9. Hybrid and Electric Cars

Students will be able to:

1. Compare energy costs and environmental impacts associated with hybrid, electric, and fossil fuel-based vehicles.
2. Determine energy efficiency improvements associated with regenerative braking.
3. Convert kinetic energy into electrical energy (rowing machine hooked to a generator, simple bike light generator; Educational Technologies hand-crank generator; hand-crank emergency radio).
4. Evaluate mineral scarcity for rare earth elements used in batteries and electric motors.

This lecture/lab module is appropriate for undergraduate students with class size up to twenty, limited by the number of electric motors for demonstration. Additional "field" demonstrations of flywheels and hybrid-electric vehicles are described in the "teaching tips" section below. Time required is 1.5 to 3 hours. The only special equipment is "the world's simplest motor," available from Educational Technology for about $10 each. Typically, student pairs build the motors, and success rate among pairs is variable and demonstrates what aspects are needed for "success." The introductory module on Electricity, Work, and Power must be completed prior to this module on hybrid and electric vehicles. The section of the module regarding rare earth elements has been adapted from a module developed by an Integrate 2012 team.

The narrative for the module is provided on the student page.

Structuring Your Classroom Time

1. Quiz & Discussion. This module typically will be delivered after the initial module on Electricity, Work, and Power, but can function as a stand-alone module. Begin the class with a quiz from the prior week's module. Have students come to class with quiz questions, and select five students to read their questions aloud. After each student recites her/his question, pause for the appropriate time for their classmates to write answers. After all five questions have been completed, ask five different students how they answered. This format allows focused discussion on the topic. Students have an opportunity to work through what is right and what is wrong with their understanding. The teacher gets feedback on the effectiveness of teaching materials and teacher delivery—what is clear and what is still muddy. Use the instructor-regulated discussion pedagogy as explained in the course overview for developing discussion of the current module.

Scaffolding Learning

It is important to help the students use what they learned in the first module to build deeper understanding of this module. As the professor, you can help them apply their general knowledge of electricity, work, and power to a consideration of automobile power. Hybrid and Electric Cars considers the historical framework for the development of automobile power, then moves through the technical advancements to improve gasoline mileage per unit of energy expended. The opening quiz reinforces the scaffolding of learning and forces students to revisit the previous module twice, once during their studies when they review for the quiz and formulate the quiz questions, and again when they participate in class discussions.

Metacognition

The flipped-classroom structure advocated for this course facilitates the development of metacognition by the students, directly involving them in the learning process. The use of student-generated questions for quiz and discussion helps students become aware of how they learn and understand the material. This is a big departure from the simple memorizing of terms and concepts that characterized much of their earlier education. Having students think of questions for quiz and discussion will inform their approach to learning in general. Another metacognitive strategy used in the course is requiring the students to apply basic science concepts to understanding a technology, and then requiring them to think about the application of that technology in the real world. The exercise of having students build an electric motor, for example, forces students to understand how the supply of electrical energy from a battery can be used to power a motor to spin a wheel. Students are then asked how a hybrid-electric car can run this process "backward" to store electrical energy in a battery. Students recognize what they know and apply what they know to understanding the latest technological advances such as advanced battery technology. Invariably, questions will be raised about the safety of the newest lithium-ion storage batteries, since the recalled Samsung Galaxy 7 batteries had design flaws that caused them to overheat and catch on fire. Students can address the safety of batteries with higher density and greater storage capacity and consider whether this leads to greater risk.

Systems-Thinking

A major aspect of this course is that students see the various technologies in the context of the global system; this requires systems-thinking. The module on Hybrid and Electric Cars examines energy inputs to the operating systems of cars (fossil fuels, either directly or indirectly) and the output of carbon to the atmosphere. The section on energy storage and release to operate a vehicle (i.e., how long does it take to recharge different battery types, how many miles per charge) reinforces systems thinking about fluxes, reservoirs and residence times. The section on rare earth elements considers mineral scarcity and the environmental system impacts of their extraction and use.

