A model for diffuse and global irradiation on horizontal surfaces

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Solar Energy (Journal of Solar Energy Science and Engineering); (USA)

DOI:https://doi.org/10.1016/0038-092X(90)90015-5· OSTI ID:6344006

Jain, P C ^[1]

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1. International Centre for Theoretical Physics, Trieste (Italy)

The intensity of the direct radiation and the diffuse radiation at any time on a horizontal surface are each expressed as fractions of the intensity of the extraterrestrial radiation. Using these and assuming a random distribution of the bright sunshine hours and not too wide variations in the values of the transmission coefficients, a number of relations for estimating the global and the diffuse irradiation are derived. Two of the relations derived, including the Angstroem correlation for estimating the global irradiation, are already known empirically while several new correlations have been derived. The relations derived in this paper are: (i) H{sub d}/H{sub o} = a{sub 1} + b{sub 1} (S/S{sub o}); (ii) H/H{sub o} = A{sub 2} + b{sub 2} (S/S{sub o}); (iii) H{sub D}/H{sub o} = a{sub 3} + b{sub 3} (H/H{sub o}); (iv) H{sub D}/H = a{sub 4} + b{sub 4} (h{sub o}/) (v) H/(H{minus}H{sub D}) = a{sub 5} + b{sub 5} (S{sub o}/S); (vi) H{sub D}/(H{minus}H{sub D}) = A{sub 6} + b{sub 6} (S{sub o}/S); (vii) H/H{sub D} = a{sub 7} + b{sub 7} (S/S{sub o}); (viii) H/H{sub D} = A{sub 1} + A{sub 2} (S/S{sub o}) + A{sub 3} (S/S{sub o}){sup 2}. The study identifies three independent basic parameters and the constants appearing in the various equations as simple functions of these three basic parameters. This provides unification and inter-relationships between the various constants. Experimental data for the diffuse irradiation, the global irradiation and the bright sunshine duration for Macerata (Italy), Salisbury and Bulawayo (Zimbabwe) is found to show good correlation for the linear eqns (i) to (vii), and the nature and the interrelationships of the constants is found to be as predicted by theory.

• OSTI ID: 6344006
• Journal Information: Solar Energy (Journal of Solar Energy Science and Engineering); (USA), Vol. 45:5; ISSN 0038-092X
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
DIFFUSE SOLAR RADIATION
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DIRECT SOLAR RADIATION
ALTITUDE
CLOUD COVER
COMPARATIVE EVALUATIONS
DAILY VARIATIONS
DATA
DUSTS
EQUATIONS
ITALY
OPACITY
ORIENTATION
OZONE
PERFORMANCE
SURFACES
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AFRICA
EUROPE
FLUIDS
GASES
INFORMATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SOLAR FLUX
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VAPORS
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WESTERN EUROPE
140100* - Solar Energy- Resources & Availability