Parabolic Trough Optical Performance Analysis Techniques

[+] Author and Article Information
Eckhard Lüpfert

 German Aerospace Center (DLR), Plataforma Solar de Almería, Spaine.luepfert@dlr.de

Klaus Pottler, Steffen Ulmer

 German Aerospace Center (DLR), Plataforma Solar de Almería, Spain

Klaus-J. Riffelmann, Andreas Neumann, Björn Schiricke

 German Aerospace Center (DLR), Solar Research, Cologne, Germany

J. Sol. Energy Eng 129(2), 147-152 (Jun 18, 2006) (6 pages) doi:10.1115/1.2710249 History: Received June 07, 2005; Revised June 18, 2006

Analysis of geometry and optical properties of solar parabolic trough collectors uses a number of specific techniques that have demonstrated to be useful tools in prototype evaluation. These are based on photogrammetry, flux mapping, ray tracing, and advanced thermal testing. They can be used to assure the collector quality during construction and for acceptance tests of the solar field. The methods have been applied on EuroTrough collectors, cross checked, and compared. This paper summarizes results in collector shape measurement, flux measurement, ray tracing, and thermal performance analysis for parabolic troughs. It is shown that the measurement methods and the parameter analysis give consistent results. The interpretation of the results and their annual evaluation give hints on identified relevant improvement potentials for the following generation of solar power plant collectors.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Shape of a EuroTrough concentrator module in expanded height scale, measured via Photogrammetry with 13 measurement targets on each of the 28 mirror facets

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Figure 2

Photogrammetric measurement of a 75m section of a EuroTrough-collector, with measurement points on the mirror facets, the collector axis, and the receiver tubes

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Figure 3

Measurement result of the 75m section of a EuroTrough ET150 collector; shape deformations in mm due to gravitational forces between collector sunset, and sunrise orientation, in expanded scale

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Figure 4

Measurement with the CTM at the EuroTrough prototype at PSA

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Figure 5

Ray patterns at the 18 absorber tubes of the EuroTrough prototype at PSA measured in August 2004

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Figure 6

Evaluated intercept factors at the measured locations of the Eurotrough prototype at PSA

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Figure 7

PARASCAN-I flux scanner mounted on the EuroTrough prototype collector, and the two sensor parts (below right, zoomed in)

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Figure 8

Experimental setup of PARASCAN-II prototype: CCD camera looking at the fiber bundle (above), front view of a 6mm section, showing three active fibers of the header (bottom, left) and front view of the fiber bundle with 32 fibers facing to the camera (bottom, right)

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Figure 9

CCD camera signal showing the image of 32 optical fibers with 0.125mm thickness. The image quality obtained in the setup shown in Fig. 9 is sufficient for the measurement of the fibers’ light intensities.

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Figure 10

Ray-tracing results of optical performance for variation of tracking offset of the collector

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Figure 11

Ray-tracing results of optical performance for transversal displacement of the absorber tube

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Figure 12

Ray-tracing results of optical performance for variations of absorber height, based on photogrammetric mirror surface data for three different collector angles

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Figure 13

Intercept factor dependence of the total beam spread for a parabolic trough collector geometry (EuroTrough geometry, 70∕75∕80mm absorber tube)

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Figure 14

Ray-tracing result for transversal absorber deviation (in mm) and tracking offset effects on the intercept factor (LS3∕EuroTrough dimensions), σtotal=7.75mrad

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Figure 15

Experimental results from EuroTrough thermal tests with tracking offset variations




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