An approach for estimating average daily global solar radiation from cloud cover in Thailand

Abstract

Global solar radiation is important for solar energy applications. In this work, an approach for estimating monthly average daily global solar radiation in Thailand was proposed. In developing this approach, cloud cover and global solar radiation measured at 24 sites in Thailand were analyzed. According to the analysis, values of normalized monthly average daily global radiation were correlated with those of monthly average cloud cover. Then linear equations relating the normalized global radiation with the cloud cover were formulated. In the next step, the values of the slope and intercept of the equations from all sites were determined. These values were interpolated to cover the entire areas of the country and they were presented as contour maps. In the final step, a general empirical equation for estimating the average daily global radiation from the cloud cover was proposed. The model coefficients for the entire areas of the country were obtained from the maps. For the validation, the general equation was used to calculate average daily global radiation at 4 sites whose data were not used in the model development process. Finally, the results were compared with the measurements and they were in good agreement.