Quoted from:[1] Tiris M. Tiris.E. Türe. Correlations of monthly-average daily global, diffuse and beam radiations with hours of bright sunshine in Gebze, Turkey[J]. Energy Conversion & Management, 1996, 37(9):1417-1421.

https://www.sci-hub.ren/10.1016/0196-8904(95)00227-8

Empirical equations have been developed which correlate the monthly-average daily horizontal global, diffuse and beam radiations with the fraction of maximum possible number of sunshine hours. These correlations are based on measured data between 1988 and 1992 from the TBTAK-MRC station in Gebze, Turkey. The correlation models have been tested by using statistical error tests.

INTRODUCTION

In some research problems associated with solar energy, the instantaneous fluxes of diffuse and beam radiation may be needed. On the other hand, the engineering design of many solar devices may require only long-term monthly averages of the hourly or daily beam and diffuse radiation. The global radiation incident on a horizontal surface and bright sunshine hours are measured by all recording stations in Turkey, while the data of diffuse radiation are very rare and refer nearly always to limited periods.

The present paper applies type (ii) correlations by using the monthly-average daily experimental data of diffuse solar radiation and sunshine duration of the Gebze location in Turkey (lat 40°46'N, long 29°26'E; altitude 182m above sea level). The coefficients in these equations were deduced, and the predicted diffuse radiation values, as calculated from the five correlations, were compared with measured values. 

This equations are recommended to estimate the monthly-average daily global and diffuse radiation on a horizontal surface for the Gebze location in Turkey.