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DOE OSTI2017

Comprehensive study of performance degradation of field‐mounted photovoltaic modules in India

Abstract The All India Survey of Photovoltaic Module Reliability 2014 is an enhanced version of the survey conducted in the previous year, with detailed characterization of PV modules including current‐voltage, infrared and electroluminescence imaging, visual inspection, insulation resistance test and interconnect breakage test. More than a thousand modules were inspected in the field and the main results of the survey are presented in this paper. The average P max degradation rate for the so‐called ‘good’ modules (Group X) is 1.33%/year which is higher than that commonly projected by manufacturers, and widely employed in financial calculations. Modules falling in the ‘not‐so‐good’ category (Group Y) show even higher degradation rates, and it is at least partly due to higher number of micro‐cracks in the modules, and increased degradation of the packaging materials like encapsulant, backsheet, etc. Modules in ‘Hot’ climates degrade faster than modules in the ‘Non‐Hot’ climates. Degradation in fill factor is the primary cause for performance degradation in the young modules (ages <5 years), whereas short‐circuit current degradation is the main contributor to power degradation in the older modules. Small installations (<100 kW p capacity) show higher degradation than large systems, which may be partly due to lack of proper due diligence by the owner at the time of procurement and installation.

Dubey, Rajiv↗

DOE OSTI2021

The causal relationship between melt pool geometry and energy absorption measured in real time during laser-based manufacturing

During laser powder bed fusion additive manufacturing, laser power absorption is governed by a pro -tean pool of molten metal that can present as a highly reflective surface, a deeply absorbing cavity, or some amalgamation thereof. These melt pool dynamics have been linked to defect creation, porosity, and surface finish quality. Although these are therefore critical for determining final part quality, their in-stantaneous influence on laser absorption have only been explored through simulation. To date, direct real-time observations have been elusive due to the locally extreme environment. In this work, we fo-cus a laser on Ti-6Al-4V powder and bare plate while quantifying the time-dependent, absolute energy absorption by monitoring omnidirectional backscattered laser intensity. We also simultaneously record the projective melt pool geometries with high-speed synchrotron x-ray imaging. We find that laser ab-sorption strongly reflects the stability of the vapor depression over a wide range of applied laser powers, oxygen content in the processing atmosphere, and with the presence of powder. During laser scanning of a powder bed surface, we find a significant absorption reduction after 400 mu s due to a dramatic change in the vapor depression aspect ratio-an event known to create porosity. Furthermore, as several industrial scan strate-gies necessitate thousands of these events during a build, their identification and control is of significant practical importance. Lastly, a normalized enthalpy model is demonstrated to be effective in quantifying the relationship between the laser absorption and cavity depth, even under transient conditions. In addi-tion to providing vital quantitative data for simulation calibration, the correlation of melt pool geometry with laser absorption during realistic processing conditions suggests the use of a total backscattered light detection system for real-time process control.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Discovery of quantum phases in the Shastry-Sutherland compound SrCu 2 (BO 3 ) 2 under extreme conditions of field and pressure

The 2-dimensional layered oxide material SrCu 2 (BO 3 ) 2 , long studied as a realization of the Shastry-Sutherland spin topology, exhibits a range of intriguing physics as a function of both hydrostatic pressure and magnetic field, with a still debated intermediate plaquette phase appearing at approximately 20 kbar and a possible deconfined critical point at higher pressure. Here, we employ a tunnel diode oscillator (TDO) technique to probe the behavior in the combined extreme conditions of high pressure, high magnetic field, and low temperature. We reveal an extensive phase space consisting of multiple magnetic analogs of the elusive supersolid phase and a magnetization plateau. In particular, a 10 x 2 supersolid and a 1/5 plateau, identified by infinite Projected Entangled Pair States (iPEPS) calculations, are found to rely on the presence of both magnetic and non-magnetic particles in the sea of dimer singlets. These states are best understood as descendants of the full-plaquette phase, the leading candidate for the intermediate phase of SrCu 2 (BO 3 ) 2

