Hands-on Activity: A New Angle on PV Efficiency
Educational Standards :
Pre-Req Knowledge (Return to Contents)
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
Each group needs:
Note: The non-expendable items (mini PV panels, multimeters, wires with alligator clamps, lamp and light bulb) are reusable for the entire four-lesson unit, as well as other projects.
For the entire class to share:
Introduction/Motivation (Return to Contents)
(Have a mini PV panel handy to show students and maneuver as you talk about its orientation.)
Photo means "light," and voltaic means "electric." A photovoltaic (PV) panel is a device that turns light into electrical energy. PV panels have been used on satellites and for power needs in remote areas for years, and are becoming more popular for providing energy to homes and buildings because they are more environmentally-friendly than conventional power solutions. You may have seen a solar panel on a home or know how they work already, but what if I gave you a PV panel to put on your own home and proposed that the person who could create the most energy over the course of the year would win $1,000! What would you do to ensure that your PV panel produced the most energy possible?
PV panels do not all make the same amount of energy when the sun shines on them. Even two identical solar panels might make completely different amounts of energy depending on some very simple differences in how they are installed. Would you like to know the secrets to designing a PV system so that it is as efficient as possible at converting sunlight to energy?
Okay, let's start with one of the most important factors that affects a PV panel's efficiency; this is also one of the easiest factors to control. Let's pretend that I gave you a PV panel for the competition, but because you are so busy with homework and studying, you decide to hire someone else to install the PV panel on your roof. When you come home from school you look up and you see that it is up-side down, so that the light-sensitive material is facing the roof. (Use a mini PV panel to show this orientation, and those that follow.) Do you think this set-up will win the competition of making the most energy possible? No! Okay, so that's an obvious error, but what if it was installed flat against your roof so that it had the same slope as the roof? Is that the best way to install it? Would it be better for it to lie horizontally and point straight up into the sky? Or, should it stand up on its edge, vertically? What is the best angle to install the PV panel so that you can generate the most energy possible over the course of the year? Engineers who design photovoltaic systems for buildings and other spaces must consider all of these questions when creating their designs.
While there is no contest or prize money for installing the world's most efficient solar panel, maximizing the energy output of each installed panel saves its owner the maximum amount of money over the lifetime of the PV panels (PV panels are costly). Let's do some experiments to see how the angle at which sunlight hits a PV panel affects its current output, which is directly related to its overall power output and efficiency.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
If you have a lamp with wattage other than 100 watts (100W), test to see how much current it creates in the panel. Or, use the sun and perform the experiment outside. Depending on the PV panel, you may need to change your multimeter setting to 10 amperes (10A) because the sun is stronger than a 100W lamp. This may also require that you move the positive (red) pin of the multimeter probes to the 10A connection for the experiment set-up (see Figure 1).
It is very important that during the experiment, the equipment set-up stays in the same location so that the measurements of current at different angles are not skewed. As necessary, use tape to secure everything in place.
Before the Activity
With the Students — Experimental Set-up
With the Students — Experiment 1: Vary the Collector Slope Beta, β
With the Students — Experiment 2: Vary the Azimuth Angle of the Panel, γ
With the Students — Create a Plot and Interpret the Experiment Results
With the Students — Activity Closure
Attachments (Return to Contents)
Safety Issues (Return to Contents)
Troubleshooting Tips (Return to Contents)
If you are outside, you may need to use the 10A setting on the multimeter.
Make sure that the wire connections are tight. If you do not get a reading on the multimeter, look for a bad connection or loose alligator clamp.
Make sure that the conductive pieces, especially the ends of the wires or leads of both the PV panel and the multimeter, are not touching any other conductive materials, such as a metal table.
The panels do not work well under fluorescent lights due to their reduced light spectrum. When setting up the circuit, use direct sunlight or an incandescent lamp to test the circuit and panel.
Investigating Questions (Return to Contents)
Assessment (Return to Contents)
Class Discussion: Solicit, integrate and summarize student responses.
Let's think about how you would place a photovoltaic (PV) panel on a roof to get the maximum amount of energy output from it. Should the PV panel be installed flat against your roof so that it has the same slope as the roof, or would it be better for it to lie horizontally and point straight up into the sky? Or should it stand up on its edge, vertically? Would it matter if you installed it on a north-facing roof or south-facing roof? What is the best angle and orientation to install the PV panel so that you can make the most energy possible over the course of the year at your specific location? (General answers: More solar energy is available around noon because the sunlight is more direct [traveling through less atmosphere], thus it is best to face the panels due south. The best tilt angle depends on the location. Generally it is optimal to place the panel at the same angle as the latitude of the location, for example in Boulder CO, this would be 40º. But, depending on the climate, and when more sunlight is available, it may be a good idea to tilt the panel a little more or less to optimize the energy potential in the summer [25º] or winter [55º]. Basically, you need to know where the sun is throughout the year and when the most sunlight is available.)
Activity Embedded Assessment
Worksheet Wrap-Up: Have students complete the graphs and investigating questions on their worksheets. As necessary, help them transfer their data to the plots and validate the data accuracy. Review and discuss the results and answers with the entire class. Review individual worksheets to gauge students' mastery of the subject.
Design It! Have students draw simple PV system designs for their school. Require the designs to be labeled with parts and angles. Have teams present their designs to the class with an engineering explanation of how they chose the angles and orientations of their systems.
Activity Extensions (Return to Contents)
Writing Practice: Have students draw PV system designs for another building or space, such as their homes or a community center. Require the designs to be labeled with parts and angles. Have students write about their PV systems as if they were part of an engineering company presenting a design to a client. Have them describe the building setting, how they chose the angle and orientation of the system, and the benefits of installing a PV system in that space.
Activity Scaling (Return to Contents)
ContributorsWilliam 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.)
Copyright© 2009 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering and Applied Science, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of these digital library curricula were developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.