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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

FEDIS (The “Fresnel Equations” for Diffuse radiation on Inclined photovoltaic Surfaces) [SWR-22-64]

The well-known Fresnel equations solve for the reflection and transmission of light for precise incident angles. The transmission of diffuse radiation incident on a planar or domed surface is often needed for real-world applications. Due to the complexity of the Fresnel equations, the analytical solution of the integration has hitherto been unobtainable over the last centuries. Therefore, this problem was numerically solved by integrating the angular transmittances in space often leading to substantial computing burden and bias in the results. To efficiently estimate the solar energy resource for a glass-covered photovoltaic (PV) module, we derive an analytical solution of diffuse transmission based on the rigorous integration of an alternate form of the Fresnel equations. The approach leads to a simple yet accurate relative transmittance model that reconciles the solar energy sensed by pyranometers and PV panels. With limited and clearly stated approximations, the complex mathematical derivation resulted in an elegant solution.

Xie, Yu↗
DOE OSTI2023

Extreme Weather Events and PV Systems Impact

The impact of extreme weather events on PV performance was studied by comparing the National Oceanic and Atmospheric Administration database on severe weather with the National Renewable Energy Laboratory's (NREL) PV Fleet database on continuous PV performance. We identified 170 systems that were immediately impacted by weather events. These severe weather events lead to a median loss of only 1 % of annual production. However, flooding and high wind events were found to have an extremely long tail extending to 60 % loss, showing that these discrete events can pose a substantial risk to PV systems. Besides the short-term impact of lost production due to outages, we also found a statistically significant increased performance loss rate (PLR) for high wind events above 90 kilometer/hour, by comparing PLR before and after these events. Similarly, hail events caused higher PLR for hail sizes of and above 25 mm indicating that more stringent hail testing for PV modules is required. In addition, very high snow loads may also cause increased PLRs, but more data are required to better quantify the impact. These findings illustrate the substantial risk extreme weather events pose short-and long-term to fielded PV installations.

extreme weather↗
DOE OSTI2021

Segmentation of Deposition Periods: An Opportunity to Improve PV Soiling Extraction

Soiling profiles are commonly assumed to have sawtooth shapes, made of alternating cleaning events and soiling deposition periods. The rates at which soiling deposit on the PV modules are considered to be constant for each period. In reality, events such as changes in climatic conditions can lead to a sudden variation in soiling deposition rate. These changes cannot be reproduced if cleanings are the only events modelled to extract soiling profiles directly from PV performance data. For this reason, in this work, the use of change points and segmented regression is proposed to improve the extraction of soiling profiles through the model of up to two deposition rates per period in between cleanings. The results show that the quality of soiling extraction can be enhanced compared to a cleanings-only identification approach if both cleanings and change points are considered.

monitoring↗
DOE OSTI2024

Solar Photovoltaic (PV) Damage Assessment After Typhoon Mawar: Findings and Recommendations for Resilient PV on Guam

A team from the National Renewable Energy Laboratory (NREL) visited Guam in August 2023 to assess failure modes of solar photovoltaic (PV) systems after Typhoon Mawar and to provide recommendations to increase the resilience of PV systems on Guam. The team visited 30 systems: commercial and utility scale, and rooftop and ground-mounted. The team observed systems with no apparent damage, as well as systems that were completely lost. Systems fared very well overall. The average failure rate of rooftop systems was 18%, with a median failure rate of 2%, meaning the few systems that suffered total loss pulled up the average. Only eight 8 of the 25 rooftop systems suffered more than 5% damage. All ground-mounted systems suffered less than 0.5% damage, aside from a carport that lost 16% of its modules. PV systems at Andersen Air Force Base suffered 5% damage on average, with a median system failure of 0.6%. In almost all cases, failures were the result of: (1) Inadequate clamping of the module frame to the mount, (2) Module mounting clamps rotating out of underlying support rail (i.e., T-bolt that rotates free at less than 60 degrees of rotation), (3) An object hitting the panel resulting in a fracture, and in some cases leading to a cascading failure of several more panels, and (4) Excessive tilt angle (in Guam, greater than 5 degrees can be a risk due to wind speed, and power production trade-offs are insignificant).

