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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Predicting cutoff L-shells of solar protons using the GPPSn particle dataset

Solar energetic protons (SEPs) arriving at the Earth trigger severe radiation storms in the near-Earth space, directly impacting space missions operating at various altitudes. Therefore, monitoring SEP events and predicting the penetration depths of solar protons are critical for aerospace sectors. Building on previous efforts, here we demonstrate the feasibility of using proton measurements from the Global Prompt Proton Sensor network (GPPSn), enabled by Los Alamos National Laboratory developed combined X-ray dosimeters aboard GPS satellites, to characterize and predict the penetration of solar protons into the geomagnetic field. The inclined medium-Earth-orbits (MEOs) of the global GPS constellation offer a unique advantage of allowing simultaneous measurements of penetrating solar protons inside both open- and closed-field line regions. Therefore, the L-profiles of ∼10s–100 MeV solar protons and their associated cutoff L-shells can be determined from the GPPSn dataset, using predefined threshold proton flux values rather than traditional flux ratios. After examining a list of SEP event intervals across solar cycles 23, 24 and 25—including the 2024 Mother’s Day superstorm, we showcase how the latest GPPSn proton dataset (release v1.10), reprocessed and calibrated, can not only be used to monitor solar proton distributions inside the dynamic geomagnetic field for individual events, but also to derive a new empirical model linking cutoff L-shells with several key space weather parameters. This newly developed SEPCL-MEO model demonstrates high predictive performance; for example, predictions for > 30 MeV solar protons yield a correlation coefficient of 0.85 and performance efficiency of 0.67 when validated against GPPSn observations. Results from this pilot study underscores the scientific and operational value of the GPPSn dataset, and this dataset—when paired with machine-learning techniques—can play a critical role in observing and predicting the effects of future incoming SEP events, including extreme ones.

58 GEOSCIENCES↗
DOE OSTI2012

CIGS Material and Device Stability: A Processing Perspective (Presentation)

This is a general overview of CIGS material and device fundamentals. In the first part, the basic features of high efficiency CIGS absorbers and devices are described. In the second part, some examples of previous collaboration with Shell Solar CIGSS graded absorbers and devices are shown to illustrate how process information was used to correct deviations and improve the performance andstability.

14 SOLAR ENERGY↗
DOE OSTI2014

Core-shell ITO/ZnO/CdS/CdTe nanowire solar cells

Radial p-n junction nanowire (NW) solar cells with high densities of CdTe NWs coated with indium tin oxide (ITO)/ZnO/CdS triple shells were grown with excellent heterointerfaces. The optical reflectance of the devices was lower than for equivalent planar films by a factor of 100. The best efficiency for the NW solar cells was η = 2.49%, with current transport being dominated by recombination, and the conversion efficiencies being limited by a back contact barrier (ϕ{sub B} = 0.52 eV) and low shunt resistances (R{sub SH} < 500 Ω·cm{sup 2})

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

III-nitride core-shell nanowire arrayed solar cells

A solar cell based on a III-nitride hybrid nanowire-film architecture is demonstrated. It consists of a vertically-aligned array of InGaN/GaN multi-quantum well core-shell nanowires, electrically connected by a coalesced p-type InGaN canopy layer. This hybrid structure allows for standard planar device processing, solving an important challenge with nanowire device integration. It also enables various advantages such as higher indium composition InGaN layers via elastic strain relief, efficient carrier collection through thin layers, and enhanced light trapping. This proof-of-concept nanowire-based device presents a path forward for high-efficiency III-nitride solar cells. Fabricated III-nitride nanowire solar cells exhibit a photoresponse out to 2.1eV and short circuit current density of ~1 mA/cm 2 (1 sun AM1.5G).

