Statistical properties of hourly global radiation
Solar Energy, 48 (3):
157--167 (1992)Abstract
The statistics of hourly global radiation are analysed for various
climates and locations, at time scales ranging from one month to
one hour. The probabilistic and sequential properties of the hourly
clearness index kt are related with a variety of parameters, including
the daily clearness index Kt and the solar altitude angle h, thereby
displaying the nonstationary and time-inhomogeneous nature of hourly
radiation. Analytical expressions for the probability distribution
of k t are proposed (truncated Gaussian functions depending on Kt
and h). The results reported in this paper provide a deeper understanding
of hourly solar radiation statistics, and explain some of the features
displayed by radiation data at longer time scales. From the practical
point of view they have implications, for example, for the construction
of models for generating synthetic radiation data, an important and
often indispensable tool for designing and simulating solar systems.