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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Investigating the Crosslinking, Degradation, and Adhesion Behavior of Photovoltaic Encapsulants Under Thermal Accelerated Aging

Degradation of photovoltaic (PV) module encapsulant characteristics that lead to mechanical embrittlement and delamination remains a cause of failure in solar installations. A multiscale reliability model connecting the encapsulant mechanical and fracture properties to the degraded molecular structure and interfacial bonding to adjacent solar cell and glass substrates was previously published. The model, developed primarily for poly(ethylene-co-vinyl acetate) 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 generalize the model. In this work, we subject fully cured EVA, POE, and EPE encapsulants to accelerated thermal aging to determine how high temperatures impact reaction kinetics. An increase in gel content (crosslinking) and decrease in crystallinity of the encapsulants under hot-aerobic (90 degrees C, 22% RH) and hot-anaerobic (90 degrees C, sealed in N 2 air) aging were observed, even in the absence of UV and crosslinking initiators. Fourier transform infrared spectroscopy (FTIR)-attenuated total reflectance analysis showed insignificant encapsulant degradation, demonstrating the critical role of UV and moisture in accelerating degradation. Adhesion testing performed on coupon-level specimens (cell/encapsulant/glass laminates) showed decreases in adhesion energy, Gc , from 5000 h of hot-dry (90 degrees C, ~1% RH) and hot-humid (90 degrees C, 60% RH) aging. POE coupons demonstrated the best stability, followed by EPE then EVA. For EVA and POE, hot-humid aged coupons experienced a larger decrease in Gc due to enhanced hydrolytic degradation. Hot-dry aging condition demonstrated that thermal degradation of the interface could be significant even if the encapsulant experiences negligible degradation in the absence of UV and elevated humidity.

accelerated aging↗
DOE OSTI2025

Sequential Stress Identifies Processing Defects in Bifacial Photovoltaic Modules That Limit Durability

Here, we use sequential stress to investigate hurdles to bifacial photovoltaic (PV) module durability from lamination defects. We test mini-modules with glass/glass (G/G) and glass/transparent-backsheet (G/TB) constructions using either ethylene vinyl acetate or polyolefin elastomer (POE) based encapsulants under a modified IEC 63209-2 sequential stress. This sequence includes multiple iterations of damp heat (DH200), full spectrum light exposure (A3), thermal cycling (TC50), and humidity/freeze (HF10). We compare indoor stress with outdoor exposure. Results show similar relative trends in degradation after a year outdoors compared to our first stress cycle. Subsequent stress cycles impart more severe damage than outdoor exposure for the short outdoor duration used here. Edge-pinch lamination defects in G/G mini-modules limit durability causing delamination and cell cracks. Conversely, we observe greater degradation in G/TB mini-modules compared to G/G in the later stages of the stress sequence when the backsheets are directly exposed to UV-containing light. Our results highlight: 1) the utility of sequential stress testing to uncover degradation modes in bifacial PV, 2) implications of using mini-modules for testing PV quality, and 3) the importance of lamination defects that must be avoided to ensure durability as the industry adopts G/G or G/TB packaging.

14 SOLAR ENERGY↗
DOE OSTI2020

Reproducing the 'Framing' by a Sequential Stress Test

The 'Framing' (local discoloration along cell edges) was induced by a simple sequential accelerated stress test (consisting of hygrothermal- and UV-stressors) applied to the PV modules with high OTR (oxygen transmission rate) backsheet, irrespective of the inclusion of UV-absorber in poly(ethylene-co-vinyl acetate) (EVA) encapsulant. UV-fluorescence imaging of the PV modules suggests that the spatially-inhomogeneous degradation of EVA material under UV-irradiating conditions is correlated to this 'Framing' indicating an underlying common mechanism. These findings would contribute to the development of test procedures to broadly mimic the actual failures observed in fielded PV.

