Correlations to estimate monthly mean daily solar global irradiation: application to Romania
Abstract
Seven existing relationships between monthly mean clearness index and the number of bright sunshine hours are tested under the climate and latitude of Romania. New (best-fit) correlations are derived. They use bright sunshine hour number or fractional total cloud amount as input. The dependence of the new sunshine-based regressions on month is stronger than their dependence on latitude. They generally underestimate the clearness index in the first half-year and overestimate it in the rest of the year. The accuracy of the new regression seems not to depend significantly on the year.
- Publication:
-
Energy
- Pub Date:
- 1999
- DOI:
- 10.1016/S0360-5442(99)00027-4
- Bibcode:
- 1999Ene....24..883B