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High Penetration, Grid Connected Photovoltaic Technology Codes and Standards: Preprint (open access)

High Penetration, Grid Connected Photovoltaic Technology Codes and Standards: Preprint

This paper reports the interim status in identifying and reviewing photovoltaic (PV) codes and standards (C&S) and related electrical activities for grid-connected, high-penetration PV systems with a focus on U.S. electric utility distribution grid interconnection.
Date: May 1, 2008
Creator: Basso, T. S.
System: The UNT Digital Library
Use of microphysical relationships to discern growth/decay mechanisms of cloud droplets with focus on Z-LWC relationships. (open access)

Use of microphysical relationships to discern growth/decay mechanisms of cloud droplets with focus on Z-LWC relationships.

Cloud droplet size distributions hence the key microphysical quantities (e.g., radar reflectivity, droplet concentration, liquid water content, relative dispersion, and mean-volume radius) are determined by different physical mechanisms, including pre-cloud aerosols as CCNs, cloud updraft, and various turbulent entrainment-mixing processes. Therefore, different relationships among these microphysical properties are expected in response to these various mechanisms. The effect of turbulent entrainment-mixing processes is particularly vexing, with different entrainment-mixing processes likely leading to different microphysical relationships. Cloud radar has been widely used to infer the cloud liquid water content (L) from the measurement of radar reflectivity (Z) using a Z-L relationship. Existing Z-L expressions have been often obtained empirically, and differ substantially (Khain et al. 2008). The discrepancy among Z-L relations, which has been hindering the application of cloud radar in measuring cloud properties, likely stems from the different relationships between the relevant microphysical properties caused by different physical processes. This study first analyzes the Z-L relationship theoretically, and identify the key microphysical properties that affect this relationship, and then address the effects of various processes on the Z-L relationship by discerning the characteristics of the relationships between the relative dispersion, droplet concentration, liquid water content, and mean-volume radius calculated from in-situ …
Date: May 1, 2008
Creator: Liu, Y.; Daum, P. H.; Yum, S. S. & Wang, J.
System: The UNT Digital Library
Where do fossil fuel carbon dioxide emissions from California go? An analysis based on radiocarbon observations and an atmospheric transport model (open access)

Where do fossil fuel carbon dioxide emissions from California go? An analysis based on radiocarbon observations and an atmospheric transport model

Characterizing flow patterns and mixing of fossil fuel-derived CO{sub 2} is important for effectively using atmospheric measurements to constrain emissions inventories. Here we used measurements and a model of atmospheric radiocarbon ({sup 14}C) to investigate the distribution and fluxes of atmospheric fossil fuel CO{sub 2} across the state of California. We sampled {sup 14}C in annual C{sub 3} grasses at 128 sites and used these measurements to test a regional model that simulated anthropogenic and ecosystem CO{sub 2} fluxes, transport in the atmosphere, and the resulting {sup 14}C of annual grasses ({Delta}{sub g}). Average measured {Delta}{sub g} in Los Angeles, San Francisco, the Central Valley, and the North Coast were 27.7 {+-} 20.0, 44.0 {+-} 10.9, 48.7 {+-} 1.9, and 59.9 {+-} 2.5{per_thousand}, respectively, during the 2004-2005 growing season. Model predictions reproduced regional patterns reasonably well, with estimates of 27.6 {+-} 2.4, 39.4 {+-} 3.9, 46.8 {+-} 3.0, and 59.3 {+-} 0.2{per_thousand} for these same regions and corresponding to fossil fuel CO{sub 2} mixing ratios (Cf) of 13.7, 6.1, 4.8, and 0.3 ppm. {Delta}{sub g} spatial heterogeneity in Los Angeles and San Francisco was higher in the measurements than in the predictions, probably from insufficient spatial resolution in the fossil …
Date: May 1, 2008
Creator: Riley, W. J.; Hsueh, D. Y.; Randerson, J. T.; Fischer, M. L.; Hatch, J. G.; Pataki, D. E. et al.
System: The UNT Digital Library
Help for the Developers of Control System Cyber Security Standards (open access)

