Hybrid vehicles normally use some
sort of combustion engine to run an auxiliary power unit. Today, fuel cell vehicles fall
under the hybrid category because they need an energy storage system for peak power
demands. But over the long term, fuel cell vehicles will probably emerge as their own
category of power system.
The large photo in this slide shows an early charge-depleting hybrid
developed in 1980 at my former design firm, Quincy-Lynn Enterprises. A charge-depleting
hybrid is essentially a battery-electric car with an on-board generator for extending the
range. This car would run about 65 miles on battery power alone, or a little more than 100
miles with the APU turned on. But charge-depleting hybrids are considered pretty much
outmoded today.
Todays combustion hybrids are like the Toyota Prius and the Honda Insight. They
are charge-sustaining hybrids. That means that the batteries never run down, and range is
the same as that of any conventional car. You drive until the liquid fuel runs out, then
pull into a service station for more fuel. But the charge-sustaining hybrid sacrifices
fuel economy for its range benefits. The charge-depleting hybrid in the photo achieved
about 100 mpg, and the Prius and Insight both get about 60 mpg. But combustion hybrids are
envisioned today as transition vehicles that will ultimately give way to fuel cell
vehicles.
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