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2. Using Wind to do Work

Primary Author; Benjamin Cuker, Hampton University, benjamin.cuker@hamptonu.edu.
Author Profile

This material was developed and reviewed through the InTeGrate curricular materials development process. This rigorous, structured process includes:

  • team-based development to ensure materials are appropriate across multiple educational settings.
  • multiple iterative reviews and feedback cycles through the course of material development with input to the authoring team from both project editors and an external assessment team.
  • real in-class testing of materials in at least 3 institutions with external review of student assessment data.
  • multiple reviews to ensure the materials meet the InTeGrate materials rubric which codifies best practices in curricular development, student assessment and pedagogic techniques.
  • review by external experts for accuracy of the science content.


This page first made public: Oct 28, 2016

Summary

This module shows students how wind (atmospheric circulation) is produced from solar radiation, gravity, and the spinning of Earth. It then develops the history of how humans have harnessed the power of the wind, from simple sails to modern wind turbines. The students learn the underlying principles of each technology and explore the social context for their development.

Learning Goals

Students will be able to:

  1. Recount the historical use of wind energy to power boats and ships, to pump water, to process grain and sugar cane, and to make electricity.
  2. Evaluate the impact of each of these technologies on the history of social development, including trade, agriculture, and human dispersal.
  3. Use data they collect to test the relationship between airfoil design and energy harnessed.
  4. Explain the basic principles involved in transferring wind energy to mechanical energy, including the roles of lift, drag, velocity, and ways to link foils to rotating shafts.
  5. Use published data sets to evaluate specific locations for siting of wind turbines, including fluctuations in wind velocity associated with altitude, latitude, and daily and seasonal cycles. Interpret US maps of wind fields—spatial and seasonal. Evaluate their state for wind farms.
  6. Articulate the potential negative and positive environmental effects of wind turbines, including economic cost and environmental impacts of wind farms.
  7. Compare electrical-generating capacity between a wind farm and a natural gas-fired power plant, including the issue of reliable base load generation.
  8. Diagram the major circulation pattern of wind on the planet and detail the underlying principles involved.

These readings and activities require synthesis, data analysis, graphing, expository writing, interpretation of tables and figures, and exploration of values. The field component exposes students to hands-on manipulation of a sailboat, taking measurements, organizing data, making graphs, and interpreting data they collect.

Context for Use

The module should be useful in a variety of courses, from introductory to more advanced settings. The module can be used as part of a green energy course, or as unit in an environmental science class. It is most appropriate for class sizes of 20 or fewer since students conduct hands-on activities.

Description and Teaching Materials

We have prepared an extensive illustrated reading for your students. We suggest you read the above in preparation for class.

Structuring your classroom time

1. Quiz & Discussion. If you are teaching this as the second module, it will be the first opportunity for the student-generated quiz questions. I like to begin class with the quiz, as it promotes timely arrival. Ask five different students to read a question they brought for the quiz. This should be based upon the material from the last class. So if you are going in the suggested order, these questions should all be from the module Electricity, Work, and Power. After each student recites her/his question, pause for the appropriate time for their classmates to write answers. After all five questions have been completed, then ask five different students how they answered. When you and the class have reached consensus on what constitutes a correct answer, have the students mark their quizzes. The time spent answering questions and grading the quiz offers opportunities for both mini-lectures to clarify a point and focus discussion on the topic. I suggest having the students write their answers on the opposite side of the paper where they wrote their quiz and discussion questions. That way you will have just one piece of paper with a grade on it from each student. Remember that you are the one in control of the questions. If students ask a poor question, you might ask them to offer an alternative question, or you may decide ad hoc to modify the question so it is better.

