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Mike Isley
Product Developer
All of your students have seen photovoltaic solar cells used in a variety of ways; however, students may have misconceptions in understanding what influences solar cell output. One survey of middle school students indicated that they knew a solar cell required light to generate electricity, but most thought it was heat that created energy and that solar cells produce more energy on a hot day than a cold day.1 Actually, solar cells are less efficient as the temperature of the cells rises above 25° C (77° F). This activity explores how ambient temperature and the angle of illumination can affect solar cell output in volts.
A typical solar cell is composed of a specially treated semiconductor wafer made of silicon or similar elements (see Figure 1). This wafer is sandwiched between 2 plates, 1 positive and the other negative. When photons of light strike the semiconductor, electrons are knocked loose from atoms of the semiconductor, and they flow through a closed circuit as electric current.2 Solar cells are connected in series or parallel to make rectangular panels that produce direct current at a given voltage and amperage.
For teacher demonstration or lab group of 2 to 4 students
Data Table 1
Angle (°) | Voltage |
---|---|
90.0 | |
60.0 | |
40.0 | |
20.0 |
Data Table 2
Temperature (° C) | Voltage |
---|---|
Angle (°) | Voltage |
---|---|
90.0 | 0.44 |
60.0 | 0.42 |
40.0 | 0.35 |
20.0 | 0.24 |
Temperature (° C) | Voltage |
---|---|
23.3 | 0.42 |
24.7 | 0.40 |
26.0 | 0.39 |
30.0 | 0.38 |
33.5 | 0.37 |
34.6 | 0.36 |
36.5 | 0.35 |
39.0 | 0.34 |
41.5 | 0.33 |
43.2 | 0.32 |
45.0 | 0.30 |
1M. Ing, M. Ward, and E Haberer. 2013. Building on students’ knowledge of solar cells. Science Scope 36 (6): 21–29.
2NASA Science News. Available at: http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells. Accessed December 11, 2013.