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Twinning microstructure in the solid-phase epitaxial crystallization of BaTiO 3

Amorphous BaTiO 3 layers deposited on SrTiO 3 (001) substrates at room temperature were subsequently crystallized using solid phase epitaxy (SPE). Heating an initially amorphous BaTiO 3 layer in air at 650 °C for 3 h resulted in crystallization with components in two distinct crystallographic orientation relationships with respect to the substrate. Part of the volume of the BaTiO 3 layer crystallized in a cube-on-cube relationship with the substrate. Other volumes crystallized in four variants of a 70.5° rotation about $\langle$110$\rangle$, resulting in a $\langle$221$\rangle$ surface normal in each case. Each of these four variants forms a Σ = 3 coincident site lattice with respect to the SrTiO 3 substrate and the cube-on-cube oriented BaTiO 3 . Heating for the same duration and temperature in a reducing gas atmosphere resulted in the formation of polycrystalline BaTiO 3 with no preferred crystallographic orientation. The dependence on the gas atmosphere indicates that it may be possible to tune the annealing time, temperature, and atmosphere to produce a single crystalline BTO on STO by SPE or produce a desired distribution of orientations.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Higher superconducting transition temperature by breaking the universal pressure relation

By investigating the bulk superconducting state via dc magnetization measurements, we have discovered a common resurgence of the superconducting transition temperatures (T c s) of the monolayer Bi 2 Sr 2 CuO 6+δ (Bi2201) and bilayer Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) to beyond the maximum T c s (T c-max s) predicted by the universal relation between T c and doping ( p ) or pressure (P) at higher pressures. The T c of underdoped Bi2201 initially increases from 9.6 K at ambient to a peak at 23 K at 26 GPa and then drops as expected from the universal T c -P relation. However, at pressures above 40 GPa, T c rises rapidly without any sign of saturation up to 30 K at 51 GPa. Similarly, the T c for the slightly overdoped Bi2212 increases after passing a broad valley between 20 and 36 GPa and reaches 90 K without any sign of saturation at 56 GPa. We have, therefore, attributed this T c resurgence to a possible pressure-induced electronic transition in the cuprate compounds due to a charge transfer between the Cu 3 d x 2 - y 2 and the O 2 p bands projected from a hybrid bonding state, leading to an increase of the density of states at the Fermi level, in agreement with our density functional theory calculations. Similar T c -P behavior has also been reported in the trilayer Br 2 Sr 2 Ca 2 Cu 3 O 10+δ (Bi2223). These observations suggest that higher T c s than those previously reported for the layered cuprate high-temperature superconductors can be achieved by breaking away from the universal T c -P relation through the application of higher pressures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

TOWARD AN EMPIRICAL THEORY OF PULSAR EMISSION. XI. UNDERSTANDING THE ORIENTATIONS OF PULSAR RADIATION AND SUPERNOVA “KICKS”

Two entwined problems have remained unresolved since pulsars were discovered nearly 50 yr ago: the orientation of their polarized emission relative to the emitting magnetic field and the direction of putative supernova “kicks” relative to their rotation axes. The rotational orientation of most pulsars can be inferred only from the (“fiducial”) polarization angle of their radiation, when their beam points directly at the Earth and the emitting polar fluxtube field is ∥ to the rotation axis. Earlier studies have been unrevealing owing to the admixture of different types of radiation (core and conal, two polarization modes), producing both ∥ or ⊥ alignments. In this paper we analyze some 50 pulsars having three characteristics: core radiation beams, reliable absolute polarimetry, and accurate proper motions (PMs). The “fiducial” polarization angle of the core emission, we then find, is usually oriented ⊥ to the PM direction on the sky. The primary core emission is polarized ⊥ to the projected magnetic field in Vela and other pulsars where X-ray imaging reveals the orientation. This shows that the PMs usually lie ∥ to the rotation axes on the sky. Two key physical consequences then follow: first, to the extent that supernova “kicks” are responsible for pulsar PMs, they are mostly ∥ to the rotation axis; and, second, most pulsar radiation is heavily processed by the magnetospheric plasma such that the lowest altitude “parent” core emission is polarized ⊥ to the emitting field, propagating as the extraordinary (X) mode.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Sci—Fri AM: Mountain — 02: A comparison of dose reduction methods on image quality for cone beam CT

