Transport Partnership
U.S. ENVIRONMENTAL PROTECTION AGENCY
Hybrid Powertra in Technology
A Glance at Clean Freight Strategies
Hybrid vehicles that use two or more distinct power sources to operate can
provide fuel savings in both long-haul combination trucks and stop-and-qo
freight applications as well as cut greenhouse gas emissions. The amount of
savings is highly dependent on the drive cycle.
What is the challenge?
When a truck decelerates or brakes, the kinetic energy of the moving vehicle is typically
lost. This energy loss is particularly large for trucks operating in urban areas, where vehicles
make frequent starts and stops. If the kinetic energy of a braking truck can be captured and
harnessed, the truck can achieve better fuel economy and lower emissions.
What is the solution?
Hybrid powertrain technology is a method to capture this energy and improve fuel econo-
my. Hybrid technology uses two power sources to move the vehicle, a main source and a
secondary source. The secondary power source provides an extra boost to the main power
source (usually an internal combustion engine) when the vehicle needs extra power, such
as when climbing a hill or accelerating to pass. This usually makes it possible to use a main
power source that operates more efficiently and could be downsized. When the main engine
is downsized, other powertrain components, such as the radiator, can be downsized as well.
One of the primary benefits of hybrid powertrain technology is the ability to reclaim a portion
of the energy otherwise lost to braking or deceleration. A variety of options exist to capture
and store this kinetic energy for later use. One option relies on the kinetic energy of the
vehicle to generate electricity, which can be stored in a battery. Another option is to store the
electricity in ultracapacitors, which charge quickly but are costly. Athird option stores energy
as hydraulic pressure. Hydraulic fluid inside a sealed cylinder pushes against a "bladder" of
inert nitrogen gas, which is compressed and thus stores energy. Flywheels have also been
used to store the extra energy.
While the first commercial applications of hybrid powertrain technology have been passen-
ger vehicles, it is actually more efficient to place hybrid technology in heavier vehicles like
trucks. Since a vehicle with greater mass requires more power to stop, more potential energy
can be recaptured during braking or deceleration. Larger vehicles also tend to have more
available space for packaging the hybrid power train components. Heavy-duty trucks typically
I Use hybrid powertrain
technology in a fleet set-
ting.
2 Set up an evalua-
tion process to assess
hybrid power train
technology with differ-
ent fleet drive cycles.
SmartWay Transport | EPA420-F09-035 | www.epa.gov/smartway | 734-214-4767 | smartway_transport@epa.go
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Hybrid Powertrain Technology
Stop & Go
Energy
and
Fuel Savings
Gallons Saved
394 gallons
CO2 Savings
4 Metric tons
Fuel Consump-
tion Reduction
NewMPG
(original MPG 8.54
MPG)
11.39mpg
Fuel Economy
Improvement
Fuel Cost Sav-
$1,497
cost more than passenger vehicles, so the additional cost for the technology can be a smaller
percentage of total vehicle cost.
Savings and benefits
In pick-up and delivery service, it is estimated that truck fuel consumption can be reduced
from 25 to 50 percent using hybrid powertrain technology. Fuel savings depend on the type
of hybrid technology, the amount of regenerative braking energy, and the amount of engine
efficiency improvements .Atypical long-haul combination truck could save about $5,000 in
fuel costs and reduce greenhouse gas emissions by over 13 metric tons per year. Benefits
for a typical stop-and-go truck include fuel savings of about $1,000 and 4 metric tons of
greenhouse gases each year. At least three major parcel delivery companies are exploring
the use of hybrid technology for step vans. Preliminary results from some parcel delivery
companies indicate hybrid trucks expect about a 40 percent improvement in fuel economy.
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SmartWay Transport | EPA420-F09-035 | www.epa.gov/smartway | 734-214-4767 | smartway_transport@epa.go
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