The applicability of hourly solar radiation models to Amman, Jordan

Abstract

Hourly and daily global and diffuse solar radiation data measured on a horizontal surface during the period 1983–1987 for Amman, Jordan are studied and analyzed. The observed ratios between monthly mean hourly to daily global and diffuse radiation are determined. The applicability of various radiation models for the estimation of hourly global and diffuse radiation from daily values of global and diffuse radiation, respectively, for Amman is tested against measured data. The normal distribution curve suggested by Jain [Solar Wind Technol.5, 7 (1988)] is found suitable for predicting hourly global radiation for Amman and it has shown excellent agreement with the observed values amobgst all other models used. The classical equation of Liu and Jordan [Solar Energy4, 1 (1960)] produced satisfactory results of hourly diffuse radiation which are much closer to the observed values as compared to that obtained using other suggested models. Comparison between results obtained using various radiation models is made by calculating the root mean squared error, RMSE, for each model used.