Modern radiotherapy uses highly conformai dose distributions and therefore relies on daily image guidance for accurate patient positioning. Kilovoltage cone beam CT is one technique that is routinely used for patient set-up and results in a high dose to the patient relative to planar imaging techniques. This study uses an Elekta Synergy linac equipped with XVI cone beam CT to investigate the impact of various imaging parameters on dose and image quality. Dose and image quality are assessed as functions of x-ray tube voltage, tube current and the number of projections in the scan. In each case, the dose measurements confirm that as each parameter increases the dose increases. The assessment of high contrast resolution shows little dependence on changes to the image technique. However, low contrast visibility suggests a trade off between dose and image quality. Particularly for changes in tube potential, the dose increases much faster as a function of voltage than the corresponding increase in low contrast image quality. This suggests using moderate values of the peak tube voltage (100 – 120 kVp) since higher values result in significant dose increases with little gain in image quality. Measurements also indicate that increasing tube current achieves the greatest degree of improvement in the low contrast visibility. The results of this study highlight the need to establish careful imaging protocols to limit dose to the patient and to limit changes to the imaging parameters to those cases where there is a clear clinical requirement for improved image quality.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

Pulse Tube Interference in Cryogenic Sensor Resonant Circuits (Final Paper)

Transition edge sensors (TES) are extremely sensitive superconducting sensors, operating at 100 mK, which can be used to detect X-rays and Cosmic Microwave Background. The goal of our project is to design the electronics to read out an array of 10000 of these sensors by using microwave signals. However, we noticed the pulse tube used to maintain cryogenic temperatures caused interference in our readout. To determine the cause of the signal distortions, we used a detector with a 370 MHz sampling rate to collect and analyze sensor data. Although this data provided little information towards the nature of the noise, it was determined through a maintenance procedure than the 0.3 mm stainless steel wires were being vibrated due to acoustic waves, which distorted the signal. Replacing this wire appeared to cease the interference from the sensor data.

42 ENGINEERING↗

DOE OSTI2015

Pulse Tube Interference in Cryogenic Sensors - Oral Presentation [Slides]

47 OTHER INSTRUMENTATION↗

DOE OSTI2019

High lifetime and mobility CdTe alloys by co-sublimation

The focus of this project was to understand controlled doping of CdTe and CdSe x Te 1-x films using group V element dopants such as nitrogen and arsenic. Using methods such as metal organic precursor injection as well as deposition of absorber with source charge incorporated with desired group V dopant. Using characterization methods such as Secondary Ion Mass Spectroscopy and capacitance vs voltage measurement dopant incorporation and activation was verified. Since our deposition system had CuCl deposition source, this source was permanently removed from the system and vacuum chamber was thoroughly cleaned out. CdSe x Te 1-x grading into CdTe has led to higher device efficiency owing to an improvement in short-circuit current (J SC ) due to its lower band-gap. More device fabrication and characterization was performed in an effort to optimize the lower band-gap CdSe x Te 1-x . This optimization was performed using different co-sublimation method where CdTe and Se were co-sublimated in varying proportion to sweep the band-gap of CdSe x Te 1-x that deposited on the substrate.

