Students examine how the orientation of a photovoltaic (PV) panel relative to the sun affects the efficiency of the panel. Using sunshine (or a lamp) and a small PV panel connected to a digital multimeter, students vary the angle of the solar panel, record the resulting current output on a worksheet, and plot their experimental results.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
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- Colorado: Math
- Colorado: Science
- International Technology and Engineering Educators Association: Technology
- Next Generation Science Standards: Science
- Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering. (Grades 9 - 12)  ...show
- Have a basic understanding of electrical circuits, including voltage, current and power.
- Know how to use a protractor to measure angles.
- Be able to record and plot data.
- Explain how the angle of a PV panel relative to the sun affects the panel's power output.
- Describe some characteristics of a well-designed PV array, including direction and orientation.
- mini PV panel ($10-30; available online; do a product search for "small solar panel" or see the Solar Panel Source Information attachment in the Photovoltaic Efficiency unit)
- multimeter ($10; available online; see the Solar Multimeter Source Information attachment in the Photovoltaic Efficiency unit)
- 2 wires with alligator clamps
- sunlight or 100-watt incandescent lamp ($8 from hardware store)
- 2 pieces of cardboard, each about the same size as the panel
- protractor (or use attached Protractor Printout; print and cut out; two per sheet)
- ruler or string (to help make accurate protractor measurements)
- Student Investigation Guide, one per team
- Investigation Worksheet, one per student
- duct tape
|array:||A group of solar panels connected to each other.|
|efficiency:||The ratio of the useful energy delivered by a dynamic system to the energy supplied to it.|
|solar radiation:||Energy emitted from the sun, including visible light, heat, UV rays, etc.|
|zenith angle:||The angle between the line pointing to the sun and the vertical.|
Before the Activity
With the Students — Experimental Set-up
- Take all materials outside, or if inside, secure the lamp to a desk or shelf.
- To support the solar panel during the experiments, tape two pieces of cardboard that are roughly the size of the panel to opposite sides of the solar panel to create an adjustable support triangle, as shown in the experimental set-up in Figure 1.
- Connect the negative and positive pins on the multimeter to the corresponding wires on the PV panel (the red pin should be connected to the red wire).
- Turn the multimeter to the direct current amps (DCA) setting for 200m. Place the panel one to two feet from the lamp. (Tips: The reading on the multimeter should be positive; if it is not, the wires are backwards. If you see only a "1" on the screen, the panel is producing more current than the multimeter can read at that setting. In this case, back the panel away from the lamp a little or move the multimeter dial to a higher current setting.)
- Point the PV panel directly at the light/sun and tape its triangle base down to prevent movement during the experiment. (The panel angle remains adjustable using the other cardboard piece.) Also be sure the lamp is secured.
- Measure the zenith angle, θz, of the sun and record it on the worksheet. Do this by placing the protractor at the front edge of the panel. Use a ruler or string pointed at the light source to help increase your accuracy in reading the angle of the light source. (Optional: Place the light source so the zenith angle is equal to the latitude of your location.)
With the Students — Experiment 1: Vary the Collector Slope Beta, β
- Lay the panel completely flat. Measure the current and record it in the first spot on the worksheet (0º).
- Make sure that the protractor is centered at the front edge of the PV panel. (If the angle is measured with the protractor in an incorrect position, it skews the data.)
- Vary the slope of the PV collector in 10º increments and record the resulting current measurements on the worksheet. (Note: If you notice a higher current reading at an angle other than the zenith angle, it may be due to the reflectance of your table surface. Take this into account when answering worksheet questions.)
With the Students — Experiment 2: Vary the Azimuth Angle of the Panel, γ
- Set the panel to the optimal slope from Experiment 1 and secure the cardboard support triangle so the panel remains at this angle.
- Remove the tape from the base. Rotate the base slightly until the current is at its maximum. Record this as the 0º reading.
- Tape the protractor to the table at the front edge of the panel so that the center of the protractor lines up with the center of the panel. Rotate the base of the panel by 10º increments to the left or right, keeping the center of the panel at the center of the protractor. Record the resulting current measurements on the worksheet. (Be sure to rotate the panel about its center and not to slide it forward or backwards during the experiment.)
With the Students — Create a Plot and Interpret the Experiment Results
- Plot the data on the graphs provided on the worksheet.
- Answer the questions on the worksheet to demonstrate your understanding of the data.
With the Students — Activity Closure
- Lead a class discussion to review the experiment results and investigating questions.
- Assign students to complete the post-activity assessment (as described in the Assessment section), creating and presenting designs for small PV systems for their school using their observations to defend their choices for angle and orientation of the panels.
- The PV panels are fragile so be careful when handling them. You may want to tape over the wire connections to be sure they are not pulled out of the back.
- 100W incandescent lamps can become extremely hot! Use caution when handling them.
- At what angle did the PV panel create the highest current? Why?
- What happens as a result of tilting the PV panel away from the sun?
- If you were to build a home at this location, how would you design the roof to optimize solar efficiency with minimal installation equipment?
- Describe the effect on the current when rotating the panel away from the sun.
- If this PV panel is mounted facing south, how efficient is it just after sunrise or before sunset compared to the efficiency at noon?
- What direction would you point your panel if you only needed to power a computer to do your homework at 4:30pm every day?
- What could you do to increase the overall efficiency of the PV panel over the course of a day?
Activity Embedded Assessment
- For lower grades, conduct this activity as a class demonstration.
- For lower grades, instead of using multimeters, connect the PV panels to small buzzers that change volume with different current values. Have students rotate the panel to different angles and observe the effect via the sound output. This way, rather than collecting data, students hear the varying volume of the buzzer in response to the changing solar panel angle to the light source. Buzzers are inexpensive ($4) and can be found at electronics and hardware stores such as RadioShack, or online at http://scientificsonline.com/.
- For upper grades, have students construct more durable and precise measurement equipment as a class project. Have them adjust the lamp angle (or panel height) to simulate the sun's angle during different hours of the day. Allow them to calculate the total amount of energy created during one day using a PV panel at different angles and the equation: power = current * voltage. Note: this requires students to also measure the voltage of the panel at each angle.
William Surles, Jack Baum, Stephen Johnson, Abby Watrous, Eszter Horanyi, Malinda Schaefer Zarske (This high school curriculum was originally created as a class project by engineering students in a Building Systems Program course at CU-Boulder.)
© 2009 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering and Applied Science, University of Colorado Boulder
Last modified: March 6, 2015