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At least 757 records · Page 42

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NASA NTRS2015

Development of a Grid-Independent Geos-Chem Chemical Transport Model (v9-02) as an Atmospheric Chemistry Module for Earth System Models

The GEOS-Chem global chemical transport model (CTM), used by a large atmospheric chemistry research community, has been re-engineered to also serve as an atmospheric chemistry module for Earth system models (ESMs). This was done using an Earth System Modeling Framework (ESMF) interface that operates independently of the GEOSChem scientific code, permitting the exact same GEOSChem code to be used as an ESM module or as a standalone CTM. In this manner, the continual stream of updates contributed by the CTM user community is automatically passed on to the ESM module, which remains state of science and referenced to the latest version of the standard GEOS-Chem CTM. A major step in this re-engineering was to make GEOS-Chem grid independent, i.e., capable of using any geophysical grid specified at run time. GEOS-Chem data sockets were also created for communication between modules and with external ESM code. The grid-independent, ESMF-compatible GEOS-Chem is now the standard version of the GEOS-Chem CTM. It has been implemented as an atmospheric chemistry module into the NASA GEOS- 5 ESM. The coupled GEOS-5-GEOS-Chem system was tested for scalability and performance with a tropospheric oxidant-aerosol simulation (120 coupled species, 66 transported tracers) using 48-240 cores and message-passing interface (MPI) distributed-memory parallelization. Numerical experiments demonstrate that the GEOS-Chem chemistry module scales efficiently for the number of cores tested, with no degradation as the number of cores increases. Although inclusion of atmospheric chemistry in ESMs is computationally expensive, the excellent scalability of the chemistry module means that the relative cost goes down with increasing number of cores in a massively parallel environment.

CTM↗

NASA NTRS2016

Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-Delay Polarization Modulators

Variable-delay Polarization Modulators (VPMs) are currently being implemented in experiments designed to measure the polarization of the cosmic microwave background on large angular scales because of their capability for providing rapid, front-end polarization modulation and control over systematic errors. Despite the advantages provided by the VPM, it is important to identify and mitigate any time-varying effects that leak into the synchronously modulated component of the signal. In this paper, the effect of emission from a 300 K VPM on the system performance is considered and addressed. Though instrument design can greatly reduce the influence of modulated VPM emission, some residual modulated signal is expected. VPM emission is treated in the presence of rotational misalignments and temperature variation. Simulations of time-ordered data are used to evaluate the effect of these residual errors on the power spectrum. The analysis and modeling in this paper guides experimentalists on the critical aspects of observations using VPMs as front-end modulators. By implementing the characterizations and controls as described, front-end VPM modulation can be very powerful for mitigating 1/ f noise in large angular scale polarimetric surveys. None of the systematic errors studied fundamentally limit the detection and characterization of B-modes on large scales for a tensor-to-scalar ratio of r= 0.01. Indeed, r less than 0.01 is achievable with commensurately improved characterizations and controls.

Miller, N. J.↗

NASA NTRS2017

System and Method for Generating a Frequency Modulated Linear Laser Waveform

A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

Pierrottet, Diego F.↗

DOE OSTI2012

Testing and Analysis for Lifetime Prediction of Crystalline Silicon PV Modules Undergoing Degradation by System Voltage Stress: Preprint

Acceleration factors are calculated for crystalline silicon PV modules under system voltage stress by comparing the module power during degradation outdoors to that in accelerated testing at three temperatures and 85% relative humidity. A lognormal analysis is applied to the accelerated lifetime test data considering failure at 80% of the initial module power. Activation energy of 0.73 eV for therate of failure is determined, and the probability of module failure at an arbitrary temperature is predicted. To obtain statistical data for multiple modules over the course of degradation in-situ of the test chamber, dark I-V measurements are obtained and transformed using superposition, which is found well suited for rapid and quantitative evaluation of potential-induced degradation. It isdetermined that shunt resistance measurements alone do not represent the extent of power degradation. This is explained with a two-diode model analysis that shows an increasing second diode recombination current and ideality factor as the degradation in module power progresses. Failure modes of the modules stressed outdoors are examined and compared to those stressed in accelerated tests.