14 SOLAR ENERGY↗
DOE OSTI2020

Conductive Adhesives for Metallization of Interdigitated Back Contact Solar Cells

The metallization and interconnection of Si solar cells to form a module is usually a multi-step process: cells are metallized individually, soldered into strings, and subsequently assembled into a module. Furthermore, the metallization process for individual cells must be compatible with the doped surfaces being contacted, which creates additional challenges when moving from diffused junctions to heterojunctions and/or passivated contact structures. To mitigate these problems and streamline module manufacturing for the case of interdigitated back contact (IBC) cell modules, we developed an approach wherein unmetallized IBC cells are bonded directly to a circuitized backsheet using a conductive adhesive (CA) that only conducts out-of-plane. The metal/CA/silicon stack is bonded by hot-pressing at 100-200 degrees C.For a CA consisting of ethylene vinyl acetate (EVA) filled with Ag-coated spheres or indium powder we find that contact resistivities in the range of 1-10 Wcm 2 are obtained, regardless of which conductive filler and which hot pressing parameters are used. XPS revealed that about 1-2 nm EVA residue bonds to the Si in these samples, suggesting the formation of an insulating barrier that is responsible for the high contact resistance. Using indium powder alone, improved contact resistivities <0.6 Wcm 2 , high shunt resistances, and an implied open-circuit voltage loss below 10 mV were obtained. Furthermore, a cost estimate is presented, indicating that substantial cost savings of up to $10/m 2 , or about $0.05/W DC , are possible through CA-based IBC module manufacturing.

14 SOLAR ENERGY↗
DOE OSTI2020

Characterization of Real-World and Accelerated Exposed PV Module Backsheet Degradation

Backsheet degradation is key to maintaining the lifetime of photovoltaic (PV) modules. Cracking, delamination, bubbling, and discoloration are main types of degradation. PV modules were collected from PV installations in multiple climatic zones. Multiple types of backsheets were obtained with poly(ethylene teraphlate) (PET) and polyamide air side layers being the largest number of backsheets retrieved. Multiple commercial PV backsheets were exposed to multiple accelerated exposures and key degradation mechanisms were identified. Polyamide backsheets showed cracking in retrieved modules and under accelerated exposures. Poly(vinylidene fluoride) (PVDF) and poly(vinyl fluoride) (PVF) showed the highest stability in retrieved and accelerated exposures. While polyamide had the largest amount of large scale degradation.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2021

Mechanistic Insights to Degradation of PERC Minimodules with Differentiated Packaging Materials & Module Architectures

In this paper, we study the degradation behavior of glass-backsheet (GB) and double glass (DG) multicrystalline sil- icon monofacial PERC minimodules, fabricated using polyolefin elastomer (POE) and ethylene vinyl acetate (EVA) encapsulants, undergoing exposures of modified damp-heat (80 °C / 85% RH), with and without full spectrum light. The completed exposure time, at this time, is 1512 hours with each step of 504 hours. Step- wise measurements are conducted throughout exposures including current-voltage (I-V ) curves, Suns-V oc , electroluminescence (EL) images, and four-point proof loading with EL for tracking changes in mechanical properties in encapsulants by cell fracture probability. The results show that GB minimodules of both encapsulants, compared to DG minimodules, experience more changes in features of I-V and Suns-V oc measurements. There is no development of PV cell cracking during proof loading as seen from EL images and the load versus load line displacement plots currently.

14 SOLAR ENERGY↗
DOE OSTI2020

Insights into Na + Diffusion in Silicon Modules under Operating Conditions: Measuring Low Concentrations by D-SIMS

Sodium induced shunting under an electric field is a challenging reliability issue in crystalline Si solar modules. The source of this Potential-Induced Degradation of the Shunting type (PID-s) is well understood and its influence on power loss has been intensively studied based on phenomenological models on cell or module level relating the experimental power-loss to stressing parameters (time, temperature, voltage). However, little is known about the Na ion migration kinetics, responsible for PID on a microscopic level, and its quantitative relation to the efficiency degradation. In this paper we present our investigations of sodium ion migration in Ethylene-Vinyl Acetate (EVA) and silicon through Dynamic Secondary Ion Mass Spectroscopy (D-SIMS). Each sample was annealed at field relevant temperatures from 60-90 °C to address typical migration mechanisms of common PV installations. Analysis of the SIMS migration profiles revealed a diffusivity constant D 0,EVA = 0.09 ± 0.14 cm 2 /s and an activation energy E A,EVA = 0.85 ± .04 eV for Na in EVA and diffusivities higher than extrapolated literature values in silicon (D 0,Si = (3.03 ± 2.42)x10 -5 cm 2 /s, and E A,Si = 0.98 ± 0.02 eV). The new insight will be included in a drift-diffusion based degradation model accounting for the partition coefficient across all relevant interfaces. This model can assist in predicting PID-failure in the field based on the given model stack and the diffusion of Na + through each material. Furthermore, this tool can be used for process optimization as well as material selection significantly reducing the cost and time to validate a technology.