Here are examples of ways to handle poor questions. Festus asks, "Define direct current electricity." You might say, "OK Festus, it is important to know what we mean by direct current, but can you make the question deeper?" If Festus succeeds in improving the question, provide praise and go forward. If Festus cannot find his way to a better question, you could then say, "How about explain one way AC and DC are similar to each other and one way they are different." Or, "What is one advantage and one disadvantage of using DC?" Sometimes students will come up with seemingly bizarre questions. Hesitate before rejecting those offerings as it may be interesting to see where the classmates go with their answers. Warning: just because a student offers a question, it does not mean they know a correct response themselves!
How to deal with student answers? Often the student asked to provide an answer will have it wrong, at least in part. Rather than providing the answer yourself, first ask other students for their responses. If nobody got it right, you might consider asking for a substitute question.

After completing the quiz process, I suggest moving on to the discussion phase. All students should have brought four questions based upon the readings/videos assigned for the new material (that day's module). Use the instructor-regulated discussion pedagogy as explained in the course overview for conducting this exercise. The length of this phase will depend on how much time you need for the rest of that day's activities. If possible, each student should have had the opportunity to ask or answer a question during this exercise. As with the quizzes, rely first on other students to produce an acceptable answer, rather than simply jumping in yourself.

Scaffolding Learning

It is important to help the students use what they learned in the first module to build deeper understanding of this module. The student readings reference important concepts from the module on Energy, Work, and Electricity. As the professor you can help them make the connections. Point out that wind turbines convert the kinetic energy of wind to kinetic energy of electricity, which may be stored as potential energy in batteries. Note that wind turbines are rated by the amount of electricity they can produce, and that this is measured as megawatts. Remind them that megawatts and watts are units of work or power (energy per unit time). The opening quiz reinforces the scaffolding of learning. It forces the students to revisit the previous module twice, once during their studies when they review for the quiz and formulate the quiz questions, and again when they participate in the quiz process in class.

Metacognition

The flipped-classroom structure advocated for this course facilitates the development of metacognition by the students, directly involving them in the learning process. The use of student-generated questions for the quiz, discussion, and post-student presentation interactions is an important strategy in teaching the students about how they learn and understand the material. This is a big departure from the simple memorizing of terms and concepts that characterized much of their earlier education. You are teaching them a new way to approach their studies that, if mastered, will inform their approach to learning in general. Another metacognitive strategy used in the course is requiring the students to apply basic science concepts to understanding a technology, and then requiring them to think about the application of that technology in the real world. The portion of the exercise that has them look at wind energy availability in their own state and apply that information to thinking about the efficacy of wind turbines moves along those lines. The wind module also offers the students the opportunity to use their sense of touch to better understand the topic. They can feel the wind on their faces and the power of the airfoils with their hands as they hold the sheet (line for adjusting the sails on a boat).

Systems Thinking

A major theme of this course is that students see the various technologies in the context of the global system, and this requires systems thinking. This module on using wind to do work provides excellent opportunities for students to exercise systems thinking. One way to use this material to teach the concept of feedback loops as stabilizing or destabilizing is to have them consider the operation of a wind turbine. The faster the wind velocity, the faster the turbine rotates and the more electrical current it produces. A consequence of increased current production is increased heat production. At very high wind speeds the turbines will shut down (generally by changing the angle of the blades, called feathering). A thermostat detects the excess heat, and this tells the controlling computer to feather the blades and stop the rotation. When the turbine cools to a set point, the thermostat allows the turbine to work again. This is an example of negative feedback loop that stabilizes the system.

Another example of the application of systems thinking is to have the students consider how wind turbines connect to the power grid. Ask them to assume that the grid has to maintain an almost constant supply of current for a large area. Then have them think about the consequences for the grid of fluctuating wind velocities. If the base load is supplied by fossil fuel plants, how must the grid system respond to maintain the required constancy?

A third example comes from seeing wind turbines in the context of sustainability and global climate change. Have the students consider how a shift away from fossil fuels to wind and solar would affect the climate and why. They will be better able to answer this question after completing Module 3 on thermal energy from the sun. But you might plant the seeds now to enhance their discovery to come.

