Physics

The Sun is the source of energy for Earth. Sunlight is not evenly distributed, so some areas receive more solar energy than others. In regions that are heated by intense solar rays, air rises. Areas of cooler air rush in to take the place of the rising, warm air. This moving air is wind.

The kinetic energy of wind can be used to generate electricity using a windmill. Wind turns the blades of a windmill, which are connected to a shaft. As the shaft rotates, it powers an electrical generator, a device that produces electricity by moving a magnet through a coil of wire. Electricity travels to transformers that convert the electricity into a form that can travel along transmission lines. In this experiment, you will design blades for a windmill then test the blades to see how they affect the voltage produced by that windmill.

Windmills, also known as wind turbines, are sometimes clustered in large areas called wind farms. In the United States, wind farms supply about 10,000 megawatts (MW) of electricity, enough to power 2.5 million homes, or less than 1 percent of the total energy produced. The largest of these farms is Horse Hollow, a 100-acre (40.5-hectare) development in Texas that houses 421 wind turbines. Texas is number one in wind-generated electricity, followed by California, Iowa, Minnesota, and Oklahoma. Most energy-producing plants are owned by public utility companies. Wind farms are different; they are usually run by businesses that sell the electricity they produce to public utilities.

Generation of electricity using the wind offers many advantages over traditional, coal-powered power plants. Wind, a renewable resource, is clean and does not produce carbon dioxide, a culprit in global warming, or oxides of sulfur and nitrogen, which contribute to acid rain. Compared to other electricity-producing technologies, wind power is economical. As a result, development of wind farms reduces the number of fossil fuel plants needed. Despite these pluses, wind farms are not a perfect solution to our growing energy demands. Winds must be blowing at a minimum of 15 miles per hour (mph) (24.14 kilometers per hour [kph]) to produce electricity, so not all locations can support turbines. Wind turbines are tall and obvious, and many people think they are unattractive. In addition, some migrating birds collide with wind turbines. As with all technologies, citizens must weigh the advantages and disadvantages of wind farms.

• small fan or hair dryer
• cork
• tape
• data table
• index card

1. Push the cork onto the shaft of the DC motor so that it turns when the motor is running.
2. Attach the index card to the cork with a piece of tape to construct windmill blades.
3. Turn on the fan by clicking on its button switch on the base. As the blades turn, observe the voltmeter. Record the voltage passing through the circuit in your data table.
4. Change the shape of the windmill blades and repeat step 3.
5. Change the size of the windmill blades and repeat step 3.
6. Change the angle of the windmill blades and repeat step 3.

1. What is the function of the voltmeter in this experiment?
2. Describe the shape, size, and angle of blades that produced the most electricity.
3. In this experiment, you only produced a very small amount of electricity. Suggest some ways to produce more electricity in the laboratory.
4. What are some advantages of wind-generated electricity? What are some disadvantages?
5. Suggest some uses for wind-generated electricity.

1. The voltmeter measures the volts, or electrical potential, produced by the windmill. The voltage reading indicates the effectiveness of the windmill in producing electrical energy.
2. Straight-sided blades, larger blades, and angled blades produced the most electricity.
3. Answers will vary but could include a larger windmill or several windmills working together.
4. Wind-generated electricity does not cause pollution, is inexpensive, and is renewable. Some people do not want windmills in their communities, windmills are noisy, and windmills can be dangerous for birds.
5. Answers will vary but could include using wind to provide power in remote areas where electricity is not available.