Kasten and Czeplak formulated equations for the estimation of solar irradiance based on cloud cover information. For their research, Kasten and Czeplak (1979) used 10-year periods from 1964 to 1973 of continuous hourly data from Hamburg, Germany. They also validated their model using German and UK data sets, thus, the coefficients they provide are from German and UK regional climatology. Initially they proceed by calculating the global horizontal irradiance under clear sky conditions IGC, and then the global and diffuse horizontal irradiances are calculated.
The ratio of global radiation IG for a given cloud amount N okta, to IGC has been shown to be independent of the solar elevation, r,
Gul and Muneer (1998) and Muneer and Gul (2000) furthered the work of Kasten and Czeplak to provide equations that can accommodate local coefficients for their data sets, as the original coefficients could not accurately estimate the irradiance in their analysis. The Kasten and Czeplak equations. (30.4-30.5) have
The diffuse component is calculated as follows:
been modified while Eq. (30.6) remains the same in both models. Equations (30.4-30.5) become as follows:
The coefficients of above formula (A, B, C, and D) are applied from estimated coefficient from this study on Seoul, Busan, Gwangju, and Daejeon.
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