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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Concentrating photovoltaic retrofit for existing parabolic trough solar collectors: Design, experiments, and levelized cost of electricity

Photovoltaics and concentrating solar thermal power are two ways for generating electricity from sunlight, albeit through different methods. Parabolic trough style powerplants represent 3.6 GW of electricity production, but many of these plants are aging and being replaced with photovoltaics. An alternative option that could be employed to leverage the sunk capital cost associated with the primary optics would be the design of a pure photovoltaic retrofit working within the existing plant architecture. Here, a secondary optical concentrator is designed to use the existing primary optics of a parabolic trough type solar thermal powerplant. The design is a v-shaped secondary concentrator resulting in a predicted concentration ratio on a 20 mm wide target of 94. The concentrating photovoltaic receiver for retrofit of an RP-3 based parabolic trough has been constructed using multi-junction concentrator photovoltaic cells and experimentally demonstrated here for the first time. Calculated performance of the cells based on cell specifications should result in 31% efficiency at 85 °C. On-sun efficiencies were measured at an average value of 21% with operational temperatures between 55 and 120 °C. Levelized cost of electricity calculations predict the system to have the potential to be below 7¢/kWh based on predicted efficiencies and 13¢/kWh based on the measured values at cell costs of $5/cm 2 .

14 SOLAR ENERGY↗
DOE OSTI2024

An MPMD approach coupling electromagnetic continuum mechanics approximations in ALEGRA

In this work, two complementary approximations for describing aspects of continuum electromagnetics in moving media are discussed: electroquasistatic and magnetoquasistatic. Each has been implemented in the finite element shock code ALEGRA for modeling dynamic electromechanical phenomena on typical engineering time scales, with fully integrated circuit coupling. The approximations can be obtained by consistent asymptotic balancing of Maxwell’s equations relative to timescales associated with magnetic diffusion, charge relaxation, and electromagnetic wave propagation. In ALEGRA, the electroquasistatic approximation is used for ferroelectric (FE) modeling, while the magnetoquasistatic approximation is used for magnetohydrodynamic (MHD) modeling. In this paper we introduce for the first time a detailed derivation of a useful quasi-steady “low-R m ” variant of the MHD approximation applicable for cases, such as with detonators, where the thermodynamic pressure arising from Joule heating dominates over magnetic forces. An additional purpose of this paper is to present a coupling mode using Multiple Program-Multiple Data (MPMD) message passing communication that allows the user to run 3D FE problems together with 2D and/or 3D MHD problems with the respective simulation domains coupled through a common circuit equation. The MPMD coupling capability is used here to model the dynamic coupling of a notional ferroelectric generator with an RP-87 exploding bridgewire detonator. The simulated bridgewire heats up and bursts under current generated by simulated depoling of the ferroelectric generator, as a demonstration of the MPMD capability.

42 ENGINEERING↗
DOE OSTI2022

Repassivation underneath salt film on stainless steel pits

The repassivation temperature (Trp) of one-dimensional artificial pits made from 316L stainless steel was investigated in 3.5 wt.% NaCl by downward temperature scanning. For a given pit depth, T rp exhibited an unexpected “S” dependence on applied potential. Further analysis shows that this relationship is derived from repassivation underneath the salt film, which is different from repassivation that occurs when the concentration of metal cations at the pit surface decreases below a critical value. This indicates that there exists a reversal in the effect of the salt film on pit growth stability, which depends on temperature, applied potential, and pit depth.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Experimental study of flash boiling spray with isooctane, hexane, ethanol and their binary mixtures

