##
* *Reflection: Problem-based Approaches
Designing a Wind Turbine (Part 3) - Section 3: Explaining the Designs

Constraint is defined as a limitation or a restriction. In solving design problems common constraints include time, cost, and materials. Students may consider time as a constraint if their design is complex and difficult to build. Some teachers add a cost constraint by "charging" more for the blade material and the number of blades the students want to build. The materials are a constraint because as teachers, we are limited to the materials at hand. In their research students have reported the use of carbon fibers. Without the budget for such expensive materials, we are all constrained by balsa wood and plastic although I have had students a use tag board.

In my student led classroom I ask the students to determine the criteria for success. They have conducted the research and through my assessments I am confident they know what they need to do. Typically students will use the following criteria:

1. Curved blade (Bernoulli's Principle) Students will say that it has to work. I ask,"Define what it needs to work." I have also had students use the word "functional". I ask for the science behind the functionality.

2. Blade complexity: time to create a prototype to test.

3. Blade size: this is also a constraint because we are constrained by the material.

The importance of the criteria is two-fold. I can increase rigor by adding criteria. I might say, "It must be 10" long and 3" in wide. Student must take additional measuring steps and it makes developing different designs more challenging.

The criteria is also important for the grading rubric. In my student led class, I ask the students, "How should I grade this activity?" We develop the rubric together. This has powerful implications because the students develop the proficient criteria under my supervision.

*Criteria vs. Constraint*

*Problem-based Approaches: Criteria vs. Constraint*

# Designing a Wind Turbine (Part 3)

Lesson 3 of 7

## Objective: SWBAT use scientific knowledge to explain several wind turbine blades ideas.

#### Preface

*3 min*

This section is all about finding the best design solution to test. In Part 2, students have started their preliminary designs and have conducted research. In Part 3 my strategies change from getting information to using information to develop ideas.

The last section, Communicating the Design integrates technology. I use the program Autodesk Inventor Pro and ask students to create a 3D image of their design.

The steps of the design process are going to be used as students gather data, draw ideas, build the airfoils and then test their designs. Refer to my lessons, I Have to Teach Engineering? and Dream Invention.

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#### Design Ideas

*15 min*

The Exploration starts with the presentation of the Design Problem, *"How can we design a wind turbine that will generate the greatest amount of energy?"* I have conducted my lesson Exploring Bernoulli's Principle and students are armed with a better understanding of wind turbines. In addition, they have written a design defense. Students are ready to look over their preliminary design from Part 2. This time students brainstorm design ideas by drawing different wind blades designs.

One of the engineering practices is to evaluate design solutions to determine the best solution. To help student develop the best idea, I use a graphic organizer called a Decision Matrix to quantify solutions. Using their own designs, students quantify their criteria and the designs using the decision matrix. I ask them to complete the criteria for an effective design by asking students what criteria are necessary for an effective wind turbine blade.

In the movie below, I explain the decision matrix and then I ask a group to explain how they have rated the designs.

In the Decision Matrix- Student Samples, the students write size, curve, and defense of the design as their criteria. In the sample it is clear that quantifying a design helps students determine the best design solution.

#### Resources

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#### Explaining the Designs

*30 min*

After they have their three designs, my strategy is W*rite to Learn*. I ask students to write two to three sentences about why each design is a good one. They use the information they learned from their research as well as the Decision Matrix. In the movie a student explains why the attributes of his design.

I explain that they can change the design if they think it will make it better. Students are using science content to describe three different designs. This can be difficult because students must use their analysis skills and writing skills to differentiate among different designs. I use the strategy Social Learning for the students that need help. Students are allowed to go to others in the class to see designs that may be unlike theirs. They still have to explain the design but having a visual reference helps to scaffold learning.

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#### Communicating the Design

*30 min*

Students now must determine which of the three designs they want to build. The first step is a drawing of the model on graph paper with dimensions. I explain the materials have a length of 13 inches long and 3.5 inches wide and they need to use those dimensions.

My next strategy is incorporating technology. I integrate technology by asking students to design using a program called Autodesk Inventor Pro. Students go to the computer and make a 3D drawing of their wind turbine blade. They print their designs and show them to me.

After they make the 3D drawing, students must defend their design. Using a 3-5 sentence paragraph, students explain why this design is the best solution. The Decision Matrix from Part 3 can be used and the students will use their research from Part 2. Students must use science vocabulary. I use a rubric as summative assessment.My strategy is to use the research they completed in Part 2 to defend their designs.

I then look over the designs and I use a strategy called Authentic Grouping. I group students according to the similarities of their designs. I have had student groups between 2-4 people. Students groups work together to discuss the attributes of the designs. Don't be surprised (or concerned) if you have a few outliers - students whose designs are different from everyone else. I share a strategy for this in my reflection.

Many of the designs look the same but there are frequently subtle differences. I explain, *"You can choose one person's design and decide to build and test it. You can also take features from more than one design and redraw it to test it. Finally you can decide you don't like any of the ideas and you can work together to make a new design."* If the students decide to redraw a new design, for pacing purposes I allow them to draw them in the notebooks.

Once the students all have the designs in 3D models or drawn in a notebook, the next job is to determine how many wind blades they want to create and test. Students go back to their research questions and determine the number of blades they want to test.

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- UNIT 1: Exploring Engineers and the Design Process
- UNIT 2: Generating Energy
- UNIT 3: Energy Sources
- UNIT 4: Measuring Energy
- UNIT 5: Exploring Non-Renewable Energy Sources
- UNIT 6: Designing for the Future: Eco Friendly Building
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- UNIT 8: Designing for the Future: Nuclear Waste Facility
- UNIT 9: Designing for the Future: Designing a Solar Car

- LESSON 1: Designing a Wind Turbine (Part 1)
- LESSON 2: Designing a Wind Turbine (Part 2)
- LESSON 3: Designing a Wind Turbine (Part 3)
- LESSON 4: Designing A Wind Turbine (Part 4)
- LESSON 5: Exploring Bernoulli's Principle
- LESSON 6: Using Scientific Formulas
- LESSON 7: Using Autodesk Inventor Pro