This project examines which types of windmill blades are most efficient at producing electricity via a generator. Build a windmill from an Erector Set and attach it to a wooden base. Use a pulley system to attach a 1.5-volt motor to the windmill. Connect the motor's output leads to an amp meter. Cut out eight blades from mat board of different shapes and sizes for a total of 24 blades (eight triangles, eight rectangles, eight squares and so forth). Place a fan 4 feet from the windmill. Place eight triangles on the windmill hub all at the same angle of your choosing. Turn on the amp meter and turn the fan on to the "high" setting. Read the meter and record the electrical output in milliamps. Change the angle of the triangles and repeat the process. Do this for all four blade shapes. Record the data on a spreadsheet and create a chart that shows which blades were most efficient and at what angles.
This project demonstrates the practical applications of solar energy. You'll need a small solar panel rated at 4.5 volts and 100 milliamps and an inexpensive radio that can run on four AA batteries (1.5 volts) and is rated for 6 DC volts. Open the back of the radio and examine the wiring. Find the negative and positive leads (black wire for positive, red for negative). Connect the leads to the corresponding negative and positive terminals on the solar panel. Move the radio into the sunlight. It should power up immediately. Try it again using indoor lighting. Some solar panels will even respond to 60-watt light bulbs.
Light's Wavelength vs. Solar Power
This project illustrates that solar cells vary in their response to different wavelengths (color) of light. You'll need a small solar panel, an amp meter (or multimeter) and some colored filters (red, orange, yellow, green, blue and violet). You can create these with colored cellophane mounted on small cardboard frames. They should be large enough to completely cover the solar panel. Find a sunny location and lay the panel on flat surface facing the sun. (Make sure it remains in the same position throughout the experiment.) Connect the meter to the solar panel and record the output in milliamps without using any of your filters. Test each color filter by covering the entire solar cell and record the results. You should be able to show that power output of the solar panel will change depending on the wavelength of the light.
From Trash to Gas: Biomass Energy
Biomass, such as vegetable peels and cow manure, can turn into gas, which can be converted to energy. In this project, you'll compare the amounts of biogas produced by different types of biomass. You'll need nine empty 2-liter soda bottles, cow manure (local farmers will be happy to donate), uncooked chopped vegetable peelings and mashed bananas (your biomass), distilled water, latex gloves, a kitchen scale, duct tape and nine balloons. With your gloves on, measure out 10 grams of cow manure and place it in one of the bottles. Repeat this for two more bottles and set them aside. Next, measure out 5 grams of cow manure and 5 grams of the vegetable peelings and put them in a bottle. Repeat the process for two more bottles. Set aside. Repeat the process, this time using 5 grams of mashed bananas instead of vegetable peels. Fill all nine bottles with distilled water nearly to the top. Label each bottle to indicate its contents. Cover the mouth of each bottle with a balloon and secure with duct tape and place them in a well-ventilated area away from sparks, electricity and open flames. For 12 days, at the same time, measure the circumference of the balloons and record your findings. Which biomass inflated the balloons the fastest? Which created the greatest inflation?