Hands-on Activity: Wind Power
Educational Standards :
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
Each group should have:
Introduction/Motivation (Return to Contents)
What causes the wind? Most people do not know that wind is caused by the uneven heating of the atmosphere. Air is heated up by the sun which causes it to rise. This produces an area of low pressure. Cooler air produces an area of high pressure and moves in under the warm air. This movement creates wind. The direction and strength of the wind are changed by the Earth's environmental surface — meaning: trees and water can change the speed and direction of the wind. Some locations always have strong winds from a particular direction, while other locations have little wind or winds that change direction frequently.
How do we measure the speed of the wind? Well, wind speed is usually measured using a cup anemometer, which typically has three cups that capture the wind. The number of times that the cups spin in a full circle per minute is counted electronically. This type of anemometer is commonly seen on weather stations and is used for meteorological observations. Normally, the anemometer is fitted with a wind vane so that it can also detect the wind direction. We are going to make a type of anemometer today.
Did you know that we can generate energy from the wind? For thousands of years, people have converted wind into energy for various work-related reasons. Have you ever seen a windmill? Windmills have been used to convert wind energy into mechanical (movement) energy for farm tasks, such as pumping water or grinding grain. Have you ever seen a modern wind farm? Modern wind turbines have special generators that can convert mechanical energy (energy from movement) into electricity. Wind is a renewable resource, which means that there will always be wind; therefore, we will always have energy from that wind.
Engineers design and create anemometers for measuring wind and machines to convert wind into energy. Engineers also work to improve many wind-powered electricity-generating machines. Engineers need to think about things like the Earth's surface, outside temperature and wind direction when designing a wind turbine. They also think about what happens on very windy days and how insects and birds might be affected by wind machines.
Procedure (Return to Contents)
How can we get energy from the wind?
All electric-generating wind turbines, no matter what size, are comprised of a few basic components: a tower, a rotor (two or three blades mounted on a shaft, like a propeller), a speed-control system, and an electrical generator. In order to most effectively capture energy, the wind turbines are mounted on a tower at least 30 meters above ground. Often, these wind turbines are assembled in groups; these populations of turbines are known as wind farms.
Wind turbines turn the kinetic energy (the energy of motion) of the wind into mechanical or electrical power. The amount of power produced by a wind generator depends on elevation, wind speed and air temperature. Wind speeds of at least 14 miles per hour are required to generate electricity. Wind turbines are best located in areas where wind speeds are 16-20 mph and the rotor is placed 50 meters high. Since cold air is denser than hot air, turbines are able to generate about 50% more power in the winter than they do during the summer.
Engineers and wind
The anemometers that engineers design are critical instruments for determining the best locations for wind-power generators. The direction and strength of the wind is very dependent on local terrain, so measurements must be made to determine the best site for wind turbines. Also, wind speed changes with height, so anemometers are necessary to determine the best height for the tower. It is essential that these wind speed measurements be very accurate, because the power generated by a wind generator is related to the cube of the wind speed (if the wind speed doubles, the power available to a wind generator increases by a factor of eight). Therefore, any error in wind speed is greatly magnified. (For example, if your anemometer overestimates the wind speed by 10%, or 110% of the actual value, then you will overestimate the power generated by roughly 33%, or 1/3.) Professional, well-calibrated anemometers have a measurement error around 1%.
Engineers are also involved in the design, construction and maintenance of wind turbines. They study aerodynamics to learn more about the flow of air and other gases and the motion of objects through them. This knowledge is important to design wind turbine rotor blades for optimum performance and to determine aerodynamic loads for structural design of the entire wind turbine. Engineers must also design turbines to work in all types of weather conditions. For example, engineers designed a wind farm in Maine that works in the bitter cold of winter. The turbines include rotor blades with a slippery, black surface to minimize the buildup of ice and concentrate the Sun's energy to melt the ice.
In addition, there are several heaters and synthetic lubricants that enable the rotors to operate in temperatures as low as –40°C.
Another concern that engineers take into consideration is the fact that wind turbines kill thousands of insects, and dead bugs on the blades can significantly reduce the efficiency of the turbines. Occasionally, utilities must stop turbines and pressure-wash hundreds of blades, which only compounds the power losses already caused by the bugs. To reduce the problems caused by insects being beaten against the blades, engineers have designed bug-free turbines using nonstick surfaces and different blade angles.
