Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing (open access)

Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing

A study was conducted to evaluate the capabilities of different numerical methods used to represent microstructure behavior at the mesoscale for irradiated material using an idealized benchmark problem. The purpose of the mesoscale benchmark problem was to provide a common basis to assess several mesoscale methods with the objective of identifying the strengths and areas of improvement in the predictive modeling of microstructure evolution. In this work, mesoscale models (phase-field, Potts, and kinetic Monte Carlo) developed by PNNL, INL, SNL, and ORNL were used to calculate the evolution kinetics of intra-granular fission gas bubbles in UO2 fuel under post-irradiation thermal annealing conditions. The benchmark problem was constructed to include important microstructural evolution mechanisms on the kinetics of intra-granular fission gas bubble behavior such as the atomic diffusion of Xe atoms, U vacancies, and O vacancies, the effect of vacancy capture and emission from defects, and the elastic interaction of non-equilibrium gas bubbles. An idealized set of assumptions was imposed on the benchmark problem to simplify the mechanisms considered. The capability and numerical efficiency of different models are compared against selected experimental and simulation results. These comparisons find that the phase-field methods, by the nature of the free energy formulation, are …
Date: April 11, 2012
Creator: Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert; Gao, Fei; Sun, Xin; Tonks, Michael et al.
Object Type: Report
System: The UNT Digital Library
Coherent electron cooling proof of principle instrumentation design (open access)

Coherent electron cooling proof of principle instrumentation design

The goal of the Coherent Electron Cooling Proof-of-Principle (CeC PoP) experiment being designed at RHIC is to demonstrate longitudinal (energy spread) cooling before the expected CD-2 for eRHIC. The scope of the experiment is to longitudinally cool a single bunch of 40 GeV/u gold ions in RHIC. This paper will describe the instrumentation systems proposed to meet the diagnostics challenges. These include measurements of beam intensity, emittance, energy spread, bunch length, position, orbit stability, and transverse and temporal alignment of electron and ion beams.
Date: April 15, 2012
Creator: M., Gassner D.; Litvinenko, V.; Michnoff, R.; Miller, T.; Minty, M. & Pinayev, I.
Object Type: Article
System: The UNT Digital Library
Draft INFL Guideline on SIMS (open access)

Draft INFL Guideline on SIMS

Secondary Ion Mass Spectrometry (SIMS) is used for elemental and isotopic analysis of solid samples. The greatest strength of SIMS is the ability to analyze very small areas (as small as 50 nm using the CAMECA NanoSIMS, for example) and to generate high-spatial resolution maps of the distribution of elements and isotopes within the sample. The measurement of the isotopic composition of sample is usually straightforward, only requiring the analysis of the sample and that of an isotopic reference material for determination of the mass bias of the instrument. Quantification of elements, however, involves the analysis of matrix matched standards for the determination of the relative sensitivity factor (a function of both the element to be analyzed and the matrix). SIMS is commonly used in nuclear forensics for exploring the heterogeneity of the material on fine spatial scale.
Date: April 2, 2012
Creator: Kristo, M J
Object Type: Report
System: The UNT Digital Library
Eliminating the Renormalization Scale Ambiguity for Top-Pair Production Using the Principle of Maximum Conformality (open access)

Eliminating the Renormalization Scale Ambiguity for Top-Pair Production Using the Principle of Maximum Conformality

The uncertainty in setting the renormalization scale in finite-order perturbative QCD predictions using standard methods substantially reduces the precision of tests of the Standard Model in collider experiments. It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the choice of renormalization scheme, leave a non-convergent renormalon perturbative series, and moreover, one obtains incorrect results when applied to QED processes. In contrast, if one fixes the renormalization scale using the Principle of Maximum Conformality (PMC), all non-conformal {l_brace}{beta}{sub i}{r_brace}-terms in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC renormalization scale {mu}{sub R}{sup PMC} and the resulting finite-order PMC prediction are both to high accuracy independent of choice of the initial renormalization scale {mu}{sub R}{sup init}, consistent with renormalization group invariance. Moreover, after PMC scale-setting, the n!-growth of the pQCD expansion is eliminated. Even the residual scale-dependence at fixed order due to unknown higher-order {l_brace}{beta}{sub i}{r_brace}-terms is substantially suppressed. As an application, we apply the PMC procedure to obtain …
Date: April 2, 2012
Creator: Brodsky, Stanley J. & Wu, Xing-Gang
Object Type: Article
System: The UNT Digital Library
Deep Residential Retrofits in East Tennessee (open access)

