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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Encapsulant Adhesion to Surface Metallization on Photovoltaic Cells

Delamination of encapsulant materials from PV cell surfaces often appears to originate at regions with metallization. Using a fracture mechanics based metrology, the adhesion of ethylene vinyl acetate (EVA) encapsulant to screen-printed silver metallization was evaluated. At room temperature, the fracture energy Gc [J/m2] of the EVA/silver interface (952 J/m2) was ~70% lower than that of the EVA/antireflective (AR) coating (>2900 J/m2) and ~60% lower than that of the EVA to the surface of cell (2265 J/m2). After only 300 h of damp heat aging, the adhesion energy of the silver interface dropped to and plateaued at ~50-60 J/m2 while that of the EVA/AR coating and EVA/cell remained mostly unchanged. Elemental surface analysis showed that the EVA separates from the silver in a purely adhesive manner, indicating that bonds at the interface were likely displaced in the presence of humidity and chemical byproducts at elevated temperature, which in part accounts for the propensity of metalized surfaces to delaminate in the field.

14 SOLAR ENERGY↗
DOE OSTI2018

Investigation of the Impact of Illumination on the Polarization-Type Potential-Induced Degradation of Crystalline Silicon Photovoltaic Modules

Accelerated potential-induced degradation (PID) testing of photovoltaic modules is conventionally conducted in the dark and at high temperature and humidity levels without considering the influence of illumination. This study investigates the impact of illumination on the polarization-type PID (PID-p) on two different types of encapsulated (glass/backsheet) crystalline silicon solar cells: 1) n-type bifacial passivated emitter rear totally diffused (the front side is facing glass and PID-stressed); and 2) p-type bifacial passivated emitter and rear cell (the rear side is facing glass and PID-stressed). The samples are stressed under the conditions of -1000 V, 40 degrees C, and 40% relative humidity and at different irradiance levels (xenon lamps). While the type-A modules show no reduction in PID-p sensitivity under illumination up to 800 W/m 2 , PID-p in the type-B modules is arrested by the light at an irradiance level as low as 10 W/m 2 . Furthermore, PID-degraded type-B modules (degradation induced in the dark) exhibit a rapid recovery (full recovery in 20 min) upon exposure to light (40 W/m 2 ). External quantum efficiency measurements on the type-B modules show that ultraviolet from 300 to 400 nm is mainly responsible for the fast recovery.

14 SOLAR ENERGY↗
DOE OSTI2014

Trial-Run of a Junction-Box Attachment Test for Use in Photovoltaic Module Qualification: Preprint

Engineering robust adhesion of the junction box (j-box) is a hurdle typically encountered by photovoltaic module manufacturers during product development and manufacturing process control. There are historical incidences of adverse effects (e.g., fires) caused when the j-box/adhesive/module system has failed in the field. The addition of a weight to the j-box during the 'damp-heat,' 'thermal-cycle,' or 'creep' tests within the IEC qualification protocol is proposed to verify the basic robustness of the adhesion system. The details of the proposed test are described, in addition to a trial-run of the test procedure. The described experiments examine four moisture-cured silicones, four foam tapes, and a hot-melt adhesive used in conjunction with glass, KPE, THV, and TPE substrates. For the purpose of validating the experiment, j-boxes were adhered to a substrate, loaded with a prescribed weight, and then subjected to aging. The replicate mock-modules were aged in an environmental chamber (at 85 degrees C/85% relative humidity for 1000 hours; then 100 degrees C/<10% relative humidity for 200 hours) or fielded in Golden (CO), Miami (FL), and Phoenix (AZ) for one year. Attachment strength tests, including pluck and shear test geometries, were also performed on smaller component specimens.

