Question: Which is more efficient, an array of solar cells or a common chemical battery, to power a small electric motor?
Hypothesis: My hypothesis is that the battery will be more efficient because batteries are smaller and take up less space. I also think they produce more power.
Conclusion: The motor ran from the battery but not from the solar cell array.
The solar cell array looks like it can run the motor. I made some
voltage and current measurements and the battery and solar cell
have different outputs. The battery puts out about 1 1/2 volts under
all loads (all resistances). The solar array put out more voltage than
the battery, about 6 1/ 2 volts under no load, but the voltage dropped
quickly as the resistance was decreased. My dad suggested I
calculate power output for both the battery and solar array.
Electrical power is calculated using this formula:
Power = Voltage (in volts) x Current (in Amps)
Surprisingly, the solar array produced more power (1.4 Watts) than
the battery (.69 Watts). The solar array produced the most power
with a load of 17 ohms, which was a higher resistance than the
motor. The battery had the characteristic that the voltage remained
the same regardless of the load (resistance). Perhaps if the solar
array was configured to produce more current at a lower voltage it
could have run the motor.
I couldn't really determine which was more efficient, because I
never really defined what I meant by efficiency. They were both
efficient in their own way. The battery could run the motor and
was more size efficient, while the solar cell could run whenever
there is light.
My experiment also shows the need to match the expected load
when designing solar arrays. Solar arrays consist of individual
solar cells that each put out a volt. They can be wired to produce
either more voltage or more current. It is important to understand the planned usage when designing solar arrays.
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Academic Excellence for 56 years ~~