2. Student Presentation. Each class should have one or two PowerPoint presentations by students, given either during the current module or at the beginning of the next module. This activity involves peer instruction. For the Hybrid and Electric Cars module, for example, students could present a case study of the "latest" hybrid/electric vehicles. A cost-benefit analysis of producing an electric car versus a gasoline-powered car could be completed. The latest information on the recycling of rare earth elements from hybrid/electric batteries and motors could be presented.

1. Present a case study of the latest all-electric cars on the US market.
2. Discuss policies put in place in the United States and other countries that encourage consumers to purchase hybrid or all-electric vehicles.
3. Outline what would be needed to complete a cost-benefit analysis of production of an electric car versus a gasoline-powered car.

3. Hands-on laboratory work. The electric motor activity will involve cooperative learning as the students will work in pairs to accomplish the task.

The module includes a lengthy introduction involving the history of automobile power. Students can read this section beforehand and/or it can be reviewed as a preamble to the section on hybrid and electric cars. The hands-on activity of building an electric motor serves to show how electricity drives the process and lets students think about the reverse reaction for electrical generation in a hydrid-electric vehicle.

TPS Exercise: Have students interpret this graph. What are gas fuels? What are liquid fuels? What are solid fuels? What is the solid black line? Does this line represent the concentration of CO₂ in the atmosphere? Exponentially, how many total grams of carbon were emitted by human activities in 2010? The total amount of carbon in the atmosphere is estimated at ~720 x 10¹⁵ g. What percentage of the atmospheric carbon currently is from human activities? How much of the atmospheric burden of carbon was contributed by human activities in 1800? If the annual contribution of carbon to the atmosphere is so small, why do we care?

Question: My Prius gets better gasoline mileage in spring and fall relative to winter and summer. Why the variability?

Think-Pair-Share exercise: Have students build an electric motor (ordered from Educational Technologies, cost is around $10 each). This will demonstrate how electrical energy from a D-cell battery can be used to power a motor. The motor works because the copper coil is a conduit for electricity from the battery. The flow of electricity creates a magnetic field with enough force to repel the opposing magnetic field from the magnet, thereby turning the coil all the way around to where the magnetic fields are opposing, and the process repeats itself. Build and experiment with the motor. This motor uses electricity from a battery to power the spinning of the coils. How would braking in a Prius operate to generate electricity for battery storage?

Wind-up generators, bike lights, radios, etc., all use this technology to generate power. Campus recreation centers or kinesiology programs may have a rowing machine flywheel hooked up to generate electricity—a possible demonstration field trip. Finally, as hybrid-electric vehicles become more prevalent on the road, perhaps a faculty member or a student drives one that could be used for demonstration.

Class Discussion: Some common uses, supply, and demand for five of the rare earth elements are shown in the above table. Have students think about the ways in which supply-demand imbalances might impact the future of clean energy initiatives, and brainstorm some feasible ways to address these issues.

The assessment methods for this module can be found on the course assessment page. It is essentially what was provided in the web space for the course overview. Below are selected Pre/Post Test questions. One approach is to have the students take the pretest for all the modules at the beginning of the class, and then to administer it again at the end of the class to document advancement in learning.

Pre-Post test questions:

• Download
  Pre/Post Test Questions and Answers for Module 9: Hybrid and Electric Cars -- private instructor-only file
  Hide
  Pre/Post Test Questions and Answers for Module 9: Hybrid and Electric Cars

  
  This file is only accessible to verified educators. If you are a teacher or faculty member and would like access to this file please enter your email address to be verified as belonging to an educator.

  Email Adress Submit

Early Electric Car Charging article by Scott Wilson

Divya, K.C. and J. Ostergaard. 2009. "Battery energy storage technology for power systems—an overview." Electric Power Systems Research 79:511-20.

Scrosati, B. and J. Garche. 2009. "Lithium batteries: status, prospects and future." Journal of Power Sources 195:2419-30.