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SESSION 2633

Evaluating the Benefits of Hybrid Vehicles Concepts Joshua Talbert, Frank Wicks and Richard Wilk Union College Schenectady, New York, 12308

Abstract

A decade ago it was generally expected that the electric vehicle would represent a clean and practical alternative to gasoline fueled vehicles. The subsequent failure of electric vehicles to be commercialized and used on a significant scale has been a combination of continued improvements of performance and decreased emissions from gasoline vehicles coupled with the fundamental limitations of electric batteries in terms of weight, energy storage capacity and charge and discharge rates.

The public’s expectations for electric vehicles has now been replaced by the promise of high mile per gallon hybrid vehicles which are fueled by downsized gasoline engines which is combined with a battery based electric motor/generator. Electric drive will be used at low speeds, engine drive at moderate power requirement conditions and the combination of engine and electric will be used for high power requirement conditions such as acceleration or passing another vehicle while going up a hill. The gasoline engine will also charge the batteries when extra capacity is available and regenerative braking can recover the kinetic energy of the vehicle while braking or the potential energy of the vehicle while descending hills.

While the benefits are relatively easy to explain qualitatively, the quantification of the benefits of a such a hybrid system, relative to a conventional or downsized gasoline engine, if it does exist is much harder to quantify.

Any engineer should be skeptical of the claimed benefits until understood and demonstrated. Students should be taught the importance of critical thinking coupled with analysis. Accordingly, as a student summer project the authors have tried to critically evaluate the claimed benefits of a hybrid vehicle, along with identifying and evaluating potentially simpler techniques for regenerative braking and for providing extra power for other conditions.

Since the analysis of any potential benefits of a hybrid vehicle requires a model of the vehicle that provides the power requirements as a function of the driving conditions along with the ability to simulate a range of realistic driving patterns. A vehicle was instrumented with an accelerometer for on line computer data acquisition and computer to calculate engine and braking power throughout a driving cycle.

The results of this test and analysis indicate that the potential fuel conservation benefits of the currently commercialized hybrid vehicles are minimal. An alternative that was evaluated

Proceedings of the 2001 American Society for Engineering Education Annual Conference and Exposition Copyright @2001, American Society for Engineering Education

to provide comparable benefits with a simpler system would be a downsized engine with a standby engine for high power requirement conditions. A simpler and possibly cost effective method for regenerative braking could use the existing battery and generator with a variable set point on the voltage regulator with the set point increased for regenerative braking conditions.

1. Background

Until two centuries ago all assisted land transportation was either by horse or other animal or else by slaves and servants transporting the more affluent. Starting in the early 1800s and then rapidly increasing over the century was rail transport powered by the steam engine. It was only about 1900 that powered personal transportation started with roughly equal portions of electric, steam and internal combustion engines. Nicolas Otto had demonstrated a four stroke per cycle internal combustion engine in 1876 that used a flame tube for ignition and required a gaseous fuel.

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Talbert, J., & Wilk, R., & Wicks, F. (2001, June), Evaluating The Benefits Of Hybrid Vehicles Concepts Paper presented at 2001 Annual Conference, Albuquerque, New Mexico. 10.18260/1-2--9236