bluuebunny/crossref_metadata_2025_split huggingface dataset:
Data Management for a Large-Scale Smart Grid Demonstration Project in Austin, Texas
Authors: Nagasawa Kazunori , Upshaw Charles R. , Rhodes Joshua D. , Holcomb Chris L. , Walling David A. , Webber Michael E. 
Published: July 2013

This paper presents a data management scheme for the Pecan Street smart grid demonstration project in Austin, Texas. In this project, highly granular data with 15-second resolution on resource generation and consumption, including total consumption of electricity, water, and natural gas and solar generation, are collected for more than 100 homes. Furthermore, this testbed, see Figure 1, of homes represents the nation’s highest density of rooftop solar PV and electric vehicles, and includes a substantial subset of homes that are highly instrumented with meters on up to 6 sub-circuits in addition to the whole-home meter. Consequently, this demonstration project generates a one-of-a-kind dataset with excellent temporal and geographic fidelity.
One consequence of this extensive dataset is that there are hundreds of parallel data streams that need to be remotely (wirelessly) collected, filtered, processed, managed, stored and analyzed to be useful for researchers. Cumulatively, they represent 100s of gigabytes of data after just a few months of collection, which represents a formidable barrier to conducting research.
In partnership with the Texas Advanced Computing Center (TACC), which is an NSF-sponsored cluster of supercomputers at UT-Austin, a data collection and management scheme has been developed. For storing the data, we have built a single column oriented database that so far has shown tremendous performance benefits. This paper shows the data schema, an example of MySQL query, and a developed program for rapid and automated data extraction, analysis and display. We expect that the findings of this work will be beneficial to researchers interested in grid-scale data management.
Estimating Atmospheric Attenuation in Central Receiver Systems
Authors: Sengupta Manajit , Wagner Michael 
Published: July 2013

Atmospheric attenuation loss between a heliostat field and receiver has been recognized as a significant source of loss in Central Receiver System. Methods that can improve estimation of attenuation loss using available measurements will be useful in reducing uncertainty in estimation of CSP plant production, particularly in locations and climates that differ in atmospheric composition from typical arid desert locations. In clear sky situations, Direct Normal Irradiance (DNI) is primarily impacted by aerosols in the atmosphere. Aerosols extinct direct radiation with the photons either being absorbed or scattered based on the aerosols optical characteristics. As aerosol loading is high close to the surface, the attenuation loss between heliostat and receivers is significantly influenced by amount of aerosols present on a particular day. The purpose of the study is to understand the impact of aerosols on attenuation loss and model this loss as a function of the ratio of measured DNI to a calculated DNI for an “aerosol-free” atmosphere. The assumption here is that the reduction in clear sky DNI due to aerosols when compared to a theoretical “clean environment” value can provide valuable information about aerosol loading at the surface and therefore attenuation loss between heliostat and receiver. Preliminary analysis shows that such an approach is viable.
Historically, human observers have measured visibility on a daily basis. While these observations are subject to varying levels of uncertainty they may be a good indicator of atmospheric attenuation between heliostat and receiver. In this paper we will review historical and recent publications to show how visibility observations contain useful information for estimating attenuation loss in central receiver systems. We will also present a simple relationship that uses visibility observations to estimate heliostat to receiver attenuation for varying separation distances.
Finite Element Modeling of Parabolic Trough Mirror Shape in Different Mirror Angles
Authors: Meiser Siw , Kleine-Büning Christoph , Uhlig Ralf , Lüpfert Eckhard , Schiricke Björn , Pitz-Paal Robert 
Published: July 2013

Deviations from the ideal shape of reflector panels for parabolic trough solar power plants have relevant impact on field efficiency and thus on the performance of the whole power plant. Analyzing the gravity-induced deformation of mirror shape for different mirror angles is relevant for performance calculation of solar parabolic trough collectors and identifying optimization potential of the mirror panels.
Two mirror model versions (stiff and elastic supports) are evaluated in four angles: in horizontal laboratory angle (mirrors facing upward with mounting points horizontally aligned), and in 0°, 45° and 90° collector angle. The resulting slope maps are calculated in a separate post-processing.
In order to evaluate the effect of gravity load on mirror shape, the deformed mirror in each evaluated angle is compared to the non-deformed mirror shape, and to the shapes in 0° (zenith) collector angle, respectively. The resulting slope deviation maps show the mirror deformation in different mirror angles. Stiffness of the mounting to the support structure has a relevant impact. Mirror deformation on elastic brackets (SDx up to 1.6 mrad) is much more pronounced than on an ideal stiff support structure (SDx up to 1.0 mrad).
Deriving Cloud Velocity From an Array of Solar Radiation Measurements
Authors: Bosch Juan L. , Zheng Yuehai , Kleissl Jan 
Published: July 2013

