Challenges in Physical Science: Windmills (Teacher's Guide)

P T LLE ES I SI L S IE E® ac • r's I A Supplemental Curriculum for Middle School Physical Science From Project DESIGNS: Doable Engineering Science Investigations Geared for Non-science Students Edited by Harold P. Coyle John L. Hines Kerry J. Rasmussen Philip M. Sadler Illustrations by Kerry J. Rasmussen Sponsored by the Harvard-Smithsonian Center for Astrophysics with funding from the National Science Foundation and additional support from the Smithsonian Institution rril ~ KENDALL/HUNT PUBLISHING COMPANY 4050 Westmark Drive Dubuque, Iowa 52002 Project DESIGNS Project Staff Philip M. Sadler, Principal Investigator Harold P. Coyle, Project Manager & Publications Manager John L. Hines, Laboratory Technician & Quality Control Marcus G. Lieberman, Education Evaluator Annette Trenga, Assistant Evaluator Marc Schwartz, Graduate Research Assistant Steve Saxenian, Graduate Research Assistant Susan H. Roudebush, Administrative Support Martha A. Lynes, Master Teacher Judith Peritz, Program Coordinator Kerry J. Rasmussen, Writer I Editor I Illustrations I Research Pamela K. R. Sears, Writer I Editor I Research (. External Auditor Stephen A. Barbato, Vice President, Educational Research & Development, Applied Educational Systems, Inc., Lancaste1; PA Curriculum Development Team (school affiliation at time of pilot trials) Stephen Adams, Lopez Island Middle School, Lopez, WA Marilynn Benim, Arendall Parrott Academy, Kinston, NC Anne D. Brown, Lincoln Middle School, Portland, ME Nancy C. Cianchetta, Parlin Junior High School, Everett, MA Matthew Coleman, Whitford Middle School, Beaverton, OR Cynthia D. Crockett, Contoocook Valley High School, Peterborough, NH Kimberly Hoffman, Doherty Memorial High School, Worceste1; MA Teresa Jimarez, Coronado High School, El Paso, TX Paul D. Jones, Montezuma High School, Montezuma, IA David E. Jurewicz, Ephraim Curtis Middle School, Sudbury, MA James F. Kaiser, Sharon Middle School, Sharon, MA Milton Kop, Maryknoll High School, Honolulu, HI Barbara Lee, Hualalai Academy, Kailua-Kona, HI James MacNeil, Concord Middle School (Sanborn), Concord, MA Linda Maston McMurry, E. M. Pease Middle School, San Antonio, TX Daniel Monahan, Cambridge Public Schools, Cambridge, MA Sarah Napier, Fayerweather Street School, Cambridge, MA Mary Ann Picard-Guerin, Cumberland Middle School, Cumberland, RI Douglas Prime, Lancaster Middle School, Lancaste1; MA Diana Stiefbold, Heights Elementary School, Sharon, MA Mary Trabulsi, Algonquin Regional High School, Northborough, MA Consultants Jeff Forthofer, Electrical Engineer Jo Harmon, Education Specialist Kim L. Kreiton, Civil Engineer Eric J. Rasmussen, Architectural Designer Cover credits: Batteries/Electromagnets/Gravity Wheel images © President and Fellows of Harvard College. Bridges/Windmill/Solar House/Blueprint images © 2000 PhotoDisc, Inc. Copyright© 2001 by President and Fellows of Harvard College ISBN 0-7872-6458-X This material is based upon work supported by the National Science Foundation under Grant No. ESI-9452767. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright owner. Classroom teachers have permission to reproduce the blackline masters in this volume for use in their classrooms. Printed in the United States of Anrnrica 10 9 8 7 6 5 4 3 2 ( To the Teacher. • • • • • • • • • • • • • • • • • • • • • • • • • • • v Introduction ••••••••••••••••••••••••••••• 1 About CHALLENGES IN PHYSICAL SCIENCE •••••••••••• 1 Introduction to the Windmills' Module •••••••••• 5 Descriptions of the Windmills' Challenges • • • • • • • • • • • •• 5 Module Goals • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 6 Scientific Concepts and Knowledge • • • • • • • • • • • • • • • • • 8 Science Process Skills • • • • • • • • • • • • • • • • • • • • • • • • • • 10 Science Technology Society • • • • • • • • • • • • • • • • • • • • • • 11 Assessment • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 11 History of Wind Power. • • • • • • • • • • • • • • • • • • • • 12 Class Preparation and Set-Up •••••••••••••••• 20 Module Materials •••••••••••••••••••••••••••••• Construction ••••••••••••••••••••••••••••••••• Troubleshooting Tips • • • • • • • • • • • • • • • • • • • • • • • • • •• Pretest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Brainstorming Questions • • • • • • • • • • • • • • • • • • • • • • •• 20 21 25 25 26 Challenge 1: Unrestricted Design-Torque •••••• 27 Challenge 1 : Data Sheet • • • • • • • • • • • • • • • • • • • • • • • • 30 Challenge 2: Restricted Design-Torque •••••••• 34 Challenge 2: Data Sheet Table of Contents •••••••••••••••••••••••• 37 iii Challenge 3: Power ••••••••••••••••••••••• 41 Challenge 3: Data Sheet ••.••••••••••••••••••••• 44 Challenge 4: Speed ••••••••••••••••••••••• 49 Challenge 4: Data Sheet •••••••••••••••••••••••• 52 Wrap-Up Activities •••••••••••••••••••••••• 57 Class Discussion Questions • • • • • • • • • • • • • • • • • • • • • . 5 7 Report Topics • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 5 7 Storyboard Frame Design • • • • • • • • • • • • • • • • • • • • • • • • 58 In-Class Assignments or Homework Assignments 59 Teacher's Note • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • .• 59 Graphing ....................................59 The History of Wind Power • • • • • • • • • • • • • • • • • • • • • • 59 Devises that Spin, Turn, and Twist • • • • • • • • • . • • • • • • • .59 Assessment • • • • • • • • • • • • • • • • • • • • • • • • • • • • 60 Assessing Student Competence • • • • • • • • • • • • • • • • • • • 60 Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Student Products • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 60 Answers for Worksheets • • • • • • • • • • • • • • • • • • • 62 Graphing Power • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 62 The History of Wind Power • • • • • • • • • • • • • • • • • • • • • • 63 Devices that Spin, Turn, and Twist • • • • • • • • • • • • • • • • • 65 Assessment Answers • • • • • • • • • • • • • • • • • • • • • • 66 Pre/Posttest • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 66 Assessment • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . 68 Content/Concept Questions • • • • • • • • • • • • • • • • • • • • • • 69 Open-Ended Questions ••••••••••••••••••••••••• 70 Rubrics •••••••••••••••••••••••••••••••• 71 Generalized Rubric for Windmills' Challenges • • • • • . • •• 71 iv Table of Contents ( Extensions and Connections • • • • • • • • • • • • • ••• 76 Extensions • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 76 Cross-Curricular Connections • • • • • • • • • • • • • • • • • • • • • 77 Resources •••••••• • + • • + • + • • • • • + • • • • • • • • • 78 World Wide Web Sites • • • • • • • • • • • • • • • • • • • • • • • • . • 78 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 ( Table of Contents v ( To the Teacher "Wow, it works! I can't believe it works!" Expressions of stunned astonishment at the accomplishment of building a working electric motor draw fellow classmates to this minute mechanical marvel. Wobbling and anemic, the motor struggles, straining to make each turn. Assembled from nails and wire, this was the first working device that this middle-schooler had ever built. Soon her classmates followed with their own successes. Over the next few weeks, their motors improved through students' innovations, discovering along the way: imbalance and balance, friction and lubrication, short circuits and insulation, and how to strengthen invisible magnetic fields. Students competed and cooperated, dissected motors from toys and shared their findings. Science was slowly mastered and skills strengthened. Journals filled with data and drawings. Soon motors whirred at 6,000 rpm and beyond, matching the performance of those in their tape recorders and toy cars. The progression of the class-from first copying a poorly performing prototype through successive improvements that revealed the underlying science-marked the birth of the DESIGNS (Doable Engineering Science Investigations Geared for Non-science Students) philosophy in my classroom twenty years ago. Building and improving devices formed the core of a technology and science course for youngsters who were still learning about their own interests and abilities. (. Inspired by the MIT undergraduate engineering competitions, challenges that are suitable to teach the elements of science and technology at the middle school level are not easy to find. Most students are unfamiliar with even the simplest of hand tools. The innards of common devices they use each day are hidden from view. It takes support and encouragement to explore the unknown. Recreating the youthful experiences reported by adults enticed into scientific and technological careers has been our aim. Such projects are too often out-ofschool events, supported by a knowledgeable adult, and are rare in families without technological expertise. Uncovering the path to exciting and lucrative careers that are too often untrod by girls and other underserved groups, DESIGNS challenges provide an exciting entry into these fields. This set of challenges is the output of an extraordinary group of teachers, educators, and scientists. With the support of the National Science Foundation and the Smithsonian Institution we have brainstormed, tested, written, drawn, invented, and struggled. We have failed more often than succeeded, but the result of our three-year effort has been worth it. This collection of activities is fun, contains much science, and is thoroughly tested in a variety of classrooms. They capture students' imaginations and energy. They are not simple to master, but the built-in rapid iteration process tends to test students' ideas rather than their spirits. Failures are frequent but small, each a learning experience that can be absorbed and used. The challenges are designed so that successful strategies are often counter-intuitive, reflecting what we have learned about children's ideas and how they change. Students exhibit little difficulty generating ideas for improvement. But only when their ideas fail do they see a need to pay attention to others' success and restructure their own thinking. To the Teacher vii This project has been the beneficiary of many previous development efforts, both our own and those of others. We have attempted to credit all those who helped directly, but we also wish to thank those who remain nameless, teachers with a great suggestion at a workshop, a clever idea from an article, a scientist's solution to a difficult problem, and most of all the thousand or so middle school students who contributed their time and passion as we worked out the bugs in our design of DESIGNS. Philip M. Sadler, Ed.D. Harvard-Smithsonian Center for Astrophysics Harvard University Graduate School of Education viii To the Teacher Introduction ~(Q)©~~ ~~~[L[L~[fll®~~ a[fll [p~w~a~~[L ~~a~[fll~~ CHALLENGES IN PHYSICAL SCIENCE Goals that Cross All Modules Each of the six CHALLENGES IN PHYSICAL SCIENCE modules contains three or more challenges. Embedded within each challenge are three important goals. They are as follows: 1. Support learning through clear student goals. Each student goal is presented as a clearly defined challenge in physical science. These challenges are invitations to students to improve the performance of a simply designed device commonly found in their world. 2. Empower students as problem-solvers. Students are encouraged to use their prior knowledge to develop strategies to make progress in each challenge. Students discover and utilize physical science concepts as they achieve the goal characterized by the challenge. 3. Encourage students to be critical creators of knowledge. Students propose, test, and eventually defend their ideas. Teachers probe student strategies and interpretations, and encourage students to assess their own and others' evidence. Students quickly recognize the goal that is posed as a challenge. For example, if the challenge is to improve a working model of a windmill, students easily visualize what is expected and what constitutes a successful outcome. The student who encounters the poorly designed windmill interacts with the basic model, decides what might be changed, makes those changes, and evaluates the results. CHALLENGES IN PHYSICAL SCIENCE makes two important assumptions about students who accept the challenge: 1) they understand the goal, and 2) they accept the goal as their own. Students who accept ownership of the goal are more likely to be motivated to complete the work they begin. Students also appreciate the link between each challenge and its real-world application. Student interaction with science is often through the technology that results from scientists' work. Each challenge offers students an interesting task centered on the theme of improving an existing design (e.g., a windmill, a battery, or an electromagnet). Introduction 1 All of the challenges were crafted so that students could easily recognize the goal, quickly obtain feedback from their work, and effectively act on that feedback. This strategy is intended to invite students to act, and to empower and support their learning once they accept the invitation. Students who accept the challenge soon find that the problem becomes very compelling. They are motivated for several reasons. The iterative nature of the activity provides timely feedback. The feedback provided by nature is always available, always impartial, and typically unambiguous. Students can quickly determine if their ideas and actions are bringing them closer to the goal they recognized in the challenge. The interaction between the challenge, the supportive teacher, and the problem-solving student is critical in helping students to be self-directed, critical creators of knowledge. CHALLENGES IN PHYSICAL SCIENCE challenges/goals are also intended to encourage teachers to continually assess whether the classroom setting supports student work in meeting the module goals. From this perspective, teachers focus on encouraging students to follow their own convictions. As a result, students are less dependent on the instructor for the "right answers." Instead, they seek to improve the strategies they use in meeting the design challenge. Often great progress is made when students discover that their beliefs are not supported in nature. Students who learn to question