Deep Residential Retrofits in East Tennessee

Executive Summary Oak Ridge National Laboratory (ORNL) is furthering residential energy retrofit research in the mixed-humid climate of East Tennessee by selecting 10 homes and guiding the homeowners in the energy retrofit process. The homeowners pay for the retrofits, and ORNL advises which retrofits to complete and collects post-retrofit data. This effort is in accordance with the Department of Energy s Building America program research goal of demonstrating market-ready energy retrofit packages that reduce home energy use by 30 50%. Through this research, ORNL researchers hope to understand why homeowners decide to partake in energy retrofits, the payback of home energy retrofits, and which retrofit packages most economically reduce energy use. Homeowner interviews help the researchers understand the homeowners experience. Information gathered during the interviews will aid in extending market penetration of home energy retrofits by helping researchers and the retrofit industry understand what drives homeowners in making positive decisions regarding these retrofits. This report summarizes the selection process, the pre-retrofit condition, the recommended retrofits, the actual cost of the retrofits (when available), and an estimated energy savings of the retrofit package using EnergyGauge . Of the 10 households selected to participate in the study, only five completed the recommended …
Date: April 1, 2012
Creator: Boudreaux, Philip R; Hendrick, Timothy P; Christian, Jeffrey E & Jackson, Roderick K
Object Type: Report
System: The UNT Digital Library
2012 Update of the Combination of CDF and D0 Results for the Mass of the W Boson (open access)

2012 Update of the Combination of CDF and D0 Results for the Mass of the W Boson

We summarize and combine the results on the direct measurements of the mass of the W boson in data collected by the Tevatron experiments CDF and D0 at Fermilab. Earlier results from CDF Run-0 (1988-1989), D0 and CDF Run-I (1992-1995) and D0 results from 1 fb{sup -1} (2002-2006) of Run-II data are now combined with two new, high statistics Run-II measurements: a CDF measurement in both electron and muon channels using 2.2 fb{sup -1} of integrated luminosity collected between 2002 and 2007, and a D0 measurement in the electron channel using 4.3 fb{sup -1} collected between 2006 and 2009. As in previous combinations, the results are corrected for inconsistencies in parton distribution functions and assumptions about electroweak parameters used in the different analyses. The resulting Tevatron average for the mass of the W boson is M{sub W} = 80,387 {+-} 16 MeV and a new world average including data from LEP II is M{sub W} = 80,385 {+-} 15 MeV.
Date: April 1, 2012
Creator: Tevatron Electroweak Working Group,
Object Type: Report
System: The UNT Digital Library
On The Origin Of High Energy Correlations in Gamma-ray Bursts (open access)

On The Origin Of High Energy Correlations in Gamma-ray Bursts

I investigate the origin of the observed correlation between a gamma-ray burst's {nu}F{sub {nu}} spectral peak E{sub pk} and its isotropic equivalent energy E{sub iso} through the use of a population synthesis code to model the prompt gamma-ray emission from GRBs. By using prescriptions for the distribution of prompt spectral parameters as well as the population's luminosity function and co-moving rate density, I generate a simulated population of GRBs and examine how bursts of varying spectral properties and redshift would appear to a gamma-ray detector here on Earth. I find that a strong observed correlation can be produced between the source frame Epk and Eiso for the detected population despite the existence of only a weak and broad correlation in the original simulated population. The energy dependance of a gamma-ray detector's flux-limited detection threshold acts to produce a correlation between the source frame E{sub pk} and E{sub iso} for low luminosity GRBs, producing the left boundary of the observed correlation. Conversely, very luminous GRBs are found at higher redshifts than their low luminosity counterparts due to the standard Malquest bias, causing bursts in the low E{sub pk}, high E{sub iso} regime to go undetected because their E{sub pk} values would …
Date: April 3, 2012
Creator: Kocevski, Daniel
Object Type: Article
System: The UNT Digital Library
N*(1535) electroproduction at high Q2 (open access)

