scholarly journals On-Sun Evaluation of the PHLUX Method for Heliostat Beam Characterization

Author(s):  
Julius Yellowhair ◽  
Clifford K. Ho

Flux distributions from solar field collectors are typically evaluated using a beam characterization system, which consists of a digital camera with neutral density filters, flux gauge or calorimeter, and water-cooled Lambertian target panel. The pixels in camera image of the flux distribution are scaled by the flux peak value measured with the flux gauge or the total power value measured with the calorimeter. An alternative method, called PHLUX developed at Sandia National Laboratories, can serve the same purpose using a digital camera but without auxiliary instrumentation. The only additional information required besides the digital images recorded from the camera are the direct normal irradiance, an image of the sun using the same camera, and the reflectivity of the receiver or target panel surface. The PHLUX method was evaluated using two digital cameras (Nikon D90 and D3300) at different flux levels on a target panel. The performances of the two cameras were compared to each other and to measurements from a Kendall radiometer. For consistency in comparison of the two cameras, the same focal length lenses and same number of neutral density filters were used. Other camera settings (e.g., shutter speed, f-stop, etc.) were set based on the aperture size and performance of the cameras. The Nikon D3300 has twice the number of pixels as the D90. D3300 provided higher resolution, however, due to the smaller pixel sizes the images were noisier, and the D90 with larger pixels had better response to low light levels. The noise in the D3300, if not corrected, could result in gross overestimation of the irradiance calculations. After corrections to the D3300 flux images, the PHLUX results from the two cameras showed they agreed to within 8% for a peak flux level of 1000 suns on the target, and less than 10% error in the peak flux when compared to the Kendall radiometer.

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Clifford K. Ho ◽  
Siri S. Khalsa

A new method is described to determine irradiance distributions on receivers and targets from heliostats or other collectors for concentrating solar power applications. The method uses a digital camera, and, unlike previous beam characterization systems, it does not require additional sensors, calorimeters, or flux gauges on the receiver or target. In addition, spillage can exist and can also be measured (the beam does not need to be contained within the target). The only additional information required besides the images recorded from the digital camera is the direct normal irradiance and the reflectivity of the receiver. Methods are described to calculate either an average reflectivity or a reflectivity distribution for the receiver using the digital camera. The novel feature of this new photographic flux (PHLUX) mapping method is the use of recorded images of the sun to scale both the magnitude of each pixel value and the subtended angle of each pixel. A test was performed to evaluate the PHLUX method using a heliostat beam on the central receiver tower at the National Solar Thermal Test Facility in Albuquerque, NM. Results showed that the PHLUX method was capable of producing an accurate flux map of the heliostat beam on a Lambertian surface with a relative error in the peak flux of ∼2% when the filter attenuation factors and effective receiver reflectivity were well characterized. Total relative errors associated with the measured irradiance using the PHLUX method can be up to 20%–40%, depending on various error sources identified in the paper, namely, uncertainty in receiver reflectivity and filter attenuation.


Author(s):  
Clifford K. Ho ◽  
Siri S. Khalsa

A new method is described to determine irradiance distributions on receivers and targets from heliostats or other collectors for concentrating solar power applications. The method uses a CCD camera, and, unlike previous beam characterization systems, it does not require additional sensors, calorimeters, or flux gauges on the receiver or target. In addition, spillage can exist (the beam does not need to be contained within the target). The only additional information required besides the digital images recorded from the CCD camera is the direct normal irradiance and the reflectivity of the receiver. Methods are described to calculate either an average reflectivity or a reflectivity distribution for the receiver using the CCD camera. The novel feature of this new PHLUX method is the use of recorded images of the sun to scale both the magnitude of each pixel value and the subtended angle of each pixel. A test was performed to evaluate the PHLUX method using a heliostat beam on the central receiver tower at the National Solar Thermal Test Facility in Albuquerque, NM. Results showed that the PHLUX method was capable of producing an accurate flux map of the heliostat beam with a relative error in the peak flux of 2%.


2013 ◽  
Vol 19 (4) ◽  
pp. 711-728 ◽  
Author(s):  
Naci Yastikli ◽  
Esra Guler

Thermographic cameras record temperatures emitted by objects in the infrared region. These thermal images can be used for texture analysis and deformation caused by moisture and isolation problems. For accurate geometric survey of the deformations, the geometric calibration and performance evaluation of the thermographic camera should be conducted properly. In this study, an approach is proposed for the geometric calibration of the thermal cameras for the geometric survey of deformation caused by moisture. A 3D test object was designed and used for the geometric calibration and performance evaluation. The geometric calibration parameters, including focal length, position of principal point, and radial and tangential distortions, were determined for both the thermographic and the digital camera. The digital image rectification performance of the thermographic camera was tested for photogrammetric documentation of deformation caused by moisture. The obtained results from the thermographic camera were compared with the results from digital camera based on the experimental investigation performed on a study area.