nature directly learn to increasingly value their experiments and become more interested in their results. Students who are motivated to accept the challenge need less assistance from the teacher to proceed. Students uncomfortable with this freedom may still seek the teacher's help. However, teachers who let the challenges guide the students help build students' confidence in their problem-solving ability. Teachers ultimately act to support student understanding of how science proceeds instead of what science has produced. CHALLENGES IN PHYSICAL SCIENCE vs. National Standards CHALLENGES IN PHYSICAL SCIENCE goals agree philosophically with the following goals for school science as articulated in the National Science Education Standards (p. 13): • Experience the richness and excitement of knowing about and understanding the natural world. • Use appropriate scientific processes and principles in making personal decisions. • Engage intelligently in public discourse and debate about matters of scientific and technological concern. However, in an attempt to go beyond philosophical agreement with these goals, CHALLENGES IN PHYSICAL SCIENCE strives to create guiding principles that help direct the work of students and teachers. To this end, CHALLENGES IN PHYSICAL SCIENCE goals support the grades 5-8 Content Standards in the National Science Education Standards for Science as Inquiry which include (p. 143): • Abilities to do scientific inquiry. • Understanding about scientific inquiry. Windmills i ( Furthermore, CHALLENGES IN PHYSICAL SCIENCE's goals directly support the grades 5-8 Science and Technology requirements in the National Science Education Standards. In particular, CHALLENGES IN PHYSICAL SCIENCE seeks to create opportunities for children so that, "as a result of activities in grades 5-8, all students should develop abilities of technological design" (p. 161). The underlying objective is that students will be able to perform the following (pp. 165-166): • Identify appropriate problems for technological design. • Design a solution or product. • Implement a proposed design. • Evaluate completed technological designs or products. • Communicate the process of technological design. All CHALLENGES IN PHYSICAL SCIENCE goals provide a framework to support scientific inquiry and technological design. This framework is the foundation on which students distinguish the difference between science and technology. Students work towards recognizing that the goal of science is to create knowledge, while the goal of technology is to apply that knowledge into developing the tools people use to solve problems. To support experimenting as well as the building of tools, CHALLENGES IN PHYSICAL SCIENCE uses materials that are inexpensive, readily available and easily recognized by students as common items that constitute a part of their everyday world. Skills that Cross All Modules Science is a unique tool for understanding nature. It assumes that systems (such as the devices in a module) can be understood by first breaking them down into parts that can be later modified. Students learn by making changes to the variables they identify within a design (e.g., increasing the number of wire wrappings in an electromagnet). Students are encouraged to experiment, generate ideas, formulate conclusions, and support their ideas and conclusions with explanations. At the end of the project the students should be able to perform the design process and fabricate their best designs. As a result, they formulate and articulate theories about how each design works. Whether their theories are naive or sophisticated, students test their beliefs through each of their design modifications. An important outcome of the module goals is that students develop both manipulative and cognitive skills in science. Three skills in particular are realized through student work: 1. Articulating and testing prior notions about how a design works. In many ways this skill represents the traditional view of what scientists do: asking questions, forming hypotheses, testing those hypotheses, etc. Students can easily identify the parts of the devices with which they are working. These "parts" represent the design variables that students can control as a scientist or engineer might. Students want to know what will happen to their designs when they choose to Introduction 3 modify, add, or remove variables. Their questions become the guiding principles behind how they test their ideas. 2. Judging the impact or magnitude of a change. When a student wonders how a change might impact the original design, the student is posing the question directly to nature. Once the change has been implemented, nature provides the answer. Students judge the impact of their own ideas. They see that not all changes result in the same effect or even have any effect. Because the teacher is outside the question-answer cycle, students concentrate on looking to nature to find answers to their questions. 3. Making convincing arguments that a change has resulted in a meaningful improvement to the design. Students are expected to evaluate the impact of changes as well as judge the magnitude of change. They are encouraged to employ tools (such as graphs, tables, and charts) to support claims that some changes had a greater impact than others, or that a change had no impact at all. To the extent that these skills are practiced in the module, CHALLENGES IN PHYSICAL SCIENCE supports the broadest standard in the National Science Education Standards. "As a result of activities in grades K-12 all students should develop understanding and abilities aligned with the following concepts and processes" (p. 117-118): • Evidence, models, and explanation: Evidence consists of observations and data on which to base scientific explanations. Using evidence to understand interactions allows individuals to predict changes in natural and designed systems. • Constancy, change, and measurement: Energy can be transferred and matter can be changed .... Changes can be quantified .... Different systems of measurement are used for different purposes. 4 Windmills Introduction to the @@~~rra[9)~tl©uu~ odule ©If ~[iu@ wnuu~rnJUaaa~~ ~[iu@]aa@uu~@~ Challenge 1: Unrestricted Design-Torque Challenge Objective Design a scale version of a windmill that will raise the greatest weight (number of nails) possible. Challenge Scenario A rancher has asked your company to design a pump that will allow him to provide water for his cattle. The pump must access water from an underground water source. Since the ranch is isolated, the only reasonable source of energy is from the wind. Your goal is to design a pump that will raise the greatest possible amount of water to the surface. Challenge 2: Restricted Design-Torque Challenge Objective Design a windmill using only the materials provided by the teacher that will lift the greatest weight (number of nails) possible. Scenario Change The rancher who ordered the wind-powered pump has just remembered to tell you that there are no paved roads leading to the ranch. Transporting the finished pump to the ranch will be a problem. The only solution is to transport all of the windmill parts in the back of a pick-up truck. Today, you must change the design of your windmill so that you use a limited amount of material. The windmill design must still lift the most weight possible. Introduction to the Windmills' Module Challenge 3: Power Challenge Objective Design a windmill that can lift the greatest amount of weight in the least amount of time. Scenario Change The ranch is located in a hot, arid (very dry) climate where water evaporates very fast. The wind-powered pump must bring water quickly to the surface and fill the stock tank in as little time as is possible. Since the aquifer (a layer of soil containing water) is several thousand feet below the Earth's surface, the windmill must be powerful. Your challenge today is to design a windmill that can lift the greatest amount of weight in the shortest time possible. Challenge 4: Speed Challenge Objective Design a windmill that is powerful enough to lift 10 nails in the shortest amount of time. Scenario Change You have learned on a recent visit to the ranch that the pipe bringing water to the surface can only hold a small volume of water at a time. You must change your design to lift a constant amount of weight in the shortest time possible. This module allows students to explore the nature of energy transfer by manipulating design elements and construction materials to create a simple windmill. Students are challenged to harness kinetic energy from the wind and transfer it for technological use. The use for the first two challenges is to lift the greatest amount of weight possible. The use for the third challenge is to enable the maximum power possible. The use for the fourth challenge is to produce the maximum speed possible. Constraints within each challenge focus on different aspects of force, motion, torque, work, power, and energy transfer. Content Goals of the Module From the perspective of the National Science Education Standards (Physical Science: Content Standard B): "As a result of their activities in grades 5-8, all students should develop an understanding of ... motions and forces (and) transfer of energy." (p. 149) The underlying concept objectives that students recognize are: Windmills • "Unbalanced forces will cause changes in the speed or direction of an object's motion." (p. 154) • "Energy is a property of many substances and is associated with ... mechanical motion. Energy is transferred in many ways." (p. 155) From the perspective of CHALLENGES IN PHYSICAL SCIENCE, the student's goal is to improve a windmill design such that it is able to lift greater loads or to lift loads at a faster rate. To this end, students encounter the following concepts in order to successfully meet this challenge: 1. Energy can be transferred from the wind to the windmill. a) The wind's energy can be used by the windmill to lift a weight. b) The wind's energy provides the force to move the blades. 2. The blades of a windmill move in a different direction from the wind's direction. a) Devices that can change the direction of a force (the wind's force) or change the amount of force are called simple machines. The windmill is a version of a simple machine: the wheel axle. 3. Using a constant wind source, there are three variables that are critical to the performance of the windmill: the surface area of the blade, the pitch of the blade, and the distance of the blade from the axle. 4. Windmills vary in the maximum amount of weight they can lift. Windmills vary in the maximum speed at which they can lift a weight. 5. Force, power, and work are not synonymous concepts. a) A force is required to lift a load. There is a maximum load that a windmill can lift. Too small a force and the load may not move. b) Power is the amount of work done in a certain time period. It is also defined as the speed at which a load is lifted. More power is required to lift a load more quickly. If two windmills can lift the same amount of weight but at different speeds, the windmill that lifts the weight faster has more power. c) Work is the application of a force over a distance. In lifting a weight to a higher position the windmill does work. 6. The pitch and size of the blade are critical. Both have an effect on how much wind the blade deflects. a) Changing either the pitch or the size of the blade changes the amount of weight the windmill lifts. 7. The distance between the hub and the blade is critical. Changing this distance will change the amount of weight that the windmill can lift and the speed at which it lifts the weight. a) A windmill with blades that are at a greater distance from the hub can lift heavier objects, but generally lifts the weight more slowly. b) A windmill with blades that are closer to the hub can generally lift weight more quickly, but it cannot lift as much weight. Introduction to the Windmills' Module 1 c) Changes in the distance between the hub and the blade (the radius) cause changes in torque. TORQUE = RADIUS x FORCE d) Changes in torque affect the speed at which the blades revolve and the amount of weight the windmill can lift. 0~tl@[f1)11tll:rtl~ ~© [fi)~@[.Q)l1~ ®[(1)<91 ~[fi)@'W~@<91~@ Torque and Power In the Windmills Module students investigate two primary concepts: torque and power: • Torque determines the amount of load that the windmill can lift. • Power determines how quickly the load is lifted. Speed is also an important concept in this module. Two different measurements of speed can be associated with windmills. The first is the speed with which the windmill turns. This is known as the rotational speed. A very common measurement of this kind of speed is revolutions per minute (rpm). The second kind of speed involves the amount of work that the windmill can perform. This kind of speed indicates how quickly the windmill can lift a load. This speed is measured in terms of distance divided by time, such as centimeters per second or feet per hour. Although rotational speed is important in this module, we will concentrate on the speed at which a load can be lifted because this allows us to directly calculate power. Variables There are three variables to consider in this module: 1. The size of the blades The wind applied to the windmill (provided by an electric fan) remains constant throughout the challenges. The students must manipulate the amount of wind force utilized by altering the design of the windmill blades: the larger the total surface area of the blade, the greater the total force on the blade. However, a greater force on the blade does not mean that the windmill will necessarily turn effectively since blade pitch is also a factor. 8 Windmills ( 2. The pitch of the blades Certain angles for the blades will produce no rotation at all, while other angles allow for a maximum speed of rotation. 