N*(1535) electroproduction at high Q2

A covariant spectator quark model is applied to study the {gamma}N {yields} N*(1535) reaction in the large Q{sup 2} region. Starting from the relation between the nucleon and N*(1535) systems, the N*(1535) valence quark wave function is determined without the addition of any parameters. The model is then used to calculate the {gamma}N {yields} N*(1535) transition form factors. A very interesting, useful relation between the A{sub 1/2} and S{sub 1/2} helicity amplitudes for Q{sup 2} > GeV{sup 2}, is also derived.
Date: April 1, 2012
Creator: G. Ramalho, M.T. Pena, K. Tsushima
Object Type: Article
System: The UNT Digital Library
Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring (open access)

Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.
Date: April 10, 2012
Creator: Byrd, J.; De Santis, S.; Sonnad, K.; Caspers, F.; Kroyer, T.; Krasnykh, A. et al.
Object Type: Article
System: The UNT Digital Library
An Assessment of Energy Potential at Non-Powered Dams in the United States (open access)

An Assessment of Energy Potential at Non-Powered Dams in the United States

fleet by 15%. A majority of this potential is concentrated in just 100 NPDs, which could contribute approximately 8 GW of clean, reliable hydropower; the top 10 facilities alone could add up to 3 GW of new hydropower. Eighty-one of the 100 top NPDs are U.S. Army Corps of Engineers (USACE) facilities, many of which, including all of the top 10, are navigation locks on the Ohio River, Mississippi River, Alabama River, and Arkansas River, as well as their major tributaries. This study also shows that dams owned by the U.S. Bureau of Reclamation hold the potential to add approximately 260 MW of capacity; the Bureau has also engaged in an effort to conduct a more detailed evaluation of its own facilities.
Date: April 1, 2012
Creator: Hadjerioua, Boualem; Wei, Yaxing & Kao, Shih-Chieh
Object Type: Report
System: The UNT Digital Library
Resolving Lifshitz Horizons (open access)

Resolving Lifshitz Horizons

Via the AdS/CFT correspondence, ground states of field theories at finite charge density are mapped to extremal black brane solutions. Studies of simple gravity + matter systems in this context have uncovered wide new classes of extremal geometries. The Lifshitz metrics characterizing field theories with non-trivial dynamical critical exponent z {ne} 1 emerge as one common endpoint in doped holographic toy models. However, the Lifshitz horizon exhibits mildly singular behaviour - while curvature invariants are finite, there are diverging tidal forces. Here we show that in some of the simplest contexts where Lifshitz metrics emerge, Einstein-Maxwell-dilaton theories, generic corrections lead to a replacement of the Lifshitz metric, in the deep infrared, by a re-emergent AdS{sub 2} x R{sup 2} geometry. Thus, at least in these cases, the Lifshitz scaling characterizes the physics over a wide range of energy scales, but the mild singularity is cured by quantum or stringy effects.
Date: April 24, 2012
Creator: Harrison, Sarah; Kachru, Shamit; Wang, Huajia & /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC
Object Type: Report
System: The UNT Digital Library
Search for the Z_1(4050)^+ and Z_2(4250)^+ States in bar B^0 to chi_{c1} K^- pi^+ and B^+ to chi_{c1} K^0_S pi^+ (open access)

Search for the Z_1(4050)^+ and Z_2(4250)^+ States in bar B^0 to chi_{c1} K^- pi^+ and B^+ to chi_{c1} K^0_S pi^+

We search for the Z{sub 1}(4050){sup +} and Z{sub 2}(4250){sup +} states, reported by the Belle Collaboration, decaying to {chi}{sub c1}{pi}{sup +} in the decays {bar B}{sup 0} {yields} {chi}{sub c1}K{sup -}{pi}{sup +} and B{sup +} {yields} {chi}{sub c1}K{sub S}{sup 0}{pi}{sup +} where {chi}{sub c1} {yields} J/{psi}{gamma}. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e{sup +}e{sup -} collider operating at center-of-mass energy 10.58 GeV, and correspond to an integrated luminosity of 429 fb{sup -1}. In this analysis, we model the background-subtracted, efficiency-corrected {chi}{sub c1}{pi}{sup +} mass distribution using the K{pi} mass distribution and the corresponding normalized K{pi} Legendre polynomial moments, and then test the need for the inclusion of resonant structures in the description of the {chi}{sub c1}{pi}{sup +} mass distribution. No evidence is found for the Z{sub 1}(4050){sup +} and Z{sub 2}(4250){sup +} resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes.
Date: April 10, 2012
Creator: Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M. et al.
Object Type: Article
System: The UNT Digital Library
National Energy and Cost Savings for New Single- and Multifamily Homes: A Comparison of the 2006, 2009, and 2012 Editions of the IECC (open access)

