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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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NASA NTRS2002

2001 Numerical Propulsion System Simulation Review

The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective, high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. Major accomplishments include the first formal release of the NPSS object-oriented architecture (NPSS Version 1) and the demonstration of a one order of magnitude reduction in computing cost-to-performance ratio using a cluster of personal computers. The paper also describes the future NPSS milestones, which include the simulation of space transportation propulsion systems in response to increased emphasis on safe, low cost access to space within NASA's Aerospace Technology Enterprise. In addition, the paper contains a summary of the feedback received from industry partners on the fiscal year 2000 effort and the actions taken over the past year to respond to that feedback. NPSS was supported in fiscal year 2001 by the High Performance Computing and Communications Program.

Lytle, John↗
DOE OSTI2022

Reducing Uncertainty of Fielded Photovoltaic Performance (Final Technical Report)

Improved analysis and reporting of photovoltaic (PV) field performance increases the certainty of owners and financiers that systems will perform as expected. Advanced module technologies (e.g., PERC, HJT, and bifacial) introduce new degradation mechanisms and performance characteristics. The FY19-21 Reducing Uncertainty project leveraged data from the ever-increasing PV fleet to develop models and understanding of the field performance of existing and new technologies. Specifically, we accomplished: report on field performance and degradation rates for high-efficiency silicon (HJT, PERC, IBC) and more conventional technologies; developed automated analysis techniques to quantify system performance (performance ratio, energy yield) and production shortfalls (soiling, degradation, availability); refined the RdTools software toolkit to bring standard, validated analysis techniques to bear on third-party data; analyzed and reported on large datasets including Treasury data and Lawrence Berkeley National Laboratory's Utility-Scale dataset to expand the high-quality degradation-rate histogram published previously; worked with industry partners and the DuraMAT data hub to enable private parties to share and aggregate PV production data anonymously, leveraging cloud-based data analysis infrastructure and publishing on US fleet-scale performance comprising over 7GW of operating systems. (https://www.nrel.gov/pv/fleet-performance-data-initiative.html). Through our industry collaborations we have engaged in NDA-covered data transfer with twelve PV fleet owners as of January 2022, with more agreements in negotiation. Our scalable cloud-based time series database contains over 30 billion rows (20TB) of PV time series data, representing over 1700 commercial and utility-scale systems, and over 7.2 GW of DC capacity (Fig 1). Initial field performance results have been distributed in several public reports. Because our fleet composition and data quality methods are continually improving, annual updates to these results are published to our PV Fleet webpage [ https://www.nrel.gov/pv/fleet-performance-data-initiative.html ] and DuraMAT data hub [DOI: 10.21948/1842958]. Another existing dissemination channel used for observed soiling losses is a map we maintain for soiling losses. Additional products developed include a report detailing fleet-wide performance index, availability, startup loss and snow loss factors, a detailed report on the 1603 grant dataset comprising over 100,000 PV systems with failure and performance details and a utility-scale report coauthored with LBNL on 31 GW of system performance.

14 SOLAR ENERGY↗
NASA NTRS2004

Design of a Pushbroom Imaging Spectrometer that Exceeds AVIRIS Performance

This slide presentation reviews the design of a Pushbroom Imaging Spectrometer, that will exceed the performance of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). The approach for the AVIRIS-II instrument is reviewed as are the specifications for the new spectrometer. Even though the pushbroom spectrometer is inherently non-uniform, the design of the AVIRIS-II provides for uniformity. Spot diagrams at the slit and at the detector inside the 27micron box are presented. A few of the challenges in the mechanical design and the making of the slit are discussed. The specifications of the 6604A detector array are reviewed. Slides showing the expected Signal to Noise Ratio performance are presented.

Airborne Visible/Infrared Imaging Spectrometer (AV↗
DOE OSTI2014

Fe{sub 3}O{sub 4}/Zeolite nanocomposites synthesized by microwave assisted coprecipitation and its performance in reducing viscosity of heavy oil

