Materials List

Each group needs:

• small DC toy motor; available at science and electronics supply catalogs, websites and stores
• 2 pieces of thin electrical wire with alligator clips, each about 50 cm or 20 inches long
• rubber band
• stiff ruler
• cylindrical-shaped cork, at least 2 cm or ¾ inch in diameter; alternative to cork: Styrofoam ball
• 4 paperclips
• scotch tape
• scissors
• 4 pieces of cardboard, each 3 x 5 cm
• (optional) safety goggles or glasses
• Wind Turbine Worksheet, one per team

For the entire class to share:

• 1 or 2 small electric fans or hair dryers
• DC voltmeter; available from electronics catalogs, websites and stores

Introduction/Motivation

Have you ever felt a really strong wind? How does it feel? Have you ever felt blown around by the wind? Wind can do work for us by moving things around. Sometimes we do not want the wind to move things, like when it blows our papers around and we have to pick them up. But sometimes we want the wind to move things around for us. For example, when the wind moves the blades of a wind turbine (a machine that converts the moving energy of wind into mechanical energy andelectrical energy), the turbine produces some useful energy (in the form of electricity).

Let's talk about what happens to get electricity from the wind. First of all, to change the wind energy to electricity, rotor blades spin the hub (center) of the turbine. Inside the turbine is an electric generator, which is a rotating machine that supplies an electrical output with voltage and current. The rotating action of the hub turns a magnet inside a coil of wire in the generator, producing electricity.

A turbine is basically a motor connected backwards. Rather than connecting a battery to the motor to make something move, a wind turbine is connected to the motor, and its movement generates electricity. You can measure how much electricity (voltage) is produced with a voltmeter.

Engineers design wind turbines that turn the kinetic energy of the wind (the movement of the wind) into mechanical or electrical power.

So, when does a wind turbine work best? The power produced by a wind turbine depends on elevation, wind speed and air temperature. Wind speeds of at least 23 kilometers (14 miles) per hour are required to generate electricity. Wind turbines are best located in areas in which wind speeds are 26-32 kph (16-20 mph) with the windmill at 50 meters (55 yards) high. That's pretty high up. The greater the wind speed, the more power generated. Think about it: when the wind blows harder, those papers move around even faster. If the wind speed doubles, the power available to a wind turbine increases by a factor of eight. That means the power doubles and doubles and doubles again!

Today, we are going to act as if we are engineers and create small-scale wind turbines that convert wind energy connected to a motor into electrical energy (voltage). Then, we will measure how the wind speed affects our little wind turbines. This will help us understand what engineers need to know when designing and placing wind turbines in the best locations.

This next session involves a collaborative task for all students

Vocabulary/Definitions

electrical energy: Electrical energy exists when charged particles attract or repel each other. Television sets, computers and refrigerators use electrical energy.

energy: The ability to do work.

generator: A device that transforms mechanical energy into electrical energy.

hub: The center part of a wheel, fan or propeller.

kinetic energy: The energy of motion. For example, a spinning top, a falling object and a rolling ball all have kinetic energy. The motion, if resisted by a force, does work. Wind and water both have kinetic energy.

mechanical energy: Mechanical energy is energy that can be used to do work. It is the sum of an object's kinetic and potential energy.

potential energy: Potential energy is the energy stored by an object as a result of its position. A roller coaster at the top of a hill has potential energy.

renewable energy: Energy that is made from sources that can be regenerated. Sources include solar, wind, geothermal, biomass, ocean and hydro (water).

rotor: The rotating part of an electrical or mechanical device.

turbine: A machine in which the kinetic energy of a moving fluid is converted into mechanical energy by causing a series of buckets, paddles or blades on a rotor to rotate.

voltmeter: An instrument that measures electromotor force in units called volts.

wind turbine: A machine that converts the moving energy of wind into mechanical and/or electrical energy.

Procedure

Before the Activity

• It is helpful to build and test a wind turbine in advance, to use as an example.
• Gather materials and make copies of the Wind Turbine Worksheet.
• Attach wires to the DC motors.
• Set up a test station with a voltmeter and a wind source (fan or hair dryer) where teams can take turns measuring the output of their wind turbine generators.
• Test to make sure the motors and voltmeters are working correctly.

With the Students

1. Divide the class into teams of two students each. Provide each team with materials and a work space.
2. Emphasize safety precautions. Students should never touch any bare or exposed metal in a circuit that is generating electricity.
3. Have students use a rubber band to attach the electric motor to the ruler with the motor shaft positioned at the end of the ruler (see diagrambelow). The ruler serves as a platform for the wind turbine.

4. Straighten out the lower part of each of four paperclips.
5. Cut out four 3 x 5 cm pieces of cardboard. Use tape to firmly attach a piece of cardboard to each paperclip.
6. Stick the straightened part of each paperclip into the curved sides of a cork to create four turbine blades. Be sure to space the blades equally around the cork.
7. Push the cork into the motor shaft. Make sure the shaft goes into the exact center of the cork.
8. Rotate the blade in the cork so that it is at a 45º angle to the flat plane of the edge of the ruler. You have completed your wind turbine!

4. In teams, have students bring their wind turbines to the testing station.
5. For one team at a time, use alligator clips to attach the free ends of the wires to a DC voltmeter. While waiting, have other teams work on the worksheet.
6. Start by placing the wind turbine about 30 cm (12 inches) away from the wind source (fan or hair dryer). Adjust the distance, depending on the strength of the wind source.
7. Turn on the wind source and measure the voltage produced. Record on the worksheet.
8. Repeat with the wind turbine at different distances from the wind source.
9. Have team members work together to complete the worksheet.
10. After all teams have had a turn at the test station and have completed their worksheets, conclude with a class discussion. Describe the movement of energy in your generator, starting with the wind and ending at the voltmeter. Review each team's results and observations. Did the turbine design of any team produce more voltage at the same distance, compared to the rest? Did anyone adjust the angle of the blades? What did that do? What happened as you moved your wind turbine closer or farther away from the wind source? How might you alter your turbine design or position to better capture the wind and produce more voltage? What factors might engineers consider when deciding where to put a wind turbine generator or a wind farm?