National Energy and Cost Savings for New Single- and Multifamily Homes: A Comparison of the 2006, 2009, and 2012 Editions of the IECC

The 2009 and 2012 International Energy Conservation Code (IECC) yield positive benefits for U.S. homeowners and significant energy savings for the nation. Moving from a baseline of the 2006 IECC to the 2009 IECC reduces average annual energy costs by 10.8%, while moving from the same baseline to the 2012 IECC reduces them by 32.1%. These reductions amount to annual energy cost savings of $168 and $497, respectively. The 2012 IECC saves $329 in energy costs compared to the 2009 IECC.
Date: April 1, 2012
Creator: Lucas, Robert G.; Taylor, Zachary T.; Mendon, Vrushali V. & Goel, Supriya
Object Type: Report
System: The UNT Digital Library
General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes (open access)

General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fields. Firstly, for toroidal field models and BHs with high enough |a/M|, coherent large-scale (i.e. >> H) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate transient relativistic jets. Secondly, for poloidal field models, poloidal magnetic flux readily accretes through the disk from large radii and builds-up to a natural saturation point near the BH. While models with |H/R| {approx} 1 and |a/M| {le} 0.5 do not launch jets due to quenching by mass infall, for sufficiently high |a/M| or low |H/R| the polar magnetic field compresses the inflow into a geometrically thin highly non-axisymmetric 'magnetically choked accretion flow' (MCAF) within which the standard linear magneto-rotational instability is suppressed. The condition of a highly-magnetized state over most of the horizon is optimal for the Blandford-Znajek mechanism that generates persistent relativistic jets with …
Date: April 26, 2012
Creator: McKinney, Jonathan C.; Tchekhovskoy, Alexander & Blandford, Roger D.
Object Type: Article
System: The UNT Digital Library
Integrating Variable Renewable Energy in Electric Power Markets: Best Practices from International Experience, Summary for Policymakers (open access)

Integrating Variable Renewable Energy in Electric Power Markets: Best Practices from International Experience, Summary for Policymakers

Many countries -- reflecting very different geographies, markets, and power systems -- are successfully managing high levels of variable renewable energy on the electric grid, including that from wind and solar energy. This document summarizes policy best practices that energy ministers and other stakeholders can pursue to ensure that electricity markets and power systems can effectively coevolve with increasing penetrations of variable renewable energy. There is no one-size-fits-all approach; each country studied has crafted its own combination of policies, market designs, and system operations to achieve the system reliability and flexibility needed to successfully integrate renewables. Notwithstanding this diversity, the approaches taken by the countries studied all coalesce around five strategic areas: lead public engagement, particularly for new transmission; coordinate and integrate planning; develop rules for market evolution that enable system flexibility; expand access to diverse resources and geographic footprint of operations; and improve system operations. This study also emphatically underscores the value of countries sharing their experiences. The more diverse and robust the experience base from which a country can draw, the more likely that it will be able to implement an appropriate, optimized, and system-wide approach.
Date: April 1, 2012
Creator: Cochran, J.; Bird, L.; Heeter, J. & Arent, D. A.
Object Type: Report
System: The UNT Digital Library
FATIGUE LIFE PREDICTION FOR STEELS IN PULSATING IRRADIATED SYSTEMS (open access)

FATIGUE LIFE PREDICTION FOR STEELS IN PULSATING IRRADIATED SYSTEMS

None
Date: April 29, 2012
Creator: Farmer, J C; Kramer, K. J. & Williams, D. J.
Object Type: Report
System: The UNT Digital Library
Application of the BISON Fuel Performance Code to the FUMEX-III Coordinated Research Project (open access)

Application of the BISON Fuel Performance Code to the FUMEX-III Coordinated Research Project

