LESSON 3 — Driving in Luxury
Class Discussion:
You will discover the tradeoffs between cost, safety, and fuel efficiency. In the second portion of this activity, you will use real data to calculate how much extra fuel is used by car electronics such as stereos, GPS devices, and DVD players.
In previous lessons, driving behavior and physical principles were discussed as reasons for differing fuel efficiency among vehicles. In this lesson, students will explore how the desire for luxury, comfort, and safety can lead to less efficient or more expensive vehicles. The safety of a vehicle is linked to its design, which includes the materials used to make the vehicle. Some materials, such as steel, are extremely strong but relatively heavy. Adding more steel supports increases the safety of the vehicle but also increases the mass. Other materials such as aluminum are just as strong, but lighter and more expensive. Standardized national safety codes often mean that the choice is between higher cost or lower fuel efficiency, not lower fuel efficiency and higher safety.
People make other decisions that can contribute to reduced fuel economy. Some people pay more for comfortable vehicles, which often have motors to move various parts within the vehicle. These motors can add bulk to the vehicle. People may also have electronic components installed in the vehicle that consume power. To power these electronics, a gasoline‐powered motor turns a belt. This motion is converted into electricity in a device called an alternator. When electrical devices such as a heated seat or a video screen are used, the motor has to work harder to supply electricity to the car. This in turn uses more gasoline and releases more emissions.
As a reminder, at the end of this module, you will be asked to create an action plan for reducing greenhouse gas emissions produced by transportation usage in their community. The final project will be produced within your learning teams.
LESSON OBJECTIVES
By the end of this lesson, students should be able to:
Explain why creating safer vehicles can decrease fuel efficiency and/or increase costs.
Describe the effect of automotive electronics on fuel efficiency.
Lesson Essential Questions:
1. How do safety and fuel efficiency affect vehicle costs?
2. How does the use of electrical components affect fuel economy?
3. What are the factors that cause people to make choices about vehicles as far as safety, comfort and efficiency?
Key Vocabulary (appropriate for a word wall):
Alternator, BTU (British thermal unit), electrical component
Class Discussion:
Ask students to review some driver behaviors as well as some design features they have learned about that affect fuel efficiency. If you had them complete the assessment (Evaluate) in Lesson 2, this is a good time to discuss those questions. Also, let us consider the following information from the following website:
http://www.fueleconomy.gov/feg/atv.shtml – Energy Requirements
In this lesson you will learn about two other factors that can affect vehicle efficiency and vehicle emissions: safety and luxury. They will also consider how people make choices about these two factors in selecting a vehicle.
Let's start with a demonstration: an aluminum soda can, a plastic water bottle (with the top cut off), a steel soup can, and a foam cup. I will be stacking textbooks (or other uniform weights) on top of the containers. Can you predict which container will be able to withstand the most force without collapsing and to record their predictions in their notebooks.
What we will find, it that the demonstration should show that the foam crumples easily, while the plastic takes several books, and the cans may not fail at all.
Let's take a look at some videos that give us insight to safety considerations and related costs when designing vehicles:
Safety consequences of vehicle size and weight
Electronic stability control (ESC) — learn about ESC and how it works
Student Activity 10:
After reviewing the aforementioned vidoes, get together with your teams to discuss the impact of safety and luxury on fuel efficiency. Be sure to enter your conclusions into your Engineering Journals.
Class Discussion:
It is important to remember that fuel‐efficient vehicles can be just as safe as less efficient vehicles. This is frequently achieved by employing lighter, more expensive materials like carbon fiber or aluminum. Engineers also continue to work to improve vehicle design so that the same amount of material can provide a safer vehicle.
Student Activity11:
I want you to think about the electrical appliances they use in their homes, including televisions, computers, and air conditioners and where the power for those appliances comes from.
Additionally, I want you to think about electrical devices that are found in a personal vehicle to include air conditioners, lights, radios, and even GPS devices and DVD players. Where does the electricity to power those devices comes from? How's does an alternator convert energy into electricity and than store a battery.
Below is a list of the power needs for several automotive electrical devices. use the conversion from gasoline to electricity (see below) to determine how much gasoline is needed to power each for an hour. The compressor for the air conditioner is powered directly by the engine, instead of by the alternator.
Note: Use the formula G = E/18,000 to find the number of gallons that would be used to run the devices above for one hour. G is the number of gallons, and E is the power in watts needed to run each device.
One gallon of gasoline can supply 36,000 watts of power per hour, of which about 50% can be converted to electricity by the alternator, for a total of about 18,000 watts of electricity per hour per gallon of gasoline. Let's look at this: 18,000 watts per hour per gallon of gasoline.
I want you to use this conversion to calculate what percentage of the gasoline in the vehicle above is being used by the electronics. Then I want you to use the current cost of gasoline to calculate the cost per hour to use all these electronic devices at once. Be sure to anotate your calculations to your Engineering Notebooks as data that you can use for your upcoming project.
You can use information on Energy Requirements from the FuelEconomy.gov site to discuss how their findings agree with the information from the Department of Energy.
Student Activity 12:
Summarize the trade‐offs in fuel efficiency when luxury devices or safety features are provided in automobiles and write this summary in your Engineering Notebooks..
Write a paragraph in your Engineering Journals, proposing ways that fuel‐efficient cars can also be safe and still appeal to consumers.
Class Discussion:
As a result of the activities we engaged in today, we should see that there is a trade‐off between fuel efficiency and cost due to safety regulations, and that excessive electronics waste fuel. Hopefully, we learned that human desires for both safety and luxury can lead to decreased fuel economy.
In Lesson 4, we will see how choices in transportation, including mass transit, can be used to reduce the amount of greenhouse gases.
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