The probability density function [formula omitted] of the clearness index: A new approach

Abstract

Utilizability methods which predict long-term average energy delivery of solar systems are all based on the precise knowledge of frequency distributions of insolation values. This paper presents a simple and physical model for the clearness index probability density function, from which frequency distributions are easily derived. The model predictions agree very well with experimental data from Guadeloupe, a tropical humid area. It is very likely that this model will apply in other tropical areas and, at the expense of a slight increase in complexity, for other climates.