In this paper, the incident solar radiation on horizontal and tilting surfaces was measured of a year using a pyranometer on the roof of Tanta University's Faculty of Science in Tanta city which is locating at Latitude (30° 41`). The average of daily global hourly solar radiation values on horizontal surfaces (H) and the global hourly solar radiation values on inclined surfaces (Ht) had been measured in the south direction of the sun for the meteorological variables. Miguel et al. correlation was used to determine hourly values of the beam and diffuse components of solar radiation (SR) from global solar irradiance. In order to attain best solar module performance throughout the year, the solar energy devices must be tilted south with a tilting angle equal to Tanta city latitude. The maximum value of Ht was 1174.15 Wm-2 in April and the minimum value of Ht was 816.11Wm-2 in October. The performance of 100 W solar silicon photovoltaic (PV) module in outdoor condition can be studied by depending on the incident values of H and Ht. The obtained results showed that the efficiencies of the 100 W solar PV module in winter, spring, summer and autumn were 4.29, 3.78, 7.56 and 4.58 %, respectively. The Maximum power point (Pmax) was calculated in July and its value was 45.98 W at solar noon and the minimum power point (Pmin) was calculated in October with value equal to 18.56 W at solar noon.