Energy Production Teacher Guide

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Unit

Energy Production

Subject

Engineering

Grade Level

Grades 3-4

Activity Names

Solar Oven

Wind Generator

Being Prepared

Students need ample time to build their designs, analyze graphs from the sensor devices, and brainstorm how to improve their designs. Allow two class periods per activity, which should provide time for debriefing when the unit is completed. Your students will be able to construct the solar ovens by themselves and most components of the wind generator. Be careful with the hot glue gun. Teachers may want to ask for parent volunteers to help with the wind generator activity. It requires a hot glue gun for two phases of the design. It would also help if the children cut out the pinwheel patterns the day before doing the activity. The small electric motors are inexpensive -- $1.00-$2.00 at science supply stores. You will also need temperature sensors and voltage sensors, along with USB connectors to allow data from the sensors to generate graphs. 

Materials: Wind Generator Activity

  • voltage sensor
  • sensor interface to enable data collection software to run (see activity)
  • small electric motor (see http://www.kelvin.com/, part #850887)
  • hot melt low-temperature glue gun
  • file folder paper for making pinwheel and other wind generator blade designs
  • scissors
  • pushpin
  • eraser, or wooden pencil with an eraser
  • electric fan

Materials: Solar Oven Activity

  • temperature sensor (you'll need a temperature probe, not a surface temperature device.)
  • sensor interface to enable data collection software to run (see activity)
  • three file folders
  • black paper
  • clear plastic from an sealable bag
  • aluminum foil
  • scissors
  • tape
  • insulation: crumpled up newspaper, cloth, packing material, etc.

Suggested Timeline

Two full class periods for experimentation, one full class period for optimizing the design solutions and debriefing.

Thinking About Discovery Questions

This unit engages students in engineering design to learn about transformation of energy in a wind generator and a solar oven. Students will construct a pinwheel wind generator and a solar oven made from common household items. Each activity includes analysis of data created by temperature sensor and voltage sensor devices that automatically generate graphs via a USB software interface. Students will begin to develop understanding of the purpose of insulation in a good oven design and the importance of blade shape in building the best wind generator. The activities will also promote appreciation of the process of engineering design.

The driving question of the Wind Generator activity is: What is the best blade design for collecting energy from the wind? Wind turbines work by using an internal generator to convert the mechanical energy of the spinning turbine shaft into electricity. The construction paper pinwheel is quite different from the wind turbines you see across the country, but either design requires blades that efficiently capture the wind's kinetic energy. When the wind blows, it pushes against the blades of the wind turbine, making them spin. They power a generator to produce electricity (in this activity, the pinwheel will power a small electric motor). When the pinwheel is spinning, the motor will generate a small amount of electricity -- students will be measuring it with a voltage sensor.

The driving question of the Solar Oven activity is:  Can you cook with sunshine? The answer is yes! A solar oven works like a mini-greenhouse, but with a few differences. The light-absorbing surface is enclosed in a tightly-sealed, well-insulated box. Sunlight comes in through a transparent material and is then absorbed and changed into heat by the black surfaces inside the box. The biggest design challenge is finding insulation material that will keep the heat in. Students will work in teams to design an oven, then attach temperature probes to figure out which design does the best job of heating up and retaining the heat.

Misconceptions

Children in this grade band often think there is a "right answer" in designing a structure or system. This activity will help them understand that real engineers work through an iterative process that involves brainstorming, building models, testing their models, comparing their own designs with other people's work, redesigning to make their structure better, and communicating their results to others. Designs that are best in one respect may be inferior in others. For example, one oven design might heat up very quickly but fail to heat evenly, while another design heats slowly but maintains an appropriate cooking temperature. Many of the best inventions in the world were invented through trial and error! And all engineering design depends on a knowledge of science to build a good structure or device.

