Quoted from:Said R ,  Mansor M ,  Abuain T . Estimation of global and diffuse radiation at Tripoli[J]. Renewable Energy, 1998, 14( 1–4):221-227.https://www.sci-hub.ren/10.1016/s0960-1481(98)00071-8

Different correlations were used to predict monthly average global and diffuse radiation on a horizontal surface at Tripoli. The estimated results are then compared with the experimental data for the year 1989-1990. Using statistical tests the RMSE, MBE and MABE to evaluate these correlations, it was found that the Dogeniaux-Lemoin, and the Erbs-Klein and Duffie correlations are the best to predict the global and the diffuse radiation respectively.

INTRODUCTION

In order to design any solar energy system or study the potential of solar energy in a region, information on the availability of solar irradiance; monthly average values of daily global radiation as well as its direct and diffuse components are needed. Although the measured global data are available for many locations in the world there are some places  that lack this data and only few places posses measured data for diffuse radiation. This had led researchers to develop models to estimate global and diffuse radiation. All models to estimate the global radiation use some meteorological parameters such as: sunshine hour duration, cloud cover ratio, precipitation, minimum, maximum and average temperatures as well as the relative and specific humidity, all of which are more available than global radiation measurements, Most models to estimate the diffused comtxment use the measured global radiation and only few use the sunshine duration.

In this work we calculated the monthly average global radiation as well as the monthly average diffuse radiation using different models for the city of Tripoli Latitude 32 ° 52' longitude 13 ° 11’rand elevation(80m). The analysis of these ealcnhtions were baaed on the measured values of monthly average daily global and monthly average daily diffuse radiation by Amer(Amer,1992) for the year 1989-1990. The Kipp and Zonen equipments (Holland) were used to measure the global and the diffuse radiation instead of Casella (England) bimctalic actinographs, and it is believed that the measured data is more informative than the previous measurements (Bad)ash et al., 1987) which was only done for the global radiation. 

In this work the analysis was based on one year measmements and longer period measurements of the diffuse radiation is recommended in order to establish a statistically more accurate trend for Tripoli and cities with a similar climate.