Fe{sub 3}O{sub 4}/Zeolite nanocomposites have been synthesized via microwave assisted coprecipitation method and show to be efficient in reducing viscosity of heavy oil compared to other Fe{sub 3}O{sub 4}/Zeolite nanocomposites prepared by conventional method. The following precursors such as FeCl{sub 3}⋅6H{sub 2}O, FeSO{sub 4}⋅7H{sub 2}O, NH{sub 4}OH, and natural zeolite of heulandite type were used in the sample preparation. In this study, the effect of Fe{sub 3}O{sub 4} composition in the composite and microwave time heating were investigated. Fe{sub 3}O{sub 4}/Zeolite nanocomposites were then characterized to study the influence on crystal structures, morphology and physicochemical properties. The characterization techniques include X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen physisorption. The results show that by increasing the microwave heating time, the degree of nanocomposite intergrowth can be enhanced. The nanocomposite was tested in catalytic aquathermolysis of heavy oil at 200°C for 6 h and the Fe{sub 3}O{sub 4}/zeolite of 1 to 4 ratios performed the highest viscosity reduction of heavy oil reaching 92%.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Retained Austenite Attributes and Mechanical Performance of Different Compositions of TRIP Steel Alloys

The main objective of this work is to correlate the different attributes of retained austenite phase in TRIP steel structure with its mechanical properties. Three different chemical compositions were used to produce TRIP steel alloys. The first alloy contains only silicon as a carbide precipitation inhibitor; in the second alloy, silicon is partially replaced with aluminum, while in the third alloy phosphorus is added to the silicon–aluminum alloy. These compositions were proposed in order to avoid the negative effect of silicon during galvanizing. These three steel alloys were cast, homogenized, hot-forged and then subjected to intercritical annealing treatment followed by cooling and isothermal treatment in salt bath with subsequent air-cooling. Microstructural characterization, using optical microscope, SEM and XRD, along with tensile testing was carried out. Retained austenite attributes include volume fraction, carbon content, total carbon content, retained austenite transformable index and its stability coefficient against strain-induced martensite (SIM) transformation. The effect of these attributes on the mechanical properties of the studied TRIP steel alloys was evaluated using tensile test date, i.e., ultimate tensile strength (UTS), ductility, yield strength to UTS ratio, performance index and strain-hardening exponent. The variation of strain-hardening rate and strain-hardening exponent with strain was also considered. The failure behavior of the studied steel alloys was investigated using SEM on tensile-tested specimens. The results show that Si/Al-alloy has the lowest retained austenite transformable index, lowest stability coefficient against SIM transformation, highest performance index and more stable and uniform variation in strain-hardening rate and strain-hardening exponent with strain. These properties satisfy the industrial constrains of the sheets used in automotive industry relating to better mechanical properties and galvanizability.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Model and Validation of Single-Axis Tracking with Bifacial PV

Single-axis tracking is a cost-effective deployment strategy for large-scale ground-mount photovoltaic systems in regions with high direct-normal irradiance. Bifacial modules in 1-axis-tracking systems boost energy yield by 4%-15% depending on module type and ground albedo, with a global average of 9%. This benefit is in addition to the 15%-25% energy gain already afforded by single-axis tracking relative to fixed-tilt deployments. Here, we compare model results against field performance data for two side-by-side bifacial/monofacial tracked systems - one in Albuquerque, NM, USA, and one in eastern Oregon. The Albuquerque system shows monthly rear irradiance gain of 10%-14.9%, and the Oregon bifacial system has an average performance ratio 9.4% higher than the monofacial system. Both results match bifacial irradiance model results within uncertainty. Simulations show that smart tracking algorithms can offer more than 1% improvement on annual energy yield by adjusting tilt angle under cloudy conditions. Finally, ray-tracing simulations investigated edge brightening, suggesting a 15%-25% increase in rear irradiance at the ends of tracker rows, but up to 20% loss from center-mounted torque tubes, creating multiple shadows.

14 SOLAR ENERGY↗
DOE OSTI2018

Multipass Scratch Behavior of Borided and Nitrided H13 Steel

AISI H13 steel was subjected to boriding and nitriding; its performance was evaluated by the progressive load scratch test, and then by the multipass scratch test (MPST), to evaluate the accumulated damage. Boriding and nitriding were carried out at a temperature of 800 and 580 °C, respectively, both treatments for 1 and 5 h of exposure time. In scratch test, a load range of 3-90 N was used for borides; a higher range (3-180 N) was chosen for nitrides. Critical loads (L{sub c}) were estimated based on optical microscope observations of the scratch tracks. Failure mechanisms and residual depths were examined by scanning electronic microscope and optical profilometry. Finally, using fractions of L{sub c,} MPST was applied on uncoated and coated samples, for 25, 50, 75 and 100 unidirectional scratch cycles. The coefficient of friction (COF) evolution was recorded and analyzed. A decrease in COF was observed as cycles go through; it was initially higher in uncoated sample; moreover, it was observed that normal load was determinant in its behavior, regardless of the treatment time. Nitrided samples exhibited less catastrophic failures over borided ones, also showed a better volume loss/load ratio performance, from 6 to 8 times better compared to borided samples.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Transient and thermo-economic analysis of MED-MVC desalination system

