Comparative Review of Solar Radiation Models for Hourly Solar Intensity Estimation in the Indonesian Tropical Region ^†

Indonesia, located along the equatorial belt, has consistently high solar irradiance, offering strong potential for renewable energy development. However, limited availability of high-resolution solar radiation data constrains accurate system design. This study aims to evaluate eight empirical models for estimating hourly solar radiation under tropical conditions and identify the most suitable approach for data-scarce regions. The novelty lies in a comparative assessment tailored to Indonesia’s tropical climate and its application to sustainable energy planning. Model performance is assessed using MBE, RMSE, and R² against measured data. The results identify the most accurate model, which serves as the basis for developing a modified model that better represents local atmospheric characteristics. The proposed model improves estimation accuracy and supports more reliable solar resource assessment for sustainable energy applications in tropical regions. These findings support improved solar resource assessment and contribute to more reliable and sustainable solar energy system development in tropical regions.