2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Xiang Li ◽  
Jianzheng Liu ◽  
Jessica Baron ◽  
Khoa Luu ◽  
Eric Patterson

AbstractRecent attention to facial alignment and landmark detection methods, particularly with application of deep convolutional neural networks, have yielded notable improvements. Neither these neural-network nor more traditional methods, though, have been tested directly regarding performance differences due to camera-lens focal length nor camera viewing angle of subjects systematically across the viewing hemisphere. This work uses photo-realistic, synthesized facial images with varying parameters and corresponding ground-truth landmarks to enable comparison of alignment and landmark detection techniques relative to general performance, performance across focal length, and performance across viewing angle. Recently published high-performing methods along with traditional techniques are compared in regards to these aspects.


2015 ◽  
Author(s):  
William A. Hockberger

The Quadrimaran was invented in France in the mid-1980s by Daniel Tollet. It was an inspired design and a radical departure from traditional ship design by a man from outside the marine industry unconstrained by industry technical practices and education. Technical experts could see it would entail more structure and subsystems than other high-performance vessels, but its promise was that those penalties would be more than offset by its claimed low power and fuel consumption. A prototype/demonstrator, Alexander, was built in 1990 and operated for five years carrying and impressing many hundreds of riders. Alexander performed beautifully and appeared to bear out what was claimed. Contracts for several Quadrimarans of different sizes came quickly, especially considering how conservative an industry this is. That was significantly due to Tollet's personal charisma and skill in selling riders on the dream of carrying passengers and freight over the water fast and in comfort, yet economically. Great skepticism prevailed in some quarters, especially among naval architects knowledgeable about AMVs (advanced marine vehicles) and early-stage whole-ship design. At technical meetings, one Quadrimaran principal would comment, for example, "Why would you carry freight across the Atlantic at 38 knots on 230,000 horsepower (a reference to the planned Fastship Atlantic TG-770) when you could do it at 60 knots on only 65,000 horsepower?" Listeners would ask how this could be possible, and he would assert again that the Quadrimaran could do it, but would decline to explain. Respected technical people were working with Tollet and his company and becoming convinced of the Quadrimaran's merit. Along with the contracts came engineers with experience in ship detail design and construction (very different from early-stage whole-ship design), or responsibilities for assessing and approving ships for service. Others were with engine and equipment suppliers. Their opinion that there was something unique and special about the Quadrimaran gave it credibility and influenced more people to accept the major claims made for it. Some dismissed the most extreme claims but still accepted the idea that the Quadrimaran was capable of unusually high performance - considerably less than was being claimed, perhaps, but high nevertheless. In hindsight it is clear the skeptics were right. Results never met expectations, nor could they have. In reality, the Quadrimaran has aspects that inherently prevent it from achieving the characteristics and performance its inventor believed attainable. It cannot be built in a commercially useful size and actually perform as intended. Why this is so will be explained. A crucial fact in the Quadrimaran's history is that Daniel Tollet and his close associates believed strongly that naval architects and engineers who had been immersed in working with the existing ship types would be unable to give the Quadrimaran the very different treatment they believed it required. (Their own educations and professional work were nontechnical.) Such people were excluded from the development of Quadrimaran designs, and the belated discovery of many fundamental technical problems can be attributed to this. The company Tollet established had a number of names over the years, and other associated entities were created at times for various purposes. In this paper they are referred to collectively as QIH (Quadrimaran International Holdings) so as not to confuse things unnecessarily. In 2004 QuadTech Marine LLC was established and acquired the Quadrimaran patent (US Patent No. 5,191,849) and related intellectual property from QIH. QuadTech laid out an extensive R&D program to close gaps in the technical background and address identified issues. In the process, additional information on earlier QIH projects and products was obtained and studied, which brought to light problems that significantly compromised the Quadrimaran's prospective performance and utility. The resulting much-reduced set of potential uses and users led the company to effectively stop pursuing Quadrimaran projects after 2009. (Note: The author was Chief Technology Officer for QuadTech Marine during 2006-9, studying the Quadrimaran and planning the R&D.)