Students at this age understand that sunlight warms objects. But they often misunderstand that different objects absorb sunlight in different ways. In addition to building the solar oven, it may help for students to compare light absorption in dark and light-colored objects. They also frequently overlook the role of light intensity. If the sun is directly overhead, the sunlight will be more intense and the solar cookers should heat up more quickly. It would be interesting to allow a follow-up for students to analyze differences in the solar cooker efficiencies between morning and afternoon classes. You might anticipate that students will have trouble identifying the forms of energy and how they are transformed in the wind generator and the solar oven. At this age, we don't expect students to have a sophisticated view of energy transformation, but they should understand that the sun provides radiant energy that is transferred by light waves. When light energy from the sun interacts with matter, it can be transformed into thermal energy. At this level, it's best not to get too deep with explanations of heat or thermal energy. Although we don't introduce kinetic and potential energy at this level, students should be able to understand that objects in motion have energy......the faster the motion, the greater the energy the object possesses. The wind generator activity will help them build a foundation to understand that motion energy can be transformed into electrical energy.

Learning Objectives

NGSS

  • Performance Expectations
    • 4-PS3-1. Use evidence to construct an explanation relating the speed of an object to the energy of that object.
    • 4-PS3-2. Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents.
    • 4-PS3-4. Apply scientific ideas to design, test, and refine a device that converts energy from one form to another.
    • 3-5-ETS1-1. Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
    • 3-5-ETS1-2. Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
    • 3-5-ETS1-3. Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
  • Disciplinary Core Ideas
    • Conservation of Energy and Energy Transfer
      • Light also transfers energy from place to place.
      • Energy can also be transferred from place to place by electric currents, which can then be used locally to produce motion, sound, heat, or light. The currents may have been produced to begin with by transforming the energy of motion into electrical energy.
    • Defining and Delimiting Engineering Problems
      • Possible solutions to a problem are limited by available materials and resources (constraints). The success of a designed solution is determined by considering the desired features of a solution (criteria). Different proposals for solutions can be compared on the basis of how well each one meets the specified criteria for success or how well each takes the constraints into account.
    • Definitions of Energy
      • The faster a given object is moving, the more energy it possesses.
      • Energy can be moved from place to place by moving objects or through sound, light, or electric currents.
    • Developing Possible Solutions
      • At whatever stage, communicating with peers about proposed solutions is an important part of the design process, and shared ideas can lead to improved designs.
      • Tests are often designed to identify failure points or difficulties, which suggest the elements of the design that need to be improved.
    • Optimizing the Design Solution
      • Different solutions need to be tested in order to determine which of them best solves the problem, given the criteria and the constraints.
    • Types of Interactions
      • Objects in contact exert forces on each other.
      • Electric, and magnetic forces between a pair of objects do not require that the objects be in contact. The sizes of the forces in each situation depend on the properties of the objects and their distances apart and, for forces between two magnets, on their orientation relative to each other.
  • Practices
    • Analyzing and Interpreting Data
      • Represent data in tables and various graphical displays (bar graphs and pictographs) to reveal patterns that indicate relationships.
    • Asking Questions and Defining Problems
      • Ask questions that can be investigated and predict reasonable outcomes based on patterns such as cause and effect relationships.
    • Constructing Explanations and Designing Solutions
      • Identify the evidence that supports particular points in an explanation.
    • Developing and Using Models
      • Develop models to describe phenomena.
    • Engaging in Argument from Evidence
      • Construct an argument with evidence, data, and/or a model.
    • Planning and Carrying Out Investigations
      • Make observations and/or measurements to produce data to serve as the basis for evidence for an explanation of a phenomenon or test a design solution.
    • Science and Engineering Practices
      • Science investigations use a variety of methods, tools, and techniques.
  • Crosscutting Concepts
    • Energy and Matter
      • Energy can be transferred in various ways and between objects.
    • Interdependence of Science, Engineering, and Technology
      • Knowledge of relevant scientific concepts and research findings is important in engineering.
    • Science is a Human Endeavor
      • Science affects everyday life.
      • Most scientists and engineers work in teams.
    • Structure and Function
      • The shape and stability of structures of natural and designed objects are related to their function(s).

NSES

  • NSES Physical Science - Transfer of energy
    • Energy is a property of many substances. It is associated with heat, light, electricity, mechanical motion, sound, nuclei and the nature of a chemical. Energy is transferred in many ways.
  • NSES Physical Science - Transfer of energy
    • The sun is a major source of energy for changes on the earth's surface. The sun loses energy by emitting light. A tiny fraction of that light reaches the earth and transfers energy from the sun to the earth. The sun's energy arrives as light with a range of wavelengths. These include visible light, infrared, and ultraviolet radiation.