14 SOLAR ENERGY↗

DOE OSTI2013

Materials and Modules for Low Cost, High Performance Fuel Cell Humidifiers

The objective of this program was to demonstrate a durable, high performance water transport membrane; and a compact, low-cost, membrane-based module utilizing that membrane for use in an automotive, stationary and/or portable fuel cell water transport exchangers. Over the past 20 years, great technical progress has been made in improving power density and durability of fuel cell stacks. Yet, operating durably at high performance levels under very dry conditions, e.g., < 20% RH at 80°C or above, remains beyond even the best fuel cell membrane electrode assemblies. Thus, today it is essential to humidify the gases supplied to the fuel cell inlets. In this work, we have produced a new, inexpensive, composite membrane capable of very high water vapor transport and low air cross-over. The composite structure consists of a very thin ionomer layer (e.g., < 5 μm) sandwiched between two microporous polymer layers. The thin ionomer layer facilitates the rapid water transport and provides an impermeable layer to prevent gas cross-over. Such an approach reduces cost, but maintains performance. The microporous layer protects the thin ionomer layer from mechanical damage during handling; confers strength to the thin layer allowing it to be more durable during use; and allows it to withstand higher automotive pressures and temperatures. The composite structure will therefore allow lower total cost while still meeting automotive humidifier water transport and durability targets. Because the transport rates of these new materials are so high, existing planar membrane humidifier module designs available at the start of the program were incapable of efficiently utilizing the high rates. Therefore, the assembled team designed, tested and demonstrated an innovative, low-cost humidifier module with customized channel geometries that can take advantage of the high the water transport rates. The objectives of the program have been fully met. The optimized membrane produced in the program has very high transport rates, nearly twice that of the closest competitive option, a homogeneous perfluorosulfonic acid (PFSA) membrane. Furthermore, the composite structure imparts significant durability advantages, allowing the membrane to remain gas impermeable during 20,000 relative humidity (RH) cycles, unlike the closest competitive options that fail very rapidly. It does suffer from a loss of performance with time at temperature because of inherent properties of the PFSA polymer, but this degradation is manageable through relatively simple system design changes. The final membrane of this program has been produced on manufacturing level equipment in a roll to roll form in the scale of hundreds of square meters. The process is readily scalable to automotive level volumes to allow production of a low-cost membrane required for this application. A full scale automotive air-to-air humidifier module has been designed, tested and built. The final module meets the design specifications required for automotive fuel cell use, and exceeds all the DOE 2017 targets for a cathode humidification module as determined in independent testing at Ford Motor Company. It has a small volume, less than 5 liters; a high water transfer rate, significantly greater than 5 g/s at the DOE specified conditions; acceptably low pressure drop; and is projected to maintain these properties over 5000 hours. Additionally, high volume cost projections suggest that the module can be produced for less than $\$$100 per unit in a scale of 500,000 units per year.

08 HYDROGEN↗

DOE OSTI2012

Operational Results of Pulse Shaping Techniques for the High Voltage Convertor Modulator

The High Voltage Converter Modulators (HVCMs) are used to power the RF klystrons used throughout the accelerator systems at Spallation Neutron Source (SNS). The output voltage of the HVCM has significant droop and ripple which, combined with low level RF (LLRF) system limitations, affect performance and efficiency of accelerator cavities. In conjunction with the progress in development of the new HVCM controller, different pulse modulation techniques were implemented and studied on the test modulator. This paper discusses the results of implementation of frequency modulation and phase modulation on output voltage. Operational data, including full average power operation, of test modulator is also discussed. Future plans for the new modulation scheme will be presented.

