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High-Performance Tunable Narrowband SIW Cavity-Based Quadrature Hybrid Coupler
摘要： This letter presents, for the first time, a tunable narrowband substrate integrated waveguide (SIW) cavity-based quadrature hybrid coupler. Four high-quality factor (Q) SIW evanescent-mode cavity resonators are employed in the design and tuned using piezoelectric actuators. This allows the proposed coupler to have wide spurious-free range (SFR), low-power consumption, and high-power handling capability compared to other tunable planar couplers. The coupler can be tuned starting from 1.32 to 2.22 GHz with a measured insertion loss range from 1.29 to 0.7 dB. Over the full range, the measured 3-dB fractional bandwidth ranges from 5% to 18% while the phase error (∠S21 ? ∠S31) absolute bandwidth measured ±5° ranges from 40 to 82 MHz with an amplitude imbalance range between 1 and 0.3 dB. The measured reflection and isolation are better than 12 and 17 dB, respectively. Moreover, the coupler has a measured SFR of 5.1–3 fo (lowest–highest frequency).
关键词： tunable quadrature hybrid coupler,Evanescent-mode (EVA) cavity,tunable resonators
更新于2025-09-23 15:22:29
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The Influence of the EVA Film Aging on the Degradation Behavior of PV Modules Under High Voltage Bias in Wet Conditions Followed by Electroluminescence
摘要： The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p-type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, Vbias = +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.
关键词： photovoltaic (PV) modules,high voltage stress,EVA film,Degradation,potential induced degradation (PID),leakage current
更新于2025-09-23 15:21:01
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Development of ethylene-vinyl acetate copolymer/graphene oxide nanocomposites for crystalline silicon photovoltaic modules
摘要： Renewable sources of energy, such as solar cells, stand out as promising sustainable alternatives, given the growing world energy demand. The crystalline silicon photovoltaic (PV) modules are the most used in the conversion of solar energy into electricity. These modules are subject to weather conditions that may cause degradation of the ethylene vinyl acetate copolymer (EVA) encapsulant (cross-linked EVA copolymer), affecting the efficiency, stability and service life of the PV conversion. In this work, the development of an encapsulant was performed, based on the addition of graphene oxide (GO) to EVA encapsulant forming the nanocomposite (EVA/GO), in order to improve the stabilization against photodegradation. Nanocomposites with GO concentrations wt. %: 0.25%, 0.50%, 0.75%, 1.0% and 2.0% were characterized by: Fourier transform infrared spectroscopy by attenuated total reflectance (ATR-FTIR) thermogravimetry (TG), and differential scanning calorimetry (DSC), before and after they underwent accelerated aging processes in Weather-Ometer and UVB rays chambers. In general, the addition of GO minimized EVA encapsulant degradation. Only the encapsulant with GO concentration of 0.25 wt% was shown as promising for photovoltaic modules, since the transparency of the films with higher concentrations was impaired.
关键词： Aging,Durability,Thermal analysis,Photovoltaic encapsulant,EVA/GO nanocomposite,Infrared spectroscopy
更新于2025-09-23 15:19:57
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Degradation in photovoltaic encapsulation strength of attachment: Results of the first PVQAT TG5 artificial weathering study
摘要： Delamination of the encapsulant in photovoltaic (PV) module technology results in immediate optical loss and may enable subsequent corrosion or mechanical damage. The effects of artificial weathering were not previously known; therefore, an empirical study was performed to survey the factors most affecting adhesion, including the ultraviolet (UV) source (ie, Xe or fluorescent lamp[s]), the optical filters for the lamp, the chamber temperature, and the relative humidity. Natural weathering was also performed at locations, including the following: Golden, Colorado; Miami, Florida; Phoenix, Arizona; QiongHai, China; Riyadh, Saudi Arabia; and Turpan, China. Specimens were constructed using a laminated glass/poly (ethylene-co-vinyl acetate)/glass geometry. The compressive shear test (CST) was used to quantify the mechanical strength of attachment, taken as a proxy for adhesion. The fractography of select specimens (including cross-sectional optical microscopy) was used to verify the failure mode (delamination or decohesion). Additional analysis of the local solar spectrum as well as the specimen temperature was performed to interpret the results of natural weathering. The goals of this study include to identify the most significant stressors, clarify where strong coupling may occur between stressors, and validate accelerated test results relative to natural weathering. The importance of specimen conditioning (for moisture) and hygrometric degradation as well as the effects of UV degradation are identified in this study.
关键词： EVA,durability,reliability,xenon,UVA-340
更新于2025-09-23 15:19:57
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Comparison and analysis of performance and degradation differences of crystalline-Si photovoltaic modules after 15-years of field operation
摘要： This paper reports on a unique evaluation-opportunity for comparing modules from two-different manufacturers that were deployed for a long-period (~15 years) under similar circumstances: (a) for the same distributed, rural-power applications, (b) operating under the same climate-conditions and geographical area, (c) with devices manufactured and installed at the same time. But these modules had very different resulting observed changes in their operational and physical characteristics over their long field-exposures. The PV modules were dispersed in a tropical climate-zone (northern-region of Minas Gerais, Brazil). Visual inspections of the two-module sets concluded that one module source (SET A) had almost no encapsulant discoloration and few indications of delamination and corrosion. In contrast, the other module source (SET B) had significant yellowing/browning, widespread-areas of delamination, and fairly extensive interconnect-corrosion. The corresponding measured changes in the electrical characteristics were: SET A having average annual loss in power of 0.4–0.5%, and SET B with 2.3–3.7%/year over their installation times. Encapsulant discoloration and delamination provided the first clues to the measured differences in module performance and are attributed to the existing climate conditions of high-ultraviolet (UV) radiation exposures and high-ambient temperatures. The bases for the performance differences of these two module sets were examined using complementary electrical, physical and chemical characterization of the module materials. The primary goal of this paper is to identify the root causes for the degradation differences (one set meeting specifications, the other not), based upon the critical module materials properties/processing and climatic exposures.