14 SOLAR ENERGY↗

DOE OSTI2019

Comparison of Electron Beam and Laser Beam Powder Bed Fusion Additive Manufacturing Process for High Temperature Turbine Component Materials, Phase II. CRADA Final Report

The evolving additive manufacturing (AM) technology is now at the point where some metallic turbine components are being fabricated for both development and production purposes. The goal of this phase II project is to continue the evaluation of AM Nickel Alloy X fabricated by electron beam (EB) or laser beam (LB) powder bed fusion (PBF) process for gas turbine applications. Microstructure, mechanical and oxidation properties characterization was conducted on test specimens produced with powders of different chemistries within the typical material specification range. Powders with high Silicon (Si) content for the LB-PBF and low Si content for the EB-PBF displayed significant cracking levels in the AM Nickel Alloy X material. Accordingly, optimum fatigue performance would require careful control of powder chemistry, optimization of the fabrication parameters for a given powder and use of hot isostatic pressing (HIP) post treatment. Oxidation testing conducted at 1472°F (800ºC) in air showed that the roughness of the EB-PBF specimens led to an increase in specimen mass change, but overall the AM specimens exhibited oxidation behavior at 1472°F (800ºC) that is appropriate for applications in gas turbine engines. Assessment of the geometric capability of the LB-PBF and EBPBF systems using artifacts representative of turbine component geometries revealed that the LB-PBF process is well-suited for the fabrication of intricate geometries needed for turbine engine fuel injector components, but further process development is required to improve the EB-PBF system feature resolution.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Improved Fundamental Understanding of Aluminum Chemistry and Interactions of Aluminate Anion with Co-Anions: ORNL Project Progress Report

The U.S. Department of Energy (DOE)’s Hanford Site in Washington State houses 177 underground storage tanks containing millions of gallons of nuclear and chemical waste with high aluminum content. Aluminum (Al) salt reactions with strong bases produce aluminum hydroxides, like boehmite (γ-AlOOH), which are main components of insoluble nuclear waste sludge. Understanding the morphology, crystallinity, and dissolution behavior of boehmite under waste tank conditions is necessary for improving waste management and mitigation strategies. The ORNL team uses in situ multimodal analysis strategy to study Al chemistry of simulated tank waste using microfluidic reactors and advanced chemical imaging and mass spectrometry (MS) techniques. Because the SALVI device is vacuum compatible and transferrable among different platforms, we can use it in scanning electron microscopy (SEM), vacuum ultraviolet single photon mass spectrometry (VUV SPI-MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study the chemical speciation and colloid stability in liquids in this project. Additionally, ex situ transmission electron microscopy (TEM) and x-ray diffraction (XRD) spectroscopy can be used to verify particle phase to further the understanding of the Al-bearing phases. This report gives a summary of the technical progress of the ORNL tasks. A plan for year 2 performance is recommended in the summary.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRS1971

The Lick-Gaertner automatic measuring system

The Lick-Gaertner automatic equipment has been designed mainly for the measurement of stellar proper motions with reference to galaxies, and consists of two main components: the survey machine and the automatic measuring engine. The survey machine is used for initial inspection and selection of objects for subsequent measurement. Two plates, up to 17 x 17 inches each, are surveyed simultaneously by means of projection on a screen. The approximate positions of objects selected are measured by two optical screws: helical lines cut through an aluminum coating on glass cylinders. These approximate coordinates to a precision of the order of 0.03mm are transmitted to a card punch by encoders connected with the cylinders.

Vasilevskis, S.↗

NASA NTRS1978

On the average configuration of the geomagnetic tail

Over 3000 hours of IMP-6 magnetic field data obtained between 20 and 33 R sub E in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5 minute averages of B sub Z as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight. The tail field projected in the solar magnetospheric equatorial plane deviates from the X axis due to flaring and solar wind aberration by an angle alpha = -0.9 y sub SM - 1.7 where Y sub SM is in earth radii and alpha is in degrees. After removing these effects the Y component of the tail field is found to depend on interplanetary sector structure. During an away sector the B sub Y component of the tail field is on average 0.5 gamma greater than that during a toward sector, a result that is true in both tail lobes and is independent of location across the tail.

