Determining the optical quality of focusing collectors without laser ray tracing

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This paper describes a novel alternative to the laser ray trace technique for evaluating the optical quality of focusing solar collectors. The new method does not require any equipment beyond what is used for measuring collector efficiency; it could therefore become part of routine collector testing. The total optical errors resulting from imperfect specularity and from inaccuracies in reflector position or slope are characterized by an angular standard deviation sigma/sub optical/, the rms deviation of the reflected rays from the design direction. The method is based on the fact that the off-axis performance of a concentrator depends on sigma/sub optical/. ... continued below

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Pages: 23

Creation Information

Bendt, P.; Gaul, H. & Rabl, A. February 1, 1980.

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Description

This paper describes a novel alternative to the laser ray trace technique for evaluating the optical quality of focusing solar collectors. The new method does not require any equipment beyond what is used for measuring collector efficiency; it could therefore become part of routine collector testing. The total optical errors resulting from imperfect specularity and from inaccuracies in reflector position or slope are characterized by an angular standard deviation sigma/sub optical/, the rms deviation of the reflected rays from the design direction. The method is based on the fact that the off-axis performance of a concentrator depends on sigma/sub optical/. An angular scan is performed, i.e., the collector output is measured as a function of misalignment angle over the entire range of angles for which there is measurable output (typically a few degrees). This test should be carried out on a very clear day, with receiver close to ambient temperature (if the latter conditions cannot be satisfied, appropriate corrections are necessary). The parameter sigma/sub optical/ is then determined by a least-squares fit between the measured and the calculated angular scan. We tested the method on a parabolic trough collector manufactured by Hexcel, but it is suitable for parabolic dishes as well. The method appears to be accurate enough to determine sigma/sub optical/ within about 10%.

Physical Description

Pages: 23

Notes

NTIS, PC A02/MF A01.

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  • Report No.: SERI/TR-333-359
  • Grant Number: EG-77-C-01-4042
  • DOI: 10.2172/5415024 | External Link
  • Office of Scientific & Technical Information Report Number: 5415024
  • Archival Resource Key: ark:/67531/metadc1073900

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • February 1, 1980

Added to The UNT Digital Library

  • Feb. 4, 2018, 10:51 a.m.

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  • March 28, 2018, 12:57 p.m.

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Bendt, P.; Gaul, H. & Rabl, A. Determining the optical quality of focusing collectors without laser ray tracing, report, February 1, 1980; United States. (digital.library.unt.edu/ark:/67531/metadc1073900/: accessed April 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.