关键词： Reliability of PV modules,Encapsulants,Module performance loss,Failure rate,Degradation modes and mechanisms,EVA
更新于2025-09-19 17:13:59
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Cu( <scp>i</scp> )a??I coordination polymers as the possible substitutes of lanthanides as downshifters for increasing the conversion efficiency of solar cells
摘要： This study tries to provide new solutions to increase the e?ciency of conversion of photons in solar cells, using photoluminescent Cu(I) coordination polymers (CPs) as possible alternative materials of lower cost, than those used today, based on lanthanides. The selected CP of chemical formula [Cu(NH2MeIN)I]n (NH2MeIN = methyl, 2-amino isonicotinate) absorbs in the utraviolet and emits in the visible region, being also easily nanoprocessable, by a simple and one-pot bottom-up approach. Nano?bers of this CP can be embedded in organic matrices such as ethyl vinyl acetate (EVA), forming transparent and homogenous ?lms, with a thermal stability of up to approximately 150 °C. These new materials maintain the optical pro-perties of the CP used as a dopant, ([Cu(NH2MeIN)I]n), with emission in yellow (570 nm) at 300 K, which is intensi?ed when the working temperature is lowered. In addition, these materials can be prepared with varying thicknesses, from a few microns to a few hundred nanometers, depending on the deposition method used (drop casting or spin coating respectively). The study of their external quantum e?ciency (EQE) found an increase in the UV range, which translates into an increase in the conversion e?ciency. The optimal CP concentration is 5% by weight in order to not diminish the transparency of the composite material. The calculated cost on the possible incorporation of this material into solar cells shows a 50% decrease over the cost reported in similar studies based on the use of lanthanides.
关键词： EVA,photoluminescent,Cu(I) coordination polymers,solar cells,downshifters,external quantum efficiency
更新于2025-09-19 17:13:59
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Analysis of the degradation of encapsulant materials used in photovoltaic modules exposed to different climates in China
摘要： This work investigates the degradation mechanisms of polymeric encapsulants used in photovoltaic modules. Two groups of photovoltaic modules, which were exposed to two typical climates, namely a hot-humid climate and a hot-dry climate, were investigated. Both types of modules were produced by Siemens Solar in 1992 and exposed to outdoor sunlight and the climate for 18 years. The results show that, depending on the climate conditions, the polymeric encapsulant materials exhibit different degradation mechanisms regarding the optical, chemical and morphological properties. The aging of polymeric encapsulant materials is, on the one hand, related to the working environment (moisture, sunlight intensity, UV content and temperature) and, on the other hand, also the conditions are not uniform across the modules: moisture ingress is more important at the edge of the module, oxygen diffusion is more important between cells than at the center of a cell, the module temperature is not uniform.
关键词： Photovoltaic module,FTIR spectroscopy,Raman spectroscopy,EVA sample,Degradation behavior
更新于2025-09-12 10:27:22
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Influence of Fragment Size on the Time and Temperature of Ethylene Vinyl Acetate Lamination Decomposition in the Photovoltaic Module Recycling Process
摘要： Photovoltaics is a commercially available and reliable technology with significant potential for long-term growth in nearly all global regions. Several research institutes and companies are working on recycling concepts for thin film modules and modules with crystalline cells. The establishment of recycling and reuse technologies appropriate and applicable to all photovoltaics (PV) modules is a key issue to be addressed as part of corporate social responsibility to safeguard the environment and to implement a fully material-circulated society without any waste. The copolymer ethylene-vinyl acetate (EVA) layer is a thermoplastic containing cross-linkable ethylene vinyl acetate, which is used to encapsulate the photovoltaic cells. The cells are laminated between films of EVA in a vacuum, under compression, and up to 150°C. The encapsulant’s primary purpose is to bond or laminate the multiple layers of the module together. In the photovoltaic module recycling process, the second important step (after mechanical dismantling of the frame) is EVA lamination removal. In this study, different parameters of the thermal delamination method used during the recycling process were experimentally tested and compared, and the most ecological and economical one is proposed.
关键词： recycling,photovoltaic,EVA
更新于2025-09-11 14:15:04
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Ultra-Compact Tunable Filtering Rat-Race Coupler Based on Half-Mode SIW Evanescent-Mode Cavity Resonators
摘要： In this paper, for the first time, an ultra-compact frequency-tunable filtering rat-race coupler based on half-mode evanescent-mode (EVA) cavity resonators is presented. Employing EVA cavity resonators in the coupler design yields attractive characteristics, such as a wide tuning range and a wide spurious-free range, while also adding filtering functionality to the device. The presented coupler is synthesized as a two pole bandpass filter using the coupling matrix method. Then, the coupling coefficients are mapped to a coupler topology. Design, simulations, and experimental validation are presented. The implemented rat-race coupler has a very compact size [0.14λg × 0.14λg (λg at 885 MHz)] achieving a 92% miniaturization in the structure footprint compared to the conventional planar one. The coupler has an 86% tuning range ranging between 0.885–1.65 GHz. Throughout the tuning range, the coupler shows an equal power splitting ratio and filtering profile with a measured insertion loss and 3-dB fractional bandwidth between 5 and 4.2 dB and 6.8% and 8%, respectively. The measured isolation is better than 30 dB. In addition, the coupler has a measured spurious-free range of 10.2 fo (at the lowest frequency) to 5.45 fo (at the highest frequency).
关键词： rat-race coupler,tunable resonators,Evanescent-mode (EVA) cavity,tunable coupler,half-mode
更新于2025-09-11 14:15:04