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Research Papers

Finite Element Modeling of Parabolic Trough Mirror Shape in Different Mirror Angles

[+] Author and Article Information
Siw Meiser

e-mail: siw.meiser@dlr.de

Christoph Kleine-Büning, Robert Pitz-Paal

Institute of Solar Research,
German Aerospace Center (DLR),
Linder Höhe,
51147 Cologne, Germany

Ralf Uhlig

Institute of Solar Research,
German Aerospace Center (DLR),
Pfaffenwaldring 38-40,
70569 Stuttgart, Germany

Contributed by the Solar Energy Division of ASME for publication in the Journal of Solar Energy Engineering. Manuscript received October 22, 2012; final manuscript received January 18, 2013; published online April 25, 2013. Assoc. Editor: Akiba Segal.

J. Sol. Energy Eng 135(3), 031006 (Apr 25, 2013) (6 pages) Paper No: SOL-12-1289; doi: 10.1115/1.4023560 History: Received October 22, 2012; Revised January 18, 2013

Deviations from the ideal shape of reflector panels for parabolic trough solar power plants can have relevant impact on field efficiency and thus on the performance of the whole power plant. Analyzing the gravity-induced deformation of mirror shape for different mirror angles is relevant for performance calculation of solar parabolic trough collectors and identifying optimization potential of the mirror panels. Two mirror model cases (stiff and elastic supports) are evaluated in four angles: in horizontal laboratory angle (mirrors facing upward with mounting points horizontally aligned), and in 0 deg, 45 deg, and 90 deg collector angle. The resulting slope maps are calculated in a separate postprocessing. In order to evaluate the effect of gravity load on mirror shape, the deformed mirror in each evaluated angle is compared to the nondeformed mirror shape, and to the shapes in 0 deg (zenith) collector angle, respectively. The resulting slope deviation maps show the mirror deformation in different mirror angles. Stiffness of the mounting to the support structure has a relevant impact. Mirror deformation on elastic brackets (SDx up to 1.6 mrad) is much more pronounced than on an ideal stiff support structure (SDx up to 1.0 mrad).

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Figures

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Fig. 1

ANSYS model of half a mirror column mounted via elastically deformable brackets (elastic case)

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Fig. 2

Deformation of stiff (left) and elastic case (right) in zenith (0 deg) collector angle. Black line corresponds to nondeformed model. Color scale in mm. Scaling factor for displacements: 1000.

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Fig. 3

Deformation in mm of stiff (left) and elastic case (right) in 90 deg collector angle. Black line corresponds to nondeformed model. Color scale in mm. Scaling factor for displacements: 1000.

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Fig. 4

Slope deviation maps and root mean square values of slope deviation (SDx) in mrad for zenith (0 deg) and 90 deg collector angle for the stiff case when compared to ideal mirror shape

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Fig. 5

Slope deviation maps and root mean square values of slope deviation (SDx) in mrad for zenith (0 deg) and 90 deg collector angle for the elastic case when compared to ideal mirror shape

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Fig. 6

Slope deviation maps and root mean square values of slope deviation (SDx) in mrad when compared to zenith collector angle

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