Development of improved solar radiation models for predicting beam transmittance

A pair of enhanced models are presented herein which, while relying only on global irradiation measurements, result in increased predictive power in estimating the hourly beam irradiation. The first model correlates the beam transmittance with clearness index and air mass. The second correlates the beam transmittance with the clearness index and with a new variable based on the temporal variation of the global radiation. The new variable helps describe the sky condition without the need of any further meteorological information. The models were developed using a new surface fitting technique applied to data which were collected at the Solar Total Energy Project in Shenandoah, Georgia (33.4°N, 84.7°W) over a five-year period.