-Mode Positioning

Monitoring system is widely used to detect the environment parameters such as temperature, humidity and position information in cold chain logistic, modern agriculture, hospital and so on. Poor position precision, high communication cost, high packet loss rate are the main problems in current monitoring system. To solve these problems, the paper presents a new monitoring system based on Narrow Band Internet of Things (NB-IoT) and BeiDou system/Global System Position (BDS/GPS) dual-mode positioning. Considering the position precision, a dual-mode positioning circuit based on at6558 is designed, and the calculation formula of the positioning information of the monitored target has been derived. Subsequently, a communication network based on wh-nb75-ba NB-IoT module is designed after compared with the LoRa technology. According to the characteristics of high time correlation of sensor data, an adaptive optimal zero suppression (AOZS) compression algorithm is proposed to improve the efficiency of data transmission. Experiments prove the feasibility and effectiveness of the system from the aspects of measurement accuracy, positioning accuracy and communication performance. The temperature and humidity error are less than 1 °C and 5% RH respectively with the selected sensor chips. The position error is decided by several factors, including the number of satellites used for positioning, the monitored target moving speed and NB-IoT module lifetime period. When the monitored target is stationary, the positioning error is about 2 m, which is less than that of the single GPS or BDS mode. When the monitored target moves, the position error will increase. But the error is still less than that of the single GPS or BDS mode. Then the AOZS compression algorithm is used in actually experiment. The compression ratio (CR) of it is about 10% when the data amount increasing. In addition, the packet loss rate test experiment proves the high reliability of the proposed system.

Dependence of adhesion on degradation mechanisms of ethylene co-vinyl acetate encapsulants over the lifetime of photovoltaic modules

The long-term reliability of encapsulation has a critical impact on the overall cost and effectiveness of photovoltaic modules. An often overlooked but important element of this reliability concerns adhesive degradation of the encapsulant, which results in delamination. This work critically examines the degradation mechanisms – deacetylation, β-scission, and hydrolytic depolymerization – primarily responsible for adhesion loss in ethylene co-vinyl acetate (EVA) encapsulants to provide evidence and clarity regarding the contribution of these mechanisms to the adhesive degradation over the lifetime of a module. EVA samples obtained from mini-modules exposed in two sets of controlled, accelerated conditions – with and without ultraviolet (UV) radiation – are characterized to find specific evidence for the proposed degradation mechanisms. The mini-modules were exposed up to 10,000 h, which represents up to 15–20 years in the field. Results affirm that initially, deacetylation dominates the degradation before scission takes over, followed by hydrolytic depolymerization. Additional analysis highlights the climacteric interdependency between deacetylation and hydrolytic depolymerization as it relates to eventual delamination, where deacetylation products catalyze interfacial hydrolysis reactions. Furthermore, effects occurring at a given interface are isolated, explicitly providing evidence for how these mechanisms are nonuniform throughout the thickness of the EVA. Results demonstrate that the EVA that interfaces with the glass as opposed to the cell experiences increased levels of degradation, explaining why this initially stronger interface becomes the preferential interface for delamination after longer periods of exposure. Additionally, elevated temperatures alone are shown to induce limited migration of sodium ions across the glass/EVA interface.

Thermal Management of IGBT Module in the Wind Power Converter Based on the ROI

Insulated gate bipolar transistor (IGBT) module is one of the most prone-to-fail components in the wind power converter (WPC). The reduction of the junction temperature swing by thermal management can improve the reliability of a WPC. Due to the lack of an applicable selection criterion, not many studies on the control target of junction temperature swing were reported. This article proposes a thermal management strategy to find the control target of junction temperature swing. The proposed strategy considers the return on investment (ROI) of thermal management as a quantitative indicator to guide the control target selection. The selected control target enables optimal benefit of the thermal management. Results show that a 1% increase in the total harmonic distortion would extend the lifetime of IGBT module by 0.144 years. Success of the proposed scheme lies in the efficient regulation of the junction temperature swing. Case studies with different mission profiles and experimental tests on a three-phase two-level inverter are presented to validate the proposed method.

Progressive cooling techniques for photovoltaic module efficiency and reliability: Comparative evaluation and optimization

The temperature of photovoltaic modules during operation is one of the most critical criteria for determining both efficiency and reliability. Alternative PV module cooling techniques have been offered as a means of lowering module temperature, lowering deterioration rates, and enhancing efficiency. In this work, progressive cooling methods including water jacket, phase change material (PCM), and heatsink are thoroughly analyzed using the finite element model. In addition, considerable improvements in the PV module efficiency and reliability are accomplished by introducing new designs for the water jacket. The results show that a water jacket with an aluminum container design performs best when the mass flow rate is 8 kg/min, resulting in a 6.8% power gain, whereas a water jacket with an aluminum pipe design performs best when the pipe diameter is 2.5 cm and the mass flow rate is 2 kg/min, resulting in a 5.2% power gain. In natural convection conditions, the PCM paraffin wax RT-42 and water jacket implementations can reach a 10 °C and 12 °C drop, respectively, whilst the heatsink can only achieve a 4 °C drop. An empirical model is also used to predict and quantify the impact of each cooling method on the durability of PV modules. Water jackets, PCM, and heatsinks all increase solder fatigue life by 154, 103, and 27%, respectively. The module lifetime owing to hydrolysis mitigation is increased by 68, 56, and 18%, respectively, with water jackets, PCM, and heatsink, while the module lifetime due to photodegradation mitigation is increased by 37, 31, and 11%, respectively.