Knowledge of diffuse radiation is essential to design and monitor passive and active solar systems. Measuring diffuse radiation is not common in most meteorological stations. Therefore, developing empirical models for many regions is inevitable. In the current study, a comprehensive review was conducted on all available monthly, daily, and hourly empirical model formats (MFs) to estimate the horizontal diffuse fraction of solar radiation (DFSR). A total of 153 monthly mean daily MFs, 159 daily MFs, and 30 hourly MFs were cited. Monthly and daily MFs were classified into six sub-categories, while hourly MFs were classified into two sub-categories. Eleven new empirical regression MFs were introduced to estimate DFSR over five cities of Iran. Results showed that errors in all 11 newly developed models are not significantly different even at the 10% probability level. The yearly average of DFSR for Bandarabbas, Kermanshah, Mashhad, Tabriz, and Zahedan were 12.41, 9.04, 7.65, 8.99, and 9.93 MJ m⁻², respectively. The generality of the newly developed models was proved by fitting them to data of four meteorological stations in the U.S.A. Comparing the newly developed models and the seven existing models showed that the newly developed models were more accurate in fitting the data.

漫辐射知识对于设计和监测被动和主动太阳能系统至关重要。在大多数气象站中，测量漫射辐射并不常见。因此，为许多地区开发经验模型是不可避免的。在当前的研究中，对所有可用的每月、每天和每小时经验模型格式 ( MF )进行了全面审查，以估计太阳辐射的水平漫射分数 ( DFSR )。总共引用了 153 个月平均每日MF、159 个每日MF和 30 个每小时MF。每月和每日MF分为六个子类别，而每小时MF分为两个子类。引入了11 个新的经验回归MF来估计伊朗五个城市的DFSR。结果表明，即使在 10% 的概率水平上，所有 11 个新开发模型的错误也没有显着差异。Bandarabbas、Kermanshah、Mashhad、Tabriz 和 Zahedan的年平均DFSR 分别为 12.41、9.04、7.65、8.99 和 9.93 MJ m ^-2。通过对美国4个气象站数据的拟合，证明了新开发模型的通用性。对比新开发模型和现有7个模型，新开发模型拟合数据更准确。