The Chevy Volt is an interesting car. On electric power, it runs quite well. While not as quick at a drag strip as a contemporary sedan, its low engine noise level allows it to produce acceleration that is perceived to be comparable to its competitors.
A serial hybrid, like the Volt, should use its gasoline engine to charge the battery. That way the gasoline engine can always run and its most efficient mode while being tuned for very quiet and smooth operation. For some reason GM engineers chose not to do that. They undoubtedly had good reasons, although those reasons I am not publicly known at this time.
What General Motors engineers did was use the gasoline motor to drive the electric motor directly, only charging the batteries when they are plugged in. As a result the rather heavy Chevy Volt is effectively powered by a noisy 1.4 L engine when the batteries are depleted. After 40 miles of operation car will become rather sluggish and may struggle to keep up with highway traffic and ascend steeper hills.
How efficient is the electrical fault system? It has a 16 kilowatt-hour battery of which GM uses 8 kilowatt-hours only running the battery from 30 to 80% of capacity in order to extend its life. GM claims a 40 mile range from those 8 kilowatt-hours. The battery itself weighs 300 pounds to store those a kilowatt hours. And it takes 3 to 8 hours to renew those a kilowatt hours.
For comparison it would take slightly less than a gallon of gasoline for a conventional internal combustion engine to produce 8kilowatt-hour of output. A gallon of gasoline has about 36 kilowatt-hour of energy and the internal combustion engine will typically be between 25% and 35% efficient. That gallon of gasoline weighs 6 pounds and takes less than 10 seconds to renew during a fill-up.
The Volt achieves its 40 mile range with 8 kilowatt-hour are having a car with very low aerodynamic resistance, very low rolling resistance and mechanical friction, and recapturing some of the energy during braking. However all of those features will be available for conventional car.
The same range is actually available for conventionally powered cars when I worked with “mini hybrid” technology. That technology does not power the car and only requires a battery of about 50 pounds. However, it recaptures some energy through regenerative braking and turns off the engine at idle. A diesel Mini Cooper with that technology achieves 60 miles per gallon on the European fuel efficiency cycle.
Does the Volt only cost 12¢ per kilowatt hour used to operate? If there were only 100 or thousand Volts in existence that would probably be the case. However, if utility generated electric power is going to propel the Volts any large number of them would require significant new investment in energy production. That in turn would require an increase in rates to finance the capital expense. Gasoline can generate power at about 30¢ per kilowatt-hours.
Rather than show hybrid power, especially plug-in hybrid power, as the wave of the future the Chevy Volt highlights how impractical this technology is and how efficient petroleum is for transportation vehicles that have to carry their own energy supplies.