3. The radius of the rotor Longer arms on the rotor produce more torque than shorter ones. (Similarly, longer levers can lift more weight.) Torque is proportional to the total weight that the windmill can lift. TORQUE = RADIUS x FORCE Wind Force Moving air particles comprising the wind strike the blades of the windmill. Some of the particles' kinetic energy is transferred to the blades, thus causing the blades to rotate. The different ways in which the air particles strike the blades allow the windmill to turn more quickly or more slowly. If the blades are positioned edge on to the wind, most of the air particles will miss striking the blades entirely, and will have little or no effect on the windmill. If the blades are turned so that they are flat toward the direction of the wind, the air particles will simply bounce back in the direction from which they originated. Again, there will be little or no effect on the windmill. However, if the blades are turned at an angle to the wind, the air particles will strike the blade surfaces and bounce off in a different direction from the wind source, transferring energy to the blade in the process. As a result, the blade is pushed ahead and the windmill turns. Radius of the Rotor The amount of weight that a windmill can lift depends upon the amount of force on the blade in the direction of motion and the radius of the rotor (the length of the windmill blades). Imagine two windmills with the same blade design and pitch. One windmill, however, has longer arms than the other. It is therefore capable of lifting more weight. The arms of a windmill act in much the same way as levers. We apply a force to the end of a lever which rotates about an axis or fulcrum. The greater the distance between the fulcrum and the point at which the force is applied, the greater the lifting or prying capacity of the lever. As with the lever, the longer the distance between the axis of rotation and the point where the force is applied, or simply, the longer the blade, the greater the amount of weight that can be lifted by the windmill. This ability to lift weight is called torque. TORQUE = RADIUS x FORCE Therefore, a windmill with blades designed to transfer the maximum amount of wind energy into rotational energy will increase its ability to lift weight by increasing the length of its arms. Introduction to the Windmills' Module Work and Power Work is defined as force times distance: WORK = FORCE x DISTANCE Speed is defined as distance traveled per unit of time: SPEED = DISTANCE/TIME Power is usually thought of as the rate at which work is done. It is defined as work done per unit of time: POWER = WORK/TIME To determine the amount of power something produces, we can measure the quantity of work done in a certain amount of time. However, since work is force times distance, we can also express power as force times distance divided by time, or more simply as force times speed. Therefore: POWER = WORK/TIME = FORCE x DISTANCE I TIME FORCE x SPEED = In this module we may interchange weight and force because the windmill is lifting weights off the floor; the force in this involves gravity pulling on the weight. In Challenge 4, students determine the power their windmills produce by measuring the amount of weight that the windmill lifts and the speed at which the weight is lifted. Students will learn that decreasing the time variable of the power equation is the key to increasing the amount of power produced by the windmill. Decreasing the length of the windmill arms decreases the lifting time. However, decreasing the arm length too much will result in a loss of torque, and thus a loss of work output. The windmill will no longer be able to handle the load. Students will learn to balance variables to find the optimum design. The following science process skills will be utilized in this module: • Hypothesizing • Measuring • Recording data • Interpreting data • Designing, testing, making design changes • Graphing [NOTE: For information on assessment of process skills, see the Rubrics section at the end of this module.] 10 Windmills 0~n@[ft}~@ Lr@~[lu[ft}@a@~ 0@~a@fcy The following STS connections are intended: • Teamwork • Competition in industry • Alternative and renewable energy sources Students' understanding of science concepts will be revealed in their work as they progress through the challenges. Assessment tools are provided for the teacher, but observation of the progress of each student, revealed in class discussions, worksheets, reports, storyboards, and design modifications will portray the complete picture of the student's progress. Introduction to the Windmills' Module 11 When did humans realize that they could use wind? A 5,000-year-old drawing is one of the first pieces of evidence that humans had learned to use the wind's power. The drawing shows a boat that ancient Egyptians used to sail the Nile River. Wind caught by the boat's rectangular sails moves the boat through the water. The weary men rowing against the river's current must have rejoiced when the wind began to gust. This meant they could save their strength and use the power of the wind to take them on their journey up river. 1 Early Uses of the Wind Once humans had learned to use the wind as a power source, they created different ways in which to use it. Over two thousand years ago ancient inventors in Persia learned to use sails to turn large flat circular stones. These stones would crush and grind grain into flour. The word "mill" means "to grind." Therefore, these wind machines are called windmills. 2 How important is flour? That depends on what you eat. Compare the food you usually eat with the food that people in Europe ate in medieval times. If the people were rich, they could afford fish, meat, and vegetables to provide the protein that their bodies required. Poor peasants, however, could only afford bread made from wheat, and porridge from oats. They depended on these grains for their protein and they needed to grind all of this grain into flour to make it usable. For 1 Eldridge, 2 14. Ibid, 15. 12 Windmills this reason, flour was extremely important to the health of poor people. Milling grain by hand is exhausting and time consuming. People who ground their flour by hand, using a tool called a quern, had to grind for at least two hours a day in order to make enough food for their families. Therefore, mills powered by animals, water, and wind saved a great deal of time and labor. 3 In the eleventh century thousands of watermills were in operation throughout Europe. These mills were often owned by lords of feudal estates, who also owned vast areas of land on which many poor people lived. The lords controlled the use of the rivers and streams where they built watermills and they charged the people to use the mills. Thus these poor people had to either pay for the use of the lord's mill or grind the flour by hand. They would take whole grains that they had grown themselves to a local mill, grind them into flour, then take home the flour to use for cooking. However, because they had no money, people usually paid the owner of the mill by giving them part of their milled flour. Windmills did not appear in Europe until the twelfth century. At this time the Crusaders learned about using the wind to power mills while traveling in the Middle East. When they returned to Europe, they told people of these wind-powered mills. The idea of a windmill was of great benefit to the poor. Unlike the rivers, the wind could not be controlled. It was free for everyone. The peasants built and operated their own windmills. They ground their own flour at almost no cost and became skilled windmill mechanics. The windmill gave power to the poor. It was an instrument of social change. 4 The lords were threatened by the many windmills that enterprising poor people constructed throughout the European countryside. The watermill owners knew that they would lose large amounts of money now that the peasants no longer needed to pay for the use of their water driven mills. In France the Catholic archbishop regulated windmills by demanding a percentage of the flour produced there. In England, lords destroyed and seized newly erected windmills. 5 3 Hills, 25. 4 Gipe, 121. Gipe, 121. 5 History of Wind Power 13 Ultimately, the lords could not exercise total control. As cities began to grow, and the population rapidly increased, there was a growing demand for a new energy source. Windmills met that need. They were cheaper to build than watermills and they did not need to be located on waterways. Thousands of windmills were erected throughout Europe. 6 Technological Innovations The earliest windmills had blades that moved on a vertical axis. Instead of harnessing a horse or donkey and forcing it to walk in a circle, blades or cloth sails pushed by the wind were used to turn the axle of the windmill. The windmills that were built throughout Europe used a horizontal axis and were called post mills. The horizontal axis connected the sails on the windmill arms to machinery inside a timber frame. The entire frame could be rotated. This made it possible to orient the sails so that they faced into the wind. When the wind changed direction, the wind smiths turned the frame. In the twelfth and thirteenth centuries, tower mills were developed from the post mills. In tower mills, the main frame and machinery of the mill were fixed. Only the cap of the mill, which held the blades or sails, was turned to face the wind. 7 In the eighteenth century, a device was invented which automatically turned the windmill into the wind. It is called a fantail, a small rotor attached to the back of the windmill. The fantail is perpendicular to the windmill blades. If the wind changes direction it no longer pushes against the windmill blades. Instead, it now turns the fantail which turns gears connected to a circular track around the windmill. The turning fantail moves the windmill blades into the wind's new direction. When the blades are in the direction of the wind, the fantail stops because it has moved out of the wind. Storms could destroy windmills. The sheer force of heavy winds would rip apart canvas sails or long fragile wooden blades. People were alert to changing weather conditions in order to act quickly to protect their mills. The post mill design made it possible for them to turn the mills out of the strong winds so that the blades did not take the wind's full force. People also designed ways to rapidly unfurl canvas sails and they developed wooden blades equipped with shutters. Like a window 6 Gipe, 121; Hills, 43. 51. 7 Hills, 14 Windmills shade, the shutters could be opened to lessen the total force of the wind on the blades. Using the Wind to Drain Water from the Land Besides propelling sailing ships and grinding grain into flour, for what other purposes were windmills designed? Windmills have been adapted to saw wood, to beat and pulp fibers of rags to make paper, to hull barley, to run fans that ventilated mining shafts, to powder flint for use in pottery, to crush chalk for cement, to press oil from seeds of plants such as colza and flax, to scutch (or separate) the woody parts of hemp and flax for use in textiles, and even to drive the bellows for an organ. 8 In the Netherlands, people found another important use for the power of the wind. People there needed more land, so they began to drain the water from large areas of flooded land near the level of the sea. People in the Netherlands built islands from clay on which they could live. Scientists have estimated that the hundreds of artificial mounds in the northern Dutch marshes were constructed from 30 times as much material as was used for the pyramid of Cheops in Egypt. 9 In the twelfth century, severe flooding in the Netherlands forced the people of the entire region to work together to develop and administer a system to save their land. They constructed dams and embankments along the coastline to protect their villages and fields against flooding from rivers and the sea. They dug drainage canals to channel excess water from the land back to the sea. 10 However, the land that they wanted to drain was primarily below sea level at high tide. Water naturally flowed onto their land, not off it. The Dutch needed a machine to lift water from the low areas, over protective embankments, to higher areas from where it could drain into the ocean. Windmills were put to the task. They were fitted with scoopwheels, which scooped and raised water from one canal and dumped it into another canal at a higher level. In the fourteenth century, the Dutch became the leading innovators in windmill design, not for the purpose of grinding grain but rather of draining land. 11 ( Hills, 11 and chapter 7. Hills, 115. to Hills, 115-6. 8 9 11 Hills, 116. History of Wind Power 15 In the following centuries the Dutch developed and fitted their windmills with a number of other devices to lift water, in addition to the scoopwheel. These devices included various types of pumps as well as the Archimedes' screw, an invention of ancient Egypt. The screw could lift water to a higher level than the scoopwheel, but it was difficult to build. It required many small pieces of wood fitted very tightly around a vertical shaft so that it would not leak water. 12 Windmills drained vast areas of land for several centuries. By the seventeenth century windmills had become the major power source in the Netherlands. By 1850, ninety percent of the power used in Dutch industries came from the wind. 13 The power of the wind helped the Dutch to become a prosperous people. The wind, however, did not always blow, and the costs of building and maintaining a windmill, although less than watermills, were still high. Coal, on the other hand, was cheaper and always available. In the nineteenth century, steam engines, using coal as fuel, began to replace windmills as a source of power on farms and in industries. They were less costly and more dependable. Dutch farmers did not have to wait for the wind so that they could drain their fields in the spring. They could also place the steam engines anywhere, whereas the windmill had to be located in a windy open area. 14 ( Windmills in the United States In the nineteenth century, men and women in the eastern United States packed their belongings and formed wagon trains to settle the western frontier. They came upon countryside very different from what they had previously known. In the east, many streams crossed the land and good wells could be simply dug by hand. In the west, however, streams were rare and underground water sources known as aquifers, were usually deep below the ground's surface. Water is very heavy. The farmers in the west had to determine a way to pull water to the ground's surface in large amounts so that they could water crops and feed livestock. Their solution: wind power. This section of the western United States is called the Great Plains. It was also known as the Great American Desert because water was scarce on the surface of the land. The water-pumping windmill made settlement of the American Great Plains possible. 