P reliminary results of the fractal classification of daily solar q irradiances

This paper deals with the fractal modeling of daily solar irradiances measured with a sampling time of 10 min for one year at Tahifet and Imehrou located in the desert of Algeria. The aim of this modeling was to estimate the fractal index and then to use it to classify the considered daily irradiances. Therefore, daily fractal and clearness indexes were used to propose a classification model that leads to three typical classes. These classes (corresponding to clear sky, partly cloudy sky and completely cloudy sky) allow us to characterize the daily irradiance profiles of both locations. The results of the classification model were then applied to the performance analysis of an autonomous photovoltaic system installed at Tahifet. Good agreement was observed between the long-term performance indicators and those obtained while studying typical cases.  2003 Published by Elsevier Ltd.