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In the spring of 1995, the University of Dubuque, Iowa, began a model solar car project for students at the elementary level. The project was inspired by the annual Junior Solar Sprint held for sixth, seventh, and eighth grade students. The University felt this project would be great for children because it would expose them to alternative energy which is rapidly increasing in popularity. The child would be able to engage in hands-on activities, thus acquiring a better understanding of mathematics and science. Encouraged to use their own creativity, the students constructed their own solar cars. As John Root's classes progressed, so did the ideas of the students. Furthermore, after learning by trial and error from the two spring classes, our summer classes were a great success.
I was able to assist John Root in many of the classes. I found that the children responded enthusiastically to the project. Many were competitive but were willing to help each other out. When the students had finished their solar cars and were able to test drive them in the sun, they became very excited. In seeing their car run along the track via the use of sunlight, all of the children became very proud of themselves for accomplishing this project.
The primary tools needed are wire cutters, X-ACTO™ knives, electric hand drill, safety glasses, hot glue gun, and other materials chosen for the solar car.
The best way to begin is to build the car's chassis, or frame. There are many possible ideas: cardboard tubes, flat boards, shoe boxes, styrofoam, or plastic bottles. One thing to remember when building the chassis is the importance of weight and stiffness. If the car is too heavy, the motor may have a hard time pushing it. Yet, if the car is too light, the wind may push it causing it to either flip over or not run in a straight line. Lighter cars are preferred but stiffness is needed for these cars.
Spools, tin cans, foam core, styrofoam, yogurt caps, or anything that resembles a wheel can be used. Again, lighter wheels may run better than heavier ones. Some type of rod will be needed to act as an axle. Tire traction is important. Rubber bands placed around the wheels may aid in traction. A weight may be placed above the back tires to help keep the wheels from slipping. Wheels should be aligned as carefully as possible in order for the car to use less energy and run in a straighter line.
Bearings are essential in reducing unnecessary friction caused by the wheels, chassis, and axle. They help the wheels and axle to move freely. We used drinking straws and glue for the bearings, but there are many other ideas including brass tubes or eye bolts. We also used a light lubricant so that the wheel and axle would slide smoothly against each other.
Last year the solar panel kits were quite inexpensive because the Department of Energy had subsidized them. This year, however, funds are not available and the kits have to be purchased at the full price of $19.99 including shipping. Extra motors are $3.50.
Students were creative with placing the solar panels in various positions. The most popular was a tilted solar panel with reflectors on both sides. The reflectors gave the cars more energy, but the children had a frustrating time making sure they weren't too heavy. The position of the solar panel is very important according to what time of day it is. Many children made their panels changeable through the use of velcro, thus, enabling them to flatten or tilt their solar panels in the direction of the sun's rays.
There were a few different ideas the children had for their transmissions. The most popular one was the belt drive, while a few opted for a gear drive.
The type of transmission used directly relates to the speed of the car. The children were able to manipulate the speed of their cars with the gear ratio. There is a back and front sprocket on the transmission, unless using a direct drive. The back sprocket that is attached to the drive wheel can be experimented with in three basic ratios when it is compared to the front sprocket attached to the motor. The back sprocket can be the same size, half the size, or one fourth the size of the front sprocket. Each rotation of the front sprocket will make the drive wheel rotate once if the back sprocket is the same size as the front, but it will rotate two to four times more if the back sprocket is smaller. If the smaller
back sprockets are used, the car will essentially move faster, which was the ideal for the children. The faster the cars moved, the happier the children were.
Aerodynamics is the key word for this final step in the construction of the solar cars. The students wanted a shape that would reduce the force of the air. Some materials we used to deflect the air around the car were cardboard, foam core, styrofoam, and plastic bottles.
The Junior Solar Sprint usually takes place each year in the spring. The participants are normally seventh and eighth grade students, but some places have sixth grade students. Teachers or anyone else interested can coordinate their own Junior Solar Sprint in local schools. See Access for more info.
Helping John Root with this project was a great lesson
Above: At the start, the PVs are uncovered and the race is on!
Above: The kids are enthusiastic about building solar racers!
in life for myself. I not only learned how solar power is converted into electricity and other technical aspects, but I also learned a great deal about children. Children possess a unique and creative quality, and a project like this allows them to explore this creativity. When I was building my car along with them, they were the ones giving me ideas on what to do and how to make my car different. They also wanted to be challenged—to be the best one in the class. After the cars were finished and we raced them for the first time, the children became very proud of their work. Some, however, were a little embarrassed because their cars may not have been as good as others. But when they saw the faster cars racing against each other they were the first ones to put aside their hurt egos and cheer.
I also realized how important hands-on projects are for children. After John explained to them how solar power works and what the procedure would be, the children were anxious to dive into the work. They were ready to accomplish a goal, and they were ready to do it together as a team. Many made mistakes, but correcting those mistakes was a great experience for them. No one failed with their projects. They all succeeded in getting their cars to play out in the sunlight and many expressed the desire to reassemble their cars to make them even better after the class was completed. Thus was displayed the great success such projects can have on children yearning to release their creativity.
Author Tina M. Sorenson, University of Dubuque, CPO 689, Dubuque, IA 52001 • Email: [email protected]
Junior Solar Sprint info or to inquire about the solar cells, Gloria Kratz, NREL, 1617 Cole Blvd., Golden, CO 80401 • 1-800-NEW-ENGY
A "Turning Point" in Solar Tracking WATTSU NTM AZIMUTH TRACKE
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.