Practical method for forecasting amounts of global solar radiation in wide area

A practical method is proposed for forecasting global solar radiation in a wide area which, in turn, is used for photovoltaic generation output forecast. For ease of forecasting procedure, the area is divided into sub-areas or groups of sites. Sites having similar weather form a group. The similarity is calculated using mean absolute deviations or correlations among the actual sunshine duration data. The forecasting procedure becomes simpler by focusing on a single representative site in each group. In addition, it is found that a common forecasting model can be successfully used for a number of different groups, which saves the operator's workload without deteriorating the forecasting accuracy.