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# How to Test the Efficiency of a Photovoltaic Cell? (page 2)

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Author: Michael Calhoun

### Materials:

Photovoltaic cell, electric hobby motor with small plastic fan blade, wires, sheet of cardboard, multimeter, protractor, 5 ohm resistor, metric ruler, and masking tape

With the exception of the protractor, tape and metric ruler all the other items can be purchased from the local RadioShack retailer or from a hobby shop also, a Tri-fold cardboard display board can be purchased from an art & crafts supply store.

An inexpensive photovoltaic or solar cell can also be ordered online from Educational Innovations, and a multimeter is available from Science in a Bag or RadioShack.

• What materials are required?
• Where can the materials be found?

### Experimental Procedure:

Data Table 1

 Photovoltaic cell area. Angle of fastest motor speed cm2 Voltage across the resistor Current in the circuit

Voltage X current

= watts/cm

Area

 Power Output Watts/cm2

 Power Output Watts/meter2

Data Table

 Photovoltaic cell efficiency %
1. Gather the following materials: photovoltaic cell, electric motor with fan, wires, cardboard sheet, multimeter, protractor, 5 ohm resistor, tape, and metric ruler.
2. Measure the length and width of the photovoltaic cell (do not include the base) and calculate the area using the following formula: Area = width x length. Record this value.
3. Place the photovoltaic cell, electric motor with fan on the piece of cardboard and secure using tape as shown. Use the wire to make the connections.
4. Bring the setup outside into direct sunlight.
5. Set the board on level ground and hold it so that the Sun casts no shadow over it.
6. Vary the angle of the electric circuit board by tipping one end of it up or down and observe what happens to the speed of the fan at different angles.
7. Readjust the angle of the electric circuit board until the fan’s speed is the fastest. Record the angle using the protractor.
8. Replace the motor-fan with a 5 ohm resistor and connect the circuit as shown.
9. Use the multimeter to measure voltage across the resistor.
10. Record the voltage.
11. Disconnect the circuit at point A and connect the multimeter and measure current in the circuit.
12. To determine how much of the energy that is reaching the photovoltaic cell is being converted into power use the following formula:
13. Record the results.
14. Then multiply the results by 10,000 to convert the value to watts/meter2
15. The following values are estimates for how much energy reaches Earth surface on a sunny day, according to the time of year
• 1000 watts/m2 on a sunny summer day
• 900 watts/m2 on a sunny autumn or spring day
• 700 watts/m2 on a sunny winter day
16. Depending on the time of year, one of the values above is the power input from the sun that is converted into electrical energy by the photovoltaic cell.
17. Use the formula to calculate the efficiency of photovoltaic cell.
18. Record the results.