# Building on Students' Knowledge of Solar Cells: Integrating Mathematics and Science to Support Engineering Design Tasks

## Article excerpt

As science teachers, you observe excitement among your middle school students when they build things, tinker with materials, and work together. The engineering design practices included in the K-12 Framework for Science Education (NRC 2012) are an attempt to harness this excitement and enthusiasm for science and engineering. Integrating engineering design into your laboratory science teaching is an engaging way to support students in learning mathematics and science concepts (Katehi, Pearson, and Feder 2009). This article describes how the three of us (an education professor, a middle school teacher who implements engineering design activities as part of a green STEM curriculum, and an engineering professor) built on student thinking to design a weeklong unit on solar energy that supported mathematics and science learning. The lesson included students designing and redesigning a model solar car and culminated in a model-solar-car race.

Preparation

Before we started the activities, we wanted to understand what students already knew about solar cells. We individually interviewed a sample of students in order to understand what solar-cell activities we should implement and whether there were particular ideas or concepts that we should emphasize or highlight. Here are some of the items we used in the interview:

* Would the amount of power generated by a solar cell depend on the amount of light hitting the solar cell? How do you know?

* Would the angle at which the light hits the solar cell affect the amount of power generated? How do you know?

* Would heat from the Sun affect the amount of power generated by the solar cell? How do you know?

* If you were going to use a solar cell as a power source, what would you do to ensure you produced as much electricity as possible? What if you were using the solar cell in a place that is really hot, like Arizona (or a place that is really cold, like Alaska)? * Do you think it would make a difference in the amount of electricity generated?

* Here is a model solar car and some materials (mirror, aluminum foil, hair dryer, flashlight, fan, ice pack, and heat pack). Which materials would you use to redesign this model solar car to ensure that you produce as much energy as possible? Why? What other materials would you like to use to make this solar car produce more energy?

From these interviews, we learned that many students noticed solar cells in their neighborhood and were aware of the installation of solar panels in the school's parking lot (Figure 1). Many students verbalized that solar cells require light to generate energy. However, most students associated heat from the Sun as a requirement for the solar cell to generate energy and incorrectly indicated that the solar cell would be more efficient on a hot day and would generate more energy in locations that are typically "hot" compared to locations that are typically "cold."

In addition to interviewing students, we also observed them participating in an exploratory activity in which a kit (Figure 2) was used to build a model solar-powered car (Figure 3). Model-solar-car kits can be purchased from various online resources such as SunWind Solar Industries (www.sunwindsolar.com), Pitsco Education (www.pitsco.com), and Sundance Solar (store.sundancesolar.com). The cost ranges from \$10 to \$30 per kit. We envisioned students working in pairs, but due to budget limitations, students worked in groups of four. We found it best that the kits not be reused from class to class within the same school year. However, if students disassemble the cars after they are finished for the school year, the motors can be reused for other science and engineering projects, and minimal additional supplies can be purchased to reuse the solar-car kits for students in the following school year. Additional information about alternative supplies can be found at the National Renewable Energy Laboratory's Junior Solar Sprint (www. …

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