سمريةمعة الجا مجلة ا: اساسيةعلوم ا ل والتطبيقية ( مجلد ال2 ( العدد) 2 ، ديسمبر) 2017 م 88 Estimating global , direct , diffuse and reflected solar radiation on horizontal and tilted surfaces in Tripoli , Libya Ali. S. Al-Nuaimi* Tarig Elmabrouk Department of physics – Faculty of Science- Omar Al-Mukhtar university – Beida – Libya E mail ; Nuaimiett@yahoo.com , Elmabrouk2010@gmail.com Keywords: Global radiation ,direct , diffuse radiation , horizontal , tilted surfaces ,Renewable Energy, Tripoli , Libya Introduction: Solar energy occupies one of the most important types of renewable energy sources . It is the energy provide by the sun .Solar radiation data are fundamental inputs for solar energy applications , such as photovoltaic , and solar thermal systems . The design of a solar energy conversion system requires knowledge regarding the availability of global solar radiation and its component at the location of interest (1). An accurate knowledge of the solar radiation data for a particular location is a pre requisite , in estimating the thermal performance and economic efficiency of solar energy systems .The availability of these data may be of the form of types of total , direct , diffuse , and reflected radiation . These data may be needed on daily , monthly or yearly time scales . Each of these forms is important and has particular usage in specific applications. In a recent report(2) Libya is the 16 th largest country in the world in terms of land mass according to OPEC.org. Its economy depends primarily on revenues from the oil sector , which contribute about 95 percent of export earning .Libya has the potential to become a renewable energy giant according to Responding to Climate Change .Libya is located on the cancer orbit line and is exposed to the sun rays through the year with long hours during the day . It boasts a very high daily solar radiation rate – on a flat coastal plain it is about 7.1 kilowatt hours per square meter per day , and in the south region it is about 8.1 kWh/m 2 /day. If we compare this amount for instance with the Great Britain we see that Great Britain has half than this amount which is about 2.95 kWh/m 2 /day . Libya could generate approximately five times the amount of energy from solar power than it currently produces in crude oil . If this country which is estimated to be 88 per cent desert used only 0.1% of its landmass to harness solar power , it could produce the equivalent to almost seven million barrels of crude oil per day in energy . Renewable energy technology is still in its very early days in Libya and a clear strategy and timetable is needed to take it forward .In particular , work needs to be done to develop the skills and knowledge needed to install and maintain renewable energy systems .(3) Many models have been developed to estimate the amount of global solar radiation on horizontal surfaces using various climatic parameter, such as sunshine hours Many authors find it is