12 Hills, 117-20. 13 Gipe, 122. 122. 14 Gipe, 16 Windmills Water was also essential to the transcontinental railroads built in the nineteenth century. The heavy locomotives were powered by steam, and for that they required water as well as coal. Huge water pumping windmills, with blades 60 feet (18 m) in diameter, as well as giant water storage tanks were built at stations all along the railways.15 As the railways brought more and more settlers to the west, the demand for windmills became enormous. At the beginning of the nineteenth century, 77 windmill companies employed approximately 2,300 workers. Windmill manufacturers strove to design more efficient and durable windmills. Thomas Perry took a scientific approach to improving windmill design. Using a test stand, he came up with a rotor that was nearly twice as efficient as previous designs. LaVerne Noyes manufactured Perry's design. The result was the Aermotor, a windmill made with stamped sheet-metal "sails." The Aermotor was so efficient, reliable, and inexpensive to manufacture that it became widely used across the United States. There are still many parts of the western United States that depend upon these windmills to pump water for livestock, wildlife, and irrigation. Today, more than one million windmills having the Aermotor design are used in countries worldwide. 16 Electricity Windmills that are attached to generators convert the force of the spinning rotor blades into electricity. Wind-powered machines that produce electricity are commonly called wind turbines. The first wind powered electric turbines were developed in the 1880s in England and the United States, not long before Thomas Edison perfected the electric light. By the 1930s on the Great Plains of the United States, hundreds of thousands of small wind turbines brought light to homes and farms. These "home light-plants" powered not only light bulbs, but also radios, electric appliances, power tools and electric pumps. 17 Later in the 1930s, however, the Rural Electrification Administration erected electric power lines throughout the United States. Electricity generated in large coal-fueled power plants was distributed easily through the power lines to both cities and rural areas. Most 15 16 Gipe, 124. Gipe, 125. 17 Gipe, 131. History of Wind Power 17 farmers found it easier and cheaper to buy this electricity than to maintain their own small wind generators and water pumping windmills. In both the Netherlands and the United States windmills provided the power to lift water and thus make it possible for settlers to live on the land. Eventually, however, other power sources replaced the windmills. In the Netherlands coal-powered steam engines gradually took over the windmill's job of pumping water. In the United States coalfired electric plants took over the windmill and wind turbine's job of providing power to families on small farms. Modern Wind Turbines In recent years, wind power has been making a comeback in the United States and other countries. Where it can be used easily, wind power is a viable, renewable source of energy. Technological innovations and greater understanding of the physics involved in harnessing the wind have made modern wind turbines increasingly efficient. Wind turbines look fast and sleek compared to traditional windmills. There is good reason for this. Grinding grain and lifting water require great amounts of force. Windmills were designed with many large, wide blades so that they could capture a lot of wind. The more wind captured by the blades, the greater the ability to grind grain or scoop water. The blades of the older windmills may have moved slowly but they could lift a great deal of weight. By contrast, electrical power can only be efficiently generated by high speed turbines. Therefore, wind turbines usually have only 2 or 3 thin blades that typically spin much faster than the blades of an old fashioned windmill. The wind turbine blades are designed to generate electricity efficiently rather than move large amounts of weight. Why not create a rotor with huge blades that will also go at high speeds? There are two problems that we would face: drag of air particles and wind speed. When huge blades move through the air, air particles drag on the blades, slowing them down. The faster the blades move, the more drag, or air resistance, they encounter. Huge blades simply cannot move as fast as sleek blades because of this problem of drag. The speed of the wind also limits the speed of the blades. Compare a small, one foot diameter pinwheel to a large windmill. In the same wind, which do you think will spin faster? In other words, which do you think will make more revolutions per second, even if you discount the problem of air resistance? Imagine that the tip of the pinwheel blade moves at the same speed as the wind. To complete one revolution it must trace out a one foot diameter circle. Imagine that 18 Windmills 1_._. ( ' the tip of the windmill blade also moves at the speed of the wind. To make one revolution, it must trace out a circle of many feet in diameter. The windmill blade will take much longer to complete a full revolution. The ancient Egyptians caught the wind with their sails so that it would move their boats. Sailors have learned to use the power of the wind to both push and pull their boats. Modern sails are designed so that wind passing over them creates aerodynamic lift; airplane wings and propellers work by using the same force of lift. These sails, wings, and propellers are called airfoils: when air passes by them, a difference in air pressure is created. The air pressure on one side of the airfoil is larger than the air pressure on the other side. Thus, the airfoil will move. The sail is pulled into the wind, and the wing is lifted into the sky. Traditional windmill blades are designed to catch the wind and to be pushed by it. However, nearly all modern turbine blades are designed as airfoils. Not only do these sleek "wings" move at higher speed than traditional windmill blades, they also take advantage of the principle of aerodynamic lift. They are capable of producing much more power than traditional blades. For the same diameter, airfoils produce twice as much power as standard windmill blades that are pushed by the wind. For the same surface area of blade, airfoils produce 50 times as much power. The Future Modern societies have been using coal, oil, and radioactive minerals to produce power. The burning oil and coal have severely polluted the environment, while the fission of uranium and plutonium in nuclear power plants creates extremely dangerous radioactive wastes that will be around for thousands of years. Harnessing the wind does not create any hazardous waste. It is a renewable source of energy. Air is always moving across our planet. Over the centuries we have gradually developed the technology and learned the physical principles that enable us to harness the wind's power with greater and greater efficiency. History of Wind Power 19 Class Preparation and Set·Up ( Materials • Vinyl insulated ring terminals (blue crimp connectors) 16-14 gauge #8 stud size (one for each rotor blade) • Dowels, 3/16 inch (5 mm) diameter, 3 inches (7.6 cm) long (one for each blade arm) • Nuts and bolts, 8-32 X 3/4 inch (1.9 cm) (one per hub/rotor assembly) • Pencil sharpener • Masking tape, 1/2 inch (1.3 cm) width • Ruler • Corrugated cardboard cut into 2 3/8 X 2 3/8 inch (6 X 6 cm) squares • Scissors • Data Sheet • Inclinometer • Rotor arm angle finder Materials for Turbine Stand Test Station • Laboratory stand • Support clamp (for laboratory stand), right angle with V-groove • Brass tubing\ 0.187 inch inside diameter, 0.215 inch outside diameter, 6 inches (15.2 cm) • Tubing cutter2 (small) • Medium size ball point pen housing3 • Plastic soda straws, approx. 0.25 inch outside diameter, 0.234 inch inside diameter, 4 inches (10.2 cm) long • Masking tape, 1 inch (2.5 cm) wide 1 K & S Engineering, Part #129 recommended (available at most hardware stores). 2 K & S Engineering, Part #296 recommended (available at most hardware stores). BicTM brand "Round Stic" medium ball point pen recommended. 3 20 Windmills - • • • • • • Dental floss Paper cup, 6 or 8 ounce (177 or 237 ml) Yard stick or meterstick Jumbo paper clips Nails, 16 D, 3 1/2 inch (8.9 cm) length, approximately 10 grams each Fan, 16 inch (40.6 cm) oscillating fan, set in stationary mode (Box fans not recommended because they usually have a dead area in the center of the wind column.) • Extension cord (grounded), 12 foot (4 meter) • Duct tape • Stop watch or timer Materials for Inclinometer • • • • Dental floss Protractor, 3 1/2 inch (10 cm) plastic Nut, 1/4-20 Masking tape Materials for Rotor Arm Angle Finder • Angle template • Glue or glue stick • Cardboard, 8 1/2 X 11 inches (21.6 X 27.9 cm) Test Stand 1. 2. 3. 4. 5. 6. 7. Remove the ink cartridge and tip from the ball point pen. Create a shaft holder by cutting a 3 1/2 inch (8.9 cm) length of the pen cylinder. Create the drive shaft by cutting a 7 inch (16.8 cm) length of brass tubing. Cut a 4 inch length straw. Slide the straw over tubing. Slide the straw/tube assembly into the ball point pen shaft. Create the rotor end of the drive shaft by winding a strip of masking tape around one end of the brass tube until it projects 1/8 inch (3 mm) from the surface of the tube. Class Preparation and Set-Up 21 8. Using masking tape, attach a length of dental floss to the other end of the brass tube. Make sure that the floss is long enough to reach the cup on the floor. 9. Wrap a strip of masking tape around middle of the ball point pen shaft until it projects 1/4 inch (6 mm) above the shaft's surface. Brass Tubing Straw Masking Tape Ball point pen plastic Masking Tape (Attach damp of test stand here.) Masking Tape (used to hold rotor blades away from test stand.) Dental Floss 10. Set the height of the support clamp on the laboratory stand to the same height as the center of the fan. 11. Attach the completed drive shaft and shaft holder to the support clamp. Do not overtighten. 12. Position the completed test stand 4 feet (1.2 m) from the front of the fan. The dental floss should extend to the floor. Weight Cup Assembly 1. Poke three holes in a paper cup, 120° apart and 1/4 inch (6 mm) from the top of the cup. 2. Insert jumbo paper clips into each hole. 3. Connect a fourth paper clip to the three clips on the cup. 4. Attach the top paper clip to the dental floss taped to the drive shaft. Windmills Inclinometer Assembly The inclinometer will allow students to measure the pitch of their rotor blades. 1. Tape a 6-inch (15.2 cm) length of dental floss to the zero point (the center of the baseline) on the small plastic protractor. 2. Attach a 1/4-20 nut to the loose end of the dental floss. This acts as a weight. Protractor Rotor Arm Angle Finder Assembly This device will allow students to position the rotor arms at specific angles 1. Glue the template provided in this module to a 8 1/2 X 11 inch (21.6 piece of corrugated cardboard. 2. Punch a 1/8 inch (3 mm) hole in the center of the template. Class Preparation and Set-Up X 27.9 cm) 23 Rotor Arm Angle Finder Template Rotor Arm Assembly 1. Attach the 3 inch (7.6 cm) dowels to the plastic sleeves of the connectors. The fit should be snug. If it is not, see the Troubleshooting Tips section on page 25. 2. Secure the connectors by putting the 8-32 X 3/4 inch (1.9 cm) bolt through the rings and fastening the nut on the other side. 3. Place the rotor on the Rotor Arm Angle Finder and position the arms so that they are equally spaced apart. 4. Slide the corrugated cardboard blades onto the dowels. Make sure that they are equidistant from the center of the rotor. 5. Adjust blades to the desired angle using the inclinometer. To do this, place the rotor arm on the desk top so that the bolt touches the desk. Hold the inclinometer, flat side up, so that the floss crosses it at 90°. The cardboard blade should be parallel to the flat side of the protractor. Keeping the center of the protractor's flat side in alignment with the wooden dowel, rotate the protractor until the floss crosses at the desired degree marking. Adjust the cardboard blade so that it is again parallel to the flat side of the protractor. Connector Wooden Dowel:t! ! Nut Brass - Tubing (Note: Masking Tape may be added around the bolt if it does not fit securely inside the brass tubing.) n Cardboard Blade Cardboard Blade Insert the wooden dowels between the corrugated folds in the cardboard. 24 Windmills 6. Wrap a piece of masking tape around the exposed threads of the bolt (approximately 2 1/2 turns around the bolt). 