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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 91 records · Page 5

Temperature and illumination dependence of silicon heterojunction solar cells with a wide range of wafer resistivities

Abstract Recently, the significant improvements in the surface and contact passivation of silicon (Si) solar cells as well as their bulk quality have shifted their operating point to higher injections. Hence, they are less dependent on wafer doping. This shift opens an opportunity of using high‐resistivity wafers for practical photovoltaic applications, introducing a promising approach to push the cell efficiency towards the intrinsic limit and to improve the module reliability by increasing the cell breakdown voltage. Therefore, insights into the performance of Si solar cells using high‐resistivity wafers at various operating temperatures are of significant interest. In this study, we investigate the temperature‐ and illumination‐dependent performance of Si heterojunction (SHJ) solar cells using a wide range of wafer resistivities (between 3 and 1000 Ω⋅cm). Although a reduction in the passivation quality of the passivating contacts is observed at elevated temperature, the impact on the temperature coefficient of the open‐circuit voltage (TC V oc )—the dominant contributor to the temperature coefficient (TC) of the cell efficiency—is very limited. Their TC V oc are still dominated by the temperature dependence of the effective intrinsic carrier concentration. Furthermore, we also find that the investigated cells are more sensitive to temperature variation at lower illumination intensities. It is noteworthy that the efficiency of the cells fabricated using high‐resistivity wafers is comparable to that of the reference cells at any given temperature, highlighting the potential of using high‐resistivity wafers for solar cells.

14 SOLAR ENERGY↗

Qualification testing of flat-plate photovoltaic modules

The placement of photovoltaic modules in various applications, in climates and locations throughout the world, results in different degrees and combinations of environmental and electrical stress. Early detection of module reliability deficiencies via laboratory testing is necessary for achieving long, satisfactory field service. This overview paper describes qualification testing techniques being used in the US Department of Energy's flat-plate terrestrial photovoltaic development program in terms of their significance, rationale for specified levels and durations, and test results.

Hoffman, A. R.↗

Light-induced effects-impacts to module performance measurements and reliability testing: An overview

The stability of solar cells is a key factor in determining the reliability of photovoltaic modules and is of great interest in the case of solar cells having a new technology which has not yet been fully developed. In particular this question arises with hydrogenated amorphous silicon (a-Si) solar cells because a-Si exhibits reversible light induced changes in its electronic properties, commonly referred to as the Staebler-Wronski effect (SWE). Continuous progress is being made in the peak conversion efficiencies of a-Si solar cells and efficiencies in excess of 11% have been achieved. However, stability is still a problem. ARCO Solar reports results on solar cells which, after over a year's exposure to sunlight, under open circuit conditions, still have about 7% conversion efficiency. Other results show a region of fast degradation for about a month, after which the degradation diminishes rapidly.

Wronski, C. R.↗

PV Module and System Reliability Research

While photovoltaic (PV) technologies have experienced widespread success and adoption, continued growth of these technologies - especially new PV technologies - requires ongoing improvements to their reliability and the testing procedures, data, and standards that underpin them. To better understand and address failure mechanisms of PV modules and systems, NREL conducts testing, models failures, analyzes performance data, helps to develop standards, and convenes expert stakeholders. This work is focused both on improving the performance of industry-dominant PV technologies and rapidly de-risking new PV technologies so they can be proven reliable without decades of field testing.

14 SOLAR ENERGY↗

Reliability Evaluation of Bifacial and Monofacial Glass/Glass Modules with EVA and non-EVA Encapsulants

