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The energy yield of a Photovoltaic (PV) power plant depends upon the dc power output of the PV module. The irradiance and temperature are the two most important parameters affecting the dc power output. This paper analyses the dc power output of a multicrystalline PV module in the realistic environmental condition with respect to solar irradiance, ambient temperature and cell temperature. The real time data is collected from a 5 MW grid connected solar PV plant located in Jaisalmer, a district in Western Rajasthan. The paper brings forward a crucial and valuable fact that the modules work more efficiently at high temperature and high solar irradiance. For a multicrystalline PV module with maximum dc power output (P max ) at STC condition equal to 118.687KW, analyzed over a period of one year it is found that maximum dc power output (P dc ) at 22 o C ambient temperature and 40 cell temperature is only 72 KW while maximum P dc at cell temperature around 50-55 o C and ambient temperature around 35-38 o C is 90-92KW. Slight negative temperature coefficient for P dc with respect to temperature is observed if ambient temperature and cell temperature is greater than 35 o C and 50 o C respectively. However power output increases in direct proportion to irradiance outweighing the change in temperature. Higher the irradiance, higher is the dc power output, higher is the efficiency and correspondingly higher is the energy yield of the PV module. The multicrystalline PV module works efficiently and gives high yield in the extremely high temperature of Western Rajasthan. Rajasthan which receives world second largest radiation has the capability to meet the energy demands of India and the world as well if solar energy is harnessed in appropriate way.

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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(V dc ) 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 o C to 60 o C but as soon as sun begins to descent, cell temperature starts reducing and V dc 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 45 o C, neither V dc 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.

The Photovoltaic technology has shown remarkable development in last few years but still lot of research is required to increase the energy yield and reduce solar electricity cost. Even a small increase in energy yield can lead to improved photovoltaic power plant performance and significant reduction in solar generated electricity cost. Evaluating real time data for determining the plants performance plays significant role as it is the climatic conditions which directly affect the power output and evaluating the climatic conditions that can lead to increase the energy yield can bring revolution in the field of solar photovoltaic. This paper evaluates simultaneous effect and role of irradiance and cell temperature on the dc voltage, dc current and dc power, the key determinant of energy yield based on the real field data set of 5 MW grid connected Solar Photovoltaic power plant of Western Rajasthan. It brings forward for the first time ever that high cell temperature plays defining positive role in increasing the energy yield and consequently improving the plant's performance in contrast to literature and research papers.

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