Help for the Developers of Control System Cyber Security Standards

A Catalog of Control Systems Security: Recommendations for Standards Developers (Catalog), aimed at assisting organizations to facilitate the development and implementation of control system cyber security standards, has been developed. This catalog contains requirements that can help protect control systems from cyber attacks and can be applied to the Critical Infrastructures and Key Resources of the United States and other nations. The requirements contained in the catalog are a compilation of practices or various industry bodies used to increase the security of control systems from both physical and cyber attacks. They should be viewed as a collection of recommendations to be considered and judiciously employed, as appropriate, when reviewing and developing cyber security standards for control systems. The recommendations in the Catalog are intended to be broad enough to provide any industry using control systems the flexibility needed to develop sound cyber security standards specific to their individual security requirements.
Date: May 1, 2008
Creator: Evans, Robert P.
System: The UNT Digital Library
Silicon Solar Cells with Front Hetero-contact and Aluminum Alloy Back Junction (Poster) (open access)

Silicon Solar Cells with Front Hetero-contact and Aluminum Alloy Back Junction (Poster)

The objectives of this report are: (1) to apply industrial back Al process in efficient n-wafer cells with a-Si:H front surface passivation; and (2) to evaluate the surface recombination velocity (SRV) of the a-Si:H passivated front surface with different surface preparation procedures.
Date: May 1, 2008
Creator: Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q. et al.
System: The UNT Digital Library
Effects of Temporal Wind Patterns on the Value of Wind-Generated Electricity in California and the Northwest (open access)

Effects of Temporal Wind Patterns on the Value of Wind-Generated Electricity in California and the Northwest

Wind power production is variable, but also has diurnal and seasonal patterns. These patterns differ between sites, potentially making electric power from some wind sites more valuable for meeting customer loads or selling in wholesale power markets. This paper investigates whether the timing of wind significantly affects the value of electricity from sites in California and the Northwestern United States. We use both measured and modeled wind data and estimate the time-varying value of wind power with both financial and load-based metrics. We find that the potential difference in wholesale market value between better-correlated and poorly correlated wind sites is modest, on the order of 5-10 percent. A load-based metric, power production during the top 10 percent of peak load hours, varies more strongly between sites, suggesting that the capacity value of different wind projects could vary by as much as 50 percent based on the timing of wind alone.
Date: May 1, 2008
Creator: Wiser, Ryan H; Wiser, Ryan H & Fripp, Matthias
System: The UNT Digital Library
Search for Low Mass SM Higgs at the Tevatron (open access)

Search for Low Mass SM Higgs at the Tevatron

None
Date: May 1, 2008
Creator: Sanders, Michiel P.
System: The UNT Digital Library
Search for the Flavor Changing Neutral Current Decay t $\to Zq$ in $p \bar{p}$ Collisions at $\sqrt{s}=1.96$ (open access)

Search for the Flavor Changing Neutral Current Decay t $\to Zq$ in $p \bar{p}$ Collisions at $\sqrt{s}=1.96$

We report a search for the flavor changing neutral current (FCNC) decay of the top quark t {yields} Zq (q = u, c) in p{bar p} collisions at {radical}s = 1.96 TeV using a data sample corresponding to an integrated luminosity of 1.9 fb{sup -1} collected by the CDF II detector. This decay is strongly suppressed in the standard model (SM) and a signal at the Tevatron would be an indication of physics beyond the SM. Using Z+ {ge} 4 jet final state candidate events, both with and without an identified bottom quark jet, we discriminate signal from background by exploring kinematic constraints present in FCNC events and obtain an upper limit of {Beta}(t {yields} Zq) < 3.7% at 95% C.L.
Date: May 1, 2008
Creator: Aaltonen, : T.
System: The UNT Digital Library
Modeling Microbunching from Shot Noise Using Vlasov Solvers (open access)

Modeling Microbunching from Shot Noise Using Vlasov Solvers

Unlike macroparticle simulations, which are sensitive to unphysical statistical fluctuations when the number of macroparticles is smaller than the bunch population, direct methods for solving the Vlasov equation are free from sampling noise and are ideally suited for studying microbunching instabilities evolving from shot noise. We review a 2D (longitudinal dynamics) Vlasov solver we have recently developed to study the microbunching instability in the beam delivery systems for x-ray FELs and present an application to FERMI{at}Elettra. We discuss, in particular, the impact of the spreader design on microbunching.
Date: May 1, 2008
Creator: Venturini, Marco; Venturini, Marco & Zholents, Alexander
System: The UNT Digital Library
Direct-Write Contacts: Metallization and Contact Formation; Preprint (open access)