The market share for bifacial modules is projected to be doubled from 30% to 60% in the next ten years. For the monofacial crystalline silicon glass/backsheet (G/B) modules, extensive reliability data has been available for over 40 years. However, practically little/no long-term field or accelerated reliability test data is available for the new generation glass/glass (G/G) bifacial modules and glass/transparent (G/T) bifacial modules. Therefore, the primary motivation of this project was to identify the reliability strengths and weaknesses of new generation G/G modules compared to G/B modules. In this 3-year project, the goal was to objectively recommend the best construction materials for the new generation G/G (bifacial) modules through a systematic experimental approach with appropriate tasks including: Evaluation of field retrieved old-generation G/G modules; Inspection of new-generation G/G modules installed in the plants; Evaluation of new-generation G/G, G/B and G/T modules using EAST (Extended Accelerated Stress Testing), CAST (Combined Accelerated Stress Testing) and FAST (Field Accelerated Stress Testing); and, dynamic literature search and review. Major accomplishments and outcomes of this project are: Accomplishments: Evaluated more than 60 field retrieved modules and constructed and characterized more than 135 mini-modules with three substrate types (G, B, and T), two encapsulant types (EVA and POE), and two cell types (monofacial and bifacial) as well as evaluated more than 30 commercial G/G and G/B modules; Subjected all the modules to multitude characterization tests and various indoor and outdoor accelerated stress tests including FAST (Field Accelerated Stress Testing), EAST (Extended Accelerated Stress Testing), and CAST (Combined Accelerated Stress Testing) to identify and correlate the failure modes in both field and lab tests. Outcomes: Based on the accelerated test results and handling/mounting experience obtained in this project, the recommended best construction for the glass/glass modules is: “Framed GG modules with cut-cells and POE encapsulant (UVpass front; UVpass back).” However, from a statistical and manufacturing point of view (along with stakeholders surveys), the following cautionary notes are added to the above-mentioned recommendation: (i) Cut cells could introduce a higher level of manufacturing issues, including a higher number of cell interconnects; (ii) POE encapsulant is more expensive than EVA and could present a delamination risk and lower throughput during manufacturing due to lower adhesion strength. Other encapsulants, such as coextruded EPE (EVA/POE/EVA), are also recommended to be investigated. The potential public benefit of the proposed project is to present the strengths and weaknesses of glass/glass modules, so an informed procurement decision can be made.

14 SOLAR ENERGY↗

Reliability Research for Photovoltaic Modules

Report describes research approach used to improve reliability of photovoltaic modules. Aimed at raising useful module lifetime to 20 to 30 years. Development of cost-effective solutions to module-lifetime problem requires compromises between degradation rates, failure rates, and lifetimes, on one hand, and costs of initial manufacture, maintenance, and lost energy, on other hand. Life-cycle costing integrates disparate economic terms, allowing cost effectiveness to be quantified, allowing comparison of different design alternatives.

Ross, Ronald J., Jr.↗

Reliability analysis of Skylab ATM solar cell modules

A detailed reliability analysis was performed on both types of Skylab Apollo telescope mount solar cell modules. Failure rates used were based on testing of several modules of each type for over 4000 thermal cycles. The analysis delineated several important differences between the failure modes of the two differently designed solar cell modules, and, more importantly, showed that the modules can be expected to meet all mission requirements.

Jones, G. M.↗

Tearing and reliability of photovoltaic module backsheets

We report that the backsheet in photovoltaic modules belongs to an important class of layered materials where the tearing behavior of the individual layers does not necessarily represent the tearing behavior of the entire backsheet. Such characteristic arises from the interaction between the individual layers during the tearing process, where one layer of the backsheet is mechanically constrained by its neighboring layers and the layers may debond from each other. The mechanical constraint and debonding change the amount of energy dissipated during tearing and affect the overall tearing energy. In this article, we exposed a wide selection of backsheets with polymers including ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), and ethylene tetrafluoroethylene (ETFE) to damp heat (85°C/85%RH) for up to 2000 hours. We report on the effect of damp heat on the tearing energy as a function of damp heat exposure. We developed a model that describes the tearing energy of a layered structure by accounting for the tearing of the individual layers in the backsheet, the effect of mechanical constraint, and the adhesive debonding between the layers. Additionally, we explore the relationship between the microstructural change in the polymers which resulted from the damp heat exposure and the mechanical properties using modulated differential scanning calorimetry (MDSC), small and wide angle X-ray scattering (SAXS and WAXS), and tensile testing.

36 MATERIALS SCIENCE↗

Highly Reliable Multi-Port Smart Inverter Modules for PV-Based Energy Systems

Generally, large electrolytic capacitors (E-caps) are required to decouple the double-line frequency power fluctuation inherent in all single-phase dc-ac or ac-dc converters. These E-caps pose the weak link in the photovoltaic (PV) inverter because they have poor reliability as a result of short life expectancy and higher equivalent series resistance (ESR) which leads to lower system efficiency. In this paper, multiport smart dual-inverter modules are proposed for residential PV inverter systems with balanced outputs to eliminate the requirement of large decoupling capacitors, thus leading to more reliable and highly efficient inverter modules. The balanced dual outputs are controlled in phase quadrature such that the double frequency current is completely eliminated. One phase supports the standalone residential loads, and the other phase interfaces with the grid, which is synchronized to the utility grid. Also, the proposed modular configuration is scalable to accommodate higher power rating by stacking and paralleling multiple modules. Simulation results for the dual-inverter modules rated for 1 kW each are presented to validate the proposed concept. Experimental results from a controller hardware-in-the-loop (CHIL) platform also verify its feasibility.

