A simple and easily implementable model for the prediction of solar irradiance for all-sky conditions : model development, preliminary evaluation and application

Abstract

A simple and easily implementable model and the associated computer code for predicting the solar irradiance at the earth’s surface have been developed. The input requirements of the model include Julian day, time, geographical latitude, atmospheric pressure and cloud cover. If the latter is not available, then the program user has the option of entering either the daily global solar flux or the duration of sunshine, from which the average cloud cover is estimated. Preliminary model evaluation has been carried out using data from two meteorological stations situated in rural and semi-rural areas of the East Midlands, United Kingdom. The scatter plots of predicted versus observed solar irradiance gave correlation coefficients approximately equal to 0.6 and slopes in the range of 0.80–0.93. The model is being implemented as a submodule within an urban air quality model. This specific application of the solar radiation model is discussed as a typical implementation. This work shows that by adopting relatively simple ‘textbook’ material, i.e., basic theory/information, one can achieve reasonably good solar radiation modelling, with outcomes that can be used for applications where accuracy is not a major requirement.