Photovoltaic forecasting through establishing solar models without using diffuse radiation measurement in Beijing

Solar diffuse radiation data is one of the most important parameters for assessing solar energy resource and designing grid connected photovoltaic system, due to the characteristics of ground solar radiation change significantly in recent years, previous solar beam-diffuse radiation separated model has been unable to true reflect the variation of solar radiation. A method for estimating diffuse radiation fraction Hd/H is proposed. Take Beijing as an example, according to the local measured radiation data during 10 years, with localized revising of Erbs, a new model is built. Then the relative number of sunshine hours S/S0 is introduced to establish the new regression equation with better fitting effect. Furthermore, the accuracy of model is validated using measured data consists of solar radiation and sunshine hours of 2011. Comparison of four models is performed through error analysis. It is found that the model including two variable is of high prediction accuracy. In most months, the error is lower than 10% The new model more in line with the radiation characteristics of the local actual, for photovoltaic system design has the reference significance.