Solar Cells and Temperature

Complexity level:	6
Project cost ($):	120
Time required:	1 day to prepare, 1 hour for experiment
Material availability:	Solar cells may be purchased from a hobby store
Safety concerns:	Heat stroke, sunstroke, dehydration - be careful when working under the sun and have an adult supervise your experiment

Hypothesis

Solar cells will have a lower power output at higher temperatures.

Overview

Solar cells convert sunlight into energy due to the photovoltaic effect. These cells are made from photovoltaic semiconductor materials. These semiconductor materials behave as insulators under normal conditions but become conductors of electricity when exposed to light.

The common types of solar cells are:

Monocrystalline solar cells which have high power output efficiency but are difficult to produce and expensive.

Polycrystalline solar cells which have a lower production cost and are therefore less expensive but they are less efficient due to inherent crystalline defects.

Amorphous solar cells ?which have lower production costs than the other 2 types mentioned above. However the power output efficiency is also the lowest amongst these three types of cells.

Solar energy is a clean and environment friendly way of generating power. The generation of solar power does not cause any pollution to the atmosphere. It also does not result in deforestation nor does it drain the earth of its natural resources.

Scientific Terms

Solar cell, photovoltaic effect, monocrystalline cells, polycrystalline cells, amorphous cells, ammeter, and voltmeter

Materials

The materials required for this experiment:

3 polycrystalline solar cells 0.5V 2.0A, 1Watt
1 digital voltmeter
1 ammeter
1 resistor 0.25ohm 4 watt
1 panel-mounted fan
1 metal plate for the solar cell to be placed on (about 200mm wider and longer than the solar cell)
1 metal plate with a hole for mounting the fan (about the size of the solar cell)
4 pieces of pan head screws M5 x 50mm, 4 pieces of pan head screw M5 x 100mm, 16 M5 nuts
2 pieces of plywood about the size of the solar cell
1 handheld infrared thermometer

Procedure

For this experiment, the independent variable is the operating temperature of the solar cell. The dependent variable is the power output from the solar cell. This is determined by measuring the voltage and current. The constants (control variables) are the resistor, lighting conditions and the solar cell type. The solar cells are assembled as shown in figure 1.
The first solar cell is placed on a metal plate. The metal plate will become hot and increase the operating temperature of the solar cell
The second solar cell is assembled using 4 pieces of 50mm screws, 4 nuts and 1 piece of plywood. This construction allows for air ventilation below the solar cell.
The third solar cell is assembled using 4 pieces of 100mm screws, 12 nuts, 1 fan, 1 piece of metal plate and 1 piece of plywood. This construction allows for forced air ventilation below the solar cell.
This experiment is conducted outdoors, preferably at noon (12pm). The assembled solar cells are kept under the sun for 30 minutes before any measurements are taken.
The resistor, voltmeter and ammeter are connected as shown in figure 2 to each cell.
The voltage and current and solar cell temperatures are taken and recorded in the table below.
The procedures 3 to 5 described above are done for all of the three setups shown in figure 1. The voltage and ampere readings are taken and recorded in the table below.
The output power of the solar cell is calculated as follows:

Power (watt) = voltage (volt) x Current (ampere)

Results

The results show that the solar cell with the lowest temperature (fan cooled) had the highest output power.

photovoltaic cell experiment
Use the graph below to plot the results in the above table.

Conclusion

The hypothesis that the power output of solar cell will be lower at higher temperatures is proven to be true.

Solar cells lose their efficiency at higher temperatures. Therefore sufficient gaps for air ventilation are necessary to keep the operating temperatures of these cells within acceptable limits. Water and fans can be used to cool the solar cells.

Also consider

The experiment can be repeated by using water to cool the solar cell.

Try to repeat the experiment using amorphous solar cells. What if the cells are cooled below freezing temperatures? How would your results differ?

References

Effect of temperature on solar panels - http://www.reuk.co.uk/Effect-of-Temperature-on-Solar-Panels.htm
How do solar panels work - http://www.glrea.org/articles/howDoSolarPanelsWork.html

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