To Study the Temporal Variation of Capacity Utilization Factor (CUF) of PV Based Solar Power Plant with Respect to Climatic Condition

Performance, quality and reliability of technology are becoming more and more important for the emerging photovoltaic markets worldwide. In this experiment the monitoring of climatic factors like, solar radiation, Ambient Temperature, Module Temperature, Relative Humidity and Wind Speed was carried out on daily basis for six months, between 7:00 A.M to 6:00 P.M. Data was measured with SCADA system. This analysis was carried out by monitoring the fluctuation in power output of the system with climatic factors. From the results, there is direct proportionality between the power output of the system and the climatic factors. The correlation between ambient air temperature, PV module temperature and CUF is strongly positive. The other climatic factor like wind speed is does not have much significant effect on CUF. The Relative humidity is negatively correlated with CUF. The correlation between solar radiation and the CUF is strongly positive. keywords: Photovoltaic, Solar Radiation, Environmental Factors, CUF, Environmental Effect.


inTROdUCTiOn
The sun provides a plentiful resource for generating clean and sustainable electricity without global warming emissions or toxic pollution.A device that converts solar energy into electricity is known as solar cell 1 .They produce electricity directly when sunlight penetrate on semiconductor is generate pairs of electrons (-) and protons (+) in the PV cells through photovoltaic effect.The basic process of solar photons energy convert in to electromagnetic energy, through which a PV cell converts sunlight into electricity, is known as photovoltaic effect 2 .Sunlight is composed of photons, or particles of solar energy.A PV cell is typically made from crystalline silicon of 12 centimeters in diameter and 0.25 millimeters thickness.In full sunlight, it generates 4 amperes of (DC) direct current at 0.5 volts or 2 watts of electrical power 3 .
The climatic factor is known as physical conditions that determine the climate in a given area.The solar photovoltaic cells output performance varies with atmospheric factors.Since sunlight is intermittent, solar cells cannot generate electricity at a constant rate and the power delivered at a certain instant is still very much a function of weather factors 4 .Solar light intensity, temperature, relative humidity and wind speed are factors that affect the output performance of solar photovoltaic system 5 .
Temperature is a physical property of matter that quantitatively expresses the common sentiments of hot and cold object.As the PV cell temperature rises above the standard operating temperature of 25 0 C, the system operates less efficiently and the voltage decreases.In this case heat can be considered as resistance to flow of electrons so effective current may also decrease.A panel temperature between 80 to 90 0 C, 0.5 % losses in efficiency per every degree rise in temperature 6 .In solar systems without batteries, temperature rise is more noticeable hence airflow above and under the panel is critical to remove heat 7 .Relative humidity defined as the ratio of water vapor actually in the air to the maximum water vapor the air can hold at a given temperature 8 .When air is relatively dry compared to its capacity then the relative humidity percentage is low.The percentage of humidity reduce the amount of visible solar radiation reception, while humidity and wind speed both acts as cooling agents that increase the output of a PV module by reducing the module temperature 9 .
The speed and direction of the wind is called wind velocity.Photovoltaic plant provides the possibility of freely orientating the panels according to sun angles.The solar panels are typically mounted at an angle of 30 degrees, with a light steel structure to keep them in position 10 .One traditional approach for smaller module installations has been to assume the highest wind load coefficients found in the wind action guidelines, a clearly uneconomical approach.The limited residual load capacity of module, combined with the use of ballast instead of penetrative fastenings, makes economical wind load coefficients desirable and often necessary 11 .The functioning of PV modules at any time depends on various ambient variables including majorly temperature, humidity, light intensity, wind velocity, and other factors 12 .Sometimes we want to get the value of instant efficiency to test the functioning of module at that instant, the main aim of this paper is to solve this kind of various problems, here an attempt has been made to obtain an equation among  efficiency, temperature, humidity, light intensity and wind velocity, so that instant efficiency of module can be estimated by knowing temperature, humidity, wind velocity, light intensity using simple devices 13 .
Capacity utilization factor is a concept which refers to the extent to which a nation or a unit actually uses its installed productive capacity 14 .Thus, it refers to the relationship between actual output that is produced with the installed equipment and the potential output which could be produced with it, if capacity was fully used.CUF is the most overused word when it comes to measuring a solar Fig. 2: Comparative accounts of climatic factors and power generation power plant performance 15 .For a Solar Photovoltaic (SPV) project, Capacity Utilization Factor (CUF) is the ratio of actual energy produced by SPV plant over the year to the equivalent energy output at its rated capacity over the yearly period 16 .

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So on the other side is CUF that completely ignores all these factors and also the de-rating or degradation of the panels.Therefore we are not convinced that the CUF is a good tool to provide insights into a solar PV system.The aim of present study is to determine the temporal variation of capacity utilization factor (CUF) of PV Based Solar Power Plant with Respect to Climatic Condition.

maTeRialS and meThOdS
The study of Climatic Factors and Capacity utilization Factor of Photovoltaic Based Solar Power Plant in natural scenario was studied and determined with effect of climatic factors.The study area falls at 23° 33' 35" N latitude, 73° 17' 07" E longitude, a PV based solar power plant is located at Village-Bhatkota (Modasa) Gujarat.The monitoring of climatic factors like, solar radiation, wind velocity, Humidity and Temperature was carried out on daily basis for six months between 7:00 A.M to 6:00 P.M.The technical information about solar PV based power plant's detail is given in table 1.
All the data was measured with the help of standard instruments and data was recorded on computer with the help of SCADA system.An integrated SCADA shall be supplied which should be capable of communicating With 6 nos 500 KW inverters and provide information of each 500 KW Power Conditioning Unit (PCU) and the Entire 3 MW Solar PV Grid connect power plant.The SCADA shall also provide Information of the instantaneous output energy and cumulative energy for each of the Inverters as well as for the 3 MW grouped Solar PV Grid connect power plant.

ReSUlT and diSCUSSiOn
The comparative account of data analyzed is given in figure 2. The temporal variation of the capacity utilization factor with different climatic factor is shown in figure 3. The average values of the data are shown in the table 2. The correlation analysis for the data is shown in table 3. Collected data was analyzed by using standard Microsoft Excel.And also found the correlation between power generation and capacity utilization factor respectively.From the correlation coefficient analysis it is been revealed that the ambient air temperature and PV module temperature is highly correlated whereas ambient air temperature and humidity and wind speed is negatively correlated.The PV module shows the similar co relation with humidity and wind speed as the ambient air temperature.The correlation between ambient air temperature, PV module temperature and capacity utilization factor was found positive.Where on other hand the correlation of wind speed and capacity utilization factor was not so significant.The correlation between relative humidity and capacity utilization factor was found negative.The correlation between solar radiation and capacity utilization factor was found strongly positive.

COnClUSiOn
From the above study it can be concluded that there is significant temporal variation in capacity utilization factor with respect to climatic condition.The variation of CUF is highly correlated with solar radiation and the correlation coefficient derived between solar radiation and CUF was found strongly positive.The CUF variation was also compared with ambient air temperature and module temperature, the variation was moderately positively correlated.While the variation among humidity and wind velocity did not affect much to the CUF variation and they are found negatively correlated to each other.

Table 2 : Average data of Climatic Factors
Fig.