14 SOLAR ENERGY↗
DOE OSTI2024

Technoeconomic feasibility of photovoltaic recycling

Abstract Photovoltaic (PV) modules are a key technology to aid the imminent transition from carbon‐based energy. End‐of‐life crystalline silicon PV modules produce a waste stream that is predominantly landfilled due to the recycling challenges associated with PV reuse economics. Current practices recycle the aluminum frame and repurpose the junction box but landfill the rest of the module. The primary challenge in recycling the remaining module is finding a technoeconomically viable method for separating the silicon and glass from the ethylene vinyl acetate (EVA) layers. This issue will rapidly expand with time as it is estimated that flat glass production for solar panels is currently unable to meet the demand for PV. Current literature suggests that chemical, thermal, and mechanical delamination offer economically feasible solutions under ideal circumstances. In this work we evaluate these methods using end‐of‐life panels and assess the economic viability. The technoeconomic study presented here suggests the most economically viable option for disposing of end‐of‐life solar panels, given current technology, is landfilling. Thermal delamination may offer an alternative route in the future. Financial incentives, which can be quantified with this work, may be required to kickstart PV recycling to help bridge externalities around environmental impact.

Crespo, Beatrice↗
DOE OSTI2022

Electronic Absorption Spectroscopy and Photochemistry of Criegee Intermediates

Interest in Criegee intermediates (CIs), often termed carbonyl oxides, and their role in tropospheric chemistry has grown massively since the demonstration of laboratory-based routes to their formation and characterization in the gas phase. This article reviews current knowledge regarding the electronic spectroscopy of atmospherically relevant CIs like CH 2 OO, CH 3 CHOO, (CH 3 ) 2 COO and larger CIs like methyl vinyl ketone oxide and methacrolein oxide that are formed in the ozonolysis of isoprene, and of selected conjugated carbene-derived CIs of interest in the synthetic chemistry community. Of the aforementioned atmospherically relevant CIs, all except CH 2 OO and (CH 3 ) 2 COO exist in different conformers which, under tropospheric conditions, can display strikingly different thermal loss rates via unimolecular and bimolecular processes. Calculated photolysis rates based on their absorption properties suggest that solar photolysis will rarely be a significant contributor to the total loss rate for any CI under tropospheric conditions. Nonetheless, there is ever-growing interest in the absorption cross sections and primary photochemistry of CIs following excitation to the strongly absorbing 1 ππ* state, and how this varies with CI, with conformer and with excitation wavelength. Furthermore, the later part of this review surveys the photochemical data reported to date, including a range of studies that demonstrate prompt photo-induced fission of the terminal O–O bond, and speculates about possible alternate decay processes that could occur following non-adiabatic coupling to, and dissociation from, highly internally excited levels of the electronic ground state of a CI.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Recycling of multilayer plastic packaging materials by solvent-targeted recovery and precipitation

Many plastic packaging materials manufactured today are composites made of distinct polymer layers (i.e., multilayer films). Billions of pounds of these multilayer films are produced annually, but manufacturing inefficiencies result in large, corresponding postindustrial waste streams. Although relatively clean (as opposed to municipal wastes) and of near-constant composition, no commercially practiced technologies exist to fully deconstruct postindustrial multilayer film wastes into pure, recyclable polymers. Here, we demonstrate a unique strategy we call solvent-targeted recovery and precipitation (STRAP) to deconstruct multilayer films into their constituent resins using a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. We show that the STRAP process is able to separate three representative polymers (polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate) from a commercially available multilayer film with nearly 100% material efficiency, affording recyclable resins that are cost-competitive with the corresponding virgin materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Gas-phase formation of the resonantly stabilized 1-indenyl (C 9 H 7 • ) radical in the interstellar medium