Patel, Gunjan P↗

DOE OSTI2013

System and method of modulating electrical signals using photoconductive wide bandgap semiconductors as variable resistors

A system and method for producing modulated electrical signals. The system uses a variable resistor having a photoconductive wide bandgap semiconductor material construction whose conduction response to changes in amplitude of incident radiation is substantially linear throughout a non-saturation region to enable operation in non-avalanche mode. The system also includes a modulated radiation source, such as a modulated laser, for producing amplitude-modulated radiation with which to direct upon the variable resistor and modulate its conduction response. A voltage source and an output port, are both operably connected to the variable resistor so that an electrical signal may be produced at the output port by way of the variable resistor, either generated by activation of the variable resistor or propagating through the variable resistor. In this manner, the electrical signal is modulated by the variable resistor so as to have a waveform substantially similar to the amplitude-modulated radiation.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Evaluation of Maxim Module-Integrated Electronics at the DOE Regional Test Centers (Presentation)

Module-embedded power electronics developed by Maxim Integrated are under evaluation through a partnership with the Department of Energy's Regional Test Center (RTC) program. Field deployments of both conventional modules and electronics-enhanced modules are designed to quantify the performance advantage of Maxim's products under different amounts of interrow shading, and their ability to be deployed at a greater ground-coverage ratio than conventional modules. Simulations in PVSYST have quantified the predicted performance difference between conventional modules and Maxim's modules from interrow shading. Initial performance results have identified diffuse irradiance losses at tighter row spacing for both the Maxim and conventional modules. Comparisons with published models show good agreement with models predicting the greatest diffuse irradiance losses. At tighter row spacing, all of the strings equipped with embedded power electronics outperformed their conventional peers. An even greater performance advantage is predicted to occur in the winter months when the amount of interrow shading mismatch is at a maximum.

14 SOLAR ENERGY↗

DOE OSTI2013

Thermal Modeling Studies for Active Storage Modules in the Calvert Cliffs ISFSI

Temperature measurements obtained for two storage modules in the Calvert Cliffs Nuclear Power Station’s Independent Spent Fuel Storage Installation (ISFSI) as part of the Used Fuel Disposition Campaign of the Department of Energy (DOE) were used to perform validation and sensitivity studies on detailed computational fluid dynamics (CFD) models of the concrete storage modules, including the dry storage canister within the modules. The storage modules in the Calvert Cliffs Nuclear Power Station’s ISFSI are a site-specific version of the standard NUHOMS® HSM. The two modules inspected each contained a 24P DSC loaded with 24 CE 14x14 spent fuel assemblies. The thermal analysis was performed using the STAR-CCM+ package, and the models developed for the specific ISFSI modules yielded temperature predictions in actual storage conditions for the concrete structure, the DSC and its contents, including preliminary estimates of fuel cladding temperatures for the used nuclear fuel. The results of this work demonstrate that existing CFD modeling tools can be used to obtain reasonable and accurate detailed representations of spent fuel storage systems with realistic decay heat loadings when the model omits specific conservatisms and bounding assumptions normally used in design-basis and safety-basis calculations. This paper presents sensitivity studies on modeling detail (for the storage module and the DSC), boundary conditions, and decay heat load, to evaluate the effect of the modeling approach on predicted temperatures and temperature distributions. Because nearly all degradation mechanisms for materials and structures comprising dry storage and transportation systems are dependent on temperature, accurate characterization of local temperatures and temperature gradients that the various components of these systems will experience over the entire storage period has been identified as a primary requirement for evaluation of very long term storage of used nuclear fuel.

long term storage↗

DOE OSTI2015

Silicon photonic heater-modulator

Photonic modulators, methods of forming photonic modulators and methods of modulating an input optical signal are provided. A photonic modulator includes a disk resonator having a central axis extending along a thickness direction of the disk resonator. The disk resonator includes a modulator portion and a heater portion. The modulator portion extends in an arc around the central axis. A PN junction of the modulator portion is substantially normal to the central axis.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2015

Low-voltage differentially-signaled modulators

Photonic modulators and methods of modulating an input optical signal are provided. A photonic modulator includes at least one modulator section and differential drive circuitry. The at least one modulator section includes a P-type layer and an N-type layer forming a PN junction in the modulator section. The differential drive circuitry is electrically coupled to the P-type layer and the N-type layer of the at least one modulator section.