14 SOLAR ENERGY↗
DOE OSTI2019

Q4 2018/Q1 2019 Solar Industry Update [Slides]

This technical presentation provides an update on the major trends that occurred in the solar industry in 2018 and the first quarter of 2019. Major topics of focus include costs and deployment, the global and U.S. supply and demand of PV, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗
DOE OSTI2017

Summary of NREL's FY13-FY15 Photovoltaic Subprogram

In this report, you will find summaries of the completed FY13-FY15 Photovoltaic projects that were funded within NREL. The summaries describe the initial motivation for the project; significant achievements, including publications, intellectual property, and collaborations; and remaining challenges. Among the NREL projects, you will find research of almost every major PV technology - from the next generation of silicon PV to relatively new organic PVs - as well as projects advancing PV module durability and characterization. Each of these projects was designed to support SunShot's goals, putting the United States one step closer to widespread use of low-cost, clean electricity.

14 SOLAR ENERGY↗
DOE OSTI2024

The Sustainable Decarbonization Challenge

Many countries have decarbonization plans that include transitioning to clean energy. Because of this, PV deployment is projected to at least double or triple in the next ten years. As we ramp up manufacturing and deployment, we aim to sustainably establish secure and just supply chains while reducing environmental impacts. This talk presents our analysis of the virgin material demands, addresses waste concerns regarding quantity and toxicity, and establishes sustainability actions that the PV community can take to ensure sustainability. The takeaway actions are prioritizing reliable, high-quality, and long-lived PV modules and enabling the fast deployment needed for decarbonization via more research and effective communication.

circular economy↗
DOE OSTI2018

Low-Cost III-V Photovoltaic Materials by Chloride Vapor Transport Deposition Using Safe Solid Precursors

Si-based photovoltaic devices dominate the market. As photovoltaic (PV) manufacturing costs have plummeted, technologies which increase efficiency have become critical. Si cell efficiencies are nearing theoretical limits and Si-based PV modules are unlikely to reach the 25-30% efficiency range. The use of III-V semiconductors is an obvious technical solution to improve efficiency, especially if they can be integrated directly with existing Si technology as tandems. High coefficients of light absorption along with tunable bandgaps and lattice constants have resulted in record conversion efficiencies for both one-sun and concentrator PV applications. GaAs, for example, has been used to manufacture single-junction photovoltaics with world-record efficiencies of 28.8% at one sun.2 However, costs for III-Vs must be dramatically reduced to produce cost-effective, high-efficiency PV solutions. III-V costs are controlled by two factors: semiconductor growth and the substrate. III-V growth is dominated today by metal-organic vapor phase epitaxy (MOVPE) with a lesser role played by molecular beam epitaxy (MBE). MOVPE costs are high due to the expense and low utilization (~30%) of precursors, modest growth rates (~100 nm min -1 ), equipment complexity, and safety infrastructure needed to handle toxic, pyrophoric gases.3 MBE costs are high due to slow growth rates and limitations of scalability. Details comparing plausible low-cost III-V growth methods are available in a review article published as a result of this project. The primary goal of this project was to demonstrate that close-spaced vapor transport (CSVT) using chloride (from HCl) as a transport agent can be used for the rapid growth of device-ready III-V layers from safe, solid-source precursors. In pursuit of this goal, we designed, built, and installed a new Cl-CSVT reactor based on insights from our previous H 2 O-CSVT growth system and in collaboration with equipment professionals at Malachite Technologies. This system was successfully used to grow epitaxial GaAs with controlled n-type doping, having mobilities similar to MOVPE. Detailed technical information and results can also be found in the primary publication resulting from this project. This work sets the stage for tackling the development of high-performance III-V single junctions and tandem devices directly on Si substrates, which was beyond the capabilities of our H2O-CSVT system. The design of the reactor’s source and substrate transfer system should allow for direct deposition of device structures. The collective innovations of our Cl-CSVT system might ultimately serve as an enabling process for commercialization of the technology through a collaboration with appropriate industrial partners.

14 SOLAR ENERGY↗
DOE OSTI2020

Design Advancement of an Indoor Soil Deposition Chamber: A Road to Standardization

An indoor soil deposition chamber has been designed and constructed at the Arizona State University Photovoltaic Reliability Lab (ASU-PRL) to simulate photovoltaic (PV) module soiling in the field. This paper discusses the next set of revisions to the design, which are organized into three categories: design improvements, cost reduction, and new features. The design process was carried out with the intention of working toward the development of a national or international soiling standard. The improvements made to the chamber are described in detail to provide a guide for other laboratories or research facilities who wish to study photovoltaic (PV) soiling.

