9. Hybrid and Electric Cars
Students will be able to:
- Compare energy costs and environmental impacts associated with hybrid, electric, and fossil fuel-based vehicles.
- Determine energy efficiency improvements associated with regenerative braking.
- 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).
- Evaluate mineral scarcity for rare earth elements used in batteries and electric motors.
Context for Use
Description and Teaching Materials
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.
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.
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.
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.
- Present a case study of the latest all-electric cars on the US market.
- Discuss policies put in place in the United States and other countries that encourage consumers to purchase hybrid or all-electric vehicles.
- 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.
Teaching Notes and Tips
Question: My Prius gets better gasoline mileage in spring and fall relative to winter and summer. Why the variability?
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:
References and Resources
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.