An exergo-economic model is used to assess the performance of a multi-effect desalination plant integrated to a mechanical vapor compressor unit (MED-MVC) with a water production capacity of 1500 $m^3$/day. The results show that the second law efficiency ($\eta_{II}$) 2.8%. The MVC and evaporator units are responsible for about 39 and 52% of the total exergy destruction, respectively. The total water price (TWP) is 1.70 $\$/m^3$ when calculated using a simple conventional economic model and 1.63 $\$/m^3$ when calculated using an exergy-based cost model. Increasing the number of effects from 1 to 6 results in a 39% reduction in the specific power consumption (SPC), a 70% increase in $\eta_{II}$ and a 24% decrease in TWP. A dynamic model is developed to investigate the effect of fluctuations of compressor work ($\dot{W}_c$) and inlet seawater temperature ($T_{sw}$) on the plant behavior and performance. The dynamic model results show that the disturbance in $\dot{W}$ has a significant effect on the plant transient behavior and may cause the plant to cease operation while a disturbance in $T_{sw}$ has only a moderate impact. Increasing $T_{sw}$ above a certain value of the steady-state condition without proper control on the plant response could lead to evaporator dry out. In term of performance, a reduction in $\dot{W}_c$ causes a decrease in the plant production capacity and SPC, while it increases the plant performance ratio (PR). On the other hand, a reduction in the inlet $T_{sw}$ causes a reduction in the plant production capacity and PR and an increase in SPC for the same compressor work. Furthermore, a comparison between a MED-MVC system and a MED integrated to a thermal vapor compressor system (MED-TVC) reveals that the latter system is rather sensitive to the reduction in $T_{sw}$ due to the presence of the condenser unit in the MED-TVC. The response of the MED-MVC system is slower than the MED-TVC which is due to the high thermal capacity of the preheaters for the feed in the MED-MVC.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Implementation of metal-friendly EAM/FS-type semi-empirical potentials in HOOMD-blue: A GPU-accelerated molecular dynamics software

We present an implementation of EAM and FS interatomic potentials, which are widely used in simulating metallic systems, in HOOMD-blue, a software designed to perform classical molecular dynamics simulations using GPU accelerations. We first discuss the details of our implementation and then report extensive benchmark tests. We demonstrate that single-precision floating point operations efficiently implemented on GPUs can produce sufficient accuracy when compared against double-precision codes, as demonstrated in test simulations of calculations of the glass-transition temperature of Cu 64.5 Zr 35.5 , and pair correlation function of liquid Ni 3 Al. Our code scales well with the size of the simulating system on NVIDIA Tesla M40 and P100 GPUs. Compared with another popular software LAMMPS running on 32 cores of AMD Opteron 6220 processors, the GPU/CPU performance ratio can reach as high as 4.6. In conclusion, the source code can be accessed through the HOOMD-blue web page for free by any interested user.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Statistical searches for microlensing events in large, non-uniformly sampled time-domain surveys: A test using palomar transient factory data

Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ∼20,000 deg{sup 2} footprint. While the median 7.26 deg{sup 2} PTF field has been imaged ∼40 times in the R band, ∼2300 deg{sup 2} have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10{sup 9} light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Nonlinear Photovoltaic Degradation Rates: Modeling and Comparison Against Conventional Methods

Although common practice for estimating photovoltaic (PV) degradation rate (RD) assumes a linear behavior, field data have shown that degradation rates are frequently nonlinear. This article presents a new methodology to detect and calculate nonlinear RD based on PV performance time-series from nine different systems over an eight-year period. Prior to performing the analysis and in order to adjust model parameters to reflect actual PV operation, synthetic datasets were utilized for calibration purposes. A change-point analysis is then applied to detect changes in the slopes of PV trends, which are extracted from constructed performance ratio (PR) time-series. Once the number and location of change points is found, the ordinary least squares method is applied to the different segments to compute the corresponding rates. The obtained results verified that the extracted trends from the PR time-series may not always be linear and therefore, “nonconventional” models need to be applied. All thin-film technologies demonstrated nonlinear behavior whereas nonlinearity detected in the crystalline silicon systems is thought to be due to a maintenance event. A comparative analysis between the new methodology and other conventional methods demonstrated levelized cost of energy differences of up to 6.14%, highlighting the importance of considering nonlinear degradation behavior