7. Push the taped end of the bolt into the brass tubing on the test stand. It should fit securely. If it does not, add or remove tape. Test Stand If the drive shaft (the ball point pen shaft) binds, check the locking bolt between the support clamp and the pen shaft to make sure that it is not exerting too much pressure. Squeezing the plastic too tightly will cause it to deform. If the drive shaft still binds, remove the straw. It is important that the drive shaft be level. It may be necessary to place a shim underneath the drive shaft support. Rotor Construction ( Dowels Dowels must fit snugly into the crimp connector plastic sleeves. If the dowels are too wide, taper them slightly with the pencil sharpener. If they are too loose, tape them to the crimp connector or soak the dowels in water (causing the wood to swell) for 10-20 minutes. Blades If blades are too loose (or sliding) on the dowel, establish the proper blade pitch and tape the blade in place. Air Flow Make sure that no one is standing directly behind the test rig or the fan. This will reduce airflow and give erratic results. If too little air flow is still a problem, increase the fan speed to the next higher setting. Make sure that the center of the fan is in line with the center of the windmill. Before displaying the standard design, administer the pretest to determine students' thoughts about windmills. Class Preparation and Set-Up Use the Pretest questions as brainstorming questions to lead a class discussion before beginning the challenges. The goal of brainstorming is for students to use or consult their experiences when dealing with these questions. This kind of support helps develop the expectation that understanding begins with challenging one's own experiences. If students suspect that the goal is to guess what the teachers want, then students are missing the necessary experience to advance their understanding. · 26 Windmills Challenge Objective Design a scale version of a windmill that will raise the greatest weight (number of nails) possible. Challenge Scenario A rancher has asked your company to design a pump that will allow him to provide water for his cattle. The pump must access water from an underground water source. Since the ranch is isolated, the only reasonable source of energy is from the wind. Your goal is to design a pump that will raise the greatest possible amount of water to the surface. Challenge 1: Unrestricted Design-Torque fJ.1 Materials • Vinyl insulated ring terminals (blue crimp connectors) 16-14 gauge #8 stud size (one for each rotor blade) • Dowels, 3/16 inch (5 mm) diameter, 3 inches (7.6 cm) long (one for each blade arm) •Nuts and bolts, 8-32 X 3/4 inch (1.9 cm) (one per hub/rotor assembly) • Pencil sharpener • Masking tape, 1/2 inch (1 .3 cm) width • Ruler • Corrugated cardboard cut into 2 3/8 X 2 3/8 inch (6 X 6 cm) squares • Scissors • Inclinometer • Rotor arm angle finder • Data Sheet (one per team per iteration) ( Windmills Troubleshooting Tips • An effective length for the arms will be approximately 3 inches (7 cm). An effective blade angle is 30°. • To facilitate consistent results, keep the fan on its lowest setting. Block the air stream from the fan with a large piece of cardboard until the team is ready to test. Begin timing when the cardboard is lifted. Procedure Set-Up • Adjust the length of the dental floss on the rotor arm so that the weight cup rests on the floor but the floss is still taut. This distance will remain constant on the data table. • Adjust the height of the fan if necessary so that it blows directly on the test stand. • To facilitate consistent results, keep the fan on its lowest setting and line up the center of the fan with the center of the windmill. Block the air stream from the fan with a large piece of cardboard until the team is ready to test. Begin timing when the cardboard is lifted. If there is still too little air flow, increase the fan speed the next higher setting. Demonstration Show students the standard rotor design and how the windmill operates. Class Discussion Ask students to explain how they think the standard design works. Ask them to speculate on how to improve its performance through design changes. Cooperative Learning Groups Challenge student teams to design a turbine that will lift the most nails. At this point there are no material or size restrictions, aside from practical considerations (e.g., rotor blades should not be so big that they are partially outside the fan's air stream). Instructions to Students Each team must complete a Design Sheet for any design it is going to test. The Design Sheet must be filled in when the team brings its rotor design to the test station. All teams must document and publish their progress. After running each test, teams post their results on a graph or chart for public viewing. Challenge 1: Unrestricted Design-Torque r stri TEAM NAME: DATE: Procedure Use the procedures below to create a windmill that will lift the most nails. Rotor Arm Assembly 1. Attach the 3 inch (7 .6 cm) dowels to the plastic sleeves of the connectors. The fit should be snug. 2. Attach as many arms as you think are necessary. Secure the connectors by putting the 8-32 X 3/4 inch (1.9 cm) bolt through the rings and fastening the nut on the other side. 3. Place the rotor on the Rotor Arm Angle Finder and position the arms so that they are equally spaced apart. 4. Slide the corrugated cardboard blades onto the dowels. Make sure that they are equidistant from the center of the rotor. Measure the distance. 5. Adjust blades to the desired angle using the inclinometer (your teacher will show you how it is used). Bolt Connector Cardboard Blade ~ Wooden Dowel Wooden Dowel:l;: : Nut : ! Brass · Tubing (Note: Masking Tape may be added around the bolt if it does not fit securely inside the brass tubing.) Connector Cardboard Blade Insert the wooden dowels between the corrugated folds in the cardboard. 30 Windmills 6. Wrap a piece of masking tape around the exposed threads of the bolt (approximately 2 1/2 turns around the bolt). 1. Push the taped end of the bolt into the brass tubing on the test stand. It should fit securely. If it does not, add or remove tape. Test Your Design 1. Your team must complete a Data Sheet for each design you wish to test before taking it to the test station. 2. In order for the test to be considered fair, the design must be able to lift the nails starting from a position on the floor. 3. All tests are public. You may modify your design based on observations of how other designs perform. Complete at least three modified designs. Challenge 1: Unrestricted Design-Torque 31 1; TEAM NAME: DATE: Description and drawing of new design: Number of Blades: - - - Distance from blade to hub: - - - Surface Area of each blade: - - - Blade pitch: _ __ Describe how this design is different from your previous design. Test Results Weight lifted (number of nails): _ _ Is this an improvement over your last design? (circle one): YES I NO 32 Windmills Challenge 1 Wrap . Up Questions for Class Discussion • Which design changes did you find to be the most useful? • Why do you think they worked so well? • What design elements do the most successful windmills have in common? • Did any other team have an idea that your team would like to try? Performance Variables • Pitch of Blades: For maximum lift blades angled (45°) into the wind stream work better than blades perpendicular (90°) to the wind stream. If angled, all blades must be sloped in the same direction and at the same degree. • Size of Blades: Larger blades lift more weight than smaller ones. • Number of Blades: Although this can affect performance, students may not notice any change in outcome. It is very difficult to measure this variable on a model of this size. • Shape of Blades: The total surface area of the blades is more important than their shape for a model of this size. • Radius of the Rotor Arms: Longer arms will lift more weight than shorter arms. (Remember, however, that they must still remain short enough to stay within the air flow from the fan.) Competence & Performance Criteria Each student's performance design should be evaluated to determine if it lifted a sufficient amount of weight. Additionally, students should be evaluated based on the results that they recorded on their Data Sheets as well as the overall organization and neatness of these sheets. Challenge 1: Unrestricted Design-Torque 33 Challenge Objective Design a windmill using only the materials provided by the teacher that will lift the greatest weight (number of nails) possible. ( •· Scenario Change The rancher who ordered the wind-powered pump has just remembered to tell you that there are no paved roads leading to the ranch. Transporting the finished pump to the ranch will be a problem. The only solution is to transport all of the windmill parts in the back of a pick-up truck. Today, you must change the design of your windmill so that you use a limited amount of material. The windmill design must still lift the most weight possible. 34 Windmills Materials • Corrugated cardboard, cut into 2 3/8 X 2 3/8 inch (6 X 6 cm) squares (three per team) • Data Sheet (one per team per iteration) • Vinyl insulated ring terminals (blue crimp connectors) 16-14 gauge #8 stud size (one for each rotor blade) • Dowels, 3/16 inch (5 mm) diameter, 3 inches (7.6 cm) long (one for each blade arm) •Nuts and bolts, 8-32 X 3/4 inch (1.9 cm) (one per hub/rotor assembly) • Pencil sharpener • Masking tape, 1/2 inch ( 1.3 cm) width • Ruler • Scissors • Inclinometer • Rotor arm angle finder ( I,, Challenge 2: Restricted Design-Torque 35 Troubleshooting Tips Restrict Windmill Design In this challenge, materials are limited (only three squares of cardboard may be used). The restricted designs of Challenge 2 allow students to more easily isolate the radius variable and thus discover its relationship to the amount of weight lifted. This directly demonstrates the concept of torque. Procedure Set-Up • Adjust the length of dental floss on the rotor arm so that the weight cup rests on the floor but the floss is still taut. This distance will remain constant on the data table. • Adjust the height of the fan if necessary so that it blows directly on to the test stand. • To facilitate consistent results, keep the fan on its lowest setting and line up the center of the fan with the center of the windmill. Block the air stream from the fan with a large piece of cardboard until the team is ready to test. Begin timing when the cardboard is lifted. If there is still too little air flow, increase the fan speed to the next higher setting. Demonstration Show students the standard rotor design and how the windmill operates. Announce that a limited supply of material is available for each design. Class Discussion Ask students to speculate on how to improve the design given the limited materials provided. Cooperative Learning Groups Challenge student teams to design a windmill that will lift the most nails using only the material provided for the rotor blades. Instructions to Students • Using only three pieces of cardboard no larger than 2 3/8 X 2 3/8 inch (6 X 6 cm) for each blade, design a windmill that will lift the greatest number of nails. 0 Each team must complete a Design Sheet for any new design to be tested. The Design Sheet must be filled in when the team brings its rotor design to the test station. • All teams must document and publish their progress. After running each test, teams post their results on a graph or chart for public viewing. 36 Windmills , >; • strict SI TEAM NAME: DATE: Procedure Use the procedures below to create a turbine that will lift the most nails using a limited supply of materials. Rotor Arm Assembly 1. Attach three dowels to the plastic sleeves of three connectors. The fit should be snug. 2. Secure the connectors by putting the 8-32 3/4 inch (1.9 cm) bolt through the rings and fastening the nut on the other side. X 3. Place the rotor on the Rotor Arm Angle Finder and position the arms so that they are 120° apart. 4. Slide the corrugated cardboard blades onto the dowels. Make sure that they are equidistant from the center of the rotor. Measure the distance. S. Adjust blades to the desired angle using the inclinometer (your teacher will show you how it is used). Bolt Connector Wooden ~ Wooden Dowel Dowel~:!Nut. Connector M Brass Cardboard Blade - Tubing (Note: Masking Tape may be added around the bolt if it does not fit securely inside the brass tubing.) Cardboard Blade Insert the wooden dowels between the corrugated folds in the cardboard. Challenge 2: Restricted Design-Torque 37 6. Wrap a piece of masking tape around the exposed threads of the bolt (approximately 2 1/2 turns around the bolt). 1. Push the taped end of the bolt into the brass tubing on the test stand. It should fit securely. If it does not, add or remove tape. Test Your Design 1. Your team must complete a Data Sheet for each design you wish to test before taking it to the test station. 2. In order for the test to be considered fair, the design must be able to lift the nails starting from a position on the floor. 3. All tests are public. You may modify your design based on observations of how other designs perform. Complete at least three modified designs. ( 38 Windmills TEAM NAME: DATE: Design number: _ _ Description and drawing of new design: ( Number of Blades: - - - Distance from blade to hub: - - - Surface Area of each blade: - - - Blade pitch: _ __ Describe how this design is different from your previous design. Test Results Weight lifted (number of nails): _ _ Is this an improvement over your last design? (circle one): YES I NO Challenge 2: Restricted Design-Torque 39 Challenge 2 Wrap . Up Questions for Class Discussion ( • Did working with a limited amount of cardboard make your job harder or easier? Explain. • What design elements do the successful windmills have in common? Performance Variables e e Pitch of Blades: Blades angled 45° to the wind stream work best. Radius of the Rotor: Longer arms will lift more weight than shorter arms. (Remember, however, that they must still remain short enough to stay within the air flow path from the fan.) Competence & Performance Criteria Each student's performance design should be evaluated to determine if it lifted a sufficient amount of weight. Additionally, students should be evaluated based on the results that they recorded on their Data Sheets as well as the overall organization and neatness of these sheets. 40 Windmills Challenge Objective Design a windmill that can lift the greatest amount of weight in the least amount of time. Scenario Change The ranch is located in a hot, arid (very dry) climate where water evaporates very fast. The wind-powered pump must bring water quickly to the surface and fill the stock tank in as little time as is possible. Since the aquifer (a layer of soil containing water) is several thousand feet below the Earth's surface, the windmill must be power- ful. Your challenge today is to design a windmill that can lift the great- est amount of weight in the shortest time possible. Challenge 3: Power 41 Materials • Vinyl insulated ring terminals (blue crimp connectors) 16-14 gauge #8 stud size (one for each rotor blade) ( • Dowels, 3/16 inch (5 mm) diameter, 3 inches (7.6 cm) long (one for each blade arm) •Nuts and bolts, 8-32 X 3/4 inch (1.9 cm) (one per hub/rotor assembly) • Pencil sharpener • Masking tape, 1/2 inch (1.3 cm) width • Ruler • Corrugated cardboard cut into 2 3/8 X 2 3/8 inch (6 X 6 cm) squares • Scissors • Inclinometer • Rotor arm angle finder • Data Sheet (one per team per iteration) ( Windmills ' ' Troubleshooting Tips Test Trials Use at least 4 or 5 nails per trial. If the machine stalls, subtract some nails. As many as 20 nails (200 grams) may be required for a very powerful design to show a decrease in speed. Procedure Set-Up • Adjust the length of the dental floss on the rotor arm so that the weight cup rests on the floor but the floss is still taut. This distance will remain constant on the data table. • Adjust the height of the fan if necessary so that it blows directly on the test stand. • To facilitate consistent results, keep the fan on its lowest setting and line up the center of the fan with the center of the windmill. Block the air stream from the fan with a large piece of cardboard until the team is ready to test. Begin timing when the cardboard is lifted. If there is still too little air flow, increase the fan speed to the next higher setting. ( Class Discussion • Ask students to define "power." Ask them to give examples of the use of power that they see and hear around them each day. • What defines a powerful windmill? Is it the fastest one? Is it the one that lifts the most weight? Instructions to Students 1. Inform the students that they have two chances to use everything that they know about windmill design to create one that is the most powerful. 