14 SOLAR ENERGY↗
DOE OSTI2020

Decay of Electrostatic Force of Dust Particles on Photovoltaic Modules

Photovoltaic (PV) energy yield loss due to solar module soiling has become increasingly important as solar module deployment is now at the hundreds of gigawatts scale and continues to grow rapidly. We have reported on direct measurements-using atomic force microscopy (AFM)-of strong electric-field-induced attraction and adhesion force (Fes) of dust particles onto solar panel that are 1 to 2 orders of magnitude stronger than the van der Waals and water capillary forces, corroborated by observing the increase in system voltage-induced soiling rate. Here, we report another characteristic of Fes on soiling-long lasting or slow decay after turning off the high voltage applied to solar panels. The Fes decay time varies in a wide time range of 1 to 10 hours, depending on two factors: 1) either/both the cell or/and particle were charged with high voltage before the voltages were turned off; and 2) how the cell was connected to the ground after the voltage was turned off-either connected through the power supply electronics, directly connected to the ground, or electrically floated. The Fes decay is understood in terms of 1) net electrical charge dissipations in both particle and cell, 2) thermal disordering of dipole polarization in the module glass dielectrics, and 3) charge redistribution by the electrostatic interaction of particle and module glass. This long-lasting Fes for hours can significantly affect the solar panel soiling after sunset, especially combined with water condensation.

14 SOLAR ENERGY↗
DOE OSTI2012

Reliability Evaluation of Concentrator Photovoltaic Modules per IEC Qualification Specifications

This project is related to the qualification testing of new generation CPV (concentrator photovoltaics) modules at lower testing costs and lower turnaround time. In this project, the first testing program was completed for two CPV manufacturers, the second testing program was completed for two manufacturers at 65% of the actual testing cost and at less than 3 months of testing turnaround time and the third testing program was completed for two manufacturers at 65% of the actual testing cost and at less than 3 months of testing turnaround time. Due to their financial situation and restructuring, Amonix (one of the CPV manufacturers) intermittently terminated the test programs.

14 SOLAR ENERGY↗
DOE OSTI2011

Challenge to Move from 'One Size Fits All' to PV Modules the Customer Needs: Preprint

Historically, PV companies requested a single qualification test for a single product. As the market has grown, there have been increasing opportunities for companies to differentiate their products while still maintaining high manufacturing volumes of each product. At the same time, as PV is deployed in an increasingly broad range of conditions, modules need to be able to withstand a wide rangeof stresses. In some cases, targeting a specific deployment condition may allow reduction of product cost. Realizing this opportunity will require the ability to confidently predict long-term performance based on accelerated tests and known weather conditions. By working together, the community can most quickly develop tests that identify which products perform well under which conditions. Thispaper discusses some of the challenges of predicting long-term PV performance, including the wide range of stresses that may be encountered, the variability of the stresses from moment to moment, the complexity of some degradation mechanisms, and the dependence of accelerated testing on module geometry. The paper also describes two international projects that deal with location-specificdurability evaluation and long-term module performance.

14 SOLAR ENERGY↗
DOE OSTI2012

NREL Test-to-Failure Protocol (Presentation)

The presentation describes the test-to-failure protocol that was developed and piloted at NREL, stressing PV modules with multiple applications of damp heat (with bias) and thermal cycling until they fail.

14 SOLAR ENERGY↗
DOE OSTI2017

Evaluation of Encapsulant Adhesion to Surface Metallization of Photovoltaic Cells: Preprint

Delamination of encapsulant materials from PV cell surfaces often appears to originate at regions with metallization. Using a fracture mechanics based metrology, the adhesion of EVA encapsulant to screen printed silver metallization was evaluated. At room temperature, the fracture energy, Gc [J/m2], of the EVA/silver interface (952 J/m2) was ~70% lower than that of the EVA/AR coating (>2900 J/m2) and ~60% lower than that of the EVA to the surface of cell (2265 J/m2). After only 300 hours of damp heat aging, the adhesion energy of the silver interface dropped to and plateaued at ~50-60 J/m2, while that of the EVA/AR coating and EVA/cell remained mostly unchanged. Elemental surface analysis showed that the EVA separates from the silver in a purely adhesive manner, indicating that bonds at the interface were likely displaced in the presence of humidity and elevated temperature, and may explain the propensity for delamination to occur at metallized surfaces in the field.

