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Research Papers

Optimized Bands: A New Design Concept for Concentrating Solar Parabolic Mirrors

[+] Author and Article Information
Lifang Li1

 ASME School of Mechatronics Engineering, Harbin Institute of Technology, 150001 Harbin, Chinalilifang2008@gmail.com

Andres Kecskemethy

 Department of Mechanical Engineering, University of Duisburg-Essen, 47057 Duisburg, Germanyandres.kecskemethy@uni-due.de

A. F. M. Arif

 ASME Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, 31261 Dhahran, Saudi Arabiaafmarif@kfupm.edu.sa

Steven Dubowsky

 ASME Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, 02139 MAdubowsky@mit.edu

1

Corresponding author.

J. Sol. Energy Eng 133(3), 031003 (Jul 19, 2011) (9 pages) doi:10.1115/1.4004351 History: Received December 06, 2010; Revised May 20, 2011; Published July 19, 2011; Online July 19, 2011

Parabolic concentrator mirrors are an important component of many solar energy systems, particularly solar mirror collectors. Precision parabolic mirrors are expensive to fabricate and to transport. Here, a new concept for designing and fabricating precision parabolic mirrors is presented. The mirror is formed from a thin flat very flexible metal sheet with a highly reflective surface. Attached to the rear surface of the mirror sheet is a backbone band whose figure is optimized to form the reflective sheet into a precision parabola when its two ends are pulled toward each other. An analytical model to optimize the shape and thickness of the band is presented. The validity of the concept is demonstrated using Finite Element Analysis (FEA) and laboratory experiments. The concept would permit flat mirror elements to be easily fabricated and efficiently packaged and shipped to field sites and assembled into the parabolic trough concentrators with potentially substantial costs reductions compared with the conventional methods.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A large solar mirror collector field located at Kramer Junction, CA [2]

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Figure 2

Schematic of solar trough collector [4]

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Figure 3

Parabolic and non-parabolic mirror cross section, (a) Reflecting mirror with ideal parabolic cross section and (b) Reflecting mirror with non-ideal cross section (circular)

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Figure 4

Leonardo di Vinci concave mirror [5]

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Figure 5

Deforming a circular arc to a parabola by distributed forces [16], (a) finite element analysis and (b) resulting applied forces (in N)

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Figure 6

Band mirror concept, (a) band mirror concept, (b) initial flat band with varying profile cross section, and (c) deformed band vertical shape

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Figure 8

Parabolic band obtained by changing the thickness, (a) varying thickness and (b) analytical thickness

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Figure 9

Constructing the variable band using layers

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Figure 10

Parabolic band obtained by changing the width

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Figure 11

Definition of focal error

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Figure 12

Focal error analysis

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Figure 13

Analytical band shape

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Figure 14

Physical model of FEA

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Figure 15

Analytical optimized band FEA results

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Figure 16

Ray tracing using the FEA results

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Figure 17

FEA optimized and analytical optimized band

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Figure 18

Ray tracing using the FEA optimized band results

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Figure 19

Focal error of optimized and rectangular band

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Figure 20

Experimental system

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Figure 21

Rectangular and optimized bands

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Figure 22

Sun light concentrated by the band mirror, (a) band mirror concentrated sunlight and (b) burn mark by focal line on plastic absorber

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Figure 23

Optical method of measurement, (a) threshold image and (b) comparison of fitting curve and predicted contour

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Figure 24

Ray tracing using optical method

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Figure 25

Focal error using optical method

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