The 1-indenyl (C 9 H 7 • ) radical, a prototype aromatic and resonantly stabilized free radical carrying a six- and a five-membered ring, has emerged as a fundamental molecular building block of nonplanar polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanostructures in deep space and combustion systems. However, the underlying formation mechanisms have remained elusive. Here, we reveal an unconventional low-temperature gas-phase formation of 1-indenyl via barrierless ring annulation involving reactions of atomic carbon [C( 3 P)] with styrene (C 6 H 5 C 2 H 3 ) and propargyl (C 3 H 3 • ) with phenyl (C 6 H 5 • ). Macroscopic environments like molecular clouds act as natural low-temperature laboratories, where rapid molecular mass growth to 1-indenyl and subsequently complex PAHs involving vinyl side-chained aromatics and aryl radicals can occur. These reactions may account for the formation of PAHs and their derivatives in the interstellar medium and carbonaceous chondrites and could close the gap of timescales of their production and destruction in our carbonaceous universe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Dehalogenation of Chlorinated Ethenes to Ethene by a Novel Isolate, “ Candidatus Dehalogenimonas etheniformans”

Dehalococcoides mccartyi strains harboring vinyl chloride (VC) reductive dehalogenase (RDase) genes are keystone bacteria for VC detoxification in groundwater aquifers, and bioremediation monitoring regimens focus on D. mccartyi biomarkers. We isolated a novel anaerobic bacterium, “Candidatus Dehalogenimonas etheniformans” strain GP, capable of respiratory dechlorination of VC to ethene. This bacterium couples formate and hydrogen (H2) oxidation to the reduction of trichloro-ethene (TCE), all dichloroethene (DCE) isomers, and VC with acetate as the carbon source. Cultures that received formate and H2 consumed the two electron donors concomitantly at similar rates. A 16S rRNA gene-targeted quantitative PCR (qPCR) assay measured growth yields of (1.2 ± 0.2) × 10 8 and (1.9 ± 0.2) × 10 8 cells per μmol of VC dechlorinated in cultures with H 2 or formate as electron donor, respectively. About 1.5-fold higher cell numbers were measured with qPCR targeting cerA, a single-copy gene encoding a putative VC RDase. A VC dechlorination rate of 215 ± 40 μmol L -1 day -1 was measured at 30°C, with about 25% of this activity occurring at 15°C. Increasing NaCl concentrations progressively impacted VC dechlorination rates, and dechlorination ceased at 15 g NaCl L -1 . During growth with TCE, all DCE isomers were intermediates. Tetrachloroethene was not dechlorinated and inhibited dechlorination of other chlorinated ethenes. Carbon monoxide formed and accumulated as a metabolic by-product in dechlorinating cultures and impacted reductive dechlorination activity. Finally, the isolation of a new Dehalogenimonas species able to effectively dechlorinate toxic chlorinated ethenes to benign ethene expands our understanding of the reductive dechlorination process, with implications for bioremediation and environmental monitoring.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Substituent effect on napthodithiophene-fused porphyrins: Understanding the unusual trend of fluorescence quantum yield quenching

A series of π-extended porphyrins containing thiophene units was prepared to investigate an unusual trend observed in the fluorescence quantum yield of naphtho[2,1-b:3,4-b']dithiophene-fused porphyrins. Monobenzoporphyrins carrying 2-thiophenyl (vinyl thiophene porphyrin) groups (2VTP, 2VTBr and Br2VTP) (numbering 2 and 3 refers to the position of sulfur on the thiophene ring) were synthesized through a Heck-based cascade reaction followed by a newly developed bromination method. These were converted to naphtho[2,1-b:3,4-b']dithiophene-fused porphyrin derivatives (FBr2VTP and F2VTBr) via ring closure with an intramolecular Scholl reaction. Increasingly larger Stokes shifts with a higher number of bromo groups were observed in the unfused π-extended molecular systems, reflecting the heavy atom effect. Fluorescence spectroscopy further confirmed the unusual trend seen in the previous work: structural rigidification in naphtho[2,1-b:3,4-b']dithiophene-fused porphyrins leads to longer fluorescence lifetimes but unexpectedly lowers the quantum yield. Adding one bromo group to the naphtho[2,1-b:3,4-b']dithiophene unit does not change this trend. Furthermore, the presence of two bromo groups prevents the quantum yield from dropping. DFT, TDDFT, and NICS analyses suggest a drastic change in aromaticity in the pyrrole ring where the naphtho[2,1-b:3,4-b']dithiophene is fused in FBr2VTP, which might contribute to the quantum yield reductions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Membrane Considerations for the All-Iron Hybrid Flow Battery

The all-iron flow battery is currently being developed for grid scale energy storage. As with all flow batteries, the membrane in these systems must meet stringent demands for ionic conductivity while limiting unwanted reactant (Fe 3+ ) crossover. In addition, for the all-iron chemistry proton transport across the membrane is highly desirable to maintain the pH levels in the negative and positive electrolytes. Two membranes are considered, Nafion and an in-house developed composite based on Daramic (a commercial microporous separator) and poly(vinyl alcohol). Their performance is compared for various metrics specific to the all-iron flow battery chemistry.