Direct-Write Contacts: Metallization and Contact Formation; Preprint

Using direct-write approaches in photovoltaics for metallization and contact formation can significantly reduce the cost per watt of producing photovoltaic devices. Inks have been developed for various materials, such as Ag, Cu, Ni and Al, which can be used to inkjet print metallizations for various kinds of photovoltaic devices. Use of these inks results in metallization with resistivities close to those of bulk materials. By means of inkjet printing a metallization grid can be printed with better resolution, i.e. smaller lines, than screen-printing. Also inks have been developed to deposit transparent conductive oxide films by means of ultrasonic spraying.
Date: May 1, 2008
Creator: van Hest, M. F. A. M.; Curtis, C. J.; Miedaner, A.; Pasquarelli, R. M.; Kaydonova, T.; Hersh, P. et al.
System: The UNT Digital Library
Direct-Write Contacts: Metallization and Contact Formation (Poster) (open access)

Direct-Write Contacts: Metallization and Contact Formation (Poster)

None
Date: May 1, 2008
Creator: van Hest, M.; Curtis, C.; Miedaner, A.; Pasquarelli, R.; Kaydanova, T.; Hersh, P. et al.
System: The UNT Digital Library
Investigation of Junction Properties in CdS/CdTe Solar Cells and Their Correlation to Device Properties: Preprint (open access)

Investigation of Junction Properties in CdS/CdTe Solar Cells and Their Correlation to Device Properties: Preprint

Secondary-ion mass spectrometry analysis of the CdS/CdTe interface shows that S diffusion in CdTe increases with substrate temperature and CdCl2 heat treatment. There is also an accumulation of Cl at the interface for CdCl2-treated samples. Modulated photo-reflectance studies shows that devices with CdCl2 heat treatment and open-circuit voltage (Voc) of 835 mV have a distinct high electric-field region in the layer with bandgap of 1.45 eV. Electron-beam induced current measurements reveal a one-sided junction for high Voc devices. The nature of the junction changes with processing. For heterojunction devices, the depletion region includes the highly defective CdS/CdTe interface, which would increase the recombination current and consequently the dark current, leading to lower Voc. In the case of CdCl2-treated cells, the n+-p junction and its high electric-field results in the junction between structurally compatible CdTe and the Te-rich CdSTe alloy, and thus, in higher Voc.
Date: May 1, 2008
Creator: Dhere, R. G.; Zhang, Y.; Romero, M. J.; Asher, S. E.; Young, M.; To, B. et al.
System: The UNT Digital Library
Design of Shallow P-Type Dopants in ZnO: Preprint (open access)

Design of Shallow P-Type Dopants in ZnO: Preprint

This paper describes approaches to lower the acceptor ionization energy in ZnO by codoping acceptors with donor or isovalent atoms and proposes a universal approach to overcome the doping polarity problem for wide-band-gap semiconductors.
Date: May 1, 2008
Creator: Wei, S.-H.; Li, J. & Yan, Y.
System: The UNT Digital Library
Stability of CIS/CIGS Modules at the Outdoor Test Facility over Two Decades: Preprint (open access)

Stability of CIS/CIGS Modules at the Outdoor Test Facility over Two Decades: Preprint

This paper discusses examining the status and question of long-term stability of copper indium diselenide (CIS) photovoltaic (PV) module performance for numerous modules that are deployed in the array field, or on the roof of, the outdoor test facility (OTF) at NREL, acquired from two manufacturers.
Date: May 1, 2008
Creator: del Cueto, J. A.; Rummel, S.; Kroposki, B.; Osterwald, C. & Anderberg, A.
System: The UNT Digital Library
Inverted GaInP/(In)GaAs/InGaAs Triple-Junction Solar Cells with Low-Stress Metamorphic Bottom Junctions: Preprint (open access)

Inverted GaInP/(In)GaAs/InGaAs Triple-Junction Solar Cells with Low-Stress Metamorphic Bottom Junctions: Preprint

We demonstrate high efficiency performance in two ultra-thin, Ge-free III-V semiconductor triple-junction solar cell device designs grown in an inverted configuration. Low-stress metamorphic junctions were engineered to achieve excellent photovoltaic performance with less than 3 x 106 cm-2 threading dislocations. The first design with band gaps of 1.83/1.40/1.00 eV, containing a single metamorphic junction, achieved 33.8% and 39.2% efficiencies under the standard one-sun global spectrum and concentrated direct spectrum at 131 suns, respectively. The second design with band gaps of 1.83/1.34/0.89 eV, containing two metamorphic junctions achieved 33.2% and 40.1% efficiencies under the standard one-sun global spectrum and concentrated direct spectrum at 143 suns, respectively.
Date: May 1, 2008
Creator: Geisz, J. F.; Kurtz, S. R.; Wanlass, M. W.; Ward, J. S.; Duda, A.; Friedman, D. J. et al.
System: The UNT Digital Library
INL Reactor Technology Complex Out-of-Service Buried Piping Hazards (open access)

