Partners
CLEAN
AUTOMOTIVE TECHNOLOGY
-S-EPA
United States
Environmental Protection
Agency
The technical organizations that contributed to the
development of the hydraulic hybrid yard
hostler are: U.S. EPA, ARM Terminals, Parker-
Hannifin, Kalmar Industries, FEV, Inc., R. H. Sheppard
Co., Inc., and Webasto.
APM TERMINALS
FEV
SHEPPARD
INNOVATION THAT WORKS
Parker
(CKalmar
Hebasto
Additional support was provided by:
Port Authority of New York & New Jersey,
and The New Jersey Department of
Environmental Protection.
1HE PORT AUTHORITY
OFNY&NJ
EPA does not endorse any specific company or enterprise.
EPA's Clean Automotive Technology Program con-
ducts this innovative research primarily to:
• Achieve ultra-low pollution emissions
• Reduce greenhouse gases
• Increase fuel efficiency
By developing cost-effective technologies, the
Clean Automotive Technology program also en-
courages manufacturers to produce cleaner and
more fuel-efficient vehicles. Fleets owners benefit
by being able to recoup the initial hybrid system
costs through lower operating costs within a few
years.
United States
Environmental Protection
Agency
National Vehicle and Fuel
Emissions Laboratory (NVFEL)
2000 Traverwood Drive
Ann Arbor, Ml 48105
Phone:(734)214-4200
www.epa.gov/otaq/technology
'
S-EPA
United States
Environmental Protection
Agency
EPA-420-F-09-022 | April 2009
Office of Transportation and Air Quality
www.epa.gov
HYDRAULIC HYBRID VEHICLES
THE WORLD'S
MOST-EFFICIENT LOWEST-COST
HYBRIDS
Series Hydraulic Hybrid
Yard Hostler
www.epa.gov/otaq/technology
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HHV-HYDRAULIC HYBRID VEHICLES
HIGHEST EFFICIENCY - LOWEST COST
Using innovative series hydraulic hybrid technology,
EPA and its industry partners have created a highly
efficient and cost-effective hybrid powertrain tech-
nology. This technology is projected to improve the
stop-and-go fuel efficiency of off-road container
tractors known as yard hostlers by 50-60 percent and
reduces C02 greenhouse gas emissions over 30 per-
cent. The unique energy recovery technology used
to stop a hydraulic hybrid vehicle also reduces brake
wear by up to 75 percent, increasing the net operat-
ing savings substantially.
Each high efficiency yard hostler could
save a terminal operator over 1,000
gallons of fuel per year.
Even more remarkable, when this technology is
manufactured in high volume it has the potential to
recoup the hybridization costs from fuel and mainte-
nance savings in three to five years.
The net lifetime fuel savings for this
vehicle's typical 12 year lifespan
could be over $35,000 (assuming fuel
costs of $3/gallon).
Hydraulic Hybrid Vehicles rely on proven inno-
vative technology which is being evaluated in
package delivery vehicles, shuttle buses, re-
fuse trucks, light duty work trucks, and SUVs.
HOW IT WORKS
This innovative technology is simple. The main compo-
nents in a series hydraulic hybrid vehicle are:
• High pressure accumulator — stores energy by
using hydraulic fluid to compress nitrogen gas much as
a battery is used to store energy in a hybrid electric
vehicle.
• Rear drive pump/motor (acting as a motor) —
converts pressurized hydraulic fluid into rotating power
for the wheels.
• Low pressure reservoir —holds the spent fluid after
it has been used by the rear drive pump/motor.
• Rear drive pump/motor (acting as a pump) —
captures braking energy by pumping hydraulic fluid
back into the high pressure accumulator.
• Engine pump/motor (acting as a pump) — creates
additional high pressure fluid needed to drive the vehi-
cle, storing any excess in the high pressure accumulator.
• Hybrid controller — monitors the driver's accelera-
tion and braking, and sends operating commands to
the various hybrid system components.
A typical yard hostler vehicle used to move containers at a sea port terminal.
The three key design features that contribute to im-
proving the fuel efficiency of hydraulic hybrid vehicles
are:
Accumulator
(Mounted
Vertically)
1. Regenerative Braking — To slow or stop the
vehicle, the rotating energy of the wheels is used to
pump fluid from the low pressure reservoir into the
high pressure accumulator. This stored energy is
then used to accelerate the vehicle. Up to 70 per-
cent of the energy normally wasted during braking
is recovered and reused.
2. Engine Shutoff (idle reduction) — Over 40 per-
cent of a yard hostler's working hours are spent
waiting at the port with the engine idling. The vehi-
cle's engine-off power steering and heating systems
allow the engine to be shut off during these waiting
periods. The unique series hybrid design also en-
ables the engine to be automatically turned off
when it is not needed, such as during braking.
These features reduce vehicle emissions, as well as
operating and maintenance costs.
3. Optimum Engine Control — In the full series
hybrid design, there is no conventional transmission
and driveshaft to directly connect the engine to the
wheels. This frees the engine to be operated at its
best efficiency "sweet" spot, achieving optimum
vehicle fuel economy.
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