2. There is no restriction on the amount of material that students may use. 3. Students may not test designs prior to the final test for each design. 4. Record all test trial results on the Data Table and complete all answers on the Data Sheet. 5. Using the data that each team has generated from testing their designs, have students fill in their data tables, calculating speed and power. 6. Graph the number of nails vs. calculated power. Use the graph to find where each particular design has the most power. 7. The team that will win the rancher's contract will be the team with the design that has the most power, based upon the information shown on the graphs. Challenge 3: Power 43 p r TEAM NAME: (:: \ DATE: Procedure Use the procedures below to create a windmill that will lift the most nails in the shortest time possible. Rotor Arm Assembly 1. Attach the 3 inch (7 .6 cm) dowels to the plastic sleeves of the connectors. The fit should be snug. 2. Secure the connectors by putting the 8-32 x 3/4 inch (1.9 cm) bolt through the rings and fastening the nut on the other side. 3. Place the rotor on the Rotor Arm Angle Finder and position the arms wherever you think that they will work best. 4. Slide the corrugated cardboard blades onto the dowels. Make sure that they are equidistant from the center of the rotor. Measure the distance. 5. Adjust blades to the desired angle using the inclinometer (your teacher will show you how it is used). Cardboard Blade Cardboard Blade Insert the wooden dowels between the corrugated folds in the cardboard. 44 Windmills 6. Wrap a piece of masking tape around the exposed threads of the bolt (approximately 2 1/2 turns around the bolt). 7. Push the taped end of the bolt into the brass tubing on the test stand. It should fit securely. If it does not, add or remove tape. Test Your Design 1. Your team must complete a Data Sheet for each design you wish to test before taking it to the test station. 2. In order for the test to be considered fair, the design must be able to lift the nails starting from a position on the floor. 3. All tests are public. You may modify your design based on observations of how other designs perform. Complete at least three modified designs. Challenge 3: Power 45 TEAM NAME: DATE: Design number: _ _ Description and drawing of new design: ( Number of Blades: - - Surface Area of each blade: _ __ Distance from blade to hub: - - Blade pitch: _ __ Describe how this design is different from your previous design. 46 Windmills Test Results 1. Record the time it took your design to lift one nail. 2. Record the distance from table to floor. 3. The speed is the distance divided over time. 4. Repeat the test with 4 nails, 8 nails, 12 nails, etc. 5. Calculate the power using the following formula: power= weight (in nails) X speed (in cm/second) Data Table Weight lifted Distance lifted Time to lift (Seconds) Speed (cm/second) Power (weight x speed) 6. What was the maximum power your windmill generated? _ _ _ __ 7. At what weight (number of nails) did your design generate maximum power? 8. What was the power at 12 nails? _ _ _ _ _ _ _ _ _ _ _ _ _ __ 9. How will you alter your design to maximize power produced at 12 nails? Challenge 3: Power 47 Challenge 3 Wrap . Up Questions for Class Discussion • What design elements do the most powerful windmills have in common? • What did you discover about power in this design challenge? NOTE: Some students may observe that the designs able to lift the most weight are not necessarily the ones that produce the most power. Performance Variables & Design Parameters • Shape of blades: Long, wide, flat blades produce more torque but at slower speeds; the windmill moves slowly but lifts a very heavy load. Small, narrow blades with a shallow pitch produce less torque, but rotate at a much higher speed. • Radius of the rotor: Students will begin to see the trade-off between torque and speed. To achieve maximum power one must strike a balance between the two. The longer the radius (distance between the center of the blade and the axle), the greater the torque; the shorter the radius, the higher the speed. Competence & Performance Criteria Each student's performance design should be evaluated to determine if it lifted a sufficient amount of weight. Additionally, students should be evaluated based on the results that they recorded on their Design Sheets as well as the organization and neatness of their Data Sheets. Look for the kinds of statements in student reports and discussions that indicate a clear understanding of the concepts. 48 Windmills Challenge Objective Design a windmill that is powerful enough to lift 10 nails in the shortest amount of time. Scenario Change You have learned on a recent visit to the ranch that the pipe bringing water to the surface can only hold a small volume of water at a time. You must change your design to lift a constant amount of weight in the shortest time possible. Challenge 4: Speed 49 Materials • Vinyl insulated ring terminals (blue crimp connectors) 16-14 gauge #8 stud size (one for each rotor blade) • Dowels, 3/16 inch (5 mm) diameter, 3 inches (7.6 cm) long (one for each blade arm) • Nuts and bolts, 8-32 X 3/4 inch (1.9 cm) (one per hub/rotor assembly) • Pencil sharpener • Masking tape, 1/2 inch (1.3 cm) width • Ruler • Corrugated cardboard cut into 2 3/8 X 2 3/8 inch (6 X 6 cm) squares • Scissors • Inclinometer • Data Sheet (one per team per iteration) • Rotor arm angle finder ( 50 Windmills . Troubleshooting Tips Students should find that a more compact, faster windmill design will produce the most efficient source of power for lifting ten nails. Procedure Set-Up • Adjust the length of the dental floss on the rotor arm so that the weight cup rests on the floor but the floss is still taut. This distance will remain constant on the data table. • Adjust the height of the fan if necessary so that it blows directly on the test stand. • To facilitate consistent results, keep the fan on its lowest setting and line up the center of the fan with the center of the windmill. Block the air stream from the fan with a large piece of cardboard until the team is ready to test. Begin timing when the cardboard is lifted. If there is still too little air flow, increase the fan speed to the next higher setting. Class Discussion • Ask students to define "speed." What does it mean? • Ask students to give examples of speed based on their day-to-day experience. Pretest Trial • Students may test their design in one timed trial before the official testing begins. They may make minor modifications to their designs based on the results of this test. They do not need to complete a design sheet prior to the test. Design Testing • When all students have had the opportunity to test and alter their designs, begin the official testing. Teams demonstrate the speed of their design one round at a time. Post the results after each round. • Teams may make design changes before the second round but they may not test any modified design before the official timed trial. Test Trials • Ask students to test their designs by lifting ten nails at once. • Ask students to graph the results of their trials and evaluate their design's performance. • Use the best time for each team. The rancher will award the construction contract to the team that lifts the ten nails in the shortest amount of time. Challenge 4: Speed 51 l DATE: TEAM NAME: Procedure Your team has two opportunities to design a windmill powerful enough to lift 10 nails in the shortest amount of time. Your official time will be the fastest of two rounds. You may modify your design before the second round of testing, but you may not test it ahead of time. Use the following procedures to construct the windmill. Rotor Arm Assembly 1. Attach the 3 inch (7 .6 cm) dowels to the plastic sleeves of the connectors. The fit should be snug. 2. Secure the connectors by putting the 8-32 x 3/4 inch (1.9 cm) bolt through the rings and fastening the nut on the other side. 3. Place the rotor on the Rotor Arm Angle Finder and position the arms wherever you think that they will work best. 4. Slide the corrugated cardboard blades onto the dowels. Make sure that they are equidistant from the center of the rotor. Measure the distance. 5. Adjust blades to the desired angle using the inclinometer (your teacher will show you how it is used). Cardboard Blade Cardboard Blade Insert the wooden dowels between the corrugated folds in the cardboard. 52 Windmills 6. Wrap a piece of masking tape around the exposed threads of the bolt (approximately 2 1/2 turns around the bolt). 7. Push the taped end of the bolt into the brass tubing on the test stand. It should fit securely. If it does not, add or remove tape. Test Your Design 1. Your team must complete a Data Sheet for each design you wish to test before taking it to the test station. 2. In order for the test to be considered fair, the design must be able to lift the nails starting from a position on the floor. Challenge 4: Speed 53 TEAM NAME: DATE: Description and drawing of new design: ( Number of Blades: - - Surface Area of each blade: - - - Distance from blade to hub: - - Blade pitch: _ __ Describe how this design is different from your previous design. 54 Windmills Test Results 1. Record the time it took your design to lift 10 nails. 2. Record the distance from table to floor. 3. The speed is the distance divided over time. 4. Try to modify your design to maximize speed and repeat steps 1-3. Data Table Weight lifted Distance lifted Time to lift Speed (distance/time) 5. What was the maximum speed your windmill generated? _ _ __ 6. What was the speed of your design at 10 nails? _ _ __ 7. How will you alter your design to maximize power produced at 10 nails? Challenge 4: Speed 55 Challenge 4 Wrap . Up Questions for Class Discussion • What design elements do the fastest windmills have in common? Compare the shapes of the blades and the arm lengths. 0 What did your team think was the most important element when designing for speed? Did you have an idea about what your rotor would look like? • Think about the rotor you designed for power in Challenge III. Compare it to the one that you just designed for speed. How are they alike? How are they different? Petformance Variables • Shape of blades: Smaller, narrower blades with a shallow pitch result in higher speeds. 0 Number of Blades: Although this can affect performance, students may not notice any change in outcome. It is very difficult to measure this variable on a model of this size. • Radius of the rotor: Students will begin to see the trade-off between torque and speed. To achieve maximum power one must strike a balance between the two. The longer the radius (distance between the center of the blade and the axle), the greater the torque; the shorter the radius, the higher the speed. Competence & Petformance Criteria Each student's performance design should be evaluated to determine if it lifted a sufficient amount of weight. Additionally, students should be evaluated based on the results that they have recorded on their Design Sheets as well as the organization and neatness of their Data Sheets. 56 Windmills rap· Up Activities Use any of the following questions to initiate a student discussion about ideas explored during the design challenges: '. 1. How are the challenges that you encountered here different from what an engineer would have to deal with when designing a windmill in the "real world"? What other factors might the engineer consider? 2. What would you do to explain how a windmill works to a young child? 3. In what other situations would your understanding of torque and power be useful? 4. In what other situations could you use your design skills or your experience building and testing models? 