Assessment of sunshine based global radiation models using data measured in Riyadh, Saudi Arabia

Many empirical correlations and models have been developed to estimate solar radiation around the world. The most commonly used parameter for estimating global solar radiation is sunshine duration since it is easily and reliably measured with widely available data. This paper reports the performance of 52 sunshine models for estimating monthly global solar radiation on horizontal surfaces in Riyadh, Saudi Arabia (24°43′N, 39–38′E; altitude: 600 m). It was found that some of the models were totally unsuitable for use in this region, while others differ in performance. Two best models were identified.