Clean Automotive Technology...
Innovation that Works
SEFft
United States
Environmental Protection
Agency
Hydraulic Hybrid Technology -
A Proven Approach
Higher fuel efficiency. Lower emissions. Reduced operating costs. Better acceleration performance.
These are just some of the advantages of the hydraulic hybrid drivetrain.
The U.S. Environmental Protection Agency (EPA) is developing this innovative technology to provide
cost-effective, ultra-clean and ultra-efficient improvements for vehicles. With a hydraulic hybrid system,
nearly all of the energy typically lost during vehicle braking is captured and used to propel the vehicle the
next time it needs to accelerate.
EPA's goals for this technology are to:
Achieve higher fuel economy
Reduce vehicle emissions
Save consumers money overtime
Maintain or improve vehicle acceleration performance
Focus on cost-effective technology that can be commercialized and transferred to the private sector
The Development of EPA's Hydraulic Hybrid Technology
EPA's multi-year research program to develop hydraulic hybrid technology has produced a proof-of-
concept test chassis that:
• Triples the fuel economy of conventional vehicles (80 miles per gallon (mpg) for a midsize family
sedan that also incorporates improved tires and aerodynamics)
• Saves the consumer money (consumer payback [i.e., recouping the higher vehicle cost] within 1 to 3
years through fuel savings and less brake wear)
• Accelerates from 0 to 60 miles per hour (mph) in approximately 8 seconds
• Attains higher fuel efficiency without using expensive lightweight materials (test weight of chassis is
3800 Ib) to facilitate commercialization
EPA's proof-of-concept test chassis
demonstrating hydraulic hybrid technology.
The hydraulic system offers great advantages for vehicles
operating in stop-and-go conditions because the system can
capture large amounts of energy when the brakes are applied.
This energy is subsequently used to propel the vehicle.
Technical challenges with hydraulic hybrids include noise and
packaging issues, but EPA is continuing to develop this
technology to resolve these issues. With the success of its
hydraulic hybrid chassis, EPA has begun to transfer the
technology to the private sector. EPA is currently developing
the hydraulic hybrid technology in urban delivery trucks and
large sport utility vehicles (SUVs) and pickup trucks; other
attractive applications include school buses, and waste
disposal trucks.
-------
Clean Automotive Technology...
Clean, efficient, cost-effective
Using Hydraulics in Urban Delivery Trucks
Urban delivery trucks are likely to be the first commercial
application of the hydraulic hybrid technology. One of the options
uses hydraulic "launch assist" or "power assist." A hydraulic
package of a reversible hydraulic pump/motor and accumulators is
added to the vehicle to optimize fuel economy, while keeping the
vehicle's conventional engine and transmission. Benefits include:
EPA's F-550 fleet demonstration vehicle
with hydraulic launch assist.
• 25 to 45 percent improvement in fuel economy for city driving
• Reduction of emissions by 20 to 30 percent (potentially up to 75 percent in certain cases)
• Better acceleration
• Less brake maintenance
• Reduced operating costs (consumer payback of 4 to 5 years for city driving)
EPA has modified a Ford F-550 delivery truck to demonstrate the technology of the hydraulic launch
assist system. EPA also has begun work to demonstrate the application of a full series hydraulic hybrid in
an urban delivery vehicle. A consumer payback of 1 to 3 years for city driving is expected.
The Next Generation of Large SUVs and Pickup Trucks
EPA's design for the large SUV or pickup truck replaces the conventional drivetrain with a hydraulic
drivetrain. This configuration of the full hydraulic design reduces the cost of the vehicle because it
eliminates the need for a transmission and transfer case. A large SUV or pickup truck equipped with a
full hydraulic drive is projected to achieve benefits such as:
• 30-40 percent improvement in fuel economy for combined city/highway driving (percentage of
improvement is much higher for city driving)
• Lower emissions
• Better acceleration
• Lower brake maintenance costs
• Reduced operating costs (consumer payback of the higher vehicle cost within 1 to 2 years for city/
highway driving)
EPA has modified a Ford Expedition to demonstrate and
further advance the full hydraulic system.
EPA also has developed clean diesel combustion
technology, which incorporates an engine design that is
simultaneously clean, efficient, and cost effective. Using
this concept in conjunction with the full hydraulic drive is
projected to improve the fuel economy of this vehicle by 85
percent (percentage is much higher for city driving).
In its efforts to advance and commercialize hydraulic hybrid
technology, EPA has developed strategic partnerships with
Ford Motor Company, Eaton Corporation, and Parker-
Hannifin.
EPA420-F-04-024
March 2004
Showcasing the use of hydraulics in a Ford Expedition.
------- |