Cool Your School – Electricity Lab
Photovoltaic Cell: Converting Light to
Electricity
Outcomes:
1. Understand that a photovoltaic cell produces DC voltage when light
shines on its surface.
2. Understand that the electrical voltage produced by a photovoltaic cell
depends in part on the intensity of the light shining on it: greater
intensity = greater voltage.
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3. Understand that the electrical voltage produced by a photovoltaic cell
is proportional to the surface area of the cell’s active surface.
Materials:
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A photovoltaic cell
A lamp
A multimeter that can measure current and voltage
Setup:
1. Set up the lamp in a place where it will shine with full brightness onto
the surface where the PV cell will be placed. A typical 100 W lamp
shining onto the surface from a distance or a foot should work fine.
2. Set up the multimeter with its probes connected to the PV cell’s
electrical terminals. Jumper wires with alligator clips may be
necessary to connect to the probe ends.
3. Refer to the setup page for the multimeter at the end of this sheet to
see how the probe plugs and dial need to be configured to make the
different measurements (current and voltage) you will be doing.
What To Do:
1. Measure the surface area of the photovoltaic cell, in square
centimeters. Surface area = length x width, assuming the cell is
rectangular.
2. Connect the multimeter probes to the PV cell’s electrical terminals and
set it to measure voltage.
3. Place the PV cell under the lamp and move it around until you find the
position where it generates a maximum voltage. Record that voltage.
4. Without changing the position of the lamp or PV cell, switch the
multimeter over to measure electrical current and record the value.
5. Calculate the power, in Watts, produced by the PV cell, with current in
Amps and voltage in Volts:
Power = Current x Voltage
Questions:
1. What happens to the voltage generated by the PV cell when you
change the angle of the cell’s face with respect to the lamp? At what
angle does the cell generate maximum voltage?
2. How many of these PV cells would you need to power a 100 W
incandescent light bulb?
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3. How many would you need to power a 20 W CFL bulb?
4. How many Watts would a full square meter (10,000 square
centimeters) of this type of photovoltaic cell produce? (Hint: First
calculate Watts per square centimeter by dividing the maximum power
generated by the cell’s surface area, in square centimeters, that you
calculated, then multiply that result by 10,000 cm.)
Further Experimentation:
Repeat the experiment, but using full sunlight instead of a lamp. To achieve
the maximum voltage and current (and thus power) from the Sun, you’ll
need to aim the PV cell’s active surface at the Sun as directly as possible.
Once you find the right position for the cell, make sure you don’t change it
between readings of voltage and current.
Once you have calculated the power that a full square meter of this PV cell
would generate, you can calculate the efficiency of the cell at converting
sunlight to electricity.
The approximate intensity of full sunlight (in a clear sky) at the Earth’s
surface is about 1000 W per square meter. So, if you divide the power that
1 square meter of PV cell generates by 1000, and multiply that result by 100
to a percentage, the result is the efficiency of the cell.
For example, if the maximum power of 1 square meter of PV cell surface is
70 Watts, then the efficiency of the cell is:
Efficiency = (70 / 1000) x 100 = 7%
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Photovoltaic Cell Worksheet
PV Cell Dimensions:
Length _______ cm
Width _______ cm
Surface Area (if a rectangle) = Length x Width: _________ cm 2
Lamp Experiment:
Maximum Voltage ________ Volts
Maximum Current ________ Amps
Maximum Power = Volts x Amps: _________ Watts
How many cells needed to power a 100 W incandescent bulb: ________
How many cells needed to power a 10 W CFL bulb: ________
Power per cm2 = Maximum Power / Surface Area: _________ W/cm2
Power per m2 = (Power per cm2) x (10,000): __________
Sun Experiment (optional):
Maximum Voltage ________ Volts
Maximum Current ________ Amps
Maximum Power = Volts x Amps: _________ Watts
Power per cm2 = Maximum Power / Surface Area: _________ W/cm2
Power per m2 = (Power per cm2) x (10,000): __________ Watts
Efficiency of PV Cell = (Power per m2 / 1000) x 100: _________%
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RED probe in “VΩmA”
BLACK probe in “COM”
DIAL to “DCA, 20m”
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This will measure electric current up
to a maximum of 20 milliAmps DC.
RED probe in “VΩmA”
BLACK probe in “COM”
DIAL to “DCV, 20”
This will measure electric voltage up
to a maximum of 20 Volts DC
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RED probe in “10ADC”
BLACK probe in “COM”
DIAL to “10A”
This will measure electric voltage up
to a maximum of 10 Amps DC.
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