14 SOLAR ENERGY↗
DOE OSTI2022

Value Proposition of UV-Absorbers in PV Module Encapsulation

Various common crystalline silicon cell technologies were exposed to UVA radiation (1.24 Wm-2 nm-1 at 340 nm peak) on the front and back faces at 45 degrees Celsius for periods up to 3000 h, representing about 3 y of solar exposure in Phoenix, Arizona, USA. The resulting degradation of the open-circuit voltage and short-circuit current is presented. Of the various cell types examined, significant levels of degradation were seen in all cases. Less degradation was generally found after UV irradiation of cell fronts and older cell types, whereas a bifacial PERC type exposed on the rear showed about 25% degradation in short circuit current, attributable to lack of a diffused surface field. Selected cells were exposed to UV irradiation with the addition of long pass UV filters to replicate UV-absorbers in encapsulants. Modern cell designs are sensitive to UV-ID because of reduced or eliminated front and back surface field and increased dependence on high quality surface passivation. Single transformation of the independent variable (t, kW h/m^2) could be used to achieve a linear model of the data to extrapolate to 50 y. Solar Advisor Model (SAM) shows appropriate filtering of UV-irradiation can improve LCOE and net present value of plant. Some advanced cell types are seen to be UV-resistant (cell level solutions also exist). Solutions therefore exist on the cell, glass, and encapsulant level. Changes over time in each of these would also need to be considered (solarization, encapsulant browning...).

ENGINEERING,SOLAR ENERGY↗
DOE OSTI2012

Modular Power Converters for PV Applications

This report describes technical opportunities to serve as parts of a technological roadmap for Shoals Technologies Group in power electronics for PV applications. There are many different power converter circuits that can be used for solar inverter applications. The present applications do not take advantage of the potential for using common modules. We envision that the development of a power electronics module could enable higher reliability by being durable and flexible. Modules would have fault current limiting features and detection circuits such that they can limit the current through the module from external faults and can identify and isolate internal faults such that the remaining modules can continue to operate with only minimal disturbance to the utility or customer. Development of a reliable, efficient, low-cost, power electronics module will be a key enabling technology for harnessing more power from solar panels and enable plug and play operation. Power electronics for computer power supplies, communication equipment, and transportation have all targeted reliability and modularity as key requirements and have begun concerted efforts to replace monolithic components with collections of common smart modules. This is happening on several levels including (1) device level with intelligent control, (2) functional module level, and (3) system module. This same effort is needed in power electronics for solar applications. Development of modular units will result in standard power electronic converters that will have a lower installed and operating cost for the overall system. These units will lead to increased adaptability and flexibility of solar inverters. Incorporating autonomous fault current limiting and reconfiguration capabilities into the modules and having redundant modules will lead to a durable converter that can withstand the rigors of solar power generation for more than 30 years. Our vision for the technology roadmap is that there is no need for detailed design of new power converters for each new application or installation. One set of modules and controllers can be pre-developed and the only design question would be how many modules need to be in series or parallel for the specific power requirement. Then, a designer can put the modules together and add the intelligent reconfigurable controller. The controller determines how many modules are connected, but it might also ask for user input for the specific application during setup. The modules include protection against faults and can reset it, if necessary. In case of a power device failure, the controller reconfigures itself to continue limited operation until repair which might be as simple as taking the faulty module out and inserting a new module. The result is cost savings in design, maintenance, repair, and a grid that is more reliable and available. This concept would be a perfect fit for the recently announced funding opportunity announcement (DE-FOA-0000653) on Plug and Play Photovoltaics.

