Heliostat Canting and Focusing Methods: An Overview and Comparison

2010 ◽  
Author(s):  
Julius Yellowhair ◽  
Clifford K. Ho
Keyword(s):  
Laser Beam ◽  
Test Facility ◽  
The Sun ◽  
Alignment Method ◽  
Advantages And Disadvantages ◽  
The Past ◽  
Thermal Test ◽  
Central Receiver ◽  
Look Back ◽  
The Individual

A central receiver power tower system consists of a field of heliostats that focus the sunlight onto the receiver on the tower. Heliostats typically consist of an array of mirror facets that track the sun throughout the day. To obtain the optimal concentrated solar flux on the receiver, the individual heliostat facets must be properly canted and focused. Several different methods have been used in the past for facet canting and focusing. These demonstrated methods and some new alignment concepts are under consideration for development and alignment of the 218 heliostats at the Sandia National Laboratories National Solar Thermal Test Facility in Albuquerque, NM. In this paper, we provide an overview and comparison of the different methods. The methods we consider are the gauge blocks, inclinometers, photogrammetry, fringe reflection, imaging with theoretical image overlays, laser beam projections, camera look-back, and target reflection methods. The advantages and disadvantages of each alignment method are identified based on several prescribed criteria for aligning the heliostats. Recommendations regarding the alignment method’s potential for efficiently and accurately aligning heliostat fields are provided.

scholarly journals A Flux Mapping Method for Central Receiver Systems

2011 ◽  
Author(s):  
Clifford K. Ho ◽  
Siri S. Khalsa
Keyword(s):  
Ccd Camera ◽  
Mapping Method ◽  
Test Facility ◽  
The Novel ◽  
Additional Information ◽  
Thermal Test ◽  
Central Receiver ◽  
Direct Normal Irradiance ◽  
Beam Characterization ◽  
Pixel Value

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%.

Operation of Large-Scale Pumps and Valves in Molten Salt

1994 ◽  
Vol 116 (3) ◽  
pp. 137-141 ◽  
Author(s):  
D. C. Smith ◽  
E. E. Rush ◽  
C. W. Matthews ◽  
J. M. Chavez ◽  
P. A. Bator
Keyword(s):  
Molten Salt ◽  
Power Plants ◽  
Large Scale ◽  
Solar Power ◽  
Test Facility ◽  
Plant Design ◽  
Thermal Test ◽  
Central Receiver ◽  
Solar Power Plants ◽  
Careful Design

The molten salt pump and valve (P&V) test loops at Sandia National Laboratories (SNL) National Solar Thermal Test Facility (NSTTF) operated between Jan. 1988 and Oct. 1990. The purpose of the P&V test was to demonstrate the performance, reliability, and service life of full-scale hot and cold salt pumps and valves for use in commercial central receiver solar power plants. The P&V test hardware consists of two pumped loops; the “Hot Loop” to simulate the hot (565°C) side of the receiver and the “Cold Loop” to simulate the receiver’s cold (285°C) side. Each loop contains a pump and five valves sized to be representative of a conceptual 60-MWe commercial solar power plant design. The hot loop accumulated over 6700 hours of operation and the cold loop over 2500 hours of operation. This project has demonstrated that standard commercial scale pump and valve designs will work in molten salt. The test also exposed some pitfalls that must be avoided in specifying such equipment. Although certainly not all of the pitfalls were discovered, careful design and specification should result in reliable or at least workable equipment.

scholarly journals The Development of the Heliostat Focusing and Canting Enhancement Technique: An Optical Heliostat Alignment Tool for the National Solar Thermal Test Facility

2011 ◽  
Author(s):  
Evan Sproul ◽  
Kyle Chavez ◽  
Julius Yellowhair
Keyword(s):  
Solar Thermal ◽  
Optical Methods ◽  
Test Facility ◽  
Moving Frame ◽  
Beam Diameter ◽  
Stationary Target ◽  
Enhancement Technique ◽  
Thermal Test ◽  
Central Receiver ◽  
Alignment Tool

A heliostat array is a field of heliostats that focuses sunlight continuously on a central receiver in a power tower solar concentration system. Each heliostat consists of a structurally mounted mirror surface capable of reflecting sunlight onto a given target throughout the day. Typically, most heliostats are actually a group of individual mirror facets on a single moving frame. To achieve highly concentrated solar flux on a central receiver, each heliostat mirror facet has to be properly aligned (both canted and focused) when attached to the heliostat frame. In order to accurately evaluate and correct heliostat facet alignment, Sandia National Laboratories (SNL) and New Mexico Tech (NMT) have developed the Heliostat Focusing and Canting Enhancement Technique (H-FACET), a new and unique heliostat alignment tool that allows technicians to make fast and effective adjustments to facet canting and focusing. H-FACET uses a high resolution digital camera mounted on top of a receiver tower to observe the image of a stationary target reflected by a heliostat. Custom image processing software compares specific measurement points on the actual target reflection image with the corresponding measurement points on an ideally reflecting heliostat. Deviations between the actual and ideal reflection points reveal facet misalignments. Additionally, a live image of the ideal and theoretical points provides real-time feedback during the alignment correction process. SNL has implemented H-FACET at the National Solar Thermal Test Facility (NSTTF). Technicians have used the canting portion of the software to successfully cant a large section of the SNL NSTTF heliostat field. Visual inspections of reflected heliostat beam patterns have demonstrated noticeable improvements in beam size and shape resulting from the use of H-FACET. Preliminary quantitative analyses of H-FACET have shown beam diameter reductions of up to fifty percent. The beam reductions resulting from the use of H-FACET will assist in minimizing beam spillage and increasing flux densities. As a result, H-FACET may be a valuable tool in increasing the annual performance of a heliostat field. This paper details the computational algorithms used in H-FACET. These algorithms include accurate models of heliostat field geometries, sun position, facet orientations and facet shapes. This paper also discusses the optical methods used to determine the orientations and surface shapes of ideally aligned facets. Lastly, it investigates probable sources of error and ways to improve H-FACET.