2020 ◽  
Vol 15 (4) ◽  
pp. 1-35
Author(s):  
Charilaos Skandylas ◽  
Narges Khakpour ◽  
Jesper Andersson

Modern software systems and their corresponding architectures are increasingly decentralized, distributed, and dynamic. As a consequence, decentralized mechanisms are required to ensure security in such architectures. Decentralized Information Flow Control (DIFC) is a mechanism to control information flow in distributed systems. This article presents and discusses several improvements to an adaptive decentralized information flow approach that incorporates trust for decentralized systems to provide security. Adaptive Trust-Aware Decentralized Information Flow (AT-DIFC + ) combines decentralized information flow control mechanisms, trust-based methods, and decentralized control architectures to control and enforce information flow in an open, decentralized system. We strengthen our approach against newly discovered attacks and provide additional information about its reconfiguration, decentralized control architectures, and reference implementation. We evaluate the effectiveness and performance of AT-DIFC + on two case studies and perform additional experiments and to gauge the mitigations’ effectiveness against the identified attacks.


1986 ◽  
Vol 36 (4) ◽  
pp. 73-76
Author(s):  
Douglas Hensley

Douglas Hensley has been an active chamber musician ever since he took up serious study of the classical guitar. He received bachelor and master's degrees under the direction of David Tanenbaum from the San Francisco Conservatory of Music and he has studied with many other musicians in private lessons and master classes. Over the past ten years he has premiered close to fifty new compositions, performed numerous U.S. premieres and the West Coast premiere of Elliott Carter's “Changes” for solo guitar. For Opus One Records in New York he has recorded Larry Polansky's “Hensley Variations” and David Loeb's “Trois Cansos” with flautist Kenneth Kramer and violist John Casten. He has also recorded a collection of duets with Japanese shakuhachi master Masayuka Koga, “Autumn Mist,” for Fortuna Records of Novato, California. His principal activities are as cofounder (with violist/violinist John Casten) and guitarist of the San Francisco-based contemporary performance ensemble ISKRA, which is made up of flute, clarinet, guitar, violin/viola, doublebass and soprano voice. Anyone with additional information about flute, viola, guitar trios (or other chamber music with guitar), or queries, is urged to contact him at 607-A Frederick St., San Francisco, CA 94117.


1998 ◽  
Vol 4 (S2) ◽  
pp. 750-751
Author(s):  
L. F. Allard ◽  
E. Voelkl ◽  
A. K. Datye ◽  
A. H. Carim

Many nanostructured materials are formed from powder precursors having ultra-fine particle sizes. Techniques of electron microscopy have proven invaluable for characterizing the structure of the precursor materials in order to better understand the fundamental processes that govern consolidation of the materials into the final nanophase structures. In recent years, the rapidly developing technique of electron holography has increasingly been applied for characterizing particle morphologies. The advent of the modern field emission microscope, which offers beam coherency sufficient to produce high contrast interference fringes for optimum hologram formation, and especially the availability of digital camera systems for hologram acquisition and rapid processing have both combined to bring electron holography to the forefront of techniques for characterization of nanostructured materials.Electron holograms typically yield phase images that can give quantitative information on crystal morphologies, but much additional information can result from digital processing of holograms.


2016 ◽  
Vol 9 (7) ◽  
pp. 2533-2547 ◽  
Author(s):  
Rita Nogherotto ◽  
Adrian Mark Tompkins ◽  
Graziano Giuliani ◽  
Erika Coppola ◽  
Filippo Giorgi

Abstract. We implement and evaluate a new parameterization scheme for stratiform cloud microphysics and precipitation within regional climate model RegCM4. This new parameterization is based on a multiple-phase one-moment cloud microphysics scheme built upon the implicit numerical framework recently developed and implemented in the ECMWF operational forecasting model. The parameterization solves five prognostic equations for water vapour, cloud liquid water, rain, cloud ice, and snow mixing ratios. Compared to the pre-existing scheme, it allows a proper treatment of mixed-phase clouds and a more physically realistic representation of cloud microphysics and precipitation. Various fields from a 10-year long integration of RegCM4 run in tropical band mode with the new scheme are compared with their counterparts using the previous cloud scheme and are evaluated against satellite observations. In addition, an assessment using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP) for a 1-year sub-period provides additional information for evaluating the cloud optical properties against satellite data. The new microphysics parameterization yields an improved simulation of cloud fields, and in particular it removes the overestimation of upper level cloud characteristics of the previous scheme, increasing the agreement with observations and leading to an amelioration of a long-standing problem in the RegCM system. The vertical cloud profile produced by the new scheme leads to a considerably improvement of the representation of the longwave and shortwave components of the cloud radiative forcing.


Sign in / Sign up

Export Citation Format

Share Document