INL recently participated in FUMEX-III, an International Atomic Energy Agency sponsored fuel modeling Coordinated Research Project. A main purpose of FUMEX-III is to compare code predictions to reliable experimental data. During the same time period, the INL initiated development of a new multidimensional (2D and 3D) multiphysics nuclear fuel performance code called BISON. Interactions with international fuel modeling researchers via FUMEX-III played a significant and important role in the BISON evolution, particularly influencing the selection of material and behavioral models which are now included in the code. BISON's ability to model integral fuel rod behavior did not mature until 2011, thus the only FUMEX-III case considered was the Riso3-GE7 experiment, which includes measurements of rod outer diameter following pellet clad mechanical interaction (PCMI) resulting from a power ramp late in fuel life. BISON comparisons to the Riso3-GE7 final rod diameter measurements are quite reasonable. The INL is very interested in participation in the next Fuel Modeling Coordinated Research Project and would like to see the project initiated as soon as possible.
Date: April 1, 2012
Creator: Williamson, R. L. & Novascone, S. R.
Object Type: Report
System: The UNT Digital Library
Annual Performance Evaluation of a Pair of Energy Efficient Houses (WC3 and WC4) in Oak Ridge, TN (open access)

Annual Performance Evaluation of a Pair of Energy Efficient Houses (WC3 and WC4) in Oak Ridge, TN

Beginning in 2008, two pairs of energy-saver houses were built at Wolf Creek in Oak Ridge, TN. These houses were designed to maximize energy efficiency using new ultra-high-efficiency components emerging from ORNL s Cooperative Research and Development Agreement (CRADA) partners and others. The first two houses contained 3713 square feet of conditioned area and were designated as WC1 and WC2; the second pair consisted of 2721 square feet conditioned area with crawlspace foundation and they re called WC3 and WC4. This report is focused on the annual energy performance of WC3 and WC4, and how they compare against a previously benchmarked maximum energy efficient house of a similar footprint. WC3 and WC4 are both about 55-60% more efficient than traditional new construction. Each house showcases a different envelope system: WC3 is built with advanced framing featured cellulose insulation partially mixed with phase change materials (PCM); and WC4 house has cladding composed of an exterior insulation and finish system (EIFS). The previously benchmarked house was one of three built at the Campbell Creek subdivision in Knoxville, TN. This house (CC3) was designed as a transformation of a builder house (CC1) with the most advanced energy-efficiency features, including solar electricity and hot …
Date: April 1, 2012
Creator: Biswas, Kaushik; Christian, Jeffrey E; Gehl, Anthony C; Jackson, Roderick K & Boudreaux, Philip R
Object Type: Report
System: The UNT Digital Library
Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint (open access)

Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint

As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.
Date: April 1, 2012
Creator: Stynes, J. K. & Ihas, B.
Object Type: Article
System: The UNT Digital Library
Deeply Virtual Compton Scattering and Meson Production at Jlab/CLAS (open access)

Deeply Virtual Compton Scattering and Meson Production at Jlab/CLAS

This report reviews the recent experimental results from the CLAS collaboration (Hall B of Jefferson Lab, or JLab) on Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) and discusses their interpretation in the framework of Generalized Parton Distributions (GPDs). The impact of the experimental data on the applicability of the GPD mechanism to these exclusive reactions is discussed. Initial results obtained from JLab 6 GeV data indicate that DVCS might already be interpretable in this framework while GPD models fail to describe the exclusive meson production (DVMP) data with the GPD parameterizations presently used. An exception is the {phi} meson production for which the GPD mechanism appears to apply. The recent global analyses aiming to extract GPDs from fitting DVCS CLAS and world data are discussed. The GPD experimental program at CLAS12, planned with the upcoming 12 GeV upgrade of JLab, is briefly presented.
Date: April 1, 2012
Creator: Jo, Hyon-Suk
Object Type: Article
System: The UNT Digital Library
Clean Firetube Boiler Waterside Heat Transfer Surfaces, Energy Tips: STEAM, Steam Tip Sheet #7 (Fact Sheet) (open access)

Clean Firetube Boiler Waterside Heat Transfer Surfaces, Energy Tips: STEAM, Steam Tip Sheet #7 (Fact Sheet)

A steam energy tip sheet for the Advanced Manufacturing Office (AMO). The prevention of scale formation in firetube boilers can result in substantial energy savings. Scale deposits occur when calcium, magnesium, and silica, commonly found in most water supplies, react to form a continuous layer of material on the waterside of the boiler heat exchange tubes. Scale creates a problem because it typically possesses a thermal conductivity, an order of magnitude less than the corresponding value for bare steel. Even thin layers of scale serve as an effective insulator and retard heat transfer. The result is overheating of boiler tube metal, tube failures, and loss of energy efficiency. Fuel consumption may increase by up to 5% in firetube boilers because of scale. The boilers steam production may be reduced if the firing rate cannot be increased to compensate for the decrease in combustion efficiency. Energy losses as a function of scale thickness and composition are given. Any scale in a boiler is undesirable. The best way to deal with scale is not to let it form in the first place. Prevent scale formation by: (1) Pretreating of boiler makeup water (using water softeners, demineralizers, and reverse osmosis to remove scale-forming …
Date: April 1, 2012
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Marine Hydrokinetic Turbine Power-Take-Off Design for Optimal Performance and Low Impact on Cost-of-Energy: Preprint (open access)

