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Technology |
Plug-in Hybrid Electric Vehicles |
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Common Engine Sizes—Conventional Vehicles vs. HEVs How Hybrid Vehicles Work
Hybrid vehicles (HEVs) work
through a combination of an internal combustion engine, a bank of batteries,
and an electric motor. This
combination varies from “mild hybrids,” which simply reduce the
engine size and boost acceleration with an electric motor—to a set up
wherein the engine runs only to produce electricity, that then runs an
electric motor. Currently, most HEVs
are somewhere between the two extremes—the vehicle can be driven either
with the engine (almost exclusively), the electric motor solely, or both the
engine and electric motor simultaneously providing power. Common
Engine Sizes—Conventional Vehicles vs. HEVs
Conventional Vehicles (CVs)
generally have larger engines than HEVs.
However, the trend is to keep HEVs similar to CVs in both look and
feel while improving fuel economy—this is best seen in the Honda
Accord. The Honda Accord HEV actually
outperforms its CV counterpart, yet maintains a significant fuel economy advantage. Below is a chart of currently available
vehicles and their engine sizes—this information was gathered from the
manufacturers’ websites. Common Questions
What is the difference between a
PHEV and a HEV? What is the difference between a
PHEV and an EV? Does a PHEV have to be plugged
in? Do I literally have to plug the
vehicle in? What’s the Difference
between a Series and Parallel HEV?. What is “Regenerative
Braking”? What’s the Advantage of a
PHEV? What’s the advantage of a
PHEV to the environment? Where can I go for more
information? How can you contact the author
of this page? PHEV is an abbreviation for Plug-in
Hybrid Electric Vehicle. These
vehicles, like other Hybrid Electric Vehicles (HEVs) have an onboard internal
combustion engine that charges batteries or otherwise provides electricity to
an electric motor. This electric motor
either assists the internal combustion engine (in parallel HEVs) or is the
sole mechanical link to the wheels (in series HEVs). What makes a PHEV different from a HEV is
its ability to charge the batteries by plugging the vehicle in. This feature has the advantage of allowing
the vehicle to run for some distance without running the internal combustion
engine at all—thus reducing the use of petroleum. Below is a schematic of how a typical PHEV
might work. What is the difference between a PHEV and a HEV? The difference between a PHEV and
HEV is that—a PHEV has all the abilities of a HEV but also can charge
its batteries by plugging in to grid-provided electricity. The primary advantage of this—is the
effective increase in fuel efficiency. What is the difference between a PHEV and a BEV? A BEV (battery electric vehicle)
must be plugged in to obtain energy to drive the vehicle and has a range
limited by the battery pack. A PHEV
may either run off the battery or off the engine, and so, the PHEV does not “have
to” be plugged in and the range is unlimited per periodic refilling of
the gasoline/fuel tank. Does a PHEV have to be plugged in? No.
Unlike electric vehicles (EVs) that have to be plugged in to charge
periodically, if a PHEV is not plugged in it will function just as a HEV
would. In fact, some HEVs have the
ability to provide electricity—for example, at a construction site or
in case of a blackout—anytime when electricity is otherwise
unavailable. Because PHEVs have all
the HEV technology included in their design, PHEVs could certainly be used
for this purpose as well. Do I literally have to plug the vehicle in? Certainly, this depends on the
manufacturer of the vehicle. There is
no reason a vehicle could not “just be plugged in.” However, for convenience many manufacturers
may decide to equip the vehicle in such a way that it automatically
“docks” when you park it in its normal (usually overnight)
spot. If this were the case you may
not have actually do anything except park it for the vehicle to charge. What is the Difference between a Series and Parallel HEV? A “parallel HEV”
maintains a mechanical linkage between the internal combustion engine and the
wheels, the electric motor supports the engine (which is still the primary
method of propulsion). Thus, the
internal combustion engine and the electric motor run “in
parallel.” If a vehicle runs
only as a parallel HEV, the engine must run all of the time. Below is a schematic for a parallel HEV. A “series HEV”
completely severs the mechanical link between the engine and the wheels. Rather, the engine serves only to produce
electricity that either is used directly to power the electric motor or
charges the batteries when the use of all the electrical production capacity
of the engine is not needed to power the motor directly. Below is a schematic for a series HEV. Some vehicles, such as the Ford
Escape Hybrid, combine these ideas. For
limited distances and under 25 mph, the Escape can run without the engine
running. However, for extended
distances and when going over 25 mph the engine provides power directly and
must run. This term
is relatively imprecise—but it usually describes a vehicle that still
uses an internal combustion engine as the primary method of propelling a
vehicle and includes some technology that provides a significant enhancement
in fuel economy (over a conventional vehicle). One example of this is the Chevy
Silverado. What
is “Regenerative Braking”? Regenerative braking is simply a
method of recovering energy while a vehicle is slowing down—energy that
would otherwise be converted to waste heat (friction between the brake pad
and rotor). In passenger vehicles,
this energy is converted to electricity to recharge batteries. This is possible because the electric motor
becomes a generator when run in reverse.
Similar technology has been used for many years on the diesel-electric
locomotives. What is the Advantage of a PHEV? Most people drive relatively short
distances on a daily basis. By running
a car off grid electricity you can double, triple, and beyond—the
effective gas-mileage of a vehicle. I
would also refer you to our advantages page (link). What is the advantage of a PHEV to the environment? Many people have criticized
vehicles that are plugged in because “they are using electricity
produced by coal.” The
implication being, we are just shifting pollution from the tailpipe to the
power plant. This relies on a critical
misunderstanding of PHEVs though. Due
to principle called “peak-load shifting” PHEVs, if charged at
night, will actually encourage more efficient electricity production. I encourage you to explore this topic further
by looking at our Advantages
Website or the websites listed here. Where can I go for more information? I encourage you to go to our links page—there
you can find links to manufacturers, advocacy and informational sites here. How can you contact the author of this page? You can the author of this page, Andrew Cobb. Or, you may contact my professor, Dr. Galen
Suppes. Also, feel free
to visit Andrew’s
newly founded blog about e-technologies. Valuable Links
General
Information Websites
Automotive Manufacturer Websites
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