14 SOLAR ENERGY↗

DOE OSTI2016

Power meter ratio method of stabilizing a resonant modulator

Methods and systems for stabilizing a resonant modulator include receiving pre-modulation and post-modulation portions of a carrier signal, determining the average power from these portions, comparing an average input power to the average output power, and operating a heater coupled to the modulator based on the comparison. One system includes a pair of input structures, one or more processing elements, a comparator, and a control element. The input structures are configured to extract pre-modulation and post-modulation portions of a carrier signal. The processing elements are configured to determine average powers from the extracted portions. The comparator is configured to compare the average input power and the average output power. The control element operates a heater coupled to the modulator based on the comparison.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2017

Photovoltaic cell module and method of forming

A photovoltaic cell module, a photovoltaic array including at least two modules, and a method of forming the module are provided. The module includes a first outermost layer and a photovoltaic cell disposed on the first outermost layer. The module also includes a second outermost layer disposed on the photovoltaic cell and sandwiching the photovoltaic cell between the second outermost layer and the first outermost layer. The method of forming the module includes the steps of disposing the photovoltaic cell on the first outermost layer, disposing a silicone composition on the photovoltaic cell, and compressing the first outermost layer, the photovoltaic cell, and the second layer to form the photovoltaic cell module.

14 SOLAR ENERGY↗

DOE OSTI2016

Design of Removable Shield Modules for Nuclear Plant Applications Using Monte Carlo Modeling - 16264

A new modular shielding system has been designed and developed for nuclear plant applications as a replacement for traditional concrete blocks and plugs. The shield comprises interlocking modules that are custom designed using CAD and Monte Carlo modelling methods. The key benefit of these new modules is that they can be quickly removed and re-installed to allow temporary access to high radiation environments e.g. for maintenance and repair of plant equipment at nuclear power plants or waste handling facilities. The traditional method for construction of these removable concrete blocks and plugs was to cast them in place. Within the aging fleet of commercial reactors, some plants are experiencing concrete degradation of these shield blocks and plugs as well as failure of lifting points. Additionally, the existing plugs are difficult to remove and re-install. The new modular system comprises a rigid steel enclosure filled with lead that can be installed in a fraction of the normal time. This approach can accelerate outage times leading to reduced dose uptake to operators and provide significant long term cost savings. Use of Monte Carlo methods enables the shielding modules to be designed efficiently for neutron and gamma ray attenuation with the minimum necessary thickness of lead and steel. Furthermore, the modelling ensures the design is not compromised by streaming pathways, for example at the overlaps between modules or through internal structural components. Shielding modules were supplied to the Brunswick Nuclear Power station (BNP), operated by Duke Energy, located in southeast United States. These modules have been installed to replace concrete shield plugs that are located on the roof above a Feed Water Heaters (FWH) bay. While specific in application, this project demonstrates that the shield module design concept could be expanded to address vertical block walls routinely found in personnel and equipment access hatches. This approach is applicable to a wide variety of new and existing nuclear facilities and will lead to improved safety and reduced lifetime costs all the way through to future decommissioning and dismantling operations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