The main goal of this study is to understand the effect of fuel properties on flash boiling sprays using multi-hole injectors. Macroscopic characteristics were investigated using Diffused Backlight Imaging (DBI) and quantified with liquid penetration length and spray angles. Phase Doppler Anemometry (PDA) was applied to measure the droplet size and velocity. Behaviors of spray with three single-component fuels (isooctane, hexane, ethanol) under different ambient pressures (100 kPa, 80 kPa, 50 kPa, 22 kPa) as well as their binary mixtures under different blend ratios (10%, 30%, 85%) were reported and analyzed. The results showed that adding ethanol or hexane to isooctane could both promote flash boiling by increasing the overall vapor pressure thus superheated degree. Under mixing ratios of 10% and 30%, sprays with ethanol blends showed more severe flash boiling comparing with sprays with hexane blends. Shorter liquid penetration and better liquid dispersion have been observed. Comparing with isooctane spray, the droplet size continuously decreased with increasing hexane content due to enhanced breakup and faster vaporization. Sprays with ethanol mixtures showed a different trend. Noticeable droplet size reduction has been observed for spray with 10% ethanol content. However, droplet size did not further decrease with higher blend ratios regardless of higher flash boiling intensity. Such observations indicate severe vaporization inhibition caused by the high latent heat of vaporization of ethanol. For sprays with all test fuels, collapsing occurred when the pressure ratio of ambient pressure to saturation pressure (Rp) dropped below 0.3.

03 NATURAL GAS↗
DOE OSTI2021

3D optical diagnostics for explosively driven deformation and fragmentation

High-speed, optical imaging diagnostics are presented for three-dimensional (3D) quantification of explosively driven metal fragmentation. At early times after detonation, Digital Image Correlation (DIC) provides non-contact measures of 3D case velocities, strains, and strain rates, while a proposed stereo imaging configuration quantifies in-flight fragment masses and velocities at later times. Experiments are performed using commercially obtained RP-80 detonators from Teledyne RISI, which are shown to create a reproducible fragment field at the benchtop scale. DIC measurements are compared with 3D simulations, which have been ‘leveled’ to match the spatial resolution of DIC. Overall, results demonstrate improved ability to identify predicted quantities-of-interest that fall outside of measurement uncertainty and shot-to-shot variability. Similarly, video measures of fragment trajectories and masses allow rapid experimental repetition and provide correlated fragment size-velocity measurements. Measured and simulated fragment mass distributions are shown to agree within confidence bounds, while some statistically meaningful differences are observed between the measured and predicted conditionally averaged fragment velocities. Together these techniques demonstrate new opportunities to improve future model validation.

42 ENGINEERING↗
DOE OSTI2021

Prostate Bed Delineation Guidelines for Postoperative Radiation Therapy: On Behalf Of The Francophone Group of Urological Radiation Therapy

Prostate bed (PB) irradiation is considered the standard postoperative treatment after radical prostatectomy (RP) for tumors with high-risk features or persistent prostate-specific antigen, or for salvage treatment in case of biological relapse. Four consensus guidelines have been published to standardize practices and reduce the interobserver variability in PB delineation but with discordant recommendations. To improve the reproducibility in the PB delineation, the Francophone Group of Urological Radiotherapy (Groupe Francophone de Radiothérapie Urologique [GFRU]) worked to propose a new and more reproducible consensus guideline for PB clinical target volume (CTV) definition.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Integrating Multiomics Information in Deep Learning Architectures for Joint Actuarial Outcome Prediction in Non-Small Cell Lung Cancer Patients After Radiation Therapy

Novel actuarial deep learning neural network (ADNN) architectures are proposed for joint prediction of radiation therapy outcomes—radiation pneumonitis (RP) and local control (LC)—in stage III non-small cell lung cancer (NSCLC) patients. Unlike normal tissue complication probability/tumor control probability models that use dosimetric information solely, our proposed models consider complex interactions among multiomics information including positron emission tomography (PET) radiomics, cytokines, and miRNAs. Additional time-to-event information is also used in the actuarial prediction.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Strain-relaxed tetragonal MAPbI 3 results in efficient mesoporous solar cells

In mesoporous organo-halide perovskite solar cells, the coexistence of tetragonal phase and cubic phase in the perovskite layer is found to result in strained crystal structure at the mesoporous TiO 2 (mp-TiO 2 )/perovskite heterointerface. This results in structural defects pinholes, grain boundaries, and interfacial porosity which is detrimental towards photovoltaic performance and device stability. The strain at the interface originates from the lattice mismatch between the mp-TiO 2 nanoparticles (NPs) and perovskite. Here, a transformative approach is demonstrated to realize relaxed and high purity tetragonal phase MAPbI 3 (RP) near the mp-TiO 2 interface region. This approach involves inserting a ~2 nm lattice matched buffer layer of cubic CsPbBr 3 between mp-TiO 2 NPs and MAPbI 3 , which serves as a template for epitaxial growth for top MAPbI 3 . As a result, the solar cell with relaxed MAPbI3 shows a power conversion efficiency (PCE) of 22.12% with significantly enhanced environmental, light, and thermal stability.