Spatio-temporal variability of solar radiation is the main variable affecting the photovoltaic power feed-in to the grid. Clouds are the main source of such variability and their velocity is a principal input to most short-term forecast models. The main goal in this study is to estimate cloud speed using radio-metric data using measurements from 8 sensors located at the UC San Diego Solar Energy test bed.
Two different methods were developed to estimate the cloud speed based on the correlation between the signals from different sensors. Our analysis showed good agreement between both methods. Additional measurements from nearby METAR and radiosonde stations also show comparable results. Both methods require high variability in the input radiation.
Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury
Authors: Wendel Mark , Riemer Bernard , Abdou Ashraf 
Published: July 2013

Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic.
Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations.
After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions.
The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into an actual SNS target.
Surface Tension Model for Particle Method Using Inter-Particle Force Derived From Potential Energy
Authors: Ishii Eiji , Sugii Taisuke 
Published: July 2013

Fluid-flow simulation within micro/nano spaces is essential for designing micro/nano devices, such as those in micro-electro-mechanical systems and nanoimprint processes. Surface tension is a dominant force in the fluid flow within micro/nano spaces. Surface-tension models can be classified into two groups: models based on continuous surface force in immiscible phases, and models based on inter-particle force in miscible phases. The surface-tension model based on inter-particle force for modeling interactions between materials would fit fluid-flow simulation within micro/nano spaces better than the surface-tension model based on continuous surface force.
We developed a surface tension model using inter-particle force for use with a particle method in a past study. However, workings of inter-particle forces in miscible phases were not verified. Furthermore, accuracy in three-dimensional simulation needed to be verified. These subjects were verified in this study using simple benchmark tests. First, cohesion based on potential energy was validated to qualitatively check the workings of inter-particle force. The phase separation from the mixed two-phase flow due to inter-particle force was simulated. Next, the inter-particle force at the gas-liquid interface was quantitatively verified using the theory of the Young-Laplace equation; the pressure in a droplet was compared in two- and three-dimensional simulations, and the predicted pressures in a droplet agreed well with this theory. The inter-particle force at the gas-liquid-solid interface for the wall adhesion of a droplet was also verified; the results for wall adhesion in three-dimensional space agreed much better than that in two-dimensional space. We found that our surface tension model was useful for simulating the fluid flow within micro/nano spaces.
CFD Simulation of Particle Transport and Dispersion in Indoor Environment by Human Walking
Authors: Goldasteh Iman , Ahmadi Goodarz , Ferro Andrea 
Published: July 2013

Particle resuspension is an important source of particulate matter in indoor environments that significantly affects the indoor air quality and could potentially have adverse effect on human health. Earlier efforts to investigate indoor particle resuspension hypothesized that high speed airflow generated at the floor level during the gate cycle is the main cause of particle resuspension. The resuspended particles are then assumed to be dispersed by the airflow in the room, which is impacted by both the ventilation and the occupant movement, leading to increased PM concentration.
In this study, a three dimensional model of a room was developed using FLUENT™ CFD package. A RANS approach with the RNG k-ε turbulence model was used for simulating the airflow field in the room for different ventilation conditions. The trajectories of resuspended particulate matter were computed with a Lagrangian method by solving the equations of particle motion. The effect of turbulent dispersion was included with the use of the eddy lifetime model. The resuspension of particles due to gait cycle was estimated and included in the computational model. The dispersion and transport of particles resuspended from flooring as well as particle re-deposition on flooring and walls were simulated. Particle concentrations in the room generated by the resuspension process were evaluated and the results were compared with experimental chamber study data as well as simplified model predictions, and good agreement was found.
Improvement of Axial-Flow Pump Part Load Behavior by a Double Inlet Nozzle
Authors: Dohmen Hans Josef , Benra Friedrich-Karl , Brinkhorst Sven 
Published: July 2013

