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Title: Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint

Abstract

As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.

Authors:
;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy Solar Energy Technologies Program
OSTI Identifier:
1040923
Report Number(s):
NREL/CP-5500-54214
TRN: US201211%%259
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: To be presented at the ASME 2012 6th International Conference on Energy Sustainability and 10th Fuel Cell Science, Engineering and Technology Conference, 23-26 July 2012, San Diego, California
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 30 DIRECT ENERGY CONVERSION; ALIGNMENT; CAMERAS; CAPITAL; DIMENSIONS; FUEL CELLS; GLASS; PARABOLIC TROUGH COLLECTORS; PERFORMANCE; SOLAR COLLECTORS; TARGETS; CSP; PARABOLIC TROUGH; ABSORBER ALIGNMENT; CONCENTRATING SOLAR POWER; TROUGH COLLECTOR; Solar Energy - Thermal

Citation Formats

Stynes, J. K., and Ihas, B. Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint. United States: N. p., 2012. Web. doi:10.1115/ES2012-91283.
Stynes, J. K., & Ihas, B. Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint. United States. doi:10.1115/ES2012-91283.
Stynes, J. K., and Ihas, B. Sun . "Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint". United States. doi:10.1115/ES2012-91283. https://www.osti.gov/servlets/purl/1040923.
@article{osti_1040923,
title = {Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint},
author = {Stynes, J. K. and Ihas, B.},
abstractNote = {As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.},
doi = {10.1115/ES2012-91283},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2012},
month = {Sun Apr 01 00:00:00 EDT 2012}
}

Conference:
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  • The National Renewable Energy Laboratory (NREL) has developed an optical measurement tool for parabolic solar collectors that measures the combined errors due to absorber misalignment and reflector slope error. The combined absorber alignment and reflector slope errors are measured using a digital camera to photograph the reflected image of the absorber in the collector. Previous work using the image of the reflection of the absorber finds the reflector slope errors from the reflection of the absorber and an independent measurement of the absorber location. The accuracy of the reflector slope error measurement is thus dependent on the accuracy of themore » absorber location measurement. By measuring the combined reflector-absorber errors, the uncertainty in the absorber location measurement is eliminated. The related performance merit, the intercept factor, depends on the combined effects of the absorber alignment and reflector slope errors. Measuring the combined effect provides a simpler measurement and a more accurate input to the intercept factor estimate. The minimal equipment and setup required for this measurement technique make it ideal for field measurements.« less
  • An analytical approach, as an extension of one newly developed method -- First-principle OPTical Intercept Calculation (FirstOPTIC) -- is proposed to treat the geometrical impact of three-dimensional (3-D) effects on parabolic trough optical performance. The mathematical steps of this analytical approach are presented and implemented numerically as part of the suite of FirstOPTIC code. In addition, the new code has been carefully validated against ray-tracing simulation results and available numerical solutions. This new analytical approach to treating 3-D effects will facilitate further understanding and analysis of the optical performance of trough collectors as a function of incidence angle.
  • A new two-stage optical design is proposed for parabolic trough solar collectors with tubular absorbers. It can boost the concentration ratio by a factor of 2.5 relative to the conventional design, while maintaining the large rim angles (i.e., low nominal f-numbers) that are desirable for practical and economical reasons. The second state involves asymmetric nonimaging concentrators of the CPC type, facing segments of the parabolic first stage. The second stage can be accommodated inside an evacuated receiver, allowing the use of first-surface silvered reflectors. The low heat loss of this design opens the possibility of producing steam at temperatures andmore » pressures of conventional power plants, using only one-axis tracking. The improvement in conversion efficiency would be substantial.« less