Wierer Jr., Jonathan J.↗
DOE OSTI2014

Production of core–shell type conducting FTO/TiO{sub 2} photoanode for dye sensitized solar cells

Core–shell type photoanode composed of electrically conducting fluorine doped tin dioxide (FTO) matrix and TiO{sub 2} shell layer was prepared and applied in dye sensitized solar cells. Effects of fluorine doping on tin dioxide based cells and precursor material on shell layer were investigated. Fluorine doped tin dioxide nanoparticles were synthesized under hydrothermal conditions and resistivity value down to 17 Ω cm was achieved. Cells constructed from FTO nanoparticles show enhanced performance compared to intrinsic SnO{sub 2}. Deposition of thin blocking TiO{sub 2} layers was conducted using ammonium hexafluorotitanate and titanium tetrachloride aqueous solutions for different dipping durations which yielded significant deviations in the layer morphology and affected cell parameters. Best results were obtained with titanium tetrachloride treated cells giving 11.51 mA/cm{sup 2} photocurrent density and they were comparable with that of pure TiO{sub 2} based cells prepared under identical conditions. - Graphical abstract: Core shell type FTO matrix was formed as TiO{sub 2} is the shell material to create a blocking layer between FTO core and the electrolyte for suppressed recombination and efficiency enhancement. Display Omitted - Highlights: • Core–shell type photoanode using conducting FTO matrix and TiO{sub 2} shell was prepared. • FTO nanoparticles having resistivity value down to 17 Ω cm was achieved. • Best cell parameters were obtained with TiCl{sub 4} treated cells. • FTO nanoparticle based cells show enhanced performance compared to intrinsic SnO{sub 2}. • Photocurrent in TiCl{sub 4} treated cells is found as comparable to pure TiO{sub 2} cell.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Low temperature grown ZnO@TiO{sub 2} core shell nanorod arrays for dye sensitized solar cell application

High aspect ratio ZnO nanorod arrays were synthesized on fluorine-doped tin oxide glasses via a low temperature solution method. By adjusting the growth condition and adding polyethylenimine, ZnO nanorod arrays with tunable length were successfully achieved. The ZnO@TiO{sub 2} core shells structures were realized by a fast growth method of immersion into a (NH{sub 4}){sub 2}·TiF{sub 6} solution. Transmission electron microscopy, X-ray Diffraction and energy dispersive X-ray measurements all confirmed the existence of a titania shell uniformly covering the ZnO nanorod's surface. Results of solar cell testing showed that addition of a TiO{sub 2} shell to the ZnO nanorod significantly increased short circuit current (from 4.2 to 5.2 mA/cm{sup 2}), open circuit voltage (from 0.6 V to 0.8 V) and fill factor (from 42.8% to 73.02%). The overall cell efficiency jumped from 1.1% for bare ZnO nanorod to 3.03% for a ZnO@TiO{sub 2} core shell structured solar cell with a 18–22 nm shell thickness, a nearly threefold increase. - Graphical abstract: The synthesis process of coating TiO{sub 2} shell onto ZnO nanorod core is shown schematically. A thin, uniform, and conformal shell had been grown on the surface of the ZnO core after immersing in the (NH{sub 4}){sub 2}·TiF{sub 6} solution for 5–15 min. - Highlights: • ZnO@TiO{sub 2} core shell nanorod has been grown on FTO substrate using low temperature solution method. • TEM, XRD, EDX results confirmed the existing of titana shell, uniformly covered rod's surface. • TiO{sub 2} shell suppressed recombination, demonstrated significant enhancement in cell's efficiency. • Core shell DSSC's efficiency achieved as high as 3.03%, 3 times higher than that of ZnO nanorods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Quantum dot cosensitized solar cell based on PMOT@CdSe@ZnO core shell nanostructures with dual emission

Quantum dot sensitized solar cell based on poly(3-methoxythiophene) (PMOT)@CdSe@ZnO core shell nanostructure were synthesized where PMOT serves as hole transport material, CdSe acts as a photosensitizer which enhances visible range absorption and also helps in injection of electrons from PMOT to ZnO where ZnO provides channel for efficient electron transport. The properties of the device were assessed with and without CdSe quantum dots and effect of annealing was also observed on the device. After the addition of CdSe QDs, the visible light absorption of PMOT@ZnO was enhanced due to increase in surface area. PMOT@CdSe@ZnO exhibited dual emission, where CdSe and ZnO exhibited visible and UV emission respectively. The interface formed between PMOT and CdSe improves the charge separation. The better photovoltaic measurement of PMOT@CdSe@ZnO over CdSe@ZnO indicates that PMOT efficiently dissociate excitons at interface and suppress the interfacial charge recombination. A power conversion efficiency of 0.989% was attained for the device PMOT@CdSe@ZnO with V{sub oc}=0.56 V and J{sub sc}=2.5 mA/cm{sup 2}. Upon annealing, the efficiency of the device was enhanced to 1.1609% with V{sub oc}=0.58, J{sub sc}=3.2 mA/cm{sup 2}. - Highlights: • Synthesized PMOT@CdSe@ZnO is biluminescent in nature. • A power conversion efficiency of 0.989% was achieved with PMOT@CdSe@ZnO device which is superior to CdSe@ZnO and PMOT@ZnO. • Upon annealing, an efficiency of 1.1609% was achieved for device PMOT@CdSe@ZnO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Fabrication of highly efficient carbon coated exfoliated tungsten disulfide nanosheets core-shell nanostructure as a promising solar-light driven photocatalyst