Timeline: 3 Class Periods

Allow one full class period for each experiment, with one day for students to prepare and share reports on their data analysis findings.

Discussion: Setting the Stage

Need-turbinediagram          Need-turbinediagram2

Wind Generator:  What would be a good design for wind generator blades?

Let students brainstorm a few minutes before they use the Drawing Tool in the interactive model. Teachers: The blades in a windmill or wind generator are intended to slow down the speed of the wind. As the wind blows, it pushes against the blades to make them spin. An inclined blade makes it easier to push the air than a perpendicular blade.

Solar Oven:

Explain how you think a solar cooker could help change people's lives.   (Responses will vary. You may want to guide the conversation by talking about the health benefits of cooking food and the convenience of using electric or gas-powered ovens and cooktops in our homes. What if your family couldn't afford electric appliances? What if you live in a part of the world that doesn't have reliable electric power? Why do we need to be sure some foods (like meat) are fully cooked?  

Additional Background

From the National Energy Education Development Project (NEED):  Like old-fashioned windmills, today’s wind turbines use blades to capture the wind’s kinetic energy. Wind turbines work because they slow down the speed of the wind. When the wind blows, it pushes against the blades of the wind turbine, making them spin. They power a generator to produce electricity. Most wind turbines have the same basic parts: blades, shafts, gears, a generator, and a cable. (Some turbines do not have gear boxes.) These parts work together to convert the wind’s energy into electricity:  

  • 1. The wind blows and pushes against the blades on top of the tower, making them spin.
  • 2. The turbine blades are connected to a low-speed drive shaft. When the blades spin, the shaft turns. The shaft is connected to a gear box. The gears in the gear box increase the speed of the spinning motion on a high-speed drive shaft.
  • 3. The high-speed drive shaft is connected to a generator. As the shaft turns inside the generator, it produces electricity.
  • 4. The electricity is sent through cables down the turbine tower to a transmission line. The amount of electricity that a turbine produces depends on its size and the speed of the wind. Wind turbines come in many different sizes. A small turbine may power one home. Large wind turbines can produce enough electricity to power up to 1,000 homes. Large turbines are sometimes grouped together to provide power to the electricity grid. The grid is the network of power lines connected together across the entire country.

Discussion: Formative Questions

Wind Generator

Prediction: If there is more wind, will the pinwheel turn faster? Will it generate more voltage? Explain why you think so.  Students may not yet be able to accurately predict how the voltage sensor will respond with a faster-turning pinwheel. Teachers might want to explain that voltage is a measure of electric force, but otherwise let students create their individual responses.

What was the maximum voltage you were able to generate? (Answers will vary.)

What was the best place to position the pinwheel in front of the fan? (Acceptable responses will indicate that the pinwheel "blades" need to be turned at an angle to the fan.)

How did your propeller compare to the pinwheel in producing a voltage? (Answers will vary, but encourage students to think carefully about why one design was better or worse than the other and be sure they back up their conclusion with data from the voltage sensor readings.)

Solar Oven

Prediction: How warm do you think you can make your solar cooker? Hot enough to warm up a cookie (60 degrees C)? Hot enough to boil water (100 degrees C)? Hot enough to cook an egg (150 degrees C)? Guess what you think the maximum temperature will be. Students should construct predictions without interference.

Describe your graph? What was its shape? What was the maximum temperature of your oven?  (Answers will vary.)

Did your maximum temperature go up or down when you added aluminum foil to the design?  (If done correctly, the temperature should've gone up.)

What type of insulation materials did you use? What happened to the temperature graph after you added the insulation? (Answers will vary. In general, student responses should discuss HOW the temperature was affected. Did it rise higher? Did the temperature sensor show a more stable temperature, or was it erratic? Did the cooker retain its heat longer after you took it out of the sun?)