INL Reactor Technology Complex Out-of-Service Buried Piping Hazards

Idaho National Laboratory (INL) Reactor Technology Complex (RTC) buried piping and components are being characterized to determine if they should be managed as hazardous waste and subject to the Hazardous Waste Management Act /Resource Conservation and Recovery Act (RCRA). RTC buried piping and components involve both active piping and components from currently operating nuclear facilities, such as the Advanced Test Reactor (ATR), and inactive lines from facilities undergoing D&D activities. The issue exists as to the proper methods to analyze and control hazards associated with D&D activities on facilities collocated with existing operating nuclear facilities, or future collocated facilities being considered with the resurgent nuclear industry. During initial characterization activities, it was determined that residual radioactive material in several inactive RTC lines and components could potentially exceed hazard category (HC) 3 thresholds. In addition, concerns were raised as to how to properly isolate active nuclear facility piping and components from those inactive lines undergoing RCRA actions, and whether the operating facility safety basis could be impacted. Work was stopped, and a potential inadequacy in the safety analysis (PISA) was declared, even though no clear safety basis existed for the inactive, abandoned lines and equipment. An unreviewed safety question (USQ) and …
Date: May 1, 2008
Creator: Gerstner, Douglas M.
System: The UNT Digital Library
Comparison of Predictive Models for Photovoltaic Module Performance: Preprint (open access)

Comparison of Predictive Models for Photovoltaic Module Performance: Preprint

This paper examines three models used to estimate the performance of photovoltaic (PV) modules when the irradiances and PV cell temperatures are known. The results presented here were obtained by comparing modeled and measured maximum power (Pm) for PV modules that rely on different technologies.
Date: May 1, 2008
Creator: Marion, B.
System: The UNT Digital Library
Damp-Heat Induced Degradation of Transparent Conducting Oxides for Thin-Film Solar Cells: Preprint (open access)

Damp-Heat Induced Degradation of Transparent Conducting Oxides for Thin-Film Solar Cells: Preprint

The stability of intrinsic and Al-doped single- and bi-layer ZnO for thin-film CuInGaSe2 solar cells, along with Al-doped Zn1-xMgxO alloy and Sn-doped In2O3 (ITO) and F-doped SnO2, was evaluated by direct exposure to damp heat (DH) at 85oC and 85% relative humidity. The results show that the DH-induced degradation rates followed the order of Al-doped ZnO and Zn1-xMgxO >> ITO > F:SnO2. The degradation rates of Al:ZnO were slower for films of higher thickness, higher substrate temperature in sputter-deposition, and with dry-out intervals. As inferred from the optical micro-imaging showing the initiation and propagation of degrading patterns and regions, the degradation behavior appears similar for all TCOs, despite the obvious difference in the degradation rate. A degradation mechanism is proposed to explain the temporal process involving thermal hydrolysis.
Date: May 1, 2008
Creator: Pern, F. J.; Noufi, R.; Li, X.; DeHart, C. & To, B.
System: The UNT Digital Library
Transparent Conducting Contacts Based on Zinc Oxide Substitutionally Doped with Gallium: Preprint (open access)

Transparent Conducting Contacts Based on Zinc Oxide Substitutionally Doped with Gallium: Preprint

Transparent conducting oxides (TCOs) are a critical element in photovoltaic devices. This paper describes research on Ga:ZnO (a TCO candidate) using a high-throughput combinatorial approach.
Date: May 1, 2008
Creator: Gorrie, C. W.; Reese, M.; Perkins, J. D.; Alleman, J. L.; S., Dabney M.; To, B. et al.
System: The UNT Digital Library
SECOND GENERATION EXPERIMENTAL EQUIPMENT DESIGN TO SUPPORT VOLOXIDATION TESTING AT INL (open access)

