Global Solar Radiation Measurements on the Horizontal Surface in Osmaniye During seven Years Period and Global Solar Radiation Estimation Using New Empirical Models

This study has two important purposes. The first purpose is to give the results of hourly and monthly mean values of daily global solar radiation measured at the horizontal surface over a period of seven years from 2014 to 2020 at Osmaniye (latitude: 37.04E, longitude: 36.22N, altitude: 118m), using 8-48 Model Black&White pyranometer. From monthly mean values of daily total solar radiation between the years of 2014-2020, annual monthly total and average solar radiation coming to the horizontal surface was calculated as 205.01 MJm-2g-1 and 17.08 MJm-2g-1, respectively. While the highest monthly global solar radiation was obtained in June to be 25.76 MJm-2g-1, the lowest values were obtained in December to be 7.63 MJm-2g-1. The second purpose is to give seven regression models (M1-7) which use Angstrom type equations developed to estimate the monthly annual global solar radiation using parameters such as monthly average sunshine duration (hour), monthly average air temperature (°C), lowest and highest air temperatures (°C), latitude () and solar declination angle () for Osmaniye province. Meteorological parameters covering the period 1987-2020 were taken from Turkish State Meteorological Service. These models developed for Osmaniye were calibrated using monthly mean values of measured daily total solar radiation, measuring with Black&White pyranometer. The monthly average total solar radiation performances estimated from the models were compared using statistical methods such as R2, MBE, MAPE, MPE, MARE, and MAE. M3 model shows the best performance for R2 and RMSE statistical error indicators, while M5 model is the best performing model for MBE, MPE, MAPE, MARE and MAE. In addition, the values of the monthly average-daily clearness index (KT) range from 0.511 to 0.634 for measured global solar radiation (H), from 0.553 to 0.621 for M5 model and from 0.538 to 0.611 for M3 model. Results show good agreement between the estimated and measured values of global solar radiation.