Solar Energy Background
1. Define voltage, current, resistance and power.
2. Objective: design a solar cell that will produce the maximum amount of power utilizing the sunlight at various times throughout
the day.
3. The variables to investigate include the following:
• Time of day: morning, noon, dusk
• Number of solar panels used: parallel vs. series
• Sun intensity: represents different seasons (light intensity 6, 8 and 10)
• Resistance: 30-80 Ω (though the actual range is 0-100 Ω)
• Shading: compare the unshaded panels with the full shading of one solar panel
4. After investigating the variables in section 3, determine the best setup that will allow for the operation of the motor and for the
storage of electricity (charging the battery) at the same time.
Variable: changing one item changes the results of the experiment.
Independent variable: a variable that is changed by the scientist. A good experiment typically has one independent variable.
Dependent variable: the observations of the experiment. The dependent variables are the items that change as a result of changing
the independent variable.
Controlled variable: quantities that the scientist wants to remain constant. The controlled variables must be observed as carefully
as the dependent variables.
Relationship of Voltage, Current, Resistance and Power
Voltage (E): a force that causes free electrons to move from one atom (or point) to another.
Current (I): the rate of electron flow through a material.
Resistance (R): the forces that oppose the flow of electron current in a conductor.
Power (P): the measure of work an electrical current can accomplish in a period of time.
E=IxR
and
P=ExI
So, what’s the difference between energy and power?
Energy is “stuff” – it can’t be created or destroyed, it’s just always there. It can, however, be converted to another form. It may be
converted to heat, moving mass, light, a chemical reaction, or electricity. Power is the rate at which that energy “stuff” is converted.
Day 1:
1. Identify the ‘parts’ of the kit.
2. List the variables used in the solar experiment.
3. Using the diagrams provided, design a series circuit using the wires, solar panels, and multimeter. Draw your circuit in the
space provided.
4. Using the diagrams provided, design a parallel circuit using the wires, solar panels, and multimeter. Draw your circuit in the
space provided.
Series Circuit:
Parallel Circuit:
Day 2: Fill in the table with the variables provided. Once finished, design your own experiment. Use the back side of the paper for
more experiments if needed.
# of Panels
Series / Parallel
Light
Angle
(Time of
Day)
Shading (Cloudy
or Sunny)
Light
Intensity
(Distance
from Sun)
1
Series
Noon
Full sun
10
2
Series
Noon
Full sun
10
3
Series
Noon
Full sun
10
2
Parallel
Noon
1 panel full shade
10
3
Parallel
Noon
1 panel full shade
10
2
Parallel
3 o’clock
1 panel half sun
10
Design your own experiment. Remember to only change 1 variable at a time.
Measured
Voltage (V)
Measured
Current
(mA)
Calculated
Power
(mW)
P=Voltage
X Current
Observations
Light / Motor
1.
Graph the Voltage for the series circuit with 1, 2, and 3 panels.
3
2
1
2.
Based on your graph, what would you predict the voltage to be in a series circuit with all 4 panels hooked up?
3.
What is the benefit of a parallel circuit? A series circuit?
4.
How did your observations change on the light or motor between series and parallel?
5.
If it takes 200 Watts (200000 mW) to run an Xbox 360 for 1 hour, based on your results how many solar panels hooked up in series
would it take to run your xbox?