-&ER&
Partners
SEPA
United States
Environmental Protection
Agency
The technical organizations that contributed to the
development of the UPS hydraulic hybrid demonstra-
tion vehicles are: U.S. EPA, UPS, Eaton Corporation,
International Truck and Engine Corporation, and the
U.S. Army - National Automotive Center. Major techni-
cal support was provided by FEV Engine Technology,
Inc., Southwest Research Institute and Morgan-Olson.
MORGAN
HOLSON
EPA does not endorse any specific company or enterprise.
CLEAN AUTOMOTIVE TECHNOLOGY
United States
Environmental Protection
Agency
EPA-420-F-09-066
October 2009
www.epa.gov/otaq/technology
NmATJCfN THAT WORKS
EPA's Clean Automotive Technology Program con-
ducts this innovative research primarily to:
• Achieve ultra-low pollution emissions
• Reduce greenhouse gases
HYDRAULIC HYBRID VEHICLES
THE WORLD'S
MOST EFFICIENT, LOWEST COST
HYBRIDS
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. Fleet owners benefit
by being able to recoup the initial hybrid system
costs through lower operating costs within a few
years.
United States
vironmental 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
World's First Full!
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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 technology. EPA has
been able to improve city fuel economy of a UPS package
car by 70 percent and reduce C02 greenhouse gas emis-
sions by 40 percent. The unique energy recovery technol-
ogy used while braking reduces brake wear by 75 percent,
increasing the net savings substantially.
A fleet owner operating one
of these high efficiency vehi-
cles would save up to 1,000
gallons of fuel each year.
-
Even more remarkable, when this technology is manufac-
tured in high volume it has the potential to cost less than
15 percent of the price of the base vehicle price; this
means owners could recoup the hybridization costs from
fuel and maintenance savings in three to five years.
The net lifetime savings over
this vehicle's typical 20 year
lifespan would be over
$50,000.
Hydraulic hybrid vehicles rely on proven innovative tech-
nology which can be applied to light-duty work trucks,
SUVs and heavy-duty urban vehicles such as city transit
buses and garbage trucks.
HOW IT WORKS
This innovative technology is simple. The main compo-
nents in a full 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— stores the low pressure
fluid after it has been used by the 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 accumula-
tor.
• Hybrid controller— monitors the driver's accelera-
tion and braking, and commands the hybrid system
components.
High Pressure Accumulator
Engine Pump/Motor | Drive Pump/Motor
The three key design features that improve the fuel
efficiency of hydraulic hybrid vehicles are:
i. 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)— The unique
hybrid design not only allows the engine to be oper-
ated at its maximum efficiency, but also enables the
engine to be completely shut off during certain
stages of operation because it is activated by the
controller only when it is needed. As a result, engine
use is cut almost in half in stop and go urban city
driving.
3. Optimum Engine Control— In the full series
hybrid design, there is no conventional transmission
and driveshaft to connect the engine directly to the
wheels. This frees the engine to be operated at its
best efficiency "sweet" spot, achieving optimum
vehicle fuel economy.
Low Pressure Reservoir
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