Evaluation of Hybrid Model for Estimating Daily Solar Radiation in Some Solar Sites of Iran

Short wavelength of solar radiation that reaches the ground used as one of the key parameters in most models those estimate the potential Evapotranspiration، such as FAO Penman-Monteith. Despite the importance of amount of radiation، its measurement is done only in small number of stations in the country. Empirical radiation models، such as Angstrom- Prescott، despite the simplicity، require calibration and their coefficients must be properly estimated. In the present study a relatively simple physical model that called hybrid model was used to estimate daily solar radiation in 10 synoptic stations، Esfahan، Bojnourd، Bandar Abbas، Tabriz، Tehran، Ramsar، Zahedan، Kerman، Kermanshah and Mashhad and the results were compared with modified Daneshyar & Sabagh models those were proposed for various climatic conditions in previous researches. using a relatively small number of meteorological parameters include temperature، relative humidity، pressure and sunshine hours، Hybrid model estimated amount of radiation with reasonable accuracy. To compare the three models، mean error (ME)، mean absolute error (MAE)، root mean square error (RMSE) and mean percentage error (MPE) statistical criteria were used. Average of each error criteria in Hybrid model، respectively are، -0. 27، 1. 27، 1. 59 and 2. 01 and in the modified Daneshyar model are، -0. 19، 2. 64، 3. 15 and 3. 42. Also in modified Sabagh model these criteria are achieved equal to 0. 91، 2. 87، 3. 93 and 11. 20. Small amount of error criteria for Hybrid model represents the relatively high performance of this model in the estimation of solar radiation in daily scale.