ALTERNATIVE ENERGY SOURCES

As a country we depend greatly on the use of oil and gas as sources of energy. (View image: Production and Cumsumption of Oil). Because it is a finite resource (and we are well aware of this in Louisiana), the use of alternative sources of energy must be explored.

My class is extremely involved in environmental issues throughout the year. One of the units we do relates to alternative energy sources. The objective is for the students to determine what types of energy sources can be used in our location and under what conditions. During this time, the class builds water wheels designed to make something move and experiments with wind power as well as designing and building machines that work using solar power.

As an introduction to the unit we brainstorm the various types of energy sources and discuss all the positive and negative effects of their use. Then, based on this list, the children determine the type of alternative energy source they believe would be best suited for use in our area. The choice is invariably solar power because of the heat in Louisiana. After this unit the children usually revise their choice because it becomes apparent to them that heat is not the necessary ingredient for solar power, it is the rays of the sun that we often do not get because of the cloud coverage.

Summary
Parabolic Solar Collectors collect the light rays of the sun. The light rays reflect off the sides equal to the angle they came in at (the angle of reflection). Because the shape of the collector is parabolic, the light rays come together at a point above the collector. This point is called the hot spot. The location of the hot spot varies based on the location of the sun, but it can be located by moving your hand around the perimeter and across the inside of the solar cooker until you find the hottest area and then raise your hand slowly until you reach the hot spot. This is usually quite hot.

Materials
Parabolic Solar Collectors (4-5 students can use one simultaneously)-an old umbrella lined with silver mylar works quite well.

Kraft flavored marshmallows (these come in different colors and are important in the assessment of knowledge).

Uncooked spaghetti noodles (as thick as possible) These are used as skewers. The kids eat them after they roast their marshmallows (no trash).

Procedures
A clear, sunny day is a necessity for this activity. (It need not be a hot day but it must be sunny).

Around 11 a.m, place the cookers in an area where no shadows will be cast on them This will allow the cookers to heat up prior to use.

Review the angle of reflection concept with the students.

Explain the method of determining the hot spot on the cookers.

Place your hand about six inches above the rim of the cooker. With your eyes closed, slowly rotate your hand around the perimeter of the cooker. When you find the spot that is hottest, slowly raise your hand until the heat comes to a localized point. The hot spot is where you want to hold your marshmallow. (This also can be determined by using a piece of paper. Place the paper over the hottest area until the light comes to a point on the paper. I prefer having the children feel the heat however.)

Have the children choose the marshmallow they would like to roast and allow them to skewer them using the spaghetti noodles.

Time to Cook
Carefully listen to the children's observations related to the various cooking time of the different colors. Allow plenty of time to discover why some get finished before others. (White will never roast. Chocolate gets finished fastest, and the others vary based on how light the color is.)

Hold a classroom discussion based on the results. If you wanted to design a solar collector what color would you want it to be? Why?

At this point the children design different types of collectors that will hold water. These are placed outside in the sun (on a clear day) and tested at 15-minute intervals to determine which heat the fastest.

Roxson Welch: Roxson Welch is a third grade teacher at Baker Heights Elementary. She is the 1993 Presidential Award for Elementary Science Teaching recipient as well as winner of the 1994 Exemplary Elementary Science Teacher for the Council of Elementary Science International and the 1994 Conservationist Teacher of the Year for the Southeastern United States.