 

Analysis

              Need-windenergy

                                                                                                            

Wind Generator

1. Describe and draw the design that seemed to generate the most voltage. (Students will use the interactive Drawing Tool to draw and describe their pictures.)

2. Make a list of the features of your propellers that seem to affect the voltage and the features that seem to have no effect. (Answers will vary, but in general, expect students to recognize that the propeller needs to have some slant to be able to capture and push the wind.)

3. How did your propeller performance compare to the propellers of other teams? (Responses will vary.)

4. What is the best blade design for collecting energy from the wind? (Ask students to be prepared to defend their conclusions with scientific data, not just with an opinion.)

 

Solar Oven Activity 

     Nasa-solarcooker2    Nasa-solarcooker3    Nasa-solarcooker5  

Background Information:  Solar ovens come in two basic varieties:  

  • The box type traps heat inside an airtight, insulated container system that provides greater heat retention. The box cooker is popular because it cooks safely at higher temperatures (200-350 degrees) and you can leave it unattended. These are the most widespread solar cookers in use today, with several hundred thousand in India alone. For this activity, children will construct the box type cooker.
  • The reflective type (also called "parabolic cookers") which will cook fastest at the highest temperatures, but require frequent adjustment and expert supervision for safe operation.
  • The panel type includes elements of both the box and curved cookers. These are very simple and inexpensive to build and work best for cooking foods with higher moisture content, which require lower heat and longer cooking time. It will maintain cooking temperatures between 200 and 250 degrees. 

 

1. After conducting the 3 temperature sensing experiments, what would you do next to improve your solar oven? Make a drawing of your best idea for design. (Students will use the interactive Drawing Tool to draw and describe their pictures.)

2. What was the maximum temperature of your oven? Explain what features worked well to increase the temperature. (Responses will vary, especially as students discuss how well their oven performed with addition of insulation materials. In general, a box-type solar cooker will produce a temperature range from approximately 200-250. You might ask students to consider whether the sun was directly overhead. If the class was held in early morning or late afternoon, this would affect the intensity of the sunlight.)

3. Explain what features worked well to increase the temperature. (Anticipated responses would include reference to adding aluminum foil as a light reflector and reasons for choosing particular insulation materials.)

4. Which meals would work best in a solar oven?  (Kids will have fun responding to this question, but may not have enough cooking experience to know. Even a great solar cooker may only get up to about 250 degrees Fahrenheit (121 degrees Celsius). This is hot enough to cook lots of meals, but not all kinds of food. You might want to lead a classroom discussion to get kids brainstorming what sorts of meals can cook slowly for several hours. Ask if their parents have ever cooked slow-roasting meats on a grill or casseroles that they leave in the oven to cook all day. Ask them if you could cook a batch of cookies in their box cookers (probably not). On the other hand, would the cookers work to warm up the cookies if they're already baked? (Yes!)

 

Further Investigation

Choice A:  Design and construct a larger solar oven (large enough for a real cooking pot). Cook a meal, such as rice, oatmeal, or hard-boiled eggs. What were you able to cook, and how long did it take?

This task is a good choice if there is adequate time for the engineering design process in building a second product. You may want to provide information about panel cookers to see if children want to experiment with another design style (see photos above). If they choose to try a panel cooker, make sure to start early in the day because these cookers don't reach as high a temperature as the box cookers. 

Choice B:  Try your solar oven at different times of the day and in different weather. Investigate these questions:  1) Will it still work when there are clouds?  2) Will it still work early or late in the day when the sun is low in the sky?   3. Will it still work if the sun is coming in through a window? 

This task is a good choice if time is limited. Ask students to predict answers to the 3 questions above. After finishing the investigation, responses should fall within this general framework: 1) Yes, the oven will still work, but cooking time will be slowed down. If it's fully cloudy, the cook time will be extended a lot.  2) The cooker will heat up fastest in mid-day when the sun is directly overhead. It heats up slowest in the morning. If it's really hot with no clouds, you need to keep an eye to be sure you don't overcook the food.  3) Generally, trying to use a solar cooker next to a window is not very effective unless you have old windows. Teachers: Newer windows have UV inhibiting materials, which significantly slows the rate of solar cooking.