14 SOLAR ENERGY↗
DOE OSTI2020

Post-detonation fireball thermometry via femtosecond-picosecond coherent anti-Stokes Raman Scattering (CARS)

Accurate knowledge of post-detonation fireball temperatures is important for understanding device performance and for validation of numerical models. Such measurements are difficult to make even under controlled laboratory conditions. Here, temperature measurements were performed in the fireball of a commercial detonator (RP-80, Teledyne RISI). The explosion and fragments were contained in a plastic enclosure with glass windows for optical access. A hybrid femtosecond-picosecond (fs-ps) rotational coherent anti-Stokes Raman scattering (CARS) instrument was used to perform gas-phase thermometry along a one-dimensional measurement volume in a single laser shot. The 13-mm-thick windows on the explosive-containment housing introduced significant nonlinear chirp on the fs lasers pulses, which reduced the Raman excitation bandwidth and did not allow for efficient excitation of high-J Raman transitions populated at flame temperatures. To overcome this, distinct pump and Stokes pulses were used in conjunction with spectral focusing, achieved by varying the relative timing between the pump and Stokes pulses to preferentially excite Raman transitions relevant to flame thermometry. Light scattering from particulate matter and solid fragments was a significant challenge and was mitigated using a new polarization scheme to isolate the CARS signal. Fireball temperatures were measured 35–40 mm above the detonator, 12–25 mm radially outward from the detonator centerline, and at 18 and 28 µs after initiation. At these locations and times, significant mixing between the detonation products and ambient air had occurred thus increasing the nitrogen-based CARS thermometry signal. Initial measurements show a distribution of fireball temperatures in the range 300–2000 K with higher temperatures occurring 28 µs after detonation.

42 ENGINEERING↗
DOE OSTI2020

Annual simulation of photovoltaic retrofits within existing parabolic trough concentrating solar powerplants

Solar power for electricity production comes from either photovoltaics or concentrating solar power plants. The former has seen rapid growth and expansion due to the rapid fall in global prices, while the latter has seen moderate growth due to ability to cheaply store thermal energy for later use. Hybridization, or combining photovoltaics with concentrating solar power represents a potential way for lowering cost while enabling long term storage. Over 5 GW of capacity exist worldwide using parabolic trough style technology for concentrating solar power which presents a unique option for optimization in the form of a photovoltaic retrofit. While it is possible to analyze the performance with detailed physics models, it is necessary to create a model that can handle simulating the plant level performance to fully understand the potential performance. Here, the first utility scale plant level model of a hybrid photovoltaic-concentrating solar power plant is developed. The model is applied to existing concentrating solar power plants around the world utilizing RP-3 mirrors without thermal energy storage to understand the impact on electricity production. Model results indicate that the photovoltaic retrofit can increase yearly electricity production by up to 30% for plants with solar multiples exceeding 1.5, and that increasing the fraction of solar energy reflected further increases the yield. The increased electrical production declines as the plant solar multiple is decreased. The minimum LCOE observed was $0.07/kWh for plants with larger solar multiple and fraction of solar energy reflected to the PV is 50% of the total aperture.

14 SOLAR ENERGY↗
DOE OSTI2024

Two Spacers, One Perovskite: Integrating Ruddlesden–Popper and Dion–Jacobson Halide Perovskites

