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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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28 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

R&D to Ensure a Scientific Basis for Qualification Tests and Standards (Final Report)

Project return on investment in a photovoltaic (PV) system depends increasingly on maintaining high energy yields, and the system lifetime is a major factor in levelized cost of electricity (LCOE). Thus, the rate of PV deployment and the success of these assets depends upon reliable long-term power generation. The overarching objective of this program is to improve photovoltaic (PV) module reliability via development of tests and standards. Where reliability problems or risk are discovered, we can design tests to ensure that these liabilities don't affect future generations of products. Customers can use these tests to understand which products are susceptible to certain degradation mechanisms, and manufacturers can use the tests to design unwanted characteristics out of their products. The work under this program identifies PV reliability needs, performs characterization that provides scientific understanding of targeted degradation mechanisms, and translates those data into practical and predictive test protocols and standards. Major accomplishments include: A model for polarization-type potential induced degradation (PID-p) was developed and validated against experimental data. NREL is currently leading a new edition of IEC 62804-1 for PID detection. PID-p can cause large losses in current and voltage for some module designs on cloudy days. Finite element modeling (FEM) and experiment was used to determine when cells crack in a module. It was shown that cells in landscape orientation are much more likely to crack than those on portrait orientation. Shortly thereafter, the first products with portrait-oriented cells were introduced. Studies of how to test for light and elevated temperature degradation (LeTID) culminated with the publication of IEC TS 63342. Software to predict the progression of LeTID was developed, validated, and made publicly available. Field validated tests and international standards for durability of PV module coatings abrasion, backsheets, and encapsulants were developed. Examples are IEC 62788-1-1, IEC 62788-2 ED2, IEC TS 62788-7-2, IEC 62788-7-3 ED1, IEC 63209-2. NREL led the development a high-temperature testing technical specification, and published guidelines that enable installers to determine whether higher-temperature testing is needed, simply based on location and mounting configuration. In a number of our case studies, variations in the bills of materials or workmanship have been associated with variations in reliability. These observations emphasize the importance of quality assurance to reliability. A framework for criticality (i.e. Pareto) analysis was developed and published. The framework helps us and other researchers determine what problems should be addressed for reliability research to have the biggest industry impact. NREL continues to participate actively in international standards development and stakeholder engagement activities, including organizing an annual PV Reliability Workshop. These activities are important for ensuring we address issues that are relevant and timely, and that we convey our results to those who may benefit.

14 SOLAR ENERGY↗
DOE OSTI2024

PV Lifetime Project (2024 NREL Annual Report)

DOE’s PV Lifetime project was initiated in 2016 with the goal of accurately characterizing the early-life evolution of photovoltaic (PV) field performance. Different PV cell and module technologies result in different initial degradation rates due to effects like light-induced degradation (LID) and light & elevated temperature-induced degradation (LeTID). To accurately characterize the initial field degradation of maximum power (Pmp) requires the use of high-accuracy indoor IV curve measurements at standard test conditions. Therefore, PV modules involved in this study are removed from the field once or twice per year and brought indoors for measurement under constant temperature and irradiance conditions.

14 SOLAR ENERGY↗
DOE OSTI2022

Hydrogen Transport from Dielectrics to poly-Si/SiOx Passivating Contacts Measured by Mass Spectrometry and Vibrational Spectroscopy

We demonstrate the relationship between Si solar cell passivation and hydrogen content of various passivating films, including hydrogenated amorphous silicon (a-Si:H), aluminum oxide (Al2O3), silicon nitride (SiNx) and combinations thereof. Through isotopic studies using quadrupole mass spectrometry (QMS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, we determine how hydrogen content and stability within each type of film relates to final passivation quality of solar cell test structures. Si solar cells using polycrystalline silicon on silicon oxide (poly-Si/SiOx) passivating contacts are at the forefront of Si solar cell research and emerging as top performers within industrial production. Performance of passivating contact Si solar cells is largely determined by a parameter known as the open-circuit voltage Voc, which directly relates to material quality within the bulk of the device and at surfaces. High Voc is achieved when defects within the bulk crystalline silicon (c-Si) and at interfaces are passivated, preventing them from acting as charge carrier recombination centers. One of the most important means of passivating defects within Si solar cells is via hydrogenation, injecting the cells with large amounts of H to satisfy dangling bonds in the bulk and at interfaces. Hydrogen is especially important in deactivating a prevalent defect in industrial p-type devices which leads to decreased device performance over long-term exposure to light, called light-induced degradation (LID). Some of the most common materials used to supply H to devices are a-Si:H, Al2O3, and SiNx, which can contain very large amounts of H. Upon annealing at elevated temperatures, the hydrogen becomes mobile enough to find and disable defect sites. However, too much hydrogen can also be problematic, sometimes leading to an effect called light and elevated temperature induced degradation (LeTID). It has been shown that these films passivate the interfaces of poly-Si passivating contacts differently, leading to differing performance. Though Al2O3 is a well-defined dielectric material, SiNx can have many different values of x depending on precursor gases and deposition conditions. We observe different FTIR and Raman spectra from different SiNx over a range of x values films to determine the bonding environments within them and further correlate the relative concentrations of Si, N, and H to the stability of H within SiNx and the passivation performance of each film. Because deuterium is chemically identical to hydrogen within these systems, but gives different signals in FTIR and Raman spectroscopy as well as in QMS, isotopic substitution can be used as an excellent tool to probe the H within films. In addition to measuring the H and D bonding within films using FTIR and Raman spectroscopy, we will use such isotopic experiments to observe H and D movement out of these hydrogenating films at elevated temperatures using QMS to determine the stability of H bonding within such systems. With these films characterized based on elemental composition, we will relate such measurements to passivation quality of these films and combinations thereof on poly-Si/SiOx contact structures using quasi-steady state photoconductance decay measurements to obtain implied open-circuit voltage (iVoc) and saturation current density J0 values. Such investigations into the performance of different passivating films and film stacks will lead to greater understanding of dielectrics in semiconductor devices, further improvements in passivated contact design, and eventually, greater proliferation of renewable solar energy worldwide.