14 SOLAR ENERGY↗
DOE OSTI2020

Reliability Analysis of Field-aged Glass/Glass PV Modules: Influence of Different Encapsulant Types

This paper presents a preliminary reliability analysis of field-aged glass/glass (G/G) PV modules. Several characterization tests were performed on more than 60 modules with two different encapsulant types (EVA and ionomer) exposed in hot-dry Arizona (AZ) climate over 10-35 years. The common degradation mode observed in both encapsulant types was the delamination of encapsulant along with encapsulant browning (EVA only), glass cracking (EVA only), and metallic corrosion over junction box area (ionomer only). The EVA encapsulated G/G modules showed the higher median power degradation rate at 0.91-1.99%/yr whereas modules with ionomer showed the lower at 0.21%/yr.

photovoltaic, failures, field exposed, glass/glass↗
DOE OSTI2022

Onymous early‐life performance degradation analysis of recent photovoltaic module technologies

Abstract The cost of photovoltaic (PV) modules has declined by 85% since 2010. To achieve this reduction, manufacturers altered module designs and bill of materials; changes that could affect module durability and reliability. To determine if these changes have affected module durability, we measured the performance degradation of 834 fielded PV modules representing 13 module types from 7 manufacturers in 3 climates over 5 years. Degradation rates ( Rd ) are highly nonlinear over time, and seasonal variations are present in some module types. Mean and median degradation rate values of −0.62%/year and −0.58%/year, respectively, are consistent with rates measured for older modules. Of the 23 systems studied, 6 have degradation rates that will exceed the warranty limits in the future, whereas 13 systems demonstrate the potential of achieving lifetimes beyond 30 years, assuming Rd trends have stabilized.

14 SOLAR ENERGY↗
DOE OSTI2018

Estimating Ultraviolet Radiation From Global Horizontal Irradiance

Terrestrial ultraviolet radiation (UV) radiation is a primary factor contributing to the degradation of photovoltaic (PV) modules' efficiency and reliability over time. Therefore, accurate knowledge of terrestrial UV incident on the surface of the PV materials is essential to understand the degradation of PV modules and provide reliable assessment of their service life. As PV is deployed in various climate zones, it is crucial that terrestrial UV information is available at various locations. However, the availability of terrestrial UV data - measured or modeled - is extremely limited. On the other hand, total solar irradiance (TS) datasets are relatively abundant. In this study, the National Renewable Energy Laboratory, its industry partners, and ASTM's International Subcommittee on Radiometry and Service Life Prediction are developing a simple method to estimate the clear-sky terrestrial UV irradiance (280-400 nm, 295-400 nm, 285-385 nm, or 295-385 nm) from total irradiance data (280-4000 nm). The goal is to provide reliable estimates of the UV received by samples as a function of location, orientation, tilt, and airmass, thus encompassing a variety of conditions. Here, the Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) model is used to estimate the UV:TS ratio under various scenarios, and examines the influences of atmospheric constituents, such as aerosols, precipitable water vapor or ozone, and of the local surface characteristics (albedo), on the predicted UV.

14 SOLAR ENERGY↗
DOE OSTI2016

Encapsulation and backsheet adhesion metrology for photovoltaic modules

Photovoltaic modules are designed to operate for decades in terrestrial environments. However, mechanical stress, moisture, and ultraviolet radiation eventually degrade protective materials in modules, particularly their adhesion properties, eventually leading to reduced solar cell performance. Despite the significance of interfacial adhesion to module durability, currently there is no reliable technique for characterizing module adhesion properties. We present a simple and reproducible metrology for characterizing adhesion in photovoltaic modules that is grounded in fundamental concepts of beam and fracture mechanics. Using width-tapered cantilever beam fracture specimens, interfacial adhesion was evaluated on relevant interfaces of encapsulation and backsheet structures of new and 27-year-old historic modules. The adhesion energy, Gc [J/m 2 ], was calculated from the critical value of the strain energy release rate, G, using G = βP 2 , where β (a mechanical and geometric parameter of the fracture specimen) and P (the experimentally measured critical load) are constants. Under some circumstances where testing may result in cracking of brittle layers in the test specimen, measurement of the delamination length in addition to the critical load was necessary to determine G. Relative to new module materials, backsheet adhesion was 95% and 98% lower for historic modules that were exposed (operated in the field) and unexposed (stored on-site, but out of direct sunlight), respectively. Encapsulation adhesion was 87-94% lower in the exposed modules and 31% lower in the unexposed module. As a result, the metrology presented here can be used to improve module materials and assess long-term reliability.

14 SOLAR ENERGY↗