Zusammenfassung
Several years of measured data on global and diffuse radiation and
sunshine duration for 40 widely spread locations in the latitude
range 36â S to 60â N are used to develop and test models for
estimating monthly-mean, daily, diffuse radiation on horizontal surfaces.
Applicability of the clearness-index (K) and sunshine fraction (S/So)
models for diffuse estimation and the effect of combining several
variables into a single multilinear equation are tested. Correlations
connecting the diffuse to global fraction (HdIH) with K and S/So
predict Hd values more accurately than their separate use. Among
clearness-index and sunshine-fraction models, S/So models are found
to have better accuracy if correlations are developed for wide latitude
ranges. By including a term for declinations in the correlation,
the accuracy of the estimated data can be marginally improved. The
addition of latitude to the equation does not help to improve the
accuracy further.
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