An additional environmental design concern includes animal protection. For example, a large wind farm in California's Altamont Pass led to the significant loss of golden eagles during the early 1990s. However, the Migratory Bird Treaty Act and the Endangered Species Act prohibit the killing of a single bird from a protected species (such as the golden eagle). This situation raised concerns about building more wind farms and prompted some design changes.
Finally, wind machines can be very inefficient because distribution of wind energy is uneven and unpredictable since the wind does not blow strongly all of the time. Electrical engineers are devising strategies to ensure that electricity supply meets electricity demand. New technologies are being developed to store surplus energy generated during windy periods for use at a calmer time.
Advantages And Disadvantages Of Large-Scale Windpower
Before the Lesson
With the Students
Attachments (Return to Contents)
Safety Issues (Return to Contents)
Students should be careful not to lose the push pins; for this reason, only pass out one pin to each group of students.
Troubleshooting Tips (Return to Contents)
Build and test a sample anemometer before trying this activity with your students.
Students will build a model anemometer in this activity that only provides an approximation of how fast the wind is blowing. A real anemometer will more accurately measure how fast the wind is blowing.
Make sure that students make an even plus sign from the cardboard strips — that is, each leg of the plus sign must be the same length. The axis of the anemometer needs to be placed precisely at the center of the cardboard plus sign. Some students may find determining the exact center of the cardboard plus sign difficult.
Assessment (Return to Contents)
Brainstorming: Brainstorm with students some advantages and disadvantages of using windpower. Write answers on the board
Activity Embedded Assessment
Data Recording: Ask each of the groups to measure and record the wind speed by counting the number of times the anemometer spins around in one minute. (Note: to make this simple, they should watch the colored cup, and as it passes the pencil, they should count/add 1). Students should take at least three measurements of the wind speed at their location.
Calculations: Have students calculate an average wind speed at their location. Consider calculating a class average as well. Discuss the minimum, maximum and average wind speed at the time of measurement.
Power Math Worksheet: Have students complete the Power Math Worksheet and check answers with another person in their group.
Toss a Question: Give the students a list of the questions below without answers. Students should work in their teams and toss a ball or wad of paper back and forth. The student with the ball asks a question and then tosses the ball to someone for an answer. If a student does know the answer, he or she tosses the ball onward until someone gets it. Go over answers at the end.
Activity Extensions (Return to Contents)
Activity Scaling (Return to Contents)
For 3rd grade students, do the activity as is.
For 4th grade students, have build the anemometer as is and ask them to see how fast the wind is blowing in different places. Does the wind blow less when close to a building or blocked by a tree?
For 5th grade students, have the students calculate wind speed in miles per hour. Also, have them calculate the speed of the wind they measured. Remember to discuss the fact that these are not very accurate measurements, but this can give them an approximate value.
rotational rate of the anemometer - revolutions per minute (rpm).
wind speed (v) - inches/second or centimeters/second
diameter - length of cardboard strips in inches or centimeters.
*remember to check your units. You may want to have them convert this to miles per hour.
Also, for older students, have them calculate the kinetic energy of the wind they measured. Remember to discuss the fact that these are not very accurate measurements, especially since the error in their wind speed is now being squared.
mass of the moving air- m, in pounds or kg
wind speed –v, in miles/hour or meters/second
*remember to check your units
Have students complete the Power Math calculations. Discuss the results. Have students use their kinetic energy values (from above) to make power calculations based on their measurements from the activity (again with the understanding that they are quite inaccurate).
Have students brainstorm ideas for ways to improve the accuracy of their models. They may even want to redesign the anemometer model and repeat the experiment.
References (Return to Contents)
Activity adapted from the California Energy Commission's website at: www.energyquest.ca.gov/projects/anemometer.html
The American Wind Association, www.awea.org
Hewitt, Paul G. Conceptual Physics, Boston, MA: Addison Wesley Publishing Company, 2004.
National Renewable Energy Laboratory, www.nrel.gov
US Department of Energy, "Wind Turbine Animation," www.energysavers.gov/your_home/electricity/index.cfm/consumer/your_home/electricity/index.cfm/mytopic=10501
USA Today, "Bugs can gum up wind-power turbines," www.usatoday.com/news/healthscience/science/enviro/2001-07-05-wind-power-bugs.htm Accessed July 2011
Other Related Information (Return to Contents)
Search for photos of wind farms, wind turbines, and wind generators at: www.nrel.gov
ContributorsAmy Kolenbrander, Jessica Todd, Malinda Schaefer Zarske, Janet Yowell
Copyright© 2005 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.