Harvesting solar energy allows for the use of cooking meals, charging both large and small batteries or drying clothes. Using solar energy can reduce long term utility expenses while taking advantage of a renewable energy source. Solar ovens, solar hot water heaters, solar stills and solar balloons are all hands-on projects students can use to learn about solar energy.
Solar ovens can be square, round or parabolic in shape, depending on the materials used to make the oven. Each model will have an outer shell made up of a cardboard box, a metal container or windshield visors that have been bent into a cone shape. A container that holds the food or water to be tested is held or suspended in the center of the outer container. The food or water container is then wrapped in a clear plastic bag to allow the sun's rays to penetrate to the middle keeping hot air trapped next to the container. The entire oven is then pointed in the direction of the sun for various amounts of time to finish the experiment.
A solar hot water heater uses a water container with tubes running from two different places, one from the bottom and one back into the top. Water flows freely down from the bottom tube and into another container, which is usually black in color, and either round or flat, which is kept pointing at the sun at all times. The type of container can vary, but the water that flows from the top container to the bottom container will heat up and then naturally rise back through the upper tube that leads back to the top water container. This circulation continues until the water in the upper container has reached a desired temperature.
Solar stills trap moisture in a small area, evaporate it to a trapped lid and then condenses back into a water container. Students will need a plastic or glass container, a cup, clear plastic wrap, a large rubber band, a small object to use a weight and water. The cup should be put inside the larger container, directly in the center. Pour water in the bottom of the container so that it does not come over the top of the cup. Cover the outer container with plastic wrap, securing it around the lid with the rubber band. Place a small object such as a pink erasure or a rock in the middle of the clear plastic wrap so that a “V” is shaped over the cup. Place this in the sun and wait for the solar energy to work.
Solar balloons offer the opportunity to experiment with different materials like clear or dark plastic, actual Mylar balloons or water balloons. Whichever variation is being used, the object should be filled with air and the bottom tightly secured. Place each balloon in the sunlight and see which one rises first, stays for how long or any other measurement the students may need to measure.