Al2O3↗
DOE OSTI2022

Correspondence: Bill of Materials Variation and Module Degradation in Utility-Scale PV Systems

We report photovoltaic (PV) modules of the same make and model are often assembled with different bills of materials (BOMs). In this correspondence, we revisit two case studies of utility-scale silicon PV systems in which these differing BOMs were associated with faster-than-expected degradation. In one of the sites, we found that different metallization paste had been used for grid lines in some cells leading to loss of contact to the cell and severe series resistance degradation. We provide details on the observation of this mechanism at two additional sites not described in the original article. In a second case study, we found that two different types of cell had been used, and that they could be distinguished by their back contact. Cells with uniform back contacts suffered from light and elevated temperature induced degradation (LeTID), while those with local back contacts did not. We also briefly describe BOM variations observed at other sites to illustrate the extent of the challenge. Our results from both sites underscore that variations in BOM, even among modules of the same make and model can lead to reliability challenges.

14 SOLAR ENERGY↗
DOE OSTI2026

PV Lifetime Project - 2025 NLR Annual Report

DOE's PV Lifetime project was initiated in 2016 with the goal of accurately characterizing the early-life evolution of photovoltaic (PV) field performance. Different PV cell and module technologies result in different initial degradation rates due to effects like light-induced degradation (LID) and light and elevated temperature-induced degradation (LeTID). To accurately characterize the initial field degradation of maximum power (Pmp) requires the use of high-accuracy indoor IV curve measurements at standard test conditions. Therefore, PV modules involved in this study are removed from the field once or twice per year and brought indoors for measurement under constant temperature and irradiance conditions. Overall annual degradation rates are as follows: our first modules to be deployed (Jinko, Trina, QCells) have annual median degradation rate between -0.4%/yr and -0.5%/yr mainly concentrated in the first year. Mission Solar, LG and Panasonic modules are all displaying modest degradation, better than -0.3% / year. Indeed, Mission Solar fielded modules degraded less than their control modules which remain indoors and un-exposed. This is also true for the LONGi monofacial modules, which had some field degradation, but not as much as the degradation of the indoor control modules. The LONGi bifacial modules on the other hand have degraded more in the field than their monofacial counterparts, although still a modest amount (-0.4 %/yr). Of the four newest module types in the study, only one has had better than average degradation. REC360NP2 (N-type TOPCon) had a slight performance increase over the first year and a half of field deployment. For the other three new module types (plus one older module type), degradation was more rapid. In our study of 16 module types, four have demonstrated degradation faster than -1%/yr: two N-type Heterojunction, one PERC bifacial and one PERC shingled module. The two heterojunction modules in our study are degrading the most rapidly. Sunpreme n-HIT bifacial modules are showing a loss rate around -1.5%/yr, for over -10% total to date. This is largely attributed to loss in front-side Isc. This is distinct from the REC 405AA-Pure modules which have degraded -6.8% in only a year and a half, for an annualized decline of -3.9 %/yr. For this module type, the decline is roughly half in Voc, with the remaining split between FF and Isc. Of the remaining two module types, Prism Solar PERC bifacial has declined -5% total since 2019, although this loss appears to have stabilized in the most recent measurement. The Solaria PowerX-400R Shingled module type has also lost around -3.2% in the first 1.5 years of field deployment. It remains to be seen if these losses will continue with time.

14 SOLAR ENERGY↗
DOE OSTI2023

pyletid [SWR 23-40]

A python library to aid in modeling and understanding light- and elevated temperature-induced degradation (LETID) and boron-oxygen light-induced degradation (B-O LID) in silicon solar cells and wafers https://github.com/NREL/PVDegradationTools/blob/main/pvdeg/letid.py https://github.com/NREL/PVDegradationTools/blob/main/pvdeg/collection.py

Karas, Joseph↗
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 OSTI2023

PV Module BOM and Test Data

This dataset contains compiled results from annual PV Module Reliability Scorecards published by PV Evolution Labs – also known as PVEL. These scorecards show summary results of PV module testing performed by PVEL and name specific models of PV modules as "Top Performers" in various tests. Full details on testing, Top Performer status and other criteria for inclusion in Scorecards are documented in reports and online documentation available from https://www.modulescorecard.pvel.com. This dataset is not affiliated with PVEL and is intended only to simplify sorting and filtering Scorecard data and finding specific PV module models and Top Performer results. Note that data included in Scorecards has evolved over time, so not all data is available for all years, and testing protocols and Scorecard criteria have been changed over time.

14 SOLAR ENERGY↗
DOE OSTI2026

Interconnect: Cooperative Research and Development Final Report, CRADA Number CRD-13-00507 (Project 4)

This CRADA modification involves analyses on a variety of CdTe-PV related materials, test structures, solar cells, and modules produced at FSLR and/or NLR and adds analysis related to module degradation and reliability. Materials will be provided by FSLR, NLR, and/or by interleaving FSLR and NLR layers and processes. Module reliability activities will include technical risk assessment, materials characterization, module and test structure characterization, modeling, accelerated test development, and outdoor testing.

14 SOLAR ENERGY↗