5. Create an analogy comparing windmills to some other device. I The following topics are suggested for student reports, presentations, or journal entries: • Write the history of how you developed your design for one of the challenges. What were the successes and failures? Why did you make your design changes? • Describe how your ideas changed during the design process from one challenge to the next. • Write a creative story featuring a windmill. Use the story to explain the concepts of torque and power. • Now that you have completed the Windmills Module, list any questions you still have about designing windmills. Include ideas for how you might find answers to your questions through research and/or experimentation. Wrap-Up Activities 51 Students obtain significant amounts of data while working on the challenges; some of these data are recorded on the data sheets. These data, as well as other information, can also be used to create a narrative poster, or storyboard. A storyboard is a formal poster which is built during the design challenges. A large sheet of cardboard or poster board can be used. Divide the sheet into several large sections. After each design iteration, ask students to record their designs on the storyboard by sketching their windmill rotor assemblies. The storyboards can be displayed in the classroom as "works in progress." The following information should be included for each frame of the storyboard: • Drawing of the design • Number of blades • Length and width of blades • Angle of blades • Length of arms • Shape of blades • Number of nails lifted • The changes made from the previous design • The changes that you would make to a future design ( 58 Windmills ln·Class sign ents or Ho e ork ssign ents Throughout the module, you may wish to assign additional work for students to complete either in class, while waiting between test trials, or at home. These activities support cross-curricular team teaching and can be assigned through other classes. You can also use the assignments as a re-teaching tool, or as part of student assessment. Students graph the data from the challenges. Students answer questions about what they have learned from reading the History of Wind Power. Students are encouraged to look around them and consider the multitude of uses for devices that spin, turn, and twist, both directly and indirectly. In-Class Assignments or Homework Assignments 59 Students have effectively mastered the concepts presented in this module if they have achieved the following: • Student can use the windmill and other devices to explain the relationships between forces. • Student has an understanding of the principals behind torque, power, and speed. • Student can calculate speed and power. • Student can graph data results. Science Process Skills The student has learned the correct science process skills if the following criteria have been met: • The student was able to define single variables during the design process and create experiments that tested the importance of each single variable. • The student has used the results of one experiment to provide information for the next. • The student has used the data sheets effectively to record information about each design. 60 Windmills Concept Knowledge Evaluate the student's knowledge of concepts by answering the following questions: • How is the student thinking about torque, power, and speed in the context of the windmill design? • Is the student able to explain torque, power, and speed using examples from the various designs? Teachers may wish to have students create final products that encapsulate the results of the challenges in a format other than the storyboard. Portfolios, posters, and reports are suggested products for this purpose, and can be used to assess the student's understanding of the module. Portfolios Students create a portfolio using copies of their data sheets as well as any written assignments. Ask students to include an introduction explaining what they learned during the module. Posters Students design a poster which explains each design challenge using drawings, diagrams, and written explanations. Reports Students select or are assigned a report topic from the list shown in the WrapUp Activities section of this module. Researching and writing reports allows students to analyze a particular challenge or concept more deeply, increasing their understanding of the module topic. Assessment 61 ns rs rksheets Graphing Power Use with student pages 41-42 Graph the following data. Plot power along the vertical axis, and number of nails along the horizontal axis. Number of Nails Power 5 2 6 10 15 20 10 25 16 30 19 20 13 35 40 45 24 50 19 26 I... ~ 15 1--~-+-~-+-~--11--~-t-~-t-~--1~~-t-~-t-~-+~----1 a... 5 10 15 20 25 30 35 40 45 50 Number of Nails Windmills Refer to your graph of the above data to answer the following questions. 1. How many nails can the windmill lift at maximum power? 45 2. What happens to the power as you increase the number of nails? The power increases until it reaches an optimum level, then it decreases. 3. As the windmill lifts more and more nails, what do you think is happening to the speed at which the nails are lifted? Use the graph to explain. The speed increases as the power increases, then decreases as the power decreases. 4. What do you think would happen to the power if you tried to lift 60 nails with this design? Explain why. The power would decrease dramatically. Perhaps the machine would not even be capable of lifting that many nails. The History of ind Power Use with student pages 43-45 Answer the following questions in complete sentences. 1. How did ancient Persian inventors use wind power? Over two thousand years ago ancient inventors in Persia learned to use sails to turn large flat circular stones. These stones would crush and grind grain into flour. 2. What does "mill" mean? "Mill" means "to grind." 3. Why was flour important to the health of poor people in medieval times? Poor people could not afford meat. They could only afford bread made from wheat and porridge from oats. They depended on these grains for their protein. 4. How did the windmill give power to poor people in the 12th century? The poor no longer had to pay for the use of watermills to grind their grain. 5. Describe two reasons that windmills met the need for a new energy source. Windmills ground grain more quickly than could be done by hand and they provided a free source of power for the poor. 6. Describe three uses of wind power that are different from propelling sailing ships and grinding grain into flour. Windmills have been used for draining water from land, for pumping water from deep underground, and for creating electricity. Answers for Worksheets 63 1. How did the Dutch use windmills? What were some design changes that they 8. 9. 10. 11 . 12. 13. 14. 15. 64 used to make the windmills work for them? The Dutch used windmills to drain the sea water from their land. They developed scoopwheels which scooped and raised water from a canal and dumped it into another canal at a higher level. They also developed various other types of scooping devices and pumps (including the use of the Archimedes' screw) to drain water from their land. What replaced wind power in the Netherlands in the 19th century? Because the wind is not predictable or reliable, the Dutch began using steam engines which burned coal to drive their pumps. What was different about the land in the Great Plains that the settlers from the eastern United States had to overcome? The Great Plains are very dry and few surface water sources were available. The majority of water is located in underground aquifers. Describe three ways that windmills were used in the settlement of the western United States. Settlers used windmills to pump water from underground for irrigation, to provide water for steam locomotives, and to bring running water to their homes. Why did Aermotor windmills become the most widely used windmill in the U.S.? The design of the Aermotor was twice as efficient as previous windmill designs. It also was reliable and inexpensive. How are modern wind turbines different from traditional windmills? Modern wind turbines are designed to move at high speeds in order to generate electricity. They are not designed to lift large amounts of weight and therefore do not need large blades that enable greater torque. In order to grind grain and lift water windmills need TORQUE. In order to produce power for electricity windmills need SPEED. What are some of the benefits of using wind power? Wind power is a free, renewable resource and produces no waste byproduct. Windmills are relatively inexpensive to construct and maintain. Windmills ( Devices that Spin, Turn, and Twist Use with student pages 4 7-48 1. Look around your home and list at least three devices that spin, turn, or twist in order to do the job (example: a can opener). Explain how you think each device works. Answers will vary but may include items such as bicycles, washing machines, dryers, fans, etc. 2. If the devices that you listed above were made bigger, would that change how each works? Explain how you think it might for each. Answers will vary depending on the items selected but should include discussions of torque and power. 3. Give an example of a device other than a windmill that uses moving air to get a job done. Explain how you think it works. Answers will vary but may include a discussion of household fans, air conditioners, or heaters. Answers for Worksheets 65 Pre/Posttest Use with student pages 9-12 and 51-54 Answer the following questions in complete sentences. 1. What are some of the ways that we use wind? Wind can be utilized in many ways but those discussed in this module include grinding grain, draining land, pumping water from underground sources, and generating electricity. 2. What is speed? Speed is distance traveled per unit of time (e.g., miles per hour or feet per second). 3. How could you measure the speed of a roller coaster as it is pulled up the first hill? Answers will vary but should include a method of measuring distance traveled in a period of time. More advanced students may express speed as power per unit of force and discuss methods of obtaining the power of the roller coaster and the force required to pull it up the hill to use in the speed calculation. 4. Suppose you wanted to see-saw with a 1,000 pound (450 kg) elephant. Draw a picture of the see-saw that you would use which would allow your weight to lift the elephant. Can you explain why this would work? The student's sketch would show a see-saw with the fulcrum very close to the elephant and very far away from the student. This design would work because the torque is increased as the lever length is increased. 5. a. If you push very hard on a revolving door, what happens? b. Does the direction in which the push is made make any difference? The harder the push, the more quickly the door moves. The door moves in the direction of the applied push. 6. If you were running a contest to judge the best windmill, what categories would you use to award prizes? Give examples. Categories might include ability to lifi the most weight and the ability to li'ft with the greatest power (or the fastest windmill). 1. How could you tell if one windmill is more powerful than another? Set up a timed test where both windmills li'ft the same amount of weight. The windmill to li'ft the weight more quickly has the most power. 8. Name several devices that use spinning, turning, or twisting actions to get the job done. Answers will vary but may include a bicycle wheel, a wrench, a screwdriver, a can opener, a fan, etc. 66 Windmills 9. Which windmill would spin faster in the same wind? B The windmill with the shorter arms (A) will spin faster. 10. What would you change about this windmill to make it lift more weight? The windmill's arms should be lengthened to make it lift more. This change will increase the torque. 11 . Explain what you think the word power means to an engineer. Power is work accomplished during a given period of time. Engineers measure the variables of force, distance, and time to calculate power. Assessment Answers 61 Assessment Use with student pages 55-57 Multiple Choice Use the graph below to answer the following questions. Power Curve 18·~~~-,--,--~-.-~~--r-~~~~~ 16 14 12 ~ ~ 10 8 6 4 2 0-1--~-,.--,--,---,--,---,---,..--r~--,--~-,---i 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Number of Nails Number of Nails 1. The power curve shows that the blade design is the most powerful at _ _ nails. A.12 2. Which statement best describes the power curve in the graph above? C. Power increases to a certain maximum point, then decreases. ( Use the pictures below to answer the following questions. A + . ·. . 3. Which design will spin the fastest with no load? A. Design A will spin the fastest. 4. Design B and Design C can both lift over 25 nails. Which design will have the most power at lifting 10 nails? B. Design B will have more power. 5. Which rotor design will lift the most nails? C. Design C will lift the most nails. 6. Examine Design A. Which of the following modifications will improve the design the most? A. Tilt the blades to an angle of 45 degrees. 68 Windmills 1. Examine Design B. Which of the following modifications will not improve the design? A. Tilt the blades to an angle of 90 degrees. 8. If the distance a cup of nails is raised is 50 cm, and the speed at which 13 nails is raised is 1.5 cm/sec, what is the power of this design? B. 19.5 nails x (cm/sec) ContentlC-oncep.t uestions Use with student pages 59-61 Answer the following questions in complete sentences. 1• You are comparing two windmill designs that have the same blade design and the same pitch. The only difference between the designs is that one has a larger radius (a greater distance from the center of the rotor to the blade ends). Explain which design will lift more weight and why. The one with the larger radius will lift more weight because the torque increases as the radius increases. The greater the torque, the more it will lift. 2. Compare the effects of a force applied to an object and a torque applied to an object. A force exerted on an object will cause the object to accelerate/move in the direction of the force. A torque exerted on an object will cause the object to turn, spin, or twist about an axis of rotation. 3. In what direction should a force be applied to produce maximum torque? If the force is applied parallel to the lever arm, the object will not rotate. To get maximum torque the force must be applied perpendicular to the arm. 4. If the wind blew directly toward both of the windmill blades shown below, would both systems work equally well? Would both move? Explain why or why not. A B In Case A the windmill would not move because the wind would not exert any torque. In other words, no portion of the force would act perpendicular to the lever arm. In Case B the force of the air would act perpendicular to the lever arm and the windmill would turn. 5. Imagine that you are trying to explain torque to a younger student using the windmill design as an example. What would you say? If you could demonstrate torque using the windmill what would you do? Answers will vary but should include a discussion of the radius of the rotor (the length of the windmill arms) and how this affects the way a force makes something turn. Assessment Answers 69 6. In what other situations or devices is torque important? a) wrenches, hammers, screw drivers b) motors, engines c) disk drives, bicycles, sewing machines 1. You and your design partner are having a disagreement. He thinks that the shape of the blades is the most important variable and you think that the most important variable is the distance of the blades from the hub (the radius of the windmill). How could you prove to your partner that you are right? Explain how you would design an experiment to prove that the radius makes a greater difference in how much weight the windmill can lift than the shape of the blades. Answers will vary but must be consistent with the concepts learned in these challenges. pen-Ended uestions Use with student page 65 1. You build a windmill that can lift 37 nails. Your friend builds a windmill that can lift 53 nails. However, when the two of you compare the speed at which each design lifts 10 nails, your windmill turns faster and thus develops more speed at this load. Explain this difference in performance. Answers will vary but should include a discussion of the fact that the friend's windmill uses greater torque which can inhibit its ability to work quickly. 