Iv curve parameters

IV curve parameters of a solar panel

1. Solar Module IV Curve Parameter's

2. Overview

3. IV Curve of Solar Cell I-V curve gives information on: – Performance ( Pmax , Voc , Isc , η and FF ) Resistance of the PV-module ( Rs and Rsh ) Improper cell and module design Improper manufacturing Faulty module manufacturing Effect of parallel and series connections Non-uniform anti-reflective coating Possible micro-cracks and/or hotspots Loose wiring in junction box

4. Open Circuit Voltage (Voc) The Voc is the Maximum Voltage From a solar cell and this occurs Zero Current. Voc depends on: – Band gap of semiconductor Amount of doping of P&N layers Material purity Light generated current . Temperature of the PV-module

5. Short Circuit Current ( Isc ) The short-circuit current is the current through the solar cell when the voltage across the solar cell is zero I sc depends on: Spectrum of light source Optical properties of the PV module (light absorption) Number of photons (i.e. power of light source / intensity) Area of PV module

6. Efficiency Of Solar Module The Efficiency is most commonly used parameter to compare the performance of one PV-module with the other . Ratio of energy output from the PV-module ( P max ) to input from the sun (P in )   η = P max / P in Or Module Wattage/Area

7. Shunt Resistance Low shunt resistance provides an alternate current path. This reduces the amount of current flowing through the solar cell and reduces the voltage. Shunt resistance should be high. • Effect is bigger at low light levels: – Less light generated current, I impact of loss is larger. – When cell has lower voltage, the impact of resistance in parallel is large.

8. Series Resistance Series resistance should be as low as possible. Or Else there will be Poor conduction These May Occur Due to Three causes, mainly poor solar cell design The movement of current through the emitter and base of the solar cell The contact resistance between the metal contact and the silicon . The resistance of the top and rear metal contacts.

9. CTM Loss CTM Loss= (( Cell wattage * No of Cell-Produced wattage )/( Cell wattage * No of Cell ))* 100 Losses May occur due to EVA Used Busbar Used TCI (Tin Copper Interconnector Glass Used Junction Box Used Distance Between Cells , String and Frames.

10. Fill Factor (FF) Fill Factor is the ratio of the maximum power from the solar cell to the product of Voc and Isc . The short-circuit current and the open-circuit voltage are the maximum current and voltage respectively from a solar cell Formula for Calculating the Fill Factor is FF = (( Vmp x*Imp)/(Voc * Isc )) *100 Fill Factor Depends Upon Series And Shunt Resistance If The Module Is Having Fill Factor of 70 t0 80% then Module Is Considered a s a Class A Quality Module

11. Standard Test Condition For Testing the Solar Panel are as Follows Temperature, ie 25 C Irradiance/Light intensity, Ie 1000W/M Air Mass, Ie 1.5 ie When The Sun is exactly Perpendicular at that time intensity will be high and when sun is at a Slant position at that time Intensity will be 1000 It Is Calculated by AM = 1/Cos  or Shadow height/Width STC Condition

12. Maximum System Voltage is is dependent upon the Some of the Factors type of the junction box and Diode Used. Type of Back sheet used Spacing between frame, cell, string, busbar . For Ex if the system voltage is 1000v then number of panels connected in series should be 20 i.e.. 1000v/ Open Circuit Voltage. If The System Voltage Is Changed Means then There will be some Changes in modules Change Of Junction Box Type of backsheet Used Gap between Cells, busbar , Frame need to be Changed. Maximum System Voltage

13. Isc of a PV Panel will be around 10A To calculate the maximum source circuit current, requires you to multiply the rated Isc value by 125% If ithe isc is 10A then 10*1.25=12.5A The maximum fuse rating of a diode is 15A Maximum Series Fuse

14. All solar cells have a temperature coefficient. As a solar panel increases in temperature, the power output of the solar panel decreases. Generally, monocrystalline solar cells have a temperature coefficient of -0.5%/ degC (Depending of Manufacturers). This means a mono solar panel will lose half of one percent of its power for every degree the temperature rises. Solar panels are all rated at 25degC, however, when solar panels are installed on a roof, they generally reach much higher temperatures Lets say a 250W monocrystalline solar panel installed on a roof is at 65degC. The solar panel’s power loss can be calculated as follows: 65degC – 25degC = 40degC 40degC x -0.5% = 20% Therefore panel power loss = 20% x 250W = 50W Therefore panel power = 200W Temperature Coefficients

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