scholarly journals Climate Measurement Plan for the Central Receiver Pilot Plant and the Solar Thermal Test Facility

1975 ◽  
Author(s):  
Keyword(s):  
Pilot Plant ◽  
Solar Thermal ◽  
Test Facility ◽  
Measurement Plan ◽  
Thermal Test ◽  
Central Receiver

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.

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%.

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