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Plot V-I characteristics & measure open circuit voltage & short circuit current of a solar panel.

OBJECT:- Plot V-I characteristics & measure open circuit voltage & short circuit current of a solar panel.

APPARATUS REQUIRED:-  Omega type ES-290 solar cell kit, patch cords.       

THEORY:-To understand the operation of a solar cell, we need to consider both the nature of the material and the nature of sunlight. Solar cells consist of two types of material, often p-type silicon and n-type silicon. Light of certain wavelengths is able to ionize the atoms in the silicon and the internal field produced by the junction separates some of the positive charges ("holes") from the negative charges (electrons) within the photovoltaic device. The holes are swept into the positive or p-layer and the electrons are swept into the negative or n-layer. Although these opposite charges are attracted to each other, most of them can only recombine by passing through an external circuit outside the material because of the internal potential energy barrier. Therefore if a circuit is made power can be produced from the cells under illumination, since the free electrons have to pass through the load to recombine with the positive holes.

SHORT CIRCUIT VOLTAGE:- The short-circuit current, Isc, is the current that flows through the external circuit when the electrodes of the solar cell are short circuited. The short-circuit current of a solar cell depends on the photon flux density incident on the solar cell, that is determined by the spectrum of the incident light. For the standard solar cell measurements, the spectrum is standardized to the AM1.5 spectrum. The Isc depends on the area of the solar cell. In order to remove the dependence of the Isc on the solar cell area, the short-circuit current density is often used to describe the maximum current delivered by a solar cell. The maximum current that the solar cell can deliver strongly depends on the optical properties (absorption in the absorber layer and total reflection) of the solar cell.

 OPEN CIRCUIT VOLTAGE:-The open-circuit voltage is the voltage at which no current flows through the external circuit. It is the maximum voltage that a solar cell can deliver. The Voc corresponds to the forward bias voltage, at which the dark current compensates the photo-current. The Voc depends on the photo-generated current density and can be calculated from assuming that the net current is zero.

The above equation shows that Voc depends on the saturation current of the solar cell and the photo-generated current.

 

CIRCUIT DIAGRAM:-

 

Figure 2.1 circuit for measurement of solar panel

 

Figure 2.2 characteristics of open circuit voltage and short circuit current

 

PROCEDURE:

  1.  ILLUMINATION CHARACTERISTICS
  1.  Make the circuit diagram
  2.  A 100W lamp is arranged over the solar panel such that light falls on it at normal. The intensity control is kept at its minimum and lamp is switched on.
  3.  The load is kept at 0 ohms and the short circuit current is noted.
  4. The intensity of the lamp is varied in steps and the current is noted at each setting. The readings are recorded in the table.

OBSERVATION TABLE:-

S. No.

Intensity(Dc Volts)

Current(Dc mA)

1

 

 

2

 

 

3

 

 

4

 

 

 

 

  1. CURRENT VOLTAGE CHARACTERISTICS
  1. The intensity o the lamp is kept at minimum. The load resistance is not connected into the circuit. The open circuit voltage is noted.
  2. The output of the solar panel is shorted. The short circuit current is noted.
  3.  The load dial is set at 100 ohms. The voltage and current are noted. The load is varied in steps.
  4. The intensity of lamp is increased. At this setting load is again varied in steps.
  5. The graph for current versus voltage is drawn.

 

 

 

 

OBSERVATION TABLE:-

S. No.

Rl (ohms)

Intensity I1

Intensity I2

Intensity I3

Voltage

Current

Voltage

Current

Voltage

Current

1

 

 

 

 

2

 

 

 

 

3

 

 

 

 

4

 

 

 

 

5

 

 

 

 

               

 

RESULT:-

  1. In short circuit case the current is found to vary linearly with the intensity
  2. The open circuit voltage developed by the panel is found to be …..Volt, .volt …volt corresponding to I1, I2, I3 respectively.

PRECAUTIONS:-

1. Shut down the kit when not in use.

2. Record the readings properly.

QUESTIONS:-            

  1. Write the factor on which the short circuit current depends?
  2. What is dark current?
  3. Write the name of materials used for solar cells?

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