Fairfield, D. H.↗

NASA NTRS1987

Auroral precipitation caused by auroral kilometric radiation

If the auroral kilometric radiation (AKR) were generated by loss cone lasing on closed field lines, as has been proposed, then it should cause substantial auroral precipitation by the pitch angle scattering of energetic electrons into the loss cone. A rough estimate for this precipitation, based upon the observed AKR amplitudes, would imply a flux of at least 2 x 10 to the 8th el/sq cm sec over the projected ionospheric footprint of an individual laser and, if most of the AKR radio lasers occupied the same electron drift an L shell, an arc of 8 km width with a minimum average flux of roughly 10 to the 9th el/sq cm sec. It is believed that this will account for auroral arcs and other aspects of auroral electron precipitation.

Calvert, W.↗

NASA NTRS1990

Techniques for hot structures testing

Hot structures testing have been going on since the early 1960's beginning with the Mach 6, X-15 airplane. Early hot structures test programs at NASA-Ames-Dryden focused on operational testing required to support the X-15 flight test program, and early hot structures research projects focused on developing lab test techniques to simulate flight thermal profiles. More recent efforts involved numerous large and small hot structures test programs that served to develop test methods and measurement techniques to provide data that promoted the correlation of test data with results from analytical codes. In Nov. 1988 a workshop was sponsored that focused on the correlation of hot structures test data with analysis. Limited material is drawn from the workshop and a more formal documentation is provided of topics that focus on hot structures test techniques used at NASA-Ames-Dryden. Topics covered include the data acquisition and control of testing, the quartz lamp heater systems, current strain and temperature sensors, and hot structures test techniques used to simulate the flight thermal environment in the lab.

Deangelis, V. Michael↗

NASA NTRS1992

The atmospheric structures of the companion stars of eclipsing binary x ray sources

This investigation was aimed at determining structural features of the atmospheres of the massive early-type companion stars of eclipse x-ray pulsars by measurement of the attenuation of the x-ray spectrum during eclipse transitions and in deep eclipse. Several extended visits were made to ISAS in Japan by G. Clark and his graduate student, Jonathan Woo to coordinate the Ginga observations and preliminary data reduction, and to work with the Japanese host scientist, Fumiaki Nagase, in the interpretation of the data. At MIT extensive developments were made in software systems for data interpretation. In particular, a Monte Carlo code was developed for a 3-D simulation of the propagation of x-rays from the neutron star through the ionized atmosphere of the companion. With this code it was possible to determine the spectrum of Compton-scattered x-rays in deep eclipse and to subtract that component from the observed spectra, thereby isolating the software component that is attributable in large measure to x-rays that have been scattered by interstellar grains. This research has culminated in the submission of paper to the Astrophysical Journal on the determination of properties of the atmosphere of QV Nor, the BOI companion of 4U 1538-52, and the properties of interstellar dust grains along the line of sight from the source. The latter results were an unanticipated byproduct of the investigation. Data from Ginga observations of the Magellanic binaries SMC X-1 and LMC X-4 are currently under investigation as the PhD thesis project of Jonathan Woo who anticipated completion in the spring of 1993.

Clark, George W.↗

NASA NTRS1992

Understanding crystallinity in aromatic polyimides

Aromatic polyimides are a class of polymers that show remarkable thermal stability, strength, and toughness. These properties make them attractive candidates for use in high-performance carbon fiber composites for airborne and spaceborne structural components. Our research centered on the development of an understanding of the underlying process of crystallite formation in a particular class of aryl polyimides for which there are some x-ray crystallographic data available. The ultimate aim of the project is to be able to develop a model sufficiently flexible to be able, on the basis of the chemical structure of a polymer in this class, to predict: (1) whether it will be prone to form crystallites; (2) crystallographic features of the crystallites; and (3) synthesis and/or processing conditions that will be favorable or unfavorable to crystallite formation. This will provide guidance to the laboratory chemists in their choice of candidate polymers and processing methods.

Celarier, Edward A.↗