14 SOLAR ENERGY↗
DOE OSTI2021

Methods for Evaluating DC Arc Incident Energy in PV Systems: Preprint

Renewable energy systems continue to be one of the fastest growing segments of the energy industry. This paper focuses on the understanding of how photovoltaic (PV) technology behaves under dc arc conditions. Emphasis is placed on the electrical safety aspect of DC arc flash incident energy evaluation. Because of the fast proliferation of PV systems and the lack of formal equivalent calculation guidelines such as IEEE 1584 for AC systems, it has been necessary to rely on different equations and models presented by various researchers over the last few years. This paper discusses the behavior of PV systems under arc conditions and presents the results of available methods to estimate the dc arc flash incident energy. This paper provides a comparative analysis of a proposed arc-flash incident energy calculation method against different laboratory tests including those performed by NREL. Detailed explanations are provided regarding the effect of PV module I-V and P-V curves under arcing conditions. Examples of the application of the proposed calculation method to the test measurements are included.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

PVDeg: Enhancing Usability and AI-Driven Multi-Mechanism Degradation Modeling

PVDeg version 0.7.0, released in December 2025, introduced major enhancements to improve usability and performance. This update reorganized tutorials and tool notebooks to create a more intuitive experience, enabling users to easily follow and adapt workflows for their specific analyses. In addition to structural improvements, both the notebooks and core logic underwent significant optimization for efficiency, robustness, and style. These refinements were supported by new testing frameworks built on nbval and pytest, adherence to PEP8 standards, and extensive code refactoring, which collectively simplify onboarding for new developers. Looking ahead, version 0.8.0 will deliver advanced AI-driven capabilities. The primary focus is to further develop and automate the degradation workflow, designed to analyze PV module degradation across diverse locations and system configurations. By integrating large language models (LLMs) to scan literature and compile a comprehensive database of materials and degradation rates, this feature will enable modeling of multiple materials and mechanisms within a single, streamlined workflow. Users will be able to evaluate degradation impacts on different system architectures under varying environmental conditions, facilitating informed decisions on bill-of-materials optimization for specific deployment scenarios. These advancements position PVDeg as a powerful, user-friendly tool for accelerating PV reliability research and system design.

14 SOLAR ENERGY↗
DOE OSTI2021

U.S. Solar Photovoltaic System and Energy Storage Cost Benchmark: Q1 2021 [Slides]

Our benchmarking method includes bottom-up accounting for all necessary system and projectdevelopment costs incurred when installing residential, commercial, and utility-scale systems, and it models the Q1 2021 costs for such systems, excluding any previous supply agreements or contracts. In general, we attempt to model the typical installation techniques and business operations from an installed-cost perspective, and our benchmarks are national averages. The residential PV-only benchmark and the commercial rooftop PV-only benchmark average costs by inverter type (string inverters, string inverters with direct current [DC] optimizers, and microinverters), weighted by inverter market share. The residential PV-only benchmark is further averaged across small installer and national integrator business models, weighted by market share. All benchmarks include variations—accounting for the differences in size, equipment, and operational use (particularly for storage)—that are currently available in the marketplace. All benchmarks assume nonunionized construction labor; residential and commercial PV systems predominantly use nonunionized labor, and the type of labor required for utility-scale PV systems depends heavily on the development process. All benchmarks assume the use of monofacial monocrystalline silicon PV modules. Benchmarks using cadmium telluride or bifacial modules could result in significantly different results. The data in this annual benchmark report inform the formulation of and track progress toward the U.S. Department of Energy (DOE) Solar Energy Technologies Office’s Government Performance and Reporting Act cost targets.

14 SOLAR ENERGY↗
DOE OSTI2020

Ultimate Bifacial Showdown: 75kW Field Results

This work presents one year results for a side-by-side comparison of 5 different bifacial technologies, deployed in a 75-kW single-axis tracked field at Golden, CO. Four PERC (multi and mono) and 1 Silicon Heterojunction manufacturers are represented. Reference strings of equivalent monofacial PV modules are also installed for a direct technology comparison and calculation of bifacial gain. Analysis indicates performance within expectation, with a cumulative model mean error within +/- 2% for both bifacial and monofacial models and cumulative bifacial energy gain between 6-9%. High accuracy string-level DC monitoring and module-level measurements are also presented, showing effects of snow and edge effects in the order of +/- 3% for non-uniform irradiance across the row. Data from a custom-module to measure shading loss from the torque-tube is installed, showing up to 6% irradiance non-uniformity for the month of January.

bifacial field validation↗
DOE OSTI2020

Understanding PV Polymer Backsheet Degradation through X-Ray Scattering

Understanding how photovoltaic (PV) module backsheet polymers age and degrade in response to environmental stresses is important for designing polymers that can maintain their structural integrity after decades of outdoor use. X-ray scattering is a powerful technique for exploring backsheet polymer structure at the angstrom- (wide-angle, WAXS) and nanometer- (small-angle, SAXS) length-scales. We present the use of SAXS and WAXS to study pristine and aged polymer backsheets. The structural insight from these techniques can be used to compare the degradation induced by accelerated testing with the degradation seen in field-aged PV materials.

