v\SmartWay
   Transport Partnership
    U.S. ENVIRONMENTAL PROTECTION AGENCY
                                      A Glance  at
                   Clean Freight Strategies
ybrid  Powertrain  Technology
 Hybrid vehicles can provide roughly $2,000 in fuel savings and cut greenhouse gas emissions by up to
 12 metric tons per year, when used in stop-and-go freight applications like parcel delivery.
 What is the challenge?
 Energy losses during deceleration and braking can
 be significant, especially in vehicles that frequently
 stop or slow down, like trucks operating in urban
 areas. In addition, many freight trucks operate under
 conditions that  require  a wide range  of engine
 performance. Engines designed to perform across a
 wide range of operating conditions tend to be less
 efficient and larger than engines designed to work
 within a less demanding range. Engine size generally
 affects  the  size  and  weight  of  other  vehicle
 components, such as the radiator. Taken together,
 the energy losses due to braking, and the extra fuel
 consumed by less-efficient  engines and  heavier
 vehicle components can account for 30 percent or
 more of a vehicle's total fuel use.


 What is the solution?
 Hybrid  powertrain technology makes it  possible to
 optimize engine size and efficiency, and capture and
 harness the energy lost during braking.  Hybrid
 vehicles have two propulsion power sources. The
 main power source is usually a conventional internal
 combustion engine.  Energy recaptured from braking
 is converted and stored until it can be reused by the
 second power source.  The second power source
 generates extra power  to  supply  "boost"  to  the
 vehicle when needed - for example, to climb a hill or
 accelerate to pass. Because the main  engine no
 longer  has to  handle  the  full  range of  power
 demands, it can be optimized to operate within its
 most   efficient  performance  range.  Engine
 optimization generally allows the engine and related
 components to be downsized as well.

 There are a variety of hybrid powertrain  designs. In
 one design, the second power source is an electric
 motor/generator, and the recaptured energy is stored
 in a battery. However, batteries are generally heavy
 and slow to charge. A variant of this design stores
 the energy in ultracapacitors, which are lighter and
 charge quickly, but are costly. A third design 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. Hydraulic systems can charge and discharge
 energy quickly, and may use a pump motor/generator
 as the second power source. Other hybrid designs
 use flywheels to store energy.
             Although the first commercial applications of hybrid
             powertrain technology  have  been in  passenger
             vehicles, it is more efficient to put hybrid technology
             on heavier vehicles like trucks. This is because a
             vehicle with greater mass requires more power to
             stop it, which represents more potential energy that
             can be recaptured during braking or deceleration.
             Larger vehicles tend to have more available space
             for packaging the hybrid powertrain components.
             Heavy-duty trucks typically cost more than passenger
             vehicles, so the additional cost for the technology is
             a smaller percent of total vehicle cost.


             The  results  are  in  ...
             In pick-up and delivery service, truck fuel economy
             can be improved from 30 to 50 percent using hybrid
             powertrain technology, depending upon the type of
             technology and the amount of energy that can be
             captured  from braking  and  deceleration  and then
             reused. A typical step van could save as much as
             $1,200 in  fuel  costs  and  reduce  greenhouse
             emissions by  more than 7  metric tons per year.
             Benefits for a typical  enclosed delivery van truck
             would be greater- at least $1,900 in fuel savings and
             12 metric tons of greenhouse emissions per year.


             Next steps
             Fleets that operate primarily in urban areas or in
             stop-and-go  applications should  consider  using
             hybrid vehicles. Transit bus, garbage truck, parcel
             delivery truck, airport parking shuttle van, and utility
             truck fleets could all potentially save fuel by using
             hybrid technology. Companies interested in learning
             more about hybrid technology and  its potential to
             improve the fuel economy of their fleets may visit the
             Internet sites of the Environmental Protection Agency
             (www.epa.gov/otaq/technology.htm)  and  the
             Department of Energy (www.ott.doe.gov). Numerous
             other web sites provide information about various
             public  and private organizations that promote and
             develop hybrid truck technology. Trucking companies
             can also learn from the experience of others in the
             freight industry. For example,  at least two major
             parcel  delivery companies are exploring the use of
             hybrid technology for step vans in commercial fleets.
             In May 2003, FedEx Express publicly announced it
             would test twenty hybrid electric trucks for potential
             use in its pick up and delivery fleet.
!. Environmental Protection Agency ^ Office of Transportation 
        February 2004. EPA420-F-03-025. ^ For more information,, visit: www.epa.gov/smartway

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