25 ENERGY STORAGE↗
DOE OSTI2023

On the 3D printing of polypropylene and post-processing optimization of thermomechanical properties

Polypropylene (PP) is a highly desirable polyolefin in various plastic industries due to its outstanding thermomechanical properties and chemical resistance. Therefore, the 3D printing of PP is an interesting avenue to explore in digitized manufacturing, where more freedom in structural designs is available for new and extended applications, such as high-performance engineering parts. Here, in this work, we 3D printed PP and studied the effect of printing parameters and post-processing conditions on the printed polymer’s thermomechanical behavior. Results showed that nozzle and bed temperatures of 220 and 100°C produced a high printing quality. Infill percentages between 80 and 90%, coupled with a 4-h annealing at 110ºC, also resulted in optimal printed properties. It is thought that PP can be potentially blended with polyethylene or other vinyl polymers for a more extended 3D printing utility and practical applications in rapid tooling and prototyping.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Digital Light Processing (DLP): 3D printing of polymer-based graphene oxide nanocomposites—Efficient antimicrobial material for biomedical devices

Bacterial infections are one of the major causes of surgical implant inefficiency and failure. Herein, we present a Nanocomposite (NC) produced by the addition of Poly(N-vinyl carbazole)-Graphene Oxide dispersion (PVK-GO) as a nanofiller to a commercial photopolymer acrylate resin and 3D printed as coatings via the Digital Light Processing technique. Characterization and bioassay results against Escherichia coli and Staphylococcus aureus confirmed the elevated thermomechanical properties and efficient antibacterial activity of the printed NC-based coatings. In conclusion, the present study demonstrates the fabrication and optimization of a PVK-GO-based NC and its potential utilization as a 3D-printable material for biomedical applications.

2D materials↗
DOE OSTI2025

In-situ polymerized and crosslinked electrolytes with interchangeable Li/Na transport for battery applications

The next generation of batteries requires electrolytes with high conductivity, mechanical stability, good adhesion with electrodes, wide electrochemical windows, and scalability. The present study introduces a concept of doped quasi single-ion conducting copolymers based on methacrylate-(trifluoromethanesulfonyl)imide (TFSI) and vinyl ethylene carbonate which at room temperature are mechanically robust and display ionic conductivities of ~0.1 mS/cm. These electrolytes can be polymerized/crosslinked in-situ, making them easily implementable in current battery manufacturing technologies. They also allow for switching between Li + and Na + transport using simple chemistry procedures. To demonstrate their potential for battery applications, the newly developed Li conductors have been tested in symmetric cells, exhibiting overall impedance below 350 Ohm and plating/stripping stability up to 1 mA/cm 2 . Moreover, lithium metal batteries incorporating this electrolyte and high-voltage Lithium Nickel Manganese Cobalt Oxide (NMC) cathodes show good capacity retention (~79%) during charging and discharging for 80 cycles at C/10 rate and a Coulombic efficiency close to 100% in the entire measurement range. The compositional, mechanical and electrochemical versatility of these electrolytes opens new venues for the design of polymer-based batteries capable of fast charging and extended cycle life, aligning with the current global green energy storage strategies.

Polymer electrolytes↗
DOE OSTI2022

Aerosol-Based Sealant for Air Ducts Technology

Aerosol-based sealant can be used to seal air duct leaks. This is done by pressurizing the ducts and injecting the spray sealant. This technology can be used to seal small (up to ½-inch diameter) and inaccessible duct leaks hidden in wall, ceiling, and floor cavities (Ternes and Hwang2001). The aerosol sealant itself is a nontoxic vinyl polymer (Kallett et al. 2000). The technology is a proprietary duct-sealing method developed jointly by the U.S. government and Aeroseal, the company that holds an exclusive license to use the technology (Ternes and Hwang 2001). Specifically, Lawrence Berkeley National Laboratory developed the aerosol-spray technology with funding from the U.S. Department of Energy (DOE), the U.S. Environmental Protection Agency, and others while Aeroseal developed the current version of the equipment and software to apply the technology in practice (Ternes and Hwang 2001).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