Highlights: • Investigated the benefits of exfoliation mechanism of WS{sub 2} nanosheets. • C@e-WS{sub 2} was successfully synthesized via two step exfoliation -hydrothermal process. • C@e-WS{sub 2} core-shell confirmed by HRTEM. • C@e-WS{sub 2} core-shell photocatalyst exhibited excellent photocatalytic activity. • Photodegradation mechanism of C@e-WS{sub 2} photocatalyst is elucidated and discussed. - Abstract: Exfoliated Tungsten disulfide (e-WS{sub 2}) nanosheets were obtained from bulk Tungsten disulfide (WS{sub 2}) in a liquid-phase ultrasonic exfoliation method using a DMF solvent. Core-shell mannered carbon coating was developed by hydrothermal process on exfoliated Tungsten disulfide (e-WS{sub 2}) to enhance the efficient charge separation, specific surface area with mesoporosity and stability for chemical processes and mechanical strains. The carbon coated e-WS{sub 2} nanosheets (C@e-WS{sub 2}) was performed by series of characterization techniques and explored to the photocatalytic degradation of malachite green (MG) dye by comparing with bulk WS{sub 2} and e-WS{sub 2}. Among all the photocatalysts highest performance was observed for the C@e-WS{sub 2}. C@e-WS{sub 2} catalyst displays more than 11 fold enhancements in the photocomposition rate of MG over bulk WS{sub 2} and nearly 8 fold improvements over e-WS{sub 2} for 90 min irradiation. In addition, for complete degradation of MG dye over the bulk WS{sub 2}, e-WS{sub 2}, and C@e-WS{sub 2} catalysts were observed at 150, 130, and 90 min under simulated solar light irradiation. The results obtained using core-shell mannered C@e-WS{sub 2} are stepping stone for developing cost-effective and noble metal-free catalysts for photodegradation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Double-shelled plasmonic Ag-TiO{sub 2} hollow spheres toward visible light-active photocatalytic conversion of CO{sub 2} into solar fuel

Double-shelled hollow hybrid spheres consisting of plasmonic Ag and TiO{sub 2} nanoparticles were successfully synthesized through a simple reaction process. The analysis reveals that Ag nanoparticles were dispersed uniformly in the TiO{sub 2} nanoparticle shell. The plasmonic Ag-TiO{sub 2} hollow sphere proves to greatly enhance the photocatalytic activity toward reduction of CO{sub 2} into renewable hydrocarbon fuel (CH{sub 4}) in the presence of water vapor under visible-light irradiation. The possible formation mechanism of the hollow sphere and related plasmon-enhanced photocatalytic performance were also briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Characterizing and improving the performance of molten-salt-steam heat exchangers in concentrating solar power plants

Shell-and-tube heat exchangers (HXs) for steam generation from molten salts in concentrating solar power (CSP) plants experience thermal fatigue due to significant temperature gradients and inherent transient operation. Molten salt-steam HX design lifespans exceed actual lifespans, and, as a consequence, designers overpredict plant profitability and operators neglect appropriate prescriptions to optimize these lifetimes. Here, this study refines HX lifespan estimates with data benchmarked against thermal-fluid mechanical modeling of stress and accumulated fatigue. Reduced-order thermal models of the molten salt-steam, shell-and-tube evaporator and superheater predict transient temperature profiles along the two HXs salt-steam flow paths. The modeled evaporator and superheater temperature profiles enable assessment of cyclic stresses within the HX tubesheets, where molten-salt HX failures are most common. Evaporator and superheater performance data from a current 110 MW elec commercial CSP plant provide a basis for validating the reduced-order HX models. HX life predictions derived from stochastic failure distributions serve as inputs for simulating and optimizing existing plant operations. The impact of the updated lifespans on overall plant revenue depends on operating scenarios. This study suggests that typical ramping rates for a CSP plant with a high-temperature Rankine cycle result in an evaporator and superheater life of approximately 10 and 25 years, respectively, compared to the design target of 30 years. Reduced HX lifespans decrease operational plant revenue on average by 4.6-5.1%. Furthermore, there may be as many as four HX replacements over the 30-year lifetime of the plant; and, purchase agreement loss due to failure to meet contractual production requirements can have ramifications that include the risk of bankruptcy.