The MOOSE fluid properties module

The fluid properties module in MOOSE~\cite{lindsay2022moose} serves a variety of fluid simulation applications based on MOOSE, including the MOOSE Navier Stokes module~\cite{moose_ns}, Pronghorn~\cite{pgh}, the MOOSE thermal hydraulics module, SAM~\cite{sam}, RELAP-7~\cite{relap7}, Sockeye~\cite{sockeye}, Pronghorn-subchannel~\cite{subchannel} and the MOOSE porous flow module~\cite{porous}. These applications are used to solve coarse mesh multi-dimensional thermal-hydraulics~\cite{pgh}, 1D systems analysis~\cite{sam,relap7} in nuclear reactor analysis, heat pipe modeling~\cite{sockeye} and porous flow simulations~\cite{porous} for underground gas storage and water seepage. The use of consistent fluid properties across fluid flow applications facilitates coupled flow simulations~\cite{anl_sam_pgh,osti_1889653}. Each application has historically driven the implementation of several fluid properties, which were later extended to be compatible with other applications. The unique diversity of applications of the module, due to its presence in MOOSE, has driven its expansion to new fluids, such as advanced nuclear reactor coolants and, more recently, arbitrary functions or tables-based property definitions, as detailed in section~\ref{content}, as well as numerous thermophysical properties and variable sets, as detailed in subsection~\ref{sec:prop}. The need for different discretizations of flow equations based on the compressibility of the fluid has motivated support for both primitive (pressure- and temperature-based) and conservative (internal energy- and specific volume-based) flow variables in the module. Thermodynamic relations are used to convert between these two formulations, as needed. The module serves a dual purpose of providing fluid properties for direct use in flow simulations and facilitating the implementation of user-specific fluid properties. Contributions of new properties for existing fluids or new fluids are strongly encouraged.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2011

Design and preliminary test results of Daya Bay RPC modules*

Resistive Plate Chamber (RPC) modules will be used as one part of the cosmic muon veto system in the Daya Bay reactor neutrino experiment. A total of 189 RPC modules will cover the three water pools in the experiment. To achieve track reconstruction and high efficiency, each module consists of 4 layers, each of which contains two sizes of bare chambers. The placement of bare chambers is reversed in different layers to reduce the overlapping dead areas. The module efficiency and patch efficiency were studied both in simulation and test of the data analysis. 143 modules have been constructed and tested. The preliminary study shows that the module and patch 3 out of 4 layers efficiency reaches about 98%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Engineering Perovskite Precursor Inks for Scalable Production of High‐Efficiency Perovskite Photovoltaic Modules

Abstract Blade coating of perovskite solar cells (PSCs) and modules has progressed considerably toward the industrial production of perovskite photovoltaics. Developing stable perovskite precursors is critical for achieving uniform coating over large areas. Here, the engineering of a perovskite precursor solution consisting of 2‐methoxyethanol (2‐Me) and 1,3‐dimethyl‐imidazolidinone (DMI) with superior intermediate phase stability that enables scalable production of efficient perovskite solar modules is reported. With this perovskite precursor solution, uniform and pinhole‐less perovskite film is deposited over a large area of > 100 cm 2 and higher‐efficiency PSCs and modules are obtained. The best‐performing unit cell and module with n‐i‐p configuration reach power conversion efficiencies of 23.4% and 20.1%, respectively. Additionally, a series of non‐destructive metrology methods, such as spectroscopic ellipsometry, hyperspectral photoluminescence, electroluminescence, and laser beam‐induced current mapping, are employed to assess and guide the development the blade‐coated perovskite modules. This results show that rational engineering of precursor inks for blade coating is promising for the scalable production of efficient perovskite solar modules.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Ultra-compact low loss electro-optical nanobeam cavity modulator embedded photonic crystal

In this paper, a hybrid electro-optical modulator based on a one-dimensional photonic crystal nanobeam cavity is proposed. The main component of the cavity builder is the indium–tin–oxide that is a transparent conductive oxide. The proposed structure is used to minimize optical losses and also to have a high-quality factor with a tunability from the distributed feedback system. The proposed modulator has a wide range of resonant tunable in a footprint of 1.892 μm{sup 2}. This structure has the ability to shift the wavelength of 1.55 μm using a very small voltage 0.1 V. Simulation results show that the proposed structure has an insertion loss of 0.027 dB, extension ratio 3.484 dB, 119.89 GHz modulation speed, and 0.59 aJ/bit modulation energy. By comparing the proposed method parameters and other modulators based on the one-dimensional photonic crystal nanobeam cavity, a significant improvement in modulation voltage, insertion losses, energy consumption, and footprint have been observed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