Representative Terrestrial Solar Brightness Profiles

[+] Author and Article Information
Andreas Neumann, Andreas Witzke

German Aerospace Center (DLR), Cologne, Germany

Scott A. Jones

Sandia National Laboratories, Albuquerque, NM

Gregor Schmitt

Institute of Physics, University of Bonn, Bonn, Germany

J. Sol. Energy Eng. 124(2), 198-204 (Apr 24, 2002) (7 pages) doi:10.1115/1.1464880 History: Received November 01, 2001; Revised January 01, 2002; Online April 24, 2002
Copyright © 2002 by ASME
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(a) Comparison of the limb darkened sun (known as the Kuiper model 2), a LBL 0.3% CSR profile, and a low CSR DLR profile (0.37%) generated out of a camera image. As each symbol represents a scan point one sees that the spacing of the DLR data is lower compared to the LBL data. Similarly, (b) comparison of the limb darkened sun, a LBL 0.3% CSR profile, and a DLR 0.37% CSR profile. Here we have a linear intensity scaling and a zoomed radius axis, which gives a look at the details of the solar limb.
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The impact of the assumed sun radius on the calculation of the CSR. A nominal 3% profile can display a CSR of 6% if 4.5 mrad is used instead of 4.65. If 4.9 mrad is used the CSR decreases to 0.6%.
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These mean profiles are taken from DLR data at different locations at approximately 10% CSR and compared to averaged LBL 11% CSR data from Barstow. The profiles are comparable within the confidence limits.
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A comparison of several LBL sunshape scans covering a wide range of CSR conditions
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A comparison of the DLR averaged sunshape profiles
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A comparison of the single DLR profile with the standard solar scan as published by 3
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Scatter plot of CSR measurements at Cologne versus the DNI in the years 1997–1999. A two-fold scattering is visible and low CSRs may also occur at low DNI.
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Frequency of occurrence of the CSR. 71.5% of the measurements are in the 0–5% CSR zone
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Subdividing the CSR measurements into DNI bins shows that low CSR may occur all over the DNI range. CSR values of >35% dominate in the 0–200 W/m2 region.




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