Solar irradiance and cell temperature are the two most important parameters governing the efficiency of PV power plant. This paper presents simultaneous impact of cell temperature and the irradiance falling on the plane of solar panels- POA (Plane of Array Irradiance) on the dc voltage(Vdc) of a multicrystalline Photovoltaic(PV) module, one of the most important parameter governing dc power and hence efficiency of (PV) power plant. In contrast to existing literature which specify negative temperature coefficient for Vdc above 25oC cell temperature, analysis in actual environmental conditions of Western Rajasthan for a grid connected multicrystalline PV power plant shows that Vdc has about -0.431%/oC temperature coefficient for cell temperature greater than 49oC and not 25oC as evaluated in laboratory. Moreover, voltage for cell temperature in the range of 49-60oC is far greater than voltage at 25-45oC. Further at very high cell temperature of about 49oC dc voltage (Vdc) reaches a point of saturation attaining 85% of its maximum rated value. It decreases slightly by about 4% as cell temperature increases from 49oC to 60oC but as soon as sun begins to descent, cell temperature starts reducing and Vdc starts increasing, maintaining nearly constant value in the range of 80-85% of its maximum rated value for about 6-8 hours. If cell temperature is less than about 45oC, neither Vdc reaches point of saturation nor does it attain constant value. Thus, high cell temperature has overall positive effect on dc voltage of a multicrystalline grid connected PV power plant. Western Rajasthan being blessed with high temperature and high insolation for 6-7 hours in a day for about eight months has the capability of high energy yield as dc power is directly proportional to dc voltage.

Multicrystalline; high cell temperature; temperature coefficient; Plane of Array Irradiance(POA); Western Rajasthan.