14 SOLAR ENERGY↗
DOE OSTI2015

MULTI-SHELL MAGNETIC TWISTERS AS A NEW MECHANISM FOR CORONAL HEATING AND SOLAR WIND ACCELERATION

We perform numerical simulations of impulsively generated Alfvén waves in an isolated photospheric flux tube and explore the propagation of these waves along such magnetic structure that extends from the photosphere, where these waves are triggered, to the solar corona, and we analyze resulting magnetic shells. Our model of the solar atmosphere is constructed by adopting the temperature distribution based on the semi-empirical model and specifying the curved magnetic field lines that constitute the magnetic flux tube that is rooted in the solar photosphere. The evolution of the solar atmosphere is described by 3D, ideal MHD equations that are numerically solved by the FLASH code. Our numerical simulations reveal, based on the physical properties of the multi-shell magnetic twisters and the amount of energy and momentum associated with them, that these multi-shell magnetic twisters may be responsible for the observed heating of the lower solar corona and for the formation of solar wind. Moreover, it is likely that the existence of these twisters can be verified by high-resolution observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Core–Shell CdS–Cu 2 S Nanorod Array Solar Cells

As an earth-abundant p-type semiconductor, copper sulfide (Cu 2 S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core–shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu 2 S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS–Cu 2 S core–shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core–shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. Furthermore, these results are a first step in the development of large-area nanostructured Cu 2 S-based photovoltaics that can be processed from solution.

14 SOLAR ENERGY↗
DOE OSTI2014

Evidence of significant down-conversion in a Si-based solar cell using CuInS{sub 2}/ZnS core shell quantum dots

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS{sub 2}/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Mesoporous multi-shelled ZnO microspheres for the scattering layer of dye sensitized solar cell with a high efficiency

Both light scattering and dye adsorbing are important for the power conversion efficiency PCE performance of dye sensitized solar cell (DSSC). Nanostructured scattering layers with a large specific surface area are regarded as an efficient way to improve the PCE by increasing dye adsorbing, but excess adsorbed dye will hinder light scattering and light penetration. Thus, how to balance the dye adsorbing and light penetration is a key problem to improve the PCE performance. Here, multiple-shelled ZnO microspheres with a mesoporous surface are fabricated by a hydrothermal method and are used as scattering layers on the TiO{sub 2} photoanode of the DSSC in the presence of N719 dye and iodine–based electrolyte, and the results reveal that the DSSCs based on triple shelled ZnO microsphere with a mesoporous surface exhibit an enhanced PCE of 7.66%, which is 13.0% higher than those without the scattering layers (6.78%), indicating that multiple-shelled microspheres with a mesoporous surface can ensure enough light scattering between the shells, and a favorable concentration of the adsorbed dye can improve the light penetration. These results may provide a promising pathway to obtain the high efficient DSSCs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

A THEORY ON THE CONVECTIVE ORIGINS OF ACTIVE LONGITUDES ON SOLAR-LIKE STARS

Using a thin flux tube model in a rotating spherical shell of turbulent, solar-like convective flows, we find that the distribution of emerging flux tubes in our simulation is inhomogeneous in longitude, with properties similar to those of active longitudes on the Sun and other solar-like stars. The large-scale pattern of flux emergence our simulations produce exhibits preferred longitudinal modes of low order, drift with respect to a fixed reference system, and alignment across the equator at low latitudes between {+-}15 Degree-Sign . We suggest that these active-longitude-like emergence patterns are the result of columnar, rotationally aligned giant cells present in our convection simulation at low latitudes. If giant convecting cells exist in the bulk of the solar convection zone, this phenomenon, along with differential rotation, could in part provide an explanation for the behavior of active longitudes.

79 ASTRONOMY AND ASTROPHYSICS↗