The sun is a powerful and free source of energy. In this experiment, it is used to cook a hot dog. All you need is a cardboard box, some foil paper, glue, a utility knife, poster board and a wiener. The box needs to be wider than a wiener and between 5 and 10 inches long. Cut a parabolic curve the length of both sides of the box. Put some glue on the upper edge and lay some foil paper on it, shiny side up. The foil needs to be as smooth as possible to reflect the sun's rays. Tape two small pieces of cardboard to the center of the box on the outside to hold a skewer for the wiener. You could use part of a wire hanger for the skewer as long as there is no paint on it. Skewer the hot dog, place in the sun and turn slowly until cooked.
Windmills can be found in many places and this experiment tests how the length of the blades and the pitch affect the energy output. Materials you need include 56 Popsicle or craft sticks, three pieces of balsa wood, a motor, a multimeter, a fan, 9 wooden craft circles, glue gun and super glue for the blades. A multimeter is an electronic tool that is used for measuring. With the sticks, balsa wood and motor, build a windmill. For the motor, you can use a DC motor or a motor from junked electronics, like a VCR. Take each craft circle and attach blades of different dimensions and at different pitches. At a 15-degree pitch there are three sizes of blades: 18 x 2 cm, 12 x 3 cm and 9 x 4 cm. Use the same dimensions for a pitch of 30 degrees and 45 degrees. One by one, apply each circle to the windmill, attach the multimeter to measure, turn on the fan for one minute and record the highest reading from the meter.
This experiment turns algae into bio-oil that could be made into biodiesel. Get a small aquarium with an air pump. Mix aquarium salts with 1 1/2 liters of bottled water and put it into the aquarium. Put in 1 1/2 liters of algae solution and put a desk lamp over the aquarium and turn it on. Every eight hours add 2 tsps of soda water. Mix 1/2 cup of plant fertilizer to 1 liter of bottled water and add 1 tsp of this solution to the aquarium every other day. Stir the water occasionally so the algae do not drop to the bottom. In three weeks, remove the algae with a strainer and let it dry for 24 hours. Wrap it in a cotton cloth and squeeze it with a juicer so that the oil comes out. You should be able to produce about 1/2 tsp of bio-oil.
You can make a scale model of a geothermal power plant to show how it works. Take a nail and hammer a small hole no bigger than 1/8 inch in diameter on the bottom of a tin can near the edge. Make another hole across from it on the other side. Attach a ruler to the can with tape or rubber bands. Put some water into a pot and cover the top with two layers of foil paper, mashing it around the edges so it seals tightly. Use the nail to make a very small hole, about 1/16 inch, in the center of the foil. Put the pot on a burner and heat until the water boils. When you see the steam coming out of the hole, hold a pinwheel over the hole and observe how fast the steam moves the pinwheel. Turn the can over and place it on the foil over the hole. Hold the pinwheel over the two holes and observe how fast it turns compared to how fast it turned before. Repeat the experiment with lots of holes in the foil: 5, 10 and 20. Each time, observe the speed of the pinwheel.