Stochastic simulation of solar radiation from sunshine duration in Sri Lanka

Abstract

A stochastic model for generating daily sunshine hours and solar radiation that reaches the earth's surface in dry zone of Sri Lanka has been developed. Historical sunshine data which represent a Weibull probability density function and universal Angstrom type equations were used in the model giving daily and monthly sunshine and solar radiation. Simulated values clearly follows the astronomical phenomenon and local atmospheric conditions. The lowest solar radiation values (14 to 15 MJ m⁻² day⁻¹) were obtained during the major rainy season. The highest values (around 20 MJ m⁻² day⁻¹) were evident around the Vernal Equinox (March and April). Sri Lanka being small in size (65,000 km²) and small latitudinal extent (<4°), the model may form the basis for more comprehensive solar radiation generating models for other areas in Sri Lanka.