science&technology - AUTOMOTIVE





Clean Automotive Technology

At EPA’s National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Michigan, Clean Automotive Technology research is underway. Clean Automotive Technology is EPA's automotive research initiative for developing unique and cost-effective technology for vehicles.


Under Clean Automotive Technology, EPA conducts this innovative research primarily to:

  • Achieve ultra-low pollution emissions
  • Increase fuel efficiency
  • Reduce greenhouse gases

By developing cost-effective technologies, Clean Automotive Technology also encourages manufacturers to produce cleaner and more fuel-efficient vehicles.  The consumer benefits in that they might be able to recoup the higher initial vehicle costs through lower operating costs within a few years.

This exciting program encourages the commercialization of promising technologies by actively pursuing the transfer of EPA's technologies into the private sector.  EPA partners with industry to maximize the viability of targeted technologies for commercial production through Cooperative Research and Development Agreements (CRADAs).  Research is done at EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Michigan.

Clean Automotive Technology has four main areas of focus.  They include Hydraulic Hybrid Research, Engine Research, Alternative Fuels Research, and Technical and Analytical Support.

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Hydraulic Hybrid Research

EPA is a research leader in the application of hydraulics in vehicles.  Hydraulic hybrid technology uses a hydraulic energy storage and propulsion system in the vehicle.  This hydraulic system captures and stores a large fraction of the energy normally wasted in vehicle braking and uses this energy to help propel the vehicle during the next vehicle acceleration.  The hydraulic system also enables the engine to operate more efficiently when it is needed.

Hydraulic hybrids draw from two sources of power to operate the vehicle - the diesel or gasoline engine and the hydraulic components.  In other words, a typical diesel-powered or gasoline powered vehicle can be fitted with hydraulic components as a secondary energy storage system.  The primary hydraulic components are two hydraulic accumulator vessels (a high-pressure accumulator capable of storing hydraulic fluid compressing inert nitrogen gas and a low-pressure accumulator) and one or more hydraulic pump/motor units.

Benefits of Hydraulic Technology:  Hydraulic drivetrains are particularly attractive for vehicle applications that entail a significant amount of stop-and-go driving, such as urban delivery trucks or school buses.  A major benefit of a hydraulic hybrid vehicle is the ability to capture and use a large percentage of the energy normally lost in vehicle braking.  Hydraulic hybrids can quickly and efficiently store and release great amounts of energy due to a higher power density.  This is a critical factor in maximizing braking energy recovered and increasing the fuel economy benefit.  While the primary benefit of hydraulics is higher fuel economy, hydraulics also increase vehicle acceleration performance.  Hydraulic hybrid technology cost-effectively allows the engine speed or torque to be independent of vehicle speed resulting in cleaner and more efficient engine operation.

Future of Hydraulics:  Hydraulic hybrid systems create a unique opportunity to optimize engine operations.  EPA has produced research concept vehicles that demonstrate the hydraulic technology.  One concept vehicle is an urban delivery truck that uses hydraulic "launch assist."  This delivery truck retains its conventional engine and transmission, but adds on a hydraulics package optimized for fuel economy. The next generation of hydraulic vehicles involves fully integrating hydraulic technology.  In this configuration, the "full" hydraulic hybrid replaces the conventional drivetrain with a hydraulic drivetrain and eliminates the need for a transmission and transfer case. Using the full hydraulic drive in conjunction with EPA's clean diesel combustion technology is projected to improve fuel economy even more.

EPA also has achieved major breakthroughs in designing hydraulic accumulators and pump/motors to be more efficient, smaller, and lighter for motor vehicle applications, which will help improve fuel efficiency.  EPA currently has cooperative research and development agreements with several private sector partners to further the development of hydraulics. (For additional information, see Partnerships.)