2. Imagine that you are trying to explain torque to a younger student using the windmill design as an example. What would you say? If you could demonstrate torque using the windmill what would you do? Answers will vary but should include a discussion of the radius of the rotor (the length of the windmill arms) and how this affects the way a force makes something turn. 3. List all of the different variables in windmill design. Which do you think are the most important? What evidence do you have from your experience building and testing designs? Answers will vary but should include discussions of blade angle, radius of the rotor, and blade design. 10 Windmills r· \ ~ .. Rubrics ®J@[fU@cr®aCT~@<9J ~M(0crCT~ 1l©rr wo[f1)<9Jmrunaa~~ ~[iu®aa@[fi)~@~ Problem Solving Problem Solving 4. Identifies creative but plausible solutions to the problem under consideration. The solutions address the central difficulties posed by the scenario, constraint or obstacle. 3. Proposes alternative solutions that appear plausible and that address the most important constraints or obstacles. 2. Presents alternative solutions for dealing with the obstacles or constraints, but the solutions do not address the important difficulties. 1. Presents solutions that fail to address the critical parts of the problem. Exploring Ideas 4. Demonstrates an extensive knowledge of information resources and commands a wide range of information-gathering techniques. Demonstrates creativity and resourcefulness in collecting ideas and creating original ideas. 3. Demonstrates a knowledge of basic information resources and commands a useful range of information-gathering techniques. 2. Demonstrates a knowledge of some basic information resources but is not aware of all necessary resources, or has command of a limited set of information-gathering techniques. 1. Demonstrates little familiarity with basic information resources or demonstrates a command of only a few basic information-gathering techniques. Evaluation/Analysis Observing 4. 3. 2. 1. Notices all detail. Notices most detail. Major errors in observations. Many major inaccuracies. Rubrics 71 Choosing a Solution 4. Decides which idea is likely to be the best solution and sets up a way to try and see if it works. 3. Selects what seems to be the best solution and tries it out in a way that will show if it works. 2. Selects what seems to be the best solution but does not try it out in a way to show that it works. 1. Selects what seems to be the best solution but does not try it out. Evaluating 4. Analyzes the information in detail, accurately and insightfully determining whether it is credible and relevant to the task. 3. Accurately determines whether information is credible and relevant to the task. 2. Makes some significant errors when determining whether information is credible and relevant to the task. 1. Makes little or no attempt to determine whether the information is credible and relevant to the task or totally misjudges the credibility and relevance of the information. Critical Thinking 4. Consistently translates issues or situations into well articulated tasks that have clearly defined goals and well articulated thinking processes. When appropriate, anticipates difficulties and develops plans to overcome them. 3. Consistently translates issues and situations into tasks that have clearly defined goals and identifiable thinking processes. 2. Sporadically translates issues and situations into tasks that have clearly defined goals and identifiable thinking processes. 1. Rarely, if ever, translates issues or situations into tasks that have clearly defined goals and identifiable thinking processes. Testing Solutions to Problems 4. Engages in effective, fair, and complete trials of the selected alternative solutions. Trials go beyond those required to solve the problem and show a commitment to an in-depth understanding of the problem. 3. Tests the selected alternatives in trials adequate to determine their utility. 2. Tries out the alternatives, but the trials are incomplete and important elements are omitted or ignored. 1. Does not satisfactorily test the selected alternatives. Experimental Inquiry 4. Demonstrates an understanding that the selection of manipulated and controlled variables determines whether or not an experiment will produce meaningful results. 3. Understands that the selection of manipulated and controlled variables determines whether or not an experiment will produce meaningful results and usually changes only one variable at a time. 12 Windmills 2. Sometimes controls variables and sometimes changes one variable, but does not realize that this has caused a change in another variable that should have been controlled in order to determine which of the two (or both) had caused the new behavior. 1. Ignores the necessity to control variables and thus conclusions made from measurements taken may be invalid. Effectively Interpreting and Synthesizing Information 4. Interprets the information or data gathered for a task in accurate and highly insightful ways. Provides a highly creative and unique synthesis of the information. 3. Accurately interprets information/data gathered for a task and concisely synthesizes it. 2. Makes significant errors in interpreting the information/data gathered from the activity or synthesizes the information imprecisely or awkwardly. 1. Grossly misinterprets the information gathered for the task or fails to synthesize it. Application Predicting/Hypothesizing 4. Makes predictions that reflect insight into the character of what makes a structure work. Uses facts and concepts of structures to make predictions. 3. Makes predictions that that follow from the facts or concepts in structures. 2. Makes predictions which display a misunderstanding of the concepts in structures. 1. Makes predictions which display many misunderstandings of the concepts in structures. Model Building 4. 3. 2. 1. The final The final The final The final process process process process or product goes beyond its intended purpose. or product serves its intended purpose. or product partially serves its intended purpose. or product does not serve its intended purpose. Concept Knowledge 4. Demonstrates deep understanding of the concept, can give a working definition and use formulas correctly. Student is able to apply the concept to a variety of situations. 3. Can give a working definition of the concept. Makes some errors in measurement and use of formulas. Student attempts to apply the concept in other situations. 2. Can give a working definition of the concept. Makes errors in measurement and use of formulas. There is little attempt to apply concept to other situations. 1. Has a vague notion about the concept and does not see how it relates to real situations. Rubrics 73 Reasoning Strategy: Experimental Inquiry 4. Provides an accurate explanation of the phenomenon. The facts, concepts, or principles used for the explanation are appropriate to the phenomenon and accurately applied. The explanation reflects thorough and careful research or understanding. 3. Provides an accurate explanation of the phenomenon. The facts, concepts, or principles used in the explanation are appropriate to the phenomenon and accurately applied with no significant errors. 2. Explains the phenomenon but misapplies or omits some facts, concepts or principles that are important for understanding the phenomenon. 1. Leaves out key facts, concepts, or principles in explaining the phenomenon, or does not use appropriate facts, concepts, or principles to explain the phenomenon. Expressing Ideas Clearly 4. Clearly and effectively communicates the main idea or theme and provides support that contains rich, vivid, and powerful detail. 3. Clearly communicates the main idea or theme and provides suitable support and detail. 2. Communicates important information but not a clear theme or overall structure. 1. Communicates information as isolated pieces in random fashion. Documentation Record keeping 4. Demonstrates mastery over record keeping. Keeps complete, accurate records neatly and well laid out. 3. Keeps complete records with occasional minor inaccuracies. 2. Keeps mostly complete records with occasional major inaccuracies. 1. Keeps incomplete records with major inaccuracies in designs, results and thinking. Collaborative Worker1 Working Toward the Achievement of Group Goals 4. Actively identifies the group's goals and works hard to meet them. 3. Is committed to the group's goals and effectively carries out assigned role and tasks. 2. Is committed to the group's goals and tasks but does not carry out assigned roles and tasks. 1. Is not committed to the group's goals and tasks and does not carry out assigned roles or tasks. 1Adapted from "Assessing Student Outcomes," Pe1formance Assessment Using the Dimensions of Learning Model, Robert J. Marzano, Debra Pickering, Jay McTighe, Association of Supervision and Curriculum Development, Alexandria, VA, 1993. 74 Windmills i · .· Petforming a Variety of Roles Within the Group 4. Effectively performs several roles within the group. 3. Effectively performs two roles within the group. 2. Attempts to perform more than one role within a group but encounters little success with the secondary role. 1. Resists opportunities or requests to perform more than one role within a group. Contributing to Group Maintenance 4. Actively helps the group identify changes needed in how the group operates and works towards carrying out those changes. 3. Helps identify changes needed and works toward carrying out those changes. 2. When prompted, helps to identify changes needed in the group and/or is only minimally involved in carrying out those changes. 1. Does not attempt to identify changes needed to make the group work better and does not work toward making changes. Rubrics 75 Extensions and Connections Demonstrate Bernoulli's Principle Design and construct aerodynamic blades that will produce lift to demonstrate Bernoulli's principle. More on Torque Alter the design of the windmill's arms radically, testing variables such as the number of arms or making arms dramatically longer or shorter. Test each design to determine its effects on torque. Pulleys Devise a pulley system between the axle and the load being lifted (cup of weights, or chain 1) so that you can double or triple the amount of weight the turbine can lift. Power Curves for Electric Motors Build a simple set-up in which an electric motor lifts weights. Record the speed at which it lifts different amounts of nails and plot this data on a graph showing power versus weight. LEGOsTM LEGO™ sets have electric motors and gears that can be added. Try building an electrically powered crane with variable gearing. Test the power of the machine for different gear combinations. Plot the results on a graph. Water Pump Challenge students to use wind power to raise a continuous stream of water from a simulated underground aquifer (an aquarium filled with gravel and water). 1 WARNING: Check with your school administrator before using a chain. These are not allowed in some schools. 76 Windmills History Relate windmill use to the study of westward expansion in the U.S. focusing on how water made available by windmills enabled railroads to open up the west for settlement. Reading Select books for student reading that focus on exploration, settlement, and life in the western parts of the U.S. during the time of westward expansion. English Assign a creative writing project for which students pretend to be moving to the west during the nineteenth century. They should include journal entries and letters to friends and family "back home" to tell them of their trip across the west and of their new home. Math Relate geometry lessons to the use of the inclinometer in measuring and drawing angles. Science Correlate science lessons on the atmosphere with discussions of wind sources, including prevailing winds and temporary, environmentally induced wind patterns. Correlate lessons on the environment with discussions on alternative energy sources including windmills. Art Show students pictures of western ("cowboy") art, emphasizing the landscapes being depicted. For example, call attention to the abundance of open plains, the lack of trees, scarcity of streams. Frederick Remington, Charles Russell, and George Catlin are three western artists of note who painted life during the westward expansion, and whose works should be easy to find in books, etc. If an art museum is accessible, arrange to visit their collections of western art. Extensions and Connections 11 Resources ! \. Windpumps and "American" Style Windmills http://www.geocities.com/yosemite/1001/windpump.htm Aermotor Windmill Company http://www.aermotorwindmill.com Challoner, Jack, Energy (Eyewitness Science Series), Darling Kindersley, New York, NY, 1993. ( Dingus, Anne, "The Windmill," Texas Monthly, v18, Jan. 1990, p. 112. Eldridge, Frank, Wind Machines, Van Nostrand Reinhold Company, New York, NY, 1980. Gipe, Paul, Wind Energy Comes Of Age, John Wiley and Sons, Inc., New York, NY, 1995. Hills, Richard L., Power from Wind: A History of Windmill Technology, Cambridge University Press, Great Britain, 1994. Marzano, Robert J., Debra Pickering, and Jay McTighe, "Assessing Student Outcomes," Performance Assessment Using the Dimensions of Learning Model, Association of Supervision and Curriculum Development, Alexandria, Virginia, 1993. National Science Education Standards, National Academy Press, Washington, D.C., 1996. van Dyck, Sara, "Wind at Work," Sierra, v75, Nov-Dec. 1990, p. 104. Weitzman, David, Windmills, Bridges, and Old Machines, Scribner, New York, NY, 1982. Woelfle, Gretchen, The Wind at Work: An Activity Guide to Windmills, Chicago Review Press, Chicago, IL, 1997. 78 Windmills