Marine Hydrokinetic Turbine Power-Take-Off Design for Optimal Performance and Low Impact on Cost-of-Energy: Preprint

Marine hydrokinetic devices are becoming a popular method for generating marine renewable energy worldwide. These devices generate electricity by converting the kinetic energy of moving water, wave motion or currents, into electrical energy through the use of a Power-Take-Off (PTO) system. Most PTO systems incorporate a mechanical or hydraulic drive train, power generator and electric control/conditioning system to deliver the generated electric power to the grid at the required state. Like wind turbine applications, the PTO system must be designed for high reliability, good efficiency, and long service life with reasonable maintenance requirements, low cost and an appropriate mechanical design for anticipated applied steady and unsteady loads. The ultimate goal of a PTO design is high efficiency, low maintenance and cost with a low impact on the device Cost-of-Energy (CoE).
Date: April 1, 2012
Creator: Beam, M.; Kline, B.; Elbing, B.; Straka, W.; Fontaine, A.; Lawson, M. et al.
Object Type: Article
System: The UNT Digital Library
Investigating the Influence of the Added Mass Effect to Marine Hydrokinetic Horizontal-Axis Turbines Using a General Dynamic Wake Wind Turbine Code: Preprint (open access)

Investigating the Influence of the Added Mass Effect to Marine Hydrokinetic Horizontal-Axis Turbines Using a General Dynamic Wake Wind Turbine Code: Preprint

This paper describes a recent study to investigate the applicability of a horizontal-axis wind turbine (HAWT) structural dynamics and unsteady aerodynamics analysis program (FAST and AeroDyn respectively) to modeling the forces on marine hydrokinetic (MHK) turbines. It summarizes the added mass model that has been added to AeroDyn. The added mass model only includes flow acceleration perpendicular to the rotor disc, and ignores added mass forces caused by blade deflection. A model of the National Renewable Energy Laboratory's (NREL) Unsteady Aerodynamics Experiment (UAE) Phase VI wind turbine was analyzed using FAST and AeroDyn with sea water conditions and the new added mass model. The results of this analysis exhibited a 3.6% change in thrust for a rapid pitch case and a slight change in amplitude and phase of thrust for a case with 30 degrees of yaw.
Date: April 1, 2012
Creator: Maniaci, D. C. & Li, Y.
Object Type: Article
System: The UNT Digital Library
The Application of Traits-Based Assessment Approaches to Estimate the Effects of Hydroelectric Turbine Passage on Fish Populations (open access)

The Application of Traits-Based Assessment Approaches to Estimate the Effects of Hydroelectric Turbine Passage on Fish Populations

One of the most important environmental issues facing the hydropower industry is the adverse impact of hydroelectric projects on downstream fish passage. Fish that migrate long distances as part of their life cycle include not only important diadromous species (such as salmon, shads, and eels) but also strictly freshwater species. The hydropower reservoirs that downstream-moving fish encounter differ greatly from free-flowing rivers. Many of the environmental changes that occur in a reservoir (altered water temperature and transparency, decreased flow velocities, increased predation) can reduce survival. Upon reaching the dam, downstream-migrating fish may suffer increased mortality as they pass through the turbines, spillways and other bypasses, or turbulent tailraces. Downstream from the dam, insufficient environmental flow releases may slow downstream fish passage rates or decrease survival. There is a need to refine our understanding of the relative importance of causative factors that contribute to turbine passage mortality (e.g., strike, pressure changes, turbulence) so that turbine design efforts can focus on mitigating the most damaging components. Further, present knowledge of the effectiveness of turbine improvements is based on studies of only a few species (mainly salmon and American shad). These data may not be representative of turbine passage effects for the hundreds …
Date: April 1, 2012
Creator: Cada, Glenn F & Schweizer, Peter E
Object Type: Report
System: The UNT Digital Library