The hybrid automobile is a strikingly new automobile technology with a number of new technological features that dramatically improve energy efficiency. This paper will briefly describe how hybrid automobiles work; what are these new technological features; why the Toyota Prius hybrid internal combustion engine operates on the Atkinson cycle instead of the Otto cycle; and what are the advantages and disadvantages of the hybrid automobile. This is a follow-up to my two previous papers on the physics of automobile engines.1,2
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For more details about the operation of the power split device, see http://www.howstuffworks.com/hybrid-car5.htm or C.W. Ayers, J.S. Hsu, L.D. Marino, C.W. Miller, G.W. Ott, Jr., and C.B. Oland, “Evaluation of 2004 Toyota Prius Hybrid Electric Drive System Interim Report,” Oak Ridge National Laboratory, ONLR/TM-2004/247.
4.
For more details on the operation of the Prius, see http://www.toyota.com/vehicles/2006/prius/key_features/hydrid_syn_drive.html or http://en.wikipedia.org/wiki/Toyota_Prius. For a more general discussion of hybrid and plug-in hybrid electric automobiles, see
Joseph J.
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See http://www.keveney.com/Atkinson.html for more information and a video on the Atkinson cycle.
6.
This is not a perfect comparison, since both the weights and drag coefficients of the Prius and Echo are different (1314 kg and 0.26 for the Prius versus 930 kg and about 0.28 for the Echo).
7.
The economics of purchasing a hybrid automobile depend upon the cost of the car, the cost of money, the various federal and state tax incentives, the number of miles driven, the cost of gasoline, and the life of the battery pack. Currently, even with the price of gasoline around $4 a gallon, the economics for the vast majority of purchasers are not attractive.
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© 2008 American Association of Physics Teachers.
2008
American Association of Physics Teachers
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