14 SOLAR ENERGY↗

Assembly jig assures reliable solar cell modules

Assembly jig holds the components for a solar cell module in place as the assembly is soldered and bonded by the even heat of an oven. The jig is designed to the configuration of the planned module. It eliminates uneven thermal conditions caused by hand soldering methods.

Ofarrell, H. O.↗

Chapter 3: Photovoltaic Module Stability and Reliability

Profits realized from investment in photovoltaic will benefit from decades of reliable operation. Service life prediction through accelerated tests is only possible if indoor tests duplicate power loss and failure modes observed in fielded systems. Therefore, detailing and quantifying power loss and failure modes is imperative. In the first section, we examine recent trends in degradation rates, the gradual power loss observed for different technologies, climates and other significant factors. In the second section, we provide a summary of the most commonly observed failure modes in fielded systems.

14 SOLAR ENERGY↗

Earth Observing System/Advanced Microwave Sounding Unit-A (EOS/AMSU-A): Reliability prediction report for module A1 (channels 3 through 15) and module A2 (channels 1 and 2)

This report documents the final reliability prediction performed on the Earth Observing System/Advanced Microwave Sounding Unit-A (EOS/AMSU-A). The A1 Module contains Channels 3 through 15, and is referred to herein as 'EOS/AMSU-A1'. The A2 Module contains Channels 1 and 2, and is referred herein as 'EOS/AMSU-A2'. The 'specified' figures were obtained from Aerojet Reports 8897-1 and 9116-1. The predicted reliability figure for the EOS/AMSU-A1 meets the specified value and provides a Mean Time Between Failures (MTBF) of 74,390 hours. The predicted reliability figure for the EOS/AMSU-A2 meets the specified value and provides a MTBF of 193,110 hours.

Geimer, W.↗

Development of MCAERO wing design panel method with interactive graphics module

A reliable and efficient iterative method has been developed for designing wing section contours corresponding to a prescribed subcritical pressure distribution. The design process is initialized by using MCAERO (MCAIR 3-D Subsonic Potential Flow Analysis Code) to analyze a baseline configuration. A second program DMCAERO is then used to calculate a matrix containing the partial derivative of potential at each control point with respect to each unknown geometry parameter by applying a first-order expansion to the baseline equations in MCAERO. This matrix is calculated only once but is used in each iteration cycle to calculate the geometry perturbation and to analyze the perturbed geometry. The potential on the new geometry is calculated by linear extrapolation from the baseline solution. This extrapolated potential is converted to velocity by numerical differentiation, and velocity is converted to pressure by using Bernoulli's equation. There is an interactive graphics option which allows the user to graphically display the results of the design process and to interactively change either the geometry or the prescribed pressure distribution.

Hawk, J. D.↗

Reliability and engineering of thin-film photovoltaic modules

Objectives were to: examine thin-film cell attributes that influence module performance and reliability, explore the lessons and applicability of crystalline-silicon module technology to thin-film modules, review the current status of thin-film module technologies, and identify problem areas and needed research. A major need is to separate the effects and resons for reversible degradatin from nonreversible degradation. Amorphous-silicon (a-Si) reliability investigations are focusing on exploratory research investigations, accelerated Arrhenius-type testing of a-Si cells, real-time outdoor exposure testing of a-Si cells, cell failure analysis, and failure mechanism research. Studies included the reduction in strength of glass by high temperature depositions on glass and laser scribing, encapsulation materials development needs, and the testing of modules. The new materials and processes in thin-film modules will require a delinquent reliability effort, including: establishment of mechanism-specific reliability goals; quantification of mechanism parameter dependencies; prediction of expected long-term degradation; identification of cost-effective solutions; and testing and failure analysis of trial solutions.

Royal, E. L.↗

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↗