Empirical Models for Estimation of Global Daily Solar Radiation in Indonesia

This study utilizes global daily solar radiation data in Indonesia with 5 years of data in Indonesia. There are some empirical models will be tested against observation data from 12 weather stations across Indonesia. Empirical models based on Julian date (N) will be compared with weather parameters to assess how global daily solar radiation (Rs) prediction interacts with daily weather parameters, such as daily precipitation (Rf), maximum daily temperature (Tx), minimum daily temperature (Tn), sunshine duration (Ss), and daily cloud coverage (Cc). Coefficient of determination (R2), the root mean square error (RMSE), and the mean absolute error (MAE) will be used as performance model indicators. The results show that all of the models show RMSE and MAE in range of 3.54–4.58 and 2.43–3.69 MJ m−2 day−1. Julian date-based empirical models are not well performed with R2 < 0.1; the weather parameters-based empirical models have better performance as individual and combined parameters. Ss has the best R2 around 0.48; the combination of Tn, Tn, Cc, Rf, and Ss performs the best results with R2 almost 0.5.