14 SOLAR ENERGY↗
DOE OSTI2022

Worldwide Physics-Based Lifetime Prediction of c-Si Modules Due to Solder-Bond Failure

Lifetime prediction of the fielded c-Si solar modules due to location-specific weather conditions has been an important topic of photovoltaic research and the economic viability of solar energy. Data analytic techniques such as the performance ratio method, Statistical clear sky model, and Suns-Vmp methods quantify the degradation from measured data of a solar farm, however, the nonlinear time-dependence and correlated degradations make it difficult to use the empirical degradation rates for ultimate lifetime projection. In this article, we propose a complementary physics-based model to predict the solder bond failure caused by mechanical stress associated with the variations of the temperature. Integrating the worldwide weather information from NASA/NSRDB databases, the model predicts the location-specific output-power degradation and the lifetime of a module due to solder bond failure. The model parameters are calibrated against qualification tests involving thermal cycling of specific batches of modules from a specific technology/manufacturer. The results may be summarized as: 1) Modules installed at higher latitudes show a longer lifetime due to reduced damage accumulation. 2) The reduction of temperature fluctuation close to large bodies of water, such as seashores, increases solder bond lifetime significantly. 3) Relatively speaking, modules installed close to the Tropic of Cancer/Capricorn (23.5 degrees North/South) suffer from a higher solder bond damage and have a shorter lifetime, suggesting a conservative design. This model should serve as a building block of a comprehensive reliability framework that can predict the lifetime of a module that experiences simultaneous and correlated degradation mechanisms involving yellowing, corrosion, and potential-induced degradation.

14 SOLAR ENERGY↗
NASA NTRS1971

Some future applications of low temperature technology in space

Low temperature technology applications are presented for relativity experiments, improved signal to noise ratio performance, and helium studies in space. The large scale, low magnetic field facility is described, as well as the principle of the London moment for relativity gyroscopes.

Fairbank, W. M.↗
NASA NTRS1974

Some aspects of optical feedback with cadmium sulfide and related photoconductors

A primary limitation of many solid state photoconductors used in electro-optical systems is their slow response in converting varying light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without adversely affecting overall signal-to-noise ratio performance. The technique is analyzed to predict the improvement possible and a system is implemented using cadmium sulfide to demonstrate the effectiveness of the technique and the validity of the analysis.

Katzberg, S. J.↗
NASA NTRS1977

Signal-to-noise ratio analysis and evaluation of the Hadamard imaging technique

The signal-to-noise ratio performance of the Hadamard imaging technique is analyzed and an experimental evaluation of a laboratory Hadamard imager is presented. A comparison between the performances of Hadamard and conventional imaging techniques shows that the Hadamard technique is superior only when the imaging objective lens is required to have an effective F (focus) number of about 2 or slower.

Jobson, D. J.↗
NASA NTRS1978

The Otto-engine-equivalent vehicle concept

A vehicle comparison methodology based on the Otto-Engine Equivalent (OEE) vehicle concept is described. As an illustration of this methodology, the concept is used to make projections of the fuel economy potential of passenger cars using various alternative power systems. Sensitivities of OEE vehicle results to assumptions made in the calculational procedure are discussed. Factors considered include engine torque boundary, rear axle ratio, performance criteria, engine transient response, and transmission shift logic.

Dowdy, M. W.↗
NASA NTRS1986

Prototype thermal bus for manned Space Station compartments

A summary is presented of NASA efforts, to February 1986, on development of an advanced thermal bus for manned spacecraft. Design details are described for a prototype to be tested in 1987 that includes a contact heat exchanger, an air cooling heat exchanger for manned cabin conditions, and an interface heat exchanger for transferring compartment heat loads to the Space Station Central Thermal Bus. The design and performance criteria defined for the thermal bus are outlined and results are reported from comparisons of the capabilities and operational costs of pumped water and two-phase evaporating/condensing heat transport concepts. The operating temperature, launch weight/thermal performance ratios, and power requirements of each concept are discussed, along with the critical technologies identified for use of a water/titanium two-phase thermal bus.

Zentner, Ronald C.↗