In highly loaded axial flow pumps considerable changes of the flow structures are known when lowering the flow rate from design point operation to part load operation. After the stall inception the backward tip flow increases in axial and radial direction upstream of the impeller forming the part load “vortex B”.
The backflow has a strong co-swirl, which is transmitted to the inlet flow. This leads to less Euler work and often to a drop of pump head. To overcome these negative effects of the stall, a so called double inlet nozzle can be used. At the University of Braunschweig this device is investigated experimentally. In this contribution the time dependent three dimensional flow fields have been numerically investigated by unsteady Reynolds averaged Navier-Stokes simulations.
The geometry of the test stand, the geometry of the numerical model and the used meshes are described. The experimental results and the numerical obtained results are compared to each other. First the measured overall performance characteristic is compared to the numerical results obtained by averaging the head and the efficiency over the last computed impeller revolution. In addition the numerical obtained flow field upstream of the inlet nozzle is compared to flow fields measured in Braunschweig by PIV method. Also the flow field is shown in regions of the pump which are not accessible by experimental methods.
Based on these results the shape of the double inlet nozzle is varied in different ways. The influence of the modifications on the flow field and the part load behavior of the pump is displayed and discussed.
Experimental Investigation of Falling Liquid Film in Vertical Downward Two-Phase Pipe Flow
Authors: Lopez Jose M. , Mohan Ram , Shoham Ovadia , Wang Shoubo , Kouba Gene 
Published: July 2013

In this research the hydrodynamics of falling liquid film in a vertical downward two-phase flow (liquid-gas) is experimentally studied.
The 4 inch clear PVC test section is 6.1 meters long, with a length to diameter ratio (L/D) of 64. The fluids utilized are compressed air, water, Conosol mineral oil (light oil) and Drake mineral oil (heavy oil). The superficial liquid velocities tested range from 12 to 72 cm/s while the superficial gas velocities range from 0.2 to 29 cm/s. The vertical facility is equipped with the state-of-the-art instrumentation for two-phase flow measurements, the capacitance Wire-Mesh Sensor (WMS), allowing two-phase flow measurements with conducting and non conducting fluids.
Experimental results show that the liquid film thickness has a quasi-linear relationship with the superficial liquid velocity for the air-water case. For the air-oil cases, at superficial liquid velocities higher than 50 cm/s, the liquid film thickness trend is affected by the liquid droplet entrainment. Furthermore, it was found that the liquid droplet entrainment increases as the superficial liquid velocity increases or the surface tension decreases. Details of the liquid droplets traveling in the gas core, wave formation, wave breakup and film thickness evolution are observed in the WMS phase reconstruction.
Statistical Procedure to Obtain Accurate Time-Resolved Measurements in Turbomachinery Environments Using Fast-Response Probes
Authors: Fernández Oro Jesús Manuel , Argüelles Díaz Katia María , Rodríguez Lastra María , Galdo Vega Mónica 
Published: July 2013

Fast-response probes in multistage turbomachinery are typically used to measure unsteady flows and turbulence in a number of traverse locations throughout the machine (rotor-stator inter-regions, inlet and outlet sections, tip clearance gaps…). When used intensively, they provide complete information of time-resolved flow structures, including wake patterns, wake mixing, wake-wake and rotor-wake interactions or turbulence transport in 2D planes and even 3D pictures if the raw signals are post-processed accurately.
The segregation between deterministic, unsteady features and turbulent scales is essential to understand the unsteady mechanisms responsible for the energy transfer and requires an accurate selection of the sampling frequencies and the total length of the measured traces to assure a valid statistical reduction. Similar considerations must be made if they are filtered in a frequency basis (for example, filtering low-scale turbulence or extracting only BPF components), employing well-designed periodograms or power spectra with minimum scatter and large periods of time integration.
This work presents the general guidelines that any statistical procedure must follow to assure that phase-locked averaging results are consistent when applied to velocity signals in multistage turbomachinery. The procedure is established in terms of convergence (residuals) and coherence (error) between time-resolved traces retrieved using different sampling frequencies and number of total samples. The possible effects of three-dimensionality, the measured regions (hub, tip, midspan) or the sensibility to turbulence levels is also explored.
The proposed methodology is applied to a low-speed axial fan, so a concise survey of usual practices employed by other authors in the literature is firstly reviewed, in order to identify fundamental parameters and values typically adopted to guarantee convergence. Finally, recommendations are made as a function of the variable analysed, the wake pattern to be described or the global disorder of the flow structures inside axial flow fans.
Thermal Management of an Air-Cooled PEM Fuel Cell: Cell Level Simulation
Authors: Andisheh Tadbir M. , Shahsavari S. , Bahrami M. , Kjeang E. 
Published: July 2013

