As mentioned before, PV panels are tested to determine their watt peak at standard test conditions (1000 W/m2 at cell temperature of 25oC ). A side-effect of having to encapsulate the PV panel is the prevention of the heat flow out of the module. Hence increasing the operating temptation of the PV panel. Higher operation solar cell temperature results in failure or degradation of the panel since elevated temperature increase stresses related with thermal expansion and boots the degradation rates by a factor of two for each 10 oC increase in temperature. In order to determine the output power form the solar cell in the field. It is very decisive to calculate the expected operating temperature of the PV module. With variations in ambient temperature and irradiance the cell temperature (Tc) can be approximated using