Hybrid organic–inorganic perovskites are a rapidly developing class of materials due to their desirable properties for optoelectronic applications such as their ease of synthesis, solution-processable film formation, tunable band gap, strong photoluminescence, good charge carrier mobilities, and high defect tolerance. Here, we present a novel 2D perovskite motif that seamlessly integrates the structural elements from both Ruddlesden–Popper and Dion–Jacobson halide perovskites. We demonstrate the incorporation of two different organic spacer cations in an ordered manner in 5 novel 2D perovskite iodide materials. Both a cyclic diammonium cation 3-(aminomethyl)piperidinium (3AMP) and a linear alkyl monoammonium cation (Cn = C n H 2n+4 N, n = 4–8) are present in distinct alternating layers, making the new series (Cn) 2 (3AMP)[PbI 4 ] 2 . The crystallization of these materials was optimized through careful temperature control to obtain precise crystal structures via single-crystal X-ray diffraction (XRD) which confirmed the presence of the two cations in distinct layers. The influence of the two spacers on optical properties including the band gaps and photoluminescence spectra are found to more closely resemble (3AMP)PbI 4 than (Cn) 2 PbI 4 , which can be attributed to the amount of distortion imposed by the 3AMP spacer on the lead iodide layers. The findings are supported by density functional theory calculations. The strong photoelectric response of solution-processed thin films shows the potential of these materials in photodetectors or photovoltaics. This unprecedented amalgamation of RP–DJ in (Cn) 2 (3AMP)[PbI 4 ] 2 in a structurally ordered fashion suggests a potential vastly underexplored phase space of 2D perovskites in which there are chemically different spacers in distinct layers of the structure, providing an additional parameter to tune perovskite properties.

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

Transport of colloidal particles in microscopic porous medium analogs with surface charge heterogeneity: experiments and fundamental role of single-bead deposition

Understanding colloid transport in subsurface environments is challenging due to complex interactions between colloids, ground water, and porous media over several length scales. Here, we study the transport of colloidal particles through bead-assembled microfluidic porous media analogs (PMAs) with surface charge heterogeneity. The pore-scale dynamics of colloidal particle deposition were measured, as well as the breakthrough curves (BTC) and retention profiles (RP) of deposited colloidal particles at the scale of the entire PMA. From pore-scale experiments, the maximum surface coverage (?max = 0.51) was measured directly, from which the surface blocking function and deposition coefficient (kpore = 3.56 s-1) were obtained. Using these pore-scale parameters, the transport of colloidal particles was modeled using a one-dimensional advection-dispersion equation under the assumption of irreversible adsorption between oppositely charged beads and colloids, showing good agreement with experimental data. This work presents a new approach to fabricate chemically heterogeneous porous media in a microfluidic device that enables direct measurements of pore-scale colloidal deposition. The approach allows a quantitative prediction of colloidal breakthrough and retention via coupling of direct measurements and an advection-dispersion-deposition model.

Guo, Yang↗
DOE OSTI2021

Role of Polycyclic Aromatic Alkylammonium Cations in Tuning the Electronic Properties and Band Alignment of Two-Dimensional Hybrid Perovskite Semiconductors

Two-dimensional hybrid organic–inorganic perovskites (HOIPs) have recently drawn intense attention as potential photovoltaic materials. However, n = 1 two-dimensional (2D) HOIPs face the challenge of low conductivity between the inorganic layers, leading to unsatisfactory device performance. Interestingly, 2D HOIPs employing π-conjugated molecules as organic moieties show energy and charge transfers between organic and inorganic layers, indicating potentially efficient carrier transport for photovoltaic applications. Nevertheless, the development of 2D HOIP-based solar cells especially utilizing polycyclic aromatic alkylammonium as cations is in its infancy. Herein, we investigated the electronic structure and band alignment of a series of n = 1 2D Ruddlesden–Popper (RP) phase HOIPs containing different polycyclic aromatic groups and alkyl chains, based on density functional theory calculations. We find that the polycyclic aromatic group plays an important role in controlling the functionality of 2D HOIPs by directly modifying band-edge states, and the band alignment at the organic–inorganic interface can be designed to promote either exciton trapping or dissociation for light-emitting or photovoltaic applications, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Anion and Cation Migration at 2D/3D Halide Perovskite Interfaces

Here, this study explores the ionic dynamics in 2D/3Dperovskite solar cells, which are known for their improved efficiency and stability. The focus is on the impact of halide choice in 3D perovskites treated with phenethylammonium halide salts (PEAX, X = Br and I). Our findings reveal that light and heat drive ionic migration in these structures, with PEA + species diffusing into the 3D film in PEABr-treated samples. Mixed-halide 3D perovskites show halide interdiffusion, with bromine migrating to the surface and iodine diffusing into the film. Cathodoluminescence microscopy reveals localized 2Dphases on the 3D perovskite, which become more evenly distributed after thermal treatment. Both PEAX salts enhance the performance of photovoltaic devices. This improvement is attributed to the passivation capabilities of the salts themselves and their respective Ruddlesden–Popper (RP) phases. Annealed PEAI-treated devices show a better balance between efficiency and statistical distribution of photovoltaic parameters.