Air-cooled polymer electrolyte membrane (PEM) fuel cells have recently been the center of attention mainly because of the simplicity they bring into the fuel cell industry. Their main advantage is the elimination of balance-of-plant subsystems such as the liquid coolant loop, heat exchanger, compressor, and air humidifier which greatly reduces the complexity, parasitic power, and cost of the overall system. In air-cooled fuel cells, air is used as a combined oxidant and coolant. However, the net power output is limited by the heat rejection rate and the overall performance and durability are restricted by high temperature gradients during stack operation. An important initial step toward this goal is accurate knowledge of the temperature distribution in the stack in order to optimize heat removal by suitable thermal management strategies.
In the present study, a three dimensional numerical model is developed that can predict the temperature distribution in cell level with an acceptable accuracy. Using this methodology, the maximum temperature in the stack as well as temperature gradients, which are two essential operating parameters for air-cooled fuel cells, can be obtained. The model is validated using experimental data for the 1020ACS fuel cell stack from Ballard Power Systems. A parametric study is performed for bipolar plate thermal conductivity and overall thermal characteristics on the cell level to examine the effects of these parameters on the maximum stack temperature, temperature gradient in the cell, and overall heat rejection rate. Based on these results, recommendations are provided for improved thermal design of air-cooled fuel cells.
Dynamic Simulation of a High Temperature Polymer Electrolyte Membrane Fuel Cell: Stack Performance
Authors: Rabiu Ademola , Nomnqa Myalelo , Ikhuomoregbe Daniel 
Published: July 2013

One of the attractions of high temperature polymer electrolyte membrane (PEM) fuel cell is the quality of the heat co-produced with power that could be recovered for use in a combined heat and power system. In this study, a one-dimensional model for a single PEM fuel cell was developed and implemented in Engineering Equations Solver (EES) environment to express the cell voltage as a function of current density among others. The single cell model was employed to investigate the energetic behaviour of a 1 kWe high temperature PEM fuel cell stack system, and the corresponding power and thermal efficiencies at different operating modes. A multiple parametric analyses using the built-in EES uncertainty propagation tool was used to determine the stack performance for the selected parameter range. The influence of the stack operating temperature, hydrogen utilization, the carbon monoxide content in the anode gas feed and the current density, on the efficiency of the fuel cell stack were studied at the required stack electrical output.
The study showed that an increase in temperature increased the stack electrical power output whilst the thermal output decreased. The stack electrical power output was seen to increase with increase in the current density and hydrogen stoichiometry. It can be seen that ratio between the electrical power and thermal output increased as the current density increases. This ratio becomes unity at an operating current density of 0.3 A/cm2, representing the optimal operating current density of the stack. An increase in the hydrogen utilization has positive effects on both the cogeneration and thermal efficiency.
Hydrogen Generation Optimization in a Hybrid Photovoltaic-Electrolyzer Using Intelligent Techniques
Authors: Maroufmashat Azadeh , Seyyedyn Farid , Roshandel Ramin , Boroushaki Mehrdad 
Published: July 2013

Hydrogen is a flexible energy carrier and storage medium and can be generated by electrolysis of water. In this research, hydrogen generation is maximized by optimizing the optimal sizing and operating condition of an electrolyzer directly connected to a PV module. The method presented here is based on Particle swarm optimization algorithm (PSO). The hydrogen, in this study, was produced using a proton exchange membrane (PEM) electrolyzer. The required power was supplied by a photovoltaic module rated at 80 watt. In order to optimize Hydrogen generation, the cell number of the electrolyser and its activity must be 9 and 3, respectively. As a result, it is possible to closely match the electrolyzer polarization curve to the curve connecting PV system’s maximum power points at different irradiation levels.
PSO is a novel method in optimization inspiring from observation of bird flocking and fish schooling. Comparing to other optimization method, not only PSO is more efficient and require lower functions of evaluations, but it leads to better results, as well.
Evaluation of Selective Catalytic Reduction Technology Retrofit for NOx Reduction in Diesel Mining Vehicles
Authors: Rubeli Brent , Gangal Mahe , Hardcastle Stephen , Caravaggio Gianni 
Published: July 2013

Two heavy-duty diesel vehicles operating in an underground salt mine were retrofitted with emission control systems based on selective catalytic reduction technology. The vehicles were then released for production in the mine and the emissions were measured periodically over 18 months.
The systems were very effective in reducing oxides of nitrogen (NOx) emissions from the diesel vehicle engines. The systems were able to provide NOx reductions of 60% to 65% over typical vehicle duty cycles.
This paper will describe the SCR systems, emissions reductions, operability issues and secondary emissions for both vehicles.