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Title: New adaptive method to optimize the secondary reflector of linear Fresnel collectors

Abstract

Performance of linear Fresnel collectors may largely depend on the secondary-reflector profile design when small-aperture absorbers are used. Optimization of the secondary-reflector profile is an extremely challenging task because there is no established theory to ensure superior performance of derived profiles. In this work, an innovative optimization method is proposed to optimize the secondary-reflector profile of a generic linear Fresnel configuration. The method correctly and accurately captures impacts of both geometric and optical aspects of a linear Fresnel collector to secondary-reflector design. The proposed method is an adaptive approach that does not assume a secondary shape of any particular form, but rather, starts at a single edge point and adaptively constructs the next surface point to maximize the reflected power to be reflected to absorber(s). As a test case, the proposed optimization method is applied to an industrial linear Fresnel configuration, and the results show that the derived optimal secondary reflector is able to redirect more than 90% of the power to the absorber in a wide range of incidence angles. Here, the proposed method can be naturally extended to other types of solar collectors as well, and it will be a valuable tool for solar-collector designs with a secondarymore » reflector.« less

Authors:
 [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
Southern California Gas Company (SCGC); USDOE
OSTI Identifier:
1343079
Alternate Identifier(s):
OSTI ID: 1417097
Report Number(s):
NREL/JA-5500-67646
Journal ID: ISSN 0038-092X
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 144; Journal Issue: C; Journal ID: ISSN 0038-092X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 47 OTHER INSTRUMENTATION; linear Fresnel; secondary reflector; concentrating solar power; incidence angle modifier; non-imaging optics

Citation Formats

Zhu, Guangdong. New adaptive method to optimize the secondary reflector of linear Fresnel collectors. United States: N. p., 2017. Web. doi:10.1016/j.solener.2017.01.005.
Zhu, Guangdong. New adaptive method to optimize the secondary reflector of linear Fresnel collectors. United States. doi:10.1016/j.solener.2017.01.005.
Zhu, Guangdong. Mon . "New adaptive method to optimize the secondary reflector of linear Fresnel collectors". United States. doi:10.1016/j.solener.2017.01.005. https://www.osti.gov/servlets/purl/1343079.
@article{osti_1343079,
title = {New adaptive method to optimize the secondary reflector of linear Fresnel collectors},
author = {Zhu, Guangdong},
abstractNote = {Performance of linear Fresnel collectors may largely depend on the secondary-reflector profile design when small-aperture absorbers are used. Optimization of the secondary-reflector profile is an extremely challenging task because there is no established theory to ensure superior performance of derived profiles. In this work, an innovative optimization method is proposed to optimize the secondary-reflector profile of a generic linear Fresnel configuration. The method correctly and accurately captures impacts of both geometric and optical aspects of a linear Fresnel collector to secondary-reflector design. The proposed method is an adaptive approach that does not assume a secondary shape of any particular form, but rather, starts at a single edge point and adaptively constructs the next surface point to maximize the reflected power to be reflected to absorber(s). As a test case, the proposed optimization method is applied to an industrial linear Fresnel configuration, and the results show that the derived optimal secondary reflector is able to redirect more than 90% of the power to the absorber in a wide range of incidence angles. Here, the proposed method can be naturally extended to other types of solar collectors as well, and it will be a valuable tool for solar-collector designs with a secondary reflector.},
doi = {10.1016/j.solener.2017.01.005},
journal = {Solar Energy},
number = C,
volume = 144,
place = {United States},
year = {Mon Jan 16 00:00:00 EST 2017},
month = {Mon Jan 16 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 2works
Citation information provided by
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  • As a line-focus concentrating solar power (CSP) technology, linear Fresnel collectors have the potential to become a low-cost solution for electricity production and a variety of thermal energy applications. However, this technology often suffers from relatively low performance. A secondary reflector is a key component used to improve optical performance of a linear Fresnel collector. The shape of a secondary reflector is particularly critical in determining solar power captured by the absorber tube(s), and thus, the collector's optical performance. However, to the authors' knowledge, no well-established process existed to derive the optimal secondary shape prior to the development of amore » new adaptive method to optimize the secondary reflector shape. The new adaptive method does not assume any pre-defined analytical form; rather, it constitutes an optimum shape through an adaptive process by maximizing the energy collection onto the absorber tube. In this paper, the adaptive method is compared with popular secondary-reflector designs with respect to a collector's optical performance under various scenarios. For the first time, a comprehensive, in-depth comparison was conducted on all popular secondary designs for CSP applications. In conclusion, it is shown that the adaptive design exhibits the best optical performance.« less
  • The two-stage linear Fresnel reflector solar concentrator is analyzed via an in-depth study of an installed, nominally 220 KW{sub t} system. The concentrator includes: a primary linear Fresnel reflector comprised of curved mirrors and a secondary nonimaging CPC-type trough with a tubular receiver. The principal practical design options for the secondary concentrator are evaluated. In this paper, via a computer simulation which includes ray-tracing of the primary reflector, the authors evaluate the sensitivity of energy output to: concentrator optical errors, system geometry, tracking mode, and the option of using flat versus curved primary mirrors. The two-stage Fresnel concentrator can bemore » considerably less expensive than the corresponding parabolic trough collector, but is found to deliver about one-fourth less yearly energy. However much of this difference could be eliminated through the use of higher-quality CPC reflectors.« less