Harnessing Solar Power

Complexity level:	5
Project cost ($):	50
Time required:	1 hour to prepare, 1 hour for experiment
Material availability:	Purchase solar cells from hobby engineering stores or from school science laboratory suppliers
Safety concerns:	Long hours of exposure to the sun may cause dizziness, dehydration or heat stroke. Make sure you drink an adequate amount of water and put on sunscreen. You should ensure that you protect yourself with an umbrella or wear a hat as you will be under the sun for a fair amount of time.

Hypothesis

Using parabolic mirrors will help achieve the highest level of photovoltaic output from solar cells.

Overview

Solar cells

Solar cells are used to harness the power of the sun, converting light into electricity. They are made from silicon, which is found in abundance on our planet. There are generally 3 types of solar cells in existence:

Monocrystalline solar cells - with a good solar energy conversion rate between 12% - 16%. However, these cells are very difficult and expensive to manufacture.

Polycrystalline solar cells - with a lower solar energy conversion rate between 11% - 13% but which are cheaper to manufacture.

Amorphous solar cells - with the lowest solar energy conversion rate between 8% - 10% and which is the cheapest to manufacture

A solar cell typically produces an output voltage of about 0.5Vdc. This voltage can be increased by connecting the solar cells in a series. To increase the output current, the solar cells need to be connected in parallel.

Solar reflectors

Solar reflectors are devices used to reflect the parallel rays of the sun onto the surface of the solar panel to enhance the efficiency of the solar cells. They are normally parabolic in shape.

Scientific Terms

Solar cell, photovoltaic cells, solar concentrator, monocrystalline cells, polycrystalline cells, amorphous cells, ammeter, voltmeter

Materials

The materials required for this experiment:

1 polycrystalline solar cell 0.5V 2.0A, 1Watt
1 mirror
1 parabolic dish
1 roll of aluminum foil
1 roll of masking tape
1 digital voltmeter
1 ammeter
1 resistor 0.25ohm 4 watt
An assistant to help hold the mirror and parabolic reflector

Procedure

For this experiment, the independent variable is the type of solar reflector used. The dependent variable is the power output from the solar cell. This is determined by measuring the voltage and current produced. The constants (control variables) are the resistor, amount of sunlight, the temperature and the type of solar panel used.
The parabolic dish is covered with the aluminum foil to give the surface a reflective finish. Be sure to use the more reflective surface of the foil. The aluminum foil is fastened to the parabolic dish using the masking tape.
This experiment is conducted outdoors under bright sunlight with minimum cloud coverage.

The solar cell is first set up without any solar reflector as shown in figure 1. The voltmeter (V) and ammeter (A) are connected as shown in figure 2. The voltage and ampere readings are taken and recorded.
Next, the mirror reflector is used and the layout is arranged as shown in figure 1. Adjust and hold the mirror so that the light is reflected onto the solar cell. The voltage and ampere readings are taken and recorded in the table below.
Finally the parabolic reflector is used and the layout is arranged as shown in figure 1. Adjust and hold the parabolic reflector so that the light is reflected on the solar cell. The voltage and ampere readings are taken once more and recorded in the table below.
The output power of the solar cell is calculated as follows:
Power (watt) oltage (volt) x Current (ampere)

Results

The results show that the use of the parabolic reflector helped to obtain the highest power output from the solar panel, followed by the mirror reflector.

Use the graph below to plot the results of the table above.

Conclusion

The hypothesis that the use of a parabolic mirror will provide the highest power output from the solar cell, and that this is followed by using a flat mirror - is proven to be true. The parabolic reflector helps to direct the most amount of sunlight towards the solar cell thus enabling it to produce electricity more efficiently.

The use of solar, wind and water energy to produce electricity is called"clean" or"green" energy. This is because these sources of energy do not produce any harmful waste (such as carbon dioxide) and do not pose a threat to our environment.

Also consider

The experiment can be repeated indoors using fluorescent lighting.

Try to repeat the experiment indoors in an air conditioned room at different temperatures, and observe whether the change in temperature affects the output of the photovoltaic cells.

References

How do solar panels work - http://www.glrea.org/articles/howDoSolarPanelsWork.html

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