New Models for Estimation of Diffuse Solar Radiation for Warri, Nigeria

Abstract

This study utilized a 22-year dataset (2001-2022) comprising monthly average daily global solar radiation, diffuse solar radiation, relative  humidity, atmospheric pressure, wind speed, and mean temperature for Warri (Latitude 5.52 oN, Longitude 5.73 oE and 6.10 m above sea  level). Nineteen models, categorized into modified Page, Liu, and Jordan models; clearness index and one variable models; two variable  models; three variable models; and four variable models, were developed and statistically tested using the following validation indices of  Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t-test, and coefficient of determination (R²).  Among the models, the linear page model from the modified Page, Liu, and Jordan category, the model that relates the diffuse solar  radiation with clearness index and mean temperature for clearness index and one variable models, the model that relates wind speed  and atmospheric pressure for two variable models, and the model that relates wind speed, atmospheric pressure and relative humidity  for three variable models were found more appropriate. Upon ranking the best-performing models from each category, the model that  relates that diffuse solar radiation with clearness index and mean temperature performed best as the most suitable model for estimating  diffuse solar radiation in Warri.