2. Student Presentation. Remember you must give the students at least one week to prepare their PowerPoints! The next portion of the class should be devoted to one or more student presentations. Here are some suggested questions. We suggest that if you have Blackboard or a similar teaching aid, you have your students post their PowerPoints in a discussion group so they may be reviewed by all the students. This activity involves peer instruction.

  1. Thousands of homes and businesses around the United States now have photovoltaic panels on their roofs to convert sunlight to electricity. Yet, few residences or businesses have their own wind turbine for making electricity. Why is small-scale wind not being widely adopted? Be sure to consider geoscience, technology, policy, and social science as you address this question.
  2. Use the latest information you can find to discuss how extensively wind energy is being used in the United States and around the world. What portion of the electricity in the United States and in the world now comes from wind? What are the shared characteristics of the places with the most use of wind energy? Be sure to consider geoscience, economics, policy, and social science as you address this.
  3. Choose a large wind farm in the United States and compare its functioning to that of a conventional fossil fuel facility powered by natural gas. Discuss the advantages and disadvantages offered by each alternative.

3. Hands-on laboratory work. This activity will involve Cooperative Learning as the students will work in groups to accomplish each task, and teaching with interactive demonstrations. The student handout explains each activity: Wind for work handout (Microsoft Word 2007 (.docx) 23kB Sep19 17). The Spreadsheets Across the Curriculum module may be useful to help the students understand graphing. It is suggested that students use Excel to do the calculations and present their work. Since Excel has gotten more complicated for students to use over the years, and many versions of Excel are extant, I suggest using YouTube as resource for tutorials. For example see: Basics of Graphing in Excel 2013 and Making Line Graphs with Excel 2010.

The first hands-on aspect requires access to the outdoors and a day with some breeze. The activity takes 2 to 3 hours, depending on the depth of exploration. It requires a body of water, the use of a sailboat with different sized sails, a measuring tape, and instruments to determine wind and boat speed. It is written for a 30-foot sailboat, but one could make simple model boats with blocks of styrofoam, wooden dowel masts, and paper sails of different sizes. Using a stopwatch and a handheld wind meter, the experiment could be done on a very small pond or in a campus fountain. The second exercise is designed for indoors. It requires an electric fan and three model Green Science Windmill Generator kits. Students see the effects of wind speed by moving the models around different distances from the fan. The models come with 6 blades, so by cutting of 3 or 4 blades the students can test the effect of blade number (surface area). This is a URL for the inexpensive kits from ENASCO. This is a handout prepared for the exercises. It is the same as appears at the end of the student readings:

Wind experiments (Microsoft Word 2007 (.docx) 22kB Jun28 17)

Teaching Notes and Tips

Students may need help in making graphs. I like to require them to master this in Excel, but Excel has gotten increasingly difficult for students to use. There is merit in having students make graphs by hand. They need help with the concepts of independent and dependent variables. This module provides a great example of how dogma changes in science, and how that may or may not be so important. The Bernoulli-based model of lift is what we all learned in high school and probably college physics. Yet for some 20 years now scientists have moved to embrace a Newtonian explanation based on the redirection of thrust, with some fluid mechanics mixed in. Despite having the theory wrong, airfoil designers have done some amazing things using empirical science.

Assessment

The assessment methods for this module can be found on the course assessment page. It includes assessing in-class participation (quiz, discussion and student presentation) and evaluating the written report produced by the students.

Pre/Post test questions:

References and Resources

An illustrated of wind power development by Darrell M. Dodge.
This provides excellent background on windmills from ancient times to the beginning of the 21st century.

The physics of sailing
This introduces the concepts of making sailboats go.

The physics of sailing Prezi
This site is similar to the one above.

The Global Wind Energy Council
This is the website for wind industry's advocacy organization. It features reports with the latest information on the wind-energy market.

American Wind Energy Association

Department of Energy Wind pages

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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »