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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 433 records · Page 24

Design and Performance Analysis of a Highly Efficient Polychromatic Full Stokes Polarization Modulator for the CRISP Imaging Spectrometer

We present the design and performance of a polychromatic polarization modulator for the CRisp Imaging SpectroPolarimeter (CRISP) Fabry–Perot tunable narrow-band imaging spectropolarimer at the Swedish 1 m Solar Telescope (SST). We discuss the design process in depth, compare two possible modulator designs through a tolerance analysis, and investigate thermal sensitivity of the selected design. The trade-offs and procedures described in this paper are generally applicable in the development of broadband polarization modulators. The modulator was built and has been operational since 2015. Its measured performance is close to optimal between 500 and 900 nm, and differences between the design and as-built modulator are largely understood. We show some example data, and briefly review scientific work that used data from SST/CRISP and this modulator.

42 ENGINEERING↗

PV Storm Hardening Costs

While solar arrays often survive severe weather events, systems are occasionally compromised and left unable to provide power. For PV systems to act as resilient power providers, they must remain operational. Building a system that is more likely to survive a storm comes at a cost, though. Previous efforts have identified various system measures and practices that can increase the likelihood of a PV system surviving a severe weather event. But what is the cost premium for a storm hardened PV system? This report provides initial estimates for the up-front cost premiums for various methods of storm hardening PV systems.

14 SOLAR ENERGY↗

DuraMAT (Durable Module Materials Consortium) Annual Report FY 2020

The Durable Module Materials Consortium (DuraMAT) launched in November 2016 with five years of funding as part of the U.S. Department of Energy’s (DOE’s) Energy Materials Network. DuraMAT is a multilab consortium, led by the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (Sandia), with SLAC National Accelerator Laboratory (SLAC) and Lawrence Berkeley National Laboratory (LBNL) as core research labs. DuraMAT’s overarching goal is to discover, develop, de-risk, and enable the rapid commercialization of improved materials, designs, predictive tests, and models for PV modules that increase performance, extend lifetime, and enable new applications. We work in partnership with our 15-member Industry Advisory Board and the technical management team in DOE’s Solar Energy Technologies Office. This document describes DuraMAT activities in FY20.

41 EE - Solar Energy Technologies Office (EE-4S)↗

Distribution of the Spectral Response of Cells in Silicon Modules - Mechanisms and Implications

Measurements of the spectral response of cells in a PV module can provide important insight into the physics of the device and are also needed for the accurate calibration of the performance of these devices using solar simulators. While techniques for measuring the spectral response of PV cells are well established, measurement of the spectral response of all cells in a module is not straightforward since in this case one has electrical access to a string of cells and not to cells individually. Here we present a new approach for testing the spectral response of individual cells in silicon modules that allows for the fast mapping of the response at different locations of the module. We show that in some cases the spectral response of different cells in a module can vary considerably and propose an underlying mechanism for this variation. We also discuss the implications of this observation for the uncertainty of the spectral correction and of the I SC calibration using a solar simulator.

modules↗

DuraMAT FY 2023 Annual Report: Toward Reliability Forecasting

The Durable Module Materials Consortium (DuraMAT) launched in November 2016 with five years of funding from the U.S. Department of Energy s (DOE's) Solar Energy Technologies Office (SETO). The program renewed in 2022 for an additional 6 years. DuraMAT is a multi-lab consortium led by the National Renewable Energy Laboratory, with Sandia National Laboratories (Sandia) and Lawrence Berkeley National Laboratory (LBNL) as core research labs. DuraMAT's overarching goal is to accelerate a sustainable, just, and equitable transition to zero-carbon electricity generation by 2035. 2023 has been a wild ride in the solar industry. Photovoltaic (PV) manufacturing is coming back to the United States, and deployment is booming again. DuraMAT has a unique opportunity to support flourishing manufacturing and deployment over the next couple of years.

durable module↗

Limits to Electrical Mobility in Lead-Halide Perovskite Semiconductors

Semiconducting polycrystalline thin films are cheap to produce and can be deposited on flexible substrates, yet high-performance electronic devices usually utilize single crystal semiconductors, owing to their superior charge-carrier mobilities and longer diffusion lengths. Here we show that the electrical performance of polycrystalline films of metal-halide perovskites (MHPs) approaches that of single crystals at room temperature. Combining temperature-dependent terahertz conductivity measurements and ab initio calculations we uncover a complete picture of the origins of charge-carrier scattering in single crystals and polycrystalline films of CH 3 NH 3 PbI 3 . We show that Fröhlich scattering of charge carriers with multiple phonon modes is the dominant mechanism limiting mobility, with grain-boundary scattering further reducing mobility in polycrystalline films. We reconcile the large discrepancy in charge-carrier diffusion lengths between single crystals and films by considering photon reabsorption. Thus, polycrystalline films of MHPs offer great promise for devices beyond solar cells, including light-emitting diodes and modulators.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Repowering: The Other Side of the Reliability Coin

Extreme weather, cracked backsheets, severe PID, poorly built modules, and installation flaws - all can compromise a solar plant's health and force repowering long before end of life. With more than 70% of U.S. PV capacity less than seven years old, the fleet is young, but its rapid expansion has introduced new materials and system designs that are still being tested under real-world conditions. As a result, reliability - not economics - is what most often drives repowering decisions. Repowering is frequently assumed to be an economically motivated choice, but our work shows that reliability concerns are the real trigger. Drawing from industry interviews, case studies, and modeling, we highlight the physical, electrical, and policy barriers owners face when deciding whether to repair, repower, or decommission. At the same time, repowering can create opportunities: renewed interconnection periods, improved energy yields, and strategic upgrades to extend system value. We present a quantitative framework using NLR's System Advisor Model (SAM) and PV in Circular Economy (PV ICE) tool to evaluate trade-offs across financial, material, and energy impacts. These findings provide practical guidance for navigating the realities of repowering today and underscore the critical role of reliability in shaping the future performance and sustainability of the PV fleet.

14 SOLAR ENERGY↗

Combined-Accelerated Stress Testing for Advanced Reliability Assessment of Photovoltaic Modules

New and previously undiscovered degradation mechanisms continue to be identified after field exposure in new photovoltaic module designs or materials oftentimes results in significant losses in investment. This is despite passing certification tests. Testing is insufficient largely due to their single-or double-stress nature. A Combined-Accelerated Stress Test (C-AST) has recently been developed. The test combines multiple stress factors of the natural environment to better replicate conditions experienced by modules in the field and detect mechanisms not a-priori known in new materials and designs.

accelerator factor modeling↗

Short-Lived Modules Need to be Efficient, Lightweight, and Circular for the Energy Transition

Deployment projections for decarbonizing the grid predict 1.75 TW of PV is needed in the United States by 2050. This entails a cumulative demand of 97 million metric tonnes of virgin materials for c-Si modules. These material needs are extraction and energy intensive, making them a key target for improving PV sustainability. Emerging PV technologies, such as perovskites, are targeting 15-year modules, high efficiencies, and circular designs. Previous analysis found that by just modifying the life expectancy to 15 years (keeping target c-Si efficiencies and BOM), an additional 1.4 TW of replacement modules are required to maintain capacity, increasing virgin material demand by 1.75x unless >95% closed-loop recycling is maintained. This study examines the effect of achieving higher efficiencies with thin-film designs and a 15-year expectancy. Higher efficiencies and thin film designs can decrease deployment and material demands, making the level of circularity more attainable. If BOM mass is reduced by 50%, closed-loop recycling rates need to be >80% to reduce virgin material demands compared to a 35-yr c-Si module. If module efficiencies are 30%, closed-loop recycling rates can be reduced to 65%. This efficiency increase also reflects that 1500 million fewer modules can be deployed, however, this is still 2000 million more modules than a 35-year module needs to deploy to achieve energy transition targets, and no PV technology is closed-loop recycled for all component materials.

circular economy↗

Q4 2019/Q1 2020 Solar Industry Update

The presentation, released quarterly, reviews major trends that occurred in the solar industry in 2019 and the first quarter of 2020. Major topics of focus will be global and U.S. supply & demand, module & system price, investment trends, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗

Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere

The formation of hazes at microbar pressures has been explored by theoretical models of exoplanet atmospheres to explain Rayleigh scattering and/or featureless transmission spectra; however observational evidence of aerosols in the low-pressure formation environments has proved elusive. Here, we show direct evidence of aerosols existing at ~1 microbar pressures in the atmosphere of the warm sub-Saturn WASP-69b using observations taken with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments on the Hubble Space Telescope. The transmission spectrum shows a wavelength-dependent slope induced by aerosol scattering that covers 11 scale heights of spectral modulation. Drawing on the extensive studies of haze in our solar system, we model the transmission spectrum based on a scaled version of Jupiter’s haze-density profile to show that the WASP-69b transmission spectrum can be produced by scattering from an approximately constant density of particles extending throughout the atmospheric column from 40 millibar to microbar pressures. These results are consistent with theoretical expectations based on microphysics of the aerosol particles that have suggested haze can exist at microbar pressures in exoplanet atmospheres.

47 OTHER INSTRUMENTATION↗

Simulating the Effect of p-n Junction Fields on TRPL Transients of Thin-Film CdTe Solar Cells

Bias-dependent time-resolved photoluminescence (TRPL) transients of thin CdTe solar cells were simulated with the goal of characterizing the effect of p-n junction fields on photoluminescence decays. It was found that, although bulk lifetime could be accurately determined in field-free samples, electric field effects in solar cells lead to systematic underestimation of bulk lifetime. Modulating field strength with the application of external bias was found to have a major impact, a result corroborated by experimental data. In particular, p-n junction fields effects were found to be effectively suppressed when a cell is put far into forward bias, enabling accurate measurement of bulk lifetime in p-n junction structures.

CdTe↗

Experimental Study of a Novel Semi-Transparent Bi-Facial Agri-Voltaic System: Initial Results

Solar (photovoltaic)-agriculture practices have experienced notable progress across several countries over the past few decades, creating a field widely known as agrivoltaics. This co-location practice has proved effective for certain crops that prefer partial shade like tomatoes, lettuce, and peppers, although it is less effective for crops needing more sun. Availability of natural sunlight with a specific spectral signature is necessary for agricultural practices as many plant species require an optimum-level and quality of sunlight for photosynthesis. The goal of this work is to model and validate ground-level irradiance for a semi-transparent bifacial solar collector equipped with a custom spectral reflector. By introducing intentional gaps between opaque solar cells, we hope to allow 50% of visible light to pass through the module. Additionally, this technology could reduce the soil temperature by 2° C, improve moisture retention, and enhance yield by providing partial solar radiation. In our model, we can calculate the total solar irradiance for the plants as a function of the cell distribution, material absorption, height of the panel and time of year with a spatial resolution of 0.0625 m2. When comparing theoretical estimates to experimental measurements of photosynthetically active radiation (PAR), we find a discrepancy of 32-48%, and a discrepancy of 19-38% after correction with TMY data.

McGraw, Duncan (ORCID:0000000256388118)↗

Methods for In Situ Electroluminescence Imaging of Photovoltaic Modules Under Varying Environmental Conditions

Electroluminescence (EL) imaging is a powerful tool used to identify defects in photovoltaic solar cells. Typically, this type of characterization is performed in the dark using a current injection that equals short-circuit current measured at standard test conditions (STC). Restricting imaging to such a temperature range limits the information obtained about the module and cells. However, it is not trivial to develop a tool that would allow for EL imaging to be performed under a wider range of temperatures. Here we demonstrate an in situ EL imaging capability developed within an environmental chamber that allows for control of sample temperatures between –40 and 90 °C. Additionally, we demonstrate EL imaging of 4-cell mini-modules (MiMo) under front-side mechanical loading. A Raspberry Pi-connected camera with short-pass filter removed is used for EL imaging. The camera is low-cost with a small form-factor, appropriate for use in a harsh, enclosed environment. The camera is installed within a thermally isolating housing mounted within the environmental chamber. Three example cases are given for MiMos that exhibit various forms of degradation including solder fatigue and cell cracking. It is shown that by measuring at conditions above and below STC, different behaviors may be identified. In some cases, restricting characterization to STC may lead to a failure to detect damage existing in the sample.

14 SOLAR ENERGY↗

Millions of Small Pressure Cycles Drive Damage in Cracked Solar Cells

Here, we applied time-varying air pressure to a PV module containing newly cracked cells. The test used a new dynamic mechanical acceleration (DMX) apparatus. We applied pressure cycles similar to natural, wind-driven cycles. Compared to standard dynamic mechanical load (DML) tests, we applied much lower pressure (10 Pa to 300 Pa RMS) and many more cycles (one million at each of four pressure levels). We present a case study on a single cell in a commercial module. We monitored electrical continuity loss across cracks using electroluminescence (EL) imaging. 10 Pa pressure cycles caused negligible change. 30 Pa pressure cycles caused permanent damage that continued worsening even after tens of thousands of cycles. After one million 30 Pa cycles, a series of 100 Pa cycles still caused new, permanent damage to existing cracks. 300 Pa cycles caused further worsening and introduced new cracks.

14 SOLAR ENERGY↗

Spatially Resolved Performance Analysis for Perovskite Solar Cells

This review explores the current state of the art in spatially resolved characterization of mixed-halide perovskite solar cells. As the size of perovskite cells and modules continues to grow, quantification of the spatial distribution of key cell parameters will become increasingly valuable in predicting ultimate cell-level performance and tracking process homogeneity. Here, both high resolution microscopic approaches using scanning techniques and camera-based methods for full-area cell and/or module analysis are discussed. The value of this local data in predicting performance losses at the cell level is particularly emphasized. Measurable physical parameters sensitive to losses of voltage, current, fill factor, and efficiency are discussed together with selected experimental results. It is demonstrated that a combination of spatially resolved cell parameter mapping/imaging can be used to quantitatively discriminate various loss contributions at high resolution. The impact and control of inhomogeneities become particularly important when upscaling from small devices to large formats compatible with industrial mass production.

14 SOLAR ENERGY↗