25 ENERGY STORAGE↗
DOE OSTI2021

Anion Exchange of Ruddlesden–Popper Lead Halide Perovskites Produces Stable Lateral Heterostructures

Heterostructures of three-dimensional (3D) halide perovskites are unstable because of facile anion interdiffusion at halide interfaces. Two-dimensional (2D) Ruddlesden–Popper halide perovskites (RPPs) show suppressed and anisotropic ion diffu-sion that could enable stable RPP heterostructures, yet the direct and general growth of lateral RPP heterostructures remains challenging. Here we show that halide miscibility in RPPs decreases with perovskite layer thickness (n), enabling the for-mation of sharp halide lateral heterostructures from n = 1 and 2 RP lead iodide microplates via anion exchange with hydro-gen bromide vapor. In contrast, RPPs with n = 3 form more diffuse lateral heterojunctions, more similar to those in 3D perov-skites. The anion exchange behaviors are further modulated by the spacer and A-site cations in the RPP structures. These new insights, and kinetic studies of the exchange reactions, enable the preparation of lateral heterostructures from various n = 2 RPPs that are more stable against anion interdiffusion and degradation for potential device applications.

Roy, Chris R.↗
DOE OSTI2021

Nucleic acid binding by SAMHD1 contributes to the antiretroviral activity and is enhanced by the GpsN modification

SAMHD1 impedes infection of myeloid cells and resting T lymphocytes by retroviruses, and the enzymatic activity of the protein—dephosphorylation of deoxynucleotide triphosphates (dNTPs)—implicates enzymatic dNTP depletion in innate antiviral immunity. Here we show that the allosteric binding sites of the enzyme are plastic and can accommodate oligonucleotides in place of the allosteric activators, GTP and dNTP. SAMHD1 displays a preference for oligonucleotides containing phosphorothioate bonds in the Rp configuration located 3’ to G nucleotides (GpsN), the modification pattern that occurs in a mechanism of antiviral defense in prokaryotes. In the presence of GTP and dNTPs, binding of GpsN-containing oligonucleotides promotes formation of a distinct tetramer with mixed occupancy of the allosteric sites. Mutations that impair formation of the mixed-occupancy complex abolish the antiretroviral activity of SAMHD1, but not its ability to deplete dNTPs. The findings link nucleic acid binding to the antiretroviral activity of SAMHD1, shed light on the immunomodulatory effects of synthetic phosphorothioated oligonucleotides and raise questions about the role of nucleic acid phosphorothioation in human innate immunity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Electrochemical metrics for corrosion resistant alloys

Abstract Corrosion is an electrochemical phenomenon. It can occur via different modes of attack, each having its own mechanisms, and therefore there are multiple metrics for evaluating corrosion resistance. In corrosion resistant alloys (CRAs), the rate of localized corrosion can exceed that of uniform corrosion by orders of magnitude. Therefore, instead of uniform corrosion rate, more complex electrochemical parameters are required to capture the salient features of corrosion phenomena. Here, we collect a database with an emphasis on metrics related to localized corrosion. The six sections of the database include data on various metal alloys with measurements of (1) pitting potential, E pit , (2) repassivation potential, E rp , (3) crevice corrosion potential, E crev , (4) pitting temperature, T pit , (5) crevice corrosion temperature, T crev , and (6) corrosion potential, E corr , corrosion current density, i corr , passivation current density, i pass , and corrosion rate. The experimental data were collected from 85 publications and include Al- and Fe-based alloys, high entropy alloys (HEAs), and a Ni-Cr-Mo ternary system. This dataset could be used in the design of highly corrosion resistant alloys.

36 MATERIALS SCIENCE↗