Arthrodesis of the first metatarsophalangeal joint. Current recommendations

1994 ◽  
Vol 84 (6) ◽  
pp. 266-280 ◽  
Author(s):  
GV Yu ◽  
JE Shook
Keyword(s):  
Metatarsophalangeal Joint ◽  
Effective Procedure ◽  
First Metatarsophalangeal Joint ◽  
Advantages And Disadvantages ◽  
The Past ◽  
Fixation Techniques ◽  
The Individual ◽  
Specific Fixation ◽  
Individual Fixation ◽  
Multiple Conditions

Fusion of the first metatarsophalangeal joint is a time-honored, effective procedure for multiple conditions. Numerous fixation techniques have been described over the years. The authors provide an extensive overview of specific fixation techniques used throughout the past 6 years. Emphasis is placed on the potential advantages and disadvantages of the individual fixation techniques.

scholarly journals Membranes, Chromatography and Membrane Chromatography. Separation Technologies for the Biopharm and Nutraceutical Era

2017 ◽  
Vol 1 (1) ◽  
Author(s):  
Aniket V. Kale ◽  
Munir Cheryan
Keyword(s):  
Pore Diffusion ◽  
Membrane Technology ◽  
Advantages And Disadvantages ◽  
The Past ◽  
Membrane Chromatography ◽  
The Individual

Membrane technology and process chromatography are widely used in the food, biopharmaceutical, nutraceutical and bioprocessing industries. Both techniques developed simultaneously and in parallel over the past few decades. The two technologies are complementary for the most part in terms of their advantages and disadvantages. Membrane chromatography integrates membranes and chromatography into one versatile technology. The resulting synergy has advantages and largely eliminates the disadvantages of the individual techniques, the most important being pore diffusion, thus leading to higher throughputs. This review compares the principles and applications of membranes, chromatography and membrane chromatography and their individual and combined roles in bioseparations.

Multidisciplinary management of vascular access for haemodialysis: from the preparation of the initial access to the treatment of stenosis and thrombosis

VASA ◽  
2011 ◽  
Vol 40 (3) ◽  
pp. 188-198 ◽  
Author(s):  
Reinhold ◽  
Haage ◽  
Hollenbeck ◽  
Mickley ◽  
Ranft
Keyword(s):  
Vascular Access ◽  
Central Venous ◽  
Advantages And Disadvantages ◽  
Multidisciplinary Study ◽  
First Results ◽  
Lower Complication ◽  
Lower Complication Rate ◽  
Access Problems ◽  
Arteriovenous Grafts ◽  
The Individual

In February 2008 a multidisciplinary study group was established in Germany to improve the treatment of patients with potential vascular access problems. As one of the first results of their work interdisciplinary recommendations for the management of vascular access were provided, from the creation of the initial access to the treatment of complications. As a rule the wrist arteriovenous fistula (AVF) is the access of choice due to its lower complication rate when compared to other types of access. The AVF should be created 3 months prior to the expected start of haemodialysis to allow for sufficient maturation. Second and third choice accesses are arteriovenous grafts (AVG) and central venous catheters (CVC). Ultrasound is a reliable tool for vessel selection before access creation, and also for the diagnosis of complications in AVF and grafts. Access stenosis and thrombosis can be treated surgically and interventionally. The comparison of both methods reveals advantages and disadvantages for each. The therapeutic decision should be based on the individual patients’ constitution, and also on the availability and experience of the involved specialists.

ADMINISTRATION MODELS IN THE SYSTEM OF FORENSIC EXAMINATION INSTITUTIONS FROM THE POSITION OF SCIENTIFIC MANAGEMENT

2016 ◽  
Vol 16 ◽  
pp. 179-184
Author(s):  
S. V. Kudryashova
Keyword(s):  
Scientific Management ◽  
Competing Values ◽  
State Institutions ◽  
Advantages And Disadvantages ◽  
Forensic Examination ◽  
Forensic Institutions ◽  
The Individual

The individual forensic activity in comparison with the activity of forensic experts of specialized state institutions is considered, the main advantages and disadvantages are determined. The directions of development of specialized state and non-state forensic institutions are presented in accordance with R. Quinn's competing values model.

Brahms, Rhythm, and the Renaissance

2012 ◽  
Vol 8 ◽  
Author(s):  
Eleanor Heisey
Keyword(s):  
Compositional Style ◽  
The Past ◽  
Piano Quartet ◽  
Look Back ◽  
Variations On A Theme

Johannes Brahms’s deep engagement with the past contributed to his compositional style in many ways. This article considers Brahms techniques that look back to and expand on those of Renaissance composers, in particular metric conflict and cadences, voice displacement, changes in proportion, rhythmic augmentation and diminution, and the hocket. Examples are taken from Brahms’s Academic Festival Overture, Variations On A Theme By Haydn, Piano Quartet in A Major, and Symphony No. 3 in F Major.

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