14 SOLAR ENERGY↗
DOE OSTI2017

Low irradiance losses of photovoltaic modules

Here, the efficiency of a photovoltaic cell/module changes, as the intensity of incident irradiance decreases, in a non linear way and these changes are referred to as low irradiance losses. In this study data from field experiments, developed and organized by the National Renewable Energy Laboratory, are used to evaluate the low irradiance losses for a variety of module technologies. The results demonstrate that the ratio of the normalized power divided by the normalized short circuit current provide a good measure of the module's low light efficiency losses after both the maximum power and the short circuit current are adjusted for temperature effects. The normalized efficiencies determined through the field data, spanning for several months, are in good agreement with those determined under controlled conditions in a solar simulator. An analytical relation for the normalized efficiency is proposed based on existing formulation for the fill factor. Despite the approximate nature of the fill factor relation, this approach produces reliable results. It will be shown that a normalized efficiency curve can be used to extract information on the series and shunt resistances of the PV module and that the shunt resistance as a function of solar irradiance can be studied. Alternately, this formulation can be used to study the low irradiance losses of a module when the internal resistances are known.

14 SOLAR ENERGY↗
DOE OSTI2018

Design and Indoor Validation of 'DUSST': A Novel Low-Maintenance Soiling Station: Preprint

One of the most relevant concerns of photovoltaic (PV) systems today is the accumulation of dust - commonly referred to as 'soiling' - because it reduces the light that reaches the solar cells (1). This soiling has a significant impact on the energy delivered by PV modules, and hence, on the cost of solar electricity. Soiling losses have been investigated around the world and show a noteworthy dependence on site location. The annual soiling losses for the United States are within 0-6%, whereas in dustier regions, such as the Middle East, India, or China, these loses can reach peak values of up to 70%. These power drops cannot be directly translated into annual energy losses, but they can still lead to higher annual energy losses compared to those in the USA or Europe. In this sense, identifying soiling becomes essential for scheduling the most adequate cleaning strategy and maximizing the PV energy production, thus reducing the operating costs.

14 SOLAR ENERGY↗
DOE OSTI2024

Determining the Crosslinking and Degradation Reaction Kinetics in Photovoltaic Encapsulants Using Accelerated Aging: Preprint

Degradation of photovoltaic (PV) module encapsulant mechanical characteristics that lead to embrittlement and delamination remains a cause of failure in solar installations. A multiscale reliability model based on detailed molecular degradation reaction kinetics was previously published, connecting the encapsulant mechanical properties (elastic modulus, yield strength, and adhesion energy) to the degraded molecular structure and interfacial bond density to adjacent solar cell and glass substrates. The model, developed primarily for poly(ethylene-co-vinyl acetate) (EVA) encapsulants, remains to be experimentally validated. Determining the degradation and crosslinking kinetics of alternative encapsulants, such as polyolefin elastomer (POE) and EVA/POE/EVA composites (EPE), can further generalize the model. Importantly, the activation energy for crosslinking of fully cured PV encapsulant products from temperature or UV is presently unknown or unavailable. In this work, we subject EVA, POE, and EPE encapsulants to a set of accelerated aging conditions, varying the temperature, UV intensity, and relative humidity. We use DSC, FTIR, and Soxhlet extraction (gel content) to characterize the encapsulants' changing molecular structure. This allows for determination of the photochemical degradation and crosslinking kinetics of the encapsulants. Preliminary results show an increase in gel content (crosslinking) and a decrease in crystallinity of EVA, POE, and EPE encapsulants under hot-aerobic (90 deg C, 22% RH) and hot-anaerobic (90oC, sealed in N2 air) accelerated aging, even in the absence of UV and crosslinking initiating agents. For a least squares regression with an assumed first-order crosslinking kinetics, the crosslinking rate parameters were computed for the three encapsulants under hot-aerobic and hot-anaerobic aging conditions. FTIR analysis showed insignificant encapsulant degradation for hot-aerobic and hot-anaerobic aging, demonstrating the critical role of UV and moisture in accelerating degradation. Aging conditions with UV exposure and elevated humidity are presently in progress.

adhesion↗