New Models for Separating Hourly Diffuse and Direct Components of Global Solar Radiation

Due to the lack of domestic hourly solar radiation measured data, models which are used to separate hourly diffuse and direct components of global solar radiation on horizontal surface are always referencing foreign models. However, because of different geographical factors (such as latitude and longitude) and meteorological conditions (such as atmospheric transparency, temperature, and humidity), it is difficult to have broad application. This study uses hourly solar radiation measured data from Shanghai to evaluate and compare models in the published literature which were used to separate hourly diffuse and direct components of global solar radiation on horizontal surface, and several relatively accurate available models are chosen. Then, new improved models are consequently proposed and compared with these existing models for calculating hourly diffuse solar radiation based on statistical parametric analysis, residual histogram analysis, and fitted curve analysis. It is found that these new improved models are in better agreement with the measured data, and they are more suitable for calculating diffuse and direct solar radiation under complicated weather conditions.