SECOND GENERATION EXPERIMENTAL EQUIPMENT DESIGN TO SUPPORT VOLOXIDATION TESTING AT INL

Voloxidation is a potential head-end process used prior to aqueous or pyrochemical spent-oxide-fuel treatment. The spent oxide fuel is heated to an elevated temperature in oxygen or air to promote separation of the fuel from the cladding as well as volatize the fission products. The Idaho National Laboratory (INL) and the Korea Atomic Energy Research Institute (KAERI) have been collaborating on voloxidation research through a joint International Nuclear Energy Research Initiative (I-NERI). A new furnace and off-gas trapping system (OTS) with enhanced capability was necessary to perform further testing. The design criteria for the OTS were jointly agreed upon by INL and KAERI. First, the equipment must accommodate the use of spent nuclear fuel and be capable of operating in the Hot Fuel Examination Facility (HFEF) at the INL. This primarily means the furnace and OTS must be remotely operational and maintainable. The system requires special filters and distinctive temperature zones so that the fission products can be uniquely captured. The OTS must be sealed to maximize the amount of fission products captured. Finally, to accommodate the largest range of operating conditions, the OTS must be capable of handling high temperatures and various oxidizing environments. The constructed system utilizes a …
Date: May 1, 2008
Creator: Wahlquit, Dennis L.; Bateman, Kenneth J. & Westphal, Brian R.
System: The UNT Digital Library
Coordinating the Global Information Grid Initiative with the NG9-1-1 Initiative (open access)

Coordinating the Global Information Grid Initiative with the NG9-1-1 Initiative

As the Department of Defense develops the Global Information Grid, the Department of Transportation develops the Next Generation 9-1-1 system. Close examinations of these initiatives show that the two are similar in architectures, applications, and communications interoperability. These similarities are extracted from the lowest user level to the highest commander rank that will be involved in each network. Once the similarities are brought into perspective, efforts should be made to collaborate between the two departments.
Date: May 1, 2008
Creator: Schmitt, Michael
System: The UNT Digital Library
The magnetized steel and scintillator calorimeters of the MINOS experiment (open access)

The magnetized steel and scintillator calorimeters of the MINOS experiment

The Main Injector Neutrino Oscillation Search (MINOS) experiment uses an accelerator-produced neutrino beam to perform precision measurements of the neutrino oscillation parameters in the 'atmospheric neutrino' sector associated with muon neutrino disappearance. This long-baseline experiment measures neutrino interactions in Fermilab's NuMI neutrino beam with a near detector at Fermilab and again 735 km downstream with a far detector in the Soudan Underground Laboratory in northern Minnesota. The two detectors are magnetized steel-scintillator tracking calorimeters. They are designed to be as similar as possible in order to ensure that differences in detector response have minimal impact on the comparisons of event rates, energy spectra and topologies that are essential to MINOS measurements of oscillation parameters. The design, construction, calibration and performance of the far and near detectors are described in this paper.
Date: May 1, 2008
Creator: Michael, : D.G.
System: The UNT Digital Library
Device Physics of Nanoscale Interdigitated Solar Cells: Preprint (open access)

Device Physics of Nanoscale Interdigitated Solar Cells: Preprint

This paper uses multidimensional device simulation to explore the physics and solar cell performance of interdigitated p-n junctions for material parameters relevant to the postulated conditions.
Date: May 1, 2008
Creator: Metzger, W. K. & Levi, D.
System: The UNT Digital Library
The effect of drying temperature on the composition of biomass (open access)

The effect of drying temperature on the composition of biomass

The compositional quality of different lignocellulosic feedstocks influences their performance and potential demand at a biorefinery. Many analytical protocols for determining the composition or performance characteristics of biomass involve a drying step, where the drying temperature can vary depending on the specific protocol. To get reliable data, it is important to determine the correct drying temperature to vaporize the water without negatively impacting the compositional quality of the biomass. A comparison of drying temperature between 45 degrees C and 100 degrees C was performed using wheat straw and corn stover. Near-infrared (NIR) spectra were taken of the dried samples and compared using principal component analysis (PCA). Carbohydrates were analyzed using quantitative saccharification to determine sugar degradation. Analysis of variance was used to determine if there was a significant difference between drying at different temperatures. PCA showed an obvious separation in samples dried at different temperatures due to sample water content. However, quantitative saccharification data shows, within a 95% confidence interval, that there is no significant difference in sugar content for drying temperatures up to 100 degrees C for wheat straw and corn stover.
Date: May 1, 2008
Creator: Houghton, T. P.; Stevens, D. N.; Wright, C. T. & Radtke, C. W.
System: The UNT Digital Library