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Abstract

The Diffuse Sky Radiation as measured with a pyranometer and shading ring must be corrected to compensate for sky radiation cut off by the ring. This correction is generally computed on the basis of the geometric area of the sky cut off and assuming isotropic sky. This assumption results in values of D-R which differ from the true value D-c by a factor "k" = D-c/D-R. The frequency distribution of k for the 2-year period was: k = 0.9 1.0 1.1 1.2 1.3 1.4 1.5 f = 1.58 51.45 32.56 12.30 1.84 0.22 0.05 There was no significant dependence of k on Solar Elevation and only a very slight dependence on Solar Declination (d). The most significant variations of k are associated with D-R/G and the following equation was found to fit the data closely: k = 1.1578 - 0.1548(D-R/G)**3 - 0.000143d When the observed data are adjusted by applying the factor k as derived from this formula 83.47 % of the data are brought within +- 5 % of the true value and 96.48 % of the data are correct within +- 10 %

Additional information

Authors: MC WILLIAMS S VALENTINA OBSERVATORY, CAHIRCIVEEN, CO. KERRY (IRELAND), VALENTINA OBSERVATORY, CAHIRCIVEEN, CO. KERRY (IRELAND)
Bibliographic Reference: EUR 8910 EN (1984) MF, 13 P., BFR 120, BLOW-UP COPY BFR 150, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989122043200 / Last updated on: 1987-01-01
Category: PUBLICATION
Available languages: en