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Research Papers

Comparison and Optimization of Heliostat Canting Methods

[+] Author and Article Information
R. Buck, E. Teufel

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

J. Sol. Energy Eng 131(1), 011001 (Jan 06, 2009) (8 pages) doi:10.1115/1.3027500 History: Received July 16, 2007; Revised March 20, 2008; Published January 06, 2009

Heliostat canting (alignment of mirror facets) is known to have a major influence on the optical efficiency of heliostat fields and therefore on the power output of solar tower plants. In recent years several canting concepts were used, mainly on- and off-axis canting. Several new canting concepts, such as stretched-parabolic or target-aligned canting, were proposed in order to improve the performance of heliostats. As solar power plants become economically more attractive, knowledge about the influence of canting becomes more important. In this context, the influence of several factors on the canting method is discussed and optimal canting strategies are described. The considered factors comprise plant power level, heliostat position in the field, heliostat area, receiver dimension, and site latitude. It is concluded that the target-aligned tracking method is superior to all other variants in the majority of cases. As for the standard azimuth-elevation tracking methods, not one of these exhibits a clear advantage. It is only the on-axis method that performs worst in all cases.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Scheme of target-aligned heliostat (Ref. 7)

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Figure 2

Stretching factors for parabolic canting

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Figure 3

AIPWI for small system with 16m2 heliostat

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Figure 4

Off-axis canting: variation of day of year and time for canting (small system, 16m2 heliostat at R=0.25 and φ=0deg)

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Figure 5

Parabolic canting: variation of sfx and sfy (small system, 16m2 heliostat at R=0.25 and φ=90deg)

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Figure 12

Influence of mirror slope error on heliostat performance for a large system with 148m2 heliostat

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Figure 11

Influence of heliostat errors on performance for a small system with 16m2 heliostat

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Figure 10

AIPWI for large system with 148m2 heliostat

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Figure 9

AIPWI for a small system with 148m2 heliostat

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Figure 8

Optimum canting parameters for parabolic and target-aligned cases (small system, 16m2 heliostat, φ=90deg)

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Figure 7

Optimum canting parameters for the off-axis case (small system, 16m2 heliostat, φ=90deg or 30deg)

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Figure 6

Influence of canting angle (small system, 16m2 heliostat, φ=90deg)

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