NOTE: You will need Adobe Acrobat Reader, available as a free download, to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

Recent Developments with Urban Delivery Vehicles

Recent Developments with Sport Utility Vehicles

On March 8, 2004, EPA unveiled the world's first full-sized hydraulic hybrid sport utility vehicle (SUV) at the 2004 Society of Automotive Engineers (SAE) World Congress in Detroit, Michigan. EPA retrofitted a Ford Expedition SUV with a hydraulic full hybrid powertrain that has been patented by EPA. EPA is estimating that this will nearly double the fuel economy and that a consumer would recoup the higher vehicle cost in less than 3 years through fuel savings and less brake wear.
Ford Expedition Hybrid

EPA's Ford Expedition Hybrid.

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Engine Research

EPA's engine research focuses on developing engines that are simultaneously clean, efficient, and cost effective, and which have high potential to produce real-world benefits. Low-emission diesel technology

Clean Diesel Combustion technology is one example of these innovative engine concepts. EPA's testing suggests the potential for a diesel engine design, using innovative air, fuel, and combustion management and conventional particulate matter aftertreatment, to achieve lower NOx levels without the need for NOx aftertreatment. EPA is developing this technology as a potential alternative with other diesel emissions control approaches (e.g., NOx adsorbers, urea selective catalytic reduction (SCR), etc.). Clean Diesel Combustion technology shows the potential to meet NOx levels "engine-out" over the entire engine operating range, to a level required for future diesel emissions standards. EPA has partnered with several automotive and engine manufacturers to evaluate the production feasibility of this technology. Using clean diesel combustion technology in conjunction with the full hydraulic drive is projected to improve fuel economy more than using either technology alone.

  • Fact Sheet: Clean Diesel Combustion -- Clean, Efficient, and Cost Effective Technology (PDF) (2 pp, 382K, EPA420-F-04-023, March 2004)
  • Presentation and speaker's notes: A Path to More Sustainable Transportation (PDF) (13 pp, 368K) (presented August 29, 2004 at the 10th Annual Diesel Engine Emissions Reduction Conference (DEER) in Coronado, CA.) This presentation includes an update on an EPA diesel combustion technology that meets the 2007 heavy duty standards with engine-out NOx emissions of less than 0.2 gm/BHP/hr without the need for any NOx aftertreatment.
  • Presentation on SAE Paper 2004-01-0933: An HCCI Engine Power Plant for a Hybrid Vehicle (PDF) (24 pp, 727K) (delivered March 10, 2004, at the SAE World Congress in Detroit, Michigan). This presentation describes work conducted at the National Vehicle and Fuel Emissions Laboratory to explore the potential use of a homogenous charge compression ignition (HCCI) as a power plant for a hybrid vehicle.

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Alternative Fuels Research

Research in this area evaluates the feasibility of running vehicles on non-petroleum fuels, such as alcohol fuels.  The use of alternative fuels can potentially lower health-related emissions, reduce greenhouse gas emissions, and create less dependence on imported oil.

EPA's advanced research in alternative transportation fuels, such as ethanol and methanol, explores their potential for providing a cost-effective means of using sustainable fuels to achieve both low emissions and high fuel economy.  Alternative fuel research consists of engine and vehicle development to achieve an economical alternative to conventional gasoline and diesel engines.

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Technical and Analytical Support

The automotive technology research carried out under Clean Automotive Technology provides EPA staff with insights that are useful in providing technical support on a wide range of automotive technology-related issues. EPA annually publishes a Light-Duty Automotive Technology and Fuel Economy Trends Report that is considered the most authoritative compilation of fuel economy data from new personal vehicles sold in the U.S. since 1975.

  • Report: A Study of Potential Effectiveness of Carbon Dioxide Reducing Vehicle Technologies. This report, prepared for EPA by the engineering firm Ricardo under subcontract to Perrin Quarles Associates, Inc., provides a detailed assessment of the carbon dioxide emissions reduction potential of a large number of conventional vehicle technology packages. Also included is a peer review of the report, as well as a presentation given by EPA to the National Research Council's Committee on Fuel Economy of Light-duty Vehicles, which provides contextual background for this report.

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General Documents

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Related Links

    Other EPA Links

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